ALBERT

Description: In this work, synthesis and investigations on chitosan-based hydrogels modified with Aloe vera juice are presented. These materials were synthesized by UV radiation. Investigations involved analysis of chemical structure by FTIR spectroscopy, sorption properties in physiological liquids, strength properties by texture analyzer, surface topography by Atomic Force Microscopy (AFM technique), and in vitro cytotoxicity by MTT test using L929 murine fibroblasts. Particular attention was focused both on determining the impact of the amount and the molecular weight of the crosslinker used for the synthesis as well as on the introduced additive on the properties of hydrogels. It was proven that modified hydrogels exhibited higher swelling ability. Introduced additive affected the tensile strength of hydrogels—modified materials showed 23% higher elongation. The greater amount of the crosslinker used in the synthesis, the more compact the structure, leading to the lower elasticity and lower sorption of hydrogels was reported. Above 95%, murine fibroblasts remained viable after 24 h incubation with hydrogels. It indicates that tested materials did not exhibit cytotoxicity toward these lines. Additionally, materials with Aloe vera juice were characterized by lower surface roughness. Conducted investigations allowed us to state that such modified hydrogels may be considered as useful for biomedical purposes.

Description: Mechanical performance of cast aluminum alloys is strongly affected by the defects formed during solidification. For example, fractography studies of the fatigue specimens have shown that fatigue failure in aluminum castings containing defects is almost always initiated from defects, among which pores are most detrimental. However, elimination of these pores is neither always economically nor technically possible. This work characterizes defects in high pressure die cast aluminum alloy as an illustrative material, but the methods used can be applicable to other types of castings and defects. The defects were evaluated using metallography as well as micro-computed tomography techniques. The variability of defects between the specimens of two sizes as well as different porosity levels are studied statistically. The distributions of defects based on location within the specimens are also analyzed. Moreover, the maximum defect size within the specimens are estimated using extreme value statistics, which can be used as an input to fatigue life prediction models. Extreme value statistics is applied on both 2D and 3D defect data. The accuracy of each approach is verified by comparing the estimated maximum defect size within the specimens with the maximum observed defects on fracture surfaces of fatigue specimens.

Description: The range of selective laser sintering (SLS) materials is currently limited, and the available materials are often of high cost. Moreover, the mechanical strength of wood–plastic SLS parts is low, which restricts the application of a SLS technology. A new composite material has been proposed to address these issues, while simultaneously valorizing agricultural and forestry waste. This composite presents several advantages, including reduced pollution associated with waste disposal and reduced CO2 emission with the SLS process in addition to good mechanical strength. In this article, a novel and low-cost Prosopis chilensis/polyethersulfone composite (PCPC) was used as a primary material for SLS. The formability of PCPC with various raw material ratios was investigated via single-layer experiments, while the mechanical properties and dimensional accuracy of the parts produced using the various PCPC ratios were evaluated. Further, the microstructure and particle distribution in the PCPC pieces were examined using scanning electron microscopy. The result showed that the SLS part produced via 10/90 (wt/wt) PCPC exhibited the best mechanical strength and forming quality compared to other ratios and pure polyethersulfone (PES), where bending and tensile strengths of 10.78 and 4.94 MPa were measured. To improve the mechanical strength, post-processing infiltration was used and the PCPC-waxed parts were enhanced to 12.38 MPa and 5.73 MPa for bending and tensile strength.

Description: Ordered mesoporous Zr-Al composite oxide materials (denoted as OMZA-x) with different Zr contents have been synthesized by a solvent evaporation-inducing self-assembly procedure associated with a thermal treatment at 100 °C. A cooperative co-assembly process of amphiphilic triblock copolymer F127 molecules and inorganic hydroxyl species originated from the hydrolysis of Zr and Al precursors was proposed to explain the synthesis of OMZA-x. Compared to ordered mesoporous alumina prepared without introducing Zr species, the resultant OMZA-x exhibited a much more ordered mesostructure combined with a distinct increase in the pore volume and specific surface area. The highly homogenous doping of Zr into the mesopore walls together with the formation of Zr-O-Al bonds can effectively enhance the thermal and hydrothermal stability of OMZA-x. For instance, the ordered mesostructure and excellent textural properties of OMZA-6 prepared with the optimum atomic ratio of Al to Zr of 6 could be well maintained even after a high-temperature treatment at 1000 °C for 1 h or a hydrothermal treatment at 100 °C for 6 h.

Description: The so-called Born–Huang ansatz is a fundamental tool in the context of ab-initio molecular dynamics, viz., it allows effectively separating fast and slow degrees of freedom and thus treating electrons and nuclei with different mathematical footings. Here, we consider the use of a Born–Huang-like expansion of the three-dimensional time-dependent Schrödinger equation to separate transport and confinement degrees of freedom in electron transport problems that involve geometrical constrictions. The resulting scheme consists of an eigenstate problem for the confinement degrees of freedom (in the transverse direction) whose solution constitutes the input for the propagation of a set of coupled one-dimensional equations of motion for the transport degree of freedom (in the longitudinal direction). This technique achieves quantitative accuracy using an order less computational resources than the full dimensional simulation for a typical two-dimensional geometrical constriction and upto three orders for three-dimensional constriction.

Description: A porous titanium structure was suggested to improve implant stability in the early healing period or in poor bone quality. This study investigated the effect of a porous structure on the osseointegration of dental implants. A total of 28 implants (14 implants in each group) were placed in the posterior mandibles of four beagle dogs at 3 months after extraction. The control group included machined surface implants with an external implant–abutment connection, whereas test group implants had a porous titanium structure added to the apical portion. Resonance frequency analysis (RFA); removal torque values (RTV); and surface topographic and histometric parameters including bone-to-implant contact length and ratio, inter-thread bone area and ratio in total, and the coronal and apical parts of the implants were measured after 4 weeks of healing. RTV showed a significant difference between the groups after 4 weeks of healing (p = 0.032), whereas no difference was observed in RFA. In the test group, surface topography showed bone tissue integrated into the porous structures. In the apical part of the test group, all the histometric parameters exhibited significant increases compared to the control group. Within the limitations of this study, enhanced bone growth into the porous structure was achieved, which consequently improved osseointegration of the implant.

Description: Pulsed electromagnetic field (PEMF) has drawn attention as a potential tool to improve the ability of bone biomaterials to integrate into the surrounding tissue. We investigated the effects of PEMF (frequency, 75 Hz; magnetic induction amplitude, 2 mT; pulse duration, 1.3 ms) on human osteoblast-like cells (SAOS-2) seeded onto wool keratin scaffolds in terms of proliferation, differentiation, and production of the calcified bone extracellular matrix. The wool keratin scaffold offered a 3D porous architecture for cell guesting and nutrient diffusion, suggesting its possible use as a filler to repair bone defects. Here, the combined approach of applying a daily PEMF exposure with additional osteogenic factors stimulated the cells to increase both the deposition of bone-related proteins and calcified matrix onto the wool keratin scaffolds. Also, the presence of SAOS-2 cells, or PEMF, or osteogenic factors did not influence the compression behavior or the resilience of keratin scaffolds in wet conditions. Besides, ageing tests revealed that wool keratin scaffolds were very stable and showed a lower degradation rate compared to commercial collagen sponges. It is for these reasons that this tissue engineering strategy, which improves the osteointegration properties of the wool keratin scaffold, may have a promising application for long term support of bone formation in vivo.

Description: The cured-in-place pipe (CIPP) method is currently the most frequently used approach for the renovation of piping without digging; this technology is suitable for pipes made from all types of material. The authors of this paper examined how chemical substances and increased temperature change samples of CIPP with vinyl-ester resin taken from a simulated installation. Changes were observed at several levels: visually via a digital optical microscope, through changes of short-term bending properties and by observation of the activity of the sample structure by means of acoustic emission (AE). Interdependencies among the observed parameters were examined, specifically, the cumulative number of hits (cnt)/deflection and flexural properties/mechanic wave velocity. The test results prove that after three weeks of immersion in a simulated aggressive environment that mirrors what may happen to CIPP in real conditions, short-term mechanical properties change. This is also proven by the results of the AE measurements. For clarity, the results include images from a digital optical microscope. In addition, this paper proves that CIPP samples have good resistance to the action of organic and inorganic acids and to increased temperatures. After three weeks of exposure to a temperature of 100 °C the CIPP flexural properties of the samples had even improved.

Description: Surgery is performed to treat various diseases. During the process, the surgical site is healed through self-healing after surgery. Post-operative or tissue adhesion caused by unnecessary contact with the surgical site occurs during the normal healing process. In addition, it has been frequently found in patients who have undergone surgery, and severe adhesion can cause chronic pain and various complications. Therefore, anti-adhesion barriers have been developed using multiple biomaterials to prevent post-operative adhesion. Typically, anti-adhesion barriers are manufactured and sold in numerous forms, such as gels, solutions, and films, but there are no products that can completely prevent post-operative adhesion. These products are generally applied over the surgical site to physically block adhesion to other sites (organs). Many studies have recently been conducted to increase the anti-adhesion effects through various strategies. This article reviews recent research trends in anti-adhesion barriers.

Description: The wide application of Nd-Fe-B permanent magnets, in addition to rare-earth metal resource constraints, creates the necessity of the development of efficient technologies for recycling sintered Nd-Fe-B permanent magnets. In the present study, a magnet-to-magnet recycling process is considered. As starting materials, magnets of different grades were used, which were processed by hydrogen decrepitation and blending the powder with NdHx. Composition inhomogeneity in the Nd2Fe14B-based magnetic phase grains in the recycled magnets and the existence of a core-shell structure consisting of a Nd-rich (Dy-depleted) core and Nd-depleted (Dy-enriched) shell are demonstrated. The formation of this structure results from the grain boundary diffusion process of Dy that occurs during the sintering of magnets prepared from a mixture of Dy-free (N42) and Dy-containing magnets. The increase in the coercive force of the N42 magnet was shown to be 52%. The simultaneous retention of the remanence, and even its increase, were observed and explained by the improved isolation of the main magnetic phase grains as well as their alignment.

Description: This research was devoted to studying the influence of the taper angle on the micro-compression of micro-pillars fabricated from near-amorphous and nanocrystalline Mo-B-C coatings. A series of micro-pillars with a taper angle between 4–14° was fabricated by focused ion beam technique. The deformation mechanism was found to be dependent on the taper and, also, on the crystallinity of the coating. In order to obtain correct values of yield strength and Young’s modulus, three empirical models of stress correction were experimentally tested, and the results were compared with nanoindentation measurements. It was shown that the average stress correction model provided comparable results with nanoindentation for the yield strength for taper angles up to ~10°. On the other hand, the average radius or area model gave the most precise results for Young’s modulus if the taper angle was

Description: The mechanical characterization of plain foamed concrete (PFC) and fiber-reinforced foamed concrete (FRFC) with a density of 700 kg/m3 was performed with compression and tension tests. FRFC was reinforced with the natural fiber henequen (untreated or alkaline-treated) at volume fractions of 0.5%, 1% and 1.5%. Polypropylene fiber reinforcement was also used as a reference. For all FRFCs, the inclusion of the fibers enhanced the compressive and tensile strengths and plastic behavior, which was attributed to the increase of specimen integrity. Under compressive loading, after the peak strength, there was no considerable loss in strength and a plateau-like regime was observed. Under tensile loading, the fibers significantly increased the tensile strength of the FRFCs and prevented a sudden failure of the specimens, which was in contrast to the brittle behavior of the PFC. The tensile behavior enhancement was higher when treated henequen fibers were used, which was attributed to the increase in the fiber–matrix bond produced by the alkaline treatment. The microscopic characterization showed that the inclusion of fibers did not modify the air-void size and its distribution. Higher energy absorption was observed for FRFCs when compared to the PFC, which was attributed to the enhanced toughness and ductility by the fibers. The results presented herein warrant further research of FRFC with natural henequen fibers for engineering applications.

Description: We utilized Ni as a floating capping layer in p-channel SnO thin-film transistors (TFTs) to improve their electrical performances. By utilizing the Ni as a floating capping layer, the p-channel SnO TFT showed enhanced mobility as high as 10.5 cm2·V−1·s−1. The increase in mobility was more significant as the length of Ni capping layer increased and the thickness of SnO active layer decreased. The observed phenomenon was possibly attributed to the changed vertical electric field distribution and increased hole concentration in the SnO channel by the floating Ni capping layer. Our experimental results demonstrate that incorporating the floating Ni capping layer on the channel layer is an effective method for increasing the field-effect mobility in p-channel SnO TFTs.

Description: Continuous fiber-reinforced manufacturing has many advantages, but the fabrication cost is high and its process is difficult to control. This paper presents a method for printing fiber-reinforced composite on the common fused filament fabrication (FFF) platform. Polylactic Acid (PLA) and Polyethylene terephthalate (PET) fibers are used as printing materials. A spatial continuous toolpath planning strategy is employed to reduce the workload of post-processing without cutting the fiber. Experimental results show that this process not only enables the printing of models with complex geometric shapes but also supports material recycling and reuse. A material recovery rate of 100% for continuous PET fiber and 83% for PLA were achieved for a better environmental impact. Mechanical tests show that the maximum tensile strength of continuous PET fiber-reinforced thermoplastic composites (PFRTPCs) is increased by 117.8% when compared to polyamide-66 (PA66).

Description: This paper presents the results of research concerning multilayered epoxy composites reinforced with different materials. The strength of multilayered composites depends, to a large extent, on the reinforcing material. The authors decided to compare the low velocity impact response and perform tensile strength tests on several composites, to ascertain the mechanical properties of the prepared composites. Five different reinforcing materials were provided for the research (two fabrics made from aramid fibers, two fabrics made from carbon fibers and one fabric made from polyethylene fibers). The composites were manufactured by the vacuum supported hand laminating method. The low velocity impact response tests were conducted with the use of a pneumatic launcher. Three strikers with different geometry (conical striker, hemispherical striker and ogival striker) were used. A comparison of the resulting damage to the composites after the impact of the strikers was based on the images obtained using an optical microscope; tensile tests were also performed. The experimental investigation showed significant differences in the mechanical properties of the composites, depending on the applied reinforcing material. It was found that, as a result of the impacts, less damage occurred in the composites which were characterized by a lower Young’s modulus and a higher tensile strength.

Description: The use of gypsum as an indoor coating material for buildings is very extensive. This means that huge amounts of gypsum waste are generated daily worldwide. Therefore, many researchers in the last years have been working on the generation of new gypsum-related materials and products that incorporate recycled gypsum waste as a replacement for the commercial one. On the other hand, trying to reduce the large amounts of plastic generated globally each year, several studies have used different types of plastic waste as aggregates for the development of new construction and building materials. However, up to now, no previous studies have been found in which any type of plastic waste has been used as an aggregate in a recycled gypsum matrix. This paper presents a study in which two different types of waste were mixed for the development of new gypsum plasters: unheated gypsum waste from industrial plasterboard production (GPW) and polycarbonate (PC) waste from rejected compact discs (CDs) and digital versatile discs (DVDs). In this sense, the mechanical and thermal performance of plasters was evaluated. Finally, in order to evaluate the changes in the microstructure of the composites, a scanning electron microscopy (SEM) analysis was conducted. The results showed a good performance of the new composites when both types of waste were combined in the mixes. New lightweight eco-efficient plasters, completely recycled, with enhanced flexural strength (by 14.8%), compressive strength (by 26.8%), and thermal conductivity (42.8% less), compared to the reference material, were achieved.

Description: The authors wish to make the following corrections to this paper [1]: replace: (37) 1 ε z = f ε m = 1 − f ε d and (39) 1 μ z = f μ m = 1 − f μ d with the correct expressions: (37) 1 ε z = f ε m + 1 − f ε d and (39) 1 μ z = f μ m + 1 − f μ d [...]

Description: In this article, an improved variant of the cuckoo search (CS) algorithm named Coevolutionary Host-Parasite (CHP) is used for maximizing the metal removal rate in a turning process. The spindle speed, feed rate and depth of cut are considered as the independent parameters that describe the metal removal rate during the turning operation. A data-driven second-order polynomial regression approach is used for this purpose. The training dataset is designed using an L16 orthogonal array. The CHP algorithm is effective in quickly locating the global optima. Furthermore, CHP is seen to be sufficiently robust in the sense that it is able to identify the optima on independent reruns. The CHP predicted optimal solution presents ±10% deviations in the optimal process parameters, which shows the robustness of the optimal solution.

Description: 3D printed biomaterials have been extensively investigated and developed in the field of bone regeneration related to clinical issues. However, specific applications of 3D printed biomaterials in different dental areas have seldom been reported. In this study, we aimed to and successfully fabricated 3D poly (lactic-co-glycolic acid)/β-tricalcium phosphate (3D-PLGA/TCP) and 3D β-tricalcium phosphate (3D-TCP) scaffolds using two relatively distinct 3D printing (3DP) technologies. Conjunctively, we compared and investigated mechanical and biological responses on human dental pulp stem cells (hDPSCs). Physicochemical properties of the scaffolds, including pore structure, chemical elements, and compression modulus, were characterized. hDPSCs were cultured on scaffolds for subsequent investigations of biocompatibility and osteoconductivity. Our findings indicate that 3D printed PLGA/TCP and β-tricalcium phosphate (β-TCP) scaffolds possessed a highly interconnected and porous structure. 3D-TCP scaffolds exhibited better compressive strength than 3D-PLGA/TCP scaffolds, while the 3D-PLGA/TCP scaffolds revealed a flexible mechanical performance. The introduction of 3D structure and β-TCP components increased the adhesion and proliferation of hDPSCs and promoted osteogenic differentiation. In conclusion, 3D-PLGA/TCP and 3D-TCP scaffolds, with the incorporation of hDPSCs as a personalized restoration approach, has a prospective potential to repair minor and critical bone defects in oral and maxillofacial surgery, respectively.

Description: Portland cement tends to exhibit negative environmental impacts; thus, it is required to find measures that will improve its green credentials. In this study, we report a blended Portland slag cement as an alternative environmentally-friendly building material in order to reduce the total carbon footprint resulted from the production of the ordinary Portland cement (OPC), which may resolve the environmental issues associated with carbon dioxide emissions. The ordinary Portland cement type I enhanced by basic oxygen steelmaking slag (BOF) is produced and casted into cubic and beam-like samples for the compressive and three-point bending tests, and the compressive and flexural strengths are experimentally measured. Numerical simulations are conducted to compare with the experimental result and satisfactory agreements are obtained. X-ray diffraction (XRD) investigations and porosity tests are then carried out using the semi-adiabatic calorimetry, which indicates that 5% BOF is the optimal ratio to accelerate the hydration process while increasing the amount of hydration products, especially at the early curing age of 3 days. Scanning electron microscope (SEM) images further indicate that BOF can be used to prevent the development of microcracks while mitigating their propagation within cement mortar. Our study indicates that the compressive strength of OPC can be critically increased by BOF at the relatively low concentrations of 5%. The blended slag cement reported in this paper provides advanced understanding on the green building material that uses byproduct wastes for the mechanical and electrical performance.

Description: Over recent years, investigations of coordination polymer thin films have been initiated due to their unique properties, which are expected to be strongly enhanced in the thin film form. In this work, a crystalline [FeII(H2O)2]2[NbIV(CN)8]∙4H2O (1) film on a transparent Nafion membrane was obtained, for the first time, via ion-exchange synthesis. The proper film formation and its composition was confirmed with the use of energy dispersive X-ray spectroscopy and infrared spectroscopy, as well as in situ Ultraviolet-Visible (UV-Vis) spectroscopy. The obtained film were also characterized by scanning electron microscopy, X-ray diffraction, and magnetic measurements. The [FeII(H2O)2]2[NbIV(CN)8]∙4H2O film shows a sharp phase transition to a long-range magnetically ordered state at Tc = 40 K. The 1 film is a soft ferromagnet with the coercive field Hc = 1.2 kOe. Compared to the bulk counterpart, a decrease in critical temperature and a significant increase in the coercive field were observed in the films indicating a distinct size effect. The decrease in Tc could also have been related to the possible partial oxidation of FeII ions to FeIII, which could be efficient, due to the large surface of the thin film sample.

Description: In this study, a highly crystalline bismuth ferrite (BFO) powder was synthesized using a novel, very simple, and cost-effective synthetic approach. It was demonstrated that the optimal annealing temperature for the preparation of highly-pure BFO is 650 °C. At lower or higher temperatures, the formation of neighboring crystal phases was observed. The thermal behavior of BFO precursor gel was investigated by thermogravimetric and differential scanning calorimetry (TG-DSC) measurements. X-ray diffraction (XRD) analysis and Mössbauer spectroscopy were employed for the investigation of structural properties. Scanning electron microscopy (SEM) was used to evaluate morphological features of the synthesized materials. The obtained powders were also characterized by magnetization measurements, which showed antiferromagnetic behavior of BFO powders.

Description: Using recyclable materials in asphalt pavement is a fundamental design approach not only for limiting the environmental impact of the construction industry, but also for reducing the overall costs of the road infrastructures. Over the past years, road agencies have developed different policies to incorporate various types of recyclable material into conventional asphalt mixtures. reclaimed asphalt pavement (RAP) is one of the most highly recycled construction materials. However, the aged RAP binder and its stiffer and brittle characteristics compared to the fresh binder may negatively affect the performance of the recycled mixture, especially when operating in cold climates. In this study, the low-temperature response of asphalt mixture prepared with single-recycled RAP (SRRAP) and double-recycled RAP (DRRAP), prepared in the laboratory, is experimentally investigated based on creep testing performed with the bending beam rheometer (BBR). Then, the data were analyzed based on three simple mathematical models to extract information on material behavior. Finally, a new indicator named thermal stress factor (TFS) on low-temperature response is proposed. Relatively poorer performance was observed from SRRAP mixture compared to the asphalt mixture prepared with virgin material. However, the low-temperature response between SRRAP and DRRAP did not present significant differences. The values of TFS support the experimental results and suggest the possibility of considering re-recycling technology for further research with the objective of a possible application in the asphalt pavement industry.

Description: Lightweight aggregate concrete manufactured by solid waste or recycled by-products is a burgeoning topic in construction and building materials. It has significant merits in mitigating the negative impact on the environment during the manufacturing of Portland cement and reduces the consumption of natural resources. In this review article, the agricultural and industrial wastes and by-products, which were used as cementitious materials and artificial lightweight aggregate concrete, are summarized. Besides, the mechanical properties, durability, and a few advanced microstructure characterization methods were reviewed as well. This review also provides a look to the future research trends that may help address the challenges or further enhance the environmental benefits of lightweight aggregate concrete manufactured with solid waste and recycled by-products.

Description: To control the degradation rate of magnesium (Mg) alloys, chitosan (CHI) and L-glutamic acid (LGA) were used as coatings on Mg-Zn-Ca alloys via dip coating. In this study, either two or seven CHI/LGA layers were applied as a coating on Mg-2.8Zn-0.8Ca alloy (ZX31) and Mg-2.8Zn-0.8Ca hemostasis clips (ZX31 clips). The morphologies, compositions, and surface roughness of the specimens were characterized via scanning electron microscopy, Fourier transform infrared spectroscopy, and surface measurement devices. The degradation rates and behavior of the specimens were evaluated by immersing them in simulated body fluids and by applying these ZX31 clips on rabbits’ uterine tubes for five weeks. The specimen with seven layers (ZX31(CHI/LGA)7) exhibited improved corrosion behavior when compared with ZX31 or ZX31(CHI/LGA)2, with a reduced degradation rate of the Mg alloy in a simulated body environment. In vivo experiments showed that ZX31 clips exhibited good biocompatibilities in each group but could not maintain the clamping function for five weeks. The weight loss of ZX31(CHI/LGA)7 was significantly lower than that of the other groups. Consequently, it was verified that CHI can be used as a protective layer on a magnesium alloy surface via in vitro and in vivo experiments.

Description: New materials that are as similar as possible in terms of structure and biology to the extracellular matrix (external environment) of cells are of great interest for regenerative medicine. Oligoproline and oligohydroxyproline derivatives (peptides 2–5) are potential mimetics of collagen fragments. Peptides 2–5 have been shown to be similar to the model collagen fragment (H-Gly-Hyp-Pro-Ala-Hyp-Pro-OH, 1) in terms of both their spatial structure and biological activity. In this study, peptides 2–5 were covalently bound to nonwovens based on chitosan and calcium alginate. Incorporation of the peptides was confirmed by Fourier transform -infrared (FT-IR) and zeta potential measurements. Biological studies (cell metabolic activity by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test and Live/Dead assay) proved that the obtained peptide-polysaccharide conjugates were not toxic to the endothelial cell line EA.hy 926. In many cases, the conjugates had a highly affirmative influence on cell proliferation. The results of this study show that conjugates of chitosan and calcium alginate with oligoproline and oligohydroxyproline derivatives have potential for use in regenerative medicine.

Description: The application of fiber-reinforced polymer (FRP) bars and ultra-high performance concrete (UHPC) in the field of civil engineering is promising. An innovative FRP bar-reinforced UHPC short-ribbed bridge deck slab, with low self-weight and high structural performance, was proposed in this study. The behavior of one-way basalt FRP (BFRP) bar-reinforced UHPC slabs under concentrated load was experimentally investigated, and compared with that of a steel bar-reinforced UHPC slab. The ultimate capacity of the one-way BFRP bar-reinforced UHPC slab was 0.59 times that of the steel bar-reinforced UHPC slab, while its ductility was better. Increasing the reinforcement ratio and loading area was beneficial to the ductility of one-way BFRP bar-reinforced UHPC slabs. Moreover, the model proposed by EI-Gamal et al. was found to be suitable for evaluating the punching shear capacities of one-way BFRP bar-reinforced UHPC slabs. However, the model failed to consider the unique strain-hardening characteristics of UHPC, which led to conservative prediction.

Description: Copper matrix nanocomposites reinforced with magnetite nanoparticles were developed using powder metallurgy. Various processing parameters were taken into consideration, such as magnetite content, compaction pressure, sintering time and temperature. The nanopowder blends were compacted using various uniaxial pressures and sintered at 650 and 800 °C in order to study the influence of processing parameters on morphology, structure, thermal, magnetic and mechanical properties. The structure and morphology of the nanocomposites analyzed by X-ray diffraction (XRD), bright field transmission electron microscopy (TEMBF) and scanning electron microscopy (SEM) showed that sintered composites retained the nanoscale characteristics of the initial Fe3O4 and Cu nanopowders. These nanocomposites have good cold-rolling deformability and Vickers micro-hardness. The Cu-xFe3O4 nanocomposites have thermal and magnetic properties that make them suitable for electronical applications.

Description: Polymeric nanoparticles (NPs) have a variety of biomedical, biotechnology, agricultural and environmental applications. As such, a great need has risen for the fabrication of these NPs in large scales. In this study, we used a high throughput fiber reactor for the preparation of poly(lactic-co-glycolic acid) (PLGA) NPs via nanoprecipitation. The fiber reactor provided a high surface area for the controlled interaction of an organic phase containing the PLGA solution with an aqueous phase, containing poly(vinyl alcohol) (PVA) as a stabilizer. This interaction led to the self-assembly of the polymer into the form of NPs. We studied operational parameters to identify the factors that have the greatest influence on the properties of the resulting PLGA NPs. We found that the concentration of the PLGA solution is the factor that has the greatest effect on NP size, polydispersity index (PDI), and production rate. Increasing PLGA concentration increased NP sizes significantly, while at the same time decreasing the PDI value. The second factor that was found to affect NP properties was the concentration of PVA solution, which resulted in increased NP sizes and decreased production rates. Flowrates of the feed streams also affected NP size to a lesser extent, while changing the operational temperature did not change the product’s features. In general, the results demonstrate that fiber reactors are a suitable method for the large-scale, continuous preparation of polymeric NPs suitable for biomedical applications.

Description: A promising way to improve the performance of luminescent materials is to combine them with noble metal nanoparticles. Herein, a set of silver/europium-doped lanthanum orthophosphate (Ag/La0.95Eu0.05PO4) nanostructures with different concentrations of silver nanoparticles were prepared and investigated. The presented overlap between the strongest europium (Eu3+) excitation line and the broad silver nanoparticle surface plasmon resonance makes the combination prospective for coupling. X-ray powder diffraction confirmed the monoclinic monazite structure. The transmission electron microscopy revealed particles with a rod-like shape and ~4 aspect ratio. Photoluminescence spectra show characteristic Eu3+ ion red emission. One of the requirements for an enhanced luminescence effect is the precise control of the distance between the noble metal nanoparticles and the emitter ion. The distance is indirectly varied throughout the change of Ag nanoparticle concentration in the La0.95Eu0.05PO4 host. The emission intensity increases with the increase in Ag nanoparticles up to 0.6 mol %, after which the luminescence decreases due to the nanoparticles’ close packing and aggregation leading to the displacement of La0.95Eu0.05PO4 from the vicinity of the metal particles and reabsorption of the emitted light. The emission intensity of La0.95Eu0.05PO4 increases more than three times when the Eu3+ excitation is supported by the localized surface plasmon resonance in the Ag/La0.95Eu0.05PO4 nanostructures.

Description: Dentine pretreatment through sandblasting procedures has been widely studied but no curve test results are currently available. Thus, the aim herein was to in vitro compare the adhesive strength in sandblasted or not samples using a universal testing machine. Thirty -two bovine teeth were divided into two groups, namely test (n = 16 bars), sandblasting with aluminum oxide particles (50 µm) was performed before the adhesion procedures), and control (n = 16 bars), where no sandblasting procedure was performed. A bi-material curve test was used to evaluate the characteristics of the dentine pretreatment in terms of tensile stress and fracture strength. A scanning electron microscope (SEM) was used to analyze the fracture topography in the composite, bonding, dentin, and at the relative interfaces. The results demonstrated a statistically significant difference between the two groups in terms of tensile stress at maximum load showing values of 84.300 ± 51.342 MPa and 35.071 ± 16.609 MPa, respectively for test and control groups (p = 0.033). Moreover, a fracture strength test showed values of 18.543 ± 8.145 MPa for test and 8.186 ± 2.833 MPa for control group (p = 0.008). In conclusion, the sandblasting treatment of the dentine significantly influenced the mechanical resistance of the adhesion in this in vitro study.

Description: Atmospheric pressure plasma (APP) deposition techniques are useful today because of their simplicity and their time and cost savings, particularly for growth of oxide films. Among the oxide materials, titanium dioxide (TiO2) has a wide range of applications in electronics, solar cells, and photocatalysis, which has made it an extremely popular research topic for decades. Here, we provide an overview of non-thermal APP deposition techniques for TiO2 thin film, some historical background, and some very recent findings and developments. First, we define non-thermal plasma, and then we describe the advantages of APP deposition. In addition, we explain the importance of TiO2 and then describe briefly the three deposition techniques used to date. We also compare the structural, electronic, and optical properties of TiO2 films deposited by different APP methods. Lastly, we examine the status of current research related to the effects of such deposition parameters as plasma power, feed gas, bias voltage, gas flow rate, and substrate temperature on the deposition rate, crystal phase, and other film properties. The examples given cover the most common APP deposition techniques for TiO2 growth to understand their advantages for specific applications. In addition, we discuss the important challenges that APP deposition is facing in this rapidly growing field.

Description: This study presents results of experimental tests on quality of dissimilar welded joints between 316L austenitic and 2304 lean duplex stainless steels, welded without ceramic backing. Fiber laser welded butt joints at a thickness of 8 mm were subjected to non-destructive testing (visual and penetrant), destructive testing (static tensile test, bending test, and microhardness measurements) and structure observations (macro- and microscopic examinations, SEM, element distribution characteristics, and ferrite content measurements). Non-destructive tests and metallographic examinations showed that the welded joints meet the acceptance criteria for B level in accordance with EN ISO 13919–1 standard. Also the results of the destructive tests confirmed the high quality of the joints: specimens were fractured in base material with lower strength—316L austenitic stainless steel and a 180° bending angle was obtained confirming the high plasticity of the joints. Microscopic examination, SEM and EDS analysis showed the distribution of alloying elements in joints. The microhardness of the autogenous weld metal was higher by about 20 HV0.2 than that of the lean duplex steel. Ferrite content in the root was about 37% higher than in the face of the weld. The Schaeffler phase diagram was used to predict the phase composition of the welded joints and sufficient compliance with the magnetic method was found. The presented procedure can be used for welding of 316L–2304 stainless steels dissimilar welded joints of 8 mm thickness without ceramic backing.

Description: It is well known that energetic demand and environmental pollution are strictly connected; the side products of vehicle and industrial exhausts are considered extremely dangerous for both human and environmental health. In the last years, the possibility to simultaneously photo-degrade water dissolved pollutants by means of ZnO nanostructures and to use their piezoelectric features to enhance the photo-degradation process has been investigated. In the present contribution, an easy and low-cost wet approach to synthetize hexagonal elongated ZnO microstructures in the wurtzite phase was developed. ZnO performances as photo-catalysts, under UV-light irradiation, were confirmed on water dissolved methylene blue dye. Piezoelectric responses of the synthetized ZnO microstructures were evaluated, as well, by depositing them into films onto flexible substrates, and a home-made layout was developed, in order to stimulate the ZnO microstructures deposited on solid supports by means of mechanical stress and UV photons, simultaneously. A relevant increment of the photo-degradation efficiency was observed when the piezopotential was applied, proposing the present approach as a completely eco-friendly tool, able to use renewable energy sources to degrade water solved pollutants.

Description: The present work explores in detail the effect of alkaline-basic electrolytes on the capacitance performance of biomass-derived carbonaceous materials used as electrodes in symmetric supercapacitors. The proof-of-concept is demonstrated by two commercial carbon products (YP-50F and YP-80F, Kuraray Europe GmbH, Vantaa, Finland), obtained from coconuts. The capacitance performance of YP-50F and YP-80F was evaluated in three types of basic electrolytes: 6 M LiOH, 6 M NaOH and 6 M KOH. It was found that the capacitance performance of YP-50F improved in the following order: NaOH 〈 LiOH 〈 KOH; Meanwhile, for YP-80F, the order changes to LiOH 〈 NaOH 〈 KOH. After 1000 cycles, the cycling stability of both YP-50F and YP-80F increased in the order NaOH 〈 LiOH 〈 KOH. This order of performance improvement is determined by both the electrolyte conductivity and the interaction between the functional groups of carbonaceous materials and alkaline electrolytes. The reactivity of the functional groups was assessed by postmortem SEM/EDS and X-ray photoelectron spectroscopy (XPS) analyses of the electrodes after prolonged cycling.

Description: The rheology of cement grouts often plays a crucial role in the success of rock grouting. In practice, the rheological parameters should be timely adjusted according to the evolution of grouting pressure, flow rate and injection time. However, obtaining the magnitude of rheological parameters is not easy to achieve under site conditions. More importantly, the ground temperature in deep rock masses is elevated higher than that on the surface or under room conditions, which has been demonstrated to strongly influence the rheological properties of grouts. Reasonable understanding and control of the rheological behavior of cement grouts at true ground temperatures is very important to the quality of grouting. This paper aims to propose a simplified method to approximately estimate the initial yield stress and viscosity of cement grouts for rock grouting under elevated ground temperature that actually exists in deep rock masses, on the basis of the flow spread test. The temperature investigated was controlled between 12 °C and 45 °C to simulate the true ground temperature in rock masses with a maximum depth of 1500 m below the surface. Taking the influences of elevated temperatures into account, a temperature-based model for estimating the initial viscosity of cement grout was successfully developed on the basis of Liu’s model and the results of the flow spread test. However, the yield stress failed to be estimated by the Lapasin model due to the absence of plastic behavior of cement grouts. In contrast, yield stress can be linearly correlated to the measured relative flow area. In this work, it was also found that the dependence of yield stress of cement grouts on relative flow area is a strongly exponential law. The temperature dependence of the viscosity of water was accounted for in both estimations of viscosity and yield stress of grouts. Significantly, it was found that the packing density of cement is dependent on the grout temperature, especially when the temperature is up to 45 °C. The proposed method in this work offers an alternative solution for technicians to reasonably control the rheological properties in the increasing applications of deep rock grouting.

Description: In this review, strategies for improving the antimicrobial properties of stainless steel (SS) are presented. The main focus given is to present current strategies for surface modification of SS, which alter surface characteristics in terms of surface chemistry, topography and wettability/surface charge, without influencing the bulk attributes of the material. As SS exhibits excellent mechanical properties and satisfactory biocompatibility, it is one of the most frequently used materials in medical applications. It is widely used as a material for fabricating orthopedic prosthesis, cardiovascular stents/valves and recently also for three dimensional (3D) printing of custom made implants. Despite its good mechanical properties, SS lacks desired biofunctionality, which makes it prone to bacterial adhesion and biofilm formation. Due to increased resistance of bacteria to antibiotics, it is imperative to achieve antibacterial properties of implants. Thus, many different approaches were proposed and are discussed herein. Emphasis is given on novel approaches based on treatment with highly reactive plasma, which may alter SS topography, chemistry and wettability under appropriate treatment conditions. This review aims to present and critically discuss different approaches and propose novel possibilities for surface modification of SS by using highly reactive gaseous plasma in order to obtain a desired biological response.

Description: The use of hybrid manufacturing to produce bimodal scaffolds has represented a great advancement in tissue engineering. These scaffolds provide a favorable environment in which cells can adhere and produce new tissue. However, there are several areas of opportunity to manufacture structures that provide enough strength and rigidity, while also improving chemical integrity. As an advancement in the manufacturing process of scaffolds, a cooling system was introduced in a fused deposition modeling (FDM) machine to vary the temperature on the printing bed. Two groups of polylactic acid (PLA) scaffolds were then printed at two different bed temperatures. The rate of degradation was evaluated during eight weeks in Hank’s Balanced Salt Solution (HBSS) in a controlled environment (37 °C–120 rpm) to assess crystallinity. Results showed the influence of the cooling system on the degradation rate of printed scaffolds after the immersion period. This phenomenon was attributable to the mechanism associated with alkaline hydrolysis, where a higher degree of crystallinity obtained in one group induced greater rates of mass loss. The overall crystallinity was observed, through differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA), and Fourier transformed infrared spectroscopy (FTIR) analysis, to increase with time because of the erosion of some amorphous parts after immersion.

Description: The elastic range in loading–unloading processes is often reduced with a Bauschinger effect. This material property may have a high impact on residual stresses and, as a result, on the performance of autofrettaged cylinders under service conditions. The objective of the present paper is to demonstrate this impact using a material model that accounts for the response of typical high-strength steel. The solution is semi-analytic and, therefore, can be used for fast and accurate analysis of the process of autofrettage. A numerical example illustrates the general solution. This example shows that the Bauschinger effect has a significant impact on the residual circumferential stress in the vicinity of the inner radius of the cylinder. This stress is the most significant quantity of autofrettaged cylinders. Therefore, the main result obtained suggests that even a moderate Bauschinger effect should be taken into account in analyses of the process of autofrettage.

Description: Autoclaved aerated concrete (AAC) self-insulation block masonry is often used for the infill walls in steel and concrete frame structures. To work together with the frame under earthquake action, it is essential to understand the seismic behavior of AAC self-insulation block masonry walls. In this paper, six AAC self-insulation block masonry walls were experimentally studied under the pseudo static test. The load-displacement hysteretic curves were drawn with the test data. The failure characteristics, loading capacity, stiffness degeneration, energy dissipation capacity and hysteretic behavior are analyzed. The results indicate that the blocks underwent internal failure due to the lower strength with a larger size, but the walls had good energy dissipation capacity with a rational bearing capacity. Accompanied by the influence of vertical compressive stress on the top surface of the walls, the cracking resistance, ultimate bearing capacity, deformability and energy dissipation capacity of the walls were affected by the masonry mortar joints. Comparatively, the walls with thin-layer mortar joints had better seismic performance than those with insulation mortar joints or with vertical joints filled by mineral wool plates. Finally, the shear capacity of the walls under seismic load is evaluated referring to the formulas of current design codes for masonry walls.

Description: Orthogonal test method was applied to analyze the strength properties of basalt-polypropylene mortar. The effect of basalt fiber length, polypropylene fiber length, basalt fiber volume content and polypropylene fiber volume content on the 28 d cube compressive strength and flexural strength were investigated. Test results show that comparing with flexural strength, the influence of basalt fiber length and polypropylene fiber length on compressive strength of mortar was greater than on flexural strength. The length of polypropylene fibers contributes the highest to the flexural strength. The effect of basalt fiber on mortar strength is the largest with 6 mm length and 4% content. Polypropylene fiber length has the greatest influence on the compressive strength of fiber mortar, followed by basalt fiber volume content. Volume content of polypropylene fiber has the greatest influence on flexural strength of fiber mortar, followed by polypropylene fiber length. According to the scoring of the efficacy coefficient method, the best ratio combination for compressive and flexural strength was the basalt fiber length of 9 mm, polypropylene fiber length of 6 mm, basalt fiber volume content of 4% and polypropylene fiber volume content of 4%. Compared with the blank samples, the 28 d compressive strength and 28 d flexural strength of the cement mortar samples were increased by 27.4% and 49% respectively. According to the test results, the properties of the fiber were analyzed and evaluated and the mechanism of fiber action and fiber microstructure were analyzed.

Description: In this paper, the effects of different hydrophobic coatings on the surface of covered electrodes on the quality of wet welded carbon steel joints were discussed. Commonly available hydrophobic substances used in industrial applications were selected for the research. The aim of using waterproof coatings was to check the possibility to decreasing the susceptibility of high-strength low-alloy S460N steel to cold cracking. During experiments diffusible hydrogen content in deposited metal determination by mercury method, metallographic macro- and microscopic testing and hardness measurements were performed. Investigations showed that waterproof coatings laid on covered electrodes can improve the quality of wet welded joints, by decreasing the Vickers HV10 hardness in heat-affected zone and decreasing the diffusible hydrogen content in deposited metal, which minimalize possibility of cold cracking.

Description: In recent years, carbon nanofibers have been investigated as a suitable reinforcement for cementitious composites to yield novel multifunctional materials with improved mechanical, electrical, magnetic, and self-sensing behavior. Despite several studies, the interactions between carbon nanofibers and Portland cement hydration products are not fully understood, with significant implications for the mechanical response and the durability at the macroscopic lengthscale. Thus, the research objective is to investigate the influence of carbon nanofibers on the nanostructure and on the distribution of hydration products within Portland cement paste. Portland cement w/c = 0.44 specimens reinforced with 0.0 wt%, 0.1 wt%, and 0.5 wt% CNF by mass fraction of cement are cast using a novel synthesis procedure. A uniform dispersion of carbon nanofibers (CNF) via a multi-step approach: after pre-dispersing carbon nanofibers using ultrasonic energy, the carbon nanofibers are further dispersed using un-hydrated cement particles in high shear mixing and mechanical stirring steps. High-resolution scanning electron microscopy analysis shows that carbon nanofibers fill nanopores and connect calcium–silicate hydrates (C–S–H) grains. Grid nano-indentation testing shows that Carbon nanofibers influence the probability distribution function of the local packing density by inducing a shift towards higher values, η = 0.76–0.93. Statistical deconvolution analysis shows that carbon nanofibers result in an increase in the fraction of high-density C–S–H by 6.7% from plain cement to cement + 0.1 wt% CNF and by 10.7% from plain cement to cement + 0.5 wt% CNF. Moreover, CNF lead to an increase in the C–S–H gel porosity and a decrease in both the capillary porosity and the total porosity. Based on scratch testing, adding 0.1 wt% CNF yields a 4.5% increase in fracture toughness and adding 0.5 wt% CNF yields a 7.6% increase in fracture toughness. Finally, micromechanical modelling predicts an increase of respectively 5.97% and 21.78% in the average Young’s modulus following CNF modification at 0.1 wt% CNF and 0.5 wt% CNF levels.

Description: A new type of sheet porous structures with functionally gradients based on triply periodic minimal surfaces (TPMS) is proposed for designing bone scaffolds. The graded structures were generated by constructing branched features with different number of sheets. The design of the structure was formulated mathematically and five types of porous structure with different structural features were used for investigation. The relative density (RD) and surface area to volume (SA/V) ratio of the samples were analyzed using a slice-based approach to confirm their relationships with design parameters. All samples were additively manufactured using selective laser melting (SLM), and their physical morphologies were observed and compared with the designed models. Compression tests were adopted to study the mechanical properties of the proposed structure from the obtained stress–strain curves. The results reveal that the proposed branched-sheet structures could enhance and diversify the physical and mechanical properties, indicating that it is a potential method to tune the biomechanical properties of porous scaffolds for bone tissue engineering (TE).

Description: A thermosetting resin system, based on bismaleimide (BMI), has been developed via copolymerization of 4,4′-diaminodiphenylsulfone with a newly synthesized graphene oxide modified using epoxy silane (ES-GO). The effect of ES-GO on the thermomechanical and mechanical properties of cured modified resin was studied. To evaluate the efficiency of the modified BMI systems, the composite samples using glass fiber cloth were molded and tested. Thermogravimetric analysis indicates that the cured sample systems displays a high char yield at lower concentrations of ES-GO (≤0.5 wt.%), suggesting an improved thermal stability. Using dynamic mechanical analysis, a marked increase in glass transition temperature (Tg) with increasing ES-GO content was observed. Analysis of mechanical properties reveals a possible effect of ES-GO as a toughener. The results also showed that the addition of 0.3 wt.% ES-GO maximizes the toughness of the modified resin systems, which was further confirmed by the result of analysis of fracture surfaces. At the same time, a molded composite with ES-GO showed improved mechanical properties and retention rate at 150 °C as compared to that made with neat resin.

Description: Coatings enriched with zinc and copper as well as calcium or magnesium, fabricated on titanium substrate by Plasma Electrolytic Oxidation (PEO) under AC conditions (two cathodic voltages, i.e., −35 or −135 V, and anodic voltage of +400 V), were investigated. In all experiments, the electrolytes were based on concentrated orthophosphoric acid (85 wt%) and zinc, copper, calcium and/or magnesium nitrates. It was found that the introduced calcium and magnesium were in the ranges 5.0–5.4 at% and 5.6–6.5 at%, respectively, while the zinc and copper amounts were in the range of 0.3–0.6 at%. Additionally, it was noted that the metals of the block S (Ca and Mg) could be incorporated into the structure about 13 times more than metals of the transition group (Zn and Cu). The incorporated metals (from the electrolyte) into the top-layer of PEO phosphate coatings were on their first (Cu+) or second (Cu2+, Ca2+ and Mg2+) oxidation states. The crystalline phases (TiO and Ti3O) were detected only in coatings fabricated at cathodic voltage of −135 V. It has also been pointed that fabricated porous calcium–phosphate coatings enriched with biocompatible magnesium as well as with antibacterial zinc and copper are dedicated mainly to medical applications. However, their use for other applications (e.g., catalysis and photocatalysis) after additional functionalizations is not excluded.

Description: The aim of this study was to evaluate the effectiveness of a moxifloxacin-loaded organic–inorganic sol-gel (A50) by locally preventing the catheter-related bloodstream infection (CRBSI) provoked by Staphylococcus epidermidis (S. epidermidis) and the effect resulting from its hydrolytic degradation on coagulation by using a rabbit in-vivo model. A50 coating can completely inhibit growth and would locally prevent CRBSI provoked by S. epidermidis. None of the coagulation blood parameters showed a significant difference constant over time between the control catheter group and the A50-coated catheter group, despite the visible silica release resulting from physiological A50 sol-gel degradation detected in serum at least during the first week. At pathological level, foreign body reaction was present in both of types of catheter, and it was characterized by the presence of macrophages and foreign body giant cell. However, this reaction was different in each group: the A50-coated catheter group showed a higher inflammation with histiocytes, which were forming granuloma-like aggregates with an amorphous crystalline material inside, accompanied by other inflammatory cells such as plasma cells, lymphocytes and mast cells. In conclusion, A50 coating a venous catheter showed excellent bactericidal anti-biofilm response since it completely inhibited S. epidermidis biofilm development and, far from showing procoagulant effects, showed slightly anticoagulant effects.

Description: Spin-freeze-drying is a promising technique to enable long-term storage of pharmaceutical unit doses of aqueous drug solutions. To investigate the sublimation of the ice during the primary phase of freeze-drying, X-ray imaging can yield crucial temporally resolved information on the local dynamics. In this paper, we describe a methodology to investigate the sublimation front during single unit-dose freeze-drying using 4D in-situ X-ray imaging. Three spin-frozen samples of different solutions were imaged using this methodology and the process characteristics were analysed and reduced to two-dimensional feature maps.

Description: In this work, the effects of the microstructure and phase constitution of cast magnesium alloy ZK60 (Mg-5.8Zn-0.57Zr, element concentration in wt.%) on the corrosion behavior in aqueous NaCl (0.1 mol dm−3) were investigated by weight-loss measurements, hydrogen evolution tests, and electrochemical techniques. The alloy was found to be composed of α-Mg matrix, with large second-phase particles of MgZn2 deposited along grain boundaries and a Zr-rich region in the central area of the grains. The large second-phase particles and the Zr-rich regions were more stable than the Mg matrix, resulting in a strong micro-galvanic effect. A filiform corrosion was found. It originated from the second-phase particles in the grain boundary regions in the early corrosion period. The filaments gradually occupied most areas of the alloy surface, and the general corrosion rate decreased significantly. Corrosion pits were developed under filaments. The pit growth rate decreased over time; however, it was about eight times larger than the general corrosion rate. A schematic model is presented to illustrate the corrosion mechanism.

Description: This paper presents a method based on signal correlation to detect delamination defects of widely used carbon fiber reinforced plastic with high precision and a convenient process. The objective of it consists in distinguishing defect and non-defect signals and presenting the depth and size of defects by image. A necessary reference signal is generated from the non-defect area by using autocorrelation theory firstly. Through the correlation calculation results, the defect signal and non-defect signal are distinguished by using Euclidean distance. In order to get more accurate time-of-flight, cubic spline interpolation is introduced. In practical automatic ultrasonic A-scan signal processing, signal correlation provide a new way to avoid problems such as signal peak tracking and complex gate setting. Finally, the detection results of a carbon fiber laminate with artificial delamination through ultrasonic phased array C-scan acquired from Olympus OmniScan MX2 and this proposed algorithm are compared, which showing that this proposed algorithm performs well in defect shape presentation and location calculation. The experiment shows that the defect size error is less than 4%, the depth error less than 3%. Compared with ultrasonic C-scan method, this proposed method needs less inspector’s prior-knowledge, which can lead to advantages in automatic ultrasonic testing.

Description: This paper presents research on the bending properties of 3 × 7 19-mm wire rope commonly used in road cable barriers. A total of 19 experimental tests were conducted. In addition, two nonlinear 3D numerical models of the wire rope using beam and solid finite elements were developed. Based on these models, four numerical simulations were carried out. The numerical results were validated against the experimental ones and a very good agreement was obtained. The main result of the research is the determination of the moment–curvature relationship for the wire rope considered. The effect of prestretching on the rope performance is discussed. The numerical results are analyzed in this paper in detail, including the behavior of the wire rope under bending and analyses of the cross-sectional and contact stresses. Suggestions concerning the type of finite element for wire rope modeling are also given. The results can be used, for example, in numerical simulations of crash tests of cable barriers.

Description: Demineralization of dental hard tissues is a well-known health issue and the primary mechanism responsible for caries and dentinal hypersensitivity. Remineralizing toothpastes are nowadays available to improve conventional oral care formulations regarding the prevention and repair of demineralization. In this paper, we analyzed the chemical-physical features of a commercial toothpaste (Biosmalto Caries Abrasion and Erosion, Curasept S.p.A., Saronno, Italy), with particular attention paid to the water-insoluble fraction which contains the remineralizing bioactive ingredients. Moreover, the efficacy of the toothpaste to induce enamel remineralization and to occlude dentinal tubules has been qualitatively and semiquantitatively tested in vitro on human dental tissues using scanning electron microscopy and X-ray microanalysis. Our results demonstrated that the water-insoluble fraction contained silica as well as chitosan and poorly crystalline biomimetic hydroxyapatite doped with carbonate, magnesium, strontium, and fluoride ions. The formulation showed excellent ability to restore demineralized enamel into its native structure by epitaxial deposition of a new crystalline phase in continuity with the native one. It was also able to occlude the dentinal tubules exposed completely by acid-etching. Overall, this study demonstrated that the tested toothpaste contained a biomimetic ionic-substituted hydroxyapatite-based active principle and that, within the in vitro conditions analyzed in this study, it was effective in dental hard tissue remineralization.

Description: This paper presents a new product, a glass laminate aluminium-reinforced epoxy (GLARE)-based thin-walled structure with a stiffener in the form of a longitudinal rib. The stiffening rib in an outer metallic layer of a GLARE-based panel was fabricated by the incremental sheet forming technique and Alclad 2024-T3 aluminium alloy sheets were used as adherends. The strength properties of the adhesive joint between the layers of the fibre metal laminates (FMLs) were determined in a uniaxial tensile test, peel drum test, tensile/shear test and short-beam three-point-bending test. Two variants of FMLs were considered, with an adhesive film and without an adhesive film between the adherends and the epoxy/glass prepreg. The FMLs were tested at three different temperatures that corresponded to those found under real aircraft operating conditions, i.e., −60 °C, room temperature and +80 °C. It was found that the temperatures do not affect the tensile strength and shear strength of the FMLs tested. However, there was a noticeable increase in the stiffness of samples stretched at reduced temperature. An additional adhesive film layer between the adherends and the glass/epoxy prepreg significantly improves the static peeling strength of the joint both at reduced and at elevated temperatures. A clear increase in the critical force at which buckling occurs has been clearly demonstrated in the uniaxial compression test of GLARE-based rib-stiffened panels. In the case of GLARE-based rib-stiffened panels, the critical force averaged 15,370 N, while for the non-embossed variant, it was 11,430 N, which translates into a 34.5% increase in critical force.

Description: The objective of the present work was to produce gastroresistant Eudragit® RS100 nanoparticles by a reproducible synthesis approach that ensured mono-disperse nanoparticles under the size of 100 nm. Batch and micromixing nanoprecipitation approaches were selected to produce the demanded nanoparticles, identifying the critical parameters affecting the synthesis process. To shed some light on the formulation of the targeted nanoparticles, the effects of particle size and homogeneity of fluid dynamics, and physicochemical parameters such as polymer concentration, type of solvent, ratio of solvent to antisolvent, and total flow rate were studied. The physicochemical characteristics of resulting nanoparticles were studied applying dynamic light scattering (DLS) particle size analysis and electron microscopy imaging. Nanoparticles produced using a micromixer demonstrated a narrower and more homogenous distribution than the ones obtained under similar conditions in conventional batch reactors. Besides, fluid dynamics ensured that the best mixing conditions were achieved at the highest flow rate. It was concluded that nucleation and growth events must also be considered to avoid uncontrolled nanoparticle growth and evolution at the collection vial. Further, rifampicin-encapsulated nanoparticles were prepared using both approaches, demonstrating that the micromixing-assisted approach provided an excellent control of the particle size and polydispersity index. Not only the micromixing-assisted nanoprecipitation promoted a remarkable control in the nanoparticle formulation, but also it enhanced drug encapsulation efficiency and loading, as well as productivity. To the best of our knowledge, this was the very first time that drug-loaded Eudragit® RS100 nanoparticles (NPs) were produced in a continuous fashion under 100 nm (16.5 ± 4.3 nm) using microreactor technology. Furthermore, we performed a detailed analysis of the influence of various fluid dynamics and physicochemical parameters on the size and uniformity of the resulting nanoparticles. According to these findings, the proposed methodology can be a useful approach to synthesize a myriad of nanoparticles of alternative polymers.

Description: Solar light is an inexpensive energy source making up for energy shortage and solving serious environmental problems. For efficient utilization of solar energy, photocatalytic materials have attracted extensive attention over the last decades. As zero-dimensional carbon nanomaterials, fullerenes (C60, C70, etc.) have been extensively investigated for photocatalytic applications. Due to their unique properties, fullerenes can be used with other semiconductors as photocatalyst enhancers, and also as novel photocatalysts after being dispersed on non-semiconductors. This review summarizes fullerene-based materials (including fullerene/semiconductors and fullerene/non-semiconductors) for photocatalytic applications, such as water splitting, Cr (VI) reduction, pollutant degradation and bacterial disinfection. Firstly, the optical and electronic properties of fullerene are presented. Then, recent advances in the synthesis and photocatalytic mechanisms of fullerene-based photocatalysts are summarized. Furthermore, the effective performances of fullerene-based photocatalysts are discussed, mainly concerning photocatalytic H2 generation and pollutant removal. Finally, the current challenges and prospects of fullerene-based photocatalysts are proposed. It is expected that this review could bring a better understanding of fullerene-based photocatalysts for water treatment and environmental protection.

Description: Nickel–Titanium (NiTi)-based shape-memory alloys (SMA) are utilized in automotive, biomedical, microsystem applications because of their excellent shape memory effect, biocompatibility and super elastic properties. These alloys are considered difficult to cut—especially with conventional technologies because of the work hardening and residual stresses. Laser-machining is one of the most effective tools for processing of these alloys especially for microsystem applications. In this work, a thorough investigation of effect of process parameters on machining of microchannels in NiTi SMA is presented. In addition, a multi-objective optimization is carried out in order to find the optimal input parameter settings for the desired output performances. The results show that the quality of microchannels is significantly affected by input parameters. Layer thickness was found to have a significant effect on taper angle of the microchannel. Scan speed, layer thickness and scan strategy were found to have significant effects on both spatter thickness and top-width error, but in opposite directions. The multi-objective optimization-minimizing taper angle and spatter thickness revealed an optimal solution that was characterized by high frequency, moderate speed and low layer-thickness and track displacement.

Description: The paper presents the test results of basalt fiber impact on a compressive and flexural strength, resistance to abrasion and porosity of Reactive Powder Concrete (RPC). The reasons for testing were interesting mechanical properties of basalt fibers, the significant tensile strength and flexural strength, and in particular the resistance to high temperatures, as well as a relatively small number of RPC tests performed with those fibers and different opinions regarding the impact of those fibers on concrete strength. The composition of the concrete mix was optimized to obtain the highest packing density of particles in the composite, based on the optimum particle size distribution curve acc. to Funk. Admixture of basalt fibers was used in quantity 2, 3, 6, 8 and 10 kg/m3, length 12 mm and diameter 18 µm. A low water-to-binder ratio, i.e., from 0.24, was obtained through application of a polycarboxylate-based superplasticizer. The introduction of up to 10 kg/m3 of basalt fibers to RPC mix was proved to be possible, while keeping the same w/c ratio equal to 0.24, with a slight loss of workability of the concrete mix as the content of fibers increased. It was found that the increase of the fiber content in RPC to 10 kg/m3, despite the w/c ratio was kept the same, caused reduction of the concrete compressive strength by 18.2%, 7.8% and 13.6%, after 2, 7, and 28 days respectively. Whereas, the flexural strength of RPC increased gradually (maximum by 15.9%), along with the fiber quantity increase up to 6 kg/m3, and then it reduced (maximum by 17.7%), as the fiber content in the concrete was further increased. The reduction of RPC compressive strength, along with the increase in basalt fibers content, leads to the increase of the total porosity, as well as the change in pore volume distribution. The reduction of RPC abrasion resistance was demonstrated along with the increase of basalt fibers content, which was explained by the compressive strength reduction of that concrete. A linear relation between the RPC abrasion resistance and the compressive strength involves a high determination coefficient equal to 0.97.

Description: Zirconium hydroxide, Zr(OH)4 is known to be highly effective for the degradation of chemical nerve agents. Due to the strong interaction force between Zr(OH)4 and the adsorbed water, however, Zr(OH)4 rapidly loses its activity for nerve agents under high-humidity environments, limiting real-world applications. Here, we report a nanocomposite material of Zr(OH)4 and graphene oxide (GO) which showed enhanced stability in humid environments. Zr(OH)4/GO nanocomposite was prepared via a dropwise method, resulting in a well-dispersed and embedded GO in Zr(OH)4 nanocomposite. The nitrogen (N2) isotherm analysis showed that the pore structure of Zr(OH)4/GO nanocomposite is heterogeneous, and its meso-porosity increased from 0.050 to 0.251 cm3/g, compared with pristine Zr(OH)4 prepared. Notably, the composite material showed a better performance for nerve agent soman (GD) degradation hydrolysis under high-humidity air conditions (80% relative humidity) and even in aqueous solution. The soman (GD) degradation by the nanocomposite follows the catalytic reaction with a first-order half-life of 60 min. Water adsorption isotherm analysis and diffuse reflectance infrared Fourier transform (DRIFT) spectra provide direct evidence that the interaction between Zr(OH)4 and the adsorbed water is reduced in Zr(OH)4/GO nanocomposite, indicating that the active sites of Zr(OH)4 for the soman (GD) degradation, such as surface hydroxyl groups are almost available even in high-humidity environments.

Description: In this study, an Inconel 625–tungsten carbide (WC) composite system was investigated by means of microstructure changes affected by both heating rate and WC content. In order to investigate how the system behaves while exposed to fast thermal processing, controlled melting using a differential thermal analysis (DTA) apparatus was performed on the powders. Two WC powders with different average grain size were used to obtain six compositions of Inconel 625–WC powder mixtures (10, 20, and 30 wt.% WC). They were analyzed under 10 and 30 °C/min heating rate in order to obtain composite samples. Results from DTA together with SEM/energy-dispersive X-ray spectroscopy (EDS) microstructural observations allowed observing material changes during solidification. Because of the extensive microsegregation of alloying elements to liquid and their reactions with C, which derived from dissolved WC, the formation of secondary phases with improved microhardness was possible. The collected results provide a better understanding of material behavior during intensive thermal processing which can be useful when designing materials for the laser additive manufacturing technique.

Description: This article presents a comparison of bone replacement materials in terms of their ability to produce living bone image at the place of their implantation. Five bone replacement materials are compared (Osteovit—porous collagen, Cerasorb Foam—collagen scaffolding of synthetic β tricalcium phosphate, Osbone—synthetic hydroxyapatite, Endobone—deproteinized bovine-derived cancellous bone hydroxyapatite, and Cerasorb—synthetic β tricalcium phosphate). Intraoral radiographs are taken immediately after implantation and 12 months later. The texture analysis was performed to assess (texture index, TI) the level of structure chaos (entropy) in relation to the presence of longitudinal elements visible in radiographs (run length emphasis moment). The reference ratio of the chaotic trabecular pattern (Entropy) to the number of longitudinal structures, i.e., trabeculae (LngREmph), is 176:100 (i.e., 1.76 ± 0.28). Radiological homogeneity immediately after the implantation procedure is a result of the similar shape of its particles (Osbone, Endobone and Cerasorb) or radiolucency (Osteovit, Cerasorb Foam). The particles visible in radiographs were similar in the LngREmph parameters applied to the reference bone, but not in the co-occurrence matrix features. The TI for Osteovit during a 12-month follow-up period changed from 1.55 ± 0.26 to 1.48 ± 0.26 (p 〉 0.05), for Cerasorb Foam from 1.82 ± 0.27 to 1.63 ± 0.24 (p 〈 0.05), for Osbone from 1.97 ± 0.31 to 1.74 ± 0.30 (p 〈 0.01), and for Endobone from 1.86 ± 0.25 to 1.84 ± 0.25 (p 〉 0.05), The observed structure in the radiological image of bone substitute materials containing calcium phosphates obtains the characteristics of a living bone image after twelve months.

Description: With continuous miniaturization of many technologies, robotics seems to be lagging behind. While the semiconductor technologies operate confidently at the nanometer scale and micro-mechanics of simple structures (MEMS) in micrometers, autonomous devices are struggling to break the centimeter barrier and have hardly colonized smaller scales. One way towards miniaturization of robots involves remotely powered, light-driven soft mechanisms based on photo-responsive materials, such as liquid crystal elastomers (LCEs). While several simple devices have been demonstrated with contracting, bending, twisting, or other, more complex LCE actuators, only their simple behavior in response to light has been studied. Here we characterize the photo-mechanical response of a linear light-driven LCE actuator by measuring its response to laser beams with varying power, pulse duration, pulse energy, and the energy spatial distribution. Light absorption decrease in the actuator over time is also measured. These results are at the foundation of further development of soft, light-driven miniature mechanisms and micro-robots.

Description: The tandem pn-type dye-sensitized solar cells (pn-DSCs) have received much attention in the field of photovoltaic technologies because of their great potential to overcome the Shockley-Queisser efficiency limitation that applies to single junction photovoltaic devices. However, factors governing the short-circuit current densities (Jsc) of pn-DSC remain unclear. It is typically believed that Jsc of the pn-DSC is limited to the highest one that the two independent photoelectrodes can achieve. In this paper, however, we found that the available Jsc of pn-DSC is always determined by the larger Jsc that the photoanode can achieve but not by the smaller one in the photocathode. Such experimental findings were verified by a simplified series circuit model, which shows that a breakdown will occur on the photocathode when the photocurrent goes considerably beyond its threshold voltage, thus leading to an abrupt increase in Jsc of the circuit. The simulation results also suggest that a higher photoconversion efficiency of the pn-DSCs can be only achieved when an almost equivalent photocurrent is achieved for the two photoelectrodes.

Description: Ensuring optimal turning conditions has a huge impact on the quality and properties of the machined surface. The condition of the cutting tool is one of the factors to achieve this goal. In order to control its wear during the turning process, monitoring was used. In this study, the acoustic emission method and measure of cutting forces during turning were used for monitoring that process. The research was carried out on a universal lathe center (CU500MRD type) using a Kistler dynamometer with assembled removable insert CCET09T302R-MF by DIJET Industrial CO., LTD. A dynamometer allows to measure forces Fx (radial force), Fy (feed force) and Fz (cutting force). The turning process was performed on a shaft with 60 mm diameter made of 304L stainless steel. The AE research was carried at Physical Acoustics Corporation with the kit that includes: recorder USB AE Node, preamplifier, AE-sensor VS 150M and computer with dedicated software used for recording and analyzing AE data. The aim of this paper is to compare selected diagnostic methods: acoustic emission and cutting forces measurement for monitoring wear of cutting tool edge. Analysis of the research results showed that both selected methods of monitoring the turning process allowed the determination of the beginning of the tool damage process.

Description: Improving the tribological performance of M50 steel under the conditions of wide load range is of great significance. In this study, the interfacial structure of surface micropores filled with Sn–Ag–Cu or Sn–Ag–Cu/whisker carbon nanotubes (whiskerCNT) of M50 material was prepared by laser additive manufacturing and high-temperature infiltration. From 2 to 22 N, the lubrication characteristics of Sn–Ag–Cu and whiskerCNT in surface micropores of M50 was investigated. Results indicate that Sn–Ag–Cu can precipitate to the worn surface and form a lubricating layer, which has a good lubricating effect. Moreover, the flow behavior of Sn–Ag–Cu on a worn surface can play the role of crack healing. At higher load, the strength of the lubricating film is enhanced by whiskerCNT, which renders the lubricating film not vulnerable to premature rupture.

Description: 3D printing is increasingly important for the rapid prototyping of advanced and tailor-made cell culture devices. In this context, stereolithography represents a method for the rapid generation of prototypes from photocurable polymers. However, the biocompatibility of commercially available photopolymers is largely unknown. Therefore, we evaluated the cytotoxicity of six polymers, two of them certified as biocompatible according to ISO 10993-5:2009, and we evaluated, if coating with Parylene, an inert polymer widely used in medical applications, might shield cells from the cytotoxic effects of a toxic polymer. In addition, we evaluated the processability, reliability, and consistency of the details printed. Human mesenchymal stem cells (MSCs) were used for cytotoxicity testing as they are widely used and promising for numerous applications in regenerative medicine. MSCs were incubated together with printed photopolymers, and the cytotoxicity was assessed. All photopolymers significantly reduced the viability of MSCs while the officially biocompatible resins displayed minor toxic effects. Further, coating with Parylene completely protected MSCs from toxic effects. In conclusion, none of the tested polymers can be fully recommended for rapid prototyping of cell culture devices. However, coating with Parylene can shield cells from toxic effects and thus might represent a viable option until more compatible materials are available.

Description: Automatic crack detection from images is an important task that is adopted to ensure road safety and durability for Portland cement concrete (PCC) and asphalt concrete (AC) pavement. Pavement failure depends on a number of causes including water intrusion, stress from heavy loads, and all the climate effects. Generally, cracks are the first distress that arises on road surfaces and proper monitoring and maintenance to prevent cracks from spreading or forming is important. Conventional algorithms to identify cracks on road pavements are extremely time-consuming and high cost. Many cracks show complicated topological structures, oil stains, poor continuity, and low contrast, which are difficult for defining crack features. Therefore, the automated crack detection algorithm is a key tool to improve the results. Inspired by the development of deep learning in computer vision and object detection, the proposed algorithm considers an encoder-decoder architecture with hierarchical feature learning and dilated convolution, named U-Hierarchical Dilated Network (U-HDN), to perform crack detection in an end-to-end method. Crack characteristics with multiple context information are automatically able to learn and perform end-to-end crack detection. Then, a multi-dilation module embedded in an encoder-decoder architecture is proposed. The crack features of multiple context sizes can be integrated into the multi-dilation module by dilation convolution with different dilatation rates, which can obtain much more cracks information. Finally, the hierarchical feature learning module is designed to obtain a multi-scale features from the high to low- level convolutional layers, which are integrated to predict pixel-wise crack detection. Some experiments on public crack databases using 118 images were performed and the results were compared with those obtained with other methods on the same images. The results show that the proposed U-HDN method achieves high performance because it can extract and fuse different context sizes and different levels of feature maps than other algorithms.

Description: Construction and demolition waste material is of great potential for use in pavement engineering. This paper aims to investigate the feasibility of ceramic waste aggregate (CA) used in cooling asphalt pavement through a series of test methods and simulation techniques. Stone mastic asphalt (SMA) containing 10%, 20%, 30%, 40%, and 50% coarse ceramic waste aggregate (CASMAs) was first designed using the Marshall method. Afterward, the road performance and thermal insulation performance of the five different CASMAs were assessed by a comprehensive lab test, including a wheel rutting test, moisture susceptibility test, bending beam test, fatigue beam test, and indoor thermal insulation test. Finally, a 2D finite-element (FE) model was developed to investigate the transient thermal field and rutting deformation response of the cooling asphalt pavement with CASMAs. Results show that CASMAs experienced degradation of rutting resistance, moisture susceptibility, and anti-cracking performance while still meeting technical requirements with CA content of up to 40%. On the other hand, CASMAs can cool the pavement’s temperature by 11.5 °C at the bottom of asphalt layers. The permanent rutting deformation of cooling asphalt pavement was 45.36% smaller than that of conventional asphalt pavement without CASMAs. Based on the test results and numerical simulation results, the optimum content of ceramic waste aggregate in stone mastic asphalt was recommended as 40%.

Description: The work assumed the possibility of the introduction natural fibers as a hybrid reinforcement of bio-polyethylene composites. Coconut fibers, basalt fibers and wood flour were used in different combination as a hybrid merger. Mechanical tests were conducted. An increase in the mechanical properties was shown as an effect of the introduction of the fibers info the polymeric matrix. A synergic influence of hybrid reinforcement was also presented. Experimental results were compared with modeling parameters. The hydrothermal and accelerated thermal ageing effects on the mechanical behavior of composites were presented. Scanning electron microscope images were observed in order to analyze structure of examined composites.

Description: To fulfil the requirements for high-resolution organic light-emitting diode (OLED) displays, precise and high-quality micrometer-scale patterns have to be fabricated inside metal shadow masks. Invar has been selected for this application due to its unique properties, especially a low coefficient of thermal expansion. In this study, a novel cost-efficient method of multi-beam micromachining of invar will be introduced. The combination of a Meopta beam splitting, focusing and monitoring module with a galvanometer scanner and HiLASE high-energy pulse laser system emitting ultrashort pulses at 515 nm allows drilling and cutting of invar foil with 784 beams at once with high precision and almost no thermal effects and heat-affected zone, thus significantly improving the throughput and efficiency.

Description: When considering the deployment of renewable energy sources in systems, the challenge of their utilization comes from their time instability when a mismatch between production and demand occurs. With the integration of thermal storages into systems that utilize renewable energy sources, such mismatch can be evened out. The use of phase-change materials (PCMs) as thermal storage has a theoretical advantage over the sensible one because of their high latent heat that is released or accumulated during the phase-change process. Therefore, the present paper is a review of latent thermal storages in hydronic systems for heating, cooling and domestic hot water in buildings. The work aims to offer an overview on applications of latent thermal storages coupled with heat pumps and solar collectors. The review shows that phase-change materials improve the release of heat from thermal storage and can supply heat or cold at a desired temperature level for longer time periods. The PCM review ends with the results from one of the Horizon2020 research projects, where indirect electrical storage in the form of thermal storage is considered. The review is a technological outline of the current state-of-the-art technology that could serve as a knowledge base for the practical implementation of latent thermal storages. The paper ends with an overview of energy storage maturity and the objectives from different roadmaps of European bodies.

Description: Magnesium hydroxide (Mg(OH)2) has a wide bandgap of about 5.7 eV and is usually considered an insulator. In this study, the energy levels of impurities introduced into Mg(OH)2 are predicted by first-principles calculations. A supercell of brucite Mg(OH)2 consisting of 135 atoms is used for the calculations, and an impurity atom is introduced either at the substitutional site replacing Mg or the interlayer site. The characteristics of impurity levels are predicted from density-of-states analysis for the charge-neutral cell. According to the results, possible shallow donors are trivalent cations at the substitutional site (e.g., Al and Fe) and cation atoms at the interlayer site (Cu, Ag, Na, and K). On the other hand, an interlayer F atom can be a shallow acceptor. Thus, valence control by impurity doping can turn Mg(OH)2 into a wide-gap semiconductor useful for electronics applications.

Description: For the last two decades, titanium dioxide (TiO2) has received wide attention in several areas such as in medicine, sensor technology and solar cell industries. TiO2-based gas sensors have attracted significant attention in past decades due to their excellent physical/chemical properties, low cost and high abundance on Earth. In recent years, more and more efforts have been invested for the further improvement in sensing properties of TiO2 by implementing new strategies such as growth of TiO2 in different morphologies. Indeed, in the last five to seven years, 1D nanostructures and heterostructures of TiO2 have been synthesized using different growth techniques and integrated in chemical/gas sensing. Thus, in this review article, we briefly summarize the most important contributions by different researchers within the last five to seven years in fabrication of 1D nanostructures of TiO2-based chemical/gas sensors and the different strategies applied for the improvements of their performances. Moreover, the crystal structure of TiO2, different fabrication techniques used for the growth of TiO2-based 1D nanostructures, their chemical sensing mechanism and sensing performances towards reducing and oxidizing gases have been discussed in detail.

Description: Concrete shrinkage is a phenomenon that results in a decrease of volume in the composite material during the curing period. The method for determining the effects of restrained shrinkage is described in Standard ASTM C 1581/C 1581M–09a. This article shows the calibration of measuring rings with respect to the theory of elasticity and the analysis of the relationship of steel ring deformation to high-performance concrete tensile stress as a function of time. Steel rings equipped with strain gauges are used for measurement of the strain during the compression of the samples. The strain is caused by the shrinkage of the concrete ring specimen that tightens around steel rings. The method allows registering the changes to the shrinkage process in time and evaluating the susceptibility of concrete to cracking. However, the standard does not focus on the details of the mechanical design of the test bench. To acquire accurate measurements, the test bench needs to be calibrated. Measurement errors may be caused by an improper, uneven installation of strain gauges, imprecise geometry of the steel measuring rings, or incorrect equipment settings. The calibration method makes it possible to determine the stress in a concrete sample leading to its cracking at specific deformation of the steel ring.

Description: High entropy alloys (HEAs) were prepared using the powder bed fusion (PBF) technique. Among titanium free alloys AlCoCrFeNiMn, CoCr1.3FeMnNi0.7, AlCoCrFeNi1.3, and AlCoCr1.3FeNi1.3 have been further investigated. A cost comparison was done for these four alloys as well as the titanium-based alloys AlCoCrFeNiTi and AlCo0.8CrFeNiTi. Such a comparison was done in order to evaluate the performance of the titanium-free alloys as the estimated cost of these will be less than for Ti-based HEAs. Hence, we have chosen four titanium free alloys and two titanium-based alloys for further processing. All these alloys were fabricated and subsequently characterized for phase, purity and performance. Scanning electron microscopy-based images were captured for microstructure characterization. EIS-based tests and potentiodynamic scans were performed to evaluate corrosion current. Hardness tests were performed for mechanical properties evaluation. Additional testing using factorial design tests was performed to evaluate the effects of various parameters to create better PBF-based HEA samples. EBSD tests, accelerated corrosion tests (mass loss), chemical analysis after degradation, microstructure analysis before and after degradation, and mechanical property comparison for finalized samples and other similar tests were executed. The details about all these HEAs and subsequent laser processing as well as behavior of these HEAs have been included in this study. It has been observed that some of the selected alloys exhibit good performance compared to Ti-based alloys, especially with respect to improvements in elastic constant and hardness relative to commercially pure Ti.

Description: For aerospace applications, honeycomb sandwich panels may have small perforations on the cell walls of the honeycomb core to equilibrate the internal core pressure with external gas pressure, which prevent face-sheet/core debonding due to pressure build-up at high temperature. We propose a new form of perforation on the cell walls of honeycomb sandwich panels to reduce the influence of the perforations on the cell walls on the mechanical properties. In this paper, the high temperature mechanical properties of a new vented Ti-6Al-4V honeycomb sandwich panel were investigated. A vented Ti-6AL-4V honeycomb sandwich panel with 35Ti-35Zr-15Cu-15Ni as the filler alloy was manufactured by high-temperature brazing. The element distribution of the brazed joints was examined by means of SEM (scanning electron microscopy) and EDS (energy-dispersive spectroscopy) analyses. Compared to the interaction between the face-sheets and the brazing filler, the diffusion and reaction between the honeycomb core and the brazing filler were stronger. The flatwise compression and flexural mechanical properties of the vented honeycomb sandwich panels were investigated at 20, 160, 300, and 440 °C, respectively. The flatwise compression strength, elastic modulus, and the flexural strength of the vented honeycomb sandwich panels decreased with the increase of temperature. Moreover, the flexural strength of the L-direction sandwich panels was larger than that of the W-direction sandwich panels at the same temperature. More importantly, the vented honeycomb sandwich panels exhibited good compression performance similar to the unvented honeycomb sandwich panels, and the open holes on the cell walls have no negative effect on the compression performance of the honeycomb sandwich panels in these conditions. The damage morphology observed by SEM revealed that the face-sheets and the brazing zone show ductile and brittle fracture behaviors, respectively.

Description: A hybrid implant with a structure mimicking that of natural bone was developed. Titanium alloy Ti–6Al–4V prepared with three-dimensional (3D)-printing technology was used to simulate the cortical-bone layer. The mismatch in the mechanical properties of bone and titanium alloy was solved by creating special perforations in the titanium’s surface. Porous ultra-high molecular weight polyethylene (UHMWPE) with high osteogenous properties was used to simulate the cancellous-bone tissue. A method for creating a porous UHMWPE structure inside the titanium reinforcement is proposed. The porous UHMWPE was studied with scanning electron microscope (SEM) to confirm that the pores that formed were open, interconnected, and between 50 and 850 μm in size. Mechanical-compression tests done on the obtained UHMWPE/titanium-hybrid-implant samples showed that their mechanical properties simulated those of natural bone.

Description: The aim of the study is to determine the energy consumption of the extrusion-cooking process of corn straw under various conditions (screw speed, moisture content), water absorption measurements and water solubility indices as well as biogas efficiency evaluation. The extrusion-cooking of corn straw was carried out using a single screw extruder with L/D = 16:1 at various rotational screw speeds (70, 90, and 110 rpm) and with various initial moisture content of raw material (25 and 40%). Prior to the process, the moisture content of the raw material was measured, and next, it was moistened to 25 and 40% of dry matter. For example, at 70 rpm extruder screw speed, the temperature range was 126–150 °C. Energy consumption of straw pretreatment through extrusion-cooking was assessed in order to evaluate the possibility of using the process in an agricultural biogas plant. Biogas and methane efficiency of substrates after extrusion was tested in a laboratory scale biogas plant and expressed as a volume of cumulative methane production for fresh matter, dry matter, and dry organic matter. Pretreated corn straw moistened to 25% and processed at 110 rpm during the extrusion-cooking processing produced the most advantageous effect for methane and biogas production (51.63%) efficiency as compared to corn straw without pretreatment (49.57%). Rotational speed of the extruder screw influenced biogas and methane production. With both dry matter and dry organic matter, the increase of rotational speed of the extruder screw improved the production of cumulated biogas and methane. Pretreatment of corn straw has a positive effect on the acquisition of cumulated methane (226.3 Nm3 Mg−1 for fresh matter, 243.99 Nm3 Mg−1 for dry matter, and 254.83 Nm3 Mg−1 for dry organic matter). Preliminary analysis of infrared spectra revealed changes in the samples also at the molecular level, thus opening up the possibility of identifying marker bands that account for specific degradation changes.

Description: This paper provides the test results of the fatigue crack growth in notched specimens under tension. The tests were performed on plane specimens with external blunt two-sided notches at room temperature. The tested material was O–Ti2AlNb titanium alloy. The tests were carried out at constant load value and constant stress ratio R = 0. The tests were done at the fatigue stand Instron under the loading change frequency of 25 Hz. The results of mechanical and structural tests of the examined alloy were presented. Scanning electron microscopy (SEM) was used in metallography, which allowed for the initial identification of intermetallic phases. The development of fatigue cracks in the tested alloy indicates that there is a tendency for brittle fracturing, which ran along the grain boundary.

Description: Nanostructured NiO and Li-ion doped NiO have been synthesized via a facile microwave technique and simulated using the first principle method. The effects of microwaves on the morphology of the nanostructures have been studied by Field Emission Spectroscopy. X-ray diffraction studies confirm the nanosize of the particles and favoured orientations along the (111), (200) and (220) planes revealing the cubic structure. The optical band gap decreases from 3.3 eV (pure NiO) to 3.17 eV (NiO doped with 1% Li). Further, computational simulations have been performed to understand the optical behaviour of the synthesized nanoparticles. The optical properties of the doped materials exhibit violet, blue and green emissions, as evaluated using photoluminescence (PL) spectroscopy. In the presence of Li-ions, NiO nanoparticles exhibit enhanced electrical capacities and better cyclability. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) results show that with 1% Li as dopant, there is a marked improvement in the reversibility and the conductance value of NiO. The results are encouraging as the synthesized nanoparticles stand a better chance of being used as an active material for electrochromic, electro-optic and supercapacitor applications.

Description: The discovery of ferroelectricity in HfO2-based materials in 2011 provided new research directions and opportunities. In particular, for atomic layer deposited Hf0.5Zr0.5O2 (HZO) films, it is possible to obtain homogenous thin films with satisfactory ferroelectric properties at a low thermal budget process. Based on experiment demonstrations over the past 10 years, it is well known that HZO films show excellent ferroelectricity when sandwiched between TiN top and bottom electrodes. This work reports a comprehensive study on the effect of TiN top and bottom electrodes on the ferroelectric properties of HZO thin films (10 nm). Investigations showed that during HZO crystallization, the TiN bottom electrode promoted ferroelectric phase formation (by oxygen scavenging) and the TiN top electrode inhibited non-ferroelectric phase formation (by stress-induced crystallization). In addition, it was confirmed that the TiN top and bottom electrodes acted as a barrier layer to hydrogen diffusion into the HZO thin film during annealing in a hydrogen-containing atmosphere. These features make the TiN electrodes a useful strategy for improving and preserving the ferroelectric properties of HZO thin films for next-generation memory applications.

Description: This paper investigates the friction process between an Fe-based coating and C45 steel with surface-active lubrication, as well as examines the coating surface before and after tribological testing. As a result, it is possible to determine whether the surface undergoes self-organization during friction. Coatings were produced by hardfacing a subeutectic alloy Fe-Mn-C-B modified by silicon, nickel, chromium and copper. Tribological tests were performed using a pin-on-disc tribometer. The pin (coating) and the disc made of steel C45 were subjected to heat treatment (hardening and tempering). The tests were carried out under loads of 3 MPa, 7 MPa and 10 MPa at a constant sliding velocity of 0.4 m/s and a sliding distance of 5700 m using a surface-active lubricant (glycerine oil). Obtained results were compared with the published results of previous tests carried out under the same conditions but under a load of 20 MPa. Obtained microscopic and spectroscopic results demonstrate that that the friction pair materials (the coating made of subeutectic alloy Fe-Mn-C-B modified by Si, Ni, Cr, Cu and C45 steel) and the surface-active lubricant cause self-organization during friction. The friction surface of the coatings has a flay-laminar structure and is covered with triboreaction products. The surface shows the presence of wear-resistant compounds such as oxides, carbides, borides and nitrides.

Description: Construction and demolition waste (CDW) accounts for at least 30% of the total solid waste produced around the world. At around 924 million tons in the European Union in 2016 and 2.36 billion tons in China in 2018, the amount is expected to increase over the next few years. Dumping these wastes in sanitary landfills has always been the traditional approach to waste management but this will not be feasible in the years to come. To significantly reduce or eliminate the amount of CDW being dumped, circular economy is a possible solution to the increasing amounts of CDW. Circular economy is an economic system based on business models which replaces the end-of-life concept with reducing, reusing, recycling, and recovering materials. This paper discusses circular economy (CE) frameworks—specifically material recovery and production highlighting the reuse and recycling of CDW and reprocessing into new construction applications. Likewise, a literature review into recent studies of reuse and recycling of CDW and its feasibility is also discussed to possibly prove the effectivity of CE in reducing CDW. Findings such as effectivity of recycling CDW into new construction applications and its limitations in effective usage are discussed and research gaps such as reuse of construction materials are also undertaken. CE and recycling were also found to be emerging topics. Observed trends in published articles as well as the use of latent Dirichlet allocation in creating topic models have shown a rising awareness and increasing research in CE which focuses on recycling and reusing CDW.

Description: Unidirectional non-crimp fabrics (UD-NCF) are often used to exploit the lightweight potential of continuous fiber reinforced plastics (CoFRP). During the draping process, the UD-NCF fabric can undergo large deformations that alter the local fiber orientation, the local fiber volume content (FVC) and create local fiber waviness. Especially the FVC is affected and has a large impact on the mechanical properties. This impact, resulting from different deformation modes during draping, is in general not considered in composite design processes. To analyze the impact of different draping effects on the mechanical properties and the failure behavior of UD-NCF composites, experimental results of reference laminates are compared to the results of laminates with specifically induced draping effects, such as non-constant FVC and fiber waviness. Furthermore, an analytical model to predict the failure strengths of UD laminates with in-plane waviness is introduced. The resulting stiffness and strength values for different FVC or amplitude to wavelength configurations are presented and discussed. In addition, failure envelopes based on the PUCK failure criterion for each draping effect are derived, which show a clear specific impact on the mechanical properties. The findings suggest that each draping effect leads to a “new fabric” type. Additionally, analytical models are introduced and the experimental results are compared to the predictions. Results indicate that the models provide reliable predictions for each draping effect. Recommendations regarding necessary tests to consider each draping effect are presented. As a further prospect the resulting stiffness and strength values for each draping effect can be used for a more accurate prediction of the structural performance of CoFRP parts.

Description: Herein, adsorption, separation, and reduction of Au(III) from its aqueous solution were studied with different amine-type, non-woven fabric (NF) adsorbents fabricated with radiation-induced graft polymerization. The adsorbents exhibited different adsorption capacities of Au(III) over a concentration range of hydrochloric acid (HCl) from 5 mM to 5 M, and the diethylamine (DEA)-type adsorbent performed best under all test conditions. The DEA-type adsorbent was inert toward other metal ions, including Cu(II), Pb(II), Ni(II), Zn(II) and Li(I), within the fixed concentration range of HCl. Flow-through adsorption tests indicated DEA-type adsorbent exhibited a rapid recovery and high adsorption capacity of 3.23 mmol/g. Meanwhile, DEA-type adsorbent also exhibited high selectivity and rapid extraction for Au(III) from its mixed solution with Pt(IV) and Pd(II). After adsorption, the reduction of Au(III) was confirmed by XRD spectra, TEM, and digital micrograph images. The results indicated that nano-sized Au particles were mainly concentrated on the adsorbent in 5 mM HCl solution. In 1 M HCl solution, not only nano-sized Au particles were found, but also micro-size Au plates precipitation occurred. This study provides a novel material for selective and efficient gold uptake from aqueous solution.

Description: This article proposes to use the acoustic emission (AE) method to evaluate the degree of change in the mechanical parameters of fiber–cement boards. The research was undertaken after a literature review, due to the lack of a methodology that would allow nondestructive assessment of the strength of cement–fiber elements. The tests covered the components cut out from a popular type of board available on the construction market. The samples were subjected to environmental (soaking in water, cyclic freezing–thawing) and exceptional (burning with fire and exposure to high temperature) factors, and then to three-point bending strength tests. The adopted conditions correspond to the actual working environment of the boards. When applying the external load, AE signals were generated, which were then grouped into classes, and initially assigned to specific processes occurring in the material. The frequencies occurring over time for the tested samples were also analysed, and microscopic observations were made to confirm the suppositions based on the first part of the tests. Comparing the results obtained from a group of samples subjected to environmental and exceptional actions, significant differences were noted between them, which included the types of recorded signal class, the frequency of events, and the construction of the microstructure. The degradation of the structure, associated with damage to the fibers or their complete destruction, results in the generation under load of AE signals that indicate the uncontrolled development of scratches, and a decrease in the frequency of these events. According to the authors, the methodology used allows the control of cement–fiber boards in use. The registration and analysis of active processes under the effect of payloads makes it possible to distinguish mechanisms occurring inside the structure of the elements, and to formulate a quick response to the situation when the signals indicate a decrease in the strength of the boards.

Description: The vacuum brazing of dissimilar electronic packaging materials has been investigated. In this research, this applies silicon particle-reinforced aluminum matrix composites (Sip/Al MMCs) to Kovar alloys. Active melt-spun ribbons were employed as brazing filler metals under different joining temperatures and times. The results showed that the maximum joint shear strength of 96.62 MPa was achieved when the joint was made using Al-7.5Si-23.0Cu-2.0Ni-1.0Ti as the brazing filler metal at 580 °C for 30 min. X-ray diffraction (XRD) analysis of the joint indicated that the main phases were composed of Al, Si and intermetallics, including CuAl, TiFeSi, TiNiSi and Al3Ti. When the brazing temperature ranged from 570 °C to 590 °C, the leakage rate of joints remained at 10−8 Pa·m3/s or better. When the joint was made using Al-7.5Si-23.0Cu-2.0Ni-2.5Ti as the brazing filler metal at 580 °C for 30 min, the higher level of Ti content in the brazing filler metal resulted in the formation of a flake-like Ti(AlSi)3 intermetallic phase with an average size of 7 µm at the interface between the brazing seam and Sip/Al MMCs. The joint fracture was generally in the form of quasi-cleavage fracture, which primarily occurred at the interface between the filler metal and the Sip/Al MMCs. The micro-crack propagated not only Ti(AlSi)3, but also the Si particles in the substrate.

Description: The understanding of the composition dependent properties and freezing-thawing (F-T) resistance of geopolymer materials is vital to their applications in cold regions. In this study, metakaolin-based geopolymer (MKG) mortars were fabricated by controlling the Si/Al ratio and the Na/Al ratio. The pore structure and strength were measured by mercury intrusion porosimetry and compression tests, respectively, which both showed obvious correlations with the material composition. Mass loss, strength loss, visual rate, and microscopic observation were adopted to assess the changes of the material properties and microstructure caused by F-T loads. The results showed that the strength-porosity relationship roughly followed a linear plot. Increases of the Si/Al ratio increased the capillary pore volume, but decreased the gel pore volume and the F-T resistance. Increases of the Na/Al ratio decreased the gel pore, but roughly enhanced the F-T resistance. The MKG mortar at the Na/Al ratio of 1.26 showed the lowest total pore volume and the best F-T resistance. The mechanisms of our experimental observations were that the abundantly distributed air voids connected by the capillary pores facilitated the relaxation of hydraulic pressures induced by the freezing of the pore liquid. The findings of this work help better clarify the compositional dependence of the pore structure, strength, and freezing-thawing resistance of MKG materials and provide fundamental bases for their engineering applications in cold regions.

Description: The resonant excitation of the surface plasmon–polariton waves by the prism structure, where a thin silver film was coated on the prism, was studied. New analytical relations between the angular and spectral sensitivities on the change of the medium refractive index, adjacent to the metal film, were obtained. In addition, the analytical relation between the full width at the half maximum of the spectral and angular resonance dependencies were found.

Description: This study develops a novel self-sensing cement composite by simply mixing reduced graphene oxide (rGO) in cementitious material. The experimental results indicate that, owing to the excellent dispersion method, the nucleation and two-dimensional morphological effect of rGO optimizes the microstructure inside cement-based material. This would increase the electric conductivity, thermal property and self-induction system of cement material, making it much easier for cementitious material to better warn about impending damage. The use of rGO can improve the electric conductivity and electric shielding property of rGO-paste by 23% and 45%. The remarkable enhancement was that the voltage change rate of 1.00 wt.%-rGO paste under six-cycle loads increased from 4% to 12.6%, with strain sensitivity up to 363.10, without compromising the mechanical properties. The maximum compressive strength of the rGO-mortar can be increased from 55 MPa to 71 MPa. In conclusion, the research findings provide an effective strategy to functionalize cement materials by mixing rGO and to achieve the stronger electric shielding property and higher-pressure sensitivity of rGO–cement composites, leading to the development of a novel high strength self-sensing cement material with a flexural strength up to 49%.

Description: Among the attractive properties of metamaterials, the capability of focusing and localizing waves has recently attracted research interest to establish novel energy harvester configurations. In the same frame, in this work, we develop and optimize a system for concentrating mechanical energy carried by elastic anti-plane waves. The system, resembling a Fabry-Pérot interferometer, has two barriers composed of Locally Resonant Materials (LRMs) and separated by a homogeneous internal cavity. The attenuation properties of the LRMs allow for the localization of waves propagating at particular frequencies. With proper assumptions on the specific ternary LRMs, the separation of scales (between the considered wave lengths and the characteristic dimension of the employed unit cells) enables the use of a two-scale asymptotic technique for computing the effective behavior of the employed LRMs. This leads to a complete analytic description of the motion of the system. Here we report the results achieved by optimizing the geometry of the system for obtaining a maximum focusing of the incoming mechanical energy. The analytic results are then validated through numerical simulations.

Description: Two new hypothetical zirconium diboride (ZrB 2 ) polymorphs: (hP6-P6 3 /mmc-space group, no. 194) and (oP6-Pmmn-space group, no. 59), were thoroughly studied under the first-principles density functional theory calculations from the structural, mechanical and thermodynamic properties point of view. The proposed phases are thermodynamically stable (negative formation enthalpy). Studies of mechanical properties indicate that new polymorphs are less hard than the known phase (hP3-P6/mmm-space group, no. 191) and are not brittle. Analysis of phonon band structure and density of states (DOS) also show that the phonon modes have positive frequencies everywhere and the new ZrB 2 phases are not only mechanically but also dynamically stable. The estimated acoustic Debye temperature, Θ D , for the two new proposed ZrB 2 phases is about 760 K. The thermodynamic properties such as internal energy, free energy, entropy and constant-volume specific heat are also presented.

Description: This paper is focused on the determination of the physicochemical properties of a composite inorganic–organic modified membrane. The electrical conductivity of a family of glassy protonic electrolytes defined by the general formula (P2O5)x(SiO2)y, where x/y is 3/7 are studied by Alternating Current electrochemical impedance spectroscopy (AC EIS) method. The reference glass was doped with polymeric additives—poly(ethylene oxide) (PEO) and poly(vinyl alcohol) (PVA), and additionally with a titanium-oxide-based filler. Special attention was paid to determination of the transport properties of the materials thus modified in relation to the charge transfer phenomena occurring within them. The electrical conductivities of the ‘dry’ material ranged from 10−4 to 10−9 S/cm, whereas for ‘wet’ samples the values were ~10−3 S/cm. The additives also modified the pore space of the samples. The pore distribution and specific surface of the modified glassy systems exhibited variation with changes in electrolyte chemical composition. The mechanical properties of the samples were also examined. The Young’s modulus and Poisson’s ratio were determined by the continuous wave technique (CWT). Based on analysis of the dispersion of the dielectric losses, it was found that the composite samples exhibit mixed-type proton mobility with contributions related to both the bulk of the material and the surface of the pore space.

Description: Two structurally different aromatic dithioesters were synthesized from two dithiols and methacryloyl chloride. The polymer networks based on methyl methacrylate and/or styrene and the new dimethacrylates were subsequently prepared. The polymerization yields of copolymers were in the range of 95–99%. The thermal and mechanical properties of the copolymers were determined by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TG/DTG), and Shore D hardness. The addition of dithioesters—1,5-NAF-S-Met (or 1,4(1,5)-NAF-CH2S-Met) (from 0.5% to 5%) to MMA- or ST-based polymers results in lowering the glass transition temperature (Tg) by about 8 °C. The thioester-containing polymers based on MMA exhibit lower thermal stability than those with ST. The polythioesters are stable up to 250 °C. The UV/vis spectra and refractive indexes of prepared liquid compositions were also measured. The 1,5-NAF-S-Met (and 1,4(1,5)-NAF-CH2S-Met) improved the refractive index values of ST and MMA compositions. The double bond conversion was also determined for all synthesized materials. The swelling studies of polymers with 20% addition of thioester crosslinkers were investigated. For all polymeric materials with 20% addition of thioesters, depolymerization of the network was carried out by thiol-thioester exchange. The depolymerization products were re-reacted in a thiol-ene reaction with 2-hydroxyethyl methacrylate by thermal initiation. The thiol-ene procedure enabled reprocessing of starting polymers and obtaining new materials characterized by distinctly different thermal, mechanical, and swelling properties. The thiol-ene materials exhibit a lower Shore hardness in the range of 20–50 °Sh, as well as decreased Tg values when compared to starting copolymers. Due to these possible exchange reactions, one can facilely manipulate the properties of the polymers which could lead to the manufacturing of the new products with the desired features. Degradation of the cross-linked structure and recycling of copolymers were also discussed.

Description: Most of the systems for the mechanical and biological treatment of waste used in Poland send the 0–80 mm fraction separated from the municipal waste stream, after biostabilization, entirely to a landfill. Such action is not in line with the adopted EU strategy focused on waste management in the circular cycle. The purpose of this work was to assess the technical feasibility of recovering the mineral fractions contained in compost-like-output (CLO) on the proprietary technological line designed for glass recovery. The research was launched in January 2019, and lasted for a subsequent 12 months. In the article, the amounts of mineral fractions possible to be separated from CLO are presented, as well as their morphological composition and selected properties being determined. The processing of CLO on the line allowed to recover on average 69.4 ± 7.0% of the glass. This product was accepted by glass recycling plants. Mineral fractions constituting waste from the glass separation process were tested for their use in winter road maintenance. Tests were also carried out confirming the possibility of using selected mineral fractions (0–10 mm) from CLO to obtain a waste cement mix useful for constructing road foundations using a standard amount of cement.

Description: The absolute pressure strongly affects the porosity and mechanical properties of castings produced by vacuum high-pressure die casting (V-HPDC) technology. The pore size, quantity and distribution of AlSi9Cu3 samples under three absolute pressures were evaluated by X-ray tomography and optical and electron microscopy. The paper presents an elaboration the stress concentration mechanism of pores affecting the tensile properties. According to a mathematical analysis of a sample under uniaxial stress, the greater the radius of the pore, the higher the stress value is at the pore perimeter. When the absolute pressure drops from 1013 mbar to 100 mbar, the porosity decreases from 6.8% to 2.8%, and the pore number and mean size decreases. In tensile tests, the pore sizes of the fracture surface decrease with decreasing absolute pressure, and the pore distribution becomes uniform. The tensile properties and extensibility of the sample are improved, and the microscopic fracture surface of the sample changes from cleavage fracture to quasi-cleavage fracture. The number, size and distribution of pores in die casting collectively affect the properties of the sample. Large-size or complex pores or pores with concentrated distributions produce large stress concentrations, decreasing the strength of the metal.

Description: As jointed plain concrete pavements (JPCP) age in South Korea, the cost of pavement maintenance is increasing annually. To extend the life of jointed concrete pavements through preventive maintenance, this study used 2017 pavement management system data to analyze the effects of traffic volume, alkali–silica reaction (ASR) grade, age, smoothness, and damaged area on the remodeling index (RMI—a measure of expressway pavement condition). In addition, this study evaluates the final RMI as well as the corresponding pavement condition and change in RMI value after conducting preventive maintenance in lieu of resurfacing or overlaying. The results demonstrated that the effect of ASR grade increased as the RMI forecast year increased and that change in surface distress (△SD) increased with age (most intensively when the pavement was 15–20 years of age). Moreover, change in international roughness index (△IRI) increased with age and traffic volume (similarly within 15–20 years of pavement age). Hence, preventive maintenance is a must for sections with high traffic volume and age even if the RMI is low. Finally, performing repairs through preventive maintenance decreases the number of expressway sections requiring resurfacing and overlaying, thus extending the life of the concrete pavement.

Description: This article presents selected aspects of an interlaminar shear strength and failure analysis of hybrid fiber metal laminates (FMLs) consisting of alternating layers of a 2024-T3 aluminium alloy and carbon fiber reinforced polymer. Particular attention is paid to the properties of the hybrid FMLs with an additional interlayer of glass composite at the metal-composite interface. The influence of hygrothermal conditioning, the interlaminar shear strength (short beam shear test), and the failure mode were investigated and discussed. It was found that fiber metal laminates can be classified as a material with significantly less adsorption than in the case of conventional composites. Introducing an additional layer of glass composite at the metal-composite interface and hygrothermal conditioning influence the decrease in the interlaminar shear strength. The major forms of damage to the laminates are delaminations in the layer of the carbon composite, at the metal-composite interface, and delaminations between the layers of glass and carbon composites.

Description: Due to the sustainable development of agriculture machines with large working widths of 4–6 m or even 9–12 m are increasingly often used for agrotechnical operations. The sowing machinery whose working widths are much bigger than the width of the seed box is equipped with a pneumatic system for transporting seeds from the seed box to coulters. One of the structural elements that affect the sowing accuracy in such seed drills is the distribution head with a diffuser. This article is about research on the influence of the distribution head deviation from the vertical position and constructional variants of the diffuser (the number of diffusion rings and the configuration of their position in the diffuser pipe, which is the distance between them) on the accuracy of distribution of a stream of rye and oat seeds (a seed-and-air stream), which differ in physical characteristics. The main elements, i.e., the innovative stream distributor in the head and the diffusion rings were made using an original design and the rapid prototyping method. The research proved that a change of 0–10° in the angle of the distribution head deviation from the vertical position significantly affected the sowing quality of oat seeds only. The position (density) of the diffusion rings in the lower section of the diffuser (near the supply elbow) was the most effective for both oat and rye seeds, where the average values of the coefficient of variation were 5.31% and 4.62%, respectively. The research results can be used to redesign the construction of the diffuser of the seed drill distribution head so as to reduce the resistance of transport of the seed-and-air mixture in order to improve seed sowing evenness.