ALBERT

Description: Hydraulic machinery repair works necessitate new materials with improved cavitation erosion resistance and simultaneously good welding properties. The present paper is concerned with the behavior at cavitation of two steels with close contents of chromium (approximately 12%) and nickel (approximate 6%) but with different carbon content (for the first 0.1% C and the second 0.036% C). The reduced carbon content is necessary for an easy welding repair work. As a result of the different chemical content, as is shown by the Schäffler diagram, the steel containing 0.1% C has a structure formed by 60% austenite and 40% martensite while those with 0.036% C has completely martensitic structure. The laboratory tests were done in two vibratory devices one with piezoelectric crystals, respecting the ASME G32-2010 Standard and the other a magnetostrictive vibratory device with nickel tube. The evaluation of the cavitation resistance was obtained with the help of cavitation erosion characteri...

Description: In this short review, we have selected three main subjects: (i) mesoporous materials, (ii) sensing applications, and (iii) the concept of nanoarchitectonics, as examples of recent hot topics in nanomaterials research. Mesoporous materials satisfy the conditions necessary not only for a wide range of applications but also for ease of production, by a variety of simple processes, which yield bulk quantities of materials without loss of their well-defined nanometric structural features. Sensing applications are of general importance because many events arise from interaction with external stimuli. In addition to these important features, nanoarchitectonics is a concept aimed at production of novel functionality of whole units according to concerted interactions within nanostructures. For the combined subject of mesoporous sensor nanoarchitectonics, we present recent examples of research in the corresponding fields categorized according to mechanism of detection including optical, electrical, and piezoelectric sensing.

Description: We report the growth of crystalline Al 2 O 3 thin films deposited by thermal Atomic Layer Deposition (ALD) at 200 °C, which up to now has always resulted in the amorphous phase. The 5 nm thick films were deposited on Ga 2 O 3 , ZnO, and Si nanowire substrates 100 nm or less in diameter. The crystalline nature of the Al 2 O 3 thin film coating was confirmed using Transmission Electron Microscopy (TEM), including high-resolution TEM lattice imaging, selected area diffraction, and energy filtered TEM. Al 2 O 3 coatings on nanowires with diameters of 10 nm or less formed a fully crystalline phase, while those with diameters in the 20–25 nm range resulted in a partially crystalline coating, and those with diameters in excess of 50 nm were fully amorphous. We suggest that the amorphous Al 2 O 3 phase becomes metastable with respect to a crystalline alumina polymorph, due to the nanometer size scale of the film/substrate combination. Since ALD Al 2 O 3 films are widely used as protective barriers, dielectric layers, as well as potential coatings in energy materials, these findings may have important implications.

Description: Epitaxial CeO 2 films with different thickness were grown on Y 2 O 3 stabilised Zirconia substrates. Reduction of cerium ions at the interface between CeO 2 films and yttria stabilised zirconia substrates is demonstrated using aberration-corrected scanning transmission electron microscopy combined with electron energy-loss spectroscopy. It is revealed that most of the Ce ions were reduced from Ce 4+ to Ce 3+ at the interface region with a decay of several nanometers. Several possibilities of charge compensations are discussed. Irrespective of the details, such local non-stoichiometries are crucial not only for understanding charge transport in such hetero-structures but also for understanding ceria catalytic properties.

Description: Low-temperature MnBi (hexagonal NiAs phase) exhibits anomalies in the lattice constants ( a ,  c ) and bulk elastic modulus (B) below 100 K, spin reorientation and magnetic susceptibility maximum near 90 K, and, importantly for high-temperature magnetic applications, an increasing coercivity (unique to MnBi) above 180  K. We calculate the total energy and magneto-anisotropy energy (MAE) versus ( a ,  c ) using DFT+U methods. We reproduce and explain all the above anomalies. We predict that coercivity and MAE increase due to increasing a , suggesting means to improve MnBi permanent magnets.

Description: We developed an on-chip microfabricated architecture for high-accuracy gate voltage modulated Seebeck coefficient measurements on an organic field-effect transistor (FET). The microfabricated device comprises integrated heaters and temperature sensors that enable simultaneous Seebeck and FET measurements on devices with practical channel lengths on the order of 50 μ m. We exemplify the capabilities of this architecture by investigating the transition from conduction in the semiconductor bulk to conduction in the accumulation layer of a conjugated polymer FET.

Description: The pyrochlore compounds Ho 2 Ti 2 O 7 and Dy 2 Ti 2 O 7 show an exotic form of magnetism called the spin ice state, resulting from the interplay between geometrical frustration and ferromagnetic coupling. A fascinating feature of this state is the appearance of magnetic monopoles as emergent excitations above the degenerate ground state. Over the past years, strong effort has been devoted to the investigation of these monopoles and other properties of the spin ice state in bulk crystals. Here, we report the fabrication of Ho 2 Ti 2 O 7 thin films using pulsed laser deposition on yttria-stabilized ZrO 2 substrates. We investigated the structural properties of these films by X-ray diffraction, scanning transmission electron microscopy, and atomic force microscopy, and the magnetic properties by vibrating sample magnetometry at 2 K. The films not only show a high crystalline quality, but also exhibit the hallmarks of a spin ice: a pronounced magnetic anisotropy and an intermediate plateau in the magnetization along the [111] crystal direction.

Description: An unexpected, strong deterioration of crystal quality is observed in epitaxial perovskite BiFeO 3 films in which microscale features have been patterned by focused-ion-beam (FIB) milling. Specifically, synchrotron x-ray microdiffraction shows that the damaged region extends to tens of μ m, but does not result in measureable changes to morphology or stoichiometry. Therefore, this change would go undetected with standard laboratory equipment, but can significantly influence local material properties and must be taken into account when using a FIB to manufacture nanostructures. The damage is significantly reduced when a thin metallic layer is present on top of the film during the milling process, clearly indicating that the reduced crystallinity is caused by ion beam induced charging.

Description: A dramatically enhanced self-assembly of GeSi quantum dots (QDs) is disclosed on slightly miscut Si (001) substrates, leading to extremely dense QDs and even a growth mode transition. The inherent mechanism is addressed in combination of the thermodynamics and the growth kinetics both affected by steps on the vicinal surface. Moreover, temperature-dependent photoluminescence spectra from dense GeSi QDs on the miscut substrate demonstrate a rather strong peak persistent up to 300 K, which is attributed to the well confinement of excitons in the dense GeSi QDs due to the absence of the wetting layer on the miscut substrate.

Description: Using in situ scanning transmission electron microscopy heating experiments, we observed the formation of a 3-dimensional (3D) epitaxial Cu-core and Ag-shell equilibrium structure of a Cu-Ag nanoalloy. The structure was formed during the thermal interaction of Cu(∼12 nm) and Ag NPs(∼6 nm) at elevated temperatures (150–300 °C) by the Ag NPs initially wetting the Cu NP along its {111} surfaces at one or multiple locations forming epitaxial Ag/Cu (111) interfaces, followed by Ag atoms diffusing along the Cu surface. This phenomenon was confirmed through Monte Carlo simulations to be a nanoscale effect related to the large surface-to-volume ratio of the NPs.

Description: We have investigated the Mn-site substitution effect in Nd 0.45 Sr 0.55 MnO 3 single crystal, which has an A -type layered antiferromagnetic ( A -AFM) phase with the 3 d x 2 − y 2 -type orbital-order. Substitution of Fe or Ga for Mn-site suppresses both the A -AFM order and competing ferromagnetic (FM) correlation, whereas Cr substitution suppresses only the A -AFM order but reactivates the underlying FM correlation via double-exchange mechanism along the AFM coupled c -direction. In Nd 0.45 Sr 0.55 Mn 0.95 Cr 0.05 O 3 , the A -AFM state with the orbital-order is changed into the orbital-disordered three-dimensional FM metallic state by applying magnetic field of μ 0 H = 12 T, which is much smaller than that of the parent compound Nd 0.45 Sr 0.55 MnO 3 .

Description: Cuprous oxide (Cu 2 O) is actively studied as a prototypical material for energy conversion and electronic applications. Here we reduce the growth temperature of phase pure Cu 2 O thin films to 300 °C by intentionally controlling solely the kinetic parameter (total chamber pressure, P tot ) at fixed thermodynamic condition (0.25 mTorr pO 2 ). A strong non-monotonic effect of P tot on Cu-O phase formation is found using high-throughput combinatorial-pulsed laser deposition. This discovery creates new opportunities for the growth of Cu 2 O devices with low thermal budget and illustrates the importance of kinetic effects for the synthesis of metastable materials with useful properties.

Description: Alloyed silicon-germanium (SiGe) nanostructures are the topic of renewed research due to applications in modern optoelectronics and high-temperature thermoelectric materials. However, common techniques for producing nanostructured SiGe focus on bulk processing; therefore little is known of the physical properties of SiGe nanocrystals (NCs) synthesized from molecular precursors. In this letter, we synthesize and deposit thin films of doped SiGe NCs using a single, flow-through nonthermal plasma reactor and inertial impaction. Using x-ray and vibrational analysis, we show that the SiGe NC structure appears truly alloyed for Si 1−x Ge x for 0.16 〈 x 〈 0.24, and quantify the atomic dopant incorporation within the SiGe NC films.

Description: In this study, we developed a new neutron-detection device using a boron gallium nitride (BGaN) semiconductor in which the B atom acts as a neutron converter. BGaN and gallium nitride (GaN) samples were grown by metal organic vapor phase epitaxy, and their radiation detection properties were evaluated. GaN exhibited good sensitivity to α-rays but poor sensitivity to γ-rays. Moreover, we confirmed that electrons were generated in the depletion layer under neutron irradiation. This resulted in a neutron-detection signal after α-rays were generated by the capture of neutrons by the B atoms. These results prove that BGaN is useful as a neutron-detecting semiconductor material.

Description: Many complex oxides display an array of structural instabilities often tied to altered electronic behavior. For oxide heterostructures, several different interfacial effects can dramatically change the nature of these instabilities. Here, we investigate LaAlO 3 /SrTiO 3 (001) heterostructures using synchrotron x-ray scattering. We find that when cooling from high temperature, LaAlO 3 transforms from the to the Imma phase due to strain. Furthermore, the first 4 unit cells of the film adjacent to the substrate exhibit a gradient in rotation angle that can couple with polar displacements in films thinner than that necessary for 2D electron gas formation. P m 3 ¯ m

Description: We report on real time-resolved Reflectance-difference (RD) spectroscopy of GaAs(001) grown by molecular beam epitaxy, with a time-resolution of 500 ms per spectrum within the 2.3–4.0 eV photon energy range. Through the analysis of transient RD spectra we demonstrated that RD line shapes are comprised of two components with different physical origins and determined their evolution during growth. Such components were ascribed to the subsurface strain induced by surface reconstruction and to surface stoichiometry. Results reported in this paper render RD spectroscopy as a powerful tool for the study of fundamental processes during the epitaxial growth of zincblende semiconductors.

Description: The internal architecture of polymeric self-assembled chiral micro-particles is studied by exploring the effect of the chirality, of the particle sizes, and of the interface/surface properties in the ordering of the helicoidal planes. The experimental investigations, performed by means of different microscopy techniques, show that the polymeric beads, resulting from light induced polymerization of cholesteric liquid crystal droplets, preserve both the spherical shape and the internal self-organized structures. The method used to create the micro-particles with controlled internal chiral architectures presents great flexibility providing several advantages connected to the acquired optical and photonics capabilities and allowing to envisage novel strategies for the development of chiral colloidal systems and materials.

Description: Iron sulfide thin films were fabricated by the electrochemical deposition method from an aqueous solution containing FeSO 4 and Na 2 S 2 O 3 . The composition ratio obtained was Fe:S:O = 36:56:8. In the photoelectrochemical measurement, a weak negative photo-current was observed for the iron sulfide films, which indicates that its conduction type is p-type. No peaks were observed in X-ray diffraction pattern, and thus the deposited films were considered to be amorphous. For a heterojunction with ZnO, rectification properties were confirmed in the current-voltage characteristics. Moreover, the current was clearly enhanced under AM1.5 illumination.

Description: We have performed high field magnetotransport measurements to investigate the interface electron gas in a high mobility SrTiO 3 /SrCuO 2 /LaAlO 3 /SrTiO 3 heterostructure. Shubnikov-de Haas oscillations reveal several 2D conduction subbands with carrier effective masses of 0.9 m e and 2 m e , quantum mobilities of order 2000 cm 2 /V s, and band edges only a few millielectronvolts below the Fermi energy. Measurements in tilted magnetic fields confirm the 2D character of the electron gas, and show evidence of inter-subband scattering.

Description: To enlighten microscopic origin of visible-light absorption in transparent amorphous semiconducting oxides, the intrinsic optical property of amorphous InGaZnO 4 is investigated by considering dipole transitions within the quasiparticle band structure. In comparison with the crystalline InGaZnO 4 with the optical gap of 3.6 eV, the amorphous InGaZnO 4 has two distinct features developed in the band structure that contribute to significant visible-light absorption. First, the conduction bands are down-shifted by 0.55 eV mainly due to the undercoordinated In atoms, reducing the optical gap between extended states to 2.8 eV. Second, tail states formed by localized oxygen p orbitals are distributed over ∼0.5 eV near the valence edge, which give rise to substantial subgap absorption. The fundamental understanding on the optical property of amorphous semiconducting oxides based on underlying electronic structure will pave the way for resolving instability issues in recent display devices incorporating the semiconducting oxides.

Description: Nickel oxide (NiO) nanocrystals epitaxially grown on (001) strontium titanate (SrTiO 3 ) single crystal substrates were characterized to investigate interface morphology and chemistry. Aberration corrected high angle annular dark field scanning transmission electron microscopy reveals the interface between the NiO nanocrystals and the underlying SrTiO 3 substrate to be rough, irregular, and have a lower average atomic number than the substrate or the nanocrystal. Energy dispersive x-ray spectroscopy and electron energy loss spectroscopy confirm both chemical disorder and a shift of the energy of the Ti L 2,3 peaks. Analysis of the O K edge profiles in conjunction with this shift, implies the presence of oxygen vacancies at the interface. This sheds light into the origin of the previously postulated minority carriers’ model to explain resistive switching in NiO [J. Sullaphen, K. Bogle, X. Cheng, J. M. Gregg, and N. Valanoor, Appl. Phys. Lett.100, 203115 (2012)].

Description: In this paper we demonstrate an add/drop filter based on SiC technology. Tailoring of the channel bandwidth and wavelength is experimentally demonstrated. The concept is extended to implement a 1 by 4 wavelength division multiplexer with channel separation in the visible range. The device consists of a p-i'(a-SiC:H)-n/p-i(a-Si:H)-n heterostructure. Several monochromatic pulsed lights, separately or in a polychromatic mixture illuminated the device. Independent tuning of each channel is performed by steady state violet bias superimposed either from the front and back sides. Results show that, front background enhances the light-to-dark sensitivity of the long and medium wavelength channels and quench strongly the others. Back violet background has the opposite behaviour. This nonlinearity provides the possibility for selective removal or addition of wavelengths. An optoelectronic model is presented and explains the light filtering properties of the add/drop filter, under differen...

Description: All papers published in this volume of IOP Conference Series: Materials Science and Engineering have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

Description: The nonradiative decay of majority electrons has been studied over a wide temperature range from 80 K to 600 K using the time-resolved free-carrier-absorption (FCA) technique. At high injection level of the highly-luminescent N-B codoped 6H-SiC epilayer, we revealed three main relaxation components of injected free electrons over ps-to-ms time ranges. By means of temperature dependency, two components can be ascribed to thermal activation of holes from a shallow (200 meV) and a deep (500 meV) acceptor. The third one, which has a hundred us-time scale, we attribute to minority hole recombination from the valance band into the electron trap (53 meV). This recombination channel seems to compete with the deep-acceptor (Boron) to-donor (Nitrogen) pair visible emission at and below 300 K.

Description: Two overlapping photoluminescent (PL) bands with a peaks (half-width) at 1.95 eV (0.45 eV) and 2.15 eV (0.25 eV), correspondingly at 300 K, are observed in heavily B-N co-doped 6H-SiC epilayers under high-level excitation condition. The low energy band dominates at low temperatures and decreases towards 300 K which is assigned to DAP emission from the nitrogen trap to the deep boron (dB) with phonon-assistance. The 2.15 eV band slightly increases with temperature and becomes comparable with the former one at 300 K. We present a modelling comprising electron de-trapping from the N-trap, i.e. calculating trapping and de-trapping probabilities. The T-dependence of the 2.15 eV band can be explained by free electron emission from the conduction band into the dB center provided by similar phonon-assistance.

Description: The thick N-B co-doped epilayers were grown by the fast sublimation growth method and the depth-resolved carrier lifetimes have been investigated by means of the free-carrier absorption (FCA) decay under perpendicular probe-pump measurement geometry. In some samples, we optically reveal in-grown carbon inclusions and polycrystalline defects of substantial concentration and show that these defects slow down excess carrier lifetime and prevent donor-acceptor pair photo luminescence (DAP PL). A pronounced electron lifetime reduction when injection level approaches the doping level was observed. It is caused by diffusion driven non-radiative recombination. However, the influence of surface recombination is small and insignificant at 300 K.

Description: Materials for optoelectronics give a fascinating variety of issues to consider. Increasingly important are white light emitting diode (LED) and solar cell materials. Profound energy savings can be done by addressing new materials. White light emitting diodes are becoming common in our lighting scene. There is a great energy saving in the transition from the light bulb to white light emitting diodes via a transition of fluorescent light tubes. However, the white LEDs still suffer from a variety of challenges in order to be in our daily use. Therefore there is a great interest in alternative lighting solutions that could be part of our daily life. All materials create challenges in fabrication. Defects reduce the efficiency of optical transitions involved in the light emitting diode materials. The donor-acceptor co-doped SiC is a potential light converter for a novel monolithic all-semiconductor white LED. In spite of considerable research, the internal quantum efficien...

Description: The nucleation and bulk growth of polycrystalline SiC in a 2 inch PVT setup using isostatic and pyrolytic graphite as substrates was studied. Textured nucleation occurs under near-thermal equilibrium conditions at the initial growth stage with hexagonal platelet shaped crystallites of 4H, 6H and 15R polytypes. It is found that pyrolytic graphite results in enhanced texturing of the nucleating gas species. Reducing the pressure leads to growth of the crystallites until a closed polycrystalline SiC layer containing voids with a rough surface is developed. Bulk growth was conducted at 35 mbar Ar pressure at 2250°C in diffusion limited mass transport regime generating a convex shaped growth form of the solid-gas interface leading to lateral expansion of virtually [001] oriented crystallites. Growth at 2350°C led to the stabilization of 6H polytypic grains. The micropipe density in the bulk strongly depends on the substrate used.

Description: Thick 6H-SiC epilayers were grown using the fast sublimation method on low-off-axis substrates. They were co-doped with N and B impurities of ≈10 19 cm −3 and (4·10 16 –5·10 18 ) cm −3 concentration, respectively. The epilayers exhibited donor-acceptor pair (DAP) photoluminescence. The micro-Raman spectroscopic study exposed a compensated n -6H-SiC epilayer of common quality with some 3C-SiC inclusions. The compensation ratio of B through 200 μm thick epilayer varied in 20-30% range. The free carrier diffusivity was studied by transient grating technique at high injection level. The determined ambipolar diffusion coefficient at RT was found to decrease from 1.15 cm 2 /s to virtually 0 cm 2 /s with boron concentration increasing by two orders.

Description: A steady improvement in material quality and process technology has made electronic silicon carbide devices commercially available. Both rectifying and switched devices can today be purchased from several vendors. This successful SiC development over the last 25 years can also be utilized for other types of devices, such as light emitting and photovoltaic devices, however, there are still critical problems related to material properties and reliability that need to be addressed. This contribution will focus on surface passivation of SiC devices. This issue is of utmost importance for further development of SiC MOSFETs, which so far has been limited by reliability and low charge carrier surface mobilities. Also bipolar devices, such as BJTs, LEDs, or PV devices will benefit from more efficient and reliable surface passivation techniques in order to maintain long charge carrier lifetimes. Silicon carbide material enables the devices to operate at higher electric fields, higher tem...

Description: Donor-acceptor co-doped SiC is a promising light converter for novel monolithic all-semiconductor white LEDs due to its broad-band donor-acceptor pair luminescence and potentially high internal quantum efficiency. Besides sufficiently high doping concentrations in an appropriate ratio yielding short radiative lifetimes, long nonradiative lifetimes are crucial for efficient light conversion. The impact of different types of defects is studied by characterizing fluorescent silicon carbide layers with regard to photoluminescence intensity, homogeneity and efficiency taking into account dislocation density and distribution. Different doping concentrations and variations in gas phase composition and pressure are investigated.

Description: We report on the investigation of the structural, chemical and optical properties of undoped and Eu-doped SiOC thin films synthetized by RF magnetron sputtering. Undoped SiOC exhibits an intense room temperature luminescence at ~ 500 nm, and an important contribution to this signal is due to the presence of Si-C bonds. Moreover, when inserted in a SiOC matrix, Eu ions have a higher solid solubility with respect to pure SiO 2 ; as a consequence, we observe a reduction of Eu clustering phenomena. Furthermore the reducing properties of SiOC, related to the presence of C, allow the prevalence of the Eu 2+ emission over the Eu 3+ one. Through the control of the annealing conditions it is possible to obtain an intense light emission at 440 nm. These properties propose SiOC as a novel and efficient Si-based host matrix for Eu and open the way to promising perspectives of Eu-based materials for photonic applications and LED fabrication.

Description: The morphology and crystal growth of devitrite crystals nucleated heterogeneously on glass surfaces have been studied. The crystals grow as fans of needles, with each needle having a characteristic [100] growth direction with respect to the centrosymmetric triclinic unit cell. An analysis of crystal growth data reported here and a reappraisal of crystal growth data reported in prior studies suggests a best estimate of 260 kJ/mol for the activation enthalpy for the crystal growth of devitrite along [100], higher than the values previously reported.

Description: Using density functional theory-based calculations, we explore the effects of oxygen vacancies and epitaxial layering on the atomic, magnetic, and electronic structure of (SrTiO 3 ) n (SrFeO 3− x ) 1 superlattices. While structures without oxygen vacancies ( x = 0) possess small or non-existent band gaps and ferromagnetic ordering in their iron layers, those with large vacancy concentrations ( x = 0.5) have much larger gaps and antiferromagnetic ordering. Though the computed gaps depend numerically on the delicate energetic balance of vacancy ordering and on the value of Hubbard U eff used in the calculations, we demonstrate that changes in layering can tune the band gaps of these superlattices below that of SrTiO 3 (3.2 eV) by raising their valence band maxima. This suggests the possibility that these superlattices could absorb in the solar spectrum, and could serve as water-splitting photocatalysts.

Description: Single crystal (1  − x ) Pb ( Mg 1 / 3 Nb 2 / 3 ) O 3 – x PbTiO 3 [ PMN – x PT] ( x  = 0.32) is a relaxor-ferroelectric material known to exhibit ‘giant’ piezoelectric behavior, with achievable strains in excess of 1% for samples of certain particular crystallographic orientations and chemical compositions close to the morphotropic phase boundary. In this study, we investigate the electric field-induced structural phase transitions in single crystal PMN –0.32 PT with time-of-flight neutron diffraction and macroscopic electrical polarization measurements, and show that both the frequency of the applied ac field and the temperature of the sample are critical factors in determining these phase transition fields.

Description: Glass nanocomposites, fabricated using borosilicate glass microspheres and antimony tin oxide (ATO) nanoparticles, were previously reported to have formed segregated networks at the boundaries of the glass particles. This resulted in an electrically conducting composite at low volume fractions (~0.5–0.8 vol%) of ATO nanoparticles. The wide range of electrical response in these borosilicate glass composites containing networks of varying concentration of ATO was examined using impedance spectroscopy. The electrical resistance of these composites varied over a range of around 12 orders of magnitude and exhibited several different types of insulator and conductor behavior. The formation of the ATO network was identified and tracked by scanning electron microscopy images and energy dispersive X-ray spectroscopy (EDS) scans. Detailed impedance spectroscopy analysis using all of the dielectric functions (impedance, permittivity, electric modulus, and admittance) was found to be an excellent method for detecting the development of the network and the effect that processing variables can have on its formation and the overall electrical properties of the nanocomposites.

Description: By combining the concept of defect chemistry and the small-polaron hopping conduction model, the present work takes an intensively considering of the electron conduction mechanism in the nonstoichiometric SnO 2 nanocrystalline film. The temperature-dependent and atmosphere-dependent relationship between the electrical conductivity and the defect reaction is outlined. To investigate the influence of temperature and atmosphere on the electrical properties of the SnO 2 nanocrystalline film, a temperature-programmed system integrated with the high-throughput screening platform of gas-sensing materials (HTSP-GM) is developed as the test tool in this work. With this platform, the temperature-dependent conductivity of SnO 2 nanocrystalline film in different atmosphere (dry air, nitrogen, and formaldehyde) was conducted. A good fit between the theoretical deductions and experimental results is achieved.

Description: We demonstrate a facile synthesis of monodisperse magnetite ( Fe 3 O 4 ) nanoparticles (NPs) via a simple wet chemical route at 180°C using oleylamine ( C 18 H 37 N ), which serves as a solvent, ligand, and surfactant. The particles have a narrow size distribution centered at about 10 nm. To provide better electron conductivity and structural stability, the as-synthesized particles are given a carbon nanocoating by pyrolysis of the residual surfactant on their surface. This pyrolysis forms a uniform thin nanocoating on each particle, and a core/shell Fe 3 O 4 /carbon NP network was thus obtained. The core/shell Fe 3 O 4 /carbon electrode shows better reversible capacity, cycle life, and rate capability than a bare Fe 3 O 4 NP electrode because of its efficient electron transport and stress relaxation provided by the thin carbon layer.

Description: Nickel ferrite (NiFe 2 O 4 ) is a major constituent of the corrosion deposits formed on the exterior of nuclear fuel cladding tubes during operation. NiFe 2 O 4 has attracted much recent interest, mainly due to the impact of these deposits, known as CRUD, on the operation of commercial nuclear reactors. Although advances have been made in modeling CRUD nucleation and growth under a wide range of conditions, the thermophysical properties of NiFe 2 O 4 at high temperatures have only been approximated, thereby limiting the accuracy of such models. In this study, samples of NiFe 2 O 4 were synthesized to provide the thermal diffusivity, specific heat capacity, and thermal expansion data from room temperature to 1300 K. These results were then used to determine thermal conductivity. Numerical fits are provided to facilitate ongoing modeling efforts. The Curie temperature determined through these measurements was in slight disagreement with literature values. Transmission electron microscopy investigation of multiple NiFe 2 O 4 samples revealed that minor nonstoichiometry was likely responsible for variations in the Curie temperature. However, these small changes in composition did not impact the thermal conductivity of NiFe 2 O 4 , and thus are not expected to play a large role in governing reactor performance.

Description: Boron carbide thin films have been synthesized via pulsed laser deposition process using Spark Plasma Sintered (SPSed) and dual-targets, respectively. Two kinds of structural evolutions have been found by investigation of bonding environments in as-deposited thin films via X-ray photoelectron spectroscopy study. With decreasing of B/C ratio, films deposited from SPSed-target show the transformation of B 11 C -CBB → B 11 C -CBC. In contrast, the films deposited from dual-target present the B 11 C -CBB → B 10 C 2 -CBB structural change.

Description: The SrTiO 3 (STO) thin films were directly grown on Si (111) substrates without buffer layer by an electron-cyclotron-resonance ion beam sputter deposition. The growth temperature was varied from 700°C to 850°C, while other parameters were kept unchanged. X-ray structural analysis demonstrates that the growth temperature has a strong influence in tuning degree of (100) orientation. The STO film grown at 800°C is found to be the highest degree of (100) orientation (98%) and a strong (100) fiber texture. For the surface morphology, the development of plate-shaped grains reveals a good correlation with the change in the degree of (100) orientation. Moreover, the leakage current–voltage characteristics of the Au /STO/ Si (111) metal-insulator-semiconductor capacitors are investigated and discussed in considerable detail.

Description: The effect of combined substitution of Sm 3+ and O 2− with Ca 2+ and F − , respectively, on the structural and superconducting properties of SmFeAsO system is investigated. It is observed that the binary doping using CaF 2 causes considerable structural as well as microstructural changes wherein the preferred orientation of (00  l ) planes and enhancement of grain size are quite interesting. Moreover, a maximum T C of 53.8 K and a transport J C of 880 A/cm 2 (12 K) are achieved in the codoped samples. The achievement of preferred orientation, enhanced T C , and the subsequent increase in J C of the modified SmFeAsO system are particularly significant for high current conductor development.

Description: Lead free piezoelectric ceramics of Y 3+ -doped Ba 1− x Ca x Zr 0.07 Ti 0.93 O 3 with x  = 0.05, 0.10, and 0.15 were prepared. Composition and temperature-dependent structural phase evolution and electrical properties of as-prepared ceramics were studied systematically by X-ray diffraction, Raman spectroscopy, impedance analyzer, ferroelectric test system, and unipolar strain measurement. Composition with x  = 0.10 performs a good piezoelectric constant d 33 of 363 pC/N, coercive field E c of 257 V/mm, remanent polarization P r of 14.5 μC/cm 2 , and a Curie temperature T m of 109°C. High-resolution X-ray diffraction was introduced to indicate presence of orthorhombic phase. Converse piezoelectric constant d 33 * of x  = 0.10 composition performed better temperature stability in the range from 50°C to 110°C. That means decreasing orthorhombic–tetragonal phase transition temperature could be an effective way to enlarge its operating temperature range.

Description: TiO 2 -doped Y 2 O 3 -stabilized ZrO 2 compounds with low thermal conductivity have been considered as a promising thermal barrier coating material. In the present research, a series of TiO 2 -doped Y 2 O 3 -stabilized ZrO 2 compounds have been synthesized and investigated. Lattice distortion and disordering caused by TiO 2 doping were observed and their effects on mechanical properties, such as fracture toughness, elastic modulus, and coefficient of thermal expansion (CTE), were also investigated. Lattice distortion enhanced the ferroelastic toughening and the fracture toughness, whereas the variation in elastic modulus and CTE is due to the lattice disordering. The combination of thermal and mechanical properties bodes well for the potential application as thermal barrier coating materials.

Description: The influence of second phase zirconia particles on the electrical properties and fracture behavior of various polycrystalline soft Pb ( Zr 1− x Ti x ) O 3 (PZT) compositions was investigated. PZT composites with yttria-stabilized tetragonal zirconia particles exhibited enhanced crack resistance in comparison to monolithic compositions, regardless of the PZT composition. The addition of zirconia, however, was found to change the PZT composition through the diffusion of zirconium, resulting in variations in the observed piezoelectric and ferroelectric responses. Through the tailoring of the PZT matrix composition, the large electromechanical response and enhanced fracture toughness could be retained. The variation in both small and large signal properties is contrasted to fracture results and crystal structure changes, as determined by X-ray diffraction.

Description: A novel method is employed for the formation of rare earth phosphate solid solution compounds with unique mesoscopic structures. Europium- and lanthanum-doped sodium borate glass microspheres and particles, ranging in sizes from 50 to 300 μm, were reacted in 0.25 M K 2 HPO 4 solution to form hollow spheres of nanocrystalline rare earth phosphate compounds by dissolution–precipitation reactions. The initially X-ray amorphous precipitated rare earth phosphate materials were heat-treated at 700°C for 2 h to form nanocrystalline compounds. Differential thermal analysis (DTA) experiments yield an average activation energy for crystallization of 394 ± 26 kJ/mol. X-ray diffraction (XRD) data indicate that samples crystallized to the monazite structure (monoclinic P2 1 /n) with unit cell volumes ranging from 306.5 Å 3 for LaPO 4 to 282.5 Å 3 for EuPO 4 and with crystallite grain sizes of 56 ± 14 nm. Compositions containing both rare earth elements formed solid solutions with the composition La (1− x ) Eu x PO 4 . Raman spectroscopy indicates that the P–O symmetric stretching vibrations (ν 1 ) change systematically from 963 cm −1 for LaPO 4 to 986 cm −1 for EuPO 4 , consistent with a systematic decrease in average P–O bond length. Photoluminescence measurements show maximum emission intensity for the La 0.65 Eu 0.35 PO 4 composition.

Description: A single crystal of α- Ca 2 [ HSiO 4 ](OH) (α- C 2 SH) was repeatedly imaged at room temperature with synchrotron mid-infrared microscopy after heating to 310°C, 340°C, 370°C, and 400°C respectively. The mechanisms of the observed phase transformations are discussed on the basis of a modular concept of the crystal structures. All images show domains of dellaite, Ca 6 [ Si 2 O 7 ][ SiO 4 ](OH) 2 , which are predominantly formed in the core of the crystal. In the crystal rim area α- C 2 SH persists in higher abundance. The mechanism of the phase transformation of α- C 2 SH into dellaite includes the following: (1) Partial formation of killalaite ( Ca 3 [ HSi 2 O 7 ](OH)) as nuclei according to the isochemical reaction 2 Ca 2 [ HSiO 4 ](OH) → Ca 3 [ HSi 2 O 7 ](OH) +  Ca (OH) 2 probably induced by anisotropic thermal expansion, local chemical fluctuations, structural (proton) disorder, and different bond strengths of the OH groups in the α- C 2 SH structure. (2) Further dehydration of killalaite and α- C 2 SH domains results in the formation of dellaite according to Ca 3 [ HSi 2 O 7 ](OH) + Ca(OH) 2  + Ca 2 [ HSiO 4 ](OH) – 2 H 2 O → Ca 6 [ Si 2 O 7 ][ SiO 4 ](OH) 2 . The results suggest that the polymerization of two isolated [ HSiO 4 ] tetrahedra takes place without dehydration according to reaction (1) rather than through condensation with simultaneous H 2 O release: 2[ HSiO 4 ] → [ Si 2 O 7 ] +  H 2 O . We suggest that reaction (1) cannot be completed at ambient pressure. Thus in the regions close to the rim of the crystals we expect the formation of x - C 2 S , which starts along the crystal edges according to Ca 2 [ HSiO 4 ](OH) → Ca 2 SiO 4  +  H 2 O . Based on a modular concept, a structural relationship between α- C 2 SH, killalaite, dellaite, and x - C 2 S has been established. Similarities and differences in the thermal behavior of α- C 2 SH and afwillite have been highlighted.

Description: The oxygen permeability of polycrystalline α-alumina wafers, which served as models for alumina scales on alumina-forming alloys, under steep oxygen potential gradients ( ) was evaluated at 1873 K. Oxygen permeation occurred by the grain-boundary (GB) diffusion of oxygen from the higher-oxygen-partial-pressure ( ) surface to the lower- surface, along with the simultaneous GB diffusion of aluminum in the opposite direction. The fluxes of oxygen and aluminum at the outflow side of the wafer were significantly larger than at the inflow side. Furthermore, Lu and Hf segregation at the GBs selectively reduced the mobility of oxygen and aluminum, respectively. A wafer with a bilayer structure, in which a Lu-doped layer was exposed to a lower and an Hf-doped layer was exposed to a higher , decreased the oxygen permeability. When the sign of was reversed, however, the oxygen permeability of the wafer was comparable to that of a nondoped wafer. Co-doping with both Lu and Hf markedly increased the oxygen permeation, presumably because the Lu-stabilized HfO 2 particles that were segregated at the GBs acted as extremely fast diffusion paths for oxygen through the large number of oxygen vacancies introduced by the solid solution of Lu in the particles.

Description: Scandium fluoride ( ScF 3 ) belongs to one of the rare compounds which exhibit isotropic negative thermal expansion. Here, a facile and environmentally friendly hydrothermal synthesis method has been presented. High-quality single-crystalline ScF 3 cubes, with an average size of 200 nm, can be easily fabricated in a large scale. Sc (NO 3 ) 3 and NH 4 HF 2 were used as precursors. The as-prepared ScF 3 demonstrates cubic symmetry ( Pm -3  m ), which was confirmed by X-ray diffraction and selected-area electron diffraction. Its uniform morphology and size were characterized by high-resolution transmission electron microscopy. Furthermore, thermal analysis was also performed in argon gas atmosphere to investigate its thermal stability.

Description: Results of the spectroscopic characteristics and upconversion luminescence in Er 3+ doped yttria ( Y 2 O 3 ) transparent ceramics prepared by a modified two-step sintering method are presented. The near-infrared (1.5 μm) luminescence properties were evaluated as a function of Er 3+ concentration. Judd–Ofelt intensity parameters, radiative rates, branching ratios, and emission lifetimes were determined and compared with results reported for Er 3+ -doped Y 2 O 3 single crystal and nanocrystals. Following pumping at 1.532 μm, weak blue (~0.41 μm, 2 H 9/2 → 4 I 15/2 ), strong green (~0.56 μm, 2 H 11/2 , 4 S 3/2 → 4 I 15/2 ), and red (~0.67 μm, 4 F 9/2 → 4 I 15/2 ) emission bands were observed as well as weak near-infrared emissions at 0.8 μm ( 4 I 9/2 → 4 I 15/2 ) and 0.85 μm ( 4 S 3/2 → 4 I 13/2 ) at room temperature. The upconversion luminescence properties under ~1.5 μm pumping were further investigated through pump power dependence and decay time studies. Sequential two-photon absorption leads to the 4 I 9/2 upconversion emission, whereas energy-transfer upconversion is responsible for the emission from the higher excited states 2 H 9/2 , 2 H 11/2 , 4 S 3/2 , and 4 F 9/2 . The enhanced red emission with increasing Er 3+ concentration most likely occurred via the cross-relaxation process between ( 4 F 7/2 → 4 F 9/2 ) and ( 4 I 11/2 → 4 F 9/2 ) transitions, which increased the population of the 4 F 9/2 level.

Description: Zirconia phase transformation is usually studied on surface. For in-depth study, three methods were proposed using Raman microspectroscopy quantitative evaluation: direct measurement on sample cross section, confocal Raman spectroscopy (CRS), and progressive pinhole aperture enlargement (PPAE). The aim of this study was to compare transformation profiles obtained with these three methods on the same sample. Three 3Y-TZP samples were aged, respectively, for 25, 72, and 90 h in artificial saliva. Transformation profiles were determined with cross-sectional measurement, CRS and PPAE. A transformation profile simulation model based on PPAE measurements is proposed, using the convolution of the excitation intensity profile and the Beer–Lambert law (optical properties of zirconia). The simulation model was validated with the determination of 3Y-TZP transformation factor, T  = 1.15 μm −1 , identical for the three aging durations. Both cross section and PPAE measured similar in-depth transformation decrease, but with a 10 μm-shift: transformed zirconia layer is more important in cross-sectional protocol (36 μm with PPAE and 46 μm with cross-sectional after 90 h aging). Complementary measurements on a 10 h aged sample, where transformation is initiated by Low-Temperature Degradation, showed that sample preparation and polishing, necessary in the cross-sectional method, were responsible for the higher transformation. PPAE method enables noninvasive in-depth measurements with limited optical and mechanical biases.

Description: New cementitious materials based on calcium hydrosilicate hydrates were recently developed as potential substitutes for ordinary portland cement, but with a reduced CO 2 footprint. The materials are produced by hydrothermal processing of SiO 2 and Ca ( OH ) 2 , giving rise to calcium silicate hydrates, followed by mechanical activation of the latter via cogrinding with various siliceous materials. Thus, the chemical composition in terms of C/S ratio could be adjusted over a broad range (1–3). In this study the synthesis of a previously unknown cementitious material produced via the combination of mechanical activation in a laboratory mill and thermal treatment of a mixture of quartz and hydrothermally synthesized calcium silicate hydrates: α- Ca 2 [ HSiO 4 ]( OH ) (α- C 2 SH ) and Ca 6 [ Si 2 O 7 ]( OH ) 6 (jaffeite) are reported. It forms independently of the type of mill used (eccentric vibrating mill, vibration grinding mill) after thermal treatment of the ground materials at 360°C–420°C. The new material is X-ray amorphous and possesses a CaO / SiO 2 ratio of 2. A characteristic feature in regards to the silicate anionic structure is the increased silicate polymerization (up to 27% Si 2 O 7 dimers) as revealed by the trimethylsilylation method. Infrared (IR) spectra show a very broad absorption band centered at about 935 cm −1 . Another characteristic feature is the presence of ~2.5 wt% H 2 O as shown by thermogravimetry (TG) coupled with IR spectroscopy. As this water is bound mostly as hydroxyl to Ca, we refer to this new cementitious material as calcium-oxide–hydroxide–silicate ( C – CH – S ). Calorimetric measurements point to a very high hydraulic reactivity which is beyond that for typical C 2 S materials. The influence of the type of grinding on the thermal behavior of α- C 2 SH upon its transformation into water-free Ca 2 SiO 4 modifications is discussed.

Description: A series of Ce 3+ , Tb 3+ , Eu 3+ tri-doped Ba 2 Y (BO 3 ) 2 Cl red-emitting phosphor have been synthesized by solid-state method. The Ce 3+ → Tb 3+ → Eu 3+ energy-transfer scheme has been proposed to realize the sensitization of Eu 3+ ion emission by Ce 3+ ions. Following this energy-transfer model, near-UV convertible Eu 3+ -activated red phosphors have been obtained in Ba 2 Y (BO 3 ) 2 Cl : Ce 3+ , Tb 3+ , Eu 3+ phosphors. Energy transfers from Ce 3+ to Tb 3+ , and Tb 3+ to Eu 3+ , as well as corresponding energy-transfer efficiencies are investigated. The combination of narrow-line red emission and near-UV broadband excitation makes Ba 2 Y (BO 3 ) 2 Cl : Ce 3+ , Tb 3+ , Eu 3+ as a novel and efficient red phosphor for NUV LED applications.

Description: Computational simulations of glass extrusion are performed to quantify the effects of material behavior and slip at the die/glass interface on the die swell. Experimental data for three glass types are used to guide the computational study, which considers glass material to be viscous with and without shear thinning and viscoelastic using the Maxwell upper-convected model. The study starts with assuming no-slip at the glass/die interface to see if material behavior alone can explain the die swell results, and then considers slip using the Navier model where interface shear is directly proportional to the relative slip speed at the interface. Consistent with the possibility of slip and intended high viscosity applications, viscosity ranging from 10 7.4 –10 8.8  Pa·s was used. Based on optimization of the various input parameters required to achieve the measured die swell and ram force values, the study concludes that interface slip occurred as only extreme values of the shear thinning parameters provided an alternative.

Description: A bilayer concept was proposed to adjust the electrical properties of NTC thermistors. The conventional NTC material Ni 0.75 Mn 2.25 O 4 was chosen as the sensitive layer, and high conductive LaMnO 3 – Ni 0.75 Mn 2.25 O 4 composite was chosen as the support layer. The bilayer NTC thermistors were successfully fabricated by classical uniaxial pressing method. After cosintering at 1235°C for 4 h, the two layers adhered well to each other without any cracking or delamination. The resistance decreased linearly with the decrease in the thickness of Ni 0.75 Mn 2.25 O 4 layer, and the B values varied between 3868 and 3901 K. After annealing at 150°C in air for 500 h, the resistance shifts at 25°C were less than 1%, which mean that the bilayer NTC thermistors had high stability.

Description: We study the magnetic properties of Ho thin films with different crystallinity (either epitaxial or non-epitaxial) and investigate their proximity effects with Nb thin films. Magnetic measurements show that epitaxial Ho has large anisotropy in two different crystal directions in contrast to non-epitaxial Ho. Transport measurements show that the superconducting transition temperature ( T c ) of Nb thin films can be significantly suppressed at zero field by epitaxial Ho compared with non-epitaxial Ho. We also demonstrate a direct control over T c by changing the magnetic states of the epitaxial Ho layer, and attribute the strong proximity effects to exchange interaction.

Description: We report the physical behavior of self-biased multi-functional magneto-mechano-electric (MME) laminates simultaneously excited by magnetic and/or mechanical vibrations. The MME laminates composed of Ni and single crystal fiber composite exhibited strong ME coupling under H dc = 0 Oe at both low frequency and at resonance frequency. Depending on the magnetic field direction with respect to the crystal orientation, the energy harvester showed strong in-plane anisotropy in the output voltage and was found to generate open circuit output voltage of 20 V pp and power density of 59.78 mW/Oe 2  g 2  cm 3 under weak magnetic field of 1 Oe and mechanical vibration of 30 mg, at frequency of 21 Hz across 1 MΩ resistance.

Description: Easy sinterable Ti 3 SiC 2 powder was synthesized from a powder mixture with a molar ratio of 1.0 Ti , 0.3 Al , 1.2 Si , and 2.0 TiC by heating at 1200°C in the flowing Ar. Here, the Al powder acts as a deoxidation agent and provides a liquid phase for the reaction. The powder compacts subjected to pressureless sintering at 1300°C in Ar had a relative density up to 99%. The results of chemical analysis and the measured lattice constant suggest that the Al–Si liquid phase was formed at approximately 1200°C and that liquid-phase sintering was promoted by the 0.1 molar ratio of Al and the 0.2 molar ratio of Si remaining in excess. The three-point bending strength, fracture toughness, and electrical resistivity of the sintered samples were 380 MPa, 4.1 MPa m 1/2 , and 0.34μΩm, respectively.

Description: Dense nanocrystalline barium strontium titanate Ba 0.6 Sr 0.4 TiO 3 (BST) ceramics with an average grain size around 40 nm and very small dispersion were obtained by spark plasma sintering at 950°C and 1050°C starting from nonagglomerated nanopowders (~20 nm). The powders were synthesized by a modified “Organosol” process. X-ray diffraction (XRD) and dielectric measurements in the temperature range 173–313 K were used to investigate the evolution of crystal structure and the ferroelectric to paraelectric phase transformation behavior for the sintered BST ceramics with different grain sizes. The Curie temperature T C decreases, whereas the phase transition becomes diffuse for the particle size decreasing from about 190 to 40 nm with matching XRD and permittivity data. Even the ceramics with an average grain size as small as 40 nm show the transition into the ferroelectric state. The dielectric permittivity ε shows relatively good thermal stability over a wide temperature range. The dielectric losses are smaller than 2%–4% in the frequency range of 100 Hz–1 MHz and temperature interval 160–320 K. A decrease in the dielectric permittivity in nanocrystalline ceramics was observed compared to submicrometer-sized ceramics.

Description: Very few studies have been directed at the compositional dependence of the intrinsic photostability of the Ge x Se 1− x binary ChG films especially for the Ge-rich films with the mean coordination number (MCN) larger than 2.67. Here, by measuring the in-situ transmission changes, it shows that the photosensitivity (e.g., photobleaching, PB) of the Ge-rich films (as compared to the GeSe 2 film) is attenuated, in fact almost completely eliminated in the film with the largest MCN. A straightforward technique, in-situ Raman spectroscopy, is used to record the time-resolved intrinsic structural changes during the irradiation of the films. The result indicates a transition from PB towards photostability occurs at the critical composition of GeSe 2 corresponding to the structural phase transition. The stressed rigid structures of the Ge-rich films inhibit any significant photo-structural changes.

Description: Although chemically inert nanosize mineral fillers have been shown to modify early cement hydration kinetics, with the effects dependent upon usage rate, particle size, and dispersibility, the effects of such fillers on the “apparent activation energy” ( E a ) of cement has not been previously examined. Here, cement E a was calculated from isothermal calorimetry performed at different temperatures with two different types of fillers (i.e., titanium dioxide and limestone) using a linear method as well as a modified ASTM C1074 method. The use of both types of nanoparticles increased the rate of cement hydration as well as accelerated the reaction rate, due to heterogeneous nucleation effect, as previously demonstrated. E a increased in the presence of nanosized fillers, demonstrating an increased temperature sensitivity of the filler-cement composites relative to ordinary cement. These results show that chemically inert nanoparticles behave fundamentally differently compared with supplementary cementitious materials such as fly ash and silica fume which instead decrease temperature sensitivity. The increased temperature sensitivity could thus be used to modify and optimize the reaction mechanism and kinetics of cement hydration, especially to increase the rate of cement hydration, to decrease setting time, and to achieve faster strength gain accounting for higher or lower temperatures during curing.

Description: The growing demand of reliable high-performance membrane materials for separation processes requires new simple, straightforward, environmental friendly, sustainable approaches for membrane fabrication. In this study, we present an environmentally friendly gel-casting, one-pot process based on ionotropic-gelation for obtaining alumina membranes. A slurry of alumina particles and the biopolymer alginate, which acts in combination with calcium iodate like a resin, was gelled in a controllable temperature dependent manner. Alumina membranes are obtained by three different shaping routes (extrusion, free-forming, casting). The suitability of extruded capillaries in a polymer-ceramic hybrid state (green body) and after sintering (1150°C for 2 h) for potential application in micro- and ultrafiltration is evaluated by monitoring the chemical and mechanical stability, permeability and separation behavior. Varying the initial alumina particle size from 200 to 900 nm, membranes with a narrow pore size distribution, predictable and tunable average pore diameters from 70 up to 480 nm and a constant open porosity of ~40%, are obtained. The permeability behavior is tested with fluorescence labeled submicron- and nano-particles. Our novel colloidal processing route represents a very versatile tool for designing and manufacturing ceramic membranes with complex shapes for micro- (〉0.1 μm) and ultrafiltration (0.1–0.01 μm).

Description: Amorphous thin films of Ti 1− y Si y (N,O) with y  ≥ 0.38 were prepared by reactive sputter deposition in a nitrogen atmosphere. Thermal annealing of the films in an ammonia flow above 800°C yielded Si (N,O) amorphous thin films dispersed with precipitated TiN nanosized particles. The film color changed with Si content y and the annealing conditions, from carrot orange to cream yellow in the as-deposited films due to their oxynitride nature, and from dark green to canary yellow and from iron blue to horizon blue at respective annealing temperatures of 800°C and 900°C due to metallic nature of the TiN nanosized particles precipitated in the annealing.

Description: A series of phosphors Ca 12(0.97− x ) Al 14 O 32 F 2 : 0.03 Ce 3+ , x Tb 3+ have been prepared by a hightemperature solid-state reaction using boric acid as flux. These oxyfluorides crystallize in cubic structure, space group. Under the near ultraviolet excitation within wavelength range 310–390 nm, Ca 12(0.97− x ) Al 14 O 32 F 2 : 0.03 Ce 3+ , x Tb 3+ phosphors exhibit an intense emission covering a broad band of 370–500 nm derived from the 5 d →4 f transitions of Ce 3+ and a characteristic emission at 544 nm of Tb 3+ . The emission can be tuned from blue to green by altering the relative ratio of Ce 3+ to Tb 3+ in the composition. The energy-transfer mechanism from Ce 3+ to Tb 3+ is investigated based on the site occupancy of the luminescence center in the crystal structure of the Ca 12 Al 14 O 32 F 2 host. More importantly, when a certain amount of boric acid is added as flux in the synthesis, the fluorescence intensity of the phosphors increases about 65%. Because of its broad excitation and efficiently tunable blue to green luminescence, the Ca 12(0.97− x ) Al 14 O 32 F 2 : 0.03 Ce 3+ , x Tb 3+ phosphors may find promising application as a near UV-convertible phosphor for white-light-emitting diodes.

Description: Ti , TiC , Al and AlN powders were mixed to synthesize Ti 2 Al ( C x N y ) ( x  +  y  〈 1) solid solutions, Ti 2 AlC x ( x  〈 1) and Ti 2 AlN -related end-members by hot isostatic pressing at 1400°C/80 MPa for 4 h. For the pure carbides, it is demonstrated that single-phased samples can only be obtained when about 15% of substoichiometry on the carbon site is applied. Such a result likely implies that Ti 2 AlC x can only exist in a narrow range of carbon composition. Ti 2 AlN nitride can be synthesized with y  = 1. Assuming that vacancy content varies linearly from 0 to 0.15 going from Ti 2 AlN to Ti 2 AlC 0.85 in the solid solutions, element concentrations have been calculated to synthesize different solid solutions. Thus, it is demonstrated that single-phased and fully dense Ti 2 Al ( C 0.23 N 0.71 ), Ti 2 Al ( C 0.45 N 0.45 ), and Ti 2 Al ( C 0.66 N 0.22 ) carbonitrides can be synthesized.

Description: The dielectric and electromechanical properties of 0.75 Bi 1/2 Na 1/2 TiO 3 –0.25 SrTiO 3 (25 ST ) as a function of temperature and frequency were studied. It is shown that the 25 ST is a relaxor ferroelectric as evidenced by the temperature-dependent dielectric relaxations with an incipient piezoelectricity featured by the presence of a reversible electric-field-induced phase transformation at room temperature. The transition occurs on a broad electric field strength range depending on field amplitude and frequency. It is also accompanied by a huge strain that is attributed to repetitive poling and depoling originating due to the reversibility of the phase transition. The 25 ST makes an attractive lead-free candidate for stack actuators as it presents a high normalized d 33 * of ~600 pm/V at a low electric field of 4 kV/mm for frequencies ranging from 0.1 up to 100 Hz.

Description: Mullite ceramics were fabricated with fly ash, clay, and Al 2 O 3 as raw materials. The effects of Al 2 O 3 content, the sintering temperature and the pickling process on the crystalline phases, sintering characteristics and microstructures were studied. With more addition amount of Al 2 O 3 and higher sintering temperature, the peak intensity of the mullite crystalline phase increased. By pickling process, mullite instead of anorthite became the main phase with little corundum. Moreover, the required sintering temperature had reduced to 1300°C and the Al 2 O 3 content also decreased to 30 wt%. The pickling process also enlarged the sintering range of the green bodies.

Description: Laminated (SiC w +SiC p )/SiC ceramic composites were fabricated by tape casting and chemical vapor infiltration (CVI), and the effect of SiC particles on strengthening/toughening of the composites was investigated. When the SiC particle content was constant, the mechanical properties of (SiC w +SiC p )/SiC composites were increased with increasing SiC whisker content. When the SiC particle content was varied, the mechanical properties of (SiC w +SiC p )/SiC composites were dependent on SiC particle content. The addition of SiC particles can increase the strength of the matrix and the crack propagation resistance, the former increased the strength and the latter increased the toughness.

Description: Sodium-doped ZnO (ZnO:Na) nanowires were grown with a high-pressure pulsed-laser deposition process on silicon substrates using sputtered gold particles as catalysts. The introduction of sodium dopants into ZnO nanowires was confirmed by both X-ray diffraction spectrum and X-ray photoelectron spectroscopy. The morphology and microstructural changes in ZnO nanowires due to sodium doping were investigated with scanning electron microscope, high-resolution transmission electron microscope, and Raman spectrum. Detailed photoluminescence studies of ZnO:Na nanowires revealed characteristic sodium acceptor-related peaks, for example, neutral acceptor-bound exciton emission (A 0 X, 3.356 eV), free-to-neutral-acceptor emission (e, A 0 , 3.314 eV), and donor-to-acceptor pair emission (DAP, 3.241 eV). This indicated that sodium doping induces stable acceptor level with a binding energy of 133 meV in ZnO:Na nanowires.

Description: Multiferroic Bi 1− x La x FeO 3 [ BLFO ( x )] ceramics with x  = 0.10–0.50 and Mn-doped BLFO ( x  = 0.30) ceramics with different doping contents (0.1–1.0 mol%) were prepared by solid-state reaction method. They were crystallized in a perovskite phase with rhombohedral symmetry. In the BLFO ( x ) system, a composition ( x )-driven structural transformation ( R 3 c → C 222) was observed at x  = 0.30. The formation of Bi 2 Fe 4 O 9 impure phase was effectively suppressed with increasing the x value, and the rhombohedral distortion in the BLFO ceramics was decreased, leading to some Raman active modes disappeared. A significant red frequency shift (~13 cm −1 ) of the Raman mode of 232 cm −1 in the BLFO ceramics was observed, which strongly perceived a significant destabilization in the octahedral oxygen chains, and in turn affected the local FeO 6 octahedral environment. In the Mn-doped BLFO ( x  = 0.30) ceramics, the intensity of the Raman mode near 628 cm −1 was increased with increasing the Mn-doping content, which was resulted from an enhanced local Jahn–Teller distortions of the ( Mn,Fe ) O 6 octahedra. Electron microscopy images revealed some changes in the ceramic grain sizes and their morphologies in the Mn-doped samples at different contents. Wedge-shaped 71° ferroelectric domains with domain walls lying on the {110} planes were observed in the BLFO ( x  = 0.30) ceramics, whereas in the 1.0 mol% Mn-doped BLFO ( x  = 0.30) samples, 71° ferroelectric domains exhibited a parallel band-shaped morphology with average domain width of 95 nm. Dielectric studies revealed that high dielectric loss of the BLFO ( x  = 0.30) ceramics was drastically reduced from 0.8 to 0.01 (measured @ 10 4  Hz) via 1.0 mol% Mn-doping. The underlying mechanisms can be understood by a charge disproportion between the Mn 4+ and Fe 2+ in the Mn-doped samples, where a reaction of Mn 4+  + Fe 2+ →Mn 3+  + Fe 3+ is taken place, resulting in the reduction in the oxygen vacancies and a suppression of the electron hopping from Fe 3+ to Fe 2+ ions effectively.

Description: n -type binary compound semiconductors such as InN, InAs, or In 2 O 3 are especial because the branch-point energy or charge neutrality level lies within the conduction band. Their tendency to form a surface electron accumulation layer prevents the formation of rectifying Schottky contacts. Utilizing a reactive sputtering process in an oxygen-containing atmosphere, we demonstrate Schottky barrier diodes on indium oxide thin films with rectifying properties being sufficient for space charge layer spectroscopy. Conventional non-reactive sputtering resulted in ohmic contacts. We compare the rectification of Pt, Pd, and Au Schottky contacts on In 2 O 3 and discuss temperature-dependent current-voltage characteristics of Pt/In 2 O 3 in detail. The results substantiate the picture of oxygen vacancies being the source of electrons accumulating at the surface, however, the position of the charge neutrality level and/or the prediction of Schottky barrier heights from it are questioned.

Description: There is a growing requirement for high-temperature piezoelectric materials in the petrochemical, automotive, and aerospace industries. Here, the piezoelectric materials of Fe and Mn comodified 0.36 BiScO 3 –0.64 PbTiO 3 (BS-PTFMn) ceramics with high Curie temperature ( T c ), large mechanical quality factor ( Q m ), and reduced strain hysteresis were presented. XRD results revealed that all the BS- PTFMn ceramics have a pure perovskite structure with tetragonal symmetry, and the ratio of c/a is insensitive to the contents of Fe . With the modifications of Fe, the dielectric loss tanδ and strain hysteresis decrease clearly, while the mechanical quality factor improves significantly. The Curie temperature, piezoelectric constant, planar electromechanical coupling factor, dielectric loss, and mechanical quality factor of the BS- PTFMn with 3% Fe content are 492°C, 235 pC/N, 0.38, 0.6%, and 280, respectively. BS-PTFMn ceramics show 50°C higher T c than BS-PT morphotropic phase boundary composition. The figure of merit (product of Q m , and k ij ) of BS-PTFMn ceramics is about five times than that of pure BS-PT ceramics. Furthermore, for the BS- PTFMn ceramics with Fe content of 3 mol%, the high field strain coefficient value calculated from the electric-field-induced strain curves ( S max / E max ) is 320 pm/V, while the strain hysteresis (under 40 kV/cm) is reduced to one fifth that of unmodified BS-PT ceramics. Moreover, the temperature-dependent electromechanical coupling coefficient and dielectric constant are very stable in the temperature range from room temperature (RT) to 450°C. These results indicated that BS- PTFMn ceramics are promising for high-temperature piezoelectric applications.

Description: It has recently been shown that a three-parameter Weibull function with a large threshold strength of ≈2 GPa is needed to accurately describe the failure strength statistics of micromachined polycrystalline silicon samples. Here, we explore how to apply this function to predict strength size effects over a size range of 100. A two-parameter function is unsatisfactory in predicting the size effect. If a three-parameter Weibull fit to only the largest specimen is used, the prediction also does not satisfactorily agree with strength data in smaller specimens. The prediction is greatly improved if the two largest specimens, a factor of 10 different in size, are used for fitting. It is further demonstrated that the threshold strength depends on geometry in notched samples due to their large stress gradients.

Description: Improved performance by texturing has become attractive in the field of lead-free ferroelectrics, but the effect depends heavily on the degree of texture, type of preferred orientation, and whether the material is a rotator or extender ferroelectric. Here, we report on successful texturing of K 0.5 Na 0.5 NbO 3 (KNN) ceramics by alignment of needlelike KNN templates in a matrix of KNN powder using tape casting. Homotemplated grain growth of the needles was confirmed during sintering, resulting in a high degree of texture parallel to the tape casting direction (TCD) and the aligned needles. The texture significantly improved the piezoelectric response parallel to the tape cast direction, corresponding to the direction of the strongest 〈001〉 pc orientation, while the response normal to the tape cast plane was lower than for a nontextured KNN. In situ X-ray diffraction during electric field application revealed that non-180° domain reorientation was enhanced by an order of magnitude in the TCD, compared to the direction normal to the tape cast plane and in the nontextured ceramic. The effect of texture in KNN is discussed with respect to possible rotator ferroelectric properties of KNN.

Description: The stability of the field-induced ferroelectric (FE) state was studied in relaxor lead-free ceramics (1 −  y )[0.81 Bi 1/2 Na 1/2 TiO 3 –0.19 Bi 1/2 K 1/2 TiO 3 ]– y BiZn 1/2 Ti 1/2 O 3 both macroscopically and microscopically. A strong dc electric field results in the formation of a stable FE state with a large piezoelectric coefficient for compositions with a small amount of Bi ( Zn 1/2 Ti 1/2 ) O 3 , which are in the non-ergodic relaxor state at room temperature. Increasing temperature promotes ergodic relaxor behavior, which is accompanied by the rapid destabilization of the induced state, that is, small relaxation times. Based on the obtained data, it is proposed that the depolarization is a two-step process consisting of an initial realignment of the FE domains and their subsequent breakup into polar nanoregions. The ergodic relaxor behavior is also promoted by increasing the Bi ( Zn 1/2 Ti 1/2 ) O 3 content. The related charge disorder results in an enhancement of random electric fields and consequently a stable FE state cannot be induced even at room temperature.

Description: The hydraulic behavior of synthetic merwinite was investigated after activation by two different methods, aiming to enhance its hydraulic activity which is weak in water. Mechanical activation, by means of extensive milling in a bead mill, led to amorphization of merwinite and a decrease in its crystallite size. The combined effect of higher specific surface area and of structural disorder resulted in a notable increase of hydraulic reactivity. The hydraulic reactivity was substantially more pronounced with chemical activation compared to mechanical activation. Crystalline and amorphous C-S-H and brucite were the main hydration products formed in the hydrated, mechanically activated merwinite, whereas portlandite precipitated additionally in the case of chemical activation. Spectroscopic analyses of FTIR and 29 Si MAS NMR verified the C-S-H formation. TEM investigations revealed formation of Mg-low C-S-H gel around the merwinite particles. Both mechanically and chemically activated merwinite systems were capable of developing mechanical strength.

Description: A systematic first-principles investigation, by using the density functional formalism with the nonlocal B3LYP approximation including a long-range dispersion correction, has been performed to calculate the structural and electronic properties and phase transitions under pressure of the three phases of ZnS (cubic zinc blende, ZB, hexagonal wurtzite, W, and cubic rock salt, RS). Numerical and analytical fittings have been carried out to determine the equilibrium unit cell geometry and equation of state parameters for the ZnS phases. The band structures, energy gap, density of states, and vibrational frequencies and their pressure dependences are investigated. The present results illustrate that both phases, W and ZB, present very similar enthalpy and the RS phase becomes thermodynamically more stable than ZB and W structures at 15.0 and 15.5 GPa, respectively. These phase transitions are accompanied by an increase of the first shell coordination number of Zn atom and by a cell volume collapse of 13.9% and 14.3% for ZB and W phases, respectively. The atomic contributions of the conduction and valence bands, as well the binding energy for the Zn 3 d orbital have been obtained.

Description: Dielectric and piezoelectric properties of CuO -added KNbO 3 (KN) ceramics were investigated. The CuO reacted with the Nb 2 O 5 , formed a CuO – Nb 2 O 5 -related liquid phase during the sintering, and assisted the densification of the KN ceramics at low temperatures. Moreover, some of the Cu 2+ ions replaced the Nb 5+ ions in the matrix and behaved as a hardener. The dielectric and piezoelectric properties of the KN ceramics were considerably influenced by the relative density. The 1.0 mol% CuO -added KN ceramic sintered at 960°C for 1.0 h, which showed a maximum relative density, exhibited a high phase angle of 86.9°, P r of 14.8 μC/cm 2 , and E c of 1.8 kV/mm. This specimen also exhibited good dielectric and piezoelectric properties: ε T 33 / ε o of 364, d 33 of 122 pC/N, k p of 0.29, and Q m of 611.

Description: Single crystal 6 H – SiC nanoribbons were in situ synthesized in large scale on the as-prepared SiC – Si ceramic substrates via a facile heat-treatment approach using ferrocene as catalyst. The as-synthesized nanoribbons were up to several millimeters long, with widths of 200–300 nm and thicknesses of 20–80 nm. A novel combination growth mechanism of vapor–liquid–solid-based and vapor–solid-tip was proposed for the growth mode of the as-synthesized nanoribbons. This study provided not only a new method for synthesizing SiC nanoribbons but also a new insight into the growth mode for SiC nanoribbons.

Description: Fracture behavior of porous glass is investigated through a combined finite element–fracture mechanics approach. In contrast to earlier studies, here, simulations embody flaw size distributions in addition to pore–pore stress interactions and crack orientation along pore surfaces. Fracture strength of porous glass shows a steep decrease up to 20% porosity and then levels off due to interacting pores. Weibull modulus varies because of the decreased probability of interactions in microstructures containing less than 2% porosity or the smallest pore diameter =48  μm. Weibull modulus strongly depends on crack size distributions for porosity less than 2% and pore–pore stress interactions for porosity greater than 5%.

Description: The microstructures and mechanical properties of Clinocardium californiense shell were investigated in relation to the different parts of shell. It is found that the shell can be divided into three parts, that is, the dorsal side, body part, and marginal side based on the variation of microstructures along the longitudinal cross section. Specifically, all areas exhibit a cross-lamellar structure on the dorsal side, and a hierarchical structure comprising three layers including inner (with a cross-lamellar structure), middle (with a complex cross-lamellar structure), and outer (with a prismatic structure) layers was observed on the body part, whereas on the marginal side, the orientation of aragonite sheets shows an obvious deflection. The structural architecture, the dimensions of different-order lamellae in the same kind of structure and the orientation between the indenting direction and aragonite sheet all contribute to the unique mechanical properties of this shell. It is also found that a low value of the ratio of hardness-to-Young's modulus ( H / E ) corresponds to an improved indentation toughness. The middle layer with the densest and most complicated structure on the body part shows the lowest H / E ratio and the highest hardness and Young's modulus.

Description: In this study, a new process for additive manufacturing (AM) of dense and strong ceramic objects is described. The lithography-based ceramic manufacturing (LCM) technique is based on the selective curing of a photosensitive slurry by a dynamic mask exposure process. The LCM technique is able to produce strong, dense and accurate alumina ceramics without virtually any geometrical limitations. With over 99.3% of a theoretical alumina density, four-point bending strength of 427 MPa, and very smooth surfaces, the LCM process distinguishes itself from other AM techniques for ceramics and provides parts with very similar mechanical properties as conventionally formed alumina.

Description: This study investigated the cooling rate effects on the magnetic properties of NiCuZn ferrites. A copper-rich phase segregated near the grain boundaries during sintering was observed. The amount of copper-rich precipitates depends strongly on the cooling rate and decreases with decreasing cooling rate. The quenched sample exhibited superior initial permeability and DC-bias-superposition characteristics due to the highest saturation magnetization and a thick nonmagnetic second phase segregated at the grain boundaries. A NiCuZn ferrite with superior initial permeability and DC superposition characteristics can be obtained by controlling the cooling rate to adjust the copper-rich precipitate thickness at the grain boundaries.

Description: Tantalum carbides are commonly processed by hot pressing, canned hot-isostatic-pressing, or spark plasma sintering because of their high melting temperatures and low diffusivities. This paper reports processing of dense ζ- Ta 4 C 3− x by reaction sintering of a Ta and TaC powder mixture ( C / Ta atomic ratio = 0.66). ζ- Ta 4 C 3− x is of interest due to its rhombohedral (trigonal) crystal structure that may be characterized as a polytype with both face-centered-cubic and hexagonal-close-packed Ta stacking sequences interrupted by stacking faults and missing carbon layers. This structure leads to easy cleaving on the basal planes and high fracture toughness. A key step in processing is the hydrogenation of the Ta powder to produce β- TaH x , a hard and brittle phase that enables efficient comminution during milling and production of small, equiaxed Ta particles that can be packed to high green density with the TaC powder. Studies of phase evolution by quantitative X-ray diffraction during sintering revealed several intermediate reactions: (1) decomposition of β- TaH x to Ta ; (2) diffusion of C from γ- TaC to Ta leading to the formation of α- Ta 2 C y ' with the kinetics described by the Avrami equation with an exponent, n  =   0.5, and an activation energy of 219 kJ/mole; (3) equilibration of α- Ta 2 C y ' and γ- TaC 0.78 phases; and (4) formation of ζ- Ta 4 C 2.56 from the equilibrated α- Ta 2 C and γ- TaC 0.78 phases with the kinetics characterized by a higher Avrami exponent ( n  ≈   3) and higher activation energy (1007 kJ/mole). The sintered material contained ~0.86 weight fraction ζ- Ta 4 C 2.56 and ~0.14 weight fraction γ- TaC 0.78 phases. The microstructure showed evidence of nucleation and growth of the ζ- Ta 4 C 2.56 phase in both the α- Ta 2 C and γ- TaC 0.78 parent phases with distinct difference in the morphology due to the different number of variants of the habit plane.

Description: (1 −  x ) Ba 0.5 Sr 0.5 TiO 3 (BST)– x MgO composite ceramics have been prepared in situ by a citrate–nitrate combustion process, and their crystal structure and effective dielectric response have been investigated systematically. Results reveal that MgO particles homogeneously disperse in BST particles. Rietveld refinement of X-ray diffraction data shows that the amount of the incorporation of MgO into BST lattice is increased with increasing the MgO volume fraction ( ƒ M ). It is identified that the incorporation of Mg 2+ into B site gives rise to the formation of F centers in the composites. Related with the incorporation of Mg 2+ into BST lattice, the permittivity of BST in the composite is strongly dependent on ƒ M , which is defined by the relation . Also, the high percolation threshold of ƒ M  = 0.60 is observed, which is well in agreement with the theoretical predictions of the modified effective medium approximation coupled with the spherical inclusion model.

Description: Two kinds of 〈111〉-oriented β-SiC films with pyramidlike and needlelike morphologies were obtained by laser chemical vapor deposition. Their mean grain size (〈 d 〉) as a function of the distance from substrate ( h ) follows power laws of 〈 d 〉 ∝ h 0.62 and 〈 d 〉 ∝ h 0.71 , respectively. The planar defects in pyramidlike films were perpendicular to the growth direction, whereas those in needlelike β-SiC films inclined to growth direction, which can be annihilated with meeting of anti-couple defect. This self-vanish of defects would develop a new approach to fabricate high quality 〈111〉-oriented β-SiC.

Description: Dielectric properties of high-purity (4N degree) rutile TiO 2 ceramics were investigated over a wide temperature (100–1073 K) and frequency (20 Hz–10 MHz) ranges. X-ray photoemission spectroscopy measurement revealed the sample possesses mixed-valent states of Ti 3+ / Ti 4+ . Four thermally activated relaxations were observed. The lowest temperature relaxation (R1) features two Arrhenius segments with activation energy of 30 and 80 meV for the low- and high-temperature segments, respectively. This relaxation was argued to be a polaron relaxation due to electrons hopping between Ti 3+ and Ti 4+ ions. The second relaxation (R2) appears around room temperature showing activation energy of 0.68 eV is believed to be a Maxwell-Wagner relaxation. The high-temperature relaxations R3 and R4 with activation energy of 0.84 and 1.26 eV were ascribed to the conduction process due to the hopping motions of singly and doubly charged oxygen vacancies, respectively.

Description: The article presents the results of research of the electrical response on elastic impact excitation of heavy concrete samples under uniaxial compression. In this paper we recorded and analyzed electrical responses during uniaxial compression of concrete samples with a constant velocity. Studies have shown that in the process of uniaxial compression of concrete samples, the transformation of amplitude–frequency characteristics of the electrical response is observed. The stage of elastic deformation of concrete samples is characterized by a centershift of gravity of the spectrum of the electrical response towards lower frequencies. Dramatic centershift of gravity of the spectrum of the electrical response to the high frequency region characterizes the beginning of fracturing.

Description: The motivation of the presented research is based on the need for development of new methods and tools for adequate simulation of FACTS devices and HVDC systems as part of real electric power systems (EPS). The Research object: An alternative hybrid approach for synthesizing VSC-FACTS and -HVDC hybrid model is proposed. The results: the VSC- FACTS and -HVDC hybrid model is designed in accordance with the presented concepts of hybrid simulation. The developed model allows us to carry out adequate simulation in real time of all the processes in HVDC, FACTS devices and EPS as a whole without any decomposition and limitation on their duration, and also use the developed tool for effective solution of a design, operational and research tasks of EPS containing such devices.

Description: In this work the effect of substrate temperature on the structural parameters (sizes of coherent scattering region, values of microstresses), phase and chemical composition, surface morphology of Co films is revealed. Moreover, the correlation between structure, cobalt content and magnetic, electrical characteristics of Co films is presented. Co films were deposited on Si (100) substrates by chemical vapor deposition using the diiminate complex Co(N'acN'ac) 2 as a precursor. The sizes of coherent scattering region, values of microsresses and phase composition of Co films were determined by the X-ray diffraction analysis. The chemical composition was identified by the Energy-dispersive X-ray spectroscopy. The surface morphology of Co films was investigated by atomic-force microscope. Magnetic characteristics were measured by vibromagnetometer and the electrical resistivity was measured by four-probe dc method. It is found that the variation of deposition conditions allo...

Description: This article presents test results of enameled winding wires, characterizing an insulation electrical and mechanical strength. Standard and original test methods were used. Note that existing standard test methods do not estimate enamel insulation resistance to the electrical loads under winding operation of variable-speed drive. We show that estimation of wire corona resistance can be done by high frequency electrical impulse testing. Wire insulation plays the main role of reliability of insulation system.

Description: The problem of particle ignition coal-water fuel (WCF) has been solved numerically, located at a high flow environment. Two different approaches to describe the physics of the process have been applied. According to the results of numerical simulation of the effect of the scale has been set about ambient temperature, the particle size on the inertia of the studied processes. A comparison of ignition delay times has been obtained using both methods of describing heat and mass transfer processes preceding fire.

Description: The focus of this article is the working range of Fricke dosimeter and modified Fricke dosimeter. This study is motivated by two research questions: (1) Is it possible to use Fricke dosimeter or modified Fricke dosimeter as an instrument for dose measurements when absorbed dose is generated by pulse electron beam? (2) What limitations do these methods have? This article tells in detail about the solutions preparing and chemical analyses. It shows that modified Fricke dosimeter may be used for measurements of absorbed dose generated by pulse electron beam up to 11 kGy. And Fricke dosimeter leads to incorrect results when local dose in solution upper than 500 Gy.

Description: Behaviour of a liquid-type automatic balancing device is modeled in this paper. To perform mathematical research the authors use a rotor model which contains a ring functioning as a reservoir coupled to a rigid shaft being rotatable in bearings. An autobalancer with several reservoirs is used for the mathematical investigation. The article provides the layout of forces acting in a multi-reservoir balancing system. Data on the effect of various factors on balancing accuracy as well as the main calculation features of a multi-reservoir autobalancer are presented. The obtained modeling results indicate that autobalancing efficiency is enhanced by increasing the number of reservoirs. An increase in the number of reservoirs causes a decrease in a critical rotor speed.

Description: The results of industrial tests of gun drills with the diameter of 2.05 mm with carbide and with steel stems are given. It is shown that the gun drills with cemented carbide stem and especially AlTiN coating have a greater resistance and greater accuracy diametrical holes sizes in comparison to gun drill with steel stem.

Description: We obtained the contact pair copper–aluminum copper coating by using a magneto plasma accelerator. The process is realized during supersonic copper plasma jet flowing into the chamber filled with the air atmosphere. Copper jet is carried out of the accelerating channel towards the aluminum target. Plasma jet is generated by coaxial magnetoplasma accelerator (CMPA) based on copper electrode system. The CMPA is supplied from the pulsed capacitive energy storage with the maximum value of stored energy of 360 kJ. The obtained copper–aluminum contact pairs have been analyzed by X–ray diffractometry and Nano hardness tester. The copper coating on the aluminum surface is uniform with thickness about 100 gm. Also in this paper it is shown that transitional contact resistance of copper–aluminum contact pair is at 2,5 times less than a direct connection of copper and aluminum (test contact pair).

Description: In this paper the synthesis of ultra dispersed graphite-like structures doped with nitrogen by using a magneto plasma accelerator is shown. The synthesis of such structures is realized during supersonic carbon plasma jet flowing into the chamber filled with the nitrogen atmosphere. Plasma jet is generated by coaxial magneto plasma accelerator (CMPA) based on graphite electrode system. The CMPA is supplied from the pulsed capacitive energy storage with the maximum value of stored energy of 360 kJ. Electrical and energy parameters of plasma flow are recorded during experiment. According to X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) methods obtained particles with well seen triangle sectors are graphite-like carbon structures doped with nitrogen atoms. This is confirmed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy analyses in which carbon- nitrogen bonding configurations have been identified.

Description: The creation of regenerative materials remains a problem for rehabilitation medicine, but the obtaining of initial substances that can cause bone tissue regeneration, possessing biological activity and creation on their basis of composite materials with specified physical and mechanical characteristics is an important scientific problem. This paper presents the investigation of physical-chemical and biological properties of bioresorbable composite material that can restore their own bone tissue of the body.

Description: Magnetometers are used for measuring the characteristics of magnetic field and magnetic properties of the material. A changeable source of a homogeneous magnetic field is necessary for verification and calibration of magnetometers. Often the Helmholtz coil is used for generating magnetic homogeneous field, but homogeneous field area generated by Helmholtz coils is confined to a small volume in the center of the coils. The paper describes result of modeling a coils system to generate a homogeneous magnetic field with increased volume in comparison to Helmholtz coils.