ALBERT

Description:    Solution precursors have been injected into the plasma gases to produce finely structured ceramic coatings with nano- and sub-micrometric features. The trajectory history and heat and mass transfer within individual solution droplets play a very important role in determining the coating microstructure. A mathematical model is developed to analyse the thermal behavior of individual precursor droplets travelling in the high temperature plasma jet. This model involves the motion and evaporation of the precursor droplet in a DC plasma jet and the heat and mass transfer within the evaporating droplet. The influence of Stefan flow, as well as the variable thermo-physical properties of the solution and the plasma gas, is considered. The internal circulation due to the relative velocity between the droplet and the plasma jet, which may be approximated by the Hill vortex, is considered as well. The trajectory, temporal droplet surface temperature, and radius variation are predicted. The temporal temperature and concentration distributions within the evaporating droplet are presented for different injection parameters. Content Type Journal Article Category Peer-Reviewed Pages 1-13 DOI 10.1007/s11666-011-9726-x Authors Yanguang Shan, School of Energy and Power Engineering, University of Shanghai for Science and Technology, Shanghai, China Yuan Hu, School of Energy and Power Engineering, University of Shanghai for Science and Technology, Shanghai, China Journal Journal of Thermal Spray Technology Online ISSN 1544-1016 Print ISSN 1059-9630

Description:    A linear stability analysis was performed in order to study the onset of thermal convection in the presence of a strong viscosity variation, with a special emphasis on the condition for the stagnant-lid (ST) convection where a convection takes place only in a sublayer beneath a highly viscous lid of cold fluid. We consider the temporal evolution (growth or decay) of an infinitesimal perturbation superimposed to a Boussinesq fluid with an infinite Prandtl number which is in a static (motionless) and conductive state in a basally heated planar layer or spherical shell. The viscosity of the fluid is assumed to be exponentially dependent on temperature. The linearized equations for conservations of mass, momentum, and internal (thermal) energy are numerically solved for the critical Rayleigh number, Ra c , as well as the radial profiles of eigenfunctions for infinitesimal perturbations. The above calculations are repeatedly carried out by systematically varying (i) the magnitude of the temperature dependence of viscosity, E , and (ii) the ratio of the inner and outer radii of the spherical shell, γ . A careful analysis of the vertical structure of incipient flows demonstrated that the dominance of the ST convection can be quantitatively identified by the vertical profile of Δ h (a measure of conversion between horizontal and vertical flows), regardless of the model geometries. We also found that, in the spherical shell relevant to the Earth’s mantle ( γ  = 0.55), the transition into ST convection takes place at the viscosity contrast across the layer r h @ 10 4 . Taken together with the fact that the threshold value of r η falls in the range of r η for a so-called sluggish-lid convection, our finding suggests that the ST-mode of convection with horizontally elongated convection cells is likely to arise in the Earth’s mantle solely from the temperature-dependent viscosity. Content Type Journal Article Category Original Article Pages 1-20 DOI 10.1007/s00162-011-0250-x Authors Masanori Kameyama, Geodynamics Research Center, Ehime University, Matsuyama, 790-8577 Japan Hiroki Ichikawa, Geodynamics Research Center, Ehime University, Matsuyama, 790-8577 Japan Arata Miyauchi, Geodynamics Research Center, Ehime University, Matsuyama, 790-8577 Japan Journal Theoretical and Computational Fluid Dynamics Online ISSN 1432-2250 Print ISSN 0935-4964

Description:    A unified generalized thermoelasticity solution for the transient thermal shock problem in the context of three different generalized theories of the coupled thermoelasticity, namely: the extended thermoelasticity, the temperature-rate-dependent thermoelasticity and the thermoelasticity without energy dissipation is proposed in this paper. First, a unified form of the governing equations is presented by introducing the unifier parameters. Second, the unified equations are derived for the thermoelastic problem of the isotropic and homogeneous materials subjected to a transient thermal shock. The Laplace transform and inverse transform are used to solve these equations, and the unified analytical solutions in the transform domain and the short-time approximated solutions in the time domain of displacement, temperature and stresses are obtained. Finally, the numerical results for copper material are displayed in graphical forms to compare the characteristic features of the above three generalized theories for dealing with the transient thermal shock problem. Content Type Journal Article Pages 1-9 DOI 10.1007/s00707-011-0597-5 Authors Ying-Ze Wang, Energy and Power Engineering Department, Jiangsu University, Zhenjiang, 212013 China Xiao-Bing Zhang, Energy and Power Engineering Department, Nanjing University of Science and Technology, Nanjing, 210094 China Xin-Nan Song, Energy and Power Engineering Department, Jiangsu University, Zhenjiang, 212013 China Journal Acta Mechanica Online ISSN 1619-6937 Print ISSN 0001-5970

Description: Based on effective medium theory, the Bruggeman equation and Maxwell-Wagner (M-W) equation were applied to extract the permittivity of SrTiO 3 and BaTiO 3 powders in slurries with various solids loadings. It was found that the margin of error for the calculated permittivity broadened with decreasing solids loading and increasing powder permittivity. However, the margin of error for permittivity calculated from the Bruggeman equation is consistently smaller than that from the M-W equation. This smaller margin of error resulted in the applicability of the Bruggeman equation to extract the permittivity for all of the slurries in this work, in contrast to the M-W equation which is restricted to dilute SrTiO 3 slurries. Therefore, for slurries of powders with high permittivity (e.g., BaTiO 3 ) or slurries with high solid loading the Bruggeman equation is necessary instead of the M-W equation.

Description: A new method was developed to fully consolidate binderless tungsten carbide and diamond powders by means of spark plasma sintering (SPS) in current-control mode (CCm). Below 900°C, the 2 cm diameter sample was slowly heated by a dc current of 1000 A. Above 900°C the imposed current was suddenly raised to 4000 A. The combination of the relatively high heating rate of 2000°C/min and the relatively short holding time of 1.5 min (above 1300°C) was successful to fabricate fully dense binderless WC/diamond composite. No graphitization of diamond was detected after ultrafast sintering as confirmed by optical and SEM microstructure observations, XRD and Raman analysis. The sample showed very high wear resistance in comparison to fully dense monolithic binderless WC compacts. The developed method, unlike previously published works, did not require any diamond coating to prevent diamond graphitization.

Description:    The advantage of combining cryomilling and pulsed gas dynamic spraying (PGDS) processes in order to produce a nanostructured, dense and wear resistant coating was demonstrated. Cryomilling was successfully employed to synthesize particulate B 4 C reinforced Al matrix nanocomposite feedstock powders, while the PGDS process shows the ability of preserving the microstructure of the starting material. In this study, nanocrystalline and conventional Al5356 + 20%B 4 C composite as well as the unreinforced Al5356 alloy feedstock powders were used. The influence of the nature of the feedstock material on the microstructure and mechanical properties of the coatings was studied. The PGDS process provides an opportunity to preserve the phase of the starting material, to produce hard and dense coatings with good cohesion between deformed particles and good adhesion to the substrate. High dry sliding wear resistance was observed when cryomilled composite material was used. Content Type Journal Article Category Peer-Reviewed Pages 1-11 DOI 10.1007/s11666-011-9727-9 Authors M. Yandouzi, Mechanical Engineering Department, University of Ottawa, Ottawa, ON K1N-6N5, Canada H. Bu, Materials Science & Engineering School, Shanghai Jiao Tong University, Shanghai, 200240 People’s Republic of China M. Brochu, Mining & Materials Engineering Department, McGill University, Montreal, QC H3A 2B2, Canada B. Jodoin, Mechanical Engineering Department, University of Ottawa, Ottawa, ON K1N-6N5, Canada Journal Journal of Thermal Spray Technology Online ISSN 1544-1016 Print ISSN 1059-9630

Description:    Repartitioning of co-solvents between particles of latex emulsions was investigated by means of a fluorescence method based on the detection of the amount of co-solvent via the solvatochromic shift of the emission maximum of a fluorescent probe, copolymerized at a low concentration. Complete repartitioning of co-solvents between particles of latex materials with a low T g (ca. 25 °C) occurred within minutes. For a hydrophilic latex with a T g of 68 °C, equilibration was achieved within an hour. Repartitioning was faster for more hydrophobic co-solvents. For a hydrophobic latex of similar T g , co-solvent repartitioning took place on the same time scale, but complete equilibration was not reached. Possibly, there is an additional slow component in the repartitioning, or the prolonged presence of co-solvent causes a structural change in the latex particles that affects the outcome of the experiment. Content Type Journal Article Category Original Contribution Pages 1-12 DOI 10.1007/s00396-011-2575-9 Authors Tanzeela N. Raja, University of Amsterdam, P.O. Box 94157, 1090 GD Amsterdam, The Netherlands Albert M. Brouwer, University of Amsterdam, P.O. Box 94157, 1090 GD Amsterdam, The Netherlands Tijs Nabuurs, DSM Coating Resins, Sluisweg 12, 5145 PE Waalwijk, The Netherlands Ronald Tennebroek, DSM Coating Resins, Sluisweg 12, 5145 PE Waalwijk, The Netherlands Journal Colloid & Polymer Science Online ISSN 1435-1536 Print ISSN 0303-402X

Description:    Micro- and nanospheres with superamphiphobic surfaces were prepared by a simple method that employed the conventional dispersion polymerization of perfluoroalkyl methacrylates in methanol. The polymerizations of 2,2,2-trifluoroethyl methacrylate (TFMA) produced microspheres with an average 4.12-μm diameter, while that of 2-(perfluorooctyl)ethyl methacrylate (POMA) provided nanospheres with a 679-nm diameter. An X-ray photoelectron spectroscopy analysis revealed that the fluorine atoms were highly concentrated on the top of the sphere surfaces. It was found that the surface coated with the spheres had a superamphiphobicity. The water contact angles were 150° for the PTFMA microspheres and 173° for the PPOMA nanospheres, while the diiodomethane contact angles were 159° for the microspheres and 160° for the nanospheres. The synergistic effect of the spherical structure and the high concentration of fluorine on the top of the surface produced the superamphiphobicity. Content Type Journal Article Category Original Contribution Pages 1-6 DOI 10.1007/s00396-011-2570-1 Authors Eri Yoshida, Department of Environmental and Life Sciences, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 441-8580, Japan Journal Colloid & Polymer Science Online ISSN 1435-1536 Print ISSN 0303-402X

Description:    The precipitation polymerizations of N - tert -butylacrylamide (N t BAM) in water are demonstrated; for example, the polymerization with potassium peroxodisulfate using a 15 g L −1 (118 mmol L −1 ) concentration of N t BAM in the feed ([N t BAM] 0 ) was performed at 70 °C for 12 h, quantitatively producing poly( N - tert -butylacrylamide) particles with a number-average diameter ( d n ) of 203 nm and a coefficient of variation ( C v ) of 4.7%. The particle sizes were controlled in the d n s range between 75 and 494 nm by changing the monomer feeds or adding an electrolyte such as NaCl. The solid contents in the resulting aqueous latex solutions ranged from 0.1 to 1.5%, whereas it increased to 4.8% by applying a “shot-growth” technique. The polymerization in water under a somewhat unique condition is described, which was started from a heterogeneous system due to the presence of significantly large amounts of monomers ([N t BAM] 0  = 50 g L −1 ). This also provided monodisperse latexes with the d n of 370 nm in 96% yield, in which the solid content reached 4.9%. Content Type Journal Article Category Original Contribution Pages 1-6 DOI 10.1007/s00396-011-2571-0 Authors Atsushi Narumi, Department of Polymer Science and Engineering, Graduate School of Science and Engineering, Yamagata University, Jonan 4-3-16, Yonezawa, 992-8510 Japan Yudai Kimura, Department of Polymer Science and Engineering, Graduate School of Science and Engineering, Yamagata University, Jonan 4-3-16, Yonezawa, 992-8510 Japan Seigou Kawaguchi, Department of Polymer Science and Engineering, Graduate School of Science and Engineering, Yamagata University, Jonan 4-3-16, Yonezawa, 992-8510 Japan Journal Colloid & Polymer Science Online ISSN 1435-1536 Print ISSN 0303-402X

Description:    The effect of rotating magnetic field (RMF) on macro/microsegregation of solute elements is investigated experimentally, and a comprehensive three-dimensional mathematical model is built, and the finite element package ANSYS ® is employed to calculate the distribution of temperature and liquid fraction along the radial direction in horizontal continuous casting of CuNi10Fe1Mn alloy hollow billet. The results show that RMF makes the temperature field and liquid fraction uniform. The original inhomogeneous columnar grain macrostructure turns into homogeneous equiaxed grain structure, and the macro/microsegregation of Ni, Fe, and Mn elements are restrained effectively with the application of RMF. Moreover, the action mechanism of RMF is discussed to explain its effect on improving the distribution of solute elements. Content Type Journal Article Pages 1-8 DOI 10.1007/s11665-011-0110-2 Authors Zhiming Yan, School of Materials Science and Engineering, Dalian Jiaotong University, Dalian, 116028 China Wenzhong Jin, Department of Mechanical and Electronic Engineering, Luoyang Institute of Science and Technology, Luoyang, 471023 China Tingju Li, School of Materials Science and Engineering, Dalian University of Technology, Dalian, 116085 China Journal Journal of Materials Engineering and Performance Online ISSN 1544-1024 Print ISSN 1059-9495