Materials Engineering

In the present study, pure, Co, Gd, and Co/Gd di-doped ZnO nanoparticles were synthesized via the co-precipitation synthesis route. The prepared samples were characterized through different techniques such as the X-ray diffraction method (XRD), scanning electron microscopy (SEM), UV-Vis spectroscopy, photoluminescence (PL)spectroscopy, and an impedance analyzer and vibrating sample magnetometer (VSM). The XRD pattern shows ZnO’s wurtzite hexagonal crystal structure; moreover, the shifting of characteristic peaks toward the lower angle indicates the inclusion of Co and Co/Gd in the ZnO host lattice. SEM micrographs show various morphologies such as rods, the agglomeration of particles, and spherical nanoparticles. The UV-Vis spectroscopy reveals that the absorption increased in the visible region and there was a substantial redshift for the doped samples. The bandgap decreased from 3.34 to 3.18 eV for the doped samples. The PL spectra show near-edge and inter-band transitions; the or...

A systematic investigation of the changes in structural and optical properties of a semi-insulating GaAs (001) wafer under high-energy electron irradiation is presented in this study. GaAs wafers were exposed to high-energy electron beams under different energies of 10, 15, and 20 MeV for absorbed doses ranging from 0–2.0 MGy. The study showed high-energy electron bombardments caused roughening on the surface of the irradiated GaAs samples. At the maximum delivered energy of 20 MeV electrons, the observed root mean square (RMS) roughness increased from 5.993 (0.0 MGy) to 14.944 nm (2.0 MGy). The increased RMS roughness with radiation doses was consistent with an increased hole size of incident electrons on the GaAs surface from 0.015 (0.5 MGy) to 0.066 nm (2.0 MGy) at 20 MeV electrons. Interestingly, roughness on the surface of irradiated GaAs samples affected an increase in material wettability. The study also observed the changes in bandgap energy of GaAs samples after irradiation...

The irregular surface roughness morphology due to ultrasonic method was used approach for increasing the high surface area of substrate and catalyst. The purpose of this paper is to show the ultrasonic and nickel electroplating methods for NiO automotive catalyst development on FeCrAl substrate. The process began with pretreatment of FeCrAl using SiC and/or Al2O3 solution agitating by ultrasonic and followed with nickel electroplating. The oxidation test was conducted for developing the NiO. The physical morphology structure of the presence NiO on the FeCrAl substrate was analyzed using scanning electron microscope (SEM) in combination with energy dispersive X-ray spectroscopy (EDS). The cross sectional observation show the NiO catalyst completely existed on the FeCrAl. The ultrasonic method increases the irregular surface roughness morphology on FeCrAl substrate that influenced the homogeneous and stability of nickel electroplating and NiO surface area development.

Viscosity modifiers (VMs) of three different kinds viz. polymethacrylate (PMA), olefin copolymer (OCP) and hydrogenated styrene-isoprene (SIP) polymer has been investigated for their anti wear (AW) properties and degradative stability towards mechanical shearing in two base stocks in the concentration range, 1.0 to 6.0% (wt/wt). The shear stability index (SSI) was substantially influenced by the chemistry and concentration of the VMs as well as by the viscosity of the base stock. Anti wear performance was also influenced by the conditions chosen in the four ball wear test machine. All the VMs showed a saturation of SSI values beyond 4% concentration in both the base stocks, while the value of percent shear loss (PSL) showed a gradual increase with the rising VM concentration.

The effect of α-Al2O3 nanoparticles (up to 5 wt.%) on the physical, mechanical, and thermal properties, as well as on the microstructural evolution of a dense magnesia refractory is studied. Sintering temperatures at 1300, 1500, and 1600 °C are used. The physical properties of interest were bulk density and apparent porosity, which were evaluated by the Archimedes method. Thermal properties were examined by differential scanning calorimetry. The mechanical behavior was studied by cold crushing strength and microhardness tests. Finally, the microstructure and mineralogical qualitative characteristics were studied by scanning electron microscopy and X-ray diffraction, respectively. Increasing the sintering temperature resulted in improved density and reduced apparent porosity. However, as the α-Al2O3 nanoparticle content increased, the density and microhardness decreased. Microstructural observations showed that the presence of α-Al2O3 nanoparticles in the magnesia matrix induced the ...

Background. Both 1,2,3- and 1,2,4-triazoles are nowadays incorporated in numerous antibacterial pharmaceutical formulations.Aim. Our study aimed to prepare three substituted 1,2,4-triazoles and to evaluate their antibacterial properties.Materials and Methods. One disubstituted and two trisubstituted 1,2,4-triazoles were prepared and characterised by physical and spectroscopic properties (melting point, FTIR, NMR, and GC-MS). The antibacterial properties were studied against three bacterial strains:Staphylococcus aureus(ATCC 25923),Escherichia coli(ATCC 25922), andPseudomonas aeruginosa(ATCC 27853), by the agar disk diffusion method and the dilution method with MIC (minimal inhibitory concentration) determination.Results. The spectroscopic characterization of compounds and the working protocol for the synthesis of the triazolic derivatives are described. The compounds were obtained with 15–43% yields and with high purities, confirmed by the NMR analysis. The evaluation of biological ...

膠體粒子(colloid)在溶液中的穩 定性一直是食品工業與清淨程序操作中 的重要影響因素。近年來，由於耐米粒子 (nano-sized particle)在各式新興工業 的潛在應用價值，其合成與製造已在學術 領域中引起廣泛的研究興趣。然而在其製 造程序中，耐米粒子懸浮液的熱力學或動 力學穩定性更是扮演決定性的角色。 一般而言，耐米粒子之間具有長距 離的凡得瓦引力，它會導致粒子之間凝絮 而產生不穩定的沉降現象。本研究之目的 在探討添加高分子至耐米粒子懸浮液中 對其穩定性之影響。高分子種類包含非吸 附性高分子(nonadsorbing polymer)、吸附性高分子、雙塊區間共聚合高分子(di-block copolymer)。我們採用類似分子模擬的蒙地卡羅 法(Monte Carlo method)，從微觀層次來 研究(a)耐米粒子之間，及(b)耐米粒子與 高分子之間的作用和結構;該系統穩定性 可反應於徑向分佈函數(radial dis- tribution function)。我們將比較未添 加高分子、添加非吸附性高分子、吸附性 高分子、及共聚合高分子的徑向分佈函 數。另外，我們也將討論耐米粒子濃度、 高分子濃度、及其鏈長對懸浮液穩定性的影響。The addition of polymers to a col-loidal dispersion creates a change in the phase behavior and the local structure of the colloidal component. This effect is of great importance in dealing with treatment of colloidal suspensions. For example, it has been known that upon adding enough nonadsorbing polymer to the system, the colloidal particles tend to cluster. The presence of the polymers induces an en-tropic- originated attraction between the colloidal particles...

本文是以蒙地卡羅法研究幾近無熱效 應高分子溶液的相平衡行為。我們發現當 溫度提高時，高分子粒子與溶劑粒子間的 自由體積差異隨之加大。在到達所謂的下 臨界溫度時，因為商的效應，使得溶劑粒 子排斥高分子，而造成相分離的現象。我 們也發現較長的高分子因為它們與溶劑粒 子的自由體積差異較大，所以相分離的起 始溫度亦較低。對於等長的高分子且溫度 相同的情況下，壓力的增加會減少高分子 與溶劑粒子間自由體積的差異，故相分離 現象會較不明顯。我們亦將模擬結果與 SAFT 理論比較，發現SAFT 理論在對於高 分子溶液定性的描繪上，有很好的預測性，但在定量上尚無法有精確的結果。The Phase equilibrium behaviors of a nearly athermal polymer/solvent solution are studied by using the Monte Carlo method. It is found that as temperature increases, the free volume differences between solvent molecules and polymer chains become larger. To a certain temperature, which is the so called Lower Critical Solution Temperature (LCST) the entropic effect dominates over the enthalpic effect, thus phase separation occurs. We have also found that phase separation takes place at lower temperature for longer chain polymer solution. By comparing the phase envelope of polymer of the same chain length but at different pressure, LCST increases as pressure increases. We have also applied the SAFT theory to...

We report here the successful shape-controlled synthesis of dielectric spinel-type ZnCr2O4 nanoparticles by using a simple sol-gel auto-combustion method followed by successive heat treatment steps of the resulting powders at temperatures from 500 to 900 °C and from 5 to 11 h, in air. A systematic study of the dependence of the morphology of the nanoparticles on the annealing time and temperature was performed by using field effect scanning electron microscopy (FE-SEM), powder X-ray diffraction (PXRD) and structure refinement by the Rietveld method, dynamic lattice analysis and broadband dielectric spectrometry, respectively. It was observed for the first time that when the aerobic post-synthesis heat treatment temperature increases progressively from 500 to 900 °C, the ZnCr2O4 nanoparticles: (i) increase in size from 10 to 350 nm and (ii) develop well-defined facets, changing their shape from shapeless to truncated octahedrons and eventually pseudo-octahedra. The samples were found...

In bone tissue engineering, Hydroxyapatite (HA) is extensively used in medical applications as an implant material to enhance bone growth formation or as drug release vehicle because of its resemblance to the components of human bones and for its excellent biocompatibility. The porous structure is generally used as a scaffolding material. Many techniqueshave been applied to fabricate HA porous scaffolds. In this work, polymeric sponge technique was employed in the preparation of HA scaffold, using gum Ghatti, a natural binder obtained from the barks of Anogeissuslatifolia species. The influence of binder concentration for various sintering temperature 1100 o C,1150 o C and 1200 o C was estimated. The Hydroxyapatite starting powder and Hydroxyapatite scaffold were characterized for phase purity, structural analysis, porosity measurements and mechanical properties. It is possible to produce Hydroxyapatite scaffolds with highly inter connecting macro ranging from 500 to 1000 μm and mic...