Advanced Materials Research Vol. 620

Abstract: Zinc oxides nanowires (ZnO NWs) were successfully synthesized on bare silicon substrates using Chemical vapour deposition (CVD) method without foreign catalyst. The ZnO NWs had good crystal quality as they exhibited a strong UV emission (373 nm) corresponding to the free exciton emission and a weak green arising from defect-related emission in PL measurement. Measurement of low temperature photoluminescence spectra show a peak of free exciton and defect bound excitons. The growth of these catalyst-free ZnO NWs was governed by Vapour-Solid (VS) mechanism.

Abstract: The in vitro cell response was investigated on flat Ti surface vs nanostructured TiO₂ nanotube surface. The titanium dioxide nanotube layers were prepared by electrochemical anodization of Ti in ethylene glycol, 5 wt% NH₄F and 1ml H₂O₂. The nanotube layered structure and morphology were characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The diameter and the length of the nanotubes are found to increase with anodization voltage. Hs27 and breast cancer cell line MCF-7 were used for cell interaction studies. Different surfaces of titanium show variation in term of growth and viability of cells. Different cell type also show different cellular responses to these surfaces. Titanium nanotube with tube diameter 90 nm promoted normal cell adherence and spreading but killed the cancer cells. The detail of the observation is discussed thoroughly in this paper.

Abstract: t was known that historical objects were highly heterogeneous. Due to the complex nature of materials and objects, extremely sensitive, spatially resolved, multi-elemental and versatile analytical instruments were needed. The techniques employed should be as a noninvasive as possible and able to give complementary information from macroscopic to nanometer scales. In this work, X-ray based spectroscopy including energy dispersive X-ray fluorescence spectroscopy (EDS), Proton-induced X-ray emission spectroscopy (PIXE), and micro-beam X-ray fluorescence spectroscopy (µ-XRF) were used to analyze chemical composition of the Lanna-style glass. Microstructure was also studied. It can be concluded that these techniques in combination are powerful for the investigation of heterogeneous glassy materials.

Abstract: Biodiesel is viewed as the most promising alternative fuel to replace petroleum-based diesel since it is derived from renewable sources such as animal fats, vegetable oil and grease. Out of various vegetable oil resources for biodiesel production, Jatropha curcas oil (JCO) is a viable choice for biodiesel because it is non-edible and can be grown easily in a harsh environment. In this study, Nd₂O₃-La₂O₃ catalyst was prepared for transesterification of JCO with methanol, in order to evaluate its potential as a heterogeneous catalyst for biodiesel production. Under suitable transesterification condition at 210 °C with catalyst amount of 3 wt.%, methanol/oil molar ratio of 45 and reaction time for 4 h, the conversion of JCO to fatty acid methyl ester (FAME) achieved was more than 93% over Nd₂O₃-La₂O₃ catalyst.

Abstract: Thin films of Cd_xZn_(1-x)S (0 x 1) were deposited on glass substrates by the chemical spray pyrolysis technique using a less used combination of chemicals. The variation of structural properties of these films in relation with composition was studied in detail. The entire study was made for a wide range of compositions of Cd_xZn _(1-x) S thin films (x=0 to 1 in steps of 0.1). XRD studies reveal that all the films are polycrystalline with hexagonal (wurtzite) structure of which reflection peaks associated with (100), (002) and (110) planes were clearly identified for all the films and inclusion of cadmium into the structure of ZnS improved the crystallinity of the films. The value of lattice constants a and c was found to vary with composition from 0.382 to 0.415 nm and 0.625 to 0.675 nm respectively.

Abstract: The aim of this study is to evaluate the radiopacity of silica (SiO₂) and zirconia (ZrO₂) particles dispersed in a bisphenol-a-glycidyl methacrylate (Bis-GMA) as a base resin and triethylene glycol dimethacrylate (TEGDMA) as a diluent. The fillers were mixed separately with bis-GMA/TEGDMA monomers, in proportions of 40, 50 and 60 wt.%. A resin matrix containing 0 wt.% filler was used as the control composition to evaluate the effect of filler loading on the radiopacity. Samples of the composites with 2.5 mm thickness were compared their radiopacity with the same thickness of the standard aluminum plate. The radiopacity of both resin matrix/SiO₂ and resin matrix/ZrO₂ composites increased gradually as the filler loading increased. The resin matrix/ZrO₂ composites possessed radiopacity higher than the standard aluminum plate. The increase of filler loading showed highly significant differences in the radiopacity as tested by ANOVA (P = 0.000).

Abstract: Tin oxide nanostructures (NS) were grown on silicon substrates by thermal evaporation method with three different parameters. These parameters were temperatures (650 °C, 750 °C and 850 °C), nickel catalyst concentrations (0, 5 and 10 milimoles) and tin powder source to substrate distances (2 cm, 4 cm and 6 cm). The parameters were found to affect the size and morphology of the synthesized nanostructures. Formation of nanospheres (NSs), nanoneedles (NNs) and nanowires (NWs) of tin oxide were observed by Scanning Electron Microscope (SEM) at different synthesis conditions. Synthesis temperature was found to have most pronounced effect on the size and morphology of the nanostructures. Catalyst concentration has affected the porosity and growth of the nanostructures. The distance between source and substrate affected the nanostructures predominately on distribution and particle size. Energy dispersion X-ray (EDX) analysis confirms the presence of tin and oxygen in all nanostructures at all synthesis conditions. X-ray diffraction (XRD) proves the formation of tin oxide phase in all samples. Significant formation of tin oxide nanowires was observed at 850 °C. Gas sensing properties of SnO₂ nanowires (NW) toward ethanol (C₂H₅OH) gas at 450°C with different volume concentration was measured. It was found SnO₂ NW had good sensing properties for C₂H₅OH at 100 ppm compared to measurements made at 25-50 ppm.

Abstract: Zinc oxide (ZnO) nanorods have been grown on silicon substrate by chemical bath deposition method in an aqueous solution that contained zinc nitrate hexahydrate and hexamethylenetetramine. The ZnO seed layer was deposited on substrate to promote growth of ZnO nanorods. Growth temperature was varying in order to form well aligned ZnO nanorods From XRD analysis confirmed that grown ZnO nanorods has wurtzite crystal structure and grown in the [10 direction. Well aligned and better size distribution of ZnO nanorods obtained at 75°C for 1h.

Abstract: Fe-Cr matrix composite reinforced with alumina with mean powder sizes of 13, 23, 24 and 64 μm was successfully obtained through powder metallurgy method. The powder mixture were blended at a rotating speed of 250 rpm for thirty minutes and uni-axially pressed at a pressure of 750 MPa. Samples identified as J13, J23, J24 and J64 according to alumina particles size were sintered in a vacuum furnace under 10^-2 Torr at a temperature of 1100°C for two hours with 10°C/minutes heating rate. The peaks of XRD patterns have been identified as belonging to the phases of Fe, Cr and alumina. The EDX analysis confirms the existence of Fe, Cr, Al and O. Reinforcing the Fe-Cr matrix with alumina particles bigger than 13 µm deteriorated the microstructure and mechanical properties of the composites. The wear coefficient for sample reinforced with 13 µm alumina particles is 2.46 × 10^-11 with compressive strength of 278 MPa. Meanwhile for sample reinforced with 64 µm alumina particles its wear coefficient is 5.09 × 10^-11 and compressive strength is 81 MPa. It is found that reinforcing smaller alumina particles sizes to Fe-Cr matrix resulted in better wear and strength properties of the composites.

Abstract: In this paper, InGaN/GaN/AlN/Si (111) structure was grown using a plasma-assisted molecular beam epitaxy (PA-MBE) technique. The structural and optical properties of grown film have been characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), high resolution X-ray diffraction (HR-XRD) and photoluminescence (PL). Indium-mole fraction has been computed to be 0.27 using XRD data and Vegards law with high grain size and low tensile strain. Room-temperature photoluminescence revealed an intense peak at 534 nm (2.3 eV) related to our sample In_0.27Ga_0.73N.