Physicochemical Properties of Diethanolamine-Functionalized Si-MCM-41

Si-MCM-41 was functionalized with 10-50wt% loading of Diethanolamine (DEA) using impregnation method and characterized for their physicochemical properties using XRD, FTIR and HRTEM. Results show that the intensity of the diffraction peaks attributed to the finger-prints of Si-MCM-41 decreases with increased loading of DEA. The peaks assign to (110), (200), and (210) planes start to disappear at DEA loading as low as 10wt%. FTIR spectra of DEA-Si-MCM-41 show presence of –N-H and –C-H peaks which confirms the functionalization of Si-MCM-41 with DEA. HRTEM micrographs of all samples clearly show the uniform hexagonal pore arrangement which proved the structural integrity of Si-MCM-41 even after functionalization with 50wt%.

Synthesis and Characterization of Al7075, Al7075-10 Vol. % Al2O3 Composite Prepared by High-Energy Ball Milling

Al7075 and Al2O3 powders were synthesized via high-energy ball mill for 15 h. Al7075 powders were mixed with 10 vol. % Al2O3, compacted by cold uniaxial compaction at 400 MPa. The green pellets were degassed at 350 oC for 30 min, and then sintered in the temperature of 600 oC under argon atmosphere for 120 min. It was shown that better density, vickers micro hardness and corrosion resistance were achieved due to refinement of grain size. HRTEM micrographs demonstrated a uniform distribution of Al2O3 particles in aluminium alloy and equilibrium η (MgZn2) precipitates along the grain boundaries.

Microwave-Assisted Precipitation Synthesis and Photoluminescence Properties of SrWO4 Mesocrystals with Different Shapes

Well-crystallized SrWO4 mesocrystals with different shapes including flower-like sphere, bundle, peanut, dumbbell, and notched sphere were controllably synthesized via a simple microwave-assisted precipitation method. X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) measurements were used to characterize these mesocrystals. XRD patterns indicate that the SrWO4 mesocrystals present a scheelite-type tetragonal structure. FESEM and HRTEM micrographs showed different shapes for the SrWO4 mesocrystals. The molar ratio of [WO42-] to [Sr2+] was found to play an important role in the morphological controlling of the resulting SrWO4 mesocrystals. With the increase of the molar ratio, the shape of the SrWO4 mesocrystals changed from flower-like sphere assembled with nanorods to notched sphere with intermediate peanut and dumbbell shapes. PL spectra measurements showed that the luminescence properties of the SrWO4 mesocrystals strongly relied on its shapes.

Synthesis and Characterization of MWCNT/CaCO3 Hybrid Compound

In this work, the chemical vapor deposition (CVD) technique was used to synthesis the multiwall carbon nanotubes/calcium carbonate (MWCNT/CaCO3) hybrid compound. A gas mixture of CH4/N2was used as the source of carbon and Ni/CaCO3was used as catalyst for the growth of the hybrid compound. The catalyst was prepared using a mixture of nickel salt and CaCO3via co-precipitation method. In short, the process involves the drying of the precipitate followed by calcinations at 900°C. Reduction process was carried under H2at 400°C and growth in CH4/N2mixture at 800°C for 30 minutes .The resulted compound was then analyzed using XRD, SEM and HRTEM. From XRD analysis the CNT/ CaCO3was successfully synthesized. HRTEM micrographs support the formation of MWCNT on the CaCO3surface.

Structure of oxidized bismuth nanoclusters

Synchrotron X-ray diffraction has determined that β-Bi2O3 is the dominant oxide phase covering hexagonal bismuth nanoclusters produced in an inert gas aggregation source. Simulated Debye–Scherrer patterns have indicated that the oxide is 20 ± 5 Å thick on average, at the surface of 320 ± 40 Å diameter clusters. A Williamson–Hall analysis of the peak broadening was used to measure the non-uniform strain in clusters. The oxidized clusters were in −0.11 ± 0.06% uniform compressive strain compared with other clusters without oxides detectable by X-ray diffraction which only have a small tensile uniform strain. High-resolution transmission electron microscopy (HRTEM) and multislice image simulations indicated a β-Bi2O3 thickness of 20–50 Å. The HRTEM micrographs show the relative orientation between the oxide and the cluster core.

Self-oriented Growth of GaN Films on Molten Gallium

ABSTRACTThis paper presents a concept of growing near single crystal quality GaN films over large areas through self-oriented growth of GaN platelets on molten gallium. The experiments were performed by nitridation of Ga films on amorphous quartz substrates using nitrogen plasma at low pressures of few mTorr. XRD texture analysis of the free standing GaN flakes with areas over 25 mm2 exhibited an overall c-axis tilt of 2.2°, while showing primary reflections from (0002) and (0004) planes. Further more, the cross-sectional TEM micrographs showed that the resulting GaN films are free from dislocation crops inside the grains but showed diffraction contrast due to small misorientation between the grains. The twist and tilt angles between adjacent columnar grains were determined using convergent beam electron diffraction technique to be less than 8° and 1°, respectively. HRTEM micrographs of the grain boundaries showed sharp interfaces with both twisted and perfect attachments.

Synthesis and Characterization of Novel Vanadium Dioxide Nanorods

ABSTRACTVanadium dioxide nanorods (B phase) have been synthesized, for the first time, using cetyltrimethylammonium bromide (CTAB) as structure-directing template in hydrothermal condition. Morphology and structure of the sample were characterized by XRD, SEM, HRTEM, XPS, TG-DTA and redox titration. The results show that the products are VO2 (B) nanorods and they are 1∼2 μm in length. HRTEM micrographs reveal that they indeed form bundles of agglomerated smaller filaments with diameters ranging from 20 to 40 nm. This filament-like shape in the nanoscale dimension leads to the exposure of a large fraction of the atoms to the surface. Thus, these materials are promising candidates for the development of new functionalized materials. TG investigation shows that there are a weight loss of 2.21 % between 250∼400 °C corresponding to removal of the organic residuals and a weight gain at about 430 °C corresponding to oxidation of vanadium with low oxidation state. The simplicity of hydrothermal process, cheapness, and availability of raw materials are advantages favoring the scaling-up of nanorods.