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31.
Cuprous oxide (Cu2O) dendrites were prepared by simple hydrothermal route at two different temperatures using starch as reducing and stabilizing agent. Scanning Electron Microscopy (SEM) revealed the alterations in morphology with reaction temperature and time. The spherical nanoparticles obtained at lower reaction temperature self-assembled into distinct dendritic nanostructures at high temperature. The mechanism of formation of dendrite over the polysaccharide template has been discussed. Transmission Electron Microscopy (TEM) revealed that the crystalline size of these dendrites in one dimension is about 50 nm. The nanoparticles were characterized by UV-vis and photoluminescence (PL) spectroscopy, X-ray diffraction (XRD), FT-IR and Thermal Gravimetry Analyzer (TGA). Impedance analysis of the nanostructures showed conductivity to be a function of temperature. 相似文献
32.
Vineet Kumar Anita Rani Sonal Rajpal Garima Srivastava Aketi Ramesh Om Prakash Joshi 《Journal of the science of food and agriculture》2005,85(9):1523-1526
Phytic acid, the heat‐stable anti‐nutritional factor, was determined in 80 cultivars/strains of Indian soybean to identify genotypes that possess low concentrations of phytic acid. Variation of values of 28.6–46.4 g kg−1 soy flour was observed. Information on the influence of growing locations with widely differing soil types on phytic acid content being scarce, phytic acid in the mature dry seeds of eight Indian soybean cultivars grown over four locations was evaluated. Variation in different varieties at different locations was 27.8–45.0 g kg−1 soy flour. Averaged over eight genotypes, the maximum mean value for phytic acid was observed at Pantnagar and the minimum at Palampur. These differences in locational mean values for phytic acid can be explained on the basis of characteristics of the soils and environment. The higher mean value at Pantnagar may be attributed to higher soil organic phosphorus, nearly neutral pH and favorable temperature from flowering to maturity. However, the lower value observed at Palampur can be explained by the acidic nature of its soil, with lower maximum and minimum temperatures prevailing from flowering to maturity. Locational and genotypic × locational effects were found to be significant (p < 0.01). The results indicated that soil characteristics and soil environment play a significant role in the accumulation of phytic acid in soybean seeds. Copyright © 2005 Society of Chemical Industry 相似文献
33.
Different rare earth substituted perovskites LaRE_xFe_(1-x)O_3(where RE=Eu~(3+),Gd~(3+),Dy~(3+),Nd~(3+)and x=0.02,0.04,0.06,0.08,0.1) with orthorhombic structure and narrow band gaps were successfully fabricated via sol-gel autocombustion method.All the substituted perovskites are found to exhibit excellent photocatalytic activity towards the oxidative degradation of dye molecules.An excellent increase in the rate constant values of pure perovskite(LaFeO_3) photocatalytic reactions is observed with the substitution of rare earth metal ions.Best results are obtained for LaNd_(0.1)Fe_(0.9)O_3 which exhibits around 7 times increase in the rate constant values for degradation reaction of SO(1.76×10~(-1) min~(-1))and RBY(1.69×10~(-1) min~(-1)) dyes. 相似文献
34.
Zhice Zhang Josephine B.M. Goodall David J. Morgan Sonal Brown Robin J.H. Clark Jonathan C. Knowles Nicola J. Mordan Julian R.G. Evans Albert F. Carley Michael Bowker Jawwad A. Darr 《Journal of the European Ceramic Society》2009,29(11):2343-2353
TiO2 doped with various loadings of nitrogen was prepared by nitridation of a nano-TiO2 powder in an ammonia/argon atmosphere at a range of temperatures from 400 to 1100 °C. The nano-TiO2 starting powder was produced in a continuous hydrothermal flow synthesis (CHFS) process involving reaction between a flow of supercritical water and an aqueous solution of a titanium salt. The structures of the resulting nanocatalysts were investigated using powder X-ray diffraction (XRD) and Raman spectroscopy. Products ranging from N-doped anatase TiO2 to phase-pure titanium nitride (TiN) were obtained depending on post-synthesis heat-treatment temperature. The results suggest that TiN started forming when the TiO2 was heat-treated at 800 °C, and that pure phase TiN was obtained at 1000 °C after 5 h nitridation. The amounts and nature of the Ti, O and N at the surface were determined by X-ray photoelectron spectroscopy (XPS). A shift of the band-gap to lower energy and increasing absorption in the visible light region, were observed by increasing the heat-treatment temperature from 400 to 700 °C. 相似文献
35.
A three-dimensional finite element analysis is conducted to estimate stresses induced by thermal cooldown in unidirectionally fiber-reinforced ceramic matrix composites. Various configurations of nonuniform fiber distributions are considered. Both cases of thermal expansion mismatch between isotropic, linearly thermoelastic fibers and matrix are studied. Significant effects of nonuniformity of fiber distributions on the local stress states are found. The initiation of various possible cracking modes is discussed in the light of these results. 相似文献
36.
We investigate the effect of a high-k dielectric in the tunnel layer to improve the erase speed-retention trade-off. Here, the proposed stack in the tunnel layer is AlLaO3/HfAlO/SiO2. These proposed materials possess low valence band offset with high permittivity to improve both the erase speed and retention time in barrier engineered silicon-oxide-nitride-oxide-silicon(BE-SONOS). In the proposed structure HfAlO and AlLaO3 replace Si3N4 and the top SiO2 layer in a conventional oxide/nitride/oxide(ONO) tunnel stack. Due to the lower conduction band offset(CBO) and high permittivity of the proposed material in the tunnel layer, it offers better program/erase(P/E) speed and retention time. In this work the gate length is also scaled down from 220 to 55 nm to observe the effect of high-k materials while scaling, for the same equivalent oxide thickness(EOT). We found that the scaling down of the gate length has a negligible impact on the memory window of the devices. Hence, various investigated tunnel oxide stacks possess a good memory window with a charge retained up to 87.4%(at room temperature) after a period of ten years. We also examine the use of a metal gate instead of a polysilicon gate, which shows improved P/E speed and retention time. 相似文献
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38.
The fatigue life behaviour and the underlying micromechanisms have been studied in two different Types of unidirectional carbon-fibre-reinforced plastics loaded in tension-tension along the fibre direction. The carbon fibres (AS4) were the same in the two composite systems. One thermoplastic matrix (polyetheretherketone, PEEK) and one thermosetting matrix (epoxy toughened with a thermoplastic additive) were used. The macroscopic fatigue behaviour was characterised by fatigue life diagrams. Surface replicas were taken intermittently during the course of the fatigue tests to monitor the active fatigue damage micromechanisms. The thermoset based composite showed a higher fatigue resistance with few microcracks initiated at distributed fibre breaks growing at a decelerating rate. The thermoplastic composite had a more pronounced fatigue degradation with a steeper fatigue life curve, which was caused by widespread propagating debonds and matrix cracks. The use of a tougher and more ductile matrix results in an inferior fatigue life performance, due to a more widely distributed accumulation of damage that propagates at a higher rate. 相似文献
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