排序方式: 共有164条查询结果,搜索用时 156 毫秒
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Li CM Robertson IM Jenkins ML Hutchison JL Doole RC 《Micron (Oxford, England : 1993)》2005,36(1):9-15
The nucleation, growth, and coalescence of silver oxide nanoparticles have been investigated dynamically and at high spatial resolution by using the electron beam of a transmission electron microscope to stimulate and to observe the processes. Under the assumption the particles are hemispherical, the growth rate was found to be proportional to the square root of the electron irradiation time. This result suggests that the rate-limiting step is the attachment of atoms to the nanoparticles. Growth of the nanoparticles occurred by the addition of columns of atoms on {111} planes. Particle impingement resulted in interpenetration of the particles and, ultimately, the formation of a grain boundary. 相似文献
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In this paper, TiO2 loaded on activated carbon fibers (ACF) was prepared by a coating treatment, followed by calcination at different temperatures in air atmosphere. The photocatalyst developed was characterized by SEM, XRD, XPS and UV-Vis adsorption spectroscopy. It was observed from SEM images that TiO2 loaded on ACF was in the form of small clusters with nanometer size. As confirmed by XRD and XPS determinations, the crystalline pattern of immobilized TiO2 was still anatase-form after calcination, and the micrographic structure and surface properties of ACF have not been damaged by the deposition process and calcination at different temperatures. Photocatalytic degradation of methylene blue (MB) in aqueous .solution was investigated using TiOE/ACF as photocatalyst. The comparison of photolysis, absorption and photocatalysis was carded out. The results indicated that the photocatalysis process of combined photocatalyst showed much higher degradation rate than that of photolysis and absorption processes. In addition, the possibility of cyclic usage of the photocatalyst was also confirmed. 相似文献
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超薄铜膜包覆的金刚石纳米复合粉体制备与表征 总被引:4,自引:0,他引:4
在氯化亚锡敏化、氯化钯活化的条件下,通过化学镀方法,成功地在纳米金刚石粉体表面制备了超薄铜膜.用X射线粉末衍射(XRD)和傅立叶红外吸收光谱(FTIR)表征了该Cu-金刚石纳米复合材料.此种复合材料在无水乙醇中超声分散5 min后的溶胶可稳定存放半年之久而不见沉降. 相似文献
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LU Chun-Ming 《高等学校化学学报》1999,20(Z1):460
The insecticide is comprehensively used in grain storage, as an ordinary mean to control insect pests. The resistance of insects and environmental pollution will be caused by heavily and continuously employing of chemical insecticide highly poisonous for human. The natural medical plants have strong toxic activity for stored-grain insects but have no pollution to the environment. Moreover,it is not easy to become resistible for insects. Therefore,the insecticide of medical plants have been developed and applied. 相似文献
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Ju-Xiang Shao Chun-Ming Gong Xiang-Yuan Li Jun Li 《Theoretical chemistry accounts》2011,128(3):341-348
Although vinyl alcohol(CH2=CHOH)molecule was found to be an important intermediate in the combustion flames of hydrocarbon (Taatjes et al. in Science
308:1887, 2005), the removal mechanism of vinyl alcohol has not been established yet. The removal mechanism is critical to characterize
the kinetics behavior of hydrocarbon in combustion chemistry and to develop the chemical models of hydrocarbon oxidation.
In this work, the potential energy surface for the unimolecular decomposition of syn-CH2=CHOH reaction has been first studied by ab initio. The kinetics and product branching ratios for the decomposition reaction
are evaluated by Variflex code in the temperature range of 500–3,000 K at 0.1, 1.0, and 100.0 atmosphere pressure. The results
show that the formation of CH3 + CHO via the CH3CHO intermediate is dominant in the decomposition reaction and its branching ratios at 0.1, 1.0, and 100.0 atm are more than
99.90, 99.30, and 89.20%, respectively, through the whole temperature range investigated. 相似文献
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针对倾斜板熔体处理晶粒细化与半固态成形原理,研究了倾斜板熔体处理过程边界层分布,建立了熔体传热和冷却速率的计算模型.计算结果表明,随着斜板倾角和熔体初始流动速度的增大,熔体在倾斜板上从层流向紊流的转变时间减少;温度边界层厚度随着熔体初始流动速度的增加而减小,斜板倾角对温度边界层厚度的影响较小;温度边界层厚度和速度边界层厚度都随熔体流动距离的增加而增大,在层流区,温度边界层厚度远大于速度边界层厚度,而在紊流区,温度边界层厚度与速度边界层厚度重合;倾斜板上熔体冷却速率与熔体厚度成反比,初始流速小于1m/s时,熔体的冷却速率沿着倾斜板长度方向逐渐增大,初始流速为1m/s时,熔体的冷却速率沿倾斜板长度方向基本不变,当初始流速大于1m/s时,熔体冷却速率沿倾斜板长度方向逐渐减小;倾斜板上熔体冷却速率在100—1000 K/s之间,属于亚快速凝固范畴. 相似文献
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研究了CO2激光局域辐照对熔石英损伤特性的影响, 发现当辐照中心温度较低时(1139 K), 辐照对损伤阈值没有明显影响, 但辐照中心温度较高时(1638 K), 辐照对损伤阈值有明显的影响, 损伤阈值随距离辐照中心间距的增大而减小, 在残余应力产生光程差最大处附近, 损伤阈值降到最小, 随着与辐照中心间距的进一步增加, 损伤阈值略有上升. 对导致此现象的原因做了分析. 由于残余应力的存在, 在辐照中心发生再损伤产生的裂纹后, 裂纹先沿径向扩展, 在残余应力产生光程差最大处附近, 裂纹转而向切向扩展, 这可能与径向和环向张应力随半径的变化有关. 在采用热处理炉退火消除残余应力时, 必须注意元件的洁净处理, 否则退火会出现析晶现象, 对损伤阈值和透射率造成不良影响.
关键词:
2激光局域辐照')" href="#">CO2激光局域辐照
熔石英
损伤特性 相似文献