共查询到20条相似文献,搜索用时 93 毫秒
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用低能离子散射谱(ISS)对比分析了与样品托有良好电接触的和与样品托绝比的金属银片,观察到荷电效应对ISS分析有严重影响。实验还表明在ISS分析时使用低能电子中和枪可以有效地消除荷电效应,还发现电子中和枪的使用对于惰性气体离子的中和作用无明显影响。 相似文献
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La2NiO4/Al2O3催化剂上CH4/CO2的重整 总被引:8,自引:1,他引:8
通过溶胶-凝胶方法制备了尖晶石结构的La2NiO4/Al2O3催化剂,采用BET,XRD和TG表征了催化剂的孔分布、比表面积、体相组成以及凝胶样品的热失重和热分解过程.将催化剂应用于CH4/CO2重整反应制合成气,考察了惰性气体和反应温度对转化率、选择性以及积碳的影响.结果表明,在高空速(GHSV=4.8×104ml/(g·h))下,CH4和CO2转化率分别为51%和60%,CO和H2的选择性约为98%和92%,惰性气体He的引入明显地提高了CH4和CO2的转化率. 相似文献
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离子刻蚀技术在扫描电镜样品制备中的应用已引起广泛注意。经离子刻蚀后既可清除样品表面的污染,揭示其表面的超微结构,又可获得样品的内部结构信息。近年来我们对几个医学生物样品作了离子刻蚀后在扫描电镜下观察,并取得了较满意的结果。 相似文献
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利用强短脉冲供电电源和一种新型的辉光放电灯联用进行阴极表面溅射,发现它与在直流供电下有不同的结果,扫描电镜进行观察,得到样品溅射表面的扫描图,结果表明,该技术的金属或合金样品表面的逐层分析提供了一种新方法。 相似文献
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毛细管柱样品容量很小,需要使用高灵敏度的检测器和小的死体积,所以,目前绝大部分的毛细管色谱分析都采用离子化检测器,其中以FID为最多。FID—毛细管柱系统不适合分析非烃类、惰性气体以及在火焰中难以电离或不电离的物质,对于FID,许多样品需要用一种溶剂来稀释,FID的定量校正因子不宜直接引用文献值,此外,在毛细管色谱应用较多的石油化工等单位都存在大量的易燃易爆气体,需严禁烟火,都比 相似文献
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Gottfried Blaschke 《Angewandte Chemie (International ed. in English)》1980,19(1):13-24
A number of racemates can be resolved into optically pure enantiomers by chromatography on optically active adsorbents. Synthetic polymers with optically active amide, amino acid, and crown ether groups, natural products such as starch and cellulose, and also microcrystalline triacetylcellulose are suitable for this purpose. Racemates can also be resolved by gas chromatography on optically active stationary phases. 相似文献
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Redox-flow batteries can, in principle, use a wide range of active materials. However, a number of simultaneous requirements must be met to make a chemistry attractive. One of the most challenging requirements is minimizing transport of active species through the membrane separating the positive and negative electrodes, and the ensuing inefficiency and capacity loss. Developing technologies to mitigate crossover, and strategies for recovering from its consequences, will enable development of successful systems with new active materials. The rate and impact of crossover depend on the nature of the active materials and their fate after they transport across the separator. Accordingly, electrolyte solutions can be classified by what happens to the active species at the opposing electrolyte. This behavior also dictates what recovery strategies may be employed, and at what frequency. This review describes desirable attributes for active materials and separators that help diminish crossover, and strategies that can be used to recover from its effects for each of the different classes of electrolytes. 相似文献
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W. Plieth 《Russian Journal of Electrochemistry》2010,46(10):1119-1124
The electrochemical processes on a growing metal layer can be described as a chain of processes consisting of nucleation and
formation of a stable grain, growth of the active grain, and death of the active grain. Considering the statistical nature
of the process chain, mean growth rate, mean lifetime, mean death rate, mean density and mean size of the active grains can
be defined. Equations for the rate of nucleation are given in the literature. Stationary growth of the metal film is achieved
if the rate of nucleation is equal to the death rate of active grains. From the condition of stationary growth an equation
for the dependence of the average grain size on the experimental parameters can be derived. Several situations of metal deposition
with different process parameters are discussed and compared with experimental results. 相似文献
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单层分散阈值和负载型催化剂的阈值效应 总被引:1,自引:0,他引:1
自发单层分散原理认为,许多负载型催化剂的活性组分可在载体表面自发分散。活性组分在载体表面的单层分散阈值可通过XRD相定量外推法等实验方法进行测定。通过单层分散阈值的测定可获取负载型催化剂表面结构、分散状态的有益信息,并为选择最佳的催化剂制备工艺条件提供依据。许多负载型催化剂活性组分的配比都可通过考察其单层分散阈值得以优化。负载型催化剂的许多物理化学性质突变值都与其单层分散阈值相联系,催化剂的阈值效应是明显的,阈值效应的提出为催化剂的研究提供了指导。 相似文献
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电沉积铁前对称交流电对阴极表面的影响 总被引:1,自引:0,他引:1
研究了低碳钢在镀铁溶液内经对称交流电处理后在表面形成活化膜的组成及厚度,观察了镀铁层与基体界面的形貌,结果发现,活化膜的厚度随活化电流密度而变化,当电流密度为7Adm ̄(-2)时,在表面形成了一个厚度为20~25nm的洁净活化膜,镀铁层与基体结合牢固。探讨了对称交流电对阴极表面的作用机理。 相似文献
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Organic photovoltaic cells commonly use an active layer with a polycrystalline bulk heterojunction. However, for simplifying the fabrication process, it may be worthwhile to use an amorphous active layer to lessen the burden on processing to achieve optimal performance. While polymers can adopt amorphous phases, molecular glasses, small molecules that can readily form glassy phases and do not crystallize over time, offer an appealing alternative, being monodisperse species. Our group has developed a series of reactive molecular glasses that can be covalently bonded to chromophores to form glass‐forming adducts, and this strategy has been used to synthesize glass‐forming donor and acceptor materials. Herein, the results of devices incorporating these materials in either partially or fully amorphous active layers are summarized. Additionally, these molecular glasses can be used as ternary components in crystalline systems to enhance efficiency without perturbing the morphology. 相似文献