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关键词： 铜量   铜铬触头材料   硫代硫酸钠标准滴定溶液   碘量法   滴定   机械行业标准   中华人民共和国  

关键词： 硫酸亚铁铵滴定法   铜铬触头材料   过硫酸   机械行业标准   硝酸银   硝酸盐   中华人民共和国  

关键词： 白云石耐火材料   化学分析方法   菱镁石   重新确认   操作步骤   试验筛   高锰酸钾标准溶液   标准样品   烧失量   校准曲线  

摘要： 菱镁石和白云石耐火材料化学分析方法ＡＳＴＭＣ５７４－８４（１９８８年重新确认）ＳｔａｎｄａｒｄＴｅｓｔＭｅｔｈｏｄｆｏｒＣｈｅｍｉｃａｌＡｎａｌｙｓｉｓｏｆＭａｇｎｅｓｉｔｅａｎｄＤＯｌｏｍｉｔｅＲｅｆｒａｃｔｄｒｉｅｓ￣［１］本标准以固定标准号Ｃ５...

摘要： The systematic fabrication of organized materials will require the 'synthesis-with-construction' of architectures over scales ranging from the molecular to the macroscopic. This article describes four key constructional processes of biomineralization (supramolecular preorganization, interfacial molecular recognition, vectorial regulation and cellular processing) and illustrates how they can provide useful biomimetic archetypes for a molecular/crystal tectonics approach in inorganic materials chemistry.

关键词： Polymers  

摘要： Molecular organization in the solid state of a homologous series of chiral and achiral polymers was studied by electron microscopy and electron diffraction. All polymers of the series had periodic molecular backbones and some contained a stereocenter substituted by nitrile groups every 16 or 17 atoms along the chain. An aliphatic unit served as a spacer between aromatic units and was part of the repeats in all polymers. This spacer contained either an even or odd number of carbons in order to generate a preference for extended or nonextended conformers, respectively. Enantiomeric enrichment of chains resulted in the formation of crystals but diastereomeric chains with even spacer formed a phase of intermediate order and those with odd spacer formed an amorphous material. Enantiomerically enriched chains are also board-shaped and organize edge-to-edge, a feature definitely not observed in one of the two unsubstituted (achiral) homologous chains studied here. The global conformational traits of chains determined if extended-chain or folded-chain crystals formed.

关键词： Ultrasonic applications  

摘要： This article will begin with an introduction to acoustic cavitation, the physical phenomenon responsible for the chemical effects of ultrasound. Some recent applications of sonochemistry to the synthesis of nanophase and amorphous metals, as well as to heterogenous catalysis, will then be highlighted. Finally, we will examine the effects of ultrasound on metal powders in liquid-solid *** chemical effects of ultrasound do not come from a direct interaction of sound with molecular species. Ultrasound has frequencies from around 15 kilohertz to tens of megahertz. In liquids, this means wavelengths from centimeters down to microns, which are not molecular dimensions. Instead, when sound passes through a liquid, the formation, growth, and implosive collapse of bubbles can occur, as depicted in Figure 1. This process is called acoustic *** specifically, sound passing through a liquid consists of expansion waves and compression waves. As sound passes through a liquid, if the expansion wave is intense enough (that is, if the sound is loud enough), it can pull the liquid apart and form a bubble (a cavity). The compression wave comes along and compresses this cavity, then another expansion wave re-expands it. So we have an oscillating bubble going back and forth, say, 20,000 times a second.

关键词： 材料化学   固体物理   固体化学   材料科学  

摘要： 本文论述材料是现代科技的物质基础，新材料的研制、开发和应用，推动着社会文明的进步。在材料科技发展中，有关学科互相交叉渗透、改革和开放的必要性；化学理论和化学反应技术的重要作用。

关键词： 材料化学   材料科学   新材料   高技术   化学制备工艺   纳米材料   21世纪   扫描隧道显微技术   纳米加工   高分辨电子显微镜  

摘要： 现代高科技的竞争在很大程度上依赖于材料科学的发展。可以说任何高科技的进步都离不开新材料的开发和利用。因而材料科学被公认为21世纪六大高科技领域(生物工程,信息,能源,材料,空间和海洋)的基石。 所谓材料,就是构造成人类生活中各种器物所用的物料。人类的文明是从使用地球上的岩石作为工具开始的。从石器时代发展到青铜器时代,又进化到铁器时代直至陶瓷时代。在这一过程中,化学的前身矿物晶体学及相关冶炼技术起着关键的作用。

关键词： 电触头材料   导电材料   银氧化锡   氧化铟   铟化合物   火焰原子吸收光谱法   报批稿   机械行业标准   中华人民共和国  

关键词： 电触头材料   导电材料   银氧化锡   氧化铟   铟化合物   报批稿   碘量法   滴定   机械行业标准   中华人民共和国