聚合物纳米孔隙增透膜制备工艺的研究

论述了聚合物纳米孔隙增透膜的制备工艺流程,分析了聚合物材料分子量、实验环境温度和湿度、溶剂挥发性等条件对纳米孔隙增透膜的影响。研究表明,聚合物材料分子量的增大、温度的降低、湿度的升高以及采用挥发性弱的溶剂都将导致增透膜孔隙尺寸的增大,孔隙越大其对光的散射损耗就会增大,所以增透膜的透过率就越低。通过大量的试验分析得出一组较理想的工艺参量:使用低分子量的聚合物材料(小于15 kg/mol),环境温度大于25℃、环境相对湿度小于30%,在采用低沸点的溶剂如四氢呋喃等措施下可有效降低增透膜散射损耗。     

The nanogranular nature of C-S-H

Despite its ubiquitous presence as binding phase in all cementitious materials, the mechanical behavior of calcium-silicate-hydrates (C-S-H) is still an enigma that has deceived many decoding attempts from experimental and theoretical sides. In this paper, we propose and validate a new technique and experimental protocol to rationally assess the nanomechanical behavior of C-S-H based on a statistical analysis of hundreds of nanoindentation tests. By means of this grid indentation technique we identify in situ two structurally distinct but compositionally similar C-S-H phases heretofore hypothesized to exist as low density (LD) C-S-H and high density (HD) C-S-H, or outer and inner products. The main finding of this paper is that both phases exhibit a unique nanogranular behavior which is driven by particle-to-particle contact forces rather than by mineral properties. We argue that this nanomechanical blueprint of material invariant behavior of C-S-H is a consequence of the hydration reactions during which precipitating C-S-H nanoparticles percolate generating contact surfaces. As hydration proceeds, these nanoparticles pack closer to center on-average around two characteristic limit packing densities, the random packing limit (η=64%) and the ordered face-centered cubic (fcc) or hexagonal close-packed (hcp) packing limit (η=74%), forming a characteristic LD C-S-H and HD C-S-H phase.     

Instrumental neutron activation analysis of mass fractions of toxic metals in plastic

It is very challenging to decompose a plastic product for the purpose of analysis of hazardous elements contained. To circumvent such technical problem, it is imperative that an analyst employ a nondestructive analytical method free of any pretreatments. The analytical results of the concentrations of toxic metals such as Cd and Cr in polypropylene for seven samples at two different levels were obtained using the instrumental neutron activation analysis. This work was intended ultimately to establish certified reference materials (CRMs) of these metals in the polypropylene, traceable to the SI. The uncertainties associated with the analytical procedures were estimated in accordance with the ISO guideline. The results were subsequently validated by a comparison with those for CRM-680 and −681 of the Bureau Communautaire de Reference (BCR), which demonstrated acceptable agreement within their uncertainty ranges.     

锂离子电池硅基负极材料的研究进展

硅基材料是新一代高容量锂离子蓄电池负极材料的典型代表,近年来已成为理论研究和应用研究的热点.本文介绍了锂离子电池硅基负极材料的制备方法、电化学性能及其研究现状,分析了硅材料作为锂离子电池负极材料存在的问题;讨论了硅材料作为锂离子电池负极材料的研究前景.并指出若能克服目前存在问题,将有望成为新一代锂离子电池负极材料.     

1．5GHz锯材超导腔的研制

介绍铌材超导腔的研制进展，重点讨论了国产铌腔的材料改性，以及相应的超导腔性能的改进．叙述了１．５ＧＨｚ铌腔的腔形设计，分析了铌材的射频性能和机械性能，制定了铌腔制作与后处理的特定工艺．最后给出了１．５ＧＨｚ铌材超导腔的低温实验结果．     

可降解磷酸酯聚合物的合成与应用研究进展

磷酸酯类聚合物在自然界中可以降解,是环境友好的化学品.其中,分子量高的聚磷酸酯近年来在医药、塑料助剂等方面有广泛应用,分子量相对较低的磷酸酯类聚合物在饲料、表面活性剂等方面很重要.按用途的不同,综述了可降解磷酸酯聚合物的合成与应用近况.     

钛酸纳米管和钛酸纳米薄片相变规律比较

TiO2与浓NaOH溶液反应可制得组成是Na2-xHxTi2O4（OH）2，0≤X≤2的纳米管。X随后处理时溶液的pH值的不同而不同，当X=2时即为钛酸纳米管。本文在考察热处理温度对钛酸纳米管和钛酸纳米薄片相变的影响时，发现它们的相变规律几乎完全相同。本文通过TEM、XRD、Raman及FT-IR光谱等技术对合成的钛酸纳米管和钛酸纳米薄片随焙烧温度的相变规律、晶粒形状及结晶程度等性质进行了比较和讨论。     

炭黑填充聚乙烯材料电阻—温度特性研究

研究了炭黑／聚乙烯导电复合材料的ＰＴＣ特性及在不同条件下的电阻变化。发现ＰＴＣ特性与体积膨胀及聚乙烯晶相的熔融有许多一致性。认为材料的体积膨胀及聚乙烯晶相熔融时炭黑颗粒均匀化扩散导致了电阻随温度上升。在较高温度下，炭黑颗粒在分子链段热运动的推动下会发生相对聚集使电阻不断减小，这是材料出现ＮＴＣ现象的原因。材料总的电阻温度特性是体积膨胀、炭黑向聚乙烯熔融区扩散及相互聚集三个因素共同作用的结果。     

非线性光学材料──水草酸铵

一水草酸铵（简称ＡＯＭ）是一种优良的电光晶体￣［１］。文献￣［１，２］报道了该晶体的晶体结构，化学式为（ＮＨ＿４）＿２Ｃ＿２Ｏ＿２·Ｈ＿２Ｏ，属正交晶系，Ｐ２２２空间群，晶胞参数ａ＝０．８０３５ｎｍ，ｂ＝１。０３１ｎｍ，ｃ＝０．３８０１ｎｍ，ｚ＝２。本文拟报道ＡＯＭ单晶生长，热化学分析，透过波段以及非线性光学性质的初步研究。