铂催化硅氢加成反应研究进展

硅氢加成反应是合成有机硅材料最重要的途径之一，铂催化剂作为其应用最广的催化剂，具有重要的意义。本文首先介绍了硅氢加成反应机理的研究现状；分析了聚合物长链段铂配合物、含多个铂原子铂簇化合物及N-杂环卡宾铂配合物均相铂催化剂的研究进展，致力于改善均相催化剂催化选择性差、催化活性难以控制等缺点；分别阐述了不同铂催化剂载体如无机二氧化硅、炭载体、金属氧化物、有机高分子、固载液等作为铂催化剂载体的优点，负载铂催化剂具有可回收、产物选择性好的优点，有效解决了工业上铂损失的问题；最后对铂催化硅氢加成反应的发展趋势进行了展望分析，铂负载能力的提高、铂负载催化剂的分离、硅氢加成反应的原理、催化范围的扩大等均是今后研究的重要方向。     

Simultaneous improvement of thermal conductivity and mechanical properties for mechanically mixed ABS/h-BN composites by using small amounts of hyperbranched polymer additives

Recently, thermal interface materials (TIMs) are in great demands for modern electronics. For mechanically mixed polymer composite TIMs, the thermal conductivity and the mechanical properties are generally lower than expected values due to the sharply increased viscosity and poor filler dispersion. This work shows that addition of a small amount of polyester-based hyperbranched polymer (HBP) avoided the trade-off in mechanically mixed ABS/hexagonal boron nitride (h-BN) composites. After adding 0.5 wt% HBP, the maximum h-BN content in the composites increased from 50 to 60 wt%. The out-of-plane, in-plane thermal conductivity, and tensile strength of ABS/h-BN with 50 wt% h-BN were 0.408, 0.517 W/mK, and 18 MPa, respectively, and were increased to 0.729, 0.847 W/mK, and 32 MPa by adding 0.5 wt% HBP, while 0.972, 1.12 W/mK, and 29.5 MPa were achieved for ABS/h-BN/HBP with 60 wt% h-BN. The morphological and rheological results proved that these enhancements are due to the improved h-BN dispersion by decreasing viscosity of composites during mixing. Theoretical modeling based on the modified effective medium theory confirmed such results and showed that the interfacial thermal resistance also decreased slightly. Thus, this work demonstrates a facile and scalable method for simultaneously improving the thermal conductivity and mechanical properties of thermoplastic-based TIMs.     

氧化钨（WO3）薄膜光电催化性能的改善及应用

半导体WO₃具有较小的禁带宽度和良好的稳定性，对可见光具有较强的吸收，在光催化和光电催化领域具有广泛的用途。然而，单一WO₃薄膜仍然存在着光生电子-空穴复合率高、光电催化活性与能量转换效率偏低等问题。本文从WO₃薄膜光电催化性能的改善及应用两个方面对近年来的研究进行了综述。在WO₃薄膜光电催化性能的改善方面，分别从有序纳米结构的构建、离子掺杂与表面修饰进行总结。同时，也归纳总结了WO₃薄膜作为光电极在分解水制氢、光电催化还原CO₂和降解有机污染物等方面的应用，并提出了WO₃薄膜在光电催化过程中存在的问题，指出WO₃有序纳米异质结的构建是提高WO₃薄膜光电催化活性的有效方法。WO₃薄膜光电极的规模制备、廉价助催化剂的使用、光电极的稳定性与耐蚀性是其实际应用过程中需要解决的问题。     

聚丙烯珠粒发泡研究进展

聚丙烯(PP)珠粒发泡材料具有优异的耐热、隔音、抗冲击以及耐化学腐蚀等性能,近年来被广泛应用在包装、建筑、汽车等行业。PP在其熔点温度附近的熔体强度会急剧下降,低熔体强度导致其难以得到好的泡孔结构,所以PP珠粒发泡的技术难度大,目前只有少数国家掌握了PP珠粒发泡的技术,因此PP珠粒发泡的研究受到了国内外的广泛关注。文中从制备工艺、发泡装备、性能改进、表征方法等方面综述了近年来国内外PP珠粒发泡的研究动态,并对该领域今后的研究方向进行了展望。     

TiB_2-ZrB_2/Ni涂层电极点焊镀锌钢板失效过程分析

目的了解TiB_2-ZrB_2/Ni涂层电极点焊镀锌钢板时的失效机理。方法通过扫描电镜(SEM)、X射线衍射仪(XRD)、显微硬度测试等表征方法,研究TiB_2-ZrB_2/Ni涂层点焊电极点焊镀锌钢板时表面结构、物相及性能的变化。结果 TiB_2-ZrB_2/Ni涂层电极对提高点焊电极寿命有很大帮助,点焊电极寿命可提高5倍左右。涂层使点焊电极表面的硬度得以明显提高,减缓了点焊电极端部塑性变形的进程。ZrB_2-TiB_2/Ni涂层在一定程度上减缓了钢板镀层与点焊电极产生合金化反应的进程。结论 ZrB_2-TiB_2/Ni涂层电极由于具有一定的塑性,点焊过程中涂层不会出现完全脱落现象。涂层作用一直持续至电极失效,电极失效的形式主要表现为塑性变形。     

氮掺杂TiO_2中空复合微球的制备及可见光光催化性能

为了提高TiO2的可见光光催化性能,以微米级聚苯乙烯微球为模板,钛酸四丁酯为前驱体,三乙胺为氮源,采用静电吸附自组装法制备了粒径为1.20μm、壳层的厚度约为30nm且球形形貌良好的氮掺杂TiO2中空复合微球,采用SEM、XPS、XRD和紫外-可见分光光度计研究了其结构及光催化性能。结果表明:氮进入TiO2晶格内取代了部分O并改变了晶格中Ti和O的化学状态,但对TiO2晶型结构没有明显影响;氮掺杂后的TiO2中空复合微球禁带宽度变窄,氮掺杂TiO2中空复合微球不仅在紫外区有较强的光吸收能力,在可见光区也表现出较强的光响应性,对甲基橙的光催化降解率较Degussa P25型纳米TiO2的明显增强。研究结果对TiO2在光催化领域的应用具有理论指导意义。     

Effects of pyrolysis temperature on the chemical composition of refined softwood and hardwood lignins

The current study uses nuclear magnetic resonance, Fourier-transform infrared spectroscopy and Raman spectroscopy to investigate the evolution of refined softwood and hardwood lignins under various pyrolytic exposures. Little chemical change occurred at pyrolysis temperatures of 250 and 300 °C, whereas significant mass loss and chemical change was observed at 400 and 500 °C. These losses were mainly attributed to evolution of methoxyl, hydroxyl, and propyl groups. Mass loss plateaued following pyrolysis at 500 °C, but rearrangements continued to occur at higher temperatures, resulting in char that became increasingly polyaromatic in nature. Following brief pyrolytic exposures at 500 and 600 °C, the refined hardwood and softwood lignins yielded coal-like products. Lignin pyrolyzed at higher temperatures yielded chars with greater order, similar in composition to coke. These coal and coke-like products are called “lignin-based carbon” (LBC). The polyaromatic nature of the LBC after high temperature pyrolysis was perceived as the result of radical formation and recombination, leading to fused aromatic structures, which occurs more readily at higher temperatures.     

高透紫外线高分子材料的研究进展

随着光学、生物、电子、军事等领域对材料的透紫外性要求越来越高,高透紫外高分子材料的应用范围也越来越广。文中综述了含氟聚酰亚胺、无定型含氟聚合物、丙烯酸酯类聚合物、环氧树脂类聚合物、有机硅聚合物等5种高透紫外线材料的制备方法,聚合物结构对紫外透过率的影响以及在光学行业,电子工业上的应用,并展望了高透紫外线高分子材料的研究方向和应用前景。     

纳米ZnO可见光催化活性的改善及其降解性能

由于半导体ZnO禁带宽度较宽,因而其可见光催化活性较差。本文分别采用N掺杂、碳包覆、贵金属修饰以及半导体复合等方式来改善纳米ZnO的可见光催化活性,并以罗丹明B为降解污染物,对比了不同材料可见光催化降解有机污染物的效率。研究结果显示以氨水为氮源,通过水热法制备的氮掺杂N-ZnO光催化剂,相比于纯ZnO,对可见光吸收增强。采用葡萄糖水热碳化法所制备的C@N-ZnO样品则对有机污染物具有强的吸附能力,贵金属沉积所获得的样品Au/C@N-ZnO与半导体复合所制备的复合结构CdS/Au/C@N-ZnO在可见光区域具有更强的吸收能力。稳态和瞬态荧光光谱显示氧缺陷、贵金属沉积以及半导体复合形成异质结可有效提高光生载流子的分离效率,从而提高催化剂的光降解效率,并对催化机理进行了初步探讨。可见光催化降解罗丹明B结果显示CdS/Au/C@N-ZnO样品的反应速率是纯ZnO的6.7倍。     

Ion-implantation modification of lithium–phosphorus oxynitride thin-films

Among various solid electrolytes, the lithium–phosphorus oxynitride (Lipon) electrolyte synthesized by sputtering of Li₃PO₄ in pure N₂ has a good ionic conductivity of 2(±1)×10⁻⁶ S cm⁻¹ at 25° C. As the nitrogen concentration increases in the Lipon electrolyte, the ionic conductivity is reported to increase as a result of a higher degree of cross-links. When Lipon films are deposited by sputtering, however, it is reported that the maximum nitrogen concentration saturates approximately at 6 at.%. By non-equilibrium processes, such as ion-implantation, nitrogen concentration can be controlled over 6 at.%. This study investigates the effect of nitrogen concentration on the ionic conductivity in Lipon films by using ion-implantation. Impedance measurements at 25° C show that the nitrogen-implanted Lipon films enhance or retard the ionic conductivity over a wide range after nitrogen-implantation, when compared with as-deposited thin-films.