聚合物包覆改性纳米二氧化钛的研究进展

综述了近年来国内外采用聚合物包覆法对纳米二氧化钛进行表面改性的研究工作,主要从改性原理和制备工艺的角度对聚合物包覆改性纳米二氧化钛的方法进行了分类阐述。对表面接枝法、微胶囊法和锚定位包覆法、原位聚合法、后处理改性法以及一些物理方法进行了举例介绍和比较。最后提出了目前聚合物包覆法改性纳米二氧化钛存在的问题和发展方向等。     

水基改性碳化硅陶瓷料浆流变性的研究

用有机硅偶联剂处理SiC粉体，在适合的上，经聚合反应再将有机的单体接枝于SiC颗粒表面上，在SiC颗粒表面上形成聚电解质包覆层，以改善SiC粒子在水介质中的分散性质。同时研究了改性SiC粉在水介质中的稳定条件，荷电性及在高固体含量下，用改性SiC粉所制备的陶瓷料浆的流变性。研究结果表明：改性后碳化硅粉在水中的分散稳定性能大大优于未改性碳化硅粉，所制备料浆体系的固体含量，分散稳定性能，粘度等参数有满足注浆成型工艺的要求。     

pH值对包覆改性SiC料浆分散特性和流变性的影响

通过zeta电位、沉降实验、流变特性、粘度等测试表征pH值对包覆改性SiC料浆分散特性和流变性的影响。研究表明:以偶联剂作为基础层,有机聚电解质作为分散功能层的有机包覆改性SiC粉体主要通过静电空间位阻效应实现稳定分散,调节pH值可以控制接枝聚合物水解产物的解离方式,从而改变了颗粒表面的电荷种类和电荷密度,包覆改性粉体的流动特性也发生变化。调整料浆pH值约11可制备出固相体积分数达56％、表观粘度为568 MPa·s的稳定料浆。     

鞣酸改性纳米二氧化硅对UV固化涂料性能的影响

通过在纳米二氧化硅-乙醇悬浮液中加入一定量鞣酸的方法,在纳米二氧化硅表面引入羟基等活性基团对纳米二氧化硅进行表面改性,并用SEM、FTIR和TG等手段对鞣酸表面改性纳米二氧化硅的改性机理进行研究。利用交流阻抗图谱(EIS)研究包覆后二氧化硅对UV固化涂料的防腐蚀性能。结果表明:鞣酸是以化学键合的方式接枝到纳米二氧化硅表面,改性后的纳米二氧化硅分散良好,鞣酸改性纳米SiO2能极大提高UV固化涂层防腐蚀效果。     

改性SiC添加剂对再生基础油摩擦性能的影响研究

通过对纳米SiC进行表面偶联或聚合物接枝,以改善SiC粒子的亲疏水状态,从而提高其与再生基础油之间的相容性,进而改善再生基础油的摩擦性能。接触角实验、FTIR、SEM和EDS结果表明,对SiC表面成功进行了改性;四球摩擦实验结果表明:硅烷偶联剂改性纳米SiC添加剂的使用,使再生基础油的平均磨斑直径从0. 72 mm降至0. 71 mm,摩擦性能稍有改善;而当使用聚合物接枝后的纳米SiC添加剂时,再生基础油的磨斑直径从0. 72 mm降至0. 62 mm,摩擦性能显著改善。     

纳米碳酸钙表面改性研究进展

简述了纳米碳酸钙的优缺点、表面改性机理、以及纳米碳酸钙的局部化学反应改性、表面包覆改性、胶囊化改性(微乳液改性)、高能表面改性及机械改性等表面改性方法;对表面活性剂、偶联剂、聚合物和无机物等纳米碳酸钙表面改性剂种类进行了综述,并对偶联剂表面改性剂进行了详述;最后对纳米碳酸钙表面改性存在问题和发展方向进行了展望.     

聚合物表面改性方法概述

聚合物表面改性方法多种多样，结合聚乙烯、聚苯乙烯、聚碳酸酯、聚甲基丙烯酸甲酯这些具体材料详细介绍目前应用广泛的溶液处理法、低温等离子体处理法、表面接枝法、离子注入法和一种新兴的原子力显微探针震荡法。前几种方法都是化学处理法，在基底上形成的新的极性表面层与体相结合一体，非常牢固；最后一种方法为物理过程，能够精确控制改性区域，对于改善材料表面微摩擦性能有重要作用。     

无机超细粒子表面改性技术研究进展

综述了无机超细粒子表面改性技术研究现状;重点介绍了局部化学反应改性和表面包覆改性.其中局部化学反应改性又包括偶联剂处理改性、与脂肪酸或醇反应改性和表面接枝聚合改性等.     

聚四氟乙烯表面改性研究进展

介绍了钠-萘溶液、等离子体、高能辐射接枝、激光辐射、离子注入等几种不同的聚四氟乙烯表面改性方法及其研究进展。     

白炭黑包覆改性技术研究进展

概述了白炭黑包覆改性技术的研究状况,并提出今后的发展建议。白炭黑表面包覆改性的方法主要包括聚合物包覆改性和无机物包覆改性,常用的聚合物包覆改性方法主要有接枝聚合法和乳液聚合法。建议今后在开发白炭黑包覆改性技术方面重点加强相关的基础理论研究工作,开发多功能的白炭黑包覆壁材,加强包覆白炭黑产品的性能及应用研究。     

Mechanical properties and indentation-induced phase transformation in 4H–SiC implanted by hydrogen ions

This paper aims to improve machining efficiency, suppress surface cracking, and reduce subsurface damage of silicon carbide (SiC). Hydrogen ions were implanted into SiC to study mechanical properties at nano and macro scales. Nanoindentation experiments were conducted using a Berkovich indenter. Firstly, the effect of ion implantation on the load-displacement curves at different indentation depths was investigated using molecular dynamics (MD) simulations. Elastic-plasticity at nanoscale was analyzed, and the values of material properties were obtained. Secondly, variability of surface morphology, phase transformation, and coordination number induced by nanoindentation with and without ion implantation was evaluated. Although ion implantation induced damage to the SiC model, the damage after nanoindentation was lower than that without ion implantation. Additionally, nanoindentation experiments were performed for small loads and high loads, respectively. The small load experiments were employed to derive material properties of the ion-implanted SiC. Improvement mechanisms of ion implantation on crack extension, fracture toughness, and elastic recovery rate were investigated under the high-load experiments. The results indicate that the amorphous structure induced by ion implantation can successfully prevent crack propagation and improve fracture toughness. The modification technology of SiC by ion implantation significantly improves the machining efficiency and the non-damage of its surface and subsurface.     

碳化硅陶瓷先驱体聚甲基硅烷的研究进展

介绍了聚甲基硅烷的主要合成方法和性能,特别是其反应活性和高温热裂解性能.综述了聚甲基硅烷及其改性先驱体应用于制备碳化硅纤维、碳化硅基复合材料、多孔陶瓷材料等领域的研究进展.聚甲基硅烷作为碳化辞陶瓷先驱体,其制备简单、热解产物接近碳化硅的化学计量比,具有广阔的应用前景.未来该领域的研究重点是聚甲基硅烷的规模化合成,低成本改性聚甲基硅烷先驱体研究,聚甲基硅烷系列复合先驱体的制备等.     

超细碳化硅表面改性技术进展

超细碳化硅（SiC）颗粒优异的物理化学性能和广泛的应用领域成为陶瓷颗粒表面改性研究的一个热点。介绍了超细SiC颗粒改性的目的和机理,从物理改性、化学改性两个方面对改性方法及研究进展情况进行了总结,并在此基础上指出了超细SiC颗粒的表面改性面临的主要问题。     

Molecular dynamics simulation of color centers in silicon carbide by helium and dual ion implantation and subsequent annealing

Atomic and close-to-atomic scale fabrication with high yield for the color centers in silicon carbide is critical in developing its applications. Combined with Wigner-Seitz method and identify diamond structure method to consider the structure around the silicon vacancy (V_Si), it is found that He ion implantation is more likely to fabricate a small number of silicon vacancies with complete structure but locating deep, while Si ion implantation is more likely to introduce more silicon vacancies with incomplete structure but a large number and closer to the near surface. Therefore, a method of dual ion implantation is proposed in this paper. By adjusting the ratio of He to Si ion concentration for dual ion implantation, the fabrication yield of color centers with depth below 5 nm can be increased compared with that of He implantation after high temperature annealing. Molecular dynamics (MD) simulation is employed to discover the underlying mechanism of V_Si color center and damage evolution by helium ion and dual ion implantation into four-hexagonal silicon carbide (4H–SiC) with subsequent annealing. Density-functional theory (DFT) calculation proves that magnetic-spin polarization enhances the stability of carbon anti-vacancy pair (C_SiV_C) defect, which indicates C_SiV_C defects are more stable than V_Si defects. The evolution of the V_Si color centers of different defect models are also calculated at various temperatures by MD, and the dynamic process of V_Si defects to C_SiV_C defects is demonstrated. It is revealed that the decrease of the V_Si color center at high temperature annealing is partly due to the transformation of some silicon vacancies to C_SiV_C defects.     

Crack Healing in Silicon Carbide

Crack healing in silicon carbide was investigated by introducing cracks into specimens and subsequently heat-treating the specimens. It was observed that cracks were healed, dramatically increasing the strength, by being filled with amorphous silica produced by the oxidation of silicon carbide. It was shown that the residual stress produced by the thermal expansion mismatch between silica within cracks and surrounding silicon carbide played a major role in the increase of the strength. Our results imply that a simple oxidation heat treatment can improve the reliability of silicon carbide components.     

改性纳米碳化硅/聚氨酯弹性体复合材料的制备

采用KH-560与KH-550反应得到新的硅烷偶联剂改性纳米碳化硅(SiC);再以2,4-甲苯二异氰酸酯(TDI)、聚氧化丙烯醚二醇(PPG2000)为原料合成预聚体,改性纳米SiC为填料、3,3’-二氯-4,4’-二氨基二苯甲烷(MOCA)为扩链剂,制备了改性纳米SiC/聚氨酯弹性体(PUE)复合材料。讨论了改性前后的纳米SiC添加量对复合材料的力学性能、耐磨性能和热稳定性的影响,并用扫描电镜分析了改性前后的纳米SiC在基体中的分散性。结果表明,改性后的纳米SiC在基体中的分散性优于纳米SiC,当改性纳米SiC质量分数为9%时,改性纳米SiC/PUE复合材料的力学性能达到最佳,耐磨性能明显改善,热失重温度提高了33℃。     

Development of Silicon Carbide Reinforced Jute Epoxy Composites: Physical,Mechanical and Thermo-mechanical Characterizations

The aim of the present study was to investigate the physical and thermo-mechanical characterization of silicon carbide filled needle punch nonwoven jute fiber reinforced epoxy composites. The composite materials were prepared by mixing different weight percentages (0–15 wt.%) of silicon carbide in needle punch nonwoven jute fiber reinforced epoxy composites by hand-lay-up techniques. The physical and mechanical tests have been performed to find the void content, water absorption, hardness, tensile strength, impact strength, fracture toughness and thermo-mechanical properties of the silicon carbide filled jute epoxy composites. The results indicated that increase in silicon carbide filler from 0 to 15 wt.% in the jute epoxy composites increased the void content by 1.49 %, water absorption by 1.83 %, hardness by 39.47 %, tensile strength by 52.5 %, flexural strength by 48.5 %, and impact strength by 14.5 % but on the other hand, decreased the thermal conductivity by 11.62 %. The result also indicated that jute epoxy composites reinforced with 15 wt.% silicon carbide particulate filler presented the highest storage modulus and loss modulus as compared with the unfilled jute epoxy composite.     

多孔碳化硅表面改性及其生物相容性的研究

采用浸渍提拉的方法将聚乙烯醇、硅溶胶、海藻酸钙等涂敷于多孔碳化硅板上对其进行改性,并通过SEM观察改性后多孔碳化硅的生物相容性,并对其处理COD的能力进行测定。实验表明：聚乙烯醇和硅溶胶可以对多孔碳化硅进行改性,改性后多孔碳化硅板的生物相容性提高,微生物负载量增大,处理COD的能力明显提高。反应5d后,PVA改性的多孔碳化硅板COD去除率由改性前的15％提高到80％;硅溶胶改性的多孔碳化硅板COD去除率由改性前的15％提高到78％。     

多孔碳化硅表面改性及其生物相容性的研究

采用浸渍提拉的方法将聚乙烯醇、硅溶胶、海藻酸钙等涂敷于多孔碳化硅板上对其进行改性,并通过SEM观察改性后多孔碳化硅的生物相容性,并对其处理COD的能力进行测定。实验表明:聚乙烯醇和硅溶胶可以对多孔碳化硅进行改性,改性后多孔碳化硅板的生物相容性提高,微生物负载量增大,处理COD的能力明显提高。反应5d后,PVA改性的多孔碳化硅板COD去除率由改性前的15%提高到80%;硅溶胶改性的多孔碳化硅板COD去除率由改性前的15%提高到78%。     

Effect of some technological parameters on structure formation in materials based on reaction-sintered silicon carbide

Results of petrographic, x-ray, chemical, and spectral investigations of the structure and composition of materials based on SiC fabricated by reaction sintering of preforms pressed from grainy silicon carbide and its mixtures with petroleum coke in molten and volatilized silicon are presented. It is shown that the structure and composition of reaction-sintered silicon carbide materials can be controlled by changing the proportion of silicon carbide and petroleum coke in the pressed preform, the coarseness of carbide and carbon particles, the density of the pressings, and the temperature of reaction sintering. It is established experimentally that secondary silicon carbide formed as a result of the reaction between petroleum coke and silicon binds the grains of the initial carbide into a dense silicon carbide skeleton, whereas the retained pores are filled with free silicon. A single-phase material consisting entirely of silicon carbide can hardly be obtained by the method of reaction sintering. In practice, this method gives double-phase (SiC-Si) and triple-phase (SiC-Si-C) materials with a maximum content of the principal phase (SiC) equal to 94–96% (mass fractions).Translated from Ogneupory i Tekhnicheskaya Keramika, No. 8, pp. 2–8, August, 1996.