陶瓷基复合材料的界面相容性研究

有关陶瓷基复合材料（CMC）的界面问题已经得到广泛的重视。为了使材料达到一个很好的刚性，在纤维与基体之间保持尽量小的界面作用力对于陶瓷纤维增强Si-C-O复合材料是非常重要的。在纤维界面上涂层有利于减小它们之间相互作用，涂层处理后的Si-C-O复合材料的弯曲强度比一般无涂层的复合材料高5倍。在介质涂层、基体、以及涂层与纤维间的三相物质中避免化学反应的发生。目前，可利用化学相容性的原理对涂层纤维进行选择。     

剑麻纤维与晶须混杂增强聚丙烯复合材料

采用熔融共混和注塑成型方法制得了剑麻短纤维(SF)和CaSO4晶须混杂增强聚丙烯(PP)复合材料，研究了复合材料的热性能、微观结构和力学性能。结果表明，晶须提高了复合材料的热稳定性，阻碍了PP的结晶，降低了复合材料中PP相的结晶度和结晶速率；SF和晶须提高了复合材料的模量和韧性，但由于混杂增强复合材料弱界面键合的制约，晶须的高强性能并没有在复合材料中充分表现出来。     

碳化硅晶须增强氮化铝复合材料的机械性能和界面研究

本研究应用热压工艺制备了致密ＳｉＣｗ／ＡｌＮ复合材料，其晶须的质量含量为１０％～３０％。当复合材料中晶须的质量含量达到３０％时，其弯曲强度增加了８５％，韧性提高了５０％。用ＳＥＭ和ＴＥＭ观察了材料的显微结构，指出弯曲强度增加是由于荷载从基体转移到晶须。断裂韧性的增加是由于裂纹偏转、裂纹分支和钉扎等作用引起。用ＨＲＥＭ对ＡｌＮ基体与ＳｉＣ晶须界面进行了初步分析和研究。     

PP与镁盐晶须复合材料性能的研究

以镁盐晶须增强聚丙烯(PP)复合材料为研究对象，添加马来酸酐接枝聚丙烯(PP-g-MAH)1与PP-g-MAH2界面改性剂来改善两者界面粘合强度及提高复合材料的力学性能；探讨了不同加工工艺流程对复合材料性能的影响。结果显示：采用PP-g-MAH1作界面处理剂的复合物体系其增强效果较好；当PP／PP-g-MAH 1／镁盐晶须的质量比为97／3／30时，复合材料的综合性能最佳。应用扫描电子显微镜(SEM)，分别对不同复合材料进行了界面形态的观察，证明与试验结果一致。     

SiCw／涂层／TZP陶瓷复合材料界面化学键的XPS和IR研究

本文用ＸＰＳ和ＩＲ测定了ＳｉＣｗ／（Ａｌ２Ｏ３，莫来石）涂层／ＴＺＰ陶瓷复合材料的界面化学键。结果表明ＳｉＣｗ／Ａｌ２Ｏ３、莫来石、ＴＺＰ界面为化学结合而Ａｌ２Ｏ３、莫来石／ＴＺＰ界面为物理结合。     

SCM晶须/高密度聚乙烯复合材料力学性能的研究

研究了硅钙镁晶须(SCM晶须)／高密度聚乙烯(HDPE)复合材料的力学性能。实验结果表明：随着SCM晶须用量的增加，复合材料的拉伸强度、弯曲强度、弯曲模量显著提高而缺口冲击强度稍有降低；利用改性聚乙烯作增容剂，可以改善基体树脂与SCM晶须的界面结合性，有助于力学性能的提高。     

表面化学改性碳酸钙晶须对环氧树脂杂化材料的结构性能影响

利用硅烷偶联剂对碳酸钙晶须表面进行化学改性,研究了表面改性对环氧树脂/碳酸钙晶须复合材料的结构与性能的影响。研究结果表明,表面化学改性能够增加环氧树脂与碳酸钙晶须的相容性,增强碳酸钙晶须与环氧树脂之间的相互作用,改善碳酸钙晶须在环氧树脂中的分散。碳酸钙晶须与环氧树脂之间的界面相互作用是复合材料能够大幅度提高冲击强度的主要原因。     

陶瓷纤维（晶须）增强陶瓷基复合材料研究进展

本文着重介绍了国内外陶瓷纤维或晶须增强陶瓷基复合材料研究现状。详细论述了这种材料今后的发展方向及有待解决的关键问题,并对陶瓷纤维或晶须与陶瓷基体物理及化学相容性以及制备工艺等方面,说明了对复合材料性能的影响。     

硅灰石晶须/MCPA6复合材料的结构与性能

采用阴离子聚合制备了硅灰石晶须/浇铸尼龙6(MCPA6)复合材料,探讨了硅灰石晶须对复合材料微观结构、性能的影响以及增强机理。FTIR结果表明硅灰石晶须加入未改变MCPA6的化学结构,复合材料属于物理共混改性。SEM分析显示硅灰石晶须的用量决定了两相界面的黏结状态;当硅灰石晶须质量分数为5%时,晶须能均匀地分散在复合材料中,界面相容性好,此时复合材料综合性能最佳。与纯MCPA6相比,硅灰石晶须/MCPA6复合材料的拉伸强度、弯曲强度和冲击强度分别提高55.3%、71.5%和58.5%,吸水率降低36%。     

晶须表面涂层对SiCw／TZP陶瓷复合材料力学性能和界面结构的影响

研究了在ＳｉＣ晶须表面涂覆１０～１００ｎｍ厚的氧化铝或莫来石对１５％（ｖｏｌ）ＳｉＣｗ／２．５Ｙ－ＴＺＰ陶瓷复合材料力学性能的影响。结果表明：涂层可显改善复合材料的力学性能，其中涂覆莫来石效果最佳，室温σ１＝１４５０ＭＰａ，Ｋ１ｃ＝１７ＭＰａ·ｍ＾１／２，１０００℃下σｆ＝５２０ＭＰａ，比无涂层的复合材料力学性能分别提高了８０％，１００％和４５％。ＳＥＭ，ＴＥＭ和ＨＲＥＭ观察表明：ＳｉＣｗ表面涂     

Effect of entropy penalty on selective distribution of aluminum borate whiskers in isotactic polypropylene (iPP)/syndiotactic polypropylene (sPP) blends

The selective distribution of aluminum borate whisker in isotactic polypropylene (iPP)/syndiotactic polypropylene (sPP) blends was studied. For iPP/sPP/whisker composites, whiskers are distributed in iPP phase, which follow the theory of interfacial tension. When Irganox 1010 is introduced into the composites, the distribution of whiskers is changed from iPP phase to sPP phase. The results of contact angle tests indicate that the characteristics of the whisker surface are modified by Irganox 1010 and the interactions between the whisker and the matrix are dominated by van der Waals type power law. An entropy-penalty process dominates the change of distribution of whiskers in the composites. The DMA tests show that the loss modulus of composites is improved when whiskers distribute in sPP phase.     

The effect of whisker orientation in SiC whisker-reinforced Si3N4 ceramic matrix composites

Si₃N₄ ceramic matrix composites reinforced by nearly unidirectionally aligned SiC whiskers have been prepared by extrusion and hot pressing. Unlike the case in traditional Si₃N₄ ceramic matrix composites reinforced by random SiC whiskers, the mechanical properties of the composites exhibit a significant dependence on whisker orientation. In the direction of whisker alignment for SiC(w)/Si₃N₄ composites, increments in bending strength and fracture toughness of 200 MPa and 3 MPa·m^1/2 are obtained respectively, compared to the values in the direction perpendicular to whisker alignment. Based on microscopic fractographic observation and micromechanics analyses, the effects of whisker orientation on toughening mechanisms are discussed. The results indicate that the whisker orientation, θ, is a decisive factor for the essential toughening mechanisms of whiskers. Only in the case of small θ and weak interface can whisker pullout occur, and whisker has maximum toughening effect. The results show that effects of whisker strengthening and toughening can be improved simultaneously through whisker oriented alignment. ©     

偶联剂对T-ZnO晶须/环氧树脂复合材料的影响

研究了偶联剂KH－560对T－ZnO晶须／环氧树脂复合材料的影响。结果表明：偶联剂KH－560分子一端通过化学键进入环氧树脂的大分子中，另一端与T－ZnO晶须形成较强的氢键，在晶须与基体之间形成有效界面层，起到桥接基体与晶须和吸收能量的作用，有利于T－ZnO晶须起增韧增强作用。偶联剂在晶须表面形成薄层有利于提高材料的拉伸和弯曲强度，而较厚层可形成柔性的缓冲区，有利于吸收应力，提高压缩和冲击性能。     

Aluminum‐borate‐whiskers‐reinforced bismaleimide composites. 1: preparation and properties

Aluminum‐borate‐whiskers‐reinforced bismaleimide (BMI/Al₁₈B₄O₃₃) composites were prepared, and the mechanical and thermal properties were investigated. Results show that the coupling agent used for surface treatment of whiskers has a great effect on the properties of these materials. Composites containing surface‐untreated whiskers, or silane‐compound‐KH 921‐treated whiskers, exhibited initially only a slight increase in the flexural strength when the whiskers weight content increased up to 5 wt%; thereafter, they showed a sharp decrease when the whiskers content was higher than 5 wt%. On the other hand, impact strength tests showed that the addition of the two kinds of whiskers decreased the impact strength of the composites. However, studies of the composite containing borate (BE4)‐treated whiskers showed that its flexural strength greatly increased with increasing whisker content. Moreover, the composite showed initially an increase in impact strength with a whisker content up to 10 wt%, then showing a slight decrease when the whisker content reached 15 wt%. Scanning electron microscopy observations revealed that the two coupling agents (KH 921 and BE4) employed in this work tend to change the fracture features of the composites from brittleness to that of ductile behaviour. Copyright © 2004 Society of Chemical Industry     

Silicon Carbide Whisker/Alumina Matrix Composites: Effect of Whisker Surface Treatment on Fracture Toughness

The fracture toughness of a 30 vol% SiC whisker/Al₂O₃ matrix composite was evaluated as a function of whisker surface chemistry. Two types of SiC whiskers (Silar-SC-9 and Tateho-SCW-1-S) were investigated. Modification of the whisker surface chemistry was achieved by subjecting the whiskers to thermal treatments under controlled atmospheres. Whisker surface chemistry, as determined by X-ray photoelectron spectroscopy, was correlated to the fracture toughness of the composites.     

Morphology and performance of potassium titanate whisker-reinforced polypropylene composites

Titanate whisker-reinforced polypropylene composites were prepared in a twin-screw extruder followed by injection molding. The whiskers were surface treated with tetrabutyl orthotitanate prior to blending. The static and dynamic mechanical properties, impact strength, and thermal properties of the composites were investigated. Static tensile measurements showed that the tensile strength and Young's modulus of the composites increased with increasing whisker content. However, the Izod impact tests indicated that the impact strength of longitudinal samples remained unchanged with the addition of whisker up to 10 wt %. Thereafter, it shows a continuous decrease with increasing whisker content. The thermogravimetric and dynamic mechanical tests demonstrated that the heat-resistance and thermooxidative stability for the composites also increased with increasing whisker content. Scanning electron microscopic observations revealed that the whiskers within the composites were oriented uniformly. The experimental data were compared with the well established mechanical models to evaluate the reinforcing efficiency. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 431–439, 1998     

Polymer whiskers of poly(4-hydroxybenzoate): Reinforcement efficiency in composites with polyamides

The reinforcing efficiency of polymer whiskers of poly(4-hydroxybenzoate) (PHB) in poly-amide-6 (PA-6) and polyamide-11 (PA-11) composites was investigated by tensile testing, scanning electron microscopy (SEM), and density measurements. The composites were prepared by mixing the whiskers into the melts of the polyamides. Ductile and stiff PA-6-composites with different crystallinities of the PA-6-matrix were investigated. In the ductile PA-6 (low crystallinity) composites, the elastic modulus E and the yield stress σ_f increase more than twice at a whisker content of 2 vol %. The increase in E and σ_f in stiff PA-6 (high crystallinity) composites is not as pronounced as in the ductile PA-6 composites, but is still remarkably higher than in the PA-11 composites, which is about 1.2 times at a whisker content of 2 vol %. At higher whisker content, the PA-6 composites show the opposite of the PA-11-composite—no further increase in E and σ_f, which may be due to an agglomoration of whiskers in the high viscous PA-6 melt. The different tensile properties of the composites can be explained by SEM analysis of the fracture surfaces, which shows that the adhesion of PA-6 to the PHB whiskers is better than of PA-11. This is due to a higher number of hydrogen bonds between the PA-6 and the whisker surface. Density measurements show that the crystallinity of the polyamides is not affected by the PHB whiskers. © 1996 John Wiley & Sons, Inc.     

Two-Dimensional Whisker Percolation in Ceramic Matrix–Ceramic Whisker Composites

A computer model that treats ceramic-powder matrix–ceramic whisker composites as a percolative network of whiskers has been developed. The model calculates the critical fraction of whiskers at the percolation threshold for a two-dimensional random network of whiskers. The computed critical fraction was found to display an inverse dependence on whisker aspect ratio. In addition, the computed critical fraction (27 vol% for a whisker aspect ratio of 7) agreed well with the zero-shrinkage whisker fraction of 30 vol% in the densification of a colloid-pressed alumina–silicon carbide composite that exhibited a two-dimensional orientation of such whiskers.     

Interfacial enhancement by shish-calabash crystal structure in polypropylene/inorganic whisker composites

The polymer matrix structure and the interface are strongly influenced by filler in semi-crystalline polymer composites because the fillers have the potential to nucleate the polymer crystallization. The structure of the nucleated crystalline polymer on filler is of particular interest and is a key to the interfacial enhancement. In this work, whiskers, with a large length/diameter ratio and with a diameter (0.2-2 μm) much larger than that of carbon nanotubes but much smaller than that of common fibers, were used to nucleate crystal morphology in polypropylene (PP)/whisker composites. The crystal morphology, interfacial adhesion and tensile properties of the composites were carefully investigated. A kind of peculiar shish-calabash crystallization morphology, with whisker serves as shish and PP spherulites serves as calabash, was observed for the first time in the thin film via PLM and in the injection molded bars by SEM. The formation mechanism of this shish-calabash structure was attributed to be that only a few nuclei could be induced on the whisker surface, which develop into large PP spherulites without hindrance, and finally stringed by the whisker, forming the shish-calabash structure. As a result, a significant improvement of interfacial interaction and tensile properties has been achieved.