纳米PbF2的介电性能

采用惰性气体蒸发和原位压结法制备了具有清洁界面的纳米PbF2块材.通过X射线衍射和介电测量,研究了物相组成、介电性能与频率和温度的关系.探讨了退火处理对试样物相组成和介电性能的影响.     

绝缘搪瓷金属基板的研究

本文介绍了电子绝缘瓷釉的发展状况，测定了瓷釉的烧结温度、热膨胀系数、软化点、瓷层厚度、粒度分布等工艺性质以及耐击穿电压、体积电阻率、介电性能等电学性质；对瓷釉颗粒和瓷层进行了SEM分析，对瓷釉进行了TG—DTA和X衍射分析，明确了瓷釉中的析晶温度和结晶相；对比了绝缘瓷釉和ECA瓷釉的电性能；讨论了烧结温度和时间对瓷层形貌。温度和频率对介电性能的影响。     

基于FDS的电机线棒环氧云母绝缘电老化特性

为解决目前大型电机定子线棒主绝缘现场无损检测手段缺乏的问题,本文采用基于介电响应理论的频域介电谱法(Frequency Domain Spectroscopy,FDS),对大型电机定子线棒真空压力浸渍(Vacuum Pressure Impregnating,VPI)少胶云母绝缘进行测试。通过对不同老化时间和温度下线棒电性能参数的对比分析,研究电老化对电机线棒绝缘介电性能的影响规律。结果表明,电老化使环氧云母绝缘材料介电性能下降,其中环氧胶所受影响最为明显,在电老化过程中分子链发生断裂使粘接能力下降,在绝缘结构中形成更多介质分界面,同时使绝缘材料中极性分子活性增强,加剧了界面极化与转向极化,使介损和介电常数随电老化时间增长而增大。     

SiC(N)/LAS吸波材料吸波性能研究

研究了由SiC(N)纳米吸收剂制备的SiC(N)/LAS吸波材料的介电性能,对影响介电性能的吸收剂的含量、吸波材料烧结温度和碳界面层等因素进行了较为全面的研究。结果表明,在1080℃以下烧结温度对陶瓷致密度的影响较大而对陶瓷介电常数的影响较小;在1080℃以上烧结温度对烧结致密度的影响较小,对陶瓷介电常数的影响较大,吸波材料介电常数的实测值与计算值之间存在很大的差异,这种差异是吸波材料制备过程中纳米级的SiC(N)促进了碳界面层形成,导致了在较高温度烧结时吸波材料介电常数对温度的敏感性,使吸波材料介电常数的实测值与计算值之间出现了很大的差异,形成的碳界面层复介电常数的虚部较高,使吸波材料对电磁波的损耗进一步升高,从而使吸波材料的吸波性能得到增强。     

纳米PbF2的介电性能

采用惰性气体蒸发和原位压结法制备了具不清洁界面的纳米PbF2块材。通过X射线衍射和介电测量，研究了物相组成、介电性能与频率和温度的关系。探讨了退火处理对试样物相组成和介电性能的影响。     

铁电陶瓷/铁氧体叠层共烧体的介电特性

采用电介质物理学等效电路分析方法研究了Pb(Ni1/3Nb2/3)O3基铁电陶瓷与NiZnCu铁氧体叠层共烧体的介电频率响应,探讨了共烧体界面对介电性能的影响.结果表明,叠层共烧体的介电常数随频率的增加而减小,介电损耗随着频率的增加先增大后减小,有明显的损耗峰出现;界面扩散层对叠层共烧体电学响应有影响,叠层共烧体等效电路可视为介电材料层、铁氧体材料层和界面扩散层C re-R re等效电路的串联,并且界面扩散层会对叠层共烧体低频部分的介电响应起作用.     

PMN-PT陶瓷的制备及介电性能

采用NaCl-KCl熔盐法制备了钙钛矿相结构的0.8PMN-0.2PT陶瓷,研究了预烧温度、烧结温度和时间等工艺参数对样品的相结构、微观结构以及介电性能的影响,与传统陶瓷工艺相比,用熔盐法制备的样品介电性能好.     

钛酸钡/环氧树脂复合材料的制备及其介电性能的研究

钛酸钡/环氧树脂(BaTiO3/EPR)复合材料是最有潜力用于嵌入式电容器的储能介质材料.以不同粒径BaTiO3(BT)与环氧树脂(EPR)复合制备了BaTiO3/EPR复合材料,主要研究了粒径和温度对其介电性能的影响.研究发现复合材料的介电常数和介电损耗均随着温度的升高而升高,这是由环氧树脂基体的膨胀以及BaTiO3的相转变共同引起的.0.1μm的BaTiO3(BT-01)和环氧树脂基体的界面结合力好,组成的复合材料比0.7μm的BaTiO3(BT-07)组成的复合材料介电性能的温度稳定性较好.     

PMN—PT陶瓷的制备及介电性能

采用NaCl-KCl熔盐法制备了钙钛矿相结构的0.8PMN-0.2PT陶瓷,研究了预烧温度,烧结温度和时间等工艺参数对样品的相结构,微观结构以及介电性能的影响,与传统陶瓷工艺相比,用熔盐法制备的样品介电性能好。     

BaTi4O9微波介质陶瓷的低温烧结

研究液相多元添加对BaTi4O9微波介质陶瓷的烧结和介电性能的影响.通过添加(CuO和V2O5)烧结助剂来达到降低烧结温度的效果,并且使其保持较好的微波、高频性能.实验结果表明在添加合适的烧结助剂下,烧结温度为1180℃时,BaTi4O9微波介质陶瓷在1MHz下的介电性能ε=41.2,tgδ=5,τ=82×10-6/℃.基本保持了良好的介电性能.     

偶联剂对玻璃纤维/环氧基复合材料界面介电性能的影响研究

本文研究了五种偶联剂对玻璃纤维浸润性能和玻璃纤维/环氧基复合材料界面介电性能的影响。结果表明,玻璃纤维经偶联剂处理后,其浸润活化能降低,与环氧树脂基体间的相容性及化学反应活性得到改善;因此赋予了玻璃纤维与环氧基体间以良好的界面粘结性能,从而提高了玻璃纤维/环氧基复合材料界面的介电性能。其提高的幅度大小与偶联剂的极性及化学结构有关。     

Effect of Seawater and Warm Environment on Glass/Epoxy and Glass/Polyurethane Composites

A study of the durability of fiber reinforced polymer (FRP) materials in seawater and warm environment is presented in this paper. The major objective of the study is to evaluate the effects of seawater and temperature on the structural properties of glass/epoxy and glass/polyurethane composite materials. These effects were studied in terms of seawater absorption, permeation of salt and contaminants, chemical and physical bonds at the interface, degradation in mechanical properties, and failure mechanisms. Test parameters included immersion time, ranging from 3 months to 1 year, and temperature including room temperature and 65°C. Seawater absorption increased with immersion time and with temperature. The matrix in both composites was efficient in protecting the fibers from corrosive elements in seawater; however moisture creates a dual mechanism of stress relaxation—swelling—mechanical adhesion, and breakdown of chemical bonds between fiber and matrix at the interface. It is observed that high temperature accelerates the degradation mechanism in the glass/polyurethane composite. No significant changes were observed in tensile strength of glass/epoxy and in the modulus of both glass/epoxy and glass/polyurethane composites. However, the tensile strength of the glass/polyurethane composite decreased by 19% after 1 year of exposure to seawater at room temperature and by 31% after 1 year of exposure at 65°C. Plasticization due to moisture absorption leads to ductile failure in the matrix, but this can be reversed in glass/polyurethane composites after extended exposure to seawater at high temperature where brittle failure of matrix and fiber were observed.     

纤维长径比对环氧复合材料动态力学性能的影响

本文研究不同纤维长径比对碳纤和玻纤环氧复合材料动态力学性能的影响.结果表明,随长径比的增大,材料的力学内耗下降而模量增加;在低长径比,碳纤复合材料的内耗值比玻纤复合材料的高.达到一定长径比后,内耗值和模量值趋于连续纤维复合材料的值.温度越高,基体模量下降,达到相同纤维刚度的使用效率所需要的长径比就越大.用材料在外载荷或热缩应力作用下,纤维及其界面上沿纤维方向上的应力大小和分布随长径比的变化规律解释上述现象.     

国产T800碳纤维用氰酸酯树脂开发及其复合材料性能

基于飞行器减重对耐高温结构复合材料的应用背景,为了拓展国产T800碳纤维增强氰酸酯复合材料体系的应用,通过对国产T800碳纤维表面上浆剂的分析,开展适于国产T800碳纤维的氰酸酯树脂基体配方设计,研究国产T800碳纤维/氰酸酯复合材料的力学性能和耐热性能,分析树脂基体对复合材料界面性能的影响。结果表明:国产T800碳纤维表面上浆剂中含有环氧基团。配方优化后的氰酸酯树脂与国产T800碳纤维复合后,复合材料的室温-湿态力学性能保持率大于74.8%,200℃力学性能保持率大于57%,玻璃化转变温度为226℃,具有优异的热机械性能和界面性能。     

偶联剂对玻璃纤维/环氧单向复合层板性能的影响

本文讨论了五种偶联剂对玻璃纤维/环氧单向复合层板电性能和力学性能的影响.结果表明,玻璃纤维经偶联剂处理后,其浸润活化能降低,与环氧树脂基体间的化学反应活性得到改善.因此偶联剂赋予玻璃纤维与环氧树脂基体间以良好的界面粘结性,从而提高了玻璃纤维/环氧单向复合层板的电性能和力学性能,其提高的幅度大小与偶联剂的化学结构有关.     

High Temperature Residual Properties of Carbon Fiber Composite Sandwich Panel with Pyramidal Truss Cores

A study on the mechanical property degradation of carbon fiber composite sandwich panel with pyramidal truss cores by high temperature exposure is performed. Analytical formulae for the residual bending strength of composite sandwich panel after thermal exposure are presented for possible competing failure modes. The composite sandwich panels were fabricated from unidirectional carbon/epoxy prepreg, and were exposed to different temperatures for different time. The bending properties of the exposed specimens were measured by three-point bending tests. Then the effect of high temperature exposure on the bending properties and damage mechanism were analyzed. The results have shown that the residual bending strength of composite sandwich panels decreased with increasing exposure temperature and time, which was caused by the degradation of the matrix property and fiber-matrix interface property at high temperature. The effect of thermal exposure on failure mode of composite sandwich panel was observed as well. The measured failure loads showed good agreement with the analytical predictions. It is expected that this study can provide useful information on the design and application of carbon fiber composite sandwich panel at high temperature.     

混酸介质加速老化条件下玻璃纤维/溴化环氧乙烯基酯复合材料的耐久性

针对纤维增强塑料排烟筒工程应用中采用的玻璃纤维/溴化环氧乙烯基酯(GF/VE)复合材料和碳纤维-玻璃纤维/溴化环氧乙烯基酯(CF-GF/VE)复合材料分别进行混酸介质(H2SO4、HF、HCl和HNO3混合溶液)加速腐蚀试验,考察了3种温度下(25℃、55℃、80℃)的混酸介质浸泡后GF/VE与CF-GF/VE复合材料的质量及弯曲性能变化,并结合动态热力学性能、微观结构等分析了材料的性能衰减机制。结果表明:相同浸泡条件下,试样GF/VE的质量增重率高于CF-GF/VE,酸性介质在GF/VE和CF-GF/VE内部的扩散活化能分别为8.798kJ·mol-1和10.959kJ·mol-1;80℃浸泡2 160h后,CF-GF/VE复合材料的弯曲强度保留率为75.29%,而GF/VE的弯曲强度保留率仅为58.84%;DMA研究结果表明:常温条件下的腐蚀浸泡对材料的玻璃化转变温度Tg影响较小,加温条件下试样的Tg显著降低;SEM研究发现:混酸介质浸泡后,试样表面出现许多孔洞,同时纤维/基体界面发生了明显的脱粘破坏。     

浸泡腐蚀对玻璃纤维-空心玻璃微珠/环氧树脂复合泡沫材料弯曲性能的影响

制备了不同纤维质量分数的玻璃纤维-空心玻璃微珠/环氧树脂复合泡沫材料。通过三点弯曲试验研究了纤维质量分数对复合泡沫材料力学性能的影响。将复合泡沫材料试件置于蒸馏水和海水中浸泡,研究了浸泡腐蚀对试件弯曲性能的影响,并结合扫描电镜照片分析其原因。研究表明:纤维质量分数越高,玻璃纤维-空心玻璃微珠/环氧树脂复合泡沫材料的吸湿率越大,且在蒸馏水中的吸湿率较海水中的更大。试件的弯曲强度随纤维质量分数增加而增大,当纤维质量分数为10%时达到最大,比未添加纤维的试件增强了51%,之后则随纤维质量分数增加逐渐降低。浸泡腐蚀降低了试件的弯曲性能,其中海水浸泡后的试件弯曲性能最低。玻璃纤维-空心玻璃微珠/环氧树脂复合泡沫材料弯曲强度降低的直接原因是浸泡腐蚀使得部分玻璃微珠和玻璃纤维与环氧树脂基体间的界面层受到破坏。     

不同湿热条件下碳纤维/环氧复合材料湿热性能实验研究

对比研究了环氧5228A树脂及碳纤维/环氧5228A树脂复合材料层合板在3种湿热环境(水煮、70℃水浸,70℃85%相对湿度)下的湿热性能,考察了湿热条件对复合材料层间剪切性能的影响规律,并从吸湿特性、物理化学特性、树脂力学性能、湿应力等方面分析了不同湿热环境下复合材料性能衰减的机制。研究表明,碳纤维/高温固化环氧树脂复合材料层间剪切性能主要是由吸湿率决定,相同吸湿率不同湿热条件下性能的下降幅度基本相同;3种湿热条件下该树脂及其复合材料未发生化学反应、微裂纹等不可逆变化,复合材料层合板湿热老化机制主要是吸入水分后基体增塑和树脂、纤维湿应变不一致导致的湿应力对复合材料性能的负面作用。     

Optimum mixing ratio of epoxy for glass fiber reinforced composites with high thermal stability

The optimum condition of glass fiber/epoxy composites was investigated according to mixing ratio of two epoxy matrices. Novolac type epoxy and isocyanate modified epoxy were used as composites matrix. Based on chemical composition of mixing matrix, optimum mixing ratio of epoxy resins was obtained through FT-IR instrument. In order to investigate thermal stability and interface of epoxy resin, glass transition temperature was observed by DSC instrument, and static contact angle was measured by reflecting microscope. Change of IR peak and T_g was conformed according to different epoxy mixing ratios. After fabrication of glass fiber/epoxy composites, tensile, compression, and flexural properties were tested by UTM by room and high temperature. The composites exhibited best mechanical properties when epoxy mixing ratio was 1:1.