石英纤维/KH308复合材料的介电性能

为研究石英纤维/聚酰亚胺（KH308）复合材料介电性能与纤维体积分数、频率、温度和吸水率之间的关系,通过热压成型法,制备了4种不同纤维体积含量的石英纤维/KH308复合材料,采用高Q谐腔法分别测试这4种复合材料在不同状态下的介电常数和介电损耗。结果表明：石英纤维/KH308复合材料的介电常数随着纤维体积分数增加而变大,介电损耗随纤维体积分数变化不大;7~18 GHz频率下,复合材料的介电常数和介电损耗基本不随频率变化;25~300℃下,复合材料的介电常数随温度增加变化比较平缓,而介电损耗随温度的增加而降低;复合材料吸水后,介电常数和介电损耗都会增加;复合材料介电常数ε<4,介电损耗tanδ<0.1,能满足导弹天线罩透波材料介电性能的要求。     

基于LCR仪的复合材料介电性能测试

介电特性应用范围非常广泛,在贮藏、加工、保鲜、灭菌灭虫、清洗分级、无损检测等诸多领域都有应用。近年来有关介电性能的测试有了很大进展,该文使用多功能LCR仪对有机一无机复合材料进行介电性能测试,并分析其微观机理。     

表面态对纳米晶BaTiO3介电性能的影响

采用硬脂酸凝胶法制备了粒度均匀的纳米晶BaTiO3，用X射线衍射分析、红外光谱分析、透射电子显微镜对产物进行了表征，研究了表面态与介电性能。结果表明，BaTiO3纳米材料表面的不完整性主要是氧空位造成的，暴露在粒子表面的是一些金属离子，随着晶粒尺寸的减小，氧空位缺陷的浓度增加，极化增强，纳米材料的这种表面状态对其介电性能有重要影响，使其静态介电常数远比常规材料的大。     

表面处理对CCTO/PVDF复合材料介电性能的影响

分别用十二烷基苯磺酸钠(SDBS)、十二烷基硫酸钠(SDS)和双-(γ-三乙氧基硅基丙基)四硫化物(Si69)对CaCu3Ti4O12(CCTO)进行处理,采用溶液法制备处理后的CCTO/聚偏氟乙烯(PVDF)复合材料。采用XRD和SEM对复合材料的物相及微观结构进行分析,研究复合材料的介电性能与CCTO表面处理的关系。结果表明:经过表面处理的CCTO添加到PVDF中,提高了PVDF的介电常数,尤其是采用Si69处理的CCTO/PVDF复合材料,在1000Hz下介电常数达到了85,是不经过改性的CCTO/PVDF复合材料的5倍。     

高介电常数PVDF/PZT/Terfenol-D复合材料的介电性能研究

以聚偏氟乙烯(PVDF)为聚合物基体,PZT为陶瓷相,稀土铁合金粒子Tedenol-D为添加组分,运用聚合物熔融压片法制备了聚合物体积含量为30%的0.3PVDF/(0.7-f)PZT/fTerfenol-D三相复合材料.研究了Tedenob-D的体积含量、频率对复合材料介电性能的影响.结果显示:Tedenol-D粒子的加入,可以提高0.3PVDF/0.7PZT复合材料的介电常数,PVDF/PZT/Terfenol-D复合材料具有介电常数高、介电损耗小的特点.     

高性能PTFE基透波复合材料的研究进展

对聚四氟乙烯 (PTFE)透波复合材料的性能、成型工艺以及研究应用现状进行了全面介绍 ,并简要评述了材料存在的问题并指出今后的研究方向。     

分体圆柱谐振腔法用于金刚石膜微波介电性能测试的研究

针对金刚石膜微波介电损耗低、厚度薄带来的微波介电性能测试难点, 研制了一台分体圆柱谐振腔式微波介电性能测试装置。利用不同直径的蓝宝石单晶样品, 用上述装置对低损耗薄膜类样品微波介电性能的测试能力及样品直径对测试结果的影响进行了实验研究。在此基础上, 使用分体圆柱谐振腔式微波介电性能测试装置对微波等离子体化学气相沉积法和直流电弧等离子体喷射法制备的高品质金刚石膜在Ka波段的微波介电性能进行了测试比较。测试结果表明, 由Raman光谱、紫外-可见光谱等分析证明品质较优的微波等离子体化学气相沉积法制备的金刚石膜具有更高的微波介电性能, 其相对介电常数和微波介电损耗值均低于直流电弧等离子体喷射法制备的金刚石膜。     

细晶粒BaTiO3陶瓷的微结构及介电性能测试

采用放电等离子烧结技术,在９００℃下得到细晶粒尺寸的、均匀的、纯ＢａＴｉＯ_３陶瓷。对样品的高分辨电镜分析表明,晶粒中只有１８０°电畴,没有９０°电畴,晶界宽度相当于两倍的晶格常数．同时观察到有部分孪晶出现．对细晶粒陶瓷介电性能的测量表明,介电常数对晶粒尺寸有明显的依赖关系,认为李晶的存在是导致小晶粒陶瓷介电常数没有迅速降低的原因之一．对这一效应,用通常的串、并联模型不能很好地拟合。     

CBS涂层对多孔氮化硅高温高频介电性能的影响

采用溶胶-凝胶法在多孔氮化硅表面制备了CaO-B2O3-SiO2(简称为CBS)微晶玻璃致密涂层.用高Q腔一腔多模扫频方法测量了样品从7.3GHz至18.4GHz频率范围内室温到1200℃的介电常数和介电损耗,研究了CBS涂层对多孔氮化硅高温高频介电性能的影响.结果表明:多孔氮化硅经表面处理后的介电常数略有增大,随着频...     

Dielectric breakdown of reactively sputtered silicon nitride

Silicon nitride layers on silicon substrates were prepared by reactive sputtering of silicon in nitrogen under conditions which led to layers of maximum dielectric strenght. Dielectric breakdown and its dependence on temperature, pulse width and layer thickness were investigated. It is shown that conversion from thermal to electronic breakdown can be achieved at low temperatures and short pulse widths. This enables the thickness dependence of breakdown to be observed. From this dependence the mean free time of carriers was found to be 1.1×10^-15 sec.     

Characterization of silicon nitride single crystals and polycrystalline reaction sintered silicon nitride by microhardness measurements

Identification of - and -phases of Si₃N₄ single crystals grown from Si melt could be made with the help of Vickers microhardness measurements. The effect of chemical additives, e.g. metallic Fe and BaF₂, on the microhardness of Si₃N₄ was also determined. Different constants involved in the empirical Meyer relationship between load and indentation diameters could be correlated with the porosity and microhardness of Si₃N₄ single crystals and polycrystalline, reaction sintered Si₃N₄.     

氮化硅晶须对反应烧结氮化硅多孔陶瓷介电性能的影响

以硅粉和氮化硅晶须为原料,通过添加30%(质量分数)成孔剂球形颗粒,以聚乙烯醇作粘结剂,采用干压成型工艺,反应烧结制备了多孔氮化硅陶瓷,分析对比了氮化硅晶须对反应烧结氮化硅多孔陶瓷介电性能的影响.实验结果表明,随着氮化硅晶须加入量的升高,氮化硅多孔陶瓷的介电常数和介电损耗都升高,介电性能恶化.     

Coverage properties of silicon nitride film prepared by the Cat-CVD method

The coverage properties of silicon nitride (Si₃N₄) films prepared by the catalytic chemical vapor deposition (Cat-CVD) technique were systematically studied. By increasing the catalyzer–substrate distance, the coverage was improved from 46 to 67% on a 1.0-μm line and space pattern. The etching rate of Cat-CVD Si₃N₄ film measured using 16BHF solution was independent of the deposited position of the micro-patterns deposited, and was approximately 3 nm/min, one order of magnitude lower than that of plasma-enhanced CVD (PE-CVD) Si₃N₄ film. This means that Cat-CVD Si₃N₄ films are denser than PE-CVD Si₃N₄ films, and that the quality at the side wall is equivalent to that on the top surface. That is, Cat-CVD Si₃N₄ films show a passivation effect, which was excellent, even at the side wall of micro-patterns. These results suggest that Si₃N₄ films prepared by Cat-CVD are suitable for the passivation films in microelectronic devices having a step configuration, such as TFT-LCDs and ULSIs.     

Interference coatings based on synthesized silicon nitride

Silicon nitrides are synthesized by ion-assisted deposition with only one coating material and a nitrogen-ion-beam source. All the SiN(x) films are amorphous and mechanically strong. A wide range of refractive indices from 3.43 to 1.72 at a wavelength of 1550 nm is obtained. Near-IR antireflection coating and a bandpass filter based on the multilayers of SiN(x) and Si are demonstrated.     

Rheological properties of aqueous silicon nitride suspensions

The effect of surface modification of Si₃N₄ particle on the colloidal behavior and the rheological properties of aqueous Si₃N₄ suspensions under steady and oscillatory conditions are investigated in detail. Due to the decrease of the oxidizing level, the isoelectric point (IEP) of the modified particle shifts to basic region gently. Attempts have been made to apply rheological models to the suspensions with various solid volume fraction (). For the as-received suspensions, the Sisco model provides the best fit in the range of 0.30 while the Casson model in 0.35 0.45. The shear behavior of modified suspensions fits to Sisco model in the range of 0.40 and Casson model in 0.45 0.54. The rheological behavior of modified suspensions is improved efficiently. The critical strain decreases and the linear viscoelastic regime narrows continuously with increasing solid concentration. For the modified suspensions, the linear viscoelastic regime broadens and the corresponding elastic modulus decreases sharply. With increasing solid concentration, the characteristic frequency shifts toward lower frequencies and the suspension transforms from more viscous to more elastic.     

Dielectric functions of PECVD-grown silicon nanoscale inclusions within rapid thermal annealed silicon-rich silicon nitride films

Spectroscopic ellipsometry (SE) measurements were carried out in order to characterize the optical properties of silicon nanoscale inclusions (Si-ni) contained in silicon-rich silicon nitride (SRSN) films. These films were deposited using the plasma enhanced chemical vapor deposition (PECVD) technique followed by rapid thermal annealing (RTA) during 1 min. We focus our study on the influence of the deposition and annealing conditions - such as the ammonia to silane flow ratio R, the annealing atmosphere and temperature - on the optical responses of the SRSN layers and the behavior of the Si-ni dielectric functions. Our results suggest that the variation of R affects in a more significant way the structure and optical properties of the SRSN films than the change of the annealing gas or temperature.     

Dielectric properties of thin solid films formed on silicon

We report on the measurement of the frequency-dependent complex permittivity, ()=()-i(), over the frequency range, 30 MHz to 6 GHz, of silicon wafers and of thin dielectric films formed on silicon. Measurements, as a function of temperature and time treatments, were obtained by means of an HP Network Analyzer and dielectric probe and the resulting ()and()plots for the silicon wafers are shown to have a Debye-type [1] profile, thereby indicating that the associated polarization mechanism is of the orientational variety.