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。     

两相复合材料等效介电常数数值计算

为精确计算复合材料等效介电常数,采用随机分布模型,在对材料电性能本构方程研究的基础上,设计了两相复合材料等效介电常数计算的体积加权平均算法(VWAM)。研究结果表明,所设计的算法计算结果稳定性较高。在复合材料组成相介电常数比值小于10时,数值计算结果与理论和实验结果吻合度非常高。在其比值大于10时,所设计的算法适用于高介电常数组成相体积分数较高情况。研究方法有望应用于多相复合材料的相关等效电磁参数计算。研究结果为复合材料设计提供参考。     

添加Cu颗粒对钛酸铜钙/聚偏氟乙烯复合材料介电性能的影响

选用金属Cu粉末作为导体相,采用溶液共混和旋涂的方法制备了钛酸铜钙/聚偏氟乙烯/Cu(CCTO/PVDF/Cu)三相复合材料。通过X射线衍射(XRD)、红外光谱(FT-IR)、介电常数、介电损耗与频率及温度谱图的测试分析对复合材料进行表征。结果表明:FT-IR和XRD分析显示出Cu粉末进入基体中,形成了第三相;介电频谱和介电温谱分析表明,当Cu含量为20%(质量分数)时,复合材料的介电常数最大,并在20~150℃的温度范围内保持了良好的温度稳定性。     

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。     

碳化钛/环氧树脂纳米复合材料的介电性能研究

采用溶液混合随后热压的方法制备了TiC/epoxy纳米复合材料.运用渗流阈值理论解释了TiC/epoxy复合材料的介电行为.研究了复合材料介电常数与填料体积百分比含量和测试频率的关系.结果表明:当TiC体积百分比含量为0.192时,复合材料的介电常数高达214(103Hz).复合材料介电常数在高测试频率范围(104～106Hz)不随频率的变化而改变.     

碳纳米管填充聚合物复合材料的介电性能研究

本文研究了未经处理的多壁碳纳米管/聚偏氟乙烯(MWNT/PVDF)复合材料体系的介电性能.发现,在低频下,复合材料的介电常数随MWNT的含量增加而迅速增加,当体积分数为2.0%时,介电常数高达300左右,并且复合材料的渗流阈值仅为1.61%(体积分数).MWNT较大的长径比和较高的电导率导致复合体系渗流阈值较低.发生渗流效应时,复合材料的介电损耗低于0.4,与频率无关.因此,可以认为未经过化学处理的碳纳米管可以大幅度改善PVDF基复合材料的介电性能.     

KH550硅烷偶联剂对复合材料结构和介电性能影响

采用KH550硅烷偶联剂对BaTiO3粉体进行了表面处理,用溶液混合法及热压工艺制备了BaTiO3/PVDF复合材料.通过扫描电子显微镜对复合材料形貌的分析发现偶联剂的用量对复合材料形态影响较大; 用傅立叶变换红外光谱仪和X射线衍射分析了偶联剂用量对BaTiO3/PVDF复合材料微观结构影响; 通过阻抗分析仪研究了复合材料的介电性能, 发现偶联剂用量对复合材料介电性能影响很大,当偶联剂用量在1%(质量分数)时,BaTiO3体积分数为40%的复合材料介电常数高达51.     

巨介电常数陶瓷CaCu3Ti4O12的研究进展

CaCu_3Ti_4O_(12)(CCTO)陶瓷具有高介电常数和高热稳定性,这使得CCTO可能在高密度信息储存、高介电电容器、大规模集成电路等领域获得广泛使用。系统地介绍了CCTO高介电常数起源的内禀机制和外禀机制,详细归纳了元素掺杂对CCTO介电特性的影响,阐述了巨介电常数与本征点缺陷的内在关联,肯定了晶粒电导赝极化理论,指出了CCTO巨介电常数陶瓷研究的重点在于:基于外禀机制的IBLC模型,通过晶胞掺杂或晶界掺杂改变晶粒或者晶界的电导,进而调控CCTO的介电损耗,使CCTO保持较高介电常数的前提下,在很宽的频率范围内使介电损耗正切值降低到0.1以下。     

石墨烯/尼龙66导电纳米复合材料的制备与性能研究

通过溶液共混法制备了石墨烯(G)/尼龙66(PA66)复合材料,通过热压得到了导电纳米复合材料试样。改变石墨烯在尼龙66中的含量,制备了不同比例的G/PA66复合材料,通过室温电导率测试发现,当石墨烯含量达到1.338%(体积分数)时,复合材料的直流体积电导率上升到9.72×10~(-3)S/m,导电渗流阚值为0.734%(体积分数);复合材料的交流体积电导率和介电常数也随石墨烯含量的上升而增加。研究表明:分散良好的石墨烯显著提高了复合材料的导电性。采用扫描电镜(SEM)、万能力学试验机及热重分析仪(TGA)对复合材料的微观形貌、力学性能、热稳定性进行了研究。结果表明,复合材料的拉伸模量升高,热稳定性增强。     

纳米BaTiO3/聚醚砜复合材料的制备和性能研究

为了改善有机介质材料的介电性能,采用溶液共混和水沉淀工艺,以聚乙二醇为分散剂,并辅以超声振荡制备了钛酸钡/聚醚砜复合材料。用透射电子显微镜和扫描电子显微镜观察复合材料的微观形态,观察到纳米钛酸钡在复合材料中均匀分散。用Q表测定复合材料的介电常数和介电损耗正切值,发现复合材料的介电常数和介电损耗正切值随着钛酸钡体积分数增加而增加,得到了复合材料的介电常数、介电损耗与钛酸钡体积分数的关系式。在兼顾可加工性能的前提下,复合材料的介电常数可达到8.2,比纯聚醚砜提高了2倍多。     

Dielectric properties of Poly(vinylidene fluoride)/CaCu3Ti4O12 composites

The possibility of obtaining relatively high dielectric constant polymer–ceramic composite by incorporating the giant dielectric constant material, CaCu₃Ti₄O₁₂ (CCTO) in a Poly(vinylidene fluoride) (PVDF) polymer matrix by melt mixing and hot pressing process was demonstrated. The structure, morphology and dielectric properties of the composites were characterized using X-ray diffraction, Thermal analysis, scanning electron microscope, and impedance analyzer. The effective dielectric constant (ε_eff) of the composite increased with increase in the volume fraction of CCTO at all the frequencies (100 Hz–1 MHz) under study. The dielectric loss did not show any variation up to 40% loading of CCTO, but showed an increasing trend beyond 40%. The room temperature dielectric constant as high as 95 at 100 Hz has been realized for the composite with 55 vol.% of CCTO, which has increased to about 190 at 150 °C. Theoretical models like Maxwell’s, Clausius–Mossotti, Effective medium theory, logarithmic law and Yamada were employed to rationalize the dielectric behaviour of the composite and discussed.     

CaCu3Ti4O12/NiCuZn铁氧体基磁电复合材料研究

将CCTO(CaCu3Ti4O12)与NiCuZn铁氧体进行复合,系统地研究了组分变化对这种新型磁电复合材料的烧结性能、晶相结构、显微结构和磁电性能的影响。随后,为了实现复合材料的低温烧结以及综合考虑复相陶瓷的磁电性能,选取80%(质量分数,下同)NiCuZn铁氧体/20%CCTO组分,以BBSZ(Bi2O3-H3BO3-SiO2-ZnO)玻璃作为助熔剂,研究了CCTO/NiCuZn铁氧体基复合材料的烧结行为和磁电性能。结果表明,掺杂BBSZ后,900℃下烧结的所有样品的密度均达到了复相陶瓷理论密度的95%,且复相陶瓷的介电常数和磁导率在1～30 MHz范围内均不依赖于频率的变化。在10 MHz的频率下,当BBSZ的含量从0增加到3%时,复相陶瓷磁导率μ从13.2增加到47.9,磁损耗tanδμ从0.022下降到0.017,同时,样品的谐振频率从109Hz左右移动到3.2×108Hz。相应地,复相陶瓷的介电常数ε从9.2增加到16,介电损耗tanδε从0.069下降到0.012。这一优异的整体性能使其有望实际应用。     

High performance CaCu3Ti4O12/cyanate ester composites with excellent dielectric properties and thermal resistance

High performance composites based on CaCu₃Ti₄O₁₂ (CCTO) and cyanate ester (CE) were successfully developed with desirable dielectric properties (high dielectric constant and low dissipation factor), outstanding thermal resistance and decreased curing temperature for embedded capacitors. CCTO was treated by γ-aminopropyl triethoxy silane, coded as CCTO(KH550), to investigate the interfacial effects on properties of composites. The addition of CCTO or CCTO(KH550) can significantly reduce the whole curing temperature of CE, while CCTO exhibits a higher catalytic capability than CCTO(KH550). Compared with cured CE resin, two kinds of composites exhibit greatly improved thermal resistance and real permittivity, meanwhile the dissipation factor is still very low. Because the interfacial polarization leads to the dependence of dielectric properties on the frequency and temperature, the improvement of interfacial adhesion for composites is beneficial to reduce the variation of dielectric properties with temperature and frequency, and thus improve the reliability of dielectric materials in applications.     

Effect of coupling agents on the dielectric properties of CaCu3Ti4O12/PVDF composites

Phase-pure calcium copper titanate (CaCu₃Ti₄O₁₂, CCTO) ceramic particles were synthesized via a sol–gel route. The CCTO was treated by bis[3-(triethoxysilyl)propyl]tetrasulfide (Si69) to give CCTO@Si69. The dielectric composites based on CCTO (or CCTO@Si69) and polyvinylidene fluoride (PVDF) were molded with desirable dielectric properties by mechanical mixing process and hot-pressing. The structures of CCTO and CCTO@Si69 were investigated by scanning electron microscopy (SEM) energy spectrum, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The stretching vibration of SO at 1096 cm⁻¹ in FTIR is an indication that chemical bond was formed between Si69 and CCTO. The influence of Si69 on the preparation and the dielectric properties of CCTO/PVDF dielectric composites were discussed. When the content of Si69 was 0.1 mL (relative to 1 g of CCTO), the dielectric constant (ε) (at a frequency of 1 kHz) of CCTO@Si69/PVDF composites reached the maximum value of 84, this value is 5.25 times that of an equal amount of CCTO of CCTO/PVDF composites (ε ≈ 16). The CCTO/PVDF and CCTO@Si69/PVDF composites had very stable dielectric properties over a wide range of temperatures (20–160 °C). These composites can be applied as high-energy–density capacitors in electronic and electrical engineering fields.     

Properties of calcium copper titanate and barium titanate filled epoxy composites for electronic applications: effect of filler loading and hybrid fillers

Inorganic ceramics such as calcium copper titanate, CaCu₃Ti₄O₁₂ (CCTO) and barium titanate (BaTiO₃) were used as fillers to produce epoxy thin film composites for capacitor application. The effects of filler types and loading range on the dielectric, tensile, morphology, and thermal properties of the epoxy thin film composites were determined. Results showed that epoxy thin film composites with 20 vol% filler loading of CCTO and BaTiO₃ showed good dielectric properties, thermal stability, and thermal conductivity. However, the tensile properties of the CCTO/epoxy thin film composite was reduced as the filler loading increased. On the other hand, the tensile properties of BaTiO₃/epoxy thin film composite improved as the filler loading increased. Hybrid fillers CCTO and BaTiO₃ filled epoxy composites were fabricated and the effect of hybrid fillers on the dielectric properties and morphology of the epoxy thin film composites were investigated. Results indicated that positive hybrid effect in dielectric constant and dielectric loss showed by the hybrid composites.     

The dielectric properties and dielectric mechanism of perovskite ceramic CLST/PTFE composites

Polytetrafluorethylene (PTFE) composites filled with perovskite (Ca,Li,Sm)TiO₃ (CLST) dielectric ceramic of various volume fractions filler up to 60% were prepared. The effects of volume fraction of ceramic filler on the microstructure and dielectric properties of the composites have been investigated. A comparative study of dielectric properties of experiment and modeling analysis has been carried out at high frequencies for the CLST/PTFE composites. The results indicate that both the dielectric constant and the dielectric loss increase with the filler. The CLST/PTFE composite with 40% ceramic has exhibited good dielectric properties: ε _r?=?7.92 (~10 GHz), tan δ?=?1.2?×?10^?3 (~10 GHz), and τ _f?=??45 ppm/°C. The dielectric properties are obviously better than most composites reported previously at high frequencies in the aspects of dielectric loss and thermal stability. The dielectric constant and dielectric loss of composites predicted by the Rother–Lichtenecker equation and the general mixing model are in good agreement with the experiment data when the volume fraction of ceramic is less than 40%. When the volume fraction of the ceramic is more than 40%, the deviation occurs. By introducing the correction factor, the theoretical values of the dielectric constant agrees well with the experimental values.     

高介电性能的陶瓷－聚合物复合材料初探

研究了用高介电性能的陶瓷材料（ＢａＴｉＯ３、ＳｒＴｉＯ３、ＴｉＯ２）与聚合物材料（聚苯乙烯、氯化聚乙烯）进行不同形式的复合，发现随陶瓷体积分数的变化，复合材料的介电系数呈线性关系变化。同时发现采用溶液聚合法比简单共混的效果好，对陶瓷材料的比较发现，表面处理后的ＢａＴｉＯ３与苯乙烯进行溶液聚合得到的复合材料具有较低的介电损耗和在高频下仍能保持较高的介电系数的性能。     

Dielectric behavior of CCTO/epoxy and Al-CCTO/epoxy composites

A composite of epoxy embedded with a giant dielectric constant material CaCu₃Ti₄O₁₂ (CCTO) was fabricated. Various theoretical models were employed to rationalize the dielectric behavior of these biphasic composites. Amongst different models that were employed to predict the dielectric properties of the composites, the effective dielectric constants (ε_eff), obtained via Yamada model were in close agreement with the experimental values. A metallic inclusion in CCTO/epoxy composite was found to be effective way to enhance its dielectric constant. A three phase percolative composite (Al-CCTO/epoxy) was fabricated and percolation theory was employed to describe its dielectric behavior.