溶胶-凝胶法制备氧化硅-氧化铝共掺杂聚酰亚胺薄膜及其性能

采用溶胶-凝胶法制备纳米二氧化硅及氧化铝溶胶,将溶胶混合后掺入正在反应的聚酰胺酸中,制得聚酰亚胺/二氧化硅-氧化铝杂化薄膜。利用扫描电子显微镜对杂化薄膜的微观形貌进行了表征,并测试了无机组分含量不同的杂化薄膜的力学性能、热稳定性及介电性能。试验结果表明,杂化薄膜材料中无机相呈现纤维结构和颗粒结构,有效地提高了薄膜的力学性能。杂化薄膜与纯膜相比,热分解温度有较大提高,且随着无机组分含量增大,热分解温度呈现先上升后下降的趋势。介电性能分析表明,杂化薄膜的介电常数和介电损耗与频率的关系符合德拜松弛极化机理。     

无机组分对聚酰亚胺杂化薄膜电性能的影响

初步探讨了聚酰亚胺薄膜在电场作用下的电学行为,采用溶胶-凝胶工艺制备了聚酰亚胺/二氧化硅纳米杂化薄膜,并对薄膜进行浸水24 h处理,利用原子力显微镜对制备的薄膜进行表面形貌表征,讨论了无机组分SiO2和水对薄膜电性能的影响.结果表明:无机组分的引入及两相间的界面形态将对杂化薄膜的电学性能产生重大的影响;偶联剂的引入使得两相间产生紧密的微相结合,并对电性能产生一定的影响.     

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。     

短切SiCf/LAS复合材料的介电性能

讨论了纤雏长度与热压保温时间对含量为25%(体积分数)的短切SiCf增强LAS玻璃陶瓷复合材料介电性能的影响.在8～12GHz频率范围内,介电性能测试结果表明,随纤维长度由2mm增加到4mm,复合材料的复介电常数实部ε′增大,而其虚部ε″及介电损耗tgδ减小.当保温时间由10min延长到20min时,复合材料的ε′增大,而其ε″与tgδ均减小;且保温20min时,其ε′、ε″与tgδ均已接近适合损耗微波能量的数值.复合材料有望成为电损耗型宽带微波损耗材料.     

PLZT（7/40/60）纳米多层膜介电特性研究

经溶胶-凝胶法制备出PLZT（7，40，60）纳米多层膜，对不同温度、不同层数，不同Zr/Ti比的PLZT薄膜的介电性能用精密阻抗分析仪进行介电特性分析。结果表明：煅烧温度的提高、薄膜层数的增加、锆含量的增加等均对PLZT薄膜的相对介电常数和介电损耗均有影响。频率为1kHz，750℃和锆含量为0．45时，薄膜的相对介电常数和介电损耗都最高。     

溶胶-凝胶法制备无机纳米/聚酰亚胺杂化膜及其表征

采用溶胶-凝胶法制备了SiO2及A12O3溶胶,并将其掺入到聚酰胺酸基体中,得到无机纳米SiO2-Al2O3/聚酰亚胺杂化膜,并对其结构性能进行了研究.实验表明,薄膜材料中无机纳米SiO2和Al2O3粒子分散均匀,与有机相存在键合;材料热分解温度有所提高.     

数字散斑相关方法测量聚酰亚胺无机纳米杂化材料的热膨胀系数

利用数字散斑相关方法计算在不同温度下聚酰亚胺无机纳米杂化膜的变形量,并以此计算出聚酰亚胺无机纳米杂化膜的热膨胀系数。实验中同时测量了掺杂有不同浓度粘土、云母和二氧化硅类无机物的聚酰亚胺薄膜的热膨胀系数,并对实验结果进行了分析。     

高频微晶玻璃介质材料的晶化研究

利用堇青石为主晶相的微晶玻璃,高频损耗小,成功地研制了一种介电常数ε＝7．2±0．2,介电损耗tgδ＜1．5×10^－4（制试频率＞1GHz）的微波材料.采用X射线衍射分析、扫描电镜、物理性能和电性能测试等技术,研究了该种玻璃晶化过程中的密度变化、晶相转变、以及电性能与晶相组成和结构的关系．     

纳米SiO2-Al2O3/聚酰亚胺杂化薄膜的制备及表征

用溶胶-凝胶法制得二氧化硅(SiO2)及三氧化二铝(Al2O3)溶胶,将其掺入到聚酰胺酸基体中,得到SiO2-Al2O3/聚酰亚胺杂化薄膜,并对其结构性能进行了研究.结果表明,薄膜材料中SiO2和Al2O3粒子分散均匀,与有机相存在键合;材料热分解温度有所提高.     

纳米Mg(OH)2-ZnO/聚酰亚胺复合薄膜的介电和热性能

采用反向沉淀法制备了Mg（OH）₂-ZnO纳米粒子,通过原位聚合和热亚胺化的方法成功制备了不同纳米Mg（OH）₂-ZnO粒子质量分数的纳米Mg（OH）₂-ZnO/聚酰亚胺（PI）复合薄膜,通过SEM、热重分析、介电谱测试仪和击穿场强测试仪对薄膜的表面形貌、热稳定性、介电性能和击穿强度进行表征和测试。结果表明：Mg（OH）₂-ZnO纳米粒子均匀地分散在PI基体中,Mg（OH）₂-ZnO/PI热稳定性下降,介电常数、介电损耗和电导率增加,击穿场强随纳米粒子增加先增加后减小,在纳米粒子含量为2%时,达到最大值296 kV/mm。     

Preparation and characterization of PI/PVDF composite films with excellent dielectric property

All-organic polyimide (PI)/poly(vinylidene fluoride) (PVDF) composite materials with high dielectric constant and low dielectric loss were fabricated via solution blending. The dielectric, mechanical, and thermal properties of the PI/PVDF composite films were studied. Results indicated that the dielectric properties of the composites were highly reinforced through the introduction of PVDF, and the composites exhibited excellent thermal stability. When the mass fraction of PVDF was adjusted to 30 wt%, the specimen demonstrated excellent thermal properties, superior mechanical properties, high dielectric constant (5.7, 1 kHz), and low dielectric loss (0.009, 1 kHz). Moreover, the dependence of the dielectric constant and dielectric loss on frequency was investigated. The composite presented stable dielectric constant and dielectric loss that were less than 0.04 within the testing frequency range of 100 Hz–10 MHz. This study demonstrated that the PI/PVDF composites were potential dielectric materials in the field of electronics.     

SiO_2含量对PI/SiO_2杂化薄膜性能的影响

聚酰亚胺与SiO2杂化形成的有机-无机杂化薄膜体现出了优异的综合性能,在催化与分离、微电子、光电和绝热材料等领域具有广泛的应用及发展潜力。杂化材料相关的研究也越来越多,就SiO2含量对聚酰亚胺/SiO2杂化薄膜的光、电、热和力学性能的影响进行综述,总结了杂化薄膜的性能随SiO2含量变化而变化的基本规律。     

The preparation,mechanical and dielectric properties of PEN/HBCuPc hybrid films

Polyarylene ether nitriles (PEN)/hyperbranched copper phthalocyanine (HBCuPc) hybrid films have been successfully fabricated via PEN mixing with HBCuPc in N-methylpyrrolidone solution, solution-casting and then co-crosslinking at high temperature. The dielectric properties of the films were measured to find that dielectric constant as well as dielectric loss of the hybrid films increased linearly with the increasing HBCuPc content without sacrificing dielectric breakdown strength compared to that of the pristine polymer. These results shows PEN/HBCuPc hybrid films have a high dielectric constant and low dielectric loss at a high operational frequency (>1 kHz). The tensile strength and elongation at break of the hybrid films were increased with the increase of HBCuPc content and the thermal stability was improved with the increase of HBCuPc content.     

Tensile,dielectric, and thermal properties of epoxy composites filled with silica,mica, and calcium carbonate

The minerals silica, mica, and calcium carbonate (CaCO₃) were used as fillers to produce epoxy thin film composites for capacitor application. The effects of filler loading and type on the morphology, tensile, dielectric, and thermal properties of the epoxy thin film composites were determined. Results showed that epoxy thin films with 20 vol% filler loading showed good dielectric properties, thermal conductivity, and thermal stability. However, the tensile properties of the thin films were reduced as the filler loading was increased due to brittleness. Dielectric constant and dielectric loss of epoxy/inorganic composite films generally increased with increasing mineral filler loading. Meanwhile, the presence of mineral filler improved the thermal stability of the thin film composites. The highest dielectric constant of 5.75 with 20 vol% filler loading at a frequency of 1 MHz was exhibited by the epoxy/CaCO₃ composite, followed by epoxy/mica and epoxy/silica. Therefore, the epoxy/CaCO₃ composite is the most potential candidate for capacitor application. Moreover, precipitated CaCO₃ provided better tensile properties and slightly improved the dielectric properties compared with mineral CaCO₃.     

Dielectric properties of on-chip-cured polyimide films

Spin-coated polyimide thin films were locally cured using microelectromechanical system microhotplates as an alternative approach to the conventional wafer-level curing process. The on-chip cured polyimide films were characterized Fourier transform infrared spectroscopy. The polyimide was found to be fully cured at a temperature over 350 °C for 1 h. The dielectric properties of 350 °C-cured polyimide films were measured over broad frequency, temperature, and humidity ranges. As is expected for most polymer materials, the dielectric constant decreased with increasing frequency due to dielectric relaxation, which may be due to the fact that multiple relaxation times (i.e., several types of polarization), rather than a single one are involved. The dissipation factor was very low and nearly flat for excitation frequencies less than 1 MHz. Both the dielectric constant and the dissipation factor increased with increasing temperature from 10 °C to 90 °C, and relative humidity (RH) from 30%RH to 95%RH, with a steeper slope at lower frequencies. These results indicate that on-chip-cured polyimide films have weak low frequency dispersion due to the aging effect at high temperature and humidity.     

Electrical and thermal properties of polyimide/silica nanocomposite

The electrical and thermal properties of thin films of polyimide/silica nanocomposites prepared via sol–gel process were studied as a function of nanosilica particles content, temperature and applied field frequency. It was found that the dielectric constant and dielectric loss of the nanocomposites decrease with both the frequency and the nanosilica content, while increase with temperature. The AC-conductivity measured in frequency range 200?kHz–1.5?MHz decreases with the filler concentration and increases with increasing temperature. For the (25?wt%) nanocomposite, it was found that the AC-conductivity increases with temperature, and the Cole–Cole plots showed that the calculated activation energy and relaxation time decrease with temperature. The observed thermal conductivity increases gently with temperature. The empirical universal law was used to fit the observed electrical data under the measuring conditions.     

Polyimide/silica/titania nanohybrids via a novel non-hydrolytic sol–gel route

Polyimide/silica/titania hybrid films were prepared via a non-hydrolytic sol–gel route. Silicic acid and titanium tetrachloride were used as the precursors of silica and titania, respectively. The absorption band of Si–O–Ti bonds in FTIR spectra of the hybrid films revealed the formation of the hybrid inorganic network between SiO₂ and TiO₂. Scanning electron microscopy results indicated that the nanometer-scaled inorganic domains were homogeneously dispersed in polyimide matrix due to the introduction of silica-stabilized TiO₂ and the interactions between organic and inorganic phases. The studies on the optical properties of the hybrid films indicated the red-shift of the absorption band increased with increasing TiO₂ content, while all the hybrid films maintained their transparencies. The surface resistances of the hybrid samples decreased with increasing TiO₂ content. The thermal decomposition temperature of the ternary hybrid films decreased slightly with increasing TiO₂ content. This kind of hybrid materials may have potential application in the preparation of opto-electronic devices.     

纳米钛酸钡掺杂聚酰亚胺基高介电复合薄膜的制备及性能

采用原位聚合法和高速砂磨法制备了纳米钛酸钡/聚酰亚胺高介电常数复合薄膜,分析了不同制备方法及钛酸钡粉体用量对复合薄膜结构和性能的影响。实验结果表明,高速砂磨法对于纳米钛酸钡粉体的分散效果优于原位分散法;钛酸钡粉体的引入,有效提高了复合薄膜的热稳定性和介电性能。当粉体的体积分数达到50%时,复合薄膜介电常数相较于纯膜提高了10倍,而介电损耗只有少量增加。     

可溶性PI／SiO2纳米复合材料中SiO2微相结构变化的研究

选取可溶性聚酰亚胺（PI）作为有机高聚物基本，通过正硅酸四乙酯（TEOS）在聚酰胺酸（PAA）的N－甲基－2－毗咯烷酮（NMP）溶液中进行溶液－凝胶反应,制备出新型的聚酰亚胺／二氧化硅（PI／SiO2)纳米复合材料，并用UV－Vis-FT-IR,SEM和光子相关法等对其溶胶－凝胶转变过程，二氧化硅微相结构的变化进行了研究，并对溶中粒子间的团聚行为作了进一步探讨，结果表明随着处理温度的升高，PAA逐步亚胺化，同时TEOS水解后的硅烃基（Si-OH)逐步缩合，由线型结构向环状结构过渡，原位生成SiO2凝胶网络，实验结果还发现热处理温的升高对二氧化硅元化粒子的尺寸无明显的影响，而光子相关法结果则表明颗粒表面活性Si-OH的存在是引起团聚的一个重要因素。