耐高温聚间苯二甲酰间苯二胺介电复合材料的制备及性能

采用水热法以二氧化钛(TiO2)纳米粒子为原料合成了高长径比钛酸钡纳米线((BaTiO3 nanowires(BTN));为了改善BTN与聚合物基体的相容性并保持BTN完整的化学结构,选择聚乙烯吡咯烷酮(PVP)作为改性剂,通过物理吸附作用将其包裹在BTN表面形成P-BTN纳米线;随后将P-BTN作为高介电常数填料加入到聚间苯二甲酰间苯二胺(PMIA)基体中制备出耐高温的PMIA介电复合材料.研究了P-BTN含量对PMIA复合材料介电性能、击穿强度的影响以及高温下P-BTN/PMIA复合材料介电性能的变化.结果表明:BTN经过PVP表面改性后,在P-BTN含量较高时依然可以均匀地分散在PMIA基体中,且与PMIA基体具有良好的相容性;随着P-BTN含量的增加,PMIA复合材料的介电常数提升明显;100 Hz时,含有15％(质量分数)P-BTN的PMIA复合材料的介电常数提升至18.5,相较于纯PMIA增加了7.4倍,同时介电损耗依然较低;在高温环境中(150～250℃),P-BTN/PMIA复合材料的介电性能稳定,没有出现明显波动,满足高温环境对材料介电性能的使用要求;此外,低含量P-BTN还可以改善PMIA介电复合材料的击穿强度,适用于更高电场强度环境中.     

AlN-堇青石玻璃复合材料的介电性能

为了研究热压温度和AlN含量对AlN-堇青石玻璃复合材料烧结和介电性能的影响,采用真空热压方法在900~1000℃低温烧结制备AlN-堇青石玻璃复合材料.利用X射线衍射、扫描电镜和阻抗分析仪对复合材料的微结构和介电性能进行了研究.结果表明,随着热压温度的提高,复合材料的相对密度增加,复合材料的介电常数和介电损耗减少;在一定的热压温度下,复合材料的介电常数和介电损耗随着AlN引入量的增加而增加.从复合材料的相组成和结构角度对以上结果予以解释,提高热压温度和增加α-堇青石数量均有利于降低复合材料的介电常数和介电损耗.制备的复合材料具有低的介电常数(5.6~6.5)和低的介电损耗(≤10-3),有望用于微电子封装领域.     

AIN-堇青石玻璃复合材料的介电性能

为了研究热压温度和AIN含量对AIN-堇青石玻璃复合材料烧结和介电性能的影响,采用真空热压方法在900～1000℃低温烧结制备AIN-堇青石玻璃复合材料,利用X射线衍射、扫描电镜和阻抗分析仪对复合材料的微结构和介电性能进行了研究,结果表明,随着热压温度的提高,复合材料的相对密度增加,复合材料的介电常数和介电损耗减少;在一定的热压温度下,复合材料的介电常数和介电损耗随着AIN引入量的增加而增加,从复合材料的相组成和结构角度对以上结果予以解释,提高热压温度和增加α-堇青石数量均有利于降低复合材料的介电常数和介电损耗,.制备的复合材料具有低的介电常数(5.6～6.5)和低的介电损耗(≤10-3),有望用于微电子封装领域.     

0-3 型压电陶瓷/ 硫铝酸盐水泥复合材料的介电性及压电性

以硫铝酸盐水泥为基体, 铌镁锆钛酸铅(PMN) 陶瓷颗粒为功能体制备了水泥基压电复合材料。重点讨论了复合材料的介电性能和压电性能。结果表明: 水泥基压电复合材料的介电温谱在- 30 ℃～150 ℃范围内较平坦, 表现出优良的介电温度稳定性, 而介电损耗随着温度的升高而增加; 水泥基压电复合材料的压电应变常数和介电常数均随着PMN 含量的增加而增大。      

Al2O3含量对Al2O3/LiTaO3复合陶瓷介电性能的影响

采用热压烧结法制备了Al₂O₃/LiTaO₃ (ALT) 陶瓷复合材料, 研究了Al₂O₃不同体积含量(5vol%、10vol%、15vol%和20vol%)对LiTaO3压电陶瓷介电性能的影响. 结果表明：随着频率的增加, 不同Al₂O₃含量的ALT陶瓷复合材料的介电常数和介电损耗均降低, 但降低的幅度不同. 少量Al₂O₃(5vol%)的添加既能增大材料的介电常数同时又降低了材料的介电损耗, 但是随着Al₂O₃含量的继续增加, ALT陶瓷复合材料的介电常数和介电损耗都增大, 其居里温度先升高后降低. Al₂O₃作为第二相不但能促进LiTaO3陶瓷烧结致密,而且对ALT陶瓷复合材料的介电性能也有提高.     

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。     

CB/CNTs/PP导电高聚物力/温度作用下介电性能的研究

以聚丙烯(PP)为基体,炭黑(CB)和碳纳米管(CNTs)为填料,通过熔融共混、注塑成型制备导电复合材料,测定电场频率、填料种类、填料含量以及温度、载荷等因素对其介电性能的影响。结果表明,室温下,随着填料含量的增加,材料介电常数和介电损耗均呈增大趋势;随着频率的增加(100 Hz～10MHz),介电常数和介电损耗首先迅速降低,然后逐渐趋于稳定;随着CNTs的加入,CB/CNTs/PP导电复合材料的介电常数明显增大,但是当填料含量达到某一定值时,继续增大CNTs的含量,介电常数反而下降;同一频率下,随着温度的升高(30～100℃),由热膨胀引起炭黑粒子间距的变化会导致介电常数减小。复合材料压缩实验表明:压缩载荷作用下,材料发生形变,基体中的CB粒子间相对位置改变,引起介电常数减小。     

[C16min]Br修饰的多壁碳纳米管及其与低密度聚乙烯复合材料的制备及介电性能

为改善多壁碳纳米管(MWNT)在低密度聚乙烯(LDPE)中的分散性及复合材料的界面特性,采用溴化-1-十六烷基-3-甲基咪唑基离子液体([C16min]Br)对MWNT进行表面改性,并用Raman光谱对改性效果进行了表征。将经过修饰的碳纳米管(MIL)与LDPE熔融共混得到MIL/LDPE复合材料,采用场发射扫描电子显微镜(FESEM)和阻抗分析仪(LCR)对复合材料的结构与介电性能进行了分析。结果表明,相比与MWNT/LDPE(渗流阈值为5.2%,介电常数为82,介电损耗为0.93),MIL/LDPE(渗流阈值为9.1%,介电常数为169,介电损耗为0.51)介电常数增大,介电损耗降低。并且在低温时,MIL/LDPE介电常数随温度的变化甚小,显示出良好的温度-介电常数特性。     

水磨工艺对Mn改性(Na0.5Bi0.5)0.88Ca0.12TiO3介电性能的影响

研究了去离子水作为球磨介质对Mn掺杂(Na0.5Bi0.5)0.88Ca0.12TiO3(BNCT)陶瓷介电性能的影响.相对于酒精,水磨样品的介电常数较小.介电常数温度曲线以及电容变化率温度曲线都比较平坦,在-55～250℃范围内,ΔC/C25℃≤±15%.介电损耗在100℃以上时明显增大.比较和分析了XRD图谱和SEM图片,并借助于EDS探讨了微观机理.     

多尺度功能性填料PVDF基纳米复合材料的制备和性能

先以两种直径(50 nm,100 nm)的羟基化钛酸钡(BT)和两种长度(10~20 nm,20~40 nm)的酸化多壁碳纳米管(MWCNTs)为功能填料,进行液相反应制备四种BT/MWCNTs杂化纳米填料(分别记为BT-A/MWCNTs-B,其中A=5,10;B=1,2),再用熔融共混-压板成型技术分别将其与PVDF复合制备出BT-A/MWCNTs-B/PVDF纳米复合材料。使用X射线衍射(XRD)、红外光谱(FTIR)、差示扫描量热分析(DSC)、扫描电子显微镜(SEM)、拉伸性能测试和介电性能测试系统研究了多尺度功能性填料BT-A/MWCNTs-B对这种纳米复合材料的组织结构和结晶性能、介电性能和力学性能的影响。结果表明,与BT/PVDF和MWCNTs/PVDF体系相比,BT-A/MWCNTs-B/PVDF纳米复合材料具有更高的结晶度和热性能,BT-10的含量(质量分数,下同)为16%、MWCNTs-2的含量为5%的BT-10/MWCNTs-2/PVDF纳米复合材料其熔融温度可达173.8℃,比纯PVDF(159.6℃)提高了14.2℃,其结晶度可达43.1%。三相BT-A/MWCNTs-B/PVDF纳米复合材料比两相纳米复合材料具有更优异的介电性能,BT-10/MWCNTs-2/PVDF纳米复合材料100Hz下的介电常数为119,为纯PVDF的14倍,其介电损耗只有0.051。BT-10/MWCNTs-2/PVDF纳米复合材料的拉伸强度和弹性模量分别达到57.7 MPa和1226 MPa。     

搅拌铸造法制备短碳纤维/AZ91复合材料的组织与性能

采用搅拌铸造法制备了不同体积分数（10vol%、15vol%、20vol%）的短碳纤维增强镁基（CF_s/AZ91）复合材料,并选取了三个挤压比和两个挤压温度对其进行热挤压变形,采用光学显微镜（OM）、SEM和TEM对CF_s/AZ91复合材料的显微组织进行了观察,并测试其室温力学性能及阻尼性能。研究结果表明,热挤压能够有效降低CF_s/AZ91复合材料气孔率;在热挤压过程中,纤维沿挤压方向定向排列,同时基体发生动态再结晶。随着挤压温度及挤压比的增大,晶粒呈现等轴状,组织更加均匀。CF_s/AZ91复合材料经过挤压后,其力学性能得到提高,屈服强度和抗拉强度随挤压比和CF_s体积分数的增大而增大,然而CF_s纤维在热挤压后发生明显断裂,限制了挤压态复合材料强度的进一步提升。低温低挤压比条件下,CF_s/AZ91复合材料具有较好的阻尼性能,随着挤压比及挤压温度的升高,CF_s/AZ91复合材料室温及高温阻尼性能均有所降低。      

α-羟基,ω-环氧基聚己内酯/环氧树脂复合体系的制备和耐热性能

利用ε-己内酯的酶促开环聚合,合成了α-羟基,ω-环氧基聚己内酯低聚物(ETPCL);利用—OH与—NCO的亲核加成反应,通过聚氨酯途径合成了环氧基封端的聚己内酯接枝环氧树脂共聚物(PCL-g-GY250);将PCL-g-GY250与分子量较高的环氧树脂GT7071进行共混,通过胺类固化剂与环氧基团的固化反应制备了不同PCL-g-GY250含量的环氧树脂复合体系(PCL-g-GY250/GT7071);利用热失重分析(TGA)及在甲苯中的溶胀实验分别对复合体系的耐热性能和交联密度进行了表征。结果表明:随PCL-g-GY250含量的增加,体系的交联网络密度逐渐下降;PCL-g-GY250的引入,使得复合体系的耐温性能得到改善:当PCL-g-GY250与GT7071的质量比为4∶1时,固化体系的5%热失重温度(T5d%)可由纯环氧固化体系的145.0℃提高到216.3℃;尤其是纯PCL-g-GY250固化体系的T5d%更是达到293.9℃,相比纯环氧树脂固化体系提高了148.9℃。     

甘氨酸硝酸盐法合成GdBaCo2O5+δ阴极材料及其性能

采用甘氨酸硝酸盐法(GNP)制备中温固体氧化物燃料电池(IT-SOFC)GdBaCo2O5+δ(GBCO)阴极材料,探索甘氨酸与金属阳离子摩尔比(G/M)等合成条件对产物性能的影响,研究了GBCO的微观形貌、晶体结构、电导率和电化学性能.结果表明,G/M为3.0的阴极粉料(GBCO-3.0)颗粒细小均匀且比表面积大,G/M在2.5～3.5之间制备的粉料经1000℃煅烧5 h可形成结晶度高的GBCO纯相.阴极材料GBCO与电解质材料Sm0.2Ce0.8O1.9(SDC)在1100℃混合煅烧,未发生明显的化学反应.在500～800℃范围内,GBCO阴极的电导率均大于100 S/cm.1050℃煅烧的GBCO-3.0阴极的极化电阻(Rp)最小,750℃为0.125.cm2.     

The effect of geometric factor of carbon nanofillers on the electrical conductivity and electromagnetic interference shielding properties of poly(trimethylene terephthalate) composites: a comparative study

In this study, the effects of filler geometry on the electrical conductivity and electromagnetic interference (EMI) shielding properties of poly(trimethylene terephthalate) (PTT) composites filled with graphene nanosheets (GNSs), carbon nanotubes (CNTs), and GNS–CNT hybrid nanofillers have been investigated. The GNSs, CNTs, and hybrid GNS–CNT were well dispersed in the PTT matrix using a simple coagulation process. GNSs were prepared from graphene oxide (GO) through hydrazine reduction, and thermal reduction of GO at two different temperatures of 1050 and 1500 °C. PTT filled with different aspect ratios and oxygen functional groups of GNS were also prepared in order to compare the electrical conductivity and EMI shielding properties. The aspect ratios of GNSs and CNTs were estimated by using an ellipsoid model. Percolation scaling laws were applied to the magnitudes of conductivity to reveal the percolation network and filler dispersion. The percolation exponent of the PTT/GNS composites was larger than that of the PTT/CNT composites. The percolated filler–filler network at which the percolation exponent changed was correlated with the filler geometric structure. GNS–CNT hybrid nanofillers formed a complex double brush structure in the PTT/GNS–CNT composites. The geometric structure, aspect ratio, and intrinsic conductivity of carbon nanofillers affected the electrical percolation threshold and EMI shielding efficiency of the composites.     

微波冶金用堇青石莫来石耐火材料制备及性能

为探索适合于微波冶金高温反应过程使用的耐高温、抗热震、低微波吸收率耐火材料,采用常压烧结法在不同温度合成了不同配比的堇青石-莫来石质耐火材料.采用XRD分析、三点弯曲法及Angilent阻抗分析等测试了烧结温度及配比对耐火材料物相组成、抗弯强度、抗热震性能及介电性能的影响规律.结果表明,随烧结温度由1400℃提高至14...     

Self-sensing of carbon fiber/carbon nanofiber–epoxy composites with two different nanofiber aspect ratios investigated by electrical resistance and wettability measurements

Electro-micromechanical techniques, wettability test, and acoustic emission (AE) were use to compare self-sensing and stress-transferring effects in single carbon fiber embedded in carbon nanofiber (CNF)–epoxy composites with two different aspect ratios. Electrical resistivity and standard deviation were used as indirect measures of comparative dispersion degree of CNF. The dispersion was observed to decrease with increasing CNF content due to an increase in the electrical contacts. Composites with higher aspect ratio exhibited better self-sensing than lower aspect ratio case. This was attributed to differences in dispersion, orientation, coagulation of CNF with different aspect ratios. The opposite effect was observed for apparent Young’s modulus, which was larger for composites with lower aspect ratio. This is probably related to better stress transfer linked to orientation effects. Work of adhesion consistently followed same trend as apparent Young’s modulus. Single carbon fiber pull-out tests and AE provided additional information on the effects of aspect ratio.     

Effect of particles size on the AC electrical behavior of iron/polystyrene composites

The AC electrical characteristics of polystyrene/Iron composites filled with iron particles of average sizes: 5, 40, 110 and 250 μm, have been investigated. The AC electrical properties were studied in frequency range (50 kHz–1 MHz), and temperature range (30–110 °C) using the impedance method. The AC-conductivity and dielectric constants were determined from the measured impedance data. It was found that the applied frequency, temperature, and iron particles size affect the electrical and dielectric properties of the composites. The AC-electrical conductivity is increasing with temperature. The dielectric constant and the dielectric loss of the composites increase with decreasing the iron particles size. The universal power-law of the electrical conductivity gives exponent with 0 < m < 1 characterizing hopping conduction. The small values of the activation energy indicate that the composite of smallest iron particle size, electrons can tunnel or hop more easily from the valence band to conduction energy band due to the reduction of interparticles separation.     

PAN-based carbon fibers/PMMA composites: thermal, dielectric, and DC electrical properties

The study deals with thermal, dielectric, and DC electrical properties of polyacrylonitrile (PAN)-based carbon fibers/poly(methyl methacrylate) composites. The polymer composites contain 0, 5, 10, 20 and 30 wt.% PAN-based carbon fibers. The thermal conductivity was studied as a function of filler content and temperature. It was found that the thermal conductivity is enhanced by addition of carbon fibers concentration and temperature. The dielectric properties were determined using impedance measurements. The results showed that the dielectric constant and dielectric loss are decreased with frequency, and increased with both temperature and fibers content. The DC electrical conductivity, temperature coefficient of resistance, and activation energy were studied as a function of fibers concentration in the temperature ranges 30–110?°C. It was found that the composites exhibit negative temperature coefficient of resistivity and enhancement of electrical conductivity with increasing temperature and carbon fibers concentration. The observed increase in the DC conductivity was explained according to the approach of conductive paths and connections between the carbon fibers.     

Influence of zeolite structure and chemistry on the electrical response and crystallization phase of poly(vinylidene fluoride)

Zeolites with framework types LTL, LTA, FAU, and MFI were synthesized and used as fillers to prepare PVDF/zeolite composites. The obtained composites showed structural and electrical dependence on the pore system and chemical content of the inorganic host. The larger polymer-zeolite electrostatic interactions of the Y and A zeolites lead the polymer to crystallize in the electroactive γ-phase, which in the case of the L zeolite is prevented due to the reduced interaction area. The solvent and water encapsulation ability of the zeolite as well as improve of the dielectric response of the composite is directly related to the Si/Al ratio, leading zeolites with lower Si/Al ratios to larger dielectric responses and encapsulation efficiencies in the composites. These effects show also some dependency on the dimensionality of the pore system; the zeolite L-containing 1D channels showing superior dielectric performance than the 3D pore system of zeolite Y.