膨胀石墨/石蜡复合相变材料的导电及发热特性

采用混合搅拌方法制备膨胀石墨（EG）/石蜡复合相变材料,测试分析了EG含量、施加电压与EG/石蜡复合相变材料体积电阻率的关系,研究了直接自发热和正温度系数（PTC）电阻发热时复合相变蓄热单元的发热特性。结果表明,随着EG含量或施加电压的增大,复合相变材料体积电阻率逐渐减小;施加电压对样品体积电阻率的影响与复合相变材料中EG含量有关,EG含量越高,施加电压对复合相变材料体积电阻率的影响越明显。当施加电压为4.0V时,EG质量分数分别为4%、5%、8%的复合相变材料体积电阻率分别只有0.5V时的0.481倍、0.185倍、0.068倍。基于复合相变材料导电特性,直接负载电压可实现复合相变材料电热转化和相变蓄热;结合PTC电阻发热可灵活控制复合相变蓄热单元加热功率,实现其快速充热。     

EPDM/LLDPE/CB复合导电体系热敏特性研究

研究了ＥＰＤＭ／ＬＬＤＰＥ／ＣＢ复合型导电高分子材料电阻率的温度依赖性，炭黑含量的依赖性及热功率特性。确定了制备热敏导电材料的最佳ＥＰＤＭ用量。实验表明，在体系临界组成和ＥＰＤＭ含量（质量）１０～２０份时，炭黑粒子能得到较均匀分布，室温电阻率较低，且具有强ＰＴＣ效应，适于制作ＰＴＣ热敏材料。     

水泥/碳黑/水性聚氨酯共混导电材料的研究

使用水性聚氨酯、导电碳黑和石墨、水泥粉体和其他助剂共混,研制开发了一种复合导电材料.实验结果表明,该涂料的体积电阻率达到103 Ω·cm.除了具有一定的导电性能以外,也具有良好的机械性能.本文介绍了材料的配制和性能,讨论了导电填料的含量与该材料导电性能之间的影响,以及水泥固体粉体含量与材料机械性能的关系.     

竹粉/呋喃树脂制备木陶瓷的研究

本文以呋喃树脂与竹粉为原料制备了木陶瓷,利用扫描电镜(SEM)、 X射线衍射(XRD)技术分别对木陶瓷的微观结构与物相进行了表征,研究了呋喃树脂含量对木陶瓷的炭得率、尺寸收缩率、密度与体积电阻率的影响.结果表明,木陶瓷是由竹炭与玻璃炭构成的复合炭材料,呋喃树脂含量对木陶瓷结晶性影响不大.呋喃树脂含量越高,木陶瓷的炭得率、密度越大,尺寸收缩率与体积电阻率越小.     

碳纤维分布状态对PE-HD/EVA/CF复合材料导电性能的影响

采用硅烷偶联剂 KH560对碳纤维(CF)进行了处理,并探讨了 CF 含量对 PE-HD/CF 以及 PE-HD/EVA/CF复合材料导电性能的影响。结果表明,随着 CF 含量的增加,PE-HD/CF 体系的体积电阻率从6.16×10~(14)Ω·cm 下降到1.54×10~7Ω·cm,表面电阻率从2.59×10~(16)Ω下降到5.74×10~9Ω;而 PE-HD/EVA/CF 复合体系中体积电阻率从1.91×10~(13)Ω·cm 下降到3.27×10~8Ω·cm,表面电阻率从5.72×10~(15)Ω下降到6.18×10~8Ω,表明加入 EVA 有利于提高复合体系的导电性能。当 CF 含量为5份时,复合材料的体积电阻率达到最小值。研究还表明,随着 CF 含量的增加,CF 沿着外力方向出现很明显的取向,沿着 CF 取向方向材料的体积电阻率和表面电阻率均有所下降。     

铁粉/聚丙烯复合材料的电磁屏蔽性能

研究铁粉含量、粒度及偶联剂对铁粉/PP复合材料导电性和电磁屏蔽性能的影响.结果表明:铁粉/PP复合材料的体积电阻率随铁粉质量含量的增加而降低,在20%时出现渗滤值,当铁粉质量含量超过30%之后,继续增大铁粉含量复合材料的体积电阻率和屏蔽效能变化不明显.铁粉含量一定时,随着铁粉目数增大,复合材料的屏蔽效能有所提高;在100MHz～1 GHz低频区域,复合材料最大电磁屏蔽效能达到了40dB.钛酸酯偶联剂为铁粉质量的4%时,能很好地改善铁粉/PP材料的导电性和屏蔽性能.     

高分子型抗静电剂的制备

采用模板诱导法和模压成型法制备了高分子型抗静电剂聚丙烯接枝苯乙烯磺酸共聚物-聚苯胺(PP-g-SPS-PANI)和抗静电聚丙烯(PP)材料,考察了盐酸用量、过硫酸铵/苯胺(APS/AN)物质的量比、原料磺化度等因素对抗静电剂产率和抗静电PP材料体积电阻率的影响.结果表明:抗静电PP材料的体积电阻率比PP降低了5个数量级;在一定范围内,增加盐酸用量和APS/AN物质的量比可提高抗静电剂产率和降低抗静电PP的体积电阻率;随着原料磺化度的提高,样品体积电阻率逐渐降低;随着样品中抗静电剂含量的提高,样品体积电阻率不断下降,但当抗静电剂质量分数超过10%后,电阻率变化不大.     

CaTiO3对（Ba,Pb）TiO3系高温PTC材料性能和显微结构的影响

研究了CaTiO3含量及烧成工艺对(Ba,Pb)TiO3基PTC陶瓷材料性能和显微结构的影响。结果表明CaTiO3的最佳添加量为3mol%,室温电阻率达到最小,PTC效应最好。SEM观察表明添加CaTiO3后晶粒更均匀致密。不同烧成工艺下材料性能的比较,结果表明烧成温度越高,温度系数越大,但室温电阻率也越大;降温阶段的保温能增强PTC效应。     

溶液法制备的CB/HDPE/UHMWPE复合材料的导电性能

以导电炭黑(CB)为填料,高密度聚乙烯(HDPE)和超高摩尔质量聚乙烯(UHMWPE)为基体,通过超声溶液分散法制备了CB/HDPE/UHMWPE复合材料,并研究了CB含量对复合材料体积电阻率和阻-温特性的影响。研究发现,当HDPE∶UHMWPE质量比为7∶3,CB含量在5%左右时,CB/HDPE/UHMWPE复合材料能够形成完善的导电网络,材料具有较好的电性能;材料的体积电阻率随着温度的升高变大,在熔点附近时剧增,且材料的正温度效应(PTC)强度在CB含量大于渗流阈值的范围内,随着CB含量的增加而逐渐减小。通过多次对复合材料进行热循环测试发现CB/HDPE/UHMWPE复合材料具有良好的热稳定性。     

镀镍碳纤维/镀镍石墨粉填充PC/ABS复合材料导电性能研究

将导电填料镀镍碳纤维(NiCF)和镀镍石墨粉填充到PC/ABS共混物中,制备一种填充型导电复合材料,分析了NiCF与镀镍石墨粉的含量及NiCF长度对复合材料导电性能的影响。结果表明,随着NiCF和镀镍石墨粉含量的增加,复合材料的体积电阻率会降低,即导电性能得到提高;与镀镍石墨粉相比,NiCF对复合材料导电性的影响更显著;PC/ABS/NiCF/镀镍石墨粉复合材料存在渗滤效应,NiCF含量在10%~15%范围内时,材料的体积电阻率急剧下降,导电性能迅速提高;复合材料颗粒长度为10 mm左右时,材料的导电性能最佳。     

金属Ni/石墨/BaTiO3基复合PTC材料的研究

探讨了降低BaTiO3基的PTC陶瓷室温电阻率的新途径，即在BaTiO3基的VIE陶瓷配方中加入石墨或金属Ni。目的是将石墨或金属Ni优良的导电性和BaTiO3陶瓷的PTC效应相结合，制备出具有较低室温电阻率又有较好PTC效应的复合材料。通过对大量实验和数据分析。优化了实验配方和工艺条件．获得了性能良好的复合PTC材料。     

掺杂对BaTiO3基PTC陶瓷材料性能的影响

概述了BaTiO3基PTC陶瓷半导化的掺杂种类和机理,综述了掺杂物的添加量和加入方式对BaTiO3基PTC陶瓷材料性能的影响,并展望了其发展趋势。通常BaTiO3陶瓷的电阻率在开始时都随施主掺杂浓度的增加而降低,当施主掺杂浓度达到某一值时,电阻率降至最低,而后随着施主掺杂浓度的提高,电阻率则迅速上升。随着受主掺杂含量的增加,材料的室温电阻率和升阻比逐渐增大,PTC性能逐步提高,当含量超过某一值时,升阻比又呈降低趋势,PTC效应有所降低,室温电阻率依然增大。由于各掺杂物的优缺点不同,近几年研究发现,双施主掺杂和施受主共掺能够很好的改善材料的性能。     

Gd_2O_3掺杂对BaTiO_3陶瓷电性能的影响

采用溶胶-凝胶法制备了掺杂不同量Gd2O3(分别为0 001、0 002、0 003、0 005、0 007mol mol)的BaTiO3陶瓷,并对其电性能进行了研究。结果表明:Gd2O3掺杂使BaTiO3陶瓷的电阻率明显下降,当添加量为0 002mol mol时,电阻率最小,为1 27×105Ω·m;晶粒电阻随着温度的变化,呈现NTC效应,而晶界电阻随着温度的变化,呈现PTC效应,而且晶界电阻远远大于晶粒电阻,说明Gd2O3掺杂BaTiO3陶瓷的PTC效应是一种晶界效应;Gd2O3掺杂使BaTiO3陶瓷的介电常数和介电损耗在低频时明显增大,在高频时又明显降低。     

Effect of additives on the electrical properties of a (Ba0.92Sr0.08)TiO3-based positive temperature coefficient resistor

In the present work, the effects of the additives (BN, Y₂O₃+Nb₂O₅, Sb₂O₃+Nb₂O₅, and Cr) on the electrical properties of (Ba_0.92Sr_0.08)TiO₃-based positive temperature coefficient resistor (PTCR) were investigated. It was noted that the addition of BN lowered the sintering temperature of the material system studied. A proper amount of BN could enhance the PTC effect, but the room-temperature resistivity would increase with increasing the content of BN. The addition of double donor Sb₂O₃+Nb₂O₅ could lead to a lower room-temperature resistivity than that of Y₂O₃+Nb₂O₅. Metal Cr was also added to further reduce the resistivity. The low room-temperature resistivity and PTC behavior was achieved by controlling both the metallic Cr content and the process of reducing sintering and oxidation treatment.     

施主掺杂BaTiO3陶瓷临界浓度的理论计算

空气中烧结各种施主掺杂的BaTiO3陶瓷时,存在一种电阻率反常现象.从热力学以及晶体结构化学的角度出发,对临界施主掺杂浓度进行了理论计算和推导.结果表明:释放氧所需的能量与施主离子的种类无关,因而临界施主掺杂浓度为一定值;临界掺杂浓度时的晶粒尺寸越小,在晶粒重结晶过程中临界施主掺杂浓度就越大.     

V2O3-Polymer Composite Thermistors

V₂O₃ was incorporated into polymer matrices to produce composite materials with low room-temperature resistivities and sizable positive temperature coefficient (PTC) resistance effects. In addition, a negative temperature coefficient effect, associated with the semiconductor-to-metal phase transition in V₂O₃, was also observed. The resistivity vs temperature curve for these composites resembles a square well with three temperature regimes in which the composite behaves like a semiconductor, a metal, and an insulator. The intensity of the PTC effect for these composites was found to be as large as 10 orders of magnitude.     

BaTiO3基PTC陶瓷凝胶注模成型

本文研究了BaTiO3基PTC陶瓷的凝胶注模成型工艺，包括浆料的制备，交联剂的用量，引发剂和催化剂用量及环境温度对可操作时间的影响规律等方面；考察了凝胶注模成型陶瓷的PTC性能。     

Electrical Characterization of a Joined Electroceramic, La0.85Sr0.15MnO3

Pieces of saw-cut La_0.85Sr_0.15MnO₃ were joined at 1150° and 1250°C under a compressive stress. The strains to form the joints were ∼0.1. Joints formed by plastic deformation were examined using scanning electron microscopy, and they were indistinguishable from the bulk. The room-temperature direct-current resistivity of the joined pieces was identical to that measured in the bulk material. This indicated that a sound, electrically conducting joint could be formed using plastic deformation (grain-boundary sliding) with little surface preparation.     

Synthesis of Y-Doped BaTiO3–(Bi1/2K1/2)TiO3 Lead-Free Positive Temperature Coefficient of Resistivity Ceramics and Their PTC Effects

As a lead-free positive temperature coefficient of resistivity (PTCR) material, (1– x mol%) BaTiO₃– x mol% (Bi_1/2K_1/2) TiO₃– y mol% Y₂O₃–0.5 mol% TiO₂ (BT– x BKT–2 y Y–0.5TiO₂) systems were prepared by the conventional solid-state reaction method. All samples containing <2 mol% BKT sintered in air possessed relatively low room-temperature resistivity (ρ₂₅) and high positive temperature coefficient (PTC) effect. However, when the BKT content exceeded 2 mol%, the sample was not semiconductive after sintering in air. The effects of sintering schedule on the properties of PTCR ceramics were discussed. The results showed that the optimum composition of BT–1BKT–0.2Y–0.5TiO₂, sintered at 1330°C for not-soaking and then fast quenched in air, achieved rather low ρ₂₅ of 28 Ω·cm and a high jump of resistivity (maximum resistivity [ρ_max]/minimum resistivity [ρ_min]) of 4.0 orders of magnitude with T _c about 155°C. The ρ₂₅ of the as-sintered sample could be further reduced to about 10 Ω·cm by annealing in N₂ at 450°C for 30 min, accompanied decrease on the PTC effect.     

施、受主掺杂对高居里点BaTiO3基PTCR陶瓷材料性能的影响

以合成的(Ba_(0.6)Pb_(0.4))TO_3为主要原料,通过电性能测试、SEM、XRD等手段分析研究了施主Nb~(5 )掺杂以及施主Nb~(5 )、受主Mn~(2 )共掺对高居里点BaTiO_3基PTCR陶瓷材料性能的影响。结果表明,施受主掺杂不影响材料基体的晶体结构,适量的施主Nb~(5 )掺杂可降低材料的室温电阻率从而改善其性能,受主Mn~(2 )掺杂提高了施主Nb~(5 )掺杂的高居里点BaTiO_3基PTCR陶瓷材料的室温电阻率且只有极少量的Mn~(2 )掺杂才使材料的PTC效应稍有提高。