金属—PTC陶瓷复合材料研究

研究低ＴｃＰＴＣＲ复合材料的制备工艺，测试所制成样品的阻温特性，通过样品Ｘ射线定性相分析，探讨该复合材料所表现的ＮＴＣ阻温特性机理。     

LLDPE/EVA/CB复合体系的导电和发热性能

对LLDPE/EVA(乙烯醋酸乙烯酯共聚物)/CB(碳黑)三元复合材料的导电性能及发热特性进行了研究。讨论了碳黑种类及含量对复合导电材料性能的影响,探讨了复合材料的伏-安特性、功率-温度特性以及辐照交联工艺对复合材料稳定性的影响。结果表明,添加乙炔碳黑,可使复合材料具有最佳的导电性及PTC(正电阻温度系数)特性,辐照交联使材料具有良好的电阻稳定性,由此制得的电缆经过一年的通电试验,其工作温度稳定在70℃±5℃,具有良好的限温作用。     

超高相对分子质量聚乙烯/石墨烯微片复合材料的导电行为研究

采用溶液混合、超声波分散的方法制备了超高相对分子质量聚乙烯（PE UHMW）/石墨烯微片（GNPs）复合材料,研究了PE UHMW/GNPs复合材料的导电行为和阻温特性。结果表明,本方法可以使GNPs在PE UHMW基体中良好地分散;复合材料表现出典型的导电渗流行为,渗流阈值为2.8 %（质量分数,下同）;在高于渗流阈值的情况下,PE UHMW/GNPs复合材料的正温度系数效应（PTC）强度随GNPs含量的增加而减小,在渗流阈值附近复合材料的PTC强度最高;PE UHMW/GNPs复合材料的阻温特性重复性较好,多次热循环后PTC强度趋于稳定。     

PE-UHMW/GNPs导电复合材料的制备和表征

采用超声溶液分散法制备出超高分子量聚乙烯/石墨烯(PE-UHMW/GNPs)导电复合材料,研究了该材料的导电渗流行为和阻-温特性。研究发现,PE-UHMW/GNPs导电复合材料的导电渗流阈值为3.8%,即当导电填料在体系中的质量分数达到3.8%时,材料内部逐渐形成较为完善的导电网络,从而实现其导电特性。研究和探讨了PE-UHMW/GNPs导电复合材料的正温度系数(PTC)效应和负温度系数(NTC)效应。研究发现,PE-UHMW/GNPs导电复合材料的PTC效应会随着GNPs含量的增加逐渐增强,当导电填料GNPs的添加量达到3.8%时,通过阻-温曲线可以观察到,PE-UHMW/GNPs导电复合材料具有最大的PTC强度和相对较低的室温体积电阻率。场发射扫描电子显微镜分析结果表明,GNPs和PE-UHMW之间的相互作用会随着热循环次数的不同而发生变化,最终会影响到材料的PTC效应。     

Fe2O3掺杂对氧化锌线性电阻的影响

利用固相烧结法制备出基础配方为ZnO–A1₂O3–MgO–TiO₂–SiO₂–Fe2O3的ZnO线性电阻。研究了Fe₂O₃掺杂量对ZnO线性电阻微观结构、阻温特性和阻频特性的影响。结果表明:当Fe₂O₃掺杂量为0.75%(质量分数)时,氧化锌线性电阻的非线性系数为1.1₂,阻温系数取得–8.23×10^–3/℃,此时样品的综合性能最好。     

硅橡胶/炭黑复合材料在外场作用下的导电响应行为

通过机械共混法制备了甲基乙烯基硅橡胶(MVQ)/炭黑(CB)复合材料,研究了复合材料的压阻特性、温阻特性、在压缩循环下的压阻稳定性和重复性能以及电阻弛豫特性,并提出了新的压阻数学模型。结果表明,在渗滤阈值附近,MVQ/CB复合材料有最显著的压阻效应;随着CB含量的增加,压阻效应出现一个临界压力;在40℃时复合材料由正温阻特性转变为负温阻特性;通过预压缩和增加压缩循环次数,可以提高压敏导电橡胶的压阻重复性和稳定性。应用隧道电流理论构建的压阻效应数学模型能同时很好地模拟MVQ/CB复合材料的正压阻系数效应和负压阻系数效应。     

聚乙烯基导电复合材料的研究

综述了近年来聚乙烯基导电复合材料研究进展,包括聚乙烯/炭黑、聚乙烯/石墨、聚乙烯/碳纳米管导电复合材料等,分析了聚乙烯基导电复合材料的导电机理,指出导电填料的种类及性质、基体材料、加工工艺均会对导电复合材料的性能产生影响。最后,研究了聚乙烯基复合材料的阻温效应,并对其应用前景进行了展望。     

多施主掺杂PTC陶瓷材料的研究

本文在双施主掺杂高ＴｃＢａＴｉＯ_３基ＰＴＣ陶瓷材料的基础上,对ＢａＴｉＯ_３的Ａ、Ｂ、Ｏ位同时进行离子置换以实现多施主掺杂,同时还研究了烧结温度对阻温特性的影响。研究结果表明,多施主掺杂试样的烧成温度对ｐ－Ｔ性能影响很大,在一定配方及工艺条件下,获得的ＰＴＣ陶瓷材料的室温电阻率变化不大,升阻比明显提高。     

微量K掺杂对样品La0.75Sr0.25-xKxMnO3的磁性、电输运及室温磁电阻的影响

采用溶胶-凝胶方法制备了系列样品La0.75Sr0.25-xKxMnO3(x=0.00,0.05,0.07,0.10).对系列样品进行了相结构、磁性和电输运性质的研究.XRD数据表明:系列样品具有完整的钙钛矿锰氧化物结构.通过对磁性和电阻率的研究发现:与双交换作用相比,A位离子的无序度2对样品的磁性和电输运的影响起主要作用.随掺杂量的增加,磁电阻的峰值逐渐增大;峰值温度逐渐下降,更接近室温.在210～280 K的温区内,磁电阻基本保持稳定.这些结果都有利于磁电阻的实际应用.     

PVDF/炭黑导电复合材料的PTC性能研究

研究炭黑种类和用量及ＰＶＤＦ种类对ＰＶＤＦ／炭黑导电复合材料ＰＴＣ特性的影响。结果表明,大粒径、比表面积小的Ｎ７６５炭黑填充导电复合材料的ＰＴＣ性能较好,出现ＰＴＣ现象的炭黑用量范围大;随着ＰＶＤＦ分子量的增大,ＰＶＤＦ／Ｎ７６５炭黑导电复合材料出现最大ＰＴＣ强度的炭黑用量减少,最大ＰＴＣ强度也随之增大。     

Pyroresistivity in conductive polymer composites: a perspective on recent advances and new applications

Conductive polymer composites (CPCs) with pyroresistive behaviour are of interest for a wide variety of applications such as safe batteries, resettable fuses, temperature sensors and self‐regulating heating devices. Due to their ease of processing, low density, tunable electrical properties, good oxidation resistance, and good flexibility and toughness, CPCs have become the preferred choice of pyroresistive materials in a number of applications. The pyroresistive behaviour of CPCs can be tuned to satisfy the specific requirements of different applications. In this perspective paper, recent progress in the use of pyroresistive CPCs is reviewed. In particular, various factors influencing their performance are discussed and compared, in connection with the associated application, with a special focus on reproducibility and positive temperature coefficient intensity levels. Some of the remaining challenges are identified, together with future prospects in this evolving field. © 2018 Society of Chemical Industry     

Effects of heat treatment on the mechanical properties at elevated temperatures of plain-woven SiC/SiC composites

The effects of heat treatment on the mechanical properties of plain-woven SiC/SiC composites at 927 °C and 1200 °C in argon were evaluated through tensile tests at room temperature and at elevated temperature on the as-received and heat-treated plain-woven SiC/SiC composites, respectively. Heat treatment can improve the mechanical properties of composites at room temperature due to the release of thermal residual stress. Although heat treatment can damage the fiber, the effect of this damage on the mechanical properties of composites is generally less than the effect of thermal residual stress. Heat treatment will graphitize the pyrolytic carbon interface and reduce its shear strength. Testing temperature will affect the expansion or contraction of the components in the composites, thereby changing the stress state of the components. This study can provide guidance for the optimization of processing of ceramic matrix composites and the structural design in high-temperature environments.     

不同炭黑填充的PVC/EPDM复合NTC材料电性能的研究

首先研究了特导炭黑(HG-1P)和乙炔炭黑(ACET)填充聚氯乙烯(PVC)单组分复合材料的逾渗行为和阻温特性:特导炭黑导电性较好,较少的填充量就能达到较低的室温电阻率,在升温过程中表现出稳定的NTC效应;乙炔炭黑导电性能偏差,达到相同的导电性需要更多填充量,在升温过程中先是出现弱的PTC效应,继而出现NTC效应。然后,引入三元乙丙橡胶(EPDM)、乙丙橡胶(EPR)作为第二组分,EVA作为第三组分,发现多组分复合材料电阻降低,阻温曲线表现出一些新的特征。     

Manufacturing and characterizations of flexible poly(dimethylsiloxane)/poly(vinyl acetate)/polythiophene ternary composite films

ABSTRACT

In this study, polythiophene and poly(dimethylsiloxane)/poly(vinyl acetate)/polythiophene ternary composites were synthesized. The new ternary composites obtained in powder and film forms were characterized using various techniques. Magnetic properties of all the materials were analyzed by Gouy balance measurements, and it was found that their conductivity mechanism is of polaron nature. The surface structure, surface roughness, and thermal properties of the prepared samples were identified by Scanning Electron Microscopy, Atomic Force Microscopy, and Thermogravimetric Analysis, respectively. The tensile-tension test studies were performed for mechanical properties. The PDMS/PVAc/PT (6%) composite demonstrated about 50% of the maximum strain value (%) of vulcanized natural rubber.     

PTC effect in HDPE filled with carbon blacks modified by Ni and Au metallic particles

Several types of positive temperature coefficient (PTC) composites are prepared by using Ni and Au modified carbon black. The major aim of this work was the lowering of the room temperature resistivity of the composites by enhancement of electrical conduction of the CB particles by incorporating metallic particles. Investigations showed that the metal particles fill the cavities and surface defects of the CB and thus surface free area reduces after modification. Metallic particles also change the nature of the CB particles after modification. Several types of PTC composites were prepared by using modified and unmodified CB by several loading level of filler. Measuring electrical properties of the PTC samples showed that the Ni modified CB reduce room temperature resistivity to lower than that of PTC composites prepared by unmodified CB. PTC composites prepared by Au modified CBs showed very different properties compared to PTC composites prepared by Ni modified CB. Their resistivities were quite higher than the others showing a poor compatibility between the matrix and Au modified CB. The effect of thermal annealing also investigated on the electrical properties of the prepared composites. Room temperature resistivities reduced for most of the samples while PTC intensities increased after annealing. Theoretical bases are employed to discuss the room temperature resistivity and PTC behavior of the composites before and after annealing. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

高密度聚乙烯/多壁碳纳米管和高密度聚乙烯/炭黑导电复合材料阻温特性的研究

采用溶液法制备了高密度聚乙烯/多壁碳纳米管（PE-HD/MWCNTs）和PE-HD/炭黑(CB)导电复合材料,并研究了该复合材料的阻温特性。结果表明,与PE-HD/CB复合材料相比,PE-HD/MWCNTs复合材料的室温电阻率更低,并且可以具有较高的正温度系数（PTC）强度和较小的负温度系数（NTC）效应,因而具有更加广泛的应用前景。同时通过对PE-HD/MWCNTs复合材料阻温全过程进行分析,发现PTC效应由碳纳米管向晶区扩散及基体体积膨胀效应共同导致,而NTC效应则是由于碳纳米管的热运动形成的相互接触所致,而并非粒子附聚。     

Temperature-dependent resistivity performance of Mn/Y-doped Ba1-xSrxTiO3 compositions with potential thermal control applications

Doped BaTiO₃ ceramics exhibit an attractive application prospect in the adaptive thermal control of electronic devices in spacecraft that originate from its remarkable positive temperature coefficient (PTC) characteristics. However, the Curie temperature of most current BaTiO₃-based PTC materials is much higher than the normal operating temperature range of electronic devices. In this work, we successfully synthesized Ba_1-xSr_xTiO₃ ceramics with a room temperature Curie point. The crystal structure, surface morphology and temperature dependence of resistivity are investigated. The Curie temperature where the crystal structure of the composition changes from a paraelectric phase to a ferroelectric phase is adjusted by increasing the doping level(x). In the temperature range 18–120 °C, the variation amplitude of resistivity exceeds 10⁴, and the positive temperature coefficient effect is as high as 10.7%/°C. The potential thermal control properties were discussed based on the experimental and theoretical analysis. The heating power of compositions can be automatically changed by varying the operating temperature. At the same initial heating power, the equilibrium temperature of the controlled equipment using the PTC heating element is lower than that when adopting an ordinary heater. Moreover, the effect of thermal control becomes more prominent as the resistivity-temperature coefficient increases.     

Synthesis and characterization of leather impregnated with bismaleimide (BMI)–Jeffamine® resins

Leather/polymer composites were prepared by impregnating chrome-tanned cattlehide with a solution containing 1,1′-(methylenedi-4,1-phenylene)bismaleimide and Jeffamine® D-230. The mechanical properties in tension, glass transition temperatures, dynamic storage moduli, and moisture absorption of the composites were measured. Impregnated samples showed significant changes in tensile properties, such as the Young's modulus and strain at break, when compared with chrome-tanned cattlehide. In addition, impact energy increased significantly upon formation of the leather/polymer composite over that of the bismaleimide–Jeffamine® resin itself. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1019–1027, 1998     

炭黑/环氧树脂复合材料的电性能研究进展

介绍了炭黑/环氧树脂(EP)复合材料的制备工艺,讨论了炭黑/EP复合材料导电性能的影响因素,评述了炭黑/EP复合材料电阻正温度系数效应的机理解释和研究进展,展望了这一类材料的研究重点和发展前景。