六方氮化硼改性聚合物基介电复合材料的研究进展

综述了近年来国内外利用六方氮化硼来改善聚合物基复合材料介电性能的研究工作进展,介绍了多种六方氮化硼的制备方法与不同复合策略的优势与不足。指出了利用六方氮化硼改善聚合物基介电复合材料性能时存在的问题和发展方向。     

六方氮化硼/碳化硅晶须填充改性聚酰亚胺导热绝缘复合材料的制备及表征

采用固相共混方法将六方氮化硼(h-BN)和碳化硅晶须(SiCw)作为导热填料对单醚酐型聚酰亚胺(PI)模塑粉进行改性,然后通过热模压工艺制备PI导热绝缘复合模压材料,并对其性能进行表征。测试结果表明:h-BN可以有效提高模塑料导热性能、热性能和电绝缘性能,但会降低材料力学性能;SiCw可以有效提高复合材料导热性能、热性能和力学性能,但会显著降低电绝缘性能。将h-BN/SiCw复配使用,在显著提高复合材料导热性能和热性能的同时又可保持其良好的力学性能和电绝缘性能。添加30%(质量分数)h-BN/SiCw(3/1),复合材料导热系数提高至1.21 W/(m·K),是未改性PI材料的4.84倍,弯曲强度为142MPa,体积电阻率为1.27×10~(14)Ω·cm,线性热膨胀系数(CTE)显著降低为55.6μm/(m·℃)。     

基于氮化硼取向结构的高导热聚合物基复合材料研究进展

简要介绍了氮化硼的分类、结构特点以及其导热特性。重点概述了近几年基于在聚合物基体中形成氮化硼取向结构制备高导热复合材料的研究进展,分析了磁场诱导法、电场诱导法、剪切诱导法、冰晶诱导法以及热压取向等方法的特点。对氮化硼取向填充的导热聚合物基复合材料的未来发展趋势进行了分析与展望,为低填充、高导热绝缘聚合物基复合材料的开发及应用提供借鉴。     

用于导热绝缘环氧树脂复合材料的氮化硼改性研究进展

环氧树脂是电子器件常用的绝缘高分子基体材料,但存在导热性偏低的问题。六方氮化硼(h-BN)常被用于环氧树脂的导热填料,而h-BN的化学惰性使其在环氧树脂中的分散性和相容性较差,限制了其作用的发挥,因而对其进行改性就成了导热绝缘环氧树脂复合材料制备中需要面对的一个重要问题。本文主要总结了近年来用于导热绝缘环氧树脂复合材料的氮化硼的改性方法及其特点,其中包括剥离、包覆、场取向和杂化等物理方法,以及功能化、偶联剂修饰、活性剂修饰、化学接枝等化学方法,并对BN改性今后的发展趋势进行了讨论。     

聚四氟乙烯-六方氮化硼纳米片复合材料研究

采用熔融柠檬酸对六方氮化硼(hBN)进行纳米化处理得到六方氮化硼纳米片(n-hBN),再将n-hBN和聚四氟乙烯(PTFE)悬浮树脂分散于硅油中进行液相混合,过滤得到混合物;然后采用冷压烧结的方法制备复合材料.采用XRD和XPS对复合材料的结构进行表征,并研究了不同n-hBN含量对复合材料力学性能、导热系数以及耐磨性能...     

聚丙烯/高密度聚乙烯/氮化硼导热复合材料的制备及性能研究

以聚丙烯（PP）/高密度聚乙烯（HDPE）共混物为基体,六方氮化硼（h-BN）为导热填料,聚丙烯接枝马来酸酐（PP-g-MAH）为相容剂,通过熔融共混法制备PP/HDPE/h-BN和PP/HDPE/h-BN/PP-g-MAH导热复合材料。采用导热系数仪、场发射扫描电镜、万能试验机、热分析仪等测试导热复合材料,研究不同含量的h-BN、PP-g-MAH对复合材料导热性、力学性能、结晶性能和耐热性的影响。结果表明：随着h-BN含量的增加,PP/HDPE/h-BN复合材料的弯曲强度、热导率和耐热性提高。当h-BN含量为20%,复合材料的弯曲强度达到41.02 MPa;当h-BN含量为25%,复合材料热导率达到0.372 1 W/（m·K）。h-BN对PP的结晶具有促进作用,提升PP的结晶速率和结晶温度。PP、HDPE与h-BN质量比为64∶16∶15时,添加5%的PP-g-MAH,增强了h-BN和基体材料的界面相容性,复合材料的弯曲强度达到42.72 MPa,拉伸强度达到26.64 MPa,热导率达到0.356 1 W/（m·K）。     

导热绝缘聚合物复合材料研究

介绍了导热绝缘聚合物复合材料,包括复合型塑料、橡胶、胶粘剂和涂层的研究进展及其导热机理、导热模型的研究情况。讨论了影响导热绝缘聚合物复合材料导热性能的因素、提高导热系数的措施及该种复合材料的制备方法,最后阐述了导热绝缘聚合物复合材料的应用及发展方向。     

聚合物/BN导热复合材料研究进展

与其他导热无机粒子相比,氮化硼粒子具有的独特结构及良好的热、电综合性能,是制备高导热、高绝缘聚合物的一类重要导热绝缘填料。综述了微、纳米氮化硼粒子填充导热聚合物的研究进展,重点讨论了氮化硼粒子的物理性能、表面改性、结构及用量等对聚合物导热、绝缘及力学性能的影响。与微米氮化硼相比,氮化硼纳米管及纳米片增强的聚合物具有高导热、高电击穿强度、高绝缘电阻、低介电常数及介电损耗、良好的力学性能。解决导热聚合物高导热与高电击穿强度间的矛盾是聚合物/氮化硼导热复合材料未来发展的方向。     

聚合物基导热绝缘复合材料的制备及逾渗模型的应用

采用乙烯一醋酸乙烯a共聚物和无机导热填料制备聚合物基导热绝缘复合材料,概述了以逾渗理论为基础的热导率计算模型,并应用所制备的导热绝缘复合材料讨论了逾渗模型的准确性。结果表明,SiC填充的复合材料具有较好的导热性能;填料体积分数达0.5时,复合材料的热导率可达1.86 W/(m0K)。研究表明,简单地运用逾渗理论在预测导热复合材料体系的热导率方面准确性不足,需要进一步考虑实际填料粒子分布与理论假设的差异以及界面相的存在等因素的影响。     

PB-1/BN导热复合材料的制备及性能研究

以聚丁烯-1(PB-1)为基体,二维片状氮化硼(BN)为导热填料,采用模压成型的方法制备了PB-1/BN导热复合材料。研究了BN用量对PB-1/BN导热复合材料导热性能、力学性能、流变性能以及结晶性能的影响。结果表明:BN的加入使复合材料的导热性能明显提高,当BN用量为50%时,复合材料的导热系数达到1.28 W/(m·K),与纯PB-1相比提高了266%;随着BN用量的增加,复合材料的力学性能明显下降;同时,其结晶温度和结晶度也有不同程度降低。     

On the synthesis of lithium boron nitride (Li3BN2)

Li₃BN₂ is a known lithium ion conductor and has been predicted lately to be a high capacity cathode for Li-ion batteries (Németh, 2014) [4]. In this study, we have investigated the synthesis of Li₃BN₂ through reactions between Li₃N and h-BN powders. Effects of the reaction temperature, holding time and reaction atmosphere on the formation of Li₃BN₂ have been evaluated. Rietveld refinement of X-ray diffraction patterns of all powders has been performed to quantify the percentage of each phase. The results show that both the reaction temperature and holding time affect strongly the percentage of Li₃BN₂ in the reaction product. Furthermore, a trace amount of oxygen in the reaction atmosphere can negatively impact the purity of the reaction product because of the high affinity of Li₃BN₂ towards oxidation.     

Defect-induced electronic conduction of tBN thin films

Two kinds of turbostratic boron nitride (tBN) thin films were deposited by sputtering with pure Ar or N₂ plasma in an ultraclean vacuum chamber. Current–voltage (I–V) characteristics of Ti/tBN/Ti structures revealed that films deposited in Ar showed at least three-orders higher conductivity with strong temperature and electric field dependence compared with those deposited in pure N₂. The origin of the higher conductivity was confirmed to be the nonstoichiometry and higher defect density of the tBN films. On the other hand, films deposited in pure N₂ plasma showed the characteristics of intrinsic insulator even though the basal plane of tBN was oriented normal to the substrate, namely, parallel to the direction of electronic conduction.     

Physical and mechanical properties of hexagonal boron nitride ceramic fabricated by pressureless sintering without additive

Hexagonal boron nitride hBN ceramic was successfully fabricated by pressureless sintering at 2100C using submicrometre hBN powders without any sintering additive. The as-prepared hBN ceramic showed a room temperature flexural strength of 30.7MPa. Its flexural strength increased with the increment of temperature in N₂ atmosphere, and it retained a strength of 57.2MPa nearly two times of the room temperature strength at 1600C due to clean grain boundaries with no glassy phase. Additionally, the as-prepared hBN ceramic showed a high thermal conductivity of 31.76Wm¹k¹ and a good thermal shock resistance, which retained a relatively high residual flexural strength of 22.6MPa 73.5 of the original flexural strength at T800C. The as-prepared hBN ceramic presents a good application prospect at high temperature.     

Effects of trimethylamine and ammonia on cBN content in the samples prepared by hydrothermal method

The previous results have proved that the phase-selective synthesis route is an effective method for preparing cubic boron nitride (cBN) from hydrothermal solutions. However, the experimental parameters are still required to be optimized in order to synthesize pure cBN at high yield. Here we report the results of investigating the effects of adding trimethylamine (N(CH₃)₃) and ammonia (NH₃·H₂O) (denoted as secondary nitrogen source) into the reacting solutions. It was found that the content of cBN could be increased by adding appropriate amount of N(CH₃)₃ and decreased with excess amount of it. On the contrary, hexagonal boron nitride (hBN) was always promoted by adding NH₃·H₂O into the reacting solutions. The samples were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectrum (FTIR) and high resolution transmission electron microscopy (HRTEM). The experimental results were briefly discussed based on a reported model.     

Modification of hexagonal boron nitride nanoparticles with fluorosilane

Surfaces of hexagonal boron nitride (hBN) nanoparticles were modified with perfluorooctyl-triethoxysilane (FTS). Experiments were performed for 40–120 min in 70–150 °C range with FTS/hBN weight ratio in the range of 0.5–1.5. The products were analyzed by FT-IR, TGA, FESEM, HRTEM and EDX. Results of FT-IR analyses indicated that modification takes place in 80 min at 150 °C under reflux with a FTS/hBN ratio of 1.5. Presence of FTS on hBN nanoparticles was confirmed by the weight losses in TGA, and by TEM, TEM-EDX analyses.