铝蜂窝增强膨胀石墨/石蜡复合材料的制备和性能研究

以石蜡(PW)为相变材料、膨胀石墨(EG)为导热增强剂和定形材料、铝蜂窝为导热和结构强度增强材料,制备了铝蜂窝增强EG/PW复合材料板。通过X射线衍射仪、红外光谱和差示量热等手段分析了铝蜂窝增强EG/PW复合材料的物相、化学结构和相变行为,测试了导热系数,并对比了PW和铝蜂窝增强EG/PW复合材料对动力锂电池的控温散热效果。结果表明:EG与PW之间未发生化学反应,EG/PW复合材料的相变潜热略低于理论计算值,过冷度变小;其导热系数随EG含量的增加而增大;与PW相比,铝蜂窝增强EG/PW复合材料对动力锂电池具有良好的控温散热效果。     

环氧树脂/改性氧化石墨复合材料的制备及性能研究

采用改进Hummers法制备了氧化石墨,用硅烷偶联剂KH550对其进行改性,并制备了环氧树脂/氧化石墨复合材料。通过导热系数测定、热重分析(TG)、扫描电子显微镜(SEM)对复合材料进行分析和表征。结果表明:加入改性后的氧化石墨可以有效提高复合材料的导热系数,含2.0wt%改性氧化石墨的复合材料导热系数为0.36 W/m·K,比纯树脂材料的导热系数提高16.1%;复合材料热分解温度比纯环氧树脂提高了49℃;改性氧化石墨的加入能够提高复合材料的断裂韧性。     

微米金刚石对电子绝缘封装胶导热性的改进(英文)

本文采用微米金刚石的掺杂改进电子绝缘封装胶的导热性能,制备了高导热的电子绝缘封装胶微米复合材料.用扫描电镜对微米金刚石复合材料的截面进行了表征.结果表明微米金刚石的掺杂能够很好的和电子绝缘封装胶进行结合,没有产生明显的两相分离,在电子绝缘封装胶中形成了良好的导热网络.用HOT DISK热常数测试仪对所制备的微米复合材料进行了导热系数的测量,结果表明,随着微米金刚石掺杂量的增加,复合材料的导热系数k有明显的提高.与纯电子绝缘封装胶的导热系数为0.24W/m*K相比,当微米金刚石掺杂量的质量百分比为12.5%时,复合材料的导热系数比纯电子绝缘封装胶的导热系数提高了29.2%.     

聚甲醛/泡沫铝合金互穿复合材料导热性能的研究

使用硅烷偶联剂KH570对孔隙率不同的泡沫铝合金进行表面改性后,通过注塑成型法制备了聚甲醛/泡沫铝合金互穿复合材料。采用傅立叶变换红外光谱仪(FT-IR)、扫描电子显微镜(SEM)和导热系数测试仪分别研究了改性后的泡沫铝合金的表面的红外结构、复合材料的界面结合问题以及所制备复合材料的导热性能。结果表明,硅烷偶联剂KH570成功接枝到了泡沫铝合金的表面;泡沫铝合金与聚甲醛两相界面结合良好;泡沫铝合金的充填提高了复合材料的导热性能。当泡沫铝合金孔隙率为60.48%~75.41%时,聚甲醛/泡沫铝合金互穿复合材料的导热系数随孔隙率(λ)的增大而降低,其导热系数在10.2945~17.6471 W/(m·K)之间。     

环氧树脂/改性氮化硅复合材料制备及性能研究

纳米氮化硅用偶联剂N97进行改性,并制得环氧树脂/改性氮化硅(EP/Si_3N_4-N97)复合材料。通过导热系数测定、热重分析(TG)、红外分析(FT-IR)、扫描电子显微镜(SEM)对复合材料进行分析和表征。结果表明,加入改性后氮化硅可以有效地提高复合材料的导热性,含1.0%(wt,质量分数)改性氮化硅的EP/Si_3N_4-N97复合材料导热系数为0.4471W/m℃,比纯树脂材料的导热系数提高了44.23%;800℃时复合材料的质量残留率是环氧树脂的1.82倍;改性氮化硅的加入提高了复合材料的断裂韧性。     

固相纳米复合材料的导热系数预测

研究了分散剂和纳米颗粒对固相纳米复合材料导热系数的影响。假设纳米颗粒在纳米流体中均匀分布,构建了一个考虑纳米颗粒尺度和分散介质影响的物理分析模型;并由此利用最小热阻力法则和比等效导热系数相等法则,建立了一个固相纳米复合材料的导热系数理论模型。计算结果表明,颗粒的体积分数和导热系数、以及分散剂导热系数的增大,都会引起复合材料导热系数的增大。     

聚合物复合材料导热性能的研究

论述了填充聚合物复合材料的导热性及其变化规律；总结了复合材料导热的理论模型和导热系数预测方程，对比研究了各种导热模型的区别与联系；分析了影响复合材料导热特性的因素。     

预测复合材料导热系数的热阻网络法

借助计算机模拟复合材料的空间结构,直接迭代求解热阻网络,得到复合材料的导热系数。分析了在随机分布条件下取样尺度对导热系数的影响,以及二维和三维条件下导热的差别。与文献中实验数据的比较表明,所述方法能够较好地预示颗粒弥散型复合材料的导热系数。     

石墨烯及其复合材料导热系数测量的研究进展

石墨烯是当下材料学研究的热点和难点,其优越的导热性能,超越了绝大多数的材料,具有广泛的运用前景。近10年来,石墨烯产业的快速发展对其导热系数准确测量的需求越来越迫切。对石墨烯及其复合材料的定义、制备方法和在散热上的应用进行了综述;介绍了传统的导热系数测量方法,以及适用于石墨烯导热系数测量的激光闪光-拉曼光谱法和电热微桥法,对比了部分文献报道的石墨烯导热系数测量值;对熔融注塑法制备的还原氧化石墨烯和聚丙烯复合材料样品的导热系数和热扩散系数进行了测量,从热扩散系数测量结果发现其导热性能存在严重的各向异性;根据测量研究进展指出当前石墨烯及其复合材料导热系数测量存在的问题,并分析了导致这些问题的原因;最后,对石墨烯及其复合材料导热系数测量的研究进展进行总结和展望。     

泡沫混凝土导热系数模型及参数修正

在Cheng-Vachon模型的基础上提出了一种针对由连续相和分散相组成的两相复合材料的新导热系数模型.通过引入一个新的参数,即分散相的修正体积含量来改进Cheng-Vachon模型不适用于分散相体积含量较大的缺点.使用新的导热系数模型预测泡沫混凝土的导热系数,与实验结果的对比表明,新的模型可以准确预测泡沫混凝土的导热系数.     

氮化铝/氮化硼/碳纳米管/硅橡胶复合材料的力致填料取向对导热性能的影响

随着科学技术的发展,电子元器件发热量大幅度增加,因此开发兼具高导热和高绝缘性能材料日益迫切。以甲基乙烯基硅橡胶（SR）为基体,碳纳米管（CNTs）、六方氮化硼（BN）以及氮化铝（AlN）为导热填料,通过机械共混法制备导热复合材料。研究3种导热填料复配对复合材料的导热性能、绝缘性能和力学性能的影响,研究填料取向对复合材料导热性能的影响,研究材料表面温升与加热时间的关系。采用Agari模型预测复合材料的理论热导率。通过热红成像、扫描电子显微镜、X射线衍射分析、热重分析等对复合材料进行表征。结果表明：随着复配导热填料中AlN用量的减少,BN和CNT_S用量的增加,复合材料的热导率逐渐升高;当AlN为80 phr,BN为68 phr,CNTs为2 phr时,复合材料的垂直热导率为1.857 W·m^-1·K^-1,平行热导率为2.853 W·m^-1·K^-1,体积电阻率为2.18×10¹² Ω·cm,拉伸强度达4.3 MPa,复合材料的综合性能较好。     

Titanium dioxide doped polyaniline

Titanium dioxide doped polyaniline has been prepared by in situ polymerization. TiO₂ nanoparticles with an average diameter about 20 nm were used as a dopant of polyaniline. The doping effect of TiO₂ was characterized and evaluated by scanning electron microscopy (SEM), Fourier transformation infrared spectroscopy (FT-IR), energy dispersive spectrometry (EDS) and electrical conductivity measurement. SEM study shows that TiO₂ nanoparticles have a strong effect on the morphology of composites. The FT-IR spectra reveal that the interaction between TiO₂ and polyaniline (PANI) is primarily based on the formation of H-bonding. Electrical conductivity measurements indicate that the conductivity of composites at low TiO₂ content is much higher than that of neat PANI, while with the increasing contents of TiO₂, the conductivity shows an orderly decrease.     

氧化石墨烯及其氧化铁复合物的原位合成

开发了在富氧Fe(acac),络合物体系中膨化氧化石墨制取氧化石墨烯/Fe2O3复合物的一步法.应用FT-IR、XRD、VSM、AFM及低温直流电导测量法对所制氧化石墨/Fe2O3复合物进行表征.FT-IR研究结果显示:膨化后,氧化石墨的环氧基团分解,同时形成了氧化铁粒子与氧化石墨烯复合物.AFM测试表明:在较高Fe2O3含量下,氧化石墨烯片层结构剥蚀形成厚达5 mm氧化石墨烯叠层.VSM研究显示:在室温和0.13 emu/g～5.5 emu/g范围内,全部复合物呈铁磁特性.这些复合物的导电性受控于准电子跃迁机制.     

Characterization and temperature-dependent conductivity of polyaniline nanocomposites encapsulating gold nanoparticles on the surface of carboxymethyl cellulose

Polyaniline nanocomposites encapsulating gold nanoparticles on carboxymethyl cellulose surface were prepared via the polymerization of aniline hydrochloride with different carboxymethyl cellulose (CMC) concentrations (wt.%) using HAuCl₄ as oxidant. The synthesized composites were characterized by Fourier transform infrared (FTIR) spectroscopy. Surface morphology was studied by electron diffraction scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The embedded crystallinity of the composites was investigated by X-ray diffraction (XRD) analyses. The electrical property of the composites was examined by temperature-dependent DC conductivity in the range of 300–500 K. The composites exhibited higher electrical conductivities with increased CMC concentration under equivalent conditions. Activation energy for electron transport was also calculated based on the conductivity data.     

Influence of interfacial modification on the thermal conductivity of polymer composites

In this study, the influence of modifying ZnO filler with surface-treating agents on the thermal conductivity of the ethylene-vinyl acetate copolymer (EVA) composites was reported. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) were applied to analyze the surface modification of ZnO filler and the fractured surface morphology of the EVA–ZnO composites. The test results indicated that surface-treating ZnO filler with the valid modifying agents (stearic acid, OL-AT16, KH-560, or NDZ-132) at right dosage and treating temperature, the thermal conductivity of the EVA–ZnO composites can be enhanced effectively on account of reducing the interfacial phonon scattering; while the dosage of modifying agents exceed a right amount, the thermal conductivity of EVA–ZnO composites modified with the small-molecule treating agents (F-1, n-Octylic acid, or stearic acid) descend more evidently with the dosage increase.     

Synthesis, characterization and conductivity studies of polypyrrole-fly ash composites

In situ polymerization of pyrrole was carried out in the presence of fly ash (FA) to synthesize polypyrrole-fly ash composites (PPy/FA) by chemical oxidation method. The PPy/FA composites have been synthesized with various compositions (10, 20, 30, 40 and 50 wt%) of fly ash in pyrrole. The surface morphology of these composites was studied with scanning electron micrograph (SEM). The polypyrrole-fly ash composites were also characterized by employing X-ray diffractometry (XRD) and infrared spectroscopy (IR). The a.c. conductivity behaviour has been investigated in the frequency range 10²–10⁶ Hz. The d.c. conductivity was studied in the temperature range from 40–200°C. The dimensions of fly ash in the matrix have a greater influence on the observed conductivity values. The results obtained for these composites are of greater scientific and technological interest.     

The unusual electrical response in polyaniline-threonine composites

Polymer-amino acid composites are a new class of polymer materials with unusual electrical property. Novel polyaniline-threonine composites combining the synthesized polyaniline and proteinogenic amino acid threonine have been prepared. The samples were characterized by Fourier-transform infrared spectra, UV-vis absorption spectra and atomic force microscopy. The unusual electrical response was found from the d.c. conductivity measurement. The carboxyl group of the amino acid threonine played an important role in the electrical conductivity. Analysis of d.c. conductivity data revealed that in the temperature range of 300 K-200 K, the d.c. conductivity was governed by Mott's 3-dimensional variable range hopping.     

气泡和气隙影响六方氮化硼/环氧树脂复合材料导热性能的有限元模拟

气泡和气隙严重影响环氧树脂基复合材料的导热性能,研究气泡和气隙对复合材料热导率的影响有助于提高导热模型的准确性,可为进一步优化环氧树脂基复合材料的导热性能提供指导方向。采用有限元方法建立一种含气泡、气隙的六方氮化硼(h-BN) /环氧树脂复合材料单胞模型,分析气泡、气隙的尺寸和数量对复合材料导热性能的影响。通过与其他模型、实验数据的对比对模型的有效性进行了验证。结果表明,随着气泡尺寸和数量的增加,h-BN/环氧树脂复合材料热导率逐渐下降,且热导率随气泡尺寸的变化曲线存在转折点,直径大于单胞厚度的气泡对复合材料热导率的影响较大。随着气隙直径和厚度的增加,h-BN/环氧树脂复合材料热导率先缓慢后快速减小、最后呈直线趋势下降;随着气隙数量的增加,h-BN/环氧树脂复合材料热导率逐渐下降,且相较于基材中的气隙,位于填料与基材界面处的气隙对热导率的减弱更显著。      

Direct current conductivity of carbon nanofiber-based conductive polymer composites: effects of temperature and electric field

Polymer composites based on high density polyethylene (HDPE) and carbon nanofiber (CNF) were fabricated by melt compounding. The dependences of electrical conductivity of HDPE-CNF composites on filler concentration, temperature, and applied electric field were investigated. The results showed that the conductivity of the HDPE-CNF composites follows the scaling law of percolation theory. Increasing temperature caused a sharp increase in the resistivity of HDPE-CNF composites near the melting temperature of HDPE, yielding a positive temperature coefficient (PTC) effect of resistance. The potential mechanisms involved in the PTC effect of such composites were analyzed. An investigation of the effect of electric field on the conductivity of HDPE-CNF composites revealed the presence of tunneling conduction. The tunneling conductivity increased with increasing filler content because of high tunneling frequency, and decreased with rising temperature as a result of gap widening between conducting CNF fillers.     

聚丙烯接枝马来酸酐修饰碳纳米管增强聚丙烯复合材料的制备及性能

采用混合溶剂的溶液法技术,对聚丙烯接枝马来酸酐(PP-g-MAH)包覆碳纳米管(MWNTs)与聚丙烯(PP)纳米复合材料的电学和力学性能进行了研究。PP-g-MAH包覆MWNTs在二甲苯溶液中呈现良好的分散性,红外结果表明,酸化碳纳米管后表面官能团如羟基、羧基与马来酸酐发生氢键作用。场发射扫描电镜(FESEM)也证明了PP-g-MAH修饰MWNTs在PP基体中分散良好,并且相容性也得到了明显改善。复合材料的拉伸强度和电导率都有较大的提高,其中导电性相比未处理碳管/聚丙烯提高了两个数量级。