三维石墨烯/环氧树脂复合材料导热特性研究

三维石墨烯具有高孔隙率、高热导率和良好的热稳定性等优点。提出利用三维石墨烯形成的连续"导热链"填充环氧树脂从而改善环氧树脂传热性能的方法,通过化学氧化还原法制备了三维石墨烯,进而采用浇注法制备三维石墨烯/环氧树脂复合材料。实验测试了导热性能、比热容和玻璃化转变温度等热物性参数。结果表明:三维石墨烯可大幅度提髙环氧树脂的导热性能。在三维石墨烯的质量分数为3%时,环氧树脂的热导率提高近7倍。研究结果为三维石墨烯在导热复合材料领域的应用提供了实验依据。     

BN/GS填充EP导热绝缘复合材料的制备

采用化学还原法,利用氮化硼(BN)和氧化石墨烯(GO)制备了一种新型的具有三维网络结构的氮化硼/石墨烯(BN/GS)复合填料,并通过共混的方式制备了环氧树脂(EP)复合材料。运用包括高阻计及四探针测试系统等多种技术手段表征复合材料的结构和性能。研究结果表明,实验成功制备了具有三维网络结构的BN/GS复合填料,复合材料的热导率和热稳定性随着填料含量的增大而获得明显提升。由于GS在这种预制复合填料中的桥接作用,显著降低了界面热阻,BN/GS复合填料相比单一填料BN对复合材料热导率增加的效果更加突出,填料量达30wt%时,BN/GS/EP的热导率达到EP的热导率的5.38倍;由于GS含量低以及BN隔断GS之间的电子传输,复合材料仍保持良好的电绝缘性能。     

贻贝仿生修饰氮化硼/石墨烯微片环氧导热绝缘材料的制备及性能研究

随着电子技术快速的发展,聚合物材料自身较低的热导率已不能满足现代电子器件的散热需求,因此提高聚合物热导率,实现高效率的传热具有重要意义。利用多巴胺优异的包覆性能实现对氮化硼(BN)粉末和石墨烯微片(GNPs)的表面修饰。然后将功能化的BN和GNPs作为导热填料,制备了系列环氧树脂(EP/BN/mBN/m(BN/GNP))导热绝缘复合材料,研究了填料的种类和含量对复合材料导热性能和电绝缘性能的影响。结果表明,经多巴胺改性后的BN和GNPs能比较均匀分散于环氧树脂体系中;当添加30 wt%的m(BN/GNP)(1∶1)填料时,复合材料的热导率达到0.61 W/(m·K),与纯环氧树脂材料相比提高了238.9%,且该复合材料仍保持优异的绝缘性能。     

非共价改性石墨烯的制备及环氧树脂复合材料导热性能

采用非共价键表面修饰制备了聚乙烯吡咯烷酮（PVP）改性的石墨烯（GR@PVP）,通过共混方式将其作为填料与环氧树脂（EP）复合得到了不同填充量的EP/GR复合材料。红外光谱和热重分析结果表明,聚乙烯吡咯烷酮成功接枝到石墨烯表面。动态力学热分析和热性能测试结果表明,EP/GR@PVP复合材料的储能模量、玻璃化转变温度和损耗因子峰高度均比EP/GR复合材料有所降低,表明聚乙烯吡咯烷酮增强了环氧树脂复合材料的柔韧性。采用扫描电子显微镜观察复合材料断面形貌,GR@PVP在环氧树脂中分散均匀,且与基体相容性好。当填料质量分数为2.0%时,EP/GR@PVP复合材料的热导率比纯EP和EP/GR复合材料分别提高了205.3%和52.6%,25℃EP复合材料的表观黏度为13.29 Pa·s,符合电子封装材料对复合材料加工黏度的需求(<20 Pa·s)。其研究为进一步制备高导热、低黏度的电子封装材料提供了一种简便的方法。     

熔盐法合成高导热磷化硼及其热管理性能研究

随着电力电子器件封装密度提高, 开发导热性能优异的热界面材料受到了广泛关注。绝大多数传统导热填料的热导率较低, 因此合成新型高导热填料是提高热界面材料导热性能的重要途径。本研究通过简单的熔盐法合成了高导热的磷化硼(BP)颗粒, 与氮化硼(h-BN)混合并通过搅拌和浇注的方法填充到环氧树脂(EP)基体中制备得到树脂基复合材料(BP-BN/EP)。实验结果表明：采用三盐法(NaCl : KCl : LiCl)合成的BP产率最高达到74%, 相对于单盐法(41%)和双盐法(39%)分别提高了33%和35%。对于BP-BN/EP复合材料, 复合材料的微结构显示BP和BN颗粒均匀分布在环氧树脂基体。当混合填料体积分数为30%时, 该复合材料的热导率达到1.81 W•m^-1•K^-1, 是纯树脂热导率(0.21 W•m^-1•K^-1)的8.6倍, 这与BP颗粒作为桥梁连接相邻BN颗粒形成导热网络有关。除此以外, 相较于不含BP的复合材料(SBN-BN/EP), BP-BN/EP复合材料展现出更加优异的热导率、热稳定性和较好的热力学性能。因此, 熔盐法合成的BP在热管理领域具有较大的应用前景。     

诱导相分离BNNS/PES/EP复合材料制备及其热物性研究

通过液相机械剥离法制备了氮化硼纳米片(BNNS)并通过硅烷偶联剂共价修饰和多巴胺非共价修饰制备了双重改性的氮化硼纳米片(KDBNNS);利用反应诱导相分离,将KDBNNS分布在环氧树脂(EP)和聚醚砜(PES)的界面上构成导热通路,制备了KDBNNS/PES/EP复合材料。采用傅里叶变换红外光谱分析、热失重分析(TGA)和共聚焦扫描显微镜等方法对其进行表征。观测到在三元复合材料内的相分离连续界面上通过分布BNNS构筑了三维导热通路。研究表明当BNNS填料质量分数仅为3%时,复合材料的热导率即可达到0.394 W·m^-1K^-1,相较于纯环氧0.194 W·m^-1K^-1提高了103%。     

氧化锌@石墨烯/环氧导热绝缘复合材料的制备及性能研究

以氧化石墨烯(GO)为载体,醋酸锌为锌源,采用溶胶-凝胶法成功制备了氧化锌@石墨烯(ZnO@rGO)复合填料并利用傅里叶变换红外光谱(FTIR)、拉曼光谱仪(Raman)、扫描电子显微镜(SEM)对复合填料的结构及微观形貌进行表征。然后以ZnO@rGO作为导热填料,制备了系列环氧树脂(ZnO@rGO/EP)导热绝缘复合材料,研究了填料含量对复合材料性能的影响。结果表明,复合填料能较均匀地分散于环氧树脂基体中,随填量的增加,ZnO@rGO(O_2)/EP复合材料的热导率不断增加,冲击强度先提高后降低。当添加22.04%(体积分数)的ZnO@rGO(O_2)填料时,复合材料的热导率达到0.58 W/(m·K),与纯环氧树脂材料相比提高了205.3%,而冲击强度由纯环氧树脂的15.9 kJ/m~2提高到25.0 kJ/m~2且该复合材料仍保持良好绝缘性能。     

环氧树脂/氮化硼/石墨烯纳米片导热复合材料的制备与性能研究

采用十八烷基三甲基溴化铵(OTAB)改性的氮化硼(BN)微粒和石墨烯纳米片(GNP)为导热填料,制备了系列环氧树脂(EP)/改性BN(BNOTAB)/GNP导热绝缘复合材料,研究了填料的种类和含量对复合材料导热性能、电绝缘性能及热稳定性能的影响。结果表明,经OTAB改性后的BN微粒能比较均匀分散于环氧树脂体系中;当m(BNOTAB)/m(GNP)=6∶4时(填料总含量为10%),复合材料的热导率达到0.48 W/(m·K),较纯环氧树脂材料提高了108.7%,而该复合材料仍保持优异的绝缘性能;TGA与DSC结果显示,BNOTAB/GNP填充微粒的加入可以提高环氧树脂复合材料的热稳定性。     

碳纳米管/天然橡胶热界面材料制备及热管理性能研究

热界面材料是解决现代高功率和高集成化电子器件热量聚集和耗散的有效手段。基于三维网络结构调控导热性能的策略,以三聚氰胺泡沫(MF)为骨架,采用化学表面改性制备碳纳米管三维网络结构(CNT),并采用真空浸润法制备碳纳米管/天然橡胶热界面复合材料(CNT/NR),研究CNT含量对材料微观结构、导热性能和热管理性能的影响。结果表明,当CNT的含量为2.2%(质量分数)时,CNT可附着于MF骨架并呈现完整连续的三维网络结构,其热界面复合材料垂直面外的导热率为1.58 W m^-1 K^-1,拉伸强度为12.9 MPa,断裂伸长率为489%,并具有显著的热管理性能,这表明CNT/NR热界面复合材料有望成为一种机具应用价值的热管理材料。     

石墨烯导热材料研究进展

石墨烯作为一种具有超高热导率的二维纳米材料,在导热领域有着广阔的应用前景.本文综述了石墨烯导热材料的研究进展,介绍了石墨烯本征热导率及其层数、缺陷、边缘情况等对热导率的影响,分析了石墨烯纤维的研究现状及存在的问题,讨论了各类石墨烯导热薄膜(纯石墨烯薄膜/石墨烯杂化薄膜/石墨烯聚合物复合薄膜)热导率的影响因素,归纳总结了各类三维石墨烯导热材料(无规分散石墨烯三维复合材料和特定结构石墨烯三维复合材料)的结构、性能与研究现状,最后指出了目前几种导热材料研究存在的问题并展望了石墨烯未来导热领域的发展方向,尤其是在LED照明、智能手机等高功率、高度集成系统中,石墨烯导热材料有着良好的发展前景.     

石墨烯季戊四醇相变复合材料导热性能的分子动力学研究

低导热是限制储能材料实际应用的一大缺点,具有极高导热系数的石墨烯可作为导热填料有效改善储能材料的导热性能。本文通过反向非平衡分子动力学的方法,借助Materials Studio软件,模拟研究了石墨烯(GE)质量分数为0.5%、1%、1.5%、2%、2.5%、3%的石墨烯/季戊四醇(GE/PE)固-固相变复合材料的导热性能和内部相互作用。结果表明:石墨烯的添加可有效提升季戊四醇的导热性能,随着GE质量分数的增加,GE/PE复合相变材料的导热率、界面热导以及相互作用能均逐渐增大,且趋势幅度相一致,材料整体导热系数的增加归因于石墨烯结构的变化。本文可为石墨烯改善季戊四醇导热性的实验研究提供指导。     

Thermal conductivity of liquid crystalline epoxy/BN filler composites having ordered network structure

BN filler was added to a liquid crystalline (LC) epoxy resin to obtain a high thermal conductive material. The LC epoxy/BN composites, which were cured at different temperatures, formed an isotropic or LC polydomain phase structure. The relationship between the network orientation containing mesogenic groups and the dispersibility of the BN filler was discussed. As a result, the thermal conductivity of the LC polydomain system was drastically enhanced even at a relatively low volume fraction of BN (30 vol%), regardless of the fact that both the LC and isotropic phase systems consisted of the same resin and filler content combination. This result is due to the formation of thermal conductive paths by the BN filler by exclusion of the BN filler from the LC domain formed during the curing process in the composite having the LC polydomain matrix.     

Synergistic Effect of Aligned Graphene Nanosheets in Graphene Foam for High‐Performance Thermally Conductive Composites

Graphene shows a great potential for high‐performance thermally conductive composite applications because of its extremely high thermal conductivity. However, the graphene‐based polymer composites reported so far only have a limited thermal conductivity, with the highest thermal conductivity enhancement (TCE) per 1 vol% graphene less than 900%. Here, a continuous network of graphene foam (GF), filled with aligned graphene nanosheets (GNs), is shown to be an ideal filler structure for thermally conductive composite materials. Compared to previous reports, a clear thermal percolation is observed at a low graphene loading fraction. The GNs/GF/natural rubber composite shows the highest TCE of 8100% (6.2 vol% graphene loading) ever reported at room temperature, which gives a record‐high TCE per 1 vol% graphene of 1300%. Further analyses reveal a significant synergistic effect between the aligned GNs and 3D interconnected GF, which plays a key role in the formation of a thermal percolation network to remarkably improve the thermal conductivity of the composites. Additionally, the use of this composite for efficient heat dissipation of light‐emitting diode (LED) lamps is demonstrated. These findings provide valuable guidance to design high‐performance graphene‐based thermally conductive materials, and open up the possibility for the use of graphene in high‐power electronic devices.     

电器封装用高效导热/阻燃环氧复合材料的制备

目的为了提高电器封装材料的安全性,制备出一种具有高效导热/阻燃的环氧复合材料。方法通过原位聚合法,采用三聚氰胺-甲醛树脂预聚体(MF)修饰石墨烯(G)/磷烯(BP)合成纳米填料,辅以环氧树脂(E51)制备高导热/阻燃的环氧复合材料。通过TGA、热线法和锥形量热法分别测试复合材料的热稳定性、导热性和阻燃性。结果研究结果表明,当MF@BP/G的质量分数为3%时,环氧复合材料的残碳量高达22.19%,相较于纯的环氧复合材料提升了76.77%;导热系数提升至0.257 W/(m∙K),提升率为27.86%;峰值热释放率、总的热释放量、峰值烟雾释放率和总的烟雾释放量分别下降了43.76%,27.72%,46.81%和28.83%。结论以MF@BP/G为功能填料,可以有效提高环氧复合材料的导热性和阻燃性,有利于提升环氧复合材料的使用安全性。     

三维石墨烯-吡咯气凝胶/环氧树脂复合材料的制备及其性能EI北大核心CSCD

通过三步法及真空辅助浸渍的方法制备了石墨烯-吡咯气凝胶/环氧树脂复合材料,该复合材料质轻并且内部的多孔石墨烯-吡咯气凝胶具有较为均一的三维结构,在与环氧树脂复合之后,这种三维结构也能很好地保留。石墨烯的三维网络为电子传导提供了快速通道,使材料的导电性能显著提高,仅有0.23%(质量分数)填料含量的石墨烯-吡咯气凝胶/环氧树脂复合材料(1G-1%P,1300℃)的电导率可以达到67.1 S/m。石墨烯-吡咯气凝胶/环氧树脂复合材料(1G-1%P,1300℃)的电磁屏蔽性能在8~12 GHz可以达到33 dB,更重要的是石墨烯-吡咯气凝胶骨架还起到了增强环氧树脂基体力学性能的作用,弯曲强度和弯曲模量与环氧树脂基体相比分别提高了60.93%和25.98%(10G-5%P,180℃),石墨烯-吡咯气凝胶的三维结构可以有效地改善材料整体的电磁屏蔽性能以及力学性能。     

BN表面改性对BN/环氧树脂复合材料导热性能的影响

采用十八烷基三甲基溴化铵（OTAB）阳离子表面活性剂对BN微米片进行有机化改性,研究了BN表面改性对BN/环氧树脂复合材料导热性能的影响。当OTAB浓度为0.6 g · L^-1时,BN表面的OTAB吸附量接近饱和。BN表面改性提高了环氧树脂对BN的浸润性,降低了BN的导热系数。SEM观察及黏度测试结果表明：BN表面改性改善了BN/环氧树脂复合材料的界面性能及体系相容性。由于界面热阻的降低,改性BN/环氧树脂复合材料的导热系数高于未改性BN/环氧树脂复合材料,当BN填充量为30%（填料与树脂基体的质量比）时,改性BN/环氧树脂复合材料的导热系数为1.03 W （m · K）^-1,是未改性BN/环氧树脂导热系数（0.48 W （m · K）^-1）的2.15倍。     

The effect of interfacial state on the thermal conductivity of functionalized Al2O3 filled glass fibers reinforced polymer composites

Rapidly increasing packaging density of electronic devices puts forward higher requirements for thermal conductivity of glass fibers reinforced polymer (GFRP) composites, which are commonly used as substrates in printed circuit board. Interface between fillers and polymer matrix has long been playing an important role in affecting thermal conductivity. In this paper, the effect of interfacial state on the thermal conductivity of functionalized Al₂O₃ filled GFRP composites was evaluated. The results indicated that amino groups-Al₂O₃ was demonstrated to be effective filler to fabricate thermally conductive GFPR composite (1.07 W/m K), compared with epoxy group and graphene oxide functionalized Al₂O₃. It was determined that the strong adhesion at the interface and homogeneous dispersion of filler particles were the key factors. Moreover, the effect of interfacial state on dielectric and thermomechanical properties of GFRP composites was also discussed. This research provides an efficient way to develop high-performance GFRP composites with high thermal conductivity for integrated circuit packaging applications.     

Graphene woven fabric-reinforced polyimide films with enhanced and anisotropic thermal conductivity

Due to the growing needs of thermal management in modern electronics, polyimide-based (PI) composites are increasingly demanded in thermal interface materials (TIMs). Graphene woven fabrics (GWFs) with a mesh structure have been prepared by chemical vapor deposition and used as thermally conductive filler. With the incorporation of 10-layer GWFs laminates (approximate 12 wt%), the in-plane thermal conductivity of GWFs/PI composite films achieves 3.73 W/mK, with a thermal conductivity enhancement of 1418% compared to neat PI. However, the out-of-plane thermal conductivity of the composites is only 0.41 W/mK. The in-plane thermal conductivity exceeds its out-of plane counterpart by over 9 times, indicating a highly anisotropic thermal conduction of GWFs/PI composites. The thermal anisotropy and the enhanced in-plane thermal conductivity can be attributed to the layer-by-layer stacked GWFs network in PI matrix. Thus, the GWFs-reinforced polyimide films are promising for use as an efficient heat spreader for electronic cooling applications.     

三维机织碳纤维/环氧树脂复合材料在两种测量方法下的热响应机制对比

采用瞬态热线法和闪光法分别测量了多种结构参数的三维机织碳纤维/环氧树脂复合材料的导热系数。通过对3D正交机织碳纤维/环氧树脂复合材料的有限元模拟可以看出,3D正交机织碳纤维/环氧树脂复合材料内经纱、纬纱和Z向纱的导热作用在不同的受热形式下会发生变化。采用瞬态热线法测量时,2.5D机织碳纤维/环氧树脂复合材料的导热系数低于2.5D经向增强结构,同时高于3D正交结构,而采用闪光法测量时,2.5D经向增强和3D正交碳纤维/环氧树脂复合材料的导热系数均小于2.5D机织结构。这是由于在使用不同的测量方法时,三维机织碳纤维/环氧树脂复合材料内部相同的纱线系统在导热过程中所起的作用并不相同。随着纤维体积含量的提高,瞬态热线法和闪光法测得的2.5D机织碳纤维/环氧树脂复合材料的导热系数都在不断提高。由于经纱的屈曲,采用闪光法测量时,导热性能提升更加明显。研究结果表明,三维机织碳纤维/环氧树脂复合材料在不同受热形式下具有不同的热响应机制。     

Mechanical and thermal properties of lightweight geopolymer composites

This research has investigated the properties of thermally insulating geopolymer composites that were prepared using waste expanded polystyrene as lightweight aggregate. The geopolymer matrix was synthetized using metakaolin and an alkaline activating solution. To improve its mechanical properties, this matrix was modified by the addition of an epoxy resin to form an organic-inorganic composite. Moreover, in order to reduce drying shrinkage marble powder was used as an inert filler. The materials obtained were characterized in terms of physico-mechanical properties, thermal performance and microstructure. The geopolymer expanded polystyrene composite have improved properties compared to Portland cement-based materials, with higher strengths and lower thermal conductivity. The research demonstrates the manufacture of sustainable lightweight thermally insulating geopolymer composites using waste expanded polystyrene.