苏州纳米所碳纳米管基散热材料研究取得进展

中科院苏州纳米技术与纳米仿生研究所先进材料部李清文研究员课题组以自行宏量制备的碳纳米管粉体为基础，通过对其进行不同基团的功能化并与商用导热硅脂复合，详细考察了功能化对碳纳米管在硅脂中的分散及其与硅脂界面浸润性的影响，     

有机硅基导热硅脂的改性及渗油机理研究

针对目前传统导热硅脂渗油现象严重的问题,以铝粉和银粉为填料制备有机硅基导热硅脂,采用硅烷偶联剂改性粉体、添加聚硅氮烷改性硅油、添加纳米氮化铝粒子3种方法改善导热硅脂的渗油性能,分别测试其在高温加热和热循环实验后的渗油性能。结果表明,3种改性导热硅脂的渗油抑制性能相较市售导热硅脂明显改善,其中添加纳米氮化铝粒子的导热硅脂渗油抑制效果最佳,其分油量为0. 049%(质量分数)。改性导热硅脂经过热循环后,渗油性未发生明显变化。     

碳纳米管/橡胶复合材料导热性能研究进展

导热橡胶在航空、航天、电子、电器领域有着广泛的应用前景。把碳纳米管填充到橡胶中,渴望获得具有优良导热性能的橡胶复合材料已成为材料领域研究的热点。本文综述了填充型导热橡胶的实验研究现状、导热橡胶的导热机理、导热模型;重点论述了碳纳米管的结构与改性、碳纳米管填充橡胶的导热性能的实验研究及理论研究进展;最后指出碳纳米管的独特结构和优异性能使其作为橡胶复合材料导热增强组分在理论上具有明显优势,但其复合材料的热物性研究仍存在一些问题有待解决;如何降低界面热阻、增加碳纳米管取向等将是提高碳纳米管/橡胶复合材料导热性能的重要解决途径。     

硅脂导热涂层改善LED散热性能的研究

研究了导热硅脂(KE3493)涂层对水下密闭环境下应用的LED灯散热情况的影响,结果表明,LED系统的集成电路板上加入导热涂层能提高LED系统的散热效率,研究结果为导热涂层应用于LED散热系统提供了参考数据.     

低迁移绝缘导热硅脂界面材料的制备及其性能研究

本研究针对航天器界面材料对高导热、绝缘、低迁移特性的要求,基于分子链缠结理论,自制长链烷基改性硅油(AMS)和含氟碳长链改性硅油(FPS)作为基体,以类球状氮化铝和片状氮化硼为导热填料,制得低迁移绝缘导热硅脂界面材料.通过不同粒径填料的粒径复配、发挥不同形貌填料的协同作用、填料表面改性等,导热硅脂的导热性能可达2.51 W/(m·K),其体积电阻为3.1×1015Ω·cm,击穿电压为10.1 kV·mm-1.对以自制改性硅油为基体制得的导热硅脂进行迁移性能测试,同时对基体硅油进行表面张力和接触角测试,结果表明,导热硅脂的迁移特性与基础油在迁移测试板上的接触角具有相关性.通过引入长支链增加硅油分子链缠结、改善基础油在涂覆面上的接触角,可有效降低导热硅脂的迁移.     

氮化铝薄膜改善LED散热性能的研究

研究了氮化铝薄膜对LED灯散热情况的影响，并与导热硅脂（Ks609）涂层的散热效果进行了比较，结果表明：导热涂层能加强LED的散热，氮化铝薄膜散热效果优于导热硅脂；对红、白、绿3种颜色LED，相同条件下，散热材料对红色LED的散热效果最好。研究结果为氮化铝薄膜应用于LED散热系统提供了参考数据。     

新型纳米铜导热硅脂的研制和性能研究

用惰性气体蒸发法和电弧等离子体法制备了纳米铜粒子,以此作为导热填料,研制出了具有高导热系数的新型纳米铜导热硅脂.在LGA 775和Socket 939计算机平台上进行了试验,结果表明,新型硅脂能大大降低CPU的工作温度,并对此进行了机理分析.     

颗粒填充型聚合物的导热性能与摩擦磨损性能研究

采用蒙特卡罗可控空间分布算法,生成网链构型的三维代表体积单元(RVE)模型,数值研究了非均匀分布下不同组分氮化铝/石墨/银导热硅脂的导热性能。制备了氮化铝、氮化铝/石墨、氮化铝/石墨/银三种填料体系的导热硅脂,并测试所有样品的热导率和体积电阻率。采用往复摩擦磨损试验机对室温下导热硅脂在钢-钢摩擦副上的载流摩擦磨损性能进行研究。利用扫描电子显微镜(SEM)观察金属表面并利用能谱分析仪(EDS)对表面元素成分进行分析。结果表明:导热填料形貌越丰富,硅脂中的导热网络越致密,氮化铝/石墨/银硅脂的最大热导率可达1.623 W/(m·K),可实现在较少填充量下获得较高热导率;氮化铝/石墨/银有限元模型模拟的结果更贴近实验测量值,可以用来预测球状/片状/棒状颗粒填充导热硅脂的导热性能;氮化铝/石墨/银导热硅脂的载流摩擦磨损性能最优,这归结于其导热性能和导电性能协同减轻电弧对金属表面的侵蚀。     

碳纳米管含量对纳米复合材料相变特性的影响

以多壁碳纳米管(CNTs)为填料,采用两步法制备了不同质量分数(0.1%~1.0%)的CNTs/石蜡复合相变材料,并对其相变特性进行了实验研究。研究表明,复合材料的相变温度几乎保持不变,但其相变潜热随碳纳米管含量的增加呈降低趋势,熔化时间和凝固时间随碳纳米管含量的增加逐渐缩短,在CNTs质量分数为1.0%时,复合相变潜热值下降了6.3%。熔化时间和凝固时间分别缩短了31.0%和25.5%。复合材料的固、液态导热系数随碳纳米管含量的增加而大幅度提高,在25℃,CNTs质量分数为0.5%时的复合相变材料的导热系数提高了13.2%,体现了良好的强化导热效果。此外,碳纳米管含量较小时,复合相变材料的粘度基本不受碳纳米管加入的影响。碳纳米管质量分数为0.5%和1.0%的复合相变材料的粘度比纯石蜡的粘度提高了1.0%和1.5%,说明碳纳米管含量是影响复合相变材料粘度的一个主要因素,进而影响复合材料的相变特性。     

碳纳米管/环氧树脂复合材料的静电自组装制备及性能

采用静电自组装法制备了均匀分散的碳纳米管环氧树脂复合材料,并对比分析了普通碳纳米管和功能化碳纳米管对环氧树脂热学和电学性能的影响。采用透射电镜(TEM)观察到碳管和树脂乳液自组装形成"葡萄藤"状结构,扫描电镜(SEM)观察发现,碳管可在环氧树脂中均匀分散并形成网络。电、热性能研究发现,添加3%普通碳纳米管可降低环氧树脂表面电阻率7个数量级,导热系数较纯树脂提高112%,而羧基化碳纳米管表面电阻率仅降低4个数量级,导热系数仅提高86%。     

Techniques for Reducing Thermal Contact Resistance in Steady-State Thermal Conductivity Measurements on Polymer Composites

The National Physical Laboratory (NPL) has developed a new variation on the established guarded hot plate technique for steady-state measurements of thermal conductivity. This new guarded hot plate has been specifically designed for making measurements on specimens with a thickness that is practical for advanced industrial composite materials and applications. During the development of this new guarded hot plate, NPL carried out an experimental investigation into methods for minimising the thermal contact resistance between the test specimen and the plates of the apparatus. This experimental investigation included tests on different thermal interface materials for use in another NPL facility based on a commercial guarded heat flow meter apparatus conforming to standard ASTM E1530-11. The results show the effect of applying different quantities of the type of heat transfer compound suggested in ASTM E1530-11 (clause 10.7.3) and also the effect on thermal resistance of alternative types of thermal interface products. The optimum quantities of two silicone greases were determined, and a silicone grease filled with copper was found to offer the best combination of repeatability, small hysteresis effect and a low thermal contact resistance. However, two products based on a textured indium foil and pyrolytic graphite sheet were found to offer similar or better reductions in thermal contact resistance, but with quicker, easier application and the advantages of protecting the apparatus plates from damage and being useable with specimen materials that would otherwise absorb silicone grease.     

热阻塞效应在有机硅树脂-碳纤织物复合材料烧蚀防热中的作用

为评价热阻塞效应对有机硅树脂-碳纤织物复合材料防热的贡献,根据有机硅树脂的烧蚀防热机理建立热响应过程数学模型,预测了有机硅树脂-碳纤织物复合材料的背面温度以及有机硅树脂的热物性参数,重点分析了热阻塞效应对有机硅树脂-碳纤织物复合材料防热性能的影响。结果表明在400 kW/m2的热流烧蚀下,有机硅树脂-碳纤织物复合材料40 s前热阻塞效应大部分来自有机硅树脂分解产生的引射气体,40 s后则完全来自于炭燃烧产生的引射气体;阻塞因子在10 s时达到最小,此刻阻挡了121.6 kW/m2的热流进入有机硅树脂内,在整个烧蚀过程中热阻塞效应减少了4.1%的总热量进入有机硅树脂内;在热物性参数中,热阻塞效应对有机硅树脂密度影响最大,导热系数和比热容次之;与增加逸出气体质量流率相比,延长有机硅树脂逸出气体的时间更能显著提高热阻塞效应,达到更好的防热效果。      

Performance of graphite nanoplatelet/silicone composites as thermal interface adhesives

Graphite nanoplatelets (GNP)/silicone composites are potential thermal interface materials due to their high thermal conductivity and compliance. In this study, performance as thermal interface materials is studied by measuring thermal contact resistance. The effect of surface roughness, particle size of GNPs, wt% GNPs, temperature and applied pressure on the thermal contact resistance of the composite coatings was determined. The GNP/silicone coating performed much better on rough surfaces than on smooth surfaces. The composite coating consisting of large GNPs is more effective than small GNPs probably due to the two times higher thermal conductivity of the former. The thermal contact resistance of the GNP/silicone composite increased by ~3–10% with an increase of temperature but remained unaffected by an increase of pressure. The comparison of GNP/silicone composite coatings with GNP-based thermal pastes showed that the former perform much better in thick bond lines.     

导电炭黑填充硅橡胶的电阻温度系数

以炭黑(CB3100)为导电相,硅橡胶为基质制备导电复合材料。研究导电橡胶中炭黑质量分数对电阻温度系数的影响,并用填料对电阻温度系数的影响。以隧道效应理论为基础,给出了导电炭黑填充橡胶的电阻温度系数计算模型,结合实验得到温度对导电炭黑/硅橡胶电阻温度系数的影响主要体现在对其电阻率的影响;基体的体积热膨胀提高复合材料的电阻率,提高了正电阻温度系数;炭黑粒子间的隧道效应降低复合材料的电阻率,增强了负电阻温度系数;在炭黑/硅橡胶中加入少量碳纳米管,利用碳纳米管和炭黑的协同补强效应,使复合材料的导电性和稳定性提高。     

柔性可拉伸硅橡胶@多壁碳纳米管/硅橡胶可穿戴应变传感纤维

基于核-壳结构设计,采用简便、低成本的浸涂-固化法制得柔性、可拉伸、高灵敏且稳定的聚二甲基硅氧烷硅橡胶@多壁碳纳米管/聚二甲基硅氧烷硅橡胶(PDMS@MWCNTs/PDMS)压阻式应变传感纤维。通过FTIR、XRD、TG、TEM对硅烷偶联剂改性多壁碳纳米管(MWCNTs-KH570)的化学结构、热稳定性和微观形貌进行了分析,深入研究了核-壳结构与MWCNTs-KH570质量分数对PDMS@MWCNTs/PDMS复合纤维导电性能、传感性能及力学性能的影响规律与机制。结果表明:羟基化MWCNTs(MWCNTs—OH)表面接枝KH570使其在壳层PDMS基体中具有良好的分散性和界面相互作用;核-壳结构的设计使PDMS@MWCNTs/PDMS复合纤维在低填充下具有高电导率和传感性能;PDMS@MWCNTs/PDMS复合纤维的导电性能与传感性能随着MWCNTs-KH570质量分数增加而提高,且在人体关节运动监测中表现出良好的可重复性和工作稳定性。      

碳包钴纳米颗粒/聚二甲基硅氧烷复合热界面材料的制备和性能

为了制备具有良好的热导率、热稳定性、导电性和柔顺性的纳米颗粒填充硅树脂复合材料,首先以乙基封端聚二甲基硅氧烷(PDMS)为基体材料,以碳包钴纳米颗粒(C@Co)为填料,采用研磨共混法制备了C@Co/PDMS复合热界面材料。然后,运用TEM、XRD、Raman和SEM分别对C@Co的微观结构、物相、石墨化程度和分散性进行了研究。最后,研究了C@Co含量对复合热界面材料的热导率、热稳定性、导电性和柔顺性的影响。结果表明:该复合热界面材料的热导率随着C@Co含量的增加而增大,当C@Co的含量为24wt%时,复合材料的热导率达到最大值1.64 W/(m·K),比纯PDMS的提高了10.7倍;TG分析表明,添加24wt%的C@Co后,复合材料的起始分解温度和最终分解温度比纯PDMS的分别提高了约70℃和80℃,说明C@Co能提高复合材料的热稳定性;随着C@Co含量的增加,复合热界面材料的电导率非线性增大,拟合试差计算的逾渗阀值为10wt%,即C@Co含量小于10wt%时复合材料的绝缘性良好,而填充24wt%的C@Co时复合材料的电导率为9.38×10-3 S·m-1;复合材料的硬度适中,处于17.6~26.8HA范围内,表明该复合材料的柔顺性较好。因此,24wt%C@Co/PDMS复合材料不仅能满足热界面材料电性能的基本要求,且具有良好的热导率、热稳定性和柔顺性。     

Improving the thermal and mechanical properties of silicone polymer by incorporating functionalized graphene oxide

Functionalized graphene oxide (FGO) was produced by reacting graphene oxide nanosheets with vinyl trimethoxy silane (VTMS). The results confirmed the attachment of VTMS molecules to the surface of GO sheets by Si–O–C bonding. The introduction of VTMS molecules led to an excellent dispersibility in tetrahydrofuran and to the complete exfoliation of FGO with a thickness of about 1.19 nm. Meanwhile, FGO/silicone polymer composites were prepared by solution blending method. The incorporation of 0.5 wt% of FGO in silicone polymer improved remarkably the thermal stability, tensile strength, and thermal conductivity of the silicone polymer composite, due to the homogeneous dispersion of FGO in the composites as well as to the strong interfacial adhesion with silicone polymer matrix. Tensile strength and thermal conductivity of the FGO/silicone polymer composite were increased by 95.6 and 78.3 %, respectively, with the addition of 0.5 wt% FGO. The 5 % weight loss temperature of the composite at 0.5 wt% FGO loading was detected 26.1 °C higher than that of silicone polymer.     

Low temperature specific heat of cry-con grease

The specific heat of Cry-Con grease, a copper loaded electrically insulating grease, was measured between 0.5 and 20 K. The low specific heat and high thermal conductivity of Cry-Con grease render it a useful thermal bonding material for calorimetric measurements on samples with low thermal conductivity.     

碳纤维含量对短碳纤维－铜复合材料性能的影响

用粉末冶金法制造了碳纤维分布均匀的碳纤维一铜复合材料，测定了复合材料的力学性能和物理性能，表明在碳纤维与铜基体之间存在界面结合，碳纤维含量对复合材料性能影响极大。