电子封装用石墨泡沫/Sn-Bi合金复合材料微观结构和热物理性能（英文）

以中间相沥青为原料,采用加压发泡法制备出不同结构和性能的高导热石墨泡沫。通过Sn-Bi合金高温熔融浸渍石墨泡沫,制备了电子封装用高导热石墨泡沫/Sn-Bi合金复合材料,系统研究了该材料的微观结构和热物理性能。结果表明,Sn-Bi合金均匀分散于石墨泡沫的孔隙结构中;复合材料的密度为3.83±0.01 g/cm~3,其热扩散系数达到163.1±3 mm~2/s,材料的热膨胀系数为8.08±0.02 ppm/K明显低于合金材料的20.7±0.02 ppm/K。通过石墨泡沫基体密度和结构的调控,可制备出低膨胀系数(8.08±0.02,16.4±0.02 ppm/K)的电子封装用高性能石墨泡沫/Sn-Bi合金复合材料。     

中间相炭微球的二次生长

为考察中间相的形成和生长机理,将一种煤沥青制备的中间相炭微球添加到另一种沥青中进行二次热缩聚,结果发现中间相炭微球可以进行二次生长。二次热缩聚中间相炭微球的产率、粒径分布、表面和断面的形貌表明添加的中间相炭微球对于沥青热缩聚过程的物理作用更为主要;二次热缩聚过程包含了添加的中间相炭微球的二次生长过程和原料沥青独立成核生长两个相互竞争的过程,中间相炭微球的添加量对这两个过程有着重要的影响;中间相炭微球的生长是基本构筑单元不断进入相界面的构筑过程。     

碳纳米管/中间相炭微球复合材料锂离子电池负极材料研究

采用热缩聚法(温度为420℃、反应时间为2 h)制备出碳纳米管/中间相炭微球复合材料。研究了碳纳米管添加量对中间相炭微球的形成和形貌的影响,以及对碳纳米管/中间相炭微球复合材料充放电性能的影响。实验结果表明,5%(质量分数)的碳纳米管添加量有利于中间相炭微球的形成,碳纳米管/中间相炭微球复合材料作为负极材料的锂离子电池充放电容量可达到337 mAh/g,20次循环后容量仍保持88%。     

泡沫炭的成核机理及其复合增强机制

以中间相炭微球(MCMB)、聚丙烯腈基炭纤维(PAN-CF)和纳米氧化锆(Zr O2)为增强体,采用自发泡法制备出泡沫炭复合材料,并研究不同增强材料对中间相沥青基泡沫炭的发泡行为和压缩强度的影响。结果表明,中间相沥青在发泡过程中遵循热点成核机制;较PAN-CF、MCMB而言,Zr O2纳米颗粒(~100 nm)对泡沫炭具有更佳的增强效果。当在中间相沥青原料中添加30%的纳米Zr O2后,泡沫炭的压缩强度可由7.57 MPa提高到31.4 MPa。     

碳纳米管对中间相炭微球制备的影响

以中温煤沥青和碳纳米管为原料进行热缩聚反应,制备出含有碳纳米管的中间相炭微球,采用扫描电子显微镜(SEM)、激光粒度仪和X射线衍射(XRD)等分析手段对其形貌及结构进行了表征。研究了添加碳纳米管对中间相炭微球形貌、粒径、产率、微晶结构及热缩聚工艺的影响。结果表明添加碳纳米管能够促进小球成核,阻止小球的融并长大,使炭微球的粒径减小,分布均匀,但过多的碳纳米管会导致球形度变差及中间相沥青产率的降低;碳纳米管的存在使石墨片层尺寸减小,石墨化程度降低;碳纳米管经过酸煮处理后,可以获得球形度更好、含有更大比例碳纳米管的中间相炭微球。     

添加松香对中间相炭微球制备的影响

以中温煤沥青为原料,松香为添加剂,通过热缩聚合法制备中间相炭微球。采用FT-IR、SEM、偏光显微镜等对所得产物进行表征,研究了松香对中间相炭微球制备的影响。研究表明松香的加入能有效限制沥青的过度聚合,不仅促进中间相炭微球的成核和生长,而且在很大程度上防止中间相炭微球的融并;当松香添加量为10%(质量分数)时,改性煤沥青经450℃热解2h可制备出球形度好、粒径均匀的中间相炭微球,其平均粒径为15.3μm,收率达44.1%。     

以中间相沥青为粘结剂的低密度高导热炭纤维网络体的研究

以中间相沥青为粘结剂, 采用500 ℃低温炭化炭纤维, 经低压模压成型、炭化和石墨化后得到低密度高导热炭纤维网络体。与以1300 ℃炭化炭纤维为原料和以酚醛为粘结剂制备的炭纤维网络体进行了比较。对粘结剂炭收率(热重分析)、样品微观形貌(扫描电子显微分析)、石墨化度及微晶尺寸(X射线衍射分析)等进行了表征。研究结果表明: 由于高炭收率和高片层取向度的中间相沥青与500 ℃低温炭化处理炭纤维共同经历后续热处理时呈现出相近的热收缩率, 因而具备良好的相互粘结性和石墨片层铆接效应, 其制备的炭纤维网络体经石墨化后密度为0.317 g?cm ^-3, 由此制备的相变复合材料的面内热导率为19.30 W·m ^-1·K ^-1, 较纯相变材料(石蜡)提升了80倍, 明显高于以1300 ℃炭化炭纤维为原料, 以中间相沥青和酚醛分别为粘结剂制备样品的面内热导率(17.03和14.47 W·m ^-1·K ^-1)。     

中间相沥青基泡沫炭的制备、结构及性能

以萘系中间相沥青为原料,考察了发泡条件、炭化和石墨化工艺对所制泡沫炭结构和性能的影响.结合粘温曲线、TG-DTG热重曲线以及不同发泡条件下泡沫炭的表面形貌分析,其最佳发泡条件为:发泡温度600℃,升温速率5℃/min,发泡压力5MPa.石墨化升温速率越低越有利于泡沫炭石墨微晶的生长及压缩强度的提高,其中以5℃/min升温至2800℃并恒温30min所制泡沫炭的压缩强度达1.38MPa.     

中间相沥青基炭泡沫体的制备、结构及性能

以合成中间相萘沥青为原料，采用加压发泡法制备孔径均匀的初生炭泡沫体，经700℃～1000℃和2300℃～2800℃热处理制备出炭化和石墨化炭泡沫体；以700℃炭化处理所得的炭泡沫体作为芯材制成夹芯复合材料。研究了原料性能、发泡以及热处理工艺参数对炭泡沫微观结构和力学性能的影响，考察了炭泡沫体夹芯复合材料的微波吸收性能。结果表明：发泡过程中保持均匀的温度场是制备孔径均匀的炭泡沫体的关键因素，压力是影响孔结构的主要因素。炭泡沫体的微晶结构、力学性能以及微波吸收性能沿xy和XZ面方向（分别表示垂直和平行于重力方向）具有各向异性。     

原生QI成核中间相炭微球的结构

以含有原生ＱＩ的煤沥青为原料,采用热缩聚方法制备出中间相炭微球,用扫描电子显微镜（ＳＥＭ）观察了中间相炭微球的形貌和断面结构,经初步判断,在实验条件下原生ＱＩ成核煤沥青基中间相炭微球更倾向于“地球仪”型结构,并对以ＱＩ为核形成中间相微球的过程进行了分析。     

The thermal and mechanical properties of graphite foam/epoxy resin composites

A series of epoxy resin (EP) filled graphite foam (GF) composites were prepared to explore a new material with good heat transfer property. The effects of the mass fraction of EP and the network structure of GFs on the thermal diffusivity and the compression strength of the composites were investigated. The thermal diffusivity of the GF/EP composite with EP mass fraction of 91.45% was raised to 6.541 mm²/s, which was 45.7 times higher than the pure EP. The thermal conductivity reached to 14.67 W/(m K), which was 43.1 times higher than the pure EP. The compression strength of the GF/EP increased 55% above the value of pure EP. In addition, the thermal diffusivity of GF/EP increased with the decrease of the mass fraction of EP. A model was formulated to calculate the pressure needed for a mass fraction of EP.     

石墨表面TiC涂层对高定向石墨/Cu复合材料热导率和抗弯强度的影响

以高温盐浴法对天然鳞片石墨粉体(GF)进行表面TiC镀层处理,然后采用真空热压烧结法制备TiCGF/Cu复合材料,研究了粉体表面涂层和GF体积分数对复合材料微观结构、热导率及抗弯强度的影响。系列测试结果表明:随着GF体积分数的降低以及粉体表面TiC镀层的形成,TiC-GF/Cu复合材料平行于GF片层方向的热导率有所降低,抗弯强度有所提升。其中在GF的体积分数占TiC-GF/Cu复合材料70%时,这种变化最为明显,平行于GF片层方向的TiC-GF/Cu复合材料热导率下降幅度最大,从676W/(m·K)下降到526 W/(m·K)。同时,TiC-GF/Cu复合材料的微观结构进一步说明,GF表面的TiC涂层对GF/Cu复合材料的断裂模型起着重要的作用。     

Three-dimensional flexible and conductive interconnected graphene networks grown by chemical vapour deposition

Integration of individual two-dimensional graphene sheets into macroscopic structures is essential for the application of graphene. A series of graphene-based composites and macroscopic structures have been recently fabricated using chemically derived graphene sheets. However, these composites and structures suffer from poor electrical conductivity because of the low quality and/or high inter-sheet junction contact resistance of the chemically derived graphene sheets. Here we report the direct synthesis of three-dimensional foam-like graphene macrostructures, which we call graphene foams (GFs), by template-directed chemical vapour deposition. A GF consists of an interconnected flexible network of graphene as the fast transport channel of charge carriers for high electrical conductivity. Even with a GF loading as low as ～0.5 wt%, GF/poly(dimethyl siloxane) composites show a very high electrical conductivity of ～10 S cm(-1), which is ～6 orders of magnitude higher than chemically derived graphene-based composites. Using this unique network structure and the outstanding electrical and mechanical properties of GFs, as an example, we demonstrate the great potential of GF/poly(dimethyl siloxane) composites for flexible, foldable and stretchable conductors.     

纳米铜/石蜡相变驱动复合材料制备及热物理性能

采用高能球磨法制备了纳米铜/石蜡复合材料。通过TEM、 SEM、 XRD和DSC对复合材料的微观形貌、 物相及相变温度和潜热进行了表征和分析, 并研究了铜含量对复合材料的热敏性、 热膨胀性和热稳定性的影响。结果表明: 石蜡包覆在铜粒表面, 能显著提高其抗氧化性, 铜/石蜡复合颗粒近似球形, 粒径约为100 nm, 多个复合颗粒易团聚形成微米级颗粒; 铜含量对相变温度没有明显影响, 但相变潜热随铜含量的增加近似线性减少; 复合材料的热敏性随着铜含量的增加而提高, 但其热膨胀性则降低; 铜质量分数为60%的复合材料具有较短的升温时间, 体膨胀率降低较小, 且多次加热后稳定性较好, 可作为此类热敏微驱动器的理想材料。     

加热条件对炭泡沫材料孔结构和性能的影响

以AR沥青为原料,利用高压釜在不同恒温条件下制备了炭泡沫,并测定了其孔结构、体积密度、显气孔率、压缩强度、常温热导率以及微晶参数.结果表明:相对于短恒温时间,长恒温时间制得的炭泡沫孔径大(412nm)、显气孔率高(83.82%)、体积密度小(0.34g/cm~3)、压缩强度高(4.92MPa),多孔连通结构更丰富.经过石墨化处理后,石墨泡沫呈现出较高的常温热导率(71.34W/(m·K))和较小的层片间距d_(002)(0.33556nm).石墨泡沫的常温比导热率能达到210(W·(m·K)~(-1)) /(g·cm~(-3)),是铜的5倍,铝的4倍.     

一维高导热C/C复合材料的制备研究

以三种沥青作为基体前驱体, 实验室自制的AR中间相沥青基纤维为增强体, 通过500℃热压成型, 随后经炭化和石墨化处理制备出一维炭/炭(C/C)复合材料。研究了前驱体沥青种类和热处理温度对复合材料导热性能的影响, 并采用扫描电子显微镜和偏光显微镜对其石墨化样品的形貌和微观结构进行表征。结果表明; C/C复合材料在沿纤维轴向的室温热扩散系数和导热率均随热处理温度的升高而逐渐增大; 由AR沥青作为基体前驱体所制备的C/C复合材料具有更加明显的沿纤维轴向取向的石墨层状结构以及最好的导热性能, 其3000℃石墨化样品沿纤维轴向的室温热扩散系数和导热率分别达到594.5 mm²/s和734.4 W/(m·K)。     

添加铜网对片层石墨/Al复合材料热物理性能的影响

使用盐浴法对片层石墨（GFs）进行表面镀Si处理,采用真空热压法制备片层石墨/Al复合材料（Si-GFs/Al）。向Si-GFs/Al复合材料中添加10vol%的铜网,研究了铜网对Si-GFs/Al复合材料热导率和力学性能的影响。使用SEM、聚焦离子束（FIB）和TEM对Si-GFs/Al复合材料的微观结构和微观界面进行表征,并分析了复合材料的断裂机制。结果表明,添加铜网使Si-GFs/Al复合材料内部出现了高聚集定向GFs带,形成高导热通道。当GFs体积分数为30vol%~40vol%时,Si-GFs/Al复合材料的热导率提升了约20%,弯曲强度提升了40%以上。当GFs体积分数为40vol%时,Si-GFs/Al复合材料热导率和弯曲强度同时达到一个优值,分别为512 W/（mK）和127 MPa。      

Effect of flame retardants on mechanical properties,flammability and foamability of PP/wood–fiber composites

The mechanical properties, flame retardancy, thermal degradation and foaming properties of wood–fiber/PP composites have been investigated. Ammonium polyphosphate (APP) and silica were used as flame retardants. The limiting oxygen index (LOI), thermal gravimetric analysis (TGA) and cone colorimeter (CONE) were employed for the study of fire retardance. At the same time, wood–fiber/PP composite foams were produced with the batch foaming technique using CO₂ as blowing agent. The effects of APP and silica content, pressure and temperature on the final cell structure were investigated. According to LOI, TGA and cone calorimeter results obtained from the experiments, APP and silica are effective flame retardants for wood–fiber/PP composites, and silica was shown to have a flame retardant synergistic effect with APP in wood–fiber/PP composite. The mechanical properties of the composites decreased with addition of flame retardants, except for the tensile strength of small amount of silica filled wood–fiber/PP composite. The results also revealed that the cellular morphologies of the foamed wood–fiber/PP composites are a strong function of the content of APP and silica as well as foaming conditions.     

石墨表面化学镀Cu对天然鳞片石墨/Al复合材料热物理性能的影响

对天然鳞片石墨（GF）进行化学镀Cu的表面处理,对化学镀Cu石墨（Cu-GF）和Al粉采用真空热压的工艺制备出镀Cu石墨/Al（Cu-GF/Al）复合材料。研究了Cu-GF/Al复合材料的微观结构和微观界面,同时也研究了Cu-GF对Cu-GF/Al复合材料热导率和抗弯性能的影响。结果表明,GF上的Cu层能抑制界面脆弱相Al₄C₃的产生,使Cu-GF/Al复合材料的抗弯性能有了显著提升。当Cu-GF体积分数从50%增加到70%时,Cu-GF/Al复合材料的抗弯强度也从104 MPa降低到74 MPa。当GF体积分数为70%时,Cu-GF/Al复合材料的热导率达到最高值为522 W/（m·K）。     

Experiments and modeling for thermal conductivity of graphite nanoplatelets/carbon composites

In this work, the graphite nanoplatelets/carbon composites were fabricated from graphite nanoplatelets and pitch powders by a hot-pressing technology followed by carbonization and graphitization. The XRD and pole figure results show that the incorporation of pitch induces the decrease of size (L_a) and orientation degree of graphitic crystallites, while the in-plane thermal conductivity of graphitized sample is increased with the increasing pitch content up to 6 wt.%, achieving a maximum value of 405 W/m K. The pitch binders are filled into the voids to bridge two or more graphite nanoplatelets particles together to form extra thermal paths, which makes a great contribution to the enhancement of thermal conductivity. A thermal conductivity model for the graphitized composites is constructed based on a bridging mechanism, and the predicted results fit well with the experimental results.