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。     

石墨表面镀Si对石墨/Al复合材料热物理性能的影响

研究了石墨粒径及表面镀Si处理对石墨/Al复合材料热物理性能的影响。结果表明:在盐浴过程中石墨表面形成了SiC层,这不仅增强了石墨-Si/Al复合材料的界面结合力,而且抑制了Al4C3相的产生。随着石墨鳞片体积分数从50%增加到70%,复合材料X-Y方向的热导率从492 W/(m·K)增加到654 W/(m·K),而且体积分数为50%的镀Si石墨/Al复合材料抗弯强度达到了81 MPa,相比未镀覆的提高了53%,是理想的定向导热电子封装材料。随着石墨粒径从500μm减小到150μm,石墨-Si/Al复合材料X-Y面方向的热导率由654 W/(m·K)降低到445 W/(m·K),但Z方向的热导率和复合材料抗弯强度变化不明显。     

多层石墨/硅树脂导热复合材料的制备与性能

以硅树脂为基体材料, 多层石墨为导热填料, 采用旋转搅拌球磨法制备了多层石墨/硅树脂导热复合材料, 研究了填料对多层石墨/硅树脂复合材料热导率、 热膨胀系数(CTE)和热稳定性的影响。结果表明, 多层石墨在硅树脂中分散性良好。多层石墨/硅树脂复合材料的热导率随多层石墨填充量的增加而增大, 填充质量分数为45%时, 热导率达到2.26 W·(m·K)^-1, 超过此值之后热导率开始下降。随着填料的增加, 多层石墨/硅树脂复合材料热膨胀系数减小。与纯硅树脂相比, 多层石墨/硅树脂复合材料热稳定性高。相同填充量下多层石墨/硅树脂比SiC/硅树脂、 AlN/硅树脂的热导率高得多, 这说明径厚比大的片状填料更易形成有效接触和导热网链。     

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。     

隐晶质石墨含量与粒径对复合材料导热性能的影响

以天然隐晶质石墨为导热填料,聚乙烯醇(PVA)为粘结剂,采用热压法制备了隐晶质石墨/PVA导热复合材料,研究了纯化前后隐晶质石墨含量与粒径对复合材料导热性能的影响。结果表明,随着石墨含量增加,复合材料的热扩散率上升。隐晶质石墨含量分别为89%和99%时,原矿隐晶质石墨制备的复合材料热扩散率分别为5.224和7.459 mm2/s,纯化后隐晶质石墨制备的复合材料热扩散率则为7.839和9.458 mm2/s,纯化后复合材料热扩散率较原矿提高;纯化前后隐晶质石墨在未球磨和以300~600 r/min球磨时,随着平均粒径的减小,复合材料的热扩散率下降。原矿球磨后隐晶质石墨/PVA复合材料热扩散率从5.224 mm2/s减小到4.682 mm2/s,纯化后球磨隐晶质石墨/PVA复合材料热扩散率从7.839 mm2/s下降到6.019 mm2/s。研究表明,隐晶质石墨/PVA复合材料导热性能随着石墨含量的提高而增强,随着石墨粒径的减小而减弱。     

基体合金对石墨/铝复合材料性能的影响

本文研究了不同基体合金(工业纯铝和LY12)对石墨/铝复合材料性能的影响,并初步探讨了其影响机理。结果表明:基体合金严重影响金属基复合材料的界面状态、基体相组织及分布,从而影响到最终复合材料的性能。与纯铝相比,LY12基体使石墨/铝复材料性能大幅度下降。     

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）。     

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。     

碳化硅颗粒增强石墨/铝复合材料的热物理性能

片层石墨/铝复合材料具有低密度、高热导率的优点,但力学性能较差,目前无法作为一种可商业化应用的电子封装材料。为了改善片层石墨/铝复合材料的热物理性能,采用真空热压法制备了碳化硅颗粒增强石墨/铝复合材料,研究了碳化硅的含量对复合材料热导率、热膨胀系数和抗弯强度的影响。结果表明,经过高频振荡工艺,碳化硅-石墨/铝复合材料中石墨的排列取向良好。添加碳化硅颗粒能明显降低复合材料的热膨胀系数,提高抗弯强度,略微降低热导率。随着碳化硅颗粒体积分数增加,碳化硅-石墨/铝复合材料内部会逐渐出现孔洞缺陷,相对密度下降。当碳化硅和石墨的体积分数分别为15vol%、50vol%时,碳化硅-石墨/铝复合材料具有最优热物理性能,此时x-y方向热导率为536 W/(m·K)、热膨胀系数为6.4×10^-6m/K,抗弯强度为102 MPa,是一种十分具有商业前景的电子封装材料。     

石墨烯纳米片增强铝基复合材料的动态力学行为

采用压制-烧结-热挤压工艺制备石墨烯纳米片(GNFs)增强铝基(Al)复合材料,并对其进行压缩性能测试。结果表明:GNFs/Al复合材料是应变率敏感材料,当应变率从10^-3s^-1提高至3×10~3s^-1时,复合材料的强度明显提高;而当应变率继续提高至5×10~3s^-1时,由于材料内部发生热软化,复合材料的强度反而表现出少许下降。动态压缩后复合材料中铝基体发生动态再结晶,且应变率越高,动态再结晶越显著;增强相GNFs则发生扭曲变形后仍保持完整结构且与基体间保持原子间结合。因此,GNFs/Al复合材料具有良好的动态压缩塑性。     

Effect of chromium carbide coating on thermal properties of short graphite fiber/Al composites

A chromium carbide coating was synthesized onto graphite fibers by molten salts method to improve the interfacial bonding and thermal properties of short graphite fiber/Al composites which were fabricated by vacuum pressure infiltration technique. The graphite fiber/Al composites with different thicknesses of chromium carbide coatings were prepared through varying plating times to investigate the influence of chromium carbide layer on the microstructures and thermal properties of the composites. The combined Maxwell–Garnett effective medium approach and acoustic mismatch model schemes were used to theoretically predict thermal conductivities of the composites. The results indicated that the chromium carbide coating formed on graphite fiber surface in molten salts consists mainly of the Cr₇C₃ phase. The Cr₇C₃-coating layer with plating time of 60 min and thickness of 0.5 μm was found to be most effective in improving the interfacial bonding and decreasing the interfacial thermal resistance between graphite fiber and aluminum matrix. The 40 vol% Cr₇C₃-coated graphite fiber/Al composite with Cr₇C₃ thickness of 0.5 μm exhibited 45.4 % enhancement in in-plane thermal conductivity of 221 W m^?1 K^?1 compared to that of uncoated composite, as well as the coefficient of thermal expansion of 9.4 × 10^?6 K^?1, which made it as very interesting material for thermal management applications.     

癸酸-棕榈酸-硬脂酸/膨胀石墨蓄能复合相变材料的制备与热性能研究

癸酸、棕榈酸、硬脂酸形成的三元低共熔物与膨胀石墨通过真空浸渍法制备出新型癸酸-棕榈酸-硬脂酸/膨胀石墨储能复合相变材料,适宜的质量比为m(癸酸)∶m(棕榈酸)∶m(硬脂酸)=77.0∶11.5∶11.5,m(癸酸-棕榈酸-硬脂酸)∶m(膨胀石墨)=13∶1。采用DSC、FT-IR、TG、SEM、冷热循环实验和蓄/放热实验研究了材料的结构和热性能。SEM和FT-IR分析结果表明低共熔物与膨胀石墨是通过物理吸附方式结合。DSC结果表明复合材料融化和凝固时的相变温度为28.93℃和16.32℃,相变潜热为137.38J/g和141.51J/g。TG结果表明复合相变材料在100℃以下具有良好的热稳定性。500次热循环和蓄/放热实验表明循环前后复合相变材料的热可靠性好,且使用寿命长。膨胀石墨的添加改善了复合材料的热性能和热导率。研究表明制备的新型复合相变材料具有合适的相变温度、较高的相变潜热和热导率,热性能稳定可靠,可用于低温蓄能领域。     

A predictive model for interfacial thermal conductance in surface metallized diamond aluminum matrix composites

As promising thermal management materials with tailored thermal expansion and light weight, diamond/aluminum composites have not exhibited desirable thermal conductivity (TC) yet, due to poor interfacial thermal conductance (ITC) between diamond and aluminum. Although some experimental studies have been made to improve the ITC by means of diamond surface metallization, there are no systematic theoretical evaluations of the influences of interface layers’ structures on the ITC yet. In terms of the components of diamond/Al interface layer, a carbide–metal–intermetallic, multi-layered interface model was established in this work, and the effects of different components and structures of interface layers on the ITC and TC of the surface metallized diamond/Al composites were predicted. The calculated results indicate that, basically, an interface layer of nanoscale thickness with high TC and large sound velocity is desirable to achieve high ITC. Under this premise, W and Mo interface layers are proposed to be the most promising candidates to improve the thermal performance of diamond/Al composites.     

碳/铝复合材料界面反应对抗拉强度的影响

本文对Ti-B法制备的碳—铝合复材料经各种处理后产生的不同程度的界面反应与其纵向抗拉强度的关系进行了研究。碳—铝界面反应主要从三方面影响复合材料的抗拉强度:①界面结合强度;②界面脆性层;⑨纤维损伤。这三者的作用程度与界面反应程度有关。界面反应不严重时,主要是界面结合强度起作用;反应较严重时,界面脆性层的影响增大;反应很严重时,纤维发生严重损伤,对材料的抗拉强度产生很大的影响。      

TA2/3A21/AZ31B复合板界面表征及力学性能研究

通过爆炸焊接法制备TA2/3A21/AZ31B三层复合板,利用光学显微镜(OM)、扫描电镜(SEM)、能谱仪(EDS)和万能试验机对复合材料的界面、金相组织和力学性能进行测试与分析。实验结果表明:通过一次爆炸焊接制备的TA2/3A21/AZ31B复合材料,其抗拉强度约为303 MPa,屈服强度约为233 MPa,断后伸长率约为9.7%;在钛/铝界面与铝/镁界面均形成爆炸焊接特有的波状结构,界面处分别形成了厚度约5 μm的Ti-Al扩散层和30 μm的Al-Mg扩散层,其剪切强度分别为132.6 MPa和116.3 MPa。与TA2/AZ31B复合材料相比较,该复合材料的力学性能有较大提升。      

Study on graphite fiber and Ti particle reinforced Al composite

Graphite fiber and Ti particle-reinforced aluminum matrix composite were produced by squeeze casting technology. A small amount of needle aluminum carbide at graphite fiber and Al interface was observed, and TiAl₃ intermetallic compound at Ti particle and Al interface was detected. Tensile strength and bending strength of the composite have been measured. The fracture surface of the composite after tensile and bending tests was observed; graphite fiber-reinforced Al was brittle fracture, whereas Ti particle-reinforced Al was ductile fracture. The corresponding fracture mechanism was discussed.     

In‐situ composite coating on powder metallurgy master alloy fabricated by vacuum hot‐pressing sintering technology

A material consisting of an in‐situ titanium carbide reinforced nickel‐aluminide (Ni₃Al) coating and a powder metallurgy master alloy was fabricated by vacuum hot‐pressing sintering technology. A metallurgical bonded, pores‐free interface between composite coating and powder metallurgy master alloy was formed at the sintering temperature of 1050 °C, pressure of 10^‐4 Pa and pressing pressure of 40 MPa. The phase, microstructure and wear behavior of composite coating were investigated. The results showed that polygonal titanium carbide particulates with various sizes were homogeneously distributed in nickel‐aluminide matrix. The sintering temperature, pressing pressure and heat from as‐reactions‐formed coating green compact facilitated the pore infiltration with transiently generated liquid phases and ensured the high‐intensity metallurgical bonding between composite coating and powder metallurgy master alloy. Due to the abnormal elevated‐temperature properties of nickel‐aluminide matrix, titanium carbide particulates reinforcement and the mechanically mixed layer protection, TiC/Ni₃Al‐coated parts demonstrated superior wear resistance and lower friction coefficient while compared with Ni₃Al‐coated parts and H13 steel.     

Application of Ti: W barrier metallization for integrated circuits

Aluminum metallization is the most widely used for contacts and interconnections in integrated circuits. However, the solid state diffusion of aluminum in silicon during contact sintering or high temperature packaging can result in junction shorting or leakage in shallow (<1 μm) emitter-base junction devices. The interposition of a barrier metal between the aluminum and the silicon is one solution to this problem. A sputter-deposited pseudo-alloy of Ti:W (10:90 wt.%) with PtSi contacts is suitable for this application. Resistivity ratio measurements on SiO₂/ ti:W/Al film test samples have shown that the resistivity of aluminum increases owing to diffusion of titanium or tungsten into the aluminum. However, the kinetic data show that no more than a 10% increase in the resistivity of the aluminum can be expected in the useful life of a device. High current stress data show that Ti:W/Al interconnections are comparable with those of aluminum films. Auger depth profiling of si/Ti:W/Al samples annealed at 450, 500 and 550°C in N₂ shows no aluminum at the Si-(Ti:W) interface. Application of the PtSi/Ti:W/Al metallization system for large-scale integrated circuits is described.     

泡沫石墨/石蜡复合相变储热材料的调温隔热性能

采用多次真空灌注方法将石蜡吸附到多孔的泡沫石墨中,制备出了泡沫石墨/石蜡复合相变储热材料。利用Hot Disk热常数分析仪和差示扫描量热分析(DSC)对该复合材料的热性能进行了测试,结果表明,石蜡充分吸附到泡沫石墨的蜂窝状微孔中,泡沫石墨的填充极大地强化了相变材料的导热能力。研究了将该复合材料用作墙体围护结构时的隔热和调温性能,并与普通轻质墙体材料作围护结构进行了对比,结果表明,复合相变储热材料能够有效地利用昼夜温差进行储热放热,有效地阻止了热量进入室内,可明显降低室内温度波动和最大值,提高人体舒适度,具有较好的调温隔热效果。