金刚石混杂碳化硅/铝复合材料的组织与热物理性能(英文)

采用理论计算与实验相结合的方法对金刚石混杂SiC/Al复合材料的热物理性能进行研究,采用微分有效介质(DEM)理论和扩展的Turner模型分别计算金刚石混杂SiC/Al复合材料的热导率和热膨胀系数。从金刚石混杂SiC/Al复合材料的微观组织可以看到SiC颗粒与Al之间结合较紧密,金刚石颗粒与Al之间结合不紧密。金刚石混杂SiC/Al复合材料的热物理性能的实验结果与理论计算趋势一致。当金刚石颗粒与SiC颗粒的体积比为3:7时,混杂SiC/Al复合材料的热导率和热膨胀系数分别提高了39%和30%。因此,当在复合材料中加入少量金刚石颗粒时,其热物理性能得到显著提高,而复合材料的成本略有提高。     

镀钨金刚石/铜复合材料的制备及导热性能（英文）

使用热扩散法在金刚石表面镀钨,并采用不同工艺参数制备镀钨金刚石/铜复合材料,观察不同样品的微观形貌,并使用激光闪射法测量样品的热导率,探索制备高热导率金刚石/铜复合材料的最佳工艺参数。研究结果表明,在金刚石表面镀钨可以改善界面结合,当镀覆时间为60 min时,镀层完整、均匀、平整,样品的热导率达到486 W/(m·K)。镀层的完整性和均匀性比镀层厚度更为重要。进一步对镀钨金刚石进行退火处理后,镀层与金刚石之间的冶金结合增强,制备得到的复合材料的热导率提高到559 W/(m·K)。     

高导热金刚石／铝和金刚石／铜复合散热材料的研究进展

人造金刚石由于其自身高的热导率、低的热膨胀系数和相对低的价格已成为制造新型散热材料的研究热点。本文主要介绍了近年来在金刚石／铝和金刚石／铜复合散热材料的致密度、合成方法、热导率、界面等方面的一些研究进展。添加活碳元素（硼、铬等）和在高压下使金刚石直接成键可能是提高金刚石／金属散热材料热导率的两种有效途径。     

Microstructure and thermal properties of copper matrix composites reinforced with titanium-coated graphite fibers

Milled form of mesophase pitch-based graphite fibers were coated with a titanium layer using chemical vapor deposition technique and Ti-coated graphite fiber/Cu composites were fabricated by hot-pressing sintering. The composites were characterized with X-ray diffraction, scanning/transmission electron microscopies, and by mea-suring thermal properties, including thermal conductivity and coefficient of thermal expansion (CTE). The results show that the milled fibers are preferentially oriented in a plane perpendicular to the pressing direction, leading to anisotropic thermal properties of the composites. The Ti coating reacted with graphite fiber and formed a continuous and uniform TiC layer. This carbide layer establishes a good metallurgical interfacial bonding in the composites, which can improve the thermal properties effectively. When the fiber content ranges from 35 vol% to 50 vol%, the in-plane thermal conductivities of the composites increase from 383 to 407 Wá(máK) -1 , and the in-plane CTEs decrease from 9.5 9 10-6 to 6.3 9 10 -6 K-1 .     

高温高压下新型金刚石/碳化硅热沉材料的热导率研究

本文针对国内外对高导热、低热膨胀系数的热沉材料需求,以金刚石为基体、硅粉为添加物,用国产六面顶压机在5.1 GPa,1 350～1 650℃的条件下,采用高压固液渗透法合成出金刚石/碳化硅陶瓷热沉材料,并对高压烧结体的相组成、密度与热导率进行了分析.研究结果表明:初始材料中硅含量、烧结时间与温度对烧结体的成分以及密度有...     

Microstructure characteristics of SiC particle-reinforced aluminum matrix composites by plasma spraying

Aluminum with 55 and 75 vol.% SiC powders were ball milled as plasma spray feedstock. The feedstock was deposited onto a graphite substrate to form a freestanding composite by air plasma spraying. The microstructure characteristics of the sprayed composite were investigated by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The SiC volume fraction and porosity in the sprayed composites depend on plasma spray conditions. The silicon phase was formed in the sprayed composites in some plasma spray conditions, and its amount was related to the input of electrical power into the plasma spray. The mechanism of silicon formation was studied. In the sprayed composites, no reaction products could be observed in the Al/SiC interface. Impurity materials from ball media, stainless steel, and ZrO₂ reacted with aluminum and silicon to form complex compounds during plasma spray deposition.     

表面镀钨层对金刚石/铜复合材料热导率的影响

采用真空微蒸发-扩散镀技术,在金刚石表面镀覆不同厚度的钨层,并结合真空熔渗法制备金刚石铜复合材料。通过X射线衍射分析镀覆层相结构,采用扫描电镜观察镀覆层表面微观形貌和复合材料中金刚石与铜界面结合形貌,分析金刚石表面镀钨层组织、结构及厚度对金刚石/铜复合材料热导率的影响。结果表明:金刚石表面镀覆钨能改善与基体的润湿性;随着镀覆层均匀性和厚度增加,复合材料热导率先增加后减小;完整均匀的镀覆层可以获得较高界面热导。     

SiC颗粒增强铁基合金复合涂层的组织

采用等离子堆焊—SiC后送粉技术制备了SiC颗粒增强铁基合金复合涂层,利用扫描电子显微镜（SEM）、X射线衍射仪（XRD）和能谱仪（EDS）对涂层的显微组织、相组成和元素分布进行了观察和测试。试验结果表明：SiC分布于马氏体基体上,原始形态保持完好,没有发生明显溶解,复合效果较好。SiC与基体界面层由预覆层、近基体区和絮状区构成。SiC边缘为CrSi2、CrSi3;近基体区耐腐蚀性相对基体较强,组织难以显示;絮状区由大量（Fe,Cr）7 C3、（Fe,Cr）23 C6碳化物和α-（Fe,Cr）固溶体组成。     

SiCw增强锌基复合材料微结构的TEM观察

通过透射电镜对碳化硅晶须增强锌基复合材料微结构的观察,发现碳化硅晶须与基体间界面结合良好,界面附近区域分别存在T（T′）相和二次析出η相,且后者与碳化硅晶须间存在一定取向关系。此外,挤压变形后碳化硅晶须中存在大量位错,层错和孪晶等缺陷,基体中η相也有孪晶产生。     

电子封装用Al/Si/SiC复合材料的显微组织与性能(英文)

采用气压浸渗法制备中体积分数电子封装用 Al/Si/SiC 复合材料。在保证加工性能的前提下,用与 Si 颗粒相同尺寸(13 μm)的 SiC 替代相同体积分数的硅颗粒制得复合材料,并研究其显微组织与性能。结果显示,颗粒分布均匀,未发现明显的孔洞。随着 SiC 的加入,强度和热导率将得到明显提高,但热膨胀系数变化较小,对使用影响也不大。讨论几种用于预测材料热学性能的模型。新的当量有效热导被引入后,H-J 模型将适用于混杂和多颗粒尺寸分布的情况。     

放电等离子烧结法制备Cu/金刚石复合材料的性能与显微组织

由于具备较高的热导率,铜/金刚石复合材料已成为应用于电子封装领域的新一代热管理材料。采用放电等离子烧结工艺（SPS）成功制备含不同金刚石体积分数的Cu/金刚石复合材料,研究复合材料的相对密度、微观结构均匀性和热导率（TC）随金刚石体积分数（50%、60%和70%）和烧结温度的变化规律。结果表明：随着金刚石体积分数的降低,复合材料的相对密度、微观结构均匀性和热导率均升高;随着烧结温度的提高,复合材料的相对密度和热导率不断提高。复合材料的热导率受到金刚石体积分数、微观结构均匀性和复合材料相对密度的综合影响。     

Predicted interfacial thermal conductance and thermal conductivity of diamond/Al composites with various interfacial coatings

The interfacial thermal conductance (ITC) and thermal conductivity (TC) of diamond/Al composites with various coatings were theoretically studied and discussed. A series of predictions and numerical analyses were performed to investigate the effect of thickness, sound velocity, and other parameters of coating layers on the ITC and TC. It is found that both the ITC and TC decline with increasing coating thickness, especially for the coatings with relatively low thermal conductivity. Nevertheless, if the coating thickness is close to zero, or quite a small value, the ITC and TC are mainly determined by the constants of the coating material. Under this condition, coatings such as Ni, TiC, Mo 2 C, SiC, and Si can significantly improve the ITC and TC of diamond/Al composites. By contrast, coatings like Ag will exert the negative effect. Taking the optimization of interfacial bonding into account, conductive carbides such as TiC or Mo 2 C with low thickness can be the most suitable coatings for diamond/Al composites.     

Numerical analysis of effective thermal conductivity associated with microstructural changes of porous SiC as an inert-matrix

In order to develop inert matrix material, evaluation of physical and chemical properties required for sintered nuclear fuel candidate materials were performed for more appropriate candidate material selection. Active research is being carried out to develop a new inert matrix material,e.g. ZrO₂, MgAl₂O₄, ZrSiO₄, and SiC, that prohibits the formation of Pu and actinides. Based on the experimental results, pressureless sintered SiC was considered to be the most appropriate candidate material. Microstructure and thermal conductivity changes were examined of the porous SiC. Effective thermal conductivity decreased by increasing porosity and decreasing the ratio between gas thermal conductivity within pores and sintered material thermal conductivity. With same porosity level, pore size and distribution have little effect on effective thermal conductivity.     

SiC颗粒增强铝基复合材料磨削中砂轮磨损与加工质量研究

颗粒增强铝基复合材料是一种典型的难加工材料。我们对电镀金刚石砂轮平面磨削加工SiC颗粒增强铝基复合材料的加工表面质量进行了实验研究。结果表明,在主轴转速为6000r／min、进给速度为300mm／min、磨削深度为0．05mm的条件下,走刀长度达到30m时砂轮直径磨损量为0．11mm,在实验所采用的加工参数条件下表面粗糙度达到Ra0．57—1．12μm,加工表面质量较高。文中还对电镀金刚石砂轮的磨损形式、磨损机理以及砂轮的修整进行了分析与介绍。     

Effects of deposition parameters on microstructure and thermal conductivity of diamond films deposited by DC arc plasma jet chemical vapor deposition

The uniform diamond films with 60 mm in diameter were deposited by improved DC arc plasma jet chemical vapor deposition technique. The structure of the film was characterized by scanning electronic microcopy(SEM) and laser Raman spectrometry. The thermal conductivity was measured by a photo thermal deflection technique. The effects of main deposition parameters on microstructure and thermal conductivity of the films were investigated. The results show that high thermal conductivity, 10.0 W/(K-cm), can be obtained at a CH4 concentration of 1.5% (volume fraction) and the substrate temperatures of 880-920 ℃ due to the high density and high purity of the film. A low pressure difference between nozzle and vacuum chamber is also beneficial to the high thermal conductivity.