金刚石增强铝基复合材料界面形成机理及导热性能

发布时间：2018-01-06 06:41

本文关键词：金刚石增强铝基复合材料界面形成机理及导热性能　出处：《北京科技大学》2017年博士论文　论文类型：学位论文

【摘要】：随着电子信息技术的不断发展,电子器件的单位面积发热量不断提高,电子器件的安全、高效运行受到严重影响。因此,急需开发新一代的电子封装散热材料来保证电子元器件的有效散热。金刚石具有优异的热物理性能,其热导率为600-2000 W/mK,是自然界中热导率最高的材料。金刚石颗粒增强金属基(metal/diamond)复合材料具备优异的热物理性能,成为新一代电子封装散热材料的代表。采用高压气体辅助熔渗法制备的Al/diamond复合材料有效结合金刚石优异的热物理性能和A1基体较低的密度以及优良的加工成形性,是新一代电子封装散热材料的研究热点。金刚石和A1之间的界面结合状态直接决定了 Al/diamond复合材料的整体性能,对复合材料界面结构的调控可实现对复合材料热物理性能的优化,是提升复合材料性能的有效方式。然而,目前针对复合材料界面结构的表征并不完善,对于A1基体和金刚石之间的界面反应机理缺乏深入研究,无法从理论上指导复合材料界面结构和导热性能的优化。本文通过高压气体辅助熔渗法制备Al/diamond复合材料,通过聚焦离子束刻蚀系统(FIB)和透射电子显微镜(TEM)等先进表征手段来研究不同制备工艺下复合材料的界面结构,深入理解界面形成机制,建立复合材料制备工艺、界面结构和导热性能之间的有效联系,进而实现Al/diamond复合材料热物理性能的提升。本文采用高压气体辅助熔渗法制备Al/diamond复合材料,通过改变复合材料制备工艺,控制A1基体和金刚石颗粒之间界面反应程度,系统研究了界面反应产物的形核和长大机制。结果表明,界面反应产物A14C3的形成是非均匀形核过程,其形核和长大受到金刚石表面状态影响。碳化物在金刚石表面台阶处形核并长大,金刚石(100)面上的碳化物与金刚石表面呈55°夹角,颗粒密度较高,尺寸较小;金刚石(111)面的碳化物颗粒平行金刚石表面,碳化物密度较小,尺寸较大。对比不同反应阶段碳化物颗粒的形貌以及复合材料热导率发现,当界面A14C3呈现细小弥散分布时,复合材料具有最高热导率。这是由于细小弥散分布的碳化物颗粒显著改善复合材料的界面结合,同时由于A14C3具有较低的热导率,细小的碳化物颗粒不显著增加界面热阻。在此基础上对金刚石颗粒进行预处理来促进金刚石表面碳结构转变,进而调整界面A14C3的形成过程。研究发现,通过预加热处理可在金刚石表面产生sp2碳结构,进而促进细小弥散的界面碳化物的形成,起到优化复合材料界面结构和热导率的作用。所制备的Al/diamond复合材料热导率从540 W/mK提高至 710W/mK。Al/diamond复合材料界面产物A14C3的水解性限制了复合材料的应用范围。通过在金刚石表面镀覆合金元素引入新的界面反应层,是优化Al/diamond复合材料界面结构的重要手段。然而,界面反应层的引入必然会影响复合材料热导率,因此需要在抑制A1基体和金刚石发生界面反应形成A14C3的前提下,对复合材料界面反应层的微观结构进行调控和优化。本文系统研究了金刚石表面Ti和W镀层在制备Al/diamond复合材料过程中的演化行为,从而获得最佳的镀层厚度和复合材料制备参数。研究表明,Ti镀层与金刚石发生化学反应生成TiC界面层,并在熔渗阶段保持稳定。随着Ti镀层厚度的增加,复合材料热导率呈现先增高后降低的趋势,当镀层厚度为200 nm时,复合材料热导率最高值为650 W/mK。对于上述现象的解释是,为降低复合材料界面热阻,应尽量减小TiC层的厚度,然而较薄的镀层无法有效改善复合材料界面结合,导致热导率下降。在低温加热过程中,TiC界面层与A1基体发生反应生成少量的A14C3相。W镀层在复合材料制备过程中与A1基体发生反应,在界面位置生成Al5W反应层。研究表明,这一界面反应较慢,可通过调控复合材料的制备工艺参数来控制界面反应层厚度,从而优化复合材料界面结构和热物理性能。当复合材料熔渗时间从10 min延长至60 min时,复合材料的热导率从520 W/mK上升至630 W/mK。虽然镀W金刚石颗粒增强铝基复合材料的热导率相对较低,但所形成的A15W界面反应层可以有效抑制复合材料中A14C3界面相的生成,扩大了复合材料的应用范围。综上所述,本文系统研究了金刚石颗粒增强铝基复合材料的界面形成机理,建立了复合材料制备工艺参数、界面结构和导热性能之间的有效联系。通过研究金刚石颗粒增强铝基复合材料的界面结构以及相应的界面结构优化手段,为复合材料的优化设计和可控制备提供了理论参考。研究结果进一步提升了金刚石颗粒增强金属基复合材料的热物理性能,可以更好地应用于电子器件散热。
[Abstract]:With the continuous development of electronic information technology, electronic device unit area heat rising, the safety of electronic devices, seriously affect the efficient operation. Therefore, electronic packaging materials are in urgent need of the development of a new generation of heat dissipation to ensure effective cooling of electronic components. Diamond has good thermal physical properties, the thermal conductivity of 600-2000 W/mK. Is the highest thermal conductivity in nature. The diamond particles reinforced metal matrix composites (metal/diamond) possess good thermal physical properties, become the representative of a new generation of electronic packaging materials. The heat assisted infiltration of Al/diamond composite materials prepared by the combination of diamond excellent thermal physical properties and A1 matrix of low density and excellent the formability of the high-pressure gas, is the research focus of a new generation of electronic packaging material for cooling. Between diamond and A1 interface directly Determines the overall performance of the Al/diamond composite material, can realize the optimization of the thermal physical properties of composite materials on the regulation of the interface structure of composite materials is an effective way to improve the properties of the composite materials. However, the characterization of the interface structure of composite materials is not perfect, for further study the mechanism of interface reaction between A1 matrix and diamond lack of optimization to guide the structure and thermal performance of composite material interface in theory. This paper through the high-pressure gas assisted infiltration of Al/diamond composite was prepared, by focused ion beam etching system (FIB) and transmission electron microscopy (TEM) and other advanced characterization methods to study the different preparation of the interface structure of composite process, in-depth understanding of the interface formation the establishment of mechanism, composite material preparation process, the effective connection between structure and thermal conductivity of the interface, and then realize the Al/diamond composite heat Physical performance. This paper uses the high pressure gas Al/diamond composites were fabricated by molten infiltration, by changing the composite material preparation process, control interface between A1 matrix and diamond particles reaction, studied interfacial reaction mechanism of nucleation and growth. The results show that the formation of interfacial reaction of A14C3 is heterogeneous nucleation the process of nucleation and growth of diamond surface is affected by the state. On the steps at the surface of Carbide Diamond Nucleation and growth of diamond (100) surface of the carbide and diamond surface at a 55 degree angle, particle density is high, small size; diamond (111) surface of carbide particles parallel to the surface of the diamond, carbide density smaller size comparison of different reaction stages. Larger morphology of carbide particles and the thermal conductivity of the composites was found, when the interface A14C3 exhibits fine dispersed, composite material has the most High thermal conductivity. This is because the fine carbide particles dispersed significantly improve the composite interface, at the same time, because A14C3 has low thermal conductivity, fine carbide particles do not significantly increase the interfacial thermal resistance. Based on the pretreatment of diamond particles to promote the carbon structure of diamond surface change, and then adjust the interface forming process A14C3. The study found that SP2 can produce carbon structure on the diamond surface by pre heating treatment, and promote the formation of interface carbide dispersed, play a role in optimization of composite interface structure and thermal conductivity. The prepared Al/diamond composite thermal conductivity limits the scope of application of composite materials from the hydrolysis product of interface 540 W/mK increased to 710W/mK.Al/diamond A14C3 composites. The interfacial reaction layer by introducing new alloy plating on diamond surface elements, is optimized for Al/d An important means of interface structure of iamond composites. However, the introduction of the interface reaction layer will affect the thermal conductivity of composite materials, so in the inhibition of A1 matrix and diamond react to form A14C3 under the premise of control and optimize the microstructure of the interfacial reaction layer. This paper studies the diamond surface Ti and W the coating in the preparation process of Al/diamond evolution behavior of composite material, so as to obtain the optimum coating thickness and composite material preparation parameters. The results show that Ti coating and diamond chemical reaction between TiC interface layer, and the infiltration stage remained stable in the melt. With the increase of Ti coating thickness, thermal conductivity of the composites is increased after the first decreased, when the coating thickness is 200 nm, the thermal conductivity of the composites is the highest value 650 W/mK. explanation for this phenomenon is, in order to reduce the interfacial thermal resistance of composite materials , should try to reduce the thickness of the TiC layer, however thin coating can not effectively improve the composite interface, resulting in decrease of thermal conductivity at low temperature. The heating process, the TiC interface layer and A1 substrate reacted to generate a small amount of A14C3 phase.W coating during the preparation of composites with A1 substrate reaction at the interface the position of formation of Al5W layer. The results show that the interface reaction is slow, can be controlled by regulating the thickness of interfacial reaction layer composite material preparation process parameters, so as to optimize the structure and thermal physical properties of composites interface. When composite infiltration time is extended from 10 min to 60 min, the thermal conductivity of composite materials increased from 520 W/mK to 630 W/mK. while W plated diamond particles reinforced aluminum matrix composites thermal conductivity rate is relatively low, but the A15W interfacial reaction layer formed can effectively inhibit the formation of A14C3 interphase in composites, expand The application of composite material. In summary, this paper studies the formation mechanism of diamond particles of aluminum matrix composites interface enhanced established composite material preparation process parameters, the effective connection between structure and thermal conductivity of the interface. The interface structure of reinforced aluminum matrix composites and the corresponding interface structure optimization by means of diamond particles in order to optimize the design of composite materials and controllable preparation. The results provide a theoretical reference to further enhance the thermal physical properties of diamond particles reinforced metal matrix composites, can be better used for heat dissipation of electronic devices.

【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB333

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