【作者】 朱强；

【导师】 赵红亮；

【作者基本信息】 郑州大学 ， 材料工程（专业学位）， 2020， 硕士

【摘要】 碳/铜复合材料(C/Cu)是目前最具有应用前景的滑动导电材料之一,因其既具有碳材料自润滑、耐磨、低热膨胀系数的优点,又具有铜金属良好的导电导热性而受到众多研究者的关注。但由于碳和铜既不润湿又不发生化学反应,因此两者很难形成良好的界面结合,导致力学性能及热物理性能较差。目前主要通过铜基体合金化和碳增强相表面改性两种方法改善碳/铜界面结合,但是仍然存在碳/铜复合材料强度与导电导热性能难以兼顾的问题。为了获得良好的碳/铜界面结合和使用性能,本文通过采用碳纤维/树脂碳(C/C)、纯碳纤维(C_f)、石墨(Graphite)、玻璃碳(GC)四种基体碳与Cu-10wt.%Ti合金复合制备了不同碳基体的碳/铜复合材料,研究基体碳种类对碳/铜界面润湿性及界面层微观组织的影响;选用优化的碳纤维/树脂碳(C/C)多孔体为基体碳制备了碳/碳-铜复合材料(C/C-Cu),并研究了C/C多孔体密度对C/C-Cu复合材料硬度、压缩强度、导电导热及热稳定性能的影响,同时与商用1.8 g/cm~3 C/C复合材料的性能进行了对比。研究结果表明:(1)C/C和C_f与Cu-Ti合金的润湿性较好,接触角分别为56.26°和40.12°,Graphite和GC与Cu-Ti合金不发生润湿,接触角均大于90°。C_f的界面层较致密均匀,且厚度最大,约5.21μm;C/C界面C原子扩散范围广,界面层厚度约4.28μm;综合评价四种基体碳与Cu-Ti合金的润湿行为及界面层组织优劣顺序为:C_f>C/C>Graphite>GC。(2)C/Cu界面层主要为Ti C相,其形成机制是C原子通过扩散进入Ti_xCu_y相反应形成了Ti C新相,而Ti C相与C相和Cu相能够完全润湿,大量的Ti C沉淀在基体碳上形成连续的界面层,从而有效改善了C/Cu界面润湿性和界面结合状态。(3)随着PIP循环增加,C/C多孔体闭孔隙率逐渐增大,增重率逐渐减小;高温热处理能提高C/C多孔体增密效率。C/C-Cu复合材料主要由C相、Cu相和Ti C相组成,C相和Cu两相形成“互联互通”的三维网络结构。随着浸渗保温时间延长,碳纤维和树脂碳界面能够形成厚度均匀、致密的Ti C层,约为2μm。(4)随着C/C多孔体密度从0.91 g/cm~3增大至1.22 g/cm~3,C/C-Cu复合材料硬度、压缩强度逐渐增大;电导率、热导率和热膨胀系数逐渐减小;C/C-Cu复合材料平行和垂直方向性能差异明显。随着温度升高,C/C-Cu复合材料平行方向热导率先增大后保持不变,垂直方向缓慢增大。此外,600℃退火热处理能有效改善复合材料冷热冲击后尺寸稳定性。相对于商用C/C复合材料,C/C多孔体密度为0.91 g/cm~3的C/C-Cu复合材料压缩强度、电导率和热导率在平行和垂直方向性能更优,经退火处理后,C/C-Cu复合材料冷热冲击后尺寸稳定性更好,其压缩强度、电导率、热导率、冷热冲击后尺寸变化率平行和垂直方向分别为190 MPa和218 MPa、4.12 MS/m和3.47 MS/m、100.12 W/(m?K)和47.30W/(m?K)、0.41%和0.04%。更多还原

【Abstract】 Carbon/copper composites(C/Cu)is currently one of the most promising sliding conductive materials.It is favored by many researchers because of the advantages of self-lubrication,wear resistance,low thermal expansion coefficient like carbon materials,and also the good electrical and thermal conductivity like copper.However,since the two phases of C and Cu neither wet nor chemically react,it is difficult to form a good interface bond,which results in poor mechanical and thermophysical properties.At present,the carbon/copper interface bond is improved mainly by copper matrix alloying and carbon phase surface modification.However,there still exists the problem that the strength of the carbon/copper composites and the electrical and thermal conductivity are difficult to balance.In order to obtain good carbon/copper interface bonding and using properties of carbon/copper composites,carbon/copper composites with different carbon matrix were prepared by using carbon fiber/resin carbon(C/C),carbon fiber(C_f),graphite(Graphite),glassy carbon(GC)and Cu-10 wt%Ti alloy in this paper.The effect of carbon matrix on the wettability and microstructure of the C/Cu interface were studied.Carbon/carbon-copper composites(C/C-Cu)were prepared by using optimized C/C.The effect of C/C substrate density on the hardness,compressive strength,electrical and thermal conductivity,and thermal stability of C/C-Cu composites was studied.Finnally,properties of C/C-Cu and commercial 1.8g/cm~3C/C composites were compared.Research indicates:(1)C/C and C_f had good wettability with Cu-Ti alloy,and the contact angles were 56.26°and 40.12°,respectively.However,Graphite and GC did not wet with Cu-Ti alloy,and the contact angles were both larger than 90°.The interface layer of C_f was dense and uniform,and had the largest thickness,which was about 5.21μm.The diffusion range of C atoms at the C/C interface was wide,and the thickness of the interface layer was about 4.28μm.The order of comprehensive evaluation of the wetting behavior of the four matrix carbons and Cu-Ti alloys was:C_f>C/C>Graphite>GC.(2)The C/Cu interface layer was mainly Ti C phase,which was formed by the reaction of C atom entering Ti_xCu_y phase through diffusion.While Ti C phase could be completely wetted with C phase and Cu phase,a large amount of Ti C precipitated on the matrix carbon.A continuous interface layer was formed,which effectively improved the C/Cu interface wettability and interface bonding state.(3)As the PIP cycle increased,the closed porosity of the C/C substrate gradually increased,and the weight gain rate gradually decreased.The high-temperature heat treatment process could improve the densification efficiency of the C/C substrate.The C/C-Cu composites was mainly composed of C phase,Cu phase and Ti C phase.A three-dimensional network structure of"interconnection"was formed by C phase and Cu phase.With the extension of the infiltration heat preservation time,the interface between C_f and resin carbon could form a uniform and dense Ti C layer,which was about 2μm.(4)As the density of the C/C substrate increased,the hardness and compressive strength of the C/C-Cu composites gradually increased,and the electrical conductivity,thermal conductivity,thermal expansion coefficient gradually decreased.The properties of C/C-Cu composites were differentparallel and vertical directions.With the increase of temperature,the parallel thermal conductivity of C/C-Cu composites increased first and then remained stability,while the vertical thermal conductivity increased slowly.The dimensional stability of the composite material after cold and hot impact was effectively improved by annealing at 600℃.Compared with commercial C/C composites,C/C-Cu composites with a density of 0.91 g/cm~3 had better compressive strength,electrical conductivity,and thermal conductivity in the parallel and vertical directions.Through annealing,the dimensional stability was better after hot and cold impact.The compressive strength,electrical conductivity,thermal conductivity,dimensional change rate after cold and hot impact in parallel and vertical directions are 190 MPa and 218 MPa,4.12 MS/m and 3.47 MS/m,100.12 W/(m?K)and 47.30 W/(m?K),0.41%and 0.04%.更多还原