掺杂稀土La减少金刚石/铜复合材料界面缺陷的研究
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摘要
采用放电等离子烧结法(SPS)制备了不同La含量的金刚石/铜复合材料。使用X射线衍射仪、扫描电子显微镜、X射线能谱仪对复合材料的物相组成、界面微观组织和元素分布进行了表征,并通过排水法测试复合材料的致密度和气孔率。基于第一性原理密度泛函理论,对含La的金刚石/铜复合材料界面电子态密度和原子间距变化进行了计算。计算结果表明,La与Cu的电子态密度在费米能级附近存在较宽的赝能隙,二者成键能力强。经周期平板模型能量优化后,La原子与Ti、Cu原子的间距均明显减小;体系中La与Cu的原子间距更小,表明稀土La与Cu基体亲和力更强。实验结果表明,稀土La大量固溶于铜基体内,促生了Cu_2La相。随着La含量的增加,存在于复合材料界面处的缝隙、孔洞等缺陷逐渐减少,复合材料的致密度逐渐上升。未添加La的复合材料气孔率为3.48%,而添加7%La的复合材料的气孔率下降至0.42%。金刚石/铜复合材料中掺杂La能有效减少界面缺陷。
Diamond/copper composites with different contents of lanthanum were prepared by spark plasma sintering(SPS).Phase composition,interfacial microstructure and elemental distribution of the composites were characterized by XRD,SEM and EDS.Relative density and porosity of the composites were tested with drainage method.The interfacial electronic state density and atomic distance variation of the lanthanum-containing diamond/copper composites were calculated based on first-principles density functional theory.The calculated results show that the electronic state density of La and Cu has a wide pseudogap near the Fermi level,and the bonding ability between La and Cu is strong.After energy optimization by periodic plate model,the atomic spacing between La and Ti or Cu is significantly reduced,and the atomic spacing between La and Cu in the system is smaller,showing that the rare earth La and Cu matrix have stronger affinity.The experimental results show that a large amount of La is dissolved in the copper matrix,promoting the formation of Cu_2 La phase.With the increase of La content,the defects such as cracks and holes in the interface of the composites gradually decrease,and the relative density of the composites is gradually improved.The porosity of the composite without La is 3.48%,while the porosity of the composite with 7%La is decreased to 0.42%.The doped La in diamond/copper composites can effectively reduce the interface defects.
Diamond/copper composites with different contents of lanthanum were prepared by spark plasma sintering(SPS).Phase composition,interfacial microstructure and elemental distribution of the composites were characterized by XRD,SEM and EDS.Relative density and porosity of the composites were tested with drainage method.The interfacial electronic state density and atomic distance variation of the lanthanum-containing diamond/copper composites were calculated based on first-principles density functional theory.The calculated results show that the electronic state density of La and Cu has a wide pseudogap near the Fermi level,and the bonding ability between La and Cu is strong.After energy optimization by periodic plate model,the atomic spacing between La and Ti or Cu is significantly reduced,and the atomic spacing between La and Cu in the system is smaller,showing that the rare earth La and Cu matrix have stronger affinity.The experimental results show that a large amount of La is dissolved in the copper matrix,promoting the formation of Cu_2 La phase.With the increase of La content,the defects such as cracks and holes in the interface of the composites gradually decrease,and the relative density of the composites is gradually improved.The porosity of the composite without La is 3.48%,while the porosity of the composite with 7%La is decreased to 0.42%.The doped La in diamond/copper composites can effectively reduce the interface defects.
引文
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[3]HASSELMAN D P H,JOHNSON L F.Effective thermal conductivity of composites with interfacial thermal barrier resistance[J].Journal of Composite Materials,1987,21(6):508-515.
[4]HELL J,CHIRTOC M,EISENMENGER-SITTNER C,et al.Characterisation of sputter deposited niobium and boron interlayer in the copper-diamond system[J].Surface&Coatings Technology,2012,208:24-31.
[5]ZAIN-UL-ABDEIN M,RAZA K,KHALID F A,et al.Numerical investigation of the effect of interfacial thermal resistance upon the thermal conductivity of copper/diamond composites[J].Materials and Design,2015,86:248-258.
[6]REN S B,SHEN X Y,GUO C Y,et al.Effect of coating on the microstructure and thermal conductivities of diamond-Cu composites prepared by powder metallurgy[J].Composites Science and Technology,2011,71(13):1550-1 555.
[7]ABYZOV A M,KIDALOV S V,SHAKHOV F M.Filler-matrix thermal boundary resistance of diamond copper composite with high thermal conductivity[J].Physics of the Solid State,2012,54(1):210-215.
[8]SCHUBERT T,CIUPIńSKIL,ZIELINńSKI W,et al.Interfacial characterization of Cu/diamond composites prepared by powder metallurgy for heat sink applications[J].Scripta Materialia,2008,58(4):263-266.
[9]MAńKOWSKI P,DOMINIAK A,DOMAńSKI R,et al.Thermal conductivity enhancement of copper-diamond composites by sintering with chromium additive[J].Journal of Thermal Analysis and Calorimetry,2014,116(2):881-885.
[10]SCHUBERT T,TRINDADE B,WEIBGARBER T,et al.Interfacial design of Cu-based composites prepared by powder metallurgy for heat sink applications[J].Materials Science and Engineering A,2008,475(1/2):39-44.
[11]GRZONKA J,KRUSZEWSKI M J,ROSIńSKI M,et al.Interfacial microstructure of copper/diamond composites fabricated via a powder metallurgical route[J].Materials Characterization,2015,99:188-194.
[12]张习敏,郭宏,尹法章,等.Cr元素对Diamond/Cu复合材料界面结构及热导性能的影响[J].稀有金属,2010,34(2):221-226.
[13]FAN Y M,GUO H,XU J,et al.Effects of boron on the microstructure and thermal properties of Cu/diamond composites prepared by pressure infiltration[J].International Journal of Minerals,Metallurgy and Materials,2011,18(4):472-478.
[14]SHEN W P,SHAO W J,WANG Q Y,et al.Thermal conductivity and thermal expansion coefficient of diamond/5wt%Si-Cu composite by vacuum hot pressing[J].Fusion Engineering and Design,2010,85(10):2 237-2 240.
[15]REN X Y,PENG Z J,WANG C B,et al.Influence of nano-sized La2O3addition on the sintering behavior and mechanical properties of WC-La2O3composites[J].Ceramics International,2015,41(10):14 811-14 818.
[16]WEI R B,ZHANG Y J,GONG H Y,et al.The effects of rare-earth oxide additives on the densification of pressureless sintering B4C ceramics[J].Ceramics International,2013,39(6):6 449-6 452.
[17]NOVIYANTO A,YOON D.Rare-earth oxide additives for the sintering of silicon carbide[J].Diamond&Related Materials,2013,38(6):124-130.
[18]XU X P,TIE X R,YU Y Q.The effects of rare earth on the fracture properties of different metal-diamond composites[J].Journal of Materials Processing Technology,2007,187(12):421-424.
[19]高云,宋月清,康志君.稀土元素La对金属胎体/金刚石复合材料粘结性能的影响[J].金刚石与磨料磨具,2000(4):3-6.