掺杂稀土La减少金刚石/铜复合材料界面缺陷的研究

Study on Reducing Interface Defects of Diamond/Copper Composites by Doping Rare Earth La

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Cu2La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 Cu2La 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.