Electronic structure,bonding characteristics,and mechanical behaviors of a new family of Si-containing damage-tolerant MAB phases M_(5)SiB_(2)(M=IVB-VIB transition metals)  

作　　者：Na NI Hanchao ZHANG Yanchun ZHOU 

机构地区：[1]School of Mechanical Engineering,Shanghai Jiao Tong University,Shanghai 200240,China [2]Science and Technology on Advanced Functional Composite Laboratory,Aerospace Research Institute of Materials&Processing Technology,Beijing 100076,China

出　　处：《Journal of Advanced Ceramics》2022年第10期1626-1640,共15页先进陶瓷（英文）

基　　金：financially supported by the National Natural Science Foundation of China(No.52072238).

摘　　要：MAB phases are layered ternary compounds with alternative stacking of transition metal boride layers and group A element layers.Until now,most of the investigated MAB phases are concentrated on compounds with Al as the A element layers.In this work,the family of M_(5)SiB_(2)(M=IVB-VIB transition metals)compounds with silicon as interlayers were investigated by density functional theory(DFT)methods as potential MAB phases for high-temperature applications.Starting from the known Mo5SiB2,the electronic structure,bonding characteristics,and mechanical behaviors were systematically investigated and discussed.Although the composition of M_(5)SiB_(2) does not follow the general formula of experimentally reported(MB)_(2z)A_(x)(MB_(2))_(y)(z=1,2;x=1,2;y=0,1,2),their layered structure and anisotropic bonding characteristics are similar to other known MAB phases,which justifies their classification as new members of this material class.As a result of the higher bulk modulus and lower shear modulus,Mo_(5)SiB_(2) has a Pugh’s ratio of 0.53,which is much lower than the common MAB phases.It was found that the stability and mechanical properties of M_(5)SiB_(2) compounds depend on their valence electron concentrations(VECs),and an optimum VEC exists as the criteria for stability.The hypothesized Zr and Hf containing compounds,i.e.,Zr_(5)SiB_(2) and Hf_(5)SiB_(2),which are more interesting in terms of high-temperature oxidation/ablation resistance,were found to be unfortunately unstable.To cope with this problem,a new stable solid solution(Zr_(0.6)Mo_(0.4))_(5)SiB_(2) was designed based on VEC tuning to demonstrate a promising approach for developing new MAB phases with desirable compositions.

关 键 词：borides MAB phases density functional theory(DFT) thermodynamic stability electronic structure mechanical properties 

分 类 号：TB33[一般工业技术—材料科学与工程]