Negative thermal expansion and phase transition of low-temperature Mg_(2)NiH_(4)  

作　　者：Qun Luo Qi Cai Qinfen Gu Yu Shi Bin Liu Xuan Quy Tran Syo Matsumura Tong-Yi Zhang Kazuhiro Nogita Tao Lyu Qian Li Fusheng Pan 

机构地区：[1]State Key Laboratory of Advanced Special Steel&Shanghai Key Laboratory of Advanced Ferrometallurgy&School of Materials Science and Engineering,Shanghai University,Shanghai 200444,China [2]Materials Genome Institute,Shanghai University,Shanghai 200444,China [3]Australian Synchrotron,ANSTO,800 Blackburn Road,Clayton,Victoria 3168,Australia [4]Department of Applied Quantum Physics and Nuclear Engineering,Kyushu University,Fukuoka 819-0395,Japan [5]Nihon Superior Centre for the Manufacture of Electronic Materials(NS CMEM),School of Mechanical and Mining Engineering,The University of Queensland,Brisbane,Queensland 4072,Australia [6]National Engineering Research Center for Magnesium Alloy,Chongqing University,Chongqing 400044,China

出　　处：《Journal of Magnesium and Alloys》2023年第9期3338-3349,共12页镁合金学报（英文）

基　　金：supported by the National Key Research and Development Program of China (2021YFB3701001);the National Natural Science Foundation of China (51871143);Shanghai Engineering Research Center for Metal Parts Green Remanufacture (No.19DZ2252900) from Shanghai Engineering Research Center Construction Project;Shanghai Rising-Star Program (21QA1403200)。

摘　　要：The negative thermal expansion(NTE) phenomenon is of great significance in fabricating zero thermal expansion(ZTE) materials to avoid thermal shock during heating and cooling. NTE is observed in limited groups of materials, e.g., metal cyanides, oxometallates, and metalorganic frameworks, but has not been reported in the family of metal hydrides. Herein, a colossal and continuous negative thermal expansion is firstly developed in the low-temperature phases of LT1-and LT2-Mg_(2)NiH_(4) between 488 K and 733 K from in-situ transmission electron microscope(TEM) video, with the volume contraction reaching 18.7% and 11.3%, respectively. The mechanisms for volume contraction of LT1 and LT2 phases are elucidated from the viewpoints of phase transformation, magnetic transition, and dehydrogenation, which is different from common NTE materials containing flexible polyhedra units in the structure. The linear volume shrinkage of LT2 in the temperature of 488-553 K corresponds to the phase transition of LT2→HT with a thermal expansion coefficient of -799.7 × 10^(-6) K^(-1) revealed by in-situ synchrotron powder X-ray diffraction. The sudden volume contraction in LT1 between 488 and 493 K may be caused by the rapid dehydrogenation of LT1 to Mg_(2)Ni. The revealed phenomenon in single composite material with different structures would be significant for preparing zero thermal expansion materials by tuning the fraction of LT1 and LT2 phases.

关 键 词：Negative thermal expansion Mg_(2)NiH_(4) Phase transformation In situ TEM In situ XRD 

分 类 号：TB34[一般工业技术—材料科学与工程]