摘要
开展了在513,523,533 K温度下硒熔体的快速压致凝固实验,分析了不同保温时间即0,30,60 min对凝固晶体尺寸及形貌的影响.发现随着保温时间的延长,晶粒不断发生聚集生长,晶粒尺寸变大.通过与相同温度、压力条件下非晶硒、超细晶体硒粉等温结晶的样品对比,否定了快压凝固结构为非晶硒、非晶硒晶化为晶体硒的可能性,认为硒熔体快压凝固的结构为晶体硒,在保温过程中晶体颗粒在晶界处可以发生聚集生长.分析发现熔体快速压致凝固法不能得到非晶硒的原因在于实验条件下非晶硒为不稳定相,非晶硒的晶化温度随压力关系在2 GPa前后表现出不同的变化趋势,推测压力对过冷液态硒的微观结构有影响.
Amorphous selenium(Se)can be easily prepared by quenching the melt,which indicates that the Se possesses the good glass-forming ability.However,crystallization occurs after rapidly compressing the melt within about 20 ms.In this work,we investigate the mechanism of rapid compression-induced crystallization from Se melt.Compressing Se melt experiments are carried out at the following temperatures:513,523 and 533 K.The melt is rapidly compressed under 2.4 GPa for about 20 ms.Different holding times,i.e.0,30,60 min after solidification are adopted.The samples are quenched to room temperature and then unloaded to ambient pressure.The X-ray diffraction analysis of the recovered sample indicates that the crystallization product is the t-Se.It is found that with the prolongation of holding time,the grain size increases due to the continuous aggregation growth of crystal grains.By comparing with the isothermal crystallization products of amorphous Se and ultrafine Se powder,it is suggested that the rapid compression-induced solidification product should be t-Se crystalline.The speculation that the solidification product is amorphous Se and it crystallizes in the cooling process does not hold true.The amorphous Se cannot be prepared through the rapid compression process on a millisecond scale.It is related to the thermal stability of amorphous Se under high pressure.It is reported that the dependence of crystallization temperature Tx on pressure i.e.dTx/dP for amorphous Se is about 40-50 K/GPa in a range of 0.1 MPa-1 GPa.However,the Tx of amorphous Se is almost constant in a range of 2-6 GPa.It means that the thermal stability of amorphous Se against crystallization does not increase with increasing pressure after 2 GPa.In this work,the temperature of 513-533 K in the experiments is higher than the Tx of amorphous Se.Therefore,the t-Se crystal is the stable phase and amorphous Se is unstable.The Se melt tends to crystallize in the supercooled liquid state after rapid compression.It is interesting to investigate the mechan
作者
王路
王菊
李娜娜
梁策
王文丹
何竹
刘秀茹
Wang Lu;Wang Ju;Li Na-Na;Liang Ce;Wang Wen-Dan;He Zhu;Liu Xiu-Ru(Key Laboratory of Advanced Technologies of Materials,Ministry of Education,School of Physical Science and Technology,Southwest Jiaotong University,Chengdu 610031,China;Center for High Pressure Science and Technology Advanced Research,Shanghai 201203,China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2021年第15期222-230,共9页
Acta Physica Sinica
基金
国家自然科学基金(批准号:10774123)
中央高校基本科研业务费(批准号:2682018ZT29)资助的课题.
关键词
高压
硒
结晶
压致凝固
high pressure
selenium
crystallization
compression-induced solidification
