MgB_2掺杂SiC的相变过程  

Phase Transition of SiC-Doped MgB_2

作　　者：冯旺军[1,2] 何祖明[1,2] 夏咏梅[1,2] 张爽[1,2] 成金娟[1,2] 

机构地区：[1]甘肃省有色金属新材料国家重点实验室,甘肃兰州730050 [2]兰州理工大学理学院,甘肃兰州730050

出　　处：《稀有金属材料与工程》2008年第A04期75-78,共4页Rare Metal Materials and Engineering

基　　金：甘肃省自然科学基金资助

摘　　要：用自蔓延法(SHS)在锥形模具内成功淬熄(CFQ)MgB2掺杂8%SiC的反应.对不同温度区域试样的XRD、SEM、EDS进行分析.结果表明:在527～650℃时Mg和B颗粒接触以扩散方式在表面发生了固—固反应,Mg的表层初次形成MgB2,在650～700℃时,包裹在初次生成的MgB2内部未反应的Mg将熔化,液态Mg的活性大大提高,以扩散、渗透的方式通过初次生成的MgB2层与B原子发生液-固反应,MgB2相界面不断地向B原子方向推进,直到完全形成MgB2;700～750℃时掺杂的SiC大部分与MgB2反应生成Mg2Si,同时有一部分C原子进入到MgB2取代了B原子,并有少量MgB2分解形成MgB4和Mg。在形核结晶过程中由于反应时间短,温度梯度大,部分Mg来不及扩散就重新结晶。The Combustion Front Quenching （CFQ） experiment of MgB2 doped with 8%SiC was successfully carried out in taper mold by self-propagating high-temperature synthesis （SHS） method. The different areas of the sample in different temperature ranges were tested by XRD, SEM and EDS. It is found that the reaction of Mg and B in solid state will occur by diffusing and MgB2 will be formed on the surface of Mg in the range from 527 ℃ to 650 ℃. When the temperature reaches the range from 650 ℃ to 700 ℃ , the Mg enwraped by the MgB2 brought at the first time will be melted and the activity of Mg will be improved. Then the melted Mg will rapidly get across the MgB2 layer and react with B in liquid by diffusing and infiltrating. The phase interface of MgB2 will not expand towards B atom until they completely come into being MgB2.When the range of temperature is from 700 ℃ to 750 ℃ , the mostly SiC will react with MgB2 and synthesize Mg2Si. At the same time, the C atoms go into MgB2 crystal lattice and substitute for B atoms. On the other hand, the slight fraction of MgB2 was decompounded into MgB4 and Mg. Owing to the short time of the reaction and the higher temperature grads, Mg has been solidified and crystallized again before some Mg can diffuse.

关 键 词：MgB2掺杂8%SiC 自蔓延法(SHS) 淬熄实验(CFQ) 相变过程 

分 类 号：O511[理学—低温物理]