Low temperature decomposition of metal borohydride drives autogenous synthesis of MgB2
Low temperature decomposition of metal borohydride drives autogenous synthesis of MgB2
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DOI：
10.1088/1361-6668/aa62d6
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发表时间：
2017-05-01
影响因子：
3.6
通讯作者：
Talbot, P. C.
中科院分区：
文献类型：
--
作者：
Mackinnon, I. D. R.;Shahbazi, M.;Talbot, P. C.
我们描述了一个低温，自生压力的方法来合成毫米级的MgB 2聚集体与高度连接的颗粒。金属硼化物如NaBH 4和KBH 4在Mg存在下在低温（即< 150 ℃）下的分解提供了在压力下的反应性硼物质，并且随后以高产率形成MgB 2。最佳合成条件包括加热至250 ° C持续> 30分钟，然后升温至450 ° C < T-max < 500 ° C和1.4MPa < P-max <2.2MPa。与KBH 4的反应在比与NaBH 4的反应（类似于80 ° C- 100 ° C）更高的温度（类似于130 ° C）下释放活性硼物质。碱金属在MgB 2中的溶解度类似于ppm水平。通过这些合成产生的MgB 2的起始超导转变温度Tc在38.3和38.5 K之间。MgB 2聚集体的磁性测量显示出与在较高温度（> 800摄氏度）下产生的粉末相当的晶粒连通性，并且表明这种合成方法对于非原位线材生产可能是有效的。
We describe a low temperature, autogenous pressure method to synthesise mm-scale MgB2 aggregates with highly connected grains. The decomposition of metal borohydrides such as NaBH4 and KBH4 at low temperature (i.e. < 150 degrees C) in the presence of Mg provides reactive boron species at pressure and subsequent formation of MgB2 in high yield. Optimum synthesis conditions include heating to 250 degrees C for > 30 min then a ramp to 450 degrees C < T-max < 500 degrees C and 1.4 MPa < P-max < 2.2 MPa. Reactions with KBH4 release reactive boron species at higher temperature (similar to 130 degrees C) than reactions with NaBH4 (similar to 80 degrees C- 100 degrees C). Alkali metal solubility in MgB2 is at similar to ppm levels. The onset superconducting transition temperature, T-c, for MgB2 produced by these syntheses ranges between 38.3 and 38.5 K. Magnetic measurements of MgB2 aggregates show a grain connectivity comparable to powders produced at higher temperature (> 800 degrees C) and suggests that this synthesis approach may be effective for ex situ wire production.