【作者】 梁锦霞；

【导师】 周美玲；

【作者基本信息】 北京工业大学 ， 材料学， 2004， 硕士

【摘要】 以 Mg 粉和 B 粉为原料，用传统无压烧结方法和放电等离子烧结方法成功地制备出 MgB2块材，并研究了其显微结构和超导电性，比较了两种方法制备得到的样品的成分，密度和微观结构。本文系统的研究了传统无压烧结合成 MgB2块材的工艺，重点讨论了制备过程中的各项参数对样品性能的影响，包括原料混合时间，烧结温度，保温时间和原料配比。实验表明，把 Mg 粉和 B 粉按原子比在 1:2≤Mg:B≤1.2:2 范围内混合，在流动的氩气中在 750℃下保温 3 个小时得到的样品杂质最少，成分单一，纯度较高。在传统烧结中，用 Mg 粉和 B 粉合成的 MgB2块材在烧结后发生膨胀现象，膨胀率大约在 4.0％左右，而且三维方向上的膨胀程度不等。与放电等离子烧结技术相比，采用传统方法合成的 MgB2块材虽然成分单一，但其密度不高。进一步的实验表明，在压制过程中增大压力可以使样品的密度提高，可达理论密度的 47％，但离理论密度还是相去甚远。本文还对放电等离子烧结技术合成 MgB2块材进行了初步的探索，讨论了烧结过程中隔离介质材料，烧结温度和加热时间对样品纯度的影响。与传统无压烧结相比，SPS 方法实现了 MgB2块材的快速烧结，使样品密度有了很大的提高，可达理论密度的 81％。且扫描电镜分析表明，与传统方法相比，SPS 方法合成的样品气孔细小，比较均匀致密，断面更加平整。最后，对传统无压烧结和放电等离子两种方法制备的样品的超导转变温度进行了测量，结果表明，两种方法合成的样品的超导转变温度均在 39 K 左右。更多还原

【Abstract】 MgB2 bulks，using magnesium powder and boron powder as starting materials,were successfully synthesized by conventional pressureless sintering (PLS) and sparkplasma sintering (SPS) methods, and their microstructure and superconductivity werestudied. The component, density and microstructure of the samples prepared bydifferent methods were also compared. In this paper, we presented a systematic study of the fabrication processes ofMgB2 and focused on discussing the effects of the fabrication parameters on theproperties of the samples including the powder mixing time, the sintering temperature,the sintering time as well as the ratio of starting materials. The experiment shows thatMgB2 bulks with single component were fabricated at 750℃ for 3 hours in theflowing argon atmosphere at the ambient pressure when the ratio of Mg powder and Bpowder is 1:2≤Mg:B≤1.2:2. It was found that MgB2 bulks expanded with a differentexpansion coefficient in three-dimension after sintering. The expansion coefficientwas found to be about 4.0％. The purity of MgB2 bulks prepared by conventionalmethod is higher than that of MgB2 bulks prepared by SPS method, but their densityis low. A further experiment shows that increasing pressure in pressing process canincrease the density of the samples and make it reach 47% of the theoretical density,however, it is far from the theoretical value. This paper also presented a primary study on the synthesis of MgB2 bulks usingSPS method, and the sintering parameters including the isolated material, thetemperature and the heating time were discussed. The results revealed that SPSmethod can make fast sintering of MgB2 bulks. The density of the bulks made by thismethod was greatly increased, which is near 81% of theoretical density compared toconventional method. Meanwhile the SEM micrographs indicate that MgB2 bulksprepared by SPS method have denser microstructure, less pores and flatter transectcompared with the bulks prepared by PLS method. At last, the superconducting transition temperature of the samples synthesized bytwo methods were measured, and the results showed that their Tc were about 39 K.更多还原