【摘要】 微波合成因合成速度快、清洁和能效高而成为一种非常有前途的材料制备方法。与常规方法相比,很多材料可以在相对较低的温度和较短的时间内用微波加热合成。该文作者利用混合微波加热技术,在短时间内由镁粉、镍粉和石墨粉合成了具有立方钙钛矿结构的金属间化合物超导材料MgCNi3。利用微波加热合成的MgCNi3,镁的挥发和氧化程度明显减少。粉末X射线衍射显示合成的样品主相为MgCNi3,还含有少量未反应的石墨粉和微量的MgO杂相。金相显微镜和扫描电镜观察表明超导样品的晶粒大小一般为2~6μm。由标准的四探针电阻方法和磁测量技术测得样品的超导起始转变温度为6.9 K,转变宽度约为0.8 K。更多还原

【Abstract】 Microwave synthesis is a very promising preparation method for many materials because it is fast,clean and energy efficient.Many materials have been synthesized by the microwave heating method at considerably lower temperature and shorter time than that of conventional methods.Superconductor MgCNi3,an intermetallic compound with a cubic perovskite crystal structure,was synthesized from Mg,Ni and graphite powders by hybrid microwave heating in a short time.Using microwave heating for the MgCNi3 synthesis,the evaporation and oxidation of magnesium can be significantly reduced.Powder X-ray diffraction(XRD) analysis indicates that the phases of the synthesised sample are MgCNi3(major phase),a small amount of unreacted graphite and little MgO.Metallographic microscope and scanning electron microscope(SEM) observation shows that the MgCNi3 grain size ranges from 2 μm to 6 μm.The onset superconducting transition temperature of the MgCNi3 sample measured by standard four-probe method and magnetization measurement was 6.9 K,and the superconducting transition width was about 0.8 K.更多还原