Nanocrystalline Ni3S2 prepared by mechanochemistry and its behavior at high temperatures and high pressure

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

卷:493

Article; Proceedings Paper

Ulbrich, K. F.¹  Campos, C. E. M.¹ 

[1] Univ Fed Santa Catarina, Dept Fis, Campus Trindade, BR-88040900 Florianopolis, SC, Brazil

关键词: Nanocrystalline Ni3S2;    Mechanochemistry;    X-ray powder diffraction;    Magnetic measurements;    High-temperature;    High-pressure;   

DOI  :  10.1016/j.jmmm.2019.165706

来源: Elsevier

【 摘 要 】

Nanocrystalline Nickel sulfide, Ni3S2, was prepared mechanochemically using ball milling in an inert atmosphere at room temperature, starting from Ni60S40 powder mixtures. X-ray powder diffraction (XRPD) was used to investigate the structural and microstructural evolution of the Ni60S40 alloy with milling time. The formation of the trigonal Ni3S2 phase (space group R32H) occurs with only 1.5 h, remaining stable up to 24 h of milling. The cell volume, lattice parameters, atomic coordinates, and isotropic atomic dislocation (thermal) parameters of the Ni3S2 phase, together with the average crystallite size and micro-strain, were determined from Rietveld analysis of the XRPD data. The average crystallite size decreases from about 37 nm to 22 nm with milling time increasing, with the same behavior happening for micro-strain. The high-temperature experiments showed that the melting point of the nanocrystalline Ni3S2 is about 660 degrees C, which is much lower than bulk. Transmission electron microscopy (TEM) images and electron diffraction patterns confirmed the nanometric size of the crystalline domains but revealed that it belongs to larger agglomerated particles (similar to 100 nm). The nanocrystalline samples have their magnetic properties characterized by vibrating sample magnetometer (VSM), showing an evolution from ferromagnetism to a mixed magnetic state as milling time increases. The high-pressure experiments revealed no phase transitions up to 20 GPa and a bulk modulus of about 143 GPa for the Ni3S2 nanophase using the least-squares fit of first-order Murnaghan equation of states.

【 授权许可】

Free