High Pressure Synthesis And Characterization Of Al-base Icosahedral Quasicrystals

Since its discovery, quasicrystal has attracted much attention for its unique crystal structure and peculiar physical properties. The most widely studied is Al-based quasicrystal such as Al-Mn and Al-Pd-Mn quasicrystal. Much interests in quasicrystals are focused on deciphering their quasiperiodic structures and the formation mechanism.In this paper, we carried out the high-pressure high-tempreature experiments to prepare quasicrystal. Optimaized process conditions and obtained, by adjusting the experimental parameters including temperature, pressure, and reaction time. Once ingots of quasicrystals was obtained successfully, plasma sintering(SPS) is further taken to relieve rescidual stress. The composition and morphology of the synthesized phase are determined by the analysis of XRD,SEM, EDS and TEM results.Meanwhile in this paper we applied CALYPSO and first-principles methods to study the Al-Pd-Mn quasiqrystals recated system. By apply CALYPSO we explored the potential structure of Al-Pd binary alloys and found ta novel high-pressure structure m-Al3Pd2, with space group of C2/m. We firstly describe its structure in detail and then calculate the elastic constants, phonon dispersion curves and the formation of the new phase in order to judge its mechanical, dynamical and thermodynamic stability. The effect of pressure and temperature on the phase transition has been studied, suggesting the new phase may be synthesized and found in high pressure and high temperature conditions.Whats more, the ratio value of B/G has also calculated in order to analyze the brittle and ductile nature of the new phase. Electronic structure calculations suggest the m-Al3Pd2 phase is metallic.