Amorphous Fe73.5Cu1Nb3Si13.5B9 alloys, prepared by a melt-spinning technique, were annealed at a temperature of 823 K under pressures in the range of 1–5 GPa and ambient pressure. The high pressure experiments were carried out in a belt-type pressure apparatus. The microstructure of the annealed alloys has been investigated by x-ray diffraction, electron diffraction, and transmission electron microscopy. Experimental results show that the initial crystalline phase in these annealed alloys is α-Fe solid solution (named as α-Fe phase below), and high pressure has a great influence on the crystallization process of the α-Fe phase. The grain size of the α-Fe phase decreases with the increase of pressure (P). The volume fraction of the α-Fe phase increases with increasing the pressure as the pressure is below 2 GPa, and then decreases (P>2 GPa). The mechanism for the effects of the high pressure on the crystallization process of amorphous Fe73.5Cu1Nb3Si13.5B9 alloy and latent applications of high-pressure annealing amorphous Fe73.5Cu1Nb3Si13.5B9 alloy have been discussed.
Carbon nitride crystals have been synthesized from C3N4H4 in the presence of a nickel-based alloy or cobalt as a catalyst at high pressure of 7 GPa and temperature of about 1400 °C. Scanning electron microscopy showed rod-like, well-faceted crystals with size of several micrometers, and the N content in these carbon nitride crystals was 47–62%. X-ray diffraction indicated the crystals were composed of α–C3N4 and β–C3N4. The experimental lattice constants of α–C3N4 (a = 6.425 Å, c = 4.715 Å ) and β–C3N4 (a = 6.419 Å, c = 2.425 Å ) agree with ab initio calculations very well.
Changes in electrical resistance of germanium were investigated during melting and cooling under high pressure. It was found that the electrical resistances of the samples dropped abruptly at an early stage of the solidification above ∼4 GPa. This result shows a metallic liquid to metallic solid transition of germanium when cooling above ∼4 GPa as compared to a metallic liquid to nonmetallic solid transition at pressures below ∼4 GPa. The mechanism of the phase evolution in the solidification process of germanium at high pressures is briefly discussed.
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