Authors: Hui Qiang Li, Long Fei Liu
Abstract: Along nucleation → crystalline growth →crystalline fraction → critical cooling rate, the relationship between the nucleation, elements, cooling rate and the Glass Forming Ability of (Cu-Zr) based glass alloys is quantitatively studied with thermodynamics method, and a better method to evaluate the critical cooling rate of glass alloys is also proposed in this paper. The computed results show that: (1) with the increase of element number, the steady state nucleation rate drops gradually. From Cu-Zr, Cu-Zr-Al, Cu-Zr-Al-Ni, to Cu-Zr-Al-Ni-Ti, the peak value of nucleation rate decreases from 1021 mol-1s-1 to 1013 mol-1s-1. It is also found the nucleation rate both drops with the substitution of Ni with Cu or Al with Zr; (2) with the increase of cooling rate, the nucleation rate drops sharply. When the cooling rate reaches 103K/s, the nucleation rates of Cu64Zr36, Cu54Zr42.5Al3.5, Cu55Zr40Al5 and Cu30Zr55Al10Ni5 drop to 109mol-1s-1, 106mol-1s-1, 107mol-1s-1 and 103mol-1s-1 accordingly.
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Authors: Agnese Stunda, Dmitrijs Jakovlevs, Lasma Poca, Liga Berzina-Cimdina
Abstract: Modification of surface morphology and composition of niobophosphate glass and glass-ceramic in the system P2O5-CaO-Nb2O5-Na2O was investigated. Amorphous, partly crystalline and crystalline samples were prepared in shape of pellet with diameter 10 mm. Samples were treated in 1 and 5 days in citric acid at 37°C and 3h in boiling HCl. Surface morphology before and after treatment was investigated by scanning electron microscopy (SEM), phase composition by X-ray powder diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX). Glass sample was smooth, after treatment in citric acid it had cracks and pit-holes on the surface. Partly crystalline sample was smooth and contained inclusions of crystalline Ca3(PO4)2 and Ca2P2O7. Platy crystals of Ca3(PO4)2 dissolved first, than bulky Ca2P2O7. Crystalline samples contained Na4Nb8P4O32 and calcium phosphate phases; surface was rough before and after treatment. EDX showed that amount of phosphorous is proportional to amount of calcium and inversely proportional to amount of sodium and niobium in glass-ceramic samples.
61
Authors: Gang Li, Zhan Zhe Zhang
Abstract: In this paper, we report a Fe-based nanocrystalline-amorphous matrix composite synthesised via partially crystallising an amorphous alloy. The microstructure of the composite was characterize. An amorphous rod of 2mm in diameter was initially prepared via injecting the melted Fe36Co36B20Si4Nb4 alloy into a copper mould in vacuum, which was confirmed to be completely amorphous by X-ray difraction(XRD). Differential scanning calorimeteric(DSC)curve shown that the span △Tx of the supercooled liquid region and the reduced glass transition temperature(Tg/Tm)for the amorphous alloy are 40 K and 0.615, respectively. The composite composed of nanocrystalline particles homogeneously dispersed in an amorphous matrix was prepared by isothermal annealing. In this course, the amorphous Fe-based sample was held for different time at different temperature. The types of the nanocrystalline phases obtained in different annealing conditions were characterised by XRD and selected-area diffraction pattern(SAED).The crystallization behavior of the amorphous Fe-based alloy was discussed.
778
Authors: Supakorn Silakate, Anucha Wannagon, Apinon Nuntiya
Abstract: The objectives of this study were to prepare leadless crystalline glazes from iron oxide by using low temperature firing (1,100°C) and to study the effect of concentration of iron oxide on the phase composition of the glaze raw materials on phase transformation in leadless iron oxide crystalline glaze. The crystalline phases were investigated by using the DTA, X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The composition of the glaze raw materials compose of nepheline syenite, colemanite, pottery stone, bentonite, ZnO, Li2CO3, SiOSubscript text2 and 10, 15 and 20%(w/w) iron oxide (Fe2O3). The glaze raw materials were ground for homogeneous mixtures by ball milling for 24h. The average particle size of the mixture was 3.86 µm. The glaze bodies were carried to firing at 1,100°C at the heating rate of 2°C/min and soaking for 0.5h. Then, the glaze bodies were cooled at the cooling rate of 1°C/min and maintained at 1,080°C for 3h and then maintained at 980°C for 1h, respectively. From the experiment results, it was found that the crystallization temperatures (Tc) of franklinite (ZnFe2O4) and anorthite (CaAl2Si2O8) depend on the concentration of iron oxide content.
18
Authors: Zhi Hong Yang, Qiao Lin, Yong He, Hai Hui Tao, Yi Ke, Guang Dong Liao
Abstract: Copper slag, containing more than 40 wt% iron, is often used for pavement of roads, building bricks and cement etc. The level of this traditional utilization technology is very poor. In this study, a new method of comprehensive utilization of copper slag was investigated. The iron of copper slag was recovered and the residual slag was transformed into glass-ceramics within the same process involving iron reduction, iron-glass separation and glass crystallization. The experimental results indicated that the ratio of iron recovery was more than 99% and the crystalline phase of the obtained glass-ceramics was diopside. With the extension of crystallization time, the content of crystalline phase and the size of crystals of the glass-ceramics increase.
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