基于气动悬浮激光加热技术YAG熔体高温热物理性能评测

doi:10.15541/jim20180104

摘要/Abstract

摘要：

钇铝石榴石Y₃Al₅O₁₂(Yttrium Aluminum Garnet, 简记为YAG)材料具有优异的光、热和电学性能, 引起了广泛关注。但高熔点和冷却过程中复杂的相选择机制, 使YAG熔体特别是熔点以下过冷区内的热物理性能参数获得困难。利用自主搭建的气动悬浮无容器激光加热装置, 基于受迫振动和光学描影等原理, 在1750~2650 K宽达900 K的温区内, 评测了YAG熔体的黏度、表面张力和密度。研究表明, 与Al₂O₃熔体相比, YAG熔体密度具有更高的温度敏感性, 具有高约1倍的平均线膨胀系数; 不同于表面张力随温度变化不敏感的Al₂O₃熔体, YAG熔体的表面张力随温度升高产生略微降低; 与Al₂O₃熔体的黏温关系相比, 在熔点以下的过冷区内发现YAG熔体具有更陡峭的黏温变化趋势。

关键词: 高温热物理性质, YAG, 气动悬浮技术, 过冷区

Abstract:

As one of the most widely used oxide in many fields, Y₃Al₅O₁₂(YAG: Yttrium Aluminum Garnet) has attracted extensive attention. However, due to its high melting point and complex mechanism for phase selection, accurate knowledge of thermo-physical properties for YAG melt, is much desired. Using an advanced aerodynamic levitation laser-melting technique, here the viscosity, surface tension and density were carefully evaluated on both thermodynamically stable, and metastable supercooled YAG melts in the temperature scope from 1750 K to 2650 K. The results indicate that density of YAG melts has a higher sensitivity than that of Al₂O₃ melts upon temperature change; and YAG melts have one time higher average line thermal expansion coefficient compared to the Al₂O₃ melts. Al₂O₃ melts’ surface tension is almost constant on temperature in the wide temperature scope, while YAG melts have a distinct decrease in surface tension following temperature increase. As to the viscosity-temperature relation, in the supercooled scope, YAG melts have a more obvious rise in viscosity upon cooling.

Key words: thermo-physical property, yttrium aluminum garnet, aerodynamic levitation technique, supercooled region

中图分类号:

TQ171

丰盛, 单志涛, 潘瑞琨, 徐博, 祖成奎, 陶海征. 基于气动悬浮激光加热技术YAG熔体高温热物理性能评测[J]. 无机材料学报, 2018, 33(12): 1297-1302.

FENG Sheng, SHAN Zhi-Tao, PAN Rui-Kun, XU Bo, ZU Cheng-Kui, TAO Hai-Zheng. Thermo-physical Property of YAG Melt Measured by Aerodynamic Levitation Technique[J]. Journal of Inorganic Materials, 2018, 33(12): 1297-1302.

图/表 6

图1 气动悬浮无容器热物理性能评测装置示意图

Fig. 1 Schematic diagram of aerodynamic levitator for evaluating thermophysical properties of melts(a) Top and bottom laser sources; (b) Dual color pyrometer and high speed pyrometer; (c) Water-cooled levitation stage; (d) Infrared transparent window separating the levitation gas from the bottom laser; (e) Inlet for levitation gas; (f) Aerodynamic conical converging-diverging levitator nozzle; (g) High speed camera (maximum frame rate 6250 fps; the frame rate for our measurement being set to be 2000 fps); (h) Bandpass filter with 10 nm (FWHM) centered around 532 nm; (i) Back lighting laser source with a wavelength of 532 nm; (j) Beam expanding optics; (k) Acoustic excitation device; (l) Gas mass flow controller

图2 YAG熔体淬冷过程表面温度随冷却时间的变化曲线

Fig. 2 Apparent temperature versus time curve for YAG melt As shown in the insert Tg is characterized from DSC measurement of the sample obtained by quenching

图3 熔体在一定温度下的实时图像

Fig. 3 Typical frame obtained from high speed camera at a certain temperature The dark hemispherical area is the shadow cast of the melt drop visible above levitation nozzle

图4 Al2O3熔体[12]和YAG熔体[22]密度随温度的变化曲线

Fig. 4 Temperature dependence of density for YAG and Al2O3 melts[12], earlier work is included[22]

图5 YAG熔体表面张力随温度的变化

Fig. 5 Temperature dependence of surface tension for YAG melt Insert shows the result of frequency sweeping at 2550 K

图6 (a)YAG熔体黏度-温度曲线（插图为YAG熔体lgη~1/T关系曲线）和(b) 2550 K时悬浮液滴受迫振动的振幅随时间的衰减曲线

Fig. 6 (a) Temperature dependence of viscosity for YAG melt (Inset: lgη versus 1/T curve for YAG melt) and (b) damping curve according to the recorded radius for YAG melt at 2550 K

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