摘要:
市场上的红宝石大都经过不同程度的热处理。泰国红宝石的改善工艺研究时间最长、效果最显著,因此,分析和对比泰国的改善工艺对改善云南红宝石具有重要意义。采用电子探针测得云南红宝石样品中除Cr3+外,还含有较高的Fe离子,是其产生杂色调的主要因素。经过泰国(密封,热处理温度为1 500~1 700°C,处理时间为8~15 h)和华东理工大学宝石检测中心(敞口,热处理温度为1 400~1 600°C,处理时间为15~24 h)的热处理工艺,均可以有效地减弱云南红宝石的杂色,使其红色调纯正,透明度提高。经该中心热处理后的红宝石表层的试剂都不同程度地呈现黄褐色调,经ICP-AES测试,黄褐色物质中含有较高的Fe离子,说明部分Fe离子从红宝石中析出。通过对比和分析经泰国和该中心热处理前、后云南红宝石的紫外-可见光吸收光谱可知,其改善工艺均可使部分Fe离子置换析出;杂色离子吸收的减弱是由于Cr3+引起相对吸收强度的增强致使红色调饱和度提高、颜色更加鲜艳的主要因素。
Abstract:
Most rubies on market have been heat-treated to some extent.The longest time on the research and the most prominent effect of treatment are in Thailand,thus it is very important to study the treatment technology of Thailand in order to enhance the quality of ruby from Yunnan Province. The ruby samples are tested by using EPMA,showing that besides Cr3+,high content of Fe ion exists in the ruby,which is the main factor for parti-colour.Bying heat treatment on the rubies respectively in Thailand(sealed,1 500~1 700(°C),t=8~15 h) and in the Gemstone Testing Centre,East China University of Science and Technology(open,1 400~1 600(°C),t=15~24 h),the parti-colour of the ruby samples are declined,with purer red and higher transparency.The reagents on the surface of the samples after heat treatment in the Gemstone Testing Centre appear yellowish-brown to some extent.Tested by ICP-AES,it is found that the yellowish-brown substance is bearing the high content of Fe ion,showing that partial Fe ion has been separated out from the samples.By contrasting and analysing the UV-VIS absorption spectra of the samples treated respectively in Thailand and in the Centre,it is shown that partial Fe ion could be separated out from the samples by the treatment in Thailand and in the Centre.The absorption of parti-coloured ions weakened is the main factor of the relative absorption of Cr3+ strengthening and the colour more vivid.
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