Process Exploration of Heat Treatment on Ruby and Sapphire from Madagascar
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摘要: 选用马达加斯加各色红、蓝宝石为研究对象，根据颜色特征分为红色、黄绿色、蓝绿色三大类。通过改变热处理温度、气氛氛围以及添加辅助剂，探讨最佳的热处理方案。通过热处理实验发现，马达加斯加红宝石样品在氧化气氛、1 500 ℃、恒温12小时条件下，热处理效果最佳，不仅消除了蓝紫色调，使红色更加鲜亮、均匀，透明度也有明显的提高；马达加斯加黄绿色、蓝绿色蓝宝石在还原气氛、1 500 ℃、恒温12小时条件下，热处理效果最佳，黄绿色调减弱，蓝色加深，甚至转变为较纯正的蓝色；马达加斯加红、蓝宝石样品裂隙较少、透明度较好，所以在不添加硼砂辅助剂的条件下即可获得较好的热处理效果。Abstract: Some pieces of Madagascar colourful corundum were chosen as samples．According to the colour characteristics，they were divided into three categories：red，yellow-green and blue-green．By changing temperatures，atmosphere and adding auxiliary agent in the heat treatment，the authors explored the best heat treatment plan.
According to the resuit of heat treatment at different temperatures，it can be found that the heat treatment of red Madagascar ruby samples should be conducted in oxidizing atmosphere at the temperature of 1 500℃.After the treatment，the tone of red Madagascar ruby samples turned brighter and the blue-violet colour was eliminated.
According to the resuit of heat treatment at different atmosphere，it can be found that the heat treatment of yellow-green and blue-green sapphires should be conducted in reducing atmosphere at the temperature 0f 1 500℃.After treatment，yellow-green tone of the samples was weakened and blue tone was deepened.The treatment can produce pure and uniform blue colour.In the experiment，the carbon power for reducing atmosphere should be avoid to contact with the samples directly，which may be difficult to remove from the samples.
It’s worth to mention that，in both oxidizing and reducing atmosphere of heat treatment，the brown stripes of samples can be eliminated effectively.So the eliminating of brown stripes is unrelated to atmosphere，but the temperature.High temperature can make the structure become loose and more conducive to the spread of Fe2+，thereby reducing the transition of 02-→Fe2+.eliminating the brown colour.
Additional，since these ruby and sapphire samples from Madagascar have few fissures and good transparency，it is no need to add borax as an auxiliary for heat treatment.The result of heat treatment shows that borax added as auxiliary agent does not improve the colour and it turns into white crystalline material at high temperature，which finally covers the surface of the sample and affects the transparency.-
Keywords:
- ruby and sapphire /
- corundum /
- heat treatment /
- Madagascar
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