[Spectroscopy Identification of Untreated and Heated Corundum].

ABSTRACT

Nowadays, a great quantity of heat treating corundums are emerging in our market. It is hard to distinguish them scientifically just by conventional methods. In order to accurately determine whether the corundums have been heated or not, we need to analyse their spectral characteristics. This paper describes the spectroscopy identification of untreated and heated corundum. The experiment is conducted as follows First, We observed the inclusions of corundum samples, then measured and recorded their infrared spectra, UV-Vis spectra by Fourier Transform Infrared Spectrometer and Ultraviolet-visible Spectrophotometer respectively. Next we chose a part of samples to heat, after the heat treatment, we recorded their spectra and made a comparison with that of untreated corundums. The results showed that we can detect the absorption peaks at 1 980 and 2 110 cm(-1) which represent diaspore in untreated ruby. However, after heat treatment, the absorption peaks disappear which means the structure of AlO(OH) has been destroyed. The sapphires which grown in alkali basalt under reductive condition appear the absorption peak at 3 310 cm(-1). However, this peak vanishes after 18 h heat treatment when the temperature is 1 600 ℃. For UV-Vis spectra of ruby, after heat treatment, the slight shift occurs in strong, wide absorption band at around 555 nm, and this band becomes more pointed. In addition, absorption intensity difference between wave crest and wave hollow increases. The absorption bands at 375, 387, 454 nm of heated sapphires are more pointed than that of the untreated sapphires, and absorption intensity difference rises. These changes in spectral characteristics can help us to distinguish untreated corundum from heat treating corundum.