Sintered transparent polycrystalline ceramics: the next generation of fillers for clarity enhancement in corundum

Publish Year: 1400
نوع سند: مقاله ژورنالی
زبان: English
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JR_SYNSINT-1-3_004

تاریخ نمایه سازی: 9 آبان 1401

Abstract:

A significant proportion of mined natural corundum (ruby and sapphire) contain fractures, which negatively affect a gemstone’s clarity and value. Over the past decades, heat treatment techniques have been developed for either fracture healing or filling to make such gems marketable. The clarity enhancement processes are mainly based on techniques which are either not durable, as in the case of lead silicate fillers, or do not yield perfect transmittance through a fracture, as in the case of borax based fluxes. Therefore, the gemstone treatment community is actively in pursuit of better techniques for clarity enhancement in corundum. Given that application of pressure is a recent advancement in the heat treatment processes of natural sapphire, it is essential to explore the possibilities regarding different outcomes such treatments can have. In this perspective paper, we have briefly described how the application of pressure during heat treatments can lead to in-situ sintering of transparent polycrystalline ceramics within the fractures of corundum, which can result in clarity enhancement. Spinel-structure based fillers can be tailored to mimic corundum in terms of tribological, chemical, and optical properties. Therefore, gemstones treated with such fillers will be durable, unlike currently used glass-based filler material. We also provide a possible explanation for ghost-fissures in sapphires heated under pressure, as being a by-product of an in-situ sintering process of ceramic fillers that are thermodynamically compatible with Al۲O۳. The prospect of transparent polycrystalline ceramics in the gem and jewelry industry opens a new field of research in this area, given that ceramic fillers can outperform currently used methods and materials for clarity enhancement in gemstones. In essence, we present a novel application for sintered transparent polycrystalline ceramics.

Keywords:

Transparent ceramics , Heat treatment , Sapphire , Transient liquid phase sintering , High temperature + pressure (HT+P)High pressure high temperature (HPHT)

Authors

Mubashir Mansoor

Department of Metallurgical and Materials Engineering, Istanbul Technical University, Maslak ۳۴۴۶۷, Istanbul, Turkey

Melya Mansoor

Department of Metallurgical and Materials Engineering, Istanbul Technical University, Maslak ۳۴۴۶۷, Istanbul, Turkey- Department of Geological Engineering, Istanbul Technical University, Maslak ۳۴۴۶۷, Istanbul, Turkey

Maryam Mansoor

Department of Metallurgical and Materials Engineering, Istanbul Technical University, Maslak ۳۴۴۶۷, Istanbul, Turkey- Department of Mining Engineering, Istanbul Technical University, Maslak ۳۴۴۶۷, Istanbul, Turkey

Ted Themelis

Department of Mining Engineering, Istanbul Technical University, Maslak ۳۴۴۶۷, Istanbul, Turkey

Filiz Çinar Şahin

Department of Metallurgical and Materials Engineering, Istanbul Technical University, Maslak ۳۴۴۶۷, Istanbul, Turkey