Gas bubbles in shaped sapphire
| Autor: | O. Bunoiu, Th. Duffar, Irina Nicoara |
|---|---|
| Přispěvatelé: | Science et Ingénierie des Matériaux et Procédés (SIMaP), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National Polytechnique de Grenoble (INPG)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS) |
| Jazyk: | angličtina |
| Rok vydání: | 2010 |
| Předmět: |
010302 applied physics
Convection Marangoni effect Materials science Bubble Crucible 02 engineering and technology [CHIM.MATE]Chemical Sciences/Material chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences Physics::Fluid Dynamics Crystal Crystallography Chemical physics 0103 physical sciences Sapphire Meniscus General Materials Science [SPI.GPROC]Engineering Sciences [physics]/Chemical and Process Engineering Liquid bubble 0210 nano-technology |
| Zdroj: | Progress in Crystal Growth and Characterization Progress in Crystal Growth and Characterization, Elsevier, 2010, 56, pp.123-145 |
| ISSN: | 0146-3535 |
| Popis: | Shaped sapphire single crystals almost always contain a typical defect: small bubbles also known as “micro-voids”. The goal of this paper is to review the existing literature and give a survey of our recent work on this specific defect. As a conclusion to our review we propose a mechanism for bubble formation and its occurrence and distribution in shaped sapphire. The bubbles contain CO which originates as a result of complex reactions between the molten alumina, Mo crucible and graphite pieces. The CO dissolves in the molten alumina and is probably present as a saturated solution whatever the growth conditions. Then the dissolved gas is rejected at the solid–liquid interface and bubble nucleation occurs where the concentration of CO is highest. Therefore, the location of the bubbles in the crystal is governed by the hydrodynamics in the meniscus, which include Marangoni convection. The bubble is finally incorporated in the crystal when it reaches a critical size which depends only on the growth rate. When a central capillary channel is used, the bubbles are located in a layer close to the surface of the crystal from where they can be easily removed by polishing. Also, all the literature agrees on the fact that interface destabilization at high velocity results in the presence of bubbles throughout the entire crystal and should be avoided. |
| Databáze: | OpenAIRE |
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