Opaque silica glass article having transparent portion and process for producing same
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United States of America Patent
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Nov 6, 2001
Grant Date -
N/A
app pub date -
Oct 16, 1998
filing date -
Oct 16, 1997
priority date (Note) -
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Abstract
An opaque silica glass article comprising a transparent portion and an opaque portion, wherein the opaque portion has an apparent density of 1.70-2.15 g/cm.sup.3 and contains 5.times.10.sup.4 -5.times.10.sup.6 bubbles per cm.sup.3, said bubbles having an averaged diameter of 10-100 .mu.m; and the transparent portion has an apparent density of 2.19-2.21 g/cm.sup.3 and the amount of bubbles having a diameter of at least 100 .mu.m in the transparent portion is not more than 1.times.10.sup.3 per cm.sup.3. The opaque silica glass article is made by a process wherein a mold is charged with a raw material for forming the opaque portion, which is a mixture comprising a silica powder with a small amount of a silicon nitride powder, and a raw material for forming the transparent portion so that the two raw materials are located in the positions corresponding to the opaque and the transparent portions, respectively, of the silica glass article to be produced; and the raw materials are heated in vacuo to be thereby vitrified.
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