Abstract:
The present invention relates to a process for production of a glass by the vacuum melting method using silica as raw material and comprises uniformly preheating a silica powder containing an accelerator for phase conversion to about 800.degree. C.; filling the preheated silica powder in a container while substantially maintaining the temperature; further heating the silica powder to convert it into a sintered body having a cristobalite phase; and then heating and melting the sintered body in vacuum for glass formation, whereby not only are improvments in raw material efficiency and productivity by shortening of the heating time achieved, but also the formation of cracks on the surface of the resulted sintered body which has been one of the important reasons for resulting in products of sub-standard can be substantially completely avoided.
Abstract:
The present invention relates to a process for the production of a glass from silica as a raw material by a vacuum melting method, in which a high quality glass is produced efficiently by compounding a silica powder containing an excess amount of the accelerator for phase conversion and silica powders containing substantially no such accelerator or by introducing silica powders in a solution containing an accelerator for phase conversion, adding an acid or basic component to the mixture to adjust the pH thereof, stirring the mixture for mixing, and subjecting the mixture to dehydration and drying to obtain silica powders containing the accelerator for phase conversion in proper quantities, filling the resultant silica powders in a vessel and heating the powder to form a sintered molded body having cristobalite phase having a self-supporting property and also having a proper matrix strength and a high porosity, and then heating the sintered body under vacuum.
Abstract:
A process for production of a glass by a vacuum melting method using silica as raw materials comprising heating silica powders in the presence of an accelerator for phase conversion to convert them into a sintered body having cristobalite phase; molding or repowdering the sintered body; containing or filling the resulted sintered body in a container having a desired shape; and then heating and melting it in vacuo for glass formation, or accumulating a plurality of the sintered bodies into a desired shape; and then heating and melting it for glass formation, whereby a high-quality glass ingot having a desired shape or a larger glass ingot can be readily obtained without reduction in productivity.
Abstract:
The invention relates to a process for the preparation of monolithic silica aerogels by drying silica gels under hypercritical conditions, which is characterized by the absence of washing of the silica gel, a high heating rate in the autoclave and purging of the autoclave after substantial removal of the solvent. Other preferred conditions are the use of an amount of water not exceeding 1.5 times the stoichiometric amount for the hydrolysis, hypercritical conditions corresponding to a temperature of 265.degree.-275.degree. C. and to a pressure of 150-200 bars, and so on. Use of the aerogels for the preparation of silica glass bodies or articles and of heat-insulating materials.
Abstract:
A method for densifying a fumed metal oxide of Groups III and IV prepared by either a vapor phase oxidation or combustion process is disclosed wherein the metal oxide is mixed with a polar liquid in a high shear mixer, the metal oxide being present in an amount of about 35-50%, to convert it into a granulated material which, when dried, will substantially all pass through a 10 mesh screen. The granulated material may then be calcined preparatory to wet milling to prepare a casting slip, or it may be vitrified directly for molding or drawing in known manner.
Abstract:
Method of preparing granular quartz glass which comprises heating a porous granulated silica gel having an alkoxy group content equal to or less than 1 weight percent and a total impurity content of less than 1 part per million, the porous granulated silica gel obtained by hydrolysis of an orthosilicic acid ester of an aliphatic alcohol at a temperature up to 1400.degree. C.
Abstract:
The instant invention is directed to the production of high purity fused silica bodies by means of a three-step process. In the first step, various specifically-defined ratios of aqueous alkali metal silicates with colloidal silica or quaternary ammonium silicate are gelled with certain organic reagents. In the second step, the gelled silicate mass is leached in weakly acid solutions to yield bodies of very high porosity, i.e., greater than 50%, with mean pore diameters ranging between about 400A-4000A, but wherein the pore diameters are extraordinarily uniform within a particular body. Lastly, the microporous body is fired briefly at temperatures above about 1350.degree. C. to consolidate the body to a solid transparent fused silica article having alkali metal contents less than 100 parts per million (PPM). The size of the pores, combined with the exceptional uniformity of pore sizes within an individual unit, is vital to achieve crack-free, homogeneous products.
Abstract:
A method of making low loss glass optical waveguides, wherein at least one coating of glass soot is deposited by the flame hydrolysis process on a starting member. The soot coating is heated to its consolidation temperature in an atmosphere containing helium and an amount of chlorine that is effective to substantially remove the water from the glass soot while the soot is being consolidated to form a dense glass layer. The starting member is removed unless it is to form a part of the optical waveguide. The resultant structure, including the dense glass body, is then drawn into a waveguide fiber.
Abstract:
A PLURALITY OF TORCH FLAMES EACH RESULTING FROM THE COMBUSTION OF GASEOUS SILICON TETRACHLORIDE AND A MIXTURE OF HYDROGEN AND OXYGEN ARE DIRECTED UPON A GRAPHITE MANDREL IN ORDER TO FORM A HIGH PURITY SILICIA ARTICLE UPON THE MANDREL. STRUCTURE MAY BE PROVIDED TO PREVENT THE BUILDUP OF DEPOSITS UPON THE NOZZLES OF THE TORCHES TO PREVENT OBSTRUCTION OF THE NOZZLE OPENINGS. ADDITIONAL GLAZING TORCHES MAY BE UTILIZED TO TREAT THE SILICA ARTICLES AS THEY ARE FORMED UPON THE MANDREL.