Osram Sylvania Inc.

Gte Laboratories Incorporated

Gautam Bandyopadhyay

Keith A Klinedinst

Kenneth W French

Silvia E Lichtensteiger

Leslie J Bowen

Joseph E Lester

Jeffrey T Neil

Sheldon I Lieberman

Hongwen Li

A method for making a tantala/silica interference filter on a vitreous substrate, which filter retains integrity at temperatures in excess of 600.degree. C., includes the steps of depositing by low pressure chemical vapor deposition a first coating of tantala/silica on the substrate, heat treating the first coating, and depositing by low pressure chemical vapor deposition a second coating of tantala/silica, the first and second coatings in combination providing a tantala/silica interference filter with a thickness of at least 3.5 microns on the vitreous substrate. There is further presented an electric lamp having an envelope and an interference filter applied thereto, in accordance with the above method.

Method for making a tantala/silica interference using heat treatment

A method for making a tantala/silica interference filter on a vitreous substrate, the filter retaining integrity at temperatures in excess of 600.degree. C., includes the steps of applying to the vitreous substrate a first coating of vitreous silica doped with submicron-sized particles, depositing on the first coating by low pressure chemical vapor deposition the filter which comprises a second coating comprising alternating layers of tantala and silica, and heat treating the substrate and first and second coatings to bond the filter to the substrate. There is further provided an electric lamp having an envelope made in accordance with the above method.

Method for making a tantala/silica interference filter on a vitreous

A method of producing crack free ceramic parts having large cross-sections is disclosed. An initial mixture of ceramic powder containing a binder and from 0.1 v/o to 10 v/o of whiskers or fibers which are made of carbon, graphite or high temperature melting or decomposition point organic polymers. The mixture is either injection molded or slip cast to form a shaped article. The shaped article is heated in a nitrogen atmosphere to a temperature of 450.degree. C. and then in an atmosphere of air at a temperature of 450.degree. C. to 600.degree. C. to completely remove the binder. The resulting binderless shaped article is then heated at 800.degree. C. for a period of time sufficient to completely remove the whiskers or fibers from the shaped articles. The article is then encapsulated in glass and hot isostatically pressed at a pressure of 30,000 psi to densify the article to approximately 99% of theoretical. The resulting article has a complex geometry and a large cross-section but without detrimental cracks.

Method of making large cross section injection molded or slip cast

A method for fabricating large, greater than one centimeter cross section, high density silicon nitride by injection molding process has been developed. The method requires use of a controlled starting powder, a novel binder removal process, a prefiring step followed by isopressing and conventional sintering.

Method for fabricating large cross section injection molded ceramic

A method for fabricating injection molded ceramic shapes suitable for densification by sintering or hot isostatic pressing has been developed. The method is applicable to ceramic articles of large, complex cross sections, greater than one centimeter, which are generally prone to external cracking during binder removal. The method requires use of a controlled starting powder, and a novel binder removal process to obtain an externally crack-free article.

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Acton, MA, United States of America

Gautam Bandyopadhyay