Accession Number : ADD014260

Title :   Method of Making Carbon Dioxide and Chlorine Free Fluoride-Based Glass.

Descriptive Note : Patent, Filed 20 Jun 88, patented 27 Jun 89,

Corporate Author : DEPARTMENT OF THE AIR FORCE WASHINGTON DC

Personal Author(s) : Hutta, Joseph J

Report Date : 27 Jun 1989

Pagination or Media Count : 4

Abstract : The present invention relates to an improved method of making fluoride-base glass free of certain contaminants, and in particular, free of carbon dioxide and chlorine. Considerable effort has expended to develop heavy metal fluoride glasses ('HMFG') as a viable family of infrared-transparent optical-materials for application as fiber waveguides and as bulk optical components. The present process is directed to typical heavy metal fluoride glasses of the compositions: (XF4+BaF2+LaF3+ALF3+YF) where X is either zirconium or hafnium and Y can represent sodium, lithium, lead, indium, or no addition. For example, the melt mixture may contain multi-component fluorides, or, alternatively, the mixed oxides or oxyfluorides plus ammonium bifluoride (NH4HF2) in a crucible, preferably made of a nonreactive inert precious metal such as platinum, platinum alloys or gold but also including vitreous or pyrolytic carbon. This crucible is placed within a furnace contained within a vacuum chamber. The chamber is evacuated to around 110 torr and then backfilled with sulphur hexafluoride (SF6) to a slight positive pressure. The mixture is then rapidly heated to about 800 + or - 10 C., held there at temperature for a brief period then rapidly cooled. The present invention is a process of providing, high optical quality heavy metal fluoride glasses that lack devitrification, straie, seed, internal bubbles, crystalline inclusions, dissolved CO2 and chlorine contamination or other defects and inhomogeneities common in glasses of this type. Patents. (aw)

Descriptors :   *CARBON DIOXIDE, *FLUORIDES, *GLASS, *MANUFACTURING, *PATENTS, BUBBLES, CARBON, CHLORINE, CONTAMINATION, FIBERS, FURNACES, GOLD, HAFNIUM, HEAVY METALS, INDIUM, INERT MATERIALS, INTERNAL, LITHIUM, MELTS, MIXING, MIXTURES, OPTICAL EQUIPMENT, OXIDES, PLATINUM, PLATINUM ALLOYS, PRECIOUS METALS, PRESSURE, PYROLYSIS, SODIUM, VACUUM CHAMBERS, VITREOUS STATE, WAVEGUIDES, ZIRCONIUM

Subject Categories : Ceramics, Refractories and Glass
      Optics

Distribution Statement : APPROVED FOR PUBLIC RELEASE