USA As Represented by Secretary of the Navy

Other

Deborah A Haught

Inna G Talmy

Curtis A Martin

Anh H Le

Monoclinic celsian (BaO.Al.sub.2 O.sub.3.2SiO.sub.2) is produced by heating a stoichiometric, powder mixture of BaCO.sub.3 (or BaC.sub.2 O.sub.4), Al.sub.2 O.sub.3, and SiO.sub.2 (preferably SiO.sub.2 gel) with monoclinic celsian seeds at from 1250.degree. C. to 1500.degree. C.

Method of preparing monoclinic BaO.A1.sub.2 O.sub.3.2SiO.sub.2

A ceramic material which is (1) ceramics based on monoclinic BaO.multidot.sub.2 O.sub.3 .multidot.2SiO.sub.2 ; (2) ceramics based on monoclinic SrO.multidot.Al.sub.2 O.sub.3 .multidot.2SiO.sub.2 ; or (3) ceramics based on monoclinic solid solution of BaO.multidot.Al.sub.2 O.sub.3 .multidot.2SiO.sub.2 and SrO.multidot.Al.sub.2 O.sub.3 .multidot.2SiO.sub.2.

Ceramic material

A ceramic electromagnetic window made of Si.sub.3 N.sub.4 particles which are bonded together by a metal phosphate binder that is an AlPO.sub.4 binder, a ZrP.sub.2 O.sub.7 binder, or mixtures thereof, wherein the Si.sub.3 N.sub.4 particles comprise from 55 to 85 volume percent of the ceramic material of the electromagnetic window with the metal phosphate binder comprising the remainder. By substituting Si.sub.3 N.sub.4 whiskers for some of the Si.sub.3 N.sub.4 particles a discontinuous fiber composite ceramic electromagnetic window is produced. The electromagnetic window may be a simple shape such as a flat or slightly curved sheet or a more complex shape such as a conical or spherical radome.

Electromagnetic window

A ceramic material made from raw coal fly ash or raw municipal solid waste fly ash and (1) sodium tetraborate or (2) a mixture of sodium tetraborate and a calcium containing material that is triple superphosphate, lime, dolomitic lime, or mixtures thereof.

Ash-based ceramic materials

A process for preparing monoclinic celsian from AlF.sub.3, Al.sub.2 O.sub.3, BaCO.sub.3, and fused SiO.sub.2 powders by heating an intimate mixture of the powders (1) at from about 700.degree. to 900.degree. C. to form topaz and then (2) at a temperature as low as 900.degree. C. to produce monoclinic celsian. The reactions take place in an atmosphere of the gases generated by the reactions.

Low temperature synthesis of high purity monoclinic celsian

A process for preparing monoclinic celsian from topaz and BaCO.sub.3, pows by heating an intimate mixture of the powders at a temperature of from 900.degree. C. to less than 1590.degree. C. in an atmosphere of the gases generated by the monoclinic celsian formation reaction itself.

Low temperature synthesis of high purity monoclinic celsian using topaz

A process in which (1) AlF.sub.3 and SiO.sub.2 or AlF.sub.3, SiO.sub.2, and Al.sub.2 O.sub.3 powders are formed into a green body of a desired shape and size; (2) the green body is heated at 700.degree. C. to 950.degree. C. in an anhydrous SiF.sub.4 atmosphere to form barlike topaz crystals; and then (3) heated in an anhydrous SiF.sub.4 atmosphere at about 1150.degree. C. to 1700.degree. C. to convert the barlike topaz crystals to needlelike single crystal mullite whiskers which form a porous, rigid felt structure. The felt has the same shape as the green body with about 1.5 or less percent change in linear dimensions. The felt can be used as preforms for ceramic-matrix or metal-matrix composites or by itself as thermal insulation.

Growing community of inventors

Sterling, VA, United States of America

Deborah A Haught