The Harshaw Chemical Company

Harshaw/filtrol Partnership

Harshaw/filtrol

Herbert Packer

King H Rosette

Carl F Swinehart

Ionic salts containing minor amounts of an activator and useful as scintillation phosphors are formed by extrusion of a macrocrystal of either a single crystal or a melt-grown multiple crystal ingot at a temperature below its melting point and under sufficient pressure to form a fully dense, homogeneous polycrystalline mass, the scintillation properties of which are essentially the same as, or better than, those of the original macrocrystal.

Extrusion of macrocrystal scientillation phosphors

A method is disclosed for hot press-forging a normally frangible optically integral crystalline mass ('optical body') in a closed die, by directly pressing a surface of the mass while it is peripherally surrounded by a crystal powder the amount of which is computed from the deformation ratio desired and the geometry of the die. The crystal powder is compacted by the non-uniformly directed forces transmitted to it by the optical body, and eventually the crystal powder is sufficiently dense so as dynamically to constrain the optical body at its peripheral surface. The dynamic constraint of the optical body while it is being forged is effected in such a way as to permit deformation of the optical body without fracturing it, and, without affecting its optical integrity. Hot press-forging the optical body by peripherally surrounding it with the crystal powder produces a stress environment in which the forces applied in a first stage, to the optical body by the ram of the forging press and, in a second stage, by the crystal powder, are non-uniform both in magnitude as well as in direction. The result is that the optical body may be deformed and forged to obtain a deformation ratio greater than 1.0 so as to obtain a fine-grain structure free of peripheral fissures and 'veiling'. Typically, a melt-grown essentially single macrocrystal of an ionic salt or of an optical oxide of aluminum or magnesium including certain optical mixed oxides such as bismuth germanium oxide, cadmium tungstate and lithium niobate, is hot press-forged while it is surrounded by a crystal powder of the same ionic salt or oxide. A polycrystalline extrudate of a melt-grown macrocrystal may also be hot press-forged in an analogous manner.

Hot press-forging of an optical body with dynamic constraint by crystal

A method is disclosed for hot press-forging a normally frangible optically integral crystalline mass ('optical body') in a closed die, by directly pressing a surface of the mass while it is peripherally surrounded by a crystal powder the amount of which is computed from the deformation ratio desired and the geometry of the die. The crystal powder is compacted by the nonuniformly directed forces transmitted to it by the optical body, and eventually the crystal powder is sufficiently dense so as dynamically to constrain the optical body at its peripheral surface. The dynamic constraint of the optical body while it is being forged is effected in such a way as to permit deformation of the optical body without fracturing it, and, without affecting its optical integrity. Hot press-forging the optical body by peripherally surrounding it with the crystal powder produces a stress environment in which the forces applied in a first stage, to the optical body by the ram of the forging press and, in a second stage, by the crystal powder, are non-uniform both in magnitude as well as in direction. The result is that the optical body may be deformed and forged to obtain a deformation ratio greater than 1.0 so as to obtain a fine-grain structure free of peripheral fissures and 'veiling'. Typically, a melt-grown essentially single macrocrystal of an ionic salt or of an optical oxide of magnesium including certain optical mixed oxides such as bismuth germanium oxide, cadmium tungstate and lithium niobate, is hot press-forged while it is surrounded by a crystal powder of the same ionic salt or oxide. A polycrystalline extrudate of a melt-grown macrocrystal may also be hot press-forged in an analogous manner.

A polycrystalline shaped article useful as a light-transmitting body or scintillation phosphor is formed from an essentially moncrystalline melt-grown macrocrystal ingot by pressing the ingot between opposed surfaces with no radial restraint, at a temperature below its melting point and under sufficient pressure to transform the ingot, in situ, into a fully dense, homogeneous, polycrystalline mass of unrestricted width. A polycrystalline shaped article useful as a light-transmitting and/or light-generating body may also be formed from a fully dense, homogeneous, optically integral polycrystalline mass by pressing the polycrystalline mass between opposed surfaces with no radial constraint, at a temperature below its melting point, but greater than one-half its melting point measured in degrees centigrade, under sufficient pressure to form a relatively larger polycrystalline mass of lesser height.

Shaped press-forged normally frangible inorganic crystals

A hot-pressed optical body which is free from absorption bands due to carbon dioxide, water, hydroxyl ion and acid fluorides in the ultraviolet, visible and near-infrared wavelength regions. Typically, the optical body is formed from a powder of an alkaline earth metal fluoride, alkali metal fluoride, or rare earth metal fluoride. One or more absorption bands due to a single impurity may be reduced or eliminated, or bands due to plural impurities may be reduced or eliminated sequentially, or simultaneously. The optical body is made by flowing a reactive, reducing gas, optionally, in combination with hydrogen fluoride gas, directly into the die cavity containing a pressable ionic fluoride powder, and either hot-pressing or extruding the powder.

Method of making an ionic fluoride optical body with reduction of

A hot-pressed optical body is disclosed which is free from absorption bands due to carbon dioxide, water, hydroxyl ion and acid fluorides in the ultraviolet, visible and near-infrared wavelength regions. Typically, the optical body is formed from a powder of an alkaline earth metal fluoride, alkali metal fluoride, or rare earth metal fluoride. One or more absorption bands due to a single impurity may be reduced or eliminated, or bands due to plural impurities may be reduced or eliminated sequentially, or simultaneously. The optical body is made by flowing a reactive, reducing gas, optionally, in combination with hydrogen fluoride gas, directly into the die cavity containing a pressable powder, and either hot-pressing or extruding the powder.

Hot-pressed ionic fluoride optical bodies free of absorption bands and

A polycrystalline shaped article useful as a light-transmitting body or scintillation phosphor is formed from an essentially monocrystalline melt-grown macrocrystal ingot by pressing the ingot between opposed surfaces with no radial restraint, at a temperature below its melting point and under sufficient pressure to transform the ingot, in situ, into a fully dense, homogeneous, polycrystalline mass of unrestricted width. A polycrystalline shaped article useful as a light-transmitting and/or light-generating body may also be formed from a fully dense, homogeneous, optically integral polycrystalline mass by pressing the polycrystalline mass between opposed surfaces with no radial constraint, at a temperature below its melting point, but greater than one-half its melting point measured in degrees centigrade, under sufficient pressure to form a relatively larger polycrystalline mass of lesser height. Wherever trace impurities in the order of about one part per million are detrimental, as in a scintillation phosphor, or where it is essential that a theoretically fully dense material, with no voids, be formed, as for example in a laser window, no method, other than press-forging a fully dense crystalline mass will suffice. In particular, windows may be press-forged which permit the transmittance of laser beams with less than 0.1% absorption, or no more absorption than is displayed by the archetype monocrystalline ingot, whichever is greater. In addition, press-forged windows are characterized by several times greater strength than that obtained with essentially single crystal ingots. Similarly, optically integral scintillation phosphors may be formed having large diameters which are theoretically not limited by the size of the largest essentially monocrystalline ingot which may be grown.

Growing community of inventors

Cleveland Heights, OH, United States of America

Herbert Packer