Abstract:
A transparent polycrystalline body having high ultraviolet transmissivity is provided. The body is preferably a sintered magnesia-alumina spinel body having a transmittance of at least 85 percent in the wavelength range from 0.4 microns to 0.8 microns and a transmittance at some wavelength in the wave length range between about 0.2 and about 0.4 microns of at least about 85 percent and a porosity of less than about 0.001 percent. The sintered body is produced by a two-step method comprising forming a closed porosity body from a spinel powder and subjecting the closed porosity body to a hot isostatic pressure treatment. The resulting body has a high transmissivity of electromagnetic radiation in the range between about 0.2 microns and about 6 microns, is resistant to abrasion or erosion, does not substantially deteriorate after exposure to ultraviolet light, and has high strength. The sintered body is useful in a variety of applications, including as a dome and window for missiles and launch tubes.
Abstract:
A tooth crown or the like dental appliance made of a fired ceramic which undergoes substantially no shrinkage when fired, the appliance being made by forming a compact of the raw pre-fired ceramic with an undersurface shaped for a precise fit onto the prepared tooth on which the appliance is to be used, and thereafter firing the compact to dense, hard monolithic structure.
Abstract:
A transparent polycrystalline body having high ultraviolet transmissivity is provided. The body is preferably a sintered magnesia-alumina spinel body having a transmittance of at least 85 percent in the wavelength range from 0.4 microns to 0.8 microns and a transmittance at some wavelength in the wavelength range between about 0.2 and about 0.4 microns of at least about 86 percent and a porosity of less than about 0.001 percent. The sintered body is produced by a two-step method comprising forming a closed porosity body from a spinel powder and subjecting the closed porosity body to a hot isostatic pressure treatment. The resulting body has high transmissivity of electromagnetic radiation in the range between about 0.2 microns and about 6 microns, is resistant to abrasion or erosion, does not substantially deteriorate after exposure to ultraviolet light, and has high strength. The sintered body is useful in a variety of applications, including as a dome and window for missiles and launch tubes.
Abstract:
A tooth crown or the like dental appliance made of a fired ceramic which undergoes substantially no shrinkage when fired, the appliance being made by forming a compact of the raw pre-fired ceramic with an undersurface shaped for a precise fit onto the prepared tooth on which the appliance is to be used, and thereafter firing the compact to dense, hard monolithic structure.
Abstract:
A method for making cast precision epoxy resin bodies and an epoxy resin formulation for use therein, the epoxy resin formulation having Component A consisting essentially of from 40 to 70% by weight epoxy novolac polymer, from 30 to 50% by weight vinyl -3-cyclohexene diepoxide and from 0 to 20% by weight 3.4 epoxy cyclohexylmethyl -3,4-epoxy cyclohexane carboxylate and Component B consisting essentially of partially hydrolyzed aryl tetracarboxylic acid dianhydride, preferably partially hydrolyzed pyromellitic acid dianhydride. in the preferred embodiments a tertiary amine catalyst is also included. These components are mixed, just before use, in a ratio of from 20 to 50 parts by weight Component B to each 100 parts by weight Component A. To make the cast precision bodies such mixture is cast in a mold of the shape desired, allowed to cure to a solid body while in the mold, and thereafter heated to cause permanent expansion thereof at least sufficient to compensate for any shrinkage occurring during the casting and hardening thereof while in the mold.
Abstract:
Le corps polycristallin ayant un facteur élevé de transmission des ultraviolets est de préférence un corps fritté en spinelle d'alumine-magnésie ayant un facteur de transmission d'au moins 85 % dans la gamme des longueurs d'ondes comprises entre 0,4 et 0,8 microns et un facteur de transmission à certaines longueurs d'ondes dans cette gamme entre 0,2 environ et 0,4 microns environ d'au moins 86 % environ et une porosité inférieure à 0,001 % environ. Le corps fritté est produit par un procédé en deux étapes consistant à former un corps à porosité fermée à partir d'une poudre de spinelle et à soumettre le corps à porosité fermée à un traitement chaud sous pression isostatique. Le corps obtenu possède un facteur de transmission élevé d'un rayonnement électromagnétique dans la plage comprise entre 0,2 microns et 6 microns environ, est résistant à l'abrasion ou à l'érosion, ne se détériore pratiquement pas après avoir été exposé à la lumière ultraviolette, et est très solide. Le corps fritté est utile dans une grande variété d'applications, y compris en temps que dôme et fenêtre pour des missiles et des tubes de lancement.
Abstract:
Un projectile pour munitions en céramique (10) est particulièrement utile pour des munitions d'entraînement ou utilisées contre des cibles. Le projectile est constitué de préférence en zircone qui est densifié par un procédé de frittage sans pression. Le projectile possède une résistance suffisante pour supporter les accélérations et les couples engendrés au moment où le projectile est tiré et pendant sa trajectoire.