Abstract: A process for making an electroluminescent phosphor having a given emission spectra A, comprises the steps of manufacturing a beginning electroluminescent phosphor having an emission spectra B, different than A. A coating is applied to the phosphor having the emission spectra B to increase the resistance of the phosphor to the deleterious effects of moisture and change the emission spectra of the phosphor to emission spectra A. The application of the coating includes the steps of reacting a coating precursor with a mixture of oxygen and ozone.

Abstract: A composition and method are provided for reducing the persistence of yttrium tantalate x-ray phosphors having the monoclinic M' structure. Persistence is reduced by incorporating a tungsten additive into the phosphor. The phosphor preferably contains at least about 4 ppm W. The method for incorporating the tungsten additive consists of adding a tungsten containing compound to the mixture of raw materials formulated to make the phosphor and firing the mixture at a temperature and for a time sufficient to form the phosphor.

Abstract: An improved blue-green emitting ZnS:Cu,Cl phosphor is made by doping the phosphor with small amounts of gold and increasing the amount of low intensity milling between firing steps. The improved phosphor has better halflife and brightness characteristics while maintaining its desired emission color.

Abstract: A improved ZnS:Cu electroluminescent phosphor having a halflife of at least about 900 hours. The halflife improvement is made by doping the phosphor with minor amounts of gold and substantially increasing the amount of low intensity milling between firing steps. The improved phosphor has a dramatically longer halflife without sacrificing brightness or exhibiting large shifts in emission color.

Abstract: An electroluminescent phosphor composed of copper activated zinc sulfide having an average particle size less than 23 micrometers and a halflife equal to or greater than the halflife of a second phosphor having a similar composition and an average particle size of at least 25 micrometers.

Abstract: A method of making an unactivated yttrium tantalate x-ray phosphor containing an aluminum additive wherein a high brightness phosphor is obtained without the use of a lithium chloride containing flux. The method includes using a high surface area aluminum oxide as the source of the aluminum additive and a lithium sulfate flux.

Abstract: A coated electroluminescent phosphor which can be copper activated zinc sulfide, copper and manganese activated zinc sulfide or copper activated zinc sulfide-selenide is disclosed having a particle size of from less than about 5 micrometers in diameter to about 80 micrometers in diameter. The coating is from about 100 to about 400 angstroms in thickness, and consists essentially of aluminum oxide and is resistant to moisture and relatively chemically inert.

Abstract: A method for increasing the brightness and halflife of an electroluminescent phosphor by increasing the average particle size of the phosphor to greater than 25 micrometers in diameter.

Abstract: A phosphor composition consisting essentially of particles of zinc sulfide electroluminescent phosphor activated with from about 0.7% by weight of about 1.3% by weight of manganese, based upon the total weight of the phosphor composition, wherein the electroluminescent emission of the phosphor has an x color coordinate value of from about 0.522 to about 0.532 and a y color coordinate value of from about 0.460 to about 0.470 and an efficiency of greater than about 5.6 lumens per watt at 115V/400 Hz. A solid state process for producing the foregoing phosphor comprises a multiple firing in order to incorporate manganese, chloride and copper ions into the zinc sulfide lattice. Controlled levels of manganese yield highly efficient electroluminescent phosphors.

Abstract: A process is disclosed for producing tungstosilicic acid which involves adding sodium silicate to a first solution of sodium tungstate while assuring that the pH of the resulting mixture is from about 2 to about 6, the pH adjustments being made with a cation exchange resin on the hydrogen cycle, to produce a second solution. The solids are removed from the second solution which is digested at a temperature of greater than about 50.degree. C. and then contacted with a cation exchange resin on the hydrogen cycle to produce a third solution which is essentially a tungstosilicic acid solution containing at least about 99% by weight of the starting tungsten as tungstosilicic acid.

Abstract: A process is disclosed for producing an electroluminescent phosphor which comprises blending a chloride flux, a copper source, and zinc sulfide to form a relatively uniform admixture, heating the admixture at a temperature of from about 1000.degree. C. to about 1300.degree. C.

Abstract: In a method for producing tungsten hexachloride which comprises reacting tungsten with chlorine gas at a temperature sufficient to result in the conversion of the tungsten to tungsten hexachloride, the improvement comprising reacting tungsten in the form of pressed pieces to convert the pieces to tungsten hexachloride having an oxygen content of less than about 0.5% by weight with the rate of conversion to tungsten hexachloride being at least about 2.3 times greater than the rate of conversion when the tungsten is in an unpressed form.

Abstract: A process is disclosed for producing ammonium tetrathiomolybdate. The process involves reacting an ammoniacal molybdate solution with hydrogen sulfide gas, the solution and the gas being in a closed system and the flow of the gas being regulated at an elevated pressure to form a slurry consisting essentially of a solid essentially all of which is ammonium tetrathiomolybdate containing a portion of the starting molybdenum and a mother liquor containing the balance of the molybdenum. The slurry is then cooled to ambient temperature and the solid is removed from the major portion of the mother liquor. The solid is then washed with water and with alcohol followed by removal of the resulting respective water and alcohol washes to remove the remaining portion of the mother liquor and soluble impurities from the solid. The resulting washed solid is then dried at ambient temperature to form the final ammonium tetrathiomolybdate.

Abstract: A process is disclosed for recovering tungsten and rhenium from a tungsten and rhenium source. The process involves firing the source in an oxidizing atmosphere at a sufficient temperature for a sufficient time to convert the tungsten and rhenium to their respective oxides, to remove a portion of the rhenium as volatilized oxide, and to form a first fired material containing essentially all of the tungsten and the remaining portion of the rhenium, increasing the surface area of the resulting oxidized tungsten, and firing the first fired material in an oxidizing atmosphere at a sufficient temperature for a sufficient time to remove essentially all of the remaining portion of the rhenium as volatilized oxidized rhenium and to form an essentially rhenium-free oxidized tungsten.

Abstract: A process is disclosed for producing ammonium tetrathiotungstate. The process involves reacting an ammoniacal tungstate solution with hydrogen sulfide gas, the solution and the gas being in a closed system and the flow of the gas being regulated at an elevated pressure to form a slurry consisting essentially of a solid essentially all of which is ammonium tetrathiotungstate containing a portion of the starting tungsten and a mother liquor containing the balance of the tungsten. The slurry is then cooled to ambient temperature and the solid is removed from the major portion of the mother liquor. The solid is then washed with water and with alcohol followed by removal of the resulting respective water and alcohol washes to remove the remaining portion of the mother liquor and soluble impurities from the solid. The resulting washed solid is then dried at ambient temperature to form the final ammonium tetrathiotungstate.

Abstract: A process for converting tungsten bearing material to sodium tungstate by adding an oxidizing reactant in small increments to a heated mixture of fused sodium hydroxide and the tungsten bearing material while the temperature is maintained at from about 500.degree. C. to about 700.degree. C.

Abstract: A process is disclosed for recovering tungsten and rhenium from a relatively impure tungsten and rhenium solution. The process involves adjusting the pH of the solution to from about 9.0 to about 10.0 to precipitate impurities, and removing the impurities. The purified solution is adjusted to a pH of from about 0.5 to about 7.0 with a mineral acid. To the purified solution is added a solution containing sufficient hexamine to subsequently form a first hexamine tungsten solid containing the major portion of the tungsten. The hexamine solution is at essentially at the same pH as that of the pH adjusted purified solution. The resulting hexamine-tungsten-rhenium mixture is agitated at a sufficiently low temperature for a sufficient time to form the first solid and a first mother liquor containing the major portion of the rhenium. The first solid is separated from the first mother liquor.

Abstract: A process is disclosed for separating tungsten from a solution containing tungstate and perrhenate ions. The process involves reacting a sufficient amount of hydrochloric acid with the solution at a sufficient temperature to form a solid containing essentially all of the tungsten and a liquor containing essentially all of the rhenium, and separating the solid from the liquor.

Abstract: A process is disclosed for recovering tungsten and rhenium from a tungsten and rhenium bearing solution. The process involves adding sufficient hydrochloric acid to the solution to form a first precipitate containing essentially all of the tungsten and a first mother liquor having an acid concentration of at least about 1.25 normal, and containing the major portion the rhenium, followed by separating the first precipitate from the first mother liquor. A source of sulfide ions is then added to the first mother liquor with agitation for a sufficient time and with the amount of sulfide ions being sufficient to form a second precipitate containing essentially all of the rhenium which was in the first mother liquor, and a second mother liquor, followed by separation of the second precipitate from the second mother liquor.

Abstract: In a process for recovering rhenium, a starting material containing tungsten and rhenium is reacted with sodium hydroxide and an oxidizing reactant to form a fused solid. The fused solid is dissolved in water to solubilize the tungsten and rhenium values and then pass through an anion exchange resin to remove the rhenium values and form a solution containing the tungsten values. The resin is stripped to obtain the rhenium values from the resin.