PROCESS FOR PREPARING HIGH PURITY ALUMINUM NITRIDE

Abstract: Process for producing high purity aluminum nitride by reacting aluminum sulfide with gaseous ammonia or gaseous nitrogen and hydrogen at a temperature above 1100<o>C. When using gaseous ammonia the preferred reaction conditions are at about 1200<o>C to 1500<o>C and at about atmospheric pressure for about 2-30 hours. When gaseous nitrogen and hydrogen are used the preferred reactin conditions are at about 1200<o>C to 1750<o>C and at pressures above atmospheric for about 2-30 hours. A high purity, low oxygen containing, free flowing powder is produced.

Description: PROCESS FOR PREPARING HIGH PURITY ALUMINUM NITRIDE The present application is a continuation in part of U.S. Patent Application Serial No. 727,993, filed April 29, 1985, entitled "Process for Preparing High Purity Aluminum Nitride". FIELD OF THE INVENTION This invention relates to the preparation of high purity aluminum nitride from ammonia, nitrogen, hydrogen or oxygen. BACKGROUND OF THE INVENTION Aluminum nitride can be prepared by a number of methods. Previous methods of preparation are briefly discussed below. One method utilizes carbothermic reduction of alumina under nitrogen atmosphere according to the following reaction AI2O3 + 3C + N2 >-2AlN + 3C0 (1) This process is said to. produce 98% A1N continuously. The major impurities of the product are said to be oxygen and carbon. Cooper, C.F., George, CM., and Hopkins, S. .J., "Preparation and Oxidation of Aluminum Nitride", In Special Ceramics 1962, Ed. by P. Popper, Published by the British Ceramic Association (1963). All figures given in % herein are weight %. Russian Patent 217,298 teaches the production of aluminum nitride from aluminum containing minerals with carbon in an N2 atmosphere in the presence of sulfur. Sulfur is used in the carbothermic reduction to assist in the removal of metallic impurities such as silicon and titanium. The amount of sulfur should not exceed that required to remove the metallic impuri¬ ties as monosulfides to prevent the sulfur from reacting with the aluminum. Shalom tried to use the same reaction to obtain aluminum oxynitride (A10N; 5AlN*9Al2θ3) . The product obtained, however, was always an impure AlN when the reactants were mixed in stoichiometric amount (i.e., one AI2O3 to three C). The major impurity was again carbon. Moshe Ish-Shalom, "Formation of Aluminum Oxynitride by Cabothermal Reduction of Aluminum Oxide in Nitrogen", J. Material Science Letters, 1, 147-149 (1982). Kuramoto and Taniguchi also used the same reaction but they were able to reduce the carbon impurity to 0.15 percent level by a careful low temperature oxidation process. The resulting powder, however, contained less than 240 pp metallic impurities and about 1.0 percent oxygen. Nevertheless, the powder was hot pressed or sintered to greater than 99 percent of the density using CaO as sintering aid. N. Kuramoto, H. Taniguchi, "Transparent AlN Ceramics", Ibid, 3, 471-474 (1984). In U.S. Patent 3,307,908 to Mandorf, aluminum metal in a finely divided carrier material such as AlN, A1F, or a mixture of the two Mandorf teaches against the presence of H2S since it interferes with the nitriding reaction. To prepare ultrafine AlN powder and to avoid the carbon impurity Hock and Nair used AMOH)3 and amorphous AI2O3 powders prepared from the hydrolysis of aluminum alkoxide to react with NH3 AI2O3 + 2NH3 »-2AlN + 3H20 (2) To avoid grain growth, the reaction was carried out at low temperatures (between 800-1350°C). Although the reaction produced AlN, the amount present in the product was generally less than 80 percent. The main impurities were various poly orphs of AI2O3. Hoch, M. and Manikantar Nair, K. , "Preparation and Characterizatio of Ultrafine Powders of Refractory Nitrides: I, AlN and Si 3 N 4 ", Cer. Soc. Bull _58_, [2], 187-190 (1979). U.I. Myakinenkov et al teaches the use of volatile compounds of aluminum with nitrogen compounds to form films of AlN. The particular system described uses an organic compound of aluminum (triethyl aluminum, boiling point 194°C) with hydrazine in a carrier gas. Reaction temperatures are 750°-1100°C. Inorganic Materials, Vol. 10, No. 10, p. 1635-1636, Oct. 1974 (Publ. March 1975). Direct reaction of aluminum with nitrogen according to the reaction 2 Al + 2 -*-2AlN (3) is an exothermic reaction. This reaction is particularly suitable for large scale AlN production. The product of reaction (3) is a highly sintered mass. As a result, the grinding of the product is required. This grinding process itself can introduce impurities. Another common impurity of this reaction is unreacted aluminum metal. Cooper et al., used about 1 wt.% LiF as a catalyst to improve the kinetics of reaction (3) . LiF was most effective compared to NaF, KHF2 and AIF3. Although they obtained relatively pure AlN powder (99.7 AlN that contained 0.009% free Al) the powders were not sinterable. Cooper, C.F., George, CM., and Winter, L. , Aluminum Nitride Crucibles: Raw Materi¬ als Preparation, Characterization and Fabrication, in Special Ceramics, Vol. 4., Ed. by P. Popper, Pub. by the British Ceramic Research Association, 1-3 (1968). In earlier work Cooper et al (1963 above) used reaction (3) to obtain 99.8-99.9% pure AlN by levitating the reacting pear-shaped high purity aluminum ball in an electromagnetic field. A variation of the method involves vaporizing aluminum by striking a d.c. arc between two aluminum electrodes in a nitrogen atmosphere. About 80 percent of the AlN product forms as hard lumps on the electrode surfaces, the remaining 20 percent deposited as a fine, reactive powder in the reaction chamber. The analysis of the lumps showed that product contained 92-94 percent AlN. The fine powder contained about 25% AlN. The remaining portions considered to be free aluminum and AI2O3 impurities which are presumed to form as a result of O2 leakage into the chamber. Heat treating these powders in vacuum at high temperature reduced their oxygen impurity and their reactivity to moisture. Long, G. and Foster, L.M., "Aluminum Nitride, Refractory for Aluminum to 2000°C", J. Amer. Soc. _42_, 53-59, (1959). Sato and Iwata used the same technique of Long and Foster but they varied, the nitrogen pressure. The maximum yield obtained (about 0.6 grams/hour) was.between 4 and 6 atmospheres of nitrogen pressure. By heat treating the powder in vacuum at 1800°C, in the same manner described by Long and Foster, they reduced the oxygen content to 0.82 percent and other impurities to 0.01 percent level. Sato, T. and Iwata, M. , "Preparation of AlN by Electric Arc Method", Nippon Kagaku Kaishi, 1869-1873, (1973). Other techniques used include thermal decomposition of AICI3NH3 complex and reduction of A1P by ammonia. These methods are likely to result in chlorine or phosphorous impurities in the AlN powder. S. Iwama describes a process for producing ultrafine powders of AlN by a reactive gas evaporation technique. Powdered aluminum nitride is produced by evaporating aluminum in an ammonia gas. An electron beam is used for heating. Use of nitrogen gas does not result in aluminum nitride. Journal of Crystal Growth 56 (1982) p. 265-269. Recently, Huseby described a method which involves the reaction of AIF3 and NH3 as shown in reaction (4) A1F 3(S) + NH 3(g ) *-AlN( s , + 3HF (g) (4) The particles of AlN powder produced by this method were rod shaped ranging in size from 1-10 microns. The oxygen content varied from 0.17 to 0.30 percent. Huseby, I.C., "Synthesis and Characterization of a High-Purity AlN Powder", J. American Cer. Soc. 66[3] , 217-220 (1983). AlN is an electrically insulating ceramic material with very high thermal conductivity (> 80 W/mK). To prepare such ceramics, however, it is required that the oxygen impurity must be reduced to the lowest possible level. A new process for reacting AI2S3 with NH3 or 2 and H2 to produce high purity AlN is revealed below. The use of aluminum sulfide as the precursor material has not been previously reported to the knowledge of the inventor and represents a novel approach. BRIEF DESCRIPTION OF THE INVENTION The invention uses the reaction of aluminum sulfide with ammonia gas or nitrogen gas and hydrogen gas to obtain aluminum nitride. BRIEF DESCRIPTION OF THE DRAWING The drawing depicts a furnace arrangement used for controlled atmosphere thermal treatments. DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENT The method described in the present invention uses the reaction between aluminum sulfide and ammonia to produce aluminum nitride according to the reaction AI2S3 + 2NH 3 »-2AlN + 3H 2 S (5) or reaction between nitrogen, hydrogen and aluminum sulfide according to the reaction AI2S3 + N2 + 3H2 ^-2A1N + 3H2S (6) To obtain high purity aluminum nitride, it is necessary to use high purity aluminum sulfide and react it with an ammonia or nitrogen, hydrogen atmosphere that has been rigorously purified to remove oxygen contamination. These reactions must be activated by heat or other means so they are normally carried out at temperatures in excess of 900°C EXAMPLE 1 An impure 0.5 g aluminum sulfide sample with a high oxygen content was placed in an alumina (AI2O3) boat which was then placed in a quartz tube in a horizon¬ tal tube furnace. The quartz tube was arranged so that flexible tubing could be attached to each end. At one end, gas was introduced and allowed to flow over the sample then out the other end, where it passed through a bubbler. After the aluminum.sample sulfide was placed in the (22°C) furnace, the apparatus was purged at room temperature with a high flow of ammonia (200 cc/ in for 10 minutes). The flow rate was then adjusted to 30 cc/min and the sample heated to 1050°C at a heating rate of 5°C/min, held at 1050°C for 3 hours, then cooled at approximately 2°C/min to room temperature while maintaining the flow of ammonia. The resulting powder was determined to be aluminum oxynitride by x-ray diffraction. This example illustrated that higher purity aluminum sulfide is needed to prepare the aluminum nitride. The oxygen present was not reacted and removed by the ammonia but remained in the aluminum oxynitride product. EXAMPLE 2 Reaction Between AI2S3 and NH3 A 7.42 gm sample of I2S3 was loaded into a sealed tube furnace in a molybdenum boat taking care to minimize contact with the ambient room atmosphere; then the furnace was evacuated with a diffusion pump. The sample was then heated under vacuum up to 200°C when the atmosphere was replaced with ammonia (NH3). The gas flow was maintained at 2cc per minute and the . heating rate controlled at about 7°C per minute until the sample reached 650°C. The heating rate was reduced to 3°C per minute until 700°C where the sample was held for 1 hour 30 minutes. Heating was restarted at 7°C per minute up to 1250°C where the sample was held for 21 hours. The sample was allowed to cool under the ammonia atmosphere to room temperature then removed for analysis. A fine powdery product resulted which x-ray diffraction showed to be AlN. A high quality, vacuum-tight glove box was used to store and manipulate the aluminum sulfide powder. To carry out the controlled atmosphere thermal treatments, a special apparatus was constructed (see Drawing). This consisted of a molybdenum wound tube furnace 100, with a high density alumina tube 101 passing through the furnace hot zone. Vacuum tight, stainless steel end plates 102,103,104 were attached to each end of the tube 101. Stainless steel tubing 105,106,107,108 was connected to the end plates 102-104 so that the sample atmosphere could be evacuated then replaced with a flowing controlled atmosphere. Tube 106 is really a T fitting that allows flow through either ' a bubbler 109 or flexible bellows 110 exhaust means not shown. Valves, of which valve 111 is typical, are used to control gas flow in the apparatus. Samples may be placed at sample points 112 and 113. Thermocouples, not shown, were connected through a gland of one end plate 102, one of which was used to monitor the temperature and the other to monitor a reference sample of aluminum nitride. Gas from a gas supply (not shown) enters at 114,115. Because aluminum sulfide is sensitive to atmospheric water vapor the powder used in this work was received from the supplier in sealed glass ampoules. The sealed ampoules were placed in an argon glove box before being opened. Once the ampoules were opened, the aluminum sulfide was stored in the glove box and the material for each experiment was weighed into a molybdenum boat in the glove box. To limit contact with the ambient atmosphere, the aluminum sulfide samples were placed in a plastic box before being removed through the airlock of the glove box. . After loading, a vacuum was applied to the sample chamber and the sample heated to 150°C The tube 101 was then filled with the desired atmosphere and a slow flow rate established. The furnace 100 was then heated at a controlled rate to the desired tempera¬ ture and held for the required time. The time was calculated from the time the hold temperature was reached until the furnace was switched off. Cool-down followed the expected exponential decay. Oxygen, nitrogen, and sulfur analyses were performed using an inert gas fusion technique. Surface analysis of some powders was performed using Electron Spectroscopy for Chemical Analysis (ESCA). X-ray diffraction spectra were collected on a standard Norelco diffractometer with a vertical axis goniometer, spinning sample holder, and theta compensation slits. Several tests were made using ammonia that are summarized in Table 1. X-ray diffraction (XRD) spectra were measured on all samples and those above 1000°C gave good agreement with the JCPDS reference pattern (25-1133) for aluminum nitride. The pattern from the 1250°C run is compared to the reference pattern in Table 2. All of those lines not accounted for by aluminum nitride are due to a minor alpha alumina impurity ( JCPDS 10-123). The only significant differences between the XRD patterns of the samples treated at 1100°C and above are in the line widths of the diffraction peaks which indicate a very fine crystal grain size. TABLE 1. EXPERIMENTS PERFORMED AS A -FUNCTION OF TIME, TEMPERATURE, AN0 ATMOSPHERE Time Temperature (hours) (°C) Atmosphere 22 1450 Ammonia 22 1350 Ammonia 22 1300 Ammoni 21 1250 Ammonia 17 1100 Ammonia 4 1100 Ammonia 2 1100 Ammonia 20 1000 Ammoni 46 900 Ammonia 16 900 Ammonia TABLE 2. COMPARISON OF THE XRD PATTERN OF THE SAMPLE HEATED AT 1250°C FOR 21 HOURS WITH THE REFERENCE XRO PATTERNS FOR ALUMINUM NITRIDE AND ALPHA ALUMINA Samp1e Pattern Reference AlN Resealed Reference A1 2 0 3 d Int d Int Int —a™ ■ -mr (A) (%) (A) (*) (%) (A) (*) 3.5 11 75 3.499 75 2.7 100 2.69 100 2.55 15 94 2.55 90 2.49 53 2.49 60 2.37 69 2.37 80 2.09 16 100 2.085 100 1.83 21 1.829 25 1.72 6 36 1.74 45 1.6 ' 14 84 1.6 80 1.56 34 1.56 40 1.41 23 1.41 30 1.38 5 34 1.374 50 1.35 3 1.35 5 1.32 14 1.32 25 1.30 6 1.30 10 1.19 7 44 1.189 8 The variation of the line width at half height of the 110 peak as a function of treatment temperature is summarized in Table 3. Even at temperatures in excess of 1300°C and times of 20 hours, the basic 5 grain size is still in the region of 2000-3000 anstroms. The size of the majority of the particles observed in an electron microscope is much larger, with a wide distribution of sizes. The particles are all fully dense and with no internal porosity. The AI2O3 XRD 10 peak intensity does not vary systematically with treatment temperature and is most likely a function of the level of exposure of the sample to atmospheric water vapor prior to firing. The effect of reaction time, however, can be clearly seen in the difference in XRD line 15 width for the 1100°C samples. The low temperature range was examined because visual observation of the silicone oil gas bubbler showed that a cloudiness occurs when an ammonia atmosphere is being used and the sample temperature is above 700°C. This cloudiness clears during the course of the experiment. TABLE 3. LINE WIDTH OF THE 110 PEAK OF ALUMINUM NITRIDE AS A FUNCTION OF TREATMENT TEMPERATURE Treatment Temperature Line Width (°C) (deg 2θ) 1450 0.3 1300 0.45 1250 0.45 1100 (17 hours) 0.65 1100 (4 hours) 0.9 1000 ' . • 2.0 Chemical analyses of powders prepared between 900°C and 1300°C were obtained for oxygen, nitrogen, and sulfur and the results are presented in Table 4. These results should be treated with caution because the total varies between approximately 90 and 110 percent, when stoichiometric amounts of aluminum are added to the totals. There is a trend in the 1100°C samples—the oxygen content increases with reduced time at temperature. This combined with the effect of time on the crystallite size suggests that at the shorter times the reaction is not complete. One sample ( 1250°C and 21 hours) was analyzed for metallic impurities by spark source mass spectrometry and the elements which were detected are given in Table 5. We also analyzed some samples with ESCA to determine whether the oxygen is uniformly distributed through the powder or is concentrated at the surface. The ESCA results show a high level of oxygen contamination on the surface of the powders analyzed—in the region of 30 weight percent for most powders analyzed. This suggests that most of the oxygen content is on the surface of the powders and is consistent with the oxygen being incorporated by a surface reaction during handling of the powders. TABLE 4. OXYGEN NITROGEN AND SULFUR CONTENTS OF AlN SAMPLES Time Temperature Nitrogen Oxygen Sulfur (hours) (°C) (*) <*) (*) 22 1300 28.5 4.5 0.17 28 1100 28.7 8.9 1.09 4 1100 27.2 9.5 1.87 2 . 1100 27.8 10.6 1.70 . 20 1000 24.9 12.6 4.40 22 900 24.3 11.2 10.30 TABLE 5. METALLIC IMPURITIES IN ALUMINUM NITRIDE PREPARED AT 1250°C FOR 21 HOURS IN AMMONIA Element ppm Element ppm Element ppm L1 20 B 20 - Na 600 Mg 400 S1 600 P 0.4 Cl 1.5 K 100 Ca 10 T1 4 V 0.4 Cr 2 Mn 6 Fe 20 N1 1 Cu 200 Zn 0.2 Sr 10 Nb 4 Mo 20 Cs 10 Ba 400 Ce 20 W 2 Aluminum nitride can be prepared by the reaction of aluminum sulfide with ammonia at temperatures above 1100°C. Below 1100°C, reactions occur but the product is not pure aluminum nitride, although the x-ray diffrac- tion pattern is very similar. Even reaction times of up to 46 hours at 900°C were not sufficient to Complete the reaction. At 1100°C and above, aluminum nitride is the product of the reaction between aluminum sulfide and ammonia and the product has a crystallite size in the range which causes x-ray line broadening. These grains are formed into dense agglomerates with a wide range of particle size which should give a high packing density in green bodies. The oxygen content of the most pure sample is 4.5 weight percent which is higher than the required level. A major source of oxygen contamination is the transfer step between the glove box and the furnace and .during the sealing of the furnace. In this part of the process, the aluminum sulfide was exposed to ambient air with consequent reaction between water vapor and the aluminum sulfide to form an aluminum oxide impurity which remains in the final product. Other possible sources of oxygen contamination are (1) water vapor in the reactant gases, (2) oxygen in the reactant gases which will react with the aluminum sulfide at high temperatures and (3) reaction of the product aluminum nitride with atmospheric water ' vapor prior to analysis. Each of these potential sources of impurity are capable of being overcome by appropriate design of the equipment and experimental procedures. EXAMPLE 3 Reaction Between AI2S3 and a Mixture of H2 and 2 A 1.7 gm sample of AI2S3 was loaded into a sealed tube furnace in a molybdenum boat taking care to minimize contact with the ambient room atmosphere; then the furnace was evacuated with a diffusion pump. The sample was then heated under vacuum up to 200°C when the atmosphere was replaced with a mixture of 75% H2 and 25% N2. The gas flow was maintained at 2cc per minute and the heating rate controlled at about 7°C per minute until the sample reached 700°C The heating rate was then reduced to 3°C per minute between 700°C and 800°C Above 800°C the sample was heated at 7°C per minute to 1350°C and held for 19.5 hours. The sample was allowed to cool under the H2:N2 atmosphere to room temperature then removed for analysis. A fine powdery product resulted which x-ray diffraction showed to be AlN. The samples are purified of contaminating sulfur molecules by the continuous flow of gases. The equipment and general procedures were the same as described for Example 2. To further increase purity all sources of contaminants such as the tube etc. could be made • of or lined with AlN. In general, the process may be described as a process for producing high purity aluminum nitride by providing a supply of aluminum sulfide; providing a supply of gaseous reactants of ammonia or gaseous nitrogen and hydrogen; and reacting the aluminum sulfide with the gaseous reactants at a temperature above 900°C and at a pressure and for a time adapted to produce high purity aluminum nitride. While reaction (5) will proceed at temperatures above 1100°C a te pera- ture range of about 1200°C to 1500°C is preferred. The pressure is preferably at about atmospheric pressure although a higher pressure may increase the reaction rate. Although the specific example gives a reaction time of 21 hours, the reaction time will vary depending on operating conditions above or below 1250°C, the pressure used and the degree to which the reaction is required to go to completion. To achieve reasonable rates of reaction, reaction times of 2-30 hours are preferred. Reaction (6) also requires temperatures above 1100°C with a temperature range of about 1200°C to 1750°C being preferred. The pressure may be at atmospher¬ ic pressure although higher pressures are preferred. The reaction rate is thereby increased and the reaction products are favored since four moles of reacting gases produce three moles of H2S. Although the specific example gives a reaction time of 19.5 hours, the reaction time will vary depending on operating conditions above or below 1350°C, the pressure used and the degree to which the reaction is required to go to completion. To achieve reasonable rates of reaction, reaction times of 2-30 hours are preferred. A powder, of a fine texture, that is adapted to give adequate reaction rates and adapted to produce suitable sintering charac- teristics as a final product should be chosen for the supply of aluminum sulfide. By appropriate selection and control of feed materials and apparatus a high purity aluminum nitride of low oxygen content can be produced. The oxygen content can be below 0.1% oxygen. The precursor aluminum sulfide material can be prepared by reacting aluminum with sulfur or H2S as shown by reactions (7 ) and (8 ) 2A1 + 3S *-Al 2 S3 (7) 2A1 + 3H 2 S ».A1 2 S 3 + 3H (8) Methods for reactions (7) and (8) are further described in Ferrante, M.J. , Stre, J.M. Ko, H.C, and Brown R.R., "Thermodynamic Properties of Aluminum Sulfide (AI2S3) High Temperature Science, 14, 91-101 (1981); Comprehensive Inorganic Chemistry, Ed. by J.C. Bailar, et al, Vol. 1, 1037, Pergamon Press (1973); and Handbook of Preparative Inorganic Chemistry, Vol. 1, 2nd Ed., p. 823, Ed. by George Brauer, Academic Press (1963). 5 An advantage of the process by using reactions (5) or (6) and (7) or (8) is that there are no oxygen ■») or carbon containing compounds involved in the reactions. The process thus offers the ability to prepare aluminum nitride without these impurities. In all of the above 10 reactions special precautions should be taken to prevent oxygen or moisture from entering the system before or during the reactions. Also, the aluminum sulfide, ammonia, and hydrogen must be protected at all times from contamination by oxygen, moisture or other impurities. 15 Further advantages of using reaction (6) for producing aluminum nitride are that at temperatures above 900°C NH3 tends to dissociate into N2 and H2; nitrogen and hydrogen are cheaper than ammonia, and nitrogen and hydrogen can be obtained and kept in 20 higher purity than ammonia with less O2, H2O vapor or other possible gaseous impurities. While the forms of the invention herein disclosed constitute presently preferred embodiments, many others are possible. It is not intended herein to mention 25 all of the possible equivalent forms or ramifications of the invention. It is to be understood that the terms used herein are merely descriptive rather than limiting, and that various changes may be made without departing from the spirit or scope of the invention.

Claims: CLAIMS I Claim: 1. A process for producing high purity aluminum nitride comprising: a. providing a supply of aluminum sulfide; b. providing a supply of gaseous ammonia; and c. reacting the aluminum sulfide and gaseous ammonia at a temperature between 1100-1500°C, and at a pressure and for a time adapted to produce a powdered high purity aluminum nitride. 2. The process of Claim 1 further comprising reacting the aluminum sulfide and gaseous ammonia at about atmospheric pressure and for a time period- of about 2-30 hours. 3. The process of Claim 1 further comprising reacting the aluminum sulfide and gaseous ammonia at a pressure higher than atmospheric pressure and for a time period of about 2-30 hours. 4. The process of Claim 1 further comprising: providing the supply of aluminum sulfide as a powder and producing a high purity powdered aluminum nitride. 5. A process for producing high purity aluminum nitride comprising: a. providing a supply of aluminum sulfide; b. providing a supply of gaseous nitrogen and hydrogen; and c. reacting the aluminum sulfide and gaseous nitrogen and hydrogen at a temperature above 1100°C, and at a pressure and for a time adapted to produce a powdered high purity aluminum nitride. 6. The process of Claim 5 further comprising reacting the aluminum sulfide and gaseous nitrogen and hydrogen at a temperature range of about 1300°C to 1750°C, at about atmospheric pressure and for a time period of about 2-30 hours. 7. The process of Claim 5 further comprising: reacting the aluminum sulfide and gaseous nitrogen and hydrogen at a temperature of about 1200°C to 1750°C, at a pressure higher than atmospheric pressure and for a time period of about 2-30 hours. 8. The process of Claim 5 further comprising: providing the supply of aluminum sulfide as a powder and producing a high purity powdered aluminum nitride.

Inventors: SEKERCIOGLU IBRAHIM, SEKERCIOGLU, IBRAHIM
Applicants: BATTELLE DEVELOPMENT CORP, BATTELLE DEVELOPMENT CORPORATION
Application year: 1986
Main classification: C01B21
IPC codes: C01B21