Method of making metal nitride powders

Description: TECHNICAL FIELD [Detailed description of the invention]

Metal nitride powder Technical field The present invention relates to a method for producing a metal nitride powder. Background technology In recent years, non-oxidizing ceramics such as metal nitrides and metal carbides with high temperature strength and corrosion resistance There is growing interest in mixes. Among these metals, aluminum nitride (AlN) is especially important due to its unique physical properties. For example, the thermal conductivity of AlN The rate is about the same as metal and alumina (Al₂O₃) Is more than 10 times, and the coefficient of thermal expansion is Comparable to kon and silicon carbide, high electrical resistivity, mechanical strength is also alumina Comparable to ceramics. The metal nitride powder can be produced by various methods. For example, Al₂O₃, Zirconia (ZrO)₂) Or titania (TiO₂) And other metal oxide powders Mix with excess charcoal powder and heat at a temperature of 1100 ° C or higher in a nitrogen-containing atmosphere To do. However, the metal nitride powder obtained by this method has the characteristics of the metal nitride powder. Unreacted carbonaceous powder that deteriorates is mixed. Unreacted carbonaceous powder is metal nitriding It can be removed by oxidizing the object at a temperature in the range of about 600 ° C to about 700 ° C. Shi However, at this temperature, even a part of the metal nitride powder is oxidized. U.S. Pat. No. 4,975,260 granted to Imai et al. Is a metal oxide. Or metal hydroxides and ammonia (NH₃) And a mixture of hydrocarbons and 130 It discloses a method for producing a metal nitride by reacting at a temperature of 0 ° C to 1600 ° C. .. Although this method is slightly improved over the conventional method, it is still in the metal nitride. Carbon remains. Moreover, it requires a temperature of at least 1300 ° C. All conjunction During the process, it is desirable to keep energy consumption as low as possible. Therefore, there is an industrial demand for a method for producing metal nitride powder at a relatively low temperature. To. Disclosure of invention The present invention provides a method for producing a metal nitride powder at a relatively low temperature. .. One aspect of the present invention includes a method for producing a metal nitride. Al, Ti or Reactant powder containing Zr oxide or Al, Ti or Zr hydroxide Heat to the reaction temperature in an atmosphere that does not participate in the reaction. Heated reactant powder, Contact with gaseous reactant mixtures containing nitrogen and carbon sources. Gas reactants The molar ratio of nitrogen to carbon in the mixture is at least about 15. Reactant powder , A part of which is kept at the reaction temperature for a sufficient time to be converted into a metal nitride powder. Another aspect of the present invention is an AlN powder or TiN powder produced by the method described above. Includes powder or ZrN powder. These and other features and advantages of the present invention are further enhanced by the description below and the accompanying figures. Let's be clear. A brief description of the drawing FIG. 1 is a diagram showing an apparatus used for producing the powder of the present invention. Figure 2 shows the X-ray diffraction of the AlN powder of the present invention produced by the reaction at 1050 ° C for 3 hours. It is a pattern. FIG. 3 shows the X-ray diffraction pattern of the TiN powder of the present invention produced by the reaction at 950 ° C for 3 hours. It's a turn. FIG. 4 shows the X-ray diffraction of the ZrN powder of the present invention produced by the reaction at 1100 ° C. for 9 hours. It is a pattern. The best mode for carrying out the invention According to the method of the present invention, AlN powder, TiN powder, ZrN powder at a relatively low temperature. Powder or YN powder can be produced. Starting point for producing nitride powder The quality is an oxide or hydroxide of Al, Ti, Zr or Y, for example Al₂O₃, TiO₂, TrO₂, Y₂O₃, Al (OH)₃, Ti (OH)₄, Zr (OH)₄Or Y (OH)₃And so on. In the following parts of the specification, Al₂O₃The method of the present invention will be described with respect to the case where AlN powder is produced from powder. But However, the following description is Al, Ti, Zr or Y if the reaction temperature is adjusted appropriately. From oxides or hydroxides of AlN powder, TiN powder, ZrN powder or YN Those skilled in the art will understand that it can also be applied to methods for producing powders. To produce AlN powder by the method of the present invention, Al₂O₃Appropriate reaction strip of powder Contact with gaseous reactant mixtures. Gas Reactant Mixtures Nitrogen Sources and Carbon Contains the source. NH₃Is a nitrogen source and CH₃If is a carbon source, the reaction is as follows Can be noted. Al₂O₃(s) + 2NH₃(g) + 3CH₄(g) 2AlN (s) + 3CO ( g) + 9H₂(g) Al₂O₃The powder is γ-Al produced by the sol-gel method.₂O₃Or Al₂O₃Such Al with a large surface area₂O₃Any powder may be used. Appropriate γ-A l₂O₃Can be purchased from distributors such as Alpha Products (Danverse, MA) .. Al used in the present invention₂O₃There is no limit to the particle size of the powder. Preferably Al₂O₃The particle size of the powder should be completely reacted with the gaseous reactant mixture to form an AlN powder. The particle size is appropriate so that Sol-gel Al₂O₃Issued on December 17, 1992 by the same applicant as the present application. Manufactured by the method described in Applicable U.S. Application No. 07 / 991,929. Can be done. Aluminum isopropoxide [Al (OiC)₃H₇)₃] Is For example, it can be dispersed in water heated to about 75 ° C, and Al (OiC)₃H₇)₃The molar ratio of water to water may be any molar ratio suitable for forming a sol. For example Al (OiC₃H₇)₃The molar ratio of water to water is about 1: 100 to about 1: 100. It is in the range of 0. Appropriate Al (OiC₃H₇)₃Is alpha products etc. Can be purchased from the seller. A small amount of HNO in the sol₃Or add other acids for the first p You may set H to about 3 and start the reaction. Becomes sufficiently viscous Acidified sol For example, it may be left for about 12 hours. Do not heat, freeze dry, vacuum dry or spray dry The gel can be powdered by any conventional method. Sufficient time after producing the powder Dry the powder and partially Al₂O₃To make it easier to handle May be good. Then, take enough time to bake this powder and Al₂O₃Even if converted to Good. For example, the powder may be baked in a He atmosphere for 30 minutes at about 500 ° C. This The powder can also be baked in the air. Induction of any reactive nitrogen compound if the nitrogen source is a gas under the reaction conditions It may be the body. For example, NH as a nitrogen source₃, N₂H₂Or N₂Can be mentioned. Easy to obtain Anhydrous NH as a nitrogen source because it is functional and easy to handle₃Is preferable. NH₃Is aero Numerous suppliers such as Allgas Company (Hartford, Connecticut) You can buy more. Nitrogen sources cause side reactions and have other effects on the nitrogenization reaction Those that do not contain impurities such as swelling are preferable. The carbon source must be a gaseous carbon-containing compound under the reaction conditions. .. For example, the carbon source includes hydrocarbons or amines. Reaction condition odor Any hydrocarbon can be used as long as it is a gas, but it has 4 or less carbon atoms. Lucan is preferable because it is easy to handle. Similarly, for example, methylamine (CH)₃NH₂) And other amines with 4 or less carbon atoms are preferable. Carbon sources are easy to obtain and use CH for that reason₄Is the most preferable. CH₄Is the Aero All Gas Company (C) It can be purchased from a number of suppliers such as Toford, Connecticut). The carbon source is , To cause side reactions or nitrogenation reactions Those that do not contain impurities that have other effects are preferable. Nitrogen and carbon sources in the gaseous reactant mixture can be sourced from separate sources. It may be mixed and supplied in advance. In either case, mix upstream of the reactor Is preferable. N: Al in the reactor₂O₃And C: Al₂O₃There is no limit to the ratio , The gaseous reactant must be used in sufficient quantity to achieve the desired conversion within the desired time. Must be. The ratio of nitrogen to carbon in the gaseous reactant mixture (N: C) is It is important to obtain a product that is virtually carbon-free. Get such a product The N: C ratio in the gaseous reactant mixture is at least about 13, which is preferred. It is about 15 to about 2000. The N: C ratio is most preferably about 30 to about 40. If necessary, H in the gaseous reactant mixture₂And virtually carbon-free The range of reaction conditions under which AlN powder can be produced can be expanded. H₂Is excessive This facilitates the conversion of oxides or hydroxides to nitrides. H₂Is a large supply It can be purchased from the institution. The reaction condition is Al₂O₃What are the suitable conditions for converting the powder to AlN? Such conditions may be used. In general, the desired reaction for conversion to AlN is at least about 8 It occurs at a temperature of 50 ° C. Can be completely converted to AlN at temperatures above about 1000 ° C .. In the text of this specification, complete conversion means the formation of a product that is substantially carbon-free. To taste. Therefore, the reaction temperature ranges from about 850 ° C to about 1275 ° C or 1299 ° C. Is. The reaction temperature is preferably about 1000 ° C to about 1275 ° C, most preferably about 1275 ° C. It is about 1000 ° C to about 1100 ° C. There is no limit to the pressure during the reaction, and it can be easily obtained. Pressure is sufficient. TiN is TiO₂React powder with gaseous reactant mixture at at least about 750 ° C Can be obtained. It can be completely converted to TiN at temperatures above about 800 ° C. Preferably, the reaction temperature is from about 800 ° C to 1275 or 1299 ° C. ZrN The powder is ZrO₂React the powder with the gaseous reactant mixture at at least about 1050 ° C. Can be obtained. It can be completely converted to ZrN at temperatures above about 1100 ° C. Good Furthermore, the reaction temperature ranges from about 1100 ° C to about 1275 ° C or 1299 ° C. is there. FIG. 1 is a diagram showing an apparatus used for producing the powder of the present invention. This device is carbon It has a source cylinder 2, a nitrogen source cylinder 4, and an inert gas cylinder 6. reaction Is carried out in a reactor 18 such as a quartz tube reactor. Appropriate amount of Al₂O₃powder Place the powder in the reactor 18 in the blast furnace 20. For example, about 11.5 ° C / min Al in reactor 18 at any suitable speed₂O₃Heat the powder until it reaches the reaction temperature .. The actual heating rate does not really matter. The temperature inside the reactor 18 is thermocouple 22 And can be adjusted with the temperature controller 24. Preferably Al₂O₃The powder is involved in the reaction Preheat in a non-abrasive atmosphere to prevent the reaction from occurring until the reaction temperature is reached. To. For example, this powder, NH₃, N₂, H₂Or He, Ne, Ar, Kr Or preheat in an inert gas such as Xe. Inert gas cylinder Stored in 6 and reacted via a molecular sieve 14, a flow meter 16, and a gas mixing chamber 12. It can be supplied to the vessel 18. Al₂O₃After reaching the reaction temperature, the desired N: A gaseous reactant mixture is fed to reactor 18 at a rate sufficient to achieve a C ratio. The gaseous reactant is the carbon source silin It can be stored in the data 2 and the nitrogen source cylinder 4. These are molecular It is supplied to the reactor 18 via a sheave 8, a flow meter 10, and a gas mixing chamber 12. reaction The exhaust gas emitted from the vessel 18 flows into the exhaust gas cleaner 26 before being discharged. Place The desired amount of Al₂O₃The reaction conditions are maintained for a sufficient time to convert the powder into AlN powder. To have. Preferably, the reaction time is sufficient for 100% conversion. Example For example, the reaction conditions can be maintained for 1-2 hours or 9 hours or more. When the reaction temperature is low, A longer reaction time is required. Gas reactant mixing after the desired transformant is obtained Stop the inflow of substances and make the atmosphere inside the reactor an atmosphere that does not participate in the reaction. Reactor And the product is then cooled at a suitable rate. The present invention will be described with reference to the following examples, but these also limit the scope of the present invention. Not. Example 1 (AlN) Approximately 0.04 g of γ-Al₂O₃Powder (Alpha Products, Danvers, M) A) was weighed and placed in a quartz boat. The powder has an average particle size of about 1 μm to about 20 μm. It was a thing. Al₂O₃A quartz boat containing powder is placed in a quartz reactor with a diameter of 2.5 cm. I put it in. NH₃1050 ° C at a heating rate of about 11.5 ° C / min under airflow The powder was heated to the corresponding temperature. NH₃Is supplied at a flow velocity of 400 mL / min did. CH after reaching the reaction temperature₄Was supplied to the reactor at a flow rate of 30 mL / min. .. This results in a N: C ratio of 1 in the gaseous reactant mixture. It became 3.33. After maintaining the reaction conditions for 9 hours, CH₄Stop supplying and cool the powder I rejected it. X-ray diffraction revealed that the powder was completely converted to AlN. X-ray photoelectric Spectroscopy revealed that the powder was substantially carbon-free. Example 2 (AlN) NH so that the N: C ratio is 22.22₃Flow rate of 400 mL / min, C H₄The same operation as in Example 1 was carried out with the flow rate of 18 mL / min. X-ray analysis Showed a complete conversion to AlN. Example 3 (AlN) NH so that the N: C ratio is 35.19₃Flow of 387 mL / min, CH₄The same operation as in Example 1 was carried out with the flow rate of 11 mL / min. Reaction condition 1 I kept the time. X-ray analysis showed that some AlN was formed. Example 4 (AlN) NH so that the N: C ratio is 29.15₃Flow rate of 395 mL / min, C H₄The same operation as in Example 1 was carried out with the flow rate of 13 mL / min. Reaction conditions Was kept for 3 hours. X-ray analysis showed complete conversion to AlN. Example 5 (AlN) NH so that the N: C ratio is 37.00₃Flow rate of 407 mL / min, CH₄The same operation as in Example 1 was carried out with the flow rate of 11 mL / min. Reaction conditions 6 I kept the time. X-ray analysis showed complete conversion to AlN. Example 6 (AlN) NH so that the N: C ratio is 35.82₃Flow rate of 394 mL / min, C H₄The same operation as in Example 1 was carried out with the flow rate of 11 mL / min. Reaction conditions Was kept for 12 hours. X-ray analysis showed complete conversion to AlN. Example 7 (AlN) NH so that the N: C ratio is 35.18₃Flow rate of 387 mL / min, CH₄The same operation as in Example 1 was carried out with the flow rate of 11 mL / min. Reaction condition 1 I kept it for 8 hours. X-ray analysis showed complete conversion to AlN. Example 8 (AlN) Reaction temperature 1000 ° C, NH₃Flow rate of 402 mL / min, CH₄Flow velocity of 12 The same operation as in Example 1 was performed at mL / min. N: C ratio is 33.50 It was. X-ray analysis showed partial conversion to AlN. Example 9 (AlN) Reaction temperature 950 ° C, NH₃Flow rate of 391 mL / min, CH₄Flow velocity of 12m The same operation as in Example 1 was performed with L / min. The N: C ratio is 32.58 Ta. X-ray analysis showed partial conversion to AlN. Example 10 (AlN) Reaction temperature 850 ° C, NH₃Flow rate of 406 mL / min, CH₄Flow velocity of 11m The same operation as in Example 1 was performed with L / min. The N: C ratio is 36.91 Ta. X-ray analysis showed that it was partially converted to AlN. The conversion rate is the place of Example 9. It was less than the case. Table 1 shows the results of Examples 1 to 10. I / I is Al₂O₃(100) plane It is the ratio of the X-ray reflection intensity of AlN (100) plane to the X-ray reflection intensity of. If the I / I is 0, it indicates that it has not been converted to AlN. If I / I is , complete Shows full conversion.<img file="JPH08504396A_D0001.tif" /> Example 11 (TiN) Titanium isopropoxide [Ti (OiC)₃H₇)₂] To the sol-gel method Approximately 0.05 g of TiN powder produced from the above was placed in a quartz boat in the same manner as in Example 1. .. Under He air flow, heating rate is about 11.5 ° C / min, and reaction temperature is up to 1050 ° C. The powder was heated. CH after reaching the reaction temperature₄And NH₃Was supplied to the reactor. At this time, NH₃Flow rate of 400 mL / min, CH₄Flow rate of 11.5 mL / mi It was set to n. As a result, the N: C ratio in the gaseous reactant mixture was 35. 3 hours After maintaining the reaction conditions, NH₃And CH₄Stop supplying The powder was cooled under He. X-ray diffraction showed complete conversion of the powder to TiN. Examples 12 ~ 15 (TiN) Similar to Example 11 at reaction temperatures of 1050 ° C, 950 ° C, 850 ° C and 750 ° C. Was performed. X-ray diffraction is complete conversion at 1050 ° C, 950 ° C and 850 ° C I showed that I did. Partial conversion was observed at 750 ° C. Table 2 shows the results of Examples 11 to 15. I / I is TiO₂(101) flat The ratio of the X-ray reflection intensity of the (101) plane of TiN to the X-ray reflection intensity of the surface. To. If the I / I is 0, it indicates that it has not been converted to TiN. When I / I is , Shows complete conversion.<img file="JPH08504396A_D0002.tif" /> Example 16 (ZrN) Zyrconyl nitrate [ZrO (OH) NO₃] Manufactured from ZrO₂Powder about 0.0 3 g was placed in a quartz boat in the same manner as in Example 1. Under He airflow, heating speed is about 11 The powder was heated to .5 ° C / min and a reaction temperature of 1100 ° C. After reaching the reaction temperature CH₄And NH₃Was supplied to the reactor. At this time, NH₃Flow rate of 400 mL / m in, CH₄The flow velocity was 11 mL / min. This mixes gaseous reactants The N: C ratio in the object was 36.7. After maintaining the reaction conditions for 9 hours, NH₃and CH₄The supply was stopped and the powder was cooled under He. X-ray diffraction completes the powder to ZrN It showed total conversion. The method of the present invention is substantially carbon-free metal nitriding at temperatures below 1300 ° C. It is an improvement of conventional technology by manufacturing products. The powder of the present invention is, for example, heat. It can be used in known techniques such as spray coating precursors. The present invention is not limited to the above specific examples described with reference to the drawings. I. Various modifications and modifications without departing from the spirit or scope of the claims of the present invention. It can be modified.