GB2169270A - Aluminum oxynitride having improved optical characteristics and method of manufacture - Google Patents
Aluminum oxynitride having improved optical characteristics and method of manufacture Download PDFInfo
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- GB2169270A GB2169270A GB08429791A GB8429791A GB2169270A GB 2169270 A GB2169270 A GB 2169270A GB 08429791 A GB08429791 A GB 08429791A GB 8429791 A GB8429791 A GB 8429791A GB 2169270 A GB2169270 A GB 2169270A
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- 229910052782 aluminium Inorganic materials 0.000 title claims abstract description 56
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 title claims abstract description 54
- 238000000034 method Methods 0.000 title claims abstract description 42
- 238000004519 manufacturing process Methods 0.000 title description 6
- 230000003287 optical effect Effects 0.000 title description 2
- 239000000843 powder Substances 0.000 claims abstract description 34
- 238000005245 sintering Methods 0.000 claims abstract description 33
- 239000000654 additive Substances 0.000 claims abstract description 25
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims abstract description 20
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 15
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 13
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 13
- 239000002245 particle Substances 0.000 claims abstract description 13
- 229910052727 yttrium Inorganic materials 0.000 claims abstract description 9
- 150000001875 compounds Chemical group 0.000 claims abstract description 8
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 claims abstract description 8
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 7
- 239000002019 doping agent Substances 0.000 claims abstract description 5
- 229910052746 lanthanum Inorganic materials 0.000 claims abstract description 5
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 claims abstract description 4
- 239000012299 nitrogen atmosphere Substances 0.000 claims abstract description 4
- 235000010210 aluminium Nutrition 0.000 claims description 51
- 239000000203 mixture Substances 0.000 claims description 34
- 238000010438 heat treatment Methods 0.000 claims description 14
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 claims description 12
- 239000006229 carbon black Substances 0.000 claims description 10
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 8
- 239000007791 liquid phase Substances 0.000 claims description 8
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 6
- 239000007789 gas Substances 0.000 claims description 6
- 239000000356 contaminant Substances 0.000 claims description 5
- 238000003801 milling Methods 0.000 claims description 5
- 238000000498 ball milling Methods 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 claims description 2
- 238000001035 drying Methods 0.000 claims description 2
- 238000000227 grinding Methods 0.000 claims description 2
- 239000012808 vapor phase Substances 0.000 claims description 2
- 229910001873 dinitrogen Inorganic materials 0.000 claims 1
- 238000001914 filtration Methods 0.000 claims 1
- 230000005540 biological transmission Effects 0.000 abstract description 5
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 abstract description 4
- 229910052796 boron Inorganic materials 0.000 abstract description 4
- 239000004411 aluminium Substances 0.000 abstract description 2
- 230000000996 additive effect Effects 0.000 description 6
- 239000000919 ceramic Substances 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 230000032258 transport Effects 0.000 description 4
- 229910052582 BN Inorganic materials 0.000 description 3
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 description 3
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 description 3
- SIWVEOZUMHYXCS-UHFFFAOYSA-N oxo(oxoyttriooxy)yttrium Chemical compound O=[Y]O[Y]=O SIWVEOZUMHYXCS-UHFFFAOYSA-N 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 239000012780 transparent material Substances 0.000 description 3
- 239000012298 atmosphere Substances 0.000 description 2
- 238000000280 densification Methods 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229920001971 elastomer Polymers 0.000 description 2
- 230000008030 elimination Effects 0.000 description 2
- 238000003379 elimination reaction Methods 0.000 description 2
- 238000011065 in-situ storage Methods 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 239000002243 precursor Substances 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- 238000007088 Archimedes method Methods 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- -1 aluminum oxy- 5 nitride Chemical class 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000005242 forging Methods 0.000 description 1
- 238000007731 hot pressing Methods 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 229910052747 lanthanoid Inorganic materials 0.000 description 1
- 150000002602 lanthanoids Chemical class 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229920002635 polyurethane Polymers 0.000 description 1
- 239000004814 polyurethane Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J161/00—Adhesives based on condensation polymers of aldehydes or ketones; Adhesives based on derivatives of such polymers
- C09J161/04—Condensation polymers of aldehydes or ketones with phenols only
- C09J161/06—Condensation polymers of aldehydes or ketones with phenols only of aldehydes with phenols
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/082—Compounds containing nitrogen and non-metals and optionally metals
- C01B21/0821—Oxynitrides of metals, boron or silicon
- C01B21/0825—Aluminium oxynitrides
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
- C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
- C04B35/581—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on aluminium nitride
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Inorganic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Ceramic Products (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
- Compositions Of Oxide Ceramics (AREA)
Abstract
A method of preparing substantially homogeneous aluminum oxynitride powder is provided comprising the steps of reacting gamma aluminum oxide with carbon in the presence of nitrogen, and breaking down the resulting powder into particles in a predetermined size range. A method of preparing a durable optically transparent body from this powder is also provided comprising the steps of forming a green body of substantially homogeneous cubic aluminium oxynitride powder and sintering said green body in a nitrogen atmosphere and in the presence of predetermined additives which enhance the sintering process. Preferred dopant additives are boron, in elemental or compound form, and at least one additional element selected from the group of yttrium and lanthanum or compounds thereof. The sintered polycrystalline cubic aluminum oxynitride has a density greater than 99% of theoretical density, an in-line transmission of at least 50% in the 0.3-5 micron range, and a resolving angle of 1 mrad or less.
Description
1 GB 2 169 270 A 1
SPECIFICATION
Aluminum oxynitride having improved ptical characteristics and method of manufacture This invention relates to durable transparent ceramic compounds. There is a need for these compounds in applications requiring substantial transmission and imaging capabilities in the visible range and the infrared range. These requirements can be found in both military and commercial applications. For ex ample, infrared transparent domes are needed for missiles and transparent envelopes are needed in dif ferent types of vapor lamps. Many transparent materials are not adequately durable for these applications, thus, the search has been directed towards developing transparent ceramics. Although many ceramic compounds satisfy the durability requirement, they are not transparent to a sufficient de gree for these applications. For instance, alumina is a very hard material but the main problem is that it is not sufficiently transparent and scatters light to an excessive degree. An additional consideration for a candidate material is the cost of manufacturing, thus, methods that require individual processing of these windows are bound to remain an unfeasible alternative from a cost point of view. From this perspective, 15 forging and hot-pressing methods are not desirable. This leaves batch processing methods as a desirable feasible alternative and sintering [ends itself to the manufacture of a plurality of units in a single run.
However, the sintering of transparent ceramics is not widely known or practiced.
Aluminum oxynitride is a promising candidate for applications requiring multi-spectral transmission ca pabilities. The only known prior attempt at producing a sintered aluminum oxynitride body is found in 20 U.S. Patent No. 4,241,000, wherein precursor powders are mixed and the sintering step is used to both react and sinter the precursor powders to produce an oxynitride body. The problem is that the resulting material is not sufficiently transparent for the applications mentioned hereinabove.
These and other problems are solved by the present invention which provides a method for producing a substantially homogeneous cubic aluminum oxynitricle powder which is particularly useful for the sin- 25 tering of the powder to produce a durable transparent ceramic window. It was found that starting with a substantially homogeneous powder of aluminum oxynitride as prepared by the present invention and using specific additives leads to an adequately transparent window in both the visible and infrared range.
This invention provides for a method of preparing homogeneous aluminum oxynitride and comprising the steps of introducing aluminum oxide powder and carbon black in a reaction chamber, providing ni- 30 trogen in said chamber, and heating said chamber to react said powder and gas to produce a reacted powder substantially comprising aluminum oxynitricle. The reacted powder may also comprise up to 15 weight percent of aluminum oxide and aluminum nitride such that the ratio of aluminum oxide to alumi num nitride is within the composition range of cubic aluminum oxynitride.
This invention further provides for a method of producing transparent sintered aluminum oxynitricle 35 bodies comprising the steps of preparing a mixture of aluminum oxide and carbon black, reacting the mixture in the presence of nitrogen and at a temperature in the range of 1550-18500C to produce alumin ium oxynitricle, forming a pressed green body of predetermined shape from said reacted mixture, placing said green body in a sintering chamber, providing doping additions in said chamber, said additives com- prising one or more elements from the group of yttrium and lanthanum, or compounds thereof, and sin- 40 tering said green body at a temperature higher than 19000C but lower than the solidus temperature of aluminum oxynitride. Preferably, the dopants are in a vapor phase during a portion of said sintering step and vapor transport to and diffuse throughout said body. The doping additives preferably comprise not more than 0.5 weight percent of weight of the green body. The preferred starting mixture has a carbon content in the range of 5.4-7.1 weight percent. Preferably, the reacted mixture is broken up in particles of size in the range of 0.5 to 5 microns, and the reacted mixture is heated in air or oxygen to remove any organic contaminants that might be present.
A polycrystalline cubic aluminum oxynitricle body having a density of at least 99% of theoretical den sity, a sample of said body having an in-line transmission of at least 50% in the wavelength range of 0.3 5 microns, said sample having a thickness of 1.45 millimeters, and preferably an image resolution of 1 50 mrad or less is the subject of application GB 8224835, The present invention produces a substantially homogeneous cubic aluminum oxynitride powder by reacting gamma-aluminum oxide with carbon in a nitrogen atmosphere. More specifically, and prefera bly, aluminum oxide (alumina) and carbon black are thoroughly dry mixed, for instance, in a Patterson- Kelly twin-shell blender for times up to two hours. Preferably, the aluminum oxide has a purity of at least 55 99.98% and an average particle size of 0.06 microns, and the carbon black has a purity of no less than 97.6% with 2.4% volatile content and an average particle size of 0.027 microns. The carbon content of the mixture preferably ranges from 5.4 to 7.1 weight percent. A preferred mixture comprises 5.6 weight per cent carbon black and 94.4 weight percent aluminum oxide. The aluminum oxide/carbon mixture is pref erably placed in an alumina crucible and reacted in an atmosphere of flowing nitrogen at temperatures 60 from 15500C to the solidus temperature of aluminum oxynitride (about 2140'C), preferably up to 1850'C for up to two hours at the maximum temperature. The preferred heat treatment is in two steps. In the first step, a temperature in the lower end of the range is preferably used for approximately one hour, whereby, for an appropriate ratio of alumina to carbon, the temperature unstable gamma-aluminum ox 66 ide is only partially reacted with carbon and nitrogen to form both alpha-aluminum oxide and aluminum 65 2 GB 2 169 270 A 2 nitride. A one hour soak at, for example, 1550'C is sufficient to convert the proper amount of Al,.O, to AIN. In the second step, a temperature in the higher end of the range, for example, 17500C is used for approximately 40 minutes, whereby alpha-aluminum oxide and aluminum nitride combine to form cubic aluminum oxynitride.
The reacted material resulting from the heat treatment is composed primarily of cubic aluminum oxy- 5 nitride, but may also contain alumina and/or aluminum nitride in amounts of up to 15 weight percent such that the ratio of aluminum oxide to aluminum nitride is within the composition range of cubic alu minum oxynitride. The amounts of alumina and aluminum nitride can be controlled by the heat treat ment and the amount of aluminum nitride produced in the first heating step which in turn depends on the amount of carbon in the starting mixture.
For a first step utilizing the preferred one hour soak at 15500C, except for Sample 5 which was treated at 1620'C, TABLE I illustrates the effect of using different amounts of carbon in the starting mixture and of different temperatures during the second step of the heat treatment.
TABLE 1 15
Weight % Temp. Time % % % Sample Carbon rcj trainsj AIN A1,0,, ALON 1 5.6 1750 40 3.2 10.0 86.8 20 2 7.1 1750 40 4.0 0 96.0 3 6.5 1750 40 1.88 0 98.12 4 5.9 1750 40 0.85 0 99.15 5.6 1820 40 Trace Trace 99.9+ The preferred heat treatment produces a resulting composition comprising substantially 100% alumi- 30 num oxynitride and corresponds to Sample 5. An alternate preferred resulting composition is that of Sample 1. The resulting aluminum oxynitride powder consists of agglomerated particles which are easily broken apart during ball milling to particles ranging in size from 0.5 to 5 microns.
The reacted material is preferably ball milled in polyurethane or rubber lines mills using methanol as a milling fluid and high alumina grinding balls. Milling time is 16 hours. The milled powder is passed 35 through a 400 mesh sieve (openings are 35 microns square) and is dried at 65'C for up to 24 hours. After drying, the powder is heated in air to 6000C for 2 hours to remove organic contaminants.
Sinterig aids are now added in the form of small amounts of preselected doping additives up to 0.5 weight percent of the aluminum oxynitride powder. The additive may also comprise an element selected from the group of yttrium and lanthanum, or compounds thereof. Other elements of the lanthanide series 40 may similarly be used. Preferably, the oxides of the elements selected are used. A combination of the doping additives may also be used as long as the total amount of additives does not exceed 0.50 weight percent. A preferred combination comprises 0.08 weight percent yttrium oxide (YO,) and 0.02 weight percent lanthanum oxide (La203). Alternatively, the doping additives may be added during the ball milling of the aluminum oxynitride powder.
The additive-containing aluminum oxynitride powder is preferably placed in rubber molds having predetermined shapes and isostatically pressed at pressures greater than 15,000 psi (103420 kPa) to produce green bodies to be used in sintering. The fabricated green bodies are set in containers in the sintering chamber. The containers are preferably composed either entirely of boron nitride or partly of boron ni- tride and partly of molybdenum metal. Sintering is then performed in a stagnant atmosphere of nitrogen 50 at 0-5 psig (0 to 34.5 kPa). To obtain substantially transparent material, sintering temperatures are higher than 19000C, but lower than the solidus temperature of aluminum oxynitride which is approximately 2140'C. Sintering is preferably carried out for a minimum of 24 hours and a maximum of 48 hours.
3 TABLE 11
GB 2 169 270 A 3 % in-line Temp. Time transmiss. (MM) % Optical Sample YO, La,O, OC h @ 4 microns Thickness Density Resolution 5 1 none ngne 1930 23 opaque 1.7 98 0.08 0.02 1930 1 5 0.82 98+ 0.08 0.02 1930 24 80 1.45 99+ <'I mrad 4 0.25 none 1930 48 53 1.35 99+ <1 mrad 5 0.08 0.02 1730 3 opaque 1.5 - 15 6 0.08 0.02 1910 8 5 0.8 98 TABLE 11 shows to some extent the effect of additives, time and temperature on the resultant transpar ency of the aluminum oxynitride. The density was measured by the Archimedes method, the in-line transmission was measured with a Perkin-Elmer 457 Grating Infrared Spectrophotometer, and the resolv ing angle was measured by using the Standard USAF 1951 Resolution Test Pattern. The temperatures are accurate to within 10'C. A temperature of 1900'C is the minimum temperature found to consistently pro duce a transparent material given the proper amount of Y,O, and/or La20,. The best amount of additive is the minimum amount needed to produce a liquid phase at the grain boundaries initially yet not be pres- 25 ent as a second phase after sintering. Although 0.1 weight percent produced the best results, smaller trace amounts as low as 0.05 weight percent may be used, provided that a liquid phase is formed at or near 1900'C which promotes rapid densification and'pore removal. This liquid phase disappears with Y and La going into solid solution with the aluminum oxynitride. This process of liquid phase sintering is thought to be present at the -sintering temperature early in the sintering process. After this, solid state 30 diffusion is the means by which the remaining porosity is eliminated and substantial transparency is achieved. Elimination of porosity by solid state diffusion is a much slower means of pore elimination so longer times are needed, 24 hours being the minimum preferred duration. This is confirmed by Samples 2 and 6, wherein, even though an adequate amount of additives was used, the samples remain translu cent because the duration of the sintering step was limited to 1 and 8 hours, respectively.
It should be understood that the additives discussed hereinabove need not be mixed in with the alumi num oxynitride powder prior to sintering nor do they need to be placed in direct contact with the green body. Again, it is sufficient that the selected additive be available within the sintering chamber for the doping of the aluminum oxynitride. Indeed an unexpected improvement in the transparency of sintered aluminum oxynitride was discovered after sintering a green body, composed strictly of aluminum oxyni- 40 tride powders, along with an adjacent green body containing yttrium oxide on a boron nitride platform.
Thus, this invention is considered to encompass other methods of introducing the additives in the sinter ing chamber to produce in situ vapor doping of the aluminum oxynitride compact.
An explanation of in situ vapor doping by the presence of specific additives for the enhancement of the sintering is believed to be as follows. At sintering temperatures, the mixture of aluminum oxynitride has 45 a significantly high vapor pressure of AI,Oy gas species. The AI,Oy gas reacts with nearby boron nitride present in the container to produce 13,03gas and/or AIBO, gas plus AIN solid. The B,O, and/or AIBO, vapors transport to and react with aluminum oxynitride to produce a liquid phase at grain boundaries which enhances the early stages of sintering. In the case yttrium oxide is used as the additive, the 13,0., also interacts with yttrium doped aluminum oxynitride or pure YO, to produce YBO, gas. The YBO, va- 50 por transports to the aluminum oxynitride and dopes it with the boron and yttrium. In the case of other elements being used as additives, the B,O, similarly reacts to provide a corresponding vapor doping of aluminum oxynitride. It is believed that this additive doping aids the final stages of sintering by causing either solute drag or second phase precipitates to pin grain boundaries and thus preventing excessive grain growth which might otherwise trap pores within the grains.
An alternative explanation is that the yttrium, or components thereof, cause the formation of a liquid phase. This liquid phase promotes rapid densification and significant pore removal in the early stages of sintering so that during the final stages of sintering there is less porosity to be eliminated and high den sity and transparency are achieved. In this mechanism, boron is necessary only for the transport of ytt rium to the aluminum oxynitride.
The method of the present invention avoids many of the problems normally associated with the prepa ration of aluminum oxynitride by mixing and reacting aluminum oxide and aluminum nitride, such as the varying purity levels, large particle sizes and wide size distribution range of commercially available alu minum nitride, the long reaction times required to form aluminum oxynitride, and the long milling times 66 required to reduce the particle size, which in turn increase the inorganic impurity content of the alumi- 65 4 GB 2 169 270 A num oxynitride. Additionally, the present method reduces the cost of manufacturing by avoiding the use of the more expensive aluminum nitride as a starting ingredient, by requiring shorter reaction times to form aluminum oxynitride, and by requiring less milling time to achieve a homogeneous sinterable powder of suitable particle size. The aluminum oxynitride powder prepared by the present method also im- proves the reproducibility of the sintering process and improves the transparency of the sintered product.
Claims (1)
- 4 1. A method of preparing homogeneous aluminum oxynitride comprising the steps of:introducing aluminum oxide powder and carbon black into a reaction chamber; providing nitrogen in said chamber; and heating said chamber to react said powders and gas to produce a reacted powder substantially com prising aluminum oxynitride.2. A method according to Claim 1 wherein:said reacted powder comprises up to 15 weight percent of aluminum oxide and aluminum nitride such 15 that the ratio of aluminum oxide to aluminum nitride is within the composition range of cubic aluminum oxynitride.3. A method according to Claim 1 or Claim 2 wherein:said aluminum oxide and carbon black are introduced as a thoroughly mixed mixture.4. A method according to any one of Claims 1 to 3 wherein:the carbon content of said mixture is in the range of 5.4 to 7.1 weight percent.5. A method according to any one of Claims 1 to 4 wherein:said aluminum oxide has a purity of 99.98% and an average particle size of approximately 0.06 mi crons, and said carbon black has a purity of 97.6% and an average particle size of approximately 0.027 microns.6. A method according to any one of Claims 1 to 5, wherein:said chamber is heated to a temperature in the range of 1550'C to the solidus temperature of alumi num oxynitride.7. A method according to Claim 6 wherein:said chamber is heated to a temperature in the range of 1550-1850'C.8. A method according to Claim 7 wherein said heating step comprises the steps of:first heating said chamber to a temperature in the lower end of said temperature range to convert the temperature unstable gamma aluminum oxide present in the mixture into the temperature stable alpha aluminum oxide; and then heating said chamber to a temperature in the upper end of said temperature range to react said 35 converted mixture of powder with said nitrogen gas to produce aluminum oxynitride.9. A method according to Claim 8 wherein:said chamber is first heated to a temperature of approximately 15500C for approximately an hour and then to a temperature of 1750' C for approximately 40 minutes.10. A method according to Claim 8 wherein:said chamber is first heated to a temperature of approximately 16200C for approximately one hour and then to a temperature of 18200C for approximately 40 minutes.11. A method according to any one of Claims 1 to 10 comprising the additional step of:milling said reacted powder to produce particles of size in the range of 0.5 to 5 microns.12. A method according to any one of Claims 1 to 11 comprising the step of:heating said powder in air until any organic contaminants present in the mixture are substantially re moved.13. A method of preparing homogeneous aluminum oxynitride comprising the step of:preparing a mixture of aluminum oxide and carbon black, the carbon content of said mixture being in the range of 5.4-7.1 weight percent; reacting in a flowing nitrogen atmosphere said mixture first at a temperature of approximately 1550'C for one hour, and then at a temperature of at least 17500C for 40 minutes; ball milling the reacted mixture with alumina grinding balls in methanol; and filtering said milled powder through a 400 mesh per inch sieve.14. A method according to Claim 12 further comprising the steps of: drying said filtered powder; and heating said powder in air to remove any organic contaminants that might be present. 15. A method according to Claim 1 conducted substantially as described herein. 16. A method of producing transparent sintered aluminum oxynitride bodies comprising the steps of:preparing a mixture of aluminum oxide and carbon black; reacting said mixture in the presence of nitrogen and at a temperature in the range of 1550-18500C to produce aluminum oxynitride; forming a pressed green body from said reacted mixture; placing said green body in a sintering chamber; providing doping additives in said chamber, said additives comprising one or more elements from the 65 GB 2 169 270 A 5 group of yttrium and lanthanum or compounds thereof; and sintering said green body in a nitrogen atmosphere at a temperature higher than 19000C but lower than the solidus temperature of aluminum oxynitride.17. A method according to Claim 16 wherein:the carbon content of said mixture is in the range of 5.4-7.1 weight percent.18. A method according to Claim 16 or Claim 17 wherein:said dopants are in a vapor phase during a portion of said sintering step.19. A method according to any one of Claims 16 to 18 wherein:in said sintering step, the dopants transport to and diffuse throughout said body.1020. A method according to any one of Claims 16 to 19 wherein:said dopants produce a liquid phase at grain boundaries during said sintering step.21. A method according to any one of Claims 16 to 20 wherein:said doping additives are mixed in with said reacted mixture.22. A method according to any one of Claims 16 to 21 wherein:said doping additives comprise not more than 0.5 weight percent of said mixture.23. A method according to any one of Claims 16 to 22 further comprising the steps of:breaking up the reacted mixture in particles of size in the range of 0.5 to 5 microns; and heating said reacted mixture to remove organic contaminants.24. A method according to Claim 16 conducted substantially as described herein.25. Homogeneous aluminum oxynitride whenever produced by a process according to any one of 20 Claims 1 to 15.26. A sintered aluminum oxynitride body whenever produced by a method according to any one of Claims 16 to 24.Printed in the UK for HMSO, D8818935, 5186, 7102.Published by The Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US29789781A | 1981-08-31 | 1981-08-31 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8429791D0 GB8429791D0 (en) | 1985-01-03 |
| GB2169270A true GB2169270A (en) | 1986-07-09 |
| GB2169270B GB2169270B (en) | 1986-12-17 |
Family
ID=23148182
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08224835A Expired GB2108945B (en) | 1981-08-31 | 1982-08-31 | Aluminum oxynitride having improved optical characteristics and method of manufacture |
| GB08429791A Expired GB2169270B (en) | 1981-08-31 | 1984-11-26 | Aluminium oxynitride having improved optical characteristics and method of manufacture |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08224835A Expired GB2108945B (en) | 1981-08-31 | 1982-08-31 | Aluminum oxynitride having improved optical characteristics and method of manufacture |
Country Status (5)
| Country | Link |
|---|---|
| JP (2) | JPS5874514A (en) |
| DE (2) | DE3249969C2 (en) |
| FR (1) | FR2512003B1 (en) |
| GB (2) | GB2108945B (en) |
| IT (2) | IT1149069B (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2126568B (en) * | 1981-08-31 | 1986-05-14 | Raytheon Co | Transparent aluminum oxynitride and method of manufacture |
| US4788167A (en) * | 1986-11-20 | 1988-11-29 | Minnesota Mining And Manufacturing Company | Aluminum nitride/aluminum oxynitride/group IVB metal nitride abrasive particles derived from a sol-gel process |
| ZA877802B (en) * | 1986-11-20 | 1989-06-28 | Minnesota Mining & Mfg | Aluminum oxide/aluminum oxynitride/group ivb metal nitride abrasive particles derived from a sol-gel process |
| FR2621574B1 (en) * | 1987-10-13 | 1990-11-09 | Innomat | PROCESS FOR THE PREPARATION OF ALUMINUM OXYNITRIDE AND ITS APPLICATION TO THE PRODUCTION OF INFRA-RED WINDOWS |
| US5096862A (en) * | 1990-08-09 | 1992-03-17 | Minnesota Mining And Manufacturing Company | Transparent ceramic composite article comprising aluminum oxide and aluminum magnesium oxynitride |
| FR2703348B1 (en) * | 1993-03-30 | 1995-05-12 | Atochem Elf Sa | Process for the preparation of powder for ceramic in optically transparent gamma aluminum oxynitride and the powder thus obtained. |
| EP0704880A3 (en) * | 1994-09-28 | 1998-09-30 | Matsushita Electric Industrial Co., Ltd. | High-pressure discharge lamp, method for manufacturing a discharge tube body for high-pressure discharge lamps and method for manufacturing a hollow tube body |
| CH688297B5 (en) * | 1994-12-16 | 1998-01-30 | Rado Montres Sa | Transparent closure element and a scratchproof watch case and watch case provided with such an element. |
| US8211356B1 (en) * | 2000-07-18 | 2012-07-03 | Surmet Corporation | Method of making aluminum oxynitride |
| DE102004001176A1 (en) * | 2004-01-05 | 2005-08-04 | Schott Ag | Technical system including at least one structural group and/or component from at least two individual parts which can be subjected to high mechanical loads and/or high temperatures up to 1100degreesC |
| KR101374215B1 (en) * | 2012-11-30 | 2014-03-13 | 한국해양대학교 산학협력단 | Synthesis method of aluminum oxynitride powder using aluminum powder |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1188011A (en) * | 1966-06-01 | 1970-04-15 | Grace W R & Co | Production of Nitrides of Actinide Metals. |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3572992A (en) * | 1967-07-05 | 1971-03-30 | Tokyo Shibaura Electric Co | Preparation of moulded and sintered aluminum nitride |
| DE1906522B2 (en) * | 1968-02-10 | 1972-01-13 | Tokyo Shibaura Electric Co. Ltd., Kawasaki, Kanagawa (Japan) | METHOD OF MANUFACTURING A Sintered ALUMINUM NITRIDE YTTRIUM OXIDE ARTICLE |
| GB1310362A (en) * | 1969-12-16 | 1973-03-21 | United States Borax Chem | Process for purification of refractory metal nitrides |
| GB1377487A (en) * | 1970-12-23 | 1974-12-18 | Tokyo Shibaura Electric Co | Heat resistant composite materials |
| US4241000A (en) * | 1978-08-24 | 1980-12-23 | The United States Of America As Represented By The Secretary Of The Army | Process for producing polycrystalline cubic aluminum oxynitride |
-
1982
- 1982-08-23 FR FR8214449A patent/FR2512003B1/en not_active Expired
- 1982-08-28 DE DE3249969A patent/DE3249969C2/de not_active Expired - Fee Related
- 1982-08-28 DE DE19823232069 patent/DE3232069A1/en active Granted
- 1982-08-30 IT IT49045/82A patent/IT1149069B/en active
- 1982-08-31 GB GB08224835A patent/GB2108945B/en not_active Expired
- 1982-08-31 IT IT68058/82A patent/IT1156502B/en active
- 1982-08-31 JP JP57151659A patent/JPS5874514A/en active Granted
-
1984
- 1984-11-26 GB GB08429791A patent/GB2169270B/en not_active Expired
-
1991
- 1991-01-31 JP JP3105230A patent/JPH0617223B2/en not_active Expired - Lifetime
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1188011A (en) * | 1966-06-01 | 1970-04-15 | Grace W R & Co | Production of Nitrides of Actinide Metals. |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2512003A1 (en) | 1983-03-04 |
| GB2108945B (en) | 1986-05-14 |
| IT1149069B (en) | 1986-12-03 |
| JPS5874514A (en) | 1983-05-06 |
| JPH0420850B2 (en) | 1992-04-07 |
| DE3232069C2 (en) | 1990-02-08 |
| JPH05294737A (en) | 1993-11-09 |
| DE3232069A1 (en) | 1983-03-24 |
| IT1156502B (en) | 1987-02-04 |
| GB8429791D0 (en) | 1985-01-03 |
| GB2108945A (en) | 1983-05-25 |
| JPH0617223B2 (en) | 1994-03-09 |
| FR2512003B1 (en) | 1987-03-20 |
| DE3249969C2 (en) | 1992-10-15 |
| GB2169270B (en) | 1986-12-17 |
| IT8249045A0 (en) | 1982-08-30 |
| IT8268058A0 (en) | 1982-08-31 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19930831 |