CA2298890A1 - A technique to produce nanometer-sized ceramic powders - Google Patents
A technique to produce nanometer-sized ceramic powders Download PDFInfo
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- CA2298890A1 CA2298890A1 CA 2298890 CA2298890A CA2298890A1 CA 2298890 A1 CA2298890 A1 CA 2298890A1 CA 2298890 CA2298890 CA 2298890 CA 2298890 A CA2298890 A CA 2298890A CA 2298890 A1 CA2298890 A1 CA 2298890A1
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- melt
- fluid medium
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B13/00—Oxygen; Ozone; Oxides or hydroxides in general
- C01B13/14—Methods for preparing oxides or hydroxides in general
- C01B13/32—Methods for preparing oxides or hydroxides in general by oxidation or hydrolysis of elements or compounds in the liquid or solid state or in non-aqueous solution, e.g. sol-gel process
- C01B13/326—Methods for preparing oxides or hydroxides in general by oxidation or hydrolysis of elements or compounds in the liquid or solid state or in non-aqueous solution, e.g. sol-gel process of elements or compounds in the liquid state
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/20—Methods for preparing sulfides or polysulfides, in general
-
- 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
- C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B6/00—Hydrides of metals including fully or partially hydrided metals, alloys or intermetallic compounds ; Compounds containing at least one metal-hydrogen bond, e.g. (GeH3)2S, SiH GeH; Monoborane or diborane; Addition complexes thereof
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G1/00—Methods of preparing compounds of metals not covered by subclasses C01B, C01C, C01D, or C01F, in general
- C01G1/02—Oxides
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
Abstract
A preferred embodiment of the present invention is a method for producing nanometer-sized ceramic powders, comprising (a) providing a pressurized fluid atomizing medium containing oxygen, nitrogen or chlorine mainly (b) providing a super-heated metal or alloy melt to a spontaneous reaction temperature (c) the reactant of the medium with the super-heated metal or alloy melt to form nanometer-sized ceramic particles.
Description
BACKROUND OF THE INVENTION
Field of the Invention The present invention relates to an method for preparing manometer-sized ceramic particles, and more particularly, it relates to prepare manometer-sized composite ceramic powders, at a high production rate.
The manometer-sized metal-oxide powders are known to exhibit unique physical and mechanical properties. The novel properties of nano-crystalline materials are the result of their small residual pore sizes, limited grain size, phase or domain dimain dimensions, and large fraction of atoms residing in interfaces. In a mufti-phase material, limited phase dimensions could imply a limited crack propagation path if the brittle phase is surrounded by ductile phase so the cracks in a brittle phase would not easily reach a critical crack size. Even with only one constituent phase, nano-crytstalline materials may be considered as two-phase materials, composed of distinct interface and crystalline phase. The possibilities for reacting, coating, and mixing various types of nanometer-sized materials create the potential for fabricating new composites with nano-sized phases and novel properties.
Ultra-fine particles with a narrow sized distribution have enormous potential in ceramic processing.
For example, a green density of 75as been achieved by compaction of nano-crystalline titanic prepared by inert gas condensation of metal vapors. Mono-dispersed particles are known to form a more uniform green micro-structure, which allows for a better control of the micro-structure during densification. In addition, smaller particles can be sintered at much lower temperatures. Not only the structure, but also the mechanical, electronic, optical, magnetic and thermal properties of nano-crystalline materials are different from those exhibited by their bulk counterparts. Specifically, ceramics fabricated from ultra-fine particles are known to possess high strength and toughness because of the ultra-small intrinsic defect sizes and the ability for grain boundaries to undergo a large plastic deformation. Additionally, ultra-fine grained metals could exhibit unusually high strength and hardness. For a review on nano-phase materials please refer to R.P. Anders, et al.
"Research Opportunities on Clusters and Cluster-Assembled Materials," in Journal of Materials Research, Vol.4, 1989, pp.704-736 and A. N. Goldstein,"Handbook of Nanophase Materials,"
Marcel Dekker, Inc., New York, 1997.
The techniques for the generation of nanometer-sized particles may be divided into three broad categories: vacuum, gas-phase, and condensed-phase synthesis. Vacuum synthesis techniques include sputtering, laser ablation, and liquid-metal ion sources. Gas-phase synthesis includes inert gas condensation, oven sources (for direct evaporation into a gas to produce an aerosol or smoke of clusters), laser-induced vaporization, laser pyrolysis, and flame hydrolysis.
Condensed-phase synthesis includes reduction of metal ions in an acidic aqueous solution, liquid phase precipitation of semiconductor clusters, and decomposition-precipitation of ionic materials for ceramic clusters.
Other methods include high-energy milling, mix-alloy processing, chemical vapor deposition (CVD), and sol-gel techniques. All of these techniques have one or more of the following problems or shortcomings:
(1) Most of these prior-art techniques suffer from a severe drawback:
extremely low production rates. It is not unusual to find a production rate of several grams a day.
Vacuum sputtering, for instance, only produces small amounts of particles at a time. Laser ablation and laser-assisted chemical vapor deposition techniques are well-known to be excessively slow processes. The high-energy ball milling method, known to be a "quantity" process, is capable of producing only several kilograms of nanometer-scaled powders in approximately 100 hours.
These low production rates, resulting in high product costs, have severely limited the utility value of nano-phase materials. There is, therefore, a clear need for a faster, more cost-effective method for preparing nanometer-sized powder materials.
Field of the Invention The present invention relates to an method for preparing manometer-sized ceramic particles, and more particularly, it relates to prepare manometer-sized composite ceramic powders, at a high production rate.
The manometer-sized metal-oxide powders are known to exhibit unique physical and mechanical properties. The novel properties of nano-crystalline materials are the result of their small residual pore sizes, limited grain size, phase or domain dimain dimensions, and large fraction of atoms residing in interfaces. In a mufti-phase material, limited phase dimensions could imply a limited crack propagation path if the brittle phase is surrounded by ductile phase so the cracks in a brittle phase would not easily reach a critical crack size. Even with only one constituent phase, nano-crytstalline materials may be considered as two-phase materials, composed of distinct interface and crystalline phase. The possibilities for reacting, coating, and mixing various types of nanometer-sized materials create the potential for fabricating new composites with nano-sized phases and novel properties.
Ultra-fine particles with a narrow sized distribution have enormous potential in ceramic processing.
For example, a green density of 75as been achieved by compaction of nano-crystalline titanic prepared by inert gas condensation of metal vapors. Mono-dispersed particles are known to form a more uniform green micro-structure, which allows for a better control of the micro-structure during densification. In addition, smaller particles can be sintered at much lower temperatures. Not only the structure, but also the mechanical, electronic, optical, magnetic and thermal properties of nano-crystalline materials are different from those exhibited by their bulk counterparts. Specifically, ceramics fabricated from ultra-fine particles are known to possess high strength and toughness because of the ultra-small intrinsic defect sizes and the ability for grain boundaries to undergo a large plastic deformation. Additionally, ultra-fine grained metals could exhibit unusually high strength and hardness. For a review on nano-phase materials please refer to R.P. Anders, et al.
"Research Opportunities on Clusters and Cluster-Assembled Materials," in Journal of Materials Research, Vol.4, 1989, pp.704-736 and A. N. Goldstein,"Handbook of Nanophase Materials,"
Marcel Dekker, Inc., New York, 1997.
The techniques for the generation of nanometer-sized particles may be divided into three broad categories: vacuum, gas-phase, and condensed-phase synthesis. Vacuum synthesis techniques include sputtering, laser ablation, and liquid-metal ion sources. Gas-phase synthesis includes inert gas condensation, oven sources (for direct evaporation into a gas to produce an aerosol or smoke of clusters), laser-induced vaporization, laser pyrolysis, and flame hydrolysis.
Condensed-phase synthesis includes reduction of metal ions in an acidic aqueous solution, liquid phase precipitation of semiconductor clusters, and decomposition-precipitation of ionic materials for ceramic clusters.
Other methods include high-energy milling, mix-alloy processing, chemical vapor deposition (CVD), and sol-gel techniques. All of these techniques have one or more of the following problems or shortcomings:
(1) Most of these prior-art techniques suffer from a severe drawback:
extremely low production rates. It is not unusual to find a production rate of several grams a day.
Vacuum sputtering, for instance, only produces small amounts of particles at a time. Laser ablation and laser-assisted chemical vapor deposition techniques are well-known to be excessively slow processes. The high-energy ball milling method, known to be a "quantity" process, is capable of producing only several kilograms of nanometer-scaled powders in approximately 100 hours.
These low production rates, resulting in high product costs, have severely limited the utility value of nano-phase materials. There is, therefore, a clear need for a faster, more cost-effective method for preparing nanometer-sized powder materials.
(2) Condensed-phase synthesis such as direct reaction of metallic silicon with nitrogen to produce silicon nitride powder requires pre-production of metallic silicon of high purity in finely powdered form. This reaction tends to produce a silicon nitride powder product which is constituted of a broad particle size distribution. Furthermore, this particular reaction does not yield a product powder finer than 100 nm (nanometers) except with great difficulty. Due to the limited availability of pure metallic silicon in finely powdered form, the use of an impure metallic powder necessarily leads to an impure ceramic product. These shortcomings are true of essentially all metallic elements, not just silicon.
(3) Some processes require expensive precursor materials to ceramic powders and could result in harmful gas that has to be properly disposed o~ For instance, the reaction scheme of 3SiCl~+4NH3=Si3N4+l2HCl involves the utilization of expensive SiC~ and produces dangerous HCl gas. Processes that begin with the high temperature treatment of expensive precursor compounds are exemplified by those disclosed in CANADA Pat. CA 2000232 (Oct. 6 , 1989 to Riedel, Ralf ), CANADA Pat. CA 2031330 (Nov. 30, 1990 to Laubach, Benno),U.S.
Pat.
5,075,090 (Dec. 24,1991 to Lewis, et al.) and U.S. Pat. 4,948,762 (Aug. 14, 1990 to Krumbe, et al.).
Pat.
5,075,090 (Dec. 24,1991 to Lewis, et al.) and U.S. Pat. 4,948,762 (Aug. 14, 1990 to Krumbe, et al.).
(4) Most of the prior-art processes are capable of producing a particular type of ceramic powder at a time, but do not permit the reparation of a uniform mixture of two or more types of nano-scaled ceramic powder at a predetermined proportion.
(5) Most of the prior-art processes require heavy and/or expensive equipment (e.g., a high power laser source or a plasma generator), resulting in high production costs.In the precipitation of ultra fine particles from the vapor phase, when using thermal plasmas or laser beams as energy sources, the particle sizes and size distribution cannot be precisely controlled. Also, the reaction conditions usually lead to a broad particles size distribution as well as the appearance of individual particles having diameters that are multiples of the average particle size. Processes that involve hot plasma- or flame-induced gas phase reactions are disclosed in several CANADA Pat. CA 2089874 (Aug. 30, 1991 to Marantz, Daniel R.), CANADA Pat. CA
2160367 (May 10, 1994 to Helble, Joseph J.), CANADA Pat. CA 2153048 (Feb. 2 , 1999 to Helble, Joseph J.),U.S.patents: e.g., 4,282,195 (Aut.4, 1981 to H.H.Hoekje), 4,689,075 (Aug.25, 1987 to Uda, et al.), 4,889,665 (Dec.26,1989 to Uda, et al.), 5,599,511 (Feb.4, 1997 to Helble, et al.), and 5,019,686 (May 28, 1991 to Marantz).
The Conventional mechanical attrition and grading processes have the disadvantages that powders can only be produced up to a certain fineness and with relatively broad particle-size distribution. As a matter of fact, with the currently familiar large-scale process for manufacturing powders it is rarely possible, or only possible with considerable difficulty, to produce powders having average particle sizes of less than 0.5 (micrometers).It is known that melt atomization technique has been employed to produce ultra fine metal powders, but rarely for producing ceramic powders directly.
This is largely due to the fact that ceramic materials such as oxides and carbides have much higher melting temperatures as compared to their metal counterparts and require ultra-high temperature melting facilities. Therefore, ultra fine ceramic particles are usually produced by first preparing ultra fine base metal particles, which are then converted to the desired ceramics by a subsequent step of oxidation, carbonization, nitrogenization, etc.. These multiple-step processes are tedious and expensive. In solution or sol-gel type processes, atomization of precursor solutions to ceramics requires an additional step of solvent removal. Furthermore, the production rates of these processes are relatively low and the final products are expensive.The present invention is to provide a technique for producing manometer-sized ceramic powder, and more particularly, it can prepare manometer-sized composite ceramic powders at a high production rate.
SUMMARY OF THE INVENTION
The nano-sized ceramic powders can be prepared rapidly using an atomizing-reaction technique by which the superheated fluid reactive element is sprayed into a reaction chamber by means of a pressured preheated fluid medium through an atomizer, then the reactive element will occur chemical reaction with the fluid medium . The reactive element is metal or alloy mainly, and the fluid medium is oxygen , nitrogen or chlorine mainly. In figure l, the metal or alloy melt 3 is supplied into the reaction chamber through a guiding pipe 2 , the pressurized reactant fluid medium is introduced into reaction chamber 4 through a nozzle 1 from inlet A . A
reaction procedures between the super-heated metal or alloy melt and the fluid medium take place in the reaction chamber immediately, and the nano-sized reactant ceramic powder can be collected in outlet B.
The above-cited superheated temperature is approximately defined to be the temperature at which the surface tension of the metal melt is negligibly small or at which the metal melt is capable of initiating a substantially spontaneous reaction with a reactant species contained in the atomizing medium. The pressurized fluid not only possesses a sufficient kinetic energy to break up the metal melt stream into finely divided droplets, but also contains active reactant species to undergo a reaction with these fine metal droplets at high temperatures in a substantially spontaneous fashion.This process comprises: (a) providing a super-heated melt of a metallic element or the alloy into a reaction chamber through an atomizer ; (b) during the melt supplying procedure, introducing a pressurized reactant fluid medium element into this atomizer for atomizing the melt and initiating a reaction between the metal melt droplets and the reactant fluid medium to produce nano-sized reactant ceramic powder. Advantages of the present invention may be summarized as follows:
1. A wide variety of nano-scaled ceramic particles can be readily produced.
The corresponding reactants may be selected from the group of hydrogen, oxygen, nitrogen, carbon, chlorine, fluorine, and sulfur to form respectively metal hydrides, oxides, nitrides, carbides, chlorides, fluorides, and sulfides and combinations thereof. No known prior-art technique is so versatile in terms of readily producing so many different types of nano-scaled ceramic powders.
2. The presently invented process makes use of the concept that a metal melt, when superheated to an ultra-high temperature (e.g., reaching 2 to 6 times its melting temperature in degrees K) has a negligibly small surface tension so that a melt stream can be easily broken up into ultra-fine droplets .So the metal element can contact with the atomizing medium as much as possible.
More particularly, when the temperature of the melt up to the critical value, the atoms of the melt can be easily chemical combined with the atoms of the atomizing medium.
3. The metal melt can be an alloy of two or more elements which are uniformly dispersed. When broken up into ultrafme clusters, these elements remain uniformly dispersed and are capable of reacting with selected reactant species to form uniformly ceramic powder particles.
4. The selected super-heat temperatures also fall into the range of temperatures within which a spontaneous reaction between a metallic element and a reactant gas such as oxygen can occur.
The reaction heat released is automatically used to maintain the reacting medium in a sufficiently high temperature so that the reaction can be self sustaining until completion. The reaction between a metal and certain gas reactant (e.g., oxygen) can rapidly produce a great amount of heat energy, which can be used to drive other reactions that occur concurrently or subsequently when other reactant elements (e.g., nitrogen) are introduced.
DESCRIPTION OF PREFERRED EMBODIMENTS
Figurel schematically shows an apparatus, in accordance with a preferred embodiment of the present invention, for preparing composite nanosized ceramic powders. This apparatus comprises four necessary main components. The superheated metal or alloy melt 3 from a smelter is supplied into the reaction chamber 4 through a guiding pipe 2 , the pressurized reactant fluid medium is introduced into reaction chamber through a nozzle 1 from inlet A . A reaction procedures between the super-heated metal or alloy melt and the fluid medium take place in the reaction chamber immediately, and the nano-sized reactant ceramic powder can be collected in outlet B. In present invention, the metallic element may be selected from the group of some low melting point elements containing bismuth(Bi), tin(Sn), lead(Pb), zinc(Zn), Indium(In), cesium(Cs) and rubidium(Rb) etc;
and the alloy may be the low melting point one in which containing foresaid low melting point metals . For example, the Bi-Sn alloy, Pb-Sn alloy, In present inventon the foresaid metal or alloy melt should be superheated to reach 3 to 6 times its melting temperature. In present invention, the fluid medium may be oxygen, nitrogen or chlorine etc; the reactant will be metal oxides ,nitrides and chlorides etc; In present invention , when the superheated melt is an alloy , the reactant will be multi-components. For example, if the melt is Sn-Zn alloy and the medium is oxygen, the reactant will be Sn02 / Zn0 nanosized composite powder.
2160367 (May 10, 1994 to Helble, Joseph J.), CANADA Pat. CA 2153048 (Feb. 2 , 1999 to Helble, Joseph J.),U.S.patents: e.g., 4,282,195 (Aut.4, 1981 to H.H.Hoekje), 4,689,075 (Aug.25, 1987 to Uda, et al.), 4,889,665 (Dec.26,1989 to Uda, et al.), 5,599,511 (Feb.4, 1997 to Helble, et al.), and 5,019,686 (May 28, 1991 to Marantz).
The Conventional mechanical attrition and grading processes have the disadvantages that powders can only be produced up to a certain fineness and with relatively broad particle-size distribution. As a matter of fact, with the currently familiar large-scale process for manufacturing powders it is rarely possible, or only possible with considerable difficulty, to produce powders having average particle sizes of less than 0.5 (micrometers).It is known that melt atomization technique has been employed to produce ultra fine metal powders, but rarely for producing ceramic powders directly.
This is largely due to the fact that ceramic materials such as oxides and carbides have much higher melting temperatures as compared to their metal counterparts and require ultra-high temperature melting facilities. Therefore, ultra fine ceramic particles are usually produced by first preparing ultra fine base metal particles, which are then converted to the desired ceramics by a subsequent step of oxidation, carbonization, nitrogenization, etc.. These multiple-step processes are tedious and expensive. In solution or sol-gel type processes, atomization of precursor solutions to ceramics requires an additional step of solvent removal. Furthermore, the production rates of these processes are relatively low and the final products are expensive.The present invention is to provide a technique for producing manometer-sized ceramic powder, and more particularly, it can prepare manometer-sized composite ceramic powders at a high production rate.
SUMMARY OF THE INVENTION
The nano-sized ceramic powders can be prepared rapidly using an atomizing-reaction technique by which the superheated fluid reactive element is sprayed into a reaction chamber by means of a pressured preheated fluid medium through an atomizer, then the reactive element will occur chemical reaction with the fluid medium . The reactive element is metal or alloy mainly, and the fluid medium is oxygen , nitrogen or chlorine mainly. In figure l, the metal or alloy melt 3 is supplied into the reaction chamber through a guiding pipe 2 , the pressurized reactant fluid medium is introduced into reaction chamber 4 through a nozzle 1 from inlet A . A
reaction procedures between the super-heated metal or alloy melt and the fluid medium take place in the reaction chamber immediately, and the nano-sized reactant ceramic powder can be collected in outlet B.
The above-cited superheated temperature is approximately defined to be the temperature at which the surface tension of the metal melt is negligibly small or at which the metal melt is capable of initiating a substantially spontaneous reaction with a reactant species contained in the atomizing medium. The pressurized fluid not only possesses a sufficient kinetic energy to break up the metal melt stream into finely divided droplets, but also contains active reactant species to undergo a reaction with these fine metal droplets at high temperatures in a substantially spontaneous fashion.This process comprises: (a) providing a super-heated melt of a metallic element or the alloy into a reaction chamber through an atomizer ; (b) during the melt supplying procedure, introducing a pressurized reactant fluid medium element into this atomizer for atomizing the melt and initiating a reaction between the metal melt droplets and the reactant fluid medium to produce nano-sized reactant ceramic powder. Advantages of the present invention may be summarized as follows:
1. A wide variety of nano-scaled ceramic particles can be readily produced.
The corresponding reactants may be selected from the group of hydrogen, oxygen, nitrogen, carbon, chlorine, fluorine, and sulfur to form respectively metal hydrides, oxides, nitrides, carbides, chlorides, fluorides, and sulfides and combinations thereof. No known prior-art technique is so versatile in terms of readily producing so many different types of nano-scaled ceramic powders.
2. The presently invented process makes use of the concept that a metal melt, when superheated to an ultra-high temperature (e.g., reaching 2 to 6 times its melting temperature in degrees K) has a negligibly small surface tension so that a melt stream can be easily broken up into ultra-fine droplets .So the metal element can contact with the atomizing medium as much as possible.
More particularly, when the temperature of the melt up to the critical value, the atoms of the melt can be easily chemical combined with the atoms of the atomizing medium.
3. The metal melt can be an alloy of two or more elements which are uniformly dispersed. When broken up into ultrafme clusters, these elements remain uniformly dispersed and are capable of reacting with selected reactant species to form uniformly ceramic powder particles.
4. The selected super-heat temperatures also fall into the range of temperatures within which a spontaneous reaction between a metallic element and a reactant gas such as oxygen can occur.
The reaction heat released is automatically used to maintain the reacting medium in a sufficiently high temperature so that the reaction can be self sustaining until completion. The reaction between a metal and certain gas reactant (e.g., oxygen) can rapidly produce a great amount of heat energy, which can be used to drive other reactions that occur concurrently or subsequently when other reactant elements (e.g., nitrogen) are introduced.
DESCRIPTION OF PREFERRED EMBODIMENTS
Figurel schematically shows an apparatus, in accordance with a preferred embodiment of the present invention, for preparing composite nanosized ceramic powders. This apparatus comprises four necessary main components. The superheated metal or alloy melt 3 from a smelter is supplied into the reaction chamber 4 through a guiding pipe 2 , the pressurized reactant fluid medium is introduced into reaction chamber through a nozzle 1 from inlet A . A reaction procedures between the super-heated metal or alloy melt and the fluid medium take place in the reaction chamber immediately, and the nano-sized reactant ceramic powder can be collected in outlet B. In present invention, the metallic element may be selected from the group of some low melting point elements containing bismuth(Bi), tin(Sn), lead(Pb), zinc(Zn), Indium(In), cesium(Cs) and rubidium(Rb) etc;
and the alloy may be the low melting point one in which containing foresaid low melting point metals . For example, the Bi-Sn alloy, Pb-Sn alloy, In present inventon the foresaid metal or alloy melt should be superheated to reach 3 to 6 times its melting temperature. In present invention, the fluid medium may be oxygen, nitrogen or chlorine etc; the reactant will be metal oxides ,nitrides and chlorides etc; In present invention , when the superheated melt is an alloy , the reactant will be multi-components. For example, if the melt is Sn-Zn alloy and the medium is oxygen, the reactant will be Sn02 / Zn0 nanosized composite powder.
Claims (4)
1. A process for preparing nanosized ceramic powders, said process comprising (a) introducing a pressurized fluid medium into the reaction chamber through an atomizer.
(b) during said fluid medium supplying procedure, providing a super-heated metal or alloy melt into the reaction chamber through a guiding pipe located the center of the atomizer. The melt can be atomized by means of the pressurized fluid medium to form ultrafine droplets, and the nanosized ceramic powders can be prepared.
(b) during said fluid medium supplying procedure, providing a super-heated metal or alloy melt into the reaction chamber through a guiding pipe located the center of the atomizer. The melt can be atomized by means of the pressurized fluid medium to form ultrafine droplets, and the nanosized ceramic powders can be prepared.
2. A process as set forth in claim 1 wherein said melt is super-heated to a reaction temperature that lies between 2 times and 6 times the melting point of said metal or alloy when expressed in terms of degrees Kelvin.
3. A process as set forth in claim 1, 2 wherein said reactant fluid medium comprises oxygen, chlorine, or negatron mainly.
4. A process as set forth in claim 1, 2 and 3 wherein one said metallic element is selected from the group of low melting point elements containing bismuth, cadmium, cesium, gallium, indium, lead, lithium, rubidium, selenium, tellurium, tin, and zinc.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2298890 CA2298890A1 (en) | 2000-02-17 | 2000-02-17 | A technique to produce nanometer-sized ceramic powders |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2298890 CA2298890A1 (en) | 2000-02-17 | 2000-02-17 | A technique to produce nanometer-sized ceramic powders |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2298890A1 true CA2298890A1 (en) | 2001-08-17 |
Family
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2298890 Abandoned CA2298890A1 (en) | 2000-02-17 | 2000-02-17 | A technique to produce nanometer-sized ceramic powders |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2298890A1 (en) |
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2000
- 2000-02-17 CA CA 2298890 patent/CA2298890A1/en not_active Abandoned
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