CA2585644A1 - Aqueous-based method for producing ultra-fine metal powders - Google Patents
Aqueous-based method for producing ultra-fine metal powders Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/16—Making metallic powder or suspensions thereof using chemical processes
- B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
- B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/05—Metallic powder characterised by the size or surface area of the particles
- B22F1/054—Nanosized particles
- B22F1/0545—Dispersions or suspensions of nanosized particles
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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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
Abstract
The present invention provides a method for forming compositions having a plurality of ultra-fine metallic particles, and compositions produced therewith, by reducing an aqueous solution of an ammonium complex of the metal. Also provided is a substrate coated with the plurality of ultra-fine metallic particles obtained in accordance with the method of the present invention.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to ultra-fine metallic compositions and methods of making the same. The present invention further relates to methods of coating various substrates with ultra-fine metallic compositions.
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to ultra-fine metallic compositions and methods of making the same. The present invention further relates to methods of coating various substrates with ultra-fine metallic compositions.
BACKGROUND OF THE INVENTION
[0002] Ultra-fine metallic particles have many unique physical and chemical characteristics, which make them ideal materials for a variety of applications, such as electronics, catalysis, metallurgy, and decorations. Compared to the various particle-producing techniques used in the art, the methods based on the chemical precipitation in solutions provide several advantages, e.g., low manufacturing cost and a very good control of the mechanism of metal particles formation. Others in the art have successfully prepared micron and submicron-size metallic powders of Co, Cu, Ni, Pb, and Ag using chemical-based techniques, such as the ones based on the reduction in alcohols or polyols. For example, U.S. Patent No.
4,539,041 discusses a method for producing micrometer-size metallic particles by using polyols to convert various metallic compounds into metal powders.
4,539,041 discusses a method for producing micrometer-size metallic particles by using polyols to convert various metallic compounds into metal powders.
[0003] U.S. Pat. Nos. 3,620,713 and3,620,714 to Short disclose a method for making platinum and platinum alloy powders for electronic components, having an average particle size of from 0.5 to 2 m, in which a platinum ammonia complex is freshly precipitated with ammonium hydroxide and then reduced with hydrazine to produce the metal. U.S.
Pat. Nos.
Pat. Nos.
4,456,473 and 4,456,474 to Jost disclose a similar process in which a silver ammonium complex is reduced in water with hydrazine, to produce particles with diameters averaging 0.6 to 5 m.
U.S. Pat. No. 5,413,617 to Lin et al. also discloses reduction of a silver ammonium complex with aqueous hydrazine under a particular temperature regime to give high surface area powder of undisclosed particle size. According to U.S. Pat. No. 4,039,317 (Montino et al.), reduction of a silver ammonium complex with hydrogen in an autoclave provides silver particles of 0.5 to 3 m diameter, while similar reduction of silver oxide suspensions without ammonia reportedly yields particles as small as 0.1 m. A gold-ammonia complex has been reduced to 4 m gold particles with aqueous bisulfite (U.S. Pat. No. 5,413,617 to Fraioli).
Express Mail No. EV 446 920 045 [0004] The polyol procedures, require complex equipment and the metallic powders produced are generally more expensive because of the cost of the organic solvents used. The aqueous methods are less costly, but except for the Montini process, which requires an autoclave, they do not produce particles smaller than about 0.5 m. The present invention provides a process capable of cost-effectively generating low-dispersion, crystalline, ultra-fine metallic particles in an aqueous medium. Such particles are highly desirable in many practical applications, especially in electronics.
SUMMARY OF THE INVENTION
U.S. Pat. No. 5,413,617 to Lin et al. also discloses reduction of a silver ammonium complex with aqueous hydrazine under a particular temperature regime to give high surface area powder of undisclosed particle size. According to U.S. Pat. No. 4,039,317 (Montino et al.), reduction of a silver ammonium complex with hydrogen in an autoclave provides silver particles of 0.5 to 3 m diameter, while similar reduction of silver oxide suspensions without ammonia reportedly yields particles as small as 0.1 m. A gold-ammonia complex has been reduced to 4 m gold particles with aqueous bisulfite (U.S. Pat. No. 5,413,617 to Fraioli).
Express Mail No. EV 446 920 045 [0004] The polyol procedures, require complex equipment and the metallic powders produced are generally more expensive because of the cost of the organic solvents used. The aqueous methods are less costly, but except for the Montini process, which requires an autoclave, they do not produce particles smaller than about 0.5 m. The present invention provides a process capable of cost-effectively generating low-dispersion, crystalline, ultra-fine metallic particles in an aqueous medium. Such particles are highly desirable in many practical applications, especially in electronics.
SUMMARY OF THE INVENTION
[0005] The present invention provides a method for forming compositions having a plurality of ultra-fine metallic particles, and the metallic composition produced therewith, where the plurality of ultra-fine metallic particles is obtained in accordance with a process including:
(a) providing a reducing solution comprising a reducing agent and a stabilizing agent;
(b) providing a metal-ammonia solution containing a metal-ammonia complex;
(c) forming a reaction mixture containing the reducing solution and the metal-ammonia solution;
(d) maintaining the reaction mixture under a condition sufficient to reduce the metal-ammonia complex to metallic particles, thereby producing the plurality of ultra-fine metallic particles; and optionally, (e) isolating the metallic particles.
(a) providing a reducing solution comprising a reducing agent and a stabilizing agent;
(b) providing a metal-ammonia solution containing a metal-ammonia complex;
(c) forming a reaction mixture containing the reducing solution and the metal-ammonia solution;
(d) maintaining the reaction mixture under a condition sufficient to reduce the metal-ammonia complex to metallic particles, thereby producing the plurality of ultra-fine metallic particles; and optionally, (e) isolating the metallic particles.
[0006] In one embodiment of the present invention, the metal-ammonia complex is the complex of ammonia with a transitional metal or a noble metal, e.g., Cu, Pd, and Ag, formed by reacting a solution comprising a metal salt with ammonium hydroxide or ammonia. In certain embodiments, the reducing agent is a saccharide, such as D-glucose. In certain embodiments, the stabilizing agent is a water-soluble resin (e.g., a natural occurring, synthetic, or semi-synthetic water-soluble resin) or gum arabic. The gum arabic may be removed during the isolation of the metallic particles through hydrolysis. The plurality of ultra-fine metallic particles may have at least one desirable feature, such as tight size distribution, low degree of agglomeration, high degree of crystallinity, and the ability to be fully re-dispersed into a liquid (e.g. an aqueous solution) to form a stable dispersion.
[0007] In another aspect, the present invention provides a substrate coated with the plurality of ultra-fine metallic particles obtained in accordance with the method disclosed herein.
[0008] Other features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating the preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
BRIEF DESCRIPTION OF THE FIGURES
BRIEF DESCRIPTION OF THE FIGURES
[0009] Figure 1 depicts an experimental set-up used in the synthesis of ultra-fine silver particles.
[0010] Figure 2 shows the FE-SEM images of ultra-fine silver particles produced using the method of the present invention. (a) 198.7 g AgNO3 and flow rate at 8 ml/min; (b) 382 g AgNO3 and flow rate at 8 ml/min; and (c) 382 g AgNO3 and flow rate at 30 ml/min. Images were acquired using a FE-SEM at two magnifications (25,000 and 100,000).
[0011] Figure 3 illustrates the particle size distribution (PSD) of silver particles as number (%) (a) and volume (%) (b), obtained from 382 g AgNO3 at a flow rate of the metallic precursor solution of 30 ml/min.
[0012] Figure 4 shows the X-ray diffraction patterns of silver particles shown in Figure 2a.
[0013] As used herein and in the appended claims, the singular forms "a,"
"an," and "the"
include plural references unless the content clearly dictates otherwise. Thus, for example, reference to "a particle" includes a plurality of such particles and equivalents thereof known to those skilled in the art, and reference to "the reducing agent" is a reference to one or more reducing agent and equivalents thereof known to those skilled in the art, and so forth. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety.
"an," and "the"
include plural references unless the content clearly dictates otherwise. Thus, for example, reference to "a particle" includes a plurality of such particles and equivalents thereof known to those skilled in the art, and reference to "the reducing agent" is a reference to one or more reducing agent and equivalents thereof known to those skilled in the art, and so forth. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety.
[0014] The present invention generally provides a simple and cost-effective chemical-based method for producing highly dispersed ultra-fine metallic powders. The present invention also provides ultra-fine metallic particles having at least one desirable feature, such as tight size distribution, low degree of agglomeration, high degree of crystallinity, and the ability to re-disperse fully into a liquid (e.g. an aqueous solution) to form stable dispersions.
[0015] The present invention provides a method for producing metallic powders, and also the metallic powders produced thereby, that comprises the steps of (a) providing a reducing solution containing a reducing agent and a stabilizing agent; (b) providing an aqueous solution containing a metal-ammonia complex; (c) forming a reaction mixture containing the reducing solution and the aqueous solution; (d) maintaining the reaction mixture under a suitable conditions (e.g. pH and temperature) for a time sufficient to reduce the metal-ammonia complex to metallic particles; and optionally, (e) isolating the metallic particles.
[0016] The process of the present invention may be used to manufacture ultra-fine particles of various metals, such as Ag, Au, Co, Cr, Cu, Fe, Ir, Mo, Ni, Nb, Os, Pd, Pt, Re, Rh, Ru, Sn, Ta, Ti, V, and W, and alloys or composites containing these metals.
The metal-ammonia complex may be mixed with a reducing composition or agent, which converts the metal ions to ultra-fine metal particles under various reaction conditions.
The metal-ammonia complex may be mixed with a reducing composition or agent, which converts the metal ions to ultra-fine metal particles under various reaction conditions.
[0017] The metal-ammonia complex used in the process of the present invention may be the complex of ammonium with those transition metals and noble metals, such as, Ag, Au, Co, Cu, In, Ir, Ni, Nb, Os, Pd, Pt, Re, Rh, and Ru, and combinations thereof, that are amenable to being produced by reduction of a precursor compound with a reducing sugar. In one embodiment, the metal-ammonia complex may be obtained by reacting a solution containing a metal salt with ammonium hydroxide or ammonia. For example, 198.7 g AgNO3 may be dissolved in 234 ml deionized water. After the silver nitrate is completely dissolved, 195 ml ammonium hydroxide is added into the silver nitrate solution with stirring.
Deionized water (291 ml) is then added to bring the overall volume of the silver ammonia solution to 720 ml.
This solution should be sealed (to prevent ammonia evaporation) and protected from light with aluminum foil.
Deionized water (291 ml) is then added to bring the overall volume of the silver ammonia solution to 720 ml.
This solution should be sealed (to prevent ammonia evaporation) and protected from light with aluminum foil.
[0018] The term "reducing composition" or "reducing agent," as used herein and in the appended claims, generally includes any reducing substance, and a combination thereof, which is capable of reducing metal ions to metallic particles, such as, without limitation, aldehydes, aldose, hydrazine hydrate, and especially reducing saccharides (including monosaccharides, disaccharides, oligosaccharides, and polysaccarides). Examples of reducing saccharides include, but are not limited to, ascorbic acid, glyceraldehyde, erythrose, threose, ribose, arabinose, xylose, lyxose, allose, altrose, glucose, dextrose, mannose, gulose, idose, galactose, talose, lactose, maltose, isomaltose, cellobiose, and starch. The nature of the reducing species and their composition in the process of the present invention may be dependent upon the particular metal being produced.
[0019] The term "stabilizing composition" or "stabilizing agent," as used herein and in the appended claims, generally includes any stabilizing substance, such as, without limitation, water soluble resins (including, e.g., naturally occurring, synthetic, and semi-synthetic water soluble resins), gum arabic, polymers, polysaccharides, glycoproteins, nucleic acids, various salts of naphthalene sulphonic-formaldehyde co-polymers, and a combination thereof, which is capable of dispersing and stabilizing the newly formed ultra-fine metallic particles in the reaction mixture and thus preventing undesirable aggregation of these particles such that the size of the resulting metallic particles is less than about 10 m, preferably, less than about I m, and more preferably, less than about 100 nm. As used herein and in the appended claims, the term "ultra-fine particles" generally includes particles having diameters of less than about 10 m, preferably, less than about 1,000 nm, and more preferably, less than about 500 nm, and even more preferably, less than about 100 nm.
[0020] The stabilizing composition used in the process of the present invention may be commanded by the particular reaction. Examples of suitable stabilizing agents include, without limitation, gum arabic, cellulose derivatives (e.g., carboxymethyl cellulose, carboxyethyl cellulose, methyl cellulose, etc.) and modified products thereof, polyvinyl alcohol and derivatives thereof, polyvinyl pyrrolidone, polyacrylamide and copolymers thereof, acrylic acid copolymers, vinylmethyl ether-maleic anhydride copolymers, vinyl acetate-maleic anhydride copolymers, various salts of naphthalene sulphonic-formaldehyde co-polymers, styrene-maleic anhydride copolymers, calcined dextrin, acid-decomposed dextrin, acid-decomposed etherified dextrin, agarose, and salmon sperm DNA. In one embodiment of the present invention, the stabilizing agent may be gum arabic. In another embodiment of the present invention, the stabilizing agent may be a salt of naphthalene sulphonic-formaldehyde co-polymer.
[0021] The stabilizing agent, such as gum arabic, may be removed after the reaction. A
number of protocols for removing the stabilizing agent are known in the art, such as, acid, alkaline, and/or enzymatic hydrolysis. In one embodiment, gum arabic may be removed from the reaction mixture after the reaction through alkaline hydrolysis. For example, the hydrolysis may be performed for extended time at high temperature (e.g. between about 70 C and about 100 C, or between about 80 C and about 90 C, or between about 82 C and about 88 C) and high pH (e.g. pH 11.5). It is generally desirable to maintain the pH of the mixture during the hydrolysis at between about 9 and about 14, or between about 10 and about 12, or between about 10.5 and about 11.5. The duration of the hydrolysis may be dictated by a number of facts, such as the amount of stabilizing agent (e.g. gum arabic) used. In various embodiments, the hydrolysis of the gum may generally be performed for about 0.2 to 10 hours, or about 1 to 5 hours, or about 2 to 3 hours.
number of protocols for removing the stabilizing agent are known in the art, such as, acid, alkaline, and/or enzymatic hydrolysis. In one embodiment, gum arabic may be removed from the reaction mixture after the reaction through alkaline hydrolysis. For example, the hydrolysis may be performed for extended time at high temperature (e.g. between about 70 C and about 100 C, or between about 80 C and about 90 C, or between about 82 C and about 88 C) and high pH (e.g. pH 11.5). It is generally desirable to maintain the pH of the mixture during the hydrolysis at between about 9 and about 14, or between about 10 and about 12, or between about 10.5 and about 11.5. The duration of the hydrolysis may be dictated by a number of facts, such as the amount of stabilizing agent (e.g. gum arabic) used. In various embodiments, the hydrolysis of the gum may generally be performed for about 0.2 to 10 hours, or about 1 to 5 hours, or about 2 to 3 hours.
[0022] The resulting ultra-fine metal particles may be isolated following standard protocols known in the art, such as by precipitation, filtration, and centrifugation. The particles may further be washed, such as by using methanol or ethanol, and dried, such as by air, N2, or vacuum.
[0023] The ultra-fine metallic particles may also have at least one desirable feature, such as, tight size distribution, low degree of agglomeration, high degree of crystallinity, ability to re-disperse fully into a liquid (e.g. an aqueous solution) to form stable dispersion, or a combination thereof.
[0024] Unlike other metallic powders appearing in the art, the system of the present invention produces metallic powders that include ultra-fine metallic particles that have a tight size distribution. The breadth of the size distribution, as used herein, generally refers to the degree of variation in the diameter of the ultra-fine metallic particles in a metallic composition.
The ultra-fine metallic particles are deemed to have a tight size distribution when the diameters of at least about 80%, preferably, at least about 85%, more preferably, at least about 95%, and most preferably 99-100% of the ultra-fine metallic particles of the present invention are within the range of N 15% N, where N is the average diameter of the ultra-fine metallic particles. The diameters of the ultra-fine metallic particles may be measured by a number of techniques, such as by electron microscopy with a scanning electron microscope (e.g. field emission scanning electron microscope).
The ultra-fine metallic particles are deemed to have a tight size distribution when the diameters of at least about 80%, preferably, at least about 85%, more preferably, at least about 95%, and most preferably 99-100% of the ultra-fine metallic particles of the present invention are within the range of N 15% N, where N is the average diameter of the ultra-fine metallic particles. The diameters of the ultra-fine metallic particles may be measured by a number of techniques, such as by electron microscopy with a scanning electron microscope (e.g. field emission scanning electron microscope).
[0025] The metallic powders produced in accordance with the present invention may also include ultra-fine metallic particles that have a low degree of agglomeration, as illustrated in Figure 3. The degree of agglomeration may be expressed using the index of agglomeration 1aggi, which is the ratio between the average particle size distribution of the metallic particles ("PSD50%") and the average diameter of the particles. The average particle size distribution may be determined by any methods known in the art, including, but not limited to, dynamic light scattering (DLS), laser diffraction, and sedimentation methods, while the average particle size may be determined by averaging the diameter of the individual ultra-fine metallic particles obtained by, e.g., electron microscopy. An Iaggi value of 1.0 indicates a complete lack of agglomeration, while an increase in Iaggi value indicates an increase in the degree of aggregation.
In one embodiment, the powders of ultra-fine metallic particles of the present invention have an Iagg, value of about 1.2 or less.
[00261 The metallic powders produced in accordance with the present invention may also include ultra-fine metallic particles that have a high degree of crystallinity. The term "degree of crystallinity," as used herein and in the appended claims, generally refers to the ratio between the size of the crystallites in the metallic powder and the diameter of the metallic particles. The size of the constituent crystallites may be deduced from XRD measurements using the Sherrer's equation, while the particle size may be determined by electron microscopy. A
larger ratio of the size of the crystallites in comparison to the diameter of the metallic particles indicates an increased degree of crystallinity and a lower internal grain boundary surface.
In one embodiment, the ultra-fine metallic particles have a high degree of crystallinity if at least about 80%, preferably, at least about 85%, more preferably, at least about 90-95%, and even more preferably, about 100% of the ultra-fine metallic particles of the present invention are highly crystalline. The high degree of crystallinity is reflected by the visible splitting of the peaks corresponding to the (220), (311), and (222) reflections in the XRD spectrum (see Figure 4).
[00271 The ultra-fine metallic particles produced in accordance with the present invention may form a free flowing dry powder in which the majority of the individual particles may not be strongly attached to each other and may be readily re-dispersed in a liquid of choice.
[00281 In another embodiment of the present invention, the ultra-fine metallic particles forms stable dispersion when re-dispersed into a liquid, such as water, or an aqueous solution, where the majority of the individual particles may move substantially freely in the liquid in which they are dispersed. In one embodiment, the particle dispersion may be stable for at least one week. In another embodiment, the particle dispersion may be stable for about 12 weeks.
[00291 The present invention further provides a substrate coated with a plurality of ultra-fine metallic particles, where the plurality of ultra-fine metallic particles have at least one desired feature, such as, tight size distribution, a low degree of agglomeration, a high degree of crystallinity, and oxidation resistance and are prepared by the methods described herein.
Preferably the substrate is coated by immersion in the reaction mixture in which the ultra-fine metallic particles are produced. The term "substrate" as used herein includes, without limitation, metallic subjects (e.g., metallic particles, flakes, tubes, and sheets), plastic materials, ceramic subjects, fibers, films, glasses, polymers, organic materials (e.g. resins), inorganic materials (e.g., amorphous carbon and carbon nanotubes), and any other object capable of being coated with the ultra-fine metallic particles produced in accordance with the present invention. The ultra-fine metallic particles may be the metallic particles of various metals, preferably, Cu, Pd, and Ag.
EXAMPLES
[0030] The following examples illustrate the present invention, which are set forth to aid in the understanding of the invention, and should not be construed to limit in any way the scope of the invention as defined in the claims which follow thereafter.
[0031] The ultra-fine silver, palladium and copper particles were prepared by reducing the metallic ammonium complex with D-glucose in the presence of gum arabic.
The experimental set-up for these experiments is illustrated in Figure 1.
[0032] Materials: Silver nitrate (AgNO3) was obtained from Ames Goldsmith Corp.
(Glens Falls, NY). Gum arabic was obtained from Frutarom Incorporated (North Bergen, NJ).
Ammonium hydroxide (NH40H, 28% in water) was purchased from Fischer Scientific Co. (Fair Lawn, NJ). Acetone, ethanol, and sodium hydroxide (NaOH) solution (10 N) were supplied by Alfa Aesar (Ward Hill, MA). D-glucose was purchased from Avocado Research Chemicals Ltd.
(Shore Road, Heyshane, Lancs.). Cupric nitrate hydrate [Cu(N03)2 2'/z H20] was obtained from J.T. Baker Chemical Co. (Phillipsburg, NJ), and palladium nitrate solution 9.0% was obtained from Umicore (South Plainfield, NJ).
(A) PREPARATION OF THE REDUCING SOLUTION
[0033] 3 liters deionised ("DI") water was heated to 55 C in an 8-1 stainless steel beaker.
When the temperature reached 55 C, 62.5 g gum arabic was slowly added into the water and dissolved by stirring the solution with a stirring propeller at low speed for 55 minutes. 36 g of D-glucose were then added to the solution. The mixture was stirred at 1700 rpm for 5 minutes.
(B) PREPARATION OF SILVER AMMONIUM COMPLEX SOLUTION
[0034] AgNO3 (198.7 g) was dissolved in 234 ml DI water in a 2-1 glass beaker.
After the silver nitrate was completely dissolved, 195 ml ammonium hydroxide was added with stirring, followed by the addition of 291 ml DI water to reach a final volume of 720 ml.
(C) PREPARATION OF ULTRA-FINE SILVER PARTICLES
'[0035] METHOD A: The reduction process was conducted by pumping the silver ammonium solution into the reducing solution at a flow rate of 8 mI/min using a peristaltic pump. When the addition of the silver complex solution was completed, the temperature was brought to 80 C. The entire process was conducted under continuous stirring (1700 rpm).
[0036] METHOD B: The D-glucose was separately dissolved in 720 ml water. The volume of the gum arabic solution was correspondingly reduced, and adjusted to a pH between 9 and 13 with sodium hydroxide. The reduction process was conducted by simultaneously pumping the silver ammonium solution and the D-glucose solution into the gum arabic solution at 8 ml/min, while maintaining the pH by the addition of sodium hydroxide solution as needed.
When the addition of the silver and D-glucose solutions was completed, the temperature was brought to 80 C. The entire process was conducted under continuous stirring (1700 rpm).
(D) HYDROLYSIS OF GUM ARABIC
[0037] The excess of gum arabic was removed by increasing the pH of the dispersion to 11.5 with 10.0 N sodium hydroxide at the temperature of about 85 C. The dispersion was maintained in the condition for 2.5 hours.
(D) PROCESSING THE SILVER POWDER
[0038] When the hydrolysis of the gum was complete, the dispersion was allowed to cool and the silver particles to settle. The supernatant was then discarded and the silver particles were washed with water through 3 successive decantations. During the last wash, 50%
ethanol (in DI
water) was added to the settled metallic deposit instead of DI water. Two more washes with pure alcohol were performed. The powder was then dried overnight on filter paper at room temperature.
(A) PREPARATION OF THE REDUCING SOLUTION
[0039] A volume of 500 ml DI water was heated to 70 C in 2-1 glass beaker.
When the temperature reached 70 C, 10 g gum arabic was slowly added into the water and dissolved by stirring the solution. 100 g of D-glucose were then added to the solution and the mixture was stirred at 1700 rpm for 5 minutes. The pH of solution was adjusted to 10.5 with 10.0 N NaOH.
(B) PREPARATION OF PALLADIUM AMMONIUM COMPLEX SOLUTION
[0040] Ammonium hydroxide (80 ml) was added quickly with stirring to 50 ml Pd(NO3)2 solution (9.0%) in a 200 ml glass beaker, followed by the addition of 50 ml DI
water (final volume: 180 ml).
(C) PREPARATION OF ULTRA-FINE PALLADIUM PARTICLES
[0041] The reducing reaction was conducted by pumping the palladium ammonium solution into the reducing solution at a flow rate of 5 ml/min using a peristaltic pump. When the addition of the palladium complex solution was complete, the temperature was brought to 80 C.
The process was conducted under continuous stirring (1700 rpm).
[0042] The hydrolysis of gum arabic and the processing of palladium powder were carried out in a similar manner as in Example 1(steps D and E).
(A) PREPARATION OF THE REDUCING SOLUTION
[0043] A volume of 500 ml DI water was heated to 70 C in 2-I glass beaker.
When the temperature reached 70 C, 25 g gum Arabic was slowly added into the water and dissolved by stirring the solution with a stirring propeller at 1700 rpm for 55 minutes.
100 g of D-glucose were then added to the solution and the mixture was stirred at 1700 rpm for 5 minutes. The pH
of solution was adjusted at 10.5 with 10.0 N NaOH.
(B) PREPARATION OF COPPER AMMONIUM COMPLEX SOLUTION
[0044] 18.2 g cupric nitrate (Cu(NO3)2 2'/2 H2O) were dissolved in 50 ml DI
water in a 200 mI glass beaker. After the cupric nitrate was completely dissolved, 100 ml ammonium hydroxide was added quickly with stirring, followed by the addition of 50 ml DI water (overall volume: 200 ml).
(C) PREPARATION OF ULTRA-FINE COPPER PARTICLES
[0045] The reduction process was conducted by pumping the cupric ammonium solution into the reducing solution at a flow rate of 5 ml/min using a peristaltic pump. When the addition of the cupric complex solution was complete, the temperature was brought to 80 C. The process was conducted with continuous stirring (1700 rpm). The remaining steps are similar to those of Example 1.
[0046] Discussed below are results obtained by the inventors in connection with the experiments of Examples 1-3:
[0047] The size of the silver particles obtained did not undergo a substantial change when the process was scaled up by a factor of two or when the flow rate of the silver ammonium complex solution was raised to 30 ml/min from 8 mI/min, suggesting a minor impact of both parameters on the size of the particles formed. For all experiments the processing yield was >97%.
[0048] The experimental conditions and results of Example I (Method A) are summarized in Table I. Method B gave somewhat smaller particles; at pH 12 particles with an average diameter of 40 nm were obtained.
Table I
Reducing solution Silver ammonium solution Average Bach size Flow rate LXp' Ag (g) Water Gum Glucose Water AgNO3 NH4OH (ml/min) size (L) arabic (g) (g) (ml) (g) (ml) (nm) 1 125 3 62.5 36 525 198.7 195 8 -70 [0049] While the foregoing invention has been described in some detail for purposes of clarity and understanding, it will be appreciated by one skilled in the art, from a reading of the disclosure, that various changes in form and detail can be made without departing from the true scope of the invention in the appended claims.
In one embodiment, the powders of ultra-fine metallic particles of the present invention have an Iagg, value of about 1.2 or less.
[00261 The metallic powders produced in accordance with the present invention may also include ultra-fine metallic particles that have a high degree of crystallinity. The term "degree of crystallinity," as used herein and in the appended claims, generally refers to the ratio between the size of the crystallites in the metallic powder and the diameter of the metallic particles. The size of the constituent crystallites may be deduced from XRD measurements using the Sherrer's equation, while the particle size may be determined by electron microscopy. A
larger ratio of the size of the crystallites in comparison to the diameter of the metallic particles indicates an increased degree of crystallinity and a lower internal grain boundary surface.
In one embodiment, the ultra-fine metallic particles have a high degree of crystallinity if at least about 80%, preferably, at least about 85%, more preferably, at least about 90-95%, and even more preferably, about 100% of the ultra-fine metallic particles of the present invention are highly crystalline. The high degree of crystallinity is reflected by the visible splitting of the peaks corresponding to the (220), (311), and (222) reflections in the XRD spectrum (see Figure 4).
[00271 The ultra-fine metallic particles produced in accordance with the present invention may form a free flowing dry powder in which the majority of the individual particles may not be strongly attached to each other and may be readily re-dispersed in a liquid of choice.
[00281 In another embodiment of the present invention, the ultra-fine metallic particles forms stable dispersion when re-dispersed into a liquid, such as water, or an aqueous solution, where the majority of the individual particles may move substantially freely in the liquid in which they are dispersed. In one embodiment, the particle dispersion may be stable for at least one week. In another embodiment, the particle dispersion may be stable for about 12 weeks.
[00291 The present invention further provides a substrate coated with a plurality of ultra-fine metallic particles, where the plurality of ultra-fine metallic particles have at least one desired feature, such as, tight size distribution, a low degree of agglomeration, a high degree of crystallinity, and oxidation resistance and are prepared by the methods described herein.
Preferably the substrate is coated by immersion in the reaction mixture in which the ultra-fine metallic particles are produced. The term "substrate" as used herein includes, without limitation, metallic subjects (e.g., metallic particles, flakes, tubes, and sheets), plastic materials, ceramic subjects, fibers, films, glasses, polymers, organic materials (e.g. resins), inorganic materials (e.g., amorphous carbon and carbon nanotubes), and any other object capable of being coated with the ultra-fine metallic particles produced in accordance with the present invention. The ultra-fine metallic particles may be the metallic particles of various metals, preferably, Cu, Pd, and Ag.
EXAMPLES
[0030] The following examples illustrate the present invention, which are set forth to aid in the understanding of the invention, and should not be construed to limit in any way the scope of the invention as defined in the claims which follow thereafter.
[0031] The ultra-fine silver, palladium and copper particles were prepared by reducing the metallic ammonium complex with D-glucose in the presence of gum arabic.
The experimental set-up for these experiments is illustrated in Figure 1.
[0032] Materials: Silver nitrate (AgNO3) was obtained from Ames Goldsmith Corp.
(Glens Falls, NY). Gum arabic was obtained from Frutarom Incorporated (North Bergen, NJ).
Ammonium hydroxide (NH40H, 28% in water) was purchased from Fischer Scientific Co. (Fair Lawn, NJ). Acetone, ethanol, and sodium hydroxide (NaOH) solution (10 N) were supplied by Alfa Aesar (Ward Hill, MA). D-glucose was purchased from Avocado Research Chemicals Ltd.
(Shore Road, Heyshane, Lancs.). Cupric nitrate hydrate [Cu(N03)2 2'/z H20] was obtained from J.T. Baker Chemical Co. (Phillipsburg, NJ), and palladium nitrate solution 9.0% was obtained from Umicore (South Plainfield, NJ).
(A) PREPARATION OF THE REDUCING SOLUTION
[0033] 3 liters deionised ("DI") water was heated to 55 C in an 8-1 stainless steel beaker.
When the temperature reached 55 C, 62.5 g gum arabic was slowly added into the water and dissolved by stirring the solution with a stirring propeller at low speed for 55 minutes. 36 g of D-glucose were then added to the solution. The mixture was stirred at 1700 rpm for 5 minutes.
(B) PREPARATION OF SILVER AMMONIUM COMPLEX SOLUTION
[0034] AgNO3 (198.7 g) was dissolved in 234 ml DI water in a 2-1 glass beaker.
After the silver nitrate was completely dissolved, 195 ml ammonium hydroxide was added with stirring, followed by the addition of 291 ml DI water to reach a final volume of 720 ml.
(C) PREPARATION OF ULTRA-FINE SILVER PARTICLES
'[0035] METHOD A: The reduction process was conducted by pumping the silver ammonium solution into the reducing solution at a flow rate of 8 mI/min using a peristaltic pump. When the addition of the silver complex solution was completed, the temperature was brought to 80 C. The entire process was conducted under continuous stirring (1700 rpm).
[0036] METHOD B: The D-glucose was separately dissolved in 720 ml water. The volume of the gum arabic solution was correspondingly reduced, and adjusted to a pH between 9 and 13 with sodium hydroxide. The reduction process was conducted by simultaneously pumping the silver ammonium solution and the D-glucose solution into the gum arabic solution at 8 ml/min, while maintaining the pH by the addition of sodium hydroxide solution as needed.
When the addition of the silver and D-glucose solutions was completed, the temperature was brought to 80 C. The entire process was conducted under continuous stirring (1700 rpm).
(D) HYDROLYSIS OF GUM ARABIC
[0037] The excess of gum arabic was removed by increasing the pH of the dispersion to 11.5 with 10.0 N sodium hydroxide at the temperature of about 85 C. The dispersion was maintained in the condition for 2.5 hours.
(D) PROCESSING THE SILVER POWDER
[0038] When the hydrolysis of the gum was complete, the dispersion was allowed to cool and the silver particles to settle. The supernatant was then discarded and the silver particles were washed with water through 3 successive decantations. During the last wash, 50%
ethanol (in DI
water) was added to the settled metallic deposit instead of DI water. Two more washes with pure alcohol were performed. The powder was then dried overnight on filter paper at room temperature.
(A) PREPARATION OF THE REDUCING SOLUTION
[0039] A volume of 500 ml DI water was heated to 70 C in 2-1 glass beaker.
When the temperature reached 70 C, 10 g gum arabic was slowly added into the water and dissolved by stirring the solution. 100 g of D-glucose were then added to the solution and the mixture was stirred at 1700 rpm for 5 minutes. The pH of solution was adjusted to 10.5 with 10.0 N NaOH.
(B) PREPARATION OF PALLADIUM AMMONIUM COMPLEX SOLUTION
[0040] Ammonium hydroxide (80 ml) was added quickly with stirring to 50 ml Pd(NO3)2 solution (9.0%) in a 200 ml glass beaker, followed by the addition of 50 ml DI
water (final volume: 180 ml).
(C) PREPARATION OF ULTRA-FINE PALLADIUM PARTICLES
[0041] The reducing reaction was conducted by pumping the palladium ammonium solution into the reducing solution at a flow rate of 5 ml/min using a peristaltic pump. When the addition of the palladium complex solution was complete, the temperature was brought to 80 C.
The process was conducted under continuous stirring (1700 rpm).
[0042] The hydrolysis of gum arabic and the processing of palladium powder were carried out in a similar manner as in Example 1(steps D and E).
(A) PREPARATION OF THE REDUCING SOLUTION
[0043] A volume of 500 ml DI water was heated to 70 C in 2-I glass beaker.
When the temperature reached 70 C, 25 g gum Arabic was slowly added into the water and dissolved by stirring the solution with a stirring propeller at 1700 rpm for 55 minutes.
100 g of D-glucose were then added to the solution and the mixture was stirred at 1700 rpm for 5 minutes. The pH
of solution was adjusted at 10.5 with 10.0 N NaOH.
(B) PREPARATION OF COPPER AMMONIUM COMPLEX SOLUTION
[0044] 18.2 g cupric nitrate (Cu(NO3)2 2'/2 H2O) were dissolved in 50 ml DI
water in a 200 mI glass beaker. After the cupric nitrate was completely dissolved, 100 ml ammonium hydroxide was added quickly with stirring, followed by the addition of 50 ml DI water (overall volume: 200 ml).
(C) PREPARATION OF ULTRA-FINE COPPER PARTICLES
[0045] The reduction process was conducted by pumping the cupric ammonium solution into the reducing solution at a flow rate of 5 ml/min using a peristaltic pump. When the addition of the cupric complex solution was complete, the temperature was brought to 80 C. The process was conducted with continuous stirring (1700 rpm). The remaining steps are similar to those of Example 1.
[0046] Discussed below are results obtained by the inventors in connection with the experiments of Examples 1-3:
[0047] The size of the silver particles obtained did not undergo a substantial change when the process was scaled up by a factor of two or when the flow rate of the silver ammonium complex solution was raised to 30 ml/min from 8 mI/min, suggesting a minor impact of both parameters on the size of the particles formed. For all experiments the processing yield was >97%.
[0048] The experimental conditions and results of Example I (Method A) are summarized in Table I. Method B gave somewhat smaller particles; at pH 12 particles with an average diameter of 40 nm were obtained.
Table I
Reducing solution Silver ammonium solution Average Bach size Flow rate LXp' Ag (g) Water Gum Glucose Water AgNO3 NH4OH (ml/min) size (L) arabic (g) (g) (ml) (g) (ml) (nm) 1 125 3 62.5 36 525 198.7 195 8 -70 [0049] While the foregoing invention has been described in some detail for purposes of clarity and understanding, it will be appreciated by one skilled in the art, from a reading of the disclosure, that various changes in form and detail can be made without departing from the true scope of the invention in the appended claims.
Claims (33)
1. A composition comprising a plurality of ultra-fine metallic particles obtained by a process comprising:
(a) providing an aqueous reducing solution comprising a reducing agent and a stabilizing agent;
(b) providing an aqueous metal-ammonia solution comprising a metal-ammonia complex;
(c) forming an aqueous reaction mixture by gradually adding the metal-ammonia solution to the reducing solution; and (d) maintaining the reaction mixture at a pH and a temperature sufficient to reduce the metal-ammonia complex to a plurality of ultra-fine metallic particles.
(a) providing an aqueous reducing solution comprising a reducing agent and a stabilizing agent;
(b) providing an aqueous metal-ammonia solution comprising a metal-ammonia complex;
(c) forming an aqueous reaction mixture by gradually adding the metal-ammonia solution to the reducing solution; and (d) maintaining the reaction mixture at a pH and a temperature sufficient to reduce the metal-ammonia complex to a plurality of ultra-fine metallic particles.
2. A composition comprising a plurality of ultra-fine metallic particles obtained by a process comprising:
(a) providing an aqueous reducing solution comprising a reducing agent;
(b) providing an aqueous metal-ammonia solution comprising a metal-ammonia complex;
(c) providing an aqueous solution of a stabilizing agent;
(d) forming a reaction mixture by gradually and simultaneously adding the reducing solution and the metal-ammonia solution to the solution of the stabilizing agent; and (d) maintaining the reaction mixture under conditions at a pH and a temperature sufficient to reduce the metal-ammonia complex to a plurality of ultra-fine metallic particles.
(a) providing an aqueous reducing solution comprising a reducing agent;
(b) providing an aqueous metal-ammonia solution comprising a metal-ammonia complex;
(c) providing an aqueous solution of a stabilizing agent;
(d) forming a reaction mixture by gradually and simultaneously adding the reducing solution and the metal-ammonia solution to the solution of the stabilizing agent; and (d) maintaining the reaction mixture under conditions at a pH and a temperature sufficient to reduce the metal-ammonia complex to a plurality of ultra-fine metallic particles.
3. The composition of claim 1 wherein the metal is selected from the group consisting of transition metals and noble metals.
4. The composition of claim 2 wherein the metal is selected from the group consisting of transition metals and noble metals.
5. The composition of claim 1, wherein the metal is selected from the group consisting of Cu, Pd, and Ag.
6. The composition of claim 2, wherein the metal is selected from the group consisting of Cu, Pd, and Ag.
7. The composition of any one of claims 1-6, wherein the reducing agent is a saccharide.
8. The composition of claim 7, wherein the reducing agent is D-glucose.
9. The composition of any one of claims 1-6, wherein the stabilizing agent is a water-soluble resin.
10. The composition of claim 9, wherein the water-soluble resin is gum arabic or a salt of a naphthalene sulphonic acid-formaldehyde co-polymer.
11. The composition any one of claims 1-6, wherein the ultra-fine metallic particles have an average diameter N of less than about 100 nm.
12. The composition of claim 11, wherein at least about 80% of the metallic particles have a diameter within a range of N ~ 15% N.
13. The composition of claim 12, wherein at least about 80% of the ultra-fine metallic particles are crystalline.
14. The composition of claim 13, wherein about 100% of the ultra-fine metallic particles are crystalline.
15. The composition of any one of claims 1-6, wherein the plurality of ultra-fine metallic particles, when re-dispersed into an aqueous liquid, forms a dispersion which is stable for at least one week.
16. The composition of claim 15, wherein the dispersion is stable for 12 weeks.
17. A method for preparing a plurality of ultra-fine metallic particles, comprising:
(a) providing an aqueous reducing solution comprising a reducing agent and a stabilizing agent;
(b) providing an aqueous metal-ammonia solution comprising a metal-ammonia complex;
(c) forming an aqueous reaction mixture by gradually adding the metal-ammonia solution to the reducing solution; and (d) maintaining the reaction mixture at a pH and a temperature sufficient to reduce the metal-ammonia complex to a plurality of ultra-fine metallic particles.
(a) providing an aqueous reducing solution comprising a reducing agent and a stabilizing agent;
(b) providing an aqueous metal-ammonia solution comprising a metal-ammonia complex;
(c) forming an aqueous reaction mixture by gradually adding the metal-ammonia solution to the reducing solution; and (d) maintaining the reaction mixture at a pH and a temperature sufficient to reduce the metal-ammonia complex to a plurality of ultra-fine metallic particles.
18. A method for preparing a plurality of ultra-fine metallic particles, comprising:
(a) providing an aqueous reducing solution comprising a reducing agent;
(b) providing an aqueous metal-ammonia solution comprising a metal-ammonia complex;
(c) providing an aqueous solution of a stabilizing agent;
(d) forming a reaction mixture by gradually and simultaneously adding the reducing solution and the metal-ammonia solution to the solution of the stabilizing agent; and (d) maintaining the reaction mixture under conditions at a pH and a temperature sufficient to reduce the metal-ammonia complex to a plurality of ultra-fine metallic particles.
(a) providing an aqueous reducing solution comprising a reducing agent;
(b) providing an aqueous metal-ammonia solution comprising a metal-ammonia complex;
(c) providing an aqueous solution of a stabilizing agent;
(d) forming a reaction mixture by gradually and simultaneously adding the reducing solution and the metal-ammonia solution to the solution of the stabilizing agent; and (d) maintaining the reaction mixture under conditions at a pH and a temperature sufficient to reduce the metal-ammonia complex to a plurality of ultra-fine metallic particles.
19. The method of claim 17 wherein the metal is selected from the group consisting of transition metals and noble metals.
20. The methodof claim 18 wherein the metal is selected from the group consisting of transition metals and noble metals.
21. The method of claim 17, wherein the metal is selected from the group consisting of Cu, Pd, and Ag.
22. The method of claim 18, wherein the metal is selected from the group consisting of Cu, Pd, and Ag.
23. The method of any one of claims 17-22, wherein the reducing agent is a saccharide.
24. The method of claim 23, wherein the reducing agent is D-glucose.
25. The method of any one of claims 17-22, wherein the stabilizing agent is a water-soluble resin.
26. The method of claim 25, wherein the water-soluble resin is gum arabic or a salt of a naphthalene sulphonic acid-formaldehyde co-polymer.
27. The method of any one of claims 17-22, wherein the ultra-fine metallic particles have an average diameter N of less than about 100 nm.
28. The method of claim 27, wherein at least about 80% of the metallic particles have a diameter within a range of N ~ 15% N.
29. The method of claim 28, wherein at least about 80% of the ultra-fine metallic particles are crystalline.
30. The method of claim 29, wherein about 100% of the ultra-fine metallic particles are crystalline.
31. The method of any one of claims 17-22, wherein the plurality of ultra-fine metallic particles, when re-dispersed into an aqueous liquid, forms a dispersion which is stable for at least one week.
32. The method of claim 31, wherein the dispersion is stable for 12 weeks.
33. The method of any of claims 17-22, wherein a substrate is submerged in the reaction mixture.
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US10/978,153 | 2004-10-29 | ||
| US10/978,153 US8470066B2 (en) | 2004-10-29 | 2004-10-29 | Aqueous-based method for producing ultra-fine metal powders |
| US10/981,074 US20060090598A1 (en) | 2004-11-03 | 2004-11-03 | Aqueous-based method for producing ultra-fine silver powders |
| US10/981,074 | 2004-11-03 | ||
| PCT/US2005/039237 WO2006050248A2 (en) | 2004-10-29 | 2005-10-31 | Aqueous-based method for producing ultra-fine metal powders |
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| CA002585644A Abandoned CA2585644A1 (en) | 2004-10-29 | 2005-10-31 | Aqueous-based method for producing ultra-fine metal powders |
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| EP (1) | EP1804987A2 (en) |
| JP (1) | JP2008519156A (en) |
| KR (1) | KR20070083988A (en) |
| CA (1) | CA2585644A1 (en) |
| WO (1) | WO2006050248A2 (en) |
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| CN101939091B (en) * | 2008-01-09 | 2013-11-20 | 尤米科尔股份公司及两合公司 | Method for preparing dispersions of precious metal nanoparticles and for isolating such nanoparticles from the dispersions |
| JP5117420B2 (en) * | 2008-03-27 | 2013-01-16 | 古河電気工業株式会社 | Method for producing copper fine particle dispersed aqueous solution and method for storing copper fine particle dispersed aqueous solution |
| JP5306966B2 (en) * | 2008-10-27 | 2013-10-02 | 古河電気工業株式会社 | Method for producing copper fine particle dispersed aqueous solution and method for storing copper fine particle dispersed aqueous solution |
| IT1393040B1 (en) | 2009-03-02 | 2012-04-11 | Colorobbia Italiana Spa | PROCESS FOR THE PREPARATION OF STABLE SUSPENSIONS OF METALLIC NANOPARTICLES AND STABLE COLLOIDAL SUSPENSIONS SO OBTAINED SO |
| JP5820202B2 (en) * | 2010-09-30 | 2015-11-24 | Ｄｏｗａエレクトロニクス株式会社 | Copper powder for conductive paste and method for producing the same |
| KR102588589B1 (en) * | 2015-05-18 | 2023-10-16 | 히데미 카키하라 | Antibacterial substances and liquid antibacterial agents and methods for producing liquid antibacterial agents |
| CN114603131B (en) * | 2022-03-07 | 2022-11-18 | 石河子大学 | Preparation method of nano-silver sol |
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| US3708313A (en) * | 1971-05-21 | 1973-01-02 | Du Pont | Metalizing compositions |
| JPS60248803A (en) * | 1984-05-22 | 1985-12-09 | Fukuda Kinzoku Hakufun Kogyo Kk | Production of silver powder |
| JPS61276907A (en) * | 1985-05-31 | 1986-12-06 | Tanaka Kikinzoku Kogyo Kk | Production of fine silver particle |
| JPS63274706A (en) * | 1987-05-02 | 1988-11-11 | Nippon Chem Ind Co Ltd:The | Production of metallic fine powder |
| JPH06299211A (en) * | 1993-04-14 | 1994-10-25 | Mitsubishi Materials Corp | Production of oxidation resistant palladium powder |
| JPH1143708A (en) * | 1997-07-23 | 1999-02-16 | Murata Mfg Co Ltd | Production of silver-palladium powder |
| JP4569727B2 (en) * | 2000-09-08 | 2010-10-27 | Ｄｏｗａエレクトロニクス株式会社 | Silver powder and method for producing the same |
| JP4627376B2 (en) * | 2001-02-20 | 2011-02-09 | バンドー化学株式会社 | Metal colloid liquid and method for producing the same |
| JP2002363618A (en) * | 2001-06-11 | 2002-12-18 | Sumitomo Electric Ind Ltd | Copper ultrafine grain and production method therefor |
| JP4144856B2 (en) * | 2002-11-29 | 2008-09-03 | 三井金属鉱業株式会社 | Method for producing silver powder comprising ultrathin plate-like silver particles |
| JP2004241294A (en) * | 2003-02-07 | 2004-08-26 | Toppan Forms Co Ltd | Conductive coating liquid containing metal nano fine particle and conductive metal foil |
| JP2004285454A (en) * | 2003-03-25 | 2004-10-14 | Konica Minolta Holdings Inc | Homogeneous fine particle of inorganic metal, and manufacturing method |
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- 2005-10-31 KR KR1020077010223A patent/KR20070083988A/en not_active Application Discontinuation
- 2005-10-31 JP JP2007539239A patent/JP2008519156A/en active Pending
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| KR20070083988A (en) | 2007-08-24 |
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