WO2006050251A2 - Procede a base de polyol permettant de produire des poudres metalliques ultra-fines - Google Patents

Procede a base de polyol permettant de produire des poudres metalliques ultra-fines Download PDF

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Publication number
WO2006050251A2
WO2006050251A2 PCT/US2005/039242 US2005039242W WO2006050251A2 WO 2006050251 A2 WO2006050251 A2 WO 2006050251A2 US 2005039242 W US2005039242 W US 2005039242W WO 2006050251 A2 WO2006050251 A2 WO 2006050251A2
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Prior art keywords
reaction mixture
particles
composition
process further
metallic
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PCT/US2005/039242
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English (en)
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WO2006050251A3 (fr
Inventor
Daniel V. Goia
Daniel Andreescu
Brendan P. Farrell
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Nanodynamics, Inc.
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Priority claimed from US10/978,154 external-priority patent/US20060090597A1/en
Priority claimed from US10/981,083 external-priority patent/US20060090601A1/en
Application filed by Nanodynamics, Inc. filed Critical Nanodynamics, Inc.
Publication of WO2006050251A2 publication Critical patent/WO2006050251A2/fr
Priority to US11/796,291 priority Critical patent/US20100136358A1/en
Publication of WO2006050251A3 publication Critical patent/WO2006050251A3/fr

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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
    • 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
    • B22F1/052—Metallic powder characterised by the size or surface area of the particles characterised by a mixture of particles of different sizes or by the particle size distribution
    • 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
    • B22F1/06—Metallic powder characterised by the shape of the particles

Definitions

  • the present invention relates generally to ultra-fine metallic powders and methods of making the same.
  • the present invention further relates to methods of depositing ultra-fine metallic powders onto various substrates.
  • Ultra-fine metallic particles have many unique physical and chemical characteristics, which make them ideal materials for applications as varied as electronics, medicine, catalysis, metallurgy, and decoration.
  • methods based on chemical precipitation from solution provide several advantages, including low manufacturing cost and control of the mechanism of metal particle formation.
  • Micron and submicron-size metallic powders of many metals such as Co, Cu, Ni, Au and Ag have been prepared using chemical techniques with a variety of reductants.
  • a particularly versatile method is the so-called "polyol process", which is based on the reduction of metal salts, oxides, or complexes by alcohols or polyols at elevated temperatures. See for example F. Fievet et al., Mat. Res.
  • Typical dispersants used in the prior art are amphiphilic or detergent-like materials, such as octylamine and octanoic acid, and polymers such as polyvinypyridine. It has been suggested (U.S. Patent No. 6,551,960) that amino alcohols might serve as the reductant in the preparation of metallic nanopowders.
  • the present invention provides a metallic composition, which comprises a plurality of ultra-fine metallic particles (e.g., ultra-fine copper, nickel, or silver particles) having one or more desirable features, such as tight size distribution, a low degree of agglomeration, a high degree of crystallinity and oxidation resistance.
  • ultra-fine metallic particles e.g., ultra-fine copper, nickel, or silver particles
  • desirable features such as tight size distribution, a low degree of agglomeration, a high degree of crystallinity and oxidation resistance.
  • the present invention provides a method for forming compositions having a plurality of ultra-fine metallic particles (e.g., ultra-fine copper, nickel, or silver particles), and the metallic compositions produced thereby, where the method includes the steps of:
  • the present invention provides a substrate coated with a plurality of ultra-fine metallic particles (e.g., ultra-fine copper, nickel, or silver particles) having at least one desirable feature, such as tight size distribution, low degree of agglomeration, , a high degree of crystallinity and oxidation resistance.
  • ultra-fine metallic particles e.g., ultra-fine copper, nickel, or silver particles
  • the metal precursor may be any metal-containing substance that is subject to reduction to the zero-valent metal by an alcoholic reducing agent, including but not limited to metal salts, metal oxides or hydroxides, and metal complexes.
  • the branched polyol dispersing agent may be a branched polyol such as l,l,l-tris(hydroxymethyl)ethane, 1,1,1- tris(hydroxymethyl)propane, 2-methylthreitol, 2-methylerythritol, or pentaerythritol.
  • the reaction mixture may further contain one or more additional dispersing agents, such as linear polyols (e.g., sorbitol and/or mannitol) and salts of naphthalene sulfonic acid/formaldehyde co-polymers.
  • the alcoholic reducing agent may be any alcoholic reductant known in the art of metal powder production, including but not limited to 1,2-propylene glycol, 1,3-propylene glycol, diethyleneglycol, or combinations thereof.
  • the method of the present invention may optionally be carried out with control of the pH of the reaction mixture (e.g., by introducing a buffering agent, such as triethanolamine).
  • the present invention provides a method of controlling the size of ultra-fine metallic particles formed by reduction of metal precursors in a liquid, which comprises moderating the pH of the reaction mixture, preferably by introduction of a buffering agent into the liquid prior to or during the reduction process.
  • the ultra-fine metallic particles are formed by reducing a metal precursor in a buffered liquid containing an alcoholic reducing agent.
  • the buffered liquid preferably contains a branched dispersing agent.
  • the invention provides improvements to the known processes for preparing metal powders by reduction of metal precursors with an alcoholic reducing agent.
  • improvements are (a) carrying out the reduction in a solvent comprising two or more glycols; (b) carrying out the reduction in the presence of a tertiary amine buffer; and (c) carrying out the reduction in the presence of a branched polyol dispersing agent.
  • These improvements may be employed alone or in combination, preferably in combination.
  • the improvements make it possible to produce ultra-fine metallic particles in a concentrated reaction mixture.
  • Figure 1 is a series of field emission scanning electron micrographs that show the effects of buffering agent TEA on copper particles produced by a method in accordance with one embodiment of the present invention, where the reaction mixture includes 50% 1,2-PG, 50-x% DEG, and x% TEA.
  • x 0;
  • x 1.5;
  • x 10.
  • Figure 2 shows the effects of buffering agent TEA on the size of copper particles produced according to one embodiment of the present invention.
  • Figure 3 illustrates the effects of various polyol compositions on the size of the copper particles produced according to one embodiment of the present invention, where the reaction mixture includes (a) 1,2-PG and TEA (90:10, v/v); (b) 1,2-PG, 1,3-PG, and TEA (50:40:10, v/v, respectively); and (c) 1,2-PG, DEG, and TEA (50:40: 10, v/v, respectively). Images were acquired using a scanning electron microscope at two magnifications (5,000x and 10,000x).
  • Figure 4 demonstrates the effects of changing the concentration of the copper salt on the size of the copper particles, where the reaction mixture includes: (a) 0.174 g/cm 3 CuCO 3 ; (b) 0.261 g/cm 3 CuCO 3 ; (c) 0.348 g/cm 3 CuCO 3 ; and (d) 0.400 g/cm 3 CuCO 3 .
  • SEM images, 500Ox magnification, scale bar 5 ⁇ m).
  • Figure 5 contains the typical XRD pattern of highly crystalline copper particles produced according to one embodiment of the present invention, displaying a pronounced split of the (220), (311), and (222) reflections.
  • Figure 6 shows the SEM images of nickel particles produced according to one embodiment of the present invention.
  • the present invention provides ultra-fine metallic particles having at least one desirable feature, such as, a tight size distribution, a high degree of crystallinity, oxidation resistance, and a low degree of agglomeration.
  • the present invention further provides a method for producing such ultra-fine metallic particles.
  • the present invention also provides a more cost- effective chemical method for producing ultra-fine metallic powders than those presently known in the art, by reducing metal precursors with an alcoholic reducing agent at higher metal concentrations than those previously used in the art to produce particles with substantially the same sizes.
  • the concentrated reaction mixtures of the present invention may therefore be used to reduce the cost of making ultra-fine metallic particles, particularly costs related to energy, resources, and waste treatment.
  • ultra-fine particles generally includes particles having diameters of about 1 nm-10 ⁇ m, preferably about 10-5,000 nm, more preferably 50-3,000 nm, and most preferably 100-1000 nm.
  • the ultra-fine metallic particles may comprise various metals, including those transition metals and noble metals, such as Ag, Au, Co, Cu, Fe, In, Ir, Mn, Mo, Ni, Os, Pd, Pt, Re, Rh, Ru, Sn, Ta, W, and combinations thereof, that are known to be amenable to preparation by the polyol process.
  • the metallic particles consist essentially of a single metal, most preferably selected from the group consisting of Cu, Ni, and Ag.
  • the methods of the present invention produce a substantially monodisperse ultra- fine metallic powder composition, i.e. a plurality of particles having a tight size distribution.
  • the breadth of the size distribution refers to the degree of variation in the diameter of the particles in a metallic powder composition.
  • the ultra-fine metallic powders of the invention may be deemed to have a tight size distribution when the diameters of at least about 80% of the particles are within the range N ⁇ 15% N, where N is the average diameter of the particles. In certain embodiments, at least about 85% of the particles are within the range N ⁇ 15% N, and in other embodiments at least about 90% of the particles are within the range N ⁇ 15% N. In optimum cases, 95% or more of the particles are within the range N ⁇ 15% N.
  • the diameters of the ultra-fine metallic particles may be measured by a number of known methods, such as by electron microscopy with a scanning electron microscope.
  • the metallic powders produced in accordance with the present invention may comprise ultra-fine metallic particles that have a low degree of agglomeration.
  • the degree of agglomeration may be expressed using the index of agglomeration I aggl , which is the ratio between the average particle size distribution ("PSD50%") and the average diameter of the particles.
  • the average particle size distribution may be determined by any methods known in the art that measure particle agglomerates, including, but not limited to, dynamic light scattering (DLS), laser diffraction, and sedimentation methods, while the average particle diameter is determined by averaging the diameters of the individual metallic particles, e.g. as determined by electron microscopy.
  • DLS dynamic light scattering
  • laser diffraction laser diffraction
  • sedimentation methods while the average particle diameter is determined by averaging the diameters of the individual metallic particles, e.g. as determined by electron microscopy.
  • the powders of ultra-fine metallic particles of the present invention have an I agg i value of about 1.2 or less.
  • the metallic powders produced in accordance with the present invention may also include ultra-fine metallic particles that have a high degree of crystallinity.
  • degree of crystallinity 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 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.
  • the ultra-fine metallic particles have a high degree of crystallinity of at least about 80%, preferably at least about 85%, more preferably at least about 90-95%, and most preferably about 99-100% 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 of a copper powder prepared according to the invention ( Figure 5).
  • the metallic powders produced in accordance with the present invention include oxidation-resistant ultra-fine particles of base metals that are normally sensitive to surface oxidation upon exposure to air in powder form.
  • the ultra-fine base metal particles undergo insubstantial oxidation when exposed to the air in an ambient indoor environment (20 0 C) for 12 months or longer.
  • the ultra-fine base metal particles of the present invention undergo insubstantial oxidation when exposed to a temperature of up to about 100 0 C in air for about 120 minutes.
  • the oxidation of the ultra-fine base metal particles may be insubstantial when they are heated in the air at 20 °C/minute to about 200-220 0 C.
  • base metal refers to metals that are susceptible to surface oxidation on prolonged exposure to air, including Co, Cu, Fe, In, Mn, Mo, Ni, Sn, Ta, W, and combinations thereof, and that are known to be amenable to preparation by the polyol process.
  • Preferred embodiments include the elements Bi, Cu, Ni, Co, and Fe. Oxidation is considered insubstantial if the ultra-fine base metal particles display an increase of less than about 5-10% in their oxygen content as measured with an oxygen analyzer (LECO Corp., St. Joseph, Michigan).
  • the present invention also provides methods for producing ultra-fine metallic particles that comprise the steps of: (a) providing a reaction mixture containing a metal precursor, a branched polyol dispersing agent, and an alcoholic reducing agent; (b) adjusting the temperature of the reaction mixture to a reaction temperature sufficient for reduction of the metal precursor to metal particles; (c) maintaining the reaction mixture at the reaction temperature for a time sufficient to reduce the metal precursor the to metal particles, thereby producing a plurality of ultra-fine metallic particles; and optionally, (d) isolating the metal particles.
  • the method of the present invention further includes controlling particle size and size distribution by moderating the pH of the reaction mixture.
  • the pH of the reaction mixture is maintained above about 6, preferably above about 7, more preferably above about 8, and most preferably between about 8 and about 9.
  • the moderation of pH is preferably achieved by introducing a buffering agent.
  • Suitable buffering agents include but are not limited to alkaline salts of weak acids, such as citrate and phosphate, and amines, such as pyridine, triethanolamine and tris(hydroxymethyl)aminomethane.
  • the buffering agent is preferably a tertiary amine, more preferably triethanolamine.
  • the buffering agent may be added prior to initiation of the reduction of the metal precursor, and be present throughout the reaction, or it may be added gradually, in portions or continuously, for example according to a schedule or under control of a pH-stat.
  • pH refers to the apparent pH as indicated on a standard pH meter when a glass calomel reference electrode is immersed in the reaction mixture.
  • the pH of a mixture with added hydroxide will initially be very high, and will swing without moderation to a low value if protons generated in the course of the reaction consume the added hydroxide.
  • the addition of an alkali metal hydroxide to the reaction mixture does not constitute moderation of the pH, unless the hydroxide is added under the control of a pH-stat.
  • the process of the present invention may be used to manufacture ultra-fine particles of various metals, including but not limited to Ag, Au, Co, Cr, Cu, Fe, In, Ir, Mo, Ni, Nb, Os, Pd, Pt, Re, Rh, Ru, Sn, Ta, Ti, V, and W, and alloys or composites containing these metals.
  • a metal precursor is mixed with an alcoholic reducing agent, which converts the metal precursor to ultra-fine metal particles under the appropriate reaction conditions.
  • Catalysts may optionally be present to accelerate the reduction of certain metals.
  • alcoholic composition or "alcoholic reducing agent,” as used herein and in the appended claims, generally encompasses both monohydroxylic and polyhydroxylic alcohols (polyols), particularly those known in the art to be suitable for use in the "polyol process" of metal powder preparation.
  • the reducing agent is preferably a polyol, and more preferably a diol.
  • Suitable alcoholic reducing agents include, but are not limited to, ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, and 1,4-butanediol.
  • the reducing agent is preferably a 1,2- diol ranging from ethylene glycol to 1,2-hexadecanediol, and will preferably have a boiling point above whatever temperature is sufficient to effect reduction of the metal precursor. Most preferably a mixture of polyols is used, as described in detail below.
  • metal precursor used in the reaction depends upon the particular metal itself and the type of ultra-fine metal particle product desired.
  • metal precursor refers to any metal-containing compound or complex that can be reduced to the elemental metal under the reaction conditions of the polyol process. The precursor need not be completely soluble in the reaction mixture.
  • Suitable precursors include, but are not limited to, metal carbonates, metal formates, metal acetates, metal halides, metal nitrates, metal oxides, metal oxalates, metal hydroxides, metal acetylacetonates, and metal-based oxyanions (e.g., tungstate, molybdate) and haloanions (e.g., hexachloroplatinate, tetrachloronickelate) in acid or salt form.
  • the metal precursor is preferably a metal carbonate.
  • Precursors may be used in hydrous or anhydrous form.
  • metal carbonates such as CuCO 3 , NiCO 3 ,
  • CoCO 3 and Ag 2 CO 3 , are used as the metal precursor for producing ultra-fine particles of Cu, Ni, Co, and Ag, respectively.
  • the use of metal carbonates is thought to be helpful in providing uniform metallic particles at high metal concentrations, as the carbonate counter ions may decompose to CO 2 and leave the system, rather than accumulating as the reduction proceeds. Consequently, the ionic strength of the reaction system does not increase substantially during the reaction, which promotes uniformity of product and stabilization of the metallic particle dispersion.
  • a mixture of metal precursors such as metal carbonates and metal acetates or metal salycilates may be used for the production of ultra-fine metallic particles.
  • organic counter ions such as acetate and salycilate
  • agents which provide organic counter ions such as acetate or salicylate may be added to the reaction system of the present invention.
  • the inventors of the present invention have discovered that, compared to the use of linear polyol dispersants, the presence of a branched polyol in the reduction reaction leads to the generation of metallic particles with a tighter size distribution, a lower degree of agglomeration, a high degree of crystallinity, and less susceptibility to oxidation.
  • the branched polyol may be used alone or as a mixture of branched and linear polyols, or as a mixture of branched polyols and ammonium or sodium salts of polynaphtalene sulfonic acid/formaldehyde co-polymers.
  • branched dispersing agent and "branched polyol” as used herein and in the appended claims refer to a polyol which has a non-linear carbon chain.
  • at least one side group on the branched polyol comprises a hydroxymethyl group.
  • Branched polyols suitable for the process of the present application include but are not limited to 2-methylthreitol, 2 methyl erythritol, l,l,l-tris(hydroxymethyl)ethane, l,l,l-tris(hydroxymethyl)propane, tris(hydroxymethyl)aminomethane, and pentaerythritol ("PE").
  • Branched polyols may have multiple roles in the reaction mixture, including functioning as a reducing agent as well as a dispersant.
  • the branched polyol is pentaerythritol.
  • linear polyols includes, without limitation, molecules containing linear chains of about 3 to about 7 carbon atoms, with three or more carbons having a hydroxyl group attached, including but not limited to sorbitol and mannitol.
  • Suitable polynaphthalene sulfonic acid/formaldehyde copolymers include, but are not limited to, DaxadTM 1 IG and other DaxadTM brands of polynaphthalene sulfonic/formaldehyde co-polymers.
  • Specific reducing polyols and polyol compositions used in the process of the present invention may be required by a particular reactions, but in general a broad range of polyols may be used in the process, such as the polyols disclosed in U.S. Patent Nos. 4,539,041 and 5,759,230, each of which is hereby incorporated herein by reference in its entirety.
  • the polyols may be in either liquid or solid form.
  • 1,2-propylene glycol 1,2-PG
  • 1,3-propylene glycol 1,3-PG
  • DEG diethyleneglycol
  • a mixture of 1,2-PG and DEG may be used as the reducing polyol.
  • the branched dispersing agent and the alcoholic reducing agent may be heated or unheated.
  • the reaction temperature will be maintained or adjusted to between 80 0 C and 350 0 C, more preferably between 110 0 C and 200 0 C.
  • 1,2-PG, DEG, and PE may be mixed and heated to bring the temperature of the mixture to about 70 0 C.
  • the required amount Of CuCO 3 may then be added into the polyol mixture at about 80-85 0 C after PE is fully dissolved.
  • the reaction mixture may further be heated to bring the temperature of the mixture to an appropriate reaction temperature.
  • a suitable reaction temperature is about 180-185 0 C. Heating may be accomplished via an external heat source such as a heated bath or mantle, or by microwave irradiation as described in U.S. Patent No. 6,746,510.
  • the process may be carried out in batch mode or as a continuous process.
  • the resulting ultra-fine metal particles may be collected by 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, N 2 , or vacuum.
  • the size and the uniformity of the ultra-fine metallic particles are affected by a variety of factors, such as the types of metal precursor, branched polyol, alcoholic agent, and dispersant used, the concentration of the metal ions, the reaction temperature, and the pH of the reaction mixture.
  • the pH of the reaction mixture may be adjusted to control the size of the ultra-fine metallic particles produced at any given metal precursor concentration.
  • the inventors have discovered that pH changes significantly affect the reduction reaction and the formation of metallic particles.
  • the pH of the reaction mixture is adjusted by adding a buffering agent.
  • buffering agent refers to an agent which, upon addition to the reaction mixture, moderates changes of the reaction mixture pH caused by H + produced during the reaction or when an acid or base is added into the reaction mixture.
  • the buffering agent is added to the reaction mixture to stabilize the pH of the reaction mixture, in order to control the size of the particles produced by the reaction system at a given concentration of a metal precursor in the reaction mixture.
  • the inventors have found that control of the pH of the reaction mixture makes it possible to produce smaller and more uniform particles than would otherwise be possible at a particular concentration of the metal precursor.
  • buffering agents include, without limitation, triethanolamine (“TEA”), 4-(2-hydroxyethyl)piperazine-l-ethanesulfonic acid (“HEPES”), 4- morpholinepropanesulfonic acid (“MOPS”), tris(hydroxymethyl)aminomethane (“Tris”), and N- [tris(hydroxymethyl)methyl]-2-aminoethanesulfonic acid (“TES”).
  • TAA triethanolamine
  • HPES 4-(2-hydroxyethyl)piperazine-l-ethanesulfonic acid
  • MOPS 4- morpholinepropanesulfonic acid
  • Tris tris(hydroxymethyl)aminomethane
  • TES N- [tris(hydroxymethyl)methyl]-2-aminoethanesulfonic acid
  • the size of ultra-fine metallic particles formed by the process of the present invention may be significantly affected by the amount of buffering agent added to the reaction mixture.
  • the pH of the reaction mixture measured at room temperature in the absence of PE decreases from about 8.6 at the beginning of the process to about 4.85 at the end of the reaction and the average size of the copper particles product is about 2.4 ⁇ m.
  • the addition of 2% TEA (final concentration) raised the final pH to about 6.20 and the size of the copper particles decreased to about 1.5 ⁇ m.
  • the pH at the end of the reaction was about 7.70 and about 8.60, respectively, and the size of the copper particles produced by the process was reduced to about 700 nm and about 300 nm, respectively.
  • the present inventors have also discovered that controlling of the pH of the reaction mixture during the reduction process dramatically reduces the cost of making ultra-fine metallic particles, by enabling the uses of a concentrated reaction system.
  • the metal concentrations in prior art polyol processes have been kept low (typically below 5-10%) in order to form ultra-fine metal particles in the sub-micrometer scale.
  • Such dilute systems consume more energy and materials to produce a given amount of ultra-fine metallic particles of a particular size than the concentrated system of the present invention.
  • the concentrated system of the present invention reduces the cost of downstream processes, and reduces the cost of discarding or recycling waste organic solvent.
  • the invention provides a method of preparing 200 g or more of an ultra-fine metal powder, having an average particle size of 1.2 ⁇ m or less, in only one liter of solvent.
  • about 100 g of Cu particles with a size of about 300 nanometers may be produced by reducing more than 200 g OfCuCO 3 in a reaction volume of only 500 ml (250 ml 1,2-PG, 200 ml DEG, and 50 ml TEA).
  • the same amount OfCuCO 3 is reduced in a reaction mixture where the pH is not moderated (250 ml 1,2-PG and 250 ml DEG), Cu particles with size of about 2.4 ⁇ m are formed.
  • the inventors have also discovered that the types of polyol used in the process affect the size and uniformity of the metallic particles produced.
  • the ultra-fine copper particles formed in reaction mixture of 1,2-PG as the sole reducing polyol exhibit a wide particle size distribution (100-700 nm).
  • the uniformity of the copper particles considerably improves when polyol mixtures, such as a mixture of 1,2-PG and 1,3-PG or a mixture of 1,2-PG and DEG, are used (see Figure 3).
  • the inventors have found that copper particles produced in a mixture of 1,2-PG and DEG have the highest uniformity (i.e., the tightest size distribution).
  • the use of DEG resulted in larger copper particles (300 nm vs. 500 nm, respectively).
  • 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 desirable feature, such as a tight size distribution, a low degree of agglomeration, a high degree of crystallinity, or oxidation resistance.
  • substrate includes, without limitation, metallic subjects (e.g., metallic particles, flakes, tubes, and sheets), plastic materials, ceramic objects, 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 particles of various metals, preferably Cu, Ni, or Ag.
  • the present invention also provides a method of coating a substrate with a plurality of ultra-fine metallic particles, by: (a) forming a reaction mixture containing the substrate, a metal precursor, a branched dispersing agent (e.g., a branched polyol), and an alcoholic reducing agent; (b) adjusting the temperature of the reaction mixture to a reaction temperature sufficient to reduce the metal precursor to metal particles; (c) maintaining the reaction mixture at the reaction temperature for a time sufficient to reduce the metal precursor to metal particles and permit the resulting metal particles to form a coating on the surface of the substance; and optionally, (d) isolating the coated substance.
  • a forming a reaction mixture containing the substrate, a metal precursor, a branched dispersing agent e.g., a branched polyol
  • an alcoholic reducing agent e.g., a branched polyol
  • the ultra-fine metallic particles may be introduced to the surface of the substrate in such a manner that they form a uniform and continuous layer(s) the surface.
  • the methods described in U.S. Patent 6,746,510, incorporated herein by reference, may readily be adapted to the methods of the present invention.
  • Copper carbonate (CuCO 3 ) and nickel carbonate (NiCO 3 ) were supplied by Shepherd Chemical Co. (Norwood, OH, U.S.A.).
  • Palladium chloride solution (PdCl 2 ) was obtained from OMG (South Plainfield, NJ, U.S.A.).
  • 1,2-PG and DEG were obtained from Alfa Aesar (Ward Hill, MA, U.S.A.).
  • 1,3-PG and PE were obtained from Avocado Research Chemicals Ltd. (Heysham, Lancashire, UK), and TEA was purchased from Aldrich (Milwaukee, WI, U.S.A.).
  • the dispersant agent (PE) was initially added to the polyol(s) and heated at a low power (10%) with a heating mantle to bring the temperature to 70 0 C.
  • the required amounts OfCuCO 3 were added into the flask at 80-85 0 C after PE was fully dissolved.
  • the CuCO 3 /polyol mixture was stirred at 500 RPM in all experiments. The mixture was then heated at 50% power until the temperature reached 180-185 0 C.
  • the copper particles obtained were washed three times with ethanol (3 x 400 mL) and were filtered using a vacuum system and Whatmann #50 filter paper. The particles were then dried overnight at 8O 0 C in a regular oven.
  • the morphology of the copper particles was investigated by scanning electron microscopy (SEM) using a JEOL JSM-6300 scanning microscope at 15 kV accelerating voltage and the magnification between 2500 and 10000. Copper powders were also analyzed by field emission scanning electron microscopy (FE-SEM) with 5 kV accelerating voltage and the same range of magnification using a JEOL JSM-7400F field emission scanning electron microscope.
  • SEM scanning electron microscopy
  • FE-SEM field emission scanning electron microscopy
  • FIG. 3a-3c show, at two magnifications (5000x and 1000Ox), the SEM images of the copper particles formed in a 1,2-PG : DEG : TEA mixture (50:40:10, v/v/v, respectively) and a 1,2-PG : 1,3-PG : TEA mixture (50:40:10, v/v/v, respectively).
  • Figure 3 includes also the SEM of copper particles obtained in a 1,2-PG : TEA mixture (90:10, v/v). Table 1 -Experimental condition and characteristics of the copper powder obtained in polyol mixtures containing TEA.
  • the present inventors have previously shown that when the amount OfCuCO 3 is changed, the size of the copper particles decreases with a decrease in the concentration of the Cu ions in the system. This trend tends to increase in the cost of producing ultra-fine Cu particles with a decreased size.
  • the pH of the reaction mixture decreases significantly as the reduction proceeds, causing a decrease in the reducing power of the polyol and a slowdown in the reaction rate of the second stage of the copper reduction (Cu + — > Cu 0 ).
  • the inventors have demonstrated that fine copper particles can be produced even in highly concentrated systems, provided that the pH of the reaction mixture is controlled.
  • the average size of the copper particles was ca. 0.5 ⁇ m for all the CuCO 3 concentrations tested, the differences between separate preparations being less than ⁇ 20%. A better homogeneity was observed at the lowest concentration, probably because of the higher dispersant : metal ratio.
  • Another factor that influences particle size is the composition of the polyol mixtures used in the precipitation process.
  • copper particles were synthesized in a single polyol (e.g., 1,2-PG)
  • a broad size distribution was obtained (1.5 - 2.6 ⁇ m).
  • the uniformity of copper particles obtained in polyol mixtures was improved, the narrowest distribution (2 - 2.8 ⁇ m) being obtained in 1,2-PG : DEG mixtures ( Figure 3).
  • NiC0 3 /polyol mixture was stirred at 500 RPM in all experiments. The mixture was continually heated (75% power to the heating mantle) until reduction was complete. The nickel powder was washed three times with ethanol (3 x 400 ml) and was filtered with a vacuum system using Whatman #50 filter paper. The powder was then dried overnight at 100 0 C in a regular oven, yielding the particles shown in Figure 6.

Abstract

L'invention concerne des particules métalliques ultra-fines monodispersées ayant un faible degré d'agglomération et un fort degré de cristallinité et de résistance à l'oxydation et des procédés de formation de ces particules. L'invention concerne un procédé de contrôle de la taille et de la composition granulométrique de particules métalliques ultra-fines par la régulation du pH du procédé de type polyol. Les procédés selon l'invention permettent d'augmenter la charge de métal dans le procédé de type polyol sans augmentation de la composition granulométrique, ce qui permet la production de particules métalliques ultra-fines à haut rendement.
PCT/US2005/039242 2004-10-29 2005-10-31 Procede a base de polyol permettant de produire des poudres metalliques ultra-fines WO2006050251A2 (fr)

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US10/981,110 US20060090599A1 (en) 2004-10-29 2004-11-03 Polyol-based method for producing ultra-fine silver powders
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US10/981,083 US20060090601A1 (en) 2004-11-03 2004-11-03 Polyol-based method for producing ultra-fine nickel powders
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CN104640653A (zh) * 2012-09-12 2015-05-20 M技术株式会社 金属微粒的制造方法
CN104889383A (zh) * 2015-05-21 2015-09-09 桂林理工大学 一种含银无水甘油悬浮液及其制备方法
CN105081343A (zh) * 2015-08-03 2015-11-25 佛山市顺德区百锐新电子材料有限公司 一种用于触摸屏uv型激光雕刻银浆的导电银粉的制造方法
CN106660131A (zh) * 2014-06-16 2017-05-10 国立大学法人大阪大学 银颗粒合成方法、银颗粒、导电浆料制造方法和导电浆料
TWI644865B (zh) * 2009-06-29 2018-12-21 國立成功大學 利用多元醇合成銅銦化物奈米粒子的方法
JP2019167595A (ja) * 2018-03-23 2019-10-03 マックエンジニアリング株式会社 貴金属のナノ粒子の製造方法

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Cited By (13)

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DE102009015470A1 (de) * 2008-12-12 2010-06-17 Byk-Chemie Gmbh Verfahren zur Herstellung von Metallnanopartikeln und auf diese Weise erhaltene Metallnanopartikel und ihre Verwendung
TWI644865B (zh) * 2009-06-29 2018-12-21 國立成功大學 利用多元醇合成銅銦化物奈米粒子的方法
US9821375B2 (en) 2012-09-12 2017-11-21 M. Technique Co., Ltd. Method for producing metal microparticles
CN104640653A (zh) * 2012-09-12 2015-05-20 M技术株式会社 金属微粒的制造方法
CN104640653B (zh) * 2012-09-12 2016-06-15 M技术株式会社 金属微粒的制造方法
US10201852B2 (en) 2014-06-16 2019-02-12 Osaka University Silver particle synthesizing method, silver particles, conductive paste producing method, and conductive paste
CN106660131A (zh) * 2014-06-16 2017-05-10 国立大学法人大阪大学 银颗粒合成方法、银颗粒、导电浆料制造方法和导电浆料
EP3156157A4 (fr) * 2014-06-16 2018-02-21 Osaka University Procédé de synthèse de particules d'argent, particules d'argent, procédé de fabrication de pâte électroconductrice et pâte électroconductrice
CN106660131B (zh) * 2014-06-16 2019-03-19 国立大学法人大阪大学 银颗粒合成方法、银颗粒、导电浆料制造方法和导电浆料
CN104889383A (zh) * 2015-05-21 2015-09-09 桂林理工大学 一种含银无水甘油悬浮液及其制备方法
CN105081343A (zh) * 2015-08-03 2015-11-25 佛山市顺德区百锐新电子材料有限公司 一种用于触摸屏uv型激光雕刻银浆的导电银粉的制造方法
JP2019167595A (ja) * 2018-03-23 2019-10-03 マックエンジニアリング株式会社 貴金属のナノ粒子の製造方法
JP7054138B2 (ja) 2018-03-23 2022-04-13 マックエンジニアリング株式会社 貴金属のナノ粒子の製造方法

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