WO2011004363A2 - Procédé et système adaptés pour fournir des informations de rétroaction émanant d'un utilisateur en ligne à propos de sites web et de logiciels informatiques - Google Patents

Procédé et système adaptés pour fournir des informations de rétroaction émanant d'un utilisateur en ligne à propos de sites web et de logiciels informatiques Download PDF

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WO2011004363A2
WO2011004363A2 PCT/IL2010/000536 IL2010000536W WO2011004363A2 WO 2011004363 A2 WO2011004363 A2 WO 2011004363A2 IL 2010000536 W IL2010000536 W IL 2010000536W WO 2011004363 A2 WO2011004363 A2 WO 2011004363A2
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copper
composition
nanoparticles
ranges
microparticles
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WO2011004363A8 (fr
WO2011004363A3 (fr
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Miron Hazani
Adi Cohen
Yaron Rosenstein
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NANOREADY Ltd
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NANOREADY Ltd
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Publication of WO2011004363A8 publication Critical patent/WO2011004363A8/fr
Publication of WO2011004363A3 publication Critical patent/WO2011004363A3/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
    • B22F1/054—Nanosized particles
    • 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
    • B22F1/0547—Nanofibres or nanotubes
    • 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
    • B22F1/0549—Hollow particles, including tubes and shells
    • 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
    • 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
    • B22F1/065—Spherical particles
    • B22F1/0655—Hollow particles
    • 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
    • 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
    • B22F1/08—Metallic powder characterised by particles having an amorphous microstructure

Definitions

  • the present invention in some embodiments thereof, relates to metallic nanoparticles and more particularly, but not exclusively, to discrete and sintered copper nano- and micro-particles and to novel methods of producing same.
  • Metal nanoparticles are finding their way into a myriad of applications in fields such as mechanical, optical, magnetic, thermal, electronic and sensory devices, as well as in the field of catalysis, due to their unique properties.
  • metallic nanocrystals have considerably reduced melting temperatures as compared with the bulk.
  • the depression in melting and annealing temperature is evident throughout the nanocrystal size regime, with the most dramatic effects observed in nanocrystals having a diameter from 2 to 6 nm. This attribute can be harnessed for a wide variety of applications that require low temperature sintering, such as electronic printing, novel adhesion techniques and composite metallic casting.
  • Low-temperature sintering is another form of high-order transformation, which is particularly appealing when considering printed electronics applications.
  • This fast growing area enables printing conductive patterns as well as active components on substrates which cannot endure classical photolithographic processes.
  • Printing of nanoparticle based inks may be achieved using several printing processes such as ink- jet, screen printing, flexography, gravure, and off-set printing. Lowering the temperature at which these inks are cured and sintered enables the application of these processes to substrates that cannot tolerate high temperatures.
  • Noncontact direct writing technologies such as inkjet printing, are advantageous not only in terms of materials cost but also in manufacturing time, since they allow precise ejection at high positioning accuracy and at controllable quantities.
  • Metallic inkjet inks are typically required to exhibit significant electrical conductivity and are often characterized by complex formulations involving solvents, surfactants and dispersants in addition to the appropriate electrically conductive materials. These materials are typically nanoparticles of conducting elements which are dispersed in the ink. The small particle size of the nanoparticles in electronic inks enables sintering at rather low temperatures, which allows fabrication on plastic and other heat-sensitive substrates.
  • nanoparticles are characterized by high surface areas, they are prone to surface oxidation, clustering and aggregation, and often suffer from irreversible agglomeration.
  • Metallic nanoparticles react easily with ambient atmospheric oxygen even at room temperature and form an oxide phase on their surface, which has an undesirable effect on their function and utilization.
  • the oxide layer might reduce the zeta potential of the nanoparticles and thus induce agglomeration and flocculation.
  • oxides of silver or gold nanoparticles are known to be electrically conductive and hence their oxidation does not have a detrimental effect on their performance
  • other metallic nanoparticles such as, for example, copper nanoparticles, often become dysfunctional upon oxidation.
  • Copper has a lower tendency for ion migration, as compared with silver and gold, which is advantageous in terms of reducing short circuits between wires and reducing the defect rate of microelectronic circuitry. Copper has an electrical conductivity similar to that of silver and is currently much cheaper than silver or gold, making it a particularly interesting candidate for electronic printing applications. However, since copper nanoparticles exhibit rapid rate of oxidation, utilizing copper nanoparticles has so far necessitated using inks containing a copper metal precursor in electronic printing applications, rather than copper nanoparticles.
  • the copper salts usually used for such methods include, for example, CuC12, Cu(NO3)2, CuSO4, (CH3COO)2Cu, copper(II) acetylacetonate, copper(II) carbonate, copper(II) cyclohexane butyrate, copper(II) stearate, copper(II) perchlorate, copper(II) ethylenediamine and Cu(0H)2.
  • reducing agents include, for example, NaHPO2, N2H4, and NaBH4.
  • Dispersing agents are typically used in the production process of copper nanoparticles.
  • examples of such dispersing agents include PVP (polyvinylpyrrolidone), CTAB (cetyltrimethylammonium bromide), SDS (sodium dodecyl sulfate) and Na-CMC (sodium carboxymethyl cellulose).
  • Nanoparticles produced according to various strategies usually possess a passivating agent to confer solubility and stability against aggregation.
  • the passivating agent also serves to arrest the growth of the particles at a pre-determined and uniform size.
  • One of the requirements from passivating agents, especially when considering nanoparticles for electronic applications, is volatility upon heating.
  • the process of thermally removing the passivating agent is sometimes referred to as thermolysis.
  • WO 2010/035258 by the present inventors, teaches a reversibly re-suspendible powder of copper nanoparticles having a raspberry-like shape and a particular particle size distribution characterized by a mean diameter of 10-200 nm and a standard deviation of 5-50 nm.
  • the present invention in some embodiments thereof, relates to metallic nanoparticles and more particularly, but not exclusively, to discrete and sintered copper nanoparticles and to novel methods of producing same.
  • the present invention teaches spherical copper nanoparticles and hollow spheroidal micro-particles with distinct surface topology and chemistry, governed by certain carboxyl-containing compounds, possessing self-similarity architecture.
  • the unique topology and chemistry of the copper nanoparticles and microparticles promote room temperature sintering, as well as promote contact between individual structures.
  • composition which includes a plurality of copper nanoparticles and/or microparticles generally shaped as spheroids and characterized by a bosselated surface topology.
  • the copper microparticles are hollow spheroidal copper microparticles.
  • the hollow spheroidal copper microparticles are characterized by an average particle size that ranges from 0.5 ⁇ m to 20 ⁇ m.
  • the hollow spheroidal copper microparticles are characterized by an average wall thickness that ranges from 50-nm to 200 nm.
  • the exterior surface of the hollow spheroidal copper microparticles exhibits an atomic concentration of carbon that ranges from 20 percent to 35 percent.
  • the exterior surface of the hollow spheroidal copper microparticles exhibits an atomic concentration of phosphorous that ranges from 0 percent to 5 percent.
  • the walls of the hollow spheroidal copper microparticles are composed of copper nanoparticles which have an average particle size that ranges from 20 nm to 200 nm.
  • the copper nanoparticles are characterized by an average diameter that ranges from 50 nm to 500 nm.
  • the curvature of each boss in the bosselated surface topology of the copper nanoparticles and/or microparticles is characterized by a mean curvature that ranges from 0.02 run '1 to 0.5 nm "1 .
  • the surface of the copper ' microparticles and/or nanoparticles is coated with fibrous copper.
  • the fibrous copper has an average fiber length that ranges from 10 nm to 100 nm, and an average thickness of 5 nm to 10 nm.
  • At least a portion of the copper microparticles and/or nanoparticles of the composition of copper particles are fused to one another.
  • the exterior surface of the fibrous-coated copper particles and/or the fused copper particles is characterized by an atomic concentration of oxygen that ranges from 20 percent to 40 percent.
  • the exterior surface of the fibrous-coated copper particles and/or the fused copper particles is characterized by an atomic concentration of carbon that ranges from 20 percent to 30 percent
  • the exterior surface of the fibrous-coated copper particles and/or the fused copper particles is characterized by an atomic concentration of nitrogen that ranges from 10 to 15 percent.
  • the exterior surface of the fibrous-coated copper particles and/or the fused copper particles is characterized by an atomic concentration- of sulfur that ranges from 0.1 to 5 percent.
  • compositions presented herein are capable of being sintered upon an application of mild mechanical pressure thereon at a temperature lower than 100 0 C or lower than 50 0 C.
  • compositions presented herein are capable of sintering upon an application of mild mechanical pressure thereon at a temperature lower than 50 0 C.
  • composition which includes a plurality of copper microparticles and/or microparticles, wherein at least a portion of the particles being fused to one another.
  • a composition which includes a plurality of copper microparticles and/or nanoparticles, the composition being capable of sintering upon an application of mild mechanical pressure thereon at a temperature lower than 100 0 C or lower than 50 0 C.
  • the process further includes filtering and drying the powder.
  • the molar ratio between the elemental zinc and the copper ion ranges from 2:1 to 1:2.
  • the molar ratio between the carboxyl-containing compound and the copper ion ranges from 5:1 to 1:1, from 4:1 to 1:1 or from 2:1 to 1:1.
  • the pH of the aqueous solution ranges from 1.5 to 5, from
  • the powder of elemental zinc has a grit size of less than 20 microns.
  • the process further includes:
  • the process is effected by mixing the copper salt with a powder of elemental zinc in an aqueous solution is effected in the presence of a sulfur- containing compound.
  • the concentration of the sulfur-containing compound ranges from 0.05 mM to 10 mM.
  • the sulfur-containing compound is selected from the group consisting of thiourea, ⁇ -mercaptoethanol, thiosemicarbazide, methyl chlorothiolformate, dithiooxamide, thioacetamide, dimethyl trithiocarbonate, ammonium diethyldithiocarbamate, 2-methyl-3-thiosemicarbazide, 4-methyl-3- thiosemicarbazide, ethylene trithiocarbonate, vinylene trithiocarbonate, 2- cyanothioacetamide, cysteine, methanethiol (CH 3 SH), ethanethiol (C 2 HsSH), 1- propanethiol (C 3 H 7 SH), 2-propanethiol (CH 3 CH(SH)CH 3 ), butanethiol (C4H 9 SH), tetrabutyl mercaptan (C(CH 3 ) 3 SH), pentanethiols (C 5 H 11 SH), coenzy
  • the copper salt is selected from the group consisting of CuSO 4 , CuCl 2 , Cu(NO 3 ) 2 , (CH 3 COO) 2 Cu, Cu(C 5 H y O 2 ) 2 , CuCO 3 , Cu[C 6 H 11 (CH 2 ) 3 CO 2 ] 2 , copper(II) stearate complex, CuCl 2 O 4 , copper(II) ethylenediamine complex and Cu(OH) 2 .
  • the carboxyl-containing compound is selected from the group consisting of citric acid, oxalic acid, ethylenediamine tetraacetic acid (EDTA), a monocarboxylic acid (formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid and capric acid), a dicarboxylic acid (malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid and terephthalic acid), a tricarboxylic acid (isocitric acid, aconitic acid, tricarballylic acid, trimesic acid and mellitic acid) and a tetracarboxylic acid (1,1,2,2-ethanetetracarboxylic acid, 1,1,4,4- butanete
  • composition which includes copper nanoparticles which are being prepared by the processes presented herein.
  • the compositions are capable of sintering upon an application of mild mechanical pressure thereon at a temperature lower than 100 0 C or lower than 50 0 C.
  • an article-of-manufacturing which includes any of the compositions presented herein.
  • the article-of-manufacturing is formed upon an application of mild mechanical pressure on the composition at a temperature lower than 100 0 C or lower than 50 0 C.
  • the article-of-manufacturing is selected from the group consisting of an inkjet ink, a dry toner, a solid macro-scaled object, an electronic component and an electronic circuit.
  • an inkjet ink composition which includes any of the compositions presented herein.
  • a toner composition which includes any of the compositions presented herein.
  • the inkjet ink composition or the toner composition is being curable upon an application of mild mechanical pressure thereon at a temperature lower than 100 0 C or lower than 50 0 C.
  • a method of printing a substantially electrically conducting element on a substantially electrically isolating substrate the method is effected by applying the inkjet ink composition or the toner composition on the substrate.
  • the method further includes, subsequent to applying the composition, pressing the substrate having the composition applied thereon to thereby form the electrically conducting element on the substantially electrically isolating substrate.
  • the method further includes, subsequent to applying the composition, heating the substrate having the composition applied thereon to thereby form the electrically conducting element on the substantially electrically isolating substrate.
  • a method of preparing a substantially electrically conducting copper element is effected by forming a shape of the element from any of the compositions presented herein and applying mild pressure on the shape at a temperature lower than
  • a method of preparing a substantially electrically conducting copper element is effected by forming a shape of the element from any of the compositions presented herein and heating the shape, thereby obtaining the copper element.
  • a method of preparing a substantially electrically conducting copper layer on at least a portion of a surface of a substrate is effected by spraying a suspension of the composition containing fused copper particles onto the surface.
  • compositions, method or structure may include additional ingredients, steps and/or parts, but only if the additional ingredients, steps and/or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.
  • a compound or “at least one compound” may include a plurality of compounds, including mixtures thereof.
  • method refers to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the chemical, pharmacological, biological, biochemical and medical arts.
  • the patent or application file contains at least one drawing executed in color.
  • FIG. 1 is an HRSEM electromicrograph at a magnification of 37,00OX, showing an exemplary hollow spheroidal micro-particles according to some embodiments of the present invention, of about 1.5 ⁇ m in size, which seem to be composed of sub-micron sized spherical copper nanoparticles of about 20 nm to 50 nm in diameter
  • FIGs. 2A-B are HRSEM electromicrographs at a magnification of 10,000X (FIG. 2A) and 40,00OX (FIG. 2B), showing in the center exemplary hollow spheroidal micro-particles according to some embodiments of the present invention, having a diameter of about 4 ⁇ m and exhibiting a bosselated surface topology;
  • FIGs. 3A-C are HRSEM electromicrographs of exemplary hollow spheroidal micro-particles according to some embodiments of the present invention, composed of smaller spherical copper nanoparticles, cantering on a hollow spheroidal micro-particle of about 15 ⁇ m at a magnification of 10,000X (FIG. 3A), 50,00OX (FIG. 3B) and 200,00OX (FIG. 3C), demonstrating the self-similarity (fractal) nature of the copper particles;
  • FIGs. 4A-C are HRSEM electromicrographs of exemplary hollow spheroidal micro-particles according to some embodiments of the present invention, composed of smaller spherical copper nanoparticles, cantering on a hollow spheroidal micro-particle of about 5 ⁇ m at a magnification of 10,000X (FIG. 4A), 5O 5 OOOX (FIG. 4B) and 200,00OX (FIG. 4C), demonstrating the self-similarity (fractal) nature of the copper particles;
  • FIG. 5 is a HRSEM electromicrograph of copper particles sintered into flat structures by applying weak manual pressure on a powder comprising hollow spheroidal micro-particles according to some embodiments of the present invention
  • FIG. 6 presents a high resolution XPS spectrum of CIs obtained for a powder of exemplary hollow spheroidal copper micro-particles according to some embodiments of the present invention, prepared using citric acid as an acid and hypophosphite as an additive;
  • FIG. 7 presents a high resolution XPS spectrum of Cu2p obtained for a powder of exemplary hollow spheroidal copper micro-particles according to some embodiments of the present invention, prepared using citric acid as an acid and hypophosphite as an additive;
  • FIG. 8 is a HRSEM electromicrograph at a magnification of 100,000X of the surface of a hollow spheroidal copper micro-particle treated with a sulfur-containing compound according to some embodiments of the present invention, showing a fibrous network of copper coating the surface;
  • FIG. 9 is a HRSEM electromicrograph at a magnification of 200,00OX of the surface of a hollow spheroidal copper micro-particle treated with a sulfur-containing compound according to some embodiments of the present invention, showing a fibrous network of copper coating the surface;
  • FIG. 10 is a HRSEM electromicrograph at a magnification of 200,00OX of the spherical copper nanoparticles tethered by the fibrous network of copper coating their surface to the surface of a spheroidal copper micro-particle after being treated with a sulfur-containing compound according to some embodiments of the present invention
  • FIG. 11 is a TEM electromicrograph showing the fibrous copper network appearing on the surface of copper particles treated with a sulfur-containing compound according to some embodiments of the present invention.
  • FIG. 12 presents the Cl XPS spectrum of CIs obtained for a powder of exemplary spherical copper nanoparticles, after being treated with a sulfur-containing compound according to some embodiments of the present invention
  • FIG. 13 presents a high resolution XPS spectrum of Cu2p obtained for a powder of exemplary spherical copper nanoparticles, after being treated with a sulfur-containing compound according to some embodiments of the present invention
  • FIG. 14 presents a high resolution XPS spectrum of NIs obtained for a powder of exemplary spherical copper nanoparticles, after being treated with a sulfur-containing compound-according to some embodiments of the present invention
  • FIG. 15 presents XPS spectrum of S2p obtained for a powder of exemplary spherical copper nanoparticles, after being treated with a sulfur-containing compound according to some embodiments of the present invention
  • FIG. 16 is a HRSEM electromicrograph of a copper nanostructure prepared with citric acid and thiourea, according to some embodiments of the present invention, showing the initial stage of surface sintering;
  • FIG. 17 is a HRSEM electromicrograph of a copper nanostructure prepared with citric acid and thiourea, according to some embodiments of the present invention, showing an intermediate stage of surface sintering;
  • FIG. 18 is a HRSEM electromicrograph of a copper nanostructure prepared with citric acid and thiourea, according to some embodiments of the present invention, showing full surface sintering. DESCRIPTION OF EMBODIMENTS OF THE INVENTION
  • the present invention in some embodiments thereof, relates to metallic nanoparticles and more particularly, but not exclusively, to discrete and sintered copper nano- and micro-particles and to methods of producing same.
  • Cementation is a well-known chemical reaction in hydrometallurgical processes, which is used, for example, to recover copper from acid leach solutions and gold from cyanide leach solutions.
  • Metal displacement reaction between copper ions and metallic zinc are used for decades to produce metallic copper, and in modern days to produce copper nanoparticles. Since this reaction involves solid zinc particles, this reaction can be regarded as a modified copper/zinc cementation process. Copper/zinc cementation reactions are known to produce large dendritic copper particles rather than discrete nano- or micro-particles.
  • WO 2010/035258 discloses a process in which copper salts such as CuSO 4 dissolved in H 2 O are reduced by elemental zinc in the presence of a phosphate containing compound such as phosphoric acid, H 3 PO 3 , and other phosphate containing compounds, such as hypophosphite, to yield copper nanoparticles.
  • a phosphate containing compound such as phosphoric acid, H 3 PO 3 , and other phosphate containing compounds, such as hypophosphite
  • the surface chemistry of the produced nanoparticles can be attenuated through controlled oxidation, adsorption of chemical species and the use of surfactants.
  • WO 2010/035258 by changing the reaction parameters and by using different organic capping layers it is possible to produce nanoparticles of different morphologies, and surface chemistries.
  • the present inventors have constructed successfully nano-scale copper building blocks that self-assemble to form or curved copper structures with a high level of predictability, depending on the composition of the building blocks.
  • the resulting particles can be used in a process which enables room temperature sintering of copper nanoparticles and microparticles.
  • the process makes use of a metal displacement reaction between copper ions and metallic zinc to produce intermediate primary copper nanoparticles, which can thereafter form spherical copper nanoparticles which then self-assemble to form hollow microstructures and/or nanostructures with unique bosselated surface morphology.
  • the invention also teaches how to promote tethering and sintering at room temperature between adjacent copper structures.
  • embodiments of the present invention involve utilizing a chemical reduction scheme carried out in an aqueous environment to produce copper nanoparticles and nanostructures which spontaneously assemble (self-assemble) into super-molecular micro-structures.
  • copper salts such as CuSO 4 dissolved in H 2 O are reduced by elemental zinc in the presence of a carboxylic acid to yield copper nanoparticles and nanostructures that self-assemble into hierarchical micro-structures.
  • various hierarchical hollow spheroidal micro-structures are micro-scale super-structures characterized by a mean diameter that ranges from 500 nm to 2000 nm (2 ⁇ m) and composed of sub-level copper nanoparticles of 50 nm to 200 nm in diameter, which have a bumpy exterior shell, suggesting that these sub-level copper nanoparticles. are themselves composed of sub-sub-level copper nanoparticles of 5 nm to 20 nm in diameter.
  • the present inventors have developed a process aimed at initiating chemically triggered tethering of nanoparticles into nano- and micro-structures. Without being bound by a particular theory, it is suggested that the mechanism of the process involves a correlation between charge density and surface flow phenomena, and maintains that singularities in charge density generate elastic stresses on the highly curved surface of the nanoparticle and thus induce curvature flow (curvature flow is a geometric flow of surfaces induced from elastic stresses whose source is curvature).
  • some embodiments of the present invention relate to a novel process of preparing a composition which comprises copper micro-particles, whereby the obtained micro-particles are uniquely characterized by their unique hollow spheroidal structure, as detailed hereinafter.
  • Embodiments of the present invention further relate to a composition that comprises copper nano- and micro-particles with unique low temperature sintering and spontaneous tethering characteristics.
  • micro-scales structures of self-similarity (fractal) character exhibit a characteristic chemical content and surface topology.
  • the surface chemistry was found to be relatively low in organic content, a feature which allows facile sintering into larger macroscopic structures.
  • the surface exhibited regular and dense bumpy or blistered topology, which can be described as bullous or bosselated, namely having small round lumps of high curvature.
  • a process of manufacturing a composition which comprises copper particles having a bosselated surface topography is effected by mixing a copper salt with a powder of elemental zinc in an aqueous solution in the presence of a carboxyl- containing compound (e.g., a carboxylic acid as defined herein) at room temperature.
  • a carboxyl- containing compound e.g., a carboxylic acid as defined herein
  • mixing the solution is effected by stirring it. In some embodiments, stirring is effected vigorously for several minutes, typically 5-15 minutes.
  • the reaction results in obtaining a powder of copper particles with desired architecture.
  • the powder is in a form of suspension in the aqueous solution.
  • obtaining the composition is effected by consecutively subjecting the obtained suspension to filtration and washing with water and ethanol, so as to afford a brown compressed wet powder ("wet cake").
  • the process continues by drying the wet cake into a dry powder.
  • the molar ratio between the zinc and the copper ion ranges from 2:1 to 1:2, or the ratio is 1:1.
  • the molar ratio between the carboxyl-containing compound and the copper ion ranges from 4:1 to 1:4, and according to some embodiments of the present invention, the molar ratio between the carboxyl-containing compound and the copper ion is 1:1.
  • the chemical conditions e.g., concentration and nature of the reactants used in the process described herein contributes to the rapid reduction of the copper salt, leading to rapid nucleation which is conductive to the formation of small nanoparticles, whereby the carboxyl- containing compound (e.g., citric acid) may serve as a passivating agent which further contributes to the retardation of aggregation and agglomeration (clumping of the resulting copper nanoparticles into an inseparable non-dispersible mass).
  • the carboxyl- containing compound e.g., citric acid
  • carboxyl-containing compound refers to an organic compound having at least one carboxyl group (-COOH), hence, in the context of the present embodiments, a carboxyl-containing compound is a carboxylic acid.
  • Exemplary carboxyl-containing compounds which are suitable for use in the context of embodiments of the invention include, but are not limited to, monocarboxylic acids such as, for example, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid and capric acid; dicarboxylic acids such as, for example, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid and terephthalic acid; tricarboxylic acids, such as, for example, citric acid, isocitric acid, aconitic acid, tricarballylic acid, trimesic acid and mellitic acid; and tetracarboxylic acids such as ethylenediamine tetraacetic acid (EDTA), 1,1,2,2-
  • the carboxyl- containing-compound is citric acid.
  • the process presented herein is intended to form metallic copper without a substrate, namely for metallic copper in the form of a suspension of copper particles, hence the process is effected while the solution wherein the process is performed- is stirred throughout the cementation reaction between the zinc and the copper salt, as well as kept at room temperature.
  • the powder of elemental zinc has a grit size of less than 20 microns, and according to other embodiments, the zinc powder has a grit size of less than 10 microns.
  • Copper salts which are usable in the context of embodiments of this aspect of the invention include, but are not limited to, copper(II) sulfate (CuSO 4 ), copper(II) chloride (CuCl 2 ), copper(II) nitrate (Cu(NO 3 ) 2 ), copper(II) acetate (Cu(CH 3 COO) 2 ), copper acetylacetonate (Cu(CsH 7 O 2 ) 2 ), copper(II) carbonate (CuCO 3 ),
  • the process of manufacturing the composition which comprises copper nanoparticies is effected such that the concentration the copper ions ranges from about 10 mM to about 150 mM; and the molar ratio between the copper ions and the elemental zinc ranges from 2:1 to 1:2. In some embodiments, the molar ratio between the copper and the zinc is 1:1.
  • the molar ratio between the copper ions and the carboxyl -containing compound ranges from 1:1 to 1:5. In some embodiments the ratio is 1:4 copper ions to carboxyl-containing compounds.
  • the concentrations of zinc, copper sulfate, and citric acid used in an exemplary process according to embodiments of the present invention can be .30 mM, 30 mM, and 60 mM respectively.
  • the ratio of zinc to copper salt is 1:1, and the ratio of zinc or copper salt to the carboxyl-containing compound is about 1:2.
  • the pH of the reaction has the ability to determine the rate of particle formation and thus the shape of the obtained primary particles, which are an intermediate form or a transition state of copper nanoparticles, which is typically not isolated or observed as discrete particles in the final composition. It was found that conducting the reaction at pH levels between 5 to 1.5 results in discrete copper particles rather than dendritic structures.
  • the pH of the reaction can be set and controlled by the choice and concentration of the carboxyl-containing compound, and optionally by adding pH-adjusting agents, such as sodium hydroxide.
  • the pH of the aqueous solution ranges from 1.5 to 5.
  • the copper nano- and micro- presented herein are formed in a pH that ranges from 2 to 4, from 3 to 4 or from 3.5 to 4.
  • optimal pH values can be obtained by adding, for example, a base such as sodium hydroxide.
  • composition comprising a plurality of particles, wherein at least a portion of which are hollow spheroidal particles with particle size at the micron range, hence hollow spheroidal micro-particles.
  • an exemplary "process according to embodiments of the invention results in copper micro-particles which are hollow spheroidal particles.
  • the particles are characterized by an average particle size that ranges from 0.5 ⁇ m to 20 ⁇ m, and a wall thickness that ranges from 50 nm to 200 nm.
  • the copper particles produced by the process according to some embodiments of the present invention seem to be formed by semi-ordered aggregation of smaller spherical copper nanoparticles having an average particle size that ranges from 20 nm to 200 nm, which themselves are composed from smaller copper nanoparticles, in what can be described as a fractal structuralism or self-similarity architecture.
  • the surface of the copper particles is characterized by a bosselated surface topology.
  • the phrase "bosselated surface topology" refers to a bullous, blistered or bubbled surface texture having round bumps or blisters arranged densely thereon.
  • the surface of the copper particles produced according to some embodiments of the present invention is further characterized by a curvature stemming from the roundness of the bumps, which can be measured as inverse of the mean radius of each boss, or bump.
  • the curvature of each boss in the bosselated surface of the copper particles is characterized by a mean curvature that ranges from 0.02 nm 1 (the inverse of a radius of 50 nm) to 0.5 nm "1 (the inverse of a radius of 2 nm).
  • the inventors have surprisingly found that contacting the obtained composition with a sulfur-containing compound further affects the architecture of the obtained particles in the composition. It was surprisingly uncovered that the step at which such a sulfur-containing compound is added also affects the resulting product. Thus, it was found that when it is added after a powder that comprises the particles is formed, filament-coated composition of copper nano- and micro-particles is obtained, and when a sulfur-containing compound is added to the reaction solution, together with the zinc and the acid, a composition of fused nano- and micro-particles is obtained.
  • the process of manufacturing copper particles is effected by:
  • the dried powder is re-suspended in an aqueous solution to thereby obtain an aqueous suspension thereof;
  • the suspension is stirred at room temperature for several reasons.
  • the formed powder is filtered and dried.
  • composition of this two-steps process comprises spherical copper particles characterized by a surface coated with fibrous metallic copper, as exemplified in Figures 8-10.
  • this fibrous metallic copper is characterized by fibers having a length of about 10 nm to 100 nm and a thickness of about 5 nm to 10 nm.
  • sulfur-containing compound as used herein, described a compound which comprises one or more sulfur atoms, optionally one or more thiocarbonyl group, and further optionally, one or more thiol group, as these are defined hereinbelow.
  • thiol or thiohydroxy refer interchangeably to a -SH group.
  • Exemplary sulfur-containing compounds in clued, without limitation, thiourea, thiosemicarbazide, methyl chlorothiolformate, dithiooxamide, thioacetamide, dimethyl trithiocarbonate, ammonium diethyldithiocarbamate, 2-methyl-3 -thiosemicarbazide, A- methyl-3-thiosemicarbazide, ethylene trithiocarbonate, vinylehe trithiocarbonate, 2- cyanothioacetamide, ⁇ -mercaptoethanol, cysteine, methanethiol (CH 3 SH), ethanethiol (C 2 H 5 SH), 1-propanethiol (C 3 H 7 SH), 2-propanethiol (CH 3 CH(SH)CH 3 ), butanethiol (C4H 9 SH), tetrabutyl mercaptan (C(CH 3 ) 3 SH), pentanethiols (C 5 H 11 SH), coenzy
  • the concentration of the sulfur-containing compound ranges from- 0.05 mM to
  • the sulfur-containing compound in some embodiments, is selected capable of acting as a localized charge density modifier on the surface of highly curved metallic copper particles, produced according to the process presented herein.
  • nanoparticles and hollow microparticles in the obtained composition are coated with the fibrous copper, and that these metallic copper filaments may lead, according to some embodiments of the present invention, to tethering between copper nano- and/or micro-particles, leading to mechanical and electrical contact between them even when produced at room temperature.
  • the present inventors have further surprisingly uncovered that when the spherical copper particles are produced in the presence of a sulfur-containing compound, their surface seems as if it was sintered and the composition obtained from such a process seems to comprise fused metallic copper particles.
  • sintering is effected by applying heat and/or pressure on pre-fabricated compositions of copper nano- and/or microparticles according to some embodiments of the present invention, tethering is observed when the filamentous coating on neighboring copper particles intertwines, and fused copper particles are observed in copper particle compositions which were prepared in the presence of a sulfur-containing compound without heat and/or pressure.
  • the term “sintered” refers to a morphological solid state of a particulate matter which has been transformed so as to fuse its particles into a substantially continuous non-particulate dense matter.
  • the term “sintered” refers to a morphological solid state wherein heat is not necessarily involved, or where no application of external of heat is involved. In the context of the present embodiments sintering may occur as a result of the application of mild mechanical pressure or the application of heat.
  • fused refers to a morphological solid state of a particulate matter which has been transformed so as to fuse its particles into a substantially continuous non-particulate loose matter.
  • fused refers to a morphological solid state wherein neither heat nor pressure is necessarily involved, but it is rather as a result of specific chemical conditions during a chemical reaction, which forms connected particles rather than discrete particles.
  • tethered refers to a morphological solid state of a particulate matter which has been transformed so as to have its particles entangled in a network of fibrous matter.
  • tethered refers to a morphological solid state which is a result of specific chemical conditions during a chemical reaction, which forms fiber-entangled particles rather than discrete particles.
  • the process of manufacturing a composition as described herein is effected by performing the mixing of the copper salt, the zinc and the carboxyl-containing compound, in the presence of a sulfur-containing compound as described herein.
  • the addition of the sulfur- containing compound is performed prior to the copper/zinc cementation reaction and thus prior to filtering and drying the powder.
  • the process is effected by adding a sulfur-containing compound to the aqueous solution containing the copper salt, the elemental zinc grit and the carbonyl-containing compound;
  • the composition obtained according to these embodiments of the invention differs from the composition obtained according to embodiments where the sulfur-containing compound is added after a powder of copper particles is formed, in that the filaments, which were clearly observable in the two-steps process, seem to be fused or sintered to the surface of the spherical copper particles in such a way so as to fuse the copper particles to one another.
  • this composition prepared with a sulfur-containing compound is characterized by fused spherical copper particles having an average particle size that ranges from 50 nm to 20 ⁇ m.
  • composition obtained by these embodiments of the invention presents a unique possibility to obtain a continuous layer of conductive metallic copper on the surface of any substrate, at room temperature and without any additional chemical, physical or mechanical step, by simply spraying an aqueous solution containing a copper salt, fine elemental zinc powder, a carboxyl-containing compound and a sulfur- containing compound onto the surface.
  • the resulting copper particles which will form in the solution would be fused to one another and therefore constitute a sintered layer on the surface of the substrate.
  • the reactions may be performed with or without the presence of a phosphorous- containing compound.
  • exemplary suitable phosphate compounds are as described in WO 2010/035258.
  • the processes of manufacturing the compositions presented herein involve reaction with are devoid of a phosphorous-containing compound.
  • compositions e.g., in the form of a powder of copper nano- and micro- particles
  • reaction parameters were further investigated and characterized by various methods, and were found to posses different architectures, influenced by the reaction parameters.
  • the obtained powder comprises hollow spheroidal copper micro-particles having an average size of about 0.5 ⁇ m to 20 ⁇ m, a wall of 50 nm to 200 nm in thickness and a bosselated surface topology.
  • Each of these copper particles seems to be comprised of a plurality of spherical copper nanoparticles.
  • X-ray photoelectron spectroscopy (XPS) spectra analyses provided the chemical composition of the resulting copper particles.
  • composition which- includes a plurality of copper nanoparticles and/or microparticles generally shaped as spheroids and characterized by a bosselated surface topology.
  • the copper nano- and micro-particles have an overall spherical shape. Accordingly, in some embodiments, the copper nanoparticles are generally shaped as spheroids, which is a close approximation to a sphere.
  • spheroids spheroidal particles
  • compositions presented herein include a plurality of particles, a portion of which are hollow spheroidal microparticles and a portion of which are spherical nanoparticles.
  • a portion of refers to a part of a physical quantity, such as surface area or weight.
  • a portion of the composition describes 1 weight percent, 10 weight percents, 50 weight percents, 70 weight percents, 80 weight percents, 90 weight percents and even 100 weight percents (meaning that the composition consists of that species), and any value therebetween, including 0 for absent (and consisting the other type of particle species).
  • the composition consists of hollow spheroidal copper microparticles.
  • the hollow spheroidal copper micro-particles are characterized by an average particle size that ranges from about 0.5 ⁇ m to about 20 ⁇ m.
  • the hollow spheroidal copper micro-particles are characterized by a wall thickness that ranges from about 50 nm to about 2 ⁇ 0 nm.
  • the composition consists of copper- nanoparticles having-a bosselated surface topology.
  • a portion of the composition includes copper- nanoparticles and another portion thereof includes hollow spheroidal copper microparticles, all of which exhibit a bosselated surface topology.
  • the copper nano- and micro-particles presented herein therefore enjoy another beneficial property, which can be referred to as a "low organic content", namely a very low percentage by weight/mass of organic molecules versus copper.
  • a quantitative measure for the content of organic molecules can be the carbon content.
  • Metallic nanoparticles having a carbon-content above a certain threshold would be considered useless for certain applications.
  • the carbon content of the copper nanoparticles presented herein is less than 20 percent of the total weight of the copper nanoparticles (their total-mass).
  • the copper nanoparticles presented herein have a carbon content of less th&n 10 percents of their total mass, or less than 5 percents of their total mass.
  • XPS analysis of powders produced using a carboxyl-containing compound such as citric acid detect relatively low presence of organic elements (O and C, and P and S when used) on the surface of the copper particle.
  • organic elements O and C, and P and S when used
  • the chemical content is relevant to the exterior of the particle, and that the core of the particle consists essentially of pure copper
  • values of 40 % and even 50 % of carbon measured by XPS are indicative of very low carbon content of the entire mass of the particle.
  • the micro- particles have an exterior surface which is characterized as comprising an atomic concentration of oxygen that ranges from 20 percent to 40 percent; an atomic concentration of carbon that ranges from 20 percent to 35 percent; and when used, an atomic concentration of phosphorous that ranges from 0 percent to 5 percent. It is noted herein that the figures present examples of the compositions according to some embodiments of the present invention, and serve as to demonstrate exemplary embodiments.
  • the wall of the hollow spheroidal copper micro-particles seems to comprise spherical copper nanoparticles having an average particle size that ranges from 20 nm to 200 run.
  • the outcome of the process presented hereinabove is a composition comprising spherical copper nanoparticles which may undergo some process of self-assembly into larger hollow spheroidal micro-particles, and/or or become coated with filamentous copper and thereafter, optionally tether to one another.
  • the spherical copper nanoparticles of the composition are characterized by an average particle size that ranges from 50 nm to 500 nm, and a bosselated surface topology, as this term is defined hereinabove.
  • the surface topology of the nanoparticles and microparticles of the compositions according to the present embodiments is characterized by round bumps or bosses, wherein the curvature of each of these bosses in the bosselated surface topology is having a mean curvature that ranges frcmr ⁇ .02 nm "1 to 0.5 nm "1 .
  • At least a portion of the plurality of pre-formed copper nanoparticles and/or microparticles, having a bosselated surface topology, may become coated with fibrous copper.
  • hollow spheroidal copper microparticles as described herein may become coated with a network of fibrous copper.
  • spherical copper nanoparticles as described herein may become coated with a network of fibrous copper.
  • both types of copper particles may become coated with a network of fibrous copper.
  • the fibrous copper is characterized by fibers having a length of about 10 nm to about 100 nm and a thickness of about 5 nm to about 10 nm.
  • This fibrous copper may be formed in such a way so as to tether neighboring particles to one another. Tethering of particles as a result of the formation of fibrous copper may occur between various types of particles, thereby forming entangled complex structures which comprise large and small particles, depending of their relative presence in the composition.
  • spherical nanoparticles may be tethered to other spherical nanoparticles; hollow microparticles may be tethered to other hollow microparticles; and spherical nanoparticles may be tethered to hollow microparticles.
  • At least a portion of the copper microparticles and/or nanoparticles become fused to one another.
  • the surface of the copper particles in the exemplary composition shown therein appears smooth, and the boundary between features on the surface of a particle or even the boundary between individual particles becomes less discernable.
  • compositions which comprise a sulfur- containing compound either the composition wherein pre-formed copper particles are treated with a sulfur-containing compound or the composition wherein the copper particles are formed in the presence of a sulfur-containing compound, was examined as exemplified in the Examples section below.
  • the exterior surface of the copper microparticles and/or nanoparticles obtained by introducing a sulfur-containing compound into the reaction mixture, or by post-treating the same with a sulfur-containing ⁇ compound is characterized as comprising an atomic concentration of oxygen that ranges from 20 percent to 40 percent.
  • the exterior surface is characterized as comprising an atomic concentration of carbon that ranges from 20 percent to 30 percent.
  • the exterior surface is characterized as comprising an atomic concentration of nitrogen that ranges from 10 to 15 percent (when nitrogen is present in the sulfur-containing compound such as thiourea).
  • the exterior surface is characterized as comprising an atomic concentration of sulfur that ranges from 0.1 to 5 percent.
  • XPS analysis of an exemplary composition prepared by exposing pre-formed copper particles to thiourea according to some embodiments of the present invention reveals the presence of nitrogen at a content of 11 % and sulfur at an amount of 0.5 %, indicating that the sulfur group is essentially eliminated from the surface of the copper particles.
  • compositions presented herein afforded either with or without a sulfur-containing compound, affords a unique capacity to sinter into macroscopic structures upon an application of mild mechanical pressure thereon at a temperature lower than 100 0 C, and even lower than 50 0 C (e.g., at room temperature).
  • HRSEM evaluation suggests that this fibrous network facilitates physical contact between copper nano- and micro-particles and can promote sintering at room temperature.
  • sub-micron and micron sized copper particles which are produced as powders according to some embodiments of the present invention, can be sintered at room temperature by manually applying very weak pressure, to yield metallic copper lines.
  • sintering of dry powders of the compositions presented herein can be afforded by applying mechanical pressure at room temperature thereon.
  • compositions presented herein are highly suitable for many applications where nanoparticles are used in general, and in particular to those applications where the nanoparticles are discrete, do not tend to form agglomerate irreversibly, and have a low carbon (organic) content.
  • an article-of-manufacturing consisting of or comprising any of the compositions presented herein.
  • Such article-of-manufacturing may be formed, according to some embodiments of the present invention, by applying a mild mechanical pressure on the composition at a temperature lower than 100 0 C, lower than 50 0 C or at room temperature.
  • milled mechanical pressure it is meant that the mechanical pressure can be applied, for example, directly by hand mediated by a small tool, or otherwise by a mechanical pressure which is less than 100 MPa, less than 10 MPa or less than 1 MPa, which is applied for less than 1 minute on a sample of 1 gram of any of the compositions presented herein.
  • the mild mechanical pressure required for sintering would be on thinly spread patterns of the compositions.
  • a powder of any of the compositions is formed, applied as a thin layer of about 0.5 micron to 50 microns on a substrate, and then pressed mildly (with less than 10 MPa or less than 1 MPa) to sinter the composition into a continuous metallic copper layer.
  • Such mechanical pressure can be applied by a roll-to-roll printing mechanism and since heating to temperatures higher than 100 0 C is not necessary, such techniques can be suitable for substrates which do not tolerate high temperatures.
  • the ability to transform copper powder (copper particles) into copper sheets or lines by applying moderate mechanical pressure can enable, for example, applications such as roll-to-roll printing of conducting patterns such as RFID antennas.
  • the article-of-manufacturing, according to-some embodiments of the present invention can be, for example, an inkjet ink, a dry toner, a solid macro-scaled object, an electronic component and an electronic circuit.
  • composition can be afforded by means of applying a suspension of the composition onto a substrate, and thereafter effecting sintering thereof by mild heat, mild pressure without heat, or a combination thereof, according to the substrate and the desired results.
  • suspension refers to a heterogeneous mixture of a solid in the form of fine solute-like particles dispersed in a liquid or solvent-like phase.
  • a suspension will have a tendency to settle, namely the fine particles of the solid matter may have the tendency to precipitate after a period of time.
  • This period of time depends on many factors, such as the substances of the particles and the liquid, the temperature and other physical parameters like stirring and shaking, and the presence of other substances, such as dispersing agents, emulsifiers, surface-active agents, thickeners and the likes.
  • the term "suspension” as used herein, is similar to the term dispersion, with the proviso that the media is a condense medium, typically a liquid.
  • a suspension is a collection of discrete and separated particles dispersed in a liquid medium.
  • the capacity to re-disperse is applicable also in liquid media, namely the capacity to re-suspend, or go from a precipitant to a suspension reversibly and reproducibly.
  • the composition is being in a form of a dispersion, or in other words, the copper nano- and/or micro- particles comprising the composition are dispersed, be it as a dry powder or as a suspension of copper particles in liquid media, such as a suspension in an aqueous medium.
  • any of the compositions presented herein can function well in certain ink formulations and processes in the field of printable electronics.
  • an exemplary article-of-manufacturing which includes the composition presented herein formulated into an inkjet ink composition.
  • Such inkjet inks are used, for example, to form electronic circuits, electronic components, electronic elements and devices by inkjet printing.
  • a method of preparing a substantially electrically conducting copper element includes forming a shape of the element from a composition as provided herein, and applying either heat or pressure, or both, onto this shape to thereby obtain the copper element.
  • an inkjet ink composition which includes a composition as presented herein.
  • a method of inkjet printing a substantially electrically conducting element on a substantially electrically isolating substrate includes applying the inkjet ink composition provided herein on the substrate.
  • the method of printing further includes, subsequent to applying the ink, curing the substrate having the inkjet ink composition applied thereon by mild heat to thereby form the electrically conducting element on the substantially electrically isolating substrate.
  • Powder metallurgy uses sintering process for making various parts out of metal powders.
  • the metal powder is compacted by placing it in a closed metal cavity (the die, matrix or mold) under pressure.
  • This compacted material is placed in an oven and sintered in a controlled atmosphere at moderate temperatures (relative to the temperature needed to melt the metal) and the metal powders coalesce and form a solid.
  • a second pressing operation, repressing can be done prior to sintering to improve the compaction and the material properties.
  • Metallic nanoparticles are therefore typically used for these applications since the cleaner (organic-free) the nanoparticles and the smaller they are, the better the end-result of a metal object will be.
  • the article-of- manufacturing described herein is a metal object of any shape and size, which is made by any powder metallurgy process and which comprises the composition according to embodiments of the present invention.
  • Exemplary objects include, but are not limited to, objects of complex structures such that are not feasible by conventional machining and other material removal methods, molten-metal casting methods or molten-metal extrusion methods, as well as simple objects, shafts, bearings, blades, pistons, housing, casing, tubing, and any object that combines the latter.
  • compositions according to some embodiments of the present invention are assumed to possess an electrostatic charge which can be used to direct them to predetermined locations on given substrates.
  • Charged copper micro-particles capable of undergoing sintering by mild mechanical pressure may enable fabrication of conductive patterns using electrophotography.
  • an exemplary article-of -manufacturing can be a dry toner, useful for example in a roll-to-roll printing technique.
  • tonener refers to a powder of charged particles which are positioned photoelectronically according to a predetermined patter onto a platform, which can then transfer the pattered particles onto a final substrate. Toners are used in printing technique such as in laser printers and photocopiers to form the printed text and images on the paper.
  • the toner is curable upon application of mild mechanical pressure thereon at a temperature lower than 100 0 C, or lower than 50 0 C.
  • the toner can therefore be used in a method of printing a substantially electrically conducting element on a substantially electrically isolating substrate, by applying the toner on the substrate and pressing the substrate having the toner applied thereon to thereby form the electrically conducting element on the substantially electrically isolating substrate.
  • any of the compositions presented herein can be fed through a rolling machine to produce conductive copper sheets not supported by a substrate.
  • nano- and micro-sized sintered copper particles can be obtained by performing a zinc/copper cementation reaction in the presence of a carboxyl-containing compound such as citric acid and a sulfur-containing compound such as thiourea.
  • a carboxyl-containing compound such as citric acid
  • a sulfur-containing compound such as thiourea
  • the resulting suspension of the composition obtained by the aforementioned process can be used to wet-spray a surface of a substrate so as to afford a layer of sintered metallic copper thereon.
  • the present inventors postulated a mechanism according to which fine filament- coated copper nanoparticles first pack into a micelle like structures, leading to spherical structures held together by virtue of weak forces; thereafter, increased surface charge density brought about by the adsorption of sulfur leads to surface flow which transforms the discrete spherical nanoparticles into a sintered body.
  • a method of preparing a substantially electrically conducting copper layer on at least a portion of a surface of a substrate which is effected by spraying a suspension of the sintered copper particles described hereinabove onto the surface.
  • the composition which is prepared by combining zinc, copper salt, a carboxyl-containing compound and a sulfur-containing compound the intrinsic tendency of the copper particles in such compositions to sinter may render heat curing and/or pressure setting unnecessary. It is expected that during the life of a patent maturing from this application many relevant metallic nanoparticles will be developed and the scope of the phrase "copper particles" is intended to include all such new technologies a priori.
  • CuSO 4 -5H 2 O was purchased from Gadot Chemicals.
  • Zinc powder grit size less than 10 micron, was purchased from Sigma-Aldrich.
  • Citric acid was purchased from Sigma-Aldrich.
  • Thiourea was purchased from Sigma-Aldrich.
  • High-Resolution Scanning Electron Microscope (HRSEM) micrographs were afforded using a Zeiss Gemini Ultruplus.
  • XPS X-ray photoelectron spectroscopy
  • Copper salt is dissolved in degassed water to thereby obtain a copper salt solution.
  • a carboxyl-containing compound is added to the solution at a ratio that ranges from 5:1 to 1:1 with respect to the copper, and stirred until fully dissolved.
  • the pH of the solution is adjusted with a hydroxyl salt to range from 1.5 to 5.
  • zinc dust grit size 10-20 micron
  • a phosphorous- containing compound is added to the copper salt solution prior to the addition of zinc.
  • the solution turns from clear green-blue to a reddish/brown lucid suspension.
  • the resulting suspension was filtered through a #42 filter paper and washed with H 2 O and ethanol.
  • the filter paper carrying the red slurry was put in a convection oven heated to 50 0 C for a few minutes, taken out, and the dried slurry, now in the form of cake, was removed from the filter paper.
  • the cake was reintroduced into the oven and heated at 50 0 C for 7 hours. This procedure results in copper nanostructures which self-assemble to form spherical copper nanoparticles and hollow spheroidal copper micro-particles.
  • the hollow spheroidal copper micro-particles were obtained when the molar ration between citric acid and copper sulfate is greater than 1:1. In cases where this molar ratio is smaller than 1:1 (less- citric acid), heavily aggregated dendritic structures were formed rather than spheres of any size.
  • the following electromicrographic analysis refers to the composition obtained as described hereinabove using 6 liters H 2 O bubbled with N 2 , 46.8 grams of CuSO 4 , 71 grams of NaH 2 PO 2 71, 60 grams of citric acid and 12 grams of powdered zinc, at pH 5.
  • composition of the above composition revealed a composition of 34.87 % oxygen, 29.37 % carbon, 30.11 % copper, 3.15 % zinc and 2.53 % phosphorous. Similar compositions, in terms of visual appearance, were obtained when the cementation reaction was performed in a solution devoid of a phosphorous-containing compound, and/or using various ingredient ratios and various carboxyl-containing compounds.
  • Figure 1 and Figures 2A-B are HRSEM electromicrographs of hollow spheroidal micro-particles, prepared as described above with citric acid and hypophosphite. As shown in the electromicrographs, the obtained particles have an average particle size of from 0.5 ⁇ m to 20 ⁇ m, and are comprised of sub-micron spherical nanoparticles each having dimensions of from 20 nm to 200 nm.
  • these hollow spheroidal copper micro-particles of various microscopic sizes are the result of an incremental self-assembly of spherical copper nanoparticles in the size range of from 5 nm to 20 nm, which pack together to form a larger spherical copper nanoparticles of from 50 nm to 200 nm, which then pack together to form the hollow spheroidal copper micro-particles being from 0.5 to 20 micron in size.
  • Such self-similarity architecture or fractal structuralism is a characteristic of the hollow spheroidal copper micro-particles described herein.
  • Figures 3 and 4 present two series of HRSEM electromicrographs in increasing magnification levels of exemplary hollow spheroidal copper micro-particles having self- similarity architecture, based on incremental packing of- smaller spherical copper nanoparticles.
  • Figure 5 is a HRSEM electromicrograph of a streak of powder of exemplary hollow spheroidal copper micro-particles, which was pressed manually using a spatula at room temperature. Upon pressure-effected sintering at room temperature, the color of the substance changed from typical saddle-brown of the powder to metallic red luster.
  • Figure 6 presents a high resolution XPS spectrum of CIs measured for a sample of hollow spheroidal copper micro-particles obtained with citric acid as described hereinabove.
  • the CIs spectrum was curve-fitted with 3 components. While the A line is related to carbon bound to hydrogen, the higher binding energy line B is assigned to
  • Figure 7 presents a high resolution XPS spectrum of Cu2p measured for a sample of hollow spheroidal copper micro-particles obtained with citric acid and with hypophosphite as an additive.
  • the Cu2p3/2 spectrum was curve-fitted with 3 components. While the lower binding energy line is related to Cu 2 O and metallic Cu
  • the higher binding energy lines can be assigned as CuO and Cu(OH) 2 .
  • the presence of a metallic Cu line is due to the fact that the surface oxide is thin enough to allow the photoelectrons from the metal to escape through the oxide layer.
  • the Cu oxide layer (estimated from the experimental Cu oxide and Cu metal peak ratio) is a few nm thick.
  • a powder of copper nano- and micro-particles is prepared according to General Procedure A presented hereinabove, and is thereafter suspended using a homogenizer in degassed water at room temperature. A sulfur-containing compound is added to the suspension and the obtained mixture is stirred for several hours. The resulting suspension is filtered and dried.
  • copper particles powder was prepared as follows: 234 grams of CuSO 4 -5H 2 O were added to 6 liters of H 2 O, pre-bubbled with N 2 for at least 10 minutes, and stirred using a homogenizer until completely dissolution was achieved. Thereafter, 345 grams of citric acid monohydrate were added and the mixture was stirred until all the citrate has dissolved. The pH of the solution was adjusted to 3.6 using sodium-hydroxide. Thereafter, 60 grams of zinc dust (grit size 10 micron) were added and the suspension was stirred vigorously using a homogenizer for another 8 minutes at room temperature. With the addition of the zinc powder the solution turns from clear green-blue to a reddish/brown lucid suspension.
  • the resulting suspension was filtered through a #42 filter paper and washed with H 2 O and ethanol.
  • the filter paper carrying the red slurry was put in a convection oven heated to 50 0 C for a few minutes, taken out, and the dried slurry, now in the form of cake, was removed from the filter paper.
  • the cake was reintroduced into the oven and heated at 50 0 C for 7 hours. This procedure resulted in a powder of spherical copper nanoparticles and hollow spheroidal copper micro-particles.
  • the resulting suspension was filtered using #42 filter paper and washed with H 2 O and ethanol.
  • the filter paper carrying the slurry was put in a convection oven heated to 50 0 C for a few minutes, taken out, and the dried slurry, now in the form of cake, was removed from the filter. The cake was then reintroduced into the oven and heated at 50 0 C for 7 hours.
  • Figure 8 is a HRSEM electromicrograph of the surface of a spheroidal copper micro-particle, obtained as described hereinabove and treated with thiourea, being completely covered with fibrous copper.
  • Figures 9 and 10 are HRSEM electromicrographs showing a surface of a hollow spheroidal copper micro-particle prepared as described hereinabove, having spherical copper nanoparticles tethered thereto by fibrous copper.
  • Figure 11 is a TEM electromicrograph showing the fibrous copper network formed on the surface of spherical copper nanoparticles and hollow spheroidal copper micro-particles, prepared as described hereinabove, due to the treatment thereof with thiourea, wherein the TEM evaluation suggests that the copper comprising these fibers is semi-crystalline.
  • the fibrous network facilitates physical contact between copper nano- and micro-particles and can promote room temperature sintering of copper nano- and micro- particles.
  • the width of the nano-filaments cannot be resolved using HRSEM even at magnifications of 200,00OX, indicating that their diameter is less than 10 nm.
  • TEM evaluation of these nano-filaments suggests that the copper therein is amorphous or semi-crystalline.
  • XPS analysis pertains to a sample prepared as described hereinabove and according to General Procedure B presented hereinabove, with 7 grams of copper particles powder, prepared according to General Procedure A as presented hereinabove, from 6 liters of H 2 O, 234 grams of CuSO 4 -5H 2 O, 345 grams of citric acid, 60 grams of zinc dust, and treated with 0.6 grams of thiourea.
  • Figure 12 presents a high resolution XPS CIs spectrum of a sample of copper particles, obtained and treated with thiourea as described hereinabove. The spectrum was curve-fitted with 5 components. While the A line can be related to carbon bound to hydrogen, the higher binding energy lines can be assigned to carbon atoms bonded to O and N in various chemical configurations.
  • Figure 13 presents a high resolution XPS Cu2p spectrum of a sample of copper particles, obtained and treated with thiourea as described hereinabove. The spectrum was curve-fitted with 6 components. While the lower binding energy line can be related to Cu 2 O (based on the Cu LMM line measurements), the higher binding energy lines can be assigned as CuO and Cu(OH) 2 . The E, G and F lines are typical shake-up lines typical for Cu bonded as Cu 2 O.
  • Figure 15 presents a high resolution XPS S2p spectrum of a sample of copper particles, obtained and treated with thiourea as described hereinabove.
  • the spectrum obtained is typical for a sulfide-like bonding state.
  • the atomic concentrations of nitrogen and sulfur on the surface of the nanoparticles are 11.5 % and
  • a carboxyl-containing compound and a sulfur-containing compound are dissolved in degassed water, and the pH of the solution is adjusted using a hydroxyl salt to range from 1.5 to 5.
  • a copper salt is dissolved in the solution, and thereafter zinc dust (grit size 10-20 micron) is added to the solution to form a suspension which, is stirred vigorously using a homogenizer for several minutes at room temperature.
  • the suspension of metallic copper particles is filtered on paper to form a cake which is washed with water and alcohol, dried in room temperature and in an oven at 50 0 C for several hours.
  • the resulting suspension was filtered using #42 filter paper and washed with H 2 O and ethanol.
  • the filter paper carrying the red slurry was put in a convection oven heated to 50 0 C for a few minutes, taken out, and the dried slurry, now in the form of cake, was removed from the filter. The cake was then reintroduced into the oven and heated at 50 0 C for 7 hours.
  • Figure 16 is a HRSEM electromicrograph showing a micelle-like packing of linear chains of copper nanoparticles, which is assumed to be the first step in the process of obtaining fused copper particles.
  • Figure 17 is a HRSEM electromicrograph showing a copper nanoparticles prepared by the procedure presented hereinabove, exhibiting a surface area in an intermediate stage in the transformation into a smooth fused morphology. As can be seen in Figure 17, most of the sub-level spherical features have sintered to form a smooth surface.
  • Figure 18 is a HRSEM electromicrograph showing copper particles prepared in the presence of thiourea as presented hereinabove, exhibiting a surface which seems to be completely fused.

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Abstract

La présente invention se rapporte à un système permettant de collecter et d'analyser des informations de rétroaction structurées émanant d'un utilisateur à propos de sites Web. Le système selon l'invention comprend une fonction de génération d'imprimé d’informations de rétroaction structurées émanant d'un utilisateur d'un site Web, qui sert à générer des imprimés d’informations de rétroaction structurées pour fournir des informations de rétroaction émanant d'un utilisateur d'un site Web à propos de l'interaction de l'utilisateur d'un site Web avec un processus basé sur un site Web. Le système selon l'invention comprend par ailleurs une fonction d'analyse d’informations de rétroaction émanant d'un utilisateur d'un site Web qui sert à collecter et à analyser automatiquement des informations de rétroaction émanant d'un utilisateur d'un site Web et saisies sur les imprimés d’informations de rétroaction structurées, la fonction servant également à fournir au moins un rapport d'analyse sur la base d’informations de rétroaction émanant d'une pluralité d'utilisateurs d'un site Web.
PCT/IL2010/000536 2009-07-05 2010-07-05 Procédé et système adaptés pour fournir des informations de rétroaction émanant d'un utilisateur en ligne à propos de sites web et de logiciels informatiques Ceased WO2011004363A2 (fr)

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US20150146012A1 (en) * 2013-11-27 2015-05-28 Sprint Communications Company L.P. Video presentation quality display in a wireless communication device
WO2015137015A1 (fr) * 2014-03-10 2015-09-17 三井金属鉱業株式会社 Poudre de cuivre

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US6620344B2 (en) * 1999-05-28 2003-09-16 Dowa Mining Co., Ltd. Copper particle clusters and powder containing the same suitable as conductive filler of conductive paste

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WO2010035258A2 (fr) 2008-09-25 2010-04-01 Nanoready Ltd. Nanoparticules de cuivre distinctes

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20150146012A1 (en) * 2013-11-27 2015-05-28 Sprint Communications Company L.P. Video presentation quality display in a wireless communication device
WO2015137015A1 (fr) * 2014-03-10 2015-09-17 三井金属鉱業株式会社 Poudre de cuivre
JP5969118B2 (ja) * 2014-03-10 2016-08-17 三井金属鉱業株式会社 銅粉
TWI648414B (zh) * 2014-03-10 2019-01-21 日商三井金屬鑛業股份有限公司 銅粉

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