CN111872411A - Preparation method of nano silver powder and nano silver powder - Google Patents
Preparation method of nano silver powder and nano silver powder Download PDFInfo
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- CN111872411A CN111872411A CN202010729104.1A CN202010729104A CN111872411A CN 111872411 A CN111872411 A CN 111872411A CN 202010729104 A CN202010729104 A CN 202010729104A CN 111872411 A CN111872411 A CN 111872411A
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
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- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
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Abstract
The invention relates to the technical field of metal powder preparation, in particular to a preparation method of nano silver powder and the nano silver powder. The applicant provides a method for preparing nano silver powder, which can obtain nano-sized and uniform nano silver powder by controlling the types, concentrations and contents of a silver source, a reducing agent and a dispersing agent and controlling the adding sequence and temperature of each component, and can avoid aggregation of the silver powder in the processes of centrifugation and drying by controlling the operation method of post-treatment, so as to obtain the nano silver powder with good dispersibility, uniform particle size and smooth surface, and the average particle size of the obtained silver powder can be controlled to be less than 100nm and even about 50 nm.
Description
Technical Field
The invention relates to the technical field of metal powder preparation, in particular to a preparation method of nano silver powder and the nano silver powder.
Background
The silver nanopowder is a powder composed of silver nanoparticles with a particle size of 20-200 nm. Because the particles are extremely tiny, the nano-composite material has the advantages of large specific surface area, high surface activity, low sintering temperature, excellent conductivity and the like, and has remarkable advantages in the application fields of physics, chemistry, biology and the like, including surface enhanced Raman scattering, conductivity, catalysis, sensing, broad-spectrum antibacterial activity and the like. In recent years, silver nanoparticles are widely used in the fields of microelectronic materials, catalytic materials, low-temperature superconducting materials, electronic pastes, optical materials, medical antibacterial materials and the like, and thus, become a research hotspot of novel functional materials. A great deal of reports on the preparation and controllability research of nano-silver at home and abroad are already made, the commonly used preparation methods comprise a plurality of methods such as a gel sol method, a micro-emulsion method, an electro-reduction method, a photoreduction method, an ultrasonic reduction method, a liquid-phase chemical reduction method and the like, and the liquid-phase chemical reduction method is generally adopted industrially.
However, the existing method for preparing the silver nanoparticles by the liquid-phase chemical reduction method has certain defects, such as unstable thermodynamic properties, large specific surface area, high surface energy, and a large number of surface defects and dangling bonds, and the particles are easy to agglomerate during drying, and are difficult to open by a mechanical method after agglomeration, so that the dispersibility is poor, and the physical properties and functions of the silver nanoparticles are seriously affected.
Disclosure of Invention
In order to solve the above problems, a first aspect of the present invention provides a method for preparing a nano silver powder, comprising the steps of:
(1) dissolving a dispersant in water at 50-65 ℃ to prepare a dispersant solution, adding a reducing agent, mixing, and adjusting the pH to 2.5-6 to obtain a reducing solution;
(2) dissolving a silver source in water to obtain a silver source solution;
(3) dropwise adding the silver source solution into the reducing solution at the speed of 3-6 mL/min to obtain silver powder slurry;
(4) and centrifuging, washing and drying the silver powder slurry to obtain the nano silver powder.
As a preferable technical scheme, in the dispersant solution, the mass percentage concentration of the dispersant is 1.5-3 wt%.
As a preferable technical scheme, the mass percentage concentration of the silver source in the silver source solution is 7-15 wt%.
As a preferable technical scheme of the invention, the weight ratio of the dispersing agent to the silver source is (0.15-0.3): 1.
as a preferable technical scheme of the invention, the weight ratio of the reducing agent to the silver source is (0.65-0.75): 1.
as a preferable technical scheme, in the step (1), a dispersant and inorganic salt are dissolved in water at 50-65 ℃ to prepare a dispersant solution, a reducing agent is added, mixing is carried out, and the pH is adjusted to 2.5-6 to obtain a reducing solution.
As a preferable technical scheme of the invention, the weight ratio of the dispersing agent to the inorganic salt is 1: (0.05-0.15).
In the centrifugal separation, the silver powder slurry is added into a solvent and centrifuged at 5000-7000 rpm.
In a preferred embodiment of the present invention, the solvent is selected from one of ethanol, hexane, acetone, and dichloromethane.
The second aspect of the invention provides a nano silver powder prepared according to the preparation method of the nano silver powder.
Compared with the prior art, the invention has the following beneficial effects: the applicant provides a method for preparing nano silver powder, which can obtain nano-sized and uniform nano silver powder by controlling the types, concentrations and contents of a silver source, a reducing agent and a dispersing agent and controlling the adding sequence and temperature of each component, and can avoid aggregation of the silver powder in the processes of centrifugation and drying by controlling the operation method of post-treatment, so as to obtain the nano silver powder with good dispersibility, uniform particle size and smooth surface, and the average particle size of the obtained silver powder can be controlled to be less than 100nm and even about 50 nm.
Drawings
FIG. 1 is an SEM image of silver powder provided in example 4 at 10.0KV acceleration voltage, 8.1mm working distance, and 100.0K magnification.
FIG. 2 is an SEM image of silver powder provided in example 4 at 10.0KV acceleration voltage, 8.1mm working distance and 50.0K magnification
Detailed Description
The disclosure may be understood more readily by reference to the following detailed description of preferred embodiments of the invention and the examples included therein. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control.
The term "prepared from …" as used herein is synonymous with "comprising". The terms "comprises," "comprising," "includes," "including," "has," "having," "contains," "containing," or any other variation thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.
The conjunction "consisting of …" excludes any unspecified elements, steps or components. If used in a claim, the phrase is intended to claim as closed, meaning that it does not contain materials other than those described, except for the conventional impurities associated therewith. When the phrase "consisting of …" appears in a clause of the subject matter of the claims rather than immediately after the subject matter, it defines only the elements described in the clause; other elements are not excluded from the claims as a whole.
When an amount, concentration, or other value or parameter is expressed as a range, preferred range, or as a range of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted to include the ranges "1 to 4", "1 to 3", "1 to 2 and 4 to 5", "1 to 3 and 5", and the like. When a range of values is described herein, unless otherwise stated, the range is intended to include the endpoints thereof and all integers and fractions within the range.
The singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. "optional" or "any" means that the subsequently described event or events may or may not occur, and that the description includes instances where the event occurs and instances where it does not.
Approximating language, as used herein throughout the specification and claims, is intended to modify a quantity, such that the invention is not limited to the specific quantity, but includes portions that are literally received for modification without substantial change in the basic function to which the invention is related. Accordingly, the use of "about" to modify a numerical value means that the invention is not limited to the precise value. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value. In the present description and claims, range limitations may be combined and/or interchanged, including all sub-ranges contained therein if not otherwise stated.
In addition, the indefinite articles "a" and "an" preceding an element or component of the invention are not intended to limit the number requirement (i.e., the number of occurrences) of the element or component. Thus, "a" or "an" should be read to include one or at least one, and the singular form of an element or component also includes the plural unless the stated number clearly indicates that the singular form is intended.
The present invention is illustrated by the following specific embodiments, but is not limited to the specific examples given below.
The invention provides a preparation method of nano silver powder, which comprises the following steps:
(1) dissolving a dispersant in water at 50-65 ℃ to prepare a dispersant solution, adding a reducing agent, mixing, and adjusting the pH to 2.5-6 to obtain a reducing solution;
(2) dissolving a silver source in water to obtain a silver source solution;
(3) dropwise adding the silver source solution into the reducing solution at the speed of 3-6 mL/min to obtain silver powder slurry;
(4) and centrifuging, washing and drying the silver powder slurry to obtain the nano silver powder.
In a preferred embodiment, the method for preparing the nano silver powder comprises the following steps:
(1) dissolving a dispersant in water at 60 ℃ to prepare a dispersant solution, adding a reducing agent, mixing, and adjusting the pH to 4.5 to obtain a reducing solution;
(2) dissolving a silver source in water to obtain a silver source solution;
(3) dropwise adding the silver source solution into the reducing solution at the speed of 5mL/min to obtain silver powder slurry;
(4) and centrifuging, washing and drying the silver powder slurry to obtain the nano silver powder.
Step (1)
In one embodiment, in the dispersant solution, the mass percentage concentration of the dispersant is 1.5-3 wt%; furthermore, in the dispersant solution, the mass percentage concentration of the dispersant is 2 wt%.
The mass percentage concentration is the weight percentage of a certain component in the solution in the total weight of the solution.
Examples of the dispersing agent include, but are not limited to, polyvinyl acid, polyvinyl pyrrolidone, polyethylene glycol, polyacrylic acid, polymethacrylic acid, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl hydroxyethyl cellulose, carboxymethyl starch, carboxyethyl starch, cyanoethyl starch, acetate starch, phosphate starch, cationic starch, polymeric starch, wheat starch, potato starch, sweet potato starch; in a preferred embodiment, the dispersant of the present invention is polyvinylpyrrolidone.
Polyvinylpyrrolidone is a water-soluble linear polymer compound and is formed by homopolymerization of monomer N-vinyl pyrrolidone (NVP). Has film forming property, cohesiveness, hygroscopicity, solubilization or coacervation effect, complexing ability with certain compounds, etc. The polyvinylpyrrolidone has both hydrophilic group and lipophilic group in its molecule, so that it can be dissolved in water and most organic solvents (such as alcohol, carboxylic acid, amine, halogenated hydrocarbon, etc.), and has low toxicity and good physiological compatibility. The solubility of polyvinylpyrrolidone in water is limited only by its own viscosity. As examples of the polyvinyl pyrrolidone, there are included, but not limited to, PVPK12, PVPK15, PVPK17 (weight average molecular weight 10100), PVPK25 (weight average molecular weight 32000), PVPK30 (weight average molecular weight 37900), PVPK45 (weight average molecular weight 152000), PVPK60, PVPK70, PVPK80, PVPK85 of bubingchu new materials science and technology (shanghai).
Preferably, the weight average molecular weight of the polyvinylpyrrolidone provided by the invention is 30000-400000.
The molecular weight is the weight average molecular weight, statistically averaged over the molecular weight. Usually expressed as Mw, which is equal to the sum of the molecular weight of each molecule multiplied by its weight fraction.
More preferably, the reducing agent of the present invention is selected from one of formaldehyde, hydrazine hydrate, ascorbic acid, sodium borohydride and formic acid; further, the reducing agent of the present invention is formaldehyde.
Further preferably, in the step (1) of the present invention, a dispersant and an inorganic salt are dissolved in water at 50 to 65 ℃ to prepare a dispersant solution, and a reducing agent is added to the dispersant solution, mixed, and adjusted to a pH of 2.5 to 6 to obtain a reducing solution.
Still more preferably, the weight ratio of the dispersant and the inorganic salt of the present invention is 1: (0.05-0.15); further, the weight ratio of the dispersant to the inorganic salt is 1: 0.075.
as examples of the inorganic salt, sodium sulfate, potassium sulfate, sodium sulfite, potassium sulfite, sodium carbonate, potassium carbonate, sodium phosphate, potassium phosphate, sodium sulfide, potassium sulfide; in a preferred embodiment, the inorganic salt of the present invention is potassium sulfate.
In a preferred embodiment, in the step (1) of the present invention, a dispersant and an inorganic salt are dissolved in water at 50 to 65 ℃ to prepare a dispersant solution, and a reducing agent and a polymer colloid are added and mixed to adjust the pH to 2.5 to 6, thereby obtaining a reducing solution.
In a more preferred embodiment, the polymer colloid of the present invention is one selected from gelatin, bone glue, xanthan gum, pectin, agar, gum arabic, tragacanth gum, locust bean gum, and soybean gum; furthermore, the polymer colloid is gelatin or Arabic gum.
Gelatin is a partially hydrolyzed product of collagen. Collagen molecule is a spiral body formed by three polypeptide chains intertwining with each other, and through the treatment of the technological process, the spiral body of the collagen molecule is degenerated and decomposed into an alpha-component of a single polypeptide chain (alpha-chain), a beta-component consisting of two alpha chains, a gamma-component consisting of three alpha chains, and molecular chain fragments which are arranged between the alpha-component and the gamma-component and are smaller than the alpha-component or larger than the gamma-component. Gelatin is a polydisperse system with a certain molecular weight distribution. In one embodiment, the gelatin of the present invention is available from Shandong Haoyao New materials, Inc.
Acacia gum is also known as gum arabic and is derived from the trunk exudate of acacia genus of Leguminosae family. Arabic gum contains high molecular polysaccharides and its calcium, magnesium and potassium salts. Mainly comprises arabinose, galactose, glucuronic acid and the like. Gum arabic is composed of two components, 70% of which are composed of polysaccharides containing no or small amounts of N, the other being a protein structure with high relative molecular mass; the polysaccharide is combined with hydroxyproline and serine in a protein peptide chain by a covalent bond; and the polysaccharide molecules linked to the proteins are highly branched acidic polysaccharides. In one embodiment, the gum arabic of the present invention is purchased from bioengineering, ltd, hongtong, anhui.
In a further preferred embodiment, the weight ratio of the polymer colloid and the reducing agent in the present invention is (0.002 to 0.01): 1; further, the weight ratio of the polymer colloid to the reducing agent is 0.005: 1.
the applicant finds that nano silver with small particle size has large specific surface area and surface energy, hard agglomeration can occur when reduction is carried out by using a stronger reducing agent such as formaldehyde, and the size distribution and the surface smoothness of the silver powder are influenced, the applicant finds that unexpectedly through experiments, after a dispersing agent with certain molecular weight is used, such as polymethyl pyrrolidone and water are uniformly mixed, a mixed solution containing polymer colloid and the reducing agent such as formaldehyde is added, the full mixing is favorable for obtaining the nano silver powder with uniform and smooth size, the generation of silver mirror reaction is avoided, a large amount of C-N, C ═ O in the polymethyl pyrrolidone can generate intermolecular action with the polymer colloid, the viscosity of the solution is adjusted, a uniform colloid solution is obtained, aldehyde groups and the like in the formaldehyde can react with the polymethyl pyrrolidone and the like, when a silver source such as silver nitrate is added for reverse reduction, under the condition of large reducing agent concentration, on one hand, formaldehyde and silver nitrate react to form instant nucleation, on the other hand, silver nitrate can also form a coordination piece with polymethyl pyrrolidone to eliminate multiple nucleation, and when the silver is reduced to be simple substance silver, a dispersing agent and polymer colloid in a colloidal solution adsorbed on the surface of the silver can also move around to block collision between silver ions, so that nano-scale silver powder is formed. And the applicants have found that when aqueous formaldehyde is added directly to the dispersant solution, there is a reduction in surface smoothness and a small amount of sticking, probably due to the uneven distribution of formaldehyde upon direct addition.
Step (2)
In one embodiment, in the silver source solution, the mass percentage concentration of the silver source is 7-15 wt%; furthermore, in the silver source solution, the mass percentage concentration of the silver source is 9.6 wt%.
Preferably, the silver source of the present invention is selected from one of silver nitrate, silver ammonia complex, silver oxide, silver carbonate, and silver carboxylate; further, the silver source of the invention is silver nitrate.
More preferably, the weight ratio of the dispersing agent and the silver source is (0.15-0.3): 1; further, the weight ratio of the dispersant to the silver source is 0.2: 1.
further preferably, the weight ratio of the reducing agent and the silver source is (0.65-0.75): 1; further, the weight ratio of the reducing agent to the silver source is 0.69: 1.
step (3)
In one embodiment, in the step (3), the silver source solution is added dropwise into the reducing solution at 50-65 ℃ at a rate of 3-6 mL/min to obtain the silver powder slurry.
Step (4)
In one embodiment, in the centrifugal separation, the silver powder slurry is added into a solvent and centrifuged at 5000-7000 rpm; further, in the centrifuge of the present invention, the silver powder slurry was added to the solvent and centrifuged at 6000 rpm.
Preferably, the solvent is selected from one of ethanol, hexane, acetone and dichloromethane; further, the solvent of the present invention is acetone.
More preferably, the centrifugation time is 8-15 min.
Further preferably, in the washing and drying, ethanol is added for washing after centrifugation, silver powder is deposited and dried to obtain the nano silver powder.
In the centrifuging and washing processes, long-chain-shaped agglomeration is easily formed due to a large number of defects and hanging hydrogen bonds on the surface of the nano silver powder, and the applicant has surprisingly found that when acetone is added for centrifuging together, the carbonyl of the acetone can replace partial hydroxyl and the surface of the silver powder is acted, the poor dispersibility of the polymethyl pyrrolidone and other dispersing agents and the acetone is beneficial to increasing mutual repulsion of an interface region, the dispersing agents are reduced from centrifuging along with the silver powder in the centrifuging process, chain-shaped agglomeration is reduced, and the maintenance of the nano size is promoted.
The second aspect of the invention provides a nano silver powder prepared according to the preparation method of the nano silver powder.
Examples
The present invention will be specifically described below by way of examples. It should be noted that the following examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention, and that the insubstantial modifications and adaptations of the present invention by those skilled in the art based on the above disclosure are still within the scope of the present invention.
Example 1
The embodiment provides a preparation method of nano silver powder, which comprises the following steps:
(1) dissolving a dispersant and inorganic salt in water at 60 ℃ to prepare a dispersant solution, adding a reducing agent, mixing, and adjusting the pH to 4.5 to obtain a reducing solution; in the dispersant solution, the mass percentage concentration of the dispersant is 2 wt%, the dispersant is polyvinylpyrrolidone, the inorganic salt is potassium sulfate, and the weight ratio of the dispersant to the inorganic salt is 1: 0.075; the reducing agent is formaldehyde;
(2) dissolving a silver source in water to obtain a silver source solution; in the silver source solution, the mass percentage concentration of a silver source is 9.6 wt%, the silver source is silver nitrate, and the weight ratio of the dispersing agent to the silver source is 0.2: 1, the weight ratio of the reducing agent to the silver source is 0.69: 1;
(3) dropwise adding the silver source solution into the reducing solution at 60 ℃ at the speed of 5mL/min to obtain silver powder slurry;
(4) adding the silver powder slurry into a solvent, centrifuging at 6000rpm for 10min, adding ethanol for cleaning, depositing silver powder, and drying to obtain nano silver powder; the solvent is acetone.
The polyvinylpyrrolidone was purchased from PVPK25, new materials science and technology (shanghai) ltd.
The present example also provides a nano silver powder prepared according to the preparation method described above.
Example 2
The embodiment provides a preparation method of nano silver powder, which comprises the following steps:
(1) dissolving a dispersant and inorganic salt in water at 60 ℃ to prepare a dispersant solution, adding a reducing agent and a polymer colloid, mixing, and adjusting the pH to 4.5 to obtain a reducing solution; in the dispersant solution, the mass percentage concentration of the dispersant is 1.5 wt%, the dispersant is polyvinylpyrrolidone, the inorganic salt is potassium sulfate, and the weight ratio of the dispersant to the inorganic salt is 1: 0.05; the reducing agent is formaldehyde, the polymer colloid is gelatin, and the weight ratio of the polymer colloid to the reducing agent is 0.01: 1;
(2) dissolving a silver source in water to obtain a silver source solution; in the silver source solution, the mass percentage concentration of a silver source is 7 wt%, the silver source is silver nitrate, and the weight ratio of the dispersing agent to the silver source is 0.15: 1, the weight ratio of the reducing agent to the silver source is 0.65: 1;
(3) dropwise adding the silver source solution into the reducing solution at 60 ℃ at the speed of 5mL/min to obtain silver powder slurry;
(4) adding the silver powder slurry into a solvent, centrifuging at 6000rpm for 10min, adding ethanol for cleaning, depositing silver powder, and drying to obtain nano silver powder; the solvent is acetone.
The polyvinylpyrrolidone was purchased from PVPK25, new materials science and technology (shanghai) ltd.
The gelatin was purchased from Shandong Haoyao New Material Co., Ltd.
The present example also provides a nano silver powder prepared according to the preparation method described above.
Example 3
The embodiment provides a preparation method of nano silver powder, which comprises the following steps:
(1) dissolving a dispersant and inorganic salt in water at 60 ℃ to prepare a dispersant solution, adding a reducing agent and a polymer colloid, mixing, and adjusting the pH to 4.5 to obtain a reducing solution; in the dispersant solution, the mass percentage concentration of the dispersant is 3 wt%, the dispersant is polyvinylpyrrolidone, the inorganic salt is potassium sulfate, and the weight ratio of the dispersant to the inorganic salt is 1: 0.15; the reducing agent is formaldehyde, the polymer colloid is Arabic gum, and the weight ratio of the polymer colloid to the reducing agent is 0.002: 1;
(2) dissolving a silver source in water to obtain a silver source solution; in the silver source solution, the mass percentage concentration of a silver source is 15 wt%, the silver source is silver nitrate, and the weight ratio of the dispersing agent to the silver source is 0.3: 1, the weight ratio of the reducing agent to the silver source is 0.75: 1;
(3) dropwise adding the silver source solution into the reducing solution at 60 ℃ at the speed of 5mL/min to obtain silver powder slurry;
(4) adding the silver powder slurry into a solvent, centrifuging at 6000rpm for 10min, adding ethanol for cleaning, depositing silver powder, and drying to obtain nano silver powder; the solvent is acetone.
The polyvinylpyrrolidone was purchased from PVPK30, new materials science and technology (shanghai) ltd.
The gum arabic is purchased from bioengineering ltd, hongtong, anhui.
The present example also provides a nano silver powder prepared according to the preparation method described above.
Example 4
The embodiment provides a preparation method of nano silver powder, which comprises the following steps:
(1) dissolving a dispersant and inorganic salt in water at 60 ℃ to prepare a dispersant solution, adding a reducing agent and a polymer colloid, mixing, and adjusting the pH to 4.5 to obtain a reducing solution; in the dispersant solution, the mass percentage concentration of the dispersant is 2 wt%, the dispersant is polyvinylpyrrolidone, the inorganic salt is potassium sulfate, and the weight ratio of the dispersant to the inorganic salt is 1: 0.075; the reducing agent is formaldehyde, the polymer colloid is Arabic gum, and the weight ratio of the polymer colloid to the reducing agent is 0.005: 1;
(2) dissolving a silver source in water to obtain a silver source solution; in the silver source solution, the mass percentage concentration of a silver source is 9.6 wt%, the silver source is silver nitrate, and the weight ratio of the dispersing agent to the silver source is 0.2: 1, the weight ratio of the reducing agent to the silver source is 0.69: 1;
(3) dropwise adding the silver source solution into the reducing solution at 60 ℃ at the speed of 5mL/min to obtain silver powder slurry;
(4) adding the silver powder slurry into a solvent, centrifuging at 6000rpm for 10min, adding ethanol for cleaning, depositing silver powder, and drying to obtain nano silver powder; the solvent is acetone.
The polyvinylpyrrolidone was purchased from PVPK25, new materials science and technology (shanghai) ltd.
The gum arabic is purchased from bioengineering ltd, hongtong, anhui.
The present example also provides a nano silver powder prepared according to the preparation method described above.
Example 5
The embodiment provides a preparation method of nano silver powder, which comprises the following steps:
(1) dissolving a dispersing agent and inorganic salt polymer colloid in water at 60 ℃ to prepare a dispersing agent solution, adding a reducing agent, mixing, and adjusting the pH to 4.5 to obtain a reducing solution; in the dispersant solution, the mass percentage concentration of the dispersant is 2 wt%, the dispersant is polyvinylpyrrolidone, the inorganic salt is potassium sulfate, and the weight ratio of the dispersant to the inorganic salt is 1: 0.075; the reducing agent is formaldehyde, the polymer colloid is Arabic gum, and the weight ratio of the polymer colloid to the reducing agent is 0.005: 1;
(2) dissolving a silver source in water to obtain a silver source solution; in the silver source solution, the mass percentage concentration of a silver source is 9.6 wt%, the silver source is silver nitrate, and the weight ratio of the dispersing agent to the silver source is 0.2: 1, the weight ratio of the reducing agent to the silver source is 0.69: 1;
(3) dropwise adding the silver source solution into the reducing solution at 60 ℃ at the speed of 5mL/min to obtain silver powder slurry;
(4) adding the silver powder slurry into a solvent, centrifuging at 6000rpm for 10min, adding ethanol for cleaning, depositing silver powder, and drying to obtain nano silver powder; the solvent is acetone.
The polyvinylpyrrolidone was purchased from PVPK25, new materials science and technology (shanghai) ltd.
The gum arabic is purchased from bioengineering ltd, hongtong, anhui.
The present example also provides a nano silver powder prepared according to the preparation method described above.
Example 6
The embodiment provides a preparation method of nano silver powder, which comprises the following steps:
(1) dissolving a dispersant and inorganic salt in water at 60 ℃ to prepare a dispersant solution, adding a reducing agent and a polymer colloid, mixing, and adjusting the pH to 4.5 to obtain a reducing solution; in the dispersant solution, the mass percentage concentration of the dispersant is 2 wt%, the dispersant is polyvinylpyrrolidone, the inorganic salt is potassium sulfate, and the weight ratio of the dispersant to the inorganic salt is 1: 0.075; the reducing agent is formaldehyde, the polymer colloid is Arabic gum, and the weight ratio of the polymer colloid to the reducing agent is 0.005: 1;
(2) dissolving a silver source in water to obtain a silver source solution; in the silver source solution, the mass percentage concentration of a silver source is 9.6 wt%, the silver source is silver nitrate, and the weight ratio of the dispersing agent to the silver source is 0.2: 1, the weight ratio of the reducing agent to the silver source is 0.69: 1;
(3) dropwise adding the silver source solution into the reducing solution at 60 ℃ at the speed of 5mL/min to obtain silver powder slurry;
(4) adding the silver powder slurry into a solvent, centrifuging at 6000rpm for 10min, adding ethanol for cleaning, depositing silver powder, and drying to obtain nano silver powder; the solvent is acetone.
The polyvinylpyrrolidone was purchased from PVPK17, new materials science and technology (shanghai) ltd.
The gum arabic is purchased from bioengineering ltd, hongtong, anhui.
The present example also provides a nano silver powder prepared according to the preparation method described above.
Example 7
The embodiment provides a preparation method of nano silver powder, which comprises the following steps:
(1) dissolving a dispersant and inorganic salt in water at 60 ℃ to prepare a dispersant solution, adding a reducing agent and a polymer colloid, mixing, and adjusting the pH to 4.5 to obtain a reducing solution; in the dispersant solution, the mass percentage concentration of the dispersant is 2 wt%, the dispersant is polyvinylpyrrolidone, the inorganic salt is potassium sulfate, and the weight ratio of the dispersant to the inorganic salt is 1: 0.075; the reducing agent is formaldehyde, the polymer colloid is Arabic gum, and the weight ratio of the polymer colloid to the reducing agent is 0.005: 1;
(2) dissolving a silver source in water to obtain a silver source solution; in the silver source solution, the mass percentage concentration of a silver source is 9.6 wt%, the silver source is silver nitrate, and the weight ratio of the dispersing agent to the silver source is 0.2: 1, the weight ratio of the reducing agent to the silver source is 0.69: 1;
(3) dropwise adding the silver source solution into the reducing solution at 60 ℃ at the speed of 5mL/min to obtain silver powder slurry;
(4) adding the silver powder slurry into a solvent, centrifuging at 6000rpm for 10min, adding ethanol for cleaning, depositing silver powder, and drying to obtain nano silver powder; the solvent is acetone.
The polyvinylpyrrolidone was purchased from PVPK45, new materials science and technology (shanghai) ltd.
The gum arabic is purchased from bioengineering ltd, hongtong, anhui.
The present example also provides a nano silver powder prepared according to the preparation method described above.
Example 8
The embodiment provides a preparation method of nano silver powder, which comprises the following steps:
(1) dissolving a dispersant and inorganic salt in water at 60 ℃ to prepare a dispersant solution, adding a reducing agent and a polymer colloid, mixing, and adjusting the pH to 4.5 to obtain a reducing solution; in the dispersant solution, the mass percentage concentration of the dispersant is 2 wt%, the dispersant is polyvinylpyrrolidone, the inorganic salt is potassium sulfate, and the weight ratio of the dispersant to the inorganic salt is 1: 0.075; the reducing agent is formaldehyde, the polymer colloid is locust bean gum, and the weight ratio of the polymer colloid to the reducing agent is 0.005: 1;
(2) dissolving a silver source in water to obtain a silver source solution; in the silver source solution, the mass percentage concentration of a silver source is 9.6 wt%, the silver source is silver nitrate, and the weight ratio of the dispersing agent to the silver source is 0.2: 1, the weight ratio of the reducing agent to the silver source is 0.69: 1;
(3) dropwise adding the silver source solution into the reducing solution at 60 ℃ at the speed of 5mL/min to obtain silver powder slurry;
(4) adding the silver powder slurry into a solvent, centrifuging at 6000rpm for 10min, adding ethanol for cleaning, depositing silver powder, and drying to obtain nano silver powder; the solvent is acetone.
The polyvinylpyrrolidone was purchased from PVPK25, new materials science and technology (shanghai) ltd.
The locust bean gum is purchased from Jiangsu Caosheng Biotech limited.
The present example also provides a nano silver powder prepared according to the preparation method described above.
Example 9
The embodiment provides a preparation method of nano silver powder, which comprises the following steps:
(1) dissolving a dispersant and inorganic salt in water at 60 ℃ to prepare a dispersant solution, adding a reducing agent and a polymer colloid, mixing, and adjusting the pH to 4.5 to obtain a reducing solution; in the dispersant solution, the mass percentage concentration of the dispersant is 2 wt%, the dispersant is polyvinylpyrrolidone, the inorganic salt is potassium sulfate, and the weight ratio of the dispersant to the inorganic salt is 1: 0.075; the reducing agent is formaldehyde, the polymer colloid is Arabic gum, and the weight ratio of the polymer colloid to the reducing agent is 0.005: 1;
(2) dissolving a silver source in water to obtain a silver source solution; in the silver source solution, the mass percentage concentration of a silver source is 9.6 wt%, the silver source is silver nitrate, and the weight ratio of the dispersing agent to the silver source is 0.2: 1, the weight ratio of the reducing agent to the silver source is 0.69: 1;
(3) dropwise adding the silver source solution into the reducing solution at 60 ℃ at the speed of 5mL/min to obtain silver powder slurry;
(4) adding the silver powder slurry into a solvent, centrifuging at 6000rpm for 10min, adding ethanol for cleaning, depositing silver powder, and drying to obtain nano silver powder; the solvent is ethanol.
The polyvinylpyrrolidone was purchased from PVPK25, new materials science and technology (shanghai) ltd.
The gum arabic is purchased from bioengineering ltd, hongtong, anhui.
The present example also provides a nano silver powder prepared according to the preparation method described above.
Example 10
The embodiment provides a preparation method of nano silver powder, which comprises the following steps:
(1) dissolving a dispersant and inorganic salt in water at 60 ℃ to prepare a dispersant solution, adding a reducing agent and a polymer colloid, mixing, and adjusting the pH to 4.5 to obtain a reducing solution; in the dispersant solution, the mass percentage concentration of the dispersant is 2 wt%, the dispersant is polyvinylpyrrolidone, the inorganic salt is potassium sulfate, and the weight ratio of the dispersant to the inorganic salt is 1: 0.075; the reducing agent is formaldehyde, the polymer colloid is Arabic gum, and the weight ratio of the polymer colloid to the reducing agent is 0.005: 1;
(2) dissolving a silver source in water to obtain a silver source solution; in the silver source solution, the mass percentage concentration of a silver source is 9.6 wt%, the silver source is silver nitrate, and the weight ratio of the dispersing agent to the silver source is 0.2: 1, the weight ratio of the reducing agent to the silver source is 0.69: 1;
(3) dropwise adding the silver source solution into the reducing solution at 60 ℃ at the speed of 5mL/min to obtain silver powder slurry;
(4) adding the silver powder slurry into a solvent, centrifuging at 6000rpm for 10min, adding ethanol for cleaning, depositing silver powder, and drying to obtain nano silver powder; the solvent is dichloromethane.
The polyvinylpyrrolidone was purchased from PVPK25, new materials science and technology (shanghai) ltd.
The gum arabic is purchased from bioengineering ltd, hongtong, anhui.
The present example also provides a nano silver powder prepared according to the preparation method described above.
Evaluation of Performance
1. And (4) SEM test: the silver powder prepared according to the method provided in the examples was subjected to SEM test, and the size, distribution, and surface properties of the silver powder were observed and evaluated:
(1) the size of the silver powder is as follows: the average grain size of the silver powder is less than 60nm in grade 1, more than or equal to 60nm and less than 80nm in grade 2, more than or equal to 80nm and less than 100nm in grade 3, and more than or equal to 100nm in grade 4;
(2) size distribution of silver powder: the silver powder in grade 1 has uniform size distribution, the gaps among the particles are obvious, aggregation is slightly generated among the particles, the silver powder in grade 2 has larger size distribution difference, aggregation is generated among a small number of particles, the silver powder in grade 3 has increased size distribution difference, aggregation is generated among part of particles, the silver powder in grade 4 has obvious size distribution difference, and aggregation is generated among most of the particles.
(3) Surface roughness of silver powder: the level 1 is that the surface of the silver powder is smooth and flat, the level 2 is that the surface of the silver powder has a small amount of unevenness, the level 3 is that the surface of the silver powder is uneven and increased, and the level 4 is that the surface of the silver powder is uneven and obvious.
The results are shown in Table 1
Table 1 performance characterization test
| Examples | Size of | Size distribution | Surface roughness |
| 1 | Level 1 | Stage 2 | Stage 2 |
| 2 | Level 1 | Level 1 | Level 1 |
| 3 | Stage 2 | Level 1 | Stage 2 |
| 4 | Level 1 | Level 1 | Level 1 |
| 5 | Stage 2 | Grade 3 | Grade 3 |
| 6 | Grade 3 | Grade 3 | Stage 2 |
| 7 | 4 stage | 4 stage | 4 stage |
| 8 | 4 stage | 4 stage | Grade 3 |
| 9 | Grade 3 | Grade 3 | Grade 3 |
| 10 | Stage 2 | Grade 3 | Stage 2 |
Wherein, FIG. 1 and FIG. 2 are SEM images of the silver powder provided in example 4 under 10.0KV acceleration voltage, 8.1mm working distance, 100.0K magnification, 10.0KV acceleration voltage, 8.1mm working distance and 50.0K magnification, respectively, and it can be seen that the surface of the silver powder is smooth and flat, the size distribution is uniform, and the average size is about 50 nm.
The foregoing examples are merely illustrative and serve to explain some of the features of the method of the present invention. The appended claims are intended to claim as broad a scope as is contemplated, and the examples presented herein are merely illustrative of selected implementations in accordance with all possible combinations of examples. Accordingly, it is applicants' intention that the appended claims are not to be limited by the choice of examples illustrating features of the invention. Also, where numerical ranges are used in the claims, subranges therein are included, and variations in these ranges are also to be construed as possible being covered by the appended claims.
Claims (10)
1. The preparation method of the nano silver powder is characterized by comprising the following steps of:
(1) dissolving a dispersant in water at 50-65 ℃ to prepare a dispersant solution, adding a reducing agent, mixing, and adjusting the pH to 2.5-6 to obtain a reducing solution;
(2) dissolving a silver source in water to obtain a silver source solution;
(3) dropwise adding the silver source solution into the reducing solution at the speed of 3-6 mL/min to obtain silver powder slurry;
(4) and centrifuging, washing and drying the silver powder slurry to obtain the nano silver powder.
2. The method for preparing silver nanoparticles powder according to claim 1, wherein the dispersant is present in the dispersant solution in an amount of 1.5 to 3 wt%.
3. The method for preparing silver nanoparticles powder according to claim 1, wherein the silver source solution has a silver source concentration of 7 to 15 wt%.
4. The method for producing a silver nanoparticle powder according to claim 1, wherein the weight ratio of the dispersant to the silver source is (0.15 to 0.3): 1.
5. the method for producing a silver nanoparticle powder according to claim 1, wherein the weight ratio of the reducing agent to the silver source is (0.65 to 0.75): 1.
6. the method for preparing silver nanoparticles powder according to any one of claims 1 to 5, wherein in the step (1), a dispersant solution is prepared by dissolving a dispersant and an inorganic salt in water at 50 to 65 ℃, and a reducing agent is added to the dispersant solution, followed by mixing and adjusting the pH to 2.5 to 6 to obtain a reducing solution.
7. The method for preparing silver nanopowder according to claim 6 wherein the weight ratio of the dispersant to the inorganic salt is 1: (0.05-0.15).
8. The method for preparing silver nanopowder according to any one of claims 1 to 5, wherein the silver powder slurry is added to a solvent and centrifuged at 5000 to 7000rpm in the centrifugation.
9. The method for preparing silver nanopowder according to claim 8, wherein the solvent is selected from one of ethanol, hexane, acetone, dichloromethane.
10. The silver nanoparticles powder, characterized by being prepared by the method for preparing silver nanoparticles powder according to any one of claims 1 to 9.
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