Disclosure of Invention
Aiming at the problems that the existing metal paste can not meet the high-precision direct-writing 3D printing process with the thickness of below 10 mu m, and the nanometer metal paste is easy to agglomerate and difficult to disperse, has poor repeatability of the manufacturing process, can not realize commercialization and the like, the invention develops a novel nanometer metal 3D printing ink and provides a preparation method and application thereof.
The invention has the following conception: the invention realizes the synthesis of the monodisperse metal nanoparticles by the synergistic action of the double reducing agents and by controlling the dosage of the reducing agents, the polymer and the reaction temperature. Wherein, a strong reducing agent such as hydrazine hydrate is used for the metal nanoparticles to quickly form crystal nuclei, and the metal nanoparticles with the particle size of 1-10 nanometers can be obtained by controlling the using amount of the strong reducing agent, and in the process, the weak reducing agent generally does not participate in the reaction due to the lower reaction temperature and only plays a role in stabilizing the metal nanoparticles with the particle size of 1-10 nanometers; then, with the rise of the reaction temperature, the activity of the weak reducing agent is obviously enhanced, so that the metal salt in the reaction system can be further reduced, and the metal particles subsequently reduced can uniformly grow on the surface of the crystal nucleus; in addition, the agglomeration rate of the metal nanoparticles can be slowed down during the reaction. In the reaction process, the polymer can also inhibit the further enlargement of the size of the large-size metal nanoparticles by coating the large-size metal nanoparticles, and can effectively inhibit the appearance of large-particle metal nanoparticles with the particle size of more than 1 mu m under the synergistic action of a weak reducing agent and a high-molecular polymer, so that the controllable synthesis of the metal nanoparticles is finally realized, and the effects of controllable size and monodispersity are achieved.
In order to achieve the object of the present invention, in a first aspect, the present invention provides a metal nanomaterial for nanometal 3D printing, the metal nanomaterial consisting of metal nanoparticles and ligands on the surface thereof; the distribution range of the particle size of the metal nano-particles is X +/-Y, wherein X is 50-500nm, and Y is less than or equal to 20 percent of X.
The ligand may be selected from at least one of polyacrylic acid (PAA), polyvinylpyrrolidone (PVP), triton, polyethylene glycol (PEG), and the like.
The metal nano material can be nano silver, nano copper, nano gold and the like.
In a second aspect, the present invention provides a method for preparing the metal nanomaterial, comprising the steps of:
A. dissolving metal salt in deionized water, adding a reducing agent I and a high molecular polymer, and uniformly mixing;
B. b, dropwise adding a reducing agent II solution into the reaction system obtained in the step A, and after dropwise adding is finished, heating to a specific temperature for reaction;
C. after the reaction is finished, cooling to room temperature, adding a poor solvent into the system to separate out a product, drying the product, redissolving the product in deionized water, and filtering the product for 1-5 times by using a filter screen with a proper pore diameter;
D. and drying the product to obtain the product.
The poor solvent may be an alcohol or a ketone having 1 to 6 carbon atoms.
Further, a step of adjusting the pH of the reaction system to 9-10 by using alkali liquor is also included between the step A and the step B.
Preferably, the alkali liquor is ammonia water, and other alkaline substances can also be used.
In the method, the specific temperature in the step B is 50-90 ℃, and the reaction time is 0.5-5 hours.
In the method, a filter screen with the aperture of 1-5 mu m is used in the step C. It should be noted that, for nanoparticle slurries of different sizes, filters of different pore sizes may be selected for filtration, wherein the pore size for filtration is generally 10 times or more the corresponding nanoparticle, for example, 100nm size particles, 1 μm pore size filter, 500nm size particles, or 5 μm pore size filter may be selected.
The metal salt can be a silver salt, a copper salt or a gold salt;
the reducing agent I can be at least one selected from hydramine with the carbon atom number less than 10, dihydrogen hypophosphite, glucose, ascorbic acid and the like; preferably at least one of diethanolamine, sodium dihydrogen hypophosphite and butanol amine.
The high molecular polymer (ligand) can be selected from at least one of polyacrylic acid, polyvinylpyrrolidone, triton, polyethylene glycol and the like, and the molecular weight of the high molecular polymer is more than or equal to 5000 Da. The main function of the method is to control the size of the metal nanoparticles.
The reducing agent II can be at least one selected from hydrazine hydrate, sodium borohydride, potassium borohydride, formaldehyde, formic acid, oxalic acid, citric acid and the like. The reducing agent II solution can be an aqueous or alcoholic solution of reducing agent II.
The ratio of the amounts of the metal salt, the reducing agent I and the reducing agent II is 1 (0.2-1) to 0.5-5.
The mass ratio of the metal salt to the high molecular polymer is (2-10): 1.
In a third aspect, the invention provides nano metal 3D printing ink which is formed by mixing 50-90% of metal nano material and 10-50% of dispersing solvent, wherein the sum of the mass percentages of the metal nano material and the dispersing solvent is 100%.
The metal nano material is the metal nano material for nano metal 3D printing or the metal nano material prepared by the method.
The dispersion solvent may be a mixture of water and an alcohol having 4 carbon atoms, and the volume ratio of water to alcohol is 1:10 to 10: 1.
Preferably, the alcohol is ethylene glycol or glycerol.
The printing ink can be used for processing metal wires with the diameter of more than or equal to 1 mu m, and the resistivity of the wires is less than 100 mu omega cm after the wires are sintered at the temperature of more than or equal to 150 ℃.
In a fourth aspect, the invention provides an application of the nano metal 3D printing ink in the field of conductive materials (printed electronic materials).
In one embodiment of the invention, the preparation method of the nano-silver 3D printing ink with the particle size of 80-120nm comprises the following steps:
(1) taking 17g of silver nitrate, dissolving the silver nitrate in 50g of deionized water, sequentially adding 40g of diethanolamine and 2.5g of polyacrylic acid, and fully and uniformly stirring; the molecular weight of the polyacrylic acid is 50000 Da;
(2) dropwise adding 6mL of 80% hydrazine hydrate solution at the rate of 10mL/h, heating to 50 ℃ after dropwise adding, and reacting for 1 h;
(3) after the reaction is finished, cooling to room temperature, adding about 300mL of ethanol, and separating out a product in a flocculent precipitate;
(4) discarding the supernatant, air-drying the precipitate, redissolving the precipitate in 15mL of deionized water, filtering the precipitate for 2 times by using a 1-micron filter screen, adding 40mL of ethanol, and separating out a product in the form of flocculent precipitate;
(5) removing supernatant, vacuumizing and drying the precipitate, and then adding a solvent mixed by water and glycol according to the volume ratio of 1:1 to obtain the nano-silver 3D printing ink with the particle size of 80-120 nm.
In another embodiment of the invention, the preparation method of the nano-silver 3D printing ink with the particle size of 450-550nm comprises the following steps:
(1) taking 17g of silver nitrate, dissolving the silver nitrate in 50g of deionized water, sequentially adding 40g of diethanolamine and 5g of polyacrylic acid, and fully and uniformly stirring; the molecular weight of the polyacrylic acid is 5000 Da;
(2) dropwise adding 10mL of 5M sodium borohydride methanol solution at the rate of 10mL/h, heating to 80 ℃ after dropwise adding, and reacting for 30 min;
(3) after the reaction is finished, cooling to room temperature, adding about 300mL of ethanol, and separating out a product in a flocculent precipitate;
(4) discarding the supernatant, air-drying the precipitate, redissolving the precipitate in 15mL of deionized water, filtering the precipitate for 2 times by using a 5-micron filter screen, adding 40mL of ethanol, and separating out a product in the form of flocculent precipitate;
(5) removing supernatant, vacuumizing and drying the precipitate, and then adding a solvent mixed by water and ethylene glycol according to the volume ratio of 1:1 to obtain the nano-silver 3D printing ink with the particle size of 450-550 nm.
In another embodiment of the present invention, a method for preparing nano-copper 3D printing ink having a particle size of 45 to 55nm includes the steps of:
(1) dissolving 25g of blue vitriol in 50g of deionized water, sequentially adding 20g of sodium dihydrogen hypophosphite and 4g of polyvinylpyrrolidone, adjusting the pH value to 9-10 by using ammonia water, and fully stirring and uniformly mixing; the molecular weight of the polyvinylpyrrolidone is 40000 Da;
(2) dropwise adding 10mL of 5M sodium borohydride methanol solution at the rate of 10mL/h, heating to 60 ℃ after dropwise adding, and reacting for 30 min;
(3) after the reaction is finished, cooling to room temperature, adding about 300ml of acetone, and separating out a product in a flocculent precipitate;
(4) discarding the supernatant, air-drying the precipitate, redissolving the precipitate in 15mL of deionized water, filtering the precipitate for 2 times by using a 1-micron filter screen, adding 40mL of acetone, and separating out a product by using flocculent precipitate;
(5) and removing supernatant, vacuumizing and drying the precipitate, and then adding a solvent mixed by water and glycol according to the volume ratio of 1:1 to obtain the nano-copper 3D printing ink with the particle size of 45-55 nm.
In another embodiment of the invention, the preparation method of the nano-copper 3D printing ink with the particle size of 180-220nm comprises the following steps:
(1) dissolving 25g of blue vitriol in 50g of deionized water, sequentially adding 10g of butanol amine and 4g of polyvinylpyrrolidone, adjusting the pH to 9-10 with ammonia water, and fully stirring and uniformly mixing; the molecular weight of the polyvinylpyrrolidone is 20000 Da;
(2) dropwise adding 10mL of 5M citric acid solution at the rate of 10mL/h, heating to 90 ℃ after dropwise adding, and reacting for 30 min;
(3) after the reaction is finished, cooling to room temperature, adding about 300ml of acetone, and separating out a product in a flocculent precipitate;
(4) discarding the supernatant, drying the precipitate, redissolving the precipitate in 15mL of deionized water, filtering the precipitate for 2 times by using a 2-micron filter screen, adding 40mL of acetone, and separating out a product by using a flocculent precipitate;
(5) and removing the supernatant, vacuumizing and drying the precipitate, and then adding a solvent mixed by water and ethylene glycol according to the volume ratio of 1:1 to obtain the nano-copper 3D printing ink with the particle size of 180-220 nm.
By the technical scheme, the invention at least has the following advantages and beneficial effects:
firstly, the nano metal particles prepared by the method can be uniformly dispersed in the solution, and the slurry can be used for a high-precision direct-writing 3D printing process with the particle size of less than 10 mu m.
The invention successfully solves a series of technical problems of particle agglomeration, difficult dispersion, uncontrollable metal nanoparticle particle size, poor process repeatability and the like which are often generated in the preparation process of the nano conductive ink.
And thirdly, the nano metal 3D printing ink provided by the invention has the advantages that the average particle size of metal nanoparticles is between 50nm and 500nm, and the single control is realized. The particle size distribution interval is X +/-Y, wherein X is 50-500nm, and Y is less than or equal to 20 percent of X.
Detailed Description
The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art, and the raw materials used are commercially available products.
The percent in the present invention means mass percent unless otherwise specified; but the percent of the solution, unless otherwise specified, refers to the grams of solute contained in 100mL of the solution.
EXAMPLE 1100 nm preparation of Ag pastes
(1) Taking 17g of AgNO3(100mmol) is dissolved in 50g of deionized water, 40g of diethanolamine and 2.5g of PAA (MW 50,000) are added in sequence, and the mixture is fully stirred and mixed evenly;
(2) dropwise adding 6ml (50mmol) of hydrazine hydrate with the content of 80% at the speed of 10ml/h, heating to 50 ℃ after dropwise adding, and reacting for 1 h;
(3) cooling to room temperature, adding about 300ml ethanol, and separating out a product in a flocculent precipitate;
(4) discarding supernatant, air drying, redissolving in 15ml deionized water, filtering twice with 1 μm filter screen, adding 40ml ethanol, and separating out product as flocculent precipitate;
(5) vacuumizing and drying, and adding mixed solvents of water and ethylene glycol in different proportions (volume ratio) of 1:1 according to requirements to prepare 100nm Ag slurries with different solid contents.
The particle size distribution is 80-120nm and no other particles exist, which is characterized by DLS (dynamic light scattering system, Nanotrac NPA 252, Microtrac, USA). The results are shown in FIG. 1.
The specific determination method is as follows: preparing a sample into a 10mg/mL solution by using deionized water, collecting data by using a Nanotrac NPA 252 device, and processing the data according to the particle distribution proportion of different size intervals after the test is finished.
EXAMPLE 2500 nm Ag paste preparation
(1) Taking 17g of AgNO3(100mmol) is dissolved in 50g of deionized water, 40g of diethanolamine and 5g of PAA (MW 5,000) are added in sequence, and the mixture is fully stirred and mixed;
(2) dropwise adding 10ml (20mmol) of 5M sodium borohydride methanol solution at the speed of 10ml/h, and after dropwise adding, heating to 80 ℃ for reaction for 30 min;
(3) cooling to room temperature, adding about 300ml ethanol, and separating out a product in a flocculent precipitate;
(4) discarding supernatant, air drying, redissolving in 15ml deionized water, filtering twice with 5 μm filter screen, adding 40ml ethanol, and separating out product as flocculent precipitate;
(5) vacuumizing and drying, adding water and glycol mixed solvent in different proportion to 1:1 (volume ratio) according to requirements, and preparing into 500nm Ag slurry with different solid contents
The particle size distribution is 450-550nm and no other particles exist by DLS characterization. The results are shown in FIG. 2.
EXAMPLE 350 nm Cu paste preparation
(1) 25g of CuSO was taken4·5H2Dissolving O (100mmol) in 50g of deionized water, sequentially adding 20g of sodium dihydrogen hypophosphite and 4g of PVP (MW 40,000), adjusting the pH value to 9-10 by using ammonia water, and fully stirring and uniformly mixing;
(2) dropwise adding 10ml (80mmol) of 5M sodium borohydride methanol solution at the speed of 10ml/h, and after dropwise adding, heating to 60 ℃ for reaction for 30 min;
(3) cooling to room temperature, adding about 300ml acetone, and precipitating the product as flocculent precipitate
(4) Discarding supernatant, air drying, redissolving in 15ml deionized water, filtering twice with 1 μm filter screen, adding 40ml acetone, and separating out product as flocculent precipitate;
(5) and (3) vacuumizing and drying, and adding mixed solvents of water and ethylene glycol in different proportions (volume ratio) 1:1 according to requirements to prepare 50nm Cu slurry with different solid contents.
The particle size distribution is 45-55nm and no other particles exist by DLS characterization. The results are shown in FIG. 3.
Example 4200 nm Cu paste preparation
(1) 25g of CuSO was taken4·5H2Dissolving O (100mmol) in 50g of deionized water, sequentially adding 10g of butanol amine and 4g of PVP (MW 20,000), adjusting the pH value to 9-10 by using ammonia water, and fully stirring and uniformly mixing;
(2) dropwise adding 10ml (100mmol) of 5M citric acid solution at the rate of 10ml/h, heating to 90 ℃ after dropwise adding, and reacting for 30 min;
(3) cooling to room temperature, adding about 300ml of acetone, and separating out a product in a flocculent precipitate;
(4) discarding supernatant, air drying, redissolving in 15ml deionized water, filtering twice with 2 μm filter screen, adding 40ml acetone, and separating out product as flocculent precipitate;
(5) vacuumizing and drying, and adding mixed solvents of water and ethylene glycol in different proportions (volume ratio) 1:1 according to requirements to prepare 200nm Cu slurry with different solid contents.
The particle size distribution is 180-220nm and no other particles exist by DLS characterization. The results are shown in FIG. 4.
Comparative example 1:
400nm Ag pastes were synthesized according to the literature Russo, A.etc., Pen-on-Paper Flexible Electronics, adv.Mater.2011,23, 3426-.
The particle size distribution of the Ag paste is shown in fig. 5 by DLS characterization.
Comparative example 2:
according to the document Lee, Y.etc., Large-scale synthesis of copper nanoparticles by chemical controlled reduction for applications of inkjet-printed electronics, Nanotechnology,2008,19,415604(DOI:10.1088/0957-4484/19/41/415604), 50nm Cu slurries were synthesized, with the specific synthetic procedure being described in the "Materials and synthesis" paragraph of their Experimental details.
The particle size distribution of the Cu slurry is shown in fig. 6 by DLS characterization.
Although the invention has been described in detail hereinabove with respect to a general description and specific embodiments thereof, it will be apparent to those skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.