High-concentration nano dispersion liquid and preparation method thereof

Abstract

The invention discloses a high-concentration nano dispersion liquid and a preparation method thereof, and belongs to the technical field of nano material preparation. In order to solve the technical problem of high-concentration uniform dispersion of nano metal particles in a water-based solvent, a chemical synthesis and physical crushing combined method is mainly adopted, dispersed powder is prepared through a supercritical drying technology, and then high-concentration dispersion liquid is prepared. According to the invention, the dispersion of noble metal particles with a concentration of more than 10000 ppm in an aqueous medium can be realized, the particle size is effectively controlled to be less than 50 nm, the stability of the dispersion liquid is improved through the surfactant, the adhesion among particles is reduced, and the long-term stability of the system is ensured.

Description

Technical Field

[0001] The invention relates to a high-concentration nanometer dispersion and a preparation method thereof, belonging to the technical field of nanometer material preparation. Background Art

[0002] Nanodispersion refers to a system formed by uniformly dispersing nanoscale particles in a liquid medium. Its unique physical and chemical form has made it widely used in many fields such as catalysis and optics.

[0003] For example, in the field of catalysis, nano-dispersions have become an important component of efficient catalysts due to their high specific surface area and surface activity. Nano-dispersions have shown excellent performance in low-temperature oxidation reactions, selective hydrogenation reactions, and fuel cells. In the field of infrared optics, nano-dispersions are one of the important synthetic raw materials for optical films. Nano-dispersions can be used to prepare films with high reflectivity / low emissivity in the band. They are an excellent infrared radiation control material and are widely used in aerospace, communications, electronics and other fields.

[0004] At present, it is difficult to prepare a stable dispersion system with a high concentration of nano-dispersion due to the high density of dispersed powder and strong surface polarity. The concentration of the prepared dispersion is usually only about 1000ppm, which leads to limited film-forming ability and catalytic effect. Therefore, the preparation of high-concentration nano-dispersion has become a key technology that needs to be solved urgently. Summary of the invention

[0005] The purpose of the present invention is to prepare a high-concentration nano-dispersion liquid, which is composed of nano-particles dispersed in an aqueous solvent with a concentration of more than 10000 ppm.

[0006] The present invention adopts the following technical solutions to achieve the above-mentioned purpose:

[0007] A method for preparing a high-concentration nano-metal dispersion comprises the following steps:

[0008] (1) Selecting a noble metal aqueous solution and adding PVP to prepare a mixed solution;

[0009] (2) Add NH3·H2O and NaCl to the mixed solution, heat and stir continuously;

[0010] (3) while the solution is still heated and stirred, a hydrazine hydrate solution is added dropwise thereto;

[0011] (4) continuing to heat the solution to which hydrazine hydrate has been added to react, while stirring continuously;

[0012] (5) centrifuging the obtained suspension with precipitate;

[0013] (6) Pour off the supernatant after centrifugation, add a solvent of equal mass to the supernatant, and stir until a relatively stable suspension is formed. Repeat step (5) several times to wash away the remaining Na + NH4 + and Cl - ions, and remove the precipitate;

[0014] (7) sand-grinding the precipitate to obtain a glue solution;

[0015] (8) subjecting the sand-milled glue solution to supercritical drying to obtain dispersed powder;

[0016] (9) According to the required concentration, H2O is added to the dispersed powder to obtain a high-concentration nanometal dispersion.

[0017] Furthermore, in step (1), the noble metal aqueous solution is an AgNO aqueous solution or a chloro complex solution of the noble metals Au, Pt, Nb, Ru, Rh or Pd, and the concentration of PVP is 0.5-2wt%.

[0018] Furthermore, in step (2), the amount of NH3·H2O and NaCl added is 1.5 to 2 times the amount of the precious metal ion, and the molar ratio of NH3·H2O to NaCl is 1:1; the heating temperature is 70 to 90°C.

[0019] Furthermore, in step (3), the concentration of the hydrazine hydrate solution is 40-60 wt%, and the amount of hydrazine hydrate added is more than 10% of the amount of the noble metal ion substance.

[0020] Furthermore, in step (4), the reaction is heated for 2 to 3 hours.

[0021] Furthermore, the centrifugal treatment in step (5) is carried out at a speed of 3000 to 5000 rpm for 3 to 5 minutes.

[0022] Furthermore, the solvent added in step (6) is deionized water, ethanol or acetone; and step (5) is repeated 3 to 4 times.

[0023] Furthermore, in step (7), the sanding particle size is selected to be 0.3 to 0.5 mm, the sanding material is selected to be zirconium oxide, the sanding medium is selected to be ethanol, and the sanding time is 10 to 15 hours.

[0024] Furthermore, in step (8), the drying medium for supercritical drying is CO2, and the drying pressure is 5 to 10 MPa.

[0025] A high-concentration nano-metal dispersion is prepared by the above preparation method.

[0026] The present invention has achieved the following beneficial effects:

[0027] 1. The preparation method of the present invention combines chemical synthesis with physical crushing methods and can achieve high-concentration dispersion of nanometal particles in an aqueous solvent by reduced pressure distillation. A dispersion of precious metals (such as Ag, Au, Pt, Nb, Ru, Rh, Pd, etc.) can be prepared. The dispersion medium is H2O, and the dispersion concentration is above 10000ppm.

[0028] 2. The preparation method of the present invention controls the chemical reaction time and physical crushing to make the metal particle size below 50nm, and achieves long-term stability of the dispersion by adding an appropriate amount of surfactant.

[0029] 3. The preparation method of the present invention adopts supercritical drying for drying, which reduces the adhesion between particles and improves the stability of the dispersion system. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The microscopic morphology of the dispersion particles prepared in Example 1;

[0031] Figure 2 The microscopic morphology of the dispersion particles prepared in Example 2;

[0032] Figure 3 This is the microscopic morphology of the dispersion particles prepared in Example 3. Specific implementation methods

[0034] In order to make the various technical features and advantages or technical effects in the above technical solutions of the present invention more obvious and easy to understand, they are described in detail below in conjunction with embodiments.

[0035] Example 1

[0036] A method for preparing a high-concentration nano-metal dispersion comprises the following steps:

[0037] (1) Select an AgNO3 aqueous solution and add 0.5 wt% PVP to prepare a mixed solution.

[0038] (2) Add 1.5 times the amount of noble metal ions of NH3·H2O and NaCl to the mixed solution in a molar ratio of 1:1, and heat to 80°C with continuous stirring.

[0039] (3) While the solution is still heated and stirred, a 50% by mass hydrazine hydrate solution is added dropwise thereto, and the amount of hydrazine hydrate added is ensured to be more than 10% of the amount of the noble metal ion substance.

[0040] (4) The solution to which hydrazine hydrate is added is heated and reacted for 2 h while being stirred continuously.

[0041] (5) The obtained suspension with precipitate was centrifuged at 3000 rpm for 3 min.

[0042] (6) Pour off the supernatant obtained after centrifugation, add an equal amount of deionized water, and stir until a relatively stable suspension is formed. Repeat step (5) 3 times to wash away the remaining Na + NH4 + and Cl - Plasma, remove the precipitate;

[0043] (7) sand grinding the precipitate after removal, with the sanding particle size selected as 0.3 mm, the sanding material selected as zirconium oxide, the grinding medium selected as ethanol, and the grinding time as 10 h, and further crushing and washing the obtained precipitate;

[0044] (8) The sand-milled glue solution is subjected to supercritical drying, CO2 is selected as the drying medium, and the drying pressure is 5 MPa to obtain dispersed powder.

[0045] (9) According to the required concentration, H2O is added to the dispersed powder to obtain a high-concentration nanometal dispersion. The morphology is shown in Figure 1 .

[0046] Example 2

[0047] A method for preparing a high-concentration nano-metal dispersion comprises the following steps:

[0048] (1) Select [Pt(NH3)4]Cl2 solution and add 2 wt% PVP to prepare a mixed solution.

[0049] (2) Add NH3·H2O and NaCl in a molar ratio of 1:1 to the mixed solution, which is twice the amount of the noble metal ion substance, and heat to 70°C with continuous stirring.

[0050] (3) While the solution is still heated and stirred, a 40% by mass hydrazine hydrate solution is added dropwise thereto, and the amount of hydrazine hydrate added is ensured to be more than 10% of the amount of the noble metal ion substance.

[0051] (4) The solution to which hydrazine hydrate is added is heated and reacted for 3 h while being stirred continuously.

[0052] (5) The obtained suspension with precipitate was centrifuged at 5000 rpm for 5 min.

[0053] (6) Pour off the supernatant obtained after centrifugation, add an equal amount of ethanol, and stir until a relatively stable suspension is formed. Repeat step (5) 4 times to wash away the remaining Na + NH4 + and Cl -Plasma, remove the precipitate;

[0054] (7) sand grinding the precipitate after removal, with the sand particle size of 0.5 mm, the sand material of zirconium oxide, the grinding medium of ethanol, and the grinding time of 15 h, and further crushing and washing the obtained precipitate;

[0055] (8) The sand-milled glue solution is subjected to supercritical drying, CO2 is selected as the drying medium, and the drying pressure is 10 MPa to obtain dispersed powder.

[0056] (9) According to the required concentration, H2O is added to the dispersed powder to obtain a high-concentration nanometal dispersion. The morphology is shown in Figure 2 .

[0057] Example 3

[0058] A method for preparing a high-concentration nano-metal dispersion comprises the following steps:

[0059] (1) Select an AgNO3 aqueous solution and add 1 wt% PVP to prepare a mixed solution.

[0060] (2) Add 1.8 times the amount of noble metal ions of NH3·H2O and NaCl to the mixed solution in a molar ratio of 1:1, and heat to 90°C with continuous stirring.

[0061] (3) While the solution is still heated and stirred, a 60% by mass hydrazine hydrate solution is added dropwise thereto, and the amount of hydrazine hydrate added is ensured to be more than 10% of the amount of the noble metal ion substance.

[0062] (4) The solution to which hydrazine hydrate is added is heated and reacted for 2.5 h with continuous stirring.

[0063] (5) The obtained suspension with precipitate was centrifuged at 4000 rpm for 4 min.

[0064] (6) Pour off the supernatant obtained after centrifugation, add an equal amount of acetone, and stir until a relatively stable suspension is formed. Repeat step (5) 4 times to wash away the remaining Na + NH4 + and Cl - Plasma, remove the precipitate;

[0065] (7) sand grinding the precipitate after removal, with the sand particle size of 0.4 mm, the sand material of zirconium oxide, the grinding medium of ethanol, and the grinding time of 12 h, and further crushing and washing the obtained precipitate;

[0066] (8) The sand-milled glue solution is subjected to supercritical drying, CO2 is selected as the drying medium, and the drying pressure is 8 MPa to obtain a dispersed powder.

[0067] (9) According to the required concentration, H2O is added to the dispersed powder to obtain a high-concentration nanometal dispersion. The morphology is shown in Figure 3 .

[0068] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. Appropriate modifications or equivalent substitutions of the technical solutions of the present invention made by ordinary technicians in the field should all be included in the protection scope of the present invention. The protection scope of the present invention shall be based on what is defined in the claims.

Claims

1. A method for preparing a high-concentration nano-metal dispersion, characterized in that: The following steps are involved: (1) Selecting a noble metal aqueous solution and adding PVP to prepare a mixed solution; (2) Add NH3·H2O and NaCl to the mixed solution, heat and stir continuously; (3) while the solution is still heated and stirred, a hydrazine hydrate solution is added dropwise thereto; (4) continuing to heat the solution to which hydrazine hydrate has been added to react, while stirring continuously; (5) centrifuging the obtained suspension with precipitate; (6) Pour off the supernatant after centrifugation, add a solvent of equal mass to the supernatant, and stir until a relatively stable suspension is formed. Repeat step (5) several times to wash away the remaining Na + NH4 + and Cl - ions, and remove the precipitate; (7) sand-grinding the precipitate to obtain a glue solution; (8) subjecting the sand-milled glue solution to supercritical drying to obtain dispersed powder; (9) According to the required concentration, H2O is added to the dispersed powder to obtain a high-concentration nanometal dispersion.

2. The preparation method according to claim 1, characterized in that In step (1), the noble metal aqueous solution is an AgNO aqueous solution or a chloro complex solution of the noble metals Au, Pt, Nb, Ru, Rh or Pd, and the concentration of PVP is 0.5-2wt%.

3. The preparation method according to claim 1, characterized in that: In step (2), the amount of NH3·H2O and NaCl added is 1.5 to 2 times the amount of the noble metal ion, and the molar ratio of NH3·H2O to NaCl is 1:1; the heating temperature is 70 to 90°C.

4. The preparation method according to claim 1, characterized in that: In step (3), the concentration of the hydrazine hydrate solution is 40-60wt%, and the amount of hydrazine hydrate added is more than 10% of the amount of the noble metal ion substance.

5. The preparation method according to claim 1, characterized in that: In step (4), the reaction is heated for 2 to 3 hours.

6. The preparation method according to claim 1, characterized in that: The centrifugal treatment conditions in step (5) are: centrifugation at a speed of 3000-5000 rpm for 3-5 min.

7. The preparation method according to claim 1, characterized in that: The solvent added in step (6) is deionized water, ethanol or acetone; and step (5) is repeated 3 to 4 times.

8. The preparation method according to claim 1, characterized in that: In step (7), the sanding particle size is selected to be 0.3-0.5 mm, the sanding material is selected to be zirconium oxide, the sanding medium is selected to be ethanol, and the sanding time is 10-15 hours.

9. The preparation method according to claim 1, characterized in that: In step (8), the drying medium for supercritical drying is CO2, and the drying pressure is 5 to 10 MPa.

10. A high concentration nano metal dispersion, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 9.

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