METHOD FOR PREPARING HOLLOW SILVER PARTICLES AND CORE-SHELL SILVER PARTICLES
A method for preparing core-shell and hollow silver particles is provided. In the method silver salts and glycine nitrate or starch are mixed with solvent to form precursor solution. The mole percentage of the silver salts over the silver salts plus glycine nitrate or starch is 5 to 50 mol %. The precursor solution is then atomized to form precursor droplets. The precursor droplets are heated by pyrolysis to form silver particles. The composition of the precursor solution can be adjusted to finely manipulate the structure of the silver particles.
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This application claims priority to Taiwan Application Serial Number 102123840, filed Jul. 3, 2013, which is herein incorporated by reference.
BACKGROUND1. Field of Invention
The present invention relates to a method of preparing silver particles. More particularly, the present invention relates to a method of preparing silver particles and core-shell silver particles, and the formed core-shell silver particles.
2. Description of Related Art
In the recent years, the core-shell and hollow silver particles have received much attention for their excellent natures and wide applicability such as conductors, electrical contacts and wound dressing. For example, the wound dressing of antibiosis and silver conductive adhesive are the major commercialized applications of the silver particles. However, the major processes of making silver particle, like reduction process and sol-gel process, are both conducted in batch and thus have less potential for mass production in view of business.
At present, most of the applications use solid silver particle, which has some issues for further improvement. For example, the solid silver particle most likely is not totally consumed after the wound dressing of antibiosis expires, which is not economic and wasting. On the other hand, the solid silver particles may sediment after a period of time of idle due to large difference of evident density between the solid silver particles and the gel solution, which makes uneven distribution of the particles in gel solution and deteriorates the properties of the product.
Concerning the silver particles with hollow structure, the major measures of preparing the hollow structure includes soft template, hard template, and Kirkendall effect. The soft template needs additional heating process step to remove polymer template and may involve carbon contamination problem. The hard template needs to use acid/base to remove the template, causing environmental pollution and need to deal with the post-treatment of acid/base. Kirkendall effect also has defects due to its complex procedures and high instrument cost.
SUMMARYTherefore, the present disclosure provides a method of preparing hollow and core-shell silver particle in a continuous process, which can provide silver particles in a mass production way for the industry and choose using glycine nitrate method as the hollow formation mechanism for the silver particles. The glycine nitrate can be removed easily during the heating process due to its low molecular weight, so as to improve the defects in prior art. The prepared core-shell and hollow silver particles can replace the solid silver particles using on the market now to improve the efficiency of silver particle.
One aspect of the present disclosure is a method for preparing core-shell and hollow silver particles includes mixing a silver salt with a glycine nitrate or starch as a solute in a polar solvent to form a precursor solution, in which the mole percentage of the silver salt over the silver salts plus glycine nitrate or starch is 5-50 mol % and the silver salt plus glycine nitrate or starch are 0.01-10 wt % to the precursor solution, atomizing the precursor solution to form a plurality of precursor droplets, and heating the precursor droplets to pyrolyze the precursor droplets and to form core-shell silver particles and hollow silver particles.
In various embodiments of the present disclosure, the silver salt is silver nitrate or silver acetate.
In various embodiments of the present disclosure, the polar solvent is water.
In various embodiments of the present disclosure, the solute weight percentage concentration of the precursor solution is 1 wt %.
In various embodiments of the present disclosure, the mole percentage of the silver salts over the silver salts plus glycine nitrate or starch of the precursor solution is between 12.5-50 mol %, the formed silver particles are the core-shell silver particles.
In various embodiments of the present disclosure, the mole percentage of the silver salts over the silver salts plus glycine nitrate or starch of the precursor solution is less than 12.5 mol %, the formed silver particles are the hollow silver particles.
In various embodiments of the present disclosure, the step of heating the precursor droplets to pyrolyze the precursor further includes evaporating the polar solvent of the precursor droplets, precipitating the solute of the precursor droplets, and pyrolyzing the solute.
Another aspect of the present disclosure provides a core-shell silver particle includes a silver core, a silver shell, encapsulating the silver core, and a hollow structure, between the silver core and the silver shell.
In various embodiments of the present disclosure, the diameter of the core-shell silver particle is about 100-1,000 nanometers.
It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed.
The invention can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows:
Reference will now be made in detail to the present embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
One aspect of the present disclosure is a method for preparing core-shell and hollow silver particles includes the following steps. Referring to
Step 110 is atomizing the precursor solution to form a plurality of precursor droplets. In various embodiments of the present disclosure, using an ultrasonic humidifier to atomize the precursor solution, where the ultrasonic frequency is 1.65 MHz when the polar solvent is water. In various embodiments of the present disclosure, the diameter of the precursor droplets is about 3-20 μm, the diameter of the precursor droplets has positive correlation with the precursor concentration. The preferable concentration range for atomizing the solution is the silver salt plus glycine nitrate or starch is 0.01-10 wt % to the precursor solution.
Step 120 is heating the precursor droplets to pyrolyze the precursor droplets to form the core-shell silver particles and the hollow silver particles. Other parts of the precursor droplets are pyrolyzed to gas. In various embodiments of the present disclosure, the heating apparatus is a temperature controllable tube furnace, which can control the temperature in the tube to three sections: preheating section (200-400° C.), calcining section (500-800° C.), and cooling section (300-500° C.). In various embodiments of the present disclosure, the heating step includes evaporating the polar solvent of the precursor droplets, precipitating the solute of the precursor droplets, and pyrolyzing the solute.
Following are some embodiments to further elaborate the method of the present disclosure, but only for explanation, should not be limited to the description of the embodiments contained herein. The scope of protection for present disclosure depends on the following claims.
EmbodimentsA. Preparing the silver particles with the precursor solution prepared from different ratio of silver nitrate and glycine nitrate.
Comparison 1: No Glycine Nitrate in the Precursor Solution
Preparing 1 wt % silver nitrate in water as the precursor solution, the experiment apparatus is as illustrated in
Referring to
Experiment 1: the mole percentage of the silver nitrate over the silver nitrate plus glycine nitrate is 25 mol % in the precursor solution
Preparing 1 wt % precursor solution, in which the mole percentage of the silver nitrate over the silver nitrate plus glycine nitrate is 25 mol %. The experiment process is the same as comparison 1.
Referring to
Experiment 2: the mole percentage of the silver nitrate over the silver nitrate plus glycine nitrate is 14.2 mol % in the precursor solution
Preparing 1 wt % precursor solution, in which the mole percentage of the silver nitrate over the silver nitrate plus glycine nitrate is 14.2 mol %. The experiment process is the same as comparison 1.
Referring to
Experiment 3: the mole percentage of the silver nitrate over the silver nitrate plus glycine nitrate is 12.5 mol % in the precursor solution
Preparing 1 wt % of precursor solution, in which the mole percentage of the silver nitrate over the silver nitrate plus glycine nitrate is 12.5 mol %. The experiment process is the same as comparison 1.
Referring to
B. Preparing the silver particles with the precursor solution prepared from different ratio of silver acetate and glycine nitrate.
Comparison 2: No Glycine Nitrate in the Precursor Solution
The experiment process is the same as comparison 1, but to change the precursor solution including 1 wt % silver nitrate to 1 wt % silver acetate.
Referring to
Experiment 4: the mole percentage of the silver acetate over the silver acetate plus glycine nitrate is 25 mol % in the precursor solution
The experiment process is the same as comparison 1, but to change the precursor solution to 1 wt % silver acetate and glycine nitrate mixture solution, in which the mole percentage of the silver acetate over the silver acetate plus glycine nitrate is 25 mol %.
Referring to
Experiment 5: the mole percentage of the silver acetate over the silver acetate plus glycine nitrate is 16.7 mol % in the precursor solution
The experiment process is the same as comparison 1, but to change the precursor solution to 1 wt % silver acetate and glycine nitrate mixture solution, in which the mole percentage of the silver acetate over the silver acetate plus glycine nitrate is 16.7 mol %.
Referring to
C. Preparing the silver particles with the precursor solution prepared from silver nitrate and starch.
Experiment 6: the mole percentage of the silver nitrate over the silver nitrate plus starch is 50 mol % in the solution
The experiment process is the same as comparison 1, but to change the precursor solution to 1 wt % silver nitrate and starch mixture solution, in which the mole percentage of the silver nitrate over the sliver nitrate plus starch is 50 mol %.
Referring to
Referring to
The present disclosure provides the method of continuously preparing the core-shell and hollow silver particles. The method not only is a continuous process that can apply in industry mass production, but also can control porosity of silver particles that can apply in the commercialized silver particle products to save the amount of silver using and the cost. Also the porosity of the silver particles can be controlled depend on the using time of the products to maximize the utility.
For example, the wound dressing of antibiosis sometimes needs to be thrown away due to reach their expiration date, but there may still have some non-reacted silver inside the silver particles. So the porosity controllable silver particle provided in the present disclosure can adjust the silver amount in the silver particle base on the expiration date to minimize the silver waste.
In silver conductive adhesive, the solid silver particles may sediment after a period of time of idle due to large difference of evident density between the solid silver particles and the gel solution, which makes uneven distribution of the particles in gel solution and deteriorates the properties of the product. Hollow silver particles, because of having air inside the particles, can evidently decrease the density of the silver particles to minimize the density difference between the solid silver particles and the gel solution to decrease the sedimentation.
Although the present invention has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims.
Claims
1. A method for manufacturing core-shell and hollow silver particles, comprising:
- mixing a silver salt with a glycine nitrate or starch as a solute in a polar solvent to form a precursor solution, wherein the mole percentage of the silver salt over the silver salts plus glycine nitrate or starch is 5 to 50 mol %;
- atomizing the precursor solution to form a plurality of precursor droplets; and
- heating the precursor droplets to pyrolyze the precursor droplets to form the core-shell silver particles and the hollow silver particles.
2. The method of claim 1, wherein, in mixing the silver salt with the glycine nitrate or the starch as the solute in the polar solvent to form the precursor solution, the silver salt plus glycine nitrate or starch are 0.01-10 wt % to the precursor solution.
3. The method of claim 1, wherein, in mixing the silver salt with the glycine nitrate or the starch as the solute in the polar solvent to form a precursor solution, the silver salt is silver nitrate or silver acetate.
4. The method of claim 1, wherein, in mixing the silver salt with the glycine nitrate or the starch as the solute in the polar solvent to form a precursor solution, the polar solvent is water.
5. The method of claim 1, wherein, in mixing the silver salt with the glycine nitrate or the starch as the solute in the polar solvent to form a precursor solution, the solute weight percentage concentration of the precursor solution is 1 wt %.
6. The method of claim 1, wherein the mole percentage of the silver salt over the silver salts plus the glycine nitrate or the starch of the precursor solution is between 12.5-50 mol %, and the formed silver particles are the core-shell silver particles.
7. The method of claim 1, wherein the mole percentage of the silver salt over the silver salts plus the glycine nitrate or the starch of the precursor solution is less than 12.5 mol %, and the formed silver particles are the hollow silver particles.
8. The method of claim 1, wherein heating the precursor droplets to pyrolyze the precursor droplets further comprising:
- evaporating the polar solvent of the precursor droplets;
- precipitating the solute of the precursor droplets; and
- pyrolyzing the solute.
9. A core-shell or hollow silver particle manufactured by the method of claim 1.
10. The silver particle of claim 9, wherein the core-shell silver particle comprising:
- a silver core;
- a silver shell encapsulating the silver core; and
- a hollow structure between the silver core and the silver shell.
Type: Application
Filed: Nov 22, 2013
Publication Date: Jan 8, 2015
Applicant: National Taiwan University of Science and Technology (TAIPEI CITY)
Inventors: Shao-Ju Shih (Taipei City), I-Chen Chien (Taipei City), Yu-Hsuan Wu (Taipei City)
Application Number: 14/086,991
International Classification: B22F 9/30 (20060101); B22F 9/06 (20060101); C22C 5/06 (20060101);