Heterogeneous precipitation preparation process of modified tin oxide powder doped with medium-low melting point oxide

Abstract

The invention discloses a heterogeneous precipitation preparation process of modified tin oxide powder doped with middle-low-melting-point oxides, and relates to the field of powder metallurgy. The preparation method comprises the following steps: coating bismuth oxide on the surface of tin oxide slurry which is prepared by a traditional acidification method and has the D50 particle size of 0.5-3 microns by utilizing a heterogeneous precipitation method, then calcining at 900-1200 DEG C, carrying out liquid-phase sintering on the tin oxide by utilizing the state of a bismuth oxide liquid phase at the temperature, and then cooling, thereby obtaining the bismuth oxide-tin oxide composite material with the D50 particle size of 0.5-3 microns. The modified tin oxide powder doped with the medium-low-melting-point oxides is spheroidic in morphology and concentrated and uniform in particle size distribution. Compared with tin oxide powder prepared through a traditional acidification tin oxide preparation process, the low-medium-melting-point oxide modified tin oxide powder prepared through the process has the advantages of being more concentrated in particle size distribution, better in particle size uniformity and easier to disperse evenly, and a silver tin oxide material good in uniformity and stable in quality can be prepared easily.

Description

Technical Field

[0001] This application relates to the technical field of powder metallurgy, and particularly to a heterogeneous precipitation preparation process for modified tin oxide powder doped with medium and low melting point oxides. Background Art

[0002] Silver tin oxide material is one of the main materials for silver-based electrical contact materials used in the low-voltage electrical appliance industry. The quality of this material mainly depends on the selection of oxides and their production and processing technology, and the morphology and particle size of tin oxide are the main factors affecting the performance of silver tin oxide.

[0003] Currently, the main processes for producing tin oxide include vaporization method, acidification method, high-energy mechanical ball milling method, etc. Since special equipment is required for producing tin oxide by vaporization method and high-energy mechanical ball milling method, and the energy consumption is relatively high, the acidification method for preparing tin oxide is the mainstream process for many enterprises at present.

[0004] The process of preparing tin oxide by acidification method is to melt metallic tin, then introduce it into water to form tin flowers, and then react with nitric acid to generate metastannic acid. Then, through washing, drying, calcination, and ball milling and pulverization, tin oxide is obtained. However, when preparing tin oxide by acidification method, due to the high temperature in the calcination stage, the formed tin oxide crystals are large-sized polyhedral crystals in morphology, and the particle size distribution is in the range of 10μm - 20μm. Even if different size requirements are achieved through subsequent adjustment and control of the ball milling process, since the polyhedral crystals are broken into small polyhedral particles with a particle size distribution of 0.1μm - 7μm after ball milling, the particle size distribution has a large span and the particles have many sharp angles, which is still not conducive to improving the processing performance of tin oxide materials. Summary of the Invention

[0005] In order to improve the problem that the existing tin oxide material has a large particle size distribution span and a polyhedral structure, which is not conducive to processing, this application provides a heterogeneous precipitation preparation process for modified tin oxide powder doped with medium and low melting point oxides.

[0006] In the first aspect, a heterogeneous precipitation preparation process for modified tin oxide powder doped with medium and low melting point oxides provided by this application adopts the following technical scheme: A heterogeneous precipitation preparation process for modified tin oxide powder doped with medium and low melting point oxides includes the following steps: S1. Dissolution: Add medium and low melting point oxides or their corresponding salts to an acid for dissolution to obtain a salt solution; S2. Mixing: Grind the tin oxide obtained by the traditional acidification process with water into a tin oxide slurry with a D50 particle size of 0.5μm - 3μm; add the salt solution to the tin oxide slurry and stir evenly to obtain a premixed slurry; S3. Precipitation: Add an alkali to the above-mentioned premixed slurry to adjust the pH to generate a tin oxide slurry doped with a precursor. S4. Drying: Wash and dry the tin oxide slurry doped with a precursor to obtain tin oxide powder doped with a precursor. S5. Calcination: Calcinate the tin oxide powder doped with a precursor at 900 °C to 1200 °C for 10 - 15 h to obtain a modified tin oxide powder doped with medium and low melting point oxides.

[0007] In this application, the heterogeneous precipitation method is used to coat medium and low melting point oxides on the surface of tin oxide with a D50 particle size of 0.5 μm to 3 μm prepared by the traditional acidification method, and then calcine at 900 °C to 1200 °C. Utilize the liquid state of medium and low melting point oxides at this temperature to perform liquid-phase sintering on tin oxide, and then cool to obtain a modified tin oxide powder doped with medium and low melting point oxides. Since the spherical liquid droplets formed by medium and low melting point oxides in the liquid state can wrap on the surface of fine tin oxide particles, it is beneficial to the growth of tin oxide particle grains and can control the morphology of tin oxide particles to be spherical-like during the growth process, thereby achieving the purpose of controlling the morphology and size of the modified tin oxide powder doped with medium and low melting point oxides. Among them, taking the modification of tin oxide powder with bismuth oxide as an example, the involved chemical reaction equation is as follows: 。

[0008] In addition, one of the key points for this application to obtain a modified tin oxide powder doped with medium and low melting point oxides with a spherical-like morphology and a concentrated and uniform particle size distribution is: in step S2, control the D50 particle size of the tin oxide slurry to be 0.5 μm to 3 μm, which is beneficial for medium and low melting point oxides to wrap tin oxide particles and improve the wrapping uniformity. Another key point for this application to obtain a modified tin oxide powder doped with medium and low melting point oxides with a spherical-like morphology and a concentrated and uniform particle size distribution is: the control of the calcination temperature in step S5. If the calcination temperature is too high, agglomeration is likely to occur; if the calcination temperature is too low, it is not conducive to the uniform coating of medium and low melting point oxides on tin oxide.

[0009] In some specific embodiments, the medium and low melting point oxides or their corresponding salts include but are not limited to bismuth oxide, antimony oxide, and sodium antimonate.

[0010] In some specific embodiments, the acid in S1 is concentrated nitric acid.

[0011] In some specific embodiments, the D50 particle size of the tin oxide slurry includes but is not limited to 0.5 μm, 0.75 μm, 1 μm, 1.25 μm, 1.5 μm, 2 μm, 2.5 μm, and 3 μm.

[0012] In some specific embodiments, the weight ratio of the medium and low melting point oxide or its corresponding salt in S1 to the tin oxide prepared by the traditional acidification method in S2 is (0.2 - 0.5):(9.5 - 9.8).

[0013] For example, the weight ratio of the medium and low melting point oxide or its corresponding salt to the tin oxide prepared by the traditional acidification method in S2 is 0.2:9.8 or 0.3:9.7 or 0.4:9.6 or 0.5:9.5.

[0014] In this application, the medium and low melting point oxide or its corresponding salt is mixed with the tin oxide prepared by the traditional acidification method in a specific weight ratio. The medium and low melting point oxide within this weight ratio range can effectively regulate the growth behavior of tin oxide particles, which is beneficial to obtaining modified tin oxide powder doped with medium and low melting point oxides with a spherical-like morphology, a concentrated and uniform particle size distribution.

[0015] In some specific embodiments, the weight ratio of the tin oxide prepared by the traditional acidification process in S2 to water is 1:(3 - 4).

[0016] Among them, if the addition amount of water is too much, the ball milling time will increase and the energy consumption will increase, while if the addition of water is too little, it is not conducive to improving the uniformity of the particle size distribution of the tin oxide slurry.

[0017] In some specific embodiments, in S3, the base is at least one of ammonia water, sodium hydroxide solution, and potassium hydroxide solution.

[0018] In some specific embodiments, in S3, adding a base to adjust the pH > 8.

[0019] In this application, adjusting the pH value of the premixed slurry > 8 can effectively promote the precipitation reaction of the medium and low melting point oxide precursor and improve its uniform distribution degree in the tin oxide slurry. This technical means ensures the coating effect of the medium and low melting point oxide on the tin oxide particles during the subsequent calcination process, thereby further improving the morphology and particle size distribution of the prepared modified tin oxide powder, making it more spherical-like and the particle size more uniform and concentrated, which is beneficial to improving the processing performance and quality stability of the silver tin oxide material.

[0020] In some specific embodiments, in S4, the tin oxide slurry doped with the precursor is washed with deionized water until the pH of the tin oxide slurry doped with the precursor is between 6.5 - 7.5, and then the washing step is ended.

[0021] In some specific embodiments, in S4, the drying temperature is controlled at 100°C to 200°C.

[0022] In some specific embodiments, in S5, before calcining the tin oxide powder doped with the precursor, the tin oxide powder doped with the precursor is first crushed, and the crushed tin oxide powder doped with the precursor is sieved through a 100-mesh sieve. Taking the sieved tin oxide powder doped with the precursor for calcination is beneficial to improving the particle size uniformity of the modified tin oxide powder doped with medium and low melting point oxides and reducing the distribution span of the particle size.

[0023] Second, a modified tin oxide powder doped with medium and low melting point oxides provided by the present application adopts the following technical solution: A modified tin oxide powder doped with medium and low melting point oxides is prepared by the heterogeneous precipitation preparation process of the modified tin oxide powder doped with medium and low melting point oxides described in any one of the above.

[0024] In summary, the present application at least includes the following beneficial technical effects: 1. The morphology of the modified tin oxide powder doped with medium and low melting point oxides in the present application becomes spherical, solving the problem that the morphology of the tin oxide obtained by the traditional acidification method for preparing tin oxide is multi-angular, which is beneficial to the processing of silver tin oxide materials.

[0025] 2. The particle size of the modified tin oxide powder doped with medium and low melting point oxides produced by the present application using the above process is more uniform and concentrated, which is beneficial to preparing a silver tin oxide material with good uniformity. Description of the Drawings

[0026] Figure 1 It is the SEM image of the modified tin oxide powder doped with bismuth oxide in Example 1 of the present application.

[0027] Figure 2 It is the SEM image of the tin oxide (after ball milling) prepared by the traditional acidification process in Comparative Example 1 of the present application.

[0028] Figure 3 It is the SEM image of the tin oxide (before ball milling) prepared by the traditional acidification process in Comparative Example 2 of the present application.

[0029] Figure 4 It is the particle size distribution diagram of the modified tin oxide powder doped with bismuth oxide in Example 1 of the present application.

[0030] Figure 5 It is the particle size distribution diagram of the tin oxide (before ball milling) prepared by the traditional acidification process in Comparative Example 2 of the present application. Specific Embodiments

[0031] The following further elaborates on the present application in combination with specific examples. Examples

[0032]

Example 1

[0033]

Example 2

[0034] Comparative Example

Comparative Example 1

[0035]

Comparative Example 2

[0036] Performance test results 1. SEM images of the modified tin oxide powder doped with bismuth oxide prepared in Example 1, the tin oxide powder in Comparative Example 1, and the tin oxide powder in Comparative Example 2 were respectively detected. Among them, the SEM image of the modified tin oxide powder doped with bismuth oxide prepared in Example 1 is as Figure 1 shown. The morphology of the obtained modified tin oxide powder doped with bismuth oxide is spherical-like, without sharp edges and corners, which is beneficial to the processing of silver tin oxide materials. The SEM image of the tin oxide powder (after ball milling) prepared by the traditional acidification method in Comparative Example 1 is as Figure 2 shown. After ball milling, the particle size of the tin oxide powder becomes smaller, but most of the particles still have an obvious multi-faceted structure. When applied to the processing of silver tin oxide materials, there is still a problem of poor dispersion uniformity. The SEM image of the tin oxide powder (before ball milling) prepared by the traditional acidification method in Comparative Example 2 is as Figure 3 shown. The morphology is large multi-faceted crystals, and it is difficult to achieve uniform dispersion when applied to the processing of silver tin oxide materials.

[0037] 2. The particle size distributions of the modified tin oxide powder doped with bismuth oxide prepared in Example 1 and the tin oxide (before ball milling) prepared by the traditional acidification process in Comparative Example 2 were respectively detected. Among them, the particle size distribution diagram of the modified tin oxide powder doped with bismuth oxide prepared in Example 1 is as Figure 4 shown, and the particle size distribution of the tin oxide (before ball milling) prepared by the traditional acidification process in Comparative Example 2 is as Figure 5 shown. The specific particle size distribution in Example 1 and Comparative Example 2 is shown in Table 1 below.

[0038] Table 1

[0039] It can be seen from the data recorded in Table 1 that among the modified tin oxide powder doped with bismuth oxide prepared in Example 1, 10% of the particle volume is less than or equal to 0.834 μm, 50% of the particle volume is less than or equal to 2.965 μm, and 90% of the particle volume is less than or equal to 6.721 μm. Among the tin oxide (before ball milling) prepared by the traditional acidification process in Comparative Example 2, 10% of the particle volume is less than or equal to 1.847 μm, 50% of the particle volume is less than or equal to 7.650 μm; 90% of the particle volume is less than or equal to 17.522 μm. Among them, the particle size distribution range of the modified tin oxide powder doped with bismuth oxide prepared in Example 1 is narrower and the uniformity is better.

[0040] Generally speaking, compared with the tin oxide powder prepared by the traditional acidification process for preparing tin oxide, the modified tin oxide powder doped with bismuth oxide prepared by the process of the present application has the characteristics of more concentrated particle size distribution, better particle size uniformity and easier uniform dispersion, which is beneficial to the preparation of a silver tin oxide material with good uniformity and stable quality.

[0041] This specific embodiment is only an interpretation of the present application, and it does not limit the present application. After reading this specification, those skilled in the art can make modifications without creative contributions to this specific embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A heterogeneous precipitation preparation process for modified tin oxide powder doped with medium and low melting point oxides, characterized in that: The following steps are involved: S1. Dissolving: adding a medium or low melting point oxide or its corresponding salt into an acid to dissolve it to obtain a salt solution; S2, mixing: adding water to the tin oxide prepared by the conventional acidification process and ball-milling it into a tin oxide slurry with a D50 particle size of 0.5 μm to 3 μm; adding the salt solution to the tin oxide slurry, stirring evenly, to obtain a premixed slurry; S3, precipitation: adding alkali to the premixed slurry to adjust the pH to generate a tin oxide slurry doped with the precursor; S4, drying: washing and drying the tin oxide slurry doped with the precursor to obtain tin oxide powder doped with the precursor; S5, calcination: calcine the tin oxide powder doped with the precursor at 900° C. to 1200° C. for 10-15 hours to obtain modified tin oxide powder doped with medium and low melting point oxides.

2. The heterogeneous precipitation preparation process of modified tin oxide powder doped with medium and low melting point oxides according to claim 1, characterized in that: The acid in S1 is concentrated nitric acid.

3. The heterogeneous precipitation preparation process of modified tin oxide powder doped with medium and low melting point oxides according to claim 1, characterized in that: The weight ratio of the medium-low melting point oxide or its corresponding salt described in S1 to the tin oxide prepared by the traditional acidification method described in S2 is (0.2-0.5): (9.5-9.8).

4. The heterogeneous precipitation preparation process of modified tin oxide powder doped with medium and low melting point oxides according to claim 1, characterized in that: The weight ratio of tin oxide produced by the conventional acidification process to water in S2 is 1:(3-4).

5. The heterogeneous precipitation preparation process of modified tin oxide powder doped with medium and low melting point oxides according to claim 1, characterized in that: In S3, the alkali is at least one of aqueous ammonia, sodium hydroxide solution, and potassium hydroxide solution.

6. The heterogeneous precipitation preparation process of modified tin oxide powder doped with medium and low melting point oxides according to claim 1, characterized in that: In S3, add alkali to adjust pH>8.

7. The heterogeneous precipitation preparation process of modified tin oxide powder doped with medium and low melting point oxides according to claim 1, characterized in that: In S4, the tin oxide slurry doped with the precursor is washed with deionized water until the pH of the tin oxide slurry doped with the precursor is between 6.5 and 7.5, and the washing step is terminated.

8. The heterogeneous precipitation preparation process of modified tin oxide powder doped with medium and low melting point oxides according to claim 1, characterized in that: In S4, the drying temperature is controlled to be 100°C-200°C.

9. The heterogeneous precipitation preparation process of modified tin oxide powder doped with medium and low melting point oxides according to claim 1, characterized in that: In S5, before calcining the tin oxide powder doped with the precursor, the tin oxide powder doped with the precursor is first crushed, and the crushed tin oxide powder doped with the precursor is passed through a 100-mesh sieve, and the sieved tin oxide powder doped with the precursor is taken for calcining.

10. A modified tin oxide powder doped with medium and low melting point oxides, characterized in that: The modified tin oxide powder doped with medium- and low-melting-point oxides is prepared by the heterogeneous precipitation preparation process described in any one of claims 1 to 9.

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