CN1623905A - Method for preparing zirconium oxide micro powder - Google Patents

Abstract

A process for preparing superfine zirconium oxide powder includes such steps as reaction between ammonia water and Zr salt in solution to obtain deposit, washing, filtering, adding it to the solution of zirconium chloride oxide to generate sol, heating while hydrolyzing to obtain deposit, washing, calcining and grinding. Its advantages are controllable and uniform granularity, and low cost.

Description

Method for preparing zirconium oxide superfine powder

Technical Field

The invention relates to a method for preparing zirconium oxide superfine powder, the powder prepared by the method has uniform particle distribution and compact structure, and is mainly used for preparing structural ceramics with high strength and high density.

Background

The existing method for preparing zirconia ultrafine powder comprises the following steps: homogeneous precipitation, coprecipitation, heating hydrolysis, etc.

Homogeneous precipitation method: zirconium oxychloride and a urea solution are uniformly mixed, the mixture is heated to above 70 ℃, urea is decomposed, and the decomposition reaction equation is as follows:

along with the continuous decomposition of urea, the pH value of the solution is continuously increased by the generated ammonia water, the solution viscosity is increased suddenly to a certain degree, and precipitates are generated because of the uncontrollable property of the growth process, the finally formed precipitates are space latticed gel, and the filtering and washing are very difficult and are difficult to be used for large-scale production.

A coprecipitation method: firstly, preparing zirconium salt into a solution with a certain concentration in water, and calling the solution B; then ammonia water is diluted to a certain concentration, and the solution is called solution A. The reaction is carried out by adopting a normal dropping method (namely, adding the solution A into the solution B) or a reverse dropping method (adding the solution B into the solution A), and gelatinous precipitate is obtained. The gel is washed and calcined to obtain superfine powder, and the method has the disadvantages of non-uniform particle size and non-uniform component distribution. In particular, the back-drop method, forms a large number of nuclei within a short period of time, and nucleation and growth are essentially instantaneous, cross-wise completed, with no means of completely separating nucleation and growth. It can be concluded from this that the size of the primary particles is also not uniform, and that the size control of the primary particles and the specific surface area can be controlled substantially only by the calcination temperature and time, and it is economically uneconomical to extend the calcination time, and generally, the control of the calcination temperature is the only means. The consequence is imperfect crystallization of the particles and the presence of pores inside the primary particles.

A hydrolysis method: namely, the zirconium oxychloride aqueous solution is heated to a certain temperature, so that hydrogen chloride is continuously volatilized, after the pH value is raised to a certain degree, spontaneous nucleation is carried out in the solution to form a crystal core, and the prepared superfine powder has inconsistent size, and in addition, the heating time is long, usually 5 to 10 days are needed, a large amount of energy is consumed, and the cost is high.

Disclosure of Invention

The invention aims to provide a method for preparing superfine zirconia powder, and the zirconia prepared by the method has controllable, uniform and consistent primary particle size, high quality, low preparation cost and high efficiency.

The purpose of the invention is realized as follows: a method for preparing zirconium oxide superfine powder is characterized in that: the method comprises the steps of utilizing a coprecipitation method to enable ammonia water and zirconium salt to react in a solution, adding generated precipitates into a zirconium oxychloride solution after washing and filtering to enable the precipitates to generate peptization, taking the sols as crystal cores, heating to enable the sols to be further hydrolyzed to generate precipitates, washing, calcining and grinding hydrolysates to prepare the nano-zirconia ultrafine powder with controllable primary particle size and uniformity.

The object of the invention is also achieved in that: the method for preparing the zirconia superfine powder is characterized by comprising the following steps: the method comprises the following steps of:

i) preparing ammonia water and zirconium oxychloride into uniform solutions A and B respectively, adding thesolution B into the solution A to ensure that the pH value is 7, and obtaining a precipitate of zirconium hydroxide;

ii) fully washing and filtering the precipitate, adding the precipitate into a zirconium oxychloride solution, and heating the solution to boiling to fully react the precipitate and the zirconium oxychloride solution to generate peptization;

iii) separating the collosol and the precipitate which is not peptized by a centrifugal method to obtain uniform zirconium hydroxide collosol;

iv) heating the sol serving as a seed crystal of hydrolysis reaction to 80-105 ℃, continuously and slowly adding a zirconium oxychloride solution to supplement zirconium ions consumed by hydrolysis, and finally obtaining zirconium hydroxide precipitate with uniform granularity and controllable size,

v) washing, calcining, grinding and spray drying the precipitate to obtain the nano-zirconia ultrafine powder.

Compared with the prior art, the invention has the following advantages: the invention combines the coprecipitation method and the heating hydrolysis method to make up for the shortages, thereby solving the problems that the nucleation and the growth of the crystal cannot be controlled and the size of the primary particles is not uniform. In the present invention, after the addition of the external crystal nucleus, spontaneous nucleation no longer occurs, the number of crystal nuclei is constant, and the size of the final particle can be controlled by the length of the hydrolysis time. Another advantage of the method is that the inoculation time of spontaneous nucleation is saved by adding external crystal nucleus instead of spontaneous nucleation, the time required by the direct hydrolysis method is shortened to 1/2, and the efficiency is greatly improved.

Drawings

The attached figure is an X-ray diffraction pattern of the zirconium oxide ultrafine powder

Detailed Description

The invention mainly aims at the defects of the prior art, combines a coprecipitation method and a heating hydrolysis method, makes up for the deficiencies of each other, and provides a method for preparing high-quality low-cost superfine zirconia powder. The basic technological process includes reaction of ammonia water and zirconium salt in solution by means of coprecipitation, filtering and washing the produced precipitate, adding zirconium oxychloride to produce peptization of the precipitate, heating the peptization to produce precipitate, washing, calcining and grinding the hydrolysate to prepare homogeneous zirconia grains with controllable size. The key steps are as follows: 1) precipitating the zirconium salt solution by using an ammonia water adding method, washing and filtering the precipitate; 2) adding the clean precipitate into a zirconium oxychloride solution, and heating to generate peptization; 3) centrifuging and settling, removing precipitate without peptization to obtain uniform sol; 4) and heating and hydrolyzing the sol to prepare the nano zirconia particles with uniform size.

According to the current research, zirconia with a stable tetragonal structure can be obtained by doping other oxides such as yttria and the like in the zirconia, and the material strength and the fracture toughness of the zirconia can be improved, so that a yttria solution can be added into a zirconia solution to prepare a mixed solution to prepare high-performance nano zirconia superfine powder.

Example 1

The method comprises the following steps of:

i)preparing zirconium oxychloride into a solution B with the concentration of 1.0M, diluting 14M ammonia water into a solution A with the concentration of 1.0M, adding the solution A into the solution B under the condition of continuous stirring to generate a precipitate of zirconium hydroxide, stopping until the pH value is 7.0, and aging for 12 hours;

ii) washing the precipitate with deionized water sufficiently until no white precipitate is detected with silver nitrate to obtain precipitate C; dissolving zirconium oxychloride in deionized water to obtain a solution D; adding the precipitate C into the solution D, adding water until the concentration of zirconium ions reaches 1.0M, and heating to boil under stirring until all precipitates are peptized;

iii) centrifuging and settling to separate the precipitate without peptization: putting the sol into a closed container, and settling for 1 hour on a centrifugal machine with a separation factor of 3600 to obtain sol E;

iv) heating the sol E to boiling, continuously and slowly adding the solution B, keeping the adding amount equal to the hydrolysis amount, stopping adding after the expected primary particle size is reached, and keeping boiling until the zirconium ions in the solution are hydrolyzed completely; in the heating process, water is continuously evaporated, and water is required to be supplemented frequently, so that the volume of the solution is kept unchanged;

v) washing the hydrolysate with deionized water, filtering, calcining at 800 ℃ for 5h to obtain granular zirconia, grinding the granular zirconia with water by a ball mill until the granularity reaches 0.2-0.3 mu m, and spray drying to obtain the finished product.

Example 2

The method comprises the following steps of:

i) preparing a mixedsolution of zirconium oxychloride and yttrium chloride and preparing an ammonia solution according to the following proportion: mixing 322 g of zirconium oxychloride with 43 g of yttrium chloride solution which can be folded into 6.4 g of yttrium oxide to prepare solution B with the concentration of 1.0M, diluting 14M ammonia water into 1.0M solution A, adding the solution A into the solution B under the condition of continuous stirring to generate zirconium hydroxide precipitate, stopping until the pH value is 7.0, and aging for 12 hours;

ii) washing the precipitate with deionized water sufficiently until no white precipitate is detected with silver nitrate to obtain precipitate C; dissolving 966 g of zirconium oxychloride in deionized water to obtain a solution D; adding the precipitate C into the solution D, adding water until the concentration of zirconium ions reaches 1.0M, and heating to boil under stirring until all precipitates are peptized;

iii) centrifuging and settling to separate the precipitate without peptization: putting the sol into a closed container, and settling for 1 hour on a centrifugal machine with a separation factor of 3600 to obtain sol E;

iv) heating the sol E to boiling, continuously and slowly adding the solution B, keeping the adding amount equal to the hydrolysis amount, stopping adding after the expected primary particle size is reached, and keeping boiling until the zirconium ions in the solution are hydrolyzed completely; in the heating process, water is continuously evaporated, and water is required to be supplemented frequently, so that the volume of the solution is kept unchanged;

v) washing the hydrolysate with deionized water, filtering, calcining at 800 ℃ for 5h to obtain granular zirconia, grinding the granular zirconia with water by a ball mill until the granularity reaches 0.2-0.3 mu m, and spray drying to obtain a finished product;

after calcination, the XRD of the zirconia particles is as shown in the figure, and all consist of tetragonal phase; the spray dried powder was subjected to cold isostatic pressing at 200Mpa and sintered at 1500 ℃ for 2 hours, and the detected density was 6.07.

Claims (4)

1. A method for preparing zirconium oxide superfine powder is characterized in that: the method comprises the steps of utilizing a coprecipitation method to enable ammonia water and zirconium salt to react in a solution, adding generated precipitates into a zirconium oxychloride solution after washing and filtering to enable the precipitates to generate peptization, taking the sols as crystal cores, heating to enable the sols to be further hydrolyzed to generate precipitates, washing, calcining and grinding hydrolysates to prepare the nano-zirconia ultrafine powder with controllable primary particle size and uniformity.

2. A process for preparing zirconia micropowder according to claim 1 characterized by: the method comprises the following steps of:

i) preparing ammonia water and zirconium oxychloride into uniform solutions A and B respectively, adding the solution B into the solution A to ensure that the pH value is 7, and obtaining a precipitate of zirconium hydroxide;

ii) fully washing and filtering the precipitate, adding the precipitate into a zirconium oxychloride solution, and heating the solution to boiling to fully react the precipitate and the zirconium oxychloride solution to generate peptization;

iii) separating the collosol and the precipitate which is not peptized by a centrifugal method to obtain uniform zirconium hydroxide collosol;

iv) heating the sol serving as a seed crystal of hydrolysis reaction to 80-105 ℃, continuously and slowly adding a zirconium oxychloride solution to supplement zirconium ions consumed by hydrolysis, and finally obtaining zirconium hydroxide precipitate with uniform granularity and controllable size,

v) washing, calcining, grinding and spray drying the precipitate to obtain the nano-zirconia ultrafine powder.

3. A process for preparing zirconia micropowder according to claim 1 characterized by: the method comprises the following steps of:

i) preparing zirconium oxychloride into a solution B with the concentration of 1.0M, diluting 14M ammonia water into a solution A with the concentration of 1.0M, adding the solution A into the solution B under the condition of continuous stirring to generate a precipitate of zirconium hydroxide, stopping until the pH value is 7.0, and aging for 12 hours;

ii) washing the precipitate with deionized water sufficiently until no white precipitate is detected with silver nitrate to obtain precipitate C; dissolving zirconium oxychloride in deionized water to obtain a solution D; adding the precipitate C into the solution D, adding water until the concentration of zirconium ions reaches 1.0M, and heating to boil under stirring until all precipitates are peptized;

iii) centrifuging and settling to separate the precipitate without peptization: putting the sol into a closed container, and settling for 1 hour on a centrifugal machine with a separation factor of 3600 to obtain sol E;

iv) heating the sol E to boiling, continuously and slowly adding the solution B, keeping the adding amount equal to the hydrolysis amount, stopping adding after the expected primary particle size is reached, and keeping boiling until the zirconium ions in the solution are hydrolyzed completely; in the heating process, water is continuously evaporated, and water is required to be supplemented frequently, so that the volume of the solution is kept unchanged;

v) washing the hydrolysate with deionized water, filtering, calcining at 800 ℃ for 5h to obtain granular zirconia, grinding the granular zirconia with water by a ball mill until the granularity reaches 0.2-0.3 mu m, and spray drying to obtain the finished product.

4. A process for preparing zirconia micropowder according to claim 1 characterized by: the method comprises the following steps of:

i) preparing a mixed solution of zirconium oxychloride and yttrium chloride and preparing an ammonia solution according to the following proportion: mixing 322 g of zirconium oxychloride with 43 g of yttrium chloride solution which can be folded into 6.4 g of yttrium oxide to prepare solution B with the concentration of 1.0M, diluting 14M ammonia water into 1.0M solution A, adding the solution A into the solution B under the condition of continuous stirring to generate zirconium hydroxide precipitate, stopping until the pH value is 7.0, and aging for 12 hours;

ii) washing the precipitate with deionized water sufficiently until no white precipitate is detected with silver nitrate to obtain precipitate C; dissolving 966 g of zirconium oxychloride in deionized water to obtain a solution D; adding the precipitate C into the solution D, adding water until the concentration of zirconium ions reaches 1.0M, and heating to boil under stirring until all precipitates are peptized;

iii) centrifuging and settling to separate the precipitate without peptization: putting the sol into a closed container, and settling for 1 hour on a centrifugal machine with a separation factor of 3600 to obtain sol E;

iv)heating the sol E to boiling, continuously and slowly adding the solution B, keeping the adding amount equal to the hydrolysis amount, stopping adding after the expected primary particle size is reached, and keeping boiling until the zirconium ions in the solution are hydrolyzed completely; in the heating process, water is continuously evaporated, and water is required to be supplemented frequently, so that the volume of the solution is kept unchanged;

v) washing the hydrolysate with deionized water, filtering, calcining at 800 ℃ for 5h to obtain granular zirconia, grinding the granular zirconia with water by a ball mill until the granularity reaches 0.2-0.3 mu m, and spray drying to obtain a finished product;

after calcination, the zirconia particles are composed entirely of tetragonal phase; the spray dried powder was subjected to cold isostatic pressing at 200Mpa and sintered at 1500 ℃ for 2 hours, and the detected density was 6.07.