CN111138203A

CN111138203A - Preparation method and application of in-situ solidified high solid content ceramic slurry

Info

Publication number: CN111138203A
Application number: CN202010041381.3A
Authority: CN
Inventors: 王士维; 陈晗; 岛井骏藏; 赵瑾; 吴事江; 杨焕顺
Original assignee: Shandong Ultraming Fine Ceramics Co ltd; Shanghai Institute of Ceramics of CAS
Current assignee: Shandong Ultraming Fine Ceramics Co ltd; Shanghai Institute of Ceramics of CAS
Priority date: 2020-01-15
Filing date: 2020-01-15
Publication date: 2020-05-12

Abstract

The invention relates to the technical field of ceramic wet forming, in particular to a preparation method and application of in-situ cured high-solid-content ceramic slurry. The preparation method of the in-situ cured high-solid-content ceramic slurry comprises the steps of adding a dispersing agent and a hydrophobic agent into water, stirring and dissolving the dispersing agent and the hydrophobic agent to enable the dispersing agent and the hydrophobic agent to fully react, then adding ceramic powder, and carrying out ball milling to obtain the high-solid-content ceramic slurry; the dispersant is carboxyl (-COO)^‑) The anionic dispersant of (1); the hydrophobic agent is a short-chain cationic surface active substance. The preparation method of the high-solid-content ceramic slurry for in-situ curing has the characteristics of less additive types, less additive amount and capability of preparing the high-solid-content slurry, and the solid-content ceramic slurry is solidThe reaction occurs spontaneously under room temperature air conditions; the invention also provides application of the ceramic powder in preparing a high-density ceramic material.

Description

Preparation method and application of in-situ cured high-solid-content ceramic slurry

Technical Field

The invention relates to the technical field of ceramic wet forming, in particular to a preparation method and application of in-situ cured high-solid-content ceramic slurry.

Background

Wet forming is an important ceramic forming process, which is characterized by the conversion of a slurry (suspension) into a wet blank. Wet forming can be mainly classified into two types according to the curing method: one is that the wet blank is obtained by a solid-liquid separation way, comprising: slip casting (Journal of the American Ceramic Society,1986,69: 882-; another is the formation of a solid by in situ solidification of a fluid, comprising: polymer additive transitions (starch (Journal of the European Ceramic Society,1998,18: 131-), agar (British Ceramic Transactions,1999,98:58-61)), gel-casting (Journal of the American Ceramic Society,1991,74: 612-), and direct-set casting (Chemtech,1995,25: 31-37).

The solid-liquid separation molding is easy to cause the density gradient problem during solid-liquid separation, while the in-situ curing molding is free from the problems, but the high polymer additive is low in solid content due to conversion, the types of free radical polymerization system additives in the injection-coagulation molding are as many as five, and the oxygen inhibition problem exists, while the direct coagulation molding (DCC) needs to realize curing by causing the slurry state change through induction factors (temperature, pH value or initiator and the like), and the application material system range is limited by the induction factors. Meanwhile, the wet green formed by in-situ curing may discharge a large amount of moisture during the drying process, and the volume may shrink, which may cause a problem of deformation or cracking. It has been found that when the solids content of the slurry is increased from 50 vol% to 58 vol%, the drying shrinkage is reduced from 4.6% to 1.5% (Journal of Materials Research,2014.29(02): p.247-251), thereby substantially reducing the risk of cracking due to drying. Therefore, the preparation of high solid content slurry becomes the key of in-situ curing and forming.

Patents CN106316456B and CN106518095B propose a new preparation method of foamed ceramic slurry capable of in-situ curing, that is, a surfactant is added in the process of preparing slurry by ball milling, particles are hydrophobically modified to obtain hydrophobically modified ceramic slurry, uniform foam is obtained by mechanical stirring, and hydrophobic particles are utilized to realize bubble stabilization, and then the slurry is cured by hydrophobic effect. The method has less organic matter addition amount, but the added hydrophobic agent is a long-chain surfactant, so that the viscosity of the slurry is obviously increased; moreover, since the presence of the long-chain surfactant causes bubbles to be introduced and fixed in the slurry during ball milling, it is difficult to remove the bubbles even by degassing, and thus, a highly dense ceramic material cannot be prepared.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a preparation method of in-situ cured high-solid-content ceramic slurry, which has the characteristics of few additive types, small addition amount and capability of preparing the high-solid-content slurry, and the curing occurs spontaneously under the room-temperature air condition; the invention also provides application of the ceramic powder in preparing a high-density ceramic material.

The preparation method of the in-situ cured high-solid-content ceramic slurry comprises the steps of adding a dispersing agent and a hydrophobic agent into water, stirring and dissolving the dispersing agent and the hydrophobic agent to enable the dispersing agent and the hydrophobic agent to fully react, then adding ceramic powder, and carrying out ball milling to obtain the high-solid-content ceramic slurry;

the dispersant is carboxyl (-COO)^-) The anionic dispersant of (1);

the hydrophobic agent is a short-chain cationic surface active substance.

Due to different charges, the hydrophobic agent can be combined with the dispersing agent so as to improve the hydrophobicity of the dispersing agent, the ceramic powder particles are regularly arranged under high shear rate due to the hydrophobic effect, so that the preparation of high-solid-content slurry is facilitated, and meanwhile, the slurry can be cured in situ due to the mutual attraction effect among hydrophobic chains.

The ceramic powder is oxide ceramic powder and/or non-oxide ceramic powder, preferably at least one of alumina, magnesia-alumina spinel, zirconia, silicon carbide and silicon nitride.

The dispersant is at least one of polyacrylamide, isobutylene and maleic anhydride copolymer.

The hydrophobic agent is at least one of tetramethylammonium hydroxide, tetramethylammonium chloride, tetraethylammonium chloride and methyl tributylammonium chloride.

The addition amount of the water repellent agent is 0.1-1%, preferably 0.1-0.5% of the mass of the ceramic powder.

The addition amount of the dispersant is 0.2-1%, preferably 0.2-0.5% of the mass of the ceramic powder.

The ball milling and mixing time is 60-120 min.

The high-solids ceramic slurry has a solids content of 40 to 58 vol%, preferably 45 to 55 vol%.

According to the invention, the dispersant and the hydrophobic agent react firstly, and then the ceramic powder is added, so that the prepared slurry has low viscosity and is easy to defoam, the prepared biscuit has small drying shrinkage, and the prepared ceramic material has higher density and higher hardness.

The high-solid-content ceramic slurry prepared by the preparation method of the in-situ cured high-solid-content ceramic slurry is applied to preparing a high-density ceramic material, the high-solid-content ceramic slurry is poured into a mold, the slurry is placed at room temperature for 20-30h to be cured, and then the high-density ceramic material is prepared through drying and demolding.

In the in-situ curing process, the dispersant is modified by the hydrophobizing agent, so that the ceramic particles are hydrophobized, the slurry is cured through the hydrophobizing action, other additives are not needed, and the formed ceramic biscuit is uniform and compact in structure and high in strength.

Compared with the prior art, the invention has the following beneficial effects:

(1) the invention adds the ceramic slurry in the preparation processContaining carboxyl (-COO)^-) The anionic dispersant and the short-chain cationic surface active substance hydrophobic agent can be combined with the dispersant by utilizing the difference of charges of the anionic dispersant and the short-chain cationic surface active substance hydrophobic agent, so that the hydrophobicity of the dispersant is improved, particles are regularly arranged under high shear rate due to hydrophobic effect, the highest solid content of the slurry is improved, the high solid content slurry is prepared, and drying shrinkage is reduced;

(2) the invention makes use of the mutual attraction between the hydrophobic chains of the dispersant and the hydrophobic agent to solidify the slurry in situ in the air atmosphere at room temperature, and the addition of the dispersant and the hydrophobic agent is little;

(3) the preparation method can be used for oxide powder and/or non-oxide powder, and has wide applicability;

(4) the ceramic biscuit prepared from the high-solid-content ceramic slurry prepared by the invention has a uniform and compact structure and higher strength.

Drawings

FIG. 1 illustrates a hydrophobic modification reaction using isobutylene and maleic anhydride copolymer as an example of a dispersant;

FIG. 2 illustrates the hydrophobic modification reaction using ammonium polyacrylate as an example of the dispersant;

FIG. 3 is a graph of viscosity (a) for examples 1-4 and comparative example 1;

FIG. 4 is a graph of storage modulus (b) for examples 1-4 and comparative example 1;

FIG. 5 is a graph of the viscosity (a) of the slurry prepared in example 5;

FIG. 6 is a plot of the storage modulus (b) of the slurries prepared in example 5;

FIG. 7 is a graph of the viscosity (a) of slurries prepared in examples 6 and 7;

FIG. 8 is a graph of storage modulus (b) of slurries prepared in examples 6 and 7;

FIG. 9 is a graph of the viscosity (a) of slurries prepared in example 8 and comparative example 2;

FIG. 10 is a graph of storage modulus (b) of slurries prepared in example 8 and comparative example 2;

fig. 11 is a graph of the viscosity of the slurry prepared in comparative example 4.

Detailed Description

The preparation of the high solid content ceramic slurry provided by the present invention and its application are exemplarily illustrated below.

Preparing water-based ceramic slurry: adding a dispersing agent and a hydrophobic agent into water, stirring and dissolving the dispersing agent and the hydrophobic agent to enable the dispersing agent and the hydrophobic agent to fully react, adding ceramic powder, and performing ball milling to obtain ceramic slurry. The powder for preparing the water-based ceramic slurry can be oxide ceramic powder such as alumina, magnesia-alumina spinel, zirconia and the like, or non-oxide ceramic powder such as silicon carbide, silicon nitride and the like, or composite ceramic powder. The solids content of the water-based ceramic slurry is in the range of 40 to 58 vol%, preferably 45 to 55 vol%. The dispersing agent is anionic dispersing agent, and can be adsorbed on the surface of ceramic particles to achieve good dispersing effect through electrostatic repulsion and steric hindrance, the selected hydrophobic agent is short-chain cationic surface active substance, and can be combined with the dispersing agent to improve the hydrophobicity of the dispersing agent due to different charges, so that the particles are regularly arranged under high shear rate due to the hydrophobic effect, thereby being beneficial to preparing high-solid-content slurry, and meanwhile, the slurry can be cured in situ due to the mutual attraction effect among hydrophobic chains.

And (3) slurry in-situ curing and forming: and pouring the water-based ceramic slurry into a mold, spontaneously curing the slurry in the air at room temperature, and then drying and demolding to obtain the ceramic biscuit.

In general, the present invention modifies the dispersant with a short chain hydrophobizing agent, resulting in hydrophobizing of the ceramic particles, which solidifies the slurry by hydrophobic interaction. The method can cure the slurry in situ without other additives, can improve the highest solid content of the slurry, prepare the slurry with high solid content, and ensure that the formed ceramic biscuit has uniform and compact structure and higher strength.

The present invention is further illustrated by the following examples, but the scope of the present invention is not limited thereto, and modifications of the technical solutions of the present invention by those skilled in the art should be within the scope of the present invention. The process is conventional unless otherwise specified, and the starting materials are commercially available from the open literature.

Example 1

(1) Preparing high-solid-content ceramic slurry: adding 0.3 wt% (relative to the mass of the alumina powder) of isobutylene and maleic anhydride copolymer (trade name Isobam600AF) serving as a dispersing agent and 0.1 wt% (relative to the mass of the alumina powder) of tetramethylammonium chloride serving as a hydrophobic agent into ultrapure water, stirring and dissolving to enable the isobutylene and the maleic anhydride copolymer to fully react, adding alumina powder with the median particle size D50-250 nm, and preparing ceramic slurry with uniform dispersion and 50 vol% of solid content by ball milling;

(2) and (3) curing the slurry: and injecting the water-based slurry into a plastic mold, standing for 24 hours, demolding, and drying at room temperature for 48 hours to obtain the ceramic biscuit.

Example 2

This example is different from example 1 only in that 0.2 wt% (based on the mass of the powder) of tetramethylammonium chloride was added as a hydrophobizing agent.

Example 3

This example is different from example 1 only in that 0.3 wt% (based on the mass of the powder) of tetramethylammonium chloride was added as a hydrophobizing agent.

Example 4

This example is different from example 1 only in that 0.4 wt% (based on the mass of the powder) of tetramethylammonium chloride was added as a hydrophobizing agent.

Comparative example 1

This comparative example differs from example 1 only in that tetramethylammonium chloride, a hydrophobicizing agent, was not added.

The high solid content ceramic slurries prepared in examples 1 to 4 and comparative example 1 were subjected to viscosity and storage modulus tests, and the results are shown in fig. 3 and 4.

As can be seen from fig. 3, although the introduction of the hydrophobic chain slightly increases the viscosity of the slurry, the viscosity of the slurry is still low, and the operation performance of the slurry is not affected; as can be seen from fig. 4, in comparative example 1 in which hydrophobicity was not introduced, the paste was not cured, whereas in examples 1 to 4 in which hydrophobic chains were introduced, the paste was cured, and the paste curing speed was increased as the number of hydrophobic molecules was increased.

Example 5

This example is different from example 4 only in that 0.3 wt% (relative to the powder mass) of ammonium polyacrylate was added as a dispersant, and the high solid content ceramic slurry prepared in example 5 was subjected to viscosity and storage modulus tests, and the test results are shown in fig. 5 and 6.

As can be seen from fig. 5 and 6, the hydrophobic modification is also applicable to dispersant ammonium polyacrylate, and the introduction of the hydrophobic chain enables the ammonium polyacrylate to have curing capability, so that in-situ curing of slurry can be realized.

Example 6

The present example is different from example 4 only in that 0.1 wt% (relative to the powder mass) of tetraethylammonium chloride is added as a water repellent agent, and the ceramic powder is a yttrium oxide and aluminum oxide composite powder.

Example 7

This example is different from example 4 only in that 0.1 wt% (based on the mass of the powder) of methyl tributyl ammonium chloride was added as a hydrophobizing agent, and silicon nitride powder was used as the ceramic powder.

The high solid content ceramic slurries prepared in examples 6 and 7 were subjected to viscosity and storage modulus tests, and the test results are shown in fig. 7 and 8.

As can be seen from fig. 7 and 8, it can be seen that different short chain hydrophobizing agents can make the dispersant have the solidification capability, and the composite ceramic powder or the non-oxide ceramic powder can be solidified for different ceramic powders.

Example 8

This example is different from example 1 only in that the ceramic slurry solid content was 58 vol%.

Comparative example 2

This comparative example differs from example 8 only in that tetramethylammonium chloride, a hydrophobicizing agent, was not added.

The high solid content ceramic slurries prepared in example 8 and comparative example 2 were subjected to viscosity and storage modulus tests, and the results are shown in fig. 9 and 10.

As can be seen from FIG. 9, the slurry without hydrophobic modification in comparative example 2 exhibited shear thickening at high shear rate, resulting in no casting of the slurry, and the slurry with hydrophobic modification in example 8 exhibited shear thinning at 100s^-1The viscosity is 1.3pa · s, which is beneficial to defoaming and subsequent pouring; as can be seen from fig. 10, the slurry introduced with the hydrophobic chains can achieve in-situ curing.

Comparative example 3

This comparative example differs from example 8 only in that 0.4% by weight (relative to the powder mass) of dodecyltrimethylammonium chloride, a long-chain hydrophobicizing agent, is added instead of tetramethylammonium chloride, a hydrophobicizing agent.

The test results show that: the long-chain hydrophobic agent and the dispersant react to generate colloidal substances, and the excessively long hydrophobic chain leads the dispersant to lose the solubility in water and cannot play a dispersing role, so that slurry cannot be prepared, and therefore, the long-chain hydrophobic agent is not suitable for the preparation method disclosed by the invention.

Comparative example 4

The comparative example adopts the sequence of introducing the hydrophobing agent in the patent CN106518095B, namely, the hydrophobing agent is added after the slurry is prepared, and the specific steps are as follows:

(1) preparing ceramic slurry: alumina powder with the median particle size D50-250 nm is used as a raw material, ultrapure water is used as a solvent, 0.3 wt% (relative to the mass of the alumina powder) of isobutylene and maleic anhydride copolymer (trade name Isobam600AF) is added as a dispersing agent, and ceramic slurry with uniform dispersion and 58 vol% of solid content is prepared by ball milling;

(2) hydrophobic modified dispersing agent: adding 0.1 wt% (relative to the mass of the alumina powder) of tetramethylammonium chloride serving as a hydrophobic agent into the ceramic slurry prepared in the step (1), and continuing ball milling for 20min to obtain ceramic slurry capable of being cured in situ;

(3) and (3) injecting the ceramic slurry prepared in the step (2) into a plastic mould, standing for 24 hours, demoulding, and drying at room temperature for 48 hours to obtain a ceramic biscuit.

The high solid content ceramic slurry prepared in comparative example 4 was subjected to a viscosity test, and the test results are shown in fig. 11.

As can be seen from FIG. 11, the viscosity of the ceramic slurry prepared in comparative example 4 was very high at 100s^-1The viscosity was 113pa · s, and in this case, bubbles in the slurry were difficult to remove, and thus the slurry could not be used for producing highly dense ceramics.

The properties of ceramic articles prepared from the two ceramic slurries were compared under the same conditions.

The ceramic greenware prepared in example 8 and comparative example 4 was calcined at 1550 ℃ for 2 hours and then cooled to obtain alumina ceramics. The ceramic green body was tested for drying shrinkage and for density and vickers hardness of the ceramic article, the results of which are shown in table 1.

TABLE 1 indexes of alumina ceramics prepared in example 8 and comparative example 4

Item	Example 8	Comparative example 4
			Density (g/cm)³)	3.96	3.88
Vickers hardness (GPa)	17.6	16.8
			Drying shrinkage (%)	1.6	1.8

As can be seen from table 1, the green body prepared in example 8 has a smaller drying shrinkage rate, and the ceramic prepared has higher compactness and higher hardness, as compared with comparative example 4.

Claims

1. a preparation method of the high solid content ceramic slurry of in-situ solidification, it is characterized in that: add dispersant, hydrophobic agent in water, stir and dissolve and add ceramic powder after making the two fully react, and ball milling makes high solid content ceramic paste;

The dispersant is an anionic dispersant containing a carboxyl group;

The hydrophobic agent is a short-chain cationic surface active substance.

2 . The method for preparing an in-situ solidified high solid content ceramic slurry according to claim 1 , wherein the ceramic powder is an oxide ceramic powder and/or a non-oxide ceramic powder. 3 .

3. The preparation method of in-situ cured high-solid content ceramic slurry according to claim 1, wherein the dispersant is at least one of polyacrylic acid amine, isobutylene and maleic anhydride copolymer.

4. the preparation method of the high solid content ceramic slurry of in-situ curing according to claim 1, is characterized in that: hydrophobic agent is tetramethyl ammonium hydroxide, tetramethyl ammonium chloride, tetraethyl ammonium chloride , at least one of methyl tributyl ammonium chloride.

5 . The preparation method of the in-situ solidified high solid content ceramic slurry according to claim 1 , wherein the amount of the hydrophobic agent added is 0.1-1% of the mass of the ceramic powder. 6 .

6 . The preparation method of the in-situ solidified high solid content ceramic slurry according to claim 1 , wherein the amount of the dispersant added is 0.2-1% of the mass of the ceramic powder. 7 .

7 . The preparation method of in-situ solidified high-solid content ceramic slurry according to claim 1 , wherein the time for ball milling and mixing is 60-120 min. 8 .

8 . The method for preparing an in-situ solidified high solid content ceramic slurry according to claim 1 , wherein the solid content of the high solid content ceramic slurry is 40-58 vol %. 9 .

9. An application of the high-solid-content ceramic slurry prepared by the method for preparing the in-situ cured high-solid-content ceramic slurry according to any one of claims 1-8, characterized in that: for preparing high-density ceramics The high-solid content ceramic slurry is poured into the mold, the slurry is placed at room temperature for 20-30 hours for curing, and then dried and demolded to obtain high-density ceramic materials.