阅读说明：本技术 一种利用无机共融盐制备亚微孔均匀分布的多孔陶瓷及其制备方法 (Porous ceramic with uniformly distributed sub-micropores prepared by using inorganic eutectic salt and preparation method thereof ) 是由 左开慧 曾宇平 夏咏锋 姚冬旭 尹金伟 梁汉琴 梅蕾 于 2020-03-18 设计创作，主要内容包括：本发明公开一种利用无机共融盐制备亚微孔均匀分布的多孔陶瓷及其制备方法。所述制备方法包括：将无机共融盐和陶瓷粉体分散到溶剂中获得混合浆料；将混合浆料干燥、成型,得到多孔陶瓷素坯；将所得多孔陶瓷素坯于1300-1850℃下保温烧结1-3小时,共融盐融化并挥发后,形成亚微孔均匀分布的多孔陶瓷。(The invention discloses a porous ceramic with uniformly distributed sub-micropores prepared by using inorganic eutectic salt and a preparation method thereof. The preparation method comprises the following steps: dispersing inorganic co-molten salt and ceramic powder into a solvent to obtain mixed slurry; drying and molding the mixed slurry to obtain a porous ceramic biscuit; and (3) sintering the obtained porous ceramic biscuit at 1300-1850 ℃ for 1-3 hours under heat preservation, and melting and volatilizing the eutectic salt to form the porous ceramic with uniformly distributed submicron pores.)

1. A preparation method for preparing porous ceramics with uniformly distributed sub-micropores by using inorganic eutectic salt is characterized by comprising the following steps:

dispersing inorganic co-molten salt and ceramic powder into a solvent to obtain mixed slurry; drying and molding the mixed slurry to obtain a porous ceramic biscuit; and (3) sintering the obtained porous ceramic biscuit at 1300-1850 ℃ for 1-3 hours under heat preservation, and melting and volatilizing the eutectic salt to form the porous ceramic with uniformly distributed submicron pores.

2. The method according to claim 1, wherein the inorganic eutectic salt is NaCl, KCl, BaCl₂、CaCl₂、KNO₃、NaNO₂At least two of them.

3. The method according to claim 1 or 2, wherein the eutectic temperature of the inorganic eutectic salt is between the drying temperature of the mixed slurry and the sintering temperature of the porous ceramic green body, preferably 140-800 ℃.

4. The production method according to any one of claims 1 to 3, wherein the ceramic powder is at least one of alumina, zirconia, silicon carbide, silicon nitride, titanium nitride, and aluminum nitride.

5. The method according to any one of claims 1 to 4, wherein the mass of the inorganic eutectic salt is 1 to 20%, preferably 5 to 10%, of the ceramic powder.

6. The method according to any one of claims 1 to 5, wherein the drying temperature is 100 ℃ and 120 ℃, and the drying time is 12 to 24 hours.

7. The production method according to any one of claims 1 to 6, wherein the molding is dry press molding and/or isostatic press molding, the dry press molding pressure is 10 to 30MPa, the isostatic press pressure is 50 to 200MPa, and the pressure holding time is 2 to 10 minutes.

8. The method according to any one of claims 1 to 7, wherein the sintering environment of the porous ceramic greenbody is air, vacuum, nitrogen or argon.

9. The porous ceramic having uniformly distributed submicron pores obtained by the production method according to any one of claims 1 to 8, wherein the porosity of the porous ceramic is 10 to 50% and the pore diameter is 0.1 to 0.8 μm.

Technical Field

The invention relates to a porous ceramic with uniformly distributed sub-micropores prepared by using inorganic eutectic salt and a preparation method thereof, belonging to the field of preparation of porous ceramics.

Background

Porous ceramics are widely applied in many fields such as filtration and catalysis. At present, the method for preparing the porous material mainly comprises an organic foam impregnation method, a pore-forming agent adding method, a sol-gel method and the like, but the method cannot prepare the porous material which is uniformly distributed and has the pore size in a submicron level. For example, the organic foam impregnation method is suitable for preparing materials with high porosity and pore size of more than or equal to 100 mu m; the sol-gel method is suitable for preparing products and film materials with nanometer-level pore sizes.

Disclosure of Invention

The invention aims to obtain the porous ceramic with uniformly distributed submicron pores, which has simple process and low preparation cost, and the method thereof.

In a first aspect, the present invention provides a method for preparing a porous ceramic having uniformly distributed micropores using an inorganic eutectic salt, comprising: dispersing inorganic co-molten salt and ceramic powder into a solvent to obtain mixed slurry; drying and molding the mixed slurry to obtain a porous ceramic biscuit; and (3) sintering the obtained porous ceramic biscuit at 1300-1850 ℃ for 1-3 hours under heat preservation, and melting and volatilizing the eutectic salt to obtain the porous ceramic with uniformly distributed submicron pores.

According to the preparation method disclosed by the invention, the inorganic eutectic salt is added into the ceramic powder, so that the material with uniformly distributed air outlets, high porosity and air hole size less than or equal to 1 mu m can be prepared, the method makes up the defects of the existing preparation method of the porous material, and the preparation method is an important innovation. In addition, the preparation method is simple, the cost is low, the method is suitable for industrial scale production, and the prepared material is widely applied to the aspects of treatment of industrial water and domestic water, purification of sewage, immobilization of biological enzyme carriers, biological adaptive carriers and the like.

Preferably, the inorganic co-molten salt is NaCl, KCl, BaCl₂、CaCl₂、KNO₃、NaNO₂At least two of them. The inorganic salt of the present invention is a part of the eutectic salt, that is, two or more inorganic salts must be present at the same time. Generally, the melting point and the gasification temperature of a single inorganic salt are high, and if the gasification temperature exceeds the temperature at which the ceramic powder is primarily sintered to form a compact structure, uniformly distributed submicron pores are not easily formed.

Preferably, the eutectic temperature of the inorganic eutectic salt is between the drying temperature of the mixed slurry and the sintering temperature of the porous ceramic biscuit, preferably 140-800 ℃. The pore-making mechanism in the submicron pore porous ceramic is that when the sintering temperature is higher than the melting temperature of the eutectic salt, the eutectic salt melts and is gasified to form pores. Because the melting temperature of the eutectic salt is far lower than the sintering densification temperature of the ceramic powder, the eutectic salt can be uniformly removed from the ceramic powder after being gasified, thereby forming uniform submicron pores. However, if the inorganic salt remains during the sintering process and is removed by washing with water at the later stage, the inorganic salt may agglomerate and be unevenly distributed due to sintering heating, so that the uniformly distributed submicron pores cannot be formed. The eutectic salt having a eutectic temperature between 140 ℃ and 800 ℃ is selected because the temperature range is preferably not lower than the drying temperature of the ceramic powder and is further lower than the sintering temperature of the ceramic powder. In an alternative embodiment, the eutectic temperature of the inorganic eutectic salt is more preferably 200-700 ℃.

Preferably, the ceramic powder is at least one of alumina, zirconia, silicon carbide, silicon nitride, titanium nitride and aluminum nitride.

Preferably, the mass of the inorganic eutectic salt is 1-20%, preferably 5-10% of the ceramic powder.

Preferably, the drying temperature of the mixed slurry is 100-120 ℃, and the drying time is 12-24 hours.

Preferably, the molding is dry pressing molding and/or isostatic pressing molding, the pressure of the dry pressing molding is 10-30MPa, the isostatic pressing pressure is 50-200MPa, and the pressure holding time is 2-10 minutes.

Preferably, the sintering environment of the porous ceramic biscuit is air, vacuum, nitrogen or argon.

Preferably, the preparation method does not comprise the step of removing the inorganic eutectic salt by water washing after sintering.

In a second aspect, the invention also provides the porous ceramic with uniformly distributed submicron pores, which is obtained by the preparation method, wherein the porosity of the porous ceramic is 10-50%, and the pore diameter is 0.1-0.8 μm.

Drawings

FIG. 1 is a flow chart of the preparation of porous ceramics with uniformly distributed sub-micropores using inorganic eutectic salts;

FIG. 2 shows addition of KCl, NaCl and BaCl₂Porous ZrO made from inorganic salts₂A microscopic topography graph (a) of the ceramic and a curve graph (b) of the influence of the content of the inorganic eutectic salt on the porosity at different sintering temperatures;

FIG. 3 shows ZrO added with no inorganic salt in comparative example 1₂A microscopic topography of the ceramic;

FIG. 4 shows the addition of NaCl and BaCl₂And CaCl₂Porous Al prepared from inorganic salt₂O₃A microscopic topography of the ceramic;

FIG. 5 shows the addition of NaCl and BaCl₂Porous Si prepared from inorganic salt₃N₄A microscopic topography of the ceramic;

the aforementioned micrographs refer to SEM images.

Detailed Description

The present invention is further illustrated by the following examples, which are to be understood as merely illustrative and not restrictive.

The invention is provided withInorganic eutectic salt and ceramic powder are used as raw materials, and the porous ceramic material with uniformly distributed submicron pores is prepared by controlling the components and content of the inorganic salt, the forming pressure, the sintering temperature and other factors. Specifically, the invention firstly obtains the inorganic eutectic salt with the melting temperature in the range of 140-800 ℃ by controlling the components of the inorganic eutectic salt. For example, (30% wtKCl +20 wt% NaCl +50 wt% BaCl)₂) The eutectic temperature of the mixture was 560 ℃, (80% BaCl)₂+ 20% NaCl) mixture at 635 ℃. This eutectic temperature may also be referred to as the onset eutectic temperature. And then, by regulating and controlling the content of inorganic eutectic salt, forming pressure, sintering temperature and other influencing factors, the porous ceramic material with the porosity and pore size of 10-70 percent and 0.1-0.8 mu m respectively is obtained.

The following is an exemplary description of the method for preparing porous ceramic with uniformly distributed sub-micropores by using inorganic eutectic salt, and the specific process flow is shown in fig. 1.

Referring to fig. 1, the inorganic eutectic salt and the ceramic powder are mixed and added into a solvent, and a better uniformity than a dry powder mixing can be obtained by wet molding. The mixture was uniformly dispersed by stirring. The inorganic co-molten salt includes but is not limited to NaCl, KCl, BaCl₂、CaCl₂、KNO₃、NaNO₂At least two of them. The inorganic eutectic salt does not use sulfate to prevent the inorganic eutectic salt from forming precipitates with certain cations in the ceramic powder.

In an alternative embodiment, the inorganic eutectic salt may be a (45 wt% NaCl +55 wt% KCl) mixture, (80 wt% BaCl)₂+ 20% by weight NaCl) mixture, (50% by weight BaCl₂+ 50% by weight NaCl mixture, (50% by weight KNO)₃+50wt％NaNO₂) Mixture, (30% wtKCl +20 wt% NaCl +50 wt% BaCl)₂) Mixture and (21% NaCl + 31% BaCl)₂+48％CaCl₂) One or more of the mixtures. The eutectic temperature of the inorganic eutectic salt is between the drying temperature of the ceramic powder and the sintering temperature of the ceramic powder, and is preferably 140-800 ℃.

The ceramic powder includes, but is not limited to, at least one of alumina, zirconia, silicon carbide, silicon nitride, titanium nitride, and aluminum nitride. Wherein the mass of the inorganic eutectic salt is 1-20% of the ceramic powder, preferably 5-10%. If the content of the inorganic eutectic salt is too high, the sintering property is damaged, and the sintering molding is not easy to realize; and if the content of the inorganic eutectic salt is too low, the pore-forming effect is not obvious.

The solvent is preferably one that does not dissolve the inorganic eutectic salt, including but not limited to, alcohols and butanone, for example, to avoid dissolving the inorganic salt with the solvent. The stirring method is not limited, and may be, for example, mechanical stirring. In an alternative embodiment, the stirring time may be 0.5-2 hours and the mechanical stirring speed may be 100-300 rpm.

And drying and sieving the obtained mixed slurry, and then forming to obtain the porous ceramic biscuit. The drying temperature is lower than the eutectic temperature of the eutectic inorganic substance, so that the phenomenon that the inorganic eutectic salt is melted without sintering and loses the pore-forming effect can be avoided. In alternative embodiments, the drying temperature may be 100-120 ℃ and the drying time may be 12-24 hours. The forming method may be dry press forming and/or isostatic press forming. Wherein, the dry pressing forming pressure can be 10-30MPa, and the isostatic pressure can be 50-200 MPa. In the above molding process, the pressure holding time may be 2 to 10 minutes.

Sintering the porous ceramic biscuit to obtain the porous ceramic with uniformly distributed submicron pores. The sintering environment can be air or atmosphere environments such as vacuum, nitrogen and argon. In some embodiments, the sintering temperature is higher than the eutectic temperature of the inorganic eutectic salt, and the sintering temperature may be 1300-. The sintering heat preservation time can be 1-3 hours.

The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art may be made in light of the above teachings. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.