CN114057477B

CN114057477B - Porous zirconium silicate prepared by dry method and preparation method thereof

Info

Publication number: CN114057477B
Application number: CN202111376324.1A
Authority: CN
Inventors: 姚润占
Original assignee: Guangzhou Shitao New Material Co ltd
Current assignee: Guangzhou Shitao New Material Co ltd
Priority date: 2021-11-19
Filing date: 2021-11-19
Publication date: 2022-09-09
Anticipated expiration: 2041-11-19
Also published as: CN114057477A

Abstract

The invention discloses a dry preparation method of porous zirconium silicate, which comprises the steps of fully mixing silicon dioxide aerogel, zirconium dioxide aerogel, silicon dioxide powder, zirconium dioxide powder and a pore-forming agent, then performing compression molding, then sintering at a high temperature, crushing and screening to obtain the porous zirconium silicate. The preparation method of the invention does not need to add water in the whole process and dry, saves a large amount of energy and manufacturing time, does not need to use chemical substances such as dispersing agents, binding agents and the like in the process of molding, and is more environment-friendly. The porous zirconium silicate prepared by the method has small-sized air holes and medium-sized air holes, and can respectively reduce the heat conduction and heat radiation of the porous zirconium silicate, so that the porous zirconium silicate has the advantages of light weight (small particle density), low heat conductivity, high service temperature and high infrared reflectivity.

Description

Porous zirconium silicate prepared by dry method and preparation method thereof

Technical Field

The invention relates to a preparation method of porous zirconium silicate and porous zirconium silicate prepared by the method, in particular to a dry method for preparing porous zirconium silicate without adding water in the whole process, and porous zirconium silicate with light weight, low thermal conductivity and high infrared reflection/scattering prepared by the method.

Background

Zirconium silicate has advantages of high melting point (2550 ℃), low thermal expansion rate, high chemical stability, etc., and has thermal conductivity (3.7W/(m.K) at 1000 ℃) similar to that of zirconium oxide. However, zirconium silicate also has two distinct disadvantages: first, albeit with zirconia (5.9 g/cm) ³ ) In contrast, zirconium silicate (4.7 g/cm) ³ ) Has a lower true density, but is like mullite (3.0 g/cm) with common refractories ³ ) Cordierite (2.6 g/cm) ³ ) The particle density of the light refractory material is influenced by the fact that the particle density is too high compared with the true density; second, the thermal conductivity of zirconium silicate is about the same as that of zirconia, but is generally equal to that of light-weight refractory bricks (thermal conductivity of 0.3 g/cm) ³ ) In contrast, there is a gap of nearly ten times. Therefore, it is necessary to develop a zirconium silicate product with low particle density and low thermal conductivity.

In order to realize low thermal conductivity, the patent CN110357117A discloses a chemical method to control the particle size of zirconium silicate to reach submicron level, and the thermal conductivity of zirconium silicate at 400 ℃ is reduced to 0.15W/(m · K), which is substantially one tenth of that of common zirconium silicate. However, this method uses a large amount of acidic substances, organic solvents, surfactants, mineralizers, etc., and if mass production is performed, it has no small influence on the environment. In addition, because the zirconia prepared by the method is in a submicron grade, small particle groups tend to agglomerate and crystallize into large particles when the zirconia is used at a high temperature, and finally the thermal conductivity of the zirconia becomes almost the same as that of common zirconium silicate.

In order to reduce the particle density, the porosity of the powder particles is generally increased by blending a base material and a pore-forming agent. Patent CN111533531A discloses a method for preparing porous mullite by blending, freeze-drying and sintering bacterial cellulose hydrogel and powder particles. The pore diameter of the mullite prepared by the method is 20-200 mu m, and the method is not very helpful for improving the thermal conductivity of the material. Patent CN102557722A discloses a method for co-firing silicon carbide powder and phenolic resin by blending, which successfully obtains a silicon carbide ceramic forming body with 70% porosity. Although the method reduces the overall particle density of the silicon carbide ceramic formed body, the thermal conductivity is reduced to a certain extent. However, the method does not further obtain porous silicon carbide powder, and does not correspondingly study the relationship among the porosity, the pore size and the thermal conductivity.

At present, the preparation of porous zirconium silicate generally adopts silicon dioxide, zirconium dioxide, water and a dispersing agent to be mixed, then a pore-forming agent and a bonding agent are added, and the mixture is added into a mould to be molded, dried, sintered and the like. Therefore, research on a preparation method of porous zirconium silicate which is more energy-saving and environment-friendly and has low particle density and low thermal conductivity is needed.

Disclosure of Invention

The present invention has been made to overcome the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide a method for preparing porous zirconium silicate without adding water in the whole process, saving energy and manufacturing time, and without using chemical substances such as a dispersant, a binder, etc., and to provide porous zirconium silicate prepared by the method, which has advantages of light weight, low thermal conductivity, and high infrared reflection/scattering.

In order to achieve the purpose, the invention adopts the technical scheme that: a dry preparation method of porous zirconium silicate comprises the following steps:

(1) weighing silicon dioxide and zirconium dioxide, wherein the silicon dioxide comprises silicon dioxide powder and silicon dioxide aerogel, and the zirconium dioxide comprises zirconium dioxide powder and zirconium dioxide aerogel;

(2) mixing the silicon dioxide and zirconium dioxide weighed in the step (1) with a pore-forming agent to obtain a mixture for forming;

(3) pouring the mixture for forming in the step (2) into a mould for compression forming to obtain a formed body;

(4) sintering the formed body obtained in the step (3) to obtain a porous zirconium silicate sintered body;

(5) and (4) crushing, finely grinding and screening the porous zirconium silicate sintered body obtained in the step (4) to obtain the porous zirconium silicate.

In the dry preparation method of porous zirconium silicate according to the present invention, silica aerogel and zirconia aerogel among them are used as fluidity imparting materials. The silica aerogel/zirconia aerogel (fluidity imparting material) is mostly characterized by a small size, which is in the nanometer level, and thus has a large specific surface area. In addition, the volumes of the silicon dioxide aerogel and the zirconium dioxide aerogel are very large, and the silicon dioxide aerogel and the zirconium dioxide aerogel can be embedded among particles of powder aggregates after being mixed with common powder, so that the silicon dioxide aerogel and the zirconium dioxide aerogel serve as dispersing agents, the volume of the powder raw materials is increased, the silicon dioxide aerogel and the zirconium dioxide aerogel have the same fluidity as that of added water, and the powder raw materials can be directly formed by dry pressing. As a preferable embodiment of the dry preparation method of the porous zirconium silicate, the sum of the mass of the silica aerogel and the zirconia aerogel is 1-100% of the total mass of the silica and the zirconia, and the sum of the mass of the silica powder and the zirconia powder is 0-99% of the total mass of the silica and the zirconia. The inventors of the present invention found in experiments that if silica aerogel and zirconia aerogel are used in an amount of less than 1% by mass of the total mass of the silica and zirconia, the fluidity of the mixture for molding after mixing is poor, press molding is difficult, or a molded body risks being disintegrated during sintering, and eventually, it is impossible to sinter the molded body into a zirconium silicate sintered body. On the other hand, silica aerogel and zirconia have higher unit prices than ordinary silica powder and zirconia powder, and if the use ratio is too high, the production cost is affected.

As a more preferable embodiment of the dry preparation method of the porous zirconium silicate, the sum of the mass of the silica aerogel and the mass of the zirconium dioxide aerogel is 10-30% of the total mass of the silica and the zirconium dioxide.

The inventor of the application finds out through experiments that when the mass sum of the silicon dioxide aerogel and the zirconium dioxide aerogel is 10-30% of the total mass of the silicon dioxide and the zirconium dioxide, the production cost can be reduced to the greatest extent on the premise of ensuring the flowability of the raw materials.

As a preferred embodiment of the dry preparation method of the porous zirconium silicate of the present invention, the center particle diameter D50 of the silica aerogel and the zirconium dioxide aerogel is less than 10 μm. In experiments, the inventors of the present invention found that if the center particle diameter D50 of the silica aerogel and the zirconia aerogel is larger than 10 μm, it is difficult to generate sufficient fluidity to the powder raw material, and finally, press molding cannot be performed.

As a more preferable embodiment of the dry preparation method of porous zirconium silicate of the present invention, the center particle diameter D50 of the silica aerogel and the zirconia aerogel is less than 1 μm. The inventors of the present application found that when the center particle diameter D50 of each of the silica aerogel and the zirconia aerogel is less than 1 μm, the characteristics of the fluidity imparting material can be further ensured.

As a preferred embodiment of the dry preparation method of porous zirconium silicate of the present invention, the mass of the silicon dioxide in the step (1) is 33% of the total mass of the silicon dioxide and the zirconium dioxide, and the mass of the zirconium dioxide is 67% of the total mass of the silicon dioxide and the zirconium dioxide. According to the chemical components of zirconium silicate, the mass ratio of silicon dioxide to zirconium dioxide is selected from the following components in percentage by mass: 67 percent. The mass ratio of each raw material was floated at 1% or more in consideration of the influence of the purity of the raw material.

In a more preferred embodiment of the dry preparation method of porous zirconium silicate of the present invention, the purity of the silica aerogel, zirconia aerogel, silica powder, and zirconia powder is 99.5% or more. In experimental studies, the inventors of the present invention found that if the impurities in the silica aerogel, zirconia aerogel, silica powder and zirconia powder are too much, the ratio of the zirconium silicate main crystal phase in the powder after sintering is affected. In addition, impurities such as alkali metal group lower the crystallization temperature of zirconium silicate, and are not favorable for the formation of pores and the control of pore size during sintering.

As a preferred embodiment of the dry preparation method of the porous zirconium silicate, the diameter of the pore-forming agent in the step (2) is 0.1-1000 μm, and the addition amount of the pore-forming agent is 1-50% of the total mass of the silicon dioxide and the zirconium dioxide.

In the preparation method of the porous zirconium silicate, the number and the size of the open pores in the zirconium silicate forming body are controlled by controlling the size and the adding amount of the pore-forming agent added into the raw materials. In experimental studies, the inventors of the present invention have found that a pore-forming agent having a uniform size and a diameter of less than 0.1 μm causes pores generated during sintering to have an excessively small pore diameter, and that the small-sized apparent porosity of the porous zirconium silicate prepared by pulverization exceeds 50%, and the pore-forming agent occupies a proportion of the medium-sized apparent pores, thereby inhibiting the reduction in thermal conductivity. If the size of the pore-forming agent is larger than 1000 mu m, a large amount of gas is generated in the space occupied by the pore-forming agent in the sintering body during sintering, so that a channel with an overlarge pore diameter is formed in the sintering body, and the control of the number of large-sized pores in the zirconium silicate in the later period is not facilitated.

In the preparation method of the porous zirconium silicate, the addition amount of the pore-forming agent is 1-50% of the total mass of the silicon dioxide and the zirconium dioxide, and the inventor of the application finds that if the addition amount of the pore-forming agent is less than 1% of the total mass of the silicon dioxide and the zirconium dioxide, the apparent porosity of the finally prepared porous zirconium silicate is less than 5%. If the pore-forming agent is added in an amount of more than 50% by mass based on the total mass of the silica and zirconia, the moldability of the molding mixture becomes poor and it becomes difficult to obtain a molded article having a sufficient strength; the use of a large amount of pore-forming agents generates excessive gas during sintering, the large apparent pore ratio of the finally prepared porous zirconium silicate exceeds 30 percent, the strength of the porous zirconium silicate is reduced, and the further reduction of the thermal conductivity is hindered; and the use of excessive pore-forming agent makes the whole apparent porosity of the porous zirconium silicate exceed 80%.

As a more preferable embodiment of the dry preparation method of the porous zirconium silicate, the diameter of the pore-forming agent in the step (2) is 10-100 μm, and the addition amount of the pore-forming agent is 5-20% of the total mass of the silicon dioxide and the zirconium dioxide. In order to balance the production cost and reduce the proportion of large-scale air pores, the diameter of the pore-forming agent is preferably 10-100 μm. In order to balance the number of open pores and the low thermal conductivity of the porous zirconium silicate, the pore-forming agent is preferably added in an amount of 5 to 20% by mass based on the total mass of the silica and the zirconia.

As a preferable embodiment of the dry preparation method of porous zirconium silicate of the present invention, the pore-forming agent is at least one of acryl resin powder, polystyrene powder, phenolic resin, and polyvinyl alcohol. The pore-forming agent used in the present application is preferably one or more of acryl resin (PMMA) powder, Polystyrene (PS) powder, phenol resin, and polyvinyl alcohol (PVA), but is not limited to the above. The pore-forming agent slowly decomposes into gases during high temperature sintering, which cause microchannels of different diameters when the gases permeate out of the shaped body. Two requirements must be met for the selection of the type of pore former: cannot be decomposed at too low a sintering temperature; the speed of decomposition cannot be too fast. If the material is decomposed at a relatively low temperature (100-200 ℃) or the decomposition speed is too high, the generation of the air holes, particularly small and medium-sized air holes, is not facilitated, and the material characteristics are influenced.

As a preferred embodiment of the dry preparation method of the porous zirconium silicate, the sintering temperature in the step (4) is 1300-1600 ℃, and the sintering time is 2-10 hours. The inventors of the present application found in experiments that if the sintering temperature is lower than 1300 ℃, the zirconium silicate crystal phase cannot be formed; if the sintering temperature exceeds 1600 ℃, the final apparent porosity and apparent pore size are affected due to further crystallization of zirconium silicate crystals. As a more preferable embodiment of the method for preparing porous zirconium silicate of the present invention, the sintering temperature is preferably 1400 to 1500 ℃ in order to ensure the formation of the zirconium silicate crystal phase and the state of the open pores.

In the preparation method of the porous zirconium silicate, crushing equipment is generally adopted in the step (5) for crushing, crushing and fine grinding to obtain the porous zirconium silicate with different sizes. Then, the obtained porous zirconium silicate is screened by sieves with different pore diameters, so that the porous zirconium silicate with the apparent porosity of 5-80% and the central particle size (D50) of 1-1000 mu m is obtained. The particle size of the sieved porous zirconium silicate has a certain relation with the ratio of large, medium and small-sized pores. Under the same preparation conditions, the larger the particle size of the porous zirconium silicate is, the larger the proportion of large-sized pores is. Under the optimized conditions, when the central particle size of the porous zirconium silicate exceeds 1000 μm, the proportion of large-sized pores exceeds 30%. In contrast, under the optimum conditions, if the central particle diameter of the porous zirconium silicate is less than 75 μm, the proportion of large-sized pores in the obtained porous zirconium silicate is less than 5%. However, the smaller the center particle size is, the better. If the central particle size of the porous zirconium silicate is less than 1 μm, the proportion of the small-sized apparent pores exceeds 50%, and the small-sized apparent pores occupy the proportion of the medium-sized pores, so that the blocking effect of the porous zirconium silicate on infrared heat radiation is influenced, and the thermal conductivity of the porous zirconium silicate at high temperature is improved. In order to reduce the occupation ratio of the large-sized pores, increase the occupation ratio of the medium-sized pores, and control the occupation ratio of the small-sized pores, the central particle size value of the porous zirconium silicate after screening is preferably 25 μm to 75 μm.

Meanwhile, the porous zirconium silicate prepared by the porous zirconium silicate dry preparation method has the apparent porosity of 5-80% and the central particle size value D50 of 1-1000 μm.

As a preferred embodiment of the porous zirconium silicate of the present invention, the porous zirconium silicate comprises the following three kinds of open pores: small-sized pores with a diameter of less than 0.7 μm, medium-sized pores with a diameter of 0.7 to 10 μm, and large-sized pores with a diameter of more than 10 μm.

In solids, heat transfer is primarily achieved by thermal conduction and radiation, and thermal convection contributes very little to heat transfer in solids and is therefore outside the scope of the present invention.

In solids, heat transfer is primarily achieved by the vibration of solid atoms. And quasi-particles that measure the collective vibrations of atoms are called phonons. In solids, heat transfer is achieved by continuous, linear collisions between phonons from the hot end to the cold end. Generally, in the crystal, if crystal boundaries, defects or impurities exist, the collision of phonons can be influenced, the phonon mean free path is increased, and further, the heat transfer is slowed down, namely, the generation of heat resistance. The means of increasing the phonon mean free path by external means is generally referred to as phonon scattering. For the same crystal, the mean free path of phonons decreases with increasing temperature. For a typical refractory material, the heat loss at medium and low temperatures is mainly due to heat transfer, and the heat transfer at medium and high temperatures is mainly due to heat radiation. At medium and low temperatures, the phonon mean free path of common solids is generally between 0.01 and 0.7 μm. If defects such as air holes with the size similar to the mean free path of phonons are added into the solid, phonon scattering can be effectively generated, the thermal resistance of the solid is increased, and the thermal conductivity is reduced. Therefore, we define the microscopic pores smaller than 0.7 μm that can enhance phonon scattering as small microscopic pores.

According to planck's law, if the characteristic size of the emitting object is slightly smaller than the length of the temperature corresponding to the infrared wavelength, the amount of heat transferred due to heat radiation is greatly reduced. Therefore, if the size of the pores of the porous zirconium silicate is slightly smaller than the wavelength of the infrared radiation at the temperature, the heat loss due to the heat radiation can be reduced, and the thermal conductivity can be reduced. Generally, the heat loss of the refractory material due to heat radiation is dominant from 300 ℃, while the maximum service temperature of zirconium silicate is 2250 ℃, and if it exceeds 2250 ℃, liquid phase may be generated to affect the service. In the interval of 300-2250 deg.c, the corresponding infrared radiation has a central wavelength of 1.3-10 microns according to the wien's displacement law. Therefore, the mesoscale pores are defined as the pores having a size of 0.7 μm to 10 μm which can reduce infrared radiation.

For open pores larger than 10 μm, neither phonon scattering can be increased to reduce thermal conduction nor infrared radiation can be reduced. If the proportion of the apparent pores larger than 10 μm is too large, the proportion of the medium-sized and small-sized apparent pores is squeezed, and the strength of the porous zirconium silicate particles is also affected. We define the microscopic pores larger than 10 μm that do not play any role as large microscopic pores.

In a more preferred embodiment of the porous zirconium silicate of the present invention, in the porous zirconium silicate, the number of small-sized pores accounts for 10 to 50% of the total number of pores, the number of medium-sized pores accounts for 20 to 70% of the total number of pores, and the number of large-sized pores accounts for 0 to 30% of the total number of pores; and the sum of the number of the small-sized air holes and the number of the medium-sized air holes accounts for 70-100% of the number of all the air holes.

In experimental research, the inventor of the present application finds that the thermal conductivity of porous zirconium silicate used at high temperature can be effectively reduced by controlling the pore size distribution of the pores in the porous zirconium silicate, namely, increasing the proportion of the medium-sized pores, adjusting the proportion of the small-sized pores, and reducing or eliminating the proportion of the large-sized pores.

In a preferred embodiment of the porous zirconium silicate of the present invention, the porous zirconium silicate has a central particle size value D50 of 25 to 75 μm. Under the same preparation conditions, the larger the particle size of the porous zirconium silicate, the larger the proportion of large-sized pores. Under the optimized condition, when the central particle size of the porous zirconium silicate exceeds 1000 μm, the proportion of large-sized pores exceeds 30%. In contrast, if the central particle size of the porous zirconium silicate is less than 75 μm under the optimum conditions, the proportion of large pores of the obtained porous zirconium silicate is less than 5%. However, the smaller the center particle size, the better. If the central grain diameter of the porous zirconium silicate is less than 1 mu m, the proportion of the small-sized apparent pores exceeds 50 percent, and the small-sized apparent pores occupy the proportion of the medium-sized pores, so that the blocking effect of the porous zirconium silicate on infrared heat radiation is influenced, and the heat conductivity of the porous zirconium silicate at high temperature is improved. In order to reduce the occupation ratio of the large-sized pores, increase the occupation ratio of the medium-sized pores, and control the occupation ratio of the small-sized pores, the central particle size value of the porous zirconium silicate after screening is preferably 25 μm to 75 μm.

Preference as to the porous zirconium silicate of the inventionIn one embodiment, the porous zirconium silicate has a particle density of 0.9 to 4.5g/cm ³ (ii) a The thermal conductivity of the porous zirconium silicate at 1000 ℃ is 0.3-3.0W/(m.K); the maximum service temperature of the porous zirconium silicate is 1600 ℃.

The particle density of the porous zirconium silicate is 0.9-4.5 g/cm ³ . When the apparent porosity of the porous zirconium silicate was 5%, the particle density was 4.5g/cm ³ (ii) a When the apparent porosity of the porous zirconium silicate was 80%, the particle density was 0.9g/cm ³ . In the same case (the large, medium and small pore sizes have the same ratio), the higher the apparent porosity is, the lower the particle density of the porous zirconium silicate is and the lower the thermal conductivity is. Therefore, in a more preferred embodiment of the porous zirconium silicate of the present invention, the porous zirconium silicate has a particle density of 0.9 to 2.5g/cm ³ 。

The porous zirconium silicate of the present invention has a thermal conductivity of 0.3 to 3.0W/(mK) at 1000 ℃. The thermal conductivity of the porous zirconium silicate is related to the apparent porosity and the ratio of large, medium and small-sized apparent pores. When the apparent porosity was 80%, the small-sized apparent porosity was 30%, the medium-sized apparent porosity was 70%, and the large-sized apparent porosity was 0%, the thermal conductivity of the porous zirconium silicate was 0.3W/(mK). When the apparent porosity was 5%, the small-sized apparent porosity was 50%, the medium-sized apparent porosity was 20%, and the large-sized apparent porosity was 30%, the thermal conductivity of the porous zirconium silicate was 3.0W/(mK). In a more preferred embodiment of the porous zirconium silicate of the present invention, the thermal conductivity of the porous zirconium silicate of the present invention at 1000 ℃ is preferably 0.3 to 1.0W/(m · K) in order to exhibit the properties of the material itself.

The maximum service temperature of the porous zirconium silicate of the invention is 1600 ℃. If the use temperature exceeds 1600 ℃, the total apparent porosity and the ratio of large, medium and small-sized apparent pores are changed due to further crystallization of zirconium silicate at high temperature, thereby affecting the performance of the porous zirconium silicate.

According to the dry preparation method of the porous zirconium silicate, silicon dioxide aerogel, zirconium dioxide aerogel, silicon dioxide powder, zirconium dioxide powder and pore-forming agent are fully mixed and then pressed into a forming body. The molded body is sintered at a high temperature to form a sintered zirconium silicate body, and the sintered body is pulverized and sieved to obtain porous zirconium silicate. The preparation method of the porous zirconium silicate adopts a dry process, does not need to add water or dry in the whole process, saves a large amount of energy and manufacturing time, does not need to use chemical substances such as a dispersing agent, a bonding agent and the like in the process of forming, and is environment-friendly. Meanwhile, in the dry preparation method of the porous zirconium silicate, the number and the size of the open pores in the zirconium silicate forming body are controlled by controlling the size and the number of the pore-forming agent in the raw materials, and the particle size distribution can be controlled by screening the crushed zirconium silicate, so that the control of the proportion of large open pores, medium open pores and small open pores is realized. On the basis of accurately controlling the quantity of the integral porosity and the size of the apparent pores of the zirconium silicate, the particle density and the thermal conductivity of the porous zirconium silicate can be well controlled, and the purpose of remarkably reducing the particle density and the thermal conductivity of the porous zirconium silicate is achieved.

The porous zirconium silicate prepared by the dry preparation method has reasonable total amount of the apparent pores and the occupation ratio of large, medium and small apparent pores, wherein the small apparent pores and the medium apparent pores can respectively reduce heat conduction and heat radiation, so that the heat conductivity of the porous zirconium silicate is as low as 0.3W/(m.K) at 1000 ℃, and the heat conductivity is greatly reduced compared with that of common zirconium silicate. And the reflectivity of the porous zirconium silicate in a visible light-near infrared region is up to more than 93 percent, and if the porous zirconium silicate is added into a refractory material, the porous zirconium silicate can play a role in enhancing infrared reflection and scattering, so that the heat-insulating and energy-saving performance of the refractory material is further improved. The porous zirconium silicate provided by the invention has the advantages of light weight (small particle density), low thermal conductivity, high service temperature and high infrared reflectivity.

Detailed Description

To better illustrate the objects, technical solutions and advantages of the present invention, the present invention will be further described with reference to specific examples.

The starting materials used in the following examples of the present invention are either directly commercially available or prepared according to conventional methods in the art, unless otherwise specified.

Example 1

In an embodiment of the porous zirconium silicate of the present invention, the porous zirconium silicate is prepared by a dry method as follows:

(1) weighing the following silicon dioxide powder, silicon dioxide aerogel, zirconium dioxide powder and zirconium dioxide aerogel in parts by weight: 32.5 parts of silicon dioxide powder, 0.5 part of silicon dioxide aerogel, 66.5 parts of zirconium dioxide powder and 0.5 part of zirconium dioxide aerogel; the central particle size D50 of the silicon dioxide aerogel and the zirconium dioxide aerogel is less than 10 mu m, and the purity of the silicon dioxide aerogel, the purity of the zirconium dioxide aerogel, the purity of the silicon dioxide powder and the purity of the zirconium dioxide powder are all more than 99.5%;

(2) mixing the silicon dioxide and the zirconium dioxide weighed in the step (1) with a pore-forming agent (polystyrene (PS) powder) to obtain a mixture for molding; the diameter of the pore-forming agent is 200 mu m, and the addition amount of the pore-forming agent is 15 percent of the total mass of the silicon dioxide and the zirconium dioxide;

(4) sintering the formed body obtained in the step (3) at the sintering temperature of 1350 ℃ for 6.5 hours to obtain a porous zirconium silicate sintered body;

(5) and (5) crushing, finely grinding and screening the porous zirconium silicate sintered body obtained in the step (4), and screening out the porous zirconium silicate with the central particle size value D50 of 70 microns to obtain the porous zirconium silicate of the embodiment.

Example 2

(1) weighing the following silicon dioxide powder, silicon dioxide aerogel, zirconium dioxide powder and zirconium dioxide aerogel in parts by weight: 0 part of silicon dioxide powder, 33 parts of silicon dioxide aerogel, 0 part of zirconium dioxide powder and 67 parts of zirconium dioxide aerogel; the central particle size D50 of the silicon dioxide aerogel and the zirconium dioxide aerogel is less than 10 mu m, and the purity of the silicon dioxide aerogel, the purity of the zirconium dioxide aerogel, the purity of the silicon dioxide powder and the purity of the zirconium dioxide powder are all more than 99.5%;

(2) mixing the silicon dioxide and zirconium dioxide weighed in the step (1) with a pore-forming agent (polyvinyl alcohol (PVA)) to obtain a mixture for forming; the diameter of the pore-forming agent is 1 mu m, and the addition amount of the pore-forming agent is 47 percent of the total mass of the silicon dioxide and the zirconium dioxide;

(4) sintering the formed body obtained in the step (3) at the sintering temperature of 1450 ℃ for 3.5h to obtain a porous zirconium silicate sintered body;

(5) and (4) crushing, finely grinding and screening the porous zirconium silicate sintered body obtained in the step (4), and screening out the porous zirconium silicate with the central particle size value D50 of 2 microns to obtain the porous zirconium silicate of the embodiment.

Example 3

(1) weighing the following silicon dioxide powder, silicon dioxide aerogel, zirconium dioxide powder and zirconium dioxide aerogel in parts by weight: 30 parts of silicon dioxide powder, 3 parts of silicon dioxide aerogel, 50 parts of zirconium dioxide powder and 17 parts of zirconium dioxide aerogel; the central particle size D50 of the silicon dioxide aerogel and the zirconium dioxide aerogel is less than 10 mu m, and the purity of the silicon dioxide aerogel, the purity of the zirconium dioxide aerogel, the purity of the silicon dioxide powder and the purity of the zirconium dioxide powder are all more than 99.5%;

(2) mixing the silicon dioxide and zirconium dioxide weighed in the step (1) with a pore-forming agent (phenolic resin) to obtain a mixture for forming; the diameter of the pore-forming agent is 50 mu m, and the addition amount of the pore-forming agent is 13 percent of the total mass of the silicon dioxide and the zirconium dioxide;

(3) pouring the mixture for forming in the step (2) into a mould for compression forming to obtain a forming body;

(4) sintering the formed body obtained in the step (3) at 1550 ℃ for 4.0h to obtain a porous zirconium silicate sintered body;

(5) and (5) crushing, finely grinding and screening the porous zirconium silicate sintered body obtained in the step (4), and screening out the porous zirconium silicate with the central particle size value D50 of 45 microns to obtain the porous zirconium silicate of the embodiment.

Example 4

(1) weighing the following silicon dioxide powder, silicon dioxide aerogel, zirconium dioxide powder and zirconium dioxide aerogel in parts by weight: 30 parts of silicon dioxide powder, 3 parts of silicon dioxide aerogel, 63 parts of zirconium dioxide powder and 4 parts of zirconium dioxide aerogel; the central particle size D50 of the silicon dioxide aerogel and the zirconium dioxide aerogel is less than 10 mu m, and the purity of the silicon dioxide aerogel, the purity of the zirconium dioxide aerogel, the purity of the silicon dioxide powder and the purity of the zirconium dioxide powder are all more than 99.5%;

(2) mixing the silicon dioxide and the zirconium dioxide weighed in the step (1) with a pore-forming agent (polyvinyl alcohol (PVA)) to obtain a mixture for forming; the diameter of the pore-forming agent is 0.1 mu m, and the addition amount of the pore-forming agent is 50 percent of the total mass of the silicon dioxide and the zirconium dioxide;

(4) sintering the formed body obtained in the step (3) at the sintering temperature of 1400 ℃ for 2.0h to obtain a porous zirconium silicate sintered body;

(5) and (4) crushing, finely grinding and screening the porous zirconium silicate sintered body obtained in the step (4), and screening out the porous zirconium silicate with the central particle size value D50 of 1 mu m to obtain the porous zirconium silicate of the embodiment.

Example 5

In an embodiment of the present invention, the porous zirconium silicate is prepared by a dry method as follows:

(1) weighing the following silicon dioxide powder, silicon dioxide aerogel, zirconium dioxide powder and zirconium dioxide aerogel in parts by weight: 26 parts of silicon dioxide powder, 7 parts of silicon dioxide aerogel, 59 parts of zirconium dioxide powder and 8 parts of zirconium dioxide aerogel; the central particle size D50 of the silicon dioxide aerogel and the zirconium dioxide aerogel is less than 10 mu m, and the purity of the silicon dioxide aerogel, the purity of the zirconium dioxide aerogel, the purity of the silicon dioxide powder and the purity of the zirconium dioxide powder are all more than 99.5%;

(2) mixing the silicon dioxide and zirconium dioxide weighed in the step (1) with a pore-forming agent (polystyrene (PS) powder) to obtain a mixture for forming; the diameter of the pore-forming agent is 1000 mu m, and the addition amount of the pore-forming agent is 1 percent of the total mass of the silicon dioxide and the zirconium dioxide;

(4) sintering the formed body obtained in the step (3) at the sintering temperature of 1500 ℃ for 10h to obtain a porous zirconium silicate sintered body;

(5) and (4) crushing, finely grinding and screening the porous zirconium silicate sintered body obtained in the step (4), and screening out the porous zirconium silicate with the central particle size value D50 of 1000 microns to obtain the porous zirconium silicate of the embodiment.

Example 6

(1) weighing the following silicon dioxide powder, silicon dioxide aerogel, zirconium dioxide powder and zirconium dioxide aerogel in parts by weight: 21 parts of silicon dioxide powder, 12 parts of silicon dioxide aerogel, 50 parts of zirconium dioxide powder and 17 parts of zirconium dioxide aerogel; the central particle size D50 of the silicon dioxide aerogel and the zirconium dioxide aerogel is less than 10 mu m, and the purity of the silicon dioxide aerogel, the purity of the zirconium dioxide aerogel, the purity of the silicon dioxide powder and the purity of the zirconium dioxide powder are all more than 99.5%;

(2) mixing the silicon dioxide and zirconium dioxide weighed in the step (1) with a pore-forming agent (phenolic resin) to obtain a mixture for forming; the diameter of the pore-forming agent is 45 mu m, and the addition amount of the pore-forming agent is 20 percent of the total mass of the silicon dioxide and the zirconium dioxide;

(4) sintering the formed body obtained in the step (3) at 1600 ℃ for 3h to obtain a porous zirconium silicate sintered body;

(5) and (4) crushing, finely grinding and screening the porous zirconium silicate sintered body obtained in the step (4), and screening out the porous zirconium silicate with the central particle size value D50 of 500 mu m to obtain the porous zirconium silicate of the embodiment.

Example 7

(1) weighing the following silicon dioxide powder, silicon dioxide aerogel, zirconium dioxide powder and zirconium dioxide aerogel in parts by weight: 14 parts of silicon dioxide powder, 19 parts of silicon dioxide aerogel, 40 parts of zirconium dioxide powder and 27 parts of zirconium dioxide aerogel; the central particle size D50 of the silicon dioxide aerogel and the zirconium dioxide aerogel is less than 10 mu m, and the purity of the silicon dioxide aerogel, the purity of the zirconium dioxide aerogel, the purity of the silicon dioxide powder and the purity of the zirconium dioxide powder are all more than 99.5%;

(2) mixing the silicon dioxide and zirconium dioxide weighed in the step (1) with a pore-forming agent (polyvinyl alcohol (PVA)) to obtain a mixture for forming; the diameter of the pore-forming agent is 30 mu m, and the addition amount of the pore-forming agent is 35 percent of the total mass of the silicon dioxide and the zirconium dioxide;

(4) sintering the formed body obtained in the step (3) at 1300 ℃ for 4.5h to obtain a porous zirconium silicate sintered body;

(5) and (5) crushing, finely grinding and screening the porous zirconium silicate sintered body obtained in the step (4), and screening out the porous zirconium silicate with the central particle size value D50 of 75 microns to obtain the porous zirconium silicate of the embodiment.

Example 8

(1) weighing the following silicon dioxide powder, silicon dioxide aerogel, zirconium dioxide powder and zirconium dioxide aerogel in parts by weight: 11 parts of silicon dioxide powder, 22 parts of silicon dioxide aerogel, 60 parts of zirconium dioxide powder and 6 parts of zirconium dioxide aerogel; the central particle size D50 of the silicon dioxide aerogel and the zirconium dioxide aerogel is less than 10 mu m, and the purity of the silicon dioxide aerogel, the purity of the zirconium dioxide aerogel, the purity of the silicon dioxide powder and the purity of the zirconium dioxide powder are all more than 99.5%;

(2) mixing the silicon dioxide and zirconium dioxide weighed in the step (1) with a pore-forming agent (polystyrene (PS) powder) to obtain a mixture for forming; the diameter of the pore-forming agent is 50 mu m, and the addition amount of the pore-forming agent is 50 percent of the total mass of the silicon dioxide and the zirconium dioxide;

(4) sintering the formed body obtained in the step (3) at the sintering temperature of 1500 ℃ for 5.5 hours to obtain a porous zirconium silicate sintered body;

(5) and (4) crushing, finely grinding and screening the porous zirconium silicate sintered body obtained in the step (4), and screening out the porous zirconium silicate with the central particle size value D50 of 20 microns to obtain the porous zirconium silicate of the embodiment.

Example 9

(1) weighing the following silicon dioxide powder, silicon dioxide aerogel, zirconium dioxide powder and zirconium dioxide aerogel in parts by weight: 27 parts of silicon dioxide powder, 6 parts of silicon dioxide aerogel, 63 parts of zirconium dioxide powder and 3 parts of zirconium dioxide aerogel; the central particle size D50 of the silicon dioxide aerogel and the zirconium dioxide aerogel is less than 10 mu m, and the purity of the silicon dioxide aerogel, the purity of the zirconium dioxide aerogel, the purity of the silicon dioxide powder and the purity of the zirconium dioxide powder are all more than 99.5%;

(2) mixing the silicon dioxide and the zirconium dioxide weighed in the step (1) with a pore-forming agent (acrylic resin (PMMA) powder) to obtain a mixture for molding; the diameter of the pore-forming agent is 1 mu m, and the addition amount of the pore-forming agent is 1 percent of the total mass of the silicon dioxide and the zirconium dioxide;

(4) sintering the formed body obtained in the step (3) at the sintering temperature of 1400 ℃ for 2.5 hours to obtain a porous zirconium silicate sintered body;

(5) and (4) crushing, finely grinding and screening the porous zirconium silicate sintered body obtained in the step (4), and screening out the porous zirconium silicate with the central particle size value D50 of 15 microns to obtain the porous zirconium silicate of the embodiment.

Example 10

Performance testing of the porous zirconium silicate of the invention

In the present embodiment, test groups 1 to 9 and control groups 1 to 9 are provided, the porous zirconium silicates of the test groups 1 to 9 are the porous zirconium silicates described in the above embodiments 1 to 9, respectively, and the porous zirconium silicates of the control groups 1 to 9 are as follows:

in the preparation process of the porous zirconium silicate of the control group 1, the raw materials and the preparation method are the same as those of the example 1 except that the compositions of zirconium dioxide are different; in the preparation of the porous zirconium silicate of control 1, zirconium dioxide comprises the following components in parts by weight: 67 parts of zirconium dioxide powder and 0 part of zirconium dioxide aerogel.

The preparation process of the porous zirconium silicate of the control group 2 is the same as that of the example 8 except that the pore-forming agent is different from that of the example 8; the pore-forming agent used in the preparation of the porous zirconium silicate of control group 2 was ammonium bicarbonate.

The preparation process of the porous zirconium silicate of the control group 3 is the same as that of the example 5 except that the diameter of the pore-forming agent is different from that of the example 5; the pore-forming agent used in the preparation of the porous zirconium silicate of control 3 had a diameter of 0.05 μm.

The preparation process of the porous zirconium silicate of the control group 4 was the same as that of example 7 except that the diameter of the pore-forming agent was different from that of example 7; the diameter of the pore-forming agent used in the preparation of the porous zirconium silicate of control 4 was 1100 μm.

The preparation process of the porous zirconium silicate of the control group 5 is the same as that of the example 6 except that the addition amount of the pore-forming agent is different from that of the example 6; the pore-forming agent used in the preparation of the porous zirconium silicate of the control group 5 was added in an amount of 0.5% of the total mass of the silica and zirconia.

The preparation process of the porous zirconium silicate of the control group 6 is the same as that of the example 9 except that the addition amount of the pore-forming agent is different from that of the example 9; the addition amount of the pore-forming agent adopted in the preparation process of the porous zirconium silicate of the control group 6 was 51% of the total mass of the silicon dioxide and the zirconium dioxide.

The preparation process of the porous zirconium silicate of the control group 7 was the same as that of example 3 except that the sintering temperature was different from that of example 3; the sintering temperature in the preparation of the porous zirconium silicate of control 7 was 1700 ℃.

In the preparation process of the porous zirconium silicate of the control group 8, the other raw materials and the preparation method are the same as those in example 4 except that the central particle size D50 of the porous zirconium silicate obtained by screening in the step (5) is different from that in example 4; the center particle diameter D50 of the zirconium silicate obtained by screening in step (5) in the production process of the porous zirconium silicate of control group 8 was 0.5 μm.

In the preparation process of the porous zirconium silicate of the control group 9, the other raw materials and the preparation method are the same as those in example 2 except that the central particle size D50 of the porous zirconium silicate obtained by screening in the step (5) is different from that in example 2; the center particle size D50 of the zirconium silicate obtained by screening in step (5) in the production process of the porous zirconium silicate of control 9 was 1050 μm.

The ratio of the total apparent porosity, the large, medium and small apparent porosity, the particle density and the thermal conductivity of the porous zirconium silicate in the test groups 1-9 and the control groups 1-9 are respectively tested as follows:

according to GB/T1966-2006 volume-weight test method for porous ceramic gas-developing rate, DXR porous ceramic gas-developing rate volume tester (Hunan Tan Gakko instruments manufacturing Co., Ltd.) is adopted to respectively measure the gas-developing rate and the ratio of large, medium and small-sized gas-developing holes of each group of the porous zirconium silicate.

According to the Archimedes principle, a porous ceramic density detector AU-1200VP (German Kostesquarrz) is adopted to respectively measure the effective volume of each group of porous zirconium silicate, and then the particle density of the powder is calculated according to the mass of the powder.

The thermal conductivity (at 1000 ℃ C.) of each group of the porous zirconium silicate was measured by LFA427 type laser thermal conductivity measuring instrument of Germany Kastan instruments manufacturing Ltd.

The test results are shown in table 1.

TABLE 1 test results of the performance test of the porous zirconium silicate of the test group and the control group

As is clear from the results in Table 1, the porous zirconium silicate of test group 1 had a total apparent porosity of 33%, wherein the small apparent porosity was 28%, the medium apparent porosity was 68%, the large apparent porosity was 4%, and the particle density was 3.1g/cm ³ The thermal conductivity is 1.9W/(m.K), and the thermal conductivity basically reaches 50 percent of that of common zirconium silicate (3.7W/(m.K)).

In the preparation process of the porous zirconium silicate of the control group 1, the addition amounts of the silica aerogel and the zirconia aerogel account for 0.5% of the total mass of the silica and the zirconia, which is lower than the minimum content of 1% in the present application, and the mixture for molding after mixing has poor fluidity and is difficult to be pressed and molded in a mold, so that subsequent processes such as sintering and crushing cannot be completed, and the porous zirconium silicate powder cannot be obtained.

In control 2, the pore former was ammonium bicarbonate. Since ammonium bicarbonate has a low decomposition temperature and is completely decomposed at a low sintering temperature, and a minute gas channel cannot be formed when zirconium silicate is formed, the porous zirconium silicate after sintering has a total apparent porosity of 2% and a thermal conductivity of 3.7W/(m · k), and thus the weight reduction is not achieved and the thermal conductivity is not lowered.

In control 3, the pore former had a particle size of 0.05. mu.m. Since the pore former size used is smaller than the minimum pore former size described herein, the small apparent porosity of the porous zirconium silicate produced exceeds the maximum value (50%) described herein, directly resulting in a thermal conductivity value exceeding the maximum value (3.0W/(m.k)) described herein.

In the control group 4, since the pore-forming agent is larger in size than the maximum pore-forming agent of the present invention, the large apparent porosity of the prepared porous zirconium silicate exceeds the maximum value (30%) of the present invention, and since the pore-forming agent is too large in size, the effective weight of the pore-forming agent is smaller within the allowable input volume range of the present invention, so that the total apparent pore amount is lower than the minimum value of the present invention, and finally the thermal conductivity of the prepared porous zirconium silicate is higher than the maximum value (3.0W/(m · k)) of the present invention.

In the control 5, since the amount of the pore-forming agent added did not reach the minimum value (1%) required by the present invention, the porous zirconium silicate prepared had a low total apparent porosity, a high small apparent porosity, a low medium apparent porosity, and a particle density and a thermal conductivity that were not within the ranges required by the present invention.

In the control group 6, the input volume of the pore-forming agent is larger than the highest value (50%) required by the present invention, so the total apparent porosity of the prepared porous zirconium silicate is higher, the particle density is lower, which directly results in insufficient strength of the porous zirconium silicate, and the porous zirconium silicate is broken into smaller particles in actual use, which directly affects the occupation ratio of the medium apparent porosity, resulting in higher actual thermal conductivity.

In the control group 7, the sintering temperature of the dried molded article exceeded the maximum sintering temperature (1600 ℃) of the present invention, which caused the excessive crystallization of zirconium silicate crystals during sintering, and the micropores generated by the pore-forming agent disappeared, directly resulting in that the apparent porosity of the crushed zirconium silicate was 0, and it became the ordinary zirconium silicate rather than the porous zirconium silicate.

In the control group 8, the central particle size of the crushed zirconium silicate is 0.5 μm and is smaller than the minimum value (1 μm) of the central particle size of the porous zirconium silicate, so that the small-sized apparent pore proportion occupies the medium-sized apparent pore proportion, and the thermal conductivity of the porous zirconium silicate is improved.

In the control group 9, the central particle size of the porous zirconium silicate after pulverization was 1050 μm, which is larger than the maximum value (1000 μm) of the central particle size described in the present invention, directly resulting in that the large apparent porosity exceeded the maximum value (30%) described in the present invention, and the thermal conductivity of the porous zirconium silicate was improved.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A dry preparation method of porous zirconium silicate is characterized by comprising the following steps:

(5) crushing, finely grinding and screening the porous zirconium silicate sintered body obtained in the step (4) to obtain porous zirconium silicate;

the mass sum of the silicon dioxide aerogel and the zirconium dioxide aerogel is 1-100% of the total mass of the silicon dioxide and the zirconium dioxide, and the mass sum of the silicon dioxide powder and the zirconium dioxide powder is 0-99% of the total mass of the silicon dioxide and the zirconium dioxide;

the pore-forming agent is at least one of acrylic resin powder, polystyrene powder, phenolic resin and polyvinyl alcohol, the diameter of the pore-forming agent is 0.1-1000 mu m, and the addition amount of the pore-forming agent is 1-50% of the total mass of the silicon dioxide and the zirconium dioxide;

the sintering temperature in the step (4) is 1300-1600 ℃.

2. The dry preparation method of porous zirconium silicate according to claim 1, wherein the sum of the mass of the silica aerogel and the zirconia aerogel is 10 to 30% of the total mass of silica and zirconia.

3. The dry preparation method of porous zirconium silicate according to claim 1 or 2, wherein the silica aerogel and the zirconium dioxide aerogel have a center particle diameter D50 of less than 10 μm.

4. The dry preparation method of porous zirconium silicate according to claim 3, wherein the silica aerogel and the zirconium dioxide aerogel have a center particle diameter D50 of less than 1 μm.

5. The dry preparation method of porous zirconium silicate according to claim 1, wherein the mass of the silicon dioxide in the step (1) is 33% of the total mass of the silicon dioxide and the zirconium dioxide, and the mass of the zirconium dioxide is 67% of the total mass of the silicon dioxide and the zirconium dioxide; the purity of the silicon dioxide aerogel, the zirconium dioxide aerogel, the silicon dioxide powder and the zirconium dioxide powder is more than 99.5 percent.

6. The dry preparation method of porous zirconium silicate according to claim 1, wherein the diameter of the pore-forming agent in step (2) is 10 to 100 μm, and the addition amount of the pore-forming agent is 5 to 20% of the total mass of the silicon dioxide and the zirconium dioxide.

7. The dry preparation method of porous zirconium silicate according to claim 1, wherein the sintering time in the step (4) is 2 to 10 hours.

8. The porous zirconium silicate prepared by the dry preparation method of porous zirconium silicate according to any one of claims 1 to 7, wherein the porous zirconium silicate has an apparent porosity of 5 to 80% and a central particle size value D50 of 1 to 1000 μm.

9. The porous zirconium silicate of claim 8, comprising the following three open pores: small-sized air holes with the diameter less than 0.7 mu m, medium-sized air holes with the diameter between 0.7 mu m and 10 mu m and large-sized air holes with the diameter more than 10 mu m; in the porous zirconium silicate, the number of small-sized air holes accounts for 10-50% of the number of all air holes, the number of medium-sized air holes accounts for 20-70% of the number of all air holes, and the number of large-sized air holes accounts for 0-30% of the number of all air holes; and the sum of the number of the small-sized air holes and the medium-sized air holes accounts for 70-100% of the number of all the air holes.

10. The porous zirconium silicate of claim 8, wherein the porous zirconium silicate has a center particle size value D50 of 25 to 75 μ ι η; the particle density of the porous zirconium silicate is 0.9-4.5 g/cm ³ (ii) a The thermal conductivity of the porous zirconium silicate at 1000 ℃ is 0.3-3.0W/(m.K); the maximum service temperature of the porous zirconium silicate is 1600 ℃.