阅读说明：本技术 一种多孔陶瓷及其制备方法和应用 (Porous ceramic and preparation method and application thereof ) 是由 江品颐 杨伟强 徐述荣 于 2019-10-25 设计创作，主要内容包括：本发明涉及一种多孔陶瓷及其制备方法和应用,且该多孔陶瓷的制备方法包括：S1、将碳纤维进行第一次超声处理和第二次超声处理；S2、将超声处理后的碳纤维进行过滤,得到碳纤维坯体；S3、将碳纤维坯体进行蒸镀蜡处理,得到含蜡的碳纤维坯体；S4、将含蜡的碳纤维坯体置于陶瓷浆料中浸渍处理,然后氧气氛围下烧结,得到多孔陶瓷。最终烧结得到的多孔陶瓷的孔为圆孔,孔径均匀,抗弯强度高,利于提高多孔陶瓷的使用效果和使用寿命。(The invention relates to a porous ceramic and a preparation method and application thereof, and the preparation method of the porous ceramic comprises the following steps: s1, carrying out primary ultrasonic treatment and secondary ultrasonic treatment on the carbon fiber; s2, filtering the carbon fiber subjected to ultrasonic treatment to obtain a carbon fiber blank; s3, carrying out wax evaporation treatment on the carbon fiber blank to obtain a wax-containing carbon fiber blank; and S4, placing the carbon fiber blank containing the wax into the ceramic slurry for dipping treatment, and then sintering in an oxygen atmosphere to obtain the porous ceramic. The pores of the porous ceramic obtained by final sintering are round holes, the pore diameter is uniform, the bending strength is high, the use effect of the porous ceramic is favorably improved, and the service life of the porous ceramic is favorably prolonged.)

1. A preparation method of porous ceramics is characterized by comprising the following steps:

s1, carrying out primary ultrasonic treatment and secondary ultrasonic treatment on the carbon fiber;

s2, filtering the carbon fiber subjected to ultrasonic treatment to obtain a carbon fiber blank;

s3, carrying out wax evaporation treatment on the carbon fiber blank to obtain a wax-containing carbon fiber blank;

and S4, placing the carbon fiber blank containing the wax into the ceramic slurry for dipping treatment, and then sintering in an oxygen atmosphere to obtain the porous ceramic.

2. The method of claim 1, wherein the first sonication comprises mixing the carbon fibers with a first dispersant and water, and performing a first sonication;

the second ultrasonic treatment comprises the steps of mixing the carbon fiber subjected to the first ultrasonic treatment with a second dispersing agent and water, and then carrying out second ultrasonic treatment;

preferably, the power of the first ultrasonic is 20-22KW, and the ultrasonic time is 1-3 h; the power of the second ultrasonic is 20-22KW, and the ultrasonic time is 20-30 min.

3. The production method according to claim 2, wherein the carbon fiber has a diameter of 3 to 8 μm; the first dispersant is ammonium polymethacrylate and/or acrylic resin; the second dispersing agent is sodium carboxymethyl cellulose and/or sodium hydroxyethyl cellulose.

4. The method according to claim 1, wherein before step S1, the method further comprises subjecting the carbon fiber to an oxidation treatment;

the temperature of the oxidation treatment is 400-450 ℃, and the oxidation time is 1-3 h.

5. The production method according to claim 1, wherein the filtration in step S2 includes pouring the carbon fiber after the ultrasonic treatment into a mold for filtration;

the die comprises a groove, and holes which are uniformly distributed are formed in the bottom of the groove;

the diameter of the holes is 1.5mm-2.5mm, and the distance between adjacent holes is 3mm-4 mm.

6. The preparation method as claimed in claim 1, wherein the wax evaporation treatment comprises placing a support in a container containing wax, heating the container to 280-320 ℃, placing the carbon fiber blank on the support and sealing the container after the wax is completely melted, and performing wax evaporation treatment for 3-6 min.

7. The production method according to claim 1, wherein the wax is a microcrystalline wax;

the solid content of the ceramic slurry is 70-80%;

the ceramic is one or more of zirconia, alumina and mullite;

the time of the dipping treatment is 10-20 min;

the sintering temperature is 1420-1480 ℃ and the time is 2-4 h.

8. A porous ceramic produced by the production method according to any one of claims 1 to 7.

9. Use of the porous ceramic of claim 8 in electronic smoke atomizers, steel making slag filtration or catalyst supports.

Technical Field

The invention particularly relates to porous ceramic and a preparation method and application thereof.

Background

The porous ceramic is a novel ceramic material, has the characteristics of good permeability, high porosity, low density, high strength, corrosion resistance, good high-temperature stability and the like, and is widely applied to the fields of metallurgy, catalyst carriers, heat-insulating materials, sound absorption and noise reduction, electronic cigarette atomization and the like. However, when the pore-forming agent is used for pore-forming in general porous ceramics, the pore morphology is mostly similar to spherical or irregular, and the particle size difference between the pore-forming agents causes uneven distribution of the pore sizes of the sintered samples, so that the strength is low, and the application of the porous ceramics is limited to a certain extent.

Disclosure of Invention

The invention aims to overcome the problems in the prior art and provide a porous ceramic, a preparation method and application thereof.

The first aspect of the present invention provides a method for preparing a porous ceramic, comprising the steps of:

s1, carrying out primary ultrasonic treatment and secondary ultrasonic treatment on the carbon fiber;

s2, filtering the carbon fiber subjected to ultrasonic treatment to obtain a carbon fiber blank;

s3, carrying out wax evaporation treatment on the carbon fiber blank to obtain a wax-containing carbon fiber blank;

and S4, placing the carbon fiber blank containing the wax into the ceramic slurry for dipping treatment, and then sintering in an oxygen atmosphere to obtain the porous ceramic.

Preferably, the first ultrasonic treatment comprises mixing the carbon fiber with a first dispersant and water, and carrying out first ultrasonic treatment; the second ultrasonic treatment comprises the steps of mixing the carbon fiber subjected to the first ultrasonic treatment with a second dispersing agent and water, and then carrying out second ultrasonic treatment;

further preferably, the power of the first ultrasonic is 20-22KW, and the ultrasonic time is 1-3 h; the power of the second ultrasonic is 20-22KW, and the ultrasonic time is 20-30 min.

Preferably, the carbon fibers have a diameter of 3 to 8 μm; the first dispersant is ammonium polymethacrylate and/or acrylic resin; the second dispersing agent is sodium carboxymethyl cellulose and/or sodium hydroxyethyl cellulose.

Preferably, before the step S1, the method further includes oxidizing the carbon fiber; the temperature of the oxidation treatment is 400-450 ℃, and the oxidation time is 1-3 h.

Preferably, the filtering in step S2 includes pouring the carbon fiber after ultrasonic treatment into a mold for filtering; the die comprises a groove, and holes which are uniformly distributed are formed in the bottom of the groove; the diameter of the holes is 1.5mm-2.5mm, and the distance between adjacent holes is 3mm-4 mm.

Preferably, the wax evaporation treatment comprises the steps of placing a support in a container containing wax, heating the container to the temperature of 280-320 ℃, placing the carbon fiber blank on the support and sealing the container after the wax is completely melted, and carrying out wax evaporation treatment for 3-6 min.

Preferably, the wax is a microcrystalline wax; the solid content of the ceramic slurry is 70-80%; the ceramic is one or more of zirconia, alumina and mullite; the time of the dipping treatment is 10-20 min; the sintering temperature is 1420-1480 ℃ and the time is 2-4 h.

The second aspect of the present invention is to provide a porous ceramic prepared by the foregoing preparation method.

The third aspect of the invention provides an application of the porous ceramic in an electronic cigarette atomizer, steel-making waste residue filtration or a catalyst carrier.

In the preparation method of the porous ceramic, the carbon fiber is subjected to ultrasonic treatment twice, so that the carbon fiber is filamentized, and the porous ceramic with round holes and uniform pore diameter is favorably obtained; in addition, the carbon fiber blank is subjected to wax evaporation treatment, a hydrophobic layer is formed on the surface of the carbon fiber blank, the influence of surface tension after the ceramic slurry soaks the fibers is reduced in the soaking process, and the carbon fiber is beneficial to keeping the filamentation after the soaking is finished; and the capillary force of the carbon fiber blank in the subsequent process is reduced, so that the carbon fiber blank is not easy to crack, peel and the like, the pore diameter uniformity of the porous ceramic is improved, and the pore diameter is basically consistent with the diameter of the carbon fiber.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

Fig. 1 shows a fracture SEM image of the zirconia porous ceramic prepared in example 1.

Fig. 2 shows a fracture SEM image of the zirconia porous ceramic prepared in comparative example 3.

FIG. 3 shows a schematic view of a mold for filtering to form a carbon fiber blank according to one embodiment.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The invention also provides a preparation method of the porous ceramic, which comprises the following steps:

s1, carrying out primary ultrasonic treatment and secondary ultrasonic treatment on the carbon fiber;

s2, filtering the carbon fiber subjected to ultrasonic treatment to obtain a carbon fiber blank;

s3, carrying out wax evaporation treatment on the carbon fiber blank to obtain a wax-containing carbon fiber blank;

and S4, placing the carbon fiber blank containing the wax into the ceramic slurry for dipping treatment, and then sintering in an oxygen atmosphere to obtain the porous ceramic.

In the preparation method of the porous ceramic, the carbon fiber is subjected to ultrasonic treatment twice to make the carbon fiber monofilament, so that the porous ceramic with round holes and uniform pore diameter can be obtained; in addition, the carbon fiber blank is subjected to wax evaporation treatment, a hydrophobic layer is formed on the surface of the carbon fiber blank, the influence of surface tension after the ceramic slurry soaks the fibers is reduced in the soaking process, and the carbon fiber is beneficial to keeping the filamentation after the soaking is finished; and the capillary force of the carbon fiber blank in the subsequent process is reduced, so that the carbon fiber blank is not easy to crack, peel and the like, the pore diameter uniformity of the porous ceramic is improved, and the pore diameter is basically consistent with the diameter of the carbon fiber.

In the present invention, the carbon fiber may be a chopped carbon fiber or a continuous carbon fiber, and different diameters of the carbon fiber may be selected to prepare porous ceramics having different pore diameters, and preferably, the diameter of the carbon fiber is 3 to 8 μm.

In the present invention, the first ultrasonic treatment in step S1 includes mixing the carbon fibers with a first dispersant and water, and performing first ultrasonic treatment. Preferably, the first dispersant is ammonium polymethacrylate and/or acrylic resin. The first dispersing agent contains carboxyl, can react with hydroxyl on the surface of the carbon fiber, and the carboxyl and the hydroxyl react to generate lipid groups, and the carboxyl and the hydroxyl are firmly connected, so that the first dispersing agent cannot lose efficacy due to subsequent processes (such as filtration and drying), and can generate a synergistic effect with the second dispersing agent in the subsequent steps, and the dispersibility of the carbon fiber in water is further improved. Meanwhile, after the first dispersing agent acts with the carbon fibers, the charge quantity carried on the surfaces of the carbon fibers is increased, the charge repulsion force among the carbon fibers is increased, and the carbon fibers are favorably filamentized.

In the invention, in order to better promote the filamentation of the carbon fibers, the power of the first ultrasonic is preferably 20-22KW, and the ultrasonic time is preferably 1-3 h. In order to better promote the ultrasonic dispersion of the carbon fibers, the mass ratio of the carbon fibers to the water is preferably (1-3): 100, and the mass ratio of the first dispersing agent to the carbon fibers is preferably (2-3): 100.

In the invention, in order to remove the first dispersant which does not react with the surface of the carbon fiber in the liquid, preferably, the carbon fiber is subjected to first filtration after first ultrasonic treatment; the first filtration is carried out by using a filter screen. The filter is not limited, and any unreacted first dispersant may be removed. For example, 150 mesh screens may be used for filtration.

In the invention, in order to further improve the repulsive force between the carbon fibers and enable the carbon fibers to be better filamentized, the carbon fibers after the first ultrasonic treatment are mixed with a second dispersant and water, and then the second ultrasonic treatment is carried out. Preferably, the second dispersing agent is sodium carboxymethylcellulose or sodium hydroxyethyl cellulose, so that the viscosity of the aqueous solution can be increased, the anti-settling property of the carbon fibers in the aqueous solution is improved, and meanwhile, a molecular chain of the second dispersing agent and polar groups (such as hydroxyl, carboxyl and the like) on the surfaces of the carbon fibers generate hydrogen bonds, so that the surfaces of the carbon fibers are surrounded by the stretched molecular chain of the second dispersing agent, the repulsive force between the carbon fibers is improved, and the first dispersing agent generates a synergistic effect to promote the filamentation and the dispersion of the carbon fibers. Preferably, the power of the second ultrasonic is 20-22KW, and the ultrasonic time is 20-30 min. In order to ensure sufficient dispersion of the carbon fibers, it is preferable that the second ultrasonic treatment be performed while stirring. In order to better promote the ultrasonic dispersion of the carbon fibers, the mass ratio of the carbon fibers to the water is preferably (2-5): 1000, and the mass ratio of the second dispersing agent to the water is preferably (1-2): 1000.

In the present invention, before step S1, the method further includes oxidizing the carbon fibers to further promote the filamentation of the carbon fibers. Preferably, the temperature of the oxidation treatment is 400-450 ℃, and the oxidation time is 1-3 h. The oxidation treatment can remove sizing agent on the surface of the carbon fiber (it needs to be stated that the sizing agent is used for better bundling the monofilament fiber), so that the subsequent filamentation treatment of the carbon fiber is facilitated; and the oxidation treatment increases active groups on the surface of the carbon fiber, such as hydroxyl, carboxyl and the like, and the active groups can carry out esterification reaction with hydroxyl in a subsequently added dispersing agent or generate hydrogen bond action with polar groups in the dispersing agent, thereby achieving the effect of modifying the surface of the carbon fiber. After the oxidation treatment, the carbon fibers can be preferably cut to 2-3mm, so that the large-range 'lap joint' effect of the fiber materials in the liquid is reduced, and the carbon fibers are favorably and better dispersed in the liquid.

In step S2 of the present invention, the carbon fiber after ultrasonic treatment is filtered to obtain a carbon fiber blank. Preferably, the filtering in step S2 includes pouring the carbon fibers subjected to ultrasonic treatment into a mold for filtering, where the mold includes a groove, and the bottom of the groove is provided with uniformly distributed holes; thereby obtaining a carbon fiber blank by filtration. After the carbon fibers are subjected to ultrasonic treatment and filamentation, the carbon fibers are filtered to form a carbon fiber blank, so that the carbon fibers in the carbon fiber blank are not parallel and connected, and the pore diameter uniformity of the porous ceramic obtained by the subsequent process is improved. The holes of the mould can be designed according to actual requirements so as to obtain the required carbon fiber blank, for example, the diameter of the holes can be 1.5mm-2.5mm, and the distance between adjacent holes is 3mm-4 mm. In a particular embodiment, as shown in fig. 3, the die is used for filtration to form a carbon fiber blank, wherein the pores have a diameter of 2 mm.

In the present invention, in order to remove the excessive dispersant, preferably, the carbon fiber body formed by filtration may be washed with water for a time of 20 to 30 min. In order to facilitate the subsequent wax evaporation treatment of the carbon fiber blank, the carbon fiber blank formed by filtration is preferably dried and then subjected to wax evaporation. The invention has no requirement on drying treatment conditions and can achieve the purpose of drying. For example, the drying temperature can be 120-150 ℃, and the drying time can be 2-4 h.

In step S3, the carbon fiber preform is subjected to a wax deposition treatment to obtain a wax-containing carbon fiber preform. The carbon fiber blank is subjected to wax evaporation treatment, a hydrophobic layer is formed on the surface of the carbon fiber blank, the influence of surface tension after the ceramic slurry soaks the fiber is reduced in the soaking process, and the carbon fiber is beneficial to keeping the filamentation after the soaking is finished; and the capillary force of the carbon fiber blank in the subsequent process (such as drying) is also reduced, so that the carbon fiber blank is not easy to crack, peel and other defects, the pore diameter uniformity of the porous ceramic is improved, and the pore diameter is basically consistent with the diameter of the carbon fiber. And the wax is deposited on the fiber lap joint points, so that the strength of the carbon fiber blank is improved, and the uniformity of the pore distribution of the final porous ceramic is increased. Preferably, the wax is a microcrystalline wax.

In step S3 of the present invention, the wax plating process is performed by evaporation, so that the wax is uniformly deposited on the surface of the carbon fiber. Preferably, the wax evaporation treatment comprises the steps of placing a support in a container containing wax, heating the container to the temperature of 280-320 ℃, placing the carbon fiber blank on the support and sealing the container after the wax is completely melted, and carrying out wax evaporation treatment for 3-6 min. If the wax plating time is too short, the wax deposition layer is thinner, and the situation that the wax deposition layer is not deposited in a part of areas can occur; if the time is too long, wax at the lap joint of the fibers can be obviously enriched relative to other areas, and pores formed among the fibers are communicated with the wax discharged in the subsequent sintering process, so that the pore diameter uniformity of the porous ceramic formed by the subsequent process is reduced.

In step S4 of the present invention, the carbon fiber green body containing wax is placed in a ceramic slurry for dipping treatment, and then sintered in an oxygen atmosphere to obtain the porous ceramic. Preferably, the carbon fiber blank containing wax is placed in ceramic slurry with the solid content of 70-80%, vacuumized for 10-20min, and then taken out and dried at the temperature of 120-150 ℃ for 2-4h to obtain the carbon fiber ceramic preform. In order to obtain a dense carbon fiber ceramic preform, the dried carbon fiber ceramic preform may be dipped again in the ceramic slurry and then dried again. And finally, sintering the carbon fiber ceramic preform in an oxygen atmosphere to obtain the porous ceramic. The carbon fibers are sintered and oxidized in an oxygen atmosphere to form pores in the ceramic. Preferably, the sintering temperature is 1420-1480 ℃ for 2-4 h.

In the present invention, the ceramic may be one or more of zirconia, alumina and mullite.

The invention also provides the porous ceramic prepared by the method. The holes of the porous ceramic are round holes, the holes are communicated with one another, the pore diameter of the porous ceramic is uniform, the bending strength of the porous ceramic is high, and the use effect and the service life of the porous ceramic are improved.

The invention also provides application of the porous ceramic in an electronic cigarette atomizer, steel-making waste residue filtration or a catalyst carrier.

The present invention will be described in detail below by way of examples, but the present invention is not limited to the following examples.

Example 1

1) Treating carbon fiber (diameter 5-6 μm) at 400 deg.C under oxygen atmosphere for 2 hr, and cutting to 2-3 mm;

2) mixing carbon fibers with acrylic resin and water, wherein the mass ratio of the carbon fibers to the water is 2:100, the mass ratio of the acrylic resin to the carbon fibers is 2:100, and ultrasonic treatment is carried out for 3 hours under the condition that the power is 21 KW;

3) filtering the carbon fibers in the liquid obtained in the step 2), wherein a filter screen is 150 meshes;

4) mixing the carbon fiber filtered in the step 3) with sodium carboxymethylcellulose and water, and carrying out ultrasonic treatment and stirring treatment for 30 min. The mass ratio of the carbon fibers to the water is 2:1000, and the mass ratio of the sodium carboxymethyl cellulose to the water is 1.5: 1000;

5) and (4) after the carbon fibers in the step 4) are filamentized, transferring the liquid into a die with a small hole at the bottom. The diameter of the small holes is 2mm, the small holes are distributed in a matrix shape, and the distance between the adjacent holes is 4 mm;

6) filtering carbon fibers contained in the liquid in the step 5) into the mold, and washing the carbon fiber blank body with pure water for 25 min;

7) drying the carbon fiber blank at 150 ℃ until the blank does not lose moisture, and taking out the blank;

8) placing a support in a container containing microcrystalline wax, heating the container to 300 deg.C, after the microcrystalline wax is melted, placing the carbon fiber blank on the support, sealing the container, and performing evaporation treatment for 3 min;

9) taking out the treated carbon fiber blank, placing the carbon fiber blank into zirconia ceramic powder slurry with the solid content of 80%, and vacuumizing for 10 min;

10) taking out the impregnated green body and drying the green body in an oven for 4 hours;

11) repeating the step of 9-10 for 2 times to obtain a compact carbon fiber ceramic prefabricated body;

12) and (3) directly sintering the carbon fiber ceramic preform in an oxygen atmosphere at 1430 ℃ for 2h to obtain the porous ceramic A1 after sintering.

Example 2

The preparation method is the same as that of example 1 except that the diameter of the carbon fiber in step 1) is 6 to 8 μm. A porous ceramic A2 was obtained.

Example 3

The preparation method is the same as that of the example 1, except that in the step 2), the mass ratio of the ammonium polymethacrylate to the carbon fibers is 3: 100; the mass ratio of the carbon fiber to the water in the step 4) is 3:1000, and the mass ratio of the sodium carboxymethyl cellulose to the water is 2: 1000. A porous ceramic A3 was obtained.

Example 4

The preparation method is the same as that of the example 1, except that the evaporation treatment time in the step 8) is 5 min. A porous ceramic A4 was obtained.

Example 5

The preparation method is the same as that of the example 1, except that the evaporation treatment time in the step 8) is 2 min. A porous ceramic A5 was obtained.

Example 6

The preparation method is the same as that of the example 1, except that the evaporation treatment time in the step 8) is 7 min. A porous ceramic A6 was obtained.

Comparative example 1

The preparation method is the same as example 1, except that the wax evaporation treatment of step 8) is not performed. A porous ceramic D1 was obtained.

Comparative example 2

The preparation method was the same as example 1 except that the ultrasonic and agitation treatment of step 4) was not performed. A porous ceramic D2 was obtained.

Comparative example 3

The preparation method was the same as example 1 except that the ultrasonic treatment of step 2) was not performed. A porous ceramic D3 was obtained.

Performance testing

(1) Porosity test method: processing the sample into a regular sample, calculating the volume V of the regular sample, weighing the weight m of the sample, and calculating by the following formula:，

whereinFor the density of zirconia after firing, the values are taken=6 g/cm³。

(2) Three-point bending strength test:

the equipment model is as follows: GP-TS8000M model universal material testing machine (Shenzhen high quality testing equipment).

The test method comprises the following steps: processing a sample into 3mm by 4mm by 35mm sample strips, chamfering edges of the sample strips along the length direction, measuring the width b and the thickness h of the sample, fixing the sample on a clamp by adopting a three-point bending method, and enabling the central axis of the sample strip to be consistent with the central axis of the clamp; setting the loading rate to be 0.5mm/min and the span L to be 30mm, and loading until the sample is broken after safety is ensured; the maximum load F is recorded and the bending strength R is calculated by the following equation:

(3) pore diameter: and carrying out scanning electron microscope SEM observation statistics on the fracture of the sample.

TABLE 1

	Porosity%	Three-point bending strength MPa	Pore size of mum
				Example 1	27.2	215	4.83-5.44
Example 2	32.9	182	5.84-7.59
				Example 3	34.7	145	4.79-5.07
Example 4	28.6	201	4.87-5.58
				Example 5	25.8	158	5.65-15.95
Example 6	29.8	162	4.86-10.86
				Comparative example 1	16.8	123	10.97-120.4
Comparative example 2	20.5	137	5.54-79.84
				Comparative example 3	29.2	144	5.08-22.84

As can be seen from the results of the examples and comparative examples in Table 1, the porosity of the porous ceramic provided by the invention can meet the actual requirement, and the porous ceramic has high strength and uniform pore diameter. As can be seen from SEM electron micrographs of FIG. 1 (example 1) and FIG. 2 (comparative example 3), the porous ceramic provided by the invention has round pores and uniform pore diameter, and is beneficial to improving the use effect (such as filtration) and prolonging the service life of the porous ceramic.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.