CN113548896A

CN113548896A - Method for manufacturing ceramic composite material and product thereof

Info

Publication number: CN113548896A
Application number: CN202010330093.XA
Authority: CN
Inventors: 谢金龙
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-04-23
Filing date: 2020-04-23
Publication date: 2021-10-26

Abstract

The invention discloses a method for manufacturing a ceramic composite material and a product thereof, wherein the method comprises the following steps: selecting silicon carbide (SiC) powder with a specific particle length-diameter ratio and a specific particle size as selected silicon carbide raw material powder; coating a PVA coating layer on the surface of a silicon carbide (SiC) powder individual by a diffusion type high-speed granulation process, and combining the selected silicon carbide raw material powder and PVA into a particulate ceramic raw material; pressing the particulate ceramic raw material into a substrate blank by a pressure forming process; sintering and shaping the ceramic substrate blank, and then cooling to prepare a continuous pore passage with the interior completely communicated with the surface; then placing the ceramic substrate blank into a homotype die with a reserved surface thickness, heating the die to a constant temperature state, and carrying out high-speed high-pressure infiltration of aluminum soup into the ceramic substrate blank for die-casting forming to complete the ceramic composite material; through the manufacturing method, the grain types of the silicon carbide (SiC) powder individuals are completely reserved, the silicon carbide (SiC) powder individuals after pressure forming can form continuous pores through the bridging effect generated by mutually felting PVA, the use amount of PVA is far lower than that of the traditional wet granulation, and the method has the advantages of high porosity, high specific surface area, green body strength improvement and environmental protection, and simultaneously, the ceramic composite material after aluminizing can achieve the effects of light weight, high rigidity, high toughness, low expansion coefficient, high stability and high heat conductivity.

Description

Method for manufacturing ceramic composite material and product thereof

Technical Field

The invention relates to the technical field of ceramic composite materials, in particular to a manufacturing method of a ceramic composite material with light weight, high heat conduction efficiency, high rigidity, high toughness and low expansion coefficient and a product thereof.

Background

At present, porous silicon carbide (SiC) ceramics have been widely used due to their excellent high-temperature strength, chemical stability, good thermal shock resistance, oxidation resistance, and the like. The crystalline powder of SiC material is a non-metal material, and there are no free electrons in the crystal structure, so it has excellent insulation. SiC heat transfer belongs to a phonon heat conduction mechanism, and when the crystal lattice is complete and has no defect, the larger the mean free path of phonons is, the higher the heat conductivity is. The SiC ceramic radiator is resistant to cold and hot impact, is not easily influenced by environmental temperature, has high porosity and a radiation type radiating mechanism, and has excellent radiating performance. For example, the ceramic radiating fin is a radiating device manufactured by a continuous porous ceramic preparation process by utilizing the physical characteristics of SiC, and has the advantages of light and thin volume and excellent radiating performance.

In general, the properties of porous ceramics depend not only on the material itself but also on the microstructure of the ceramic. The pore structure of the porous ceramic, such as pore diameter, pore distribution, pore directionality, etc., can be controlled by the preparation process. Therefore, the preparation process has great influence on the performance of the porous SiC ceramic. In general, a manufacturing process (process) of porous SiC ceramics includes: mixing, molding, sintering and the like. (Advanced Ceramics, 2017, 38(6): 412-. The known method for manufacturing porous ceramics is basically to add a pore-forming agent (organic matter) to a ceramic raw material, support the ceramic raw material during high-pressure forming, and burn off the organic matter during high-temperature sintering, and the burned-off part forms fine pores in the ceramic body.

The granted Chinese patent for invention (grant publication No. CN104072190B) indicates that there are many methods for preparing silicon carbide porous ceramics, including additive foaming process, organic foam impregnation process, sol-gel process, etc. However, the porous ceramics prepared by the methods have the problems that the porosity and the strength cannot be obtained at the same time (for example, SiC porous ceramics prepared by an organic foam impregnation method, the porosity generally can reach 70-80%, but the strength is lower than 10MPa), the pore shape is not easy to control, the specific surface area is small, and the like.

The method aims to solve the problems that the porosity of the SiC porous ceramic is low, the pore shape is not easy to control and the like. The invention of Chinese invention patent publication No. CN104072190B is characterized in that 2.5-8.8% of Al2O3 is taken as a burning aid, 55-80% of dark green nano SiC micro powder is taken as a substrate material, 10-35% of PMMA (polymethyl methacrylate) micro powder is taken as a pore-forming agent, and 1.2-7.5% of phenolic resin is taken as a binder in percentage by mass; mixing the sintering aid, the matrix material and the binder in a ball mill for 8-12 h; and adding the mixed powder and the pore-forming agent into a mixer, mixing for 10-30 min, and performing dry pressing molding.

The granted Chinese patent of invention (grant publication No. CN1187291C) uses yeast powder as a new pore former material. Mixing the materials to prepare slurry, dividing yeast powder into six particle size gradients by six screening gradients of 30-300 meshes, mixing the six particle size gradients with the slurry, drying to prepare dry powder, performing dry pressing molding under the pressure of 20-100 MPa, then firing at 1100-1350 ℃ in air atmosphere, and preserving heat for 1-5 hours to prepare the silicon carbide porous ceramics with different pore diameters.

The published Chinese patent application (application publication No. CN106588085A) aims to solve the problems of difficult regulation and control of pore size distribution and size, small specific surface area and low mechanical strength of porous ceramics in the existing method for preparing SiC porous ceramics. Uniformly mixing flour and yeast by using deionized water, and kneading into dough; fermenting the dough at constant temperature, and then freeze-drying to obtain porous dough; carbonizing the porous dough to obtain a carbon porous framework; and placing the carbon porous skeleton on a reaction silicon source, sintering, and cooling to room temperature to obtain the high-temperature-resistant structural SiC porous ceramic.

The granted Chinese invention patent (grant publication No. CN104193395B) is designed by the composition proportion, namely the proportion of the expanded graphite, the metal silicon powder and the organic adhesive is controlled, so that the reaction product is mainly silicon carbide; in addition, the density of the mixture of the three is controlled, the porosity of the porous silicon carbide ceramic can be accurately controlled, the porous silicon carbide ceramic with the controllable porosity of 40-80% can be prepared, and the porous silicon carbide ceramic has the characteristics of controllable porosity and uniform porosity.

The preparation method of the porous SiC ceramic comprises the following steps: the silicon carbide (SiC) powder is mainly mixed with other materials (e.g., binder, pore-forming agent) required by an optional preparation method to prepare a ceramic raw material with a suitable size, which is generally called a granulation process. Generally, the ceramic raw material is granulated in a wet process, i.e., water and a large amount of solvent or binder are added during the granulation process, and therefore, the ceramic raw material must be dried after the granulation process is completed. Dry granulation, however, eliminates the addition of water or solvent, and only adds binder under high speed rotation of the powder, thus the humidity is much lower than wet granulation, and the drying time is fast. Dry granulation requires more stringent parameter conditions than wet granulation, and requires more complicated control of the properties of the raw material. The method has the advantages that various substances harmful to the environment, such as a dispersing agent, a modifier, a softener and the like, are not added into the raw materials, the drying time is short, the energy is saved, and the dry granulation finished product has high consistency and good fluidity. The finished product is mainly characterized in that the porosity and the pore size can be controlled during high-pressure molding, so that a continuous pore passage with the inside completely communicated with the surface is formed.

The ceramic composite material is prepared by a gravity casting infiltration method, namely, after the ceramic sheet is heated to about 1000 ℃, the heated ceramic sheet is placed in a gravity casting infiltration mold, and molten aluminum is introduced into the mold for die-casting molding; because of the above-mentioned uncertainty and disadvantages of the conventional ceramic substrate manufacturing method, the manufacturing process stability is poor and the yield is very low, so there is a need for improvement.

Disclosure of Invention

The present invention provides a method for manufacturing a ceramic composite material and a product thereof, aiming at the defects of the prior art.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a method for manufacturing a ceramic composite material and a product thereof, the method for manufacturing the ceramic composite material is characterized in that: comprises the following steps:

a sorting step: selecting the length-diameter ratio of the particles: 1: 0.75 to 1: 0.9, silicon carbide (SiC) powder with the particle size of 3 to 15 microns (mum) is used as the selected silicon carbide raw material powder;

and (3) granulating: mixing the selected silicon carbide raw material powder with polyvinyl alcohol (PVA), coating a PVA coating layer on the surface of a silicon carbide (SiC) powder individual, and combining the PVA coating layer and the silicon carbide (SiC) powder individual into a particulate ceramic raw material, wherein the PVA content accounts for 0.1-0.8% (wt%) of the particulate ceramic raw material;

pressure forming: pressing the micro-particle ceramic raw material into a ceramic substrate blank by a pressure forming process at a fixed forming pressure;

sintering: sintering and shaping the ceramic substrate blank, and then cooling to prepare a continuous pore passage with the interior completely communicated with the surface; and a high-pressure high-speed aluminizing step: and then placing the ceramic substrate blank into a homotype die with a reserved surface thickness, heating the die to a constant temperature state, and carrying out high-speed high-pressure infiltration of aluminum soup into the ceramic substrate blank for die-casting molding to complete the ceramic composite material.

Further, the sorting step comprises: and distributing the silicon carbide (SiC) powder into a plurality of grading grades according to the particle size, and selecting the silicon carbide (SiC) powder with the required grading grade as the selected silicon carbide raw material powder according to the requirement of the ceramic substrate blank.

Further, the grading level includes 10 grading levels.

Further, as a preferred embodiment of the granulating step, the content of PVA therein is 0.1 to 0.8% (wt%) in terms of the weight percentage of the particulate ceramic raw material.

Further, the preferable technical scheme of the granulating step comprises: the selected silicon carbide raw material powder is rotated and turned by a high-speed diffusion blade knife to be thrown and raised, and the PVA is uniformly sprayed by a high-pressure coil pipe to be combined with the selected silicon carbide raw material powder in a diffusion mode to form the micro-particle ceramic raw material.

Further, the preferred molding pressure of the pressure molding step is 300-1500 kilograms per square centimeter (kg/cm 2).

Further, the ceramic substrate blank prepared in the pressure forming step is leveled and kept standing for 24 hours, and then the sintering step is continued.

Further, the preferable technical scheme of the sintering step comprises the following steps: sintering and shaping the ceramic substrate blank at the temperature range of 1050-1450 ℃ according to the default temperature control process.

Further, the preferable technical scheme of the sintering step comprises the following steps: heating the ceramic substrate blank to a default sintering temperature in a temperature rising section for 8-12 hours, then maintaining the sintering temperature for 2-8 hours, and finally cooling to the normal temperature after 6-8 hours.

Further, the high pressure high speed aluminizing step is carried out by: the temperature range of the die in the heating constant temperature state is 200-600 ℃.

The invention has the beneficial effects that: silicon carbide (SiC) powder with specific particle length-diameter ratio and particle size is selected as selected silicon carbide raw material powder, through the step of a diffusion type high-speed granulation process, the particle types of silicon carbide (SiC) powder individuals are completely reserved and are not easy to wear, bridging effect can be generated between the silicon carbide (SiC) powder individuals after pressure forming through mutual felt adhesion of PVA to form continuous pores, the use amount of PVA is far lower than that of traditional wet granulation, and the silicon carbide (SiC) powder has the advantages of high porosity, high specific surface area, green body strength improvement and environmental protection. The porosity, density and specific surface area can be easily adjusted by the grading mode, and simultaneously, the ceramic composite material of the aluminum metal outer surface layer is formed by high-pressure high-speed aluminizing.

Drawings

FIG. 1 is a flow chart of the steps of one embodiment of a method of making a ceramic composite of the present invention.

FIG. 2 is a schematic view showing the microstructure of a particulate ceramic starting material obtained in the granulation step of the method for producing a ceramic composite material according to the present invention.

Fig. 3 is a schematic view of the microstructure of a ceramic raw material produced by a conventional wet granulation process.

FIG. 4 is a schematic view showing the progress of temperature control in the sintering step of the method for producing a ceramic composite material according to the present invention.

FIG. 5 is a schematic view showing the structure of a ceramic composite material according to an embodiment of the die-cast molding by the high-pressure high-speed alumetizing step of the method for producing a ceramic composite material according to the present invention.

In the figure, 10-fine particles of ceramic raw material; 11-silicon carbide (SiC) powder; 12-PVA coating layer;

21-individual silicon carbide (SiC) powders; 22-PVA dough; 30-a ceramic substrate blank;

40-aluminum metal outer surface layer; s2-granulating; s3-a pressure forming step; s4-sintering step;

s5-high pressure high speed aluminizing step; a-ceramic composite material.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

As shown in FIG. 1, a preferred embodiment of the method for manufacturing a ceramic composite material according to the present invention comprises the steps of:

s1, sorting: selecting the length-diameter ratio (or Slenderness ratio) of the particles: 1: 0.75-1: 0.9, and silicon carbide (SiC) powder 11 with the particle size of 3-15 microns (micrometer) is used as selected silicon carbide raw material powder;

s2, granulating: mixing the selected silicon carbide (SiC) powder 11 with Polyvinyl Alcohol (PVA), coating a PVA coating layer 12 on the surface of the silicon carbide (SiC) powder 11, and combining the PVA coating layer 11 and the silicon carbide (SiC) powder 11 into a particulate ceramic raw material 10; as a preferred embodiment of the granulation step, the PVA content is 0.1 to 0.8% (wt%) by weight of the particulate ceramic starting material;

s3, pressure forming: pressing the particulate ceramic raw material 10 into a ceramic substrate blank A by a pressure forming process;

s4, sintering: sintering and shaping the ceramic substrate blank A, and then cooling to prepare a continuous pore passage with the interior completely communicated with the surface; and S5, a high-pressure high-speed aluminizing step: and then placing the ceramic substrate blank A into a homotype mould with a reserved surface thickness, heating the mould to a constant temperature state, and carrying out high-speed high-pressure infiltration of aluminum soup into the ceramic substrate blank A for die casting and molding to complete the ceramic composite material.

The preferable technical scheme of the sorting step S1 further includes: the silicon carbide (SiC) powder 11 is distributed into a plurality of grading grades according to the particle size, and the silicon carbide (SiC) powder 11 with the required grading grade is selected as the selected silicon carbide raw material powder according to the requirement of a finished product. Preferably, the grading level comprises 10 grading levels. And selecting the required grading grade silicon carbide (SiC) powder 11 as the selected silicon carbide raw material powder according to the requirements of finished products. Thus, the porosity, density and specific surface area can be easily adjusted by means of grading.

The granulation step S2 is a special granulation process (referred to as a dry granulation process) which the present inventors have developed, and is referred to as a "diffusion type high-speed granulation process", and the particulate ceramic material 10 after the granulation step is sintered without using a pore-forming agent to form continuous pores, so that toxic organic substances are not emitted during sintering, and the sintering time is not required to be lengthened to discharge the organic substances because there is no impurity.

The preferred embodiment of the diffusion type high-speed granulation process is that the selected silicon carbide (SiC) powder 11 is rotated and turned by a high-speed diffusion blade to be thrown and raised, and the PVA is uniformly sprayed by a high-pressure coil pipe to be combined with the selected silicon carbide raw material powder in a diffusion mode to form the particulate ceramic raw material A. In other words, the silicon carbide (SiC) powder 11 is stirred at a high speed and is thrown up and combined with the liquid PVA sprayed into the granulation chamber by pressure into the particulate ceramic raw material a, completing the granulation step. Wherein PVA is coated on the surface of the silicon carbide (SiC) powder 11 to form a PVA coating layer 12, and in a common situation, the silicon carbide (SiC) powder 11 individuals can be felted together through PVA to form an irregular spherical granular ceramic raw material 10 (see a second figure); the granulation step of the invention has short preparation time and extremely small PVA dosage, can greatly reduce the abrasion of the silicon carbide (SiC) powder 11 in the granulation process and avoid the change of the length-diameter ratio of the silicon carbide (SiC) powder 11. According to the invention, a PVA coating layer 12 is formed on the surface of the silicon carbide (SiC) powder 11 individuals through a diffusion type high-speed granulation process, and then in the forming process stage, the silicon carbide (SiC) powder 11 individuals can be adhered together through mutually felting PVA to form the ceramic raw material 10 in irregular spherical particles, so that the porosity can be increased.

Compared with the traditional wet granulation method in which PVA is added as a binder, silicon carbide (SiC) powder and PVA are placed in a container and stirred, the stirring is easy to form lumps, the traditional dry granulation method needs more PVA (accounting for about 3.0 wt%), as shown in the third figure, the microstructure is that a plurality of silicon carbide (SiC) powder units 21 are adhered to the same larger PVA lumps 22 to form a micro-particle ceramic powder, and the micro-particle ceramic powder prepared by the traditional wet granulation method is approximately spherical in shape, has better fluidity and is not easy to form pores. The granulation procedure of the present invention is compared with the characteristics of conventional wet granulation as follows:

a. the granulation step of the invention can completely retain the granular shape of the silicon carbide (SiC) powder 11, is not easy to wear, and avoids the change of the length-diameter ratio of the silicon carbide (SiC) powder 11.

b. The fine particulate ceramic material 10 produced in the granulation step S2 can retain a constant porosity, and can increase the average porosity when the ceramic base material body 30 is molded.

c. The amount of PVA binder added in the conventional wet granulation process is required to be greater than 3.0 wt%, and the PVA content in the granulation step of the present invention is less than 0.8 wt% (wt%) of the particulate ceramic starting material 10.

d. A large amount of organic solvent is required to be added in the traditional wet granulation, and the environmental protection property is low.

In the method, the particulate ceramic raw material A finished in the granulation step S2 can form pores through mechanical bridging, the ceramic substrate blank 30 is pressed in the subsequent pressure forming step at a proper forming pressure according to the requirement of a finished product, and the formed ceramic substrate blank 30 has a continuous pore structure, so that the problem of discontinuous pores formed by the traditional pore-forming agent or foaming process can be solved, and the porosity, the blank structure strength and the specific surface area of the ceramic substrate blank 30 can be improved.

The pressure forming step S3 is to press the ceramic substrate blank 30 at a suitable forming pressure according to the requirement of the finished product, wherein the preferred forming pressure is 300-1500 kg/cm (kg/cm 2). In a preferred embodiment, in the pressure forming step, the mold is subjected to floating adjustment to evenly distribute the pressure to the ceramic substrate blank 30, the particulate ceramic raw material 10 is pressed into the ceramic substrate blank 30 by a fixed pressure forming process, and then the ceramic substrate blank 30 is flatly placed for 24 hours until the stress is completely released, and then the step of S4 and sintering is continued; therefore, the ceramic substrate blank 30 after pressure forming has uniform density distribution and good structural strength, and the corners are not easy to crack.

The preferable technical scheme of the sintering step S4 comprises the following steps: and sintering and shaping the ceramic substrate blank 30 at the temperature range of 1050-1450 ℃ according to a default temperature control process (such as heating-holding-cooling). Referring to the fourth diagram, in a preferred embodiment of the temperature control process, in the temperature rising section, the ceramic substrate cup 30 is heated to the default sintering temperature within a range of 1050 ℃ to 1450 ℃ for 8 to 12 hours (Hrs ℃) (depending on the ratio of the grading grades of the particulate ceramic raw material 10), then the sintering temperature is maintained for 2 to 8 hours in the sintering section, and finally in the temperature lowering section, in an embodiment of the high pressure high speed aluminizing step S5: the temperature range of the die in the heating constant temperature state is 200-600 ℃.

The ceramic composite material a (see fig. 5) produced by the above method is characterized in that: the ceramic composite material A is a ceramic composite material A formed by aluminizing a ceramic substrate blank 30 to form an aluminum metal outer surface layer 40, wherein continuous pore channels are completely communicated from the inside to the surface of the ceramic substrate blank 30, so that the ceramic composite material A can be bonded in a completely communicated manner.

The above examples are intended to illustrate rather than to limit the invention, and all equivalent changes and modifications made by the methods described in the claims of the present invention are intended to be included within the scope of the present invention.

Claims

1. A method of making a ceramic composite, comprising: comprises the following steps:

sorting: selecting the length-diameter ratio of the particles: 1: 0.75 to 1: 0.9, silicon carbide (SiC) powder with the particle size of 3 to 15 microns (mum) is used as the selected silicon carbide raw material powder;

and (3) granulation: mixing the selected silicon carbide raw material powder with polyvinyl alcohol (PVA), coating a PVA coating layer on the surface of a silicon carbide (SiC) powder individual, and combining the PVA coating layer and the silicon carbide (SiC) powder individual into a particulate ceramic raw material, wherein the PVA content accounts for 0.1-0.8% (wt%) of the particulate ceramic raw material;

and (3) sintering: sintering and shaping the ceramic substrate blank, and then cooling to prepare a continuous pore passage with the interior completely communicated with the surface; high-pressure high-speed aluminizing: and then placing the ceramic substrate blank into a homotype die with a reserved surface thickness, heating the die to a constant temperature state, and carrying out high-speed high-pressure infiltration of aluminum soup into the ceramic substrate blank for die-casting molding to complete the ceramic composite material.

2. The method of manufacturing a ceramic composite material according to claim 1, wherein: the granulating step comprises: the selected silicon carbide raw material powder is rotated and turned by a high-speed diffusion blade knife to be thrown and raised, and the PVA is uniformly sprayed by a high-pressure coil pipe to be combined with the selected silicon carbide raw material powder in a diffusion mode to form the micro-particle ceramic raw material.

3. A method of making a ceramic composite material and the product thereof according to claim 1 or 2, wherein: the sorting step comprises: and distributing the silicon carbide (SiC) powder into a plurality of grading grades according to the particle size, and selecting the silicon carbide (SiC) powder with the required grading grade as the selected silicon carbide raw material powder according to the requirement of the ceramic substrate blank.

4. A method of manufacturing a ceramic composite material according to claim 3, characterized in that: the grading level comprises 10 grading levels.

5. The method of manufacturing a ceramic composite material according to claim 1, wherein: the molding pressure in the pressure molding step is 300-1500 kilograms per square centimeter (kg/cm 2).

6. The method of manufacturing a ceramic composite material according to claim 1, wherein: the ceramic substrate blank produced by the pressure forming step is leveled and left to stand for 24 hours and then the sintering step is continued.

7. The method of manufacturing a ceramic composite material according to claim 1, wherein: the sintering step is to sinter and shape the ceramic substrate blank at a default sintering temperature according to a default temperature control process, wherein the temperature range of the sintering temperature is 1050-1450 ℃.

8. The method for producing a ceramic composite material according to claim 7, wherein: the sintering step is that the ceramic substrate blank is heated to the default sintering temperature within 8-12 hours, then the sintering temperature is maintained for 2-8 hours, and finally the temperature is reduced to the normal temperature within 6-8 hours.

9. The method for manufacturing a ceramic composite material according to claim 1, wherein: in the high-pressure high-speed aluminizing step, the temperature range of the die in the heating constant temperature state is 200-600 ℃.

10. A ceramic composite material produced by the method for producing a ceramic composite material according to any one of claims 1 to 9, characterized in that: the ceramic composite material is formed by aluminizing a ceramic substrate blank to form an aluminum metal outer surface layer, wherein continuous pore channels are completely communicated from the inside to the surface of the ceramic substrate blank, so that the ceramic composite material can be completely connected and bonded.