CN113135757A

CN113135757A - Ceramic primary blank forming method based on microwave in-situ sintering and product

Info

Publication number: CN113135757A
Application number: CN202110473283.1A
Authority: CN
Inventors: 魏青松; 冯琨皓; 毛贻桅
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2021-04-29
Filing date: 2021-04-29
Publication date: 2021-07-20

Abstract

The invention belongs to the technical field related to additive manufacturing, and discloses a ceramic primary blank forming method based on microwave in-situ sintering and a product. The method comprises the following steps: preparing a microwave absorbent and SiC powder; and carrying out three-dimensional spray printing by utilizing the SiC powder, spraying the microwave absorbent on the surface of a sliced layer after the sliced layer is formed by spray printing in the three-dimensional spray printing process, and then carrying out microwave heating on the sliced layer to carry out in-situ heating, sintering and forming on the sliced layer so as to form each sliced layer by layer and obtain a required ceramic blank. The invention also discloses a product prepared by the method. The invention solves the problems that the organic binder is easy to block an ink path to corrode a nozzle and the strength of the primary blank is low, and the in-situ sintering and forming process omits the subsequent curing and degreasing heat treatment procedures and simplifies the manufacturing process.

Description

Ceramic primary blank forming method based on microwave in-situ sintering and product

Technical Field

The invention belongs to the technical field related to additive manufacturing, and particularly relates to a ceramic primary blank forming method based on microwave in-situ sintering and a product.

Background

Three-dimensional Printing (3 DP) is also called as binder spraying technology, is one of additive manufacturing technologies, and mainly utilizes a spray head to selectively spray a liquid binder to bond, stack and form discrete powder layer by layer so as to obtain a required product, and can be applied to the preparation of complex parts such as ceramics, plastics, metals and the like. Compared with the traditional process, the method has the advantages of high forming speed, no need of a die, no influence of the geometric complexity of parts, recyclable materials and the like. However, the existing three-dimensional jet printing technology still has the following defects or problems when forming ceramic products:

firstly, organic binders are prone to clogging and corrosion of the spray head. At present, the adhesive is mainly an organic adhesive (such as polyvinyl alcohol, phenolic resin and furan resin), can bond ceramic powder due to long molecular chains, high content and high viscosity, has low decomposition temperature, and can be almost completely removed through subsequent heat treatment. However, because the molecular chain is long, the viscosity is high, and the molecular chain is easy to separate out when being heated, the nozzle and the ink path are easy to block when in use and are difficult to clean, so that the equipment has low stability and poor reliability, and meanwhile, the precision of printing parts is reduced and the service life of the nozzle is prolonged;

secondly, the strength of the initial blank is low, the post-treatment procedures are more, and the performance is difficult to meet the requirements required by use. The three-dimensional ceramic jet printing mainly adopts organic binder to bond powder particles layer by layer, and the formed ceramic blank has larger porosity and low strength. After the spray printing is finished, the spray printing is difficult or impossible to directly take out of the forming cavity, a series of complicated heat treatment processes of integral heating solidification, degreasing and sintering are needed, and technological parameters such as temperature, time and the like need to be strictly controlled in each step.

In order to solve the above problems, some patents have been disclosed to improve the binder formulation and the post-treatment process, so as to improve the strength of the ceramic green body and meet the use requirements. For example, patents CN111875394A and CN110105073A respectively use water-based styrene-acrylic acid copolymer resin and hydroxyethyl acrylate, hydroxypropyl acrylate as a base, and a polyethylene phthalate wetting agent as an auxiliary to reduce the surface tension of the binder, so that the binder is more permeable, and the contact area with the ceramic powder is increased to improve the strength of the green body, but the green body is still a high molecular long-chain organic substance, and the possibility of blocking a spray head still exists in the use process; patent CN107098714A discloses a heat treatment process method for three-dimensional spray-printed formed silicon carbide ceramics, which comprises the steps of firstly preparing an initial blank by using an organic binder, and then carrying out drying degreasing, chemical vapor deposition and hot isostatic pressing heat treatment to obtain a compact part with good high-temperature comprehensive performance, but the process of the method is more complicated than the traditional method, and the subsequent hot isostatic pressing treatment limits the three-dimensional spray-printed forming of the part with a complex hollow structure; patent CN105562623A discloses a method for quickly forming sodium silicate sand, which uses a mixed solution of sodium silicate and polyvinyl alcohol as a binder to perform three-dimensional spray printing on a sand mold, and then uses microwaves to perform heating and curing of each layer, but the essence still uses an organic binder, which damages a nozzle and an ink path, and simultaneously, the formable raw material is single, and the strength requirement of the sand mold is low, which cannot meet the use requirement of ceramic parts.

In conclusion, the three-dimensional spray printing can quickly form various ceramic blanks with complex shapes, the cost is greatly reduced, the process time is greatly shortened, but in the prior art, organic binders are adopted for spray printing, ink paths are easily blocked, nozzles are easily corroded, the formed blanks are low in strength, a series of post-treatments are needed to meet the requirements of transportation and use, and the process is complex.

Disclosure of Invention

Aiming at the defects or improvement requirements of the prior art, the invention provides a ceramic primary blank forming method and a product based on microwave in-situ sintering, on the basis of the existing three-dimensional spray printing technology, an inorganic microwave absorbent is prepared to replace the traditional organic binder, the resistivity of silicon carbide ceramic is adjusted, the dielectric property of the silicon carbide ceramic is improved, the silicon carbide ceramic can absorb microwaves, and the problems that the organic binder is easy to block an ink path and corrode a nozzle and the strength of the primary blank is low are solved, wherein the in-situ sintering forming omits the subsequent curing and degreasing heat treatment processes, and simplifies the manufacturing process.

In order to achieve the above object, according to the present invention, there is provided a method for forming a ceramic preform based on microwave in-situ sintering, the method comprising the steps of:

preparing a microwave absorbent and SiC powder; and carrying out three-dimensional spray printing by utilizing the SiC powder, spraying the microwave absorbent on the surface of a sliced layer after the sliced layer is formed by spray printing in the three-dimensional spray printing process, and then carrying out microwave heating on the sliced layer to carry out in-situ heating, sintering and forming on the sliced layer so as to form each sliced layer by layer and obtain a required ceramic blank.

More preferably, the microwave absorbent is an inorganic microwave absorbent, the viscosity is less than 2mPa · s, the pH value is 6.9-7.1, and the surface tension is 20-40 mN/m. Further preferably, in the microwave heating, the microwave power is 200W-800W, the heating time of each layer is 0.5 s-6 s, and the heating temperature is 300 ℃ to 800 ℃.

Further preferably, the microwave absorbent is prepared according to the following method:

mixing water-soluble inorganic salt, a high-molecular modifier and deionized water to form a mixed solution, measuring the pH value of the mixed solution, and then adding organic acid to enable the pH value of the mixed solution to be 6.9-7.1 so as to obtain the required microwave absorbent.

Further preferably, in the microwave absorbent, the mass fraction of deionized water is 60 wt% to 75 wt%, the mass fraction of water-soluble inorganic salt is 25 wt% to 40 wt%, the mass fraction of high molecular modifier is less than or equal to 2.5 wt%, and the balance is organic acid.

Further preferably, the water-soluble inorganic salt is one or more of chloride, bromide, carbonate, sulfate, nitrate, phosphate, meta-aluminate and hydroxide containing one or more elements of Al, Fe, Ni and N.

Further preferably, the polymer modified material is one or more of polyethylene glycol, glycerol, furfuryl alcohol, starch and cellulose.

Further preferably, the organic acid is one or both of acetic acid and oxalic acid.

Further preferably, the SiC powder is prepared by:

selecting alpha-SiC powder with the particle size of 40-50 mu m and the particle size of 10-20 mu m, mixing the alpha-SiC powder with the particle size of 50-80 percent (50-20) by volume fraction ratio, and then performing ball milling and grinding to obtain the required SiC powder.

According to another aspect of the present invention, there is provided a ceramic preform product obtained by the above-mentioned forming method.

Generally, compared with the prior art, the technical scheme of the invention has the following beneficial effects:

1. according to the invention, the microwave absorbent is sprayed on the sliced layer, and then the powder is bonded with each other by microwave heating to realize layer-by-layer solidification and forming of the blank body, the microwave absorbent replaces the traditional binder, so that the problems that the traditional organic binder is easy to corrode a spray head and block an ink path and the like are solved, the possibility of damaging the spray head is reduced, the stability and reliability of equipment are improved, and the cost is greatly reduced; meanwhile, the microwave absorbent is adjusted in price in the primary ceramic blank, so that the dielectric property of the ceramic powder is greatly improved;

2. according to the invention, the microwave absorbent is adopted to replace the traditional binder, the bonding property among particles is better after the green body is cured, the primary blank strength is greatly improved, the subsequent steps of curing, degreasing and the like are avoided, the process is simplified, the cost is saved, the microwave modifier is utilized to increase the dielectric property of the ceramic powder, and the powder fully absorbs the microwave, so that the heating in-situ curing can be realized at a lower temperature, and then the final sintering treatment can be directly carried out;

3. the invention provides a selective microwave absorbent spraying method, and the method adopts microwave heating to carry out in-situ sintering forming, and then sintering can be carried out to obtain compact parts, because carburization or siliconizing is not needed in the process, the amount of residual carbon and silicon is reduced, the strength and SiC content of the parts are improved, the solid phase content of the final parts is very high, and the problems that a large amount of residual silicon or residual carbon is generated after the traditional organic binder is formed, the content of silicon carbide is only about 50%, the strength and the use requirements of the parts are seriously influenced and the like are solved;

4. the three-dimensional spray printing equipment nozzle is composed of tens of thousands of micron-sized micro-channels, and if the viscosity of the modifier is too high, the fluidity is reduced, and the modifier is difficult to be normally sprayed out of the nozzle; the spray head can be corroded when the acidity and alkalinity are too high, the water-soluble inorganic salt is used as the main solute, and the pH value is kept neutral; the surface tension is related to the wettability, the modifier and the powder are difficult to wet when the surface tension is too large, the modification effect cannot be exerted, the modifier with too small surface tension has too strong wettability and permeates into an unprinted area to influence the dimensional precision of a part, the microwave heating power is 200-800W and 0.5-6 s to ensure that the powder can be cured at a lower temperature, and household microwave equipment can meet the requirements and has low requirements on the equipment; the preparation of the modifier mainly ensures that the content of the modified element is enough to change the dielectric property of SiC, and the microwave absorption efficiency of the primary blank can be influenced, so that the mechanical property of the primary blank is influenced; the proportion of the large particles and the small particles is used as raw materials, and the small particles are used as filling phases to be filled in gaps among the large particles, so that the density of the primary blank can be effectively improved, and the mechanical property of the primary blank is further improved.

Drawings

FIG. 1 is a schematic diagram of microblog solidification constructed in accordance with a preferred embodiment of the invention;

FIG. 2 is a schematic diagram of a microwave in-situ sintering three-dimensional jet printing process apparatus constructed in accordance with a preferred embodiment of the present invention;

fig. 3 is a schematic flow diagram of a microwave in-situ sintering three-dimensional jet printing process constructed in accordance with a preferred embodiment of the present invention.

The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein:

1-printing nozzle, 2-powder spreading roller, 3-powder supplying cylinder, 4-forming cylinder, 5-printing part and 6-microwave heating furnace.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

As shown in figure 1, the invention provides a method for forming a silicon carbide ceramic blank by three-dimensional spray printing based on microwave in-situ sintering, which specifically comprises the following steps:

s1, preparing an inorganic microwave absorbent suitable for an industrial spray head, respectively dissolving water-soluble inorganic salt and a high-molecular modifier in deionized water, fully mixing the water-soluble inorganic salt and the high-molecular modifier, measuring the pH value, and then adding organic acid to adjust the pH value of the solution to 7-8 to obtain the microwave absorbent.

Preferably, the microwave absorbent comprises the following components in percentage by weight: 60-75 wt% of deionized water, 25-40 wt% of water-soluble inorganic salt, 0-2.5 wt% of polymer modifier and organic acid, wherein the water-soluble inorganic salt is a wave-absorbing modifying element for providing a ceramic material, the polymer modifier is used for adjusting the viscosity and surface tension of the solution, and the organic acid is used for adjusting the pH of the solution. Deionized water is used as a solvent, and the inorganic salt can improve the wave-absorbing performance, just change the dielectric performance of SiC in the temperature range so as to absorb microwave for solidification, and simultaneously ensure that the modifier meets the requirements of viscosity and surface tension.

Preferably, the water-soluble inorganic salt is one or more of chloride, bromide, carbonate, sulfate, nitrate, phosphate, meta-aluminate and hydroxide containing one or more elements of Al, Fe, Ni and N. The Al, Fe, Ni and N elements can be doped to adjust the resistivity of the silicon carbide ceramic, thereby improving the dielectric property of the silicon carbide ceramic, enabling the silicon carbide ceramic to absorb microwaves, and heating and sintering the silicon carbide ceramic at an internal temperature.

Preferably, the polymer modified material is one or more of polyethylene glycol, glycerol, furfuryl alcohol, starch and cellulose.

Preferably, the organic acid is one or two of acetic acid and oxalic acid.

Preferably, the final inorganic microwave absorbent has a viscosity of less than 2 mPas, a pH of 7 to 8, and a surface tension of 20 to 40 mN/m. Preferably, the specific configuration method is as follows:

A. weighing water-soluble inorganic salt and a high molecular modifier required by balance according to a certain component;

B. dissolving, dissolving the weighed water-soluble inorganic salt and the polymer modifier in water, and uniformly stirring;

C. and adjusting the pH value, testing the pH value of the solution in the previous step by using test paper, and titrating organic acid by using a dropper to adjust the pH value of the solution to be 7-8.

S2, preparing double-peak SiC powder, selecting commercial alpha-SiC powder with the average particle size of 10-100 mu m, mixing the powder with the average particle size according to a certain proportion, and performing ball milling and grinding to obtain the SiC powder for three-dimensional jet printing.

Preferably, the bimodal mixed powder can increase the bulk density, so that the particles can be bonded in a larger area, and the strength of the blank after printing and curing is improved.

Preferably, the average particle size of large particles is 50-70 μm, the average particle size of small particles is 10-20 μm, and the volume fraction ratio of the powder of the large particles to the powder of the small particles is (50-80): (50-20).

Preferably, the powder is measured by a measuring cylinder, mixed with a certain amount of stainless steel balls, put into a ball mill together, and added into a grinding bottle for grinding after a certain time to obtain SiC spherical particles.

Preferably, the diameter of the stainless steel ball is 2 mm-6 mm, the ball-material ratio is set to (3:1) - (10:1), the rotating speed is set to 100 r/min-250 r/min, the time is set to 1 h-3 h, and the grinding time is set to 10 h-24 h.

Preferably, the ball mill is cooled in air for 10 minutes after 30 minutes to avoid excessive temperature in the tank.

Preferably, after ball milling and mixing, the bulk density of the powder is 50-70%, the fluidity Hausner ratio is 1.35-1.6, and the silicon carbide ceramic powder with the grain diameter of 50-70 μm and the bimodal particle diameter of 10-20 μm are uniformly mixed.

S3 spray printing is started, as shown in fig. 2, the silicon carbide ceramic powder prepared above is loaded into the powder supply cylinder 3 of the three-dimensional spray printing equipment, a layer of the powder is uniformly spread on the forming table of the forming cylinder 4 by using the powder spreading roller 2, and the printing nozzle 1 selectively sprays the microwave absorber on the surface of the powder layer according to the introduced three-dimensional part information. And (3) after each layer is finished, combining and sealing the microwave heating furnaces 6 arranged at the two sides of the forming table top, carrying out microwave heating on the forming table top, absorbing microwaves among the powder particles doped with the modified elements, diffusing mass points in the powder particles under the action of heat so as to sinter and form the particles in situ, and sintering and forming the powder among the layers. And then, the forming cylinder descends by one layer thickness, the powder supply cylinder ascends by 1-1.5 times of the layer thickness, the processes are repeated until the integral forming of the part is completed, and the part is heated by microwaves at 800W for 0.5-3 h for final curing after the forming is completed, so that the required ceramic primary blank can be obtained.

Preferably, the powder spreading layer is 0.1-0.5 mm thick, the ink jet amount is 40-80%, the scanning speed of the spray head is 0.35-2.5 m/s, and the powder spreading speed is 0.05-0.7 m/s.

Preferably, the microwave power is 200W-800W, the heating time of each layer is 0.5 s-6 s, and the heating temperature is 300 ℃ to 800 ℃.

The bending strength of the ceramic primary blank finally obtained by preparation can reach 10-20 MPa.

The main principle of microwave in-situ sintering forming is as follows: the microwave is an electromagnetic wave silicon carbide ceramic material with the wavelength of 1 m-1 mm, the dielectric property is poor, the microwave is difficult to absorb to heat the interior of the material, and after the elements of N, Fe, Ni and Al are added, the resistivity of the silicon carbide powder is regulated and controlled to enable the silicon carbide powder to have ideal wave absorbing performance, so that the microwave sintering condition is met. When the ceramic powder is stacked layer by layer, the interior of the modified ceramic powder generates dielectric loss under the action of microwave electromagnetic force, and the temperature is integrally raised from inside to outside, so that the mass points in the modified ceramic powder can obtain enough capacity for migration at a lower temperature, thereby reaching the temperature required by sintering, promoting the bonding among powder particles and densifying the material. In the printing process, after the inorganic microwave absorbent is sprayed on each layer of powder, the powder is sintered in situ by using microwaves, and the bonding between the layers is more compact, so that the strength of the obtained primary blank is far greater than that of the primary blank under the organic binder, the carrying requirement can be directly met, and the printing process has the advantages of low required sintering temperature, high heating speed, short sintering time, no pollution and the like.

The present invention will be further described with reference to the following specific examples.

The embodiment of the invention provides a method for forming a ceramic primary blank by three-dimensional spray printing based on microwave in-situ sintering, which comprises the following specific implementation steps as shown in figure 3:

example 1

A method for forming silicon carbide ceramic based on microwave sintering and three-dimensional spray printing comprises the following steps:

s1 preparing the microwave absorbent, weighing 75 wt% of deionized water, 25 wt% of ferric nitrate powder by mass fraction and 0.5 wt% of glycerin by mass fraction.

Dissolving ferric nitrate powder and glycerol in deionized water, stirring uniformly to fully diffuse, measuring the viscosity of the solution by using a rotary measuring instrument, measuring the surface tension of the solution by using a surface tensiometer, and measuring the pH value by using a pH meter.

Then 0-0.5 wt% of acetic acid is dripped to adjust the pH value of the microwave absorbent;

the final solution binder viscosity was 1.3 mPas, ph 7.1, surface tension 21 mN/m.

S2 silicon carbide powder particles are prepared, and alpha-SiC powder with the particle size of 50 mu m and 10 mu m is selected.

Measuring by using a measuring cylinder, mixing according to the average particle size of 80 vol% 50 μm and the average particle size of 20 vol% 10 μm, adding into a ball mill, mixing at normal temperature for 1h by adopting small balls and low milling speed, setting the mass ratio of the ball powder to be 10:1 to obtain large spherical particles, and then crushing in a grinding bottle for 24h to obtain the powder for three-dimensional jet printing.

S3 printing and forming the primary blank: and (3) spreading the prepared powder on a forming table board according to the layer thickness of 0.1mm, setting the powder spreading speed to be 0.15m/s, the powder spreading layer thickness to be 0.1mm, the ink jet quantity to be 50%, the scanning speed to be 0.5m/s, setting the microwave power to be 300W, heating time to be 1.5s, accumulating layer by layer, and finally performing microwave curing for 1h under 800W to obtain a high-strength primary blank, wherein the bending strength can reach 10.15 MPa.

Example 2

s1 preparing the microwave absorbent, selecting 65 wt% deionized water, weighing 33.5 wt% aluminum chloride powder by a balance, and weighing 1 wt% glycerin.

Dissolving aluminum chloride powder and glycerol in deionized water, stirring uniformly to make them fully diffuse, measuring viscosity of the solution by using a rotary measuring instrument, measuring surface tension of the solution by using a surface tension meter, and measuring pH value by using a pH meter.

the final solution binder viscosity was 1.65 mPas, ph 7.0 and surface tension 29 mN/m.

Measuring by using a measuring cylinder, mixing according to the average particle size of 80 vol% 50 μm and the average particle size of 20 vol% 10 μm, adding into a ball mill, mixing at normal temperature for 1h by adopting small balls and low milling speed, setting the mass ratio of the ball powder to be 7:1 to obtain large spherical particles, and then crushing in a grinding bottle for 20h to obtain the powder for three-dimensional jet printing.

S3 printing and forming the primary blank: and spreading the prepared powder on a forming table board according to the layer thickness of 0.15mm, setting the powder spreading speed to be 0.15m/s, the powder spreading layer thickness to be 0.15mm, the ink jet amount to be 60%, the scanning speed to be 0.75m/s, the microwave power to be 400W, the heating time to be 5s, accumulating layer by layer, and finally performing microwave curing at 800 ℃ for 1.5h to obtain a high-strength primary blank, wherein the bending strength can reach 15.30 MPa.

Example 3

s1 preparing the microwave absorbent, selecting 60 wt% deionized water, measuring 38.5 wt% aluminum chloride powder by using a balance, and measuring 1.4 wt% furfuryl alcohol.

Then 0-0.1 wt% of acetic acid is dripped to adjust the pH value of the microwave absorbent;

the final solution binder viscosity was 1.83 mPas, ph 7.0, surface tension 20 mN/m.

Measuring by using a measuring cylinder, mixing according to the average particle size of 80 vol% 50 μm and the average particle size of 20 vol% 10 μm, adding into a ball mill, mixing at normal temperature for 1h by adopting small balls and low milling speed, setting the mass ratio of the ball powder to be 6:1 to obtain large spherical particles, and then crushing in a grinding bottle for 20h to obtain the powder for three-dimensional jet printing.

S3 printing and forming the primary blank: and spreading the prepared powder on a forming table board according to the layer thickness of 0.2mm, setting the powder spreading speed to be 0.2m/s, the powder spreading layer thickness to be 0.2mm, the ink jet amount to be 65%, the scanning speed to be 0.80m/s, the microwave power to be 600W, the heating time to be 4s, accumulating layer by layer, and finally performing microwave curing at 800 ℃ for 0.5h to obtain a high-strength primary blank, wherein the bending strength can reach 19.36 MPa.

Example 4

s1 preparing the microwave absorbent, selecting 65 wt% deionized water, weighing 35 wt% aluminum chloride powder by mass fraction with a balance, and weighing 1.5 wt% furfuryl alcohol.

the final solution binder viscosity was 1.83 mPas, ph 7.0, surface tension 40 mN/m. .

Measuring with a measuring cylinder, mixing according to the average particle size of 70 vol% 50 μm and the average particle size of 30 vol% 10 μm, adding into a ball mill, mixing at normal temperature for 1h at a ball powder mass ratio of 6:1 with small balls and low milling speed to obtain large spherical particles, and pulverizing in a grinding bottle for 20h to obtain the powder for three-dimensional jet printing.

S3 printing and forming the primary blank: and spreading the prepared powder on a forming table board according to the layer thickness of 0.2mm, setting the powder spreading speed to be 0.2m/s, the powder spreading layer thickness to be 0.2mm, the ink jet amount to be 65%, the scanning speed to be 0.80m/s, the microwave power to be 300W, the heating time to be 1s, accumulating layer by layer, and finally performing microwave curing at 800 ℃ for 0.5h to obtain a high-strength primary blank, wherein the bending strength can reach 13.21 MPa.

Example 5

s1 preparing the microwave absorbent, selecting 75 wt% deionized water, weighing 40 wt% aluminum chloride powder by using a balance, and weighing 2 wt% furfuryl alcohol.

the final solution binder viscosity was 2 mPas, ph 6.9, surface tension 26 mN/m.

Measuring with a measuring cylinder, mixing according to the average particle size of 50 vol% and the average particle size of 50 vol% of 10 μm, adding into a ball mill, mixing at normal temperature for 1h at a ball powder mass ratio of 6:1 by adopting small balls and low milling speed to obtain large spherical particles, and then crushing in a grinding bottle for 20h to obtain the powder for three-dimensional jet printing.

S3 printing and forming the primary blank: and spreading the prepared powder on a forming table board according to the layer thickness of 0.2mm, setting the powder spreading speed to be 0.2m/s, the powder spreading layer thickness to be 0.2mm, the ink jet amount to be 65%, the scanning speed to be 0.80m/s, the microwave power to be 300W, the heating time to be 0.5s, accumulating layer by layer, and finally performing microwave curing at 800 ℃ for 0.5h to obtain a high-strength primary blank, wherein the bending strength can reach 11.15 MPa.

Example 6

s1 preparing the microwave absorbent, selecting 60 wt% deionized water, measuring 25 wt% aluminum chloride powder by using a balance, and measuring 2.5 wt% furfuryl alcohol.

the final solution binder viscosity was 1.83 mPas, ph 7.0 and surface tension 26 mN/m.

S3 printing and forming the primary blank: and spreading the prepared powder on a forming table board according to the layer thickness of 0.2mm, setting the powder spreading speed to be 0.2m/s, the powder spreading layer thickness to be 0.2mm, the ink jet amount to be 65%, the scanning speed to be 0.80m/s, the microwave power to be 800W, the heating time to be 6s, accumulating layer by layer, and finally performing microwave curing at 800 ℃ for 0.5h to obtain a high-strength primary blank, wherein the bending strength can reach 19.25 MPa.

Example 7

s1 preparing the microwave absorbent, selecting 65 wt% deionized water, weighing 33.5 wt% aluminum chloride powder and 1 wt% furfuryl alcohol by a balance.

the final solution binder viscosity was 2 mPas, ph 7.0, surface tension 26 mN/m.

S3 printing and forming the primary blank: and spreading the prepared powder on a forming table board according to the layer thickness of 0.2mm, setting the powder spreading speed to be 0.2m/s, the powder spreading layer thickness to be 0.2mm, the ink jet amount to be 65%, the scanning speed to be 0.80m/s, the microwave power to be 200W, the heating time to be 1s, accumulating layer by layer, and finally performing microwave curing at 800 ℃ for 0.5h to obtain a high-strength primary blank, wherein the bending strength can reach 14.56 MPa.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A ceramic primary blank forming method based on microwave in-situ sintering is characterized by comprising the following steps:

2. The method for forming a ceramic primary blank based on microwave in-situ sintering, according to claim 1, wherein the microwave absorbent is an inorganic microwave absorbent, the viscosity is less than 2 mPa-s, the pH value is 6.9-7.1, and the surface tension is 20-40 mN/m.

3. The method for forming a ceramic preform based on microwave in-situ sintering as claimed in claim 1, wherein in the microwave heating, the microwave power is 200W-800W, and the heating time of each layer is 0.5 s-6 s.

4. The method for forming a ceramic preform based on microwave in-situ sintering according to claim 2, wherein the microwave absorber is prepared according to the following method:

mixing water-soluble inorganic salt, a high-molecular modifier and deionized water to form a mixed solution, measuring the pH value of the mixed solution, and then adding organic acid to enable the pH value of the mixed solution to be 7-8 so as to obtain the required microwave absorbent.

5. The method for forming a ceramic primary blank based on microwave in-situ sintering, according to claim 4, wherein in the microwave absorbent, the mass fraction of deionized water is 60-75 wt%, the mass fraction of water-soluble inorganic salt is 25-40 wt%, the mass fraction of high molecular modifier is less than or equal to 2.5 wt%, and the others are organic acid.

6. The method for forming ceramic preforms based on microwave in-situ sintering according to claim 4 or 5, wherein the water-soluble inorganic salt is one or more of chloride, bromide, carbonate, sulphate, nitrate, phosphate, meta-aluminate, hydroxide containing one or more elements of Al, Fe, Ni, N.

7. The method for forming the ceramic preform based on the microwave in-situ sintering as claimed in claim 4 or 5, wherein the polymer modified material is one or more of polyethylene glycol, glycerol, furfuryl alcohol, starch and cellulose.

8. The method for forming a ceramic primary blank based on microwave in-situ sintering as claimed in claim 4 or 5, wherein the organic acid is one or both of acetic acid and oxalic acid.

9. The method for forming a ceramic primary blank based on microwave in-situ sintering, according to claim 1, characterized in that the SiC powder is prepared by the following method:

10. A ceramic preform product obtained by the forming method of any one of claims 1 to 9.