CN113121246A

CN113121246A - Core-shell black ceramic particles for 3D printing and preparation method and application thereof

Info

Publication number: CN113121246A
Application number: CN202110406847.XA
Authority: CN
Inventors: 刘战强; 辛明泽; 王兵
Original assignee: Shandong University
Current assignee: Shandong University
Priority date: 2021-04-15
Filing date: 2021-04-15
Publication date: 2021-07-16

Abstract

The invention belongs to the technical field of additive manufacturing of black powder ceramics and composite ceramics, and particularly relates to core-shell black ceramic particles for 3D printing, and a preparation method and application thereof. Core-shell black ceramic particles for 3D printing, comprising: the black ceramic substrate and the coating layer are arranged, and the thickness of the coating layer is 50-100 nm; the coating material is selected from metal oxides. The invention uniformly disperses the black ceramic matrix in the precursor suspension, and the polymerization reaction is carried out under certain conditions, so as to form a modified layer with a certain space structure on the surface layer of the coated black ceramic matrix, and the required powder material coated with the low-scattering and reinforcing phase modified layer is obtained after drying and heat treatment, thereby reducing the absorption and scattering of the black ceramic material to ultraviolet light in the photocuring process. Meanwhile, the ceramic material prepared by 3D printing of the core-shell black ceramic particles has larger thickness and excellent compactness and mechanical property.

Description

Core-shell black ceramic particles for 3D printing and preparation method and application thereof

Technical Field

The invention belongs to the technical field of additive manufacturing of black powder ceramics and composite ceramics, and particularly relates to core-shell black ceramic particles for 3D printing, and a preparation method and application thereof.

Background

The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

3D printing (3DP), a technique for constructing objects by layer-by-layer printing using bondable materials such as powdered metals or plastics based on digital model files, is one of the rapid prototyping techniques, also known as additive manufacturing. Representative 3D printing manufacturing techniques mainly include: the light-cured forming technology of which the raw material is photosensitive resin, the fused deposition manufacturing technology of which the raw material is hot-melt resin, the selective laser sintering technology of which the raw material is non-metal powder and the selective laser melting technology of which the raw material is metal powder. The ceramic parts prepared by the photocuring additive manufacturing technology based on the Digital Light Processing (DLP) technology of the mask image projection technology are gradually developed from the photocuring molding technology, have high precision and excellent mechanical properties, and are particularly suitable for manufacturing miniature and high-precision parts. However, DLP technology has relatively strict requirements on the absorption and scattering of ultraviolet light by materials, so that the ceramics prepared by photocuring molding are mainly limited to white oxide ceramics such as aluminum oxide materials.

In addition, although the prior art discloses that some materials with low refractive index are coated on the outer layer of the black ceramic powder, the thickness of the coating layer is small and is only 2-20nm, so that more coating layers or coating layers with different refractive indexes are required to be arranged to weaken the phenomena of scattering and light absorption, and impurity ions are easily introduced by using an organic precipitator to influence the bonding strength and the mechanical property of a formed blank body. There are also some printing methods, which can increase the curing thickness, but the compactness after curing is poor and the mechanical properties are low.

Disclosure of Invention

In order to solve the problems of small thickness of a black ceramic particle coating layer, complex preparation method, low thickness of a single-layer cured layer of a ceramic blank prepared from black ceramic particles and difficult forming, the invention provides the core-shell black ceramic particles for 3D printing, and the preparation method and the application thereof. The core-shell black ceramic particles are used for 3D printing, the thickness of a single-layer curing layer can be 70 microns +/-5 microns, a composite ceramic blank prepared by using the ceramic particles for 3D printing is obtained, the printing efficiency of the sintered ceramic is improved by 50-65% compared with that of the ceramic prepared by using unmodified powder, and after sintering, the density is improved by 4-8% and the bending strength is improved by 20-25%.

Specifically, the invention is realized by the following technical scheme:

in a first aspect of the present invention, there is provided a core-shell black ceramic particle for 3D printing, comprising:

the black ceramic substrate and the coating layer are arranged, and the thickness of the coating layer is 50-100 nm;

the coating material is selected from metal oxides.

In a second aspect of the present invention, a method for preparing core-shell black ceramic particles for 3D printing is provided, including: mixing the black ceramic matrix with a precursor of the metal oxide, adjusting the pH value, standing, drying and calcining to obtain the metal oxide.

In a third aspect of the present invention, there is provided a photocuring printing method including: the core-shell black ceramic particles for 3D printing are mixed with photosensitive resin to prepare composite ceramic slurry, photocuring printing is performed, and the ceramic is obtained after sintering.

In a fourth aspect of the invention, a composite ceramic prepared by a photocuring printing method is provided.

In a fifth aspect of the invention, an application of core-shell black ceramic particles for 3D printing in the field of 3D printing is provided.

One or more embodiments of the present invention have the following advantageous effects:

1) the invention uniformly disperses the black ceramic matrix in the precursor suspension, and the black ceramic matrix is subjected to polymerization reaction under certain conditions, so that a modified layer is formed on the surface layer of the coated black ceramic matrix, a core-shell structure with the black ceramic matrix as a core and the coating layer as a shell is prepared, and the required powder material coated with the low-scattering and reinforcing phase modified layer is obtained after drying and heat treatment, so that the absorption and scattering of the black ceramic material to ultraviolet light in the photocuring process are reduced. The thickness of the coating layer of the core-shell black ceramic particles prepared by the invention is 50-100nm, and the effect of weakening scattering and light absorption phenomena is obvious.

2) The core-shell black ceramic particles can be prepared by adding the reinforcing phase material into the core-shell black ceramic particles, so that the high-efficiency preparation of the low-light-absorption and low-scattering modified material on the surface layer of the black ceramic material powder can be realized, the core-shell black ceramic particles with the coating layer thickness of 50-100nm can be prepared by only one reaction, and a plurality of layers of coating layers are not required.

3) According to the invention, the black ceramic particles and the metal oxide precursor are mixed, and are subjected to stirring and pH adjustment treatment, compared with the method of directly mixing the black ceramic particles and the metal salt solution, the method has the advantages that a precipitator is not required, the operation difficulty is reduced, impurity ions are prevented from being introduced, and the strength of the printed ceramic blank is improved. In addition, the invention can coat any single or composite low-light absorption low-scattering and reinforcing phase modified material capable of preparing precursor materials on the surface layer of the black ceramic powder, thereby realizing the high-efficiency preparation of the black powder ceramic and the composite ceramic, and having simple and convenient operation and strong expansibility.

4) The disclosed photocuring printing method uses two sintering steps, the first sintering step is used for removing resin materials, and the second sintering step is used for improving the compactness and mechanical strength of ceramic materials. The compactness, the hardness tested by a Vickers hardness tester, the bending strength tested by a three-point bending test and the like are represented by an Archimedes drainage method, and the results show that compared with the ceramic prepared by unmodified powder, the printing efficiency of the ceramic prepared by modified powder is improved by 50-65%, the compactness is improved by 4-8%, and the bending strength is improved by 20-25%.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention. Embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein:

FIG. 1 is a flowchart of a process for preparing a composite ceramic material by 3D printing using core-shell black ceramic particles according to example 1 of the present invention;

fig. 2 is a schematic operation diagram of the preparation of a composite ceramic material by 3D printing using core-shell black ceramic particles according to example 1 of the present invention.

Detailed Description

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out according to conventional conditions or according to conditions recommended by the manufacturers.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

In order to solve the problems of small thickness of a black ceramic particle coating layer, complex preparation method, low thickness of a single-layer cured layer of a ceramic blank prepared from black ceramic particles and difficult forming, the invention provides the core-shell black ceramic particles for 3D printing, and the preparation method and the application thereof. The core-shell black ceramic particles are used for 3D printing, a composite ceramic curing layer with a single-layer curing layer thickness of 70 +/-5 microns can be prepared, the printing efficiency of the ceramic prepared by using the modified powder is improved by 50-65% compared with that of the ceramic prepared by using unmodified powder, the density is improved by 4-8% after sintering, and the bending strength is improved by 20-25%.

The thickness of the single-layer curing layer is the maximum curing layer thickness which can be reached by the slurry by carrying out unconstrained exposure on the slurry under the set exposure parameters. The larger the thickness of the single-layer cured layer is, the easier the curing molding is. At the same time, higher cure thicknesses may improve interlayer bonding to reduce cracks in the final ceramic. Monolayer cure thickness is an important parameter in determining the thickness of the sliced layer, printing efficiency, and print quality.

In order to ensure that the cured layers have good interlayer adhesion during photocuring, the thickness of the single-layer cured layer is 2-3 times of the thickness of the slice. Therefore, when the ceramic green body is exposed without constraint, the larger the thickness of the single-layer cured layer is, the higher the interlayer adhesive force is during printing, and the more stable the structure of the printed ceramic green body is.

Before a composite ceramic blank is subjected to photocuring additive manufacturing or 3D printing, a black ceramic matrix is uniformly dispersed in a precursor suspension, a polymerization reaction occurs under a certain condition, a modification layer with a certain space structure is formed on the surface layer of the coated black ceramic matrix, a required powder material coated with a low-scattering and reinforcing phase modification layer is obtained after drying and heat treatment, the absorption and scattering of ultraviolet light in the photocuring process of the black ceramic matrix are reduced, and a reinforcing phase material is added simultaneously, so that the efficient photocuring additive preparation of the black ceramic matrix and the composite ceramic is realized. The improved black ceramic matrix and the improved composite ceramic are simple in printing preparation process, free of complex equipment support, low in preparation cost and easy to popularize.

Specifically, the invention is realized by the following technical scheme:

the coating material is selected from metal oxides.

The ceramic slurry prepared by coating the silicon carbide fiber material with low light absorption and low scattering alumina by using a surface layer modification method has obviously improved photocuring performance compared with the ceramic slurry prepared by coating the silicon carbide fiber material without the modified material, wherein the thickness of a single-layer curing layer, the ceramic density, the mechanical property of ceramic and the like are greatly improved.

However, the inventors have found that the larger the thickness of the coating layer, the better the coating layer thickness. In the 3D printing technology, the particle size of the printing raw material is between hundreds of nanometers and tens of micrometers, and if the thickness of the coating layer is too small, the reduction effect on scattering and light absorption is not obvious; if the thickness of the coating layer is too large, the thickness is between hundreds of nanometers and microns, although the scattering and light absorption effects can be weakened, the required surface layer modification time is too long, and meanwhile, the thickness of the modified layer is too large, so that the components of the printed ceramic material are changed, and the mechanical property is reduced.

In one or more embodiments of the invention, the black ceramic matrix is selected from oxide ceramics and/or non-oxide ceramics;

preferably, the non-oxide ceramic is selected from at least one of boron nitride, diamond, silicon carbide, aluminum nitride, tungsten carbide, titanium nitride, boron carbide.

In one or more embodiments of the present invention, the metal oxide is selected from at least one of oxides of aluminum, magnesium, and titanium.

In one or more embodiments of the present invention, the metal oxide precursor is selected from the group consisting of aluminum isopropoxide, magnesium nitrate hexahydrate, tetrabutyl titanate, methyltriethoxysilane.

The corresponding proportions of different precursors and acid catalysts are different. The corresponding acid of aluminum isopropoxide is nitric acid, the corresponding acid of magnesium nitrate hexahydrate is citric acid, the corresponding acid of tetrabutyl titanate is nitric acid, and the corresponding acid of methyltriethoxysilane is hydrochloric acid.

The precursor raw materials are all analytically pure.

In the invention, the reaction principle of the black ceramic matrix and the metal oxide precursor is as follows:

dissolving alkoxide or other metal organic matters of each component required by the modified layer in water, adding an acid catalyst, carrying out hydrolysis reaction under a proper environment temperature condition, forming a coating layer on the surface of a base material along with the polymerization reaction, and then preparing the required modified layer on the surface of the base material through a series of processes such as drying, sintering and the like.

The metal salt solution adopts a chemical precipitation method according to the reaction principle of the metal salt solution, and salt ions in the solution and a precipitator are subjected to precipitation reaction to form insoluble precipitates which are deposited on the surface of a material to form a coating.

Preferably, the preparation method comprises: stirring and mixing a precursor of the metal oxide with deionized water to prepare a precursor suspension, adding the black ceramic matrix into the precursor suspension, adding acid, stirring, standing, drying and calcining to obtain the catalyst.

The method comprises the steps of firstly selecting black ceramic matrixes such as silicon carbide fiber powder, short carbon fiber powder, silicon carbide powder and the like as modified objects, preparing precursor suspension of a required low light absorption, low scattering or enhanced phase material by selecting aluminum isopropoxide, tetrabutyl titanate and the like, uniformly dispersing the black ceramic matrixes to be coated in the precursor suspension, carrying out polymerization reaction under certain conditions, forming a modified layer with a certain space structure on the surface layer of the coated powder material, and drying and carrying out heat treatment to obtain the required low light absorption, low scattering rate or enhanced phase material on the surface layer of the coated powder material. The powder material with the modified surface layer is mixed with photosensitive resin to prepare improved composite ceramic slurry for 3D printing additive manufacturing of black powder ceramic and composite ceramic.

Preferably, the molar ratio of the precursor of the metal oxide to the deionized water is 1: 100-140; preferably 1: 120;

preparing a precursor solution according to the molar ratio of water to the precursor of the metal oxide of 100-150:1, preferably 120:1, stirring, and adding 50-80g of ceramic matrix powder after uniformly stirring.

Preferably, the stirring and mixing, the acid adding and stirring and the standing temperature are 75-90 ℃;

preferably, the acid is selected from nitric acid, which is analytically pure, 63-68%;

preferably, the acid is added to a pH of 6 and stirred for 10-30min, preferably 20 min;

the nitric acid plays a role of a catalyst, the acid or the alkali plays a role of catalyzing the hydrolysis reaction, and turbidity or precipitation is easy to generate under the alkaline condition; and under proper acidic condition, clear precursor solution can be obtained. When the pH value is about 6, the prepared precursor solution is clear and stable.

The purpose of adding acid and stirring is to uniformly mix the solution and fully hydrolyze. The influence on the thickness of the coating layer is the standing coating time, when the coating time is 8-16 hours, the mass of the black ceramic matrix is increased rapidly, and the weight gain rate and the time are in a substantially linear relation; after 16h, the increase in mass of the black ceramic matrix became slow.

Preferably, ultrasonic mixing is further included before the acid adding and stirring, and the ultrasonic mixing time is 0.5-3h, preferably 2 h. The powder materials to be coated are dispersed by ultrasonic, and one is to reduce the adhesion among the powder materials and avoid the uneven coating of the materials; and secondly, a contact interface with a larger surface area is formed between the powder material and the precursor suspension, and a modifying material with a larger thickness is coated on the surface layer of the powder, so that the better low-absorption scattering performance to ultraviolet light is ensured to be exerted when the slurry prepared from the treated powder material is used for photocuring production.

Preferably, the standing time is 10-15h, preferably 12 h;

preferably, the drying condition is drying at 60-100 ℃ for 12-48h, preferably drying at 80 ℃;

preferably, the calcination condition is 800-1200 ℃ calcination for 1-3h, preferably 1000 ℃ calcination for 1 h.

In a preferred embodiment of the invention, silicon carbide fiber powder is taken as a coated object, aluminum isopropoxide is taken as a precursor, aluminum isopropoxide and deionized water are mixed at 80 ℃ to prepare a precursor suspension, the molar ratio of the aluminum isopropoxide to the deionized water is 1:120, the silicon carbide fiber powder and the precursor suspension are ultrasonically mixed for 2h to be uniformly dispersed, nitric acid is added to adjust the pH value to 6, the mixture is kept stand for 12h, dried at 80 ℃ and calcined at 1000 ℃ for 1h, and the silicon carbide composite material is obtained.

The surface-modified aluminum oxide material has the performances of high-temperature stability and cohesiveness, and can fully exert the cohesiveness advantage in the surface-modified process of powder; meanwhile, the alumina material has high hardness and high wear resistance, and can play a role of a reinforcing phase to realize the preparation of the composite ceramic.

The silicon carbide fiber surface layer is coated with the aluminum oxide material with small ultraviolet absorption scattering, and the silicon carbide fiber surface layer is suitable for improving the photocuring performance of the silicon carbide fiber composite ceramic slurry. The alumina material has the characteristics of low refractive index, low absorption and scattering of ultraviolet light, good cohesiveness, good high-temperature stability, good chemical compatibility with a silicon carbide fiber matrix and the like, and belongs to an easily-coated surface layer modified material.

The surface layer modification method is adopted as an improved method for realizing the efficient preparation of the black ceramic material powder, a material with uniform chemical components and low light absorption and scattering can be adhered to the surface layer of the powder, and the advantages of small light absorption and scattering and good light curing performance of the modified material can be fully exerted in the process of preparing the composite ceramic material by light curing.

After the operation, a layer of evenly distributed aluminum oxide material with small ultraviolet absorption scattering can be coated on the surface layer of the silicon carbide fiber powder. And testing the adhesion and uniform distribution of the modified material on the surface layer of the silicon carbide fiber powder by using X-ray Energy Dispersive Spectroscopy (EDS) or X-ray photoelectron spectroscopy (XPS). Multiple experiments prove that under the preparation parameters, the silicon carbide fiber surface layer can form an aluminum oxide film with the thickness of 50-100 nm.

In a third aspect of the present invention, there is provided a photocuring printing method including: and mixing the core-shell black ceramic particles for 3D printing with photosensitive resin to prepare composite ceramic slurry, and carrying out photocuring printing and sintering to obtain the composite ceramic slurry.

In one or more embodiments of the invention, the composite ceramic slurry has a solids content of 30-40 vol%, preferably 35 vol%;

preferably, the light-curing agentThe chemical printing parameters are as follows: the optical power is 40-60mW/cm²Exposure time is 20-40 s; the thickness of the model section was 25 μm.

Preferably, the photocuring printing parameters are: ultraviolet wavelength of 405nm and optical power of 50mW/cm²Exposure time 30 s;

preferably, the sintering adopts two-stage sintering, the first stage of degreasing sintering is carried out at the temperature of 900-1200 ℃ for 1-3h, and the second stage of vacuum sintering is carried out at the temperature of 1300-1600 ℃ for 1-2 h;

preferably, the first stage of degreasing and sintering is carried out, wherein the sintering temperature is 1000 ℃, and the time is 2 hours;

preferably, the second stage of vacuum sintering is carried out at 1500 ℃ for 1.5 h.

The additive manufacturing method for preparing the composite ceramic by adopting the photocuring molding technology can obtain the ceramic with high manufacturing precision and good mechanical property, and can fully exert the performance advantage of the photocuring technology in the additive manufacturing process of the composite ceramic.

The fourth aspect of the invention provides a composite ceramic blank prepared by the photocuring printing method.

Preferably, the 3D printing field is selected from the field of printing of black ceramic materials.

The present invention is described in further detail below with reference to specific examples, which are intended to be illustrative of the invention and not limiting.

Example 1

Mixing and stirring aluminum isopropoxide and deionized water at 90 ℃, wherein the molar ratio is 1:120, adding 60g of silicon carbide fiber powder after uniformly stirring, ultrasonically dispersing for 2h, adding nitric acid to adjust the pH value of the solution to 6, stirring for 20min, standing at 90 ℃ for 12h, drying at 80 ℃, and calcining at 1000 ℃ for 1h to obtain the core-shell black ceramic particles for 3D printing.

Mixing the core-shell black ceramic particles for 3D printing with photosensitive resin to prepare mixed slurry,the mixed slurry has a solid content of 35%, and the 3D printing parameters are: ultraviolet light wavelength of 405nm and light power of 50mW/cm²And exposing for 30s to obtain a cured ceramic blank, degreasing for 2h at 1000 ℃, and sintering for 1.5h at 1500 ℃ to obtain a ceramic sample.

FIG. 1 is a flowchart illustrating a process of preparing a composite ceramic material by 3D printing using core-shell black ceramic particles according to the present embodiment; fig. 2 is a schematic diagram illustrating an operation of preparing a composite ceramic material by 3D printing using core-shell black ceramic particles according to the present embodiment.

The silicon carbide fiber prepared in the embodiment forms an aluminum oxide film with the thickness of 70-80nm on the surface layer, and the composite ceramic blank with the thickness of a single-layer curing layer of 70 +/-5 mu m is prepared by photocuring 3D printing.

Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A core-shell shaped black ceramic particle for 3D printing, comprising:

the coating material is selected from metal oxides.

2. The core-shell black ceramic particles for 3D printing according to claim 1,

the black ceramic matrix is selected from oxide ceramic and/or non-oxide ceramic;

3. The core-shell black ceramic particles for 3D printing according to claim 1,

the metal oxide is at least one selected from oxides of aluminum, magnesium, and titanium.

4. The method of preparing core-shell black ceramic particles for 3D printing according to any one of claims 1 to 3, comprising: mixing the black ceramic matrix with a precursor of the metal oxide, adjusting the pH value, standing, drying and calcining to obtain the metal oxide.

5. The method of preparing core-shell black ceramic particles for 3D printing according to claim 4, wherein the metal oxide precursor is selected from the group consisting of aluminum isopropoxide, magnesium nitrate hexahydrate, tetrabutyl titanate, methyltriethoxysilane;

preferably, the preparation method comprises: stirring and mixing a precursor of the metal oxide with deionized water to prepare a precursor suspension, adding the black ceramic matrix into the precursor suspension, adding acid, stirring, standing, drying and calcining to obtain the catalyst;

preferably, the acid is selected from nitric acid;

preferably, ultrasonic mixing is further included before the acid adding and stirring, and the ultrasonic mixing time is 0.5-3h, preferably 2 h;

preferably, the standing time is 10-15h, preferably 12 h;

preferably, the drying condition is drying at 60-100 ℃ for 12-48h, preferably 80 ℃;

6. The preparation method of the core-shell black ceramic particles for 3D printing according to claim 4 comprises the following steps: taking silicon carbide fiber powder as a coated object, taking aluminum isopropoxide as a precursor, mixing aluminum isopropoxide and deionized water at 80 ℃ to prepare a precursor suspension, wherein the molar ratio of aluminum isopropoxide to deionized water is 1:120, ultrasonically mixing the silicon carbide fiber powder and the precursor suspension for 2h to uniformly disperse the silicon carbide fiber powder and the precursor suspension, adding nitric acid to adjust the pH value to 6, standing for 12h, drying at 80 ℃ and calcining at 1000 ℃ for 1h to obtain the silicon carbide composite material.

7. A photocuring printing method, comprising: the core-shell black ceramic particles for 3D printing according to any one of claims 1 to 3 are mixed with photosensitive resin to prepare composite ceramic slurry, and photocuring printing and sintering are carried out to obtain the composite ceramic slurry.

8. The photocuring printing method according to claim 7, wherein the composite ceramic slurry has a solid content of 30-40%, preferably 35%;

preferably, the photocuring printing parameters are: the optical power is 40-60mW/cm²Exposure time is 20-40 s;

9. A composite ceramic body prepared by the photocuring printing method of claim 7 or 8.

10. Use of the core-shell shaped black ceramic particles for 3D printing of any one of claims 1 to 3 in the field of 3D printing;