阅读说明：本技术 一种熔融态3d直写打印浆料及其制备方法和应用 (Molten 3D direct-writing printing slurry and preparation method and application thereof ) 是由 张斗 王小峰 赵连仲 熊慧文 于 2020-06-16 设计创作，主要内容包括：本发明公开了一种熔融态3D直写浆料及其制备方法和应用,所述熔融态3D直写打印浆料为采用改性剂对陶瓷先驱体改性,所得改性陶瓷先驱体粉末再加热至250℃～300℃所得熔融态的物质,所述陶瓷先驱体为聚碳硅烷。所述改性剂选自聚丙烯,超支化液态聚碳硅烷,液态聚乙烯基硅烷,聚二甲基硅氧烷中的至少一种。本发明首创的提供了一种熔融态的3D直写打印浆料,即是一种完全无溶剂的3D直写打印浆料,通过控制温度即可以简单的控制浆料流变性能。相比于溶液、悬浮液浆料,采用本发明中的熔融态的3D直写打印浆料制备的陶瓷结构表面十分光滑,内部几乎没有缺陷,去除了打印后的坯体需要脱除溶剂的过程,克服了溶剂对坯体的不利影响。(The invention discloses molten 3D direct-writing slurry and a preparation method and application thereof, wherein the molten 3D direct-writing printing slurry is a molten substance obtained by modifying a ceramic precursor by using a modifier and heating the obtained modified ceramic precursor powder to 250-300 ℃, and the ceramic precursor is polycarbosilane. The modifier is selected from at least one of polypropylene, hyperbranched liquid polycarbosilane, liquid polyvinyl silane and polydimethylsiloxane. The invention provides the molten 3D direct-writing printing slurry for the first time, namely the 3D direct-writing printing slurry completely free of solvent, and the rheological property of the slurry can be simply controlled by controlling the temperature. Compared with solution and suspension slurry, the ceramic structure prepared by adopting the molten 3D direct-writing printing slurry has a very smooth surface and almost no defects in the interior, the process that a printed blank needs to be subjected to solvent removal is eliminated, and the adverse effect of the solvent on the blank is overcome.)

1. The molten 3D direct-writing printing paste is characterized in that: the molten 3D direct-writing printing slurry is a molten substance obtained by modifying a ceramic precursor by using a modifier and heating the obtained modified ceramic precursor powder to 250-300 ℃, wherein the ceramic precursor is polycarbosilane, and the modifier is at least one selected from polypropylene, hyperbranched liquid polycarbosilane, liquid polyvinyl silane and polydimethylsiloxane.

2. The molten state 3D direct write printing paste according to claim 1, wherein: the molten 3D direct-writing printing slurry is used for 10s^-1The viscosity at shear rate is 100 to 1000 Pa.s.

3. The molten state 3D direct write printing paste according to claim 1, wherein: the addition amount of the modifier is 1-5% of the mass of the ceramic precursor.

4. The molten state 3D direct write printing paste according to claim 1, wherein: the molecular weight of the polycarbosilane is 1000-2000 g/mol.

5. Method for preparing a molten state 3D direct write printing paste according to any of claims 1 to 4, characterized in that: the method comprises the following steps:

step one

Adding polycarbosilane and a modifier into an organic solvent, reacting for 4-8 hours at 100-140 ℃ to obtain a mixed solution, drying the mixed solution, grinding and sieving, and taking undersize products to obtain modified ceramic precursor powder;

step two

And (3) placing the modified ceramic precursor powder in a printing needle cylinder, introducing nitrogen into the needle cylinder, heating to 250-300 ℃ at the speed of 5-10 ℃/min, preserving the temperature for 30-60 min, and removing bubbles to obtain the molten 3D direct-writing printing slurry.

6. The method for preparing a molten state 3D direct-write printing paste according to any one of claim 5, wherein:

in the first step, the organic solvent is selected from one of xylene, tetrahydrofuran and toluene;

in the first step, the drying temperature is 100-140 ℃, the drying time is 12-24 hours, and the drying pressure is less than or equal to-0.1 MPa;

in the first step, the mesh number of the screen used for sieving is 100 meshes.

7. Use of a molten state 3D direct write printing paste according to any of claims 1 to 5, characterized in that: and applying the molten 3D direct-writing printing slurry to the preparation of 3D ceramics.

8. The use of a molten state 3D direct write printing paste according to claim 7, wherein: the process of 3D direct-writing printing of the ceramic material comprises the following steps: according to the designed three-dimensional structure, the ceramic slurry is printed layer by layer through 3D direct writing printing equipment to obtain a three-dimensional structure rough blank, then the three-dimensional structure rough blank is subjected to pre-oxidation reaction for more than or equal to 24 hours at 180-250 ℃ in a cross-linking atmosphere to obtain a pre-oxidized blank body, and then the pre-oxidized blank body is pyrolyzed to obtain the 3D ceramic.

9. The use of a molten state 3D direct write printing paste according to claim 8, wherein: the crosslinking atmosphere is selected from one of air, ozone, chlorine, cyclohexene, n-heptene and octyne; the flow rate of the crosslinking atmosphere is 40-60 ml/min.

10. The use of a molten state 3D direct write printing paste according to claim 8, wherein: the pyrolysis temperature is 1000-1400 ℃, and the pyrolysis time is 1-2 h.

Technical Field

The invention belongs to the technical field of 3D printing materials, and particularly relates to molten 3D direct-writing slurry and a preparation method and application thereof.

Background

The 3D printing technology is to digitally slice a three-dimensional model into a two-dimensional cross section, and add and manufacture parts in a point-by-point, line-by-surface mode, so that a structure which is difficult to process or cannot be processed by the traditional process can be realized. Among them, the direct writing molding technology was proposed as an inexpensive 3D printing technology by Joseph Cesarano III and the like of Sandia national laboratory in the united states for the first time. The method can achieve large aspect ratios and size control ranges, and can achieve three-dimensional structures with unsupported features. The ink used for printing has high design freedom of the components of the raw materials, and can realize the three-dimensional forming of metal, ceramic and even living cells.

When the direct-writing forming technology is used for preparing the ceramic three-dimensional material, the components, the microstructure mechanism and the rheological property of the slurry are key and difficult points. In order to maintain the shape of the paste after extrusion, it is required that the paste have appropriate rheological properties, one method is to uniformly disperse the ceramic powder in water or other organic solvents, and the purpose of controlling the rheological properties of the paste is achieved by adjusting the PH or ion concentration, and the other method is to cure the paste by applying external conditions, such as ultraviolet light, thermal stimulation, and the like. Such as: franch, P.Scanferla, L.Zeffiro, H.Elsayed, A.Balielo, G.Giacomello, M.Pasetto, P.Colombo, Direct ink writing of geopolymer inks, J.Eur center Soc 37(6) (2017)2481-2489.C.M.Larson, J.J.Choi, P.A.Gallardo, S.W.Henderson, M.D.Nick, G.Rajapalalan, R.F.Shepherd, Direct ink writing of Silicon Carbide for Microwave Optics, Adv Eng Mater 18 (2016) (39-45. H.Checkn, X.F.F.Wang, W.Microwave Optics, Zv encg Mater 18 (2016) (19, J.Z10 J.Zymicro, Zymicro, Zymid of Yeast ceramic graphics J.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.S. 12, (8) of Yeast ceramic adhesive, Zymotrying, Zymotk.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K.K..

In previous reports, designed slurry is often in the form of solution or suspension, and the rheological property of the slurry is often very sensitive to the concentration of solute, especially solvent with strong volatility, which results in difficult control of the rheological property of the slurry. On the other hand, a large amount of solvent remains in the formed blank, and a large amount of microcracks and pores are inevitably left in the blank in the process of removing the solvent.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a molten state 3D direct-writing printing slurry and a preparation method and application thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention relates to molten 3D direct-writing printing slurry, which is a molten substance obtained by modifying a ceramic precursor by using a modifier and heating the obtained modified ceramic precursor powder to 250-300 ℃, wherein the ceramic precursor is Polycarbosilane (PCS), and the modifier is at least one selected from polypropylene, hyperbranched liquid polycarbosilane, liquid polyvinylsilane and polydimethylsiloxane.

The invention provides the molten 3D direct-writing printing slurry for the first time, which is the completely solvent-free 3D direct-writing printing slurry, and the rheological property of the slurry can be simply controlled by controlling the temperature.

The molten 3D direct-writing printing slurry is obtained by heating modified ceramic precursor powder to be molten, polycarbosilane is the most common and stable ceramic precursor, but the brittleness of polycarbosilane is high.

In a preferable scheme, the molten 3D direct-writing printing slurry is used for 10s^-1At shear rateThe viscosity of (b) is 100 to 1000Pa.s, preferably 100 to 300 Pa.s.

In a preferred scheme, the addition amount of the modifier is 1-5% of the mass of the ceramic precursor.

The adding amount of the modifier is controlled within the preferable range, so that the brittleness of the polycarbosilane can be completely improved, and the phenomenon that excessive modifier is introduced to precipitate in the process of reducing the temperature of a precursor to form defects and leave cracks can be avoided.

In a preferable scheme, the molecular weight of the polycarbosilane is 1000-2000 g/mol.

The invention relates to a preparation method of molten 3D direct-writing printing slurry, which comprises the following steps:

step one

Adding polycarbosilane and a modifier into an organic solvent, reacting for 4-8 hours at 100-140 ℃ to obtain a mixed solution, drying the mixed solution, grinding and sieving, and taking undersize products to obtain modified ceramic precursor powder;

step two

And (3) placing the modified ceramic precursor powder in a printing needle cylinder, introducing nitrogen into the needle cylinder, heating to 250-300 ℃ at the speed of 5-10 ℃/min, preserving the temperature for 30-60 min, and removing bubbles to obtain the molten 3D direct-writing printing slurry.

In the actual operation, in step one, the reaction is carried out under stirring.

Preferably, in the first step, the organic solvent is selected from one of xylene, tetrahydrofuran and toluene.

In the preferable scheme, in the first step, the drying temperature is 100-140 ℃, the drying time is 12-24 hours, and the drying pressure is less than or equal to-0.1 MPa.

Preferably, in the first step, the mesh number of the screen used for screening is 100 meshes.

The invention relates to application of molten 3D direct-writing printing paste, which is used for preparing 3D ceramics.

Preferably, the process of 3D direct-write printing of the ceramic material comprises: according to the designed three-dimensional structure, the ceramic slurry is printed layer by layer through 3D direct writing printing equipment to obtain a three-dimensional structure rough blank, then the three-dimensional structure rough blank is subjected to pre-oxidation reaction for more than or equal to 24 hours at 180-250 ℃ in a cross-linking atmosphere to obtain a pre-oxidized blank body, and then the pre-oxidized blank body is pyrolyzed to obtain the 3D ceramic.

In the practical application process, in the process of placing the modified ceramic precursor powder into a printing needle cylinder, a needle head, a piston and an air duct are synchronously connected, and then the whole is arranged on a clamp on a Z axis; introducing nitrogen into the needle cylinder, heating to 250-300 ℃ at the speed of 5-10 ℃/min, preserving the temperature for 30-60 min, removing bubbles to obtain a molten modified ceramic precursor, simultaneously setting the temperature of a forming platform of the direct-writing forming device to be 150-195 ℃, then automatically controlling the air pressure of the needle cylinder arranged on a Z axis by a computer by means of the three-dimensional structure pattern required by computer-aided design, so that the slurry flows out of the needle nozzle and is deposited on an X-Y axis forming platform moving according to a program, thereby obtaining a first layer structure; thereafter, the Z-axis is moved or rotated precisely upwards to a height determined by the structural solution, and the second layer formation will be carried out on the first layer structure; and then, obtaining a rough blank with a three-dimensional lattice structure in a layer-by-layer superposition mode, wherein the air pressure range is 1-1000 PSI, and the moving speed of the forming platform is 0.1-500 mm/s.

Further preferably, the crosslinking atmosphere is selected from one of air, ozone, chlorine, cyclohexene, n-heptene and octyne.

Further preferably, the flow rate of the crosslinking atmosphere is 40-60 ml/min.

Further preferably, the pyrolysis temperature is 1000-1400 ℃, and the pyrolysis time is 1-2 h.

Principles and advantages

The invention provides the molten 3D direct-writing printing slurry for the first time, namely the 3D direct-writing printing slurry completely free of solvent, and the rheological property of the slurry can be simply controlled by controlling the temperature.

Compared with solution and suspension slurry, the ceramic structure prepared by adopting the molten 3D direct-writing printing slurry has a very smooth surface and almost no defects in the interior, the process that a printed blank needs to be subjected to solvent removal is eliminated, and the adverse effect of the solvent on the blank is overcome.

The molten 3D direct-writing printing paste is obtained by modifying and heating a common ceramic precursor by using a small amount of modifier, and the preparation method is simple.

Drawings

FIG. 1: an electron scanning microscope picture of the three-dimensional SiC ceramic structure obtained in example 1;

FIG. 2: scanning electron microscope pictures of the three-dimensional SiC ceramic structures obtained in comparative example 1.

Detailed Description

The invention is further illustrated, but not limited, by the following examples: