PRECURSOR MATERIAL FOR THE PRODUCTION OF SILICON CARBIDE CONTAINING MATERIALS

Abstract

The invention relates to a method for the production of a composition, in particular a SiC precursor granulate, for use in additive manufacturing from a solution or dispersion.

Claims

1. A method for the production of a silicon carbide precursor granulate, comprising: (a) producing a solution or dispersion comprising: (v) at least one silicon-containing compound, (vi) at least one carbon-containing compound, (vii) at least one solvent or dispersant, and (viii) optionally doping and/or alloying reagents, and (b) removing the solvent or dispersant.

2. The method according to claim 1, wherein in the second method step (b) a powdery composition is obtained.

3. The method according to claim 2, wherein the powdery composition comprises particle sizes selected from 1 μm to 1,000 μm, 0.5 μm to 500 μm, 1 μm to 200 μm, 10 μm to 100 μm, and 40 μm to 80 μm.

4. The method according to claim 1, wherein the silicon-containing compound is selected from silanes, silane hydrolysates, orthosilicic acid and mixtures thereof.

5. The method according to claim 4, wherein the silicon-containing compound is a silane selected from tetraalkoxysilanes, trialkoxyalkylsilanes, tetraethoxysilane, tetramethoxysilane, and triethoxymethylsilane.

6. The method according to claim 1, wherein in step (a), at least one of the components is heated to a temperature selected from 30 to 100° C., 40 to 80° C., and 50 to 70° C.

7. The method according to claim 1, wherein the solvent or dispersant is selected from water, organic solvents and mixtures thereof.

8. The method according to claim 7, wherein the solvent is an organic solvent selected from alcohols, esters, ketones, amines, amides, sulfoxides, methanol, ethanol, 2-propanol, acetone, ethyl acetate, N,N-dimethylformamide, dimethyl sulfoxide, and mixtures thereof.

9. The method according to claim 1, wherein the carbon-containing compound is selected from sugars, sucrose, glucose, fructose, invert sugar, maltose, starch, starch derivatives, organic polymers, phenol-formaldehyde resin, resorcinol-formaldehyde resin, and mixtures thereof.

10. The method according to claim 9, wherein the carbon-containing compound is selected from sugars, starch, starch derivatives and mixtures thereof.

11. The method according to claim 1, wherein the solution or dispersion further comprises at least one catalyst.

12. The method according to claim 11, wherein the catalyst is an acid or a base.

13. The method according to claim 1, wherein in step (b) the solvent or dispersant is removed at an elevated temperature and/or under reduced pressure.

14. The method according to claim 1, further comprising: (c) thermally treating the composition obtained in step (b).

15. The method according to claim 14, wherein the composition in step (c) is heated to a temperature selected from 300 to 900° C., 400 to 800° C., and 500 to 700° C.

16. A silicon carbide precursor granulate prepared by the method of claim 1.

17. The precursor granulate of claim 16, which is in a liquid composition or, suspension.

18-19. (canceled)

Description

[0181] The figures show according to

[0182] FIG. 1 a cross-section along an xy-plane of an apparatus for carrying out a method for the production of three-dimensional objects from the precursor granulate according to the invention, and

[0183] FIG. 2 an enlarged section of FIG. 1, which in particular shows the three-dimensional object produced.

[0184] The method is explained below on the basis of the representation of the figures by preferred embodiments in a non-limiting manner.

[0185] The apparatus 1 comprises a building field in an xy-plane, which is perpendicular to an xz-plane, the building field extension 2 of which is shown in the x-direction in FIG. 1. On the build field, a three-dimensional object is generated from a powdery composition 3, in particular a precursor granulate described above, by selective radiation of laser beams 4. The building field is configured to be movable by the piston 6 in the z-direction at least in certain areas, in particular along a z-axis which is perpendicular to the xy-plane. In the embodiment shown in the figure, the entire build field is configured to be movable by the piston 6 over its build field extension 2, in particular the entire extension of the build field in the x and y directions. However, it is also possible that according to an alternative embodiment not shown in the figure, only selected areas of the construction field are movable in the z-direction, i.e. along a z-axis. Areas of the construction field can thus be configured, for example, in the form of stamps, which in particular can be moved independently of one another in the z-direction, so that selected areas of the construction field can be moved in the z-direction.

[0186] The construction field shown in the figure comprises a powder bed of the composition 3 according to the invention, in particular of the precursor granulate according to the invention. Adjacent to the construction field, storage devices 7 are provided for receiving and dispensing the composition 3. According to the form of execution shown in the figure, the storage devices 7 are provided with pistons movable in the z-direction, in particular along a z-axis, so that by moving the piston in the z-direction either a space is created in the storage device 7 for receiving the composition 3 or the composition is pressed out of the storage device 7, in particular into the region of the construction field.

[0187] After being discharged from the storage device 7, the composition 3 is distributed in a homogeneous uniform film on the construction field by a distribution device 8, wherein excess composition 3 can always be received in an opposite storage device 7. The distribution device 8 is exemplarily shown in the figure representation in the form of a roller.

[0188] The apparatus 1 comprises means for generating laser beams, in which laser beams 4 are generated. The laser beams 4 can be deflected via deflection means 10, in particular at least one mirror arrangement, onto the construction field, so that the three-dimensional object 5 is obtained there.

[0189] When carrying out the method for the production of silicon carbide-containing three-dimensional objects, a thin film of the composition 3 is presented now on the construction field and then by selective site-resolved radiation of laser beams 4 generated in the means for generating laser beams 9 and deflected via the deflection means 10 is heated and melted or decomposed into its components, so that a layer of a silicon carbide-containing compound is obtained.

[0190] Subsequently, the build field area is lowered at least slightly with the aid of the piston 6 and further composition 3 is dispensed from a storage device 7, which is homogeneously distributed on the build field in the form of a thin film by the distribution device 8.

[0191] This forms a new layer of composition 3 which can then be irradiated. Excess composition 3 is taken up again in the opposite storage device 7.

[0192] Subsequently, by means of the laser beams 4, the film is irradiated and heated in a site-selective manner, whereby a new layer of the three-dimensional object 5 made of a silicon carbide-containing material is formed. By repeating these method steps, the three-dimensional object 5 is finally built up.

[0193] In FIG. 2, an enlarged section of the construction area is shown, and in particular the various layers 11 of silicon carbide-containing material which build up the three-dimensional object 5 are shown. The individual layers 11 are shown only to illustrate the present invention. The individual layers are usually not recognizable on the three-dimensional object 5, since homogeneous objects of silicon carbide-containing material are obtained by the method described.

[0194] The subject-matter of the present invention is illustrated below by the working examples in a non-limiting manner.

WORKING EXAMPLES

[0195] 1. Production of a Precursor Granulate Based on Silanes and Its Use

[0196] For the production of a precursor granulate, 67.1 g of invert sugar syrup solution with a sugar content of 72.2% is added to a mixture of 35 ml of demineralized water and 110 ml of ethanol (purity >99% with 1% methyl ethyl ketone as denaturant) and 8.70 g of anhydrous citric acid and is heated to 70° C. After the citric acid has dissolved, 100 ml of tetraethyl orthosilicate (tetraethoxysilane) is added over a period of 30 minutes at 70° C. with stirring.

[0197] After the citric acid has dissolved, 100 ml of tetraethyl orthosilicate (tetraethoxysilane) is added over a period of 30 minutes at 70° C. with stirring. The previously clear solution shows a weak opalescence.

[0198] After the solution is clear again, the solvent is quickly removed in vacuo (30 mbar).

[0199] A colorless dry granulate is formed, which can be adjusted to particle sizes between 2 cm and 100 μm by using different stirrers and adjusting the stirring speeds.

[0200] The colorless granules are suitable for a wide range of applications for the production of silicon carbide-containing materials, in particular silicon carbide granules, silicon carbide wafers, for the production of foams and fibers from silicon carbide by CVD (chemical vapor deposition) methods or also in additive manufacturing processes.

[0201] To obtain a reduced granulate with a higher density, the colorless granulate is heated to temperatures of 500 to 800° C. under inert gas and in a vacuum. A cocoa-colored to black granulate is obtained, the density of which is increased by about 10 to 20% compared with the colorless granulate described above, and which is referred to below as reduced granulate.

[0202] The reduced dark granules are excellently suited for additive manufacturing, in particular for powder bed processes such as selective synthetic crystallization or selective laser sintering described above. Likewise, the reduced dark granules can also be used in an excellent manner for material desposition methods, such as deposition welding.

[0203] 2. Production of a Precursor Granulate Based on Pyrogenic Silicic Acid and Its Use

[0204] For the production of the precursor granulate, 67.1 g of invert sugar syrup solution with a sugar content of 72.2% is mixed with 140 ml of fully demineralized water and 27.1 g of fumed silica with an average particle size of 200 nm and is heated to 70° C. for 30 minutes with stirring. The water is then rapidly removed in vacuo (30 mbar).

[0205] A colorless dry granulate is obtained, which can be adjusted to particle sizes between 2 cm and 100 μm by using different stirrers and adjusting the stirring speeds.

[0206] The colorless granulate corresponds in its properties and uses to the precursor granulate described in 1.).

[0207] To obtain a reduced granulate with a higher density, the colorless granulate is heated to temperatures of 500 to 800° C. under inert gas and in vacuum. A cocoa-colored to black granulate is obtained, the density of which is increased by about 10 to 20% compared with the colorless granulate described above, and which is referred to below as reduced granond in all respects to the reduced granulate described under 1.).

TABLE-US-00001 Reference signs: 1 Apparatus 2 Building field extension 3 Composition 4 Laser beam 5 Object 6 Piston 7 Storage device 8 Distribution device 9 Means for generating laser beams 10 Deflection means 11 Layer