Eco-friendly method for manufacturing of porous silicon carbide structure
The present invention relates to an eco-friendly method for preparing a porous silicon carbide structure, which is capable of preparing a porous silicon carbide structure having meso- or macro-sized pores without using a harmful phenolic resin as a carbon source.
1. A method for preparing a porous silicon carbide structure, comprising:
preparing a first solution by dispersing a carbon source and a binder in a solvent;
preparing a second solution by dispersing a silicon source in a solvent;
preparing a slurry by adding the second solution to the first solution and mixing the same;
obtaining a powder wherein the carbon source is coated on the surface of the silicon source by granulating the slurry;
forming a preform of a predetermined shape from the powder; and
heat-treating the preform,
wherein the carbon source does not comprise a phenolic resin.
2. The method for preparing a porous silicon carbide structure according to claim 1 , wherein the carbon source is carbon black having an average particle diameter (d 50 ) of 0.08-45 μm and a specific surface area of 80-200 m 2 /g.
3. The method for preparing a porous silicon carbide structure according to claim 2 , wherein the carbon source further comprises 3-10 wt % of one selected from a group consisting of a single-walled carbon nanotube (SWCNT), a double-walled carbon nanotube (DWCNT), a multi-walled carbon nanotube (MWCNT) and a mixture thereof having a length of 10-30 μm based on 100 wt % of the carbon source.
4. The method for preparing a porous silicon carbide structure according to claim 1 , wherein the binder is a silane-based binder selected from a group consisting of hexadecyltrimethoxysilane, trimethoxymethylsilane, trimethoxy(propyl)silane, trimethoxyhexylsilane and a mixture thereof.
5. The method for preparing a porous silicon carbide structure according to claim 1 , wherein the silicon source is a silicon powder having an average particle diameter of 0.2-10 μm.
6. The method for preparing a porous silicon carbide structure according to claim 1 , wherein the solvent of the first solution and the second solution is selected from a group consisting of ethanol, isopropyl alcohol (IPA) and a mixture thereof.
7. The method for preparing a porous silicon carbide structure according to claim 1 , wherein the second solution is added to the first solution such that a molar ratio (C/Si) of the carbon source and the silicon source is 1.0-2.5.
8. The method for preparing a porous silicon carbide structure according to claim 7 , wherein the second solution is added little by little while stirring the first solution and then mixed at 200-400 rpm.
9. The method for preparing a porous silicon carbide structure according to claim 1 , wherein, before granulating the slurry, a processing aid selected from a group consisting of polyvinyl butyral (PVB), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP) and a mixture thereof is added to the slurry.
10. The method for preparing a porous silicon carbide structure according to claim 1 , wherein the granulation of the slurry is performed by drying the slurry under a vacuum atmosphere at 20-40° C. for 30-60 minutes such that the solvent remains at a content of 1-5 wt %.
11. The method for preparing a porous silicon carbide structure according to claim 1 , wherein the powder wherein the carbon source is coated on the silicon source has an average particle diameter of 50-200 μm.
12. The method for preparing a porous silicon carbide structure according to claim 1 , wherein the powder is formed into the preform of a predetermined shape by compressing at 0.3-1 MPa.
13. The method for preparing a porous silicon carbide structure according to claim 1 , wherein the preform is heat-treated firstly at 100-200° C. for 1-3 hours, heat-treated secondly at 500-800° C. for 30 minutes to 3 hours after raising temperature at a rate of 5-10° C./min and heat-treated thirdly at 1150-1400° C. for 10-24 hours after raising temperature at a rate of 1-10° C./min, wherein the first heat treatment, the second heat treatment and the heat treatment are performed continuously under an inert atmosphere.
14. The method for preparing a porous silicon carbide structure according to claim 1 , wherein the preform is heat-treated under an inert atmosphere at 1150-1400° C. for 10-24 hours after raising temperature at a rate of 1-3° C./min.
15. The method for preparing a porous silicon carbide structure according to claim 1 , which further comprises, after the heat treatment is completed, removing carbon remaining in the porous silicon carbide structure through oxidation.
16. The method for preparing a porous silicon carbide structure according to claim 1 , wherein the porous silicon carbide structure comprises β-phase silicon carbide.
17. The method for preparing a porous silicon carbide structure according to claim 1 , wherein the porous silicon carbide structure has a specific surface area of 30-100 m 2 /g, an average pore size of 5-200 nm, a porosity of 60-80% and a compressive strength of 10-30 MPa.