Silicon carbide synthesis from agricultural waste
This disclosure concerns a method of making silicon carbide involving adding one from the group of rice husk material, sorghum, peanuts, maple leaves, and/or corn husk material to a container, creating a vacuum or an inert atmosphere inside the container, applying conventional heating or microwave heating, heating rapidly, and reacting the material and forming silicon carbide (SiC).
1. A method of making SiC comprising:
adding one selected from the group consisting of rice husk material, sorghum, nuts, nut shells, maple leaves, fruit pits, and corn husk material to a container;
wherein the container is a covered boron nitride crucible;
creating a vacuum or an inert atmosphere inside the container;
applying heat;
heating rapidly the one selected from the group consisting of rice husk material, sorghum, nuts, nut shells, maple leaves, fruit pits, and corn husk material;
wherein the step of heating is accomplished by using a millimeter-wave beam and wherein the frequency of the millimeter-wave beam is about 83 GHz, the total beam power is about 5 kW, and the power density is about 0.3 kW/cm 2 ; and
reacting the one selected from the group consisting of rice husk material, sorghum, nuts, nut shells, maple leaves, fruit pits, and corn husk material and forming silicon carbide;
wherein the silicon carbide is nanoparticles and nanorods of SiC in a pure form.
2. The method of claim 1 further comprising the step of:
heating the one selected from the group consisting of rice husk material, sorghum, nuts, nut shells, maple leaves, fruit pits, and corn husk material to a temperature of about 1400-1500° C.
3. The method of claim 2 further comprising the step of:
maintaining the temperature of about 1400-1500° C. for about 1 to about 10 minutes.
4. The method of claim 3 further comprising the step of:
cooling the container.
5. The method of claim 4 wherein the vacuum is a modest vacuum environment which prevents oxidation and silica formation.
6. A method of producing nanorods and nanoparticles of silicon carbide comprising:
milling rice husks into a fine rice husk powder;
mixing the fine rice husk powder with a Polyvinyl alcohol (PVA) binder in a ratio of 0.95 rice husk to 0.05 PVA by weight;
pressing fine rice husk powder into a pellet;
directing a millimeter-wave beam to the pellet and thereby increasing the localized temperature;
heating the pellet to a temperature of about 1900° C.;
maintaining the temperature of the pellet at about 1900° C.; and
cooling the pellet which thereby forms nanorods and nanoparticles of silicon carbide and other products.
7. The method of claim 6 wherein the steps of heating the pellet, maintaining the heat, and cooling the pellet involve a total time of about 10 minutes.
8. The method of claim 7 wherein the frequency of the millimeter-wave beam is 83 GHz, the total beam power is about 5 kW, and the power density is about 0.3 kW/cm 2 with the microwave radiation directed at the pellet.
9. The method of claim 8 further comprising the step of:
using electron microscopy on a JEOL JSM-7001FLV SEM to characterize the structure of the silicon carbide and using TEM to further analyze the nanostructure wherein samples were prepared by transferring a few drops of alcohol containing the nanorods and nanoparticles of silicon carbide to a carbon coated fine mesh Cu-grid and were imaged using Phillips CM 30 and JEOL 2200 FX transmission electron microscopes.
10. The method of claim 9 further comprising the step of utilizing a SPEX jar mill in a Polycarbonate jar with Polytetrafluoroethylene milling media.
11. The method of claim 10 wherein the pellets are about 0.5 inch pellets pressed using a Carver press and die set.