Sol-gel process for the manufacture of high power switches
According to one embodiment, a photoconductive semiconductor switch includes a structure of nanopowder of a high band gap material, where the nanopowder is optically transparent, and where the nanopowder has a physical characteristic of formation from a sol-gel process. According to another embodiment, a method includes mixing a sol-gel precursor compound, a hydroxy benzene and an aldehyde in a solvent thereby creating a mixture, causing the mixture to gel thereby forming a wet gel, drying the wet gel to form a nanopowder, and applying a thermal treatment to form a SiC nanopowder.
1. A method, comprising:
mixing at least a sol-gel precursor compound, and a hydroxy benzene in a solvent thereby creating a mixture;
causing the mixture to gel thereby forming a wet gel;
drying the wet gel to form a nanopowder; and
applying a first thermal treatment to the nanopowder to form a SiC nanopowder,
wherein drying the wet gel comprises at least one of freeze drying, spray drying and supercritical drying.
2. The method of claim 1 , further comprising adding at least one catalyst to the mixture prior to causing the mixture to gel.
3. The method of claim 2 , wherein the catalyst is selected from the group consisting of: ammonium hydroxide and sodium carbonate.
4. The method of claim 1 , wherein causing the mixture to gel comprises adjusting a pH of the mixture and/or heating the mixture at a gelation temperature for a gelation time.
5. The method of claim 1 , wherein the hydroxy benzene is selected from a group consisting of: resorcinol, catechol, hydroquinone, phloroglucinol and mixtures thereof.
6. A method, comprising:
mixing at least a sol-gel precursor compound, and a hydroxy benzene in a solvent thereby creating a mixture;
causing the mixture to gel thereby forming a wet gel;
drying the wet gel to form a nanopowder; and
applying a first thermal treatment to the nanopowder to form a SiC nanopowder,
wherein the first thermal treatment includes heating the nanopowder at a temperature less than or equal to about 1100° C. in an atmosphere comprising hydrogen and at least one of argon and helium to form the SiC nanopowder.
7. The method of claim 6 , further comprising applying a second thermal treatment to the SiC nanopowder, wherein the second thermal treatment includes heating the SiC nanopowder at a temperature ranging from about 1350° C. to about 1700° C. in an atmosphere comprising hydrogen and at least one of argon and helium.
8. The method of claim 6 , wherein the first thermal treatment includes heating the nanopowder at a temperature equal to or less than about 1100° C. in an atmosphere comprising 4% hydrogen in argon for about 2 hours.
9. The method of claim 7 , wherein the second thermal treatment includes heating the SiC nanopowder at a temperature ranging from about 1350° C. to about 1650° C. in an atmosphere comprising 4% hydrogen in argon.
10. A method, comprising;
mixing a silicon-containing sol-gel precursor compound, a hydroxy benzene and an aldehyde in a solvent thereby creating a mixture, wherein the silicon sol-gel precursor compound comprises silicon tetrachloride, wherein the hydroxy benzene is selected from the group consisting of: resorcinol, catechol, hydroquinone, phloroglucinol and mixtures thereof;
causing the mixture to gel thereby forming a wet gel;
drying the wet gel to form a nanopowder; and
applying a first thermal treatment to the nanopowder to form a SiC nanopowder, wherein the first thermal treatment includes heating the nanopowder at a temperature less than or equal to about 1100° C. in an atmosphere comprising hydrogen and at least one of argon and helium to form the SiC nanopowder;
applying a second thermal treatment to the SiC nanopowder, wherein the second thermal treatment includes heating the SiC nanopowder at a temperature ranging from about 1350° C. to about 1650° C. in an atmosphere comprising hydrogen and at least one of argon and helium, and applying pressure ranging from about 5,000 psi to 50,000 psi to the SiC nanopowder; and
applying a third thermal treatment to the SiC nanopowder, the third thermal treatment including heating the SiC nanopowder in air at a temperature less than about 450° C. to remove excess carbon,
wherein the SiC nanopowder has a density in a range from about 1 g/cm 3 to about 3.2 g/cm 3 .
11. The method of claim 10 , further comprising adding a dopant to the mixture prior to causing the mixture to gel, wherein the dopant comprises at least one of phosphorous, tungsten, aluminum, zinc, and titanium.
12. The method of claim 11 , further comprising adding a catalyst to the mixture prior to causing the mixture to gel, the catalyst including sodium carbonate.
13. The method of claim 12 , further comprising washing the wet gel to remove dissolved nitrates prior to drying the wet gel.
14. The method of claim 10 , wherein the SiC nanopowder includes a combination of 6H—SiC, and 4H—SiC.
15. The method of claim 10 , further comprising sintering the SiC nanopowder, wherein the sintering includes at least one of spark plasma sintering and hot isostatically pressing the SiC nanopowder in loose form.
16. The method of claim 10 , wherein drying the wet gel comprises at least one of freeze drying, spray drying and supercritical drying.
17. The method of claim 10 , wherein the hydroxy benzene is resorcinol.