Metal boride aerogels
A metal boride aerogel includes a three-dimensional aerogel structure comprising metal boride particles having an average diameter of less than one micron. A method is disclosed for forming a metal boride aerogel including dispersing boron nanoparticles in a solution of a metal salt, forming a boron-loaded metal oxide precursor gel using the dispersed boron nanoparticles in the solution of the metal salt, drying the boron-loaded metal oxide precursor gel to form a boron-loaded metal oxide precursor aerogel, and heating the boron-loaded metal oxide precursor aerogel to form a metal boride aerogel. The metal boride aerogel is essentially free of metal oxide.
1. A metal boride aerogel, comprising:
a three-dimensional aerogel structure comprising metal boride particles having an average diameter of less than one micron,
wherein the metal boride particles consist of a single metal and boron.
2. The metal boride aerogel as recited in claim 1 , wherein the metal boride particles include particles having a metal boride selected from the group consisting of: hafnium boride, zirconium boride, and titanium boride.
3. The metal boride aerogel as recited in claim 1 , wherein the metal boride particles in the three-dimensional aerogel structure include a metal selected from the group consisting of: hafnium, zirconium, titanium, vanadium, molybdenum, tantalum, niobium, chromium, tungsten, iron, cobalt, nickel, lanthanum, magnesium, and uranium.
4. A metal boride aerogel comprising: a three-dimensional aerogel structure comprising metal boride particles having an average diameter of less than one micron,
wherein the metal boride aerogel has, at least in part, a composition of metal boride carbon oxide denoted as MB x C y O z , wherein x is a number in a range of greater than zero and less than ten,
wherein y is a number in a range of greater than zero and less than ten,
wherein z is a number in a range of greater than or equal to zero and less than ten.
5. The metal boride aerogel as recited in claim 1 , wherein the average diameter is less than about 100 nanometers.
6. The metal boride aerogel as recited in claim 1 , wherein the metal boride aerogel is electrically insulating.
7. The metal boride aerogel as recited in claim 6 , wherein the metal boride aerogel has an electrical conductivity of about 1 siemens per centimeter or less.
8. The metal boride aerogel as recited in claim 1 , wherein a thermal conductivity of the metal boride aerogel is in a range of less than about 10 watts per meter kelvin and greater than zero.
9. The metal boride aerogel as recited in claim 1 , wherein the metal boride aerogel comprises a metal boride material, the metal boride material having a melting temperature in a range of greater than 1000 degrees Celsius and less than 3500 degrees Celsius.
10. The metal boride aerogel as recited in claim 1 , having a surface area in a range of about 50 milligram per cubic centimeter o about 1,000 milligram per cubic centimeter.
11. The metal boride aerogel as recited in claim 1 , wherein the metal boride aerogel is essentially free of metal oxide.
12. The metal boride aerogel as recited in claim 1 , wherein the aerogel is a single phase aerogel.
13. The metal boride aerogel as recited in claim 1 , wherein the aerogel is essentially free of boron oxide.
14. The metal boride aerogel as recited in claim 1 , wherein the aerogel has essentially no free boron metal.
15. The metal boride aerogel as recited in claim 1 , wherein a hardness of the metal boride aerogel is in a range of about 0.5 to about 20 Megapascal.
16. The metal boride aerogel as recited in claim 1 , wherein the metal boride particles have a melting temperature in a range of greater than 1000° C. to less than about 3500° C. thereby rendering the metal boride aerogel resistant to sintering.
17. A method for forming the metal boride aerogel as recited in claim 1 , the method comprising:
dispersing boron nanoparticles in a solution of a metal salt;
forming a boron-loaded metal oxide precursor gel using the dispersed boron nanoparticles in the solution of the metal salt;
drying the boron-loaded metal oxide precursor gel to form a boron-loaded metal oxide precursor aerogel; and
heating the boron-loaded metal oxide precursor aerogel to form the metal boride aerogel, wherein the metal boride aerogel is essentially free of metal oxide.
18. The method as recited in claim 17 , wherein the metal salt includes one metal selected from the group consisting of: hafnium, zirconium, titanium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, iron, cobalt, nickel, lanthanum, germanium, yttrium, manganese and magnesium.
19. The method as recited in claim 17 , wherein the metal salt is selected from the group consisting of: metal chloride, metal nitride, and metal alkoxide.
20. The method as recited in claim 17 , wherein an average diameter of the boron nanoparticles is in a range of greater than zero and less than ten microns.
21. The method as recited in claim 17 , wherein an average diameter of the boron nanoparticles is in a range of greater than zero and less than 100 nanometers.
22. The method as recited in claim 17 , wherein forming the boron-loaded metal oxide precursor gel comprises an epoxide-assisted sol-gel process.
23. The method as recited in claim 22 , wherein the epoxide-assisted sol-gel process includes an epoxide selected from the group consisting of: propylene oxide, trimethylene oxide, dimethylene oxide, and ethylene oxide.
24. The method as recited in claim 22 , wherein a duration of time of forming boron-loaded metal oxide precursor gel is greater than zero minutes and less than ten minutes.