Primary voltaic sources including nanofiber Schottky barrier arrays and methods of forming same
Primary voltaic sources include nanofiber Schottky barrier arrays and a radioactive source including at least one radioactive element configured to emit radioactive particles. The arrays have a semiconductor component and a metallic component joined at a metal-semiconductor junction. The radioactive source is positioned proximate to the arrays such that at least a portion of the radioactive particles impinge on the arrays to produce a flow of electrons across the metal-semiconductor junction. Methods of producing voltaic sources include reacting at least one carbon oxide and a reducing agent in the presence of a substrate comprising a catalyst to form a solid carbon product over the substrate. Material is disposed over at least a portion of the solid carbon product to form a nanofiber Schottky barrier array. A radioactive source is disposed adjacent the nanofiber Schottky barrier array.
1. A primary voltaic source, comprising:
a Schottky barrier array comprising a semiconductor component and a metallic coating over the semiconductor component, the semiconductor component and the metallic coating joined at a metal-semiconductor junction, the semiconductor component comprising at least one selected from the group consisting of a semiconductor carbon nanotube and a carbon nanofiber, the Schottky barrier array defining a plurality of voids therein; and
a radioactive source comprising at least one radioactive element configured to emit radioactive particles and positioned proximate to the Schottky barrier array such that at least a portion of the radioactive particles impinge on the Schottky barrier array to produce a flow of electrons across the metal-semiconductor junction, the radioactive source occupying at least a portion of the plurality of voids.
2. The primary voltaic source of claim 1 , wherein the Schottky barrier array comprises a plurality of semiconductor carbon nanotubes, and wherein an interior surface of the plurality of semiconductor carbon nanotubes defines the voids.
3. The primary voltaic source of claim 1 , where the radioactive source comprises at least one material selected from the group consisting of gases, liquids, solids, gels, and foams.
4. The primary voltaic source of claim 3 , wherein the Schottky barrier comprises a plurality of semiconductor carbon nanotubes defining interstices, and wherein the radioactive source is disposed within the interstices.
5. The primary voltaic source of claim 1 , wherein the Schottky barrier comprises a plurality of semiconductor carbon nanofibers and the metallic coating formed over the plurality of semiconductor nanofibers, wherein a first end of each semiconductor nanofiber is secured to a substrate.
6. The primary voltaic source of claim 5 , wherein the plurality of semiconductor nanofibers comprises a first plurality and a second plurality of the semiconductor nanofibers, wherein the first plurality of semiconductor nanofibers is secured outwardly from a first side of the substrate and the second plurality of semiconductor nanofibers is secured outwardly from a second, opposite side of the substrate.
7. The primary voltaic source of claim 5 , wherein each semiconductor nanofiber of the plurality comprises a material of the same type as a material of the substrate, and wherein each semiconductor nanofiber of the plurality forms an electrically conductive contact site with the substrate.
8. The primary voltaic source of claim 7 , wherein the metallic coating formed over the plurality of nanofibers forms an electrically conducting continuous layer over at least a portion of each semiconductor nanofiber of the plurality and over at least a portion of the substrate.
9. The primary voltaic source of claim 5 , wherein each semiconductor nanofiber of the plurality comprises a semiconductor carbon fiber nanotube with a metallic coating.
10. The primary voltaic source of claim 1 , wherein:
the Schottky barrier array comprises a first plurality of semiconductor nanofibers secured outwardly from a first substrate and a first metallic coating formed over the plurality of semiconductor nanofibers;
the voltaic source comprises a second Schottky barrier array comprising a second plurality of semiconductor nanofibers secured outwardly from a second substrate and a second metallic coating formed over the second plurality of semiconductor nanofibers; and
a major surface of the second substrate is oriented substantially parallel to a major surface of the first substrate.
11. The primary voltaic source of claim 1 , wherein the radioactive source comprises at least one low-energy particle emitter.
12. The voltaic source of claim 11 , wherein the at least one low-energy particle emitter is configured to emit particles having an energy of less than about 0.2 MeV.
13. The primary voltaic source of claim 1 , wherein the radioactive source comprises at least one material selected from the group consisting of tritium, beryllium-10, carbon-14, silicon-32, phosphorous-32, cobalt-60, krypton-85, strontium-90, cesium-137, promethium-147, americium-241, radium-226, lead-210, polonium-210, radium-228, actinium-227, thorium-228, uranium-234, uranium-235, curium-242, and curium-244.
14. The primary voltaic source of claim 1 , wherein the radioactive source comprises tritium and americium-241.
15. The primary voltaic source of claim 1 , wherein the radioactive source is integrated with the metallic coating of the Schottky barrier array.
16. The primary voltaic source of claim 1 , wherein the radioactive source is integrated with the semiconductor component of the Schottky barrier array.
17. A method for producing a primary voltaic source, comprising:
reacting at least one carbon oxide and a reducing agent in the presence of a substrate comprising a catalyst to form a solid carbon product over the substrate;
disposing a material over at least a portion of the solid carbon product to form a Schottky barrier array comprising a semiconductor component and a metallic coating over the semiconductor component, the semiconductor component comprising at least one selected from the group consisting of a semiconductor carbon nanotube and a carbon nanofiber, the semiconductor component and the metallic coating joined at a metal-semiconductor junction, the Schottky barrier array defining a plurality of voids therein; and
disposing a radioactive source comprising at least one radioactive element configured to emit radioactive particles proximate to the Schottky barrier array such that the radioactive source occupies at least a portion of the plurality of voids and such that at least a portion of radioactive particles leaving the radioactive source impinge on the Schottky barrier array to produce a flow of electron across the metal-semiconductor junction.
18. The method of claim 17 , wherein reacting at least one carbon oxide and a reducing agent comprises reacting carbon dioxide with a reducing agent comprising hydrogen, an alkane, or an alcohol.
19. The method of claim 17 , wherein reacting at least one carbon oxide and a reducing agent comprises forming a solid carbon product having semiconductor properties.
20. The method of claim 19 , wherein disposing a material over at least a portion of the solid carbon product comprises disposing the metallic coating over the solid carbon product.
21. The method of claim 17 , wherein disposing a radioactive source proximate to the Schottky barrier array comprises disposing at least one material selected from the group consisting of tritium, beryllium-10, carbon-14, silicon-32, phosphorous-32, cobalt-60, krypton-85, strontium-90, cesium-137, promethium-147, americium-241, radium-226, lead-210, polonium-210, radium-228, actinium-227, thorium-228, uranium-234, uranium-235, curium-242, and curium-244 adjacent the Schottky barrier array.