Patent Number: 
Section: claims

1. An encapsulated β− particle emitter, the emitter comprising:a. a sol-gel derived core that comprises a β−-emitting radioisotope; andb. an encapsulant enclosing the core through which at least some of the β− emissions from the β−-emitting radioisotope pass, wherein the encapsulant comprises a substrate and a cover and at least a portion of the encapsulant is electrically conductive. 2. The encapsulated β− particle emitter of claim 1, wherein substantially all of the substrate and cover are electrically conductive. 3. The encapsulated β− particle emitter of claim 1, wherein the cover is an electrically conductive sheet and the substrate is an electrically conductive sheet that is thicker than the cover and is able to support the core and cover without substantial deformation. 4. The encapsulated β− particle emitter of claim 3, wherein the β−-emitting radioisotope is 147Pm. 5. The encapsulated β− particle emitter of claim 4, wherein the core has a mass thickness no greater than about 2 mg/cm2. 6. The encapsulated β− particle emitter of claim 5, wherein the substrate has a mass thickness that is no greater than about 2.5 mg/cm2 and the cover has a mass thickness that is no greater than about 0.6 mg/cm2. 7. The encapsulated β− particle emitter of claim 6 having a β− particle emission efficiency of at least about 50%, wherein the substrate and the cover consist essentially of aluminum and the substrate has a thickness that is no more than about 8 μm and the cover has a thickness that is no more than about 2 μm. 8. The encapsulated β− particle emitter of claim 1, wherein the β−-emitting radioisotope is at a concentration that is substantially uniformly throughout the sol-gel derived core. 9. The encapsulated β− particle emitter of claim 1, wherein the β−-emitting radioisotope is selected from the group consisting of 3H, 10Be, 14C, 36Cl, 59Fe, 60Fe, 60Co, 63Ni, 79Se, 87Rb, 90Sr, 93Zr, 94Nb, 95Tc, 99Mo, 99Tc, 106Ru, 107Pd, 110Ag, 111Ag, 121Sn, 124Sb, 125Sb, 129I, 134Cs, 135Cs, 137Cs, 144Ce, 146Pm, 147Pm, 151Sm, 150Eu, 152Eu, 154Eu, 160Tb, 166Ho, 170Tm, 171Tm, 182Ta, 185W, 188W, 194Os, 204Tl, 227Ac, 228Ra, 241Pu, and combinations thereof. 10. The encapsulated β− particle emitter of claim 1, wherein the β−-emitting radioisotope is selected from the group consisting of 3H, 63Ni, 90Sr, and 147Pm. 11. The encapsulated β− particle emitter of claim 1, wherein the encapsulant has a density that is no greater than about 9 g/cm3. 12. The encapsulated β− particle emitter of claim 11, wherein the encapsulant comprises one or more elements selected from the group consisting of Be, Al, and Ti. 13. The encapsulated β− particle emitter of claim 11, wherein the encapsulant consists essentially of aluminum or a low-density aluminum-based alloy. 14. The encapsulated β− particle emitter of claim 1, wherein the sol-gel derived core, in addition to the β−-emitting radioisotope, comprises oxides of elements selected from the group consisting of silicon, boron, zirconium, titanium, aluminum, and combinations thereof. 15. The encapsulated β− particle emitter of claim 1, wherein the sol-gel derived core, in addition to the β−-emitting radioisotope, comprises oxides of silicon. 16. The encapsulated β− particle emitter of claim 15, wherein the sol-gel derived core further comprises oxides of titanium in amount of up to 40 percent by weight of the sol-gel derived core. 17. A method for making an encapsulated β− particle emitter, the method comprising:a. depositing a β−-emitting radioisotope-containing sol-gel on a surface of a substrate;b. curing the deposited β−-emitting radioisotope-containing sol-gel to form a solid radioactive oxide coating comprising the β−-emitting radioisotope and an oxide; andc. placing a cover, at least a portion of which is an electrically conductive sheet, on the deposited β−-emitting radioisotope-containing sol-gel so that cover in combination with the substrate encapsulate the cured deposited β−-emitting radioisotope-containing sol-gel. 18. The method of claim 17, wherein the cover is placed on the deposited β−-emitting radioisotope-containing sol-gel before the curing is complete. 19. The method of claim 18 further comprising heat treating the encapsulated β− particle emitter in order to condense the cured β−-emitting radioisotope-containing sol-gel. 20. The method of claim 19, wherein the heat treating comprises heating the encapsulated β− particle emitter to a temperature within the range of about 60° C. to about 80° C. for a duration of about 12 hours. 21. The method of claim 17, wherein the surface of the substrate is contacted with a coupling agent before the β−-emitting radioisotope-containing sol-gel is deposited on the surface of the substrate, wherein the β−-emitting radioisotope-containing sol-gel further comprises a coupling agent, or a combination thereof in order to enhance the adhesion between the cured β−-emitting radioisotope-containing sol-gel and the surface of the substrate. 22. The method of claim 21, wherein the coupling agent is an alkoxy silane. 23. The method of claim 22, wherein the coupling agent is glycidoxypropyltrimethoxysilane. 24. The method of claim 17, wherein the cover is an electrically conductive sheet that has a mass thickness that is no greater than about 0.6 mg/cm2 and the substrate is an electrically conductive sheet that has mass thickness that is no greater than about 2.5 mg/cm2 and is able to support the core and cover without substantial deformation. 25. The method of claim 24, wherein the substrate and cover each consist essentially of aluminum, a low-density aluminum-based alloy, titanium, a low-density titanium-based alloy, or combinations thereof. 26. The method of claim 17, wherein the β−-emitting radioisotope is at a concentration that is substantially uniformly throughout the β−-emitting radioisotope-containing sol-gel. 27. The method of claim 17, wherein the β−-emitting radioisotope is selected from the group consisting of 10Be, 59Fe, 60Fe, 60Co, 63Ni, 79Se, 87Rb, 90Sr, 93Zr, 94Nb, 98Tc, 99Mo, 99Tc, 106Ru, 107Pd, 110Ag, 111Ag, 121Sn, 124Sb, 125Sb, 134Cs, 135Cs, 137Cs, 144Ce, 146Pm, 147Pm, 151Sm, 150Eu, 152Eu, 154Eu, 160Tb, 166Ho, 170Tm, 171Tm, 182Ta, 185W, 188W, 194Os, 204Tl, 227Ac, 228Ra, 241Pu, and combinations thereof. 28. The method of claim 17, wherein the β−-emitting radioisotope is selected from the group consisting of 63Ni, 90Sr, and 147Pm. 29. The method of claim 17, wherein the β−-emitting radioisotope is 147Pm. 30. The method of claim 17, wherein the cured β−-emitting radioisotope-containing sol-gel has a mass thickness no greater than about 2 mg/cm2. 31. The method of claim 17, wherein the β−-emitting radioisotope-containing sol-gel, in addition to the β−-emitting radioisotope, comprises alkoxides of oxides of elements selected from the group consisting of silicon, boron, zirconium, titanium, aluminum, and combinations thereof. 32. The method of claim 17, wherein the β−-emitting radioisotope-containing sol-gel, in addition to the β−-emitting radioisotope, comprises alkoxides of silicon. 33. The method of claim 32, wherein the β−-emitting radioisotope-containing sol-gel further comprises alkoxides of titanium in amount of up to 40 percent by weight of the β−-emitting radioisotope-containing sol-gel. 34. A directly charged beta (negatron) nuclear decay capacitor comprising:a. an encapsulated β− particle emitter that comprises:i. a sol-gel derived core that comprises a β−-emitting radioisotope; andii. an encapsulant enclosing the core through which at least some of the β− emissions from the β−-emitting radioisotope pass, wherein the encapsulant comprises a substrate and a cover and at least a portion of the encapsulant is electrically conductive;b. an electrically conductive collector for collecting β− particles from the encapsulated β− particle emitter; andc. a dielectric between the encapsulated β− particle emitter and the electrically conductive collector. 35. The directly charged beta (negatron) nuclear decay capacitor of claim 34, wherein the dielectric has a dielectric strength of at least about 200V/micron and a density that is no greater than about 2.5 g/cm3. 36. The directly charge beta (negatron) nuclear decay capacitor of claim 35, wherein the dielectric is an electrical insulating material or a vacuum. 37. The directly charge beta (negatron) nuclear decay capacitor of claim 35, wherein the dielectric comprises polyimides. 38. The directly charged beta (negatron) nuclear decay capacitor of claim 35, wherein at least the portion of the collector for which β− particles from the emitter will be incident is a metal and wherein: (a) the dielectric suppresses the emission of secondary electrons from said metallic portion of the collector, (b) the directly charged beta (negatron) nuclear decay capacitor further comprises a secondary suppression coating on said metallic portion of the collector, or (c) both (a) and (b). 39. The directly charged beta (negatron) nuclear decay capacitor of claim 38, wherein dielectric comprises one or more radiation-resistant polymers and the secondary suppression coating comprises one or more radiation-resistant polymers, graphite, or a combination thereof. 40. The directly charged beta (negatron) nuclear decay capacitor of claim 39, wherein the one or more radiation-resistant polymers are selected from the group consisting of polyimides, polyetherimdes, polyamideimides, polyphenylene sulfides, polyetheretherketones, polystyrenes, polyarylates, polyarylamides, polyethersulfides, polysulfones, polyamides, polyphenyloxides, and combinations thereof. 41. The directly charged beta (negatron) nuclear decay capacitor of claim 34 further comprising a multiplicity of encapsulated β− particle emitters, a multiplicity of electrically conductive collectors, or a multiplicity of encapsulated β− particle emitters and a multiplicity of electrically conductive collectors. 42. The directly charged beta (negatron) nuclear decay capacitor of claim 34, the cover is an electrically conductive sheet and the substrate is an electrically conductive sheet that is thicker than the cover and is able to support the core and the cover without substantial deformation. 43. The directly charged beta (negatron) nuclear decay capacitor of claim 34, wherein the β−-emitting radioisotope is selected from the group consisting of 63Ni, 90Sr, and 147Pm. 44. The directly charged beta (negatron) nuclear decay capacitor of claim 34, wherein the encapsulated β− particle emitter has a β− particle emission efficiency of at least about 50%, the substrate and the cover consist essentially of aluminum, and the substrate has a thickness that is no more than about 8 μm and the cover has a thickness that is no more than about 2 μm. 45. The directly charged beta (negatron) nuclear decay capacitor of claim 34, wherein the sol-gel derived core, in addition to the β−-emitting radioisotope, comprises oxides of elements selected from the group consisting of silicon, boron, zirconium, titanium, aluminum, and combinations thereof. 46. A method of performing work, the method comprising delivering the electrical energy of a directly charged beta (negatron) nuclear decay capacitor through a circuit, wherein the directly charged beta (negatron) nuclear decay capacitor comprises:a. an encapsulated β− particle emitter that comprises:i. a sol-gel derived core that comprises a β−-emitting radioisotope; andii. an encapsulant enclosing the core through which at least some of the β− emissions from the β−-emitting radioisotope pass, wherein the encapsulant comprises a substrate and a cover and at least a portion of the encapsulant is electrically conductive;b. an electrically conductive collector for collecting β− particles from the encapsulated β− particle emitter; andc. a dielectric between the encapsulated β− particle emitter and the electrically conductive collector. 47. A directly charged beta (negatron) nuclear decay capacitor comprising a β− particle emitter, an electrically conductive collector for collecting β− particles from the β− particle emitter, and a dielectric between the encapsulated β− particle emitter and the electrically conductive collector, wherein at least the portion of the collector for which β− particles from the emitter will be incident is a metal and is contact with a volume of one or more radiation-resistant polymers that suppress the emission of secondary electrons from said metallic portion of the collector. 48. The directly charged beta (negatron) nuclear decay capacitor of claim 47, wherein the one or more radiation-resistant polymers are selected from the group consisting of polyimides, polyetherimdes, polyamideimides, polyphenylene sulfides, polyetheretherketones, polystyrenes, polyarylates, polyarylamides, polyethersulfides, polysulfones, polyamides, polyphenyloxides, and combinations thereof. 49. The directly charge beta (negatron) nuclear decay capacitor of claim 48, wherein the one or more radiation-resistant polymers in the form of a film.