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Lessons Learned in Fabrication of a High-Specific-Torque Concentric Magnetic Gear
Magnetic gearing is being investigated at NASA as a replacement to conventional mechanical gearing in aerospace applications. Some key benefits of magnetic gears over mechanical gearing are torque transmission without mechanical contact, decreased transmission noise, less frequent maintenance, and lack of lubrication. In order to take advantage of these benefits in aerospace applications, magnetic gearing must be shown to provide high enough specific torque (torque per unit mass). Prototype 2 (PT-2), developed to maximize specific torque, and fabricated at NASA Glenn Research Center, has shown promising specific torque comparable to low torque mechanical gears. This work will briefly review the electromagnetic and structural design of PT-2, provide detailed information on fabrication and assembly, examine build errors, walk through rebuild efforts to improve operation, and conclude with remarks on build difficulties and opportunities for improvement in future prototypes.
Lessons Learned in Fabrication of a High-Specific-Torque Concentric Magnetic Gear
Magnetic gearing is being investigated at NASA as a replacement to conventional mechanical gearing in aerospace applications. Some potential benefits of magnetic gears over mechanical gearing are torque transmission without mechanical contact, decreased transmission noise, and no required lubrication. However, in order to be a viable alternative for aerospace applications, magnetic gearing must be shown to provide high enough specific torque (torque per unit mass). NASA's second magnetic gearing prototype (PT-2) was able to achieve promising specific torque on par with low torque mechanical gearboxes. This work will briefly review the electromagnetic and structural design of PT-2, provide detailed information on fabrication and assembly, examine build errors, walk through rebuild efforts to improve operation, and conclude with remarks on build difficulties and opportunities for improvement in future prototypes.
Graphene-Supported Monometallic and Bimetallic Dimers for Electrochemical CO 2 Reduction
Bimetallic catalysts are attractive alternatives to extend the parameter space that can be tuned for support interactions and catalytic performance. In this study, we have investigated the smallest bimetallic catalysts dimers supported on defective graphene for the electrochemical reduction of CO 2 to CH 4 based on a first-principles approach and the computational hydrogen electrode model. The monometallic and bimetallic dimers formed from Group 10 (Ni, Pd, Pt) and group 11 (Cu, Ag, Au) elements are characterized by a positively charged anchoring atom occupying the vacancy site of graphene and a neutral or slightly negatively charged antenna atom sticking out from the graphene surface. The strong selective binding of these dimers ensures their high stability. Possible rate-limiting steps are identified from the full reaction pathways to generate CH4. Overall, Pt-2, AgNi, Pd-2, and AgPt are the best candidates with the lowest overpotential values of 0.37, 0.69, 0.69, and 0.76 V, respectively. It is found that the alloy effect and the interaction with support help to optimize the property. These metallic dimers, however, retain nonmonotonous property relationships that give opportunity to go beyond scaling behavior and look for a few atom catalysts that have unique properties to reduce rate-limiting potentials and improve the catalytic performance.