Understanding the ORR Electrocatalysis on Co-Mn Oxides
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99 GENERAL AND MISCELLANEOUS↗
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Development & Validation of Low-Cost, Highly-Durable, Spinel-Based Materials for SOFC Cathode-Side Contact (Final Report)
A cathode-side contact layer is required to provide and maintain stable electrical conduction paths between the interconnect and cathode in a solid oxide fuel cell (SOFC) stack assembly and thus minimize the ohmic resistance and stack power loss. Current cathode-interconnect contact materials are based on noble metals, electrically-conductive perovskites, their composite materials, etc. These materials are either too expensive or do not possess the overall balanced performance required for the cathode-side contact application. To achieve the DOE SOFC system cost and performance stability goals, a new generation of low-cost, high-performance contact materials needs to be developed. In this project, spinel-based materials thermally converted from the Fe-Ni and Co-Mn based alloy precursors were developed and validated for the cathode-side contact application. The precursor alloy compositions were optimized via a combination of composition screening in the (Ni,Fe) 3 O 4 and (Mn,Co) 3 O 4 spinel system, alloy design using physical metallurgy principles, and cost considerations. The alloy powders with the desired composition and particle size were manufactured via gas atomization. The optimal process parameters for thermal conversion of these alloy precursor layers to a spinel-based layer were identified, i.e., 900°C x 2h in air, which is close to the initial stack firing condition. The area-specific resistances (ASRs) of the interconnect/contact/cathode test assemblies with the developed contact layer were determined for various durations (up to 5000 h) under simulated cathodic operation conditions. Some of the alloy-derived spinel contacts exhibited the lowest ASR and ASR degradation rate. The in-stack performance of the most promising alloy-derived contact layer is currently being evaluated via stack testing. To reduce the stack cost, the Co-Mn based alloy powders were utilized as the precursor for synthesis of dense spinel-based interconnect coating. By optimizing both the initial powder size/distribution and the alloy powder composition, a dense (Mn,Co) 3 O 4 -based spinel coating was achieved. Furthermore, co-sintering of the coating/contact dual-layer structure under the initial stack firing condition was realized by utilizing the tailored Co-Mn alloy precursors. Cost analysis of the developed technology indicated a total stack cost reduction of around 10.6% with the implementation of co-sintering of the interconnect coating and the contact layer during initial stack firing. Since low-cost processes such as screen printing is utilized in the precursor application and no reduction heat treatment is needed for the coating formation, the developed technology can be readily implemented at the industrial partner’s manufacturing facilities with no additional capital investment needed.
08 HYDROGEN↗
Development of a chemical-free process utilizing ozone oxidative precipitation for the recovery of cobalt and manganese from acid mine drainage
Acid mine drainage (AMD) has been identified as a viable secondary resource of Co, and Mn. However, recovery of these elements while treating AMD is challenging due to the unfavorable pH and Eh conditions for Co-Mn precipitation. This study investigated the effects of various ligands (hydroxide, carbonate, ammonium, sulfate, and phosphate) and oxidizers (sodium persulfate, potassium permanganate, and ozone) on the precipitation of Co-Mn from AMD through experimental and solution chemistry studies. Ozone was found to be the most effective agent for the recovery of these elements. Based on the results, an AMD treatment process was formulated for selective recovery of multiple critical elements, including Al, REEs, Co, and Mn. More than 95 % of Co and Mn were recovered through the proposed process utilizing chemical-less ozone oxidative precipitation. In conclusion, a precipitate containing 0.9 % Co and 54.6 % Mn was obtained from an AMD source containing 0.9 ppm Co and 41.8 ppm Mn.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Optically controlling the competition between spin flips and intersite spin transfer in a Heusler half-metal on sub–100-fs time scales
The direct manipulation of spins via light may provide a path toward ultrafast energy-efficient devices. However, distinguishing the microscopic processes that can occur during ultrafast laser excitation in magnetic alloys is challenging. Here, we study the Heusler compound Co 2 MnGa, a material that exhibits very strong light-induced spin transfers across the entire M-edge. By combining the element specificity of extreme ultraviolet high-harmonic probes with time-dependent density functional theory, we disentangle the competition between three ultrafast light-induced processes that occur in Co 2 MnGa: same-site Co-Co spin transfer, intersite Co-Mn spin transfer, and ultrafast spin flips mediated by spin-orbit coupling. By measuring the dynamic magnetic asymmetry across the entire M-edges of the two magnetic sublattices involved, we uncover the relative dominance of these processes at different probe energy regions and times during the laser pulse. Our combined approach enables a comprehensive microscopic interpretation of laser-induced magnetization dynamics on time scales shorter than 100 femtoseconds.
36 MATERIALS SCIENCE↗
Materials Data on MnCo3 by Materials Project
Co3Mn is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Mn is bonded to twelve equivalent Co atoms to form MnCo12 cuboctahedra that share corners with twelve equivalent MnCo12 cuboctahedra, edges with twenty-four equivalent CoMn4Co8 cuboctahedra, faces with six equivalent MnCo12 cuboctahedra, and faces with twelve equivalent CoMn4Co8 cuboctahedra. All Mn–Co bond lengths are 2.48 Å. Co is bonded to four equivalent Mn and eight equivalent Co atoms to form CoMn4Co8 cuboctahedra that share corners with twelve equivalent CoMn4Co8 cuboctahedra, edges with eight equivalent MnCo12 cuboctahedra, edges with sixteen equivalent CoMn4Co8 cuboctahedra, faces with four equivalent MnCo12 cuboctahedra, and faces with fourteen equivalent CoMn4Co8 cuboctahedra. All Co–Co bond lengths are 2.48 Å.
36 MATERIALS SCIENCE↗
Materials Data on MnCo by Materials Project
CoMn is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Mn is bonded in a body-centered cubic geometry to eight equivalent Co atoms. All Mn–Co bond lengths are 2.47 Å. Co is bonded in a body-centered cubic geometry to eight equivalent Mn atoms.
36 MATERIALS SCIENCE↗
Materials Data on MnCo3 by Materials Project
Co3Mn is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Mn is bonded to twelve equivalent Co atoms to form MnCo12 cuboctahedra that share corners with six equivalent MnCo12 cuboctahedra, corners with twelve equivalent CoMn4Co8 cuboctahedra, edges with eighteen equivalent CoMn4Co8 cuboctahedra, faces with eight equivalent MnCo12 cuboctahedra, and faces with twelve equivalent CoMn4Co8 cuboctahedra. There are six shorter (2.43 Å) and six longer (2.47 Å) Mn–Co bond lengths. Co is bonded to four equivalent Mn and eight equivalent Co atoms to form distorted CoMn4Co8 cuboctahedra that share corners with four equivalent MnCo12 cuboctahedra, corners with fourteen equivalent CoMn4Co8 cuboctahedra, edges with six equivalent MnCo12 cuboctahedra, edges with twelve equivalent CoMn4Co8 cuboctahedra, faces with four equivalent MnCo12 cuboctahedra, and faces with sixteen equivalent CoMn4Co8 cuboctahedra. There are a spread of Co–Co bond distances ranging from 2.44–2.48 Å.
36 MATERIALS SCIENCE↗