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Materials Data on CoRh by Materials Project

CoRh crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are two inequivalent Rh sites. In the first Rh site, Rh is bonded to six equivalent Rh and six Co atoms to form distorted RhCo6Rh6 cuboctahedra that share corners with twelve RhCo6Rh6 cuboctahedra, edges with twelve RhCo6Rh6 cuboctahedra, edges with twelve CoCo6Rh6 cuboctahedra, faces with six equivalent RhCo6Rh6 cuboctahedra, and faces with twelve CoCo6Rh6 cuboctahedra. All Rh–Rh bond lengths are 2.66 Å. All Rh–Co bond lengths are 2.62 Å. In the second Rh site, Rh is bonded to ten equivalent Rh and six Co atoms to form distorted RhCo6Rh10 cuboctahedra that share corners with ten CoCo6Rh6 cuboctahedra, corners with twelve RhCo6Rh6 cuboctahedra, edges with eight CoCo6Rh6 cuboctahedra, edges with sixteen RhCo6Rh6 cuboctahedra, faces with sixteen equivalent RhCo6Rh10 cuboctahedra, and faces with eighteen CoCo6Rh6 cuboctahedra. There are a spread of Rh–Rh bond distances ranging from 2.66–5.31 Å. All Rh–Co bond lengths are 2.62 Å. There are three inequivalent Co sites. In the first Co site, Co is bonded to six equivalent Rh and six equivalent Co atoms to form distorted CoCo6Rh6 cuboctahedra that share corners with twelve CoCo6Rh6 cuboctahedra, edges with twelve equivalent RhCo6Rh6 cuboctahedra, edges with twelve CoCo6Rh6 cuboctahedra, faces with six equivalent CoCo6Rh6 cuboctahedra, and faces with twelve equivalent RhCo6Rh6 cuboctahedra. All Co–Co bond lengths are 2.66 Å. In the second Co site, Co is bonded to six Rh and six equivalent Co atoms to form distorted CoCo6Rh6 cuboctahedra that share corners with five equivalent RhCo6Rh10 cuboctahedra, corners with twelve CoCo6Rh6 cuboctahedra, edges with ten RhCo6Rh6 cuboctahedra, edges with twelve CoCo6Rh6 cuboctahedra, faces with six equivalent CoCo6Rh6 cuboctahedra, and faces with fifteen RhCo6Rh6 cuboctahedra. All Co–Rh bond lengths are 2.62 Å. All Co–Co bond lengths are 2.66 Å. In the third Co site, Co is bonded to six Rh and six equivalent Co atoms to form distorted CoCo6Rh6 cuboctahedra that share corners with five equivalent RhCo6Rh10 cuboctahedra, corners with twelve CoCo6Rh6 cuboctahedra, edges with ten RhCo6Rh6 cuboctahedra, edges with twelve CoCo6Rh6 cuboctahedra, faces with six equivalent CoCo6Rh6 cuboctahedra, and faces with fifteen RhCo6Rh6 cuboctahedra. All Co–Co bond lengths are 2.66 Å.

36 MATERIALS SCIENCE↗

Counterflow Regolith Heat Exchanger

A problem exists in reducing the total heating power required to extract oxygen from lunar regolith. All such processes require heating a great deal of soil, and the heat energy is wasted if it cannot be recycled from processed material back into new material. The counterflow regolith heat exchanger (CoRHE) is a device that transfers heat from hot regolith to cold regolith. The CoRHE is essentially a tube-in-tube heat exchanger with internal and external augers attached to the inner rotating tube to move the regolith. Hot regolith in the outer tube is moved in one direction by a right-hand - ed auger, and the cool regolith in the inner tube is moved in the opposite direction by a left-handed auger attached to the inside of the rotating tube. In this counterflow arrangement, a large fraction of the heat from the expended regolith is transferred to the new regolith. The spent regolith leaves the heat exchanger close to the temperature of the cold new regolith, and the new regolith is pre-heated close to the initial temperature of the spent regolith. Using the CoRHE can reduce the heating requirement of a lunar ISRU system by 80%, reducing the total power consumption by a factor of two. The unique feature of this system is that it allows for counterflow heat exchange to occur between solids, instead of liquids or gases, as is commonly done. In addition, in variants of this concept, the hydrogen reduction can be made to occur within the counterflow heat exchanger itself, enabling a simplified lunar ISRU (in situ resource utilization) system with excellent energy economy and continuous nonbatch mode operation.

Zubrin, Robert↗