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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Mn2O3 by Materials Project

Mn2O3 is Hausmannite-like structured and crystallizes in the orthorhombic Pbca space group. The structure is three-dimensional. there are five inequivalent Mn3+ sites. In the first Mn3+ site, Mn3+ is bonded to six O2- atoms to form a mixture of distorted edge and corner-sharing MnO6 octahedra. The corner-sharing octahedra tilt angles range from 48–61°. There are a spread of Mn–O bond distances ranging from 1.92–2.28 Å. In the second Mn3+ site, Mn3+ is bonded to six O2- atoms to form a mixture of distorted edge and corner-sharing MnO6 octahedra. The corner-sharing octahedra tilt angles range from 48–60°. There are a spread of Mn–O bond distances ranging from 1.94–2.29 Å. In the third Mn3+ site, Mn3+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing MnO6 octahedra. The corner-sharing octahedra tilt angles range from 48–50°. There are a spread of Mn–O bond distances ranging from 1.99–2.12 Å. In the fourth Mn3+ site, Mn3+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing MnO6 octahedra. The corner-sharing octahedra tilt angles range from 48–50°. There are a spread of Mn–O bond distances ranging from 1.99–2.12 Å. In the fifth Mn3+ site, Mn3+ is bonded to six O2- atoms to form a mixture of distorted edge and corner-sharing MnO6 octahedra. The corner-sharing octahedra tilt angles range from 48–61°. There are a spread of Mn–O bond distances ranging from 1.95–2.32 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Mn3+ atoms. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Mn3+ atoms. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Mn3+ atoms. In the fourth O2- site, O2- is bonded to four Mn3+ atoms to form distorted corner-sharing OMn4 tetrahedra. In the fifth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Mn3+ atoms. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Mn3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mn2O3 by Materials Project

Mn2O3 is Corundum structured and crystallizes in the trigonal R-3c space group. The structure is three-dimensional. Mn3+ is bonded to six equivalent O2- atoms to form a mixture of corner, edge, and face-sharing MnO6 octahedra. The corner-sharing octahedra tilt angles range from 47–60°. There are three shorter (2.03 Å) and three longer (2.11 Å) Mn–O bond lengths. O2- is bonded to four equivalent Mn3+ atoms to form a mixture of distorted corner and edge-sharing OMn4 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Development of Manganese and Iron Mixed Metal Oxides for Thermochemical Energy Storage

Energy storage plays an essential role for sustainable and renewable energy use in an effort to reduce carbon emissions. Thermochemical energy storage (TCES) is a favorable alternative to fossil fuel energy systems and a promising solution to the intermittency problem of renewable energy sources (such as solar energy). TCES stores energy in the form of chemical bonds using reversible redox reactions (such as manganese metal oxides). This study developed manganese oxide (Mn2O3) and iron oxide (Fe2O3) with an inert dispersant of silicon dioxide (SiO2) (Mn-Fe-Si) for potential large scale energy storage application. These metal oxides are nontoxic, cheap, and relatively abundant. The materials were prepared with varying metal oxide content using physical mixing in a ball mill, pressure pelletization and calcination at different temperatures. Redox cycle tests were conducted using differential scanning calorimetry combined with thermogravimetric analysis (TGA-DSC). The Mn-Fe-Si materials had higher cyclability and energy release compared to the pure metal oxides and manganese oxide with SiO2. The calcination temperature had a significant effect on releasable energy due to the interactions between the oxides. The Mn-Fe-Si mixture calcined at high temperature (1000oC) showed the highest average energy storage density.

Wilkinson, Olivia↗
NASA NTRS1989

Manganese oxide microswitch for electronic memory based on neural networks

A solid-state, resistance tailorable, programmable-once, binary, nonvolatile memory switch based on manganese oxide thin films is reported. MnO(x) exhibits irreversible memory switching from conducting (on) to insulating (off) state, with the off and on resistance ratio of greater than 10,000. The switching mechanism is current-triggered chemical transformation of a conductive MnO(2-Delta) to an insulating Mn2O3 state. The energy required for switching is of the order of 4-20 nJ/sq micron. The low switching energy, stability of the on and off states, and tailorability of the on state resistance make these microswitches well suited as programmable binary synapses in electronic associative memories based on neural network models.

Ramesham, R.↗
NASA NTRS2004

Direct Electrolytic Deposition of Mats of Mn(x)O(y) Nanowires

Mats of free-standing manganese oxide (MnxOy) nanowires have been fabricated as experimental electrode materials for rechargeable electrochemical power cells and capacitors. Because they are free-standing, the wires in these mats are electrochemically accessible. The advantage of the mat-of-nanowires configuration, relative to other configurations of electrode materials, arises from the combination of narrowness and high areal number density of the wires. This combination offers both high surface areas for contact with electrolytes and short paths for diffusion of ions into and out of the electrodes, thereby making it possible to charge and discharge at rates higher than would otherwise be possible and, consequently, to achieve greater power densities. The nanowires are fabricated in an electrolytic process in which there is no need for an electrode binder material. Moreover, there is no need to incorporate an electrically conductive additive into the electrode material; the only electrically conductive material that must be added is a thin substrate contact film at the anchored ends of the nanowires. Hence, the mass fraction of active electrode material is close to 100 percent, as compared with about 85 percent in conventional electrodes made from a slurry of active electrode material, binder, and conductive additive pressed onto a metal foil. The locations and sizes of the nanowires are defined by holes in templates in the form of commercially available porous alumina membranes. In experiments to demonstrate the present process, alumina membranes of various pore sizes and degrees of porosity were used. First, a film of Au was sputtered onto one side of each membrane. The membranes were then attached, variously, to carbon tape or a gold substrate by use of silver or carbon paste. Once thus attached, the membranes were immersed in a plating solution comprising 0.01 M MnSO4 + 0.03 M (NH4)2SO4. The pH of the solution was kept constant at 8 by addition of H2SO4 or NH4OH as needed. Mn(x)O(y) nanowires were potentiostatically electrodeposited in the pores in the alumina templates. Depending on the anodic deposition potentials, Mn(x)O(y) was deposited in various oxidation states [divalent (Mn3O4), trivalent (Mn2O3), or tetravalent (MnO2)]. The Mn(x)O(y) wires were made free-standing (see figure) by dissolving the alumina templates, variously, in KOH or NaOH at a concentration of 20 volume percent.

Myung, Nosang↗