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Briquetting of Natural and Anthropogenic Raw Materials for Ferroalloys Production
Published in Aitber Bizhanov, Briquetting in Metallurgy, 2022
The manganite (MnO(OH)) dehydrates to form pyrolusite or β-kurnakit (2MnOOH = Mn2O3 + H2O) in the temperature range 300-450°C. At temperatures above 400°C, psilomelane of manganese ore transforms to hollandite or Hausmannite Exothermic peaks with a maximum temperature of 795.8°C in brex No. 1 and 801.0°C in brex No. 2 are most likely associated with the dissociation of pyrolusite and the formation of β-kurnakit which is accompanied by oxygen release and mass loss. The same peak in brex No. 3 at a temperature of 742.8°C is not followed by a loss of mass; it can be explained by the effects of recrystallization of amorphous phases. 13-kurnakit decomposes in the temperature range 900-1050°C, and the formation of 13-Hausmannite takes place [3]. In the range 1080-1250°C, β-Hausmannite is polymorphically converted to γ-Hausmanite
Oxide Based Supercapacitors I-Manganese Oxides
Published in Ling Bing Kong, Nanomaterials for Supercapacitors, 2017
Ling Bing Kong, Wenxiu Que, Lang Liu, Freddy Yin Chiang Boey, Zhichuan J. Xu, Kun Zhou, Sean Li, Tianshu Zhang, Chuanhu Wang
Representative SEM images of the samples are shown in Fig. 4.28(A–C), demonstrating the general morphology of the Mn3O4 nano-octahedrons [76]. Every octahedron was constructed by two inverted pyramids connected at the square base, thus having eight triangular facets. The edges between the facets were very sharp, while all the facets had a very smooth surface without any obvious defects, as illustrated in Fig. 4.28(C). Average side length of the square base of the octahedrons was 160 nm. Figure 4.28(D) shows XRD pattern of the Mn3O4 nano-octahedrons, exhibiting strong and sharp diffraction peaks, which implied that the sample had been highly crystallized. The sample was a mixture of two manganese oxides, hausmannite Mn3O4 as major phase and pyrolusite MnO2 as minor phase. No other impurities were observed in the XRD pattern.
Mn, 25]
Published in Alina Kabata-Pendias, Barbara Szteke, Trace Elements in Abiotic and Biotic Environments, 2015
Alina Kabata-Pendias, Barbara Szteke
Manganese occurs mainly at +2 oxidation stage, but may change valences up to +7. It is a member of the Fe family, and is highly associated with Fe, in all geochemical processes. There are many Mn minerals, mainly together with other metals, especially with Fe. The most common is pyrolusite, β-MnO2; other minerals are manganite, γ-MnOOH; hausmannite, Mn3O4; and rodochrozite; MnCO3. The Mn oxide mineral birnessite, (Na0.3Ca0.1K0.1)(Mn4+,Mn3+)2O4·1.5 H2O, of an unconfirmed composition, is formed due to precipitation in lakes, oceans, and groundwater. It is a major component of desert varnish and deep sea Mn nodules, exhibits a large adsorption capacity to several metals (Cd, Co, Cu, Pb, and Zn), and has a high oxidizing potential (Feng et al. 2007). Sorption capacity of MnO2 for several metals is comparable to that of goethite and hematite.
Effect of soft template variation on the synthesis, physical, and electrochemical properties of Mn3O4 nanomaterial
Published in Inorganic and Nano-Metal Chemistry, 2020
Muhammad Danish, Muhammad Tayyab, Arusa Akhtar, Ataf Ali Altaf, Samia Kausar, Shafiq Ullah, Muhammad Iqbal
Among these manganese oxides, hausmannite (Mn3O4) is more stable with abundant manganese oxide. It has potential features such as homogeneous structure, low cost, environment friendly, ion exchange, and molecular adsorption.[9] Because of such characteristics, hausmannite is useful in applications of sensors, lithium-ion batteries, supercapacitors, and solid oxide fuel cells (SOFCs).[10] Besides electrochemical applications, they are also employed in catalytic fields such as active catalysts in the reduction of nitrobenzene and oxidation of carbon monoxide.[11] The potentiality of these nanoparticles is also obvious from their unique ability to remove dye from their aqueous solution as an adsorbent material.[12] These applications depend on the efficiency of nanomaterials that can be increased by enhancing the surface area, morphology, and nanostructure of the material using different templates.[13,14]