Über Manganoxyde. VII. Darstellung und Eigenschaften von Braunsteinen. I (Die δ‐Gruppe der Braunsteine)

Abstract

Es wird ein kurzer Überblick über den derzeitigen Stand der Braunsteinforschung gegeben. Die Untersuchungsmethoden werden mitgeteilt.δ‐Braunsteine werden nach mehreren Verfahren hergestellt und charakterisiert. Beim Erhitzen an der Luft wandeln sich die δ‐Braunsteine bei etwa 100 °C in γ″‐MnO2 um. Bei weiterer Temperaturerhöhung entsteht β′‐MnO2, das dann in β‐MnO2 übergeht; anschließend tritt unter Sauerstoffabgabe Bildung von α‐Mn2O3 ein.Bei den „fremdionenhaltigen”︁ δ‐Braunsteinen findet beim Tempern Umwandlung in α‐MnO2 statt.

Investigation on the co-precipitation of transuranium elements from alkaline solutions by the method of appearing reagents

“…(Glemser et al 1961, Regner et al 1963, Sterr et al 1969, Giovanoli et al 1970, and Yamamoto et al 1980. The chemical composition of this practically amorphous product varies between (I) -NqMn,,On.9H,O and (11) -Mn,0,33H,0 (Gmelin 1973a andGiovanoli et al 1973).…”

“…The transformation of MnOi to MnO, can be carried out using different reductants (Gmelin 1973a, Glemser et al 1961, Regner et al 1963, Sterr et al 1969, and Giovanoli et al 1970. In most cases, hydrogen peroxide (H202) is used for this process.…”

Cycle stability of birnessite manganese dioxide for electrochemical capacitors

“…Within the category of metal oxides, systems based on manganese dioxide are presently receiving considerable attention from the scientific community [6]. With a myriad of available synthesis methods [7][8][9][10][11][12][13][14], and as a result wide ranging morphologies, coupled with good faradaic electrochemical performance, low cost and environmental friendliness, this class of materials represents an interesting and promising area of research.…”

Origin, mineralogy, and chemistry of manganiferous and ferruginous precipitates found in sand and gravel deposits in Finland

“…In the experiments of Brown et al (1971), natural birnessite changed to cryptomelane and then crystallized as hausmannite at 600°C after passing through an amorphous state. Glemser et al (1961) observed that birnessite containing foreign cations lost water at 110-125°C and converted to cryptomelane at 370-500°C and to bixbyite upon further heating. McMurdie and Golovato (1948) report that cryptomelane may convert directly to hausmannite or go through an intermediate stage of bixbyite because of impurities.…”