[en] Manganese dioxide has been used to scavenge radionuclides from water solutions. In this work the behaviour of MnO₂ with uranium and plutonium has been studied by batch equilibration experiments, column experiments and cartridge experiments. 8 refs.; 2 figs.; 3 tabs

[en] We present a band-selective NMR method to probe the constituent electronic bands separately in the condensed molecular matter. This method is applied to an organic-inorganic π-d hybrid metal, and its utility to give the static and dynamic spin susceptibilities for the constituent bands is demonstrated. The analysis of the results uncovers an exotic feature; the antiferromagnetic and ferromagnetic correlations are enhanced in separate bands in a single material. This finding provides a novel scope connecting the metal-insulator transitions in this system and the manganese oxides

[en] Polycrystalline CuMn₂O₄ is synthesized by solid state reaction method. Structural and magnetization studies reveal that the sample is multiphase with CuMn₂O₄ as primary phase and Mn₃O₄ as secondary phase. Magnetocaloric properties such as isothermal magnetic entropy change (−ΔS _M) and refrigerant capacity (RC) are evaluated from isothermal magnetization data. Value of isothermal magnetic entropy change ($|\mathrm{\Delta <!--\; ??\; -->}{S}_M|$) in the 40–80 K temperature range is 3.5–4.6 J kg⁻¹K⁻¹, for a field change of ΔH = 70 kOe. Value of refrigeration capacity (RC) evaluated for the same field change (ΔH = 70 kOe) is ∼190 J/kg for the T _cold and T _hot pair of 40 and 90 K respectively. Also value of $|\mathrm{\Delta <!--\; ??\; -->}{S}_M|$ remains almost constant over a broad temperature range of 60–80 K. (paper)

[en] We investigate the influence of MnO₂ polymorphism form on MnO₂/Ag₂O hydrogen getter. The results show that the performances strongly depend on the polymorphism form of manganese oxide. The nsutite γ-MnO₂ phase, which consists of a random intergrowth of MnO₂–ramsdellite and MnO₂–pyrolusite building blocks, shows the more promising performances to trap H₂ via the formation of hydroxyl groups. This observation is especially relevant for compounds with a low pyrolusite/ramsdellite ratio and a high rate of microtwinnings

[en] In 1986 Alex Mueller and Georg Bednorz of IBM Zurich discovered high-temperature superconductivity in copper-based oxides. This finding, which was rewarded with the Nobel Prize for Physics in the following year, triggered intense research into the properties of the transition metal oxides. Since then scientists have questioned the very nature of the metallic state in these materials. A few years after the initial discovery, in 1993, more excitement greeted reports that certain manganese oxides showed a huge change in electrical resistivity when a magnetic field was applied. This effect is generally known as magnetoresistance, but the resistivity change observed in these oxides was so large that it could not be compared with any other forms of magnetoresistance. The effect observed in these materials the manganese perovskites was therefore dubbed ''colossal'' magnetoresistance to distinguish it from the giant magnetoresistance observed in magnetic multilayers. In this article the author explains why magnetoresistance is an expanding field of physics research. (UK)

[en] In the present report the sorption character of uranium (IV) in the static conditions on the thin layer sorbents with application of the clinoptilolite of the Chankan deposit of the Republic of Kazakhstan is shown. A wide circle of metal hydroxides - in both the individual form and in the their mixture - is used. It is shown that the most sorptive capacity against the uranium (IV) has the modified clinoptilolite of MnO₂

[en] Periodically ordered mesoporous manganese oxides were synthesized in a single and double replication procedure. Mesoporous SBA-15 and -16 silica and their reverse replica carbons were successively used as hard templates. The silica and carbon pore systems were infiltrated with Mn(NO₃)₂·xH₂O or Mn(AcAc)₂, which was then converted to Mn₂O₃ at 873 K: the silica and carbon matrix were finally removed by NaOH solution or calcinations in air. The structure of the mesoporous Mn₂O₃, using a carbon template, corresponds to that of the original SBA-15 and SBA-16 silica. The products consist of hexagonally arranged cylindrical mesopores with crystalline pore walls or cubic mesoporous pores. The structure of replica has been confirmed by XRD, TEM analysis, and its electrochemical properties were tested with cyclic voltammetry. Formation of Mn₂O₃ inside the mesoporous carbon pore system showed much improved electrical properties

[en] Highlights: • The layered MnO₂ nanosheets are used for oxygen reduction reaction. • The MnO₂ nanosheets exhibit a high catalytic activity for oxygen reduction. • Oxygen reduction involves a coexisting pathways via 2- and 4-electron transfer. - Abstract: In this study, a novel layered manganese oxide (MnO₂) nanosheets was prepared by using a facile method with graphene oxide as the template, and its electrocatalytic performance was studied. The results of cyclic voltammograms (CV) and the rotating disk electrode (RDE) measurements show that the MnO₂ nanosheets possess excellent electrocatalytic activity for oxygen reduction reaction (ORR) in alkaline medium. The electron transfer number of the nanosheets electrode was measured to be 3.4, which lied between the two-electron and four-electron processes, suggesting that the oxygen reduction on nanosheets might proceed by a coexisting pathway involving the two-electron and four-electron transfer

[en] The resistivity of Pr_0.65Ca_0.35MnO₃ films prepared by pulsed laser deposition has been measured in the temperature range 4.2-300 K. The formation of metallic phase is suggested by the analysis of the temperature dependence of resistivity at low temperatures under zero-magnetic field. It is shown that the appearance of the charge-ordered state at 205 K can be controlled by the lattice strains accumulated during the film growth. The charge-ordering energy gap was estimated to be 77.5 meV from the experimental data. Experimental results are interpreted on the basis of the phase-separation model. (author). Letter-to-the-editor

[en] The slime formation in acidic electrolytes of copper with several metallic impurities has been studied. On Pb-Ca-SN anode surface firstly the formation of PbSO₄ takes place, then, it is transformed in PbO₂, which covers the anode surface. It was experimentally established the formation of a manganese dioxide layer at the anode. This layer was always composed of a thick external layers of non-adhering and easily removable scales, and of a thin internal layer, which adheres relatively well to the surface of the electrode. It was found that the manganese dioxide present in the slime is of different nature: a non-adhering layer produced by electrolysis (ε-MnO₂) on the PbO₂ surface and a pure chemical precipitate in the solution (β-MnO₂). Lead sufate was found on the β-MnO₂ layer when iron was in the electrolyte. When arsenic or antimony was present in the electrolyte, the slime was lead sulfate amorphous compounds of these ions. Slime of Chilean electrowinning (EW) plants is also discussed. (Author) 33 refs