Papers by Keyword: Manganese Oxide

Abstract: In this study beads like nanoparticles of manganese oxide with different doping of iron concentrations from 2% to 10% were deposited on ultrasonically cleaned glass substrate by chemical bath deposition technique. Different analytical techniques including XRD, SEM, DRS and VSM were utilized to analyze the structure, morphology, optical and magnetic properties. XRD analysis confirms the crystallite size of Fe-MnO₂ were between 13.70 nm to 46.46 nm, morphological examination indicated that Fe-MnO₂ have cubic and beads-like structures. SEM have revealed the average grain size of 613.3 nm and non-uniform deposition of thin film, DRS analysis confirms that pure MnO has band gap energy 2.90 eV and is decreased with increasing concentration of iron i.e shifted towards lower band gap energy semiconductor materials, VSM reveals that magnetization increases with increase in iron concentration. The best properties were obtained at 6% iron doping because, with further increase in doping concentration, the structure started to distort.

Abstract: Manganese-oxide material prepared by simple sol-gel method was used as an adsorbent of Hg(II) in aqueous solution. X-ray diffraction pattern and Raman spectroscopy were conducted to prove the cryptomelane crystal. The Hg(II) adsorption behavior of the synthesized material well obeyed kinetic models of pseudo-second-order and Elovich equations indicating a chemisorption from the collected kinetic parameters. 500 mg_Hg2+/g_cryptomelane of equilibrium uptake capacity from pseudo-second-order and 7.87x10³ mg_Hg2+/g_cryptomelane/day of initial adsorption rate from the Elovich model were obtained for adsorption of Hg²⁺ cation over cryptomelane adsorbent. Desorption constant of 0.018 g_cryptomelane/mg_Hg is a significant small value, in comparison to initial adsorption rate, proposing a possible chemisorption for remediation of Hg(II) on cryptomelane structure.

Abstract: In this study, the α and β modifications of MnO₂ have been successfully synthesized by the hydrothermal method. The obtained materials have been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and low-temperature nitrogen adsorption. In addition, the supercapacitor performance of the materials has been pre-tested to assess their suitability for practical applications. The average particle size of the α modification is 12-15 nm, and the β modification is 14-18 nm. The surface areas of the α and β modifications of MnO₂ are 200 m²/g and 70 m²/g, respectively. The average pore sizes are 3.2 nm and 5.3 nm, respectively. The specific capacitance of 40 F/g is observed at 1 mV/s, which has been recorded using cyclic voltammetry and constant current charge-discharge cycling in 30 % aqueous KOH solutions. It has been determined that the specific capacitance of the β - MnO₂/electrolyte system decreases from 40 F/g to 15 F/g with an increase in the scan rate from 1 to 30 mV/s. In addition, the total capacitance of the material was divided into the electric double layer capacitance and the diffusion-controlled redox capacitance due to the Faraday reverse redox reactions. Finally, the pseudocapacitance contribution has been determined to be 90 % of the total specific capacitance.

Abstract: Ceria stabilized zirconia with critical grain size is found to exhibit higher strength and higher resistance towards low temperature moisture degradation, The mechanical properties are greatly influenced by the size of the tetragonal grains. The effectiveness of doping with MnO2 (0.2 to wt %) in retarding degradation mechanical properties of ceria stabilized tetragonal zirconia (Ce-ZrO2) was evaluated by pressureless sintering within a temperature range from 1250°C-1550°C. Impact of manganese oxide to the mechanical properties and ageing resistance to the Ce-ZrO2 is truly beneficial. 0.4 wt% MnO2 at 1450°C revealed that, the tetragonal grain size was not affected by dopant level.With optimum dopant the 3 mol% ceria (3Ce-ZrO2) ceramic demonstarted the Vicker hardness of 11.8 GPa , fracture toughnessof 10.0 MPam^1/2, flexural strength 920 MPa and Young modulus of 210 GPa. The 3Ce-ZrO2 doped with 0.4wt% MnO2 sintered 1450°C could be the best building block for biomedical applications.

Abstract: Mn₃O₄ nanosheets were deposited electrochemically on graphene modified carbon cloth (G–CC). The graphene layer improved significantly the hydrophilic property of carbon cloth and its compatibility with active materials, as a result, lower resistance and better structural stability were obtained for Mn₃O₄/G–CC compared with those for the electrode based on neat carbon cloth. Furthermore, the Mn₃O₄/G–CC possessed a capacitance of 1335 mF cm^–2 at a current density of 2 mA cm⁻², and a capacitance retention of up to 88 % after 2000 cycles at 10 mA cm^–2. It is believed that manganese oxide was anchored strongly on graphene layer through C–O–metal bonds, and the graphene layer on the surface of the CC could serve as elastic buffering layers to release the strain within manganese oxide, resulting the remarkable improvements in electrochemical performance. These excellent characteristics make this kind of the composites promising candidates as high performance electrodes for supercapacitor.

Abstract: Nanostructured manganese-containing oxide coatings on titanium were formed by method of plasma electrolytic oxidation in tetraborate aqueous electrolyte containing manganese acetate with and without the acetonitrile addition. These oxide layers with high content of manganese and coated by ordered "leaf-like" mesh nanostructures are formed in the electrolyte without acetonitrile addition. The oxide layers are displayed high acitivity towards oxidation CO and photoactivity in the degradation reaction of methylene blue. The addition of acetonitrile into electrolyte results in the change in the morphology of the coating surface, a significant reduction in the manganese content and, as a consequence, practical loss of activity in the oxidation of CO in CO₂ and a reduction in the photocatalytic activity in the decomposition of methylene blue.

Abstract: The nickel and manganese oxides (Ni-Mn oxides) were prepared by a simple co-precipitation process with sodium carbonate (Na₂CO₃) as precipitant. The products are the mixture of nickel oxides, manganese oxides and their solid solution. The phase and morphology of the synthesized product were characterized by X-ray diffraction and field emission scanning electron microscope. The electrochemical capacitive characterization was performed using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrical impedance spectroscopy (EIS) measurements in a 6mol/L KOH aqueous solution electrolyte. The result shows that a maximal specific capacitance value when stoichiometric amounts of NiCl₂ and MnCl₂ are equal (cationic ratio of Ni:Mn=1:1) which the specific capacitance is 110 F/g (at a current density of 1A/g). Overall we found that the nickel and manganese oxides have better electrochemical performance compared to the single parts, and while the introduction of nickel oxides can further improve the performance.

Abstract: The effect of manganese oxide (MnO₂) and aluminum oxide (Al₂O₃) addition of up to 1 wt% in yttria-stabilized tetragonal zirconia polycrystals (Y-TZP), sintered in air at 1450oC, was examined. The low temperature degradation resistance was observed by immersing the sample in Ringer solution at 37oC over a period of 8 weeks, whereby the weight loss and the SEM image of sample was analyzed to generate the degradation pattern of the sample. Additions of 0.6wt% Al₂O₃/ 0.4wt% MnO₂ were found to be beneficial in retarding the ageing of the ceramics sample. Therefore the sample was deemed beneficial in the use of orthopedic applications.

Abstract: In this work, modified nano-mesh structured Mn-based oxide electrode material and the supercapacitors are researched. Three types of conducting polymers, i.e. polyaniline (PANI), polypyrrole (PPy) and polythiophene (PTs) are considered to modify Mn-based oxide electrodes. The results of field emission scanning electron microscope show that conducting polymer film can form porous structure on Mn-based oxide electrode, this special structure is beneficial to the improvement of specific surface area, so that the specific capacitance can be increased. The specific capacitance of the supercapacitors assembled by Mn-based oxide/conducting polymer composite electrodes are tested, resulting that the maximum initial specific capacitance is 843 F g^-1, cycle life is 10⁵ times. Compared to supercapacitors assembled by general Mn-based oxide electrodes, this Mn-based oxide/conducting polymer material electrode can improve the specific capacitance up to 1.4~1.9 times, and the conductivity and cycle stability can be increased at the same time.

Abstract: Manganese oxide (MnO_x) thin films were prepared on stainless steel (SS) 304 by galvanostatic (GS) mode of electrodeposition technique using different precursors; 0.1 M potassium permanganate (KMnO₄) and 0.1 M manganese sulfate (MnSO₄) solutions. The electrodeposition condition was set at a constant current of 1 mA/cm². Different precursors provide MnO_x thin films with different morphologies. Using KMnO₄ as a precursor, the MnO_x thin film was deposited (MnO_x-K), while using MnSO₄ as a precursor, the MnO_x nanosheets with a thickness of approximately 40 nm were formed (MnO_x-S). XPS results evidence the formation of manganese oxide with different oxidation states composition by different precursors. Electrochemical measurements were carried out in a three-electrode setup using Pt and Ag/AgCl electrodes as counting and reference electrodes, respectively and 1M Na₂SO₄ aqueous solution as electrolyte. MnO_x-K at a deposition time of 10 min shows the highest specific capacitance of 233.55±19.01 F/g. The specific capacitance improvement of MnO_x-K may be attributed to MnO_x nanosheet structure which increases surface area of electrode.