Sodium manganese oxide plays an important role in the cathode application of sodium ion batteries. In this study, sodium manganese oxide Na 2 Mn 3 O 7 (NMO) with a triclinic structure was successfully synthesized via a low-cost, simple conventional mixing method. NaMnO materials were synthesized by mixing Na 2 CO 3 precursors and the two different types of Mn precursors, namely MnO 2 by a solid method (the sample C) and MnCl 2 by a solgel method (the Sample D). The calcination of both samples was carried out at 800°C for 3 h. The results shown that the thermal behavior and crystal characteristics of the Sample D are slightly better than another one. Nevertheless, the Sample C exhibits a better microstructure, showing rod-like particles more dominant than particular particles. In addition, the Sample C reveals a little bit larger surface area than the Sample D.
This current study successfully synthesized Na2Mn3O7 in two steps. Firstly, the synthesis of MnO from NaCl and MnCl2.4H2O precursors. NaCl was mixed with citric acid as a chelating agent, while MnCl2.4H2O was mixed with two types of chelating agents (citric acid and 1% chitosan). The solutions of [NaCl-a chelating agent] and [MnCl2.4H2O-a chelating agent] were stirred for ±2 hours. The solutions were hydrothermally heated at 150°C for 6 hours and then calcined at 800°C for 1 hour in a nitrogen condition. The MnO presence was then analyzed using an XRD method. As a comparison, another sample was water leached. Then, it was examined by an XRD method. Secondly, the synthesis of Na2Mn3O7 from MnO and Na2CO3 powder was carried out through a solid method. The calcination was carried out at 800°C for ±3 hours in an oxidizing atmosphere. The XRD results showed the presence of Na2Mn3O7 in the final products of both samples. Based on these experimental results, the sample [NaCl-citric acid; MnCl2.4H2O-1%chitosan] showed higher purity than the sample [NaCl-citric acid; MnCl2.4H2O-citric acid], so that it had a higher intensity of the Na2Mn3O7 phase than the sample [NaCl-citric acid; MnCl2.4H2O-citric acid]. Besides, the Cl- ions removal after calcination greatly affected the intensity of the MnO and Na2Mn3O7 formed.
Bi-type superconductor is a high-temperature superconductor with mainly applied in the field of electricity. Silver is used as a wire sheath which causes the price of this wire production to be high. In this study Bi(Pb)-Sr-Ca-Cu-O (BPSCCO) wires were made by using stainless-steel (SS316) tubes which is cheaper and is not change its properties by the temperature of the formation of BPSCCO at 860°C. The preparation of superconducting wire is done by the Powder-In-Tube method, sintering and withdrawing/ rolling process. TiO2 powder was added to analyze the effect on the formation of BPSCCO. Based on analyzing results, there is a dominant impurity phase that has been formed, namely Fe2.5Ti0.5O4. We found that in the use of stainless-steel tubes and the TiO2 powder (5wt%), 2223 phase was not formed. Although, small amounts of Bi2Sr2CaCu2O8 (2212) and Bi10Sr10Cu5O29 (2201) phases were found. Resistance versus temperature test using cryogenic equipment results indicate that there are symptoms of a low critical temperature around 10 K. 2212 and 2201 phases are thought to cause a low critical temperature in the samples, even though the decrease in electrical resistance does not reach zero. While the morphology of superconducting wire is quite well characterized from fairly even grains and only a small amount of porosity is formed.
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