Manganese oxides synthesized via microwave-assisted hydrothermal method: phase evolution and structure refinement

Materia

article

Roumanos Georges Dib Neto¹  Wagner Costa Macedo¹  José Diego Fernandes¹  Agda Eunice de Souza¹  Silvio Rainho Teixeira¹  Kleper de Oliveira Rocha¹  Elson Longo² 

[1] Universidade Estadual Paulista;Universidade Federal de São Carlos

关键词: Manganese Oxides;    Hausmannite;    Microwave-Assisted Hydrothermal Method;    Rietveld Refinement;   

DOI  :  10.1590/1517-7076-RMAT-2022-48061

学科分类：工程和技术（综合）

来源: Universidade Federal do Rio de Janeiro * Coordenacao dos Programas de Pos-Graduacao de Engenharia

【 摘 要 】

Manganese oxides were synthesized during 40 min at 140 ºC via Microwave-Assisted Hydrothermal (MAH)method and treated at different temperatures in order to evaluate the phase evolution using structure refinement(Rietveld method). The samples obtained were heat treated at temperatures defined by means of thermal analysis(160 ºC, 480 ºC, 715 ºC, 870 ºC, 920 ºC and 1150 ºC) and analyzed by X-Ray Diffractometry (XRD), X-RayFluorescence (XRF), Fourier Transform Infrared (FTIR) spectroscopy, Raman scattering, UV-Vis absorptionand Scanning Electron Microscopy (SEM). Structural characterizations allowed to identify five distinct phases:α-MnO2, Mn3O4, Mn5O8, Na2Mn5O10 and Na4Mn9O18 with weight percentages dependent on the heat treatment.The hausmannite structure (average crystallite size ranging from 28.9 nm to 99.1 nm) is present in all samplesand go through various oxidation and reduction processes from 160 ºC to 1150 ºC without any major variationin the lattice parameters. Chemical characterizations identifies the presence of Na+ ions in all samples, either assubstitution defects or as components of specific crystalline structures (Na2Mn5O10 and Na4Mn9O18), showingthat the synthesized manganese oxides works as Na+ intercalation compounds, important materials for energystorage devices optimization. The results presented enables a better interpretation of the thermal and structuralcharacteristics of manganese oxides synthesized via MAH.

【 授权许可】

CC BY