Synthesis and Vibration Spectroscopy of Nano-Sized Manganese Oxides (original) (raw)
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Formation and magnetic behaviour of manganese oxide nanoparticles
Materials Science and Engineering: B, 2010
The formation and magnetic behaviour of nanoparticles of various manganese oxides have been studied. For synthesis, manganese oxalate dihydrate is first produced via sol-gel process and then decomposed in oxygen, air, nitrogen, or argon ambient at different temperatures. The decomposition process leads to emergence of Mn 3 O 4 which undergoes oxidation, oxidation-reduction, or reduction process subsequently depending upon the availability of oxygen to yield Mn 2 O 3 in air/O 2 and MnO in argon/nitrogen ambient. A partial reaction causes retention of some Mn 3 O 4 alone or Mn 3 O 4 and Mn 5 O 8 together as secondary phase(s). The magnetic susceptibility ( ) data reveal (i) antiferro-magnetic nature for Mn 2 O 3 , Mn 5 O 8 and MnO with Néel temperature 75 K, 131 K and 115 K, respectively, (ii) orthorhombic to cubic crystallographic transition in Mn 2 O 3 at 310 K for the first time, and (iii) ferri-magnetic character for Mn 3 O 4 with Curie temperature 46 K. Further, it is demonstrated that a small quantity of Mn 3 O 4 always remains in the products and can be detected by susceptibility data below 50 K only with bifurcation in ZFC and FC curves and blocking temperature in the range 30-40 K. Also, the decomposition of manganese oxalate at 1100 • C for 4 h in air leads to formation of pure Mn 3 O 4 with saturation magnetization of 1.85 B per molecule and coercivity of 4750 Oe at 10 K.
Raman and infrared spectromicroscopy of manganese oxides
Journal of Alloys and Compounds, 2009
Confocal micro-Raman and micro-FT-IR spectroscopies have been used to probe the phase composition of nominally pure single-crystal MnO and mixed MnO-Mn 3 O 4 samples, grown by the method of chemical transport reactions on MgO(1 0 0) substrate. The presence of spinel Mn 3 O 4 phase has been clearly detected in both samples by Raman and FT-IR spectroscopies. The size of the spinel Mn 3 O 4 phase regions has been estimated to be below 20 m.
XANES studies of modified and newly synthesized nanostructured manganese oxides
Journal of Electron Spectroscopy and Related Phenomena, 2009
The interesting chemical and physical properties of Mn-oxide-based nanomaterials offer a variety of technological applications. The novel Mn-oxide properties reached through synthetic design have the potential to be of tremendous contribution to modern, environmental friendly chemistry. A problem of Mn oxide crystal chemistry is that, even within a single mineral, Mn atoms can exhibit multiple valence states. An average oxidation state for Mn atoms can be easily and quite reasonably measured, however, determining the individual proportions/("weights") of Mn(IV), Mn(III), and Mn(II) in a non-destructive way is considerably more difficult. We applied X-ray absorption near edge spectroscopy (XANES) to investigate the Mn environment and to improve fundamental understanding of the structural chemistry and morphology of nanostructured Mn-oxides to produce desirable chemical and physical properties.
Synthesis, characterization, optical and sensing property of manganese oxide nanoparticles
2014
Manganese oxide nanoparticles were prepared by thermal decomposition of manganese oxalate. Manganese oxalate was synthesized by reacting 1:1 mole ratio of manganese acetate and ammonium oxalate along with sodium dodecyl sulfate (SDS). The structural characterization of manganese oxalate and manganese oxide nanoparticles was analyzed by XRD. The XRD spectrum confirms the crystal structure of the manganese oxide and manganese oxalate. In addition, the average grain size, lattice parameter values were also calculated using XRD spectrum. Moreover, the diffraction peaks were broadened due to the smaller size of the particle. The band gap of manganese oxide was calculated from optical absorption, which was carried out by DRS UV-Visible spectroscopy. The morphology of manganese oxide nanoparticles was analyzed by SEM images. The FT-IR analysis confirms the formation of the manganese oxide from manganese oxalate nanoparticles. The electrochemical sensing behavior of manganese oxide nanoparticles were investigated using hydrogen peroxide by cyclic voltammetry.
Chemical Vapor Synthesis and Characterization of Manganese Oxides
Chemical Vapor Deposition, 2011
Manganese oxide nanoparticles are synthesized by a chemical vapor process using manganese(0) carbonyl as the precursor. The synthesis temperature of the materials is varied from 500 to 1500 °C at 200 °C intervals. These nanomaterials are characterized by X‐ray powder diffraction (XRD), transmission electron microscopy (TEM), Brunauer‐Emmett‐Teller (BET) surface area, and X‐ray photoelectron spectroscopy (XPS). XRD shows that the manganese oxide nanoparticles synthesized at 500, 700 – 1100, 1300, and 1500 °C are mainly MnO2, Mn2O3, Mn2O3/Mn3O4, and Mn3O4, respectively. The TEM and BET results also confirm that the particle size is on the nanometer scale with a large specific surface area (SSA) of 81 – 215 m2 g−1. XPS indicates the catalysts to have manganese oxidation states of (2+), (3+), or (4+) depending on the synthesis temperature.
2020
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 XRD, XRF, FTIR spectroscopy, Raman scattering and 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 samples and go through various oxidation and reduction processes from 160 ºC to 1150 ºC without any major variation in the lattice parameters. The results presented enables a better interpretation of the thermal and structural characteristics of manganese oxides synthesiz...
European Journal of Inorganic Chemistry, 2012
We synthesized manganese oxide (MnO and Mn3O4) nanocrystals with various sizes and shapes by the thermal reaction of a MnII–oleate complex through a “heat‐up process”. When a MnII–oleate complex was thermally decomposed in non‐coordinating hydrocarbon solvents, uniformly sized MnO nanocrystals with cubic and octahedral shapes were produced. We were able to synthesize anisotropic, multibranched MnO nanocrystals by the oriented attachment of MnO truncated‐nanocube building blocks. When the MnII–oleate complex was heated in 1‐hexadecene in the presence of strongly coordinating carboxylic acid surfactants, spherical nanocrystals were generated, and their diameter was controlled in the range 3–13 nm by varying the chain length of the carboxylic acid. When oleyl alcohol was added to the Mn–oleate complex in phenyl ether, tetrahedral MnO nanocrystals were synthesized. The as‐synthesized MnO nanocrystals were oxidized in air to Mn3O4 or MnO/Mn3O4 core–shell structures, which exhibited excha...
Room temperature ferromagnetic behavior of manganese/manganese oxides nanocomposites
Materials Letters, 2018
Three different manganese oxide nanocomposites such as Mn3O4, Mn5O8, and Mn2O3 along with metallic-Mn were synthesized via a single route depending on calcination temperature. Structural, electrical, and magnetic properties were assessed for the synthesized nanocomposites. The real and imaginary parts of dielectric constants decreased at the lower frequency and then remained constant at the higher frequency for all the three types of nanocomposites. The permeability of the nanocomposites also followed the same order. Mn/Mn5O8 nanorods showed strong ferromagnetic behavior at room temperature although Mn-nanoparticles and Mn5O8 are paramagnetic and antiferromagnetic in nature respectively.
IOSR Journal of Applied Physics, 2017
Manganese oxide and Cobalt doped Manganese oxide nanoparticles are synthesized by solvothermal route using ethylene glycol as a solvent. The structural investigations are done by X-ray diffraction (XRD). The average grain size and lattice parameters are calculated. The particle size is confirmed by scanning electron microscope (SEM) analysis. The functional groups exists in the material are construed by Fourier transform infrared (FTIR) spectral analysis. The chemical composition and purity of the samples are inspected by using Energy-dispersive X-ray spectral analysis (EDAX).The optical properties are analyzed by Ultraviolet-Visible (UV-Vis) spectroscopy. A UV-Vis spectra shows that Cobalt doped Manganese oxide nanoparticles acquires blue shift. The magnetic properties of all the samples are reported using vibrating sample magnetometer (VSM) at room temperature. The values of saturation magnetization, retentivity, coercivity and squareness ratio are obtained from the magnetic studies.