Soft Synthesis Method Research Articles

A Novel Approach to Continuous and Scalable Synthesis of Cation-Disordered Rocksalt Cathodes

Cation disordered rocksalts (DRX) are an emerging class of high energy density LIB cathodes that can utilize earth-abundant and low-cost redox active transition metals. The DRX cathodes can be synthesized through a rich chemistry of transition metals, where commonly, metal-oxide precursors are combined with lithium source via ball-milling and calcined to achieve cation disordered phase. In this work, we present a new alternative synthesis method to the traditional solid-state synthesis, which provides scalable and continuous production of cathode precursors. A soft synthesis method in aqueous media was adopted to produce Mn-rich cathode precursors in large scale, through which homogenous mixing of the introduced transition metal cations was achieved. Here we report the electrochemical and structural properties of as-synthesized DRX cathodes with various Mn-compositions.

Electrical Properties of Cobalt Substituted NZCF and ZNCF Nanoparticles Prepared by the Soft Synthesis Method

The soft chemical method was adopted for the synthesis of cobalt substituted nickel-zinc and zinc-nickel ferrites (Ni0.95-xZn0.05CoxFe2O4 and Zn0.95-xNi0.05CoxFe2O4 for x= 0.01, 0.02, 0.03, 0.04, 0.05, and 0.06. We have recently studied the structural, morphological, magnetic properties, initial permeability, and dielectric constant of the samples. They are found with cubic ferromagnetic spinel structure along with the morphology suitable for high-density recording media. The effective initial permeability μi (μeff) is found to depend on magnetocrystalline anisotropy constant K1 and grain size D. From this present study, the dc resistivity is found to increase linearly with Co2+ substitution for both ZNCF and NZCF ferrites up to x=0.04. After that, the material changes its ferromagnetism to paramagnetism thereby increasing the activation energy. The difference between the two magnetic states (Ferro and para) in NZCF is found to be greater than in ZNCF. The phase transition helps to determine the Curie temperature. The ac conductivity takes place by the hopping of charge carriers called polarons. The conductivity is enhanced with frequency.

Preparation and characterization of supported RuxIr(1-x)O2 nano-oxides using a modified polyol synthesis assisted by microwave activation for energy storage applications

A simple and soft synthesis method, namely the polyol route, is proposed to synthesize RuxIr(1-x)O2 mixed-oxide nanoparticles deposited on a high surface area carbon support, with controlled size and size distribution, and composition. The samples are characterized by TGA, XRD, TEM, XPS and Raman analyses. Their behaviors as supercapacitors and catalysts for oxygen evolution reaction (OER) have been investigated in 0.5M H2SO4 medium. It was demonstrated that pure RuO2 presented the highest supercapacitive property, and that addition of iridium leads to decrease this property. On the other hand, pure RuO2 presented the lower onset potential for OER, but tended to be passivated as the potential was increased. Addition of iridium led to limit or to avoid the catalyst passivation and to increase the activity at high potential, but also to shift positively the OER onset potential.

Synthesis and characterization of erbium-doped YAlO3 phosphor.

In the yttrium aluminium system, the YAlO3 phosphor is a prominent host because of the yttrium aluminium ratio (1:1). Phosphor was synthesized by the solid-state reaction method at variable concentrations of erbium (0.1-2.5 mol%). This method is suitable for large-scale production and is a less time-consuming method when compared with the soft synthesis method. The prepared sample was characterized by X-ray diffraction technique and the crystallite size was calculated by Scherer's formula. Vibrational and bending analysis of prepared phosphor for optimized concentration of erbium ion is described based on the Fourier transform infrared spectroscopic technique. The photoluminescence (PL) emission spectra of prepared phosphor for variable concentrations of erbium ion were recorded and the excitation spectrum was found to be at 291 nm with three shoulder peaks at 305, 270 and 242 nm. For 291 nm excitation, the emission spectrum was found at 546 nm and 552 nm. PL intensity increased with increasing concentrations of erbium and after 2 mol% emission intensity decreased due to concentration quenching. Spectrophotometric determination of YAlO3:Er(3+) is described by CIE co-ordinates and shows an intense emission in the green region such that the prepared phosphor can act as a single host for green light emission. Thermoluminescence glow curve analysis of the YAlO3:Er(3+) phosphor was recorded for different ultraviolet (UV) light exposures and gamma exposure. Different gamma doses 0.5-2 kGy show a linear response. Kinetic parameters were calculated by the peak shape method.

Soft Synthesis Route and Characterization of Superparamagnetic Mn1/2Fe1/2(H2PO4)2·2H2O and Its Decomposed Product

The superparamagnetic Mn1/2Fe1/2(H2PO4)2·2H2O was synthesized by a soft synthesis method using a Mn(c)−Fe(c)−H3PO4 system in water−acetone medium at ambient temperature. The synthesized Mn1/2Fe1/2(H2PO4)2·2H2O decomposed through the dehydration and the phosphate condensation reactions at high temperature and yielded binary manganese iron cyclotetraphosphate MnFeP4O12. The XRD and FTIR results of the synthesized Mn1/2Fe1/2(H2PO4)2·2H2O and the decomposed MnFeP4O12 indicate the pure monoclinic phase with space group P21/n and C2/c, respectively. The thermal behaviors and superparamagnetic properties of Mn1/2Fe1/2(H2PO4)2·2H2O and MnFeP4O12 in this work differed from the single compounds (M(H2PO4)2·2H2O and M2P4O12, where M = Mn, Fe) and the binary compounds (Mn0.5Fe0.5(H2PO4)2·xH2O) reported in previous works. The kinetic and thermodynamic functions for thermal decomposition of Mn1/2Fe1/2(H2PO4)2·2H2O were studied and confirmed as reaction mechanisms. Vibrational frequencies of breaking bonds in two thermal...

Structural phase transition and magnetic properties of the Sr 2FeRe 1− xBx′O 6 ( B′=Nb, Ta; x=0, 0.1) double perovskites

The double perovskites, Sr 2FeReO 6 and Sr 2FeRe 0.9 M 0.1O 6 ( M=Nb, Ta) have been obtained by soft synthesis methods which yield homogeneous particles of micrometric grain size. The materials have been studied by X-ray and neutron powder diffraction, scanning electron microscopy and magnetic measurements. Rietveld refinements show that the compounds adopt a tetragonal I4/ mmm structure at high temperatures and monoclinic P2 1/ n below the transition temperature. The magnetic structures were determined by neutron powder diffraction at 100 and 300 K for the Sr 2FeReO 6, Sr 2FeRe 0.9Nb 0.1O 6 and Sr 2FeRe 0.9Ta 0.1O 6 phases, respectively. Evidence for a ferrimagnetic coupling between the Fe 3+ and Re 5+ sublattices has been observed. Magnetic measurements yield magnetic moments lower than the theoretical ones being in accord with the antisite disorder of 25% in the B– B′ positions.