One-step Solid-state Reaction Method Research Articles

Electrochemical performance of LiVPO4F/C synthesized by different methods

LiVPO4F/C samples were synthesized by one-step solid-state reaction and two-step solid-state reaction methods, respectively. The X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical performance tests were adopted to characterize the properties of LiVPO4F/C. XRD results show that the LiVPO4F/C samples prepared by one-step solid-state reaction method have the same triclinic structure (space group as that synthesized by conventional two-step solid-state reaction. SEM image exhibits that the particle size of LiVPO4F/C prepared by one-step solid-state reaction method is smaller than that of the sample synthesized by two-step solid-state reaction. The improved electrochemical properties of the LiVPO4F/C are attributed to the depressed grain size and enhanced electrical conductivity produced via one-step solid-state reaction method using oxalic acid as both reduction agent and carbon sources. AC impedance measurements also show that the LiVPO4F/C synthesized by one-step solid-state reaction route significantly decreases the charge-transfer resistance.

Effects of carbon source and carbon content on electrochemical performances of Li4Ti5O12/C prepared by one-step solid-state reaction

Li4Ti5O12/C composites were synthesized by one-step solid-state reaction method using four commonly used organic compounds or organic polymers as carbon source, i.e., polyacrylate acid (PAA), citric acid (CA), maleic acid (MA) and polyvinyl alcohol (PVA). The physical characteristics of Li4Ti5O12/C composites were investigated by X-ray diffraction, electron microscopy, Raman spectroscopy, particle size distribution and thermogravimetry-derivative thermogravimetry techniques. Their electrochemical properties were characterized by cyclic voltammograms, electrochemical impedance spectra, constant current charge–discharge and rate charge–discharge. These analyses indicated that the carbon source and carbon content have a great effect on the physical and electrochemical performances of Li4Ti5O12/C composites. An ideal carbon source and appropriate carbon content effectively improved the electrical contact between the Li4Ti5O12 particles, which enhanced the discharge capacity and rate capability of Li4Ti5O12/C composites. PAA was the best carbon source for the synthesis of Li4Ti5O12/C composites. When the carbon content was 3.49wt.% (LiOH·H2O/PAA molar ratio of 1), as-prepared Li4Ti5O12/C showed the maximum discharge capacity. At 0.2C, initial capacity of the optimized sample was 168.6mAhg−1 with capacity loss of 2.8% after 50 cycles. At 8 and 10C, it showed discharge capacities of 143.5 and 132.7mAhg−1, with capacity loss of 8.7 and 9.9% after 50 cycles, respectively.

Superconductivity induced by doping Rh in CaFe2−xRhxAs2

In this paper, we report the synthesis of iron-based superconductors CaFe2−xRhxAs2 using a one-step solid state reaction method that crystallizes in the ThCr2Si2-type structure with a space group I4/mmm. The systematic evolution of the lattice constants demonstrates that the Fe ions are successfully replaced by the Rh. By increasing the doping content of Rh, the spin–density–wave (SDW) transition in the parent compound is suppressed and superconductivity emerges. The maximum superconducting transition temperature is found at 18.5 K with a doping level of x=0.15. The temperature dependence of dc magnetization confirms superconducting transitions at around 15 K. The general phase diagram was obtained and found to be similar to the case of the Rh-doping Sr122 system. Our results explicitly demonstrate the feasibility of inducing superconductivity in Ca122 compounds by higher d-orbital electron doping; however, different Rh-doping effects between FeAs122 compounds and FeAs1111 systems still remains an open question.

Enhanced critical current properties in Ba0.6K0.4+xFe2As2 superconductor by overdoping of potassium

Phase-pure polycrystalline Ba0.6K0.4+xFe2As2 with 0≤x≤0.1 were prepared using a one-step solid-state reaction method. We found that overdoping of potassium can improve the critical current density (Jc). High-field Jc for samples with x=0.1 is three times higher than that for samples with x=0. Overdoping of K has minimal effect on the critical transition temperature (Tc). Less than 0.5 K degradations in Tc was measured for samples with x=0.1. Transmission electron microscopy (TEM) revealed high concentration of dislocations in samples with x=0.1, resulting in enhanced flux pining. Further analyses on magnetization loops for powder samples confirm that K overdoping can promote intragrain Jc. Our results indicate that slight excess of K in Ba0.6K0.4Fe2As2 superconductor is beneficial to high-field applications.

One-step synthesis and structural quantitative analysis of La 2/3Sr 1/3MnO 3/La 1.4Sr 1.6Mn 2O 7 composites

La 2/3Sr 1/3MnO 3/La 1.4Sr 1.6Mn 2O 7 composites with arbitrary weight percentage were prepared using a one-step solid-state reaction method. The experimental results demonstrated that addition of K 2CO 3 during preparation favored the formation of the composites even though the K + ions were volatilized under the high temperatures of sintering. Full quantitative analysis with the Rietveld method showed that the content of La 1.4Sr 1.6Mn 2O 7 phase decreased and the fraction of the La 2/3Sr 1/3MnO 3 phase increased as the amount of K 2CO 3 was increased.

Low-temperature synthesis of SmO0.8F0.2FeAs superconductor with Tc = 56.1 K

We report a systematic study on the effect of sintering temperatureon the structural and superconducting properties of nominalSmO0.8F0.2FeAs fabricated by a simple one-step solid state reaction method. A detailed correlationbetween the sintering temperature, structure, onset transition temperature (Tc) and criticalcurrent density (Jc) has been found in all samples of each batch. Most importantly,samples sintered at a low temperature clearly show highTc, for example theTc of the samplessintered at 850 °C is even above 53 K, and the samples prepared at1000 °C display thehighest Tc of 56.1 K reported so far. Furthermore, the samples sintered at1000 °C also show the highestRRR and the lowest ρ(57 K), indicating the low impurity scattering and enhanced carrier density. However, the maximumJc of10 510 A cm − 2 at 5 K in the self-field was achieved in the samples sintered at1100 °C. Thedependence of Tc on the a-axis lattice constant indicates that the sintering temperature has a strong influence on theeffective substitution level of F for O. This result suggests that annealing at a temperature of ∼ 1000 °C seems much better for obtaining high quality 1111 phaseoxypnictides, compared to the commonly used temperatures of around1200 °C.

Preparation and characterization of LiTi2O4 anode material synthesized by one-step solid-state reaction

LiTi2O4 anode material for lithium-ion battery has been prepared by a novel one-step solid-state reaction method using Li2CO3, TiO2, and carbon black as raw materials. X-ray diffraction, scanning electron microscopy, energy-dispersive spectrometry, and the determination of electrochemical properties show that the single phase of LiTi2O4 with spinel crystal structure is formed at 850 °C by this new method, and the lattice parameter is about 8.392 A. The primary particle size of the LiTi2O4 powder is about 0.5–1.0 μm and its morphology is similar to a sphere. The lithium ion insertion voltage of LiTi2O4 anode material is about 1.50 V versus lithium metal, the initial discharge capacity is about 133.6 mAh g-1, the charge–discharge voltage plateau is very flat, and no solid electrolyte interface film is formed when working potential is more than 1.0 V. The reaction reversibility and the cycling stability are excellent, and the high rate performance is good.

Superconductivity induced by doping Ru in SrFe 2−xRu xAs 2

Using one-step solid state reaction method, we have successfully synthesized the superconductor SrFe 1− x Ru x As. X-ray diffraction indicates that the material has formed the ThCr 2Si 2-type structure with a space group I4/mmm. The systematic evolution of the lattice constants demonstrates that the Fe ions are successfully replaced by the Ru. By increasing the doping content of Ru, the spin-density-wave (SDW) transition in the parent compound is suppressed and superconductivity emerges. The maximum superconducting transition temperature is found at 13.5 K with the doping level of x = 0.7. The temperature dependence of DC magnetization confirms superconducting transitions at around 12 K. Our results indicate that similar to non-isoelectronic substitution, isoelectronic substitution contributes to changes in both the carrier concentration and internal pressure, and superconductivity could be induced by isoelectronic substitution.

One-step Synthesis of LiVPO4F/C Cathode Material with High Performance

Abstract LiVPO4F/C cathode material was synthesized by a novel one-step solid-state reaction method using humic acid as both reduction agent and carbon sources. The SEM image showed that the particles merged with each other to form a porous structure. Electrochemical test showed that the initial discharge capacity of LiVPO4F/C powder was 139 mA h g−1 and the capacity was 132 mA h g−1 after 30 cycles.

A simple molten salt method to synthesize single-crystalline potassium titanate nanobelts

Single-crystalline K 2Ti 6O 13 nanobelts with 100–300 nm in diameter and 10–50 μm in length have been synthesized via a facile and simple one-step solid-state chemical reaction method. The K 2Ti 6O 13 nanobelts were characterized by a range of methods including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Energy dispersive X-ray spectroscopy (EDS), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). Furthermore, the effects of the reaction temperature, the reaction time, and the weight ratio of reactants on the ultimate products are discussed.

Large-scale synthesis of single-crystal alpha manganese sesquioxide nanowires via solid-state reaction

Smooth single-crystal α-Mn 2O 3 nanowires have been fabricated using a one-step solid-state reaction method. X-ray diffraction patterns show that the nanowires have pure phase of α-Mn 2O 3. Transmission electron microscopy was employed to investigate the size and morphology of the products. The α-Mn 2O 3 nanowires exhibit mean diameter of 50 nm and length of 10 μm. Selected-area electron diffraction pattern demonstrates the single-crystal structure of the α-Mn 2O 3 nanowires, which are in good agreement with the X-ray diffraction results. The processes of the reactions and the phase transitions were also studied by using a simultaneous thermal gravimetric/differential thermal analyzer. It is found that the concentration of the precursor MnCO 3 is a crucial factor in the formation of the nanowires. This work provides the probability of the industrialization of fabricating smooth single-crystal α-Mn 2O 3 nanowires.

Preparation and characterization of nanosized Zn–Co spinel oxide by solid state reaction method

ZnCo2(C2O4)3·6H2O nanocrystal was prepared by a one-step solid state reaction method at room temperature under ambient conditions using oxalic acid as a chelating agent. Adding oxalic acid to the mixture of zinc acetate dihydrate and cobalt acetate tetrahydrate, grinding and subsequently calcining the precursor at different temperatures, the pink precursor was attained. Thermogravimetric analysis and differential scanning calorimetry have been used to study the thermal behaviors of the precursor, which reveal that the precursor is a compound. Powder X-ray diffraction data show that the sample obtained by heating the precursor between 350 °C and 550 °C for 3 h is a single-phase cubic material having the spinel-type structure, which can be confirmed by infrared spectra. Transmission electron microscopy images show that the grain size of the precursor and the products are about 50 nm and 20 nm, respectively.

Preparation and kinetics of the thermal decomposition of nanosized CuC2O4−ZnC2O4·2H2O

The physical mixture of nanosized CuC2O4−ZnC2O4·2H2O, as precursors of CuO−ZnO, have been prepared by the one-step solid state reaction method at room temperature. The thermal decomposition processes taking place in the solid state oxalate mixture of nanometer CuC2O4−ZnC2O4·2H2O have been studied in static air using TG, DSC, XRD and TEM techniques. TEM showed that the grain size of the decomposition product is 5–15 nm. The values of the activation energyEα were determined using the isoconversional procedure of KAS method and the Ozawa method. The most possible mechanism functionf(α) of the thermal decompositions of nanosized CuC2O4−ZnC2O4·2H2O are defined using the comparative method, function models of the decomposition of CuC2O4 and ZnC2O4 follow the same mechanism function “Avrami-Erofeev equation”. The pre-exponential factorA is obtained on the basis ofEα andf(α), thus the thermal analysis kinetic triplet of the decompositions of nanosized CuC2O4−ZnC2O4·2H2O are determined.

Preparation and Characterization of CuO Nanocrystals

Monoclinic CuO nanoparticles were prepared by using a one-step solid state reaction method under ambient conditions. The CuO particles with an average size of 12 nm were pressed into pellets under high pressure. They were studied by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy. The CuO grains in pellets grow with time at room temperature. The gradual increase in the grain size with time is clearly reflected in their Raman spectra and the XRD results. The correlation between the Raman spectra and the crystal dimension is discussed.