High Temperature Mixing Method Research Articles

Interfacial Engineering of MoS2/V2O3@C-rGO Composites with Pseudocapacitance-Enhanced Li/Na-Ion Storage Kinetics.

Molybdenum sulfide has been widely investigated as a prospective anode material for Li+/Na+ storage because of its unique layered structure and high theoretical capacity. However, the enormous volume variation and poor conductivity limit the development of molybdenum sulfide. The rational design of a heterogeneous interface is of great importance to improve the structure stability and electrical conductivity of electrode materials. Herein, a high-temperature mixing method is implemented in the hydrothermal process to synthesize the hybrid structure of MoS2/V2O3@carbon-graphene (MoS2/V2O3@C-rGO). The MoS2/V2O3@C-rGO composites exhibit superior Li+/Na+ storage performance due to the construction of the interface between the MoS2 and V2O3 components and the introduction of carbon materials, delivering a prominent reversible capacity of 564 mAh g-1 at 1 A g-1 after 600 cycles for lithium-ion batteries and 376.3 mAh g-1 at 1 A g-1 after 450 cycles for sodium-ion batteries. Theoretical calculations confirm that the construction of the interface between the MoS2 and V2O3 components can accelerate the reaction kinetics and enhance the charge-ionic transport of molybdenum sulfide. The results illustrate that interfacial engineering may be an effective guide to obtain high-performance electrode materials for Li+/Na+ storage.

Heterogeneous interface-boosted zinc storage of H2V3O8 nanowire/Ti3C2Tx MXene composite toward high-rate and long cycle lifespan aqueous zinc-ion batteries

In this study, H2V3O8/MXene composites as cathode for zinc-ion batteries (ZIBs) were synthesized via one-step high-temperature mixing hydrothermal method. H2V3O8 nanowires with high active sites and Ti3C2Tx MXene with high conductivity promoted efficient Zn2+ storage of H2V3O8/MXene electrode. For zinc storage, the H2V3O8/MXene electrode obtained excellent overall performance with high discharge specific capacity (437.3 mAh g−1 after 500 cycles at 3 A g−1), superior fast charge/discharge ability (highest capacity with 420 mAh g−1 at 10 A g−1), and impressive long-term lifespan (323 mAh g−1 over 9000 cycles at 10 A g−1). The combination of 2D MXene nanosheets and H2V3O8 has the synergistic effect of improving electrical conductivity, enhancing pseudocapacitance and alleviating the volume change of H2V3O8 during insertion/deinsertion process, resulting in high rate and long cycle stability electrochemical performance. Density functional theory calculations further reveal that the interfacial electric field within the H2V3O8-MXene interface leads to the exceptional zinc ion diffusion kinetic and superior zinc storage capacity, thereby achieving outstanding electrochemical activity. This work reveals the effect of the interfacial interaction between the highly conductive 2D MXene material and H2V3O8 on the performance of ZIBs, providing a suitable strategy for efficient energy storage of zinc.

Synthesis of heterostructured dual metal sulfides by a high-temperature mixing hydrothermal method as an ultra-high rate anode for Li-ion batteries

A novel approach is reported to fabricate flower-like Cu2S/MoS2/rGO by using a high-temperature mixing hydrothermal method. The synthesized Cu2S/MoS2/rGO composite shows excellent rate capability and long cycling durability.

Ultrathin Nanoribbons of in Situ Carbon-Coated V3O7·H2O for High-Energy and Long-Life Li-Ion Batteries: Synthesis, Electrochemical Performance, and Charge–Discharge Behavior

The ever-growing demands of Li-ion batteries (LIBs) for high-energy and long-life applications, such as electrical vehicles, have prompted great research interest. Herein, by applying an interesting one-step high-temperature mixing method under hydrothermal conditions, ultrathin V3O7·H2O@C nanoribbons with good crystallinity and robust configuration are in situ synthesized as promising cathode materials of high-energy, high-power, and long-life LIBs. Their capacity is up to 319 mA h/g at a current density of 100 mA/g. Moreover, the capacity of 262 mA h/g can be delivered at 500 mA/g, and 94% of capacity can be retained after 100 cycles. Even at a large current density of 3000 mA/g, they can still deliver a high capacity of 165 mA h/g, and 119% of the initial capacity can be kept after 600 cycles. Importantly, their energy density is up to 800 Wh/kg, which is 48-60% higher than those of conventional cathode materials (such as LiCoO2, LiMn2O4, and LiFePO4), and they can maintain an energy density of 355 Wh/kg at a high power density of 8000 W/kg. Furthermore, based on ex situ X-ray diffraction and X-ray photoelectron spectroscopy technology, their exact charge-discharge behavior is reasonably described for the first time. Excitingly, it is found for the first time that the as-synthesized V3O7·H2O@C nanoribbons are also great promising cathode materials for Na-ion batteries.

Elucidating the effects of high temperature mixing method under hydrothermal condition (HTMM) on grain refinements and assembling structures

Crystal size and microstructure are of great importance in determining the physical and chemical properties of functional materials, and refine powders, especially their assembled porous structures have potential application in ceramic fabrication, absorption, catalysts and drug delivery, due to their characters of high activity and large specific surface area. Herein, high temperature mixing method under hydrothermal condition (HTMM) was adapted to synthesize barium strontium titanate [(Ba, Sr)TiO3, BST] powders with various Ba/Sr ratios (x=0.5, 1.0, 3.0 and 4.0). In comparison with conventional hydrothermal synthesis (CHS), the effects of HTMM on grain refinement and porous structure formation were exclusively investigated. XRD and SEM results indicated that, in the given condition, BST powders prepared by HTMM were much smaller than that by CHS, especially at a lower Ba/Sr ratio. Additionally, assembled porous architectures were constructed by HTMM. It's believed that the high temperature mixing process and continuous rotation contributed to the grain refinement and assembled porous structure, respectively. The assumption was further confirmed through the synthesis of sodium niobate (NaNbO3) powders by HTMM. It's demonstrated that HTMM is advantageous in preparation of refine powders and porous assembled architectures.

A general and simple method to synthesize well-crystallized nanostructured vanadium oxides for high performance Li-ion batteries

A general and remarkably simple high-temperature mixing method was applied to synthesize three kinds of vanadium oxides with high electrochemical performances.

Fabrication of BaTiO3 nanoparticles and its formation mechanism using the high temperature mixing method under hydrothermal conditions

Barium titanate (BaTiO3) single-crystalline nanoparticles have been prepared via high temperature mixing method (HTMM) under hydrothermal conditions. The crystallized products were characterized by X-ray diffraction (XRD), filed emission scanning electron microscopy (FESEM), X-ray fluorescence (XRF), Raman spectra, transmission electron microscopy (TEM). The BaTiO3 nanoparticles can be prepared at dilute KOH as compared with the method mixed at room temperature. The results show that the stoichiometric BaTiO3 nanoparticles were synthesized at [Ba/Ti]solution=1. The high temperature will significantly narrow the solubility difference between the barium and titanium sources and leads to a burst nucleation from the solution. The defect mechanism is used to illustrate the time-dependent transformation from cubic to tetragonal phase.

Synthesis and Characterization of K(Ta<SUB><I>x</I></SUB>Nb<SUB>1−<I>x</I></SUB>)O<SUB>3</SUB> Particles by High Temperature Mixing Method Under Hydrothermal and Solvothermal Conditions

KTa(x)Nb(1_x)O3 (KTN) particles with an orthorhombic perovskite structure were synthesized via a high temperature mixing method (HTMM) under hydrothermal and solvothermal conditions. The obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high-resolution transmission electron microcopy (HRTEM). The influences of alkaline concentration and Ta doping amounts on the phase structure and morphology of the obtained powders were investigated. The results showed that KTN powders could be solvothermally prepared when the KOH concentration is as low as 0.5 M. In comparison with the hydrothermal process, supercritical isopropanol plays an important role in synthesizing KTN particles under milder conditions. The KTa(0.4)Nb(0.6)O3 particles solvothermally synthesized in isopropanol are made of well crystallized and single crystalline particles with a size of about 100-200 nm. Room temperature PL studies excited at different wavelengths reveal five emission bands centered at about 421 nm, 446 nm, 468 nm, 488 nm, and 498 nm, respectively. The supercritical process proposed here provides a new potential route for synthesizing other perovskite-type materials.

Ultra-long VO2 (A) nanorods using the high-temperature mixing method under hydrothermal conditions: synthesis, evolution and thermochromic properties

Well-crystallized, ultra-long VO2 (A) nanorods were synthesized using a facile high-temperature mixing method (HTMM) under hydrothermal conditions. The as-obtained products were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-Vis-NIR, differential scanning calorimetry and Fourier transform infrared spectroscopy. The effect of W doping on the phase-transition properties of VO2 (A) was also studied. The results indicate that the optimal synthesis condition of VO2 (A) using the HTMM is hydrothermal treatment at 240 °C for 48 h with a 3 : 1 molar ratio of the reducing agent to the vanadium source. The reason why the polymorphic forms of VO2 show different colors is that the light in the visible region reflected by the samples is different. The phase-transition temperature of the pure VO2 (A) is 154.75 °C, which is significantly lower than the 162 °C reported previously. When a small amount of W is doped, VO2 (A) will be transformed into other polymorphic forms, which indicates that the crystal structure of VO2 (A) is highly sensitive to limited doping. Importantly, the as-obtained pure VO2 (A) shows good thermochromic properties and optical-switching characters. A crystal growth mechanism for VO2 (A), oriented-attachment–exfoliation–recrystallization–oriented-attachment, is proposed and described in detail.

Synthesis of (K, Na) (Nb, Ta)O3 lead-free piezoelectric ceramic powders by high temperature mixing method under hydrothermal conditions

A facile hydrothermal route via high temperature mixing method was used to synthesize (K, Na) (Nb, Ta)O3 lead-free piezoelectric ceramic powders. The influence of Ta doping and K+/(K++Na+) molar ratios in the starting solution on the resultant powders were investigated by X-ray diffraction, scanning electron microscope, transmission electron microscopy, and selected area electron diffraction. The Ta element was successfully doped into the alkaline niobate structure to form crystalline (K, Na) (Nb, Ta)O3 lead-free piezoelectric ceramics powder. The microstructure, piezoelectric, ferroelectric, and dielectric properties of the sintered (K, Na) (Nb, Ta)O3 ceramics from the obtained powders were investigated. The piezoelectric coefficient (d33), electromechanical coupling coefficient (kp), dielectric constant (ɛr), and remnant polarization (Pr) of the sample sintered at 1180°C show optimal values of 210pC/N, 34.0%, 2302, and 19.01μC/cm2, respectively.

Characterization and synthesis of KTa0.1Nb0.9O3 particles via high temperature mixing method under hydrothermal conditions

KTa0.1Nb0.9O3 (KTN) particles with an orthorhombic perovskite structure have been synthesized via a high temperature mixing method (HTMM) under hydrothermal conditions. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high-resolution transmission electron microcopy (HRTEM). The influence of alkaline concentration and solvent composition on the phase structure and morphology of the obtained powders was investigated. The results show that the well-crystallized KTN powders with sizes of 200–500nm are successfully prepared at temperatures as low as 240°C when the KOH concentration is 2.0M and the isopropanol/water (I/W) volume ratio equals to 100/0.

Synthesis of (K,Na)NbO3 particles by traditional hydrothermal method and high-temperature mixing method under hydrothermal–solvothermal conditions

Pure (K,Na)NbO3 (KNN) powders have been successfully prepared by using traditional hydrothermal method and high-temperature mixing method (HTMM) under solvothermal and hydrothermal conditions. The products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) to show the change of phase, morphology, and size of the as-prepared particles with the alkalinity of the starting solution. Compared with the traditional hydrothermal method, smaller particles with higher phase purity are prepared using HTMM under hydrothermal conditions. It is found that the alkalinity has significant effects on the crystal size. The KNN grain size first increases and then decreases with increasing alkalinity. Typical samples solvothermally synthesized in a mixed solvent with isopropanol/deionized water ratio of 50/50 by volume were made of well-crystallized single-crystalline nanoparticles with size of about 500 nm.

Phase evolution of (K, Na)NbO 3 powder prepared by high temperature mixing under hydrothermal conditions

(Na, K)NbO 3 (KNN) powders were successfully prepared by high temperature mixing method (HTMM) under hydrothermal conditions to study the effect of reaction time on the formation of KNN for three K +/(K + + Na +) ratios of 0.6, 0.7 and 0.8. The products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED), to show the change of phase and morphology of the as-prepared particles with the K +/(K + + Na +) molar ratio in the solution. Pure Na-rich KNN monoclinic phase and pure K-rich KNN orthorhombic phase could be obtained quickly after mixing the solutions at high temperature when the K +/(K + + Na +) molar ratio was either 0.6 or 0.8. When the K +/(K + + Na +) molar ratio was 0.7, however, the K-rich KNN orthorhombic phase grain formed first, followed by the Na-rich KNN monoclinic phase grain, with the two phases coexisting in the final product.

Crystallographic study of lead-substituted hydroxyapatite synthesized by high-temperature mixing method under hydrothermal conditions

Abstract The solid solutions in the system of Ca and Pb hydroxyapatite, Ca10−χPbχHA (χ = 0–10), were successfully synthesized by high-temperature mixing method (HTMM) at 200 °C for 12 h under hydrothermal conditions. The samples were characterized by X-ray diffraction, chemical analysis and electron microscopic observation, and the site of the metal ions in the solid solutions was analyzed with the Rietveld method. The lattice parameters of the solid solutions prepared by both of the methods didn’t vary linearly with Pb contents, and they have two turning points of 0.4 and 0.6 of Pb content. It was found that Pb ions in the solid solutions preferentially occupied the M (2) site in the apatite structure. HTMM gives Ca–Pb HA solid solutions much better crystallization. However, due to the formation of intermediate compound of Pb3O2(OH)2 in the Pb(NO3)2·4H2O solution before mixing with (NH4)2HPO4 solution at 200 °C, HTMM causes the decrease of crystallization of the samples with high Pb content.

Synthesis of (K, Na)NbO 3 particles by high temperature mixing method under hydrothermal conditions

In order to prepare the pure (K, Na)NbO 3(KNN) particles with higher crystallinity, the high temperature mixing method (HTMM) under hydrothermal conditions was carried out in this work. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM). The results indicate that the KNN particles size decrease gradually with the increase of mineralization concentration in the starting solution. The ratio of K +/(K + + Na +) in the starting solution has a great effect on the phase of the products, and several phases coexist in the product when the ratio of K +/(K + + Na +) in the starting solution is 0.7.

Synthesis and crystallographic study of Pb–Sr hydroxyapatite solid solutions by high temperature mixing method under hydrothermal conditions

The solid solutions in the system of Pb and Sr hydroxyapatite, Sr 10− x Pb x HAp ( x = 0–10), were successfully synthesized by high-temperature mixing method (HTMM) at 160 °C for 12 h under hydrothermal conditions. The samples were characterized by X-ray diffraction, chemical analysis and electron microscopic observation, and the site of the metal ions in the solid solutions was analyzed with the Rietveld method. The lattice constants, both a and c, of the solid solutions varied linearly with Pb content. It was found that Pb ions in the solid solutions preferentially occupied the M(2) site in the apatite structure. HTMM gives Sr–Pb HAp solid solutions much better crystallization. However, due to the formation of intermediate compound of Pb 3O 2(OH) 2 in the Pb(NO 3) 2·4H 2O solution before mixing with (NH 4) 2HPO 4 solution at 160 °C, HTMM causes the decrease of crystallization of the samples with high Pb content.

Morphology variation of cadmium hydroxyapatite synthesized by high temperature mixing method under hydrothermal conditions

Cadmium hydroxyapatite (Cd HAp) pure crystals were synthesized by high temperature mixing method under hydrothermal conditions using the solutions of Cd(NO3)2·4H2O and (NH4)2HPO4. The influences of pH values and reaction time on the structure and morphology of Cd HAp crystals were investigated. The results indicate that the pH value has a great influence on the morphology which varies from bulk-like to fiber with the increase of the pH value. The intermediate phase of Cd5H2(PO4)4·4H2O is formed in the weak alkali reaction medium of (NH4)2HPO4 at pH 9, and it take long time to be dissolved and changed into pure phase of bulk-like Cd HAp crystal. In the strong alkali reaction medium of (NH4)2HPO4 solution at pH 11, the intermediate phase of Cd2P2O7·5H2O is formed, and then dissolved, and rapidly changed to pure phase of Cd HAp fiber. Cd3(OH)5NO3 crystals are formed in the nitrate solution before mixing at 200°C, its influences on crystallinity, morphology and size of Cd HAp crystals were also discussed.

Hydration of β-dicalcium silicate at high temperatures under hydrothermal conditions

Hydration of β-dicalcium silicate was carried out under hydrothermal conditions at different temperatures from 50 °C to 400 °C up to 5 days by using two methods to start the reactions at room temperature or at a desired reaction temperature. 9 C-S-H phases with the same Ca/Si ratio as precursor (γ-dicalcium silicate hydrate and α-dicalcium silicate hydrate and dellaite), Ca-rich compositions (jaffeite and reinhardbraunsite), Si-rich compositions (Ca 8Si 5O 18, kilchoanite and foshagite), and C-S-H gel were obtained at the initial stage of the hydration of β-dicalcium silicate. The reaction products were different in dependence in the hydrothermal processes. It was found that α-dicalcium silicate hydrate was directly formed from β-dicalcium silicate at low temperatures below 220 °C. The products obtained at above 240 °C were different in dependence in the hydrothermal processes, due to the different decomposition route of γ-dicalcium silicate hydrate, the initial product from β-dicalcium silicate. The room temperature mixing method gave reinhardbraunsite and kilchoanite through Ca 8Si 5O 18. In the case of the high temperature mixing method, γ-dicalcium silicate hydrate decomposed to from Ca 8Si 5O 18 and reinhardbraunsite with jaffeite, then Ca 8Si 5O 18 decomposed to from jaffeite and kilchoanite, and final products at 400 °C were reinhardbraunsite and foshagite which was formed from kilchoanite.

HYDROTHERMAL SYNTHESIS AND CRYSTALLOGRAPHIC STUDY OF Ca-Sr HYDROXYAPATITE SOLID SOLUTIONS

A continuous series of solid solutions in the system of strontium and calcium hydroxyapatite, Ca10-xSrxHAP (x= 0-10), was successfully synthesized by both high-temperature mixing method (HTMM) and low-temperature mixing method (LTMM) at 200°C for 12 hours under hydrothermal conditions. The samples were characterized by chemical analysis, electron microscopic observation and X-ray powder-pattern fitting. The site of the metal ions in the solid solutions was analyzed by the Rietveld method. The lattice constants of the solid solutions prepared by both of the methods varied linearly with Sr contents. It was found that Sr2+ ions in the solid solutions prepared by these two methods preferentially occupied the Ca (II) site in the apatite structure.

Enthalpies of formation of the palladium sulphides

A high-temperature mixing calorimetry method has been used for the thermochemical study of the Pd-S system. The standard molar enthalpies of formation of the palladium sulphides were derived by measuring the heat effect associated with the formation of a low-melting (Pd+S) liquid alloy from the elements, and the effects associated with the formation of the same melt from the sulphide investigated and one of the pure constituent elements. The following values are reported for the standard enthalpies of formation for the four sulphides studied: ΔfHm°(PdS, 298.15 K)=−(78.1±11.0) kJ·mol−1; ΔfHm°(Pd16S7, 298.15 K)=−(580.1±36.2) kJ·mol−1; ΔfHm°(Pd3S, 298.15 K)=−(96.5±10.5) kJ·mol−1; ΔfHm°(Pd4S, 298.15 K)=−(99.2±11.2) kJ·mol−1.