Synthesis Temperature Research Articles

Colloidal Synthesis of (PbBr2)2(AMTP)2PbBr4 a Periodic Perovskite "Heterostructured" Nanocrystal.

Heterostructures in nanoparticles challenge our common understanding of interfaces due to quantum confinement and size effects, giving rise to synergistic properties. An alternating heterostructure in which multiple and reoccurring interfaces appear in a single nanocrystal is hypothesized to accentuate such properties. We present a colloidal synthesis for perovskite layered heterostructure nanoparticles with a (PbBr2)2(AMTP)2PbBr4 composition. By varying the synthetic parameters, such as synthesis temperature, solvent, and selection of precursors, we control particle size, shape, and product priority. The structures are validated by X-ray and electron diffraction techniques. The heterostructure nanoparticles' main optical feature is a broad emission peak, showing the same range of wavelengths compared to the bulk sample.

The Chemistry of Spinel Ferrite Nanoparticle Nucleation, Crystallization, and Growth.

The nucleation, crystallization, and growth mechanisms of MnFe2O4, CoFe2O4, NiFe2O4, and ZnFe2O4 nanocrystallites prepared from coprecipitated transition metal (TM) hydroxide precursors treated at sub-, near-, and supercritical hydrothermal conditions have been studied by in situ X-ray total scattering (TS) with pair distribution function (PDF) analysis, and in situ synchrotron powder X-ray diffraction (PXRD) with Rietveld analysis. The in situ TS experiments were carried out on 0.6 M TM hydroxide precursors prepared from aqueous metal chloride solutions using 24.5% NH4OH as the precipitating base. The PDF analysis reveals equivalent nucleation processes for the four spinel ferrite compounds under the studied hydrothermal conditions, where the TMs form edge-sharing octahedrally coordinated hydroxide units (monomers/dimers and in some cases trimers) in the aqueous precursor, which upon hydrothermal treatment nucleate through linking by tetrahedrally coordinated TMs. The in situ PXRD experiments were carried out on 1.2 M TM hydroxide precursors prepared from aqueous metal nitrate solutions using 16 M NaOH as the precipitating base. The crystallization and growth of the nanocrystallites were found to progress via different processes depending on the specific TMs and synthesis temperatures. The PXRD data show that MnFe2O4 and CoFe2O4 nanocrystallites rapidly grow (typically <1 min) to equilibrium sizes of 20-25 nm and 10-12 nm, respectively, regardless of applied temperature in the 170-420 °C range, indicating limited possibility of targeted size control. However, varying the reaction time (0-30 min) and temperature (150-400 °C) allows different sizes to be obtained for NiFe2O4 (3-30 nm) and ZnFe2O4 (3-12 nm) nanocrystallites. The mechanisms controlling the crystallization and growth (nucleation, growth by diffusion, Ostwald ripening, etc.) were examined by qualitative analysis of the evolution in refined scale factor (proportional to extent of crystallization) and mean crystallite volume (proportional to extent of growth). Interestingly, lower kinetic barriers are observed for the formation of the mixed spinels (MnFe2O4 and CoFe2O4) compared to the inverse (NiFe2O4) and normal (ZnFe2O4) spinel structured compounds, suggesting that the energy barrier for formation may be lowered when the TMs have no site preference.

A competitive trivalent-europium-activated phosphor: Achieving highly efficient red light emission in a sodium-rich garnet host

The reaction temperature is key factor for light-emitting phosphors synthesized by solid state method because it directly determines the crystallinity and further affects the luminescence property of the phosphors. While high temperature certainly benefits to the solid diffusion in reaction, it would waste enormous energy during long time heating. Herein, a novel Eu3+-activated and highly efficient red phosphor, NaGd2Ga3Ge2O12:Eu3+, is reported. By the reconstruction of the traditional Y3Al5O12 garnet host into the sodium-rich NaGd2Ga3Ge2O12 one, huge decrease of the synthesis temperature is successfully achieved. More importantly, such decrease of the synthesis temperature does not dissatisfy the luminescence property of the NaGd2Ga3Ge2O12:Eu3+ phosphors. Instead, the Eu3+ in the NaGd2Ga3Ge2O12 exhibits extremely high quantum yield up to 96.78% upon 394 nm excitation, showing great competitiveness among other iso-structral garnet hosts. This work indicates that the introduction of sodium in the eight-coordinated rare earth site of the garnet host can not only reduce the energy consumption during the stage of phosphor synthesis but also avoid the loss of excitation energy during the light converting stage of the Eu3+ to a large extent. By fabricating the as-synthesized red phosphor into a near-UV chip together with commercial green and blue phosphors, quality white light-emitting diodes with satisfactory color rendering index (as high as 90) and correlated color temperature (as low as 3986 K) can be easily obtained.

Iron Ascorbate Threonine (II) as a New Chelated Form of Essential Iron for Food Fortification

Microelements are an extremely important part of the diet of any living organism. However, in order to achieve its maximum digestibility, a man has to search for new nutrient forms. Microelements in the chelated complexes composition keep greater digestibility compared to such popular forms as inorganic and organic, therefore, the development of new chelated microelement forms is relevant. The research aimed at developing and studying a biologically active chelate complex of the essential microelement iron with ascorbic acid and the essential amino acid L-threonine (iron ascorbate threonine (II)). The thesis presents a method for obtaining the complex, its stability study, IR spectroscopy of the resulting compound and the antioxidant activity research of milk enriched with iron ascorbate threonine (II) complex. The stability study of the developed complex demonstrated that the developed complex was stable in neutral and acidic environments, unstable in an alcaline environment. The authors revealed that an increase in the mixing time and synthesis temperature led to the iron ascorbate (II) destruction; the complex formation was due to chelating iron through the carboxyl group and the α-amino group of L-threonine and hydroxyl groups attached to the C2 and C3 atoms of ascorbic acid. The final stage of the study concerns the antioxidant activity of milk enriched with a complex of the essential microelement iron with ascorbic acid and the essential amino acid L-threonine. A man found that the developed complex exhibited antioxidant activity at the level of 40 % of the trolox activity; determined that the antioxidant milk activity increased by 42.8 % relative to the control milk sample. The results obtained enables to conclude that the iron ascorbate threonine (II) complex demonstrates antioxidant activity and can be used for the functional food products development.

Исследование зависимости физико-химических свойств флуоресцентных гибридных полимерных носителей от условий гидротермального синтеза

Currently, the search for new types of carriers for low-molecular weight substances, as well as the development of optimal methods for the effective encapsulation of these substances are important tasks of modern chemistry and pharmacology. However, there are still limitations in this area, among which one of the most significant is the lack of the optimal carrier capable of stably retaining a low-molecular weight substance. The work presents hybrid polymer structures obtained by in situ hydrothermal synthesis as an effective candidate for these purposes. The fluorescent dye rhodamine B has been used as a model low-molecular weight substance for encapsulation into the structures. The resulting hybrid polymer structures demonstrated good stability when stored in an aqueous environment for 336 h with the release of the low-molecular weight dye rhodamine B no more than 2%. In addition, the influence of the conditions for obtaining hybrid carriers (including the composition of the carriers (thickness of the polymer shell and the presence of a calcium carbonate core) and synthesis temperature) on their physical-chemical characteristics has been studied. Thus, the optimal approach for obtaining fluorescent hybrid polymer carriers with a set of desired properties has been revealed. In particular, it has been shown that the optimal production conditions are hydrothermal synthesis temperature of 180 °C and the absence of CaCO 3 core inside the polyelectrolyte shell which allow us to obtain a stable hybrid polymer carrier with bright fluorescence. The results presented in this study can be used to create functional platforms and systems with tunable fluorescent properties and the ability to deliver low-molecular weight substances.

Efficient degradation of naproxen in wastewater using Ag-deposited ZnO nanoparticles anchored on a house-of-cards-like MFI-type zeolite: Preparation and physicochemical evaluations of the photocatalyst

We utilized Pr6-diquat-5 as an organic structure-directing agent (OSDA) to synthesize hierarchically intergrown ZSM-5 (HI-ZSM-5) as a catalytic support. ZnO particles were deposited onto HI-ZSM-5 via precipitation to remediate naproxen (NPX) in wastewater, while Ag was photo-deposited onto ZnO to prevent electron-hole pair recombination. XRD analysis revealed crystalline structures and particle sizes influenced by synthesis temperatures, and FT-IR confirmed ZnO and Ag deposition onto HI-ZSM-5 surfaces. Based on N2 adsorption-desorption isotherms, all samples exhibited Type I and IV isotherms with H4-type hysteresis loops, indicating the presence of both micro- and mesopores within HI-ZSM-5. XPS analysis confirmed the presence of peaks indicating Zn in ZnO and metallic Ag interacting with ZnO. TEM analysis identified aggregated Ag/ZnO nanoparticles in the photocatalysts, while EDX confirmed uniform element distribution. FE-SEM images revealed a uniform distribution of ZnO and Ag on HI-ZSM-5 with “house-of-cards” morphologies. PL analysis indicated reduced electron-hole recombination and an extended lifespan. NPX photodegradation experimental results showed that the reaction rate constant of the 3 %AZ composite was 2.8 times higher than that of ZnO/HI-ZSM-5 (0.0163 vs. 0.059 min−1, respectively). Evaluation of influential operating parameters demonstrated 90.8 % elimination of NPX under optimum conditions: a catalyst dosage of 1.5 g L−1 at pH 5 within 120 min. The impact of common anions on NPX decontamination and the catalyst's capability for COD and TOC removal (up to 62.6 and 53.4 %, respectively) was also discussed. The 3 %AZ optimum catalyst could be recycled for 5 cycles with remarkable reusability, maintaining 80.1 % removal efficiency after five regeneration cycles.

Innovative syntheses of immobilized CuxO semiconductors grown on 3D prints and their photoelectrochemical activity for sulfamethoxazole degradation

Traditional copper oxide manufacturing processes require high energy consumption, high synthesis temperatures, and long process times. This study proposes an innovative additive manufacturing process to support immobilized copper oxide, offering greater design flexibility and customization. CuxO semiconductors were synthesized on 3D-printed substrates via the anodization process and evaluated for their effectiveness in degrading sulfamethoxazole (SMX). XRD analysis of the samples revealed the presence of both CuO and Cu2O crystalline phases, this mixture of oxides helps to expand the absorption range of visible light. The immobilized CuxO semiconductors exhibited band gaps ranging between 1.6 and 1.8 eV. Negative current densities and Mott-Schottky analysis confirmed the nature of the p-type semiconductor. Semiconductors grown by 3D printing demonstrated remarkable degradation capacity for the antibiotic sulfamethoxazole (SMX), achieving 60% degradation after 360 minutes under visible light. Kinetic degradation tends to be a first-order and zero-order model. TOC analysis further revealed the formation of reaction intermediates during SMX degradation, ultimately leading to the mineralization of the contaminant. Based on these results, we report, for the first time CuxO semiconductors grown on large 3D-printed substrates as promising photocatalysts for the degradation of emerging water pollutants. Based on these results, we report, for the first time, that CuxO semiconductors grown on large 3D-printed substrates are promising photocatalysts for the degradation of emerging water contaminants. Furthermore, it should be emphasized that the proposed method is faster and does not require subsequent thermal treatments for its functionalization, making it attractive for various industrial applications.

Effect of synthesis temperature on the structural morphology of a metal–organic framework and the capacitor performance of derived cobalt–nickel layered double hydroxides

Three-dimensional interconnected nickel–cobalt layered double hydroxides (NiCo-LDHs) were prepared on nickel foam by ion exchange using a cobalt-based metal–organic framework (Co-MOF) as a template at different temperatures. The effects of the Co-MOF preparation temperature on the growth, mass, morphology, and electrochemical properties of the Co-MOF and derived NiCo-LDH samples were studied. The synthesis temperature from 30 to 50 °C gradually increased the mass of the active material and the thickness of the Co-MOF sheets grown on the nickel foam. The higher the temperature is, the larger the proportion of Co3+. β-Cobalt hydroxide (β-Co(OH)2) sheets were generated above 60 °C. The morphology and mass loading pattern of the derived flocculent layer clusters of NiCo-LDH were inherited from metal-organic frameworks (MOFs). The areal capacitance of NiCo-LDH shows an inverted U-shaped curve trend with increasing temperature. The electrode material synthesized at 50 °C had a tremendous specific capacitance of 7631 mF·cm−2 at a current density of 2 mA·cm−2. The asymmetric supercapacitor assembled with the sample and active carbon (AC) achieved an energy density of 55.0 Wh·kg−1 at a power density of 800.0 W·kg−1, demonstrating the great potential of the NiCo-LDH material for energy storage. This work presents a new strategy for designing and fabricating advanced green supercapacitor materials with large power and energy densities.

Li1.3Al0.3Ti1.7(PO4)3 (LATP) solid electrolytes synthesized by microwave-assisted hydrothermal reactions for Li all-solid-state battery applications

Sub-micron LATP solid electrolytes have been prepared via a facile microwave-assisted hydrothermal method. The structure and ionic conductivity of LATP has been investigated as a function of hydrothermal synthesis temperature by powder X-ray diffraction (XRD), thermal analysis, scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). The hydrothermal synthesis temperature is pivotal in controlling the uniformity of the LATP particle size distribution and the surface morphology of the electrolyte. Optimal LATP pellets prepared from powder synthesized at 180 °C exhibit an ionic conductivity of 1.4 × 10−4 S cm−1 at 298 K, while variable temperature measurements yielded activation energy of 0.253 eV for Li diffusion. These favorable values could reflect the uniform particle size distribution, high crystallinity and a relative density as high as 97 %. The optimum electrolyte material was applied in an NCM523/LATP/Graphite pouch cell, which demonstrated a stable capacity (≥ 92.5 % at a Coulombic efficiency of ∼100 %) for >400 cycles. The results indicate that LATP synthesized by microwave-assisted hydrothermal methods performs very effectively as a solid electrolyte and is a credible candidate for all-solid-state LIBs.

Fluorescent Carbonized Polymer Dots Derived from o-phenylenediamine and its Photonic Application.

Optimizing the optoelectronic characteristics of low-dimensional carbon dots (CDs) through surface modifications and doping has proven instrumental in tailoring them for diverse applications. This study explores a facile and economical hydrothermal synthesis method for generating Carbonized Polymer Dots using o-phenylenediamine at different temperatures. The resulting materials exhibit structural and morphological variations linked to the synthesis temperature. A transition from carbon dots (CDs) embedded in reduced graphene oxide (rGO)-like sheet structures at low temperatures to the core-shell structure at the highest temperature is observed in HR-TEM, implying the formation of CPDs. X-ray photoelectron spectroscopy (XPS) corroborates these findings, showing an augmented degree of graphitization in alignment with HR-TEM results. The photoluminescence spectra of CPDs synthesized at the lowest temperature exhibit multiple emission peaks, resulting in a yellowish-orange color. Utilizing these CPDs to fabricate light-emitting diodes (LEDs) produces a vivid bright-green emission with CIE coordinates (0.378, 0.522). Moreover, the CPDs demonstrate solvatochromism across diverse solvents of varying polarity, covering the entire visible spectrum. This intriguing solvatochromic effect positions the CPDs as promising materials for polarity probing applications.

SSZ-13 membranes on novel silica carbide monoliths for efficient CO2 separation

The usage of normal alumina supports brings the uncertain and undesirable aluminum transformation to the high-silica zeolite membranes to reduce Si/Al ratio in framework. In this current study, a novel aluminum-free silica carbide (SiC) monolithic support is used for the synthesis of SSZ-13 membranes with enhanced Si/Al ratio for the first time. Moreover, this high-porosity and monolithic SiC support enables membrane to increase gas permeance and surface-to-volume ratio. High-quality SSZ-13 membranes were prepared after rational modification of synthesis parameters such as synthesis temperature and time and support material. The effects of test temperature, pressure drop, feed flow rate and humidity on separation performance of the monolithic membranes were studied. The formation mechanism of SSZ-13 membrane was also investigated. The Si/Al ratio and CO2 permeance of SSZ-13 membranes on SiC monolith were 100% and 60% higher than that of membrane on alumina monolith, respectively. This monolithic membrane had comparable separation performance but about 2.3 times higher surface-to-volume ratios to the reported tubular zeolite membranes. This solution could be suitable to prepare other high-silica and all-silica zeolite membranes.

Synthesis of BaZrS3 and BaS3 Thin Films: High and Low Temperature Approaches

Current research efforts in the field of the semiconducting chalcogenide perovskites are directed towards the fabrication of thin films and subsequently determine their performance in the photovoltaic application. These efforts are motivated by the outstanding properties of this class of materials in terms of stability, high absorption coefficient near the band edge and no significant health concerns compared to their halide counterparts. The approach followed here is to use stacked precursor layers and is adopted from other chalcogenide photovoltaic materials like the kesterites and chalcopyrites. The successful synthesis of BaZrS3 from stacked layers of BaS and Zr and annealing at high temperatures (~1100 °C) with the addition of elemental sulfur is demonstrated. However, the film shows the presence of secondary phases and a flawed surface. As an alternative to this, BaS3 could be used as precursor due to its low melting point of 554 °C. Previously, the fabrication of BaS3 films was demonstrated, but in order to utilize them in the fabrication of BaZrS3 thin films, their microstructure and processing are further improved in this work by reducing the synthesis temperature to 300 °C, resulting in a smoother surface. This work lays the groundwork for future research in the fabrication of chalcogenide perovskites utilizing stacked layers and BaS3.

Impact of tannic acid on iron oxide nanoclusters synthesized by a polyol solvothermal method

Raspberry-shaped iron oxide nanostructures (RSNs) correspond to oriented aggregated and hollow clusters of nanograins exhibiting a high saturation magnetization and a superparamagnetic behaviour. These nanostructures are promising for a wide range of applications, such as magnetic separation, catalysis, pollution control, and nanomedicine. However, for most applications, particularly nanomedecine and depollution, high colloidal stability is required, and the isoelectric point of iron oxide is around 6–7. Therefore, these nanoclusters need to be coated with a surfactant to obtain colloidal suspensions in water. Here, we have developed a one-pot polyol solvothermal synthesis process to coat these promising nanoclusters with tannic acid (TA), a natural compound with antimicrobial properties, which has been little studied with these nanoclusters. Different parameters of the synthesis were adjusted, such as the molar ratio TA:Fe, the synthesis temperature and duration. We showed that TA interferes deeply in the RSNs synthesis mechanism with the observed reduction of iron(III) to iron(II), the complexation of TA with iron, the formation of intermediate phases, as well as the growth of a parasitic iron carbonate phase and the loss of the oriented aggregation and hollowness of the iron oxide RSNs. Considering all these parameters, the optimal synthesis conditions were thus established (TA:Fe ratio = 0.010, temperature of 200°C and duration of 10.5 h), leading to RSNs with small nanograins, a rather high surface area (82 m2/g), high saturation magnetization (74 emu/g) and good colloidal stability. By combining different characterization techniques, a new synthesis mechanism was proposed different from previously established for RSNs without TA, based on strong TA-iron oxide interfaces.

Optimization of Synthesis Reaction Parameters of AgNPs Derived from Laser trilobum Plant for Foodborne Pathogens

In this study, the antimicrobial activity of silver nanoparticles (AgNPs L21, AgNPs L22) produced using aqueous extracts of the Laser trilobum harvested in 2021 and 2022 was optimized. The experimental design and optimization of antimicrobial activity were performed using the response surface method (RSM). Using RSM, independent variables, such as silver concentration, extraction time, and synthesis temperature, were optimized as a result of the inhibition zone diameter against Staphylococcus aureus, Escherichia coli, Salmonella Typhimurium, and Listeria monocytogenes. Based on the optimization results, the extraction time, silver concentration, and temperature for AgNP L21 and L22 synthesis were determined to be 60 min, 5 mM, and 25 °C, respectively. When the XRD and TEM results of the nanoparticles synthesized under optimal conditions were evaluated, it was determined that the AgNPs were spherical in shape and had an average size of 30 ± 12 nm. Our study revealed that the year of harvest is unimportant for nanoparticles synthesized from L. trilobum, using a cheap and simple method that does not require toxic substances. Owing to the antimicrobial activity of nanoparticles produced under optimal conditions, it is possible to biocontrol and prevent contamination by these bacteria in food science and industry.

Waste oxy-fuel combustion integrated with supercritical CO2 cycle and high-temperature electrolysis technologies for e-methanol production: A feasibility analysis

The municipal solid waste (MSW) oxy-fuel incineration power plant based on the supercritical carbon dioxide (sCO2) cycle integrated with high-temperature electrolysis technology has been developed with the aim of compensating the energy penalties of air separation unit (ASU), reducing the carbon emission and producing renewable methanol by CO2 hydrogenation process. Results shows that the suitable excess oxygen ratio, flue gas circulation ratio and methanol synthesis temperature are 1.1, 0.74 and 240 °C, respectively. The thermal efficiency of proposed system reaches 74.83%, above the that of traditional MSW incineration power plant. In addition, environmental analysis shows that the carbon retention index (CRI) is 97.76%, and the goal of near zero carbon emission can be achieved. Economic analysis demonstrates that the levelized cost of methanol (LCOM) of proposed system is 728.40 $/t, which is more than double the current market price of methanol. However, with the technological breakthrough and expansion of market scale in the further, e-methanol shows economic competitiveness when the cost of water electrolysis unit is reduced to 40 M$/250 MW and carbon emission credit is higher than 70 $/t. This work is innovative, and provides a high-efficiency and sustainable MSW disposal and energy recovering scheme for e-methanol production.

Synthesis of nano- and ultra-fine refractory carbide powders by low-temperature calcium-carbothermic process and their grain growth during sintering

Metal carbides are widely used in various applications as catalysts, components of composite materials, cutting tools, and abrasive materials where the particle/grain size has a great impact on target properties. Here, we report a facile way to synthesize nano- and ultra-fine carbides of IVb-Vb groups, including high-entropy carbides, which are of interest nowadays due to their superior properties, by the combination of calcium-hydride reduction of metal oxides and the direct reaction of the reduced metals with carbon in one production step. By tailoring the synthesis parameters, it is possible to obtain the carbide powders of a size in the range of 50–1500 nm with high crystallinity. The average particle size is found to be dependent on the homologous synthesis temperature and follows a power law. We have also shown the possibility of obtaining ultrafine-grained bulk carbides (d = 0.24–0.9 μm) via spark-plasma sintering at a temperature of 1500–1650 °C with a relative density >95 % without using additives. The HEC (Ti,Zr,Nb,Hf,Ta)C has a higher activation energy of grain growth (collective recrystallization) compared to binary TaCx (x = 0.8 and 1), which confirms the effect of lattice distortion on diffusion coefficients. The suggested fabrication route can be widely used for nano and ultrafine carbide powder preparation on the industrial scale.

Easy synthesis of Au nanoparticles at low temperature using Saponin quillaja sp. and its photocatalytic activity

With Saponin quillaja sp usage as a reducing and stabilizing agent, it was possible to obtain Gold Nanoparticles (AuNPs) at low temperature in short reaction times. The nanoparticles obtained have different sizes and are a function of the synthesis temperature, presenting by Uv–vis spectrocopy the characteristic band at 540 nm of the surface plasmon of the Au nanoparticles. By electron diffraction it was determined that the phase they show is cubic centered on the face, in addition, the AuNps, when impregnated with TiO2, show a strong photocatalytic activity for the reduction of CO2 to other products.

Epitaxial Growth of Large-Scale 2D CrTe2 Films on Amorphous Silicon Wafers With Low Thermal Budget.

2D van der Waals (vdW) magnets open landmark horizons in the development of innovative spintronic device architectures. However, their fabrication with large scale poses challenges due to high synthesis temperatures (>500 °C) and difficulties in integrating them with standard complementary metal-oxide semiconductor (CMOS) technology on amorphous substrates such as silicon oxide (SiO2) and silicon nitride (SiNx). Here, a seeded growth technique for crystallizing CrTe2 films on amorphous SiNx/Si and SiO2/Si substrates with a low thermal budget is presented. This fabrication process optimizes large-scale, granular atomic layers on amorphous substrates, yielding a substantial coercivity of 11.5 kilo-oersted, attributed to weak intergranular exchange coupling. Field-driven Néel-type stripe domain dynamics explain the amplified coercivity. Moreover, the granular CrTe2 devices on Si wafers display significantly enhanced magnetoresistance, more than doubling that of single-crystalline counterparts. Current-assisted magnetization switching, enabled by a substantial spin-orbit torque with a large spin Hall angle (85) and spin Hall conductivity (1.02 × 107 ℏ/2e Ω⁻¹ m⁻¹), is also demonstrated. These observations underscore the proficiency in manipulating crystallinity within integrated 2D magnetic films on Si wafers, paving the way for large-scale batch manufacturing of practical magnetoelectronic and spintronic devices, heralding a new era of technological innovation.

One-step molten salt synthesis of high entropy oxides

High-entropy oxides (HEOs) have received widespread attention owing to their tunable properties and vast composition spaces. However, the universal synthesis of HEOs with high purity still faces challenge. In this work, a one-step molten salt method is reported for the synthesis of phase-pure rock salt-type (Mg0.2Co0.2Ni0.2Cu0.2Zn0.2)O. When used as an anode material for lithium-ion batteries, (Mg0.2Co0.2Ni0.2Cu0.2Zn0.2)O exhibits high specific capacity and cycling stability, maintaining a capacity retention of 94% after 220 cycles (0.2 A g−1). The superior performance can be attributed to accelerated electron and ion transport as well as enhanced Li adsorption/coupling induced by internal defects. To further demonstrate the wide applicability of the molten salt method, single-phase spinel and pyrochlore HEOs are also successfully synthesized. The presented molten salt method, with its ease of operation, homogeneous reaction environment and low synthesis temperatures, makes it an ideal synthesis technique for the development of novel HEO powders, especially for electrode materials.

Preparation of Si3N4 powder by carbothermal reduction and nitridation of glucose and water glass

Herein, Si3N4 powders were successfully synthesized via carbothermal reduction nitridation of glucose and water glass as starting materials. The effects of synthesis temperature, glucose-to-water glass molar ratio, and Si3N4 seeding on the production were investigated. The results show that the reduction rate of silica increases with increasing temperature. The highest Si3N4 yield of 98.5 % was observed at 1450 °C after 400 min. The conversion of amorphous silica to Si3N4 was increased when the molar ratio of glucose/water glass was from 3.6 to 9.0 and is slightly affected when this ratio is greater than 9.0. Moreover, the maximum nitrogen content (N wt%) was 39.1 % when Si3N4/water glass molar ratio was 0.05. In the early stage of the reduction process, SiO2 is mainly reduced to SiC which is then converted to Si3N4.