Search Results (1,478)

Vanadium–titanium magnetite (VTM) is an iron ore abundantly available in China. The dominant utilization route is blast furnace smelting; however, Ti in the ore deteriorates sinter strength, making it urgent to clarify Fe-Ti-Ca interactions during sintering. In this work, single-phase FeTiO₃ and Fe₂TiO₄ were synthesized and each paired with CaO to fabricate diffusion couples. The couples were heated at 1200 °C for 30, 60, 90, and 120 min to investigate their interdiffusion behaviors and microstructure recombination mechanisms. The results show that, at 1200 °C, solid-state diffusion—not interfacial reaction—controls mass transfer in both FeTiO₃-CaO and Fe₂TiO₄-CaO systems. Distinct Fe-rich and Ti-rich sublayers appear within the reaction zone, and banded CaTiO₃ forms adjacent to the FeTiO₃/Fe₂TiO₄ matrices. The interdiffusion coefficients were determined to be 4.08 × 10⁻¹⁰ cm²·s⁻¹ and 7.81 × 10⁻¹⁰ cm²·s⁻¹, and the growth of the reaction layer follows a parabolic law, which can be expressed as x² = 2 × 1.562 × 10⁻⁹ t and x² = 2 × 0.8159 × 10⁻⁹ t, respectively. The coefficients of determination exceed 0.90, indicating reliable regression fits. Full article

W-type hexaferrites with compositions Ba_0.5Sr_0.5Zn_2-xMe_xFe₁₆O₂₇ (Me = Fe, Ni, Co, Cu, Mn; x = 1) and Ba_0.5Sr_0.5Zn_2−xMn_xFe₁₆O₂₇ (x = 0–2.0) were synthesized via solid-state reaction and optimized using a two-step calcination process to obtain single-phase or nearly single-phase structures. Their electromagnetic (EM) wave absorption properties were investigated by fabricating composites with 10 wt% epoxy and measuring the complex permittivity and permeability across two frequency bands: 0.1–18 GHz and 26.5–40 GHz. Reflection loss (RL) was calculated and visualized as two-dimensional (2D) maps with respect to frequency and sample thickness. In the 0.1–18 GHz range, only the Co-substituted sample exhibited strong ferromagnetic resonance (FMR) and broadband absorption, achieving a minimum RL of −41.5 dB at 4.84 GHz and a −10 dB bandwidth of 11.8 GHz. In contrast, the other Ba_0.5Sr_0.5Zn_2-xMe_xFe₁₆O₂₇ samples (Me = Fe, Mn, Ni, Cu) showed no significant absorption in this range due to the absence of FMR. However, all these samples clearly exhibited FMR characteristics and distinct absorption peaks in the 26.5–40 GHz range, particularly the Mn-substituted series, which demonstrated RL values below −10 dB over the 32.0–40 GHz range with absorber thicknesses below 1 mm. The FMR frequency varied depending on the substitution type and amount. In the Mn-substituted series, the FMR frequency was lowest at x = 1.0 and increased as x deviated from this composition. This study confirms the potential of Co-free W-type hexaferrites as efficient, cost-effective, and broadband EM wave absorbers in the 26.5–40 GHz range. Full article

The solid-state reactions between Fe₂O₃ and molecular sulfur sources could produce FeS nanoparticles efficiently, while the functions of these molecules have been ignored except for the role as sulfur sources. In this work, thioacetamide and thiourea were employed as sulfur sources for the solid-state reactions with Fe₂O₃ to explore their effects on the microstructure and electrochemical performance of the produced FeS. Despite the slight difference in one functional group for two molecules (−CH₃ against −NH₂), thiourea leads to a more complex reaction pathway with FeS₂ as the intermediate phase, while no such an intermediate phase is observed in the reaction with thioacetamide. The former yields FeS of 2D nanoflakes as the final products, compared with the aggregated nanoparticles in reactions with thiourea. As a result, the nanoflakes exhibit a higher discharge capacity with enhanced stability (388.9 mAh∙g⁻¹ vs. 374.7 mAh∙g⁻¹ above 1 V). According to the reaction pathways, the formation of FeS nanoflakes and superior electrochemical performance were addressed, paving a route for the solid-state reactions with molecules to develop high-performance sulfide electrode materials. Full article

Mechanochemical methods have received much attention in the synthesis and design of all-solid-state battery materials in recent years due to their advantages of being green, efficient, easy to operate, and solvent-free. In this review, common mechanochemical methods, including high-energy ball milling, twin-screw extrusion (TSE), and resonant acoustic mixing (RAM), are introduced with the aim of providing a fundamental understanding of the subsequent material design. Subsequently, the discussion focuses on the application of mechanochemical methods in the construction of solid-state electrolytes, anode materials, and cathode materials, especially the research progress of mechanical energy-induced polymerization strategies in building flexible composite electrolytes and enhancing interfacial stability. Through the analysis of representative work, it is demonstrated that mechanochemical methods are gradually evolving from traditional physical processing tools to functional synthesis platforms with chemical reaction capabilities. This review systematically organizes its development and research trends in the field of all-solid-state battery materials and explores potential future breakthrough directions. Full article

The 1:1 stoichiometric reactions of α-amino isobutyric acid (H₂Aib) and diaminosilanes of the type SiRR′(NR¹R²)₂ (SiMe₂(imidazol-1-yl)₂, SiMe₂(NHnPr)₂, and SiRR′(pyrrolidin-1-yl)₂ with R,R′ = Me,Me, Me,H, Me,Vi, and Et,Et) afforded the pentacoordinate silicon complexes (Aib)SiRR′(HNR¹R²) with the release of one equivalent of HNR¹R². Single-crystal X-ray diffraction analyses confirmed the coordination of the N-donor Lewis base (i.e., imidazole, n-propylamine, and pyrrolidine, respectively) in an axial position of the distorted trigonal-bipyramidal Si-coordination sphere, trans to the carboxylate O atom of the Si-chelating Aib-dianion. The N–H moieties of the adduct-forming Lewis bases are involved in N–H⋯O hydrogen bonds with carboxylate groups of adjacent complex molecules, thus supporting the supramolecular structures of these adducts. The equatorially bound NH group of the Aib-dianion is involved in N–H⋯O hydrogen bonds in most cases, and it gives rise to residual dipolar coupling of the ¹⁴N nucleus with its directly bound atoms C and Si, thus causing characteristic shapes of both the ²⁹Si and ¹³C NMR signals of these two atoms in the solid-state spectra. In contrast to the adduct-formation reactions, the analogous conversion of H₂Aib and SiMe₂(NHtBu)₂ did not afford an amine adduct. Instead, a second equivalent of H₂Aib entered the reaction, and the ionic silicon complex [tBuNH₃]⁺[(Aib)₂SiMe]⁻ was obtained and characterized by crystallography and solution NMR spectroscopy. Full article

Geometrically frustrated magnets exhibit exotic excitations due to competing interactions between spins. The spinel compound MgCr₂O₄, a three-dimensional Heisenberg antiferromagnet, hosts both spin-wave and spin-resonance modes, but the origin of its resonant excitations remains debated. Suppressing magnetic order via non-magnetic doping can help isolate these modes in neutron scattering studies. We synthesized Ga³⁺ and Cd²⁺-doped MgCr₂O₄ via solid-state reaction and analyzed their structure and magnetism. Ga³⁺ doping (0–20%) causes anomalous lattice shrinkage due to site disorder from Ga³⁺ occupying both Mg²⁺ and Cr³⁺ sites. Magnetically, Ga³⁺ doping drives the system from the antiferromagnetic order to a spin-glass state, fully suppressing magnetic ordering at 20% doping. In contrast, Cd²⁺ replaces only Mg²⁺, expanding the lattice and meantime inducing strong spin-glass behavior. At 10% Cd²⁺, long-range antiferromagnetic order is entirely suppressed. Thus, 10% Cd-doped MgCr₂O₄ offers an ideal platform to study the resonant magnetic excitations without any spin-wave interference. Full article

This study employed the solid-state method to prepare perovskite-type high-entropy oxide materials La(Co_0.2Cr_0.2Fe_0.2Mn_0.2Ni_0.2)O₃ and La(Co_0.2Cr_0.2Ni_0.2Ga_0.2Ge_0.2)O₃ with equimolar ratios at the B-site and explored the effects of sintering temperature on the phase structure and electrochemical properties of high-entropy oxide ceramics. The results show that after sintering at 1300$°\mathrm{C}$, both samples exhibit orthorhombic perovskite structures. Both have a relative density of >97%, while La(Co_0.2Cr_0.2Ni_0.2Ga_0.2Ge_0.2)O₃ has a significantly larger grain size. Using these materials as electrodes, the cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) results indicate that the working electrode made of La(Co_0.2Cr_0.2Ni_0.2Ga_0.2Ge_0.2)O₃ shows higher oxidation reaction activity in CV measurements and achieved a specific capacitance of 74.3 F/g at a current density of 1 A/g in GCD measurements, which still maintained 73% of its initial specific capacitance (54.3 F/g) when the current density was increased to 10 A/g. Its capacitance retention rate is 10 percentage points higher than that of La(Co_0.2Cr_0.2Fe_0.2Mn_0.2Ni_0.2)O₃ at high current densities, demonstrating superior rate performance. Full article

Skutterudite (CoSb₃)-based thermoelectric materials are regarded as one of the most promising candidates for mid-temperature commercial thermoelectric applications, thanks to their excellent electrical performance and alloy-based attributes. By utilizing techniques such as doping, microstructure design, and high-temperature solid-state reactions, synthesis of Brass_x/Co₄Sb_11.5Te_0.5 (x = 0.1, 0.3, 0.5, 0.7, representing wt%) in composite form can be rapidly achieved. XRD analysis indicates that the prepared Brass_x/Co₄Sb_11.5Te_0.5 samples primarily exhibit the CoSb₃ crystal structure, with the formation of minor impurity phases such as Cu₁₃Te₇ and ZnTe. SEM and EDS analyses reveal that the sample is composed of nanoscale equiaxed grains, some of which are micrometer in size, with a large number of microporous structures distributed uniformly, forming abundant grain boundaries. By co-doping with brass and tellurium (Te), the carrier concentration can be effectively regulated, thereby enhancing the power factor of CoSb₃-based thermoelectric materials. Meanwhile, the introduction of nanostructures, grain boundaries, and defects optimizes the microstructure of the samples, leading to a reduction in the lattice thermal conductivity of the CoSb₃-based thermoelectric materials. At a testing temperature of 781 K, Brass_0.1/Co₄Sb_11.5Te_0.5 achieved a maximum power factor of 1.86 mW·m⁻¹·K⁻², a minimum lattice thermal conductivity of 1.02 W/(mK), and a maximum thermoelectric figure of merit ZT of 0.81. Full article

Bacterial infections cause serious problems associated with wound treatment and serious complications, leading to serious threats to the global public. Bacterial resistance was mainly attributed to the formation of biofilms and their protective properties. Hydrogels suitable for irregular surfaces with effective antibacterial activity have attracted extensive attention as potential materials. In this study, a succinoglycan-riclin-zinc-phthalocyanine-based composite (RL-Zc) hydrogel was synthesized through an amine reaction within an hour. The hydrogel was characterized via FT-IR, SEM, and rheology analysis, exhibiting an elastic solid gel state stably. The hydrogel showed large inhibition circles on E. coli as well as S. aureus under near-infrared irradiation (NIR). RL-Zc hydrogel exhibited positively charged surfaces and possessed a superior penetrability toward bacterial biofilm. Furthermore, RL-Zc hydrogel generated abundant single oxygen and mild heat rapidly, resulting in disrupted bacterial biofilm as well as amplified antibacterial effectiveness. A metabolomics analysis confirmed that RL-Zc hydrogel induced a metabolic disorder in bacteria, which resulted from phospholipid metabolism and oxidative stress metabolism related to biofilm disruption. Hence, this study provided a potential phototherapy for biofilm-induced bacterial resistance. Full article

Facing energy and environmental issues is recognized globally as one of the major challenges for sustainable development, to which sustainable chemistry can make significant contributions. Strontium ferrate-based materials belong to a little-known class of perovskite-type compounds in which iron is primarily stabilized in the unusual 4+ oxidation state, although some Fe³⁺ is often present, depending on the synthesis and processing conditions and the type and amount of dopant. When doped with cerium at the Sr site, the SrFeO_3−δ cubic structure is stabilized, more oxygen vacancies form and the Fe⁴⁺/Fe³⁺ redox couple plays a key role in its functional properties. Alone or combined with other materials, Ce-doped strontium ferrates can be successfully applied to wastewater treatment. Specific doping at the Fe site enhances their electronic conductivity for use as electrodes in solid oxide fuel cells and electrolyzers. Their oxygen storage capacity and oxygen mobility are also exploited in chemical looping reactions. The main limitations of these materials are SrCO₃ formation, especially at the surface; their low surface area and porosity; and cation leaching at acidic pH values. However, these limitations can be partially addressed through careful selection of synthesis, processing and testing conditions. This review highlights the high versatility and efficiency of cerium-doped strontium ferrates for energy and environmental applications, both at low and high temperatures. The main literature on these compounds is reviewed to highlight the impact of their key properties and synthesis and processing parameters on their applicability as sustainable thermocatalysts, electrocatalysts, oxygen carriers and sensors. Full article

Metal–air batteries have excellent theoretical energy density and economic advantages through abundant anode materials and open cathode structures. However, the actual energy efficiency of metal–air batteries is much lower than the theoretical value due to the effect of polarization voltage during battery operation, limiting the power output and thus hindering their practical application. This review systematically dissects the origins of polarization: slow oxygen reduction/evolution reaction (ORR/OER) kinetics, interfacial resistance, and mass transfer bottlenecks. We highlight cutting-edge strategies to mitigate polarization, including atomic-level engineering of air cathodes (e.g., single-atom catalysts, low Pt catalysts), biomass-derived 3D porous electrodes, and electrolyte innovations (additives to inhibit corrosion, solid-state electrolytes to improve stability). In addition, breakthroughs in metal–H₂O₂ battery design using concentrated liquid oxygen sources are discussed. Together, these advances alleviate the battery polarization bottleneck and pave the way for practical applications of metal–air batteries in electric vehicles, drones, and deep-sea devices. Full article

The advancement of high-performance sodium-ion batteries (SIBs) necessitates cathode materials that exhibit both structural robustness and long-term electrochemical stability. Na₃V₂(PO₄)₃ (NVP), with its NASICON-type framework, is a promising candidate; however, its inherently low electronic conductivity restricts full capacity utilization. In this study, carbon-coated and Cu-substituted Na₃V₂(PO₄)₃ (NVCP) composites were synthesized via a solid-state reaction using agarose as a carbon source. Structural and morphological analyses confirmed the successful incorporation of Cu²⁺ ions into the rhombohedral lattice without disrupting the crystal structure and the formation of uniform conductive carbon layers. The substitution of Cu²⁺ induced increased carbon disorder and partial oxidation of V³⁺ to V⁴⁺, contributing to enhanced electronic conductivity. Consequently, NVCP exhibited excellent long-term cycling performance, maintaining over 99% of its initial capacity after 500 cycles at 0.5 C. Furthermore, the electrode demonstrated outstanding high-rate capabilities, with a capacity recovery of 97.98% after cycling at 20 C and returning to lower current densities. These findings demonstrate that Cu substitution combined with carbon coating synergistically enhances structural integrity and Na⁺ transport, offering an effective approach to engineer high-performance cathodes for next-generation SIBs. Full article

Bi₆Fe₂Ti₃O₁₈ (BFTO) ceramics were synthesized via a solid-state reaction route using stoichiometric amounts of Bi₂O₃, TiO₂, and Fe₂O₃ powders. A thermal analysis of the powder mixture was conducted to optimize the heat treatment parameters. Energy-dispersive X-ray spectroscopy (EDS) confirmed the conservation of the chemical composition following calcination. Final densification was achieved through hot pressing. The crystal structure of the sintered samples, examined via X-ray diffraction at room temperature, revealed a tetragonal symmetry for BFTO ceramics sintered at 850 °C. Electron backscatter diffraction (EBSD) provided detailed insight into the crystallographic orientation and microstructure. Broadband dielectric spectroscopy (BBDS) was employed to investigate the dielectric response of BFTO ceramics over a frequency range of 10 mHz to 10 MHz and a temperature range of −30 °C to +200 °C. The temperature dependence of the relative permittivity (ε_r) and dielectric loss tangent (tan δ) were measured within a frequency range of 100 kHz to 900 kHz and a temperature range of 25 °C to 570 °C. The impedance data obtained from the BBDS measurements were validated using the Kramers–Kronig test and modeled using the Kohlrausch–Williams–Watts (KWW) function. The stretching parameter (β) ranged from ~0.72 to 0.82 in the impedance formalism within the temperature range from 200 °C to 20 °C. Full article

A series of Cu-MnO_x/GF catalytic electrodes, with graphite felt (GF) pretreated via microwave modification as the catalyst carrier, were prepared under various hydrothermal conditions and characterized using X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), X-ray photoelectron spectroscopy (XPS), N₂ adsorption–desorption, and Raman spectroscopy. The catalytic oxidation activity of catalytic Cu-MnO_x/GF electrodes toward toluene was evaluated in an all-solid-state electrocatalytic device under mild operating conditions. The evaluation results demonstrated that the microwave-modified catalytic electrode exhibited high electrocatalytic activity toward toluene oxidation, with Cu-MnO_x/700W-GF exhibiting significantly higher catalytic activity, indicating that an increase in catalyst loading capacity can promote the removal of toluene. Only CO₂ and CO were detected, with no other intermediates observed in the reaction process. Moreover, the catalytic effect was significantly affected by the relative humidity. The catalytic oxidation of toluene can be fully realized under a certain humidity, indicating that the conversion of H₂O to strongly oxidizing ·OH on the catalytic electrode is a key step in this reaction. Full article

The ability of earth-abundant metals to serve as catalysts for the oxygen reduction reaction is of increasing importance given the prominence of this reaction in several emerging technologies. It is now recognized that both the primary and secondary coordination environments of these catalysts can be modulated to optimize their performance. In this present work, we describe two Co^II complexes [Co^II(PaPy₂Q)](OTf) (1) and [Co^II(PaPy₂N)](OTf) (2) that catalyze chemical and electrochemical dioxygen reduction. Both 1 and 2 contain Co^II centers in a N₅⁻ coordination environment, but 2 has a naphthyridine group that places a nitrogen atom in the secondary coordination sphere. Solid-state X-ray crystallography and solution-state spectroscopic measurements reveal that, apart from this second-sphere nitrogen in 2, complexes 1 and 2 have essentially identical properties. Despite these similarities, 2 performs the chemical reduction of dioxygen ~10-fold more rapidly than 1. In addition, 2 has an enhanced performance in the electrochemical reduction of dioxygen compared to 1. Both complexes yield a significant amount of H₂O₂ in the chemical reduction of dioxygen (>25%). The enhanced catalytic performance of 2 is attributed to the presence of the second-sphere nitrogen atom, which might enable the efficient protonation of cobalt–oxygen intermediates formed during turnover. Full article