Influence of Fe and Cu Co-Doping on Structural,Magnetic and Electrochemical Properties of CeO2 Nanoparticles

The nanoparticles of CeO₂, Ce_0.98Fe_0.02O₂, and Ce_0.78Fe_0.02Cu_0.20O₂ were synthesized using the co-precipitation-synthesis technique. The effect of co-doping of Fe and Cu on structural, optical, and magnetic properties as well as specific capacitance have been studied using X-ray diffraction (XRD), scanning-electron microscopy (SEM), UV-visible spectroscopy, Raman spectroscopy, dc magnetization, and electrochemical measurements at room temperature. The results of the XRD analysis infer that all the samples have a single-phase nature and exclude the formation of any extra phase. Particle size has been found to reduce as a result of doping and co-doping. The smallest particle size was obtained to be 5.59 nm for Ce_0.78Fe_0.02Cu_0.20O₂. The particles show a spherical-shape morphology. Raman active modes, corresponding to CeO₂, were observed in the Raman spectra, with noticeable shifting with doping and co-doping indicating the presence of defect states. The bandgap, calculated using UV-Vis spectroscopy, showed relatively low bandgap energy (1.7 eV). The dc magnetization results indicate the enhancement of the magnetic moment in the samples, with doping and co-doping. The highest value of saturation magnetization (1.3 × 10⁻² emu/g) has been found for Ce_0.78Fe_0.02Cu_0.20O₂ nanoparticles. The electrochemical behavior studied using cyclic-voltammetry (CV) measurements showed that the Ce_0.98Fe_0.02O₂ electrode exhibits superior-specific capacitance (~532 F g⁻¹) along with capacitance retention of ~94% for 1000 cycles.     

Structural Morphology and Optical Properties of Strontium-Doped Cobalt Aluminate Nanoparticles Synthesized by the Combustion Method

The study of structural morphology and the optical properties of nanoparticles produced by combustion methods are gaining significance due to their multifold applications. In this regard, in the present work, the strontium-doped cobalt aluminate nanoparticles were synthesized by utilizing Co_1−xSr_xAl₂O₄ (0 ≤ x ≤ 0.5) L-Alanine as a fuel in an ignition cycle. Subsequently, several characterization studies viz., X-ray diffraction (XRD), energy-dispersive X-ray (EDX) analysis, high-resolution scanning electron microscopy (HRSEM), Fourier transform infrared spectroscopy (FTIR), ultraviolet (UV) spectroscopy and vibrating sample magnetometry (VSM) were accomplished to study the properties of the materials. The XRD analysis confirmed the cubic spinel structure, and the average crystallite size was found to be in the range of 14 to 20 nm using the Debye–Scherrer equation. High-resolution scanning electron microscopy was utilized to inspect the morphology of the Co_1−xSr_xAl₂O₄ (0 ≤ x ≤ 0.5) nanoparticles. Further, EDS studies were accomplished to determine the chemical composition. Kubelka–Munk’s approach was used to determine the band gap, and the values were found to be in the range of 3.18–3.32 eV. The energy spectra for the nanoparticles were in the range of 560–1100 cm⁻¹, which is due to the spinel structure of Sr-doped CoAl₂O₄ nanoparticles. The behavior plots of magnetic induction (M) against the magnetic (H) loops depict the ferromagnetic behavior of the nanomaterials synthesized.     

Electrical and Structural Properties of Li1.3Al0.3Ti1.7(PO4)3—Based Ceramics Prepared with the Addition of Li4SiO4

The currently studied materials considered as potential candidates to be solid electrolytes for Li-ion batteries usually suffer from low total ionic conductivity. One of them, the NASICON-type ceramic of the chemical formula Li_1.3Al_0.3Ti_1.7(PO₄)₃, seems to be an appropriate material for the modification of its electrical properties due to its high bulk ionic conductivity of the order of 10⁻³ S∙cm⁻¹. For this purpose, we propose an approach concerning modifying the grain boundary composition towards the higher conducting one. To achieve this goal, Li₄SiO₄ was selected and added to the LATP base matrix to support Li⁺ diffusion between the grains. The properties of the Li_1.3Al_0.3Ti_1.7(PO₄)₃−xLi₄SiO₄ (0.02 ≤ x ≤ 0.1) system were studied by means of high-temperature X-ray diffractometry (HTXRD); ⁶Li, ²⁷Al, ²⁹Si, and ³¹P magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR); thermogravimetry (TG); scanning electron microscopy (SEM); and impedance spectroscopy (IS) techniques. Referring to the experimental results, the Li₄SiO₄ additive material leads to the improvement of the electrical properties and the value of the total ionic conductivity exceeds 10⁻⁴ S∙cm⁻¹ in most studied cases. The factors affecting the enhancement of the total ionic conductivity are discussed. The highest value of σ_tot = 1.4 × 10⁻⁴ S∙cm⁻¹ has been obtained for LATP–0.1LSO material sintered at 1000 °C for 6 h.     

Structural,Morphological, Electronic Structural,Optical, and Magnetic Properties of ZnO Nanostructures

ZnO nanostructures were grown on a Si(111) substrate using a vapor–liquid–solid (VLS) growth procedure (pristine ZnO) and annealed via a rapid thermal-annealing process in an argon atmosphere at 1100 °C (Ar-ZnO). The synthesized ZnO nanostructures were investigated through structural, electronic structural, morphological, optical, and magnetic characterizations. X-ray diffraction and selective area electron diffraction (SAED) measurements revealed that both samples exhibited the hexagonal wurtzite phase of nanocrystalline ZnO. Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy carried out at the O K-edge inferred the presence of the intrinsic-defect states. Field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy images displayed the formation of ZnO nanostructures. The photoluminescence (PL) spectra demonstrated an emission band in the UV region along with an additional defect band in the visible region. PL spectral analysis confirmed the presence of intrinsic defects in Ar-ZnO nanowires, contributing to the enhanced emission in the visible region. The Raman spectra showed the characteristic band (434 cm⁻¹) corresponding to the vibrational modes of hexagonal wurtzite ZnO, with an additional band attributable to intrinsic defects. DC magnetization measurements showed a ferromagnetic response in both samples with enhanced coercivity in Ar-ZnO (~280 Oe). In brief, both samples exhibited the presence of intrinsic defects, which are found to be further enhanced in the case of Ar-ZnO. Therefore, it is suggested that intrinsic defects have played an important role in modifying the optical and magnetic properties of ZnO with enhanced results for Ar-ZnO.     

Magnetic Control of Fe3O4 Nanomaterial for Fat Ablation in Microchannel

In this study, surface modification of iron (II, III) oxide Fe₃O₄ nanoparticles by oleic acid (OA) coating is investigated for the microablation of fat in a microchannel. The nanoparticles are synthesized by the co-precipitation method and then dispersed in organic solvent prior to mixing with the OA. The magnetization, agglomeration, and particle size distribution properties of the OA-coated Fe₃O₄ nanoparticles are characterized. The surface modification of the Fe₃O₄ nanoparticles reveals that upon injection into a microchannel, the lipophilicity of the OA coating influences the movement of the nanoparticles across an oil-phase barrier. The motion of the nanoparticles is controlled using an AC magnetic field to induce magnetic torque and a static gradient field to control linear translation. The fat microablation process in a microchannel is demonstrated using an oscillating driving field of less than 1200 Am⁻¹.     

Magnetic Anisotropy and Microstructure in Electrodeposited Quaternary Sn-Fe-Ni-Co Alloys with Amorphous Character

Sn-Fe-Ni-Co quaternary alloys, in the composition range of 37–44 at% Sn, 35–39 at% Fe, 6–8 at% Ni and 13–17 at% Co, were prepared by direct current (DC) and pulse plating (PP) electrodeposition. The alloy deposits were characterized by XRD, ⁵⁷Fe and ¹¹⁹Sn conversion electron Mössbauer spectroscopy, SEM-EDX and magnetization measurements. XRD revealed the amorphous character of the quaternary alloy deposits. The dominant ferromagnetic character of the deposits was shown by magnetization and Mössbauer spectroscopy measurements. Room temperature Mössbauer spectra showed minor paramagnetic phases, where their occurrences (~3–20%) are correlated to the electrodeposition parameters (J_dep from −16 to −23 mA/cm² for DC, J_pulse from −40 to −75 mA/cm² for PP), the composition and the saturation magnetization (~52–73 emu/g). A considerable difference was found in the magnetization curves applying parallel or perpendicular orientation of the applied fields, indicating magnetic anisotropy both in DC and pulse plated alloy coatings.     

The Gd2−xMgxZr2O7−x/2 Solid Solution: Ionic Conductivity and Chemical Stability in the Melt of LiCl-Li2O

Materials with pyrochlore structure A₂B₂O₇ have attracted considerable attention owing to their various applications as catalysts, sensors, electrolytes, electrodes, and magnets due to the unique crystal structure and thermal stability. At the same time, the possibility of using such materials for electrochemical applications in salt melts has not been studied. This paper presents the new results of obtaining high-density Mg²⁺-doped ceramics based on Gd₂Zr₂O₇ with pyrochlore structure and comprehensive investigation of the electrical properties and chemical stability in a lithium chloride melt with additives of various concentrations of lithium oxide, performed for the first time. The solid solution of Gd_2−xMg_xZr₂O_7−x/2 (0 ≤ x ≤ 0.10) with the pyrochlore structure was obtained by mechanically milling stoichiometric mixtures of the corresponding oxides, followed by annealing at 1500 °C. The lattice parameter changed non-linearly as a result of different mechanisms of Mg²⁺ incorporation into the Gd₂Zr₂O₇ structure. At low dopant concentrations (x ≤ 0.03) some interstitial positions can be substituted by Mg²⁺, with further increasing Mg²⁺-content, the decrease in the lattice parameter occurred due to the substitution of host-ion sites with smaller dopant-ion. High-density ceramics 99% was prepared at T = 1500 °C. According to the results of the measurements of electrical conductivity as a function of oxygen partial pressure, all investigated samples were characterized by the dominant ionic type of conductivity over a wide range of pO₂ (1 × 10^–18 ≤ pO₂ ≤ 0.21 atm) and T < 800 °C. The sample with the composition of x = 0.03 had the highest oxygen-ion conductivity (10⁻³ S·cm⁻¹ at 600 °C). The investigation of chemical stability of ceramics in the melt of LiCl with 2.5 mas.% Li₂O showed that the sample did not react with the melt during the exposed time of one week at the temperature of 650 °C. This result makes it possible to use these materials as oxygen activity sensors in halide melts.     

(Cr1−xAlx)N Coating Deposition by Short-Pulse High-Power Dual Magnetron Sputtering

The paper deals with the (Cr_1−xAl_x)N coating containing 17 to 54 % Al which is deposited on AISI 430 stainless steel stationary substrates by short-pulse high-power dual magnetron sputtering of Al and Cr targets. The Al/Cr ratio in the coating depends on the substrate position relative to magnetrons. It is shown that the higher Al content in the (Cr_1−xAl_x)N coating improves its hardness from 17 to 28 GPa. Regardless of the Al content, the (Cr_1−xAl_x)N coating manifests a low wear rate, namely (4.1–7.8) × 10⁻⁹ and (3.9–5.3) × 10⁻⁷ mm³N⁻¹m⁻¹ in using metallic (100Cr6) and ceramic (Al₂O₃) counter bodies, respectively. In addition, this coating possesses the friction coefficient 0.4–0.7 and adhesive strength quality HF1 and HF2 indicating good interfacial adhesion according to the Daimler-Benz Rockwell-C adhesion test.     

Structural,Magnetic, and Electrical Properties of CoFe2O4 Nanostructures Synthesized Using Microwave-Assisted Hydrothermal Method

Magnetic nanostructures of CoFe₂O₄ were synthesized via a microwave-assisted hydrothermal route. The prepared nanostructures were investigated using X-ray diffraction (XRD), field emission electron microscopy (FE-SEM), energy dispersive X-ray (EDX) spectroscopy, high-resolution transmission electron microscopy (HR-TEM), selective area electron diffraction (SAED) pattern, DC magnetization, and dielectric spectroscopy measurements. The crystal structure studied using HR-TEM, SAED, and XRD patterns revealed that the synthesized nanostructures had a single-phase nature and ruled out the possibility of any secondary phase. The lattice parameters and unit cell volume determined from the XRD data were found to be 8.4821 Å and 583.88 ų. The average crystallite size (~7.0 nm) was determined using Scherrer’s equation. The FE-SEM and TEM micrographs revealed that the prepared nanostructures had a spherical shape morphology. The EDX results showed that the major elements present in the samples were Co, Fe, and O. The magnetization (M) versus temperature (T) measurements specified that the CoFe₂O₄ nanostructures showed ferromagnetic ordering at room temperature. The blocking temperature (T_B) determined using the M-T curve was found to be 315 K. The magnetic hysteresis (M-H) loop of the CoFe₂O₄ nanostructures recorded at different temperatures showed the ferromagnetic behavior of the CoFe₂O₄ nanostructures at temperatures of 200 K and 300 K, and a superparamagnetic behavior at 350 K. The dielectric spectroscopy studies revealed a dielectric constant (ε′) and loss tangent (tanδ) decrease with the increase in the frequency, as well as demonstrating a normal dispersion behavior, which is due to the Maxwell–Wagner type of interfacial polarization. The values of ε′ and tanδ were observed to increase with the increase in the temperature.     

Structure and Magnetic Properties of SrFe12−xInxO19 Compounds for Magnetic Hyperthermia Applications

In this work, complex studies of the structure and magnetic properties of SrFe_12−xIn_xO₁₉ powders obtained by the mechanochemical and citrate methods were carried out. The solubility of In in strontium hexaferrite SrFe₁₂O₁₉ at 1200 °C was determined. The structure and properties of the powders were studied using X-ray diffraction analysis, Mössbauer spectroscopy and scanning electron microscopy. Measurements of magnetic properties in magnetic fields up to 1600 kA/m were also performed. Additionally, the hyperthermia effect was investigated. The possibility of controlling the coercivity of the samples in the range from 188.9 kA/m to 22.3 kA/m and saturation magnetization from 63.5 A·m²/kg to 44.2 A·m²/kg with an increase in the degree of In doping was also demonstrated. Investigation of the magnetic hyperthermia of the samples was carried out by temperature measurement with an IR camera when they were introduced into alternating magnetic fields of various frequencies (144, 261 and 508 kHz) and amplitudes (between 11.96 and 19.94 kA/m). According to the study result, there was detected the heating of the SrFe_12−xIn_xO₁₉ sample (x = 1.7). The highest values of magnetic hyperthermia of the sample were observed in a 19.94 kA/m magnetic field and a frequency of 261 kHz. At a concentration of 56.67 g/L, the sample was heated from 23 to 41 °C within 2 min. The parameters SLP (specific loss power) and ILP (intrinsic loss power) were calculated.     

Synthesis and Characterization of TiO2 Nanotubes (TiO2-NTs) with Ag Silver Nanoparticles (Ag-NPs): Photocatalytic Performance for Wastewater Treatment under Visible Light

In this work, we present the influence of the decoration of TiO₂ nanotubes (TiO₂-NTs) with Ag silver nanoparticles (Ag-NPs) on the photocatalysis of emerging pollutants such as the antibiotic diclofenac sodium. The Ag-NPs were loaded onto the TiO₂-NTs by the anodization of metallic titanium foils. Diclofenac sodium is an emerging pollutant target of the pharmaceutical industry because of its negative environmental impact (high toxicity and confirmed carcinogenicity). The obtained Ag-NP/TiO₂-NT nanocomposites were characterized by X-ray diffraction (XRD), photoluminescence spectroscopy (PL), scanning electron microscopy (SEM), transmission spectroscopy (TEM), and X-ray photoelectron spectroscopy (XPS). In order to study the photocatalytic behavior of Ag-NPs/TiO₂-NTs with visible cold LEDs, the possible photocatalytic mechanism of antibiotic degradation with reactive species (O₂°⁻ and OH°) was detailed. Moreover, the Langmuir–Hinshelwood model was used to correlate the experimental results with the optimized catalyst. Likewise, reuse tests showed the chemical stability of the catalyst.     

Normally-off Hydrogen-Terminated Diamond Field-Effect Transistor with SnOx Dielectric Layer Formed by Thermal Oxidation of Sn

SnO_x films were deposited on a hydrogen-terminated diamond by thermal oxidation of Sn. The X-ray photoelectron spectroscopy result implies partial oxidation of Sn film on the diamond surface. The leakage current and capacitance–voltage properties of Al/SnO_x/H-diamond metal-oxide-semiconductor diodes were investigated. The maximum leakage current density value at −8.0 V is 1.6 × 10⁻⁴ A/cm², and the maximum capacitance value is measured to be 0.207 μF/cm². According to the C–V results, trapped charge density and fixed charge density are determined to be 2.39 × 10¹² and 4.5 × 10¹¹ cm⁻², respectively. Finally, an enhancement-mode H-diamond field effect transistor was obtained with a V_TH of −0.5 V. Its I_DMAX is −21.9 mA/mm when V_GS is −5, V_DS is −10 V. The effective mobility and transconductance are 92.5 cm²V⁻¹ s⁻¹ and 5.6 mS/mm, respectively. We suspect that the normally-off characteristic is caused by unoxidized Sn, whose outermost electron could deplete the hole in the channel.     

Crystalline Quality,Composition Homogeneity,Tellurium Precipitates/Inclusions Concentration,Optical Transmission,and Energy Band Gap of Bridgman Grown Single-Crystalline Cd1−xZnxTe (0 ≤ x ≤ 0.1)

Cd_1−xZn_xTe (0 ≤ x ≤ 0.1) ingots were obtained by Bridgman’s method using two different speeds in order to find the optimal conditions for single-crystalline growth. Crystalline quality was studied by chemical etching, the elemental composition by wavelength dispersive spectroscopy (WDS), tellurium (Te) precipitates/inclusions concentration by differential scanning calorimetry (DSC), optical transmission by Fourier transformed infrared spectrometry (FTIR), and band gap energy (Egap) by photoluminescence (PL). It was observed that the ingots grown at a lower speed were those of the best crystalline quality, having at most three grains of different crystallographic orientation. The average dislocations density in all of them were similar and correspond to materials of good quality. EPMA results indicated that the homogeneity in the composition was excellent in the ingots central part. The concentration of Te precipitates/inclusions in all ingots was below the instrument (DSC) detection limit, 0.25% wt/wt. In the case of wafers from Cd_0.96Zn_0.04Te and Cd_0.90Zn_0.10Te ingots, the optical transmission was better than that of commercial materials and varied between 60% and 70%, while for pure CdTe, the transmission range was between 50% and 55%, the latter being decreased by the presence of Te precipitates/inclusions. The band gap energy Eg of different wafers was experimentally obtained by PL measurements at 76 K. We observed that Eg increased with the Zn concentration of the wafers, following a linear regression comparable to those proposed in the literature, and consistent with the results obtained with other techniques.     

Structural,Magnetic, Dielectric and Piezoelectric Properties of Multiferroic PbTi1−xFexO3−δ Ceramics

PbTi_1−xFe_xO_3−δ (x = 0, 0.3, 0.5, and 0.7) ceramics were prepared using the classical solid-state reaction method. The investigated system presented properties that were derived from composition, microstructure, and oxygen deficiency. The phase investigations indicated that all of the samples were well crystallized, and the formation of a cubic structure with small traces of impurities was promoted, in addition to a tetragonal structure, as Fe³⁺ concentration increased. The scanning electron microscopy (SEM) images for PbTi_1−xFe_xO_3−δ ceramics revealed microstructures that were inhomogeneous with an intergranular porosity. The dielectric permittivity increased systematically with Fe³⁺ concentration, increasing up to x = 0.7. A complex impedance analysis revealed the presence of multiple semicircles in the spectra, demonstrating a local electrical inhomogeneity due the different microstructures and amounts of oxygen vacancies distributed within the sample. The increase of the substitution with Fe³⁺ ions onto Ti⁴⁺ sites led to the improvement of the magnetic properties due to the gradual increase in the interactions between Fe³⁺ ions, which were mediated by the presence of oxygen vacancies. The PbTi_1−xFe_xO_3−δ became a multifunctional system with reasonable dielectric, piezoelectric, and magnetic characteristics, making it suitable for application in magnetoelectric devices.     

Facile Synthesis of CoSe/Co3O4-CNTs/NF Composite Electrode for High-Performance Asymmetric Supercapacitor

Electrode materials are key factors for supercapacitors to endow them with excellent electrochemical properties. Here, a novel hybrid structure of a CoSe/Co₃O₄-CNTs binder free composite electrode on nickel foam was prepared via a facile flame method, followed by an electrodeposition process. Benefitting from the synergetic effects of the multicomponent (with low resistances of 1.542 Ω cm² and a moderate mesoporous size of 3.12 nm) and the enlarged specific surface area of the composite material (77.4 m² g⁻¹), the CoSe/Co₃O₄-CNTs composite electrode delivers a high specific capacitance of 2906 F g⁻¹ at 5 mV s⁻¹ with an excellent rate stability. The fabricated CoSe/Co3O4-CNTs/NF//AC ASC exhibits a high energy density of 43.4 Wh kg⁻¹ at 0.8 kW kg⁻¹ and a long cycle life (92.7% capacitance retention after 10,000 cycles).     

Low-Temperature Rapid Sintering of Dense Cubic Phase ZrW2−xMoxO8 Ceramics by Spark Plasma Sintering and Evaluation of Its Thermal Properties

In this study, we report a low-temperature approach involving a combination of a sol–gel hydrothermal method and spark plasma sintering (SPS) for the fabrication of cubic phase ZrW_2−xMo_xO₈ (0.00 ≤ x ≤ 2.00) bulk ceramics. The cubic-ZrW_2−xMo_xO₈ (0.00 ≤ x ≤ 1.50) bulk ceramics were successfully synthesized within a temperature range of 623–923 K in a very short amount of time (6–7 min), which is several hundred degrees lower than the typical solid-state approach. Meanwhile, scanning electron microscopy and density measurements revealed that the cubic-ZrW_2−xMo_xO₈ (0.00 ≤ x ≤ 1.50) bulk ceramics were densified to more than 90%. X-ray diffraction (XRD) results revealed that the cubic phase ZrW_2−xMo_xO₈ (0.00 ≤ x ≤ 1.5) bulk ceramics, as well as the sol–gel-hydrothermally synthesized ZrW_2−xMo_xO₇(OH)₂·2H₂O precursors correspond to their respective pure single phases. The bulk ceramics demonstrated negative thermal expansion characteristics, and the coefficients of negative thermal expansion were shown to be tunable in cubic-ZrW_2−xMo_xO₈ bulk ceramics with respect to x value and sintering temperature. The cubic-ZrW_2−xMo_xO₈ solid solution can thus have potential applications in electronic devices such as heat sinks that require regulation of thermal expansion.     

Synthesis and Characterization of Sn/SnO2/C Nano-Composite Structure: High-Performance Negative Electrode for Lithium-Ion Batteries

Tin oxide (SnO₂) and tin-based composites along with carbon have attracted significant interest as negative electrodes for lithium-ion batteries (LIBs). However, tin-based composite electrodes have some critical drawbacks, such as high volume expansion, low capacity at high current density due to low ionic conductivity, and poor cycle stability. Moreover, complex preparation methods and high-cost carbon coating procedures are considered main challenges in the commercialization of tin-based electrodes for LIBs. In this study, we prepared a Sn/SnO₂/C nano-composite structure by employing a low-cost hydrothermal method, where Sn nanoparticles were oxidized in glucose and carboxymethyl cellulose CMC was introduced into the solution. Scanning electron microscope (SEM) and transmission electron microscope revealed the irregular structure of Sn nanoparticles and SnO₂ phases in the conductive carbon matrix. The as-prepared Sn/SnO₂/C nano-composite showed high first-cycle reversible discharge capacity (2248 mAhg⁻¹) at 100 mAg⁻¹ with a first coulombic efficiency of 70%, and also displayed 474.64 mAhg⁻¹ at the relatively high current density of about 500 mAg⁻¹ after 100 cycles. A low-cost Sn/SnO₂/C nano-composite with significant electrochemical performance could be the next generation of high-performance negative electrodes for LIBs.     

3D Porous MXene (Ti3C2Tx) Prepared by Alkaline-Induced Flocculation for Supercapacitor Electrodes

2D layered MXene (Ti₃C₂T_x) with high conductivity and pseudo-capacitance properties presents great application potential with regard to electrode materials for supercapacitors. However, the self-restacking and agglomeration phenomenon between Ti₃C₂T_x layers retards ion transfer and limits electrochemical performance improvement. In this study, a 3D porous structure of Ti₃C₂T_x was obtained by adding alkali to a Ti₃C₂T_x colloid, which was followed by flocculation. Alkaline-induced flocculation is simple and effective, can be completed within minutes, and provides 3D porous networks. As 3D porous network structures present larger surface areas and more active sites, ions transfer accelerates, which is crucial with regard to the improvement of the superior capacitance and rate performance of electrodes. The sample processed with KOH (K-a-Ti₃C₂T_x) exhibited a high capacity of approximately 300.2 F g⁻¹ at the current density of 1 A g⁻¹. The capacitance of the samples treated with NaOH and LiOH is low. In addition, annealing is essential to further improve the capacitive performance of Ti₃C₂T_x. After annealing at 400 °C for 2 h in a vacuum tube furnace, the sample treated with KOH (K-A-Ti₃C₂T_x) exhibited an excellent specific capacitance of approximately 400.7 F g⁻¹ at a current density of 1 A g⁻¹, which is considerably higher than that of pristine Ti₃C₂T_x (228.2 F g⁻¹). Furthermore, after 5000 charge–discharge cycles, the capacitance retention rate reached 89%. This result can be attributed to annealing, which can further remove unfavourable surface groups, such as –F or –Cl, and then improve conductivity capacitance and rate performance. This study can provide an effective approach to the preparation of high-performance supercapacitor electrode materials.     

The Preparation of {001}TiO2/TiOF2 via a One-Step Hydrothermal Method and Its Degradation Mechanism of Ammonia Nitrogen

{001}TiO₂/TiOF₂ photocatalytic composites with a high activity {001} crystal plane were prepared by one-step hydrothermal methods using butyl titanate as a titanium source and hydrofluoric acid as a fluorine source. X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), raman spectroscopy, N₂ adsorption-desorption curve (BET), UV-Vis diffuse absorption spectroscopy (UV-Vis DRS), X-ray photoelectron spectroscopy (XPS), and fluorescence spectroscopy (PL) were used to evaluate the structure, morphology, specific surface area, optical properties, and photocarrier separation ability of {001}TiO₂/TiOF₂. Ammonia nitrogen was taken as the target pollutant, and the degradation performance of the catalyst was investigated. The results show that hydrofluoric acid improves the content of {001} crystal plane of TiO₂ with high activity; it also improves the specific surface area and dispersion of the composite material and adjusts the ratio of {001}TiO₂ to TiOF₂ in the composite material to enhance the absorption capacity of the composite material and reduce the band gap width of the composite material. The degradation rate of ammonia nitrogen by 100 mg F15 is 93.19% when the initial concentration of ammonia nitrogen is 100 mg/L and pH is 10. Throughout the reaction process, the {001}TiO₂/TiOF₂ composite produces superoxide anion radical (·O₂⁻) and hydroxyl radical (·OH) to oxidize NH₃·H₂O and generate N₂ accompanied by a small amount of NO₃⁻ and NO₂⁻.     

Study of the Structure,Magnetic, Thermal and Electrical Characterisation of ZnCr2Se4: Ta Single Crystals Obtained by Chemical Vapour Transport

The new series of single-crystalline chromium selenides, Ta-doped ZnCr₂Se₄, was synthesised by a chemical vapour transport method to determine the impact of a dopant on the structural and thermodynamic properties of the parent compound. We present comprehensive investigations of structural, electrical transport, magnetic, and specific heat properties. It was expected that a partial replacement of Cr ions by a more significant Ta one would lead to a change in direct magnetic interactions between Cr magnetic moments and result in a change in the magnetic ground state and electric transport properties of the ZnCr_2−xTa_xSe₄ (x = 0.05, 0.06, 0.07, 0.08, 0.1, 0.12) system. We found that all the elements of the cubic system had a cubic spinel structure; however, the doping gain linearly increased the ZnCr_2−xTa_xSe₄ unit cell volume. Doping with tantalum did not significantly change the semiconductor and magnetic properties of ZnCr₂Se₄. For all studied samples (0 ≤ x ≤ 0.12), an antiferromagnetic order (AFM) below T_N~22 K was observed. However, a small amount of Ta significantly reduced the second critical field (H_c2) from 65 kOe for x = 0.0 (ZnCr₂Se₄ matrix) up to 42.2 kOe for x = 0.12, above which the spin helical system changed to ferromagnetic (FM). The H_c2 reduction can lead to strong competition among AFM and FM interactions and spin frustration, as the specific heat under magnetic fields H < H_c2 shows a strong field decrease in T_N.