Facile synthesis of metal-doped Ni-Zn ferrite from treated Zn-containing electric arc furnace dust

Metal-doped Ni-Zn ferrite with a spinel structure was directly synthesized from treated zinc-containing electric arc furnace dust (Zn-containing EAFD) by solid state reaction method, realizing the transformation of solid waste to high value-added material. First, NiCl₂·6H₂O was added to the treated Zn-containing EAFD before calcination. Then, the effects of the mass ratio of treated Zn-containing EAFD to NiCl₂·6H₂O (R_TZE/N, g g⁻¹) and the calcination temperature on the synthesis and magnetic properties of as-synthesized samples were systematically investigated by X-ray diffraction, Raman spectroscopy and physical property measurement. It was found that R_TZE/N and calcination temperature significantly influenced the synthesis of single-phase spinel ferrite and their magnetic properties. Pure metal-doped Ni-Zn ferrite, exhibiting good magnetic properties of higher saturation magnetization (Ms, 60.5 emu g⁻¹) and lower coercivity (Hc, 49.8 Oe), was obtained when the calcination temperature was controlled at 1100 °C for 2 h with a R_TZE/N of 1:0.9.     

Synthesis and electrochemical properties of nickel oxide/carbon nanofiber composites

The electrospinning of polyacrylonitrile (PAN) with a polyaniline and graphene sol–gel mixture produced uniform, smooth fibers with an average diameter of 0.3 μm. These electrospun fibers were stabilized for 2 h at 200 °C and then carbonized at 800 °C for 5 h. Composites were prepared by depositing Ni(OH)₂ on the carbon nanofibers (CNFs) and calcining them at different temperatures. The composites were characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The effect of the calcination temperatures on the electrochemical properties was studied using cyclic voltammetry and electrochemical impedance spectroscopy. The specific capacitance (SC) was found to be highest (738 F g⁻¹) at a calcination temperature of 400 °C. The charge transfer resistance (R_p) decreased as the calcination temperature was increased. However, the electrical double layer capacitance (EDLC) increased with an increase in the calcination temperature. The EDLC increased from 0.144 F g⁻¹ at a calcination temperature of 100 °C to 485 F g⁻¹ at a calcination temperature of 500 °C.     

Magnetic,magnetostrictive, and AC impedance properties of manganese substituted cobalt ferrites

In this study, we investigated the effects of substituting Mn³⁺ for some Fe³⁺ in spinel lattice on the structure, magnetic properties, magnetostriction behavior, and AC impedance characteristics of cobalt ferrites. The manganese substituted cobalt ferrites (Co–Mn ferrites), CoMn_xFe_2−xO₄, with x varied from 0 to 0.3 in 0.1 increments, were prepared by solid-state reaction. XRD examination confirmed that all sintered Co-based ferrites had a single-phase spinel structure. The average grain size, obtained from SEM micrographs, increased from 8.2 μm to 12.5 μm as the Mn content (x) increased from 0 to 0.3. Both the Curie temperature and coercivity of Co-based ferrites decreased with greater amounts of Mn, while the maximum magnetization (at H=6 kOe) of Mn-substituted cobalt ferrites was larger than that of the pure Co-ferrite. Magnetostrictive properties revealed that the pure Co-ferrite had the largest saturation magnetostriction (λ_S), about −167 ppm, and the CoMn_0.2Fe_1.8O₄ sample exhibited the highest strain sensitivity (|dλ_⊥/dH|_m) of 2.23×10⁻⁹ A⁻¹m among all as-prepared Co-based ferrites. In addition, AC impedance spectra analysis revealed that the real part (Z′) of the complex impedance of Co–Mn ferrites was lower than that of pure Co-ferrite in the low frequency region, and the Co-based ferrites exhibited semiconductor-like behavior.     

Polymer-derived mesoporous Ni/SiOC(H) ceramic nanocomposites for efficient removal of acid fuchsin

In this paper, magnetic porous Ni-modified SiOC(H) ceramic nanocomposites (Ni/SiOC(H)) were successfully prepared via a template-free polymer-derived ceramic route, which involves pyrolysis at 600 °C of nickel-modified allylhydridopolycarbosilane (AHPCS-Ni) precursors synthesized by the reaction of allylhydridopolycarbosilane (AHPCS) with nickel(II)acetylacetonate (Ni(acac)₂). The resultant Ni/SiOC(H) nanocomposites are comprised of in-situ formed nanoscaled Ni socialized with small amounts of NiO and nickel silicides embedded in the amorphous SiOC(H) matrix. The materials show ferromagnetic behavior and excellent magnetic properties with the saturation magnetization in the range of 1.71–7.08 emu g⁻¹. Besides, the Ni/SiOC(H) nanocomposites are predominantly mesoporous with a high BET surface area and pore volume in the range of 253–344 and 0.134–0.185 cm³ g⁻¹, respectively. The measured porosity features cause an excellent adsorption capacity towards a template dye acid fuchsin with the adsorption capacity Q_t at 10 min of 80.7–85.8 mg g⁻¹ and the Q_e at equilibrium of 123.8–129.8 mg g⁻¹.     

Microwave-enhanced catalytic degradation of phenol over nickel oxide

A mix-valenced nickel oxide, NiO_x, was prepared from nickel nitrate aqueous solution through a precipitation with sodium hydroxide and an oxidation by sodium hypochlorite. Further, pure nickel oxide was obtained from the NiO_x by calcination at 300, 400 and 500 °C (labeled as C300, C400 and C500, respectively). They were characterized by thermogravimetry (TG), X-ray diffraction (XRD), nitrogen adsorption at −196 °C and temperature-programmed reduction (TPR). Their catalytic activities towards the degradation of phenol were further studied under continuous bubbling of air through the liquid phase. Also, the effects of pH, temperature and kinds of nickel oxide on the efficiency of the microwave-enhance catalytic degradation (MECD) of phenol have been investigated. The results indicated that the relative activity affected significantly with the oxidation state of nickel, surface area and surface acidity of nickel oxide, i.e., NiO_x (>+2 and S_BET = 201 m² g⁻¹) ≫ C300 (+2 and S_BET = 104 m² g⁻¹) > C400 (+2 and S_BET = 52 m² g⁻¹) > C500 (+2 and S_BET = 27 m² g⁻¹). The introduction of microwave irradiation could greatly shorten the time of phenol degradation.     

Chitosan modified with Reactive Blue 2 dye on adsorption equilibrium of Cu(II) and Ni(II) ions

This study aimed at immobilizing Reactive Blue 2 (RB 2) dye in chitosan microspheres through nucleophilic substitution reaction. The adsorbent chemical modification was confirmed by Raman spectroscopy and thermogravimetric analysis. This adsorption study was carried out with Cu(II) and Ni(II) ions and indicated a pH dependence, while the maximum adsorption occurred around pH 7.0 and 8.5, respectively. The pseudo second-order kinetic model resulted in the best fit with experimental data obtained from Cu(II) (R = 0.997) and Ni(II) (R = 0.995), also providing a rate constant, k₂, of 4.85 × 10⁻⁴ and 3.81 × 10⁻⁴ g (mg min)⁻¹, respectively, thus suggesting that adsorption rate of metal ions by chitosan-RB 2 depends on the concentration of ions on adsorbent surface, as well as on their concentration at equilibrium. The Langmuir and Freundlich isotherm models were employed in the analysis of the experimental data for the adsorption, in the form of linearized equations. Langmuir model resulted in the best fit for both metals and maximum adsorption was 57.0 mg g⁻¹ (0.90 mmol g⁻¹) for Cu(II) and 11.2 mg g⁻¹ (0.19 mmol g⁻¹) for Ni(II). The Cu(II) and Ni(II) ions were desorbed from chitosan-RB 2 with aqueous solutions of EDTA and H₂SO₄, respectively.     

Self-assembly and guest binding of nickel(II) macrocyclic complex with pentyl groups and cis,cis-1,3,5-cyclohexanetricarboxylic acid

Reaction of the nickel(II) macrocyclic complex 1 including pendant pentyl groups in MeCN/H₂O mixed solvent with deprotonated cis,cis-1,3,5-cyclohexanetricarboxylic acid (CTC^3 −) resulted in two-dimensional (2-D) coordination polymer [Ni(C₁₈H₄₂N₆)]₃[C₆H₉(COO)₃]₂·6H₂O·6CH₃CN (2). The crystal structure of 2 indicates that each nickel(II) macrocyclic unit binds two CTC^3 − ions in trans position and each CTC^3 − ion coordinates three nickel(II) macrocyclic complexes to form a 2-D layer with hexagonal motif. The dried solid of 2 differentiates MeOH, EtOH, and PhOH in toluene solvent with the K_f values of 1.38, 2.11, and 6.68 M^− 1, respectively.     

Synthesis and characterization of 2-imino-indole nickel complexes and their ethylene oligomerization study

A series of 2-imino-indole derivatives and their neutral nickel complexes were synthesized and characterized. A single-crystal X-ray analysis of [Ni(C₁₀H₇)(C₁₈H₁₆ClN₂)(PPh₃)] shows the nickel center adopted a square-planar coordination geometry. The nickel complexes act solely as effective catalysts for ethylene oligomerization with the activity up to 2.05 × 10⁴ g ethylene mol⁻¹ h⁻¹.     

Heat generation properties in AC magnetic field for Y3Fe5O12 powder material synthesized by a reverse coprecipitation method

Ferrimagnetic Y₃Fe₅O₁₂ powder was synthesized by a reverse coprecipitation method in order to study its heat generation property in an AC magnetic field. An orthorhombic YFeO₃ phase having a small particle size (<100 nm) was obtained for the samples calcined at a low temperature. The maximum heat generation ability in an AC magnetic field was obtained for the Y₃Fe₅O₁₂ ferrite powder by calcination at 1100 °C. The heat generation ability was reduced for the samples calcined at a higher temperature. The particle growth with the formation of the cubic single phase might influence the heat generation ability. The heat generation ability and the hysteresis loss value were proportional to the cube of the magnetic field (H³), because the coercivity value of the B–H curve was proportional to the square of the amplitude of the AC magnetic field (H²). The heat generation ability (W g⁻¹) of the Y₃Fe₅O₁₂ sample sintered at 1100 °C can be expressed by the equation 2.2×10⁻⁴∙f∙H³ using the frequency (f/kHz) and the magnetic field (H/kA m⁻¹), which has the highest heat generation ability of the reported magnetic materials. The hysteresis loss value for the B–H curve agreed with the heat generation ability of the samples calcined at 1100 °C and lower temperatures.     

The additive-free electrode based on the layered MnO2 nanoflowers/reduced,graphene oxide film for high performance supercapacitor

The MnO₂ nanoflowers/reduced graphene oxide composite is coated on a nickel foam substrate (denoted as MnO₂ NF/RGO @ Ni foam) via the layer by layer (LBL) self-assembly technology without any polymer additive, following the soft chemical reduction. The layered MnO₂ NF/RGO composite is uniformly anchored on the Ni foam skeleton to form the 3D porous framework, and the interlayers have access to lots of ions channels to improve the electron transfer and diffusion. This special construction of 3D porous structure is beneficial to the enhancement of electrochemical property. The specific capacitance is up to 246 F g⁻¹ under the current density of 0.5 A g⁻¹. After 1000 cycles, it can retain about 93%, exhibiting excellent cycle stability. The electrochemical impedance spectroscopy measurements confirm that MnO₂ NF/RGO @ Ni foam electrode has lower R_ESR and R_CT values when compared to MnO₂ @ Ni foam and RGO @ Ni foam. This study opens a new door to the preparation of composite electrodes for high performance supercapacitor.     

Hydrazine hydrate-induced hydrothermal synthesis of MnFe2O4 nanoparticles dispersed on graphene as high-performance anode material for lithium ion batteries

Herein, a MnFe₂O₄/graphene (MnFe₂O₄/G) nanocomposite has been synthesized via a facile N₂H₄·H₂O-induced hydrothermal method. During the synthesis, N₂H₄·H₂O is employed to not only reduce graphene oxide to graphene, but also prevent the oxidation of Mn²⁺ in alkaline aqueous solution, thus ensuring the formation of MnFe₂O₄/G. Moreover, MnFe₂O₄ nanoparticles (5–20 nm) are uniformly anchored on graphene. MnFe₂O₄/G electrode delivers a large reversible capacity of 768 mA h g⁻¹ at 1 A g⁻¹ after 200 cycles and high rate capability of 517 mA h g⁻¹ at 5 A g⁻¹. MnFe₂O₄/G holds great promise as anode material in practical applications due to the outstanding electrochemical performance combined with the facile synthesis strategy.     

Porous carbon spheres as anode materials for sodium-ion batteries with high capacity and long cycling life

Porous carbon spheres (PCSs) with high surface area were fabricated by the reaction of D-Glucose monohydrate precursor with sodium molybdate dihydrate (Na₂MoO₄·2H₂O) via a facile hydrothermal method followed by carbonization and aqueous ammonia solution (NH₃·H₂O) treatment. The as-prepared PCSs exhibit a highly developed porous structure with a large specific surface area and show an excellent electrochemical performance as anode material of sodium-ion batteries (SIBs). A reversible capacity of 249.9 mA h g⁻¹ after 50 cycles at a current density of 50 mA g⁻¹ and a long cycling life at a high current density of 500 mA g⁻¹ are achieved. The excellent cycling performance and high capacity make the PCSs a promising candidate for long cycling SIBs.     

3D network-like porous MnCo2O4 by the sucrose-assisted combustion method for high-performance supercapacitors

3D network-like porous MnCo₂O₄ nanostructures have been successfully fabricated through a facile and scalable sucrose-assisted combustion route followed by calcination treatment. Benefiting from its advantages of the unique 3D network-like architectures with large specific surface area (216.15 m² g⁻¹), abundant mesoporosity (2–50 nm) and high electronic conductivity, the as-prepared MnCo₂O₄ electrode displays a high specific capacitance of 647.42 F g⁻¹ at a current density of 1 A g⁻¹, remarkable capacitance retention rate of 70.67% at current density of 10 A g⁻¹ compared with 1 A g⁻¹, and excellent cycle stability (only 6.32% loss after 3000 cycles). The excellent electrochemical performances coupled with facile and cost effective method will render the as-fabricated 3D network-like porous MnCo₂O₄ as a promising electrode material for supercapacitors.     

Electrospun ZnO–SnO2 composite nanofibers with enhanced electrochemical performance as lithium-ion anodes

ZnO–SnO₂ composite nanofibers with different structures were synthesized by a simple electrospinning approach with subsequent calcination at three different temperatures using polyacrylonitrile as the polymer precursor. The electrochemical performance of the composites for use as anode materials in lithium-ion batteries were investigated. It was found that the ZnO–SnO₂ composite nanofibers calcined at 700 °C showed excellent lithium storage properties in terms of cycling stability and rate capability, compared to those calcined at 800 and 900 °C, respectively. ZnO–SnO₂ composite nanofibers calcined at 700 °C not only delivered high initial discharge and charge capacities of 1450 and 1101 mAh g⁻¹, respectively, with a 75.9% coulombic efficiency, but also maintained a high reversible capacity of 560 mAh g⁻¹ at a current density of 0.1 A g⁻¹ after 100 cycles. Additionally, a high reversible capacity of 591 mAh g⁻¹ was obtained when the current density returned to 0.1 A g⁻¹ after 50 cycling at a high current density of 2 A g⁻¹. The superior electrochemical performance of ZnO–SnO₂ composite nanofibers can be attributed to the unique nanofibrous structure, the smaller particle size and smaller fiber diameter as well as the porous structure and synergistic effect between ZnO and SnO₂.     

Simple fabrication of a Fe2O3/carbon composite for use in a high-performance lithium ion battery

A simple approach was developed for the fabrication of a Fe₂O₃/carbon composite by impregnating activated carbon with a ferric nitrate solution and calcinating it. The composite contains graphitic layers and 10 wt.% Fe₂O₃ particles of 20–50 nm in diameter. The composite has a high specific surface area of ∼828 m² g⁻¹ and when used as the anode in a lithium ion battery (LIB), it showed a reversible capacity of 623 mAh g⁻¹ for the first 100 cycles at 50 mA g⁻¹. A discharge capacity higher than 450 mAh g⁻¹ at 1000 mA g⁻¹ was recorded in rate performance testing. This highly improved reversible capacity and rate performance is attributed to the combination of (i) the formation of graphitic layers in the composite, which possibly improves the matrix electrical conductivity, (ii) the interconnected porous channels whose diameters ranges from the macro- to meso- pore, which increases lithium-ion mobility, and (iii) the Fe₂O₃ nanoparticles that facilitate the transport of electrons and shorten the distance for Li⁺ diffusion. This study provides a cost-effective, highly efficient means to fabricate materials which combine conducting carbon with nanoparticles of metal or metal oxide for the development of a high-performance LIB.     

Investigation of Li5Cr7Ti6O25 as novel anode material for high-power lithium-ion batteries

In this work, Li₅Cr₇Ti₆O₂₅ as a new anode material for rechargeable batteries is fabricated through a simple sol-gel method at different calcination temperatures. The X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, charge/discharge curve and cyclic voltammograms are utilized to study the crystal structures, morphologies and electrochemical properties of as-obtained Li₅Cr₇Ti₆O₂₅ samples. The impact of calcination temperatures on morphologies and electrochemical properties of Li₅Cr₇Ti₆O₂₅ is discussed in detail. The test result shows that the 800 °C is a proper calcination temperature for Li₅Cr₇Ti₆O₂₅ with excellent electrochemical properties. Cycled at 200 mA g⁻¹, it displays a high initial reversible capacity of 146.6 mA h g⁻¹ and retains a considerable capacity of 130.8 mA h g⁻¹ after 300 cycles. Even cycled at large current density of 500 mA g⁻¹, the initial reversible capacity of 129.6 mA h g⁻¹ with the capacity retention of 88% after 300 cycles is achieved, which is obviously higher than that of Li₅Cr₇Ti₆O₂₅ prepared at 700 °C (80.5 mA h g⁻¹ and 68%) and 900 °C (98.4 mA h g⁻¹ and 80%). In addition, in-situ XRD analysis reveals that Li₅Cr₇Ti₆O₂₅ exhibits a reversible structural change during lithiation and delithiation processes. The above prominent electrochemical performance indicates the great potential of the Li₅Cr₇Ti₆O₂₅ obtained at 800 °C as anode material for rechargeable batteries.     

Enhanced electrochemical properties of LiFePO4–silicon composites as positive electrode materials fabricated using a solid-state method

LiFePO₄–silicon composites were fabricated by using a solid-state method for applying positive electrodes in lithium ion batteries. The LiFePO₄–silicon composites were characterized with X-ray diffraction and field emission scanning electron microscopy. Their electrochemical properties were investigated with cyclic voltammetry, electrochemical impedance spectroscopy, and charge–discharge tests. The added silicon not only suppressed the surface corrosion caused by the decreasing H⁺ concentration in the electrolyte, but it also acted as a barrier between the LiFePO₄ particles and LiPF₆ electrolyte, thereby preventing the dissolution of Fe²⁺ in the electrode and enhancing the electrolyte/active material interactions. This resulted in improved lithium-ion transfer kinetics and excellent positive electrode performance, especially at high current densities and different operating temperatures (0, 25, and 50 °C). At 25 °C, the LiFePO₄ composite containing 2 wt% of silicon delivered the best electrochemical performance with a lithium-ion diffusion coefficient of 1.81×10⁻⁹ cm² s⁻¹, a specific discharge capacity of 143 mA h g⁻¹ for the initial cycle, and a capacity retention of 98% after 100 cycles. In contrast, the corresponding values for the pure LiFePO₄ were 1.19×10⁻¹¹ cm² s⁻¹, 115 mA h g⁻¹, and a capacity retention of 76% after 100 cycles, respectively.     

Synthesis and characterization of nickel phosphonopropionate hybrid materials

Hydrothermal reaction of nickel acetate with 3-phosphonopropionic acid and 4,4′-bipyridine resulted in two novel phosphonate compounds Ni(HO₃PC₂H₄COO)(4,4′-bpy)(H₂O) · 0.5(4,4′-bpy) (bpy = bipyridine) (I) and Ni(O₃PC₂H₄COOH)(4,4′-bpy)(H₂O)₃ · H₂O (II). Single-crystal X-ray studies reveal that self-assemblies between the ligands and metal ion result in layer (I) and chain (II) structures. Magnetic measurement of I indicate there are ferromagnetic couplings between adjacent Ni²⁺ ions (C = 1.29 cm³ mol⁻¹ K and θ = 2.25 K).     

Sodium borohydride as the hydrogen supplier for proton exchange membrane fuel cell systems

This paper introduces and discusses the latest research on the use of H₂ generated via the NaBH₄ hydrolysis reaction for proton exchange membrane fuel cells (PEMFCs). To realize the NaBH₄–PEMFC system, many hydrolysis catalysts such as Ru/anion-exchange resins, Pt/LiCoO₂, Co powder/Ni foam, PtRu/LiCoO₂ and Ru/carbon have been proposed. Through these efforts, the hydrolysis reaction conversion approached 100%. In addition, the average H₂ generation rate based on most of the reports generally ranged from 0.1 to 2.8 H₂ l min^− 1 g^− 1 (catalyst), which produced a level of PEMFC performance equivalent to 0.1–0.3 kW g^− 1 (catalyst). However, it was also reported that the H₂ generation rate was 28 H₂ l min^− 1 g^− 1 (catalyst) with the catalyst of Pt/carbon (acetylene black).Considering these reports and the advantageous features of NaBH₄ hydrolysis, the NaBH₄–PEMFC system seems to be technologically feasible and would constitute an alternative system of supplying H₂ in fuel cells.However, some challenges remain, such as the deactivation of the catalyst, the treatment of the by-products, and the proper control of the reaction rate. In addition, if the price of NaBH₄ were to be further reduced, this system could become the most powerful competitor in portable application fields of PEMFC.     

Effect of core-shell reversal on the structural,magnetic and adsorptive properties of Fe2O3-GO nanocomposites

Effect of core-shell reversal on the nanocomposites of graphene oxide (GO) and ferric oxide (Fe₂O₃) was studied. Fe₂O₃@GO core-shell nanosheets were synthesized by sonication method, while the GO@Fe₂O₃ core-shell nanospheres by employing N,N′-dicyclohexylcarbodimide as the binding agent for the wrapping of GO sheets on pre-formed Fe₂O₃ nanoparticles (NPs). The phase composition, crystallinity and morphology of the nanocomposites were characterized by FT-IR, TEM, SEM-EDS, VSM, BET surface area study and XRD techniques. The saturation magnetization (M_s) was 1.25 and 0.51 emu g⁻¹ for GO@Fe₂O₃ and Fe₂O₃@GO respectively owing to the dependence of magnetic properties on the reversal of core-shell. BET analysis revealed the surface area of 100.32 m² g⁻¹ and 45.69 m² g⁻¹ for GO@Fe₂O₃ and Fe₂O₃@GO nanocomposites respectively. The fabricated nanocomposites were analyzed as adsorbents for the uptake of Pb (II) ions. The impact of various factors affecting adsorption process such as pH, adsorbent dose, contact time, temperature and metal ion concentration was also investigated. GO@Fe₂O₃ core-shell nanospheres showed a higher adsorption capacity for Pb (II) ions as compared to Fe₂O₃@GO core-shell nanosheet with the maximum adsorption capacities (q_m) of 303.0 and 125.0 mg g⁻¹ respectively. The equilibrium data was estimated by Freundlich, Langmuir, D-R and Temkin isotherm models. Thermodynamic analysis confirmed the spontaneous and exothermic nature of the adsorption process. The adsorption kinetics was significantly fitted to pseudo-second order model. The results confirmed that core-shell reversal can significantly alter the adsorptive properties of Fe₂O₃-GO nanocomposite