Preparation of Magnetic Cu0.5Mg0.5Fe2O4 Nanoparticles and Kinetics of Thermal Process of Precursor

Cu_0.5Mg_0.5Fe₂O₄ precursor was synthesized by solid-state reaction at low heat using CuSO₄?5H₂O, MgSO₄?6H₂O, FeSO₄?7H₂O, and Na₂C₂O₄ as raw materials. The spinel Cu_0.5Mg_0.5Fe₂O₄ was obtained via calcining precursor above 300?°C in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry (TG/DSC), Fourier transform FT-IR, X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), and vibrating sample magnetometer (VSM). The result showed that Cu_0.5Mg_0.5Fe₂O₄ obtained at 600?°C had a saturation magnetization of 36.8?emu?g^?1. The thermal process of Cu_0.5Mg_0.5Fe₂O₄ precursor experienced two steps, which involved the dehydration of the five and a half crystal water molecules at first, and then decomposition of Cu_0.5Mg_0.5Fe₂(C₂O₄)₃ into crystalline Cu_0.5Mg_0.5Fe₂O₄ in air. Based on the Kissinger equation, the values of the activation energy associated with the thermal process of the precursor were determined to be 85 and 152?kJ?mol^?1 for the first and second thermal process steps, respectively.     

Magnetic Nanocrystalline Mg0.5Zn0.5Fe2O4: Preparation, Morphology Evolution, and Kinetics of Thermal Decomposition of Precursor

Mg_0.5Zn_0.5Fe₂(C₂O₄)₃?H₂O was synthesized by solid-state reaction at low heating temperatures using MgSO₄?7H₂O, ZnSO₄?7H₂O, FeSO₄?7H₂O, and Na₂C₂O₄ as raw materials. The spinel Mg_0.5Zn_0.5Fe₂O₄ was obtained via calcining Mg_0.5Zn_0.5Fe₂(C₂O₄)₃?H₂O above 400 °C for 1 h in air. The Mg_0.5Zn_0.5Fe₂(C₂O₄)₃?H₂O and its calcined products were characterized by thermogravimetry and differential scanning calorimetry (TG/DSC), Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). The results showed that Mg_0.5Zn_0.5Fe₂O₄ obtained at 400 °C had a specific saturation magnetization of 27.3 emu?g^?1. The thermal process of Mg_0.5Zn_0.5Fe₂(C₂O₄)₃?H₂O experienced three steps, which are: first, the dehydration of water of crystallization and decomposition of Mg_0.5Zn_0.5C₂O₄ into MgO and ZnO, then the reaction of Fe₂(C₂O₄)₃ with MgO and ZnO into amorphous Mg_0.5Zn_0.5Fe₂O₄, and at last the crystallization of Mg_0.5Zn_0.5Fe₂O₄. Based on the KAS equation and the OFW equation, the values of the activation energies associated with the thermal process of Mg_0.5Zn_0.5Fe₂(C₂O₄)₃?H₂O were determined to be 69±11 and 71±9 kJ?mol^?1 for the first and second thermal process steps, respectively.     

Magnetic Properties of Cu0.48Ni0.52Fe2O4 and Thermal Process of Precursor

The spinel Cu_0.48Ni_0.52Fe₂O₄ was synthesized by calcining Cu_0.48Ni_0.52Fe₂(C₂O₄)₃?5H₂O above 300 °C in air for 1.5 h. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, FT-IR, X-ray powder diffraction, and vibrating sample magnetometer. The result showed that magnetic properties of Cu_0.48Ni_0.52Fe₂O₄ were influenced by calcination temperature, and Cu_0.48Ni_0.52Fe₂O₄ obtained at 600 °C had a specific saturation magnetization of 40.0 emu?g^?1. The thermal process of Cu_0.48Ni_0.52Fe₂(C₂O₄)₃?5H₂O below 450 °C experienced two steps which involved, at first, the dehydration of the five crystal water molecules, then decomposition of Cu_0.48Ni_0.52Fe₂(C₂O₄)₃ into cubic Cu_0.48Ni_0.52Fe₂O₄ in air. In the DTG curve, two DTG peaks indicated that precursor experienced mass loss of two steps.     

Synthesis of Spinel MnCo2O4 by Thermal Decomposition of Carbonates and Kinetics of Thermal Decomposition of Precursor

The cubic MnCo₂O₄ was prepared by calcining MnCO₃-2CoCO₃?1.5H₂O above 600 ^°C in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy, and vibrating sample magnetometer. The result showed that high-crystallized MnCo₂O₄ with cubic structure [space group Fd-3m(227)] was obtained when the precursor was calcined above 600 ^°C in air for 6 h. Magnetic characterization indicated that cubic MnCo₂O₄ behaved weak magnetic behavior at room temperature. The thermal process of the precursor in air experienced three steps, which are: first, the dehydration of 1.5 water molecules, then the decomposition of MnCO₃-2CoCO₃ into cubic MnO₂ and cubic Co₃O₄, and at last the reaction of MnO₂ with Co₃O₄ into cubic MnCo₂O₄. Based on the KAS equation, the values of the activation energies associated with the thermal process of MnCO₃-2CoCO₃?1.5H₂O were determined.     

Co0.5Mn0.5La x Fe 2−x O4 Magnetic Particles: Preparation and Kinetics Research of Thermal Transformationof the Precursor

Co_0.5Mn_0.5La _x Fe_2?x O₄ precursor was synthesized by solid-state reaction at low temperatures using CoSO₄ ?7H₂O, MnSO₄ ?H₂O, FeSO₄ ?7H₂O, La(NO ₃)₃ ?6H₂O, and Na₂ CO ₃ ?10H₂O as raw materials. Co_0.5Mn_0.5La _x Fe_2?x O₄ was obtained by calcining carbonates precursor in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, X-ray powder diffraction, scanning electron microscopy, and vibrating sample magnetometer. A high-crystallized Co_0.5Mn_0.5La _x Fe _2?x O₄ with a cubic structure was obtained when the precursor was calcined at 700 °C in air for 2 h. The specific saturation magnetizations and coercivity of Co_0.5Mn_0.5La _x Fe_2?x O₄ depend on the calcination temperature and composition. The thermal transformation of Co_0.5Mn_0.5CO₃–Fe₂O₃?0.967H₂O from 700 °C in air presented two steps. The values of the activation energies associated with the thermal transformation of Mn_0.5Co_0.5CO₃–Fe₂O₃?0.967H₂O were determined based on the Kissinger–Akahira–Sunose (KAS) equation     

Synthesis and characterization of novel ferromagnetic PPy-based nanocomposite

Polypyrrole(PPy)/Zn_0.5Cu_0.5Fe₂O₄ nanocomposite was prepared by a simple, general and inexpensive in situ polymerization of pyrrole in the presence of Zn_0.5Cu_0.5Fe₂O₄ nanoparticles in w/o microemulsion. The effects of PPy coating on the magnetic properties of Zn_0.5Cu_0.5Fe₂O₄ were investigated. By means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectra, scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) technique, the microstructure and magnetic property of samples were characterized. The SEM analysis indicated that PPy was deposited on the porous surface of Zn_0.5Cu_0.5Fe₂O₄. The results were shown that the magnetic parameters such as saturation magnetization and coercivity of Zn_0.5Cu_0.5Fe₂O₄ decreased upon PPy coating.     

Cellulose-precursor synthesis of nanocrystalline Co0.5Cu0.5Fe2O4 spinel ferrites

Nanocrystalline Cu_0.5Co_0.5Fe₂O₄ powders were prepared via a metal-cellulose precursor synthetic route. Cellulose was used as a fuel and a dispersing agent. The resulting precursors were calcined in the temperature range of 450–600 °C. The phase development of the samples was determined by using Fourier transform infrared (FT-IR) spectroscopy and powder X-ray diffraction (XRD). The field-dependent magnetizations of the nanopowders were measured by vibrating sample magnetometer (VSM). All XRD patterns are of a spinel ferrite with cubic symmetry. Microstructure of the ferrites showed irregular shapes and uniform particles with agglomeration. From XRD data, the crystallite sizes are in range of 16–42 nm. Saturation magnetization and coercivity increased with increasing calcining temperature due to enhancement of crystallinity and reduction of oxygen vacancies.     

Nanocrystalline LaFeO3 preparation and thermal process of precursor

Nanocrystalline LaFeO₃ was synthesized by calcining precursor La₂(CO₃)₂(OH)₂–Fe₂O₃?1.5H₂O in air. XRD analysis showed that precursor dried at 80 °C was a mixture containing orthorhombic La₂(CO₃)₂(OH)₂ and amorphous Fe₂O₃?1.5H₂O. Orthorhombic LaFeO₃ with highly crystallization was obtained when La₂(CO₃)₂(OH)₂–Fe₂O₃?1.5H₂O was calcined at 900 °C in air for 2 h. Magnetic characterization indicated that the calcined product at 900 °C behaved weak magnetic behavior at room temperature. The thermal process of La₂(CO₃)₂(OH)₂–Fe₂O₃?1.5H₂O experienced five steps, which involves, at first, dehydration of 0.8 absorption water, then dehydration of 0.7 crystal water, decomposition of orthorhombic La₂(CO₃)₂(OH)₂ into orthorhombic LaCO₃OH, reaction of two LaCO₃OH into hexagonal La₂O₂CO₃ and crystallization of tetragonal Fe₂O₃, at last, reaction of hexagonal La₂O₂CO₃ with tetragonal Fe₂O₃ into orthorhombic LaFeO₃. In the DTG curve, four DTG peaks indicated the precursor experienced mass loss of four steps.     

Synthesis of nanocrystalline Ni0.5Zn0.5Fe2O4 ferrite and study of its magnetic behavior at different temperatures

Ni_0.5Zn_0.5Fe₂O₄ ferrite nanocrystals with average diameter in the range of 1–2 nm have been synthesized by reverse microemulsion. X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) are used to characterize the structural, morphological and magnetic properties. X-ray analysis showed that the nanocrystals possess cubic spinel structure. The absence of hysteresis, negligible remanence and coercivity at 300 K indicate the superparamagnetic character and single domain in the nanocrystalline Ni_0.5Zn_0.5Fe₂O₄ ferrite materials. The nanocrystalline Ni_0.5Zn_0.5Fe₂O₄ ferrite were annealed at 600 °C. As a result of heat treatment the average particle size increases from 2 nm to 5 nm and the corresponding magnetization values have increased to 21.69 emu/g at 300 K. However, at low temperature of 100 K, the annealed samples show hysteresis loop which is the characteristic of a superparamagnetic to ferromagnetic transition. In addition, a comparative study of the magnetic properties of Ni_0.5Zn_0.5Fe₂O₄ ferrite nanocrystals obtained from reverse microemulsion has been carried out with those obtained from the general chemical co-precipitation route.     

Magnetically separable Zn1-xCuxFe2O4 (0 ≤ x ≤ 0.5) nanocatalysts for the transesterification of waste cooking oil

Copper doped zinc ferrite Zn_1-xCu_xFe₂O₄ (0 ≤ x ≤ 0.5) spinels were synthesized via sonication assisted microwave method. The prepared nanoparticles were characterized by XRD, FTIR, HR-SEM, EDX, DRS and VSM analysis. Average crystallite size were in range 5.84 nm to 8.55 nm. FTIR results reveal, bands at 420 cm⁻¹ (Zn²⁺O²⁻) and 547 cm⁻¹ (Fe³⁺O²⁻) confirming tetrahedral and octahedral positions of the spinel structure formation. All the samples showed ferromagnetic behavior at room temperature. The Zn_0.5Cu_0.5Fe₂O₄ sample showed high saturation magnetization (M_s = 74.09 emu/g) and high magnetic moment (3.0 μ_B). The prepared magnetic nano spinels were subsequently employed to evaluate the catalytic activity for biodiesel production. The transesterification process followed pseudo first order rate kinetic model. An excellent catalytic activity for biodiesel production was acheived (98.9%) and the catalyst was recoverable quickly using an external magnet.