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.     

Nanocrystalline Cu0.5Zn0.5Fe2O4: Preparation and Kinetics of Thermal Decomposition of Precursor

Cu_0.5Zn_0.5Fe₂O₄ precursor was synthesized by solid-state reaction at low heat using CuSO₄?5H₂O, ZnSO₄?7H₂O, FeSO₄?7H₂O, and Na₂CO₃?10H₂O as raw materials. The spinel Cu_0.5Zn_0.5Fe₂O₄ was obtained via calcining precursor above 600 ^°C. The precursor and its calcined products were characterized by thermogravimetry and differential thermal analyses (TG/DTA), Fourier transform infrared spectroscopy (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 highly crystallization Cu_0.5Zn_0.5Fe₂O₄ was obtained when the precursor was calcined at 600 ^°C for 2 h. Magnetic characterization indicated that calcined products above 600 ^°C behaved with strong magnetic properties. The kinetics of the thermal decomposition of the precursor was studied using the TG technique. Based on the KAS equation, the values of the activation energy for the thermal decomposition of the precursor were determined.     

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.     

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 High Catalytic Activity Magnetic Fe3O4 Supported Pd Nanocatalyst

This study reports the fabrication and characterization of magnetically recyclable catalysts of Fe₃O₄–Pd nanocomposite as highly effective catalysts for reduction reactions in liquid phase. The characterization of Fe₃O₄–Pd MRCs were done by X-ray powder diffraction, ?nfrared spectroscopy, thermal analyzer, transmission electron spectroscopy, ?nductively coupled plasma, UV-Vis spectroscopy, vibrating sample magnetometer, respectively. The reduction of Pd²⁺ was accomplished with polyethylene glycol 400 (PEG-400) and Fe₃O₄ nanoparticles were prepared by co-precipitation of FeCI₃?6H₂O and FeCl₂?4H₂O. Thus formed Fe₃O₄–Pd MRCs showed a very high activity in reduction reactions of 4-nitro-aniline and 1,3-di-nitrobenzene in liquid phase. Magnetic character of this system allowed recovery and multiple use without significant loss of its catalytic activity.     

Effect of chloride ion on crystalline phase transition of iron oxide produced by ultrasonic spray pyrolysis

Ultrafine spherical Fe₂O₃ powders with controllable morphology and crystal phase were synthesized by ultrasonic spray pyrolysis. In this experiment, we chose three common ferric salts (Fe(NO₃)₃·9H₂O, FeSO₄·7H₂O or FeCl₂·4H₂O) as precursor solution and regulated the concentration of chlorine ion (Cl^?) in precursor solution to produce Fe₂O₃ particles. The morphology, crystal structure and magnetic property of prepared Fe₂O₃ particles were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Vibrating sample magnetometer (VSM). The diameter of the obtained Fe₂O₃ products ranged from 0.2 to 2?μm. And the product obtained from FeCl₂ precursor solution was magnetic, which was composed of hexagonal α-Fe₂O₃ and cubic γ-Fe₂O₃ from XRD results. We also calculated the weight percent of α-Fe₂O₃ and γ-Fe₂O₃ in the product through XRD quantitative analysis. However, with the addition of Cl^? in Fe(NO₃)₃ or FeSO₄ precursor solution, the products turned from non-magnetic to magnetic, whose pure α-Fe₂O₃ phase became to α-Fe₂O₃ and γ-Fe₂O₃ multi-phase. Besides, the weight percent of γ-Fe₂O₃ and the amount of M_s increased with the Cl^? concentration in precursor solution improving. According to the research, it can be inferred that the presence of Cl^? inhibits the phase transition of γ-Fe₂O₃ to α-Fe₂O₃ at high temperature.     

Synthesis of Perovskite Pr1.1MnO3.15 and Phase Evolution and Magnetic Properties

Pr_1.1MnO_3.15 precursor was synthesized by solid-state reaction at low temperatures using Pr(NO₃)₃?6H₂O, MnSO₄?H₂O, and Na₂C₂O₄ as raw materials. Pr_1.1MnO_3.15 was obtained by calcining a precursor, 1.1/2Pr₂(C₂O₄)₃–MnC₂O₄?5.3H₂O, over 1,000 ^°C 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 Pr_1.1MnO_3.15 with an orthorhombic structure was obtained when the precursor was calcined over 1,000 ^°C in air for 2 h. Magnetic characterization indicated that orthorhombic Pr_1.1MnO_3.15 behaved with weak magnetic properties. The thermal transformation of the precursor from ambient temperature to 1,050 ^°C in air presented four steps: the dehydration of 5.3 crystal waters; the reaction of MnC₂O₄ with 0.75O₂ into 1/2Mn₂O₃ and the two CO₂ molecules; the reaction of 1.1/2Pr₂(C₂O₄)₃ with 0.825O₂ into 1.1/2Pr₂O₂CO₃ and of 2.75CO₂ molecules; and the reaction of 1.1/2Pr₂O₂CO₃ with 1/2Mn₂O₃ into Pr_1.1MnO_3.15 and 0.55CO₂     

Giant Magnetic Heat Induction of Magnesium‐Doped γ‐Fe2O3 Superparamagnetic Nanoparticles for Completely Killing Tumors

Magnetic fluid hyperthermia has been recently considered as a Renaissance of cancer treatment modality due to its remarkably low side effects and high treatment efficacy compared to conventional chemotheraphy or radiotheraphy. However, insufficient AC induction heating power at a biological safe range of AC magnetic field (H_appl·f_appl < 3.0–5.0 × 10⁹ A m^?1 s^?1), and highly required biocompatibility of superparamagnetic nanoparticle (SPNP) hyperthermia agents are still remained as critical challenges for successful clinical hyperthermia applications. Here, newly developed highly biocompatible magnesium shallow doped γ‐Fe₂O₃ (Mg_0.13‐γFe₂O₃) SPNPs with exceptionally high intrinsic loss power (ILP) in a range of 14 nH m² kg^?1, which is an ≈100 times higher than that of commercial Fe₃O₄ (Feridex, ILP = 0.15 nH m² kg^?1) at H_appl·f_appl = 1.23 × 10⁹ A m^?1 s^?1 are reported. The significantly enhanced heat induction characteristics of Mg_0.13‐γFe₂O₃ are primarily due to the dramatically enhanced out‐of‐phase magnetic susceptibility and magnetically tailored AC/DC magnetic softness resulted from the systematically controlled Mg²⁺ cations distribution and concentrations in octahedral site Fe vacancies of γ‐Fe₂O₃ instead of well‐known Fe₃O₄ SPNPs. In vitro and in vivo magnetic hyperthermia studies using Mg_0.13‐γFe₂O₃ nanofluids are conducted to estimate bioavailability and biofeasibility. Mg_0.13‐γFe₂O₃ nanofluids show promising hyperthermia effects to completely kill the tumors.     

Gas-liquid detonation synthesis of CNTs@Fe/Fe3C composites and their application as electrode materials for double-layer capacitors

Abstract

The carbon nanotubes doping with Fe and Fe₃C nanocrystal (CNTs@Fe/Fe₃C) are successfully synthesized by the gas-liquid detonation (GLD) decomposition of CH₄, O₂, C₁₀H₁₀Fe and C₁₀H₈. The composition and structural properties of the as-obtained composites were investigated by XRD, TEM, XPS and Raman spectroscopy. The obtained composites were also applied to the electric double-layer capacitor. The results showed that the specific capacitance of CNTs@Fe/Fe₃C can reach 125?F·g^?1 at the current density of 100?mA·g^?1 and after 10000 cycles the capacitance retention is 93.1% at a current density of 2?A·g^?1.     

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.