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     

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     

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.     

Microwave hydrothermal synthesis of nanoporous cobalt oxides and their gas sensing properties

In this paper, the precursors were synthesized by microwave hydrothermal method using Co(NO₃)₂·6H₂O as raw material, CO(NH₂)₂ and KOH as precipitants, respectively. The precursors and calcined products were characterized by XRD, FESEM, and BET-BJH. The results show that both constituent and synthetic condition can determine the products morphology. When using KOH as precipitant, hollow Co₃O₄ nanorings were obtained whose precursor was synthesized at 140 °C for 3 h and calcined at 500 °C in air for 2 h. While using CO(NH)₂, Co₃O₄ like-nanochains were obtained whose precursor was synthesized at 110 °C for 1 h and calcined at 420 °C in air for 2 h, and Co₃O₄ nanosheets were obtained while their precursor was synthesized at 140 °C for 3 h and calcined at 500 °C in air for 2 h. The sensitivity test of Co₃O₄ to alcohol reveals that the hollow Co₃O₄ nanorings show the best sensitivity, porous Co₃O₄ like-nanochains are superior to that of the porous nanosheets.     

Preparation and characterization of uniform coated particles (Cobalt compounds on cadmium compounds)

Uniformly dispersed particles of CdCO₃ were prepared by homogeneous precipitation from aqueous solutions of cadmium sulphate and urea at the elevated temperatures. These particles were then employed as cores for coating with 2CoCO₃·Co(OH)₂·H₂O from cobalt nitrate and urea solutions at 85°C. In the absence of cores, when heated under similar conditions, the coating solutions produced nearly uniform particles of 2CoCO₃·Co(OH)₂·H₂O. On calcination at 700°C, the core [CdCO₃], coated [CdCO₃/2CoCO₃·3Co(OH)₂], and coating precursor [2CoCO₃·Co(OH)₂·H₂O] particles transformed into CdO, CdO/Co₃O₄, and Co₃O₄, respectively. No sintering occurred during calcination and the particles preserved their morphological features to a significant extent.     

Nanocrystalline LaMnO3 preparation and kinetics of crystallization process

Precursor of nanocrystalline LaMnO₃ was synthesized by solid-state reaction at low heat using La(NO₃)₃·6H₂O, MnSO₄·H₂O, and Na₂CO₃·10H₂O as raw materials. XRD analysis showed that precursor was a mixture containing orthorhombic La₂(CO₃)₃·8H₂O and rhombohedral MnCO₃. When the precursor was calcined at 800 ^°C for 2 h, pure phase LaMnO₃ with rhombohedral structure was obtained. Magnetic characterization indicated that rhombohedral LaMnO₃ behaved weak magnetic properties. The thermal process of the precursor experienced four steps, which involved the dehydration of crystallization water at first, and then decomposition of manganese carbonate into MnO₂, and decomposition of La₂(CO₃)₃ and MnO₂ together into La₂O₂CO₃ and Mn₂O₃, and lastly reaction of monoclinic La₂O₂CO₃ with Mn₂O₃ and formation of rhombohedral LaMnO₃. Based on the Kissinger equation, the value of the activation energy associated with the formation of rhombohedral LaMnO₃ was determined to be 260 kJ mol^?1. The value of the Avrami exponent, n, was equal to 1.68, which suggested that crystallization process of LaMnO₃ was the random nucleation and growth of nuclei reaction.     

Preparation of MnCo2O4 whiskers and spheroids through thermal decomposition of Mn1/3Co2/3C2O4 · 2H2O

The mixed oxalate Mn_1/3Co_2/3C₂O₄ · 2H₂O has been prepared in the form of whiskers 2–5 μm in diameter and up to 50 μm in length and spheroidal nanofiber arrays 20 μm in diameter using two different coprecipitation procedures. Thermal decomposition of this oxalate in air has led to the formation of MnCo₂O₄ particles very similar in morphology to their oxalate precursor. The materials have been characterized by chemical analysis, thermogravimetry, x-ray diffraction. IR spectroscopy, and scanning electron microscopy.     

Ni-doped MnCo2O4 nanoparticles as electrode material for supercapacitors

The Mn_1-xNi_xCo₂O₄ (0.00?≤?x?≤?0.20) nanoparticles were synthesized by a simple PAN-solution route. XRD, TEM, SAED, FESEM, XANES, XPS, and BET techniques were used to investigate the structural and morphology of Ni-doped MnCo₂O₄ nanoparticles. The effect of Ni ions substitution in MnCo₂O₄ nanoparticles on the electrochemical properties was examined on three-electrode systems. The results show that the substitution of Mn with Ni ions can improve the electrochemical properties of MnCo₂O₄ nanoparticles. The Mn_1-xNi_xCo₂O₄ electrode with x?=?0.15 exhibits the highest specific capacitance of 378 F g^?1 at the current density of 1 A g^?1. After 1000 charge-discharges times, this electrode has good capacity retention of 85%. The good capacitance characteristics and cyclic stability indicate that these Mn_1-0.85Ni_0.15Co₂O₄ nanoparticles could be applied as active materials for energy storage devices.