Calcination Temperature Of Precursor Research Articles

Separation of valuable metals from low nickel matte to prepare NiCo2O4 materials: Optimization of oxidative leaching process and improvement of electrochemical properties of materials

The economical and efficient utilization of intermediate low nickel matte has become an important goal of nickel smelting industry. In this work, an innovative process of oxidative leaching of valuable metal from low nickel matte to prepare NiCo2O4 materials was proposed based on the materials utilization of mineral. The addition method and speed of ammonium persulfate in the oxidative leaching process was investigated to improve the extraction of valuable metals. The key factors affecting the leaching of valuable metals and the optimum leaching condition were determined by orthogonal experiments, and the extraction of Ni, Cu, and Co was 92.3 %, 97.1 % and 96.6 %, respectively. The leaching mechanism was clarified and the advantages of the leaching process were compared and analyzed. The kinetics of oxidative leaching process was studied by timing sampling method, and the control model, activation energy and kinetic equation of Ni, Cu and Co leaching were determined by analyzing the data with unreactive shrinkage model. The effects of Ni:Co ratio and calcination temperature of precursor on the properties of NiCo2O4 were investigated using the leaching solution removing iron and copper as raw materials. The NiCo2O4 material with the Ni:Co ratio of 1:2 prepared by calcining precursor at 750 ℃ for 3 h has a specific capacitance of 864F/g when the current density is 1 A/g. The prepared NiCo2O4 materials show good capacitance performance and has potential to be used as capacitor electrodes. This work combines metal extraction with product materialization, which is expected to help the metallurgical industry effectively shorten the industrial production process and reduce production costs.

Preparation of NASICON Silico Phosphates of Composition Na1 + xZr2SixP3 – xO12 by Pyrolysis of Solution in Melt

A new method for preparing Na1 + xZr2SixP3 – xO12 (0 x 3) based on pyrolysis of solution containing a mixture of organic components in rosin melt has been proposed. Effect of superstoichiometric amounts of sodium and phosphorus on the phase composition of synthesis products has been proved. It has been found that precursor for the sample of maximal purity of phase composition is prepared at molar ratio Na : Zr : Si : P = (1.15 + x) : 2 : x : (y – x), where y = 3 (1.20 + x)/(1 + x). Precursor calcination temperature is 1000°C. Different NASICON compositions without crystalline admixtures have been obtained in the range 1.5 ≤ x ≤ 2.12. The prepared samples have been studied by X-ray powder diffraction and scanning electron microscopy. The disclosed method of synthesis is promising for the preparation of NASICON as both bulk materials and thin layer coatings.

Effect of Mg doping on the infrared emissivity of ZnO powders at high temperature

Infrared emissivity of semiconductor material determines infrared radiation capability of semiconductor material. In recent years, researchers have focused on the infrared emissivity performance of ZnO at room temperature. The infrared emissivity performance of ZnO at high temperatures is rarely studied. In this paper, Zn1-xMgxO powders were prepared by sol-gel method. The infrared emissivity of powders with different x (x = 0, 0.01, 0.03, 0.05, 0.07) were investigated from room temperature to 800 °C. The composition and calcination temperature of precursors were determined by DSC, and the changes in morphology, particle size, microstructure and phase compositions were studied by SEM, EDS and XRD separately. The changes of infrared emissivity of powders with different Mg doping concentrates from room temperature to 800 °C are explained by dielectric mechanism, conduction mechanism and lattice vibration mechanism, and the varies of infrared emissivity with temperature, which showing a U-shaped curve are also explained by the three mechanisms mentioned above. An effective and convenient method for regulating the infrared emissivity of ZnO is provided in this paper.

Synthesis of nanoV 3.6 Mo 2.4 O 16 and their catalytic activity in the selective oxidation of toluene

Molybdenum vanadate is a novel vanadate. It is a functional material with good magnetic, electrical and catalytic properties. However, it is rarely used in the selective catalytic oxidation field, while the transition metal molybdenum and vanadium are usually used as a catalytic oxidation catalyst, the complex oxide and salt are naturally concerned. The structure of high-quality single crystalline Molybdenum vanadate (V3 .6Mo2.4O16) nanorods was synthesised by sol–gel method and high-temperature solid-state reaction. The effects of vanadium and molybdenum molar ratio and calcination temperature on the preparation of V3.6Mo2.4O16 were studied. The structure of the catalyst was characterised by X-ray diffraction, thermogravimetry, X-ray photoelectron spectroscopy, scanning electron microscope and transmission electron microscope. The experimental results show that the molar ratio of vanadium–molybdenum is 10:7 when the precursor calcination temperature is 540°C, the single crystalline V3.6Mo2.4O16 nanorods with regular shape has been obtained, the diameter of about 200 nm and the length up to tens of micrometres and the surface is smooth. Catalytic oxidation of toluene to benzaldehyde is used as a probe reaction for nanoV3.6Mo2.4O16. The catalytic activity of the catalyst is good, the conversion of toluene is 39.8% and the selectivity of benzaldehyde is 70.1%.

Catalytic Oxidation of Carbon Monoxide on Pd-Containing LaMnO3 Perovskites

The substitution of 0.05 mol La with Pd enhances the activity of the LaMnO3 in CO oxidation. La0.9Pd0.1MnO3 and La0.85Pd0.15MnO3 catalysts exhibit a very high activity, which depends on the conditions of perovskite preparation. Monolithic catalysts display a higher activity during CO oxidation when based on La1−xPdxMnO3 than LaMn1−xPdxO3 perovskites. The activity of the catalysts is determined by the concentration of palladium on the catalyst surface, which increases as the precursor calcination temperature is raised from 650 to 800 °C. The size of the specific surface area of the perovskites has smaller influence on the activity of the catalysts.

Methane gas-sensing and catalytic oxidation activity of SnO2–In2O3 nanocomposites incorporating TiO2

The InO1.5–SnO2 nanocomposites incorporating TiO2 were synthesized by a controlled co-precipitation method as sensing materials of a novel semiconductor CH4 sensor. Through manipulating the total salt concentration, cation ratio, precipitation pH, aging time and calcination temperature, the nanocrystalline composites were successfully derived with chemical homogeneity and superior thermal stability compared to tin oxide. The gas-sensing and catalytic activity for methane oxidation were examined in a micro fixed bed reaction system. The experimental results showed that the nanocomposites exhibited high gas-sensing and catalytic activity, and these performances depended on composition of composites, calcination temperature of precursors and sensor operating temperature. It was found that the sensing behavior was straightforwardly related to the catalytic activity. The sensing and catalytic activity was greatly enhanced by the introduction of metal elements or oxide surface coatings. To guide for the search of better sensor materials or suitable additives, it is necessary to understand the sensing mechanism of the semiconductor oxide gas sensors by temperature-programmed desorption (TPD) study and X-ray photoelectron spectroscopic (XPS) analysis.

Sintering behaviors of bismuth titanate synthesized by a coprecipitation method

Ultrafine bismuth titanate (BiT) powder has been fabricated by a coprecipitation method. It is found that sintering behaviors of BiT strongly depend on the calcination temperature of precursor. The calcination temperature of 450 °C below crystallization is high enough to decompose most of BiT precursor to avoid the cracks in sintered samples, and also low enough to ensure high sinterability, which facilitates the densification of BiT ceramics. Additionally, the crystallization of amorphous powders during the process of sintering also contributes to an enhancement in densification. BiT ceramic with the relative density >95% can be obtained at a temperature as low as 825 °C from the powder calcined at 450 °C.