INFLUENCE OF TECHNOLOGICAL PARAMETERS ON THE CHEMICAL COMPOSITION OF CALCIUM POLYPHOSPHATES FROM PHOSPHORITES CENTRAL KYZYLKUM

The aim of the research was to study the effect of temperature, the ratio of P2O5EPA:P2O5PRM and the duration of calcination on the content of various forms of P2O5 in calcium polyphosphate. The effect of calcination temperature from 150 to 300 °C, the ratio of P2O5EPA:P2O5FRM from 2,15 to 4,50 and the duration of the process from 20 to 120 minutes on the changes in various forms of P2O5 were studied. It was shown that with increasing temperature to 200-250 °C the content of the total (ortho + poly) assimilable form of Р2О5 increases and then decreases, passing through a maximum. The content of assimilable orthophosphates with an increase in the calcination temperature first sharply decreases to a temperature of 200 °C, and then more smoothly changes at temperatures from 200 °C to 300 °C. The content of assimilable polyforms P2O5 is increased independently of the ratio of P2O5EPA: P2O5PRM to a temperature of 200 °C. With a further increase in temperature in calcium polyphosphate with a ratio of P2O5EPA:P2O5PRM equaled to 2,15, the content of the P2O5 poly decreases by 5%, and at higher ratios P2O5EPA:P2O5PRM increases by 5-10% compared to a temperature of 200 °C. Upon reaching a temperature of 300 °C, the content of the P2O5 polyforms decreases on average by 10-20%, independently of the ratio of P2O5EPA:P2O5PRM. With an increase in the calcination duration from 20 to 40 minutes at temperatures of 200 and 240 °C, the content of the total assimilable form of P2O5 significantly increases. A further increase in the duration of calcination does not lead to a significant increase in the assimilable form of P2O5 as at a temperature of 260 °C. The content of the water-soluble form of P2O5 varies from 6,80-17,52% to 24,30-43,43%, regardless of the temperature and duration of calcination of 20-120 minutes

Suppression of abnormal grain growth in K0.5Na0.5NbO3: phase transitions and compatibility

This work presents the suppression of abnormal grain growth in bulk ceramic K0.5Na0.5NbO3 (KNN). The suppression is enabled by precise control of the starting powder morphology through match of milling and calcination duration. A comparative temperature-dependent analysis of the resulting sample morphology, phase transitions and related electronic material properties reveals that abnormal grain growth is indeed a major influence in material property deterioration, as has theoretically been suggested in other works. However, it is shown that this abnormal grain growth originates from the calcined powder and not from sintering and that all subsequent steps mirror the initial powder morphology. In specific, the results are discussed with respect to the predictions of the compatibility theory and microstructure. Despite the material’s multi-scale heterogeneity, the suppression of abnormal grain growth allows for the achievement of significantly improved functional properties and it is reported that this development is correctly predicted by the compatibility theory within the borders of microstructural integrity. It could be demonstrated that functional fatigue is strongly minimised, while thermal and electronic properties are improved when abnormal grain growth is suppressed by powder morphology control.

Optimization of Cu/TiO2 Preparation Variables Using Response Surface Method for Photodegradation of Diisopropanolamine

The Cu/TiO2photocatalyst preparation variables namely Cu loading, calcination temperature and calcination duration were optimized using response surface methodology. A set of experiments were conducted to obtain the response data which was then analyzed using Design Expert software. The analysis of variance revealed that COD removal from aqueous DIPA solution fitted a quadratic polynomial model with high coefficient of determination (R2= 0.99). The Cu loading was found to be the most significant variable, which then followed by calcination time and the least significant variable was calcination temperature. The optimum condition for the preparation of Cu/TiO2photocatalyst for photodegradation of aqueous diisopropanolamine solution was observed at 1.8 wt% Cu loading calcined at 425 °C for 1.0 h. At the optimum condition, 61.15 % of COD removal was achieved. The optimum conditions of the current study will be used for kinetic study.

Study on Calcination Process of Serpentine Mixed with Ammonium Sulfate

The research involves the calcination of QingHaiQiLian serpentine with ammonium sulfate in order to extract magnesium, and evaluates calcination results through the mass of water leaching residue that comes from the calcination, dissolution and filtration process. Optimal calcination parameters of serpentine and ammonium sulfate determined by orthogonal experiments, single-factor experiments, elemental analysis and SEM analysis are: calcination duration of 1h, calcination temperature of 700°C, ammonium sulfate dosage of 90g (or mass ratio of ammonium sulfate to serpentine sample (m1/m2) of 3:2), under which condition a magnesium extraction rate of 62.75% can be achieved.

Effect of Different Calcination Duration on Physicochemical Properties of Vanadium Phosphate Catalysts

Vanadium phosphate catalysts have been prepared by calcining VOHPO44·0.5H2O which were prepared via two methods i.e. organic (VPO method) and dihydrate (VPD method) routes for different duration under anaerobic atmosphere. Increasing the calcinations duration led to a decrease in total surface area. It is also promote the formation of V5+phase in the catalysts. Scanning electron microscopy clearly revealed that the morphologies of all catalysts composed of plate-like crystallites that were arranged into the characteristic of rosette cluster. However, by increasing the pretreatment duration in an inert environment, the rosette-shape of the clusters which normally obtained in reaction condition was collapsed. Prolong the duration of N2calcination also resulted in an increment in the amount of oxygen desorbed (from O2-TPD) and removed (obtained from H2-TPR).