Synthesis Of Cu, Co, Ni Phosphate Functional Materials And Kinetics Of Thermal Process

Phosphate functional materials play an important role in whether production or life, and is still one of the research hot. In this study, NH4CuPO4·H2O and the precursors of LiCoPO4and LiNiPO4are successfully synthesis by solid-state reaction at low heating temperature. Pure LiCoPO4and LiNiPO4are obtained by calcining the precursors, and crystalline Cu2P2O7is the thermal decomposition product of NH4CuPO4·H2O. The precursors and their calcined products are characterized by XRD, TG/DTG/DTA and FTIR. Their morphology features are obtained by SEM. Non-isothermal kinetics of thermal decomposition process and isothermal kinetics of crystallization process are study based on TG/DTG/DTA curves and crystalline. Thermal process of these substance below800degree Celsius are discuss to obtain kinetic parameters Ea, g(a) and A.The experimental results show that NH4CUPO4·H2O is monoclinic crystal with flake structure [space group P21/a(14)], and its calcined product at700degree Celsius is monoclinic Cu2P2O7. Thermal decomposition process of NH4CUPO4·H2O is experience three stage of dehydration, deamination and intramolecular condensation. Stage Ⅰ and Ⅱ of thermal decomposition process of NH4CuPO4·H2O are single-step reaction. The activation energies, pre-exponential factor and mechanisms calculated by isoconversional method for stage Ⅰ and Ⅱ are117.7±7.7kJ·mol-1and167.9±8.4kJ·mol-1,1.24×1011s-1and1.32×1012s-1, random nucleation and subsequent growth, and three dimensional diffusion, respectively. Stage III is multistep reaction process. The experimental results also show that orthorhombic LiCoPO4and LiNiPO4crystal with particle shape [space group Pnma(62)] are obtained by calcining the precursors above400degree Celsius. Thermal decomposition process of the precursors of LiCoPO4and LiNiPO4are divided into two stages to discuss. Stages I of thermal decomposition process of the precursors are single-step reaction. The activation energies, pre-exponential factor and mechanisms calculated by isoconversional method for stages Ⅰ are90.7kJ·mol-1and86.25kJ·mol-1,9.17×109min-1and2.24×1010min-1, two-dimensional diffusion and random nucleation and subsequent growth, respectively. Stages Ⅱ are multistep reaction process, study by distributed activation energy model. Based on the JMA equation, the activation energies of crystallization processes of LiCoPO4and LiNiPO4are51.24kJ·mol-1and47.89kJ·mol-1, respectively. And crystallization mechanisms are random nucleation and subsequent growth. After fitting test, the results suggested that the methods of thermal process kinetics study of these phosphate functional materials are reliably.