Preparation And Properties Of Ultrafine Zinc Phosphate Powder

In the thesis, ultrafine zinc phosphate powder was synthesized by hydrothermal method. The structure and morphology of the products were identified by XRD, FTIR, TG/DTG and SEM. The effect of reaction conditions on the structure, particle size and morphology of the products were discussed, and the optimum process prepared by the good dispersion of ultrafine zinc phosphate anti-corrosion pigment was found. Meanwhile, ultrafine CaZn2(PO4)2 powder was synthesized by adding new cationic calcium. Based on the orthogonal experiment, the effects of the ratio of reactants, reaction temperature and reactant time on the particle size and morphology were studied to choose the best synthesis conditions, the reaction mechanism and the dehydrate process were analyzed by XRD and TG. Finally, the ultrafine Zn3(PO4)2 and CaZn2(PO4)2 were used to waterborne epoxy corrosion paint and the corrosion performance was evaluated. The obtained rules were as follows:1. Study on the synthesis of the ultrafine Zn3(PO4)2·4H2O:ultrafine Zn3(PO4)2 powder was prepared by hydrothermal reaction of ZnSO4·H2O and Na2HPO4, it was found that reactant temperature, reactant time and the types of surfactants was the significant effect of the morphology and structure. Zinc phosphate with the different content of crystal water was obtained in different drying temperatures, when the drying temperatures is 60℃, zinc phosphate with four crystal water was analyzed by FTIR, three dehydrate process was identified by TG/DTG, and the total loss weight was the same of theoretical four water weight, the structure of the product is Zn3 (PO4)2·4H2O.2. The effect of the addition of ammonia to control reaction PH on the product yield was studied, the result shows the product yield gradually increase with the growth of ammonia content, and the by-product ammonium zinc phosphate was generated, the reaction PH to 7.9 is relatively appropriate.3. Study on the synthesis of the ultrafine CaZn2(PO4)2:the significant factor which affects the average particle size are ascertained in three factor:the molar ratio of n(Ca):n(Zn), reaction temperature and reactant time. The analysis results show the biggest impact is water hot temperature, the second is the reaction time, and the minimum is the molar ratio. By SEM analysis, the molar ratio of reactant n(Ca):n(Zn) is 1:2, the impurities of product is almost non-existent. The optimum reaction conditions by orthogonal test are as follows:n(Ca):n(Zn) is 1:2, the temperatures is 80℃, the reaction time is 8h.4. The reaction mechanism showed that the ultrafine Ca[Zn(OH)3]2·2H2O was prepared using the media Ca[Zn(OH)3]2·2H2O and phosphoric acid by the hydrothermal method. By TG analysis, CaZn2(PO4)2·2H2O decomposed to CaZn2(PO4)2 by two dehydration reactions, the first stage of dehydration temperature was from 95℃to 393℃, and the second stage of dehydration temperature was from 403℃to 553℃.5. The ultrafine Zn3(PO4)2 and CaZn2(PO4)2 was applied to waterborne epoxy corrosion paint, the physical properties and corrosion properties were also studied. The electrochemical measurement shows that the maximum of electrochemical impedance of coating was emerged, the corresponding contents of zinc phosphate was 15%(wt).The corrosion mechanism showed that the insoluble complex formed between Zn2+ and epoxy resin inhibited the cathode electrochemical reaction, and protected the metal matrix.