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中国化学会第十七届全国胶体与界面化学学术会议

作者： Yurong Ma Fenghua Chen School of Chemistry and Chemical Engineering Beijing Institute of Technology College of Chemistry Peking University

Guanine is one of the most widespread organic crystals existing in organisms, which has superior optical properties and exhibits structural colors. The excellent optical properties of biogenic guanine crystals contribute to the exquisite control on the polymorph, morphology, size and highly-ordered hierarchical microstructure assemblies of guanine crystals and cytoplasm. controlled crystallization of guanine crystals with particular polymorphs, morphologies, exposing crystal faces was investigated in both water and organic solvents in the presence of additives. controlled crystallization of guanine monohydrate, anhydrous guanine α and β form in pure phase were realized for the first time under mild conditions in aqueous solution without the presence of additives by changing the guanine concentrations and pH values. Amorphous guanine was synthesized by a one-step synthesis process in large scale, which transformed to anhydrous guanine β form in pure phase. Characterizations using FTIR and ss-NMR showed that anhydrous guanine β and amorphous guanine had similar short-range order structure, which might be the reason for the controlled transformation from amorphous phase to thermodynamically meta-stable anhydrous guanine β form. Anhydrous guanine β form nanoplatelets in pure phase were obtained via amorphous guanine by using polymer additives in organic solvents, which expose（100） face with extremely high refractive index. Guanine analogues had strong influence for the polymorphs and the morphologies of guanine in formamide. Furthermore, a novel crystal phase of anhydrous guanine consisting of N9-G purine ring was obtained by dehydration of guanine monohydrate（GM） at 111 °C, termed as dehydrated-GM, which is the first reported tautomeric polymorph of AG（N7-G purine ring）. The Dehydrated-GM has very good water harvest ability（8 wt%） with a fast rate（ in 30 min） even at relatively low room humidity（below 20 %） and low temperature（40 °C）.

关键词： bioinpired minerlization controlled crystallization guanine amorphous precursor

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Synthesis of LiFePO_4 using FeSO_4·7H_2O byproduct from TiO_2 production as raw material

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Rare Metals 2009年第6期28卷 612-617页

作者： PENG Zhongdong CAO Yanbing ZHOU Yulin HU Guorong School of Metallurgical Science and Engineering Central South University Changsha 410083 China

As the byproduct of TiO2 industrial production, impure FeSO4.7H2O was used for the synthesis of LiFePO4. With the purified solution of FeSO4-7H2O, ***2O was prepared by a normal titration method and a controlled crystallization method, respectively. Then LiFePO4 materials were synthesized by calcining the mixture of FePO4,xH2O, LizCO3, and glucose at 700℃ for 10 h in flowing Ar. The results indicate that the elimination of ***2O impurities reached over 95%, and using FePO4-xH2O prepared by the controlled crystallization method, the obtained LiFePO4 material has fine and sphere-like particles. The material delivers a higher initial discharge specific capacity of 149 mAh.g^-1 at a current density of 0.1C rate （1C = 170 mA.g^-0）; the discharge specific capacity also maintains above 120 rnAh.g^-1 after 100 cycles even at 2C rate. Thus, the employed processing is promising for easy control, low cost of raw material, and high electrochemical performance of the prepared material.

关键词： lithium ion battery cathode material LiFePO4 FePO4 controlled crystallization

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