Abstract VO2(M) structures with various shapes were synthesized by vacuum annealed VO2 metastable phase, and this metastable phase (VO2(B/D)) were formed by hydrothermal method used H2C2O4 and V2O5 powders as starting reactants. The phase structure, morphology, surface composition and phase transition characteristics of VO2 were characterized by XRD, SEM, XPS and DSC. Obtained results show that the VO2's metastable phase structure and morphology strongly depended on the n-butanol/water ratio, molar ratio of V2O5 and H2C2O4 and molar concentration of V2O5, which leads a different synthesis pathway. The influence mechanism has also been studied. Low n-butanol/water ratio (2:45) and low molar ratio (1:1, 1:2) favor the formation of VO2(B) nanosheets/nanorods while high n-butanol/water ratio (45:2) and high molar concentration (0.22 mol/L) favor the formation of VO2(D) micro/nanospheres. Ultimately, the VO2(M) nanoparticles can be obtained at a relatively low vacuum annealing temperature of 300 °C, and with a lowest TC was as low as 55.43 °C. In addition, the effect of vacuum annealing temperature and morphology on the phase transition characteristic of VO2(M) has also been studied.

中文翻译：

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水热煅烧法相和形状控制合成 VO2

摘要 通过真空退火的 VO2 亚稳态相合成了各种形状的 VO2(M) 结构，并以 H2C2O4 和 V2O5 粉末为起始反应物，通过水热法形成了这种亚稳态相 (VO2(B/D))。通过XRD、SEM、XPS和DSC对VO2的相结构、形貌、表面组成和相变特征进行了表征。所得结果表明，VO2 的亚稳相结构和形态强烈依赖于正丁醇/水比、V2O5 和 H2C2O4 的摩尔比以及 V2O5 的摩尔浓度，这导致了不同的合成途径。也研究了影响机制。低正丁醇/水比 (2:45) 和低摩尔比 (1:1, 1:2) 有利于 VO2(B) 纳米片/纳米棒的形成，而高正丁醇/水比 (45:2) 和高摩尔浓度（0. 22 mol/L) 有利于 VO2(D) 微/纳米球的形成。最终，VO2(M)纳米颗粒可以在相对较低的真空退火温度300°C下获得，最低TC低至55.43°C。此外，还研究了真空退火温度和形貌对VO2(M)相变特性的影响。