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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Size-Dependent Thermodynamic Properties of Two Types of Phase Transitions of Nano-Bi2O3 and Their Differences
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Size-Dependent Thermodynamic Properties of Two Types of Phase Transitions of Nano-Bi2O3 and Their Differences

机译：纳米Bi2O3两种相变的大小依赖性热力学性质及其差异

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摘要

The thermostability of nanomaterials has crucial influences on their performances and applications, but the effect of regularities of particle size on the crystal transition and melting thermodynamics for the same kind of nanoparticles and the relationships of the thermodynamics between the two types of phase transitions are unclear. In this paper, we proposed a core-shell model applied to the crystal transition and melting of nanospheres, and on this basis, the equations of size-dependent thermodynamic properties for crystal transition and melting were deduced. Experimentally, we prepared nano-Bi2O3 with different particle diameters by the hydrothermal method and determined the crystal transition (from phase alpha to delta) and melting behaviors of nano-Bi2O3 by differential scanning calorimetry. The experimental results indicate that the effects of particle size on the two types of phase-transition thermodynamic properties of nano-Bi2O3 are dramatic. We found that the effect of regularities of particle size on the thermodynamic properties of the two types of phase transitions are uniform; with the particle size of nano-Bi2O3 decreasing, the temperatures, enthalpies, and entropies of the phase transitions decrease, the thermodynamic properties are all linearly related to the reciprocal of the particle diameter, and all of the experimental results of the two types of phase transitions are consistent with the theoretical formulas. Surprisingly, we found that the two types of phase transitions are correlative. The differences in temperature and thermodynamic properties of phase transitions between the two types of phase transitions are also size-dependent and linearly related to the reciprocal of the particle diameter. The results are consistent with the theoretical analysis. The theory and size-dependent regularities can provide important references for the preparations, researches, and applications of nano-Bi2O3 and other nanoparticles.
机译：纳米材料的热稳定性对其性能和应用的影响至关重要，但是粒度对晶体过渡和熔化热力学的规则性的影响以及两种类型转变之间的热力学的关系尚不清楚。在本文中，我们提出了一种应用于纳米球的晶体壳模型，在此基础上，推导出晶体转变和熔化的大小依赖热力学性质的方程。通过实验，我们通过水热法制备具有不同粒径的纳米Bi2O3，并确定通过差示扫描量热法测定纳米Bi2O3的晶体转变（来自相α至Delta）和熔化行为。实验结果表明，粒度对纳米Bi2O3两种相转移热力学性质的影响是显着的。我们发现，粒度规律对两种相变的热力学性质的影响是均匀的;随着纳米Bi2O3的粒度减小，期间转变的温度，焓和熵减小，热力学性质全部与粒径的往复式线性相关，以及两种阶段的所有实验结果过渡与理论公式一致。令人惊讶的是，我们发现两种类型的相变是相关的。两种相变之间的相变的温度和热力学性质的差异也与粒径的往复相互依赖和线性相关。结果与理论分析一致。该理论和规模依赖性规则可以为纳米-Bi2O3和其他纳米颗粒的制剂，研究和应用提供重要的参考。

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