Leonardi E, Floris A, Bose S, D'Aguanno B
CRS4, PST, Pula 09010, Italy.
School of Chemistry, University of Lincoln, Brayford Pool, LN6 7TS Lincoln, United Kingdom.
ACS Nano. 2021 Jan 26;15(1):563-574. doi: 10.1021/acsnano.0c05892. Epub 2020 Dec 21.
The specific heat behavior in bulk nanomaterials (NMs) obtained by adding nanoparticles to pure suspending media has attracted a lot interest in recent years. Controversial results about NMs specific heat () have been reported in the literature, where nanoparticles (NPs) of different sizes and materials were suspended in solid and liquid salts at different concentrations and temperatures. However, a unified picture explaining the enhancements and diminutions by adding NPs to pure salts is still missing. In this work, we present a general theoretical thermostatic model aimed at describing the behavior in two-component ionic bulk nanomaterials containing NPs. The model, designed to work in the dilute regime, divides the NM in three regions: bulk suspending medium (SM), nanoparticles, and interface regions. It includes the effects of temperature, NP size, and NP concentration (mass fraction), allowing us to calculate variations with respect to the pure SM and the ideal NM (where NP and SM are assumed to not interact). We then use the model to interpret results of our classical molecular dynamics simulations, which we perform in the solid and liquid phases of NMs representative of three different classes, defined according to the atomic interactions at the interface. The analysis reveals nontrivial and competing effects influencing , such as system-dependent atomic rearrangements at the interface, vibrations of the NP as a whole and variations coming from the individual NP and SM specific heats. Our study contributes to the interpretation of past controversial results and helps in designing NMs with improved thermal properties, which is highly relevant for industrial applications in thermal energy storage and renewable energy production.
近年来，通过向纯悬浮介质中添加纳米颗粒获得的块状纳米材料（NMs）的比热行为引起了广泛关注。文献中报道了关于纳米材料比热（）的有争议的结果，其中不同尺寸和材料的纳米颗粒（NPs）以不同浓度和温度悬浮在固体和液体盐中。然而，仍然缺少一个统一的图景来解释通过向纯盐中添加纳米颗粒导致的比热增强和降低。在这项工作中，我们提出了一个通用的理论恒温模型，旨在描述含有纳米颗粒的双组分离子块状纳米材料中的比热行为。该模型设计用于稀溶液体系，将纳米材料分为三个区域：块状悬浮介质（SM）、纳米颗粒和界面区域。它包括温度、纳米颗粒尺寸和纳米颗粒浓度（质量分数）的影响，使我们能够计算相对于纯悬浮介质和理想纳米材料（假设纳米颗粒和悬浮介质不相互作用）的比热变化。然后，我们使用该模型来解释我们的经典分子动力学模拟结果，这些模拟是在代表三种不同类别的纳米材料的固相和液相中进行的，这三种类别是根据界面处的原子相互作用定义的。分析揭示了影响比热的复杂且相互竞争的效应，例如界面处依赖于体系的原子重排、纳米颗粒整体的振动以及来自单个纳米颗粒和悬浮介质比热的变化。我们的研究有助于解释过去有争议的结果，并有助于设计具有改进热性能的纳米材料，这对于热能存储和可再生能源生产中的工业应用高度相关。
