Reversible and irreversible colossal barocaloric effects in plastic crystals
Reversible and irreversible colossal barocaloric effects in plastic crystals
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DOI：
10.1039/c9ta10947a
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发表时间：
2020-01-14
影响因子：
11.9
通讯作者：
Tamarit, Josep-Lluis
中科院分区：
文献类型：
--
作者：
Aznar, Araceli;Lloveras, Pol;Tamarit, Josep-Lluis
在涉及到强分子取向无序的相变中，极大的潜热交换导致了塑料晶体作为一种可行的固态压热环保制冷技术的解决方案的提议。本文测定了四种新戊烷[C(CH3)(4)]：(NH2)C(CH2OH)(3)(简称Tris)、(NH2)(CH3)C(CH2OH)(2)(AMP)、(CH3)C(CH2OH)(3)(PG)和(CH3)(3)C(CH2OH)(NPA)的可逆压热响应。所有这些材料在有序塑性相变时都表现出巨大的熵变化，这是竞争压力热材料的基本要求。然而，我们指出，同样重要的是，验证使用压力也可以实现大的大气压效应，虽然压力适中，但足够大，以克服依赖于压力的滞后。根据这个量，用准直接法，我们确定了每种化合物实现可逆大气压效应所需的最小压力p(Rev)。具体地说，我们发现PG和NPA的p(Rev)分别较小和中等，因此显示出与当前冰箱中使用的有害流体相当的巨大可逆大气压效应，从而证实了塑料晶体作为优秀替代品的潜力。相反，在Tris和AMP中，所获得的p(Rev)过大，从而产生可用于循环应用的可逆的高压热效应。
The extremely large latent heat exchanged in phase transitions involving strong molecular orientational disordering has recently led to the proposal of plastic crystals as a feasible solution for solid-state barocaloric eco-friendly cooling technologies. Here we determine the reversible barocaloric response of four plastic crystals derived from neopentane [C(CH3)(4)]: (NH2)C(CH2OH)(3) (TRIS for short), (NH2)(CH3)C(CH2OH)(2) (AMP), (CH3)C(CH2OH)(3) (PG) and (CH3)(3)C(CH2OH) (NPA). All of them display colossal entropy changes at their ordered-plastic phase transition, which is a primal requirement for competitive barocaloric materials. However, we show that it is also important to verify that the large barocaloric effects can be achieved using pressures that, while being moderate, are large enough to overcome the pressure-dependent hysteresis. From this quantity and using the quasi-direct method, we determine the minimum pressure needed to achieve reversible barocaloric effects, p(rev), for each compound. Specifically, we find a small and moderate p(rev) for PG and NPA, respectively, which therefore display colossal reversible barocaloric effects comparable to harmful fluids used in current refrigerators and thus confirm the potential of plastic crystals as excellent alternatives. Instead, in TRIS and AMP, the obtained p(rev) is excessive to yield reversible barocaloric effects useful for cyclic applications.