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A new adsorbent coating for the adsorber unit of an adsorption heat pump made of hybrid, organic-inorganic microfibres was prepared and characterized. Different coatings were obtained by the electrospinning of polyvinylpyrrolidone (PVP) solutions added with different quantities of tetraethyl orthosilicate (TEOS). PVP is a polymer with water adsorption capability and the TEOS addition allowed to increase the thermal stability of microfibres. The aim, indeed, was to preserve the polymeric structure of microfibres in order to obtain coatings with high flexibility and mechanical strength. The results demonstrated that TEOS concentrations in the range of 5-13 wt.% produced microfibre coatings of non-woven textile structure with both good water affinity and good thermal stability. SEM images of coatings showed that the deposited microfibre layers have both a high surface area and a high permeability representing a significant advantage in adsorption systems.Coatings 2019, 9, 443 2 of 12 and silica tetrahedra that form a crystalline nanoporous structure with hydrophilic behavior [14,15]. Although zeolites are the ideal adsorbing solid for the elevated thermal stability, their use in adsorption systems is limited by the high regeneration temperatures. The desorption of water vapor from the zeolite porosity requires temperatures above 300 • C for the complete material dehydration [16,17]. The ideal exploitation of this technology, indeed, is the coupling with low temperature heat sources (T < 150 • C), like solar thermal panels or waste combustion fumes [11,18]. For such a reason, other adsorbing materials have been proposed and sometimes used in solid sorption applications, like silica gel, alumino-phosphour zeotypes (AlPO and SAPO), and metalorganic frameworks (MOF). AlPO and SAPO are interesting for their high adsorption capacity, their good structural stability, and low regeneration temperatures but they are difficult to find on the market and costly [19,20]. MOF are new adsorbing materials with large water capacity and low regeneration temperatures, but their structural stability is still an open issue and they are expensive and difficult to find in large quantities [21,22]. Among others, silica gel is the adsorbent most used in commercial adsorption chillers mainly for its low cost and large availability on the market although it shows a lower water adsorption capacity and problems of morphological and thermal stability [22][23][24][25].Over the years, the scientific community has focused not only on the development of the porous material but also on the engineering of the absorber, the heat exchanger module where the adsorbent material is located. In order to reduce heat transfer resistances, the porous material distribution around the heat exchanger surfaces is very important. Zeolites and silica gel are generally used in form of granules or powder and the simplest and most used solution is to fill the free space between the fins of the heat exchanger with the adsorbent granules. In this case, however, the poor co...

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To investigate the transition mechanisms of forsterite from a glassy to molten state, we performed molecular dynamics calculations in a temperature range of 10–3000 K. The results show that the thermal expansion coefficient changes remarkably at around 1567 K during heating from 10 K. This temperature is the transition point from glassy to liquid states. To investigate the mechanisms of the phase transition, shear viscosity and self-diffusion processes of atoms were analyzed. The result shows that the increasing rates of diffusion coefficients with heating change at around 1300 and 1800 K. This suggests that a diffusion mechanism changes in the supercooled liquid state. From the observation of the trajectories of atoms, it was found that atoms migrate through discontinuous hopping in the supercooled liquid matrices. The hopping probability of atoms, which is located in positions with higher Si and lower Mg densities, is higher than the average probability at low temperatures. The result indicates a dynamical correlation between the hops of atoms in the supercooled liquid state, while Brownian motion is the main mechanism of diffusion in the liquid phase at temperatures above the melting point. The mechanism of the glass–liquid transition of forsterite is important for understanding the evolution process of minerals in space.