• Energy Research

Abstract The effect of matrix compound on the behaviour of a silane-zeolite composite coatings on 6061 aluminium alloy was evaluated. It was observed that silane molecules containing long aliphatic chain or reduced hydroxyl groups influenced wettability and mechanical performances of coatings. Silane compounds with long alkyl chain or bi-hydroxyl groups allowed to obtain more adherent and hydrophobic coatings. Furthermore, composite coatings characterised by multi-component silanes mixture (short and long chain molecules) evidenced affordable impact resistance compared to coating made of silanes with aliphatic chain functional groups.

For the thermochemical performance implementation of Mg(OH)2 as a heat storage medium, several hybrid materials have been investigated. For this study, high-performance hybrid materials have been developed by exploiting the authors’ previous findings. Expanded graphite (EG)/carbon nanotubes (CNTs)-Mg(OH)2 hybrid materials have been prepared through Mg(OH)2 deposition-precipitation over functionalized, i.e., oxidized, or un-functionalized EG or CNTs. The heat storage performances of the carbon-based hybrid materials have been investigated through a laboratory-scale experimental simulation of the heat storage/release cycles, carried out by a thermogravimetric apparatus. This study offers a critical evaluation of the thermochemical performances of developed materials through their comparison in terms of heat storage and output capacities per mass and volume unit. It was demonstrated that both EG and CNTs improves the thermochemical performances of the storage medium in terms of reaction rate and conversion with respect to pure Mg(OH)2. With functionalized EG/CNTs-Mg(OH)2, (i) the potential heat storage and output capacities per mass unit of Mg(OH)2 have been completely exploited; and (ii) higher heat storage and output capacities per volume unit were obtained. That means, for technological applications, as smaller volume at equal stored/released heat.

Sustainable development principles aim to re-utilize wastes to reduce their impact on the environment. In this context, the present contribution shows preliminary results on the preparation of innovative synthetic lightweight aggregates, starting from biomass-derived fly ash and high-density polyethylene (HDPE), to be used in geotechnical applications. The present work focuses on the manufacturing process of aggregate blends (including the selection of the right proportions of the two components) as well as on the relative determination of (i) physical–chemical properties (i.e., chemical composition, morphological analysis, mineral leachability, water absorption, specific gravity, grain size distribution); (ii) permeability features and (iii) mechanical properties (one-dimensional compression and shear strength behavior). The results, gathered from the new synthetic lightweight aggregates and compared with the corresponding ones obtained in a previous study conducted on natural and synthetic lightweight aggregates, appear promising for a potential utilization in geotechnical engineering.

Abstract This work reports the results of an experiment study on anti-corrosion coatings obtained by the direct growth of zeolite Y films on aluminium substrates by an amine-modified hydrothermal synthesis. In particular, the effect of the TEA (triethanolamine) presence was evaluated in terms of coating performances by varying synthesis times and drying temperatures. The morphological analysis showed that the films were homogeneous and compact up to 120 μm in thickness. Peel tests confirmed the good adhesive properties of all kinds of investigated coatings. In the end, electrochemical tests, carried out in 3.5% NaCl and in Ca(OH) 2 saturated solution, showed good barrier properties offered by this type of coating. Low drying temperature allowed to keep TEA entrapped in the zeolite structure so that it greatly influenced corrosion protection behaviour.

Abstract Newly developed hybrid materials made of magnesium hydroxide and carbon nanotubes were proposed as heat storage medium for MgO/H2O/Mg(OH)2 chemical heat pumps. Samples were synthesized by deposition-precipitation method varying the Mg(OH)2 load (32–52 wt.%) and the type of carbon nanotubes, pristine or functionalized. The performances of the synthesized materials were evaluated by thermogravimetric analysis, which simulates the chemical heat pump cycle. The presence of the carbonaceous material positively affected the reaction performances, so that the hybrid materials showed improved heat storage/output capacity and faster heat output rate compared to pure Mg(OH)2. The functionalization treatment and a proper Mg(OH)2 load were fundamental to better the dispersibility of Mg(OH)2 into the carbon nanotubes bundles which in turn enhanced the thermochemical performance of the active material, fully exploiting for the first time its maximum potential heat storage capacity, that is ∼1300 kJ/kgMg(OH)2, thus bringing the development of this technology to a level closer to its industrial application.

Nowadays, waste thermal energy represents a huge quantity of energy that, in most cases, is unfortunately dispersed rather than recovered. Although it is well known that its recovery could result in a considerable impact reduction of human activities on the environment, it is still a challenging issue. In view of this, absorption chillers and heat pumps, based on the use of porous materials capable of reversibly adsorbing and desorbing water vapor, can be considered among the preferred systems to recover waste thermal energy, especially at medium–low temperatures. This study deals with the preparation and performance of a new generation of advanced adsorbent materials specifically produced as coatings for water adsorption systems driven by low temperature heat sources (around 150 °C). The proposed coating consists of hybrid SAPO-34/polyacrilonitrile microfibers directly deposited on the surface to be coated by means of the electrospinning technique. Their zeolite morphology and concentrations, as well as their distribution over the polymeric microfibers, were key variables in achieving the best combination of adsorption properties and hydrothermal stability of the coating.

In the present work, the optimization of a new coating formulation was investigated, taking attention to an industrially focused research approach used for the engineering design of the adsorber. The adsorbent was a composite zeolite or silica-gel based coating applied by using new flexible polymer matrices. The FC-80 formulation represents a good compromise between mechanical stability and absorption capacity. Using the developed coating process, a new compact HEX design was developed to reach the AHP target performance with easy and fast manufacturing. The specific cooling power of the coated heat exchanger was estimated to be about 500 W/kg of adsorbent. The new coated HEX was integrated in a new adsorption chiller and has been tested by a laboratory test-rig under realistic operating conditions. Results of preliminary testing demonstrated that the prototype provides a cooling capacity of around 10 kW with a COP of 0.54.