Reaction flash sintering for producing high quality functional ceramics within seconds

For ceramic materials, it has been recently shown in literature that applying a small electric field and a small DC current through a sample produces sudden sintering (within seconds) at relatively low temperatures. This method is known as Flash Sintering and it has been applied to number of materials. In this work it is shown that both chemical reaction and sintering can be combined into a single flash sintering experiments. This new approach is known as Reaction Flash Sintering. To demonstrate the feasibility of this method, a multiferroic material, BiFeO3, is prepared from a stoichiometric mixture of Bi2O3 and Fe2O3 oxides. Thus, in a single process, dense nanostructured BiFeO3 ceramics are obtained by applying an electric field of 50 V cm-1 and with a current limit of 35 mA mm-2 within seconds at a furnace temperature of about 625 °C. The resulting materials were pure-phase perovskites without any evidence of secondary phases, sillenite or mullite, that are commonly present in materials prepared by conventional procedures. Moreover, samples were electrically insulating, as measured by complex impedance spectroscopy. It is shown here that the synthesis of pure single-phase ceramics of complex oxides from stoichiometric mixtures of single oxides is possible by reaction flash sintering, even for materials difficult to prepare by conventional procedures. This discovery is a breakthrough in materials preparation

A national data-based energy modelling to identify optimal heat storage capacity to support heating electrification

Heating decarbonisation through electrification is a difficult challenge due to the considerable increase in peak power demand. This research proposes a novel modelling approach that utilises easily accessible national-level data to identify the required heat storage volume in buildings to decrease peak power demand and maximises carbon reductions associated with electrified heating technologies through smart demand-side response. The approach assesses the optimal shifting of heat pump operation to meet thermal heating demand according to different heat storage capacities in buildings, which are defined in relation to the time (in hours) in which the heating demand can be provided directly from the heat battery, without heat pump operation. Ten scenarios (S) are analysed: two baselines (S1–S2) and eight load shifting strategies (S3–S10) based on hourly and daily demand-side responses. Moreover, they are compared with a reference scenario (S0), with heating currently based on fossil fuels. The approach was demonstrated in two different regions, Spain and the United Kingdom. The optimal heat storage capacity was found on the order of 12 and 24 h of heating demand in both countries, reducing additional power capacity by 30–37% and 40–46%, respectively. However, the environmental benefits of heat storage alternatives were similar to the baseline scenario due to higher energy consumption and marginal power generation based on fossil fuels. It was also found that load shifting capability below 4 h presents limited benefits, reducing additional power capacity by 10% at the national scale. The results highlight the importance of integrated heat storage technologies with the electrification of heat in highly gas-dependent regions. They can mitigate the need for an additional fossil-based dispatchable generation to meet high peak demand. The modelling approach provides a high-level strategy with regional specificity that, due to common datasets, can be easily replicated globally. For reproducibility, the code base and datasets are found on GitHub

Seville history insight through their construction mortars

Seville is intimately linked to its historic role and extensive cultural heritage. The city has been occupied by Romans, Arabs and Christians, who built important historical buildings. Roman (first–second centuries) and Arabic (eleventh century) buildings, medieval Shipyard (thirteenth century), San Isidoro and Santa Maria de las Cuevas monasteries (fifteenth century), Santa María de las Cuevas (fifteenth century modified in eighteenth century), El Salvador Church (eighteenth century), the Royal Ordnance building (eighteenth century) and Santa Angela de la Cruz convent (twentieth century) performed with lining mortars, and mortars used in building stones (City Hall and Marchena Gate), all of them located in Seville (Spain), have been studied. Ninety-four mortar samples (employed as structural, plaster, coating) originally used or applied in restoration processes have been collected to perform an archaeometry study. The ratio of CO2 mass loss to hydraulic water (H2O) mass loss, and the mineralogical characterization by X-ray diffraction has been used to compare the mortars used in the different historical periods. Mainly hydraulic mortars were widely used in all these studied monuments as most mortars showed CO2/H2O ratios within the 4–10 range. Moreover, the thermal analysis curves also showed a broad temperature range for the thermal decomposition of the carbonate fraction of the mortars.Peer reviewe

Supercooled sodium acetate aqueous solution for long-term heat storage to support heating decarbonisation

Heating decarbonisation through electrification requires the development of novel heat batteries. They should be suitable for the specific application and match the operation conditions of domestic renewable energy sources. Supercooled liquids, often considered a drawback of phase change materials, are among the most promising technologies supporting heating decarbonisation. Although some studies have shed light on stable supercooling, the fundamentals and stability remain open problems not always accompanied by relevant experimental investigations. This research critically analyses the physic and chemistry of sodium acetate (SA, NaCH3COO) aqueous solution, a low-cost, non-toxic, and abundant compound with stable supercooling for long-term heat storage. It has an appropriate phase change temperature for high-density heat storage using heat pumps or solar thermal technologies in residential applications. The existing discrepancies in literature are critically discussed through a systematic experimental evaluation, providing novel insights into efficient material design and appropriate boundary conditions for reliable material use in long-term heat batteries. Despite previous studies showing that the thermal reliability and stability of sodium acetate aqueous solution as a supercooled liquid for heat storage cannot be guaranteed, this study demonstrates that through an appropriate encapsulation and sealing method, the peritectic composition of sodium acetate solution (p-SA 58 wt%) can be used as a supercooled liquid for long-term heat storage with a stable melting temperature of 57 °C, appropriate for domestic heat technologies. It is demonstrated that energy storage efficiency can be maintained under cycling, with a constant latent heat storage capacity of 245 kJ/kg and a volumetric storage density of 314 MJ/m3. It was confirmed that the material should achieve a fully-melted state for stable supercooling. Finally, local cooling and retaining seed crystals through high pressure were highlighted as the most suitable basic principles for successful crystallization and heat release. This promising material can store energy for long periods without latent heat losses due to its stable subcooling. Latent heat can be released when required at any selected time and temperature just by a simple activation process

Pressure Effect on the Multicycle Activity of Natural Carbonates and a Ca/Zr Composite for Energy Storage of Concentrated Solar Power

This work is focused on the use of the Calcium-Looping process (CaL) in Concentrated Solar Power (CSP) plants for Thermochemical Energy Storage (TCES). Cheap, abundant and nontoxic natural carbonate minerals, such as limestone and dolomite, can be employed in this application to store energy through the cyclic calcination/carbonation of CaCO₃. In a recent work, a closed CO₂ cycle has been proposed for an efficient CaL-CSP integration in which the CO₂ in excess effluent from the carbonator is used to generate electricity by means of a gas turbine. Process simulations show that the thermoelectric efficiency is enhanced as the carbonator pressure and temperature are increased provided that the multicycle CaO conversion is not affected. On the other hand, the use of just one reactor for both calcination and carbonation has been suggested to reduce capital cost. However, the experimental results shown in the present work indicate that sintering is notably enhanced as the pressure in the reactor is increased. Such an adverse effect is mitigated for a ZrO₂/CaCO₃ composite with a low Zr content as compared to natural carbonates. These results are relevant to process simulations for better assessing the global efficiency of the CaL-CSP integration