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The cost of materials is one of main obstacles for the development of thermochemical energy storage. Compared with traditional inorganic salt hydrates, a mineral named ettringite can easily overcome this limit thanks to its large resource from cementitious materials. Meanwhile, possession of high energy density (about 500 kWh/m3), low corrosiveness, non-toxicity and low working temperature (~ 60 °C) around or below common heat resource (solar energy, industrial waste heat, urbane heat system, and even combination with grid) makes ettringite very competitive to be used in an integrated thermal energy storage system. In this paper, the analysis on the available data for structure, preparation of material, thermal conversion, reaction enthalpies, carbonation durability, and ionic substitution of ettringite has been established. Moreover, potential research directions and solutions to improve thermal performance of ettringite-based materials are proposed.

The mismatch between renewable energy supply and demand requires energy storage technologies to work out the dilemma. In the thermal energy field, ettringite-based energy storage seems to be a good solution thanks to its high energy density and low material cost. It can store excess solar energy to meet the heating and domestic hot water demand in buildings. Therefore, the current work experimentally examines the energetic performance of an ettringite-based material made of commercial cements. The TG-DSC analysis shows the energy storage capacity of the investigated material is as high as 282 kWh/m3 original hydrated materials. Besides, the laboratory reactor tests prove the charging temperature is as low as 55–65°C for ettringite. Under operating conditions, the average energy-releasing power during the full period is about 33.3 W/kg while the maximum power is about 915 W/kg original hydrated materials, which are significantly higher than most materials from the literature. The best volumetric energy-releasing density and the corresponding prototype storage density of the fixed-bed obtained are 176 kWh/m3 original hydrated materials and 104 kWh/m3, respectively.

The use of ettringite-based materials for thermochemical heat energy storage has attracted researchers' attention in recent years since ettringite has advantages like low material cost and high energy storage density (~500 kWh/m3). However, carbonation, which modifies its structure and reduces the capacity of energy storage, is an important hindrance to real applications. To address this issue, the present study focuses on the carbonation kinetics of three ettringite-based and corresponding meta-ettringite-based materials (dehydrated samples) exposed to different relative humidity (RH) and CO2 concentrations. A mixture of 80 wt% pre-blended Calcium Aluminate Cement/20 wt% OPC (C80P20) proved to be the most resistant against CO2. The hydrated and dehydrated C80P20 grains carbonated slowly at 50% RH and 1 vol% CO2, consuming little ettringite after 28 days. At 90% RH, carbonation was accelerated such that all ettringite and meta-ettringite materials were depleted at 11 days with vaterite and aragonite as the main calcium carbonates. The produced CaSO4 hydrates were found as hemihydrate at 70% RH and gypsum at 90% RH. Finally, the thermal energy storage capacity (TESC) of the material was systematically quantified as essentially decreasing with the carbonation degree of ettringite-based materials.

One of the main challenge in belite, ye'elimite and ferrite cement is the control of the belite phase reactivity. We propose to study two mechanisms that impact belite hydration kinetic: the first mechanism is linked to available space for hydration products and can be seen as a decrease of water accessibility to cement surface and the second concerns the cement fineness. We used a thermodynamic model that can predict phase assemblage and we found good correlations between this model and the results obtained with XRD measurement and Rietveld refinement.

More attention on renewable energy has been attracted after the achievement of Paris Agreement against climate change. Solar-based technology is supposed to be one of the most promising green energy technologies for residential buildings since its wide thermal usage for hot water and heating. However, the seasonal mismatch between its energy-production and consumption makes buildings need an energy storage system to improve the efficiency of renewable energy use. Indeed, even if different kinds of energy storage systems using sensible or latent heat already exist, thermochemical energy storage can be then recommended by considering the problems of energy dissipation during storage and low energy density for the first two methods. As potential thermochemical storage materials, ettringite (3CaO∙Al2O3∙3CaSO4∙32H2O) based materials possess high energy densities (~500 kWh/m3), low material cost (3) and low storage temperature (~60−70°C), compared to salt hydrates of similar energy density like SrBr2·6H2O (42 k€/m3, ~80°C), LaCl3·7H2O (38 k€/m3, ~100°C) and MgSO4·7H2O (5 k€/m3, ~150°C). Therefore, ettringite-based materials have the possibility to be largely used in building sector by being coupled to normal solar collector systems via reversible chemical reactions (Equation (1)): (i) charging mode: hot air or hot water (>70°C) from solar collectors dehydrates ettringite to meta-ettringite, and consequently store heat to chemical energy; ii) discharging mode: humid air is pumped to material container to rehydrate meta-ettringite, and consequently release stored chemical energy as heating. However, the lack of extensive examination leads to poor knowledge on their thermal properties and limits maturity of this technology. Therefore, the aim of this work is to characterize the capacity of an ettringite-based material (named C80P20, containing ~70 wt.% ettringite) in terms of thermal energy storage by Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Besides, a modular reactor adapting to thermal characterizations of C80P20 particles has been developed for various weights (up to 300 grams). In our case, the energy density of pure ettringite is around 1012 J/g while 708 J/g for C80P20 powder in TGA-DSC. First preliminary results from modular reactor demonstrate a general energy density of 150 kWh/m3 released by the hydration process of C80P20 grains (pre-dehydrated at 80 °C) at 25 °C and 85% relative humidity. Moreover, the reactor is intended to study the durability of the energy storage material over time, and also as function of the number of charging/discharging cycles.CaO∙Al2O3∙3CaSO4∙32H2O ettringite+heat↔3CaO∙Al2O3∙3CaSO4∙32-XH2Ometa-ettringite+XH2O

Ettringite-based thermochemical energy storage has been recommended to be used in buildings for thermal energy supply because of its low material cost (

We investigated the effect of thin viscoelastic polymer coatings around aggregate particles on the mechanical properties of “micro-concretes” with a maximum aggregate diameter of 10 mm. Aggregate particles > 5 mm were pre-treated with a latex at dosages of up to 2% by mass and dried prior to using the treated aggregate in the micro-concrete mix. Cured prisms were tested in flexion. The results show that thin polymer coatings on aggregates have a significant effect on micro-concrete cracking behaviour at much lower polymer dosages than are commonly used in polymer-modified mortars. We observed a significant improvement in post-peak energy absorption relative to the use of the same amount of polymer dispersed in the bulk paste. But, under the conditions tested here, reductions in the strengths and moduli of the composites due to the polymer additions appear to have more than outweighed the observed positive effects of increases in fracture energy and characteristic length.

The addition of a finely-ground ion-exchange resin makes it possible to modify the hydration kinetics of C3S pastes. Analyses of the liquid phase in pastes and more dilute suspensions show that the resin exchanges calcium ions for sodium ions very rapidly during the early stage of hydration and therefore the concentration of silica in solution increases. The resin impacts the hydration of C3S by other mechanisms which depends on the resin quantity added. For a high resin quantity, the induction period is very short, but the longer-term hydration is enhanced compared to a reference sample without resin. We hypothesize that the surface of the resin can provide sites for the nucleation and growth of C–S–H hydrates and/or portlandite far away from the surface of the C3S grains. This consequently increases the quantity of hydrates that can precipitate before a continuous hydrate layer forms over the surfaces of C3S particles.

We report a comprehensive proton NMR relaxation study of the water confined in the evolving porous structure of hardened gypsum prepared with different water-to-plaster ratios (w/p) and increasing additions of crushed gypsum. This study gives some new information on the microstructure, the water distribution, and the hydration kinetics without any drying or perturbing preparation. The bi-exponential transverse magnetization decay reveals the existence of two water populations in slow exchange. However, the different behaviors of these populations during saturation and desaturation experiments show evidence of a fast exchange of each population with the surface. Two modes of organization of the microstructure of this material are identified through an original model of exchange as a function of the water-to-plaster ratio (0.4or = w/por = 0.6 and 0.7or = w/por = 1). A clear gap is shown in the exchange rate value above w/p = 0.6 that could be representative of a percolation threshold. Both the method and the theory presented can be applied more widely to other porous media with reactive surface areas.

The main difficulty related to DoseMapper correction is to generate an appropriate CD datacollection to feed DoseMapper and to generate DoseRecipe in a user friendly way, especially with a complex process mix. We could heavily measure the silicon and create, in feedback mode, the corresponding DoseRecipe. However, such approach in a logic fab becomes a heavy duty due to the number of different masks / product / processes. We have observed that process CD variability is significantly depending on systematic intrawafer and intrafield CD footprints that can be measured and applied has generic pre-correction for any new product/mask process in-line. The applied CD correction is based on a CD (intrafield: Mask + Straylight & intrawafer: Etch Bias) variability "model" handled by the FAB APC (Advanced Process Control). - Individual CD profile correction component are generated "off-line" (1) for Intrafield Mask via automatic CD extraction from a Reticle CD database (2) for Intrafield Straylight via a CD "model" (3) for Intrawafer Etch Bias via engineering input based on process monitoring. - These CD files are handled via the FAB APC/automation system which is remotely taking control of DoseMapper server via WEB services, so that CD profiles are generated "off-line" (before the lot is being processed) and stored in a profile database while DoseRecipes are created "real-time" on demand via the automation when the lot comes to the scanner to be processed. DoseRecipe and CD correction profiles management is done via the APC system. The automated DoseRecipe creation is now running since the beginning of 2011 contributing to bring both intrafield and intrawafer GATE CDu below 1nm 3sigma, for 45/40 & 28nm nodes.

The existence of a large number of installed systems operating around 1.3 μm, particularly for analog CATV distribution, has motivated amplifier research in this wavelength range, with emphasis on Praseodymium Doped Fiber Amplifiers (PDFA) [1], [2].