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Recycled ceramics from industrial wastes, compared with traditional high-purity ceramics, present high market potential as refractory materials due to their low cost production process with very friendly environmental impacts. In order to study the feasibility of using recycled ceramics as the encapsulation material in the application of high temperature Latent Heat Thermal Energy Storage system, this paper investigates the compatibility of recycled ceramics with three kinds of aluminium-silicon alloys at high temperature. The recycled ceramics explored are Cofalit from asbestos containing waste and steel slags. The study consists of a steady state thermal treatment of both ceramics in contact with the three different alloys at 1000°C for 100 hours, and a post instrumental characterization of ceramic samples by Environmental Scanning Electron Microscopy and Energy Dispersive Spectrometry, to understand the chemical and structural transformation of each ceramics. Results show that Cofalit has chemical interactions with aluminium alloys, while steel slag presents an excellent corrosion resistance to molten aluminium alloys and is further recommended as an encapsulation material for molten aluminium alloys at high temperature. more...

At present there is an intense research for developing alternative sensible heat storage materials, such as natural rocks and recycled ceramics, able to work in concentrated solar power plants at high temperatures. This work demonstrates the potential of flint rocks as an economic and efficient filler material to be used with air as heat transfer fluid in packed bed storage system. Four facies of flint rocks were collected from south of France. To predict the performance of the storage system, crystalline structure, thermo-physical and thermo-mechanical properties of the studied rocks have been identified. For this purpose, the candidate rocks were subjected to extensive experimental characterizations under a series of thermal cycles. XRD, SEM, DSC/TGA, pycnometer, LFA, dilatometer, high temperature ultrasonic testing and nano-indenter method have been used to analyze these samples. Consequently, the 400 °C was identified as ideal temperature for the heat treatment process of flint. The obtained results from the four analyzed samples have been compared together and with currently used storage materials. The results gathered from this paper prove the potential of flint in terms of high density, good specific heat capacity and good thermal stability up to 400 °C to be used as filler material in energy storage applications relevant for low and medium temperature solar power plants. more...

International audience; The aim of this work was to highlight feasibility of a new approach to synthesize Activated-Carbon (AC)/TiO2 composite materials. The main interest of these materials is for pollutants removal applications thanks to their multi-functionality. AC/TiO2 composites were prepared by one-step mechanosynthesis route. Morphological and structural properties were investigated through SEM, EDS, XRD, and BET techniques. It was found that the preparation process leads to the formation of an aggregate shape homogenously composed AC/TiO2 powder with a narrow particles size distribution, which mean diameter was 3.75 μm. Initial component structural properties were found to be strongly affected by the process, resulting in significant changes of TiO2 crystallinity and AC microtexture. The introduction of 5 min pauses during the process was enough to totally preserve TiO2 phases, crystallinity, and AC microporous network. Composites multi-functional properties were investigated using batch adsorption and photodegradation experiments. Adsorption studies revealed that AC/TiO2 aggregates exhibit good adsorption capacity with caffeine and a maximum adsorbed amount of 353 mg.g−1. Photocatalytic experiments highlighted that AC/TiO2 presents a photo-oxidation ability. Photodegradation apparent kinetic rate fitted with a first-order law gave a value of 1.04 × 10-5 s-1 for the composite and ten times higher for pure TiO2. These results allowed to conclude that mechanosynthesis is an effective route to produce bi-functional AC/TiO2 composites with efficient adsorption capacity for water treatment applications. It also suggests the need of further radiative transfer studies to understand light scattering and absorption inside these materials, which could lead to some improvement of these promising materials. more...

Recycled ceramics from industrial wastes, compared with traditional high-purity ceramics, present high market potential as refractory materials due to their low cost production process with very low environmental impacts. However, there still exists a research gap of how recycled ceramics behave while in contact with liquid metal. In order to study the feasibility of using recycled ceramics as the encapsulation material in the application of high temperature Latent Heat Thermal Energy Storage system, this paper investigates the compatibility of recycled ceramics with three kinds of aluminium-based alloys at high temperature, with a comparison to the corrosion resistant behaviour of alumina. The recycled ceramics explored include Cofalit from asbestos containing waste, blast furnace slags from steel production, and coal fly ashes sintered ceramics from incineration plants. The study consists of a steady state thermal treatment of ceramic samples in contact with the three different alloys at 1000°C for 100 hours, and a post instrumental characterization of ceramic samples by Environmental Scanning Electron Microscopy, Energy Dispersive Spectrometry and X-ray diffractometer, to understand the chemical and structural transformation of the ceramics. Results demonstrate that Cofalit shows chemical stability with Al99% but instability with AlSi5% and AlSi12%. Blast furnace slag presents quite good thermochemical stability towards molten AlSi5% and AlSi12%. Coal fly ashes sintered ceramics are highly interactive towards all three aluminium alloys. In conclusion, besides alumina, Cofalit is recommended as alternative encapsulation material for molten Al99%, while blast furnace slag being recommended for molten AlSi5% and AlSi12%. NRF (Natl Research Foundation, S’pore) Accepted version more...

The crystallization behaviour of aluminosilicate glasses of lanthanum (LAS) and yttrium (YAS) containing 2–8 mol% of Ln 2 O 3 (Ln = La or Y), 12–30 mol% of Al 2 O 3 , and 64–80 mol% of SiO 2 has been studied by DTA, XRD and SEM-EDX analysis. X-ray diffraction results indicate the presence of the mullite phase and La 2 Si 2 O 7 in the monoclinic high-temperature G form (group space P2 1 /c) for the LAS glasses, and mullite y-Y 2 Si 2 O 7 in the monoclinic structure (group space C2/m) and a small amount of β-Y 2 Si 2 O 7 in the orthorhombic structure (space group Pna2) for the YAS. For both cases, very little tridymite phase is observed. The results also show that the values of T g for YAS are higher than those for LAS glasses. The crystallization of LAS glasses is more difficult than that of YAS. For all samples, we observed only one kind of mullite (Al/Si = 3.14). more...

International audience; Recycled ceramics made of inertized asbestos containing wastes have been submitted to high pressure/temperature cycling tests in the operating range of ACAES and CSP applications. Ten successive cycles between room conditions and 610 °C/30 bars for a cumulated duration of 2500 h lead to a validation of the ability of the material to resist to those constrains. The Wollastonite/Augite initial structure is gradually transformed in a unique Augite containing material. While mechanical parameters and density are unchanged, thermal capacity is reduced by 5% and thermal conductivity increased by 30%. This last result offers an advantageous way to enhance the thermal conductivity of those recycled ceramics, a key parameter to control the charge/discharge power in TES systems. more...