A series of iron- and/or aluminium-doped apatite-type lanthanum silicates (ATLS) La
9.83Si
6
‐
x
‐
y
Al
xFe
yO
26
±
δ
(x
=
0, 0.25, 0.75, and 1.5, y
=
0, 0.25, 0.75, and 1.5) were synthesized using ...the mechanochemical activation (MA), solid state reaction (SSR), Pechini (Pe) and sol–gel (SG) methods. The total conductivity of the prepared materials was measured under air in the temperature range 600–850
°C using 4-probe AC impedance spectroscopy. Its dependence on composition, synthesis method, sintering conditions and powder particle size was investigated. It was found that for electrolytes of the same composition, those prepared via mechanochemical activation exhibited the highest total specific conductivity, which was improved with increasing Al- and decreasing Fe-content. The highest conductivity value at 700
°C, equal to 2.04
×
10
−
2
S
cm
−
1
, was observed for the La
9.83Si
5Al
0.75Fe
0.25O
26
±
δ
electrolyte. La
9.83Si
4.5Fe
1.5O
26
±
δ
electrolyte samples synthesized using the Pechini method exhibited higher conductivity when sintered conventionally than when spark-plasma sintering (SPS) was used.
► Fe- and/or Al-doped apatite-type lanthanum silicates (ATLS) for SOFC applications. ► Conductivity of ATLS pellets prepared from powders synthesized via different methods. ► ATLS prepared via mechanochemical activation exhibited the highest conductivity. ► ATLS via Pechini method: Pressureless sintering preferable to spark-plasma-sintering.
•Ilmenite-based oxygen carriers were developed for packed-bed chemical looping.•Addition of Mn2O3 increased mechanical strength and microstructure of the carriers.•Oxygen carriers were able to ...withstand creep and thermal cycling up to 1200°C.•Ilmenite-based granules are a promising shape for packed-bed reactor conditions.
Chemical looping combustion (CLC) is a promising carbon capture technology where cyclic reduction and oxidation of a metallic oxide, which acts as a solid oxygen carrier, takes place. With this system, direct contact between air and fuel can be avoided, and so, a concentrated CO2 stream is generated after condensation of the water in the exit gas stream. An interesting reactor system for CLC is a packed bed reactor as it can have a higher efficiency compared to a fluidized bed concept, but it requires other types of oxygen carrier particles. The particles must be larger to avoid a large pressure drop in the reactor and they must be mechanically strong to withstand the severe reactor conditions. Therefore, oxygen carriers in the shape of granules and based on the mineral ilmenite were subjected to thermal cycling and creep tests. The mechanical strength of the granules before and after testing was investigated by crush tests. In addition, the microstructure of these oxygen particles was studied to understand the relationship between the physical properties and the mechanical performance.
It was found that the granules are a promising shape for a packed bed reactor as no severe degradation in strength was noticed upon thermal cycling and creep testing. Especially, the addition of Mn2O3 to the ilmenite, which leads to the formation of an iron–manganese oxide, seems to results in stronger granules than the other ilmenite-based granules.
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•Different particles have been developed and tested for application in a packed-bed CLC reactor.•Ilmenite was chosen as base material due to its good reactivity with syngas, the ...natural availability and related low cost.•A suitable oxygen-carrier was developed using ilmenite as base material and Mn2O3 as additive.•No significant differences in the reduction and oxidation reactivity of the different granules were observed.
Chemical-looping combustion (CLC) is a promising technology that integrates power production and CO2 capture with a low energy penalty. CLC has been successfully demonstrated using interconnected fluidized bed reactor systems. However, high pressure operation allows the use of inherently more efficient power cycles than low pressure fluidized bed solutions. With the aim to work at elevated pressures, dynamically operated packed-bed reactors have been proposed for CLC.
In a packed-bed CLC reactor bigger oxygen carrier particles are used to avoid very large pressure drops and the required mechanical properties of these particles are quite different from the properties needed in a fluidized bed CLC system. In this work different particles have been developed and tested for application in a packed-bed CLC reactor. Ilmenite was chosen as base material because of its good reactivity with syngas, the natural availability and related low cost. Different ilmenite pellets with different composition and shape were developed and their mechanical properties before and after thermal and chemical cycling were analysed and compared. The reactivity of the particles and the influence of different reaction conditions were also studied in a thermogravimetric analyser. It was found that the thermal and chemical stresses produced an important deterioration of the mechanical properties of the pellets. The type of additive used during the production process showed an important effect on the mechanical properties of the granules. Only the granules produced with Mn2O3 as additive demonstrated acceptable suitable mechanical properties after thermal and chemical cycling.
One of the main target of the French ANR CONDOR (2009–2011) project coordinated by EDF-EIFER was the elaboration of proton conducting BaCe0,9Y0,1O3−δ-based cells using processes suitable at ...industrial level. Thus, commercial powders produced at kilogram scale (anode, electrolyte and cathode) have been analysed and used. Then, elaboration of protonic ceramic half-cells by co-pressing method from 25 mm to 80 mm in diameter has been assessed in order to establish the suitability of this shaping method regarding industrial requirements. According to results, the co-pressing method is relevant for the elaboration of cells up to 40 mm in diameter (laboratory experiment). A sintering step was carried out to densify the electrolyte layer to get a gas-tight membrane. Nickelate-based cathodes were screen-printed and electrochemical performances of the final assembly have been measured. Electrical power up to 180 mW cm−2 at 600 °C has been obtained on both 25 and 40 mm cells.
•Commercial powders produced at kilogram scale have been analysed and used.•The maximum power density of around 180 mW cm−2 is obtained at 600 °C on both sizes.•The co-pressing method is only efficient at the laboratory scale.
Thin-wall YBCO single-domain bulk materials present merits of reduced oxygen diffusion paths and large specific areas suitable for a fast oxygenation and a good thermal exchange. The progressive ...oxygenation under high pressure has been proposed to rapidly produce crack-free superconductors with stimulated trapping properties owing to speeding up of the oxygen diffusion. Thin-wall YBCO single domains grown by using top-seeded melt growth process were successfully oxygenated by applying this annealing treatment. Under oxygen pressure of 10 MPa, the influence of the dwell time and temperature on trapping properties was investigated. The trapped field was found to increase with up to 12 h and reach an optimum at . A 700 mT trapped field has been obtained on a large thin-wall single domain (46 mm in diameter) classically oxygenated, while waiting the delivery of a suitable high oxygen pressure furnace for such size.
This paper provides an overview of objectives, structure and first results of the DEMOYS project, financially supported by the European Commission in the frame of the 7th FP Energy. The project ...started on May 1, 2010 and brings together fifteen Partners, including three Universities, five Research Organizations and seven Industries. The objective of DEMOYS is the development of thin mixed conducting membranes for O2 and H2 separation by using a “Plasma Spraying – Thin Film” PS-TF) in combination with nano-porous, highly catalytic layers.
We report on our progress in the preparation of single domain of high temperature superconducting (HTS) bulk YBCO and GdBCO cryomagnets with multiple holes. Three mains steps have been explored and ...discussed in this study:
Gd
2
BaCuO
5
(Gd211) and Y
2
BaCuO
5
(Y211) and thin wall preforms shaping by the extrusion technique.
GdBa
2
Cu
3
O
3
(Gd123) YBa
2
Cu
3
O
3
(Y123) single domain obtained from Y211 using the Seed Infiltration Growth (SIG) process.
Annealing under high oxygenation pressure in order to improve the superconducting properties.
The thin wall samples with larger specific areas offer some advantages as better thermal exchange, shorter oxygen diffusion paths, possibility to reinforce the material to overcome the mechanically stresses during magnetization. The process and the microstructural features at various stages of processing, with particular emphasis on the characteristics of Gd211 and Y211 inclusions are discussed. Properties like the magnetic trapped field at different temperatures, the superconducting transition temperatures, and critical current densities of the resulting composites are presented and compared with their values in samples processed by other variants of the melt textured growth process.
In this work we report on a novel concept for the preparation of gas selective composite membranes by a simple and robust synthesis protocol involving a controlled
in-situ
polycondensation of ...functional alkoxysilanes within the pores of a mesoporous ceramic matrix. This innovative approach targets the manufacture of thin nanocomposite membranes, allowing good compromise between permeability, selectivity and thermomechanical strength. Compared to simple infiltration, the synthesis protocol allows a controlled formation of gas separation membranes from size-adjusted functional alkoxysilanes by a chemical reaction within the mesopores of a ceramic support, without any formation of a thick and continuous layer on the support top-surface. Membrane permeability can thus be effectively controlled by the thickness and pore size of the mesoporous layer, and by the oligomers chain length. The as-prepared composite membranes are expected to possess a good mechanical and thermomechanical resistance and exhibit a thermally activated transport of He and H
2
up to 150 °C, resulting in enhanced separation factors for specific gas mixtures e.g. F
H2/CO
∼ 10; F
H2/CO2
∼ 3; F
H2/CH4
∼ 62.
Thin-wall single domains with artificial patterned holes are highly interesting for stimulating superconducting and mechanical properties of bulk YBCO materials. YBCO single domains were successfully ...grown from multiple holes preforms by using TSIG or TSMG techniques. The thin-wall configuration enables a remarkable improvement in flux trapping and superconducting properties whatever the used growth process. Progressive oxygenation under high pressure associated to the large specific areas was shown to boost the material performances. A trapped field maximum of 0.84 T was recorded at 0.2 mm above the top surface of a 16 mm thin wall pellet at 77 K. Such complex geometry can be easily and abundantly produced by using an extrusion process. We report for the first time to our knowledge the growth of a single domain from an extruded preform. Thin-wall samples were then impregnated by resign/alloy for mechanical reinforcement.
Drilled YBCO bulk materials have been reported to possess good superconducting properties owing to their large specific areas which promote thermal exchange and oxygen diffusion. Extrusion process ...can be used as an outstanding way to develop artificially thin-wall YBCO ceramics. YBa2Cu3O7-δ single domains were successfully grown by using Top-Seeded Infiltration Growth from extruded Y2BaCuO5 preforms with artificial holes. They show a free-crack microstructure with a uniform distribution of Y2BaCuO5 inclusions. The flux mapping confirmed the single-domain criterion, and the critical current density was found larger than the one of the drilled material. The extruded ceramics were impregnated by resign/Fe-metal for reliability reinforcement.
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