Porous Metal Substrate Research Articles

Plasma Spray Physical Vapor Deposition of La1−x Sr x Co y Fe1−y O3−δ Thin-Film Oxygen Transport Membrane on Porous Metallic Supports

Plasma spray physical vapor deposition (PS-PVD) is a very promising route to manufacture ceramic coatings, combining the efficiency of thermal spray processes and characteristic features of thin PVD coatings. Recently, this technique has been investigated to effectively deposit dense thin films of perovskites particularly with the composition of La0.58Sr0.4Co0.2Fe0.8O3−δ (LSCF) for application in gas separation membranes. Furthermore, asymmetric type of membranes with porous metallic supports has also attracted research attention due to the advantage of good mechanical properties suitable for use at high temperatures and high permeation rates. In this work, both approaches are combined to manufacture oxygen transport membranes made of gastight LSCF thin film by PS-PVD on porous NiCoCrAlY metallic supports. The deposition of homogenous dense thin film is challenged by the tendency of LSCF to decompose during thermal spray processes, irregular surface profile of the porous metallic substrate and crack and pore-formation in typical ceramic thermal spray coatings. Microstructure formation and coating build-up during PS-PVD as well as the annealing behavior at different temperatures of LSCF thin films were investigated. Finally, measurements of leak rates and oxygen permeation rates at elevated temperatures show promising results for the optimized membranes.

Characterization of 430L porous supports obtained by powder extrusion moulding for their application in solid oxide fuel cells

The characterization of 430L stainless steel planar porous supports obtained by powder extrusion moulding was performed in this work. A thermoplastic multicomponent binder based on high density polyethylene and paraffin wax was selected for the process. Green supports were shaped by extrusion moulding, and subsequently the binder was removed by a thermal cycle previously optimized. Sintering was carried out at different temperatures in low vacuum. Density of sintered parts was measured by Archimedes' method and porosity was also evaluated through a microstructural analysis by optical microscopy. The porosity degree of samples sintered at low temperature was close to 35% which is a very suitable value for their application in SOFCs. Tensile tests were carried out in order to determine mechanical strength as a function of porosity degree. Based on these results, the best feedstock composition and processing parameters were selected. The oxidation behaviour in static air at high temperature was studied, and formed oxides were characterized in a scanning electron microscope equipped with energy dispersive analysis of X-rays. X-ray diffraction experiments were performed in order to identify the formed oxides based on formula Fe2−xCrxO3. The results of these studies showed that this kind of ferritic stainless steel would be more suitable to be used as anodic supports where a rich hydrogen atmosphere is employed. Preliminary deposition tests allowed obtaining a homogeneous Ni–YSZ anode layer with a thickness of 10μm on the porous metallic substrates.

Development of a Porous Metal Substrate for Metal Supported SOFCs Using a Fe-Cr-Al Stainless Steel

Metal supported cells with porous metallic substrates made of stainless steels are expected to drastically improve remaining issues of durability and cost for solid oxide fuel cells (SOFCs). In this study, we succeeded in fabricating a porous alloy substrate for SOFC using a Fe-Cr-Al type stainless steel, which showed excellent heat resistance. We investigated the application of the alloy substrate for the cathode side and good heat resistance and relatively low contact resistance between the alloy substrate and La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) was obtained at 700oC in air.

Coating Developments for Metal-Supported Solid Oxide Fuel Cells

Metal supported cells are considered the next generation of Solid Oxide Fuel Cells due to higher robustness and cost-efficiency. However, improvement of the low temperature performance (< 700°C), increased durability and the use of manufacturing routes compatible to the metal substrate are key parameters for success. Coatings for porous metal supports in order to improve the oxidation resistance of the metal, reduce the chromium evaporation and poisoning, and increase the conductivity of the protective oxide scale, are developed. The oxidation of coated and non-coated substrates in air and wet hydrogen has been compared and shows that it is possible to increase the oxidation resistance at 600°C in air by more than 10 and wet hydrogen by more than 1000 by coating the pre-sintered porous metal substrate.

Ceramic nanocomposites based on oxides of transition metals for ionistors

Low-temperature synthesis methods are used to produce nanoceramic materials for electrodes of the following ionistors: (ZrO2)0.6(In2O3)0.4, praseodymium cobaltite, as well as neodymium, lanthanum, and nickel chromites; they operate in the presence of an ion-conducting phosphorosilicate separator membrane and phosphate impregnation. Film electrodes of ionistors are fabricated that consist of nanocrystalline oxide materials deposited as a thin film on a porous electroconductive metal substrate, i.e., foamed nickel. The MnO2-foamed nickel electrode has a specific capacity of 45.0 F g−1, which is compared with that of industrial supercapacitors.

High temperature stability of porous metal substrates under highly humidified hydrogen conditions for metal supported Solid Oxide Fuel Cells

Porous Crofer Fe22Cr stainless steel supports for tubular Solid Oxide Fuel Cells (SOFC) were developed and tested successfully under hydrogen fuel with 50% humidification at 800°C. Corrosion resistance and stability as a function of operation lifetime, porosity and thermal cycling were studied through the investigation of oxide growth and microstructure. Oxidation reactions followed subparabolic kinetics and substrates with porosities between 25 and 40% showed long-term stability over 4500h and suitable properties for metal‐supported SOFC technology application.

Improved reoxidation tolerance of Ni–Fe metal support for LaGaO3 thin film electrolyte cell

Effects of reoxidation and reduction treatment of a Ni–Fe metallic anode substrate were investigated as a function of reoxidation period and temperature. The NiFe2O4 composite anode substrate was highly dense before the reduction treatment. However, after reduction for 2h in H2 atmosphere, the dense oxide composite substrate was changed to a porous metal substrate consisting of a Ni–Fe alloy. The metallic substrate was then reoxidized in 100% O2. When the reoxidation treatment was performed, the porous substrate regained its original density. However, XRD patterns of the reoxidized substrate still exhibited strong Ni base alloy peaks. Moreover, SEM–EDX analysis showed that a large part of the reoxidized substrate was porous and a dense iron base oxide layer formed at the surface of the substrate. In addition, after reduction for 2h with hydrogen gas, the substrate returned to a porous metal substrate again. Therefore, in spite of slightly increased anodic IR loss and a small fuel-leakage, which was observed after the reoxidation and reduction cycles, the Ni–Fe metal supported cell showed an excellent reoxidation tolerance at 973K.

Preparation, characterization and microstructural optimization of a thin γ-alumina membrane on a porous stainless steel substrate

► A mesoporous γ-Al 2 O 3 membrane was synthesized on conventional α-Al 2 O 3 substrates. ► γ-Al 2 O 3 membrane was potential for CO 2 separation at high pressure test conditions. ► Thus, it was required to provide the membrane layer with more strength. ► α-Alumina substrate was substituted with porous stainless steel. ► A stainless steel supported α-Al 2 O 3 membrane with better properties was synthesized. In this work, a supported mesoporous (MEP) γ-Al 2 O 3 membrane was synthesized on conventional α-Al 2 O 3 substrates by sol–gel dip coating process. In the following, the preparation of a novel metallic–ceramic composite membrane was studied, which incorporated desirable properties of both ceramic membrane and porous metallic substrate. For this purpose, mesoporous alumina membrane layer was developed on a porous 316L stainless steel substrate. The substrate was prepared by loose powder sintering and modified by soaking–rolling and fast drying method. The prepared membranes were characterized using scanning electron microscope (SEM), field emission scanning electron microscope (FESEM), X-ray diffractometer (XRD) and N 2 -adsorption/desorption measurements (BET analyses). The results revealed that a defect-free γ-alumina membrane with 2.1 nm average pore size can be produced. Permeation tests with N 2 gas revealed that the stainless steel substrate had 40 times more permeability than conventionally used alumina support. Additionally, single gas permeation of γ-alumina membrane for CO 2 and N 2 was compared. It was observed that CO 2 could be separated from N 2 by the MEP γ-Al 2 O 3 membrane in high pressure permeation condition, where stainless steel presents superior mechanical strength than alumina as a substrate.

Treatment of recurrent THR dislocation using of a cementless dual-mobility cup: A 59 cases series with a mean 8 years’ follow-up

Instability is one of the most feared complications following total hip replacement (THR). In France, dual-mobility cups are widely used in acetabular revision for instability; few studies, however, have focused on this type of implant. The gain in stability provided by the dual-mobility implant allows the risk of dislocation to decrease by the sole revision of the acetabular component in case of recurrent instability. This hypothesis was tested over medium-term follow-up of a series of cementless dual-mobility cups implanted during isolated acetabular revision for recurrent dislocation. A series of THR revision for instability was analyzed retrospectively. Inclusion criteria were: recurrent THR dislocation treated by cementless dual-mobility cup, between 1995 and 2001. Radiological analysis used Imagika™ software. Fifty-nine patients were included; nine died before radioclinical follow-up could be performed; none of the survivors were lost to follow-up. Mean follow-up was 8 years (range, 6-11 years). There was one early dislocation without recurrence; the dislocation rate was 1.7%. At follow-up, mean PMA score was 16.5 (12-18) and mean Harris score 86.7 (49-99). Radiologically, there was no loosening or migration, but 19% of X-ray views showed less than 1mm wide peri-acetabular radiolucency. With dislocation as censoring criterion, 8-year survivorship was 98% (95% CI: 95-100%). The dislocation rate (1.7%) and clinical results were better than in most series of revision by constrained cup for recurrent dislocation. The high rate of peri-acetabular radiolucency would seem to relate to the external coating of the cup: aluminum oxide in the Novae-1 implant and aluminum oxide/hydroxyapatite in the Novae-E. The use of dual-mobility cups to treat THR instability gave satisfactory results. We recommend dual-mobility cups with hydroxyapatite surface treatment over a porous metallic substrate, rather than with an aluminum oxide or an aluminum oxide/hydroxyapatite bilayer coating. Level IV. Retrospective Study.

High temperature oxidation of porous alloys for solid oxide fuel cell applications

Metal-supported solid oxide fuel cells are regarded as a new generation of SOFC devices. The use of porous metal substrate provides a high mechanical strength of a SOFCs' support and lowers the cost of fuel cells. In this study, powders of PI600, 317L and 430L steel grades were used to prepare porous metallic supports. After sintering at different temperatures, their porosity and high temperature corrosion resistance were evaluated. Cyclic thermogravimetric analysis, X-ray diffractometry and SEM imaging were used to describe properties of these porous alloys. Electrical properties were studied for selected samples. The influence of porosity on resulting properties was elucidated. The porosity changes measured between oxidation cycles were presented. Results showed that the properties of porous alloys differ significantly from those of dense ones. The high temperature corrosion rate is high and is strongly influenced by the porosity level. Open porosity decreases rapidly upon oxidation at 800 °C. As an outcome of this study, the PI600 alloy performs best among those investigated; however, better corrosion resistant materials are needed for SOFCs' supports operating at 800 °C.

Air Dehydration Membranes for Nonaqueous Lithium–Air Batteries

Robust, thin-sheet membranes were prepared and tested as an -permeating moisture barrier for the operation of nonaqueous Li–air batteries in ambient air. A membrane sheet was attached onto a carbon air electrode filled with a nonaqueous Li-ion electrolyte solution to supply dry oxygen from ambient air for the electrode reaction and to mitigate potential loss of the solvent from the electrode by evaporation. The membrane was prepared by depositing an -selective coating layer on the exterior surface of a thin porous metal substrate sheet. Silicalite zeolite and poly(tetrafluoroethylene) (PTFE) were used as inorganic and polymeric hydrophobic-type materials, respectively, for the membrane preparation in this work. A thin , dense-phase PTFE film supported on a porous metal sheet provided the best battery performance. This kind of membrane enabled the Li–air batteries with carbon black air electrodes to operate in ambient air [at 20% relative humidity (RH)] for 21 days. The specific capacity of 1022 mAh/g carbon and specific energy of 2792 Wh/kg carbon were obtained for the battery discharged to 2.0 V. The Li–air battery equipped with the selective membrane showed a much better performance in ambient air operation (20% RH) than the reference battery tested in a dry air box (1% RH).

Porous metallic substrates for superconducting coatings

By an example of porous metal tubes and thin plates prepared from the stainless steel powder a simple method is described of preparation of porous metallic substrates for superconducting coatings. The tubes outer diameter is 12 mm, length up to 300 mm, wall thickness about ∼1.5 mm. The plate size is 85×85 mm, thickness 1 mm. We used the classic method of powder metallurgy, without any fillers. After sintering, the tube had a density 2.5–3.4 g cm−3 and open porosity 55–65%. The microstructure of the tubes and plates surfaces and breaks was studied using scanning electron microscopy. The porous tubes were prepared also from powdered copper, nickel, titanium, and chromium, as well as from mixtures of stainless steel and copper, nickel and pseudoalloy Cu(30%)-Cr. The first coatings with superconducting compound MgB2 were prepared.

High Power SOFC Using LSGM Film on NiFe Porous Bi-metal Substrate

Sr and Mg doped LaGaO3 (LSGM) thin film was prepared on NiO-Fe2O3 bi-metal substrate by Pulsed Laser Deposition (PLD) method. Substrate preparation conditions were studied at different sintering temperatures in order to optimize the preparation condition for dense disk with smooth surface. By the thermal reduction, the substrate was changed to a porous Ni-Fe metal substrate. The volumetric shrinkage and porosity of the substrate were also studied at different reduction temperature and the suitable reduction temperature exists at 973 K for porous metal substrate. Stoichiometric composition of LSGM film was successfully prepared by optimal deposition parameter and target composition. Structure of the deposited film was changed from amorphous to crystalline perovskite structure during the annealing at 1073 K for 2 h. Sm0.5Sr0.5CoO3 was prepared as cathode by slurry coating method. The maximum power density (MPD) was achieved a value of 1.6 and 0.9 W/cm2 at 973 and 873 K, respectively, on porous Ni-Fe metal substrate. Even at 673 K, MPD of 0.1 W/cm2 was achieved.

Recent Development Aspects of Metal Supported Thin-Film SOFC

The metal supported solid oxide fuel cell (MSC) technology has attained high interest for the electrical power supply of vehicles by auxiliary power units (APUs) which operate independently from the main engine. Its main advantages compared to other SOFC technologies are higher mechanical stability and better thermal and redox behaviour, which are indispensible for mobile applications. For many years, Plansee has developed and fabricated porous metallic substrates, interconnector plates and protective coatings for various types of SOFCs which are used in mobile as well as in stationary applications. Plansee has recently developed technologies for the production of MSCs in close co-operation with outlines various partners from science and industry. This paper results of this development.

Design and synthesis of thin palladium membranes on porous metal substrate for hydrogen extraction

Membrane separation is regarded nowadays as a preferred method for production of purified hydrogen. Palladium (Pd) is an attractive membrane material due to its ability to dissociate molecular hydrogen into atoms. It is usually deposited on the porous substrate that can provide good mechanical support and reduce the thickness of the membrane for maximizing hydrogen permeability. Pd membrane used for hydrogen separation must be thin enough to increase hydrogen flux and reduce cost while remaining thick enough to retain adhesion, attrition resistance and mechanical integrity during high temperature cycles. In this paper, the progress of electroless deposition of Pd around the pore area at surface of porous stainless steel was recorded and a bridge structure that was formed during the membrane deposition around the pore area of the substrate was illustrated. After that, the porous substrate was modified using micro-or nano-size metal or metal oxide particles in order to reduce pore size in the substrate surface. The experimental results obtained from hydrogen permeation through the Pd membranes having the thickness from 400 nm to 18 μm built on both modified and original porous stainless steel substrates demonstrate that these thin membranes are solid and they can be used at the temperature of 550°C and hydrogen pressure difference of 3.447x105 Pa. The proposed processing will allow optimizing the design and fabrication of thin Pd membranes on different porous substrates for hydrogen separation.

Catalytic roughening of surface layers of BDD for various applications

The surface layers of BDD electrodes have been roughened through excavation by small Ni, Co and Pt particles in a flowing gas mixture of H 2(10%) and N 2(90%) between 800 °C and 1000 °C. The specific surface area of the BDD evaluated with the double layer capacitance was enhanced by the excavation of up to nearly 15 times as much pristine BDD electrode. The following potential applications for the surface-roughened BDD were proposed: (1) interlayer of the porous oxide catalyst layer and metal substrate of IrO 2–Ta 2O 5/(Ti or Nb) electrode, for instance, and (2) supporting material with large surface area for catalyst metal particles.

High performance metal-supported solid oxide fuel cells fabricated by thermal spray

Metal-supported solid oxide fuel cells (SOFCs) have been fabricated and characterized in this work. The cells consist of porous NiO–SDC as anode, thin SDC as electrolyte, and SSCo as cathode on porous stainless steel substrate. The anode and electrolyte layers were consecutively deposited onto porous metal substrate by thermal spray, using standard industrial thermal spray equipment, operated in an open-air atmosphere. The cathode materials were applied to the as-sprayed half-cells by screen-printing and heat-treated at 800 °C for 2 h. The cell components and performance were examined by scanning electron microscopy (SEM), X-ray diffraction, leakage test, ac impedance and electrochemical polarization at temperatures between 500 and 700 °C. The half-inch button cells exhibit a maximum power density in excess of 0.50 W cm −2 at 600 °C and 0.92 W cm −2 at 700 °C operated with humidified hydrogen fuel, respectively. The half-inch button cell was run at 0.5 A cm −2 at 603 °C for 100 h. The cell voltage decreased from 0.701 to 0.698 V, giving a cell degradation rate of 4.3% kh −1. Impedance analysis indicated that the cell degradation included 4.5% contribution from ohmic loss and 1.4% contribution from electrode polarization. The 5 cm × 5 cm cells were also fabricated under the same conditions and showed a maximum power density of 0.26 W cm −2 at 600 °C and 0.56 W cm −2 at 700 °C with dry hydrogen as fuel, respectively. The impedance analysis showed that the ohmic resistance of the cells was the major polarization loss for all the cells, while both ohmic and electrode polarizations were significantly increased when the operating temperature decreased from 700 to 500 °C. This work demonstrated the feasibility for the fabrication of metal-supported SOFCs with relatively high performance using industrially available deposition techniques. Further optimization of the metal support, electrode materials and microstructure, and deposition process is ongoing.

Pd–Ag membrane synthesis: The electroless and electro-plating conditions and their effect on the deposits morphology

The effect of electroless and electro-plating conditions on the Pd and Ag deposits morphology obtained on porous metal substrate was investigated from the membrane synthesis viewpoint. Linear sweep voltammetry was applied for the polarization characteristics of electroless plating baths. The Pd electroless deposits ([Pd]/[N 2H 4] = 16 mM/5.6 mM) and Ag electrodeposits ([Ag] = 100 mM, current density = 2 mA/cm 2) showed good substrate pore penetration. However, for the electroless Ag deposits ([Ag]/[N 2H 4] = 3 mM/5.6 mM), poor pore penetration was observed. The Ag electroless bath polarization curve indicated that within 15–25 mV electrode over potential, the entire deposition process was limited by the diffusion of Ag ions to the substrate surface. The plating conditions such as low [Ag]/[N 2H 4] ratio (20 mM/4 mM) or substrate stirring lowered the Ag deposition over potential and produced Ag deposits with good pore penetration, therefore suitable for the membrane preparation. Three membranes, M-1 (Pd by electroless method and Ag by electro-plating method), M-2 and M-3 (both Pd and Ag by electroless method) were prepared by the multilayer Pd–Ag sequential deposition approach. The membranes showed low activation energy for the H 2 permeation (M-1, M-2 and M-3 = 4.9, 4.3 and 11.5 kJ/mole respectively) after annealing at 550 °C (24 h). The low activation energy after annealing was due to the formation of Pd–Ag alloy. The SEM and EDX analysis after annealing showed fairly uniform distribution of Pd and Ag throughout the cross-section of the membranes.

Preparation of LaGaO3Based Oxide Thin Film on Porous Ni-Fe Metal Substrate and its SOFC Application

LaGaO₃ thin film was prepared on Ni-Fe metal porous substrate by Pulsed Laser Deposition method. By the thermal reduction, the dense NiO-Fe₃O₄ substrate is changed to a porous Ni-Fe metal substrate. The volumetric shrinkage and porosity of the substrate are controlled by the reduction temperature. It was found that a thermal expansion property of the Ni-Fe porous metal substrate is almost the same with that of LaGaO₃ based oxide. LaGaO₃ based electrolyte films are prepared by the pulsed laser deposition (PLD) method. The film composition is sensitively affected by the deposition temperature. The obtained film is amorphous state after deposition. After post annealing at 1073 K in air, the single phase of LaGaO₃ perovskite was obtained. Since the thermal expansion coefficient of the film is almost the same with that of LSGM film, the obtained metal support LSGM film cell shows the high tolerance against a thermal shock and after 6 min startup from room temperature, the cell shows the almost theoretical open circuit potential.

Vapor and water permeabilities and moisture absorbability of organosilicate coatings

A setup was designed for determining the vapor and water permeabilities of coatings and films on porous metal substrates at temperatures of 40°C and higher. The setup was used to determine the vapor and water permeabilities of five organosilicate coatings, namely, OS-51-03 (green), OS-51-03A (green), OS-11-07 (green), OS-11-07A (green), and OS-12-03 (white). The thickness of the coatings was in the range 90–130 μm. The water permeability of all the coatings under investigation was found to be higher than their vapor permeability. The lowest vapor and water permeabilities were observed for the OS-51-03 coating (the vapor permeability was 2.76 × 10−5 mg/m h Pa). The moisture absorption of the green coatings, the OS-12-03 white composite, and the varnish coatings based on the KO-921 varnish and a mixture of the KO-915 and KO-075 varnishes were investigated. No correlation between the moisture absorption and the water permeability was revealed. It was established that the KO-921 varnish coating possesses the lowest water absorbability (0.85%).