High Temperature Fabrication Research Articles

Tribological Behavior of Ni-based Self-lubricating Composites with the Addition of Ti3SiC2 and Ag2W2O7

The tribological properties of Nickel-based composites containing Ti3SiC2 and Ag2W2O7 fabricated by spark plasma sintering against Si3N4 balls were investigated using a ball-on-disk tribometer from room temperature to 600 °C. The tribolayers formed on the friction surface and their effects on the tribological properties of composites at different temperatures were discussed based on the worn surface characterization. The results show that Ag2W2O7 is decomposed into metallic silver and CrWO4 during the high-temperature fabrication process. The composite with the addition of 20 wt% Ti3SiC2 and 5 wt% Ag2W2O7 exhibits a friction coefficient of 0.33–0.49 and a wear rate of 7.07×10−5–9.89×10−5 mm3/(Nm) over a wide temperature range from room temperature to 600 °C. The excellent tribological properties at a wide temperature range are attributed to the formation of a glaze layer at low temperature and a tribooxide layer at high temperature, which can provide a low shearing strength for the synergistic effects of Ag and tribooxides.

Relaying delivery of excited state electrons for fully printable perovskite solar cells via ultra-thin gradient PCBM/perovskite heterojunction

The high-temperature fabrication process for fully printable perovskite solar cell (PSC) limits its synchronization passivation with device fabrication. Herein we have creatively developed a post-decoration process (PDP) using phenyl-C61-butyric acid methyl ester (PCBM) in chlorobenzene anti-solvent, which not only induces the regrowth of perovskite crystals reducing grain boundaries, but also realizes the relaying delivery of excited state electrons from perovskite to TiO2 in virtue of the ultra-thin PCBM/perovskite heterojunction. The champion device with PCBM achieved a power conversion efficiency of 14.12% with an open circuit voltage of 0.91 V, a current density of 24.03 mA/cm2 and a fill factor of 0.64. It provides a simple approach towards high efficiency without sacrificing long-term stability of fully printable perovskite solar cells.

Field-Driven Athermal Activation of Amorphous Metal Oxide Semiconductors for Flexible Programmable Logic Circuits and Neuromorphic Electronics.

Despite extensive research, large-scale realization of metal-oxide electronics is still impeded by high-temperature fabrication, incompatible with flexible substrates. Ideally, an athermal treatment modifying the electronic structure of amorphous metal oxide semiconductors (AMOS) to generate sufficient carrier concentration would help mitigate such high-temperature requirements, enabling realization of high-performance electronics on flexible substrates. Here, a novel field-driven athermal activation of AMOS channels is demonstrated via an electrolyte-gating approach. Facilitating migration of charged oxygen species across the semiconductor-dielectric interface, this approach modulates the local electronic structure of the channel, generating sufficient carriers for charge transport and activating oxygen-compensated thin films. The thin-film transistors (TFTs) investigated here depict an enhancement of linear mobility from 51 to 105.25 cm2 V-1 s-1 (ionic-gated) and from 8.09 to 14.49 cm2 V-1 s-1 (back-gated), by creating additional oxygen vacancies. The accompanying stochiometric transformations, monitored via spectroscopic measurements (X-ray photoelectron spectroscopy) corroborate the detailed electrical (TFT, current evolution) parameter analyses, providing critical insights into the underlying oxygen-vacancy generation mechanism and clearly demonstrating field-induced activation as a promising alternative to conventional high-temperature annealing strategies. Facilitating on-demand active programing of the operation modes of transistors (enhancement vs depletion), this technique paves way for facile fabrication of logic circuits and neuromorphic transistors for bioinspired computing.

Geographically re-oriented magmatic and metamorphic foliations from ODP Hole 735B Atlantis Bank, Southwest Indian Ridge: Magmatic intrusion and crystal-plastic overprint in the footwall of an oceanic core complex

When core pieces are drilled they lose all geographic information, making crustal-scale structural analysis of in situ oceanic crust near impossible. In order to better understand the orientation of deformation fabrics in the footwall, and therefore the formation and evolution of the lower oceanic crust, magmatic and high-temperature metamorphic foliations were re-oriented back to the geographic reference frame over the interval 90–600 m below sea floor from Ocean Drilling Program Hole 735B at the Atlantis Bank oceanic core complex, Southwest Indian Ridge. Fractures measured on cores were correlated with borehole images of fractures to re-orient core pieces, and therefore re-orient any element within those core pieces. Simple 2-D models of extension predict that high-temperature fabrics should dip toward or away from the spreading ridge, however, only ∼30% of each foliation type follows this prediction. The lack of systematic orientation of high temperature deformation foliations seems to indicate that there is a complex 3-D orientation and distribution of magmatic and metamorphic foliations with respect to the detachment shear zone and that the strains that these foliations recorded is not compatible with simple plane strain assumptions related to ridge-perpendicular extension at slow-spreading ridges.

Progress in fabrication of second generation high temperature superconducting tape at Shanghai Superconductor Technology

The development and application of second generation high temperature superconducting (2G-HTS) tapes have attracted much attention in China recently. Progress in upscaling high performance 2G-HTS tape production at Shanghai Superconductor Technology (SST) is reported in this paper. With ion beam assisted deposition, biaxially textured buffer layers with a configuration of CeO2/LaMnO3/MgO/Y2O3/Al2O3/C-276 have successfully been fabricated. In-plane and out-of-plane texture degrees of CeO2 films achieve 2°–4° and 2°, respectively. A multi-plume multi-turn pulsed laser deposition (PLD) system combined with the so-called ‘radiation assisted conductive heater’ has been proposed and further developed for REBCO layer deposition. Our effort was focused on minimizing the temperature variations in the deposition region by modifying the heating shield that assists the conductive heater of the drum-like cylinder. A tape travelling speed of 100–180 m h−1 can be achieved with a steady temperature profile when passing through the deposition zone, which is very beneficial for the growth of the REBCO layer. Taking advantage of the liquid phase growth mode, several compositions of superconducting films with a thickness in the range of 1–2.5 μm have been grown with high growth rates of over 40 nm s−1. Furthermore, the microstructures and superconducting performance were investigated in detail. Based on these studies, superconducting tapes with piece lengths of up to 500 meters have been developed. High Ic values at 77 K, self-field (over 520 A cm−1 width) or at low temperature, high magnetic field conditions (over 560 A/4 mm width at 4.2 K, 10 T, perpendicular field) have been achieved. Lamination and jointing techniques have also been developed by SST for power and magnet applications.

Highly efficient semitransparent CsPbIBr2 perovskite solar cells via low-temperature processed In2S3 as electron-transport-layer

Inorganic perovskite solar cells (IPSCs) with CsPbIBr2 as the light harvester have attracted tremendous attention owing to its thermal stability, low cost and facile manufacture, where electron transport layer (ETL) plays indispensable roles of charge separation, electron transportation and hole-blocking. Although TiO2 is widely used as an ETL, its high-temperature fabrication and low electron mobility hinder the performance and application of IPSCs. Herein, we have proposed a low-temperature (70 °C) chemical bath deposition (CBD) method with different time to prepare In2S3 films as the ETL of IPSCs. By regulating the deposition time of In2S3 films to 85 min, our best-performing device has obtained a high PCE of 5.59% with reduced hysteresis, which is a relative high efficiency for CsPbIBr2 IPSCs by low-temperature fabrication at present. However, the TiO2-based device shows a low efficiency of 5.02% and serious hysteresis. Meanwhile, the In2S3-based devices exhibit improved stability under ambient conditions without encapsulation. Experimental results precisely clarify that this enhanced photovoltaic performance is attributed to the suitable band alignment, low resistance, low recombination of photo-generated carriers at the interface of ETL/perovskite. Promisingly, our low temperature fabricated perovskite and ETL layers might broaden new insights for solution-processed flexible devices.

Large‐Area All‐Printed Temperature Sensing Surfaces Using Novel Composite Thermistor Materials

AbstractSurfaces which can accurately distinguish spatial and temporal changes in temperature are critical for not only flow sensors, microbolometers, process control, but also future applications like electronic skins and soft robotics. Realizing such surfaces requires the deposition of thousands of thermal sensors over large areas, a task ideally suited for printing technologies. Negative temperature coefficient (NTC) ceramics represent the industry standard in temperature sensing due to their high thermal coefficient and excellent stability. A drawback is their complex and high temperature fabrication process and high stiffness, prohibiting their monolithic integration in large area or flexible applications. As a remedy, a printable NTC composite that combines a rapid and scalable all‐printed fabrication process with performances that are on par with conventional NTC ceramics is demonstrated. The composite consists of micrometer‐sized manganese spinel oxide particles dispersed in a benzocyclobutene matrix. The sensor has a B coefficient of 3500 K, with a 4.0% change in resistance at 25 °C, comparable to bulk ceramics. The selected polymer binder yields a composite exhibiting less than a 1 °C change in resistance to changes in humidity. The sensor's scalability is validated by demonstration of a A4‐sized temperature sensing sheet consisting of over 400 sensors.

Controlled deposition of density defects for understanding mechanical reduction on 2D C/SiC composites

Continuous carbon fiber reinforced silicon carbide matrix composites (C/SiCs) have been widely used in aeronautic and astronautic fields because of their more attractive high temperature properties with less structural weight. However, density defects (DD) with randomness and unpredictability will have a serious impact on the mechanical properties of the laminated C/SiC composites (2D C/SiCs). A novel method was presented, by masking graphite-papers with different sizes on the surface of the ground C/SiC composite plates and then automatically produced various size low density region to tentatively imitate the DD once high temperature fabrication of SiC matrix. The mechanical reduction on 2D C/SiCs with different size DD (Rdd, thus was defined as ratio of DD width D to whole sample length L) was investigated subsequently. Results show that, tensile strength of the C/SiCs continuously decreased from original 241.7 MPa to final 212.2 MPa when the Rdd below 30%. There trended to stable tendency above 88.8% of original strength with further increase of the Rdd. Meanwhile, compressive strength was subjected to a larger decrease from original 280.3 MPa to final 232.2 MPa and then tended to be constant at 82.2% of original strength when the Rdd further increased. The compressive strength decreased to a greater extent and tended to stabilize earlier as the Rdd increased. It pointed out that the DD caused higher sensitivity to the compressive strength of the C/SiCs than to the tensile strength. In addition, as the Rdd increased, both tensile and compressive elastic modulus decreased to the nearly same extent, eventually falling to 83.25% of the initial value, indicating that the increased DD fewly further reduced the stiffness.

A novel delamination defects designed for understanding mechanical degradation in a laminated C/SiC composites

Delamination defects are especially easy to be formed in the processing of a C/SiC composites laminated layer by layer of carbon cloths (2D C/SiCs), causing a significant effect on the mechanical properties and failure modes. A novel method was presented, by embedding polytetrafluoroethylene paper into the 2D carbon fiber cloths and then automatically produce delamination defect once high temperature fabrication of SiC matrix, to tentatively understand mechanical degradation behaviors of laminated 2D C/SiC composites with different sizes of delamination defects (Rd, thus was defined as ratio of delamination defects width D to gauge length L). For tension, the tensile strength was first subjected to a sudden decrease with a slight reduction in elastic modulus when delamination defects occurred. With further increase of Rd, the tensile strength and elastic modulus do not decrease sharply but tend to be stable. For compression, the compressive strength had continuous and nearly linear decrease from original 345.41 MPa to final 275.72 MPa with relatively large variation in compressive modulus when the Rd increased. It can be also observed from the macro fractured sections that the failure modes of 2D C/SiC composites under tension and compression are completely different. The compression was bearded mainly by the matrix while the tension was bearded mainly by the fibers, leading to a result that the width of the delamination defects in laminated 2D C/SiC composites propagated more easily under the compression than under the tension.

A Fabrication and Measurement Method for a Flexible Ferroelectric Element Based on Van Der Waals Heteroepitaxy

Flexible non-volatile memories have received much attention as they are applicable for portable smart electronic device in the future, relying on high-density data storage and low-power consumption capabilities. However, the high-quality oxide based nonvolatile memory on flexible substrates is often constrained by the material characteristics and the inevitable high-temperature fabrication process. In this paper, a protocol is proposed to directly grow an epitaxial yet flexible lead zirconium titanate memory element on muscovite mica. The versatile deposition technique and measurement method enable the fabrication of flexible yet single-crystalline non-volatile memory elements necessary for the next generation of smart devices.

A Fabrication and Measurement Method for a Flexible Ferroelectric Element Based on Van Der Waals Heteroepitaxy.

Flexible non-volatile memories have received much attention as they are applicable for portable smart electronic device in the future, relying on high-density data storage and low-power consumption capabilities. However, the high-quality oxide based nonvolatile memory on flexible substrates is often constrained by the material characteristics and the inevitable high-temperature fabrication process. In this paper, a protocol is proposed to directly grow an epitaxial yet flexible lead zirconium titanate memory element on muscovite mica. The versatile deposition technique and measurement method enable the fabrication of flexible yet single-crystalline non-volatile memory elements necessary for the next generation of smart devices.

Natural convective flow of a magneto-micropolar fluid along a vertical plate

This paper presents a numerical study of natural convective flow of an electrically conducting viscous micropolar fluid past a vertical plate. Internal heat generation (IHG) versus without IHG in the medium are discussed in the context of corresponding similarity solutions. Results are presented in terms of velocity, angular velocity, temperature, skin friction in tabular forms, local wall-coupled stress, and Nusselt number. Computations have been accomplished by parametrizing the micropolar, micro-rotation, magnetic field, suction parameters, and the Prandtl number. Several critical issues are addressed at the end of the paper with reference to a previous study by El-Hakiem. The study is relevant to high-temperature electromagnetic materials fabrication systems.

High-temperature and short-time hydrothermal fabrication of nanostructured ZSM-5 catalyst with suitable pore geometry and strong intrinsic acidity used in methanol to light olefins conversion

High temperature hydrothermal synthesis method was developed to preparation of nanostructured ZSM-5 molecular sieves at short crystallization time. A series of catalysts were synthesized at various temperatures and crystallization times for achievement of pure ZSM-5 phase with MFI structure. The synthesized catalysts were investigated with XRD, FESEM, EDX, BET-BJH, FTIR and TPD-NH3 techniques. The results revealed that hydrothermal synthesis conditions generally affected the nucleation rate, particle size, textural properties and acidic nature of ZSM-5 catalysts. It was found that pure ZSM-5 materials with high crystallinity could be obtained at specific crystallization conditions of about 300 °C for 1.5 h and also 350 °C for 0.5 h. Increasing the hydrothermal temperature to 350 °C and decreasing the crystallization time to 0.5 h led to the formation of small particles with high specific surface area of 392 m2/g. Furthermore, ammonia TPD spectra showed that ZSM-5(300-1.5) catalyst contained higher amount of acid sites and less acid strength compared to ZSM-5(350-0.5) catalyst. The catalytic performance of samples was studied for conversion of methanol to light olefins under different reaction conditions. Interestingly, the proper pore geometry along with the strong intrinsic acidity resulted in a tendency for excessive production of light olefins for ZSM-5(350-0.5) catalyst. The selectivity of light olefins over this catalyst was increased about 94% in the long time on stream (2100 min). Also, the possible reaction pathway for ZSM-5 synthesis at high temperatures was discussed in details.

Observation of new-type magnetic skymrions with extremerely high temperature stability and fabrication of skyrmion-based race-track memory device

Nanoscle magnetic skyrmions are topologically protected vortex-like spin textures that have been regarded as a promising candidate for the transport of information in further spintronic applications based on the racetrack memory concept due to their nanoscale dimension, stable particle-like feature, and an ultralow threshold for current-driven motion. Recently, most of the skyrmions are observed in chiral magnetic materials, such as MnSi, FeGe, Co-Mn-Zn, where the Dzyaloshinskii-Moriya interaction is active. However, their overall low thermal stability is one of the major factors hindering the practical applications. In this paper, we report the observation of a new-type magnetic skyrmion with extremerely high temperature stability in the centrosymmetric frustrated magnet Fe3Sn2, and the fabrication of skyrmion-based race-track memory device based on Fe3Sn2 by using focused ion beam. This compound is a rare example of ferromagnetic frustrated magnet that exhibits a high Curie temperature Tc up to 640 K. As the temperature decreases from 640 K to 100 K, it undergoes a spin reorientation during which the easy axis rotates gradually from the c-axis to the ab-plane. The Fe3Sn2 has a layered rhombohedral structure with the alternate stacking of the Sn layer and the Fe-Sn bilayer along the c-axis. By a high-temperature flux method, we grow high-quality Fe3Sn2 single crystal. The in-situ Lorentz transmission electron microscopy (LTEM) observations demonstrate that this compound can host skyrmions at room temperature (RT). In contrast to the skyrmions of the chiral magnets, they possess various spin textures and are transformed from topologically trivial bubbles under a high external magnetic field of 800 mT. By using the FIB technique, we fabricate a geometrically confined nanostripe with a width of 600 nm and thickness of 250 nm. The in-situ LTEM observations demonstrate that a single chain of skyrmions with uniform spin textures can be created at RT. The investigations on the temperature stability of the single skyrmion chain reveal that it shows an extremerely high temperature stability that the size of and the distance between the skyrmions in the chain can keep unchanged at temperatures varying from RT up to a record-high temperature of 630 K. The observation of a highly stable single skyrmion chain in the geometrically confined Fe3Sn2 nanostripe can be attributed to (1) the weak temperaturedependent magnetic anisotropy Ku of the Fe3Sn2 crystal, and (2) the formation of edge states at the boundaries of the nanostripes. The observation of new-type magnetic skymrion with extremerely high temperature stability and the fabrication of skyrmion-based race-track memory devices are very important steps towards the applications in skyrmionbased spintronic devices.

Structural and chemical evolution of the CdS:O window layer during individual CdTe solar cell processing steps

Oxygenated cadmium sulfide (CdS:O) is often used as the n-type window layer in high-performance CdTe heterojunction solar cells. The as-deposited layer prepared by reactive sputtering is XRD amorphous, with a bulk composition of CdS0.8O1.2. Recently it was shown that this layer undergoes significant transformation during device fabrication, but the roles of the individual high temperature processing steps was unclear. In this work high resolution transmission electron microscopy coupled to elemental analysis was used to understand the evolution of the heterojunction region through the individual high temperature fabrication steps of CdTe deposition, CdCl2 activation, and back contact activation. It is found that during CdTe deposition by close spaced sublimation at 600 °C the CdS:O film undergoes recrystallization, accompanied by a significant (∼30%) reduction in thickness. It is observed that oxygen segregates during this step, forming a bi-layer morphology consisting of nanocrystalline CdS adjacent to the tin oxide contact and an oxygen-rich layer adjacent to the CdTe absorber. This bilayer structure is then lost during the 400 °C CdCl2 treatment where the film transforms into a heterogeneous structure with cadmium sulfate clusters distributed randomly throughout the window layer. The thickness of window layer remains essentially unchanged after CdCl2 treatment, but a ∼25 nm graded interfacial layer between CdTe and the window region is formed. Finally, the rapid thermal processing step used to activate the back contact was found to have a negligible impact on the structure or composition of the heterojunction region.

Stoichiometric Control of Electrocatalytic Amorphous Nickel Phosphide to Increase Hydrogen Evolution Reaction Activity and Stability in Acidic Medium

AbstractThis work describes the electrocatalysis of amorphous nickel phosphide (Ni‐P) electrodeposited onto copper metal foil, for its use as a non‐noble metal catalyst for the hydrogen evolution reaction (HER) in 0.5 M H2SO4. Although electrodeposition offers many advantages over conventional high temperature and high pressure fabrication techniques, there are very few reports on the preparation of Ni‐P electrocatalysts via electrodeposition. This Ni‐P electrocatalyst exhibits good activity in acidic medium, with a potential of –222 mV to achieve 10 mA cm–2 cathodic current density. This potential is comparable to that of electrodeposited Pt black (–104 mV), and much better than that of electrodeposited Ni (–480 mV). An unusual long‐term stability in acidic medium was demonstrated by the –222 mV potential remaining constant after 5000 cyclic voltammetric sweeps in 0.5 M H2SO4. Importantly, the stoichiometry of the nickel phosphide films can be easily varied from an atomic % of phosphorus from 15 % to as high as 24 % by modifications to the electrodeposition conditions. Such a high phosphorous loading is greater than is generally reported with electrodeposited Ni‐P materials. In addition, we observed Ni‐P films electrodeposited at lower temperatures (∼ 3 °C) result in higher phosphorous loading, which gives rise to enhanced stability as well as activity. Electrodeposited amorphous Ni‐P can therefore be used as an active, stable and Earth‐abundant metal catalyst for the HER in acidic electrolytes.

Trimming the electrical properties on nanoscale YBa2Cu3O7−x constrictions by focus ion beam technique

High temperature superconducting (HTS) nanostructure has a great potential in photon sensing at high frequency due to its fast recovery time. For maximising the coupling efficiency, the normal resistance of the nanostructure needs to be better matched to that of the thin-film antenna, which is typically few tens of ohm. We report on the fabrication of nanoscale high temperature superconducting YBa2Cu3O7−x (YBCO) constrictions using Gallium ion focus ion beam (FIB) technique. The FIB has been used to both remove the YBCO in lateral dimension and also tune its critical current and normal resistance by a combination of surface etching and implantation on the YBCO top layer. High critical current density of 2.5 MA/cm2 at 77 K can be obtained on YBCO nanobridges down to 100 nm in width. Subsequent trimming of the naobridges can lead to a normal resistance value over 50 Ω. Simulation of the Ga ion trajectory has also been performed to compare the measurement results. This method provides a simple step of fabricating nanoscale superconducting detectors such as hot electron bolometer.

Deformation of mantle pyroxenites provides clues to geodynamic processes in subduction zones: Case study of the Cabo Ortegal Complex, Spain

In the Herbeira massif, Cabo Ortegal Complex, Spain, a well exposed assemblage of deformed dunites and pyroxenites offers a unique opportunity to investigate key upper mantle tectonic processes. Four types of pyroxenites are recognized: clinopyroxenites with enclosed dunitic lenses (type-1), massive websterites (type-2), foliated and commonly highly amphibolitized clinopyroxenites (type-3) and orthopyroxenites (type-4). Field and petrological observations together with EBSD analysis provide new insights on the physical behavior of the pyroxenes and their conditions of deformation and reveal the unexpected journey of the Cabo Ortegal pyroxenites.We show that, during deformation, type-1 pyroxenites, due to their enclosed dunitic lenses, are more likely to localize the deformation than types-2 and -4 pyroxenites and may latter act as preferred pathway for fluid/melt percolation, eventually resulting in type-3 pyroxenites. All pyroxenite types display a similar response to deformation. Orthopyroxene deformed mostly by dislocation creep; it shows kink bands and undulose extinction and its fabric is dominated by [001](100). Clinopyroxene displays subgrain rotation, dynamic recrystallization and fabric with [010] axes clustering next to the foliation pole and [001] axes clustering next to the lineation suggesting activation of [001]{110} and [001](100) in some samples. These observations are in good agreement with deformation at temperatures greater than 1000 °C. Olivine in type-1 and type-4 pyroxenites shows [100](010) or [001](010) fabrics that are consistent with deformation at temperatures >1000 °C and may indicate deformation in a hydrous environment. The amphibole [001](100) fabric gives insights on a lower-temperature deformation episode (∼800 to 500 °C). Our results, interpreted in the light of published experimental data, together with the regional geological and geochemical studies are consistent with the following tectonic evolution of the Cabo Ortegal pyroxenites: (1) delamination from an arc root in a mantle-wedge setting at temperatures above 1000 °C and (2) introduction into a relatively softer subduction channel where deformation was accommodated by localized shear zones, thus preserving the high-temperature fabrics of pyroxenites. The Cabo Ortegal pyroxenites may therefore be seen as a rare exposure of deformed mantle-wedge material.

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia (YSZ) Scaffolds by In Situ Carbon Templating Xerogels.

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) scaffolds with tunable specific surface areas up to 80 m2·g-1. An aqueous solution of a zirconium salt, yttrium salt, and glucose is mixed with propylene oxide (PO) to form a gel. The gel is dried under ambient conditions to form a xerogel. The xerogel is pressed into pellets and then sintered in an argon atmosphere. During sintering, a YSZ ceramic phase forms and the organic components decompose, leaving behind amorphous carbon. The carbon formed in situ serves as a hard template, preserving a high surface area YSZ nanomorphology at sintering temperature. The carbon is subsequently removed by oxidation in air at low temperature, resulting in a porous, nanostructured YSZ scaffold. The concentration of the carbon template and the final scaffold surface area can be systematically tuned by varying the glucose concentration in the gel synthesis. The carbon template concentration was quantified using thermogravimetric analysis (TGA), the surface area and pore size distribution was determined by physical adsorption measurements, and the morphology was characterized using scanning electron microscopy (SEM). Phase purity and crystallite size was determined using X-ray diffraction (XRD). This fabrication approach provides a novel, flexible platform for realizing unprecedented scaffold surface areas and nanomorphologies for ceramic-based electrochemical energy conversion applications, e.g. solid oxide fuel cell (SOFC) electrodes.

Improvement of corrosion properties of porous alloy supports for solid oxide fuel cells

The development of protective coatings for porous metal supports is critical for sufficient life time for the fuel cells by enabling improved oxidation resistance, reduced chromium evaporation, and increased conductivity of the protective oxide scale. The oxidation of coated and non-coated substrates has been compared, and shows that it is possible to increase the oxidation resistance at 600 °C in air by a factor of 10 and in wet hydrogen by a factor of 1000, after vacuum coating of the porous metal supports by infiltration of a lanthanum–manganese–cobalt solution and fast curing in air at 900 °C. Chromium evaporation is also lowered by a factor of 10 in air at 600 °C. The experiments on pre-coated porous metal supports verify that the coating is well suited to use for metal supported fuel cells prepared by a low temperature fabrication route (below 1100 °C). An alternative coating procedure for coating of the metal supports after co-sintering of the anode and electrolyte has also been investigated and is well suited for the high-temperature fabrication route. For the high temperature fabrication route, the oxidation tests at 600 °C for 500 h in air and 100 h in wet hydrogen showed that post-coating is better than the pre-coating approach since the cell sintering steps has a detrimental effect on the pre-coated samples.