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La1-xSrxMnO3 is a well-known oxygen electrode for reversible solid oxide cells (RSOCs). However, its poor ionic conductivity limits its performance in redox reaction. In this study, we selected Sm0.5Sr0.5CoO3-δ (SSC) as catalyst and Sm0.2Ce0.8O1.9 (SDC) as ionic conductor and sintering inhibitor to co-modify the La0.65Sr0.35MnO3 (LSM) oxygen electrode through an alternate infiltration method. The infiltration sequence of SSC and SDC showed an influence on the morphology and performance of LSM oxygen electrode, and the influence was gradually weakened with the increasing infiltration time. The polarization resistance of the alternately infiltrated LSM-SSC/SDC electrode was 0.08 Ω cm2 at 800 °C in air, which was 3.36% of the LSM electrode (2.38 Ω cm2). The Ni-YSZ/YSZ/LSM-SSC/SDC single cell attained a maximum power density of 1205 mW cm−2 in SOFC mode at 800 °C, which was 8.73 times more than the cell with LSM electrode. The current density achieved 1620 mA .cm−2 under 1.5 V at 800 °C in SOEC mode and the H2 generation rate was 3.47 times of the LSM oxygen electrode.

Oxide dispersion strengthened materials are commonly used for high-temperature applications. Among other possibilities, these oxides are mostly introduced by mechanical alloying comprising cold welding and fracturing of powders by high-impact loads during milling. However, despite their outstanding high-temperature performance, these materials are still not established because of their laborious and thus expensive processing. Therefore, to improve mechanical alloying’s efficiency, the effect of lower milling temperatures is investigated on an oxide-dispersion strengthened high-entropy-alloy in the proposed study. To this end, prealloyed FeCrMnNiCo powders were milled together with yttria at cryogenic and room temperature by using a novel attritor cryomill. Powders milled at both temperatures were subsequently compared regarding their macroscopic morphology, amount and size distribution of detectable yttria as well as defect structure by means of high-resolution scanning electron microscopy and X-ray diffraction, respectively. Investigations showed a significant decrease of powder particle size and an insignificant influence on their aspect-ratio at cryogenic conditions. Furthermore, the phase fraction of detectable yttria got reduced by cryomilling, indicating increased dissolution or at least refinement. Additionally, a higher full width at half maximum accompanied by increased stacking fault probability of the fcc FeCrMnNiCo matrix gained by X-ray diffraction measurements suggests an improved milling efficiency during cryomilling intensified by higher defect density as well as strength of FeCrMnNiCo powders.

Pure niobium substrates were coated using laser cladding method. Pure molybdenum, Yttria Stabilized Zirkonia (YSZ) and corundum (Al2O3) powders were used as coating materials. Coatings were deposited on specimens as seperate paths with 3÷10mm width and 40mm of length. Two different laser power 3kW and 4kW were tested during deposition. In order to assess the quality of the Mo-YSZ and Mo-Al2O3 coatings, the light microscopy, Scanning Electron Microscopy (SEM), chemical analysis (EDS) and Vickers hardness test investigation were performed. The surface roughness and wear volume were also measured. As a result of YSZ-Mo powder cladding on the Nb substrate the composite layers were obtained without cracks and porosity not exceeding 1 μm. In addition, an increase in hardness of about 450 HV0.5 was revealed. As a result of Al2O3-Mo powder cladding on the Nb substrate the composite layers with many voids and cracks were obtained for each of the cladding variants.

A new oxide dispersion strengthened Cu–0.7wt-%Cr–0.11wt-%Zr material was processed via mechanical alloying (MA) and hot isostatic pressing (HIP). A fine dispersion of yttria particles (Y2O3) was in...

Studies of Ni-yttria-stabilized zirconia (YSZ) fuel electrode degradation mechanisms in solid oxide electrolysis cells (SOECs) are complicated by the different possible Ni-YSZ microstructures and compositions, and the variations in the H2/H2O ratio encountered in an electrolysis stack. Here we describe a life testing scheme aimed at providing survey results on degradation as a function of the H2O-H2 composition, with life tests carried out at five different steam contents from 90% to 10%. A Ni-YSZ-supported symmetric cell geometry is employed both with and without infiltrated nanoscale gadolinia-doped ceria (GDC). Impedance spectroscopy is utilized to observe changes in electrochemical characteristics during the life test, and a transmission-line-based equivalent circuit is used to model the data. Post-test electrode microstructures were observed. The results suggest that the GDC infiltrant reduces the electrode polarization resistance and provides more stable electrode polarization over a range of conditions.

The cobalt/iron-containing perovskites are the most promising cathodes for the intermediate-temperature solid oxide fuel cell (IT-SOFC). However, these cathodes are generally not directly applied on the currently available commercial yttria-stabilized zirconia (YSZ) electrolyte due to the issues of over-firing, harmful reaction and thermal incompatibility. BaCo0.4Fe0.4Zr0.1Y0.1O3-δ (BCFZY) which contains both zirconium and yttrium ions can theoretically be more compatible with the YSZ electrolyte. This paper focuses on the surficial and interfacial properties of BCFZY directly prepared with YSZ under different conditions. The surface of BCFZY by the glycine-nitrate process (GNP) can form the nanoparticles in contrast to that by solid-state reaction (SSR). The peak power density of the cell with BCFZY-GNP cathode directly on YSZ electrolyte can reach 1250 mW cm−2 at 750 °C, which is hardly achieved on the reported traditional cobalt/iron-containing cathodes. It is proved that BCFZY-GNP cathode fired at 900 °C can show more distinct nanoparticles with extensive specific surface area and better BCFZY|YSZ interface, which can promote both oxygen exchange and ion incorporation processes.

Thin film solid oxide fuel cells (TF–SOFCs) having anode–substrate nanostructure that was optimized for the low-temperature operation were fabricated. Nickel thin film anodes with four different anode thicknesses were deposited on anodic aluminum oxide templates, nanoporous substrates having two different pore sizes, by the sputtering method. Subsequently, a yttria-stabilized zirconia (YSZ) electrolyte and platinum cathode were deposited on them, which completed the entire fuel cell structure. The anode nanostructure of fuel cells in six combinations was analyzed by the cross-sectional view, surface microscopy method, and three-dimensional morphology observation. Those investigations enabled the anode nanostructure to be identified, such as the anode porosity and the roughness of the interface between anodes and electrolytes. Then, the six TF–SOFCs were electrochemically characterized in a 500 °C operating environment. The maximum power densities were obtained through the i–V–P curves, and the highest performance of 294.1 mW/cm2 was measured in the cell having a combination of 200 nm–sized porous aluminum anodic oxide (AAO) and 1200 nm–thick Ni anode. This showed up to 20.1% improvement over the other cells. EIS analysis showed that the optimized ohmic and faradaic resistance originated from each part of the unique TF–SOFC structure.

Ceramic membranes are attractive for thermal management applications due to its lightweight and ultralow thermal conductivity, while it is indispensable to address the long-standing obstacle of its poor mechanical stability and degradation under thermal shock. In this work, a series of the organic polymer template-modulated yttria doped zirconia (YDZ) nanofibrous membranes with lightweight, superior mechanical and thermal stability are developed through a cost-effective, scalable sol-gel electrospinning and subsequent calcination method. The YDZ membranes demonstrate excellent flexibility and foldability, which can be attributed to the tetragonal phase and small crystallite size of the YDZ fibers due to the presence of yttria. Besides, the fibrous size, grain size, mechanical and thermal stability of YDZ nanofibrous membranes could be tailored by varying the species and molecular weight of polymer template. The remarkable performances are obtained through the poly(vinyl pyrrolidone) (PVP) template YDZ nanofibrous membranes, featuring the superior tensile strength up to ∼ 4.82 MPa, excellent flexibility with bending rigidity ∼ 26 mN, robust thermal stability up to 1,200 °C, ultra-low thermal conductivity of 0.008–0.023 W·m−1·K−1 (25–1,000 °C), and excellent flame retardancy with tolerance of flame up to 1,000 °C. The remarkable properties can be attributed to the smaller fibrous size, and higher grain size resulting from PVP template. This robust material system is ideal for thermal superinsulation with a wide range of uses from energy saving building applications to spacecraft.

Two different alloys were developed from the mixtures of pre-alloyed powders consisting of ferroalloys to get the required composition of austenitic stainless steel via the powder metallurgy techni...

This work studies the effect of the electronic conductivity of a commercially used yttria-stabilised zirconia (YSZ) electrolyte on solid oxide fuel cell performance. For the first time, an experimental method is used to measure the electronic conductivity of YSZ in commercially manufactured and operated single cells. An inert-gas step addition (ISA) method is employed to measure the electronic conductivity in the form of voltage changes at the open-circuit state. Since the electronic conductivity allows oxide ion transfer and water generation at the anode, a reduction in open-circuit voltage (EOCV) occurs due to the increased water partial pressure. The step increase in the anode flow rate in the ISA method reduces water partial pressure and raises EOCV. The EOCV change is then converted into internal leakage currents and electronic resistivities. The YSZ's electronic resistivity obtained in this work is comparable to the results obtained using the Hebb-Wagner polarisation technique and the oxygen permeation method.

CO2 electrochemical reduction in solid oxide electrolysis cells is an effective way to combine CO2 conversion and renewable electricity storage. A Au layer is often used as a current collector, whereas Au nanoparticles are rarely used as a cathode because it is difficult to keep nanosized Au at high temperatures. Here we dispersed a Au layer into Au nanoparticles (down to 2 nm) at 800 °C by applying high voltages. A 75-fold decrease in the polarization resistance was observed, accompanied by a 38-fold improvement in the cell current density. Combining electronic microscopy, in situ near-ambient pressure X-ray photoelectron spectroscopy, and theoretical calculations, we found that the interface between the Au layer and the electrolyte (yttria-stabilized zirconia (YSZ)) was reconstructed into nano-Au/Zr-suboxide interfaces, which are active sites that show a much lower reaction activation energy than that of the Au/YSZ interface. The formation of Zr-suboxides promotes Au dispersion and Au nanoparticle stabilization due to the strong interaction between Au and Zr-suboxides.

Ruddlesden−Popper layered oxide, La0.25Sr2.75FeNiO7-δ (LSFN) is evaluated as a potential electrode material for symmetrical solid oxide fuel cells. The in-situ formation of Ni–Fe alloy nanoparticles on the LSFN surface in reducing atmosphere can be believed to enhance the activity towards hydrogen oxidation reaction. LSFN exhibit maximum conductivity of 221.2 S/cm and 0.206 S/cm in air and hydrogen environment. Furthermore, LSFN is mixed with GDC powder to form a composite electrode for symmetric solid oxide fuel cells (SSOFC). Results show that with the combination of GDC, the maximum power density of YSZ-based SSOFC enlarges from 232.3 mW cm−2 to 348.5 mW cm−2, and related polarization resistance reduces from 0.359 Ω cm2 to 0.108 Ω cm2. The improved performance is attributed to the enlarged triple-phase boundary with the mixing of GDC. In addition, YSZ-based SSOFC with the LSFN-GDC composite electrode shows a stable performance in intermediate-temperature SSOFCs within 200 h, which indicates that LSFN-GDC composite material is a prospective symmetrical electrode for SSOFC.

In this study, in situ reflection high-energy electron diffraction patterns were used to observe the preparation of high-quality indium tin oxide (ITO) films on yttria-stabilized zirconia (001) substrates using laser molecular-beam epitaxy at different growth pressures and temperatures. X-ray diffraction images showed that increasing the growth temperature or decreasing the pressure diminished the out-of-plane lattice length of the film because of the increased lattice relaxation. Atomic force microscope images and scanning electron microscope showed some crack formations probably due to the release of the strain, causing an increase in the lattice length instead of decrease at the temperature range from 350 to 400 °C. High-resolution transmission electron microscopy showed that the interface between the ITO film and substrate was sharply defined, which indicates the high quality of the film. The sheet resistance of the film increased with increasing growth temperature or pressure, while the optical bandgap did not decrease monotonically because of the effects of strain in the film. Because of the strain, the ITO film initially grew as three-dimensional (3D) islands, like semiconductor quantum dots, and then changed to a quasi-two-dimensional form as the film thickness increased from 1 to 30 nm. The sheet resistance decreased rapidly as the film thickness increased from 20 to 150 nm, but the rate of decrease slowed as the film thickness increased from 150 to 500 nm. The film transmissivity was not significantly affected by the film thickness, growth temperature, or growth pressure.

Two types of dense and toughened 3Y-TZP zirconia implants were fabricated by the sintering of green compacts. Then, the sintered properties of the two implants were compared. Slip-cast and post-sintered all-ceramic zirconia implants were fabricated by the heat treatment at 1450 °C for 2 h using optimal slurry conditions (60 wt% solid content, 1 wt% dispersant, and pH 12). Computer-aided design and manufacturing (CAD/CAM)-machined and post-sintered zirconia crowns, supplied by a dental hospital, were obtained by sintering at 1650 °C for 5 h. The X-ray diffraction results indicated that the phase composition of the slip-casted specimen was completely tetragonal, but the CAD/CAM machined sample was composed of mixed phases of main tetragonal and minor monoclinic crystals. The sintered density and Vickers hardness of the slip-casted specimen were 6.07 g/cm3 and 1367 Hv, respectively, and these were higher than those of the CAD/CAM machined specimen. From the comparative results of the surface microstructure, hardness, and roughness between the two sintered specimens, the slip-casted specimen was found to have higher surface roughness and mechanical hardness, smaller grain size, and less surface micro-cracks than the CAD/CAM machined specimen.

Hydrogen production via solid oxide electrolysis cell (SOEC) is world widely concerned with the new energy revolution. The SOEC performance must be enhanced for the practical application. In this study we report a high-performance Ce0.9Co0.1O2-δ-LSM-YSZ (CC-LSM-YSZ) oxygen electrode, in which Ce0.9Co0.1O2-δ nanoparticles are loaded on LSM-YSZ scaffold and characterized by XRD, SEM, O2-TPD and H2-TPR. Under 50% absolute humidity (A.H), the cell with 1CC-LSM-YSZ, 2CC-LSM-YSZ, 3CC-LSM-YSZ and 4CC-LSM-YSZ oxygen electrode delivers a current density of 0.63, 0.94, 1.14 and 1.26A cm−2 at 1.3 V, which is 1.7, 2.5, 3.0 and 3.3 times higher than the blank LSM-YSZ cell, respectively. The hydrogen generation rate of the 4CC-LSM-YSZ cell is as high as 873 m L cm−2 h−1 under 70% A.H. The DRT results demonstrate the accelerated charge transfer reaction on LSM-YSZ-Ce0.9Co0.1O2-δ oxygen electrode. LSM-YSZ-Ce0.9Co0.1O2-δ has the potential for the application of oxygen electrode in SOEC technology.

Plasma Spray Physical Vapour Deposition (PS-PVD) method was designed for production of ceramic layer on nickel superalloys. In typical process before deposition the base material is heated by plasma up to 900 °C. In present article the yttria stabilized zirconia (YSZ) was deposited on low melting point materials: 2017A-type aluminium alloy and Cu-ETP copper. The influence of power current, process time and powder feed rate on structure and thickness of obtained coatings was analysed. During first deposition process the overheating of Al-sample was observed and as result the power current was decreased to 1600 A. In the next experimental the approx. 5 mm thick dense coating was formed. During experimental processes of YSZ deposition on copper the thickness of coating increased from approx. 5 to 22 mm. The copper-oxide layer was formed under ceramic layer. The microscopic assessment showed the difficulties in formation of columnar ceramic layer on use base materials. The obtained coating was characterized by dense structure as a result of lower plasma energy during process. The increasing of power current is not possible in the case of overheating of base material.

In the article first tests of production of YSZ ceramic coatings using PS-PVD method on graphite were presented. The influence of hydrogen addition on structure and morphology of columns was analyzed. It was shown that width of the columns increased with the increase of hydrogen content in the plasma. The presence of re-solidified oxide vapors between ceramic columns was observed. The obtained results showed the possibility of using of YSZ ceramic layer as a protective layer for metallurgical applications.

TiAl intermetallics can be considered an alternative for conventional nickel superalloys in the high-temperature application. A TBC (Thermal Barrier Coatings) with ceramic topcoat with columnar structure obtained using EB-PVD (electron beam physical vapour deposition) is currently used to protect TiAl intermetallics. This article presents the new concept and technology of TBC for TiAl intermetallic alloys. Bond coats produced using the slurry method were obtained. Si and Al nanopowders (70 nm) were used for water-based slurry preparation with different composition of solid fraction: 100 wt.% of Al, 50 wt.% Al + 50 wt.% Si and pure Si. Samples of TNM-B1 (TiAl-Nb-Mo) TiAl intermetallic alloy were used as a base material. The samples were immersed in slurries and dried. The samples were heat treated in Ar atmosphere at 1000 °C for 4 h. The outer ceramic layer was produced using the new plasma spray physical vapour deposition (PS-PVD) method. The approximately 110 μm thick outer ceramic layers contained yttria-stabilised zirconium oxide. It was characterised by a columnar structure. Differences in phase composition and structures were observed in bond coats. The coatings obtained from Al-contained slurry were approximately 30 μm thick and consisted of two zones: the outer contained the TiAl3 phase and the inner zone consisted of the TiAl2 phase. The second bond coat produced from 50 wt.% Al + 50 wt.% Si slurry was characterised by a similar thickness and contained the TiAl2 phase, as well as titanium silicides. The bond coat formed from pure-Si slurry had a thickness < 10 μm and contained up to 20 at % of Si. This suggests the formation of different types of titanium silicides and Ti-Al phases. The obtained results showed that PS-PVD method can be considered as an alternative to the EB-PVD method, which is currently applied for deposition a columnar structure ceramic layer. On the other hand, the use of nanopowder for slurry production is problematic due to the smaller thickness of the produced coating in comparison with conventional micro-sized slurries.

This communication summarizes the use of double-skinned membranes for hydrogen separation in presence of TiO2 based catalyst (PtReCe/TiO2). The use of this type of membrane avoids the direct contact between catalyst particles and surface of the Pd-based hydrogen selective layer due to the presence of a mesoporous YSZ/γ-Al2O3 layer. The PdAg layer is protected by the mesoporous layer from direct contact with catalyst particles, avoiding erosion and possible chemical interactions. In comparison with a conventional PdAg membrane, the hydrogen flux of DS-membrane was observed not to be compromised during test carried out at 400 °C.

The oxygen surface kinetics and mechanism of oxygen interaction between oxygen from the gas phase and yttria-stabilised zirconia nano-sized powder have been studied by pulse 18O/16O isotope exchange (PIE) in dry (O2) and humid (mixture O2 + H2O with pH2O = 2.6 kPa at T = 22 °C) oxygen atmospheres in comparison with micro-sized powder. Dependences of the heterogeneous oxygen exchange rate (rH) in the temperature range from 550 to 900 °C, and oxygen partial pressure range in the carrier gas and pulses of 5–19% have been obtained. It has been established that the presence of water causes a decrease in the heterogeneous oxygen exchange rate due to the presence of strongly bound hydroxyl groups in the nanopores of the sample. Differences between the mechanisms of isotopic exchange for dry and humid atmospheres have been found in this temperature range (550–700 °C). The observed differences are associated with the interaction of the gas phase and hydroxyls in the adsorbed layer of the oxide. An original method for the separation of the contributions of three types of oxygen exchange for dry and humid atmospheres has been proposed.

Sulfur poisoning is a crucial problem for solid oxide fuel cell (SOFC) anode leading to increasing research works on the development of the anode materials with high sulfur tolerance. By the first principle calculations of hydrogen sulfide dissociation and sulfur atoms diffusion at the interface between the Ni or Mo-doped-nickel and Yttria-Stabilized Zirconia (YSZ), we find that Mo-doped-Ni/YSZ anode not only increases the hydrogen sulfide dissociation barriers, but also increases the barriers of the sulfur diffusion to the oxygen vacancy at the interface of Ni and YSZ, especially for YSZ in oxygen enriched conditions. Here we offer a new theoretical study of Mo-doped-Ni/YSZ sulfur poisoning tolerance at the interface.

As a novel processing technology, plasma spray-physical vapor deposition (PS-PVD) enables coatings to be deposited mainly from vapor phase. To explore the potential advantages of such a plasma spray-based processes, the deposition mechanisms and their dependency on process conditions should be better investigated. In this work, yttria partially stabilized zirconia thermal barrier coatings with quasi-columnar structure were fabricated by PS-PVD. The morphologies of the coatings for each set of deposition durations (from 30 ms to 100 s) and spray distances range from 800 to 1000 mm were studied. Besides, a design-of-experiment was used to investigate the non-line-of-sight capability of PS-PVD coatings, which were deposited on flat superalloy substrates that mounted on a static cylindrical graphite holder approximately 40 mm in diameter at various deposition angle (from 0° to 270°). Moreover, the residual stresses in the topcoat and thermally grown oxide scale were measured non-destructively using Raman spectroscopy and photoluminescence piezospectroscopy, respectively. The stage growth process of PS-PVD coatings was obtained by electron backscattered diffraction characterization of the crystal orientations and distributions of crystal size. The various microstructures of the coatings help to improve the understanding of the deposition mechanisms of PS-PVD coatings.

In this study, the Yttrium Stabilized Zirconia (YSZ) thin films were deposited on the sapphire substrate (Al2O3) by dip-coating method using simple ethanol-based YSZ suspension. The layer thickness of YSZ films were varied by sintering at 1300°C. Phase change and structural evolution in YSZ films were observed by conducting X-ray diffraction (XRD) analyses. The microstructures and the surface morphology of the deposited films were examined using Atomic Force Microscope (AFM) and Field Emission Scanning Electron Microscope (FESEM). The XRD pattern revealed a phase change from cubic to monoclinic with an increase in YSZ layer thickness. The crystallite size was varied in the range of 9.68–42.98 nm with the changes in the layer thickness. Meanwhile, the AFM image analyses showed a layer thickness-dependent variation in the grain size (205.83–373.77 nm) and the RMS surface roughness (16.72–36.44 nm). The FESEM images of the achieved film exhibited the occurrence of a dense morphology. It was concluded that by controlling the layer thickness of the deposited films, their improved structure and morphology can be achieved.

The world’s experience in using hafnium in two important parts of high-temperature thermal barrier coatings, such as the top thermal barrier layer and bond coat layer, was analyzed. In the top thermal barrier layer, hafnium is present as HfO2 completely or partially stabilized by yttria (or other rare-earth oxides). Another approach is to use hafnium dioxide as an addition to conventional coatings based on ZrO2 stabilized completely or partially. Electron-beam physical vapor deposition (EB-PVD) and air plasma spray process (APS) are most common techniques for applying thermal barrier coatings containing hafnium dioxide. Magnetron sputtering turned out to be successful as well. Compared to the 8YSZ coating, the 7.5YSH coating showed reduced Young’s modulus, 30% lower thermal conductivity (decreased to 0.5–1.1 W/(m · K)) at high temperatures for HfO2 stabilized with 27 wt.% Y2O3, and higher sintering resistance and heat resistance. Doping of ZrO2 and HfO2 by several stabilizers proved to be promising: specifically, doping by a mixture of one trivalent ion larger than Y3+ and another trivalent ion smaller than Y3+, preserving the metastable structure of the t′ phase. The importance of phase diagrams for a correct choice of the top coat composition and doping elements for the bond coat is shown. Doping the bond coat with a small amount (up to 1 wt.%) of hafnium improved its cyclic oxidation resistance and increased the adhesion of the thermally grown oxide layer to the bond coat and strength of the latter.

In this study the bilayer composite electrodes based on LaNi0.6Fe0.4O3-δ (LNF) electronic conductor and Bi2O3-based electrolytes doped with Er (Bi1.6Er0.4O3, EDB) and Y (Bi1.5Y0.5O3, YDB) have been developed and their performance has been investigated in the dependence on the electrolyte content and sintering conditions. The polarization resistance of the optimized electrodes with electrolyte content of 50 wt % in the functional layer and with the LNF-EDB-CuO collector is in a range of 0.65–1.09 Ω cm2 at 600 °C and 0.10–0.12 Ω cm2 at 700 °C. The polarization characteristics of the Bi-based electrodes are compared with those for the composite electrodes based on LNF and Ce0.8Sm0.2O1.9 (SDC). The developed electrodes have been tested in a SOFC mode in the anode-supported cells with a thin film electrolyte of YSZ/YDC (Y-doped zirconia/ceria). The single cells with such cathodes are shown to have performance characteristics that are several times higher than that for the cell with a standard platinum cathode. This is due to the optimized content and dispersity of the components; high conductivity of ionic and electronic constituents of the composite electrodes; greatly extended triple phase boundary (TPB) of the electrochemical reaction and advanced electrode design with collector providing uniform current distribution.

The yttria-stabilized zirconia (YSZ) ceramic has been proved to be a promising material for abradable seal coatings. In this research, abradable seal coatings named C-YSZ and M-YSZ were prepared by applying the conventional plasma spraying method with improved nanostructured powders and by the mixed solution precursor plasma spraying technique, respectively. A study on the microstructure, mechanical properties, oxidation resistance and hot corrosion resistance was conducted on both C-YSZ and M-YSZ coatings by using scanning electron microscopy, transmission electron microscopy, muffle furnace and x-ray diffractometer. The results show that the C-YSZ coating presents larger-size pores with denser YSZ structures and grains showing size larger than 100 nm distributed around the pores compared with M-YSZ, in which the pores are much smaller and the grain size is 20-30 nm. As a result, the M-YSZ coating displays lower hardness and bond strength compared with C-YSZ. The oxidation tests show that the M-YSZ coating possesses better oxidation resistance due to the nanostructure topcoat compared with C-YSZ. However, the hot corrosion tests indicate that both the C-YSZ coating and the M-YSZ coating fail to present ideal hot corrosion resistance.

Straightforward deposition protocols to coat flat surfaces are widely available. However, there are multiple constraints in coating a concave or convex surface, especially on the inner surface of narrow tubes. Coated surface helps in corrosion protection, internal cleanliness, strength, and alloy casting, and it also enhances product aesthetics. In the present work, a solution-based deposition protocol was developed to coat oxide films (Y2O3, Al2O3 among others) of tunable thickness (400 nm to 4 μm) on the inner surface of quartz tubes (inner diameter (ID) ∼ 2, 3, 5, 6, and 10 mm; length (L) ∼ 20, 110, and 500 mm) with the help of a venturimeter-based apparatus. In the course of this study, it was revealed that coating on the curved surface needed substantial optimization of the deposition parameters to minimize mainly the tearing and thinning of the film. Choice of organic solvents, acetic acid, precursor concentrations, and solution containing a binder element, such as ethyl cellulose (EC), was optimized to achieve homogeneous coating. An optimal upward air flow (speed 44 m/min) was maintained during drying the coating to prevent solvent condensation prior to annealing the film at 500-1000 °C in air for 30 min. The coating was studied with X-ray diffractometry (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDAX), and Raman spectroscopy. These coated tubes were used as a mold during injection casting of Ni rod at 1450 °C. Surface of the cast Ni was studied for Si as well as yttrium contaminations with EDAX. Raman spectra from a demolded quartz tube (retrieved from casting chamber) revealed characteristic Ag and Fg vibrational modes of cubic Y2O3 phase, indicating good thermal stability and adhesive features of the present coating.

In the present study, APS Al2O3-YAG layers containing 10, 20, and 40 wt.% YAG were deposited as the intermediate layer between the MCrAlY bond coat and the YSZ top coat of double-ceramic-layered TBC (DCL-TBC) on the Ni-based superalloy substrate. Then, the effect of its YAG content on the oxidation behavior of the coated sample was investigated. Microstructural studies of the coatings showed that adding Al2O3-YAG intermediate layer to DCL-TBC system reduced the growth rate and thickness of the TGO layer due to the influence of reactive element, reduction in oxygen inward diffusion, and inhibition in the formation of detrimental mixed oxides as the TGO layer. The cyclic oxidation test at 1050 °C indicated that the oxidation resistance of the coating with the Al2O3-20 wt.% YAG layer was better than that of the other samples.

It is proposed that dual conductive electrolytes have the potential to improve properties of MCFC by using oxygen ion conductors as matrix material, creating what is termed composite electrolyte. In this work we present the results of testing a novel type of electrolyte of molten carbonate fuel cell which consists of Yttria Stabilized Zirconia impregnated by Lithium/Potassium carbonates. Polarization curves were obtained for temperatures between 500 °C and 800 °C. Without very accurate measurements it is not easy to determine the additional electric charge provided by oxygen ions (O=). We made an attempt to build a mathematical model which takes into account both conductivities and, based on the model, estimated the ratio of electric charge provided by oxygen ions and carbonate ions.

A novel integrated cell with O2-|YSZ|Pt|O2(air) reference and counter electrodes was constructed using a short yttria-stabilized zirconia solid electrolyte (YSZ) tube. Combining with cyclic voltammetry and potentiostatic electrolysis methods, green electrochemical preparation of Si from solid SiO2 in CaCl2 melt at 1173 K was studied via an experimental apparatus containing the novel integrated cell under completely carbon-free conditions; the effect of electrolysis time on the morphology of the Si product was also investigated by scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDS). The results show that the morphology of the product obtained from potentiostatic electrolysis at a low overpotential (? 1.6 V) undergoes an evolution from SiO2 raw powder with different sizes to aggregates of spherical particles and small particles with partial reduction, and then to Si nuclei, and finally to Si wires or flakes. The morphology of electrolytic products has little relation with that of SiO2 raw powder and may be controlled by applying different potentials. Furthermore, the longer the electrolysis time, the more the Si wires grow, and the higher the Si purity overall. It is feasible that the experimental apparatus without the sealed stainless steel reactor and any carbonaceous materials can be used to prepare Si from solid SiO2 in CaCl2 melt and release O2 gas at the same time.

As the cathode is a central component of Solid Oxide Fuel Cells (SOFCs), evaluation of cathodes for SOFCs has become a favorite research subject. In the present research, a comprehensive impedance spectroscopy (EIS) analysis is performed to understand the effect of zirconium replacement by cerium on polarization characteristics of La0.7Sr0.3MnO3 (LSM)–Zr0.84Y0.16O1.92 (YSZ8) composite cathode. Three solid oxide fuel cell electrolytes, Ce0.42Zr0.42Y0.16O1.92 (CZY), Ce0.84Y0.16O1.92 (CY) and YSZ8 prepared by solid state reaction, were mixed with appropriate amount of LSM compound to prepare three composite cathodes named LSM–x wt% CZY, LSM–x wt% CY and LSM–x wt% YSZ (x = 30, 50 and 70). The X-ray diffraction analysis has been revealed that LSM is chemically agreeable with all electrolytes, and no undesired reaction happened between them throughout the sintering procedure up to 1350 °C. The thermal expansion coefficients (TECs) for all the prepared electrolyte materials and LSM cathode, show that they are thermomechanically compatible with each other. Results of the electrochemical analysis of symmetrical cells show that the lowest polarization of 0.38 is found by the composition 0.5LSM–0.5YSZ and the highest polarization resistance of 2.72 Ω cm2 is exhibited by the composition 0.3LSM–0.7CZY in the temperature range of 600–850 °C. The composites having YSZ8 and CZY sintered at 1250 °C and CY sintered at 1350 °C showed the maximum electrochemical performance of the cathodes.

The integrity and properties of ceramic coatings produced by atmospheric plasma spraying are highly controlled by the splat morphology and splat interconnection. In this study, the influence of selected parameters (spray angle, surface velocity of the spray gun, and substrate temperature) on splat morphology and coating microstructure was investigated. A favorite set of spray gun parameters, of which their effects on splat morphology and coating microstructure have been verified by previous experiments, were used to conduct the experiments for the present work. It was found that depositing fully molten particles on a hot substrate increases the fraction of disk-like splats by about 60% at the expense of the fraction of irregular splats. Preheating the substrate also increases the pore count and level of coating porosity, while it does not influence the density of segmentation cracks. In contrast, the surface velocity of the spray gun does not affect the splat morphology while a slow speed decreases the coating porosity and plays a significant role in generating segmentation cracks. Shifting the spray angle by 15�� distorts up to 20% of disk-like splats and slightly decreases the porosity level. However, changing the spray angle does not affect the generation of segmentation cracks., Journal of thermal spray technology;Vol. 30. 2021, pp 1015���1027

CeO2-based surface modification is established as an effective strategy for improving the electrochemical performance of solid oxide electrolysis cells (SOECs), but the relevant mechanism has not been fully explored yet. Here, we employ focused ion beam-scanning electron microscopy to examine the microstructural evolution of bare nickel-based yttrium-stabilized zirconia (Ni/YSZ) electrode (reference cell) and Gd-doped CeO2 (CGO)-infiltrated Ni/YSZ electrode (optimized cell) before and after 100-h durability test. The initial current density of the optimized cell was 1.16 A cm−2 (at 1.3 V), which was 1.5 times larger than that of the reference cell. The voltage of the reference cell degraded dramatically due to a 1.16% reduction in the volume fraction of Ni, while the optimized cell showed a negligible degradation with a minor change in the volume fraction of Ni. It was confirmed that CGO nanoparticles formed a protective layer on the Ni surface during the electrolysis process, which prevented further evaporation of Ni. Overall, the infiltration of CGO into traditional Ni/YSZ electrode prevented decrease in the triple-phase boundary density and reduced the resistance by providing additional active sites for hydrogen evolution reaction. We believe that this work provides an efficient strategy for developing high-performance and long-term stable SOECs.

The two-layer structured YSZ/NiCrAlY coatings were modified with dot shape by laser remelting. The microstructure, phase composition and thermal cycling behaviors of the as-sprayed and laser-treated coatings with different laser dot distances were investigated. The thermal cycling behaviors of the as-sprayed and laser-treated coatings were studied systematically at 1000 °C. The results indicated that the coating with 3 mm distance between the laser-treated zone, namely the dot distance, showed the longest thermal cycling lifetimes, which was approximately 2.5 times as much as that of the as-sprayed coating. For one thing, the columnar grains and segmented cracks in the dot units were beneficial for accommodating the thermal stresses of coatings during thermal cycling. For another, a certain number of microcracks in the dot units could release the driving force for crack propagation, namely the elastic energy.

The use of compositionally complex ZrO2-based ceramics doped with a mixture of yttrium-subgroup rare-earth metal (REM) oxides for the deposition of thermal barrier coatings (TBCs) was studied. For research, a heavy concentrate (HC) of yttrium-subgroup REM oxides, consisting of (wt.%) 13.3 Y2O3, 1.22 Tb4O7, 33.2 Dy2O3, 8.9 Ho2O3, 21.8 Er2O3, 1.86 Tm2O3, 12.5 Yb2O3, 0.57 Lu2O3, and 6.65 other oxides (including 3.2 Al2O3), and Y2O3 and M-ZrO2 powders were chosen. The targets for depositing electron-beam ceramic TBC layers—both standard and compositionally complex ones—were made of ceramic mixtures including (wt.%) M-ZrO2–7 Y2O3 and 90 M-ZrO2–10 HC. The properties of the compositionally complex and standard yttria-stabilized ZrO2-based ceramic layers in electron-beam TBCs applied in one process cycle were compared. Two-layer metal/ceramic TBCs were deposited onto model blades by directional crystallization from the ZhS-26VI alloy employing an UE-174 industrial electron-beam installation (ELTECHMACH, Vinnytsia). The ceramic M-ZrO2–7 Y2O3 topcoat was denoted as YSZ and 90 M-ZrO2–10 HC as HCSZ. The MZP-6 alloy (nickel–chromium–aluminum–yttrium) was used to form an inner heat-resistant bond coat. This resulted in rough dense glassy coatings differing by color: light-gray YSZ and dark-gray HCSZ. The coatings were 90–95 μm thick on the blade back side and 90 μm thick on the pressure side. Both coatings included the F-ZrO2 phase. Feather-like microstructures emerged in the coatings. The YSZ topcoat contained two types of dense structures, represented by columns and branched formations, and the HCSZ layer was of irregular microstructure with wide feather-like formations growth together. The laminar microstructure of the ceramic topcoat was due to the process features peculiar to electron-beam deposition. The YSZ topcoat had the following microhardness: 3884 MPa on the back side and 6052 MPa on the pressure side. The HCSZ topcoat had much lower microhardness: 1381 MPa on the back side and 1679 MPa on the pressure side. The compositionally complex coating withstood 161 thermal cycles and the standard coating 138 thermal cycles. Previous studies showed that ZrO2 stabilization with concentrates of yttrium-subgroup REM oxides was promising for the microstructural design of TBC ceramic topcoats.

One of the most technologically beneficial engineering ceramics is yttria stabilized zirconia (YSZ). As a result, research interest about YSZ has been intensive for many years. In this study, the lattice thermal conductivity and oxygen diffusion coefficient of YSZ are investigated at different temperatures (from 700 K to 1300 K) and zero pressure with the Green-Kubo formalism. We find that the lattice thermal conductivity decreases as the temperature increases, particularly at low temperatures and it shows a slightly temperature independence at high temperatures. The results demonstrate that the YSZ has quite a low thermal conductivity compared with pure zirconia. We also show that the oxygen tracer diffusion coefficient, as calculated from the mean square displacements, has an activation energy of 0.85eV.

This study aims to fabricate partially stabilized zirconia (PSZ)-titanium (Ti) composites to produce implants having ceramic and metallic characteristics. To fabricate such materials via powder metallurgy, sintering reactions must be suppressed. In this study, ceramic-coated Ti powder was used as a starting material to suppress Ti oxide formation. Yttria was coated on Ti powder using the sol-gel technique, the Ti powder was mixed with PSZ powder, and the mixed powders were sintered. From the results of optical microscopy and XRD analysis, dense PSZ-Ti composites containing the yttria phase were successfully fabricated without any reaction products. Hardness and bend tests revealed that the hardness and elastic modulus of the composites increased with the increase of PSZ content and agreed with the predicted values based on the rule of mixtures. Bend tests also revealed that the strength did not improve, as the brittle yttria phase preferentially fractured in the composites subjected to bending.

Sr segregation is one of the key issues affecting the performance and durability of lanthanum strontium cobalt ferrite electrode (LSCF) for solid oxide cells (SOCs). In this study, we investigated the Sr segregation behavior in LSCF under compression with purpose of simulating the operating condition of LSCF electrode in an assembled SOC stack. The electrochemical performance of LSCF electrode in a symmetric cell was evaluated by impedance spectrometry. The Sr segregation behavior on the surface of LSCF electrodes was investigated by energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). It was confirmed that the compression load would suppress the formation of SrO on the surface of LSCF during long-term holding in air at 800 °C, resulting in significantly improved durability compared with the LSCF electrode without compression. Furthermore, it was revealed that the type of materials (YSZ, GDC and Pt) in contact with LSCF would also affect the Sr segregation in LSCF. In particular, contacting with YSZ under compression would induce more SrO formation on the surface of LSCF than GDC and Pt.

This study investigates the microstructure evolution and mechanical properties of bare and Co coated AISI 441 ferritic stainless steel/YSZ ceramic reactive air brazed joints achieved by Ag–CuO braze for Solid Oxide Fuel/Electrolysis Cells applications. Interfacial microstructure of steel/YSZ joints is analyzed by SEM and TEM with EDS. A thick and porous oxide layer rich in Fe, Cr, and Cu is found in bare steel/YSZ ceramic joints, which is induced by the severe oxidation and its intense reaction with CuO during the brazing process. For the coated steel/YSZ ceramic joint, a comparably dense and uniform (Co, Fe, Cu)3O4 spinel layer is formed on the steel surface, which is tightly bonded with Ag–CuO braze without visible bonding defects. Meanwhile, the oxidation of steel substrates and its interaction with CuO is significantly suppressed. Co coated steel/YSZ joints possess reliable mechanical properties with the shear strength of 51 MPa, which is 54.5% higher than that of bare steel/YSZ ceramic joints (33 MPa). Besides, the microstructure evolution of coated steel/YSZ ceramic joints during brazing is schematically illustrated by a physical model.

In aeroengines, thermal barrier coatings (TBCs) are usually utilized to protect the hot components from hot gases. The ability to predict the TBC failure is crucial to avoid economic losses. In this study, plasma-sprayed 8 wt.% yttria-stabilized zirconia (YSZ) coatings were subjected to corrosion by calcium–magnesium–aluminosilicate (CMAS, 33CaO–9MgO–13Al2O3–45SiO2) glass at 1250 °C. After the test, two morphologies were observed on the coating surface. At the sample edges, the coating underwent over-sintering because of the locally high temperature: the molten glass easily penetrated the YSZ layer and reacted with it; and iron spinel was detected on the surface. In the sample central region submitted to a relatively lower temperature, a dense layer consisting of both CMAS glass and YSZ was formed. The analysis of the self-luminescence of the YSZ coating after corrosion revealed the presence of sintered regions on the coating surface, which increased as the corrosion temperature increased. This came with a decrease in the coating luminescence. This study shows that the self-luminescence properties can be used to monitor the degree of corrosion and predict the failure of the coating.

Recently, due to the unique advantage in ionic conductivity, semiconductor–ionic conductor composite (SIC) has been widely applied as electrolyte for solid oxide fuel cell (SOFC), and the suitable anode and cathode should be chosen to match the SIC electrolyte. Inspired by this ideology, the semiconductor lanthanum nitrate (LaNiO3) with perovskite structure was prepared by sol-gel method and then composed with ionic conductor yttrium-stabilized zirconia (YSZ) to form LaNiO3-YSZ SIC, which was applied as electrolyte membrane, simultaneously the Li2CO3–LaNiO3 composite and Ni0.8Co0.15Al0.05LiO2 (NCAL) were respectively utilized as anode and cathode for fuel cell construction. Through optimizing the electrolyte composition, such device based on LaNiO3-YSZ electrolyte and Li2CO3–LaNiO3 anode received a supreme performance of 505 mW/cm2 at 550 °C, and the maximum power density can also maintain at 350 mW/cm2 even as the temperature dropped to 475 °C. The excellent performance is attributed to the decent ionic conductivity of LaNiO3-YSZ electrolyte and the outstanding catalysis activity of electrodes. In addition, we have found that the addition of Li2CO3 component into anode can substantially enhance the cell performance. Our result demonstrates that the multifunctional LaNiO3 can be simultaneously applied as electrolyte and anode for low-temperature SOFC.

Development of biocompatible dental implants has attained significant impact in dental industry. In the present work, we report for the development of biocompatible nano-Yttria-stabilized Zirconia (YSZ) coatings on 316L stainless steel (316L SS) obtained by EPD process followed by sintering at air atmosphere. The surface morphology and electrochemical performance of nano-YSZ-coated 316L SS were investigated to evaluate its corrosion behavior in artificial saliva medium. The surface morphology and composition of the coatings were characterized by XRD, Raman, and FESEM with EDAX, respectively. The electrochemical performance of the uncoated metal and nano-YSZ-coated 316L SS samples were evaluated in artificial saliva medium using electrochemical techniques such as Open Circuit Potential – time measurement (OCP), Electrochemical Impedance Spectroscopy (EIS), and Cyclic Potentiodynamic Polarization (CPP). The nano-YSZ-coated 316L SS thin film possess significant electrochemical and biocompatibility properties compared to uncoated metal. Nano-YSZ-coated 316L SS (70 V, 5 min, 800 °C) acts as an active and also as a good barrier against corrosive ions and resists ions penetration from artificial saliva to the metal surface.

CMAS corrosion is one of the significant failure mechanisms for thermal barrier coatings (TBCs). In this work, the corrosion behaviors and wettability of CMAS on M-YTaO4 at 1350 °C are studied to evaluate the M-YTaO4 ceramics’ potential to replace YSZ. The results show that the contact angles of CMAS on M-YTaO4 with different time (1 min, 0.5 h, 4 h, 10 h and 24 h) are around 14.3° (14.4°14.4°, 14.4°, 14.3° and 14.2°, respectively), and larger than that on YSZ (8.0°, 1 min), which means the wettability of CMAS on M-YTaO4 is worse than that on YSZ and which is benefit to improve its corrosion resistance. The thickness of reaction layer is increasing with elapsed time, but the increasing rate is decreased, and the maximum reaction thickness is 31.42 μm at 24 h. There are four main phases after reaction, which are M-YTaO4, M’-YTaO4, Ca2Ta2O7 and Y2Si2O7. For the effects of lattice distortion and thermodynamics reason, M’-YTaO4 can retain steadily at room temperature. Besides, the chemical reaction process between CMAS and yttrium tantalite is also be discussed.