Yttria-stabilized Zirconia Particles Research Articles

Solid-state transformation composite filler: A new strategy to strengthen ceramic/metal joint

Residual stress is the main hindrance to achieve a robust ceramic/metal brazed joint. In this study, yttria stabilized zirconia (YSZ) particles was fabricated into solid-state transformation composite filler, which was proposed as a new strategy to strengthen Ti3SiC2/Cu brazed joint. After detailed characterization conducted on YSZ particles and brazed joint, the abnormal expansion properties of YSZ and its strengthening brazed joint mechanism were clarified. The content of Y2O3 in YSZ had significant effects on the phase transformation of ZrO2 from tetragonal to monoclinic. When 3 mol.% Y2O3 was added, the maximum phase transformation occurred at about 500 ◦C, half of brazing temperature, during the cooling process. The phase transformation of ZrO2 effectively released residual stress in the joint, which was induced by both temperature changes and residual stress. The abnormal volume expansion during phase transformation decreased the thermal mismatch of brazed joint further to strengthen brazed joint.

The effects of phase interfaces in SmFeN/YSZ composite thermal barrier materials on electromagnetic wave-absorbing properties

Yttria-stabilized zirconia (YSZ) oxide ceramic powder is a thermal-barrier material used to fabricate thermal barrier coatings (TBC). In this study, to improve the electromagnetic wave (EMW) absorbing properties of TBCs, microwave-absorbing samarium iron nitrogen (SmFeN) particles were used to prepare SmFeN/yttria-stabilized zirconia (YSZ) composites. To study the effect of the SmFeN/YSZ interfaces on the EMW-absorbing properties of the SmFeN/YSZ composite, SmFeN/YSZ interfaces were built in different ways in composite materials having the same mass ratio of 1:1, for example, SmFeN and YSZ particles homogeneously mixed together, SmFeN/YSZ interfaces perpendicular and parallel to the EMW incident direction, and different interfaces between YSZ and SmFeN. Thus, the microwave absorbing performance of the samples, including the electromagnetic parameters, attenuation coefficient, eddy-loss current (C0), impedance matching, and minimum reflection loss (RLmin) values were examined and analyzed. The results demonstrate that interfaces perpendicular to the direction of the EMWs can increase the contact area and enhance the interfacial absorption effect. Further, when the wave-absorbing agent was placed in the middle of the composite, its wave-absorbing effect was the best among all the samples, yielding RLmin = −27.824 dB and effective absorption bandwidth (EAB) = 8.5453 GHz (effective absorption frequency range 7.9256–16.4709 GHz for a 7.2-mm-thick layer). Crucially, the frequency and bandwidth at which the best absorption occurred could be tuned by adjusting the thickness of the coating. This is because the interfaces in the samples resulted in polarization enhancement and anomalous dispersion, leading to large dielectric losses. Overall, the use of a coaxial measurement technique is highly efficient for EMW absorbing body design and process simulations.

A nozzle design for mitigating particle slowing in the bow shock region during micro-cold spray of 8 YSZ films

During micro-cold spray deposition, also referred to as the aerosol deposition method or vacuum kinetic spraying, performed with conventional nozzles, the particle impact velocities decrease drastically with particle size for fine particles <500 nm in diameter due to slowing in the stagnation region. A new design for a nozzle that contains pressure relief channels is proposed that allows the pressure in the stagnation region downstream of the bow shock to be reduced. This reduced stagnation pressure results in less particle slowing compared to conventional nozzle geometries, particularly for smaller or less dense particles. The effects of the channel geometry on the particle impact velocity are systematically investigated by independently varying the channel parameters. Calculations show that the impact velocities for 100 and 200 nm yttria stabilized zirconia particles is increased by 111% and 31%, respectively, for a selected pressure relief channel nozzle when compared to a comparable conventional nozzle. Although impact velocities are increased, a tradeoff exists with this nozzle design in that the particle focusing in the nozzle is decreased and some of the particles may be removed from the aerosol by the channels. Experiments using a nitrogen as a carrier gas at ∼40 kPa upstream pressure show that, despite the loss of larger particles into the relief channels, the deposition efficiency is improved by 300% when depositing films from fine 8 YSZ powder with the pressure relief nozzle compared to a conventional nozzle.

The solid particle erosion performance of tungsten inert gas yttria-stabilized zirconia - Inconel 625 composite cladding

The yttria-stabilized zirconia (YSZ) - Inconel 625 (IN625) composite cladding was deposited on a stainless steel substrate using a tungsten inert gas welding manipulator to protect it from solid particle erosion. Erosion wear tests were carried out at room temperature according to the ASTM G76-18 procedure. The surface of the tested material was exposed to a jet of alumina erodent particles at impact angles of 30 and 90°, respectively. Scanning electron microscopy images were utilized to examine the morphologies of the eroded surface and the microstructure of cladding. The erosive performance of YSZ - IN625 composite cladding was 3.5 and 2.4 times compared to the substrate at different impact angles. Improved microhardness and fracture toughness resulting from the favourable interaction between the hard ceramic YSZ particles and the IN625 matrix led to the enhanced erosion performance of composite cladding. Micro-cutting and ploughing were the predominant wear mechanisms in the substrate during the solid particle erosion test at a 30° impact angle, whereas the indentation-induced plastic deformation was domi­nant at a 90° impact angle. The results also revealed that the micro-cutting, detached splats and fissures were responsible for the wear in composite cladding at 30 and 90° impact angles.

Multiscale observation of nano-oxide particles in oxide-dispersion-strengthened Cu alloys

Cu alloys with high durability and high thermal and electric conductivities are the key to achieving a more energetically efficient and eco-friendly future. Noble Zr-added oxide-dispersion-strengthened Cu alloys (ODS-Cu) with high strengths are promising materials for meeting all future service requirements. In this study, three-dimensional atom probe (3D-AP) and transmission electron microscopy (TEM) revealed that the majority of nano-oxide particles in the Zr-added ODS-Cu were novel yttria-stabilized zirconia (YSZ) particles with a diameter of less than 4 nm, which were completely different from Y2Zr2O7 and Y4Zr3O12 observed in other Zr-added ODS alloys. Multiscale observations including small-angle X-ray scattering (SAXS), 3D-AP, and TEM were performed to clarify the morphology of the oxide particles in the Zr-added ODS-Cu. Further strength enhancement through microstructural homogenization and specific incremental strength values were proposed.

Characterization of Yttria-Stabilized Zirconia (YSZ) following high temperature hydrogen exposures of molybdenum-YSZ composites

Molybdenum matrix ceramic-metal (cermet) composites containing 40–70 vol% yttria stabilized zirconia (YSZ) particles (as a surrogate for ceramic fuel particles) were produced via spark plasma sintering (SPS) and exposed to flowing hydrogen at high temperature (2000–2630 K). Both steady state and thermally cycled (4 cycles with intermediate cooling to room temperature) conditions were examined for a constant total hot testing time of 80 min. Due to the high hydrogen permeability in Mo at these temperatures, pronounced microstructural degradation was observed in YSZ particles located many millimeters below the sample surface. Observed changes to the YSZ particles from the hot hydrogen testing include partial matrix debonding, thermal expansion, redeposition of material, phase changes to a monoclinic phase and cracking/bubble formation on the YSZ grain boundaries. Overall, the YSZ particles exhibited acceptable tolerance to this extreme operating environment.

Preparation of yttria-stabilized zirconia electrolyte via atmospheric plasma spraying for metal-supported solid oxide fuel cells

Plasma spraying under low chamber pressure has been proven to be capable of preparing dense MS-SOFC electrolytes, but it is costly and inefficient. In this study, atmospheric plasma spraying (APS) as a low-cost and high efficiency alternative was attempted to prepare yttria-stabilized zirconia (YSZ) electrolyte. Different spraying distances were adopted to investigate the effects of in-flight particle states on the coating microstructure and properties. The results show that due to the YSZ particle temperature increasing with spraying distance, the YSZ splats have more internal microcracks and more regular morphologies. At the spraying distance of 80 mm, the high particle velocity and plasma heating effect combine to create a dense YSZ coating with a porosity of 3.56 %. Additionally, the nanohardness and elastic modulus of this coating reaches 15.6 ± 0.8 GPa and 209.6 ± 4.5 GPa, respectively. The MS-SOFC with the dense YSZ electrolyte, achieve a maximum power density of 902 mW⋅cm-2 and ohmic resistance of 0.10 Ω⋅cm2 at 900 °C. This work demonstrates the feasibility of APS in the efficient preparation of MS-SOFCs electrolytes through optimized particle deposition.

Sintering of 3YSZ doped with lithium via modified wet chemical method

Yttria-stabilised zirconia (YSZ) materials are of great interest due to their mechanical properties, chemical inertness, low thermal conductivity and high ionic conductivity. However, a high temperature is required to consolidate the YSZ, while homogeneity problems may arise. This study proposes a modified wet chemical method for commercial YSZ sintering started from a scalable colloidal solution containing yttrium and lithium in an aqueous medium. This homogeneous mixture, adjusted by pH and Li/Y content, transforms into intermediate phases that play a key role as "cement" linking YSZ particles at low sintering temperatures. The originality consists of the use of the citric acid enabling the formation of either porous or dense microstructure depending on processing conditions. A complete follow-up of the transformation of compounds throughout the process, from liquid phase to cement, is proposed and enables us to propose the consolidation mechanism that will be useful for further optimization.

Corrosion and microstructural characterization of molybdenum cermets following hydrogen exposure up to 2630K

Ceramic-metallic (cermet) fuels are a promising fuel type for space nuclear thermal propulsion (NTP). A key feasibility issue of NTP fuels is the hydrogen chemical compatibility of candidate fuels in the proposed extreme operating temperatures for NTP systems (≥2500 K). In this study, molybdenum matrix cermets containing 40–70 vol% yttria stabilized zirconia (YSZ) particles (as a surrogate for ceramic fuel particles) were produced via spark plasma sintering (SPS) and exposed to flowing hydrogen at high temperature (2000–2630 K). Both steady state and thermally cycled (4 cycles with intermediate cooling to room temperature) conditions were examined for a constant total high temperature exposure duration of 80 min. Following testing, the Mo matrix appears robust in a Mo-YSZ cermet and exhibits acceptable mass loss (<1 wt%) with a sublinear dependence on exposure time (⅓ - ¼ power) based on hydrogen testing at 2500–2630 K with thermal cycling. Moderately higher mass losses were observed for thermally cycled (4 times) vs. isothermal specimens. The subsurface Mo-YSZ interface also remains intact despite indications of debonding at the surface. Significant hydrogen attack occurs on the YSZ particle grain boundaries in the interior of the samples at 2500–2630 K.

Characterization of pulse electric current sintered Ti-6Al-4V ternary composites: Role of YSZ-Si3N4 ceramics addition on structural modification and hydrogen desorption

In this study, we fabricated Ti-6Al-4V composites using pulse electric current (spark plasma) sintering technique and examined the influence of yttria-stabilized zirconia (YSZ) and silicon nitride (Si3N4) particles on microstructural, mechanical properties. Moreover, we investigated the effects of YSZ and Si3N4 on hydrogen uptake rate of the fabricated composites. The formation of new phases in addition to the parent α and β phases corroborates the increased hardness property exhibited by the Ti-6Al-4V composites. Further, the improvement in the hardness property was ascribed to Orowan strengthening effect due to resistance offered by cross dislocation pinning effect of closely packed particles. From the nanomechanical test, the penetration depth of the unreinforced Ti-6Al-4V alloy was maximum at a value of 272.57 nm, while all the reinforced alloys exhibited reduced penetration depth, thereby increasing the stiffness and strength of the Ti-6Al-4V composites. Other nanomechanical analyses such as nanohardness, elastic modulus, and creep were also improved in the reinforced composites in comparison with the Ti-6Al-4V alloy. The amount of hydrogen absorbed by the specimens was measured, and the Ti-6Al-4V composite with the highest proportion of Si3N4 reinforcement exhibited the highest hydrogen concentration.

Role of YSZ Particles on Microstructural, Wear, and Corrosion Behavior of Al-15%Mg2Si Hybrid Composite for Marine Applications

This study aims to investigate the microstructural alterations, mechanical properties, sliding wear behavior, and corrosion properties of Al-15%Mg2Si composites with different contents of yttria-stabilized zirconia (YSZ). Al-15%Mg2Si composites with the different contents of YSZ (0, 3, 6, and 9 wt.%) were fabricated using the stir-casting technique. The fabricated composites were characterized by means of optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS), Vickers hardness tester, linear reciprocating tribometer (LRT), and electrochemical test. The results showed that with the introduction of YSZ particles, the average size of the primary Mg2Si particles in the base composite was 137.78 µm, which was reduced to 88.36 µm after adding 9 wt.% YSZ. The aspect ratio of Mg2Si particles also decreased from 3, for the base composite, to 1.27 in the composite containing 9 wt.% YSZ. Moreover, the hardness value displays an incremental trend from 102.72 HV, as recorded for the base in situ composite, to 126.44 HV in the composite with 9 wt.% YSZ. On top of that, the Al-15%Mg2Si-9%YSZ demonstrates exceptional wear resistance, with the lowest wear rate of 0.46 mm3/km under a 25 N applied load. Its average coefficient of friction (COF) was recorded at 0.42, which is lower than both the 3 and 6 wt.% of YSZ-containing composites. The smoother worn surface in Al-15%Mg2Si-9%YSZ hybrid composite implies the abrasion phenomenon, as dominant wear behavior is milder than the other fabricated composites. On top of that, the Al-15%Mg2Si-9%YSZ also possesses optimum corrosion resistance. The corrosion rate is 0.080 mmpy, comparable to the 0.164 mmpy rate obtained in the in situ composite.

Entering a New Dimension in Powder Processing for Advanced Ceramics Shaping.

Filigree structures can be manufactured via two-photon polymerization (2PP) operating in the regime of nonlinear light absorption. For the first time, it is possible to apply this technique to the powder processing of ceramic structures with a feature size in the range of the critical defect sizes responsible for brittle fracture and, thus, affecting fracture toughness of high-performance ceramics. In this way, tailoring of advanced properties can be achieved already in the shaping process. Traditionally, 2PP relies on transparent polymerizable resins, which are diametrically opposed to the usually completely opaque ceramic resins and slurries. Here a transparent and photocurable suspension of nanoparticles (resin) with very high mass fractions of yttria-stabilized zirconia particles (YSZ) is presented. Due to the extremely well-dispersed nanoparticles, scattering of light can be effectively suppressed at the process-relevant wavelength of 800nm. Sintered ceramic structures with a resolution of down to 500nm are obtained. Even at reduced densities of 1-4g cm-3 , the resulting compressive strength with 4.5GPa is equivalent or even exceeding bulk monolithic yttria-stabilized zirconia. A ceramic metamaterial is born, where the mechanical properties of yttria-stabilized zirconia are altered by changing geometrical parameters, and gives access to a new class of ceramic materials.

A study of the processing and characterization of RSM optimized YSZ-Inconel625 wear-resistant TIG weld cladding

The present investigation focuses on developing a wear-resistant Yttria Stabilized Zirconia (YSZ) reinforced Inconel-625 (IN625) based TIG weld composite cladding on the AISI 304 stainless steel substrate. TIG welding current, scanning speed, standoff distance and YSZ reinforcement % were the primary input process parameters for cladding deposition. For the optimization of process parameters, cladding was deposited at different parametric settings, and their microhardness and sliding wear resistance was calculated as the output responses, according to Box Behnken Design (BBD) under Response Surface Methodology (RSM). Feedstock powders, developed claddings and worn samples were examined to study their surface morphology, microstructure, element composition and different phases using the SEM, Optical Microscopy, EDS, and XRD techniques. The result revealed that welding current and scanning speed are the most significant factors which govern the mechanical and tribological properties of cladding. The cladding was deposited at an optimized welding current 70 A, scanning speed of 192 mm min−1, standoff distance of 2 mm, and 25 wt.% YSZ reinforcement concentration revealed the fine and dense microstructure, resulting in maximum hardness and minimum wear. The microstructure was observed to be columnar dendrites, which grew epitaxially from the substrate. The addition of YSZ particles into the IN625 matrix resulted in the formation of Cr2O3 and ZrO2 stable oxides along with γ-Ni (FCC) phases. The wear test showed that the weight loss in claddings was mainly due to abrasive wear.

Controlled synthesis of Bi2O3–YSZ composite powders and their sintering behavior for high‐performance electrolytes

AbstractBismuth oxide (Bi2O3) is a promising additive to decrease the sintering temperature of yttria‐stabilized zirconia (YSZ)‐based electrolyte for solid oxide fuel cell application. However, Bi2O3 tends to grow into large column bars (&gt;50 µm) in a chemical coprecipitation method, which dramatically limits the mixing uniformity of Bi2O3 and YSZ, even much worse than that of mechanical mixing. In this study, the reaction temperature was increased from room temperature to 90°C to increase the number of nucleation during the violate reaction between Bi3+ solution and YSZ suspension in NaOH. On this basis, the violence of the reaction was further moderated by adding half of NaOH first, then YSZ powders and the other half of an NaOH solution. The size of Bi2O3 was further decreased to sub‐micrometer and Bi2O3 was homogeneously mixed with YSZ particles, even when its addition amount was as large as 20 mol%. These composite powders effectively promoted the sintering behavior of YSZ. The sintering temperature of YSZ was decreased to 900 and 1000°C with 10 and 5 mol% Bi2O3 doping, respectively. Increasing the doping ratio induced severe volatilization of Bi2O3 and pore formation. Raising the sintering temperature (no more than 1200°C) enhanced the doping effect of Bi2O3 into the YSZ lattice but induced instability in the YSZ crystal structure.

Effect of nano yttria-stabilized zirconia on properties of Ni-20Cr composite coatings

In the present work, 5 wt.% and 10 wt.% yttria-stabilized zirconia (YSZ) nanoparticles were reinforced in Ni-20Cr powder and deposited on boiler tube steel using a high-velocity oxy-fuel spraying process. The effect of YSZ reinforcement on microhardness, surface roughness and porosity was investigated. The hardness was the highest for nanocomposite coating reinforced with 10 wt.% YSZ and hardness was found to increase with a decrease in porosity. The coating microstructure and elements were characterized using field emission scanning electron microscopy (FE-SEM) with an energy dispersive spectroscope (EDS). The constituents of the coating were identified using X-ray diffractometer. It was found that the composite coating with 10 wt.% YSZ reinforced nanocomposite coating has the highest microhardness, in the range of 1008-1055 hv. During the coating process, nano YSZ particles were dispersed in the gaps between the micrometric Ni-20Cr particles, providing a better coating matrix than conventional Ni-20Cr. The Ni-20Cr with 10 wt.% of YSZ nanoparticles showed better results in terms of mechanical and microstructural properties during the investigation.

Preparation and characterization of Cu-GO and Cu-GO-YSZ nanocomposite coating by electrochemical deposition for improved mechanical and anti-corrosion properties

Graphene oxide (GO) and yttria-stabilized zirconia (YSZ) nanoparticle reinforced copper (Cu) matrix nanocomposite coatings were successfully fabricated via direct current electroplating from a copper sulfate electrolyte. Influences of particle concentration (GO/YSZ) in electrolyte, electrodeposition time and applied current density on composition, microstructural and anti-corrosion performance of Cu-GO and Cu-GO-YSZ composite coatings were explored. The corrosion behaviors were evaluated by electrochemical measurement. Results indicated the composite coatings exhibit a uniform and compact surface which was made up of stacked granules, exhibiting morphologies that nanoflake-like structures dispersed on the pyramid-like copper matrix granule clusters network. The crystallite sizes of Cu-GO first increased and then decreased as GO, time and current density increased, while it varied little for Cu-GO-YSZ composite coating. The preferred orientation of Cu matrix composite coating was oriented (220) texture. The content of incorporated GO increased with the introduction of YSZ into the Gu-GO matrix. The Gu-GO coating contains 93.3 wt% Cu and 5.5 GO, and the Gu-GO-YSZ coating contains 91.7 wt% Cu and 7.6 wt% GO. The average roughness Ra of Cu-GO and Cu-GO-YSZ were 240 ± 7 nm and 236 ± 40 nm, respectively. The addition of GO nanosheets could improve the microhardness and decrease the COF of Cu matrix. Both self-lubrication effect and load-bearing capability were improved by introducing GO and YSZ together in the Cu matrix. Deposits obtained at 30 mA cm−2, 30 min, 0.1 g L−1 GO and 10 g L−1 YSZ particles own the optimal corrosion resistance with the maximum Rp. It reveals that corrosion resistance was enhanced by the presence of GO nanosheets in Cu matrix for physical isolation effect of GO and the preferred orientation (220) plane, which benefited the formation of passive film.

Development of Yttria-stabilized zirconia reinforced Inconel 625 metal matrix composite by laser powder bed fusion

Ni-based superalloys can withstand a temperature of around 1400 K, while the gas turbine can endure a temperature of around 1800 K thanks to thermal barrier coatings such as Yttria stabilized zirconia (YSZ). The present work attempts to introduce a method for modifying commercial Inconel 625 metal powder to enhance the properties of the additively manufactured component for high temperature applications. Inconel 625 was modified by decorating the particles with submicron Yttria-stabilized zirconia (YSZ) particles in order to develop a metal matrix composite material. The goal of this modification was: 1) to enhance the mechanical properties of the Inconel 625 parts after laser powder bed fusion (LPBF) additive manufacturing; 2) to modify the microstructure of the LPBF parts. The influence of LPBF process parameters on surface integrity, microstructure, porosity, and microhardness of the fabricated samples was analyzed for both Inconel 625 and YSZ decorated Inconel samples. Wide ranges of laser power (50–150 W), and volumetric input energy densities (30–270 J/mm3) were examined to fabricate the parts. A Microhardness increase of 30% was observed in laser-fused composite samples after decorating the initial Inconel 625 powder particles with 1 wt% of YSZ. In addition, the microstructural analysis revealed that the addition of YSZ submicron particles stimulates heterogenous nucleation and results in microstructure refinement during LPBF of Inconel 625.

Nanoscale Analysis of LSM/YSZ Interfaces within Composite Cathodes for Commercial Solid Oxide Fuel Cells

While performance degradation for solid oxide fuel cells (SOFCs) comes in many forms, one important contributor is cation transport during long-term operation. This transport alters the chemical composition at electrode/electrolyte interfaces. These interfaces are carefully engineered to provide the critical reaction sites for oxidation and reduction reactions that regulate SOFC electrical production. Therefore, fundamental understanding of the chemical evolution of these interfaces is critical. The current study coordinates scanning transmission electron microscopy (STEM) with atom probe tomography (APT) in order to probe composition at the nanoscale across cathode/electrolyte interfaces for anode-supported commercial SOFCs. These SOFCs contain a porous composite cathode layer, consisting of sintered (La0.8Sr0.2)0.95MnO3 cathode particles and yttria-stabilized zirconia (YSZ) electrolyte particles. SOFCs are operated up to 500 hours in duration at a current density of 0.75 A/cm2 (or at open circuit) and at an operation temperature of 800°C. Measured cell voltage increases over the first 100 hours of operation, followed by a steady and linear drop in cell voltage that translates to 5.35% performance loss per 1000 hours. STEM-based energy dispersive spectroscopy (EDS) indicates nanoscale Mn-oxide formation at LSM particle surfaces after 500 hours of operation. Compositional profiles acquired by APT across LSM/YSZ particle interfaces indicate as-sintered interfaces are chemically well-defined, but La and Mn penetrate up to 5 nm into YSZ particles over the course of 500 hours. Additionally, as-sintered LSM particles exhibit measurable Mn enrichment within 20 nm of an adjacent YSZ particle. After 100 hours of operation, A-site deficiency is restored for LSM particle surfaces adjacent to YSZ. Meanwhile, the YSZ composition adjacent to LSM exhibits depletion in Y content over the first 100 hours of operation. These results suggest that initial cell voltage increase within 100 hours of operation corresponds to both Mn and Y transport at LSM/YSZ interfaces. STEM-based electron energy loss spectroscopy (EELS) provides additional insight regarding local cation valence states in relation to measured composition variations for these LSM/YSZ interfaces.

Inkjet 3D Printing of Functional Layers of Solid Oxide Fuel Cells (SOFCs) and Electrolyzers (SOEs)

Hydrogen production using renewable energy sources could enable the technological objectives to be met of decarbonising electrical power generation, energy storage to mitigate renewable energy intermittency and balancing electrical power supply and demand. The required reactors and processes need to be efficient, economic, durable, and of scalable design and fabrication. Additive manufacturing, e.g. by inkjet printing of ceramic particles offers novel means of fabricating solid oxide fuel cells and electrolysers with reproducible geometries, predictable densities of triple phase boundaries, and upscaling of electrode | electrolyte interfacial areas using imaginative 3D structures, thereby decreasing specific costs.We shall present results of using 3D inkjet printing, currently with ca. 10 mm lateral resolution, followed by sintering, for fabrication of SOFCs and SOEs. Having characterised their particle size distributions, zeta potentials and rheologies, colloidal dispersions of < ca. 200 nm yttria-stabilised zirconia (8-YSZ), NiO and lanthanum strontium manganite (LSM) particles were formulated. Having optimised inkjet printing parameters, these dispersions were used for printing 3D structures using a Ceradrop X-Serie piezoelectric DOD printer with a DIMATIX Sapphire QS-256/30 AAA printhead with 52 µm nozzle diameters. Gas-tight planar YSZ electrolyte layers were printed and sintered with ca. 10 mm thicknesses, onto porous Ni(O)-YSZ substrates. Porous LSM electrode layers also were printed on pressed YSZ substrates; cracking of printed layers due to capillary forces were mitigated by avoiding attractive depletion potentials and judicious control of sintering conditions. Detailed optimization of printing parameters, droplet size and substrate temperatures will be presented for electrolyte and electrode layers.

Investigation of solution acidity influence on the morphological structure and physical and mechanical properties of particle-reinforced tungsten alloys

Yttria-stabilized zirconia particle–reinforced tungsten alloys were fabricated by using azeotropic distillation process coupled with powder metallurgy techniques. The influence of pH value of the original solution on the precursor powders’ morphology and wear and mechanical properties of alloys was deeply studied. It showed that the precursor powder synthesized under solution with pH of 2 possesses finer particle size. The grain sizes of tungsten reinforced alloys obtained with different pH values vary from 2 to 6 μm, extremely smaller than that of pure tungsten. When pH value increases from 2 to 8, more and more bonding zirconia particles are obtained. The reinforced tungsten alloy prepared based on the solution of pH equal to 2 has better morphological and mechanical properties than the other two alloys prepared based on the solution of pH values of 5 and 8, respectively. The wear resistance of the reinforced tungsten alloy increases firstly and then decreases with the doping amount of zirconia particles. It is confirmed that the pH 2 value and chemical composition of the tungsten alloy with 3.0 wt. % Zr(Y)O2 exhibit the best wear resistance. The mechanical properties of the particle-reinforced tungsten alloy are improved with the decrease of pH value. The ultimate compressive strength and ultimate strain values of pH 2 reach to 1009 MPa and 0.23, respectively. The evolution of the relative density and associated porosity increases with the pH value. The abrasion mechanism was analyzed in detail.