Co-sintering Technique Research Articles

Preparation of ultra-high permeability dual-layer Al2O3 hollow fiber supports for zeolite membrane fabrication

Four-channel dual-layer Al2O3 hollow fiber with ultra-high permeability and mechanical strength was prepared by co-extrusion and co-sintering technique for the first time and used as support for NaA zeolite membranes fabrication. The macroporous inner layer of the Al2O3 hollow fiber, composed by large Al2O3 particle, gives supports the high permeability and mechanical strength, while the thin out layer, composed by small particles, provides an even and smooth surface for zeolite membrane growth. By using SiO2 as the sintering aid, the sintering temperature of the inner layer was reduced and match with that of the outer layer. The effects of SiO2 adding amount, sintering temperature, Al2O3 particle size and their content on the structure and properties of the prepared hollow fiber were investigated systematically. At a sintering temperature of 1520 °C, a dual-layer hollow fiber with surface pore size of 0.38 μm and fracture load of 24.52 N, exhibits pure water flux as high as 22.23 m3 m 2 h−1 bar−1. The NaA membrane prepared on this support achieved a flux of 14.14 kg m−2 h−1 and a separation factor >10,000 in pervaporation separation of EtOH/H2O solution (90 wt%, 75 °C). This work provides an efficient and low-cost way to prepare ceramic hollow fiber support for high-performance zeolite membrane fabrication.

One-step fabrication of asymmetric alumina ceramic membranes with tunable pore parameters for oil-water separation

Porous ceramic membranes with low-cost and high performance are desirable in industrial filtration field. To improve the performance while reducing the production cost, various measures were developed, however, pre-sintering of supports, preparation of membrane-forming suspensions and adoption of extensive organic additives that involved were adverse to cost reduction. Herein, cost-effective one-step co-pressing and co-sintering technique was proposed to prepare asymmetric ceramic membranes. The results revealed that pore parameters and performance of the fabricated membranes could be adjusted by altering mole ratio of Al2O3 to SiO2 (Al2O3/SiO2) in the support and sintering temperature. The influence of supports on the permeation flux of membranes surpassed that of the parameters of membrane layer. Additionally, the oil rejection rate of the membranes exceeded 96 % within 2 min and even reached 100 % (~60 min), the water flux and steady-state feed flux were 1330–1730 L·m−2·h−1 and 470–620 L·m−2·h−1 at 1 bar, respectively. Moreover, cake filtration was the main fouling mechanism throughout the separation process. This research provides a feasible and simple method for preparing low-cost high-performance ceramic membrane for wastewater treatment.

Thermal consequences of sintering the borosilicate matrix blue-green color release properties

Color transformation glass ceramics were produced of borosilicate matrix co-doped (SrBaSm)Si2O2N2:(Eu3+Ce3+) blue–green (B-G) (abbreviated as (SBS)SON:(EuCe) B-G) phosphors using a two-step co-sintering technique. The shift in illumination characteristics and drift of chromaticity coordinates (CIE) of (SBS)SON:(EuCe) (B-G) phosphors and hue transformation glass ceramics were investigated over a 600–800 ºC sintering thermal range. With rising sintering heat, the illuminated strength and inner quantum yield (QY) of (abbreviated as B-G) phosphors and glass ceramics reduced. Once the sintering heat was raised above 750 ºC, the phosphors and hue transformation glass ceramics showed nearly no high point among their luminescence photoluminescence (PL) and photoluminescence excitation (PLE) bands of color. B-G phosphors have low heating steadiness at more elevated temperatures, according to the findings. The glass matrix destructed the phosphors lattice layout and the Ce3+ in the phosphors was oxidized to Ce4+, resulting in a reduction in the luminous characteristics of the color transformation glass ceramics.

New insights into single-step fabrication of finger-like anode/electrolyte for high-performance direct carbon solid oxide fuel cells: Experimental and simulation studies

Cell preparation techniques and design parameters have significant impacts on the electrochemical performance of direct carbon solid oxide fuel cells (DC-SOFCs). In this work, a finger-like nickel-based anode/electrolyte has been successfully fabricated in a single step via the tape-casting combined phase-inversion and co-sintering technique, which simplified the preparation process and reduced the fabrication cost. The finger-like anode/electrolyte exhibited identical microstructure and exceptional adhesion, ensuring the absence of any cracks during the co-sintering process. As a result, the corresponding single cell delivered a very competitive output of 436 mW cm−2 at 850 °C using activated carbon as fuel. Moreover, it operated stably for 20.1 h under 100 mA with a high fuel utilization of 22.5% at 850 °C. Model verification was also performed by comparative analysis of the effects of the finger-like pore length, anode thickness, cathode thickness, and electrolyte thickness on the cell performance using numerical simulation, which generated the resultant two-dimensional distributions of CO molar concentration, current density, O2 molar concentration, and temperature as well as the power output of the cell. Simulation results verified the experimental findings that DC-SOFC performance was enhanced with increases in the finger-like pore length and cathode thickness, and with decreases in the anode and electrolyte thicknesses. This work provides valuable insights into further optimizing the cell design and manufacturing process, paving the way for the development of high-performance DC-SOFCs.

High-efficiency yellow-emitting La3Si6N11:Ce phosphor-in-glass for laser-driven white lighting

To cope with the market competition of solid-state lighting, there is an urgent need for an efficient and stable fluorescent conversion material that can be used in high-performance lighting. A novel and unique nitride phosphor, La3Si6N11:Ce3+ (LSN), exhibits a wider luminescence spectrum and better thermal quenching performance than Y3Al5O12:Ce3+ (YAG). In this study, LSN phosphors are dispersed in a SiO2–B2O3–CaO–Na2O glass system, and a series of LSN phosphor-in-glass (LSN PiG) samples are prepared by a low-temperature co-sintering technique. The luminescence, thermal stability, microstructure and photoluminescence properties are investigated. The internal quantum efficiency of LSN:Ce PiG (85%) is close to that of the original phosphor (90%). Under excitation of a 450 nm blue laser diode, the LSN PiG produces white light with a luminescence efficiency of 145.91 lm/W, and a luminous flux of 209lm is achieved. Moreover, the color rendering index of LSN is much higher than that of YAG, reaching 73, indicating that LSN PiGs have good application prospects as yellow converters in high-power laser lighting.

A limiting current hydrogen sensor based on BaHf0.8Fe0.2O3-δ dense diffusion barrier and BaHf0.7Sn0.1In0.2O3-δ protonic conductor

A limiting current hydrogen sensor was successfully prepared by the co-pressing and co-sintering method using proton-electron mixed conductor BaHf0.8Fe0.2O3-δ as the dense diffusion barrier instead for small hole and BaHf0.7Sn0.1In0.2O3-δ as proton conducting electrolyte. The BaHf0.8Fe0.2O3-δ and BaHf0.7Sn0.1In0.2O3-δ powders were synthesized by high temperature solid state method. The phase composition, microstructure, chemical stability and conductivity of materials were characterized. Sensing performance of the hydrogen sensor was tested. The results show that dense BaHf0.8Fe0.2O3-δ and BaHf0.7Sn0.1In0.2O3-δ layer are closely combined together by the co-pressing and co-sintering technique at 1600 °C for 8 h and clear boundaries are observed between two pure perovskite phases. BaHf0.8Fe0.2O3-δ shows excellent chemical stability for pure H2 and CO2, water steam and 200 ppm H2S/Ar. Meanwhile, as the dense diffusion barrier, BaHf0.8Fe0.2O3-δ possesses considerable proton and electron conductivity compared with small hole. The sensor shows a stable limiting current platform in 0–600 ppm H2 at 400–600 °C at a certain voltage range due to dense BaHf0.8Fe0.2O3-δ layer forming diffusion control. The limiting current (ΔIL) has a good linear dependence on the hydrogen concentration. In addition, there is a good linear relationship between log(ILT) and 1000/T, and the Arrhenius model of limiting current is log(ILT) = 6.21-4.96 × 1000/T, and the hydrogen diffusion activation energy is 0.98 eV. The sensor has good long-term stability and high anti-interference capability to O2, CO2 or H2S, but water vapor has a certain effect on sensing performance.

Fabrication of a dual-layer ceramic mesoporous membrane with high flux via a co-sintering process

The application of ceramic mesoporous membranes is mainly limited by the trade-off between separation performance and fabrication cost. Here, a co-sintering technique is employed to fabricate ZrO 2 dual-layer ceramic mesoporous membranes with high separation precision and water permeance. Based on a coarse ceramic substrate, dual layers that could effectively decrease the fabrication cost and time were co-sintered. By doping zirconia nanoparticles in the sublayer, the sintering temperature could be decreased, and a high bonding strength was achieved between the dual layers. It is demonstrated that the permeance can be finely tuned by controlling the thickness of the sublayer. The resulting membrane exhibited a high water permeance of 280 L m −2 h −1 bar −1 and a molecular weight cut-off of 40–50 kDa. The zirconia mesoporous membrane was employed for sol separation, affording a 100% rejection rate toward SiO 2 nanoparticles. The cost-effective ZrO 2 mesoporous membrane exhibits significant application potential for the separation of industrial SiO 2 sols. • A dual-layer ceramic mesoporous membrane was prepared by the co-sintering process. • ZrO 2 nanoparticles were doped in the sublayer to increase the bonding strength of the membrane. • The resulting mesoporous membrane exhibited a 100% retention rate and highly stable permeance for SiO 2 sol separation.

High color rendering index composite phosphor-in-glass for high-power white laser lighting

The aim of this study is to investigate a thermally robust white color converter for high-power solid-state lighting, especially laser lighting. Lu3Al5O12:Ce3+/CaAlSiN3:Eu2+ phosphor-in-glass samples (LuAG&CASN-PiGs) were synthesized via a low temperature co-sintering technique. The prepared LuAG&CASN-PiGs exhibited remarkably high internal quantum efficiency of 87 %. Tunable warm white light-emitting diodes (wLED) were acquired by tailoring the sample thicknesses and phosphor contents. The optimized sample showed a high luminous flux of 183.68 lm under a blue laser diodes (LDs). In addition, the chromaticity of white LDs based on the LuAG&CASN-PiGs shifted from cool to warm white by changing the sample thicknesses. High quality white light in wLDs was achieved (Ra＝95). More importantly, the constructed LuAG&CASN-PiG converted LDs with a heat sink exhibited the luminous efficiency of 216.79 lm W−1. The results revealed that the prepared LuAG&CASN-PiG had great potential for application in solid-state laser light sources.

Stability study of triple layer hollow fiber in solid oxide fuel cell with methane as fuel

Solid oxide fuel cell (SOFC) is an attractive device that can convert chemical into energy. Recently, the triple layer hollow fiber (TLHF) opens up a new discovery of higher power output. This study investigates the fabrication of TLHF in solid oxide fuel cell consisting anode/anode functional layer (AFL)/electrolyte (NiO-YSZ/NiO-YSZ/YSZ) via single-step phase inversion-based co-extrusion combined with co-sintering technique using methane as fuel. TLHF formed sandwich-like structure that corresponds to the anode and AFL with dense electrolyte. Initially, the open circuit voltage (OCV) was 1.1 V, after 90 min, the OCV dropped to 0.2 V due to the carbon deposits that caused poisoning. Meanwhile, the power density also reduces from 0.8 to 0.33 Wcm−2. SEM image carbon shows the carbon deposited causing crack and reached electrolyte layer. TEM of the Ni catalyst indicates there are multilayer of graphite exhibit at the Ni particle courtesy of the carbon deposits. The results showed the graphite causing the performance to decrease which is corresponding to the usage of methane as fuel.

A limiting current oxygen sensor prepared by a co-pressing and co-sintering technique

La0.8Sr0.2Ga0.8Mg0.2O3–δ (LSGM) and La0.8Sr0.2(Ga0.8Mg0.2)1–xCrxO3–δ (LSGMC, 0.1 ≤ x ≤ 0.9) were synthesized by a solid-state reaction and characterized by X-ray powder diffraction (XRD), thermal expansion, and DC four-probe method. A limiting current oxygen sensor using LSGM solid electrolyte and LSGMC (x = 0.7) dense diffusion barrier was prepared by a co-pressing and co-sintering technique and the sensing performances were evaluated. XRD shows the presence of a crystal structure in the series belonging to Pm-3m (No. 221) for x = 0–0.9. Electrical conductivity and thermal expansion coefficients first decrease and then increase with increasing x. LSGMC (x = 0.7) is the most suitable ceramic material and is selected as dense diffusion barrier. There is a directly proportional relationship between limiting current and oxygen concentration, and the equation iL(mA)=3.65CO2(%) is established from the measured data by simple regression analysis. The Arrhenius model for limiting current is logiL(mA)=3.11−2.16/T(K), and the activation energy for oxygen diffusion is 0.43 eV.

A novel single-step fabrication anode/electrolyte/cathode triple-layer hollow fiber micro-tubular SOFC

Micro-tubular solid oxide fuel cells (MT-SOFCs) have attracted much attention due to; higher volumetric output density, greater tolerance to cycling, quicker start-up capability and better mobility. Fabrication process of MT-SOFCs is one of the critical factor that ensures the success of a cell. There are three main components (i.e. anode, electrolyte and cathode) in the development of MT-SOFCs which are generally fabricated through separated and multiple laborious steps. This study aims to produce a novel anode/electrolyte/cathode (NiO-CGO/CGO/LSCF-CGO) triple-layer hollow fiber (TLHF) in a single-step using phase inversion based co-extrusion combined with co-sintering technique. The challenge lies within the diverse sintering behaviors among the anode, electrolyte and cathode layers at some point of the cell fabrication. In this study, the TLHF was found being able to survive the co-sintering at 1450 °C resulting a defect free precursor producing 0.48 Wcm−2 maximum power densities at 525 °C, which is comparable with the cell fabricated using conventional multiple-step process.

Fabrication and Characterization of Ni-GDC/GDC Half-Cell Manufactured By Tape Casting and Reactive Magnetron Sputtering Processes As Half-Cell for SOFC

In this work, anode-supported solid oxide fuel cells (SOFCs) has been manufactured by tape casting and co-sintering technique. NiO and GDC (10% Gd), used for the anode-supported (as) and the anode functional layer (afl) powders, with an initial size of -40 mesh and -100 mesh particle size respectively, were milled by using zirconia balls in a Turbula-(System Schatz from WAB) times up to 24 to 48 hours. Half-cell, 28 mm of diameter, Ni-GDC10 composite anodes have been elaborated by slurry based tape casting method for anode supported solid oxide fuel cell. The chosen ceramic powders in suspension were prepared with the mass ratio of 65:35 for NiO to GDC10. The microstructural morphological /porosity/surface features of the half-cell were analyzed by Scanning Electron Microscopy (SEM), XRD and 3D profilometry before and after different annealing treatment. Pycnometry and porosimetry techniques were primarily used to determine pore size and pore volume by equation Washburn and Ideal gas law-method. Depending on the results, work on the support anode (AS) Ni-GDC will continue in particular to avoid the presence of the residual phase of carbon resulting from the use of an agent poro formers with graphite. The obtained cell after sintering was seen without any deformation or crack. One of the ways followed to remove the residual graphite is increase of the temperature and / or sintering time.The pre-sintered anode green tape was coated with a GDC electrolyte film by reactive magnetron sputtering using PEM techniques. An Alcatel SCM650 sputtering chamber was used for synthesizing the dense GDC layers. A Ce-Gd metallic target (90-10% at) was powered by a pinnacle + pulsed current generator from Advanced Energy. The structural, microstructural and morphological features of the half-cells were determined by XRD, SEM and 3D profilometry as deposited and after different annealing treatments. Finally, the EIS measurements were performed on Ni-GDC/GDC half-cells under 60 sccm nitrogen by the means of a Solartron SI 1260 impedance / gain analyzer from 20 MHz to 0.1 Hz with 11 points per decade.

Facile fabrication of Eu3+ activated YAG:Ce3+ glass ceramics exhibiting high thermal stability and tunable luminescence for warm white LEDs

To relieve the issues of high correlated color temperature and low color rendering index, it is urgent to develop an inorganic color converter materials with both red- and yellow-emission to replace the conventional organic resin/silicon-based color converter and acquire warm white light-emitting diodes (WLEDs). In our work, transparent glass–ceramics (GCs) containing Ce3+:Y3Al5O12 (Ce3+:YAG) yellow phosphors and Eu3+ ions are successfully fabricated by using low temperature co-sintering technique. And then the microstructure and luminescence properties of the GC are investigated in detail. Importantly, the impact of Ce3+:YAG phosphors concentration, Eu3+ ions concentration, co-sintering time and the GC thickness on optical performances are also systematically demonstrated. Impressively, the as-fabricated samples exhibit an efficient red emission at 611 nm owing to the 5D0→7F2 transition of Eu3+. Subsequently, the temperature-dependent luminescence and thermal quenching is also investigated. Finally, the constructed WLEDs show an optimal luminous efficacy of 120.85 lm/W, a color rendering index of 70.2 and a correlated color temperature of 5267 K. All the results indicate that the as-fabricated GC would have potential practical applications in high-power WLEDs.

Low-temperature co-sintering technique for the fabrication of multi-layer functional ceramics for solid oxide fuel cells

The low-temperature co-sintering technique for the fabrication of the multi-layered electrolyte supported on a planar anode substrate is demonstrated for solid oxide fuel cells (SOFCs). A NiO/gadolinia-doped ceria (GDC) anode substrate is fabricated using tape casting and lamination processes, and yttria-stabilized zirconia (YSZ) bottom electrolyte and GDC top electrolyte layers are sequentially screen-printed, followed by co-sintering at 1230°C. The electrolyte layers are successfully densified at an extremely low processing temperature by promoting the sinterability of the individual components, and a continuously graded electrolyte structure is constructed to suppress the delamination of the electrolyte films. Based on the camber analysis, the cell structure is optimized to minimize the structural distortion and eliminate the processing defects. The low-temperature co-sintering technique presented in this study is expected to widen the material selection and resolve the compatibility issues associated with high-temperature processing for the fabrication of SOFCs.

Anode supported planar solid oxide fuel cells with the large size of 30 cm × 30 cm via tape-casting and co-sintering technique

In this work, the NiO−8YSZ/8YSZ half-cells for planar ASCs with the large size of 30 cm × 30 cm are prepared by optimizing both the sintering characteristics and the sintering temperature. The shrinkage rates, open porosities and flexural strength of the half-cells are investigated systematically. The large size half-cells which are prepared by the tape-casting, co-sintering and two-step sintering method show the optimal comprehensive performances with the sintering temperature being 1350 °C. The NiO+8YSZ/8YSZ/LSM+8YSZ anode-supported single cells are obtained at the sintering temperature of 1050 °C. The maximum measurement power at output voltage of 0.8 V of the two cells and 1.6 V of the stack can reach 32.6 W, 34.7 W and 67.3 W, respectively. The two-cells stack is successively discharged under constant current of 5 A for 316 h with the degradation rate of 1.58% kh−1 and 30 A for 1161 h with no degradation at the temperature of 750 °C. The large size ASCs show the good mechanical strength and an acceptable degradation.

Fabrication and characterization of Ni-SSZ gradient anodes/SSZ electrolyte for anode-supported SOFCs by tape casting and co-sintering technique

In this work, anode-supported solid oxide fuel cells (SOFCs) has been successfully prepared by tape casting and co-sintering technique. The structure contains the thin and dense 10% Sc2O3-stabilized-ZrO2 (SSZ) electrolyte layer and the anode layers with continuous porosity gradient. The decomposition of organic additives and the shrinkage of green tape were analyzed by thermo-gravimetric and differential thermal analyses (TG-DSC) and thermal dilatometry. The microstructure morphologies and the porosity of anodes were examined by SEM and Archimedes method. The obtained anodes with continuous porosity gradient facilitate diffusion of the fuel gas and enlarge electrochemical active three phase boundaries. The open circuit voltage (OCV) was close to 1.1 V. The maximum power densities of single cell with graded Ni-SSZ anode were higher than non-gradient Ni-SSZ anode at 600, 650, 700, 750 and 800 °C and were 0.15, 0.30, 0.51, 0.70 and 1.00 W cm−2, respectively. Rp of cell with graded Ni-SSZ anode was lower than that of non-gradient Ni-SSZ anode.

Micro-porous calcium phosphate coatings on load-bearing zirconia substrate: Processing, property and application

This study presents the design, processing, properties and potential applications of a novel layered bio-ceramic composites consisting of three different micro-porous calcium phosphate coatings on strong zirconia cores manufactured using a recently developed slip coating-deposition and coating-substrate co-sintering technique. Detailed microstructures of the three graded micro-porous calcium phosphate coatings, and the coating/substrate interface have been investigated. Also, the flexural strength of the bio-ceramic composite and the bonding state between the coatings and zirconia substrate have been characterized. A preliminary and limited in vitro cell test indicates that the new scaffold composite has no cytotoxicity to the fibroblasts which can attach, proliferate and grow on the coating surfaces. Because of the combination of bio-function and strength, such layered load-bearing bio-ceramic composites are a potential candidate for large-scale head bone repairs.

Investigation of Cobalt-Free Cathode Material Ba<sub>0.5</sub>Sr<sub>0.5</sub>Fe<sub>0.8</sub>Cu<sub>0.2</sub>O<sub>3−δ</sub> for Micro-Tubular SOFC with Asymmetric Structure Anode

A cobalt-free perovskite oxide Ba0.5Sr0.5Fe0.8Cu0.2O3−δ (BSFCu) is applied as the cathode material for intermediate temperature micro-tubular solid oxide fuel cells (SOFCs) with asymmetric structure anode. The NiO-YSZ hollow fiber anode as support was prepared by the phase inversion technique. The as-prepared fiber anode shows a special asymmetric structure consisting of porous sponge-like structure in the middle and finger-like porous structure on the inner and outer side. Dense thin YSZ electrolyte membrane and SDC transition layer were deposited on the NiO-YSZ hollow fiber anode by a vacuum-assisted dip-coating and co-sintering technique. Laboratory-sized micro-tubular single cells of NiO-YSZ/YSZ+SDC/BSFCu-SDC were tested at 650-750°C with humidified H2 as the fuel and static ambient air as the oxidant. The peak power densities of 437.2, 326.5 and 214.4 mWcm-2 can be obtained at 750, 700 and 650°C, respectively. The experimental results indicate that the cobalt-free perovskite oxide BSFCu is a promising cathode material candidate for the developed intermediate temperature micro-tubular SOFC with asymmetric hollow fiber anode.

Anode performance control of micro-tubular SOFC via wet coating method

A cathode-supported micro SOFC was prepared via co-sintering technique of a scandia-stabilized zirconia (ScSZ) electrolyte layer and a micro-tubular (La,Sr) xMnO 3−δ (LSM) support, and subsequent deposition of various anode layers by dip-coating method. The micro-tubular SOFCs were electrochemically evaluated in a humidified H 2 (3% H 2O) atmosphere. An LSM-Ce 0.9Gd 0.1O 1.95 activation layer was also introduced between the cathode tube and the electrolyte layer in order to improve the catalytic activation at the cathode side. The micro SOFCs exhibited a stable open circuit voltage above 1.05 V at 650 °C, and the cells with the anode film thicknesses of 8, 30 and 50 μm generated a maximum power density of 36, 49 and 126 mW/cm 2, respectively. And, the cell with 50 μm thick anode layer showed about 10 times higher exchange current density than the others, which indicates that the anode performance on the cathode-supported micro SOFC was greatly affected by the thickness of the anode coating layer.

High‐Performance, Anode‐Supported, Microtubular SOFC Prepared from Single‐Step‐Fabricated, Dual‐Layer Hollow Fibers

A high-performance, microtubular solid oxide fuel cell is developed using an improved electrolyte/anode dual-layer hollow fiber fabricated via a novel coextrusion and co-sintering technique. The technique allows control over the porosity of the anode, resulting in an increase in the power output to almost double what has been previously reported.