Conventional Furnace Sintering Research Articles

Characterization of Na2Zn2TeO6 ceramic solid electrolyte densified by hot pressing

AbstractIn this work, we applied hot pressing (HP) for the densification of Na2Zn2TeO6 (NZTO) at lower temperature than conventional furnace sintering (FS). Calcined NZTO powder was densified by HP at 700°C for 1 h under uniaxial pressure of 20 and 60 MPa using a graphite mold. By increasing the uniaxial pressure to 60 MPa for HP, high relative density above 90% was obtained. As‐prepared NZTO by HP showed total (bulk + grain‐boundary) ionic conductivity of 0.29 mS cm−1 at room temperature, which is lower than NZTO prepared by FS at 800°C (=0.4 mS cm−1) with lower relative density (<85%). It was found that the contribution of grain‐boundary resistance in as‐prepared NZTO by HP is larger than NZTO by FS. We confirmed that the grain‐boundary resistance was significantly reduced by post‐annealing. Consequently, total conductivity at room temperature was improved to 0.42 and 0.56 mS cm−1 by annealing at 700 and 800°C for 2 h, respectively. X‐ray photoelectron spectroscopy analysis indicated that the residual carbon‐contained secondary phases were reduced by post‐annealing. These secondary phases could be formed by the carbon contamination from a graphite mold used for HP, and their removal by post‐annealing results in the improvement of ionic conduction at grain‐boundary.

Characterization of garnet-type Li6SrLa2Bi2O12 ceramic electrolyte for all-solid-state Li-ion batteries

We investigated electrochemical properties of garnet-type Li6SrLa2Bi2O12 (LSLBO) ceramic electrolyte for all-solid-state Li-ion batteries. Hot pressing at 750 °C was applied for the densification of LSLBO and the relative density of obtained sample reached 94 %. Hot-pressed LSLBO showed bulk and total ionic conductivity of 1.8 × 10−4 S cm−1 and 1.1 × 10−4 S cm−1, which is much higher than sintered LSLBO by a conventional furnace sintering and spark plasma sintering reported in previous works. Cyclic voltammogram of LSLBO showed the electrochemical stability at the operating potential for most cathode materials for Li-ion batteries. It was found that LSLBO has a certain degree of thermal compatibility with LiCoO2 cathode up to about 700 °C. The obtained results indicates the possibility of LSLBO for the application to catholyte in oxide-based all-solid-state batteries.

Characterization of Garnet-Type Li6SrLa2Bi2O12 Solid Electrolyte for LiCoO2 Cathode Composite in All-Solid-State Battery

Together with the development of inorganic solid lithium (Li) ion conducting materials for the use as solid electrolytes, the formation of intimate solid-solid interface between electrode active material and solid electrolyte is pivotal for realizing high performance all-solid-state Li-ion batteries (LiBs) with high safety and reliability. Oxide-based solid electrolytes have the advantages of good chemical stability and ease of handling, but for many of them, the high temperature processing is required for the densification, which may cause undesired side reactions with electrode active materials during the processing.Although garnet-type oxide solid electrolyte Li6SrLa2Bi2O12 (LSLBO) has lower ionic conductivity than widely studied garnet-type Li7La3Zr2O12 (LLZO), LSLBO can be sintered at much lower temperatures than LLZO [1,2]. Therefore, there is a possibility to suppress the side reaction with electrode active materials during high-temperature sintering for fabricating oxide-based all-solid-state LiBs.In this study, we prepared dense LSLBO or composites of LiCoO2 (LCO) cathode and LSLBO by hot pressing (HP). LSLBO densified at 750 °C for 1 hour showed high relative density of 95%. The densification temperature of LSLBO by HP confirmed in this work is 100–150 °C lower than Bi-doped LLZO with the formula of Li6La3ZrBiO12 (LLZBO) [3, 4]. Bulk and total (bulk + grain conductivity) ionic conductivity of LSLBO fabricated by HP attained to 2.1 × 10-4 and 1.1 × 10-4 S/cm at room temperature, which is much higher than LSLBO prepared by a conventional furnace sintering (FS) [1] and spark plasma sintering (SPS) [2]. The electrochemical stability of LSLBO at an electrical potential from 3 to 6 V vs. Li/Li+ was also confirmed by measuring the cyclic voltammogram.From XRD analysis of mixed LSLBO and LCO powders after annealing, LSLBO and LCO were found to be thermally compatible at temperature below 800 °C and LCO-LSLBO composite densified at 700 °C for 1 hour by HP showed mixed conducting properties with both electronic and ionic conductivity of 10-5-10-4 S/cm at room temperature. From galvanostatic charge and discharge testing of sintered LCO-LSLBO composite sheet, we found that electrochemical performance of LCO is not degraded by co-sintering with LSLBO. These results suggest that LSLBO solid electrolyte can be applied for LCO cathode composite in oxide-based all-solid-state LiBs.

Low driving field-induced large strain in ternary lead-free Na0.5Bi0.5TiO3-SrTiO3-ABO3 piezoceramics

In this letter, three ternary lead-free Na0.5Bi0.5TiO3-SrTiO3-ABO3 piezoceramics (ABO3 = LiNbO3, BaZrO3, and LaFeO3) were studied. The addition of ABO3 into Na0.5Bi0.5TiO3-SrTiO3 ceramic induces a ferroelectric tetragonal-to-ergodic relaxor pseudocubic phase transition, resulting in the significant disruption of ferroelectric order with the shift of the ferroelectric-relaxor transition temperature down to below room temperature. The conventional furnace sintering and microwave sintering methods are conducted in this study to improve the electric field-induced strain properties of BNST-LN piezoceramic. Interestingly, the Na0.5Bi0.5TiO3-SrTiO3-LiNbO3 sample sintered via microwave sintering method shows an ultrahigh normalized strain of 995 pm/V at an ultralow driving field of 2 kV/mm, suggesting a potential candidate for lead-free piezoactuator applications.

Picosecond Laser Cutting-Assisted Rapid Laser Reactive Sintering for the Fabrication of Crack-Free Protonic Ceramic Electrochemical Cells

Nowadays, greenhouse gas emissions have become a more severe problem. Renewable energy sources are crucial to solve this problem. Protonic ceramic fuel cells (PCFCs) have been considered ideal for energy conversion and storage applications. Compared to oxide-ion, proton, as the charge carrier, has a much lower transport activation energy. This property leads to the wide application of protonic ceramics in intermediate-temperature electrochemical devices [1]. However, the refractory property of typical protonic ceramics makes the conventional furnace sintering methods for PCFCs ineffective and time-consuming. The rapid laser reactive sintering (RLRS), with the assistance of sintering aids, has shown its ability to sinter protonic ceramics in a short time (< 10 s) from cost-effective raw materials of oxides and carbonates. We have successfully demonstrated the feasibility of preparing crack-free BaCe0.7Zr0.1Y0.1Yb0.1O3-δ (BCZYYb) electrolyte samples by RLRS [2]. However, it is not easy to achieve crack-free samples with a large area. Therefore, eliminating the cracks during sintering is key to sinter large area samples.In the process of RLRS, the protonic ceramic experiences significant thermal stress. The cracks introduced by thermal stress originated from both sides of the straight stripe-shaped samples and propagated into the center area. In this work, we fabricated PCFC half cells using the RLRS method. In the half cell, we chose the 40wt% BCZYYb+60wt% NiO and BCZYYb as anode and electrolyte, respectively. The anode was 3D printed with 80mm in length, 15mm in width, and 200-300μm in thickness. The electrolyte was spray-coated on the anode surface. 1.0wt% of NiO added to the electrolyte served as the sintering aid. As mentioned before, during RLRS, the cracks originate from both sides of the samples. Because of the contact angle of the slurry on the substrate, both sides of the rectangular half cells have thickness variance, and this kind of inconsistency caused stress concentration. We utilized a picosecond laser to cut both sides of the samples. Besides, the thermal effect of picosecond laser can sinter a small area to provide compressive stress to the bulk of the sample due to sintering shrinkage. The cut samples with a reduced width of 11mm were then sintered using CO2 laser in a scanning manner. A sample with a length of 80mm and a width of 11mm was prepared successfully. The combination of picosecond laser cutting and RLRS enabled us to manufacture large area crack-free co-sintered BCZYYB half cells quickly. Keywords: 3D printing, Laser sintering, Reactive sintering, Picosecond laser, Protonic ceramic fuel cell. References Mu, S., Zhao, Z., Huang, H., Lei, J., Peng, F., Xiao, H., & Brinkman, K. S. (2020). Advanced Manufacturing of Intermediate-Temperature Protonic Ceramic Electrochemical Cells. The Electrochemical Society Interface, 29(4), 67.Mu, S., Zhao, Z., Lei, J., Hong, Y., Hong, T., Jiang, D., ... & Tong, J. (2018). Engineering of microstructures of protonic ceramics by a novel rapid laser reactive sintering for ceramic energy conversion devices. Solid State Ionics, 320, 369.

Ultra-Fast Laser Fabrication of Alumina Micro-Sample Array and High-Throughput Characterization of Microstructure and Hardness

In the light of recent advances in material informatics, there is a great demand for high-throughput approaches of sample fabrication and property characterization. Currently, no high-throughput approach has been demonstrated for the fast sampling of the microstructure and the correlated properties. In this paper, we demonstrate the ultra-fast fabrication of an alumina sample array and the high-throughput hardness characterization of these sample units. The alumina sample array was fabricated using picosecond (PS) laser micromachining and CO2 laser sintering within a short time (i.e., less than a few minutes). After laser sintering, the hardness of these sample units was characterized using micro-indentation, and the microstructure was observed using scanning electron microscopy (SEM). In each sample unit, the microstructure was uniform for the entire top surface and within about 20 µm depth from the top surface. The relative density (RD) and corresponding micro-hardness of the sample units was found to continuously vary over a wide range from 89% RD with 600 kgf/mm2 hardness to 99% RD with 1609 kgf/mm2 hardness. For these laser-sintered samples, the correlation of hardness and relative density of the alumina matched well with the literature reports on sintered alumina obtained using conventional low-throughput furnace sintering experiments.

Effect of processing route on the structural and functional properties of manganese doped zinc oxide

The structural and functional properties of zinc oxide (ZnO) can be tuned by the processing route. In this work, we compare the effect of two different processing routes, conventional furnace sintering (FS) and spark plasma sintering (SPS), on the properties of pure ZnO and manganese doped ZnO (MZO). Structural and Raman studies were used to characterize the defects and confirm Mn incorporation in the ZnO lattice. Photoluminescence studies were used to identify the type of defects formed. The role of these defects and Mn doping on the induced magnetism was studied using vibrational sample magnetometer. A comparative study of both the synthesis routes showed that SPS is a viable process to induce defects in semiconductor oxides and for modulating the electronic and magnetic properties.

Rapid Laser Reactive Sintering for Sustainable and Clean Preparation of Protonic Ceramics.

One of the essential challenges for energy conversion and storage devices based on protonic ceramics is that the high temperature (1600–1700 °C) and long-time firing (>10 h) are inevitably required for the fabrication, which makes the sustainable and clean manufacturing of protonic ceramic devices impractical. This study provided a new rapid laser reactive sintering (RLRS) method for the preparation of nine protonic ceramics [i.e., BaZr0.8Y0.2O3−δ (BZY20), BZY20 + 1 wt % NiO, BaCe0.7Zr0.1Y0.1Yb0.1O3−δ (BCZYYb), BCZYYb + 1 wt % NiO, 40 wt % BCZYYb + 60 wt % NiO, BaCe0.85Fe0.15O3−δ–BaCe0.15Fe0.85O3−δ (BCF), BaCo0.4Fe0.4Zr0.1Y0.1O3−δ (BCFZY0.1), BaCe0.6Zr0.3Y0.1O3−δ (BCZY63), and La0.7Sr0.3CrO3−δ (LSC)] with desired crystal structures and microstructures. Following this, the dual-layer half-cells, comprising the porous electrode and dense electrolyte, were prepared by the developed RLRS technique. After applying the BCFZY0.1 cathode, the protonic ceramic fuel cell (PCFC) single cells were prepared and tested initially. The derived conductivity of the RLRS electrolyte films showed comparable proton conductivity with the electrolyte prepared by conventional furnace sintering. The initial cost estimation based on electricity consumption during the sintering process for the fabrication of PCFC single cells showed that RLRS is more competitive than the conventional furnace sintering. This RLRS can be combined with the rapid additive manufacturing of ceramics for the sustainable and clean manufacturing of protonic ceramic energy devices and the processing of other ceramic devices.

Microwave assisted reactive sintering for Al doped Li7La3Zr2O12 lithium ion solid state electrolyte

Li6.28Al0.24La3Zr2O12 (Al-LLZO) solid electrolyte for Li-ion battery was prepared by a microwave-assisted reactive sintering (MARS) method. When sintered by the MARS method, the Al-LLZO cubic phase formed at 1000 °C, which is 100 °C lower than that in a conventional furnace sintering method. With the increase of sintering temperature and holding time in MARS, the relative density of Al-LLZO samples goes up. Also, the improved conductivity is related to the decrease of pore number between Al-LLZO grains. And the reduced grain boundary resistivity contributes the most to total reduced resistivity compared with the grain resistivity. The Li-ion conductivity of the Al-LLZO samples prepared by MARS at 1200 °C for 3 h reaches 1.06 × 10−4 s cm−1 at 25 °C and the value of conduction activation energy is 0.36 eV at 25–150 °C.

Solid-State Battery Fabricated By Li3.5Ge0.5V0.5O4 Electrolyte

Oxides are generally non-flammable, durable and non-toxic materials; high safety and reliability in a battery system is assured by the use of oxide as an electrolyte instead of the highly-reactive non-aqueous liquid. To develop an oxide-based solid-state all-lithium-ion battery (ASS-LIB) for large-scale applications such as next-generated wireless IoT devices, the thicknesses of stacked electrode and electrolyte layers need to be curtailed to several ten to hundred μm order. Although the powder technology is an easy formula for obtaining such thick electrode layers, some sort of powder interfacial design is required for the fast-ionic transfer at the electrode/electrolyte hetero-interface. Present-progressive oxide-based electrolytes as perovskites or garnets have high conductivities of ≈ 10-3 S cm-1, but were generally difficult to design the ionic-transferable interface since most electrode materials easily engage in thermochemical reactions with the aforementioned electrolytes. In present study, γ-Li3PO4-type Li3.5Ge0.5V0.5O4 (LGVO), which was one of the Lithium Super-Ionic Conductor (LISICON) families, was focused on as electrolyte of the SS-LIB.1 The LGVO was synthesized via a conventional solid-state reaction, in which pre-prepared Li4GeO4 and pre-prepared Li3VO3 were used as the starting materials. The required amount of each material was ground and cold-pressed into a pellet, and then heated at 700 °C for 12 h. A single γ-Li3PO4-type phase was identified by a powder XRD pattern of the mortar-milled pellet. The prepared LGVO powder was put in a 80 mL ZrO2 cap with five of 20 mm ZrO2 disks, and was further-crushed by disk mill for obtaining sub-micron-sized fine powder before sintering processes. Samples for AC impedance measurement were prepared by two sintering process; conventional furnace sintering (CFS) of uniaxial pressing powder and SPS of Au/ LGVO powder/Au. (Both sides were polished and coated with Au after CFS process.) The sintering temperature and time at CFS and SPS were 700 °C, 2 h and 650 °C, 1 min, respectively. Total Li-ion conductivities for LGVO SPS pellet was 9.5 × 10-5 S cm-1 at 25 °C, which was slightly higher than that of CFS pellet: 8.5 × 10-5 S cm-1 because of the minimalizing grain-boundary resistance. The conductivity was enhanced due to reducing the high-resistive layer near the grain boundary by a short period of SPS process, which has been confirmed in case of γ-Li3PO4-type Li3.5Ge0.75S0.25O4.2 No impurity peak was observed in the powder XRD pattern of the LiNi1/3Mn1/3Co1/3O2 (NMC)-LGVO co-sintered composite produced by either CFS or SPS. This result indicates that the LGVO is thermally-stable during fabricating SS-LIB by powder process. Composite electrode powder was prepared from a mixture of 50 wt% NMC and 50 wt% LGVO. A layer-stacking compact (Au | composite electrode powder | LGVO powder as separator) was co-sintered by SPS process at 500 °C for 1 min. A lithium foil was used as a reference/counter electrode. A poly-(ethylene oxide)-based dry polymer electrolyte film was inserted between the lithium foil and the LGVO electrolyte to reduce the interfacial resistance with adhesion. Electrochemical charge-discharge test was performed at a constant current of 50 μA cm-2 at 60 °C. The SS-LIB shows the reversible charge/discharge capacities of over 120 mAh g-1 thanks to using LGVO electrolyte, which possess the relatively high conductivity of ≈ 10-4 S cm-1 and high thermally-stability even under co-sintering with NMC electrode. Acknowledgements This work was financially supported by the Advanced Low Carbon Technology Research and Development Program of the Japan Science and Technology Agency for Specially Promoted Research for Innovative Next Generation Batteries (JST-ALCA SPRING). Reference s : [1] J. Kuwano and A. R. West, Mat. Res. Bull., 15 (1980) 1661. [2] T. Okumura, S. Taminato, T. Takeuchi and H. Kobayashi, ACS Appl. Energy Mater., 1 (2018) 6303.

Facile One Step Rapid Laser Reactive Processing of Protonic Ceramic Electrochemical Cells

Greenhouse gas emissions are becoming more and more serious issue with fossil fuels combustion. Renewable energy sources are the key to solve this problem. Protonic ceramic electrochemical cell (PCEC) is a high-efficiency and cost-effective device for the conversion of renewable electricity into storable fuels (e.g., hydrogen). Because the poor sintering properties of protonic ceramics, conventional furnace sintering methods for PCECs are usually ineffective, which needs long-term and high-temperature firing. A new one-step rapid laser reactive sintering method was developed for achieving fully densified protonic ceramic electrolyte films [1]. Motived by the discovery of rapid laser processing method , we fabricated PCEC single cells through one-step rapid laser scanning. In this cell, the BaCe0.7Zr0.1Y0.1Yb0.1O3-δ (BCZYYb) was selected as electrolyte materials duo to the high ionic conductivity at relatively low temperatures [2]. (BCZYYb) with NiO cermet materials (40:60 wt%) were selected as fuel electrode. BaCe0.6Zr0.3Y0.1O3-δ (BCZY63) was selected oxygen electrode scaffold for further nanoscale phase catalyst infiltration. The porous fuel electrode layer of cell was prepared by 3D printing from the paste comprised of the mixed powders of NiO and BCZYYb stoichiometric amounts precursor solids (BaCO3, CeO2, ZrO2, Y2O3, and Yb2O3). The electrolyte was spray coated on the fuel electrode surface. The coating slurry was composed of BCZYYb stoichiometric amounts precursor solids, 1 wt% NiO was added in it as sintering aid. Then, the scaffold pastes of BCZY63 stoichiometric amounts precursor solids was spray coated on the top surface of BCZYYb green layer. Laser irradiation on the surface of this green single cells in few seconds. Those precursor solids converted into pure BCZYYb phase (both in fuel electrode and electrolyte layer) and BCZY63 phase (scaffold) by solid-state reactive during the laser scanning processing. The fuel electrode layer and oxygen electrode scaffold layer exhibited expected nanoporous microstructure. The BCZYYb electrolyte layer was fully densified with a thickness of ~20 μm, and bond together with the porous electrodes tightly without crack and curvature. The active oxygen electrode material BaCo0.4Fe0.4Zr0.1Y0.1O3−δ nanoparticles were infiltrated into the porous BCZY63 scaffold and calcinated at moderate temperatures. A protonic ceramic electrochemical cell was manufactured successfully with Ideal sandwich structure. This cell exhibited a moderate electrochemical performance. Keywords: Rapid Laser sintering, Protonic ceramic fuel cell, Solid-state reactive sintering, 3D printing.

Spark Plasma Sintering of Porous Materials Made of 1Kh18N9T Corrosion-Resistant Steel Fibers

Conventional furnace sintering of porous materials made of 1Kh18N9T corrosion-resistant steel fibers leads to abnormal grain growth resulting in a bamboo-like structure, significantly affecting the mechanical properties of these materials. Spark plasma sintering has been employed to make porous samples of 1Kh18N9T corrosion-resistant steel fibers. The yield stress of these samples is 1.5 times higher than that of the samples produced by furnace sintering for 2 h at 1200°C.

Innovative 3D-manufacture of structured copper supports post-coated with catalytic material for CO2 methanation

Innovative copper 3D-structures were manufactured by additive manufacturing (AM) technique for application as catalytic supports in CO2 methanation. The influence of the sintering temperature, atmosphere and technique (pulsed electrical current sintering (PEC) vs conventional furnace sintering) was investigated. The microstructural evolution of the support was analysed by low-temperature N2 adsorption, scanning electron microscopy (SEM), optical microscopy (OM) and X-ray diffraction (XRD). It was found that reducing sintering atmosphere decreases the inner porosity of the fibres of the structures till ca. 0.1%. Fibres of the sample sintered by PEC were found to be as dense as the ones processed with conventional sintering, however PEC sintering results in the unwanted surface oxidation. Adhesion strength of the catalytic coating on copper supports was benchmarked with stainless steel supports. Both Ni/alumina coated structured supports and conventional packed-bed catalyst were examined in CO2 conversion to methane. No deactivation was observed after 80 h time-on-stream in the presence of 10 ppm H2S. The addition of 10 ppm H2S to the stream did not significantly change the structured catalyst performance, although negligible carbon deposition on the catalyst surface was observed.

Enhancement of lithium-ion conductivity for Li&lt;sub&gt;2.2&lt;/sub&gt;C&lt;sub&gt;0.8&lt;/sub&gt;B&lt;sub&gt;0.2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; by spark plasma sintering

Lithium-ion conductivity of Li2.2C0.8B0.2O3 pellet is 2.1 × 10−6 S cm−1 at 30°C after sintering at 450°C by spark-plasma sintering (SPS) process, which is about three times higher than the conductivity of the pellet sintered at 660°C in conventional furnace. The ionic resistance at grain boundary was especially minimalized by SPS process, which would be related to the grain-growth suppression under densification as confirmed by surficial SEM image. Improvement of charge–discharge capacity could be measured at all-solid-state lithium battery assembled by the SPS process (LiCoO2–Li2.2C0.8B0.2O3 composite electrolyte/Li2.2C0.8B0.2O3/dry polymer/Li foil) compared with the same compositions of the battery assembled by conventional furnace sintering, which would be due to the enhancement of the ionic transfer at LiCoO2/Li2.2C0.8B0.2O3 hetero interface as well as Li2.2C0.8B0.2O3/Li2.2C0.8B0.2O3 grain-boundary resistance.

Sustainable production of titanium foams for biomedical applications by Concentrated Solar Energy sintering

Porous titanium foams were successfully sintered using a solar parabolic concentrator, of vertical axis and 2kW power, in argon atmosphere. Green pellets were previously prepared following the space holder powder manufacturing route using NaCl as soluble spacer. Titanium foams were fully sintered at lower temperature and shorter time than in conventional furnace sintering. Moreover, porosity achieved ranges between 58% and 77%, with dual size range: larger porous ranging from 500 to 1000µm resulting from the NaCl particles; and smaller porous of 1–10µm due to the powder sintering. Both the porosity and the porous size obtained for titanium foams produced by solar sintering fulfil the requirements for load-bearing and scaffold applications in tissue engineering.

Oxide-Based All-Solid-State Lithium-Ion Batteries Assembled By Spark Plasma Sintering

Oxides are generally non-flammable, durable and non-toxic materials; high safety and reliability in a battery system are assured by the use of oxide as an electrolyte instead of the highly-reactive non-aqueous liquid. To develop an oxide-based all-solid-state lithium-ion battery (ASS-LIB) for applications such as electric vehicles, the thicknesses of stacked electrode and electrolyte layers need to be curtailed to several ten to hundred μm order. This must be achieved through powder technology. In oxide-based ASS-LIB, the good contact interfaces should be prepared by a simple powder sintering process, and also produces little ion-blocking impurities. Well-known lithium-ion conductive oxides based on the garnet, perovskite, and NASICON-type structures possess high bulk conductivities of over 10-4 S cm-1; however, these oxides required sintering at high temperature beyond 1273 K to facilitate good contact between the electrode and electrolyte layers. In addition, most positive electrode materials produce impurities after sintering via, for example, their decomposition. To address these issues, the ASS-LIBs were assembled by the use of lithium-ion conductive oxides with low melting point and/or the use of spark plasma sintering (SPS), which could be processed at low temperature with relatively short time.[1] Although the Li-ion conductivity of Li2CO3 was extremely low (about 10-12 S cm-1 at room temperature), the ion-blocking impurities were hardly formed at the electrode/Li2CO3 electrolyte interface since Li2CO3 could be sintered at lower temperatures below 973 K. Li2+x C1-x B x O3, which is isostructural with Li2CO3, is also a Li-ion conductive oxide. According to the literature, the Li-ion conductivity was enhanced dramatically from 10-7 to 10-3 S cm-1 at 473 K as x in Li2+x C1-x B x O3 changes from 0 to 0.25. [2] We used Li2.2C0.8B0.2O3 as electrolyte material and assembled ASS-LIB by SPS method for reducing impurities under sintering. Li2.2C0.8B0.2O3 was synthesized using Li2CO3, LiOH·H2O, and H3BO3 as the starting materials via a conventional solid-state reaction. The required amount of starting materials was ground and heated at 873 K for 10 h in air. The obtained powder was cold-pressed into a pellet and re-heated at 923 K for 10 h in air twice. A single phase of Li2.2C0.8B0.2O3 was identified by a powder XRD pattern of the synthesized product. For ion conductivity measurements, the prepared Li2.2C0.8B0.2O3 was firstly put in a 80 mL ZrO2 cap with five of 5 mm ZrO2 disks, and was crushed by disk mill. Samples for AC impedance measurement were prepared by two sintering methods; conventional furnace sintering (CFS) of uniaxial pressing powder and SPS of Au/ Li2.2C0.8B0.2O3 powder/Au. (Both sides were polished and coated with Au after the CFS method.) The sintering temperature and time at CFS and SPS were 923 K, 2h and 723 K, 1 min, respectively, for densification over 90%. Total Li-ion conductivities for Li2.2C0.8B0.2O3 SPS pellet was 2.1 x 10-6 S cm-1at 303 K, which was higher than that of CFS pellet: 6.7 x 10-7 S cm-1. The growth of Li2.2C0.8B0.2O3 grain was less observed at SEM image of the SPS pellet. The total conductivity was enhanced about three times by suppressing the grain growth via the SPS method, due probably to reducing the high-resistive layer near the grain boundary, which would be formed by long-term duration via the CFS method. Composite electrode powder was prepared from a mixture of 70 wt% LiCoO2 and 30 wt% Li2.2C0.8B0.2O3 electrolyte. Au/composite electrode powder/Li2.2C0.8B0.2O3 powder was assembled by SPS method under the same condition for the sample of AC impedance measurement. Lithium foil was used as a reference/counter electrode. A poly(ethylene oxide)-based polymer electrolyte film was inserted between the lithium foil and the Li2.2C0.8B0.2O3 electrolyte as a separator to reduce the interfacial resistance with adhesion as possible. Electrochemical charge-discharge test was performed at a constant current of 10 μA cm-2 at 333 K between 4.2 and 2.0 V vs. Li/Li+. The ASS-LIB showed an initial charge-discharge profile which is similar to the liquid electrolyte case, and the discharge capacity was 118 mAh g-1. No impurity peak was observed in the powder XRD pattern of the LiCoO2-Li2.2C0.8B0.2O3 composite electrode after SPS method. Thus, we have successfully prepared the oxide-based ASS-LIB, working with demonstrating the comparable discharge capacity to the LIB using liquid electrolyte, by the combination of the low-melting Li2.2C0.8B0.2O3 and the rapid sintering method.

Flash-Sintering and Characterization of La0.8Sr0.2Ga0.8Mg0.2O3-δ Electrolytes for Solid Oxide Fuel Cells

La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM), a promising electrolyte material for intermediate temperature solid oxide fuel cells, can be sintered to a fully dense state by a flash-sintering technique. In this work, LSGM is sintered by the current-limiting flash-sintering process at 690°C under an electric field of 100Vcm−1, in comparison with up to 1400°C or even higher temperature in conventional furnace sintering. The resultant LSGM samples are investigated by scanning electron microscopy, X-ray diffraction, and electrochemical impedance spectroscopy. The SEM images exhibit well-densified microstructures while XRD results show that the perovskite structure after flash-sintering does not changed. EIS results show that the conductivity of LSGM sintered by the current-limiting flash-sintering process increases with sintering current density value. The conductivity of samples sintered at 120mAmm−2 reaches 0.049σcm−1at 800°C, which is approximate to the value of conventional sintered LSGM samples at 1400°C. Additionally, the flash-sintering process is interpreted by Joule heating theory. Therefore, the current-limiting flash-sintering technique is proved to be an energy-efficient and eligible approach for the densification of LSGM and other materials requiring high sintering temperature.

Effect of Microwave and Conventional Heating on Sintering Behavior of Cu-10vol.%SiC Nanocomposites

Effect of heating mode and sintering temperature on sinterability of ex-situ Cu-10vol.%SiC composites was investigated. The Cu and SiC powder mixture were mechanically alloyed for 5 hours at 100 rpm in a planetary ball mill under argon atmosphere. The as-milled powders of Cu-10vol.%SiC were compacted and sintered in conventional tube furnace and microwave furnace at 700°C, 800°C, and 900°C. Microwave reduces the processing time significantly along with higher heating rates when compared to conventional tube furnace. Based on XRD result, the average Cu crystallite size is 80.49 nm after milling and its value remained under 100 nm after sintering. Microwave gave relatively smaller crystallite size than tube furnace. SEM revealed the homogeneous distribution of SiC particles in the Cu matrix in both heating mode. Relatively higher densification parameter was obtained by microwave furnace sintered at 900°C. This temperature was defined as an optimum sintering temperature and microwave sintering was claimed to exhibit much better sinterability than conventional tube furnace sintering.

Production and wear property of electroless Ni-plated B4C-AstaloyCr-M composites

AbstractNickel (Ni) matrix reinforced with boron carbide (B4C) has been produced by conventional furnace sintering at various temperatures. A uniform Ni layer on B4C powders was deposited prior to sintering using electroless plating technique, allowing close surface contact between particles. A composite consisting of quaternary additions, a ceramic phase, B4C, within a matrix of Ni and AstaloyCr-M powders has been prepared at a temperature range of 1000°C–1200°C under Ar shroud. X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) study, compressive testing, and hardness measurements were employed to characterize the properties of the composite. Experimental results showed that the best properties as compressive strength σmax and hardness (HB) were obtained at 1150°C. Wear resistance was relatively higher than cast iron.

마이크로파 소결법을 이용한 Bi0.5Na0.5TiO3계 적층형 세라믹 액추에이터 제조

A comparative study has been attempted for microwave and conventional sintering of lead-free <TEX>$Bi_{0.5}Na_{0.5}TiO_3(BNT)$</TEX>-based multilayer ceramic actuators(MLAs). It was found that microwave sintering (MWS) could be successfully applied to the co-firing of piezoceramic/AgPd MLAs with a 10 times shorter firing cycle as well as <TEX>$100^{\circ}C$</TEX> lower firing temperature (<TEX>$850^{\circ}C$</TEX>) for sufficient densification than conventional furnace sintering (<TEX>$950^{\circ}C$</TEX>). Furthermore, MWS-derived specimens showed better electric field-induced strain than that of CFS-derived specimens by effectively suppressing interdiffusions between ceramic and electrode layers.