Journal of Asian Ceramic Societies

Khan, Muhammad Zubair; Iltaf, Asim; Ishfaq, Hafiz Ahmad; Khan, Fahd Nawaz; Tanveer, Waqas Hassan; Song, Rak-Hyun; Mehran, Muhammad Taqi; Saleem, Mohsin; Hussain, Amjad; Masaud, Zubair

doi: 10.1080/21870764.2021.1920135pmid: N/A

Solid oxide fuel cells (SOFCs) offer numerous advantages in terms of high efficiency and clean electrochemcial energy conversion devices. However, owing to high operation temperature, this technology is restricted to stationary applications and leads to components degradation and long-term stability issues. The development of new design and their modifications for improving the electrochemical performance at intermediate temperatures and durability of the SOFC components are very important to bring this technology one step closer to the market. In this context, the current research on the development, properties, performance, and stability of geometrically modified flat-tubular (FT) SOFC cell and the stack is reviewed in detail. This advanced design exhibits higher performance compared to the tubular type and longer stability in comparison to the planar type SOFCs. The application of the interconnect material is emerging as the key factor influencing the electrical output of the FT-SOFC and operation at high temperatures and current density are the critical issues for cell durability. New stack designs are discussed in detail and experimental findings are summarized.

Murai, Kazuki; Funamizu, Yosuke; Ogura, Toshihiko; Nishio, Keishi

doi: 10.1080/21870764.2021.1911060pmid: N/A

Biomineralization is the process by which biominerals, minerals composed of bioinorganic matter possessing a controlled structure and orientation and a biomacromolecular assembly with an ordered structure that acts as a 3D template, are formed. In this study, we investigated the fabrication of organic/inorganic hybrid gels by bioinspired mineralization in peptide hydrogels. An Ac-(VHVEVS)3-CONH2 peptide was used as a multifunctional template with a mineral source supply capability and structural controllability that facilitates the formation of hydrogels via self-assembly. Hydrogels with varying viscoelastic strengths were prepared from the designed peptide by controlling the concentration of calcium ions added as cross-linking agents. The peptide hydrogel supplied carbonate anions as the mineral source through the hydrolysis of urea and mineralized CaCO3 with controlled morphology on the peptide network. With increases in the concentration of calcium ions added, the morphology of the mineralized CaCO3 changed from a fibrous structure to a thin film. This implies that the nucleation and growth mechanisms of CaCO3 formed by bioinspired mineralization were affected not only by the morphology and supply rate of the mineral source by the peptide network acting as a multifunctional template, but also by the viscoelastic strength of the hydrogel that served as a 3D reaction field.

Wang, Xuejiao; Sun, Meng; Fu, Ying; Liu, Weigang; Wang, Qiushi; Wang, Chuang; Li, Ji-Guang

doi: 10.1080/21870764.2021.1915632pmid: N/A

Rare earth double tungstates Na(Gd,RE)(WO4)2 (RE = Eu/Yb-Er) were successfully obtained from layered rare earth hydroxide precursors via sacrificial reaction at 200°C with molar ratio WO4 2-/RE3+ = 2.5 for 24 h reaction without calcination and the employment of any organic reagents. The temperature sensing performances of Na(Gd,RE)(WO4)2 (RE = Eu/Yb-Er) were comparatively investigated by analyzing the temperature-dependent down-conversion (DC) and up-conversion (UC) luminescence spectra. The DC phosphors Na(Gd,Eu)(WO4)2 were found to be well capable of sensing temperature via fluorescence lifetime (FL) mode. The UC phosphors Na(Gd,Yb,Er)(WO4)2 were capable of sensing temperature via both FL mode and fluorescence intensity ratio (FIR) mode through thermally coupled 2H11/2,4S3/2 levels (I 520/I 552), and non thermally coupled 2H11/2,4F9/2 energy levels (I 520/I 670). The UC phosphors Na(Gd,Yb,Er)(WO4)2 have maximum absolute sensitivity (SA ) and maximum relative sensitivity (SR ) of 174 × 10−4 K−1 (548 K) and 80 × 10−4 K−1 (298 K) for the thermally coupled 2H11/2,4S3/2 levels and maximum SA and SR of ~260 × 10−4 K−1 (300–550 K) and 96 × 10−4 K−1 (298 K) for the non-thermally coupled 2H11/2,4F9/2 energy levels.

Yan, Mingwei; Zhang, Jiayu; Yang, Yumin; Liu, Kaiqi; Sun, Guangchao

doi: 10.1080/21870764.2021.1917113pmid: N/A

A novel MgO-C-Al-Si refractory with low carbon content used in bottom-blowing elements was prepared, and its phase composition and microstructural evolution were investigated by XRD, SEM and EDS after being treated at 1200–1600°C in flowing nitrogen. Results show that the samples are composed of MgO, Al4C3, SiC, Al4SiC4, MgAl2O4, Mg3Al2N4 and Al2O3 at 1200–1400°C, while the samples are composed of MgO, Al4C3, SiC, Al4SiC4, Al4Si2C5, MgAl2O4, Mg3Al2N4 and Al2O3 at 1500–1600°C. Al and Si present gradient reactivity at high temperatures and Al has priority over Si to react with MgO, forming MgAl2O4. Based on the microstructure analysis, we find that the higher the temperatures are, the more abundant the products. Al(g), Al2O(g), SiO(g), Mg(g) and CO(g), as the gas–gas reaction substances, react to form many of Al4SiC4 flakes containing Mg, O and N within pores or gaps of the refractory, along with trace amounts of SiC whiskers and MgAl2O4 spinel whiskers. In addition, the surface morphology of the magnesia aggregates is modified by the MgAl2O4 spinels and Al4SiC4 flakes, owing to the synergistic effect of Al and Si. Further, some physical properties are also characterized.

Uvarov, Valerii Ivanovich; Kapustin, Roman Dmitrievich; Kirillov, Andrei Olegovich; Loryan, Vazgen Edvardovich

doi: 10.1080/21870764.2021.1920133pmid: N/A

A porous, catalytically active membrane based on α-Al2O3 powder with ultrafine additives of MgO+SiC+SiO2 and catalytically active components of Cr2O3 + Fe2O3 was synthesized in one stage. Double-sided compacting at P = 70–100 MPa and sintering at T = 1300°C were used. The open porosity of the resulting membrane was 38%, and the pore size was from 1 to 3 µm. The influence of structural-dimensional factors, such as material morphology, porosity and pore size, on the catalytic characteristics of the synthesized membranes was studied. The dependences of the structural-dimensional factors from the particle size of the initial powders, their ratio in the mixture, as well as on the method and pressure of compaction were established. The obtained catalytic membrane was used for dehydrogenation of isoamylenes into isoprene. At T = 600°C, the yield of isoprene was up to ~9%, the selectivity ~20%. The conversion of the isoamylene fraction was 46%. During 6 hours of the experiment, the decrease in the catalytic activity of the system was not observed.

Liang, Baoyan; Dai, Zhen; Zhang, Wangxi; Li, Qisong; Niu, Dongming; Zhang, Yanli; Jiao, Mingli; Yang, Li; Guan, Xiaoyan

doi: 10.1080/21870764.2021.1920136pmid: N/A

In this study, we investigated the formation of TiC nanosheets from carbon black and Ti3AlC2 mixtures in NaCl-KCl eutectic salt. The effects of raw material ratio, molten salt ratio, and heating temperature on TiC formation were studied in detail. Results show that carbon black may enhance the decomposition of amounts of Ti3AlC2 at 1,100°C by heat treatment without salt addition, while molten salt plays key roles in the total decomposition of Ti3AlC2 and the formation of TiC nanosheets at 1,000°C. Higher heating temperature and excess carbon black benefits the synthesis of high content TiC. The as-synthesized TiC nanosheets are approximately 15 nm thick and 80–220 nm long. We propose a possible reaction mechanism that governs TiC formation in molten salts and explain the observations based on kinetic considerations.

Nguyen, Huu Hien; Shirai, Takashi; Xin, Yuzin; Dang, Quoc Khanh; Nanko, Makoto

doi: 10.1080/21870764.2021.1920156pmid: N/A

Influences of TiO2 or Y2O3 dopants on pressure-assisted sintering of polycrystalline Al2O3 were investigated to control the microstructure of sintered Al2O3 as well as to improve the homogeneity of transparent Al2O3 samples. The transparent polycrystalline Al2O3 samples with and without the dopants were fabricated by two-step pulsed electric current sintering (TS-PECS). By the grain boundary segregation by the dopants, both TiO2 and Y2O3 depressed the densification and grain growth processes during the sintering of polycrystalline Al2O3. The principle originalities of this work include the relationship between the homogeneities of microstructure and of optical transmittance of large-size polycrystalline Al2O3 and the consequent doping strategy for controlling of homogeneity of transparent polycrystalline Al2O3 prepared by two-step PECS. Doping of Y2O3 dramatically reduced the grain size of polycrystalline Al2O3 and improved its optical transparency. The homogeneity of the microstructure and the optical transparency of the large-sized polycrystalline Al2O3 with 0.1 mol% Y2O3 was improved. The addition of TiO2 also slightly retarded densification and reduced the grain size of the sintered Al2O3 samples. However, TiO2 dopant is not good for applications of transparent Al2O3 because it caused a dark color in transparent polycrystalline Al2O3 samples by uncertain reasons.

Le, Duc Thang; Cho, Jeong Ho; Ju, Heongkyu

doi: 10.1080/21870764.2021.1920157pmid: N/A

Toward the development of infrared (IR) detectors, nickel–manganite-based thin films were initially prepared from (Ni0.2Mn2.8–x Cu x )Cl2 (0.010 ≤ x ≤ 0.040) solutions using the liquid flow deposition (LFD) method. The influence of Cu on the negative temperature coefficient of resistance (NTCR) characteristic of the films annealed at 400°C was investigated. It was found that the incorporation of Cu can effectively enhance electrical conductivity; however, it degrades both the thermal sensitivity and stability of the nickel–manganite films. The investigation was extended by further modifying the composition with Zn. The results revealed that by co-doping Cu with a proper amount of Zn the temperature coefficient of resistance (TCR) could be tailored, while a relatively low resistivity (ρ) of the final products was retained. Specially, when 0.01 mol Zn was added to a precursor solution containing 0.025 mol Cu, the resulting specimen possessed a TCR = 2.82% K–1 and a ρ = 820 Ω (measured at RT). More importantly, compared to Zn-free films, the (Zn,Cu) co-doped compositions showed much improved electrical stability, with an aging coefficient (ΔR/R) as low as 4.6%, after aging at 150°C in air for 500 h. The results suggest that the (Zn,Cu) co–doped (Ni,Mn)3O4 thin films have a promising application in IR detectors.

Jiang, Yan-Ping; Zhou, Hang-Lv; Tang, Xin-Gui; Liu, Qiu-Xiang; Li, Wen-Hua; Tang, Zhen-Hua

doi: 10.1080/21870764.2021.1920158pmid: N/A

Bi2FeCrO6 (BFCO) thin films were fabricated by sol-gel method. Digital and analog resistive switching behaviors were sequentially observed in Au/BFCO/FTO/Glass structure by applying a continuous cyclic voltage. By analyzing formation mechanism of the two types of the resistive switching behaviors, it is found that the digital resistive behavior conductance mechanism is a bulk-limited conduction, and the analog resistive switching behavior is accompanied with rectification effects and negative differential resistance behaviors, which are considered as interface-limited conductivity behaviors. So the change of digital and analog resistive switching behaviors may be result of the transformation of conductive mechanism. These research results will help us to design and manufacture digital and analog multifunctional resistive switching memory devices.

Mamatha, Sirisala; Biswas, Papiya; Ramavath, Pandu; Das, Dibakar; Johnson, Roy

doi: 10.1080/21870764.2021.1920159pmid: N/A

Paste rheology and printing parameters contribute to a great extent to engineer the properties of ceramic parts produced through 3D printing process. Alumina paste, which showed shear thinning behavior, was prepared using optimum concentration of additives. Paste was 3D printed and effect of printing parameters such as printing speed, length to diameter (L/D) ratio of nozzle, self-standing distance of extrudate, filling pattern and filling angle have been studied. Additionally, effect of the substrate material on which the extrudate is printed was also elucidated. A printing speed of 5–6 mm/s, an L/D ratio of 25 mm and self-standing distance of 1.25 ± 0.25 mm are found to be optimum. Further, a filling pattern of rectilinear geometry along with filling angle of 90° is found to be desirable. Out of the substrates evaluated, polished metal surface is found to be relatively better to achieve close tolerances. The alumina samples printed under optimized conditions are found to possess integrity with respect to the structure and close to pre-designed dimensions. Sintered samples were found to be free of crack and exhibited a density of 3.88 g/cc (97.5% of theoretical density). Density and hardness (16.5 GPa) of printed part correlates well with the microstructure consisting of grains of average size of 9.68 μm.