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51.
Lawrence K. Q. Yan Sze Kee Tam Ka Y. Fung Ka M. Ng 《American Institute of Chemical Engineers》2020,66(8):e16272
Due to the complexity of the screen-printing operation and the rheological behaviors of the screen-printable paste, such a paste is usually formulated by trial-and-error. In this report, a systematic procedure, based on heuristics and mechanistic models, for the design of a screen-printable paste is developed. The procedure is demonstrated by a case study of the formulation of a conductive paste of copper particles. 相似文献
52.
Ting Luo Qihang Yang Hongtao Yu Jingsong Liu 《Journal of the American Ceramic Society》2020,103(2):1079-1087
Ba2Ti9O20 single-phase ceramics were prepared by reaction sintering method using TiO2 and BaCO3 as raw materials after heat treating at 1150°C for 10 hours. Furthermore, the formation mechanism and microstructure evolution of Ba2Ti9O20 ceramics prepared by reaction sintering method were investigated. The formation behavior of Ba2Ti9O20 phase was analyzed from the perspective of diffusion, where the reaction activation energy required for the process was calculated to be about 386.17 kJ/mol. Combined with the scanning electron microscopy and the energy dispersive spectrometer, it was revealed that the pores on Ba2Ti9O20 grains in the process of reaction sintering might be caused by the absence of oxygen element. Meanwhile, the reason for the roughness of ceramic surface was that the local inhomogeneous distribution of barium on the surface of Ba2Ti9O20 grain leaded to the enrichment of titanium. 相似文献
53.
William Huddleston Frederick Dynys Alp Sehirlioglu 《Journal of the American Ceramic Society》2020,103(3):1527-1535
Sintering of LiNi0.33Mn0.33Co0.33O2 cathode material was investigated for potential application in all-electric aerospace propulsion systems utilizing new architectural concepts. All-solid-state batteries, while inherently safe, may not reach the high energy density required for next generation propulsion systems. To meet this performance requirement, multifunctionality of sintered active material may achieve systems level weight savings through simultaneous load bearing and electrochemical energy storage performance. The effects of sintering conditions on structural stability, chemistry, densification, grain size, fracture strength and electrical conductivity were quantified for the active cathode material. X-ray diffraction and inductively coupled plasma results indicated the structure and stoichiometry were maintained across the range of processing conditions to facilitate intercalation. Densification was achieved by sintering at 1050°C in ambient atmosphere, but grain coarsening was observed for higher temperatures and longer hold times. Mechanical strength was improved with reduction in porosity, but excessive grain growth decreased strength, providing a maximum of 50 MPa for samples sintered at 1050°C for 10 hours. Electrical conductivity initially improved with densification, but significantly diminished as the microstructure coarsened. The optimal sintering condition of 1050°C maximized mechanical fracture strength and electrical conductivity, with shorter sintering times preferred. 相似文献
54.
This research presents an analysis of the influence of graphene reinforcement on the thermal and mechanical properties of silicon carbide ceramics, at 2.5% (wt%) graphene content. The SiC composites, containing various carbon nanofillers (graphene oxide and graphene nanoparticles), were sintered by the classical two stage spark plasma sintering method. Two current modes were used, the continuous mode and the pulsed current mode. The results from photothermal radiometry and investigations of the mechanical properties showed that graphene additives significantly improve the thermal properties and toughness of material, sintered from a SiC powder. An 45% growth in the toughness was observed, which increased from 1.21 to 1.75?MPa/m1/2. The thermal diffusivity value also increased from 0.60 to 0.71?cm2/s and giving an improvement in thermal properties of 18%. The friction coefficient reached 7% giving an increase in value from 0.62 to 0.66. Microscopic investigations supported the photothermal radiometry (PTR) results. Whilst, thermal imaging revealed homogeneity of the local thermal properties of the products fabricated from the starting SiC powder. 相似文献
55.
Zhentao Wang Yanwei Zeng Chuanming Li Zhupeng Ye Liangliang Cao Yuan Zhang 《Ceramics International》2018,44(9):10328-10334
Gd3+ and Fe3+ co-doped cerium oxide electrolytes, Ce0.9Gd0.1‐xFexO2-δ (x?=?0.00, 0.01, 0.03, 0.05, 0.07, 0.10), were prepared by co-precipitation for ultrafine precursor powders and sintering for densified ceramic pellets. The crystal and microscopic structures were characterized by XRD, FESEM and Raman spectroscopy and their electrical properties were studied by AC impedance spectroscopy and the measurement of single cell's outputs. In comparison with Ce0.9Gd0.1O1.95, the ceramic pellets of Ce0.9Gd0.1‐xFexO2-δ with a relative density of 95% can be obtained after sintered at 1000?°C for 5?h, showing a remarkably enhanced sintering performance with a sintering temperature reduction of 500?°C, which might be ascribed to the highly activated migration of constituent species in the cerium oxide lattice doped with Gd3+ and Fe3+ions. Moreover, the electrical conductivity of Ce0.9Gd0.1‐xFexO2-δ can be significantly enhanced depending on the mole fraction x, with Ce0.9Gd0.07Fe0.03O1.95 exhibiting the highest electrical conductivity of 38 mS/cm at 800?°C, about 36% higher than that of Ce0.9Gd0.1O1.95 electrolyte sintered at 1500?°C for 5?h. So, The Gd3+ and Fe3+ co-doped cerium oxide would be an excellent candidate electrolyte for ILT SOFCs due to its prominent sintering performance and enhanced electrical conductivity. 相似文献
56.
The present study focuses on the sintering of silicon carbide-based ceramics (SiC) by liquid phase sintering (LPS) followed by characterization of the produced ceramics. AlN/Re2O3 mixtures were used as additives in the LPS process. In the first step, the LPS-SiC materials were produced in a graphite resistance furnace in the form of discs at different temperatures. The conditions with the best results regarding real density and relative density were taken as reference for sintering in the form of prismatic bars. In the second step, these samples were evaluated regarding fracture toughness (KIC), by the Single Edge V Notch Beam – SEVNB – method, and flexural strength. KIC behavior was evaluated according to the depth and curvature radius of the notches. Reliable KIC values were presented when the ceramic displayed a small curvature radius at the notch tip. When the radius was large, it did not maintain the square root singularity of the notch tip. Tests were carried out to determine KIC values in atmospheric air and water. KIC results were lower in water than air, with a decrease ranging between 2.56% and 11.26%. The observations indicated a direct grain size correlation between KIC values and fracture strength of the SiC ceramics. 相似文献
57.
Sialon-ZrN composites have been fabricated by a combination of reaction bonding and post-gas-pressure sintering. Composites with different amount of ZrN were post sintered at 1600, 1700 and 1800?°C under a nitrogen pressure of 0.7?MPa for 6?h. The results showed that mass loss due to decomposition increased with increasing sintering temperature. The mass loss at 1600 and 1700?°C was comparable, and below 3% even for the highest ZrN content of 50?wt%, but ranged between 6% and 9% for samples post sintered at 1800?°C with 10–50?wt% ZrN. Composites sintered at 1700?°C had the highest relative density (> 97%) and lowest open porosity (< 2%), and this was independent of ZrN content. The incorporation of the ZrN particles was observed to have an effect on the mechanical properties of the composites. The highest hardness (16.05?±?0.17?GPa) was observed for the composite sintered at 1700?°C with 20?wt% ZrN but decreased with higher ZrN contents, due to a weak bonding between the ZrN particles and the Sialon matrix. The fracture toughness showed a continuous increase with increasing ZrN content, due to the effect of the weak bonding on toughening mechanisms such as crack branching, crack deflection and crack bridging. The highest fracture toughness (5.35?±?0.18?MPa?m1/2) was observed for the composited sintered at 1700?°C with 50?wt% ZrN. 相似文献
58.
Zohre Ahmadi Behzad Nayebi Mehdi Shahedi Asl Iman Farahbakhsh Zohre Balak 《Ceramics International》2018,44(10):11431-11437
Taguchi design of experiments methodology was used to determine the most influential spark plasma sintering (SPS) parameters on densification of TiB2–SiC ceramic composites. In this case, four processing factors (SPS temperature, soaking time, applied external pressure and SiC particle size) at three levels were examined in order to acquire the optimum conditions. The statistical analysis identified the sintering temperature as the most effective factor influencing the relative density of TiB2–SiC ceramics. A relative density of 99.5% was achieved at the optimal SPS conditions; i.e. temperature of 1800?°C, soaking time of 15?min and pressure of 30?MPa by adding 200-nm SiC particulates to the TiB2 matrix. The experimental measurements and predicted values for the relative density of composite fabricated at the optimum SPS conditions and reinforced with the proper SiC particle size were almost similar. The mechanisms of sintering and densification of spark plasma sintered TiB2–SiC composites were discussed in details. 相似文献
59.
Qian Liu Fangfang Qi Junyan Wu Liu Zhang Guopu Shi Zhi Wang 《Ceramics International》2018,44(10):11136-11142
TiN–Ti/Al2O3 composites of varying TiN content (0–20?vol%) were prepared by vacuum hot-pressing sintering at different temperatures (1400?°C and 1500?°C) to investigate how TiN affected the mechanical properties and electrical conductivity of the composites. Sintered samples with added TiN exhibited better performance than those without it. The sample with 20?vol% TiN sintered 1500?°C had an optimal relative density of 99.49, Vickers hardness of 14.94?GPa, flexural strength of 321.55?MPa, and electrical resistivity of 1474.7?μΩ?cm. However, this increased temperature did not improve the best sample resistivity of 930.3?μΩ?cm, which was obtained at 1400?°C. Form SEM images and XRD patterns, the positive effect of TiN on composite mechanical properties may be ascribed to its good performance of high hardness and strength, a decrease of the brittle intermetallic phase, the form of AlTi3N, and the impact of the fine-grained strength of the TiN phase. 相似文献
60.
Mei Zhang Tiechui Yuan Ruidi Li Siyao Xie Minbo Wang Qigang Weng 《Ceramics International》2018,44(4):3571-3579
Micron-sized boron carbide (B4C) powders were subjected to spark plasma sintering (SPS) under temperature ranging from 1700 °C to 2100 °C for a soaking time of 5, 10 and 20 min and their densification kinetics was determined using a creep deformation model. The densification mechanism was interpreted on the basis of the stress exponent n and the apparent activation energy Qd from Harrenius plots. Results showed that within the temperature range 1700–2000 °C, creep deformation which was controlled by grain-boundary sliding or by interface reaction contributed to the densification mechanism at low effective stress regime (n = 2,Qd = 459.36 kJ/mol). While at temperature higher than 2000 °C or at high stress regime, the dominant mechanism appears to be the dislocation climb (n = 6.11). 相似文献