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31.
《Ceramics International》2016,42(9):11248-11255
Nanostructured hydroxyapatite (HA)–graphene nanosheet (GN) composites have been fabricated by spark plasma sintering consolidation. Nanostructual evolution of the bioceramic-based composites during further high temperature heat treatment is characterized and enhanced mechanical strength is assessed. GN keeps intact after the treatment and its presence at HA grain boundaries effectively inhibits HA grain growth by impeding interconnection of individual HA grains. Microstructural characterization discloses strong coherent interfaces between GN and the (300) plane of HA crystals. This particular matching state in the composites agrees well with the competitive theoretical pull-out energy for single graphene sheet being departed from HA matrix. The toughening regimes that operate in HA–GN composites at high temperatures give clear insight into potential applications of GN for ceramic matrix composites. 相似文献
32.
Mingfei Xiao Aditya Sadhanala Mojtaba Abdi-Jalebi Tudor H. Thomas Xinglong Ren Tao Zhang Hu Chen Remington L. Carey Qijing Wang Satyaprasad P. Senanayak Cameron Jellett Ada Onwubiko Maximilian Moser Hailiang Liao Wan Yue Iain McCulloch Mark Nikolka Henning Sirringhaus 《Advanced functional materials》2021,31(7):2007359
The measurement of the mechanical properties of conjugated polymers can reveal highly relevant information linking optoelectronic properties to underlying microstructures and the knowledge of the glass transition temperature (Tg) is paramount for informing the choice of processing conditions and for interpreting the thermal stability of devices. In this work, we use dynamical mechanical analysis to determine the Tg of a range of state-of-the-art conjugated polymers with different degrees of crystallinity that are widely studied for applications in organic field-effect transistors. We compare our measured values for Tg to the theoretical value predicted by a recent work based on the concept of effective mobility ζ. The comparison shows that for conjugated polymers with a modest length of the monomer units, the Tg values agree well with theoretically predictions. However, for the near-amorphous, indacenodithiophene–benzothiadiazole family of polymers with more extended backbone units, values for Tg appear to be significantly higher, predicted by theory. However, values for Tg are correlated with the sub-bandgap optical absorption suggesting the possible role of the interchain short contacts within materials’ amorphous domains. 相似文献
33.
《Ceramics International》2017,43(17):15010-15017
During the last decade, fabrication of high-quality graphene films by chemical vapor deposition (CVD) for nanoelectronics and optoelectronic applications has attracted increasing attention. However, processing of large-area monolayer and defect-free graphene films is still challenging. In this work, we have studied the effect of processing conditions on the self-limited growth of graphene monolayers on copper foils during low pressure CVD both experimentally and theoretically based on thermokinetics and kinetics of Langmuir adsorption. The effect of copper pre-treatment, growth time, and carbon potential of the atmosphere (indicated by the methane-to-hydrogen gas ratio, r) on the quality of graphene nanosheets (number of layers, surface roughness and the lateral size) were studied. Microscopic studies show that careful pre-treatment of the copper foil by electropolishing provides a suitable condition for the self-limited growth of graphene with minimum surface roughness and defects. Raman spectroscopy and atomic force microscopy determine that the number of graphene sheets decreases with increasing the carbon potential while smother surfaces are attained. Large-area monolayer graphene films are obtained at relatively high carbon potential (r=1) and controlled growth time (10 min) at 1000 °C. Measurement of the electrical response of the prepared monolayer graphene films on SiO2 (300 nm)/Si substrates in a field effect transistor (FET) device shows a high mobility of 2780 cm2 V−1 s−1. Interestingly, the device exhibits p-type semiconducting behavior with the Dirac point at a gate voltage of 25 V. The finding show a great promise for graphene-based FET devices for future nanoelectronics. 相似文献
34.
The amorphous InGaZnO (a-IGZO) thin film transistors (TFTs) with sputtered silver source/drain (S/D) and gate electrodes were investigated and developed. The sputtered single-film Ag was confirmed to be unfit for the electrodes of a-IGZO TFTs because of its bad contact with a-IGZO and atom diffusion into insulators. Accordingly the sputtered Mo films were proposed to serve as the capping layers, indicating that the 20-nm-thick Mo could effectively form ohmic contact with the a-IGZO, prevent the Ag diffusion into the SiOx, and make good adhesion to the glass substrates. The devices with multi-layer S/D and gate electrodes (Mo/Ag/Mo) were successfully fabricated, exhibiting the reasonably good performance and thus proving the application of the sputtered silver electrodes into a-IGZO TFTs was possible. 相似文献
35.
《Journal of Parallel and Distributed Computing》1996,35(1):67-75
This paper examines the performance of synchronous checkpointing in a distributed computing environment with and without load redistribution. Performance models are developed, and optimum checkpoint intervals are determined. The analysis extends earlier work by allowing for multiple nodes, state-dependent checkpoint intervals, and a performance metric which is coupled with failure-free performance and the speedup functions associated with implementation of parallel algorithms. The analytic results for synchronous checkpointing without load redistribution are compared to measurements of a synthetic parallel algorithm with user-level checkpointing. Expressions for the optimum checkpoint intervals for synchronous checkpointing with and without load redistribution are used to determine when load redistribution is advantageous. 相似文献
36.
《Acta Metallurgica Materialia》1992,40(9):2155-2165
Fox and Tabbernor [Acta metall. mater.39, 669 (1991)] have recently measured the four lowest structure factors F(G) of NiAl using highly accurate high energy electron diffraction. We present here a systematic comparison of their results with ab initio band theory, in the context of the local density formalism. We find very good agreement for the three of the four lowest measured structure factors, while our F(200) is ∼0.4 e/cell higher. We tentatively attribute this difference to uncertainties in the treatment of the temperature factors in non-monoatomic compounds. Indeed, comparing with experiment our calculation for the monoatomic Si crystal (where the temperature term factors out), we find that theory reproduces the measured structure factors to within a very small deviations of ∼0.02 e/atom. We have also examined the effect of high Fourier components that are not currently amenable to measurements on the ensuing NiAl deformation electron density distribution (DEDD) maps. We find that the truncation of the Fourier series after four structure factors misses the directional d-like charge lobes near the Ni sites. We show that static and dynamic DEDD give a similar picture of the bonding. 相似文献
37.
Effect of Ni-coated MoS2 on microstructure and tribological properties of (Cu−10Sn)-based composites
《中国有色金属学会会刊》2020,30(9):2480-2490
The (Cu−10Sn)−Ni−MoS2 composites, prepared by powder metallurgy, were studied for the effects of Ni-coated MoS2 on the microstructure, mechanical properties and lubricating properties. The mechanism of effects of Ni and MoS2 on the properties of composites was analyzed through a comparative experiment by adding Ni and MoS2 separately. The results show that the nickel wrapping around the MoS2 particles decreases the reaction rate of MoS2 with the copper matrix, and greatly improves the bonding of the matrix. The composites with 12 wt.% Ni-coated MoS2 (C12) show the optimum performance including the mechanical properties and tribological behaviors. Under oil lubrication conditions, the friction coefficient is 0.0075 with a pressure of 8 MPa and a linear velocity of 0.25 m/s. The average dry friction coefficient, sliding against 40Cr steel disc, is measured to be 0.1769 when the linear velocity and pressure are 0.25 m/s and 4 MPa, respectively. 相似文献
38.
39.
目的探究石墨烯基防护涂层/碳钢体系在原油储罐沉积水中的防护机制。方法以实际原油储罐的沉积水为腐蚀介质,以自制石墨烯底漆和石墨烯面漆为防护涂层体系,采用交流阻抗谱、动电位极化曲线,结合盐雾实验探究石墨烯涂层体系在沉积水中的腐蚀行为和失效衍化机制。结果石墨烯底漆在浸泡初期对碳钢具有一定的防护效果,随着浸泡时间的延长,水分子逐渐渗透涂层,涂层逐渐失效。采用石墨烯面漆和石墨烯底漆搭配,可显著提高涂层对碳钢在沉积水中的防护性能,浸泡46 d后,涂层电阻仍为162 M?·cm。结论石墨烯底漆和石墨烯面漆涂层体系对储罐底板在沉积水中具有良好的防护性能,研究成果对油罐底板涂层防护选材具有理论指导意义。 相似文献
40.