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101.
《Ceramics International》2022,48(9):12217-12227
In the development of high-performance lithium-ion batteries (LIBs), the composition and structure of electrode materials are of critical importance. Silicon has a theoretical specific capacity 10 times that of graphite, nonetheless, its application as an anode material confronts challenge as it undergoes huge volume change and pulverization amidst the alloying and dealloying processes. Herein, a novel method to prepare a multilayer Si-based anode was proposed. Three layers, SiO2, nickel and triethylene glycol (TEG), were coated successively on Si nanoparticles, which served respectively as the sources of SiOx, sacrificial templates and carbon. Nickel can not only serve as a hollow template, but also play a catalytic role, which makes carbonization and redox reactions occur synchronously under a mild condition. Amid the carbonization process of TEG at 450 °C, several-nm-thick SiO2 layer can react with the as-derived carbon to form a silicon suboxides (SiOx (0 < x < 2)) intermedium layer. After removing the nickel template, a micro-nano scaled Si@SiOx@void@C with conformal multilayer-structure can be obtained. The BET specific surface area and pore volume of powders were increased dramatically because of the derivation of abundant voids, which can not only buffer the swelling effect of silicon, but also provide richer ionic conductivity. The as-assembled half-cell with Si@SiOx@void@C as the anode material possesses high capacity (~1000 mAh g?1 at 3 A g?1), long cycle life (300 cycles with 77% capacity retention) and good rate performance (558 mAh g?1 at 5 A g?1). 相似文献
102.
Xiaobiao Shang Weifeng Zhang Jinhui Peng Hua Chen Shenghui Guo 《Drying Technology》2014,32(13):1608-1613
We propose a theoretical guideline for prediction of maximum microwave absorption in microwave drying by optimizing the thickness of a silica sand layer based on analysis of reflection loss (RL). The microwave RL of the silica sand layer was studied over the moisture content of 1% to 5% at 20°C and the silica sand (5% moisture content) in the temperature range of 20 to 100°C at 2.45 GHz. The calculated RL for various moisture contents and temperatures shows that the RL sensitively depends on the thickness of the silica sand. There are absorption peaks in the RL patterns, and the microwave absorption peak shifts towards a smaller thickness side as the moisture content and temperature of the silica sand increase. We also show that the intensity of microwave absorption peaks in the RL patterns of silica sand decrease with decreasing moisture content, and achieve the highest absorption at 60°C. 相似文献
103.
Piotr Macech 《Thin solid films》2009,517(18):5399-5403
Nanoscopic defects present in ultrathin (~ 6 nm) silica films covalently attached to gold substrates through a gold oxide layer exhibit a voltammetric response consistent with a random array of ultramicroelectrodes. These pinholes can be passivated via electrochemical polymerization of phenol to create insulating poly(phenylene) oxide plugs as documented by atomic force microscopy and infrared reflectance-absorbance spectroscopy. Passivation of pinholes is ~ 99.5% complete after 550 voltammetric cycles of oxidative electropolymerization. 相似文献
104.
A simple method was developed to directly deposit silver nanoparticles on the surface of silica spheres. The photochemical reduction was carried out by ultraviolet irradiation in air atmosphere at room temperature. The [Ag(NH3)2]+was reduced to silver atoms upon ultraviolet irradiation. Silver atoms subsequently deposited on the surface of silica spheres and agglomerated into silver nanoparticles. Silica spheres with silver nanoparticles of different size and density can be simply controlled by adjusting the UV-light irradiation time. The silver nanoparticles deposited on silica spheres were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, and field emission scanning electron microscopy. 相似文献
105.
Shogo Takahara Tomoko Yoshida Tetsuo Tanabe Moritami Okada Qiu Xu 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2006,250(1-2):377-381
We have investigated in-reactor luminescence (IRL) from a silica glass at temperatures ranging from 100 K to 250 K. The IRL consists mainly of a broad emission band peaked at 2.7 eV assigned to oxygen deficient centers produced in the silica glass under the in-reactor irradiation. The 2.7 eV emission intensity linearly increased with the irradiation time and its increasing rate was larger for higher irradiation temperatures. However, this temperature dependence is inconsistent with that for the defect production rate and the cause is not clear at present. The initial intensity of the 2.7 eV IRL band increases with temperature, showing an activation energy of ca 21 meV. This value is much lower than those observed in the temperature dependence of the 2.7 eV photoluminescence (PL) and the cathodeluminescence (CL) induced by 8 keV electron irradiation. These results suggest that in IRL, some electrons excited to higher energy levels than the luminescence level are likely transferred to the luminescence state without thermal activation, resulting in a lower activation energy in their temperature dependence. 相似文献
106.
107.
Myung-Geun?Song Jong-Yun?Kim Sung-Ho?Cho Jong-Duk?KimEmail author 《Korean Journal of Chemical Engineering》2004,21(6):1224-1230
Microwave-hydrothermal processes for the synthesis of mesoporous silica were investigated with different pathways and mixture
conditions at 373 K, and the corresponding structures to the hydrothermal method were synthesized within a very short crystallization
time. 2-D hexagonally ordered arrays of MCM-41 materials via the direct electrostatic assembly pathway of ST and mediated
templating pathways of S+X-I+ with CTAB were synthesized, and cubic mesophase of MCM-48 was also prepared within 2 hrs of microwave heating without adding
alcohol. Nonionic surfactants with ethylene oxide (EO) moiety as structure-directing agents were used for the preparation
of ordered array of hexagonal or cubic mesostructured silica via the charge matching principle of (S0H+)(X-I+). Although the detailed roles of microwaves may differ for each process, microwaves accelerate the formation of multiply
charged silicate oligomers, initiating mesophase assembly. Therefore, the use of microwave radiation can transfer energy uniformly
and quickly, and complete the syntheses of mesostructured materials within a short time 相似文献
108.
The silica fume (SF) is used in civil engineering, in particular for the manufacture of high performance concrete.In order to better understand the gain in strength of the concretes containing SF, the microstructural aspect has been examined.Mixtures of SF–Lime pastes present a hydraulic setting which is due to the formation of a C–S–H phase (calcium silicate hydrate). The latter is semi-crystallized. It is characterized by the lines of X-ray diffraction, hk0 such as: 3,06 Å (220), 2,80 Å (400) and 1,83 Å (040).The mix design SF–Lime paste is thus a simplified approach of that of the mixtures SF–OPC in which the main reaction is the fixation, by the SF, of lime coming from the hydration of C3S in the form of C–S–H.Tests have been carried out on two varieties of SF resulting from the same furnace with the presence of lime or Portland cement. The results show that the presence of certain impurities, by their actions on the solubility of silica plays a significant role on the evolution of the hydration of the principal components of Portland cements and the kinetics of lime fixation by the SF.Among the impurities contained in the SF, carbon delays considerably the hydration of the principal components of Portland cement (C3S and C3A) as well as the pozzolanic reactivity of the silica fume without removing it. 相似文献
109.
A metal matrix composite (MMC) was fabricated using Al as the base metal which was reinforced by a ceramic material silica gel. This article shows detail fabrication stages in the production of MMC. The properties were considered with regard to the saturation point of the reinforcement of silica gel into the metal matrix of Al-Si alloy which was found out experimentally. Here the improvement of the mechanical properties of Al-silica gel MMC composite were studied with respect to that of pure Al-Si alloy. Different tests were conducted to show the results. Conventional ingot metallurgy with infiltration technique using vortex method had been employed in the fabrication process. The test results show that there are improvements by 17.14%, 13.46%, 11.48%, and 18.18% on compressive strength, impact strength, Brinell hardness value, and Rockwell hardness no respectively of Al-silica gel MMC over the pure Al-Si alloy. 相似文献
110.
Computation of radar absorbing silicon carbide foams and their silica matrix composites 总被引:5,自引:0,他引:5
SiC-foams and their composites were studied as novel stealthy materials by numerical simulations. The reflection coefficients of various SiC-foams are found to be strongly dependent on the SiC volume fractions, electric conductivities and frequency. A foaming SiC allows to reach high level of electromagnetic wave absorbing ability when the SiC volume fraction and the conductivity at proper values comparing to SiC-particles and SiC-bulk, Which due to an increase of electromagnetic energy dissipation in foaming structures and an improvement of the conjugation condition with free space. It is of most importance that SiC-foams exhibit artificial magnetic properties that can absorb the magnetic energy of electromagnetic waves. The electromagnetic absorbability of the silica composites are significantly decreased compared to that of the SiC-foams alone for the larger impedance mismatch with free space. 相似文献