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31.
A series of nanosized Fe–Mn–Cu–K composite catalysts was prepared by a supercritical combined technology. The nanosized catalysts were characterized by means of XRD, TEM and BET techniques, and tested for catalytic performance under Fischer–Tropsch synthesis (FTS) reaction conditions. The catalyst synthesized by the supercritical combined technology has some excellent properties. Additionally, the drying and crystallization of nanosize catalyst could be achieved simultaneously by this supercritical combined technology. The addition of Mn, Cu and K promoters can improve the catalytic performance properties of the catalyst, including lower CH4 and CO2 formation rates, and higher production rates of desired light-olefin. The optimal performance with a 95.7% CO conversion and a 46.5% light-olefin yield was obtained by using a catalyst component of Fe/Mn/Cu/K = 60:25:10:8.5. In summary, optimal catalytic performance was obtained by using the nanosized catalyst under supercritical reaction conditions, resulting in higher CO conversion, less byproduct CO2 formation, and a higher yield of light-olefin. 相似文献
32.
This investigation shows that in absence of the chemical reductant and the other protective reagents, the host-guest interaction and the molar ratio of dendrimers/Au3+ other than size and shape of the templates play an important role for the preparation of stable gold hybrid colloids by 60Co γ-ray irradiation using spherical PAMAM-G5 as nonlinear polymeric template. The hybrid colloid resultants comprised of the ordered nano-crystal and the random non-crystal part, which has been confirmed by HRTEM, display spherical structure and the polydispersity of the size distribution in the range of nanometer scale. The dendrimer/gold hybrid colloids are formed by the intramolecular and intermolecular adsorption action between PAMAM-G5 template and gold nanoparticles, respectively. 相似文献
33.
Processing and creep properties of Sn-Cu composite solders with small amounts of nanosized Ag reinforcement additions 总被引:3,自引:0,他引:3
F. Tai F. Guo Z. D. Xia Y. P. Lei Y. F. Yan J. P. Liu Y. W. Shi 《Journal of Electronic Materials》2005,34(11):1357-1362
In this research, nanosized Ag reinforcement particles were incorporated by mechanical means into a promising lead-free solder,
Sn-0.7Cu, in an effort to improve the comprehensive property of the Sn-0.7Cu solder. Wettability, mechanical performance,
and creep-rupture life tests were conducted to study the difference between Sn-0.7Cu solder and its composite solder with
different Ag reinforcement volume fractions. Experimental results indicated that the composite solders and their joints showed
better wettability and mechanical properties, as well as longer creep-rupture lives, than Sn-0.7Cu solder. The composite solder
with 1vol.%Ag reinforcement addition exhibited the best comprehensive property as compared to the composite solders with other
reinforcement volume fractions. Systematic creep-rupture life tests were conducted on the 1vol.%Ag-reinforced Sn-0.7Cu-based
composite solder joints. Significant enhancement of the creep-rupture lives were found in the composite solder joints under
different stress and temperature combinations as compared to the Sn-0.7Cu solder joint. Ductile rupture surfaces were exhibited
in most of the broken solder joints. 相似文献
34.
Man Sig Lee Seong Soo Park Gun-Dae Lee Chang-Sik Ju Seong-Soo Hong 《Catalysis Today》2005,101(3-4):283-290
TiO2 nanoparticles were prepared using hydrolysis of titanium tetraisopropoxide in W/O microemulsions consisting of water, nonionic Brij series surfactants with different hydrophilic and Tween series surfactants with different hydrophobic group, and cyclohexane. The properties of these particles were characterized by TEM, XRD, FT-IR, TGA and DTA. The photocatalytic degradation of p-nitrophenol has been studied in order to compare the photocatalytic activity of prepared nanosized titania. TiO2 particles calcined at 500 °C have a stable anatase phase which has no organic surfactants and the product completely transforms into the anatase phase above 300 °C and the rutile phase begins to appear at 600 °C regardless of surfactants. The particles are shown to have a spherical shape and have an uniform size distribution but the shape becomes distorted with a decrease of hydrophilic group chain length according to rapid hydrolysis of water and titanium alkoxide. In addition, the crystallite size and crystallinity increase with a decrease of hydrophilic and hydrophobic group chain length and an increase of calcination temperature. The photocatalytic activity increases with an increase of hydrophilic and hydrophobic group length and the titania calcined at 500 °C shows the highest activity on the photocatalytic degradation of p-nitrophenol regardless of surfactants. 相似文献
35.
Hydrothermal synthesis of titanium dioxide using acidic peptizing agents and their photocatalytic activity 总被引:1,自引:0,他引:1
Jun Ho Kim Byung Ho Noh Gun-Dae Lee Seong-Soo Hong 《Korean Journal of Chemical Engineering》2005,22(3):370-374
We have prepared TiO2 nanoparticles by the hydrolysis of titanium tetraisopropoxide (TTIP) using HNO3 as a peptizing agent in the hydrothermal method. The physical properties of nanosized TiO2 have been investigated by TEM, XRD and FT-IR. The photocatalytic degradation of orange II has been studied by using a batch
reactor in the presence of UV light. When the molar ratio of HNO3/TTIP was 1.0, the rutile phase appeared on the titania and the photocatalytic activity decreased with an increase of HNO3 concentration. The crystallite size of the anatase phase increased from 6.6 to 24.2 nm as the calcination temperature increased
from 300 °C to 600 °C. The highest activity on the photocatalytic decomposition of orange II was obtained with titania particles
dried at 105 °C without a calcination and the photocatalytic activity decreased with increasing the calcination temperature.
In addition, the titania particles prepared at 180 °C showed the highest activity on the photocatalytic decomposition of orange
II.
This paper was prepared at the 2004 Korea/Japan/Taiwan Chemical Engineering Conference held at Busan, Korea between November
3 and 4, 2004. 相似文献
36.
The conditions for the preparation of stable nanosized barium titanate suspensions with high solids content for the production of aqueous tape casting are identified. The rheological behavior of colloidal barium titanate suspension with Ammonium polyacrylate (NH4-PAA) as a dispersant to aid the powder dispersion has been investigated. Nanosized barium titanate powder was synthesized by a continuous high-gravity reactive preparation (HGRP) technique, and then annealed at 900 °C for 2 h. Measuring the zeta potential, the particle size distributions and ball-milling time, assessed the optimum conditions of the suspension with low viscosity and stability. An isoelectric point (IEP) at pH = 2.8 was found. Particle size distribution tests identified an optimum pH value about 10 and an optimum dispersant addition about 1.2 wt.% (based on the dry powder weight). As the ball-milling time was longer than 8 h, the amount NH4-PAA adsorbed on the barium titanate reached to saturation. The maximum solid content attained during this work was 45 vol.% at pH of 10, with dispersant addition 1.2 wt.%. High green density value (up to ∼55.4% of the theoretical density) in BaTiO3 sheet was achieved with a solid content 40 vol.%. After sintering at 1200 °C for 2 h a final density of 95% is reached. 相似文献
37.
Mono-disperse Ni0.5Zn0.5Fe2O4 spinel ferrite particles have been synthesized directly via the hydrothermal method using sodium dodecyl sulfate (SDS) as surfactant. Particle size could be varied from 6 to 19 nm by changing the experiment parameters. X-ray diffraction, high resolution TEM images confirmed the high crystallinity of ferrite nanocrystals. The effects of precursor suspension pH value, reaction temperature and surfactant (SDS) concentration on phase purity, particle size and dispersed property were discussed. The results indicated that mono-disperse Ni0.5Zn0.5Fe2O4 spinel ferrite nanoparticle had been obtained at pH value range (8–9), reaction temperature (90 °C) and moderate SDS concentration (>0.2 mM). The magnetic measurement shows that as prepared Ni0.5Zn0.5Fe2O4 nanoparticle possesses good super-paramagnetic behavior. We also put forward a primary experimental model to shed light on the controllability of the monodispersity of the nanosized particles. 相似文献
38.
39.
《Ceramics International》2021,47(19):26720-26731
Synthetic biphasic bioceramics composed of hydroxyapatite (HA) and other calcium phosphates (CPs) can provide promising efficiency in the treatment of bone defects based on the rapid dissolution of the CPs, to allow its replacement by freshly formed bone, along with the slow resorption of the HA, to preserve the volume of the grafted area. For this purpose, the present study was conducted to prepare nanosized biphasic calcium phosphate (n-BCP) using a facile mechanochemical process. The experimental outputs were also compared to the commercial-grade HA in terms of physicochemical features. The Rietveld refinement was utilized to calculate the phase contents and crystal structures of the composites, including crystallite size, lattice parameters, and unit cell volume. Besides, the atomic arrangement of Ca1, Ca2, PO43−, and OH− groups in the hexagonal crystal structure of HA and triclinic structure of anhydrous dicalcium phosphate (DCPA) was determined. The phase fraction, crystallite size, and the powder density of the biphasic structures, which were derived by Rietveld refinement, were found to be affected by ball-milling. In addition to biphasic structures, a monolithic hexagonal HA with an isotropic crystal growth was formed after 7 h of ball-milling under an argon atmosphere. The in vitro test in a simulated body fluid (SBF) confirmed the bioactivity of the biphasic structure through the formation of a bone-like apatite layer after one week. 相似文献
40.
Nanosized zirconia was prepared by a hydrothermal method using ZrOCl2·8H2O and NaOH as raw materials. The obtained ZrO2 powders were soaked in the phosphate solution with different concentrations. The as-prepared ZrO2 powders and the powders treated with phosphate solution were calcined at different temperatures from 600 to 1000 °C. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and X-ray photoelectronic spectroscopy (XPS). The experimental results show that the untreated nanosized ZrO2 grow and agglomerate to bulk when the ZrO2 powders were calcined at high temperatures, while the ZrO2 powders treated with phosphate solution grow slowly and remain nanosized crystal at the same calcination temperature. This phenomenon implied that phosphate treatment played an important role in inhibiting the crystal grain growth of ZrO2. The possible inhibition mechanism could be explained to that P species on the surface of ZrO2 can reduce the grain boundary mobility and prevent direct contact of ZrO2 particles. 相似文献