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991.
Graphene nanosheets were synthesized in large quantities using a chemical approach. Field emission electron microscope observation revealed that loose graphene nanosheets agglomerated and crumpled naturally into shapes resembling flower-petals. High resolution transmission electron microscope analysis, Raman spectroscopy and ultraviolet-visible spectroscopy measurements confirmed the graphitic crystalline structure of the graphene nanosheets. The nanosheets exhibited an enhanced lithium storage capacity as anodes in lithium-ion cells and good cyclic performance. 相似文献
992.
Stacked TS-1 [NSTS-1(MW)] has been prepared by microwave synthesis and applied to the epoxidation of linear olefins with H2O2 under mild conditions, and the epoxidation activities were compared with the non-stacked TS-1 and the conventional TS-1, which were also synthesized by microwave and by typical hydrothermal method, respectively. Stacking of TS-1 crystals was accomplished by using microwave which facilitated the dehydration of hydroxyl groups on the external surface of crystallites through the selective absorption of microwave onto Ti species. The stacked crystallites seemed to allow the running pore structure in the b-axis orientation through the crystallites in the stacked morphology. Besides this unique pore structure, the stacked TS-1 showed peculiar features like higher hydrophobicity and enhanced catalytic property than typical TS-1. Moreover, the NSTS-1(MW) showed the highest activity in the epoxidation of linear olefins among three catalysts, and also coincided with the differences in the adsorption of linear aliphatics due to strong interaction with the straight channel in the stacked morphology, which gave larger Henry’s constants, obtained by the tracer chromatographic analysis, as the increase in the carbon chain length. 相似文献
993.
Hyun Ju Park Young-Kwon Park Jong-In Dong Joo-Sik Kim Jong-Ki Jeon Seung-Soo Kim Jinsoo Kim Byungho Song Junhong Park Kyung-Jin Lee 《Fuel Processing Technology》2009
The kinetic parameters for the pyrolysis of Oriental white oak were evaluated by thermogravimetric analysis (TGA). The white oak was pyrolyzed in a fluidized bed reactor with a two-staged char separation system under a variety of operating conditions. The influence of the pyrolysis conditions on the chemical and physical characteristics of the bio-oil was also examined. TGA showed that the Oriental white oak decomposed at temperatures ranging from 250 to 400 °C. The apparent activation energy ranged from 160 to 777 kJ mol− 1. The optimal pyrolysis temperature for the production of bio-oil in the fluidized bed unit was between 400 and 450 °C. A much smaller and larger feed size adversely affected the production of bio-oil. A higher fluidizing gas flow and higher biomass feeding rate were more effective in the production of bio-oil but the above flow rates did not affect the bio-oil yields significantly. Recycling a part of the product gas as a fluidizing medium resulted the highest bio-oil yield of 60 wt.%. In addition, high-quality bio-oil with a low solid content was produced using a hot filter as well as a cyclone. With exception of the pyrolysis temperature, the other pyrolysis conditions did not significantly affect the chemical and physical characteristics of the resulting bio-oil. 相似文献
994.
In this work the corrosion behaviors of zirconia refractory (partially MgO-stabilized zirconia) was investigated in CaO–SiO2 –MgO–CaF2 slag with varying CaF2 content at 1873 K. To figure out the corrosion mechanism, the characteristics of present slag at high temperature were examined in terms of melting temperature and vaporization behaviors. Corrosion experiment and melting temperature measurement were carried out by heating microscope (HM) and the vaporization phenomenon was investigated by thermo gravimetry–differential scanning calorimetry. After experiment, the corroded interfaces of zirconia refractory by slag were analyzed by scanning electron microscope-energy dispersive spectroscopy and electron probe microanalysis. With an addition of CaF2 , three different layers were formed at the interface of slag and zirconia refractory. Furthermore, the corrosion behaviors of zirconia refractory were found to be continuously accelerated with an increase of CaF2 which facilitated the dissolution of intermediate compound. On the other hand, melting temperature of CaO–SiO2 –MgO–CaF2 slag showed no continuous decrease with an increase of CaF2 . Also, considerable vaporization of fluoride gas was occurred in high CaF2 containing slag during HM experiment which might cause a gradual change of slag composition and also environmental pollution. From the results, present study suggested that a proper amount of CaF2 should be added when it is used for enhancing refining capacity of slag in order not to cause any severe damage of zirconia-based refractory by slag. 相似文献
995.
Hoo Kun Lee Myeong Soo Jeong Joo Wan Park Hyun Soo Park Jong Hyun Cho 《Korean Journal of Chemical Engineering》1990,7(1):13-17
An absorption efficiency of packed column removing nitrogen oxides with water and NaOH solution under atmospheric pressure
was studied. The efficiency and the acidity produced by absorption of NO, were measured in a packed column. The model developed
that was based on the mass-transfer information for packed column and absorption mechanism accompanying the chemical reaction
was compared with experimental results. Predictions using the model presented by the previous paper (part 1) was shown well
to agree with from the experimental results (part II). The efficiency of NOx, absorption is largely dependent on the height of packing material and the partial pressure of NOx in the feed gas. The efficiency of NOx absorption decreases with the increase of the acidity produced by recycling of water as a scrubber liquid. For the recycle
mode with an aqueous NaOH solution as a scrubber liquid, NOx absorption efficiency is shown to be constant until all of the COH- in the scrubber liquid are converted into CH+. 相似文献
996.
Characteristic behavior in the graft copolymerization of acrylamide/N-(1,1-dimethyl-3-oxybutyl)acrylamide (AM/DAAM) comonomers onto dextran by Ce(IV)-induced initiation was investigated. From a preliminary study, it was found that ceric ammonium nitrate polymerized AM/DAAM comonomer mixtures and diacetone acrylamide, but not acrylamide alone in the aqueous solution. The effect of grafting conditions on the graft copolymerization product was studied with the aid of aqueous size exclusion chromatography and the anthrone reagent. The selectivity of formation of the graft copolymer over random copolymer was found to increase as the reaction temperature and AM/DAAM ratio increased and as both the Ce(IV)/Dextran molar ratio and HNO3 concentration decreased. After establishing optimum grafting conditions, graft copolymer samples were prepared, and their aqueous solution behavior studied as functions of structure, temperature, and added salts. 相似文献
997.
The size of the primary particles in aerosol agglomerates is determined in part by the interplay of surface growth, coagulation, and sintering. These processes are modelled by a one-dimensional (1-D) discrete-sectional model, DISGLOM2, which predicts the evolution of agglomerate and primary particle size distributions. DISGLOM2 is an extended version of DISGLOM (Rogak 1997), in which particles smaller than the "melting diameter" were assumed to sinter instantly while bigger particles did not sinter at all. Gradual sintering, "condensational obliteration" (whereby primary particles are lost during heavy surface growth), and diffusional wall deposition have been incorporated into DISGLOM2. Results from DISGLOM2 were comparable with those from 2-D sectional models, but DISGLOM2 was much faster. In addition, DISGLOM2 includes the effects of "condensation" of small spherical particles on large agglomerates, which were not modelled previously. The effect of condensation was shown to be significant at low temperature. DISGLOM2 was used to predict the primary particle diameter of titania particles generated by precursor reaction. By adding gradual sintering, the growth rate of agglomerate particles by coagulation was slightly decreased and the primary particle size considerably increased compared with the results given by DISGLOM. Although DISGLOM2 is an efficient model of the relevant physical processes, the predictions are sensitive to the kinetics of precursor reactions and particle sintering, which can be difficult to characterize in real experimental systems. 相似文献
998.
金刚石有序排列锯片切割性能的研究 总被引:4,自引:2,他引:4
在金刚石锯片刀头表面上,金刚石颗粒的切割效率取决于金刚石颗粒之间的间距分布和单个金刚石的磨损状况。在这项研究中,试图分析金刚石颗粒之间的间距分布,在锯片的加工中,金刚石颗粒是人工有序排布的,将这种金刚石有序排列的锯片的切割特性与普通锯片的切割特性做了对比。金刚石颗粒的平均间距定为4mm,使用浓度为1.1ct/cm^3的美国40/50目的金刚石。在完成切割之后,在金刚石有序排列的锯片上,80%的金刚石颗粒可观测到其间距仍保持在2~6mm的范围内, 相似文献
999.
In this study solid-state NMR spectroscopy was used to identify structure and guest distribution of the mixed N2 + CO2 hydrates. These results show that it is possible to recover CO2 from flue gas by forming a mixed hydrate that removes CO2 preferentially from CO2/N2 gas mixture. Hydrate phase equilibria for the ternary CO2–N2–water system in silica gel pores were measured, which show that the three-phase H–Lw–V equilibrium curves were shifted to higher pressures at a specific temperature when the concentration of CO2 in the vapor phase decreased. 13C cross-polarization (CP) NMR spectra of the mixed hydrates at gas compositions of more than 10 mol% CO2 with the balance N2 identified that the crystal structure of mixed hydrates as structure I, and that the CO2 molecules occupy mainly the abundant 51262 cages. This makes it possible to achieve concentrations of more than 96 mol% CO2 gas in the product after three cycles of hydrate formation and dissociation. 相似文献
1000.
Migration of some sorbing chemical species has been studied in a single rock fracture of 1 m scale in order to understand
the transport behavior of contaminants at underground environments. For the tracers, tritium and anions were used as nonsorbing
ones and some sorbing cations such as Sr, Co and Cs were used as well. The experimental study was focused on the identification
of the retardation and matrix diffusion of the tracer in the fracture. The hydraulic conductivity in the fracture was determined
from the pressure differentials between pairs of boreholes. The hydraulic data were used with a variable aperture channel
model to characterize the aperture distribution in the fracture. A transport model has been developed to describe the migration
of the solutes in the flow field by using a particle tracking method. Results were plotted in the form of elution curves and
migration plumes in the fracture. The experimental elution curves have been explored with the transport model which takes
into account sorption and diffusion into the rock matrix. This comparison may contribute to further understanding on the heterogeneous
flow field and the interactions between rock and chemical species. 相似文献