Advanced Materials Research Vols. 550-553

Abstract: SrFeCoO_3-δ oxides have been synthesized by citrate method and the effect of sintering temperature on the structure of the samples has been analyzed. The experimental results show that the samples sintered at different temperatures are mainly composed of SrFe_0.5Co_0.5O₃ with perovskite structure. The impure phases decrease and the intensity of the diffraction peaks of the SrFe_0.5Co_0.5O₃ perovskite phase increases with the increase of the sintering temperature. High pure SrFe_0.5Co_0.5O₃ perovskite phase can be obtained after sintering at 1000°C and 1100°C. The particle size with irregular morphology increases with the increase of the sintering temperature.

Abstract: This paper presents a study on the impact of the nucleation supercooling degree of nanofluids. Three different mass fraction TiO₂-H₂O nanofluids with 20nm TiO₂ were prepared by supersonic oscillator through appending hydrophilic dispersant into deionized water. TiO₂-H₂O nanofluids and deionized water were tested by the experiments of freezing synchronous. The experimental results show that nanofluids have remarkably lower supercooling degree than deionized water, and the time of beginning nucleation is ahead of deionized water, also the total freezing time is lower than that of deionized water. And the influences of different cooling temperature to the supercooling degree were observed, with the cooling temperature increasing, the supercooling degree reduced.

Abstract: Changes of nutrient cycle and balance in agricultural ecosystem will bring heavy impacts not only on land production, but also on ecological and environmental condition. We studied on the balances of main nutrients (carbon, nitrogen and phosphor) and their long-term changes in a typical arable ecosystem in North China, based on the resource data got from household surveys combined with land use data derived from remote sensing imagery. The results show that C and N balances of large-scale irrigated land changed from deficits in 1945 into great surpluses in 2002, respectively, and P surpluses also doubled in 2002. C, N and P balances in overall arable ecosystem showed significant surpluses despite of decreased total arable area after 60 years. Contrarily, C and N fluxes of arable landscape in 1945 showed overall deficits. Nutrient balance changes of arable lands were impacted mainly by anthropogenic factors such as fertilizer input, land productivity crop residue utility and land use.

Abstract: The reaction of N₂ with lithium at electrode in lithium ion batteries was reported in this paper. At room temperature, N₂ can react with lithium, mainly at anode, to form Li₃N in an electrochemical system very easily during charge-discharge cycles. Li₃N has been characterized by XPS. Experimental results also revealed that the higher of the current density and higher of the temperature resulted in quicker of the nitrogen-fixation reaction. The reaction can be brought about almost completely in the lithium ion batteries at room temperature. This could be a new method for preparation of Li₃N at room temperature.

Abstract: Experiments on chromatography separation are taken for ASP flooding. Mass transfer equation is estabilished and mutiple adsorption factor is obtained. Mutiple adsorption factor is used to analyze the experiment results. The Mass transfer property of alkali, surfactant and polymer during single fooding and ASP flooding and the effect on interfacial tension of oil/solution are discussed. The results show the diffrence of hesteris degree of alkali, surfactant and polymer deduce the chromatography separation, lowing the active of ASP flooding. Accoding to interfacial tension, the efficent length of ASP slug is discussed.

Abstract: Kinetic analysis of silicon carbide prepared by carbon-thermal reduction is introduced in this paper. Through the dynamic analysis, kinetic parameters of Si-C are calculated, and it is estimated that the time required reaction materials of different diameter completely converted to SiC at different temperatures. Reaction time is nearly 1 hour long when the reaction particle diameter is 1μm around 1900K.

Abstract: Thermal properties of intumescent fire-retardant materials are important parameters as input data in modeling combustion behavior of these materials in fire. However, Data regarding thermal properties especially thermal diffusivity of these composites are sparse. In this paper, intumescent fire-retardant polypropylene (IFR-PP) and char formed after the combustion of IFR-PP materials by the cone calorimeter at heat flux level of 50 kW/m2 are studied to obtain the thermal diffusivity data of them. Study results show the value of thermal diffusivity for IFR-PP tends to decrease when the temperature increase especially in higher temperatures. Thermal diffusivity of char formed after the combustion of IFR-PP material decreases gradually with the rise of temperature. Thermal diffusivity value measured at room temperature could not be used as input parameters in a combustion model when it is established to simulate the burning behavior of IFR-PP composites in fire.

Abstract: The CO2 gasification of three coal chars were investigated for determining the gasification reactivity and the kinetic parameters. Experiments were conducted in a fluidized-bed reactor at temperature of 1173 k, 1273 k and 1373 k at atmospheric pressure. Gasification kinetic parameters of the samples were determined using Homogeneous model and shrinking-core model. It is found that the gasification reaction under chemical-reaction-rate control, the gasification reactivity of coal char are strongly dependent on the rank of coals and gasification temperature. Both models could describe CO2 gasification equally well, these kinetic values are comparable with the reported in the literature for the other chars under chemical control conditions.

Abstract: The pyrolysis tests of Shenhua coal and Shenhua direct liquefaction residue have been carried out using thermogravimetric at the differential heating rate. The kinetic parameters k and E were calculated using DAEM method. Results show DAME model can describe the pyrolysis behavior of Shenhua coal within the range of 20% to 95%, the activation energy of coal pyrolysis ranges from 53.98 to 279.38 kJ/mol, and DAME model can describe the behavior of Shenhua direct liquefaction residue within the range of 10% to 80%, the activation energy of residue pyrolysis is about 170 kJ/mol. The results of which are basically consistent with the experimental data.

Abstract: The pressure drop at critical fluidization for two-dimensional vibrated fluidized bed(240 mm×80 mm) was studied, with large particle glass beads of average diameters dp of 1.8mm, 2.5mm and 3.2mm.The effect of the vibration strength, the static bed height and the particle diameter on the pressure drop was analyzed. The results of the study show that the pressure drop decreases with the increase of the vibration strength. It plays an even more prominent part with decreases of the static bed height and the particle diameter. The empirical correlation equations to predict the pressure drop was established, and the results of the prediction was compared with the experimental data, the error is in range of ±10%. The results can provide references for future design and research on the vibrated fluidized bed.