Papers by Author: Dong Xu Li

Abstract: Hollow silica microspheres with porous surface were synthesized by using the pollen grains as biotemplate through an in-situ synthesis process, in which the pollen grains were surface modified by ammonium oleate. Scanning electron microscopy, Fourier transform infrared spectroscopy and nitrogen adsorption-desorption porosimetry analyzer were applied to investigate the as-prepared microspheres. Bovine serum albumin was used as the model drug to estimate the adsorption property. And the effect of the different amount of tetraethoxysilane during the synthesis process were discussed in this paper. Results indicated that the hierarchical network of the pollen wall could be well replicated through this method, in which the hydrophobic interaction between the pollen wall and surfactant as well as the electrostatic interaction between the surfactant and the hydrolysate of tetraethoxysilane were considered as the key factors for the replication. The hollow silica microspheres have loading capacity for the model drug, and the adsorption property of this microsphere could be easily adjusted by changing the amount of tetraethoxysilane.

Abstract: Finite element method (FEM) was used for analyzing the heat transfer problems of the PCMs and phase change gypsum board. The simulation results showed that the heat transfer rate of composite PCMs (phase change materials) is higher than the PCMs, the mixture of diatomite improved the heat transfer performance of PCMs. Compared with blank gypsum board,the cold side temperature of phase change gypsum board was decreased, and the temperature rise rate of the cold side was also delayed. The cold side temperature difference between gypsum board and phase change gypsum board was decreasing as the ongoing of heat transfer process.

Abstract: Monodispersed iron phosphate hollow microspheres with high uniformity were synthesized by using the rape pollen grains as biotemplate. The as-prepared microspheres were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, energy disperses spectroscopy and scanning electron microscopy. The shell of the microspheres was found to be a bilayer structure composed with a compact inner layer and rough outer layer. Through the investigation of the adsorption behavior of the pollen grains, the formation of the bilayer structure was attributed to the selective permeation of the pollen wall. The inner layer was formed by the ion passed through the pollen wall and adsorbed on the pollen core; while the outer layer was formed by the coating of the particles could not permeate the pollen wall. When the pollen grains were removed by the calcinations, both of the precipitate in the pollen and on the pollen wall were condensed to from the hollow microspheres with a shell of bilayer. This process provides us with a new insight on the preparation of the hollow microspheres with special structure using the pollen grains as biotemplate. The microspheres with core/shell or multilayer structure should be achieved by utilization of the selective permeation of the pollen wall.

Abstract: Lauric acid(LA) and capric acid(CA) were mixed into binary mixture, whose melting temperature was predicted with Schroder’s equation and tested in step cooling curve method. Then latent heat was tested by DSC, and T-history method was used to test thermal conductivity of binary mixtures, heating and cooling characteristics were studied through expanded perlite(EP) adsorption of binary mixtures. Results show that Schroder’s equation can be used to predict melting temperature of fatty acid, and binary mixture prepared of 6:4 molar ratio has a high latent heat and its temperature is within a range that meets indoor comfort temperature. Thermal conductivity and the heating and cooling characteristics of the mixtures reveals that the thermal conductivity of fatty acid phase change material(PCM) is low, which restricts its latent heat release rate.

Abstract: Fatty acid phase change materials(PCMs) and composite diatomite PCMs were prepared in this study, the phase change temperature of different mole ratio lauric acid(LA) and capric acid(CA) PCMs were tested by step cooling curve method, thermal physical performance of the prepared PCMs were tested by differential scanning calorimeter (DSC). A new type of lightweight phase change gypsum wallboard incorporated with LA-CA/diatomite composite PCMs was prepared, and the thermal performance of this material was studied. The results showed that the LA and CA could form an eutectic mixture. DSC results indicated that the phase change temperature of the PCMs and composite diatomite PCMs are both 26.7°C, the latent heat of the PCMs are 142.2J/g and 73.5J/g, respectively. Thermal performance test of the gypsum wallboard indicated that the temperature difference of the phase change gypsum wallboard at different moment is lower than the blank gypsum wallboard, which showed a better energy storage function of the phase change gypsum wallboard.

Abstract: Coal gangue and limestone were used as raw materials with fluorite and gypsum as the mineralizer. The activation mechanism of calcined coal gangue with calcium and the pore structure of its hydrating slurry are discussed. The experimental results show that during calcinations F- and [SO4]2- come into the framework and react deeper with CaO at 850-950°C to create hydraulic-activity C12A7 and C2S. Pore structure analysis of the hydrating slurry indicates that adding gypsum and fluorite into coal gangue is more propitious to strengthen the slurry and optimize the pore distribution than only of gypsum.

Abstract: This paper studied on preparation, mechanical and thermal properties of two PCM wallboards made of gypsum and paraffin composite, PCM particles wallboard and PCM bag packed wallboard. Density, flexural and compressive strength and thermal conductivity of PCM particles wallboards deceased as PCM particles dosage increasing. Only PCM particles wallboard with PCM particles dosage 30% is suitable. Thermal comparison between PCM wallboards and pure gypsum wallboard shows that two PCM wallboards have better thermal properties and PCM wallboards can be used in building envelope to cut down building energy-consumption.

Abstract: Flue gas desulphurization (FGD) gypsum and fly ash are two kinds of solid waste in coal-fired power plant. The possible displacement content of fly ash in gypsum plaster was investigated in this paper. The effect of various chemicals retarders, such as Citric acid, sodium citrate and SC gypsum retarder, and water retention agent on the setting time, flexural strength and compressive strength of gypsum plaster was also studied. The results demonstrate that gypsum plaster has maximum mechanical properties and enough setting time at the rate of 20% fly ash replacing calcined gypsum; SC gypsum retarder effectively delays the setting time and has lower strength loss; The optimum level of water-retention agent for effective utilization of gypsum plaster is 0.2%.

Abstract: Organophilic Bentonite / Paraffin composite phase change energy storage materials (OB/P PCM composite) were prepared by melting intercalation method. Under high temperature, no melt paraffin seep out from the PCM of organophilic bentonite/paraffin (OB/P) mass ratio is 2:1, which paraffin content is largest. Samples were tested by X ray diffraction (XRD), Scanning Electron Microscope (SEM), Differential scanning calorimetry (DSC) and Fourier Transform Infrared Spectroscopy (FTIR). Paraffin was well intercalated into layerd bentonite. Melting point and fussion heat of composite PCM with mass ratio2:1 are 45.7 °C and 68.7 kJ/kg, it can be added to solar energy.

Abstract: The Present Research Investigates the Compressive and Durable Properties of Concretes with Fly Ash (FA), a by-Product of Coal-Fired Power Plants. for this Purpose, a Reference Sample and Twenty-one Concretes Containing FA Were Tested. the FA Was Sieved to 200, 300, and 400 Mesh. then FA Was Mixed into Concrete with Different Content. Compressive Strength at 7 and 28 Days, and Chloride Penetration Properties Were Measured. it Is Concluded that FA Can Be Used in the Production of Concrete. in Addition, the FA Concretes Present Satisfactory Physical Properties. when Proper Amount of FA Were Added the Concrete Properties Can Be Better than the Blank one.