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Preparation and characterization of a porous silicate material from silica fume
Yinmin Zhang,Haiping Qi,Yaqiong Li,Yongfeng Zhang,Junmin Sun 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.12
A porous silicate material derived from silica fume was successfully prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared (FT-IR) spectroscopy, Thermogravimetry and Differential thermal gravity (TG-DTG), N2 adsorption and desorption isotherms, and scanning electron microscopy (SEM). Raw silica fume was analyzed by XRD, FT-IR and SEM. The analysis results of silica fume indicated that SiO2 in silica fume is mainly determined as amorphous state, and that the particles of raw silica fume exhibited characteristic spherical structure with a diameter of from 50 nm to 200 nm. The preparation of the porous silicate material involved two steps. The first step was the extraction of the SiO3 2− leachate from raw silica fume. The maximum value of SiO3 2− extraction yield was obtained under the following conditions: reaction temperature of 120 oC, reaction time of 120 min, NaOH concentration of 15%, and alkali to SiO2 molar ratio of 2. The second step was the preparation of the porous silicate material though the reaction of SiO3 2− leachate and Ca(OH)2 suspension liquid. The optimum preparation conditions were as follows: preparation temperature of 90 oC, preparation time of 1.5 h, Si/Ca molar ratio of 1 : 1, and stirring rate of 100 r/min. The BET surface area and pore size of the porous silicate material were 220.7m2·g−1 and 8.55 cm3/g, respectively. The porous silicate material presented an amorphous and unordered structure. The spectroscopic results indicated that the porous silicate material was mainly composed of Si, Ca, O, C, and Na, in the form of Ca2+, SiO3 2−, CO3 2− and Na+ ions, respectively, which agreed with the XRD, TG-DSC, and FT-IR data. The N2 adsorption-desorption isotherm mode indicates that the porous silicate material belonged to a typical mesoporous material. The porous silicate material presented efficiency for the removal of formaldehyde: it showed a formaldehyde adsorption capacity of 8.01mg/g for 140 min at 25 oC.
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Qiang Zhang,Wenyuan He,Yinmin Wang,Dazhao Pei,Xue Jun Zheng 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.5
The sonication processing was added in front of the freeze-drying as an intermediate processing before the molybdenum disulfide (MoS2) aerogel was synthesized. It is distinguishing with the traditional hydrothermal reaction to combine the sonication processing and freeze-drying in our method. The structure, morphology, specific surface area and pore size distribution were characterized, and the electrochemical performances were measured in 0.5M Na2SO4 electrolyte for the MoS2 aerogel and flower-like MoS2. As for comparison, they are of porous structure and microsphere structure, and their specific surface areas are 55.14 m2 g -1 and 38.12 m2 g -1. The specific capacitances are 166.7 F g -1 and 119.2 F g -1 at the scan rate of 5 mV s -1, and the capacity retentions are 87.7% and 81.6% after 3000 charge/discharge cycles. For the enhanced mechanism, the high specific surface of the MoS2 aerogel causes high specific capacitance, and the unique porous structure could buffer volume expansion to improve retention ability during charge/discharge processes. The MoS2 aerogel may thus be a promising electrode material for supercapacitors.
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