Xiufeng Ren

FTIR spectroscopic studies of lithium tetrafluoroborate in propylene carbonate + diethyl carbonate mixtures

FTIR (Fourier transformed infrared) spectra have been collected and analyzed for solutions of lithium tetrafluoroborate in propylene carbonate (PC), diethyl carbonate (DEC), and PC+DEC mixtures. It has been shown that the carbonyl stretch bands of PC and DEC, the ring of PC and the ether oxygen stretch bands of DEC are all very sensitive to the interaction between Li(+) and the solvent molecules. New shoulders appear and the original bands split with the addition of LiBF4, indicating that a strong interaction between Li(+) and molecules of PC and DEC exists through the oxygen group of C=O and ring of PC and both C=O oxygen and ether oxygen atoms of DEC. In addition, no preferential solvation of Li(+) in LiBF4/PC+DEC solutions was detected.

Enhanced thermal conductivity in a hydrated salt PCM system with reduced graphene oxide aqueous dispersion

The phase change enthalpy, thermal conductivity, thermal stability and thermal reliability of a novel reduced graphene oxide (r-GO) containing phase change material (PCM) r-GO/CaCl2·6H2O were investigated. The material was made by the aqueous dispersion of r-GO and calcium chloride dihydrate (CaCl2·2H2O) according to the mass ratio of CaCl2 and crystal water in CaCl2·6H2O. The thermal conductivity of the phase change material increased by ∼80% when using ∼0.018% (by weight) of r-GO with a ∼2.7% decrease of enthalpy (i.e., storage capacity), while using ∼0.018% of graphite led to an increase of thermal conductivity by ∼14% and a decrease of enthalpy by ∼5.6%. Additionally, the surface active agent for dispersing r-GO had the extra function of enhancing the system stability and reliability. The decomposing temperatures of r-GO/CaCl2·6H2O were higher than those of CaCl2·6H2O. After 100 cycles, the melting and crystallizing enthalpies of r-GO/CaCl2·6H2O decreased to 178.4 J g−1 and 150.7 J g−1 from 180.6 J g−1 and 153.7 J g−1, dropping by 1.2% and 2.0%, respectively, while for CaCl2·6H2O they decreased to 178.9 J g−1 and 147.8 J g−1 from 185.6 J g−1 and 161.8 J g−1, dropping by 3.7% and 8.7%, respectively. The thermal conductivity enhancement of CaCl2·6H2O with r-GO was markedly superior compared to that with graphite and other thermal conductive additives reported in previous literature, and the provided method (i.e., preparing aqueous dispersions of additives firstly and synthesizing hydrated salt PCMs with corresponding salts subsequently) was also applicable for other functional additives that cannot be directly dispersed well to modify the thermal properties of hydrated salt PCM systems.

Roles of ethylene glycol solvent and polymers in preparing uniformly distributed MgO nanoparticles

Abstract This study focus on specifying the roles of solvent ethylene glycol (EG) and polymers for synthesis of uniformly distributed magnesium oxide (MgO) nanoparticles with average crystallite size of around 50 nm through a modified polyol method. Based on different characterization results, it was concluded that, Mg2+ ions was precipitated by the −OH and CO32− ions decomposed from urea in ethylene glycol (EG) medium (CO(NH2)2 → NH3 + HNCO, HNCO + H2O → NH3 + CO2), thus forming well crystallized Mg5(CO3)4(OH)2 (H2O)4 precursor which could be converted to MgO by calcination. Surface protectors PEG and PVP have no obvious influences on cyrtsal structure, morphology and size uniformity of as-prepared precursors and target MgO nanoparticles. In comparison with polymers PEG and PVP, solvent EG plays an important role in controlling the morphology and diameter uniformity of MgO nanoparticles.

Investigation and preparation of CeO2-TiO2/FA (fly ash) SCR catalyst

ABSTRACT CeO2-TiO2/FA catalysts with the selective catalytic reduction (SCR), using industrial solid waste-Fly Ash (FA) as the supporter was prepared by sol-gel and insuccation methods. Ammonia was used as reducing gas to detect the catalytic performance of as-prepared catalyst. Surface structure and catalytic properties of the catalyst were characterized by using BET, XRD, SEM and denitrification tests, respectively. It was confirmed that the loading of CeO2 and TiO2 on FA supporter led to the increased the specific surface area of catalysts, which resulted in the enhanced catalytic performance toward removing NOx. The NOx conversion over this catalyst can reach 95.3%.

Investigation and Preparation of High Active Nano-MgO Thin SphericalMaterial

High active MgO precursor was prepared by high-temperature spray thermal decomposition method using saturated MgCl2 as raw materials. And high active nano-MgO thin spherical materials were prepared by MgO precursor being calcined at different temperatures after multiple hydration, purification, and filtration. The XRD, TG, DSC and SEM were employed to characterize the phase structure and micro-morphology of spherical materials whose formation mechanism was researched. And its activity (average pore size and surface area) was detected by using BET-BJH of N2 adsorption to get the optimum calcination temperature. The results showed that high active nano-MgO thin spherical material was periclase structure, its surface of nano-flake or rod-like, and thin sphere with diameter of 30∼100 nm and aperture of 10∼60 nm. The aperture was decreased while the surface area, microporous volume and surface activity were increased with preparation process were optimized, for example, calcination temperatures. Nano-MgO thin spherical material with a purity of 99.2 wt% was obtained at 900°C. And BET surface area of nano-sphere reached a maximum value of 31.6 m2/g with nest-like structure of particle uniform dispersion and average aperture of 11.2 nm. Meanwhile, the maximum absorption of N2 was gotten.