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Qian Y.,Shanghai JiaoTong University | Wei P.,Shanghai JiaoTong University | Jiang P.,Shanghai JiaoTong University | Li Z.,Shanghai JiaoTong University | And 2 more authors.
Composites Science and Technology | Year: 2013

In this article, mesoporous flame retardant (Al-SBA-15) was prepared by post-grafting of aluminum isopropoxide on the surface of mesoporous silica (SBA-15). X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectrum (FT-IR) and N2 adsorption-desorption measurement were utilized to investigate the structure of mesoporous materials. Al-SBA-15, SBA-15 and fumed silica were added into polylactide, respectively, to carry on comparative study. Results showed limiting oxygen index (LOI) of polylactide composite was significantly increased by Al-SBA-15, accompanied with UL-94V-0 rating. Moreover, the incorporation of 0.5wt% of Al-SBA-15 reduced the peak of heat release rate of PLA composite by 15.1% compared with pure PLA and decreased the produced smoke amount. Al-SBA-15 reduced the volatile products of PLA during thermal degradation process that was detected by mass spectroscopy (MS). Al-SBA-15 also improved the hydrolysis resistance and tensile properties of PLA composite. Results showed that Al-SBA-15 was a high-effective additive to improve the fire-resistance, smoke inhibition, hydrolysis resistance and mechanical properties of PLA. © 2013 Elsevier Ltd. Source

Lin B.,Shandong University | Su H.,Shandong University | Ma G.,Shandong University | Liu Y.,Shandong University | Hou Q.,Shandong Non metallic Materials Institute
RSC Advances | Year: 2016

Serum paraoxonase 1 (PON1) is a calcium-dependent enzyme that can catalyze the hydrolysis of multiple substrates, including lactones, thiolactones, carbonates, esters and phosphotriesters, as well as the formation of a variety of lactones. To better understand the lactonase mechanism of PON1, the hydrolysis of dihydrocoumarin, which is considered as a native substrate of PON1, has been investigated by using a combined quantum mechanics and molecular mechanics (QM/MM) approach. Two possible reaction pathways with either Glu53 or His115 acts as the general base have been considered. On the basis of our calculations, these two pathways correspond to the overall energy barriers of 12.5 and 9.0 kcal mol-1, respectively. During the catalytic reaction, if one of the two residues (Glu53 and His115) acts as the catalytic base, the other one forms strong hydrogen bonding interaction with the attacking hydroxide to facilitate the hydrolysis. However, mutation studies reveal that Glu53 is necessary for hydrolysis, whereas His115 is not essential but can promote the activity of PON1. Natural population analysis indicates that the catalytic Ca2+ does not act as Lewis acid but plays structural role in fixing the orientations of the substrate and related residues. In addition, Asp269 is found to coordinate with Ca2+ cation and facilitate the protonation of the alkoxide leaving group by forming hydrogen bond with lactone. These results can explain the fact that mutation of Glu53 results in the loss of activity of PON1, and the hydrolysis of dihydrocoumarin is unaffected by mutation of H115. © The Royal Society of Chemistry 2016. Source

Qian Y.,Shanghai JiaoTong University | Wei P.,Shanghai JiaoTong University | Jiang P.,Shanghai JiaoTong University | Li Z.,Shanghai JiaoTong University | And 3 more authors.
Energy Conversion and Management | Year: 2013

Shape-stabilized co-crystallized poly (ethylene glycol) (PEG) composites were prepared by sol-gel process. Tetraethoxysilane was utilized as supporting matrix precursor. The crystallization property as well as thermal energy storage properties of PEG was influenced by silica network. The combination of PEG 2k and PEG 10k with suitable ratio (3:1 by weight) led to synergistically increased fusion enthalpy attributed to cocrystallization effect. Furthermore, halogen-free flame retarded PEG composites were obtained using diammonium phosphate as flame retardant. With suitable composition, the latent heat value of flame retarded PEG composite was 96.7 kJ/kg accompanied with good thermal stability and improved flame retardancy properties. Fourier transform infrared spectrum (FT-IR), X-ray diffraction (XRD), polarized optical microscope (POM) and scanning electron microscope (SEM) were used to characterize the structure of PEG composites. Thermal stability properties of PEG composites were investigated by thermogravimetric analyzer (TGA). Char residue obtained from muffle furnace of PEG composites was analyzed by SEM and FT-IR. Flame retardancy properties of PEG composites were estimated by pyrolysis combustion flow calorimeter. Results showed that it was potential for shape-stabilized halogen-free flame retarded PEG composite to be applied in thermal energy storage field. © 2013 Published by Elsevier Ltd. Source

Liu A.,Shandong University | Han S.,Shandong University | Che H.,Shandong University | Hua L.,Shandong Non metallic Materials Institute
Langmuir | Year: 2010

A fluorescent material with methylene viologen units bonded into the pore walls of the mesoporous MCM-48 silica is synthesized using the method of periodic mesoporous organosilicas with bridging groups (PMOs), in which the methylene viologen units are located within the channel walls through the cohydrolysis and cocondensation of dichloride of N,N'-bis(trithoxysilylmethyl)- 4,4'-bipyridinium (VP) and tetraethoxysilane (TEOS). It is found, that the suspension of the hybrid emits fluorescence at ca. 380 and 420 nm, which is attributed to the Si state (π*→π) of the viologen and the charge-transfer complex between the bipyridinium units as electron acceptor and accompanying halide (Br-, Cl-) as donor components, respectively. The fluorescent emission intensity increases with increasing the amount of the VP covalently bonded to MCM-48 framework. The fluorescent intensity of VP adsorbed on the surface of the pore channel, of MCM-48 was greatly weaker than that of the hybrid MCM-48-VP at the same molar ratio of TEOS to VP. No fluorescence was observed for pure VP. The different fluorescent intensity is ascribed to the fact that restricted degree of the rotation between two pyridine rings is different. It could be prospected that this material is potentially applied in drug delivery and. fluorescence probing for medical diagnosis and synchronous therapy. © 2010 American Chemical Society. Source

Yang F.F.,Shandong University | Yang F.F.,Shandong Non metallic Materials Institute | Yan S.S.,Shandong University | Yu M.X.,Shandong Non metallic Materials Institute | And 11 more authors.
Journal of Alloys and Compounds | Year: 2013

A series of FeCoB-SiO2 granular films were deposited on Kapton flexible substrates by magnetron co-sputtering technique at room temperature. All films are amorphous with granular morphology. The coercivity in the easy axis (Hce) and the resistivity (ρ) decrease with the decrease of the Ar pressure, but they decrease with the increase of the film thickness. The granular films deposited at low Ar pressure exhibit obvious in-plane uniaxial magnetic anisotropy. Excellent soft magnetic properties with the Hce as low as 1.57 Oe was obtained in the 500 nm films deposited at 0.3 Pa. In addition, high ρ (∼3.5 mΩ cm), relatively high complex permeability (μ′ = 152.8 at low frequency and μmax″=221.2) and ferromagnetic resonance frequency (fr ∼ 3.61 GHz) were simultaneously obtained. © 2012 Elsevier B.V. All rights reserved. Source

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