Urvi Panchal
,
Krunal Modi
,
Manthan Panchal
,
Viren Mehta
,
Vinod K. Jain
催化学报
doi:10.1016/S1872-2067(15)61021-X
合成了新型四甲氧基间苯二酚-四酰肼(TMRTH),并作为还原剂和封端剂用于合成水分散性稳定的Pd纳米粒子(PdNPs)。采用紫外-可见光谱、透射电镜、能量散射谱和粉末X射线衍射对所得TMRTH-PdNPs样品进行了表征。结果表明,所制纳米粒子具有多分散性,粒径为5±2 nm,并在Suzuki-Miyuara交叉偶联反应中可重复使用5次,具有较高的催化效率。该纳米催化剂在反应时间、催化剂用量和可重复使用性能等方面优于常规Pd催化剂。另外, TMRTH-PdNPs样品对革兰(氏)阳性菌具有较好的抗菌活性,因而有望用于一些生物领域。
关键词:
钯纳米粒子
,
间苯二酚杯芳烃
,
Suzuki-Miyuara交叉偶联反应
,
纳米催化
,
重复使用性能
材料科学技术（英）
Electrochemical impedance spectra (EIS) technique was adopted to evaluate the water sorption behaviour of an epoxy freestanding film in a 0.5 mol/L sodium chloride solution at 20 degrees C. The methods for obtaining the capacitance data from EIS data were compared. The Brasher- Kingsbury (BK) and corresponding modified version (Modi-BK) models were used to calculate the water uptake in film and the gravimetric results were presented for comparisons. According to the discussion of the discrepancy of water content in film obtained from two models, a new method was proposed to indicate the organic film structure.
关键词:
epoxy;capacitance;water sorption;EIS;organic coatings;paint systems;part i;barrier;ideal
Applied Surface Science
For further prolonging the serve life of silicone rubber (SIR) for outdoor insulation and increasing its resistance of pollution flashover, surface modi. cations of SIR were carried out via CF(4) capacitively coupled plasma at radio frequency (RF) power of 60, 100 and 200 W for a treatment time up to 20 min under CF(4) flow rate of 20 sccm. Static contact angle measurement was employed to estimate the change of hydrophobicity of the modified SIR. The variation of the surface functional groups of the modified SIR was observed by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectrum and X-ray photoelectron spectroscopy (XPS). The surface topography was observed by atom force microscopy (AFM). The results indicate that the static contact angle of SIR surface is improved from 100.7 degrees to 150.2 degrees via the CF(4) plasma modi. cation, and the super-hydrophobic surface of modified SIR, which corresponds to a static contact angle of 150.2 degrees, appears at RF power of 200 W for a 5-min treatment time. According to the results, it is suggested that the formation of super-hydrophobic surface is ascribed to the co-action of the increase of roughness created by the ablation reaction of CF(4) plasma and the formation of [SiF(x)(CH(3))(2) (x)-O-](n) (x = 1, 2) structure produced by the direct attachment of F atoms to Si. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.
关键词:
Silicone rubber;Super-hydrophobic;CF(4) plasma;XPS;AFM;improved adhesion;rough surfaces;hydrophobicity;polyethylene;fluorination;polymers;energy;films
Bin Yu
材料科学技术（英）
Color stability of dental resin modified glass ionomer (RMGI) has been a challenge to dentistry; therefore, systematic changes in 2-hydroxyethyl methacrylate (HEMA) content were performed experimentally to find an idea to enhance the color stability. Changes in color ( ΔEab*) and color coordinates (ΔL*, Δa* and Δb*) of experimental 10-50 wt pct HEMA-added dental glass ionomers (HAGIs) and corresponding RMGIs were determined after 5000 cycles of thermocycling. Color changes of HAGIs were not influenced by the HEMA content while ΔL*, Δa* and Δb values were in°uenced by the HEMA content. Color stability of 30% or 40% HEMA-added HAGIs was not different from those of the commercial RMGIs. Since the in°uence of HEMA itself on the color stability of HAGIs was limited, compositional modi¯cation to increase the color stability of these materials should be developed.
关键词:
Glass ionomer
,
HEMA
,
color coordinate
,
thermocycling
Bin Yu
材料科学技术（英）
Color stability of dental resin modified glass ionomer (RMGI) has been a challenge to dentistry; therefore, systematic changes in 2-hydroxyethyl methacrylate (HEMA) content were performed experimentally to find an idea to enhance the color stability. Changes in color ( ΔEab*) and color coordinates (ΔL*, Δa* and Δb*) of experimental 10-50 wt pct HEMA-added dental glass ionomers (HAGIs) and corresponding RMGIs were determined after 5000 cycles of thermocycling. Color changes of HAGIs were not influenced by the HEMA content while ΔL*, Δa* and Δb values were in°uenced by the HEMA content. Color stability of 30% or 40% HEMA-added HAGIs was not different from those of the commercial RMGIs. Since the in°uence of HEMA itself on the color stability of HAGIs was limited, compositional modi¯cation to increase the color stability of these materials should be developed.
关键词:
Glass ionomer
,
HEMA
,
color coordinate
,
thermocycling
Electrochimica Acta
Mesoporous silica SBA-15 was surface-modi fled by gamma-glycidoxypropyltrimethoxy silane (GPTMS), and novel poly(ethylene oxide) (PEO)-based composite polymer electrolytes (CPE) using the silane-modified SBA-15 (SBA-15-GPTMS) as filler were prepared and characterized. The results of the low-angle X-ray diffraction (XRD) patterns and Fourier-transform infrared (FT-IR) spectroscopy indicated that GPTMS has been successfully attached to the surface of SBA-15 with a high degree of mesoscopic hexagonal pore structure. The incorporation of SBA-15-GPTMS in the PEO-LiClO(4) matrix effectively reduced the PEO crystallinity and obviously improved the conductivity and electrochemical stability of the CPEs. The CPE with 10 wt.% SBA-15-GPTMS provided the highest conductivity among all the tested CPEs, about 2-3 orders of magnitude higher than that of the PEO-LiClO(4) matrix below the melting temperature of PEO. The reasons that the CPEs using SBA-15-GPTMS as filler showed higher conductivity than that with SBA-15 were discussed. (c) 2009 Elsevier Ltd. All rights reserved.
关键词:
Composite polymer electrolyte;PEO;Silane-modified SBA-15;Ionic;conductivity;ionic-conductivity;triblock copolymer;batteries;sio2
Chengwei Liao
,
Jianchun Chen
,
Yang Li
,
Rui Tu
,
Chunxu Pan
材料科学技术（英）
In general, the modification performance of Al−Sr master alloys is primarily dependent upon the morphologies and sizes of the Al4Sr intermetallic phase. In this paper, the crystal structure, morphologies, sizes, hardness and elastic modulus of Al4Sr in Al{Sr master alloys prepared from variant processes were studied by means of optical metallurgical microscope, X-ray diffraction (XRD), scanning electron microscopy (SEM), and nanoindentation system. The results revealed that the microstructures and modi¯cation performance of the Al4Sr phase were related to the preparation processes. That is to say, when a "direct reaction-hot extrusion" process was used, the Al4Sr phase exhibited a homogeneous distribution in the Al matrix with small size and roundish shapes, which ensured the Al−Sr master alloy wire advantages involving high recovery, good reproducibility, no delitescence of modification, no corrosion on equipments, and good workability. However, in the case of the traditional "direct reaction" process, the Al4Sr phase was in large size with shapes of rectangular stripe and plates, which limited the Sr content increasing due to the brittleness of the Al−Sr alloy. It was also found that the morphology and size of the Al4Sr phases changed during heat treatment at high temperature up to 600 °C.
关键词:
Intermetallics
,
null
,
null
,
null
,
null
