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991.
Microcapsules containing phase change materials (microPCMs) with melamine-formaldehyde (MF) shells have been applied in many
thermo-regulation or thermo-saving fields. However, it is still essential to decrease the residual formaldehyde and enhance
the mechanical properties of MF shells. The objective of this work was to fabricate a series of microPCMs containing paraffin
by an in situ polymerization method using methanol-modified melamine-formaldehyde (MMF) prepolymer as shell material and investigate
the physicochemical properties and mechanical characters of these microPCMs. FT-IR analysis indicates that the methanol-modified
method can reduce the free formaldehyde in shell material through increasing the cross-linking structure. Optical microphotographs
and SEM morphologies show that the microPCMs have regular globe shape with smooth surface. With the increasing of emulsion
stirring rates from 1,000 to 5,000 rpm, the average diameters decreased sharply from 27 to 2.5 μm. The phase change temperature
(T
m) of microPCMs samples with the core/shell ratios of 3/1, 2/1, 1/1, and 2/1 are 22.6, 23.0, 23.4, and 23.9 °C, which are nearly
equaled to the T
m of pure paraffin (22.5 °C). Mechanical properties test data show that the MMF shells have larger yield point value than that
of MF shell for microPCMs with the same core/shell ratio, which means that the methanol-modified method shell can greatly
enhanced the resistance of deformation for MF shells. Moreover, MMF shells can resist the interface extrusion force in epoxy
resin owing to their higher yield point of enhanced MMF shell. 相似文献
992.
Cai-Feng Wang He-Yi Xie Yu-Peng Cheng Li Chen Michael Z. Hu Su Chen 《Colloid and polymer science》2011,289(4):395-400
This paper describes the first synthesis of cadmium sulfide (CdS)-poly(lactic acid) (PLA) nanocomposites and their transparent
fluorescent films by covalently grafting PLA onto the surfaces of CdS nanocrystals (NCs). Synthesis of the nanocomposites
involved two steps. Lactic acid (LA)-capped CdS NCs were first prepared by reacting cadmium chloride (CdCl2) with sodium sulfide (Na2S) using LA as the organic ligand in H2O/N,N-dimethylformamide (DMF) solution. CdS–PLA nanocomposites were then formed by in situ ring-opening polymerization of lactide
on the surface of modified CdS NCs. We also demonstrated herein the fabrication of the transparent fluorescent films of CdS–PLA
nanocomposites by blending as-prepared nanocomposites with high-molecular-weight PLA. The as-prepared CdS NCs and their nanocomposites
were studied by transmission electron microscopic imaging, thermogravimetric analyses, and spectroscopic measurements (ultraviolet–visible
absorption and photoluminescence). The results revealed that the CdS–polymer nanocomposites exhibited good optical properties
in terms of their photoluminescence and transparency. 相似文献
993.
Jun-Feng Su Xin-Yu Wang Zhen Huang Yun-Hui Zhao Xiao-Yan Yuan 《Colloid and polymer science》2011,289(14):1535-1542
Microencapsulated phase change materials (microPCMs) have been widely applied in solid matrix as thermal-storage or temperature-controlling
functional composites. The thermal conductivity of these microPCMs/matrix composites is an important property need to be considered.
In this study, a series of microPCMs have been fabricated using the in situ polymerization with various core/shell ratio and
average diameter; the thermal conductivity of microPCMs/epoxy composites were investigated in details. The results show that
the microPCMs have smooth surface and regular global shape with compact methanol–melamine–formaldehyde shell. The shell thickness
does not greatly influence the phase change behaviors of PCM. Moreover, smaller microPCMs embedded in epoxy can improve the
thermal transmission ability of composites. The effect of thermal conductivity of composites can be improved with higher volume
fraction (10–30%) of microPCMs; and smaller size microPCMs with the same content of PCM may also enhance the thermal transmission
area in matrix. Modeling analysis of relative thermal conductivity indicates that mixing higher thermal conductivity additive
in PCM or matrix is an appropriate method to improve the thermal conductivity of microPCMs/matrix composites. 相似文献
994.
硫脲修饰Cd掺杂ZnO水溶性量子点的制备及表征 总被引:1,自引:0,他引:1
在非水稀溶液中以聚乙烯吡咯烷酮K-30为稳定剂,硫脲为表面修饰剂,制备Cd掺杂ZnO水溶性量子点荧光体;同时研究了基质的优化及硫脲含量对ZnO量子点发光性能的影响,Eu和Li的共掺杂对ZnO:Cd量子点发光性能的影响.采用紫外光谱、荧光发射光谱、红外光谱和透射电镜、XRD对样品进行表征.结果表明:经Cd优化基质后、Eu和Li的共掺杂使量子点荧光强度明显增强;硫脲修饰后纳米颗粒分布更加均匀、晶粒更小、荧光光谱蓝移、量子点产率增加;该样品XRD衍射峰是馒头峰.属于无定形态;红外光谱图中因硫脲引起的NH2和C-NH2伸缩振动吸收峰分别为3189.0,1088.2 cm-1,硫脲修饰的最佳浓度大约为32 mg/mL.该量子点制备方法简单易行,具有较好的稳定性及高荧光量子效率,为进一步应用于生物标记奠定基础. 相似文献
995.
Chou HL Lai FJ Su WN Pillai KC Sarma LS Hwang BJ 《Langmuir : the ACS journal of surfaces and colloids》2011,27(3):1131-1135
A layer growth mechanism of Pt-Ru bimetallic nanoparticles has been proposed with supporting experiments and calculations by density functional theory (DFT). Elongated Pt atoms on Ru nanoparticles were synthesized via a two-step route, and their structural details were obtained by high-resolution transmission electron microscopy. Because of the intrinsic mismatch of lattice spacing between the two elements, such an unusual growth was analyzed with the DFT simulations to explore the mystery of the growth mechanism. Pt atoms would rearrange the packing order and adjust the Pt-Pt atomic distance, and so do the Ru nanoparticles in order to achieve the optimal energy status of the bimetallic system. The resultant Pt(111) layers could stack on top of the Ru(0001) core more tightly by fitting the pockets left between the Ru atoms. The findings give insight into the formation mechanism of the nanosized Pt-Ru bimetallic catalyst and pave the way for designing bimetallic catalysts with tailored properties at the atomic level. 相似文献
996.
Yu ZhaoHong-Bin Zhang Ji-Kai LiuJia Su Yan LiZhu-Jun Yao Qin-Shi Zhao 《Tetrahedron letters》2011,52(1):139-142
Two interesting unprecedented fragmentations of 13-oxo-taxyunnansin A (3), initiated by treatment with tBuOK and Red-Al, respectively, have been discovered, optimized and successfully applied to the synthesis of novel abeo-paclitaxel and abeo-docetaxel derivatives. Eight new derivatives of abeo-paclitaxel and abeo-docetaxel possessing the structurally simplified 11 (15→1)-abeo-taxane skeleton with an oxetane ring and π bond conjugate system were accordingly prepared for the further evaluation of anticancer activities. 相似文献
997.
998.
Xiuhui He Zhaohong Su Qingji Xie Chao Chen Yingchun Fu Li Chen Ying Liu Ming Ma Le Deng Dilan Qin Yueping Luo Shouzhuo Yao 《Mikrochimica acta》2011,172(1-2):95-102
A simple, cheap, and nonpolluting method was developed for the cloud point extraction of gold (Au) and palladium (Pd). It is based on the complexation reaction of Au and Pd with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) and micelle mediated extraction of the complex using the non-ionic surfactant poly(ethylene glycol) mono-p-nonylphenyl ether (PONPE 7.5). Under the optimized experimental conditions, the enrichment factors are 16 and 17 for Au and Pd, respectively, for 15?mL of preconcentrated solution. The limits of detection are 3.8???g?L?1 and 1.8???g?L?1 for Au and Pd, respectively. The relative standard deviations are 1.4% for Au and 0.6% for Pd (n?=?11). The method was successfully applied to the determination of Au and Pd in certified reference materials and mine samples. Figure
CPE of gold(III) and palladium(II) 相似文献
999.
We report on a novel anti-interference and pH-modulation device (herein after referred to as ??device??). It is based on electrodialysis and can continuously increase the pH value of the carrier solution and - at the same time - remove interfering analytical signals obtained for ascorbic acid (AA) and uric acid (UA). The ??device?? was coupled to the FIA-amperometric detection of glucose. The linear range is from 1???mol?L?1 to 0.4?mmol?L?1, with a sensitivity of 213???A?cm?2?mM?1 and a detection limit of 1???mol?L?1 at a signal-to-noise ratio of 3. The method was used to sucessfully determine glucose in serum. This study represents a novel technique for overcoming analytical interference and is expected to find applications in liquid chromatography, for example in on-line pH-modulation if different pH values are needed for separation and detection. Figure
As shown in the figure, a specific electrolytic current was applied between the two electrodes. Thus H2O in the cathode chamber was electrolyzed to produce H2 and OH-. Then the OH- moved through the anion exchange membrane and got into the packed column by electromigration, where it mixed with the carrier solution of Na2SO4. Meanwhile, the SO 4 2- of the carrier solution moved through the other anion exchange membrane and entered the anode chamber. Therefore, the carrier solution of Na2SO4 was partly converted into NaOH after passing through the ??device??. 相似文献
1000.
Automated flow-based anion-exchange method for high-throughput isolation and real-time monitoring of RuBisCO in plant extracts 总被引:1,自引:0,他引:1
In this work, a miniaturized, completely enclosed multisyringe-flow system is proposed for high-throughput purification of RuBisCO from Triticum aestivum extracts. The automated method capitalizes on the uptake of the target protein at 4 °C onto Q-Sepharose Fast Flow strong anion-exchanger packed in a cylindrical microcolumn (105 × 4 mm) followed by a stepwise ionic-strength gradient elution (0-0.8 mol/L NaCl) to eliminate concomitant extract components and retrieve highly purified RuBisCO. The manifold is furnished downstream with a flow-through diode-array UV/vis spectrophotometer for real-time monitoring of the column effluent at the protein-specific wavelength of 280 nm to detect the elution of RuBisCO. Quantitation of RuBisCO and total soluble proteins in the eluate fractions were undertaken using polyacrylamide gel electrophoresis (PAGE) and the spectrophotometric Bradford assay, respectively. A comprehensive investigation of the effect of distinct concentration gradients on the isolation of RuBisCO and experimental conditions (namely, type of resin, column dimensions and mobile-phase flow rate) upon column capacity and analyte breakthrough was effected. The assembled set-up was aimed to critically ascertain the efficiency of preliminary batchwise pre-treatments of crude plant extracts (viz., polyethylenglycol (PEG) precipitation, ammonium sulphate precipitation and sucrose gradient centrifugation) in terms of RuBisCO purification and absolute recovery prior to automated anion-exchange column separation. Under the optimum physical and chemical conditions, the flow-through column system is able to admit crude plant extracts and gives rise to RuBisCO purification yields better than 75%, which might be increased up to 96 ± 9% with a prior PEG fractionation followed by sucrose gradient step. 相似文献