Preparation of monolithic column and its application in p-CEC

A novel monolithic stationary phase having long alkyl chain ligands was introduced and evaluated in pressurized-capillary electrochromatography of small neutral and charged compounds. The monolithic column was prepared by the in situ copolymerization of ethylene dimethacrylate, 1-hexadecene, allyl alcohol and 2-acrylamido-2-methyl-1-propanesulfonic acid in a quaternary porogenic solvent mixture consisting of 1,4-butanediol, cyclohexanol, dodecanol and water.

Preparation and characterization of microencapsulated hexadecane used for thermal energy storage

Polyurea microcapsules about 2.5 mum in diameter containing phase change material for thermal energy storage application were synthesized and characterized by interfacial polycondensation method with toluene-2,4-diisocyanate and ethylenediamine as monomers in an emulsion system. Hexadecane was used as a phase change material and OP, which is nonionic surfactant, and used as an emulsifier. The chemical structure and thermal behavior of the microcapsules were investigated by FTIR and thermal analysis respectively. The results show encapsulated hexadecane has a good potential as a solar energy storage material.

Preparation of highly active Pt/C cathode electrocatalysts for DMFCs by an improved aqueous impregnation method

An improved aqueous impregnation method was used to prepare 40 wt% Pt/C electrocatalysts. TEM analysis of the samples showed that the Pt particles impregnated for a short time have a very narrow size distribution in the range of 1-4 nm with an average size of 2.6 nm. UV-vis spectroscopy measurements verified that the redox reaction between PtCl62- and formaldehyde took place with a slow rate at ambient temperature via a two-step reaction path, where PtCl42- serves as an intermediate. The use of the short-time-impregnated 40 wt% Pt/C as cathode electrocatalysts in direct methanol fuel cells yields better performance than that of commercial 40 wt% Pt/C electrocatalyst. Experimental evidence provides clues for the fundamental understanding of elementary steps of the redox reactions, which helps in guiding the design and preparation of highly dispersed Pt catalyst for fuel cells.

Preparation and characterization of multiwalled carbon nanotube-supported platinum for cathode catalysts of direct methanol fuel cells

Multiwalled carbon nanotube-supported Pt (Pt/MWNT) nanocomposites were prepared by both the aqueous solution reduction of a Pt salt (HCHO reduction) and the reduction of a Pt ion salt in ethylene glycol solution. For comparison, a Pt/XC-72 nanocomposite was also prepared by the EG method. The Pt/MWNT catalyst prepared by the EG method has a high and homogeneous dispersion of spherical Pt metal particles with a narrow particle-size distribution. TEM images show that the Pt particle size is in the range of 2-5 nm with a peak at 2.6 nm, which is consistent with 2.5 nm obtained from the XRD broadening calculation. Surface chemical modifications of MWNTs and water content in EG solvent are found to be the key factors in depositing Pt particles on MWNTs. In the case of the direct methanol fuel cell (DMFC) test, the Pt/MWNT catalyst prepared by EG reduction is slightly superior to the catalyst prepared by aqueous reduction and displays significantly higher performance than the Pt/XC-72 catalyst. These differences in catalytic performance between the MWNT-supported or the carbon black XC-72-supported catalysts are attributed to a greater dispersion of the supported Pt particles when the EG method is used, in contrast to aqueous HCHO reduction and to possible unique structural and higher electrical properties when contrasting MWNTs to carbon black XC-72 as a support.

Facile preparation of water-soluble fluorescent silver nanoclusters using a polyelectrolyte template

We report a new approach for the synthesis of fluorescent and water-soluble Ag nanoclusters, using the common polyelectrolyte poly(methacrylic acid) as the template.

Preparation of Prussian blue@Pt nanoparticles/carbon nanotubes composite material for efficient determination of H2O2

In this study, the fabrication of an efficient amperometric hydrogen peroxide sensor with favorable properties is presented. Prussian blue (PB) was catalytically synthesized by Pt nanoparticles (Pt-nano) from ferric ferricyanide aqueous solution to form PB@Pt-nano hybrid, and it was confirmed by transmission electron microscope (TEM) and optical spectra. The electrochemical behavior of PB@Pt-nano was highly improved through its integration with poly(diallyldimethylammonium chloride) modified carbon nanotubes (PCNTs).

Novel Method for Preparation of Polypropylene Blends with High Melt Strength by Reactive Compounding

Ultrafine full-vulcanized polybutadiene rubber(UFBR) with particle sizes of ca. 50-100 nm were used for modifying mechanical and processing performances of polypropylene(PP) with PP-g-maleic anhydride(PP-g-MA) as a compatibilizer for enhancing the interfacial adhesion between the two components. The morphology, dynamical rheology response and mechanical properties of the blends were characterized by means of SEM, rheometer and tensile test, respectively.

Preparation of Hollow Carbon and Silicon Carbide Fibers with Different Cross-Sections by using Electrospun Fibers as Templates

Hollow carbon nanofibers with circular and rectangular opening were prepared by using electrospun silica fibers as templates. Silica fibers were synthesized by electrospinning, and they were coated with a carbon layer formed by thermal decomposition and carbonization of polystyrene under a nitrogen atmosphere. Hollow carbon nanofibers with circular and rectangular openings were then obtained after the silica core was etched by hydrofluoric acid. The carbon nanofibers with different morphologies also could be used as templates to fabricate silicon carbide fibers. The silicon carbide fibers with circular and rectangular openings could be obtained by using hollow carbon nanofibers and carbon belts as templates, respectively.

Preparation and characterization of poly(piperazineamide) composite nanofiltration membrane by interfacial polymerization of 3,3 ',5,5 '-biphenyl tetraacyl chloride and piperazine

Most nanofiltration (NF) membranes are composite and have a polyamide thin film prepared by interfacial polymerization. Their performances mainly correlate the structure of the thin film and monomers used for its preparation. In this work, a novel thin-film composite (TFC) nanofiltration membrane was successfully prepared from 3,3',5,5'-biphenyl tetraacyl chloride (mm-BTEC) and piperazine (PIP) through interfacial polymerization. Attenuated reflectance infrared (ATR-IR) and X-ray photoelectronic spectroscopy (XPS) were used to characterize the chemical composition of the membrane surface. The membrane performance was optimized by studying preparation parameters including monomer concentration, reaction time, and pH of aqueous phase.

Preparation and characterization of La2Zr2O7 coating with the addition of Y2O3 by EB-PVD

Thermal barrier coatings (TBCs) of La2Zr2O7 (LZ) with the addition of 3 wt.% Y2O3 (LZ3Y) were deposited by electron beam-physical vapor deposition (EB-PVD). The phase stabilities, thermophysical and mechanical properties, and chemical compositions of these ceramics and coatings were studied in detail. The phase stability and thermal expansion behavior of LZ3Y bulk material are identical to those of LZ bulk material, but the mechanical properties of the former are superior to those of the latter. Elemental analysis and X-ray diffraction indicate that compositional deviation of LZ coating can be optimized after doping by 3 wt.% Y2O3, Y2O3 acts as a dopant as well as a process regulator. The optimal composition of LZ3Y coating could be effectively achieved by the addition of excess Y2O3 into the ingot and by properly controlling the current of electron beam (i.e. similar to 650 mA).

Preparation of bioactive glass ceramic nanoparticles by combination of sol-gel and coprecipitation method

SiO2-CaO-P2O5 ternary bioactive glass ceramic nanoparticles were prepared via the combination of sol-gel and coprecipitation processes. Precursors of silicon and calcium were hydrolyzed in acidic solution and gelated in alkaline condition together with ammonium dibasic phosphate. Gel particles were separated by centrifugation, followed by freeze drying, and calcination procedure to obtain the bioactive glass ceramic nanoparticles. The investigation of the influence of synthesis temperature on the nanopartilce's properties showed that the reaction temperature played an important role in the crystallinity of nanoparticle. The glass ceramic particles synthesized at 55 degrees C included about 15% crystalline phase, while at 25 degrees C and 40 degrees C the entire amorphous nanopowder could be obtained.

Preparation of a blocked isocyanate compound and its grafting onto styrene-b-(ethylene-co-1-butene)-b-styrene triblock copolymer

The epsilon-caprolactam was used to block the isocyanate group to enhance the storage stability of allyl (3-isocyanate-4-tolyl) carbamate. The spectra of FTIR and NMR showed that blocked allyl (3-isocyanate-4-tolyl) carbamate (BTAI) possesses two chemical functions, an 1-olefin double bond and a blocked isocyanate group. The FTIR spectrum showed BTAI could regenerate isocyanate group at elevated temperature. DSC and TG/DTA indicated the minimal dissociation temperature was about 135 degrees C and the maximal dissociation rate appeared at 226 degrees C. Then the styrene-b-(ethylene-co-1-butene)-b-styrene triblock copolymer (SEBS) was functionalized by BTAI via melt free radical grafting. The effect of temperature, monomer and initiator concentrations on the grafting degree and grafting efficiency was evaluated. The highest grafting degree was obtained at 200 degrees C. The grafting degree and grafting efficiency increased with the enhanced concentration of BTAI or initiator.

Preparation and Characterization of Melt Grafting 2-acrylamido-2-methyl-1-propanesulfonic Acid onto Pre-Irradiated Linear Low Density Polyethylene

Linear low density polyethylene (LLDPE) was functionalized with 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) by using -ray pre-irradiation in air in a twin-screw extruder. Fourier-transformed infrared spectroscopy (FT-IR) and electron spectroscopy for chemical analysis (ESCA) were used to characterize the formation of LLDPE-g-AMPS copolymers. The content of AMPS in LLDPE-g-AMPS was determined by using element analysis instrument. The effects of concentrations of monomer, reaction temperature and pre-irradiation dose on degree of grafting were investigated. The critical surface tension of LLDPE-g-AMPS was measured by using contact angle method. The influences of the degree of grafting on crystallization properties were studied by using DSC. Compared with neat LLDPE, the crystallization temperature increased about 4C, and crystallinity decreased with increasing degree of grafting. Crystallization rates of grafted LLDPE were faster than that of plain LLDPE at the same crystallization temperature.

Rectangular Silver Nanorods: Controlled Preparation, Liquid-Liquid Interface Assembly, and Application in Surface-Enhanced Raman Scattering

In this paper, we for the first time report a polyol method for large-scale synthesis of rectangular silver nanorods in the presence of directing agent and seeds. This method has some clear advantages including simplicity, high quality, and ease of scaleup. Silver nanowires or silver nanorods with a submicrometer diameter could also be facilely prepared when the reaction parameters are slightly changed. Furthermore, a liquid-liquid assembly strategy has been employed to construct uniform rectangular silver nanorod arrays on a solid substrate which could be used as surface-enhanced Raman scattering (SERS) substrates with high SERS activity, stability, and reproducibility. It is found that the SERS spectra obtained from the probe molecules with the different concentrations show different SERS intensifies. As the concentration of 4-aminothiophenol (4-ATP) or rhodamine 6G (R6G) increases, the SERS intensities progressively increase. The enhancement factor for 4-ATP and R6G should be as large as 5.06 x 10(4) or much larger than the value of 5.06 x 10(8), respectively.

Preparation and Bioactivity of the Composite of PLGA and Hydroxyapatite Nanocrystals Surface-grafted with L-lactic Acid Oligomer

The hydroxyapatite (HA) nanocrystals of 100-200 nm in length and 20-30 nm in width were hydrothermally synthesized by the reaction of phosphoric acid and calcium hydroxide. Lactic acid oligomer surface grafted HA(op-HA) nanoparticles were obtained by oligomeric lactic acid with a certain molecular weight grafting onto the HA surface to form a Ca carboxylate bond in the absence of any catalyst. The op-HA was further blended with poly(lactide-co-glycolide) (PLGA) to prepare the nanocomposite of op-HA/PLGA. FTIR, TGA, ESEM and EDX were used to analyze grafting reaction, the graft ratio of op-HA, surface topography and calcium deposition of the composites, respectively. The rabbit osteoblasts were seeded and cultured on the surface of composites in vitro. The cell morphology, adhesion, proliferation and gene expression were evaluated with FITC staining, NIH image J software and the analysis of real-time PCR, respectively. The results show that the graft ratio of op-HA is 8.3% (mass fraction). The op-HA/PLGA nanocomposite possessed more suitable surface properties, including roughness and plenty of calcium and phosphor. It exhibited better cell adhesion, spreading and proliferation of rabbit osteoblasts, compared to pure PLGA.