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.

Fabrication, characterization of spherical CaWO4:Ln@MCM-41(Ln=Eu3+, Dy3+, Sm3+, Er3+) composites and their applications as drug release systems

Spherical MCM-41 particles with a diameter of about 150 nm have been successfully coated with CaWO4:Ln (Ln = Eu3+, Dy3+, Sm3+, Er3+) phosphor layers through a simple Pechini sol-gel process. The obtained CaWO4:Ln@MCM-41 composites, which kept the mesoporous structure of MCM-41 and the luminescent properties of phosphors, were investigated as a drug delivery system using aspirin (ASPL) as a model drug.

Solvothermal synthesis and characterization of Ln (Eu3+, Tb3+) doped hydroxyapatite

Luminescent Ln (Eu3+, Tb3+) doped hydroxyapatite (Eu:HAp, Tb:HAp) phosphors were successfully fabricated via the cetyltrimethylammonium bromide (CTAB)/n-octane/n-butanol/water microemulsion-mediated solvothermal process. The structure, morphology, and optical properties were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), Fourier transform infrared spectroscopy (FT-IR), and photoluminescence (PL) spectra as well as the kinetic decays, respectively.

Click-together azobenzene dendrons: Synthesis and characterization

We synthesized 1,2,3-triazole-linked azobenzene dendrons of four generations. No protection-deprotection approach was needed during the generation development via click reaction. The photoisomerization of azobenzene dendrons was Studied using UV-vis spectra. The cis isomers of these dendrons were more stable than trans isomers in the dark; however, the cis isomers could be quickly converted to trans forms under visible light exposure in seconds. The trans form could change to cis form reversibly by UV irradiation as well.

Preparation and characterization of Gd2O3:Eu3+ luminescence nanotubes

The size controllable Gd2O3:Eu3+ luminescence nanotubes were successfully prepared using a simple method by coating gadolinium compounds on the carbon nanotubes and then firing the carbon nanotubes. The morphology of the obtained Gd2O3:Eu3+ nanotubes was determined by transmission electron microscopy (TEM). It was found that the obtained nanotubes have the outer diameters of similar to 100 nm, the inner diameters of similar to 50 nm, and the lengths of several tens of microns. The sizes of Gd2O3:Eu3+ nanotubes can be easily controlled by changing the reaction times and the concentration of reactants.

Synthesis and characterization of (Zn,Cd)TiO3 by a modified sol-gel method

Ilmenite-type (Zn1-xCdx)TiO3 (0 <= x <= 0.15 and 0.8 <= x <= 1.0) was synthesized by a modified sol-gel route including the Pechini process via two-step heat treatments. The thermal stability of (Zn1-xCdx)TiO3 depended on the amount of cadmium content. The as-synthesized (Zn1-xCdx)TiO3 (0 <= x <= 0.15 and 0.8 <= x <= 1.0) showed higher thermal stability than that of ZnTiO3. The variation of the dielectric constant of all synthesized (Zn1-xCdx)TiO3 samples for all measurement frequencies showed a similar tendency.

Aging behavior and mechanical properties of Mg-Gd-Ho alloys

The Mg-8Gd-0.6Zr-xHo (x = 1, 3 and 5, mass%) alloys were prepared by casting technology, and structures, aging strengthening mechanism and mechanical properties of the alloys were investigated. The age behaviors and the mechanical properties are improved by adding Ho addition. The structures of the alloys are characterized by the present of rosette-shaped equiaxed grains. The peak hardness value of the Mg-8Gd-0.6Zr-3Ho alloy is 100 Hv, which is about 30% higher than that of Mg-8Gd-0.6Zr alloy.

The effect of La or Ce on ageing response and mechanical properties of cast Mg-Gd-Zr alloys

Mg-8Gd-0.6Zr-1RE (RE = La or Ce, wt.%) alloys were prepared by casting. The microstructures, age hardening behavior and mechanical properties were investigated. The results show that the addition of 1 wt.% La or Ce to a Mg-8Gd-0.6Zr alloy reduces the dendrite arm spacing and slightly improves the mechanical properties and age hardening response.

Preparation and characterization of polyimide/Al2O3 hybrid films by sol-gel process

A sol-gel process has been developed to prepare polyimide (PI)/Al2O3 hybrid films with different contents of Al2O3 based on pyromellitic dianhydride (PMDA) and 4,4'-oxydianiline (ODA) as monomers. FESEM and TEM images indicated that Al2O3 particles are relatively well dispersed in the polyimide matrix after ultrasonic treatment of the sol from aluminum isopropoxide and thermal imidization of the gel film. The dimensional stability, thermal stability, mechanical properties of hybrid PI films were improved obviously by an addition of adequate Al2O3 content, whereas, dielectric property and the elongation at break decreased with the increase of Al2O3 content. Surprisingly, the corona-resistance property of hybrid film was improved greatly with increasing Al2O3 content within certain range as compared with pure PI film.

Preparation and Characterization of Interpenetration Polymer Network Films Based on Poly(vinyl alcohol) and Poly(acrylic acid) for Drug Delivery

A series of full interpenetrating polymer network (full-IPN) films of poly(acrylic acid) (PAA)/poly (vinyl alcohol) (PVA) were prepared by radical solution polymerization and sequential IPN technology. Attenuated total reflectance-Fourier transform infrared spectroscopy, swelling properties, mechanical properties, morphology, and glass transition temperature of the films were investigated. FTIR spectra analysis showed that new interaction hydrogen bonds between PVA and PAA were formed. Swelling property of the films in distilled water and different pH buffer solution was studied. Swelling ratio increased with increasing PAA content of IPN films in all media, and swelling ratio decreased with increasing PVA crosslink degree. Tensile strength and elongation at break related not only to the constitution of IPNs but also to the swelling ratio of IPNs.

Bis(2,2 '-bipyridine)(5,6-epoxy-5,6-dihydro-[1,10] phenanthroline)ruthenium: Synthesis and electrochemical and electrochemiluminescence characterization

In this work, an electrochemiluminescence (ECL) reagent bis(2,2'-bipyridine)(5,6-epoxy-5,6-dihydro-[1,10]phenanthroline)ruthenium complex (Ru-1) was synthesized, and its electrochemical and ECL properties were characterized. The synthesis of Ru-1 was confirmed by IR spectra, element analysis, and H-1 NMR spectra. For further study, its UV-vis absorption and fluorescence emission spectra were investigated. Ru-1 also exhibited quasi-reversible Ru-II/Ru-III redox waves in acetonitrile solution. The aqueous ECL behaviors of Ru-1 were also studied in the absence and in the presence of tripropylamine.

Characterization of High Melt Strength Polypropylene Synthesized via Silane Grafting Initiated by In Situ Heat Induction Reaction

High melt strength polypropylene (HMSPP) was synthesized by in situ heat induction reaction, in which pure polypropylene (PP) powders without any additives were used as a basic resin and vinyl trimethoxysilane (VTMS) as a grafting and crosslinking agent. The grafting reaction of VTMS with PP was confirmed by FTIR. The structure and properties of HMSPP were characterized by means of various measurements. The content of grafted silane played a key role on the melt strength and melt flow rate (MFR) of HMSPP. With increasing the content of grafted silane, the melt strength of HMSPP increased, and the MFR reduced. In addition, due to the existence of cross-linking structure, the thermal stability and tensile strength of HMSPP were improved compared with PP.

Highly Uniform and Monodisperse Ba2CIF3 Microrods: Solvothermal Synthesis and Characterization

One-dimensional hexagonal Ba2CIF3 microrods with highly uniform morphology and size have been successfully synthesized via a facile solvothermal method at a low temperature (160 degrees C). X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the samples. The synthesis process, based on a phase-transfer and separation mechanism, allows the control of properties such as particle size and shape in low dispersity by bonding the surfactant oleic acid to the crystal surface.

Facile Synthesis and Characterization of Single Crystalline Bi2S3 with Various Morphologies

Single crystalline Bi2S3 With various morphologies (wires, rods, and flowers) has been successfully prepared via a simple polyol solution process and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) techniques. The morphologies of Bi2S3 crystals are highly dependent on the experimental parameters, including the reaction temperature, reactant ratio, sulfur source, and additive. The adjustment of these parameters can lead to an obvious shape evolution of products, and the growth mechanism has been proposed.

Characterization and electrocatalytic application of a fullerene/ionic-liquid composite

A fullerene/ionic-liquid composite was explored. Transmission Electron Microscopy (TEM) study showed that in the composite, C-60 mainly exists as nano-clusters, Raman spectrum proved that the composite formed only by physical Mix of C-60 and 1-Butyl-3-methyl-imidazolium hexafluorophosphate (BMIPF6), the combination did not change the chemical naturation of C-60. The electrochemical properties of the composite modified electrode, including the electrode reaction control function and the interfacial potential effect were studied.