The mechanical properties of magnesium matrix composites reinforced with 10 wt.% W14Al86 alloy particles

The Mg-based metal matrix composite reinforced by 10 wt.% W14Al86 alloy particles has been prepared by mechanical alloying and press-forming process. X-ray diffraction studies confirm the formation of the composite. Microstructure characterization of the samples reveals the uniform distribution of fine W14Al86 alloy. Mechanical properties characterization revealed that the reinforcement of W14Al86 alloy lead to a significant increase in hardness and tensile strength of Mg and AZ91.

Chemical effects of cationic surfactant and anionic surfactant used in organically modified montmorillonites on degradation and fire retardancy of polyamide 12 nanocomposites

Three kinds of organically modified Na+-montmorillonites (OMMTs), including two kinds of octadecylammonium modified montmorillonite with different contents of octadecylammonium and a kind of sodium dodecylsulfonate (SDSo) modified montmorillonite, were used to prepare polyamide 12 (PA12)/OMMT nanocomposites. Effects of the modifiers on degradation and fire retardancy of PA12/OMMT nanocomposites were investigated. Acid sites formed in cationic surfactant modified MMT via Hoffman decomposition could accelerate degradation of PA12 at high temperature. However, catalytic effect of the acid sites on carbonization of the degradation products promoted char barrier formation, which reduced heat release rate (HRR). Higher content of cationic surfactant in OMMT is beneficial to fire retardancy of PA12 nanocomposites and the dispersion states of OMMT have assistant effects. In contrast, Na+-montmorillonite (Na-MMT) and anionic surfactant modified MMT (a-MMT) could not form acid sites on the MMT layers; in this case, fire retardancy of PA12/Na-MMT appears to have no improvement and PA12/a-MMT appears to have limited improvement.

Brittle-ductile transition of particle toughened polymers: influence of the matrix properties

It was theoretically pointed out that the product of the yield stress and yield strain of matrix polymer that determined the brittle-ductile transition (BDT) of particle toughened polymers. For given particle and test condition, the higher the product of the yield stress and the yield strain of the matrix polymer, the smaller the critical interparticle distance (IDc) of the blends was. This was why the IDc (0.15 mum) of the polypropylene (PP)/rubber blends was smaller than that (0.30 mum) of the nylon 66/rubber blends, and the IDc of the nylon 66/rubber blends was smaller than that (0.60 mum) of the high density polyethylene (HDPE)/rubber blends.

Facile preparation of amperometric laccase biosensor with multifunction based on the matrix of carbon nanotubes-chitosan composite

The carbon nanotubes-chitosan (CNTs-CS) composite provides a suitable biosensing matrix due to its good conductivity, high stability, and good biocompatibility. Enzymes can be firmly incorporated into the matrix without the aid of other cross-linking reagents. The composite is easy to form insoluble film in solution above pH 6.3. Based on this, a facilely fabricated amperometric biosensor by entrapping laccase into the CNTs-CS composite film has been developed. At pH 6.0, the fungi laccase incorporated into the composite film remains better catalytic activity than that dissolved in solution. The system is in favor of the accessibility of substrate to the active site of laccase, thus the affinity to substrates is improved greatly, such as 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt (ABTS), catechol, and 0, with K. values of 19.86 mu M, 9.43 mu M, and 3.22 mM, respectively. The major advantages of the as-prepared biosensor are: detecting different substrates (ABTS, catechol, and 02), possessing high affinity and sensitivity, durable long-term stability, and facile preparation procedure. On the other hand, the system can be applied in fabrication of biofuel cells as the cathodic catalysts based on its good electrocatalysis for oxygen reduction.

Synthesis of asymmetric H-shaped block copolymer by the combination of atom transfer radical polymerization and living anionic polymerization

A new asymmetric H-shaped block copolymer (PS)(2)-PEO-(PMMA)(2) has been designed and successfully synthesized by the combination of atom transfer radical polymerization and living anionic polymerization. The synthesized 2,2-dichloro acetate-ethylene glycol (DCAG) was used to initiate the polymerization of styrene by ATRP to yield a symmetric homopolymer (Cl-PS)(2)-CHCCCCH2CH2OH with an active hydroxyl group. The chlorine was removed to yield the (PS)(2)-CHCOOCH2CH2OH ((PS)(2)-OH). The hydroxyl group of the (PS)(2)-OH, which is an active species of the living anionic polymerization, was used to initiate ethylene oxide by living anionic polymerization via DPMK to yield (PS)(2)-PEO-OH. The (PS)(2)-PEO-OH was reacted with the 2,2-dichloro acetyl chloride to yield (PS)(2)-PEO-OCCHCl2 ((PS)(2)-PEO-DCA). The asymmetric H-shaped block polymer (PS)(2)-PEO-(PMMA)(2) was prepared via ATRP of MMA at 130 degrees C using (PS)(2)-PEO-DCA as initiator and CuCl/bPy as the catalyst system. The architectures of the asymmetric H-shaped block copolymers, (PS)(2)-PEO-(PMMA)(2), were confirmed by H-1 NMR, GPC and Fr-IR.

The first synthesis of a water-soluble alpha-cyclodextrin/C-60 supramolecular complex using anionic C-60 as a building block

A novel supramolecular inclusion complex of alpha-CD/C-60 was synthesized using anionic C-60. The reaction progress was monitored in situ by visible and near-IR spectroscopy. The obtained complex was characterized by UV-vis, C-13 NMR, MALDI-TOF, and cyclic voltammetry. The induction and dispersion forces are considered to be the major driving forces for the formation of a resulting alpha-CD/C-60(.-) inclusion complex.

Conformational changes of beta-lactoglobulin induced by anionic phospholipid

Conformational changes of beta-lactoglobulin (beta-LG) induced by anionic phospholipid (dimyristoylphosphatidylglycerol, DMPG) at physiological conditions (pH 7.0) have been investigated by UV-VIS, circular dichroism (CD) and fluorescence spectra. The experimental results suggest that beta-LG-DMPG interactions cause beta-LG a structural reorganization of the secondary structure elements accompanied by an increase in alpha-helical content, and a loosening of the protein tertiary structure. The interaction forces between beta-LG and DMPG are further evaluated by fluorescence spectra. The fluorescence spectral data show that conformational changes in the protein are driven by electrostatic interaction at first, then by hydrophobic interaction between a protein with a negative net charge and a negatively charged phospholipid.

Numerical simulation of mesoscopic mechanical behaviors of gradual multi-fiber-reinforced polymer matrix composites

To simulate the deformation and the fracture of gradual multi-fiber-reinforced matrix composites, a numerical simulation method for the mesoscopic mechanical behaviors was developed on the basis of the finite element and the Monte Carlo methods. The results indicate that the strength of a composite increases if the variability of statistical fiber strengths is decreased.

Stress transfer and damage evolution simulations of fiber-reinforced polymer-matrix composites

The stress transfer from broken fibers to unbroken fibers in fiber-reinforced thermosetting polymer-matrix composites and thermoplastic polymer-matrix composites was studied using a detailed finite element model. In order to check the validity of this approach, an epoxy-matrix monolayer composite was used as thermosetting polymer-matrix composite and a polypropylene (PP)-matrix monolayer composite was used as thermoplastic polymer-matrix composite, respectively. It is found that the stress concentrations near the broken fiber element cause damage to the neighboring epoxy matrix prior to the breakage of other fibers, whereas in the case of PP-matrix composites the fibers nearest to the broken fiber break prior to the PP matrix damage, because the PP matrix around the broken fiber element yields. In order to simulate composite damage evolution, a Monte Carlo technique based on a finite element method has been developed in the paper. The finite element code coupled with statistical model of fiber strength specifically written for this problem was used to determine the stress redistribution. Five hundred samples of numerical simulation were carried out to obtain statistical deformation and failure process of composites with fixed fiber volume fraction.

Controlling dispersed state and exfoliation process of clay in polymer matrix

In the present review, the authors do not try to provide a comprehensive review of researches on polymer/clay nanocomposites (PCNs), but some examples to demonstrate different exfoliation processes of the clay in various polymer matrixes and the dispersed state of clay. Interaction between polymers and layered silicates plays an important role in adjusting the exfoliation process of layered silicates and the microstructure of polymer nanocomposites. Properties of polymer/layered silicate nanocomposites mainly depend on the dispersed state of layered silicates. The authors will also address the outline of the present research in the direction of PCNs including the discussion of technical problems and their possible solutions.

Electrochemical and spectroscopic study on the interaction of cytochrome c with anionic lipid vesicles

The structure and the electron-transfer of cytochrome c binding on the anionic lipid vesicles were analyzed by electrochemical and various spectroscopic methods. It was found that upon binding to anionic lipid membrane, the formal potential of. cytochrome c shifted 30 mV negatively indicating an eager redox interaction than that in its native state. This is due to the local alteration of the coordination and the heme crevice. The structural Perturbation in which a molten globule-like state is formed during binding to anionic lipid vesicles is more important. This study may help to understand the mechanism of the electron-transfer reactions of cytochrome c at the mitochondrial membrane.

Multi-color long-lasting phosphorescence of rare earth ions in CdSiO3 matrix

A series of rare earth ions doped CdSiO3:RE3+(RE=Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) multi-color long-lasting phosphorescence phosphors are prepared by the conventional high-temperature solid-state method. The results of XRD measurement indicate that the products fired under 1050degreesC for 3 h have a good crystallization without any detectable amount of impurity phase. Rare earth ions doped CdSiO3 phosphors possess excellent luminescence properties. When rare earth ions such as Y3+, La3+, Gd3+, Lu3+, Ce3+, Nd3+, Ho3+, Er3+, Tm3+ and Yb3+ are introduced into the CdSiO3 host, one broadband centered at about 420 nm resulting from traps can be observed. In the case of other earth ions such as Pr3+, Sm3+, Eu3+, Tb3+ and Dy3+, their characteristic line emitting as well as the similar to420 nm broadband luminescence can be obtained. The mixture of their characteristic line emitting with the similar to420 nm broadband luminescence results in various afterglow color.

Preparation and luminescence properties of hybrid materials containing europium(III) complexes covalently bonded to a silica matrix

A new kind of luminescent organic-inorganic hybrid material (denoted Hybrid I) consisting of europium 1,10-phenanthroline complexes covalently attached to a silica-based network was prepared by a sol-gel process. 1,10-Phenanthroline grafted to 3-(triethoxysilyl)propyl isocyanate was used as one of the precursors for the preparation of an organic-inorganic hybrid materials. For comparison purposes, the hybrid material (denoted Hybrid II) in which phenanthroline was not grafted onto the silica backbone of the frameworks was also prepared. Elemental analysis; NMR, FT-IR, UV/vis absorption, and luminescence spectroscopies, and luminescence decay analysis were used to characterize the obtained hybrid materials. It is shown that the homogeneity of Hybrid I is superior to that of Hybrid II, and a higher concentration europium can be incorporated into Hybrid I than Hybrid II. Excitation at the ligand absorption wavelength (283 nm) resulted in the strong emission of the Eu3+ D-5(0)-F-7(J) (J = 0-4) transition lines as a result of the efficient energy transfer from the ligands to the EU3+ in Hybrid I. The number of water molecules coordinated to the europium ion was estimated, and the structure of the as-synthesized Hybrid I was predicted on the basis of the experimental results.