Materials Science Forum Vols. 675-677

Abstract: NiTi alloys are widely used for bone implants due to their good mechanical properties. However, they can suffer certain disadvantages, such as leaching of toxic nickel ions and poor osteoinductive properties. A porous (Ca, P)-doped TiO2 /dense Ti double coatings on NiTi alloy with porous (Ca, P)-doped TiO2 coating as the top layer and a dense Ti coating as the interlayer should possess a very good combination of bioactivity and chemical stability. In this paper, the double coatings were formed by applying a duplex process of arc ion plating (AIP) and micro-arc oxidation (MAO). X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) have been used to investigate the microstructure and morphology of the coatings.

Abstract: In the present study, the compatibility and degradability of L-tyrosine derived polycarbonate(PC)/Poly(ethylene glycol) blend were investigated. The PC was synthesized in our laboratory. Blends of the polymers with compositions 95/5, 85/15, 75/25,50/50 and 25/75 w/w were prepared by solution-casting. The blends were characterized by FT-IR,DSC,XRD,SEM. No obvious two phases were observed. Analysis of water absorption revealed that the combination of PC and PEG improved the hydrophilicity of PC. DSC and SEM analysis implied that all those components in consideration were compatible well in the blend formulation systems.Tg of the blends decreased with increasing PEG content. With the increase of the soft segment PEG content, the water retention ratio increases from 37% to 83%.

Abstract: Poly(styrene-divinylbenzene) microspheres were prepared by seed swelling polymerization in the presence of tung oil methyl esters. First, the core monodisperse polystyrene microspheres were prepared by a dispersion polymerization method. Using polystyrene microspheres as seed, tung oil methyl esters as a functional monomer, divinylbenzene as crosslinker, poly(styrene-divinylbenzene) microspheres were prepared by seed swelling polymerization. Then they were characterized by using FT-IR spectroscopy, TG/DSC and optical microscopy. Results showed that the tung oil methyl esters did participate in the copolymerization of styrene and divinylbenzene.

Abstract: This paper describes an effect of fluctuation in fiber orientation on the tensile properties of sliver-based green composites. The composites were reinforced with slivers of high-strength natural fibers extracted from plants named curaua. Then a surface optical micrograph of the composites with the fiber fluctuation was obtained. The micrograph was divided into many fine segments, and the fiber orientation angle in each segment was measured. Results show that the tensile strength depends on autocorrelation coefficients expressing the degree of fluctuation in fiber orientation, as well as the fiber orientation angles. However, the Young’s modulus was dependent only on the angles, rather than on autocorrelation coefficients. In addition, a statistical concept was applied to an orthotropic analysis for prediction of the Young’s modulus. The predicted Young’s moduli showed better agreement with the experimental results.

Abstract: Various crystal forms of calcium carbonate were successfully synthesized with CaCl2 and Na2CO3 in 10%(V/V) egg white protein solution system at 20 °C, 40 °C and 60 °C, respectively. The obtained calcium carbonate were characterized by SEM, XRD, FTIR and TG. In addition, the possible mechanism of crystal formation were analyzed. The results indicated that egg white protein could regulate the crystal forms of calcium carbonate and the calcium carbonate, which contained a small amount of egg white protein and consisted of mixed calcite and aragonite, was mainly spherical. With the temperature rosing, the vaterite content gradually increased while the calcite decreased.

Abstract: NiTi shape memory alloy is widely used as biomaterial for its superior mechanical properties and good biocompatibility. Effective protocols based on the surface oxidation mechanisms, which would precisely control the formation of surface oxide, should be designed and implemented to improve the biocompatibility of NiTi alloy based biomaterials. To shed light on the TiOx species formation mechanism on NiTi surface, density functional theory (DFT) based calculations were carried out to study the adsorption and reactions of O2 on the NiTi alloy (100) surface. O2 is found activated and will decompose upon adsorption. At higher O2 coverage, the reconstructed bridge configuration will generate (110) surface of TiO2, and the hollow configuration will evolve to (100) surface of TiO. The formation of TiO2 phase is thermodynamically favored, but only feasible when the temperature is enough high. At lower temperature, the atomic diffusion is slowed down, and the surface reconstruction will be limited. This explains why TiO2 will be dominant TiOx at higher temperature, and TiO will exist at lower temperature. Our current work provides more insights on the initial oxidation of NiTi surface, and these findings would be beneficial to improve NiTi alloy based biomaterials, and might guide the design of new functional materials.

Abstract: The modified rice straw fibers (MRSF) were prepared by suspension polymerization technique of butyl acrylate (BA) monomer and rice straw fibers (RSF) in water solution. FTIR test indicated that PBA was coated and absorbed on RSF.The biodegradable composites were prepared with the MRSF and poly(lactic acid) (PLA) by HAAKE rheometer. Mechanical properties showed that the tensile strength of PLA/MRSF composites were (W (%) =7.98%) increased by 6 MPa compared with blank sample. The possible reason was that the good interfacial adhesion between PLA and MRSF, which was demonstrated by SEM.

Abstract: Rice straw/Poly(butylene succinate)(PBS) composites were prepared by injection molding machine. The influence of content and particle size of rice straw on the mechanical properties of composites indicated that with the increase of rice straw content the tensile strength and fracture strain of the composites was decreased. With the same content of rice straw, the smaller particle size, the more obvious decreased. The influence of dosage of silane coupling agent(SCA) on the composites was studied, the result indicated that with the increase of SCA content, the interface of composite materials significantly improved, the Young’s modulus increased 362% after rice straw was treated by SCA. Thermal analysis showed that the adding of coupling agent didn’t undermine the thermodynamic stability of the composites.

Abstract: The mollusk shell mobilizes calcium from environment for skeletal mineralization. This occurs through synthesizing solids in solution in the presence of organic molecules of specific interior regions of the conch shell. The ultrastructure of the Hemifusus tuba conch shell living in the Huang/Bo sea area is investigated in the paper. It is shown that the composition and microstructure of the mollusk shell vary in different positions. The prodissoconch shell consists only of aragonite with the crossed-lamellar microstructure. While the spiral shell and the body shell of the Hemifusus tuba conch shell are composed of one calcite layer and several aragonite layers. The calcite layer consists of cylindrical grains, but the aragonite layers are crossed-lamellar ultrastructure. The margin of shell aperture is only composed of calcite with cylindrical grains. This natural optimization of the shell microstructure is intimately due to the growth of the organic matrix. The process of growth allows a constant renewal of the material, thus enabling the functional adaptation of the shells.

Abstract: Hydrophilic ciprofloxacin hydrochloride and hydrophobic sirolimus were used as model drugs, and poly(dl-lactic-co-glycolic acid) 50/50 (PLGA 50/50) was used as the drug carrier to investigate the effects of hydrophilicity/hydrophobicity of a drug on its release properties from PLGA films. The results showed that ciprofloxacin hydrochloride induced faster release curves than sirolimus, and it also promoted the weight loss of films, while sirolimus inhibited the weight loss of films. However, both drugs inhibited the degradation of biodegradable carrier.