A new integration algorithm for finite deformation of thermo-elasto-viscoplastic single crystals

An algorithm for integrating the constitutive equations in thermal framework is presented, in which the plastic deformation gradient is chosen as the integration variable. Compared with the classic algorithm, a key feature of this new approach is that it can describe the finite deformation of crystals under thermal conditions. The obtained plastic deformation gradient contains not only plastic defor- mation but also thermal effects. The governing equation for the plastic deformation gradient is obtained based on ther- mal multiplicative decomposition of the total deformation gradient. An implicit method is used to integrate this evo- lution equation to ensure stability. Single crystal 1 100 aluminum is investigated to demonstrate practical applications of the model. The effects of anisotropic properties, time step, strain rate and temperature are calculated using this integration model.

NONISOTHERMAL CRYSTALLIZATION AND MORPHOLOGY OF POLY(BUTYLENE SUCCINATE)/LAYERED DOUBLE HYDROXIDE NANOCOMPOSITES

Biodegradable poly（butylene succinate） （PBS） and layered double hydroxide （LDH） nanocomposites were prepared via melt blending in a twin-screw extruder. The morphology and dispersion of LDH nanoparticles within PBS matrix were characterized by transmission electron microscopy （TEM）, which showed that LDH nanoparticles were found to be well distributed at the nanometer level. The nonisothermal crystallization behavior of nanocomposites was extensively studied using differential scanning calorimetry （DSC） technique at various cooling rates. The crystallization rate of PBS was accelerated by the addition of LDH due to its heterogeneous nucleation effect; however, the crystallization mechanism and crystal structure of PBS remained almost unchanged. In kinetics analysis of nonisothermal crystallization, the Ozawa approach failed to describe the crystallization behavior of PBS/LDH nanocomposites, whereas both the modified Avrami model and the Mo method well represented the crystallization behavior of nanocomposites. The effective activation energy was estimated as a function of the relative degree of crystallinity using the isoeonversional analysis. The subsequent melting behavior of PBS and PBS/LDH nanocomposites was observed to be dependent on the cooling rate. The POM showed that the small and less perfect crystals were formed in nanocomposites.

MORPHOLOGY, CRYSTALLIZATION AND MECHANICAL PROPERTIES OF POLY(ε-CAPROLACTONE)/GRAPHENE OXIDE NANOCOMPOSITES

A series of nanocomposites based on poly（ε-caprolactone） （PCL） and graphene oxide （GO） were prepared by in situ polymerization. Scanning electron microscopy observation revealed not only a well dispersion of GO but also a strong interfacial interaction between GO and the PCL matrix, as evidenced by the presence of some GO nanosheets embedded in the matrix. Effects of GO nanofillers on the crystal structure, crystallization behavior and spherulitic morphology of the PCL matrix were investigated in detail. The results showed that the crystallization temperature of PCL enhanced significantly due to the presence of GO in the nanocomposites, however, the addition of GO did not affect the crystal structure greatly. Thermal stability of PCL remarkably increased with the addition of GO nanosheets, compared with that of pure PCL. Incorporation of GO greatly improved the tensile strength and Young＇s modulus of PCL without a significant loss of the elongation at break.

Salen-iron Complexes: Synthesis, Characterization and Their Reactivity with Lactide

Schiff-base metal complexes as efficient catalysts are widely used in ring-opening polymerization of cycle esters. The salen Fe complexes were formed with their excellent biocompatibility and less toxicity. A series of salen Fe complexes were designed in this work in order to study the activity and control of polymerization of lactide. The salen Fe complexes＇ activities changed with the ligands configuration and substituent groups.

SYNTHESIS AND CHARACTERIZATION OF POLY(ε-CAPROLACTONE)/Fe_3O_4 NANOCOMPOSITES BY IN SITU POLYMERIZATION

A series of magnetic nanoeomposites based on poly（s-caprolactone） （PCL） and Fe3O4 nanoparticles were prepared using a facile in situ polymerization method. The chemical structures of the PCL/Fe3O4 nanocomposites were characterized by Fourier transform infrared （FTIR） spectroscopy. Results of wide-angle X-ray diffraction （WAXD） showed that the incorporation of the Fe3O4 nanoparticles did not affect the crystallization structure of the PCL. Both scanning electron microscopy （SEM） and transmission electron microscopy （TEM） were used to characterize the morphology and dispersion of the Fe3O4 nanoparticles within the as-synthesized nanocomposites. Results of differential scanning calorimetry （DSC） and polarizing optical microscopy （POM） showed that the crystallization temperature was raised and the spherulites size decreased by the presence of Fe3O4 nanoparticles in the nanocomposites due to the heterogeneous nucleation effect. The thermal stability of the PCL was depressed by incorporation of Fe3O4 nanoparticles from thermogravimetric analysis （TGA）. The superparamagnetic behavior of the PCL/Fe3O4 nanocomposites was testified by the superconducting quantum interference device （SQUID） magnetometer analysis. The obtained biodegradable nanocomposites will have a great potential in magnetic resonance imaging contrast and targeted drug delivery.

Electrochemical hydrogen storage properties of melt-spun Ti0.9Zr0.1V0.2Ni1.5La0.5 alloy

The Ti0.9Zr0.1V0.2Ni1.5La0.5 alloy samples were synthesized by melt-spinning technique at the different wheel velocity （cooling rate）, and the structure and electrochenfical hydrogen storage properties were investigated. The result indicated that the structure of the melt-spun ribbons mainly contains C14 Laves phase and V-based solid solution phase. The discharge capacity, cyclic stability, high-rate discharge ability and electrochemical kinetic of the alloy electrodes are correlated with the cooling rate （wheel velocity）, and the maximum discharge capacity is over 200 mA.h/g at the wheel velocity of 20 m/s.