Advanced Materials Research Vol. 1048

Abstract: A new bacterial cellulose regenerated cellulose membrane (RBC) has been prepared by phase inversion method in LiCl/DMAC solution. The effects of coagulation concentrations on the physical properties of the RBC membranes were studied and optimized. Features of the RBC of membranes obtained using 0%~40% N,N-Dimethylacetamide (DMAC), such as water absorption percentage, porosity (Pr), ultrafilter rate (UFR), and tensile strength were investigated. The RBC membranes prepared with 40% DMAC solution as coagulant exhibit a smooth surface and a high tensile strength with suitable UFR. RBC showed improved permeabilities for urea and vitamin B₁₂ when compared with commercial cellulose membranes.

Abstract: This study evidently indicated that basalt glass powder is not only far cheaper than chopped basalt fiber, but also has better reinforcing effect than basalt fiber in terms of key mechanical properties. Basalt glass powder and chopped basalt fiber were mixed with fir sawdust to produce wood composite panel, at the mass ratios of 0%, 5%, 10%, 15%, 20% and 25%. Compared with the unreinforced wood composite, the tensile and bending strengths of panels reinforced by basalt glass powder increased up to 94.3% and 43.3% respectively, when the powder contents were 15% and 10%; the ultimate increase of tensile and bending strengths were 50.8% and 34.4% respectively, when the content of chopped basalt fiber was 10%.

Abstract: The structure development of poly (L-lactic acid)(PLLA) during the uniaxial drawing was investigated by means of in-situ simultaneous wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) measurements. When the quenched amorphous film of PLLA was drawn at 77.2 oC, which was well above the glass transition temperature of PLLA, two different crystal structures were formed depending on the strain. The mesophase, which has 10₃ helix with large amount of packing disorder, was formed at the early stage of drawing, followed by the crystal transformation into α’ form (ε ≥ 1.5). SAXS measurement showed that the kebab formation begins at the stage later than that of meso-α’ transition. It strongly suggests that the transition takes place inside the shish structure. The development of kebab leads to the enhancement of mechanical response, which is found to be the origin of the strain hardening of PLLA.

Abstract: The flame method is a kind of new method for preparation of carbon nanotubes. The hydrocarbon gas (acetylene, ethylene, methane) or carbon monoxide is often selected as carbon source gas in this method. Carbon monoxide is a kind of effective carbon source gas in preparation of carbon nanotubes from the high temperature flame compared with hydrocarbon gases. The pentacarbonyl iron is served as catalyst precursor in the experiment. Austenitic stainless steel type316 is selected as sampling substrate in the flame experiment. The carbon nanotubes from the controllable flame have graphite well-crystallized and less structural defects relatively. The nanotube diameter consistency is also relatively good. Carbon monoxide began to decompose at higher temperature than that of hydrocarbon gas and its decomposition rate is suitable for the synthesis of carbon nanotubes in the flame. In addition, the carbon monoxide has the ability to split large iron catalyst particles and prefers to react with iron catalyst. But only a few carbon nanotubes mixed with lots of iron catalyst particles, soot and amorphous carbon particles come into being when low mass flow of carbon monoxide is provided.

Abstract: This paper investigated the macro-mechanical properties of three dimension porous materials consisted of periodically arrayed base units with random pore distribution using homogenization theory. The model of base unit using random numbers was established. A finite element method of homogenization equations was derived for the three dimension periodic structures and was applied to the calculation of the equivalent elastic modulus of porous materials with various porosities.The results shows the equivalent elastic modulus of three dimension porous material has significantly negative correlation with the porosity of material (p < 0.001) and the regression equation is E=(-19.4)ρ+17.6(E=equivalent elastic modulus, ρ=porosity ) when the elastic modulus of the solid matrix is 18 Gpa.

Abstract: Poly (lactic) acid (PLA)/poly (caprolactone) (PCL) blends nanofibers, with mean diameter about 600nm, were prepared by electrospinning. This research focused on the morphological and thermal properties of nanofibers made from PLA/PCL bends with different PCL content. The results showed that the addition of PCL could improve the morphology of the nanofibers. The film with blend fiber at PLA/PCL ratio of 80:20 is characterized with the smoothest surface and the highest orientation. The diameter distribution of blend fibers is wider than that of pure PLA. The glass-transition temperature of PLA for blend fiber is higher than that of pure PLA, and their melting temperature is lower than that of pure PLA. It can be used in biomedical field for degradable membrane, anti-adhesive film and medical equipment.

Abstract: Polystyrene beads modified with ester group for the separation of n-heptane/toluene have been successfully prepared. The synthesized beads were characterized by fourier transform infrared spectroscopy and thermogravimetric analysis. The effects of ester group on equillibrium swelling ratio and toluene selectivity were studied. The selective factor firstly increases then decreases with the increasing of ester group content. When the content of ester group is 30%, selective factor reaches maximum, the value is 1.62. Polystyrene beads modified with ester group show excellent thermal stability.

Abstract: In order to get a stable heat preserved property of temperature control textile, the sandwich structure of thermochromic phase change nanofibers/ woven composite materials was made by electrospinning, weaving and simple suture. In this material, the thermochromic powder acted as a temperature indicator, lauric acid is selected as phase change material. The morphologies and heat preserved property were characterized by SEM, a digital single lens camera and an increase-decreased temperature system test, respectively. The results showed that such composite materials exhibited an obviously heat preserved property; it took 17mins to decrease the temperature from 50 °C to 30 °C, which was 4 mins longer than the weaves.

Abstract: Drying deformation of radiata pine boards results in a great loss of revenue to the wood industry. A computer simulation model, which is capable of predicting the drying quality of radiata pine boards, was developed in this paper for pre-grading and for setting of drying schedules in sawmills. Moreover, Logs must be sawn into slabs before drying. Accordingly, the geometrical configurations of boards were generated. Next, the structures of knot-containing boards were modelled on the basis of the growth features of branches. Later, the 2D and 3D scenario simulations of different knot shapes and knot types were performed and illustrated specifically. In the last, the key points in the model development were found and stated.

Abstract: SiO_2f/SiO₂ composites reinforced with 3D six-directional preform were fabricated by silicasol-infiltration-sintering method. To characterize the mechanical properties of the composites, mechanical testing was carried out under various loading conditions, including tensile and shear loading. All of the testing curves exhibited highly nonlinear behavior. The results indicated that the 3D six-directional braided SiO_2f/SiO₂ composites exhibited superior tensile properties and good shear resistant. Therefore, the 3D six-directional braided composites developed can well meet the demands of the thermal structure component.