Advanced Materials Research Vols. 750-752

Abstract: SiO₂ nanoparticles was synthesized by F127/MMA/(NH₃+H₂O)/TEOS inverse microemulsion, the formation and morphology of nanoparticles were analyzed by Ultraviolet-visible spectrum and transmission electron microscopy, and scanning electron microscope. The results showed that SiO₂ nanoparticles were spherical structure and its average particle size was about 25 nanometers. The number of SiO₂ nanoparticles in the microemulsion and hybrid membrane was increased slightly with the increase of TEOS content. However, agglomeration of SiO₂ nanoparticles appeared in the hybrid membranes at high TEOS content.

Abstract: Using chemical bath deposition (CBD) deposited CdS thin films for two times and prepared CdS films contained different thickness Dy-doping layer by connecting using the vacuum electron beam evaporation method, then studied the structure, surface morphology, optical and electrical properties of the films. The results show that no-doped CdS films are the cubic structure and preferentially oriented in the (111) directions. Its conductive type is N type. After Dy doping the CdS thin films are mixed structure by cubic and hexagonal phase, the conductive type is still N type, the uniformity and compactness of the films are improved. At the same time, the proportion of Cd and S atoms in Dy-doping films are more close to the stoichiometric ratio. Dy-doping can also reduce the resistivity of the films, result in an increase of carrier concentration and improve the transmittance in the visible region.

Abstract: Thin films of amorphous/microcrystalline silicon transition zone prepared at different substrate temperature by very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) have been studied in this paper. The influence of substrate temperature on microstructure,photoelectric properties and growth of these materials have been investigated. The results show that in a certain extent with the increase of substrate temperature,the structure of material evaluated from amorphous to microcrystalline,the deposition rate and dark conductivity ,the photosensitivity had been improved.However,the optical conductivity had been reduced. The optimized substrate temperature for thin films deposition under our current growth system is about 240°C,at which deposition rate can reach 0.6nm/s.

Abstract: In the framework of the mean field approximation, a transverse Ising model (TIM) was adopted to analyze the polarization properties of temperature-graded ferroelectric films under two boundary conditions, free boundary condition (FBC) and clamped boundary condition (CBC). Due to the ferroelectric distortion aroused by temperature gradient across the film, the elastic thermal stress increased. A distribution function was introduced to characterize the different boundary conditions. The results show that boundary conditions have very important influence on film properties. Polarizations under FBC are larger than that under CBC, polarization variations aroused by changed film thickness and temperature gradient under FBC are not as obvious as that under CBC, and films under different boundary conditions present obviously different physical behavior.

Abstract: The poly (vinylidene fluoride)/poly (methyl methacrylate)(PVDF/PMMA) composite fibrous membranes with different blend ratio for use as separator of lithium-ion batteries have been developed by electrospinning technique. The surface morphology and crystal structure of electrospun PVDF/PMMA composite fibrous membranes are characterized using scanning electron microscopy (SEM), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and differential scanning calorimetry (DSC).The results indicated that the addition of PMMA into PVDF increased the fiber diameter, decreased the crystalline of electrospun composite fibrous membranes and the good molecular level interaction between these two polymers were obtained. Meanwhile,electrospun PVDF/PMMA (90/10) composite fibrous membranes exhibited the highest ionic conductivity of 2.54×10^-3S/cm at room temperature with electrochemical stability of up to 5.0V.

Abstract: The laponite-poly (L-lactide) composite films are prepared by the method of solution blending with polylactide (PLA) and laponite. The result shows that the homogeneous and smooth composite film is prepared with 1, 4-dioxane. Thermogravimetry analysis (TG) and tensile strength studies demonstrate that the thermal stability and tensile strength are improved with the laponite added. The scanning electron microscopy (SEM) measurement indicates that the pores of composite films get uniform and network structure is more and more compact with compared to pure PLA film. The present study reveals that the laponite as a complexing agent can improve the mechanical properties and thermal stability of PLA.

Abstract: Graphite-amorphous carbon films were grown by sputtered Ni target in Ar/CH4 mixture atmosphere. The impacts of N2 import into reaction system on the structures and properties of the graphite-amorphous carbon films were studied. The results shown that graphite-amorphous carbon films with good hardness, elastic and friction coefficient were obtained at the N2/CH4 flow ratio below 20/80. Beyond the flow ratio of 20/80, the number and size of nanocrystal graphite decrease induce the bad hardness, elastic and friction coefficient of the graphite-amorphous films. Graphite-amorphous carbon films properties were possible correlate with the size and number of nanocrytal graphite and its crosslinking degree to carbon network, especially the former.

Abstract: The poly (lactide-co-trimethylene carbonate) copolymers are prepared by ring opening polymerization and catalyzed by SnOct and their films are prepared by blow molding. The ¹HNMR study demonstrates that PLA-PTMC copolymers were successfully obtained and the graft way is A-B model. The water vapor permeability (WVP) of the films decreases with the increasing TMC content due to the formation of denser structure. The mechanical measurement reveals that the tensile strength of blown films has been declined with the increasing TMC content, but the elongation at break is improved and the tensile strength can be satisfied for the requirement of film product. Therefore, the copolymer film will be great prospect in the application of food and beverage packing.

Abstract: Star copolymers of ε-caprolactone and L-lactide (ε-CL/L-LA) were synthesized with different compositions in the presence of pentaerythritol and using stannous octoate as catalyst. The copolymers were characterized by ¹H NMR spectra analysis and then blown into films in a single-screw extruder. The mechanical properties study show that the copolymers differed widely in their elongation at break and tensile strength according to the ratio of monomers and pentaerythritol in the copolymerization. The tensile strength of the films deriving from extrusion is much higher than that obtained through solvent volatilization.

Abstract: Polypropylene/polysulfone composite ultrafiltration membrane was prepared though coating method using microporous polypropylene hollow fiber membrane as a support layer and polysulfone membrane as a functional layer. Membranes of different pore sizes were prepared by L-S phase translation though changing the concentration of PS. The properties of the composite membrane include water flux and rejections of PEG-2000 were studies. The flux of 78 L/m²h and 98 % rejection was achieved at PS concentration of 11%, Polyvinylpyrrolidone of 4 %, liquid phase coagulation time of 3 hours.