Advanced Materials Research Vol. 773

Abstract: As a new-generation green composite, core-shell structure nature fibers/ polymer composites (NFPC) has been recently developed and used to enhance performance characteristics of composites. The shell layer, made of thermopolymers unfilled or filled with minerals or nature fibers and other additives, plays a critical role in enhancing overall composite properties. The co-extrusion technology for different structural and material combinations are, however, needed to achieve desired processing. In this paper, co-extrusion technology and core-shell structure NFPC have been discussed by systematically studying the effect of structure on properties of NFPC. The result of this paper can help provide a fundamental base for developing new functional applications of core-shell structure NFPCs.

Abstract: Bamboo/HDPE/PA6 composites have been discussed by systematically studying the effect of formulation on thermal expansion properties. PA6 filled HDPE seemed not significantly influence LTEC of HDPE/PA composites system when the PA loading level increased form 0 % to 20%. It was investigated that BF significantly reduced LTEC value compared with LTEC of HDPE/PA. The reduction of the LTEC appear in HDPE/bamboo composites was dependent on the matrix and filler. Coupling agent can make the LTEC of HDPE/bamboo composites reduced, but the reduction was larger than that of only filler.

Abstract: A series of MAl₂O₄ (M=Ni²⁺ and Mg²⁺) catalysts with high catalyst activity was prepared via co-precipitation. Higher sintering temperature is favorable to catalyst activity. As-prepared MAl₂O₄ catalysts were characterized by X-ray diffraction, scanning electronic microscopy, and BrunauerEmmettTeller method. MAl₂O₄ catalysts were evaluated using the heating values of bio-oils derived from the catalytic pyrolysis of microalgae. The heating value of the bio-oils is enhanced along with the increased sintering temperature of MAl₂O₄ catalysts. The highest heating value using MAl₂O₄ catalysts sintered at 700 °C was 36.298 MJ/kg, which was higher than the value when using ZSM-5.

Abstract: By using Isopropyl tri (dioctylpyrophosphate) titanate modified nanoSi0₂. Poly (ε-caprolactone)(PCL) and Poly (Butylene Succinate Adipate)(PBSA) blends was prepared by melt mixing. Its structure and mechanical properties were studied respectively with infrared spectrometer (FT-IR), universal material testing machine and scanning electron microscope (SEM),and analysis the degradation behavior by soil buried experiment The results showed that the modified nanoSi0₂ content is 4%, the mechanical properties of composite degradation material is improved obviously. The SEM results showed that a low amount of modified nanoSi0₂ can be dispersed evenly in the blends, while agglomeration of was observed in blends with increasing modified nanoSi0₂ content. Compared with SEM image after degradation, the degradation behavior of the composites was good.

Abstract: Transition films of amorphous hydrogenated silicon (a-Si:H) to microcrystalline silicon (μc-Si:H) have attracted much attention due to the stability, high overall quality for solar cells configuration. Hydrogenated amorphous and microcrystalline silicon films were deposited on glass substrates by a conventional plasma enhanced chemical vapor deposition (PEVCD) varying the substrate temperature from 275 to 350 °C. A silane concentration of 4% and a total flow rate of 100 sccm were used at a gas pressure of 267 Pa. The film thicknesses of the prepared samples were between 700 and 900 nm estimated from the optical transmission spectra. The deposition rates were between 0.2 and 0.3 nm/s. The phase composition of the deposited silicon films were investigated by Raman spectroscopy. The transition from amorphous to microcrystalline silicon was found at the higher temperatures. The crystallization process of the amorphous silicon can be affected by the substrate temperature. A narrow structural transition region was observed from the changes of the crystalline volume fraction. The dark electrical conductivity of the silicon films increased as the substrate temperature increasing.

Abstract: In this paper, MoS₂ nanoflakes was prepared by a vacuum freeze-drying method. Electrochemical performance of MoS₂ nanoflakes has been investigated through cyclic voltammetry, electrochemical impedance spectroscopy analyzer. The results demonstrated that the new electrode maintains a relatively high power density and a good cycle performance in 6 M KOH electrolyte. A maximum specific capacitance of 0.11 F g^-1 in an aqueous electrolyte solution has been obtained. The supercapacitor devices exhibit excellent long cycle life along with ~ 40% specific capacitance retained after 500 cycle at scan rates of 500 mV s¹.

Abstract: The melting and recrystallization behavior of Poly(ethylene terephthalate) (PET)/ Attapulgite(At) nanocomposites after isothermal crystallization from the melt was studied by Step-scan differential scanning calorimetry (SDSC). The influence of At contents, crystallization temperature and crystallization time on the melting process were examined. Two melting endotherms(in the SDSC C_P.A curves, reversible part) and one recrystallization exotherm (in the SDSC C_P.IsoK curves, irreversible part)of PET/At nanocomposites after isothermal crystallization were observed during the melt process. This ascribes to the melting-recrystallization mechanism .The low temperature endotherm attributes to the melting of primary crystal formed during the isothermal treating and the high temperature endotherm resulting from the melting of recrystallization materials. The reason why more recrystallization happened with the increase of At content was given and the process of recrystallization was described in detail. The effects of crystal perfection and recrystallization were minimized by increasing of crystallization temperature and time.

Abstract: Shape-stabilized phase change material (PCM) composed of polyethylene glycol and silica hollow nanospheres was prepared by a vacuum impregnating method. Thermal properties of the composite PCM were investigated by various techniques. Lower phase change temperature and enthalpy of the composite PCM were observed. It is concluded that the phase change properties of the composite PCM are influenced by the adsorption confinement of the PEG segments from the porous structure of the silica hollow nanospheres.

Abstract: The scale inhibition of the ESA/AMPS copolymer under the magnetic field or electrostatic field was researched by using static scale inhibition experiments. The result showed that there were synergistic scale inhibition effect between magnetic field and ESA/AMPS copolymer, and the electrostatic field and ESA/AMPS copolymer also had synergistic scale inhibition. The scale inhibition rate of both magnetic field and ESA/AMPS copolymer on CaCO3 increased by 12% as compared with that of ESA/AMPS copolymer alone. And the synergistic scale inhibition rate on Ca3(PO4)2 increased by 42.4% .The increased scale inhibition rate of the ESA / AMPS copolymer on CaCO3 with electrostatic field was 19%,and the scale inhibition rate on Ca3(PO4)2 could increace 73.3%.

Abstract: Typical defects such as delamination and water/oil ingression existed in honeycomb composites during manufacturing and in-service period. The defects can reduce the performance of the composites significantly. The paper presented a nondestructive defect recognition method for honeycomb composites using pulsed thermography. In this study, based on analysis of the heat transfer in the object with two different medias, the relationship between the surface temperature and the thermal property of subsurface defects has been deduced; the surface temperature expression is put forward to consider the interaction of subsurface defects. In order to simulate the defects, CFRP sandwiched sample with different subsurface defects (debonding, water in the honeycomb core and oil in the honeycomb core) of the same volume inserted in the machined flat-bottom holes, the sample is heated with a short pulse of light, and the sample surface temperature is captured by infrared camera, and the data is processed to measure thermal diffusivity for the subsurface defects. The order of the measured thermal diffusivity is according with the theoretical value. The experiment results provide the feasibility of different defects recognition, and the influence factors are discussed.