Applied Mechanics and Materials Vols. 275-277

Abstract: Fatigue stiffness degradation behaviour of woven composite π joint subjected to tensile-tensile cycle loading is studied. Because of the complex structural configuration of woven composite π joints and a variety of failure modes, there exhibited four stiffness degradation modes in fatigue test. For example, stable slight reduction mode, abruptly decreasing mode, step decreasing mode and constant stiffness mode. Each stiffness degradation mode has a corresponding failure mode in fatigue test.

Abstract: Base on the micro-structure of self-healing 2.5D-C/SiC composite, a new mechanical model was established, By changing the tensile strength of matrix and volume fraction of boron carbide, the tensile behavior of self-healing 2.5D-C/SiC composite in weft direction was studied. The result shows that the increase of volume fraction of boron carbide has little influence on the tensile behavior in weft direction, and the influence is primarily due to the change of the tensile strength of matrix.

Abstract: A novel combination of optical fibers and one dimensional (1-D) ZnO nanobelts is presented. Three samples were produced in different heat treatment (300°C and 600°C). A new model was introduced to study silica optical fibers. It was found that the green photoluminescence (PL) of samples is obvious but shows some changes in respective atmosphere. Different buffer layers of polyvinly alcohol (PVA) and ZnO thin film are main factors leading to the differences in PL spectrum. These results support that the novel optical fibers obtained by 1-D ZnO nano-material are available and may lead us another road to self-luminous optical fibers.

Abstract: NiFe2O4 nanoparticles was successfully synthesized by hydrothermal decomposition of a gel of Ni-Fe-EG (EG=ethylene glycol) in water solution. The crystal structure and morphologies of the products were characterized by X-ray diffraction (XRD) and Transmission electron microscopy (TEM). All the diffraction peaks in XRD patterns revealed that the as-synthesized nanoparticles were pure NiFe2O4. TEM images disclosed that the particle sizes of the nanoparticles were in the range of 10 − 25nm. The cyclic voltammetry (CV) and galvanostatic charge/discharge results tested in 6M KOH solution revealed a double layer capacitive behavior and a revisable charge/discharge property.

Abstract: SAPO-11 and SAPO-47 crystals have been synthesized using diethylamine (DEA) as the structure-directing agent (SDA) and their morphology have been controlled successfully by varying aging duration. The single crystals were obtained in a short aging duration while film and island-like crystals were obtained in a long aging duration. The effect of SiO2/Al2O3 ration and content of HF on SAPO-47 crystals have been investigated. High molar ration of SiO2/Al2O3 and high content of HF is tend to synthesize larger crystals of SAPO-47. All the samples were characterized by XRD and SEM.

Abstract: Halloysite nanotubes (HNTs) surface-grafting poly(D,L-lactide) (g-HNTs) were synthesized by bulk ring-opening polymerization of D,L-lactide using stannous octoate as catalyst and HNTs as co-initiator. Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and zeta potential measurement were employed to elucidate the structure and properties of HNTs before and after grafting with D,L-lactide. FTIR spectrum certified the existence of poly(D,L-lactide) chains on the surface of g-HNTs. The amount of surface-grafted poly(D,L-lactide) measured by TGA was 4.6% in weight. The grafted poly(D,L-lactide) chains on the surfaces of HNTs can relieve the clustering effect of HNTs to some extents.

Abstract: Submicro-scaled graphite flakes with uniform distribution on the surface of carbon fiber were grown in situ by catalytic chemical vapor deposition with natural gas as feedstock. Morphology and structure parameter of graphite flakes were characterized by scanning electron microscope and Raman spectroscopy respectively. The results show that graphite flakes with assistance of iron hydroxide aqueous collosol had better shape, higher density and graphitization degree compared with specimen prepared with ferric chloride solution. The size in plane of as grown graphite flakes is in the range of 1-3 μm. Microcrystal domain size of graphite flakes is calculated about 5 nm according to ration of intensity of D band to G band in Raman spectra.

Abstract: Nanostructured Al-25at.%Fe-5at.%Ni intermetallics were prepared directly by mechanical alloying (MA) in a high-energy planetary ball-mill. The phase transformations and structural changes occurring in the studied material during mechanical alloying were investigated by X-ray diffraction (XRD). Scanning electron microscopy (SEM) was employed to examine the morphology of the powders. Thermal behavior of the milled powders was examined by differential thermal analysis (DTA). The solid solutions of Fe (Al) and Ni (Fe) in the Al70Fe25Ni5 system are observed at the early milling stage. The solid solutions transforms into amorphous and disordered Al (Fe, Ni) phase. The last milling products in the Al70Fe25Ni5 system are Al3Ni2, AlFe3 and AlFe0.23Ni0.77 phases.

Abstract: The precursor was prepared by cohydrolysis reactions of Ti(OC₂H₅)₄ and Tb(OC₂H₅)₆ around micelles of cetyltrimethylammonium bromide processed by ultrasonic before the cohydrolysis reactions. After calcined the precursor, Terbium doped anatase with a three-dimensionally interconnected hierarchical meso/mesoporous structure had been successfully prepared using an ultrasonic-assisted routine of sol-gel. The three-dimensionally interconnected hierarchical meso/mesoporous structure of the prepared material was proved by high resolution transmission electron microscopy and N₂ adsorption-desorption analysis. The material prepared displays a pore width distribution curve of single peak at 17.8 nm and displays a range from 6 nm to 42 nm, and possesses a BET area of 105 m²/g and a porosity of 0.65 cm³/g. The results of XPS analysis show that Ti exists in the Ti⁴⁺ form and Ti-O-Tb/H and Ti-O-Ti bonds exist in the surface of the mesoporous material prepared. The terbium-doped sensitive material prepared possessing a three-dimensionally interconnected hierarchical meso/mesoporous structure is conducive mass-transferring and light-harvesting, and shows that a photocatalytic activity for phenol is about 4.9 times than that of commercial P25 titania under a very weak UV-Vis irradiation condition.

Abstract: Nitrogen doped graphene (NG) was synthesized by chemical vapor deposition at 950 °C, using metal tetrapyrazinoporphyrazine (MPTpz, M= Fe, Co, the mass ratio of FePTPz/ CoPTpz is 1: 1) as a precursor. IR testing of FePTpz indicates the existence of C−N and C=N, which was prepared through microwave method. The NG shows a uniformly distributed and cotton-like structure. TEM images suggests that the single and multilayer NG coexists in the products and it is of a graphite-like structure. Electrocatalytic activity of the NG towards oxygen reduction reaction (ORR) was investigated by the cyclic voltammetry at different scan rates from 20 mV·s-1 to 100 mV·s-1 in an acidic solution. Peak currents and background currents of the NG rose as the scan rate increasing. The maximum peak current is 290.24 mA·cm−2, exhibiting well electrocatalytic activity of the NG toward ORR.