Applied Mechanics and Materials Vols. 182-183

Abstract: The novel biodegradable poly(ε-caprolactone)/TiO₂ nanocomposite materials were successfully prepared via in situ in the presence of modified-TiO₂ initiator and Sn(Oct)2 catalyst. The relationships between morphology, molecular weight, and properties were investigated by means of SEM, TGA, DSC and GPC. A tendency of the nanoparticles to form aggregates was observed, especially at higher fillers contents. The molecular weight of PCL matrix was dependent on the amount of the TiO₂ fillers

Abstract: In this paper, besides the single method of air blowing and thermal condensation, a new two-step combining method was taken to modulate the pitch precursor for carbon fibers: the ethylene tar pitch was first air-blown under 280 °C for 10 h, and then thermal-condensed in nitrogen under 380 °C. Then group composition, elemental and thermal analysis, FT-IR, SEM and polarized optical micrographs were used in this paper, and the influence of different methods of modulation on the performance of pitches was discussed. The results revealed that neither in the method of air blowing nor thermal treatment can the pitch with a high softening point and coking value but no mesophase be produced. However, isotropic spinnable pitch with high softening point (286 °C), coking value (80.2%) and superior thermal stabilities can be synthesized in the two-step combining method. Carbon fibers from such pitches had been produced through melt-spinning, stabilization and carbonization, they showed uniform diameters (about 15.5 μm) with smooth and homogeneous surfaces. After stabilization and carbonization, the shrinkage of carbon fibers’ diameter was limited to 6%.

Abstract: The effect of Co substitution for Be on the glass-forming ability and mechanical properties was investigated in Ti₃₅Zr₃₀Be_27.5-xCu_7.5Co_x (x=0, 3.5, 7.5, 11.5 at.%) alloys by using X-ray diffractometry (XRD), differential scanning calorimetry (DSC), high-resolution transmission electron microscopy (HRTEM) and compression test. With the substitution of Co for Be, glass-forming ability (GFA) is significantly enhanced and fully amorphous rods with a diameter of up to 12 mm were produced in the alloy with 3.5 and 7.5 at.% Co. The Ti₃₅Zr₃₀Be₂₄Cu_7.5Co_3.5 bulk glassy alloy exhibits good plasticity of 4% during compressive applied load at ambient temperature in conjunction with distinct yield strain of 2% and high fracture strength of 2196 MPa. The effect of the addition of Co on the structure and deformation behavior of the Ti₃₅Zr₃₀Be_27.5-xCu_7.5Co_x (x=0, 3.5, 7.5, 11.5 at.%) alloys is discussed.

Abstract: In this paper, a new type indoor air filtration material was developed using three raw materials (wool, carbon fiber and activated carbon powder). Optimum fabrication parameters were adopted in needle-punched process to fabricate the air filtration material. The effect of carbon fiber, wool layer number and activated carbon powder content were analyzed in thermal stability test and formaldehyde removal test, and results showed the addition of carbon fiber enhance the thermal stability, and synergistic effect of wool and activated carbon powder played an essential role in formaldehyde sorption process.

Abstract: The objective of present work is to investigate the effect of macroscopic pores on the damping behavior of Zn-Al eutectoid alloy. The damping behavior of the foamed Zn-Al (FZA) eutectoid alloy prepared by air pressure infiltration process with macroscopic pores is characterized by internal friction (IF). Macroscopic pores size are on the order of a millimetre (0.51.0mm). The IF was measured on a multifunction internal friction apparatus (MFIFA) at frequencies of 0.5, 1.0 and 3.0 Hz over the temperature range of 25 to 400°C, while continuously heating temperature. The damping capacity of the FZA eutectoid alloy, with two different porosity and sizes of macroscopic pores, were compared with that of bulk Zn-Al eutectoid alloy specimen. The damping capacity of the materials is shown to increase with introducing macroscopic pores. Finally, the operative damping mechanisms in the FZA eutectoid alloy were discussed in light of IF measurements.

Abstract: A novel hyperbranched polyurethane solid-solid phase change heat storage material (HB-PUPCM) using hyperbranched polyester as chain extender was synthesized via a two-step process. Differential scanning calorimetry (DSC) and polarizing optical microscopy (POM) were performed to investigate the phase transition behaviors and crystalline morphology. The results indicated that the HB-PUPCM was a good polymeric solid-solid phase change heat storage material.

Abstract: Linearlinking polystyrene nanospheres (LPSs) with uniform size dispersion were synthesized by the emulsifier-free emulsion polymerization method. And with the adding of divinylbenzene (DVB) crosslinking polystyrene nanospheres (CPSs) was also prepared. It was found out that the partical size of prepared nanospheres changed with the continuous increment of added DVB. The sulfonation of resultant polystyrene nanospheres yielded solids with sulfonic acid groups. The relationship between nanospheres material structure and attached acid groups was investigated in detail. It was observed that the amount of added DVB is the main factor which can affect the amount and thermal stability of attached sulfonic acid groups. The catalytic performance of resultant solid acid catalysts was evaluated through the esterification reaction of methanol with acetic acid. Moreover, the prepared sulfonated polystyrene nanospheres show higher acetic acid conversion than the commercial one, therefore the sulfonated nanospheres could be an excellent potential replacement for liquid acid catalyst.

Abstract: Ti containing hydrogenated diamond like carbon films (Ti-DLC) was deposited on Si substrates at room temperature by magnetron sputtering Ti-twin target in methane and argon mixture atmosphere via changing the substrate bias voltage. The Ti atomic concentration in the film is less than 0.57% and exists mainly in the form of metallic titanium rather than TiC, confirmed by XPS analysis. The internal compressive stress of the film decreases monotonically with the substrate bias voltage increase. However, the hardness values of the film keep at level (12 GPa) without almost any obvious change with the increase of the substrate bias voltage. Furthermore, Ti-containing DLC film prepared at -1600 V substrate bias voltage shows an extremely low wear rate (~10^-9 mm³/Nm) and low friction coefficient (0.09).

Abstract: CZTS thin film, a potential candidate for application as absorber layer in thin film solar cells, has drawn much attention in these years due to its excellent photoelectric performance and nontoxic components. It provides a brief description of the development of CZTS thin film for solar cells, and surveys several methods of depositing CZTS films, then introduces the crystal structure of CZTS which is a problem for composition ratio affecting the properties of CZTS thin films. Here we also outline the development and the structure of solar cells based on CZTS thin films.

Abstract: In order to improve the repairing quality of aircraft envelope of the aluminum alloy LY12， the cerium conversion coating technology was studied by using the surface modification technique. Principle experiment was on the basis of aviation repair technological requirement, refers to the related technique, through examination of corrosion resistance and wear resistance performance of cerium conversion coating, the principal composition of the formula for making cerium conversion coating:Ce(NO₃)₃ + KMnO₄+ Ce-1 (chemical additive), In order to determine each composition of the formula and the technology parameters scientifically, L₉(3⁴) orthogonal testing method was adopted, and the formula of surface modification solution was optimized, the technological conditions for making cerium conversion coating on the surface of aircraft envelope were determined. Results of corrosion resistance and wear resistance of the cerium conversion coating on the surface of the aluminum alloy LY12 aircraft envelope obtained by the new technology showed: 1. On the given test conditions, the best content of each chemical composition in the formula of modification solution for making cerium conversion coating on the surface were: l.Ce(NO₃)₃：14g/L,KMnO₄：1g/L,addictive Ce-1:0.3g/L；Main technology parameters were ：pH=1.5～2.7;temperature：20°C；time:15~25 min.；2. Under the same test condition, the corrosion resistance of surface of the cerium conversion coating obtained in test modification solution was better than Alodine 1001 obtained from Bombardier Corporation of Canada, and can meet the repairing demands of Aircraft Envelope.