Papers by Author: Wei Zhang

Abstract: Differences in secondary structure among Bombyx mori (B. mori) silk and two wild silks of Antheraea yamamai (A. yamamai) and Antheraea pernyi (A. pernyi) were investigated by CP/MAS 13C NMR Spectroscopy. The β-sheet structure was primary in three silk, and B. mori silk had the highest β-sheet structure. Although amino acid compositions are very similar for two wild silk, their secondary structures had significant difference. A. yamamai silk contained more α-helix structure, whereas more β-turn and random coil structures formed in A. pernyi silk. B. mori silk was mainly composed of anti-parallel β-sheet structure, however, the parallel β-sheet structure was advantage in the two wild silks, and A. yamamai silk contained more anti-parallel β-sheet conformation than A. pernyi silk.

Abstract: Tussah silk fibroin (TSF)/hydroxyapatite (HAP) composites were prepared using the co-precipitation method. The results indicate that pure HAP presents needle-like structure with a length of 120-160 nm and a width of 30-40 nm. TSF/HAP composite prepared by adding 8% TSF exhibits a spherical structure, while with the increase of TSF content, the morphology of the composites changed from spherical to short rod, and the length of composite increases from 78 to 146 nm, but the width keep stability. FTIR spectra show the absorption peaks of TSF/HAP composite attributed to the amide and PO43- shift with the addition of TSF, indicating the existence of interaction between HAP and TSF molecules. TSF/HAP composites show a weak crystalline structure, being similar to nano-HAP existed in human bone tissue, thus suggesting that TSF molecules affect the crystallinity of HAP. TG analysis shows that TSF/HAP composite prepared by adding 17.6% TSF contains 11% TSF.

Abstract: The law of low-cycle fatigue with hold time at elevated temperature is investigated in this paper. A new life prediction model for the situation of fatigue and creep interaction is developed, based on the damage due to fatigue and creep. In order to verify the prediction model, strain-controlled low-cycle fatigue tests at temperature 693K, 823K and 873K and fatigue tests with various hold time at temperature 823K and 873K for 316L austenitic stainless steel were carried out. Good agreement is found between the predictions and experimental results.

Abstract: In the present work, the mechanical properties of 321 stainless steel pressure equipments exposed to an accident fire in a chemical unit were investigated. The performance and microstructure of this material were described by chemical compositions analysis, tensile test, scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The experiment results showed that the mechanical properties of the material were degraded. The grains on the external surface of the fracture became coarse. These results indicated that serious damage to 321 stainless steel had been induced by extreme heat of the fire and this pressure vessel could not be used anymore.