Applied Mechanics and Materials Vol. 576

Abstract: To investigate the growth dynamics of the single void during Czochralski silicon growth as well as capture the basic features of the diffusion-controlled dynamic mechanisms, a phase field method has been developed. The free energy of the system involving the chemical free energy and the gradient energy is presented. Numerical tests were performed to examine the capability of this model, and the results show that: the void grows due to the absorption of vacancies in the matrix, which essentially reduces the free energy of the system; with the growth of the void, there forms vacancy concentration gradient towards the void in the matrix; the increase of initial vacancy concentration contributes to a larger void size and growth rate.

Abstract: A systematic study on electronic and optical properties of Sn-doped ZnO with and without O vacancy has been performed using first-principles method. Our results revealed that the band gap of Sn-doped ZnO without O vacancy become narrow, demonstrating as red-shift and the electrons near the Fermi level originates from the delocalized Sn-5s. However, as O vacancy is introduced, Sn-5p states locate near the Fermi level. Furthermore, it is found that the optical absorption edge has been obviously changed after Sn doping in ZnO with and without O vacancy. Interestingly, in the low energy region, one new peak is observed for Sn-doped ZnO with O vacancy, due to the electron transition between Sn-5p and O-2p. The calculated results identify that O vacancy can improve the absorption of the visible light in Sn-doped ZnO.

Abstract: Paper withdrawn at author's request

Abstract: The monodisperse Mn₂O₃ nanooctahedron, Mn₃O₄ nanorices, NiO nanoflowers and Cu₂O nanoroses have been synthesized via a facile solvothermal approach in the presence of poly (vinyl-pyrrolidone)/stearic acid (PVP/SA) as capping agent. Field-emission scanning electron microscopes (FESEM) and X-ray powder diffraction (XRD) were employed to detect the prepared products. Furthermore, the synthetic method appears to be a general approach and other metal oxide materials with various well-defined nano/microstructures can be fabricated by the similar method. The as-obtained metal oxides nanostructures were used as catalyst in CO oxidation, and the octahedral Mn₂O₃ nanoparticles exhibited relatively high activity. Complete conversion CO to CO₂ can be achieved at a temperature as low as 240 °C over Mn₂O₃ catalyst, which was about 70 and 100 °C lower than that of Mn₃O₄ and NiO, respectively.

Abstract: The photonic crystal has the property that electromagnetic waves with interval of frequency in photonic band gap (PBG) can not be propagated, so it has important applying and researching value. The traditional one-dimensional photonic crystal is with narrow band gap width, and the reflection within the band is small, especially the band gap is sensitive to the incident angle and the polarization of light. A new photonic band gap (PBG) structure, metallodielectric photonic crystal by inserting metal film in the medium can overcomes the shortcomings mentioned above. The one-dimensional Ag/SiOx photonic crystal was prepared, and theoretical and experimental researches were developed. The results show that photonic band gap appears gradually and the band gap width increase with increasing of period of repeating thickness. With the thickness of Ag film increasing, the band gap width increases, but the starting wavelength of the photonic band gap keeps unchanged. With thickness of SiOx film increasing, the band gap width of photonic band gap also increases, but it is not obvious and starting wavelength increases.

Abstract: The properties of in-situ (Si+Al₂O₃)/Al composites fabricated from Al-SiO₂ reaction system are investigated by X-Ray Diffraction, Scanning Electron Microscope and Differential Scanning Calorimetry technologies. The results indicate that the Si phase is plate shaped and the Al₂O₃ phase is mainly round and ellipsoidal. The composite prepared by this method have performances of low density, high conductivity and small thermal expansion coefficient (<10×10^-6/K) which meets the performance requirements of electronic packaging materials.

Abstract: The NaCl-KCl-K₂HfCl₆ electrolyte successfully prepared by the reaction of HfCl₄ with equimolar NaCl-KCl. Microstructure, surface morphology and components of the electrolyte were analyzed by XRD, SEM, and EDS. The results show that HfCl₄ preferentially reacts with KCl when KCl and NaCl coexist or conversion relationship exist between Na₂HfCl₆ and K₂HfCl₆. The removal rates of oxygen reached 96.98%in electrorefining of hafnium attributed to high stability and low volatility of the electrolyte.

Abstract: Perovskite oxides SrFe_0.5Co_0.5O_3-δ sample was synthesized by citrate method. The structures and morphology of materials were analyzed by XRD and SEM respectively. The powder sintered at 850°C was used as photocatalyst for degrading the methyl orange solution under a high pressure mercury 400W lamp. Some effects on the photocatalytic degradation of methyl orange, such as the irradiation time, catalyst dose, initial concentration, pH value and H₂O₂ were investigated in the process. The results showed the photocatalytic degradation efficiency of Methyl orange was up to 94.55% in 100 mL10 mg/L methyl orange solution containing 0.2 g catalyst for irradiation time of 120 min

Abstract: A series of poly (hydroxyethyl methacrylate)-g-polycarboxybetaine methacrylate ester (PHEMA-g-PCBMAE) hydrogels were synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization in the presence of crosslinker. Then differential scanning calorimetry (DSC) was used to characterize PHEMA-g-PCBMAE hydrogels. The compression stresses of these hydrogels were investigated to evaluate the mechanical properties. The mechanical study suggested that PHEMA-g-PCBMAE hydrogels presented improved mechanical strengths comparing with polycarboxybetaine methacrylate ester (PCBMAE) hydrogel. Besides, the antimicrobial properties of PHEMA-g-PCBMAE hydrogels also estimated by using Staphylococcus aureus as a model bacterial.