Papers by Author: Ping Yang

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Authors: Li Meng, Ping Yang, Zude Zhao, Wei Min Mao
Abstract: Orientation mapping based on EBSD technique was applied to analyze the rules of orientation evolution of grains in AZ31 magnesium alloy. Results show that not only under deformation strain rate of 1×10-2s-1, but under 4×10-4s-1(the superplastic deformation condition), grains in all samples with initial textures rotate gradually to near basal orientation ({0002} || compression plane) at different ways, and basal texture becomes stronger with increasing strain, which indicates plastic slip plays an important role during hot deformation. Otherwise, no evident non-basal pyramidal slip of as some studies mentioned was observed in the sample with the initial basal texture, and the basal orientation is kept unchanged during the deformation process, which suggests that basal slip is the uppermost plastic slip mechanism in this sample. In addition, the phenomenon of viscous laminar flow was observed in the sample with initial basal texture.
Authors: Olaf Engler, Ping Yang, Günter Gottstein, J. Jura, Jan Pospiech
Authors: Jin Wang, P. Li, H. Sun, Ping Yang, Y.X. Leng, Ji Yong Chen, Nan Huang
Abstract: We report a study involving chitosan chains immobilized on poly (ethylene terephthalate) (PET) films by plasma and ultraviolet (UV) grafting modification. The surface structure of the modified PET is determined by means of attenuated total reflection Fourier transform infraed spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The results show that the chains of chitosan are successfully grafted on the surface of PET. Platelet adhesion evaluation in vitro is conducted to examine the blood compatibility in vitro. Scanning electron microscopy (SEM) and optical microscopy reveal that the amounts of adhered, aggregated and morphologically changed platelets are reduced on the chitosan-immobilized PET films. The number of platelet adhered on the modified film is reduced by almost 48% compared to the amount of platelets on the untreated film. Our result thus shows that chitosan immobilized on the PET surface improves blood compatibility.
Authors: Ping Yang, Li Meng, Wei Min Mao, Leng Chen
Abstract: Orientation mapping based on EBSD technique was applied to reveal the orientations of new grains and their relationships to the surrounding matrices, to analyze Kikuchi band contrast and the influence of strain rates on local orientation evolution. This information is used to understand the dynamic recrystallization mechanism and the relative contribution of plastic slip versus grain boundary glide or grain rotation related with super-plasticity. For this purpose samples with different initial textures were deformed by (quasi-)plain strain compression at two strain rates. It is suggested that the dynamic recrystallization in this alloy proceeds in continuous way by progressive subgrain rotation. No evident non-basal slip of was observed by referring texture evolution in the sample with initial basal texture. A high strain rate promotes more contribution of plastic slip accompanied by fast orientation changes. The fact that groups of grains with very similar orientations in basal oriented samples is discussed in terms of viscous flow.
Authors: Ping Yang, Olaf Engler, Günter Gottstein
Authors: Hong Bin Su, Ping Yang, Jin Biao Wang, Nan Huang
Abstract: In this paper, both geometrical and electronic properties of rutile TiO2 (110) surfaces have been investigated using First-Principles Density-Functional calculations with CASTEP code, the model of stoichiometric surface is a (2x1) super-cell which has 12 atomic-layer slabs with the bottom 6 held fixed, the bridging-oxygen vacancy surface has been constructed by removing a neutral bridging oxygen atom from this surface. For the stoichiometric surface, the atom relaxations are: Ti6f (+0.2865Å), Ti5f (-0.1039Å), O3f (+0.2433Å) and Ob (+0.0075Å), we find no reconstruction and no surface states in the band gap, the density of states (DOS) is similar to the bulk except the lower conduction band intensity, in accord with recent experiments. Whereas, as a result of bridging-oxygen vacancy, the atom relaxations exchanged and reconstruction occur. The 2 excess electrons left behind removal of one bridge O atom are localized on the Ti-t2g conduction band orbitals, convert some of the Ti4+ ions into Ti3+ ions and result a compensatory shift in the Fermi level. The band gaps we calculated for stoichiometric surface is similar to the bulk, but its increase can be found for Ob vacancy surface.
Authors: Jun Ying Chen, Yong Xiang Leng, Sh.N. Ge, Ping Yang, Jin Wang, H. Sun, Guo Jiang Wan, An Sha Zhao, Nan Huang
Abstract: In the work reported here, titanium oxide film were synthesized using magnetron sputtering from a high-purity Ti metal target while sustaining a differential oxygen partial pressure of from 0.02 to 0.30 Pa. The biological behavior of endothelial cells grown on the film surface was studied by in vitro human umbilical vein endothelial cell (HUVEC) culture investigation. Our studies revealed that the adherence, growth, and proliferation of endothelial cells on different Ti-O film surfaces were strongly affected by the oxygen partial pressure. The biocompatibility mechanisms of ECs on Ti-O film surfaces were explored using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), a-step profilometry, scanning electron microscopy (SEM), and atomic force microscopy (AFM). We conclude that the various film characteristics such as structure, composition and surface morphology due to the different oxygen partial pressures significantly influence the biological behavior of EC.
Authors: Cong Zhen Han, Jing An Li, Dan Zou, Xiao Luo, Ping Yang, An Sha Zhao, Nan Huang
Abstract: The micro-patterned TiO2 nanotube has been anticipated for potential application for cardiovascular implanted devices for its excellent drug loading/ release function and biocompatibility. However, its mechanical behavior has rarely been studied as the cardiovascular devices. The tube length is a crucial factor which not only decides the drug loading ability but also influences the devices’ mechanical behavior. Therefore, in this work, the micro-patterned TiO2 nanotubes with different tube length (MNT2, MNT4 and MNT6) were fabricated, and their surface energy, residual stress, tensile tolerability and blood flow shear stress tolerability were determined, respectively. The results showed that the microstructure reduced the surface energy of the nanotubes surfaces, enhanced or reduced surface tensile tolerability when parallel or vertical to the strain orientation, and also increased the nanotubes surfaces residual stress; In addition, both micro/nano and single nano surfaces possessed good blood flow shear stress tolerability. These results indicated that the micro/nano surfaces possesses excellent mechanical properties for surface modification of cardiovascular devices.
Authors: Qi Yi Wang, Ping Yang, Ju Huang, Jun Liang, Hong Sun, Nan Huang
Abstract: Low hemocompatibility is a major problem of biomaterials that come in contact with blood. Surface modification has become an important way to improve the hemocompatibility of medical implants and interventional devices. Recently, researchers attempt to investigate the possibility of silicon oxynitride (Si-N-O) films to be applied as novel coating of blood-contacting biomaterials. However, no detailed investigation has been conducted. In this study, our work was focused on the optimization of the hemocompatibility of Si-N-O films prepared on single-crystal silicon wafers by unbalance magnetron sputtering (UBMS). The structure and chemical composition of films were characterized by X-ray photoelectron spectrometry (XPS), and their physical chemistry property was characterized by contact angle measurements. Platelet adhesion test was performed to investigate the platelet adhesion and activation. Our results suggested that films composed of Si3N4 and SiOx (x<2) exhibited better hemocompatibility than low temperature isotropic pyrolitic carbon (LTIC) that is a common material used in blood-contacting implants. It was also revealed that the higher N/O ratio in films composed of Si3N4 and SiOx (x<2) was attributed to the lower platelet adhesion and activation, and the interaction of samples with plasma proteins was demonstrated to play an important role in the adhesion and activation of platelets.
Authors: Feng Wen, Nan Huang, H. Sun, Ping Yang, Jin Wang
Abstract: Amorphous hydrogenated carbon (a-C:H) thin films were deposited on silicon wafers and Ti6Al4V substrate using plasma ion immersion implantation and deposition (PIII-D) at room temperature (R.T.). The composition and structure of a-C:H films were employed by X-ray photoelectron spectra (XPS) and Raman spectra. Nano-indenter tests measured the hardness of the films. In addition, wettability and bloodcompatibility were investigated. In this paper, the effects of hydrogen content on structure, mechanical properties, surface wettability and haemocompatibility were discussed.
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