Chun Hua Xu

Hydrophilic/Hydrophobic Behavior on Ti Foil Surface Prepared by Anodization

Hydrophilic/hydrophobic behavior on Ti foil surface prepared during anodization process was examined. The titanium foils were anodized in electrolyte contained 0.25wt% NH4F, 2.5vol% water and the ethylene glycol under direct voltage of 40V at room temperature for 3h. The anodized specimens were oscillated in ultrasonic clearer for 10 min or 30 min. The surface morphologies of the specimens during different stages of the process were observed by field-emission scanning electron microscopy (FESEM). The wettability of specimen surface was estimated by measuring contact angle (CA) of water droplets on specimen surface. The results show wetting angle on the surface of the Ti specimens after anodization process is at the range of 149° to 153°, indicating hydrophobic or even superhydrophobic property. CAs on the anodized specimens after oscillation in ultrasonic clearer is at the range of 25° to 42°, indicating the hydrophilic property. Hydrophilic/hydrophobic behavior on Ti foil surface during the process was explained by morphology on titanium surface.

Effect of Oxygen Partial Pressure on Formation of Fe2O3 Nanostructure during Thermal Oxidation

In this paper, effect of oxygen partial pressure on formation of Fe2O3 nanostructure during Thermal Oxidation was studied. Fe2O3 nanostructure was formed by controlling oxidation conditions (Po2) and using the method of thermal oxidation. To begin with, a piece of pure iron in a ceramic crucible was put in the tube furnace (SYS-G-Z-13). Next the metallic Fe was oxidized at 500°C for 4 hours, under different oxygen partial pressure including pure argon (Po2 = 0atm), air Po2 = 0.21atm) and pure oxygen (Po2 = 1atm) to produce nanostructure, respectively. The surface morphology of the oxidized specimens was observed by SEM. The crystalline structure of the nanostructure was determined by transmission electron microscope. The experimental results show that the density of nanosheets increases with increasing oxygen partial pressure.

Preparation of PST Ferroelectric Thin Films by Sol-Gel Process

Sol-gel method is used for the formation of Pb0.499Sr0.499TiO3 (PST)thin films. The initial films were prepared with spin coating sol solution on silicon wafer and drying at room temperature and then heating coated dry sol film at 400°C for 10min. This process was repeated for 1-4 times to obtain 4 initial films with different thicknesses. The 4 initial films were annealed at 700°C for 2h to obtain PST ceramics films. The morphologies of the surface and cross-section of PST films were observed with a scanning electronic microscope (SEM). The phase structures of PST films were analyzed using X-ray diffraction meter (XRD). Experimental results show that PST film prepared by coating sol on silicon with different thicknesses can be high smooth,uniform and compact film.

Oxidation behavior of Cu-38at%Zn foils after surface mechanical attrition treatment

Abstract A commercial Cu-38at%Zn foil was subjected to surface mechanical attrition treatment (SMAT) processing. The isothermal oxidation behavior of the SMAT Cu-38at%Zn over the temperature range ...

Preparation of PZT Ferroelectric Thin Films by Sol-Gel Process

Sol-gel method is used for the formation of Pb(Zr0.63Ti0.37)O3(PZT) thin films. The initial films were formed with spin coating sol solution on silicon wafer and drying coated wet sol film at 300°C for 5min. This process was repeated for 1-4 times to obtain 4 initial films with different thicknesses. 4 initial films were annealed at 500°C for 2h to obtain PZT ceramics films. The morphologies of the surface and cross-section of PZT films were observed with a scanning electronic microscope (SEM). The phase structures of PZT films were analyzed using an X-ray diffraction meter (XRD). Experimental results show that PZT film prepared by coating wet sol on silicon once can be high smooth and compact film.

Microstructure Characterization of Rapid Solidification Al Alloy Foil

The AlMn and AlMnSi foils were fabricated by rapid solidification technology. The phase transformation temperatures, microstructures and distribution of elements were characterized by Differential Scanning Calorimetry (DSC), Transmission Electron Microscope (TEM), X-ray Diffraction (XRD) and Energy Disperse Spectroscopy (EDS) respectively. The result shows that the phases of AlMn7 nanofoil conclude Al, Al6Mn and quasicrystal phase, the crystal size is about 120nm; the phases of AlMn5Si5 nanofoil conclude Al, Al4.01MnSi0.74 and Al9Mn3Si, the crystal size is about 60nm. The phase transformation temperatures of AlMn7 and AlMn5Si5 nanofoils are 543K and over 873K, respectively. The microstructure morphology of AlMn7 nanofoil are rod, block and petal-like, but the microstructure morphology of AlMn5Si5 nanofoil is homogeneous globular.

Synthetics of ZnO Nanowires on GaN/Sapphire Substrate by Gold Catalyst

ZnO nanowires were grown on Au-coated GaN layer on c-plane sapphire by chemical vapor deposition (CVD). As-prepared ZnO oxides were characterized by a scanning electron microscope (SEM) and a transmission electron microscope (TEM). The results show that the growth of ZnO nanowires strongly depends on the location of GaN/sapphire substrates. The diameters of the resulting nanowires were in the range 60 nm with typical length about 10μm. The formation of ZnO nanowires with different morphologies at various positions of the substrate is explained by the mechanisms of vapor-solid and vapor-liquid-solid, respectively.

The Influence of Si Content on the Microstructure of Rapidly Solidified AlMnSi Foil

The AlMn and AlMnSi foils were fabricated by rapid solidification technology. The microstructures of the foils with various Si content were studied by transmission electron microscope (TEM). The phases of the foils were indentified by X-ray diffractometer (XRD); the phase transformation temperatures of the foils measured by differential scanning calorimeter (DSC). The results showed that addition of Si in the AlMn foil can improve the heat stability (phase transformation temperature) from 543K to over 873K. The addition of Si can change the phase structure of the foils. The phases of AlMn foil conclude Al and Al6Mn while the phases of AlMnSi foils with 3% Si or 5% Si addition become Al and Al4.01MnSi0.74. The addition of Si can also change the microstructure morphology of the foils from the rod, block and petal-like to the homogeneous globular. With the increase in Si content, the grain sizes of the foils were refined.

Growth of Nanostructure on Cu0.62Zn0.38 after SMAT during Thermal Oxidation

Commercial Cu0.62Zn0.38foil was subjected to surface mechanical attrition treatment (SMAT) processing. The original and SMAT Cu0.62Zn0.38 foils are thermally oxidized at 500°C under N2-5%O2 gas environments, at a pressure of 1 atm for 3 hours. The oxidized specimens were characterized with a scanning electron microscope, an X-ray diffractometer. It is found that nanosheets are easily formed on the SMAT specimen surface. The favorable formation of nanosheets relates to twin–matrix lamellae structure.

In Situ TEM Observation of Phase Transformation for Bio-Medical Shape Memory TiNbSn Alloy

TiNbSn alloy has high specific strength, low modulus of elasticity, excellent corrosion resistance, no side effects, such as toxic and exhibits shape memory effects after appropriate technical processing. This alloy may substitute as NiTi shape memory alloy to become the new generation of biological materials. It has been reported the studies of this alloy, such as the component and proportion, processing technology, mechanical properties and corrosion resistance. Based on the previous research, the bio-metal material, Ti-10Nb-5Sn alloy was heated and cooled repeatedly in a heater system located in TEM chamber and, at the same time, was observed in situ using a high resolution transmission electron microscope to study the memory property of the alloy and the mechanism of the transformation between austenite β and martensite phase. The results show that, during heating stage from 295K to 400K, the martensite began to dissolve at 355K, and the martensite disappeared completely at 385K, meanwhile, the austenite was created. During cooling stage from 400K to 295K, the martensite begins to take shape at 353K and the transformation was completed at 333K. The alloy can memory the room and high temperature structures, showing two-way memory functions. The high-temperature austenite of Ti-10Nb-5Sn alloy shows body-centered cubic β phase with the unit cell parameter a=0.3283nm; the martensite at room temperature shows orthorhombic NbTi4 phase (M) with the unit cell parameters a=0.3152nm, b=0.4854nm, c=0.4642nm. The orientation relationship between M phase and β phase is , , , , and . The crystal plane , as the habit plane, transforms into during the transformation from β to M phases. The martensite transformation mechanism is that the and transform to and through the tiny migration of atoms.