Bicrystalline ZnO nanowires synthesized are composed of two crystals that form a twin structure parallel to the (0114) plane with a growth direction closely parallel to [0111] and the (2110) side facet. The twin structure is suggested to be a key factor in leading the axial growth of the nanowire. The photoluminescence spectra of the nanowires show a weak UV emission at 385 nm and a strong green emission at 495 nm. The green emission intensity of the nanowires depends on the different level of oxygen vacancies in the ZnO nanowires.

We have developed a simple solid-vapor approach for controlled growth of the tetraleg ZnO nanostructure at high yield. The length of the tetraleg is 2-3 mm and the edge size of its centering nucleus is 70-200 nm. Our electron microscopy study gives the first direct evidence about the existence of the octahedral multiple twin nucleus, which is confirmed to be responsible for the formation of the tetraleg ZnO nanostructure. The tetraleg ZnO nanostructure is likely to be a candidate as building blocks for contructing photonic crystals.

During stress corrosion cracking of Cu3Au alloy, a dealloyed layer on the surface will be formed because of preferential dissolution of Cu. Molecular dynamics (MD) simulations showed that Cu3Au crystal with a dealloyed layer on one surface and one end fixed will be deflected after prolonged relaxation because of a tensile stress generated at or near the dealloyed layer interface. The deflection and then the tensile stress increases with the depth of dealloyed layer and the vacancy concentration in the dealloyed layer. MD simulations for a single edge crack under mode I loading show that, no matter what the crack orientation is, edge dislocation is first emitted from the crack tip followed by large amounts of screw dislocations as loading proceeds, and the crack begins to extend when dislocation emission and motion reach a certain condition. The critical stress intensity for dislocation emission is decreased from KIe = 0:62 MPam1/2 with no dealloyed layer around the crack (to simulate loading in air) to K*Ie = 0:58 MPam1/2 with a dealloyed layer introduced around the crack (to simulate SCC), and the critical stress intensity for crack extending after emitting large amounts of screw dislocations is decreased from KIp = 1:14 to K*Ip = 1:0 MPam1/2 correspondingly. This indicated that a dealloyed layer-induced tensile stress can help the applied stress to enhance dislocation emission and crack extension, and results in SCC.

Uniform tetrapod-like zinc oxide (T-ZnO) nanorods were produced in bulk quantity by oxidation of Zn powders. Field-emission scanning electron microscope and transmission electron microscopy investigations showed that T-ZnO nanorods were high-quality nanocrystals. The length of legs of T-ZnO nanorods was 2-3 lm and the edge size of centering nucleus was 70-150nm. The growth of T-ZnO nanorods was controlled by a vapor-solid (VS) mechanism. UV emission peak at 380nm and green emission peak at 495 nm were observed at room temperature, which was assigned to the near band-edge emission and the deep-level emission, respectively.

Three-dimensions molecular dynamics (MD) method by employing the embedded atom method (EAM) potential is used to simulate the effect of stress corrosion-induced dealloyed layer existed on the surface of a crack of Cu2Au alloy on dislocation emission and crack propagation. The simulations show that the existence of a dealloyed layer enhances dislocation emission and crack propagation, i.e., decreases the critical stress intensity for dislocation emission from KIe = 0.62 MPam1/2 to KI*e = 0.556 MPam1/2 and that for crack propagating after emitting large amounts of dislocations from KIP = 1.14 MPam1/2 to KIP * = 1.06 MPam1/2. This indicates that dealloyed layer-induced tensile stress can help the applied stress to enhance dislocation emission and crack extension.

relation between average free path (M) and ductile deformation energy (γ) was proposed, and on the basis of it, a quantitative analysis was conducted for studying the effects of the structural parameters on fracture strength of WC-Co cemented carbides. The results show that, for different WC-Co cemented carbides with different cobalt contents, there exist different critical WC grain size Rc and critical free path of binder Mc. Rc and Mc act as the criteria that determine the growth behavior of crackles. When average free path of cobalt binder M < Mc, or WC grain size R < Rc, crackles will expand mainly across cobalt binder, which will result in intergranular fracture; when M > Mc or R > Rc, transgranular fracture will happen; when M = Mc or R = Rc, concurrence of intergranular fracture and transgranular fracture will take place. Rc and Mc will decrease with increasing of cobalt content, followed by increasing of fracture strength. The dimension of crackles in the circular fissure-breeding district is also a determinative factor to affect fracture strength of cemented carbides.

Experimental results show that the exchange coupling field (Hex) of NiFe/FeMn for Ta/NiFe/FeMn/ Ta multilayers is higher than that for spin-valve multilayers Ta/NiFe/Cu/NiFe/FeMn/Ta. In order to find out the reason, the composition and chemical states at the surface of Ta(12 nm)/NiFe(7 nm), Ta(12 nm)/NiFe(7 nm)/Cu(4 nm), and Ta(12 nm)/NiFe(7 nm)/Cu(3 nm)/NiFe(5 nm) were studied using x-ray photoelectron spectroscopy. The results show that no elements from lower layers float out or segregate to the surface in the first and second samples. However, Cu atoms segregate to the surface of Ta(12 nm)/NiFe(7 nm)/Cu(3 nm)/NiFe(5 nm) multilayers,ie., Cu atoms segregate to the NiFe/FeMn interface for Ta/NiFe/Cu/NiFe/FeMn/Ta multilayers.We believe that the presence of Cu atoms at the interface of NiFe/FeMn is one of the important factors which causes the exchange coupling field (Hex) of Ta/NiFe/Cu/NiFe/FeMn/Ta to be weaker than that of Ta/NiFe/FeMn/Ta.

The brittle fracture surfaces of Ti3AI+Nb and Ti3A1 were investigated with a scanning tunneling microscope (STM) under ambient conditions using a mechanically cut platinuin iridium alloy wire and electrochemically etched tungsten tips. The results show that the fracture surf'aces consist of cleavage steps with dimensions of the order of 2nm for Ti3AI+Nb and 60nm for Ti3AI, similar to cleavage surfaces observed by scanning electron microscopy. Some cavities between the microcleavage steps on the scale of a few nanometers were observed for Ti3AI+Nb. The reproducibility of the STM images under ambient conditions depends on the applied bias voltage. The quality of the STM images obtained via tungsten tips is better.