离子束溅射沉积Co膜光学特性的尺寸效应研究

本文采用离子束溅射沉积了不同厚度的Co膜 ,利用Lambda 90 0分光光度计 ,对不同厚度的Co膜从波长为 310nm到 130 0nm范围测量了薄膜的反射率和透射率。选定波长为 310、35 0、4 0 0、4 30、5 5 0、6 32、80 0、12 0 0nm时对薄膜的反射率、透射率和吸收率随薄膜厚度变化的关系进行讨论。实验结果显示 ,Co膜的光学特性都有明显的尺寸效应。对在可见光范围内同一波长时的反射率和透射率随薄膜厚度变化关系的实验结果作于同一图上 ,发现反射率曲线与透射率曲线都有一个处在网状膜阶段的交点 ,这个交点对应的厚度作为特征厚度 。

Effect of deposition parameters on micro-and nano-crystalline diamond films growth on WC-Co substrates by HFCVD

The characteristics of hot filament chemical vapor deposition（HFCVD） diamond films are significantly influenced by the deposition parameters, such as the substrate temperature, total pressure and carbon concentration. Orthogonal experiments were introduced to study the comprehensive effects of such three parameters on diamond films deposited on WC-Co substrates. Field emission scanning electron microscopy, atomic force microscopy and Raman spectrum were employed to analyze the morphology, growth rate and composition of as-deposited diamond films. The morphology varies from pyramidal to cluster features with temperature decreasing. It is found that the low total pressure is suitable for nano-crystalline diamond films growth. Moreover, the substrate temperature and total pressure have combined influence on the growth rate of the diamond films.

Erosion-corrosion behavior of Pd-Co and Pd-Cu films on 316L stainless steel in simulated PTA slurry environment

Pd-Co films with the Co content varying from 21.9% to 34.62%（mole fraction） and Pd-Cu（5% Cu, mole fraction） film were electrodeposited on 316 L stainless steel, and the erosion-corrosion resistance of the Pd-Co and Pd-Cu plated samples in a simulated boiling pure terephthalic acid（PTA） slurry environment was studied with methods of mass loss test, polarization measurement and scanning electron microscopy（SEM）. Under the static state condition, both the Pd-Cu and Pd-Co plated samples exhibit good corrosion resistance and the Pd-Cu film behaves slightly better. However, with increasing the stirring speed, the corrosion rate of the Pd-Cu plated samples increases obviously while that of the Pd-Co plated samples shows only slight increase. Higher microhardness and lower surface roughness of Pd-Co film than those of Pd-Cu film, as well as good corrosion resistance, may be the main reasons for better erosion-corrosion resistance in the strong reductive acid plus erosion environment.

Co evolutions for WC-Co with different Co contents during pretreatment and HFCVD diamond film growth processes

Systematical researches were accomplished on WC-Co with different Co contents(6%,10%and 12%,mass fraction).Based on the XPS and EDX,from orthogonal pretreatment experiments,it is indicated that the acid concentration,the time of the acid pretreatment and the original Co content have significant influences on the Co-removal depth(D).Moreover,the specimen temperature,original Co content and Co-removal depth dependences of the Co evolution in nucleation,heating(in pure H2 atmosphere)and growth experiments were discussed,and mechanisms of Co evolutions were summarized,providing sufficient theoretical bases for the deposition of high-quality diamond films on WC-Co substrates,especially Co-rich WC-Co substrates.It is proven that the Co-rich substrate often presents rapid Co diffusion.The high substrate temperature can promote the Co diffusion in the pretreated substrate,while acts as a Co-etching process for the untreated substrates.It is finally found that the appropriate Co-removal depth for the WC-12%Co substrate is 8-9μm.

Diffusion of H2, CO, N2,O2 and CH4 Through Nanoporous Carbon Membranes

Diffusion of pure H2, CO, N2,O2 and CH4 gases through nanoporous carbon membrane is investigated by carrying out non-equilibrium molecular dynamics （NEMD） simulations. The flux, transport diffusivity and activation energy for the pure gases diffusing through carbon membranes with various pore widths were investigated. The simulation results reveal that transport diffusivity increases with temperature and pore width, and its values have a magnitude of 10^-7 m^2·s^-1 for pore widths of about 0.80 to 1.21 nm at 273 to 300 K. The activation energies for the gases diffusion through the membrane with various pore widths are about 1-5 kJ·mol^-1, The results of transport diffusivities are comparable with that of Rao and Sircar （J. Membr. Sci., 1996）, indicating the NEMD simulation method is a good tool for predicting the transport diffusivities for gases in porous materials, which is always difficult to be accurately measured by experiments.

Substrate temperature dependence of chemical state and magnetoresistance characteristics of Co–TiO2 nanocomposite films

Co−TiO2 nanocomposite films were prepared via magnetron sputtering at various substrate temperatures.The films comprise Co particles dispersed in an amorphous TiO2 matrix and exhibit coexisting ferromagnetic and superparamagnetic properties.When the substrate temperature increases from room temperature to 400℃,Co particles gradually grow,and the degree of Co oxidation significantly decreases.Consequently,the saturation magnetization increases from 0.13 to 0.43 T at the same Co content by increasing the substrate temperature from room temperature to 400℃.At a high substrate temperature,conductive pathways form among some of the clustered Co particles.Thus,resistivity rapidly declines from 1600 to 76μΩ·m.The magnetoresistive characteristic of Co−TiO2 films is achieved even at resistivity of as low as 76μΩ·m.These results reveal that the obtained nanocomposite films have low Co oxidation,high magnetization and magnetoresistance at room temperature.

Magnetization and coercivity in Co/Pt multilayers with constant total Co layer thickness

Co/Pt multilayers with perpendicular anisotropy were deposited using a dc magnetron sputtering system under high vacuum.Magnetization process was investigated by the measurement of magnetic components parallel and perpendicular to the applied field.A dependence of the coercivity of Co/Pt multilayers on the Co layer thickness was reported,in which the total thickness of Co layers kept constant.It is observed that the coercivity increases with the increment of Co layer thickness.For the samples with the same Co layer thickness while different total Co layer thickness,the coercivity first increases and then decreases with the increase of the total thickness of Co layers.This effect could be attributed to the competition between the reduction of HC related to incoherent reversal and the step-up of HC contributed by the magnetic polarization of Pt atoms at the interface of Co and Pt layers during magnetization reversal.The results show that the change of the coercivity is strongly related to the Co layer thickness,but not the total thickness of Co layers.The dependence of the coercivity on the angle between an applied field and the easy axis shows that the nucleation mode is dominant in magnetization reversal process of the samples.

Coculture of elongated neuron axon with poly (D,L-lactide-co-glycolide) biomembrane in vitro

Objective: To elongate human nerve axon in cultu re and search for suitable support matrices for peripheral nervous system trans plantation. Methods: Human embryo cortical neuronal cells,seeded on poly ( D,L-lactide-co-glycolide) (PLGA) membrane scaffolds,were elongated with a se lf-made neuro-axon extending device. The growth and morphological changes of n euron axons were observed to measure axolemmal permeability after elongation. Ne urofilament protein was stained by immunohistochemical technique.Results: Human embryo neuron axon could be elongated and cultur ed on the PLGA membrane and retain their normal form and function. Conclusions: Three dimensional scaffolds with elongated neuron axon have the basic characteristics of artificial nerves,indicating a fundement al theory of nerve repair with elongated neuron axon.