Papers by Keyword: Film

Abstract: A novel route to prepare hydrophobic mesoporous SiO2 films is reported in this paper. A two step process involving tetraethyl orthosilicate (TEOS) as a precursor and cetyltrimethyl ammonium bromide (CTAB) as a template prepared SiO2 sol catalyzed by hydrochloric acid. The films are prepared by dip-coating process. It has been found that the films have low dielectric constant and good mechanical properties. Preliminary results present a very positive prospective for intermetal dielectric applications.

Abstract: MoSx/Au films about 1μm in thickness were deposited on 9Cr18 steel substrate discs by magnetron sputtering method. The chemical composition and chemical states of the as-deposited films were determined by X-ray photoelectron spectroscopy (XPS). The effect of high loads (15~50N) on tribological behaviors of the MoSx/Au films in vacuum was studied by pin-disc wear tests. The pins were made of 2Cr13 steel. The morphologies of as-deposited films and wear track were observed by scanning electron microscopy (SEM). The results show the friction coefficient and the wear life of the films decrease with the increase of load at a sliding velocity of 1.6 m•s-1. The wear life of the films at 15N can reach 2000m. The friction process of the films can be divided into four stages based on typical variation of friction coefficient with sliding time in vacuum, e.g. running-in stage, steady stage, severe damage stage and thorough wear stage. In steady stage, the films peel in small pieces and the abrasion mechanism appears delamination wear. When the film was damaged thoroughly, the wear test carried out between 2Cr13 pin/9Cr18 disc. The adhesive wear becomes the dominant abrasion mechanism.

Abstract: The titania films codoped by aluminum and nitrogen have been prepared by cathodic vacuum arc with titanium aluminum alloy target in an O2/N2 gas mixture. The films were characterized by X-ray diffraction (XRD), X-rayphotoelectron spectra (XPS) and ultraviolet-visible spectra (UV–vis). The results showed that all films annealled were crystalline anatase structure with a (101) preferential orientation, XPS revealed that Al and N were successfully doped into the lattice of TiO2. The optical properties of the films revealed that the spectrum response of the Al, N-codoped TiO2 films extended from the UV region to the visible region. The absorption of the Al, N-codoped TiO2 film in the visible region(>400 nm) was enhanced, compared with the pure TiO2 film and N-doped TiO2 film. The Al, N-codoped TiO2 film showed the best photocatalytic activities for the oxidative destruction of Acid Fuchsin (AF) under visible light irradiation.

Abstract: Electroplating was employed to prepare Cu films on Fe substrates and Ni substrates. The average internal stresses in Cu films were measured in situ by cantilever beam test. The distribution of the internal stresses in Cu films was investigated. The results show that the average internal stresses and the distributed internal stresses in Cu films decrease abruptly with the increase of film thickness when the films are thinner. The interfacial stresses in Cu films are very large and growth stresses are very small. The average internal stresses in Cu films, which were caused by the adjustment of the electron densities at either side of the interface, were calculated roughly using a modified Thomas–Feimi–Dirac electron theory. For the same substrate and the same film, the theoretical value of the average internal stress in film is about equal to the experimental value. It shows that the theoretical calculation model of internal stress is of accuracy.

Abstract: The sintering of thin films is widely used for surface coatings and because of its technological importance has generated extensive research interest. During the sintering process, the thin film is constrained by the substrate, which generates considerably high levels of stresses. Crackings are often observed and are considered as one of the major problems of the surface coating technique. This paper has proposed a new numerical method in order to tackle the traditional difficulties in simulating multi-crackings during constrained sintering. Main features of the present method include: (i) the material data is represented by an anisotropic constitutive law, (ii) a new numerical scheme is developed for the crack initialization and growth based on the material point method, (iii) the 3D viscous film shrinkage model is solved by using a dynamic FE scheme, and (iv) the random nature of the initial green body density is represented by statistical variabilities. It is shown that the model proposed by the present paper is capable for the nucleation and propagation of multi-cracks in a straightforward manner. Cracking patterns are shown to be consistent with experimental understandings. The focus of the paper is on the numerical issues and demonstrating the capacity of the model.

Abstract: We calculate the temperature of excited plasma, found that will be enhanced with pulse energy increased. The delay time and the pulse energy were very important to the LIBS signal and define the -0.5μs was very suitable to this experiment, determined the intensity of emission spectra was linear to the pulse energy when the delay time was fixed. By change the delay time, got the emission of bivalence ionization of Zn was just less than 500ns.At last, we had researched the effect of element concentration and the thickness of film on signal intensity. When the concentration of Al being increased from 2.5% to 5%, the intensity of signal enhanced double. At the same time the content of Zn being decreased from 78% to 76%, the intensity of signal had just no change.

Abstract: Using La(NO3)3•nH2O and Ni(CH3COO)2•4H2O as starting materials, alcohol mixed with methoxyethanol as solvent, the LaNiO3 (LNO) solution was prepared. Using this solution, conducting LNO films with sheet resistance of 10Ω were obtained. XRD and HRTEM indicate that the LNO films are epitaxially grown on LaAlO3 (LAO) substrates. Using Pb(CH3COO)2•3H2O, La(NO3)3•nH2O, Ti(OC4H9)4, Zr(OC4H9)4 as starting materials, the PZT films were prepared on the LNO films. The PZT films are c-oriented. The as-prepared PZT film has a remanent polarization of 34.7µC/cm2, superior to the PZT film with random orientation and a remanent polarization of 18.4µC/cm2 prepared on ITO/quartz substrate.

Abstract: In the present study, we try to prepare hydrophobic film coated on stainless steel as the bipolar plate for polymer electrolyte membrane fuel cell (PEMFC). Magnetron sputtering (MS) was adoped to prepare the Cr3Ni2/Cr2N multi-layer coated on stainless steel. The corrosion resistance and electrical conductance of the coated substrate were tested. The water contact angles were measured. The film exhibits improved corrosion resistance and electrical conductance. The corrosion current is 0.58µA.cm-2 and the contact resistance at 240N.cm-2 is 8.5mΩ.cm2. Meanwhile, it is a kind of hydrophobic film with water contact angle of 107o. The performance shows strong dependance on microstructural characteristics. The nano-protrudes on the SS304/Cr3Ni2/Cr2N surface result in the film with hydrophobic property, just like the effect of lotus surface.

Abstract: Relaxation and local structure changes of a molten TiAl alloy film during quenching have been investigated by molecular dynamics simulations within the framework of embedded atom method (EAM). The details of atom motions are analyzed using mean square displacement (MSD). Accompanying with massive atom rearrangement at a certain quenched temperature and time, local structural patterns are identified by decomposing peaks of pair distribution functions (PDFs) according to the pair analysis(PA) technique. The relaxation factor clearly reveals two relaxation processes involving in slow relaxation and fast relaxation of the quenched liquid TiAl film. Concerning the studied film, the obtained results reveal how quenched temperatures affect local structure changes.

Abstract: In this work, we report the directed self organization of multilayer thin film devices with colloidal nanoparticles through Layer-by-Layer (LbL) technique [1]. Self-organization of nanoparticles into assemblies to create novel nanostructures is getting increasing research attention in microelectronics, medical, energy and environmental applications. Directed self-organization of nanoparticles [2] into multilayer thin films were achieved by LbL growth through the interaction of oppositely charged of colloidal nanoparticles on substrates of any kind and shapes. Multilayer thin film devices were fabricated using multilayers of gold (conducting) nanoparticles separated by a dielectric nanoparticulate layer of zinc sulphide. The thin films obtained have been studied extensively and the changes in surface morphology, the optical absorption characteristics, thickness, uniformity, adhesion, and conduction behavior are reported. Current voltage (I-V) characteristics of multilayer devices with an increasing number of deposition cycles show an initial current blockade until an onset voltage value, which increases linearly upon the additional layers stacked in devices [3]. A conductive behavior of the device was observed upon exceeding the onset voltage. Moreover, I-V behavior showed that the conduction onset voltage increases linearly depending on the numbers of layers in the final device controlled by the deposition cycles. Systematic I-V characteristics in the forward and reverse biased conditions demonstrated rectifying behaviors in the onset of conduction voltage which makes these films attractive for future electronic device applications.