Defects and Diffusion in Ceramics XI

Paper Title Page

Authors: Aman Deep Acharya, Girjesh Singh, S.B. Shrivastava
Abstract: The Diffusion Trapping Model has been used to obtain the positron annihilation Doppler broadening lineshape parameter in ZnO and O+, B+, N+, Al+ implanted ZnO films. The concentration of vacancy clusters is found to be related to the atomic number and the fluence of the implanted ion. The S-parameter is found to be largest in the case of implantation of Al+ ions and is minimum for the implantation of B+ ions. Thus, the vacancy clusters are found to be largest in the case of Al+ implantation. The calculated results have been compared with the experimental value.
Authors: S.A. Aly
Abstract: The optical properties of tungsten oxide (WO3) films prepared by DC sputtering on unheated glass substrates with different film thicknesses have been studied. The structural characteristics of the samples were investigated using X-ray diffraction. The optical properties of the prepared films were studied by transmittance and reflectance measurements, and the integrated transmittance (TUV, TVIS, and TNIR) and absorption (AUV, AVIS, and ANIR) in UV, VIS and NIR regions. The integrated UV absorption and transmittance are varied with the film thicknesses, also, no remarkable change in VIS and NIR regions was observed. The dependence of refractive index as well as extinction coefficient on wavelength was also reported. The energy gap was calculated and is located around 3.25 eV.
Authors: Jian Ling Li, Decai Li
Abstract: In this paper, we first analyzed the nano-magnetic fluid composition and properties. Then we studied the characteristics of nano-magnetic fluid magnetization and magnetization mechanism. In addition, we also studied the nano-Fe3O4 magnetic particle size and surface modification effect on the magnetic properties of magnetic fluids. Nano-magnetic fluid is a new type of liquid nano-composite functional material. It also has magnetism and mobility, and therefore it has many unique properties and a wide range of applications. Nano-magnetic fluid magnetization characteristic is one of its main properties, its performance and application of magnetic fluid play a decisive role.
Authors: Oleg Velichko, Olga Burunova
Abstract: Simulation of arsenic clustering in Si at a temperature of 750 degrees Celsius has been carried out. It has been shown that considering the formation of singly or doubly negatively charged clusters that incorporate one or two arsenic atoms and point defects, one obtains a good fit to the measured values of electron density. It is supposed that we have the initial stage of clustering, when the concentration of complexes with one arsenic atom incorporated is high enough and the diffusion of these mobile particles provides for the formation of more stable clusters incorporating two arsenic atoms.
Authors: Hai Li Yang, Yu Zhu Zhang, Yun Gang Li, Guo Zhang Tang, Kuo Jia
Abstract: A Si diffusion layer on grain-oriented low-silicon steel substrates was produced by pulse electrodeposition in KCl-NaCl-NaF-SiO2 molten salt and the effect of current density upon the composition and microstructure of the siliconized layer was investigated. The results showed that by glow discharge spectrometry (GDS), the change of Si content of siliconized layers was similar in the range of 20-60 mA/cm2. Si content in the surface was maximum, and then dropped sharply within the surface layer (< 7 m). The Si content remained nearly constant in the middle part of the siliconized layer. The content of Si near to the substrate decreased relatively slowly. The Si content in the surface and the layer thickness increased with increasing current density. Cross-sectional observations revealed that the Si diffusion layers had a two-layer structure: the top layer composed of columnar grains grown perpendicularly to the substrate surface and a transition layer with equiaxed grains was close to the substrate. In addition, the thickness of the layer was too small when the current density was 20 mA/cm2, while the layer became more porous as the current increased from 40 to 60 mA/cm2 according to SEM observations. The optimum current density for deposition was 30 mA/cm2.
Authors: M.A. Abdel-Rahman, Alaa Aldeen Ahmed, Emad A. Badawi
Abstract: The aim of this work was to study the resistance of this type of alloy to quenching. Hardness measurements can be defined as macro-, micro- or nano- scale, according to the forces applied and the displacements obtained. This effect can also be studied using a nuclear, (PALT): positron annihilation lifetime, technique [1]. Microhardness is the hardness of a material, as determined by forcing an indenter such as a Vickers or Knoop indenter into the surface of the material under a 15 to 1000gf load; the indentations are usually so small that they must be measured using a microscope. These samples were quenched at different temperatures ranging from 50 to 500oC. We studied the effect of the quenching temperature upon the hardness measurements. We also studied this variation via the positron annihilation (lifetime) parameter. It is clear from the Vickers hardness that 1050 has the lowest value of Hv, while 6063 is higher and 6066 has the highest values of Hv. Also we could observe ( recognize) that the Hv (number) is reduce as a function of temperature (6066) but for (1050) and (6063) there is no observation of a variation in Hv (number) as a function of quenching temperature. The same observation was also made for 1050, 6063 and 6066 via the lifetime measurements. Here, 6063, 6066 give higher values than 1050. It is clear that the data from both techniques (positron annihilation lifetime and Vickers hardness) for 1050 ingot Al gives lower values of both parameters for Hv and lifetime technique. While Hv for 6066 is higher than the values of 6063 alloy at the same quenching temperature. Using the lifetime technique, one cannot distinguish between the 6063 and 6066 alloys. The applied force has no real effect upon the levels of the hardness values. Also, alloys 6066 and 6063 were defined as heat-treatable alloys but 1050 is not a heat-treatable alloy. The Hv of the 1050 is not affected by the changes in quenching temperature. Alloy 6066 heat-treatable alloy is more affected by the heat treatment than is 6063 alloy, and this is related to the structure of the precipitates in these alloys since 6066 alloy has much more Si and Mg than does the 6063 alloy. The Hv values vary from 14 to 23.9 for 6063 alloy and from 15.7 to 69.8 for 6066 alloy; in comparison with ingot alloy (1050) where it varies from 10.4 to 18.6.
Authors: G.P. Tiwari, V.D. Alur, E. Ramadasan
Abstract: This paper presents hydrogen concentration profiles in notched tensile test specimens which have been charged electrolytically with hydrogen, with and without the application of a tensile load. A standard 8mm ASTM tensile specimen, extended at one end, is employed. This extended portion serves as a cathode during electrolytic charging. In order to facilitate the application of a load during charging, the specimen is firmly held in a specially designed fixture with the help of threads that are provided on each end of the gauge section. A notch is provided, in the gauge section, to create a stress gradient. At the end of charging, 3mm-thick disc specimens are cut from the specimen and analyzed for their hydrogen content using the inert gas fusion technique. The results show that the presence of tensile stress enhances the rate of hydrogen ingress as well as the net hydrogen concentration in the matrix. In the absence of stress, diffusion down the concentration gradient controls the hydrogen distribution within the specimen. Surface area plays an important role in the accumulation of hydrogen across any section in the specimen. If the available surface area is greater, the local hydrogen concentration is enhanced. Sheathing of the charging section with a 3mm-thick jacket of pure uranium causes a significant improvement in the hydrogen concentration along the entire length of the specimen. However, the presence of a 100µm-thick coating of titanium in the charging section of the specimen did not cause any significant change in the hydrogen concentration of the specimen. The main advantage of this charging procedure is that the test portion of the specimen does not come into contact with the electrolyte, and the hydrogen reaches the test portion of the specimen via diffusion through the matrix. Hence, microstructural damage to the specimen during the entry of high-fugacity hydrogen into the matrix is avoided.
Authors: A. Lodder
Abstract: The driving force on an ion in a metal due to an applied electric field, called the electromigration force, is built up out of two contributions, a wind force and a direct force. The wind force is due to the scattering of the current carrying electrons off the ion. The direct force works on the effective charge of the ion. In the present work we concentrate on the direct force on a migrating proton embedded in an electron gas. For this force a sign change is obtained as soon as a bound state is formed. In recent calculations hardly a sign change was seen, although a bound state was found in a self-consistent-potential for lower electron densities. Here we show that a supplementary term shows up, as soon as one accounts for the bound state explicitly. By this the problem has been solved regarding a possible lack of completeness of the published formalism. The results presented are based on square-well model potentials. By using different depths it is possible to show results for potentials without a bound state and accommodating one bound state.

Showing 1 to 8 of 8 Paper Titles