Solid State Phenomena Vols. 124-126

Abstract: In this paper, we present ab-initio study on the energy configurations, minimum energy path (MEP), and migration energy of neutral indium atom during diffusion in silicon crystal. From the ab-initio calculation of electronic structure, we could figure out the transient atomistic configurations during the indium diffusion in silicon. We found that the lowest-energy structure (Ins + Sii Td) consists of indium sitting on a substitutional site for stabilizing a silicon self-interstitial in a nearby tetrahedral position. The second lowest-energy structure was found to be Ini Td, the interstitial indium at the tetrahedral position. We employed the climbing image nudged elastic band (CINEB) method for estimating the MEP between the two local energy minima and the migration energy of the neutral indium, and obtained the MEP of 0.79 eV.

Abstract: Developments of tetrahedral amorphous carbon (ta-C) films having low residual compressive stress are essential to extend the applicability of the films. The annealing of the ta-C films was known to be an effective way for the reduction the stress of the films. However, the effects of annealing on the atomic structure of ta-C films have not been fully understood. The atomic structure changes by the annealing were studied using molecular dynamics simulation. The simulation showed that the annealing caused an increase of the atomic volume of ta-C film, which explained the stress reduction partially. However, the tendency of the stress reduction was different to high and low stress films. The annealing substantially reduced the stresses of high stress films compared to those of low stress films. Atomic structure analysis showed that the reason for the asymmetric stress reduction resulted from the relaxation of highly distorted bonds that existed in as-deposited films.

Abstract: In the study, an interlayer was observed in a nano-meter scale SiO2 overlayer on Si substrate by X-ray reflectivity(XRR) analysis and a new method is introduced for the XRR analysis of SiO2 ultra-thin films on Si substrate. The normalized reflectivity curves were analyzed by fitting with the calculated reflectivity curves which were also normalized with the same reference curves. The XRR analyses show that the variation of the positions of the thickness fringes in the measured reflectivity curve is caused by the interference effect from two oxide layers of different refractive indices and of different thicknesses with each other. The result indicates that there exists a SiO2 interlayer of a different refractive index between the SiO2 overlayer and the Si substrate. The analytical method used in the study determines the thickness of a ultra-thin SiO2 layer on Si with low uncertainty.

Abstract: We performed grand canonical Monte Carlo simulations on the series of MOFs, that are Metal-Organic Frameworks having various organic linkers and nanocube frameworks, to find out rational design and synthetic strategies toward efficient hydrogen storage materials. The adsorption amounts of hydrogen molecules showed diverse range according to the variation of parameter values. This indicated that the hydrogen adsorption was sensitive to the values of parameters corresponding to the non-bonding interactions. The optimization of the parameters was done to fit the experimental results at 77 K. After the parameterization of the potential function, we adopted this condition to predict the adsorption amount of hydrogen molecules on IRMOF-3, which has NH2 group as the substituent of hydrogen bonded to benzene ring. The calculation results showed good agreement with experimental adsorptions and we analyzed the adsorption sites of each MOF and the relationship between the adsorption characteristics and the hydrogen uptake capacity.

Abstract: A cold spray process is a relatively new process using high velocity metallic particles for surface modifications. Metallic powder particles which are injected into a converging-diverging nozzle are accelerated to supersonic velocities. In this study a comparative study was performed to figure out the effect of curvature on gas and particle flow in converging-diverging nozzle. And, the critical radius of curvature in converging and diverging section of nozzle and the behavior of the gas and particle flow were determined and calculated, respectively.

Abstract: It is quite difficult to accurately measure the mechanical properties of thin films. Currently, there are several methods (or application) available for measuring mechanical properties of thin films. Their properties, however, have been determined by indirect methods such as cantilever beam test and diaphragm bulge test. This paper reports the efforts to develop a direct strain measurement system for micro/nano scale thin film materials. The proposed solution is the Visual Image Tracing (VIT) strain measurement system coupled with a micro tensile testing unit, which consists of a piezoelectric actuator, load cell, microscope and CCD cameras. The advantage of this system is the ability to monitor the real time images of specimen during the test in order to determine its Young’s modulus and Poisson’s ratio at the same time. Stress-strain curve, Young’s modulus, yield strength and Poisson’s ratio of copper thin film measured using VIT system are presented.

Abstract: The squareness factor γ used to evaluates for criterion allowing quick estimation of the quality of NdFeB melt-spun powders on Stoner–Wohlfarth model. For the powder compaction of 6.4 g/cm3 mass density, the measured value γ=0.48 serves the evidence of the Stoner – Wohlfarth behaviour of the powder grains and the preparation conditions are optimal for producing Stoner – Wohlfarth particles. For the powder compaction of given mass densities the calibration curve of the squareness factor γ is presented. We can observe one more thing that for the ideal, full dense compaction of NdFeB Stoner – Wohlfarth particle the squareness factor γ can not be large than 0.53.

Abstract: Bottom ash generated from municipal solid waste incinerators in metropolitan areas contain calcium and aluminum compounds. As a result of a carbonation reaction, calcite and a calcium aluminum compound (Na6CaAl6Si6O24, Ca2Al2SiO7) as well as amorphous aluminum oxide can be found in bottom ash. Due to this, Cu and Pb leaching concentrations decrease via a carbonation process. Recently, the study of artificial carbonation reaction has been actively investigated, but most of these studies have been carried out utilizing an aqueous solution method with high water content. In this study, the carbonation reaction takes place in an aqueous environment, but does not occur on the surface of the particle. However, to cause the encapsulation of a particle with calcite, calcium aluminum compound and amorphous aluminum oxide, these must be formed on the surface of particle. Therefore in this study, a low water content encapsulation method of bottom ash from municipal solid waste incinerator was investigated with a view to immobilize Cu and Pb via a carbonation reaction. As seem in the results, the encapsulation effect appeared to be successful, with a water content of 20%.

Abstract: The catalytic filter, a ceramic filter supported SCR catalyst, is a promising material for treating particulates and NOX simultaneously. Recently, it is found that a SiC filter supported V2O5- WO3-TiO2 [commercial catalyst system] shows a reasonable SCR activity around 320 °C [1]. In order to improve its catalytic activity at low temperatures, the effects of Pt and MnOX addition on the catalytic filter are investigated. The macro-porous TiO2 film was firstly coated on the pore surface of SiC filter element using the solution composed of the preformed TiO2 particles (P25). Catalytic filters were prepared by the impregnation of TiO2 coated-SiC filter in the solution containing the catalyst components. The MnOX-added catalytic filter showed very wide temperature window from 150-340 °C, providing NX slip concentration less than 20 ppm for the treatment of 700 ppm NO at a face velocity of 2 cm/s. Pt added-catalytic filter shifted the optimum working temperature towards the lower temperatures (180-240 °C) compared to the one without Pt (280-330 °C). It is understood that MnOX in the catalyst system roles as the main catalyst component while Pt rose as a electron modification additive.

Abstract: To improve lipase activity and make the particulate carrier for practical application, lipase was conjugated to chitosan(Mwavg=80,000) by immine reaction. The lipase activity of conjugate was 93% of its initial activity at room temperature for 7 months, whereas the intact lipase activity decreased to 40%. And then, lipase-chitosan conjugate was intercalated within porous silica. The composite was characterized by X-ray diffraction, scanning electron microscopy, thermo gravimetric analysis. The Pore size was regulated in the range of 5~15nm. The maximum enzyme activity of lipase-chitosan conjugate needs the structure with 15nm pore of mesoporous silica. The resultant composite was found to have the free flowing property and keep up inner lipase activity.