Defect and Diffusion Forum Vol. 391

Abstract: To verify the effect of 0.13 % vanadium addition (% in weight) on the wear resistance of a railroad wheel steel with 0.7 % carbon, twin-disc rolling-sliding test were performed. These two steels were named 7V and 7C. The test discs were analyzed to verify the superficial conditions and wear mechanisms using SEM (Scanning Electron Microscopy) and roughness measurements. After 100,000 cycles running it was concluded that without the presence of debris, the 7V steel presented a reduction in 35 % the mass loss compared to 7C steel. For the 7V steel, in the test without debris, the discs presented small cracks (10 μm long), very near (3 μm deep) the surface, but in the test with the presence of debris, the disc surfaces presented delaminated material and long cracks (100 μm long) faraway from surface (up to 72 μm deep). The presence of debris also increased the roughness parameters in 7V steel: average Rz jumped from near 6 μm in the steel without debris to near 26 μm in the steel with debris.

Abstract: In this study, titanium dioxide nanoparticles were synthesized for possible application in enhanced oil recovery. Sol-gel method was employed with titanium (IV) isopropoxide as the precursor. The prepared materials were characterized using Powder X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), High-Resolution Transmission electron microscopy (HRTEM) and Brunauer–Emmet–Teller (BET) techniques. Reaction parameter such as calcination temperature was varied during the preparation to obtain the uniform TiO₂ nanoparticles with the smallest particle size and high surface area. The results of study revealed that 400 °C is the optimum calcination temperature in preparing TiO₂ nanoparticles producing the smallest crystallite and particle sizes. XRD results indicated that the nanoparticles have formed anatase phase at 400 °C and achieved low crystallite size of 7.27 nm with the smallest average particle size of 19.53 nm through FESEM and HRTEM observations. BET analysis had achieved the highest surface area 103.64 m²/g.

Abstract: In the equilibrium processing methods the system Al-C does not show any solid solubility which means that carbon is not soluble in aluminum. In this work an investigation of mechanical alloying on system Al-C was presented to force the dissolution. Using different techniques such as the X-ray diffraction and scanning electron microscopy (SEM), it was proved the force of dissolution by studying the specters for different milling time and by flowing the evolution during annealing into a DSC. Furthermore, morphology of phases has been studied.

Abstract: Lithium-silicon compounds are promising materials as negative electrodes in Li-ion-batteries. The diffusion of Li in electrode materials is important for charging/discharging rates, maximum specific capacity and possible side reactions. In order to further the development of novel negative electrode materials for lithium-ion batteries, understanding the basic principles of atomic transport is of high importance. Thin Li_xSi films were investigated, which were produced by reactive ion-beam co-sputtering of segmented elemental Li and Si targets. Li tracer self-diffusion experiments were done on Li_xSi|⁶Li_xSi heterostructures and ⁶Li and ⁷Li isotopes depth profiles were analysed by secondary ion mass spectrometry before and after annealing. Diffusivities were extracted by comparing the experimental depth profiles to analytical solutions of the diffusion equation. The diffusivities for low Li concentrations x < 0.1 in Li_xSi follow the Arrhenius law between 140 and 325 °C with an activation energy of 1.4 eV. A trap-limited diffusion mechanism is suggested, comparable to hydrogen diffusion in hydrogenated amorphous silicon. In contrast, for x ≈ 0.4 complete isotope interdiffusion is observed directly after deposition at room temperature. These results indicate a significant acceleration of diffusion with increasing Li content as suggested in literature by theoretical calculations [1].

Abstract: Effects of cation nonstoichiomtry on crystal structure parameters, microstructure, and dielectric properties of ceramics (Na_0.5+xBi_0.5)TiO₃ and (Na_0.5-xBi_0.5)TiO₃ with Bi/Na<1 and of solid solutions [(Na_0.5Bi_0.5)_1-xK_x]TiO₃ and (Na_0.5Bi_0.5)(Ti_1-xMg_x)O₃ with x = 0 – 0.1 have been studied. Changes in the unit cell parameters and microstructure of the samples observed in ceramics prepared correlate well with both preparation conditions and radii of substituting cations. Ferroelectric phase transitions near ~ 400 K and ~ 600 K were confirmed ib the systems studied. Phase transitions near ~ 400 K demonstrate a pronounced relaxor behavior determined by the presence of polar regions in a nonpolar matrix. Besides, additional anomalies related to presence of relaxing dipoles formed by oxygen vacancies were observed on temperature dependences of dielectric permittivity at temperatures higher than 700 K. The results obtained confirmed that increase in nonstoichiometry lead to increase in ionic conductivity of the samples.

Abstract: The increase in waste generation affects the daily lives of millions of people. This study is about the waste of the polypropylene and oyster shell. Some of the present research focuses on strategic proactive measures incorporating life cycle analysis, and others on end-of-pipe, traditional waste management technology evaluations. In all recovery actions, economic benefits are related with direct and indirect gains. Decreasing the use of raw materials and waste materials, obtaining valuable spare parts and other financial opportunities like second hand market are among direct gains. The objective is meet the waste of the polypropylene and oyster shell and measure the structure of reverse logistic to these waste. The structure of the reverse logistic is to increaser amount more volume the waste and to be viable to treatment. The study intend approach the chain reverse of the waste and show the limitation and opportunities this process. Is hoped to find the results of the characterization and discover what ways is possible to application.

Abstract: For the most part, Surface tension is relying upon the force adjusted on a drop that is pending or hanging and inevitably is disengaged. Surfaces of fluids normally covered with what goes about as a tiny film. In spite of the fact that this evident film has little quality, it nevertheless acts like a thin membrane and resists being broken. This accepted to be the reason for the attractive forces between the atoms inside a given framework. All atoms are pulled in one to the next in extent to the result of their masses and conversely as the squares of the separation between them. Surface tension for both mineral and oil crude systems is investigated and the value was recorded. In addition, this value for mineral oil system showed higher value than foamy crude oil system, whereas foamy oil saturated methane crude oil system showed lower value than foamy oil saturated methane mineral oil. Surface tension in its general form is believed to have a significant feature in reservoir engineering calculations as well as in further studies related to improved oil production and in designing enhanced oil recovery plans. Moreover, CH₄, C₂H₆ and CO₂ oil systems investigated for the initial production, drawdown experiments. After the investigation, the behaviour is identical for almost one-day and two-days.

Abstract: Cu doped CeO₂ nanopowder was synthesized by hydrothermal process at 180°C for 2~10h. The average size and distribution of the synthesized Cu doped CeO₂ nanopowder was controlled by reaction times. The crystallinity of the synthesized Cu doped CeO₂ nanoparticles was investigated by X-ray diffraction (XRD). The morphology of the synthesized Cu doped CeO₂ nanoparticles was observed by FE-SEM. The specific surface area of the synthesized Cu doped CeO₂ nanoparticles was measured by BET. The crystal size of the synthesized Cu doped CeO₂ nanoparticles decreased with decreasing reaction times. The average size of the synthesized Cu doped CeO₂ nanoparticles was below 10nm and narrow, respectively. The shape of the synthesized Cu doped CeO₂ nanoparticles was spherical type. The specific surface area of the synthesized Cu doped CeO₂ nanoparticles increased with decreasing reaction times. Antibacterial properties of Cu doped CeO₂ were analyzed by MIC method. The synthesized Cu doped CeO₂ nanopowders showed antibacterial properties against E.coli and B.sub bacteria.

Abstract: No recrystallization of austenite, Tnr, has an important influence on the transformed phase fractions and the final crystallographic texture after hot deformation. This paper investigates the evolution of microstructure and texture components during hot-rolling in two austenitic region based on Tnr along with three different cooling trajectory and coiling in dual-phase steels and high strength low alloys steel. The recrystallization of the austenite, the austenite deformation followed by the austenite-to-ferrite transformation influence the final microstructure and texture in dual phase steels, have been examined by means of optical microscopy, X-ray diffraction (XRD) measurements. Recrystallized and deformed austenite have clearly different texture components and, due to the specific lattice correspondence relations between the parent austenite phase and its transformation products, the resulting ferrite textures are different as well.

Abstract: Over the past decade, Dual Phase steels are extensively used in the automotive industry to reduce the weight of the vehicles. The Fiber laser welding has been showing superior weld quality over other laser welding methods. DP 600 grade is most widely used grade among DP steels. Influence of heat input on microstructural and mechanical properties for the given thickness has been investigated. Widths of weld zone and Heat Affected Zone have decreased with decreasing the heat input. Rapid cooling rates in the fusion zone have resulted in martensitic structure and hardness also increased in proportional. Tensile test and notch tensile test of the welded joints have been confirmed that weld joints are stronger than that the base material. From the ensile test along the weld joint of all heat inputs, it has been observed that lower heat input weld joints have shown better properties over the others.