Procedia Materials Science最新文献

This paper deals with the optical modeling of thin hydrogenated microcrystalline silicon films grown on flexible low-cost iron-nickel alloy substrates by low-temperature (175 °C) plasma-enhanced chemical vapor deposition. This material serves as the absorber in solar cells and hence it has direct impact on the resulting solar cell performance. Since the crystallinity and the material quality of hydrogenated microcrystalline silicon films evolve during the growth, the deposited film is inhomogeneous, with a rather complex structure. Real-time spectroscopic ellipsometry has been used to trace the changing composition of the films. In-situ ellipsometric data taken for photon energies from 2.8 to 4.5 eV every 50 seconds enabled us to study the evolution of the monocrystalline silicon fraction of the hydrogenated microcrystalline silicon films.

In order to understand the effect of the difference in chemical composition and microstructure of bond coat (BC) layer on delamination properties, pushout tests were performed on modeled air plasma-sprayed thermal barrier coatings (APS-TBCs). Nickel-platinum-aluminides (Ni-Pt-Al), hafnium modified nickel-platinum-aluminides (Ni-Pt-Al-Hf) and NiCoCrAlY alloys were used as BC alloy. Hafnium and aluminum oxide were formed in needle like shape when the Ni-Pt-Al-Hf alloy was used. Vickers hardness of BC alloy decreased up to 50 hours heat exposure and then increased with increasing heat exposure time. Interfacial delamination toughness increased and then decreased with the increase in heat exposure time.

In order to simplify the structural integrity assessment of double cracked stainless steel piping, plastic collapse stress of asymmetric double notched pipes subjected to combined tension and bending was investigated. The experimental plastic collapse stress of the asymmetric double notched pipe is compared with the theoretical plastic collapse stress of the single notched pipe. The experimental plastic collapse points were over the theoretical collapse limit curve. The integrity of asymmetric double cracked stainless steel pipes subjected to combined tension and bending can be evaluated simply and conservatively using the theoretical plastic collapse stress of the single notched pipe.

To analyze the images of structures, we often detect the edges of grains. Since the grain boundaries are not so clear, it takes a lot of time to detect them, manually. Here, we present a support method to detect the edge from structure images. We make blurry images clear by solving non-linear partial differential equations numerically. Combining ordinary image analysis methods, we can detect edges of grains easily. In this note, we introduce the results of our method and discuss the possibility of this method.

Presented paper introduces an innovative principle of fatigue life assessment suggested for WWER nuclear power plants. The subject of this work is to take into account the corrosion environment influence in actual methodology of low-cycle fatigue (LCF) assessment and prediction. The aim of this paper is to summarize the current status of the Czech proposal of corrosion fatigue assessment and prediction. The first project focused on base steel materials, which are used in primary circuit of WWER-440, started in 2010. The basic idea of Czech environmental fatigue correction factor has been introduced on international PVP conference in 2013. The new project linked to the previous one is focused on the additional area of welding joints. Theoretical base is completed by experimental verifications of proposed environmental correction factor. The subject of actually running theoretical-experimental program covers similar metal welds of austenitic stainless steel 08CH18N10T and results will be available in 2015. Moreover LCF tests in corrosion environment of dissimilar metal welds are under preparation. Experimental work is based on LCF strain-controlled tests in primary water environment of WWER-440.

Two organic compounds (naphthalene and formaldehyde) were investigated for their sorption properties on to multiwall carbon nanotubes in original state and purified using acid treatment. Nice enhancement of sorptive ability was observed after nanotube purification. Smaller organic molecule was adsorbed in higher weight percentage (reaching 30 wt.%) than naphthalene (approx.13 wt.%). Molecular modeling confirmed adsorption centers of organics on carbon nanotubes being located on the outside area or close to center of nanotube, then having the lowest energy of adsorption.

The paper deals with minor phase evolution in a Cu – bearing grain oriented electrical steel during the following production steps of the AlN + Cu industrial processing route: hot rolling of slabs, the 1^st cold rolling + decarburization annealing and the 2^nd cold rolling + slow laboratory heating to the temperature of primary recrystalization. Thermocalc calculations were used for prediction of the effect of copper additions on equilibrium phases in the temperature interval 450 – 850 °C. Minor phase evolution was studied by using transmission electron microscopy. Hot rolling was accompanied by dissolution of copper rich sulfides. Slow cooling of coils after hot rolling resulted in precipitation of Fe₃C along ferrite grain boundaries. Decarburization annealing after the 1^st cold rolling was accompanied by dissolution of Fe₃C, re-precipitation of fine Cu₂S, (Mn,Cu)S and very intensive precipitation of nitrides (AlN and Si₃N₄). Slow laboratory heating after the 2^nd cold rolling to the onset of primary recrystallization (620 °C) did not cause precipitation of any other minor phase. No copper rich metallic particles (ɛ - Cu) formed during the production steps investigated. Most fine particles of inhibition phases formed during decarburization annealing.

In this paper, the effects of the existence of inclusion or missing cells on the overall in-plane mechanical behavior of micro-lattice plate is discussed by using the numerical finite element analysis. The micro-lattice plate can be manufactured using the selective metal laser melting technique, and various shapes of its micro-architecture can be easily produced even if there are non-uniform cells. In particular, effects of boundary condition of the plate's edges, cell's geometry and the shapes of non-uniform region on the initial stiffness and plastic collapse strength are investigated. Also, based on the numerical results, empirical equations for estimating these mechanical properties are proposed.

If subsurface flaws are detected that are close to component free surfaces, flaw-to-surface proximity rule is used to determine whether the flaws should be treated as subsurface flaws as is, or transformed to surface flaws. However, specific factors for the proximity rules on transforming subsurface to surface flaws differ among fitness-for-service codes. The objective of the paper is to reveal the proximity factor from the stress intensity factor interaction between the subsurface flaw and the free surface.

The non-magnetic TiO₂ powder and magnetically modified TiO₂ powder were employed for the sorption experiments. FeSO₄.7H₂O was used for synthesis of magnetically responsive TiO₂. The non-magnetic and prepared magnetic materials were characterized by scanning electron microscopy and X-ray diffraction methods. The particle size and specific surface area were determined. A detailed study of the adsorption process performed using batch adsorption experiments was carried out with various concentrations of lead ions and contact time. A flame atomic absorption spectrometer was used for determination of Pb²⁺ ions concentration in solution. Adsorption process has been modeled by the Langmuir and Freundlich isotherms using linear and non-linear regression. The results showed that the adsorption of Pb²⁺ ions on the magnetic and non-magnetic TiO₂ particles occurred in a monolayer. Presence of magnetic iron oxides particles on the surface of sorbents increased the adsorption rate, and increased the maximum amount of adsorbed Pb²⁺ ions per mass in comparison with adsorption on the non-magnetic TiO₂ particles. The magnetically modified TiO₂ particles allow magnetic separation of the sorbents with already adsorbed ions of pollutants.