Diffusion in Solids and Liquids IV

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Authors: Andreas Öchsner
Abstract: The presence of atomic oxygen at internal metal-ceramic oxide interfaces signi¯- cantly affects the physical properties of the interfaces which in turn affects the bulk properties of the material. The application of numerical tools such as the ¯nite element method requires some conceptional considerations if results from different finite element meshes of methods should be comparable. This paper summarises some of these thoughts in order to provide the right basis for comparative investigations.
Authors: Seyed Mohammad Hossein Hosseini, Markus Merkel, Christian Augustin, Andreas Öchsner
Abstract: This paper investigates the thermal properties of a new type of hollow sphere struc- tures. For this new type, the sphere shell is perforated by several conical holes in order to open the inner sphere volume. The effective thermal conductivity of perforated sphere structures in a primitive cubic arrangement is numerically evaluated for different material combinations and compared to sphere structures without perforation.
Authors: Irina V. Belova, Graeme E. Murch, Thomas Fiedler, Andreas Öchsner
Abstract: In this paper, we review the recent developed method based around lattice-based random walks and the Monte Carlo method. This method, which is now called the Lattice Monte Carlo method, permits complex phenomenological problems in diffusion, thermal conductivity and elasticity to be addressed. It is shown how the effective mass diffusivity, thermal diffusivity/thermal conductivity and the bulk modulus in composites can be calculated and also how concentration profiles and temperature profiles can be determined in situations where the diffusivity depends on position and concentration and the thermal conductivity depends on position and temperature respectively.
Authors: Elena V. Levchenko, Alexander V. Evteev, Irina V. Belova, Graeme E. Murch
Abstract: . In this paper, carbon diffusion in cementite is studied by molecular dynamics simulation. An assumption that carbon-carbon interaction occurs only indirectly via neighbouring iron atoms is used. An interstitial mechanism of carbon diffusion in cementite is revealed. The principal tracer diffusion coefficients and activation parameters of carbon diffusion in cementite are calculated for the temperature range 1223-1373 K and compared with the available published experimental data.
Authors: Carlos Roberto Grandini, Luciano Henrique de Almeida, Renata Abdallah Nogueira, Terlize Cristina Niemeyer
Abstract: Titanium alloys are excellent implant materials for orthopedic applications due to their desirable properties, such as good corrosion resistance, low elasticity modulus, and excellent biocompatibility. The presence of interstitial elements (such as oxygen and nitrogen) causes strong changes in the material’s mechanical properties, mainly in its elastic properties. Study of the interaction among interstitial elements present in metals began with Snoek’s postulate, that a stress-induced ordering of interstitials gives rise to a peak in the mechanical relaxation (internal friction) spectra. In the mechanical relaxation spectra, each species of interstitial solute atom gives rise to a distinct Snoek’s peak, whose temperature and position depend on the measurement frequency. This effect is very interesting because its peculiar parameters are directly related to the diffusion coefficient (D) for the interstitial solute. This paper presents a study of diffusion of heavy interstitial elements in Ti-35Nb-7Zr-5Ta alloys using mechanical spectroscopy. Pre-exponential factors and activation energies are calculated for oxygen and nitrogen in theses alloys.
Authors: Carlos Roberto Grandini, Emerson Haruiti Kamimura, José Roberto Severino Martins, Hugo Ricardo Zschommler Sandim, Odila Florêncio
Abstract: Metals with a bcc crystalline structure such as Ti-13V-11Cr-3Al alloys have their physical properties significantly changed through the addition of interstitial elements such as oxygen and nitrogen. These metals can dissolve substantial amounts of interstitial elements forming solid solutions. Mechanical spectroscopy measurements constitute a powerful tool for studying interactions of these interstitial elements with other elements that make up the alloy. From these measurements, it is possible to obtain information regarding diffusion, interstitial concentration, interaction between interstitials, and other imperfections of the crystalline lattice. In this paper, Ti-13V-11Cr-3Al alloys with several amount of nitrogen, in a solid solution, were studied using mechanical spectroscopy (internal friction) measurements. The results presented complex internal friction spectra which were resolved in a series of constituent Debye peaks corresponding to different interactions and interstitial diffusion coefficients. Pre-exponential factors and activation energies were calculated for nitrogen in theses alloys.
Authors: A.N. Dmitriev, Yu.A. Chesnokov
Abstract: The proposed balance logic-statistical model of the blast furnace process is based on the use of material and thermal balances along with calculations of heat- and mass exchange taking into account the non-uniformity of gas and burden distribution on the radius of the furnace and influence of the basic metallurgical characteristics of iron ore raw materials and coke on the indices of blast furnace operation. As a check of the applicability of the model, calculations on the most critical parameters of the blast furnace process – the smelting of ferromanganese and iron nickel with a graphical representation of heat- and mass exchange processes, dynamics of oxides reduction on the height and radius of the blast furnace have been carried out.

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