Papers by Keyword: Nickel

Abstract: Solids show the feature of internal friction and the feature of fatigue. As a cause for the both features we assume the migration of atomic items. The driving forces for the migration of the atomic items can be mechanical stress gradients and temperature gradients. In an earlier publication formulas have been derived for the internal friction and for the fatigue. From these formulas follows a relation between internal friction and fatigue. The mechanical stress gradients are the cause of the background of internal friction which shows a monotonous rise with temperature. Temperature gradients in the solid can be produced by total internal friction. In contrast to the background of internal friction the temperature dependence of the total internal friction shows maxima and minima. Because of the relations between internal friction and fatigue the temperature dependence of fatigue shows that the fatigue is caused by temperature gradients. The relation between internal friction and fatigue also shows the influence of the internal friction on the fatigue curve.

Abstract: Dry methane reforming (DRM) has recently received considerable attention as a perspective CO₂ utilization technology allowing the valorization natural gas and biogas. The commercialization of the DRM process depends on the use of more stable and active catalysts. The nickel-based catalysts are commonly used in the DRM reaction as they are effective in hydrogen production and nickel is a less expensive material compared to noble metals. However, Ni-based catalysts undergo fast deactivation. The stability of nickel catalysts in DRM reaction may be enhanced by introduction of supports or promoters with basic and/or redox properties. Thus, in this work, Ceria-Zirconia supports were modified by rare earth metals such as Lanthanum, Praseodymium and Yttrium in order to stabilize the raw materials and to promote the catalytic activity. Nickel was then impregnated on such supports and the modified catalysts were tested in dry methane reforming for syngas production since it was already reported that a promotion with nickel and yttrium lead to better activity in DRM catalytic tests over mesoporous materials. All promoted catalysts were characterized by the means of S_BET, XRD, TEM, H₂-TPR, CO₂-TPD in order to define the physical, textural and chemical properties. The influence of basicity on the catalytic activity was clearly evidenced. Moreover, the influence of Nickel loading was also studied. It was evidenced that an optimal Ni loading is needed in order to reach higher activity and stability in DRM.

Abstract: The copper alloys, which were added Nickel show high corrosion resistance. Therefore, they are generally used in environments of poor quality fuel. However, it is expected that we reduce the amount of Ni in copper alloy, due to increase of Nickel consumption in recent years. We used five different types of sintered material samples that are different in the content of Nickel in the present study, to investigate the influence of Ni content to corrosion resistance quantitatively. These samples were used for the experiment of open circuit potentials, anodic and cathodic polarization curves measurements. To simulate environment in poor quality fuel we employed solution of 0.5 M Na₂S + 0.1 M NaOH (pH = 13.05). The experiment of open circuit potentials shows that samples that the content of Nickel is less than 42 mass% were formed passivation film on surface of sample during aeration. The experiment of polarization curves measurements show that the each sample was implied behavior of forming passivation film corresponding to potential-pH diagram of Cu in anodic region basically. In addition, the 36.4 mass% Nickel was remarkably improved corrosion resistance.

Abstract: Recycling and storage of galvanic production sludges requires significant costs and they are strictly regulated by environmental documents. At the same time, the sludges contain a significant amount of non-ferrous metals, including nickel, which are preferable to extract. To evaluate the extracting nickel possibility from the sludges and selecting a method for their processing, it is necessary to study the chemical, phase, fractional material composition.

Abstract: The paper dwells upon the specifics of worn spots being formed on a silicon-carbide crystal in microscratching of iron, cobalt, and nickel. Analysis was done using a Versa 3D dual-beam electron microscope. The chemical composition of worn spots was studied by local X-ray microanalysis. It was found out that the amount of metal transferred to the silicon-carbide worn spot was associated with the electron structure of metal atoms.

Abstract: This research aims to study the simultaneous silicon-modified pack aluminizing method using silica (SiO₂) from Rice Husk Ash (RHA) which contains 99.45% SiO₂ in comparison with commercial SiO₂ in the form of quartz. Samples can thus be categorized into two groups: quartz-doped and RHA-doped. Simultaneous silicon-modified pack aluminizing of pure nickel was performed at 1000°C for 4 hours under an argon atmosphere. The pack used in this research was prepared from aluminum (Al), ammonium chloride (NH₄Cl), alumina (Al₂O₃) and silica (SiO₂, i.e. quartz and RHA) powder at ratios of 29:2:60:9 by weight, respectively. Post aluminized samples were characterized by glancing incident-angle X-ray diffractometer (GIXD). Quantitative analysis of the layer was performed using energy dispersive spectroscopy (EDS). A scanning electron microscope (SEM) was employed to observe the resulting microstructure. It was found that simultaneous silicon-modified pack aluminizing can be successfully performed by doping RHA and quartz into the pack. The aluminized layer consists of Ni₂Al₃ and NiAl₃ with a small amount of silicon. RHA was found to be more effective than quartz as a silicon source providing a higher amount of silicon in the aluminized layer. Moreover, using RHA successfully forms a silicon-rich interdiffusion layer beneath the typical aluminized layer.

Abstract: A sandwich structure of Ni/Nb/4H-SiC was prepared and annealed at different temperature from 750°C to 1050°C. The electrical property and crystalline structure of Ni/Nb electrode was characterized by transmission line method and X-ray diffraction. It was found that the annealing temperature and the thickness of Ni/Nb layer played an important role in obtaining Ohmic contact. A low specific contact resistance of 1.1×10^-5 Ω·cm² was obtained when the Ni(50nm)/Nb(50nm) electrode was annealed at 1050°C. The Ohmic contact mechanism of Ni/Nb/4H-SiC was proposed.

Abstract: 4H-SiC pMOSFETs with Al-doped S/D and NbNi silicide ohmic contacts were demonstrated and were characterized at up to a temperature of 200 °C. For the pMOSFETs, silicides on p-type 4H-SiC with Nb/Ni, NbNi alloy, Ni and Nb/Ti were investigated, and the Nb/Ni silicide with the contact resistance of 5.04×10^-3 Ωcm² were applied for the pMOSFETs.

Abstract: Nickel (Ni) is the most widely used metal for the formation of ohmic contact on n-type SiC. However, the irregular contact can potentially cause degradation in the device performance. To form the uniform ohmic interface, titanium (Ti) was applied as a barrier layer. Ni/Ti/SiC and Ti/Ni/SiC contact metal structures were prepared, and ohmic contacts were formed using a rapid thermal annealing process. The interfacial properties of both contact metal structures were enhanced by applying the Ti layer. The specific contact resistance of ohmic contacts showed a slightly lower or similar value (~ low 10⁵ Ωcm²) compared with the specific contact resistance values formed from only the Ni contact metal.

Abstract: In this work, magnetic force microscopy (MFM) tips coated with a nickel thin-film were prepared and characterized for applications in the measurement of the magnetic write field. Nickel films with various thicknesses in a range of 20 – 80 nm were deposited on silicon substrates and silicon atomic force microscopy (AFM) tips by electron beam evaporation. Film surface morphologies and magnetic properties of the coated nickel films were investigated by using AFM and vibrating sample magnetometry (VSM). The rms roughness increased with the film thickness and was in a range between 0.1 and 0.3 nm. VSM results revealed that the mean coercive field of the nickel films was 20 Oe and there was an increase in the coercivity as the film thickness increased. In addition, the prepared MFM tips were evaluated for the tip response to the dc and ac magnetic field generated from perpendicular write heads. It was found that the MFM tip had the best response to the write field when coated with 60 nm thick nickel film. The coating thickness over 60 nm was inapplicable due to the cantilever bending caused by the film stress.