Materials Literature
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The design and performance of silicon nitride (Si3N4) dies for the semi-solid processing of steels is studied by the example of a punch and a lower swage in upset forging. The observed failure mechanisms and degradation effects are related to short-term effects resulting from mechanical and thermal loads and long-term…
The origin of high hole conduction in BaCuQF (Q=S,Se) was investigated by photoemission measurements and full-potential linearized augmented plane wave band-structure calculations. In both compounds, the large dispersion near the top of the valence band is realized by admixed states of Cu 3d and S 3p or Se 4p orbitals…
We have performed morphological analysis of samples of Fe nanowires encapsulated into aligned multiwalled carbon nanotubes (Fe-MWCNTs) via Fe57 Mössbauer spectroscopy. The aligned Fe-MWCNTs were obtained by pyrolysis of ferrocene onto an oxidized Si substrate. Transmission Mössbauer spectroscopy (TMS) and backscattere…
A significant increase in durability of cryogenically treated tools after quenching was reported by a number of publications [1, 2]. As research studies show [4, 5, 6, 7], the main reason for this is the kind of carbides precipitated during tempering at temperature range of 150 –200 0C, which is different than in the…
Nonideal electrode surfaces cause significant degree of electron reflection from collector during thermionic converter operation. The effect of the collector surface structure on the converter performance was assessed through the development of several electron reflection suppression materials using various thin film…
When moisture uptake in a polymer is associated with swelling, it induces stresses which interact with the entire diffusion process. This coupling is addressed in this paper, which extends immediately to the diffusion of other fluids, like solvents. First, the generalized chemical potential is used to analyze the effe…
To be suitable for integrated optical devices, (Pb,La)(Zr,Ti)O3 (PLZT) ferroelectric thin films require high crystalline quality, low surface roughness, high optical index, and high transparency. In this paper, PLZT thin films have been grown in situ on indium tin oxide (ITO) coated quartz substrates by rf magnetron s…
Direct growth of carbon nanotubes (CNTs) on silicon is of great importance for their potential exploitation in the semiconductor industry. In this article we investigate the chemical vapor deposition growth of CNTs on Si substrates from ethylene precursor using an iron catalyst. We observe that CNTs are produced only…
We report on the structural and magnetic properties of V-doped AlN thin films deposited on c-plane (001) sapphire by reactive cosputtering. The AlN crystal structure was maintained, with decreasing c lattice parameter, as V content increased to 1.58at.%. No secondary phase was found. Films exhibited ferromagnetism at…
A series of sintered composite materials was fabricated from Parascan™ barium strontium titanate (BSTO) and Trans-Tech nickel zinc ferrite powders. The ferrite loading was varied from zero (BSTO only) to 100wt% (ferrite only). X-ray diffraction data show the presence of a third, nonmagnetic phase that sets the ferrite…
The phase transitions of Ge2Sb2Te5 (GST) films after bombardment with 40keV N2+ ions were investigated. Comparing the nitrogen incorporated GST films with a pure GST film, the suppression of a crystalline grain growth was more effective in the N2+ implanted GST film than in a nitrogen codeposited GST film, i.e., x-ray…
Bismuth-doped LaAlO3 was prepared in the form of solid solution, La(1−x)BixAlO3 (0⩽x⩽0.2), by solid-state reactions. The materials were characterized by x-ray diffraction and dielectric spectroscopy. With increasing bismuth amount (x), the dielectric constant increases from 31.6 for pure LaAlO3 to 34.6 for x=0.2, whil…
The polycrystalline nanosize (∼60nm) of (1−x)Pb(Fe2∕3W1∕3)O3–x(BiFeO3) solid solutions with a wide range of concentrations (0⩽x⩽0.20) were fabricated using a mechanical activation followed by a conventional solid-state reaction technique. The formation of single-phase material and better solubility of two phases [i.e.…
We present a theoretical study on the structural and electronic modifications caused by random nitrogen substitution in carbon tubular and branched nanostructures. Finite cluster calculations with hydrogen saturation of the tube ends were performed. Geometry optimizations were carried out through semiempirical quantum…
The essential first step in semi-solid forming is to obtain a high grain density during the initial stages of solidification of an alloy melt. This is usually done by a combination of cooling and convection. If the grain density is too low, the resulting structure is one of conventional coarse dendrites, unsuitable fo…
The size effect in barium titanate (BaTiO3) was investigated both experimentally and theoretically. Tetragonal BaTiO3 powders with average sizes from 80to420nm were directly prepared by different hydrothermal methods. The tetragonality of the hydrothermal BaTiO3 decreased with decreasing particle size, which exhibited…
A field summation method is used to determine the effective ε and μ of metamaterial structures. The numerical implementation of this method using commercial software is comprehensively described. The field summation method is shown to predict accurately the reflection and transmission coefficients of thin slabs of met…
Minority electron diffusion length was measured in p-type, Sb-doped ZnO as a function of temperature using the electron beam induced current technique. A thermally induced increase of electron diffusion length was determined to have an activation energy of 184±10meV. Irradiation with a low energy (5kV) electron beam a…
This paper compiles all the data from our tracer diffusivity studies in single crystalline 2/1-mullite. As tracers we used the rare stable isotopes 18O and 30Si and the artificial pseudo-stable isotope 26Al. Secondary-ion mass spectrometry was applied to analyze the depth distribution of the tracer isotopes after the…
We calculate the band structures of BaO and BaS using the local density approximation and the GW approximation (GWA). The Ba 4d states are treated as valence states. We find that BaO is an indirect band-gap semiconductor and BaS is a direct band-gap semiconductor. The results show that the band gaps of GWA agree excel…