Function Of Temperature In Vacuum Research Articles

Effect of Si content on the uniaxial tensile behavior of Mo-Si solid solution alloys

Recrystallized binary Mo-0.2 wt.% Si (Mo-0.68 at.% Si) and Mo-0.3 wt.% Si (Mo-1.0 at.% Si) alloys and a ternary Mo-0.75 wt.% Si-0.14 wt.% B (Mo-2.5 at.% Si-1.2 at.% B) alloy were tested in uniaxial tension as a function of temperature in vacuum and the results are compared to previous results on recrystallized commercial purity (CP) Mo and a binary Mo-0.1 wt.% Si (Mo-0.34 at.% Si) solid solution alloy. Yield strength increases with increasing Si content at all temperatures examined except at room temperature where the 0.1 wt.% Si alloy demonstrates softening; atomistic simulation confirms this behavior to be associated with Si segregation to the core and the associated ease of kink nucleation. Tensile ductility at room temperature rapidly deteriorates with increasing Si content in solid solution but in the Mo-0.3 wt.% Si solid solution alloy, tensile ductility of ~10% was measured at 300°C and thereafter, it increases rapidly at higher temperatures. Serrated flow occurs in the temperature range 600°C~800°C with the serration amplitude increasing with increasing Si content; atomistic simulation illustrates O trapping by Si in solid solution and subsequent de-trapping/release at higher temperatures that can account for the onset temperature delay of serrated flow in these Mo-Si solid solution alloys relative to commercial purity Mo. The serrated flow phenomenon is accompanied by significant work hardening; the presence of dislocation tangles, dipoles and prismatic loops in specimens fractured above ≥ 700°C accounts for the observed work hardening.

Implantation of cobalt in SnO2 thin films studied by TDPAC

Here we report time differential perturbed angular correlation (TDPAC) results of Co-doped SnO2 thin films. Making use of stable Co and radioactive 111In implanted at the Bonn Radioisotope Separator with energies of 80 keV and 160 keV, respectively, it was possible to study the dopant incorporation and its lattice location during annealing. The hyperfine parameters have been probed as a function of temperature in vacuum. Two quadrupole interactions were observed. At high temperatures the dominant fraction for the probe nuclei can be assigned to the Cd-incorporation at the cation substitutional site in a highly disordered structure, obtained after implantation, to high crystallinity for the measurements at 873 K and 923 K. The similarity in TDPAC spectra obtained in undoped SnO gives indirect evidence that In and Co diffuse to different depths during the annealing process. Other interpretations will be discussed.

The tensile response of Mo, Mo–Re and Mo–Si solid solutions

Recrystallized, commercially pure Mo, binary Mo–27at.% Re, and as-extruded and variously annealed Mo–0.3at.% Si alloys were tested in uniaxial tension as a function of temperature in vacuum. The Mo–Re solid solution is significantly stronger than Mo and retains the strength to at least 800°C. The alloy exhibits serrated flow in the 500°C–800°C range and this is accompanied by a continuous decrease in ductility with increasing temperature in this temperature range. The recrystallized Mo–0.3at.% Si alloy is softer than pure Mo at room temperature and has high ductility (~60% tensile elongation). In the worked condition, it is significantly stronger (σy>600MPa) but still is ductile at room temperature (~10% tensile elongation). The observation of ductility at room temperature in this Mo–0.3at.% Si solid solution alloy has important implications for multiphase ternary Mo–Si–B alloys of technological interest.

Effect of temperature on electrical resistivity of a hydrogenated LaNi 5 thin film

The electrical resistivity of a hydrogenated LaNi5 thin film has been investigated as a function of temperature in vacuum and in hydrogen. While the film was heated in vacuum for the first time, the change in resistivity exhibited different characteristics during different ranges of temperatures due to the competition of two effects owing to the lattice scattering of conductive electrons and the number of them. The resistivity had a sharp drop near 600 K, which originates from the formation of high conducting lanthanum hydride and nickel due to a reaction between the dissolved hydrogen and LaNi5. The change in resistivity was not repeatable during the successive heating and cooling processes. When the film was heated under a hydrogen atmosphere, a drop in resistivity occurred near 700 K due to the reaction between LaNi5 and the hydrogen atmosphere. The film showed a linear temperature dependence of receptivity with completeness of the reaction. It was found that the reaction was irreversible. The film lost the ability of hydrogen absorption after the reaction, and it had a phase change from LaNi5 to LaH and Ni. This result was supported by x-ray diffraction patterns.

Surface composition of a tin–lead alloy

The surface and near surface composition of a single phase tin–lead alloy whose bulk composition was 99.83 at.% tin and 0.17 at.% lead has been measured as a function of temperature in vacuum and in an oxidizing ambient. In vacuum, the outer monolayer of the surface is enriched in lead at all temperatures studied (≊65% at.% Pb at 23 °C). From the measured lead surface composition as a function of temperature, a heat of segregation of 4.7 kcal/mole is calculated. The data obtained in an oxidizing ambient indicate that the near surface composition is dependent on the oxygen partial pressure as well as the temperature at which the sample is annealed.