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Application of Computational Thermodynamics for Magnesium Alloys Development
Published in Leszek A. Dobrzański, George E. Totten, Menachem Bamberger, Magnesium and Its Alloys, 2020
In the Knudsen effusion method (vapor pressure method) [21], a small amount of volatile species in the gas phase effuses through a small orifice of 0.1–1 mm with negligible influence of the equilibrium in the Knudsen cell. The vapor is ionized and analyzed with a mass spectrometer. The partial pressure of a species can be calculated from its ionization area and intensity through a calibration factor determined by a reference material with known partial pressure.
A new method of measuring ruthenium activity in ruthenium-containing alloys by using thermogravimetric analysis
Published in Journal of Nuclear Science and Technology, 2022
Jiazhan Liu, Kunihisa Nakajima, Shuhei Miwa, Noriko Shirasu, Masahiko Osaka
However, aRu of Ru-containing alloys is difficult to be measured by the traditional methods, such as the famous Knudsen cell mass spectrometry and torsion-effusion methods due to the too-low vapor pressure of Ru metal [13,14]. Kleykamp [15] measured aRu of the Ru0.5Pd0.5 alloy at 1100 and 1200 K by the electromotive force (EMF) method. The results showed a huge discrepancy with those calculated by the Calphad method. It is known that the Calphad method can well reproduce the phase diagram of the Ru–Pd system [12], and thus, the accuracy of the values of aRu in this system calculated is assured to some extent. These suggest the failure of the EMF method in measuring aRu of alloys. It is inferred that this failure may result from the internal oxidation of Ru in the alloys because the formation of RuOx gases was confirmed in experiments [15]. Therefore, to accurately determine aRu in the Ru-containing alloys, a new method was proposed in this study and used to remeasure aRu values in Ru–Pd system. The measured values were hoped to be useful in further optimization of the thermodynamic parameters of the Ru–Pd system through the Calphad method.
Resistive switching memory performance in oxide hetero-nanocrystals with well-controlled interfaces
Published in Science and Technology of Advanced Materials, 2020
Takafumi Ishibe, Yoshiki Maeda, Tsukasa Terada, Nobuyasu Naruse, Yutaka Mera, Eiichi Kobayashi, Yoshiaki Nakamura
Fe3O4 NCs on Ge nuclei were formed on Si substrates in the chamber equipped with Knudsen cell for Ge and an electron beam evaporator for Fe in the following way. As-doped Si(111) substrates with dimensions of 2 mm×7 mm×0.3 mm were introduced into ultrahigh vacuum chamber at a base pressure of 1 × 10−8 Pa. After degassing the substrates at 500°C for 6 h, Si(111) clean surfaces were obtained by flashing at 1250°C. The ultrathin SiO2 films with the thickness of 0.3 nm were formed on Si(111) substrates by oxidizing the Si surfaces at 600°C for 10 min under an oxygen pressure of 2 × 10−4 Pa [17,21–26]. Epitaxial Ge nuclei with an areal density of ~1011 cm−2 were formed by depositing 25 MLs of Ge onto the ultrathin SiO2 films at 600°C. 1–30 MLs of Fe were deposited on Ge nuclei at RT for coating Ge nucleus surfaces. Finally, Fe3O4 NCs were grown on Fe-coated Ge nuclei by deposition of 21 ML Fe on the Ge nuclei at RT under an oxygen pressure of 2 × 10−4 Pa. In this Fe3O4 growth by Fe deposition at low-pressure oxygen atmosphere, oxygen vacancies are likely generated in Fe3O4 [27,28]. For the above-mentioned Fe coating and Fe3O4 growth, the oblique Fe deposition was performed in the direction of out-of-plane incident angle of 25º, enabling the formation of isolated Fe3O4 NCs on Ge nuclei, which details are reported in our previous study [26]. For Fe and Ge deposition, Fe and Ge fluxes are 0.13 and 0.35 ML/min, respectively. To enhance their crystallinities, Fe3O4 NCs were post-annealed at 250-400°C for 30 min under an oxygen pressure of 2 × 10−4 Pa.