Corrosion resistance consolidation of a diaphragm type vacuum sensor
This paper describes the corrosion resistance consolidation of a diaphragm type vacuum sensor using a high corrosion resistance material. Initially, we had fabricated a vacuum sensor using a Ru based thin film amorphous alloy, whose high corrosion resistance was confirmed in wet tests. In the high corrosion gas tests, however, the sensor resists NF<inf>3</inf> and COF<inf>2</inf> gases but does not resist ClF<inf>3</inf> gas. Therefore, we searched for new Ni based amorphous alloys which can also resist ClF<inf>3</inf> using a combinatorial search based on a MEMS process. We were able to fabricate new sensors using Ni<inf>56</inf>Nb<inf>33</inf>Ti<inf>11</inf> and Ni<inf>49</inf>Nb<inf>35</inf>Ti<inf>16</inf> amorphous alloys which were shown to resist all three mentioned gases.
Microforming of three-dimensional microstructures from thin-film metallic glass
Thin-film metallic glasses (TFMGs) are characterized by an absence of size effect, high strength and high elastic limit due to their amorphous nature. As such, these materials are considered to be ideal candidates for microelectromechanical systems (MEMS). Furthermore, the TFMGs soften and show viscous flow within a certain temperature range called the supercooled liquid region (SCLR), which allows the TFMGs to be easily formed into three-dimensional (3-D) microstructures. The viscous flow in the SCLR is also useful for annealing and relaxing inner residual stresses of TFMGs. In the present paper, TFMG microcantilevers are fabricated by surface micromachining techniques. In order to heat and form the cantilevers, a local laser heating and microforming system is introduced, and the conditions of laser power and heating time that can not only form the cantilevers but also can maintain the amorphous nature of the TFMG are examined. Finally, based on the results of these investigations, microcantilevers having a 90/spl deg/ bend and a 90/spl deg/ twist, respectively, are successfully fabricated.
The corrosion behavior of sputter-deposited amorphous Mo-Zr alloys in 12 M HCl
Abstract Amorphous Mo-Zr alloys were prepared in a wide composition range of 40–80 at% zirconium by a magnetron sputtering method. The sputter-deposited Mo-Zr alloys exhibit lower corrosion rates than those of molybdenum and zirconium in 12 M HCl solution open to air at 30 °C. The corrosion resistance of Mo-Zr alloys increases with increasing alloy zirconium content, but molybdenum and zirconium improve the corrosion resistance synergistically. Mo-Zr alloys containing 60 at% or more zirconium exhibit a passive region in a wide potential range without transpassive dissolution of molybdenum. The presence of zirconium suppresses both the cathodic reaction for hydrogen evolution and the anodic reduction. The air-formed film is composed of a double oxyhydroxide of zirconium and molybdenum. Spontaneously passivated films on the alloys containing less than and more than 40 at% of zirconium are composed of molybdenum-enriched and zirconium-enriched oxyhydroxides, respectively. They seem to consist of a bilayer structure; the outer zirconium and inner molybdenum oxyhydroxides. Weak points in each layer in the bilayered passive film seem to be protected mutually by another layer. This appears to be responsible for the high corrosion resistance of the Mo-Zr alloys in comparison with alloy constituents.