Engineering topics
Ostrogorsky, A.
Publications and source records attributed to Ostrogorsky, A..
Reproducible Crystal Growth Experiments in Microgravity Science Glovebox at the International Space Station (SUBSA Investigation)
Solidification Using a Baffle in Sealed Ampoules (SUBSA) is the first investigation conducted in the Microgravity Science Glovebox (MSG) Facility at the International Space Station (ISS) Alpha. 8 single crystals of InSb, doped with Te and Zn, were directionally solidified in microgravity. The experiments were conducted in a furnace with a transparent gradient section, and a video camera, sending images to the earth. The real time images (i) helped seeding, (ii) allowed a direct measurement of the solidification rate. The post-flight characterization of the crystals includes: computed x-ray tomography, Secondary Ion Mass Spectroscopy (SIMS), Hall measurements, Atomic Absorption (AA), and 4 point probe analysis. For the first time in microgravity, several crystals having nearly identical initial transients were grown. Reproducible initial transients were obtained with Te-doped InSb. Furthermore, the diffusion controlled end-transient was demonstrated experimentally (SUBSA 02). From the initial transients, the diffusivity of Te and Zn in InSb was determined.
Solidification Using the Baffle in Sealed Ampoules
Solidification Using a Baffle in Sealed Ampoules (SUBSA) is the first investigation conducted in the Microgravity Science Glovebox (MSG) Facility at the International Space Station (ISS) Alpha. In July, August and September of 2002, 8 single crystals of InSb, doped with Te and Zn, were directionally solidified in microgravity. Ground based tests, related numerical modeling and images of the growth process obtained in microgravity are presented.
Microgravity Science Glovebox Investigations SUBSA
Solidification Using a Baffle in Sealed Ampoules (SUBSA) is a Microgravity Science Glovebox Investigation manifested for the UF2 flight, on the U.S. Orbiter 111, to the International Space Station (ISS). SUBSA complements the "parent" flight investigation CG13 (Space-and Groundbased Crystal Growth Using a Baffle). During directional solidification, the disk-shaped baffle acts as a partition, creating a small melt zone at the solid-liquid interface. As a result, the level of buoyancy-driven convection at the interface is significantly reduced. In space, the baffle will reduce convection driven by residual micro acceleration. The baffle reduces the Rayleigh number (Ra) of the melt by a factor of 103. The combined effect of the baffle and microgravity will yield a reduction in Ra by a factor of 107 to 109 approaching effectively the acceleration conditions in "nanogravity". The results of ground based tests and numerical modeling will be presented. The furnace for directional solidification (flight hardware and the ground unit) was developed by Tec-Masters Inc. The flight ampoules were produced jointly at Rensselaer, Tec-Masters Inc. and Crystallod Inc.