The purpose of this research project is to clarify the interfacial phenomena between the molten steel and the oxide melts from the viewpoints of thermophysical properties of these liquids. In our project, using an electrostatic levitation furnace (ELF) in the International Space Station (ISS) we obtain density, surface tension and viscosity of oxide melts and also try to obtain interfacial tension between the molten steel and the oxide melts by the modified oscillating drop technique. The research work contributes the precise process control for the high advantage steels products. Because in iron and steel making processes interfacial tension plays important role for the control of molten steel flow at the interface between molten steel and oxide melts. We, therefore, propose the novel technique to obtain temperature dependence of interfacial tension between molten iron and molten oxides by core-shell form droplet including interface between two liquids using electrostatic levitation, which achieve the containerless conditions. The proposal of the novel technique of interfacial tension measurements using ELF in KIBO was accepted in 2012-JAXA-AO for International Research Participation on ISS-KIBO. In the manuscript, we introduce our research project outline and current status for the future ISS experiments.
Preparation of steel-slag core-shell droplet sample is necessary for the measurement of interfacial tension between molten steel and slag/flux by the oscillating droplet technique in international space station (ISS). In the present work, the engulfment of molten iron by molten slag/flux was investigated by melting the iron and slag/flux mixed powder compact with arc melting. The slag/flux used are blast furnace (BF) slag, ilmenite (IL)/lime titania (LT)/low hydrogen (LH) type coating fluxes. We found that molten iron was entirely encapsulated by molten IL flux at high temperature and the iron/flux core-shell structure was maintained after cooling, which means IL flux is a favorable material for the interfacial measurement in ISS. In addition, the engulfment of molten iron by simulated molten BF slag was discussed based on spreading coefficient and a numerical simulation of coalescence of two droplets
The Electrostatic Levitation Furnace (ELF) is one of the experiment facilities for materials science, which will be on board Japanese Experiment Module “Kibo” of the International Space Station (ISS) in 2015. Since JAXA decided twenty years ago that ISS levitation furnace control method should be Coulomb force, we continued further research experiments and development of ground models. In 2011, JAXA has proceeded to the development phase of ELF and we are now ready to finish the development of ELF. JAXA plans to study thermophysical properties of many kinds of the oxides which cannot be measured on earth. In addition, creation of new materials is another objective of space experiments using ELF. Both is expected to contribute to a new discovery of scientific research and industrial applications. This paper shows the overview of ELF including the history of design concept.
As a part of ground support activities for the upcoming experiments in the International Space Station (ISS), convection inside a molten Zr, one of flight samples was numerically predicted. The sample will be processed with the materials science laboratory – electromagnetic levitation (MSL-EML) facility which has already been installed in the European deck. Thermophysical properties, such as, heat capacity, thermal conductivity, viscosity and surface tension of the molten Zr will be measured. The validity of some of these properties are significantly affected by convection during the measurements and the convection must be predicted in advance to help design the space experiments. Utilizing the magnetohydrodynamic (MHD) model developed in the previous research, a series of simulations was performed in order to investigate the convection during the space experiments.
In order to measure the surface tension and viscosity of high temperature melts with high viscosity, a method using sample rotation is developed. An electrostatically levitated melt was spun with a rotating magnetic field, and the shape evolution of the sample was observed. Especially, the bifurcation behavior was closely monitored by a high speed camera. The experiments confirmed that the rotation frequency at the bifurcation could be precisely measured by monitoring the fluctuation of the power of the He-Ne laser reflected at the sample surface, and thus, the surface tension could be calculated based on the theory. As for the viscosity measurements, preliminary experiments showed that the speed of the shape evolution after the bifurcation was related to the viscosity of the sample.
To clarify the relationship between ventilation efficiency and autonomic nervous activity under microgravity condition induced by parabolic flight, ventilation efficiency, the ratio of abdominal-to-thoracic motion (Vabd/Vrib), the duration of expiratory phase of respiration (TE/TTot) and sympathetic nervous activity were measured in human subjects. Microgravity resulted in a reduction of the ventilation efficiency and increase of sympathetic nervous activity. Furthermore, Vabd/Vrib increased and TE/TTot decreased during microgravity. In addition, we observed using a video-recorder that subject’s trunk was extended during microgravity exposure. These results suggest that the change of subject’s posture might decrease abdominal motion and expiratory phase, and induce increase in sympathetic nervous activity. Thus, autonomic nervous activity does not always play key role to regulate ventilation efficiency in case of exposure to microgravity. Moreover, it is suggested that subject’s posture affects autonomic nervous activity under microgravity condition.