Containerless processing techniques eliminate physical contact with container walls and enable improved chemical purity over more conventional techniques. Acoustic, aerodynamic, and electromagnetic containerless processing technologies have been developed, evaluated, and applied in experiments at Intersonics. Incorporated and in other laboratories This has resulted in an advanced understanding of these technologies and significant experimental data on a variety of high temperature systems. The operational characteristics and capabilities of several experimental techniques and systems developed at Intersonics are presented. Results of experiments performed using these techniques are also presented.
No contamination from container is expected to produce the ultrapure material or to minimize the lattice defects in space material experiments in low gravity, typically 1 x 10-3- 1 X 10-6 G. Stable levitation is necessary to achieve these experiments. Such levitation can be attained by two electrostatic forces of a modified two dimensional quadrupole electrode system that we have developed. However, stable levitation will be broken by disturbance such as a residual acceleration due lo motions of the crews, pumps, switching or other operations in the space station, even if only one of these forces acts on the levitated material. Unstable levitation occurs and may cause the failure of the experiment as a result. Hence, it is important to understand the characteristics of the motion of the sample with the disturbance. This report describes locus of motion, period of one cycle and displacement of the levitated material simulated by numerical calculation using computer when the disturbance is a Gaussian distribution varied with lime under low gravity condition. Furthermore, the centrifugal force acting on the sample was also discussed.
A charged sample levitates statically in a modified two dimensional quadrupole electrostatic levitation apparatus under low gravity such as 1 x 10 -3 - 1 x 10 -4 G This report describes sample motion which the disturbance assumed to be a Gaussian distribution varied with time acts on it only to the gravitational direction Simulation showed graphically that motion is nearly a simple harmonic motion with small logarithmic decrement. Furthermore, it was cleared that (1) period of oscillation (2) the relation between an applied voltage and maximum tolerable disturbance. (3) logarithmic decrement under disturbance or no disturbance. In addition, the necessity of position control was pointed out to obtain stable levitation. PID (Proportional Integral and Derivative) control was tried for this purpose. It was able to give the excellent position control, where the motion by PID control was compared with that of non-PID control. Further, the relation between recovery time, which the time until the sample levitates statically after the disappearance of the disturbance, and the three constants contained within PID equation. The results are also reported.
Evaporation and convection experiments on a 80PbO-20B2O3 (mol%) melt held on a platinum wire were conducted under microgravity in a drop shaft (490m free fall. 10-4g, 10sec) and on an aircraft (10-2g, 20sec). Companion experiments were also conducted at 2 g by banking the aircraft at 60 degree. Material evaporated from the melt on the platinum wire in a radial direction in the drop shaft experiments and condensed as small spherical particles on the glass enclosure. The gravity level affected the convection pattern of the evaporated material (panicles) in the aircraft experiments. The small glass particles collected on the surface of the glass enclosure were analyzed with a scanning electron microscope and electron probe microanalyzer. Uniform spherical particles (from 0.2 to 0.3 micrometers) were produced under microgravity while deformed particles of variable diameter (from 0.1 to 1 micrometer) were produced under 2 g.
In-situ observation of some transparent model alloys are very important in understanding the solidification mechanisms during cooling. This article introduces the apparatus and experimental procedures of direct observation of the monotectic model alloy using the drop capsule at Japan Microgravity Center (JAMIC) in Hokkaido. Microgravity conditions of 10-4g in 10 seconds are obtained in this capsule. The succinonitrile-ethanol model alloy is used and cooled at the top, center or bottom of the glass cell. A video camera records the behavior of the solidification and separation of the liquid droplets before and during the drop. The special attention given for performing the experiments in the drop capsule are also described.
Electrical resistance R of Liquid Bi-Ca alloy (ca. 65at%Ga) was measured under the low gravity, which was obtained by the launch of S520 rocket. On the cooling process from 573 K to coexistence temperature TL (539K), the temperature coefficient of R ∂ R / ∂ T, increases. Below TL the increasing tendency of ∂ R / ∂ T becomes steep down to TL - 14K. These tendencies are not so clear for the reference experiment under 1G. Moreover, the degree of supercooling is far larger for the low gravity than for 1G. These differences are explained by the differences of convection effects of fluctuating domains. It is concluded that very low gravity condition is effective to clarify the substantial feature of critical phenomena, supercooling behavior, phase separation process and spinodal for liquids with critical mixing.