Taylor G. Wang

Acoustic bubble removal method

A method is described for removing bubbles (14) from a liquid bath (12), such as a bath of molten glass to be used for optical elements. Larger bubbles are first removed by applying acoustic energy resonant to a bath dimension (H) to drive the larger bubbles toward a pressure well (30) where the bubbles can coalesce and then be more easily removed. Thereafter, submillimeter bubbles (50) are removed by applying acoustic energy of frequencies resonant to the small bubbles to oscillate them and thereby stir liquid immediately about the bubbles to facilitate their breakup and absorption into the liquid (16).

Acoustic particle separation

A method is described which uses acoustic energy to separate particles of different sizes, densities, or the like. The method includes applying acoustic energy resonant to a chamber (14) containing a liquid or gaseous medium to set up a standing wave pattern that includes a force potential well wherein particles within the well are urged towards the center, or position of minimum force potential. A group of particles to be separated is placed in the chamber, while a non-acoustic force such as gravity is applied, so that the particles (50-52 in FIG.2) separate with the larger or denser particles moving away from the center of the well to a position near its edge and progressively smaller lighter particles moving progressively closer to the center of the well. Particles are removed from different positions within the well, so that particles are separated according to the positions they occupy in the well.

Metal shell technology based upon hollow jet instability

Spherical shells of submillimeter size are sought as ICF targets. Such shells must be dimensionally precise, smooth, of high strength, and composed of a high atomic number material. We describe a technology for the production of shells based upon the hydrodynamic instability of an annular jet of molten metal. We have produced shells in the 0.7–2.0 mm size range using tin as a test material. Specimens exhibit good sphericity, fair concentricity, and excellent finish over most of the surface. Work involving a gold–lead–antimony alloy is in progress. Droplets of this are amorphous and possess superior surface finish. The flow of tin models that of the alloy well; experiments on both metals show that the technique holds considerable promise.

Acoustic system for material transport

A system is described for acoustically moving an object within a chamber, by applying wavelengths of different modes to the chamber to move the object between pressure wells formed by the modes. In one system, the object (96, FIG. 7) is placed in a first end portion of the chamber while a resonant mode is applied along the length of the chamber that produces a pressure well (86) at that location. The frequency is then switched to a second mode that produces a pressure well (100) at the center of the chamber, to draw the object thereto. When the object reaches the second pressure well and is still travelling towards the second end of the chamber, the acoustic frequency is again shifted to a third mode (which may equal the first mode) that has a pressure well (106) in the second end portion of the chamber, to draw the object thereto. A heat source (108) may be located near the second end of the chamber to heat the sample, and after the sample is heated it can be cooled by moving it in a corresponding manner back to the first end portion of the chamber. The transducers (88, 98, 110) for levitating and moving the object may be all located at the cool first end of the chamber.

Acoustic suspension system

An acoustic levitation system is described, which can utilize a single acoustic source (12) and a small reflector (14) to stably levitate a small object (16) while the object is processed as by coating or heating it. The system includes a concave acoustic source (12) which has locations on opposite sides of its axis that vibrate towards and away from a focal point (36, FIG. 2) to generate a converging acoustic field. A small reflector (14) is located near the focal point, and preferably slightly beyond it, to create an intense acoustic field that stably supports a small object near the reflector. The reflector can be located about one-half wavelength (L, FIG. 3) from the focal point and can be concavely curved to a radius of curvature (L) of about one-half the wavelength, to stably support an object one-quarter wavelength (N) from the reflector.

Containerless processing technologies at the Jet Propulsion Laboratory

Abstract Residual gravity in space processing would entail contact of the material with its container and hence prevent it from retaining its natural shape, in case of molten metal, and risk its contamination. JPL developed systems for avoiding such contacts, and experimented them in the laboratory. One is based on the properties of acoustics, the specimen being held at the nodes of resonant waves. The other ensures levitation by electrostatic means. These systems are defined and discussed, and the first favorable results presented.

A technique for thick polymer coating of inertial-confinement-fusion targets

A novel technique has been developed to coat a thick layer (15–50 μm) of polymer materials on inertial‐confinement‐fusion (ICF) targets. In this technique, the target and the coating material are independently positioned and manipulated. The coating material is first dissolved in an appropriate solvent to form a polymer solution. The solution is then atomized, transported, and allowed to coalesce into a droplet in a stable acoustic levitating field. The ICF target mounted on a stalk is moved into the acoustic field by manipulating a three‐dimensional (3‐D) positioner to penetrate the surface membrane of the droplet and thus the target is immersed in the levitated coating solution. The 3‐D coordinates of the target inside the droplet are obtained using two orthogonally placed television cameras. The target is positioned at the geometric center of the droplet and maintained at that location by continuously manipulating the 3‐D device until the coating layer is dried. Tests of this technique using a polymer ...

Investigation of Metallic and Metallic Glass Hollow Spheres for Fusion Target Application

High quality metallic and metallic-glass microballoons (MMB and MGMB) are of considerable interest for fusion target applications on account of the intrinsic properties of these materials such as high density, high strength and high atomic number. We report the first successfully formed submillimeter and millimeter spherical shells of tin and of a gold-lead-antimony alloy by means of the hollow-jet instability technique developed by one of us (JMK). Examination of tin specimens by means of SEM has revealed that surface quality varied from poor to excellent. Whereas this metal has been employed only as a convenient and inexpensive material, the gold alloy is important because it is hard, has high atomic number, and may be solidified into the amorphous state through the provision of a modest cooling rate. We have produced AuPbSb spherules up to 1.5 mm in diameter using LN 2 or chilled methanol as a coolant, and have found that these amorphous samples possess a superb surface smoothness compatible with fusion target requirements. Hollow spheres currently made of this alloy have an average O.D. of 2000 μm.

Gravity and conduction driven melting in a sphere

In the Stefan and Neumann problems fundamentally characterizing melting, unmolten portions of a solid undergoing phase changes within spherical containers are assumed to remain stationary. An approach to these issues that is related to the theories of lubrication and film condensation is presently employed in conjunction with an approximate, closed-form solution of melting within spheres. It is shown that a group of dimensionless parameters containing Prandtl, Archimides and Stefan numbers can describe the melting process. Also given are the results of fundamental heat transfer experiments performed on the melting of a phase-change medium in a spherical shell.

Space Processing Viewed by a Scientist-Astronaut

An account is given of NASA astronaut T. G. Wangs 1985 experiences with Spacelab-borne containerless processing experiment equipment handling and experimental management. The mission in question was marred by the initial malfunction of the zero-gravity materials-processing experiment package; Wangs first task was accordingly to attempt repairs, and led to his living inside the experiment package for 2.5 days in order to operate the system as well as possible, on a 16-hr workday basis, with the assistance of two other astronauts.