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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Control of Convection in Containerless Processing

Many different containerless processing techniques are employed in materials research, with the common goals of eliminating chemical reactions with the crucible and reducing heterogeneous nucleation sites. Each containerless method has different driving forces for flow in a liquid sample, and each has different relations between the flow variables and the process parameters. Often more than one technique is required to achieve the objectives of an experimental program. For example, one project requires solidification experiments over a range of almost two orders of magnitude in flow velocity, in both laminar and turbulent flow, while another requires a particular combination of shear rate and cooling rate, leading to a different processing strategy. The results of a modeling effort to determine the best combination of methods to meet the requirements of these two different experimental programs are presented.

Hyers, R. W.↗
NASA NTRS1990

Modular Containerless Processing Facility

The Modular Containerless Processing Facility (MCPF) of the Space Station Freedom, being developed by the Jet Propulsion Laboratory, is described. The MCPF will be capable of positioning, manipulating, and performing processing operations on samples completely free of container walls. It will be comprised of a host facility and a series of interchangeable plug-in modules. Initial iterations of MCPF modules will be flown on the U.S. Microgravity Laboratory (USML) series of Shuttle flights. The Drop Physics Module schedualed to fly on USML-1 in March 1992 is also considered.

Morrison, Andrew D.↗
NASA NTRS2001

The Role of Convection and Growth Competition in Phase Selection in Microgravity: Controlled Convection in the Containerless Processing of Steel Alloys

Containerless processing using electromagnetic levitation (EML) is a powerful technique in the investigation of reactive molten metal systems. On ground, the power required to overcome the weight of the sample is sufficient to cause significant heating and induce substantial melt convection. In microgravity, the heating and positioning fields may be decoupled and the field strength may be varied to achieve the desired level of convection within the limits set by the geometry of the levitation coil and the sample size. From high-speed digital images of the double recalescence behavior of Fe-Cr-Ni alloys in ground-based testing and in reduced-gravity aboard the NASA KC-135 parabolic aircraft, we have shown that phase selection can be predicted based on a growth competition model. An important parameter in this model is the delay time between primary nucleation and subsequent nucleation of the stable solid within the liquid/metastable solid array. This delay time is a strong function of composition and a weak function of the undercooling of the melt below the metastable liquidus. From the results obtained during the first Microgravity Sciences Laboratory (MSL-1) mission, we also know that convection may significantly influence the delay time, especially at low undercoolings. Currently, it is unclear what mechanism controls the formation of a heterogeneous site that allows nucleation of the austenitic phase on the pre-existing ferrite skeleton. By examining the behavior of the delay time under different convective conditions, we hypothesize that we can differentiate between several of these mechanisms to gain an understanding of how to control microstructural. evolution. We will anchor these predictions by examining samples quenched at different times following primary recalescence in microgravity. A second important parameter in the growth competition model is the identification of the growth rate of the stable phase into the semi-solid array that formed during primary recalescence. Current dendritic growth theory is inadequate in predicting solidification behavior under these conditions as metallographic analyses show that stable phase growth proceeds along the interface between the metastable solid and residual liquid. Since growth velocity is independent of the initial undercooling relative to the metastable liquidus, we hypothesize that purely thermal effects can be separated from other important growth model parameters by careful selection of the liquid composition in a ternary system.

Matson, D. M.↗
NASA NTRS1983

Containerless processing technology

A brief review of containerless processing activities sponsored by NASA's Microgravity Science Division is presented. Attention is given to ground based systems such as shot tower processing of molten materials, single axis levitation and flight processing concepts including BeO processing aboard the Space Shuttle, a medium temperature three-axis acoustic positioning system and a high temperature single axis acoustic positioning system. In the future, more sophisticated experiments will be conducted using improved measurement techniques which will quantitatively define the advantages of containerless processing, as well as improve the understanding of nuclear kinetics and of the thermophysical properties of materials at high temperatures.

Oran, W. A.↗
NASA NTRS2012

Containerless Processing Studies in the MSFC Electrostatic Levitator

Levitation or containerless processing represents an important tool in materials research. Levitated specimens are free from contact with a container, which permits studies of deeply undercooled melts, and high-temperature, highly reactive materials. Containerless processing provides data for studies of thermophysical properties, phase equilibria, metastable state formation, microstructure formation, undercooling, and nucleation. Levitation techniques include: acoustic, aero-acoustic, electromagnetic, and electrostatic. In microgravity, levitation can be achieved with greatly reduced positioning forces. Microgravity also reduces the effects of buoyancy and sedimentation in melts. The European Space Agency (ESA) and the German Aerospace Center (DLR) jointly developed an electromagnetic levitator facility (MSL-EML) for containerless materials processing in space. The MSL-EML will be accommodated in the European Columbus Facility on the International Space Station (ISS). The electrostatic levitator (ESL) facility at the Marshall Space Flight Center provides support for the development of containerless processing studies for the ISS. The capabilities of the facility and recent results will be discussed.

Rogers, J. R.↗
NASA NTRS1983

Review of the containerless processing technologies and facilities

Material processing techniques which can most fully utilize the advantages provided by space are related to containerless processing. An avoidance of physical contact between the melt and the walls of a container leads to an elimination of container-induced contamination and heterogeneous nucleation. Containerless processing facilities development by NASA will provide a basis for the performance of precursor experiments and processing technologies studies prior to Space Shuttle flights. Attention is given to acoustic containerless processing, electromagnetic containerless processing, electrostatic levitation technology, drop tubes, and the use of zero-G KC-135 aircraft flights for tests and training purposes.

Wang, T. G.↗
NASA NTRS1985

Acoustic Levitation Containerless Processing

This research program consists of the development of acoustic containerless processing systems with applications in the areas of research in material sciences, as well as the production of new materials, solid forms with novel and unusual microstructures, fusion target spheres, and improved optical fibers. Efforts have been focused on the containerless processing at high temperatures for producing new kinds of glasses. Also, some development has occurred in the areas of containerlessly supporting liquids at room temperature, with applications in studies of fluid dynamics, potential undercooling of liquids, etc. The high temperature area holds the greatest promise for producing new kinds of glasses and ceramics, new alloys, and possibly unusual structural shapes, such as very uniform hollow glass shells for fusion target applications. High temperature acoustic levitation required for containerless processing has been demonstrated in low-g environments as well as in ground-based experiments. Future activities include continued development of the signals axis acoustic levitator.

Whymark, R. R.↗
NASA NTRS1991

Development of high temperature containerless processing equipment and the design and evaluation of associated systems required for microgravity materials processing and property measurements

The development of high temperature containerless processing equipment and the design and evaluation of associated systems required for microgravity materials processing and property measurements are discussed. Efforts were directed towards the following task areas: design and development of a High Temperature Acoustic Levitator (HAL) for containerless processing and property measurements at high temperatures; testing of the HAL module to establish this technology for use as a positioning device for microgravity uses; construction and evaluation of a brassboard hot wall Acoustic Levitation Furnace; construction and evaluation of a noncontact temperature measurement (NCTM) system based on AGEMA thermal imaging camera; construction of a prototype Division of Amplitude Polarimetric Pyrometer for NCTM of levitated specimens; evaluation of and recommendations for techniques to control contamination in containerless materials processing chambers; and evaluation of techniques for heating specimens to high temperatures for containerless materials experimentation.

Rey, Charles A.↗
NASA NTRS1990

Containerless processing of amorphous ceramics

The absence of gravity allows containerless processing of materials which could not otherwise be processed. High melting point, hard materials such as borides, nitrides, and refractory metals are usually brittle in their crystalline form. The absence of dislocations in amorphous materials frequently endows them with flexibility and toughness. Systematic studies of the properties of many amorphous materials have not been carried out. The requirements for their production is that they can be processed in a controlled way without container interaction. Containerless processing in microgravity could permit the control necessary to produce amorphous forms of hard materials.

Weber, J. K. Richard↗
NASA NTRS1993

Containerless processing of undercooled melts

The investigation focused on the control of microstructural evolution in Mn-Al, Fe-Ni, Ni-V, and Au-Pb-Sb alloys through the high undercooling levels provided by containerless processing, and provided fundamental new information on the control of nucleation. Solidification analysis was conducted by means of thermal analysis, x-ray diffraction, and metallographic characterization on samples processed in a laboratory scale drop tube system. The Mn-Al alloy system offers a useful model system with the capability of phase separation on an individual particle basis, thus permitting a more complete understanding of the operative kinetics and the key containerless processing variables. This system provided the opportunity of analyzing the nucleation rate as a function of processing conditions and allowed for the quantitative assessment of the relevant processing parameters. These factors are essential in the development of a containerless processing model which has a predictive capability. Similarly, Ni-V is a model system that was used to study duplex partitionless solidification, which is a structure possible only in high under cooling solidification processes. Nucleation kinetics for the competing bcc and fcc phases were studied to determine how this structure can develop and the conditions under which it may occur. The Fe-Ni alloy system was studied to identify microstructural transitions with controlled variations in sample size and composition during containerless solidification. This work was forwarded to develop a microstructure map which delineates regimes of structural evolution and provides a unified analysis of experimental observations. The Au-Pb-Sb system was investigated to characterize the thermodynamic properties of the undercooled liquid phase and to characterize the glass transition under a variety of processing conditions. By analyzing key containerless processing parameters in a ground based drop tube study, a carefully designed flight experiment may be planned to utilize the extended duration microgravity conditions of orbiting spacecraft.

Perepezko, J. H.↗
NASA NTRS1985

Advanced Containerless Processing Technology

Breadboards for high temperature containerless processing systems are to be developed, the principles of operation are to be studied, the performance is to be characterized, the limitations identified, and the influence of the acoustic field on the samples established. The subjects to be addressed are experimental and theoretical studies of: (1) acoustic positioning and manipulation capabilities in a high temperature gradient environment (from 26 C to 990 C); (2) acoustic waveforms, harmonic contents, power transfer, sample transport and stability associated with high temperature gradient system; (3) high temperature ground based levitation systems which will allow melting, processing, and solidifying samples without crucibles in the laboratory, (4) KC-135 and laboratory tests of various acoustic geometries which may have spherical applications in the Materials Processing in Space Program; and (5) provide technical information to Acoustics Containerless Experimental System (ACES) engineering team and establish the operation conditions for ACES.

Wang, T. G.↗
NASA NTRS1983

MEA/A-1 experiment 81F01 conducted on STS-7 flight, June 1983. Containerless processing of glass forming melts

The space processing of containerless, glassforming melts on board the space shuttle flight STS-7 is investigated. Objectives include; (1) obtain quantitative evidence for the supression of heterogeneous nucleation/crystallization, (2) study melt homogenization without gravity driven convection, (3) procedural development for bubble free, high purity homogeneous melts inmicro-g, (4) comparative analysis of melts on Earth and in micro g, and (5) assess the apparatus for processing multicomponent, glass forming melts in a low gravity environment.

Day, D. E.↗
NASA NTRS1991

Containerless processing at high temperatures using acoustic levitation

Advanced techniques are presented which facilitate the development of inert or reducing atmospheres in excess of 2000 K in order to improve processing of containerless capabilities at higher temperatures and to provide more contamination-free environments. Recent testing, in the laboratory and aboard the NASA KC-135 aircraft, of a high-temperature acoustic positioner demonstrated the effectiveness of a specimen motion damping system and of specimen spin control. It is found that stable positioning can be achieved under ambient and heated conditions, including the transient states of heat-up and cool-down. An incorporated high-temperature levitator was found capable of processing specimens of up to 6-mm diameter in a high-purity environment without the contaminating effects of a container at high temperatures and with relative quiescence.

Rey, C. A.↗
NASA NTRS1991

Applications of containerless processing in the studies of metals and alloys

The use of containerless processing in nucleation and microstructural studies of alloys is reviewed in terms of approaches and recent results. Drop-tube studies of niobium based on a statistical approach are discussed, and experiments are described which permit the study of the solidification front across the surface of a specimen. The various alloys studied are reviewed in terms of facilitated observations of metastability, chemical homogeneity, and microstructural refinement. Heterogeneous nucleation is reported for a preexponential factor of 10 exp 27 and a critical free energy of 46-56kT. The theoretical relationship between undercooling and solidification velocity correlates with containerless test observations at large solute concentrations. Containerless processing is effective for studying the properties of liquid metals or accessing the metastable thermodynamic regime.

Bayuzick, R. J.↗
NASA NTRS1984

Containerless-Processing Module

High-temperature, containerless-processing module positions and melts molten glass or metal without contact with container wall. Fluid masses manipulated, stirred, and controlled by acoustic forces. Module provides photographic monitoring and transfer of solidified specimens to storage bins.

Wang, T. G.↗
NASA NTRS1990

Containerless processing of undercooled melts

All practical solidification processes involve some level of melt undercooling. Usually in bulk liquids crystallization is initiated at a heterogeneous nucleation site at low undercooling. The realization of appreciable levels of liquid undercooling requires some control over the kinetics of crystal nucleation. One level of control is available in containerless processing where the capability to melt and solidify samples without a container removes a major source of impurities and heterogeneous nucleation sites which can be effective in promoting large undercooling and in studying other potential nucleants. The microgravity environment offers a unique opportunity for containerless processing of large liquid samples with negligible melt disturbance and continuous temperature measurement throughout processing. Perhaps the most important potential for microgravity containerless processing lies in the significant structural control to develop distinct microstructures and metastable phases during solidification at high undercooling.

Perepezko, J. H.↗
NASA NTRS1982

Overview of containerless processing technologies

Many of the experiments to be carried out in the Space Shuttle will require containerless processing techniques that will provide manipulation and control of weightless (molten) materials without physical contact with container walls or other holding devices. The variety of containerless processing technologies now being developed for space- and ground-based materials processing facilities is surveyed. It is shown how the utilization of air jets or high-intensity acoustic, electromagnetic, or electrostatic fields can produce forces that support and manipulate materials. Most of the present containerless research seeks to develop high-temperature systems capable of melting and resolidifying materials. An introduction to available NASA test facilities is provided.

Barmatz, M.↗
NASA NTRS1986

Containerless processing technology

Ground- and space-based containerless processing levitation devices are described. Experiments performed in the MSFC drop tube, the JPL drag-free drop facilities, a single-axis tuned cavity acoustic levitator furnace on TEXUS-I, and a three-axis acoustic levitator and furnace on the STS-11 mission are discussed. Neither acoustic interference nor aerodynamic levitation trials have yielded promising results in sounding rocket and STS based experiments. An electrostatic levitator has furnished a high degree of positioning control with multiple objects in a terrestrial laboratory.

Naumann, R. J.↗