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Research Containing: Pore Formation and Mobility Investigation

SUBSA and PFMI Transparent Furnace Systems Currently in use in the International Space Station Microgravity Science Glovebox

by on 9 June 2015in Physical Sciences No comment

The Solidification Using a Baffle in Sealed Ampoules (SUBSA) and Pore Formation and Mobility Investigation (PFMI) furnaces were developed for operation in the International Space Station (ISS) Microgravity Science Glovebox (MSG). Both furnaces were launched to the ISS on STS-111, June 4, 2002, and are currently in use on orbit. The SUBSA furnace provides a maximum temperature of 850 C and can accommodate a metal sample as large as 30 cm long and 12mm in diameter. SUBSA utilizes a gradient freeze process with a minimum cooldown rate of 0.5C per min, and a stability of +/- 0.15C. An 8 cm long transparent gradient zone coupled with a Cohu 3812 camera and quartz ampoule allows for observation and video recording of the solidification process. PFMI is a Bridgman type furnace that operates at a maximum temperature of 130C and can accommodate a sample 23cm long and 10mm in diameter. Two Cohu 3812 cameras mounted 90 deg apart move on a separate translation system which allows for viewing of the sample in the transparent hot zone and gradient zone independent of the furnace translation rate and direction. Translation rates for both the cameras and furnace can be specified from 0.5micrometers/sec to 100 micrometers/sec with a stability of +/-5%. The two furnaces share a Process Control Module (PCM) which controls the furnace hardware, a Data Acquisition Pad (DaqPad) which provides signal condition of thermal couple data, and two Cohu 3812 cameras. The hardware and software allow for real time monitoring and commanding of critical process control parameters. This paper will provide a detailed explanation of the SUBSA and PFMI systems along with performance data and some preliminary results from completed on-orbit processing runs.

Related URLs:
http://dx.doi.org/10.2514/6.2003-1362

Experiments Conducted Aboard the International Space Station: The Pore Formation and Mobility Investigation (PFMI) and the In-Space Soldering Investigation (ISSI): A Current Summary of Results

by on 9 June 2015in Physical Sciences No comment

Experiments in support of the Pore Formation and Mobility Investigation (PFMI) and the In-Space Soldering Investigation (ISSI) were conducted aboard the International Space Station (ISS) with the goal of promoting our fundamental understanding of melting dynamics, solidification phenomena, and defect generation during materials processing in a microgravity environment. Through the course of many experiments a number of observations, expected and unexpected, have been directly made. These include gradient-driven bubble migration, thermocapillary flow, and novel microstructural development. The experimental results are presented and found to be in good agreement with models pertinent to a microgravity environment. Based on the space station results, and noting the futility of duplicating them in Earth’s unit-gravity environment, attention is drawn to the role ISS experiments/hardware can play to provide insight to potential materials processing techniques and/or repair scenarios that might arise during long duration space transport and/or on the lunar/Mars surface.

Related URLs:
http://dx.doi.org/10.2514/6.IAC-06-A2.2.10

Observation of an Aligned Gas – Solid Eutectic during Controlled Directional Solidification aboard the International Space Station – Comparison with Ground-based Studies

by on 9 June 2015in Physical Sciences No comment

Direct observation of the controlled melting and solidification of succinonitrile was conducted in the glovebox facility of the International Space Station (ISS). The experimental samples were prepared on ground by filling glass tubes, 1 cm ID and approximately 30 cm in length, with pure succinonitrile (SCN) in an atmosphere of nitrogen at 450 millibar pressure for eventual processing in the Pore Formation and Mobility Investigation (PFMI) apparatus in the glovebox facility (GBX) on board the ISS. Real time visualization during controlled directional melt back of the sample showed nitrogen bubbles emerging from the interface and moving through the liquid up the imposed temperature gradient. Over a period of time these bubbles disappear by dissolving into the melt. Translation is stopped after melting back of about 9 cm of the sample, with an equilibrium solid-liquid interface established. During controlled re-solidification, aligned tubes of gas were seen growing perpendicular to the planar solid/liquid interface, inferring that the nitrogen previously dissolved into the liquid SCN was now coming out at the solid/liquid interface and forming the little studied liquid = solid + gas eutectic-type reaction. The observed structure is evaluated in terms of spacing dimensions, interface undercooling, and mechanisms for spacing adjustments. Finally, the significance of processing in a microgravity environment is ascertained in view of ground-based results.

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Morphological Evolution of Directional Solidification Interfaces in Microgravity: An Analysis of Model Experiments Performed on the International Space Station

by on 9 June 2015in Physical Sciences No comment

A series of experiment performed using the Pore Formation and Mobility Investigation (PMFI) apparatus within the Microgravity Science Glovebox (MSG) facility on board the International Space Station (ISS( has provided video images of the morphological evolution of a three-dimensional interface in a diffusion controlled regime. The experiment samples, 1 cm inner diameter and approximately 30 cm in length, are filled with alloys of succinonitrile (SCN) and water. The compositions of the samples processed and analyzed are 0.25, 0.5 and 1.0 wt% water. Experimental processing parameters of temperature gradient and translation speed, as well as camera settings, were remotely monitored and controlled from the ground Telescience Center (TSC) at the Marshall Space Flight Center. Images obtained from the on-orbit experiments have been received and are being analyzed. A ground-based thin-sample directional solidification system for correlation to flight experiments is described. Using this ground-based system, a series of experiments has been performed for direct comparison with the flight data. The initial results of these comparisons as well as implications to future microgravity experiments are presented and discussed.

Related URLs:
http://dx.doi.org/10.2514/6.2005-917

Disruption of an Aligned Dendritic Network by Bubbles During Re-melting in a Microgravity Environment

by on 9 June 2015in Physical Sciences No comment

The Pore Formation and Mobility Investigation (PFMI) utilized quartz tubes containing succinonitrile and 0.24 wt% water “alloys” for directional solidification (DS) experiments which were conducted in the microgravity environment aboard the International Space Station (ISS; 2002–2006). The sample mixture was initially melted back under controlled conditions in order to establish an equilibrium solid-liquid interface. During this procedure thermocapillary convection initiated when the directional melting exposed a previously trapped bubble. The induced fluid flow was capable of detaching and redistributing large arrays of aligned dendrite branches. In other cases, rapidly translating bubbles originating in the mushy zone dislodged dendrite fragments from the interface. The detrimental consequence of randomly oriented dendrite arms at the equilibrium interface upon reinitiating controlled solidification is discussed.

Related URLs:
http://dx.doi.org/10.1007/s12217-011-9297-y

Materials research conducted aboard the International Space Station: Facilities overview, operational procedures, and experimental outcomes

by on 9 June 2015in Physical Sciences No comment

The Microgravity Science Glovebox (MSG) and Maintenance Work Area (MWA) are facilities aboard the International Space Station (ISS) have been successfully used to conduct experiments in support of, respectively, the Pore Formation and Mobility Investigation (PFMI) and the In-Space Soldering Investigation (ISSI). The capabilities of these facilities are briefly discussed and then demonstrated by presenting “real-time” and subsequently down linked video-taped examples from the abovementioned experiments. Data interpretation, ISS telescience, some lessons learned, and the need of such facilities for conducting work in support of understanding materials’ behavior, particularly fluid processing and transport scenarios, in low-gravity environments, is discussed.

Related URLs:
http://www.sciencedirect.com/science/article/pii/S0094576508000465