CSLM-3 (Coarsening in Solid-Liquid Mixtures-3)
January, 2012 – The CSLM-3 team is developing a plan to
prepare six sample processing units containing lead-tin dendrite samples
provided by the Principal Investigator Peter Voorhees. The
CSLM-3 team is developing a CSLM-3 schedule and the Science Requirements Document
during February 2012.
CSLM-2 Status
February 10, 2011 – The Principal Investigator Peter Voorhees
at Northwestern University has analyzed the CSLM-2 high volume fraction samples
from the six successful SPU’s and is writing a CSLM-2 Report to document
the science results.
April 30, 2008 – CSLM-2 completed operations of 3 SPU’s containing
high volume fraction samples on board the International Space Station. Two
SPU’s contained samples to repeat the processing of 2 SPU’s that
did not process correctly in December 2007, plus one SPU to complete the high
volume fraction test matrix. All three SPU’s operated properly completing
the six SPU high volume fraction test matrix.
March 11, 2008 – CSLM-2 launched 3 SPU’s containing high volume
fraction samples on board the Space Shuttle STS-123/Flight 1J/A.
December 30, 2007 – CSLM-2 completed operations of 5 SPU’s
containing high volume fraction samples on board the International Space Station. Two
of the 5 SPU’s did not operate properly.
August 8, 2007 – CSLM-2 launched 5 SPU’s containing high volume
fraction samples on board the Space Shuttle STS-118/Flight 13A.1.
* Go to information on CSLM-2R...
Overview
The Coarsening in Solid-Liquid Mixtures (CSLM) experiment
is a materials science space flight experiment whose purpose is to
investigate the kinetics of competitive particle growth within a liquid
matrix. During coarsening, small particles shrink by losing atoms
to larger particles, causing the larger particles to grow. In this
experiment solid particles of tin will grow (coarsen) within a liquid
lead-tin eutectic matrix. By conducting this experiment in a microgravity
environment, a greater range of solid volume fractions can be studied,
and the effects of convection present in terrestrial experiments will
be negligible. The flight hardware consists of two separable pieces
of equipment, the sample processing unit (SPU) and the electronic
control unit (ECU).
Research Description
CSLM-2 samples are processed inside the Sample Processing
Unit (SPU), which has a large, cylindrical sample chamber. After a
sample is completed, pressurized water is pumped into the chamber
to quench the sample, cooling it for removal. This system can quench
the sample from 185C (the temperature required to initiate coarsening
in tin-lead (Sn-Pb) samples) to 120C in only 6 seconds.
The Electronics Control Unit (ECU) provides power and the software
that controls all stages of processing. Parameters and status are
displayed on the ECU's LCD screen. The ECU controls the temperature
inside the SPU sample chamber and monitors and records the sample's
temperature. The quenching stage can be initiated automatically or
controlled manually by the crew. A base plate attaches the SPU and
ECU to the Microgravity Science Glovebox (MSG) work volume floor.
Operational Requirements
CSLM-2 will be conducted inside the sealed MSG work
volume. The crew must load and initiate each run. Quenching can be
initiated manually. Data captured by the ECU is transferred to the
MSG laptop for storage and downloading to the ground-based researchers.
The samples are a mixture consisting of Sn (tin)-rich particles in
a Pb-Sn liquid, a mixture that has a low sintering temperature and
a high coarsening rate, making it perfect for studying Ostwald ripening.
Space Applications
In any mixture that contains particles of different
sizes, the large particles tend to grow while the smaller particles
shrink in a process called coarsening. Tiny oil droplets coalescing
into a large blob are one illustration, but the process occurs in
solids as well. Coarsening occurs on Earth during the processing of
any metal alloy and thus the coarsening process affects products from
dental fillings to turbine blades. Since the properties of an alloy
are linked to the size of the particles within the solid, coarsening
can be used to strengthen materials. This is the case with the majority
of aluminum alloys used commercially today. Conversely, if the coarsening
process proceeds too long the material can weaken. This occurs in
jet turbine blades and is one of the reasons why turbine blades must
be replaced after a certain number of hours of service. Thus developing
accurate models of the coarsening process is central to creating a
wide range of new materials from those used in automobiles to those
used in space applications. Solid-liquid systems are ideal systems
to study this coarsening process. However, gravity can induce particle
sedimentation and thus hamper the studies of coarsening in these mixtures
on Earth. The microgravity environment of the Space Station allows
scientists to study the process of coarsening with reduced interference
from the sedimentation that occurs on Earth.
Earth Applications
On Earth, materials that contain pores
created and trapped during solidification degrade properties and cause
a distinct weakening in the overall structure of the cast product.
Determining what causes these problems will lead to the development
of improved manufacturing processes for materials.
Previous Missions
CSLM-1, a precursor to CSLM-2, was conducted
on STS-83 and STS-94. CSLM-2 was conducted during ISS Increment 7
CSLM-2 operated 5 SPU's on ISS during Increment 16 in December 2007. CSLM-2
operated 3 SPU's on ISS during Increment 17 in April 2008.
Future Missions
The CSLM-2 SPU's that were operated on the ISS
during Increment 16 and Increment 17 have been returned to earth on
the Shuttle. The CSLM-2 Principal Investigator is currently
analyzing the samples from the SPU's returned. |
