Consolidation of nanoencapsulated powder sheets with photons

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Consolidation of nanoencapsulated powder sheets
with photons

• William Hofmeister, Lino Costa, Zbigniew
  Sikorski University of Tennessee Space Institute
• Adrian Sabau Oak Ridge National Laboratory
• Dean Baker Advanced Powder Solutions

PowderMet 2007, May 14-16, 2007, Denver Colorado
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acknowledgements

• At UTSI Kate Lansford
• This work was performed under NASA Marshall
  CONTRACT NNM06AB11C.
• Assistance of Dr. Ken Cooper (Aries Work Package
  Manager) and Curtis Manning (Rapid Prototyping
  Manager) of the NASA Net Shape/Rapid Prototype
  Manufacturing Center
• Additional ORNL participants Jim Kiggans, Ronald
  D. Ott, and Craig A. Blue D. B. Kothe of Oak
  Ridge National Laboratory for providing access to
  the Telluride code for the computations done in
  this study.
• Some parts of this research was sponsored by the
  Laboratory Directed Research and Development
  Program of Oak Ridge National Laboratory (ORNL),
  managed by UT-Battelle, LLC for the U. S.
  Department of Energy under Contract No.
  DE-AC05-00OR22725.

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Basic concept
Powders considered in this paper are nickel
coated 3M micro balloons.
Question? Can we consolidate these powders into
useful shapes with photons?
Photo by UC Davis
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Starting material

• 3M on the G-850 Ceramic (Mullite) micro-balloons
• Composition wt 45-55 Si, 20-30 Al, 3-6 Ca, 2-4
  Fe.
• Target crush strength gt 60000 psi
• True density 2.1 g/cc
• thermal conductivity is 2 W/mK

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Photon sources

• High Density IR Lamp (ORNL)
• 300,000 watts
• Broadband (0.2 1.4 micron)
• Diode pumped Ytterbium fiber laser
• 1000 watts
• IR 1.075 microns
• CO2 gas laser
• 3000 watts
• Long wavelength 10.6 microns

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Scattering and length scales
Photons encountering particles much smaller than
the wavelength of light will undergo Rayleigh
Scattering
Powders on the order of the wavelength will
scatter light as predicted by Mie scattering.
http//hyperphysics.phy-astr.gsu.edu/hbase/atmos/b
lusky.html
10.6 m light
1.064 m light
Mie Scattering from a 10 micron nickel sphere
http//www.philiplaven.com/mieplot.htm
van de Hulst
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Calculate the extinction of a beam in a powder bed

• Coating reflectance (0.73 _at_ 1.06m - 0.98 _at_ 10.6m)
• Scattering on a single sphere (anisotropy
  parameter)
• Diffusion approximation

Basically More absorption at shorter
wavelengths More absorption for smaller
spheres Greater penetration at longer wavelength
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One dimensional model of powder heating

• Is it possible to melt the nickel layer and
  preserve the glass sphere?

1D heat transfer model for a Ni coated hollow
micro-sphere
Laser power 350W Beam radius 0.1 mm Scan
speed 4.5 m/s
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ORNL IR Lamp

• Powders green compact on quartz substrate
• Pulse heating (preheat then fuse)
• Thermal conductivity of packed bed (lt2 W/mK)
• Absorptivity 1

Results of finite element model showing
temperature at positions measured from the top
surface.
Schedule of heat pulses
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Sample Preparation

• Mix with water soluble binder
• Gently press powder into 3mm thick compact
• Bake under heat lamp
• Scan with laser
• Remove by sonication in solvent

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Consolidation of Ni Coated Microspheres
Fiber laser (200 Watts 0.2 mm beam size) Scan
head (250 mm/s) He atmosphere
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Fiber Laser results
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CO2 laser results
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IR Lamp results
More melted glass !
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Summary

• There is modeling.
• and there is real life
• Need optically good coatings for better
  penetration into powder bed