Synthesis of SolGel Precursors for Ceramics from Lunar and Martian Soil Simulars

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Synthesis of Sol-Gel Precursors for Ceramics from
Lunar and Martian Soil Simulars

• Laurent Sibille
• NASA / Marshall Space Flight Center
• BAE Systems Analytical Solutions
• Jose A. Gavira-Gallardo and Djamila
  Hourlier-Bahloul
• University of Granada, Spain
  University of Limoges, France

Space Resources Roundtable VI November 2,
2004
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In-Situ Resource Utilization
A strategy for the next step in Space exploration

• Identify materials processing issues and propose
  / test processing strategies to enable human
  operations on the surface of the Moon/Mars using
  ISRU concepts.

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Living off the landaway from Earth
Planetary Outpost Survival O2 and H2O
production Energy production Propellants Habitat
Mining, extraction and production of basic
elements and molecules Gases, metals, metal
oxides, water
Why SiO2? Highly abundant SiO2 is source of O2
and Si Exploitation of solar energy via Si-based
photovoltaics is favored. Multiple applications
electrical insulator (power grid), ceramics and
glasses (protective coatings, windows)
How? On Mars silica solubilization in
supercritical CO2 (K. Debelak, Vanderbilt) Molten
oxide electrolysis (D. Sadoway, MIT) Beam-aided
melting and silica sublimation from regolith (A.
Ignatiev, U. Houston)
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In search of the right way to extract SiO2
High temperature approaches Direct pyrolysis of
silicates1 Electrolysis of silicate melts2 Molten
oxide electrolysis involve Handling of hot
silicate melts, vapors High energy needs,
High risks (low G) Low temperature
techniques Dissolution of silicates in
hydrofluoric acid (HF) or fluorine involve
Extreme toxicity and corrosivity of HF High
risks 1C. L. Senior, Lunar Oxygen Production
by Pyrolysis in Resources of Near-Earth Space,
eds. J. S. Lewis, M. S. Matthews M. L.
Guerrieri, University of Arizona Press (1993),
pp. 179-197. 2L.A. Haskin R.O. Colson,
Production by magma Electrolysis of Lunar
Soils, in Engineering, Construction and
Operations in Space III, vol. II, eds. W.Z.
Sadeh, S. Sture R.J. Miller, ASCE (1992), pp.
651-665.
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A chemical, energy-poor approach to extract SiO2
for Space exploration?

• Two promising approaches
• Functionalization in basic medium with diols
  (catechol, ethylene glycol)1
• Acidic dissolution in alcoholic medium2
• Silica reacts readily with Ethylene Glycol and
  strong bases such as the group I metal
  hydroxides, e.g. KOH and group II oxides, e.g.
  BaO
• Higher stability of EG over catechols in
  oxidating atmospheres

S.L. Gillett, Organic-based dissolution of
silicates as an approach to element extraction
from lunar regolith, Proc. Second Lunar Dev.
Conference, July 2000 1 R.M. Laine, K.Y.
Blohowiak, T.R. Robinson, M.L. Hoppe, P. Nardi,
J. Kampf J. Uhm, Synthesis of pentacoordinate
silicon complexes from SiO2, Nature (1991), v.
353, pp. 642-644. 2G.B. Goodwin M.E. Kenney, A
New Approach to the Synthesis of Alkyl Silicates
and Organosiloxanes, in Inorganic and
Organometallic Polymers, eds. Zeldin, Martel,
Wynne Allcock, ACS Symposium Series 360 (1988),
pp. 238-248.
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Lunar soil analog
JSC1 Moon Volcanic ash deposit San Francisco
volcano field near Flagstaff, AZ. Sieved
coarsely, impact milled. Air dried. Average water
content 2.70 0.3 wt. Major crystalline
phases Plagioclase (Na,Ca)(Si,Al)4O8 Pyroxene
XY(Si, Al)2O6 Olivine (Mg,Fe)2SiO4 Minor
minerals Ilmenite (FeTiO3), Chromite (FeCr2O4),
traces of clay. ½ volume of typical particle is
glass of basaltic composition Contains
plagioclase needles, oxide minerals a few
micrometers in size.
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Martian soil analog
JSC1 Mars Weathered volcanic ash from Puu Nene
volcano on Hawaii. Close spectral analog to the
bright regions of Mars. Sieved coarsely (grain
size 5 1000mm). Air dried. Significant water
content loss of 7.8 wt at 100C Major
crystalline phases Plagioclase (Ca)(Si,Al)4O8
Ti-Magnetite (Ti)Fe3O4 Minor minerals Olivine
(Mg,Fe)2SiO4, Pyroxene XY(Si, Al)2O6
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Lunar simular (JSC1 Moon) Martian simular (JSC1
Mars) Mixed with KOH in 11 mass ratio. 500 ml
of ethylene glycol (1L steel vessel) Heated
to 200C under reflux continuous agitation, N2
flow Water removal by reflux in Soxhlet body
(molecular sieve)
Fig. 1
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Results
Determination of Silica concentration by
colorimetric analysis Visible light absorption
by silicomolybdic acid (lmax352nm) (Fig. 2).
Fig. 2 Silica concentration as a function of
reaction time for experiments done with JSC1 Moon
(blue and red) and JSC1 Mars (black) soil
simulars.
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Silica polymerization The silicoglycolate
solution was precipitated or polymerized by
catalyzed hydrolysis in acidic medium using HCl
and HNO3. The production of powder or monolithic
gels was controlled by varying the amount of
catalyst and water (Fig. 3). No gel or
precipitate obtained from EG / KOH
Fig. 3 Monolithic gels from Lunar (left) and
Martian (right) soil simulars.
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Solvent elimination Suspension of silica polymer
particles collected by successive centrifugation
and ethanol washes. Pellet dried in air, ambient
pressure. Monolithic gels aged in water followed
by ethanol solvent exchange. Ethanol replaced by
liquid CO2 in a critical point dryer. CO2 removed
above its critical point to yield aerogels (Fig.
4).
Fig. 4 Aerogels obtained from silica extracted in
basic ethylene glycol from JSC1 Moon.
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Results
X-ray Fluorescence Spectroscopy Powder from gel
formed by slow hydrolysis of silica extracted
from Lunar soil analog (JSC1 Moon)
Counts
Energy (KeV)
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Results
Fig. 5 TGA profile under N2 at 15C/min of
precipitated sol after ambient pressure drying in
air at 80C. The red curve represents dMass/ dT
versus T.
Fig. 6 XPS spectrum of JSC1 Moon aerogel. X-ray
source Mg Ka.
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A
B
C
Fig. 10 Glassy ceramic as product of pyrolysis
at 20C/min to 870C in inert atmosphere of a
sol-gel powder obtained from JSC1 Moon. A)
Optical micrograph, B) Scanning Electron
Microscopy (SEM) and C) EDS microprobe.
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Conclusion

• Chemical dissolution of Silica in basic ethylene
  glycol from mineral analogs of soils found on the
  Moon and Mars.
• Sol-gel materials containing Si, Al, and Fe were
  obtained using recyclable reagents and little
  energy compared to mineral reduction techniques
  at high temperatures.
• Aerogels, ceramics and glasses have been
  produced from these sol-gel precursors.

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Acknowledgements
Stephen Gillett (U. of Nevada Reno) Denise
Edwards (Alabama AM) Jeffrey Weimer (UAH) for
XPS use Paul Carpenter (BAE Systems) for EDS/SEM
work James Coston (MSFC) for ESEM work Tim Huff
(MSFC) for TGA work Funding for this study was
provided by the Marshall Space Flight Center
Directors Discretionary Fund.