Published on January 20, 2008
Synthesis of Sol-Gel Precursors for Ceramics from Lunar and Martian Soil Simulars : 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 In-Situ Resource Utilization: In-Situ Resource Utilization Identify materials processing issues and propose / test processing strategies to enable human operations on the surface of the Moon/Mars using ISRU concepts. A strategy for the next step in Space exploration Living off the land…away from Earth: Living off the land…away from Earth 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) 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 … In search of the “right way” to extract SiO2…: 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. 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. A chemical, energy-poor approach to extract SiO2 for Space exploration? Lunar soil analog: 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. Martian soil analog: Martian soil analog JSC1 Mars Weathered volcanic ash from Pu’u 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 100°C Major crystalline phases: Plagioclase (Ca)(Si,Al)4O8 Ti-Magnetite (Ti)Fe3O4 Minor minerals: Olivine (Mg,Fe)2SiO4, Pyroxene XY(Si, Al)2O6 Slide8: Lunar simular (JSC1 Moon) Martian simular (JSC1 Mars) Mixed with KOH in 1:1 mass ratio. 500 ml of ethylene glycol (1L steel vessel) Heated to 200°C under reflux continuous agitation, N2 flow Water removal by reflux in Soxhlet body (molecular sieve) Fig. 1 Results: Results Determination of Silica concentration by colorimetric analysis Visible light absorption by silicomolybdic acid (lmax=352nm) (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. Slide10: Fig. 3 Monolithic gels from Lunar (left) and Martian (right) soil simulars. 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 Slide11: 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. Slide12: Energy (KeV) Counts Results X-ray Fluorescence Spectroscopy Powder from gel formed by slow hydrolysis of silica extracted from Lunar soil analog (JSC1 Moon) Results: Results Fig. 5 TGA profile under N2 at 15°C/min of precipitated sol after ambient pressure drying in air at 80°C. The red curve represents δMass/ δT versus T. Fig. 6 XPS spectrum of JSC1 Moon aerogel. X-ray source Mg Ka. Slide15: Fig. 10 Glassy ceramic as product of pyrolysis at 20°C/min to 870°C in inert atmosphere of a sol-gel powder obtained from JSC1 Moon. A) Optical micrograph, B) Scanning Electron Microscopy (SEM) and C) EDS microprobe. A C B Slide16: 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. Conclusion Acknowledgements: Acknowledgements Stephen Gillett (U. of Nevada Reno) Denise Edwards (Alabama A&M) 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 Director’s Discretionary Fund.