| Lunar Ceramics Lunar ceramics include pressed and sintered regolith, melted and cast basalt from mare regolith, and glass from highland plagioclase. Highland plagioclase consists of NaAlSi3O8 and CaAl2Si2O8, albite and anorthite respectively. See: http://www.belmont.k12.ca.us/ralston/programs/itech/SpaceSettlement/spaceresvol3/glassncer1.htm Anorthositic highland regolith can be heated to 1200 C. to drive off FeO and at 1500 C. and higher MgO and SiO2 will boil off. At 2000 C. and higher Na2O and K2O will boil off. These oxides might be condensed and separated in a "still" made of ceramic blocks brazed or welded together. Magnesium oxide makes firebrick good to about 3000 C. in atmospheric pressure but it will sublimate in the vacuum at about 1400 C., so MgO firebrick could only be used for electric furnaces in pressurized modules. After heating highland regolith either cement with about 40% CaO, 50% Al2O3 and 10% SiO2 or calcium aluminate (if all SiO2 is boiled out), CaAl2O4, will remain. The molten cement will have to be pulverized with power hammers and ground in ball mills to get cement powder to mix with sand (sieved regolith) and gravel (screened out of regolith), some calcium sulfate and water to make concrete for floors in upported inflated modules and steel modules made on the Moon. An iron or steel floor might be added over the concrete floor to spread out forces on the module floor if say some heavy hammering with power hammers is going on to prevent cracking of the concrete that heavy machines will be bolted to. Silica, SiO2, if pure enough melts at 1700-1800 C. and has a very low thermal coefficient of expansion. Furnace linings that can handle molten steel and iron could be made of silica bricks brazed or welded together with microwaves or electron beams. Impure silica can serve as glass with a lower m.p. for low stress applications that don't require transparency too like glass electrical insulators for power lines or kitchen ware. Molten glass can even be extruded into fibers, spun, woven into glass cloth or used to make glass fiber reinforced glass composite materials. Molten basalt can also be extruded into fibers, spun, woven perhaps, and used as mineral fiber wool for insulation indoors. Glass wool and mineral fiber wool won't make good thermal insulators in the vacuum since their insulating properties arise from the fact that they contain a lot of air. Vacuum makes a good thermal insulator and so does plain regolith. Glass cloth coated with aluminum or magnesium might make "tents" for shielding vehicles, machines and heat radiators from sunlight. Glass cloth could also be used for electrical wire insulation, although some electrical devices might require plastic insulation made from carbon, hydrogen and nitrogen harvested from vast areas of regolith. Bus bars might be coated with glass for electrical insulation. Cement powder and/or calcium aluminate powder could be leached in sulfuric acid contained in apparatus made of high silicon alloy iron possibly with cast basalt linings that resist corrosion by H2SO4. Silica, water, calcium sulfate and aluminum sulfate will form. Silica resists sulfuric acid and is not water soluble. CaSO4 is barely soluble in water and Al2(SO4)3 is highly soluble in water. The silica and calcium sulfate can be filtered out by a glass wool filter and the aluminum sulfate solution passed through. This solution will then be boiled down to get dry aluminum sulfate and recover the water for restocking H2SO4. The dry aluminum sulfate can then be roasted at about 1000 C. to decompose it to alumium oxide and drive off sulfur oxide vapors that will be used to restock acid supplies. The silica and CaSO4 can be separated electrostatically. Aluminum oxide makes a good abrasive and can be used for emery paper and emery wheels. It also makes a ceramic that melts at 2000 C. Some upported zirconium oxide might be mixed with molten Al2O3 to make a better ceramic for furnace crucibles. Alumina, 99.5%, has a Moh's hardness of 8-9 as compared to 6.5 for tool steel and 9-10 for silicon carbide. From: http://www.ferroceramic.com/alumina_99_table.htm we read: Alumina represents the most commonly utilized ceramic material in industry. Purity levels are available from 85% through 99.9%. This is because of extremely superior abrasion, high temperature and chemical resistance. It is electrically insulating as well. This material has an excellent cost to part life performance record. Applications include wear and heat resistant liners, mechanical and pump seals, nozzles, semiconductor equipment components, insulators, etc Silica from the acid leach will have uses and CaSO4 will be used as a cement drying time retarder and also to make plaster boards and other things from medical casts to molds for casting aluminum and magnesium when mixed with water and dried. Calcium sulfate is plaster of Paris. It can also be reacted with carbon at 1500 C. to get calcium oxide that melts at about 2500 C. Calcium oxide might not make a very strong ceramic but it can be reacted with an excess of carbon in a high temp electrical furnace to make calcium carbide that can be reacted with water to make acetylene gas. Acetylene gas can be used for welding. It can also be deposited on hot silicon substrates to make carbon nanotube ultracapacitors. Ceramic blocks containing spinel-MgAl2O4 and some silicates that melts about 1350 C. can be obtained directly from magma electrolysis. These might be used to make more electrolysis furnaces by stacking cast interlocking bricks, welding or brazing them together and surrounding them with thermal insulating regolith (0.01-0.001 W/mK) contained by a steel or iron jacket. Titanium dioxide obtained by flushing ilmenite with hot hydrogen gas at about 1000 C. could be sintered to make bricks, tiles or blocks that melt at 1900 C. Ilmenite alone, extracted from mare regolith electrostatically, has semiconducting properties and might be used as a solar cell, but will it make a high power transistor for induction furnace oscillators...we must wonder??? TiO2 reacted with an excess of carbon in a high temp furnace will form titanium carbide-TiC. This might be used as a high temp. electrode in magma electrolysis furnaces and possibly a cutting tip for drills and milling machines. Silica reacted with an excess of carbon will form silicon carbide and that can be used as an abrasive, a grinder, a drill or milling machine cutting tool, or high power electronic transistors. Finally, cast basalt made by melting mare regolith, can be used for tiles, bricks, pipes, kitchen ware, and tubes conveying abrasive materials like regolith itself or cement powders. Cast basalt has a Moh's hardness of 8 and is more abrasion resistant than steel. It can be carved and cut with tungsten carbide tipped tools while hard steel tools will wear out fast. A ceramics hardness chart can be found at: http://www.reade.com/Particle_Briefings/mohs_hardness_abrasive_grit.html |
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