Word: silica
(lookup in dictionary)
(lookup stats)
Dates: during 1980-1989
Sort By: most recent first
(reverse)
Concerned that their Neolithic treasures would quickly disintegrate if exposed to humidity and sunlight, museum officials placed them in a darkened room, under glass and resting on a bed of blue and white silica gel that absorbs moisture. To view the objects, visitors press a button, which turns on display lights (filtered to block any destructive ultraviolet light) for only 90 seconds...
...teeth can be bonded during a single visit to the dentist. Diluted phosphoric acid is applied to the natural tooth, etching microscopic pores into the enamel. Next comes a coat of liquid plastic to seal the tooth. Then a paste composed of plastic and finely ground quartz, glass or silica is patted on in thin layers tinted to match the natural teeth and molded into the desired shape. After each layer is applied, it is exposed for up to 40 seconds to either ultraviolet or visible light beams. This triggers a reaction that hardens and bonds the layer...
Post-flight inspections of the thermal protection system, a blanket of 31,000 silica tiles which protects the 122-foot long orbiter from the heat of reentry, revealed only minor damage and no missing tiles, White said. The tiles had been a problem on Columbia's first flight in April, and were a source of many of the delays that set the $10-billion shuttle project more than three years behind schedule...
...these TV views also revealed a possible hitch: a handful of the spacecraft's 30,000 or so silica tiles, essential for insulating Columbia against the flaming, 2,400° F heat of re-entry into the atmosphere, had fallen off. Apparently they were shaken loose during maximum vibrations in the first few moments of the launch, possibly when the solid-fuel rockets were kicked away. The tiles, about a dozen in all, came from the area just above the orbital maneuvering engines on either side of the rudder. Mission controllers quickly pointed out that this was a noncritical...
...time and time again, if all goes well, reducing the cost of working in space and vastly increasing its possibilities. Columbia is designed to ascend like a rocket, orbit as an all-purpose freight truck and passenger bus, ward off melting re-entry temperatures with an armor of glazed silica tiles, then land like an airplane?or like an 80-ton glider...