(72) A new material that combines the temperature and corrosion resistance of ceramics with many of the properties of metals was described at a recent meeting of the American Chemical Society by Development Center at Schenectady, New York. The material is a lightweight composite, consisting of silicon carbide filaments separated by a silicon filler. The silicon carbide-one of the most heat-resistant materials known-provides the composite with its high temperature strength; the silicon filler accounts for the composite's toughness and its ability to bend under stress. With likely applications in gas turbines, coal gasifies, and other high temperature machinery, the material can operate at temperatures in excess of 1, 350°C-some 200°C above the limit for components fabricated from most heat-resistant structural metals and alloys.
26. The new material described in this passage is composed of _____. A. ceramic and metals B. silicon carbide C. silicon carbide and silicon D. metals and alloys
27. Which of the following descriptions of the new material is NOT true? A. It is not easily broken B. It won't be worn away by acid C. It is not easily affected by heat D. It won't change shape under stress
28. According to the passage, we silicon carbide in the composites is replaced by some other substance now in use, the composite will probably _____. A. not be able to stand such high temperature B. not be as tough C. be lighter in weight D. be more resistant to heat
29. According to the passage, the new material _____. A. is produced by using high temperature machinery such as gas turbines and coal gasifies B. can be melted and used for marking machines at a temperature above 1,350°C C. cannot withstand temperatures higher than 1, 350°C D. can be used in making gas turbines and coal gasifies
30. According to the passage, most heat-resistant structural metals and alloys can stand heat up to _____. A. more than 1,350°C B. about 200°C C. about 1,150°C D. about 1,550°C
silicon carbide in the composites is replaced by some other substance now in use, the composite will probably _____.
