IV Read the text. Composite Ceramics

Advanced ceramic materials have such interesting properties that mechanical engineers are becoming more and more interested in their use as structural parts. Ceramic cutting tools have been in use for some time. However, it is only during the last twenty years that there have been rapid development in this field because of the development of new composite ceramics. Composite materials are materials in which two or more different substances, such as metals, ceramics, glasses, or polymers are combined without chemical reaction, As a result one can produce a material with properties different from those of any of the individual constituents. The constituents of a composite would retain their individual characteristics. Recently engineers have developed various kinds of composite ceramics which must combine an increased toughness with the same hardness and strength of usual ceramics. A promising recent development is the addition of a tiny quantity of metal to increase toughness and tool life. Thus, at room and high temperatures (10000 C) the composite ceramics for cutting tools should possess the following properties: high strength, high toughness, high hardness, high thermal shock resistance and high chemical inertness.

Теxt 9

IV Read the text. An Encyclopedia on a Tiny Crystal

Scientists have discovered that a laser beam can be effectively used to record alphanumeric data and sound on crystals. According to Russian researchers a method for recording information on crystals by means of a laser has already been developed, but advanced technologies are needed to make it commercially applicable. At present researchers are looking for the most suitable chemical compounds to be used as data storages and trying to determine optimum recording conditions. Theoretically, the entire " Great Soviet Encyclopedia" can be recorded on a single tiny crystal.

As far back as 1845, Michael Faradey discovered that a light beam reverses its polarization as it passes through a magnetized crystal. Scientists of our day have used this phenomenon to identify crystalline materials capable of storing information. Lasers have been successfully employed to record information on and read it off. No ideal data storage crystal has yet been found, but it is obvious now that the future of computer engineering lies in lasers and optoelectronics. As paper gave way to magnetic tape, so the latter is to be replaced by tiny crystals.