Task 1. Give Ukrainian equivalents to the following words and word combinations.

Placer, obesity, bearing, malleable, inlay, to tarnish, strength, thick-film paste, to resist, balance wheel, dentistry, volatile, jewelry, red heat, integrated circuit, hardness, sponge, alumina, emissions, purification, coating, exhaust, reforming, spark plugs.

Task 2. Fill in the correct words and word combinations from the list below. Use each word only once.

Properties, mixture, devices, coatings, a means of, exhausts, true, alloyed, applications, considerable, ordinary, switching.

1. … systems 7. … amount

2. protective … 8. automobile …

3. at … temperatures 9. outstanding catalytic …

4. in … state 10. … purifying the gas

5. miniature solid-state 11. … of gases

6. … compound 12. various …

Task 3. Fill in the gaps with the verbs from the list below used in the proper tense form.

To increase, to provide, to be, to use, to diffuse, to absorb, to alloy, to be, to find, to discover, not to tarnish.

1. Palladium … extensively in medicine, e.g., it is widely used in dentistry, often alloyed with platinum and gold in dental inlays.

2. It … in 1803 by Wollaston.

3. Palladium also … with platinum for various applications in jewelry.

4. It … a steel-white metal, which … in the air, and … the least dense and lowest melting of the platinum group of metals.

5. It … a considerable amount of hydrogen gas - a unique property of palladium.

6. When annealed, it is soft and ductile, cold working greatly … its strength and hardness.

7. It also … associated with the nickel-copper deposits of South Africa and Ontario.

8. Hydrogen readily … through heated palladium and this … a means of purifying the gas.

UNIT 17 NON-FERROUS METALS. TANTALUM

Tantalum is a grayish silver, heavy, and very hard metal. When pure, it is ductile and can be drawn into fine wire, which can be used as a filament for evaporating metals such as aluminium. Tantalum is almost completely immune to chemical attack at temperatures below 150°C, and is attacked only by hydrofluoric acid, acidic solutions containing the fluoride ion, and free sulphur trioxide. The element has a melting point exceeded only by tungsten and rhenium.

Isolation of tantalum appears to be complicated. Tantalum minerals usually contain both niobium and tantalum. Since they are so similar chemically, it is difficult to separate them. Tantalum can be extracted from the ores by first fusing the ore with alkali, and then extracting the resultant mixture into hydrofluoric acid. Current methodology involves the separation of tantalum from these acid solutions using a liquid-liquid extraction technique. In this process tantalum salts are extracted into the ketone MIBK (methyl isobutyl ketone). The niobium remains in the solution.

After conversion to the oxide, metallic tantalum can be made by reduction with sodium or carbon. Electrolysis of molten fluorides is also used.

Uses. Tantalum metal has a number of important uses. It is used to make steels with desirable properties such as high melting point, high strength, good ductility. These find use in aircraft and missile manufacture. It is very inert and so useful in the chemical and nuclear industries to line reactors.

Tantalum wires were those used first for light bulbs (now tungsten is preferred). The metal is immune to body liquids and the body tolerates the metal well. Therefore, tantalum has widespread use for surgical use. For instance, it can be used in sutures and as cranial repair plates. The metal is used in the electronics industry for capacitors.

The oxide is used to make special glass with a high index of refraction for camera lenses.

Forming and Stamping. Most sheet metal work in tantalum is done with metal of thickness ranging from 0.004 to 0.060 inch. Blanking or punching presents no difficulties. Steel dies are used. The clearance between the punch and die should be close to 6 percent of the thickness of the metal being worked. Close adherence to this clearance is important, and the use of light oil or perchloroethylene is recommended to prevent scoring of the dies. Trichloroethane is also acceptable.

Form stamping techniques are similar to those used with mild steel, except that precautions should be taken to prevent seizing or tearing of the metal. Dies may be made of steel except where there is considerable slipping of the metal, in which case aluminum bronze or beryllium copper, should be used. Low melting may be used for experimental work or short runs. Rubber or pneumatic die cushions should be used where required. Annealed tantalum takes a permanent set of forming and does not spring back from the dies.

It should be kept in mind that tantalum does not work-harden as rapidly as most metals. Dies should be made of aluminum bronze, although the punch may be steel if there is not too much slippage encountered.