Санкт-петербургского государственного университета высшее профессиональное образование т. А. Степанова, И. Ю. Ступина
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limbs — конечности; molten — рас плавленный; filling — пломба (зубная); conventional — обычный; plate— покрывать металлом; bake — запекать; chip — откалываться; рее! — ше лушиться Text 10 В Прочтите текст про себя (контрольное время чтения — б минут). Uses of Indium Indium finds most of its uses as an addition to other materials for the purpose of obtaining more desirable properties. Indium and its compounds also find uses in jewellery, pharma- ccuticals, mcdicincs, mordants for dycstuffs, and also in low-mclting- point alloys. Indium forms alloys with many metals; some of them arc lead, thallium, tin, silver, gold, platinum, mercury, bismuth, and sodium. Alloys o f Au-In have good brazing characteristics. For example, the alloy of 77.S per cent Au and 22.5 per cent In has a working temperature of about 500°C. This enables the alloy to be used on metal pieces with glass inserts. Indium alloys arc very corrosion-resistant. Low-melting alloys could also be used in making casts for broken limbs; a form is made around the broken member and the molten alloy poured into it. The alloy would be at a temperature which would cause no discomfort to the patient. In dental work, indium amalgamated with mercury was frequently used. In fact, this must have been the first commercial use of indium. The resulting fillings were harder, more resistant to corrosion and discoloration than conventional fillings and looked little different. 75 Indium cannot be plated on ferrous metals directly. However, by first coating the iron or steel with a metal such as zinc, cadmium, or some similar metal which has a higher clcctrodc potential than the iron or steel and indium plate could be deposited successfully. After such a plate is deposited the article is baked at a temperature slightly above the melting point of indium for several hours. The indium and the other non-ferrous metal diffuse into one another, to producc a uniform plate which would not chip or peel and which would be non-porous. Indium can be plated directly on non-ferrous metals. Generally, the plate is diffused into the base metal by the method mentioned above. Such coatings are more resistant to certain kinds of chcmical attack than the base metal and arc usually harder. Упр. 4. Что нового вы узнали из текста 10 В? Упр. 5. Разделите текст на тематические части и озаглавьте каж дую часть. Упр. б. Скажите, что говорится в тексте: 1) о сферах применения индия и его соединений; 2) о сплавах индия с другими металлами; 3) о применении индия в медицине. Упр. 7. Найдите в тексте место, т е говорится об особенностях нане сения слоя индия иа металлы. Переведите этот отрывок на русский язык. жүктеу/скачать 5,96 Mb. Достарыңызбен бөлісу:
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