| Sahiplik | Değer |
| İsim | WHAT IS GLASS? |
| Açıklama | WHAT IS GLASS? Scientist do not yet know precisely but generally it may be said that is the substance formed by melting mixtures of various inorganic substance and then cooling the melt in a manner which prevent crystallisation –that is ,the molecules never arrange themselve in a crystalline pattern.The many differnt class,with properties differing according to the raw material used,can be made. Silica sad(SiO2)is the main integredient of most commercially important glasses but very high temperature are neeeded to melt silica alone Fused silica,which is used for several temperature appplications,vitrifies when melted at about 1,700 °C.Glasss melting at lower temperature can be made by adding fluxing-agents to the silica sad;for instance soda ash(Na2CO3).The addition of 25 Per cent of soda ash to silica sand reduced the melting temperature to about 800 °C.But the resulting subtance is the waterglass(Na2SiO3),which is souble in water. However,a stabilizer such as limenstone(CaCO3)can be added and can be made basically from 15 part sand (SiO2) 5 part soda ash(Na2SiO3) 4 part limenstone(CaCO3) The raw material having been carefully weighed are mixed and heating to about 1,500 °C,and over a period of time they gradually melt and react.To assist melting,15 Per cent to 30 Per cent of cullent(scrap glass) is often added to those raw materials.Great care is taken to ensure that this cullet added to the batch is of the same composition as that being melted.And variation could spoil the quality of the glass produced. The Early History of Glassmaking No one knows when or where glass was first made. The first objects crafted entirely of glass were beads from Mesopotamia and ancient Egypt dating from about 2500 BC. Small glass vessels that were neither blown nor molded but were painstakingly sculpted from solid blocks of glass have been found and are estimated to be about 4,000 years old. The earliest ... |
| Dosya Adı | Bağlantı www.edubilim.com_endustri1-155-2.doc |
| Dosya Boyutu | Link |
| Dosya Tipi | doc (Mime Tipi: link) |
| Ekleyen | admin |
| Ekleme tarihi: | 15.10.2008 16:13 |
| İnceleyenler | Herkes |
| Kontrol Eden | Editor |
| İndirme sayısı | 0 İndirme sayısı |
| En son güncelleme | 14.10.2008 16:14 |
| Anasayfa | http://www.edubilim.com |
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