Porcelain type clays

Traditionally, opium is smoked with a pipe, typically around 20 inches long. Opium pipes are usually made of wood, and the type of wood used often denotes the wealth of the smoker. Poor smokers typically use pipes made from bamboo, while wealthier smokers may have pipes constructed of ebony. About three-quarters down the shaft of the pipe rests the bowl, a hollow structure that can be made of metal, porcelain, or clay, again depending on the quality of the pipe. The hollow pipe is sealed on one end and has an opening on the other, through which the user takes in the smoke. 

Type of porcelain Kaolin (Clay) Quartz (wt.%) Feldspar Firing temperature CC)... 

Ceramics of this type require the presence of a significant amount of clay for their forming and sintering. These ceramics include porcelain, earthenware, stoneware, bricks and related products, and fireclay. The latter is dealt with in a separate chapter on refractories. 

The most common type is the triaxial earthenware composed of clay, quartz and feldspar. It differs from porcelain in the lower firing temperature such that the sintering process does not produce complete densification. This is why earthenware is not translucent, and shows a comparatively low strength. Water absorption in open pores varies over wide range (8 — 22 %). 

Typical prehistoric pottery, called earthenware, requires temperatures between 900 and l,200°C (l,650-2,200°F) to vitrify. Fine porcelain pottery made from kaolin clay is fired at l,280-l,350°C (2,300-2,400°F) it is white and often translucent. A modem kitchen stove will produce temperatures ca. 260°C (500°F). An open wood fire produces temperatures in the range of 800-900°C (l,450-l,650°F). Closed kilns, a kind of oven, can reach temperatures of l,000°C (l,830°F) or more. Table 6.1 provides some information on firing temperatures, kiln conditions, and the type of ceramic produced. The conditions of firing determine the color of the pottery that is produced. 

Low-permittivity ceramics are widely used for their insulative properties. The major requirements are good mechanical, thermal, and chemical stability good thermal shock resistance low-cost raw materials and low fabrication costs. These include the clay- and talc-based ceramics also known as electrical porcelains. A large-volume use of these materials is as insulators to support high tension cables that distribute electric power. Other applications include lead-feedthroughs and substrates for some types of circuits, terminal connecting blocks, supports for high-power fuse holders, and wire-wound resistors. 

Kaolin ite AljlOHj Si Os (Figure M64) Type A + silicate layer on one side White to yellow. The principal component of porcelain clay... 

However, to meet the increasing demands, boosted by the Industrial Revolution, of industry and society, mass production of ceramic products from natural raw materials began. Depending on the type of product, various proportions of clay-, quartz- and feldspars were used, and methods proven in the production of earthenware and porcelain applied ( 2. Tradition continued. Clay tradition)). The products include a. big high-voltage insulators for power supply lines, made in most cases of so-called technical porcelain which contains more quartz and AI2O3 than traditional porcelain b. sanitary ware—this term includes a series of products used for sanitary purposes, such as washbasins, toilet bowls, bidets, etc. c. Acid-resistant ceramics used for drains and sewers d. Ceramic tiles for walls and floors. 

Vitreous ceramics, which derive their name from the Latin word for glass, vitreus, are possibly the oldest and most widely used types of ceramic materials. Marco Polo introduced them in Western Europe in the fourteenth century, and European potters strove for decades to duplicate the quality of the Chinese porcelains. In addition to porcelain they include china, pottery, and brick. Typically, they are made fiom clays such as hydrous aluminosilicate mixed with other inert materials. Ware is formed when the clays are in the wet state, after which they are dried and fired. Various additives are used to provide desired properties. 

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