Ceramic crucibles are vessels used in high-temperature furnaces to hold materials like metals and glass. They are stable at high temperatures and commonly used in manufacturing, research, and the arts. The choice of chemical composition affects the temperature and pressure at which the crucible is useful. Ceramic crucibles have been used for metalworking since 5000 BC and have evolved over time.
In general, a crucible is a vessel, or dish, used to hold a sample inside a high-temperature furnace. A pottery crucible is made of a ceramic material, such as kiln-fired clay. Ceramic crucibles are chemically and physically stable at high temperatures, and are therefore used to work with materials that must be handled at very high temperatures, such as metals and glass.
Ceramic crucibles are commonly used in manufacturing, especially metallurgy, analysis and quality control. They are also common tools in research environments in fields such as materials science, earth sciences and engineering. Crucibles are also found in use in the arts, both for working with metals and pigments.
The feature that makes a crucible useful is the ability to withstand higher temperatures than whatever material is placed in it. This allows you to melt and manipulate the material inside the crucible without destroying the container. Being physically and chemically stable at high temperatures is a characteristic also called refractory.
The ceramics themselves are nonmetallic, inorganic, crystalline, or amorphous solids that have been fired, cooled, and glazed during their creation. Commonly known within ceramics, ceramics are characterized by their smooth and relatively inert surface. An inert, or non-reactive, surface is not only useful but essential for a crucible. If the surface is reactive, materials within the crucible itself may begin to mix with the contents of the crucible at high temperatures.
A ceramic crucible can be made from a variety of starting materials including silica, zircon, spinel, alumina and magnesite. The desired chemical composition of the ceramic crucible depends on the application, as each composition reacts differently to temperature and pressure. Alumina crucibles are particularly common as they are relatively inexpensive and withstand a wide variety of temperature environments.
Regardless of the application, a variety of characteristics must be considered when choosing a ceramic crucible. Chemical composition is usually the most significant characteristic, as it most directly affects the temperatures and pressures at which the crucible will be useful. Other relevant features include total capacity, overall shape, and wall and bottom thickness.
Ceramic crucibles have been used for metalworking since about 5000 BC. Used in the smelting of copper, tin, and iron throughout history, crucible designs have changed and evolved as metalworking techniques have developed. The fact that the design and use of crucibles have changed over time makes them historically interesting and quite useful to archaeologists. Early crucibles were irregularly shaped, often inconsistent in thickness, and usually not extremely refractory. Most modern crucibles are manufactured to an almost unlimited set of specifications and are used at higher temperatures and pressures than once thought possible.
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