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A crucible is a container used to heat up materials to extremely high temperatures or melt metals. Crucibles can be produced from any material that can survive temperatures high enough to melt or otherwise change their contents. Ceramics are a crucial material for making crucibles. The actual materials that make up ceramics are non-metallic, inorganic, crystalline, or amorphous solids that have been heated, cooled, and coated during the production process. Ceramics are distinguished by having a smooth, inert surface. A crucible needs an inert surface, also known as a non-reactive surface, to avoid mixing with the contents. According to their raw materials, performance, and intended usage, ceramic crucibles can be classified as quartz, corundum, boron nitride, zirconia, etc. crucibles.
Ceramic crucibles have been employed for metalworking since approximately 5000 BC. Crucibles have been used in the smelting of copper, tin, and iron throughout history. As metallurgy skills advanced, so did their design. Numerous raw minerals, including silica, zircon, spinel, alumina, and magnesite, can be used to create a ceramic crucible. Considering that each chemical composition responds to temperature and pressure differently, the desired chemical composition of the ceramic crucible depends on the application.
Alumina crucibles are a scientific name for corundum crucibles with about 99.7% of the material being alumina Al2O3, having traces of MgO and SiO2. Due to their low cost and ability to resist a range of temperature conditions, alumina crucibles are particularly popular. They are strong and resistant to melting, high temperatures, acid and alkali, rapid cooling, intense heat, and chemical corrosion. Corundum crucible is a great material for melting samples - it works well for some weakly alkaline materials such as anhydrous Na2CO3, but not for Na2O2, NaOH, etc. Fluxes are compounds that are both strongly alkaline and acidic and are used to melt samples. In a redox atmosphere of 1650°C–1700°C, the 99.70% pure alumina crucible has good high-temperature insulation and mechanical strength, and the maximum temperature can quickly approach 1800°C. Depending on the circumstances of the application. Many sizes and shapes of alumina crucibles are available.
Common varieties of Boron Nitride (PBN) are Cubic Boron Nitride (CBN) and Hexagonal Boron Nitride. The boron nitride crucible is typically made of P-BN. P-BN ceramics are excellent heat dissipation and high-temperature insulating materials because of their excellent heat resistance, thermal stability, thermal conductivity, and dielectric strength at high temperatures. Due to PBN's excellent chemical stability, it can withstand the erosion of the majority of molten metals. It is ideal for harsh environmental conditions like semiconductor manufacturing processes because of its high thermal conductivity and low thermal expansion properties depending on the substance employed. PBN crucibles are frequently employed in the smelting of semiconductors and metals. With atmospheric protection, it can withstand temperatures of up to 2100°C and 1800°C, respectively. generally protect with argon or nitrogen (atmospheric protection is to prevent the crucible from oxidation).
Further Reading: Use Guide of Pyrolytic Boron Nitride Crucible
A graphite crucible is a type of melting vessel commonly used for non-ferrous, or non-iron, metals like gold, silver, aluminum, or brass. Due to its great temperature endurance and low reactivity with molten metals, the carbon material known as graphite is frequently utilized for crucibles. Graphite and clay are generally combined to create a solid container when they are molded and burned at extremely high temperatures. Graphite crucibles can be brittle, like many ceramic vessels, and need to be handled carefully. Graphite crucible’s inherent softness has a wide range of uses, including as an addition in lubricant formulas, structural materials, and metallic alloys.
A graphite crucible should be properly stored and conditioned. It is crucial to precondition a new graphite crucible before using it. After two hours at 500 degrees Fahrenheit (260 degrees Celsius) in the oven, the crucible should be taken out and allowed to slowly cool in a dry area. Removing moisture keeps the crucible from splitting. Crucibles need to be dried off and reconditioned if they become wet. They should never be stored near moisture.
The steady progression of chemical processes depends on ceramic crucibles. Ceramic crucibles are crucial pieces of chemical equipment used for melting down materials, an effective way to reuse scrap items. Ceramic crucibles make it easier to recycle metallic materials because they can easily be cast into new objects or combined into new alloys.
