Numerous thermal processing formats are available to researchers and manufacturers handling relatively small-volume samples or operations with low throughput. At these scales, benchtop laboratory ovens tend to excel – yet the geometry of the thermal processing chamber can be a limiting factor in certain application areas.
Research and development (R&D) into the generation of fine ceramic filaments led to the very first cylindrical heating chambers in the early 20th Century, and the tube furnace has since become a common sight on factory floors and in materials laboratories worldwide.
In this blog post, Thermcraft explores when to use a tube furnace in more detail.
The eponymous component in a tube furnace is the heating chamber. This is comprised of a circular furnace wall made of high-temperature ceramic; either formed from a full cylindrical element or two semi-cylindrical elements that close to form a single void. Refractory heating coils or ribbons are embedded into the ceramic to surround a central chamber with uniformly distributed heaters. This architecture guarantees the highest possible thermal uniformity for processing both inorganic and organic compounds.
Two primary types of tube furnace are available from Thermcraft:
Tube furnaces are used for a broad range of thermal processes, including: inorganic and organic purification; accelerated aging; annealing; coating; drying; and much more. As a result, they have proven integral in a broad range of heat treatment markets.
The primary reason to use a tube furnace is the unmatched thermal uniformity offered by cylindrical heaters. Components in a single-zone chamber are subjected to consistent heating values exceeding 1000°C (1832°F) across a full 360° axis, which ensures optimal distribution of heat across the full cross-section of the part. This makes tube furnaces ideal for sensitive thermal processing applications, such as thermocouple calibration.
Tube furnaces can also be integrated with multiple heating zones to elevate the processing capabilities of the instrument. This allows a fully-controllable temperature gradient to finely-tune the heat-up and cool down stages of thermal processing. It can also limit peak temperatures to specific areas of interest on a part – typically the central section, which leaves either end safe to handle with additional machinery. This is useful in a range of materials testing applications, enabling accurate characterizations of material mechanical properties at elevated temperatures.
Thermcraft specializes in the development of custom furnace solutions for specific customer requirements. With decades’ experience in thermal processing and vertical integration of bespoke heat treatment solutions, we can reliably collaborate with you to resolve any processing challenges.
If you would like to learn more about the various accessories, controls, and additional mechanical alterations we can make to our standard range of tube furnaces, simply contact a member of the Thermcraft team today.
A tube furnace is an electric heating device used to conduct syntheses and purifications of inorganic compounds and occasionally in organic synthesis. One possible design consists of a cylindrical cavity surrounded by heating coils that are embedded in a thermally insulating matrix. Temperature can be controlled via feedback from a thermocouple. More elaborate tube furnaces have two (or more) heating zones useful for transport experiments. Some digital temperature controllers provide an RS-232 interface, and permit the operator to program segments for uses like ramping, soaking, sintering, and more. Advanced materials in the heating elements, such as molybdenum disilicide (MoSi2) offered in certain models can now produce working temperatures up to 1800 °C. This facilitates more sophisticated applications.[1] Common material for the reaction tubes include alumina, Pyrex, and fused quartz, or in the case of corrosive materials molybdenum or tungsten tubes can be used.
The tube furnace was invented in the first decade of the 20th century and was originally used to manufacture ceramic filaments for Nernst lamps and glowers.[2]
Illustrative applications
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An example of a material prepared using a tube furnace is the superconductor YBa2Cu3O7. A mixture of finely powdered CuO, BaO, and Y2O3, in the appropriate molar ratio, contained in a platinum or alumina "boat," is heated in a tube furnace at several hundred degrees under flowing oxygen. Similarly tantalum disulfide is prepared in a tube furnace followed by purification, also in a tube furnace using the technique of chemical vapor transport.[3] Because of the availability of tube furnaces, chemical vapor transport has become a popular technique not only in industry (see van Arkel–de Boer process) but also in the research laboratory.
Tube furnaces can also be used for thermolysis reactions, involving either organic or inorganic reactants. One such example is the preparation of ketenes which may employ a tube furnace in the 'ketene lamp'. Flash vacuum pyrolysis often utilize a fused quartz tube, usually packed with quartz or ceramic beads, which is heated at high temperatures.
References
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