The Role of Gold Insulation in Transparent Tube Laboratory Furnaces

Due to its superficial monetary value, gold (Au) is one of the most sought-after precious metals in the world. It also possesses beneficial electro- and thermomechanical behavior for manufacturing and engineering applications.

Gold has a thermal conductivity of around 310 Watts per meter-Kelvin W/(mK) from room temperature up to 225 °C (437 °F) and exceptional reflectivity to infrared (IR) radiation, so it is frequently utilized to create faceplates for space suits and protective films for satellites.

These coveted properties are slowly being acknowledged in a wider scope of fields. Most recently, gold has been utilized for thermally-efficient heat shieldings in the engine bays of Formula One cars. Gold has been looked at as a possible insulator for innovative transparent tube laboratory furnaces.

The excessive operating temperatures of typical heat treatment environments is the key challenge of using gold in laboratory furnaces. Normal thermal processing for analytical applications needs heating chambers which can facilitate temperatures of over 1000 °C.

Gold possesses a melting point of 1064 °C and is subject to thermal warping at much lower temperatures. Thermcraft has developed a unique solution to this problem. This article explores how gold is successfully utilized as an insulator in their unique Transparent Tube Laboratory Furnace.

Where is Gold Installed on the Laboratory Furnace?

The TransTemp laboratory tube furnace is made up of three concentric tubes of Pyrex glass and quartz. Inside the outermost Pyrex tube is a thin film of gold which is approximately 80 nanometers (nm) thick. This reflective layer is created as a series of gold ‘islands’ which are separated with uncoated channels of Pyrex. The gold films lightness establishes the distance between these islands.

What Does the Gold Mirror Achieve?

This gold thin film acts as a reflector of the IR energy produced by the brazed coil heating elements inside the second tube. It reflects these wavelengths back into the heating chamber continuously in order to amplify the thermal uniformity over up to 60% of the process tube.

The ambient air which is outside the tube ensures the film stays at a low temperature and limits the risk of thermal degradation. The reflectivity of the gold mirror verifies that extremely low levels of heat are transmitted through the film itself and instead, is redirected back into the heating chamber.

As it features high transmissivity of many visible wavelengths of light, the selective reflectivity of gold is perfect for laboratory furnaces. Light gold films are reasonably transparent, allowing analysts to observe process conditions directly in situ. Heavier gold films increase the opacity of the outer Pyrex tube naturally, whilst increasing the thermal and electrical efficiency of the Transparent Tub Laboratory Furnace.

This information has been sourced, reviewed and adapted from materials provided by Thermcraft, Inc.

For more information on this source, please visit Thermcraft, Inc.


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