One Process Ceramic Foam Sintering and Debinding

The Fraunhofer Institute for Ceramic Technologies and Systems (IKTS) in Dresden, Germany, performs research into advanced ceramics, ranging from preliminary research through to a host of advanced applications. IKTS specializes in the manufacture of industrial powder processing technologies and the development of functional ceramics, prototype structural ceramics, and cermet (ceramic-metal hybrids).

IKTS research has led to the development of a complex and innovative ceramic foam material which can be employed in various industry sectors. Foamed ceramics are of particular interest for energy management and filtration applications, and also form the basis for ceramic carriers in the catalyst industry. They are perfect for the filtration of liquefied and dust material. Foamed ceramics offer the ideal combination of low mass and mechanical strength and are being utilized in metal matrix composites.

Custom designed solution based on an RHF chamber furnace and a G-range tube furnace

Custom designed solution based on an RHF chamber furnace and a G-range tube furnace

Silicon Carbide Heated Furnace

For its latest project, IKTS needed a custom-designed, silicon carbide heated furnace with a working temperature of 1400 °C and a chamber capacity of 35 l for the debinding and sintering of ceramic foams.

The custom design is based on a standard CARBOLITE RHF furnace, the range of which includes 4 chamber capacities: 3, 8, 15 and 35 liters and three maximum temperatures: 1400, 1500 and 1600 °C. Gases, such as toxic cyanide, nitrogen dioxide or isocyanate are produced during the production of foamed ceramics by combustion of polyurethane and organic binders. This means the gas should be subjected to a catalytic treatment to burn them off as completely as possible. The solution was to install an after-burner containing a modified tube furnace from CARBOLITE’s G-range, which is equipped with an inconel steel tube. This is then filled with a ceramic honeycomb with the catalyst on the surface, making it possible to completely burn off toxic gases containing up to 150 g of polyurethane. A fan with a capacity of 150 l/minute to 250 l/minute pulls the atmosphere through the tube furnace in which the catalyst is located, and the cleaned gases subsequently enter the exhaust system at the Fraunhofer Institute.

The furnace system was developed as a fully automated solution for the two-stage process of debinding and sintering. For the debinding cycle, the furnace is gradually heated from room temperature to 600 °C. During this period, the emitted gas is let out from the chamber and allowed to pass over the catalyst. However, it is crucial to protect the catalyst as the temperature should not exceed 700 °C.

In order to guard the catalyst during the subsequent sintering at 1290 °C, the exhaust fan is switched off at a furnace temperature of 600 °C. This ensures that the catalyst is invariably kept at its ideal temperature, is not overheated, and cannot be damaged by hot gases which travel over it. The temperature of the furnace chamber is tracked by a thermocouple; over-temperature protection with a separate circuit ensures that the furnace is prevented from over-heating. Additionally, a complex flip-flop control system protects the tube furnace heating elements. Even with the rising temperature of the exhaust gases, the right temperature of the catalyst is always maintained and the heating elements are not over-loaded.

Features

Debinding and Sintering Furnace

  • Very good temperature uniformity during sintering
  • ‘Flip-flop’ protection for tube furnace elements
  • Adjustable suction volume with automatic cut-off for sintering process
  • Long-life catalyst
  • Specific catalyst for burning PU
  • Separate temperature control for chamber and catalyst

G-Range Tube Furnaces

The G-range of tube furnaces provides a flexible solution for heating samples of various sizes, up to a maximum heated length of 1200 mm. There is no integral work tube in these furnaces, but the use of tube adapters enables the same furnace to accept a wide range of tube diameters up to 170 mm. In addition, the rapid and easy exchange of tubes allows the use of different tube materials and helps prevent cross-contamination of samples.

While the after-burner provided for IKTS is based on a single zone vertical tube furnace, the G-range is also available as a 3-zone version which offers an extended uniform zone. The heated length is grouped into three zones, each with its own controller – the two end zone controllers monitor the temperature of the center zone temperature and offset the heat loss from the tube ends. The G-range can be modified for use with inert atmosphere and/or vacuum to 10-6 mbar, thanks to a range of insulation plugs and tube end seals.

Features

Tube and Chamber Furnaces

  • Maximum chamber and tube furnace temperatures of 1100 – 1800 °C
  • Range of tube diameters and heated lengths available
  • Range of chamber sizes available
  • Element protection in chamber furnaces available

G-range tube furnaces

The G-range tube furnaces are available in horizontal and vertical configuration.

Carbolite Gero Ltd.

This information has been sourced, reviewed and adapted from materials provided by CARBOLITE GERO Ltd.

For more information on this source, please visit CARBOLITE GERO.

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