TOM-AC – Monitoring sintering under defined atmosphere

Quality of sintering and other heat treatments

Heat treatments need precise conditions to yield best results and ideally the processes can be monitored in situ to gain a better understanding. Ceramics and powder metallurgical materials are densified and strengthened by way of sintering. This process determines the quality of the final product – and accounts for a considerable part of production costs.
As sintering shrinkage is the most telling indicator of the sintering state, close monitoring of the shrinkage during the heat treatment can be used to optimize the processing parameters. Weight loss and dimensional changes during debinding provide information on how to optimize debinding cycles. Weight gain and optical inspection allow for the in situ measurement of infiltration processes.
 

Our task

• Monitoring the sintering shrinkage without mechanical impact of the measuring device on the samples
• Recording  of any warpage of the sample during sintering even if the sample shape is quite irregular
• Heat treatment in vacuum, inert or reducing atmosphere
• Measurement of weight changes in controlled atmosphere
• Determining the wetting behavior of melts on solid substrates
• Monitoring infiltration processes in situ

Furnace with controlled atmospheres and dilatometer

TOM-AC is the combination of a high temperature (2000 ºC), a high temperature graphite furnace (2400 °C) or a full metal molybdenum furnace (1650 °C) with an optical dilatometer. The crosslight silhouette of the sample is recorded by a CMOS camera. A special optical system provides distortion free imaging even if the sample is displaced, e.g. due to thermal expansion.

Special image analysis software

Dimensional changes of the sample are registered by special image analysis software; the sample may be of any shape as long as its complete silhouette remains within the measuring window (diameter 50 mm). The volume of samples which are rotationally symmetrical can be optionally calculated.

A measurement every second

Measurements are taken every second so that rapid changes can be registered. Furthermore, melting and wetting phenomena can be investigated by examining the wetting angles and infiltration kinetics.

Comfortable use

TOM-AC is controlled by a standard PC and operated via a comfortable graphical user interface. Besides the data on dimensional changes, saved as ASCII-files, single images and time-lapsed videos of the thermal treatment can be obtained. The resolution of TOM-AC is about 2 µm with very high reproducibility.

Non-contact optical measuring mode

• No mechanical impact on the sample
  
• No moveable mechanical part
   

Two-dimensional silhouette recording

• Measuring of anisotropic sintering processes and warpage
• Monitoring of wetting, melting and infiltration phenomena
• Simultaneous recording of up to 20 parameters
   

Image processing software

• Automatic compensation of shifts within the measuring window
• Optimization of the image contrast by illumination control
• Measurements every second in order to record rapid dimension changes
• High reproducibility
   

Atmosphere control

• Automatic switching between pumping and gas flow
• Computer control of gas mixtures (Ar, N₂, H₂, CO)
• High vacuum conditions

TOM-AC is optionally available with a weight sensor for the simultaneous gravimetric investigation of the sample.
A further option is the equipment for measuring samples loaded with uni-axial force.