Iron
This figure depicts the linear thermal expansion and physical
coefficient of thermal expansion (physical CTE) of iron. The sample was
measured at a heating rate of 5 K/min in a helium atmosphere. At 906°C
(peak temperature in the physical alpha) a shrinkage step was detected.
This is due to a change in the lattice structure (bcc -> fcc).
Another change in the lattice structure (fcc -> bcc) was detected at
1409°C. The deviation between the measured and literature transition
temperatures is due to a small impurity content.
Alumina green body
An alumina green body was tested with the DIL 402 C employing the
NETZSCH Rate Controlled Sintering (RCS) software. The measurement was
carried out at a heating rate of 10 K/min. The start/stop mode of the
RCS software was used. The threshold value was 10 µm/min (0.046 %/min).
The heating rate was reduced by RCS during sintering to achieve a
constant shrinkage rate. The influence of additives (e.g. organic
binder, clays) was measured up to 1150°C. The main sintering step
occured between 1150°C and 1350°C.
Glass Ceramic - Zerodur
Zerodur is a glass ceramic produced by Schott Glas in Mainz, Germany.
It is designed for zero thermal expansion around room temperature. This
material is often used for high performance terrestrial telescopes. The
figure shows the linear thermal expansion between -150°C and 100°C. The
sample was measured twice at a heating rate of 3 K/min in a helium
atmosphere. The measured CTEs between 0°C and 50°C are in excellent
agreement with the literature values (Schott brochures).
Silicon nitride
Because of its excellent thermal and mechanical properties, silicon
nitride is used more and more for high-tech applications (e.g. valves
in automobile engines). Of course, the properties of the final parts
are heavily influenced by the production/sintering process. Depicted in
this figure is the thermal expansion of a silicon nitride green body.
The sintering step starting at 1201°C is due to the influence of the
sintering additives. The main shrinkage step occured at 1424°C
(extrapolated onset). The effect above 1760°C is most probably due to
evaporation of additives.
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