Investigations on fused silica

With EPLEXOR® HT series GABO QUALIMETER Testanlagen GmbH shows worldwide the first DMTS instrument providing a temperature range up to 1500°C. This class of instrument is aimed for providing investigations on glass, metals, ceramics and even new high temperature composite materials in the high temperature range.

Figure 1: High temperature oven

Figure 1 exhibits a high temperature oven system. The sample holder shown in Figure 1 is a 3-Point Bending device (flexture test device). Our exclusively designed sample holders produced with new high temperature materials enables the user to carry out test procedures without an inert gas supply.

Figure 2: Temperature sweep on silica glass Figure 2 shows the test results obtained for different fused silica. Rectangular glass samples with dimensions of 5 mm (width) x 2 mm (thickness) x 30 mm (length) were investigated (temperature sweep). For both samples a test frequency of 1 Hz and a heating rate of 2 Kelvin/min were applied. The sample holder used for this test was a newly designed asymmetrically 3-Point Bending device. The damping properties (tan delta) in function of the temperature are significantly different from each other.

Resolution
At what accuracy can tan delta be determined?

This picture shows the 3-Point Bending IE*I modulus and the loss factor tan delta of a glass, showing a glass transition above 500 °C. Typical for this 3-Point Bending experiment are the low absolute values for the visco-elastic damping in dependence on the temperature. Such minimal tan delta values, corresponding to phase shift between force and sample deformation, can only be determined with an extremely high resolution in the phase shift measurement. We therefore have equipped our spectrometer series EPLEXOR® with a high precision phase angle determination. The resolution is better than tan delta ≤10-4 .

A new tool for tests on very stiff, but brittle low damping materials
- asymmetrical 3-Point Bending device -

The picture shows the asymmetrical 3-Point Bending storage modulus E‘ and the loss factor tan delta of a glass showing a glass transition temperature of above 400 °C. The observed tan delta peak with a maximum at 200 °C has to be related to thermically activated molecular motions of the Na+- ions within the glass. Friction processes due to the interaction between the sample and the sample holder can be totally suppressed. Therefore the asymmetrical 3-Point Bending device enables the user to investigate brittle low damping materials ( tan delta ~0.0002) with a very high accuracy in tan delta measurement.