Nickel-loading experiments

Fig. 3 (curves a and b) shows results obtained with a lower COj/CH ratio of two. It can be seen that the higher nickel loaded catalyst (4% Ni/ZrOJ also lost activity under these conditions. The catalyst with the lowest loading of nickel (1. WoNi/ZrOj) was stable under these conditions and showed no weight loss on TGA/DSC analysis. Fig. 3 (curve c) gives the results for the 1,1% Ni/Zr02 catalyst obtained with a C(VCH4 ratio of unity. The TGA/DSC experiment on this sample showed that there was some carbon deposition (2% weight loss). 

Experiments showed [425] [449] that the particle size after prolonged sintering depends little on nickel loading. In practice, it appears that a maximum particle size stabilises at a given temperature as the movement of these particles becomes very slow [415]. 

The main point to be made here is that the phase shift data obtained from spectral interferometry has two contributions surface motion and optical effects. These two contributions to the phase versus time data can be separated by performing these experiments at two angles of incidence and two polarizations, at technique we term ultrafast d3mamic ellipsometry. The optical effects during shock breakout in nickel films were hidden because they produce phase shifts of the same sign as that caused by surface motion. Ultrafast dynamic ellipsometry allowed that contribution to be measured [71]. In our experiments on bare metals, the observed optical effects are due to changes in the material s complex conductivity under shock loading. We will see below that this is only one of several kinds of optical effects that can be observed in these and other materials. 

Vessels are loaded with terrestrial cellulose, lake sediment cellulose, or water and graphite (as a carbon source) and sealed in an argon atmosphere, followed by heating (pyrolysis) at 1050 °C in an evacuated quartz tube. The addition of an encapsulating quartz tube has been incorporated to prevent repeated oxidation of the outer nickel surface and to simplify the cleaning procedure. Heating has been increased from 950 °C used in the original experiments to 1050 °C to account for the insulation of the quartz tube (see Motz et al, 1997). 

---