Experimental results quartz particles

A series of bottle point erqreriments was conducted to assess the wettability of these materials. The solid materials were equilibrated with an aqueous lO MNaCl solution for at least 24 hours. PCE, dyed red to inqrrove visualization, was then added to the soil/aqueous phase slurry and the mixture was shaken. No surface active agents were added to these systems. Experimental results indicate a range of wetting conditions (Figure 4). The quartz sand system serves as a water-wet standard (bottle 1). The Ann Aibor II soil and Utica shale also exhibit water-wet behavior (bottles 2 and 3). In these three bottles, PCE is present as a distinct phase and does not coat the soil particles. In contrast, the Garfield oil shale and Waynesburg coal (bottles 4 and 5) systems appear organic-wet. In these systems, only the clear aqueous phase is visible above the soil and PCE coats the surfaces of diese natural materials. 

The latest experiments on the adsorption of the group-5 pentabromides on the quartz surface (presumably modified with KBr aerosol particles) [190] have, however, shown the following sequence in the adsorption energy DbBrs < NbBrs < TaBrs, in contrast to the former experiments [188] and recent theoretical predictions [164]. This new experimental result has not yet found its explanation. 

In this section we compare the theory of the preceding two sections with experimental measurements of infrared extinction by small particles. Comparisons between experiment and theory for spheres of various solids, most notably alkali halides and magnesium oxide, have been published in the scientific literature many of these papers are cited in this chapter. In most of this work, however, there is an arbitrary normalization of theory and experiment, which tends to hide discrepancies. For this reason, most theoretical calculations in this section are compared with mass-normalized extinction measurements. The new measurements presented here were made in the Department of Physics at the University of Arizona. A group of solids was selected to illustrate different aspects of surface modes. Results on amorphous quartz (Si02) particles, for example, illustrate the agreement between experi-... 

Strictly speaking, Eq. (14-16) is valid only for integrated intensities, and the same is true of all other intensity equations in this chapter. Yet it has been found possible to determine the quartz content of dusts with satisfactory accuracy by simply measuring maximum intensities. This short cut is permissible here only because the shape of the diffraction lines is found to be essentially constant from sample to sample. There is therefore a constant proportionality between maximum and integrated intensity and, as long as all patterns are made under identical experimental conditions, the measurement of maximum intensities gives satisfactory results. Quite erroneous results would be obtained by this procedure if the particle size of the samples were very small and variable, since then a variable amount of line broadening would occur, and this would cause a variation in maximum intensity independent of sample composition. 

Secondly, we performed an MD simulation of heating quartz up to 1300 K. We have mainly used a system of 432 particles for the periodic boundary condition, while 324- and 576-particle systems have also been studied for comparison. MD results for the temperature dependence of the molar volume and cell parameters shows quite good agreement with experimental data (Fig. 6) [43]. The volume expansion coefficient abruptly... 

Figure 6. The MD results for the thermal expansion of the volume (a) and cell parameters (b) of quartz, and the temperature dependence of the u parameter of silicon. Open squares represent the 432-particle system with typical magnitude of the fluctuation, while full circles and open circles represent the 324- and the 576-particle systems. The solid line shows show experimental data.

---