X-ray gravitational sedimentation

Theory for concentration determination with the x-ray gravitational sedimentation technique... 

ISO/WD 13317-3 Determination of Particle Size Distribution by Gravitational Liquid Sedimentation Methods- Part 3 (1996) The X-ray Gravitational Technique, 360... 

Sedimentation Techniques. Other techniques that effect a physical separation include gravitational or centrifugal sedimentation, in which particles or emulsion droplets are separated on the basis of size and density. The separation that occurs can be quantified by monitoring X-ray or light absorbance as a function of position. Stokes law then can be used to determine the particle size distribution from the absorbance data as a function of the sedimentation time (73, 74). 

The x-ray observations by Ihn et al. showed that the o-axis is oriented normal to the surface of the mats, implying that mats are formed by whiskers laying flat down on top of each other. But the preferred orientation is of the same kind as the anisotropy already described above for regular solution-grown films. Not surprisingly, the same type of anisotropy was found for PQT from cyclohexanone [110] and n-dodecane [93]. Importantly it was found that the orientation effect is not related whatsoever to the sedimentation (caused by gravitation) of whiskers into mats, because the anisotropy was found to exist also in mats taken from the vertical walls of the vessel after evaporation of the solvent. The question about the acmal mechanism for the preferred orientation therefore remains unanswered. Concerning the thickness of the whiskers MSrdalen et... 

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