Sample packing density

This is expected assuming the ideal homogeneity of both the incident beam and the sample packing density. The former is true for small divergence slit openings, and the latter is true for the used sample, which was prepared from the nearly spherical particles. 

Bollin and Bauman (96) described a simple sample-packing technique which is capable of accurate reproduction of sample-packing density. The... 

In reflection of radiation at solid matte surfaces, diffuse and specularly reflected energies are superimposed. The intensity of the diffusely reflected energy is dependent on the angles of incidence and observation, but also on the sample packing density, sample crystalline structure, refractive index, particle size distribution, and absorptive qualities. Thus, an ideal diffusely reflecting surface can only be approximated in practice, even with the finest possible grinding of the samples. There are always... 

Samples can be concentrated beyond tire glass transition. If tliis is done quickly enough to prevent crystallization, tliis ultimately leads to a random close-packed stmcture, witli a volume fraction (j) 0.64. Close-packed stmctures, such as fee, have a maximum packing density of (]) p = 0.74. The crystallization kinetics are strongly concentration dependent. The nucleation rate is fastest near tire melting concentration. On increasing concentration, tire nucleation process is arrested. This has been found to occur at tire glass transition [82]. 

PETN density favors Mader s detonation product computations since, as shown above, Mader calculates that the amount of free carbon decreases with a decrease in PETN packing density The product compns measured by Ornellas (Table 8) and the Mader CJ compositions differ appreciably. The Q s are, however, very similar. The agreement between calorimeter and computed Q s is certainly unexpected in view of the different product compns. Nevertheless, as stated in Vol 7, H38—39, there is rather good agreement between calorimeter Q s for confined samples and the CJ Q s computed by Mader (Ref 40) for expls that are not too deficient in oxygen. The following tabulation illustrates this ... 

As it has been discussed in previous section, from a practical point of view1, and also for comparison between adsorbents, hydrogen adsorption capacities should be reported in a volumetric basis, which makes necessary to know the sample density. Unfortunately, papers reporting hydrogen adsorption capacities of MOFs in volumetric basis use the crystal density of the materials, which is not realistic for this application because it does not include the inter-particle space. Crystal densities of MOFs can vary between 0.2 and 1.3 g cm 3 36 39, and similar to what happens with tap and packing densities of carbon materials, crystal densities of MOFs decreases when porosity increases. Therefore, as in the case of carbon materials (see Figure 5) a maximum is observed when the hydrogen uptake in volumetric basis is plotted versus the porosity of the MOFs samples, and a compromise between density and porosity is necessary from a practical point of view. 

In diffuse reflection spectroscopy, the spectrometer beam is reflected from, scattered by, or transmitted through the sample, whereas the diffusely scattered light is reflected back and directed to the detector. The other part of the electromagnetic radiation is absorbed or scattered by the sample [124,125]. Changes in band shapes or intensity as well as signal shifts can be affected by morphological and physicochemical properties of the sample or combinations thereof (e.g., chemical absorptions, particle size, refractive index, surface area, crystallinity, porosity, pore size, hardness, and packing density [126]). Therefore, NIR diffuse reflection spectra can be interpreted in dependence of various physical parameters [127]. 

By comparing experimental results obtained in carbonizations at high packing density (dilatometer samples) with those carried out on loose bulk samples it can be shown that the processes during carbonization are qualitatively the same despite quantitative differences. 

V=Vol occupied by sample Note This density is called in Ref 21, Method 201.3 as "Bulk or Apparent Density , but actually it is "Packed Density", because it is detd after the material has been packed and tapped. Compare with "Bulk Density detn described in previous item (m) and with "packed density detn, described in the next item (o)... 

Moisture and oil determination by NMR with respect to bulk/packing density or sample weight. 

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