Bulk solid sampling

Bulk solids—Sampling. 2. Sampling. 3. Gases—Analysis. 4. Liquids— Analysis. I. Title. II. Series. 

If the sample is a bulk solid sample and is an electrical conductor, it is possible to use it as the cathode of a kind of spectral lamp whose functioning principle is identical to that described for a hollow cathode lamp (cf. Section 13.5.1 and Figure 14.5). The atoms sputtered and removed from the surface of the sample are excited by the plasma. This GD-OES technique provides a rapid and accurate surface analysis, less susceptible to matrix effects and sample homogeneity. It has the advantage of yielding spectra with low background levels whose emission lines are narrow since atomization takes place at lower temperatures than that of the previous techniques. 

Different vertical loads can be applied to a bulk solid sample of known mass, and compression of the sample is recorded electronically (Thomson, 1997). With these data, powder contact volume versus compressive force or stress can also be represented. Bulk density of a solid is a function of consolidation stress and changes during flow as the stress changes. Because the mass consolidating load and volume are known, the relationship can be plotted as shown in Figure 6. 

The random coil model ignores the role of the solvent a poor solvent will tend to cause the coil to tighten a good solvent does the opposite. Therefore, calculations based on this model are best regarded as lower bounds to the dimensions of a polymer in a good solvent and as an upper bound for a polymer in a poor solvent, The model is most reliable for a polymer in a bulk solid sample, where the coil is likely to have its natural dimensions. 

Bulk solid samples must be machined or polished into the correct shape, and this must be done without contaminating the surface from the grinding material or altering the surface composition by polishing out a soft phase, for example. The surface must be cleaned of any lubricant or oil used in the machining process before analysis. 

For bulk solid samples such as metals and alloys, the easiest way to do this is to choose an emission line of the major matrix element as the internal standard line. For example, an iron emission hne would be used in steels, a Cu line in copper alloys, and so on. If the sample is a powder, either the major element can be used or a separate element added to all standards and samples. 

XRF is used for the analysis of solid and liquid samples. For quantitative analysis the surface of the sample must be as flat as possible, as will be discussed in the applications section. There are two classes of sample holders, cassettes for bulk solid samples and cells for loose powders, small drillings, and liquids. A typical cassette for a flat bulk solid such as a polished metal disk, a pressed powder disk, a glass or polymer flat is shown in Fig. 8.26(a). The cassette is a metal cylinder, with a screw top and a circular opening or aperture, where the sample will be exposed to the X-ray beam. The maximum size for a bulk sample is shown. The sample is placed in the cassette. For a system where the sample is analyzed face down, the cassette is placed with the opening down and the... 

Figure 8.26 (a) Sample cassette for bulk solid samples, (b) Position of a bulk solid in the face-down... 

Reproducible stress conditions on the bulk solid sample both at compaction (consolidation) and failure illustrated as item/item . 

Ter Borg reports about experiences from wall friction experiments with more than 500 bulk solid samples from the chemical industry [7], The results of a statistical analysis of the best combinations of bulk solid and wall material are shown in Fig. 15. For the case of axisymmetric flow (vertical cylinder with conical hopper) the percentage of silos showing... 

As noted in Fig. 11.2, guest polymers may be recovered from their CD-ICs in the form of bulk solid samples by treating the polymer-CD-IC crystals with warm water or another CD solvent, which is a non-solvent for the guest... 

There is an important difference between the two techniques in that photons, produced by XRF, can pass through a relatively large thickness of a solid sample, typically 4000 nm, whereas electrons can penetrate only about 2 nm. This means that AES is more useful in the study of solid surfaces, whereas XRF gives information referring more to the bulk of a solid or liquid. 

Bulk density is easily measured from the volume occupied by the bulk solid and is a strong func tion of sample preparation. True density is measured by standard techniques using liquid or gas picnometry Apparent (agglomerate) density is difficult to measure directly. Hink-ley et al. [Int. ]. Min. Proc., 41, 53-69 (1994)] describe a method for measuring the apparent density of wet granules by kerosene displacement. Agglomerate density may also be inferred from direcl measurement of true density and porosity using Eq. (20-42). 

Usually, particle size has relatively little effect on Raman line shapes unless the particles are extremely small, less than 100 nm. For this reason, high-quality Raman spectra can be obtained from powders and from polycrystalline bulk specimens like ceramics and rocks by simply reflecting the laser beam from the specimen surface. Solid samples can be measured in the 90° scattering geometry by mounting a slab of the solid sample, or a pressed pellet of a powder sample so that the beam reflects from the surface but not into the entrance slit (Figure 3). 

As already remarked in Sect. 4.5.1 (Introduction), LA was primarily designed as a technique for direct sampling in the bulk analysis of solid samples. The main advantages of LA are the possibility of ablating all types of solid material (metals, isolators, glasses, crystals, minerals ceramics, etc.), no special requirements on the... 

Direct solid sampling (bulk metal, thin film, compacted powder, solution residues)... 

Ozone diffuses readily into amorphous region of the polyethylene (32) and oxidation probably occurs much deeper in the solid sample. Ozone also attacks the crystalline part of polyethylene but it has a slow initiation stage followed by more rapid oxidation (13). Because ozone does not diffuse into the crystalline regions (13.32). oxidation is restricted to the surface. The resulting oxidized functional groups on the crystalline regions will remain at the surface, whereas those formed in the amorphous region can diffuse into the bulk. 

Charged particle activation analysis (CPAA) is based on charged particle induced nuclear reactions producing radionuclides that are identified and quantified by their characteristic decay radiation. CPAA allows trace element determination in the bulk of a solid sample as well characterization of a thin surface layer. 

XPS has typically been regarded primarily as a surface characterization technique. Indeed, angle-resolved XPS studies can be very informative in revealing the surface structure of solids, as demonstrated for the oxidation of Hf(Sio.sAso.5)As. However, with proper sample preparation, the electronic structure of the bulk solid can be obtained. A useful adjunct to XPS is X-ray absorption spectroscopy, which probes the bulk of the solid. If trends in the XPS BEs parallel those in absorption energies, then we can be reasonably confident that they represent the intrinsic properties of the solid. Features in XANES spectra such as pre-edge and absorption edge intensities can also provide qualitative information about the occupation of electronic states. 

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