Powder Characterization 1 Objectives

Gereg and Capolla developed process parameters determined by a model laboratory bench scale Carver press, model C (Carver Inc. Savannah, Georgia, U.S.A.), which were translated to production scale compactor parameters (6). Their study provided a method to predict whether a material is suitable for roller compaction. Their study objectives were to characterize properties of the material to identify process parameters suitable to achieve the necessary particle size and density using the dry granulation process and then translate laboratory information to a production scale roller compactor. Actually, information developed from a Carver press was correlated and scaled-up to a production scale Fitzpatrick roller compactor. Model IR 520 (Fitzpatrick Co., Elmhurst, Illinois, U.S.A.) The compactor produced very similar powder granule characteristics as the Carver press. Various lactose materials, available as lactose monohydrate or spray dried lactose monohydrate, were used as the model compounds. Results indicated that a parametric correlation could be made between the laboratory bench Carver press and the production scale compactor, and that many process parameters can be transferred directly. 

The object of this experiment is to determine the crystal structure of a solid substance from x-ray powder diffraction patterns. This involves determination of the symmetry classification (cubic, hexagonal, etc.), the type of crystal lattice (simple, body-centered, or face-centered), the dimensions of the unit cell, the number of atoms or ions of each kind in the unit cell, and the position of every atom or ion in the unit cell. Owing to inherent limitations of the powder method, only substances in the cubic system can be easily characterized in this way, and a cubic material will be studied in the present experiment. However, the recent introduction of more accurate experimental techniques and sophisticated computer programs make it possible to refine and determine the structnres of crystals of low syimnetiy from powder diffraction data alone. 

The ATR objective has a polished face of diamond, germanium or zinc selenide (ZnSe) that is pressed into contact with the sample (Sawyer et al. 2008). Infrared reflection is attenuated by absorption within a surface layer a few micrometers deep. In this case, a good contact is required, but that is easy for most polymers, and the advantage is that no sample preparation is required. Therefore, powders, films, gels and even polymer solutions can be characterized. 

The main objective of the project, ie. to study the reaction bonding technique as an effective way to produce porous silicon carbide ceramics, has been successfully achieved. This includes the colloidal processing of the precursor powders, compaction through slip-casting, and finally sintering to achieve the muilitization reaction. Characterization of the sintered and polished samples using SEM and XRD have confirmed the formation of the muliite phase. 

Example 10.1. Consider Figure 11. which resulted from hierarchic clustering of 19 tungsten powders being characterized by 11 trace elements. Partitions with different degrees of refinement are obtained by horizontal cuts of the dendrogram. At the lower end. all objects occur as separated classes at the upper end. all objects are fused in a single class. The level at which certain subclasses are fused (vertical direction) may be interpreted as their dissimilarity. As a... 

In the last decade confocal laser scanning microscopy (CLSM) was shown to be a helpful tool for various further tasks of microparticle characterization (Lamprecht et al., 2000a, b, c). It minimizes the light scattered from out-of-focus structures, and permits the identification of several compounds through use of different fluorescence labels. Therefore, CLSM can be applied as a non-destructive visualization technique for microparticles. Moreover, CLSM allows visualization and characterization of structures not only on the surface, but also inside the particles, provided the carrier matrices are sufficiently transparent and can be fluorescently labeled by collecting several coplanar cross-sections, a three-dimensional reconstruction of the inspected objects is possible. Figure 6.13 shows the application of CLSM to investigatation of the cross-sectional structures of spray-dried powders of maltodextrin (MD) with a dextrose equivalent value of DE = 2 and 20. Florescein sodium salt was dissolved in the feed solution as a fluorescent probe of the carrier... 

Spectroscopic techniques have been employed extensively for monitoring and control of processes in different fields. Since a detailed review of the applications of spectroscopic techniques in distinct areas is certainly beyond the objectives of the chapter, the interested reader should refer to textbooks and surveys for additional details [ 10,27,30,33,43,44]. It is also important to emphasize that most publications available in the field of polymer and polymerization reactions make use of spectrometers for off-line characterization of polymer properties. Typical applications include identification of polymer materials [82], evaluation of copolymer and polymer blend compositions [83, 84], evaluation of monomer and polymer compositions during polymerizations [85], determination of additive content in polymer samples [86, 87], and estimation of end-use properties of polymer materials. End-use properties analyzed include the degree of crystallinity of polymer samples [88], the degree of orientation of polymer films [85], the hydroxyl number of polyols [89], the melt flow index of polymer pellets [90], and the intrinsic viscosity of polymer powders [91], the morphology of... 

Infrared spectroscopy is predominantly performed in the Fourier-transform mode and then commonly abbreviated as FTIR. The great advantage of FTIR spectroscopy is the great number of measurement options (and accessories), that allow spectra to be taken conveniently from just about any kind of sample. Polymeric powders can be characterized by pressing them into the conventional KBr pellets, but also, without any sample preparation, by diffuse reflectance (DRIFT). Very thin films of polymers can be measured in the conventional transmission mode, but any kind of film (thick or thin), as well as large polymeric objects, can be measured by ATR. ATR probes can also be used to characterize solutions... 

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