Powder characterization morphology

International Cooperation - This program is actively involved in and supportive of the cooperative work being done by researchers in West Germany, Sweden, and the United States under an ao cement with the International Energy Agency. That work, ultimately aimed at development of international standards includes physical, morphological, and microstructural characterization of ceramic powders and dense ceramic bodies, and mechanical characterization of dense ceramics. Japan is expected to participate in Subtask 6, a new powder characterization research subtask. 

Characterization. Ceramic bodies are characterized by density, mass, and physical dimensions. Other common techniques employed in characterizing include x-ray diffraction (XRD) and electron or petrographic microscopy to determine crystal species, stmcture, and size (100). Microscopy (qv) can be used to determine chemical constitution, crystal morphology, and pore size and morphology as well. Mercury porosknetry and gas adsorption are used to characterize pore size, pore size distribution, and surface area (100). A variety of techniques can be employed to characterize bulk chemical composition and the physical characteristics of a powder (100,101). 

To further characterize the event it is first necessary to identify critical features of the initial configuration that will strongly influence the process. For powder compacts, the most obvious features are the morphological characteristics of the powders, their microstructures, and the porosity of the compact. For solid density samples, the grain structure, grain boundaries, defect level, impurities, and inclusions are critical features. 

Preliminaries. The combustion of suspended dusts and powders is quite complex and only imperfectly understood. The complexity stems from both fundamental and practical considerations. On the fundamental side, the ignition of suspensions of finely divided solids is influenced by hard-to-quantify factors such as the time-varying concentration of solids, the chemical activity and morphology of the particulate, and the degree of confinement provided by the vessel. On the practical side, industrial conditions are seldom sufficiently well-controlled or characterized to justify application of existing theoretical models. For all the above reasons, this chapter can provide only a very abbreviated coverage of ignition basics. The reader is referred to other sources for in-depth treatment of dust and powder explosions (Bodurtha, 1980 Bartknecht, 1981 Bartknecht, 1987). 

The respirable powders of a DPI cannot be characterized adequately by single-particle studies alone bulk properties must also be assessed since they contribute to ease of manufacture and affect system performance. Primary bulk properties include particle size, particle size distribution, bulk density, and surface area. These properties, along with particle electrostatics, shape, surface morphology, etc., affect secondary bulk-powder characteristics such as powder fiow, handling, consolidation, and dispersibility. 

Two important morphological parameters characterizing ball-milled powders are the particle and grain size of constituent phases within the powders. In our laboratory, the size measurement of the powder particles is carried out by attaching loose powder to sticky carbon tape and taking pictures under secondary electron (SE) mode in the SEM. The images are then analyzed by an image analysis software. The size of the powders is calculated as the particle equivalent circle diameter, ECD = AA/nf, where A represents the projected particle area. Usually from -300 to 700 particles are analyzed for each batch. 

Ghadiri, M., Farhadpour, F. A., Clift, R. and Seville, J. P. K. (1991). Particle Characterization Size and Morphology. In Powder Metallurgy An Overview. Ed. Jenkins and Wood. London Institute of Metals. 

Microspheres intended for nasal administration need to be well characterized in terms of particle size distribution, since intranasal deposition of powder delivery systems is mostly determined by their aerodynamic properties and particle sizes. Commonly used methods for particle size determinations described in the literature are sieving methods [108], light microscopy [58], photon correlation spectroscopy [66], and laser diffractometry [25,41,53,93], The morphology of the microparticles (shape and surface) has been evaluated by optical, scanning, and transmission electron microscopy [66, 95],... 

A brief review of the diffraction phenomenon and the effect of crystallite size is presented. Applications of XRD to catalyst characterization are illustrated, including correlation of XRD powder patterns to molecular structural features, determination of Pt crystallite size and others. Factors that affect the appearance of XRD powder patterns, such as framework structure perturbations, extra-framework material, crystal morphology, impurities, sample preparation, instrument configurations, and x-ray sources, are discussed. 

In fact, peak broadening is just one of several effects observed in XRD powder patterns that can be used to gain characterization information about various catalyst systems. Particularly in zeolite systems, factors such as framework structure perturbations and modifications, extra-framework material, crystal morphology, impurities, and instrument configurations can produce observable differences in the XRD patterns, which require close scrutiny, in some cases, to understand and utilize. 

It has been shown how various factors can affect the appearance of XRD patterns and how the subtle differences in those patterns can be used to gain valuable structural and characterization information. It is clear that in order to understand a material and define it properly, all of these factors must be examined carefully. Techniques in addition to XRD, particularly electron microscopy, but also sorption and spectroscopy, should be utilized when attempting to understand the nature of a new catalyst material. Finally, it must be recognized that published XRD powder data for a given material can tell much about its structural nature but, to interpret the XRD data properly, it is also necessary to be aware of sample history, data collection parameters, morphology, etc. In short, one must know as much as possible about the various factors that affect the x-ray diffraction characteristics of catalyst materials. 

Description Catalyst in mineral-oil-slurry is metered into the reactor together with co-catalyst and modifier. The proprietary supported catalyst developed by BP has control morphology, super-high activity and very high sterospecifity. The resulting PP product is characterized by narrow particle size distribution, good powder flowability, minimum catalyst residues, noncorrosiveness, excellent color and low odor. 

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