Application of Powders

P York. Application of powder failure testing equipment in assessing effect of glidants on flowability of cohesive pharmaceutical powders. J Pharm Sci 64 1216-1221, 1975. 

One application of powder diffraction is phase identification. Since zeolites of the same structure type give similar powder patterns, the powder pattern can be used as a fingerprint to identify the zeolite type. Furthermore, when multiple phases are present, the powder pattern is a superposition of the patterns for each of the separate phases and the relative overall intensities of the peaks is related to the amount of each phase. Thus patterns from mixtures of phases can be analyzed to determine the identity and relative amount of each phase. 

A basic, yet crucially important, application of powder XRD is in the identification ( fingerprinting ) of crystalline phases, based on the fact that different crystal structures give rise to distinct powder XRD patterns. Qualitative characterization of materials in this manner finds applications in many scientific disciplines (both academic and industrial), including quality control, polymorph screening, and the characterization of products from rapid throughput crystallization experiments [97, 98]. 

Any solid can be pulverized into particles of small size not all can be fabricated into the smooth supports we have discussed in this chapter. This consideration alone —not to mention the many practical applications of powdered solids —encourages us to look for a relationship that describes the junction of a liquid interface with such solids. One thought might be to compress the powder into a pellet and treat the surface of the pellet in the same way as we have treated other solid surfaces. On a fine scale the surface of such a pellet is rough, however, so hysteresis effects should be severe. Therefore we look for some alternative approach. 

Fig. 3. Multistage countercurrent application of powdered activated carbon.

The simplicity and advantages of the routine application of powder diffraction techniques for the chemical analysis and identification of polycrystalline materials were pointed out by Hull [9], who stated "that every crystalline substance gives a pattern that the same substance always gives the same pattern," and by the pioneering work of Hanawalt et al. [10]. 

Another variation of the enantioselective inclusion complexation procedure leading to optical resolution is the application of powdered host compounds in the... 

In the industrial field, modified silica assists the development of advanced materials. Modified silica powders are used as a filler in rubbers and in new-type gas sensors. Most industrial applications involve the use of strongly related materials such as glass fibres or thin Si02 layers. We wish to restrict ourselves to a discussion of the application of powdered silica and a short indication of related compounds. 

The application of color to a substrate in the form of a spray of finely divided colorant is an accepted practice for metal coatings (3.,4). The feasibility of dyeing polyester fabrics by the application of powdered disperse dyes to the fabric has been demonstrated (5) however, many development problems such as efficient recovery of unfixed dye and the homogeneous application of dye mixtures need to be resolved. Likewise, the use of 100% solids" systems as, for example, radla-tion-cureable finishes will also require considerable development work. 

DEVELOPMENT AND APPLICATION OF POWDERED BUTADIENE-STYRENE RUBBER FOR MODIFICATION OF RIGID PVC... 

The simplest application of powder diffraction is to identify a crystalline phase. One merely runs the powder pattern of the solid and records either 29 values or rf-spacings or both. This information is given by the program and can be printed directly on the pattern. Then one may consult a database such as the JCPDS file. These initials refer to the JCPDS. As a result of the complexity of keeping pace with the ever growing fist of known phases, the operation grew and was renamed the International Centre for Diffraction Data (ICDD), headquartered in Newton Square, Pennsylvania. 

One useful way of applying the powder quite controllably is to use a vessel like a pepper-pot or sugar-sifter. The application can be controlled by the size and distribution of holes in the dispenser, and by applying a steady vibration to it. Some experimentation will always be necessary in order to achieve satisfactory application of powder. Any change in the particle size of the powder will significantly affect the distribution, so that once a suitable technique has been developed, care must be taken to maintain the particle size and the purity. Any major change in humidity will also affect particle flow and film formation. 

Hersey J. The development and applicability of powder mixing theory. Int J Phar Tech Pro Mfr 1979 1(1) 6-13. 

A number of variants are possible in two-layer-single stoving coatings, depending on whether the layers are applied wet or dry via electrostatic application of powder (see Section 5.4.5.2). 

Powder diffraction is very well suited for studies at non-ambient conditions. Naturally, one of the early applications of powder diffraction was high temperature studies of phase transformations. Development of equipment for low temperature and high-pressure studies quickly followed. Later, application of powder diffraction for in situ, time-resolved and in operando studies were successfully pursued. 

This book is an advanced introductory text about modern methods and applications of powder diffraction in research. A strong working knowledge of diffraction and crystallography is assumed. This book does not present a basic introduction to crystallography and diffraction from crystals, which is available in many introductory texts and other books, such as the excellent Fundamentals of Powder Diffraction by Pecharsky and Zavalij (Kluwer Academic Publishers, Boston, 2003). This book presents a broad overview of current methods and applications, including their theory and practice, with useful information on getting started in these methods. The book is written by renowned experts in the respective techniques. 

It is believed that this method of comparing two different powders most likely has an important future in industrial processing. Particle shape is very sensitive to the conditions under which the particles are made. Slight variations, which may not be measurable with normal means in an industrial operation, will significantly alter particle shape. Consequently, this characteristic can become a powerful tool not only for understanding the process but also for its control. In the long run, an equally important application of powder signatures may be their use in specifications. 

A very interesting application of powder MAS and MQMAS NMR to the investigation of the high-temperature sequence of phase transitions of LiRbS04 appeared.77 The central transition of 87Rb was investigated within 373-488 K, where five phases separated by four phase transitions are expected. The three main phase transitions affect the EFG parameters and the spin-lattice relaxation rate, and a critical behavior was evidenced and related to a damped soft mode. The MQMAS experiment permits to separate the chemical shift contribution from the second-order-induced quadrupolar isotropic shift in a single experiment, and indicates that the evolution of the chemical shift is almost continuous. Two different rubidium sites are clearly evidenced above 438 K, while X-ray could detect them only above 457 K. MQMAS data show a similar electronic environment for these two sites. 

Solvent-free organomagncsiimi compounds are usually obtained as amorphous or microcrystalline polymeric materials. Tor this reason. X-ray diffraction studies depend either on the application of powder diffraction techniques 143.441 or on special and/or fortuitous meihods of crystallization (32.45 - The structures 6.1-6.4 thus determined all follow essentially the same pattern a polymeric chain formed from mutually perpendicular four-mcinbered rings Mg R connected via spiro magnesium atoms as shown in Scheme 9.5. 

Figure 11.7 Concentration profiles after application of powdered CP for 45 min (crosses) and 120 min (circles).

Application of powder X-ray diffraction for the analysis of polymorphic purity of A/-(4-nitrophenyl)-A/-morpholinothiourea (37) samples prepared by conventional solution synthesis in dichloromethane and mechanochemical liquid-assisted grinding approach. At low concentration, polycrystalline powder of form I precipitates out, while of form II precipitates from more concentrated soiution and mechanochemical synthesis. 

Die focus of much of the preceding discussion has been issues associated with diffraction data measurement and processing. Di action techniques continue to develop at a rapid pace. Applications of powder neutron diffraction and, particularly, exploitation of the properties of synchrotron X-radiation in single crystal and high resolution powder diffraction experiments were highlighted here. Several of the techniques mentioned such as microcrystal diffraction, time-resolved Laue diffi action and differential anomalous diffraction are still at early stages of development. 

CATALYTIC APPLICATIONS OF POWDERED Pd NANOCLUSTERS MACROMOLECULAR GRAFTING... 

Particle size is the most important parameter in practical applications of powder particles. Usually, powder is constituted by particles of various sizes therefore, it is necessary to obtain not only the mean particle size but also the size distribution. Recently, methods for particle size analysis have been greatly developed, especially analytical techniques with rapid response, high repeatability, and covering a wide range of particle sizes, as in the case of the laser scattering and diffraction methods. 

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