Miscellaneous Topics

3 Miscellaneous Topics Surface Studies and Chemical Reactions 

The Mossbauer effect has given useful information in the study of chemical reactions which involve surface states and chemisorption. Reproducibility of data and their interpretation are difficult in this type of work because the adsorbing material may be affected by its pre-history. Comparisons have to be made with iron cations in compounds of known site symmetry. 

A sample of high-area silica gel impregnated to 3 wt % Fe with Fe-enriched iron(III) nitrate, and then calcined to produce small-particle FeaOs, and subsequently reduced in hydrogen can be used as a supported iron catalyst material. The Mossbauer spectrum shows the presence of both Fe  

An attempt has been made to study Co atoms on the surfaces of single crystals of tungsten and silver by measuring the anisotropy of the recoil-free fraction, but lack of detailed knowledge of the type of site occupied by the impurity nucleus at the surface precludes an unambiguous interpretation [102]. 

Zeohtes also have considerable application as catalysts. Iron in the +3 oxidation state is introduced by ion-exchange methods [103]. However, attempted adsorption of Fe ions causes complete breakdown of the structure with any retained iron being in the +3 state. Dehydration of the zeolite causes non-reversible reduction of the iron. Adsorption of Fe salts on ion-exchange resins of the sulphonated styrene-divinyl benzene and quaternary ammonium types has httle effect on the iron resonances and indicates very weak binding of the ions to the resin [104]. Spin-relaxation effects and temperature-dependent paramagnetic hyperfine structure have been recorded and interpreted in detail for Fe ions adsorbed on exchange resins [105, 106], and a number of other recent papers have shown interest in this new field [107]. 

In this section three miscellaneous topics in the area of agglomeration shall be discussed, namely, dry pelletization, spherical agglomeration in liquid suspension, and spontaneous or inadvertent agglomeration of fine particles. 

A number of studies (F3, 12, M4, V2) have shown that, provided the constituent particles are small enough, any particulate material will pelletize by systematic agitation without the use of a binder. The rate of agglomeration is greatly accelerated in the presence of relatively large-size solid particles or agglomerates. These seeds, nominally plus 200 mesh in size, are usually the recycled pellets of the powder itself. 

Typical results of the dry pelletizing process when a charge of carbon black and its plus 52-mesh seeds is tumbled in a drum (12) are shown in Figs. 31 and 32. Initially, the seeds grow in size rapidly by snowballing. The dip in the bulk density of the seeds (Fig. 32) suggests that the deposited layers are quite porous in the beginning but get compacted in due course to 

In the initial stage the amount of fines consumed per unit charge weight depends only on the total number of drum revolutions, independent of the rotational speed (12, M6). The disappearance rate per unit charge weight and per drum revolution of the fines varies directly with seed density, the 

Kawashima and Capes (K8) have studied the kinetics of microagglomeration, using as a model system a suspension of narrow size-distribution sands in carbon tetrachloride and 20% aqueous calcium chloride solution as the bonding liquid. The mean diameter of the pellet produced ranges from about 0.5 mm to almost 1.5 mm. The size distribution are log normal in a reduced 

Some basic lamina and laminate behavioral characteristics were deliberately overlooked in the preceding discussion. Among them are plastic or nonlinear deformations, viscoelastic behavior, and wave propagation. 

Shear-stress-shear-strain curves typical of fiber-reinforced epoxy resins are quite nonlinear, but all other stress-strain curves are essentially linear. Hahn and Tsai [6-48] analyzed lamina behavior with this nonlinear deformation behavior. Hahn [6-49] extended the analysis to laminate behavior. Inelastic effects in micromechanics analyses were examined by Adams [6-50]. Jones and Morgan [6-51] developed an approach to treat nonlinearities in all stress-strain curves for a lamina of a metal-matrix or carbon-carbon composite material. Morgan and Jones extended the lamina analysis to laminate deformation analysis [6-52] and then to buckling of laminated plates [6-53]. 

Viscoelastic characteristics of composite materials usually result from a viscoelastic-matrix material such as epoxy resin. General stress analysis of viscoelastic composites was discussed by Schapery [6-54]. An important application to laminated plates was made by Sims [6-55]. 

Wave propagation in an inhomogeneous anisotropic material such as a fiber-reinforced composite material is a very complex subject. However, its study is motivated by many important applications such as the use of fiber-reinforced composites in reentry vehicle nosetips, heatshields, and other protective systems. Chou [6-56] gives an introduction to analysis of wave propagation in composite materials. Others have applied wave propagation theory to shell stress problems. 

Salkind, VTOL Aircraft, in Applications of Composite Materials, Michael J. Salkind and Geoffry S. Hollister (Editors), ASTM STP 524, American Society for Testing and Materials, 1973, pp. 76-107 (reprinted with permission). 

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Table 5. Miscellaneous Topical Hemostatics and Action Mechanisms...

A. H. M. Renfrew, Reactive dyes for Textile Fibres the Chemistry of Activated n-bonds as Reactive Groups and Miscellaneous Topics, Society of Dyers and Colourists, Bradford, 1999. 

Table IV. Laser Experiments Thermodynamic Measurements and Miscellaneous Topics...

The kinetics experiments are subdivided into classical kinetics experiments, Table XX photochemistry, Table XXI catalysis, oscillating reactions and miscellaneous topics in kinetics, Table XXII. 

Table XXII. Experiments on Catalysis, Oscillating Reactions and Miscellaneous Topics in Kinetics...

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