Grain size effects

Our communication describes grain size effect in XRF of powder and powder slurry-like substances in terms of the generalized model ... 

An overview of the superplastic behavior of aluminum alloys to demonstrate the grain-size effect is depicted in Fig. 1, in which the quantitative relation between the logarithm of the optimum strain rate for superplastic flow and the grain size (plotted as the logarithm of reciprocal grain size) is clearly shown [4]. The slope of the curve in Fig. 1 is noted to be about 3. 

The occurrence of irreversible fatigue phenomena and grain-size effects indicates that important features of the SMA phenomenon lie outside the domain of equilibrium thermodynamics. Nevertheless, details of the SMA T-x (and T-P-x) phase diagram are clearly important for the understanding and engineering of this curious thermal effect. 

Frey, M.H. et al. (1998) The role of interfaces on an apparent grain size effect on the dielectric properties for ferroelectric barium titanate ceramics, Ferroelectrics, 206-207, 337-53. 

The observed phenomena can be explained by relaxation processes in the condensed state (14). Grain size effects on the electron relaxation were observed also for optical behaviour of Au-PPFC films (4,5). 

Huang H., Sun C. Q., Zhang T. and Hing P., Grain-size effect on ferroelectrics Pb(Zr,.,TiJ03 solid solutions induced by surface bond contraction, Phys. Rew. B 63 (2000) pp.ll84112(l-9). 

Harrison RJ, Salje EKH (1994) X-ray diffraction study of the displacive phase transition in anorthoclase, grain-size effects and surface relaxations. Phys Chem Minerals 21 325-329 Hayward SA, Salje EKH, Chrosch J (1998) Local fluctuations in feldspar frameworks. Mineral Mag 62 639-645... 

Wang, A. (1999) Some grain size effects on Raman scattering for in situ measurements on rocks and soils-experimental tests and modelling. 30th Lunar and Planetary Science Conference, Houston, TX. 

Methods for correcting for grain-size effects in studies on heavy metal concentrations in estuarine and coastal sediments have been discussed by Ackermann (1980). There is, unfortunately, no one standard method for particle-size normalisation and a wide range of techniques are in use (Table 2.3). The method which often involves the least effort is the correction which uses comparison with rubidium (Rb) as a conservative element (Ackermann, 1980). This technique relies on the fact that Rb has a similar ionic radius to potassium (K) and so substitution of Rb for K will take place in clay minerals. Furthermore, Rb is present in the sand fraction in very much smaller concentrations than in the clay or silt fraction and concentrations of the element in sediments are rarely influenced by anthropogenic activity. Another advantage of the use of Rb is that it is often routinely analysed by X-ray fluorescence along with a suite of pollutant trace metals. 

Table 2.3 Methods for the reduction of grain-size effects in sediment samples references listed are examples of the applications and/or discussion of the use of the techniques)... 

Ackermann, F. (1980) A procedure for correcting the grain size effect in heavy metal analyses of estuarine and coastal sediments. Environmental Technology Letters 1, 518-27. 

So far, extensive experimental studies on grain size effects have been made [4]. 

Table 3-2 Methods for the Reduction of Grain Size Effects in Sediment Samples (for References see Salomons Forstner, 1984)...

Generally, five types of elements have been distinguished according to their distribution in sediment cores from Lake Erie (Kemp et al., 1976) (i) Diagenetically mobile elements such as Fe, Mn and sulfur (ii) carbonate elements, carbonate-c and calcium (iii) nutrient elements, organic C, H, and P (iv) enriched elements, such as Cu, Cd, Zn Pb, and Hg and (v) conservative elements, e.g. Si, K, Ti, Na, and Mg. Comparison of group (iv) elements of environment concern with "conservative" elements (v) seem to be particularly useful for the reduction of grain size effects, since no separation step is required. 

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