Grain-size

Grain Size Distribution of Zinc in Two Sediment Samples from Saddle River, Upstream (M. 16.6) and Downstream (M. 0.5) from an Urbanized Area of Lodi, New Jersey (after Data from Wilber Hunter, 1979) 

Different methods for grain size correction are compiled in Table 3-2 (after Forstner Wittmann, 1979 De Groot et al., 1982 Forstner Schoer, 1984). These methods will mostly reduce (not elimiate ) the 

Correction for inert mineral Quartz-free sediment Thomas (1972) 

Treatment with dilute acids 0.1 M hydrochloric acid Gross etal. (1971) 

On the other hand, it has been argued by Ackermann (1980) that separation of fraction 20 p.m, which can also be performed with nylon sieves should be favoured at least for coastal sediments, where the correlation with conservative elements has been found to be better with this fraction than with fraction 63 (im (see below). Also for organic pollu tants, separation of fraction 20 um seem to compare favourably with other grain size fractions (Hellmann, 1983). 

A few studies on grain size of minerals in midoceanic ridge chimneys have been published. Feely et al. (1987) described the grain size of mineral particles in the smoke and sediment samples from southern Juan de Fuca Ridge. They report the following grain sizes sphalerite 0.3-100 p.m in diameter (usually less than 20 p.m) pyrite 0.1-10 p.m Fe-Si, Ca-Si phases 5-150 p.m. Converse et al. (1984) reported the grain size 

Very fine-grained sulfides (n x 10 xm), which are common in Kuroko ores (Shikazono, unpublished), have not been reported from midoceanic ridge chimneys. However, SEM (scanning electron microscope) observations of Kuroko and Mariana chimneys indicate that the minerals are aggregates of very fine-grained crystals. Therefore, SEM observation is necessary to measure grain size of individual mineral crystals. However, data from SEM observations of midoceanic ridge chimneys are scarce. 

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It is applied along with traditional methods to test strength properties, hardness, to determine standardized characteristics of stamping, grain size and other structural-sensitive characteristics. 

Figure C2.17.9. Size-dependent changes in PXRD linewidtlis. PXRD can be used to evaluate tire average size of a sample. In tliese cases, different samples of nanocrystalline titania were analysed for tlieir grain size using tire Debye-Scherr fonnula. As tire domain size increases, tire widtlis of tire diffraction peaks decrease.

Unlike melting and the solid-solid phase transitions discussed in the next section, these phase changes are not reversible processes they occur because the crystal stmcture of the nanocrystal is metastable. For example, titania made in the nanophase always adopts the anatase stmcture. At higher temperatures the material spontaneously transfonns to the mtile bulk stable phase [211, 212 and 213]. The role of grain size in these metastable-stable transitions is not well established the issue is complicated by the fact that the transition is accompanied by grain growth which clouds the inteiyDretation of size-dependent data [214, 215 and 216]. In situ TEM studies, however, indicate that the surface chemistry of the nanocrystals play a cmcial role in the transition temperatures [217, 218]. 

Small amounts of yttrium (0.1 to 0.2%) can be used to reduce the grain size in chromium, molybdenum, zirconium, and titanium, and to increase strength of aluminum and magnesium alloys. 

Grain size distributions for sediments and soils are used to determine the amount of sand, silt, and clay present in a sample. For example, a grain size of 2 mm serves as a boundary between gravel and sand. Grain size boundaries for sand-silt and silt-clay are given as 1/16 mm and 1/256 mm, respectively. 

Prefix Abrasive type Grain size Grade Structure Bond type Manufacturer s record... 

The commercial sintered spinel and M-type ferrites have a porosity of 2—15 vol % and a grain size in the range of 1—10 ]lni. In addition, these materials usually contain up to about 1 wt % of a second phase, eg, CaO + Si02 on grain boundaries, originating from impurities or sinter aids. 

Fig. 8. Dielectric constant (1 kHz) vs temperature for BaTiO ceramics of A, l-)Tm grain size, and B, 50-)Tm grain size.

Columnar Structure and Grain Size. Most of the deposited films reported in the Hterature have a so-called columnar stmcture (see Fig. 

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