Fine-grain developers characteristics

The sampling method employed allowed us to build upon the research literature and develop a more fine-grained rubric as shown in Table 2. It uses six characteristics that originated from the terminology used in the laboratory manuals to describe five levels of inquiry grounded in the data that we collected and analyzed. 

As backfill materials become more fine-grained, caution must be exercised in selecting design parameters and factors of safety to allow for the more complex shear strength and corrosion characteristics of these finer grained materials. Even with these finer grained elastic materials, however, adequate designs can be developed. 

Nuri et al. (1982) reported on the characteristics of rare-earth-added steels, especially the solidification microstructure (including the spacing, length and inclination of dendrite arms) and microsegregation with some consideration of the relevant mechanisms. Microstructural observations revealed that in the rare-earth-added steel fine-grained dendrites at the surface develop extensively, with the adjoining columnar dendrites growing less than those in rare-earth-ffee steel. This difference in the solidification structure has an effect on the secondary structure after solidification. 

This is the most widely used method for the determination of the phase composition of powders. The x-ray diffractometer contains a source of monochromatic x-rays that irradiate the sample and are diffracted from atomic planes and detected. The angle of diffraction of x-rays by the crystalline planes is characteristic of the crystal structure, and the intensity of scattered radiation is characteristic of the atomic composition. In recent years, automated data processing has enabled higher accuracy and speed. A number of problems are encountered in the quantitative determination of phases in fine powders. Some of these are overlap of phase peaks (e.g., in silicon nitride), orientation of grains, and presence of coarse particles. The last produces distortion of the diffraction data. A number of standard reference materials for XRPD have been developed for use in improving the quality of data [37]. 

A similar reaction route has been developed for reaction bonded mullite (RBM, aluminum silicate). In this case the powder formulation also includes a source of silicon (silicon metal, silicon carbide, or silica), in addition to aluminum metal and alumina, and the final product contains mullite as the major phase. The RBM process is frequently modified by additions of zircon (ZrSi04), which provide an additional source of silicon and result in a dispersion of fine zirconia particles in the product which restricts grain growth to ensure a fine uniform microstructure. It is again possible to reduce residual porosity while retaining the near-net-shape characteristics, but at the time of writing this process is still under development and some way from commercial exploitation. 

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