Viewing Microstructures of Materials Using the Optical Microscope

This lesson plan introduces students to microscopy using a light microscope. The unit will provide a background of light optical microscopy and the ways of manipulating the tool in order to optimize viewing of a sample. Students will gain a basic understanding of how the microscope works and learn to identify its components. A step by step module procedure is included. This document will serve as a framework for instructors and may be downloaded in PDF format

03_1887Ohuchi.indd

ABSTRACT We have undertaken a detailed analysis of the X-ray photoelectron spectra obtained from the three polymorphs of Al 2 SiO 5 ; andalusite, sillimanite, and kyanite. Comparison of the spectra was made based on the chemical bonding and structural differences in the Al-and Si-coordination within each polymorph. The spectra for Si(2p) for all three polymorphs are nearly identical, consistent with the fact that all the Si atoms are in 4-fold (tetrahedral) coordination, whereas the binding energies, peak shapes, and peak widths for Al(2p) vary depending on the type of polymorph. The upper-valence band for all three polymorphs is characterized by four main features derived from O(2p), Al(3s), Al(2p), Si(3s), and Si(3p), and the differences in their contributions are observed. The density of state of the Al 2 SiO 5 polymorphs is relatively featureless compared to those observed from α-SiO 2 and α-Al 2 O 3 , suggesting that the orbital overlaps span a greater range in energy. The observed band gap energy for Al 2 SiO 5 (sillimanite) was ~9.1eV, a value in between those for α-SiO 2 (~8.6eV) and α-Al 2 O 3 (~9.6eV). The conduction band feature of Al 2 SiO 5 was experimentally compared to those of α-SiO 2 and α-Al 2 O 3 , and shown that it is indeed intermediate between the α-SiO 2 and α-Al 2 O 3 phases