ASTM D8075-16 (R2021) pdf free download.Standard Guide for Categorization of Microstructural and Microtextural Features Observed in Optical Micrographs of Graphite.
1.1 This guide covers the identification and the assignment of microstructural and microtextural features observed in optical rnicrographs of graphite. The objective of this guide is to establish a consistent approach to the categorization of such features to aid unambiguous discussion of optical micrographs in the scientific literature. It also provides guidance on specimen preparation and the compilation of micrographs.
1.2 The values stated in SI units are to be regarded as the standard.
4. Significance and Use
4.1 The purpose of this guide is to provide a framework for consistent description of microstructural and microtextural features visible in optical micrographs of graphite. It also provides some guidance on sample preparation and image processing.
5. Optical Microscopy Methods
5.1 Three different methods of illumination are generally employed in optical microscopy: optical or bright field (BF), fluorescence under UV light, and polarized light. While bright field and polarized light methods can be undertaken directly on a prepared graphite surface, fluorescence requires the sample to be impregnated with a resin incorporating a fluorescent dye prior to preparation of the graphite surface. It is common for all three methods of illumination to be used in the characterization of graphite microstructure and texture so that resin impregnation is a standard procedure in sample preparation. It should also be noted that resin impregnation stabilizes the graphite matrix and protects porosity from dust intrusion during polishing of the surface being prepared for examination.
5.2 If the sample requires impregnation, a low-viscosity resin is used to impregnate and encapsulate the sample. The resin can have a small amount of fluorescent dye added for observation under ultraviolet (UV) light. Once impregnated with resin and cured, the encapsulated sample is ready for preparation of an examination face.
5.3 The selected face of the sample is prepared for microscopic examination by grinding it using progressively finer silicon carbide (SiC) papers to 2500 grit (8.4 .im ± 0.5 aim). The face is then further polished with a diamond suspension to a I im finish. The same procedure is employed for both untreated and impregnated graphite samples. At this stage. the prepared face of the sample is ready for optical examination.
5.4 With BF illumination, the sample is observed using white light at normal incidence. Within the constraints of the optical resolution, this method of illumination allows micro- structural features in the sample to be seen.
5.5 With fluorescence microscopy, incident UV light causes the dye in the resin to fluoresce, thus showing the extent of resin penetration into the sample and an indication of areas of open porosity. This method requires full impregnation of the accessible porosity by the resin, which can be influenced by the viscosity of the resin and extent of evacuation. The method is less revealing in terms ot characterizing microstructure in fine-grained material because of incomplete penetration of the porosity by the resin.ASTM D8075 pdf download.