ASTM D8075-16(R2021) pdf free download

ASTM D8075-16(R2021) pdf free download.Standard Guide for Categorization of Microstructural and Microtextural Features Observed in Optical Micrographs of Graphite
1. Scope
1.1 This guide covers the identification and the assignment of microstructural and microtextural features observed in optical micrographs 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 speci- men preparation and the compilation of micrographs. 1.2 The values stated in SI units are to be regarded as the standard. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.4 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
3. Terminology
3.1 The definitions listed below cover terms used in this guide and apply specifically to the optical microscopy of graphite. Properties and features not apparent under the optical microscope are avoided where possible. Definitions may not exactly match those adopted in general scientific usage but should not be at variance. General terms have not been redefined with graphite-specific meanings or optical microscopy-specific meanings. As with the identification of features in micrographs, some definitions have become unclear to differences in usage and this guide provides the basis for a more consistent approach. 3.2 Definitions: 3.2.1 accommodation cracks, n—(also referred to as Mrozowski-like cracks) cracks and voids formed between basal planes and at domain interfaces throughout the graphite microstructure from thermal contraction of the graphite during carbonization/graphitization (sometimes referred to as calcina- tion cracks), from chemical decomposition of the liquid crystal hydrocarbon precursor in graphite manufacture (also referred to as calcination cracks) and following cooling after graphiti- zation (manufacture). In irradiated graphite, they also comprise cracks arising from anisotropic responses to irradiation. 3.2.2 agglomerate, n—in manufactured carbon and graph- ite product technology, composite particle containing a number of grains. 3.2.3 binder, n—substance such as coal tar pitch or petro- leum pitch, used to bond the coke or other filler material prior to baking. 3.2.4 crystallite, n—in manufactured carbon and graphite product technology, a region of regular crystalline structure having parallel basal planes. 3.2.5 filler, n—in manufactured carbon and graphite prod- uct technology, particles that comprise the base aggregate in an unbaked green-mix formulation (also referred to as coke particles, grist particles, or filler grains).
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 ofthe graphite surface. It is common for all three methods ofillumination to be used in the characterization of graphite microstructure and texture so that resin impregna- tion 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 polish- ing 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 micro- scopic examination by grinding it using progressively finer silicon carbide (SiC) papers to 2500 grit (8.4 µm 6 0.5 µm). The face is then further polished with a diamond suspension to a 1 µm 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.