1、Designation: D4616 95 (Reapproved 2013)Standard Test Method forMicroscopical Analysis by Reflected Light andDetermination of Mesophase in a Pitch1This standard is issued under the fixed designation D4616; the number immediately following the designation indicates the year oforiginal adoption or, in
2、the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers laboratory procedures for thepreparation of granular and mel
3、ted samples for microscopicanalysis using reflected light to identify and estimate theamount and size of the mesophase.1.2 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information on
4、lyand are not considered standard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limita
5、tions prior to use.2. Referenced Documents2.1 ASTM Standards:2D329 Specification for AcetoneD1160 Test Method for Distillation of Petroleum Products atReduced PressureD2318 Test Method for Quinoline-Insoluble (QI) Content ofTar and PitchD3104 Test Method for Softening Point of Pitches (MettlerSoften
6、ing Point Method)D4296 Practice for Sampling PitchE11 Specification for Woven Wire Test Sieve Cloth and TestSievesE562 Test Method for Determining Volume Fraction bySystematic Manual Point Count3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 cenospheresusually a minor componen
7、t of coal tarpitch. They are formed by the rapid pyrolysis of unconfinedcoal particles that are carried over from the coke oven to thetar. Microscopically, they appear like hollow spheres or seg-ments thereof (see Fig. 1), and are typically sized from about10 to 500 m. In polarized light (crossed po
8、larizers), acenosphere may be optically active. The size of the anisotropicpattern or mosaic depends upon the rank of the coal carbon-ized. Cenospheres are harder than the continuous phase andpolish in relief (see Fig. 1).3.1.2 coke-oven-cokeusually a minor component of coaltar pitch. It originates
9、in carry-over from the coke oven to thetar side. It differs from cenospheres only in terms of its shapeand porosity. Coke-oven-coke is angular and less porous.3.1.3 isotropic phaseusually the predominant, andcontinuous, phase. It is a complex mixture of organic aromaticcompounds composed mainly of c
10、arbon and hydrogen. Atroom temperature, the isotropic phase is a glass-like solid. It isoptically inactive in polarized light (see Fig. 1 and Fig. 2).3.1.4 mesophasean optically anisotropic liquid crystalcarbonaceous phase that forms from the parent liquor whenmolecular size, shape, and distribution
11、 are favorable. In theearly stages of its development, mesophase usually appears asspheroids. The planar molecules are lined up equatorially asshown schematically in Fig. 3. This equatorial arrangementmay be distinguished in crossed polarized light. Under crossedpolarizers, the distinctive mesophase
12、 spheroids, with theircomplex extinction patterns shown in Fig. 2, can be readilyseen.33.1.4.1 spheroidsAt magnifications of 400 and 500, theminimum spheroid size which can be resolved with confidenceis 4 m in diameter. At magnifications of 1000 to 1800, theminimum spheroid size that can be resolved
13、 with confidence isabout 2 m in diameter. Typically, the upper size may be 100m. Mesophase spheroids are relatively soft and do not formrelief structures (see Fig. 4). Quinoline insoluble particles oftenaggregate at the interface between the continuous isotropicphase and mesophase.1This test method
14、is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.05 on Properties of Fuels, Petroleum Coke and Carbon Material.Current edition approved May 1, 2013. Published August 2013. Originallyapproved in 1986. Last previous
15、 edition approved in 2008 as D4616 95 (2008).DOI: 10.1520/D4616-95R13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM
16、 website.3Amore complete discussion will be found in a paper by Honda, H., Kimura, H.,and Sanada, Y., “Changes of Pleochroism and Extinction Contours in CarbonaceousMesophase,” Carbon, 9, 1971, pp. 695697.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2
17、959. United States13.1.4.2 isotropic phaseThe isotropic phase is more solublethan the mesophase in solvents such as toluene. Solventetching is achieved by soaking the polished surface in toluenefor a few seconds, rinsing the surface with cold flowing water,FIG. 1 Photomicrographs of a Coal Tar Pitch
18、 at 500 Magnification in Polarized Light (Crossed Polarizers) and Bright Light Showingthe Isotropic Phase, Natural Quinoline Insolubles, and a Cenosphere.FIG. 2 Photomicrographs of a Heat-Treated Coal Tar Pitch at 500 Magnification in Polarized Light (Crossed Polarizers) Showing Natu-ral Quinoline I
19、nsolubles and Mesophase SpheroidsD4616 95 (2013)2and drying in a current of hot air. Etching produces sharplydefined mesophase spheroids (see Fig. 4).3.1.5 mineral matterformed when minute particles of thecoke oven charge are carried over into the coke oven collectingmain during the charging operati
20、on. The tiny coal particles aredigested in the collecting main tar, resulting in a residue that isrich in mineral matter. This mineral matter is identified underbright field illumination by its high reflectivity, in the case ofpyrite, and its low reflectance in the case of clay, quartz, andcarbonate
21、s. The association of mineral matter with insolubleorganic matter from coal aids in its identification.3.1.6 normal quinoline insolubles(sometimes termed“true,” natural or “primary” quinoline insolubles)a carbonblack-like solid phase in coal tar pitch that is produced bythermal cracking of organic c
22、ompounds in the tunnel headabove the coal charge in a by-product coke oven. The indi-vidual spherically-shaped particles are usually less than 2 min diameter. A typical coal tar pitch may contain from about1 % to about 20 % (by weight) of normal quinoline insolubles.The normal quinoline insolubles a
23、re relatively hard. They areoutlined in bright incident light because they stand out in relieffrom the softer isotropic phase (see Fig. 1).3.1.6.1 DiscussionSometimes the term primary QI is usedto describe all quinoline insoluble materials that are carriedover during the coking operation (cenosphere
24、s, mineral matter,normal, QI, and so forth).3.1.6.2 normal quinoline insoluble materialObserved un-der crossed polarizers, the normal quinoline insoluble materialdisplays a Brewster cross pattern (see Fig. 1 and Fig. 2). Thisinterference figure remains stationary when the specimen isrotated through
25、360. The onionskin arrangement can beobserved in particles with a minimum diameter of 2 m at highmagnification (1000 to 2000) under cross polarizers.3.1.6.3 DiscussionThe quinoline insolubles content is de-termined by Test Method D2318 and represents the totalamount of natural quinoline insolubles,
26、cenospheres, coke-oven-coke, pyrolytic carbon, refractory, reactor coke, and freeash in a pitch. Additionally, the quinoline insolubles willcontain any insoluble species from the isotropic phase and theinsoluble portion of the mesophase. Hence, the quinolinesoluble fraction is composed of the bulk o
27、f the isotropic phaseand the soluble fraction of the mesophase. However, thequinoline insoluble test is not necessarily a true measure of thesolid constituents of pitch.Normal QI with radial symmetry is produced by oxy-cracking during the early portion of the coking cycle whenpartially oxidizing con
28、ditions can exist, and is referred to ascombustion black (see Fig. 5a). Normal QI with concentricsymmetry is produced by thermal cracking later in thecoking cycle under reducing conditions, and is referred to asthermal black (see Fig. 5b). These two symmetries can onlybe differentiated using electro
29、n microscopy.4,5The quinolineinsolubles content determined by Test Method D2318 issometimes greater than that anticipated on the basis of theconcentration of the quinoline insolubles during distillationor heat treatment to produce the final pitch. The difference isknown as the “secondary” quinoline
30、insolubles content, andis traditionally regarded as the mesophase content. Thisequivalence of secondary quinoline insolubles and mesoph-ase is erroneous because the mesophase may be partiallysoluble in quinoline.3.1.7 pyrolytic carbona carbon that originates as a depositon the upper walls, tunnel he
31、ad, and standpipes of a coke ovendue to thermal cracking. It is usually a minor phase in coal tarpitch, highly variable in shape and porosity, and may be sizedup to 500 m. It is usually optically active under crossedpolarizers. The fine sized domains are commonly referred to asspherulitic, while the
32、 coarser anisotropic domains are calledpyrolytic. Spherulitic and pyrolytic carbons are highlyreflecting, relatively hard materials and stand out in relief fromthe softer isotropic phase.3.1.8 reactor cokea material that originates on the walls ofthe pipestill reactor used in the distillation or hea
33、t treatment toproduce pitch from either coal tars or petroleum oils. It isthermally more advanced than reactor mesophase. It is usuallya minor component of pitch and may be sized up to 200 m. Itmay be angular or rounded, and it may be relatively porouswith a coarse appearance under crossed polarizer
34、s. It isdistinguished from the reactor mesophase mentioned in 3.1.9by its relative hardness, which causes it to show up in relief inbright field illumination.3.1.9 reactor mesophasea material that originates on thewalls of the pipestill or reactor used in the distillation or heattreatment to produce
35、 pitch from either coal tars or petroleumoils. It is usually a minor component of pitch and may be sizedup to 200 m. It may be angular or rounded, and it may berelatively porous. Under crossed polarizers reactor mesophase4Bertau, B.L., and Souffrey, B., “Composition of Tar and Pitches as a Result of
36、the SpecificAspects of the Coking Plant,” Coke Making International, Vol 2 , 1990,pp. 6163.5Lafdi, K., Bonnamy, S., and Oberlin, A., “TEM Studies of Coal TarsCrudeTar and its Insoluble Fractions,” Carbon, Vol 28, No. 1, 1990, pp. 5763.FIG. 3 Structure of Mesophase SpheroidD4616 95 (2013)3has a coars
37、e mosaic appearance. In contradistinction to thereactor coke mentioned in 3.1.8, reactor mesophase is com-paratively soft and shows no relief in bright field illumination.3.1.10 refractoryusually a minor component that origi-nates from the coke oven walls, doors, and patches due to wearand degenerat
38、ion; another component is charge hole sealant. Itcan be recognized under the microscope through opticalproperties, hardness, shape, and associated minerals.4. Summary of Test Method4.1 Arepresentative sample with a softening point of at least212F (100C), as measured by Test Method D3104 (Mettlermeth
39、od), is crushed to a specific particle size and encapsulatedin resin. Alternatively, a representative molten pitch sample ispoured into a mold, or a representative crushed sample ismelted and poured into a mold. If the Mettler softening point isless than 212F (100C), it is raised to 212 to 248F (100
40、 to120C) by vacuum distillation. The encapsulated, or molded,sample is ground and polished to a flat surface for examinationin reflected light.4.2 The mesophase spheroid content of a representativesample is identified and the proportion determined on a volumebasis by observing a statistically adequa
41、te number of points.Only the area proportion is determined on a surface section ofa sample; however, the area and volume proportion are thesame when the components are randomly distributed through-out the sample.5. Significance and Use5.1 Sometimes coal tar and petroleum pitches are heattreated ther
42、eby forming mesophase spheroids. The mesophasemay be partially soluble in quinoline and cannot be estimatedby the quinoline insoluble test (Test Method D2318). This testmethod provides for the identification, quantitative estimation,and size determination of mesophase spheroids.5.2 The mesophase ini
43、tially forms as spheroids that maycoalesce to form a variety of asymmetrical shapes. Thesmallest mesophase particle that can be detected with certaintyat 400 or 500 magnification is 4 m in diameter; mesophaseparticles sizes less than 4 m should be ignored. If mesophasematerial less than 4 m in size
44、is of interest, then magnifica-tions of 1000 to 1800 shall be used and the results should beFIG. 4 Photomicrographs of a Heat Treated Coal Tar Pitch at 500 Magnification in Bright Field Showing the Effectiveness of EtchingWith Toluene to Accentuate the Interface Between Mesophase Spheroids and the I
45、sotropic PhaseFIG. 5 The Structure of a Normal Quinoline Insoluble ParticlesD4616 95 (2013)4appropriately identified. This method is limited to determiningminor levels of mesophase, that is, 20 % mesophase.6. Apparatus6.1 Grinder, Pulverizer, or Mill, for crushing the represen-tative sample and mort
46、ar and pestle or other equipment suitablefor reducing the particle size of a 100-g sample to less than 8mesh (2.4 mm).6.2 SievesU. S. sieve No. 8. See Specification E11.6.3 Vacuum Distillation Apparatus, such as that specified inTest Method D1160.6.4 Vacuum Chamber, equipped with an observation win-
47、dow.6.5 Hotplate or Laboratory Oven, possibly fitted to receiveinert gas.6.6 Bakelite Rings,6-81 in. (25 mm) or 114 in. (32 mm) indiameter.6.7 Grinding and Polishing EquipmentOne or several lapson which the pitch specimens can be ground and polished to aflat, scratch-free surface. Laps may be made o
48、f aluminum, iron,brass, bronze, lead, glass, wax, or wood. Equipment that has 8in. (203 mm) diameter disk laps that can rotate at 150 to 400rpm, and that has an automatic sample holder attachment isrecommended.9,86.8 Sample CleanerSome equipment is essential forcleaning the specimens between the dif
49、ferent grinding orpolishing stages. This may be an ultrasonic device or a simplestream of water and an air jet for drying.6.9 MicroscopeAny polarizing microscope with the capa-bility for observations by reflected light (for example, metal-lurgical or opaque-ore microscopes) may be employed. Thepolarizer may be of the Nicol prism or sheet type. All opticalcomponents (objective, eyepiece, polarizer, and analyzer) shallbe of a quality to permit examination of the dry specimen atmagnifications up to 400 to 500 under crossed po
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