1、Designation: D 4616 95 (Reapproved 2008)An American National StandardStandard Test Method forMicroscopical Analysis by Reflected Light andDetermination of Mesophase in a Pitch1This standard is issued under the fixed designation D 4616; the number immediately following the designation indicates the y
2、ear oforiginal adoption or, in 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 the
3、preparation of granular and melted 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
4、are provided for information onlyand 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 appl
5、ica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 329 Specification for AcetoneD 1160 Test Method for Distillation of Petroleum Productsat Reduced PressureD 2318 Test Method for Quinoline-Insoluble (QI) Contentof Tar and PitchD 3104 Test Method for Soften
6、ing Point of Pitches (MettlerSoftening Point Method)D 4296 Practice for Sampling PitchE11 Specification for Wire Cloth and Sieves for TestingPurposesE 562 Test Method for Determining Volume Fraction bySystematic Manual Point Count3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1
7、 cenospheresusually a minor component 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 5
8、00 m. In polarized light (crossed polarizers), 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 compon
9、ent of coaltar pitch. It originates 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, and con-tinuous, phase. It is a complex mixture of organic
10、aromaticcompounds composed mainly of carbon 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 whenm
11、olecular size, shape, and distribution 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 crosse
12、dpolarizers, the distinctive mesophase spheroids, with theircomplex extinction patterns shown in Fig. 2, can be readilyseen.33.1.4.1 spheroidsAt magnifications of 4003 and 5003,the minimum spheroid size which can be resolved withconfidence is 4 m in diameter. At magnifications of 1000 to1This test m
13、ethod 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 Dec. 1, 2008. Published February 2009. Originallyapproved in 1986. Last
14、 previous edition approved in 2005 as D 461695(2005).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 website.3Amore c
15、omplete 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. 695697.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United St
16、ates.FIG. 1 Photomicrographs of a Coal Tar Pitch at 5003 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 5003 Magnification in Polarized Light
17、 (Crossed Polarizers) ShowingNatural Quinoline Insolubles and Mesophase SpheroidsD 4616 95 (2008)218003, the minimum spheroid size that can be resolved withconfidence is about 2 m in diameter. Typically, the upper sizemay be 100 m. Mesophase spheroids are relatively soft and donot form relief struct
18、ures (see Fig. 4). Quinoline insolubleparticles often aggregate at the interface between the continu-ous isotropic phase and mesophase.3.1.4.2 isotropic phaseThe isotropic phase is moresoluble than the mesophase in solvents such as toluene. Solventetching is achieved by soaking the polished surface
19、in toluenefor a few seconds, rinsing the surface with cold flowing water,and 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 dur
20、ing the charging operation. 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 cl
21、ay, quartz, andcarbonates. 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 bytherm
22、al cracking of organic compounds 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 norma
23、l quinoline insolubles are 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 coki
24、ng operation (cenospheres, 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 spe
25、cimen isrotated through 360. The onionskin arrangement can beobserved in particles with a minimum diameter of 2 m at highmagnification (1000 to 20003) under cross polarizers.3.1.6.3 DiscussionThe quinoline insolubles content isdetermined by Test Method D 2318 and represents the totalamount of natura
26、l quinoline insolubles, 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 i
27、s composed of the bulk of 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 oxycrackingduring the early portion of the coking cycle when
28、partiallyoxidizing conditions can exist, and is referred to as combustionblack (see Fig. 5a). Normal QI with concentric symmetry isproduced by thermal cracking later in the coking cycle underreducing conditions, and is referred to as thermal black (seeFig. 5b). These two symmetries can only be diffe
29、rentiatedusing electron microscopy.4,5The quinoline insolubles contentdetermined by Test Method D 2318 is sometimes greater thanthat anticipated on the basis of the concentration of thequinoline insolubles during distillation or heat treatment toproduce the final pitch. The difference is known as th
30、e“secondary” quinoline insolubles content, and is traditionallyregarded as the mesophase content. This equivalence of sec-ondary quinoline insolubles and mesophase is erroneous be-cause the mesophase may be partially soluble in quinoline.3.1.7 pyrolytic carbona carbon that originates as a depositon
31、the upper walls, tunnel head, 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 t
32、o asspherulitic, while the coarser anisotropic domains are calledpyrolytic. Spherulitic and pyrolytic carbons are highly reflect-ing, relatively hard materials and stand out in relief from thesofter isotropic phase.3.1.8 reactor cokea material that originates on the wallsof the pipestill reactor use
33、d in the distillation or heat treatmentto produce 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 appear
34、ance under crossed polarizers. It isdistinguished from the reactor mesophase mentioned in 3.1.94Bertau, B.L., and Souffrey, B., “Composition of Tar and Pitches as a Result ofthe Specific Aspects of the Coking Plant,” Coke Making International,Vol2,1990, pp. 6163.5Lafdi, K., Bonnamy, S., and Oberlin,
35、 A., “TEM Studies of Coal TarsCrudeTar and its Insoluble Fractions,” Carbon, Vol 28, No. 1, 1990, pp. 5763.FIG. 3 Structure of Mesophase SpheroidD 4616 95 (2008)3by its relative hardness, which causes it to show up in relief inbright field illumination.3.1.9 reactor mesophasea material that originat
36、es on thewalls of the pipestill or reactor used in the distillation or heattreatment to produce 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 r
37、eactor mesophasehas a coarse 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 patch
38、es due to wearand degeneration; 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 Tes
39、t Method D 3104 (Mettlermethod), 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 i
40、s raised to 212 to 248F (100 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 obse
41、rving a statistically adequate 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
42、pitches are heattreated thereby forming mesophase spheroids. The mesophasemay be partially soluble in quinoline and cannot be estimatedby the quinoline insoluble test (Test Method D 2318). This testmethod provides for the identification, quantitative estimation,and size determination of mesophase sp
43、heroids.5.2 The mesophase initially forms as spheroids that maycoalesce to form a variety of asymmetrical shapes. Thesmallest mesophase particle that can be detected with certaintyat 4003 or 5003 magnification is 4 m in diameter; me-sophase particles sizes less than 4 m should be ignored. IfFIG. 4 P
44、hotomicrographs of a Heat Treated Coal Tar Pitch at 5003 Magnification in Bright Field Showing the Effectiveness of EtchingWith Toluene to Accentuate the Interface Between Mesophase Spheroids and the Isotropic PhaseFIG. 5 The Structure of a Normal Quinoline Insoluble ParticlesD 4616 95 (2008)4mesoph
45、ase material less than 4 m in size is of interest, thenmagnifications of 1000 to 18003 shall be used and the resultsshould be appropriately identified. This method is limited todetermining minor levels of mesophase, that is, #20 % me-sophase.6. Apparatus6.1 Grinder, Pulverizer, or Mill, for crushing
46、 the represen-tative sample and mortar 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 D 1160.6.4 Vacuum Chamb
47、er, equipped with an observation win-dow.6.5 Hotplate or Laboratory Oven, possibly fitted to receiveinert gas.6.6 Bakelite Rings,6, 7, 81 in. (25 mm) or 114 in. (32 mm) indiameter.6.7 Grinding and Polishing EquipmentOne or severallaps on which the pitch specimens can be ground and polishedto a flat,
48、 scratch-free surface. Laps may be made of aluminum,iron, brass, bronze, lead, glass, wax, or wood. Equipment thathas 8 in. (203 mm) diameter disk laps that can rotate at 150 to400 rpm, and that has an automatic sample holder attachmentis recommended.8, 96.8 Sample CleanerSome equipment is essential
49、 forcleaning the specimens between the different 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
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