1、Designation: D 4616 95 (Reapproved 2005)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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers laboratory procedures for th
3、epreparation 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 app
5、lica-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 PressuresD 2318 Test Method for Quinoline-Insoluble (QI) Contentof Tar and PitchD 3104 Test Method for Soft
6、ening Point of Pitches (MettlerSoftening Point Method)D 4296 Practice for Sampling PitchE11 Specification for Wire-Cloth Sieves for Testing Pur-posesE 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 mineral matterformed when minute particles of thecoke oven charge are carried over into the coke ov
10、en collectingmain during 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 reflecta
11、nce in the case of clay, quartz, andcarbonates. The association of mineral matter with insolubleorganic matter from coal aids in its identification.3.1.4 refractoryusually a minor component that originatesfrom the coke oven walls, doors, and patches due to wear anddegeneration; another component is
12、charge hole sealant. It canbe recognized under the microscope through optical properties,hardness, shape, and associated minerals.3.1.5 isotropic phaseusually the predominant, and con-tinuous, phase. It is a complex mixture of organic aromaticcompounds composed mainly of carbon and hydrogen. Atroom
13、temperature, the isotropic phase is a glass-like solid. It isoptically inactive in polarized light (see Fig. 1 and Fig. 2).3.1.6 mesophasean optically anisotropic liquid crystalcarbonaceous phase that forms from the parent liquor whenmolecular size, shape, and distribution are favorable. In theearly
14、 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 crossed1This test method is under the jurisdiction of ASTM Committee D0
15、2 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, 2005. Published May 2005. Originallyapproved in 1986. Last previous edition approved in 2000 as D 4616 95 (2000).2Fo
16、r 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C70
17、0, West Conshohocken, PA 19428-2959, United States.polarizers, the distinctive mesophase spheroids, with theircomplex extinction patterns shown in Fig. 2, can be readilyseen.33.1.6.1 At magnifications of 4003 and 5003, the minimumspheroid size which can be resolved with confidence is 4 m indiameter.
18、 At magnifications of 1000 to 18003, the minimumspheroid size that can be resolved with confidence is about 2m in diameter. Typically, the upper size may be 100 m.Mesophase spheroids are relatively soft and do not form reliefstructures (see Fig. 4). Quinoline insoluble particles oftenaggregate at th
19、e interface between the continuous isotropicphase and mesophase.3.1.6.2 The isotropic phase is more soluble than the me-sophase in solvents such as toluene. Solvent etching isachieved by soaking the polished surface in toluene for a fewseconds, rinsing the surface with cold flowing water, anddrying
20、in a current of hot air. Etching produces sharply definedmesophase spheroids (see Fig. 4).3.1.7 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 compounds in
21、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 are relativel
22、y hard. They areoutlined in bright incident light because they stand out in relieffrom the softer isotropic phase (see Fig. 1).NOTE 1Sometimes the term primary QI is used to describe allquinoline insoluble materials that are carried over during the cokingoperation (cenospheres, mineral matter, norma
23、l, QI, and so forth).3.1.7.1 Observed under crossed polarizers, the normalquinoline insoluble material displays a Brewster cross pattern(see Fig. 1 and Fig. 2). This interference figure remainsstationary when the specimen is rotated through 360. Theonionskin arrangement can be observed in particles
24、with aminimum diameter of 2 m at high magnification (1000 to20003) under cross polarizers.NOTE 2The quinoline insolubles content is determined by TestMethod D 2318 and represents the total amount of natural quinolineinsolubles, cenospheres, coke-oven-coke, pyrolytic carbon, refractory,reactor coke,
25、and free ash in a pitch.Additionally, the quinoline insolubleswill contain any insoluble species from the isotropic phase and theinsoluble portion of the mesophase. Hence, the quinoline soluble fractionis composed of the bulk of the isotropic phase and the soluble fraction ofthe mesophase. However,
26、the quinoline insoluble test is not necessarily atrue measure of the solid constituents of pitch.Normal QI with radial symmetry is produced by oxycrackingduring the early portion of the coking cycle when partiallyoxidizing conditions can exist, and is referred to as combustionblack (see Fig. 5a). No
27、rmal 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 differentiatedusing electron microscopy.4,5The quinoline insolubles contentdetermined by Test Method
28、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 the“secondary” quinoline insolubles content, and is traditionallyregarded as the mesophase content
29、. This equivalence of sec-ondary quinoline insolubles and mesophase is erroneous be-cause the mesophase may be partially soluble in quinoline.3.1.8 pyrolytic carbona carbon that originates as a depositon the upper walls, tunnel head, and standpipes of a coke ovendue to thermal cracking. It is usuall
30、y 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 coarser anisotropic domains are calledpyrolytic. Spherulitic and pyro
31、lytic carbons are highly reflect-ing, relatively hard materials and stand out in relief from thesofter isotropic phase.3.1.9 reactor cokea material that originates on the wallsof the pipestill reactor used in the distillation or heat treatmentto produce pitch from either coal tars or petroleum oils.
32、 It isthermally more advanced than reactor mesophase. It is usually3Amore 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 695697.4Bertau, B.L., and Souffrey, B., “Comp
33、osition of Tar and Pitches as a Result ofthe Specific Aspects 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. 1 Photomicrographs
34、of a Coal Tar Pitch at 5003Magnification in Polarized Light (Crossed Polarizers) and BrightLight Showing the Isotropic Phase, Natural Quinoline Insolubles,and a Cenosphere.D 4616 95 (2005)2a minor component of pitch and may be sized up to 200 m. Itmay be angular or rounded, and it may be relatively
35、porouswith a coarse appearance under crossed polarizers. It isdistinguished from the reactor mesophase mentioned in 3.1.10by its relative hardness, which causes it to show up in relief inbright field illumination.3.1.10 reactor mesophasea material that originates on thewalls of the pipestill or reac
36、tor 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 reactor mesophasehas a coarse mosaic app
37、earance. In contradistinction to thereactor coke mentioned in 3.8, reactor mesophase is compara-tively soft and shows no relief in bright field illumination.4. Summary of Test Method4.1 Arepresentative sample with a softening point of at least212F (100C), as measured by Test Method D 3104 (Mettlerme
38、thod), 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 (1
39、00 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 adeq
40、uate 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.FIG. 2 Photomicrographs of a Heat-Treated Coal Tar Pitch at 5003 Magnification in Pola
41、rized Light(Crossed Polarizers) Showing Natural Quinoline Insolubles and Mesophase SpheroidsFIG. 3 Structure of Mesophase SpheroidD 4616 95 (2005)35. Significance and Use5.1 Sometimes coal tar and petroleum pitches are heattreated thereby forming mesophase spheroids. The mesophasemay be partially so
42、luble 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 spheroids.5.2 The mesophase initially forms as spheroids that maycoalesce to form a variety of
43、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. Ifmesophase material less than 4 m in size is of interest, thenmagnifications of 1000 to 18003 shall be
44、 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 the represen-tative sample and mortar and pestle or other equipment suitablefor reducing the p
45、article 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 Chamber, equipped with an observation win-dow.6.5 Hotplate or Laboratory Oven, possibly fitted to re
46、ceiveinert gas.6.6 Bakelite Rings6, 1 in. (25 mm) or 114 in. (32 mm) indiameter.76Bakelite, a trademark of the Union Carbide Corporation, Old Ridgebury Road,Danbury, CT, 06817, has been found satisfactory for this purpose. If you are awareof alternative suppliers, please provide this information to
47、ASTM InternationalHeadquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee1, which you may attend.7Rings supplied by Buehler Ltd., 41 Waukegan Road, Lake Bluff, IL, and LecoCorporation, 3000 Lakeview Ave., St. Joseph, MI, 49085, have been foun
48、dsatisfactory for this purpose. If you are aware of alternative suppliers, please providethis information to ASTM International Headquarters. Your comments will receivecareful consideration at a meeting of the responsible technical committee1, whichyou may attend.FIG. 4 Photomicrographs of a Heat Tr
49、eated 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 (2005)46.7 Grinding and Polishing EquipmentOne or severallaps on which the pitch specimens can be ground and polishedto a flat, 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 r
