ASTM D4616-95(2018)
(Test Method)Standard Test Method for Microscopical Analysis by Reflected Light and Determination of Mesophase in a Pitch
Standard Test Method for Microscopical Analysis by Reflected Light and Determination of Mesophase in a Pitch
SIGNIFICANCE AND USE
5.1 Sometimes coal tar and petroleum pitches are heat treated thereby forming mesophase spheroids. The mesophase may be partially soluble in quinoline and cannot be estimated by the quinoline insoluble test (Test Method D2318). This test method provides for the identification, quantitative estimation, and size determination of mesophase spheroids.
5.2 The mesophase initially forms as spheroids that may coalesce to form a variety of asymmetrical shapes. The smallest mesophase particle that can be detected with certainty at 400× or 500× magnification is 4 μm in diameter; mesophase particles sizes less than 4 μm should be ignored. If mesophase material less than 4 μm in size is of interest, then magnifications of 1000× to 1800× shall be used and the results should be appropriately identified. This method is limited to determining minor levels of mesophase, that is, ≤20 % mesophase.
SCOPE
1.1 This test method covers laboratory procedures for the preparation of granular and melted samples for microscopic analysis using reflected light to identify and estimate the amount and size of the mesophase.
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered 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 appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:D4616 −95 (Reapproved 2018)
Standard Test Method for
Microscopical Analysis by Reflected Light and
Determination of Mesophase in a Pitch
This standard is issued under the fixed designation D4616; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E562Test Method for Determining Volume Fraction by
Systematic Manual Point Count
1.1 This test method covers laboratory procedures for the
preparation of granular and melted samples for microscopic
3. Terminology
analysis using reflected light to identify and estimate the
3.1 Definitions of Terms Specific to This Standard:
amount and size of the mesophase.
3.1.1 cenospheres—usually a minor component of coal tar
1.2 Thevaluesstatedininch-poundunitsaretoberegarded
pitch. They are formed by the rapid pyrolysis of unconfined
as standard. The values given in parentheses are mathematical
coal particles that are carried over from the coke oven to the
conversions to SI units that are provided for information only
tar. Microscopically, they appear like hollow spheres or seg-
and are not considered standard.
ments thereof (see Fig. 1), and are typically sized from about
1.3 This standard does not purport to address all of the
10µm to 500µm. In polarized light (crossed polarizers), a
safety concerns, if any, associated with its use. It is the
cenospheremaybeopticallyactive.Thesizeoftheanisotropic
responsibility of the user of this standard to establish appro-
pattern or mosaic depends upon the rank of the coal carbon-
priate safety, health, and environmental practices and deter-
ized. Cenospheres are harder than the continuous phase and
mine the applicability of regulatory limitations prior to use.
polish in relief (see Fig. 1).
1.4 This international standard was developed in accor-
3.1.2 coke-oven-coke—usually a minor component of coal
dance with internationally recognized principles on standard-
tar pitch. It originates in carry-over from the coke oven to the
ization established in the Decision on Principles for the
tar side. It differs from cenospheres only in terms of its shape
Development of International Standards, Guides and Recom-
and porosity. Coke-oven-coke is angular and less porous.
mendations issued by the World Trade Organization Technical
3.1.3 isotropic phase—usually the predominant, and
Barriers to Trade (TBT) Committee.
continuous, phase. It is a complex mixture of organic aromatic
2. Referenced Documents
compounds composed mainly of carbon and hydrogen. At
2.1 ASTM Standards: room temperature, the isotropic phase is a glass-like solid. It is
optically inactive in polarized light (see Fig. 1 and Fig. 2).
D329Specification for Acetone
D1160TestMethodforDistillationofPetroleumProductsat
3.1.4 mesophase—an optically anisotropic liquid crystal
Reduced Pressure
carbonaceous phase that forms from the parent liquor when
D2318Test Method for Quinoline-Insoluble (QI) Content of
molecular size, shape, and distribution are favorable. In the
Tar and Pitch
early stages of its development, mesophase usually appears as
D3104Test Method for Softening Point of Pitches (Mettler
spheroids. The planar molecules are lined up equatorially as
Softening Point Method)
shown schematically in Fig. 3. This equatorial arrangement
D4296Practice for Sampling Pitch
may be distinguished in crossed polarized light. Under crossed
E11Specification forWovenWireTest Sieve Cloth andTest
polarizers, the distinctive mesophase spheroids, with their
Sieves
complex extinction patterns shown in Fig. 2, can be readily
seen.
This test method is under the jurisdiction of ASTM Committee D02 on
3.1.4.1 spheroids—Atmagnificationsof400×and500×,the
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
minimumspheroidsizewhichcanberesolvedwithconfidence
SubcommitteeD02.05onPropertiesofFuels,PetroleumCokeandCarbonMaterial.
Current edition approved Dec. 1, 2018. Published December 2018. Originally
is 4µm in diameter.At magnifications of 1000× to 1800×, the
approved in 1986. Last previous edition approved in 2013 as D4616–95(2013).
DOI: 10.1520/D4616-95R18.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM AmorecompletediscussionwillbefoundinapaperbyHonda,H.,Kimura,H.,
Standards volume information, refer to the standard’s Document Summary page on andSanada,Y.,“ChangesofPleochroismandExtinctionContoursinCarbonaceous
the ASTM website. Mesophase,” Carbon, 9, 1971, pp. 695–697.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4616−95 (2018)
minimumspheroidsizethatcanberesolvedwithconfidenceis combustion black (see Fig. 5a). Normal QI with concentric
about 2µm in diameter. Typically, the upper size may be symmetry is produced by thermal cracking later in the
100µm. Mesophase spheroids are relatively soft and do not cokingcycleunderreducingconditions,andisreferredtoas
formreliefstructures(seeFig.4).Quinolineinsolubleparticles thermal black (see Fig. 5b). These two symmetries can only
4,5
often aggregate at the interface between the continuous isotro- bedifferentiatedusingelectronmicroscopy. Thequinoline
pic phase and mesophase. insolubles content determined by Test Method D2318 is
sometimes greater than that anticipated on the basis of the
3.1.4.2 isotropicphase—Theisotropicphaseismoresoluble
concentration of the quinoline insolubles during distillation
than the mesophase in solvents such as toluene. Solvent
orheattreatmenttoproducethefinalpitch.Thedifferenceis
etching is achieved by soaking the polished surface in toluene
known as the “secondary” quinoline insolubles content, and
for a few seconds, rinsing the surface with cold flowing water,
is traditionally regarded as the mesophase content. This
and drying in a current of hot air. Etching produces sharply
equivalence of secondary quinoline insolubles and mesoph-
defined mesophase spheroids (see Fig. 4).
ase is erroneous because the mesophase may be partially
3.1.5 mineral matter—formed when minute particles of the
soluble in quinoline.
cokeovenchargearecarriedoverintothecokeovencollecting
3.1.7 pyrolytic carbon—acarbonthatoriginatesasadeposit
main during the charging operation.The tiny coal particles are
on the upper walls, tunnel head, and standpipes of a coke oven
digested in the collecting main tar, resulting in a residue that is
due to thermal cracking. It is usually a minor phase in coal tar
rich in mineral matter. This mineral matter is identified under
pitch, highly variable in shape and porosity, and may be sized
bright field illumination by its high reflectivity, in the case of
up to 500µm. It is usually optically active under crossed
pyrite, and its low reflectance in the case of clay, quartz, and
polarizers.Thefinesizeddomainsarecommonlyreferredtoas
carbonates. The association of mineral matter with insoluble
spherulitic, while the coarser anisotropic domains are called
organic matter from coal aids in its identification.
pyrolytic. Spherulitic and pyrolytic carbons are highly
3.1.6 normal quinoline insolubles—(sometimes termed
reflecting,relativelyhardmaterialsandstandoutinrelieffrom
“true,” natural or “primary” quinoline insolubles)—a carbon
the softer isotropic phase.
black-like solid phase in coal tar pitch that is produced by
3.1.8 reactorcoke—amaterialthatoriginatesonthewallsof
thermal cracking of organic compounds in the tunnel head
the pipestill reactor used in the distillation or heat treatment to
above the coal charge in a by-product coke oven. The indi-
produce pitch from either coal tars or petroleum oils. It is
vidual spherically-shaped particles are usually less than 2µm
thermally more advanced than reactor mesophase. It is usually
in diameter. A typical coal tar pitch may contain from about
a minor component of pitch and may be sized up to 200µm. It
1% to about 20% (by weight) of normal quinoline insolubles.
may be angular or rounded, and it may be relatively porous
The normal quinoline insolubles are relatively hard. They are
with a coarse appearance under crossed polarizers. It is
outlinedinbrightincidentlightbecausetheystandoutinrelief
distinguished from the reactor mesophase mentioned in 3.1.9
from the softer isotropic phase (see Fig. 1).
by its relative hardness, which causes it to show up in relief in
3.1.6.1 Discussion—SometimesthetermprimaryQIisused bright field illumination.
to describe all quinoline insoluble materials that are carried
3.1.9 reactor mesophase—a material that originates on the
overduringthecokingoperation(cenospheres,mineralmatter,
walls of the pipestill or reactor used in the distillation or heat
normal, QI, and so forth).
treatment to produce pitch from either coal tars or petroleum
3.1.6.2 normal quinoline insoluble material—Observed un-
oils.Itisusuallyaminorcomponentofpitchandmaybesized
der crossed polarizers, the normal quinoline insoluble material
up to 200µm. It may be angular or rounded, and it may be
displays a Brewster cross pattern (see Fig. 1 and Fig. 2). This
relatively porous. Under crossed polarizers reactor mesophase
interference figure remains stationary when the specimen is
has a coarse mosaic appearance. In contradistinction to the
rotated through 360°. The onionskin arrangement can be
reactor coke mentioned in 3.1.8, reactor mesophase is com-
observedinparticleswithaminimumdiameterof2µmathigh
paratively soft and shows no relief in bright field illumination.
magnification (1000× to 2000×) under cross polarizers.
3.1.10 refractory—usually a minor component that origi-
natesfromthecokeovenwalls,doors,andpatchesduetowear
3.1.6.3 Discussion—The quinoline insolubles content is de-
termined by Test Method D2318 and represents the total and degeneration; another component is charge hole sealant. It
can be recognized under the microscope through optical
amount of natural quinoline insolubles, cenospheres, coke-
oven-coke, pyrolytic carbon, refractory, reactor coke, and free properties, hardness, shape, and associated minerals.
ash in a pitch. Additionally, the quinoline insolubles will
4. Summary of Test Method
contain any insoluble species from the isotropic phase and the
insoluble portion of the mesophase. Hence, the quinoline
4.1 Arepresentativesamplewithasofteningpointofatleast
soluble fraction is composed of the bulk of the isotropic phase
212°F (100°C), as measured by Test Method D3104 (Mettler
and the soluble fraction of the mesophase. However, the
quinolineinsolubletestisnotnecessarilyatruemeasureofthe
Bertau, B.L., and Souffrey, B., “Composition of Tar and Pitches as a Result of
solid constituents of pitch.
theSpecificAspectsoftheCokingPlant,” Coke Making International,Vol2,1990,
Normal QI with radial symmetry is produced by oxy-
pp. 61–63.
cracking during the early portion of the coking cycle when
Lafdi, K., Bonnamy, S., and Oberlin, A., “TEM Studies of Coal Tars—Crude
partially oxidizing conditions can exist, and is referred to as Tar and its Insoluble Fractions,” Carbon, Vol 28, No. 1, 1990, pp. 57–63.
D4616−95 (2018)
method), is crushed to a specific particle size and encapsulated flat,scratch-freesurface.Lapsmaybemadeofaluminum,iron,
in resin.Alternatively, a representative molten pitch sample is brass, bronze, lead, glass, wax, or wood. Equipment that has
poured into a mold, or a representative crushed sample is 8in. (203mm) diameter disk laps that can rotate at 150 to 400
meltedandpouredintoamold.IftheMettlersofteningpointis r/min, and that has an automatic sample holder attachment is
9,8
less than 212°F (100°C), it is raised to 212°F to 248°F recommended.
(100°Cto120°C)byvacuumdistillation.Theencapsulated,or
6.8 Sample Cleaner—Some equipment is essential for
molded, sample is ground and polished to a flat surface for
cleaning the specimens between the different grinding or
examination in reflected light.
polishing stages. This may be an ultrasonic device or a simple
4.2 The mesophase spheroid content of a representative stream of water and an air jet for drying.
sampleisidentifiedandtheproportiondeterminedonavolume
6.9 Microscope—Any polarizing microscope with the capa-
basis by observing a statistically adequate number of points.
bility for observations by reflected light (for example, metal-
Only the area proportion is determined on a surface section of
lurgical or opaque-ore microscopes) may be employed. The
a sample; however, the area and volume proportion are the
polarizer may be of the Nicol prism or sheet type. All optical
same when the components are randomly distributed through-
components(objective,eyepiece,polarizer,andanalyzer)shall
out the sample.
be of a quality to permit examination of the dry specimen at
magnifications up to 400× to 500× under crossed polarizers.
5. Significance and Use
For magnifications greater than 500×, 0.1 immersion objec-
5.1 Sometimes coal tar and petroleum pitches are heat
tives shall be used. The analyzer should be oriented 90° with
treated thereby forming mesophase spheroids. The mesophase
respect to the polarizer for cross polarizer examination. Any
may be partially soluble in quinoline and cannot be estimated
light source that can be regulated for stable output with
by the quinoline insoluble test (Test Method D2318). This test
sufficient intensity for photography with cross polarizers may
method provides for the identification, quantitative estimation,
be used. The microscope shall have a circular stage that is
and size determination of mesophase spheroids.
capable of rotating a specimen through 360°. The stage shall
alsobeofsuchtypethatthespecimencanbequicklyadvanced
5.2 The mesophase initially forms as spheroids that may
coalesce to form a variety of asymmetrical shapes. The by definite fixed increments in two perpendicular directions,
suchasastagewithclickstops.Ifanelectricallyoperatedstage
smallest mesophase particle that can be detected with certainty
at 400× or 500× magnification is 4 µm in diameter; mesophase is used, incremental steps in one direction across the specimen
may be actuated by the counter switches. One eyepiece of the
particles sizes less than 4 µm should be ignored. If mesophase
material less than 4 µm in size is of interest, then magnifica- microscope should be fitted with a graticule or cross-hair. If
tionsof1000×to1800×shallbeusedandtheresultsshouldbe other
...
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D4616 − 95 (Reapproved 2018)
Standard Test Method for
Microscopical Analysis by Reflected Light and
Determination of Mesophase in a Pitch
This standard is issued under the fixed designation D4616; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E562 Test Method for Determining Volume Fraction by
Systematic Manual Point Count
1.1 This test method covers laboratory procedures for the
preparation of granular and melted samples for microscopic
3. Terminology
analysis using reflected light to identify and estimate the
amount and size of the mesophase. 3.1 Definitions of Terms Specific to This Standard:
3.1.1 cenospheres—usually a minor component of coal tar
1.2 The values stated in inch-pound units are to be regarded
pitch. They are formed by the rapid pyrolysis of unconfined
as standard. The values given in parentheses are mathematical
coal particles that are carried over from the coke oven to the
conversions to SI units that are provided for information only
tar. Microscopically, they appear like hollow spheres or seg-
and are not considered standard.
ments thereof (see Fig. 1), and are typically sized from about
1.3 This standard does not purport to address all of the
10 µm to 500 µm. In polarized light (crossed polarizers), a
safety concerns, if any, associated with its use. It is the
cenosphere may be optically active. The size of the anisotropic
responsibility of the user of this standard to establish appro-
pattern or mosaic depends upon the rank of the coal carbon-
priate safety, health, and environmental practices and deter-
ized. Cenospheres are harder than the continuous phase and
mine the applicability of regulatory limitations prior to use.
polish in relief (see Fig. 1).
1.4 This international standard was developed in accor-
3.1.2 coke-oven-coke—usually a minor component of coal
dance with internationally recognized principles on standard-
tar pitch. It originates in carry-over from the coke oven to the
ization established in the Decision on Principles for the
tar side. It differs from cenospheres only in terms of its shape
Development of International Standards, Guides and Recom-
and porosity. Coke-oven-coke is angular and less porous.
mendations issued by the World Trade Organization Technical
3.1.3 isotropic phase—usually the predominant, and
Barriers to Trade (TBT) Committee.
continuous, phase. It is a complex mixture of organic aromatic
2. Referenced Documents
compounds composed mainly of carbon and hydrogen. At
room temperature, the isotropic phase is a glass-like solid. It is
2.1 ASTM Standards:
D329 Specification for Acetone optically inactive in polarized light (see Fig. 1 and Fig. 2).
D1160 Test Method for Distillation of Petroleum Products at
3.1.4 mesophase—an optically anisotropic liquid crystal
Reduced Pressure
carbonaceous phase that forms from the parent liquor when
D2318 Test Method for Quinoline-Insoluble (QI) Content of
molecular size, shape, and distribution are favorable. In the
Tar and Pitch
early stages of its development, mesophase usually appears as
D3104 Test Method for Softening Point of Pitches (Mettler
spheroids. The planar molecules are lined up equatorially as
Softening Point Method)
shown schematically in Fig. 3. This equatorial arrangement
D4296 Practice for Sampling Pitch
may be distinguished in crossed polarized light. Under crossed
E11 Specification for Woven Wire Test Sieve Cloth and Test
polarizers, the distinctive mesophase spheroids, with their
Sieves
complex extinction patterns shown in Fig. 2, can be readily
seen.
This test method is under the jurisdiction of ASTM Committee D02 on
3.1.4.1 spheroids—At magnifications of 400× and 500×, the
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
minimum spheroid size which can be resolved with confidence
Subcommittee D02.05 on Properties of Fuels, Petroleum Coke and Carbon Material.
Current edition approved Dec. 1, 2018. Published December 2018. Originally
is 4 µm in diameter. At magnifications of 1000× to 1800×, the
approved in 1986. Last previous edition approved in 2013 as D4616 – 95 (2013).
DOI: 10.1520/D4616-95R18.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM A more complete discussion will be found in a paper by Honda, H., Kimura, H.,
Standards volume information, refer to the standard’s Document Summary page on and Sanada, Y., “Changes of Pleochroism and Extinction Contours in Carbonaceous
the ASTM website. Mesophase,” Carbon, 9, 1971, pp. 695–697.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4616 − 95 (2018)
minimum spheroid size that can be resolved with confidence is combustion black (see Fig. 5a). Normal QI with concentric
about 2 µm in diameter. Typically, the upper size may be symmetry is produced by thermal cracking later in the
100 µm. Mesophase spheroids are relatively soft and do not coking cycle under reducing conditions, and is referred to as
form relief structures (see Fig. 4). Quinoline insoluble particles thermal black (see Fig. 5b). These two symmetries can only
4,5
often aggregate at the interface between the continuous isotro- be differentiated using electron microscopy. The quinoline
pic phase and mesophase. insolubles content determined by Test Method D2318 is
sometimes greater than that anticipated on the basis of the
3.1.4.2 isotropic phase—The isotropic phase is more soluble
concentration of the quinoline insolubles during distillation
than the mesophase in solvents such as toluene. Solvent
or heat treatment to produce the final pitch. The difference is
etching is achieved by soaking the polished surface in toluene
known as the “secondary” quinoline insolubles content, and
for a few seconds, rinsing the surface with cold flowing water,
is traditionally regarded as the mesophase content. This
and drying in a current of hot air. Etching produces sharply
equivalence of secondary quinoline insolubles and mesoph-
defined mesophase spheroids (see Fig. 4).
ase is erroneous because the mesophase may be partially
3.1.5 mineral matter—formed when minute particles of the
soluble in quinoline.
coke oven charge are carried over into the coke oven collecting
3.1.7 pyrolytic carbon—a carbon that originates as a deposit
main during the charging operation. The tiny coal particles are
on the upper walls, tunnel head, and standpipes of a coke oven
digested in the collecting main tar, resulting in a residue that is
due to thermal cracking. It is usually a minor phase in coal tar
rich in mineral matter. This mineral matter is identified under
pitch, highly variable in shape and porosity, and may be sized
bright field illumination by its high reflectivity, in the case of
up to 500 µm. It is usually optically active under crossed
pyrite, and its low reflectance in the case of clay, quartz, and
polarizers. The fine sized domains are commonly referred to as
carbonates. The association of mineral matter with insoluble
spherulitic, while the coarser anisotropic domains are called
organic matter from coal aids in its identification.
pyrolytic. Spherulitic and pyrolytic carbons are highly
3.1.6 normal quinoline insolubles—(sometimes termed
reflecting, relatively hard materials and stand out in relief from
“true,” natural or “primary” quinoline insolubles)—a carbon
the softer isotropic phase.
black-like solid phase in coal tar pitch that is produced by
3.1.8 reactor coke—a material that originates on the walls of
thermal cracking of organic compounds in the tunnel head
the pipestill reactor used in the distillation or heat treatment to
above the coal charge in a by-product coke oven. The indi-
produce pitch from either coal tars or petroleum oils. It is
vidual spherically-shaped particles are usually less than 2 µm
thermally more advanced than reactor mesophase. It is usually
in diameter. A typical coal tar pitch may contain from about
a minor component of pitch and may be sized up to 200 µm. It
1 % to about 20 % (by weight) of normal quinoline insolubles.
may be angular or rounded, and it may be relatively porous
The normal quinoline insolubles are relatively hard. They are
with a coarse appearance under crossed polarizers. It is
outlined in bright incident light because they stand out in relief
distinguished from the reactor mesophase mentioned in 3.1.9
from the softer isotropic phase (see Fig. 1).
by its relative hardness, which causes it to show up in relief in
bright field illumination.
3.1.6.1 Discussion—Sometimes the term primary QI is used
to describe all quinoline insoluble materials that are carried
3.1.9 reactor mesophase—a material that originates on the
over during the coking operation (cenospheres, mineral matter,
walls of the pipestill or reactor used in the distillation or heat
normal, QI, and so forth).
treatment to produce pitch from either coal tars or petroleum
3.1.6.2 normal quinoline insoluble material—Observed un-
oils. It is usually a minor component of pitch and may be sized
der crossed polarizers, the normal quinoline insoluble material
up to 200 µm. It may be angular or rounded, and it may be
displays a Brewster cross pattern (see Fig. 1 and Fig. 2). This
relatively porous. Under crossed polarizers reactor mesophase
interference figure remains stationary when the specimen is
has a coarse mosaic appearance. In contradistinction to the
rotated through 360°. The onionskin arrangement can be
reactor coke mentioned in 3.1.8, reactor mesophase is com-
observed in particles with a minimum diameter of 2 µm at high
paratively soft and shows no relief in bright field illumination.
magnification (1000× to 2000×) under cross polarizers.
3.1.10 refractory—usually a minor component that origi-
3.1.6.3 Discussion—The quinoline insolubles content is de- nates from the coke oven walls, doors, and patches due to wear
and degeneration; another component is charge hole sealant. It
termined by Test Method D2318 and represents the total
amount of natural quinoline insolubles, cenospheres, coke- can be recognized under the microscope through optical
properties, hardness, shape, and associated minerals.
oven-coke, pyrolytic carbon, refractory, reactor coke, and free
ash in a pitch. Additionally, the quinoline insolubles will
4. Summary of Test Method
contain any insoluble species from the isotropic phase and the
insoluble portion of the mesophase. Hence, the quinoline
4.1 A representative sample with a softening point of at least
soluble fraction is composed of the bulk of the isotropic phase
212 °F (100 °C), as measured by Test Method D3104 (Mettler
and the soluble fraction of the mesophase. However, the
quinoline insoluble test is not necessarily a true measure of the
Bertau, B.L., and Souffrey, B., “Composition of Tar and Pitches as a Result of
solid constituents of pitch.
the Specific Aspects of the Coking Plant,” Coke Making International, Vol 2 , 1990,
Normal QI with radial symmetry is produced by oxy-
pp. 61–63.
cracking during the early portion of the coking cycle when 5
Lafdi, K., Bonnamy, S., and Oberlin, A., “TEM Studies of Coal Tars—Crude
partially oxidizing conditions can exist, and is referred to as Tar and its Insoluble Fractions,” Carbon, Vol 28, No. 1, 1990, pp. 57–63.
D4616 − 95 (2018)
method), is crushed to a specific particle size and encapsulated flat, scratch-free surface. Laps may be made of aluminum, iron,
in resin. Alternatively, a representative molten pitch sample is brass, bronze, lead, glass, wax, or wood. Equipment that has
poured into a mold, or a representative crushed sample is 8 in. (203 mm) diameter disk laps that can rotate at 150 to 400
melted and poured into a mold. If the Mettler softening point is r/min, and that has an automatic sample holder attachment is
9,8
less than 212 °F (100 °C), it is raised to 212 °F to 248 °F recommended.
(100 °C to 120°C) by vacuum distillation. The encapsulated, or
6.8 Sample Cleaner—Some equipment is essential for
molded, sample is ground and polished to a flat surface for
cleaning the specimens between the different grinding or
examination in reflected light.
polishing stages. This may be an ultrasonic device or a simple
4.2 The mesophase spheroid content of a representative stream of water and an air jet for drying.
sample is identified and the proportion determined on a volume
6.9 Microscope—Any polarizing microscope with the capa-
basis by observing a statistically adequate number of points.
bility for observations by reflected light (for example, metal-
Only the area proportion is determined on a surface section of
lurgical or opaque-ore microscopes) may be employed. The
a sample; however, the area and volume proportion are the
polarizer may be of the Nicol prism or sheet type. All optical
same when the components are randomly distributed through-
components (objective, eyepiece, polarizer, and analyzer) shall
out the sample.
be of a quality to permit examination of the dry specimen at
magnifications up to 400× to 500× under crossed polarizers.
5. Significance and Use
For magnifications greater than 500×, 0.1 immersion objec-
5.1 Sometimes coal tar and petroleum pitches are heat
tives shall be used. The analyzer should be oriented 90° with
treated thereby forming mesophase spheroids. The mesophase
respect to the polarizer for cross polarizer examination. Any
may be partially soluble in quinoline and cannot be estimated
light source that can be regulated for stable output with
by the quinoline insoluble test (Test Method D2318). This test
sufficient intensity for photography with cross polarizers may
method provides for the identification, quantitative estimation,
be used. The microscope shall have a circular stage that is
and size determination of mesophase spheroids.
capable of rotating a specimen through 360°. The stage shall
5.2 The mesophase initially forms as spheroids that may also be of such type that the specimen can be quickly advanced
by definite fixed increments in two perpendicular directions,
coalesce to form a variety of asymmetrical shapes. The
smallest mesophase particle that can be detected with certainty such as a stage with click stops. If an electrically operated stage
is used, incremental steps in one direction across the specimen
at 400× or 500× magnification is 4 µm in diameter; mesophase
particles sizes less than 4 µm should be ignored. If mesophase m
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D4616 − 95 (Reapproved 2013) D4616 − 95 (Reapproved 2018)
Standard Test Method for
Microscopical Analysis by Reflected Light and
Determination of Mesophase in a Pitch
This standard is issued under the fixed designation D4616; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method covers laboratory procedures for the preparation of granular and melted samples for microscopic analysis
using reflected light to identify and estimate the amount and size of the mesophase.
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered 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 appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D329 Specification for Acetone
D1160 Test Method for Distillation of Petroleum Products at Reduced Pressure
D2318 Test Method for Quinoline-Insoluble (QI) Content of Tar and Pitch
D3104 Test Method for Softening Point of Pitches (Mettler Softening Point Method)
D4296 Practice for Sampling Pitch
E11 Specification for Woven Wire Test Sieve Cloth and Test Sieves
E562 Test Method for Determining Volume Fraction by Systematic Manual Point Count
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 cenospheres—usually a minor component of coal tar pitch. They are formed by the rapid pyrolysis of unconfined coal
particles that are carried over from the coke oven to the tar. Microscopically, they appear like hollow spheres or segments thereof
(see Fig. 1), and are typically sized from about 1010 μm to 500 μm. 500 μm. In polarized light (crossed polarizers), a cenosphere
may be optically active. The size of the anisotropic pattern or mosaic depends upon the rank of the coal carbonized. Cenospheres
are harder than the continuous phase and polish in relief (see Fig. 1).
3.1.2 coke-oven-coke—usually a minor component of coal tar pitch. It originates in carry-over from the coke oven to the tar side.
It differs from cenospheres only in terms of its shape and porosity. Coke-oven-coke is angular and less porous.
3.1.3 isotropic phase—usually the predominant, and continuous, phase. It is a complex mixture of organic aromatic compounds
composed mainly of carbon and hydrogen. At room temperature, the isotropic phase is a glass-like solid. It is optically inactive
in polarized light (see Fig. 1 and Fig. 2).
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.05 on Properties of Fuels, Petroleum Coke and Carbon Material.
Current edition approved May 1, 2013Dec. 1, 2018. Published August 2013December 2018. Originally approved in 1986. Last previous edition approved in 20082013
as D4616 – 95 (2008).(2013). DOI: 10.1520/D4616-95R13.10.1520/D4616-95R18.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4616 − 95 (2018)
FIG. 1 Photomicrographs of a Coal Tar Pitch at 500× Magnification in Polarized Light (Crossed Polarizers) and Bright Light Showing
the 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 Insolubles and Mesophase Spheroids
3.1.4 mesophase—an optically anisotropic liquid crystal carbonaceous phase that forms from the parent liquor when molecular
size, shape, and distribution are favorable. In the early stages of its development, mesophase usually appears as spheroids. The
D4616 − 95 (2018)
planar molecules are lined up equatorially as shown schematically in Fig. 3. This equatorial arrangement may be distinguished in
crossed polarized light. Under crossed polarizers, the distinctive mesophase spheroids, with their complex extinction patterns
shown in Fig. 2, can be readily seen.
3.1.4.1 spheroids—At magnifications of 400× and 500×, the minimum spheroid size which can be resolved with confidence is
4 μm 4 μm in diameter. At magnifications of 10001000× to 1800×, the minimum spheroid size that can be resolved with confidence
is about 2 μm in diameter. Typically, the upper size may be 100 μm. 100 μm. Mesophase spheroids are relatively soft and do not
form relief structures (see Fig. 4). Quinoline insoluble particles often aggregate at the interface between the continuous isotropic
phase and mesophase.
3.1.4.2 isotropic phase—The isotropic phase is more soluble than the mesophase in solvents such as toluene. Solvent etching
is achieved by soaking the polished surface in toluene for a few seconds, rinsing the surface with cold flowing water, and drying
in a current of hot air. Etching produces sharply defined mesophase spheroids (see Fig. 4).
3.1.5 mineral matter—formed when minute particles of the coke oven charge are carried over into the coke oven collecting main
during the charging operation. The tiny coal particles are digested in the collecting main tar, resulting in a residue that is rich in
mineral matter. This mineral matter is identified under bright field illumination by its high reflectivity, in the case of pyrite, and
its low reflectance in the case of clay, quartz, and carbonates. The association of mineral matter with insoluble organic matter from
coal aids in its identification.
3.1.6 normal quinoline insolubles—(sometimes termed “true,” natural or “primary” quinoline insolubles)—a carbon black-like
solid phase in coal tar pitch that is produced by thermal cracking of organic compounds in the tunnel head above the coal charge
in a by-product coke oven. The individual spherically-shaped particles are usually less than 2 μm 2 μm in diameter. A typical coal
tar pitch may contain from about 1 % to about 20 % (by weight) of normal quinoline insolubles. The normal quinoline insolubles
are relatively hard. They are outlined in bright incident light because they stand out in relief from the softer isotropic phase (see
Fig. 1).
3.1.6.1 Discussion—
FIG. 3 Structure of Mesophase Spheroid
A more complete discussion will be found in a paper by Honda, H., Kimura, H., and Sanada, Y., “Changes of Pleochroism and Extinction Contours in Carbonaceous
Mesophase,” Carbon, 9, 1971, pp. 695–697.
D4616 − 95 (2018)
FIG. 4 Photomicrographs of a Heat Treated Coal Tar Pitch at 500× Magnification in Bright Field Showing the Effectiveness of Etching
With Toluene to Accentuate the Interface Between Mesophase Spheroids and the Isotropic Phase
Sometimes the term primary QI is used to describe all quinoline insoluble materials that are carried over during the coking
operation (cenospheres, mineral matter, normal, QI, and so forth).
3.1.6.2 normal quinoline insoluble material—Observed under crossed polarizers, the normal quinoline insoluble material
displays a Brewster cross pattern (see Fig. 1 and Fig. 2). This interference figure remains stationary when the specimen is rotated
through 360°. The onionskin arrangement can be observed in particles with a minimum diameter of 2 μm 2 μm at high
magnification (1000(1000× to 2000×) under cross polarizers.
3.1.6.3 Discussion—
The quinoline insolubles content is determined by Test Method D2318 and represents the total amount of natural quinoline
insolubles, cenospheres, coke-oven-coke, pyrolytic carbon, refractory, reactor coke, and free ash in a pitch. Additionally, the
quinoline insolubles will contain any insoluble species from the isotropic phase and the insoluble portion of the mesophase. Hence,
the quinoline soluble fraction is composed of the bulk of the isotropic phase and the soluble fraction of the mesophase. However,
the quinoline insoluble test is not necessarily a true measure of the solid constituents of pitch.
Normal QI with radial symmetry is produced by oxycracking during the early portion of the coking cycle when partially
oxidizing conditions can exist, and is referred to as combustion black (see Fig. 5a). Normal QI with concentric symmetry is
produced by thermal cracking later in the coking cycle under reducing conditions, and is referred to as thermal black (see Fig.
4,5
5b). These two symmetries can only be differentiated using electron microscopy. The quinoline insolubles content determined
by Test Method D2318 is sometimes greater than that anticipated on the basis of the concentration of the quinoline insolubles
during distillation or heat treatment to produce the final pitch. The difference is known as the “secondary” quinoline insolubles
content, and is traditionally regarded as the mesophase content. This equivalence of secondary quinoline insolubles and
mesophase is erroneous because the mesophase may be partially soluble in quinoline.
3.1.7 pyrolytic carbon—a carbon that originates as a deposit on the upper walls, tunnel head, and standpipes of a coke oven due
to thermal cracking. It is usually a minor phase in coal tar pitch, highly variable in shape and porosity, and may be sized up to
500 μm. 500 μm. It is usually optically active under crossed polarizers. The fine sized domains are commonly referred to as
spherulitic, while the coarser anisotropic domains are called pyrolytic. Spherulitic and pyrolytic carbons are highly reflecting,
relatively hard materials and stand out in relief from the softer isotropic phase.
Bertau, B.L., and Souffrey, B., “Composition of Tar and Pitches as a Result of the Specific Aspects of the Coking Plant,” Coke Making International, Vol 2 , 1990, pp.
61–63.
Lafdi, K., Bonnamy, S., and Oberlin, A., “TEM Studies of Coal Tars—Crude Tar and its Insoluble Fractions,” Carbon, Vol 28, No. 1, 1990, pp. 57–63.
D4616 − 95 (2018)
FIG. 5 The Structure of a Normal Quinoline Insoluble Particles
3.1.8 reactor coke—a material that originates on the walls of the pipestill reactor used in the distillation or heat treatment to
produce pitch from either coal tars or petroleum oils. It is thermally more advanced than reactor mesophase. It is usually a minor
component of pitch and may be sized up to 200 μm. 200 μm. It may be angular or rounded, and it may be relatively porous with
a coarse appearance under crossed polarizers. It is distinguished from the reactor mesophase mentioned in 3.1.9 by its relative
hardness, which causes it to show up in relief in bright field illumination.
3.1.9 reactor mesophase—a material that originates on the walls of the pipestill or reactor used in the distillation or heat
treatment to produce pitch from either coal tars or petroleum oils. It is usually a minor component of pitch and may be sized up
to 200 μm. 200 μm. It may be angular or rounded, and it may be relatively porous. Under crossed polarizers reactor mesophase
has a coarse mosaic appearance. In contradistinction to the reactor coke mentioned in 3.1.8, reactor mesophase is comparatively
soft and shows no relief in bright field illumination.
3.1.10 refractory—usually a minor component that originates from the coke oven walls, doors, and patches due to wear and
degeneration; another component is charge hole sealant. It can be recognized under the microscope through optical properties,
hardness, shape, and associated minerals.
4. Summary of Test Method
4.1 A representative sample with a softening point of at least 212°F (100°C),212 °F (100 °C), as measured by Test Method
D3104 (Mettler method), is crushed to a specific particle size and encapsulated in resin. Alternatively, a representative molten pitch
sample is poured into a mold, or a representative crushed sample is melted and poured into a mold. If the Mettler softening point
is less than 212°F (100°C),212 °F (100 °C), it is raised to 212212 °F to 248°F (100248 °F (100 °C to 120°C) by vacuum
distillation. The encapsulated, or molded, sample is ground and polished to a flat surface for examination in reflected light.
4.2 The mesophase spheroid content of a representative sample is identified and the proportion determined on a volume basis
by observing a statistically adequate number of points. Only the area proportion is determined on a surface section of a sample;
however, the area and volume proportion are the same when the components are randomly distributed throughout the sample.
5. Significance and Use
5.1 Sometimes coal tar and petroleum pitches are heat treated thereby forming mesophase spheroids. The mesophase may be
partially soluble in quinoline and cannot be estimated by the quinoline insoluble test (Test Method D2318). This test method
provides for the identification, quantitative estimation, and size determination of mesophase spheroids.
5.2 The mesophase initially forms as spheroids that may coalesce to form a variety of asymmetrical shapes. The smallest
mesophase particle that can be detected with certainty at 400× or 500× magnification is 4 μm in diameter; mesophase particles sizes
less than 4 μm should be ignored. If mesophase material less than 4 μm in size is of interest, then magnifications of 10001000×
to 1800× shall be used and the results should be appropriately identified. This method is limited to determining minor levels of
mesophase, that is, ≤20 % mesophase.
6. Apparatus
6.1 Grinder, Pulverizer, or Mill, for crushing the re
...
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