1、Designation: D 3849 07Standard Test Method forCarbon BlackMorphological Characterization of CarbonBlack Using Electron Microscopy1This standard is issued under the fixed designation D 3849; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev
2、ision, 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 the morphological characteriza-tion of carbon black primary aggregates fro
3、m transmissionelectron microscope images. These measurements are used toderive the mean particle and aggregate size of carbon black inthe dry (as manufactured) state, from CAB chip dispersion orremoved from a rubber compound.1.2 The values stated in SI units are to be regarded as thestandard. The va
4、lues in parentheses are for information only.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 regula
5、tory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 6556 Test Method for Carbon BlackTotal and ExternalSurface Area by Nitrogen Adsorption3. Terminology3.1 Definitions:3.1.1 General:3.1.1.1 carbon black aggregatea discrete, rigid colloidalentity that is the smallest dispersibl
6、e unit; it is composed ofextensively coalesced particles. Carbon black aggregate size isa distributional property; therefore, the term aggregate sizeimplies the mean value from multiple measurements.3.1.1.2 carbon black particlea small spheroidally shaped,paracrystalline, non-discrete component of a
7、n aggregate; it canonly be separated from the aggregate by fracturing. Carbonblack particle size is a distributional property; therefore, theterm particle size implies the mean value from multiplemeasurements.3.1.1.3 glow dischargea plasma of ionized gas that isformed in a high-voltage field at pres
8、sures of about 3 to 20 Pa(25 to 150 3 10-3torr). An alternating current (a-c) glowdischarge using air is effective in cleaning and oxidizing thesurface of carbon substrates to improve the wetting character-istics of polar vehicles containing pigment dispersions.3.1.1.4 substratea thin film that is u
9、sed to support elec-tron microscope specimens. Evaporated carbon films are com-monly used because of relatively good mechanical strength,stability, and conductivity.3.1.2 Aggregate Dimensional Properties from Image Analy-sis:3.1.2.1 area (A)the two-dimensional projected area of thecarbon black aggre
10、gate image.3.1.2.2 perimeter (P)the total boundary length of anaggregate.3.1.2.3 volume (V)an estimate of the volume of thecarbon black aggregate using stereological principles.3.1.3 Image Analysis:3.1.3.1 dilationthe converse of erosion. This process isaccomplished by changing any OFF pixel to ON i
11、f it hasgreater than a preset minimum of ON neighbors. This processcauses image features to grow in size, which fills in smallbreaks in features, internal voids, or small indentations alongthe feature surface.3.1.3.2 erosionthe process by which image features arereduced in size by selectively removi
12、ng pixels from theirperiphery. It consists of examining each binary pixel andchanging it from ON to OFF if it has greater than a presetminimum of neighbors that are OFF. It serves a number ofuseful functions, such as smoothing feature outlines andseparating features touching each other.1This test me
13、thod is under the jurisdiction of ASTM Committee D24 on CarbonBlack and is the direct responsibility of Subcommittee D24.81 on Carbon BlackMicroscopy and Morphology.Current edition approved July 1, 2007. Published August 2007. Originallyapproved in 1980. Last previous edition approved in 2004 as D 3
14、849 04.2For 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.1Copyright ASTM International, 100 Barr Harbor Drive,
15、PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.3.3 featureareas within a single continuous boundarythat have gray-level ranges that allow them to be distinguishedfrom the background area outside the feature via thresholding.3.1.3.4 thresholdingselecting a range of brightness suchth
16、at discrimination is possible between the feature and thebackground. The gray levels within carbon black imagesbecome lower with decreasing particle size.4. Significance and Use4.1 Carbon black morphology significantly affects the tran-sient and end-use properties of carbon black loaded polymersyste
17、ms. A carbon blacks particle size distribution is its singlemost important property, and it relates to degree of blacknessand rubber reinforcement. For a given loading of carbon black,blackness and reinforcement increase with smaller particlesize. Aggregate size and shape (structure) also affect a c
18、arbonblacks end-use performance, as higher carbon black structureincreases viscosity and improves dispersion. The stiffness(modulus) of elastomer systems becomes significantly higherwith increasing structure. The preferred method for measuringthese properties is transmission electron microscopy.4.2
19、Carbon black aggregate dimensional and shape proper-ties are dependent upon the nature of the system in which thesample is dispersed, as well as the mixing procedure.5. Apparatus5.1 Electron Microscope, transmission-type, with a point-to-point resolution of 1.0 nm or better. Operating voltagesshould
20、 be high enough to provide the desired resolution andlow enough to produce images of sufficient contrast. Recom-mended voltages can be in the 60 to 120 kV range. Themicroscope column should contain a liquid nitrogen-cooledanti-contamination device or a “cold finger” to reduce samplecontamination and
21、 to maintain column cleanliness. For imageacquisition, the microscope should include a charge-coupleddevice (CCD) camera mounted either above or below theinstruments viewing chamber.5.2 Image Analysis System, consisting at minimum of aTEM-interfaced camera capable of 640 3 480 pixel or betterresolut
22、ion, a computer equipped with frame grabbing hardwareto capture TEM images digitally, and software to performmorphological operations and measurements on image featuresand store resulting data. Operations must include background/noise elimination, thresholding, and edge smoothing. Area andperimeter
23、are then measured on features in the processedimages.5.3 Two-Roll Mill.5.4 Vacuum Evaporator, standard-type, for preparing car-bon films to be used as substrates for electron microscopy. Theevaporator should be capable of reducing the absolute pressureto 1.3 mPa (1 3 10-5torr) and should also contai
24、n thenecessary apparatus for a-c glow discharge.5.5 Ultrasonic Generator, variable power tank-type orprobe that provides sufficient energy to give acceptable disper-sion.5.6 Dry Box, capable of maintaining a relative humiditylevel of no greater than 30 %.5.7 Analytical Balance, with an accuracy of a
25、bout 0.5 mg.5.8 Electrically Heated Tube Furnace, capable of beingheated to 800 to 900C under an inert environment, with theability to introduce and remove the sample boat to the heatedzone without allowing oxygen intrusion.5.9 Pyroprobe, capable of being heated from 150 to 1000Cin an inert environm
26、ent.5.10 Carbon Rods, approximately 3.1 mm in diameter.5.11 Carbon Rod Sharpener.5.12 Glass Microscope Slides, 25 by 75-mm.5.13 Test Tubes, 75 by 10-mm, 4-cm3capacity, 0.5-mm wallthickness, with corks.5.14 Transfer Pipets, disposable Pasteur-type, 225 mm long,1-mm inside diameter at tip.5.15 Rubber
27、Bulbs, for pipets.5.16 Glass Vials, 40-cm3capacity, with solvent-resistanttops.5.17 Bchner Funnel, No. 3, 111-mm inside diameter.5.18 Filter Paper, general purpose.5.19 Carbon Coated Electron Microscope Specimen Grids,3-mm diameter, 200 to 300 mesh. Commercially available orcan be prepared as descri
28、bed in Annex A1.5.20 Wire Screening, with openings approximately 1 mm2.5.21 Tweezers, fine-tipped.5.22 Spatulas, micro-type with V-shaped spoon that isapproximately 2 mm wide at top and 12.5 mm long.5.23 Fluorocarbon Duster.5.24 Lens Tissue, lint-free.5.25 Porcelain Boats, for pyrolysis, 98 mm long,
29、 15 mmwide at top.5.26 Centrifuge, high speed (15 000 to 20 000 r/min) withhead for 75 by 10 mm test tubes.5.27 Beakers, 2000-cm3capacity.6. Reagents and Materials6.1 Chloroform, reagent grade.6.2 Tetrahydrofuran (THF), reagent grade.6.3 1,2-Dichloroethane, reagent grade.6.4 Ethyl Acetate, reagent g
30、rade.6.5 Poly (Vinyl Formal) Resin, Grade 15/95.6.6 Cellulose Acetate Butyrate Resin (CAB).6.7 Phthalate-Type Plasticizer (such as santicizer).7. Sample PreparationDispersion Procedures7.1 Dry Carbon Black (Sonic Bath):7.1.1 Weigh 8 to 10 mg of carbon black into a test tubecontaining 1 cm3of solvent
31、 (typically chloroform or THF).NOTE 1With experience, it may not be necessary to weigh eachcarbon black sample, as an estimated amount from the microspatula maybe sufficient. There is considerable latitude in the amount of carbon blackused. The finer N100 and N200 blacks may require somewhat less ca
32、rbonblack than the coarser semi-reinforcing types.7.1.2 Adjust the power of the ultrasonic bath for maximumagitation; this may require that the water level be adjusted. Asthe ultrasonic energy heats the water in the bath, ice should beadded to control the temperature in order to maintain maximumdisp
33、ersive capability.7.1.3 Place the stoppered test tube containing the carbonblack and solvent mixture into the most intense part of theD3849072ultrasonic field and allow the mixture to agitate for 3 to 5 min.The test tube should be held with tongs or mounted in a simplewire holder.7.1.4 Transfer a sm
34、all portion of the concentrated carbonblack-solvent mixture into another test tube containing 1 cm3of fresh solvent. The amount of concentrate required increaseswith particle size. Blend the mixture by repeatedly transferringthe sample between the transfer pipet and the test tube, thencork the test
35、tube and repeat the ultrasonic dispersion proce-dure.7.1.5 Check the concentration of the diluted dispersion byextracting a small amount into the tip of the pipet and viewingagainst a white background. For tread grade carbon blacks, thedispersions should be relatively transparent, becoming some-what
36、 darker with increasing particle size. The diluted disper-sions for very coarse carbon blacks such as N700 to N900series will be on the threshold of complete opacity. If neces-sary, adjust the concentration by adding more concentrate orsolvent as required, then repeat the ultrasonic agitation. Thevo
37、lume of the carbon black-solvent mixture should be main-tained at approximately 1 cm3. If considerable dilution isrequired, the excess volume above 1 cm3should be discarded.NOTE 2Areasonable degree of latitude exists for achieving the properconcentration levels in the final dispersions for different
38、 grades of carbonblack. Concentration and overall dispersion quality are best determined byscreening the actual specimens in the electron microscope and thenmaking the necessary adjustments.7.1.6 Place a specimen grid with carbon substrate (film sideup) on a piece of filter paper. Remove a small amo
39、unt of thefinal diluted dispersion using a fresh pipet and place one dropon the grid as close to the center as possible, from a height ofabout 12 mm. Allow the specimen to dry for about 1 min on apiece of filter paper. This specimen preparation procedureshould be performed in a dry box if the relati
40、ve humidity in theroom exceeds 30 %.7.1.7 For TEM grids that contain formvar or residual CAB(CAB chip dispersions), place the TEM grid in an appropriatesample holder, place in the pyrolysis chamber and allowadequate time for the chamber to be purged by an inert gas toprevent oxidation of the sample.
41、 Pyrolize the specimen grid ata sufficient temperature (typically greater than 550C) toremove the poly (vinyl formal) film or CAB, or both.7.1.8 Acceptable dispersions of a carbon black in the drystate and removed from a rubber compound (SBR) are illus-trated for N-220 and N-774 carbon blacks in Fig
42、s. 1 and 2.7.2 Dry Carbon Black (Ultrasonic Probe):7.2.1 Weigh 5 to 10 mg of carbon black into a 30-cm3glassvial and add approximately 20 cm3of solvent (typicallychloroform).NOTE 3With experience, it may not be necessary to weigh eachcarbon black sample, as an estimated amount from the microspatula
43、maybe sufficient. There is considerable latitude in the amount of carbon blackused. The finer N100 and N200 blacks may require somewhat less carbonblack than the coarser semi-reinforcing types.7.2.2 Place the vial containing the carbon black and solventinto an ice-water bath.7.2.3 Insert the probe t
44、o a depth of approximately 2.5 cminto the vial and ultrasonicate at 40 to 50 watts for 10 min.NOTE 4The ultrasonic probe and ice-water bath containing theFIG. 1 Ultrasonic Dispersions of N-220 Carbon BlackD3849073sample vial should be housed in an acoustic enclosure to reduce cavitationnoise.7.2.4 T
45、ransfer a small portion (approximately 2 to 4 cm3)ofthe concentrated carbon black/solvent mixture into another vialand add 20 cm3of fresh solvent. An additional three-minutesonication is recommended.7.2.5 Check the concentration of the diluted dispersion byextracting a small amount into a pipet and
46、then placing 1 dropon a white filter paper. For tread grade carbon blacks, thedispersions should be relatively transparent, becoming some-what darker with increasing particle size. The dispersion forvery coarse carbon blacks, such as N700 to N900 series, will beon the threshold of complete opacity.7
47、.2.6 If necessary, adjust the concentration by adding moreconcentrate or solvent as required, then repeat the ultrasonicagitation. The volume of the carbon black-solvent mixtureshould be maintained at approximately 20 cm3. Repeat 7.2.5.NOTE 5Areasonable degree of latitude exists for achieving the pr
48、operconcentration levels in the final dispersions for different grades of carbonblack. Concentration and overall dispersion quality are best determined byscreening the actual specimens in the electron microscope and thenmaking the necessary adjustments.7.2.7 When the final dispersion drop on the fil
49、ter paper is inan acceptable color range, place a specimen grid with a thincarbon substrate (film side up) on a piece of filter paper. Usinga fresh pipet, remove a small amount of the final dispersion andplace one drop on the grid as close to the center as possible,from a height of about 12 mm. Allow the specimen grid to dryfor approximately 1 min on the filter paper. (If the relativehumidity is greater than 35 %, purge ultra-high purity nitrogenover the specimen grid retaining the sample.)7.2.8 Place the grid into the microscope and examine thedispersion fo
