1、Designation: D3849 07 (Reapproved 2011)Standard Test Method forCarbon BlackMorphological Characterization of CarbonBlack Using Electron Microscopy1This standard is issued under the fixed designation D3849; the number immediately following the designation indicates the year oforiginal adoption or, in
2、 the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the morphological characteriza-tion of carbon black primary
3、 aggregates from 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 thes
4、tandard. The values 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-b
5、ility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D6556 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 small
6、est dispersible 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
7、component of an 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
8、 field at pressures 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
9、film that is used 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 thecarb
10、on black aggregate 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
11、 pixel to ON if 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 sele
12、ctively removing 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
13、.1This test method 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 Nov. 1, 2011. Published January 2012. Originallyapproved in 1980. Last previous edition approved
14、 in 2007 as D3849 07. DOI:10.1520/D3849-07R11.2For 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
15、 International, 100 Barr Harbor Drive, 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 thresholdin
16、gselecting a range of brightness suchthat 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 propert
17、ies of carbon black loaded polymersystems. 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 siz
18、e and shape (structure) also affect a carbonblacks 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 i
19、s transmission electron microscopy.4.2 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
20、 nm or better. Operating voltagesshould 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 fi
21、nger” to reduce samplecontamination and 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 capa
22、ble of 640 3 480 pixel or betterresolution, 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,
23、 and edge smoothing. Area andperimeter 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 mP
24、a (1 3 10-5torr) and should also contain 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 An
25、alytical Balance, with an accuracy of about 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 heate
26、d from 150 to 1000Cin an inert environment.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
27、-mm inside diameter at tip.5.15 Rubber 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. Commerciall
28、y available orcan be prepared as described 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 Porc
29、elain Boats, for pyrolysis, 98 mm long, 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, rea
30、gent grade.6.4 Ethyl Acetate, reagent grade.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 int
31、o a test tubecontaining 1 cm3of solvent (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 N
32、200 blacks may require somewhat less carbonblack 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 tempe
33、rature in order to maintain maximumdispersive capability.7.1.3 Place the stoppered test tube containing the carbonblack and solvent mixture into the most intense part of theD3849 07 (2011)2ultrasonic field and allow the mixture to agitate for 3 to 5 min.The test tube should be held with tongs or mou
34、nted in a simplewire holder.7.1.4 Transfer a small 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 trans
35、fer pipet and the test tube, thencork the test 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 shoul
36、d be relatively transparent, becoming some-what 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 requir
37、ed, then repeat the ultrasonic agitation. Thevolume 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 properconcentratio
38、n 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.7.1.6 Place a specimen grid with carbon substrate (film sideup)
39、 on a piece of filter paper. Remove a small amount 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 procedur
40、eshould be performed in a dry box if the relative 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
41、an inert gas toprevent oxidation of the sample. 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-
42、trated for N-220 and N-774 carbon blacks in Figs. 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
43、, 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 carbonblack than the coarser semi-reinforcing types.7.2.2 Place the vial containing the carbon black and solvent
44、into an ice-water bath.7.2.3 Insert the probe to 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 BlackD3849 07 (2011)3sample vial should be housed in
45、an acoustic enclosure to reduce cavitationnoise.7.2.4 Transfer 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 d
46、ispersion byextracting a small amount into a pipet and 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 N90
47、0 series, will beon the threshold of complete opacity.7.2.6 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 5Are
48、asonable degree of latitude exists for achieving the properconcentration 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 adju
49、stments.7.2.7 When the final dispersion drop on the filter 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
