1、Designation: D5671 95 (Reapproved 2011)Standard Practice forPolishing and Etching Coal Samples for MicroscopicalAnalysis by Reflected Light1This standard is issued under the fixed designation D5671; the number immediately following the designation indicates the year oforiginal adoption or, in the ca
2、se 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 practice covers laboratory procedures for preparingan etched, polished surface of gra
3、nular and block samples ofcoal for examination with a microscope using reflected lightillumination.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if a
4、ny, 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 regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D121 Terminology of Coal and CokeD2797 Practice f
5、or Preparing Coal Samples for Microscopi-cal Analysis by Reflected LightD2798 Test Method for Microscopical Determination of theVitrinite Reflectance of CoalD2799 Test Method for Microscopical Determination of theMaceral Composition of CoalD4596 Practice for Collection of Channel Samples of Coalin a
6、 MineD5192 Practice for Collection of Coal Samples from Core3. Terminology3.1 Terminology used in this standard can be found inTerminology D121.4. Summary of Practice4.1 A subsplit of a representative sample obtained in accor-dance with Practice D4596 and prepared in accordance withPractice D2797 or
7、 a block of coal obtained in accordance withPractice D5192 is polished to a flat, scratch-free surface, thereflectance of vitrinite is determined on a subsplit in accor-dance with Test Method D2798, and then other subsplits arechemically etched using an acidified potassium permanganatesolution.5. Si
8、gnificance and Use5.1 Components observable in surfaces of coal samplesprepared in accordance with the laboratory procedures of thispractice will have differential relief that will aid in theirmaceral identification by visual classification and enablesidentification of plant parts or tissues that fo
9、rmed the coal.5.2 Samples prepared by this practice can be used formicroscopical determination of the volume percent of physicalcomponents of coal in accordance with Test Method D2799.6. Apparatus6.1 Ultrasonic Cleanerlarge enough for sample holderand sample preparations to be immersed in cleaning s
10、olution.6.2 Beakersglass beakers, 50, 100, and 500 ml capacity,one each for each etching setup.6.3 Stirring Rodsglass, approximately 20 cm long.6.4 Hot Plateelectric or gas-heated with capability fortemperature control and rotating stirring magnets.6.5 Watch Glassesglass, 100200 mm in diameter de-pe
11、nding on size of specimen blocks to be etched.6.6 Graduated Cylindersglass, 25 and 100 ml.6.7 Grinding and Polishing Equipmentone or several lapson which the coal briquets or blocks can be ground andpolished to a flat, scratch-free surface. Laps may be made ofaluminum, iron, brass, or bronze.7. Reag
12、ents7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee on1This practice is under the jurisdiction of ASTM Committee D05 on Coal andCoke and is the direct responsibility of
13、 Subcommittee D05.28 on PetrographicAnalysis of Coal and Coke.Current edition approved April 1, 2011. Published June 2011. Originallyapproved in 1995. Last previous edition approved in 2005 as D5671 - 95(2005).DOI: 10.1520/D5671-95R11.2For referenced ASTM standards, visit the ASTM website, www.astm.
14、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 C700, West Conshohocken, PA 19428-2959, United States.Analytical
15、Reagents of the American Chemical Society wheresuch specifications are available.3Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the quality of theetch.7.2 Potassium Permanganate (KMnO4), crystals.7.3 Sodiu
16、m Sulfite (Na2SO3), anhydrous, granular.7.4 Sulfuric Acid (H2SO4), 47 % H2SO4.7.5 Sodium Hydroxide solution, dissolve 10 g NaOH crys-tals in 90 g deionized water at room temperature.8. Materials8.1 Grinding AbrasivesWater-resistant, adhesive-backedsilicon carbide papers of 45, 32, and 15 m (240, 400
17、, and 600grit). Two or more of these can be used according to a plansuch as one of those listed in Table 1.8.2 Polishing AbrasivesLevigated aluminum oxide pow-ders of 1.0 m size (aqueous suspension) and colloidal silica of0.06 m size (in a prepared NaOH suspension).8.3 Lap CoveringsChemotextile mate
18、rial backed withwater-resistant adhesive or similar quality lap coverings. Rec-ommendations of the manufacturer of the polishing abrasiveused should be followed for choice of lap covering.8.4 Diamond Impregnated Lap WheelImpregnated withdiamonds of 6 m size.8.5 Detergent or Sonic Cleaning SolutionAn
19、y nonoxidiz-ing detergent may be used for cleaning sample surfaces aftereach grinding and polishing stage.8.6 BinderA potting epoxy resin and hardener or pottingpolyester resin and hardener that has a curing temperature lessthan 100C.8.7 Sample MoldsPrepared for block samples and is madefrom potting
20、-type silicone rubber.8.8 Release AgentSpray silicon or any other preparationthat does not damage the molds or adversely affect the coal ormounting medium may be used to coat the inside of thebriquette mold and facilitate ejection of the briquet.NOTE 1Molds prepared from silicone rubber as described
21、 in Appen-dix X1 do not require release agent.9. Sample Preparation9.1 Coal Briquets:9.1.1 Prepare granular samples as briquets in accordancewith Practice D2797.9.2 Coal Blocks:9.2.1 Obtain specimens from core or as blocks of coal froma mining face.9.2.2 Trim specimens to about 0.5 mm smaller than t
22、hevolume of the silicone rubber molds.9.2.3 Air dry the specimens to remove visible surfacemoisture.NOTE 2Overdrying specimens of low rank coals at any point inpreparation can cause slaking or severe desiccation of specimen. Incontrast, underdrying of specimens will prevent epoxy from settingproperl
23、y.9.2.4 Mix resin and hardener according to manufacturersinstructions.9.2.5 Place specimens and labels into silicone rubber moldsand pour resin mixture over the specimens and labels up to thelevel of the top of the molds. Allow to cure, then remove thespecimens from the molds.10. Preparation of Samp
24、le Surface10.1 Grind and polish on the base surfaces of the briquet orblock on a lap in a wet slurry to obtain a surface suitable formicroscopical examination. Grinding and polishing should bedone with automated equipment. Use a series of abrasives ofdecreasing particle size according to a plan such
25、 as one of thosedescribed in Table 1.11. Determination of Etching Time11.1 In this procedure, the etching time is determined fromthe relationship between optimum etching time and measuredreflectance of unetched polished vitrinite (Fig. 1).11.1.1 Measure reflectance of vitrinite on a subsplit inaccor
26、dance with Test Method D2798.11.1.2 Using the relationship shown in Fig. 1, determine theetching time required for obtaining an optimum etch of thepolished sample surface.3Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For suggestions on the t
27、esting of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,MD.TABLE 1 Suggested Plans for Grinding and Pol
28、ishing ofBriquets and BlocksPlanNo.Grinding with Silicon Carbide Paper PolishingStage 1 Stage 2 Stage 3 Stage 1 Stage 21 45 m(240 grit)22 m(400 grit)15 m(600 grit)1 m Alumina 0.06 mColloidalSilica222m(400 grit)15 m(600 grit). 1 m Alumina 0.06 mColloidal SilicaFIG. 1 Determination of Etching Time for
29、 Coal on the Basis ofMeasured Vitrinite ReflectanceD5671 95 (2011)212. Etching Procedure412.1 Preparation of etching solution: To 100 ml deionizedwater, add and mix 25 g KMnO4,and5mlH2SO4(concentrated). Caution: always add acid to water.12.2 Preparation of rinsing solution: To 100 ml deionizedwater,
30、 add 25 g Na2SO3and5mlH2SO4. Stir solution until allNa2SO3has dissolved.12.3 Heat the etching solution in a water bath until most ofthe KMnO4has dissolved.12.4 Pour part of the heated solution into a watch glass andsubmerse the polished coal surface in the etching solution forthe time as determined
31、from Fig. 1 and in accordance with11.1.12.5 Remove the coal surface from the solution and imme-diately rinse with flowing deionized water for 23 s to removeetching solution.12.6 Submerse the coal surface into the rinsing solution forone min or until all purplish stain has been removed.12.7 Clean the
32、 coal surface ultrasonically in deionized waterfor one minute.12.8 Dry the surface with a stream of compressed airimmediately after removing from ultrasonic bath.NOTE 3For some samples, a small area of the polished surface can bemasked using cellophane tape smoothed so as to prevent any etchingeffec
33、ts.3After etching, this tape is removed which produces a line thatdemarcates the etched and unetched areas.NOTE 4For block samples of low rank coal, primarily less than 0.5 %reflectance, blocks can be stored in a shallow bath of deionized water toprevent slaking or severe drying. Prior to examinatio
34、n, the sample surfacecan be dried with a stream of compressed air. Some low rank coals mayalso require using a diluted etching solution for the time shown in Fig. 1.13. Keywords13.1 coal microscopical analysis; etching; polishingAPPENDIX(Nonmandatory Information)X1. PREPARATION OF SILICONE RUBBER MO
35、LDS FOR COAL BLOCKS5X1.1 Construct a wooden block that will fit the blockholder of the grinding and polishing equipment. This woodenblock will be the size of the samples that will be prepared. Sandall sides of the wooden block to remove severe scratches(generally to a sanding fineness of about 90 m
36、(120 grit).X1.2 Construct a mold holder using a smooth surfacedcardboard box that is at least 1 cm larger in all dimensions thanthe wooden block.X1.3 Mix part of the silicone rubber according to manu-facturers directions and pour a layer of rubber that is about 1cm thick into the bottom of the mold
37、holder. Allow rubber tocure.X1.4 Place the wooden block centered, on top of the layerof cured rubber, pour mixed silicone rubber around the outsideof the mold up to level with the surface of thewooden block(Fig. X1.1). Allow rubber to cure.X1.5 Eject the wooden block from the mold. Mold is readyto u
38、se for coal block sample preparation.4Modified from procedure outlined in Stach, Ernst, 1935, Lehrbuch derKohlenpetrographie: Berlin, Borntraeger, 293 p.; Teichmller, M. L., 1941, The finestructures of American coals in polished samples and thin sections: Reichsamt frdas Jahr 1940, Band 61, p. 2055.
39、5Adapted from Moore, T.A., 1991, “Using Silicone Rubber Molds,” The Societyof Organic Petrology Newsletter , vol 8, no. 2, p. 45.FIG. X1.1 Cross Section View of Materials Used to Prepare aSilicone Rubber Mold for Coal BlocksD5671 95 (2011)3ASTM International takes no position respecting the validity
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