1、Designation: C791 12Standard Test Methods forChemical, Mass Spectrometric, and SpectrochemicalAnalysis of Nuclear-Grade Boron Carbide1This standard is issued under the fixed designation C791; the number immediately following the designation indicates the year oforiginal adoption or, in the case of r
2、evision, 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 These test methods cover procedures for the chemical,mass spectrometric, and spectrochemical anal
3、ysis of nuclear-grade boron carbide powder and pellets to determine compli-ance with specifications.1.2 The analytical procedures appear in the following order:SectionsTotal Carbon by Combustion in an Inductive Furnace andInfrared Measurement7-16Total Boron by Titrimetry and ICP OES 17-27Isotopic Co
4、mposition by Mass Spectrometry 28-32Pyrohydrolysis 33-40Chloride by Constant-Current Coulometry 41-49Chloride and Fluoride by Ion-Selective Electrode 50-58Water by Constant-Voltage Coulometry and Weight Loss onDrying59-62Metallic Impurities 63 and 64Soluble Boron by Titrimetry and ICP OES 65-79Free
5、Carbon by a Coulometric Method 80-892. Referenced Documents2.1 ASTM Standards:2C750 Specification for Nuclear-Grade Boron Carbide Pow-derC751 Specification for Nuclear-Grade Boron Carbide Pel-letsD1193 Specification for Reagent Water3. Significance and Use3.1 Boron carbide is used as a control mater
6、ial in nuclearreactors. In order to be suitable for this purpose, the materialmust meet certain criteria for assay, isotopic composition, andimpurity content. These methods are designed to show whetheror not a given material meets the specifications for these itemsas described in Specifications C750
7、 and C751.3.1.1 An assay is performed to determine whether thematerial has the specified boron content.3.1.2 Determination of the isotopic content of the boron ismade to establish whether the content is in compliance with thepurchasers specifications.3.1.3 Impurity content is determined to ensure th
8、at themaximum concentration limit of certain impurity elements isnot exceeded.4. Reagents4.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents o
9、f the American Chemical Society,where such specifications are available.3Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.4.2 Purity of WaterUnless otherwise indicated, refere
10、ncesto water shall be understood to mean reagent water conformingto Specification D1193.5. Safety Precautions5.1 Many laboratories have established safety regulationsgoverning the use of hazardous chemicals and equipment. Theusers of these methods should be familiar with such safetypractices.6. Samp
11、ling6.1 Criteria for sampling this material are given in Specifi-cations C750 and C751.1These test methods are under the jurisdiction of ASTM Committee C26 onNuclear Fuel Cycle and are the direct responsibility of Subcommittee C26.03 onNeutron Absorber Materials Specifications.Current edition approv
12、ed June 1, 2012. Published July 2012. Originally approvedin 1975. Last previous edition approved in 2011 as C791 11. DOI: 10.1520/C0791-12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume
13、 information, refer to the standards Document Summary page onthe ASTM website.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for Labora
14、toryChemicals, BDH Ltd., Poole, Dorset, U.K. and the United States Pharmacopeia andNational Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.TOTAL CARBON BY COMBUSTI
15、ON IN ANINDUCTIVE FURNACE AND INFRAREDMEASUREMENT7. Scope7.1 This method covers the determination of total carbon innuclear-grade boron carbide in either powder or pellet form.8. Summary of Test Method8.1 The sample and added combustion accelerators (mostlytungsten-and iron-granules) are heated in a
16、n inductive furnaceunder oxygen atmosphere. The high-frequency field of thefurnace couples with electrically conductive components ofsample and combustion accelerators. The sample is heated totemperatures not lower than 1400C and the total carboncontent of the sample is released as carbon dioxide an
17、d,partially, as carbon monoxide. The reaction gas is passedthrough a gas-treatment train to ensure that any carbonmonoxide formed is converted to carbon dioxide and to removedust and moisture. The reaction gas is then transferred to theinfrared absorption cell of the analyzer. The molecular absorp-t
18、ion of carbon dioxide is measured by using a narrow-bandoptical filter which is translucent for the wavelength of thecharacteristic infrared absorption of carbon dioxide. The massfraction of carbon dioxide in the reaction gas is proportional topeak-area of the transient absorption signal. The mass f
19、ractionof carbon in the sample is calculated by using a calibrationfunction established by suitable calibration standards measuredunder comparable conditions.9. Interferences9.1 At the specification limits usually established fornuclear-grade boron carbide, interferences are insignificant.10. Appara
20、tus10.1 Commonly used laboratory equipment and specialequipment according to the following:10.1.1 Carbon analyzer, with induction furnace and infraredabsorption cell, suitable to correctly determine the massfraction of carbon within the concentration range given byboron carbide.NOTE 1The correctness
21、 of the analysis result can be proved by usingmatrix analogous reference materials or by comparing with an indepen-dent alternative test method.10.1.2 Analytical balance, capable of reading to the nearest0.01 mg.10.1.3 Ceramic crucible, for example, mullite or alumina.10.1.4 Crucible lid with hole,
22、for example, mullite oralumina.11. Reagents11.1 Reagents of known analytical grade shall be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.11.1.1 Tungsten granulesNOTE 2Depending on the particl
23、e size of the material the decompo-sition of the sample in the furnace may be improved by partially replacingtungsten granules by tin granules. Tungsten/tin-mixtures are commerciallyavailable.11.1.2 Iron granules11.1.3 Calibration samples, with defined carbon content,preferably certified reference m
24、aterials with composition andcarbon content similar to the analyzed material. Also suitableare primary substances preferably carbonates.11.1.4 Oxygen, purity $ 99.998 % v/v.11.1.5 Pneumatic gas, for example, nitrogen, purity$99.9 % v/v.12. Sampling and Sample Preparation12.1 Sampling has to be perfo
25、rmed in a way that the sampleto be analyzed is representative for the total amount ofmaterial. In an unknown drying state the sample has to be driedat (110 6 5)C to constant weight. The sample is cooled downto ambient temperature in a desiccator and stored therein.NOTE 3Drying for2hisnormally suffic
26、ient.12.2 The sample material must have a particle size of#150m (No. 100 sieve). Inhomogeneous sample material has to behomogenized. Standard apparatus and procedures for crushing,milling and homogenization may be used provided that nocontamination occurs which lessens the accuracy of the deter-mina
27、tion.13. Calibration13.1 The calibration has to be performed daily according tothe manufacturers instructions. It has to be ensured that themass of carbon in the calibration sample and test sample arewithin the same order of magnitude.NOTE 4This is achieved by choosing a suitable calibration substan
28、ceand adapted weights.13.2 The calibration has to be done according to Section 14.14. Procedure14.1 Preparation of AnalysisCeramic crucibles (10.1.3)and crucible lids (10.1.4) have to be cleaned prior to use byfiring in a muffle furnace at 1200C for 1 h. After that, theyhave to be stored in a desicc
29、ator.14.2 Determination of Blank Value (Method Blank)Thesame procedure according to 14.4 has to be applied, howeverwithout addition of boron carbide. At least three blanks shouldbe determined at least once in each 8-h shift in which totalcarbon analyses are made.14.3 Conditioning of Carbon AnalyzerP
30、rior to making theinitial analysis, condition the carbon analyzer by performing atleast two analysis runs. The same procedure according tosection 14.4 has to be applied, however only adding a smallamount of boron carbide (that is, a spatula-tip of boroncarbide).14.4 Determination of Carbon ContentA
31、sub-sample of20 to 30 mg of boron carbide powder prepared in accordanceto Section 6 is weighed to the nearest 0.01mg into the ceramiccrucibles (10.1.3) cleaned according to section 14.1.NOTE 5Using modern carbon analysis devices with an automatedcalculation of the mass fraction of carbon in the sub
32、sample the samplemass has to be entered using the internal or external keyboard. UsingC791 122carbon analysis devices which measure the absolute mass of carbon of thesample the sample mass has to be noted for later calculations.The sample in the crucible is covered with approximately 0.9g and 1.8 g
33、of iron and tungsten granules (11.1.1 and 11.1.2),respectively. For mixing, the crucible has to be shaken care-fully. Afterwards, the crucible is closed with the lid (10.1.4),placed into the induction furnace and the combustion cycle isstarted. Using modern carbon analysis devices the carboncontent
34、is calculated and displayed on the internal or externalscreen or printed out.NOTE 6For the measurement of carbon as main component (B4Capproximately 20 %) carbon analysis devices which collect the formedcarbon dioxide in a trap are recommended. By heating the trap thecollected carbon dioxide is rele
35、ased and passed to the infrared absorptioncell. This leads to a uniform and reproducible release of carbon dioxideand, thus, to an improved repeatability.Each sample has to be analyzed at least two times. If thesingle values of the double-test are deviating more than a givendegree, depending on the
36、repeatability of the method, then theanalysis has to be repeated according to Section 14.Ifnecessary, the sample has to be homogenized according toSection 12.15. Calculation15.1 The carbon content w (Ctotal) of the sample has to becalculated under consideration of sample mass and blankvalues. The ca
37、rbon content as mean of the corrected singlevalues of the multiple determinations shall be expressed inmass fractions in % and rounded off in accordance to theuncertainty of measurement.Calculate the mass fraction of carbon as follows:w Ctotal! 5mc mblank! 3 100ms(1)where:mc= absolute mass of carbon
38、 in the sample, mg,mblank= absolute mass of carbon in the blank sample, mg,andms= sample mass, mgNOTE 7Most state of the art analyzers automatically calculate themass fraction of carbon for each measurement after input of blank valuesand sample masses.16. Precision and Bias (1)4NOTE 8Please see Ref
39、(2) for all precision and bias statements, exceptthose denoted by Ref (3).16.1 Within the frame of the certification of the boroncarbide powder European reference material ERM-ED102,5the following precision and bias data were obtained applyingthe described total carbon method. (See table below.)Elem
40、ent Total CarbonMethodERM-ED102,certified valueBias of mean of totalcarbon method tocertified value,% (relative)Mean,%Repeatability Sr,%Reproducibility SR,%Mean,%Uncertainty,%C 21.06 0.07 0.25 21.01 0.28 +0.24TOTAL BORON BY TITRIMETRY AND ICP OES17. Scope17.1 This method covers the determination of
41、total boron insamples of boron carbide powder and pellets by titrimetry andICPOES.The recommended amount of boron for each titrationis 100 6 10 mg.18. Summary of Method18.1 Powdered boron carbide is mixed with alkaline re-agents and this mixture is fused to decompose the boroncarbide. The melt is di
42、ssolved in diluted hydrochloric acid andheated or purged with nitrogen to remove carbon dioxide. Theboron as boric acid is titrated with standardized sodiumhydroxide solution, using the mannitoboric acid procedure (3),(4), and (5). Alternatively, the boron in the samples solution ismeasured using IC
43、P OES.NOTE 9Sodium carbonate or a mixture of sodium carbonate andpotassium carbonate (1:1) is normally used as alkaline reagent todecompose the boron carbide.19. Interferences19.1 TitrimetryMetallic impurities in high concentrationsmay distort the inflection points of the titration and should beprec
44、ipitated from the sample solution using barium carbonate.No distortion was found for concentrations ofAl 100 g.61.8.2 AccuracyOver a 2-month period, 17 sodium tar-trate standards containing 300 to 1000 g of water wereanalyzed and the recovery varied from 95 to 101 %.62. Weight Loss on Drying Method6
45、2.1 Scope:62.1.1 This method covers the determination of water andother volatile substances in boron carbide powder by a gravi-metric method.62.2 Summary of Method:62.2.1 The boron carbide powder sample is heated in asuited heating device. The mass before and after heating ismeasured by weighing and
46、 the difference expressed as loss ondrying (LOD) in mass %.62.3 Interferences:62.3.1 Because of possible oxidation of boron carbide theprocedure must be carried out under inert gas conditions attemperatures above 150C.62.4 Apparatus:62.4.1 Analytical Balanceat least capable of reading tothe nearest
47、0.01 mg.62.4.2 Sample Boatfor example, labware glass, quartz,steel, nickel, platinum, suited to carry a sample mass requiredfor a reliable determination of LOD.62.4.3 Heating Devicecapable for a reproducible settingof the temperature specified for LOD measurement.NOTE 48Temperature and heating time
48、for LOD measurement areusually agreed between buyer and seller. Commonly used temperaturesand heating time are 110C, 400C, 500C and 2 h, respectively.NOTE 49For temperatures below 150C drying cabinets or commer-cially available moisture analyzers with halogen lamp heating are wellsuited. For higher
49、temperatures a tube-furnace with inert gas flushing canbe used.62.5 Preparation:62.5.1 The sample boats are dried at the temperature se-lected for LOD measurement, cooled down to room tempera-ture in a desiccator and stored therein. For temperatures above150C metal samples boats must be used.62.6 Procedure:62.6.1 Take the weight of the empty sample boat, preparedaccording to 62.5.1.62.6.2 Fill the boron carbide powder into the sample boat(usually 5 g) and take the weight again.62.6.3 Place the sample boat in the heating device and, ifrequired,
