1、Designation: D3720 90 (Reapproved 2011)Standard Test Method forRatio of Anatase to Rutile in Titanium Dioxide Pigments byX-Ray Diffraction1This standard is issued under the fixed designation D3720; the number immediately following the designation indicates the year oforiginal adoption or, in the cas
2、e 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 determination of the ratio ofanatase to rutile in titanium diox
3、ide pigments. The method isalso applicable to pigment mixtures and pigmented coatingscontaining titanium dioxide.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety
4、 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 regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D215 Practice for the Chemical Ana
5、lysis of White LinseedOil Paints3D2371 Test Method for Pigment Content of Solvent-Reducible PaintsD2698 Test Method for Determination of the PigmentContent of Solvent-Reducible Paints by High-Speed Cen-trifugingD3925 Practice for Sampling Liquid Paints and RelatedPigmented Coatings3. Summary of Test
6、 Method3.1 The X-ray diffraction pattern obtained from a material ischaracteristic of that material. The intensity of a diffractionpeak entirely due to one component of a mixture is dependentupon the amount of that substance in the mixture. To a minorextent the peak intensity of the component is als
7、o dependent onthe mass absorption coefficient of other materials present.Since the test method utilizes the ratio of the intensities ofdiffraction peaks of two chemically similar materials, it isexpected that the effects of other constituents will be the samefor both materials.3.2 The intensity of t
8、he diffraction maxima for anatase andrutile is measured by X-ray diffractometry. The intensity of theanatase peak is converted to anatase content relative to rutileand the rutile content is determined by difference.3.3 The X-ray diffraction measurement is made on singlepigments, pigment mixtures, fi
9、lms of pigmented coatings, andfilms prepared from liquid coatings, if interfering materials arenot present. When interfering materials are present, the pig-ment is separated from the redissolved (or ignited film, or fromthe liquid coating and treated to isolate the titanium dioxide.4. Significance a
10、nd Use4.1 This test method is used by titanium dioxide pigmentmanufacturers and users for process control and productacceptance.5. Interferences5.1 Calcium sulfate interferes, but its effect is eliminated bychemical removal (see Practice D215). It is desirable to assureby analysis that any residual
11、CaSO4is considerably less thanthe level of anatase being sought. The insoluble residue afterremoval of calcium sulfate should be ignited above 700C.Chrome yellow and the valentinite form of antimony trioxidealso interfere if not removed. High amounts of iron renderanalysis difficult due to increased
12、 background (see Note 1).Additives, such as antimony and zinc, and impurities, such asniobium and zirconium, are generally present in solid solutionand thus would not have interfering diffraction peaks. Surfacetreatments such as silica and alumina do not interfere. Extremedifferences in particle siz
13、e between the anatase and rutileportions affect the results.NOTE 1Background scatter due to high iron levels in a sample may bereduced by use of a cobalt or molybdenum target tube in place of thecopper target tube. The background may be eliminated for all practical1This test method is under the juri
14、sdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.31 on Pigment Specifications.Current edition approved June 1, 2011. Published June 2011. Originallyapproved in 1978. Last previous edition approved in 2005 as
15、D3720 - 90 (2005).DOI: 10.1520/D3720-90R11.2For 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.3Withdrawn. The la
16、st approved version of this historical standard is referencedon www.astm.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.purposes by use of a curved crystal monochromator equipped with agraphite crystal in conjunction with a copp
17、er target tube.5.2 In the calculation of converting the ratio to percent it isimplicitly assumed that the sum of anatase and rutile is 100 %,an assumption normally made in TiO2pigment systems. Othermaterials present would interfere to the extent that they dilutethe sample. The third polymorphic form
18、 of TiO2, brookite,would have such an effect. However, it reportedly does notoccur in commercial titanium dioxide pigments.6. Apparatus6.1 X-Ray DiffractometerThe principle components ofthis instrument are: (a) X-ray generator, (b) copper target X-raytube, (c) goniometer, (d) detector, (e) electroni
19、c circuit panel,(f) computer (if used), and (g) strip chart recorder or printer.6.2 Operating ConditionsThe X-ray tube voltage andfilament current and other settings are selected to record X-raydiffraction peaks of weak intensities.6.2.1 Nickel Filter, to remove Cu K beta radiation if amonochromator
20、 is not used. Cu K beta radiation will producea diffraction line from the rutile phase of TiO2that appears atthe same 2u angle as the anatase analytical line.6.3 Typical Apparatus Conditions:6.3.1 High-Voltage Power SupplySelect X-ray tube volt-age, filament current, and other settings so that 0.1 %
21、 anatasegenerates a signal with intensity at least four times the noiselevel.6.3.2 DetectorScintillation detector operating at optimumvoltage.6.3.3 Pulse Height AnalyzerSettings will depend on in-strumentation used.6.3.4 SlitsReceiving slit, 0.15; others, 1.6.3.5 Chart Speed, 12.5 mm (12 in.)/min.6.
22、3.6 Goniometer Speed,14 /min, scanning or 0.02 stepswith 4.8 s per step.6.3.7 Time Constant,5.6.3.8 Scanning Range,2u = 28 to 24.6.3.9 Scale FactorsFor samples of low anatase content ascale factor of 100 counts full scale is normally used for the2u = 26 to 24 range (anatase diffraction maximum), and
23、 ascale factor of 5000 counts full scale is normally used for the2u = 28 to 26 range (rutile diffraction maximum). The scalefactors may be changed depending on the level of anataseexpected in the sample.7. Reagents7.1 Purity of ReagentsUntreated rutile and anatase gradesof titanium dioxide pigments
24、are used to make syntheticstandards for calibration. The crystalline structures of thereagents must be 100 % rutile and 100 % anatase as determinedby examining these materials by X-ray diffraction to assure thispurity.7.2 Mixing ReagentsA series of rutile standards of vary-ing rutile content are pre
25、pared to cover the range of interest bythoroughly mixing known amounts of 100 % rutile and 100 %anatase together. The pigments are dispersed in a solvent suchas isopropyl alcohol and then mixed, followed by air drying.This dry cake is ground up using a mortar and pestle to ensurehomogeneity.8. Hazar
26、ds8.1 X-ray producing equipment can be dangerous to boththe operator and persons in the immediate vicinity unless safetyprecautions are strictly observed. Refer to the manufacturersinstruction manual. Exposure to excessive quantities ofX-radiation may be injurious to health. Therefore, users shoulda
27、void exposing any parts of their bodies, not only to the directbeam, but also to secondary or scattered radiation that occurswhen an X-ray beam strikes or has passed through anymaterial. It is strongly recommended that users check thedegree of exposure by film carried on them or by the use ofdosimet
28、ers and that blood counts be made periodically. Beforeutilizing the equipment, all persons designated or authorized tooperate X-ray instrumentation or supervise its operation,should have a full understanding of its nature and should alsobecome familiar with established safe exposure factors by acare
29、ful study of the National Bureau of Standards Handbook“X-Ray Recommendations of the International Roentgen RayCommittee on X-Ray Protection” and other standard publica-tions on the subject. Inquiries should be made of state agenciesas to existing requirements.9. Specimen Preparation9.1 Powder Sample
30、s:9.1.1 Packing the specimen in the specimen holder to obtaina planar surface is one of the most important phases in X-rayanalysis. Ripples or indentures in the specimen surface causevariations in the test because of an error of eccentricity and achange in the intensities of the peaks. The chance of
31、 preferredorientation of pigmentary TiO2is remote because of its smallparticle size.9.1.2 Pack the specimen in a die suitably constructed toaccommodate the specimen holder for the goniometer. Applyconstant pressure with a hydraulic press (see Note 2). Alterna-tively, place the specimen holder on a f
32、lat, smooth firm surfaceand pack the specimen into the opening by applying constantand firm pressure with a flat blade. The possibility of variationsamong different bags of the same lot should be considered.NOTE 2Use of a set procedure with a hydraulic press will improvespecimen preparation uniformi
33、ty compared to hand-packed specimens.This is particularly true where more than one person is involved inspecimen preparation.9.2 Coatings on Metal Panels:9.2.1 Cut the coated panel into the proper shape and size tofit an adjustable specimen holder and analyze without furtherpreparation. This assumes
34、 that interferences are not present(see Section 5).9.3 Liquid Coating Samples:9.3.1 Sample material in accordance with Practice D3925.9.3.2 Liquid coating samples without interfering materialspresent (see Section 5) are analyzed as cast films of the totalpaint on aluminum or other suitable substrate
35、.A 25 to 50-m (1to 2-mil) dry film thickness is adequate.9.3.3 Liquid paint samples with interfering materials pres-ent (see Section 4) must not be analyzed until the interferingcomponents are removed. This can be accomplished by cen-trifuging (Test Methods D2371 or D2698) to separate the totalpigme
36、nt. The separated pigment is treated according to theD3720 90 (2011)2Insoluble Matter section of Practice D215 to obtaininterference-free TiO2. Quantitative results are not required foreither separation procedure.10. Procedure10.1 Record the X-ray diffraction maxima of the anataseand of the rutile p
37、eak by scanning the range between 2u =26to 24 and 2u = 28 to 26, respectively. Scan each range twice.10.2 Draw the baseline between the lowest points of thetrace on each side of the peak. Measure the peak height abovethe baseline expressed in chart units, centimetres, counts persecond, or other conv
38、enient units for the anatase and rutilepeaks. Average the net peak heights of the duplicate runs.10.3 Since only ratios are used, the peak heights need onlybe corrected for differences, if any, in the scale factors used forthe two peaks.Any consistent units can be used, not just countsper second.10.
39、4 Prior to and after analyzing the unknown sample,analyze one of the standards to verify instrument stability.11. Calculations11.1 Determine the value of the constant, K, as followsK 5 Ia/Ir!/Wa/Wr!where:Ia= net intensity of the anatase diffraction peak,Ir= net intensity of the rutile diffraction pe
40、ak,Wa= weight of anatase, andWr= weight of rutile.11.1.1 K is equal to the slope of a calibration plot obtainedwhen the intensity ratio Ia/Iris plotted as a function of Wa/Wr,using data derived from a series of standards that span theconcentration range of interest. Routine calibration proceduresare
41、 followed.4,5NOTE 3The value of K is influenced by the instrument conditionsselected in Section 5. Data for standards and test samples must becollected using the same conditions.11.2 Calculate the anatase level relative to rutile from thepeak intensities above background as follows:Percent anatase 5
42、11 1 KIrIa3 10012. Precision12.1 On the basis of an interlaboratory test of this testmethod in which four operators in four laboratories tested twomaterials with composition approaching 100 or 0 % anatase orrutile, the within-laboratory standard deviation was found to be0.06 % for a single determina
43、tion. The between-laboratoriesstandard deviation was found to be 0.07 % absolute for resultseach the mean of two determinations. Based on these standarddeviations, the following criteria should be used for judging theprecision of results at the 95 % confidence level.12.1.1 RepeatabilityTwo results o
44、btained by the sameoperator should be considered suspect if they differ by morethan 0.18 % absolute for materials approaching 100 or 0 %.12.1.2 ReproducibilityTwo results, each the mean of twodeterminations, obtained by operators in different laboratoriesshould be considered suspect if they differ b
45、y more than 0.22 %absolute for materials approaching 100 or 0 %.13. Keywords13.1 anatase pigment analysis; rutile; titanium oxide analy-sis; X-ray diffraction.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this stand
46、ard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be review
47、ed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible
48、 technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Cons
49、hohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).4Myers, H. and Spurr, R., Analytical Chemistry, Vol 29, 1957, p. 760.5Zingaro, P. W., Norelco Reporter, Vol 5, No. 56.D3720 90 (2011)3
