1、Designation:E280913Standard Guide forUsing Scanning Electron Microscopy/X-Ray Spectrometry inForensic Paint Examinations1This standard is issued under the fixed designation E2809;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the ye
2、ar 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 guide is an outline of methods for scanningelectron microscopy(SEM)intended for use by forensic paintexaminers.T
3、his guide is intended to supplement informationpresented in Guide E1610.1.2 The methods used by each examiner or laboratory orboth depend upon sample size,sample suitability,and labora-tory equipment.1.3 The term“scanning electron microscopy”occasionallyrefers to the entire analytical system includi
4、ng energy disper-sive X-ray spectrometry(EDS)or wavelength dispersive X-rayspectrometry(WDS)or both.1.4 This guide does not cover the theoretical aspects ofmany of the topics presented.1.5 This guide cannot replace knowledge,skill,or abilityacquired through appropriate education,training,and experi-
5、ence and should be used in conjunction with sound profes-sional judgment.1.6 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.7 This standard does not purport to address all of thesafety concerns,if any,associated with its use.I
6、t 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:2E766 Practice for Calibrating the Magnification of a Scan-ning Electron Microsco
7、peE1492 Practice for Receiving,Documenting,Storing,andRetrieving Evidence in a Forensic Science LaboratoryE1508 GuideforQuantitative AnalysisbyEnergy-Dispersive SpectroscopyE1610 Guide for Forensic Paint Analysis and ComparisonE1732 Terminology Relating to Forensic Science3.Terminology3.1 Definition
8、sFor additional terms commonly employedfor general forensic examinations,see Terminology E1732.3.1.1 backgroundX-rays(Bremsstrahlung,brakingradiation,continuous spectrum),nnonspecific X-ray radia-tion with a continuous energy range from zero up to the beamvoltage in which background radiation result
9、s from the decel-eration of beam electrons in the atomic Coulombic field.3.1.1.1 DiscussionA typical X-ray spectrum consists ofboth a continuous background and peaks from characteristicX-rays.3.1.2 backscattered electrons,nprimary beam electronsthat are scattered from the sample after undergoing few
10、inelastic interactions.3.1.2.1 DiscussionThe probability of backscattering isproportional to the atomic number.3.1.3 bulk analysis,ntype of scanning electron micros-copy(SEM)analysis that determines the average elementalcomposition of a material in which the area of analysis is aslarge as possible a
11、nd may be achieved by a single large arearaster or the summed results from multiple smaller area rasters.3.1.4 cathodoluminescence,nemission of photons in theultraviolet(UV),visible(Vis),and infrared(IR)regions of theelectromagnetic spectrum as a result of electron beam interac-tion with certain mat
12、erials.3.1.5 characteristic X-rays,nX-ray emission resultingfrom de-excitation of an atom following inner shell ionizationin which the energy of the X-rays is related to the atomicnumber of the atom,providing the basis for energy dispersiveX-ray spectrometry(EDS).3.1.5.1 DiscussionA typical X-ray sp
13、ectrum consists ofboth a continuous background and peaks from characteristicX-rays.1This guide is under the jurisdiction of ASTM Committee E30 on ForensicSciences and are the direct responsibility of Subcommittee E30.01 on Criminalis-tics.Current edition approved Feb.15,2013.Published April 2013.DOI
14、:10.1520/E2809-13.2For 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.Copyright ASTM International,100 Barr Harbor Dri
15、ve,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.1.6 charging,nnegative charge accumulation on either anonconductive sample or a sample that is not properlygrounded.3.1.6.1 DiscussionThis effect may interfere with imageformation and X-ray analysis because of beam deflection.Itcan usua
16、lly be eliminated by the application of a conductivecoating.3.1.7 detector fluorescence peak(dead-layer peak,siliconinternal fluorescence peak),npeak resulting from the emis-sion of characteristic X-rays in a thin layer of inactive crystalarea in the front of an EDS detector.3.1.7.1 DiscussionThe peak is characteristic of the type ofdetector,such as silicon for a lithium-drifted silicon detector.Ina silicon detector,this peak may appear at 0.2%apparentconcentration.3.1.8 electron probe microanal
