Handbook of Analytical Methods for Materials Copyright © 2001 by Materials Evaluation and Engineering, Inc. 31 Combustion Methods - High temperature combustion is used to determine carbon and sulfur content in a variety of materials, both organic and inorganic. The sample is accurately weighed and placed in a ceramic crucible or combustion boat, often along with combustion accelerators. The crucible is placed in a high-temperature furnace which is then flooded with oxygen. The furnace is heated to 1370 - 1425°C, causing the combustion of the carbon and sulfur in the sample to form CO, CO 2 , and SO 2 . The gases are separated and analyzed by infrared absorption or thermal conductivity detectors. A heated catalyst is used to convert the CO to CO 2 prior to detection. The infrared absorption detector measures the absorption of the infrared wavelengths characteristic to CO 2 and SO 2 .The amount of infrared absorption at these wavelengths is correlated to a quantitative content based on standards and the weight of the original specimen. The thermal conductivity detectors monitor the thermal conductivity of the carrier gas. As the evolved gases pass the detector, changes in the thermal conductivity correspond to a change in the gas (e.g. from the inert carrier gas to hydrogen) and the amount of evolved gas present. These changes corre- spond to the amount of CO 2 and SO 2 generated and indicate the amount of sulfur or carbon in the original specimen. IG - Inert gas fusion is a quantitative analytical technique for determining the concentrations of nitrogen, oxygen, and hydrogen in ferrous and nonferrous materials. The sample is accurately weighed and placed in a pure graphite crucible in a fusion furnace with an inert gas atmosphere. The crucible is heated to 2000 - 3000°C, resulting in the sample fusing to a molten state. The hydrogen and nitrogen gases dissociate from the molten material and are carried away from the fusion chamber as H 2 and N 2 . The oxygen released from the material bonds with carbon (from the graphite crucible) to form CO or CO 2 and is carried away. An inert carrier gas flushes the gases evolved from the sample out of the fusion chamber. The fusion gases are separated and carried to the detector. The individual concentrations for the evolved gases are detected by infrared absorption (for CO and CO 2 only) or thermal conductive techniques (N 2 , H 2 , CO, and CO 2 ) as described for Combustion Methods above. ANALYTICAL INFORMATION Spark-OES - The intensities of the characteristic wavelengths of emitted photons are measured and compared to intensities for known standards to provide quantitative results. All metallic elements plus carbon, sulfur, and phosphorus can be detected, with analysis for most performed simultaneously. The minimum detection limits are in the parts-per-million range. XRF - The energy of each x-ray and the number of x-rays for each energy are measured. Elements from beryllium to uranium can be detected. The minimum detection limits are typically in the parts-per-million range. Because thecharacteristic x-ray intensity will vary with the thickness of films on a dissimilar substrate, the thickness of thin films can also be measured by XRF. QUANTITATIVE CHEMICAL A NALYSIS Handbook of Analytical Methods for Materials Copyright © 2001 by Materials Evaluation and Engineering, Inc. 32 ICP-OES - The intensities of the characteristic wavelengths are measured and compared to intensi- ties for known standards to provide quantitative results. All metallic elements can be detected, with analysis for most performed simultaneously. The minimum detection limits are typically parts-per-million to parts-per-billion for the dissolved samples. Since specimens for this technique are solutions, standards suitable for most material types can be easily prepared. Combustion methods - Quantitative results are obtained for carbon and sulfur contents in metals, inorganics, and organics. Lower detection limits for carbon range from 0.1 to 10 parts per-million with upper detection limits of 2.5 - 3.5 %. Lower detection limits for sulfur range from 0.1 to 50 parts per-million with upper detection limits of 0.2 - 2.5 %. IG - Quantitative results for most metals and alloys can be obtained in the parts-per-million to parts-per-billion range for nitrogen, hydrogen, and oxygen. TYPICAL APPLICATIONS • Alloy identification for ferrous and non-ferrous materials • Industrial alloy verification for quality control • Mineral and Cement composition • Sulfur, chlorine, lead, etc.,determination in petroleum products • Additives to polymers • Trace metals in alloys, water, or solutions • Contamination of water or solutions SAMPLE REQUIREMENTS Spark -OES - The sample must be a conductive metallic solid with a minimum diameter of 5 mm or larger, depending on the instrument. XRF - The samples may be solids, liquids or powders. Samples often require little or no preparation prior to analysis. Qualitative analysis may use samples as small as 1 mm across. Quantitative analysis may require a larger sample, up to 30 mm in diameter. ICP-OES - The samples may be solid or in a solution. A few grams of a solid sample are typically needed for digestion and dilution. For samples in solution, at least several milliliters may be required for dilution. Combustion methods - One gram or less of a solid, chips, or powder sample is typically required. Samples should not be contaminated with sulfur or carbon prior to analysis. IG - One gram of material is required for nitrogen or oxygen determination. Samples may be solids, chips, or powders. Hydrogen determination generally requires two grams of a solid sample. QUANTITATIVE CHEMICAL A NALYSIS Handbook of Analytical Methods for Materials Copyright © 2001 by Materials Evaluation and Engineering, Inc. 33 ROCKWELL HARDNESS TESTING DESCRIPTION OF TECHNIQUE Rockwell hardness testing is a general method for measuring the bulk hardness of metallic and poly- mer materials. Although hardness testing does not give a direct measurement of any performance properties, hardness of a material correlates directly with its strength, wear resistance, and other properties. Hardness testing is widely used for material evaluation because of its simplicity and low cost relative to direct measurement of many properties. Specifically, conversion charts from Rockwell hardness to tensile strength are available for some structural alloys, including steel and aluminum. Rockwell hardness testing is an indentation testing method. The indenter is either a conical diamond (brale) or a hard steel ball. Different indenter ball diameters from 1/16 to 1/2 in. are used depending on the test scale. To start the test, the indenter is “set” into the sample at a prescribed minor load. A major load is then applied and held for a set time period. The force on the indenter is then decreased back to the minor load. The Rockwell hardness number is calculated from the depth of perma- nent deformation of the indenter into the sample, i.e. the difference in indenter position before and after application of the major load. The minor and major loads can be applied using dead weights or springs. The indenter position is measured using an analog dial indicator or an electronic device with digital readout. The various indenter types combined with a range of test loads form a matrix of Rockwell hardness scales that are applicable to a wide variety of materials. Each Rockwell hardness scale is identified by a letter designation indica- tive of the indenter type and the major and minor loads used for the test. The Rockwell hardness number is expressed as a combination of the measured numerical hardness value and the scale letter preceded by the letters, HR. For example, a hardness value of 80 on the Rockwell A scale is reported as 80 HRA. FOSNOITACILPPALACIPYT SELACSTSETLLEWKCOR ELACSSNOITACILPPA A,sleetsniht,sedibracdetnemeC ylnO.sleetsdenedrah-esacwollahs ediwarevosuounitnocsitahtelacs .sessendrahlairetamfoegnar Bdna,sleetstfos,reppoc,munimulA .norielbaellam Cpeed,snoridrah,sleetsdenedraH .muinatit,sleetsdenedrah-esac Ddenedrah-esacmuidem,sleetsnihT .norielbaellamcitilraepdna,sleets E,muisengam,munimula,noritsaC .slatemgniraebdna Ftfos,nihtdnasreppocdelaennA .latemteehs G,reppocmuillyreb,eznorbrohpsohP .snorielbaellamdna H daeldna,cniz,munimulA ,M,L,K V,S,R,P tfosyrevrehtodnaslatemgniraeB .slairetamnihtro N,CRH,ARHrofsaslairetamemaS roeguagrennihttub,DRHdna .shtpedesac T,FRH,BRHrofsaslairetamemaS .eguagrennihtroftub,GRHdna Y,X,Wyarpsamsalp,slairetamgniraeB .sgnitaoc Handbook of Analytical Methods for Materials Copyright © 2001 by Materials Evaluation and Engineering, Inc. 34 ANALYTICAL INFORMATION Regular Rockwell Hardness Testing - Measures the bulk hardness of the material. There are separate scales for ferrous metals, nonferrous metals, and plastics. Common Rockwell hardness scales include A, B,C and F for metals and M and R for polymers. Superficial Rockwell Hardness Testing - A more surface-sensitive measurement of hardness than regular Rockwell scales. This technique is useful for testing thin samples, samples with hardness gradients at the surface, and small areas. Superficial Rockwell hardness scales are N and T for metals and W, X and Y for nonmetallic materials and soft coatings. TYPICAL APPLICATIONS • Quality control for metal heat treatment • Incoming material inspection • Weld evaluations in steels and other alloys • Grade verification for hard plastics • Failure analysis SAMPLE REQUIREMENTS Testing is typically performed on flat or cylindrical samples. Cutting and/or machining are often required to obtain suitable test specimens from complex-shaped components. Smooth parallel surfaces, free of coatings, scale and gross contamina- tion, are required for testing. The specific finish requirements depend on the material and test scale. Samples 6 in. (150 mm) thick or larger can be accommodated. The minimum sample size depends on the sample hardness and test scale. Cylindrical samples as small as 1/8 in. (3 mm) in diameter, and thin sheets 0.006 in. (150 µm) thick, are the minimum size for testing. ROCKWELL HARDNESS TESTING Rockwell Hardness Tester selacStseTssendraHllewkcoR lobmySelacSrotartenePgkdaoL AelarB06 BllaB.ni-61/1001 CelarB051 DelarB001 EllaB.ni-8/1001 FllaB.ni-61/106 GllaB.ni-61/1051 HllaB.ni-8/106 KllaB.ni-8/1051 LllaB.ni-4/106 MllaB.ni-4/1001 PllaB.ni-4/1051 RllaB.ni-2/106 SllaB.ni-2/1001 VllaB.ni-2/1051 selacSretseTlaicifrepuS N54,N03,N51elarBN54,03,51 T54,T03,T51llaB.ni-61/154,03,51 W54,W03,W51llaB.ni-8/154,03,51 X54,X03,X51llaB.ni-4/154,03,51 Y54,Y03,Y51llaB.ni-2/154,03,51 Handbook of Analytical Methods for Materials Copyright © 2001 by Materials Evaluation and Engineering, Inc. 35 SCANNING ELECTRON MICROSCOPY DESCRIPTION OF TECHNIQUE Scanning electron microscopy (SEM) is a method for high-resolution imaging of surfaces. The SEM uses electrons for imaging, much as a light microscope uses visible light. The advantages of SEM over light microscopy include much higher magnification (>100,000X) and greater depth of field up to 100 times that of light microscopy. Qualitative and quantitative chemical analysis information is also obtained using an energy dispersive x-ray spectrom- eter (EDS) with the SEM. (See Handbook section on EDS analysis.) The SEM generates a beam of incident electrons in an electron column above the sample chamber. The electrons are produced by a thermal emission source, such as a heated tungsten filament, or by a field emission cathode. The energy of the incident electrons can be as low as 100 eV or as high as 30 keV depending on the evaluation objectives. The electrons are focused into a small beam by a series of electromagnetic lenses in the SEM column. Scanning coils near the end of the column direct and position the focused beam onto the sample surface. The electron beam is scanned in a raster pattern over the surface for imaging. The beam can also be focused at a single point or scanned along a line for x-ray analysis. The beam can be focused to a final probe diameter as small as about 10 Å. The incident electrons cause electrons to be emitted from the sample due to elastic and inelastic scattering events within the sample’s surface and near-surface material. High-energy electrons that are ejected by an elastic collision of an incident electron, typically with a sample atom’s nucleus, are referred to as backscattered electrons. The energy of backscattered electrons will be comparable to that of the incident elec- trons. Emitted lower-energy electrons resulting from inelas- tic scattering are called secondary electrons. Secondary electrons can be formed by collisions with the nucleus where substantial energy loss occurs or by the ejection of loosely bound electrons from the sample atoms. The energy of secondary electrons is typically 50 eV or less. To create an SEM image, the incident electron beam is scanned in a raster pattern across the sample's surface. The SEM Image of Metal Foam Structure Electron Beam Interaction Diagram Handbook of Analytical Methods for Materials Copyright © 2001 by Materials Evaluation and Engineering, Inc. 36 emitted electrons are detected for each position in the scanned area by an electron detector. The intensity of the emitted electron signal is displayed as brightness on a cathode ray tube (CRT). By sychromizing the CRT scan to that of the scan of the incident electron beam, the CRT display represents the morphology of the sample surface area scanned by the beam. Magnification of the CRT image is the ratio of the image display size to the sample area scanned by the electron beam. Two electron detector types are predominantly used for SEM imaging. Scintillator type detectors (Everhart-Thornley) are used for secondary electron imaging. This detector is charged with a positive voltage to attract electrons to the detector for im- proved signal to noise ratio. Detectors for backscattered electrons can be scintillator types or a solid-state detector. The SEM column and sample chamber are at a moderate vacuum to allow the electrons to travel freely from the electron beam source to the sample and then to the detectors. High-resolution imaging is done with the chamber at higher vacuum, typically from 10 -5 to 10 -7 Torr. Imaging of nonconductive, volatile, and vacuum-sensitive samples can be performed at higher pressures. ANALYTICAL INFORMATION Secondary Electron Imaging - This mode provides high-resolution imaging of fine surface mor- phology. Inelastic electron scattering caused by the interaction between the sample's electrons and the incident electrons results in the emission of low-energy electrons from near the sample's surface. The topography of surface features influences the number of electrons that reach the secondary electron detector from any point on the scanned surface. This local variation in electron intensity creates the image contrast that reveals the surface morphology. The secondary electron image resolution for an ideal sample is about 3.5 nm for a tungsten-filament elec- tron source SEM or 1.5 nm for field emission SEM. Backscatter Electron Imaging - This mode pro- vides image contrast as a function of elemental composition, as well as, surface topography. Back- scattered electrons are produced by the elastic interactions between the sample and the incident electron beam. These high-energy electrons can SCANNING ELECTRON MICROSCOPY Corrosion Product on Inside of Copper Tubing Laser Welded Wire Handbook of Analytical Methods for Materials Copyright © 2001 by Materials Evaluation and Engineering, Inc. 37 escape from much deeper than secondary electrons, so surface topography is not as accurately resolved as for secondary electron imaging. The production effeciency for backscattered electrons is proportional to the sample material's mean atomic number, which results in image contrast as a function of composition, i.e., higher atomic number material appears brighter than low atomic number material in a backscattered electron image. The optimum resolution for backscattered electron imaging is about 5.5 nm. Variable Pressure SEM - Traditionally, SEM has re- quired an electrically-conductive sample or continuous conductive surface film to allow incident electrons to be conducted away from the sample surface to ground. If electrons accumulate on a nonconductive surface, the charge buildup causes a divergence of the electron beam and degrades the SEM image. In variable-pressure SEM, some air is allowed into the sample chamber, and the interaction between the electron beam and the air mol- ecules creates a cloud of positive ions around the electron beam. These ions will neutralize the negative charge from electrons collecting on the surface of a nonconductive material. SEM imaging can be performed on a nonconductive sample when the chamber pressure is maintained at a level where most of the electrons reach the sample surface, but there are enough gas molecules to ionize and neutralize charging. Variable pressure SEM is also valuable for examination of samples that are not compatible with high vacuum. Quantitation - Image magnification is calibrated against a reference standard. Lateral feature dimen- sions can be readily quantified to an accuracy of less than 0.1 µm. Computer analysis of images can quantify area or volume fractions and particle shapes and sizes. Data Formats - Images can be recorded on Polaroid instant film, low-cost video prints, videotape, or as bitmap (.bmp), tagged- image (.tif), or other computer file formats. TYPICAL APPLICATIONS • Microscopic feature measurement • Fracture characterization • Microstructure studies • Thin coating evaluations • Surface contamination examination • IC failure analysis SCANNING ELECTRON MICROSCOPY Cleavage Fracture in Steel Intergranular Fracture in Steel Handbook of Analytical Methods for Materials Copyright © 2001 by Materials Evaluation and Engineering, Inc. 38 SAMPLE REQUIREMENTS In a large-chamber SEM, samples up to 8 in. (200 mm) in diameter can be readily accommodated. Larger samples, up to 12 in. (300 mm) across can be loaded with limited stage movement. Sample height is typically limited to ~2 in. (50 mm). Backscattered electron imaging can be performed on conductive or noncon- ductive samples. For secondary electron imaging, samples must be electrically conductive. Nonconduc- tive materials can be evaporatively coated with a thin film of carbon, gold or other conductive material to obtain conductivity without significantly affecting observed surface morphology. Samples must be compatible with at least a moderate vacuum. For high-resolution secondary electron imaging, the sample environment is at a pressure of 1 x 10 -5 Torr or less. The pressure can be ad- justed up to about 2 Torr for vacuum sensitive samples. SCANNING ELECTRON MICROSCOPY Fatigue Fracture in Aluminum Handbook of Analytical Methods for Materials Copyright © 2001 by Materials Evaluation and Engineering, Inc. 39 SECONDARY ION MASS SPECTROMETRY DESCRIPTION OF TECHNIQUE Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) is an analytical technique used to obtain elemental and molecular chemical data about surfaces (static SIMS), and detect parts per billion (ppb) concentrations of impurities in semiconductors and metals (dynamic SIMS). All ele- ments, including hydrogen, are detectable by SIMS. In ToF-SIMS analysis, the sample is placed in an ultrahigh vacuum environment where primary ions bombard the sample and sputter atoms, molecules, and molecular fragments from the sample surface. The mass of the ejected particles (i.e., second- ary ions) are analyzed via time-of-flight mass spectrometry. In the ToF analyzer, ejected ions are accelerated into the analyzer with a common energy, but at different velocities depending on the particle mass. Due to the differences in these velocities, smaller ions move through the analyzer faster than the larger ions. The mass of the secondary ions are determined by their travel time through the analyzer. SIMS is a surface-sensitive analysis method, since only the secondary ions generated in the outermost 10 to 20 Å region of a sample surface can overcome the surface binding energy and escape the sample surface for detection and analysis. ANALYTICAL INFORMATION Mass Spectrum - SIMS analysis identifies the elemental and ion composition of the uppermost 10 to 20 Å of the analyzed surface from positive and negative mass spectra. The high resolution of the ToF analyzer can distinguish species whose masses differ by only a few millimass units. Depth Profile - During SIMS analysis, the sample surface is slowly sputtered away. Continuous analysis obtains composition information as a function of depth. Depth resolution of a few angstroms is possible. High-sensitivity mass spectra can be recorded or reconstructed at any depth of the profile. ToF-SIMS Positive Secondary Ion Map Handbook of Analytical Methods for Materials Copyright © 2001 by Materials Evaluation and Engineering, Inc. 40 Secondary Ion Mapping - A SIMS map measures the lateral distribution of elements and mol- ecules on the sample’s surface. To obtain a SIMS map, a highly focused primary ion beam is scanned in a raster pattern across the sample surface, and the secondary ions are analyzed at specific points on a grid pattern over the selected surface area. Image brightness at each point is a function of the relative concentration of the mapped element or molecule. Lateral resolution is less than 0.1 µm for elements and about 0.5 µm for large molecules. TYPICAL APPLICATIONS • Identifying lubricants on magnetic hard discs • Measuring dopant distributions in semiconductors • Profiling thickness of insulating films on glass • Mapping elemental and molecular patterned surfaces • Identifying compounds in thin organic films • Determining the extent of crosslinking in polymers SAMPLE REQUIREMENTS Sample size cannot exceed 3.5 in. (85 mm) in any lateral direction. Height should not exceed 0.8 in (20 mm). Sample must be compatible with ultra-high vacuum (>1x10 -9 Torr). SECONDARY ION MASS SPECTROMETRY . Tester selacStseTssendraHllewkcoR lobmySelacSrotartenePgkdaoL AelarB06 BllaB.ni-61/1001 CelarB051 DelarB001 EllaB.ni-8/1001 FllaB.ni-61/106 GllaB.ni-61/1051 HllaB.ni-8/106 KllaB.ni-8/1051 LllaB.ni -4/ 106 MllaB.ni -4/ 1001 PllaB.ni -4/ 1051 RllaB.ni-2/106 SllaB.ni-2/1001 VllaB.ni-2/1051 selacSretseTlaicifrepuS N 54, N03,N51elarBN 54, 03,51 T 54, T03,T51llaB.ni-61/1 54, 03,51 W 54, W03,W51llaB.ni-8/1 54, 03,51 X 54, X03,X51llaB.ni -4/ 1 54, 03,51 Y 54, Y03,Y51llaB.ni-2/1 54, 03,51 Handbook of Analytical Methods for Materials Copyright © 2001 by Materials Evaluation and Engineering,. reconstructed at any depth of the profile. ToF-SIMS Positive Secondary Ion Map Handbook of Analytical Methods for Materials Copyright © 2001 by Materials Evaluation and Engineering, Inc. 40 Secondary Ion. HRA. FOSNOITACILPPALACIPYT SELACSTSETLLEWKCOR ELACSSNOITACILPPA A,sleetsniht,sedibracdetnemeC ylnO.sleetsdenedrah-esacwollahs ediwarevosuounitnocsitahtelacs .sessendrahlairetamfoegnar Bdna,sleetstfos,reppoc,munimulA .norielbaellam Cpeed,snoridrah,sleetsdenedraH .muinatit,sleetsdenedrah-esac Ddenedrah-esacmuidem,sleetsnihT .norielbaellamcitilraepdna,sleets E,muisengam,munimula,noritsaC .slatemgniraebdna Ftfos,nihtdnasreppocdelaennA .latemteehs G,reppocmuillyreb,eznorbrohpsohP .snorielbaellamdna H daeldna,cniz,munimulA ,M,L,K V,S,R,P tfosyrevrehtodnaslatemgniraeB .slairetamnihtro N,CRH,ARHrofsaslairetamemaS roeguagrennihttub,DRHdna .shtpedesac T,FRH,BRHrofsaslairetamemaS .eguagrennihtroftub,GRHdna Y,X,Wyarpsamsalp,slairetamgniraeB .sgnitaoc Handbook of Analytical Methods for Materials