Springer Handbook of Metrology and Testing

This chapter reviews the methodologies of measurement and testing. It gives an overview of metrology and presents the fundamentals of materials characterization as a basis for which are treated in parts B, C, and D of the handbook.

This chapter describes the basic elements of metrology, the system that allows measurements made in different laboratories to be confidently compared. As the aim of this chapter is to give an overview of the whole field, the development of metrology from its roots to the birth of the Metre Convention and metrology in the 21st century is given.

Technology and todayʼs global economy depend on reliable measurements and tests that are accepted internationally. As has been explained in Chap. 1, metrology can be considered in categories with different levels of complexity and accuracy. All scientific, industrial, and legal metrological tasks need appropriate quality methodologies, which are compiled in this chapter.

Measurements of the chemical compositions of materials and the levels of certain substances in them are vital when assessing and improving public health, safety and the environment, are necessary to ensure trade equity, and are required when monitoring and improving industrial products and services. Chemical measurements play a crucial role in most areas of the economy, including healthcare, food and nutrition, agriculture, environmental technologies, chemicals and materials, instrumentation, electronics, forensics, energy, and transportation.

For each technique, information is provided on the principle(s) of operation, the scope of the technique, the nature of the sample that can be used, qualitative analysis, traceable quantitative analysis, and key references. Examples of representative data are provided for each technique, where possible.

The methods compiled in this chapter are important in many areas of materials science and technology because various physical properties of materials (mechanical, thermal, electronic, optical, magnetic, dielectric, biological) depend on their geometric architecture, on scales ranging from the atomic or nanoscopic to the semimicroscopic. Some of the properties are governed only by an elementary atomic group in the structural hierarchy while others are brought about by cooperative functioning of multiple phases or microscopic structures in different dimensions. Corresponding to the vast variety of materials and their properties, a wide range of experimental techniques are available, so that the choice of which technique to employ on starting a study may not be clear. In this respect one should also bear in mind that some of the techniques presented in this chapter are based on physical principles, which are also relevant to the measurement methods compiled in Chaps. 6 and 11.

This chapter covers the three main techniques of surface chemical analysis: Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS), and secondary ion mass spectrometry (SIMS), which are all still rapidly developing in terms of instrumentation, standards, and applications. AES is excellent for elemental analysis at spatial resolutions down to 10 nm, and XPS can define chemical states down to 10 μm. Both analyze the outermost atom layers and, with sputter depth profiling, layers up to 1 μm thick.

Dynamic SIMS incorporates depth profiling and can detect atomic compositions significantly below 1 ppm. Static SIMS retains this high sensitivity for the surface atomic or molecular layer but provides chemistry-related details not available with AES or XPS. New reference data, measurement standards, and documentary standards from ISO will continue to be developed for surface chemical analysis over the coming years.

The chapter also discusses surface physical analysis (topography characterization), which encompasses measurement, visualization, and quantification. This is critical to both component form and surface finish at macro-, micro-, and nanoscales. The principal methods of surface topography measurement are stylus profilometry, optical scanning techniques, and scanning probe microscopy (SPM). These methods, based on acquiring topography data from point-by-point scans, give quantitative information on surface height with respect to position. The integral methods, which are based on a different approach, produce parameters that represent some average property of the surface under examination. Measurement methods, as well as their application and limitations, are briefly reviewed, including standardization and traceability issues.

Materials used in engineering applications as structural components are subject to loads, defined by the application purpose. The mechanical properties of materials characterize the response of a material to loading.

The mechanical loading action on materials in engineering applications may be static or dynamic and can basically be categorized as tension, compression, bending, shear, and torsion. In addition, thermomechanical loading effects can occur (Chap. 8). There may also be gas loads from the environment, leading to gas/materials interactions (Chap. 6) and to transport phenomena such as permeation and diffusion.

The mechanical loading action and the corresponding response of materials can be illustrated by the well-known stress–strain curve (for definition see Sect. 7.1.2). Its different regimes and characteristic data points characterize the mechanical behavior of materials treated in this chapter in terms of elasticity (Sect. 7.1), plasticity (Sect. 7.2), hardness (Sect. 7.3), strength (Sect. 7.4), and fracture (Sect. 7.5). Methods for the determination of permeation and diffusion are compiled in Sect. 7.6.

If materials – solids, liquids or gases – are heated or cooled, many of their properties change. This is due to the fact that thermal energy supplied to or removed from a specimen will change either the kinetic or the potential energy of the constituent atoms or molecules. In the first case, the temperature of the specimen is changed, since temperature is a measure of the average kinetic energy of the elementary particles of a sample. In the second case, e.g. the binding energy of these particles is altered, which may cause a phase transition.

Thermal properties are associated with a material-dependent response when heat is supplied to a solid body, a liquid, or a gas. This response might be a temperature increase, a phase transition, a change of length or volume, an initiation of a chemical reaction or the change of some other physical or chemical quantity.

Basically, almost all of the other materials properties treated in Part C, namely mechanical, electrical, magnetic, or optical properties, are temperature-dependent (except a material that is especially designed to be resistant to temperature variations). For example, temperature influences mechanical hardness, electrical resistance, magnetism, or optical emissivity. Temperature is also of importance to the characterization of material performance (Part D) as it influences materials integrity when subject to corrosion, friction and wear, biogenic impact or material–environment interactions. Temperature effects related to these areas are dealt with in the other chapters of this book dedicated to those topics. Only if those properties are needed to explain measuring methods within this chapter are they are outlined in the following sections.

In this chapter, a number of materials properties are selected and called thermal properties, where the effect of thermal energy treatment plays the major role compared to electrical, magnetic, chemical or other effects. The presentation of measurement methods for thermal properties is organized into five parts, referring to:

Electronic materials – conductors, insulators, semiconductors – play an important role in todayʼs technology. They constitute electrical and electronic devices, such as radio, television, telephone, electric light, electromotors, computers, etc. From a materials science point of view, the electrical properties of materials characterize two basic processes: electrical energy conduction (and dissipation) and electrical energy storage.

In this chapter, the main methods to characterize the electrical properties of materials are compiled. Sections 9.2 to 9.5 describe the measuring methods under the following headings

As an introductory overview, in Sect. 9.1 the basic categories of electrical materials are outlined in adopting the classification and terminology of the chapter Electronic Properties of Materials of Understanding Materials Science by Hummel [1].

Magnetic materials are one of the most prominent classes of functional materials, as introduced in Sect. 1.3. They are mostly inorganic, metallic or ceramic in nature and typically multicomponent when used in applications (e.g. alloys or intermetallic phases). Their structure can be amorphous or crystalline with grain sizes ranging from a few nanometers (as in high-end nanocrystalline soft magnetic materials) to centimeters (as in grain-oriented transformer steels). They are available as powders, cast, sintered or composite materials, ribbons or even thin films and find a huge variety of applications in transformers, motors, generators, medical system sensors, and microelectronic devices.

The aim of this chapter is to give advice as to which methods are most applicable to determine the characteristic magnetic properties of any of the materials mentioned above. Magnetic thin-film structures have recently gained significant scientific and economic importance. Not only can their properties deviate from the respective bulk materials but novel phenomena can also occur, such as giant and tunnel magneto-resistance, which lead to their application in read heads and their likely future application to nonvolatile magnetic solid-state memory (MRAM). Therefore, we have added a section that explains the important peculiarities special to thin films, in which we summarize the most relevant measurement techniques.

Section 10.1 will give a short overview to enable the reader to differentiate between the various manifestations of magnetism, different materials and their related properties. For a deeper understanding, of course, textbooks should be used (see the references given in Sect. 10.2). Section 10.2 covers the standard measurement techniques for soft and hard magnetic materials. The tables at the beginning of Sect. 10.2.1 are a valuable guide to choose the best technique for any given property to be measured. It is anticipated that this chapter will cover theoverwhelming needs for a routine characterization of soft and hard magnetic materials in their various forms. Section 10.3 introduces an elegant, novel and extremely fast technique, the so-called pulse field magnetometer, to measure the hysteresis loop of hard magnetic materials and thereby to determine the remanent magnetization, the anisotropy field and coercivity, respectively. This method has been developed only recently and is not yet comprehensively covered in textbooks. It is therefore described in more detail with a critical discussion of possible measurement errors and calibration requirements. Finally, as mentioned above, Sect. 10.4 addresses features peculiar to magnetic thin films and recommends techniques for their magnetic characterization. It comprises an overview of magneto-resistive effects occurring in magnetic thin films or multilayers where the electrical resistivity depends on external magnetic fields. These devices find important applications as read heads in hard-disc drives and as sensors in the automotive and automation industries. The standard measurement to determine the field response (change in resistance within a given field range) is simply a resistivity measurement, as described in Chap. 9, except that it needs to be done in an external magnetic field. These electrical techniques are therefore not covered in this chapter.

In bulk and thin-film ferromagnets properties such as remanent magnetization and coercivity often depend on the time scale used in the measurement (Sects. 10.1.6, 10.3.3). Time-dependent measurements needed, e.g., to predict the stability of the material in applications are not explicitly described in this chapter since, in principle, any sensitive magnetometer can be used for these measurements. In research, sophisticated methods are used to resolve magnetization dynamics on pico- or even femtosecond time scales. A detailed description of these more specialized methods is beyond the scope of this handbook.

At present, optical measurement methods are the most powerful tools for basic and applied research and inspection of the characteristic properties of a variety of materials, especially following the development of lasers and computers. Optical measurement methods are widely used for optical spectroscopy including linear and nonlinear optics and magneto-optics, conventional and unconventional optical microscopy, fiber optics for passive and active devices, optical recording for CD/DVD and MO disks, and various kinds of optical sensing.

In this chapter, as an introduction to the following sections, the concept and fundamentals of optical spectroscopy are described in Sect. 11.1, including optical measurement tools such as light sources, detectors and spectrometers, and standard optical measurement methods such as reflection, absorption, luminescence, scattering, etc. A short summary of laser instruments is also included. In Sect. 11.2 the microspectroscopic methods that have recently become quite useful for nano-science and nano-technology are described, including single-dot/molecule spectroscopy, near-field optical spectroscopy and cathodo-luminescence spectroscopy using scanning electron microscopes. In Sect. 11.3 magneto-optics such as Faraday rotation is introduced and the superlattice of semi-magnetic semiconductors is applied for the imaging measurement of magnetic flux patters of superconductors as an example of spintronics. Section 11.4 is devoted to fascinating subjects in laser spectroscopy, such as nonlinear spectroscopy, time-resolved spectroscopy and THz spectroscopy. In Sect. 11.5 fiber optics is summarized, including transmission properties, nonlinear optical properties, fiber gratings, photonic crystal fibers, etc. In Sect. 11.6 optical recording technology for high-density storage is described in detail, including the measurement methods for the characteristic properties of phase-change and magneto-optical materials. Finally, in Sect. 11.7 a variety of optical sensing methods are described, including the measurement of distance, displacement, three-dimensional shape, flow, temperature and, finally, the human body for bioscience and biotechnology.

This chapter begins with a section on basic technology for optical measurements. Sections 11.2–11.4 deal with advanced technology for optical measurements. Finally Sects. 11.5–11.7 discuss practical applications to photonic devices.

Corrosion is defined as the interaction between a metal and its environment that results in changes in the properties of the metal, and which may lead to significant impairment of the function of the metal. In most cases the interaction between the metal and the environment is an electrochemical reaction where thermodynamic and kinetic considerations apply. Depending on the characteristics of the corrosion system various types of corrosion occur.

In this chapter all test methods available today are described. For scientific purposes as well as investigations in the laboratory so called conventional electrochemical test methods with direct current are primarily used (Sect. 12.1). In addition, newer techniques have been proposed (Sect. 12.1) that are based on dynamic system analysis (Sect. 12.2.1) or that allow study of corrosion processes in situ with spatial resolution down to 20 μm (Sects. 12.2.2 and 12.2.3). In the following sections a distinction has been made between testing for performance of corrosion protection measures such as inhibitors (Sect. 12.8) and testing that focuses on specific types of corrosion. In this context it is advisable to differentiate between corrosion without (Sect. 12.4) and with mechanical loading (Sect. 12.5) including hydrogen-assisted cracking (Sect. 12.8) which has some similarities to stress corrosion. High-temperature corrosion (Sect. 12.6) has a different mechanistic background than electrolytic corrosion because it is a corrosion process at a metal/gas or metal/salt interface. Exposure and on-site testing (monitoring) require specific considerations in the design of test facilities, probes and the interpretation of results (Sect. 12.4).

Another important source of information regarding corrosion testing is that edited by Baboian [12.1].

Almost all mechanical systems, artificial or natural, involve the relative motion of solid components. Wherever two surfaces slide or roll against each other, there will be frictional resistance, and wear will occur. The response of materials to this kind of interaction, often termed tribological, depends not only on the precise nature of the materials, but also on the detailed conditions of the contact between them and of the motion. Friction and wear are system responses, rather than material properties. The measurement of tribological behavior therefore poses particular challenges, and a keen awareness of the factors that influence friction and wear is essential.

This chapter provides definitions of the key concepts in Sect. 13.1, and provides a rationale for the design and selection of test methods in Sect. 13.2. Various standard and other tribological test methods are comprehensively reviewed in Sect. 13.3, which is followed by descriptions of methods used for the quantitative assessment of both friction (Sect. 13.4) and wear (Sect. 13.5). Methods used for characterizing worn surfaces and wear debris are addressed in Sect. 13.6.

Materials as constituents of products or components of technical systems rarely exist in isolation and many must cope with exposure in the natural world. This chapter describes methods that simulate how a material is influenced through contact with living systems such as microorganisms and arthropods. Both unwanted and desirable interactions are considered. This biogenic impact on materials is intimately associated with the environment to which the material is exposed (Materials-Environment Interaction, Chap. 15). Factors such as moisture, temperature and availability of food sources all have a significant influence on biological systems. Corrosion (Chap. 12) and wear (Chap. 13) can also be induced or enhanced in the presence of microorganisms. Section 14.1 introduces the categories between desired (biodegradation) and undesired (biodeterioration) biological effects on materials. It also introduces the role of biocides for the protection of materials. Section 14.2 describes the testing of wood as a building material especially against microorganisms and insects. Section 14.3 characterizes the test methodologies for two other groups of organic materials, namely polymers (Sect. 14.3.1) and paper and textiles (Sect. 14.3.2). Section 14.4 deals with the susceptibility of inorganic materials such as metals (Sect. 14.4.1), concrete (Sect. 14.4.2) and ceramics (Sect. 14.4.3) to biogenic impact. Section 14.5 treats the testing methodology concerned with the performance of coatings and coating materials. In many of these tests specific strains of organisms are employed. It is vital that these strains retain their ability to utilize/attack the substrate from which they were isolated, even when kept for many years in the laboratory. Section 14.6 therefore considers the importance of maintaining robust and representative test organisms that are as capable of utilizing a substrate as their counterparts in nature such that realistic predictions of performance can be made.

There is no usage of materials without interaction with the environment. Material–environment interactions are relevant for all types of materials, be they of inorganic or organic in origin. Interactions with the environment can cause damage to materials but also might lead to an improvement of materials properties (e.g. oxidative passivation of aluminium or patina formation on copper surfaces). Interactions with the environment might also occur prior to the usage of materials, i.e. in the production phase. For example, before steel can be used for manufacturing of metal products, iron ore has to be extracted and processed.

The impact of the environment on the processes of the materials cycle (Fig. 1.15) will be discussed in Sect. 15.1.1 of this chapter. An important material–environment interaction, especially for inorganic materials, is corrosion, which has already been addressed in Chap. 12. Also the biological impact on organic and inorganic materials can be manifold and are presented in Chap. 14. Environmental mechanisms that impair the functioning of organic polymeric materials – such as weathering, ultraviolet (UV) radiation, moisture, temperature and high-pH environments – are the topics of Sect. 15.1.2. The influence of materials on the indoor climate and measurement methods to characterize emissions from materials are treated in Sect. 15.2. Fire exhibits a drastic impact on materials; methods to characterize the flammability and fire behavior of materials are discussed in Sect. 15.3.

The performance of materials – as constituents of the components of engineering systems – is essential for the functionality of engineering systems in all branches of technology and industry. Instrumental for characterizing the performance of materials are In this chapter the following experimental and theoretical methods for performance control and condition monitoring are compiled.

This chapter gives an overview of the molecular dynamics (MD) simulation method. In the first section, the basics techniques of MD will be introduced so that the reader is able to start actual calculations. In the following three sections, several applications of MD simulation, some adapted for actual materials and others concerned with idealized model systems, will be presented. In the second section, a simulation study of diffusionless transformations such as the martensitic transformation and solid-state amorphization is presented. Analysis of amorphous and crystalline structures is described in Chap. 5 in this handbook. MD calculations of the processes involved in the preparation of amorphous alloys by rapid solidification as well as annealing processes in these alloys are discussed in the third section. In the last section, the investigation of atomic diffusion processes in liquid and solid (crystalline and amorphous) phases by MD simulation is explored. Readers may also refer to Chap. 7 concerning atomic diffusion processes in materials.

Constitutive models play an important role when characterizing structural materials in order to evaluate their thermomechanical behavior. The experimental characterization of materials (using techniques discussed in Part C of this Handbook) involves measuring and controlling macroscopic variables such as force, displacement and temperature. Concise models are also of great use when characterizing the continuous media used to create structural materials, because phenomenological modeling can be carried out regardless of the internal material structure. This continuum modeling usually successfully describes the behavior of various classes of material under complex boundary conditions.

This chapter presents phenomenological constitutive models from both macroscopic and microscopic viewpoints:

Finite element methods (FEM) and finite difference methods (FDM) are numerical procedures for obtaining approximated solutions to boundary-value or initial-value problems. They can be applied to various areas of materials measurement and testing, especially for the characterization of mechanically or thermally loaded specimens or components. (Experimental methods for these fields have been treated in Chaps. 7 and 8.)

The principle is to replace an entire continuous domain of a body of interest by a number of subdomains in which the unknown function is represented by simple interpolation functions with unknown coefficients. Thus, the original boundary-value problem with an infinite number of degrees of freedom is converted into a problem with a finite number of degrees of freedom approximately.

Phase diagrams offer various areas of materials science and technology indispensable information for the comprehension of the properties of materials. The microstructure of solid materials is generally classified according to the size of the constituents – for example, at the electron, atomic, or granular level (Sect. 1.3). Accordingly, fundamental principles like quantum mechanics, statistical mechanics, or thermodynamics are applied individually to describe the physical properties. Phases are important features of material because they characterize homogeneous aggregations of matter with respect to chemical composition and uniform crystal structure. The various functions of a material are closely related to the phases and structures of the materialʼs composition. Therefore, to develop a material with a maximum level of desired functions, it is essential to undertake design of the structure in advance.

Phase diagrams are composed by means of experimental measurements, as well as statistical thermodynamic analysis. The construction of phase diagram calculations based on experiments and thermodynamic analysis are generally referred to as the calculation of phase diagrams (CALPHAD) approach [20.1]. This method provides a very accurate understanding of the properties originating in the macroscopic character of the material under study.

This chapter is organized in three parts: for metastable phase equilibria in the Fe–Be,

and Co–Al binary systems are shown.

The term phase field has recently become known across many fields of materials science. The meaning of phase field is the spatial and temporal order parameter field defined in a continuum-diffused interface model. By using the phase field order parameters, many types of complex microstructure changes observed in materials science are described effectively. This methodology has been referred to as the phase field method, phase field simulation, phase field modeling, phase field approach, etc. In this chapter, the basic concept and theoretical background for the phase field approach is explained in Sects. 21.1 and 21.2. The overview of recent applications of the phase field method is demonstrated in Sects. 21.3 to 21.6.

Phase field models have been successfully applied to various materials processes including solidification, solid-state phase transformations and microstructure changes. Using phase field methodology, one can deal with the evolution of arbitrary morphologies and complex microstructures without explicitly tracking the positions of interfaces. This approach can describe different processes such as diffusion-controlled phase separation and diffusionless phase transition within the same formulation. It is rather straightforward to incorporate the effect of coherency and applied stresses, as well as electrical and magnetic fields.

Since phase field methodology can model complex microstructure changes quantitatively, it will be possible to search for the most desirable microstructure using this method as a design simulation, i.e., through computer trial-and-error testing. Therefore, the most effective strategy for developing advanced materials is as follows. First, we elucidate the mechanism of microstructure changes experimentally, then we model the microstructure evolutions using the phase-field method based on the experimental results, and finally we search for the most desirable microstructure while simultaneously considering both the simulation and experimental data.

In the general overview on materials and their characteristics, outlined in Sect. 1.3, it has been stated that materials and their characteristics result from the processing of matter. Thus, condensed matter physics is one of the fundamentals for the understanding of materials. The Monte Carlo Method, which is a powerful method in this respect, is presented in this final chapter of the Handbookʼs Part E on Modelling and Simulation Methods as follows:

First, the principles of this simulation technique are introduced

Second, the application of the Monte Carlo Method is explained in considering selected areas of materials science.