This article provides a detailed account of X-ray spectroscopy used for elemental identification and determination. It begins with an overview of the operating principles of X-ray fluorescence (XRF) spectrometer, as well as a comparison of the operating principles of wavelength-dispersive spectrometer (WDS) and energy-dispersive spectrometer (EDS). This is followed by a discussion on the mechanism and effects of X-ray radiation, X-ray emission, and X-ray absorption. The article then discusses components used, operation, and applications of WDS and EDS. Some of the factors and processes involved in sample preparation for XRF analysis are also included. The article further provides information on the practical procedure for and the applications of WDS and EDS qualitative and quantitative analyses.

Radiography is a nondestructive-inspection method that is based on the differential absorption of penetrating radiation by the part or test piece (object) being inspected. This article discusses the fundamentals and general applications of radiography, and describes the sources of radiation in radiographic inspection, including X-rays and gamma rays. It deals with the characteristics that differentiate neutron radiography from X-ray or gamma-ray radiography. The geometric principles of shadow formation, image conversion, variation of attenuation with test-piece thickness, and many other factors that govern the exposure and processing of a neutron radiograph are similar to those for radiography using X-rays or gamma rays.

This article provides an introduction to x-ray spectrometry, and discusses the role of electromagnetic radiation, x-ray emission, and x-ray absorption. It focuses on the instrumentation of wavelength-dispersive x-ray spectrometers, and energy dispersive x-ray spectrometers (EDS) that comprise x-ray tubes, the analyzing system, and detectors. The fundamentals of EDS operation are described. The article also provides useful information on preparation of various samples, explaining the qualitative and quantitative analyses of EDS. It reviews the applications of the x-ray spectrometry.

Metal transparency and interaction with X-rays have been recognized as obvious candidate principles from which methods for in situ monitoring of solidification processes could be developed. This article describes the use of X-ray imaging-based techniques to investigate interface morphology evolution, solute transport, and various process phenomena at spatiotemporal resolutions. It discusses the three viable imaging techniques made available by synchrotron radiation for the real-time investigation of solidification microstructures in alloys. These include two-dimensional X-ray topography, two-dimensional X-ray radiography, and ultra-fast three-dimensional X-ray tomography.

This article provides a detailed account of extended x-ray absorption fine structure (EXAFS). It begins with a description of the fundamentals of EXAFS, providing information on the physical mechanism, single-scattering approximation, and multiple-scattering effects. This is followed by a discussion on the use of synchrotron radiation as an X-ray source for EXAFS. Data-reduction procedures used to extract EXAFS signals are then described. The article also provides information on the analysis of x-ray absorption near-edge structure spectrum and ends with a discussion on the unique features and applications of EXAFS.

Radiography is the process or technique of producing images of a solid material on a paper/photographic film or on a fluorescent screen by means of radiation particles or electromagnetic waves of short wavelength. This article reviews the general characteristics and safety principles associated with radiography. There are two main aspects of safety: monitoring radiation dosage and protecting personnel. The article summarizes the major factors involved in both and discusses the operating characteristics of X-ray tubes. It describes the various methods of controlling scattered radiation: use of lead screens; protection against backscatter and scatter from external objects; and use of masks, diaphragms, collimators, and filtration. The article concludes with a discussion on image conversion media, including recording media, lead screens, lead oxide screens, and fluorescent intensifying screens.

This article provides an introduction to extended x-ray absorption fine structure (EXAFS). It describes the fundamentals of EXAFS with an emphasis on the physical mechanism, the single-scattering approximation, and multiple-scattering effects. The article discusses the use of synchrotron radiation as the x-ray source for EXAFS experiments. It also describes the typical EXAFS data analysis of pure nickel at 90 K, and explains the near-edge structure analysis of vanadium. The article presents a discussion on the unique features and applications of EXAFS.

The raw materials used in thermal spray processes are a critical parameter in the finished coating because the variations in their size, morphology, chemistry, and phase composition can significantly impact coating properties. Therefore, it is important to test and characterize the raw materials. This article discusses various characterization methods for powders. Topics discussed include: methods for determining particle size and/or size distribution; powder and coating stoichiometry; particle chemistry; and phase analysis by x-ray diffraction. This article discusses the characterization of thermal spray powders which involves the determination of particle size and/or size distribution and phase analysis by x-ray diffraction. It provides information on preferential volatilization and rapid solidification that influence compositional differences. Wet chemical methods, spectographic analysis, and atomic absorption spectrometry are also discussed.

X-ray imaging is a nondestructive evaluation (NDE) technique in which x-ray waves interact with an observed sample to generate images from which information about the examined object can be derived. This article discusses x-ray imaging systems and applications, presenting the history and role of x-ray imaging. It describes different setups that are implemented at various facilities that conduct x-ray imaging for different types of metal AM processes. The article also discusses different types of dynamics observed in experimental metal AM processes using x-ray imaging systems. It presents the future of x-ray imaging in metal AM.

Computed tomography (CT) is an imaging technique that generates a three-dimensional (3-D) volumetric image of a test piece. This article illustrates the basic principles of CT and provides information on the types, applications, and capabilities of CT systems. A comparison of performance characteristics for film radiography, real-time radiography, and X-ray computed tomography is presented in a table. A functional block diagram of a typical computed tomography system is provided. The article discusses CT scanning geometry that is used to acquire the necessary transmission data. It also provides information on digital radiography, image processing and analysis, dual-energy imaging, and partial angle imaging, of a CT system.

X-ray topography is the general term for a family of x-ray diffraction imaging techniques capable of providing information on the nature and distribution of imperfections. This article provides a detailed account of x-ray topography techniques, providing information on the historical background and development trends in x-ray diffraction topography. The discussion covers the general principles, components of systems, and applications of x-ray topography techniques, namely conventional X-ray topographic techniques and synchrotron x-ray topographic techniques.

This article discusses various concepts of micro x-ray diffraction (XRD) used for the examination of materials in situ. The discussion covers the principles, equipment used, sample preparation procedure, considerations for calibrating a detector, steps for performing data analysis, and applications and interpretation of micro-XRD.

X-ray radiography and computed tomography (CT) are nondestructive testing (NDT) tools particularly well suited to additive manufacturing (AM). A brief overview of NDT for AM is presented in this article, including other NDT methods, followed by identifying the key advantages and requirements for x-ray radiography and CT in AM. Less widely known applications of CT are also presented, including powder characterization, the evaluation of lattice structures, surface roughness measurements, and four-dimensional CT involving interrupted (before-after) CT scans of the same parts, or even in situ scans of the same part subjected to some processing or loading conditions. The article concludes with a discussion on the limits and some guidelines for the use of x-ray and CT for various AM materials.

Digital radiography is a technique that uses digital detector arrays (linear or area) to capture an X-ray photonic signal and convert it to an electronic signal for display on a computer. This article begins with an overview of real-time radiography and provides a schematic illustration of a typical radioscopic system using an X-ray image intensifier. It discusses the advantages and limitations of real-time radiography. Computed radiography (CR) is one of the radiography techniques that utilizes a reusable detector comprised of photostimuable luminescence (PSL) storage phosphor. The article provides a schematic illustration of a typical storage phosphor imaging plate. It concludes with a discussion on the benefits of digital radiography.

This article describes the methods of X-ray diffraction analysis, the types of information that can be obtained, and its interpretation. The discussion covers the basic theories of X-rays and various types of diffraction experiments, namely single-crystal methods for polychromatic and monochromatic beams, powder diffraction methods, and the Rietveld method.

X-ray diffraction techniques are useful for characterizing crystalline materials, such as metals, intermetallics, ceramics, minerals, polymers, plastics, and other inorganic or organic compounds. This article discusses the theory of x-rays and how they are generated and detected. It also describes the crystalline nature of certain materials and how the geometry of a unit cell, and hence crystal lattice, affects the direction and intensity of diffracted x-ray beams. The article concludes with several application examples involving measurements on single and polycrystalline materials.

This article discusses the techniques and applications of synchrotron x-ray diffraction, providing information on x-ray generation, monochromation, and crystallography. X-ray diffraction techniques covered include single-crystal and powder diffraction. Some of the factors involved in the construction and development of macromolecular x-ray crystallography are also described.

Film radiography requires the development of the exposed film so that the latent image becomes visible for viewing. It describes the general characteristics of film, including speed, gradient, and graininess, and the factors affecting film selection and exposure time. The article discusses the three major inspection techniques for tubular sections, namely, the double-wall, double-image technique; the double-wall, single-image technique; and the single-wall, single-image technique. It illustrates the arrangements of penetrameters and identification markers for the radiography of plates, cylinders, and flanges. The article discusses various control methods, including the use of lead screens; protection against backscatter and scatter from external objects; and the use of masks, diaphragms, collimators, and filtration. The radiographic appearance of specific types of flaws is also discussed. The article concludes with a discussion on two methods of radiographic film processing: manual and automatic processing.