This article provides an overview of the adoption of additively manufactured materials in dentistry. It discusses the practical workflows of a three-dimensional printing technology, vat photopolymerization. Three subgroups of the vat photopolymerization process are laser beam or classic stereolithography apparatus (SLA), direct light processing, and liquid-crystal-display-masked SLA. The article covers two subgroups of 3D printing resins-based appliances, namely intraoral and extraoral appliances. Information on various types of dental appliances and the fabrication of in-office appliances is provided. The article also reviews fourth-dimension printing and discusses the applications of the personalized care model in medicine and dentistry.

Thermal inspection comprises all methods in which heat-sensing devices or substances are used to detect irregular temperatures. Inspection of workpieces can be used to detect flaws and undesirable distribution of heat during service. Though there are several methods of thermal inspection and many types of temperature-measuring devices and substances, this article focuses only on thermography, which is the mapping of isotherms, or contours of equal temperature, over a test surface, and on thermometry, which is the measurement of temperature. Thermography techniques can be classified as contact thermographic methods using cholesteric liquid crystals, thermally quenched phosphors, and heat-sensitive paints, and noncontact techniques using hand-held infrared scanners, high-resolution infrared imaging systems, and thermal wave interferometer systems. Contact thermometric inspection devices include bolometers, thermocouples, thermopiles, and meltable substances, whereas radiometers and pyrometers come under the noncontact category.

Ultrasonic inspection is a nondestructive method in which beams of high-frequency acoustic energy are introduced into a material to detect surface and subsurface flaws, to measure the thickness of the material, and to measure the distance to a flaw. This article provides a detailed account of ultrasonic flaw detectors, including ultrasonic transducers and types of search units and couplants. The article describes pulse-echo and transmission inspection methods and data interpretation. The general characteristics of ultrasonic waves and the factors influencing ultrasonic inspection are also addressed. The article concludes with a review of the advantages and disadvantages of ultrasonic inspection compared with other methods applications of the technique.

This article is a compilation of abbreviations, symbols, and tradenames for terms related to the properties, selection, processing, and applications of the most widely used nonmetallic engineering materials.

Visual inspection (VI) is the oldest inspection technique man has used as a quality-control tool to evaluate products, assess their final form in terms of fabrication accuracy and external features based on experience, and decide on their acceptance or rejection. This article discusses the basic principles of visual inspection in terms of direct visual examination and indirect visual examination as well as advantages and limitations of visual inspection. It reviews the factors affecting the effectiveness of VI as a nondestructive testing (NDT): lighting conditions of observation, condition of surface under inspection, physical state/condition of inspector, proper training of personnel and level of expertise, and knowledge of applicable standards. The article provides schematic illustrations of rigid borescopes, fiberscopes, and videoscopes. It concludes with a discussion on automated optical inspection systems.

Gallium-base components can be found in a variety of products ranging from compact disk players to advanced military electronic warfare systems, owing to the factor that it can emit light, has a greater resistance to radiation and operates at faster speeds and higher temperatures. This article discusses the uses of gallium in optoelectronic devices and integrated circuits and applications of gallium. The article discusses the properties and grades of gallium arsenide and also provides information on resources of gallium. The article talks about the recovery techniques, including recovery from bauxite, zinc ore and secondary recovery process and purification. The article briefly describes the fabrication process of gallium arsenide crystals. Furthermore, the article gives a short note on world supply and demand of gallium and concludes with research and development on gallium arsenide integrated circuits.

This article introduces various techniques commonly used in the characterization of semiconductors, namely single-crystal, polycrystalline, amorphous, oxide, organic, and low-dimensional semiconductors and semiconductor devices. The discussion covers material classification, fabrication methods, sample preparation, bulk/elemental characterization methods, microstructural characterization methods, surface characterization methods, and electronic characterization methods.

This article begins with the one-component, or unary, diagram for magnesium. The diagram shows what phases are present as a function of the temperature and pressure. When two metals are mixed in the liquid state to produce a solution, the resulting alloy is called a binary alloy. The article describes the various types of solid solutions such as interstitial solid solutions and substitutional solid solutions. Free energy is important because it determines whether or not a phase transformation is thermodynamically possible. The article discusses the thermodynamics of phase transformations and free energy, as well as kinetics of phase transformations. It concludes with a description of solid-state phase transformations that occur when one or more parent phases, usually on cooling, produces a phase or phases.

This article reviews the applications of traditional glasses in architecture, transportation, construction, houseware, containers, and fibers. It also describes uses of specialty glasses for aerospace and military applications, biomedical and dental applications, chemical-resistant applications, lighting, information display, electronic processing and electronic devices, optical and ophthalmic products, and communications equipment.

Rapid solidification is a tool for modifying the microstructure of alloys that are obtained by ordinary casting. This article describes the fundamentals of the four microstructural changes, namely, microsegregation, identity of the primary phase, identity of the secondary phase, and the formation of noncrystalline phases. It considers three factors to understand the fundamentals of these changes: heat flow, thermodynamic constraints/conditions at the liquid-solid interfaces, and diffusional kinetics/microsegregation. These factors are described in detail.

This article discusses the three different modeling approaches for grain structures formed during solidification of metallic alloys: direct modeling of dendritic structure, direct modeling of grain structure, and indirect modeling of grain structure. The main construction bases, the scale at which it applies, and the mathematical background are presented for each modeling approach. The article concludes with a table that presents a comparison of the main inputs/outputs, approximations, numerical methods, kinetics laws, and applications for the three approaches to modeling of dendritic grain solidification.

This article illustrates the equilibrium phase diagram for an aluminum-silicon system, showing the metastable extensions of liquidus and solidus lines. It describes the classification and microstructure of the aluminum-silicon eutectic. The article presents the theories of solidification and chemical modification of the aluminum-silicon eutectic.

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 an overview of the types, properties, and applications of traditional and advanced ceramics and glasses. Principal product areas for traditional ceramics include whitewares, glazes, porcelain enamels, structural clay products, cements, and refractories. Advanced ceramics include electronic ceramics, optical ceramics, magnetic ceramics, and structural ceramics.

This article is a compilation of definitions of terms related to materials characterization techniques.

Nondestructive inspection (NDI) methods for cast iron are used to ensure that the parts supplied perform as required by the purchaser. This article focuses on the principal nondestructive methods used to inspect for anomalies in cast irons and to determine if the volume, shape, size, or number of these anomalies exceeds the maximum allowed by the purchaser. The nondestructive methods include visual inspection, dimensional inspection, liquid penetrant inspection, magnetic-particle inspection, eddy-current inspection, radiographic inspection, ultrasonic inspection, resonant testing, and leak testing. The technique, strengths, and weaknesses of each of the nondestructive methods are also discussed.

Ultrasonic inspection is a family of nondestructive methods in which beams of high-frequency mechanical waves are introduced into materials, using transducers, for the detection and characterization of both surface and subsurface anomalies and flaws in the material. This article describes the basic equipment in ultrasonic inspection systems, and lists the advantages and disadvantages of these systems. It discusses the applications of ultrasonic inspection and also the general characteristics of ultrasonic waves in terms of wave propagation, longitudinal waves, transverse waves, surface waves, and lamb waves. The article reviews the major variables in ultrasonic inspection, including frequency, acoustic impedance, angle of incidence, and beam intensity. It discusses the attenuation of ultrasonic beams and provides information on the pulse-echo and transmission methods for implementing ultrasonic inspection.

This article is a compilation of terms and definitions related to materials characterization.