Premanent magnet refers to solid materials that have sufficiently high resistance to demagnetizing fields and sufficiently high magnetic flux output to provide useful and stable magnetic fields. Permanent magnet materials include a variety of alloys, intermetallics, and ceramics. This article discusses the composition, properties, and applications of permanent magnetic materials, such as hysteresis alloys used in motors. It primarily focuses on the stability of magnetic fields that influences reversible and irreversible losses in magnetization with time, and the choice of magnet material, component shape and magnetic circuit arrangement.

Superconductivity has been found in a wide range of materials, including pure metals, alloys, compounds, oxides, and organic materials. Providing information on the basic principles, this article discusses the theoretical background, types of superconductors, and critical parameters of superconductivity. It discusses the magnetic properties of selected superconductors and types of stabilization, including cryogenic stability, adiabatic stability, and dynamic stability. The article also focuses on alternating current losses in superconductors, including hysteresis loss, penetration loss, eddy current loss, and radio frequency loss. Furthermore, the article describes the flux pinning phenomenon and Josephson effects.

Niobium-titanium alloys (NbTi) became the superconductors of choice in the early 1960s, providing a viable alternative to the A-15 compounds and less ductile alloys of niobium-zirconium. This can be attributed to the relative ease of fabrication, better electrical properties, and greater compatibility with copper stabilizing materials. This article discusses the ramifications of design requirements, selection criteria and processing methods of superconducting fibers and matrix materials. It provides information on the various steps involved in the fabrication of superconducting composites, including assembly, welding, isostatic compaction, extrusion, wire drawing, twisting, and final sizing. The article also provides a detailed account of the properties and applications of NbTi superconducting composites.

This article discusses the chief magnetic characteristics of permanent magnet materials. It provides a detailed description on nominal compositions; principal magnet designations; magnetic, physical, and mechanical properties; selection criteria; and applications of the permanent magnet materials, which include magnet steels, magnet alloys, alnico alloys, platinum-cobalt alloys, cobalt and rare-earth alloys, hard ferrites, iron-chromium-cobalt alloys, and neodymium-iron-boron alloys.

Superconductors are materials that exhibit a complete disappearance of electrical resistivity on lowering the temperature below the critical temperature. A superconducting material must exhibit perfect diamagnetism, that is, the complete exclusion of an applied magnetic field from the bulk of the superconductor. Superconducting materials that have received the most attention are niobium-titanium superconductors (the most widely used superconductor), A15 compounds (in which class the important ordered intermetallic Nb3Sn lies), ternary molybdenum chalcogenides (Chevrel phases), and high-temperature ceramic superconductors. This article provides an overview of basic principles of superconductors and the different classes of superconducting materials and their general characteristics.

This article reviews the phase diagrams, alloy with third element additions, layer growth, critical current density, and matrix materials of A15 superconductors. It describes the production methods of tape conductors (chloride deposition, and surface diffusion) and multifilamentary wires (rod process, modified jelly roll process, niobium tube process, in-situ process, powder metallurgy process, and jelly roll method). The article focuses on reaction heat treatment, which is required at the end of wire processing to convert the ductile components to the desired, but brittle, superconductor. Finally, it discusses the applications of A15 superconductors in commercial magnets, power generation, power transmission, high-energy physics, and fusion.

Ceramic materials serve important insulative, capacitive, conductive, resistive, sensor, electrooptic, and magnetic functions in a wide variety of electrical and electronic circuitry. This article focuses on various applications of advanced ceramics in both electric power and electronics industry, namely, dielectric, piezoelectric, ferroelectric, sensing, magnetic and superconducting devices.

This article discusses the ferromagnetic properties of soft magnetic materials, explaining the effects of impurities, alloying elements, heat treatment, grain size, and grain orientation on soft magnetic materials. It describes the types of soft magnetic materials, which include high-purity iron, low-carbon irons, silicon (electrical) steels, nickel-iron alloys, iron-cobalt alloys, ferritic stainless steels, amorphous metals, and ferrites (ceramics). Finally, the article provides a short note on alloys for magnetic temperature compensation.

Power sources are apparatuses that are used to supply current and voltages that are suitable for particular welding processes. This article describes power sources for arc welding, resistance welding, and electron-beam welding. The more-common welding processes that use constant-current and constant-voltage power sources are listed in a table. The article describes the open-circuit voltage characteristics and power source control methods. The control methods employ either pulse width modulation (PWM) or frequency modulation (FM).

Powder metallurgy (PM) techniques are effective in making magnetically soft components for use in magnetic part applications. This article provides an account of the factors affecting magnetism, permeability, and hysteresis losses. It includes information on the magnetic properties of PM materials that are used in the magnetic part applications, namely, pure iron, phosphorus irons, ferritic stainless steels, 50 nickel-50 iron, and silicon irons. The article describes the factors that affect and optimize magnetic properties. It contains a table that lists the magnetic properties possible in metal injection molding parts. The article also discusses ferromagnetic cores used in alternating current applications and some permanent magnets, such as rare earth-cobalt magnets and neodymium-iron-boron (neo) magnets.

Designing of induction heating, or, generally electro technological installations, requires mathematical modeling for solving problems related to various physical phenomena, including electromagnetic (EM), thermal, mechanical, fluidic, and metallurgical fields. This article focuses on the solution of Maxwell's equations (MEs) and provides some basic information regarding the heat transfer and fluid equations, because these physical phenomena usually are strongly coupled to magnetic and electric fields. The solutions are usually obtained by using specific numerical methods such as finite-element method, finite difference method, boundary-element method or volume-integral method, and direct-solution method. The article also discusses the typical structure of commercial codes (preprocessor, solver, and postprocessor) to solve field problems mainly in finite-element method.

Rare earth metals belong to Group IIIA of the periodic table that includes scandium, yttrium, and the lanthanide elements which are lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. This article classifies the rare earth metals based on their purity level, which are designated as research grades (>99.8% pure) and commercial grades (95% - 98% pure), and describes the preparation and purification, including solid-state electrolysis. It further discusses physical, mechanical, and chemical properties; electronic configurations; crystal structures, and explains the alloy forming characteristics of rare earth elements. The article concludes by describing the various applications of commercial-grade rare earth elements and commercial alloys, which incorporates rare earth elements as additives.

Magnetically soft materials are characterized by their low coercivity, an essential requirement for irons and steels selected for any application involving electromagnetic induction cycling. This article provides information on ferromagnetic material properties and how they are affected by impurities, alloying additions, heat treatment, residual stress, and grain size. It also describes classification and testing methods for magnetically soft materials such as high-purity iron, low-carbon steels, silicon steels, iron-aluminum alloys, nickel-iron alloys, iron-cobalt alloys, ferrites, and stainless steels. The article also addresses corrosion resistance and provides insights on the selection of alloys for power generation applications, including motors, generators, and transformers. A short note on the design and fabrication of magnetic cores is also included.

This article briefly describes the capabilities of gas chromatography/mass spectrometry, which is used to qualitatively and quantitatively determine organic (and some inorganic) compound purity and stability and to identify components in a mixture. The discussion covers in more detail gas chromatography/mass spectrometry (GC/MS) instrumentation, interpreting mass spectra, GC/MS methodology, and GC/MS advances. Sample preparation, which is very important in GC/MS to avoid erroneous data and to minimize maintenance and troubleshooting of the instrument, is also discussed. Further, the article highlights the state of the art in the MS detector technology.

Gas analysis by mass spectrometry, or gas mass spectrometry, is a general technique using a family of instrumentation that creates a charged ion from a gas phase chemical species and measures the mass-to-charge ratio. This article covers gas analysis applications that do not use chromatographic separation to physically isolate components of the sample prior to analysis. It is intended to provide an understanding of gas analysis instrumentation and terminology that will help make informed decisions in choosing an instrument and methodology appropriate for the data needed. Mass-analyzer technologies for gas mass spectrometry, namely quadrupole mass filters, magnetic sector mass filters, and time-of-flight mass analyzers are covered. Common factors to consider in choosing an analyzer for static or continuous gas measurement are also described. In addition, the article presents some examples of applications of gas mass spectrometry.

Metal powders are used as fuels in solid propellants, fillers in various materials, such as polymers or other binder systems, and for material substitution. They are also used in food enrichment, environmental remediation market, and magnetic, electrical, and medical application areas. This article reviews some of the diverse and emerging applications of ferrous and nonferrous powders. It also discusses the functions of copier powders and the processes used frequently for copier powder coating.

The discovery of the high-critical-temperature oxide superconductors has accelerated the interest for superconducting applications due to its higher-temperature operation at liquid nitrogen or above and thus reduces the refrigeration and liquid helium requirement. It also permits usage of the high-critical-temperature oxides in magnets or power applications in high-current-carrying wire or tape with acceptable mechanical capability. This article discusses the powder techniques mainly based on the production of an oxide powder precursor, which is then subjected to various processing, including powder-in-tube processing, vapor deposition processing, and melt processing. It further discusses the microstructural, anisotropy and weak link influences on these processes.

Spinodal transformation is a phase-separation reaction that occurs from kinetic behavior. This article discusses the theory of spinodal decomposition, and outlines the methods used in the characterization of spinodal structures in metal matrices.

Electron spin resonance (ESR), or electron paramagnetic resonance (EPR), is an analytical technique that can extract a great deal of information from any material containing unpaired electrons. This article explains how ESR works and where it applies in materials characterization. It describes a typical ESR spectrometer and explains how to tune it to optimize critical electromagnetic interactions in the test sample. It also identifies compounds and elements most suited for ESR analysis and explains how to extract supplementary information from test samples based on the time it takes electrons to return to equilibrium from their resonant state. Two of the most common methods for measuring this relaxation time are presented as are several application examples.

This article describes the test techniques that are available for monitoring crack initiation and crack growth and for obtaining information on fatigue damage in test specimens. These techniques include optical methods, the compliance method, electric potential measurement, and gel electrode imaging methods. The article discusses the magnetic techniques that are primarily used as inspection techniques for detecting fatigue cracks in structural components. It details the principles and operation procedures of the liquid penetrant methods, positron annihilation techniques, acoustic emission techniques, ultrasonic methods, eddy current techniques, infrared techniques, exoelectron methods, and gamma radiography. The article explains the microscopy methods used to determine fatigue crack initiation and propagation. These include electron microscopy, scanning tunneling microscopy, atomic force microscopy, and scanning acoustic microscopy. The article also reviews the X-ray diffraction technique used for determining the compositional changes, strain changes, and residual stress evaluation during the fatigue process.