Search Results for superconducting materials, superconductivity, superconductors

This article reviews the history of superconductivity from its discovery in the early 1900s to the renewed interest in the mid-1980s spurred by the development of high-temperature superconducting devices. It identifies some of the materials in which superconductivity has been observed, including metals and alloys, compounds, and oxides, and discusses their properties as well as potential applications. The article also explains how various superconducting materials are produced and provides a foundation for understanding the basic operating principles.

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.

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.

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.

This article focuses on different thin-film deposition techniques used to make superconducting films and discusses the properties and advantages of high-critical-temperature and low-critical-temperature materials in a number of applications, including signal processing and analog electronic devices. The article gives a brief introduction on superconducting materials, substrates and buffer layers and discusses the major deposition techniques such as, electron-beam co-evaporation, sputtering from either a composite target or multiple sources and laser ablation. The article also describes the in-situ film growth techniques for producing atomic oxygen by radio frequency excitation or microwave discharge or with ozone.

Ternary molybdenum chalcogenides stands for a vast class of materials, whose general formula is MxMO6X8, where, M is a cation and X is a chalcogen (sulfur, selenium, or tellurium). Possible applications of some of these are as high field superconductors (that is, >20 T, or 200 kG). This article discusses the fabrication methods of PbMo6S8 (PMS) and SnMo6S8 (SMS), including hot processing and cold processing. It provides a short note on the superconducting properties of PMS wire filaments and their applications in processes requiring high magnetic fields, such as high-energy physics, thermonuclear fusion, and nuclear magnetic resonance.

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.

This article presents a general description of pulsed-laser deposition. It describes the components of pulsed-laser deposition equipment. The article also discusses the effects of angular distribution of materials. Finally, the article reviews the characteristics of high-temperature superconductors and ferroelectric materials.

The drawing process, one of the oldest metal forming operations, allows excellent surface finishes and closely controlled dimensions to be obtained in long products that have constant cross sections. This article discusses the basic mechanics and preparation steps of drawing. It presents an overview of the processes, equipment, dies and die materials, and lubrication associated with drawing of rod, wire, bar, and tube. The article also provides a discussion on the design considerations and manufacturing of commercial superconducting multifilamentary conductors.

Metallic glasses can be prepared by solidification of liquid alloys at cooling rates sufficient to suppress the nucleation and growth of competing crystalline phases. This article presents a historical survey of the study of metallic glasses and other amorphous metals and alloys. This includes a discussion of synthesis and processing methods, structure and morphology, and a description of the electronic, magnetic, thermodynamic, chemical, and mechanical properties of metallic glasses. In addition, the article describes the development of metallic glasses as materials for technical applications.

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.

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.

Coextrusion is defined as the simultaneous extrusion of two or more metals to form an integral product that can be carried out using conventional extrusion or drawing equipment at a temperature appropriate to the metal system being formed. This article discusses the applications, billet configurations, and metal flow modes of coextrusion. It presents the analytical studies of coextrusion: deformation energy methods, lower-bound (slab) analyses, upper-bound analyses, and finite-element analyses. These studies are used to identify the regime of material properties and process variables for which sound extrusions can be obtained. The article concludes with a discussion on the state-of-the-art of coextrusion that assists in developing process models, which accurately describe both the macroscopic and microscopic aspects of a process.

This article provides a discussion on the operation of various methods and sensors that have been used or have the potential to be used for on-line, real-time monitoring of localized corrosion. These include the electrochemical noise (ECN) method, nonelectrochemical methods, the galvanically coupled differential flow cell, galvanically coupled crevice cell, coupled multielectrode sensor, and electrochemical biofilm activity sensor.