This article discusses postconsumer plastics recyclate quantities, the classification of plastics recycling into primary, secondary, tertiary, and quaternary categories, and how the life cycle of plastics is affected by recycling. The recycling processes of polyethylene terephthalate (PET), which accounts for the largest percentage of plastic recycling, high-density polyethylene (HDPE) plastics, the other large-volume plastic recyclate, as well as vinyl resins and polycarbonate resins are described. The life cycle of plastics has four phases: poly formation, part fabrication, product service, and disposal. Landfilling is still the primary method of final disposal, and incineration is another option, but recycling has become a viable alternative. The article presents a comparison between secondary and tertiary recycling.

Ores, which consist of the primary valuable mineral, predominant gangue content, valuable by-products, and detrimental impurities, are extracted and directed to mineral processing. This article describes the mineral processing facilities, such as crushers, grinders, concentrators, separators, and flotation devices that are used for particle size reduction, separation of particles according to their settling rates in fluids and dewatering of concentrate particles. It explains the basic principles, flow diagrams, ore concentrate preparation methods, and equipment of major types of metallurgical processes, including pyrometallurgical, hydrometallurgical, and electrometallurgical processes.

Heat treatment of aluminum alloys is assessed by various quality-assurance methods that include metallographic examination, hardness measurements, mechanical property tests, corrosion-resistance tests, and electrical conductivity testing. The use of hardness measurements in the quality assurance of heat treated aluminum products is effectively used in conjunction with the measurement of surface electrical conductivity. This article provides a detailed discussion of the error sources in eddy-current conductivity measurements. It also presents useful information on the variation of electrical conductivity of alloy 2024 samples as a function of aging time at different isothermal holding temperatures.

This article introduces the fundamental concepts of chemical thermodynamics and chemical kinetics in describing presolidification phenomena. For metallurgical systems, the most important thermodynamic variables are enthalpy and Gibbs free energy. A qualitative demonstration of the interrelationship between phase diagrams and thermodynamics is presented. The article discusses processes that generally limit the rates of chemical processes. These include nucleation of the product phase and interphase mass transport. The article provides a discussion on the dissolution of alloy with melting point lower than bath temperature and dissolution of alloy that is solid at bath temperatures.

This article discusses the process considerations and deposit properties of nickel plating. It describes the Watts solution and the anode materials used. The article focuses on the nickel plating processes used for decorative, engineering, and electroforming purposes. It provides information on the quality control of nickel plating. It concludes with a review of the environmental, health, and safety considerations associated with nickel plating.

This article provides a brief account of glow discharge mass spectrometry (GDMS) for direct determination of trace elements in solid samples and for fast depth profiling in a great variety of innovative materials. It begins by describing the general principles of GDMS. This is followed by a discussion on the various components of a GDMS system as well as commercial GDMS instruments. A description of processes involved in specimen preparation and cleaning in GDMS is then presented. Various problems pertinent to multielemental calibrations in GDMS are discussed along with measures to overcome them. The article further provides information on the processes involved in the analytical setup of parameters in GDMS, covering the steps involved in the analysis of GDMS data. It ends with a section on the application and interpretation of GDMS in the metals industry.

Ceramic and glass manufacturers take environmental regulations into consideration during all stages of the product cycle, from research and development to purchasing, processing, end use, and disposal. Ceramic and glass products are finding application in the construction industry and as raw materials for other processes. This article describes the recycling of in-process scrap and industrial wastes (fly ash, red mud, metallurgical waste, and other waste products), and applications of these recycled products. It focuses on environmental regulations such as Resource Conservation and Recovery Act and Clean Air Act. The Clean Air Act requires all states to meet minimum emissions standards for nitrogen-oxygen compounds, volatile organic compounds, and carbon monoxide.

This article describes the paint systems generally used to protect steel structures, steel sheet, and bridges from corrosion, and how they deter corrosion. It provides a discussion on the basic design criteria of steel structures for corrosion protection. The article also explains the differences between prepaint and postpaint, and the steps involved in prepaint processing of steel. It presents the selection guideline for paint system evaluation. The advantages of corrosion protection are also discussed.

Tantalum is one of the most versatile corrosion-resistant metals known. The outstanding corrosion resistance and inertness of tantalum are attributed to a very thin, impervious, protective oxide film that forms on exposure of the metal to slightly anodic or oxidizing conditions. This article provides a discussion on the mechanism of corrosion resistance and on the behavior of tantalum in different corrosive environments, namely, acids; salts; organic compounds; reagents, foods, and pharmaceuticals; body fluids and tissues; and gases. It contains several tables that summarize the effects of acids, salts, and miscellaneous corrosive reagents on tantalum and applications for tantalum equipment in chemical, pharmaceutical, and other industries. Finally, the article presents a discussion on hydrogen embrittlement, the galvanic effects, and cathodic protection of tantalum and describes the corrosion resistance of different types of tantalum-base alloys.

This article discusses the general characteristics, primary and secondary fabrication methods, product forms, and corrosion resistance of zirconium and hafnium. It describes the physical metallurgy of zirconium and its alloys, providing details on allotropic transformation and anisotropy that profoundly influences the engineering properties of zirconium and its alloys. Tables listing the values for chemical composition and tensile properties for nuclear and nonnuclear grades of zirconium are also provided.

This article addresses two issues on thermodynamics, namely, the calculation of solubility lines and the calculation of the activity of various components. It discusses alloying elements in terms of their influence on the activity of carbon. The article describes the desulfurization and deoxidation of cast iron and steel. It illustrates the thermodynamics of the iron-carbon system and the iron-silicon system. The article examines solubility and saturation degrees of carbon in multicomponent iron-carbon systems. One of the main applications of the thermodynamics of the iron-carbon system is the calculation of structure-composition correlations. The article concludes with information on the structural diagrams, such as Maurer diagram and Laplanche diagram, for cast iron.

Electrodeposits of cadmium are used to protect steel and cast iron against corrosion. This article provides an overview of the surface preparation of, and brighteners used in, cyanide baths. It focuses on the anode system, current density, deposition rates, and bath temperature of cadmium plating with attention to the materials of construction and equipment used. The article provides a description of the selection of plating method with examples, applications, and several postplating processes of cadmium plating.

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.

Vacuum induction melting (VIM) is often done as the primary melting operation followed by secondary melting (remelting) operations. This article presents the process description of VIM and illustrates potential processing routes for products, which are cast from VIM ingots or electrodes. It describes the VIM refinement process, which includes removal of trace elements, nitrogen and hydrogen degassing, and deoxidation. The article concludes with information on production of nonferrous materials by VIM.

The design and analysis of aerospace and industrial composite components and assemblies requires a detailed knowledge of materials properties, which, in turn, depend on the manufacturing, machining, and assembly methods used. This article, through several tables and graphs, provides the mechanical properties, physical properties, and service characteristics of representative composite fiber-resin combinations, including thermoplastic matrix composites such as thermoplastic polyester resins, thermoplastic polyamide resins, and thermoplastic polysulfone resins, and thermoset matrix composites such as thermoset polyester resins, thermoset phenolic resins, thermoset epoxy resins, thermoset polyimide resins, and thermoset bismaleimide resins.

Nontraditional finishing processes include electrochemical machining (ECM), electrodischarge machining (EDM), and laser beam machining. These processes belong to nonabrasive finishing methods where surface generation occurs with an insignificant amount of mechanical interaction between the processing tool and the workpiece surfaces. This article provides information on the equipment used, applications, process capabilities, and limitations of ECM and EDM.

This article describes high-performance liquid chromatography and ultra-high-performance liquid chromatography that are used to separate and quantify the chemical components in any sample that can be dissolved in a liquid. This includes pharmaceutical drugs, medicinal plant extracts, food constituents, flavors, fragrances, industrial chemicals, pesticides, and pollutants. Readers are introduced to the most commonly employed mode, reverse-phase chromatography, with examples and an exclusive focus on commercially available instruments and consumables. The discussion covers the various processes involved in liquid chromatography, including assessing a separation of sample components, adjusting the mobile phase, choosing the stationary phase, optimizing a separation, preparing real samples, and analyzing complex samples.

This article provides a detailed account of the various alkaline and acid plating baths used for electrolytic copper plating. Dilute cyanide and Rochelle cyanide baths, high-efficiency sodium and potassium cyanide baths, alkaline noncyanide copper plating baths, and alkaline copper pyrophosphate baths, are discussed. The article reviews acid plating baths such as copper sulfate bath and copper fluoborate bath. It also presents information on the surface preparation considerations, bath composition, and operating variables of copper plating as well as the equipment used.

This article provides a detailed discussion on the types of furnace atmospheres required for heat treating. These include generated exothermic-based atmospheres, generated endothermic-based atmospheres, generated exothermic-endothermic-based atmospheres, generated dissociated-ammonia-based atmospheres, industrial gas nitrogen-base atmospheres, argon atmospheres, and hydrogen atmospheres. Atmospheres for backfilling, partial pressure operation, and quenching in vacuum are also discussed. Furnace atmospheres constitute four major groups of safety hazards in heat treating: fire, explosion, toxicity, and asphyxiation. The article reviews the fundamentals of principal gases and vapors. It describes how the evaluation of the atmospheric requirements of heat treating furnaces is influenced by factors such as cost of operation and capital investment.