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Series: ASM Handbook
Volume: 2
Publisher: ASM International
Published: 01 January 1990
DOI: 10.31399/asm.hb.v02.a0001089
EISBN: 978-1-62708-162-7
..., 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...
Abstract
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.
Series: ASM Handbook
Volume: 2
Publisher: ASM International
Published: 01 January 1990
DOI: 10.31399/asm.hb.v02.a0001091
EISBN: 978-1-62708-162-7
..., 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...
Abstract
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.
Series: ASM Handbook
Volume: 1
Publisher: ASM International
Published: 01 January 1990
DOI: 10.31399/asm.hb.v01.a0001050
EISBN: 978-1-62708-161-0
... strength is affected by the condition of the grain boundaries and, in particular, the grain-boundary carbide morphology and distribution. Vacuum induction melting offers more control over alloy composition and homogeneity than all other vacuum melting processes. The primary purification reaction occurring...
Abstract
The initial cast superalloy developments in the United States centered on cobalt-base materials. Nickel-base and nickel-iron-base superalloys owe their high-temperature strength potential to their gamma prime content. For polycrystalline superalloy components, high-temperature strength is affected by the condition of the grain boundaries and, in particular, the grain-boundary carbide morphology and distribution. Vacuum induction melting offers more control over alloy composition and homogeneity than all other vacuum melting processes. The primary purification reaction occurring in the process is the removal of melt contained oxygen by means of a reaction with carbon to form carbon monoxide. A number of casting processes can provide near-net shape superalloy cast parts, but essentially all components are produced by investment casting. The solidification of investment cast superalloy components is precisely controlled so that the microstructure, which ultimately determines mechanical properties, remains consistent. Heat treating cast superalloys involves homogenization and solution heat treatments or aging heat treatments.
Series: ASM Handbook
Volume: 2A
Publisher: ASM International
Published: 30 November 2018
DOI: 10.31399/asm.hb.v02a.a0006483
EISBN: 978-1-62708-207-5
...Abstract Abstract This article describes the Bayer process for the purification of alumina. The process includes four major stages: digestion, clarification, precipitation, and calcination. The article discusses the aluminum electrolytic process in terms of aluminum electrolysis cell design...
Abstract
This article describes the Bayer process for the purification of alumina. The process includes four major stages: digestion, clarification, precipitation, and calcination. The article discusses the aluminum electrolytic process in terms of aluminum electrolysis cell design, magnetohydrodynamic forces, and cathode lining. It reviews the electrochemical reactions and thermodynamics for aluminum electrolysis standard Gibbs. The article also describes the cell operations and cell stability, as well as the key indicators of cell performance. It schematically illustrates the typical costs producing aluminum in an aluminum smelter. The article also discusses various environmental issues, such as fluoride recovery; perfluorocarbons, polycyclic aromatic hydrocarbons, and sulfur emissions; spent pot lining; and development of inert anodes and CO2 emissions.
Series: ASM Handbook
Volume: 13A
Publisher: ASM International
Published: 01 January 2003
DOI: 10.31399/asm.hb.v13a.a0003587
EISBN: 978-1-62708-182-5
... with the container material. This article describes a test method performed using thermal convection loop for corrosion studies of molten salts. It discusses the purification of salts that are used in the Oak Ridge molten salt reactor experiment. The article also reviews the corrosion characteristics of nitrates...
Abstract
Molten salts, or fused salts, can cause corrosion by the solution of constituents of the container material, selective attack, pitting, electrochemical reactions, mass transport due to thermal gradients, and reaction of constituents and impurities of the molten salt with the container material. This article describes a test method performed using thermal convection loop for corrosion studies of molten salts. It discusses the purification of salts that are used in the Oak Ridge molten salt reactor experiment. The article also reviews the corrosion characteristics of nitrates/nitrites and fluoride salts with the aid of illustrations and equations.
Series: ASM Handbook
Volume: 13A
Publisher: ASM International
Published: 01 January 2003
DOI: 10.31399/asm.hb.v13a.a0003599
EISBN: 978-1-62708-182-5
...Abstract Abstract Electrochemical refining is the purification process for producing commercially pure metals from crude metals. This article describes the principles of electrochemical reactions. It discusses the physical properties of the basic components of electrochemical refining cell...
Abstract
Electrochemical refining is the purification process for producing commercially pure metals from crude metals. This article describes the principles of electrochemical reactions. It discusses the physical properties of the basic components of electrochemical refining cell. The article also explains the engineering considerations required in the refining process. Theoretical and technological principles of electrochemical refining are illustrated, with examples.
Series: ASM Handbook
Volume: 2
Publisher: ASM International
Published: 01 January 1990
DOI: 10.31399/asm.hb.v02.a0001115
EISBN: 978-1-62708-162-7
..., silicon crystals as large as 150 mm (6 in.) in diameter have been made by the floating zone method ( Ref 3 ). Vacuum Melting Zone refining of materials often is conducted in a dynamic vacuum in order to enhance the degree of purification. However, many metals—particularly those with high melting...
Abstract
The electronic microcircuit industry has placed severe demands on metal suppliers to provide metals of the highest reproducible purity attainable as a result of the constant quest for the true values of physical and chemical properties of metals. This article describes the commonly used methods for ultrapurification of metals produced by electrolytic processes, including fractional crystallization, zone refining, vacuum melting, distillation, chemical vapor deposition, and solid state refining techniques. In addition, it describes the trace element analysis and resistance-ratio test methods used to characterize purity. Tables list the values for resistance ratios of zone-refined metals and their corresponding chemical compositions, and provide an example of the detection of impurities to concentrations in the parts per billion range, utilizing a combination of the glow discharge mass spectroscopy method and Leco combustion methods.
Series: ASM Handbook
Volume: 13C
Publisher: ASM International
Published: 01 January 2006
DOI: 10.31399/asm.hb.v13c.a0004154
EISBN: 978-1-62708-184-9
..., as deposits accumulate, they restrict flow to the surface. Typical boiler deposits are largely hardness precipitates (calcium and magnesium salts) and metal oxides. The nature of these deposits is typically a function of the makeup water purification system. Hardness deposits are most common with softened...
Abstract
This article briefly describes water and steam chemistry, which influence the effect of corrosion in boilers. The appropriate control measures to prevent corrosion in boilers are also presented. The article provides a discussion on the common causes of fluid-side corrosion such as flow-accelerated corrosion, oxygen pitting, chelant corrosion, caustic corrosion, acid corrosion, organic corrosion, phosphate corrosion, hydrogen damage, and corrosion-assisted cracking.
Series: ASM Desk Editions
Publisher: ASM International
Published: 01 December 1998
DOI: 10.31399/asm.hb.mhde2.a0003169
EISBN: 978-1-62708-199-3
Abstract
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.
Book: Powder Metallurgy
Series: ASM Handbook
Volume: 7
Publisher: ASM International
Published: 30 September 2015
DOI: 10.31399/asm.hb.v07.a0006121
EISBN: 978-1-62708-175-7
... 2 O, is the main intermediate used in the production of tungsten oxide and metal powders. This compound is a result of the hydrometallurgical purification and separation of various tungsten ore concentrates and secondary raw material sources ( Ref 1 , 2 , 3 ). The key features of today's modern...
Abstract
Refractory metals are extracted from ore concentrates or scrap, processed into intermediate chemicals, and then reduced to metal, usually in powder form. This article discusses the raw materials needed and the processing steps for producing pure and alloyed refractory metal powders. The effects of processing conditions on the physical and chemical properties of tungsten, molybdenum, tantalum, niobium, and rhenium powders are reviewed.
Book: Surface Engineering
Series: ASM Handbook
Volume: 5
Publisher: ASM International
Published: 01 January 1994
DOI: 10.31399/asm.hb.v05.a0001245
EISBN: 978-1-62708-170-2
.... Decomposition products of the additives accumulate in solution with time and are removed by purification with activated carbon. In modern solutions, continuous filtration through active carbon removes deleterious decomposition products without significant removal of the addition agents themselves. Several...
Abstract
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.
Series: ASM Handbook
Volume: 9
Publisher: ASM International
Published: 01 December 2004
DOI: 10.31399/asm.hb.v09.a0003777
EISBN: 978-1-62708-177-1
... as a powder or sponge and is further purified in the solid or the liquid state. Solid-state purification occurs during sintering; liquid-state purification occurs during vacuum arc melting or electron beam melting in high vacuum. Consolidated high-purity tantalum has also been produced by the thermal...
Abstract
This article describes various procedures used in the metallographic preparation of niobium, tantalum, molybdenum, and tungsten alloys. It provides information on sectioning, grinding, mounting, polishing, and electrolytic etching as well as alternate procedures that have been used on refractory metals. The article presents and analyzes several micrographs, provides etchant formulas for various materials, and discusses the unique characteristics of rhenium and its alloys.
Series: ASM Desk Editions
Publisher: ASM International
Published: 01 November 1995
DOI: 10.31399/asm.hb.emde.a0003013
EISBN: 978-1-62708-200-6
... attention turned to the recycling of engineering (durable) plastics. Each of these materials presents unique challenges for disposal, collection, identification, separation, and purification. However, new technologies are being developed steadily, and prospects are good for increased recycling...
Abstract
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.
Series: ASM Handbook
Volume: 13C
Publisher: ASM International
Published: 01 January 2006
DOI: 10.31399/asm.hb.v13c.a0004151
EISBN: 978-1-62708-184-9
... (synthetic gas) coolers and then water quenched to remove particulates and water-soluble impurities such as NH 3 and chlorides. After quenching, H 2 S is removed in one of several commercially available gas-purification systems, for instance, the Selexol process. The purified gas is then fed to a gas...
Abstract
This article focuses on high-temperature corrosion in synthetic gas (syngas) coolers. Extensive laboratory corrosion studies on both model and commercial alloys are summarized. The article describes the material selection criteria for long-term performance of materials in service. It provides information on the fuels with chlorine contents used in gasification plants.
Series: ASM Handbook
Volume: 4E
Publisher: ASM International
Published: 01 June 2016
DOI: 10.31399/asm.hb.v04e.a0006289
EISBN: 978-1-62708-169-6
... of the rate of purification of the aluminum matrix from the solute atoms, that is, copper and magnesium in the case of 2024 alloy. After isothermal aging at 190 °C (374 °F) for approximately 50 h, the final alternating-current conductivity as measured by the eddy-current method approaches the nominal value...
Abstract
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.
Book: Casting
Series: ASM Handbook
Volume: 15
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.hb.v15.a0005189
EISBN: 978-1-62708-187-0
... (going back to the winning of ores, if desired), melt purification from scrap recycling, and alloy additions. Chemical processes are also involved in making molds and cores, the casting and solidification processes, the microstructural development of alloys, and the phase changes that occur after casting...
Abstract
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.
Series: ASM Handbook
Volume: 2
Publisher: ASM International
Published: 01 January 1990
DOI: 10.31399/asm.hb.v02.a0001090
EISBN: 978-1-62708-162-7
... important for environmental reasons, germanium is precipitated, usually along with iron, during the purification of the ZnSO 4 electrolyte prior to electrolysis. Germanium is one of several impurities that have an adverse effect on zinc electrolysis. If the germanium concentration is high enough...
Abstract
Germanium is a semiconducting metalloid element found in Group IV A. Germanium is used in the field of electronics, infrared optics, and in the fields of gamma ray spectroscopy, catalysis, and fiber optics. This article discusses the sources, manufacturing, and processing of germanium, and focuses on the chemical properties of various germanium compounds, including germanium halides, germanates, germanides, germanes, inorganic, and organogermanium compounds. It also tabulates the physical, thermal, electronic, and optical properties of germanium, and explains the economical aspects and specifications of germanium. The article describes the analytical and test methods of germanium, including gravimetric method, titrimetric method, and spectral method. It provides a short note on toxicology, and concludes with the uses of germanium in different fields.
Book: Powder Metallurgy
Series: ASM Handbook
Volume: 7
Publisher: ASM International
Published: 30 September 2015
DOI: 10.31399/asm.hb.v07.a0006078
EISBN: 978-1-62708-175-7
.... However, the sponge is very strong and cannot be easily crushed to “release” the trapped MgCl 2 . The main drawback of Kroll's process is that the time required for purification of titanium sponge by vacuum distillation can exceed 4 to 5 days, depending on the size of the titanium sponge block. Since...
Abstract
This article provides a summary of the conventional technologies used for titanium powder production. It focuses on the various processes for titanium powder production, namely, Hunter, Kroll, Armstrong, MER, TIRO, FFC-Cambridge, Chinuka, and CSIR processes. Employment of titanium powder significantly improves the synthesis of titanium and its alloys.
Book: Surface Engineering
Series: ASM Handbook
Volume: 5
Publisher: ASM International
Published: 01 January 1994
DOI: 10.31399/asm.hb.v05.a0001247
EISBN: 978-1-62708-170-2
... solution clean-up, including removal of excess sodium carbonate, purification with zinc dust, treatment with activated carbon, and filtration. Formation and Elimination of Carbonate Sodium carbonate forms in the cyanide bath as a result of the decomposition of sodium cyanide and the reaction...
Abstract
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.
Book: Powder Metallurgy
Series: ASM Handbook
Volume: 7
Publisher: ASM International
Published: 30 September 2015
DOI: 10.31399/asm.hb.v07.a0006087
EISBN: 978-1-62708-175-7
... + + 2 NH 3 + H 2 → M o + 2 NH 4 + Generally, processing begins with leaching of ores and includes purification and separation stages prior to reduction. Reduction potential may be estimated by comparing the electrochemical potential of the metal ion...
Abstract
This article provides a discussion on the process descriptions, processing conditions, and processing variables of the most common chemical methods for metal powder production. These methods include oxide reduction, precipitation from solution, and thermal decomposition. Methods such as precipitation from salt solution and gas, chemical embrittlement, hydride decomposition, and thermite reactions are also discussed. The article also discusses the methods used to produce powders electrolytically and the types of metal powders produced. The physical and chemical characteristics of these powders are also reviewed.