bluuebunny/crossref_metadata_2025 huggingface dataset:
Silicon Carbide
Authors: Divakar R. , Chia K. Y. , Kunz S. M. , Lau S. K.
Published: July 2004

Silicon carbide, SiC, is a crystalline material having a color that varies from nearly clear through pale yellow or green to black, depending on the amount of impurities. It occurs naturally only as the mineral moissanite in the meteorite iron of Canon Diablo, Arizona. The commercial product, which is made in an electric furnace, is usually obtained as an aggregate of iridescent crystals. The iridescence is caused by a thin layer of silica produced by superficial oxidation of the carbide. The loose black or green grain of commerce is prepared from the manufactured product by crushing and grading for size. Traditionally, the metallurgical, abrasive, and refractory industries are the largest users of silicon carbide. SiC is also used for heating elements in electric furnaces, in electronic devices, and in applications where its resistance to nuclear radiation damage is advantageous. The development of advanced pressureless sintering and complex shape‐forming technologies has led to silicon carbide becoming one of the most important structural ceramics. Silicon carbide has found wide acceptance in wear‐, erosion‐, and corrosion‐resistant applications; it has demonstrated excellent performance as a heat‐exchanger material; it is also being evaluated for prototype high temperature gas turbine engine component applications. The measurements made on commercial, polycrystalline products should not be interpreted as being representative of single‐crystal silicon carbide. The pressureless‐sintered silicon carbides, being essentially single‐phase, fine‐grained, and polycrystalline, have properties distinct from both single crystals and direct‐bonded silicon carbide refractories. Silicon carbide may crystallize in the cubic, hexagonal, or rhombohedral structure. Silicon carbide is a leading candidate material for rotating and static components in many gas turbine engine applications. As is the case for other ceramics, silicon carbide is brittle in nature. The strength of a silicon carbide component is determined by preexisting flaws introduced into the material during processing. Sintered silicon carbide retains its strength at elevated temperatures. Silicon carbide is a semiconductor: it has a conductivity between that of metals and insulators or dielectrics. Silicon carbide is comparatively stable. The only violent reaction occurs when SiC is heated with a mixture of potassium dichromate and lead chromate. There are several routes to preparing SiC powders. Methods that have been examined include growth by sublimation from the vapor phase, carbothermic reduction, and crystallization from a melt. The high modulus, high intrinsic strength, and temperature stability make SiC, in the form of whiskers, platelets, and fibers, a promising candidate reinforcement material for metal, polymer, and ceramic matrix composites. Silicon carbide has been described as a mild inhalation irritant. The threshold limit value for silicon carbide in the atmosphere is 5 mg/m3.
Semiconductors, Silicon‐Based Semiconductors
Authors: Rose Kenneth
Published: July 2004

Their unique properties have allowed silicon‐based semiconductor devices, especially metal/oxide/semiconductor field‐effective transistors (MOSFETs), to dominate the electronics industry. Exponentially increasing numbers of transistors on single chips of silicon have led to exponential improvements in chip performance. The properties of silicon as an electronic material, the dependence of carrier statistics on doping, and carrier transport are reviewed because they determine device behavior. The characteristics of transistors, both bipolar and MOSFET, depend on the properties of
p–n
junctions. An abrupt
p–n
junction places acceptor‐doped,
p
‐type silicon next to donor‐doped
n
‐type silicon. The performance of
n–p–n
bipolar transistors depends on minority electrons injected into the
p
‐type base by the forward‐biased base‐emitter
p–n
junction reaching the reverse‐biased base‐collector
p–n
junction.
n
‐Channel MOSFETs depend on electrons traveling between

\documentclass{article}\pagestyle{empty}\begin{document}${n^{+}}$\end{document}

source and drain junctions through an
n
‐type surface channel. This surface channel is induced by a voltage applied across the MOS capacitor formed by a polysilicon metal gate over an oxidized silicon surface. The unique low concentration of surface states, which can be achieved at a thermally oxidized Si–SiO
2
boundary, is the basis of MOSFET technology. The ability to shrink the dimensions of these devices without radically altering their behavior (scaling) has allowed the microelectronics industry to place exponentially increasing numbers of MOSFETs on a single chip. Generally speaking, the growth of the microelectronics industry has been the result of device scaling rather than fundamental changes in device physics. Variations of silicon technology are leading to devices with deep submicrometer dimensions or new applications such as thin‐film transistors for flat‐panel displays, flash memories, or power devices. Variations in silicon technology such as silicon on insulator, silicon–germanium alloys, or silicon carbide are briefly reviewed.
Silk
Authors: Kaplan David L. , Mello Charlene , Fossey Stephen , Arcidaicono Steven
Published: July 2004

Silks are naturally spun fibrous proteins most often associated with the silkworm and spiders. Silk fibers are unusual in combining strength, toughness, and compressibility. The proteins are characterized primarily by a β‐sheet secondary structure consisting of a highly crystalline region as well as regions of lower crystallinity. Silkworm cocoon fibers have been used in textiles for thousands of years. Spider silk, of which there are many different types, has not been domesticated. Water‐soluble silk proteins are synthesized and stored in the silk glands until spun into fibers, at which point they become insoluble in water. The spinning process is regulated by the organism and involves the extrusion of the soluble silk in a liquid crystalline state through spinnerets. Silks are stable to approximately 230°C. Membranes have been formed from silks that provide a useful means to explore secondary structure and to entrap enzymes. Worldwide production of silkworm silk for textiles is expected to increase. Future applications depend on the success of biotechnology to provide adequate production levels of specifically tailored silk compositions.
Silver and Silver Alloys
Authors: Etris Samuel F.
Published: July 2004

The workability, beauty, and bacteriocidal effects of silver have made it a most desirable metal since ancient times. The combination of desirable properties and the total resistance of silver to the formation of oxides has established its position as a critical metal for a myriad of advanced technology applications. Silver also imparts the properties to the many metals with which it forms commercially important alloys. Among its many important salts, the halides stand as unique photosensitive salts, providing the basis for high quality photography as well as for photochromic glass.

More obscure properties of silver such as its high thermal reflectivity are also being fully exploited. For example, silver is used to provide energy‐saving domestic window glass. The unique interaction of silver and oxygen is being used to advantage in the superconductor industry. The superior fatigue resistance and lubricity of silver make it an essential component of high performance jet engines.
Fluorine Compounds, Inorganic, Silver
Authors: Meshri Dayal T.
Published: July 2004

Four binary fluorides, two mixed valent fluorides, and several fluorocomplexes of silver are known. Both silver fluoride and silver difluoride, used as fluorinating reagents, are commercially available, as are silver hexafluoroantimonate, silver hexafluorophosphate, silver tetrafluoroborate, and silver trifluoroacetate. Silver fluoride is also used in batteries and as an antimicrobial agent; the silver fluorocomplexes are used primarily in organic synthesis.
Simultaneous Heat and Mass Transfer
Authors: Wenzel Leonard A.
Published: July 2004

In process operations where material is transferred between phases, usually between liquid and vapor phases, the transport process may be described in terms of heat transfer and mass transfer. When both expressions are developed and handled simultaneously, the resulting equations show that heat and mass transfer affect each other. Equations applied to humidification and dehumidification processes are presented. These expressions could equally well be applied to drying, evaporation, or crystallization processes. The conceptual design of counterflow cooling towers or dehumidification towers is discussed, as are the mechanical and operating features of these columns, costs, and environmental impacts. In all of these processes the air–water system is usually of concern. Thus the properties of moist air are developed and displayed on psychrometric charts.
Size Enlargement
Authors: Capes C. Edward , Darcovich K.
Published: July 2004

Size enlargement concerns those processes which bring together fine powder particles into larger masses to improve the properties of the powders. Many diverse industries benefit from size enlargement processes. Examples discussed herein include fertilizer granulation, iron ore pelletization, tablet feeds for pharmaceuticals, instant food products, and the processing of mineral and chemical products.

This article considers primarily those processes in which the creation of coarse granular material from fines is the objective. The characteristics of individual agglomerates are important only in their effect on the properties of the bulk granular product.

Following initial discussion of particle‐bonding mechanisms and the theory and measurement of agglomerate strength, size enlargement processes and equipment, including principal design parameters, are described. These processes are considered on the basis of the principal mechanism used to bring the particles together into agglomerates. The categories used are agglomeration by tumbling and other agitation methods, pressure compaction and extrusion methods, heat reaction, fusion, and drying methods, and agglomeration from liquid suspensions by competitive wetting.
Size Measurement of Particles
Authors: Trottier Remi , Kaye Brian
Published: July 2004

The size distribution of particles is of importance to a wide variety of particulate systems in the chemical process industries. The compacting and sintering behavior of metallurgical powders, flow characteristics of granular materials, hiding power of paint pigments, and the combustion efficiency of coal and sprayed liquids all depend on particle size. The various means of data representation in particle size measurements are defined and sampling procedures are presented. Methods of size measurement ranging from the historical yet still useful sieving, through the use of modern instrumentation such as laser diffraction equipment and optical counters, are discussed.
Sodium Sulfates
Authors: Butts David
Published: July 2004

Sodium sulfate, Na
2
SO
4
, is principally used as a filler in soaps and detergents and in the manufacturing process of kraft paper. These uses consume about 65% of the world's production. It is also used in glassmaking, in cattle‐feed mixes, in cellulose sponge, in metallurgical refining, and as a cement and plaster hardener. Both sodium sulfate and sodium bisulfate, NaHSO
4
, are used to adjust the pH of various solutions and to dilute certain dyes. Sodium bisulfate is a mild acid safe for household cleaning and where a mild acid is needed. About half of the sodium sulfate production is derived from naturally occurring salts and brines. The other half is produced as a by‐product in the manufacture of rayon, sodium dichromate, resorcinol, and silica pigments.
Sodium Hydroxide
Authors: Eggeman Tim
Published: July 2004

Sodium Hydroxide (Caustic Soda) falls in a group of commodity chemicals which also includes chlorine, Cl
2
; sodium carbonate (soda ash), Na
2
CO
3
; potassium hydroxide (caustic potash), KOH; and hydrochloric acid (muriatic acid or anhydrous), HCl. Chlorine and caustic soda are the two most important products in this group, ranking among the top ten chemicals in the United States. The applications for chlorine and the alkalies are so varied that there is hardly a consumer product which is not dependent on one or both of them at some manufacturing stage. Chlorine and caustic soda are coproducts of the electrolysis of aqueous solutions of sodium chloride, NaCl (commonly called brine). Conversion of aqueous NaCl to Cl
2
and NaOH is achieved in three types of electrolytic cells: the diaphragm cell, the membrane cell, and the mercury cell. The distinguishing feature of these cells is the manner by which the electrolysis products are prevented from mixing with each other, thus ensuring proper purity. Solution mining of salt and the availability of asbestos resulted in the dominance of the diaphragm process in North America, whereas solid salt and mercury availability led to the dominance of the mercury process in Europe. Japan imported its salt in solid form and, until the development of the membrane process, also favored the mercury cell for production. Sodium hydroxide, NaOH, mol wt 39.998, is a brittle, white, translucent crystalline solid. Because of its corrosive action on all human body tissue, it is also known as caustic soda. Aqueous solutions of caustic soda are highly alkaline. Hence caustic soda is primarily used in neutralization reactions to form sodium salts. Reactions of NaOH with natural products are complex. They include solubilization of cotton in rubber reclaiming, cotton scouring, refining of vegetable oils, and removal of lignin and hemicellulose in the Kraft pulping process. The only caustic soda production process besides electrolysis is the soda–lime process, practiced by companies which do not participate in the chlorine market. Three forms of caustic soda are produced to meet customer needs: purified diaphragm caustic (50% Rayon grade), 73% caustic, and anhydrous caustic. Caustic soda is classified as a corrosive material by the DOT, and it has a marked corrosive action on all body tissue. Inhalation of the dust or mist can cause damage to the upper respiratory tract. During handling, all persons should wear proper protective clothing, safety goggles or a full face shield, rubber gloves, boots, and a caustic‐resistant apron or suit. Disposal of waste or spilled caustic soda must be carried out by properly trained personnel.
Sodium Bromide
Authors: Kust Roger N.
Published: July 2004

Sodium bromide is the most common and available alkali bromide, occurring in both the anhydrous and dihydrate forms. The anhydrous salt is hygroscopic but not deliquescent and has a very high solubility in water. Commercial quantities are prepared from bromine and sodium hydroxide solutions. Sodium bromide is moderately toxic by ingestion and can affect the gastrointestinal and central nervous systems and the skin. A primary use of sodium bromide is as a heavy, clear brine fluid in completing and working over oil and gas wells. Another principal use of sodium bromide is in industrial wastewater treatment. When activated with hypochlorites or isocyanurates sodium bromide becomes a very effective biocide. Sodium bromide is used in the photographic industry, has some application as a cocatalyst, as a wood preservative, and as a pharmaceutical.
Sodium Iodide
Authors: Merrell Philip H. , Peters Elizabeth M.
Published: July 2004

Sodium iodide, its occurrence, physical properties, manufacture, economic aspects, and uses are described. It is produced by acid–base reaction yielding no by‐products and is stored on the basic side to retard oxidation.

This important halide salt is used in medicine as a detector for such devices as computer‐assisted tomography scans and positron emission tomography. It tends to form the dihydrate at temperatures below 65°C and is deliquescent, which makes it much different in handling characteristics from its potassium counterpart.
Soil Chemistry of Pesticides
Authors: Kearney Philip C. , Shelton Daniel R. , Koskinen William C.
Published: July 2004

Pesticide sales have held steady at about 500,000 t annually in the United States since the 1970s. Groundwater monitoring studies show that a small percent of a few compounds are actually being detected in the parts per billion range. The degradation and retention processes in soils determine the amounts and types of pesticides that leach into groundwater. The principal reactions that degrade pesticides in the environment occur primarily on or in soils. Soil microorganisms catalyze the enzymatic oxidation, reduction, and hydrolysis of most pesticides. Chemical reactions in soils yield many of the same products as the biochemical reactions mediated by soil microorganisms. Sorption processes bind pesticides and prevent movement either within or outside the soil matrix. Soil organic matter is the principal sorbent for most organic pesticides. Pesticides are sorbed to soil particles by van der Waals forces, hydrogen bonding, dipole–dipole interactions, ion exchange, and covalent bonding mechanisms. Development of new active pesticides, biotechnology, sustainable agricultural practices, and evolving regulations will lower the future amounts of pesticides detected in soil and water.
Solders and Brazing Filler Metals
Authors: Rabinkin Anatol
Published: July 2004

Solders and brazing filler metals are special alloys used to join parts, whether of metallic, ceramic, or composite material, into an assembly through metallurgical bonding. Solders melt below 723 K; brazing filler metals, above. The essence of the joining processes in which these alloys are used is described. Special attention is paid to joint design, part preparation before processing, and the specifics of soldering and brazing processes. A complete classification of solders and brazing filler metals, mostly based on composition of alloys and their compatibility with various classes of steel and alloys, is given, as are general recommendations for potential applications of each group of brazing filler metals and solders. Health and safety factors associated with usage during manufacturing processes are discussed.
Solvents, Industrial
Authors: Sullivan Don A.
Published: July 2004

Aromatic and aliphatic hydrocarbons are the most widely used industrial solvents; other solvent classes include alcohols, ketones, esters, ethers, glycols, glycol ethers, amines, and aldehydes. Solvents are used to dissolve polymers and other solutes for application or to remove grease and other contaminants in cleaning processes. Extraction processes employ solvents to separate one material from another by selective dissolution. Solvents also function as reaction media and heat‐transfer fluids for industrial processes. An important solvent use is as a raw material, in which the solvent reacts with other compounds to form new useful substances.

Proper solvent selection has a large impact on the success of the operation in which the solvent is used, including economic effects, technical adequacy, safety issues, and environmental impacts. Solvency characteristics, evaporation behavior, flash point, solvent balance, and solvent toxicity must all be considered. These requirements must be evaluated regardless of the specific use.

Regulations aimed at reducing ambient ozone concentrations have the greatest impact of any of the regulations on solvent usage. Even though industrial processes account for a minority share of emissions, regulations adopted at the federal and state level influence which solvents are used, the amount used, and the way they are used. Regulations have also given impetus to the development of new technologies and products that decrease solvent emission to minimize environmental impact. Regulatory pressures will gradually reduce overall solvent usage, and shift usage away from certain solvents, but industrial solvents will continue to be used.
Sorbic Acid
Authors: Dorko Catherine L. , Ford George T. , Baggett Madelyn S. , Behling Alison R. , Carman Harold E.
Published: July 2004

Sorbic acid, ie,trans,trans‐2,4‐hexadienoic acid, and its derivatives are commonly used as antimicrobials for food, pharmaceuticals, animal feeds, cosmetics, and industrial uses. Sorbic acid is a white crystalline solid having low water solubility but greater solubility in fats and alcohol. Potassium sorbate has greater water solubility than sorbic acid and is available as white granules or powder. Because the sorbic acid molecule contains two double bonds, oxidation occurs in the presence of molecular oxygen or peroxide compounds. Other reactions related to the chemical properties are also described. Sorbic acid can be found naturally in the oil of the ripened rowan berry. Commercially available sorbates are typically manufactured by the reaction of crotonaldehyde with a ketene to form an intermediate, which is further processed and purified. Purified forms include food and drug grades conforming to the specifications of theFood Chemicals Codexand theNational Formulary. Analytical methods to quantify sorbates include titration, gas chromatography, and high performance liquid chromatography. Sorbic acid is metabolized to carbon dioxide and water in the same way as other food fatty acids and has low toxicity. For most food products in the United States, there are no maximum usage levels for sorbates.
Soybeans and Other Oilseeds
Authors: Wolf Walter J.
Published: July 2004

The four principal U.S. oilseed crops are soybeans, cottonseed, peanuts, and sunflower seed. The physical characteristics of the plants and seeds, chemical compositions of the seeds, harvesting and storage of the crops, and processing of the crops into oil and defatted meal are described for the primary products of the industry. Production figures and prices of the oilseeds and their products are presented. The oils of these crops are used primarily for human consumption. Minor quantities go into industrial products. The defatted meals serve mainly as protein sources in animal feeds, but small amounts are processed into protein ingredients used by the food industry. Nutritional properties and antinutritional factors of the oils and meals are reviewed. Direct food uses of soybeans, peanuts, and sunflower seed are also covered.
Space Processing
Authors: Naumann Robert J.
Published: July 2004

The microgravity environment of a spacecraft in low Earth orbit has proved to be a useful tool for materials research because it allows processes to be carried out under better controlled and greatly simplified transport conditions. A brief historical overview is given describing how this discipline evolved from a plan for using space for manufacturing unique materials of great commercial value into one of utilizing it as a laboratory for studying the role of transport in various processes. Several case studies are presented in the areas of protein crystal growth, small‐molecule crystal growth from solution, Bridgman growth, vapor growth, electrodeposition, and tests of fundamental theories. A number of these experiments have produced surprising and unexpected results, whereas others have suggested improved processing techniques for use on Earth.
Spices
Authors: Rogers James A.
Published: July 2004

This article emphasizes the use of spices in flavorings; other applications are known. The use of essential oils, derived from spices by various methods, and oleoresins, derived from spices by extraction, are components of flavor; their applications are included in this section. The quintessence of some spices, the essential oils, are described more fully elsewhere (see Essential oils).

Topics discussed include history of spice and spice trade; food and beverage labeling; production and economic considerations with comparison of past import and export levels of spices and oleoresins with 1993 levels; and presentation of source, usage, and flavor characteristics of common individual spices.
Coating Processes, Spray Coating
Authors: Coeling K. J.
Published: July 2004

The devices used to apply a surface coating to a workpiece by spraying are discussed. Atomization methods include airless, supercritical fluid, air, electrostatic, and rotary. The principle of atomization, typical operating conditions, spray characteristics, and limitations are presented for each method. The use of electrostatic forces to increase the efficiency of spray particle transfer to the workpiece is also discussed. The best method to spray coat a given surface depends on the characteristics of the material to be sprayed, the part configuration, the surface characteristics desired, and the application rate required.
Stains, Industrial
Authors: Tucker Ron W.
Published: July 2004

Wood substrates vary in consistency and appearance, making it necessary for the finisher to depend on artistic skills to create an attractive piece of furniture. Formulating the materials to be used in the finishing process can only be done if the chemist has a knowledge of the art of wood finishing. Unlike metal, plastic, or other substrates that require coatings, wood is unique in that no two pieces are the same. Different grain patterns, cell structure, or multiple species used in making a piece of furniture require different finishing materials to be used to achieve the desired appearance. Each material used in finishing wood is an important part of a system. No part of the finishing system is more important than the role that the stain plays. Whether it is to make up for extreme differences in color or texture or to highlight and add contrast to the wood, stains and the manner in which they are used determine whether a particular furniture item will appeal to the consumer.
Nonwoven Fabrics, Staple Fibers
Authors: Vaughn E. A.
Published: July 2004

This article provides a comprehensive overview of the production methods, properties, and uses of nonwoven fabrics. The discussion includes a brief introduction, short history, and compilation of definitions of a nonwoven fabric. The processes used to manufacture nonwovens are grouped into four categories according to parent technology: textile, paper, extrusion, and hybrid, and into four sequences of operation: fiber selection, web formation, bonding, and finishing. Descriptions and illustrations of the manufacturing sequences follow. Production trends and product applications are discussed.
Steel
Authors: Paxton Harry
Published: July 2004

Paxton, Harry (Carnegie Mellon University). Steel is the generic name for a group of ferrous metals composed principally of iron but containing some carbon and generally other elements as well. These iron–carbon alloys are the most plentiful and useful of the metallic materials, whether for infrastructure construction, consumer goods from automobiles to cutlery, or spacecraft. Durability and versatility are evidenced by the wide range of physical and mechanical properties.

The manufacture of the two allotropes of steels is presented, including the electric furnace and the oxygen steelmaking process. Raw materials and addition agents, casting, plastic working, and metallography and heat treatment are described. The iron–iron‐carbide phase diagram is discussed, as are the various types of alloy steels, including stainless steels. Properties and composition are summarized.
Sterilization Techniques
Authors: Augurt Thomas A. , van Asten J.A.A.M.
Published: July 2004

Sterilization technology, rendering material devoid of contaminants, especially living organisms, is of primary importance in industries as diverse as food processing and space exploration. Generally, however, this technology is more readily associated with the health‐care profession and industry or the electronics industry. The focus herein is on the sterilization of materials and devices used in the former. The destruction of microorganisms, including the kinetics and thermodynamics of the process, the equipment necessary, and methods used for monitoring and testing such destruction, is discussed. Sterilants may be gases or liquids used at ambient or high temperatures, or ionizing radiation. The most frequently used sterilant is moist heat or steam. Packaging techniques and materials for sterile substances are presented. The roles of sterilization and comparable techniques used in the food processing industry are considered.
Steroids
Authors: Morgan Bradley P. , Moynihan Melinda S.
Published: July 2004

Steroids are members of a large class of lipid compounds called terpenes that are biogenically derived from the same parent compound, isoprene, C5H8. Steroids contain or are derived from the perhydro‐1,2‐cyclopentenophenanthrene ring system and are found in a variety of different marine, terrestrial, and synthetic sources. Nonhormonal steroids, eg, sterols and bile acids; vitamin D; and hormonal steroids, eg, the human sex hormones (androgens, estrogens, and progestins) and corticosteroids (glucocorticoids and mineralocorticoids) play critical roles in the physiology and biochemistry of most living creatures. Other naturally occurring steroids, such as plant steroids, marine steroids, ecdysteroids, cardiac steroids, steroid alkaloids, and steroid antibiotics, have a plethora of biological activities and uses. Many synthetic steroids are the product of pharmaceutical research that has resulted in the development of several steroid‐based medicines with a market value over $10 billion. Among the medicinally important synthetic steroids, are antihormones, anesthetics, antiinflammatories, antiasthmatics, contraceptive drugs, antibiotics, anticancer agents, cardiovascular agents, and osteoporosis drugs.
Stimulants
Authors: Craig Charles R.
Published: July 2004

A large number of chemical entities have the capacity to stimulate the mammalian central nervous system (CNS). These CNS stimulants are chemically diverse and usually categorized according to pharmacological properties as analeptics, psychomotor stimulants, and antidepressants. These agents, together with their structures and related potencies, are discussed. The analeptic stimulants, including strychnine, picrotoxin, bicuculline, and pentylenetetrazol, have few clinical uses, but are important laboratory tools. Psychomotor stimulants such as amphetamine and cocaine are widely abused for their psychomotor effects. However, other compounds having similar sympathomimetic but less, although significant, CNS stimulant properties are employed to treat asthma, attention‐deficit hyperactivity disorder, and sometimes as an aid in weight reduction. Other psychomotor stimulants having even less CNS activity are widely consumed in caffeine‐containing beverages. Antidepressants, including monoamine oxidase inhibitors, tricyclic antidepressants, and newer compounds such as selective serotonin reuptake inhibitors, are widely used to treat clinical depression.
Strontium and Strontium Compounds
Authors: Hibbins Stephen G.
Published: July 2004

The main application for strontium, an alkaline‐earth metal, is in the form of strontium compounds. The carbonate, used in cathode ray tubes (CRTs) for color televisions and color computer monitors, is used both in the manufacturing of the glass envelopes of CRTs and in the phosphors which give the color. Owing to use as a eutectic modifier in aluminum–silicon casting alloys, rapid growth of metal production has occurred. The addition of strontium changes the microstructure of the alloy, resulting in improved ductility and strength in cast aluminum automotive parts such as wheels, intake manifolds, and cylinder heads. Strontium metal is also used as an inoculant in ductile iron castings. Other applications include modifying the structure of 6000 series aluminum extrusion alloys, reducing the shrinkage microporosity in magnesium gravity‐casting alloys, and as an addition to lead alloys used for starting, lighting, and ignition batteries. Chemical and physical properties and discussions of specific strontium compounds are provided.
Advanced Ceramics, Structural Ceramics
Authors: Pascucci Marina R. , Neil Jeffrey T. , Natansohn Samuel
Published: July 2004

Advanced structural ceramics are those ceramics intended for use as load‐bearing members. They are materials that combine the properties and advantages of traditional ceramics, such as chemical inertness, high temperature capability, and hardness, with the ability to carry a significant mechanical stress. Advanced structural ceramics are more expensive than traditional ceramics. Most of the advanced structural ceramics under development today are based on silicon nitride, Si3N4; silicon carbide, SiC; zirconia, ZrO2; or alumina, Al2O3. Advanced structural ceramics typically possess some combination of high temperature capabilities, high strength, toughness or flaw tolerance, high hardness, mechanical strength retention at high temperatures, wear resistance, corrosion resistance, thermal shock resistance, creep resistance, and long‐term durability. The relationship between processing and properties is especially critical for advanced structural ceramics because subsequent successful operation in severe environments often requires carefully controlled compositions and microstructures. Fabrication generally takes place in four steps: powder processing, consolidation/forming, densification, and finishing. The focus has been on applications for gas turbine, diesel, and spark‐ignited engines. Advanced structural ceramics are also under investigation for use in numerous other high performance applications including metal‐cutting and shaping tools, and various military applications. Exposure limits for silicon carbide and powders of zirconium compounds (including zirconium dioxide) have been established by ACGIH. The solid ceramics present no apparent health hazard.
Styrene
Authors: Chen Shiou‐Shan
Published: July 2004

Chen, Shiou‐Shan (Raytheon Engineers & Constructors). Styrene, the simplest and most important member of a series of aromatic monomers, is produced in large quantities for polymerization. Its versatility has resulted in the manufacture of plastics, including polystyrene, ABS, SAN, styrene–butadiene latex, SBR, and unsaturated polyester resins. Polystyrene accounts for 65% of total styrene demand. Rapid growth in styrene production has been seen worldwide since 1970, including, since the 1980s, in the Pacific Rim. Many factors contribute to its growth. Chief among these are that it can be polymerized and copolymerized under a variety of conditions by common methods and that the raw materials, benzene and ethylene, are produced in large quantities in refineries and can be supplied through pipelines. The two process routes used commercially for manufacture of styrene, dehydrogenation, and coproduction with propylene oxide, are covered. Both routes use ethylbenzene as the intermediate.

The commodity nature of the product and easy access to licensed processes have enabled new producers in developing countries to enter the global styrene market. Timing is important as price fluctuates broadly and rapidly. A large number of styrene derivatives have been reported, and several have been used for manufacturing small‐volume specialty polymers, including vinyltoluene,para‐methylstyrene, α‐methylstyrene, and divinylbenzene.
Styrene Plastics
Authors: Priddy Duane B.
Published: July 2004

This article examines both styrene plastics, including such commodity styrenic resins as general‐purpose polystyrene, high impact polystyrene, styrene–acrylonitrile, and acrylonitrile–butadiene–styrene, and specialty resins such as ionomers, styrene derivatives, and tactic polystyrenes. Topics discussed include styrenic plastic properties such as stress–strain, creep, stress relaxation, fatigue, impact strength, surface appearance, and melt properties, as well as rubber modification and glass filling of styrene plastics. Styrene plastics manufacturing processes and the chemistry of styrene polymerization are both described, the former with an emphasis on the most widely used continuous free‐radical reaction designs, the latter mainly on the industrially important free‐radical mechanism; other mechanisms by which styrene can be polymerized, ie, anionic, cationic, and Ziegler‐Natta, are also mentioned. The description of free‐radical polymerization of styrene covers spontaneous initiation, chemical initiators, chain‐transfer agents, and living free‐radical polymerization. Copolymerization of styrene with other monomers is also discussed. Other topics covered include fabrication processes, ie, injection molding, extrusion, thermoforming, and blow molding; additives; economic aspects; characterization techniques; health and safety issues; foamed polystyrene; and environmental issues, including recycling.
Sugar, Sugar Economics
Authors: Toth Laszlo
Published: July 2004

Mass consumption of sucrose (table sugar) far outweighs by volume the consumption of other types of sugars marketed. Industrial production of sugar (sucrose) is based on sugarcane and sugar beet processing. Cane and beet sugars when properly manufactured are identical in physical, chemical, electric, and thermodynamic properties, though the histories of their development are very different. In addition to providing essential nutritional value, the sugar industry has had a large impact on human history and social evolution, and many records of its fascinating role in war and peace exist.

The major role of sugar in supplying the caloric needs of the world's population had evolved by the beginning of the twentieth century. Although the effect of World War II on the sugar industry was drastic, the healthy recovery that occurred during postwar years is indicated, along with the European sugar industry experiencing extensive automation and closing of many small factories. Numbers of processing facilities by country and type in 1995 are given, illustrating the extent of global recovery.

Despite a great expansion in the world sugar industry, U.S. processing suffered setbacks resulting from the appearance of corn sweeteners, noncaloric sweeteners, and the effects of generally misguided health movements.

World production, consumption, and price statistics, as well as the worldwide sugar balance, are provided.
Sulfoxides
Authors: Willer Rodney
Published: July 2004

Sulfoxides are compounds that contain a sulfinyl group covalently bonded at the sulfur atom to two carbon atoms. Sulfoxides represent an intermediate oxidation level between sulfides and sulfones. The naturally occurring sulfoxides often are accompanied by the corresponding sulfides or sulfones. The only commercially important sulfoxide is the simplets member, dimethyl sulfoxide.

Sulfoxides occur widely in small concentrations in plant and animal tissues. Properties, synthesis and manufacture, health and safety factors, and uses are discussed.
Fluorine Compounds, Inorganic, Sulfur
Authors: Evans Francis E. , Mani Ganpat
Published: July 2004

The two most commercially important sulfur‐containing inorganic fluorine compounds are fluorosulfuric acid and sulfur hexafluoride. Fluorosulfuric acid is used as a fluorinating reagent in the preparation of such compounds as boron trifluoride and silicon tetrafluoride, and as a catalyst in organic reactions for alkylation, acylation, polymerization, sulfonation, and isomerization. Fluorosulfuric acid is itself a strong acid. When combined with certain inorganic fluorides, the system exhibits superacid properties. Properties, manufacture, and uses are discussed.

Of the known sulfur fluorides, sulfur hexafluoride and sulfur tetrafluoride are available commercially. Sulfur hexafluoride, nonflammable and of high chemical stability, has a high dielectric, and is used widely in electrical and electronic equipment such as circuit breakers, capacitors, microwave components, etc. Sulfur tetrafluoride is used as a fluorinating reagent. Properties, manufacture, and uses are described. Other sulfur fluorides are discussed.
Sulfonation and Sulfation
Authors: Knaggs Edward A. , Nepras Marshall J.
Published: July 2004

Sulfonation and sulfation are chemical processes for introducing the sulfur trioxide moiety into organic entities. These processes are utilized in both batch and continuous modes to produce anionic surfactants, cyclic intermediates, dyes, pigments, medicinals, pesticides, sweeteners, lubricant additives, and polymeric specialty chemicals.

Reagents for sulfonation and sulfation include sulfur trioxide, its derivatives and adducts, and sulfur dioxide and its derivatives. Liquid sulfur trioxide is the most reactive available reagent and is moderated by vaporization and dilution with inert dry gases, by use of reaction solvents, or by using adducting agents.

Sulfonation processes and products including alkylbenzene sulfonates lignosulfonates, petroleum sulfonates, and sulfosuccinates, are described, as well as sulfated and alkoxylated alcohols. Continuous falling film gaseous sulfur trioxide sulfonation/sulfation, the method of choice for sulfonating flowable liquid feedstocks, is emphasized. Choice of reagent depends on the chemistry involved, derived product quality, as well as economic and environmental considerations.
Sulfuric and Sulfurous Esters
Authors: McCormack W. B. , Lawes B. C.
Published: July 2004

Sulfuric and sulfurous acids form a series of esters analogous to those from other acidic materials. The hydrogen of the acid is replaced by a carbon‐containing group. Because two hydrogens are present in the sulfur‐based acids, there are two series of esters. Replacement of one hydrogen results in an acid ester. If both hydrogens are replaced, whether with the same, with different, or with bifunctional substituents, symmetrical and unsymmetrical diesters form. Dimethyl sulfate, diethyl sulfate, and long‐chain monoalkyl alkali metal sulfates are the compounds of practical interest. Dialkyl sulfates have been used to introduce a methyl or ethyl group into a wide variety of organic compounds. The long‐chain monoalkyl hydrogen sulfates, in the form of their alkali metal or alkylammonium salts, are valuable as surface‐active agents and are used commercially. The short‐chain monoalkyl hydrogen sulfates are intermediates in commercial conversion routes from olefins to alcohols.
Sulfuric Acid and Sulfur Trioxide
Authors: Muller Thomas L.
Published: July 2004

Sulfuric acid, an important article of commerce since the mid‐1700s, is one of the largest‐volume basic chemicals in the world. It is used in a wide variety of applications, including production of basic chemicals, steel, copper, fertilizer, fibers, plastics, gasoline, explosives, electronic chips, batteries, and pharmaceuticals. Sulfuric acid is typically less costly than other acids and can be readily handled in steel or common alloys at normal commercial concentrations. Sulfuric acid, oleum, fuming sulfuric acid, and the anhydride sulfur trioxide are discussed. The contact processes for sulfuric acid manufacture are discussed, as are the equipment necessary and the corresponding materials of construction. Safe handling practices are given.
Sulfonic Acids
Authors: Tully Paul S.
Published: July 2004

Tully, Paul S. (Stepan Co.). Organic sulfonic acids having the formula RSO3H are described herein. Typical R‐groups are derived from organic radicals based on alkanes, alkenes, alkynes, and arenes. These groups may contain a wide variety of secondary functionalities. A wide variety of sulfonic acids and their derivatives are used industrially on a large scale in the manufacture of surfactants, dyes, inks, dispersing agents, and polymers. Those sulfonic acids that find broad application as catalysts in both alkylation processes and general organic reactions are also disclosed. More esoteric applications in the areas of custom organic syntheses and biological research involving sulfonic acid is described, as is the environmental fate of linear alkylbenzenesulfonic acid and its sulfonates.
Sulfamic Acid and Sulfamates
Authors: Yoshikubo Katsumasa , Suzuki Michio
Published: July 2004

Sulfamic acid (amidosulfuric acid) is a monobasic, inorganic, dry acid, the monoamide of sulfuric acid, produced in crystalline form. The acid is highly stable at room temperature. Aqueous solutions are ranked as strong acids similar to hydrochloric acid and sulfuric acid. Sulfamic acid is available in dry form, permitting a convenient packing and handling operation. Sulfamic acid is used in chemical cleaning, sulfonation reactions, removal of nitrite, as a chlorine vehicle, and for a variety of other applications. Sulfamic acid is also used as a raw material of sodium cyclohexylsulfamate, which is a synthetic sweetener. Some sulfamates are also commercially available.
Water, Supply and Desalination
Authors: Lior Noam , Bakish Robert
Published: July 2004

This article addresses water supply and use with special emphasis on the role and nature of water desalination. The major desalination processes, using membranes or distillation, are described. These are multistage flash evaporation (MSF), multi‐effect distillation (ME), vapor compression distillation (VC), freeze–desalination, reverse osmosis (RO), and electrodialysis (ED). The use of renewable energy for water desalination by solar stills, ocean–thermal energy conversion plants, wind, and photovoltaic cells is presented. Two of the key technical problems in desalination, scale deposition and prevention, and corrosion and the proper choice of materials to resist it, are discussed. Basic equations are provided for the evaluation and preliminary design of MSF and RO, which are currently the leading water desalination processes. The leading professional and governmental organizations involved with desalination, and their activities, are described.
Composite Materials, Survey
Authors: Morton J. , Cantwell W. J.
Published: July 2004

Composite materials are defined as macroscopic combinations of two or more materials. The development of high performance fiber composites is outlined. Composites are classified as fibrous, laminated, and particulate. Details of the nature and fabrication processes of common fibers–glass, carbon, and aramid are presented. Polymer‐based matrix materials are classified as thermosetting or thermoplastic, and common examples of each type are discussed. Methods of fabricating composites are reviewed. Theories of reinforcement are introduced for unidirectional laminated composites.
Carbides, Survey
Authors: Oyama S. Ted , Kieffer Richard
Published: July 2004

Carbon reacts with many elements of the Periodic Table to form a diverse group of compounds known as carbides, some of which are extremely important in technology. Their applications are varied, ranging from cutting tools and structural materials to magnetic and electronic components, and superconductive devices. For example, calcium carbide, CaC2, is a source of acetylene; silicon carbide, SiC, and boron carbide, B4C, are used as abrasives; tungsten carbide, WC, and titanium carbide, TiC, find use as structural materials. Cementite, Fe3C, and the multimetallic complexes of Co, W, Cr, Fe, and Mo with carbon are the components in tool steels and Stellite‐type alloys responsible for their hardness, wear resistance, and excellent cutting performance. Binary compounds of carbon are divided into four main groups: the salt‐like, metallic, diamond‐like, and volatile compounds of carbon. The nature of the bonding is correspondingly of ionic, metallic, semiconductor, or covalent character, but these divisions are not rigid and there are a number of transitional cases. For the metallic carbides, the solid‐state structures and chemical properties reflect an increase in metalspelectron count. Carbides are generally prepared by the direct reaction of carbon with metals or metal‐like materials at elevated temperatures. Their most outstanding properties are extreme hardness and physical strength combined with high temperature stability.