Materials Handbook 15th ed - G. Brady_ H. Clauser_ J. Vaccari (McGraw-Hill_ 2002) Episode 14 pptx

An old alloy, used in India for utensils and known as bidery metal, contained 31 parts zinc, 1 lead, and 2 copper, fluxed with resins.. A white metal sheet now much used for making stamp

have made these alloys obsolete The bearing alloy known in England

as motor bronze is a babbitt with about twice the copper of a

stan-dard babbitt One analysis gives tin, 84%; antimony, 7.5; copper, 7.5;and bismuth 1 An old alloy, used in India for utensils and known as

bidery metal, contained 31 parts zinc, 1 lead, and 2 copper, fluxed

with resins It was finished with a velvety-black color by treating

with a solution of copper sulfate A white metal sheet now much

used for making stamped and formed parts for costume jewelry andelectronic parts is zinc with up to 1.5% copper and up to 0.5 titanium.The titanium with the copper prevents coarse-grain formation, rais-ing the recrystallization temperature The alloy weighs 2% less than

copper, and it plates and solders easily Zilloy-20 is pure zinc with no

more than 1% of other elements In rolled strip it has a tensilestrength up to 27,000 lb/in2(186 MPa) and elongation of 35%

WILLOW. The wood of the trees Salix coerulea and S alba, native to

Europe, but grown in many other places It is best known as a ial for cricket bats made in England The American willows are

mater-known as black willow, from the tree S nigra, and western black

willow, from the tree S lasiandra The wood is also employed for

making artificial limbs and for articles where toughness and shrinking qualities are valued The wood is brownish yellow; has afine, open grain; and has a density of about 30 lb/ft3(481 kg/m3) It is

non-of the approximate hardness non-of cherry and birch Japanese willow

is from the tree S urbaniana It has a closer and finer texture and a

browner color Black willow has a maximum crushing strength lel to the grain of about 1,500 lb/in2 (10 MPa) Salicin, also called

paral-salicoside and saligenin, is a glucoside extracted from several

species of willow bark of England and also from the American aspen

It is a colorless, crystalline material of composition (OH)4C6H7 OO 

C6H4CH2OH, decomposing at 394°F (201°C) and soluble in water and

in alcohol It is used in medicine as an antipyretic and tonic, and as areagent for nitric acid It hydrolyzes to glucose and salicyl alcohol,

and the latter is oxidized to salicylic acid, C6H4(OH)COOH

Aspirin, acetyl salicylic acid, is used as an antipyretic and

anal-gesic

WIRE CLOTH. Stiff fabrics made of fine wire woven with plain, looseweave, used for screens to protect windows, for guards, and for sievesand filters Steel and iron wire may be used—plain, painted, galva-nized, or rustproofed—or various nonferrous metal wires areemployed It is usually put up in rolls in widths from 18 to 48 in (46

to 122 cm) Screen cloth is usually 12, 14, 16, and 18 mesh, but wire

cloth in copper, brass, or Monel metal is made regularly in meshes

from 4 to 100 The size of wire is usually from 0.009 to 0.065 in (0.023

to 0.165 cm) in diameter Wire cloth for fine filtering is made in very

fine meshes Mesh indicates the number of openings per inch and has

no reference to the diameter of wire A 200-mesh cloth has 200 ings each way on a square inch, or 40,000 openings per square inch(6.4 cm2) Wire cloth as fine as 400 mesh, or having 160,000 openingsper square inch (6.4 cm2), is made by wedge-shaped weaving,although 250 wires of the size of 0.004 in (0.010 cm) when placed par-allel and in contact will fill the space of 1 in (2.5 cm) Very fine-meshwire cloth must be woven at an angle since the globular nature ofmost liquids will not permit passage of the liquid through microscopicsquare openings One wire screen cloth, for filtering and screening,has elongated openings One way the 0.0055-in (0.0140-cm) wirecount is 200 per inch (2.5 cm), while the other way the 0.007-in(0.018-cm) warp wire count is 40 per inch (2.5 cm)

open-Wire fabrics for reentry parachutes are made of heat-resistant

nickel-chromium alloys, and the wire is not larger than 0.005 in(0.013 cm) in diameter to give flexibility to the cloth Wire fabrics forion engines to operate in cesium vapor at temperatures to 2400°F(1316°C) are made with tantalum, molybdenum, or tungsten wire,0.003 to 0.006 in (0.008 to 0.015 cm) in diameter, with a twill weave.Meshes to a fineness of 350 by 2,300 can be obtained Porosity unifor-mity is controlled by pressure calendaring of the woven cloth, but forextremely fine meshes in wire cloth it is difficult to obtain the unifor-mity that can be obtained with porous sintered metals

Where accuracy of sizing is not important, as in gravel or orescreening, wire fabric is made with oblong or rectangular openingsinstead of squares to give faster screening High-manganese steelwire is used for rock screens For window screening in tropical cli-mates or in corrosive atmospheres, plastic filaments are sometimes

substituted for the standard copper or steel wire Lumite screen

cloth is woven of vinylidene chloride monofilament 0.015 in (0.038

cm) in diameter in 18 and 20 mesh The impact strength of the plasticcloth is higher than that of metal wire cloth, but it cannot be used for

screening very hot materials Lektromesh is copper or nickel screen

cloth of 40 to 200 mesh made in one piece by electrodeposition It can

be drawn or formed more readily than wire screen, and circular orother shapes can be made with an integral selvage edge

WIRE GLASS. A sheet glass used in building construction for windows,doors, floors, and skylights, having woven wire mesh embedded in thecenter of the plate It does not splinter or fly apart as common glasswhen subjected to fire or shock, and it has higher strength than com-mon glass It is made in standard thicknesses from 0.125 to 0.375 in

(0.318 to 0.953 cm) and in plates 60 by 110 in (1.5 by 2.8 m) and 61 by

140 in (1.5 by 3.6 m) Underwriters’ specifications call for a minimumthickness of 0.25 in (0.635 cm) Wire glass is made with plain, rough,

or polished surfaces, or with ribbed or cobweb surface on one side fordiffusing the light and for decorative purposes It is also obtainable incorrugated sheets, usually 27.75 in (70.5 cm) wide Wire glass 0.25 in(0.635 cm) thick weighs 2.25 lb/ft2(11 kg/m2) Plastic-coated wire meshmay be used to replace wire glass for hothouses or skylights where less

weight and fuller penetration of light rays are desired Cel-O-Glass, of

Du Pont, is a plastic-coated wire mesh in sheet form

WOLLASTON WIRE. Any wire made by the Wollaston process of wire drawing It consists of inserting a length of bare drawn wire into

fine-a close-fitting tube of fine-another metfine-al, the tube fine-and core then beingtreated as a single rod and drawn through dies down to the requiredsize The outside jacket of metal is then dissolved away by an acid

that does not affect the core metal Platinum wire as fine as 0.00005

in (0.00013 cm) in diameter is made commercially by this method,and gold wire as fine as 0.00001 in (0.00002 cm) in diameter is alsodrawn Wires of this fineness are employed only in instruments Theyare marketed as composite wires, the user dissolving off the jacket

Taylor process wire is a very fine wire made by the process of

drawing in a glass tube The process is used chiefly for obtaining finewire from a material lacking ductility, such as antimony, or extremelyfine wire from a ductile metal The procedure is to melt the metal oralloy into a glass or quartz tube, and then draw down this tube withits contained material Wire as fine as 0.00004 in (0.00012 cm) indiameter is made, but only in short lengths

WOOD. A general name applied to the cut material derived from

trees A tree, as distinguished from a bush, is designated by the U.S.

Forest Service as a woody plant with a single erect stem 3 in (7.6 cm)

or more in diameter at 4.5 ft (1.4 m) above the ground, and at least 12

ft (3.7 m) high But this definition is merely empirical since in thecold climate of northern Canada, perfect, full-grown trees 10 to 15

years old may be only 6 in (15 cm) high Timber, in general, refers to standing trees, while lumber is the sawed wood used for construction

purposes In construction work the word timber is often applied to

large pieces of lumber used as beams

Wood is an organic chemical compound composed of approximately49% carbon, 44 oxygen, 6 hydrogen, and 1 ash It is largely celluloseand lignin The wood of white pine is about 50% cellulose, 25 lignin,and the remainder sugars, resin, acetic acid, and other materials.Wood is produced in most trees by a progressive growth from the out-

side In the spring, when sap flows rapidly, a rapid formation of largecells takes place, followed by a slower growth of hard and close cells insummer In some woods, such as oak, there is a considerable difference

in quality and appearance between the spring and summer woods Insome long-lived trees, such as Douglas fir, there is a decrease instrength between the outside wood with narrow rings and the wide-

ringed wood of the interior Heartwood is the dark center of the tree

which has become set, and through which the sap has ceased to flow

Sapwood is the outer, live wood of the tree; unless treated, it has low

decay resistance The grain of sawed lumber results from sawingacross the annual growth rings, varied to produce different grains.Wood is seasoned either by exposing it to the air to dry or by kilndrying The former method is considered to give superior quality, but

it requires more time, is expensive, and is indefinite Numerous testsmade at the U.S Forest Products Laboratory did not reveal any supe-riority in air-dried wood when kiln drying was well done Solvent sea-soning is a rapid process consisting of circulating a hot solventthrough the wood in a closed chamber California redwood, when sea-soned with acetone at 130°F (54°C), yields tannin and some otherchemicals as by-products Seasoned wood, when dry, is always

stronger than unseasoned wood Tank woods are selected for

resis-tance to the liquids to be contained Tanks for vinegar and foodstuffscontaining vinegar, such as pickles, are of white oak, cypress, or west-ern red cedar Beer tanks are of white oak or cypress Tanks for aging

wine are of redwood, oak, or fir The traditional violin woods are

spruce and curly maple, although sugar maple is also used

The term log designates the tree trunk with the branches removed.

Balk is a roughly squared log; plank is a piece cut to rectangular

sec-tion 11 in (28 cm) wide; deal is a piece 9 in (23 cm) wide; and batten

is a piece 7 in (18 cm) wide Board is a thin piece of any width less than 2 in (5 cm) Flitch is half a balk, cut in two lengthwise.

Scantling is a piece sawed on all sides Shakes are longitudinal

splits or cracks in the wood due to shrinkage or decay

All woods are divided into two major classes on the basis of the type

of tree from which they are cut Hardwoods are from broad-leaved, deciduous trees Softwoods are from conifers, which have needle- or

scalelike leaves and are, with few exceptions, evergreens These terms

do not refer to the relative hardnesses of the woods in these two

classes Hardwood lumber is available in three basic categories:

fac-tory lumber; dimension lumber, or dimension parts; and ished market products The important difference between factory

fin-lumber and dimension parts is that factory fin-lumber grades reflect theproportion of the pieces that can be cut into useful smaller pieces,while the dimension grades are based on use of the entire piece

Finished market products are graded for their end use with little or noremanufacturing Examples of finished market products are flooring,siding, ties, timbers, trim, molding, stair treads, and risers The rulesadopted by the National Hardwood Lumber Association are consideredstandard in grading factory lumber The grades from the highest to thelowest quality are as follows: firsts, the top quality, and seconds, both

of which are usually marketed as one grade called firsts and seconds(FAS); selects; and common grades No 1, No 2, No 3A, and No 3B.Sometimes a grade is further specified, such as FAS one face, whichmeans that only one face is of the FAS quality Another designation,WHND, sometimes used, means that wormholes are not considereddefects in determining the grade Dimension lumber, generally gradedunder the rules of the Hardware Dimension ManufacturersAssociation, are of three classes: solid dimension flat stock, kiln-drieddimension flat stock, and solid dimension squares Each class may berough, semifabricated, or fabricated Rough dimension blanks are usu-ally kiln-dried and are supplied sawn and ripped to size Surfaced orsemifabricated stock has been further processed by gluing, surfacing,etc Fabricated stock has been completely processed for the end use.Solid dimension flat stock has five grades: clear—two faces, clear—oneface, paint, core, and sound Squares have three grades if rough (clear,select, sound) and four if surfaced (clear, select, paint, sound)

There are two major categories of softwood lumber: construction

and remanufacture Construction lumber is of three general types: stress-graded; non-stress-graded, also referred to as yard lumber; and appearance lumber Stress-graded lumber is structural lum-

ber never less than 2 in (5 cm) thick, intended for use where definitestrength requirements are specified The allowable stresses specifiedfor stress-graded lumber depend on the size, number, and placement

of defects Because the location of defects is important, the piece must

be used in its entirety for the specified strength to be realized graded products include timbers, posts, stringers, beams, decking,and some boards

Stress-Typical non-stress-graded lumber items include boards, lath, battens, cross-arms, planks, and foundation stock Boards, some- times referred to as commons, are one of the more important

non-stress-graded products They are separated into three to five ferent grades, depending upon the species and lumber manufacturingassociation involved Grades may be described by number (No 1, No.2) or by descriptive terms (construction, standard) First-grade boardsare usually graded primarily for serviceability, but appearance is alsoconsidered Second- and third-grade boards are often used togetherfor such purposes as subfloors and sheeting Fourth-grade boards areselected not for appearance but for adequate strength The appear-

ance category of construction lumber includes trim, siding, flooring,ceiling, paneling, casing, and finish boards Most appearance lumbergrades are designated by letters and combinations of letters, and are

also often known as select grades Typical grades of lumber

remanu-facture are the factory grades and industrial clears Factory select

and select shop are typical high grades of factory lumber, followed by

No 1, No 2, and No 3 shop Industrial clears are used for cabinetstock, door stock, and other products where excellent appearance,mechanical and physical properties, and finishing characteristics areimportant The principal grades are B&BTR, C, and D

Metallized wood is wood treated with molten metal so that the

cells of the wood are filled with the metal Fusible alloys, with ing points below the scorching point of the wood, are used The wood

melt-is immersed in molten metal in a closed container under pressure.The hardness, compressive strength, and flexural strength of thewood are increased, and the wood becomes an electric conductorlengthwise of the grain Woods are also metallized with a surfacecoating of metal by vacuum deposition

Sugar pine is one of the most widely used pattern woods for

foundry patterns It replaces eastern white pine, which is scarcer andnow usually more costly Poplar is used for patterns where a firmerwood is desired; cherry or maple is employed where the pattern is to

be used frequently or will be subject to severe treatment Densifiedwood is also used for patterns required to be very wear-resistant.Mahogany is used for small and intricate patterns where a firm tex-ture and freedom from warpage are needed However, for small cast-ings made in quantities on gates, aluminum or brass is morefrequently used

Excelsior is an old trade name, still used, for continuous, curly,

fine wood shavings employed as a packing material for breakablearticles It is light and elastic, and it is also used as a cushioning andstuffing material It is usually made from poplar, aspen, basswood, orcottonwood A cord of wood produces about 1,500 lb (680 kg), but itmay be made as a by-product from other woodworking It is also

called wood fiber and wood wool, but these terms more properly

refer to fibers of controlled size and length used with a resin binder

for molding into handles, knobs, and other imitation wood parts Several plastics are suitable for imitation wood, also called synthetic

wood and plastic lumber And environmental concerns regarding

global deforestation have increased prices of certain woods, makingplastics more cost-competitive

Some wood for special purposes comes from roots or from bushes

The briar used for tobacco pipes is from the roots of the white

heath, Erica arborea, of north Africa Substitutes for briar are the

burls of the laurel and rhododendron Yareta, used for fuel in the

cop-per region of Chile, is a mosslike, woody plant which grows on thesunny northern mountain slopes at altitudes above 12,000 ft (3,658m) and requires several hundred years to reach a useful size

WOOD FLOUR. Finely ground dried wood employed as a filler and asreinforcing material in molding plastics and in linoleum, and as anabsorbent for nitroglycerin It is made largely from light-colored soft-woods, chiefly pine and spruce, but maple and ash flours are pre-ferred where no resin content is desired Woods containing essentialoils, such as cedar, are not suitable Wood flour is produced from saw-dust and shavings by grinding in burr mills It has the appearance ofwheat flour The sizes commonly used are 40, 60, and 80 mesh; thefinest is 140 mesh Grade 1, used as a filler in rubber and plastics,has a particle size of 60 mesh and a specific gravity of 1.25, but 80and 100 mesh are also used for plastic filler Since wood flour absorbsthe resin or gums when mixed in molding plastics and sets hard, it issometimes mixed with mineral powders to vary the hardness andtoughness of the molded product

Vast quantities of sawdust are obtained in the sawmill areas.

Besides being used as a fuel, it is employed for packing, for finishingmetal parts in tumbling machines, for making particleboard, and fordistilling to obtain resins, alcohols, sugars, and other chemicals.Some sawdust is pulped, and as much as 20% of such pulp can beused in kraft paper without loss of strength Hickory, walnut, and

oak sawdusts are used for meat smoking, or for the making of

liq-uid smoke, which is produced by burning the sawdust and

absorb-ing the smoke into water For the rapid production of bacon andother meats, immersion in liquid smoke imitates the flavor ofsmoked meat Some sawdust is used for agricultural mulch and fer-

tilizer by chemical treatment to accelerate decay Bark fuel is

shredded bark, flash-dried and pelletized with powdered coal

Particleboard, made by compressing sawdust or wood particles

with a resin binder into sheets, has uniform strength in all tions, and a smooth, grainless surface When used as a core forveneer panels, it requires no cross-laminating Mechanical pulp fornewsprint can be made from sawdust but the quantity available is

direc-usually not sufficient The material known as ground wood, of

fine-mesh fibers, is made from cord wood, about 1 ton of fibers being

produced from one cord of pulpwood Plastic wood, usually

mar-keted as a paste in tubes for filling cavities or seams in wood ucts, is wood flour or wood cellulose compounded with a syntheticresin of high molecular weight that will give good adhesion but notpenetrate the wood particles to destroy their nature The solvent is

kept low to reduce shrinkage When cured in place, the material can

be machined, polished, and painted

WOOD PRESERVATIVES. These fall into two general classes: oils, such

as creosote and petroleum solutions of pentachlorophenol; and

waterborne salts that are applied as water solutions Coal tar osote, a black or brownish oil made by distilling coal tar, is the oldest

cre-and still one of the more important cre-and useful wood preservatives.Because it has recently been classified as a carcinogen, its use isexpected to decrease Its advantages are high toxicity to wood-destroying organisms; relative insolubility in water and lowvolatility, which impart to it a great degree of permanence under themost varied use conditions; ease of application; ease with which itsdepth of penetration can be determined; general availability and rela-tively low cost; and long record of satisfactory use

Creosotes distilled from tars other than coal tar are used to some

extent for wood preservation For many years, either cold tar or

petroleum oil has been mixed with cold tar creosote in various

pro-portions to lower preservative costs

Water-repellent solutions containing chlorinate phenols, principallypentachlorophenol, in solvents of the mineral spirit type have beenused in commercial treatment of wood by the millwork industry sinceabout 1931 Pentachlorophenol solutions for wood preservation gener-ally contain 5% (by weight) of this chemical, although solutions withvolatile solvents may contain lower or higher concentrations.Preservative systems containing water-repellent components are soldunder various trade names, principally for the dip or equivalent treat-ment of window sash and other millwork According to federal specifi-cations the preservative chemicals may not contain less than 5%pentachlorophenol

Standard wood preservatives used in water solution include acid

copper chromate, ammoniacal copper arsenite, chromated per arsenate, zinc naphthenate, chromated zinc chloride, and fluor chrome arsenate phenol These preservatives are often

cop-employed when cleanliness and paintability of the treated wood arerequired The chromated zinc chloride and fluor chrome arsenate phenolformulations resist leaching less than preservative oils, and are seldomused where a high degree of protection is required for wood in groundcontact or for other wet installations Several formulations involvingcombinations of copper, chromium, and arsenic have shown high resis-tance to leaching and very good performance in service The ammonia-cal copper arsenite and chromated copper arsenate are included inspecifications for such items as building foundations, building poles,utility poles, marine piling, and piling for land and freshwater use

Organic sulfones are another class of wood preservatives offering high

degrees of protection One such product is diiodomethyl p-tolyl

sul-fone, with trade name Amical, from Angus Chemical Co.

WOOL. The fine, soft, curly hair or fleece of the sheep, alpaca, vicuña,

certain goats, and a few other animals The specific designation wool

always means the wool of sheep Sheep’s wool is one of the most

important commercial fibers because of its good physical qualities andits insulating value, especially for clothing, but it now constitutes onlyabout 10% of the textile fiber market It is best known for its use in

clothing fabrics, called woolens These are designated under a variety

of very old general trade names such as a loosely woven fabric called

flannel, or the fine, smooth fabric known as broadcloth Cheviot is a

close-napped, twill-woven fabric, and tweed is a woolen fabric with a coarse surface, usually with a herringbone-twill weave Serge is a twill-woven worsted fabric Worsteds are wool fabrics made from

combed-wool yarn, usually from long, smooth wool Wool is alsoemployed for packings and for insulation, either loose or felted, and formaking felts The average amount of wool shorn from sheep in theUnited States is 8.1 lb (3.7 kg) per animal

Wool differs from hair in fineness and its felting and spinning erties The latter are due to the fine scales of the wool fibers Thefinest short-staple wool has as many as 4,000 scales to the inch (2.5cm), and the average long-staple wool has about 2,000 scales per inch(2.5 cm) These scales give wool its cohesive qualities Some animalshave both wool and hair, while others have wool only when young.There is no sharp dividing line between wool and hair

prop-Wool quality is by fineness, softness, length, and scaliness Fiberdiameters vary from 0.0025 to 0.005 in (0.0064 to 0.013 cm) Longwools are generally heavy Fibers below 3 in (7.6 cm) in length are

known as clothing wool, and those from 3 to 7 in (7.6 to 17.8 cm) are called combing wools Long wools are fibers longer than 7 in (17.8 cm) The term apparel wool generally means clothing wool of fine weaving quality from known sources Fleece wool is the unscoured

fiber It may contain as much as 65% grease and dirt, but this is theform in which wool is normally shipped because it then has the pro-tection of the wool fat until it is manufactured Wool is very absorbent

to moisture and will take up about 33% of its weight of water, and insome areas moisture and dirty grease are added to fleece wool to

increase weight Carpet wools are usually long, nonresilient fibers from sheep bred in severe climates, such as the Mongolian wool.

The only breed of sheep developed for wool alone is the merino In

Australia the corriedale and the polworth sheep are dual-purpose

animals for wool and meat

The finest of sheep wools come from the merino sheep, but these vary according to the age of breeding of the animal The Lincoln

sheep produces the longest fiber It is lustrous but very coarse.

Luster of wool depends upon the size and smoothness of the scales,but the chemical composition is important The molecular chains arelinked with sulfur, and when sulfur is fed to the sheep, in some defi-cient areas the quality of the wool is improved Crimpiness in wool isdue to the open formation of the scales A fine merino will have 24crimps per inch (2.5 cm), whereas a coarse crossbreed will have only 6per inch (2.5 cm) Strength of wool fibers often depends upon thehealth of the animal and the feeding

One-quarter of the world production of wool is in Australia.Argentina ranks second in production, with the United States third.But the United States is a lamb-eating nation, and a large proportion

of the animals are slaughtered when 4 to 8 months old, and most ofthe others are kept only one season for one crop of wool New Zealand,Uruguay, Russia, and England are also important producers England

is the center of wool-sheep breeding, with more varieties than anyother country In general, warm climates produce fine wools, and hotclimates produce thin, wiry wools, but the fundamental differences

come from the type of animal and the feeding The reused wool from old cloth was originally called shoddy, but the name has an opprobri-

ous signification in the United States, and is not used by ers to designate the fabrics made from reclaimed wool Shoddy is used

manufactur-in mixtures with new wool for clothmanufactur-ing and other fabrics Extract

wool is shoddy that is recovered by dissolving out the cotton fibers of

the old cloth with sulfuric acid Short fibers of shoddy, less than 0.5 in

(1.27 cm), are known as mungo fibers They are used in woolen blends to obtain a napped effect Reprocessed wool is fiber obtained from waste fabric which has not been used Noils are short fibers pro-

duced in the combining of wool tops for making worsteds They are

used for woolen goods and felt Zeset, of Du Pont, a shrinkproofing agent for wools, is a variant of Surlyn T, a terpolymer of 70% ethyl-

ene, 6 methacryloyl chloride, and 24 vinyl acetate It prevents age and pilling under ordinary laundry methods, does not affect color,and increases the tensile strength of the fiber But all resinous addi-tives tend to harden the fiber and lessen the drape and feel.Conversely, each dry cleaning of wool fabric decreases the natural oilcontent and hardens the fiber

shrink-WOOL GREASE. A brownish, waxy fat of a faint, disagreeable odor,obtained as a by-product in the scouring of wool The purified grease

was formerly known as degras and was used for leather dressing, in

lubricating and slushing oils, and in soaps and ointments; but it is now

largely employed for the production of lanolin and its derivatives,

chiefly for cosmetics Wool grease contains lanoceric acid;

lanopalmic acid, C15H30O3; and lanosterol, a high alcohol related to

cholesterol All of these can be broken down into derivatives

Lanolin is a purified and hydrated grease, also known as lanain,

and in pharmacy as lanum and adeps lanae It has a melting point

of about 104°F (40°C) and is soluble in alcohol Lanolin is basically awax consisting of esters of sterol alcohols combined with straight-chain fatty acids, and with only a small proportion of free alcohols Itcontains about 95% of fatty acid esters, but its direct use as an emol-lient depends on the 5% of free alcohols and acids However, morethan 30 derivatives are obtained from lanolin, and these are used inblends to give specific properties to cosmetics They are often mar-keted under trade names, and some of the ingredients may be synthe-sized from raw materials other than wool grease, or chemicallyaltered from wool-grease derivatives

A variety of products used in cosmetics and pharmaceuticals aremade by fractionation or chemical alteration of lanolin They are alsouseful in compounding plastics and industrial coating, but are gener-

ally too scarce and expensive for these purposes Ethoxylated

lano-lin and ethoxylated lanolano-lin alcohols are used in water-soluble

emulsions and conditioners Solulan is a general trade name for these materials Lanolin oil and lanolin wax are made by solvent fractionation of lanolin Viscolan and Waxolan are these products.

Isopropyl lanolates, with trade name Amerlate, are soft,

hydrophylic solids which liquefy easily and are used in cosmetics as

emollients, emulsifiers, and pigment dispersants Amerlate LFA is

derived from lanolin hydroxy acids containing iso-acids The highhydroxyl content produces the emollient and emulsifying qualities

Barium lanolate, made by saponification, is used as an

anticorro-sion agent It is antiphobic and is also used as an anticaking agent In

a 25% barium concentration it is used for hard lubricating grease

Ethoxylan is an ethylene oxide derivative of lanolin, soluble in

water and in alcohol, and used in shampoos Ceralan is a waxy solid

melting at 131°F (55°C) to an amber-colored, viscous liquid It is amixture of monohydroxyl alcohols, obtained by splitting lanolin, andcontains 30% sterol, and free cholesterol It forms water-in-oil emul-sions and is used in cosmetics as a dispersing and stiffening agent

and as an emollient Acetylated lanolin is made by reacting lanolin

with polyoxyethylenes They are clear, nongreasy liquids soluble inwater, oils, and alcohol The acetylated lanolin is hydrophobic and oil-soluble, and is used as an odorless, nontacky emollient in cosmet-

ics Acylan, from Croda Chemicals, is a soft solid with a bland odor

that is employed in baby products, hair grooms, creams, and

ceuticals Oil-based solutions of Acylan are clear, forming soft, waxy,

hydrophobic films Satulan of the same firm is a hydrogenated

lanolin useful in products for skin protection.

Veriderm, of Upjohn Co., is a substitute for lanolin as an

emol-lient It contains about the same percentage of triglycerol esters offatty acids, free cholesterol, and saturated and unsaturated hydrocar-bons as occurs in the natural human skin oils Cholesterol is one of

the most important of the complex sterols, or zoosterols, from

ani-mal sources It is produced from lanolin, but also from other sources,

and used in drugs and cosmetics Amerchol L-101 is a liquid

non-ionic cholesterol containing other sterols Wool grease from the

scour-ing of wool was originally called Yorkshire grease Moellon degras

is not wool grease, but is a by-product of chamois leather making Thesheepskins are impregnated with fish oil, and when the tanning iscomplete, they are soaked in warm water and the excess oil is pressedout to form the moellon degras

WROUGHT IRON. Commercially pure iron made by melting white castiron and passing an oxidizing flame over it, leaving the iron in aporous condition which is then rolled to unite it into one mass Asthus made, it has a fibrous structure, with fibers of slag through theiron in the direction of rolling It is also made by the Aston process ofshooting Bessemer iron into a ladle of molten slag Modern wroughtiron has a fine dispersion of silicate inclusions which interrupt thegranular pattern and give it a fibrous nature

The value of wrought iron is in its corrosion resistance and ity It is used chiefly for rivets, staybolts, water pipes, tank plates,

ductil-and forged work Minimum specifications for ASTM wrought iron

call for a tensile strength of 40,000 lb/in2(276 MPa), yield strength of24,000 lb/in2 (165 MPa), and elongation of 12%, with carbon not over

0.08%, but the physical properties are usually higher Wrought iron

4D has only 0.02% carbon with 0.12 phosphorus, and the fine fibers

are of a controlled composition of silicon, manganese, and rus This iron has a tensile strength of 48,000 lb/in2(331 MPa), elon-

phospho-gation 14%, and Brinell hardness 105 Mn wrought iron has 1%

manganese for higher impact strength

Ordinary wrought iron with slag may contain frequent slag cracks,and the quality grades are now made by controlled additions of sili-cate, and with controlled working to obtain uniformity But for tanks

and plate work, ingot iron is now usually substituted Merchant bar

iron is an old name for wrought-iron bars and rods made by

faggot-ing and forgfaggot-ing Iron-fibered steel is soft steel with fine iron wire worked into it Staybolt iron may be wrought iron, but was origi- nally puddled charcoal iron Lewis iron, for staybolts, is highly

refined, puddled iron with a tensile strength of 52,000 lb/in2 (359MPa) and elongation of 30%.

The Norway iron formerly much used for bolts and rivets was a

Swedish charcoal iron brought to America in Norwegian ships.

This iron, with as low as 0.02% carbon, and extremely low silicon, fur, and phosphorus, was valued for its great ductility and toughnessand for its permeability qualities for transformer cores Commercialwrought iron is now usually ingot iron or fibered low-carbon steel

sul-YARNS. Assemblages or bundles of fibers twisted or laid together toform continuous strands They are produced with either filaments orstaple fibers Single strands of yarns can be twisted together to form ply

or plied yarns, and ply yarns in turn can be twisted together to formcabled yarn or cord Important yarn characteristics related to behaviorare fineness (diameter or linear density) and number of twists per unit

length The measuring of fineness is commonly referred to as yarn number Yarn numbering systems are somewhat complex, and they are

different for different types of fibers Essentially, they provide a sure of fineness in terms of weight per unit or length per unit weight

mea-Cotton yarns are designated by numbers, or counts The

stan-dard count of cotton is 840 yd/lb (1,690 m/kg) Number 10 yarn istherefore 8,400 yd/lb (16,900 m/kg) A No 80 sewing cotton is 80840,

or 67,200 yd/lb (135,500 m/kg)

Linen yarns are designated by the lea of 300 yd (274 m) A

10-count linen yarn is 10  300, or 3,000 yd/lb (6,048 m/kg)

The size or count of spun rayon yarns is on the same basis as

cot-ton yarn The size or count of rayon filament yarn is on the basis of

the denier, the rayon denier being 492 yd (450 m), weighing 0.00011

lb (5 cg) If 492 yd of yarn weighs 0.00011 lb, it has a count of 1denier If it weighs 0.0011 lb (10 cg), it is No 2 denier Rayon yarnsrun from 15 denier, the finest, to 1,200 denier, the coarsest

Reeled silk yarn counts are designated in deniers The

interna-tional denier for reeled silk is 547 yd (500 m) of yarn weighing

0.00011 lb If 547 yd weighs 0.0022 lb (1 g), the denier is No 20 Spunsilk count under the English system is the same as the cotton count.Under the French system the count is designated by the number of

skeins weighing 2.205 lb (1 kg) The skein of silk is 1,094 yd (1,000 m).

A ply yarn is one that has two or more yarns twisted together A

two-ply yarn has two separate yarns twisted together The separateyarns may be of different materials, such as cotton and rayon A six-ply yarn has six separate yarns A ply yarn may have the differentplies of different twists to give different effects Ply yarns are strongerthan single yarns of the same diameter Tightly twisted yarns makestrong, hard fabrics Linen yarns are not twisted as tightly as cotton

because the flux fiber is longer, stronger, and not as fuzzy as the

cot-ton Filament rayon yarn is made from long, continuous rayon

fibers, and it requires only slight twist Fabrics made from filament

yarn are called twalle Monofilament is fiber heavy enough to be used alone as yarn, usually more than 15 denier Tow consists of mul-

tifilament reject strands suitable for cutting into staple lengths for

spinning Spun rayon yarn is yarn made from staple fiber, which is

rayon filament cut into standard short lengths

YUCCA FIBER. The fiber obtained from the leaves of a number of

desert plants of the genus Yucca of the lily family native to the

south-western United States and northern Mexico The fiber is similar tofibers from agave plants and is often confused with them and withistle The heavier fibers are used for brushes, and the lighter fibersare employed for cordage and burlap fabrics In Mexico the word

palma designates yucca fibers and grades of istle as well as palm-leaf

fibers Palma samandoca is fiber from the plant Samuela osana, the date yucca It is also called palma istle Palmilla fiber

carner-is from Y elata Palma pita carner-is a fiber from Y treculeana Pita fiber

used for coffee bags in Colombia and Central America is from a

differ-ent plant Other yucca fibers come from the plants Y glauca, Y cata, and Y gloriosa Some varieties of Y baccata also yield edible

bac-fruits The roots of species of yucca yield saponin which is alsoobtained as a by-product in extracting the yucca fiber

ZINC. A bluish-white, crystalline metal, symbol Zn, with a specificgravity of 7.13, melting at 788°F (420°C) and boiling at 1662°F(906°C) The commercially pure metal has a tensile strength, cast, ofabout 9,000 lb/in2 (62 MPa) with elongation of 1%, and the rolledmetal has a strength of 24,000 lb/in2 (165 MPa) with elongation of35% But small amounts of alloying elements harden and strengthenthe metal, and it is seldom used alone Zinc is used for galvanizingand plating; for making brass, bronze, and nickel silver; for electricbatteries; for die castings; and in alloyed sheets for flashings, gutters,and stamped and formed parts The metal is harder than tin, and anelectrodeposited plate has a Vickers hardness of about 45 Zinc is alsoused for many chemicals

The old name spelter, often applied to slab zinc, came from the

name spailter used by Dutch traders for the zinc brought from China.

The first zinc produced in the United States in 1838 came from New

Jersey ore Sterling spelter was 99.5% pure Special high-grade zinc

is distilled, with a purity of 99.99%, containing no more than 0.006%lead and 0.004 cadmium High-grade zinc, used in alloys for die cast-

ing, is 99.9% pure, with 0.07 maximum lead Brass special zinc is

99.10% pure, with 0.06 maximum lead and 0.5 maximum cadmium.

Prime western zinc, used for galvanizing, contains 1.60%

maxi-mum lead and 0.08 maximaxi-mum iron Zinc crystals produced for

elec-tronic uses are 99.999% pure metal

On exposure to the air, zinc becomes coated with a film of carbonate

and is then very corrosion-resistant Zinc foil comes in thicknesses

from 0.001 to 0.006 in (0.003 to 0.015 cm) It is produced by position on an aluminum drum cathode and stripping off on a collect-

electrode-ing reel But most of the zinc sheet contains a small amount of

alloying elements to increase the physical properties Slight amounts

of copper and titanium reduce grain size in sheet zinc In cast zinc thehexagonal columnar grain extends from the mold face to the surface

or to other grains growing from another mold face, and even veryslight additions of iron can control this grain growth Aluminum isalso much used in alloying zinc In zinc used for galvanizing, a smalladdition of aluminum prevents formation of brittle alloy layer,increases ductility of the coating, and gives a smoother surface Smalladditions of tin give bright, spangled coatings

Zinc has 12 isotopes, but the natural material consists of 5 stable

isotopes, of which nearly half is zinc 64 The stable isotope zinc 67,

occurring to the extent of about 4% in natural zinc, is sensitive to tinyvariations in transmitted energy, giving off electromagnetic radia-tions which permit high accuracy in measuring instruments It mea-sures gamma-ray vibrations with great sensitivity and is used in thenuclear clock

Zinc powder, or zinc dust, is a fine, gray powder of 97% minimum

purity usually in 325-mesh particle size It is used in pyrotechnics, inpaints, as a reducing agent and catalyst, in rubbers as a secondary dis-

persing agent and to increase flexing, and to produce Sherardized

steel Sherardizing consists in hot-tumbling steel parts in a closed

drum with the zinc powder It is a form of galvanizing, and controlledzinc coatings of 0.1 to 0.4 oz/ft2 (0.4 to 1.8 g/cm2) of surface give goodcorrosion protection In paints, zinc powder is easily wetted by oils It

keeps the zinc oxide in suspension and hardens the film Mossy zinc,

used to obtain color effects on face brick, is a spangly zinc powder made

by pouring the molten metal into water Feathered zinc is a fine grade

of mossy zinc Photoengraving zinc for printing plates is made from

pure zinc with only a small amount of iron to reduce grain size andalloyed with not more than 0.2% each of cadmium, manganese, and

magnesium Cathodic zinc, used in the form of small bars or plates

fastened to the hulls of ships or to underground pipelines to reduce trolytic corrosion, is zinc of 99.99% purity with iron less than 0.0014 to

elec-prevent polarization Merrillite is high-purity zinc dust Zinc serves as the anode in the zinc-air battery, which, for powering electric vehi-

cles, has demonstrated much greater storage capacity than the

com-mon lead-acid battery.

ZINC ALLOYS. Alloys of zinc are mostly used for die castings for rative parts and for functional parts where the load-bearing andshock requirements are relatively low Since the zinc alloys can becast easily in high-speed machines, producing parts that weigh lessthan brass and have high accuracy and smooth surfaces that requireminimum machining and finishing, they are widely used for suchparts as handles, and for gears, levers, pawls, and other small parts.Zinc alloys for sheet contain only small amounts of alloying elements,with 92 to 98% zinc, and the sheet is generally referred to simply as

deco-zinc or by a trade name The modified deco-zinc sheet is used for

stamped, drawn, or spun parts for costume jewelry and electronics,and it contains up to 1.5% copper and 0.5 titanium The titaniumraises the recrystallization temperature, permitting heat treatmentwithout coarse-grain formation

Hartzink had 5% iron and 2 to 3 lead, but iron forms various

chemical compounds with zinc and the alloy is hard and brittle

Copper reduces the brittleness Germania bearing bronze

con-tained 1% iron, 10 tin, about 5 each of copper and lead, and the

bal-ance zinc Fenton’s alloy had 14% tin, 6 copper, and 80 zinc; and

Ehrhard’s bearing metal contained 2.5% aluminum, 10 copper, 1

lead, and a small amount of tin to form copper-tin crystals Binding

metal, for wire-rope slings, has about 2.8% tin, 3.7 antimony, and the

balance zinc Pattern metal, for casting gates of small patterns, was

almost any brass with more zinc and some lead added, but is nowstandard die-casting metal

Zinc alloys are commonly used for die castings, and the zinc used is

high-purity zinc known as special high-grade zinc ASTM AG40A (SAE 903) is the most widely used; others include AC41A (SAE 925), Alloy 7, and ILZRO 16 All typically contain about 4%

aluminum, small amounts of copper and very small amounts of nesium AG40A has a density of 0.24 lb/ft3(6,643 kg/m3), an electricalconductivity 27% that of copper, a thermal conductivity of 65 Btu/(ft

mag-h °F) [113 W/(m  K)], an ultimate tensile strength of 41,000 lb/in2

(283 MPa), and a Brinell hardness of 82 AC41A is stronger [48,000lb/in2 (331 MPa)] and harder (Brinell 91), a trifle less electrically andheat-conductive, and similar in density The alloys have much greaterunnotched Charpy impact strength than either die-cast aluminum ormagnesium alloys, but are not especially heat-resistant, losing aboutone-third of their strength at temperatures above about 200°F (93°C).Both alloys have found wide use for auto and appliance parts, espe-cially chromium-plated parts, as well as for office equipment parts,

hardware, locks, toys, and novelties Alloy 7 is noted primarily for itsbetter castability and the smoother surface finish it provides It is asstrong as AG40A, though slightly less hard, and more ductile ILZRO

16 is not nearly as strong [33,000 lb/in2 (228 MPa)], but more creep-resistant at room and elevated temperatures

The most recent casting alloys are three high-aluminum zinc

casting alloys for sand and permanent-mold casting: ZA-8, ZA-12,

and ZA-27, the numerals in the designations indicating

approxi-mate aluminum content They also contain more copper thanAG40A and AC41A, from 0.5 to 1.2% in ZA-12 to 2 to 2.5 in ZA-27,and a bit less magnesium As sand-cast, ultimate tensile strengthsrange from 36,000 to 40,000 lb/in2 (248 to 276 MPa) for ZA-8 and58,000 to 64,000 lb/in2(400 to 441 MPa) for ZA-27 Unlike the com-mon die-casting alloys, the ZA alloys also exhibit clearly definedtensile yield strengths: from 28,000 lb/in2 (193 MPa) minimum forsand-cast ZA-8 to 53,000 lb/in2 (365 MPa) for sand-cast ZA-27.Tensile modulus is roughly 12106 lb/in2 (83,000 MPa) Also,because of their greater aluminum content, they are lighter in

weight than the die casting alloys Zinc-copper-aluminum alloys developed at General Motors and designated ACuZinc alloys, are

noted for high tensile strength and superior creep resistance.ACuZinc 5, with 5% copper and 3 aluminum, has a tensile strength

of 59,000 lb/in2 (407 MPa) ACuZinc 10, with 10% copper and 3.5aluminum, has a creep strength of 8,000 lb/in2 (55 MPa) at 120°F(49°C) for 0.2% creep in 10,000 h

Manganese-zinc alloys, with up to 25% manganese, for

high-strength extrusions and forgings, are really 60–40 brass with part ofthe copper replaced by an equal amount of manganese, and are classi-fied with manganese bronze They have a bright white color and are

corrosion-resistant Zam metal, for zinc-plating anodes, is zinc with

small percentages of aluminum and mercury to stabilize against acid

attack A zinc-aluminum-oxide coating imparts corrosion

resis-tance to steel underhood and underbody auto parts Developed byMetal Coatings International, it consists of zinc and aluminum flakes

in a waterborne, neutral pH solution that complies with regulationsgoverning emission of volatile organic compounds It is applied bydipping or spraying Baking during curing forms an insoluble matrix

of silicon, aluminum, and zinc oxides between the flakes for corrosionprotection

CorroBan, of Pure Coatings Inc., is an electrolytically deposited

coating of 82 to 89% zinc, balance nickel, which resists corrosion as

well as cadmium plating Zinc solders are used for joining minum The tin-zinc solders have 70 to 80% tin, about 1.5 alu-

alu-minum, and the balance zinc The working range is 500 to 590°F

(260 to 310°C) Zinc-cadmium solder has about 60% zinc and 40

cadmium The pasty range is between 510 and 599°F (266 and315°C)

A group of wrought alloys, called superplastic zinc alloys,

have elongations of up to 2,500% in the annealed condition Thesealloys contain about 22% aluminum One grade can be annealedand air-cooled to a strength of 71,000 lb/in2(490 MPa) Parts made

of these alloys have been produced by vacuum forming and by acompression molding technique similar to forging but requiringlower pressures

ZINC CHEMICALS. With the exception of the oxide, the quantities ofzinc compounds consumed are not large compared with many othermetals, but zinc chemicals have a very wide range of use, being essen-tial in almost all industries and for the maintenance of animal andvegetable life Zinc is a complex element and can provide someunusual conditions in alloys and chemicals

Zinc oxide, ZnO, is a white, water-insoluble, refractory powder

melting at about 3587°F (1975°C), having a specific gravity of 5.66 It

is much used as a pigment and accelerator in paints and rubbers Itshigh refractive index, about 2.01, absorption of ultraviolet light, andfine particle size give high hiding power in paints, and make it alsouseful in such products as cosmetic creams to protect against sun-burn Commercial zinc oxide is always white, and in the paint indus-

try is also called zinc white and Chinese white But with a small

excess of zinc atoms in the crystals, obtained by heat treatment, thecolor is brown to red

In paints, zinc oxide is not as whitening as lithopone, but it resiststhe action of ultraviolet rays and is not affected by sulfur atmo-

spheres, and is thus valued in outside paints Leaded zinc oxide,

consisting of zinc oxide and basic lead sulfate, is used in paints, butfor use in rubber the oxide must be free of lead The lead-free variety

is also called French process zinc oxide Canfelzo is one such

product, from Pigment & Chemical Corp In insulating compoundszinc oxide improves electrical resistance In paper coatings it gives

opacity and improves the finish Zinc-white paste for paint mixing usually has 90% oxide and 10 oil Zinc oxide stabilizers, composed

of zinc oxides and other chemicals, can be added to plastic moldingcompounds to reduce the deteriorating effects of sunlight and othertypes of degrading atmospheres

Zinc oxide crystals are used for transducers and other

piezoelec-tric devices The crystals are hexagonal and are effective at elevatedtemperatures, as the crystal has no phase change up to its disassocia-tion point The resistivity range is 0.2 to 3.9   in (0.5 to 10   cm)

Zinc oxide has luminescent and light-sensitive properties which areutilized in phosphors and ferrites But the oxygen-dominated zincphosphors used for radar and television are modifications of zinc sul-

fide phosphors The zinc sulfide phosphors which produce

lumines-cence by exposure to light are made with zinc sulfide mixed withabout 2% sodium chloride and 0.005 copper, manganese, or other acti-vator, and fired in a nonoxidizing atmosphere The cubic crystal struc-ture of zinc sulfide changes to a stable hexagonal structure at 1868°F(1020°C), but both forms have the phosphor properties Thin films

and crystals of zinc selenide with purities of 99.999% are used for

photo- or electroluminescent devices Zinc selenide is also used foroptical lenses in CO2laser systems Zinc sulfide is a white powder of

composition ZnS H2O, and is also used as a paint pigment, for

whitening rubber, and for paper coating Cryptone is zinc sulfide for

pigment use in various grades, some grades containing barium fate, calcium sulfide, or titanium dioxide Multilayer coatings of zincsulfide and yttria protect zinc sulfide infrared sensor windows of mis-siles and military aircraft from harsh flight environments

sul-Zinc is an amphoteric element, having both acid and basic

prop-erties, and it combines with fatty acids to form metallic soaps, or with

the alkali metals or with ammonia to form zincates Sodium

zin-cate is used for waterproofing asbestos-cement shingles Zinc stearate, ZN(C18H35O2)2, is a zinc soap in the form of a fine, white

powder used in paints and in rubber A USP grade of 325 mesh is

used in cosmetics Aquazinc and Liquizinc, of Rubba, Inc., are zinc

stearate dispersions in water used as an antitack agent in milling

rubber Zinc acetate, Zn(C2H3O2)2, is a white solid partly soluble inwater, used as a mordant, as a wood preservative, in porcelain glazes,and as a mild antiseptic in pharmaceuticals

Zinc sulfate, ZnSO4 7H2O, is the chief material for supplying zinc

in fertilizers, agricultural sprays, and animal feeds For these poses it is used in the form of white vitriol containing 22% zinc, or asthe monohydrate, ZnSO4 H2O, containing 37% zinc Zink Gro is a

pur-water-soluble grade for dry-blended fertilizers for correction of zinc

deficiencies It is from Eagle-Picher Industries, Inc Zinc chloride, a

white, crystalline, water-soluble powder, ZNCl2, was formerly animportant preservative for wood, and railway crossties treated with

the material were called Burnettized wood But it is highly soluble

and leaches out of the wood, and is now chromated and copperized

with sodium bichromate and cupric chloride Copperized CZC, of

Koppers Co., Inc., for treating wood against rot and termites, is perized chromated zinc chloride zinc chloride is also used for vulcan-izing fiber, as a mordant, in mercerizing cotton, in dry batteries, in

cop-disinfecting, and in making many chemicals Spirits of salts and

butter of zinc are old names for the material.

Zinc chromate, used chiefly as a pigment and called zinc yellow

and buttercup yellow, is stable to light and in sulfur atmospheres,

but has a lower tinting strength than chrome yellow, although it isless subject to staining and discoloration It is a crystalline powder ofspecific gravity 3.40 It is only slightly soluble in water, but willabsorb 24 lb (11 kg) of linseed oil per 100 lb (45 kg) Zinc chromatesare made by reacting zinc oxide with chromate solutions, and theymay vary; but the usual composition is 4ZnO 4CrO3 K2O 3H2O

Zinc bichromate, ZnCr2O7, is an orange-yellow pigment The zinc

peroxide used in dental pastes and cosmetics as a mild antiseptic is

a white powder, ZnO2, containing 8.5% active oxygen Organic salts of

zinc that have achieved commercial prominence are zinc

naphthen-ate and zinc pyrithione The former is available in 6 and 8% grades

for prevention of wood rot and decay, in solvent- and water-dispersible

formulations Nap-All and M-Gards are from Mooney Chemicals, Inc., and Zinclear is from Standard Tar Products Co Olin Corp.’s

Zinc Omadine, a zinc pyrithione, is employed as an antidandruff

agent, for preserving cosmetics, in metalworking fluids, and as anantimicrobial on textiles

Fluidized zinc titanate (FZT) can serve as a sorbent to remove

99% of the sulfur dioxide in power plants using sulfur-containing coal

In a process developed at Research Triangle Institute with the U.S.Department of Energy, the sorbent can be continuously recirculatedand the sulfur absorbed recovered from the regenerator off-gas Use

of the sorbent is an alternative to cooling the coal gas to remove fur, then having to reheat it to produce electricity

sul-ZINC ORES. The metal zinc is obtained from a large number of ores,but the average zinc content of the ores in the United States is onlyabout 3%, so that they are concentrated to contain 35 to 65% beforetreatment The sulfide ores are marketed on the basis of 60% zinccontent, and the oxide ores on the basis of 40% zinc content

Sphalerite, or zinc blende, is the most important ore and is found

in quantities in Missouri and surrounding states and in Europe.Sphalerite is a zinc sulfide, ZnS, containing theoretically 67% zinc Ithas a massive crystalline or granular structure and a Mohs hardness

of about 4 When pure, its color is white; it colors yellow, brown,green, to black with impurities The ores from New York State areround and concentrated by flotation to an average of 58% zinc and 32sulfur, which is then concentrated by roasting to 68 zinc and 1 sulfur

It is then sintered to remove lead and cadmium and finally smeltedwith coke, and the zinc vapor condensed The Silesian zinc blende,

known as wurtzite, contains 15% zinc, 2 lead, and some cadmium.

Calamine is found in New Jersey, Pennsylvania, Missouri, and

Europe It is the ore that was formerly mixed directly with copper for

making brass The ore usually contains only about 3% zinc, and isconcentrated to 35 to 45%, and then roasted and distilled Calamine

is zinc silicate, 2ZnO SiO2 H2O It is a mineral occurring in tal groups of a vitreous luster, and it may be white, greenish, yellow,

crys-or brown The specific gravity is 3.4, and Mohs hardness 4.5 to 5 It

occurs in Arkansas with smithsonite, a zinc carbonate ore, ZnCO3

Franklinite is an ore of both the metals zinc and manganese Its

approximate composition is (FeZnMo)O (FeMn)2O3, but it showswide variation in the proportions of the different elements It is found

in the zinc deposits of New Jersey The zinc is converted into zincwhite, and the residue is smelted to form spiegeleisen The mineralfranklinite occurs in massive granular structure with a metallic lus-ter and an iron-black color

The ore zincite is used chiefly for the production of the zinc oxide

known as zinc white employed as a pigment Zincite has the tion ZnO, containing theoretically 80.3% zinc The mineral has usually

composi-a mcomposi-assive grcomposi-anulcomposi-ar structure with composi-a deep-red to orcomposi-ange strecomposi-aked color

It may be translucent or almost opaque Deep-red specimens from theworkings at Franklin, New Jersey, are cut into gemstones for costume

jewelry Willemite is an anhydrous silicate, Zn2SiO4, containing retically 58.5% zinc When manganese replaces part of the zinc, the ore

theo-is called troostite It theo-is in hexagonal prtheo-isms of white, yellow, green, or

blue; manganese makes it apple-green, brown, or red The specific ity is about 4 and Mohs hardness 5.5 The crushed ore is used in makingfluorescent glass The ore is widely dispersed in the United States

grav-ZIRCONIA A white, crystalline powder which is zirconium oxide,

ZrO2, with a specific gravity of 5.7, Mohs hardness 6.5, and refractiveindex 2.2 When pure, its melting point is about 5000°F (2760°C), and

it is one of the most refractory of the ceramics It is produced by ing zircon sand and dolomite at 2500°F (1371°C) and leaching out thesilicates The material is used as fused or sintered ceramics and forcrucibles and furnace bricks From 4.5 to 6% of CaO or other oxide isadded to convert the unstable monoclinic crystal to the stable cubicform with a lowered melting point

react-Fused zirconia, used as a refractory ceramic, has a melting point of

4620°F (2549°C) and a usable temperature to 4450°F (2454°C) The

Zinnorite fused zirconia of Norton Co is a powder that contains less

than 0.8% silica and has a melting point of 4900°F (2704°C) A sintered

zirconia can have a specific gravity of 5.4, a tensile strength of 12,000

lb/in2(83 MPa), compressive strength of 200,000 lb/in2(1,379 MPa), and

Knoop hardness of 1,100 Zircoa B is stabilized cubic zirconia used for making ceramics Zircoa A is the pure monoclinic zirconia used as a

pigment, as a catalyst, in glass, and as an opacifier in ceramic coatings

Zirconia brick for lining electric furnaces has no more than 94%

zirconia, with up to 5 calcium oxide as a stabilizer, and some silica

It melts at about 4300°F (2371°C), but softens at about 3600°F

(1982°C) The IBC 4200 brick of Ipsen Industries, Inc., is zirconia

with calcium and hafnium oxides for stabilizing It withstands peratures to 4200°F (2316°C) in oxidizing atmospheres and to

tem-3000°F (1849°C) in reducing atmospheres Zirconia foam is

mar-keted in bricks and shapes for thermal insulation With a porosity

of 75% it has a flexural strength above 500 lb/in2 (3 MPa) and acompressive strength above 100 lb/in2 (0.7 MPa) For use in cru-cibles, zirconia is insoluble in most metals except the alkali metalsand titanium It is resistant to most oxides, but with silica it formsZrSiO4, and with titania it forms ZrTiO4 Since structural disinte-gration of zirconia refractories comes from crystal alteration, thephase changes are important considerations The monoclinic mater-ial, with a specific gravity of 5.7, is stable to 1850°F (1010°C) andthen inverts to the tetragonal crystal with a specific gravity of 6.1and volume change of 7% It reverts when the temperature againdrops below 1850°F (1010°C) The cubic material, with a specificgravity of 5.55, is stable at all temperatures to the melting point,which is not above 4800°F (2649°C) because of the contained stabi-lizers A lime-stabilized zirconia refractory with a tensile strength

of 20,000 lb/in2(138 MPa) has a tensile strength of 10,000 lb/in2(69

MPa) at 2370°F (1299°C) Stabilized zirconia has a very low

coef-ficient of expansion, and white-hot parts can be plunged into coldwater without breaking The thermal conductivity is only aboutone-third that of magnesia It is also resistant to acids and alkalies

and is a good electrical insulator Diamond Z refers to a line of

“unbreakable” buttons made of zirconia, fired at 3200°F (1760°C),polished and coated to look like ivory Developed by Adolph CoorsCo., they are sold by ACX Technologies for high-priced shirts

Toughening mechanisms, by which a crack in a ceramic can bearrested, complement processing techniques that seek to eliminate

crack-initiating imperfections Transformation toughening relies on

a change in crystal structure (from tetragonal to monoclinic) that nia or zirconium dioxide (ZrO2) grains undergo when they are subjected

zirco-to stresses at a crack tip Because the monoclinic grains have a slightlylarger volume, they can “squeeze” a crack shut as they expand in thecourse of transformation Due to ZrO2’s transformation-toughening abil-ities, which impart higher fracture toughness, research interest inengine applications has been high In order for ZrO2 to be used in high-temperature, structural applications, it must be stabilized or par-tially stabilized to prevent a monoclinic-tetragonal phase change.Stabilization involves the addition of calcia, magnesia, or yttria followed

by some form of heat treatment PSZ ceramic, the toughest known

ceramic, is being investigated for diesel-engine applications

A new zirconia ceramic being developed is tetragonal zirconia

polycrystal (TZP) doped with Y2O3 Designated Y-TZP, it has the

most impressive room-temperature mechanical properties of any conia ceramic The commercial applications of TZP zirconia includescissors having TZP blades suitable for industrial use for cuttingtough fiber fabrics, e.g., Kevlar, cables, and ceramic scalpels for surgi-cal applications One unique application is fish knives The knifeblades are Y-TZP and can be used when the delicate taste of raw fishwould be tainted by slicing with metal-blade knives Tungsten-car-bide-reinforced Y-TZP, developed by Toray Industries and NipponTungsten Co of Japan, has five times the thermal conductivity of Y-TZP and high hardness, strength, toughness, and heat resistance

zir-Magnesia-stabilized PSZ, Mg-PSZ, is fired at a higher

tempera-ture than Y-TZP and, thus, develops a larger grain size: 1,970 to 3,940

in (50 to 100
m) versus 11.8 to 31.5
in (0.3 to 0.8
m).Consequently, Mg-PSZ is slightly porous while Y-TZP is virtually free

of porosity However, this porosity does not affect its sealing behavior

in valve applications Mg-PSZ is not as strong as Y-TZP, but it isslightly tougher and, thus, more resistant to erosion by particleimpingement Also, Mg-PSZ has not exhibited susceptibility to low-temperature degradation in warm, moist environments even with justtrace amounts of water vapor, which has limited Y-TZP to moisture-free valve applications

Another zirconia ceramic–developed material is

zirconia-tough-ened alumina (ZTA) ZTA zirconia is a composite polycrystalline

ceramic containing ZrO2as a dispersed phase (typically about 15 ume %) Close control of initial starting-powder sizes and sinteringschedules is thus necessary in order to attain the desired ZrO2 parti-cle dimensions in the finished ceramic Hence the mechanical proper-ties of the composite ZTA ceramics limit current commercialapplications to cutting tools and ceramic scissors

vol-PSZ is also finding application in the transformation toughening ofmetals used in the glass industry as orifices for glass fiber drawing

This material is being termed zirconia grain-stabilized (ZGS)

platinum.

Zirconia is produced from the zirconium ores known as zircon and

baddeleyite The latter is a natural zirconium oxide, but is

obtain-able commercially only from Minas Gerais, Brazil It is also called

zirkite and Brazilite Zircon is zirconium silicate, ZrO2 SiO2,and comes chiefly from beach sands The commercial sand is found inFlorida, Brazil, India, Sri Lanka, Australia, and western Africa The

sands are also called zirkelite and zirconite, or merely zircon

sand The white zircon sand from India has a zirconia content of 62%

and contains less than 1% iron Beach sands of New South Wales arenaturally concentrated to an average of 74% zircon, but Australianzircon is shipped on a basis of 65% zirconia Zircon sand may be useddirectly for making firebricks, as an opacifier in ceramics, and for

mold facings Clear zircon crystals are valued as gemstones since

the high refractive index gives great brilliance The colorless natural

crystals are called Matura diamonds, and the yellow-red are known

as jacinth.

Zirconia fiber, used for high-temperature textiles, is produced

from zirconia with about 5% lime for stabilization The fiber ispolycrystalline, has a melting point of 4700°F (2593°C), and with-stands continuous temperatures above 3000°F (1649°C) Thesefibers are produced by Union Carbide as small as 118 to 394
in (3

to 10
m) and are made into fabrics for filter and fuel cell use

Zirconia fabrics are woven, knitted, or felted of short-length

fibers and are flexible Ultratemp adhesive, of Aremco Products, for high-heat applications, is zirconia powder in solution At

1100°F (593°C) it adheres strongly to metals and withstands

tem-peratures to 4400°F (2427°C) Zircar, of Union Carbide, is zirconia

fiber compressed into sheets to a density of 20 lb/ft3 (320 kg/m3) Itwithstands temperatures up to 4500°F (2482°C) and has low ther-mal conductivity It is used for insulation and for high-temperaturefiltering

ZIRCONIUM. A silvery-white metal, symbol Zr, having a specificgravity of 6.5 and melting at about 3362°F (1850°C) It is moreabundant than nickel, but is difficult to reduce to metallic form as

it combines easily with oxygen, nitrogen, carbon, and silicon Themetal is obtained from zircon sand by reacting with carbon andthen converting to the tetrachloride, which is reduced to a sponge

metal for further production of shapes The ordinary sponge

zirco-nium contains about 2.5% hafzirco-nium, which is closely related and

difficult to separate The commercial metal usually containshafnium, but reactor-grade zirconium, for use in atomic work, ishafnium-free

Commercially pure zirconium is not a high-strength metal, having

a tensile strength of about 32,000 lb/in2 (221 MPa), elongation 40%,and Brinell hardness 30, or about the same physical properties aspure iron Because of its low neutron-capture cross section, thermalstability, and corrosion resistance, it is the standard metal for fuel-rodcladding and core components in nuclear reactors It is employedmostly in the form of alloys but may be had in 99.99% pure single-crystal rods, sheets, foil, and wire for superconductors, surgical

implants, and vacuum-tube parts The neutron cross section of nium is 0.18 barn, compared with 2.4 for iron and 4.5 for nickel Thecold-worked metal, with 50% reduction, has a tensile strength ofabout 82,000 lb/in2 (565 MPa), with elongation of 18% and Brinellhardness of 95 The unalloyed metal is difficult to roll and is usuallyworked at temperatures to 900°F (482°C) Though nontoxic, the metal

zirco-is pyrophoric because of its heat-generating reaction with oxygen,necessitating special precautions in handling powder and fine chipsresulting from machining operations

The metal has a close-packed hexagonal crystal structure, whichchanges at 1583°F (862°C) to a body-centered cubic structure which isstable to the melting point At 572 to 752°F (300 to 400°C) the metalabsorbs hydrogen rapidly, and above 392°F (200°C) it picks up oxy-gen At about 752°F it picks up nitrogen, and at 1472°F (800°C) theabsorption is rapid, increasing the volume and embrittling the metal.The metal is not attacked by nitric (except red fuming nitric), sulfu-ric, or hydrochloric acids, but is dissolved by hydrofluoric acid It alsoresists phosphoric acid, most organic acids including acetic andformic, strong alkalis, and molten salts And it is one of the few mate-rials that works well in alternating contact with strong acids andbasic environments

Zirconium powder is very reactive, and for making sintered

met-als it is usually marketed as zirconium hydride, ZrH2, containingabout 2% hydrogen which is driven off when the powder is heated to300°C For making sintered parts, alloyed powders are also used

Zirconium copper, containing 35% zirconium, zirconium nickel,

with 35 to 50% zirconium, and zirconium cobalt, with 50%

zirco-nium, are marketed as powders of 200 to 300 mesh

Small amounts of zirconium are used in many steels It is a erful deoxidizer, removes the nitrogen, and combines with the sul-

pow-fur, reducing hot-shortness and giving ductility Zirconium steels

with small amounts of residual zirconium have a fine grain and areshock-resistant and fatigue-resistant In amounts above 0.15% thezirconium forms zirconium sulfide and improves the cutting quality

of the steel Zirconium alloys generally have only small amounts

of alloying elements to add strength and resist hydrogen pickup

Zircoloy 2, for reactor structural parts, has 1.5% tin, 0.12 iron,

0.10 chromium, 0.05 nickel, and the balance zirconium Tensilestrength is 68,000 lb/in2 (469 MPa), elongation 37%, and Rockwell

B hardness 89; at 600°F (316°C) it retains a strength of 30,000lb/in2(207 MPa)

Small amounts of zirconium in copper give age-hardening andincrease the tensile strength Copper alloys containing even small

amounts of zirconium are called zirconium bronze They pour

more easily than bronzes with titanium, and they have good cal conductivity Zirconium-copper master alloy for adding zirco-nium to brasses and bronzes is marketed in grades with 12.5 and

electri-35% zirconium A nickel-zirconium master alloy has 40 to 50%

nickel, 25 to 30 zirconium, 10 aluminum, and up to 10 silicon and 5

iron Zirconium-ferrosilicon, for alloying with steel, contains 9 to

12% zirconium, 40 to 47 silicon, 40 to 45 iron, and 0.20 maximum

carbon, but other compositions are available for special uses SMZ

alloy, for making high-strength cast irons without leaving residual

zirconium in the iron, has about 75% silicon, 7 manganese, 7 nium, and the balance iron A typical zirconium copper for electrical

zirco-use is Amzirc It is oxygen-free copper with only 0.15% zirconium

added At 752°F (400°C) it has an electrical conductivity of 37% ofelectrolytic-tough-pitch copper (C11100), tensile strength of 52,000lb/in2 (359 MPa), and elongation of 9% The softening temperature

is 1076°F (580°C)

Zirconium alloys with high zirconium content have few uses

except for atomic applications Zircoloy tubing is used to contain

the uranium oxide fuel pellets in reactors since the zirconium does

not have grain growth and deterioration from radiation Zirconia

ceramics are valued for electrical and high-temperature parts and

refractory coatings Zirconium-oxide powder, for flame-sprayed

coatings, comes in either hexagonal or cubic crystal form

Zirconium silicate, ZrSi2, comes as a tetragonal crystal powder Itsmelting point is about 3000°F (1649°C) and Knoop hardness is about1,000

Zirconium carbide, ZrC2, is produced by heating zirconia with bon at about 3632°F (2000°C) The cubic crystalline powder has a hard-ness of Knoop 2,090 and melting point of 6404°F (3540°C) The powder

car-is used as an abrasive and for hot-pressing into heat-rescar-istant and

abrasion-resistant parts Zirconium oxychloride, ZrOCl2 8H2O, is acream-colored powder soluble in water that is used as a catalyst, in the

manufacture of color lakes, and in textile coatings Zirconium-fused

salt, used to refine aluminum and magnesium, is zirconium chloride, a hygroscopic solid with 86% ZrCl4 Zirconium sulfate,

tetra-Zr(SO4)2 4H2O, comes in fine, white, water-soluble crystals It is used

in high-temperature lubricants, as a protein precipitant, and for

tan-ning to produce white leathers Soluble zirconium is sodium

zirco-nium sulfate, used for the precipitation of proteins, as a stabilizer for

pigments, and as an opacifier in paper Zirconium carbonate is used

in ointments for poison ivy, as the zirconium combines with the

hydroxy groups of the urushiol poison and neutralizes it Zirconium

hydride has been used as a neutron moderator, although the energy

moderation may be chiefly from the hydrogen

The Structure of Matter

Elements, or atoms, are the basic building blocks of all tangible

materials in the universe There are 92 natural elements, or materialatoms, almost all of which are stable, from hydrogen, atomic number

1, or element 1, to uranium, or element 92 Elements of higher atomicweight than uranium are made, but they are unstable, their timedecay being measured progressively as half-life

The atom gets its name from the Greek word atomos, meaning

indi-visible, and it is not divisible by ordinary chemical means The ments are used either alone or in combination for making useful

ele-products They combine either as mechanical mixtures or as

chemi-cal compounds In a mixture each element retains its original

nature and energy, and the constituents of the mixture can be rated by mechanical means In chemical compounds of two or moreelements, the original elements lose their separate identities; the newsubstance formed has entirely different properties, and the atomicenergy stored within the compound is not equal to the sum of the ele-mental energies The atoms in chemical compounds are bonded by

sepa-electrons An alloy is usually a combination of chemical compounds

and mixtures, the metal mixtures in the matrix being gaged by their

maximum fused or liquid solubility, known as the eutectic point.

With the elements the number of different compounds, or useful stances, that can be made by varying the combinations of elementsand the proportions is infinite

sub-The known atoms are arranged progressively in a periodic table

by atomic number, based on the atomic weight of the element

with hydrogen as the unit of mass, though oxygen may be taken asthe point of calculation The atom is not a solid, but a region of energyparticles in motion At various energy levels the geometric shape of

the electron orbit changes, and the apparent ring, or electron shell

structure, is the energy-level extension of the orbital pattern The tances and space covered are so vast in relation to the size of the par-ticle, and the speeds are so great, that the interior of the atom might

dis-be considered mostly empty space As a single atom is a billion ormore times the size of an electron, it is estimated that if the spacewithin the atom could be removed, a thimbleful of atoms would weighmillions of tons If the copper atom were magnified 10 billion times,the electrons that the chemist employs to connect it with anotheratom of a molecule would still be too tiny to be seen Thus, a solidmetal used for construction is a region of relatively vast space popu-lated by energy particles in perpetual motion

The term space chemistry was first used at the beginning of the

twentieth century by the Dutch physicist van’t Hoff, the founder of

modern physical chemistry, but the subject was not new It may besaid that modern atomic science, equipped with advanced experimen-tal methods and testing instruments, has taken up where the Greeks,working only with geometry and the theoretical deductions of meta-physics, left off at their School of Numbers about 450 B.C The Greeksreasoned that all matter came from one source, made from a qualita-

tively indeterminable primordial unit, the monad, now known as

energy It was stated to be incorporeal, but vital and always in

motion This idea of a nonmaterial basis of tangible materials, nownecessary for modern scientific analysis of materials, is intrinsic inhuman logic It came to the Greeks from the Ionians, survivors of theCretan civilization antedating 3000 B.C., and appears in the HebraicGenesis, in the Sanskrit Vedas, and in the Taoism of ancient China.Energy is in harmonic motion, in waves or rays, and may be said to

become a particle of mass when the frequency is 1, that is, a closed unit cycle All materials give off light when activated, and light rays

have the fastest known speed, 186,000 mi/s (300,000 m/s)

More than 70 new elements, to element 168, have been projected,though not all have been synthesized These are higher elementsmade by additions to natural elements Atoms may also be broken

down by the application of high energy The process known as fission

is usually by electric energy built up to extremely high voltage by onant pulsation in a magnetic field in a manner akin to that of thegeneration of lightning in the clouds More than 30 subatomic parti-

res-cles have been isolated Fissionable elements are normally

consid-ered to be only those of high atomic weight and radioactivity, andrelative unstability, but all elements are fissionable

A subatomic unit may be considered as both a wave and a particle The nucleus of the atom is a relative term The proton is identical

to the nucleus of the hydrogen atom, and is one unit of positive tricity The nuclei of all other elements consist of combinations of pro-tons and neutrons The electrons of the various atoms appear to orbitaround the nucleus, but the electron, though considered a negatively

elec-charged particle, is also a beta ray, and the axis of its vortex motion

is in calculable relativity to the respective positron A detachedpositron has only a momentary existence In conjunction with an elec-tron, it forms an atomlike structure known as positronium A spheronmay contain one or more neutrons, and atoms having different num-

bers of neutrons are called isotopes and are of different atomic

weights and different physical properties

The helium atom of mass 4, positive charge 2, and zero valence

has two protons and two neutrons, with the protons apparently in

opposite polarity This combination is called an alpha particle.

Alpha particles are emitted at high velocity from radioactive

ele-1070 STRUCTURE AND PROPERTIES OF MATERIALS

ments, expelling the detached electrons, and when captured aredeposited as helium These usually come from outer-ring spheronsand not necessarily from the inner nucleus The expelled electronsare beta rays When these collide with a nucleus, high-frequency

X-rays break off Gamma rays are emitted from some radioactive

elements The difference between X-rays and gamma rays is their gin and wavelength Gamma rays come from the nucleus; X-rayscome from electrons striking matter Few of the high-energy X-rayscoming from the sun penetrate the atmosphere

ori-Gamma rays from the sun come only in infrequent bursts, and the

cosmic rays from space are also entirely protons, or stripped ions of

hydrogen Cosmic rays appear to travel at about the speed of light

Mesons from cosmic rays appear to carry unit charges as beta rays

do, but they have more energy and greater range While beta rays arestopped in human skin, mesons can cause damage throughout thebody High-energy cosmic rays are stopped by the atmosphere, andonly a small proportion penetrate to the earth’s surface

The neutron is a particle of neutral charge with a mass

approxi-mately that of a proton A neutron has a mass 1,838 times that of anelectron, while a proton has a mass 1,836 times that of an electron.High-energy bombardment of nuclei or an individual nucleus yields elec-tron positrons, mesons, and neutrinos In recent work, these seeminglyfundamental particles have been subdivided into quarks and gluons

In the technology of producing and processing materials, the atom isnot subdivided, although in some operations of electrochemistry andelectronics the electron is detached, and particles and rays are alsoemployed, especially for activation With respect to combining ele-

ments, metallurgy is high-energy chemistry In a solid metal, as in

other materials, the atom does not appear alone, and the physical erties of a metal or alloy derive chiefly from the molecular structure.Elements having one, two, or three outside valence electrons are

prop-metals In chemical reactions they can release these electrons and

form positive metal ions The elements having five, six, or seven outer

electrons are nonmetals An element with four outer electrons is a

semimetal and can react as either a metal or a nonmetal An

ele-ment with eight outer electrons is said to have zero valence and is

normally inactive, but by special energy application, or catalyzation,the linkage of the spherons can be broken and the electrons freed forchemical reactions

The elements that make up all the planets and the stellar systems

of the universe appear to be the same as those of the earth There aremany theories for the original formation of the material elements, butthe subject pertains to astronomy rather than to materials technol-ogy, and involves the mathematics of progressive assembly of energy

waves into monoquantic vortices which constitute mass While ments do not have life in the same sense as the term is used for ani-mals and plants, they do have intrinsic habits that can be controlledand altered by changing the environmental conditions Elements aregregarious, and atoms separate only when activated by extremes ofenergy, as with high heat, and they tend to congregate even when dis-sipated in water or air.

ele-Elements have orderly, calculable habits of combining into

mole-cules, or geometrically shaped units bonded to their own kind or to

atoms of other elements Compounding the elements into useful rials is done by the addition or subtraction of energy with considera-tion of time and space Even the automatic reactions of two elements

mate-in proximity, known as chemical affmate-inity, and the seemmate-ing holdmate-ing action of stabilizing agents depend upon a transfer of energy.

The term crystal is usually applied only to molecular structures

which at normal temperatures are hard solids that form into nounced geometric shapes or are capable of being split on precise

pro-planes Solids without apparent planes are termed amorphous But

the crystal shapes tabulated for metals usually represent merely the

typical position pattern of the atoms Single crystals may be cut from

natural crystals, grown by flame melting, or grown chemically by

application of heat and pressure Seed crystals used to initiate

growth are grains or particles made up of many molecules, while a

unit crystal is the unit molecule or, in some cases, the unit pattern of

the lattice, and these determine the shape and nature of the structure

In microscopy the structures of aluminum and silver appear optically

as similar cubes, but the unit crystal of aluminum in the solid stateforms both a cube and a lattice, while the unit crystal of silver forms

no cube and does not lattice, and the metal grains are talline Usually, the smaller the grain size, the nearer the approach tothe physical properties of the single crystal so that large single crys-tals are sometimes made by compacting extremely fine powders

cryptocrys-Quasicrystalline solids are a category of matter intermediatebetween crystals and amorphous materials, such as glasses Termed

quasicrystals, they consist of atoms in ordered arrays, but the

pat-terns they form do not recur at precisely regular intervals

All elements convert progressively from solid to gaseous form by theapplication of energy, usually by heat application, and vice versa by the

extraction of heat The terms solid, liquid, and gas are phase changes

depending on the mobility of the molecule caused by changes in its

three-dimensional shape A gaseous element is one that is a gas at ordinary

temperatures and pressures, such as hydrogen At extremely low

tem-peratures a hydrogen crystal should be a hard, white metal of tocrystalline structure with straight planes of cleavage Liquid

cryp-1072 STRUCTURE AND PROPERTIES OF MATERIALS

hydrogen for rocket fuel normally has a molecule of conical shape in

spin When catalyzed by hot platinum, it changes to an ovaloid shapewhich can pass through a smaller molecular sieve, and it also requires

20% less storage space per unit of fuel These forms are called ortho

hydrogen and meta hydrogen, but are both H2

Phase changes often occur within the solid stage, and the change in

dimensions of the material, called creep, is the effect from change in

volume of the molecules With some materials the liquid stage is soshort as to be undetectable, appearing to pass directly from solid to

vapor, and this transition is called sublimination All molecules

have energy transition points at which they break down to free theoriginal elements or to interact and combine with other available ele-ments to form new compounds For example, iron molecules, havingfree electrons, disintegrate easily in the presence of air or moisture to

form iron oxides This process is called corrosion; in organic materials

it is called decay The molecule of gold has no free electrons and,

because of its high energy, is not broken down easily by the influence

of other elements Thus it is said to be noncorrosive In the case ofaluminum, oxygen from air cross-links the free electrons on the sur-face of the grains and protects the metal from further corrosion

In metallurgy and the metalworking industries, the elements arenormally not used alone in a pure state, and as solids and liquids only

in molecular forms In casting metals and alloys from a melt, the time

of solidification is short, and without the application of high energy, as

in the form of high pressure, there is no growth into large single tals Growth is usually into particles, or grains, which may be singlecrystals or irregular conglomerates of unit crystals In the contraction

crys-of cooling, however, grain boundaries may be so close as to be tectable even at a magnification of 2 million to 1 Thus the impuritiesare likely to be in the unmatched open spaces among the crystals andnot interstitial But with some latticing molecules, such as copper,there is room within the lattice for smaller atoms or molecules, such

unde-as those of beryllium, without interference with the paths of bondingelectrons In the aluminum lattice there appears to be no such room.Organic and other chemicals are usually produced from the ele-

ments by synthesis, that is, built up by progressive steps logically

deduced from known data and theories concerning the natural habitsand characteristics of the atoms and their elementary groups A com-

pound may thus be written as a chemical formula which expresses

graphically the specific number and locations of the atomic elements

in the compound In some degree this system is also used in the

pro-duction of ceramics, i.e., compounds or compound mixtures based on

metallic oxides, where the resultant material is expressed in age proportions of the crystal formulas Alloys are usually made by

batch-mixing the elements, and the resultant material is expressed inweight percentages of the contained elements, not in terms of themolecular structure on which the physical properties of the alloydepend.

1074 STRUCTURE AND PROPERTIES OF MATERIALS

The Natural Elements

Atomic

THE STRUCTURE OF MATTER 1075

The Natural Elements (Continued)

Atomic

1076 STRUCTURE AND PROPERTIES OF MATERIALS

Specific Gravity and Density of Materials