Реферат Aluminium

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Review

>Aluminium


>Content

 

1.Introduction

2.Characteristics

3.Isotopes

4.Naturaloccurrence

5. Production andrefinement

6.Recycling

7. Chemistry

7.1Oxidation state +1

7.2Oxidation state +2

7.3Oxidation state +3

7.4Analysis

8.Applications

8.1 Generaluse

8.2Aluminiumcompounds

8.3Aluminiumalloys instructuralapplications

8.4Householdwiring

9.History

10.Etymology

10.1Nomenclaturehistory

10.2Present-dayspelling

11. Healthconcerns

12.Effect onplants

13.Conclusion

14.References


1.Introduction

 

>Aluminiumis asilverywhite andductilemember of theboron group ofchemicalelements.Ithas thesymbolAl;itsatomicnumberis 13.Itisnotsoluble inwaterundernormalcircumstances.Aluminiumis themostabundant metal in theEarth'scrust, and thethirdmostabundantelementtherein,afteroxygen andsilicon.Itmakes upabout 8%byweight of theEarth’ssolidsurface.Aluminiumistooreactivechemically tooccur innatureas a free metal.Instead, itisfoundcombined inover 270differentminerals.[4] Thechiefsource ofaluminiumisbauxiteore.

>Aluminiumisremarkableforitsability toresistcorrosiondue to thephenomenon ofpassivation andfor themetal'slowdensity.Structuralcomponentsmadefromaluminium anditsalloysarevital to theaerospaceindustry andveryimportant inotherareas oftransportation andbuilding.Itsreactivenaturemakes itusefulas acatalyst oradditive inchemicalmixtures,includingbeingused inammoniumnitrateexplosives toenhanceblast power.

Generalproperties

>Name,symbol,numberaluminium,Al, 13

>Elementcategoryother metal

Group,period,block 13, 3,p

Standardatomicweight 26.9815386(13)g·mol1

Electronconfiguration [>Ne]3s23p1

>Electronspershell 2, 8, 3 (>Image)

>Physicalproperties

>Phasesolid

>Density (>nearr.t.) 2.70g·cm3

>Liquiddensityatm.p. 2.375g·cm3

>Meltingpoint 933.47 K, 660.32 °З, 1220.58 °F

>Boilingpoint 2792 K, 2519 °З, 4566 °F

>Heat of fusion 10.71kJ·mol1

>Heat ofvaporization 294.0kJ·mol1

>Specificheatcapacity (25 °З) 24.200J·mol1·K1

>Vaporpressure

>P/Pa 1 10 100 1k 10k 100k

>atT/K 1482 1632 1817 2054 2364 2790

>Atomicproperties

>Oxidationstates 3, 2[1], 1[2]

(>amphotericoxide)

>Electronegativity 1.61 (>Paulingscale)

>Ionizationenergies

(>more)1st: 577.5kJ·mol1

>2nd: 1816.7kJ·mol1

>3rd: 2744.8kJ·mol1

>Atomicradius 143pm

>Covalentradius 121±4pm

>VanderWaalsradius 184pm

>Miscellanea

>Crystalstructureface-centeredcubic

>Magneticorderingparamagnetic[3]

>Electricalresistivity (20 °З) 28.2n·m

>Thermalconductivity (300 K) 237W·m1·K1

>Thermalexpansion (25 °З) 23.1µm·m1·K1

>Speed of sound (>thinrod) (>r.t.) (>rolled) 5,000m·s1

>Young'smodulus 70GPa

>Shearmodulus 26GPa

>Bulkmodulus 76GPa

>Poisson ratio 0.35

>Mohshardness 2.75

>Vickershardness 167MPa

>Brinellhardness 245MPa

>CASregistrynumber 7429-90-5


2.Characteristics

 

>Aluminiumis asoft,durable,lightweight,malleable metalwithappearancerangingfromsilvery todullgrey,depending on thesurfaceroughness.Aluminiumisnonmagnetic andnonsparking.Itisalsoinsoluble inalcohol,though itcanbesoluble inwater incertainforms. Theyieldstrength ofpurealuminiumis 7–11MPa,whilealuminiumalloyshaveyieldstrengthsrangingfrom 200MPa to 600MPa.[5]Aluminiumhasaboutone-third thedensity andstiffness ofsteel.Itisductile, andeasilymachined,cast,drawn andextruded.

>Corrosionresistancecanbeexcellentdue to athinsurfacelayer ofaluminiumoxide thatformswhen the metalisexposed toair,effectivelypreventingfurtheroxidation. Thestrongestaluminiumalloysarelesscorrosionresistantdue togalvanicreactionswithalloyedcopper.[5]Thiscorrosionresistanceisalsooftengreatlyreducedwhenmanyaqueoussaltsarepresenthowever,particularly in thepresence ofdissimilarmetals.

>Aluminiumatomsarearranged in aface-centredcubic (>fcc)structure.Aluminiumhas astacking-faultenergy ofapproximately 200mJ/m.[6]

>Aluminiumisone of thefewmetals thatretainfullsilveryreflectance infinelypowderedform,making itanimportantcomponent ofsilverpaints.Aluminiummirrorfinishhas thehighestreflectance ofany metal in the 200–400nm (>UV) and the 3000–10000nm (>farIR)regions,while in the 400–700nmvisiblerange itisslightlyoutdonebytin andsilver and in the 700–3000 (>nearIR)bysilver,gold, andcopper.[7]

>Aluminiumis agoodthermal andelectricalconductor,byweightbetterthancopper.Aluminiumiscapable ofbeing asuperconductor,with asuperconductingcriticaltemperature of 1.2kelvin and acriticalmagneticfield ofabout 100gauss.[8]


3.Isotopes

 

>Aluminiumhasnineisotopes,whose massnumbersrangefrom 23 to 30. Only27Al (>stableisotope) and26Al (>radioactiveisotope,t1/2 = 7.2 105 y)occurnaturally;however,27Alhas anaturalabundance of 99.9+ %.26Alisproducedfromargon in theatmospherebyspallationcausedbycosmic-rayprotons.Aluminiumisotopeshavefoundpracticalapplication indatingmarinesediments,manganesenodules,glacialice,quartz in rockexposures, andmeteorites. The ratio of26Al to10Behasbeenused tostudy therole oftransport,deposition,sedimentstorage,burialtimes, anderosion on 105 to 106yeartimescales.[9]Cosmogenic26Alwasfirstapplied instudies of theMoon andmeteorites.Meteoroidfragments,afterdeparturefromtheirparentbodies,areexposed tointensecosmic-raybombardmentduringtheirtravelthroughspace,causingsubstantial26Alproduction.Afterfalling to Earth,atmosphericshieldingprotects themeteoritefragmentsfromfurther26Alproduction, anditsdecaycanthenbeused todetermine themeteorite'sterrestrialage.Meteorite researchhasalsoshown that26Alwasrelativelyabundantat thetime offormation ofourplanetarysystem.Mostmeteoritescientistsbelieve that theenergyreleasedby thedecay of26Alwasresponsiblefor themelting anddifferentiation ofsomeasteroidsaftertheirformation 4.55billionyearsago.[10]


4.Naturaloccurrence

 

>In theEarth'scrust,aluminiumis themostabundant (8.3%byweight)metallicelement and thethirdmostabundant of allelements (>afteroxygen andsilicon).[11]Because ofitsstrongaffinity tooxygen,however, itisalmostneverfound in theelemental state;instead itisfound inoxides orsilicates.Feldspars, themost common group ofminerals in theEarth'scrust,arealuminosilicates.Nativealuminium metalcanbefoundas aminorphase inlowoxygenfugacityenvironments,suchas theinteriors ofcertainvolcanoes.[12]Italsooccurs in themineralsberyl,cryolite,garnet,spinel andturquoise.[11]Impurities inAl2O3,suchaschromium orcobaltyield thegemstonesruby andsapphire,respectively.PureAl2O3,knownasCorundum,isone of thehardestmaterialsknown.[11]

>Althoughaluminiumisanextremely common andwidespreadelement, the commonaluminiummineralsarenoteconomicsources of the metal.Almost allmetallicaluminiumisproducedfrom theorebauxite (>AlOx(OH)3-2x).Bauxiteoccursas aweatheringproduct oflowiron andsilicabedrock intropicalclimaticconditions.[13]Largedeposits ofbauxiteoccur inAustralia,Brazil,Guinea andJamaicabut theprimaryminingareasfor theoreare inGhana,Indonesia,Jamaica, Russia andSurinam.[14]Smelting of theoremainlyoccurs inAustralia,Brazil, Canada,Norway, Russia and the United States.Becausesmeltingisanenergy-intensiveprocess,regionswithexcessnaturalgassupplies (>suchas the UnitedArabEmirates)arebecomingaluminiumrefiners.


5. Production andrefinement

 

>Althoughaluminiumis themostabundantmetallicelement in theEarth'scrust, itisrare inits freeform,occurring inoxygen-deficientenvironmentssuchasvolcanicmud, and itwasonceconsidered aprecious metalmorevaluablethangold.Napoleon III,emperor of France,isreputed tohavegiven abanquetwhere themosthonouredguestsweregivenaluminiumutensils,while theotherguestshad tomakedowithgold.[15][16] The WashingtonMonumentwascompleted,with the 100ounce (2.8kg)aluminiumcapstonebeingput inplace onDecember 6, 1884, inanelaboratededicationceremony.Itwas thelargestsinglepiece ofaluminiumcastat thetime.At thattime,aluminiumwasasexpensiveassilver.[17]Aluminiumhasbeenproduced incommercialquantitiesforjustover 100years.

>Aluminiumis astronglyreactive metal thatforms ahigh-energychemicalbondwithoxygen.Compared tomostothermetals, itisdifficult toextractfromore,suchasbauxite,due to theenergyrequired toreducealuminiumoxide (>Al2O3).Forexample,direct reductionwithcarbon,asisused toproduceiron,isnotchemicallypossible,sincealuminiumis astrongerreducingagentthancarbon.Howeverthereisanindirectcarbothermic reductionpossiblebyusingcarbon andAl2O3whichformsanintermediateAl4C3 andthiscanfurtheryieldaluminum metalat atemperature of1900-2000°C.Thisprocessisstillunderdevelopment.Thisprocesscostslessenergy andyieldsless CO2than theHall-Hroultprocess.[18]Aluminiumoxidehas ameltingpoint ofabout 2,000 °З.Therefore, itmustbeextractedbyelectrolysis.Inthisprocess, thealuminiumoxideisdissolved inmoltencryolite andthenreduced to thepure metal. Theoperationaltemperature of the reductioncellsisaround 950 to 980 °З.Cryoliteisfoundas amineral inGreenland,but inindustrialuse ithasbeenreplacedby asyntheticsubstance.Cryoliteis achemicalcompound ofaluminium,sodium, andcalciumfluorides: (>Na3AlF6). Thealuminiumoxide (awhitepowder)isobtainedbyrefiningbauxite in the Bayerprocess ofKarl Bayer. (>Previously, theDevilleprocesswas thepredominantrefiningtechnology.)

Theelectrolyticprocessreplaced theWhlerprocess,whichinvolved the reduction ofanhydrousaluminiumchloridewithpotassium.Both of theelectrodesused in theelectrolysis ofaluminiumoxidearecarbon.Once therefinedaluminaisdissolved in theelectrolyte,itsionsare free tomovearound. Thereactionat thecathodeis:

>Al3+ + 3 e Al

>Here thealuminiumionisbeingreduced. Thealuminium metalthensinks to thebottom andistapped off,usuallycastintolargeblockscalledaluminiumbilletsforfurtherprocessing.

>At theanode,oxygenisformed:

2O2 O2 + 4 e

>Thiscarbonanodeisthenoxidizedby theoxygen,releasingcarbondioxide:

>O2 + З CO2

Theanodes in a reductioncellmustthereforebereplacedregularly,sincetheyareconsumed in theprocess.

>Unlike theanodes, thecathodesarenotoxidizedbecausethereisnooxygenpresent,as thecarboncathodesareprotectedby theliquidaluminiuminside thecells.Nevertheless,cathodesdoerode,mainlydue toelectrochemicalprocesses and metalmovement.Afterfive totenyears,depending on thecurrentused in theelectrolysis, acellhas toberebuiltbecause ofcathodewear.

Worldproductiontrend ofaluminiumAluminiumelectrolysiswith theHall-Hroultprocessconsumes alot ofenergy,butalternativeprocesseswerealwaysfound tobelessviableeconomically and/orecologically. Theworldwideaveragespecificenergyconsumptionisapproximately 15±0.5kilowatt-hoursperkilogram ofaluminiumproduced (52 to 56MJ/kg). Themostmodernsmeltersachieveapproximately 12.8kW·h/kg (46.1MJ/kg). (>Comparethis to theheat ofreaction, 31MJ/kg, and theGibbs freeenergy ofreaction, 29MJ/kg.)Reduction linecurrentsforoldertechnologiesaretypically 100 to 200kA;state-of-the-artsmelters[19]operateatabout 350kA.Trialshavebeenreportedwith 500kAcells.

Electric powerrepresentsabout 20% to 40% of thecost ofproducingaluminium,depending on thelocation of thesmelter.Smelterstend tobesituatedwhereelectric powerisbothplentiful andinexpensive,suchasSouthAfrica,Ghana, theSouthIsland of NewZealand,Australia, thePeople'sRepublic of China, theMiddleEast, Russia,Quebec and British Columbia in Canada, andIceland.[20]

>Aluminiumoutput in2005In 2005, thePeople'sRepublic of Chinawas thetopproducer ofaluminiumwithalmost aone-fifth worldshare,followedby Russia, Canada, and the USA,reports the BritishGeologicalSurvey.

>Over the last 50years,Australiahasbecome amajorproducer ofbauxiteore and amajorproducer andexporter ofalumina.[21]Australiaproduced 62milliontonnes ofbauxite in 2005. TheAustraliandepositshavesomerefiningproblems,somebeing high insilicabuthave theadvantage ofbeingshallow andrelativelyeasy tomine.[22]

>Aluminiumis astronglyreactive metal thatforms ahigh-energychemicalbondwithoxygen.Compared tomostothermetals, itisdifficult toextractfromore,suchasbauxite,due to theenergyrequired toreducealuminiumoxide (>Al2O3).Forexample,direct reductionwithcarbon,asisused toproduceiron,isnotchemicallypossible,sincealuminiumis astrongerreducingagentthancarbon.Howeverthereisanindirectcarbothermic reductionpossiblebyusingcarbon andAl2O3whichformsanintermediateAl4C3 andthiscanfurtheryieldaluminum metalat atemperature of1900-2000°C.Thisprocessisstillunderdevelopment.Thisprocesscostslessenergy andyieldsless CO2than theHall-Hroultprocess.[18]Aluminiumoxidehas ameltingpoint ofabout 2,000 °З.Therefore, itmustbeextractedbyelectrolysis.Inthisprocess, thealuminiumoxideisdissolved inmoltencryolite andthenreduced to thepure metal. Theoperationaltemperature of the reductioncellsisaround 950 to 980 °З.Cryoliteisfoundas amineral inGreenland,but inindustrialuse ithasbeenreplacedby asyntheticsubstance.Cryoliteis achemicalcompound ofaluminium,sodium, andcalciumfluorides: (>Na3AlF6). Thealuminiumoxide (awhitepowder)isobtainedbyrefiningbauxite in the Bayerprocess ofKarl Bayer. (>Previously, theDevilleprocesswas thepredominantrefiningtechnology.)

Theelectrolyticprocessreplaced theWhlerprocess,whichinvolved the reduction ofanhydrousaluminiumchloridewithpotassium.Both of theelectrodesused in theelectrolysis ofaluminiumoxidearecarbon.Once therefinedaluminaisdissolved in theelectrolyte,itsionsare free tomovearound. Thereactionat thecathodeis:

>Al3+ + 3 e Al

>Here thealuminiumionisbeingreduced. Thealuminium metalthensinks to thebottom andistapped off,usuallycastintolargeblockscalledaluminiumbilletsforfurtherprocessing.

>At theanode,oxygenisformed:

2O2 O2 + 4 e

>Thiscarbonanodeisthenoxidizedby theoxygen,releasingcarbondioxide:

>O2 + З CO2

Theanodes in a reductioncellmustthereforebereplacedregularly,sincetheyareconsumed in theprocess.

>Unlike theanodes, thecathodesarenotoxidizedbecausethereisnooxygenpresent,as thecarboncathodesareprotectedby theliquidaluminiuminside thecells.Nevertheless,cathodesdoerode,mainlydue toelectrochemicalprocesses and metalmovement.Afterfive totenyears,depending on thecurrentused in theelectrolysis, acellhas toberebuiltbecause ofcathodewear.

Worldproductiontrend ofaluminiumAluminiumelectrolysiswith theHall-Hroultprocessconsumes alot ofenergy,butalternativeprocesseswerealwaysfound tobelessviableeconomically and/orecologically. Theworldwideaveragespecificenergyconsumptionisapproximately 15±0.5kilowatt-hoursperkilogram ofaluminiumproduced (52 to 56MJ/kg). Themostmodernsmeltersachieveapproximately 12.8kW·h/kg (46.1MJ/kg). (>Comparethis to theheat ofreaction, 31MJ/kg, and theGibbs freeenergy ofreaction, 29MJ/kg.)Reduction linecurrentsforoldertechnologiesaretypically 100 to 200kA;state-of-the-artsmelters[19]operateatabout 350kA.Trialshavebeenreportedwith 500kAcells.

Electric powerrepresentsabout 20% to 40% of thecost ofproducingaluminium,depending on thelocation of thesmelter.Smelterstend tobesituatedwhereelectric powerisbothplentiful andinexpensive,suchasSouthAfrica,Ghana, theSouthIsland of NewZealand,Australia, thePeople'sRepublic of China, theMiddleEast, Russia,Quebec and British Columbia in Canada, andIceland.[20]

>Aluminiumoutput in2005In 2005, thePeople'sRepublic of Chinawas thetopproducer ofaluminiumwithalmost aone-fifth worldshare,followedby Russia, Canada, and the USA,reports the BritishGeologicalSurvey.

>Over the last 50years,Australiahasbecome amajorproducer ofbauxiteore and amajorproducer andexporter ofalumina.[21]Australiaproduced 62milliontonnes ofbauxite in 2005. TheAustraliandepositshavesomerefiningproblems,somebeing high insilicabuthave theadvantage ofbeingshallow andrelativelyeasy tomine.[22]


6.Recycling

 

>Aluminiumis 100%recyclablewithoutanyloss ofitsnaturalqualities.Recovery of the metalviarecyclinghasbecomeanimportantfacet of thealuminiumindustry.

>Recyclinginvolvesmelting thescrap, aprocess thatrequiresonlyfivepercent of theenergyused toproducealuminiumfromore.However, asignificantpart (up to 15% of theinputmaterial)islostasdross (>ash-likeoxide).[23]

>Recyclingwas alow-profileactivityuntil thelate1960s,when thegrowinguse ofaluminiumbeveragecansbrought it to the publicawareness.

>In Europealuminiumexperiences highrates ofrecycling,rangingfrom 42% ofbeveragecans, 85% ofconstructionmaterials and 95% oftransportvehicles.[24]

>Recycledaluminiumisknownassecondaryaluminium,butmaintains thesamephysicalpropertiesasprimaryaluminium.Secondaryaluminiumisproduced in awiderange offormats andisemployed in 80% of thealloyinjections.Anotherimportantuseisforextrusion.

>Whitedrossfromprimaryaluminiumproduction andfromsecondaryrecyclingoperationsstillcontainsusefulquantities ofaluminiumwhichcanbeextractedindustrially.[25] Theprocessproducesaluminiumbillets,togetherwith ahighlycomplexwastematerial.Thiswasteisdifficult to manage.Itreactswithwater,releasing amixture ofgases (>including,amongothers,hydrogen,acetylene, andammonia)whichspontaneouslyignites oncontactwithair;[26]contactwithdampairresults in therelease ofcopiousquantities ofammoniagas.Despitethesedifficulties,however, thewastehasfounduseas afiller inasphalt andconcrete.[27]


7. Chemistry

 

7.1Oxidation state +1

 

>AlHisproducedwhenaluminiumisheated inanatmosphere ofhydrogen.Al2Oismadebyheating thenormaloxide,Al2O3,withsiliconat 1800 °З in avacuum.[28]

>Al2ScanbemadebyheatingAl2S3withaluminiumshavingsat 1300 °З in avacuum.[28]Itquicklydisproportionates to thestartingmaterials. Theselenideismade in aparallelmanner.

>AlF,AlCl andAlBrexist in thegaseousphasewhen thetri-halideisheatedwithaluminium.Aluminiumhalidesusuallyexist in theformAlX3,where Xis F,Cl,Br, orI.[28]

7.2Oxidation state +2

 

>Aluminiummonoxide,AlO,hasbeendetected in thegasphaseafterexplosion[29] and instellarabsorptionspectra.[30]

7.3Oxidation state +3

 

>Fajans'rulesshow that thesimpletrivalentcationAl3+isnotexpected tobefound inanhydroussalts orbinarycompoundssuchasAl2O3. Thehydroxideis aweakbase andaluminiumsalts ofweakacids,suchascarbonate,cannotbeprepared. Thesalts ofstrongacids,suchasnitrate,arestable andsoluble inwater,forminghydrateswithatleastsixmolecules ofwater ofcrystallization.

>Aluminiumhydride, (>AlH3)n,canbeproducedfromtrimethylaluminium andanexcess ofhydrogen.Itburnsexplosively inair.Itcanalsobepreparedby theaction ofaluminiumchloride onlithiumhydride inethersolution,butcannotbeisolated freefrom thesolvent.Alumino-hydrides of themostelectropositiveelementsareknown, themostusefulbeinglithiumaluminiumhydride,Li[AlH4].Itdecomposesintolithiumhydride,aluminium andhydrogenwhenheated, andishydrolysedbywater.Ithasmanyuses inorganicchemistry,particularlyas areducingagent. Thealuminohalideshave asimilarstructure.

>Aluminiumhydroxidemaybepreparedas agelatinousprecipitatebyaddingammonia toanaqueoussolution ofanaluminiumsalt.Itisamphoteric,beingboth averyweakacid, andformingaluminateswithalkalis.Itexists invariouscrystallineforms.

>Aluminiumcarbide,Al4C3ismadebyheating amixture of theelementsabove 1000 °З. Thepaleyellowcrystalshave acomplexlatticestructure, andreactwithwater ordiluteacids togivemethane. Theacetylide,Al2(C2)3,ismadebypassingacetyleneoverheatedaluminium.

>Aluminiumnitride,AlN,canbemadefrom theelementsat 800 °З.Itishydrolysedbywater toformammonia andaluminiumhydroxide.Aluminiumphosphide,AlP,ismadesimilarly, andhydrolyses togivephosphine.

>Aluminiumoxide,Al2O3,occursnaturallyascorundum, andcanbemadebyburningaluminium inoxygen orbyheating thehydroxide,nitrate orsulfate.As agemstone,itshardnessisonlyexceededbydiamond,boronnitride, andcarborundum.Itisalmostinsoluble inwater.Aluminiumsulfide,Al2S3,maybepreparedbypassinghydrogensulfideoveraluminiumpowder.Itispolymorphic.

>Aluminiumiodide,AlI3,is adimerwithapplications inorganicsynthesis.Aluminiumfluoride,AlF3,ismadebytreating thehydroxidewithHF, orcanbemadefrom theelements.Itconsists of agiantmoleculewhichsublimeswithoutmeltingat 1291 °З.Itisveryinert. Theothertrihalidesaredimeric,having abridge-likestructure.

>Whenaluminium andfluoridearetogether inaqueoussolution,theyreadilyformcomplexionssuchas [>AlF(H2O)5]2+,AlF3(H2O)3, and [>AlF6]3.Ofthese, [>AlF6]3is themoststable.Thisisexplainedby thefact thataluminium andfluoride,whicharebothverycompactions, fittogetherjustright toform theoctahedralaluminiumhexafluoridecomplex.Whenaluminium andfluoridearetogether inwater in a 1:6molar ratio, [>AlF6]3is themost commonform,even inratherlowconcentrations.

>Organometalliccompounds ofempiricalformulaAlR3exist and,ifnotalsopolymers,areatleastdimers ortrimers.Theyhavesomeuses inorganicsynthesis,forinstancetrimethylaluminium.

7.4Analysis

 

Thepresence ofaluminiumcanbedetected inqualitativeanalysisusingaluminon.


8.Applications

 

8.1 Generaluse

 

>Aluminiumis themostwidelyusednon-ferrousmetal.[31] Globalproduction ofaluminium in 2005was 31.9milliontonnes.Itexceeded that ofanyother metalexceptiron (837.5milliontonnes).[32]Relativelypurealuminiumisencounteredonlywhencorrosionresistance and/orworkabilityismoreimportantthanstrength orhardness. Athinlayer ofaluminiumcanbedepositedonto aflatsurfacebyphysicalvapourdeposition or (>veryinfrequently)chemicalvapourdeposition orotherchemicalmeans toformopticalcoatings andmirrors.Whensodeposited, afresh,purealuminium filmservesas agoodreflector (>approximately 92%) ofvisible light andanexcellentreflector (>asmuchas 98%) ofmedium andfarinfraredradiation.

>Purealuminiumhas alowtensilestrength,butwhencombinedwiththermo-mechanicalprocessing,aluminiumalloysdisplay amarkedimprovement inmechanicalproperties,especiallywhentempered.Aluminiumalloysformvitalcomponents ofaircraft androcketsas aresult oftheir highstrength-to-weight ratio.Aluminiumreadilyformsalloyswithmanyelementssuchascopper,zinc,magnesium,manganese andsilicon (>e.g.,duralumin). Today,almost allbulk metalmaterials thatarereferred tolooselyas ">aluminium,"areactuallyalloys.Forexample, the commonaluminiumfoilsarealloys of 92% to 99%aluminium.[33]

>Some of themanyusesforaluminium metalare in:

>Transportation (>automobiles,aircraft,trucks,railwaycars,marinevessels,bicycles etc.)assheet,tube,castings etc.

>Packaging (>cans,foil, etc.)

Construction (>windows,doors,siding,buildingwire, etc.)

Awiderange ofhouseholditems,fromcookingutensils tobaseballbats,watches.[34]

>Streetlightingpoles,sailingshipmasts,walkingpoles etc.

>Outershells ofconsumerelectronics,alsocasesforequipmente.g.photographicequipment.

>Electricaltransmissionlinesfor powerdistribution

>MKMsteel andAlnicomagnets

>Superpurityaluminium (SPA, 99.980% to 99.999%Al),used inelectronics andCDs.

>Heatsinksforelectronicappliancessuchastransistors andCPUs.

>Substratematerial ofmetal-corecoppercladlaminatesused in highbrightnessLEDlighting.

>Powderedaluminiumisused inpaint, and inpyrotechnicssuchassolidrocketfuels andthermite.

 

8.2Aluminiumcompounds

 

>Aluminiumammoniumsulfate ([>Al(NH4)](SO4)2),ammoniumalumisusedas amordant, inwater purification andsewagetreatment, inpaperproduction,as a foodadditive, and inleathertanning.

>Aluminiumacetateis asaltused insolutionasanastringent.

>Aluminiumborate (>Al2O3B2O3)isused in theproduction ofglass andceramic.

>Aluminiumborohydride (>Al(BH4)3)isusedasanadditive tojetfuel.

>Aluminiumbronze (>CuAl5)

>Aluminiumchloride (>AlCl3)isused: inpaintmanufacturing, inantiperspirants, inpetroleumrefining and in theproduction ofsyntheticrubber.

>Aluminiumchlorohydrateisusedasanantiperspirant and in thetreatment ofhyperhidrosis.

>Aluminiumfluorosilicate (>Al2(SiF6)3)isused in theproduction ofsyntheticgemstones,glass andceramic.

>Aluminiumhydroxide (>Al(OH)3)isused:asanantacid,as amordant, inwater purification, in themanufacture ofglass andceramic and in thewaterproofing offabrics.

>Aluminiumoxide (>Al2O3),alumina,isfoundnaturallyascorundum (>rubies andsapphires),emery, andisused inglassmaking.Syntheticruby andsapphireareused inlasersfor theproduction ofcoherent light.Usedas arefractory,essentialfor theproduction of highpressuresodiumlamps.

>Aluminiumphosphate (>AlPO4)isused in themanufacture: ofglass andceramic,pulp andpaperproducts,cosmetics,paints andvarnishes and inmakingdentalcement.

>Aluminiumsulfate (>Al2(SO4)3)isused: in themanufacture ofpaper,as amordant, in afireextinguisher, inwater purification andsewagetreatment,as a foodadditive, infireproofing, and inleathertanning.

>AqueousAluminiumions (>suchasfound inaqueousAluminiumSulfate)areused totreatagainstfishparasitessuchasGyrodactylussalaris.

>Inmanyvaccines,certainaluminiumsaltsserveasanimmuneadjuvant (>immuneresponsebooster) toallow theprotein in thevaccine toachievesufficientpotencyasanimmunestimulant.

8.3Aluminiumalloys instructuralapplications

 

>Aluminiumalloyswith awiderange ofpropertiesareused inengineeringstructures.Alloysystemsareclassifiedby anumbersystem (>ANSI) orbynamesindicatingtheirmainalloyingconstituents (>DIN and ISO).

Thestrength anddurability ofaluminiumalloysvarywidely,notonlyas aresult of thecomponents of thespecificalloy,butalsoas aresult ofheattreatments andmanufacturingprocesses. Alack ofknowledge oftheseaspectshasfromtime totimeled toimproperlydesignedstructures andgainedaluminium abadreputation. (>Seemainarticle)

>Oneimportantstructurallimitation ofaluminiumalloysistheirfatiguestrength.Unlikesteels,aluminiumalloyshavenowell-definedfatiguelimit,meaning thatfatiguefailurewilleventuallyoccurunderevenverysmallcyclicloadings.Thisimplies thatengineersmustassesstheseloads anddesignfor afixed liferatherthananinfinite life.

>Anotherimportantproperty ofaluminiumalloysistheirsensitivity toheat. Workshopproceduresinvolvingheatingarecomplicatedby thefact thataluminium,unlikesteel,willmeltwithoutfirstglowingred.Formingoperationswhere ablowtorchisusedthereforerequiressomeexpertise,sincenovisualsignsreveal howclose thematerialis tomelting.Aluminiumalloys,like allstructuralalloys,alsoaresubject tointernalstressesfollowingheatingoperationssuchaswelding and casting. The problemwithaluminiumalloys inthisregardistheirlowmeltingpoint,whichmakethemmoresusceptible todistortionsfromthermallyinducedstressrelief.Controlledstressreliefcanbedoneduringmanufacturingbyheat-treating theparts inanoven,followedbygradualcooling—ineffectannealing thestresses.

Thelowmeltingpoint ofaluminiumalloyshasnotprecludedtheiruse inrocketry;evenforuse inconstructingcombustionchamberswheregasescanreach 3500 K. TheAgenaupperstageengineused aregenerativelycooledaluminiumdesignforsomeparts of thenozzle,including thethermallycriticalthroatregion.

8.4Householdwiring

 

>Compared tocopper,aluminiumhasabout 65% of theelectricalconductivitybyvolume,although 200%byweight.Traditionallycopperisusedashouseholdwiringmaterial.In the1960saluminiumwasconsiderablycheaperthancopper, andsowasintroducedforhouseholdelectricalwiring in the United States,eventhoughmanyfixtureshadnotbeendesigned toacceptaluminiumwire.Insomecases thegreatercoefficient ofthermalexpansion ofaluminiumcauses thewire toexpand andcontractrelative to thedissimilar metalscrewconnection,eventuallyloosening theconnection.Also,purealuminiumhas atendency tocreepundersteadysustainedpressure (to agreaterdegreeas thetemperaturerises),againloosening theconnection.Finally,Galvaniccorrosionfrom thedissimilarmetalsincreased theelectricalresistance of theconnection.

>All ofthisresulted inoverheated andlooseconnections, andthis inturnresulted infires.Buildersthenbecamewary ofusing thewire, andmanyjurisdictionsoutlaweditsuse inverysmallsizes in newconstruction.Eventually,newerfixtureswereintroducedwithconnectionsdesigned toavoidloosening andoverheating. Thefirstgenerationfixturesweremarked ">Al/Cu" andwereultimatelyfoundsuitableonlyforcopper-cladaluminiumwire,but the secondgenerationfixtures,whichbear a ">CO/ALR"coding,areratedforuncladaluminiumwire.Toadaptolderassemblies,workersforestall theheating problemusing aproperly-donecrimp of thealuminiumwire to ashort ">pigtail" ofcopperwire. Today, newalloys,designs, andmethodsareusedforaluminiumwiring incombinationwithaluminiumtermination.


9.History

 

>AncientGreeks andRomansusedaluminiumsaltsasdyeingmordants andasastringentsfordressingwounds;alumisstillusedas astyptic.In 1761Guyton deMorveausuggestedcalling thebasealumalumine.In 1808,HumphryDavyidentified theexistence of a metalbase ofalum,whichheatfirsttermedalumium andlateraluminum (>seeEtymologysection,below).

The metalwasfirstproduced in 1825 (inanimpureform)by Danishphysicist andchemist HansChristianrsted. Hereactedanhydrousaluminiumchloridewithpotassiumamalgam andyielded alump of metallookingsimilar totin.[35]FriedrichWhlerwasaware oftheseexperiments andcitedthem,butafterredoing theexperiments ofrstedheconcluded thatthis metalwaspurepotassium. Heconducted asimilarexperiment in 1827bymixinganhydrousaluminiumchloridewithpotassium andyieldedaluminium.[35]Whlerisgenerallycreditedwithisolatingaluminium (>Latinalumen,alum),butalsorstedcanbelistedasitsdiscoverer.[36]Further,PierreBerthierdiscoveredaluminium inbauxiteore andsuccessfullyextractedit.[37]FrenchmanHenriEtienneSainte-ClaireDevilleimprovedWhler'smethod in 1846, anddescribed hisimprovements in abook in 1859,chiefamongthesebeing thesubstitution ofsodiumfor theconsiderablymoreexpensivepotassium.

(>Note: Thetitle ofDeville'sbookis Del'aluminium,sesproprits,safabrication (>Paris, 1859).Devillelikelyalsoconceived theidea of theelectrolysis ofaluminiumoxidedissolved incryolite;however,Charles MartinHall andPaulHroultmighthavedeveloped themorepracticalprocessafterDeville.)

>Before theHall-Hroultprocesswasdeveloped,aluminiumwasexceedinglydifficult toextractfromitsvariousores.Thismadepurealuminiummorevaluablethangold[citationneeded].Bars ofaluminiumwereexhibitedalongside the Frenchcrownjewelsat theExpositionUniverselle of1855[citationneeded], andNapoleon IIIwassaid[citationneeded] tohavereserved aset ofaluminiumdinnerplatesfor hismosthonouredguests.

>Aluminiumwasselectedas thematerial tobeusedfor theapex of the WashingtonMonument in 1884, atimewhenoneounce (30grams)cost thedailywage of a commonworker on theproject;[38]aluminiumwasabout thesamevalueassilver.

TheCowlescompaniessuppliedaluminiumalloy inquantity in the United States andEnglandusingsmelterslike thefurnace ofCarlWilhelm Siemensby 1886.[39]Charles MartinHall ofOhio in theU.S. andPaulHroult of Franceindependentlydeveloped theHall-Hroultelectrolyticprocess thatmadeextractingaluminiumfrommineralscheaper andisnow the principalmethodusedworldwide. TheHall-HeroultprocesscannotproduceSuperPurityAluminiumdirectly.Hall'sprocess,[40] in 1888with thefinancialbacking ofAlfred E.Hunt,started the PittsburghReduction Company todayknownas Alcoa.Hroult'sprocesswas inproductionby 1889 inSwitzerlandatAluminiumIndustrie,now Alcan, andat BritishAluminium,nowLuxfer Group and Alcoa,by 1896 inScotland.[41]

>By 1895 the metalwasbeingusedas abuildingmaterialasfarawayasSydney,Australia in thedome of theChiefSecretary's Building.

>Manynaviesuseanaluminiumsuperstructurefortheirvessels,however, the 1975fireaboardUSSBelknap thatguttedheraluminiumsuperstructure,aswellasobservation ofbattledamage to Britishshipsduring theFalklandsWar,led tomanynaviesswitching to allsteelsuperstructures. TheArleighBurkeclasswas thefirstsuchU.S.ship,beingconstructedentirely ofsteel.

>In 2008 theprice ofaluminiumpeakedat .>45/lb inJulybutdropped to [>fde_1327536049_9510364723_1327536049_4013567932_5552].7/lbbyDecember.[42]


10.Etymology

 

10.1Nomenclaturehistory

 

Theearliestcitationgiven in theOxford EnglishDictionaryforanywordusedas anameforthiselementisalumium,which Britishchemist andinventorHumphryDavyemployed in 1808for the metalhewastrying toisolateelectrolyticallyfrom themineralalumina. Thecitationisfrom hisjournalPhilosophicalTransactions: ">Had Ibeensofortunateas..tohaveprocured themetallicsubstances Iwas insearch of, Ishouldhaveproposedforthem thenames ofsilicium,alumium,zirconium, andglucium."[43]

>By 1812,Davyhadsettled onaluminum. Hewrote in thejournal ChemicalPhilosophy: ">Asyet Aluminumhasnotbeenobtained in aperfectly freestate."[44]But thesameyear,ananonymouscontributor to theQuarterly Review, a Britishpolitical-literaryjournal,objected toaluminum andproposed thenamealuminium, ">forsoweshalltake theliberty ofwriting theword, inpreference toaluminum,whichhas alessclassicalsound."[45]

The ->iumsuffixhad theadvantage ofconforming to theprecedentset inothernewlydiscoveredelements of thetime:potassium,sodium,magnesium,calcium, andstrontium (all ofwhichDavyhadisolatedhimself).Nevertheless, ->umspellingsforelementswerenotunknownat thetime,asforexampleplatinum,known toEuropeanssince thesixteenthcentury,molybdenum,discovered in 1778, andtantalum,discovered in 1802.

The ->umsuffix on theotherhand,has theadvantage ofbeingmoreconsistentwith theuniversalspellingaluminafor theoxide,aslanthanais theoxide oflanthanum, andmagnesia,ceria, andthoriaare theoxides ofmagnesium,cerium, andthoriumrespectively.

Thespellingusedthroughout the19thcenturybymostU.S.chemistsended in ->ium,but commonusageislessclear.[46] The ->umspellingisused in theWebster'sDictionary of 1828,as itwas in 1892whenCharles MartinHallpublishedan advertisinghandbillfor his newelectrolyticmethod ofproducing the metal,despite hisconstantuse of the ->iumspelling in all thepatents[40]hefiledbetween 1886 and 1903.[47]Ithasconsequentlybeensuggested that thespellingreflectsaneasier topronouncewordwithonefewersyllable, or that thespelling on theflierwas amistake.Hall'sdomination ofproduction of the metalensured that thespellingaluminumbecame thestandard inNorth America; theWebsterUnabridgedDictionary of 1913,though,continued touse the ->iumversion.

>In 1926, the American ChemicalSocietyofficiallydecided tousealuminum initspublications; Americandictionariestypicallylabel thespellingaluminiumas a Britishvariant.

10.2Present-dayspelling

 

>Mostcountriesspellaluminiumwithan іbefore ->um.In the United States, thespellingaluminiumislargelyunknown, and thespellingaluminumpredominates.[48][49] The CanadianOxfordDictionaryprefersaluminum,whereas theAustralianMacquarieDictionaryprefersaluminium.

The International Union ofPure andApplied Chemistry (>IUPAC)adoptedaluminiumas thestandardinternationalnamefor theelement in 1990,butthreeyearslaterrecognizedaluminumasanacceptablevariant.Hencetheirperiodictableincludesboth.[50]IUPACofficiallyprefers theuse ofaluminium initsinternalpublications,althoughseveralIUPACpublicationsuse thespellingaluminum.[51]


11. Healthconcerns

 

>Despiteitsnaturalabundance,aluminiumhasnoknownfunction inlivingcells andpresentssometoxiceffects inelevatedconcentrations.Itstoxicitycanbetraced todeposition inbone and thecentralnervoussystem,whichisparticularlyincreased inpatientswithreducedrenalfunction.Becausealuminiumcompeteswithcalciumforabsorption,increasedamounts ofdietaryaluminiummaycontribute to thereducedskeletalmineralization (>osteopenia)observed inpreterminfants andinfantswithgrowthretardation.Invery highdoses,aluminiumcancauseneurotoxicity, andisassociatedwithalteredfunction of theblood-brainbarrier.[52] Asmallpercentage ofpeopleareallergic toaluminium andexperiencecontactdermatitis,digestivedisorders,vomiting orothersymptomsuponcontact oringestion ofproductscontainingaluminium,suchasdeodorants orantacids.Inthosewithoutallergies,aluminiumisnotastoxicas heavymetals,butthereisevidence ofsometoxicityif itisconsumed inexcessiveamounts.[53]Although theuse ofaluminiumcookwarehasnotbeenshown tolead toaluminiumtoxicity ingeneral,excessiveconsumption ofantacidscontainingaluminiumcompounds andexcessiveuse ofaluminium-containingantiperspirantsprovidemoresignificantexposurelevels. Studieshaveshown thatconsumption ofacidicfoods orliquidswithaluminiumsignificantlyincreasesaluminiumabsorption,[54] andmaltolhasbeenshown toincrease theaccumulation ofaluminium innervous andosseustissue.[55]Furthermore,aluminiumincreasesestrogen-relatedgeneexpression inhumanbreastcancercellscultured in thelaboratory.[56]Thesesalts'estrogen-likeeffectshaveled totheirclassificationas ametalloestrogen.

>Because ofitspotentiallytoxiceffects,aluminium'suse insomeantiperspirants,dyes (>suchasaluminumlake), and foodadditivesiscontroversial.Althoughthereislittleevidence thatnormalexposure toaluminiumpresents arisk tohealthyadults,[57]severalstudiespoint torisksassociatedwithincreasedexposure to themetal[citationneeded].Aluminium in foodmaybeabsorbedmorethanaluminiumfromwater.[58]Someresearchershaveexpressedconcerns that thealuminium inantiperspirantsmayincrease therisk ofbreastcancer,[59] andaluminiumhascontroversiallybeenimplicatedas afactor inAlzheimer'sdisease.[60]

>According to TheAlzheimer'sSociety, theoverwhelmingmedical andscientificopinionis thatstudieshavenotconvincinglydemonstrated acausalrelationshipbetweenaluminium andAlzheimer'sdisease.[61]Nevertheless,somestudies[which?]citealuminiumexposureas ariskfactorforAlzheimer'sdisease,assomebrainplaqueshavebeenfound tocontainincreasedlevels of themetal[citationneeded]. Research inthisareahasbeeninconclusive;aluminiumaccumulationmaybe aconsequence of thediseaseratherthan acausalagent.Inanyevent,ifthereisanytoxicity ofaluminium, itmustbevia averyspecificmechanism,sincetotalhumanexposure to theelement in theform ofnaturallyoccurringclay insoil anddustisenormouslylargeover alifetime.[62][63] Scientific consensusdoesnotyetexistaboutwhetheraluminiumexposurecoulddirectlyincrease therisk ofAlzheimer'sdisease.[61]


12.Effect onplants

 

>Aluminiumisprimaryamong thefactors thatreduceplantgrowth onacidsoils.Although itisgenerallyharmless toplantgrowth inpH-neutralsoils, theconcentration inacidsoils oftoxicAl3+cationsincreases anddisturbsrootgrowth andfunction.[64][65][66]

>Mostacidsoilsaresaturatedwithaluminiumratherthanhydrogenions. Theacidity of thesoilistherefore aresult

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