求一篇关于火药的英文简介,不长,两三分钟内能读完就行,口语课-查字典问答网
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  求一篇关于火药的英文简介,不长,两三分钟内能读完就行,口语课上要用.太长了,哪个哥们来个短点的

  求一篇关于火药的英文简介,不长,两三分钟内能读完就行,口语课上要用.

  太长了,哪个哥们来个短点的

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2020-04-22 23:34
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  Gunpowder,alsocalledblackpowder,isanexplosivemixtureofsulfur,charcoalandpotassiumnitrate,KNO3(alsoknownassaltpetre/saltpeter)thatburnsrapidly,producingvolumesofhotsolidsandgaseswhichcanbeusedasapropellantinfirearmsandasapyrotechniccompositioninfireworks.Thetermgunpowderisalsooftenusedmorebroadlytodescribeanypropellantpowderusedinfirearms.Modernfirearmsdonotusethetraditionalgunpowder(blackpowder)describedinthisarticle,butinsteadusesmokelesspowder.Inthisarticle,thetermsgunpowderandblackpowderareusedinterchangeably.

  Gunpowderisclassifiedasalowexplosivebecauseofitsslowdecompositionrateandconsequentlylowbrisance.Lowexplosivesproduceasubsonicdeflagrationwaveratherthanthesupersonicdetonationwaveproducedbybrisants,orhighexplosives.Thegasesproducedbyburninggunpowdergenerateenoughpressuretopropelabullet,butnotenoughtodestroythebarrelofafirearm.Thismakesgunpowderlesssuitableforshatteringrockorfortifications,wherehighexplosivessuchasTNTarepreferred.

  Theterm"blackpowder"wascoinedinthelate19thcenturytodistinguishpriorgunpowderformulationsfromthenewsmokelesspowdersandsemi-smokelesspowders.(Semi-smokelesspowdersfeaturedbulkvolumepropertiesthatapproximatedblackpowderintermsofchamberpressurewhenusedinfirearms,buthadsignificantlyreducedamountsofsmokeandcombustionproducts;theyrangedincolorfrombrownishtantoyellowtowhite.Mostofthebulksemi-smokelesspowdersceasedtobemanufacturedinthe1920s.)[1][2][3]

  Blackpowderisagranularmixtureof

  anitrate—typicallypotassiumnitrate(KNO3)—whichsuppliesoxygenforthereaction;

  charcoal,whichprovidesfuelforthereactionintheformofcarbon(C);

  sulfur(S),which,whilealsoafuel,lowersthetemperatureofignitionandincreasesthespeedofcombustion.

  Potassiumnitrateisthemostimportantingredientintermsofbothbulkandfunctionbecausethecombustionprocessreleasesoxygenfromthepotassiumnitrate,promotingtherapidburningoftheotheringredients.[4]Toreducethelikelihoodofaccidentalignitionbystaticelectricity,thegranulesofmodernblackpowderaretypicallycoatedwithgraphite,whichpreventsthebuild-upofelectrostaticcharge.

  Thecurrentstandardcompositionforblackpowdermanufacturedbypyrotechnicianswasadoptedaslongagoas1780.Itis75%potassiumnitrate,15%softwoodcharcoal,and10%sulfur.[5]Theseratioshavevariedoverthecenturiesandbycountry,andcanbealteredsomewhatdependingonthepurposeofthepowder.Forinstance,coarsergradesofblackpowder,unsuitableforuseinfirearmsbutadequateforblastingrockinquarryingoperations,iscalledblastingpowderratherthangunpowder;itisoftenmadewiththecheapersodiumnitratesubstitutedforpotassiumnitrateinproportionsof60%nitrate,20%charcoaland20%sulfur.[citationneeded]

  Theburnrateofblackpowdercanbechangedbycorning.Corningfirstcompressesthefineblackpowdermealintoblockswithafixeddensity(1.7g/cm³).Theblocksarethenbrokenupintogranules.Thesegranulesarethensortedbysizetogivethevariousgradesofblackpowder.IntheUnitedStates,standardgradesofblackpowderrunfromthecoarseFggradeusedinlargeboreriflesandsmallcann

2020-04-22 23:36:55

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