材料导论第一章答案.doc

Chaper1Introduction
第一章导论

P17-18Problems
1-1~1-4：略

1-5EnvironmentalandOtherEffect
1-5.Steelisoftencoatedwithathinlayerofzincifitistobeusedoutside.Whatcharacteristicsdoyouthinkthezincprovidestothiscoated,orgalvanized,steel?Whatprecautionsshouldbeconsideredinproducingthisproduct?Howwilltherecyclabilityoftheproductbeaffected?
问题大意：钢铁表面的镀锌有什么作用？镀锌时应注意哪些问题？镀锌后钢铁的回收会受到什么影响？
Thezincprovidescorrosionresistancetotheironintwoways.Iftheironiscompletelycoatedwithzinc,thezincprovidesabarrierbetweentheironandthesurroundingenvironment,thereforeprotectingtheunderlyingiron.Ifthezinccoatingisscratchedtoexposetheiron,thezinccontinuestoprotecttheironbecausethezinccorrodespreferentiallytotheiron(seeChapter22).Tobeeffective,thezincshouldbondwelltotheironsothatitdoesnotpermitreactionstooccurattheinterfacewiththeironandsothatthezincremainsintactduringanyformingofthegalvanizedmaterial.Whenthematerialisrecycled,thezincwillbelostbyoxidationandvaporization,oftenproducinga“zincdust”thatmayposeanenvironmentalhazard.Specialequipmentmayberequiredtocollectandeitherrecycleordisposeofthezincdust.
答案大意：镀锌层可以防止钢铁腐蚀，机理如下：1、在钢铁与外部环境间产生阻隔；2、在钢铁暴露后，锌仍能以牺牲阳极的方式保护钢铁。镀锌时应注意锌层与钢铁间的结合并防止发生在锌与钢铁界面间的反应。在镀锌钢铁回收时，锌会形成“锌尘”对环境产生危害。

1-6.Wewouldliketoproduceatransparentcanopyforanaircraft.Ifweweretouseaceramic(thatis,traditionalwindowglass)canopy,rocksorbirdsmightcauseittoshatter.Designamaterialthatwouldminimizedamageoratleastkeepthecanopyfrombreakingintopieces.
问题大意：用单纯的玻璃制造的飞机座舱罩易碎，如何改进才能减少其破坏造成的损失或防止其破碎？
Wemightsandwichathinsheetofatransparentpolymerbetweentwolayersoftheglass.Thisapproach,usedforwindshieldsofautomobiles,willpreventthe“safety”glassfromcompletelydisintegratingwhenitfails,withthepolymerholdingthebrokenpiecesofglasstogetheruntilthecanopycanbereplaced.
Anotherapproachmightbetouseatransparent,“glassy”polymermaterialsuchaspolycarbonate.Somepolymershavereasonablygoodimpactpropertiesandmayresistfailure.Thepolymerscanalsobetoughenedtoresistimpactbyintroducingtinyglobulesofarubber,orelastomer,intothep