合金納米顆粒的結構和熱力學特征.pdf

1、華東師范大學碩士學位論文合金納米顆粒的結構和熱力學特征姓名：魏嵐申請學位級別：碩士專業(yè)：材料物理與化學指導教師：孫得彥20110420AbstractOverthepastyears，alloyclustershaveraisedgreatinterests，mostattentionshavebeenpaidonthosewithsmallsizes，andtheirmeltingbehaviorsarenotwellstudiedI

2、nthisthesis，byemployingtheMolecularDynamicmethod，wehavestudiedthestructuresandmeltingnaturesofA1一GabinaryalloyclustersWeobtainedsomeconllTlOnmeltingbehaviors，andthestructuralcharacters，aswellastheirchangewithsizesandconc

3、entrationsAccordingtoourstudies，wefoundthatGaatomswouldsegregatetothesurfaceoftheclustersandformthecoreshellstructuresThereasonlieson：1)thesizeofGaatomsisquitelargerthanthatofA1atoms；2)thesurfaceenergyofGaatomsisabitsmal

4、lerthanthatofA1atomsTheinnerstructuresoftheclustersareclosedrelatedtotheconcentrationofGaatomsIftheamountofGaatomsisquitesmall，thereisatendencytoformapurecoreconsistedofA1atomsonlyAndthecontentofGaatomsincoreswillincreas

5、ewiththeincreaseofthetotalconcentrationofGaatomsinclustersAstheconcentrationofGaatomsisfixed，amaximumnumberofAIatomstoformacriticalclusterwithpurecoreofA1atomsisalsoobtainedThestructuresoftheA1一Gaclustershavestrongeffect

6、sonthemeltingbehaviorsThemeltingprocessesbeginfromthesurfaceoftheclustersSinceGaatomsCOVerthesurfacesandformtheshells，thesurfacemeltingstageisactuallythemeltingofGaatomsThemeltingtemperaturesofsurfacemeltingwillincreasew

7、iththeincreaseofthecontentofGaatomsoftheclustersSincethemeltingtemperatureofGaatomsisverylowtherewillbealargetemperaturedifferencebetweenthesurfacemeltingandthecompletemeltingIftheclusterhasapurecoreofAlatoms，thecomplete

8、meltingtemperatureswillcometoverycloseAnditwilldecreasewiththeincreaseoftheconcentrationoftheGaatomsincoreWhentheclustersarecompletelymelted，thestructuresoftheliquidclustersaresimilartothoseofthesolidonesThatis，thepureco