合金納米顆粒的結(jié)構(gòu)和熱力學(xué)特征.pdf

1、華東師范大學(xué)碩士學(xué)位論文合金納米顆粒的結(jié)構(gòu)和熱力學(xué)特征姓名：魏嵐申請(qǐng)學(xué)位級(jí)別：碩士專業(yè)：材料物理與化學(xué)指導(dǎo)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