用液相沉淀法制备超细氧化铝的实验研究Word格式.docx
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本文以廉价的工业氢氧化铝为原料,以碳酸氢钠为沉淀剂,采用液相沉淀法制备氢氧化铝前驱体,然后煅烧得超细氧化铝粉体。
在超细氧化铝制备过程中,主要探讨各种因素对氧化铝的粒径、松装密度以及参考指标氧化铝收率的影响,并且研究了不同的干燥方法以及不同干燥起始温度对超细氧化铝粉末团聚的影响。
在NaAl(OH)4-NaHCO3体系中,首先设计了单因素实验,探索了各个因素对对氧化铝制备的影响,然后再挑选出四个主要的影响因素,以正交实验法筛选出制备过程的优化工艺条件。
得出结论如下:
(1)反应温度和NaAl(OH)4浓度对粉末的平均粒径影响最大,而pH值和碳酸氢钠浓度影响较小。
若使氧化铝的平均粒径最小,最优条件为:
反应温度为35℃,NaAl(OH)4浓度为0.6mol/L,pH值为11.5,碳酸氢钠的浓度为1.0mol/L。
在此条件下重复实验,所得氧化铝的平均粒径为:
0.65μm。
(2)反应温度和pH值对氧化铝收率具有显著性影响,而反应物浓度基本没有什么影响,可以忽略不计。
若使氧化铝收率最大,最佳反应条件:
反应温度为35℃,NaAl(OH)4浓度为0.4mol/L,pH值为11,碳酸氢钠的浓度为1.0mol/L。
在此条件下重复实验,所得收率为:
96.05%。
(3)反应温度和NaAl(OH)4浓度对粉末的松装密度影响最大,而pH值和碳酸氢钠浓度影响较小。
若使氧化铝的松装密度最小,最优条件为:
反应温度为35℃,NaAl(OH)4浓度为0.6mol/L,pH值为12,碳酸氢钠的浓度为1.2mol/L。
验证所得粉末松装密度为:
0.149g/mL。
最后通过对不同条件下的粉末的平均粒径和松装密度的进行表征,综合产物的收率,确定了最优方案:
体系反应温度T=35℃,NaAl(OH)4浓度C=0.6mol/L,pH值=11.5,碳酸氢钠的浓度C=1.0mol/L。
通过验证实验发现,在此条件下,三项指标中达到的效果都较好。
(4)通过洗涤和控制沉淀速度除去大部分钠,而高温煅烧也能除去部分钠。
最后测得超细氧化铝粉末的纯度为99.79%。
最后通过对不同干燥方式的研究可知:
无水乙醇在干燥过程中能起到一定的分散作用,能有效控制粉末的团聚;
并且干燥起始温度与干燥温度相同的干燥体系,得到粉末的粒径和松装密度更小;
而压力对氧化铝粉体的性能影响不大。
关键词:
超细氧化铝;
沉淀法;
团聚;
分散剂;
干燥
AbstractUltrafinealuminawithexcellentpropertiessuchashighmeltingpoint,highheat-resistance,highcorrosion-resistance,goodelectricalinsulation,etc,isaveryimportantspecialfunctionmaterials.Therearediversifiedmethodsforitspreparation,andtheprecipitationmethodiswidelyused,whichgenerallyusescheaperinorganicmaterials,simplerequipmentandtechnologicalprocesses,meanwhile,thepowderproductisofhighpurity,smallparticlesizeandnarrowsizedistribution.Hence,liquidprecipitationmethodispracticalandquitecompetitive.Inthispaper,theprecursorofAl(OH)3wassynthesizedwiththeprecipitationmethodbyusingthebargaintechnicalAl(OH)3asthestartingmaterials,NaHCO3astheprecipitant,thenpreparedtheultrafinealuminapowersaftersintering.Theinfluenceofthefactorsonparticlesize,thereferenceindexyieldandpackingdensityofaluminatopreparationwerediscussed,andstudingtheeffectsofdifferentdryingmethodsandthedifferentstartingtemperatureofdryingonagglomerationofultrafinealuminapowder.FortheNaAl(OH)4-NaHCO3system,first,theinfluencetopreparationbyexperimentsofsinglefactorisdiscussed,thenchoosingfourmajorfactors,andtheoperationconditionsareoptimizedbyorthogonaldesign.Mainconclusionsareasfollows:
(1)TheeffectofthereactiontemperatureandtheNaAl(OH)4concentrationontheaverageparticlesizeisthelargest,theeffectofpHandtheNaHCO3concentrationontheaverageparticlesizeissmaller,theoptimumconditionsare:
thereactiontemperatureis35℃,theNaAl(OH)4concentrationis0.6mol/L,thepHis11.5,theNaHCO3concentrationis1.0mol/L.Repeatingtheexperimentundertheoptimumcondition,theaverageparticlesizeis0.65μmatthatcondition.
(2)ThereactiontemperatureandpHhavethemostsignificanteffectontheyieldofalumina,butthereactantconcentrationshavenobiginfluenceonyieldofaluminaanditcanbenegligible.Theoptimumconditionsare:
thereactiontemperatureis35℃,theNaAl(OH)4concentrationis0.4mol/L,thepHis11,theNaHCO3concentrationis1.0mol/L.Repeatingtheexperimentundertheoptimumcondition,theyieldofaluminagetto96.05%.(3)TheeffectofthereactiontemperatureandtheNaAl(OH)4concentrationontheaveragepackingdensityisthelargest,theeffectofpHandtheNaHCO3concentrationonthepackingdensityissmaller.Togetthesmallerpackingdensity,theoptimumconditionsare:
thereactiontemperatureis35℃,theNaAl(OH)4concentrationis0.6mol/L,thepHis12,theNaHCO3concentrationis1.2mol/L.Repeatingtheexperimentundertheoptimumcondition,thepackingdensityis0.149g/mL.Finally,characterizatingtheaverageparticlesizeandthepackingdensityofultrafinealuminapowder,synthesizetheyieldofalumina,fixedtheoptimumcondition:
thereactiontemperatureis35℃,theNaAl(OH)4concentrationis0.6mol/L,thepHis11.5,theNaHCO3concentrationis1.0mol/L.Accordingtheconfirmatorytest,theresultsofthreeindexes
arebetter.(4)Itcanremovemostofthesodiumbywashingandcontrollingthevelocityofprecipitation,anditalsocanremovepartsofsodiumbyhigh-temperaturesintering.Thepurenessoftheultrafinealuminapowderis99.79%.Itcanbefoundthatbystudyingseveraldifferentdryingway:
theabsoluteethylalcoholhavesomedispersionandcancontroleffectivelytheagglomerationofpowder;
thesystemforthestartingtemperatureofdryingassameasthedryingtemperature,theaverageparticlesizeandthepackingdensityofultrafinealuminapowderissmallerofthatsystem;
andthepressurehasnobigeffectfortheperformanceofultrafinealuminapowder.Keywords:
ultrafinepowder;
methodofprecipitation;
agglomeration;
dispersantagent;
drying
目录
第一章概论................................................................................................................................1
1.1引言..........................................................................................................................................1
1.2超细氧化铝的性质与应用..................................................................................................1
1.2.1超细氧化铝在陶瓷行业的应用.....................................................................................2
1.2.2超细氧化铝在生物医学领域的应用.............................................................................2
1.2.3超细氧化铝在半导体领域的应用.................................................................................2
1.2.4超细氧化铝在表面防护层领域的应用.........................................................................2
1.2.5超细氧化铝在光学领域的应用.....................................................................................3
1.3超细氧化铝粉末的制备方法.............................................................................................3
1.3.1气相法.............................................................................................................................3
1.3.2固相法.............................................................................................................................4
1.3.3液相法.............................................................................................................................5
1.4超细氧化铝的团聚产生机理以及消除方法.....................................................................7
1.4.1团聚的产生机理.............................................................................................................7
1.4.2硬团聚的消除方法.........................................................................................................8
1.5课题的提出...........................................................................................................................9
第二章实验部分.........................................................................................................................10
2.1实验原料及其分析...........................................................................................................10
2.1.1实验原料.......................................................................................................................10
2.1.2工业氢氧化铝中二氧化硅的测定...............................................................................11
2.2主要仪器设备.....................................................................................................................12
2.3实验步骤与流程图.............................................................................................................13
2.4机理分析............................................................................................................................14
2.4.1铝酸钠溶液的稳定性...................................................................................................14
2.4.2沉淀反应机理分析.......................................................................................................14
2.5本章小结.............................................................................................................................15
第三章超细氧化铝的制备........................................................................................................15
3.1引言.....................................................................................................................................15
3.2制备工艺研究....................................................................................................................16
3.2.1分散剂的选择...............................................................................................................16
3.2.2沉淀剂的选择...............................................................................................................16
3.2.3前驱体的TG-DTA图、XRD图和粒径分布图........................................................17
3.2.4沉淀剂加入方式的影响...............................................................................................21
3.3各因素对氧化铝平均粒径的影响....................................................................................23
3.3.1体系pH值的影响........................................................................................................23
3.3.2反应温度的影响...........................................................................................................24
3.3.3反应物浓度的影响.......................................................................................................25
3.3.4分散剂添加量的影响...................................................................................................26
3.3.5反应时间的影响...........................................................................................................27
3.4超细氧化铝粉末制备的正交实验设计............................................................................28
3.4.1正交实验设计...............................................................................................................28
3.4.2正交实验结果的表征.......................................................................