二氧化钛纳米颗粒粒径影响因素的研究
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摘要
纳米TiO_2是一种应用非常广泛的纳米材料,其具有的光催化性在太阳能电池,光催化合成等诸多方面显示出十分诱人的前景。而二氧化钛光催化活性与其粒径密切相关,并且颗粒粒径特性对颗粒产品的性能产生极大的影响,这就要求对颗粒粒径的影响因素有很好的了解和控制。
采用火焰CVD法,在丙烷/空气扩散火焰中氧化前驱物(TiCl_4)制备纳米二氧化钛颗粒,研究进气条件对TiO_2纳米颗粒粒径的影响,并初步研究了进气条件对颗粒晶型的影响。本文共讨论了4种不同的进气条件,结果发现:丙烷与空气流速决定火焰的温度;丙烷流速越大,颗粒粒径则越大;而空气流速越大,颗粒粒径却越小;TiCl_4流速越高,颗粒粒径越大;而载气流速的升高对颗粒粒径大小几乎没有影响。
应用CFD商业软件fluent,引入颗粒动力学模型(Pratsinis,1998),模拟表面氧化反应、稀释作用以及热迁移现象对颗粒粒径的影响,结果表明:包含表面氧化反应的颗粒粒径要大于相同位置不包含表面氧化反应的颗粒粒径,而且表面氧化只是发生在反应的初期,在离燃烧室入口较近处对颗粒粒径有着较大的影响,在出口处由于先驱物和氧化剂浓度的关系对颗粒粒径几乎没有影响;气体稀释作用在火焰区域影响很大,明显抑制了颗粒粒径的增长,而在非火焰区域,湍流稀释作用很小,对颗粒粒径增长几乎不再发生抑制作用;如果同时考虑稀释作用与表面氧化作用,会发现气体对氧化产物TiO_2的稀释作用,明显抑制了颗粒的增长速度,对出口颗粒粒径的影响起决定性作用,而表面氧化反应仅在中心轴附近区域对颗粒粒径有较大的影响;热迁移作用对颗粒粒径的影响较小,仅在火焰内部对颗粒粒径有一定的影响。
As an important nanosized material, TiO_2 nano-particle is applicable to production and living widely.Its photocatalytic activity is widely used for solar battery and photocatalytic synthesization and so on.Particle characteristics like size and size distribution mainly influence the final product quality and photocatalytic activity of TiO_2.This emphasizes the need for discussion and control for the influencing factor of particle size.
The CVD method is used to produce TiO_2 nano-particle in the propane-air diffusion flame. The effect of different operating conditions on particle size and crystal form is investigated. There are four different operating conditions analyzed. The results show that temperature is influenced mainly by the rate of propane and air; the higher the rate of propane is, the bigger particle size is, while the higher the rate of air is, the less particle size is; besides particle size is consistent with the rate of TiCl_4; while the influence of the rate of carried gas on particle size is negligible.
Using the commercial CFD-code FLUENT and the additional fluid-particle dynamics (Pratsinis, 1998), the simulation of the effect of surface oxidation reaction , dilution and thermophoretic on particle size is performed. The result show that, mean particle diameter with surface oxidation reaction considered is bigger at the same position. Meanwhile the influence of surface oxidation reaction on particle size is obvious at the beginning of reaction but negligible at the outlet because of the relation between precursor and oxidant concentration. The increase of particle size is evidently restrained by dilution in the flame region, but hardly in the non-flame region due to the little effect of dilution. If we take the surface oxidation reaction and dilution into consideration, the dilution restrains obviously the velocity growth and affects deeply the particle size, while surface oxidation reaction effect merely particle size near the centerline.we also find that thermophoretic just have a little influence on particle size inside the flame.
采用火焰CVD法,在丙烷/空气扩散火焰中氧化前驱物(TiCl_4)制备纳米二氧化钛颗粒,研究进气条件对TiO_2纳米颗粒粒径的影响,并初步研究了进气条件对颗粒晶型的影响。本文共讨论了4种不同的进气条件,结果发现:丙烷与空气流速决定火焰的温度;丙烷流速越大,颗粒粒径则越大;而空气流速越大,颗粒粒径却越小;TiCl_4流速越高,颗粒粒径越大;而载气流速的升高对颗粒粒径大小几乎没有影响。
应用CFD商业软件fluent,引入颗粒动力学模型(Pratsinis,1998),模拟表面氧化反应、稀释作用以及热迁移现象对颗粒粒径的影响,结果表明:包含表面氧化反应的颗粒粒径要大于相同位置不包含表面氧化反应的颗粒粒径,而且表面氧化只是发生在反应的初期,在离燃烧室入口较近处对颗粒粒径有着较大的影响,在出口处由于先驱物和氧化剂浓度的关系对颗粒粒径几乎没有影响;气体稀释作用在火焰区域影响很大,明显抑制了颗粒粒径的增长,而在非火焰区域,湍流稀释作用很小,对颗粒粒径增长几乎不再发生抑制作用;如果同时考虑稀释作用与表面氧化作用,会发现气体对氧化产物TiO_2的稀释作用,明显抑制了颗粒的增长速度,对出口颗粒粒径的影响起决定性作用,而表面氧化反应仅在中心轴附近区域对颗粒粒径有较大的影响;热迁移作用对颗粒粒径的影响较小,仅在火焰内部对颗粒粒径有一定的影响。
As an important nanosized material, TiO_2 nano-particle is applicable to production and living widely.Its photocatalytic activity is widely used for solar battery and photocatalytic synthesization and so on.Particle characteristics like size and size distribution mainly influence the final product quality and photocatalytic activity of TiO_2.This emphasizes the need for discussion and control for the influencing factor of particle size.
The CVD method is used to produce TiO_2 nano-particle in the propane-air diffusion flame. The effect of different operating conditions on particle size and crystal form is investigated. There are four different operating conditions analyzed. The results show that temperature is influenced mainly by the rate of propane and air; the higher the rate of propane is, the bigger particle size is, while the higher the rate of air is, the less particle size is; besides particle size is consistent with the rate of TiCl_4; while the influence of the rate of carried gas on particle size is negligible.
Using the commercial CFD-code FLUENT and the additional fluid-particle dynamics (Pratsinis, 1998), the simulation of the effect of surface oxidation reaction , dilution and thermophoretic on particle size is performed. The result show that, mean particle diameter with surface oxidation reaction considered is bigger at the same position. Meanwhile the influence of surface oxidation reaction on particle size is obvious at the beginning of reaction but negligible at the outlet because of the relation between precursor and oxidant concentration. The increase of particle size is evidently restrained by dilution in the flame region, but hardly in the non-flame region due to the little effect of dilution. If we take the surface oxidation reaction and dilution into consideration, the dilution restrains obviously the velocity growth and affects deeply the particle size, while surface oxidation reaction effect merely particle size near the centerline.we also find that thermophoretic just have a little influence on particle size inside the flame.
引文
[1]许并社.纳米材料及应用技术.北京:化学工业出版社.2004.
[2]谢洪勇.粉体力学与工程.北京:化学工业出版社,2003.
[3]洪若瑜,任志强,李洪钟.扩散火焰燃烧法合成纳米二氧化钛[J].过程工程学报,2004,4:502-508.
[4]田地,于刚,张彭义等.碳黑改性二氧化钦对气相中甲苯的光催化降解.太阳能学报,2002,02,23(1):66-69.
[5]柳闽生,杨迈之.半导体纳米粒子的基本性质及光电化学特性.化学通报,1997(1):20-24.
[6]宋晓岚,邱冠周,杨华明.超细功能粉体的机械化学合成研究进展.金属矿山,2004第7期:9-11.
[7]刘维平,邱定蕃,马瑞新.超细粉体制备及测量技术研究进展.IM&P化工矿物与加工,2003年第3期.
[8]甘礼华,岳天仪,李光明.薇乳液法制备γ-Al_2O_3超细末及其表征.同济大学学报(自然科学版),1996,24(2):194-197
[9]杨柯,刘阳,尹红.纳米二氧化钛的制备技术研究.中国陶瓷,2004,40(4):8-12.
[10]郭新,袁润章.化学气相淀积在无机新材料制备中的应用.材料科学与工程,1994,12(1):58-61.
[11]吴孟强,张其翼,陈艾.凝胶-燃烧法合成纳米晶SnO_2粉体.硅酸盐学报,2002,30(2):247-253.
[12]赵东林,潘正伟,周万城.激光法气相合成纳米Si/C/N复相粉体.西安工程学院学报,1998,20(4):56-58.
[13]Wenhua Zhu,Sotiris E.Pratsinis.Flame Synthesis of Nanosize Powders-Effect of Flame Configuration and Oxidant Composition.Nanotechnology,1996,P65.
[14]M.R.Zachariah,D.Chin,H.G.Semerjian,J.L.Katz.Comb.Sci.Tech.,1977,17:p119.
[15]M.Choi,J.Cho,J.Lee,H.W.Kim.Measurements of Silica Aggregate Particle Growth Using Light Scattering and Thermophoretic Sampling in a Coflow Diffusion Flame.Journal of Nanoparticle Research,1999,1:169-183.
[16]谢洪勇,宁桂玲等.火焰CVD法制备纳米TiO2和纳米SiO2的实验与理论研究.过程工程学报,2002,2:183-186.
[17]张薇,孙雪,谢洪勇.Preparation of Nano Titanium Dioxide in Propane/air Diffusion Flame.过程工程学报,2004第4卷增刊:509-514.
[18]F.E.Kruis,K.A.Kusters and S.E.Pratsinis.A Simple Model for the Evolution of the Characteristics of Aggregate Particles Undergoing Coagulation and Sintering.Aerosol Science and Technology,1993,19:514-526.
[19]S.Tsantilis,S.E.Pratsinis,V.Haas.Simulation of Synthesis of Palladium Nanoparticles in a Jet Aerosol Flow Condenser.J.Aerosol Sci.1999,30(6):785-803.
[20]A.Schild,A.Gutschl,H.M" uhlenweg,S.E.Pratsinis.Simulation of Nanoparticle Production in Premixed Aerosol Flow Reactors by Interfacing Fluid Mechanics and Particle Dynamics.Journal of Nanoparticle Research,1999,1:305-315.
[21]Patrick T.Spicer,Olivier Chaoul,Stavros Tsantilis,Sotiris E.Pratsinis.Titania formation by TiCl_4 gas phase oxidation,surface growth and coagulation.Aerosol Science,2002,33:17-34.
[22]Johannessen T.,S.E.Pratsinis,H.Livbjerg.Computational Analysis of Coagulation and Coalescence in the Flame Synthesis of Titania Particles.Powder Technology,2001,118:242-250.
[23]Mingzhou Yu,Jianzhong Lin,Tatleung Chan.Numerical simulation of nanoparticle synthesis in diffusion flame reactor.Powder Technology,2007,180:9-20.
[24]李云.火焰CVD法合成纳米颗粒的数值模拟(硕士学位论文).大连:大连理工大学,2005.
[25]潘洪亮.火焰CVD法合成纳米颗粒的数值模拟(硕士学位论文).大连:大连理工大学,2006.
[26]董南航.火焰CVD法合成纳米颗粒的数值模拟(硕士学位论文).大连:大连理工大学,2007.
[27]Fluent Inc.Fluent:User' Guide:Fluent 6.0.USA:Fluent Inc 2001.
[28]王俏,齐红军.超细粉体材料前景广阔.当代化工,2002,31(2):98-100.
[29]陶文铨,数值传热学.西安:西安交通大学出版社2002:509.
[30]陈义良,张孝春,孙慈,季鹤鸣.燃烧原理.北京:航空工业出版社,1992,363-366.
[31]朱谷君.工程传热传质学.北京:航空工业出版社,1989,514-515.
[32]NIST.
[33]张薇.火焰CVD法制备纳米颗粒材料不完全燃烧过程数值模拟(硕士学位论文).大连:大连理工大学2006.
[34]Atsuo k,Katsuki k,Shigeharu m.Growth and transformation of TiO_2 crystallites in aerosol reactor[J].AIChE Journal,1991,37(3):347-359.
[35]P.petri a,Jorma j,Olivier r,et al.Mobility size development and the crystalliza- tion path during aerosol decomposition synth- esis of TiO2 particles[J].Aerosol Science,2001,32:615-630.
[36]刘秀红,赵尹,姜海波.扩散火焰法控制TiO_2纳米晶粒径和晶型的研究[J].非金属矿,2006,4(29):19-33.
[37]王志义,史献峰,崔作林.ZnO异质复合对纳米TiO2晶型转变和晶粒生长的影响[J].硅酸盐学报,2006,34(9):1079-1083.
[38]Kobata A.,K.Kusakabe & S.Morooka.Growth and transformation of TiO2 crystallites in aerosol reactor.1991.AIChE J.37,347-359.
[39]谢洪勇,宁桂玲,毛中强,王达望,孙雪.火焰CVD法制备TiO2纳米颗粒材料的实验与理论研究,过程工程学报,第2卷增刊(2002)183-186.
[40]T.Matsoukas,S.K.Friedlander,Dynamics of aerosol agglomerate formation,J.Colloid Interface Sci.146 2 1991,495-506.
[41]Fuchs,N.A.Mechanics of aerosols.New York:Pergamon Press,1964.
[42]Pratsinis S.E.,H.Bai,P.Biswas,M.Frenklach & S.V.R.Mastrangelo.Kinetics of TIC14Oxidation,J.Am.Ceram.Soc.,1990,73,2158-2162.
[43]T.Johannessen,"Implementing User-defined Scalars/Functions in Fluent - A practical example",Department of Chemical Engineering,Technical University of Denmark,1999.
[44]孙文策.工程流体力学.大连:大连理工出版社1995:P31.
[45]Seinfeld,J.H..Atmospheric chemistry and physics of air pollution.New York:Wiley,1986.
[46]陶文铨.计算传热学的近代发展.北京:科学出版社,2000,233-234.
[2]谢洪勇.粉体力学与工程.北京:化学工业出版社,2003.
[3]洪若瑜,任志强,李洪钟.扩散火焰燃烧法合成纳米二氧化钛[J].过程工程学报,2004,4:502-508.
[4]田地,于刚,张彭义等.碳黑改性二氧化钦对气相中甲苯的光催化降解.太阳能学报,2002,02,23(1):66-69.
[5]柳闽生,杨迈之.半导体纳米粒子的基本性质及光电化学特性.化学通报,1997(1):20-24.
[6]宋晓岚,邱冠周,杨华明.超细功能粉体的机械化学合成研究进展.金属矿山,2004第7期:9-11.
[7]刘维平,邱定蕃,马瑞新.超细粉体制备及测量技术研究进展.IM&P化工矿物与加工,2003年第3期.
[8]甘礼华,岳天仪,李光明.薇乳液法制备γ-Al_2O_3超细末及其表征.同济大学学报(自然科学版),1996,24(2):194-197
[9]杨柯,刘阳,尹红.纳米二氧化钛的制备技术研究.中国陶瓷,2004,40(4):8-12.
[10]郭新,袁润章.化学气相淀积在无机新材料制备中的应用.材料科学与工程,1994,12(1):58-61.
[11]吴孟强,张其翼,陈艾.凝胶-燃烧法合成纳米晶SnO_2粉体.硅酸盐学报,2002,30(2):247-253.
[12]赵东林,潘正伟,周万城.激光法气相合成纳米Si/C/N复相粉体.西安工程学院学报,1998,20(4):56-58.
[13]Wenhua Zhu,Sotiris E.Pratsinis.Flame Synthesis of Nanosize Powders-Effect of Flame Configuration and Oxidant Composition.Nanotechnology,1996,P65.
[14]M.R.Zachariah,D.Chin,H.G.Semerjian,J.L.Katz.Comb.Sci.Tech.,1977,17:p119.
[15]M.Choi,J.Cho,J.Lee,H.W.Kim.Measurements of Silica Aggregate Particle Growth Using Light Scattering and Thermophoretic Sampling in a Coflow Diffusion Flame.Journal of Nanoparticle Research,1999,1:169-183.
[16]谢洪勇,宁桂玲等.火焰CVD法制备纳米TiO2和纳米SiO2的实验与理论研究.过程工程学报,2002,2:183-186.
[17]张薇,孙雪,谢洪勇.Preparation of Nano Titanium Dioxide in Propane/air Diffusion Flame.过程工程学报,2004第4卷增刊:509-514.
[18]F.E.Kruis,K.A.Kusters and S.E.Pratsinis.A Simple Model for the Evolution of the Characteristics of Aggregate Particles Undergoing Coagulation and Sintering.Aerosol Science and Technology,1993,19:514-526.
[19]S.Tsantilis,S.E.Pratsinis,V.Haas.Simulation of Synthesis of Palladium Nanoparticles in a Jet Aerosol Flow Condenser.J.Aerosol Sci.1999,30(6):785-803.
[20]A.Schild,A.Gutschl,H.M" uhlenweg,S.E.Pratsinis.Simulation of Nanoparticle Production in Premixed Aerosol Flow Reactors by Interfacing Fluid Mechanics and Particle Dynamics.Journal of Nanoparticle Research,1999,1:305-315.
[21]Patrick T.Spicer,Olivier Chaoul,Stavros Tsantilis,Sotiris E.Pratsinis.Titania formation by TiCl_4 gas phase oxidation,surface growth and coagulation.Aerosol Science,2002,33:17-34.
[22]Johannessen T.,S.E.Pratsinis,H.Livbjerg.Computational Analysis of Coagulation and Coalescence in the Flame Synthesis of Titania Particles.Powder Technology,2001,118:242-250.
[23]Mingzhou Yu,Jianzhong Lin,Tatleung Chan.Numerical simulation of nanoparticle synthesis in diffusion flame reactor.Powder Technology,2007,180:9-20.
[24]李云.火焰CVD法合成纳米颗粒的数值模拟(硕士学位论文).大连:大连理工大学,2005.
[25]潘洪亮.火焰CVD法合成纳米颗粒的数值模拟(硕士学位论文).大连:大连理工大学,2006.
[26]董南航.火焰CVD法合成纳米颗粒的数值模拟(硕士学位论文).大连:大连理工大学,2007.
[27]Fluent Inc.Fluent:User' Guide:Fluent 6.0.USA:Fluent Inc 2001.
[28]王俏,齐红军.超细粉体材料前景广阔.当代化工,2002,31(2):98-100.
[29]陶文铨,数值传热学.西安:西安交通大学出版社2002:509.
[30]陈义良,张孝春,孙慈,季鹤鸣.燃烧原理.北京:航空工业出版社,1992,363-366.
[31]朱谷君.工程传热传质学.北京:航空工业出版社,1989,514-515.
[32]NIST.
[33]张薇.火焰CVD法制备纳米颗粒材料不完全燃烧过程数值模拟(硕士学位论文).大连:大连理工大学2006.
[34]Atsuo k,Katsuki k,Shigeharu m.Growth and transformation of TiO_2 crystallites in aerosol reactor[J].AIChE Journal,1991,37(3):347-359.
[35]P.petri a,Jorma j,Olivier r,et al.Mobility size development and the crystalliza- tion path during aerosol decomposition synth- esis of TiO2 particles[J].Aerosol Science,2001,32:615-630.
[36]刘秀红,赵尹,姜海波.扩散火焰法控制TiO_2纳米晶粒径和晶型的研究[J].非金属矿,2006,4(29):19-33.
[37]王志义,史献峰,崔作林.ZnO异质复合对纳米TiO2晶型转变和晶粒生长的影响[J].硅酸盐学报,2006,34(9):1079-1083.
[38]Kobata A.,K.Kusakabe & S.Morooka.Growth and transformation of TiO2 crystallites in aerosol reactor.1991.AIChE J.37,347-359.
[39]谢洪勇,宁桂玲,毛中强,王达望,孙雪.火焰CVD法制备TiO2纳米颗粒材料的实验与理论研究,过程工程学报,第2卷增刊(2002)183-186.
[40]T.Matsoukas,S.K.Friedlander,Dynamics of aerosol agglomerate formation,J.Colloid Interface Sci.146 2 1991,495-506.
[41]Fuchs,N.A.Mechanics of aerosols.New York:Pergamon Press,1964.
[42]Pratsinis S.E.,H.Bai,P.Biswas,M.Frenklach & S.V.R.Mastrangelo.Kinetics of TIC14Oxidation,J.Am.Ceram.Soc.,1990,73,2158-2162.
[43]T.Johannessen,"Implementing User-defined Scalars/Functions in Fluent - A practical example",Department of Chemical Engineering,Technical University of Denmark,1999.
[44]孙文策.工程流体力学.大连:大连理工出版社1995:P31.
[45]Seinfeld,J.H..Atmospheric chemistry and physics of air pollution.New York:Wiley,1986.
[46]陶文铨.计算传热学的近代发展.北京:科学出版社,2000,233-234.