Kempaiah Murukanahally Devaraju

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博士学位論文の要旨及び審査結果の要旨 (Summary of Thesis(DR))othe

Kempaiah, Murukanahally Devaraju

Tohoku University Repository (TOUR) / 東北大学機関リポジトリ

Morphology Control and PhotochemicalProperties of Rare Earth Oxides Particles bySolvothermal Reactions著者 Kempaiah Murukanahally Devaraju学位授与機関 Tohoku University学位授与番号 学術(環)博第125号URL http://hdl.handle.net/10097/51226ケンパイア,ムルカナハリ　デバラジュ氏　　　　　　名　Kempaiah, Murukanahally Devaraju授　与　学　位　博士(学術)学　位　記　番　号　学術(環)博第125号学位授与年月　日　　平成22年月3月25日学位授与の根拠法規　学位規則第4条第1項研究科,専攻の名称　東北大学大学院環境科学研究科(博士課程)環境科学専攻学位論文題目　MorphologyControlandPhotochemical PropertiesofRareEa仙0Xidespa,ticles by Solvothermal Reactions (ソルポサーマル反応による希土類酸化物粒子の形態制御と光化学特性)東北大学教授　佐藤　次雄主査　東北大学教授　佐藤　次雄　　東北大学教授　吉岡　敏明東北大学教授　垣花　星人(多元物質科学研究所)Chapter l･ General introductionThe present human society is very well practiced with the use or excellent technological materials･ Incertain case, the performance of thefunctional materials decreases withtime since the properties depends on manyfactors including the morphology'preparation method and physicoIChemical properties･ The requlrement Oftechnological materials has been increaslng day-by-day･ However, the researchers should look fわrenvironmentally benign materials and techniques fわr the preparation of advanced materials in order to make surethe safetyof human kind･ Moreover, Once should take care about the negative impact of the process or thefunctional materials. 1n order to save energy, time and money we need to develop facile methods for thepreparation of RlnCtional materials and materials fわr environmental applications･ Moreover recent researchdevelopments on rare earth oxides shows that the morphology and size control can improve the photochemicalproperties･ Many methods were used to control the morphology and size offunctionally Important rare earthoxides. However an easy, Cost effective and rapid method has not been realized yet･ The present work proposes asolvothemal re仙Xing route and subcritical and supercritical solvothe-al/hydrothe-al method to control themorphology and improve the photochemical properties･chapter 2･ Renuxing solvother,mal synthesis and photoluminescence properties of RE3'(RE3'= Eu, Tm andTb) doped Y203 nanOCryStalsTwo different synthesis routes were adopted in order to prepare dispersed RE3'(旺3+- Eu, Tm and Tb)doped Y20 nanocrystals･ Route1 1 is coIPreCipitation refluxing calcinations where in a coIPreCipitated gel powderwas ,efluxed in different organic solvents i･e. propyleneglycol, 1, 31butanediol and polyethylene glycol and thereaction temperature was near to the boiling point of respective organic solvents･ Each solvent showed differenceon the particle size and m叩hology befわre and a鮎r calcinations･-89-Fig. 2. As prepared sample via routel1(a)and route-2 (b)･580　600　620　640　660　680WavelengthJn m660Fig. 3. Photolumねescence spectra of calcined samples atVariouscalcinations temperattueHowever,the as-prepared sample in polyethylene glycol showed good dispersion with 60-80 rLm in diameter andimproved photohminescence propertyover conventional product･ Route-2 is refluxing calcinations wherethepreparation was camied out by taking desired amount of rare earthaqueous solution in mixed solution containingmethanol-ethylene glycoland hexane-ethylene glycol followed by renuxing at 70and 1 70 oC for 2h･ The particleprepared by route-2 showed great particles dispersion before and after calcinations when compared to the particlesprepared via route-1 (Fig.2). The calcined samples after prepared via route-2 showed excellent room temperattwephotoluminescence propertyas shownin Fig 3･chapter 3. Hydrothermal synthesis of RE3'(RE3㌧ Eu, Tm and Tb) doped Y203 nanOSPheres, rods,bundles of rods and nanotubesUntilknOw a rapid method for morphologyand size controlled syn也esis of REつ+ (RE3+-Eu, Tm and Tb) doped Y203 materials wi也Outuslng any Surfactant or template is not reported･Herein, we prepared these materials with　spher.　　　　rodsvarious morphology and size in血e absence ofsurfactant and template･ Aqueous solution of20 ml of 0.25 M YC13 aqueous solution and0.25 mmol of rare earthchloride (Tm3', Tb3' 200咋　　　　2500C　　　　2800C　　　3200Cand Eu3･) powder corresponding to Fig･ 4･ Form如ion mechanism of rare earthoxide doped nanotube5 m01% rare earth ion doping were used as starting materials･ The experiments were carried out at 200-320 0C forabout 5 min. The as prepared materials were identified as hexagonal Y(OH)3 and rare earthion doped Y203nanotubes were prepared by calcination of the as-prepared product in air at 500 oC for 4 h･ The asIPreParedmaterials at 200 oC, 250 oC and 280 0C exhibited sphere, rodsand bundles of rods shaped morphology (Fig･ 4)-90-with20-150 nm beforeand after calcinations.Where as the sample prepared at 320 0C exhibited beautifulnanotubes (Fig. 4) like morphology and optical properties of RE3+ (RE3+- Eu, Tm and Tb) doped Y203 nanOtubeswere discussed.chapter 4･ Supercritical solvothermal synthesis and characterization of RE3'(RE3'= Eu aTLd Tb) dopedY203　microspheres,microcubes and hollowmicrospheresMicron sized rare earthoxide particlesare necessary forthe operation of low voltage systems such asFED and CRT･S. Herein, we prepared rare earth RE3+ (RE3+- Eu and Tb) doped Y203 microspheres, microcubesand hollow microspheres (Fig. 5) at supercritical conditions. Metalsalts and mixed solution of water/ethanol,water/methanoland water/I-propanol were used to controlthe morphology･ The synthesis was carried out forshort period of reaction time (5-10 min),the formation mechanism was illustratedand effect of reactiontemperature, pH and reaction time was investigated･ The morphology does not change even aRer calcinationsatvery high temperature (900 oC). The effect of morphology onthe photoluminescence propeny was discussed･Asaresult,the highest emission is obtained for the hollow microspheres due to itsunlque mOrPhology･rF賢r!lpm　　　　　　　2 pmFig･ 5･ FESEM of as prepared microsphere, microcubesand hollow microspheres5. Stlbcritical and supercritical solvothermal synthesis and characteriZ:ation of CeO2 nanOrOdsl nahOSPberelhollow hanOSPheres and 3Dmicro/natLOStrllCtⅦreCeO2 nanOrOds and nanospheres were prepared by justchangingthe source of starting materials at supercriticalconditions. CeO2 nanOrOds were obtained using CeC13.7H20 asstarting material･Where as CeO2 nanOSPheres were obtainedwhen Ce(NO3)3.6H20 was used as starting material. EthanOland methanol were used as solvothermal reacting solvents. Theas-prepared nanorod and nanosphere exhibited 300-500 nm indiameterand exhibit excellent UV shielding propedy andcatalytic activity　by CO oxidation･ Surfactant assistedsolvothermal synthesis at subcritical conditions were carried伽　　仰　　加OUOtuOtS-空u8-I-100.150rlm -A-200-250rITl -I-400.500rm -■-C○TTWCbl BO2 ■ 1 00　　200　　300　　400　　500TcmFN>r tLJre (℃)Fig. 6. Ca alytic activity for CO oxidationout forthe preparation of CeO2 hollow nanospheres with 500-150 nm in diameter･ The cheapand non-toxic-91-pvA500# was used as surfactant with varying amount･ The excellent UV shielding activityand size dependentcatalytic activityby CO oxidation (Fig･6) after calcinations was investigated･ Using ethylene glycol as solvent･ceo2 3D micro/nanostructures were also synthesized withimproved catalytic activity･ The formation mechanismof hollow nanospheres and CeO2 3D micro/nanostructures was illustrated･chapter 6･ Supercritical synthesis and characterization of CeO2-ZrO2 mixed oxides for catalyticapplication ～Untilknow, several methods wereused forthepreparation of CeO2-ZrO2 mixed oxides ei血er need highcalcinations temperature or long experimental duration･Herein, we propose a direct and rapid me血od to prepareceo21ZrO2 mixed oxides withdifferent Zr content･ In atypical preparation, 36 ml of mixed aqueous solutions ofcepIl.)2(NO3)6 and ZrO(NO3)･2H20 (Ce + Zr = 1 M)were taken in a beaker containing 4 ml of ethanol, ethyleneglycoland polyethylene glycol, followed by stirring for I 5min and也e resulted blood red colored solution (10 ml)偶成伽瓜e!胡瓜0　0　0　0　0　0　AU("o色l毒葛■ 02E04のCOOBOO1000 TerTPqatLrBr qFig･ 7･ Oxygen storage capacity at variouswas t,ansferred t. 20 ml volume of batch reactors (4 reactors). temperaturesThen,the reactors were heated at 400 oCunder autogeneous pressure of ca･ 40 MPa for 10 min･ CeO2and ZrO2were also prepared withthe same experimental conditions･ The prepared CeO2-ZrO2mixed oxides showed spheremorphology withdifferent diameter size depending upon organic solvents usedinthe symthesis･ The lowestparticle size (<10 nm) is obtained forthe sample prepared in polyethyleneglycol andthese particles showedexcellent oxygen storage capacity咋ig･7) and CO oxidation ability･Chapter 7･ CoTLClusionsThe purpose ofthisthesis is develop a low cost, rapidand easy methods to controlthe morphology of rareearthoxides particlesandalso to improvethe photochemical properties･ Forthat･ we have proposed solvothermalmethod to prepare dispersed RE3'(RE3'= Eu, Tmand Tb) doped Y203 materials with20-80 nm in diameterandtheir optical properties were studied･ A rapid hydrothermalSymthesis was used to prepare FtE3'(貼3'- Eu, Tmand Tb) doped Y20, materials with various morphology and size･ The obtained nanotubes showed interestingoptical properties･ A supercritical solvothermal method was successfully used to prepare micron sized particleswith microsphere, microcubesand hollow microspheres morphology and photoluminescenece propertywasmeasuredand compared･CeO2 Withinteresting morphologleS Were Prepared via subcriticaland supemiticalsolvo血emal conditions w仙improved UV shielding ability and catalytic activity･ A direct me仇od fbr血epreparation of CeO2-ZrO2 materials to improve the catalytic propedy was propOSed･-92-論文審査結果の要旨希土椀財ヒ物は多様な分野で利用されており､それらの機能性の高度発現のためにE胡辞l粉末の形態の精密制御が必要であるo本研究は､水や剤財ヒ合物を反応溶媒とするソルポサーマル反応により希土塀財ヒ物の形態をナノからマクロまで階層的に制御する手法を開発し､蛍光特性､紫外線吸収相生､環櫛引ヒ触媒特性等の光化学相生に及古軒｢形態や結晶化度の影響について系統的に調べた研究であり､全編7章よりなる.第1番淵論であり､希甥財ヒ物の合成法､光化学特性などに関する過去の研究を網羅し､その特徴を述べ､また､重要ながら未解明な事項を列挙し､その上で､本研究の日掛す方向とその概要を述べている｡第2章は､ :剤財ヒ合物を溶媒として用いるソルポサーマル還流反応により､ Eu3+, Tm3', Tb3+ドープY203前駆体ナノ粒子を合成した後､空気中仮暁により前駆体の形態を転写したEu3+, Tm3', Tb3+ドープY20｡ナノ粒子を合成する手法を開発するとともに､生成物の蛍光相生に及ぼす形態や鰭晶化度の影響について明らかにした｡第3章は､水熱反応によりEu3', Tm3', Tb3'ドープY20｡前駆体ナノ粒子を合成した後､空気中仮既により前駆体の形態を転写したEu3+, Tm3十, Tb3'ドープY203ナノ粒子を合成する手法を開発するとともに､生成物の蛍光特性に及ぼす形態や結晶化度の影響について明らかにした｡第4章は､有機溶媒を用いる超臨界ソルポサーマル反応によりEu3', Tb3'ドープY2ql前駆体立方体粒子や中空疎拒駈子を合成した後､空気中仮暁により前駆体の形態を転写したEu3', Tb3+ドープY205立方体粒子や中空飾択粒子を合成する手法を開発するとともに､生成物の蛍光特性に及ぼす形態や結晶化変の影響について明らかにした｡第5章は､有機溶媒を用いる超臨界ソルポサーマル反応によりCeOけノロッドやナノ粒子を合成する手法を開発するとともに､生成物の紫外線吸収特性やCO酬出虫媒特性に及ぼす形態や結晶化度の影響について明らかにした｡第6章は､有機溶媒を用いる超臨界ソルポサーマル反応によりCe02-ZrO2ナノ粒子を合成する手法を開発するとともに､生成物の酸素吸蔵能やCO浄化触媒特性に及古珊ヒ学組成の影響について明らかにした｡第7章は結論であり､各章の結言を要約している｡以上､本論文は､多様な分野において工業的に重要な希土鰯酎ヒ物粒子の形態制御技術を開発するとともに､光化学特性に及ぼす諸因子の影響について系統的に調べた研究であり､環境科学､物質科学の分野甲発展に寄与するところ少なくない.よって,本論文相専土(学術)の学位論文として合格と認めるo-93-

Morphology Control and Photochemical Properties of Rare Earth Oxides Particles by Solvothermal Reactions

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ソルポサーマル反応による希土類酸化物粒子の形態制御と光化学特性

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