Influence of the Ratio of Ethanol to Water on the Agglomeration of Al2O3/Y2O3-ZrO2 Nanoparticles

JOURNAL OF RARE EARTHSVol 25, Suppl., Dec. 2007, P 31Influence of the Ratio of Ethanol to Water on the agglomeration of Al2 O3/Y,03-ZrO, NanoparticlesLi Xiuhua(李秀华)2, Du Juanjuan(杜娟娟), Zhu Liying(朱丽颖)2, Cheng Huijie(成慧杰),Wang Lingwei(王灵伟)12(I. Key Laboratory of Advanced Ceramics and Machining Technology( Tianjin University ), Ministry of Education, Tian-jin 300072, China; 2. School of Materials Science and Engineering, Tianjin University, Tianyin 300072, China)Abstract: A method of heating ethanol-aqueous salt solution combined with co-precipitation was used to synthesize Al203/ZrO2 nanoparticles. The analysis of DSC and XRD revealed that the transformation temperature from amorphous to crystalphase was about 850 C. The grain size was increased with the raising of calcine temperature. The alcohol-water ratio didnot affect the formation of main crystal phases, but affected the agglomeration of nanoparticles based on the results ofTEM. When alcohol-water ratio was 5: 1, the dispersion of nanoparticles was good. When there was not alcohol, the dis-persion of nanoparticles was poor because there was only pure co-precipitation reaction and the speed of co-precipitationreaction was too high to have enough time of PEG. dispersing particleKey words: ZO2: Al2O3: Y2O3; nanoparticle; agglomerationCLC number: TF123 Document code: A Article ID: 1002-0721(2007)-0031-04A method of heating ethanol-aqueous salt solution preparation of 2Y-TZP nano-powder by the method ofhas been used toprepare nano-powder in receico-precipitationyears -3. An important process of the method is aIn this work, the method of heating of acoholheating process of ethanol-aqueous salt solution. Whensolution combinedthe alcohol-aqueous salt solution is heated, dielectric prepare AL20, /Z102(Z 02 matrix)nano-powder. For theconstant decreases significantly, which causes the re- decrease of agglomeration, NHHCO, was chosen as theduction of the solvation energy and the salt solubilityprecipitant. The influence of different ratio of ethanol toAs a result, the salt solution becomes supersaturated, water on agglomeration was investigatedthe gelatinous precipitation produces gradually. Theformation of the gel makes the ions, which have not1 Experimentalprecipitated, disperse uniformly in gelatinous precipFig 1 shows the flow chart of the experimenttation. Thus, it is advantageous to the uniform disper- The mixed aqueous solution of 0. 25 molL-I was pre-sion of each ingredient in precursors. In 1998, Liw4 prepared successfully ZHO2 (Y20, )nano-powderpared according to 20% Al203+80%(3%Y2O3-ZNO,). The solution was heated and stirred on a elec-by the method. In 2004, Chen G used the methodtromagnet mixer to make Y203 dissolve completelycombined co-precipitation process to prepare ZrO2/Then, the solution was divided into three equalAl2O, nano-powder(Al203 matrix), and studied the in-tion. Different volume of alcohol was separatelyfluluence of ammonia and NH, HCO, as precipitant on to the first one and the second one for the volume ratioagglomerate size. It was discovered that the two kinds of alcohol to water 5: 1 and 2: 1. The third one had onof precipitants were different. Because different pre- alcohol. PEG400 and PEG4000 as dispersant werecipitants have different anions, which leads to different added to each solution. Every solution was heated tonts in precursors. The result showed that 75 C for 6 h in the water-bath. The co-precipitationNHAHCO, as the precipitating agent was better than process was carried out on electromagnetic mixer atammonia. In 2003, Tang J N[6room temperature. The gel-like precipitate was addedNH,HCO, was one kind of good precipitant during the to lion1.8mol·L1中国煤化工Received date: 2006-12-09; revised date: 2007-04-18CNMHGFoundation item: The authors acknowledges the financial support of Tianjin University Youth Foundation and Tangshan Ceramics Limited CompanyBiography: Li Xiuhua (1964-)Female, Doctor, Vice-professor: Reasearch interest: material science*Correspondingauthor(e-mail:Ixh502@yahoo.comJOURNAL OF RARE EARTHS, Vol 25, Suppl., Dec. 2007ZrOCl, 8HOAl(NO) 9H,OHeated and stirredAdd alcohol and PEYaOdeionized waterHeatedAdded to NHHCO, and layedWashedFig 1 Flow chart of preparation of Al 20,/Zr02 powderwith pH 7-8 at about 3 ml.min. Three kinds oftsuspending liquids were layed for 12 h for complete reaction. The precipitate was washed repeatedly withAtdistilled water for removal of CI", dewatered by ethanol, dried at 100C and calcined at 500. 900, and1000C for 2 h. Wet precipitates dewatered after co-900ceprecipitation were analyzed by dSC and TG. The crys-talline phases of powders calcined at different temperatures were deduced by a RIGAKU D/Max 2500V/PCautomatic X-ray diffractometer. The microstructureand size of powders were observed by a Japan JEOL20(°)100CX-ll transmission electron microscope2 Results and discussionFig 2 shows the DSC-TG of wet gel obtainedwhen acohol-water ratio is 5:1. There is a obviousheat absorption peak at about 130 C, which may become from the evaporation of water, alcohol, and1000 degrees Catsupolymer. At about 350 C, there is an exothermicpeak that may be the result of carbonate decomposition. The exothermic peak at about 850C may bedue to the transformation from the amorphous to the01020304050crystal. The weight lost gradually decreases after va-2e/°)conization and all of weight lost is about 40%Fig 3(a) shows the XRD results of calcined pow-goodegrees Celsus500 degrees Celsus中国煤化工CNMHGm10℃alysis ot powders(a)Alcohol: water= 5: 1;(b)Alcohol: water =2: 1; (c)NoFig 2 TG-DSC analysis of wet gelalcoholLi X H ef al. Influence of the Ratio of Ethanol to Water on the agglomerationders prepared when acohol-water ratio is 5: 1. The possible that the gathering of precipitates leads to someAlO3/Zro2 powder calcined at 500 C is amorphousagglomerates due to the high speed of co-precipitationIt is deduced that amorphous phase should be kept to process. When there is no alcohol, no alcohol-water850C based on DSC-TG analysis. The powder calheating reaction, there is only pure co-precipitationcined at 900 C is crystal phases mainly consist of t- reaction. Because the speed of co-precipitation reac-zrO2 and a-Al20,. The diffraction patten of powder tion was too high to have enough time of PEG. dispercalcined at 1000C is similar to that calcined at 900 sing particles, therefore, the agglomerate degree wasC, but the peak width reduces, which shows the biggestgrain size has already grown up. The grain size can beIn the researches of Li Wl4)and Chen G QS)calculated based on the(111)face of t-ZrO2(eqelement Y was introducd by Y (NO, )3.6H,0. In this(1))rk, the element Y was introducd by Y203. ItD=A/Bcosshown that Y,O can be dissolved in solution ofwhere D is grain size, B is the width of the peak at ZrOCl2.8H20 by stirring and heating, achieving unhalf the peak maximum, 8 is the diffraction angle, a form mixing of Zr**and Y*. It is known that an imis the wave length, and K=1. According to the portant stage in heating acohol-aqueous salt solutionequation(1),D increases when p decreasesfor the preparation of nano Al203/Zr02 powder is theIn addition, when alcohol-water ratio was production of gelatinous precipitates. When acoholchanged, main crystal phases were still t-ZrO2. Thus, aqueous ZroCl, 8H,0 solution was heated,chemicalalcohol-water ratio did not affect the formation of main constituent of the precipitate is Zr,02(OH)BCL.Thecrystal phases( Figs. 3(b)and(c))reaction equation may be expressed as follow,Fig 4 shows the TEM photograph of the dried 4Zn0C1,+ 6H, 0= zr40,(OH)CL+4HCI(2precipitate before calcine when alcohol-water ratio is5: 1. A few agglomerates, mainly composed of flatnano-particles(20-30 nm), can beFigs. 5(a),(b)and(c)show the TEM photo-graphs of powers calcined at 900C, prepared respec-ively when alcohol: water is 5: 1, alcohol: water is 2: 1and there is no alcohol. The powder in Fig. 5(a)hasthe least agglomerates, and particle size is approximately 40 nm. The agglomerates in Fig. 5(b)is lessthan that in Fig. 5(c). Under the condition of no ethanol, many compact agglomerates can be seen. It isdeduced that when the alcohol-water ratio is 5: 1, thealcohol-water heating reaction may be complete, andthe PEg molecules in the solution make gelatinousprecipitates well dispersed due to enough time, whichlead to the least agglomerates after co-precipitationWhen the alcohol-water ratio is 2: 1. the alcohol-waterating reaction is possibly incomplete. Thus, it is降中国煤化工So nmCNMHFig5 TEM photograph of powder calcined at 900 CFig 4 TEM photograph of dried precipitate(a)Alcohol: water=5: 1;(b)Alcohol: water 2 1: (c)NoJOURNAL OF RARE EARTHS, Vol 25, Suppl., Dec. 2007But even if acohol-aqueous Al(NO,)3 9H20 solu- attracting force each other, which led to reduce theon was heated for 6 h, there was still no precipitate to possibility of forming bridge oxygen bond Zr-0-Zr be-educed that when the acohol-aqueous tween particles during drying and calciningsolution of ZrOCI28H20, Al(NO3)3 9H20 and Y20heated,the hydrolysis reaction of Y* and Al+is sup-3 Conclusionsessed due to low pH. The precipitation of Y*canAl203/Y203-ZH02(Zr02 matrix) nano powder wnot be formed. But the quantity of Al(NO, )3 9H20 is successfully prepared by the heating of acohol-aqueousrelatively large, a few precipitates of AP+may be pro- salt solution combined with co-precipitation. It wasduced(Eq (3)). Thus, the precipitates may be com- shown that the agglomeration of powder was affectedposed of ZrO2(OH)8 CL and Al(OH)3, while Y+ by acohol-water ratio. When acohol-water ratio isfreely disperses in them5: 1, the dispersion of powder is gooAP++3H20= Al(OH)3+3H+ReferencesIn this work, the gelling speed of acohol-waterratio 5: I was higher than acohol-water ratio 2: 1 in [1] Wu Qisheng. Stabilized Y-Ce-ZrO2 nanopowder preparedheating process, which indicated the speeding up ofalcohol to hydrolysis reaction. The appearance of[]. Journal of the Chinese Ceramic Society(in Chin.white gelatinous precipitates in achohol-water ratio 2: 12004,32(9):1170solution was different from the result of Li wll.The[2] Li Wei, Gao Lian, Guo Jingkun. Investigation of thesolution concentration in this work is 1/4 of the litera-process of synthesizing ZrO2 nanoparticles by heating of alohol-aqueous sate solutions [J]. 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