高分子網(wǎng)絡(luò)凝膠法制備納米氧化鋅的工藝控制_英文_

1、· 1782 ·2009年高分子網(wǎng)絡(luò)凝膠法制備納米氧化鋅的工藝控制吳建鋒,劉孟,方斌正,張鋒意,趙娜,徐曉虹(武漢理工大學(xué)材料科學(xué)與工程學(xué)院,武漢 430070摘要:以乙酸鋅Zn(Ac2為原料,丙烯酰胺(AM為單體,N,N亞甲基雙丙烯酰胺(MABM為網(wǎng)絡(luò)劑,采用高分子網(wǎng)絡(luò)凝膠法制備了納米ZnO粉體,研究了其制備過(guò)程中反應(yīng)物濃度、引發(fā)劑(NH42S2O8含量、溶液的pH值及各反應(yīng)條件對(duì)納米ZnO晶粒尺寸的影響。X射線衍射分析結(jié)果表明:納米ZnO顆粒的平均晶粒大小隨Zn2+起始濃度及引發(fā)劑含量的增加而增加,隨溶液pH值的增加而減小。確定了用高分子網(wǎng)絡(luò)凝膠法制備納米ZnO粉體的最

2、佳工藝參數(shù)為:反應(yīng)溫度80;反應(yīng)時(shí)間2h;干燥溫度100;干燥時(shí)間4h。關(guān)鍵詞:高分子網(wǎng)絡(luò)凝膠法;納米氧化鋅;平均晶粒尺寸;制備工藝控制中圖分類(lèi)號(hào):TB303;TB34 文獻(xiàn)標(biāo)志碼:A 文章編號(hào):04545648(200910178209PROCESS CONTROL OF ZINC OXIDE NANO-CRYSTALLINE PREPARED BY APOLYACYLAMIDE-GEL METHODWU Jianfeng,LIU Meng,FANG Binzheng, ZHANG Fengyi,ZHAO Na,XU Xiaohong(School of Materials Science

3、and Engineering, Wuhan University of Technology, Wuhan 430070, ChinaAbstract: Nanosized ZnO powders were synthesized from zinc acetate by a polyacrylamide-gel method. Acrylamide and N,N methylenebisacrylamide were used in the synthesis as a monomer, and a network reagent, respectively. The effects o

4、f the parameters (such as reactant concentration, content of reaction initiator (NH42S2O8, pH value of solvent, etc. on the properties of the nanosized ZnO powders were investigated. The crystalline characteristics of the powders was determined by X-ray diffraction. The results indi-cate that the na

5、nosized ZnO all belong to a hexagonal structure, and the average crystalline grain size decreases with the decreasing of reactant concentration and the reaction initiator content and increasing pH value. In addition, the synthesis process parameters can be optimized at the reaction temperature of 80

6、 for 2h and drying at 100 for 4h.Key words: polyacrylamide-gel method; nanometer zinc oxide; mean crystal size; process controlNanosized ZnO particles are an inorganic functional material. As known, the nano-sized particles of ZnO have some characteristics such as surface/interface, small size, quan

7、tum size and macro-quantum tunneling as well, which can not be provided by the bulk materials. Since the nanosized ZnO particles exhibit semiconducting, piezoelectric, fluorescence and photoelectric multiple properties, they have widely been applied to piezoresis-tance, conducting materials, lumines

8、cent materials, pho-toelectron element, gas sensor, photo catalyst and coating materials, etc.1 The existing methods for the preparation of nanosized ZnO particles include solgels method, chemical precipitation, hydro-thermal, microemulsion and fog-spray heat-decomposing method. Any method has its o

9、wn default as a result of limitation surrounding. Odier firstly used a polyacrylamide-gel method to pre-pare nanosized YBa2Cu3O7x powders.23 The particles of the powder could not move freely and dispersed uni-formly in the network configuration due to the limitation of gel network. In the process of

10、 gel, drying and decom-posing, however, the particles had little chance to contact and reunite, which was propitious to obtain the nanosized powders with small size, high purity and uniform disper-sion. Therefore, the polyacrylamide-gel method has been widely used for preparing various nanosized pow

11、ders due to the unique merits. Jiang et al.4 reported that a solid electrolyte nanosized SrCe0.90Y0.10O2.95 powder was syn-thesized by the method, and the crystalline grain size of the powder was in a range of 31 to 50nm. Liu et al.5 reported that a superfine NiO powder was synthesized by收稿日期:200811

12、05。修改稿收到日期:20090420?；痦?xiàng)目:國(guó)家支撐計(jì)劃(2008ACB41B00資助項(xiàng)目。第一作者:吳建鋒(1963,男,博士,教授。Received date:20081105. Approved date: 20090420. First author: WU Jianfeng (1963, male, Ph.D., professor.E-mail: wujf第37卷第10期2009年10月硅酸鹽學(xué)報(bào)JOURNAL OF THE CHINESE CERAMIC SOCIETYVol. 37,No. 10October,2009吳建鋒等:高分子網(wǎng)絡(luò)凝膠法制備納米氧化鋅的工藝控制&#

13、183; 1783 ·第36卷第10期the polyacrylamide-gel method, and its crystalline size was in a range of 1550nm with the uniform size distri-bution and well crystallization. Shao et al. 6 reported that a nanosized ZnO was synthesized at low decomposing temperature by the method, and the crystalline size of

14、 the powder with the purity of 99.0% was in range of 830 nm with a great specific surface area. Han et al.7 re-ported that the photo catalytic properties of a nanosized ZnO/polyvinyl acetate composite film were characterized by using fading effect of methyl orange solution under the irradiation of i

15、ncandescent lamp. The results indi-cated that the decolonization proportion of methyl orange was 60% when using the composite film, but the decolo-nization proportion was not changed when using a pure nanosized ZnO film or a pure PV Ac(polyvinyl acetate film. Yuan et al. 8 reported that a light abso

16、rbability of nanosized ZnO could be better when the particle-size became smaller, and the flat particles of ZnO have a higher absorbability, compared to the spherical particles.The objective of this work is to investigate the effect of powder preparation process parameters on the average crystalline

17、 size, the average crystallinity and the cell pa-rameters of nanosized ZnO particles synthesized by a polyacrylamide-gel method. These parameters involved reactant concentration, content of reaction initiator, pH value of solvent, etc.1 Experimental1.1 Synthesis of powderUsing polyacrylamide-gel met

18、hod, this work made the aqueous solution by dissolving zinc acetate (Zn(Ac2 in water. The pH value of aqueous solution was adjusted by adding HNO3. Acrylamide (AM and N,N methylene- bisacrylamide (MABM were used as a monomer and as a network reagent, respectively. After mixing AM and MABM in a mass

19、ratio of of 5:1, the 30% (in mass, the same below mixture were added to the 70% Zn2+ aque-ous solution. The aqueous solution was heated to solute completely, and then polymerized at a certain tempera-ture for several hours to obtain a white translucent wet gel by a solicitation action of ammonium pe

20、rsulfate (NH42S2O8. The wet gel was dried to obtain a dried gel in a drying cabinet at a certain temperature. Finally the dried gel was calcinated in a furnace at 600 for 1h to produce a white nanosized ZnO powder.1.2 CharacterizationThe X-ray diffraction (XRD patterns were obtained using a X-ray di

21、ffracto meter (Model D/MAX,Japan with Cu K radiation (=0.154178nm. The phase com-positions and the average crystalline grain sizes were deter-mined by the Scherrer equation. The cell parameters a and c were estimated from the data of the corresponding diffrac-tion peaks.The crystallinity is estimate

22、d by follow eqation:=100%II×(1 where, is crystallinity; I is intensity of diffraction peak; I is omnidirectional intensity.2 Results and discussion2.1 Zn2+ concentrationFigure 1 shows the XRD patterns of nanosized ZnO particles obtained at different Zn2+ concentrations. The XRD result showed th

23、at each peak JCPDF could be compatible with the card No.361451. The patterns show that the nanosized ZnO particles all belonged to the hex-agonal system. Only there is a little difference in the peak position and the peak intensity. Tables 1 and 2 show their average crystal size, the average crystal

24、linity and the cell parameters as well. The cell parameters increase to dif-ferent extents as a result of cell expansion, when the crystalline size decreases to nanoscale (the cell parame-ters of ZnO crystalline: a=0.03249nm, c=0.05206nm. The average crystalline sizes increased with increasing Zn2+

25、starting concentration. Also, the corresponding dif-fraction angle moved rightwards owing to the lattice dis-tortion (see Fig.2. In addition, the half peak width of ZnO (110 crystal face decreases with increasing of Zn2+ starting concentration, indicating that the lattice became integrity at the con

26、centration of Zn2+ of 0.50mol/L. Fig.1 XRD patterns of nanosize ZnO prepared at different starting concentrations of Zn2+ and calcined at 600for 1hThe reactant concentration can affect productive rate, the crystalline size, and the response speed as well as reaction homogeneity of product. A lower c

27、oncentration can result in a low productive rate. A higher concentra-tion can improve the productivity, but it is easy to cause the partial response no uniformity, which lead to the in-硅酸鹽學(xué)報(bào)· 1784 ·2009年crease of crystalline size and the broader size distribution (seeTable 1. Tables 1 and

28、2 showed that the higher con-centration should be used to obtain of the particle in a proper crystalline size with and the narrower size distri-bution. Therefore, 0.35mol/L of Zn2+ starting concentra-tion was used.Table 1 Average crystalline grain size of nanosized ZnO prepared at different starting

29、 concentrations of Zn2+ ionsGrain size calculated according the intensity of diffraction peakof each crystal face/nmSample No. Concentration of Zn2+/(molL1(100 (002 (101 (102 (110 (103Average crystalline grain size/nm 11 0.10 28.7 29.3 27.2 22.3 25.7 23.4 26.10 12 0.20 33.4 34.1 31.1 27.1 28.7 26.1

30、30.08 13 0.35 33.2 34.1 30.9 28.6 31.8 29.5 31.35 14 0.50 39.0 37.9 35.9 29.0 34.8 30.4 34.50Table 2 Average crystallinity and cell parameters ofnanosized ZnO prepared at different startingconcentrations of Zn2+ ionsCell parameterSample No. Average crystallinity/%a/nm c/nm 11 85.86 0.32574 0.5216912

31、 86.31 0.32533 0.5211013 86.07 0.32544 0.5211014 86.02 0.32525 0.52131 Fig.2 XRD patterns of nanosized ZnO (110 crystal face pre- pared at different starting concentrations of Zn2+2.2 Reaction initiator contentThe (NH42S2O8 is a kind of thermal decomposition ini-tiator. Its aqueous solution could de

32、compose to produce some primary free radical SO4 with high activity. Whats more, SO4 could separately open the olefinic bond of AM and MBAM to form the monomer free radical through addition reaction. The monomer free radical re-acted immediately with other monomer molecular form-ing more chain free

33、radical to promote the chain growth. When the chain free radical reached to a certain density, the activity of free radical would vanish.This is because the adjacent chain free radical could form easily a stable polymer. Therefore, the initiator con-tent could play an important role in the gelatin s

34、tability, which affects the final size of the ZnO crystalline.Figure 3 shows the XRD patterns of nanosized ZnO particles prepared at different initiator contents. The av-erage crystalline size, the average crystallinity and cell parameters were estimated from diffraction data (see Ta-bles 3 and 4. T

35、he average crystalline size increases with the increasing of initiator content. The integrity lattice appears a slight difference among the diffraction peaks shown in Fig.4. Fig.3 XRD patterns of nanosized ZnO prepared at different contents of (NH42S2O8 and calcined at 600 for 1h The reaction rate w

36、ould be lower if initiator content was extremely low. The active molecular chain has shortened and the rapid polyreation of free radical forced the monomer molecular to polymerize on the finite quan-tity active chain. It also forced to form macromolecule polymer with low degree of cross linking, whi

37、ch was also disadvantageous to the even distribution of nanometer ZnO. Therefore, the reaction initiator content also has an impact on the crystalline grain size and the size distribu-tion of nanosized ZnO.吳建鋒 等:高分子網(wǎng)絡(luò)凝膠法制備納米氧化鋅的工藝控制· 1785 ·第36卷第10期Table 3 Average crystalline grain size of

38、nanosized ZnO prepared at different contents of reaction initiarGrain size calculated according the intensity of diffraction peak of each crystal face/nmSample No.Concentration of Zn 2+/(mol L 1Molar ratio of reaction initiator to monomer double-bond(100 (002 (101 (102 (110 (103Average crystalline g

39、rain size /nm21 0.35 1:20 27.9 27.3 24.0 20.4 21.7 20.2 23.58 22 0.35 1:10 30.2 32.2 26.2 21.3 25.8 22.9 26.43 23 0.351:532.7 36.0 30.0 21.3 32.9 26.529.90Table 4 Average crystallinity and cell parameters ofnanosized ZnO prepared at different contents of reaction initiarCell parameter Sample No.Aver

40、age crystallinity/%a /nmc /nm 21 86.35 0.325 57 0.521 13 22 85.15 0.325 25 0.520 84 23 86.36 0.325 47 0.521 24 Fig.4 XRD patterns of nanosized ZnO (101 crystal face prepared at different contents of reaction initiator 2.3 pH value of solutionFigures 5 and 6 show the XRD patterns of nanosized ZnO par

41、ticles prepared at different pH values of solution. The diffraction peak of the patterns wear off and the peak width gradually broadens with the increasing of pH values. The corresponding average crystalline size reduces, the crystallization also tended to the integrity. (see Tables 5 and 6.It is th

42、rough the cross linking reaction of linear poly-mer that the macromolecule network configuration of polymer gelatin was built up. In the condition of acidity or alkalinity, there is a great deal of ionogenics. The io-nogenics would be ionized with pH value of the solution, leading to the dissociatio

43、n of hydrogen bond in molecular chain. The pH value could affect the network configura-tion of gelatin.A lower pH value could give the branched chain of acrylamide generating imide. The insoluble solidification was produced from the cross linking reaction, which would affect the stability of gelatin

44、. A higher pH valueFig.5 XRD patterns of nanosized ZnO prepared at differentsolution pH values and calcined at 600 for 1hFig.6 XRD patterns of nanosized ZnO (110 crystal faceprepared at different solution pH valuescould accelerate the hydrolyzation of monomer acryla-mide to produce NH 3. The acrylam

45、ide generated the N-tripropylacrylamide (NTP by chain transfer, and the reaction sped up with increasing pH value. Based on these reasons, the content of polyacrylamide gel de-creased. Moreover, with increasing the NTP, macro-molecule free radical turned to be new active free radical through chain t

46、ransfer, that will lead the mean network configuration to go against.硅 酸 鹽 學(xué) 報(bào)· 1786 ·2009年Table 5 Average crystalline grain size of nanosized ZnO prepared at different solution pH valuesGrain size calculated according the intensity of diffraction peak ofeach crystal face/nmSample No.Conce

47、ntration of Zn 2+/(mol L 1pH value of solution(100 (002 (101 (102 (110 (103Average crystalline grain size/nm31 0.35 1 39.0 37.9 35.9 29.0 34.8 30.4 34.50 32 0.35 3 30.7 33.0 30.5 29.3 34.6 32.6 31.78 33 0.35 5 27.2 28.7 25.0 20.6 24.1 21.4 24.50 340.35628.3 25.8 25.4 21.2 23.8 22.024.42Table 6 Avera

48、ge crystallinity and cell parameter ofnanosized ZnO prepared at different solution pH valuesSample No.Average crystallinity/% Cell parameter a /nmCell parameter c /nm31 86.02 0.325 25 0.521 31 32 86.07 0.325 42 0.521 50 33 86.77 0.325 41 0.520 84 34 87.73 0.325 31 0.521 12Also, the pH value of solut

49、ion has an effect on the hy-drolysis rate of ammonium persulfate. The hydrolysisrate and S 2O 82ions concentration satisfied the first-level,and H + has made an impact of catalysis in the reaction. The hydrolysis rate of ammonium persulfate increased with increasing H +, leading to the rapid polyrea

50、ction and the incomplete cross linking reaction of gelatin. The range of pH value applied was thus 56 in the experiments. 2.4 Reaction temperature Figures 7 and 8 show the XRD patterns of nanosized ZnO particles prepared at different reaction temperatures. The nanosized particles with a good crystal

51、linity could be obtained at different temperatures. Although the peak intensity for the particles at 70 and at 90 was greater than that at 80 , the shape of diffraction peak at 80 was more obvious than other temperature. Tables 7 and 8 show the average crystalline grain size, the aver-age crystallin

52、ity and cell parameters of the nanosized particles obtained at various temperatures.When the reaction temperature is lower, polyreaction slows down even cant carry on owing to the lower reac-tivity of cross linker. Then, the cross linking degree reduced which leads to the ineffective influence of ne

53、twork con-figuration. Furthermore, a lower reaction temperature could not give the natural polyreaction of reaction initiator. A higher temperature could enhance the activity of monomer, increase the polyreaction rate, and shorten the polyreaction time. However, the polyreaction occurred due to the

54、release of polymeric heat, resulting in the inef-fective cross linking and the increased difficulty of the network configuration to obtain the nanosized ZnO particles with the narrower size distribution. In addition, the po-lymerization process is an exothermic process of freeradical combination. Th

55、e increase of polymerizationFig.7 XRD patterns of nanosized ZnO prepared at differentreaction temperatures for 2 h and calcined at 600 for 1 hFig.8 XRD patterns of nanosized ZnO (103 crystal faceprepared at different reaction temperaturestemperature could enhance the decomposition of the reac-tion r

56、ate of the initiator and the reactive activity energy, which increases the reaction rate of chain initiation. Also, the well gelatin system could not be obtained at a higher concentration of free radical increased and a lower polymerization degree.第 36 卷第 10 期 Table 7 Sample No. 41 42 43 吳建鋒 等：高分子網(wǎng)絡(luò)

57、凝膠法制備納米氧化鋅的工藝控制 · 1787 · Average crystalline grain size of nanosized ZnO prepared at different reaction temperatures Grain size calculated according the intensity of diffraction peak of Reaction temperature/ 70 80 90 each crystal face/nm (100 43.7 41.9 43.7 (002 44.3 42.1 45.7 (101 41.0 38

58、.1 41.8 (102 39.8 34.7 35.4 (110 42.8 40.6 42.5 (103 39.4 35.9 39.3 41.83 38.88 41.40 Average crystalline grain size/nm Concentration of Zn /(molL 0.35 0.35 0.35 2+ 1 Table 8 Average crystallinity and cell parameter of nanosized ZnO prepared at different reaction temperatures Average crystallinity/% 87.61 85.94 85.77 Cell parameter a/nm 0.324 57 0.325 36 0.324 97 Cell parameter c/nm 0.520 42 0.5.21 36 0.521 09 Sample No. 41 42 43 2.5 Reaction time Figure 9 shows the XRD patterns of nanosized ZnO particles prepared at different reaction time. Clearly, the peak intensity someh