磁場誘導水熱合成法

1、1 - 1報告：李牣報告：李牣組員：李軍雷、岳國強、顧曉紅、陳梅組員：李軍雷、岳國強、顧曉紅、陳梅2007年年12月月27日日1 - 2主要內容主要內容 水熱法簡介水熱法簡介 磁場誘導磁性金屬納米粒子線磁場誘導磁性金屬納米粒子線型組裝型組裝 磁場誘導鐵氧體納米材料的取磁場誘導鐵氧體納米材料的取向生長向生長1 - 3 使用特殊設計的裝置，人為地創(chuàng)造一個高溫高壓環(huán)境，由于高溫高壓下水的解離常數(shù)增大、黏度大大降低、水分子和離子的活動性增加，可使那些在通常條件下不溶或難溶于水的物質溶解度、水解程度極大提高，從而快速反應合成新的產物。1 - 4 首先營養(yǎng)料在水熱介質里溶解,以離子、分子團的形式進入溶液。

2、利用強烈對流(釜內上下部分的溫度差而在釜內溶液產生) 將這些離子、分子或離子團被輸運到放有籽晶的生長區(qū)(即低溫區(qū)) 形成過飽和溶液,繼而結晶。水熱法生產的特點是粒子純度高、分散性好、晶形好且可控制,生產成本低。用水熱法制備的粉體一般無需燒結,這就可以避免在燒結過程中晶粒會長大而且雜質容易混入等缺點。影響水熱合成的因素有:溫度的高低、升溫速度、攪拌速度以及反應時間等。 1 - 5密封結構釜體壓力、溫度無機分子（反應物）溶劑合成添加劑晶核、產物1 - 6磁場誘導鈷納米晶的組裝H N Niu, et al J. Mater. Chem., 2003, 13, 15磁場誘導磁性金屬納米粒子線型組裝磁場

3、誘導磁性金屬納米粒子線型組裝1 - 7Co(CH3CO2)24H2OC2H5OHMixed at room temperatureMixed solutionAH2NCH2CH2NH2 was added dropwiseMixed solutionBA brown solution of Co(en)32+80 wt% H4N2H2O Teflon-lined stainless steelautoclavesvigorous stirring for 10 minutes1 - 8ACenCoenACCo23)(232OHenNCoOHHNenCo22422346242THE CHEMIC

4、AL REACTION FOR THE SYNTHESIS OF COBALT NANOCRYSTALLITES 低溫還原過程獲得純的Co 納米晶體粒徑大約10-30nm, 這些鈷納米晶體積聚形成直徑大約13m的球形粒子以降低表面能。1 - 9405060708090100I BA0042011121031101021010021002/ oXRD PATTERNS OF COBALT NANOCRYSTALLITES PREPARED AT 110 FOR 36 HOURS WITH A 0.25T MAGNETIC FIELD (A), AND WITHOUT MAGNETIC FIELD

5、 (B). 1 - 10 a) SEM micrographs of Co wires obtained at 110 for 36 hours under a 0.25T external magnetic field, b) higher magnification of a), and c) HRTEM image of a particle in the wire, showing that the particle is single crystalline. The magnified SEM image shows nearly parallel wires, HRTEM sug

6、gests that the wire is composed of Co nanocrystallites. 1 - 11 SEM micrographs of products prepared at 110 for 24 hours a, b) without and c) with a 0.25T external magnetic field. b) is the magnified image of a).在無外磁場的情況下，球形粒子在任意方向上通過偶極作用堆積在一起，故沒有明顯的取向排列。1 - 12 SEM images of cobalt formed under a 0.2

7、5T magnetic field for a) 12h, b) 24h, respectively. c) An enlargement of the boxed region in b) is shown in c), showing spherical particles self-assembly to form a linear chain. d) Magnified image of c), showing the connection of spherical particles in a wire. 1 - 13 納米級鈷單晶顆粒團聚成粒徑約13微米的球形多晶顆粒。 微 米 多

8、晶 球 沿 著磁 場 方 向有 序 堆 積形 成 球 形的鏈。球形的鏈向光滑的線過渡。 在外加磁場誘導下，球形顆粒有序堆積最終形成幾乎平行的的線陣列。微米多晶球在無外磁場的作用下無序堆積。無外加磁場作用的條件下，小球雜亂堆積，無特定形貌 通過偶極的誘導形成的鼓狀的鏈結構在0.25T外磁場誘導下，球形粒子沿著外磁場方向通過相互偶極定向自組裝，形成線狀陣列結構。1 - 14-10-50510-800-600-400-2000200400600800 BAM emu/cm3H KOeThe hysteresis loops measured at room temperature for produ

9、ces obtained with (A) and without (B) external magnetic field。 磁化強度和矯頑力都要明顯高于沒加外磁場所獲得的產物。這可能與鈷納米粒子在外磁場誘導下呈線形排列，形成永久的磁極有關。1 - 15磁場誘導針形鎳納米晶的一維組裝H.L. Niu, et al J. Phys. Chem. B ( in press)1 - 16Ni(CH3CO2)2PEGCTABdistilled watermixed in a flask at room temperatureMixed solution AA grass-green color sol

10、utionStrongly stirring for half an hourA half-hour ultrasound treatmentNi2+ ions dispersed homogeneously5 mL of 80 wt % hydrazinehydrate solution was added dropwiseMixed solution BStronglystirring for several minutesNiN2H461 - 17Ni(AC-)2+2en Ni(en)22+2AC- (1)2Ni(en)22+N2H4+4OH- 2Ni+N2+4en+4H2O (2) A

11、C = CH3COO , en = NH2CH2CH2NH2THE CHEMICAL REACTION FOR THE SYNTHESIS OF NICKEL NANOCRYSTALLITES 1 - 18405060708090 Intensity (a. u.)Two theta (degree)(111)(200)(220)XRD pattern of nickel nanocrystallites prepared with a 0.25T magnetic field applied .1 - 19SEM micrographs of products prepared at 70

12、for 3 hours without a) and with a 0.25T magnetic field applied b).通過低溫水熱方法形成針形鎳納米晶，針形鎳納米晶自組裝形成直徑約200納米的多晶鎳納米線。1 - 20Representative TEM images of two samples obtained a) without and b) with a 0.25T external magnetic field applied. a1) Inset in a) shows an image of a sample post-synthesis magnetic ali

13、gnment of ZF sample under a 0.25T magnetic field. c) A magnified image of a wire within b), of which c1 and c2 are two SAED patterns taken on the surface of a wire and an acicular nanocrystallite, respectively, and c3 is its HRTEM image.外磁場誘導下形成的線為直線，無外磁場誘導下形成曲線。1 - 21Sketch of ideal process of asse

14、mbly of acicular Ni particles induced by an external magnetic field.外磁場使針形鎳納米晶沿著易磁化軸111方向一維自組裝。易磁化軸111方向與多晶線的長軸方向是一致的。1 - 22-4-2024-60-40-200204060cba M emu/gH kOeThe hysteresis loops measured at room temperature for three samples obtained a) with a 0.25T and b) without an external magnetic field ap

15、plied, c) the hysteresis loop (line of dashes) of the nanorods post-synthesis magnetic alignment under a 0.25T magnetic field. 在外磁場誘導下形成的鎳多晶線的飽和磁化強度比無外磁場誘導下形成的鎳多晶線的飽和磁化強度大 。1 - 23 Jun Wang etal.Advanced Materials 2004, 16, No.21 - 24FeCl2H2ONaOHH4N2H2ODistilled water,degassed with N2 for 0.5hAn aque

16、ous solution of Fe2+ ionsN2H4H2O dissolved with sodium hydroxied dropped slowlyMixed solutionPut it into a Teflon-lined stainless autoclaveKeeped at 130 for 6h,then Cooled to room tempreture naturallyThe product1 - 25Fe2+N2H4 Fe3+NH3Fe2+Fe3+OH- Fe3O41 - 261 - 270.25T: Diameter： 35100 nm, length ：0.4

17、82.7m 0.35T: diameter: 20 nm, length: 0.8m 1 - 281 - 29 電子衍射圖和高分辨電鏡照片可以看出該Fe3O4 納米線是單晶。Fe3O4 納米線晶格條紋間距約為0.48 nm，與（111）晶面間距相吻合。確定該納米線是沿110方向生長。1 - 30 N2H4.H2O能將能將Fe2+緩慢氧化為緩慢氧化為Fe3+, Fe3+與與Fe2+在堿性的條件下，以在堿性的條件下，以2：1的比例沉淀形成的比例沉淀形成Fe3O4；同時，在磁性誘導作用下沿著同時，在磁性誘導作用下沿著110方向定向生長方向定向生長成成Fe3O4納米線。納米線。 由于磁鐵的磁場強度有限，同時，由于磁鐵的磁場強度有限，同時，F(xiàn)e3+與與Fe2+生生成成Fe3O4較快，造成較快，造成Fe3O4納米線與顆粒同時存在。納米線與顆粒同時存在。 增加磁場強度達增加磁場強度達0.35T，有更多的納米線生成。有更多的納米線生成。說明磁場誘導對磁性物質的形貌產生很大的影響。1 - 311 - 32 有磁樣品的飽和磁化強度比無磁樣品要有磁樣品的飽和磁化強