络合剂和交联剂对凝胶法制备TbMnO_3纳米颗粒的影响

Influence of Chelating Agents and Crosslinking on TbMnO_3 Nanoparticles Prepared by a Gel Route

采用改进的聚丙烯酰胺凝胶法制备了TbMnO3纳米颗粒.以Tb和Mn的无机盐水溶液为原料,通过加入丙烯酰胺使溶液成胶,在溶液成胶过程中,丙烯酰胺聚合形成高分子网络骨架,为粒子提供生长的空间.利用热重(TG)分析、差示扫描量热(DSC)分析、傅里叶变换红外光谱仪(FTIR)及X射线衍射(XRD)等多种手段研究了干凝胶的热分解及TbMnO3的形成.实验表明,分别以柠檬酸和EDTA作为络合剂,在800℃煅烧温度下均可制备出高纯TbMnO3纳米颗粒,但产物的颗粒尺寸和形貌与络合剂的选取有关.扫描电子显微镜(SEM)观察显示,以柠檬酸为络合剂制得的样品,颗粒形貌规整,呈球形,颗粒尺寸分布较窄,平均粒径约为67 nm;以EDTA为络合剂制得的样品,颗粒形态主要以长球形和近球形为主,兼有少量的杆状,平均颗粒尺寸约为115 nm.此外,实验还发现,在前驱体溶液中加入适量的双丙烯酰胺,可以使产物颗粒的尺寸适度减小,形貌变得更为规整.磁滞回线测量结果表明,TbMnO3纳米颗粒在室温下表现为顺磁性.

A modified polyacrylamide gel route was used to fabricate TbMnO3 nanopartieles. In this route, the aqueous solution of inorganic Tb and Mn salts was gelled by using aerylamide and during the gelation process, acrylamide was polymerized to form a polymer network, which provided a structural fi＇amework for the growth of particles. Thermogravimetrie （TG） analysis, differential scanning calorimetry （DSC） analysis, Fourier transform infrared speetrometer（FTIR） and X-ray diffraction （XRD） were combinatively used to investigate the thermal decomposition process of xerogel and the formation of TbMnO3 phase. It is demonstrated that high-phase-purity TbMnO3 nanopartieles ean be prepared separately by using citric acid and ethylenediamine-tetraaeetie acid （EDTA） at a sintering temperature of 800 ℃. However, the particle size and morphology of the products are found to be dependent on the choice of ehelating agent. Scanning electron microscope （SEM） observation reveals that the particles prepared by using citric acid as the chelating agent are regularly spherieal in shape and highly uniform in size with adiameter of about 67 nm, while the sample prepared by using EDTA mainly consists of sphere-, ellip- soid-, and rod-like particles with an average particle size of about 115 nm. In addition, it is found that adding an appropriate amount of bisacrylamide to the precursor solution can lead to a moderate reduction in particle size and a more regular particle morphology. Magnetic hysteresis loop measurements indicate that the TbMnO3 nanoparticles exhibit paramagnetism at room temperature