聚丙烯酰胺凝胶法在合成三元金属氧化物材料中的应用

发布时间：2018-06-05 02:14

本文选题：聚丙烯酰胺凝胶法 + 铁酸盐磁性材料　；参考：《电子科技大学》2015年博士论文

【摘要】：纳米材料在信息存储、记录介质、药物传送、磁致冷器件、污水处理、催化等领域具有广泛的应用,因而备受广大科研人员的青睐。高分散、形貌可控的纳米材料以期提高其物理化学性质,尤其是磁性纳米颗粒所表现出的比块体材料更加新颖的特性,吸引了众多科研人员的研究兴趣。本论文通过聚丙烯酰胺凝胶法制备了(Mg,Al,Mn,Ca,Sr,Ba)-铁酸盐磁性材料和铝酸锌发光材料,并研究了它们的相纯度、热学、光学和磁学性质。具体的研究内容涉及以下几个方面:(1)以酒石酸为络合剂制备了(Bi,Ca,La,Sr,Y,Al,Mn)Fe O_3粉体。X射线衍射(XRD)结果表明,以Bi、Ca、La、Sr和Y的金属硝酸盐作为原材料制备M(M=Bi,Ca,La,Sr,Y)Fe O_3时,不能获得纯相的目标产物;然而以Al和Mn的金属硝酸盐作为原材料制备M(M=Al,Mn)Fe O_3时,获得了纯相的目标产物。有意义的是,M(M=Al,Mn)Fe O_3的晶体结构与α-Fe2O_3或Mn2O_3的晶体结构类似。通过结合差式扫描量热(DSC)分析和XRD等数据分析,研究了M(M=Al,Mn)Fe O_3的相变行为。扫描电镜(SEM)观察显示,其形貌强烈地依赖于烧结温度。但是,其形貌的变化,不仅取决于络合剂的选择,而且取决于络合剂所络合的金属离子的种类以及与金属离子的配位能力。基于实验结果,对其生长机制、络合机理或发光机理进行了分析。为了获得纯相的MFe O_3铁酸盐磁性材料,选择合适的络合剂是关键。(2)以乙二胺四乙酸(EDTA)为络合剂制备了三种不同的(Mg,Ca,Ba)铁酸盐磁性纳米颗粒。有意义的是,铁酸盐磁纳米颗粒的形貌、尺寸以及磁学性质不但与烧结温度有关,且与加入前驱体溶液中的多糖和碳等有机物有关。研究发现,由于金属离子的配位能力不同,EDTA在络合金属离子方面具有选择性,导致最终获得的产物具有不同的形貌和分散性。通过加入不同的多糖,能有效地防止凝胶在干燥过程中塌缩。在前驱体溶液中加入少量的碳颗粒,抑制了(Mg,Ca,Ba)铁酸盐相的形成,改善了样品的表面形貌,提高了它的磁矩比(SQR)值。此外,采用伽玛射线辐照辅助聚丙烯酰胺凝胶法制备的Mg Fe_2O_4纳米颗粒的磁矩比强烈依赖于辐照剂量,随着辐照剂量的增加,其磁矩比增大。(3)以柠檬酸作为络合剂制备了Sr Fe_(12)O_(19)纳米颗粒,研究了不同烧结温度对其相变、形貌以及磁学性质的影响。通过在前驱体溶液中添加碳颗粒研究了碳以及烧结温度对Sr Fe_(12)O_(19)纳米颗粒的相变行为、形貌以及磁学性质的影响。研究表明,碳颗粒和烧结温度能加速六方Sr Fe_(12)O_(19)相的形成,同时能获得高分散的Sr Fe_(12)O_(19)纳米颗粒并提高了它的SQR值。由于Sr:Fe=1:12,Sr离子的比例相对较少,形成Sr CO_3的中间过程的可能性很小,碳在烧结过程中起了一个助燃剂的作用。通过研究不同温度烧结的样品,得到了矫顽力、剩磁、饱和磁化强度以及SQR值随烧结温度变化的规律。(4)以Al2(SO4)3?18H2O、Al Cl3?6H2O或Al(NO_3)3?9H2O作为铝源,制备了三种不同的Zn Al2O4样品,研究了不同铝源对Zn Al2O4纳米颗粒的相纯度、形貌、光学性质以及发光性质的影响。研究表明:随着颗粒尺寸的增加,其带隙值减小。荧光光谱分析发现,在325 nm波长的激光激发下,Zn Al2O4纳米颗粒在400 nm出现了一个主要的发射带和在410和445 nm出现了两个弱的荧光发射峰,其色度坐标为(0.1729,0.0048)。发光实验表明,以Al(NO_3)3?9H2O制备的Zn Al2O4纳米颗粒的荧光发射强度最强,逐次是以Al2(SO4)3?18H2O和Al Cl3?6H2O制备的Zn Al2O4纳米颗粒。其结果的不同,是由于带隙和缺陷类型的不同共同作用引起的。感兴趣的是,类似的方法可以用来合成金属氧化物纳米颗粒,包括发光材料、高温超导、光催化剂、磁性材料以及热电材料等,通过采用不同的金属源,最终获得最优的工艺参数,提高目标产物的物理化学性质。尽管采用聚丙烯酰胺凝胶法制备了MFe O_3、MFe_2O_4、MFe_(12)O_(19)和MAl2O4等材料,但它们的力学、热学、光学、电学、磁学性质以及合成机理还需进一步研究。另外,可将这一方法推广到其它纳米材料的制备和改善它们的物理化学性质上,尤其是多元金属氧化物纳米颗粒的制备,并将其应用在工业领域。
[Abstract]:Nanomaterials have been widely used in the fields of information storage, recording medium, drug delivery, magnetic induced cooling devices, sewage treatment and catalysis, which have attracted much attention of researchers. The nano materials with high dispersion and controllable morphology are expected to improve their physical and chemical properties, especially the magnetic nanoparticles show more new than bulk materials. The characteristics of glumes attracted the interest of many researchers. In this paper, (Mg, Al, Mn, Ca, Sr, Ba) - ferromagnetic materials and zinc aluminate luminescent materials were prepared by polyacrylamide gel method, and their phase purity, thermal, optical and magnetic properties were studied. The contents of the study involved the following aspects: (1) tartaric acid was the collaterals The result of.X ray diffraction (XRD) of Fe O_3 powder (Bi, Ca, La, Sr, Y, Al, Mn) shows that the target product of pure phase can not be obtained. It is significant that the crystal structure of M (M=Al, Mn) Fe O_3 is similar to the crystal structure of alpha -Fe2O_3 or Mn2O_3. By combining differential scanning calorimetry (DSC) analysis and XRD data analysis, the phase transition behavior of M (M=Al, Mn) is studied. The scanning electron microscopy (SEM) observation shows that the morphology is strongly dependent on the sintering temperature. However, the change of its morphology, It depends not only on the selection of complexing agents, but also on the types of metal ions complexed by complexing agents and their coordination with metal ions. Based on the experimental results, the mechanism of its growth, the mechanism of complexation and the mechanism of luminescence are analyzed. In order to obtain the pure phase MFe O_3 ferromagnetic material, the selection of the appropriate complexing agent is the key. (2) Three different (Mg, Ca, Ba) ferromagnetic nanoparticles were prepared by ethylenediamine tetra acetic acid (EDTA) as complexing agent. It is significant that the morphology, size and magnetic properties of the ferrite nanoparticles are related not only to the sintering temperature, but also to the organic compounds, such as polysaccharides and carbon, in the solution of the precursor. With the different coordination ability, EDTA is selective in complexing metal ions, resulting in different morphology and dispersion of the final products. By adding different polysaccharides, the gel can be effectively prevented from collapsing during the drying process. The formation of (Mg, Ca, Ba) ferrite phase is inhibited by adding a small amount of carbon particles in the precursor solution. In addition, the magnetic moment ratio of Mg Fe_2O_4 nanoparticles prepared by gamma ray irradiation assisted polyacrylamide gel method is strongly dependent on the dose of irradiation, and the ratio of magnetic moment increases with the increase of irradiation dose. (3) Sr Fe_ (12) O_ (19) nanometers are prepared with citric acid as complexing agent. The effects of different sintering temperatures on the phase transition, morphology and magnetic properties of Sr Fe_ (12) O_ (19) nanoparticles were investigated by adding carbon particles in the precursor solution. The effects of carbon particles and sintering temperature on the phase transition behavior, morphology and magnetic properties of the nanoparticles were investigated. The results showed that the carbon particles and sintering temperatures could accelerate the six square Sr Fe_ (12) O_ (12) O_ ( 19) the formation of Sr Fe_ (12) O_ (19) nanoparticles and its SQR value are obtained at the same time. Due to the relatively small proportion of Sr:Fe=1:12 and Sr ions, the possibility of forming the intermediate process of Sr CO_3 is very small. Carbon plays a role of a combustion promoter in the sintering process. Force, remanence, saturation magnetization and SQR value change with the sintering temperature. (4) three different Zn Al2O4 samples were prepared with Al2 (SO4) 3? 18H2O, Al Cl3? 6H2O or Al (NO_3) 3? 9H2O as aluminum sources. The effects of different aluminum sources on the phase purity, morphology, optical properties and luminescence properties of the nanoparticles were investigated. With the increase of particle size, the band gap value decreases. The fluorescence spectrum analysis shows that under 325 nm wavelength laser excitation, Zn Al2O4 nanoparticles appear a major emission band at 400 nm and two weak fluorescence emission peaks appear at 410 and 445 nm, and their chromaticity coordinates are (0.1729,0.0048). The luminescence experiment shows that Zn with Al (NO_3) 3? 9H2O The fluorescence intensity of Al2O4 nanoparticles is the strongest, and the Zn Al2O4 nanoparticles are prepared by Al2 (SO4) 3? 18H2O and Al Cl3? 6H2O. The difference is due to the different joint effects of band gap and defect type. It is interesting that similar methods can be used to synthesize metal oxide nanoparticles, including luminescent materials, high temperature. Superconductors, photocatalysts, magnetic materials and thermoelectric materials and so on. By using different metal sources, the optimum technological parameters are obtained and the physical and chemical properties of the target products are improved. Although MFe O_3, MFe_2O_4, MFe_ (12) O_ (19) and MAl2O4 are prepared by the polyacrylamide gel method, their mechanical, thermal, optical, electrical, magnetic and magnetic properties are obtained. In addition, this method can be extended to the preparation and improvement of the physical and chemical properties of other nanomaterials, especially the preparation of polymetallic oxide nanoparticles, and applied in the industrial field.
【学位授予单位】：电子科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB383.1

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