【作者】 张丽娜；

【导师】 苏碧桃；

【作者基本信息】 西北师范大学 ， 物理化学， 2018， 硕士

【摘要】 尖晶石四氧化三铁（Fe₃O₄）是软铁磁性物质,用不同的金属离子取代Fe₃O₄晶格中的Fe²⁺,可有效地改变它的结构和物理化学性能,以适应不同的应用。本文以Fe（NO₃）₃和Zn（NO₃）₂为原料,分别使用板栗壳CS、土豆渣PR及土豆淀粉PS为碳源,利用一步水热法绿色制备了Zn²⁺取代的Fe₃O₄/C(Zn_xFe_1-xFe₂O₄/C)纳米复合材料,主要研究内容和表征结论如下:1.先以板栗壳为碳源,使用Fe（NO₃）₃为单一铁源,一步水热法制备了Fe₃O₄@C,考察不同因素（反应温度,水热时间及CS用量）对产物性能的影响,探索出制备Fe₃O₄@C纳米复合材料的最佳条件,通过XRD、FT-IR、XPS、SEM、TEM、BET和VSM对材料进行表征。XRD、FT-IR、XPS分析结果显示,本实验在不添加其它任何试剂（如沉淀剂、碱性试剂、还原剂等）的条件下,通过调控板栗壳CS的用量,即可保证适量Fe3+→Fe²⁺的转化,从而保证了Fe3+→Fe₃O₄转化,获得具有良好磁性能的Fe₃O₄@C磁性纳米复合材料。在水热反应过程中,板栗壳CS不仅可以作为碳源,而且还发挥了还原剂和碱性试剂的作用。SEM和TEM结果表明,Fe₃O₄@C纳米复合材料复制了板栗壳的形貌,说明板栗壳在合成过程中充当了模板的作用。BET和VSM结果分析显示,随着板栗壳的加入样品有一定的孔道结构和磁性能,在最佳的水热条件下得到的样品比表面积为51.1 m2?g-1,饱和磁化强度（Ms）值为65.73 emu?g-1。在此基础上以不同的化学计量比,用Zn²⁺取代Fe²⁺制备出一系列的Zn_xFe_1-xFe₂O₄/C（x:0.0?1.0）纳米复合材料。研究了Zn²⁺取代对Fe₃O₄结构及Zn_xFe_1-xFe₂O₄/C样品磁性能及吸附性能的影响。表征结果表明,Zn²⁺的引入使得Fe₃O₄的饱和磁化强度明显下降（65.73→7.30 emu·g-1）,而样品的吸附性能却增强（平衡吸附量qe:8.05→22.40 mg·g-1）,且吸附行为符合二级动力学模型。2.在第一部分的基础上,分别以土豆渣PR和土豆淀粉PS为碳源,分别探索出制备Fe₃O₄/C的最佳条件。探讨了水热温度,水热反应时间以及PR和PS的用量对磁性Fe₃O₄形成的影响。研究结果表明,Fe3+离子在PR或PS表面吸附和富集,并通过PR或PS将Fe3+部分还原为Fe²⁺,有利于Fe3+→Fe₃O₄的转化,同时自身转化为C材料,说明Fe₃O₄和C材料是一步获得的。在水热过程中PR和PS不仅发挥了碳源和还原剂的作用,而且还发挥了碱性试剂作用。在最佳制备Fe₃O₄/C的基础上,用一定量的Zn²⁺对Fe₃O₄中的Fe²⁺进行取代,研究取代后样品的结构以及磁性和吸附性能的变化。对制备的材料经过XRD、FT-IR、XPS、FESEM、EDS、BET以及VSM表征分析。从XRD和XPS表征结果可知:Zn²⁺确实取代了Fe₃O₄中的Fe²⁺,且随着Zn²⁺含量的增加,样品的比表面积增大而饱和磁化强度降低。以PR为碳源的Zn_xFe_1-xFe₂O₄/C样品的比表面积从46增加到83.2 m2?g-1,饱和磁化强度Ms从79.09降低到18.06emu?g-1;以PR为碳源的Zn_xFe_1-xFe₂O₄/C样品的的比表面积从43增加到91m2?g-1,饱和磁化强度Ms从74.79降低到9.998 emu?g-1。此外,还对所得样品进行了吸附实验,结果表明,随着Zn²⁺掺杂量从0→1.0,样品的吸附性能明显增强。更多还原

【Abstract】 Spinel ferroferric oxide（Fe₃O₄）is a soft ferromagnetic material.Replacement of Fe2+ in the Fe₃O₄ lattice with different metal ions can effectively change its structure,physical and chemical properties to suit different applications.In this paper,a series of Zn²⁺-substituted Fe₃O₄/C(Zn_xFe_1-xFe₂O₄/C)nanocomposites were prepared via a novel one-step hydrothermal method by using Fe（NO₃）₃ and Zn（NO₃）₂ as the source of iron and zinc respectively and chestnut shell（CS）,potato residue（PR）and potato starch（PS）as carbon source.The main research and characterization conclusions are as follows:（1）First,the CS and Fe（NO₃）₃ were respectively used as carbon source and single iron source to prepare Fe₃O₄@C nanocomposites via one step hydrothermal method.The effects of hydrothermal temperature,hydrothermal reaction time and the amount of CS on the formation of target Fe₃O₄ were investigated,and the magnetic and adsorption performance of the Fe₃O₄@C nanocomposites were studied,respectively.The typical results were drawn through XRD,FT-IR,XPS,TEM,SEM,BET and VSM analysis.In this experiment,the transformation amount of Fe³⁺ into Fe2+(Fe³⁺→ Fe2+)could be ensured by regulating the amount of CS without any other reagents（such as precipitation agent and reducing agent）,which guaranteed the convert of Fe³⁺ into Fe₃O₄(Fe³⁺ → Fe₃O₄).In the hydrothermal process,the CS not only served as carbon source,but also functioned as reducing agent,alkaline reagent,and template.The results of BET and VSM analysis showed that the obtained samples had a certain pore structure and magnetic performance with the added of CS,the specific surface area was reached to 51.1 m2·g-1,and the saturation magnetization（Ms）value was 65.73 emu·g-1 under optimal hydrothermal conditions.On this basis,a series of Zn_xFe_1-xFe₂O₄/C（x: 0.0?1.0）nanocomposites were prepared by substituting Zn²⁺for Fe2+at different stoichiometric ratios.The effect of Zn²⁺ substitution on the structure of Fe₃O₄ and the samples(Zn_xFe_1-xFe₂O₄/C)magnetic and adsorption performance were investigated.Characterization results showed that the introduction of Zn²⁺made the saturation magnetization（Ms）of the samples decrease significantly（65.73→7.30 emu·g-1）,while the adsorptionperformance increase（the equilibrium adsorption amount qe: 8.05→22.40 mg·g-1）.Furthermore,the adsorptive kinetic behavior of the samples followed the pseudo-second-order kinetic model.（2）On the basis of the first part,the optimal conditions for the preparation of Fe₃O₄/C were explored respectively using potato starch（PR）and potato starch（PS）as carbon sources.The effect of the hydrothermal temperature,reaction time and the amount of used PR and PS on the formation of magnetic phase Fe₃O₄ were investigated.The results demonstrated that Fe³⁺ions were adsorbed and enriched on the surface of PR or PS and partially reduced to Fe2+ by PR or PS,which facilitated the convertion Fe³⁺ to Fe₃O₄,accompanied by the formation C materials,imlying the Fe₃O₄ and C material were one-step obtained.In the hydrothermal progress,PR and PS not only acted as C source and reducting agent,but also provided the necessary basic condition for the reaction to occur.On the basis of optimally prepared Fe₃O₄/C,a certain amount of Zn²⁺was used to replace Fe2+ in Fe₃O₄.The structure of the substituted sample and magnetic and adsorption performance were studied.The prepared samples were characterized by XRD,FT-IR,XPS,FESEM,EDS,BET and VSM.From the XRD and XPS characterization results,it could be found that Zn²⁺ indeed replaced Fe2+ in Fe₃O₄,and with the increase of Zn²⁺ content,the specific surface area of the sample increased and the saturation magnetization decreased.With the increase of Zn²⁺,the morphology of the samples changed greatly and the surface area increased,while the saturation magnetization decreased.In addition,the adsorption experiment was also carried out on the obtained the samples,the results showed that with the Zn²⁺substituting amount from 0 to 1.0,the adsorption performance of the sample was significantly enhanced.The specific surface area of Zn_xFe_1-xFe₂O₄/C sample with PR as carbon source increased from 46 to 83.2 m2·g-1,saturation magnetization Ms decreased from 79.09 to 18.06 emu·g-1,and the specific surface area of the Zn_xFe_1-xFe₂O₄/C with PR as carbon source increased from 43 to 91 m2·g-1,and the saturation magnetization Ms decreased from 74.79 to 9.998 emu·g-1.In addition,adsorption experiments were also performed on the obtained samples.The results showed that with the Zn²⁺ content from 0 to 1.0,the adsorption performance of thesamples was significantly enhanced.更多还原