Abstract An original non-hydrolytic sol-gel approach, using 2-ethyl-1,3-hexanediol as reactive solvent, was proposed to synthetize nanostructured magnetite. Iron-oxide nanoparticles were prepared and studied as a function of the precursor-to-solvent ratio. The crystallization degree of nanoparticles was followed by the combined Rietveld and Reference Intensity Ratio method. This procedure has allowed the determination of both amorphous and crystalline content of nanomagnetite, using hematite as suitable internal standard. The results of Rietveld method show that the crystalline content decreases as the precursor-to-solvent is increased, ranging from 67 to 60 wt%. Information on the crystallite size-strain distribution and microstructural evolution of nanocrystals was supplied by line profile analysis of the powder diffraction patterns, employing the Whole Powder Pattern Modeling analysis: the obtained log-normal distribution curves become increasingly narrow and symmetrical, while nanoparticle microstrain increases as the precursor concentration is increased. The dimensional analysis of the Transmission Electron Microscopy images has allowed to obtain the nanoparticle grain-size distribution. Nanoparticle dimensions decreases from 15 to 9 nm increasing the precursor concentration. The comparison between the results of X-ray diffraction and microscopic characterization techniques highlighted the effect of several factors, such as size, shape and microstructure of magnetite nanoparticles, on their functional magnetic response. Magnetic characterizations show that magnetite nanoparticles are not in the superparamagnetic phase even at room temperature, independent of the precursor concentration. On the other hand, the room-temperature saturation magnetization, ranging from 73 to 60 emu/g, is a function of the nanoparticle average size, decreasing as the precursor concentration increases.

中文翻译：

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在非水解溶胶-凝胶合成中使用 2-乙基-1,3-己二醇作为创新反应溶剂获得的 Fe 3 O 4 纳米晶的结构表征和功能相关性

摘要 提出了一种以2-乙基-1,3-己二醇为反应溶剂的非水解溶胶-凝胶法合成纳米结构磁铁矿。制备和研究氧化铁纳米颗粒作为前体与溶剂比率的函数。纳米颗粒的结晶度由 Rietveld 和参考强度比的组合方法跟踪。该程序允许使用赤铁矿作为合适的内标来测定纳米磁铁矿的无定形和结晶含量。Rietveld 方法的结果表明，结晶含量随着前体溶剂的增加而降低，范围从 67 到 60 wt%。通过粉末衍射图案的线轮廓分析提供了关于纳米晶体的微晶尺寸-应变分布和微观结构演变的信息，采用Whole Powder Pattern Modeling分析：得到的对数正态分布曲线变得越来越窄和对称，而纳米颗粒微应变随着前体浓度的增加而增加。透射电子显微镜图像的尺寸分析允许获得纳米颗粒粒度分布。纳米颗粒尺寸从 15 nm 减小到 9 nm，增加了前体浓度。X 射线衍射结果与显微表征技术之间的比较突出了几个因素，如磁铁矿纳米粒子的大小、形状和微观结构，对其功能磁响应的影响。磁性表征表明，即使在室温下，磁铁矿纳米粒子也不处于超顺磁性相，与前体浓度无关。另一方面，室温饱和磁化强度为 73 至 60 emu/g，是纳米颗粒平均尺寸的函数，随着前体浓度的增加而降低。