Abstract

Superparamagnetic gels based on polyacrylamide and magnetite were synthesized by the in situ preparation of magnetite nanoparticles in polyacrylamide (PAM) physical hydrogels at different polymer concentrations. The formation of magnetite nanoparticles and their magnetic properties were characterized by Fourier transform infrared (FTIR) spectroscopy, rheometry, X-ray diffractometry (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). FTIR spectroscopy showed that all composite gels had features related to pure PAM. The structural characterization by Rietveld method revealed an average crystallite size below 18 nm and SEM micrographs of the gel with Fe₃O₄ showed that the particles have spherical structures. The rheology-related measurements indicated that the gels had a strong pseudoplastic character. Magnetic measurements confirmed the superparamagnetic behavior of the obtained magnetite nanoparticles, both in the form of pure powder and within PAM gel matrix. Magnetite crystallite size decreased as PAM content was increased, which was explained as a function of thermodynamic and kinetic effects.

摘要

通过在不同聚合物浓度的聚丙烯酰胺 (PAM) 物理水凝胶中原位制备磁铁矿纳米颗粒，合成了基于聚丙烯酰胺和磁铁矿的超顺磁性凝胶。通过傅里叶变换红外 (FTIR) 光谱、流变仪、X 射线衍射仪 (XRD)、扫描电子显微镜 (SEM) 和振动样品磁力仪 (VSM) 对磁铁矿纳米颗粒的形成及其磁性进行了表征。FTIR 光谱表明所有复合凝胶都具有与纯 PAM 相关的特征。Rietveld 方法的结构表征显示平均微晶尺寸低于 18 nm 和含有 Fe ₃ O ₄的凝胶的 SEM 显微照片表明颗粒具有球形结构。流变学相关测量表明凝胶具有很强的假塑性。磁性测量证实了所获得的磁铁矿纳米颗粒的超顺磁性行为，无论是在纯粉末的形式还是在 PAM 凝胶基质中。随着 PAM 含量的增加，磁铁矿晶粒尺寸减小，这被解释为热力学和动力学效应的函数。