Narayanaswamy Venkatesha, Al-Omari Imaddin A, Kamzin Aleksandr S, Issa Bashar, Tekin Huseyin O, Khourshid Hafsa, Kumar Hemant, Mallya Ambresh, Sambasivam Sangaraju, Obaidat Ihab M
Department of Physics, United Arab Emirates University, Al-Ain 15551, United Arab Emirates.
Department of Physics, Sultan Qaboos University, P.O. Box 36, Muscat PC 123, Oman.
Nanomaterials (Basel). 2021 May 7;11(5):1231. doi: 10.3390/nano11051231.
Mixed ferrite nanoparticles with compositions CoMnFeO ( = 0, 0.2, 0.4, 0.6, 0.8, and 1.0) were synthesized by a simple chemical co-precipitation method. The structure and morphology of the nanoparticles were obtained by X-ray diffraction (XRD), transmission electron microscope (TEM), Raman spectroscopy, and Mössbauer spectroscopy. The average crystallite sizes decreased with increasing , starting with 34.9 ± 0.6 nm for MnFeO ( = 0) and ending with 15.0 ± 0.3 nm for CoFeO ( = 1.0). TEM images show an edge morphology with the majority of the particles having cubic geometry and wide size distributions. The mixed ferrite and CoFeO nanoparticles have an inverse spinel structure indicated by the splitting of A peak at around 620 cm in Raman spectra. The intensity ratios of the A(1) and A(2) peaks indicate significant redistribution of Co and Fe cations among tetrahedral and octahedral sites in the mixed ferrite nanoparticles. Magnetic hysterics loops show that all the particles possess significant remnant magnetization and coercivity at room temperature. The mass-normalized saturation magnetization is highest for the composition with = 0.8 (67.63 emu/g), while CoFeO has a value of 65.19 emu/g. The nanoparticles were PEG (poly ethylene glycol) coated and examined for the magneto thermic heating ability using alternating magnetic field. Heating profiles with frequencies of 333.45, 349.20, 390.15, 491.10, 634.45, and 765.95 kHz and 200, 250, 300, and 350 G field amplitudes were obtained. The composition with = 0.2 (CoMnFeO) with saturation magnetization 57.41 emu/g shows the highest specific absorption rate (SAR) value of 190.61 W/g for 10 mg/mL water dispersions at a frequency of 765.95 kHz and 350 G field strength. The SAR values for the mixed ferrite and CoFeO nanoparticles increase with increasing concentration of particle dispersions, whereas for MnFeO, nanoparticles decrease with increasing the concentration of particle dispersions. SARs obtained for CoMnFeO and CoFeO nanoparticles fixed in agar ferrogel dispersions at frequency of 765.95 kHz and 350 G field strength are 140.35 and 67.60 W/g, respectively. This study shows the importance of optimizing the occupancy of Co among tetrahedral and octahedral sites of the spinel system, concentration of the magnetic nanoparticle dispersions, and viscosity of the surrounding medium on the magnetic properties and heating efficiencies.
采用简单的化学共沉淀法合成了组成为CoMnFeO（ = 0、0.2、0.4、0.6、0.8和1.0）的混合铁氧体纳米颗粒。通过X射线衍射（XRD）、透射电子显微镜（TEM）、拉曼光谱和穆斯堡尔光谱对纳米颗粒的结构和形貌进行了研究。平均晶粒尺寸随着 的增加而减小，对于MnFeO（ = 0），起始尺寸为34.9±0.6 nm，对于CoFeO（ = 1.0），最终尺寸为15.0±0.3 nm。TEM图像显示出边缘形态，大多数颗粒具有立方几何形状且尺寸分布较宽。拉曼光谱中约620 cm处A峰的分裂表明混合铁氧体和CoFeO纳米颗粒具有反尖晶石结构。A(1)和A(2)峰的强度比表明Co和Fe阳离子在混合铁氧体纳米颗粒的四面体和八面体位点之间发生了显著的重新分布。磁滞回线表明，所有颗粒在室温下都具有显著的剩余磁化强度和矫顽力。质量归一化饱和磁化强度对于 = 0.8的组成最高（67.63 emu/g），而CoFeO的值为65.19 emu/g。对纳米颗粒进行了聚乙二醇（PEG）包覆，并使用交变磁场检测其磁热加热能力。获得了频率为333.45、349.20、390.15、491.10、634.45和765.95 kHz以及磁场幅度为200、250、300和350 G的加热曲线。对于 = 0.2（CoMnFeO）且饱和磁化强度为57.41 emu/g的组成，在频率为765.95 kHz和磁场强度为350 G时，10 mg/mL水分散体的比吸收率（SAR）值最高，为190.61 W/g。混合铁氧体和CoFeO纳米颗粒的SAR值随颗粒分散体浓度的增加而增加，而对于MnFeO纳米颗粒，其SAR值随颗粒分散体浓度的增加而降低。在频率为765.95 kHz和磁场强度为350 G时，固定在琼脂铁凝胶分散体中的CoMnFeO和CoFeO纳米颗粒的SAR值分别为140.35和67.60 W/g。本研究表明了优化Co在尖晶石体系四面体和八面体位点中的占有率、磁性纳米颗粒分散体的浓度以及周围介质的粘度对磁性和加热效率的重要性。
