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首页> 外文期刊>Journal of Non-Crystalline Solids: A Journal Devoted to Oxide, Halide, Chalcogenide and Metallic Glasses, Amorphous Semiconductors, Non-Crystalline Films, Glass-Ceramics and Glassy Composites >Structural and magnetic properties of gamma- and epsilon-Fe2O3 nanoparticles dispersed in silica matrix
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Structural and magnetic properties of gamma- and epsilon-Fe2O3 nanoparticles dispersed in silica matrix

机译：分散在二氧化硅基质中的γ-和ε-Fe2O3纳米颗粒的结构和磁性

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摘要

Fabrication of composite materials by in situ generation of gamma- and epsilon-Fe2O3 nanoparticles in a SiO2 matrix through sol-gel process is reported. The process involves the hydrolysis and condensation of 1:3:10:x (x = 0.05, 0.1 and 0.2) molar ratios of tetraethoxysilane, absolute ethanol, nitric acid (0.16 N) and ferric nitrate, respectively, and subsequent thermal-treatment at temperatures ranging from 110 to 1000 degrees c. The in situ generation and growth of gamma- and epsilon-Fe2O3 nanoparticles, and their distribution in SiO2 matrix strongly depend on the concentration of Fe3+ ions and thermal-treatment temperatures. The restricted growth of Fe2O3 in SiO2 matrix seems to stabilize the metastable epsilon-Fe2O3 phase and prevent the formation of alpha-Fe2O3 even at 1000 degrees C. Further, the presence of Fe2O3 nanoparticles in SiO2 matrix modified the gel morphology on thermal-treatment, leading to strong structural and chemical changes which influence the magnetic properties to a large extent. The concentration of individual magnetic phase (gamma- and epsilon-Fe2O3) in the samples, the particle size and distribution, and thermal-treatment temperature determine the net magnetic moment, shape of the hysteresis loop (symmetric or concentric), coercivity and magnetic phase transition.
机译：报道了通过溶胶-凝胶法在SiO 2基体中原位生成γ-和ε-Fe2 O 3纳米颗粒来制造复合材料。该工艺涉及四乙氧基硅烷，无水乙醇，硝酸（0.16 N）和硝酸铁的摩尔比分别为1：3：10：x（x = 0.05、0.1和0.2）的水解和缩合，然后在125℃进行热处理。温度范围为110至1000摄氏度。 γ-和ε-Fe2O3纳米粒子的原位生成和生长以及它们在SiO2基质中的分布在很大程度上取决于Fe3 +离子的浓度和热处理温度。 SiO2基体中Fe2O3的有限生长似乎可以稳定亚稳态的ε-Fe2O3相，甚至在1000摄氏度时也可以阻止α-Fe2O3的形成。此外，SiO2基体中Fe2O3纳米颗粒的存在改变了热处理时的凝胶形态，导致强烈的结构和化学变化，从而在很大程度上影响磁性能。样品中单个磁相（γ-和ε-Fe2O3）的浓度，粒径和分布以及热处理温度决定了净磁矩，磁滞回线的形状（对称或同心），矫顽力和磁相过渡。

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