Fe基纳米晶的高性能磁流体研究

Study on High-Performance Fe-Based Nanocrystals Magnetorheological Fluids

摘要: 为优化磁流变液的热稳定性与磁学性能，采用机械合金法制备Fe基软磁合金纳米晶粒子，经表面改性后与高粘度载液混合，通过搅拌与热处理获得具有高磁性能与热稳定性的磁流变液。用X射线衍射仪分析磁性粒子的物相；扫描与透射电子显微镜观察磁性粒子的微观形貌特征；振动样品磁强计测试磁流变液的磁滞回线参数；并利用旋转粘度计评估磁流变液的粘度变化及热稳定性。结果表明：在两种磁流变液体系中，Fe₇₀Ni₁₂B₁₄Si₄纳米晶粒子饱和磁化强度(Bs) 165.78 emu/g，剩磁(Br) 7.29 emu/g，矫顽力(Hcb) 10.63 kA/m；Fe₈₂B₁₄Si₄的Bs为160.19 emu/g，Br为6.98 emu/g，Hcb为11.19 kA/m。经表面改性后，两种合金纳米晶粒子的磁性能均出现小幅下降。无论是改性前还是改性后，Fe₇₀Ni₁₂B₁₄Si₄粒子的饱和磁化强度与剩磁均高于Fe₈₂B₁₄Si₄粒子。表明其所含Ni元素可有效增强合金的磁性能。随着磁性粒子质量分数的增加，两种磁流变液的磁性能显著提升，而粘度则随温度升高呈逐渐下降趋势。在25℃下，当磁性粒子的质量分数为35%时，Fe₇₀Ni₁₂B₁₄Si₄磁流变液Bs为75.60 emu/g；Br为7.35 emu/g；Hcb为9.18 kA/m；粘度为7.56 × 10⁴ mPa·s；Fe₈₂B₁₄Si₄磁流变液Bs为60.91 emu/g；Br为7.05 emu/g；Hcb为8.51 kA/m；粘度为7.08 × 10⁴ mPa·s。该磁流变液具有较高的磁性能和优异的热稳定性，为高性能磁流变液材料提供了重要依据。

Abstract: To optimize the thermal stability and magnetic properties of magnetorheological fluids, Fe-based soft magnetic alloy nanocrystals were prepared using the mechanical alloying method. After surface modification, they were mixed with a high-viscosity carrier liquid, and through stirring and heat treatment, magnetorheological fluids with high magnetic performance and thermal stability were obtained. The phase of the magnetic particles was analyzed using X-ray diffraction; the microscopic morphology characteristics of the magnetic particles were observed with scanning and transmission electron microscopes; the hysteresis loop parameters of the magnetorheological fluid were tested using a vibrating sample magnetometer; and a rotational viscometer was used to evaluate the viscosity changes and thermal stability of the magnetorheological fluid. The results showed that in two magnetorheological fluid systems, Fe₇₀Ni₁₂B₁₄Si₄ nanocrystals had a saturation magnetization (Bs) of 165.78 emu/g, remanence (Br) of 7.29 emu/g, and coercivity (Hcb) of 10.63 kA/m; Fe₈₂B₁₄Si₄ had a Bs of 160.19 emu/g, Br of 6.98 emu/g, and Hcb of 11.19 kA/m. After surface modification, the magnetic performance of both alloy nanocrystals showed a slight decrease. Regardless of whether they were modified or not, the Fe₇₀Ni₁₂B₁₄Si₄ particles had higher saturation magnetization and remanence than the Fe₈₂B₁₄Si₄ particles, indicating that the Ni element effectively enhances the alloy’s magnetic performance. With the increase in the mass fraction of magnetic particles, the magnetic properties of both magnetorheological fluids were significantly improved, while the viscosity gradually decreased with increasing temperature. At 25˚C, when the mass fraction of magnetic particles was 35%, the Fe₇₀Ni₁₂B₁₄Si₄ magnetorheological fluid had Bs of 75.60 emu/g, Br of 7.35 emu/g, Hcb of 9.18 kA/m, and viscosity of 7.56 × 10⁴ mPa·s; the Fe₈₂B₁₄Si₄ magnetorheological fluid had Bs of 60.91 emu/g, Br of 7.05 emu/g, Hcb of 8.51 kA/m, and viscosity of 7.08 × 10⁴ mPa·s. These magnetorheological fluids possess high magnetic performance and excellent thermal stability, providing an important basis for high-performance magnetorheological fluid materials.