Particle oxidation constitutes a serious ageing phenomenon in magnetorheological suspensions, bringing about deterioration in performance. This study describes commercial carbonyl iron particles that were successfully coated with poly(amidoamine) dendrons and then applied as an oxidation-resistant dispersed phase in magnetorheological suspensions. A synthesis method was adhered to whereby the particles were sequentially treated with ethylenediamine and methyl acrylate, leading to the formation of generation 2 and 2.5 dendrons; these had the capacity for composite particles with a nano-scale dendritic layer to be prepared on their surfaces. Success in applying the coating was confirmed by various techniques, including XPS, TEM, EDX, FTIR and Raman spectroscopy. The controlled approach adopted to coating the carbonyl iron particles resulted in them exhibiting sufficient oxidation stability, with only an ~ 4.5–4.7% decrease in saturation magnetization. Of interest was that their magnetorheological suspensions demonstrated ca 4.8% and 4% higher dynamic yield stress than a suspension based on non-modified particles at the highest intensity of magnetic field investigated, i.e. 438 kA m^–1. Notably, sedimentation stability was evaluated by a unique method that involved the use of a tensiometer with a specific testing probe. The aforementioned coating process led to enhanced sedimentation stability of the magnetorheological suspensions based on coated particles possibly due to decrease in the overall density of the particles, enhanced dispersion stability and reduction in the size of their agglomerates in the silicone oil mixtures that were confirmed by optical microscopy. Modification of the particles as proposed has the potential to overcome one of the primary drawbacks of magnetorheological suspensions, this being oxidation instability (which leads to what is referred to as “in-use-thickening”), without negatively affecting their performance in the presence of a magnetic field.

颗粒氧化在磁流变悬浮液中构成严重的老化现象，从而导致性能下降。这项研究描述了商业化的羰基铁颗粒，它们成功地被聚（酰胺基胺）树突包覆，然后在磁流变悬浮液中用作抗氧化分散相。坚持一种合成方法，依次用乙二胺和丙烯酸甲酯处理颗粒，导致形成第2代和第2.5代树突。这些具有在其表面上制备具有纳米级树突层的复合颗粒的能力。通过各种技术（包括XPS，TEM，EDX，FTIR和拉曼光谱法）证实了涂层的成功应用。采用控制方法涂覆羰基铁颗粒后，它们表现出足够的氧化稳定性，饱和磁化强度仅降低了约4.5-4.7％。令人感兴趣的是，在研究的最高磁场强度（即438 kA m）下，其磁流变悬浮液的动态屈服应力比基于非改性颗粒的悬浮液高约4.8％和4％。^–1。值得注意的是，沉降稳定性是通过一种独特的方法进行评估的，该方法涉及使用带有特定测试探针的张力计。前述涂覆方法导致基于涂覆的颗粒的磁流变悬浮液的沉积稳定性增强，这可能是由于颗粒的总体密度降低，分散稳定性增强以及在硅油混合物中的附聚物的尺寸减小所致，这通过光学方法得到了证实。显微镜检查。如所提出的，对粒子的改性具有克服磁流变悬浮液的主要缺点之一的潜力，这是氧化不稳定性（导致所谓的“使用中增稠”），而不会对存在的性能产生负面影响磁场