【作者】 李敬民；

【导师】 晁月盛；

【作者基本信息】 东北大学 ， 材料物理与化学， 2008， 硕士

【摘要】 磁流变液(Magnetorheogical Fluid)是由软磁颗粒,载液以及添加剂组成的稳定的悬浮液,其具有流体特性和智能可控的特点,可应用于减震器、离合器、肿瘤治疗、磁流变抛光等方面,对磁流变体的研究已成为材料科学领域的热点课题。目前磁流变液中的软磁粒子主要以羰基铁粉为主,但由于羰基铁粉制备成本比较高,限制了磁流变液在工业上广泛应用。氧化铁皮是钢铁生产中产生的固体废弃物,虽然目前已经有多种回收再利用方法,但都不完善,急需找到一种更有效的方法来提高其附加值。本文以氧化铁皮为原料,用硫酸溶解并经过提纯净化得到纯净的硫酸亚铁(FeSO4)溶液,采用沉淀法制备α-Fe2O3纳米粉末。然后用氢气将其还原得到微米级还原铁粉,将所得铁粉与适量硅油混合制备还原铁粉磁流变液并研究其性能。制备纳米氧化铁过程中对沉淀剂的选择、反应温度,煅烧温度进行了探讨。通过XRD、TEM、IR、MS(Mossbauer spectrum)对样品进行表征。结果表明：选择碳酸铵作为沉淀剂效果最佳；反应温度控制在50℃,在500℃煅烧2h,氧化铁红的含量98.77%,颗粒呈球形和椭球形两种形态,粒度在30-50nm；所得到的纳米氧化铁的平均超精细磁场,随煅烧的温度的升高而增大,主要是由两个方面引起的：表面效应与小颗粒的集体磁激发效应。纳米氧化铁的粒度对还原时间及还原后所得铁粉颗粒形貌有很大影响。纳米氧化铁颗粒由小到大,通过SEM观察铁粉形貌变化趋势是：由杆状到球状,并且所需还原时间增加。500℃煅烧得到的纳米氧化铁,经650℃还原3h,得到的还原铁粉铁元素的含量可达99.2%,通过Mossbauer spectrum进一步分析,其中纯铁为93.1%,Fe-N固溶体含量为6.9%。还原铁粉的颜色为灰白色,密度为0.66g/cm3。经测量还原铁粉的饱和磁化强度与羰基铁粉相当,并且磁场在0-250kA/m时,还原铁粉对磁场响应要好于羰基铁粉；根据载液选择要求,选择硅油作为载液。根据与载液的相溶性,选择NQ-71为表面活性剂,并用其对还原铁粉进行包覆处理,结果显示：包覆后的还原铁粉更容易在载液中分散。通过MCR301型流变仪对磁流变液力学性能以及表观粘度进行测试。测试结果表明：还原铁粉磁流变液剪切应力在较低的磁场下就可以迅速增大,达到最大值,更有利于在实际工程中的应用；磁流变液性能稳定受温度和剪切速率影响不大,其沉降稳定性优于羰基铁粉磁流变液；无外磁场和施加中等强度磁场时,磁流变液的表观粘度随着剪切速率的增大都出现明显剪切稀化现象,经拟合符合Bingham流体；向磁流变液中加入四氧化三铁纳米粒子对磁流变液的剪切应力影响很显著,当四氧化三铁的质量分数为0.8%时,增大效果最明显；当质量分数继续增大时,磁流变液的剪切应力反而降低；添加四氧化三铁会使磁流变液的粘度增大,并且随着质量分数的增大而增大。更多还原

【Abstract】 As a member of smart materials, Magnetorheological fluid (MRF) usually consists of micron-sized soft magnetic particles, carrier liquid and additive. They show a unique ability to undergo rapid, nearly completely reversible, significant changes in their rheology once an external magnetic field is applied. MRF can be applied in shock damper, clutch, tumor therapy, magnetorheological polishing, and so on. Now study on MRF has already been a hot subject in material science field. Currently the magnetic particles in MRF are mainly carbonyl iron dust. However, the cost of carbonyl iron dust is higher, which restricts MRF’s application in industry. Now it is urgent to find a new way of reusing the iron scale which is the solid waste during the preparation of iron and steel, although there have been some methods of recycling. In this paper Iron scale as starting material was solved by H2SO4, and FeSO4 solution was got after purification. Then a-Fe2O3 powder was prepared by precipitation method using FeSO4 After a-Fe2O3 was reduced by H2, the reduced ferrous powder was mixed with silicone oil to prepare iron magnetorheogical fluid (MRF) and the properties of MRF were studied.During the preparation of nm a-Fe2O3 powder, the selection of precipitants and the temperatures of reaction and incineration were discussed. And the samples were characterized by TG-DTA analysis, X-ray diffraction, FI-IR, TEM and Mossbauer spectrum.(NH4)2CO3 as the precipitant was the best selection. The mass fraction of a-Fe2O3,which was prepared after reaction at 50℃and incineration at 500℃for 2h, is 98.77%.The patterns of a-Fe2O3 particles, the size of which was between 30nm and 50nm, have spheric shape and spheroidicity. The average hyperfine magnetic field increased as the temperature of incineration increased due to surface effect and magnetic induced effect of microaggregates.The size of a-Fe2O3 particle had effects on the time of reducing and the patterns of reduced ferrous powder. The patterns of reduced ferrous powder changed from bacillary to spheric shape and the required time of reducing became longer as the size of a-Fe2O3 particles increased. The mass fraction of Fe element in iron dust reduced at 650℃for 3h from a-Fe2O3 calcined at 500℃was 99.2%.In iron dust the mass fraction of malleable cast-iron was 93.1% and the mass fraction of Fe-N solid solution was 6.9% by mossbauer spectrum analysis. The color of reduced ferrous powder was hoar and the density of reduced ferrous powder was 0.66 g/cm3.The saturation magnetization of reduced ferrous powder was the same as that of carbonyl iron dust and the response property of reduced ferrous powder is better than carbonyl iron dust under magnetic field between 0 and 250kA/m.According to the requirements of carrier and solubility in carrier, silicone oil and NQ-71 were selected as carrier and surfactant respectively. The results showed that after reduced ferrous powder was coated, it dispersed better in silicone oil.The properties of MRF were tested by MCR301 rheometer. The iron MRF not only had good stability, but also could reach its maximum shear stress quickly under low magnetic field. And these features can be helpful to apply prepared iron MRF in actual projects.This phenomenon that under no magnetic field the viscosity of MRF decreased as the rate of shear increased was the same as others reported and after the curves were fitted, prepared iron MRF belonged to Bingham fluid model. When applied medium magnetic field the viscosity of MRF decreased as the rate of shear increased. This showed prepared iron MRF also belonged to Bingham fluid model under medium magnetic field. The shear stress and viscosity increased when the nm Fe3O4 particles were added in iron MRF and the experiments showed that when the mass fraction of nm particles was 0.8% the increase was the biggest and when the mass fraction of nm particles continued to increase the shear stress began to decrease.更多还原