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High Flowdity Injection Ferrite Materials

Author: ZuoQiaoQin
Tutor: JiangLiQiang；QiaoLiang
School: Zhejiang University of Technology
Course: Materials Science
Keywords: strontium ferrites Bi2O3 liquid phase mechanism oil acid fluidity
CLC: TQ138.11
Type: Master's thesis
Year: 2011
Downloads: 46
Quote: 0
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Abstract


Electronic devices and components developed towards the light, complicate and high performance direction since 20th century. Compared with sintering and molding press process,injection molding process can be used in manufacturing complicate and high size precision electronic devices and components, usually called all-in-one molding and net size shaping （do not need mechanical workout）, in the fields such as micromachine rotor, magnetic ring, magnetic roller in duplicator, sensors and so on. Nowadays, domestic bonded magnetic powders can only be used in preparing some low value-added plastic magnetic components. This directly results in the low product competition. So investigating and preparing magnetic powder for injection molding which has proper morphology and size making use of domestic raw materials has very positive aspects of realistic significance.The strontium ferrites with Bi2O3 addition were prepared by conventional solid phase synthesis process. The effects of Bi2O3 additives on the phase compositions, microstructure and the intrinsic coercive force of strontium ferrites at different calcining temperatures were investigated. The experimental results indicate that the liquid phase containing Bi accelerates the reaction of SrO and Fe2O3 for forming Sr-ferrites and improves the growth of particles at the firing temperature of 1050?C, which increases the intrinsic coercive forces of Sr-ferrites. Under the circumstances of adding Bi2O3, the as-received Sr-ferrite particles have the size of about 1.2?m with good sphericity and the high intrinsic coercive force exceeding 300KA/m. This benefits manufacturing the bonding ferrites with high filler contents. In addition, a possible mechanism was proposed to interpret the influence of trace of Bi2O3 addition on the morphology of strontium ferrite particles: SrO and Fe2O3 dissolve in the Bi2O3 liquid, and thereafter form SrM phase in it. The liquid layers enwrap the SrM phase and become thinner as SrM phase grows outward. When all the SrO and Fe2O3 particles are consumed, Sr-ferrites stop growing and come into being homogeneous particles with near spherical shape.Nylon 6/ferrite/oil acid composites were prepared by using a twin-screw extruder. The fluidity of the composites were measured by using the melt flow rate（MFR） equipment. The melting and crystallization behavior were characterized by differential scanning calorimetry（DSC）. The microscopic morphology was observed by the scanning electron microscope（SEM）. The results show that the fluidity of the composites is significantly improved with the addition of oil acid. At the same time, the crystallization temperature of Nylon 6 is increased and the melting temperature of nylon 6 is decreased when oil acid is used. The crystallinity of Nylon 6 with oil acid addition is also decreased from the thermal change in the crystallization. The study on the mechanism of oil acid effects show that the main reason of improving fluidity may be attributed to the decrease of the force between long-chain molecules of nylon 6 with the addition of oil acid, which increases the activity of molecular chains at the high processing temperature. The improvement of the fluidity of nylon6 benefits achieving ferrite/nylon 6 composites with high filler contents.

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CLC: > Industrial Technology > Chemical Industry > Inorganic compounds, the chemical industry of the metal elements > Inorganic compounds of the first the Ⅷ family metal elements > Inorganic compounds of iron elements > Inorganic compounds of iron
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