Yerli Hammaddelerle Stronsiyum Hekzaferrit (sro.6fe2o3) Mıknatıs Üretiminde Parametrelerin Nihai Ürüne Etkileri

Abstract

Son yıllarda stronsiyum hekzaferrit mıknatıslar üzerinde yapılan çalışmalar, manyetik özelliklere etki eden parametreler üzerine yoğunlaşmıştır. Bu parametreler; Kalsinasyon sıcaklığı ve süresi, tane boyutu, sinterleme sıcaklığı ve süresi, SrO/Fe2O3 mol oranı ile katkı elementleri şeklindedir. Bu çalışmanın amacı, yerli hammadde olan çelikhane tufali ve sölestin cevherinden elde edilen stronsiyum karbonat kullanarak stronsiyum ferrit mıknatıs üretmek, sentezleme işlemlerinin nihai ürününü etkileyen parametrelerini (kalsinasyon sıcaklığı ve süresi, empürite bileşimleri vs) incelemek ve böylece mıknatıs üretiminde yurt dışı bağımlılığını azaltmaktır. Bu çalışma ile stronsiyum hekzaferrit üretimi için tufalin, demir oksit kaynağı olarak kullanılabileceği görülmüştür. Alaşımsız düşük karbonlu çelik üretiminde oluşan tufalde bulunan %98.7 – 99.4 aralığındaki Fe2O3, stronsiyum hekzaferrit sentezi için ihtiyaç duyulan demir oksit (hematit) miktarını karşılamaktadır. Tufalin atmosferik koşulda yüksek sıcaklıklarda yapılan ısıl işlemle sağlanan manyeyit–hematit dönüşümü öğütmede ince boyuta ulaşmayı kolaylaştırmaktadır. Manyeyit–hematit dönüşümü ile tufalin sertlik değerinin düşmesi tufalin öğütülme performansını arttırmaktadır. Empürite içeriği fazla olan tufal ile üretilen kalsinasyon ürünlerinin XRD analizlerinde fazların büyük oranı SrO.6Fe2O3 ‘dır. Empürite içeriği düşük olan tufal ile iki farklı süre ve sıcaklıkta üretilen kalsinasyon ürünlerinde fazların tamamı SrO.6Fe2O3 ‘dır. Tufalde bulunan empüriteler, kalsinasyon ürünlerindeki SrO.6Fe2O3 fazının oranını düşürmektedir.

Exposed to the magnetic field and magnetic material that is gained the magnetization define as magnetic material. Magnetic products have 8 billion dollars worth market share. Generally it is used for electric motors, motor parts and various computer applications. Having the biggest market share NdFeB magnets showed %40 percent increase from 2007 to date. Especially for the last 7 years their demand grew exponentionally inrelation to the growing electronic market.500.000 Tons of magnet is produced annualy. Biggest producers are Chine, India, Japan, Brasil, European Contries and U.S.A. Especially due to their electrical properties, electronic ceramic materials forms %90 of the ceramic material production. Grain size, the amount of vacancy and composition are an important part of the crystal structure of magnetic materials that have such this electrical properties. Studies that made here in are regarding stronsium hexaferrit. Hardness magnetic materials have the followings ; Lower permeability Higher remanence Higher coercive (coercivity) has area. Hard ferrite ceramic magnets that can be used in; Generators Relays and motors Speaker and the phone ringing Toys and has a lot more use in the field. In recent years, studies on strontium hexaferrite magnets are especially focused on parameters that affect the magnetic properties. These parameters are the calcination temperature and duration, grain size, sintering temperature and durarion, SrO/Fe2O3, mole fraction, empurities. The aim of this study is to produce strontium ferrite magnet by using strontium carbonate that can be obtained from oxide scale and celestine which are national raw material and to investigate the parameters (calcination temperature, and duration, empurities etc.) that affect final material of synthesis process also to decrease dependence on overseas regarding production of magnets. It was seen that oxide scale can be used as source of iron oxide to produce strontium hexaferrite. Fe2O3 in the rage of %98.7–99.4 comprising in production of unalloyed low carbon steel meet the necessary amount of iron oxide. In this study basically strontium carbonate and scaling were used. The scale that defined as oxide layer formed on the surface of slab have not been taken notice and only used as solid waste in Turkey. There are only several applications in integrated facilities regarding scale in addition to projects not carried out. Usage of this material as secondary would be derived profit. In this study basically stronsium carbonate and scaling were used. The scale that defined as oxide layer formed on the surface of slab have not been taken notice and only used as solid waste in Turkey. There are only several applications in integrated facilities regarding scale in addition to projects not carried out. Usage of this material as secondary would be derived profit. Oxid covers basically are form as three different phases on steel. These phases are hematite, magnetite and wustite. The phases available on scale, Hematite (Fe2O3) layer are generally available exterior. This phase also have rich oxygen content. Magnetite (Fe3O4) have lower oxygen content than hematite’s. Wustite (FeO) have lowest ocygen content in the deepest layer. Strotium carbonete’s color is white. Generally strontium carbonate that known as celestine are derived from reaction with amonium or sodium sulfate. Stoichiometric ratios of the strontium ferrite magnet, are obtained from strontium oxide that determined according to the hematite phase used in source of iron. Stoichiometric ratio to be obtained in general should be determined by the formula MO.6Fe2O3. In scope of this study, followings are the process that made respectively, Scale hase become a powder by milling. For ease grinding descaling preferably, by heat treatment at high temperature, depending on the phase shift processing step may be used. Descaling milled powder, strontium carbonate stoichiometrically kept at high temperature in order to form together hematite strontium hexaferrite hematite oxide layer is provided to the phase transformation. Stoichiometric ratio of strontium hexaferrite and close ratios of strontium carbonates are mixed. At the selected temperature and duration of calcination are made. Calcination of the powder at high temperatures as a result of the build up can be seen in the sintering effect. Therefore, fine-grained powders can be obtained by short-term milling in the next experiments. Transformation of stronsium hexaferrit are ensured. Tranformation of strontium hexaferrit was observed according to the choosen parameters bu XRD analyse. Mangnetite hematite transformation that obtained from heat treating made in atmospherical conditions with high temperature facilitate the reaching fine grain scale on grinding The decrease of the hardness of scales with mangnetite hematite transformation increase the performance of milling. In XRD analyses of calcination products that obtained from scale which consist of impurity a lot, the largest percentage of phases are SrO.6Fe2O3. The all phases of the scale which consist of low impurity and calcination products that producted at two different temperature and durations are SrO.6Fe2O3. Impurities in scale decrase the ratio of SrO.6Fe2O3 phase in calcination products.