• Applied Chemistry for Engineering
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• v.17 no.3
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• pp.267-273
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• 2006

We have prepared PP/Ba-ferrite composite fabrics by a melt-blown spinning method and investigated the relationship between the properties of PP/Ba-ferrite composite fabrics and melt-blown processing factors. A PP composite containing Ba-ferrite as a magnetic particulate filler was prepared in the form of pellet from PP resin and Ba-ferrite powder by melt compounding using a single extruder. Screw turning force (rpm), DCD (die-to-collector distance), and Ba-ferrite content were changed. We measured diameters of fiber, mechanical, thermal, and magnetic properties for the composited PP fabrics. The elongation was increased and a fiber diameter and tensile strength were decreased as the spinning distance increased or screw turning force decreased. The crystallinity was increased with increasing spinning distance according to XRD. It was assumed that the orientation of crystalline domain in the neat PP without ferrite was increased by drawing in mechanical direction, however, the orientation in the PP composite was decreased according to XRD analysis. We measured a magnetic property of PP nonwoven fabric containing Ba-ferrite powder. A coercive force, maximum magnetization, and residual magnetization are reduced with the spinning distance. According to the result of TGA measurement, the heat resistance was increased with the Ba-ferrite powder content and with decreasing the spinning distance.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.4
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• pp.153-158
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• 2003

This thesis deal with ferroelectric and ferromagnetic materials. PZT/Ferrite ceramics were made by the making process using PZT powder and garnet ferrite powder. PZT and ferrite are mixed as much 90%-10%, 50%-50%, and so on. After making samples, we are polishing samples until thickness is 0.1~0.2mm. We measured all kinds of samples in room temperature and applied magnetic field from -4500 to 4500 Oersted and conducted test of magnetical and electrical measurement using VSM and lpC resolution electrometer calibrated with RT66A pulsed tester. From this measurement, we can calculate tunability of these samples using C value obtained from P-E loop. As a result, it was able to measure magnetic characteristic when two matter had each other component ratio, and it was compound. However, it confirmed the possibility that was able to have ferroelectric characteristic with you in PZT 90% and ferrite 10%. Therefore, If this thing comes for PZT 50% and ferrite 50% have ferroelectric characteristic as him in a compound sample ore, can use this in an oscillator, supersonic waves detector in addition to a piezoelectric element. It may contribute to multipurpose of an element and demands such as a miniaturization of equipment, efficiency, reduce of a price which can use a characteristic of two components.

• Applied Chemistry for Engineering
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• v.17 no.4
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• pp.420-425
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• 2006

Nano sized mixed metal hexagonal ferrite powders with improved magnetic properties have been prepared by sol-gel method using propylene oxide as a gelation agent. To obtain the desired ferrite, two different metal ions were used. One of the ions has only +2 formal charge. The key step in the processes is that hydrated $Ba^{2+}$ or $Sr^{2+}$ ions are hydrolyzed and condensed at the surface of the previously formed $Fe_{2}O_{3}$ gel. In this processes, all the reaction can be finished within a few minutes. The magnetic properties of the produced powder were improved by heat treatment. The highest values of the magnetic properties were achieved at temperature $150^{\circ}C$ lower than those of the previously published values. The highest observed values of coercivity and the saturation magnetization of Sr-ferrite and Ba-ferrite powder were 6198 Oe, 5155 Oe and 74.4 emu/g, 68.1 emu/g, respectively. The ferrite powder annealed at $700^{\circ}C$ showed spherical particle shapes. The resulting spheres which were formed by the aggregation of nanoparticles with size 3~5 nm have diameter around 50 nm. The powder treated at $800^{\circ}C$ showed hexagonal-shaped grains with crystallite size above 500 nm.

• Journal of the Korean Magnetics Society
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• v.14 no.1
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• pp.18-24
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• 2004

Ni-Zn ferrite powder was synthesized from metal nitrates, Fe(N $O_3$)$_3$$.$9 $H_2$O, Ni(N $O_3$)$_2$$.$6 $H_2$O, Zn(N $O_3$)$_2$$.$6 $H_2$O by wet direct process to make high permeability material. The composition of the ferrite powder is (N $i_{0.284}$F $e_{0.053}$Z $n_{0.663}$)F $e_2$ $O_4$. Ni-Zn ferrite powder is compounded by precipitating metal nitrates with NaOH in vessel at 90$^{\circ}C$ synthetic temperature for 8 hours. Calcination temperature and sintering temperature were 700$^{\circ}C$ and 1150$^{\circ}C$-1250$^{\circ}C$ respectively for 2 hours. The same compound powder was extracted from metal oxide by wet ballmilling. We compared the properties of powder and the electromagnetic characteristics of the sintered cores obtained from the two different processes. Wet direct process produces smaller particle size with narrower distribution and higher purified ferrite which cores has high permeability and high magnetization.

• Journal of the Korean Ceramic Society
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• v.31 no.10
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• pp.1181-1187
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• 1994

Sr-ferrite powders were synthesized by molten salt method. The process of powder formation was investigated by controlling the size and shape (sphere and acicular) of starting materials. The morphology of resulting ferrite was plate-like regardless of the shape of starting materials, Fe2O3 powders. As a result, the formation of Sr-ferrite in the molten salt was proceeded by solution-precipitation.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.90-91
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• 2002

영구자석 재료용 Sr-ferrite의 제조에 mechanical alloying (기계적 합금화)기술을 적용해서 초미세 결정립으로 구성된 고보자력의 Sr-ferrite를 제조해서 높은 보자력을 실현할 수 있는 것으로 보고하고 있다[1]. 그러나 이 새로운 방법으로 제조한 Sr-ferrite는 높은 보자력을 갖기는 하지만, 대단히 미세한 결정립들이 결합하여 입자를 구성하고 있어 자장을 가해서 입자를 배향시키기가 어렵다. 따라서 이 재료는 등방성 분말로 밖에 이용할 수 없는 결정적인 문제점이 있다. (중략)

• Resources Recycling
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• v.7 no.4
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• pp.43-49
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• 1998

We investigated the effects of the powder characteristics of various domestic iron oxides (${\alpha}Fe_2O_3$) on the magnetic properties of Sr-ferrites The particle size and the distribution of iron oxides were classified hy three different rerinning methods, and greatly a affected on the magn$\xi$tic prope$\pi$ies and the mmphology of Sr-ferntes. The agglomeration of Ruthner iron oxides and the large particles of Chemirite (CY) above $0.80{\mu}\textrm{m}$ were degraded the prope며es of Sr-fcrrites. The optimal magnetic prope$\pi$ies of Srt territes, showing 68.2 emu/g of saturation magnetization and 4300 Oe of intrinsic coerClvity, were achieved at the following c conditions; Chemirite (P2EP) iron oxides of $0.14{\mu}\textrm{m}$ molar ratio of 5.8. and calcination of $1150^{\circ}C$/1 hr.

• Journal of the Korean Ceramic Society
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• v.29 no.7
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• pp.539-543
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• 1992

The continuous growth method was developed for Mn-Zn Ferrite single crystals. It is a new process that the polycrystalline MnχZn1-χFe2O4 raw materials are supplied continuously from the powder feeding system to the crucible heated by R.F. induction and melted in the crucible, and after the single crystals seed is attached to crucible's hole, the crystals are pulled downward with rotation. Growing the crystals by using the growth method different from the conventional Bridgman or Floating Zone method, we defined the factors having effect on the crystal growing through the pre-experiments. They are temperature distribution in the crucible, melt velocity according to its height, wettability between the crucible's bottom and melt. Therefore, Mn-Zn Ferrite single crystals were to be grown by attaining the appropriate melt height in the crucible, powder feeding rate, temperature gradient between the crucible and interface, crystal growing speed, and this method was confirmed to have possibility for single crystal growing.

• Journal of the Korea Safety Management & Science
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• v.2 no.4
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• pp.197-208
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• 2000

ABS sensor ring has been manufactured by powder metallurgy (P/M) method using 400 series ferrite stainless steel. The results are following. It is supposedly sufficient to use for control computer due to good experimental results of magnetic characteristics. Compared with sensor ring made by iron, 400 series ferrite stainless steel has shown a good corrosion resistance without an addition surface treatment. Thus the decreasing production process has been obtained. As a result mechanical characteristics of hardness and tensile test, 400 series ferrite stainless steel shown a good endurance when it is combined to constant velocity joint(C/V), and has a good hardness properties endurable to sand and pebble impact. The products before sintering are much more corrodible in the condition of spray test of salt water and ammonia than humidity and nitrogen condition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1991.10a
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• pp.33-36
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• 1991

For its outstanding magnetic property, preparations of MnZn ferrite were studied with various method. In this study, MnZn ferrite powders were prepared from ammonium oxalate and mixed metal sulfate by the controlled coprecipitation process. Considering to low dissolved each metal ion, high production yield and particle size, the established optimum reaction conditon by the statistical analysis of each results are that reaction temperature is $25^{\circ}C$, concentration of metal sulfate is 0.3M, molar ratio of ammonium oxalate/metal sulfate is 1.1:1. The effective experimental factor and characterization of the precipitated powder at optimum condition were studied.