Nb$_2$O$_{5}$ 첨가가 Mn-Zn Ferrites의 전자기적 특성에 미치는 효과

서정주,신명승,한영호,Suh, Jung-Ju,Shin, Myung-Seung,Han, Young-Ho 한국재료학회 1995 한국재료학회지 Vol.5 No.8

저손실 망간징크 페라이트에서 CaO-SiO$_2$첨가는 입계에 높은 전기저항층을 형성시켜 와류에 의한 손실을 감소시키는 것으로 알려져 있다. 본 실험에서는 Nb$_2$O$_{5}$ 를 제 3의 첨가제로 사용하여 저손실 망간징크 페라이트에서의 전자기적 물성변화를 관찰하였다. Nb$_2$O$_{5}$ 300ppm 이상 첨가시 부분적인 과대입자 성장이 관찰되었으며, 200ppm 첨가시 CaO-SiO$_2$만 첨가한 시편에 비하여 밀도가 증가하였다. Nb$_2$O$_{5}$ 첨가시에는 100ppm 이하의 SiO$_2$첨가에서 우수한 전력손실 특성이 나타났으며, 고온 소결시 Nb$_2$O$_{5}$-CaO를 첨가한 시편에서 낮은 전력손실을 나타내었다. It is well known that the addition of CaO-SiO$_2$to Mn-Zn ferrites forms an insulating grain bounary layer with high electrical resistivity. This study investigated the effect of Nb$_2$O$_{5}$ on the electromagnetic properties of high frequency low loss Mn-Zn ferrites. The addition of 300ppm Nb$_2$O$_{5}$ developed an exaggerated grain growth while the addition of CaO-SiO$_2$addition with 200ppm Nb$_2$O$_{5}$ more effectively increased the density than that without Nb$_2$O$_{5}$. The addition of Nb$_2$O$_{5}$ showed the lower power loss below 100 ppm SiO$_2$and the Nb$_2$O$_{5}$-CaO addition lowered the power loss at higher sintering temperature.

능동 비틀림 제어에 용이한 블레이드의 스파형상 선정

배재성,신명승 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.4

여러 분야에서 능동적 비틀림 제어기법에 대한 연구가 활발히 수행되고 있다. 효율적인 비틀림제어를 위해 블레이드는 동일한 비틀림하중에 대해 낮은 응력을 갖는 동시에 큰 비틀림변형을 가져야 한다. 본 연구에서는 능동 비틀림 제어에 용이한 블레이드를 찾기 위해 5 개의 각기 다른 스파를 갖는 블레이드에 대해 2 차원 단면 해석 과 3 차원 유한요소해석을 수행하였다. 2 차원 단면해석에서 얻은 결과들을 이용해 3 차원 유한요소해석을 진행하였다. 이번 연구에서 설정한 조건에서 2 차원 단면해석과 3 차원 유한요소 해석결과들은 동일한 하중조건에서 C 형상의 보를 갖는 블레이드가 능동적 비틀림 제어에 가장 용이한 형상이라는 것을 보여주었다. On wide variety of fields, studies on active twist control are becoming more active. For effective twist control, blades have to have low torsional stresses with high torsional deformations to the same magnitude of torque acting on its crosssection. In this study, 2D sectional analysis and 3D finite element analysis were made for 5 different blades with each having different cross –sections which have different spars. The results from 2D sectional analysis, were then put into 3D blade deformation and stress calculations which lead to analysis. Outcomes from 2D and 3D analysis, showed that on the same torque and concentrated load conditions, the blade with ‘C’ shaped spar was the best of all the blades which were used in this study.

소결조건이 Mn-Zn Ferrites의 전자기적 물성에 미치는 효과

최윤호,신명승,한승기,한영호 한국세라믹학회 1997 한국세라믹학회지 Vol.34 No.6

The effects of sintering temperature and oxygen partial pressure on the electromagnetic properties of Mn-Zn ferrites were investigated. The grain increased with increasing temperature. The power loss at 100 kHz was decreased, while the power loss at 500 kHz was increased as the grain size increased with sintering temperature. Sintering with low oxygen partial pressure at 115$0^{\circ}C$ resulted in high density and initial permeability, and decreased the power loss at 100 kHz and 500 kHz. The oxygen partial pressure lower than 10-2 atm. during heating, significantly suppressed the hysteresis loss. However, the oxygen activity did not affect the grain size of sintered cores.

$SiO_2$와 CaO 첨가가 Mn-Zn Ferrites의 전자기적 물성에 미치는 영향

서정주,신명승,한영호 한국세라믹학회 1995 한국세라믹학회지 Vol.32 No.9

The current experiment has quantitatively investigated the effect of the content of CaO and SiO2 on the microstructure, density, electrical resistivity, power loss and initial permeability of manganese zinc ferrites. The density increased initially with CaO and SiO2 content and the further addition showed an adverse effect. The excess addition of CaO and SiO2 developed a discontinuous grain growth with numerous pores inside grains and lowered the electrical resistivity. The initial permeability decreased with increasing the content of SiO2. The samples with relatively low power loss showed that half of the total loss at 10$0^{\circ}C$, 100 kHz and 2000 Gauss was due to the eddy current loss.

입자분포가 Mn-Zn Ferrite의 전자기적 물성에 미치는 경향

강남규,서정주,신명승,한명호 한국세라믹학회 1998 한국세라믹학회지 Vol.35 No.10

고주파 저손실 재질로 사용되는 Mn-Zn ferrites의 제조공정 중 입도분포제어가 전자기적 물성에 미치는 효과에 관하여 연구하였다. 입도분포는 분쇄시간을 변화시켜 제어하였으며 철의 유입을 막기위하여 지르코니아볼을 사용하였다. 분쇄시간이 증가함에 따라 입자크기는 2.1 $\mu\textrm{m}$에서 1.0$\mu\textrm{m}$로 감소하였으며, 비표면적은 0.55에서 3.21m2/g으로 증가하였다. 비표면적 값이 증가할수록 소결체의 밀도는 증가하였으며, 높은 비표면적을 가진 분말의 경우 1300$^{\circ}C$ 이 상의 고온에서 소결할 때 불균일한 미세구조와 과대입성장이 발생하였으며, 전자기적 물성감소가 나타났다. The effects of particle size distribution have been investigated on the high frequency low loss Mn-Zn fer-rites. The particle size distribution was controlled by milling time. Zirconia ball and engineering plastic jar were employed to avoid iron contamination from the milling media. As increasing the milling time BET value was increased from 0.55 to 3.21m2/g and mean particle size was decreased from 2.1 $\mu\textrm{m}$ to 1.0$\mu\textrm{m}$ The large specific surface area of initial powder resulted in the high density of sintered core. However starting powders with high BET lead to inhomogeneous grain growth as well as poor electromagnetic pro-perties at sintering temperature above 1300$^{\circ}C$.

Corrosion and inhibition process of carbon steel in LiBr-H2O solution

조윤호,한상무,서호진,신명승,우성민,정시영 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.6

Lithium bromide (LiBr)-H 2 O triple-effect absorption chillers are supposed to have a much higher carbon steel corrosion rate under high temperature than double-effect ones. Although the annual corrosion rate was investigated in our previous study, a simple extrapolation with experimental data for a short period of time can cause very significant errors because the corrosion process becomes quite complicated if a corrosion inhibitor exists in the solution. Therefore, in this study, corrosion and inhibition characteristics over time have been investigated for carbon steel specimens in LiBr-H 2 O solution under the optimal operation conditions of double- and triple-effect absorption chillers. Pyrex tube ampoules containing a carbon steel specimen and the 63 % LiBr-H 2 O solution with a corrosion inhibitor (lithium molybdate, Li 2 MoO 4 ) were prepared and placed in a high-temperature oven at 150 °C and 200 °C, which are typical operation temperatures of double- and triple-effect absorption chillers, respectively. After various exposure times (25–4000 hours), the ampoules were opened and analyzed using three methods: Analysis of mass loss, solution analysis, and microscopic image analysis. Results indicated that the passive films were formed not linearly with time but rapidly at the beginning. Moreover, the concentration of the corrosion inhibitor (Li 2 MoO 4 ) should be maintained above 100 ppm for stable passive films. To explain the experimental data, a model with three stages of corrosion and inhibition process was proposed. The present study is expected to give important information for the development of triple-effect absorption chillers.

Mn - Zn 페라이트의 전·자기적 물성에 미치는 공정변수의 영향 고찰

황진현(J. H. Hwang),신명승(M. S. Shin),한영호(Y. H. Han) 한국자기학회 1997 韓國磁氣學會誌 Vol.7 No.2

The effect of oxide additive system and Po₂ condition on the power loss, microstructure, initial permeability (μi), sintered body density, μi vs. temperature curve of Mn-Zn ferrites has been investigated. The density and permeability increased with various additive systems while the power loss decreased. It was confirmed that the oxide additives are grain boundary materials and do not change the magnetic properties of Mn-Zn ferrites such as Tspm and Tc. The μi vs. T curve indicated that Tspm moved to the higher temperature as Po₂ increased. It was also confirmed that the microstructure of Mn-Zn ferrites was independent of the Po₂ control during cooling.

MoO₃ 첨가가 Mn - Zn Ferrites의 투자율에 미치는 영향

장정수(J. S. Jang),신명승(M. S. Shin),한영호(Y. H. Han) 한국자기학회 2001 韓國磁氣學會誌 Vol.11 No.1

The effect of MoO₃ addition on the permeability of Mn-Zn ferrites was studied. 600 ppm, 800 ppm and 1,000 ppm of MoO₃ were added to the main composition after calcination. Ferrite cores were sintered at 1350 ℃ for 3hrs, followed by cooling according to the equilibrium oxygen concentration. The initial permeability was about 8,000 with heating rate 5℃/min for 3hrs without MoO₃ addition. When 600 ppm and 800 ppm of MoO₃ were added, the initial permeabilities, 13,200 and 13,550 were obtained, respectively. However, the sample with 1,000 ppm MoO₃ showed lower permeabilities because of abnormal grain growth. At the heating rate 10℃/min, the ferrite cores with 1,000 ppm MoO₃ demonstrated the highest initial permeability greater than 15,000, without exaggerated grain growth.