BaCO₃-Fe₂O₃系의 固體反應 및 바륨페라이트의 磁氣的 性質에 미치는 粉碎時間의 影響

南孝悳,安永奉 영남대학교 공업기술연구소 1985 연구보고 Vol.13 No.2

The effects of ball-mill time on the soild state reaction in the system BaCO₃-Fe₂O₃and the magnetic properties of Ba-ferrite (FaFe₁₂??) have been studied. BaCO₃-Fe₂O₃mixturess were prepared by ball-milling for varying lengths of time; 5, 15, 30, 80 and 200 hours. Techniques employed were thermogravimetry, X-ray diffraction analysis, scanning electron microscopy and B-H curve tracer. It was shown that the aggregation states and superparamagnetic size fractions obtained by increasing ball-mill time have remakable effects on solid state reactions and magnetic properties of Ba-ferrite; i.e. the coercive force and remanent magnetization increased with increasing ball-mill time going through a maximum at around 15 hours ball-mill time.

부분수산법에 의한 PZT 세라믹스의 제작 및 압전특성

남효덕,강성환 嶺南大學校 基礎科學硏究所 1991 基礎科學硏究 Vol.11 No.-

?? (hereafter referred as PZT) powder was prepared by partial oxalate method using ?? powder (hereafter referred as ZTO) and lead nitrate and oxalate powders. The piezoelectric properties of ceramics sintered from the resulting PZT powder at low temperatures were also studied. ZTO powder was derived by hydrothermal processing using both ZrO₂and TiO₂powders at 1100,1200 and 1300℃. The ZTO powder was then dispersed in oxalic acid followed by the addition of lead nitrate to provide intimate homegeneous mixing of lead ions around each ZTO particle. The presence of single perovskite phase of PZT powder which was calcined about 710℃ was revealed from the X-ray diffraction pattern. From particle size analysis, the average particle size produced by partial oxalate method was smaller than that by the conventional mixed oxide technique. The resulting PZT powder was sintered to dense body having the density of 7.9g/㎤ above 1100℃, which is somewhat lower than the sintering temperature by the conventional techniques. The dielectric and piezoelectric properties of PZT ceramics sintered from the powder prepared by partial oxalate method were measured, and the results showed improved properties over the conventional solid-state reaction tchnique. In particular, the powder prepared from the ZTO calcined at 1100℃ proved to be the best among the powders investigated in this study.

Mn을 첨가한 (Pb₁_xSrx) (Zr₁_zTiz)O₃계 압전세라믹스의 전기적 특성

남효덕,김응수 嶺南大學校 工業技術硏究所 1988 연구보고 Vol.16 No.2

(Pb₁_x Srx) (Zr?? Tj??)O₃piezoelectric ceramics were fabricated by the ordinary firing method at the temperature range of 1180~1240℃. The effects of the additive MnCO₃and substituent SrCO₃on the sintering and the electrical properties were investigated. The experimental results indicated that the specimens containing 5mol% SrCO₃and 0.6wt% MnCO₃, sintered at 1220℃, showed the best piezoectrical and dielectrical characteristics. Electromechanical coupling coefficient (kp) increased while the Curie temperature(Tc) decreased with increasing of SrCO₃ amount. Additive MnCO₃was shown to contribute to improve mechanical quality factor(Qm), which is one of important characteristics of piezoelectric ceramics.

전도성 충전물을 이용한 도전성 판재의 제조기술 개발

남효덕,이현석,박봉국 嶺南大學校 工業技術硏究所 2003 工業技術硏究所論文集 Vol.31 No.1

As an effort of developing efficient materials for shielding EM waves, a fibrous sheet for shielding EMI is developed by adding conductive filler to fibrous sheet during hardening process. From the aspect that the conductivity is inversely proportional to the square value of the length of added material, the conductive filler is fabricated by electroless plating with nickel and copper to the polymer textile power which has very high anisotropy. The conducting sheet was also fabricated by applying proper amount of highly efficient conductive filler to the fibrous sheet. The results obtained by measuring the shielding characteristics of 1㎒∼1㎓ frequency range showed the EMI suppressing effectiveness of 10∼20 ㏈.

유한요소법과 경계요소법을 이용한 음향트랜스듀서의 음향방사 특성 해석

남효덕,서희돈,고영준,장호경 嶺南大學校 工業技術硏究所 2001 工業技術硏究所論文集 Vol.29 No.2

The acoustic characteristics of the acoustic transducer was simulated by using the finite element method(FEM) and boundary element method(BEM). After meshing the inside closed boundary of the acoustic transducer, pressure gradients, isobaric lines, directivity characteristics and acoustic impedances were calculated by using the FEM and characteristics of 3-D free field sound pressure, directivity characteristics and radiation efficiency were simulated by using the BEM. It was shown that the usefulness of the design and the fabrication for the acoustic transducer from the results.

옥소화합물 CTR의 제작 및 그 전기적 특성

남효덕 嶺南大學校 工業技術硏究所 1981 연구보고 Vol.9 No.2

(Ag ₁-??Cu??)₂Cdl₄(0 ≤x≤1) critical temperatue resistances (CTR) were fabricated by sintering the mixture of Cul, AgI and CdI₂ at 260℃ for one hour. The electerical characteristics of the CTR were also investigated. The x-dependent critical temperature for the CTR was between 30 and 60℃ and Φ value of the fabricated CTR was about 3.4 for x=0.5 sample.

Ba-ferrite의 생성 및 자기적 성질에 미치는 Bi₂O₃첨가효과

남효덕 嶺南大學校 工業技術硏究所 1982 연구보고 Vol.10 No.1

The effects of additives Bi₂O₃on the solid state reaction for the system BaCO₃-Fe₂O₃and magnetic properties of Ba-ferrites. Techniques employed were thermogravimetry, X-ray diffraction analysis, scanning electron microscopy and B-H curvetracer. It was found that small additions of Bi₂O₃lowered the optimum sintering temperature and greatly improved megnetic properties of Ba-ferrites. It is estimated that the higher remanent magnetization and coercive force is due to the slower crystal growth at the lower sintering temperature. During firing, a large part ofthe Bi₂O₃volatilized, as was established from weight loss.

UHF 대역의 휴대전화 착신기능 제한 시스템의 설계 및 제작

남효덕,김종석,김병철 嶺南大學校 工業技術硏究所 2001 工業技術硏究所論文集 Vol.29 No.2

As demands grow for restricting use of cellular phones by attendants in the public places such as conference rooms, churches, and playhouses etc., a call blocking system against UHF band cellular signals is developed for other attendants who do not want to be disturbed by the phone rings. The idea of preventing a cellular phone from ringing was developed from the fact that the system radiates interferent signals having 0.1 to 0.05 watts of CW wave, makes it possible to increase the error rates of output signal of PSK modem, and hence makes the cellular phone Impossible to receive the right call signal. The system designed in this study was set up and tested in the several public places and found itself very effective.

X선 촬영인자의 변화에 따른 영상의 주관적인 화질 평가

권덕문,박명환,김성환,박종삼,이준일,남효덕 대구보건대학 2001 대구보건대학 論文集 Vol.21 No.-

In this study, visual recognition of X-ray images were estimated using hawlet charts. The resolution has achieved excellent result when densities of film were 1.0~1.5. The more thickness of object was increase, the more the resolution was decrease, because scattered X-ray were increased. The more distance of object to film was increase, the more the resolution was decrease, because groedel effect. The more focal spot size was increase, the more resolution was decrease, because unsharpness was increase. The more field size was increase and grid ratio was decrease, the more resolution was decrease, because scattered X-ray were increase. As a result, we could to improve image quality by determination of resolution according to Radiography parameters. And, we proved that hawlet charts were useful for estimate of image quality and set up x-ray radiography.

Star Test Pattern을 이용한 X-선관 등가초점의 측정

권덕문,박종삼,이준일,남효덕 대구보건대학 1999 대구보건대학 論文集 Vol.19 No.-

In this study, equivalent focal spot sizes of X-ray tube were measured by star test pattern. As a result, the focal size was proportional to tube current and inversely proportional to tube voltage. Although tube current was increased the focal size was almost constant, when tube voltage is large than 80kVp. And, focal size was more increased at high tube current or low tube voltage. Resolution was more excellent if focal size was small. We confirmed what the radiation energy was distributed as edge band distribution in focus, because the intensity of energy at side was larger than in center.