용융염합성법에 의한 $Sr_2(Ta_{1-x}Nb_x)_2O_7$ 세라믹스의 저온소성과 유전특성

남효덕 한국전기전자재료학회 1995 전기전자재료학회지 Vol.8 No.2

Solid solutions Sr$_{2}$(Ta$_{1-x}$ Nb$_{x}$)$_{2}$O$_{7}$, (x=0.0-1.0), composed of strontium tantalate(Tc=-107.deg. C) and strontium-niobate(Tc=1342.deg. C) were prepared by the conventional mixed oxide method and the flux method(molten salt synthesis method). Phase relation, sintering temperature, grain-orientation and dielectric properties for sintered ceramic samples were investigated with different compositions. Both Curie temperature and dielectric constant at Curie temperature were increased, and sintering behavior and the degree of grain-orientation were improved with the increase of Nb content. The single phase Sr$_{2}$(Ta/sib 1-x/Nb$_{x}$)$_{2}$O$_{7}$ powder was synthesized by using the flux method at lower temperatures, and sintering temperature was also reduced by using the flux method-derived powder than using the mixed oxide-derived powder. Sintering characteristics and dielectric properties of the specimens prepared by the flux method were better than those derived through the conventional mixed oxide method.thod.hod.

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 ㏈.

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.

薄板狀水晶振動子의 두께振動

南孝悳 영남이공대학 1977 論文集 Vol.6 No.-

A mathematical theory is presented giving the relations between the clastic constants and the frequencies of piezoelectric vibration for an infinite plate of homogeneous but aeolotropic materail. The results of this calculation is then applied to determine the three mutually orthogonal vibration modes of quartz crystal, one of the above throe modes is generally piezoelectrically excitable.

水晶의 彈性 및 壓電氣係數

南孝悳 영남이공대학 1976 論文集 Vol.5 No.-

The transformation theory of elastic and piezoelectric constants of quartz cystal is presented by the symmetrical properties of 2-fold to x axis and 3-fold to z axis. The results of this calculation will be applied to analysis of various vibrational modes and their mutual interference.

Nd8Fe86-xNbxB6 (x = 0, 1, 2, 3) 초미세립복합상 영구자석의 자기적 특성 연구

남효덕,김성준,박경석,김응찬 한국물리학회 2009 새물리 Vol.58 No.2

A precisely refined Mössbauer study revealed that the intergranular phase that forms between the α-Fe and the Nd2Fe14B phases in NdFeNbB alloys plays a significant role in the magnetic properties. By the addition of Nb into the Nd8Fe86B6 composition, the coercivity was found to be increased by 25% due to a refinement of the average grain size of both the soft and the hard magnetic phases, which decreased from 50 nm for virgin Nd8Fe86B6 to 25 nm for Nd8Fe86B6 alloys. Nb addition was confirmed to stabilize the Nd8Fe86B lattice by preventing thermal vibration of the sites in the Nd8Fe86B lattice at which Fe atoms were replaced by Nb atoms. The enhanced coercivity originated the exchange hardening of the soft and amorphous phases surrounding the hard magnetic Nd8Fe86B crystals. NdFeNbB 합금에서 α-Fe와 Nd2Fe14B상 사이에 형성된 입간결정립이 초미세립 복합상의 자기특성에 큰 영향을 미치고 있음을 정밀한 뫼스바우어 분광학 분석을 통해 조사하였다. Nd2Fe14B+α-Fe 재료에서 얻은 최대자기특성은 Br = 9.791 kG, iHc = 5.565 kOe, 그리고 (BH)max = 14.61 MGOe였고, 이 경우, 각 존재상의 부피분율은 α-Fe; 24.2%, Nd2Fe14B; 53.1%, 입자간; 22.7 %였음을 확인하였다. Nd8Fe86B6 조성에 첨가한 Nb는 평균 입자 크기를 50 nm에서 25 nm로 정제함으로써 보자력을 25% 정도 증가시켰다. 첨가원소 Nb의 역할은 Nd2Fe14B 격자의 열적진동을 억제함으로써 Nd2Fe14B 격자를 안정화시킴은 물론 연자성상 α-Fe의 교환경화를 일으킴으로 인해 보자력을 증가시켰다.

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.

용융염 합성법에 의한 PLZT 세라믹스의 제작과 그 전기적.광학적 특성

남효덕 한국세라믹학회 1986 한국세라믹학회지 Vol.23 No.4

$(Pb_{1-x} La_x)(Zr_{0.65} Ti_{0.35})_{1-x/4}O_3$ (PLZT X/65/35) powders were prepared by molten salt synthesis using NaCl-K Cl and conventional calcining of oxides. The effects of molten salt on formation and charactrization of PLZT powder and on dielectric piezolectric and optical properties of PLZT ceramics were studied, The completed PLZT powder formation in the presence of fused salt was attained at 50-10$0^{\circ}C$ lower temperature than that in solid state reaction and the particle size of the powder made by molten salt synthesis was markedly increased with increasing calcining temperature. The substitution of Na and/or K ions in NaCl-KCl for Pb ion in process of molten salt synthesis was increased with increasing La concentration Z. These substituted Na and/or K ions were identified as the origins of decreasing coupl-ing factor and optical transmittance of PLZT ceramics.

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.

CO₂ Laser의 製作과 特性

南孝悳,朴成培 영남이공대학 1977 論文集 Vol.6 No.-

Gas flowing type CO2 laser of intermediate power was designed and constructed with domestic materials. A. typical laser has 140 cm optical cavity distance and 2cm discharge tube cross section. Two internally mounted cavity mirrors were concave of 200 cm radii. And they were coated with multi-layers of extremely pure gold and ZnS alternatively in this laboratory. The reflectivity of mirrors for the I. R 10.6 micron showed nearly 98 percent which was perfectly suitable for laser. The reliability of all laser materials and gas injection were examined on various lasing conditions such as the gas pressure, mixing ratio of gases and excitation currents, and the conditions were appeared to be satisfactory. Also the output of this laser was estimated about 30 watts for an optimum condition in our experiment. Therefore, we believe that the further improvement of lasing action will attain more powerful laser beam.