세라믹/금속 접합체의 응력해석에 있어서 유한요소법의 이용

정영수 가야대학교 세라믹연구소 1999 가야대학교 논문집 Vol.8 No.-

유한요소법은 금속과 세라믹과의 접합체의 응력분포를 계산하는데 있어서 유효한 방법이고 많이 이용되고 있다. 그러나 접합체에서는 탄성해석시 접합면의 corner 부근에 응력특이점이 존재하기 때문에 응력의 절대값을 구할 수 없다는 단점이 있다. 또한 금속의 소성변형을 고려한 탄소성해석에 있어서는 소성변형에 대한 상세한 data가 부족하기 때문에 한계가 있다. 본연구에서는 이러한 문제를 해결하기 위한 방법을 제시하기 위하여 실험을 통한 열응력의 크기측정, 비교분석과 유한요소법에 의한 계산을 통화여 정확한 응력분포와 응력의 절대값을 구하는 방법을 제시하고자 하였다.

sic에 대한 Brazing Alloy의 Wetting에 미치는 Ti의 영향에 대한 고찰

정영수 가야대학교 세라믹연구소 1999 가야대학교 논문집 Vol.8 No.-

세라믹을 brazing alloy를 이용하여 접합하고자 할 때 brazing alloy의 세라믹에 대한 wetting이 필요하다. Wettability가 좋다는 것은 그만큼 강한 결합을 의미하며 이를 위하여 기존 금속용 brazing alloy에 Ti 등의 활금속을 첨가하여야 한다. 그러면 wettability가 크게 개선되면서 강건한 접합체를 형성할 수 있게 된다. 본 연구에서는 Ti에 의한 wettability 개선효과를 실험으로 확인하고 이에 대한 해석을 위하여 brazing alloy의 Ti첨가에 따른 표면에너지의 변화를 이론적으로 에측하고자 하였다. 또한 Ti가 첨가된 brazing alloy와 세라믹과의 계면에서의 Ti거동과 계면에너지의 변화에 대해서도 model을 만들어 계산을 시도하고 실험결과와 비교하였다.

코발트-아연 페라이트의 결정구조와 이온분포

신형섭 가야대학교 세라믹연구소 1999 가야대학교 논문집 Vol.8 No.-

Co-Zn spinel ferrites (Co₁?Zn?Fe₂O₄x=0~1) were synthesized by the coprecipitation-oxidation method. The crystal structures, cation distributions snd ion sizes of ferrites were studied by X-ray diffraction Rietveld analysis snd magnetic property. The lattice parameters of Co-Zn spinel freeites nonlinearly increased becauses. Up to Zn:Co=1:1 in the Co-Zn spinel ferrites, the cobalt substitute primarily the octahedral sites. Beyond that the cobalt seems to go intothe tetrahedral sites as well.

Preparation of Spherical Fine Alumina Powders by Vesicle Methods.

Kim,Chang-Hyun 가야대학교 세라믹연구소 1999 가야대학교 논문집 Vol.8 No.-

Transmittance Electron Microscopy (TEM) was to monitor the response of vesicle size and the agglomeration between vesicle with a variety of expeimental parameters. Vesicle sizes decreased as the conication temperature increased and the concerntration of phosphathidylcholine(pc) increased. Abonormal vesicle growth by the intervesicle agglometeration and coalescence observed at 0.2M of aluminum ion concentration. We jeve synthesized fine powder ofmonodispersed spherical alumina and investigated the thermal effect of phosphidylcholine forming vesicles on the characteristics of synthesized fine particles of alumina. It has been concipitates that pc thermal behavior restraining mass transport between precipitates up to 900℃. The effect leads to produce fine powder of monodispersed spherical alumina with prmary particles of 50nm in size at 1100℃.

기액반응법을 이용한 구형 미세 지르코니아 분체 합성시 농도에 대한 영향

김창현 가야대학교 세라믹연구소 1999 가야대학교 논문집 Vol.8 No.-

Zirconia has been used as refractories in glass-melting and steel-fabrication area due to its refractoriness and chemical stability. stability. recently, it is drawing a concern on its new applicability as a new ceramics in various areas. in electronics, it has been practically used as oxygen sensor in measuring owygen contents in molten steel and combustion systems etc. its application for structural use is also being extended. In this experiment, zirconia powder was preared by gas-liquid phase reaction, a kind of precipitation method. in the case of using this method, the shape and size distribytion of precipitated powders were affected with the mass of nitrogen gas used as a carrier gas and the pH value and the concentration of solution. In this study, I examined the effect of concentration of solution on the particle size, particle size distribution, and agglomerating degree. The glassy phase was obtained as concentrations increases. The change of surface chage is acaused by the interparticular agglomeration. The precipitate was redissolved into the wateromn the surface of precipitate itself and through the polymerization, it agglomerated. It is widely spread that obtained glassy phase have a influence on the propert of powder. But it has not been reported on the caange of powder properties depending on the condition of glassy phgase formation. After decomposition for 4hors at 700℃, ,mean diameter of particles increases, deviation of composition from intial composition due to the loss of unreacted metal ions during precipitation reaction is diminished and agglomerated powder appear in overall range of concentration.

PZT의 압전 및 열화특성

손정호 가야대학교 세라믹연구소 1999 가야대학교 논문집 Vol.8 No.-

The M-site substituted (Pb??M??)(Zr??Ti??)O₃ (M=Pb, Ba, Sr, Ca) system was prepared and its dielectric and degradation phenomena in piezoelectric characteristics were investigated. The single phase of perovskite (Pb??M??)(Zr??Ti??)O₃ compouynds were synthesized after calcining at 850℃ 4 hours and sintering at 1200?? for 2 hours. The sintered density of the samples was about 7.5g/㎤. The solid solution limits of Ba and Sr in (Pb??-Ba??)(Zr??Ti??)O?? and (Pb?-Sr?)(Zr?-Ti?)O₃ were X=0.2, and that of Ca in (Pb?Ca?)(Zr?-Ti?)O? was x=0.1. (Pb?Ba?)(Zr?Ti?)O₃ and (Pb?Sr?)(Zr?Ti?)O? showed relatively stable characteristics in degradation phenomena and piezoelectric characteristics were improved by the M-site substitution.

(LaSm)Nb₃O 계의 유전이상

손정호 가야대학교 세라믹연구소 1999 가야대학교 논문집 Vol.8 No.-

The peovskite type unit cell of (La₁??Sm??)Nb₃O?? contains two oxygen octahedra of equal size. One of the A-site is partially occupied by 2/3 of the La?? ions, the other is vacancy. The Nb?ions are displaced from the center of the octsahedra due to ordered vacancy layer of A-site. Dielectric anomaly behavior and phase transition temperature variation were investigated for (La₁??Sm??)Nb₃O??. The jump of some 2/3 La?? ions leads to increase the moving paths due to the generation of new vacancies at the middle empty sites and thus this result is comfirmed to clear the dielectric anomaly.

XRD 및 Mossbauer 분광 분석에 의한 N₁Cd-Fe₂O₄ ferrite계 연구

이상훈 가야대학교 세라믹연구소 1999 가야대학교 논문집 Vol.8 No.-

Ni₁??Cd?-Fe₂O₄(0.0≤x≤1.0) ferrite의 구조와 미시적 성질 변호를 XRD 와 M?ssbauer 분광분석법을 이용해 연구하였다. 시료는 건식 세라믹 소결법을 이용해 제조되었으며 XRD 회절 패턴 분석결과 격자상수는 Cd 함량 증가에 따라 8.344Å에서 8.179Å로 증가하였고 모든 시료는 단일 spinel 상을 보였다. 이성질체 이동치는 Cd ion의 함량증가와 무관하게 뚜렸한 변화를 보이지 않았으며 핵 사중극자 분열치는 x≥6.0인 조성에서 B-site에서만 큰값을 보였다. 초미세 자기장은 x≤0.4인 준강자성 spectrum 에서 Cd 함량 증가에 따라 B-site 는 518kOe에서 360kOe로 감소하고 A-site는 486kOe에서 340kOe로 감소 하였다.

TeO₂-Pbo와 TeO₂-MoO₃tellurite 유리에 대한 구조특성-IR과 Raman 스펙트라

이상기 가야대학교 세라믹연구소 1999 가야대학교 논문집 Vol.8 No.-

The properties of the tellurite glasses such as glass transition temperature (T??), infrared spectrum and Raman spectrum were measured TeO₂and TeO₂-M??O??(PbO, MoO₃) glasses with a second component selected from typical modifier and glass former. IR and Raman spectra revealed that the addition of PbO increased the fraction of the TeO₃trigonal pyramid structural unit with non-bridging oxygens, and Tg values decreased down to 270℃ with increasing the cintents of PbO up to 25mol%. On the other hand, the addition of MoO₃ did not change the fraction of the from TeO₄trigonal bipyramid to TeO₃trigonal pyramid and T?values were increase up to 320℃ with increasing the contents of MoO₃up to 25mol%.

Pb(Mn⅓Sb⅔)O₃-PZT계의 미세구조 및 압전특성

손정호 가야대학교 세라믹연구소 1999 가야대학교 논문집 Vol.8 No.-

In this study, perovskite single phase of Pb(Mn??Sb??)O₃-PZT cermics without pyrochlore phase was successfully synthesized, and the dielex\ctric and Piezoelectric properities of the ceramics as a function of Zr/Ti were examined. In the single perovskite Pb[(Mn??Sb??)??Zr??Ti₁]O₃system, the morphotropic phase boundary was Pb[(Mn??Sb??)??Zr??Ti₁??]O₃ where the content of Zr=0.475. The electro-mechanical coupling factor k??, mechanical quality factor Q? and the dielectric cinstant of the composition were 0.59, 1600, and 1150, respectively. When the samples are sintered at low temperature of 1000℃, the extra diffraction peak of X-ray was not observed, which implies that the low temperature sintering for multi layer piezoelectric transformer is highly applicable.