구조용 세라믹 복합 재료의 기술현황

조원승 대한금속재료학회 1996 대한금속재료학회 학술대회 개요집 Vol.1996 No.0

냉연강판의 강종에 따른 인장변형특성 비교 조사연구

조원승,유연철,이준정,윤주돈 대한금속재료학회 1985 대한금속재료학회 학술대회 개요집 Vol.1985 No.0

AlN/hBN 복합재료의 기계적 성질

조원승,조명우,이재형,안현욱,윤영식 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.8

AlN-BN ceramic composites were fabricated and their mechanical properties were investigated. The relative density of hot-pressed composites decreased with increasing BN content, but over 99% could be obtained with 30 vol% BN in AlN. YAG was formed in the composites and monolithic AlN as a second phase by the reaction between Y2O3, added as sintering aid, and Al2O3. As expected, Vickers hardness and Young's modulus decreased with increasing BN content. The three-point flexural strength also showed similar behavior decreasing from 500 MPa of monolith down to 250 MPa by the addition of 30 vol% BN. However, interestingly, the standard deviation of the strength values decreased significantly as BN was added to AlN. As a result, the Weibull modulus of the AlN-30 vol% BN composite was 21.3, which was extremely high. Fractography and crack path studies revealed that BN platelets induced grain pull-out and crack bridging in a bigger scale during crack propagation. Consequently, fracture toughness increased as more BN was added, reaching 4.5 MPa√m at 40 vol% BN. AlN-BN세라믹 복합재료를 제조하여 이의 기계적 성질을 조사하였다. 소결체의 상대밀도는 h-BN 첨가량의 증가와 더불어 약간 감소하였으나 30 vol% BN 첨가에도 상대밀도 99%를 얻을 수 있었다. Al2O3와 Y2O3와의 반응에 의해 2차상인 YAG상이 생성되었다. 비커스 경도와 영율은 예상대로 BN 양이 증가함에 따라 감소하였다. 3점 굽힘 강도 역시 BN 첨가에 의해 감소하였으며, 30 vol% 첨가는 AlN 단미에 비해 약 50%의 감소를 가져 왔다. 그러나 강도 값의 표준편차는 BN의 첨가로 급격히 작아졌으며, 이에 따라 30 vol% BN을 함유한 복합체의 와이블 계수는 세라믹 재료로는 매우 높은 21.3이 얻어졌다. 매우 거친 복합체의 파단면과 압입균열의 전파 양상은 결정립의 풀아웃 현상에 의한 균열가교의 흔적을 많이 보여주었다. 특히 BN이 많이 첨가될수록 균열가교의 스케일이 커졌으며, 따라서 파괴인성은 BN이 첨가됨에 따라 증가하여 40 vol% BN일 때 4.5 MPa√m로서 AlN 단미의 2배가 넘었다.. AlN-BN 복합체의 높은 와이블 계수는 강도가 세라믹스에서의 일반적인 결함보다는 판상의 BN입자 크기와 양에 좌우되며, 또한 BN의 첨가에 따라 파괴인성의 증진하기 때문이었을 것으로 생각된다.

비철금속 합금판재와 냉연강 판재의 인장변형 특성

이준정,조원승,류연철,윤주돈 대한금속재료학회(대한금속학회) 1989 대한금속·재료학회지 Vol.27 No.11

The tensile deformation behavior of copper, brass, nickel silver, phosphorous bronze and cold rolled steel sheets were studied. Based on true stress-true strain curves obtained by the uniaxial tension test at a constant cross-head speed, several constitutive equations were determined utilizing the regression analysis, and applicability of these equations to describe the stress-strain behavior of the non-ferrous alloys was investigated. In the present study, a Modified Voce equation, σ= B - (B - A) exp(-nε-C) is suggested, where a new term "C" has been incorporated into the exponential term of the Voce equation. The Modified Voce equation fits best with the experimental data of the nonferrous alloys and cold rolled steel sheets tested. From detail analysis of the exponential term, the value of "C/n" is found to be equal to the amonunt of pre-strain.

Structure and photoluminescence properties of Ba2TiSi2O8 glass ceramics prepared by aerodynamic levitation

정상교,조원승,이지환 한양대학교 세라믹연구소 2015 Journal of Ceramic Processing Research Vol.16 No.4

Spherical Ba2TiSi2O8 (BTS) and Dy3+-doped BTS glass were prepared by aerodynamic levitation. The glass prepared by aerodynamic levitation demonstrated enhanced glass stability. The crystallization rate of the levitated sample was slower than that of the conventional melt-quenched glass. When the heat treatment temperature was increased, the lattice parameter, a, of the nanocrystalline BTS crystal formed in the glass decreased, but the lattice parameter, c, increased. This was mainly due to the crystallization-induced stress during the crystallization process. Nanocrystallized Dy3+-doped BTS glass exhibited yellow (575 nm), red (669 nm), and blue (484 nm) luminescence. The intensities of all emission peaks increased with increasing heattreatment temperature due to the increased crystallization of BTS crystals. Nanocrystallized BTS glass ceramic prepared by aerodynamic levitation is potentially useful for optical devices, such as visible semiconductor lasers, optical switches, and amplifiers.

방전 플라즈마 소결법에 의한 다공성 알루미나 세라믹스의 제조

신현철,조원승,신승용,김준규,Shin, Hyun-Cheol,Cho, Won-Seung,Shin, Seung-Yong,Kim, Jun-Gyu 한국세라믹학회 2002 한국세라믹학회지 Vol.39 No.12

고강도의 다공성 알루미나 세라믹을 제조하기 위하여, 기공 전구체로서 흑연을 첨가한 후, 방전 플라즈마 소결시의 제조조건을 체계적으로 조사하였다. 제조한 다공성 알루미나에 대하여, 기공률과 기공분포 및 압축강도 등을 조사하였다. 알루미나에 흑연을 10∼50 vol%까지 첨가하여 방전 플라즈마 소결법으로 1차 소결체를 제조한 후, 공기 중 흑연을 열분해시켜 최종적으로 다공성 알루미나를 제조하였다. 그 결과, 소결온도 1000${\circ}C$, 유지시간 3 min, 압력 30 MPa, 승온속도 80${\circ}C$/min, 펄스방법 12:2의 조건에서 높은 기공률의 다공성 소결체를 얻을 수 있었다. 일례로, 10∼30 vol%의 흑연을 첨가하여 제조한 다공성 알루미나의 경우, 약 50∼57%의 높은 기공률을 나타내었다. 또한, 흑연의 함량이 증가함에 따라 개기공률은 지속적으로 증가하였다. 이러한 기공특성과 흑연함량의 상호관계는 클러스터의 수와 크기에 의존하는 퍼콜레이션 모델에 의해 설명될 수 있다. 한편, 10∼30 vol%의 흑연을 첨가하여 제조한 다공성 알루미나의 경우, 55∼200 MPa의 높은 강도값을 나타내었다. 이와 같은 강도의 향상은 펄스전원에 의한 분말 입자간 방전 및 자기발열작용의 영향으로 생각된다. In order to develope the porous alumina ceramics with high strength, the pore characteristics and compressive strength were investigated in terms of relation to the conditions of spark-plasma sintering and the contents of graphite as a pore precursor. Porous alumina bodies were successfully prepared by spark-plasma sintering and burning out graphite in air. High porous bodies were fabricated by sintering at 1000${\circ}C$ for 3 min under a pressure of 30 MPa, heating rate of 80${\circ}C$/min and on-off pulse type of 12:2. For example, alumina bodies prepared by the addition of 10∼30 vol% graphite showed high porosity of 50∼57%. Also, the open porosity increased with graphite content. The relationship between pore characteristics and graphite contents could be explained by percolation model depending on cluster number and size. Porous alumina bodies prepared by the addition of 10∼30 vol% graphite showed the high compressive strength of 55∼200 MPa. This great improvement in strength was considered to be mainly due to the spark-plasma discharges and the self-heating action between particles.

가압연소소결(HPCS)법에 의한 TiC-Cr$_3$C$_2$ 복합체의 제조

오장환,조원승,최상욱,최장민 한국세라믹학회 1998 한국세라믹학회지 Vol.35 No.3

Cr3C2 -dispersed TiC composites were prepared via HPCS(high pressure-self combustion sintering) pro-cess using mixtures of Ti, Cr and a carbon source for the purpose of increasing the facture toughness and sinterability of TiC. In this study the microstructure and properties of the composites were investigated in terms of relation to the carbon source the particle size of Ti and the amount of Cr. It was found that car-bon black was the most effective carbon source among the various carbon sources tested and the reaction was more effective as the particle size of Ti decreased. Among the sintered composites of Ti-C-Cr system the one with 30wt% Cr showed the best physical properties with 0.5% in apparent porosity 98.8% in re-lative density 18.2 GPa in hardness and 4.46 MPa.m1/2 in fracture toughness. In addition it was observed that the lattice constant of TiC decreased gradually with increasing the amount of Cr.

$BaTiO_3$계 세라믹스의 전기적 성질과 미세조직에 미치는 부분산화 Ti 분말 첨가의 영향

김준규,조원승,박경순,Kim, Jun-Gyu,Jo, Won-Seung,Park, Gyeong-Sun 한국재료학회 2000 한국재료학회지 Vol.10 No.10

본 연구에서는 부분산화한 Ti 분말을 첨가한 $BaTiO_3$계 세라믹스를 진공중 $1350^{\circ}C$에서 1 h 소결하여 제조하였다. 공기중 가열후 전기적 성질과 미세조직에 미치는 부분산화한 Ti분말 첨가량의 효과를 조사하였다. 그 결과, 5~7vol%의 부분산화한 Ti분말을 첨가한 반도성 $BaTiO_3$계 세라믹스는 비정항의 변화크기가 $10^5$이상인 우수한 PTCR 특성을 나타내었고 또한, 고다공질과 미립화된 조직을 얻을 수 있었다. 5 vol%의 부분산화한 Ti 분말을 첨가한 $BaTiO_3$계 세라믹스의 상대밀도와 입도는 각각 54%, $1.3\;{\mu\textrm{m}}$였다. 부분산화한 Ti 분말의 첨가에 의한 $BaTiO_3$계 세라믹스의 PTCR 특성 발현은 입계에서의 산소 흡착에 기인하였는데, 이는 Heywang모델로써 설명할 수 있었다. $BaTiO_3$-based ceramics with partially oxidized Ti powders were prepared by sintering at $1350^{\circ}C$ for 1 h in v vacuum, and then heated in air. In this study, the effect of partially oxidized Ti powders on electrical properties and microstructures of $BaTiO_3$-based ceramics was investigated. It was found out that the semiconductive $BaTiO_3$-based ceramics beζame to show excellent PTCR (more than $10^5$) characteristic by adding 5~7 vol% of partially oxidized Ti powder. Also, it was found out that the sintered compact had extremely porous and fine-grained microstructure. The relative density and grain size of sintered compact with 5 vol% of partially oxidized Ti powders were 54% and $1.3\;{\mu\textrm{m}}$, respectively. The mechanism for the development of PTCR characteristic in $BaTiO_3$-based ceramics with partially oxidized Ti powders due to the adsorption of oxygen at grain boundaries, and could be explained, based on Heywang model.

비철금속합금 판재의 가공경화지수에 관한 연구

유연철,조원승 대한금속재료학회 1984 대한금속재료학회 학술대회 개요집 Vol.1984 No.1

다공성 $BaTiO_3$계 세라믹스의 흡착산소와 전기적 성질

김준규,조원승,유연철,박경순,Kim, Jun-Gyu,Jo, Won-Seung,Yu, Yeon-Cheol,Park, Gyeong-Sun 한국재료학회 2001 한국재료학회지 Vol.11 No.10

Electrical properties of porous $BaTiO_3-based$ ceramics were investigated from the viewpoint of adsorbed oxygen. Namely, the effects of heat-treatment temperature ($450-600^{\circ}C$) and measuring atmosphere (oxygen and nitrogen) on the PTCR characteristics of the porous $BaTiO_3-based$ ceramics were investigated. It was found that the PTCR characteristics of the porous $BaTiO_3-based$ ceramics was developed at $\geq$55$0^{\circ}C$, and the magnitude of the PTCR characteristics increased with increasing heat-treatment temperature. It was also found that the magnitude of the PTCR characteristics in the porous $BaTiO_3-based$ ceramics increased in oxygen atmosphere, whereas decreased in nitrogen atmosphere during heating and cooling.