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LPS-SiC 세라믹스 제조시 소결조제 SiO₂의 영향
정헌채(Hun-Chae Jung),윤한기(Han-Ki Yoon),박준수(Jun-Soo Park),A.Kohyama 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
Monolithic liquid phase sintered SiC (LPS-SiC) was made by hot pressing method with nano-SiC powder whose a particle size is 30nm and less on the average. Alumina (Al₂O₃), yttria (Y₂O₃) and silica (SiO₂) were used for sintering additives. To investigate effects of SiO₂, Al₂O₃/Y₂O₃ composition was fixed and then ratios of SiO₂ were changed as four kinds. Materials have been sintered for 1 hour at 1760 ℃, 1780 ℃ and 1800 ℃ under the pressure of 20MPa. The system of sintering additives which affects a property of sintering as well as the influence depending on compositions of sintering additives were investigated by measurement of density, mechanical properties such as flexural strength elastic modulus were investigated to make sure of the optimum condition which is about matrix of SiCf/SiC composites. Sintered density, flexural strength of fabricated LPS - SiC increased with increasing the sintering temperature. Particularly, relative density of sintered body at 1800 ℃ with the less content of SiO₂, specimen of AYSa-1800 was 95 %. Also, flexural strength and elastic modulus were 587.5 ㎫ and 216.3 ㎬, respectively. It is superior values than that of LPS-SiC with Al₂O₃-Y₂O₃ system.
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LPS-SiC 세라믹스 제조특성에 미치는 소결온도의 영향
박이현(Yi-Hyun Park),정헌채(Hun-Chae Jung),김동현(Dong-Hyun Kim),윤한기(Han-Ki Yoon),A. Kohyama 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
SiC materials have been extensively studied for high temperature components in advanced energy system and advanced gas turbine. However, the brittle characteristics of SiC such as low fracture toughness and low strain-to fracture still impose a severe limitation on practical applications of SiC materials. For these reasons, SiC<SUB>f</SUB>/SiC composites can be considered as a promising for various structural materials, because of their good fracture toughness compared with monolithic SiC ceramics. But, high temperature and pressure lead to the degradation of the reinforcing fiber during the hot pressing. Therefore, reduction of sintering temperature and pressure is key requirements for the fabrication of SiC<SUB>f</SUB>/SiC composites by hot pressing method. In the present work, Monolithic LPS-SiC was fabricated by hot pressing method in Ar atmosphere at 1760 ℃, 1780 ℃, 1800 ℃ and 1820 ℃ under 20 MPa using Al₂O₃ - Y₂O₃ system as sintering additives in order to low sintering temperature. The starting powder was high purity β-SiC nano-powder with an average particle size of 30 ㎚. Monolithic LPS-SiC was evaluated in terms of sintering density, micro-structure, flexural strength, elastic modulus and so on. Sintered density, flexural strength and elastic modulus of fabricated LPS-SiC increased with increasing the sintering temperature. In the micro-structure of this specimen, it was found that grain of sintered body was grown from 30 ㎚ to 200 ㎚.
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나노인덴테이션기법을 이용한 ZnO/Si 박막의 기계적 특성
윤한기(Han-Ki Yoon),정헌채(Hun-Chae Jung),손종윤(Jong-Yoon Sohn),유윤식(Yun-Sik Yu) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
Recently there has been a great world-wide interest in developing and characterizing new nano-structured materials. These newly developed materials are often prepared in limited quantities and shapes unsuitable for the extensive mechanical testing. The development of depth sensing indentation methods have introduced the advantage of load and depth measurement during the indentation cycle. In the present work, ZnO thin films are prepared on Si(111), Si(100) substrates at different temperatures by pulsed laser deposition(PLD) method. Because the potential energy in c-axis is low, the films always show c-axis orientation at the optimized conditions in spite of the different substrates. Thin films are investigated by X-ray diffractometer and Nano indentation equipment. From these measurements it is possible to get elastic modulus and hardness of ZnO thin films on Si substrates.
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LPS - SiC 세라믹스의 굽힘강도 특성에 미치는 미시조직 영향
윤한기(HAN-KI YOON),정헌채(HUN-CHAE JUNG) 한국해양공학회 2006 韓國海洋工學會誌 Vol.20 No.5
In this study, monolithic liquid phase sintered SiC (LPS-SiC) was made by the hot pressing method with nano-SiC powder, whose particle size is 30 ㎚ and less on the average. Alumina (Al₂O₃), yttria (Y₂O₃), and silica (S<SUB>i</SUB>O₂) were used for sintering additives. To investigate the effects of S<SUB>i</SUB>O₂, the Al₂O₃/Y₂O₃ composition was fixed and the ratio of S<SUB>i</SUB>O₂ was changed, with seven different ratios tested. And to investigate the effects of the sintering temperature, the sintering temperature was changed, with 1760℃, 1780℃, and 1800℃ being used with a S<SUB>i</SUB>O₂ ratio of 3 wt%. The materials were sintered for 1 hour at 1760℃, 1780℃ and 1800℃ under a pressure of 20 ㎫. The effects on sintering from the sintering system used, as well as from the composition of the sintering additives, were investigated by density measurements. Mechanical properties, such as flexural strength, were investigated to ensure the optimum conditions for a matrix of SiCf/SiC composites. Sintered densityand the flexural strength of fabricated LPS-SiC increased with an increase in sintering temperature. Particularly, the relative density of a sintered body at 1800℃ with a non-content of S<SUB>i</SUB>O₂, a specimen of AYS0-1800, was 95%. Also, flexural strength was about 750㎫.
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윤한기,정헌채,김부안 동의대학교 산업기술개발연구소 2005 産業技術硏究誌 Vol.19 No.-
Monolithic Liquid Phase Sintered SiC (LPS-SiC) was fabricated by hot pressing method under 20 MPa using sintering additives at different temperature such as 1760 ℃, 1780 ℃, 1800 ℃ and 1820 ℃. The starting powder was high purity 13-SiC nano-powder with an average particle size of 30 nm. Compositionsof sintering additives were Al_(2)O_(3) Y_(2)O_(3) = 60.7 and 1.5 (wt%). Monolithic LPS-SiC was evaluated in terms of sintering density, hardness and fracture toughness through indentation fracture method by the Vickers hardness tester. Sintered density, hardness and fracture toughness of fabricated LPS-SiC increased with increasing the sintering temperature. It is higher value than that of fabricated SiC by the chemical vapor deposition method.
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