SiC/C 경사기능재료의 열충격 시험과 열응력 모사

김유택,이성철,최근혁 한국결정성장학회 1998 韓國結晶成長學會誌 Vol.8 No.4

$SiCl_4/C_3H_8/H_2$계를 사용하여 흑연기판 위에 순수한 SiC층과 SiC/C FGM층을 CVD법에 의해 증착한 후 thermal shock 시험을 통하여 두 시편의 열적 성질을 조사하였다. Thermal shock 시험시 두가지 시편 내부의 이론적인 열응력 차이를 알아보기 위해 상용프로그램을 이용하여 시편내의 온도분포, 열응력 분포를 계산하였다. SiC/C FGM층을 증착한 시편이 순수한 SiC층을 증착한 시편보다 계산상으로 경계면에서 우수한 열응력 완화효과를 나타내는 것으로 판단되었고 실험적으로로 FGM 시편의 경우 $\Delta$T=1600K의 열충격에도 견딜수 있는 것을 확인하여 이론과 실험이 일치하는 것을 입증하였다. Monolithic SiC and SiC/C FGM layers were deposited on the graphite substrates by the CVD method and their thermal properties of the two specimens were investigated by thermal shock test for comparison. Temperature profiles and thermal stress distributions on thermal shock test were calculated by a commercially used computer program to see the thermal stress differences inside of two specimens. The specimens coated with FGM were expected to show a efficient relaxation of thermal stresses at the interface and they were not cracked under the actual $\Delta$T=1600 K experimental condition. This result proved that the experimental results were well accorded with the expectation from the theoretical calculations.

Recycling of dust wastes as lightweight aggregates

김유택,J.H. Kim,K.G. Lee,강승구 한양대학교 세라믹연구소 2005 Journal of Ceramic Processing Research Vol.6 No.2

Various kinds of industrial dust wastes were recycled by a wet ceramic process. Compounding various dusts gave allowed us compositional variation of dust wastes which originated from various places and conditions. One of the main problems for recycling wastes is caused by compositional variations. Success in recycling depends on how to control compositions and maintain the allowed purity level in the wastes. Grouping of dust wastes into three categories and compounding were introduced to raw material preparation processes for the successful recycling of various dusts. Pretreatment processes were also important to stabilize heavy metals in the raw materials. These processes consist of ion exchange, control of electrolyte concentration and pH etc. After these processes, industrial dust wastes were turned into safe, ecological construction materials such as bricks or lightweight aggregates by a final sintering process. Various kinds of industrial dust wastes were recycled by a wet ceramic process. Compounding various dusts gave allowed us compositional variation of dust wastes which originated from various places and conditions. One of the main problems for recycling wastes is caused by compositional variations. Success in recycling depends on how to control compositions and maintain the allowed purity level in the wastes. Grouping of dust wastes into three categories and compounding were introduced to raw material preparation processes for the successful recycling of various dusts. Pretreatment processes were also important to stabilize heavy metals in the raw materials. These processes consist of ion exchange, control of electrolyte concentration and pH etc. After these processes, industrial dust wastes were turned into safe, ecological construction materials such as bricks or lightweight aggregates by a final sintering process.

경제개발(經濟開發) 5개년계획(個年計劃)을 성공(咸功)시키는 길

김유택,Kim, Yu-Taek 한국과학기술정보연구원 과학기술정보센터 1963 Journal of Information Science Theory and Practice Vol.1 No.1

재활용 폐자원에 따른 지오폴리머의 특성변화 연구

김유택,김현정,장창섭,Kim, Yoo-Teak,Kim, Hyun-Jung,Jang, Chang-Sub 한국결정성장학회 2012 한국결정성장학회지 Vol.22 No.3

본 연구는 알칼리 활성화제로 NaOH와 물유리를 사용하고 리젝트애쉬와 고로슬래그를 혼합하여 지오폴리머를 제조하였다. 리젝트애쉬와 고로슬래그의 치환율과 물유리와 NaOH의 농도에 따른 압축강도를 측정하였다. 압축강도 측정결과로는 알칼리 활성화제로 NaOH 1 wt%, 물유리 3 wt%와 전량 고로슬래그를 사용한 경우 재령 28일차 강도가 38.91 MPa의 성능을 나타내었다. 압축강도 증진의 중요한 요인은 알칼리 활성화제의 비율과 리젝트애쉬와 고로슬래그의 치환율에 의한 것이었다. In this study, geopolymer was prepared with reject ash and blast furnace slag using NaOH as an alkali activator and water glass. The aim of this study was to investigate the compressive strength variation according to the contents of NaOH and water glass and replacement ratio of reject ash (RA) and blast furnace slag (BS). The compressive strength measured after 28 days was 38.91 MPa for the geopolymer which consist of 100 % of BS with 1 wt% NaOH and 3 wt% water glass. The major factor for improving compressive strength was the alkali activator proportion and the replacement ratio of RA and BS.

Effect of addition of As-received IGCC slag in making geopolymer

김유택,채태성 한양대학교 세라믹연구소 2018 Journal of Ceramic Processing Research Vol.19 No.5

It is a known fact that the cement production is responsible for almost 5% of total worldwide CO2 emission, the primary factoraffecting global warming. Geopolymers are valuable as ordinary Portland cement (OPC) substitutes because geopolymersrelease 80% less CO2 than OPC and have mechanical properties sufficiently similar to those of OPC. Therefore, geopolymershave proven attractive to eco-friendly construction industries. Geopolymers can be fabricated from aluminum silicatematerials with alkali activators such as fly ash, blast furnace slag, and so on. Integrated gasification combined cycle (IGCC)slag has been used for fabricating geopolymers. In general, IGCC slag geopolymers are fabricated with finely ground andsieved (<128 mesh) IGCC slag. The grinding process of as-received IGCC slag is one of the main costs in geopolymerproduction. Therefore, the idea of using as-received IGCC slag (before grinding the IGCC slag) as aggregates in thegeopolymer matrix was introduced to reduce production cost as well as to enhance compressive strength. As-received IGCCslag (0, 10, 20, 30, 40 wt%) was added in the geopolymer mixing process and the mixtures were compared. The compressivestrength of geopolymers with an addition of 10 wt% as-received IGCC slag increased by 19.84% compared to that with noadditional as-received IGCC slag and reached up to 41.20MPa. The enhancement of compressive strength is caused by asreceivedIGCC slag acting as aggregates in the geopolymer matrix like aggregates in concrete. The density of geopolymersslightly increased to 2.1-2.2 g/cm3 with increasing slag addition. Therefore, it is concluded that a small addition of as-receivedIGCC slag into the geopolymer can increase compressive strength and decrease the total cost of the product. Moreover, thedirect use of as-received IGCC slag may contribute to environment protection by reducing process time and CO2 emission.

폐자원의 분류/선별을 통한 지오폴리머 특성 개선 연구

김유택,김현정,장창섭,Kim, Yooteak,Kim, Hyunjung,Jang, Changsub 한국결정성장학회 2012 韓國結晶成長學會誌 Vol.22 No.6

본 연구에서는 비산회를 자력선별한 후 알칼리 활성화제인 수산화나트륨과 물유리를 사용하여 지오폴리머를 제조하였다. 자력 선별전의 원료, 자력 선별된 두 가지 종류의 자력 및 비자력 원료를 사용한 지오폴리머 시편에 대한 압축강도를 측정하여 비교하였다. 비자력 비산회 원료를 사용한 지오폴리머 시편에서 가장 좋은 압축강도가 나올 것으로 예상하였으나, 실제로는 자력선별하지 않은 원재료 비산회와 고로슬래그를 사용한 경우에 재령 28일차 압축강도가 27.54 MPa로 가장 우수하였다. 이 결과에서, 자력선별 후 CaO 성분 농축으로 수화반응 증진에 의한 강도발현 증진 효과 보다는 자력선별에 의해 지오폴리머 형성반응에 필요한 실리카와 알루미나 성분이 오히려 줄어들어 지오폴리머 축합반응이 감소하여 오히려 압축강도 측면에서는 물성 개선효과가 없는 것으로 판명되었다. Geopolymer was made using magnetic separation fly ash with NaOH(Sodium Hydroxide) and the water glass as alkali activators in this study. Compressive strength of geopolymers ceramics was measured and analyzed according to the type of materials. Under the conditions of fly ash without magnetic separation and 28 day curing after molding, the compressive strength of the geopolymer reached up to 28 MPa.

소형 스크류식 원심펌프의 기액 이상류 특성

김유택,다나카카즈히로,이영호,Kim, You-Taek,Tanaka, Kazuhiro,Lee, Young-Ho 한국유체기계학회 1999 한국유체기계학회 논문집 Vol.2 No.4

A screw-type centrifugal pump was manufactured to carry primarily solids and its impeller had a wide flow passage. However, there was an effect on the flow passage shape on delay of the choke due to entrained air not being clarified yet. Moreover, because its impeller has a particular shape, only few studies have tried to clarify the pump performance and details of internal flow pattern of that pump. For this reason, we carried out the pump performance experiment under air-water two-phase flow condition with different impeller tip clearances, pump rotational speeds and void fractions by using a small screw-type centrifugal pump designed to acquire basic data. In a general centrifugal pump, it was reported that there was a loss of pump head from single-phase flow to the choke due to air entrainment near the best efficiency point being large. However, the loss near the best efficient point in a screw-type centrifugal pump became less than that in a general centrifugal pump.

공기흡입에 의한 스크류식 원심펌프의 양수불능 특성에 관한 연구

김유택 한국유체기계학회 2003 한국유체기계학회 논문집 Vol.6 No.3

석탄회 및 용융폐기물 슬래그에 소량의 알칼리 활성화제를 첨가한 무시멘트 모르타르의 특성

김유택,이경우,Kim, Yootaek,Lee, Kyongwoo 한국결정성장학회 2015 韓國結晶成長學會誌 Vol.25 No.6

현재 전 세계적으로 지구온난화의 주범인 $CO_2$ 저감을 위한 노력을 하고 있으며, 산업발전에 필요한 화력발전 등에서 발생한 부산물을 재활용하는 방안이 시급하다. 따라서 본 연구는 산업부산물인 비산재와 폐기물 슬래그를 이용하여 모르타르 경화체를 제작하였으며 알칼리 활성화제 첨가에 따른 물성을 비교하기 위해 비교적 낮은 농도인 3 M의 NaOH solution을 사용하였고, 이 경화체에 초임계 이산화탄소 조건($40^{\circ}C$, $80kgf/cm^2$ pressure, 60 min)에서 탄산화를 통하여 $CO_2$를 경화 체내에 안정적으로 고정화 시켜 이에 따른 물성을 평가하였다. 탄산화 인자인 CaO의 함량이 많을수록 탄산화율은 높게 나타났으며, 탄산화 후 무게변화율이 최대 약 12 % 증가하였다. 탄산화 후 압축강도는 전과 비슷한 수준이었으며, 이를 통해 탄산화를 통해 $CO_2$를 안정하게 고정화시킨 친환경 소재에 적용 가능성을 확인할 수 있었다. 또한 탄산화 반응 후에 생성되는 $H_2O$로 인해 추가적인 양생을 통해 장기적인 관점에서 탄산화를 통해 물성향상 또한 기대해 볼 수 있을 것으로 생각된다. Recently the world wide efforts reduce occurrence of $CO_2$; global warming main reason. The aim of this study is to improve recycling rate of the fly ash (FA) and fused waste slag (FWS) from the power plant and to carbonate under supercritical condition ($40^{\circ}C$, $80kgf/cm^2$ pressure, 60 min) for $CO_2$ fixation. Specimens of mortar with various mixing ratios of FA, FWS (from 100:0 to 20:80 in 5 steps of 20 % reduction each time), distilled water and 3 M NaOH alkali activators were prepared. As a result, the proportion of weight change ratio increases with CaO content, to 12 % after carbonation under the supercritical condition. There is difference of compressive strength between the carbonated and the alkali activator mortar specimens. The stabilization of $CO_2$ fixation through carbonation which could confirm the applicability of the eco-friendly materials without loss of compressive strength.

세라믹 표면 분석을 위한 반사전자현미경(REM) 및 고에너지반사전자회절(RHEED)

김유택 한국세라믹학회 2002 세라미스트 Vol.5 No.3