• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2003년도 학술대회지
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• pp.91-94
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• 2003

Ceramic femoral heads in the total hip replacement have been developed to reduce the polyethylene liner wear. Alumina and zirconia (3Y-TZP) are using in clinical application worldwide and there are many good test reports. However, alumina has a risk of catastrophic failure, and zirconia has the low temperature degradation in spite of enhanced fracture toughness. Recently, novel zirconia/alumina composite having low temperature degradation-free character and high fracture tough . was developed and it leads the lower wear 3f polyethylene than alumina and zirconia. In the present study, in order to optimise the microstructure of low temperature degradation (LTD)-free zirconia/alumina composite for the best wear resistance of polyethylene, various compositions of (LTD)-free zirconia/alumina composites were fabricated, and the sliding wear of UHMWPE against these novel composites were examined and compared with that against alumina and zirconia ceramics used for total hip joint heads.

• 한국재료학회지
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• 제10권1호
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• pp.83-89
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• 2000

$Si_3N_4$에 2wt% $Al_2O_3$와 6wt% $Y_2O_3$을 첨가한 분말을 가스압 소결 방법으로 시편을 제조하였다. 이때 소결시 시간변화에 따른 공기 중에서 마모 특성을 비교하였다. 소결 시간에 따른 마모 특성의 변화는 기계적 성질, 즉, 파괴인성 등이 영향을 주는 것으로 나타났다. 소결 시간이 길어지면 큰 elongated 입자의 과잉성장에 따라 곡강도 및 파괴인성이 낮아져 이 결과 마모가 증가되었다. 이때 나타난 결과에 의하면 공기 중에서 질화규소의 마모특성에 영향을 주는 인자는 여러 가지 기계적 특성 중에서 파괴인성 및 곡강도가 미치는 영향이 크게 나타났다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.926-931
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• 2002

Although ceramic plates with many micro-hales are used as MCP (Micro-channel plate) for electron amplification, catalytic converters, filters, electrical insulators and thermal conductors in integrated circuits, the drilling of micro-hales in the ceramics is difficult because of their low thermal conductivity, high hardness and brittleness. Therefore, in this work, the machining of ceramic green body fellowed by sintering of green body was employed fur fabricating ceramic plates with many micro-holes. The micro-drilling of alumina green body was performed with diamond abrasive WC drills, and the cutting force w.r.t. drilling times was measured for the determination of toot life. From the investigation of the wear of micro-drill tip w.r.t. drilling times, the wear mechanism of tip during micro-drilling of ceramic green body was suggested.

• Journal of Korean Vacuum Science & Technology
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• 제5권1호
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• pp.1-6
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• 2001

We measured the simultaneous, time-resolved spectra of photon emission, electron emission, and frictional force during the abrasion single crystal MgO with a diamond stylus in vacuum. phE and EE signal can be detected with millisecond resolution during the wear of a single crystal MgO substrate with a diamond stylus. The emissions and wear behavior are strong function of surface condition, load and stylus velocity. Measurement on annealed vs as-received material show that the luminescence is primarily due to deformation, and the electron emission is primarily due to fracture. These emissions provide insight into the processes responsible for catastrophic failure of ceramics in wear applications.

• 한국세라믹학회지
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• 제33권5호
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• pp.479-484
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• 1996

The tribological properties of ceramics are very important in the application to engineering ceramic parts such as mechanical seal slurry valve disc and so on. In this study the effect of graphite addition on the mechanical and tribological properties of RBSC/graphite composites were investigated. The composites were prepared by adding graphite powder to the mixture of SiC powder metallic siliconcarbon black and alumina. Bending strength water absorption friction coefficient the amount of worn out material at a certain time and maximum surface roughness(Rmax) of the prepared composites were measured and crystalline phases were examined with XRD. The composite containing 5 vol% graphite powder showed improved bending strength due to high green density and decreased friction coefficient and wear resistance. The friction coefficient and the wear resistance of the composite were increased by adding graphite powder up to 10 vol% They decreased however as increasing the amount of graphite powder more that 10vol% There was no linear relationship between the tribological properties and bending strength of the composites.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 금형가공 심포지엄
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• pp.245-252
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• 2002

Ultrasonic machining technology has been developed over recent years for the manufacture of cost-effective and quality-assured precision parts for several industrial application such as optics, semiconductors, aerospace, and automobile. Ultrasonic machining process is an efficient and economical means of precision machining of ceramic materials. The process is non-thermal, non-chemical and non-electric md hardly creates changes to the mechanical properties of the brittle materials machined. This paper describes the characteristics of the micro-hole of $Al_2O_3$ by ultrasonic machining with tungsten carbide tool. The effects of various parameters of ultrasonic machining, including abrasives, machining force and pressure, on the material removal rate, hole quality, and tool wear presented and discussed. The ultrasonic Machining of micro-holes in ceramics has been under taken and the machining mechanism in the ultrasonic machining of ceramics based on the fracture-mechanics concept has been analyzed.

• Journal of Advanced Marine Engineering and Technology
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• 제33권7호
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• pp.1026-1033
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• 2009

Fine ceramics have high strength, excellent wear resistance, chemical stability and high strength at high temperature and are receiving attention in various fields such as construction, engineering, aerospace and marine science. Finish machining process is required to obtain precise ceramics components because sintering process necessary for obtaining high strength and high quality ceramics reduces the dimensions of components and precision of shape. But high strength and brittleness of ceramics materials cause difficulty in processing. So a process for obtaining wanted dimensions is studying using high temperature which makes ceramics softened and thermal affected recently. Laser beam is a very useful optical device for these kinds of processes. Laser process such as laser cutting, laser machining, laser heat treatment and laser-assisted machining(LAM) is researching to manufacture practical ceramics components using intense laser source which can cause local softening and damage of workpiece. In this paper, microstructural and mechanical properties of silicon nitride heated are studied as a basic study for researching of ceramics process by laser beam. The surface variation of HIP and SSN-silicon nitride was analyzed with SEM and EDS. A processing at $1,300^{\circ}C$ or above causes N element to combine into $N_2$ gas and the gas busts from surface. These phenomena make bloat, craters and heat defects on the surface of silicon nitride. Also, oxygen content is largely increased to oxidize the surface and it causes changing of phases and reducing of hardness of surface.

• 한국세라믹학회지
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• 제39권6호
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• pp.558-565
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• 2002

국내화력발전소의 비산재를 재활용하고자 결정화유리를 제조하여 그 물리적 특성을 평가하였다. 용융석탄재의 융점을 낮게 하기 위하여 CaO와 유리의 결정화를 유도하기 위하여 TiO$_2$를 첨가하였다. 저융점의 유리를 제조 후, 일단계 열처리 (950~105$0^{\circ}C$에서 30~240분)에 의하여 결정화유리를 제조하였다. 그 결과로, 제조된 결정화유리는 새로운 미세한 결정상(a=7.4480, b=10.2381, c=4.3940 A, $\alpha$=94.9, $\beta$=98.6, ${\gamma}$=108.5$^{\circ}$)을 갖고, 높은 경도(7.1~7.6 GPa)와 고 내마모성을 나타냈다. 이처럼 화력발전소의 비산재와 CaO의 공급원인 조개껍질로 제조된 결정화유리는 자원 재활용, 건축자재로 사용될 수 있는 새로운 응용성을 보여주었다.

• 대한심미치과학회지
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• 제24권2호
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• pp.101-121
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• 2015

지르코니아 폴리크리스탈은 (Y-TZP) 다른 치과용 세라믹에 비해 기계적 강도와 파절저항성이 우수하다. 지르코니아 기반 세라믹은 캐드캠 시스템을 바탕으로 고정식 수복물 제작에 성공적으로 소개되어 왔다. 이는 고정식 수복물을 위한 금속 구조물의 임상적 대안으로 제시되었다. 지르코니아 수복물의 가장 흔한 합병증은 상부 도재의 파절이다. 다른 옵션은 고도로 반투명한 지르코니아를 전부지르코니아 고정식 수복물로 사용하는 것이다. 본 논문에서는 전부지르코니아 수복물의 장점, 지르코니아 수복물의 임상적용, 지대치 삭제, 대합치 마모, 지르코니아와 레진시멘트와의 접착, 그리고 기공소와의 의사소통에 관하여 보고하였다.

• The Korean Journal of Ceramics
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• 제3권1호
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• pp.47-51
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• 1997

The dense sintered bodies of Si/SiC composite with various Si contents could be fabricated by changing the green density in the forming process. The Si/SiC/graphite composites with various graphite contents could be also fabricated by changing a graphite content in the starting composition. Their mechanical and tribological properties were characterized and wear mechanism was also studided. The hardness and strength of the Si/SiC and the Si/SiC/graphite were decreased with increasing the contents of free Si and graphite, respectively. However, the friction coefficient and specific wear rate had no specific relations to their hardness and strength. Adhesion of free Si was a main factor to determine a wear resistance of the Si/SiC composite. In the case of the Si/SiC/graphite, solid lubricationl and liquid reservoir of the graphite particles played the main role of the reduction of the friction force. In the torque test to estimate the possibility of practical of practical applications, the value of torque between the Al2O3 disk and Si/SiC/graphite disk was 1/6 lower compared with two $Al_2O_3$ disks on the basis of 100,000 cycles.