• 한국세라믹학회지
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• 제44권10호
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• pp.580-584
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• 2007

The ZrC layer instead of SiC layer is a critical and essential layer in TRISO coated fuel particles since it is a protective layer against diffusion of fission products and provides mechanical strength for the fuel particle. In this study, we carried out computational simulation before actual experiment. With these simulation results, Zirconium carbide (ZrC) films were chemically vapor deposited on $ZrO_2$ substrate using zirconium tetrachloride $(ZrCl_4),\;CH_4$ as a source and $H_2$ dilution gas, respectively. The change of input gas ratio was correlated with growth rate and morphology of deposited ZrC films. The growth rate of ZrC films increased as the input gas ratio decreased. The microstructure of ZrC films was changed with input gas ratio; small granular type grain structure was exhibited at the low input gas ratio. Angular type structure of increased grain size was observed at the high input gas ratio.

• 대한기계학회논문집A
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• 제21권10호
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• pp.1571-1579
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• 1997

The development of a new material which should be continuously use under severe environment of very high temperature has been urgently requested. For the development of such super-heat resistant materials, the main problem is not only to make the superior thermal barrier properties but also to actively release thermal stress. So, a new concept of functionally graded material(FGM) has been proposed to overcome this problem. A composition and microstructure of FGM are varied continuously from place to place in ways designed to provide it with the maximum function of mitigating the induced thermal stress. So, FGM can be applied in the aerospace, the electronic and the medical field, etc.. In this study, thermal stress analysis of sintering PSZ/NiCrAlY graded material was conducted theoretically using a finite-element program. The temperature condition was sintering temperature assuming a cooling-down process up to room temperature. Fracture damage mechanism was anlayzed by the parameters of residual stress. It could be known that FGM provided with the function of mitigating the induced thermal stress.

• 열처리공학회지
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• 제20권2호
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• pp.72-77
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• 2007

Abrasive wear between piston ring face and cylinder liner is an extremely unpredictable and hard-to-reproduce phenomenon that significantly decreases engine performance. Wear by abrasion are forms of wear caused by contact between a particle and solid material. Abrasive wear is the loss of material by the passage of hard particles over a surface. From the pin-on-disk test, particle dent test and scuffing test, abrasive wear characteristics of diesel engine cylinder liner-piston ring have been investigated. Pin-on-disk test results indicate that abrasive wear resistance is not simply related to the hardness of materials, but is influenced also by the microstructure, temperature, lubricity and micro- fracture properties. In particle dent test, dent resistance stress decreases with increasing temperature. From the scuffing test by using pin-on-disk tester, scuffing mechanisms for the soft coating and hard coating were proposed and experimentally confirmed.

• 분석과학
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• 제6권2호
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• pp.181-195
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• 1993

SUS(Stainless Steel) 분말을 이용하여 기존의 고가 내마모 소결부품을 대체할 수 있는 새로운 내마모재의 개발 가능성을 조사하였다. SUS 조성의 분말에 Cu, ZrC, C 및 Ti 등의 합금원소를 첨가하여 소결체의 밀도, 소결시의 수축률 및 경도의 변화를 조사하였다. 이러한 첨가원소의 영향 중에서 가장 뛰어난 기계적 성질을 나타낸 것은 Ti을 첨가한 SUS재였으며, 3% Ti 첨가시 기존의 내마모 소결 부품을 대체할 수 있는 수축률(6.5%), 밀도($7.35g/cm^3$) 및 경도(43HRC)를 보여 주었다.

• 한국세라믹학회지
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• 제37권4호
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• pp.320-326
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• 2000

Development of texture in SiC materials by hot-pressing and subsequent annealing was studied. Crystallographic texture type was characterized by measuring X-ray pole figures on the perpendicular plane to the hot-pressing direction. Observed all pole figures were nearly axially symmetric (fiber texture). In case of ${\beta}$-SiC materials, the pole density of basal plane (0004) increased as annealing time increased, in contrast, other planes (hkil) of ${\beta}$-SiC materials and all planes of ${\alpha}$-SiC materials nearly remained unchanged. In the case of ${\beta}$-SiC materials, therefore, a weak texture of (0001) plane at the normal direction took place in the 8h annealed samples, resulting from grian growth. The fracture toughness values of ${\alpha}$-SiC materials measured in both planes parallel and perpendicular to the hot-pressing direction were very similar. However, the fracture toughness of ${\beta}$-SiC materials measured parallel to the hot-pressing direction were higher than that measured perpendicular to the hot-pressing derection, relatively, because of the texture and the microstructure anisotropy.

• 한국세라믹학회지
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• 제45권1호
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• pp.1-29
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• 2008

In last two decades, an impressive progress has been recorded in terms of developing new materials or refining existing material composition/microstructure in order to obtain better performance in biomedical applications. The success of such efforts clearly demands better understanding of various concepts, e.g. biocompatibility, host response, cell-biomaterial interaction. In this article, we review the fundamental understanding that is required with respect to biomaterials development, as well as various materials and their properties, which are relevant in applications, such as hard tissue replacement. A major emphasize has been placed to present various design aspects, in terms of materials processing, of ceramics and polymer based biocomposites, Among the bioceramic composites, the research results obtained with Hydroxyapatite (HAp)-based biomaterials with metallic (Ti) or ceramic (Mullite) reinforcements as well as $SiO_2-MgO-Al_2O_3-K_2O-B_2O_3-F$ glass ceramics and stabilized $ZrO_2$ based bioinert ceramics are summarized. The physical as well as tribological properties of Polyethylene (PE) based hybrid biocomposites are discussed to illustrate the concept on how can the physical/wear properties be enhanced along with biocompatibility due to combined addition of bioinert and bioactive ceramic to a bioinert polymeric matrix. The tribological and corrosion properties of some important orthopedic metallic alloys based on Ti or Co-Cr-Mo are also illustrated. At the close, the future perspective on orthopedic biomaterials development and some unresolved issues are presented.

• 한국전기전자재료학회논문지
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• 제33권6호
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• pp.495-499
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• 2020

Power factor improvement at high temperatures has been a major research topic for the development of skutterudite thermoelectric materials. Here, we attempted to optimize the process parameters for manufacturing skutterudite materials, especially for p-type systems. We focused on the effect of aging time variation to maximize the high-temperature performance of the Ce-filled Fe³CoSb¹² skutterudite system. The optimized aging time was concluded to be a key parameter for the formation of single-phase nanostructures in this p-type skutterudite system. The optimized condition was effective in reducing the bipolar effect at high temperature ranges by increasing the carrier concentration in the p-type system. To confirm the conclusions, the electrical conductivity, Seebeck coefficient, and power factor were measured. The results matched well with the microstructure and with those of an XRD analysis performed for the system.

• 한국재료학회지
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• 제26권2호
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• pp.90-94
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• 2016

In this study, to increase the strength and enhance the sintering property of $Al_2O_3$, $Y_2O_3$ and $La_2O_3$ were added; the effects of these additions on the sintering characteristics of $Al_2O_3$ were observed. Adding 1% of $Y_2O_3$ to $Al_2O_3$ repressed the development of abnormal particles and reduced the grain boundary migration of $Al_2O_3$, curbing pores to capture particles; as such, the material showed a fine microstructure. But, when over 2% of $Y_2O_3$ was added, the sintering property was reduced because of abnormal particle grain growth and pore formation in particles. Adding 1% of $Y_2O_3$ and $La_2O_3$ to $Al_2O_3$ led to the development of abnormal particles and formed pores in the particles; when over 3% of $La_2O_3$ was added, the sintering property was reduced because the shape of the $Al_2O_3$ particles changed to angled plates.

• 한국초전도ㆍ저온공학회논문지
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• 제8권3호
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• pp.37-40
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• 2006

Oxide buffer layers for YBCO coated conductors were fabricated using MOD processing and development of microstructure and texture were investigated. A $CeO_2$ buffer layers were formed on RABiTS tape. Acetate-based precursor solution was employed to synthesize the precursor solution. Subsequently, the precursor solution was stabilized and modified with triethanolamine. $CeO_2$ precursor gel film was coated and annealed in $Ar/H_2$ atmosphere at high temperature. An annealed $CeO_2$ film shows mixed orientation with high (001) texturing. It was shown that (111) texture of $CeO_2$ layers were enhanced by multiple coating. This degradation was attributed to development of microcracks in the multiply coated $CeO_2$ films. Also discussed are the synthesis and the characterization of $La_2Zr_2O_7$ (LZO) buffer layers on RABiTS tape. A biaxially textured LZO buffer layer was fabricated with MOD processing method using metal alkoxide based precursor solution. It was shown that the LZO film were epitaxially grown on RABiTS tape and crack-free & uniform surface was obtained after annealing in $Ar/H_2$ atmosphere.

• Applied Microscopy
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• 제50권
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• pp.24.1-24.11
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• 2020

The development of the femtosecond laser (fs laser) with its ability to provide extremely rapid athermal ablation of materials has initiated a renaissance in materials science. Sample milling rates for the fs laser are orders of magnitude greater than that of traditional focused ion beam (FIB) sources currently used. In combination with minimal surface post-processing requirements, this technology is proving to be a game changer for materials research. The development of a femtosecond laser attached to a focused ion beam scanning electron microscope (LaserFIB) enables numerous new capabilities, including access to deeply buried structures as well as the production of extremely large trenches, cross sections, pillars and TEM H-bars, all while preserving microstructure and avoiding or reducing FIB polishing. Several high impact applications are now possible due to this technology in the fields of crystallography, electronics, mechanical engineering, battery research and materials sample preparation. This review article summarizes the current opportunities for this new technology focusing on the materials science megatrends of engineering materials, energy materials and electronics.