• Korean Journal of Materials Research
• /
• v.8 no.6
• /
• pp.538-544
• /
• 1998

The spallation of a thermal barrier coating layer depends on the formation of brittle spinels. thermal expansion mismatch between ceramic and metal. the phase transformation of a ceramic layer and residual stress of coating layer. In this work. the formation mechanism of oxide scale formed by oxidation treatment at 90$0^{\circ}C$ was investigated in order to verify oxidation behavior at the interface between E-beam coated $Zr0_2$-7wt.% $Y_20_3$ and plasma sprayed CoNiCrAIY. Some elements distributed in the bond coating layer were selectively oxidized after oxidation. At the initial time of oxidation. AI-depletion zone and $\alpha$-$Al_O_3$,O, were formed at the bond coating layer by the AI-outward diffusion. After layer grew until critical thickness. spinels. $Cr_20$, and $C0_2CrO_4$ by outward diffusion of Co. Cr, Ni were formed. It was found that the formation of spinels may be related to the spallation of $Zr0_2$-7wt.% $Y_20_3$ during isothermal oxidation.

• Korean Journal of Materials Research
• /
• v.8 no.10
• /
• pp.969-974
• /
• 1998

The effect of vanadium, which is known to decrease the stacking fault energy of Fe-base alloys, on the microstructure and elevated temperature sliding wear resistance of Fe-20Cr- 1.7C- 1Si alloy was investigated. The maximum amount of vanadium maintaining the austenitic matrix seems to be about 3wt.% in Fe-20Cr- 1.7C-1Si-xV (x = 0, 1, 3, 6. lOwt.%) alloys and the austenitic alloys showed better wear resistance than ferritic alloys. It was considered to be due to the low stacking fault energy and $\gamma->\alpha$ strain-induced phase transformation at rmm temperature. It was shown from elevated temperature sliding tests up to .$225^{\circ}C$ that the addition of vanadium increases the temperature, at which the transition from oxidative wear to adhesive wear occur, and the amount of d formed at $225^{\circ}C$. Thus, it was considered that the addition of vanadium improves the elevated temperature sliding wear resistance of Fe-20Cr- 1.7C - 1Si by reducing the increasing rate of stacking fault energy with temperature and by increasing Ma temperature.

• 대한공업교육학회지
• /
• v.31 no.2
• /
• pp.155-176
• /
• 2006

The purpose of this study was to explore the strategies for applying TRIZ to technology education. This study was carried out through literature review on contradiction, 40 principles, 76 standard solutions, multi screen method, effects, the law of technology evolution, and ARIZ, and questionnaire survey to investigate the validity. Through this study the strategies for applying TRIZ to technology education were proposed and the validity was identified. Only the '40 Principles' was appropriate to technology education of elementary and middle school. The results of this study were as follows; In elementary school technology education, segmentation, extraction, local quality, asymmetry, consolidation, universality, counterweight, do it in reverse, mediator, self service, dispose, flexible membranes or thin films, changing the color, homogeneity, rejecting and regenerating parts, and composite materials were suitable. And in middle school technology education, segmentation, extraction, local quality, asymmetry, consolidation, universality, counterweight, prior counteraction, prior action, cushion in advance, do it in reverse, dynamicity, partial or excessive action, continuity of useful action, convert harm into benefit, mediator, self service, dispose, flexible membranes or thin films, changing the color, homogeneity, rejecting and regenerating parts, transformation of properties, phase transition, thermal expansion, and composite materials were suitable.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.7 no.6
• /
• pp.1056-1063
• /
• 2006

Thermal evaporated 10 nm-Ni/l nm-Ir/(or polycrystalline)p-Si(100) and 10 nm-$Ni_{50}Co_{50}$/(or polycrystalline)p-Si(100) films were thermally annealed using rapid thermal annealing fur 40 sec at $300{\sim}1200^{\circ}C$. The annealed bilayer structure developed into Ni(Ir or Co)Si and resulting changes in sheet resistance, microstructure, phase and composition were investigated using a four-point probe, a scanning electron microscopy, a field ion beam, an X-ray diffractometer and an Auger electron spectroscope. The final thickness of Ir- and Co-inserted nickel silicides on single crystal silicon was approximately 20$\sim$40 nm and maintained its sheet resistance below 20 $\Omega$/sq. after the silicidation annealing at $1000^{\circ}C$. The ones on polysilicon had thickness of 20$\sim$55 nm and remained low resistance up to $850^{\circ}C$. A possible reason fur the improved thermal stability of the silicides formed on single crystal silicon substrate is the role of Ir and Co in preventing $NiSi_2$ transformation. Ir and Co also improved thermal stability of silicides formed on polysilicon substrate, but this enhancement was lessened due to the formation of high resistant phases and also a result of silicon mixing during high temperature diffusion. Ir-inserted nickel silicides showed surface roughness below 3 nm, which is appropriate for nano process. In conclusion, the proposed Ir- and Co- inserted nickel silicides may be superior over the conventional nickel monosilicides due to improved thermal stability.

• Resources Recycling
• /
• v.14 no.2
• /
• pp.10-18
• /
• 2005

The manufacture property of anhydrous calcium sulfate (anhydrite Ⅱ) from flue gas desulfurization (FGD) gypsum discharged from domestic thermoelectric power plants to apply as an auxiliary material of cement and concrete by high temperature treatment were investigated. The FGD gypsum was completely converted to anhydrite Ⅱ at the temperature of 700$^{\circ}C$ and the retention time of 1 hr. In the phase transformation process, particle size was also changed. The chemical composition, particle size and heat property of anhydrite Ⅱ made from the FGD gypsum were similar to them of natural gypsum. In the leaching test of sulfate ion (SO$_4^{2-}$) at the temperature of 90$^{\circ}C$ and the retention time of 1 hr, the amount of leached SO$_4^{2-}$ for the anhydrite Ⅱ that was sintered at 700$^{\circ}C$ for 1 hr was about 50 wt.% based on that of natural gypsum. In addition, the amount of leached SO$_4^{2-}$ for the anhydrite Ⅱ by adding the slaked lime of 3 wt.% decreased about 70 wt.% comparing with that of natural gypsum. In the application test, the compressive strength of cement and concrete manufactured by using the anhydrite Ⅱ as an auxiliary material were similar or superior compared with them of cement and concrete done by natural gypsum as an auxiliary material.

• Journal of Korean Classical Literature and Education
• /
• no.38
• /
• pp.103-138
• /
• 2018

This study examines the modern succession, transformation and significance of enjoyment methods of classical literature (art) with a focus on the characteristics of those methods that appeared when the performances of the traditional era began to be displayed on the stage of the theaters in modern Seoul. The clues to the reasons for this type of enjoyment can be found in newspapers, magazine articles, and advertisements from the early 20th century. The emergence of stage theaters at the beginning of the modern era caused a sweeping change in the performance environment, including the fact that it was possible for all kinds of people to enjoy art beyond the existing socioeconomic hierarchies or barriers of status, that the performers were given employment through the theater, and that the audience had the tendency of the general public of an unspecified number because the audience was able to see the performances only by paying the viewing fee. The way of enjoying traditional performances also changed based on these new adaptations: the performances were sequential, show-oriented, and re-contextualized as public performances. It is significant that in the traditional era, performers and audiences had been segregated according to their status and a strict hierarchy; now, such cultural norms were breaking down in favor of a kind of equality. In addition, it was possible for the audience to experience sensory enjoyment, and theater brought about a new kind of popular consumer enjoyment of an artistic product. Of course, though, it is possible to look back and find problems related to the contemporary context, but the traditional performances, which were the main performances for the lower class, took the first place on the modern theater stage, and as a result, no one can deny that it became possible to move forward in the first phase of an era of public performance.

• Journal of the Korean Society for Heat Treatment
• /
• v.32 no.5
• /
• pp.212-223
• /
• 2019

This study is to investigate the relationship between microstructural factors and tensile properties after aging heat treatment of the 15-5PH stainless steel at the temperature range of $450^{\circ}C$, $500^{\circ}C$ and $550^{\circ}C$ for various time. For the aging time of 2 hours, hardness showed maximum at $450^{\circ}C$ and then decreased with increasing aging temperature. While, hardness decreased gradually during aging $450^{\circ}C$, $500^{\circ}C$ and $550^{\circ}C$ from 1 hour to 5 hours but the hardness nearly unchanged until the 100 hours after 5 hours aging. When aging at $450^{\circ}C$, Cu atoms preferentially aggregated at the prior austenite grain boundaries and martensite lath boundaries, and Cu concentration at those boundaries was nearly unchanged even after aging for 100 hours. Therefore it was suggested that the coherency is still maintained after 100 hours aging at $450^{\circ}C$. Aging at $500^{\circ}C$ and $550^{\circ}C$ results in an increase in the concentration of Ni at the martensite lath boundaries and prior austenite grain boundaries, resulting in the formation of reversed austenite. Especially, when aged at $550^{\circ}C$ for 100 hours, the concentration of Ni remarkably increased at those boundaries, and thus the microstructure of herring bone shape was appeared. Considering the migration of Ni atom to the lath boundaries and prior austenite grain boundaries, Ni atoms contributed greatly to the formation of reversed austenite. On the other hand, it was found that Cu atoms hardly moving to those boundaries may not be contributed to the formation of reversed austenite. When aging at $450^{\circ}C$, the coarsening of the precipitated Cu atoms proceeded very slowly with increasing aging time, therefore the decrease in strengths were small but the reduction area was considerably increased due to the softening of the matrix. At the aging temperature of $500^{\circ}C$ and $550^{\circ}C$, the strengths decreased and the elongation and reduction area increased due to the appearance of the reversed austenite. Especially, the increase of reduction area was remarkable.

• Journal of KIBIM
• /
• v.10 no.1
• /
• pp.9-22
• /
• 2020

Recently, BIM has been extended to infrastructures such as roads and bridges, and the demand for BIM standard development for ports is increasing internationally. Due to the low level of utilization of classification system and drawing standards compared to other infrastructures, and the closed nature of national security facilities, ports have insufficient level of connection and sharing environment among external systems or users. In addition, since the standardization of data for port facilities is not made, it is still necessary to establish an independent DB for each system and to ensure interoperability of data between these systems since it does not have a shared environment among similar data. Therefore, the purpose of this study is to develop and verify IFC, the international standard for BIM, in order to cope with the BIM environment and to be commonly used in the design, construction, and maintenance of port facilities. To this end, we build a standard schema with port-specific Express Notation according to buildingSMART International's standard development methodology. First, domestic and international reference model standards were analyzed to derive components such as space and facilities of port facilities. Based on this, the components of the port facility were derived through the codification, categorization, and normalization process developed by the research team. This was extended based on the port BIM object classification system developed by the research team. Normalization results were verified by designers and associations. Then, IFC schema construction was based on Express-G data modeling based on IFC 4 * 2 Candidate, which is a bridge candidate standard based on IFC4 (ISO16739), and IFC 4 * 3 Draft, which is developed by buildingSMART International. The final schema was validated using the commercialized validation tool. In addition, in order to verify the structural verification of the port IFC schema, the transformation process was verified by converting the caisson model into a Part21 file. In the future, this result will not only be used as a delivery standard for port BIM products, but will also be applied as a linkage standard between systems and a common data format for port BIM platforms when BIM is used in the maintenance phase. In particular, it is expected to be used as a core standard for data exchange in the port maintenance stage.

• Journal of Powder Materials
• /
• v.28 no.2
• /
• pp.143-149
• /
• 2021

In this study, (GaN)_1-x(ZnO)_x solid solution nanoparticles with a high zinc content are prepared by ultrasonic spray pyrolysis and subsequent nitridation. The structure and morphology of the samples are investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The characterization results show a phase transition from the Zn and Ga-based oxides (ZnO or ZnGa₂O₄) to a (GaN)_1-x(ZnO)_x solid solution under an NH3 atmosphere. The effect of the precursor solution concentration and nitridation temperature on the final products are systematically investigated to obtain (GaN)_1-x(ZnO)_x nanoparticles with a high Zn concentration. It is confirmed that the powder synthesized from the solution in which the ratio of Zn and Ga was set to 0.8:0.2, as the initial precursor composition was composed of about 0.8-mole fraction of Zn, similar to the initially set one, through nitriding treatment at 700℃. Besides, the synthesized nanoparticles exhibited the typical XRD pattern of (GaN)_1-x(ZnO)_x, and a strong absorption of visible light with a bandgap energy of approximately 2.78 eV, confirming their potential use as a hydrogen production photocatalyst.

• Korean Journal of Mineralogy and Petrology
• /
• v.35 no.4
• /
• pp.423-430
• /
• 2022

Pressure-dependent elastic behavior and chemical reaction of natural sepiolite (Mg₈Si₁₂O₃₀(OH)₄·12H₂O) was studied under two different pressure-transmitting medium (PTM) conditions using synchrotron X-ray powder diffraction. Under non pore-penetrating silicone oil PTM, we observed that the b-axis length increases up to ca. 3.6 GPa, marking an anisotropic compression region with negative linear compressibility of β^b= -0.0012 GPa^-1, which then decreases at 7.7 GPa. Under pore-penetrating water PTM, the anisotropic compression behavior is enhanced with doubled negative linear compressibility of β^b= -0.0025 GPa^-1 up to 3.2 GPa, where transformation into stevensite is observed upon ex-situ temperature treatment at 280 ℃ as confirmed via XRD and SEM. Derived bulk moduli (K₀) and linear compressibilities (β) were compared to other structurally and chemically related minerals.