• 한국표면공학회지
• /
• 제30권4호
• /
• pp.272-280
• /
• 1997

The Thermal Barrier Coation(TBC) to improve the that barrier and wear resistant propenrty in high temperature ofthe aircraftength between the accumlation of the aircraft engine and the automobile engine has usually the two layer structure. One is a creamic top layer for heat insulation and the other is a metal bond layer to facilitate the bond strength between the top ceramic layer and the substrate. But, the coated layers should be peeled off because of the accumulation of the thermal stress by the differance of the thermal expantion coefficient between metal and ceramics in a hrat cyclic environment. In this study, the intermediate layer by plasm spray process was introduced to reduce the thermal stress. The powders of plasm spray coating were the Yttria Stabilized Zirconia (YSZ), the Magnesia Stabillized Zirconia(MSZ) and NiCrAlY. the intermediate layer was sprayed with the powders of the bond cast for the purpose of test were executed. The high temperature wear resistance tends to decreasnceee wear and thermal shock test were exeucuted. The high temperature were resistance of the YSZ TBC is better that of the MSZ TBC. The wearrsistance tends to decrease accoring to incresing the temperature between $400^{\circ}C$to $600^{\circ}C$. The thermal shock life of the 3 layer TBC with YSZ top casting was the most outstanding thermal shock rsisstasnce. This means that the intermediate layer should play an importnat roll to alleviate the diffrerence of the thermal expansion coef frcients between metallic layer and cermics layer.

• 한국재료학회지
• /
• 제24권11호
• /
• pp.625-631
• /
• 2014

To investigate the deformation properties of TiC-(5-20) mol% Mo solid solution single crystals at high temperature by compression testing, single crystals of various compositions were grown by the radio frequency floating zone technique and were deformed by compression at temperature from 1250K to 2270K at strain rates from $5.1{\times}10^{-5}$ to $5.9{\times}10^{-3}/s$. The plastic flow property of solid solution single crystals was found to be clearly different among a three-temperature range (low, intermediate and high temperature ranges) whose boundaries were dependent on the strain rate. From the observed property, we conclude that the deformation in the low temperature range is controlled by the Peierls mechanism, in the intermediate temperature range by the dynamic strain aging and in the high temperature range by the solute atmosphere dragging mechanism. The work softening tends to become less evident with an increasing experimental temperature and with a decreasing strain rate. The temperature and strain rate dependence of the critical resolved shear stress is the strongest in the high temperature range. The curves are divided into three parts with different slopes by a transition temperature. The critical resolved shear stress (${\tau}_{0.2}$) at the high temperature range showed that Mo content dependence of ${\tau}_{0.2}$ with temperature and the dependence is very marked at lower temperature. In the higher temperature range, ${\tau}_{0.2}$ increases monotonously with an increasing Mo content.

• 한국세라믹학회지
• /
• 제34권3호
• /
• pp.265-265
• /
• 1997

• 한국전기화학회:학술대회논문집
• /
• 한국전기화학회 2001년도 춘계총회 및 학술발표회
• /
• pp.45-45
• /
• 2001

• Journal of Forest and Environmental Science
• /
• 제38권4호
• /
• pp.284-289
• /
• 2022

This study was conducted to determine the seed dormancy types of Sambucus racemosa subsp. pendula Nakai and S. williamsii Hance. Low temperature stratification (1, 2, 3, 4 months) and GA3 treatment (1,000 mg/L) were performed on seeds to determine the type of seed dormancy. After the treatment, seeds were placed on a petri dish at 25℃ under light conditions. The germination rate and mean germination time were investigated. Results showed that cold stratification was effective in breaking the dormant state of the seed in both species. In the low temperature stratification treatment, the seed germination performance was improved as the treatment period was prolonged. Gibberellin treatment was effective in breaking the dormant state of S. racemosa subsp. pendula without low temperature stratification. However, S. williamsii did not break the dormant state of the seed by gibberellin treatment without low temperature stratification treatment. In the gibberellin treatment, germination performance was improved according to the low temperature stratification treatment period. As a result of this study, the seeds of S. williamsii have both an intermediate complex and a deep complex morphophysiological dormancy (MPD). In comparison, it was found that the S. racemosa subsp. pendula had intermediate composite MPD.

• 한국작물학회지
• /
• 제37권1호
• /
• pp.28-36
• /
• 1992

쌀알의 알칼리붕괴도와 호화온도 및 수분흡수율간의 관계를 밝히기 위하여 50품종의 쌀을 이용하여 4농도의 알칼리용액에서 쌀알의 붕괴반응을 조사하였으며 알칼리붕괴반응에 근거하여 선발한 24품종에 대하여는 알칼리용액에서의 침지시간에 따른 쌀알의 붕괴정도, 가열온도 및 시간에 따른 쌀알의 완전호화율 그리고 21$^{\circ}C$ 및 77$^{\circ}C$의 물에 쌀을 침지했을 때의 흡수율 등을 조사하였다. 1. 자포니카형 및 통일형품종들의 알칼리붕괴도의 차이는 KOH 1.2%농도에서 가장 확실히 나타났지만 각 품종의 알칼리붕괴반응을 정확히 알기위해서는 KOH 1.2% 및 1.4%에서 쌀알의 붕괴도를 검정하는 것이 좋았다. 2. 4개수준의 알칼리농도에서 조사한 붕괴도에 근거하여 공시품종을 3품종군으로 나눌 수 있었는데 알칼리용액에 쌀알을 침지한 후 경과시간에 따른 붕괴반응에도 품종간 차이가 있었다. 3. 알칼리 붕괴반응이 크게 다른 품종군간에는 가열온도 및 시간에 따른 호화립비율의 차이가 분명하여 알칼리붕괴도가 낮은 품종의 쌀이 높은 쌀에 비하여 완전호화에 필요한 온도가 높았고 호화소요시간도 길었으나 동일한 품종군내에서도 품종간 차이가 있었다. 4. 알칼리붕괴도가 아주 낮았던 품종군의 쌀은 알칼리붕괴도가 중간 또는 높은 품종군에 비하여 상온(21$^{\circ}C$) 및 가열(77$^{\circ}C$)흡수율이 아주 낮았고 알칼리붕괴도가 중간인 품종군은 높은 품종군에 비하여 상온에서의 초기 수분흡수속도가 느렸다.

• 한국재료학회지
• /
• 제23권11호
• /
• pp.625-630
• /
• 2013

In this study, intermediate-mixed powders were prepared by loading zirconia powders initially in a ball-mill jar and loading alumina powders afterward; the initial-mixed powders were produced by loading zirconia and alumina powders together in the ball-mill jar. The effect of such differences in mixing method on the mechanical properties was investigated. In intermediate-mixed powders, the volume fraction of large particles slightly increased and, simultaneously, zirconia particles formed agglomerates that, due to early ball-mill loading of the zirconia powders only, were more dispersed than were the initial-mixed powders. For the intermediate-mixed powders, zirconia agglomerates were destroyed more quickly than were initial-mixed powders, so the number of dispersed zirconia particles rose and the inhibitory effect of densification due to the addition of a second phase was more obvious. In the microstructure of intermediate-mixed powders, zirconia grains were homogeneously dispersed and grain growth by coalescence was found to occur with increasing sintering temperature. For the initial-mixed powders, large zirconia grains formed by localized early-densification on the inside contacts of some zirconia agglomerates were observed in the early stages of sintering. The intermediate-mixed powders had slightly lower hardness values as a whole but higher fracture toughness compared to that of the initial-mixed powders.

• Bulletin of the Korean Chemical Society
• /
• 제17권12호
• /
• pp.1127-1131
• /
• 1996

[FeⅡ2(N-Et-HPTB)Cl2]BPh4(1), where N-Et-HPTB is the anion of N,N,N',N'-tetrakis(N-ethyl-2-benzimidazolylmethyl)-2-hydroxy-l,3-diaminopropane, has been synthesized to model dioxygen binding to the diferrous centers of proteins. 1 has a singly bridged structure with a μ-alkoxo of N-Et-HPTB and contains two five-coordinate iron(Ⅱ) centers with two chloride ligands as exogenous ligands. 1 exhibits an electronic spectrum with a λmax at 336 nm in acetone. 1 in acetone exhibits no EPR signal at 4 K, indicating diiron(Ⅱ) centers are antiferromagnetically coupled. Exposure of acetone solution of 1 to O2 at -90 ℃ affords an intense blue color intermediate showing a broad band at 586 nm. This absorption maximum of the dioxygen adduct(1/O2) was found in the same region of μ-l,2-peroxo diiron(Ⅲ) intermediates in the related complexes with pendant pyridine or benzimidazole ligand systems. However, this blue intermediate exhibits EPR signals at g = 1.93, 1.76, and 1.59 at 4 K. These g values are characteristic of S = 1/2 system derived from an antiferromagnetically coupled high-spin Fe(Ⅱ)Fe(Ⅲ) units. 1 is the unique example of a (μ-alkoxo)diferrous complex which can bind dioxygen and form a metastable mixed-valence intermediate. At ambient temperature, most of 1/O2 intermediate decays to form a diamagnetic species. It suggests that the dacay reaction of the intermediate might be bimolecular, implying the formation of mixed-valence tetranuclear species in transition state.

• 한국재료학회지
• /
• 제5권2호
• /
• pp.157-168
• /
• 1995

The effects of Mo additions on the microstructure and the room temperature deformation behavior of polysynthetically twinned (PST) crystals of TiAl were studied in order to get a basic conception for alloying additions on the two-phase TiAl compounds with the lamellar structure. It was found that the Mo additions in TiAl PST crystals increase both the yield stress and tensile elongation to fracture but the increase in yield stress deppend on the angle $\Phi$at which the lamellar boundaries lie from the loading axis. The large difference in yield stress between specimens deformed parallel($\Phi = 0^\circ$)or perpendicular($\Phi = 90^\circ$) to the loading axis and those deformed in intermediate orientations could be plained by the difference in Mo content between the TiAl and the $$Ti_{3}Al$ phases. It was also found that the Mo-doped specimens with intermediate orientation fail by cracking zigzag across to the lamellar boundaris, which is the same fracture mode as that of binary specimens with intermediate orientations tested in vacuum This suggests that Mo atoms are thought to play a role to reduce the environmental embrittlement of binary PST crystals, resulting in increasing the tensile ductility.

• Ocean and Polar Research
• /
• 제37권4호
• /
• pp.265-278
• /
• 2015

We analyzed the North Pacific Intermediate Water (NPIW) that was simulated in 25 coupled general circulation models (CGCMs) using historical and Representative Concentration Pathway 4.5 (RCP4.5) scenario experiments of Coupled Model Intercomparison Project Phase 5 (CMIP5), focusing on the evaluation of the performance of HadGEM2-AO. A large inter-model diversity in salinity, density, and depth of the NPIW exists even though the multi-model ensemble mean (MME) is comparable to observations. It was found that the depth of the NPIW tends to be deeper in the models in which the NPIW is relatively saltier. HadGEM2-AO simulates the lightest NPIW having the lowest salinity at shallower depth, compared with other CGCMs. Future projections of the NPIW show that the temperature of the NPIW increases, but the density decreases in all CMIP5 models. It was shown that the salinity of the NPIW decreases in most models and the decrease tends to be larger in models simulating the lighter NPIW. The HadGEM2-AO projects moderate changes in the temperature and density of the NPIW out of the CMIP5 models.