• Journal of the Korean Vacuum Society
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• v.16 no.6
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• pp.474-478
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• 2007

Nanostructures of $SiN_x$ were made by bombardment of ionized $N_2$ on Si surface and subsequent annealing. Atomic force micrograph showed the density of $SiN_x$ nanostructures was $3\times10^{10}/cm^2$. Their lateral size and height were 40$\sim$60 nm and 15 nm, respectively. The chemical state of the nanostructure was measured using X-ray photoelectron spectroscopy, which changed from $SiN_x$ to $Si_3N_4\;+\;SiN_x$ as the bombarding ionized gas current increases. Upon annealing, transmission electron micrograph showed a clear evidence for crystalline Si phase formation inside the $SiN_x$ nanostructures. Photoluminescence peak observed at around 400nm was thought to be originated from the interface states between the nanocrystalline Si and surrounding $SiN_x$ nanostructures.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.1
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• pp.1-8
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• 2007

Environment factors related to the distribution of organic matter in surface seawater and sediments were investigated to estimate main pollution sources and range of their influence in Gwangyang Bay. The main pollution sources for the factors that affect organic matter distribution could be divided into three main sources: fresh water runoffs from Seomjin and Dong River, Gwangyang-si domestic sewage, and Yosu Industrial Complex. Considering the characteristics in horizontal distributions of the environmental factors in water column, sediment, and water current regime, the influencing range of these main sources was likely to be divided into three areas within the bay as follows: Area I receiving lots of fresh water from Seomjin River, Area II receiving lots of domestic sewage from Gwangyang-si and fresh water of Dong River, Area III receiving lots of materials from Yosu Industrial Complex. Area I seems to be characterized as low salinity, high concentration of $NO_3-N,\;and\;SiO_2-Si$, Area II as low salinity, high concentration of $NO_3-N,\;NH_4-N,\;and\;SiO_2-Si$, and Area III as high water temperature, high concentration of $NH_4-N,\;and\;PO_4-P$ in water column, high concentration of $NH_4-N,\;PO_4-P,\;and\;SiO_2-Si$ in surface sediments.

• Polymer Science and Technology
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• v.8 no.3
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• pp.293-297
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• 1997

• ALGAE
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• v.19 no.1
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• pp.49-57
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• 2004

This study was performed to obtain basic information on the ecology of Zostcra marina and to promote efficient conservation of this species which has been decline in Gamak Bay, Yeosu, Korea. Whater column characteristics and eelgrass morphology at Anpori, Jangsuri and Wonpori were investigated every month from December 1999 to November 2000. The water temperature, salinity and pH at the three sites were 10.0-27.0${\circ}C$,29.4-34.7% and 8.1-8.5, respectively. The water temperature at Anpori tended to be slightly lower than that at the other locations; the salinity at Wonpori from July to November was a little lower than that of the other locations. The concentrations of $NO_2$-N, $NO_3$_N, $NH_4$-N, $PO_4$-P and $Si(OH)_4$-Si at the three sites were 0.9-1.3, 2.0-6.2, 7.8-9.0, 3.0-3.6 and 22.2-30.2 uM, respectively. The concentration of $NO_3$-N at Wonpori from June to November was somewhat lower than that at the other locations; that of NH4-N at Jansuri was somewhat lower than the others. The mean shoot height and leaf width of the Anpori, Jangsuri and Wonpori populations were 80.6 cm and 0.9 mm, 90.0 cm and 1.0 mm, and 95.3 cm and 1.0 mm, respectively. The mean total shoot weight of the Anpori, Jangsuri and Wonpori ones was 24.5,31.0 and 29.7 & respectively. The mean leaf and branch numbers of the Anpori, Jangsuri and Wonpori populations were 16.5 and 2.6, 16.1 and 2.4 and 15.4 and 2.6 individuals, respectively. The correlation coefficients between shoot height and water temperature, leaf width and total shoot weight, leaf number and branch number, and $Si(OH)_4$-Si and $NO_3$-N were 0.726, 0.692, 0.862, and 0.693, respectively. The coefficients between shoot height and $NO_3$-N, total shoot weight and NO_3$-N, water temperature and $Si(OH)_4$-Si, water temperature and salinity, and water temperature and $NO_3$-N were -0.716, -0.536, -0.775, -0.685 and -0.685, respectively. The first four principal components explain 71.1% of the total sample variance. For axis 1, shoot height and water temperature tended to correlate with the population of Jansuri, followed by the Wonpori population, and $Si(OH)_4$-Si and $NO_3$-N tended to correlated strongly with the Anpori population. For axis 2, total weight, leaf width, leaf number and branch number showed a tendency to correlate with the Anpori and Jangsuri populations. For axis 3, the Anpori population tended to be influenced by $NO_2$-N and $PO_4$-P. For axis 4, the Wonpori and Jangsuri populations tended to be affected by salinity. The tendency, however, differed according to season.

• Journal of the Korean Ceramic Society
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• v.39 no.10
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• pp.955-962
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• 2002

The microstructure change of brazed $Si_3N_4$/Stainless steel 316 joint with Cu buffer layer were examined to clarify the effects of brazing process conditions such as brazing time and temperature on the mechanical properties and reliability of brazed joints. For the brazed joint above 900${\circ}C$, the Cu buffer layer was completely dissolved into brazing alloy and the thickness of reaction product formed at $Si_3N_4$/brazing alloy joint interface was abruptly increased, which could increase the amounts of residual stress developed in the joint. The fracture strength of brazed $Si_3N_4$/Stainless steel 316 joint with Cu buffer layer at 950${\circ}C$ was much reduced comparing to those of joints brazed at the lower temperature. But, it was found that the effects of brazing time was not critical on the mechanical properties as well as the reliability of $Si_3N_4$/Stainless steel 316 joint with Cu buffer layer brazed at the temperature below 900${\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.385-386
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• 2008

This paper reports the design of the ultra low power consumption microhotplates for high temperatures. The microhotplates consisting of a platinum-based heating element on AlN/poly 3C-SiC layers were designed. The microhotplate is a $600\times600{\mu}m^2$ square shaped membrane made of $1{\mu}m$ thick ploy 3C-SiC suspended by four legs. The microhotplate was compared with $Si_3N_4/SiO_2/Si_3N_4$(NON) structure microhotplate by COMSOL simulation system. Thermal uniformity, power consumption and thermal characterizations of microhotplates based on 3C-SiC thin film are better than microhotplates with NON structure.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.162-162
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• 2017

AlCrN 코팅은 높은 경도, 낮은 표면 조도 등의 상온에서의 우수한 기계적 특성 이외에 고온에서 안정한 합금상의 형성으로 인하여 우수한 내열성을 보이는 코팅이며, Si을 첨가하여 나노복합구조를 갖는 AlCrSiN 코팅은 고경도 특성을 나타내는 나노결정립과 고내열성을 나타내는 $Si_3N_4$ 비정질이 동시에 존재함으로써 뛰어난 고온 특성까지 보유하여 공구 코팅으로의 적용 가능성이 크다. 본 연구에서는, 가혹화된 공구사용 환경 대응 하는 더욱 우수한 내마모성 및 내열성을 보이는 코팅막을 개발하기 위해 AlCrN/AlCrSiN 이중층 코팅을 합성하였다. 합성된 코팅의 구조 및 물성을 분석하기 위해 field emission scanning electron microscopy(FE-SEM), nano-indentation, atomic force microscopy(AFM) 및 ball-on-disk wear tester를 사용하였다. 내열성을 확인하기 위하여 코팅을 furnace에 넣어 500, 600, 700, 800, 900도에서 30분 동안 annealing한 후에 nano-indentation을 사용하여 경도를 측정을 하였다. 5:5, 7:3, 9:1의 두께 비율로 AlCrN/AlCrSiN 이중층 코팅을 합성하였으며 모든 코팅의 두께는 $3{\mu}m$로 제어되었다. AlCrN 코팅층의 두께가 증가할수록, 이중층 코팅의 경도 및 내마모성은 점차 향상되었지만 코팅의 밀착력은 감소하였다. 일반적으로 AlCrN 코팅은 상대적으로 높은 잔류응력을 갖고 있으므로, AlCrN 층의 두께비율이 증가함에 따라 코팅내의 잔류응력이 높아져 코팅의 경도는 증가하고 밀착특성은 낮아진 것으로 판단된다. AlCrSiN 상부층 공정시 기판 바이어스 전압을 -50 ~ -200V 로 증가시키면서 이중층 코팅을 합성하였다. XRD 분석 결과, 공정 바이어스 전압이 증가함에 따라 AlCrSiN 상부층은 점차 비정질화 되었고, 코팅의 경도와 표면 특성이 향상되는 것을 확인하였다. 이러한 특성 향상은 높은 바이어스 인가가 이온 충돌효과의 증가를 야기시켰으, 이로 인해 치밀한 코팅층 합성에 의한 결과로 판단된다. AlCrN/AlCrSiN 이중층 코팅을 어닐링 한 후 경도 분석 결과, -150, -200V에서 합성한 코팅은 900도 이상에서 26GPa 이상의 높은 경도를 보인 것으로 보아 우수한 내열성을 갖는 것으로 확인 되었다. 이는 AlCrSiN 상부층의 높은 Si 함량 (11at.%) 으로 인한 충분한 $Si_3N_4$ 비정질상의 형성과, 고바이어스 인가로 인한 AlCrN 결정상과 $Si_3N_4$ 비정질상의 고른 분배가 코팅의 내열성을 향상시키는데 기여를 한 결과로 판단된다.

• Proceedings of the IEEK Conference
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• 2000.11b
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• pp.221-224
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• 2000

We have successfully demonstrated metal-ferroel-ectric-insulator-semiconductor (MFIS) devices using Al/LiNbO$_{3}$/SiN/Si structure. The SiN thin films were made into metal -insulator- semiconductor (MIS) devices by thermal evaporation of aluminum source in a dot away on the surface. The interface property of MFIS from 1MHz & quasistatic C-V is good and the memory window width is about 1.5V at 0.2V/s signal voltage sweep rate. The gate leakage current density of MFIS capacitors using a aluminum electrode showed the least value of 1x10$^{-8}$ A/$\textrm{cm}^2$ order at the electric field of 300㎸/cm. And the XRD patterns shows the probability of applications of LN for MFIS devices for FeRAMs on amorphous SiN buffer layer.

• Journal of the Korean Ceramic Society
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• v.22 no.4
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• pp.33-39
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• 1985

A composition containing a-$Si_3N_4$ with 5w/0 $Y_2O_3$ and 4w/0 $Al_2O_3$ was hot-pressed at 1, $650^{\circ}C$ and 350kg/$cm^2$ for 1.5hrs and specimens of the same composition were pressureless-sintered at 1, 75$0^{\circ}C$ for 1.5 and 5hrs. By X-ray diffraction it was found that hot-pressed specimens were consisted of $\alpha$-and $\beta$-$Si_3N_4$ and sintered specimens were consisted of $\beta$-$Si_3N_4$ and $Si_3N-4Y_2O_3$ which was crystallized out from the grainboundary phase. The 5-hr sintered specimens had higher degree of crystallization than the 1.5 hr sintered specimens. Among these three different specimens the 5-hr sintered specimens showed the highest strength by hot MOR test at 1, 00$0^{\circ}C$. The SPT diagram for the 5-hr sintered $Si_3N_4$ was constructed by measurements of the stress rate dependence of fracture strength.

• Journal of the Korean Ceramic Society
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• v.30 no.4
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• pp.265-272
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• 1993

Effect of mixing homogeneity in powder mixtures of Si3N4 and sintering additive (10mol% YAG) prepared by coprecipitation on the mechanical properties of pressureless-sintered body was investigated. Sintering was performed in a graphtie furnace at 1850℃ for 0.5h under 0.15MPa N2 atmosphere using Si3N4 powder bed. Results from the measurement of Young's modulus, Vickers hardness, 4-point-bending strength, and KIC for the coprecipitation-treated (CP) and the mechanically-mixed specimens(MM) showed that a remarkable improvement in flexural strength and Weibull parameter can be achieved for the CPspecimens: (677±68MPa, 12.0) for CP samples and (539±108MPa, 5.5) for MM. Other properties were almost same irrespective of preparation methods.