• Journal of the Korean Ceramic Society
• /
• v.29 no.7
• /
• pp.551-557
• /
• 1992

X-ray diffraction patterns, IR spectra and zeta-potentials of silicon nitride and $\beta$-Sialon powders were investigated before and after surface manipulations. $\beta$-Sialon powder was produced from Hadong Kaolin by the carbothermic reduction and simulataneous nitridation. Isoelectric points of as-prepared Si3N4 and $\beta$-Sialon powders were 8.4 and 7.4, respectively. After both silicon nitride and $\beta$-Sialon powders were oxidized at 80$0^{\circ}C$ for 24 h in air, the isoelectric points of these powders corresponded to that of silica (pH=3). I case of the addition of Darvan C as deflocculant, its isoelectric point was 3 and zeta-potential was nearly constant in the range of pH 5~12. When SN 7347 was used as deflocculant, its isoelectric point was 8.3 and zeta-potential over -156 mV was measured above pH 11.

• Journal of Powder Materials
• /
• v.18 no.3
• /
• pp.238-243
• /
• 2011

Al/AlN composites were synthesized by mechanical alloying using process control agents(PCAs). Three different PCAs which contain N element, were examined to see the effectiveness of ball-milling and the nitridation during sintering. Among examined PCAs, $C_8H_6N_4O_5$ was the most effective to facilitate ball-milling and to form nitrides during a subsequent sintering. By a proper control of ball-milling and sintering, we could obtained surface-hardened Al-based composites.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.28A no.9
• /
• pp.736-742
• /
• 1991

N$^{+}$poly gate NMOSFETs and p$^{+}$ poly gate (surface type) PMOSFETs with three different gate oxides(SiO2, NO, and ONO) were fabricated. The rapid thermal nitridation and reoxidation techniques have been applied to gate oxide formation. The current drivability of the ONO NMOSFET shows larger values than that of the SiO2 NMOSFET. The snap-back occurs at a lower drain voltage for SiO$_2$ cases for ONO NMOSFET. Under the maximum substrate current bias conditions, hot-carrier effects inducting threshold voltage shift and transconductance degradation were investigated. The results indicate that ONO films exhibit less degradation in terms of threshold voltage shift. It was confirmed that the ONO samples achieve good improvement of hot-carrier immunity. In a SiO$_2$ SC-PMOSFET, with significant boron penetration, it becomes a depletion type (normally-on). But ONO films show excellent impurity barrier properties to boron penetration from the gate.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09a
• /
• pp.663-664
• /
• 2006

Sintered Ti(C,N)-based cermets were treated with hot isostatic pressing (HIP) at different nitrogen pressures. The tribological properties of the treated cermets have been evaluated. The results show that a hard near-surface area rich in TiN formed after HIP treatment. The cermets treated at higher pressure had a relatively lower friction coefficient and specific wear rate. In all cases the microhardness of treated cermets is higher than that without HIP natridation. The wear mechanisms of cermets were hard particle flaking-off and ploughing. It was also found that the HIP natridation is well-suited for improving the tribological properties of cermets.

• Journal of the Korean Vacuum Society
• /
• v.7 no.4
• /
• pp.320-327
• /
• 1998

The chemical aspects of nitridated surface of sapphire(0001) have been studied by X-ray photoelectron spectroscopy. Nitridated layer was formed by remote plasma enhanced-ultrahigh vacuum deposition at a low temperature range. It was confirmed that this nitridated surface was mainly consists of AIN layer. The relative amounts of nitrogen reacted with AL on the sapphire surface and their surface morphology were investigated with X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) as a function of radio-frequency power, reaction temperature, and reaction time. The amounts of atomic nitrogen activated by plasma which was subsequently incorporated into sapphire were increased with RF power. But the amounts of nitrogen reacted with AI in sapphire was initially increased and then remained constant. However, the relative amounts of AIN were nearly constant with irrespective of nitridation temperature and time. Furthermore, a depth porfile of nitridated layer with XPS showed that the nitridated surface consisted of three layers with different stoichiometry.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.27 no.1
• /
• pp.39-44
• /
• 2014

Silicon nitride thin film deposited with Plasma Enhanced Chemical Vapor Deposition was treated by a nitrogen plasma generated by Inductively Coupled Plasma at room temperature. The treatment was investigated by Fourier Transform Infrared Spectroscopy and Atomic Force Microscopy on the surface at various RF source powers at two RF bias powers. The amount of hydrogen was reduced and the surface roughness of the films was decreased remarkably after the plasma treatment. In order to understand the causes, we analyzed the plasma diagnostics by Optical Emission Spectroscopy and Double Langmuir Probe. Based on these analysis results, we show that the nitrogen plasma treatment was effective in the improving of the properties silicon nitride thin film for flexible display.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2014.11a
• /
• pp.256-257
• /
• 2014

The effects of the preparation conditions of ZnO-modified TaON on the photocatalytic activity for degradation of rhodamine B dye (Rh. B) under simulated solar light were investigated. The ZnO/TaON nanocomposite were prepared by loading particulate $Ta_2O_5$ with ZnO using different ZnO contents, followed by thermal nitridation at 1123 K for 5 h under $NH_3$ flow (20 ml min.1). The asprepared samples were characterized by XRD, UV-Vis-DRS, and SEM-EDX. The results revealed that the band gap energy absorption edge of as prepared nanocomposite samples was shifted to a longer wavelength as compared to ZnO and $Ta_2O_5$, and the 60 wt% ZnO/TaON nanocomposite exhibited the highest percentage (99.2 %) of degradation of Rh. B and the highest reaction rate constant ($0.0137min^{-1}$) in 4 h which could be attributed to the enhanced absorption of the ZnO/TaON nanocomposite photocatalyst. Hence, these results suggest that the ZnO/TaON nanocomposite exhibits enhanced photocatalytic activity for the degradation of rhodamine B under simulated solar light irradiation in comparison to the commercial ZnO, $Ta_2O_5$, and TaON.

• Journal of the Korean Ceramic Society
• /
• v.20 no.3
• /
• pp.211-216
• /
• 1983

This work aims at characterizing silicon grains and its compacts. In order to remove iron silicon grains were washed with 5N hydrochloride at 60-7$0^{\circ}C$ for 170 hrs, and then followed the chemical analysis by atomic absorption spectrophotometer X-ray diffraction analysis SEM observation and specific surface area determination by B. E. T. Mixtures of graded silicon particles with two or three different sizes were made into packings by mechanical vibration. The mixtures were used to make compacts with 10 mm in diameter and 70mm in length by isostatically pressing at 1, 208 kg/$cm^2$ (20 kpsi) and 4, 255kg/$cm^2$ (60 kpsi) respectively. Bulk densities of packings and compacts were measured. A slip made of magnesium nitrate solution and fine silicon particles was spray-dried and then decomposed at 30$0^{\circ}C$ for the purpose of coating the uniform layer of magnesium oxide on the surface of particles. The results obtained are as follows: (1) About two thirds of iron content could be removed from silicon by washing silicon powders with hydrochloride. (2) Uniform layer of magnesium oxide on the surface of silicon could be prepared by spray-drying suspension and by decomposing it. (3) B. E. T. specific surface area of fine silicon particles was 2, 826.753$m^3$/kg. (4) In the binary system with two sizes of 40-53$\mu\textrm{m}$ particles and <10$\mu\textrm{m}$ particles the maximum bulk density of packing was 55% of theoretical value and that of compacts made at the pressure of 4, 255 kg./$cm^2$ (60 kpsi) was 73% of theoretical value. (5) In the ternary system with three sizes the maximum bulk density of packing was 1.43 g/$cm^3$and that of compacts was 1.80g/$cm^3$which is equivalent to 77.6% of theoretical value. The composition of the closest compact was consisted of 50% of 40-53$\mu\textrm{m}$ particles 20% of 10-30$\mu\textrm{m}$ particles and 30% of <10$\mu\textrm{m}$ parti-cles.

• Korean Journal of Materials Research
• /
• v.7 no.11
• /
• pp.986-990
• /
• 1997

LED와 LD의 수명과 효율은 결정에 존재하는 결함의 밀도에 반비례하며, 이러한 결함의 밀도는 적당한 기판을 사용하거나, 기판의 표면을 적절하게 제어함으로써 줄일 수 있다. GaN성장시 원자 단위의 매끄러운 표면은 완충충 성장이나 질화처리를 함으로써 얻어질 수 있다. 이렇게 얻어진 원자 단위의 매끄러운 표면에 의해 기판과 박막상이의 계면 자유에너지가 감소하기 때문에 2D성장이 촉진된다. 사파이어(AI$_{2}$O$_{3}$(0001))기판을 사용한 GaN 왕충충성장과 진화처리에 대한 최적조건은 AFM(Atomic Force Microscope)측정 결과에 의해 결정되었다. AFM에 의해 얻어진 표면 평활도의 개념은 사파이어 기판을 사용한 GaN박막성장의 최적조건을 결정하는 데 있어서 높은 신뢰도를 가질 수 있다.

• Journal of Powder Materials
• /
• v.12 no.3
• /
• pp.214-219
• /
• 2005

In order to investigate the formation of AlN, mechanical alloying was carried out in $N_2$ and $NH_3$ atmosphere. Differential thermal analysis (DTA), x-ray diffraction (XRD) and chemical analysis were carried out to examine the formation behavior of aluminum nitrides. No diffraction pattern of AlN was observed in XRD analysis of the as-milled powders in $NH_3\;or\;N_2$ atmosphere. However, DTA and chemical analysis indicated that the precursors for AlN were formed in the Al powders milled in $NH_3$ atmosphere. The AlN precursors transformed to AlN after heat treatment at and above $600^{\circ}C$. It was considered that the reaction between Al and $NH_3$ was possible by the formation of fresh Al surface during mechanical alloying of Al powders.