• 한국세라믹학회지
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• 제46권6호
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• pp.668-672
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• 2009

Heavy metal ion immobilization properties of microporous ettringite (3Ca$O{\cdot}Al_2O_3{\cdot}3CaSO_4{\cdot}32H_2$) body were examined using standard solutions of typical heavy metals. Microporous Ettringite body with desirable shape for an ionic adsorbent was obtained by the self hardening of the paste prepared from the mixture of tricalcium aluminate($C_3$A) and gypsum(CaS$O_4{\cdot}2H_2$O). Crushed grains of ettringite were soaked in each standard solutions of Pb, Co, Cd, Mn and Cr concentrated at 200 ppm. In order to evaluate the ionexchange and immobilization ability, the ionic concentration of the filtrate solution as well as the solution obtained after leaching test was measured. As a result, for the heavy metal ions excepting Cr, porous ettringite body was revealed to be excellent in ionic exchange and immobilization properties though some ions eluted at the severe condition of pH 2. The adsorption and keeping capacity for four heavy metals showed the order of $Pb{>}Co{>}Cd{>}$Mn.

• 한국안광학회지
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• 제5권2호
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• pp.207-210
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• 2000

일축가압 소결 및 열처리하여 SiC-TiC 안경렌즈 절삭용 재료를 제조하였다. TiC의 함량은 0, 10, 20, 30wt%이었다. 일축가압소결 후 열처리한 안경렌즈 절삭용 복합재료의 미세구조는 TiC의 양에 크게 의존하였다. TiC의 함량이 증가할수록 파괴인성값이 증가됨을 알 수 있었다. 광학현미경과 X-ray 회질분석을 통하여 미세구조와 상분석을 하였다. 시편의 미세구조는 길게자란 SiC입자와 기지형의 TiC입자로 구성되었다. 본 연구에서 연구된 안경렌즈 절삭용 시편의 대표적인 경도와 파괴인성은 각각 14.9GPa과 $5.7MPa{\cdot}m^{1/2}$이었다.

• 한국세라믹학회지
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• 제26권3호
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• pp.323-330
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• 1989

Wear restance titanium carbonitride (TiCN) films were deposited on the SKH9 tool steels and WC-Co cutting tools by plasma assisted chemical vapor deposition (PACVD) using a gaseous mixture of TiCl4, CH4, N2, H2 and Ar. The effects of the deposition temperature and RF(Radio Frequency) power on the deposition rate, chlorine content and crystallinity of the deposited layer were studied. The experimental results showed that the stable and adherent films could be obtained above the deposition temperature of 47$0^{\circ}C$ and maximum deposition rate was obtained at 485$^{\circ}C$. The deposition rate was much affected by RF power and maximum at 40W. The crystallinity of the deposited layer was improved with increasing the deposition temperature and RF power. The TiCN films deposited by PACVD contained much chlorine. The chlorine content in the TiCN films was affected by deposition conditions and decreased with improving the crystallinity of the deposited layer. The deposited TiCN films deposited at the deposition temperature of 52$0^{\circ}C$ and RF power of 40W had an uniform surface with very fine grains of about 500$\AA$ size. The microhardness of the deposited layer was 2,300Kg/$\textrm{mm}^2$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.456-459
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• 2000

Thin films of vanadium oxide(V$O_x$) have been deposited by r.f. magnetron sputtering from $V_2$$O_5$ prget in gas mixture of argon and oxygen. Crystal structure, surface morphology, chemical composition and bonding properties of films in-situ annealed in $O_2$ ambient with various heat-treatment conditions are characterized through XRD, SEM, AES, RBS and FTIR measurements. The filrns annealed below 200 $^{\circ}C$are amorphous, and those annealed above 30$0^{\circ}C$ are polycrystalline. The growth of grains and the transition of vanadium oxide into the higher oxide have been obsenred with increasing the annealing temperature and time. The increase of O/V ratio with increasing the annealing temperature and time is attributed to the diffusion of oxygen and the partial filling of oxygen vacancies. It is observed that the oxygen atoms located on the V-0 plane of $V_2$$O_5$ layer participate more readily in the oxidation process.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.190.2-190.2
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• 2013

Vanadium dioxide ($VO_2$) has been widely attracted for academic research and industrial applications due to its metal-insulator transition (MIT) temperature close to room temperature. We synthesized VOx film on (0001) sapphire substrate with vanadium target (purity: 99.9%) using DC magnetron sputtering in Ar ambience at a pressure of $10^{-3}$ Torr at $400{\sim}700^{\circ}C$. The VOx film subsequently was annealed at difference temperatures in ambience of Ar and $O_2$ gas mixture at $60{\sim}800^{\circ}C$. The structural properties of the films were investigated using scanning electron microscopic (SEM), x-ray diffraction (XRD) and x-ray absorption fine structure (XAFS) measurements. SEM reveal that small grains formed on the substrates with a roughness surface. XRD shows oriented $VO_2$(020) crystals was deposited on the $Al_2O_3$(006) substrate. From I-V measurements, the electric resistance near its MIT temperature were dramatically changed by ${\sim}10^4$ during heating and cooling the films. We will also discuss the temperature-dependent local structural changes around vanadium atoms using XAFS measurements.

• 열처리공학회지
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• 제23권6호
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• pp.315-322
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• 2010

Effect of hardenability, grain size and microstructural change according to the change of austenitizing temperature was analyzed in Jominy hardenability test of AISI 51B20 steel. Grain growth was small, 7 ${\mu}m$ and 12 ${\mu}m$ austenite grain sizes at austenitizing temperature of $900^{\circ}C$ and $1000^{\circ}C$, respectively, while rapid grain growth was observed up to 30 ${\mu}m$ austenite grain size at austenitizing temperature of $1100^{\circ}C$. As austenitizing temperature increased from $900^{\circ}C$ to $1100^{\circ}C$, hardenability in the region within 15 mm from end-quenched surface decreased due to the grains growth of bainite and martensite mixture, on the other hand the hardenability in the region exceeding 15 mm from end-quenched surface increased. Increased hardenability was attributed to different microstructures; pearlite, fine pearlite and bainite, and bainite and martensite structures at austenitizing temperature of $900^{\circ}C$, $1000^{\circ}C$ and $1100^{\circ}C$, respectively.

• 한국표면공학회지
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• 제29권5호
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• pp.563-569
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• 1996

Degradation of $Zn_3N_2$ films is studied by using several analytical techniques. Polycrystalline $Zn_3N_2$ films prepared by reactie rf magnetron sputtering are kept in the air. Electrical and optical properties are measured by using van der Pauw technique and double-beam spectrometry. Structure and chemical bonding states are studied by X-ray diffraction(XRD), Fourier transfer infrared ray spectroscopy(FT-IR) and X-ray photoelectron specroscopy (XPS). Significant differences are observed in optical properties between the degraded film and the ZnO film. XRD analysis reveals that the degraded film contains very small ZnO grains because very weak and broad ZnO peaks are observed. XPS and FT-IR measurements reveal the formation of $Zn(OH)_2$ in the degraded film. The existence of N-H bonds in degraded films is exhibited from the N 1s spectra. $Zn_3N_2$ change into the mixture of ZnO, $Zn(OH)_2$ and an ammonium salt.

• 한국전기전자재료학회논문지
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• 제21권5호
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• pp.463-467
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• 2008

Aluminum nitride (AlN) thin films have been deposited on Au electrodes by using reactive RF magnetron sputtering method in a gas mixture of Ar and $N_2$ at different substrate temperature. It was found that substrate temperature was varied in the range up to $400^{\circ}C$, highly c-axis oriented film can be obtained at $300^{\circ}C$ with full width at half maximum (FWHM) $3.1^{\circ}$. Increase in surface roughness from 3.8 nm to 5.9 nm found to be associated with increase in grain size, with substrate temperature; however, the AlN film fabricated at $400^{\circ}C$ exhibited a granular type of structure with non-uniform grains. The Al 2p and N 1s peak in the X-ray photoelectron spectroscopy (XPS) spectrum confirmed the formation of Al-N bonds. The XPS spectrum also indicated the presence of oxynitrides and oxides, resulting from the presence of residual oxygen in the vacuum chamber. It is concluded that the AlN film deposited at substrate temperature of $300^{\circ}C$ exhibited the most desirable properties for the application of high-frequency surface acoustic devices.

• 천문학회지
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• 제46권6호
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• pp.235-242
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• 2013

We compare mass-loss rates of OH/IR stars obtained from radio observations with those derived from the dust radiative transfer models and IR observations. We collect radio observational data of OH maser and CO line emission sources for a sample of 1533 OH/IR stars listed in Suh & Kwon (2011). For 1259 OH maser, 76 CO(J=1-0), and 55 CO(J=2-1) emission sources, we compile data of the expansion velocity and mass-loss rate. We use a dust radiative transfer model for the dust shell to calculate the mass-loss rate as well as the IR color indices. The observed mass-loss rates are in the range predicted by the theoretical dust shell models corresponding to $\dot{M}=10^{-8}M_{\odot}/yr-10^{-4}M_{\odot}/yr$. We find that the dust model using a simple mixture of amorphous silicate and amorphous $Al_2O_3$ (20% by mass) grains can explain the observations fairly well. The results indicate that the dust radiative transfer models for IR observations generally agree with the radio observations. For high mass-loss rate OH/IR stars, the mass-loss rates obtained from radio observations are underestimated compared to the mass-loss rates derived from the dust shell models. This could be because photon momentum transfer to the gas shell is not possible for the physical condition of high mass-loss rates. Alternative explanations could be the effects of different dust-to-gas ratios and/or a superwind.

• 한국지구과학회지
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• 제42권4호
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• pp.425-444
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• 2021

Investigating the physical and chemical properties of riverine wetlands is necessary to understand their distribution characteristics and depositional environment. This study investigated the physical (particle size, color, and type) and chemical properties (organic, inorganic, and moisture contents) of sediments in Samrak wetland, located in the Nakdong River estuary area in Busan, South Korea. The particle size analysis indicated that the hydraulic conductivity values for the coarse grain and the mixture of coarse and fine grains ranged from 2.03 to 3.49×10^-1 cm s^-1 and 7.18×10^-3 to 1.24×10^-7 cm s^-1, respectively. In-situ water quality and laboratory-based chemical analyses and radon-222 measurement were performed on groundwater and surface water in the wetland and water from the nearby Nakdong River. The physical and chemical properties of Samrak wetland was characterized by the sediments in the vertical and lateral direction. The concentrations of chemical components in the wetland groundwater were distinctly higher than those in the Nakdong River water though the wetland groundwater and Nakdong River water equally belonged to the Ca-HCO₃ type.