• Journal of the Korean Ceramic Society
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• v.26 no.3
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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/$\textrm{mm}^2$.

• Journal of Powder Materials
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• v.28 no.4
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• pp.342-351
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• 2021

Because of its unique properties, tungsten is a strategic and rare metal used in various industrial applications. However, the world's annual production of tungsten is only 84000 t. Ammonium paratungstate (APT), which is used as the main intermediate in industrial tungsten production, is usually obtained from tungsten concentrates of wolframite and scheelite by hydrometallurgical treatment. Intermediates such as tungsten trioxide, tungsten blue oxide, tungstic acid, and ammonium metatungstate can be derived from APT by thermal decomposition or chemical attack. Tungsten metal powder is produced through the hydrogen reduction of high-purity tungsten oxides, and tungsten carbide powder is produced by the reaction of tungsten powder and carbon black powder at 1300-1700℃ in a hydrogen atmosphere. Tungsten scrap can be divided into hard and soft scrap based on shape (bulk or powder). It can also be divided into new scrap generated during the production of tungsten-bearing goods and old scrap collected at the end of life. Recycling technologies for tungsten can be divided into four main groups: direct, chemical, and semi-direct recycling, and melting metallurgy. In this review, the current status of tungsten smelting and recycling technologies is discussed.

• Journal of the Korean institute of surface engineering
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• v.54 no.3
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• pp.133-138
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• 2021

Ternary Ti-X-N coatings, where X = Al, Si, Cr, O, etc., have been widely used for machining tools and cutting tools such as inserts, end-mills, and etc. Ti-Al-N-O coatings were deposited onto silicon wafer and WC-Co substrates by a cathodic arc evaporation (CAE) technique at various negative substrate bias voltages. In this study, the influence of substrate bias voltages during deposition on the microstructure and mechanical properties of Ti-Al-N-O coatings were systematically investigated to optimize the CAE deposition condition. Based on results from various analyses, the Ti-Al-N-O coatings prepared at substrate bias voltage of -80 V in the process exhibited excellent mechanical properties with a higher compressive residual stress. The Ti-Al-N-O (-80 V) coating exhibited the highest hardness around 30 GPa and elastic modulus around 303 GPa. The improvement of mechanical properties with optimized bias voltage of -80 V can be explained with the diminution of macroparticles, film densification and residual stress induced by ion bombardment effect. However, the increasing bias voltage above -80 V caused reduction in film deposition rate in the Ti-Al-N-O coatings due to re-sputtering and ion bombardment phenomenon.

• Journal of the Korean institute of surface engineering
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• v.54 no.3
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• pp.139-143
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• 2021

Cr-Al-N coatings were deposited onto WC-Co substrates using a cathodic arc evaporation (CAE) system. CAE technique is recognized to be a very useful process for hard coatings because it has many advantages such as high packing density and good adhesion to metallic substrates. In this study, the influence of deposition temperature as a key process parameter on film growth behavior and mechanical properties of Cr-Al-N coatings were systematically investigated and correlated with microstructural changes. From various analyses, the Cr-Al-N coatings prepared at deposition temperature of 450℃ in the CAE process showed excellent mechanical properties with higher deposition rate. The Cr-Al-N coatings with deposition temperature around 450℃ exhibited the highest hardness of about 35 GPa and elastic modulus of 442 GPa. The resistance to elastic strain to failure (H/E ratio) and the index of plastic deformation (H³/E² ratio) were also good values of 0.079 and 0.221 GPa, respectively, at the deposition temperature of 450℃. Based on the XRD, SEM and TEM analyses, the Cr-Al-N coatings exhibited a dense columnar structure with f.c.c. (Cr,Al)N multi-oriented phases in which crystallites showed irregular shapes (50~100nm in size) with many edge dislocations and lattice mismatches.

• Journal of the Korean institute of surface engineering
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• v.56 no.5
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• pp.335-340
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• 2023

Quinary component of 3㎛ thick Ti-Al-Si-Cu-N films were deposited onto WC-Co and Si wafer substrates by using an arc ion plating(AIP) system. In this study, the influence of copper(Cu) contents on the mechanical properties and microstructure of the films were investigated. The hardness of the films with 3.1 at.% Cu addition exhibited the hardness value of above 42 GPa due to the microstructural change as well as the solid-solution hardening. The instrumental analyses revealed that the deposited film with Cu content of 3.1 at.% was a nano-composites with nano-sized crystallites (5-7 nm in dia.) and a thin layer of amorphous Si₃N₄ phase.

• Journal of Powder Materials
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• v.23 no.4
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• pp.282-286
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• 2016

A sintered body of $TiB_2$-reinforced iron matrix composite ($Fe-TiB_2$) is fabricated by pressureless-sintering of a mixture of titanium hydride ($TiH_2$) and iron boride (FeB) powders. The powder mixture is prepared in a planetary ball-mill at 700 rpm for 3 h and then pressurelessly sintered at 1300, 1350 and $1400^{\circ}C$ for 0-2 h. The optimal sintering temperature for high densities (above 95% relative density) is between 1350 and $1400^{\circ}C$, where the holding time can be varied from 0.25 to 2 h. A maximum relative density of 96.0% is obtained from the ($FeB+TiH_2$) powder compacts sintered at $1400^{\circ}C$ for 2 h. Sintered compacts have two main phases of Fe and $TiB_2$ along with traces of TiB, which seems to be formed through the reaction of TiB2 formed at lower temperatures during the heating stage with the excess Ti that is intentionally added to complete the reaction for $TiB_2$ formation. Nearly fully densified sintered compacts show a homogeneous microstructure composed of fine $TiB_2$ particulates with submicron sizes and an Fe-matrix. A maximum hardness of 71.2 HRC is obtained from the specimen sintered at $1400^{\circ}C$ for 0.5 h, which is nearly equivalent to the HRC of conventional WC-Co hardmetals containing 20 wt% Co.

• Korean Journal of Environmental Agriculture
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• v.30 no.1
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• pp.9-15
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• 2011

BACKGROUND: This study was conducted to evaluate the effects of the fertilizer sources and ground cover mulches on nutrient release, growth, and photosynthesis in small one-year-old apple (Malus ${\times}$ domestica Borkh.) trees in controlled conditions. METHODS AND RESULTS: Treatments included no fertilizer (NF), commercial organic fertilizer (CF), and poultry litter (PL) for fertilizer treatments, and wood chips (WC), shredded paper (SP), green compost (GC), and grass clippings (GR) for cover mulch treatments. All treatments were applied proportionally based on the volume ratio equivalent to the soil. CF, PL, and GR treatments that had optimum carbon (C) and nitrogen (N) ratios (less than 30:1) for N mineralization through the microbes released the greatest $NH_4^+$ concentrations in the pot media at 90 days after the treatments, but GC mulch with the optimum C:N ratio did not. CF-, PL- and GR-treated plants had the largest leaf area, thickest stem diameter, longest shoot extension, and greater dry matter production. CONCLUSION(s): CF and PL showed an suitable organic nutrient source for improving plant growth in an orchard. Interestingly, GR also could be a nutrient source for tree growth, if vegetation competition is controlled by maintaining vegetation height and recycling enough grass clippings to the soil in an orchard.

• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4270-4274
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• 2011

A method is proposed for determining chromium content in the carbon steel pipes of a nuclear power plant (NPP) to evaluate wall thinning caused by flow-accelerated corrosion (FAC). A flat file was used to obtain filings samples. To assess sampling quality, a disk form of SRM 1227 was ground with the flat file, and the amount of Cr in the filings was determined by ICP-AES. The content of chromium in the filings of SRM 1227 was estimated as six times higher than the certified value due to the contamination of chromium in the file. To eliminate chromium contamination from the file, it was coated with WC-12Co using high-velocity oxygen-fuel (HVOF) spraying systems. After obtaining filings samples using the coated file, Cr content in four types of disk-form SRMs was determined by ICP-AES. The recoveries of Cr in the disk-form SRMs were in the range of 95.4-102.6%, with relative standard deviations from 0.43 to 3.0%. The Cr contents in the filings collected from the used outlet headers of the nuclear power plants using the flat file coated were in the range of 0.11-0.19%.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.93-93
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• 2017

고전력 펄스 전원공급장치를 이용한 마그네트론 스퍼터링(high-power impulse magnetron sputtering; HiPIMS)과 직류(direct current; DC) 전원공급장치를 이용한 마그네트론 스퍼터링(DC 스퍼터링)을 이용하여 제조한 티타늄 질화물(titanium nitride; TiN) 박막의 특성을 비교하였다. HiPIMS와 DC 스퍼터링 공정 중에 빗각증착을 적용하여 TiN 박막의 미세구조와 기계적 특성의 변화를 확인하였다. TiN 박막을 코팅하기 위한 기판으로 스테인리스 강판(SUS304)과 초경(cemented carbide; WC-10wt.%Co)을 사용하였다. 기판은 알코올과 아세톤으로 초음파 처리를 실시하여 기판 표면의 불순물을 제거하였다. 기판 청정 후 진공용기 내부의 기판홀더에 기판을 장착하고 $2.0{\times}10^{-5}torr$의 기본 압력까지 진공배기를 실시하였다. 진공 용기의 압력이 기본 압력에 도달하면 아르곤(Ar) 가스를 진공용기 내부로 ${\sim}10^{-2}torr$의 압력으로 주입하고 기판홀더에 라디오 주파수(radio frequency; rf) 전원공급장치를 이용하여 - 800 V의 전압을 인가하여 글로우 방전을 발생시켜 30 분간 기판 표면의 산화막을 제거하는 기판청정을 실시하였다. 기판청정이 완료되면 기본 압력까지 진공배기를 실시하고 Ar과 질소($N_2$)의 혼합 가스를 진공용기 내부로 ${\sim}10^{-3}torr$의 압력으로 주입하여 HiPIMS와 DC 스퍼터링으로 TiN 박막 제조를 실시하였다. 빗각의 크기는 $45^{\circ}$와 $-45^{\circ}$이었다. 제조된 TiN 박막은 주사전자 현미경, 비커스 경도 측정기 그리고 X-선 회절 분석기를 이용하여 특성을 분석하였다. HiPIMS로 제조한 TiN 박막은 기판 전압을 인가하지 않아도 색상이 노란색을 보이지만, DC 스퍼터링으로 제조한 TiN 박막은 기판 전압을 인가하지 않으면 노란색을 보이지 않고 어두운 갈색에 가까운 색을 보였다. TiN 박막의 경도는 HiPIMS로 제조한 TiN 박막이 DC 스퍼터링으로 제조한 TiN 박막보다 높았다. 이러한 TiN 박막의 특성 차이는 DC 스퍼터링과 비교하여 높은 HiPIMS의 이온화율에 의한 결과로 판단된다. 빗각을 적용한 TiN 박막은 미세구조 변화를 보였으며 이러한 미세구조 변화는 TiN 박막의 특성에 영향을 미치는 것을 확인하였다.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.1
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• pp.25-32
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• 2020

Generally, high-temperature, high-pressure, high-priced sintering equipment is used for diamond sintering, and conductivity is a problem for improving the surface modification of the sintered body. In this study, to improve the efficiency of diamond sintering, we identified a new process and material that can be sintered at low temperature, and attempted to develop a composite thin film that can be discharged by doping boron gas to improve the surface modification of the sintered body. Sintered bodies were sintered by mixing Si and two diamonds in different particle sizes based on CIP molding and HIP molding. In CVD deposition, CVD was performed using WC-Co cemented carbide using CH₄ and H₂ gas, and the specimen was made conductive using boron gas. According to the experimental results of the sintered body, as the Si content is increased, the Vickers hardness decreases drastically, and the values of tensile strength, Young's modulus and fracture toughness greatly increase. Conductive CVD deposited diamond was boron deposited and discharged. As the amount of boron added increased, the strength of diamond peaks decreased and crystallinity improved. In addition, considering the release processability, tool life and adhesion of the deposition surface according to the amount of boron added, the appropriate amount of boron can be confirmed. Therefore, by solving the method of low temperature sintering and conductivity problem, the possibility of solving the existing sintering and deposition problem is presented.