• Polymer(Korea)
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• v.25 no.1
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• pp.142-150
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• 2001

Until now rubber industry field has used organic solvent base adhesive, there was always existed a fire risk, variety of quality and harmfulness of human body. To solve this problem we were developed a new adhesive that was maked by raw materials of hydrocarbon series which has the properties of nonvolatile and high flash point. Because of this new adhesive has the properties of nonvolatile and non-harmfulness to the human body, we expected to solve the problems of a fire hazard and the pollution of the environmental. Instead of the rubber binder that is used to a present adhesive, the new idea is adopted in a new type of adhesive. Nonvolatile solvent penetrated to the rubber surface and caused the swelling in rubber surface and as a result of this action, it has the self-adhesive power. In comparision with the present adhesive a new type of adhesive remarkably improved the maintenance time of adhesion and the durability of this adhesive showed similar aspect. Because it did not exhibit a drop of physical properties of rubber which was caused by swelling effect, we estimate that new type adhesive are very stable and not reacted to several rubber additives. While present adhesive appear the crack at cutting surface of curing rubber that caused by gas, new type adhesive not exist these crack.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1999.10a
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• pp.3-4
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• 1999

최근 산업이 고속도화, 고능률화 및 고정멸화의 추세로 발전함에 따라 우수한 내마모성, 인성, 고온 안정성 및 내구성을 갖는 공구 및 금형을 요구하게 되었다. 그러나 이와같은 성질들은 어떤 단일 재료에서는 얻을 수 없으며 적당한 기판공구나 금혈위에 내마모성 보호피막을 coating함으로 비교적 저렴하게 얻을 수 있다. 화학증착법으로 TiC, TiN등을 증착시킬때에는 $1000^{\circ}C$정도의 반응온도가 필요하며 이러한 증착온도는 모재가 초경합금일때는 문제가 안되나 강재일 경우 모재의 연화와 칫수변화의 문제를 야기시킨다. 최근에는 플라즈마를 사용하여 증착반응온도를 $550^{\circ}C$ 이하로 낮추는 플라즈마 화학 증착볍(PACVD)이 대두되고 있다. 그러나 이 방법어서 는 뚱착하려는 금속원소가 TiCl4의 형태로 공급되고 있으므로 생성된 층이 염소를 포함하고 있다. 이 층에 잔존하는 염소는 층의 기계적 성질을 저하시키고 층내의 stress를 유발시킨다. 또한 HCI개스의 생성으로 인하여 펌프 및 장비의 부식이 촉진 된다 이러한 결점을 극복하기 위하여 금속유기화합물 전구체(metallo-organic precursor)로 $TiCl_4$를 대체하고자 하는 연구가 활발하게 진행되고 있으며 본 연구실에서 이에 대하여 연구한 결과를 소개하고자 한다. diethylamino titanium을 전구체로 사용하여 $H_2,\;N_2,\;Ar$분위기하에서 pulsed d.c.를 사용하는 MO-PACVD에 의하여 $150~250^{\circ}C$의 저온에서 Al 2024 기판에 TiCN층 형 성을 하였다. 전구체 증발온도는 $74~78^{\circ}C$의 온도범위어야 하며 고경도의 코탱층은 54% duty, 14.2kHz, 450V의 조건에서 얻어졌으며 duty, 주파수, 전압이 증가함에 따라 경도는 저하되었다. 이때의 표면 morphology를 SEM으로 조사한바 dome structure가 크게 발달되었음을 알 수 있었다. 본 실험의 온도 범위내에서 얻은 TiCN 증착반응의 활성화에너지는 7.5Kcal/mol이었다. 증착된 TiCN층은 우수한 내마모섣을 나타내었으며 스크래치테스트 결과 17N의 엄계하중을 나타내었다. 본 연구에서 변화 시킨 duty, 주파수, 전압의 범위에서는 층의 밀착력은 크게 변화하지 않았다. titanium isopropoxide를 전구체로 사용하여 Hz, Nz 분위기하에서 d.c.를 사용하는 MO-PACVD에 의하여 Ti(NCO) 코팅층을 SKDll, SKD61, SKH9 공구강에 형성시키는 공정을 개발하였다. 최적의 Ti(NCO) 코탱층을 얻기 위해 유입전구체 부피%의 양은 향착압력의 5%를 넘지 않아야 되고 수소와 젤소 가스비가 1:1일 때 가장 높은 코팅층의 경도값을 나타내었다. 수소와 질소 가스비가 3:7일 때 TiFeCr(NCO)의 복화합물 코팅층이 형성됨을 알 수 있었고 500t의 증착온도에서 얻은 Ti(NCO) 코팅층이 높은 경도값과 좋은 내식성을 나타내었다. 또한 이와같은 Ti(NCO) 코팅공정과 본 실험실에서 개발한 확산층만 형성시키는 plsma nitriding 공정을 결합하여 복합코탱층을 형성하였는데 이 복합코팅층은 고경도와 우수한 내마모성, 내식성 뿐만 아니라 10)N 이상의 뛰어난 밀착력을 나타내었다. 현재 많이 사용되고 있는 PVD법은 step coverage가 좋지 않은 점과 cost intensive p process라는 단점이 있다. MO-PACVD법은 이러한 문제를 해결할 수 있는 방법으로서 앞으로 지속적인 도전이 요구되는 분야이다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.351-352
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• 2011

그래핀(Graphene)은 2차원 평면구조의 $sp^2$ 탄소 결합으로 이루어진 물질이다. 일반적으로 그래핀은 탄소 원자 한층 정도의 얇은 두께를 가지면서 강철의 100배 이상 높은 강도, 다이아몬드보다 2배 이상 뛰어난 열 전도성, 그리고 규소보다 100배 이상 빠른 전자이동도 등의 매우 우수한 특성을 지닌다. 그래핀을 합성하거나 얻는 방법에는, 기계적 박리법(Micro mechanical exfoliation), 산화흑연(graphite oxide)을 이용한 reduced graphene oxide(RGO)방법과 탄화 규소(SiC)를 이용한 epitaxial growth 방법 등이 있지만, 대 면적화가 어렵거나 구조적 결함이 큰 문제점이 있다. 반면, 탄화수소(hydrocarbon)를 탄소 공급원으로 하는 열화학 기상 증착법(Thermal chemical vapor deposition, TCVD)은 구조적 결함이 상대적으로 적으면서 대 면적화가 가능하다는 이점 때문에 최근 가장 많이 이용되고 있는 방법이다. TCVD를 이용, 니켈, 몰리브덴, 금, 코발트 등의 금속에서 그래핀 합성연구가 보고되었지만, 대부분 수 층(fewlayer)의 그래핀이 합성되었다. 하지만, 구리 촉매를 이용하는 것이 단층 그래핀 합성에 매우 효율적이라는 연구결과가 보고되었다. 구리의 경우, 낮은 탄소융해도(solubility of carbon) 때문에 표면에서 self limiting 과정을 통하여 단층 그래핀이 합성된다. 그러나 단층 그래핀 일지라도 면저항(sheet resistance)이 매우 높고, 이론적 계산값에 비해 전자이동도(electron mobility)가 낮게 측정된다. 이러한 원인은 구조적 결함에서 기인된 것으로써 산업으로의 응용을 어렵게 만들기 때문에 양질의 단층 그래핀 합성연구는 필수적이다[1,2]. 본 연구에서는 TCVD를 이용하여 구리 포일(25 ${\mu}m$, Alfa Aeser) 위에 메탄가스를 탄소공급원으로 하여 수소를 함께 주입하고, 메탄가스의 양과 합성시간, 열처리 시간을 조절하면서 균일한 단층 그래핀을 합성하였다. 합성된 그래핀을 $SiO_2$ (300 nm)기판위에 전사(transfer)후 라만 분광법(raman spectroscopy)과 광학 현미경(optical microscope)을 통하여 분석하였다. 그 결과, 열처리 시간이 증가할수록 촉매로 사용된 구리 포일의 grain size가 커짐을 확인하였으며, 구리 포일 위에 합성된 그래핀의 grain size는, 구리 포일의 grain size에 의존하여 커짐을 확인하였다. 또한 동일한 grain 내의 그래핀은 균일한 층으로 합성되었다. 이는 기계적 박리법, RGO 방법, epitaxial growth 방법으로 얻은 그래핀과 비교하여 매우 뛰어난 결정성을 지님이 확인되었다. 본 연구를 통하여 면적이 넓으면서도 결정성이 매우 뛰어난 양질의 단층 그래핀 합성 방법을 확립하였다.

• Journal of the East Asian Society of Dietary Life
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• v.18 no.6
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• pp.989-996
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• 2008

In this study we assessed the effects of gamma irradiation ($0.5{\sim}3\;kGy$) on the microbial and physico-chemical characteristics of maesil (Prunus mume) stored for 9 days at $20^{\circ}C$. Total aerobic bacteria, yeasts and molds were significantly decreased with increases in the irradiation dosage. In terms of the Hunter's color value, irradiated samples evidenced a higher b-value, but a lower a-value than the non-irradiated samples. Hardness was reduced with increment in the irradiation dose level. The contents of total sugar, hydrogen donating activity and organic acids were not affected by irradiation. The reducing sugar contents of the irradiated samples were superior to those of the non-irradiated samples. Vitamin C contents were reduced with the progression of storage periods and increases in the dosage level. These results demonstrated that gamma irradiation of 0.5 to 3 kGy affected the microbiological safety of maesil, but did not affect the physico-chemical characteristics(total sugar, hydrogen donating activity and organic acid) but the Hunter's color value, hardness, and vitamin C contents of the maesil deteriorated with gamma irradiation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.5376-5383
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• 2011

The objective of this study is the development of carbon-recycle technology, that converts carbon dioxide captured from flue gas to carbon monoxide or carbon for reuse in industrial fields. It is difficult to decompose $CO_2$ because $CO_2$ is very stable molecule. And then metal oxide was used as an activation agent or catalyst for the decomposition of $CO_2$ at low temperature. Metal oxides, which converts $CO_2$ to CO or C, were prepared using Ni-ferrite by solid state method and hydrothermal synthesis in this study. TPR/TPO and TGA were used as an analysis method to analyze the decomposition characteristics of $CO_2$. As the results, the reduction area of $H_2$ was high value at 15 wt% of NiO and the decomposition area of $CO_2$ was superior capacity at 5 wt% of NiO. However, TGA data showed contrary results that reduction area of $H_2$ was 28.47wt% and oxidation area by $CO_2$ was 26.95wt% at 2.5 wt% of NiO, one of the Ni-ferrite powders synthesized using solid state method. $CO_2$ decomposition efficiency was 94.66% and it is excellent results in comparison with previous studies.

• Clean Technology
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• v.27 no.2
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• pp.190-197
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• 2021

Kraft lignin is a by-product of the pulp and paper industry, obtained as a black liquor after the extraction of cellulose from wood through the Kraft pulping process. Right now, kraft lignin is utilized as a low-grade boiler fuel to provide heat and power but can be converted into high-calorific biofuels or high-value chemicals once the efficient catalytic depolymerization process is developed. In this work, the multi-functional catalyst of Ru-Mg-Al-oxide, which contains hydrogenation metals, acid, and base sites for the effective depolymerization of kraft lignin are prepared, and its lignin depolymerization efficiency is evaluated. In order to understand the role of different active sites in the lignin depolymerization, the three different catalysts of MgO, Mg-Al-oxide, and Ru-Mg-Al-oxide were synthesized, and their lignin depolymerization activity was compared in terms of the yield and the average molecular weight of bio-oil, as well as the yield of phenolic monomers contained in the bio-oil. Among the catalysts tested, the Ru-Mg-Al-oxide catalyst exhibited the highest yield of bio-oil and phenolic monomers due to the synergy between active sites. Furthermore, in order to maximize the extent of lignin depolymerization over the Ru-Mg-Al-oxide, the effects of reaction conditions (i.e., temperature, time, and catalyst loading amount) on the lignin depolymerization were investigated. Overall, the highest bio-oil yield of 72% and the 3.5 times higher yield of phenolic monomers than that without a catalyst were successfully achieved at 350 ℃ and 10% catalyst loading after 4 h reaction time.

• Journal of the Korea Organic Resources Recycling Association
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• v.28 no.4
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• pp.15-22
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• 2020

The landfill gas produced in landfill is generally made up of methane(CH4) and carbon dioxide(CO2) of more than 90%, with the remainder made up of hydrogen sulfide(H2S). However, separate pre-treatment facilities are essential as hydrogen sulfide contained in landfill gas is combined with oxygen during the combustion process to generate sulfur oxides and acid rain combined with moisture in the atmosphere. Various desulfurization technologies have been used in Korea to desulfurize landfill gas. Although general desulfurization processes apply various physical and chemical methods, such as treatment of sediment generation according to the CaCO3 generation reaction and treatment through adsorbent, there is a problem of secondary wastes such as wastewater. As a way to solve this problem, a biological treatment process is used to generate and treat it with sludge-type sulfide (S°) using a biological treatment process.In this study, as a basic study of technology for utilizing the biological treatment by-products of hydrogen sulfide in landfill gas, an experiment was conducted to use the by-product as a mixture of concrete. According to the analysis of the mixture concrete strength of sulfur products, the mixture of sulfur by-products affects the strength of concrete and shows the highest strength value when mixing 10%.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.3
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• pp.103-111
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• 2021

Hexagonal shape Si crystals were grown by the mixed-source hydride vapor phase epitaxy (HVPE) method of mixing solid materials such as Si, Al and Ga. In the newly designed atmospheric pressure mixed-source HVPE method, nuclei are formed by the interaction between GaCl_n, AlCl_n and SiCl_n gases at a high temperature of 1200℃. In addition, it is designed to generate a precursor gas with a high partial pressure due to the rapid reaction of Si and HCl gas. The properties of hexagonal Si crystals were investigated through scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), high-resolution X-ray diffraction (HR-XRD), and Raman spectrum. From these results, it is expected to be applied as a new material in the Si industry.

• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.555-561
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• 2011

The objective of this study is the development of carbon recycle technology which converts $CO_2$ captured from flue gas to CO or carbon and reuse in industrial fields. Since $CO_2$ is very stable and difficult to decompose, metal oxide was used as an activation agent for the decomposition of $CO_2$ at low temperature. Metal oxides which convert $CO_2$ to CO or carbon at $500^{\circ}C$ were prepared using Zn-ferrite by the solid state reaction and hydrothermal synthesis. The behaviors of $CO_2$ decomposition were studied using temperature programmed reduction/oxidation (TPR/TPO) and thermogravimetric analyzer (TGA). Zn-ferrite containing 5 wt% ZnO showed the largest reduction and oxidation. Reduction by $H_2$ was 26.53 wt%, oxidation by $CO_2$ was 25.73 wt% and 96.98% of adsorbed $CO_2$ was decomposed to $CO_2$ and carbon with excellent oxidation-reduction behaviors.

• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.1-10
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• 2023

Due to the development of the industrial revolution, regulations on exhaust emissions have been continuously strengthened to reduce the rapidly increasing greenhouse gas emissions. The use of environmentally friendly fuels is essential to meet these regulations. Hydrogen has been attracting attention as a future environmentally friendly fuel, but due to its material properties, it faces significant challenges in handling and storage. As an alternative, ammonia has been proposed. Ammonia can be easily liquefied at room temperature compared to hydrogen and has a high energy density. In order to examine the applicability of ammonia as an engine fuel, experiments were conducted to investigate the effects of changes in combustion control parameters in a direct injection ammonia combustion engine. The experiments were conducted by varying two variables: spark timing and excessive air ratio. Observations were made on combustion stability and the trends of exhaust emissions such as nitrogen oxides and unburned ammonia under the conditions of an engine speed of 1,500 rpm and medium to high loads (brake torque of 200 Nm). By optimizing the combustion control parameters, conditions for stable combustion even when using ammonia as the sole fuel were identified, and plans are underway to apply strategies for future expansion of the operating range.