• Title/Summary/Keyword: noble gas

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Hydrocarbon Gas-sensing Properties of Catalytic Combustion Type Gas Sensor (접촉연소식 가스센서의 탄화수소계 가스 감응 특성)

  • Lee, Dae-Sik;Lee, Sang-Mun;Nam, Ki-Hong;Han, Sang-Do;Lee, Duk-Dong
    • Journal of Sensor Science and Technology
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    • v.8 no.4
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    • pp.327-332
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    • 1999
  • Catalytic combustion type gas sensors were fabricated by using noble metal(Pt and Pd) added ${\gamma}-Al_2O_3$ powder with specific surface area of $200\;m^2/g$. The fabricated sensor showed power consumption of 500 mW at the operating voltage of 1.75 V and high sensitivity of about 120 mV for butane, methane, or propane 100%LEL, respectively. The sensor properties also showed good linearity to hydrocarbon gas concentration variation, reproductivity and stability for relative humidity variation. And it showed high stability in butane ambient for 100 days.

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A review of smart exsolution catalysts for the application of gas phase reactions (기상 반응용 스마트 용출 촉매 연구 동향)

  • Huang, Rui;Kim, Hyung Jun;Han, Jeong Woo
    • Ceramist
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    • v.23 no.2
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    • pp.211-230
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    • 2020
  • Perovskite-type oxides with the nominal composition of ABO3 can exsolve the B-site transition metal upon the controlled reduction. In this exsolution process, the transition metal emerges from the oxide lattice and migrates to the surface at which it forms catalytically active nanoparticles. The exsolved nanoparticles can recover back to the bulk lattice under oxidation treatment. This unique regeneration character by the redox treatment provides uniformly dispersed noble metal nanoparticles. Therefore, the conventional problem of traditional impregnated metal/support, i.e., sintering during reaction, can be effectively avoided by using the exsolution phenomenon. In this regard, the catalysts using the exsolution strategy have been well studied for a wide range of applications in energy conversion and storage devices such as solid oxide fuel cells and electrolysis cells (SOFCs and SOECs) because of its high thermal and chemical stability. On the other hand, although this exsolution strategy can also be applied to gas phase reaction catalysts, it has seldomly been reviewed. Here, we thus review recent applications of the exsolution catalysts to the gas phase reactions from the aspects of experimental measurements, where various functions of the exsolved particles were utilized. We also review non-perovskite type metal oxides that might have exolution phenomenon to provide more possibilities to develop higher efficient catalysts.

Optimization of the Pt Nanoparticle Size and Calcination Temperature for Enhanced Sensing Performance of Pt-Decorated In2O3 Nanorods

  • Choi, Seung-Bok;Lee, Jae Kyung;Lee, Woo Seok;Ko, Tae Gyung;Lee, Chongmu
    • Journal of the Korean Physical Society
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    • v.73 no.10
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    • pp.1444-1451
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    • 2018
  • The surface-to-volume ratio of one-dimensional (1D) semiconductor metal-oxide sensors is an important factor for achieving good gas sensing properties because it offers a wide response area. To exploit this effect, in this study, we determined the optimal calcination temperature to maximize the specific surface area and thereby the sensitivity of the sensor. The $In_2O_3$ nanorods were synthesized by using vapor-liquid-solid growth of $In_2O_3$ powders and were decorated with the Pt nanoparticles by using a sol-gel method. Subsequently, the Pt nanoparticle-decorated $In_2O_3$ nanorods were calcined at different temperatures to determine the optimal calcination temperature. The $NO_2$ gas sensing properties of five different samples (pristine uncalcined $In_2O_3$ nanorods, Pt-decorated uncalcined $In_2O_3$ nanorods, and Pt-decorated $In_2O_3$ nanorods calcined at 400, 600, and $800^{\circ}C$) were determined and compared. The Pt-decorated $In_2O_3$ nanorods calcined at $600^{\circ}C$ showed the highest surface-to-volume ratio and the strongest response to $NO_2$ gas. Moreover, these nanorods showed the shortest response/recovery times toward $NO_2$. These enhanced sensing properties are attributed to a combination of increased surface-to-volume ratio (achieved through the optimal calcination) and increased electrical/chemical sensitization (provided by the noble-metal decoration).

Char Oxidation Characteristics of High Ash Coal in Drop Tube Furnace (고회분탄의 촤 산화 반응 특성 연구)

  • An, Ke-Ju;Lee, Byoung-Hwa;Kim, Sang-In;Kim, Man-Cheol;Kim, Seung-Mo;Jeon, Chung-Hwan
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.4
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    • pp.405-413
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    • 2013
  • The char oxidation characteristics of high ash coal were experimentally investigated at several temperatures (from 900 to $1300^{\circ}C$) for 4 types of coals (Gunvor, Glencore, Noble, and ECM) under atmospheric pressure in a drop tube furnace (DTF). The char reaction rate was calculated from the exhaust gas concentrations (CO and $CO_2$) using FT-IR, and the particle temperature was measured using the two-color method. In addition, the activation energy and pre-exponential factor for high ash coal char were calculated based on the Arrhenius equation. The results show that as the ash content increases, the particle temperature and area reactivity decreases. This is because in high ash coal, the large heat capacity of the ash, ash vaporization, and relatively low fixed carbon content of ash suppress combustibility during char oxidation. As a result, the higher ash content of coal leads to high activation energy.

A Downwardly Deflected Symmetric Jet to prevent Edge Overcoating in Continuous Hot-Dip Galvanizing (연속식 용융아연도금 공정에서 단부 과도금 현상을 방지하기 위한 하향 대칭 분류유동 연구)

  • Ahn, Gi-Jang;Chung, Myung-Kyoon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.10 s.241
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    • pp.1156-1162
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    • 2005
  • In this study, a noble method is proposed to prevent the edge overcoating (EOC) that may develop near the edge of the steel strip in the gas wiping process of continuous hot-dip galvanizing. In our past study (Trans. of the KSME (B), Vol. 27, No. 8, pp. $1105\~1113$), it was found that EOC is caused by the alternating vortices which are generated by the collision of two opposed jets in the region outside the steel strip. When the two opposed jets collide at an angle much less than $180^{o}$, non-alternating stable vortices are established symmetrically outside the steel strip, which lead to nearly uniform pressure on the strip surface. In order to deflect both jets downward by a certain angle, a cylinder with small diameter is installed tangentially to the exit of the lower lip of the two-dimensional jet. In order to find an optimum cylinder diameter, the three dimensional flow field is analysed numerically by using the commercial code, STAR-CD. And the coating thickness is calculated by using an integral analysis method to solve the boundary layer momentum equation. In order to compare the present noble method with the conventional baffle plate method to prevent the EOC, the flow field with a baffle plate is also calculated. The calculation results show that the tangentially installed cylinder at the bottom lip of the jet exit is more effective than the baffle plate to prevent EOC.

Synthesis of the Carbon Nano/micro Coils Applicable to the Catalyst Support to Hold the Tiny Catalyst Grain (매우 작은 크기의 촉매 알갱이를 지지하기 위한 촉매 지지대용 탄소 나노/마이크로 코일의 합성)

  • Park, Chan-Ho;Kim, Sung-Hoon
    • Journal of the Korean Vacuum Society
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    • v.22 no.6
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    • pp.277-284
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    • 2013
  • Carbon coils could be synthesized using $C_2H_2/H_2$ as source gases and $SF_6$ as an incorporated additive gas under thermal chemical vapor deposition system. The Ni layer on the $SiO_2$ substrate was used as a catalyst for the formation of the carbon coils. The characteristics (formation densities, morphologies, and geometries) of the as-grown carbon coils on the substrate with or without the $H_2$ plasma pretreatment process were investigated. By the relatively short time (1 minute) $H_2$ plasma pretreatment on the Ni catalyst layered-substrate prior to the carbon coils synthesis reaction, the dominant formation of the carbon microcoils on the substrate could be achieved. After the relatively long time (30 minutes) $H_2$ plasma pretreatment process, on the other hand, we could obtain the noble-shaped geometrical nanostructures, namely the formation of the numerous carbon nanocoils along the growth of the carbon microcoils. This noble-shaped geometrical nanostructure seemed to play a promising role as the good catalyst support for holding the very tiny Ni catalyst grains.

Synthesis of Pt@TiO2 Nano-composite via Photochemical Reduction Method (광화학 환원방법을 이용한 Pt@TiO2 나노 복합체 합성)

  • Kim, Ji Young;Byun, Jong Min;Kim, Jin Woo;Kim, Young Do
    • Journal of Powder Materials
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    • v.21 no.2
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    • pp.119-123
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    • 2014
  • Pt has been widely used as catalyst for fuel cell and exhausted gas clean systems due to its high catalytic activity. Recently, there have been researches on fabricating composite materials of Pt as a method of reducing the amount of Pt due to its high price. One of the approaches for saving Pt used as catalyst is a core shell structure consisting of Pt layer on the core of the non-noble metal. In this study, the synthesis of Pt shell was conducted on the surface of $TiO_2$ particle, a non-noble material, by applying ultraviolet (UV) irradiation. Anatase $TiO_2$ particles with the average size of 20~30 nm were immersed in the ethanol dissolved with Pt precursor of $H_2PtCl_6{\cdot}6H_2O$ and exposed to UV irradiation with the wavelength of 365 nm. It was confirmed that Pt nano-particles were formed on the surface of $TiO_2$ particles by photochemical reduction of Pt ion from the solution. The morphology of the synthesized Pt@$TiO_2$ nano-composite was examined by TEM (Transmission Electron Microscopy).

Decomposition of Sulfuric Acid at Pressurized Condition in a Pt-Lined Tubular Reactor (관형 Pt-라이닝 반응기를 이용한 가압 황산분해반응)

  • Gong, Gyeong-Taek;Kim, Hong-Gon
    • Transactions of the Korean hydrogen and new energy society
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    • v.22 no.1
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    • pp.51-59
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    • 2011
  • Sulfur-Iodine (SI) cycle, which thermochemically splits water to hydrogen and oxygen through three stages of Bunsen reaction, HI decomposition, and $H_2SO_4$ decomposition, seems a promising process to produce hydrogen massively. Among them, the decomposition of $H_2SO_4$ ($H_2SO_4=H_2O+SO_2+1/2O_2$) requires high temperature heat over $800^{\circ}C$ such as the heat from concentrated solar energy or a very high temperature gas-cooled nuclear reactor. Because of harsh reaction conditions of high temperature and pressure with extremely corrosive reactants and products, there have been scarce and limited number of data reported on the pressurized $H_2SO_4$ decomposition. This work focuses whether the $H_2SO_4$ decomposition can occur at high pressure in a noble-metal reactor, which possibly resists corrosive acidic chemicals and possesses catalytic activity for the reaction. Decomposition reactions were conducted in a Pt-lined tubular reactor without any other catalytic species at conditions of $800^{\circ}C$ to $900^{\circ}C$ and 0 bar (ambient pressure) to 10 bar with 95 wt% $H_2SO_4$. The Pt-lined reactor was found to endure the corrosive pressurized condition, and its inner surface successfully carried out a catalytic role in decomposing $H_2SO_4$ to $SO_2$ and $O_2$. This preliminary result has proposed the availability of noble metal-lined reactors for the high temperature, high pressure sulfuric acid decomposition.

Burning Rate Estimate Method of Solid Propellants at High Pressure Condition (고압에서 작동하는 고체 추진제 연소속도 추정 방법)

  • Choi, Hanyoung;Lee, Dongsun;Sung, Hong-Gye;Lee, Wonmin;Kim, Eunmi
    • Journal of the Korean Society of Propulsion Engineers
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    • v.26 no.1
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    • pp.28-37
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    • 2022
  • The burning rate estimation method of solid propellants, based on closed bomb tests, has been introduced. The composition of the combustion gas is determined by using CEA and the Noble-Abel equation of state for high pressure operation conditions. Covolume taking into account the collision among molecules due to the actual volume of the molecule is modeled by LJ potential. A cubic form function is applied to calculate the volume change of propellant grains during combustion. The estimated burning rates of five different grain configuation at high pressure are fairly compared with BRLCB results within the maximum error of 6%.

Photobioreactor Engineering: Design and Performance

  • Suh, In-Soo;Lee, Choul-Gyun
    • Biotechnology and Bioprocess Engineering:BBE
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    • v.8 no.6
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    • pp.313-321
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    • 2003
  • This review summarizes the recent advances in high-density algal cultures in the field of algal biotechnology. Photobioreactor engineering for economical and effective utilization of algae and its products has made impressive and promising progress. Bioprocess engineers have expedited the design and the operation of algal cultivation systems. Many of them in use today are open systems due to cost considerations, and closed photobioreactors have recently attracted a considerable attention for the production of valuable biochemicals or for special applications. For high-density cultures, the optimization of environmental factors in the photobioreactors have been explored, including light delivery, CO$_2$and O$_2$gas transfer, medium supply, mixing and temperature. It is expected that further advanced photobioreactor engineering will enable the commercialization of noble algal products within the next decade.