• Title/Summary/Keyword: TEM Journal

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Sliding Wear Mechanism of the High-Nitrogen Austenitic 18Cr-l8Mn-2Mo-0.9N Steel (고질소 Fe-l8Cr-l8Mn-2Mo-0.9N 강의 미끄럼 마멸 기구)

  • Kim, S.D.;Kim, S.J.;Kim, Y.S.
    • Transactions of Materials Processing
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    • v.15 no.2 s.83
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    • pp.112-117
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    • 2006
  • Sliding wear mechanism of a high nitrogen austenitic 18Cr-18Mn-2Mo-0.9N steel has been investigated. Dry sliding wear tests of the steel were carried out at various loads of IN-10N under a constant sliding speed condition of 0.15m/s against AISI 52100 bearing steel balls. Solution ($1050^{\circ}C$) and isothermal aging ($900^{\circ}C$) heat treatments were performed on the steel and the effect of the heat treatments on the wear was investigated. Wear rates of the solution-treated steel specimen remained low until 5N load, and then increased abruptly at loads above 5N. The rates of isothermally aged specimens were low and increased gradually with the applied load. Worn surfaces, their cross sections, and wear debris of the steel specimens were examined with a scanning electron microscopy. Phases of the heat-treated specimen and the wear debris were identified using XRD. The transformed phase underneath a sliding track was investigated and analyzed using a TEM. Effects of the phase transformation during the wear and $Cr_{2}N$ precipitates formed during the isothermal aging on the wear of the austenitic steel were discussed.

The Influence of Microstructure on the Bauschinger Effect in X80 Grade API Steel (X80급 API 강의 바우싱거 효과에 미치는 미세조직의 영향)

  • Park, J.S.;Kim, D.W.;Chang, Y.W.
    • Transactions of Materials Processing
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    • v.15 no.2 s.83
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    • pp.118-125
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    • 2006
  • API steel is used for line-pipe to transport the oil and natural gas. As the recent trends in the development of API steel are towards the use of larger diameter and thicker plate, many researches have been studied to achieve higher strength, higher toughness and lower yield ratio in API steel. However, the strength of API steel after pipe forming is changed depending on the competition of the Bauschinger effect and work hardening which are affected by the strain history during pipe forming process. So, the purpose of this study is to investigate the influence of microstructure on the Bauschinger effect for API steel. To change the microstructure of API steel we have changed the hot rolling condition and the amounts of V and Cu addition. The compression-tensile test and the microstructure observation by OM and TEM were conducted to investigate the yield strength drop and the correlation between the Bauschinger effect and microstructure of API steel. The experimental results show that the increase of polygonal ferrites volume fraction increases the Baushcinger effect due to the back stress which comes from the increase of mobile dislocation density at polygonal ferrite interior during the compressive deformation. The hot rolling condition was more effective on the Bauschinger effect in API steel than the small amount of V and Cu addition.

Case Report of Asbestosis

  • Lee, Yong-Hwan;Chang, Hee-Kyung;Kiyoshi Sakai;Naomi Hisanaga;Chung, Yong-Hyun;Han, Jeong-Hee;Yu, Il-Je
    • Toxicological Research
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    • v.17 no.3
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    • pp.163-165
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    • 2001
  • A patient,58 years of age, with suspected 0/l pneumoconiosis since 1993, complained of a dry cough and exertioning dyspnea for 6 months. He had worked in an asbestos company for more than 20 years from 1974. He was subsequently diagnosed with an interstitial lung disease during an annual special health check-up for asbestos workers. h chest X-ray showed an interstitial lung disease and high-resolution computed tomography (HRCT) showed a round opaque asbestosis with chronic hypersensitivity pneumonitis. A pulmonary function test indicated that the patient had a mild restrictive lung disease with FEV1 1.67 litters and 82% FEVl/FVC. The bronchoalveloar larvage fluid included many asbestos bodies, indicating previous exposure to asbestos. Transmission electron microscopy (TEM) using an energy dispersive X-ray analyzer (EDX) revealed many asbestos bodies consisting of mainly crocidolite fibers (6,071$\times$$10^6$fibers/g of dry lung). The patient had an unusually high asbestos content of 6,112$\times$$10^6$ asbestos fibers/9 of dry lung.

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Catalysis of carbon black for hydrogen production by butane decomposition reaction (부탄의 직접분해로부터 수소 생산을 위한 카본블랙의 촉매적 작용)

  • Yoon, Suk-Hoon;Han, Gi-Bo;Park, No-Kuk;Ryu, Si-Ok;Yoon, Ki-June;Han, Gui-Young;Lee, Tae-Jin
    • New & Renewable Energy
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    • v.2 no.4 s.8
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    • pp.70-77
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    • 2006
  • The butane decomposition over the catalyst is an attractive method for the hydrogen production. The objective of the work was investigated the catalysis of carbon black in butane decomposition reaction. The Butane decomposition was performed over carbon black catalyst in a range of $500-1100^{\circ}C$. The butane conversion of thermal decomposition and catalytic decomposition were increased with increasing the reaction temperature The butane conversion of the thermal decomposition was higher than the butane conversion of the catalytic decomposition. Hydrogen and methane were mostly observed in the butane decomposition over $1000^{\circ}C$. Especially, the hydrogen yield was steadily increased with raising the reaction temperature, It could be known that the hydrogen yield of the catalytic decomposition was higher than one of the thermal cracking because the hydrogen productivity was improved by the catalyst. The deactivation of the catalyst was not observed in the reactivity test. The surface and crystalline of the fresh and used catalysts were characterized by TEM, BET surface area and XRD analysis, respectively. The fresh carbon black particles had mostly smoothly round-shaped surfaces. In the surface of the carbon black after the reaction, the deposited carbon was formed as the protrusion-shaped carbon and the cone-shaped. The proper peaks of carbon black appeared in XRD analysis.

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Aging Characteristics of NOx Storage and Reduction Catalyst for Lean-bum Natural Gas Vehicles (린번 천연가스자동차용 NOx 흡장촉매의 열화특성)

  • Choi, Byung-Chul;Lee, Choon-Hee
    • Transactions of the Korean Society of Automotive Engineers
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    • v.15 no.3
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    • pp.147-152
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    • 2007
  • This study investigates the aging characteristics of NOx storage and reduction(NSR) catalyst on the emission conditions of lean burn natural gas vehicles. We designed various NSR catalysts using by the double-layer washcoat technology to increase of a surface area and a thermal durability performance of the catalysts. The experiments were conducted with 3 kinds of the NSR catalysts, which were manufactured using by a honeycomb cordierite substrate. It was found that Ba is weak in the thermal aging because it has lower melting temperature than that of precious metals (PMs). The suitable loading amount of Ba in this study should be about 42 g/L from the results of the NOx adsorption and the NOx reduction efficiency. The major reason in deactivation of the NSR catalyst is the decrease of the adsorption site owing to the agglomeration and sintering of Ba rather than PM aging by hydrothermal aging. It was confirmed by results of BET, SEM and TEM.

Effect of Chemical Composition on Tensile Property in TRIP-assisted Multiphase Steel for Automobile Structure (차량구조용 변태유기소성(TRIP)형 복합조직강의 인장성질에 미치는 화학조성의 영향)

  • Lee, Ki-Yeol;Bang, Il-Hwan;Ma, Ah-Ram;Kim, Young-Sun
    • Transactions of the Korean Society of Automotive Engineers
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    • v.15 no.3
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    • pp.106-113
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    • 2007
  • The effect of chemical composition on the microstructural change and tensile property in TRIP-assisted steels with different chemical composition was investigated by using SEM, TEM, XRD and UTM. As a result of microscopic observation, the morphology of retained austenite could be identified as two types : a granular type in a steel containing higher sillicon and a film type in a steel having higher carbon. For the case of higher carbon-containing steel with a tensile strength of 860 MPa and a total elongation of 38%, film-typed retained austenite could be observed between lath bainitic ferrite. Actually, metastable retained austenite was a requisite for the good formability, which means that chemical composition plays a significant role in the microstructure and tensile property of TRIP-assisted steels. With respect to tensile property, the steels containing suitable silicon and manganese, respectively, showed a typical TRIP effect in stress-strain curve, while a steel containing higher manganese content exhibited the assimilar behavior shown in dual phase steel.

Electrospinning Fabrication of Poly(vinyl alcohol)/Pullulan/TiO2 Nanofibers (전기방사를 이용한 Poly(vinyl alcohol)/Pullulan/TiO2 나노부직포의 제조)

  • Yang, Seong Baek;Choi, Woo Seok;Hyun, Jae Min;Shin, Jae Cheon;Choi, Jin Hyun;Yeum, Jeong Hyun
    • Textile Coloration and Finishing
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    • v.26 no.3
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    • pp.195-200
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    • 2014
  • Poly(vinyl alcohol)(PVA)/pullulan/titanium dioxide($TiO_2$) composite nanofibers were produced at different $TiO_2$ concentrations(1 and 3 wt.%) using the electrospinning method. The parameters of electrospinning including polymer contents, voltage and tip-to-collector distance(TCD) were optimized for fabrication process. The study showed that the best condition to make PVA/pullulan nanofiber and effect of $TiO_2$ nanoparticles. The PVA/pullulan/$TiO_2$ nanofibers were characterized by scanning electron microscope(SEM), transmission electron microscope(TEM), Thermogravimetric analysis (TGA) and X-ray diffraction(XRD).

Ultrastructural Study on the Spermatogenesis of the Marbled Sole, Limanda yokohamae (Teleostei: Pleuronectidae) (문치가자미(Limanda yokohamae)의 정자형성에 관한 미세구조적 연구)

  • An, Cheul-Min;Lee, Jung-Sick;Huh, Sung-Hoi
    • Applied Microscopy
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    • v.29 no.4
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    • pp.427-435
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    • 1999
  • Spermatogenesis and fine structure of the spermatozoon of the marbled sole, Limanda yokohamae were examined by means of the scanning and transmission electron microscopy. The process of spermatogenesis of the marbled tole is similar to that of other teleost with external fertilization. During the spermiogenesis, chromatin that has been became fine]y granular progressively condenses into many large globules and that homogeneously condensed in the spermatozoan head. A spermatozoon consists of head and tail, and the acrosome is absent. The cytoplasmic collar contained eight mitochondria is observed in the posterior part of the head. The well -developed axonemal lateral fins are observed in the tail. In the TEM observation, the cross section of the axial filament shows '9+2' axonemal structure of microtubules, and the numerous vesicles are observed in the cytoplasm.

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Estimation of Electron Dose Rate using CCD Camera (CCD 카메라를 이용한 전자빔 조사량의 예측)

  • Kim, Jin-Gyu;Kim, Young-Min;Kim, Youn-Joong;Lee, Sang-Hee;Hong, Ki-Min;Oh, Sang-Ho
    • Applied Microscopy
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    • v.39 no.1
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    • pp.79-83
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    • 2009
  • We report a useful method to estimate the electron dose rate which may be a decisive factor to characterize sample properties. Even though most mircoscopes have their own exposure meters, there are several practical concerns when such exposure meters are used to measure the electron dose rate: 1) Specimen should be avoided within the entire area of exposure meter; 2) beam current has to be always recorded whenever the operation mode is changed; 3) the electron dose rate can not be calculated for the beam current beyond the detectable range. To overcome these limitations, we suggest a useful method which utilize a CCD (charge coupled device) camera which is now a popular detector to obtain the final electron micrographs. We have evaluated the CCD sensitivity using the linear relationship between electron current on the exposure meter and counter ratio on the CCD camera which are built in KBSI-HVEM (high voltage electron microscope). Applying the new method, we obtained the CCD sensitivity which are approximately 0.039 counts/$e^-$ and 1.37 counts/$e^-$ for the Top-TV and the HV-GIF CCD cameras, respectively.

Welding behavior between Zn-coated steel plate and free cutting carbon steel rod by Nd:YAG laser beam (Nd:YAG 레이저빔을 이용한 아연도금강판(SECC)과 쾌삭강봉(SUM24L)의 용접에 관한 연구)

  • 노영태;김병철;김도훈;윤갑식
    • Laser Solutions
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    • v.4 no.3
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    • pp.30-39
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    • 2001
  • This work was tamed out to apply a laser welding technique in joining between a Zn coated low carbon steel plate(SECC) and a free cutting carbon steel shaft(SUM24L) with or without W coating. Experiments were carried out and analysed by applying the FD(factorial design)method to obtain the optimum Laser welding condition. Optical microscopy, SEM, TEM and XRD analyses were performed in order to observe the microstructures in the fusion zone and the HAZ. Mechanical properties of the welded specimens were examined by microhardness test, tensile test and twist test. There was no flawed Zn in the fusion zone by EDS analysis. This means that during the welding process, Zn gas could be eliminated by appropriate shielding gas flow rate and butt welding gap. Ni coating itself did not influence on the tensile strength and hardness. However, twist bending strength and the weld depth of the Ni-coated free cutting carbon steel were lower as compared with those of the uncoated free cutting carbon steel. It was attributed to a lower absorbance of laser beam to the shin Ni surface. According to the results of the factorial design tests, the twist bending strength of welded specimens was primarily affected by pulse width, laser power, frequency and speed.

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