The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Jorma Jokiniemi - One of the best experts on this subject based on the ideXlab platform.
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effect of air staging on Fine Particle dust and gaseous emissions from masonry heaters
Biomass & Bioenergy, 2014Co-Authors: Kati Nuutinen, Jorma Jokiniemi, Olli Sippula, Heikki Lamberg, J Sutinen, P Horttanainen, Jarkko TissariAbstract:Abstract There is a need to decrease the detrimental Particle and gaseous emissions from residential wood combustion appliances. One encouraging alternative is to stage the air supply which improves the combustion conditions in small appliances. In this study, two types of combustion technologies were studied in conventional masonry heaters (CMH) and modern masonry heaters (MMH). Air staging in the MMHs considerably reduced the Particle and gas emissions. The greatest reduction was observed in gaseous and particulate organic emissions. Methane emissions were reduced by 74%–91% and carbon monoxide by 26%–81%. The reduction of Fine Particle mass (PM 1 ) was 14%–58%. Elemental carbon (EC, i.e. soot) emission increased in small combustion appliances but declined in large appliances. In addition, dust (TSP, Total Suspended Particulate matter i.e. Dust) emissions from hot flue gas were compared with the Fine Particle mass emissions from diluted sample. PM 1 emissions measured from diluted flue gas were 1.1–4.4-fold as compared to TSP collected from hot flue gas. This may be attributable to the fact that organic vapors partially had penetrated into the TSP filter in a gaseous form whereas when they were diluted, semivolatile species condensed on the Particles. It can be concluded that air staging is an effective way to reduce gaseous and organic emissions from batch combustion appliances. Particle emission measured from diluted flue gas represents a more realistic results than TSP (hot sampling), because in dilution, also the organic fraction of the Particle emissions is taken into account.
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Fine Particle and gas emissions from the combustion of agricultural fuels fired in a 20 kw burner
Energy & Fuels, 2008Co-Authors: Jarkko Tissari, Olli Sippula, Jyrki Kouki, Kari Vuorio, Jorma JokiniemiAbstract:Emissions from the combustion of agricultural biomasses have not been studied extensively. In this study, the effects of different biomasses and mixed fuels on Fine Particle (PM1) and gas emissions from a residential cereal burner were investigated. The cereal seeds of oat and rape, rape bark pellets, and wood pellets were the main fuels. In addition, oat was mixed with peat and kaolin and wood with kaolin. The gas emissions of NOx, SO2, and HCl were clearly higher from cereal or mixed-cereal fuels than from pure wood fuel. The emissions of carbon monoxide (CO), organic gaseous carbon (OGC), PM1 and the Particle numbers from the cereal fuels did not differ significantly from the emissions of wood fuels, although the fuel ash contents were substantially higher. The release of alkali metals varied substantially between different fuels, probably due to large differences in ash chemical compositions. In contrast to wood fuels, phosphate contributed significantly to the formation of Fine Particles in the cerea...
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Fine Particle and gas emissions from the combustion of agricultural fuels fired in a 20 kw burner
Energy & Fuels, 2008Co-Authors: Jarkko Tissari, Olli Sippula, Jyrki Kouki, Kari Vuorio, Jorma JokiniemiAbstract:Emissions from the combustion of agricultural biomasses have not been studied extensively. In this study, the effects of different biomasses and mixed fuels on Fine Particle (PM1) and gas emissions from a residential cereal burner were investigated. The cereal seeds of oat and rape, rape bark pellets, and wood pellets were the main fuels. In addition, oat was mixed with peat and kaolin and wood with kaolin. The gas emissions of NOx, SO2, and HCl were clearly higher from cereal or mixed-cereal fuels than from pure wood fuel. The emissions of carbon monoxide (CO), organic gaseous carbon (OGC), PM1 and the Particle numbers from the cereal fuels did not differ significantly from the emissions of wood fuels, although the fuel ash contents were substantially higher. The release of alkali metals varied substantially between different fuels, probably due to large differences in ash chemical compositions. In contrast to wood fuels, phosphate contributed significantly to the formation of Fine Particles in the cerea...
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a novel field measurement method for determining Fine Particle and gas emissions from residential wood combustion
Atmospheric Environment, 2007Co-Authors: Jarkko Tissari, Jorma Jokiniemi, Kati Hytonen, Jussi LyyranenAbstract:Abstract Emission data from residential wood combustion are usually obtained on test stands in the laboratory but these measurements do not correspond to the operational conditions in the field because of the technological boundary conditions (e.g. testing protocol, environmental and draught conditions). The field measurements take into account the habitual practice of the operators and provide the more reliable results needed for emission inventories. In this study, a workable and compact method for measuring emissions from residential wood combustion in winter conditions was developed. The emissions for Fine Particle, gaseous and PAH compounds as well as Particle composition in real operational conditions were measured from seven different appliances. The measurement technique worked well and was evidently suitable for winter conditions. It was easy and fast to use, and no construction scaffold was needed. The dilution of the sample with the combination of a porous tube diluter and an ejector diluter was well suited to field measurement. The results indicate that the emissions of total volatile organic carbon (TVOC) (17 g kg −1 (of dry wood burned)), carbon monoxide (CO) (120 g kg −1 ) and Fine Particle mass (PM 1 ) (2.7 g kg −1 ) from the sauna stove were higher than in the other measured appliances. In the masonry heaters, baking oven and stove, the emissions were 2.9–9 g kg −1 TVOC, 28–68 g kg −1 CO and 0.6–1.6 g kg −1 PM 1 . The emission of 12 PAHs (PAH 12 ) from the sauna stove was 164 mg kg −1 and consisted mainly of PAHs with four benzene rings in their structure. PAH 12 emission from other appliances was, on average, 21 mg kg −1 and was dominated by 2-ring PAHs. These results indicate that despite the non-optimal operational practices in the field, the emissions did not differ markedly from the laboratory measurements.
Jarkko Tissari - One of the best experts on this subject based on the ideXlab platform.
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effect of air staging on Fine Particle dust and gaseous emissions from masonry heaters
Biomass & Bioenergy, 2014Co-Authors: Kati Nuutinen, Jorma Jokiniemi, Olli Sippula, Heikki Lamberg, J Sutinen, P Horttanainen, Jarkko TissariAbstract:Abstract There is a need to decrease the detrimental Particle and gaseous emissions from residential wood combustion appliances. One encouraging alternative is to stage the air supply which improves the combustion conditions in small appliances. In this study, two types of combustion technologies were studied in conventional masonry heaters (CMH) and modern masonry heaters (MMH). Air staging in the MMHs considerably reduced the Particle and gas emissions. The greatest reduction was observed in gaseous and particulate organic emissions. Methane emissions were reduced by 74%–91% and carbon monoxide by 26%–81%. The reduction of Fine Particle mass (PM 1 ) was 14%–58%. Elemental carbon (EC, i.e. soot) emission increased in small combustion appliances but declined in large appliances. In addition, dust (TSP, Total Suspended Particulate matter i.e. Dust) emissions from hot flue gas were compared with the Fine Particle mass emissions from diluted sample. PM 1 emissions measured from diluted flue gas were 1.1–4.4-fold as compared to TSP collected from hot flue gas. This may be attributable to the fact that organic vapors partially had penetrated into the TSP filter in a gaseous form whereas when they were diluted, semivolatile species condensed on the Particles. It can be concluded that air staging is an effective way to reduce gaseous and organic emissions from batch combustion appliances. Particle emission measured from diluted flue gas represents a more realistic results than TSP (hot sampling), because in dilution, also the organic fraction of the Particle emissions is taken into account.
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Fine Particle and gaseous emissions from normal and smouldering wood combustion in a conventional masonry heater
Atmospheric Environment, 2008Co-Authors: Jarkko Tissari, Olli Sippula, Kati Hytonen, Jussi Lyyranen, Unto Tapper, Anna Frey, Karri Saarnio, Arto Pennanen, Risto Hillamo, R O SalonenAbstract:The Fine Particle and gas emissions from the residential wood combustion (RWC) appear to be a major contributor to winter-time pollution in Europe. In this study, we characterised the effect of two different combustion conditions on particulate and gaseous emissions from a conventional masonry heater. Normal combustion (NC) is the best available operational practice for the heater, whereas smouldering combustion (SC) mimicked slow heating combustion. It was found that the operational practice in RWC can significantly influence the quantity and quality of Particle and gaseous emissions into the atmosphere. In SC, the emissions of carbon monoxide were 3.5-fold, total volatile organics 14-fold and PM1 6-fold to those of NC, whereas the mass of the inorganic compounds (“Fine ash”) and Particle number emissions were lower from SC than from NC. According to electron microscopy analyses, the observed Fine ash Particles seemed to occur mainly as separate spherical or irregularly shaped Particles but not as agglomerates. UltraFine (<100 nm) Fine ash Particles were composed mainly of K, S and Zn, but also in a lesser extent of C, Ca, Fe, Mg, Cl, P and Na. Large agglomerates were found to contain mainly carbon and are considered to be primarily soot Particles. The larger spherical and irregularly shaped Particles were composed of same alkali metal compounds as ultraFine Particles, but they were probably covered with heavy organic compounds. From SC, Particles were composed mainly of carbon compounds and they had a more closed structure than the Particles from NC, due to organic matter on the Particles. In the present experiments, the ultraFine mode in the Particle number distributions seemed to be determined mainly by the amount of released ash forming material in combustion, and the shifting of Particle size during different combustion conditions seemed to be determined by the amount of condensed organic vapour in the flue gas.
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Fine Particle and gas emissions from the combustion of agricultural fuels fired in a 20 kw burner
Energy & Fuels, 2008Co-Authors: Jarkko Tissari, Olli Sippula, Jyrki Kouki, Kari Vuorio, Jorma JokiniemiAbstract:Emissions from the combustion of agricultural biomasses have not been studied extensively. In this study, the effects of different biomasses and mixed fuels on Fine Particle (PM1) and gas emissions from a residential cereal burner were investigated. The cereal seeds of oat and rape, rape bark pellets, and wood pellets were the main fuels. In addition, oat was mixed with peat and kaolin and wood with kaolin. The gas emissions of NOx, SO2, and HCl were clearly higher from cereal or mixed-cereal fuels than from pure wood fuel. The emissions of carbon monoxide (CO), organic gaseous carbon (OGC), PM1 and the Particle numbers from the cereal fuels did not differ significantly from the emissions of wood fuels, although the fuel ash contents were substantially higher. The release of alkali metals varied substantially between different fuels, probably due to large differences in ash chemical compositions. In contrast to wood fuels, phosphate contributed significantly to the formation of Fine Particles in the cerea...
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Fine Particle and gas emissions from the combustion of agricultural fuels fired in a 20 kw burner
Energy & Fuels, 2008Co-Authors: Jarkko Tissari, Olli Sippula, Jyrki Kouki, Kari Vuorio, Jorma JokiniemiAbstract:Emissions from the combustion of agricultural biomasses have not been studied extensively. In this study, the effects of different biomasses and mixed fuels on Fine Particle (PM1) and gas emissions from a residential cereal burner were investigated. The cereal seeds of oat and rape, rape bark pellets, and wood pellets were the main fuels. In addition, oat was mixed with peat and kaolin and wood with kaolin. The gas emissions of NOx, SO2, and HCl were clearly higher from cereal or mixed-cereal fuels than from pure wood fuel. The emissions of carbon monoxide (CO), organic gaseous carbon (OGC), PM1 and the Particle numbers from the cereal fuels did not differ significantly from the emissions of wood fuels, although the fuel ash contents were substantially higher. The release of alkali metals varied substantially between different fuels, probably due to large differences in ash chemical compositions. In contrast to wood fuels, phosphate contributed significantly to the formation of Fine Particles in the cerea...
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a novel field measurement method for determining Fine Particle and gas emissions from residential wood combustion
Atmospheric Environment, 2007Co-Authors: Jarkko Tissari, Jorma Jokiniemi, Kati Hytonen, Jussi LyyranenAbstract:Abstract Emission data from residential wood combustion are usually obtained on test stands in the laboratory but these measurements do not correspond to the operational conditions in the field because of the technological boundary conditions (e.g. testing protocol, environmental and draught conditions). The field measurements take into account the habitual practice of the operators and provide the more reliable results needed for emission inventories. In this study, a workable and compact method for measuring emissions from residential wood combustion in winter conditions was developed. The emissions for Fine Particle, gaseous and PAH compounds as well as Particle composition in real operational conditions were measured from seven different appliances. The measurement technique worked well and was evidently suitable for winter conditions. It was easy and fast to use, and no construction scaffold was needed. The dilution of the sample with the combination of a porous tube diluter and an ejector diluter was well suited to field measurement. The results indicate that the emissions of total volatile organic carbon (TVOC) (17 g kg −1 (of dry wood burned)), carbon monoxide (CO) (120 g kg −1 ) and Fine Particle mass (PM 1 ) (2.7 g kg −1 ) from the sauna stove were higher than in the other measured appliances. In the masonry heaters, baking oven and stove, the emissions were 2.9–9 g kg −1 TVOC, 28–68 g kg −1 CO and 0.6–1.6 g kg −1 PM 1 . The emission of 12 PAHs (PAH 12 ) from the sauna stove was 164 mg kg −1 and consisted mainly of PAHs with four benzene rings in their structure. PAH 12 emission from other appliances was, on average, 21 mg kg −1 and was dominated by 2-ring PAHs. These results indicate that despite the non-optimal operational practices in the field, the emissions did not differ markedly from the laboratory measurements.
Jun Komotori - One of the best experts on this subject based on the ideXlab platform.
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Effect of atmospheric-controlled induction-heating Fine Particle peening on electrochemical characteristics of austenitic stainless steel
Surface & Coatings Technology, 2018Co-Authors: Shoichi Kikuchi, Jun Komotori, Shota Iwamae, Hiroyuki Akebono, Keisuke KadotaAbstract:Abstract Atmospheric-controlled induction-heating Fine Particle peening (AIH-FPP) using Cr and Mo shot Particles in a N 2 atmosphere was introduced to improve the electrochemical characteristics of AISI 316 austenitic stainless steel. The surface microstructure of the AIH-FPP-treated specimen was characterized using scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX). AIH-FPP can be used to form transferred and diffused layers of shot Particles on the surface of austenitic stainless steel. The thickness of the diffusion layers of Cr shot Particles tended to increase with the heating time in the AIH-FPP process, whereas the Cr concentration at the surface tended to decrease. Electrochemical polarization tests were performed in 3 wt% NaCl + H 2 SO 4 and 20 wt% NaCl environments at 343 K using a three-electrode electrochemical cell connected to a computer driven potentiostat to examine the corrosion resistance of austenitic stainless steel treated with AIH-FPP. The pitting potential of the AIH-FPP-treated specimen was higher than that of the untreated specimen. In particular, there was clear improvement in the pitting potential of austenitic stainless steel by AIH-FPP with Cr shot Particles following peening with Mo shot Particles. AIH-FPP using Cr and Mo shot Particles in a N 2 atmosphere is an effective method of improving the electrochemical characteristics of austenitic stainless steel.
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effects of Fine Particle peening on oxidation behavior of nickel titanium shape memory alloy
Materials Transactions, 2014Co-Authors: Shoichi Kikuchi, Yutaka Kameyama, Masayoshi Mizutani, Jun KomotoriAbstract:The effects of Fine Particle peening (FPP) on oxidation behavior of nickeltitanium shape memory alloy (NiTi alloy) were evaluated. After FPP treatment, oxidation process was performed at 300, 400 and 500°C for 30min in N220vol%O2 atmosphere. Surface microstructures of oxidized specimens pre-treated with FPP were characterized using scanning electron microscope (SEM), glow discharge optical emission spectroscopy (GD-OES), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction analysis (XRD). Oxide layers formed on the specimens pre-treated with FPP were thinner than those on the un-peened ones. Amorphous titanium oxides (TiO and TiO2) were formed on the un-peened specimens by oxidation process, whereas a nickel oxide (NiO) was created on the FPP-treated surface oxidized at temperature greater than 400°C as well as titanium oxides. This was because an amorphous structure created by FPP accelerated the outward growth of nickel oxide during the subsequent oxidation process. Moreover, the effects of surface oxide layers on the biocompatibility of NiTi alloy were investigated. Due to the formation of a thin oxide layer which contains nickel element, the oxidized specimen pre-treated with FPP showed higher amount of nickel ion elution than that of the oxidized one during the cell culture tests. These results suggest that microstructural feature of surface oxide layer strongly affects the biocompatibility of NiTi alloy. [doi:10.2320/matertrans.M2013336]
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effect of specimen hardness and shot Particle hardness on residual stress and fatigue properties of scm435h steel performed by Fine Particle peening
Journal of The Society of Materials Science Japan, 2011Co-Authors: Shoichi Kikuchi, Yo Hirota, Jun KomotoriAbstract:In order to determine the Fine Particle peening (FPP) treatment conditions that generate a high compressive residual stress, the effect of specimen hardness and shot Particle hardness on residual stress was investigated. The results showed that the higher the generated specimen hardness, the higher the compressive residual stress at the surface. Additionally, in the case of high hardness specimens, the shot Particle hardness affected the residual stress. This was because shot Particle was deformed during the FPP treatment process. Furthermore, in order to clarify the effect of FPP treatment on fatigue properties of SCM435H steel with different hardnesses, fatigue tests were performed at room temperature using a rotational bending fatigue testing machine. In the case of higher hardness substrate, the fatigue strength was dominantly increased by FPP treatment ; however, in the case of lower hardness substrate, the increasing level was very small. This was because compressive residual stress generated on the surface of higher hardness specimen was much larger than that generated on lower hardness specimen and the higher compressive residual stress remained on the surface of higher hardness specimen under the application of cyclic loading. These results indicate that the FPP treatment is highly significant to improve the fatigue strength for higher hardness substrate.
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Fatigue properties of gas nitrided austenitic stainless steel pre-treated with Fine Particle peening
International Journal of Fatigue, 2010Co-Authors: Shoichi Kikuchi, Yasuhito Nakahara, Jun KomotoriAbstract:The nitrided layer of austenitic stainless steel is typically extremely thin due to the existence of a passive film at the surface. In order to facilitate the diffusion of nitrogen into the material, a Fine Particle peening (FPP) treatment was performed prior to gas nitriding. The effects of the FPP treatment on gas nitriding behavior and consequent fatigue properties of AISI 316 steel were evaluated. Surface microstructures of the FPP treated specimens prior to gas nitriding were characterized using a micro-Vickers hardness tester, scanning electron microscope (SEM), optical microscope, electron probe micro analyzer (EPMA) and X-ray diffraction (XRD). The FPP treatment generated a local stratification pattern which exhibits high dislocation densities. During the subsequent nitriding process, nitrogen diffused into this unique structure, resulting in an increase in the surface hardness. Fatigue tests on a number of specimens with differing surface treatments were performed at room temperature using a rotational bending fatigue testing machine. The FPP treated specimen prior to gas nitriding exhibited the highest fatigue strength. After the fatigue tests, fracture surfaces were observed using an SEM in order to investigate the high-cycle fatigue properties.
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effect of Fine Particle peening treatment prior to nitriding on fatigue properties of aisi 4135 steel
Journal of Solid Mechanics and Materials Engineering, 2008Co-Authors: Shoichi Kikuchi, Jun KomotoriAbstract:In this study, a new hybrid surface modification process, Fine Particle peening (FPP) treatment prior to nitriding, was proposed. In order to clarify the effects of FPP treatment prior to nitriding on the fatigue strength of notched AISI 4135 steel with a stress concentration factor Kt of 2.36, fatigue tests were conducted at room temperature using a rotational bending fatigue testing machine. Hardness and residual stress distributions were measured in order to characterize the surface-modified layer. As a result, the surface hardness of the FPP-treated specimen before nitriding was higher than that of the nitrided specimen. The surface microstructures of treated specimens were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The crystal structure of the compound layer of the FPP-treated specimen before nitriding was different to that of the nitrided specimen. The compound layer of the FPP-treated specimen was dense. This suggests that FPP treatment prior to nitriding is very effective for improvement of the fatigue strength of steel.
Zhengda Yang - One of the best experts on this subject based on the ideXlab platform.
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a combined wet electrostatic precipitator for efficiently eliminating Fine Particle penetration
Fuel Processing Technology, 2018Co-Authors: Zhengda Yang, Yi Wang, Chenghang Zheng, Chengsi Liang, Daqing HuAbstract:Abstract Improving the removal efficiency of Fine Particle is significant for the elimination of Particle emission from coal-fired power plants. This work reports a combined wet electrostatic precipitator (WESP) enhanced by a novel perforated pre-charger to efficiently remove Fine Particle from wet flue gas. Penetration and charging characteristics of Fine Particle through the WESP were evaluated as a function of Particle size. The collection performance was investigated under controlled gas temperatures and varied electrical conditions. Results showed that there was a maximum penetration ratio around 0.1 μm and it decreased with the increasing applied voltage. A portion of the escaping Fine Particles were not charged through the WESP, and the size limit for partial charging can be reduced to 0.025 μm when the applied voltage increased to 32 kV. Reducing gas temperature leaded to an obvious improvement in collection efficiency for Particles in the size range of 0.1–1.0 μm. The test results of different electrodes showed that both the corona current and maximum collection efficiency ranked in the order of pin > sawtooth > rod. With the assistance of pre-charger, the Particle charging was significantly improved and the charge amount was more than doubled. Consequently, the effective migration velocity for PM 0.1 , PM 1.0 and PM 2.5 increased by 69.9%, 65.7% and 34.2%, respectively. Actual application results showed that the average PM emission level can be reduced to 0.43 mg/m 3 by the combined WESP in a 1000 MW coal-fired power plant.
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Fine Particle migration and collection in a wet electrostatic precipitator
Journal of The Air & Waste Management Association, 2017Co-Authors: Zhengda Yang, Chenghang Zheng, Qianyun Chang, Yi WangAbstract:ABSTRACTElectrostatic precipitation is considered as an effective technology for Fine Particle removal. A lab-scale wet electrostatic precipitator (ESP) with wire-to-plate configuration was developed to study Particle migration and collection. The performance of the wet ESP was evaluated in terms of the corona discharge characteristics, total removal efficiency and fractional removal efficiency. The corona discharge characteristics and Particle removal abilities of the wet ESP were investigated and compared with dry ESP. Particle removal efficiency was influenced by discharge electrode type, SO2 concentration, specific collection area (SCA) and Particle/droplet interaction. Results showed that the Particle removal efficiency of wet ESP was elevated to 97.86% from 93.75% of dry ESP. Three types of discharge electrodes were investigated. Higher Particle removal efficiency and larger migration velocity could be obtained with fishbone electrode. Particle removal efficiency decreased by 2.87% when SO2 concentr...
Shoichi Kikuchi - One of the best experts on this subject based on the ideXlab platform.
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Effect of atmospheric-controlled induction-heating Fine Particle peening on electrochemical characteristics of austenitic stainless steel
Surface & Coatings Technology, 2018Co-Authors: Shoichi Kikuchi, Jun Komotori, Shota Iwamae, Hiroyuki Akebono, Keisuke KadotaAbstract:Abstract Atmospheric-controlled induction-heating Fine Particle peening (AIH-FPP) using Cr and Mo shot Particles in a N 2 atmosphere was introduced to improve the electrochemical characteristics of AISI 316 austenitic stainless steel. The surface microstructure of the AIH-FPP-treated specimen was characterized using scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX). AIH-FPP can be used to form transferred and diffused layers of shot Particles on the surface of austenitic stainless steel. The thickness of the diffusion layers of Cr shot Particles tended to increase with the heating time in the AIH-FPP process, whereas the Cr concentration at the surface tended to decrease. Electrochemical polarization tests were performed in 3 wt% NaCl + H 2 SO 4 and 20 wt% NaCl environments at 343 K using a three-electrode electrochemical cell connected to a computer driven potentiostat to examine the corrosion resistance of austenitic stainless steel treated with AIH-FPP. The pitting potential of the AIH-FPP-treated specimen was higher than that of the untreated specimen. In particular, there was clear improvement in the pitting potential of austenitic stainless steel by AIH-FPP with Cr shot Particles following peening with Mo shot Particles. AIH-FPP using Cr and Mo shot Particles in a N 2 atmosphere is an effective method of improving the electrochemical characteristics of austenitic stainless steel.
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effects of Fine Particle peening on oxidation behavior of nickel titanium shape memory alloy
Materials Transactions, 2014Co-Authors: Shoichi Kikuchi, Yutaka Kameyama, Masayoshi Mizutani, Jun KomotoriAbstract:The effects of Fine Particle peening (FPP) on oxidation behavior of nickeltitanium shape memory alloy (NiTi alloy) were evaluated. After FPP treatment, oxidation process was performed at 300, 400 and 500°C for 30min in N220vol%O2 atmosphere. Surface microstructures of oxidized specimens pre-treated with FPP were characterized using scanning electron microscope (SEM), glow discharge optical emission spectroscopy (GD-OES), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction analysis (XRD). Oxide layers formed on the specimens pre-treated with FPP were thinner than those on the un-peened ones. Amorphous titanium oxides (TiO and TiO2) were formed on the un-peened specimens by oxidation process, whereas a nickel oxide (NiO) was created on the FPP-treated surface oxidized at temperature greater than 400°C as well as titanium oxides. This was because an amorphous structure created by FPP accelerated the outward growth of nickel oxide during the subsequent oxidation process. Moreover, the effects of surface oxide layers on the biocompatibility of NiTi alloy were investigated. Due to the formation of a thin oxide layer which contains nickel element, the oxidized specimen pre-treated with FPP showed higher amount of nickel ion elution than that of the oxidized one during the cell culture tests. These results suggest that microstructural feature of surface oxide layer strongly affects the biocompatibility of NiTi alloy. [doi:10.2320/matertrans.M2013336]
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effect of specimen hardness and shot Particle hardness on residual stress and fatigue properties of scm435h steel performed by Fine Particle peening
Journal of The Society of Materials Science Japan, 2011Co-Authors: Shoichi Kikuchi, Yo Hirota, Jun KomotoriAbstract:In order to determine the Fine Particle peening (FPP) treatment conditions that generate a high compressive residual stress, the effect of specimen hardness and shot Particle hardness on residual stress was investigated. The results showed that the higher the generated specimen hardness, the higher the compressive residual stress at the surface. Additionally, in the case of high hardness specimens, the shot Particle hardness affected the residual stress. This was because shot Particle was deformed during the FPP treatment process. Furthermore, in order to clarify the effect of FPP treatment on fatigue properties of SCM435H steel with different hardnesses, fatigue tests were performed at room temperature using a rotational bending fatigue testing machine. In the case of higher hardness substrate, the fatigue strength was dominantly increased by FPP treatment ; however, in the case of lower hardness substrate, the increasing level was very small. This was because compressive residual stress generated on the surface of higher hardness specimen was much larger than that generated on lower hardness specimen and the higher compressive residual stress remained on the surface of higher hardness specimen under the application of cyclic loading. These results indicate that the FPP treatment is highly significant to improve the fatigue strength for higher hardness substrate.
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Fatigue properties of gas nitrided austenitic stainless steel pre-treated with Fine Particle peening
International Journal of Fatigue, 2010Co-Authors: Shoichi Kikuchi, Yasuhito Nakahara, Jun KomotoriAbstract:The nitrided layer of austenitic stainless steel is typically extremely thin due to the existence of a passive film at the surface. In order to facilitate the diffusion of nitrogen into the material, a Fine Particle peening (FPP) treatment was performed prior to gas nitriding. The effects of the FPP treatment on gas nitriding behavior and consequent fatigue properties of AISI 316 steel were evaluated. Surface microstructures of the FPP treated specimens prior to gas nitriding were characterized using a micro-Vickers hardness tester, scanning electron microscope (SEM), optical microscope, electron probe micro analyzer (EPMA) and X-ray diffraction (XRD). The FPP treatment generated a local stratification pattern which exhibits high dislocation densities. During the subsequent nitriding process, nitrogen diffused into this unique structure, resulting in an increase in the surface hardness. Fatigue tests on a number of specimens with differing surface treatments were performed at room temperature using a rotational bending fatigue testing machine. The FPP treated specimen prior to gas nitriding exhibited the highest fatigue strength. After the fatigue tests, fracture surfaces were observed using an SEM in order to investigate the high-cycle fatigue properties.
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effect of Fine Particle peening treatment prior to nitriding on fatigue properties of aisi 4135 steel
Journal of Solid Mechanics and Materials Engineering, 2008Co-Authors: Shoichi Kikuchi, Jun KomotoriAbstract:In this study, a new hybrid surface modification process, Fine Particle peening (FPP) treatment prior to nitriding, was proposed. In order to clarify the effects of FPP treatment prior to nitriding on the fatigue strength of notched AISI 4135 steel with a stress concentration factor Kt of 2.36, fatigue tests were conducted at room temperature using a rotational bending fatigue testing machine. Hardness and residual stress distributions were measured in order to characterize the surface-modified layer. As a result, the surface hardness of the FPP-treated specimen before nitriding was higher than that of the nitrided specimen. The surface microstructures of treated specimens were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The crystal structure of the compound layer of the FPP-treated specimen before nitriding was different to that of the nitrided specimen. The compound layer of the FPP-treated specimen was dense. This suggests that FPP treatment prior to nitriding is very effective for improvement of the fatigue strength of steel.