The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Minoru Isshiki - One of the best experts on this subject based on the ideXlab platform.
-
Purification of Hafnium by Hydrogen Plasma Arc Melting
MATERIALS TRANSACTIONS, 2011Co-Authors: Kouji Mimura, Keigo Matsumoto, Minoru IsshikiAbstract:Purification of two kinds of Hf metal, a high-purity Hf (HP-Hf) with 99.7 mass% and a low-purity Hf (LP-Hf) with 98 mass%, by hydrogen Plasma Arc Melting (HPAM) has been carried out and the removal behavior of various impurity elements has been examined. Many metallic impurities (Fe, Al, Cr, Cu, Mn, Sn, Ti etc.) in the melted Hf, with higher vapor pressures than that of Hf, were removed to the very low levels by vaporization during HPAM and their removal rates increased with the hydrogen content of Plasma Arc. Then, the purity (except for Zr, O, N and C) of LP-Hf and HP-Hf were improved to nearly 99.998% and above 99.999%, respectively, after 60 min of 20%H2+Ar Plasma Arc Melting. For the removal of Fe, Al, Cu and Ti from Hf, the refining effect of HPAM under atmospheric pressure was found to be superior to that of EBM under high vacuum. Therefore, HPAM has been confirmed to be a very useful method for the purification of Hf and the dissociated and activated hydrogen atoms formed in the high temperature Plasma Arc must play an important role for the unique refining process of HPAM.
-
hydrogen effect on refining of mo metal by ar h2 Plasma Arc Melting
Materials Letters, 2010Co-Authors: Jae-won Lim, Kouji Mimura, Masahito Uchikoshi, Good-sun Choi, Dai Miyawaki, Sangbae Kim, Minoru IsshikiAbstract:Abstract The refining effect of Ar/Ar–H 2 Plasma Arc Melting (PAM) was investigated and the purity of Mo metals was evaluated by glow discharge mass spectrometry (GDMS). Most impurities in the Mo metals except for W were removed by Ar/Ar–H 2 PAM down to a few mass ppm levels, and the purities of respective Mo metals refined by Ar/Ar–20%H 2 PAM were improved up to 4N(99.9943%) and 5N(99.9996%). It is also found that Ar–H 2 PAM provides excellent decarburization, deoxidation, and denitrogenization. This confirmed that the refining effect is chemically induced by activated hydrogen atoms during Ar–H 2 PAM.
-
Preparation of High-Purity Cobalt by Anion-Exchange Separation and Plasma Arc Melting
Metallurgical and Materials Transactions B, 2010Co-Authors: Masahito Uchikoshi, Kouji Mimura, Hideka Shibuya, Junichi Imaizumi, Tamás Kékesi, Minoru IsshikiAbstract:High-purity Co was prepared with valence-controlled anion-exchange separation, oxidation refining using Plasma Arc Melting, and H_2-Ar Plasma Arc Melting on a pilot scale. The result of a laboratory-scale experiment indicated that the slower flow rate is more effective to remove the impurities by anion-exchange separation. However, the separation efficiency is reduced by scaling up the column from the laboratory to pilot scale. The discussion of the decrease in the separation efficiency implies that the distribution coefficient increases as the concentration of the adsorbate is lowered, but a reduced slower flow rate might increase the final purity of Co. In addition to anion-exchange separation, Co oxidation refining using Plasma Arc Melting was useful. Consequently, a high-purity Co of 99.9998 pct by mass excluding gaseous elements was prepared, which represents the highest purity reported.
-
Refining effect of hydrogen Plasma Arc Melting on titanium sponges
Materials Letters, 2010Co-Authors: Kouji Mimura, Jae-won Lim, Masahito Uchikoshi, Good-sun Choi, S.-w. Cho, Minoru IsshikiAbstract:Abstract Hydrogen Plasma Arc Melting (HPAM) of commercial Ti sponges (> 99.7%) was examined. Ti sponges had main impurities such as Fe, Al, Cl and Mn. These main impurities could be reduced more efficiently by HPAM than by Ar PAM. Other small amount of impurities also had a tendency of reduction by HPAM. In addition, it was found that each removal degree is attributable to a differential refining effect caused by the difference of initial impurity concentration. For the unique refining effect of HPAM, dissociated and activated hydrogen atoms involved in the high temperature Plasma Arc are considered to play an important role in the Melting process.
-
Purity evaluation of Ta metal refined by Ar/Ar−H2 Plasma Arc Melting
Metals and Materials International, 2008Co-Authors: Jae-won Lim, Kouji Mimura, Good-sun Choi, Minoru IsshikiAbstract:The refining effect of Ar/Ar-H2 Plasma Arc Melting (PAM) was investigated and the purity of Ta metals was evaluated by glow discharge mass spectrometry (GDMS). Most impurities in the Ta metals were removed by Ar/Ar-H2 PAM, down to a few mass ppm levels, and the purities of respective Ta metals refined by Ar/Ar-20% PAM were improved up to 5N5 (99.9995 %) and 5N7 (99.99972 %). It was also found that the deoxidation reaction under hydrogen Plasma condition is enhanced by a remarkable decrease in the oxygen concentration of the Ta metal refined by Ar-H2 PAM.
Jae-won Lim - One of the best experts on this subject based on the ideXlab platform.
-
Brief review of removal effect of hydrogen-Plasma Arc Melting on refining of pure titanium and titanium alloys
International Journal of Hydrogen Energy, 2016Co-Authors: Ki-min Roh, Jae-won LimAbstract:Abstract In this study, the effect of hydrogen-Plasma Arc Melting (HPAM) on the removal of metallic and gaseous impurities from pure titanium and titanium alloys is briefly reviewed according to the previous results and a newly added experiment. The highest removal degree (RD) of metallic impurities from pure titanium by HPAM with an Ar-20 vol.% of H 2 gas is 84.8%. In the titanium alloys, the RD values of the metallic impurities of the Ti Ni, Ti Mo, Ti Al, and Ti 6Al 4V alloys regarding HPAM with an Ar-20 vol.% of H 2 gas are 82.6%, 86.2%, 49.1%, and 76.6%, respectively. The total amount of gaseous impurities such as O, N, C, and H was decreased to 962 ppm from 2697 ppm, whereby a high RD value of 64.6% is shown despite the strong affinity of titanium regarding gaseous elements. It is suggested that HPAM exerts a dramatic effect on the removal of metallic impurities from pure titanium and titanium alloys, and it is appropriate for the refining of titanium alloys whereby a significant weight loss needs to be avoided. Thereby, HPAM process can be applied to industrial refining of commercial titanium and titanium alloys.
-
Preparation of 6N grade silicon ingot by combined purification processes from waste silicon cutting sludge
International Journal of Materials Research, 2015Co-Authors: Hyekyoung Kim, Back-kyu Lee, Hankwon Chang, Hee Dong Jang, Jae-won LimAbstract:Abstract This study is aimed at fabricating ultrahigh-purity silicon ingots from silicon cutting sludge – a byproduct of the ingot for solar cells cutting process. Firstly, silicon powder from the silicon cutting sludge was recovered by 1st purification, such as ultrasonication, centrifugation, and acid treatment before preparation of the silicon ingots. After the 1st purification, the silicon cutting sludge yielded silicon powder with a purity of 99.7612 %. The 1st-purified silicon powder was subjected to 2nd purification – 3 cycles hydrogen Plasma Arc Melting (HPAM), resulting in ultrahigh-purity silicon ingot with a purity of 99.9999 %. HPAM has been verified to be an effective process for removal of B and P – the major impurities of silicon for semiconductors and solar cells – to levels of total ≤ 0.3 ppm.
-
Preparatio no f6 Ng rad es ilico ni ngot by combined purification processe s from waste silicon cuttin gs ludge
2015Co-Authors: Jae-won LimAbstract:This study is aime da tf abricating ultrahigh-purit ys ilicon ingots from silico nc utting sludge –a byproduct of the ingot for solar cells cutting process .F irstly, silico np owder from the silico nc utting sludge was recovered by 1 st purification, such as ultrasonication, centrifugation, and acid treatment before preparation of the silico ni ngots. After the 1 st purification, the silicon cutting sludge yielded silico np owder with ap urity of 99.7612 %. The 1 st -purified silicon powder was subjected to 2 nd purification –3c ycles hydrogen Plasma Arc Melting (HPAM) ,r esultin gi nu ltrahigh-purity silicon ingot wit ha purit yo f9 9.9999 %. HPAM has been verified to be an effective process for removal of Ba nd P– the major impurities of silico nf or semiconductors and solar cells –t ol evel so ft otal £ 0.3 ppm.
-
Removal of metallic impurities from Ti binary alloy scraps using hydrogen Plasma Arc Melting
Journal of Alloys and Compounds, 2013Co-Authors: Back-kyu Lee, Chang-youl Suh, Jae-won LimAbstract:Abstract In the present study, we produced button ingots using hydrogen Plasma Arc Melting (HPAM), which enabled refining while suppressing the loss of alloy components as much as possible, in order to recycle Ti–Ni, Ti–Mo, and Ti–Al alloy scraps. When 20% hydrogen was added and the scraps were melted for 20 min, the weight losses were RD ) of impurities for the Ti–Ni, Ti–Mo, and Ti–Al alloys were 82.6%, 86.2%, and 49.1%, respectively. The Ti–Ni and Ti–Mo alloys showed a refining effect nearly identical to the level of RD for pure titanium obtained in the same way. In contrast, the refining effect for the Ti–Al alloy was not as good as those for the other alloys because of the properties of the alloy component, Al.
-
hydrogen effect on refining of mo metal by ar h2 Plasma Arc Melting
Materials Letters, 2010Co-Authors: Jae-won Lim, Kouji Mimura, Masahito Uchikoshi, Good-sun Choi, Dai Miyawaki, Sangbae Kim, Minoru IsshikiAbstract:Abstract The refining effect of Ar/Ar–H 2 Plasma Arc Melting (PAM) was investigated and the purity of Mo metals was evaluated by glow discharge mass spectrometry (GDMS). Most impurities in the Mo metals except for W were removed by Ar/Ar–H 2 PAM down to a few mass ppm levels, and the purities of respective Mo metals refined by Ar/Ar–20%H 2 PAM were improved up to 4N(99.9943%) and 5N(99.9996%). It is also found that Ar–H 2 PAM provides excellent decarburization, deoxidation, and denitrogenization. This confirmed that the refining effect is chemically induced by activated hydrogen atoms during Ar–H 2 PAM.
Kouji Mimura - One of the best experts on this subject based on the ideXlab platform.
-
Purification of Hafnium by Hydrogen Plasma Arc Melting
MATERIALS TRANSACTIONS, 2011Co-Authors: Kouji Mimura, Keigo Matsumoto, Minoru IsshikiAbstract:Purification of two kinds of Hf metal, a high-purity Hf (HP-Hf) with 99.7 mass% and a low-purity Hf (LP-Hf) with 98 mass%, by hydrogen Plasma Arc Melting (HPAM) has been carried out and the removal behavior of various impurity elements has been examined. Many metallic impurities (Fe, Al, Cr, Cu, Mn, Sn, Ti etc.) in the melted Hf, with higher vapor pressures than that of Hf, were removed to the very low levels by vaporization during HPAM and their removal rates increased with the hydrogen content of Plasma Arc. Then, the purity (except for Zr, O, N and C) of LP-Hf and HP-Hf were improved to nearly 99.998% and above 99.999%, respectively, after 60 min of 20%H2+Ar Plasma Arc Melting. For the removal of Fe, Al, Cu and Ti from Hf, the refining effect of HPAM under atmospheric pressure was found to be superior to that of EBM under high vacuum. Therefore, HPAM has been confirmed to be a very useful method for the purification of Hf and the dissociated and activated hydrogen atoms formed in the high temperature Plasma Arc must play an important role for the unique refining process of HPAM.
-
hydrogen effect on refining of mo metal by ar h2 Plasma Arc Melting
Materials Letters, 2010Co-Authors: Jae-won Lim, Kouji Mimura, Masahito Uchikoshi, Good-sun Choi, Dai Miyawaki, Sangbae Kim, Minoru IsshikiAbstract:Abstract The refining effect of Ar/Ar–H 2 Plasma Arc Melting (PAM) was investigated and the purity of Mo metals was evaluated by glow discharge mass spectrometry (GDMS). Most impurities in the Mo metals except for W were removed by Ar/Ar–H 2 PAM down to a few mass ppm levels, and the purities of respective Mo metals refined by Ar/Ar–20%H 2 PAM were improved up to 4N(99.9943%) and 5N(99.9996%). It is also found that Ar–H 2 PAM provides excellent decarburization, deoxidation, and denitrogenization. This confirmed that the refining effect is chemically induced by activated hydrogen atoms during Ar–H 2 PAM.
-
Preparation of High-Purity Cobalt by Anion-Exchange Separation and Plasma Arc Melting
Metallurgical and Materials Transactions B, 2010Co-Authors: Masahito Uchikoshi, Kouji Mimura, Hideka Shibuya, Junichi Imaizumi, Tamás Kékesi, Minoru IsshikiAbstract:High-purity Co was prepared with valence-controlled anion-exchange separation, oxidation refining using Plasma Arc Melting, and H_2-Ar Plasma Arc Melting on a pilot scale. The result of a laboratory-scale experiment indicated that the slower flow rate is more effective to remove the impurities by anion-exchange separation. However, the separation efficiency is reduced by scaling up the column from the laboratory to pilot scale. The discussion of the decrease in the separation efficiency implies that the distribution coefficient increases as the concentration of the adsorbate is lowered, but a reduced slower flow rate might increase the final purity of Co. In addition to anion-exchange separation, Co oxidation refining using Plasma Arc Melting was useful. Consequently, a high-purity Co of 99.9998 pct by mass excluding gaseous elements was prepared, which represents the highest purity reported.
-
Refining effect of hydrogen Plasma Arc Melting on titanium sponges
Materials Letters, 2010Co-Authors: Kouji Mimura, Jae-won Lim, Masahito Uchikoshi, Good-sun Choi, S.-w. Cho, Minoru IsshikiAbstract:Abstract Hydrogen Plasma Arc Melting (HPAM) of commercial Ti sponges (> 99.7%) was examined. Ti sponges had main impurities such as Fe, Al, Cl and Mn. These main impurities could be reduced more efficiently by HPAM than by Ar PAM. Other small amount of impurities also had a tendency of reduction by HPAM. In addition, it was found that each removal degree is attributable to a differential refining effect caused by the difference of initial impurity concentration. For the unique refining effect of HPAM, dissociated and activated hydrogen atoms involved in the high temperature Plasma Arc are considered to play an important role in the Melting process.
-
Purity evaluation of Ta metal refined by Ar/Ar−H2 Plasma Arc Melting
Metals and Materials International, 2008Co-Authors: Jae-won Lim, Kouji Mimura, Good-sun Choi, Minoru IsshikiAbstract:The refining effect of Ar/Ar-H2 Plasma Arc Melting (PAM) was investigated and the purity of Ta metals was evaluated by glow discharge mass spectrometry (GDMS). Most impurities in the Ta metals were removed by Ar/Ar-H2 PAM, down to a few mass ppm levels, and the purities of respective Ta metals refined by Ar/Ar-20% PAM were improved up to 5N5 (99.9995 %) and 5N7 (99.99972 %). It was also found that the deoxidation reaction under hydrogen Plasma condition is enhanced by a remarkable decrease in the oxygen concentration of the Ta metal refined by Ar-H2 PAM.
D. Elanski - One of the best experts on this subject based on the ideXlab platform.
-
Refining Effect of Hydrogen Plasma Arc Melting and Trace Impurity Analysis by Glow Discharge Mass Spectrometry
Geosystem Engineering, 2007Co-Authors: Jae-won Lim, D. Elanski, Kouji Mimura, Good-sun Choi, Minoru IsshikiAbstract:ABSTRACT Recently, hydrogen Plasma Arc Melting (HPAM) has been expected to be a practical Melting and refining technique for metals and alloys. The effect of H2 addition to the Ar Plasma gas on the purification of metals and alloys has been described by possible chemical reactions of impurities with activated hydrogen atoms on a molten metal as well as the increase in temperature of a metal surface. Trace impurity concentration of refined metals is determined using glow discharge mass spectrometry (GDMS). This method is used to determine trace elements quantitatively because GDMS is a direct solid-state analytical method that uses no chemical process and provides reliable quantitative concentrations for most elements below 0.01 ppm. We reviewed the refining effect of HPAM for several metals by trace impurity analysis using GDMS.
-
Thermodynamic estimation of hydride formation during hydrogen Plasma Arc Melting
Journal of Alloys and Compounds, 2006Co-Authors: D. Elanski, Jae-won Lim, Kouji Mimura, Minoru IsshikiAbstract:Abstract The purification effect by hydrogen Plasma Arc Melting (HPAM) and the respective probabilities of hydride formation for several metals were investigated. Commercially pure Fe, Cr, Ti, V, Zr, Nb, and Ta metals were melted for 60 min using Ar–30 vol% H 2 Plasma gas at 5.3 kPa (Ta at 101.3 kPa). Results showed that the degree of removal of each impurity in the metals increases concomitant with the increased vapor pressure difference between the impurity and the metal. This study further established that addition of hydrogen to the Plasma gas increases the metal surface temperature, which is a main reason for the superior purification provided by Ar–H 2 Plasma Arc Melting. Thermodynamic calculations showed that the main part of impurities transfers to the gas phase as atomic species, whereas Sb can predominantly form hydrides over other corresponding atomic species.
-
impurity removal from zr nb and ta metals by hydrogen Plasma Arc Melting and thermodynamic estimation of hydride formation
Journal of Alloys and Compounds, 2006Co-Authors: D. Elanski, Jae-won Lim, Kouji Mimura, Minoru IsshikiAbstract:Abstract Commercial Zr, Nb and Ta have been purified by hydrogen Plasma Arc Melting (HPAM) and the removal degree of impurities was compared with the results of thermodynamic estimations. In the case of Zr and Nb, 40–60% of the total amount of impurities was removed by Ar Plasma Melting and 60–80% by HPAM. The Ta Melting by HPAM allowed to remove 80% of the total amount of impurities and to decrease the concentration of almost impurities down to a few mass ppb levels. For the systems with Ar–H 2 Plasma gas, experimental and calculated results are closer to each other than that for the system with Ar Plasma gas. According to the thermodynamic calculations, none of impurities forms hydrides in the gas phase because of the high Melting temperatures of these metals. The effect of H 2 addition to the Plasma gas on the enhancement of the impurity removal may be attributed to the increase of the surface temperature of molten metals.
-
Impurity removal from Fe, Cr, Ti, and V metals by hydrogen Plasma Arc Melting and thermodynamic estimation of hydride and sulfide formation
Journal of Alloys and Compounds, 2005Co-Authors: D. Elanski, Jae-won Lim, Kouji Mimura, Minoru IsshikiAbstract:Abstract Experimental data of Fe, Cr, Ti, and V metals purified by Ar and Ar-30 vol% H 2 Plasma Arc Melting was compared with results of thermodynamic estimations. The Fe metal refined by Ar and Ar-30 vol% H 2 Plasma gas at 101.3 and 5.3 kPa had approximate 45% removal degree of the total impurities. On the other hand, Co, Ni, Zr, Nb, and Mo were not reduced from the Fe metal due to their lower vapor pressures than that of Fe. At 5.3 kPa, hydrogen Plasma Arc Melting of Ti and V, which have lower initial impurity contents than that of Fe, resulted in a removal degree of near 40% of impurities, while the average removal degree of impurities in the Cr metal close to 30%. Thermodynamic estimation could explain qualitatively a tendency of each impurity behavior. It was shown by the thermodynamic calculations that several impurities, namely Mn, S and P, form hydrides with relatively high pressures compared with pressures of atomic species. Furthermore, It was also confirmed that the formation of some sulfides in the gas phase including FeS, SiS and GeS affects the behavior of S and sulfide forming elements.
-
Purification of tantalum by means of hydrogen Plasma Arc Melting
Materials Letters, 1997Co-Authors: D. Elanski, Kouji Mimura, Taizo Ito, Minoru IsshikiAbstract:Abstract Further purification of commercially pure Ta metal ( > 99.9%) by hydrogen Plasma Arc Melting (HPAM) has been examined under a pressure of 101.3 kPa using Ar-30 vol% H 2 Plasma gas. Most impurities, except for Nb, Mo and W, are removed down to a few mass ppb levels. Concentrations of the elements which deteriorate the large scale integrated circuit performance, such as Fe, Th and U, are also decreased by two or more orders of magnitude. The final concentrations of many impurities in Ta purified by HPAM are lower than those achieved by electron beam Melting (EBM) of Ta. The use of Ta, instead of W, as a cathode inside the Plasma torch, makes it possible to avoid contamination of the Ta melt with W and Th from the thoriated W cathode commonly used. Possibility for the removal of Th, U and W from the Ta melt during HPAM was also discussed on the basis of thermodynamic calculations.
Carlos José De Araújo - One of the best experts on this subject based on the ideXlab platform.
-
thermal microstructural and elastic modulus behavior of ti50ni50 xnbx x 0 25 at shape memory alloys obtained by Plasma Arc Melting
Journal of Alloys and Compounds, 2021Co-Authors: Melânea Almeida Ramalho Medeiros, Carlos José De AraújoAbstract:Abstract Ternary alloys based on the NiTi system with the addition of Nb have attracted attention for several areas of engineering, due to improvements in the shape memory properties. In this work, six TiNiNb compositions were obtained by Plasma Arc Melting under controlled atmosphere, with Nb contents of 5%, 10%, 15%, 20% and 25% Nb in the Ti50Ni50−xNbx system (% at). This work aims to evaluate the influence of Nb content on the microstructure, phase transformation and elastic modulus behavior of the ternary alloy compared to the equiatomic binary NiTi alloy. Differential scanning calorimetry (DSC) show that after a heat treatment of 900 °C for 1 h, all studied compositions present a single-step phase transformation during cooling and heating. Nb addition has a limited effect over phase transformation temperatures, with the onset of martensite transformation remaining practically constant. The microstructure of the alloys is constituted by B2 NiTi austenite matrix in the samples with 0% and 5% Nb, and by B19′ NiTi martensite in the samples with 10–25% Nb, all surrounded by an eutectic phase rich in Nb (β-Nb). Scanning electron microscopy (SEM) revealed microstructures with the presence of dendrites with a large amount of β-Nb that evolved in size with increasing Nb content. The Nb addition and consequent microstructure changes contributed to the decrease in the average hardness, going from 527 HV in NiTi to values between 259 and 396 HV in TiNiNb alloys. The Nb content, however, had a weaker effect over the highest modulus of elasticity, which was highest in the Ti50Ni30Nb20 alloy (66 GPa) and lowest in the Ti50Ni45Nb5 alloy (52 GPa), representing a less than 10% variation.
-
Thermal, microstructural and elastic modulus behavior of Ti50Ni50−xNbx (x = 0–25%at) shape memory alloys obtained by Plasma Arc Melting
Journal of Alloys and Compounds, 1Co-Authors: Melânea Almeida Ramalho Medeiros, Carlos José De AraújoAbstract:Abstract Ternary alloys based on the NiTi system with the addition of Nb have attracted attention for several areas of engineering, due to improvements in the shape memory properties. In this work, six TiNiNb compositions were obtained by Plasma Arc Melting under controlled atmosphere, with Nb contents of 5%, 10%, 15%, 20% and 25% Nb in the Ti50Ni50−xNbx system (% at). This work aims to evaluate the influence of Nb content on the microstructure, phase transformation and elastic modulus behavior of the ternary alloy compared to the equiatomic binary NiTi alloy. Differential scanning calorimetry (DSC) show that after a heat treatment of 900 °C for 1 h, all studied compositions present a single-step phase transformation during cooling and heating. Nb addition has a limited effect over phase transformation temperatures, with the onset of martensite transformation remaining practically constant. The microstructure of the alloys is constituted by B2 NiTi austenite matrix in the samples with 0% and 5% Nb, and by B19′ NiTi martensite in the samples with 10–25% Nb, all surrounded by an eutectic phase rich in Nb (β-Nb). Scanning electron microscopy (SEM) revealed microstructures with the presence of dendrites with a large amount of β-Nb that evolved in size with increasing Nb content. The Nb addition and consequent microstructure changes contributed to the decrease in the average hardness, going from 527 HV in NiTi to values between 259 and 396 HV in TiNiNb alloys. The Nb content, however, had a weaker effect over the highest modulus of elasticity, which was highest in the Ti50Ni30Nb20 alloy (66 GPa) and lowest in the Ti50Ni45Nb5 alloy (52 GPa), representing a less than 10% variation.