Pub Date : 2001-06-20DOI: 10.2320/MATERTRANS.42.961
M. Hasegawa, T. Higuchi, Masayuki Tanaka, T. Tsukamoto, Shik Shin, H. Takei
The electronic structure of metallic oxide PdCoO 2 has been investigated by photoemission and inverse photoemission spectroscopies. It is found that the finite density of states at the Fermi level in the spectra is observed at the low photon energy where the ionization cross-section of Pd 4d increases with decreasing photon energy. Resonant photoemission spectra of PdCoO 2 at photon energies near the Co 3p to 3d and Pd 4p to 4d absorption thresholds, indicate no density of states at the Fermi level in the partial density of states of Co 3d, and finite density of states at the Fermi level in the partial density of states of Pd 4d, respectively. These results indicate that the main contribution to the density of states at the Fermi level is Pd 4d and that the low resistivity of PdCoO 2 is attributable to the itinerancy of the Pd 4d electrons.
{"title":"Electronic structure of delafossite-type metallic oxide PdCoO2 : Special Issue on Structure and Electronic Properties in the Pseudogap Systems","authors":"M. Hasegawa, T. Higuchi, Masayuki Tanaka, T. Tsukamoto, Shik Shin, H. Takei","doi":"10.2320/MATERTRANS.42.961","DOIUrl":"https://doi.org/10.2320/MATERTRANS.42.961","url":null,"abstract":"The electronic structure of metallic oxide PdCoO 2 has been investigated by photoemission and inverse photoemission spectroscopies. It is found that the finite density of states at the Fermi level in the spectra is observed at the low photon energy where the ionization cross-section of Pd 4d increases with decreasing photon energy. Resonant photoemission spectra of PdCoO 2 at photon energies near the Co 3p to 3d and Pd 4p to 4d absorption thresholds, indicate no density of states at the Fermi level in the partial density of states of Co 3d, and finite density of states at the Fermi level in the partial density of states of Pd 4d, respectively. These results indicate that the main contribution to the density of states at the Fermi level is Pd 4d and that the low resistivity of PdCoO 2 is attributable to the itinerancy of the Pd 4d electrons.","PeriodicalId":18264,"journal":{"name":"Materials Transactions Jim","volume":"28 1","pages":"961-964"},"PeriodicalIF":0.0,"publicationDate":"2001-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81719332","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-06-20DOI: 10.2320/MATERTRANS.42.956
R. Funahashi, I. Matsubara, H. Ikuta, T. Takeuchi, U. Mizutani
Thermoelectric properties of (Ca, Sr, Bi) 2 Co 2 O 5 (Co-225) single crystalline whiskers with a layered structure were measured over a wide temperature range 100-973 K. Both Seebeck coefficient and electrical resistivity exhibited fairly complex temperature dependences in this temperature range. The whole temperature range studied is divided into four distinct regions (I) to (IV), depending on observed characteristic temperature dependences of both Seebeck coefficient and electrical resistivity. From more or less linearly temperature dependent Seebeck coefficient in region (I) in combination with unique temperature dependences of both resistivity and Hall coefficient, we conclude the presence of a small pseudogap with a width of a few meV across the Fermi level. Complex magnetic properties are observed: the antiferromagnetic transition at 22 K but the hysteresis in the M-H curve remains up to room temperature. This is taken as evidence for the existence of Co atoms situated in different magnetic environments. The possession of large Seebeck coefficients exceeding 100 μV K -1 in this system is attributed to the presence of the pseudogap at the Fermi level.
在100-973 K的宽温度范围内，测量了层状结构(Ca, Sr, Bi) 2co2o5 (Co-225)单晶晶须的热电性能。在此温度范围内，塞贝克系数和电阻率都表现出相当复杂的温度依赖性。根据观察到的塞贝克系数和电阻率的特征温度依赖性，将整个温度范围划分为四个不同的区域(I)至(IV)。从区域(I)或多或少线性依赖温度的塞贝克系数，结合电阻率和霍尔系数的独特温度依赖，我们得出结论，在费米能级上存在一个宽度为几meV的小赝隙。观察到复杂的磁性:在22k时发生反铁磁跃迁，但M-H曲线的磁滞一直保持到室温。这被认为是Co原子存在于不同磁环境的证据。该体系具有超过100 μV K -1的大塞贝克系数是由于费米能级上存在赝隙。
{"title":"Thermoelectric properties of (Ca, Sr, Bi)2Co2O5 whiskers : Special Issue on Structure and Electronic Properties in the Pseudogap Systems","authors":"R. Funahashi, I. Matsubara, H. Ikuta, T. Takeuchi, U. Mizutani","doi":"10.2320/MATERTRANS.42.956","DOIUrl":"https://doi.org/10.2320/MATERTRANS.42.956","url":null,"abstract":"Thermoelectric properties of (Ca, Sr, Bi) 2 Co 2 O 5 (Co-225) single crystalline whiskers with a layered structure were measured over a wide temperature range 100-973 K. Both Seebeck coefficient and electrical resistivity exhibited fairly complex temperature dependences in this temperature range. The whole temperature range studied is divided into four distinct regions (I) to (IV), depending on observed characteristic temperature dependences of both Seebeck coefficient and electrical resistivity. From more or less linearly temperature dependent Seebeck coefficient in region (I) in combination with unique temperature dependences of both resistivity and Hall coefficient, we conclude the presence of a small pseudogap with a width of a few meV across the Fermi level. Complex magnetic properties are observed: the antiferromagnetic transition at 22 K but the hysteresis in the M-H curve remains up to room temperature. This is taken as evidence for the existence of Co atoms situated in different magnetic environments. The possession of large Seebeck coefficients exceeding 100 μV K -1 in this system is attributed to the presence of the pseudogap at the Fermi level.","PeriodicalId":18264,"journal":{"name":"Materials Transactions Jim","volume":"4 1","pages":"956-960"},"PeriodicalIF":0.0,"publicationDate":"2001-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79271612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-05-20DOI: 10.2320/MATERTRANS.42.820
Chang-Bae Park, Soon-Min Hong, J. Jung, C. Kang, Yong-Eui Shin
UBM-coated Si-wafer was fluxlessly soldered with glass substrate in N 2 atmosphere using plasma cleaning method. The bulk Sn-37 mass%Pb and Sn-3.5 mass%Ag solders were rolled to the sheet of 100 μm thickness in order to achieve bonding to Si-wafer by fluxless 1st reflow process. The oxide layer on the solder surface was analyzed by AES (Auger Electron Spectroscopy). After 1st reflow the Si-wafer with a solder disk was plasma-cleaned, and soldered to glass by 2nd reflow soldering process without flux in N 2 atmosphere. The thickness of oxide layer decreased with increasing plasma power and cleaning time. The optimum plasma treatment condition in this study was 500 W for 12 min and at this condition, 100% bonding ratio for Sn-3.5 Ag and over 80% bonding ratio for Sn-37Pb solder were achieved. The intermetallic compound of continuous Cu 6 Sn 5 was observed along the Si-wafer/solder interface but discrete Cu 6 Sn 5 along the glass/solder interface and the different shapes of Cu 6 Sn 5 were caused by different thickness of Cu as a pad. The fracture of the tensile test specimen occurred at not only solder/UBM and solder/TSM interface but also in Si-wafer and glass substrate.
采用等离子体清洗法，在氮气气氛中对ubm包覆硅片与玻璃衬底进行无焊锡焊接。将Sn-37质量%Pb和Sn-3.5质量%Ag焊料轧制成100 μm厚的片状材料，采用无助熔剂第一次回流工艺与硅片结合。采用俄歇电子能谱(AES)对焊料表面氧化层进行了分析。在第一次回流焊后，等离子体清洗带有焊盘的硅片，在氮气气氛中进行第二次回流焊，无助焊剂焊接到玻璃上。氧化层厚度随等离子体功率和清洗时间的增加而减小。本研究的最佳等离子体处理条件为500 W, 12 min，在此条件下，Sn-3.5 Ag和Sn-37Pb焊料的键合率分别达到100%和80%以上。在硅片/钎料界面上观察到连续的Cu 6 - Sn - 5金属间化合物，而在玻璃/钎料界面上观察到离散的Cu 6 - Sn - 5金属间化合物，并且Cu厚度的不同导致了Cu 6 - Sn - 5金属间化合物的形状不同。拉伸试样的断裂不仅发生在钎料/UBM和钎料/TSM界面，还发生在硅片和玻璃基板上。
{"title":"A study on the fluxless soldering of Si-wafer/glass substrate using Sn-3.5 mass%Ag and Sn-37 mass%Pb solder : Special issue on basic science and advanced technology of lead-free electronics packaging","authors":"Chang-Bae Park, Soon-Min Hong, J. Jung, C. Kang, Yong-Eui Shin","doi":"10.2320/MATERTRANS.42.820","DOIUrl":"https://doi.org/10.2320/MATERTRANS.42.820","url":null,"abstract":"UBM-coated Si-wafer was fluxlessly soldered with glass substrate in N 2 atmosphere using plasma cleaning method. The bulk Sn-37 mass%Pb and Sn-3.5 mass%Ag solders were rolled to the sheet of 100 μm thickness in order to achieve bonding to Si-wafer by fluxless 1st reflow process. The oxide layer on the solder surface was analyzed by AES (Auger Electron Spectroscopy). After 1st reflow the Si-wafer with a solder disk was plasma-cleaned, and soldered to glass by 2nd reflow soldering process without flux in N 2 atmosphere. The thickness of oxide layer decreased with increasing plasma power and cleaning time. The optimum plasma treatment condition in this study was 500 W for 12 min and at this condition, 100% bonding ratio for Sn-3.5 Ag and over 80% bonding ratio for Sn-37Pb solder were achieved. The intermetallic compound of continuous Cu 6 Sn 5 was observed along the Si-wafer/solder interface but discrete Cu 6 Sn 5 along the glass/solder interface and the different shapes of Cu 6 Sn 5 were caused by different thickness of Cu as a pad. The fracture of the tensile test specimen occurred at not only solder/UBM and solder/TSM interface but also in Si-wafer and glass substrate.","PeriodicalId":18264,"journal":{"name":"Materials Transactions Jim","volume":"8 1","pages":"820-824"},"PeriodicalIF":0.0,"publicationDate":"2001-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91331880","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-01-20DOI: 10.2320/MATERTRANS.42.128
X. Li, J. Tian, S. Li, Zhongguang Wang
By using a vertical sectioning method (VSM) or secondary electron line scanning method (SELSM), the fractal dimension D S for surface, D L for scanning profile were measured quantitatively on some typical fracture surfaces, namely cleavage fractures, dimple fractures and fatigue fractures of composite materials. It was shown that the measured value of D S relates differently to the impact energy values of materials for cleavage or dimple fractures. The microstructure of materials should be considered comprehensively when relating D S to the mechanical properties of materials. It is found that the correlation between the fractal dimension and the impact energy obtained by SELSM and VSM methods appears to be quite similar. Moreover, the quantitative measurements on the fatigue fracture surfaces of SiC/AI composite materials showed that SiC volume fraction has a strong effect on fractal dimension D S , and that there is an obvious difference in the D S values for fatigue fractures which are due to different fracture mechanisms. These results show that it is possible to reflect the fracture mechanism using D S and relate it to the fracture properties of materials.
{"title":"Application of a fractal method to quantitatively describe some typical fracture surfaces : Special issue on recent progress in understanding of materials fracture","authors":"X. Li, J. Tian, S. Li, Zhongguang Wang","doi":"10.2320/MATERTRANS.42.128","DOIUrl":"https://doi.org/10.2320/MATERTRANS.42.128","url":null,"abstract":"By using a vertical sectioning method (VSM) or secondary electron line scanning method (SELSM), the fractal dimension D S for surface, D L for scanning profile were measured quantitatively on some typical fracture surfaces, namely cleavage fractures, dimple fractures and fatigue fractures of composite materials. It was shown that the measured value of D S relates differently to the impact energy values of materials for cleavage or dimple fractures. The microstructure of materials should be considered comprehensively when relating D S to the mechanical properties of materials. It is found that the correlation between the fractal dimension and the impact energy obtained by SELSM and VSM methods appears to be quite similar. Moreover, the quantitative measurements on the fatigue fracture surfaces of SiC/AI composite materials showed that SiC volume fraction has a strong effect on fractal dimension D S , and that there is an obvious difference in the D S values for fatigue fractures which are due to different fracture mechanisms. These results show that it is possible to reflect the fracture mechanism using D S and relate it to the fracture properties of materials.","PeriodicalId":18264,"journal":{"name":"Materials Transactions Jim","volume":"43 1","pages":"128-131"},"PeriodicalIF":0.0,"publicationDate":"2001-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84406224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-01-01DOI: 10.2320/MATERTRANS.42.928
R. Tamura, T. Asao, And Shin Takeuchi
In order to gain an insight into the roles of the local atomic environment and the long-range quasiperiodicity in the electronic transport of the icosahedral quasicrystal, a direct comparison of the electrical resistivity of icosahedral quasicrystals, (1/0, 1/0, 1/0) and (2/1, 2/1, 2/1) crystalline approximants in the Al-Pd-TM (TM=Fe, Ru, Os) ternary systems has been made on the basis of the same alloy system. The trend of the resistivity of 1/0-cubic approximants, which are the lowest order crystalline analogues to the icosahedral phase, already possesses a nonmetallic character, while the 2/1-cubic approximants exhibit quite similar behavior to that of the corresponding quasicrystals. The present result strongly suggests that the effect of the long-range quasiperiodicity beyond the lattice periodicity of 2/1-cubic approximant phase on the electronic transport is of less significance and the electronic transport of approximants and quasicrystals is mainly determined by the local atomic environment of a scale less than 2.0 nm.
{"title":"Roles of quasiperiodicity and local environment in the electronic transport of the icosahedral quasicrystals in Al-Pd-TM (TM=Fe, Ru, Os) systems : Special Issue on Structure and Electronic Properties in the Pseudogap Systems","authors":"R. Tamura, T. Asao, And Shin Takeuchi","doi":"10.2320/MATERTRANS.42.928","DOIUrl":"https://doi.org/10.2320/MATERTRANS.42.928","url":null,"abstract":"In order to gain an insight into the roles of the local atomic environment and the long-range quasiperiodicity in the electronic transport of the icosahedral quasicrystal, a direct comparison of the electrical resistivity of icosahedral quasicrystals, (1/0, 1/0, 1/0) and (2/1, 2/1, 2/1) crystalline approximants in the Al-Pd-TM (TM=Fe, Ru, Os) ternary systems has been made on the basis of the same alloy system. The trend of the resistivity of 1/0-cubic approximants, which are the lowest order crystalline analogues to the icosahedral phase, already possesses a nonmetallic character, while the 2/1-cubic approximants exhibit quite similar behavior to that of the corresponding quasicrystals. The present result strongly suggests that the effect of the long-range quasiperiodicity beyond the lattice periodicity of 2/1-cubic approximant phase on the electronic transport is of less significance and the electronic transport of approximants and quasicrystals is mainly determined by the local atomic environment of a scale less than 2.0 nm.","PeriodicalId":18264,"journal":{"name":"Materials Transactions Jim","volume":"38 1","pages":"928-932"},"PeriodicalIF":0.0,"publicationDate":"2001-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88523370","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2000-12-01DOI: 10.2320/MATERTRANS1989.41.1651
S. Sato, T. Imanaga, E. Matsubara, M. Saito, Y. Waseda
The usefulness and validity of energy dispersive grazing incidence X-ray reflectometry (ED-GIXR) have been demonstrated for characterizing the liquid/liquid and liquid/solid interfaces. The present method appears to hold promise in reducing difficulty of conventional angular dispersive method due to absorption with an upper half liquid layer by enabling the use of high energy white X-ray radiation and obtaining much higher reflected intensity. An apparatus newly built for the exclusive use of the ED-GIXR is described with some selected examples of X-ray reflectivity profiles of solution/mercury and solution/electrode interfaces.
{"title":"Application of Energy Dispersive Grazing Incidence X-ray Reflectometry Method to Structural Analysis of Liquid/Liquid and Liquid/Solid Interfaces","authors":"S. Sato, T. Imanaga, E. Matsubara, M. Saito, Y. Waseda","doi":"10.2320/MATERTRANS1989.41.1651","DOIUrl":"https://doi.org/10.2320/MATERTRANS1989.41.1651","url":null,"abstract":"The usefulness and validity of energy dispersive grazing incidence X-ray reflectometry (ED-GIXR) have been demonstrated for characterizing the liquid/liquid and liquid/solid interfaces. The present method appears to hold promise in reducing difficulty of conventional angular dispersive method due to absorption with an upper half liquid layer by enabling the use of high energy white X-ray radiation and obtaining much higher reflected intensity. An apparatus newly built for the exclusive use of the ED-GIXR is described with some selected examples of X-ray reflectivity profiles of solution/mercury and solution/electrode interfaces.","PeriodicalId":18264,"journal":{"name":"Materials Transactions Jim","volume":"16 1","pages":"1651-1656"},"PeriodicalIF":0.0,"publicationDate":"2000-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79330933","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2000-12-01DOI: 10.2320/MATERTRANS1989.41.1663
Young-Joo Oh, Sang-Yoon Lee, Jung-Soo Byun, J. Shim, Y. Cho
The formation of non-metallic inclusions with variations in various oxygen, nitrogen and titanium contents in low carbon steels has been studied. The relationship between the nature of non-metallic inclusions and the formation of acicular ferrite has been also investigated. It is found that the non-metallic inclusions observed in this study are mainly consist of Ti 2 O 3 and TiN together with a small amount of other complex oxides containing Mn and Si. It has been confirmed that Ti 2 O 3 and TiN play an important role in formation of acicular ferrite as a nucleation site and an austenite grain refiner, respectively. But it is not clear yet whether TiN acts as a nucleation site or not. It is also found that the volume fraction of inclusions is more effective than the type or size distribution of the non-metallic inclusions on the formation of acicular ferrite.
{"title":"Non-Metallic Inclusions and Acicular Ferrite in Low Carbon Steel","authors":"Young-Joo Oh, Sang-Yoon Lee, Jung-Soo Byun, J. Shim, Y. Cho","doi":"10.2320/MATERTRANS1989.41.1663","DOIUrl":"https://doi.org/10.2320/MATERTRANS1989.41.1663","url":null,"abstract":"The formation of non-metallic inclusions with variations in various oxygen, nitrogen and titanium contents in low carbon steels has been studied. The relationship between the nature of non-metallic inclusions and the formation of acicular ferrite has been also investigated. It is found that the non-metallic inclusions observed in this study are mainly consist of Ti 2 O 3 and TiN together with a small amount of other complex oxides containing Mn and Si. It has been confirmed that Ti 2 O 3 and TiN play an important role in formation of acicular ferrite as a nucleation site and an austenite grain refiner, respectively. But it is not clear yet whether TiN acts as a nucleation site or not. It is also found that the volume fraction of inclusions is more effective than the type or size distribution of the non-metallic inclusions on the formation of acicular ferrite.","PeriodicalId":18264,"journal":{"name":"Materials Transactions Jim","volume":"67 1","pages":"1663-1669"},"PeriodicalIF":0.0,"publicationDate":"2000-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76797258","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2000-12-01DOI: 10.2320/MATERTRANS1989.41.1616
H. Shibata, H. Ohta, Atsushi Suzuki, Y. Waseda
For transparent materials such as silicate glasses, an absorber layer of a laser beam and an emitter layer of an infrared ray are essentially required for measuring thermal diffusivity by the laser flash method with an infrared ray detector. Platinum (thickness: 1.0 μm) and molybdenum (thickness: 0.7 μm) thin layers were formed by sputtering on both sides of a transparent specimen with a disk shape. Then such metal coating was tested at elevated temperatures. The platinum thin layer was found to work well to measure thermal diffusivity of silica glass at temperature below 1000 K. The molybdenum coating was also successfully applied to the measurement of thermal diffusivity for silicate glass in the temperature range between 750 and 1569 K with considering radiative heat transfer inside the specimen.
{"title":"Applicability of Platinum and Molybdenum Coatings for Measuring Thermal Diffusivity of Transparent Glass Specimens by the Laser Flash Method at High Temperatures","authors":"H. Shibata, H. Ohta, Atsushi Suzuki, Y. Waseda","doi":"10.2320/MATERTRANS1989.41.1616","DOIUrl":"https://doi.org/10.2320/MATERTRANS1989.41.1616","url":null,"abstract":"For transparent materials such as silicate glasses, an absorber layer of a laser beam and an emitter layer of an infrared ray are essentially required for measuring thermal diffusivity by the laser flash method with an infrared ray detector. Platinum (thickness: 1.0 μm) and molybdenum (thickness: 0.7 μm) thin layers were formed by sputtering on both sides of a transparent specimen with a disk shape. Then such metal coating was tested at elevated temperatures. The platinum thin layer was found to work well to measure thermal diffusivity of silica glass at temperature below 1000 K. The molybdenum coating was also successfully applied to the measurement of thermal diffusivity for silicate glass in the temperature range between 750 and 1569 K with considering radiative heat transfer inside the specimen.","PeriodicalId":18264,"journal":{"name":"Materials Transactions Jim","volume":"133 1","pages":"1616-1620"},"PeriodicalIF":0.0,"publicationDate":"2000-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76483622","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2000-12-01DOI: 10.2320/MATERTRANS1989.41.1593
Guofeng Zhang, M. Morishita, M. Inada, K. Kôyama
Corrosion of NiMo 2 B 2 -dispersed Ni-based alloy containing Co, Mn, Cr, Fe or Cu was examined by measuring the mass loss and the corrosion potential in 6 mass%HNO 3 aqueous solution and by metallography. The corrosion was accelerated by addition of Co or Mn while it was retarded by addition of Cr, Fe or Cu. In particular, the addition of Cu greatly improved the corrosion resistance. The corrosion proceeded by a mechanism in which the Ni-matrix phase worked as anode while the NiMo 2 B 2 phase worked as cathode. The addition of Cu shifted the corrosion potential of the Ni-matrix phase to the noble side by about 15 mV, and consequently the difference in the corrosion potential between the Ni-matrix phase and the NiMo 2 B 2 phase decreased, As a result the preferential corrosion of the Ni-matrix phase was extremely retarded.
{"title":"Effect of Cu on the corrosion resistance of a NiMo2B2-Dispersed Ni-based alloy","authors":"Guofeng Zhang, M. Morishita, M. Inada, K. Kôyama","doi":"10.2320/MATERTRANS1989.41.1593","DOIUrl":"https://doi.org/10.2320/MATERTRANS1989.41.1593","url":null,"abstract":"Corrosion of NiMo 2 B 2 -dispersed Ni-based alloy containing Co, Mn, Cr, Fe or Cu was examined by measuring the mass loss and the corrosion potential in 6 mass%HNO 3 aqueous solution and by metallography. The corrosion was accelerated by addition of Co or Mn while it was retarded by addition of Cr, Fe or Cu. In particular, the addition of Cu greatly improved the corrosion resistance. The corrosion proceeded by a mechanism in which the Ni-matrix phase worked as anode while the NiMo 2 B 2 phase worked as cathode. The addition of Cu shifted the corrosion potential of the Ni-matrix phase to the noble side by about 15 mV, and consequently the difference in the corrosion potential between the Ni-matrix phase and the NiMo 2 B 2 phase decreased, As a result the preferential corrosion of the Ni-matrix phase was extremely retarded.","PeriodicalId":18264,"journal":{"name":"Materials Transactions Jim","volume":"1 1","pages":"1593-1598"},"PeriodicalIF":0.0,"publicationDate":"2000-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73462305","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2000-12-01DOI: 10.2320/MATERTRANS1989.41.1599
N. Nomura, K. Yoshimi, S. Hanada
Mo-40 mol%TiC and Mo-20 mol%Nb-40 mol%TiC in-situ composites were synthesized by hot-pressing mixed Mo, Nb and TiC powders, Both composites consist of two phases, Mo solid solution (A2) and TiC (B 1), after hot-pressing at 2073 K and 70 MPa for 2 h followed by annealing at 2073 K for 24 h. Porosity of hot-pressed compacts decreased by Nb addition to Mo-40 mol%TiC. The composites have different microstructural features. Clusters consisting of fine bcc particles are observed in sizes similar to original Nb powder in Mo-20 mol%Nb-40 mol%TiC, while there are no clusters in Mo-40 mol%TiC. These composites show excellent strength superior to monolithic TiC at high temperatures. The addition of Nb to Mo-40 mol%TiC suppresses effectively intergranular fracture above 1473 K. Furthermore, fracture toughness of these composites is higher than that of monolithic TiC. Fracture toughness of Mo-20 mol%Nb-40 mol%TiC is slightly lower than that of Mo-40 mol%TiC. The obtained results are discussed in relation to microstructural characteristics.
{"title":"Mechanical Properties of Mo–Nb–TiC In-situ Composites Synthesized by Hot-Pressing","authors":"N. Nomura, K. Yoshimi, S. Hanada","doi":"10.2320/MATERTRANS1989.41.1599","DOIUrl":"https://doi.org/10.2320/MATERTRANS1989.41.1599","url":null,"abstract":"Mo-40 mol%TiC and Mo-20 mol%Nb-40 mol%TiC in-situ composites were synthesized by hot-pressing mixed Mo, Nb and TiC powders, Both composites consist of two phases, Mo solid solution (A2) and TiC (B 1), after hot-pressing at 2073 K and 70 MPa for 2 h followed by annealing at 2073 K for 24 h. Porosity of hot-pressed compacts decreased by Nb addition to Mo-40 mol%TiC. The composites have different microstructural features. Clusters consisting of fine bcc particles are observed in sizes similar to original Nb powder in Mo-20 mol%Nb-40 mol%TiC, while there are no clusters in Mo-40 mol%TiC. These composites show excellent strength superior to monolithic TiC at high temperatures. The addition of Nb to Mo-40 mol%TiC suppresses effectively intergranular fracture above 1473 K. Furthermore, fracture toughness of these composites is higher than that of monolithic TiC. Fracture toughness of Mo-20 mol%Nb-40 mol%TiC is slightly lower than that of Mo-40 mol%TiC. The obtained results are discussed in relation to microstructural characteristics.","PeriodicalId":18264,"journal":{"name":"Materials Transactions Jim","volume":"56 1","pages":"1599-1604"},"PeriodicalIF":0.0,"publicationDate":"2000-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85792748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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