The Experts below are selected from a list of 285 Experts worldwide ranked by ideXlab platform
Norio Tagawa - One of the best experts on this subject based on the ideXlab platform.
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Slider Wear on Disks Lubricated by Ultra-Thin Perfluoropolyether Lubricants with Different Molecular Weights
Tribology Letters, 2014Co-Authors: Nagayoshi Kobayashi, Hiroshi Tani, Tsuyoshi Shimizu, Shinji Koganezawa, Norio TagawaAbstract:In this study, the wear properties of a magnetic head slider on disks lubricated by ultra-thin perfluoropolyether (PFPE) Lubricants with different molecular weights were evaluated by the continuous sliding of magnetic head sliders using the slider contact by the dynamic flying height control. Two types of PFPE Lubricants (Z-tetraol and D-4OH) with different molecular weights were evaluated. Results show that the slider wear depended on the coverage of the Lubricant film; i.e., the Lubricant film with sufficient coverage reduced slider wear. The Lubricant film with a low molecular weight (low-Mw), including a Lubricant material with a Fomblin and Demnum main chain, exhibited better coverage on a diamond-like carbon surface. Sliders with a low-Mw Lubricant film showed less wear than those of a high molecular weight (high-Mw), and the depletion of the low-Mw Lubricant film was less than that of the high-Mw Lubricant film.
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depletion of monolayer liquid Lubricant films induced by laser heating in thermally assisted magnetic recording
Tribology Letters, 2012Co-Authors: Norio Tagawa, Takao Miki, Hiroshi TaniAbstract:In this study, Lubricant depletion due to high-frequency pulsed-laser heating, with a heating rate of ~108–109 K/s, was investigated for Lubricant films with thicknesses of greater than and less than one monolayer. The conventional Lubricants, Zdol2000 and Ztetraol2000, were used. It was found that the critical temperature at which the Lubricants begin to deplete was strongly dependent on the Lubricant film thickness. For Lubricant film thicknesses of less than one monolayer, this temperature was approximately 170 °C higher than that for thicknesses of greater than one monolayer. To analyze the Lubricant depletion mechanism, we examined the tested Lubricant films, using temperature-programmed desorption (TPD) spectroscopy, in which the heating rate was 0.3 K/s. It was found that the Lubricant depletion characteristics could be explained using the experimental TPD results for the tested Lubricant films. The depletion mechanism involves the desorption or decomposition of the Lubricant molecules, which interact with the diamond-like carbon thin films when the Lubricant film thickness is less than one monolayer. Therefore, we concluded that the TPD results were highly effective for evaluating the Lubricant depletion characteristics induced by rapid laser heating, even though the heating rates are substantially different.
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Lubricant Pickup of Ultra-Thin PFPE Lubricants With Different Backbone Structures
IEEE Transactions on Magnetics, 2010Co-Authors: Hiroshi Tani, Kazumi Iwasaki, Y Maruyama, M Nakayama, Norio TagawaAbstract:Lubricant pickups on different perfluoropolyether (PFPE)-Lubricant (Z-tetraol, D-4OH, and QA-40) films were compared by using a slider surface analyzing (SSA) tester developed to observe the Lubricant thickness mapping on the slider surfaces after the heads slide on the disk surfaces. These Lubricants have the same four OH functional end-groups but different backbones. Z-tetraol showed the least Lubricant pickup among the four Lubricants. D-4OH and QA-40 showed considerable pickup at a large clearance of 30-mW back-off. The pickup volumes of each Lubricant disk with a similar mobile Lubricant thickness were different, and D-4OH showed the largest pickup volume among these Lubricants. An MD simulation was performed to understand the difference in the Lubricant pickup of the three types of Lubricants. The intermolecular force between the slider and the Lubricant molecules was different for these Lubricants. This difference in the intermolecular force depended on the dipole-dipole interaction between the end-groups and the slider surface, and the dipole-dipole interaction was affected by the conformation of the Lubricant molecules. Therefore, it is estimated that the Lubricant pickup phenomenon is influenced by the conformation of the Lubricant molecules, and D-4OH with a strong -OH function at the Lubricant surface exhibited considerable Lubricant pickup.
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Effect of Temperature on the Spreading Characteristics of Molecularly Thin Liquid Lubricant Films in Hard Disk Drives
STLE ASME 2008 International Joint Tribology Conference, 2008Co-Authors: Norio Tagawa, Kenta Mori, Atsunobu Mori, Masako IkegamiAbstract:In this study, the effect of temperature on the spreading characteristics of ultra-thin liquid Lubricant films in hard disk drives (HDD) was investigated by using three types of Lubricants, namely, Zdol2000, Ztetraol2000, and A20H2000. The apparent diffusion coefficient of individual Lubricants was evaluated and compared by varying the temperature of disk substrates. As a result, it was found that the mobility of each Lubricant increases with the temperature. However, the rate of mobility increase is different for each Lubricant, depending on the Lubricant material. Furthermore, there exists no quantitative correlation between the mobility increase for ultra-thin liquid Lubricant films and the viscosity decrease in bulk Lubricant materials due to a rise in the temperature. It was also found that among the test Lubricants, A20H2000 has the highest robustness for temperature change. In addition, it could be observed that the evaporation of the mobile fraction of Lubricants occurred remarkably over a temperature range of 50– 80 °C.Copyright © 2008 by ASME
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Effects of ultra-thin liquid Lubricant films on contact slider dynamics in hard-disk drives
Tribology International, 2007Co-Authors: Norio Tagawa, Yoshiaki Tashiro, Atsunobu MoriAbstract:Abstract This paper describes the effects of ultra-thin liquid Lubricant films on contact slider dynamics in hard-disk drives. In the experiments, the contact slider dynamics as well as ultra-thin liquid Lubricants behavior are investigated using three types of Lubricants, which have different end-groups and molecular weight as a function of Lubricant film thickness. The dynamics of a contact slider is mainly monitored using acoustic emission (AE). The disks are also examined with a scanning micro-ellipsometer before and after contact slider experiments. It is found that the Lubricant film thickness instability occurs as a result of slider–disk contacts, when the Lubricant film thickness is thicker than one monolayer. Their unstable Lubricant behavior depends on the chemical structure of functional end-groups and molecular weight. In addition, it is also found that the AE RMS values, which indicate the contact slider dynamics, are almost same, independent of the end-groups and molecular weight for the Lubricants, when the Lubricant film thickness is approximately one monolayer. The molecular weight, however, affects the contact slider dynamics, when the Lubricant film thickness is less than one monolayer. In other words, the AE RMS values increase remarkably as the molecular weight for the Lubricant increases. When the Lubricant film thickness is more than one monolayer, the AE RMS values decrease because of the effect of mobile Lubricant layer, while the Lubricant instability affects the contact slider dynamics. Therefore, it may be concluded that the Lubricant film thickness should be designed to be approximately one monolayer thickness region in order to achieve contact recording for future head–disk interface.
M. Petrov - One of the best experts on this subject based on the ideXlab platform.
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Research into Oil-based Colloidal-Graphite Lubricants for Forging of Al-based Alloys
2011Co-Authors: Alexander N. Petrov, Pavel A. Petrov, M. PetrovAbstract:The presented paper describes the topical problem in metal forging production. It deals with the choice of an optimal Lubricant for forging of Al‐based alloys. Within the scope of the paper, the properties of several oil‐based colloidal‐graphite Lubricants were investigated. The physicochemical and technological properties of these Lubricants are presented. It was found that physicochemical properties of Lubricant compositions have an influence on friction coefficient value and quality of forgings.The ring compression method was used to estimate the friction coefficient value. Hydraulic press was used for the test. The comparative analysis of the investigated Lubricants was carried out. The forging quality was estimated on the basis of production test. The practical recommendations were given to choose an optimal oil‐based colloidal‐graphite Lubricant for isothermal forging of Al‐based alloy.
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Research into Oil‐based Colloidal‐Graphite Lubricants for Forging of Al‐based Alloys
2011Co-Authors: Alexander N. Petrov, Pavel A. Petrov, M. PetrovAbstract:The presented paper describes the topical problem in metal forging production. It deals with the choice of an optimal Lubricant for forging of Al‐based alloys. Within the scope of the paper, the properties of several oil‐based colloidal‐graphite Lubricants were investigated. The physicochemical and technological properties of these Lubricants are presented. It was found that physicochemical properties of Lubricant compositions have an influence on friction coefficient value and quality of forgings.The ring compression method was used to estimate the friction coefficient value. Hydraulic press was used for the test. The comparative analysis of the investigated Lubricants was carried out. The forging quality was estimated on the basis of production test. The practical recommendations were given to choose an optimal oil‐based colloidal‐graphite Lubricant for isothermal forging of Al‐based alloy.
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Research into water-based colloidal-graphite Lubricants for forging of carbon steels and Ni-based alloys
International Journal of Material Forming, 2010Co-Authors: Alexander N. Petrov, Pavel A. Petrov, M. PetrovAbstract:The presented paper describes the topical problem in metal forging production. It deals with the choice of an optimal Lubricant for forging of carbon steels and Ni-based alloys. Within the scope of the paper, the properties of several water-based colloidal-graphite Lubricants were investigated. The physicochemical and technological properties of these Lubricants are presented. It was found that physicochemical properties of Lubricant compositions have an influence on friction coefficient value and as a result on die life during forging process. The ring compression method was used to estimate the friction coefficient value. Both mechanical press and screw press were used for the test. The comparative analysis of the investigated Lubricants was carried out. The die life was estimated on the basis of statistics obtained with the help of an automated forging line. The practical recommendations were given to choose an optimal water-based colloidal-graphite Lubricant for forging of carbon steel or Ni-based alloy.
Atsunobu Mori - One of the best experts on this subject based on the ideXlab platform.
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Effect of Temperature on the Spreading Characteristics of Molecularly Thin Liquid Lubricant Films in Hard Disk Drives
STLE ASME 2008 International Joint Tribology Conference, 2008Co-Authors: Norio Tagawa, Kenta Mori, Atsunobu Mori, Masako IkegamiAbstract:In this study, the effect of temperature on the spreading characteristics of ultra-thin liquid Lubricant films in hard disk drives (HDD) was investigated by using three types of Lubricants, namely, Zdol2000, Ztetraol2000, and A20H2000. The apparent diffusion coefficient of individual Lubricants was evaluated and compared by varying the temperature of disk substrates. As a result, it was found that the mobility of each Lubricant increases with the temperature. However, the rate of mobility increase is different for each Lubricant, depending on the Lubricant material. Furthermore, there exists no quantitative correlation between the mobility increase for ultra-thin liquid Lubricant films and the viscosity decrease in bulk Lubricant materials due to a rise in the temperature. It was also found that among the test Lubricants, A20H2000 has the highest robustness for temperature change. In addition, it could be observed that the evaporation of the mobile fraction of Lubricants occurred remarkably over a temperature range of 50– 80 °C.Copyright © 2008 by ASME
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Effects of ultra-thin liquid Lubricant films on contact slider dynamics in hard-disk drives
Tribology International, 2007Co-Authors: Norio Tagawa, Yoshiaki Tashiro, Atsunobu MoriAbstract:Abstract This paper describes the effects of ultra-thin liquid Lubricant films on contact slider dynamics in hard-disk drives. In the experiments, the contact slider dynamics as well as ultra-thin liquid Lubricants behavior are investigated using three types of Lubricants, which have different end-groups and molecular weight as a function of Lubricant film thickness. The dynamics of a contact slider is mainly monitored using acoustic emission (AE). The disks are also examined with a scanning micro-ellipsometer before and after contact slider experiments. It is found that the Lubricant film thickness instability occurs as a result of slider–disk contacts, when the Lubricant film thickness is thicker than one monolayer. Their unstable Lubricant behavior depends on the chemical structure of functional end-groups and molecular weight. In addition, it is also found that the AE RMS values, which indicate the contact slider dynamics, are almost same, independent of the end-groups and molecular weight for the Lubricants, when the Lubricant film thickness is approximately one monolayer. The molecular weight, however, affects the contact slider dynamics, when the Lubricant film thickness is less than one monolayer. In other words, the AE RMS values increase remarkably as the molecular weight for the Lubricant increases. When the Lubricant film thickness is more than one monolayer, the AE RMS values decrease because of the effect of mobile Lubricant layer, while the Lubricant instability affects the contact slider dynamics. Therefore, it may be concluded that the Lubricant film thickness should be designed to be approximately one monolayer thickness region in order to achieve contact recording for future head–disk interface.
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Effects of End-Group Functionality and Molecular Weight of Ultra-Thin Liquid Lubricant Films on Contact Slider Dynamics in Hard Disk Drives
ASME STLE 2004 International Joint Tribology Conference Parts A and B, 2004Co-Authors: Norio Tagawa, Yoshiaki Tashiro, Atsunobu MoriAbstract:This paper describes the effect of end-group functionality and molecular weight of ultra-thin liquid Lubricant films on contact slider dynamics in hard disk drives. In the experiments, the contact slider dynamics as well as ultra-thin liquid Lubricants behavior are investigated using three kinds of Lubricants which have different end-groups and molecular weight as a function of Lubricant film thickness. The dynamics of a contact slider is mainly monitored using Acoustic Emission (AE). The disks are also examined with a scanning micro-ellipsometer before and after contact slider experiments. It is found that the Lubricant film thickness instability due to de-wetting occurs as a result of slider-disk contacts, when the Lubricant film thickness is thicker than one monolayer. Their unstable Lubricant behavior depends on the chemical structure of functional end-groups and molecular weight. In addition, it is also found that the AE RMS values, which indicate the contact slider dynamics, are almost equivalent, independent of the end-groups and molecular weight for the Lubricants, when the Lubricant film thickness is around one monolayer. The molecular weight, however, affects the contact slider dynamics, when the Lubricant film thickness is less than one monolayer. In other words, the AE RMS values increase remarkably as the molecular weight for the Lubricant increases. When the Lubricant film thickness is more than one monolayer, the AE RMS values decrease because of the effect of mobile Lubricant layer, while the Lubricant de-wetting instability affects the contact slider dynamics. Therefore, it would be concluded that the Lubricant film thickness should be designed to be around one monolayer thickness region in order to achieve contact recording for future head-disk interface.Copyright © 2004 by ASME
Lin Wu - One of the best experts on this subject based on the ideXlab platform.
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modelling and simulation of the Lubricant depletion process induced by laser heating in heat assisted magnetic recording system
Nanotechnology, 2007Co-Authors: Lin WuAbstract:A model for Lubricant flow dynamics under a scanning laser beam has been constructed for a heat-assisted magnetic recording system. The effects of evaporation, thermocapillary stress and thermoviscosity on the Lubricant depletion on both glass and aluminium disks are systematically studied. Our results indicate that both evaporation and thermocapillary stress are able to deplete non-negligible amount of Z-type PFPE Lubricants with a low molecular weight from the disk surface within nanoseconds. Evaporation is the dominant Lubricant removal mechanism when low molecular weight Lubricant is used. Evaporation is significantly reduced when high molecular weight PFPE Lubricants are used. Our simulations show that the performance of head/disk interface of heat-assisted magnetic recording systems may be significantly deteriorated when Lubricants with improper properties are used.
Alexander N. Petrov - One of the best experts on this subject based on the ideXlab platform.
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Research into Oil-based Colloidal-Graphite Lubricants for Forging of Al-based Alloys
2011Co-Authors: Alexander N. Petrov, Pavel A. Petrov, M. PetrovAbstract:The presented paper describes the topical problem in metal forging production. It deals with the choice of an optimal Lubricant for forging of Al‐based alloys. Within the scope of the paper, the properties of several oil‐based colloidal‐graphite Lubricants were investigated. The physicochemical and technological properties of these Lubricants are presented. It was found that physicochemical properties of Lubricant compositions have an influence on friction coefficient value and quality of forgings.The ring compression method was used to estimate the friction coefficient value. Hydraulic press was used for the test. The comparative analysis of the investigated Lubricants was carried out. The forging quality was estimated on the basis of production test. The practical recommendations were given to choose an optimal oil‐based colloidal‐graphite Lubricant for isothermal forging of Al‐based alloy.
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Research into Oil‐based Colloidal‐Graphite Lubricants for Forging of Al‐based Alloys
2011Co-Authors: Alexander N. Petrov, Pavel A. Petrov, M. PetrovAbstract:The presented paper describes the topical problem in metal forging production. It deals with the choice of an optimal Lubricant for forging of Al‐based alloys. Within the scope of the paper, the properties of several oil‐based colloidal‐graphite Lubricants were investigated. The physicochemical and technological properties of these Lubricants are presented. It was found that physicochemical properties of Lubricant compositions have an influence on friction coefficient value and quality of forgings.The ring compression method was used to estimate the friction coefficient value. Hydraulic press was used for the test. The comparative analysis of the investigated Lubricants was carried out. The forging quality was estimated on the basis of production test. The practical recommendations were given to choose an optimal oil‐based colloidal‐graphite Lubricant for isothermal forging of Al‐based alloy.
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Research into water-based colloidal-graphite Lubricants for forging of carbon steels and Ni-based alloys
International Journal of Material Forming, 2010Co-Authors: Alexander N. Petrov, Pavel A. Petrov, M. PetrovAbstract:The presented paper describes the topical problem in metal forging production. It deals with the choice of an optimal Lubricant for forging of carbon steels and Ni-based alloys. Within the scope of the paper, the properties of several water-based colloidal-graphite Lubricants were investigated. The physicochemical and technological properties of these Lubricants are presented. It was found that physicochemical properties of Lubricant compositions have an influence on friction coefficient value and as a result on die life during forging process. The ring compression method was used to estimate the friction coefficient value. Both mechanical press and screw press were used for the test. The comparative analysis of the investigated Lubricants was carried out. The die life was estimated on the basis of statistics obtained with the help of an automated forging line. The practical recommendations were given to choose an optimal water-based colloidal-graphite Lubricant for forging of carbon steel or Ni-based alloy.
