Plasma electrolytic oxidation （PEO） is carried out on 6061 Al-alloys in a weak alkaline electrolyte containing NaOH, Na2SiO3 and NaCl. Centered on the correlation of composition and structure, analyses by means of X...Plasma electrolytic oxidation （PEO） is carried out on 6061 Al-alloys in a weak alkaline electrolyte containing NaOH, Na2SiO3 and NaCl. Centered on the correlation of composition and structure, analyses by means of X-ray diffration （XRD）, scanning electron microscope （SEM） and energy dispersive spectrometry （EDS） are conducted on the specimens, which have been PEO-treated under hybrid voltages of different direct current （DC） values （140-280 V） with constant alternate current （AC） amplitude （200 V）. Attention is paid to the composition, properties and growth mechanism of oxide layers formed with hybrid voltages. Moreover, the main effects of DC value are discussed. Ceramic layers with a double-layer structure which combines hard outer and soft inner layers are found to be consist of α-Al2O3,γ-Al2O3 and mullite. With the DC values increasing, the growth of the ceramic layers tends to have increasingly obvious three-stage feature.展开更多
As a solid lubricant, silver-palladium (Ag-Pd) alloy coating was investigated for the application to high temperature stud bolt. A glue layer nickel (Ni) film was deposited on the surface of the hex bolt sample and th...As a solid lubricant, silver-palladium (Ag-Pd) alloy coating was investigated for the application to high temperature stud bolt. A glue layer nickel (Ni) film was deposited on the surface of the hex bolt sample and then Ag-Pd alloy coating was performed on it using ion plating method. The friction coefficient of Ag-Pd alloy film coated bolt was lower than that of N-5000 oil coated bolt by the result of axial force measurement. The cyclic test of heat treatment was conducted to evaluate the durability of Ag-Pd alloy film coated bolt. In a cycle, sample was assembled into the block using torque wrench, followed by heating and disassembling. It was not successful to disassemble the N-5000 oil coated bolt from the block after only one cycle. However, the Ag-Pd alloy film coated bolt was able to be disassembled softly till 12 cycles.展开更多
Resistive strain sensors(RSS)with ultrasensitivity have attracted much attention as multifunctional sensors.However,since most ultrasensitive RSS are designed by cracked conductive metals,the sensing performance is se...Resistive strain sensors(RSS)with ultrasensitivity have attracted much attention as multifunctional sensors.However,since most ultrasensitive RSS are designed by cracked conductive metals,the sensing performance is severely degraded due to accumulated structural deformation with consecutive cycles.To overcome such limitation,newly designed structures have been suggested,but the development of mechanosensors exhibiting superior stability and ultrasensitivity still remains a challenge.Here,we demonstrate that vertical graphene(VG)RSS with high sensitivity(gauge factor greater than 5000),remarkable durability(>10,000 cycles),and extraordinary resilience can serve multifunctional applications.We find that well-defined cracks on tufted network structure result in highly reversible resistance variation,especially revivable status even after broken current path,confirmed by microscopic in situ monitoring.The VG integrated with a wireless sensing system exhibits excellent timbre recognition performance.Our findings provide inspirable insights for mechanosensing system,making VG a promising component for future practicable flexible sensor technologies.展开更多
基金Changwon National University in 2008 and National IT Industry Program Agency(NIPA-2009-C-C1090-0903-0007)
文摘Plasma electrolytic oxidation （PEO） is carried out on 6061 Al-alloys in a weak alkaline electrolyte containing NaOH, Na2SiO3 and NaCl. Centered on the correlation of composition and structure, analyses by means of X-ray diffration （XRD）, scanning electron microscope （SEM） and energy dispersive spectrometry （EDS） are conducted on the specimens, which have been PEO-treated under hybrid voltages of different direct current （DC） values （140-280 V） with constant alternate current （AC） amplitude （200 V）. Attention is paid to the composition, properties and growth mechanism of oxide layers formed with hybrid voltages. Moreover, the main effects of DC value are discussed. Ceramic layers with a double-layer structure which combines hard outer and soft inner layers are found to be consist of α-Al2O3,γ-Al2O3 and mullite. With the DC values increasing, the growth of the ceramic layers tends to have increasingly obvious three-stage feature.
基金the research fund of the Korea Institute of Materials Science, a subsidiary branch of the Korea Institute of Machinery and Materialssupported by a grant from the Fundamental R&D Program for Core Technology of Materials funded by the Ministry of Knowledge Economy, Republic of Korea
文摘As a solid lubricant, silver-palladium (Ag-Pd) alloy coating was investigated for the application to high temperature stud bolt. A glue layer nickel (Ni) film was deposited on the surface of the hex bolt sample and then Ag-Pd alloy coating was performed on it using ion plating method. The friction coefficient of Ag-Pd alloy film coated bolt was lower than that of N-5000 oil coated bolt by the result of axial force measurement. The cyclic test of heat treatment was conducted to evaluate the durability of Ag-Pd alloy film coated bolt. In a cycle, sample was assembled into the block using torque wrench, followed by heating and disassembling. It was not successful to disassemble the N-5000 oil coated bolt from the block after only one cycle. However, the Ag-Pd alloy film coated bolt was able to be disassembled softly till 12 cycles.
基金support from the National Research Foundation of Korea (NRF)grant funded by the Korean government (No.2016R1E1A1A01942649)support from the National Research Foundation of Korea (NRF)grant funded by the Korean government (2018R1D1A1B07048109 and 2021R1F1A1050726)+1 种基金support from the National Research Foundation of Korea (NRF)grant funded by the Korean government (grant nos.2018R1D1A1B07045581)from a Korea University Grant.
文摘Resistive strain sensors(RSS)with ultrasensitivity have attracted much attention as multifunctional sensors.However,since most ultrasensitive RSS are designed by cracked conductive metals,the sensing performance is severely degraded due to accumulated structural deformation with consecutive cycles.To overcome such limitation,newly designed structures have been suggested,but the development of mechanosensors exhibiting superior stability and ultrasensitivity still remains a challenge.Here,we demonstrate that vertical graphene(VG)RSS with high sensitivity(gauge factor greater than 5000),remarkable durability(>10,000 cycles),and extraordinary resilience can serve multifunctional applications.We find that well-defined cracks on tufted network structure result in highly reversible resistance variation,especially revivable status even after broken current path,confirmed by microscopic in situ monitoring.The VG integrated with a wireless sensing system exhibits excellent timbre recognition performance.Our findings provide inspirable insights for mechanosensing system,making VG a promising component for future practicable flexible sensor technologies.
