The present study is focused on the evaluation of the tribological performance of novel Ni/h BN and Ni/WS_2 composite coatings electrodeposited from an additive-free Watts bath with the assistance of ultrasound. Lubri...The present study is focused on the evaluation of the tribological performance of novel Ni/h BN and Ni/WS_2 composite coatings electrodeposited from an additive-free Watts bath with the assistance of ultrasound. Lubricated and non-lubricated scratch tests were performed on both novel composite coatings and on standard Ni deposits used as a benchmark coating to have an initial idea of the effect of the presence of particles within the Ni matrix. Under lubricated conditions, the performance of the Ni/h BN composite coating was very similar to the benchmark Ni coating, whereas the Ni/WS_2 behaved quite differently, as the latter did not only show a lower coefficient of friction, but also prevented the occurrence of stick-slip motion that was clearly observed in the other coatings. Under non-lubricated conditions, whereas the tribological performance of the Ni/hBN composite coating was again very similar to that of the benchmark Ni coating, the Ni/WS_2 composite coatings again showed a remarkable enhancement, as the incorporation of the WS_2 particles into the Ni coating not only resulted in a lower coefficient of friction, but also in the prevention of coating failure.展开更多
We demonstrate a passively Q-switched Yb：LSO laser based on tungsten disulphide （WS2） saturable absorber op- erating at 1034 nm and 1056 nm simultaneously. The saturable absorbers were fabricated by spin coating me...We demonstrate a passively Q-switched Yb：LSO laser based on tungsten disulphide （WS2） saturable absorber op- erating at 1034 nm and 1056 nm simultaneously. The saturable absorbers were fabricated by spin coating method. With low speed, the WS2 nanoplatelets embedded in polyvinyl alcohol could be coated on a BK7 glass substrate coated with high-refractive-index thin polymer. The shortest pulse width of 1.6 gs with a repetition rate of 76.9 kHz is obtained. As the pump power increases to 9 W, the maximum output power is measured to be 250 mW, corresponding to a single pulse energy of 3.25 μJ. To the best of our knowledge, this is the first time to obtain dual-wavelength Q-switched solid-state laser using few-layer WS2 nanoplatelets.展开更多
Ni-based submicron WS2/CaF2 self-lubricating composite coatings were produced on carbon steel substrate by high velocity oxygen fuel(HVOF) spray processing, and the microstructure and mechanical properties of the coat...Ni-based submicron WS2/CaF2 self-lubricating composite coatings were produced on carbon steel substrate by high velocity oxygen fuel(HVOF) spray processing, and the microstructure and mechanical properties of the coatings were investigated. Non-uniform microstructure characterized by some pores and microcracks is observed in the produced composite coatings, which leads to low microhardness value, low adhesive strength and low frictional coefficient. For Ni45-5%CaF2-10%WS2 (mass fraction) and Ni45-10%CaF2-5%WS2 (mass fraction) coatings, under the test condition of load 40 N and speed 2 m/s, the friction coefficients obtained at room temperature are in the range of 0.35-0.48 and 0.31-0.41, respectively. The friction coefficients of two kinds of coatings increase to 0.4-0.63 and 0.35-0.46, respectively, at the test speed of 1 m/s. And the Ni45-10%CaF2-5%WS2 coating presents the minimum friction coefficient of 0.32-0.38 and good anti-wear properties at 400 ℃.展开更多
Two-dimensional （2D） crystals have a multitude of forms, including semi-metals, semiconductors, and insulators, which are ideal for assembling isolated 2D atomic materials to create van der Waals （vdW） heterostruc...Two-dimensional （2D） crystals have a multitude of forms, including semi-metals, semiconductors, and insulators, which are ideal for assembling isolated 2D atomic materials to create van der Waals （vdW） heterostructures. Recently, artificially-stacked materials have been considered promising candidates for nanoelectronic and optoelectronic applications. In this study, we report the vertical integration of layered structures for the fabrication of prototype non-volatile memory devices. A semiconducting-tungsten-disulfide-channel-based memory device is created by sandwiching high-density-of-states multi-layered graphene as a carrier-confining layer between tunnel barriers of hexagonal boron nitride （hBN） and silicon dioxide. The results reveal that a memory window of up to 20 V is opened, leading to a high current ratio （〉103） between programming and erasing states. The proposed design combination produced layered materials that allow devices to attain perfect retention at 13% charge loss after 10 years, offering new possibilities for the integration of transparent, flexible electronic systems.展开更多
基金TSB (now Innovate UK)EPSRC in UK for their funding through the KTP scheme
文摘The present study is focused on the evaluation of the tribological performance of novel Ni/h BN and Ni/WS_2 composite coatings electrodeposited from an additive-free Watts bath with the assistance of ultrasound. Lubricated and non-lubricated scratch tests were performed on both novel composite coatings and on standard Ni deposits used as a benchmark coating to have an initial idea of the effect of the presence of particles within the Ni matrix. Under lubricated conditions, the performance of the Ni/h BN composite coating was very similar to the benchmark Ni coating, whereas the Ni/WS_2 behaved quite differently, as the latter did not only show a lower coefficient of friction, but also prevented the occurrence of stick-slip motion that was clearly observed in the other coatings. Under non-lubricated conditions, whereas the tribological performance of the Ni/hBN composite coating was again very similar to that of the benchmark Ni coating, the Ni/WS_2 composite coatings again showed a remarkable enhancement, as the incorporation of the WS_2 particles into the Ni coating not only resulted in a lower coefficient of friction, but also in the prevention of coating failure.
基金Project supported by the National Scientific Research Project of China(Grant No.61177047)Beijing Municipal Natural Science Foundation+1 种基金China(Grant No.1102005)the Basic Research Foundation of Beijing University of Technology,China(Grant No.X3006111201501)
文摘We demonstrate a passively Q-switched Yb：LSO laser based on tungsten disulphide （WS2） saturable absorber op- erating at 1034 nm and 1056 nm simultaneously. The saturable absorbers were fabricated by spin coating method. With low speed, the WS2 nanoplatelets embedded in polyvinyl alcohol could be coated on a BK7 glass substrate coated with high-refractive-index thin polymer. The shortest pulse width of 1.6 gs with a repetition rate of 76.9 kHz is obtained. As the pump power increases to 9 W, the maximum output power is measured to be 250 mW, corresponding to a single pulse energy of 3.25 μJ. To the best of our knowledge, this is the first time to obtain dual-wavelength Q-switched solid-state laser using few-layer WS2 nanoplatelets.
基金Project(50575081) supported by the National Natural Science Foundation of China
文摘Ni-based submicron WS2/CaF2 self-lubricating composite coatings were produced on carbon steel substrate by high velocity oxygen fuel(HVOF) spray processing, and the microstructure and mechanical properties of the coatings were investigated. Non-uniform microstructure characterized by some pores and microcracks is observed in the produced composite coatings, which leads to low microhardness value, low adhesive strength and low frictional coefficient. For Ni45-5%CaF2-10%WS2 (mass fraction) and Ni45-10%CaF2-5%WS2 (mass fraction) coatings, under the test condition of load 40 N and speed 2 m/s, the friction coefficients obtained at room temperature are in the range of 0.35-0.48 and 0.31-0.41, respectively. The friction coefficients of two kinds of coatings increase to 0.4-0.63 and 0.35-0.46, respectively, at the test speed of 1 m/s. And the Ni45-10%CaF2-5%WS2 coating presents the minimum friction coefficient of 0.32-0.38 and good anti-wear properties at 400 ℃.
文摘Two-dimensional （2D） crystals have a multitude of forms, including semi-metals, semiconductors, and insulators, which are ideal for assembling isolated 2D atomic materials to create van der Waals （vdW） heterostructures. Recently, artificially-stacked materials have been considered promising candidates for nanoelectronic and optoelectronic applications. In this study, we report the vertical integration of layered structures for the fabrication of prototype non-volatile memory devices. A semiconducting-tungsten-disulfide-channel-based memory device is created by sandwiching high-density-of-states multi-layered graphene as a carrier-confining layer between tunnel barriers of hexagonal boron nitride （hBN） and silicon dioxide. The results reveal that a memory window of up to 20 V is opened, leading to a high current ratio （〉103） between programming and erasing states. The proposed design combination produced layered materials that allow devices to attain perfect retention at 13% charge loss after 10 years, offering new possibilities for the integration of transparent, flexible electronic systems.
