The performance of a lubricant largely depends on the additives it involves.However,currently used additives cause severe pollution if they are burned and exhausted.Therefore,it is necessary to develop a new generatio...The performance of a lubricant largely depends on the additives it involves.However,currently used additives cause severe pollution if they are burned and exhausted.Therefore,it is necessary to develop a new generation of green additives.Graphene oxide(GO)consists of only C,H and O and thus is considered to be environmentally friendly.So the tribological properties of the few-layer GO sheet as an additive in hydrocarbon base oil are investigated systematically.It is found that,with the addition of GO sheets,both the coefficient of friction(COF)and wear are decreased and the working temperature range of the lubricant is expanded in the positive direction.Moreover,GO sheets has better performance under higher sliding speed and the optimized concentration of GO sheets is determined to be 0.5wt%.After rubbing,GO is detected on the wear scars through Raman spectroscopy.And it is believed that,during the rubbing,GO sheets adhere to the sliding surfaces,behaving like protective films and preventing the sliding surfaces from contacting with each other directly.This paper proves that the GO sheet is an effective lubricant additive,illuminates the lubrication mechanism,and provides some critical parameters for the practical application of GO sheets in lubrication.展开更多
We report a simple solution-processed method for the fabrication of low-cost,flexible optical limiting materials based on graphene oxide(GO) impregnated polyvinyl alcohol(PVA) sheets.Such GO–PVA composite sheets disp...We report a simple solution-processed method for the fabrication of low-cost,flexible optical limiting materials based on graphene oxide(GO) impregnated polyvinyl alcohol(PVA) sheets.Such GO–PVA composite sheets display highly efficient broadband optical limiting activities for femtosecond laser pulses at 400,800,and 1400 nm with very low limiting thresholds.Femtosecond pump–probe measurement results revealed that nonlinear absorption played an important role for the observed optical limiting activities.High flexibility and efficient optical limiting activities of these materials allow these composite sheets to be attached to nonplanar optical sensors in order to protect them from light-induced damage.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.51335005,51321092)National Key Basic Research Program of China(973 Program,Grant No.2013CB934200)the Foundation for the Supervisor of Beijing Excellent Doctoral Dissertation(Grant No.20111000305)
文摘The performance of a lubricant largely depends on the additives it involves.However,currently used additives cause severe pollution if they are burned and exhausted.Therefore,it is necessary to develop a new generation of green additives.Graphene oxide(GO)consists of only C,H and O and thus is considered to be environmentally friendly.So the tribological properties of the few-layer GO sheet as an additive in hydrocarbon base oil are investigated systematically.It is found that,with the addition of GO sheets,both the coefficient of friction(COF)and wear are decreased and the working temperature range of the lubricant is expanded in the positive direction.Moreover,GO sheets has better performance under higher sliding speed and the optimized concentration of GO sheets is determined to be 0.5wt%.After rubbing,GO is detected on the wear scars through Raman spectroscopy.And it is believed that,during the rubbing,GO sheets adhere to the sliding surfaces,behaving like protective films and preventing the sliding surfaces from contacting with each other directly.This paper proves that the GO sheet is an effective lubricant additive,illuminates the lubrication mechanism,and provides some critical parameters for the practical application of GO sheets in lubrication.
基金financial support from the Guangdong Innovative Research Team Program of China (201101C0105067115)DSTA Singapore (Project DSTA-NUS-DIRP/9010100347)National Research Foundation Singapore (R398-001-062-281)
文摘We report a simple solution-processed method for the fabrication of low-cost,flexible optical limiting materials based on graphene oxide(GO) impregnated polyvinyl alcohol(PVA) sheets.Such GO–PVA composite sheets display highly efficient broadband optical limiting activities for femtosecond laser pulses at 400,800,and 1400 nm with very low limiting thresholds.Femtosecond pump–probe measurement results revealed that nonlinear absorption played an important role for the observed optical limiting activities.High flexibility and efficient optical limiting activities of these materials allow these composite sheets to be attached to nonplanar optical sensors in order to protect them from light-induced damage.
