The influence of liquid viscoelasticity on the interaction between cavitation bubbles and free surfaces is of great practical significance in understanding bubble dynamics in biological systems. A series of millimeter...The influence of liquid viscoelasticity on the interaction between cavitation bubbles and free surfaces is of great practical significance in understanding bubble dynamics in biological systems. A series of millimeter cavitation bubbles were induced by laser near the free surfaces of the water and viscoelastic polyacrylamide (PAM) solutions with different concentrations. The effects of liquid viscoelasticity on the interactions of cavitation bubbles with free surfaces are analyzed from the perspectives of the evolution of free surface and bubble dynamics. The experimental results show that as the dimensionless standoff distance increases, the evolutions of free surface behaviors in all experimental fluids can be divided into six types of water mounds, i.e., breaking wrinkles, spraying water film, crown, swallowed water spike, hillock, and slight bulge. All the critical values of the dimensionless distance dividing different types decrease with increasing concentration. The evolutions of first four types of water mounds in PAM solutions differ from those in the water. Water droplets splashing in different directions are produced around the breaking wrinkles in the water. Meanwhile, the breaking wrinkles in PAM solution move with the “liquid filaments” towards the central axis. The water spike in the pattern of spraying water film in PAM solution is more stable than that in the water. As the solution concentration increases, the water skirt in the pattern of crown contracts earlier and faster, and the rate of increase in the height of the water skirt decreases. For swallowed water spike in PAM solution, the upper part of the newly formed water spike is not significantly thicker than the middle part, and thus the water waist structure does not form. Liquid viscoelasticity inhibits the bubble growth and collapse, and the bubble migration as well, especially in the second period. Shorter and thicker cavities are formed in PAM solutions with higher concentration, while slender and stable cavities formed in the water at the same dimensionless distance. The velocity and displacement of the tip of bullet jet both decrease as the solution concentration increases.展开更多
This study investigates the interactions between cavitation bubbles and the interfaces of two immiscible liquids,with practical implications and potential applications in the fields such as ultrasonic emulsification a...This study investigates the interactions between cavitation bubbles and the interfaces of two immiscible liquids,with practical implications and potential applications in the fields such as ultrasonic emulsification and wastewater treatment.To explore the influence of liquid viscosity on the interaction between the cavitation bubble and flat liquid-liquid interface,visualization experiments were performed on the laser-induced cavitation bubbles near two liquid-liquid interfaces composed of deionized water and two silicone oils with different viscosities(50 mPa·s,500 mPa·s)by using high-speed photography.Three different positions were employed for the generation of cavitation bubbles,i.e.,at the interface,in the water,and in the silicone oil.The evolutions of cavitation bubbles and the corresponding interface deformations at different dimensionless standoff distancesγbetween the cavitation bubble and the interface were observed.The results show that the difference in the viscosity of silicone oil significantly affects the physical phenomena occurred during the interaction between the millimeter-scale cavitation bubble and the interface.On this basis,the qualitative and quantitative analyses for the cavitation bubble jet dynamics indicate that the critical value ofγfor jet penetration through the interface between the water and the higher-viscosity silicone oil(interface 2,γ=0.33)is lower than that for the interface between the water and the lower-viscosity silicone oil(interface 1,γ=0.69).Besides,the jet generated by the cavitation bubble near interface 1 possesses a higher maximum velocity.These indicate that increased viscosity inhibits the development of the jet.The cavitation bubbles that initiate in the water near Interface 1 consistently migrate away from the interface and do not split,while those near interface 2 would migrate towards the interface at intermediateγand would split atγ<0.91.In addition,the jet behaviours of cavitation bubbles near interface 2 at differentγare examined and classified into four types.展开更多
Despite the great leap forward perovskite solar cells(PSCs)have achieved in power conversion efficiency,the device instability remains one of the major problems plaguing its commercialization.Dopant-free hole transpor...Despite the great leap forward perovskite solar cells(PSCs)have achieved in power conversion efficiency,the device instability remains one of the major problems plaguing its commercialization.Dopant-free hole transport material(HTM)has been widely studied as an important strategy to improve the stability of PSCs due to its avoidance of moisture-sensitive dopants and cumbersome doping process.In this work,a series of dopant-free HTMs L1F,L2F and L3F based on D-A-π-A-D configuration were synthesized through two steps of reaction.L3F presents a high glass transition temperature of 1800C and thermal decomposition temperature of 4480C.Notably,electron paramagnetic resonance signals of L1F,L2F and L3F powders indicate the open-shell quinoidal diradical resonance structure in their aggregation state due to aggregation-induced radical effect.All these HTMs present higher hole mobility than dopant-free Spiro-OMeTAD,and the dopant-free L3F-based PSC device achieves the highest power conversion efficiency of 17.6%among them.In addition,due to the high hydrophobic properties of L1F,L2F and L3F,the perovskite films spin-coated with these HTMs exhibit higher humidity stability than doped SpiroOMeTAD.These results demonstrate a promising design strategy for high glass transition temperature dopant-free hole transport material.The open-shell quinoid-radical organic semiconductors are not rational candidates for dopant-free HTMs for PSC devices.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.51806051).
文摘The influence of liquid viscoelasticity on the interaction between cavitation bubbles and free surfaces is of great practical significance in understanding bubble dynamics in biological systems. A series of millimeter cavitation bubbles were induced by laser near the free surfaces of the water and viscoelastic polyacrylamide (PAM) solutions with different concentrations. The effects of liquid viscoelasticity on the interactions of cavitation bubbles with free surfaces are analyzed from the perspectives of the evolution of free surface and bubble dynamics. The experimental results show that as the dimensionless standoff distance increases, the evolutions of free surface behaviors in all experimental fluids can be divided into six types of water mounds, i.e., breaking wrinkles, spraying water film, crown, swallowed water spike, hillock, and slight bulge. All the critical values of the dimensionless distance dividing different types decrease with increasing concentration. The evolutions of first four types of water mounds in PAM solutions differ from those in the water. Water droplets splashing in different directions are produced around the breaking wrinkles in the water. Meanwhile, the breaking wrinkles in PAM solution move with the “liquid filaments” towards the central axis. The water spike in the pattern of spraying water film in PAM solution is more stable than that in the water. As the solution concentration increases, the water skirt in the pattern of crown contracts earlier and faster, and the rate of increase in the height of the water skirt decreases. For swallowed water spike in PAM solution, the upper part of the newly formed water spike is not significantly thicker than the middle part, and thus the water waist structure does not form. Liquid viscoelasticity inhibits the bubble growth and collapse, and the bubble migration as well, especially in the second period. Shorter and thicker cavities are formed in PAM solutions with higher concentration, while slender and stable cavities formed in the water at the same dimensionless distance. The velocity and displacement of the tip of bullet jet both decrease as the solution concentration increases.
基金Project supported by the National Natural Science Foundation of China(Grant No.51806051)supported by the Natural Science Foundation of Heilongjiang Province of China(Grant No.LH2022E062).
文摘This study investigates the interactions between cavitation bubbles and the interfaces of two immiscible liquids,with practical implications and potential applications in the fields such as ultrasonic emulsification and wastewater treatment.To explore the influence of liquid viscosity on the interaction between the cavitation bubble and flat liquid-liquid interface,visualization experiments were performed on the laser-induced cavitation bubbles near two liquid-liquid interfaces composed of deionized water and two silicone oils with different viscosities(50 mPa·s,500 mPa·s)by using high-speed photography.Three different positions were employed for the generation of cavitation bubbles,i.e.,at the interface,in the water,and in the silicone oil.The evolutions of cavitation bubbles and the corresponding interface deformations at different dimensionless standoff distancesγbetween the cavitation bubble and the interface were observed.The results show that the difference in the viscosity of silicone oil significantly affects the physical phenomena occurred during the interaction between the millimeter-scale cavitation bubble and the interface.On this basis,the qualitative and quantitative analyses for the cavitation bubble jet dynamics indicate that the critical value ofγfor jet penetration through the interface between the water and the higher-viscosity silicone oil(interface 2,γ=0.33)is lower than that for the interface between the water and the lower-viscosity silicone oil(interface 1,γ=0.69).Besides,the jet generated by the cavitation bubble near interface 1 possesses a higher maximum velocity.These indicate that increased viscosity inhibits the development of the jet.The cavitation bubbles that initiate in the water near Interface 1 consistently migrate away from the interface and do not split,while those near interface 2 would migrate towards the interface at intermediateγand would split atγ<0.91.In addition,the jet behaviours of cavitation bubbles near interface 2 at differentγare examined and classified into four types.
基金financially supported by the Natural Science Foundation of China(Nos.51973063 and 22375065)。
文摘Despite the great leap forward perovskite solar cells(PSCs)have achieved in power conversion efficiency,the device instability remains one of the major problems plaguing its commercialization.Dopant-free hole transport material(HTM)has been widely studied as an important strategy to improve the stability of PSCs due to its avoidance of moisture-sensitive dopants and cumbersome doping process.In this work,a series of dopant-free HTMs L1F,L2F and L3F based on D-A-π-A-D configuration were synthesized through two steps of reaction.L3F presents a high glass transition temperature of 1800C and thermal decomposition temperature of 4480C.Notably,electron paramagnetic resonance signals of L1F,L2F and L3F powders indicate the open-shell quinoidal diradical resonance structure in their aggregation state due to aggregation-induced radical effect.All these HTMs present higher hole mobility than dopant-free Spiro-OMeTAD,and the dopant-free L3F-based PSC device achieves the highest power conversion efficiency of 17.6%among them.In addition,due to the high hydrophobic properties of L1F,L2F and L3F,the perovskite films spin-coated with these HTMs exhibit higher humidity stability than doped SpiroOMeTAD.These results demonstrate a promising design strategy for high glass transition temperature dopant-free hole transport material.The open-shell quinoid-radical organic semiconductors are not rational candidates for dopant-free HTMs for PSC devices.
