Waterborne ultrafine particles of epoxy resin were prepared by phase inversion technique. The results of SEM revealed that the particles diameter was in the range of 50 to 100 nm and the effects on amount of water req...Waterborne ultrafine particles of epoxy resin were prepared by phase inversion technique. The results of SEM revealed that the particles diameter was in the range of 50 to 100 nm and the effects on amount of water required at phase inversion point were also discussed.展开更多
Silane coupling agent KH560 was used to modify the surface of nano-α-Al<sub>2</sub>O<sub>3</sub> in ethanol-aqueous solution with different proportions. The particle size of nano-α-Al<sub&...Silane coupling agent KH560 was used to modify the surface of nano-α-Al<sub>2</sub>O<sub>3</sub> in ethanol-aqueous solution with different proportions. The particle size of nano-α-Al<sub>2</sub>O<sub>3</sub> was determined by nano-particle size analyzer, and the effects of nano-α-Al<sub>2</sub>O<sub>3</sub> content, ethanol-aqueous solution ratio and KH560 dosage on the dispersion and particle size of nano-α-Al<sub>2</sub>O<sub>3</sub> were investigated. The material structure before and after modification was determined by Fourier transform infrared spectroscopy (FTIR). Aqueous polyurethane resin and inorganic components are combined with modified nano-α-Al<sub>2</sub>O<sub>3</sub> dispersion to form chromium-free passivation solution. The solution is coated on the galvanized sheet, the adhesion and surface hardness are tested, the bonding strength of the coating and the surface hardness of the substrate are discussed. The corrosion resistance and surface morphology of the matrix were investigated by electrochemical test, neutral salt spray test and scanning electron microscope test. The chromium-free passivation film formed after the modification of nano-α-Al<sub>2</sub>O<sub>3</sub> increases the surface hardness of galvanized sheet by about 85%. The corrosion resistance of the film is better than that of a single polyurethane film. The results show that the surface hardness and corrosion resistance of polyurethane resin composite passivation film are significantly improved by the introduction of nano-α-Al<sub>2</sub>O<sub>3</sub>.展开更多
Aim To obtain a kind of electrorheological (ER) flind with high comprehensive properties in order to satisfy the needs of engineering application. Methods A new type of dispersed phase── composite ultrafine particle...Aim To obtain a kind of electrorheological (ER) flind with high comprehensive properties in order to satisfy the needs of engineering application. Methods A new type of dispersed phase── composite ultrafine particles (UFP) was obtained by the method of microemulsion, which was used to mix with silicon oil. aam electroinduced stress and apparent viscosity of the ER fluids with three different volume fractions were tested under the conditions of different temperatures, electric fields and shear rates. Results A series of systematic tests show that the new type of ER fluids with volume fraction of 30% possesses obvious ER effect. Conclusion The double layers polarization plays an important role in ER effect.展开更多
Ultrafine particles prepared by evaporating pure Fe in CH4 atmosphere using arc-dischargeheating method, were found to consist of Fe-C solid solution, γ-Fe and Fe3C phases. EfFect of annealing temperature on phase tr...Ultrafine particles prepared by evaporating pure Fe in CH4 atmosphere using arc-dischargeheating method, were found to consist of Fe-C solid solution, γ-Fe and Fe3C phases. EfFect of annealing temperature on phase transformation and hyperfine interactions has been investigated by Mossbauer spectroscopy, X-ray diffraction (XRD), differential thermal analysis and thermogravimetry (DTA-TG), transmission electron microscopy (TEM), oxygen determination and vibrating sample magnetometer (VSM) measurements. It was observed that phase transformation of γ-Fe to α-Fe occurs during annealing in vacuum. The mechanism causing the change of hyperfine interactions with annealing temperature differs for Fe-C solution and interstitial compounds. DifFerence of hyperfine interactions of Fe-C solid solution in the starting sample and its annealed samples is ascribed to the improvement of activation of interstitial carbon atoms. Stress-relieving in structure of annealed Fe3C particle can result in a weak influence on hyperfine interactions. Parameters fitted to the Mossbauer spectra show the existence of superparamagnetism in all the samples. Absorbed and combined oxygen on particle surface of the starting sample were determined.展开更多
The composition distribution in Fe50Pd50 alloy ultrafine particles prepared by inert gas condensation method was investigated in details by means of X-ray diffraction technique through deconvolution of the X-ray diffr...The composition distribution in Fe50Pd50 alloy ultrafine particles prepared by inert gas condensation method was investigated in details by means of X-ray diffraction technique through deconvolution of the X-ray diffraction data. The microscopic composition distribution in the alloy UFP was identified, which is caused by nonuniformity of the melt, fractional distillation during the evaporation process and statistical fluctuation during nucleation and coalescence of the alloy particles. The composition distribution affects the properties of the alloy UFP展开更多
Ce0.6Zr0.4O2 solid solution ultrafine particle was prepared in the cyclohexane/water/OP-10/n-hexanol reversed microemulsion. The quasi-ternary phase diagram investigations showed that the system has narrow W/O type mi...Ce0.6Zr0.4O2 solid solution ultrafine particle was prepared in the cyclohexane/water/OP-10/n-hexanol reversed microemulsion. The quasi-ternary phase diagram investigations showed that the system has narrow W/O type microemulison region, so it is the proper system to prepare Ce0.6Zr0.4O2 solid solution ultrafine particle. Some physical-chemical techniques such as TG/DTA, XRD, BET, and HRTEM are used to characterize the resultant powders. The results show that the fluorite cubic Ce0.6Zr0.4O2 solid solution is obtained at 400 ℃. The surface area is （146.7 m^2·g^-1）, which is higher than the surface area for sol-gel prepared sample （59.5m^2·g^-1）. HRTEM images indicated that the Ce0.6Zr0.4O2 solid solution ultrafine particle is well-crystallized, narrow size distribution, less agglomeration, within mean size of 5 -7 nm.展开更多
Air pollution by particulate matter(PM)is one of the main threats to human health,particularly in large cities where pollution levels are continually exceeded.According to their source of emission,geography,and local ...Air pollution by particulate matter(PM)is one of the main threats to human health,particularly in large cities where pollution levels are continually exceeded.According to their source of emission,geography,and local meteorology,the pollutant particles vary in size and composition.These particles are conditioned to the aerodynamic diameter and thus classified as coarse(2.5–10μm),fine(0.1–2.5μm),and ultrafine(<0.1μm),where the degree of toxicity becomes greater for smaller particles.These particles can get into the lungs and translocate into vital organs due to their size,causing significant human health consequences.Besides,PM pollutants have been linked to respiratory conditions,genotoxic,mutagenic,and carcinogenic activity in human beings.This paper presents an overview of emission sources,physicochemical characteristics,collection and measurement methodologies,toxicity,and existing control mechanisms for ultrafine particles(UFPs)in the last fifteen years.展开更多
Lanthanummodified lead titanate(PLT14) ultrafine particles were synthesized by means of stearic acid gel method. The structure of the samples was characterized using Xray diffraction(XRD) and TEM. The crystal graphic ...Lanthanummodified lead titanate(PLT14) ultrafine particles were synthesized by means of stearic acid gel method. The structure of the samples was characterized using Xray diffraction(XRD) and TEM. The crystal graphic parameters of the samples were calculated. The Raman spectra of PLT14 powders at a high pressure as well as a high temperature reveal that the phase transition pressure or temperature shifts to a lower pressure or temperature with the decrease of grain size.展开更多
Fluidized chemical vapor deposition (FCVD) technology was developed for coating SnO 2 thin film on ultrafine Al 2O 3 particles.Transmission electron microscopy (TEM) and high resolution electron microscopy (HREM) ...Fluidized chemical vapor deposition (FCVD) technology was developed for coating SnO 2 thin film on ultrafine Al 2O 3 particles.Transmission electron microscopy (TEM) and high resolution electron microscopy (HREM) analyses demonstrated that SnO 2 films with different structures were deposited through controlling the coating temperature, reactant concentration, etc .. Nanocrystalline SnO 2 film was formed at 572.15K by gas phase reaction of SnCl 4 and H 2O.Electron probe microanalyser (EPMA) and energy dispersive spectrometer (EDS) analyses indicated that the distribution of nanocrystalline SnO 2 over inner and outer part of the Al 2O 3 agglomerates was homogeneous.展开更多
The idea of free energy has been used in the discussion of physical conditions for nucleaton of clusters and or ultrafine particles on substrates.The physical picture of ultrafine particle growth are explained.,Condit...The idea of free energy has been used in the discussion of physical conditions for nucleaton of clusters and or ultrafine particles on substrates.The physical picture of ultrafine particle growth are explained.,Conditions of epitaxial growth are also discussed.展开更多
Fe 100- x Ni x alloys of ultrafine particle with the average grain size of about 10 nm were synthesized by mechanically alloying process. The samples were investigated by X ray diffraction and measure...Fe 100- x Ni x alloys of ultrafine particle with the average grain size of about 10 nm were synthesized by mechanically alloying process. The samples were investigated by X ray diffraction and measurements of the saturation magnetization and coercivity force. Both b.c.c and f.c.c phase exist within a wide range for Fe 100- x Ni x , while x ≤45. The effective magnetic anisotropy K e was measured by applying the law of approach to saturation. The value of K e decreases with an increase of Ni content. It is noticed that the strain anisotropy makes a large contribution to the magnetic anisotropy. The estimation of grain size leads to the determination of the single domain critical size and domain wall energy. The exchange stiffness and exchange integral deduced from the relationship between the effective magnetic anisotropy and domain wall energy are in agreement with that calculated by other methods.展开更多
Laser Doppler Anemometer has been used to measure the flow field characteristics near the interface around a moving bubble in the presence of ultrafine particles. In order to model a moving bubble, the bubble was fixe...Laser Doppler Anemometer has been used to measure the flow field characteristics near the interface around a moving bubble in the presence of ultrafine particles. In order to model a moving bubble, the bubble was fixed into the counter flow liquid by a metal mesh. Experimental materials are air and water, and the particles are complex oxidate powder. Experiments were carried out under the operating conditions: the liquid flow velocity u 0 is 12.6 cm/s, the equivalent diameter d e is 0.6 cm, the mass concentration of particle is 0.2 0 0 ,the average particle diameter is about 10 nm and the density is 2 g/cm 3. The velocity profiles of both frontal and tail vortex areas were measured respectively. The experimental results show that the velocity fields are obviously changed in the existence of particles. In the frontal area of the bubble, both tangential and normal velocities decrease due to the presence of particles, but in tail vortex area, the tangential velocities increase remarkably, and normal velocities rise gradually from the center towards the fringe in the opposite tendency to that of no particles. The influences of flow field change in the presence of particles on gas liquid mass transfer are analyzed and discussed.展开更多
The deposition of ultrafine particles, in the human respiratory tract, from four highly impacted megacities across the globe, was evaluated by using a pulmonary deposition model. It was found that, for the locations s...The deposition of ultrafine particles, in the human respiratory tract, from four highly impacted megacities across the globe, was evaluated by using a pulmonary deposition model. It was found that, for the locations studied, an average of 62% of atmospheric particles was retained in the respiratory system. As expected, the model shows that smaller particles penetrate deeper in the airways. In addition, it’s shown that children are more susceptible than adults, retaining 8% more ultrafine particles.展开更多
Particulate pollution is a global risk factor that seriously threatens human health.Fine particles(FPs)and ultrafine particles(UFPs)have small particle diameters and large specific surface areas,which can easily adsor...Particulate pollution is a global risk factor that seriously threatens human health.Fine particles(FPs)and ultrafine particles(UFPs)have small particle diameters and large specific surface areas,which can easily adsorb metals,microorganisms and other pollutants.FPs and UFPs can enter the human body in multiple ways and can be easily and quickly absorbed by the cells,tissues and organs.In the body,the particles can induce oxidative stress,inflammatory response and apoptosis,furthermore causing great adverse effects.Epidemiological studies mainly take the population as the research object to study the distribution of diseases and health conditions in a specific population and to focus on the identification of influencing factors.However,the mechanism by which a substance harms the health of organisms is mainly demonstrated through toxicological studies.Combining epidemiological studies with toxicological studies will provide a more systematic and comprehensive understanding of the impact of PM on the health of organisms.In this review,the sources,compositions,and morphologies of FPs and UFPs are briefly introduced in the first part.The effects and action mechanisms of exposure to FPs and UFPs on the heart,lungs,brain,liver,spleen,kidneys,pancreas,gastrointestinal tract,joints and reproductive system are systematically summarized.In addition,challenges are further pointed out at the end of the paper.This work provides useful theoretical guidance and a strong experimental foundation for investigating and preventing the adverse effects of FPs and UFPs on human health.展开更多
Waterborne nanoscale carbon black dispersion （NCBD） was widely used in inkjet printing, spun.dyeing fibers and coloration fabrics. In this paper, NCBD was prepared using sodium carboxymethyl cellulose （CMC） as dis...Waterborne nanoscale carbon black dispersion （NCBD） was widely used in inkjet printing, spun.dyeing fibers and coloration fabrics. In this paper, NCBD was prepared using sodium carboxymethyl cellulose （CMC） as dispersant. Effects of CMC viscosity, ultrasonic time and oxidation with hydrogen peroxide on carbon black （CB） particle size were discussed. The results showed that CB particle size decreased by mechanical agitation while it Increased by ultrasonic with the increase of CMC viscosity. Uitrasonk is a more effective method to disperse CB particles than that of mechanical agitation. CB particle size lbviously decreased with itcreasing ultrasonic time and arrived at about 160 nm for 60min.In addition,oxidation with 2 mol/L of H2O2 and 0.2wt% of CMC300 reduced CB particle size to 160nm at 90℃ for 2.5h.展开更多
Ambient particles severely threaten human health worldwide.Compared to larger particles,ultrafine particles(UFPs)are highly concentrated in ambient environments,have a larger specific surface area,and are retained for...Ambient particles severely threaten human health worldwide.Compared to larger particles,ultrafine particles(UFPs)are highly concentrated in ambient environments,have a larger specific surface area,and are retained for a longer time in the lung.Recent studies have found that they can be transported into various extra-pulmonary organs by crossing the air-blood barrier(ABB).Therefore,to understand the adverse effects of UFPs,it is crucial to thoroughly investigate their bio-distribution and clearance pathways in vivo after inhalation,as well as their toxicological mechanisms.This review highlights emerging evidence on the bio-distribution of UFPs in pulmonary and extra-pulmonary organs.It explores how UFPs penetrate the ABB,the blood-brain barrier(BBB),and the placental barrier(PB)and subsequently undergo clearance by the liver,kidney,or intestine.In addition,the potential underlying toxicological mechanisms of UFPs are summarized,providing fundamental insights into how UFPs induce adverse health effects.展开更多
Automotive brake rotors are commonly made from gray cast iron(GCI).During usage,brake rotors are gradually worn off and periodically replaced.Currently,replaced brake rotors are mostly remelted to produce brand-new ca...Automotive brake rotors are commonly made from gray cast iron(GCI).During usage,brake rotors are gradually worn off and periodically replaced.Currently,replaced brake rotors are mostly remelted to produce brand-new cast iron products,resulting in a relatively high energy consumption and carbon footprint into the environment.In addition,automotive brakes emit airborne particles.Some of the emitted particles are categorized as ultrafine,which are sized below 100 nm,leading to a series of health and environmental impacts.In this study,two surface treatment techniques are applied,ie.,high-velocity oxygen fuel(HVOF)and laser cladding(LC),to overlay wear-resistant coatings on conventional GCI brake rotors in order to refurbish the replaced GCI brake rotor and to avoid the remelting procedure.The two coating materials are evaluated in terms of their coefficient of friction(CoF),wear,and ultrafine particle emissions,by comparing them with a typical GCI brake rotor.The results show that the CoF of the HVOF disc is higher than those of the GCI and LC discs.Meanwhile,HVOF disc has the lowest wear rate but results in the highest wear rate on the mating brake pad material.The LC disc yields a similar wear rate as the GCI disc.The ultrafine particles from the GCI and LC discs appeared primarily in round,chunky,and flake shapes.The HVOF disc emits unique needle-shaped particles.In the ultrafine particle range,the GCI and HVOF discs generate particles that are primarily below 100 nm in the running-in period and 200 nm in the steady state.Meanwhile,the LC disc emitted particles that are primarily~200 nm in the entire test run.展开更多
Fine and ultrafine particles possess great potential for industrial applications ascribed from their huge specific surface area and ability to provide good gas–solid contact.However,these powders are inherently cohes...Fine and ultrafine particles possess great potential for industrial applications ascribed from their huge specific surface area and ability to provide good gas–solid contact.However,these powders are inherently cohesive,making it challenging to achieve smooth flow and fluidization.This challenge can be well-resolved by nanoparticle modulation(nano-modulation),where a small amount of nanoparticles is uniformly mixed with the cohesive fine/ultrafine powders.Through nano-modulation,the fluidization system of cohesive powders exhibits distinguishable minimum fluidization velocity,enlarged bed expansion ratio(particularly the dense phase expansion),and scarcer,smaller,and slower moving bubbles,indicating improved flow and fluidization quality.The purpose of the current work is to systematically summarize the state-of-the-art progress in the fluidization and utilization of fine and ultrafine particles via the nanoparticle modulation method.Accordingly,a broader audience can be enlightened regarding this promising fine/ultrafine particle fluidization technology,so as to provoke their attention and encourage interdisciplinary integration and industry-academia collaborative research.展开更多
基金This project is supported by the Scientific Fund of Polymer Physics Laboratory,Institute of Chemistry,Chinese Academy of Sciences.
文摘Waterborne ultrafine particles of epoxy resin were prepared by phase inversion technique. The results of SEM revealed that the particles diameter was in the range of 50 to 100 nm and the effects on amount of water required at phase inversion point were also discussed.
文摘Silane coupling agent KH560 was used to modify the surface of nano-α-Al<sub>2</sub>O<sub>3</sub> in ethanol-aqueous solution with different proportions. The particle size of nano-α-Al<sub>2</sub>O<sub>3</sub> was determined by nano-particle size analyzer, and the effects of nano-α-Al<sub>2</sub>O<sub>3</sub> content, ethanol-aqueous solution ratio and KH560 dosage on the dispersion and particle size of nano-α-Al<sub>2</sub>O<sub>3</sub> were investigated. The material structure before and after modification was determined by Fourier transform infrared spectroscopy (FTIR). Aqueous polyurethane resin and inorganic components are combined with modified nano-α-Al<sub>2</sub>O<sub>3</sub> dispersion to form chromium-free passivation solution. The solution is coated on the galvanized sheet, the adhesion and surface hardness are tested, the bonding strength of the coating and the surface hardness of the substrate are discussed. The corrosion resistance and surface morphology of the matrix were investigated by electrochemical test, neutral salt spray test and scanning electron microscope test. The chromium-free passivation film formed after the modification of nano-α-Al<sub>2</sub>O<sub>3</sub> increases the surface hardness of galvanized sheet by about 85%. The corrosion resistance of the film is better than that of a single polyurethane film. The results show that the surface hardness and corrosion resistance of polyurethane resin composite passivation film are significantly improved by the introduction of nano-α-Al<sub>2</sub>O<sub>3</sub>.
文摘Aim To obtain a kind of electrorheological (ER) flind with high comprehensive properties in order to satisfy the needs of engineering application. Methods A new type of dispersed phase── composite ultrafine particles (UFP) was obtained by the method of microemulsion, which was used to mix with silicon oil. aam electroinduced stress and apparent viscosity of the ER fluids with three different volume fractions were tested under the conditions of different temperatures, electric fields and shear rates. Results A series of systematic tests show that the new type of ER fluids with volume fraction of 30% possesses obvious ER effect. Conclusion The double layers polarization plays an important role in ER effect.
文摘Ultrafine particles prepared by evaporating pure Fe in CH4 atmosphere using arc-dischargeheating method, were found to consist of Fe-C solid solution, γ-Fe and Fe3C phases. EfFect of annealing temperature on phase transformation and hyperfine interactions has been investigated by Mossbauer spectroscopy, X-ray diffraction (XRD), differential thermal analysis and thermogravimetry (DTA-TG), transmission electron microscopy (TEM), oxygen determination and vibrating sample magnetometer (VSM) measurements. It was observed that phase transformation of γ-Fe to α-Fe occurs during annealing in vacuum. The mechanism causing the change of hyperfine interactions with annealing temperature differs for Fe-C solution and interstitial compounds. DifFerence of hyperfine interactions of Fe-C solid solution in the starting sample and its annealed samples is ascribed to the improvement of activation of interstitial carbon atoms. Stress-relieving in structure of annealed Fe3C particle can result in a weak influence on hyperfine interactions. Parameters fitted to the Mossbauer spectra show the existence of superparamagnetism in all the samples. Absorbed and combined oxygen on particle surface of the starting sample were determined.
文摘The composition distribution in Fe50Pd50 alloy ultrafine particles prepared by inert gas condensation method was investigated in details by means of X-ray diffraction technique through deconvolution of the X-ray diffraction data. The microscopic composition distribution in the alloy UFP was identified, which is caused by nonuniformity of the melt, fractional distillation during the evaporation process and statistical fluctuation during nucleation and coalescence of the alloy particles. The composition distribution affects the properties of the alloy UFP
文摘Ce0.6Zr0.4O2 solid solution ultrafine particle was prepared in the cyclohexane/water/OP-10/n-hexanol reversed microemulsion. The quasi-ternary phase diagram investigations showed that the system has narrow W/O type microemulison region, so it is the proper system to prepare Ce0.6Zr0.4O2 solid solution ultrafine particle. Some physical-chemical techniques such as TG/DTA, XRD, BET, and HRTEM are used to characterize the resultant powders. The results show that the fluorite cubic Ce0.6Zr0.4O2 solid solution is obtained at 400 ℃. The surface area is （146.7 m^2·g^-1）, which is higher than the surface area for sol-gel prepared sample （59.5m^2·g^-1）. HRTEM images indicated that the Ce0.6Zr0.4O2 solid solution ultrafine particle is well-crystallized, narrow size distribution, less agglomeration, within mean size of 5 -7 nm.
基金financial support from ColcienciasColombia(Project 141180764164,Contract 815-2018)。
文摘Air pollution by particulate matter(PM)is one of the main threats to human health,particularly in large cities where pollution levels are continually exceeded.According to their source of emission,geography,and local meteorology,the pollutant particles vary in size and composition.These particles are conditioned to the aerodynamic diameter and thus classified as coarse(2.5–10μm),fine(0.1–2.5μm),and ultrafine(<0.1μm),where the degree of toxicity becomes greater for smaller particles.These particles can get into the lungs and translocate into vital organs due to their size,causing significant human health consequences.Besides,PM pollutants have been linked to respiratory conditions,genotoxic,mutagenic,and carcinogenic activity in human beings.This paper presents an overview of emission sources,physicochemical characteristics,collection and measurement methodologies,toxicity,and existing control mechanisms for ultrafine particles(UFPs)in the last fifteen years.
文摘Lanthanummodified lead titanate(PLT14) ultrafine particles were synthesized by means of stearic acid gel method. The structure of the samples was characterized using Xray diffraction(XRD) and TEM. The crystal graphic parameters of the samples were calculated. The Raman spectra of PLT14 powders at a high pressure as well as a high temperature reveal that the phase transition pressure or temperature shifts to a lower pressure or temperature with the decrease of grain size.
文摘Fluidized chemical vapor deposition (FCVD) technology was developed for coating SnO 2 thin film on ultrafine Al 2O 3 particles.Transmission electron microscopy (TEM) and high resolution electron microscopy (HREM) analyses demonstrated that SnO 2 films with different structures were deposited through controlling the coating temperature, reactant concentration, etc .. Nanocrystalline SnO 2 film was formed at 572.15K by gas phase reaction of SnCl 4 and H 2O.Electron probe microanalyser (EPMA) and energy dispersive spectrometer (EDS) analyses indicated that the distribution of nanocrystalline SnO 2 over inner and outer part of the Al 2O 3 agglomerates was homogeneous.
文摘The idea of free energy has been used in the discussion of physical conditions for nucleaton of clusters and or ultrafine particles on substrates.The physical picture of ultrafine particle growth are explained.,Conditions of epitaxial growth are also discussed.
文摘Fe 100- x Ni x alloys of ultrafine particle with the average grain size of about 10 nm were synthesized by mechanically alloying process. The samples were investigated by X ray diffraction and measurements of the saturation magnetization and coercivity force. Both b.c.c and f.c.c phase exist within a wide range for Fe 100- x Ni x , while x ≤45. The effective magnetic anisotropy K e was measured by applying the law of approach to saturation. The value of K e decreases with an increase of Ni content. It is noticed that the strain anisotropy makes a large contribution to the magnetic anisotropy. The estimation of grain size leads to the determination of the single domain critical size and domain wall energy. The exchange stiffness and exchange integral deduced from the relationship between the effective magnetic anisotropy and domain wall energy are in agreement with that calculated by other methods.
文摘Laser Doppler Anemometer has been used to measure the flow field characteristics near the interface around a moving bubble in the presence of ultrafine particles. In order to model a moving bubble, the bubble was fixed into the counter flow liquid by a metal mesh. Experimental materials are air and water, and the particles are complex oxidate powder. Experiments were carried out under the operating conditions: the liquid flow velocity u 0 is 12.6 cm/s, the equivalent diameter d e is 0.6 cm, the mass concentration of particle is 0.2 0 0 ,the average particle diameter is about 10 nm and the density is 2 g/cm 3. The velocity profiles of both frontal and tail vortex areas were measured respectively. The experimental results show that the velocity fields are obviously changed in the existence of particles. In the frontal area of the bubble, both tangential and normal velocities decrease due to the presence of particles, but in tail vortex area, the tangential velocities increase remarkably, and normal velocities rise gradually from the center towards the fringe in the opposite tendency to that of no particles. The influences of flow field change in the presence of particles on gas liquid mass transfer are analyzed and discussed.
基金This work received funding support from CNPq(National Counsel of Technological and Scientific Development,process 404104/2013-4)CAPES(Coordination for the Improvement of Higher Education Personnel)and Araucária Foundation.
文摘The deposition of ultrafine particles, in the human respiratory tract, from four highly impacted megacities across the globe, was evaluated by using a pulmonary deposition model. It was found that, for the locations studied, an average of 62% of atmospheric particles was retained in the respiratory system. As expected, the model shows that smaller particles penetrate deeper in the airways. In addition, it’s shown that children are more susceptible than adults, retaining 8% more ultrafine particles.
基金financial support received from the National Natural Science Foundation of China (No.82173486)the Natural Sciences Foundation of Tianjin City of China (No.12JCYBJC19100)+1 种基金the Scientific Research Program of Tianjin Education Commission (No.2019KJ167)The Program of Tianjin Key Laboratory of Oral and Maxillofacial Function Reconstruction (No.2021KLMS10)。
文摘Particulate pollution is a global risk factor that seriously threatens human health.Fine particles(FPs)and ultrafine particles(UFPs)have small particle diameters and large specific surface areas,which can easily adsorb metals,microorganisms and other pollutants.FPs and UFPs can enter the human body in multiple ways and can be easily and quickly absorbed by the cells,tissues and organs.In the body,the particles can induce oxidative stress,inflammatory response and apoptosis,furthermore causing great adverse effects.Epidemiological studies mainly take the population as the research object to study the distribution of diseases and health conditions in a specific population and to focus on the identification of influencing factors.However,the mechanism by which a substance harms the health of organisms is mainly demonstrated through toxicological studies.Combining epidemiological studies with toxicological studies will provide a more systematic and comprehensive understanding of the impact of PM on the health of organisms.In this review,the sources,compositions,and morphologies of FPs and UFPs are briefly introduced in the first part.The effects and action mechanisms of exposure to FPs and UFPs on the heart,lungs,brain,liver,spleen,kidneys,pancreas,gastrointestinal tract,joints and reproductive system are systematically summarized.In addition,challenges are further pointed out at the end of the paper.This work provides useful theoretical guidance and a strong experimental foundation for investigating and preventing the adverse effects of FPs and UFPs on human health.
基金Supported by National Natural Science Foundation of China( No.50173012) and863Hi-tech Research and Development Program ofChina (2002AA327120)
文摘Waterborne nanoscale carbon black dispersion （NCBD） was widely used in inkjet printing, spun.dyeing fibers and coloration fabrics. In this paper, NCBD was prepared using sodium carboxymethyl cellulose （CMC） as dispersant. Effects of CMC viscosity, ultrasonic time and oxidation with hydrogen peroxide on carbon black （CB） particle size were discussed. The results showed that CB particle size decreased by mechanical agitation while it Increased by ultrasonic with the increase of CMC viscosity. Uitrasonk is a more effective method to disperse CB particles than that of mechanical agitation. CB particle size lbviously decreased with itcreasing ultrasonic time and arrived at about 160 nm for 60min.In addition,oxidation with 2 mol/L of H2O2 and 0.2wt% of CMC300 reduced CB particle size to 160nm at 90℃ for 2.5h.
基金funded by the National Key Research and Development Program of China(2019YFC1804503 to YX)the National Natural Science Foundation of China(82003414 to YX).
文摘Ambient particles severely threaten human health worldwide.Compared to larger particles,ultrafine particles(UFPs)are highly concentrated in ambient environments,have a larger specific surface area,and are retained for a longer time in the lung.Recent studies have found that they can be transported into various extra-pulmonary organs by crossing the air-blood barrier(ABB).Therefore,to understand the adverse effects of UFPs,it is crucial to thoroughly investigate their bio-distribution and clearance pathways in vivo after inhalation,as well as their toxicological mechanisms.This review highlights emerging evidence on the bio-distribution of UFPs in pulmonary and extra-pulmonary organs.It explores how UFPs penetrate the ABB,the blood-brain barrier(BBB),and the placental barrier(PB)and subsequently undergo clearance by the liver,kidney,or intestine.In addition,the potential underlying toxicological mechanisms of UFPs are summarized,providing fundamental insights into how UFPs induce adverse health effects.
基金The authors are grateful for the financial support from FORMAS:Swedish Research Council for Sustainable Development(No.2020-02302)(Nescup project)The research also received funding from European Union's Horizon 2020 research and innovation programme(No.954377)(nPETS project).
文摘Automotive brake rotors are commonly made from gray cast iron(GCI).During usage,brake rotors are gradually worn off and periodically replaced.Currently,replaced brake rotors are mostly remelted to produce brand-new cast iron products,resulting in a relatively high energy consumption and carbon footprint into the environment.In addition,automotive brakes emit airborne particles.Some of the emitted particles are categorized as ultrafine,which are sized below 100 nm,leading to a series of health and environmental impacts.In this study,two surface treatment techniques are applied,ie.,high-velocity oxygen fuel(HVOF)and laser cladding(LC),to overlay wear-resistant coatings on conventional GCI brake rotors in order to refurbish the replaced GCI brake rotor and to avoid the remelting procedure.The two coating materials are evaluated in terms of their coefficient of friction(CoF),wear,and ultrafine particle emissions,by comparing them with a typical GCI brake rotor.The results show that the CoF of the HVOF disc is higher than those of the GCI and LC discs.Meanwhile,HVOF disc has the lowest wear rate but results in the highest wear rate on the mating brake pad material.The LC disc yields a similar wear rate as the GCI disc.The ultrafine particles from the GCI and LC discs appeared primarily in round,chunky,and flake shapes.The HVOF disc emits unique needle-shaped particles.In the ultrafine particle range,the GCI and HVOF discs generate particles that are primarily below 100 nm in the running-in period and 200 nm in the steady state.Meanwhile,the LC disc emitted particles that are primarily~200 nm in the entire test run.
文摘Fine and ultrafine particles possess great potential for industrial applications ascribed from their huge specific surface area and ability to provide good gas–solid contact.However,these powders are inherently cohesive,making it challenging to achieve smooth flow and fluidization.This challenge can be well-resolved by nanoparticle modulation(nano-modulation),where a small amount of nanoparticles is uniformly mixed with the cohesive fine/ultrafine powders.Through nano-modulation,the fluidization system of cohesive powders exhibits distinguishable minimum fluidization velocity,enlarged bed expansion ratio(particularly the dense phase expansion),and scarcer,smaller,and slower moving bubbles,indicating improved flow and fluidization quality.The purpose of the current work is to systematically summarize the state-of-the-art progress in the fluidization and utilization of fine and ultrafine particles via the nanoparticle modulation method.Accordingly,a broader audience can be enlightened regarding this promising fine/ultrafine particle fluidization technology,so as to provoke their attention and encourage interdisciplinary integration and industry-academia collaborative research.
