大气气溶胶因其对气候和公众健康的影响而成为当今环境研究领域的中心课题.单颗粒分析是目前国际上大气气溶胶研究的一个前沿领域,该方法具有高的时间和空间分辨率,能够提供全颗粒物分析所无法提供的大量信息.利用自主研制的单颗粒气溶...大气气溶胶因其对气候和公众健康的影响而成为当今环境研究领域的中心课题.单颗粒分析是目前国际上大气气溶胶研究的一个前沿领域,该方法具有高的时间和空间分辨率,能够提供全颗粒物分析所无法提供的大量信息.利用自主研制的单颗粒气溶胶质谱仪(single particle aerosol mass spectrometer,SPAMS),对广东鹤山地区气溶胶进行在线分析.重点分析含金属颗粒的相关性、数浓度和可能的来源,并简单介绍该仪器的产业化情况.展开更多
Aluminum alloy samples, 6061-T6 and 2219-T42, were exposed to Caribbean seawater for 90 d. The fluctuations of open circuit potential, considered as electrochemical noise (EN), were used to characterize and compare in...Aluminum alloy samples, 6061-T6 and 2219-T42, were exposed to Caribbean seawater for 90 d. The fluctuations of open circuit potential, considered as electrochemical noise (EN), were used to characterize and compare initial pitting events, which appeared on their surfaces. EN analysis was carried out using the power spectral density (PSD) vs frequency. The decrease of the β exponent in PSD graphs indicated a release of spontaneous energy with the progress of pit formation in seawater. The fluctuations were associated with the breakdown and formation of new corrosion layers. The values of β exponent in PSD graphs suggest that corrosion process of AA2219-T42 alloy occurs as a persistent non-stationary process, the dynamics of which is controlled by fractional Brownian motion (fBm), while on AA6061-T6 alloy the corrosion process was dominated by stationary and weakly persistent features, with the contribution of fractional Gaussian noise (fGn). After the exposure in seawater, SEM-EDX analysis revealed insoluble intermetallic particles on the alloys, rich in Cu or Fe and irregularly distributed. The preferential dissolution of Mg and Al occurs from the S-phase (Al2CuMg) of AA2219-T42 alloy.展开更多
Butt friction stir welding between pure copper and AA5754 alloy was carried out.Reinforcing SiC nanoparticles were utilized in friction stir welded(FSW)joints to decline the harmful effects of intermetallic compounds....Butt friction stir welding between pure copper and AA5754 alloy was carried out.Reinforcing SiC nanoparticles were utilized in friction stir welded(FSW)joints to decline the harmful effects of intermetallic compounds.Tensile tests,micro-hardness experiments,scanning electron microscopy and X-ray diffraction analysis were applied to studying the properties of welded joints.The joints with a travel speed of 50 mm/min and a rotation speed of 1000 r/min showed the best results.The presence of nano-sized SiC particles reduced the grain size of aluminum and copper in the stir zone(SZ)from 38.3 and 12.4μm to 12.9 and 5.1μm,respectively.The tensile strength of the joint in the presence of reinforcing SiC nano-particles was~240 MPa,which is~90%of that for the aluminum base.Furthermore,the highest microhardness of the weld zone was significantly increased from HV 160 to HV 320 upon the addition of SiC nano-particles.The results also showed that raising the heat generation in FSW joints increased the amount of Al_(4)Cu_(9) and Al_(2)Cu intermetallic compounds.展开更多
Under various electromagnetic induction heating powers,different Al3Ti/Al composites were fabricated by in-situ synthesis method from aluminum and titanium fibers.Microstructures and particles distribution of the comp...Under various electromagnetic induction heating powers,different Al3Ti/Al composites were fabricated by in-situ synthesis method from aluminum and titanium fibers.Microstructures and particles distribution of the composites were examined by XRD,SEM and EDS.The results show that no other intermetallic compounds beside Al3Ti can be in-situ synthesized.Around the titanium fibers,the reaction zones and diffusion zones can be obviously found.Due to the stirring of the electromagnetic function,the formation of the micro-cracks inside the reaction zone was conducive to the peeling off of the Al3Ti particles,and ensures the continuous reaction between liquid aluminum and titanium fibers,as well as the diffusion of Al3Ti particles.At the same time,there were secondary splits of Al3Ti particles located in diffusion zones.Two-body abrasion test shows that with the increase of induction heating power,the wear rates of the composites reduced and the number of grooves decreased.展开更多
Single-phase Ag2Al intermetallic nanoparticles, and Ag and Al metallic nanoparticles were synthesized by the flow-levitation （FL） method. Measurements of d-spacings from X-ray diffraction and electron diffraction co...Single-phase Ag2Al intermetallic nanoparticles, and Ag and Al metallic nanoparticles were synthesized by the flow-levitation （FL） method. Measurements of d-spacings from X-ray diffraction and electron diffraction confirmed that the intermetallic nanoparticles had the hexagonal Ag2Al structure. The morphology, crystal structure and chemical composition of Ag2Al nanoparticles were investigated by transmission electron microscopy, X-ray diffraction and induction-coupled plasma spectroscopy. A thin amorphous coating was formed around the particles when exposed to air. Based on the XPS measurements, the surface coating of the Ag2Al nanoparticles could most likely be aluminum oxide or silver aluminum oxide. Therefore, the single-phase nanocrystalline Ag2Al intermetallic compound particles can be produced by adjusting some experimental parameters in FL method.展开更多
The nano particles have demonstrated great potential to improve the heat transfer characteristics of heat transfer fluids.Possible parameters responsible for this increase were studied. The heat transfer profile in th...The nano particles have demonstrated great potential to improve the heat transfer characteristics of heat transfer fluids.Possible parameters responsible for this increase were studied. The heat transfer profile in the nanolayer region was combined with other parameters such as volume fraction, particle radius thermal conductivity of the fluid, particle and nanolayer, to formulate a thermal conductivity model. Results predicting the thermal conductivity of nanofluids using the model were compared with experimental results as well as studies by other researchers. The comparison of the results obtained for the Cu O/water and Ti O2/water nanofluids studied shows that the correlation proposed is in closest proximity in predicting the experimental results for the thermal conductivity of a nanofluid. Also, a parametric study was performed to understand how a number of factors affect the thermal conductivity of nanofluids using the developed correlation.展开更多
The contribution of anthropogenic mineral aerosol dust has been of interest to understand the impact of dust aerosols on climate, and the health of workers occupational exposure. Several studies have been investigated...The contribution of anthropogenic mineral aerosol dust has been of interest to understand the impact of dust aerosols on climate, and the health of workers occupational exposure. Several studies have been investigated the physical and chemical properties mainly in particulate matter. However, the characterizations have not extended diameters below to 1.0 μm. In this study, it described chemical composition and shape measurements of individual aerosol particles with 50% cut-off diameters less than 1.1 μm emitted at ceramic-tile manufacturing. Four emission sites of process were selected, and their samples were collected using a cascade-impactor, investigated using X-ray diffraction, energy dispersive X-ray spectroscopy, and digital image processing, where the data were analysed applying a combination of principal component and cluster analysis. Particles of tectosilicate （quartz, zeolite）, phyllosilicate （illite, montmorillonite）, and inosilicate （calcium silicate） were founded in all sampling sites; also, silicates mixed with transition metals oxides used as pigments （e.g., Fe, Ti, Co, Ni, Zn and Mo）. Silicates were granulated and flat crystals with a transparent, translucent appearance; otherwise, the mixture had flake shapes and opaque appearance. Analyses of multivariate data showed that the process stages emissions were related with specific composition and shape suggesting the use three measurements related （1） the internal axis, （2） roundness and （3） roughness to isolate particles shapes, and the presence of transition metals oxides as emissions tracer of the ceramic industry.展开更多
In this paper, we proposed a five-zone model to predict the elastic modulus of particulate reinforced metal matrix composite. We simplified the calculation by ignoring structural parameters including particulate shape...In this paper, we proposed a five-zone model to predict the elastic modulus of particulate reinforced metal matrix composite. We simplified the calculation by ignoring structural parameters including particulate shape, arrangement pattern and dimensional variance mode which have no obvious influence on the elastic modulus of a composite, and improved the precision of the method by stressing the interaction of interfaces with pariculates and maxtrix of the composite. The five- zone model can reflect effects of interface modulus on elastic modulus of composite. It overcomes limitations of expressions of rigidity mixed law and flexibility mixed law. The original idea of five zone model is to put forward the particulate/interface interactive zone and matrix/interface interactive zone. By organically integrating the rigidity mixed law and flexibility mixed law, the model can predict the engineering elastic constant of a composite effectively.展开更多
In a lab of the CAS Institute of Process Engineering（IPE）in Beijing,Winifred Uduak Anake,a visiting woman scientist from Covenant University.Nigeria was dashing to finish testing the 100 plus samples she collected f...In a lab of the CAS Institute of Process Engineering（IPE）in Beijing,Winifred Uduak Anake,a visiting woman scientist from Covenant University.Nigeria was dashing to finish testing the 100 plus samples she collected from her home country.＂1 am trying to find out the type and amount of hazardous trace metals bound to the tiny particles trapped on the filters,＂she explained：＂out of worries about their possible threat to human health.＂Before concluding her three-month stay she needed to complete examining the morphology of the particles,total trace metals,展开更多
This study aimed to determine the amount of total polluting matter emitted into the atmosphere from heating and industrial-based emissions and the total pollution bulk of Tokat city center. The annual cycles of some h...This study aimed to determine the amount of total polluting matter emitted into the atmosphere from heating and industrial-based emissions and the total pollution bulk of Tokat city center. The annual cycles of some heavy metal in particulate matters have been investigated at this area in order to elucidate temporal variations as well as major sources processes responsible for their formation. Air particulate samples were collected from three different locations situated around Tokat. These samples were determined for heavy metals by using Flame or graphite-furnace Atomic absorption spectroscopy. Particulate matter concentrations up to 52.43μg/m^3 were observed in sampling area. The initial results of the chemical analysis showed that concentration values of heavy metals in air particles observed were higher than the World Health Organization （WHO） guideline limit values.展开更多
Nanomaterials have attracted considerable interest owing to their unique physicochemical properties.The wide application of nanomaterials has raised many concerns about their potential risks to human health and the en...Nanomaterials have attracted considerable interest owing to their unique physicochemical properties.The wide application of nanomaterials has raised many concerns about their potential risks to human health and the environment.Metal oxide nanopartides（MONPs）,one of the main members of nanomaterials,have been applied in various fields,such as food,medicine,cosmetics,and sensors.This review highlights the bio-toxic effects of widely applied MONPs and their underlying mechanisms.Two main underlying toxicity mechanisms,reactive oxygen species（ROS）-and non-ROS-mediated toxidties,of MONPs have been widely accepted.ROS activates oxidative stress,which leads to lipid peroxidation and cell membrane damage.In addition,ROS can trigger the apoptotic pathway by activating caspase-9 and-3.Non-ROS-mediated toxicity mechanism includes the effect of released ions,excessive accumulation of NPs on the cell surface,and combination of NPs with specific death receptors.Furthermore,the combined toxicity evaluation of some MONPs is also discussed.Toxicity may dramatically change when nanomaterials are used in a combined system because the characteristics of NPs that play a key role in their toxicity such as size,surface properties,and chemical nature in the complex system are different from the pristine NPs.展开更多
文摘大气气溶胶因其对气候和公众健康的影响而成为当今环境研究领域的中心课题.单颗粒分析是目前国际上大气气溶胶研究的一个前沿领域,该方法具有高的时间和空间分辨率,能够提供全颗粒物分析所无法提供的大量信息.利用自主研制的单颗粒气溶胶质谱仪(single particle aerosol mass spectrometer,SPAMS),对广东鹤山地区气溶胶进行在线分析.重点分析含金属颗粒的相关性、数浓度和可能的来源,并简单介绍该仪器的产业化情况.
基金the partial financial support of this study from CONACYT (Grant 179110)
文摘Aluminum alloy samples, 6061-T6 and 2219-T42, were exposed to Caribbean seawater for 90 d. The fluctuations of open circuit potential, considered as electrochemical noise (EN), were used to characterize and compare initial pitting events, which appeared on their surfaces. EN analysis was carried out using the power spectral density (PSD) vs frequency. The decrease of the β exponent in PSD graphs indicated a release of spontaneous energy with the progress of pit formation in seawater. The fluctuations were associated with the breakdown and formation of new corrosion layers. The values of β exponent in PSD graphs suggest that corrosion process of AA2219-T42 alloy occurs as a persistent non-stationary process, the dynamics of which is controlled by fractional Brownian motion (fBm), while on AA6061-T6 alloy the corrosion process was dominated by stationary and weakly persistent features, with the contribution of fractional Gaussian noise (fGn). After the exposure in seawater, SEM-EDX analysis revealed insoluble intermetallic particles on the alloys, rich in Cu or Fe and irregularly distributed. The preferential dissolution of Mg and Al occurs from the S-phase (Al2CuMg) of AA2219-T42 alloy.
文摘Butt friction stir welding between pure copper and AA5754 alloy was carried out.Reinforcing SiC nanoparticles were utilized in friction stir welded(FSW)joints to decline the harmful effects of intermetallic compounds.Tensile tests,micro-hardness experiments,scanning electron microscopy and X-ray diffraction analysis were applied to studying the properties of welded joints.The joints with a travel speed of 50 mm/min and a rotation speed of 1000 r/min showed the best results.The presence of nano-sized SiC particles reduced the grain size of aluminum and copper in the stir zone(SZ)from 38.3 and 12.4μm to 12.9 and 5.1μm,respectively.The tensile strength of the joint in the presence of reinforcing SiC nano-particles was~240 MPa,which is~90%of that for the aluminum base.Furthermore,the highest microhardness of the weld zone was significantly increased from HV 160 to HV 320 upon the addition of SiC nano-particles.The results also showed that raising the heat generation in FSW joints increased the amount of Al_(4)Cu_(9) and Al_(2)Cu intermetallic compounds.
基金Project(2015DFR50990-01)supported by International Cooperation Project of Ministry of Science and Technology of ChinaProjects(18JS060,18JS075)supported by the Shaanxi Key Laboratory of Nano-materials and Technology,China。
文摘Under various electromagnetic induction heating powers,different Al3Ti/Al composites were fabricated by in-situ synthesis method from aluminum and titanium fibers.Microstructures and particles distribution of the composites were examined by XRD,SEM and EDS.The results show that no other intermetallic compounds beside Al3Ti can be in-situ synthesized.Around the titanium fibers,the reaction zones and diffusion zones can be obviously found.Due to the stirring of the electromagnetic function,the formation of the micro-cracks inside the reaction zone was conducive to the peeling off of the Al3Ti particles,and ensures the continuous reaction between liquid aluminum and titanium fibers,as well as the diffusion of Al3Ti particles.At the same time,there were secondary splits of Al3Ti particles located in diffusion zones.Two-body abrasion test shows that with the increase of induction heating power,the wear rates of the composites reduced and the number of grooves decreased.
基金Project (10804101) supported by the National Natural Science Foundation of China
文摘Single-phase Ag2Al intermetallic nanoparticles, and Ag and Al metallic nanoparticles were synthesized by the flow-levitation （FL） method. Measurements of d-spacings from X-ray diffraction and electron diffraction confirmed that the intermetallic nanoparticles had the hexagonal Ag2Al structure. The morphology, crystal structure and chemical composition of Ag2Al nanoparticles were investigated by transmission electron microscopy, X-ray diffraction and induction-coupled plasma spectroscopy. A thin amorphous coating was formed around the particles when exposed to air. Based on the XPS measurements, the surface coating of the Ag2Al nanoparticles could most likely be aluminum oxide or silver aluminum oxide. Therefore, the single-phase nanocrystalline Ag2Al intermetallic compound particles can be produced by adjusting some experimental parameters in FL method.
文摘The nano particles have demonstrated great potential to improve the heat transfer characteristics of heat transfer fluids.Possible parameters responsible for this increase were studied. The heat transfer profile in the nanolayer region was combined with other parameters such as volume fraction, particle radius thermal conductivity of the fluid, particle and nanolayer, to formulate a thermal conductivity model. Results predicting the thermal conductivity of nanofluids using the model were compared with experimental results as well as studies by other researchers. The comparison of the results obtained for the Cu O/water and Ti O2/water nanofluids studied shows that the correlation proposed is in closest proximity in predicting the experimental results for the thermal conductivity of a nanofluid. Also, a parametric study was performed to understand how a number of factors affect the thermal conductivity of nanofluids using the developed correlation.
文摘The contribution of anthropogenic mineral aerosol dust has been of interest to understand the impact of dust aerosols on climate, and the health of workers occupational exposure. Several studies have been investigated the physical and chemical properties mainly in particulate matter. However, the characterizations have not extended diameters below to 1.0 μm. In this study, it described chemical composition and shape measurements of individual aerosol particles with 50% cut-off diameters less than 1.1 μm emitted at ceramic-tile manufacturing. Four emission sites of process were selected, and their samples were collected using a cascade-impactor, investigated using X-ray diffraction, energy dispersive X-ray spectroscopy, and digital image processing, where the data were analysed applying a combination of principal component and cluster analysis. Particles of tectosilicate （quartz, zeolite）, phyllosilicate （illite, montmorillonite）, and inosilicate （calcium silicate） were founded in all sampling sites; also, silicates mixed with transition metals oxides used as pigments （e.g., Fe, Ti, Co, Ni, Zn and Mo）. Silicates were granulated and flat crystals with a transparent, translucent appearance; otherwise, the mixture had flake shapes and opaque appearance. Analyses of multivariate data showed that the process stages emissions were related with specific composition and shape suggesting the use three measurements related （1） the internal axis, （2） roundness and （3） roughness to isolate particles shapes, and the presence of transition metals oxides as emissions tracer of the ceramic industry.
基金Funded by Academician Foundation of Chongqing Project (2002-6285).
文摘In this paper, we proposed a five-zone model to predict the elastic modulus of particulate reinforced metal matrix composite. We simplified the calculation by ignoring structural parameters including particulate shape, arrangement pattern and dimensional variance mode which have no obvious influence on the elastic modulus of a composite, and improved the precision of the method by stressing the interaction of interfaces with pariculates and maxtrix of the composite. The five- zone model can reflect effects of interface modulus on elastic modulus of composite. It overcomes limitations of expressions of rigidity mixed law and flexibility mixed law. The original idea of five zone model is to put forward the particulate/interface interactive zone and matrix/interface interactive zone. By organically integrating the rigidity mixed law and flexibility mixed law, the model can predict the engineering elastic constant of a composite effectively.
文摘In a lab of the CAS Institute of Process Engineering（IPE）in Beijing,Winifred Uduak Anake,a visiting woman scientist from Covenant University.Nigeria was dashing to finish testing the 100 plus samples she collected from her home country.＂1 am trying to find out the type and amount of hazardous trace metals bound to the tiny particles trapped on the filters,＂she explained：＂out of worries about their possible threat to human health.＂Before concluding her three-month stay she needed to complete examining the morphology of the particles,total trace metals,
文摘This study aimed to determine the amount of total polluting matter emitted into the atmosphere from heating and industrial-based emissions and the total pollution bulk of Tokat city center. The annual cycles of some heavy metal in particulate matters have been investigated at this area in order to elucidate temporal variations as well as major sources processes responsible for their formation. Air particulate samples were collected from three different locations situated around Tokat. These samples were determined for heavy metals by using Flame or graphite-furnace Atomic absorption spectroscopy. Particulate matter concentrations up to 52.43μg/m^3 were observed in sampling area. The initial results of the chemical analysis showed that concentration values of heavy metals in air particles observed were higher than the World Health Organization （WHO） guideline limit values.
基金supported by the National Natural Science Foundation of China(21371115,11025526,40830744, 41073073,and 21101104)the National Basic Research Program of China(2011CB933402)+1 种基金the Innovation Program of Shanghai Municipal Education Commission(14YZ025)the Program for Innovative Research Team in University(IRT13078)
文摘Nanomaterials have attracted considerable interest owing to their unique physicochemical properties.The wide application of nanomaterials has raised many concerns about their potential risks to human health and the environment.Metal oxide nanopartides（MONPs）,one of the main members of nanomaterials,have been applied in various fields,such as food,medicine,cosmetics,and sensors.This review highlights the bio-toxic effects of widely applied MONPs and their underlying mechanisms.Two main underlying toxicity mechanisms,reactive oxygen species（ROS）-and non-ROS-mediated toxidties,of MONPs have been widely accepted.ROS activates oxidative stress,which leads to lipid peroxidation and cell membrane damage.In addition,ROS can trigger the apoptotic pathway by activating caspase-9 and-3.Non-ROS-mediated toxicity mechanism includes the effect of released ions,excessive accumulation of NPs on the cell surface,and combination of NPs with specific death receptors.Furthermore,the combined toxicity evaluation of some MONPs is also discussed.Toxicity may dramatically change when nanomaterials are used in a combined system because the characteristics of NPs that play a key role in their toxicity such as size,surface properties,and chemical nature in the complex system are different from the pristine NPs.
