This paper presents the effect of open dumping of municipal solid waste(MSW) on soil characteristics in the mountainous region of Himachal Pradesh, India. The solid waste of dumpsite contains various complex character...This paper presents the effect of open dumping of municipal solid waste(MSW) on soil characteristics in the mountainous region of Himachal Pradesh, India. The solid waste of dumpsite contains various complex characteristics with organic fractions of the highest proportions. As leachate percolates into the soil, it migrates contaminants into the soil and affects soil stability and strength. The study includes the geotechnical investigation of dump soil characteristics and its comparison with the natural soil samples taken from outside the proximity of dumpsites. The geochemical analysis of dumpsite soil samples was also carried out by scanning electron microscopy(SEM) and energy dispersive X-ray spectroscopy(EDS).Visual inspection revealed that the MSW consists of high fraction of organics, followed by paper. The soil samples were collected from five trial pits in the dumpsites at depths of 0.5 m, 1 m and 1.5 m. Then the collected soil samples were subjected to specific gravity test, grain size analysis, Atterberg’s limit test,compaction test, direct shear test, California bearing ratio(CBR) test and permeability analysis. The study indicated that the dumpsite soils from four study regions show decreasing trends in the values of maximum dry density(MDD), specific gravity, cohesion and CBR, and increasing permeability as compared to the natural soil. The results show that the geotechnical properties of the soils at all four study locations have been severely hampered due to contamination induced by open dumping of waste.展开更多
The cyclic multilayer alloy (CMA) coatings of Zn-Co have been developed galvanostatically on mild steel (MS), using single bath technique. Depositions were carried out using square current pulses. Corrosion behaviors ...The cyclic multilayer alloy (CMA) coatings of Zn-Co have been developed galvanostatically on mild steel (MS), using single bath technique. Depositions were carried out using square current pulses. Corrosion behaviors of the coatings were evaluated by potentiodynamic polarization and electrochemical impedance method, supported by dielectric spectroscopy. The cyclic cathode current densities (CCCD’s) and number of layers were optimized for highest corrosion stability of the coatings. The CMA coating developed at 3.0/5.0 A/dm2, having 300 layers, represented as (Zn-Co) 3.0/5.0/300 was found to exhibit ~ 40 times better corrosion resistance compared to monolayer coating, developed from same bath for same time. Substantial improvement in the corrosion resistance of CMA coatings is attributed to layered coating, having alternatively different phase structures, evidenced by XRD study. The formation of multilayer and corrosion mechanism was analyzed using Scanning Electron Microscopy.展开更多
Iron and copper bimetallic system(catalyzed Fe-Cu process)is a promising technology for alkaline nitrobenzene-containing wastewater treatment.However,little is currently known about the changes of treatment efficiency...Iron and copper bimetallic system(catalyzed Fe-Cu process)is a promising technology for alkaline nitrobenzene-containing wastewater treatment.However,little is currently known about the changes of treatment efficiency with time going.This research investigated the long-term performance of the catalyzed Fe-Cu process to reduce nitrobenzene(NB)in alkaline wastewater.In addition,the changes of the metal surfaces morphologies and matters before and after the reaction were analyzed by scanning electron microscopy(SEM)in conjunction with energy-dispersion spectroscopy(EDS)and X-ray diffraction spectros-copy(XRD).The results showed that the surface properties of copper almost remained unchanged after weeks of operation,which spelled its strong chemical stability and resistance to poisoning.Moreover,the results indicated that there were two reasons for the treatment efficiency decreasing with time.One was the gradual iron element consumption due to corro-sion.The other was iron reactivity weakened due to the precipitates accumulation on the surfaces that were mainly Fe_(3)O_(4) and FeCO.展开更多
目的:建立含银敷料的表征和银体外释放及鉴别释放液中纳米银和银离子的实验方法;探讨其在相关产品检测中的应用。方法:通过扫描电子显微镜(SEM)、X射线能量色散谱仪(EDS)、X射线光电子能谱仪(XPS)对含银敷料进行形貌及银颗粒价态分析表...目的:建立含银敷料的表征和银体外释放及鉴别释放液中纳米银和银离子的实验方法;探讨其在相关产品检测中的应用。方法:通过扫描电子显微镜(SEM)、X射线能量色散谱仪(EDS)、X射线光电子能谱仪(XPS)对含银敷料进行形貌及银颗粒价态分析表征;采用摇床法及往复支架法考察含银敷料在纯水和模拟体液(SBF)中的释放特性。通过体外细胞毒性研究,讨论材料表征与细胞毒性风险评价的相关性。结果:通过使用10 k D滤膜的超滤管实现了纳米银颗粒的有效分离,并通过调整释放液中氯离子/银离子的浓度比排除了SBF释放液中可能存在的氯化银颗粒物的干扰。利用所建立的规范性试验方法对实验所用的2种含银敷料进行了评价。其结果显示2种含银敷料均含纳米银,往复支架法体外释放试验显示含银烧烫伤贴24 h内在纯水和SBF中释放总银分别为5.24、12.41μg·cm-2,表明在SBF中的总银释放量高于纯水中释放量(约2倍);且SBF中银颗粒的释放比例略高于纯水中的释放比例。细胞毒性评价(MTT、LDH)的结果显示含银烧烫伤贴细胞毒性大于含银创伤贴,与总银释放量呈正相关。结论:本课题建立的含银敷料表征和银释放特性的实验方法,能够有效地判定敷料中是否含有纳米银及是否有纳米银颗粒的释放,为正确地对含银敷料进行风险评估及合理有效的监管提供科学依据。展开更多
The principal forces driving the efficient enrichment and encapsulation of arsenic(As) into nanoscale zero-valent iron(nZVI) are the disordered arrangement of the atoms and the gradient chemical potentials within the ...The principal forces driving the efficient enrichment and encapsulation of arsenic(As) into nanoscale zero-valent iron(nZVI) are the disordered arrangement of the atoms and the gradient chemical potentials within the core-shell interface. The chemical compositions and the fine structure of nZVI are characterized with a combination of spherical aberration corrected scanning transmission electron microscopy(Cs-STEM), X-ray energy-dispersive spectroscopy(XEDS), electron energy loss spectroscopy(EELS), and high-resolution X-ray photoelectron spectroscopy(HR-XPS). Atomically resolved EELS at the oxygen K-edge unfolds that the Fe species in nZVI are well stratified from Fe(Ⅲ) oxides in the outermost periphery to a mixed Fe(Ⅲ)/Fe(Ⅱ) interlayer, then Fe(Ⅱ) oxide and the pure Fe(0) phase. Reactions between As(Ⅴ)and nZVI suggest that a well-structured local redox gradient exists within the shell layer, which serves as a thermodynamically favorable conduit for electron transfer from the iron core to the surface-bound As(Ⅴ). HR-XPS with ion sputtering shows that arsenic species shift from As(Ⅴ), As(Ⅲ)/As(Ⅴ) to As(Ⅴ)/As(Ⅲ)/As(0) from the iron oxide shell–water interface to the Fe(0) core. Results reinforce previous work on the efficacy of nZVI for removing and remediating arsenic while the analytical TEM methods are also applicable to the study of environmental interfaces and surface chemistry.展开更多
Elastomeric materials show promise as potential micro-fillers in brake linings.They can provide vibration damping and acoustic advantages in intermittent and abrupt impact applications such as braking.The elastomeric ...Elastomeric materials show promise as potential micro-fillers in brake linings.They can provide vibration damping and acoustic advantages in intermittent and abrupt impact applications such as braking.The elastomeric material can be salvaged from non-biodegradable automotive tires,thereby providing an opportunity to reuse materials that will otherwise be discarded in landfills.Both tribological and thermomechanical performances of the waste tire rubber were assessed to determine their potential for use as micro-fillers in the brake linings of commercial vehicles with a gross weight less than 16 tons.Accordingly,the brake lining materials were fabricated with fine waste tire rubber particulates(WTRPs)as the micro-fillers,phenolic-R resin as the binder,graphite as the dry lubricant,laterite as the co-filler,and coconut coir for natural fiber reinforcement.The effects of increasing the WTRP weight fraction on the brake response of the linings were analyzed,and the different compositions were benchmarked against a commercial brake lining.Mechanical characterization comprising compressive strength,hardness,density,and porosity studies were carried out.Frictional and wear characteristics of the linings were analyzed using a rotary tribometer with simultaneous thermal monitoring.The manufactured lining with 15 wt%WTRPs exhibited a mean friction coefficient of^0.38,a specific volumetric loss rate of 1,662μm3/(N?m),and improved thermal response.Using optical microscopy and scanning electron microscopy(SEM)with energy dispersive spectroscopy(EDS),wear surface morphology studies compared the relative development of primary and secondary plateaus and revealed the redistribution of wear debris,leading to the stability of the coefficient of friction.展开更多
Soils contain various kinds of crystalline to amorphous solid particles with at least one dimension in the nanoscale （〈 100 nm）. These nanoparticles contribute greatly to dynamic soil processes such as soil genesis...Soils contain various kinds of crystalline to amorphous solid particles with at least one dimension in the nanoscale （〈 100 nm）. These nanoparticles contribute greatly to dynamic soil processes such as soil genesis, trace element cycling, contaminant transport, and chemical reaction. The nano-sized fraction of an Anthrosol was obtained to determine the occurrence, chemical composition, structure, and mineral phases of nanoparticles using high-resolution transmission electron microscopy （HRTEM） equipped with an energy-dispersive X-ray spectroscopy. Selected area electron diffraction or the fast Fourier transform of high-resolution images was used in structural characterization of the nanoparticles with HRTEM. Two nanoscale mineral types, i.e., mineral nanoparticles and nanomi- nerals, were observed in the Anthrosol. Mineral nanoparticles in soil included well crystalline aluminumsilicate nanosheets, nanorods, and nanoparticles. Nanosheets with a length of 120-150 nm and a width of about 10-20 nm were identified as chlorite/vermiculite series. The presence of clear lattice fringe spacing in HRTEM image of nanoparticles indicated that mineral nanoparticles had a relatively good crystallinity. The nanomineral ferrihydrite also existed in the Anthrosol. The HRTEM images and the particle size distribution histogram suggested that these ferrihydrite nanoparticles were quite homogeneous, and had a narrow size distribution range （1-7 nm） with a mean diameter of 3.6 4- 1.6 nm. Our HRTEM observation indicated that mineral nanoparticles and nanominerals were common and widely distributed in Anthrosols. HRTEM and selected area diffraction or lattice fringe spacing characterization provided further proofs to the structure of nanoparticles formed in soil.展开更多
文摘This paper presents the effect of open dumping of municipal solid waste(MSW) on soil characteristics in the mountainous region of Himachal Pradesh, India. The solid waste of dumpsite contains various complex characteristics with organic fractions of the highest proportions. As leachate percolates into the soil, it migrates contaminants into the soil and affects soil stability and strength. The study includes the geotechnical investigation of dump soil characteristics and its comparison with the natural soil samples taken from outside the proximity of dumpsites. The geochemical analysis of dumpsite soil samples was also carried out by scanning electron microscopy(SEM) and energy dispersive X-ray spectroscopy(EDS).Visual inspection revealed that the MSW consists of high fraction of organics, followed by paper. The soil samples were collected from five trial pits in the dumpsites at depths of 0.5 m, 1 m and 1.5 m. Then the collected soil samples were subjected to specific gravity test, grain size analysis, Atterberg’s limit test,compaction test, direct shear test, California bearing ratio(CBR) test and permeability analysis. The study indicated that the dumpsite soils from four study regions show decreasing trends in the values of maximum dry density(MDD), specific gravity, cohesion and CBR, and increasing permeability as compared to the natural soil. The results show that the geotechnical properties of the soils at all four study locations have been severely hampered due to contamination induced by open dumping of waste.
文摘The cyclic multilayer alloy (CMA) coatings of Zn-Co have been developed galvanostatically on mild steel (MS), using single bath technique. Depositions were carried out using square current pulses. Corrosion behaviors of the coatings were evaluated by potentiodynamic polarization and electrochemical impedance method, supported by dielectric spectroscopy. The cyclic cathode current densities (CCCD’s) and number of layers were optimized for highest corrosion stability of the coatings. The CMA coating developed at 3.0/5.0 A/dm2, having 300 layers, represented as (Zn-Co) 3.0/5.0/300 was found to exhibit ~ 40 times better corrosion resistance compared to monolayer coating, developed from same bath for same time. Substantial improvement in the corrosion resistance of CMA coatings is attributed to layered coating, having alternatively different phase structures, evidenced by XRD study. The formation of multilayer and corrosion mechanism was analyzed using Scanning Electron Microscopy.
基金This study was financially supported by the National High Technology Research and Development Program of China(863 Program).The researchers in the testing laboratory of Materials and Engineering College of Tongji University are highly appreciated for their helpful on XRD,SEM and EDS tests.
文摘Iron and copper bimetallic system(catalyzed Fe-Cu process)is a promising technology for alkaline nitrobenzene-containing wastewater treatment.However,little is currently known about the changes of treatment efficiency with time going.This research investigated the long-term performance of the catalyzed Fe-Cu process to reduce nitrobenzene(NB)in alkaline wastewater.In addition,the changes of the metal surfaces morphologies and matters before and after the reaction were analyzed by scanning electron microscopy(SEM)in conjunction with energy-dispersion spectroscopy(EDS)and X-ray diffraction spectros-copy(XRD).The results showed that the surface properties of copper almost remained unchanged after weeks of operation,which spelled its strong chemical stability and resistance to poisoning.Moreover,the results indicated that there were two reasons for the treatment efficiency decreasing with time.One was the gradual iron element consumption due to corro-sion.The other was iron reactivity weakened due to the precipitates accumulation on the surfaces that were mainly Fe_(3)O_(4) and FeCO.
文摘目的:建立含银敷料的表征和银体外释放及鉴别释放液中纳米银和银离子的实验方法;探讨其在相关产品检测中的应用。方法:通过扫描电子显微镜(SEM)、X射线能量色散谱仪(EDS)、X射线光电子能谱仪(XPS)对含银敷料进行形貌及银颗粒价态分析表征;采用摇床法及往复支架法考察含银敷料在纯水和模拟体液(SBF)中的释放特性。通过体外细胞毒性研究,讨论材料表征与细胞毒性风险评价的相关性。结果:通过使用10 k D滤膜的超滤管实现了纳米银颗粒的有效分离,并通过调整释放液中氯离子/银离子的浓度比排除了SBF释放液中可能存在的氯化银颗粒物的干扰。利用所建立的规范性试验方法对实验所用的2种含银敷料进行了评价。其结果显示2种含银敷料均含纳米银,往复支架法体外释放试验显示含银烧烫伤贴24 h内在纯水和SBF中释放总银分别为5.24、12.41μg·cm-2,表明在SBF中的总银释放量高于纯水中释放量(约2倍);且SBF中银颗粒的释放比例略高于纯水中的释放比例。细胞毒性评价(MTT、LDH)的结果显示含银烧烫伤贴细胞毒性大于含银创伤贴,与总银释放量呈正相关。结论:本课题建立的含银敷料表征和银释放特性的实验方法,能够有效地判定敷料中是否含有纳米银及是否有纳米银颗粒的释放,为正确地对含银敷料进行风险评估及合理有效的监管提供科学依据。
基金the National Natural Science Foundation of China(11475127,51578396,41673096,and 41772243)National Postdoctoral Program for Innovative Talents(BX201700172)
文摘The principal forces driving the efficient enrichment and encapsulation of arsenic(As) into nanoscale zero-valent iron(nZVI) are the disordered arrangement of the atoms and the gradient chemical potentials within the core-shell interface. The chemical compositions and the fine structure of nZVI are characterized with a combination of spherical aberration corrected scanning transmission electron microscopy(Cs-STEM), X-ray energy-dispersive spectroscopy(XEDS), electron energy loss spectroscopy(EELS), and high-resolution X-ray photoelectron spectroscopy(HR-XPS). Atomically resolved EELS at the oxygen K-edge unfolds that the Fe species in nZVI are well stratified from Fe(Ⅲ) oxides in the outermost periphery to a mixed Fe(Ⅲ)/Fe(Ⅱ) interlayer, then Fe(Ⅱ) oxide and the pure Fe(0) phase. Reactions between As(Ⅴ)and nZVI suggest that a well-structured local redox gradient exists within the shell layer, which serves as a thermodynamically favorable conduit for electron transfer from the iron core to the surface-bound As(Ⅴ). HR-XPS with ion sputtering shows that arsenic species shift from As(Ⅴ), As(Ⅲ)/As(Ⅴ) to As(Ⅴ)/As(Ⅲ)/As(0) from the iron oxide shell–water interface to the Fe(0) core. Results reinforce previous work on the efficacy of nZVI for removing and remediating arsenic while the analytical TEM methods are also applicable to the study of environmental interfaces and surface chemistry.
文摘Elastomeric materials show promise as potential micro-fillers in brake linings.They can provide vibration damping and acoustic advantages in intermittent and abrupt impact applications such as braking.The elastomeric material can be salvaged from non-biodegradable automotive tires,thereby providing an opportunity to reuse materials that will otherwise be discarded in landfills.Both tribological and thermomechanical performances of the waste tire rubber were assessed to determine their potential for use as micro-fillers in the brake linings of commercial vehicles with a gross weight less than 16 tons.Accordingly,the brake lining materials were fabricated with fine waste tire rubber particulates(WTRPs)as the micro-fillers,phenolic-R resin as the binder,graphite as the dry lubricant,laterite as the co-filler,and coconut coir for natural fiber reinforcement.The effects of increasing the WTRP weight fraction on the brake response of the linings were analyzed,and the different compositions were benchmarked against a commercial brake lining.Mechanical characterization comprising compressive strength,hardness,density,and porosity studies were carried out.Frictional and wear characteristics of the linings were analyzed using a rotary tribometer with simultaneous thermal monitoring.The manufactured lining with 15 wt%WTRPs exhibited a mean friction coefficient of^0.38,a specific volumetric loss rate of 1,662μm3/(N?m),and improved thermal response.Using optical microscopy and scanning electron microscopy(SEM)with energy dispersive spectroscopy(EDS),wear surface morphology studies compared the relative development of primary and secondary plateaus and revealed the redistribution of wear debris,leading to the stability of the coefficient of friction.
基金Supported by the National Natural Science Foundation of China (No. 40971131)the Ph.D. Program Foundation of Ministry of Education of China (No. 20090101110088)
文摘Soils contain various kinds of crystalline to amorphous solid particles with at least one dimension in the nanoscale （〈 100 nm）. These nanoparticles contribute greatly to dynamic soil processes such as soil genesis, trace element cycling, contaminant transport, and chemical reaction. The nano-sized fraction of an Anthrosol was obtained to determine the occurrence, chemical composition, structure, and mineral phases of nanoparticles using high-resolution transmission electron microscopy （HRTEM） equipped with an energy-dispersive X-ray spectroscopy. Selected area electron diffraction or the fast Fourier transform of high-resolution images was used in structural characterization of the nanoparticles with HRTEM. Two nanoscale mineral types, i.e., mineral nanoparticles and nanomi- nerals, were observed in the Anthrosol. Mineral nanoparticles in soil included well crystalline aluminumsilicate nanosheets, nanorods, and nanoparticles. Nanosheets with a length of 120-150 nm and a width of about 10-20 nm were identified as chlorite/vermiculite series. The presence of clear lattice fringe spacing in HRTEM image of nanoparticles indicated that mineral nanoparticles had a relatively good crystallinity. The nanomineral ferrihydrite also existed in the Anthrosol. The HRTEM images and the particle size distribution histogram suggested that these ferrihydrite nanoparticles were quite homogeneous, and had a narrow size distribution range （1-7 nm） with a mean diameter of 3.6 4- 1.6 nm. Our HRTEM observation indicated that mineral nanoparticles and nanominerals were common and widely distributed in Anthrosols. HRTEM and selected area diffraction or lattice fringe spacing characterization provided further proofs to the structure of nanoparticles formed in soil.
