An experimental program was conducted to explore the impact of nanosilica on the microstructure and mechanical characteristics of cemented sandy soil.Cement agent included Portland cement type II.Cement content was 6%...An experimental program was conducted to explore the impact of nanosilica on the microstructure and mechanical characteristics of cemented sandy soil.Cement agent included Portland cement type II.Cement content was 6% by weight of the sandy soil.Nanosilica was added in percentages of 0%,4%,8% and 12% by weight of cement.Cylindrical samples were prepared with relative density of 80% and optimum water content and cured for 7 d,28 d and 90 d.Microstructure characteristics of cementnanosilica-sand mixtures after 90 d of curing have been explored using atomic force microscopy(AFM),scanning electron microscopy(SEM) and X-ray diffraction(XRD) tests.Effects of curing time on microstructure properties of cemented sandy soil samples with 0% and 8% nanosilica have been investigated using SEM test.Unconfined compression test(for all curing times) and compaction test were also performed.The SEM and AFM tests results showed that nanosilica contributes to enhancement of cemented sandy soil through yielding denser,more uniform structure.The XRD test demonstrated that the inclusion of nanosilica in the cemented soil increases the intensity of the calcium silicate hydrate(CSH) peak and decreases the intensity of the calcium hydroxide(CH) peak.The results showed that adding optimum percentages of nanosilica to cement-stabilized sandy soil enhances its mechanical and microstructure properties.展开更多
In the French concept of deep nuclear waste repositories,the galleries should be backfilled with excavated argillite after the site has been filled.Some additives like lime could be used to improve the mechanical char...In the French concept of deep nuclear waste repositories,the galleries should be backfilled with excavated argillite after the site has been filled.Some additives like lime could be used to improve the mechanical characteristics of the argillite.After thousands of years,the degradation of the concrete lining of the galleries will generate an alkaline solution（pH value 12） that will diffuse through the backfill.This study presents the effect of a saturated Ca（OH）_2 solution circulation through lime-treated sample at 60 ℃ for 3,6 and 12 months,respectively.The effect of such circulation on the lime-treated Manois argillite（MA） was assessed by petrographical examination coupled to image analysis and scanning electron microscopy（SEM） equipped with energy dispersive X-ray（EDX） analyser of soil pieces.The objective of this study is to make the link among the mineralogical transformations,the textural and mechanical changes produced in the compacted clayey soil as a consequence of the alkaline solution circulation.展开更多
Ce^（3＋） substituted Cu-spinel nanoferrites CuCe_xFe_（2-x）O_4（x=0.00, 0.02, 0.04, 0.06, 0.08 and 0.10） were synthesized via sol-gel self-combustion hybrid route. Single phase spinel ferrite of Cu nanoferrites we...Ce^（3＋） substituted Cu-spinel nanoferrites CuCe_xFe_（2-x）O_4（x=0.00, 0.02, 0.04, 0.06, 0.08 and 0.10） were synthesized via sol-gel self-combustion hybrid route. Single phase spinel ferrite of Cu nanoferrites were examined using X-ray diffraction（XRD） analysis whereas the multiphase structure was observed as Ce contents increased from x=0.06. Field emission scanning electron microscopy（FESEM）, Thermogravimetric and differential thermal analysis（TGA and DTA） and Fourier transform infrared spectroscopy（FTIR） were used to find out the morphology phase and metal stretching vibrations of Ce^（3＋） substituted nanocrystalline ferrites. The crystallite size was increased and found in the range of 25-91 nm. The agglomerations in Cu ferrite samples increase as the Ce^（3＋） concentration increases. The magnetic properties such as remanence, saturation magnetization, coercivity, Bohr magneton and magnetocrystalline anisotropy constant（K） were determined using M-H loops recorded from a vibrating sample magnetometer（VSM）. Saturation magnetization, remanence and coercivity are increased as the Ce^（3＋）contents increase in Cu nanocrystalline samples. Moreover, law of approach to saturation（LoA） was used to calculate the maximum value of saturation for Ce-doped Cu nanoferrites. The soft magnetic behaviour of the Cu nanoferrite is observed as compared to the samples substituted with the increased Ce contents in Cu nanocrystalline ferrite. Bohr magneton and magnetocrystalline anisotropy are found to increase with the substitution of rare earth Ce^（3＋） contents in Cu spinel nanocrystalline ferrite. Cedoped Cu nanocrystalline ferrites with excellent properties may be suitable for potential applications in sensing, security, switching, core, multilayer chip inductor, biomedical and microwave absorption applications.展开更多
In this study,the effects of hybridizing micron-sized titanium particles with nano-sized boron carbide particles on the microstructural and mechanical properties of Mg-Ti composite were investigated.Microstructural ch...In this study,the effects of hybridizing micron-sized titanium particles with nano-sized boron carbide particles on the microstructural and mechanical properties of Mg-Ti composite were investigated.Microstructural characterization revealed grain refinement attributed to the presence of uniformly distributed micro-Ti particles embedded with nano-B_(4)C particulates.Electron back scattered diffraction(EBSD)analyses of the Mg-(Ti+B_(4)C)BM hybrid composite showed relatively more localized recrystallized grains and lesser tensile twin fraction,when compared to Mg-Ti.The evaluation of mechanical properties indicated that the best combination of strength and ductility was observed in the Mg-(Ti+B_(4)C)BM hybrid composite.The superior properties of the Mg-(Ti+B_(4)C)BM hybrid composite when compared to Mg-Ti can be attributed to the presence of nano-reinforcement,the uniform distribution of the hybridized particles and the better interfacial bonding between the matrix and the reinforcement particles achieved by nano-B_(4)C addition.展开更多
In-situ upgrading by heating is feasible for low-maturity shale oil,where the pore space dynamically evolves.We characterize this response for a heated substrate concurrently imaged by SEM.We systematically follow the...In-situ upgrading by heating is feasible for low-maturity shale oil,where the pore space dynamically evolves.We characterize this response for a heated substrate concurrently imaged by SEM.We systematically follow the evolution of pore quantity,size(length,width and cross-sectional area),orientation,shape(aspect ratio,roundness and solidity)and their anisotropy—interpreted by machine learning.Results indicate that heating generates new pores in both organic matter and inorganic minerals.However,the newly formed pores are smaller than the original pores and thus reduce average lengths and widths of the bedding-parallel pore system.Conversely,the average pore lengths and widths are increased in the bedding-perpendicular direction.Besides,heating increases the cross-sectional area of pores in low-maturity oil shales,where this growth tendency fluctuates at<300℃ but becomes steady at>300℃.In addition,the orientation and shape of the newly-formed heating-induced pores follow the habit of the original pores and follow the initial probability distributions of pore orientation and shape.Herein,limited anisotropy is detected in pore direction and shape,indicating similar modes of evolution both bedding-parallel and bedding-normal.We propose a straightforward but robust model to describe evolution of pore system in low-maturity oil shales during heating.展开更多
The inhibition effect of three azole compounds, 2-aminobenzimidazole（ABM）, 2-aminothiazole（AT） and 2-aminobenzothiazole（ABT）, on the corrosion of mild steel in a 1 mol/L HCI solution was investigated by means of...The inhibition effect of three azole compounds, 2-aminobenzimidazole（ABM）, 2-aminothiazole（AT） and 2-aminobenzothiazole（ABT）, on the corrosion of mild steel in a 1 mol/L HCI solution was investigated by means of potentiodynamic polarization measurement, electrochemical impedance spectroscopy（EIS） and scanning electron microscopy（SEM）. The correlation between inhibition efficiency and molecular structure of inhibitor was theoretically studied via quantum chemical calculations. The results show that the inhibition efficiency（η） of the inhibitors follows the order of ηABT〉ηAT〉ηABM. Moreover, ABM, AT and ABT belong to mixed-type inhibitors. The adsorption of the inhibitors on the steel surface follows the Langmuir adsorption isotherm, with both physisorption and chemisorption.展开更多
The change of conductivity, thickness and scanning electron microscopy （SEM） appearance of the anode film of CrWMn in 10% NaNO3 at different anode potential either with or without the magnetic field applied are inve...The change of conductivity, thickness and scanning electron microscopy （SEM） appearance of the anode film of CrWMn in 10% NaNO3 at different anode potential either with or without the magnetic field applied are investigated by testing film resistance, galvanostatic transient and using SEM to design magnetic circuit in magnetic assisted electrochemical machining （MAECM）. The experiments show that the anode film has semi-conducting property. Compared with the situation without magnetic field applied, the resistance of the film formed at 1 .SV （anode potential） increased and decreased at 4.0V while B=0.4T and the magnetic north pole points toward anode. The SEM photo demonstrates that the magnetic field will densify the film in the passivation area and quicken dissolution of the anode metal in over-passivation area. Based on the influence of magnetic field on electrochemical machining（ECM） due to the changes of the anode film conductivity behavior, the magnetic north pole should be designed to point towards the workpiece surface that has been machined. Process experiments agree with the results of test analysis.展开更多
In this study,orthogonal experiments were conducted to investigate the influence of expandable graphite(EG),dimethyl methylphosphonate(DMMP),triethanolamine(TEA),and isocyanate content on the compressive and bonding s...In this study,orthogonal experiments were conducted to investigate the influence of expandable graphite(EG),dimethyl methylphosphonate(DMMP),triethanolamine(TEA),and isocyanate content on the compressive and bonding strengths,oxygen index,and fluidity of rigid polyurethane foam(RPUF).The results revealed that EG significantly increased the oxygen index of RPUF,enlarged the diameter of foam cells,and decreased the cell-closed content in foam;thus,leading to a pressure drop in RPUF.However,excessive EG was capable of reducing the fluidity of polyurethane slurry.TEA exhibited significant influence on the compressive strength of RPUF,which dropped initially,and then increased.DMMP had a remarkable effect on the flame retardant property and compressive strength of RPUF.Compressive strength of RPUF initially displayed an increase followed by a decrease with increasing dosage of DMMP,and achieved the maximum value at DMMP dosage of 4%.DMMP could effectively reduce the diameter of RPUF cells leading to an increase in the percentage of close area in foam.DMMP displayed the flame-retardation effects mainly in the gas phase leading to a significant enhancement in the oxygen index of RPUF.Moreover,the compressive strength and bonding strength of RPUF decrease significantly with the increase of isocyanate content due to the increased blowing efficiency by the CO_2.The oxygen index and flowing length of foam increased with the increase in isocyanate dosage.展开更多
To meet the ever-increasing construction demands around the world during recent years,reinforcement and stabilization methods have been widely used by geotechnical engineers to improve the performances and behavior of...To meet the ever-increasing construction demands around the world during recent years,reinforcement and stabilization methods have been widely used by geotechnical engineers to improve the performances and behavior of fine-grained soils.Although lime stabilization increases the compressive strength of soils,it reduces the soil ductility at the same time.Recent research shows that random fiber inclusion modifies the brittleness of soils.In the current research,the effects of lime and polypropylene(PP)fiber additions on such characteristics as compressive and shear strengths,failure strain,secant modulus of elasticity(E50)and shear strength parameters of mixtures were investigated.Kaolinite was treated with 1%,3% and 5% lime by dry weight of soil and reinforced with 0.1% monovalent PP fibers with the length of 6 mm.Samples were prepared at optimum conditions and cured at 35℃ for 1 d,7 d and 28 d at 90% relative humidity and subsequently subjected to uniaxial and triaxial compression tests(UCT and TCT)under cell pressures of 25 kPa,50 kPa and 100 kPa.Results showed that inclusion of random PP fibers to clay-lime mixtures increases both compressive and shear strengths as well as the ductility.Lime content and curing period were found to be the most influential factors.Scanning electron microscopy(SEM)analysis showed that lime addition and the formation of cementitious compounds bind soil particles and increase soil/fiber interactions at interface,leading to enhanced shear strength.The more ductile the stabilized and reinforced composition,the less the cracks in roads and waste landfill covers.展开更多
The exceptional physical properties and unique layered structure of two-dimensional(2D)materials have made this class of materials great candidates for applications in electronics,energy conversion/storage devices,nan...The exceptional physical properties and unique layered structure of two-dimensional(2D)materials have made this class of materials great candidates for applications in electronics,energy conversion/storage devices,nanocomposites,and multifunctional coatings,among others.At the center of this application space,mechanical properties play a vital role in materials design,manufacturing,integration and performance.The emergence of 2D materials has also sparked broad scientific inquiry,with new understanding of mechanical interactions between 2D structures and interfaces being of great interest to the community.Building on the dramatic expansion of recent research activities,here we review significant advances in the understanding of the elastic properties,in-plane failures,fatigue performance,interfacial shear/friction,and adhesion behavior of 2D materials.In this article,special emphasis is placed on some new 2D materials,novel characterization techniques and computational methods,as well as insights into deformation and failure mechanisms.A deep understanding of the intrinsic and extrinsic factors that govern 2D material mechanics is further provided,in the hopes that the community may draw design strategies for structural and interfacial engineering of 2D material systems.We end this review article with a discussion of our perspective on the state of the field and outlook on areas for future research directions.展开更多
Objective:This study deals with the effect of phosphoric acid etching and conditioning on enamel micro-tensile bond strengths(μTBSs)of conventional and resin-modified glass ionomer cements(GICs/RMGICs).Methods:Forty-...Objective:This study deals with the effect of phosphoric acid etching and conditioning on enamel micro-tensile bond strengths(μTBSs)of conventional and resin-modified glass ionomer cements(GICs/RMGICs).Methods:Forty-eight bovine incisors were prepared into rectangular blocks.Highly-polished labial enamel surfaces were either acid-etched,conditioned with liquids of cements,or not further treated(control).Subsequently,two matching pre-treated enamel surfaces were cemented together with one of four cements[two GICs:Fuji I(GC),Ketac Cem Easymix(3M ESPE);two RMGICs:Fuji Plus(GC),RelyX Luting(3M ESPE)]in preparation forμTBS tests.Pre-treated enamel surfaces and cement-enamel interfaces were analyzed by scanning electron microscopy(SEM).Results:Phosphoric acid etching significantly increased the enamelμTBS of GICs/RMGICs.Conditioning with the liquids of the cements produced significantly weaker or equivalent enamelμTBS compared to the control.Regardless of etching,RMGICs yielded stronger enamelμTBS than GICs.A visible hybrid layer was found at certain enamelcement interfaces of the etched enamels.Conclusions:Phosphoric acid etching significantly increased the enamelμTBSs of GICs/RMGICs.Phosphoric acid etching should be recommended to etch the enamel margins before the cementation of the prostheses such as inlays and onlays,using GICs/RMGICs to improve the bond strengths.RMGICs provided stronger enamel bond strength than GICs and conditioning did not increase enamel bond strength.展开更多
The kinetic,morphological,crystallographic,and magnetic characteristics of thermally induced martensites in Fe-13.4wt% Mn-5.2wt%Mo alloy were investigated by scanning electron microscopy（SEM）,transmission electron m...The kinetic,morphological,crystallographic,and magnetic characteristics of thermally induced martensites in Fe-13.4wt% Mn-5.2wt%Mo alloy were investigated by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,and M（o｜¨）ssbauer spectroscopy.The experimental results reveal that two types of thermal-induced martensites,e（hcp） andα＇（bcc） martensites,are formed in the as-quenched condition,and these transformations have athermal characters.Mo addition to the Fe-Mn alloy does not change the coexistence ofεandα＇ martensites with the Mn content between 10wt%and 15wt%.Besides,M（o｜¨）ssbauer spectra reveal a paramagnetic character with a singlet for theγ（fcc） austenite andεmartensite phases and a ferromagnetic character with a broad sextet for theα＇ martensite phase. The volume fraction ofα＇ martensite forming in the quenched alloy is much more than that of theεmartensite.展开更多
The mechanical properties of fibers were notably improved by incorporating 2,2＇-bis（trifluoromethyl）benzidine（TFMB） into 3,3＇,4,4＇-biphenyltetracarboxylic dianhydride（s-BPDA） and p-phenylenediamine（PPD） bac...The mechanical properties of fibers were notably improved by incorporating 2,2＇-bis（trifluoromethyl）benzidine（TFMB） into 3,3＇,4,4＇-biphenyltetracarboxylic dianhydride（s-BPDA） and p-phenylenediamine（PPD） backbone.The best strength and modulus of BPDA/PPD/TFMB polyimide（PI） fiber（diamine molar ratio of PPD/TFMB= 90/10） were 1.60 and 90 GPa,respectively,which was over two times that of BPDA/PPD PI fiber.SEM image showed that the cross-section of fibers at each stage was round and voids free.Besides,the ＂skin-core＂ and microfibrillar structure were not observed.The thermal properties of PI fibers were also investigated.The results showed that the fibers owned excellent thermal stability,moreover,the structural homogeneity of fibers were significantly improved by heat-drawn stage.The T g values were found to be around 300 °C by dynamic mechanical analysis（DMA）.Wide angle X-ray diffraction（WAXD） and small angle X-ray scattering（SAXS） experiments indicated that the order degree of longitudinal and lateral stacks,the molecular orientation and the structural homogeneity of fibers were improved in the preparation process of fibers.展开更多
The aim of this work was to study the degradation behavior of Ti-6Al-4V alloys for dental applications in acidic artificial saliva with fluoride ion using electrochemical techniques, optical microscopy, scanning elect...The aim of this work was to study the degradation behavior of Ti-6Al-4V alloys for dental applications in acidic artificial saliva with fluoride ion using electrochemical techniques, optical microscopy, scanning electron microscopy（SEM）, and energy dispersive spectrometry（EDS）. The experimental results showed that fluoride ion had significant influence on the degradation of Ti-6Al-4V alloys, and there was an obvious critical concentration of fluoride ion（about 0.1wt%）. With increasing fluoride ion concentration, the corrosion potential（Ecorr） of alloys moved toward negative and the impedance of alloys decreased, meanwhile, noticeable transformation from minimum corrosion to severe pitting corrosion was observed on alloys surface following the dissolution of TiO2 passive films, leading to the decrease of the corrosion resistance of alloys. The electrochemical dissolution of TiO2 passive films involved a nucleophilic attack of fluoride atom to the titanium atom of TiO2. In addition, Ca^（2＋）and Na~＋ in acidic saliva may involve the surface reactions and make the reactions more complex.展开更多
Unsaturated loess in natural sites loses stability as the overburden load continuously increases.Traditional soil modifiers such as cement and fly ash affect the surrounding environment.A new type of material,i.e.,lig...Unsaturated loess in natural sites loses stability as the overburden load continuously increases.Traditional soil modifiers such as cement and fly ash affect the surrounding environment.A new type of material,i.e.,lignin,is environmentally friendly and able to increase the strength of loess.However,the engineering characteristics of the improved loess under unsaturated conditions are not yet clear.In this study,the soil-water characteristic curves(SWCCs)of lignin-improved loess samples were determined from 0 kPa to 700 kPa using a pressure plate instrument,and then,they were fitted using the van Genuchten(VG)model and the Fredlund and Xing(FX)model.In addition,the effects of the lignin content and sample preparation methods on the SWCCs were investigated to determine the optimal lignin content and a suitable sample preparation method for loess foundations.As the lignin content increases,the matric suction and residual water content of the improved loess increase.The suction stress increases with the increasing lignin contents of 1%–2%.At lignin contents of 3%–4%,the suction stress begins to decrease and the samples prepared using the slurry method has a lower suction stress than that prepared using the wet mixing method.The air entry value(AEV)increases with increasing lignin content.In addition,scanning electron microscopy(SEM)was used to investigate the microstructural variations.It was found that after the addition of lignin,the entrapment of the loess particles by the lignin fibers created some larger particles and smaller pore diameters,which in turn led to poor connectivity of the loess pores.These changes cause the matric suction of the modified loess to increase.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
Aerosol samples were collected in the Shiyi Glacier, Qilian Mountains from July 24 to August 19, 2012 and analyzed for major water-soluble ionic species(F-, Cl-, NO2-, NO3-, SO42-, Na+, NH4+, K+, Mg2+and Ca2+) by ion ...Aerosol samples were collected in the Shiyi Glacier, Qilian Mountains from July 24 to August 19, 2012 and analyzed for major water-soluble ionic species(F-, Cl-, NO2-, NO3-, SO42-, Na+, NH4+, K+, Mg2+and Ca2+) by ion chromatography. SO42-and NH4+were the most abundant components of all the anions and cations, with average concentrations of 94.72 and 54.26 neq/m3, respectively, accounting for 34% and 20% of the total water-soluble ions analyzed. These mean ion concentrations were generally comparable with the background conditions in remote sites of the Qilian Mountains, but were much lower than those in certain cities in China. The particles were grouped into two dominant types according to their morphology and EDX signal: Si-rich particles and Fe-rich particles. Backward air mass trajectory analysis suggested that inland cities may contribute some anthropogenic pollution to this glacier, while the arid and semi-arid regions of central Asia were the primary sources of the mineral particles.展开更多
Environmentally friendly thermosetting composites were successfully prepared by conventional blending wheat gluten as matrix,glycerol as plasticizer and silica as filler followed by thermo-molding of the mixture at 12...Environmentally friendly thermosetting composites were successfully prepared by conventional blending wheat gluten as matrix,glycerol as plasticizer and silica as filler followed by thermo-molding of the mixture at 120℃.The strong interfacial interaction between silica particles and gluten proteins leaded to an increase in storage modulus and a decrease in loss factor as revealed by dynamic mechanical analysis.The moisture absorption and elongation at break decrease while Young s modulus and tensile strengt...展开更多
Titanium matrix composites reinforced with a-Al2O3 and TiB2 particles were fabricated by in situ synthesis from a Ti-Al-B2O3 system. The reaction processes and microstructure were analyzed by using differential scanni...Titanium matrix composites reinforced with a-Al2O3 and TiB2 particles were fabricated by in situ synthesis from a Ti-Al-B2O3 system. The reaction processes and microstructure were analyzed by using differential scanning calorimetry（DSC）, scanning electron microscopy（SEM） and X-ray diffraction（XRD）. The results showed that the reactions in the Ti-Al-B2O3 system can occur spontaneously and consist of three steps： 1） 15 Al ＋ 7B2O3 → 7α-Al2O3 ＋ AlB12 ＋ 2B; 2） 14 B ＋ 2Al → AlB12 ＋ AlB2 and 3） 7Ti ＋ AlB（12） ＋ AlB2 → 7TiB2 ＋ 2Al. The final reinforcements were composed of α-Al2O3 and TiB2 particles, which were uniformly distributed in the titanium matrix.展开更多
文摘An experimental program was conducted to explore the impact of nanosilica on the microstructure and mechanical characteristics of cemented sandy soil.Cement agent included Portland cement type II.Cement content was 6% by weight of the sandy soil.Nanosilica was added in percentages of 0%,4%,8% and 12% by weight of cement.Cylindrical samples were prepared with relative density of 80% and optimum water content and cured for 7 d,28 d and 90 d.Microstructure characteristics of cementnanosilica-sand mixtures after 90 d of curing have been explored using atomic force microscopy(AFM),scanning electron microscopy(SEM) and X-ray diffraction(XRD) tests.Effects of curing time on microstructure properties of cemented sandy soil samples with 0% and 8% nanosilica have been investigated using SEM test.Unconfined compression test(for all curing times) and compaction test were also performed.The SEM and AFM tests results showed that nanosilica contributes to enhancement of cemented sandy soil through yielding denser,more uniform structure.The XRD test demonstrated that the inclusion of nanosilica in the cemented soil increases the intensity of the calcium silicate hydrate(CSH) peak and decreases the intensity of the calcium hydroxide(CH) peak.The results showed that adding optimum percentages of nanosilica to cement-stabilized sandy soil enhances its mechanical and microstructure properties.
文摘In the French concept of deep nuclear waste repositories,the galleries should be backfilled with excavated argillite after the site has been filled.Some additives like lime could be used to improve the mechanical characteristics of the argillite.After thousands of years,the degradation of the concrete lining of the galleries will generate an alkaline solution（pH value 12） that will diffuse through the backfill.This study presents the effect of a saturated Ca（OH）_2 solution circulation through lime-treated sample at 60 ℃ for 3,6 and 12 months,respectively.The effect of such circulation on the lime-treated Manois argillite（MA） was assessed by petrographical examination coupled to image analysis and scanning electron microscopy（SEM） equipped with energy dispersive X-ray（EDX） analyser of soil pieces.The objective of this study is to make the link among the mineralogical transformations,the textural and mechanical changes produced in the compacted clayey soil as a consequence of the alkaline solution circulation.
文摘Ce^（3＋） substituted Cu-spinel nanoferrites CuCe_xFe_（2-x）O_4（x=0.00, 0.02, 0.04, 0.06, 0.08 and 0.10） were synthesized via sol-gel self-combustion hybrid route. Single phase spinel ferrite of Cu nanoferrites were examined using X-ray diffraction（XRD） analysis whereas the multiphase structure was observed as Ce contents increased from x=0.06. Field emission scanning electron microscopy（FESEM）, Thermogravimetric and differential thermal analysis（TGA and DTA） and Fourier transform infrared spectroscopy（FTIR） were used to find out the morphology phase and metal stretching vibrations of Ce^（3＋） substituted nanocrystalline ferrites. The crystallite size was increased and found in the range of 25-91 nm. The agglomerations in Cu ferrite samples increase as the Ce^（3＋） concentration increases. The magnetic properties such as remanence, saturation magnetization, coercivity, Bohr magneton and magnetocrystalline anisotropy constant（K） were determined using M-H loops recorded from a vibrating sample magnetometer（VSM）. Saturation magnetization, remanence and coercivity are increased as the Ce^（3＋）contents increase in Cu nanocrystalline samples. Moreover, law of approach to saturation（LoA） was used to calculate the maximum value of saturation for Ce-doped Cu nanoferrites. The soft magnetic behaviour of the Cu nanoferrite is observed as compared to the samples substituted with the increased Ce contents in Cu nanocrystalline ferrite. Bohr magneton and magnetocrystalline anisotropy are found to increase with the substitution of rare earth Ce^（3＋） contents in Cu spinel nanocrystalline ferrite. Cedoped Cu nanocrystalline ferrites with excellent properties may be suitable for potential applications in sensing, security, switching, core, multilayer chip inductor, biomedical and microwave absorption applications.
文摘In this study,the effects of hybridizing micron-sized titanium particles with nano-sized boron carbide particles on the microstructural and mechanical properties of Mg-Ti composite were investigated.Microstructural characterization revealed grain refinement attributed to the presence of uniformly distributed micro-Ti particles embedded with nano-B_(4)C particulates.Electron back scattered diffraction(EBSD)analyses of the Mg-(Ti+B_(4)C)BM hybrid composite showed relatively more localized recrystallized grains and lesser tensile twin fraction,when compared to Mg-Ti.The evaluation of mechanical properties indicated that the best combination of strength and ductility was observed in the Mg-(Ti+B_(4)C)BM hybrid composite.The superior properties of the Mg-(Ti+B_(4)C)BM hybrid composite when compared to Mg-Ti can be attributed to the presence of nano-reinforcement,the uniform distribution of the hybridized particles and the better interfacial bonding between the matrix and the reinforcement particles achieved by nano-B_(4)C addition.
基金financially supported by the National Key Research and Development Program of China(Grant No.2022YFE0129800)the National Natural Science Foundation of China(Grant No.42202204)。
文摘In-situ upgrading by heating is feasible for low-maturity shale oil,where the pore space dynamically evolves.We characterize this response for a heated substrate concurrently imaged by SEM.We systematically follow the evolution of pore quantity,size(length,width and cross-sectional area),orientation,shape(aspect ratio,roundness and solidity)and their anisotropy—interpreted by machine learning.Results indicate that heating generates new pores in both organic matter and inorganic minerals.However,the newly formed pores are smaller than the original pores and thus reduce average lengths and widths of the bedding-parallel pore system.Conversely,the average pore lengths and widths are increased in the bedding-perpendicular direction.Besides,heating increases the cross-sectional area of pores in low-maturity oil shales,where this growth tendency fluctuates at<300℃ but becomes steady at>300℃.In addition,the orientation and shape of the newly-formed heating-induced pores follow the habit of the original pores and follow the initial probability distributions of pore orientation and shape.Herein,limited anisotropy is detected in pore direction and shape,indicating similar modes of evolution both bedding-parallel and bedding-normal.We propose a straightforward but robust model to describe evolution of pore system in low-maturity oil shales during heating.
基金Supported by the National Natural Science Foundation of China（No.51171094）.
文摘The inhibition effect of three azole compounds, 2-aminobenzimidazole（ABM）, 2-aminothiazole（AT） and 2-aminobenzothiazole（ABT）, on the corrosion of mild steel in a 1 mol/L HCI solution was investigated by means of potentiodynamic polarization measurement, electrochemical impedance spectroscopy（EIS） and scanning electron microscopy（SEM）. The correlation between inhibition efficiency and molecular structure of inhibitor was theoretically studied via quantum chemical calculations. The results show that the inhibition efficiency（η） of the inhibitors follows the order of ηABT〉ηAT〉ηABM. Moreover, ABM, AT and ABT belong to mixed-type inhibitors. The adsorption of the inhibitors on the steel surface follows the Langmuir adsorption isotherm, with both physisorption and chemisorption.
基金National Defense Foundation of China (No.51318030401).
文摘The change of conductivity, thickness and scanning electron microscopy （SEM） appearance of the anode film of CrWMn in 10% NaNO3 at different anode potential either with or without the magnetic field applied are investigated by testing film resistance, galvanostatic transient and using SEM to design magnetic circuit in magnetic assisted electrochemical machining （MAECM）. The experiments show that the anode film has semi-conducting property. Compared with the situation without magnetic field applied, the resistance of the film formed at 1 .SV （anode potential） increased and decreased at 4.0V while B=0.4T and the magnetic north pole points toward anode. The SEM photo demonstrates that the magnetic field will densify the film in the passivation area and quicken dissolution of the anode metal in over-passivation area. Based on the influence of magnetic field on electrochemical machining（ECM） due to the changes of the anode film conductivity behavior, the magnetic north pole should be designed to point towards the workpiece surface that has been machined. Process experiments agree with the results of test analysis.
基金supported by the National Natural Science Foundation of China(No.51304027)China Postdoctoral Science Foundation(2014M560567 and 2015T80730)+4 种基金Shandong Province Science and Technology Development Plan(2014GSF120012)the State Key Program of Coal Joint Funds of National Natural Science Foundation of China(Nos.51134020 and U1261205)Shandong Province Natural Science Foundation(No.ZR2011EL036)the Doctoral Scientific Research Foundation of Binzhou University(No.2013Y06)the Key Technology Projects for Preventing Major Accident of National Security State Administration of Work Safety
文摘In this study,orthogonal experiments were conducted to investigate the influence of expandable graphite(EG),dimethyl methylphosphonate(DMMP),triethanolamine(TEA),and isocyanate content on the compressive and bonding strengths,oxygen index,and fluidity of rigid polyurethane foam(RPUF).The results revealed that EG significantly increased the oxygen index of RPUF,enlarged the diameter of foam cells,and decreased the cell-closed content in foam;thus,leading to a pressure drop in RPUF.However,excessive EG was capable of reducing the fluidity of polyurethane slurry.TEA exhibited significant influence on the compressive strength of RPUF,which dropped initially,and then increased.DMMP had a remarkable effect on the flame retardant property and compressive strength of RPUF.Compressive strength of RPUF initially displayed an increase followed by a decrease with increasing dosage of DMMP,and achieved the maximum value at DMMP dosage of 4%.DMMP could effectively reduce the diameter of RPUF cells leading to an increase in the percentage of close area in foam.DMMP displayed the flame-retardation effects mainly in the gas phase leading to a significant enhancement in the oxygen index of RPUF.Moreover,the compressive strength and bonding strength of RPUF decrease significantly with the increase of isocyanate content due to the increased blowing efficiency by the CO_2.The oxygen index and flowing length of foam increased with the increase in isocyanate dosage.
文摘To meet the ever-increasing construction demands around the world during recent years,reinforcement and stabilization methods have been widely used by geotechnical engineers to improve the performances and behavior of fine-grained soils.Although lime stabilization increases the compressive strength of soils,it reduces the soil ductility at the same time.Recent research shows that random fiber inclusion modifies the brittleness of soils.In the current research,the effects of lime and polypropylene(PP)fiber additions on such characteristics as compressive and shear strengths,failure strain,secant modulus of elasticity(E50)and shear strength parameters of mixtures were investigated.Kaolinite was treated with 1%,3% and 5% lime by dry weight of soil and reinforced with 0.1% monovalent PP fibers with the length of 6 mm.Samples were prepared at optimum conditions and cured at 35℃ for 1 d,7 d and 28 d at 90% relative humidity and subsequently subjected to uniaxial and triaxial compression tests(UCT and TCT)under cell pressures of 25 kPa,50 kPa and 100 kPa.Results showed that inclusion of random PP fibers to clay-lime mixtures increases both compressive and shear strengths as well as the ductility.Lime content and curing period were found to be the most influential factors.Scanning electron microscopy(SEM)analysis showed that lime addition and the formation of cementitious compounds bind soil particles and increase soil/fiber interactions at interface,leading to enhanced shear strength.The more ductile the stabilized and reinforced composition,the less the cracks in roads and waste landfill covers.
基金the Natural Sciences and Engineering Research Council(NSERC)of CanadaNational Natural Science Foundation of China(Grant Nos.12202430,12241202)+1 种基金USTC Research Funds of the Double First-Class Initiative(Grant No.YD2090002011)the China Scholarship Council。
文摘The exceptional physical properties and unique layered structure of two-dimensional(2D)materials have made this class of materials great candidates for applications in electronics,energy conversion/storage devices,nanocomposites,and multifunctional coatings,among others.At the center of this application space,mechanical properties play a vital role in materials design,manufacturing,integration and performance.The emergence of 2D materials has also sparked broad scientific inquiry,with new understanding of mechanical interactions between 2D structures and interfaces being of great interest to the community.Building on the dramatic expansion of recent research activities,here we review significant advances in the understanding of the elastic properties,in-plane failures,fatigue performance,interfacial shear/friction,and adhesion behavior of 2D materials.In this article,special emphasis is placed on some new 2D materials,novel characterization techniques and computational methods,as well as insights into deformation and failure mechanisms.A deep understanding of the intrinsic and extrinsic factors that govern 2D material mechanics is further provided,in the hopes that the community may draw design strategies for structural and interfacial engineering of 2D material systems.We end this review article with a discussion of our perspective on the state of the field and outlook on areas for future research directions.
基金Project supported by the National Natural Science Foundation of China(No.20973152)the Zhejiang Provincial Natural Science Foundation of China(No.Y2080045)
文摘Objective:This study deals with the effect of phosphoric acid etching and conditioning on enamel micro-tensile bond strengths(μTBSs)of conventional and resin-modified glass ionomer cements(GICs/RMGICs).Methods:Forty-eight bovine incisors were prepared into rectangular blocks.Highly-polished labial enamel surfaces were either acid-etched,conditioned with liquids of cements,or not further treated(control).Subsequently,two matching pre-treated enamel surfaces were cemented together with one of four cements[two GICs:Fuji I(GC),Ketac Cem Easymix(3M ESPE);two RMGICs:Fuji Plus(GC),RelyX Luting(3M ESPE)]in preparation forμTBS tests.Pre-treated enamel surfaces and cement-enamel interfaces were analyzed by scanning electron microscopy(SEM).Results:Phosphoric acid etching significantly increased the enamelμTBS of GICs/RMGICs.Conditioning with the liquids of the cements produced significantly weaker or equivalent enamelμTBS compared to the control.Regardless of etching,RMGICs yielded stronger enamelμTBS than GICs.A visible hybrid layer was found at certain enamelcement interfaces of the etched enamels.Conclusions:Phosphoric acid etching significantly increased the enamelμTBSs of GICs/RMGICs.Phosphoric acid etching should be recommended to etch the enamel margins before the cementation of the prostheses such as inlays and onlays,using GICs/RMGICs to improve the bond strengths.RMGICs provided stronger enamel bond strength than GICs and conditioning did not increase enamel bond strength.
基金supported by the Kirikkale University Scientific Research Fund(Nos.2008/34 and 2008/35)
文摘The kinetic,morphological,crystallographic,and magnetic characteristics of thermally induced martensites in Fe-13.4wt% Mn-5.2wt%Mo alloy were investigated by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,and M（o｜¨）ssbauer spectroscopy.The experimental results reveal that two types of thermal-induced martensites,e（hcp） andα＇（bcc） martensites,are formed in the as-quenched condition,and these transformations have athermal characters.Mo addition to the Fe-Mn alloy does not change the coexistence ofεandα＇ martensites with the Mn content between 10wt%and 15wt%.Besides,M（o｜¨）ssbauer spectra reveal a paramagnetic character with a singlet for theγ（fcc） austenite andεmartensite phases and a ferromagnetic character with a broad sextet for theα＇ martensite phase. The volume fraction ofα＇ martensite forming in the quenched alloy is much more than that of theεmartensite.
基金Supported by the Science & Technology Development Program of Jilin Province,China(No.20100537)
文摘The mechanical properties of fibers were notably improved by incorporating 2,2＇-bis（trifluoromethyl）benzidine（TFMB） into 3,3＇,4,4＇-biphenyltetracarboxylic dianhydride（s-BPDA） and p-phenylenediamine（PPD） backbone.The best strength and modulus of BPDA/PPD/TFMB polyimide（PI） fiber（diamine molar ratio of PPD/TFMB= 90/10） were 1.60 and 90 GPa,respectively,which was over two times that of BPDA/PPD PI fiber.SEM image showed that the cross-section of fibers at each stage was round and voids free.Besides,the ＂skin-core＂ and microfibrillar structure were not observed.The thermal properties of PI fibers were also investigated.The results showed that the fibers owned excellent thermal stability,moreover,the structural homogeneity of fibers were significantly improved by heat-drawn stage.The T g values were found to be around 300 °C by dynamic mechanical analysis（DMA）.Wide angle X-ray diffraction（WAXD） and small angle X-ray scattering（SAXS） experiments indicated that the order degree of longitudinal and lateral stacks,the molecular orientation and the structural homogeneity of fibers were improved in the preparation process of fibers.
基金Funded by the National Natural Science Foundation of China(No.50801057)the National Basic Research Priorities Program of China(No.2005DKA10400-CT-1-08-06)+1 种基金the Special Fund for Basic Scientific Research of Central Colleges,China University of Geosciences(Wuhan)(No.007-G1323521109)the National Natural Science Fundation of China(81641035 and 81401524)
文摘The aim of this work was to study the degradation behavior of Ti-6Al-4V alloys for dental applications in acidic artificial saliva with fluoride ion using electrochemical techniques, optical microscopy, scanning electron microscopy（SEM）, and energy dispersive spectrometry（EDS）. The experimental results showed that fluoride ion had significant influence on the degradation of Ti-6Al-4V alloys, and there was an obvious critical concentration of fluoride ion（about 0.1wt%）. With increasing fluoride ion concentration, the corrosion potential（Ecorr） of alloys moved toward negative and the impedance of alloys decreased, meanwhile, noticeable transformation from minimum corrosion to severe pitting corrosion was observed on alloys surface following the dissolution of TiO2 passive films, leading to the decrease of the corrosion resistance of alloys. The electrochemical dissolution of TiO2 passive films involved a nucleophilic attack of fluoride atom to the titanium atom of TiO2. In addition, Ca^（2＋）and Na~＋ in acidic saliva may involve the surface reactions and make the reactions more complex.
基金funded by the Natural Science Foundation of the Inner Mongolia Autonomous Region(Grant No.2020BS04003)the Project of High-Level Talent Research in Inner Mongolia University(Grant No.12000-15031942)the National Natural Science Foundation of China(Grant No.51778590,51879131).
文摘Unsaturated loess in natural sites loses stability as the overburden load continuously increases.Traditional soil modifiers such as cement and fly ash affect the surrounding environment.A new type of material,i.e.,lignin,is environmentally friendly and able to increase the strength of loess.However,the engineering characteristics of the improved loess under unsaturated conditions are not yet clear.In this study,the soil-water characteristic curves(SWCCs)of lignin-improved loess samples were determined from 0 kPa to 700 kPa using a pressure plate instrument,and then,they were fitted using the van Genuchten(VG)model and the Fredlund and Xing(FX)model.In addition,the effects of the lignin content and sample preparation methods on the SWCCs were investigated to determine the optimal lignin content and a suitable sample preparation method for loess foundations.As the lignin content increases,the matric suction and residual water content of the improved loess increase.The suction stress increases with the increasing lignin contents of 1%–2%.At lignin contents of 3%–4%,the suction stress begins to decrease and the samples prepared using the slurry method has a lower suction stress than that prepared using the wet mixing method.The air entry value(AEV)increases with increasing lignin content.In addition,scanning electron microscopy(SEM)was used to investigate the microstructural variations.It was found that after the addition of lignin,the entrapment of the loess particles by the lignin fibers created some larger particles and smaller pore diameters,which in turn led to poor connectivity of the loess pores.These changes cause the matric suction of the modified loess to increase.
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.
基金supported by the National Natural Science Foundation of China (Nos. 41201065, 41121001, 41261017, 41171057, 41161012)Funds for Creative Research Groups of China (No. 41121001)+3 种基金the Foundation for Excellent Youth Scholars of CAREERI, CAS (No. 51Y251B51)the SKLCS Foundation (No. SKLCSZZ-2012-01-01)the National Basic Research Program of China (Nos. 2010CB951003, 2010CB951404)the Knowledge Innovation Project of the Chinese Academy of Sciences (No. KZCX2-EW-311)
文摘Aerosol samples were collected in the Shiyi Glacier, Qilian Mountains from July 24 to August 19, 2012 and analyzed for major water-soluble ionic species(F-, Cl-, NO2-, NO3-, SO42-, Na+, NH4+, K+, Mg2+and Ca2+) by ion chromatography. SO42-and NH4+were the most abundant components of all the anions and cations, with average concentrations of 94.72 and 54.26 neq/m3, respectively, accounting for 34% and 20% of the total water-soluble ions analyzed. These mean ion concentrations were generally comparable with the background conditions in remote sites of the Qilian Mountains, but were much lower than those in certain cities in China. The particles were grouped into two dominant types according to their morphology and EDX signal: Si-rich particles and Fe-rich particles. Backward air mass trajectory analysis suggested that inland cities may contribute some anthropogenic pollution to this glacier, while the arid and semi-arid regions of central Asia were the primary sources of the mineral particles.
基金the National Natural Science Foundation of China(No.50473039).
文摘Environmentally friendly thermosetting composites were successfully prepared by conventional blending wheat gluten as matrix,glycerol as plasticizer and silica as filler followed by thermo-molding of the mixture at 120℃.The strong interfacial interaction between silica particles and gluten proteins leaded to an increase in storage modulus and a decrease in loss factor as revealed by dynamic mechanical analysis.The moisture absorption and elongation at break decrease while Young s modulus and tensile strengt...
基金Funded by National Natural Science Foundation of China(Nos.51571118 and 51371098)Natural Science Foundation of Jiangsu Province(No.BK20141308)
文摘Titanium matrix composites reinforced with a-Al2O3 and TiB2 particles were fabricated by in situ synthesis from a Ti-Al-B2O3 system. The reaction processes and microstructure were analyzed by using differential scanning calorimetry（DSC）, scanning electron microscopy（SEM） and X-ray diffraction（XRD）. The results showed that the reactions in the Ti-Al-B2O3 system can occur spontaneously and consist of three steps： 1） 15 Al ＋ 7B2O3 → 7α-Al2O3 ＋ AlB12 ＋ 2B; 2） 14 B ＋ 2Al → AlB12 ＋ AlB2 and 3） 7Ti ＋ AlB（12） ＋ AlB2 → 7TiB2 ＋ 2Al. The final reinforcements were composed of α-Al2O3 and TiB2 particles, which were uniformly distributed in the titanium matrix.
