It is imperative to develop multifunctional erosion and corrosion resistant coatings for compressor blades of aircraft engines in harsh environment.PVD(Physical Vapor Deposition)technology has the advances in processi...It is imperative to develop multifunctional erosion and corrosion resistant coatings for compressor blades of aircraft engines in harsh environment.PVD(Physical Vapor Deposition)technology has the advances in processing erosion-resistant coatings;however,the performance of PVD coatings to combat corrosion depends on various coating defects.Determining and comparing the corrosion performances of PVD TiN/Ti coating and uncoated TC4 alloy was the main objective of present work.The 960 h salt spray corrosion and 116 h hot corrosion tests were conducted to simulate the grounding and working environments of the aircraft compressors.The corrosion mechanisms due to the coating defects such as pinhole,columnar boundary and large grain were analyzed based on the OM,Confocal microscope,electrochemical measurements,SEM,XRD and EDS results.Owing to the disordered state associated with the columnar boundary and the coating defect,nitrogen could be easily replaced by oxygen in the hot corrosion process,these structures were channels for fast diffusion of oxygen.Moreover,the Gibbs energy changes of Ti oxidation and TiN oxidation were thermodynamically calculated according to the working condition of aircraft compressors,and considerable research effort was focused on mapping out the phase diagram of Ti,TiN and high pressure gases.The findings of this research can provide insights into developing multifunctional coatings for future aircraft engines.展开更多
Fe/Mo composite coatings were prepared by air plasma spraying （APS） using Fe-based and Mo-based amorphous and nanocrys- talline mixed powders. Microstructural studies show that the composite coatings present a layer...Fe/Mo composite coatings were prepared by air plasma spraying （APS） using Fe-based and Mo-based amorphous and nanocrys- talline mixed powders. Microstructural studies show that the composite coatings present a layered structure with low porosity due to adding the self-bonded Mo-based alloy. Corrosion behaviors of the composite coatings, the Fe-based coatings and the Mo-based coatings were in- vestigated by electrochemical measurements and salt spray tests. Electrochemical results show that the composite coatings exhibit a lower polarization current density and higher corrosion potentials than the Fe-based coating when tested in 3.5wt% NaC1 solutions, indicating supe- rior corrosion resistance compared with the Fe-based coating. Also with the increase in addition of the Mo-based alloy, a raised corrosion re- sistance, inferred by an increase in corrosion potential and a decrease in polarization current density, can be found. The results of salt spray tests again show that the corrosion resistance is enhanced by adding the Mo-based alloy, which helps to reduce the porosity of the composite coatings and enhance the stability of the passive films.展开更多
Three novel Cu-Ni-A1 brazing filler alloys with Cu/Ni weight ratio of 4：1 and 2.5-10 wt% Al were developed and characterized, and the wetting of three Cu-Ni-Al alloys on WC-8Co cemented carbide were investigated at 1...Three novel Cu-Ni-A1 brazing filler alloys with Cu/Ni weight ratio of 4：1 and 2.5-10 wt% Al were developed and characterized, and the wetting of three Cu-Ni-Al alloys on WC-8Co cemented carbide were investigated at 1190-1210 ℃ by the sessile drop technique. Vacuum brazing of the WC-8Co cemented carbide to SAE1045 steel using the three Cu-Ni-Al alloys as filler metal was further carried out based on the wetting test results. The interfacial interactions and joint mechanical behaviors involving microhardness, shear strength and fracture were analyzed and discussed. The experimental results show that all the three wetting systems present excellent wettability with final contact angles of less than 5 °and fast spreading. An obvious degeneration layer with continuous thin strip forms in the cemented carbide adjacent to the Cu-Ni-A1/WC-8Co interface. The variation of microhardness in the joint cross-section is closely related to the interactions （such as diffusion and solid solution） of WC-8Co/Cu-Ni-Al/steel sys- tem. Compared with the other two brazed joints, the WC-8Co/Cu-19Ni-SAl/steel brazed joint presents more reliable interlayer microstructure and mechanical property while brazing at the corresponding wetting temperatures for 5 rain, and its average shear strength is over 200 MPa after further optimizing the brazing temperature and holding time. The joint shear fracture path passes along the degeneration layer, Cu-Ni-A1/WC-8Co interface and brazing interlayer, showing a mixed ductile-brittle fracture.2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.展开更多
To research the dynamic mechanical properties and road performances of flame retardant asphalt mortars and mixtures, four different asphalt mortars/mixtures were prepared: a reference group and three asphalt mortars/m...To research the dynamic mechanical properties and road performances of flame retardant asphalt mortars and mixtures, four different asphalt mortars/mixtures were prepared: a reference group and three asphalt mortars/mixtures containing composite flame retardant materials(M-FRs) of different proportions. Temperature sweep, frequency sweep, repeated creep test, force ductility test and bending beam rheological test were carried out to research the dynamic mechanical properties of asphalt mortars containing M-FRs; wheeltracking test, low-temperature bending test and freeze-thaw split test were used to study the road performances of asphalt mixtures containing M-FRs. The results show that high-temperature performances of the three flame retardant asphalt mortars improve greatly, while low-temperature cracking resistances decline. Both hightemperature performances and water stabilities of asphalt mixtures containing M-FRs are quite good and exceed the specification requirements. However, their low-temperature performances decline in different degrees. In summary, besides their good flame retardancy, the flame retardant asphalt mortars and mixtures also exhibit acceptable road performance.展开更多
Ni-base metal–intermetallic laminate composites were obtained from in situ reaction synthesis between Ni and Al foils by utilizing plasma activated sintering. The effects of Ni foil thickness on the microstructure an...Ni-base metal–intermetallic laminate composites were obtained from in situ reaction synthesis between Ni and Al foils by utilizing plasma activated sintering. The effects of Ni foil thickness on the microstructure and tensile properties of the composites were investigated. The results show that the phases forming during reaction synthesis are independent of the starting thickness of the Ni foils. However, thicker reacted layers are obtained in the samples fabricated from 100 lm Ni foils（Ni100） than those obtained in the samples from 50 lm Ni foils（Ni50）when treated at the same process. The tensile strength of Ni100 samples increases with the temperature increasing at the expense of ductility. Dissimilarly, Ni50 composites treated at higher temperatures exhibit enhanced strength and ductility. Both Ni50 and Ni100 laminate fracture in a similar mechanism. Cracking first occurs in the brittle intermetallic layers. These original cracks result in shear bands in Ni layers emitted from the crack tips, and thus producing local stress concentration, which initiates new cracks in adjacent intermetallic layers. The multiplication of cracks and shear bands leads to the failure of the laminates.展开更多
The semi-solid deformation behavior of Til4 was investigated using compression tests at deformation temperatures between 1 273 and 1 423 K with strain rate of 5×10^-2 s^-1. Moreover, the fraction solid at differe...The semi-solid deformation behavior of Til4 was investigated using compression tests at deformation temperatures between 1 273 and 1 423 K with strain rate of 5×10^-2 s^-1. Moreover, the fraction solid at different temperatures was also measured by image analysis. The results showed that the deformation temperature had strong effects on the flow stress, and the stress increased with the decrease of deformation temperature. The maximum stress depended greatly on the fraction solid, and a sharp decrease in stress occurred at a solid fraction between 0.94 and 0.98 （temperature from 1 323 to 1 373 K）. This decrease was related to the decrease in the amount of solid bridges between grains. Because of the partial solid/liquid segregation during deformation, the experimental strain rates were much lower than those calculated by the flow of liquid incorporating solid particles, which suggested that the main deformation mechanism between 1 323 and 1 373 K was still plastic deformation of solid particles.展开更多
Two highly emissive pyrenoviologen derivatives were synthesized and used to fabricate fluorescent sensors for detection of picric acid(PA)with good sensitivity and selectivity.The sensitivity of the sensor was attribu...Two highly emissive pyrenoviologen derivatives were synthesized and used to fabricate fluorescent sensors for detection of picric acid(PA)with good sensitivity and selectivity.The sensitivity of the sensor was attributed to the specific electrostatic association effect of the cationic pyrenoviologens to the picrate anions,which also gave the sensor special selectivity among other compounds with similar structure.The electron transfer between them was attributed to the fluorescence response.Fluorescence lifetime measurements revealed that the quenching is static in nature.The novel and efficient pyrenoviologen derivatives-based sensors offered a strategy to fabricate real-life PA sensor.展开更多
Geopolymer concrete(GPC)has been developed as a sustainable alternative to traditional cement-based concrete using industrial waste materials.Thus,reducing greenhouse gas emissions in concrete production can be expect...Geopolymer concrete(GPC)has been developed as a sustainable alternative to traditional cement-based concrete using industrial waste materials.Thus,reducing greenhouse gas emissions in concrete production can be expected.This study employed the life cycle assessment(LCA)method to evaluate geopolymer concrete's cost and life-cycle carbon dioxide(CO_(2))emissions.Moreover,the critical transportation radius of the geopolymer is estimated.Then,evaluation results were compared with ordinary Portland cement(OPC),considering three concrete construction methods:cast-in-place,ready-mixed,and precast.In particular,the service life of two types of concrete in sulfuric acid environments is considered.Compared with OPC concrete,the results show that geopolymer concretes can significantly reduce the cost and CO_(2)emissions when one or a small amount of alkali activator is used or alkali-containing materials are used to replace some alkali activators.However,the advantages would be reversed by the rising alkali dosages,which account for cost increases and carbon emissions.When considering the service life in special environments,geopolymer concrete in sulfuric acid environments corresponds to fewer carbon emissions,94%-97%decreased compared with OPC concrete.Finally,compared with OPC concrete,the newly developed limestone calcined clay cement(LC3)avoids high-temperature calcination and dramatically reduces carbon dioxide emissions.Compared to OPC concrete,LC3 concrete has a 19%reduction in CO_(2) emissions.And geopolymer concrete that takes alkali-activate materials for superseding alkalis also produces less carbon dioxide emissions.In particular,CO_(2) emissions from FA-SF geopolymer concrete are approximately 50%lower than OPC concrete.In addition,the use of alkali activators significantly weakens the cost advantage of geopolymers.But after accounting for waste disposal costs,the average net cost of fly ash-based geopolymer concrete can be more than 30% lower than that of OPC concrete.The average net cost of slag-based geopolymer concrete is 7%-45%lower than that of OPC concrete.The findings of this work provide the basis for further development of geopolymer concretes obeyed environmental protection.展开更多
Salt freezing damage has severe impacts on durability of cement-based materials(CBMs).Calcined layered double hydroxide(CLDH),as an efficient environmental-friendly adsorption material,can impart excellent salt freezi...Salt freezing damage has severe impacts on durability of cement-based materials(CBMs).Calcined layered double hydroxide(CLDH),as an efficient environmental-friendly adsorption material,can impart excellent salt freezing resistance to CBMs.In this work,salt freezing resistance improvement of CBMs incorporated with CLDH was experimentally evaluated by chloride binding capacity,mass loss rate,relative dynamic elastic modulus,setting time,compressive strength,and micro structure tests.Beside these,the salt freezing damage model was established to effectively express the quantitative relationship between influencing factors and evaluation indexes of the salt freezing resistance of CBMs.Results show that CLDH can reconstruct its original layered structure to form reconstructed layered double hydroxide(RLDH).RLDH combines with chloride ions to form RLDH-Cl recrystallization,which can improve chloride binding capacity and pore structures of CBMs to relieve the salt freezing damage.The salt freezing damage model indicates that the suitable CLDH content can evidently alleviate the salt freezing damage,which facilitates the quantitative analysis of the effect of CLDH on the salt freezing resistance of CBMs.展开更多
Infectious disease outbreaks have seriously endangered global health owing to the scarcity of testing materials and techniques.Diversified materials and methods should be urgently developed for rapid detection and dis...Infectious disease outbreaks have seriously endangered global health owing to the scarcity of testing materials and techniques.Diversified materials and methods should be urgently developed for rapid detection and discrimination of pathogenic microorganisms.Conjugated polymer(CP)materials are macromolecular compounds comprising numerous covalently bonded luminescent units.They have excellent light-harvesting and optical signal amplification capabilities owing to the transmission of excitation energy along their backbone.In recent years,CP materials have aroused research enthusiasm in the biosensors field because of their outstanding optoelectronic properties.This brief manuscript provides an overall review of recent progress achieved in CP-based systems for pathogen sensing.展开更多
Ice adhesion to materials is a significant concern in many fields. Hydrophobic surface has been used for anti-icing in fields of aircraft or transmission line, which prove to be efficacious and economical. However, su...Ice adhesion to materials is a significant concern in many fields. Hydrophobic surface has been used for anti-icing in fields of aircraft or transmission line, which prove to be efficacious and economical. However, such technique is seldom employed for road deicing, because of the texture and service environment of pavement. Instead, deicers such as rock salt are frequently used, which leads to serious corrosion problem of roads and bridges. In this paper, a number of studies that characterize mechanism of ice adhesion to common substrates, specifically to pavement, are reviewed. The most important researches undertaken on ice adhesion strength affecting factors are presented. An overview of studies carried out to find hydrophobie surface for asphalt and cement concrete pavement antiicing are presented. It was verified that the hydrophobicity had high correlation with icephobicity, and nano-engineered asphalt and cement concrete pavement surface exhibited favorable hydrophobicity, and also had good performance on weakening pavement-ice bonding. However, most ice-repelling pavements obtain hydrophobic surface via low surface energy coating, which could not exist on pavement for a long time under wheel abrasion. And the nano/micro structures on hydrophobic surfaces are also vulnerable and consumable. Thus, the long-term effect of hydrophobic surface still need to be improved, and durability of the hydrophobic surface should be the research and development priorities of ice-repelling pavement.展开更多
Numerous studies showed that synthetic fibers are effective for reinforcing the mechanical performance of the asphalt mixture due to their high strength properties,ductility,and durability characteristics.In this pape...Numerous studies showed that synthetic fibers are effective for reinforcing the mechanical performance of the asphalt mixture due to their high strength properties,ductility,and durability characteristics.In this paper,the objective is to present a review of the reinforcement effect of synthetic fiber on the mechanical performance of the asphalt mixture.This paper reviews the relevant literature on the characterizations and applications of synthetic fibers to improve different mechanical properties of asphalt mixes,which can provide a reference for the applications and development of synthetic fibers in asphalt pavement.The characteristics of common synthetic fibers are introduced and the utilization of synthetic fibers in asphalt mixture is discussed.Different surface treatment methods for fiber are reviewed and it is found that surface treatment can improve the performance of the synthetic fibers in asphalt mixtures,especially the chemical surface treatment method.The influence of synthetic fiber addition on the mechanical properties of the asphalt concrete such as rutting resistance,tensile strength,water stability performance,and cracking resistance are then discussed.The research results show that aramid,glass,and polyester fibers improve the fatigue cracking resistance of asphalt mixture.Polyester fibers,polyamide fibers,and carbon fibers are used to improve resistance to the permanent deformation of asphalt pavement.展开更多
Spherical AlN powders with micrometer size have attracted great attention owing to their good fluidity and dispersity. However, the industrial preparation methods usually require high temperature and long soaking time...Spherical AlN powders with micrometer size have attracted great attention owing to their good fluidity and dispersity. However, the industrial preparation methods usually require high temperature and long soaking time, which lead to the high cost and limit the wide application of the products. Herein, nearly spherical AlN particles with the average size of 2.5 μm were successfully synthesized via an in-situ combustion synthesis method. The effect of N_(2) pressure, NH_(4)Cl content, and Al particle size on the combustion reaction procedure, phase composition, and microstructure of the products was systematically investigated. The results showed that the decreased N_(2) pressure, increased NH_(4)Cl content, and Al particle size led to the decreasing of combustion temperature and speed, which further affected the morphology of the products. As a result, low N_(2) pressure(0.2 MPa), a small amount of NH4Cl(0.5 wt%), and fine Al particles(~2.5 μm) contributed to a moderate combustion temperature and facilitated the formation of nearly spherical AlN particles. In addition, based on the gas-releasing assisted quenching experiments and thermo-kinetic analysis, a two-step growth mechanism for the nearly spherical AlN particles was rationally proposed. The present method shows the advantages of low cost and high efficiency for preparing nearly spherical AlN particles, which can be used as raw materials for electronic substrates and fillers for packaging materials.展开更多
Prompting high content of reclaimed asphalt pavement(RAP) to be used in road building and maintenance has drawn great attention. The application of rejuvenators is an efficient way to ensure the performance of recycle...Prompting high content of reclaimed asphalt pavement(RAP) to be used in road building and maintenance has drawn great attention. The application of rejuvenators is an efficient way to ensure the performance of recycled asphalt mixtures. However, as various types of rejuvenators emerging, limited understanding about rejuvenation poses challenges to put effective ones into use. For precisely evaluating the performance of rejuvenators, plenty of studies were conducted to ascertain the fundamental mechanism of rejuvenating from the microscopic view. This paper provides an overview of studies focusing on the change inside asphalt after adding rejuvenators. Chemical compositions of rejuvenators were collected as basic information. Both laboratorial experiments and molecular dynamic simulations were investigated to not only compare the effectiveness of several rejuvenators but also explain the rejuvenating mechanism. Finally, functional groups of rejuvenator structures were comprehensively examined to provide global understanding about how chemical compositions influence the efficacy of rejuvenators. This review highlights that the essential capacity of a true rejuvenator is to disturb asphaltene agglomerations. Besides, the molecular structures of rejuvenators will not only affect their deagglomerating abilities but also the performances of diffusion and durability. It has been found that gel-permeation chromatography(GPC) analysis is effective in evaluating the performance of rejuvenators, while Fourier transform infrared spectroscopy(FT-IR) and SARA(saturates, aromatics, resins and asphaltenes) analysis are only suitable for assessing asphalt oxidization. In addition, comparing some tests can only detect changes, molecular dynamic simulation can reveal the mechanism both of data and vision. The results of this work can provide comprehensive knowledge for the evaluation and development of rejuvenators.展开更多
Two-electron neutral aqueous organic redox flow batteries(AORFBs)hold more promising applications in the power grid than one-electron batteries because of their higher capacity.However,their development is strongly li...Two-electron neutral aqueous organic redox flow batteries(AORFBs)hold more promising applications in the power grid than one-electron batteries because of their higher capacity.However,their development is strongly limited by the structural instability of the highly reduced species.By combining the extendedπ-conjugation structure of the anolytes and the enhanced aromaticity of the highly reduced species,we reported a series of highly conjugated and inexpensive arylene diimide derivatives(NDI,PDI,and TPDI)as novel two-electron storage anolyte materials for ultrastable AORFBs.Matched with(ferrocenylmethyl)trimethylammonium chloride(FcNCl)as catholyte,arylene diimide derivative-based AORFBs showed the highest stability in two-electron AORFBs to date.The NDI/FcNCl-based AORFB delivered 98.44%capacity retention at 40 mA cm^(−2)for 350 cycles;TPDI/FcNCl-based AORFB also showed remarkable stability with 97.22%capacity retention at 20 mA cm^(−2)over 200 cycles.This finding lays the theoretical foundation and offers a reference for improving the stability of two-electron AORFBs.展开更多
Microwave heating,which is used for pre-treatment of concrete before it is comminuted,stands as a strong candidate for selective liberation of multiphase materials like concrete.This paper is concerned with the select...Microwave heating,which is used for pre-treatment of concrete before it is comminuted,stands as a strong candidate for selective liberation of multiphase materials like concrete.This paper is concerned with the selective liberation of concrete's raw constituents(particularly aggregate)for recycling by considering the water content of concrete as a parameter of microwave heating for the first time.The deterioration law of the concrete's performance was characterized by the variation in the splitting tensile strength and relative dynamic modulus after heating by microwave at different water contents.Besides,tests were conducted to evaluate the performance of the interface transition zone(ITZ)between aggregate and mortar as well as to investigate the reasons for the stripping behavior of aggregate-mortar,which included the interface tensile strength test,temperature measurement,and porosity test.The deterioration law of splitting tensile strength and relative dynamic modulus revealed that the performance of concrete was subject to different degrees of damage depending on the water content.Furthermore,experimental results showed that interface bonding strength between aggregate and mortar was dramatically impaired,and a large temperature difference was generated between the aggregate and mortar during microwave heating.Meanwhile,the permeable pores increased considerably even when the specimens were dried.In the presence of water,the intactness of ITZ between aggregate and mortar was destroyed by microwave heating,and its performance was significantly lowered,which led to the occurrence of stripping behavior between aggregate and mortar.This was reaffirmed by the microstructure presented by scanning electron microscopy.Thus,the newly developed microwave pretreatment improved by providing appropriate water contents for concrete corresponding to different strength grades is a promising method for recycling aggregate from waste concrete.展开更多
基金supported by National Science and Technology Major Project of China(2017-VII-0012-0107)National Natural Science Foundation of China(No.51405506)Natural Science Basic Research Plan in Shaanxi Province of China(No.2019JQ-309)。
文摘It is imperative to develop multifunctional erosion and corrosion resistant coatings for compressor blades of aircraft engines in harsh environment.PVD(Physical Vapor Deposition)technology has the advances in processing erosion-resistant coatings;however,the performance of PVD coatings to combat corrosion depends on various coating defects.Determining and comparing the corrosion performances of PVD TiN/Ti coating and uncoated TC4 alloy was the main objective of present work.The 960 h salt spray corrosion and 116 h hot corrosion tests were conducted to simulate the grounding and working environments of the aircraft compressors.The corrosion mechanisms due to the coating defects such as pinhole,columnar boundary and large grain were analyzed based on the OM,Confocal microscope,electrochemical measurements,SEM,XRD and EDS results.Owing to the disordered state associated with the columnar boundary and the coating defect,nitrogen could be easily replaced by oxygen in the hot corrosion process,these structures were channels for fast diffusion of oxygen.Moreover,the Gibbs energy changes of Ti oxidation and TiN oxidation were thermodynamically calculated according to the working condition of aircraft compressors,and considerable research effort was focused on mapping out the phase diagram of Ti,TiN and high pressure gases.The findings of this research can provide insights into developing multifunctional coatings for future aircraft engines.
基金financially supported by the Special Fund for Basic Scientific Research of Central Colleges, Chang’an University (No.CHD2011JC126)the Special Fund for Basic Research Support Plan of Chang’an Universitythe Open Fund of the Engineering Research Center of Transportation Materials, Ministry of Education of China
文摘Fe/Mo composite coatings were prepared by air plasma spraying （APS） using Fe-based and Mo-based amorphous and nanocrys- talline mixed powders. Microstructural studies show that the composite coatings present a layered structure with low porosity due to adding the self-bonded Mo-based alloy. Corrosion behaviors of the composite coatings, the Fe-based coatings and the Mo-based coatings were in- vestigated by electrochemical measurements and salt spray tests. Electrochemical results show that the composite coatings exhibit a lower polarization current density and higher corrosion potentials than the Fe-based coating when tested in 3.5wt% NaC1 solutions, indicating supe- rior corrosion resistance compared with the Fe-based coating. Also with the increase in addition of the Mo-based alloy, a raised corrosion re- sistance, inferred by an increase in corrosion potential and a decrease in polarization current density, can be found. The results of salt spray tests again show that the corrosion resistance is enhanced by adding the Mo-based alloy, which helps to reduce the porosity of the composite coatings and enhance the stability of the passive films.
基金supported by the National Natural Science Foundation of China (No. 51572112)the Natural Science Foundation of Jiangsu Province (No. BK20151340)+2 种基金the Six Talent Peaks Project of Jiangsu Province (No. 2014-XCL-002)the Innovation/Entrepreneurship Program of Jiangsu Province (No. [2015]26)the Qing Lan Project (No. [2016]15)
文摘Three novel Cu-Ni-A1 brazing filler alloys with Cu/Ni weight ratio of 4：1 and 2.5-10 wt% Al were developed and characterized, and the wetting of three Cu-Ni-Al alloys on WC-8Co cemented carbide were investigated at 1190-1210 ℃ by the sessile drop technique. Vacuum brazing of the WC-8Co cemented carbide to SAE1045 steel using the three Cu-Ni-Al alloys as filler metal was further carried out based on the wetting test results. The interfacial interactions and joint mechanical behaviors involving microhardness, shear strength and fracture were analyzed and discussed. The experimental results show that all the three wetting systems present excellent wettability with final contact angles of less than 5 °and fast spreading. An obvious degeneration layer with continuous thin strip forms in the cemented carbide adjacent to the Cu-Ni-A1/WC-8Co interface. The variation of microhardness in the joint cross-section is closely related to the interactions （such as diffusion and solid solution） of WC-8Co/Cu-Ni-Al/steel sys- tem. Compared with the other two brazed joints, the WC-8Co/Cu-19Ni-SAl/steel brazed joint presents more reliable interlayer microstructure and mechanical property while brazing at the corresponding wetting temperatures for 5 rain, and its average shear strength is over 200 MPa after further optimizing the brazing temperature and holding time. The joint shear fracture path passes along the degeneration layer, Cu-Ni-A1/WC-8Co interface and brazing interlayer, showing a mixed ductile-brittle fracture.2018 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.
基金Funded by the National Key Technology R&D Program for the 12th Five-Year Plan(No.2011BAE27B04)
文摘To research the dynamic mechanical properties and road performances of flame retardant asphalt mortars and mixtures, four different asphalt mortars/mixtures were prepared: a reference group and three asphalt mortars/mixtures containing composite flame retardant materials(M-FRs) of different proportions. Temperature sweep, frequency sweep, repeated creep test, force ductility test and bending beam rheological test were carried out to research the dynamic mechanical properties of asphalt mortars containing M-FRs; wheeltracking test, low-temperature bending test and freeze-thaw split test were used to study the road performances of asphalt mixtures containing M-FRs. The results show that high-temperature performances of the three flame retardant asphalt mortars improve greatly, while low-temperature cracking resistances decline. Both hightemperature performances and water stabilities of asphalt mixtures containing M-FRs are quite good and exceed the specification requirements. However, their low-temperature performances decline in different degrees. In summary, besides their good flame retardancy, the flame retardant asphalt mortars and mixtures also exhibit acceptable road performance.
基金financially supported by the National Natural Science Foundation of China (No. 51002115)the Special Fund for Basic Scientific Research of Central Colleges, Chang’an University (No. 2011JC139)the Foundation of State Key Laboratory for Mechanical Behavior of Materials (No. 20121203)
文摘Ni-base metal–intermetallic laminate composites were obtained from in situ reaction synthesis between Ni and Al foils by utilizing plasma activated sintering. The effects of Ni foil thickness on the microstructure and tensile properties of the composites were investigated. The results show that the phases forming during reaction synthesis are independent of the starting thickness of the Ni foils. However, thicker reacted layers are obtained in the samples fabricated from 100 lm Ni foils（Ni100） than those obtained in the samples from 50 lm Ni foils（Ni50）when treated at the same process. The tensile strength of Ni100 samples increases with the temperature increasing at the expense of ductility. Dissimilarly, Ni50 composites treated at higher temperatures exhibit enhanced strength and ductility. Both Ni50 and Ni100 laminate fracture in a similar mechanism. Cracking first occurs in the brittle intermetallic layers. These original cracks result in shear bands in Ni layers emitted from the crack tips, and thus producing local stress concentration, which initiates new cracks in adjacent intermetallic layers. The multiplication of cracks and shear bands leads to the failure of the laminates.
基金Funded by the National Natural Science Foundation of China(No.51201019)the Special Fund for Basic Scientific Research of Central Universities(No.2013G3314002)
文摘The semi-solid deformation behavior of Til4 was investigated using compression tests at deformation temperatures between 1 273 and 1 423 K with strain rate of 5×10^-2 s^-1. Moreover, the fraction solid at different temperatures was also measured by image analysis. The results showed that the deformation temperature had strong effects on the flow stress, and the stress increased with the decrease of deformation temperature. The maximum stress depended greatly on the fraction solid, and a sharp decrease in stress occurred at a solid fraction between 0.94 and 0.98 （temperature from 1 323 to 1 373 K）. This decrease was related to the decrease in the amount of solid bridges between grains. Because of the partial solid/liquid segregation during deformation, the experimental strain rates were much lower than those calculated by the flow of liquid incorporating solid particles, which suggested that the main deformation mechanism between 1 323 and 1 373 K was still plastic deformation of solid particles.
基金supported by the National Natural Science Foundation of China(Nos.21603016,21704081,51603016 and21704005)Shaanxi College Students Innovation and Entrepreneurship Training Program(No.S201910710282)
文摘Two highly emissive pyrenoviologen derivatives were synthesized and used to fabricate fluorescent sensors for detection of picric acid(PA)with good sensitivity and selectivity.The sensitivity of the sensor was attributed to the specific electrostatic association effect of the cationic pyrenoviologens to the picrate anions,which also gave the sensor special selectivity among other compounds with similar structure.The electron transfer between them was attributed to the fluorescence response.Fluorescence lifetime measurements revealed that the quenching is static in nature.The novel and efficient pyrenoviologen derivatives-based sensors offered a strategy to fabricate real-life PA sensor.
基金supported by the National Natural Science Foundation of China(51978070)Key Research and Development Plan Project of Shaanxi Province(2023-YBSF-110).
文摘Geopolymer concrete(GPC)has been developed as a sustainable alternative to traditional cement-based concrete using industrial waste materials.Thus,reducing greenhouse gas emissions in concrete production can be expected.This study employed the life cycle assessment(LCA)method to evaluate geopolymer concrete's cost and life-cycle carbon dioxide(CO_(2))emissions.Moreover,the critical transportation radius of the geopolymer is estimated.Then,evaluation results were compared with ordinary Portland cement(OPC),considering three concrete construction methods:cast-in-place,ready-mixed,and precast.In particular,the service life of two types of concrete in sulfuric acid environments is considered.Compared with OPC concrete,the results show that geopolymer concretes can significantly reduce the cost and CO_(2)emissions when one or a small amount of alkali activator is used or alkali-containing materials are used to replace some alkali activators.However,the advantages would be reversed by the rising alkali dosages,which account for cost increases and carbon emissions.When considering the service life in special environments,geopolymer concrete in sulfuric acid environments corresponds to fewer carbon emissions,94%-97%decreased compared with OPC concrete.Finally,compared with OPC concrete,the newly developed limestone calcined clay cement(LC3)avoids high-temperature calcination and dramatically reduces carbon dioxide emissions.Compared to OPC concrete,LC3 concrete has a 19%reduction in CO_(2) emissions.And geopolymer concrete that takes alkali-activate materials for superseding alkalis also produces less carbon dioxide emissions.In particular,CO_(2) emissions from FA-SF geopolymer concrete are approximately 50%lower than OPC concrete.In addition,the use of alkali activators significantly weakens the cost advantage of geopolymers.But after accounting for waste disposal costs,the average net cost of fly ash-based geopolymer concrete can be more than 30% lower than that of OPC concrete.The average net cost of slag-based geopolymer concrete is 7%-45%lower than that of OPC concrete.The findings of this work provide the basis for further development of geopolymer concretes obeyed environmental protection.
基金This work is supported by Science and Technology Development Project of Xinjiang Production and Construction Corps (No. 2021DB005)Project of Department of Transport of Shaanxi Province (21-53K)+1 种基金the Central Plains Thousand People Plan of Henan Province (204200510004)the Fundamental Research Funds for the Central Universities, CHD (300102312724, 300102312402). The authors also thank to the reviewers for their valuable comments and suggestions concerning our manuscript.
文摘Salt freezing damage has severe impacts on durability of cement-based materials(CBMs).Calcined layered double hydroxide(CLDH),as an efficient environmental-friendly adsorption material,can impart excellent salt freezing resistance to CBMs.In this work,salt freezing resistance improvement of CBMs incorporated with CLDH was experimentally evaluated by chloride binding capacity,mass loss rate,relative dynamic elastic modulus,setting time,compressive strength,and micro structure tests.Beside these,the salt freezing damage model was established to effectively express the quantitative relationship between influencing factors and evaluation indexes of the salt freezing resistance of CBMs.Results show that CLDH can reconstruct its original layered structure to form reconstructed layered double hydroxide(RLDH).RLDH combines with chloride ions to form RLDH-Cl recrystallization,which can improve chloride binding capacity and pore structures of CBMs to relieve the salt freezing damage.The salt freezing damage model indicates that the suitable CLDH content can evidently alleviate the salt freezing damage,which facilitates the quantitative analysis of the effect of CLDH on the salt freezing resistance of CBMs.
基金supported by the Natural Science Foundation of China(No.21704005)Fundamental Research Funds for the Cen-tral Universities(No.300102310106).
文摘Infectious disease outbreaks have seriously endangered global health owing to the scarcity of testing materials and techniques.Diversified materials and methods should be urgently developed for rapid detection and discrimination of pathogenic microorganisms.Conjugated polymer(CP)materials are macromolecular compounds comprising numerous covalently bonded luminescent units.They have excellent light-harvesting and optical signal amplification capabilities owing to the transmission of excitation energy along their backbone.In recent years,CP materials have aroused research enthusiasm in the biosensors field because of their outstanding optoelectronic properties.This brief manuscript provides an overall review of recent progress achieved in CP-based systems for pathogen sensing.
基金the financial support from the Special Fund for Basic Scientific Research of Central Colleges, Changan University (310831151080, 310831153409, 310831153315 and 310831151085)Natural Science Basic Research Plan in Shaanxi Province of China (2017JQ2025)+1 种基金Xi'an Science and Technology Planning Project (2017137SF/WM031)Transportation Construction & Technology Project of Shanxi Department of Transportation (No. 16-2-12)
文摘Ice adhesion to materials is a significant concern in many fields. Hydrophobic surface has been used for anti-icing in fields of aircraft or transmission line, which prove to be efficacious and economical. However, such technique is seldom employed for road deicing, because of the texture and service environment of pavement. Instead, deicers such as rock salt are frequently used, which leads to serious corrosion problem of roads and bridges. In this paper, a number of studies that characterize mechanism of ice adhesion to common substrates, specifically to pavement, are reviewed. The most important researches undertaken on ice adhesion strength affecting factors are presented. An overview of studies carried out to find hydrophobie surface for asphalt and cement concrete pavement antiicing are presented. It was verified that the hydrophobicity had high correlation with icephobicity, and nano-engineered asphalt and cement concrete pavement surface exhibited favorable hydrophobicity, and also had good performance on weakening pavement-ice bonding. However, most ice-repelling pavements obtain hydrophobic surface via low surface energy coating, which could not exist on pavement for a long time under wheel abrasion. And the nano/micro structures on hydrophobic surfaces are also vulnerable and consumable. Thus, the long-term effect of hydrophobic surface still need to be improved, and durability of the hydrophobic surface should be the research and development priorities of ice-repelling pavement.
基金This project was supported by Key Research and Development Project of Shaanxi Province(2022GY-427)The first author also gratefully acknowledges the financial support from China Scholarship Council(202006560071).
文摘Numerous studies showed that synthetic fibers are effective for reinforcing the mechanical performance of the asphalt mixture due to their high strength properties,ductility,and durability characteristics.In this paper,the objective is to present a review of the reinforcement effect of synthetic fiber on the mechanical performance of the asphalt mixture.This paper reviews the relevant literature on the characterizations and applications of synthetic fibers to improve different mechanical properties of asphalt mixes,which can provide a reference for the applications and development of synthetic fibers in asphalt pavement.The characteristics of common synthetic fibers are introduced and the utilization of synthetic fibers in asphalt mixture is discussed.Different surface treatment methods for fiber are reviewed and it is found that surface treatment can improve the performance of the synthetic fibers in asphalt mixtures,especially the chemical surface treatment method.The influence of synthetic fiber addition on the mechanical properties of the asphalt concrete such as rutting resistance,tensile strength,water stability performance,and cracking resistance are then discussed.The research results show that aramid,glass,and polyester fibers improve the fatigue cracking resistance of asphalt mixture.Polyester fibers,polyamide fibers,and carbon fibers are used to improve resistance to the permanent deformation of asphalt pavement.
基金supported by the National Natural Science Foundation of China (Nos. 51872222 and 51002115)the Shaanxi Innovation Capacity Support Program (2018TD-031)the State Key Laboratory for Mechanical Behavior of Materials (20202208)。
文摘Spherical AlN powders with micrometer size have attracted great attention owing to their good fluidity and dispersity. However, the industrial preparation methods usually require high temperature and long soaking time, which lead to the high cost and limit the wide application of the products. Herein, nearly spherical AlN particles with the average size of 2.5 μm were successfully synthesized via an in-situ combustion synthesis method. The effect of N_(2) pressure, NH_(4)Cl content, and Al particle size on the combustion reaction procedure, phase composition, and microstructure of the products was systematically investigated. The results showed that the decreased N_(2) pressure, increased NH_(4)Cl content, and Al particle size led to the decreasing of combustion temperature and speed, which further affected the morphology of the products. As a result, low N_(2) pressure(0.2 MPa), a small amount of NH4Cl(0.5 wt%), and fine Al particles(~2.5 μm) contributed to a moderate combustion temperature and facilitated the formation of nearly spherical AlN particles. In addition, based on the gas-releasing assisted quenching experiments and thermo-kinetic analysis, a two-step growth mechanism for the nearly spherical AlN particles was rationally proposed. The present method shows the advantages of low cost and high efficiency for preparing nearly spherical AlN particles, which can be used as raw materials for electronic substrates and fillers for packaging materials.
基金supported by the National Natural Science Foundation of China(51978070)the Shaanxi Natural Science Basic Research Project(2020JM-265)。
文摘Prompting high content of reclaimed asphalt pavement(RAP) to be used in road building and maintenance has drawn great attention. The application of rejuvenators is an efficient way to ensure the performance of recycled asphalt mixtures. However, as various types of rejuvenators emerging, limited understanding about rejuvenation poses challenges to put effective ones into use. For precisely evaluating the performance of rejuvenators, plenty of studies were conducted to ascertain the fundamental mechanism of rejuvenating from the microscopic view. This paper provides an overview of studies focusing on the change inside asphalt after adding rejuvenators. Chemical compositions of rejuvenators were collected as basic information. Both laboratorial experiments and molecular dynamic simulations were investigated to not only compare the effectiveness of several rejuvenators but also explain the rejuvenating mechanism. Finally, functional groups of rejuvenator structures were comprehensively examined to provide global understanding about how chemical compositions influence the efficacy of rejuvenators. This review highlights that the essential capacity of a true rejuvenator is to disturb asphaltene agglomerations. Besides, the molecular structures of rejuvenators will not only affect their deagglomerating abilities but also the performances of diffusion and durability. It has been found that gel-permeation chromatography(GPC) analysis is effective in evaluating the performance of rejuvenators, while Fourier transform infrared spectroscopy(FT-IR) and SARA(saturates, aromatics, resins and asphaltenes) analysis are only suitable for assessing asphalt oxidization. In addition, comparing some tests can only detect changes, molecular dynamic simulation can reveal the mechanism both of data and vision. The results of this work can provide comprehensive knowledge for the evaluation and development of rejuvenators.
基金supported by the Natural Science Foundation of China(grant nos.22175138 and 21875180)the National Key Research and Development Program of China(grant no.2021YFB3200700)+4 种基金the Key Research and Development Program of Shaanxi(grant no.2021GXLH-Z023)the Independent Innovation Capability Improvement Project of Xi’an Jiaotong University(grant no.PY3A066)the Fundamental Research Funds for the Central Universities(grant no.xhj032021008-03)the Regional Innovation Capability Guidance Program of Shaanxi Province the Fundamental(grant no.2022QFY08-01)the Research Funds for the Central Universities(grant no.xzy022022001).
文摘Two-electron neutral aqueous organic redox flow batteries(AORFBs)hold more promising applications in the power grid than one-electron batteries because of their higher capacity.However,their development is strongly limited by the structural instability of the highly reduced species.By combining the extendedπ-conjugation structure of the anolytes and the enhanced aromaticity of the highly reduced species,we reported a series of highly conjugated and inexpensive arylene diimide derivatives(NDI,PDI,and TPDI)as novel two-electron storage anolyte materials for ultrastable AORFBs.Matched with(ferrocenylmethyl)trimethylammonium chloride(FcNCl)as catholyte,arylene diimide derivative-based AORFBs showed the highest stability in two-electron AORFBs to date.The NDI/FcNCl-based AORFB delivered 98.44%capacity retention at 40 mA cm^(−2)for 350 cycles;TPDI/FcNCl-based AORFB also showed remarkable stability with 97.22%capacity retention at 20 mA cm^(−2)over 200 cycles.This finding lays the theoretical foundation and offers a reference for improving the stability of two-electron AORFBs.
基金the financial support from the open project funds for National Major Science and Technology Infrastructure of Materials Service Safety Assessment Facilities,China(MSAF-2020-106)the National Natural Science Foundation of China(No.51808051)。
文摘Microwave heating,which is used for pre-treatment of concrete before it is comminuted,stands as a strong candidate for selective liberation of multiphase materials like concrete.This paper is concerned with the selective liberation of concrete's raw constituents(particularly aggregate)for recycling by considering the water content of concrete as a parameter of microwave heating for the first time.The deterioration law of the concrete's performance was characterized by the variation in the splitting tensile strength and relative dynamic modulus after heating by microwave at different water contents.Besides,tests were conducted to evaluate the performance of the interface transition zone(ITZ)between aggregate and mortar as well as to investigate the reasons for the stripping behavior of aggregate-mortar,which included the interface tensile strength test,temperature measurement,and porosity test.The deterioration law of splitting tensile strength and relative dynamic modulus revealed that the performance of concrete was subject to different degrees of damage depending on the water content.Furthermore,experimental results showed that interface bonding strength between aggregate and mortar was dramatically impaired,and a large temperature difference was generated between the aggregate and mortar during microwave heating.Meanwhile,the permeable pores increased considerably even when the specimens were dried.In the presence of water,the intactness of ITZ between aggregate and mortar was destroyed by microwave heating,and its performance was significantly lowered,which led to the occurrence of stripping behavior between aggregate and mortar.This was reaffirmed by the microstructure presented by scanning electron microscopy.Thus,the newly developed microwave pretreatment improved by providing appropriate water contents for concrete corresponding to different strength grades is a promising method for recycling aggregate from waste concrete.
