To evaluate the tensile behavior of metal foils by resistance heating(RH)assisted tensile testing system accurately,this study proposed to embed a digital image correlation(DIC)system with laser speckles for the measu...To evaluate the tensile behavior of metal foils by resistance heating(RH)assisted tensile testing system accurately,this study proposed to embed a digital image correlation(DIC)system with laser speckles for the measurement of full-field strain distribution.Furthermore,the sample structures were optimized to achieve uniform temperature and strain distribution.An infrared camera was used to monitor the temperature distribution.Rectangular samples instead of dog-bone shaped samples were proposed.A model for calculating the temperature distribution was established to optimize the sample structure.The parameters that influence the temperature distribution and tensile behavior were studied.As results,compared to the strain measured by a non-contact extensometer,the maximum deviation of the strain measured by DIC was less than 6%when the nominal strain was larger than 0.013.It is confirmed that the proposed tensile testing system is reliable for measuring the temperature and full-field strain distributions.Sample shape influenced temperature distributions of smaller samples while it almost had no influence on the temperature distributions of larger samples.The temperature difference was not affected by the material type but by the sample size.The proposed rectangular shape was validated to be feasible for RH assisted tensile testing.The sample length was successfully optimized for a more uniform temperature distribution by the established model.Although the tensile deformation was not influenced by the sample shape,the temperature distribution resulted in a non-uniform strain distribution before achieving ultimate tensile strength.Longer effective sample length between two clamping jigs contributed to a more uniform temperature distribution and material deformation.A more accurate evaluation of high-temperature tensile behavior for metal foils can be achieved by the proposed RH assisted tensile testing system using rectangular samples with an optimized structure.展开更多
The resistance heating method has been one of the prospective techniques for hot processing and welding techniques. The thermal behavior under different densities of electric current and the effect of electric current...The resistance heating method has been one of the prospective techniques for hot processing and welding techniques. The thermal behavior under different densities of electric current and the effect of electric current at temperature of 780 oC using low density of electric current of 6.70 A/mm^2 on the B2+O lamellar microstructure were investigated for Ti2AlNb alloy sheet. The stable temperature denoted a balanced state between the Joule heat and the dissipation of heat including heat conduction, convection and radiation while the distribution of temperature was nonuniform. The highest temperatures of electric current heating samples increased as the density of electric current was elevated. In order to understand the specific effect of electric current on B2+O microstructure, heat treatment for microstructural homogeneity was introduced to this study. After that, according to the microstructural observations by common characterization techniques in the resistance-heating sample and the isothermal furnace-heating sample after homogenizing treatment, few significant differences in content and orientation of phases can be directly and explicitly found except the thermal effect from the applied electric current. The results will provide reference to this prospective forming and welding techniques and the application for Ti2AlNb alloys using resistance heating in the near future.展开更多
Fruit trees face various adverse environmental factors,such as extreme hydrothermal changes,soil salinization and low precipitation,leading to different types of stress.High temperature is one of the main factors affe...Fruit trees face various adverse environmental factors,such as extreme hydrothermal changes,soil salinization and low precipitation,leading to different types of stress.High temperature is one of the main factors affecting the growth of fruit trees,and an appropriate ambient temperature is a necessary condition for the normal growth and development of fruit trees.Since the 20th century,due to the intensification of the greenhouse effect and global warming,there has been a significant increase in the occurrence and duration of extreme hot weather in summer has been occurring frequently and for longer durations.Thus,the growth and production of fruit trees are affected by severe hightemperature stress.Therefore,this paper primarily summarized the impacts of high-temperature stress on fruit growth and development,flowering,fruiting,fruit setting and quality.It also discussed the physiological and biochemical responses of fruit trees to high-temperature stress,research progress on the molecular mechanisms and signal transduction pathways underlying fruit tree resistance to heat or high temperature,and research on the investigation of relevant metabolites of fruit trees under stress conditions.The future research directions were discussed,and prospects and potential difficulties were proposed to serve a reference for further investigation on the high-temperature tolerance of fruit trees.展开更多
Polyimide(PI)is widely used in high-tech fields such as microelectronics,aerospace,and national defense because of its excellent optical properties,high-and low-temperature resistance,and good dimensional stability.To...Polyimide(PI)is widely used in high-tech fields such as microelectronics,aerospace,and national defense because of its excellent optical properties,high-and low-temperature resistance,and good dimensional stability.To achieve the desired properties of PI,the monomers 2,6-diaminopyrimidin-4-ol(DAPD)and 6-(2,3,5,6-tetrafluoro-4-vinylphenoxy)pyrimidin-2,4-diamine(DAFPD),which contains crosslinkable functional groups,were designed and synthesized successfully and copolymerized with 4,4'-oxydianiline(ODA)and 4,4-hexafluoroisopropylphthalic anhydride(6FDA).The prepared PI film(PI-3),with rigid backbones and loose packing had excellent heat resistance(Td5%=489℃)and optical properties(T450=82%).Furthermore,a crosslinked PI film(c-PI-3)with more heat-resistant(Td5%=524℃)and better mechanical properties(σ=125.46MPa),can be obtained through thermal crosslinking of tetrafluorostyrene.In addition,the changes in the properties caused by the proportion of DAFPD added during copolymerization are discussed comprehensively.This study provides a promising candidate for heat-resistant PI materials.展开更多
Lvhanliangyou 888 is a new hybrid rice combination jointly bred by the Institute of Rice Research of Anhui Academy of Agricultural Sciences and Anhui Agricultural University.It was developed using Wan 28S as the femal...Lvhanliangyou 888 is a new hybrid rice combination jointly bred by the Institute of Rice Research of Anhui Academy of Agricultural Sciences and Anhui Agricultural University.It was developed using Wan 28S as the female parent and Lvhui 888 as the male parent,and was approved by Anhui Provincial Crop Variety Approval Committee in 2023.Lvhanliangyou 888 possesses excellent characteristics such as high quality,drought resistance,heat resistance,disease resistance,and lodging resistance.It is suitable for promotion and cultivation as a water-saving and drought-resistant rice variety in the single-season rice areas of Anhui Province.This paper describes the breeding process,characteristics,and key cultivation points of Lvhanliangyou 888.展开更多
Epoxy resin is widely used in electronic packaging due to its exceptional performance,particularly the low-temperature curable thiol/epoxy system,which effectively minimizes thermal damage to sensitive electronic comp...Epoxy resin is widely used in electronic packaging due to its exceptional performance,particularly the low-temperature curable thiol/epoxy system,which effectively minimizes thermal damage to sensitive electronic components.However,the majority of commercial thiol curing agents contain hydrolysable ester bonds and lack rigid structures,which induces most of thiol/epoxy systems still suffering from unsatisfactory heat resistance and hygrothermal resistance,significantly hindering their application in electronic packaging.In this study,we synthesized a tetrafunctional thiol compound,bis[3-(3-sulfanylpropyl)-4-(3-sulfanylpropoxy)phenyl]sulfone(TMBPS)with rigid and ester-free structures to replace traditional commercial thiol curing agents,pentaerythritol tetra(3-mercaptopropionate)(PETMP).Compared to the PETMP/epoxy system,the TMBPS/epoxy system exhibited superior comprehensive properties.The rigid structures of bisphenol S-type tetrathiol enhanced the heat resistance and mechanical properties of TMBPS/epoxy resin cured products,outperforming those of PETMP/epoxy resin cured products.Notably,the glass transition temperature of TMBPS/epoxy resin cured products was 74.2℃which was 11.8°C higher than that of PETMP cured products.Moreover,the ester-free structure in TMBPS contributed to its enhanced resistance to chemicals and hygrothermal conditions.After undergoing 1000 h of hightemperature and high-humidity aging,the tensile strength and adhesion strength of TMBPS-cured products were 73.33 MPa and 3.39 MPa,respectively exceeding 100%and 40%of their initial values,while PETMP-cured products exhibited a complete loss of both tensile strength and adhesion strength.This study provides a strategy for obtaining thermosetting polymers that can be cured at low temperatures and exhibit excellent comprehensive properties.展开更多
The cooling rate of the center and edge of vacuum induction melting(VIM)or vacuum arc remelting(VAR)ingots exhibit substantial difference,leading to markedly distinct dendritic structures and precipitates.The current ...The cooling rate of the center and edge of vacuum induction melting(VIM)or vacuum arc remelting(VAR)ingots exhibit substantial difference,leading to markedly distinct dendritic structures and precipitates.The current lack of precise predictions for dendritic segregation and the distribution of precipitates in ingot makes it difficult to determine the annealing and homogenization heat treatment process.Thus,clarifying the impact of cooling rate on the solidification behavior of alloy is significantly important.The dendritic structure and precipitation characteristics of as-cast C-HRA-3 Ni–Cr–Co–Mo-based heat-resistant alloy were investigated using Thermo-Calc thermodynamic calculations,scanning electron microscopy observations,and electron probe microanalyzer.Based on high temperature observation system,the effects of cooling rate on the dendritic structure,dendritic segregation,and precipitation in this alloy were explored.The results showed that the precipitates in the as-cast C-HRA-3 alloy primarily consist of blocky Ti(C,N)phases,large-sized Ti(C,N)–M_(6)C–M_(23)C_(6) symbiotic phases and M_(6)C–M_(23)C_(6) carbides,and small-sized dispersed M_(6)C and M_(23)C_(6) carbides surronding these symbiotic phases.The primary constituent elements of these precipitates are Mo,Cr,C,and Ti,which predominantly concentrate in the interdendritic regions of the as-cast alloy.There is a clear power-law relationship between the secondary dendrite arm spacing and the cooling rate.The dendritic segregation ratio of Mo,Cr,and Ti exhibits a piecewise functional relationship with the cooling rate,under equiaxed dendritic solidification condition.These predictive models and theoretical analyses were validated using numerical simulations and experimental results from the 200 kg grade VIM electrode.展开更多
The use of biomass feedstocks for the manufacture of high-performance polymers can help expand their range of applications and reduce their dependence on finite fossil resources.However,improving the heat resistance a...The use of biomass feedstocks for the manufacture of high-performance polymers can help expand their range of applications and reduce their dependence on finite fossil resources.However,improving the heat resistance and hydrophilicity of bio-based polyesters remains a significant challenge.Herein,we introduce N,N'-trans-1,4-cyclohexane-bis(pyrrolidone-4-methylcarboxylate)(CBPC),a novel bio-based tricyclic dibasic ester synthesized from renewable dimethyl itaconic acid and trans-1,4-cyclohexane diamine via an aza-Michael addition reaction.As a unique comonomer,CBPC features a rigid tricyclic backbone that significantly enhances chain packing and thermal stability,whereas its pyrrolidone side groups impart tunable polarity and improved hydrophilicity.Using CBPC,diphenyl carbonate,and 1,4-butylene glycol,a series of PBCC copolymers with 10 mol%-30 mol%CBPC was synthesized via ester-exchange and melt polycondensation methods.Incorporation of CBPC raised the melting temperature(Tm)from 56.8℃to 225.8℃and the initial decomposition temperature(Td5%)from 258.0℃to 306.7℃,positioning PBCC among the most heat-resistant bio-based polyesters reported.Additionally,the pyrrolidone units enabled transformation from hydrophobic to hydrophilic.This study demonstrates that CBPC is an effective and innovative building block for the design of bio-based polymers with enhanced thermal and surface properties,offering a promising strategy for the development of high-performance sustainable materials.展开更多
Commercial wrought high-strength Cu-Cr-Zr alloys face limited high-temperature properties due to the rapid coarsening or dissolution of Cr precipitates.Here,we report a laser powder bed fusion(LPBF)fabricated Cu-0.84C...Commercial wrought high-strength Cu-Cr-Zr alloys face limited high-temperature properties due to the rapid coarsening or dissolution of Cr precipitates.Here,we report a laser powder bed fusion(LPBF)fabricated Cu-0.84Cr-0.42Zr(wt.%)alloy with exceptional heat resistance after aging.Primary Cr@Cu_(5)Zr phase(∼39.8 nm)with core-shell structure and a high density of heat-stable dislocations were intro-duced from the rapid solidification of LPBF and enabled the alloy to gain significant improvement in high-temperature properties.After aging treatment,secondary Cr and Cu_(51)Zr_(14)phases(∼3.4 nm)were precipitated,in which Zr solute was segregated at one side of the Cr phase,enhancing the thermal sta-bility of Cr phase.The excellent combinations of strength and thermal conductivity were achieved at or above 400℃.Particularly at 600℃,the aged sample not only exhibited a high tensile strength of∼196 MPa,which significantly surpassed that of wrought Cu-Cr-Zr alloys,but also possessed a thermal conductivity of∼349 W/(m K)comparable to that of pure copper.展开更多
Acrylonitrile–butadiene–styrene(ABS)is the main material used in fused deposition modeling(FDM),which has good toughness and strength,but the single ABS material has poor heat resistance,which tends to cause warping...Acrylonitrile–butadiene–styrene(ABS)is the main material used in fused deposition modeling(FDM),which has good toughness and strength,but the single ABS material has poor heat resistance,which tends to cause warping and deformation during the printing process.Polycarbonate(PC)exhibits good performance in heat resistance,allowing it to maintain stable performance at higher temperatures.In this work,PC was used as a blending modifier to prepare five kinds of ABS/PC composite filaments,and the mechanical and thermal properties of the ABS/PC(Acrylonitrile-butadiene-styrene/Polycarbonate)composite filaments were studied and analyzed.Results showed that the glass transition temperature(Tg)of the blend increased continuously as the PC content increased.When the mass fraction of ABS/PC was 50/50,the glass transition temperature of the blend increased by 21.21%,and the tensile strength of the composites reached 40.23 MPa,which was an increase of 36.47% compared with that of pure ABS.However,the impact strength of the composites decreased with the addition of PC.Moreover,with the increase in the mass fraction of PC,the printing accuracy error increased from 0.02 to 0.18 mm.The results of this paper will promote the improvement of ABS printing performance and enrich the available materials for FDM.展开更多
The effect of intermetallic compounds on the heat resistance of transition joint was investigated. The experiment of post-weld heat treatment for the hot roll bonded titanium alloy-stainless steel joint using nickels ...The effect of intermetallic compounds on the heat resistance of transition joint was investigated. The experiment of post-weld heat treatment for the hot roll bonded titanium alloy-stainless steel joint using nickels interlayer was carried out, and the interface microstructure evolution due to heat treatment was presented. There was not found significant interdiffusion at stainless steel/nickel interface, when the specimens were heat treated in the temperature range of 600-800 °C for 10 and 30 min, while micro-cracks occurred at the stainless steel/nickel interface heat treated at 700 °C for 30 min. The thickness of intermetallic layers at nickel/titanium alloy interface increased at 600 °C, and micro-cracks occurred at 700 and 800 °C. The micro-cracks occurred between intermetallic layers or between intermetallic layer and nickel interlayer as well. The tensile strength of the transition joint decreased with the increase of heat treatment temperature or holding time.展开更多
The precipitation characteristics and effect on strengthening mechanism of Cu-rich phases during short-time and long-time aging for Super 304H steels with different Cu content were investigated using X-ray diffraction...The precipitation characteristics and effect on strengthening mechanism of Cu-rich phases during short-time and long-time aging for Super 304H steels with different Cu content were investigated using X-ray diffraction （XRD）, scanning electron microscope （SEM） and transmission electron microscope （TEM）. The results show that the size of Cu-rich phase particles increases, the interspace of Cu-rich phase particles decreases and the density of Curich phases increases with the increase of Cu content during short-time aging （approximately 800 h） at 650℃ for Super 304H steels. During long-time aging （more than 2 000 h） at 650 ℃, Cu-rich phase precipitates sufficiently and the strengthening effect of Cu-rich phase is preferable in Super 304H steel containing Cu of 4%. The strengthening effect of Cu-rich phase in Super 304H steels containing Cu of 2.2% or 5% is weaker than that with Cu of 4% during long-time aging （more than 2 000 h）.展开更多
Tempering is an important process for T/P92 ferritic heat-resistant steel from the viewpoint of microstructure control, as it facili- tates the formation of final tempered martensite under serving conditions. In this ...Tempering is an important process for T/P92 ferritic heat-resistant steel from the viewpoint of microstructure control, as it facili- tates the formation of final tempered martensite under serving conditions. In this study, we have gained deeper insights on the mechanism underlying the microstructural evolution during tempering treatment, including the precipitation of carbides and the coarsening of martensite laths, as systematically analyzed by optical microscopy, transmission electron microscopy, and high-resolution transmission electron mi- croscopy. The chemical composition of the precipitates was analyzed using energy dispersive X-ray spectroscopy. Results indicate the for- mation of M3C （cementite） precipitates under normalized conditions. However, they tend to dissolve within a short time of tempering, owing to their low thermal stability. This phenomenon was substantiated by X-ray diffraction analysis. Besides, we could observe the precipitation of fine carbonitrides （MX） along the dislocations. The mechanism of carbon diffusion controlled growth of M23C6 can be expressed by the Zener＇s equation. The movement of Y-junctions was determined to be the fundamental mechanism underlying the martensite lath coarsening process. Vickers hardness was estimated to determine their mechanical properties. Based on the comprehensive analysis of both the micro- structural evolution and hardness variation, the process of tempering can be separated into three steps.展开更多
A novel novolac curing agent containing both naphthalene and dicyclopentadiene (DCPD) moieties was prepared to produce a highly heat-resistant cured polymer network. The chemical structure was characterized using Four...A novel novolac curing agent containing both naphthalene and dicyclopentadiene (DCPD) moieties was prepared to produce a highly heat-resistant cured polymer network. The chemical structure was characterized using Fourier transform infrared spectroscopy, nuclear magnetic resonance, mass spectrometry, and gel permeation chro-matography analyses. The thermal properties of the resulting polymer from diglycidyl ether of bisphenol A epoxy resin cured with the novel curing agent were evaluated using dynamic mechanical thermal analysis and thermogra-vimetric analysis. Compared with the conventional curing agent, the resulting polymer cured with naphtha-lene/DCPD navolac shows considerable improvement in heat resistant properties such as higher glass transition temperature (Tg) and thermal stability. The result also shows better moisture resistance because of the hydrophobic nature of naphthalene/DCPD structure.展开更多
The evolution of precipitates of S31042 steel during 700 ℃ aging was investigated by using a scanning elec- tron microscope, a transmission electron microscope, and electron energy spectrum technology. The various co...The evolution of precipitates of S31042 steel during 700 ℃ aging was investigated by using a scanning elec- tron microscope, a transmission electron microscope, and electron energy spectrum technology. The various combi nations of M23C6, MX, NbCrN, and σ and G phases in the steel were found at different aging states. In the begin ning of aging, M23C6 precipitates swiftly along the grain boundaries. When the aging time exceeds 6 000 h, precipita- ted M23C6 carbides along the grain boundaries turn to be granular. It was found that Si element segregates to grain boundaries during above process, which may enhance the granular shape of M23C6 carbides and its transformation to and G phases. When the aging time exceeds 10 000 h, various shaped a phase and granular G phase appear along the grain boundaries and there are no continuous M23C6 carbides along the grain boundaries. Meanwhile, a large quantity of granular M23C6 carbides and a minor amount of G phase precipitate near the grain boundaries. Based on the segre- gation of silicon to the grain boundaries, a precipitation evolution model during aging was concluded.展开更多
T122 steel has been used to produce superheater or reheater of ultra supercritical boilers. With the help of chemical phase extraction and mierostructure characterization, the performance of aging precipitates of T122...T122 steel has been used to produce superheater or reheater of ultra supercritical boilers. With the help of chemical phase extraction and mierostructure characterization, the performance of aging precipitates of T122 steel, such as M23C6 carbide, Laves phase and MX phase was investigated, the strengthening mechanism of the steel was discussed, and the thermal yield stress of lath substructure, dislocations and precipitates of the steel were calculated. It was found that lath substructure and dislocations dominated the strengthening attribution and precipitation hardening went second to the strengthening attribution.展开更多
A bisphenol epoxy resin was used as modifier to increase the heat resistance of condensed poly-nuclear aromatic （COPNA） resin. The basic properties of COPNA resin and modified resin were characterized by Fourier tra...A bisphenol epoxy resin was used as modifier to increase the heat resistance of condensed poly-nuclear aromatic （COPNA） resin. The basic properties of COPNA resin and modified resin were characterized by Fourier transform infrared spectroscopy （FT-IR）, nuclear magnetic resonance spectroscopy （1H-NMR）, vapor pressure osmometry （VPO） and elemental analysis （EA）. Average structural parameters of resins were calculated by the improved Brown-Ladner method, and heat resistance of resins was tested by thermogravimetric analysis （TGA）. The chemical structure, mechanical properties and heat resistivity of the resin/graphite composites prepared with different resins were compared. The results show that the adhesive property and heat resistance of COPNA resin can be remarkably improved by addition of 5 wt.% epoxy resin. The reason is that the reactions between epoxy groups of epoxy resin and hydroxyl groups of COPNA resin improve the heat resistance and adhesive property of COPNA resin. Electric motor brushes with good mechanical properties and low electrical resistivity were successfully prepared by using the modified resin as binder.展开更多
Fe-Cr-Ni heat resistant alloys with aluminum and silicon addition, alone and in combination, were melted using an intermediate frequency induction furnace with a non-oxidation method. By the oxidation weight gain meth...Fe-Cr-Ni heat resistant alloys with aluminum and silicon addition, alone and in combination, were melted using an intermediate frequency induction furnace with a non-oxidation method. By the oxidation weight gain method, the oxidation resistances of the test alloys were determined at 1,200 ℃ for 500 hours. According to the oxidation weight gains, the oxidation kinetic curves were plotted and the functions were regressed by the least squares method. The results show that the oxidation kinetic curves follow the power function of y = ax^b （a〉0, 0〈b〈1）. The effects of scale compositions on oxidation resistance were studied further by analyses using X-ray diffraction （XRD） and scanning electron microscope （SEM）. It is found that the composite scale compounds of Cr203, a-Al2O3, SiO2 and FeCr2O4, with compact structure and tiny grains, shows complete oxidation resistance at 1,200℃. When the composite scale lacks a-Al2O3 or SiO2, it becomes weak in oxidation resistance with a loose structure. By the criterion of standard Gibbs formation free energy, the model of the nucleation and growth of the composite scale is established. The forming of the composite scale is the result of the competition of being oxidized and reduced between aluminum, silicon and the matrix metal elements of iron, chromium and nickel. The protection of the composite scale is analyzed essentially by electrical conductivity and strength properties.展开更多
Based on dislocation reaction theory and Avrami equation, a constitutive equation model was developed to describe dynamic recovery and dynamic recrystallization during hot deformation of T122 heat resistant steel, whi...Based on dislocation reaction theory and Avrami equation, a constitutive equation model was developed to describe dynamic recovery and dynamic recrystallization during hot deformation of T122 heat resistant steel, which have taken the effect of dynamic strain aging into account. Uniaxial hot compression test had been carried out over a wide range of strain rate （0.01 to 10 s-1 ） and temperature （900 to 1 200 ~C） with the help of Gleeble 3500. Obtained experimental data was applied to determine the material parameters in proposed constitutive equations of T122 steel, by using the non-linear least square regress optimization method. The calculated constitutive equations are quantita- tively in good agreement with experimentally measured curves and microstructure observation. It shows that propose constitutive equation T122 steel is able to be used to predict flow stress of T122 steel during hot deformation in aus- tenite temperature scope.展开更多
Polyl(lactide),PLA,suffers from bitleness and low heat deflection temperature(HDT),which limits its application as an engineering plastic.In this work,poly(L-lactide)/poly(D-lactide)/ethylene-vinyl acetate glycidyl me...Polyl(lactide),PLA,suffers from bitleness and low heat deflection temperature(HDT),which limits its application as an engineering plastic.In this work,poly(L-lactide)/poly(D-lactide)/ethylene-vinyl acetate glycidyl methacrylate random copolymer(PLLA/PDL A/EVM-GMA=1/1/x)composites were prepared by melt blending,and the in situ formed EVM-g PLA copolymers improved the compatibility between PLA and EVM-GMA.Subsequently,the blends were subjected to a two-step annealing process during compression molding,i.e.first annealing at 120℃ to rapidly form a certain amount of stereocomplex(sc)crystallites as nucleation sites,and then annealing at 200℃ to guide the formation of new sccrystallites.Both differential scanning calorimetry(DSC)and wide angle X-ray dffrction(WAXD)measurements confirmed the formation of highly stereocomplexed PLA products.Mechanical results showed that the PLLA/PDLA blend with 20 wt%of EVM-GMA had a notched impact strength up to 65 kJ/m2 and an elongation at break of 48%,while maintaining a tensile strength of 40 MPa.Meanwhile,dynamic mechanical analysis(DMA)and heat deflection tests showed that the PLA composite had an HDT up to 142℃ which is 90℃ higher than that of normal PLA products.Scanning electron microscopy(SEM)confirmed the fine dispersion of EVM-GMA particles,which facilitated to understand the toughening mechanism.Furthermore,the highly stereocomplexed PLA composites simultaneously exhibited excellent chemical and hydrolysis resistance.Therefore,these fascinating properties may extend the application range of sc PLA material as an engineering bioplastic.展开更多
基金supported by Japan Society for the Promotion of Science(JSPS KAKENHI Grant number JP19H02476,JP20K21074)30^(th)ISIJ Research Promotion Grant and The Light Metal Educational Foundation。
文摘To evaluate the tensile behavior of metal foils by resistance heating(RH)assisted tensile testing system accurately,this study proposed to embed a digital image correlation(DIC)system with laser speckles for the measurement of full-field strain distribution.Furthermore,the sample structures were optimized to achieve uniform temperature and strain distribution.An infrared camera was used to monitor the temperature distribution.Rectangular samples instead of dog-bone shaped samples were proposed.A model for calculating the temperature distribution was established to optimize the sample structure.The parameters that influence the temperature distribution and tensile behavior were studied.As results,compared to the strain measured by a non-contact extensometer,the maximum deviation of the strain measured by DIC was less than 6%when the nominal strain was larger than 0.013.It is confirmed that the proposed tensile testing system is reliable for measuring the temperature and full-field strain distributions.Sample shape influenced temperature distributions of smaller samples while it almost had no influence on the temperature distributions of larger samples.The temperature difference was not affected by the material type but by the sample size.The proposed rectangular shape was validated to be feasible for RH assisted tensile testing.The sample length was successfully optimized for a more uniform temperature distribution by the established model.Although the tensile deformation was not influenced by the sample shape,the temperature distribution resulted in a non-uniform strain distribution before achieving ultimate tensile strength.Longer effective sample length between two clamping jigs contributed to a more uniform temperature distribution and material deformation.A more accurate evaluation of high-temperature tensile behavior for metal foils can be achieved by the proposed RH assisted tensile testing system using rectangular samples with an optimized structure.
基金Project(51875122)supported by the National Natural Science Foundation of China
文摘The resistance heating method has been one of the prospective techniques for hot processing and welding techniques. The thermal behavior under different densities of electric current and the effect of electric current at temperature of 780 oC using low density of electric current of 6.70 A/mm^2 on the B2+O lamellar microstructure were investigated for Ti2AlNb alloy sheet. The stable temperature denoted a balanced state between the Joule heat and the dissipation of heat including heat conduction, convection and radiation while the distribution of temperature was nonuniform. The highest temperatures of electric current heating samples increased as the density of electric current was elevated. In order to understand the specific effect of electric current on B2+O microstructure, heat treatment for microstructural homogeneity was introduced to this study. After that, according to the microstructural observations by common characterization techniques in the resistance-heating sample and the isothermal furnace-heating sample after homogenizing treatment, few significant differences in content and orientation of phases can be directly and explicitly found except the thermal effect from the applied electric current. The results will provide reference to this prospective forming and welding techniques and the application for Ti2AlNb alloys using resistance heating in the near future.
基金supported by the“JBGS”Project of Seed Industry Revitalization in Jiangsu Province[Grant No.JBGS(2021)021]the Earmarked Fund for Jiangsu Agricultural Industry Technology System[Grant No.JATS(2022)510]。
文摘Fruit trees face various adverse environmental factors,such as extreme hydrothermal changes,soil salinization and low precipitation,leading to different types of stress.High temperature is one of the main factors affecting the growth of fruit trees,and an appropriate ambient temperature is a necessary condition for the normal growth and development of fruit trees.Since the 20th century,due to the intensification of the greenhouse effect and global warming,there has been a significant increase in the occurrence and duration of extreme hot weather in summer has been occurring frequently and for longer durations.Thus,the growth and production of fruit trees are affected by severe hightemperature stress.Therefore,this paper primarily summarized the impacts of high-temperature stress on fruit growth and development,flowering,fruiting,fruit setting and quality.It also discussed the physiological and biochemical responses of fruit trees to high-temperature stress,research progress on the molecular mechanisms and signal transduction pathways underlying fruit tree resistance to heat or high temperature,and research on the investigation of relevant metabolites of fruit trees under stress conditions.The future research directions were discussed,and prospects and potential difficulties were proposed to serve a reference for further investigation on the high-temperature tolerance of fruit trees.
基金supported by the National Key Research and Development Program of China(No.2022YFB3603101)。
文摘Polyimide(PI)is widely used in high-tech fields such as microelectronics,aerospace,and national defense because of its excellent optical properties,high-and low-temperature resistance,and good dimensional stability.To achieve the desired properties of PI,the monomers 2,6-diaminopyrimidin-4-ol(DAPD)and 6-(2,3,5,6-tetrafluoro-4-vinylphenoxy)pyrimidin-2,4-diamine(DAFPD),which contains crosslinkable functional groups,were designed and synthesized successfully and copolymerized with 4,4'-oxydianiline(ODA)and 4,4-hexafluoroisopropylphthalic anhydride(6FDA).The prepared PI film(PI-3),with rigid backbones and loose packing had excellent heat resistance(Td5%=489℃)and optical properties(T450=82%).Furthermore,a crosslinked PI film(c-PI-3)with more heat-resistant(Td5%=524℃)and better mechanical properties(σ=125.46MPa),can be obtained through thermal crosslinking of tetrafluorostyrene.In addition,the changes in the properties caused by the proportion of DAFPD added during copolymerization are discussed comprehensively.This study provides a promising candidate for heat-resistant PI materials.
基金Supported by Sub-project of National Key Research and Development Program of China(2024YFD2300301-05)The Young Talent Program of Anhui Academy of Agricultural Sciences(QNYC-202109QNYC-202208).
文摘Lvhanliangyou 888 is a new hybrid rice combination jointly bred by the Institute of Rice Research of Anhui Academy of Agricultural Sciences and Anhui Agricultural University.It was developed using Wan 28S as the female parent and Lvhui 888 as the male parent,and was approved by Anhui Provincial Crop Variety Approval Committee in 2023.Lvhanliangyou 888 possesses excellent characteristics such as high quality,drought resistance,heat resistance,disease resistance,and lodging resistance.It is suitable for promotion and cultivation as a water-saving and drought-resistant rice variety in the single-season rice areas of Anhui Province.This paper describes the breeding process,characteristics,and key cultivation points of Lvhanliangyou 888.
基金the support of the Science and Technology Commission of Shanghai Municipality(STCSM,No.20dz1203600)the Experimental Center of Materials Science and Engineering in Tongji University。
文摘Epoxy resin is widely used in electronic packaging due to its exceptional performance,particularly the low-temperature curable thiol/epoxy system,which effectively minimizes thermal damage to sensitive electronic components.However,the majority of commercial thiol curing agents contain hydrolysable ester bonds and lack rigid structures,which induces most of thiol/epoxy systems still suffering from unsatisfactory heat resistance and hygrothermal resistance,significantly hindering their application in electronic packaging.In this study,we synthesized a tetrafunctional thiol compound,bis[3-(3-sulfanylpropyl)-4-(3-sulfanylpropoxy)phenyl]sulfone(TMBPS)with rigid and ester-free structures to replace traditional commercial thiol curing agents,pentaerythritol tetra(3-mercaptopropionate)(PETMP).Compared to the PETMP/epoxy system,the TMBPS/epoxy system exhibited superior comprehensive properties.The rigid structures of bisphenol S-type tetrathiol enhanced the heat resistance and mechanical properties of TMBPS/epoxy resin cured products,outperforming those of PETMP/epoxy resin cured products.Notably,the glass transition temperature of TMBPS/epoxy resin cured products was 74.2℃which was 11.8°C higher than that of PETMP cured products.Moreover,the ester-free structure in TMBPS contributed to its enhanced resistance to chemicals and hygrothermal conditions.After undergoing 1000 h of hightemperature and high-humidity aging,the tensile strength and adhesion strength of TMBPS-cured products were 73.33 MPa and 3.39 MPa,respectively exceeding 100%and 40%of their initial values,while PETMP-cured products exhibited a complete loss of both tensile strength and adhesion strength.This study provides a strategy for obtaining thermosetting polymers that can be cured at low temperatures and exhibit excellent comprehensive properties.
基金funded by the National Key R&D Program Funded Projects(No.2021YFB3704102).
文摘The cooling rate of the center and edge of vacuum induction melting(VIM)or vacuum arc remelting(VAR)ingots exhibit substantial difference,leading to markedly distinct dendritic structures and precipitates.The current lack of precise predictions for dendritic segregation and the distribution of precipitates in ingot makes it difficult to determine the annealing and homogenization heat treatment process.Thus,clarifying the impact of cooling rate on the solidification behavior of alloy is significantly important.The dendritic structure and precipitation characteristics of as-cast C-HRA-3 Ni–Cr–Co–Mo-based heat-resistant alloy were investigated using Thermo-Calc thermodynamic calculations,scanning electron microscopy observations,and electron probe microanalyzer.Based on high temperature observation system,the effects of cooling rate on the dendritic structure,dendritic segregation,and precipitation in this alloy were explored.The results showed that the precipitates in the as-cast C-HRA-3 alloy primarily consist of blocky Ti(C,N)phases,large-sized Ti(C,N)–M_(6)C–M_(23)C_(6) symbiotic phases and M_(6)C–M_(23)C_(6) carbides,and small-sized dispersed M_(6)C and M_(23)C_(6) carbides surronding these symbiotic phases.The primary constituent elements of these precipitates are Mo,Cr,C,and Ti,which predominantly concentrate in the interdendritic regions of the as-cast alloy.There is a clear power-law relationship between the secondary dendrite arm spacing and the cooling rate.The dendritic segregation ratio of Mo,Cr,and Ti exhibits a piecewise functional relationship with the cooling rate,under equiaxed dendritic solidification condition.These predictive models and theoretical analyses were validated using numerical simulations and experimental results from the 200 kg grade VIM electrode.
基金financially supported by the Provincial Project of Science and Technology(No.2023112258)Tianshan Talent Training Program(No.2024TSYCCX0112)+1 种基金Talent Introduction and Start Foundation for Young Scientists of Shihezi University(No.2022ZK004)Program for Young Innovative Talents of Shihezi University(No.CXFZ202302)。
文摘The use of biomass feedstocks for the manufacture of high-performance polymers can help expand their range of applications and reduce their dependence on finite fossil resources.However,improving the heat resistance and hydrophilicity of bio-based polyesters remains a significant challenge.Herein,we introduce N,N'-trans-1,4-cyclohexane-bis(pyrrolidone-4-methylcarboxylate)(CBPC),a novel bio-based tricyclic dibasic ester synthesized from renewable dimethyl itaconic acid and trans-1,4-cyclohexane diamine via an aza-Michael addition reaction.As a unique comonomer,CBPC features a rigid tricyclic backbone that significantly enhances chain packing and thermal stability,whereas its pyrrolidone side groups impart tunable polarity and improved hydrophilicity.Using CBPC,diphenyl carbonate,and 1,4-butylene glycol,a series of PBCC copolymers with 10 mol%-30 mol%CBPC was synthesized via ester-exchange and melt polycondensation methods.Incorporation of CBPC raised the melting temperature(Tm)from 56.8℃to 225.8℃and the initial decomposition temperature(Td5%)from 258.0℃to 306.7℃,positioning PBCC among the most heat-resistant bio-based polyesters reported.Additionally,the pyrrolidone units enabled transformation from hydrophobic to hydrophilic.This study demonstrates that CBPC is an effective and innovative building block for the design of bio-based polymers with enhanced thermal and surface properties,offering a promising strategy for the development of high-performance sustainable materials.
基金supported by the National Natural Science Foun-dation of China(Nos.52127802 and 52431008).
文摘Commercial wrought high-strength Cu-Cr-Zr alloys face limited high-temperature properties due to the rapid coarsening or dissolution of Cr precipitates.Here,we report a laser powder bed fusion(LPBF)fabricated Cu-0.84Cr-0.42Zr(wt.%)alloy with exceptional heat resistance after aging.Primary Cr@Cu_(5)Zr phase(∼39.8 nm)with core-shell structure and a high density of heat-stable dislocations were intro-duced from the rapid solidification of LPBF and enabled the alloy to gain significant improvement in high-temperature properties.After aging treatment,secondary Cr and Cu_(51)Zr_(14)phases(∼3.4 nm)were precipitated,in which Zr solute was segregated at one side of the Cr phase,enhancing the thermal sta-bility of Cr phase.The excellent combinations of strength and thermal conductivity were achieved at or above 400℃.Particularly at 600℃,the aged sample not only exhibited a high tensile strength of∼196 MPa,which significantly surpassed that of wrought Cu-Cr-Zr alloys,but also possessed a thermal conductivity of∼349 W/(m K)comparable to that of pure copper.
基金the Natural Science Foundation of Shandong Province(grant no.ZR2020KF024)Yantai City Science and Technology Plan Project(grant no.2022ZDCX016)+1 种基金the University Research Project of Shandong Province(grant no.J17KB007)Natural Science Foundation of Shandong Jiaotong University(grant no.Z201937).
文摘Acrylonitrile–butadiene–styrene(ABS)is the main material used in fused deposition modeling(FDM),which has good toughness and strength,but the single ABS material has poor heat resistance,which tends to cause warping and deformation during the printing process.Polycarbonate(PC)exhibits good performance in heat resistance,allowing it to maintain stable performance at higher temperatures.In this work,PC was used as a blending modifier to prepare five kinds of ABS/PC composite filaments,and the mechanical and thermal properties of the ABS/PC(Acrylonitrile-butadiene-styrene/Polycarbonate)composite filaments were studied and analyzed.Results showed that the glass transition temperature(Tg)of the blend increased continuously as the PC content increased.When the mass fraction of ABS/PC was 50/50,the glass transition temperature of the blend increased by 21.21%,and the tensile strength of the composites reached 40.23 MPa,which was an increase of 36.47% compared with that of pure ABS.However,the impact strength of the composites decreased with the addition of PC.Moreover,with the increase in the mass fraction of PC,the printing accuracy error increased from 0.02 to 0.18 mm.The results of this paper will promote the improvement of ABS printing performance and enrich the available materials for FDM.
基金Project(AWPT-M07)supported by the State Key Laboratory of Advanced Welding and Joining,Harbin Institute of Technology
文摘The effect of intermetallic compounds on the heat resistance of transition joint was investigated. The experiment of post-weld heat treatment for the hot roll bonded titanium alloy-stainless steel joint using nickels interlayer was carried out, and the interface microstructure evolution due to heat treatment was presented. There was not found significant interdiffusion at stainless steel/nickel interface, when the specimens were heat treated in the temperature range of 600-800 °C for 10 and 30 min, while micro-cracks occurred at the stainless steel/nickel interface heat treated at 700 °C for 30 min. The thickness of intermetallic layers at nickel/titanium alloy interface increased at 600 °C, and micro-cracks occurred at 700 and 800 °C. The micro-cracks occurred between intermetallic layers or between intermetallic layer and nickel interlayer as well. The tensile strength of the transition joint decreased with the increase of heat treatment temperature or holding time.
基金Sponsored by National Science and Technology Support Plan of China (2007BAE51B02)
文摘The precipitation characteristics and effect on strengthening mechanism of Cu-rich phases during short-time and long-time aging for Super 304H steels with different Cu content were investigated using X-ray diffraction （XRD）, scanning electron microscope （SEM） and transmission electron microscope （TEM）. The results show that the size of Cu-rich phase particles increases, the interspace of Cu-rich phase particles decreases and the density of Curich phases increases with the increase of Cu content during short-time aging （approximately 800 h） at 650℃ for Super 304H steels. During long-time aging （more than 2 000 h） at 650 ℃, Cu-rich phase precipitates sufficiently and the strengthening effect of Cu-rich phase is preferable in Super 304H steel containing Cu of 4%. The strengthening effect of Cu-rich phase in Super 304H steels containing Cu of 2.2% or 5% is weaker than that with Cu of 4% during long-time aging （more than 2 000 h）.
基金financially supported by the China National Funds for Distinguished Young Scientists(No.51325401)the International Thermonuclear Experimental Reactor(ITER)Program Special Project(No.2014GB125006)+1 种基金the National Natural Science Foundation of China(No.51104107)the Major State Basic Research Development Program(No.2014CB046805)
文摘Tempering is an important process for T/P92 ferritic heat-resistant steel from the viewpoint of microstructure control, as it facili- tates the formation of final tempered martensite under serving conditions. In this study, we have gained deeper insights on the mechanism underlying the microstructural evolution during tempering treatment, including the precipitation of carbides and the coarsening of martensite laths, as systematically analyzed by optical microscopy, transmission electron microscopy, and high-resolution transmission electron mi- croscopy. The chemical composition of the precipitates was analyzed using energy dispersive X-ray spectroscopy. Results indicate the for- mation of M3C （cementite） precipitates under normalized conditions. However, they tend to dissolve within a short time of tempering, owing to their low thermal stability. This phenomenon was substantiated by X-ray diffraction analysis. Besides, we could observe the precipitation of fine carbonitrides （MX） along the dislocations. The mechanism of carbon diffusion controlled growth of M23C6 can be expressed by the Zener＇s equation. The movement of Y-junctions was determined to be the fundamental mechanism underlying the martensite lath coarsening process. Vickers hardness was estimated to determine their mechanical properties. Based on the comprehensive analysis of both the micro- structural evolution and hardness variation, the process of tempering can be separated into three steps.
文摘A novel novolac curing agent containing both naphthalene and dicyclopentadiene (DCPD) moieties was prepared to produce a highly heat-resistant cured polymer network. The chemical structure was characterized using Fourier transform infrared spectroscopy, nuclear magnetic resonance, mass spectrometry, and gel permeation chro-matography analyses. The thermal properties of the resulting polymer from diglycidyl ether of bisphenol A epoxy resin cured with the novel curing agent were evaluated using dynamic mechanical thermal analysis and thermogra-vimetric analysis. Compared with the conventional curing agent, the resulting polymer cured with naphtha-lene/DCPD navolac shows considerable improvement in heat resistant properties such as higher glass transition temperature (Tg) and thermal stability. The result also shows better moisture resistance because of the hydrophobic nature of naphthalene/DCPD structure.
文摘The evolution of precipitates of S31042 steel during 700 ℃ aging was investigated by using a scanning elec- tron microscope, a transmission electron microscope, and electron energy spectrum technology. The various combi nations of M23C6, MX, NbCrN, and σ and G phases in the steel were found at different aging states. In the begin ning of aging, M23C6 precipitates swiftly along the grain boundaries. When the aging time exceeds 6 000 h, precipita- ted M23C6 carbides along the grain boundaries turn to be granular. It was found that Si element segregates to grain boundaries during above process, which may enhance the granular shape of M23C6 carbides and its transformation to and G phases. When the aging time exceeds 10 000 h, various shaped a phase and granular G phase appear along the grain boundaries and there are no continuous M23C6 carbides along the grain boundaries. Meanwhile, a large quantity of granular M23C6 carbides and a minor amount of G phase precipitate near the grain boundaries. Based on the segre- gation of silicon to the grain boundaries, a precipitation evolution model during aging was concluded.
基金Item Sponsored by National Hi-Tech Research and Development Program of China (863 program) (2006AA03Z513)
文摘T122 steel has been used to produce superheater or reheater of ultra supercritical boilers. With the help of chemical phase extraction and mierostructure characterization, the performance of aging precipitates of T122 steel, such as M23C6 carbide, Laves phase and MX phase was investigated, the strengthening mechanism of the steel was discussed, and the thermal yield stress of lath substructure, dislocations and precipitates of the steel were calculated. It was found that lath substructure and dislocations dominated the strengthening attribution and precipitation hardening went second to the strengthening attribution.
基金supported by the National Natural Science Foundation of China (Nos. 51172285, 51372277)the Fundamental Research Funds for the Central Universities (14CX02060A)the Natural Science Foundation of Shandong Province (ZR2011EL030)
文摘A bisphenol epoxy resin was used as modifier to increase the heat resistance of condensed poly-nuclear aromatic （COPNA） resin. The basic properties of COPNA resin and modified resin were characterized by Fourier transform infrared spectroscopy （FT-IR）, nuclear magnetic resonance spectroscopy （1H-NMR）, vapor pressure osmometry （VPO） and elemental analysis （EA）. Average structural parameters of resins were calculated by the improved Brown-Ladner method, and heat resistance of resins was tested by thermogravimetric analysis （TGA）. The chemical structure, mechanical properties and heat resistivity of the resin/graphite composites prepared with different resins were compared. The results show that the adhesive property and heat resistance of COPNA resin can be remarkably improved by addition of 5 wt.% epoxy resin. The reason is that the reactions between epoxy groups of epoxy resin and hydroxyl groups of COPNA resin improve the heat resistance and adhesive property of COPNA resin. Electric motor brushes with good mechanical properties and low electrical resistivity were successfully prepared by using the modified resin as binder.
基金supported financially by Komatsu of Japan,grant number31370011370804,in Shandong University,China.
文摘Fe-Cr-Ni heat resistant alloys with aluminum and silicon addition, alone and in combination, were melted using an intermediate frequency induction furnace with a non-oxidation method. By the oxidation weight gain method, the oxidation resistances of the test alloys were determined at 1,200 ℃ for 500 hours. According to the oxidation weight gains, the oxidation kinetic curves were plotted and the functions were regressed by the least squares method. The results show that the oxidation kinetic curves follow the power function of y = ax^b （a〉0, 0〈b〈1）. The effects of scale compositions on oxidation resistance were studied further by analyses using X-ray diffraction （XRD） and scanning electron microscope （SEM）. It is found that the composite scale compounds of Cr203, a-Al2O3, SiO2 and FeCr2O4, with compact structure and tiny grains, shows complete oxidation resistance at 1,200℃. When the composite scale lacks a-Al2O3 or SiO2, it becomes weak in oxidation resistance with a loose structure. By the criterion of standard Gibbs formation free energy, the model of the nucleation and growth of the composite scale is established. The forming of the composite scale is the result of the competition of being oxidized and reduced between aluminum, silicon and the matrix metal elements of iron, chromium and nickel. The protection of the composite scale is analyzed essentially by electrical conductivity and strength properties.
基金Sponsored by National High-Tech Research and Development Program (863Program) of China (2003AA331060)
文摘Based on dislocation reaction theory and Avrami equation, a constitutive equation model was developed to describe dynamic recovery and dynamic recrystallization during hot deformation of T122 heat resistant steel, which have taken the effect of dynamic strain aging into account. Uniaxial hot compression test had been carried out over a wide range of strain rate （0.01 to 10 s-1 ） and temperature （900 to 1 200 ~C） with the help of Gleeble 3500. Obtained experimental data was applied to determine the material parameters in proposed constitutive equations of T122 steel, by using the non-linear least square regress optimization method. The calculated constitutive equations are quantita- tively in good agreement with experimentally measured curves and microstructure observation. It shows that propose constitutive equation T122 steel is able to be used to predict flow stress of T122 steel during hot deformation in aus- tenite temperature scope.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51873082 and 51903106)Fundamental Research Funds for the Central Universities(No.JUSRP11928).
文摘Polyl(lactide),PLA,suffers from bitleness and low heat deflection temperature(HDT),which limits its application as an engineering plastic.In this work,poly(L-lactide)/poly(D-lactide)/ethylene-vinyl acetate glycidyl methacrylate random copolymer(PLLA/PDL A/EVM-GMA=1/1/x)composites were prepared by melt blending,and the in situ formed EVM-g PLA copolymers improved the compatibility between PLA and EVM-GMA.Subsequently,the blends were subjected to a two-step annealing process during compression molding,i.e.first annealing at 120℃ to rapidly form a certain amount of stereocomplex(sc)crystallites as nucleation sites,and then annealing at 200℃ to guide the formation of new sccrystallites.Both differential scanning calorimetry(DSC)and wide angle X-ray dffrction(WAXD)measurements confirmed the formation of highly stereocomplexed PLA products.Mechanical results showed that the PLLA/PDLA blend with 20 wt%of EVM-GMA had a notched impact strength up to 65 kJ/m2 and an elongation at break of 48%,while maintaining a tensile strength of 40 MPa.Meanwhile,dynamic mechanical analysis(DMA)and heat deflection tests showed that the PLA composite had an HDT up to 142℃ which is 90℃ higher than that of normal PLA products.Scanning electron microscopy(SEM)confirmed the fine dispersion of EVM-GMA particles,which facilitated to understand the toughening mechanism.Furthermore,the highly stereocomplexed PLA composites simultaneously exhibited excellent chemical and hydrolysis resistance.Therefore,these fascinating properties may extend the application range of sc PLA material as an engineering bioplastic.
