In order to develop a comprehensive understanding about the effect of different holding time under rapid heating on the microstructural evolution and mechanical properties of transformation-induced plasticity （TRIP）...In order to develop a comprehensive understanding about the effect of different holding time under rapid heating on the microstructural evolution and mechanical properties of transformation-induced plasticity （TRIP） steel, continuous annealing process simulations were performed using a thermal system with resistance heating method. The morphology and distribution of all phases present in the microstructure and the mechanical properties of TRIP steel were revealed. It appeared that the final tensile strength of the TRIP steel increased and retained austenite car bon content decreased with increasing holding time. An overlap between ferrite recrystallization and austenitization was observed during intercritical holding. In addition, the work hardening of the samples was evaluated by calculat ing the instantaneous ~l value as a function of the true strain. The difference in work hardening behavior corresponds to the rate of the retained austenite transformation during straining, which can be attributed to the carbon content and the morphology of the retained austenite.展开更多
The optical observation results of neocrystallization nucleation and growth of fine fully lamellar (FFL) α 2/ γ microstructure of a TiAl based alloy in rapid heating cyclic heat treatment process were reported. The ...The optical observation results of neocrystallization nucleation and growth of fine fully lamellar (FFL) α 2/ γ microstructure of a TiAl based alloy in rapid heating cyclic heat treatment process were reported. The characteristics of α+γ→α transformation under rapid heating conditions were analysed. A model for explaining the nucleation and growth mechanism of FFL α 2/ γ microstructure was proposed.展开更多
Modified electrically assisted(EA) rapid heating of Al–Si-coated hot stamping steel is suggested, and the intermetallic evolution in the coating during heating is experimentally investigated. In the modified EA rapid...Modified electrically assisted(EA) rapid heating of Al–Si-coated hot stamping steel is suggested, and the intermetallic evolution in the coating during heating is experimentally investigated. In the modified EA rapid heating, a continuous electric current for a suitable duration is applied to a specimen to heat it to a temperature slightly below the melting temperature of the coating. The temperature of the specimen is then kept constant for a specified dwell time. The result of the microstructural analysis shows that the modified EA rapid heating could effectively increase the thickness of the intermetallic layer between the coating and steel substrate much faster than conventional furnace heating and induction heating. The effectiveness of EA rapid heating may be due to the athermal effect of the electric current on the mobility of atoms, in addition to the well-known resistance heating effect. EA rapid heating also provides a technical advantage in that partial austenization can be easily achieved by properly placing the electrodes, as demonstrated in the present study.展开更多
Influence of severe cold deformation of titanium alloy Ti-1.5%A1-6.8%Mo-4.5%Fe in metastable β condition on the evolution of phase composition, microstructure, and tensile properties during continuous rapid heating w...Influence of severe cold deformation of titanium alloy Ti-1.5%A1-6.8%Mo-4.5%Fe in metastable β condition on the evolution of phase composition, microstructure, and tensile properties during continuous rapid heating was studied. As-deformed alloy was characterized by quasi-amorphous single-phase β condition with an abnormal temperature dependence of electric resistance that was normalized after 48 h exposure at room temperature as a result of isothermal ω phase precipitation. Subsequent rapid heating with a rate of 5 ℃/s caused recovery and recrystallization. Tensile properties of the alloy after different treatments were determined and discussed.展开更多
Gasification of biomass tar by pyrolysis is a valuable source for renewable energy,providing chemicals,a precursor to carbon material and potentially a raw material for liquid fuel.In this research,experimental studie...Gasification of biomass tar by pyrolysis is a valuable source for renewable energy,providing chemicals,a precursor to carbon material and potentially a raw material for liquid fuel.In this research,experimental studies via thermal gravimetric analysis(TGA)of biomass tar were implemented at three rapid heating rates(i.e.,10 K/min,50 K/min,100 K/min,respectively)in a nitrogen atmosphere.On the basis of analytical methods utilized in thermal dynamics and physical chemistry,the results showed that the thermogravimetric curve(TG)of the biomass moved in a high-temperature direction with an increase in the heating rate.The greater the heating rate,the steeper the curve and the lower the resolution,the lag phenomenon of the temperature being more significant.Concurrently,a differential thermal analysis(DTA)was one of the methods employed to study the relationship between the temperature difference and the temperature or time of the tested substance and a reference substance.The peak temperature and maximum reaction rate of the differential thermal analysis curve(DTA)increased as the heating rate,the volatiles and the molecular residence time of the biomass was shortened at a higher heating rate,thereby potentially inhibiting the generation of carbon and increasing the production and yield of liquid fuel.展开更多
The pure α-Ti samples were heated at an extremely high rate （～10^6 K/s） to the temperature of β phase zone followed by a rapidly quenching in an electro-pulsing treatment. After the treatment, micrometer-thick la...The pure α-Ti samples were heated at an extremely high rate （～10^6 K/s） to the temperature of β phase zone followed by a rapidly quenching in an electro-pulsing treatment. After the treatment, micrometer-thick lamellar substructures were generated within the original equiaxed α-Ti coarse grains. Misorientations across adjacent lamellae are of a few degrees. The ultrafine lamellar substructures originated from a non-equilibrium α-β-α’ phase transformation during rapidly heating-quenching process with a short exposure time at high temperatures. Tensile strength was increased by about 100 MPa due to the formation of the ultrafine lamellar substructure while the same tensile plasticity （elongation-to-failure） was maintained relative to the original sample. The strengthening effect could be attributed to the effective blockage of dislocation motions by a high density of sub-boundaries.展开更多
A rapid-heating method in the absence of electric/magnetic field was achieved by introducing a self-propagating-combustion （SHS） as heating source. The effect of heating rate on the alumina grain growth was explored...A rapid-heating method in the absence of electric/magnetic field was achieved by introducing a self-propagating-combustion （SHS） as heating source. The effect of heating rate on the alumina grain growth was explored based on this rapid-heating method. Comparing with the alumina prepared by two different heating ratios （greater than 1 000 ℃/min in SItS and about 50 ℃/min in common pressureless sintering furnace）, it was revealed that the rapid heating could promote the grain growth greatly without pressure during sintering. However, if a pressure was applied simultaneously, the grain growth would be almost completely restrained. Since these observations are quite different from the expectation, a new grain growth model was proposed.展开更多
Three kinds of high-purity A12O3 powders, whose average paticle size is 0. l, 0.3 and 3.0 mp respectively, were used as thestarting power, and their compacts were fired in the radio-frequency plasma generated at a pre...Three kinds of high-purity A12O3 powders, whose average paticle size is 0. l, 0.3 and 3.0 mp respectively, were used as thestarting power, and their compacts were fired in the radio-frequency plasma generated at a pressure of 80 Pa using N, as the working gas.Experimental results show that the 0. 1 and 0.3 mp powder compacts can be sintered to nearly the theoretical density within 60 s and thissintering is almost finished in the heating period. It is concluded that the mechanism of liquid sintering, the electric charge effect of Al2O3powder, and the effect of tempetrature gradient in the compacts can affect simultaneously on the rapid densification of the compacts inthe plasma sintering.展开更多
In rapid thermal processing of a semiconductor wafer, it is important to keep a given temperature rising speed of the wafer during the temperature rising process. We made an experimental apparatus to measure the tempe...In rapid thermal processing of a semiconductor wafer, it is important to keep a given temperature rising speed of the wafer during the temperature rising process. We made an experimental apparatus to measure the temperature rising speed of a ceramic ball of 2 mm in diameter heated with four halogen lamp heaters. The heating rate of the halogen lamp heaters was controlled by computer to keep a given temperature rising speed of 50 ℃/s with a controlling time interval of 0.1 s. We examined the effect of various heating control methods on the error of the temperature rising speed of the ceramic ball. We found that a combined method of control with prepared correlation and PID （proportional integral derivative） control is a good method to decrease the error of the temperature rising speed. The average error of the temperature rising speed is 0.5 ℃/s, and the repetition error is almost zero for the temperature rising speed of 50 ℃/s from 330 ℃ to 370 ℃. We also measured the effects of artificial control delay time and measuring error of the monitoring temperature on the error of the temperature rising speed.展开更多
Heat treatment plays an important role in tailoring the mechanical properties of powder-metallurgy(PM)titanium alloys.However,only limited work about the rapid heat treatment(RHT)of PM titanium alloys has been reporte...Heat treatment plays an important role in tailoring the mechanical properties of powder-metallurgy(PM)titanium alloys.However,only limited work about the rapid heat treatment(RHT)of PM titanium alloys has been reported.In this work,RHT was applied to PM Ti-5Al-5Mo-5V-1Cr-1Fe alloy after hot rolling to study the evolution of its mechanical properties and the influence of residual pores on its properties.Through hot rolling and annealing,a fine and uniformα+βstructure with few residual pores is ob-tained.During RHT,the primaryαdissolves gradually and completes in theβregion,and theβgrains then grow,resulting in the continuous decrease in elongation after aging.Moreover,the tensile strength first increases and then decreases with increasing RHT temperature,owing to the increase in volume fraction of secondaryαinα+βregion and theβgrain growth inβregion.In contrast to the RHT of cast-and-wrought titanium,the negative influence of residual pores lowers the RHT temperature for obtaining the highest tensile strength to a temperature below theβ-transus temperature.Despite the negative influence of the residual pores,retained primaryαand fineβgrains with fine secondaryαinside contribute to achieving a good strength/ductility balance(1570 MPa and 6.1%,respectively).Addi-tionally,although at higher cycles to failure,the negative influence of residual pores increases as it affects the crack initiation zone at the subsurface,the good resistance of secondaryαto fatigue crack propaga-tion still enhances the fatigue strength considerably(about 300 MPa).This work suggests a cost-effective strategy to produce titanium alloys with high performance.展开更多
The effects of process parameters in rapid heat cycle moulding （RHCM） on parts warpage were investigated. A vehicle-used blue-tooth front shell （consisting of ABS material） was considered as a part example manufac...The effects of process parameters in rapid heat cycle moulding （RHCM） on parts warpage were investigated. A vehicle-used blue-tooth front shell （consisting of ABS material） was considered as a part example manufactured by RHCM method. The corresponding rapid heat response mould with an innovational conformal heating/cooling channel system and a dynamic mould temperature control system based on the Jll-W-160 type precise temperature controller was proposed. During heating/cooling process, the mould was able to be heated from room temperature to 160 ~C in 6 s and then cooled to 80 ~C in 22 s. The effects of processing conditions in RHCM on part warpage were investigated based on the single factor experimental method and Taguchi theory. Results reveal that the elevated mould temperature reduces unwanted freezing during the injection stage, thus improving mouldability and enhancing part quality, whereas the overheated of mould temperature will lead to defective product. The feasible mould temperature scope in RHCM should be no higher than 140 ~C, and the efficient mould temperature scope should be around the polymer heat distortion temperature. Melt temperature as well as injection pressure effects on warpage can be divided into two stages The lower stage gives a no explicit effect on warpage whereas the higher stage leads to a quasi-linear downtrend. But others affect the warpage as a V-type fluctuation, reaching to the minimum around the heat distortion temperature. Under the same mould temperature condition, the effects of process parameters on warpage decrease according to the following order, packing time, packing pressure, melt temperature, injection pressure and cooling time, respectively.展开更多
The cold-island effect of urban wetlands has received increasing attention in recent years due to its important role in the alleviation of urban heat islands.Hangzhou,a representative rapidly urbanizing city with rich...The cold-island effect of urban wetlands has received increasing attention in recent years due to its important role in the alleviation of urban heat islands.Hangzhou,a representative rapidly urbanizing city with rich wetlands in China,was selected as a case study for researching the changes that the urban wetlands have undergone and their impact on the urban thermal environment.Land surface temperature(LST) was acquired from the thermal infrared data of Landsat 5 Thematic Mapper(TM) images in 1990,1995,2000,2006,and 2010,using the single-channel method.The results are as follows:1) considering the changes in land use,the urban wetlands located to the west of Hangzhou have decreased significantly during 1990–2010 because of rapid urbanization.In the Xixi Wetland,the change in land use was relatively small and most of the water body and vegetation were preserved.However,to the east of the Xixi Wetland,large areas of water body and vegetation have been replaced by built-up land as a result of the urbanization process;2) considering the change in LST,it was found from land surface temperature retrieval that the changing spatial pattern of the thermal field was highly correlated with land use changes.Low temperature regions of the eastern Xixi Wetland were gradually eroded by high temperature regions,and the centroid of the heat island in East Xixi was found to be constantly shifting westward.In addition,the difference in LST between the Xixi Wetland and East Xixi has increased;3) considering the impact factors for this area,land use structure and patch shape were found to have a significant impact on LST,shown by the results of multiple linear stepwise regressions.Increasing the size of the wetlands in urban planning is considered to be the most effective measure in alleviating the urban heat island effect.Moreover,reducing the spatial complexity of landscape patches also contributes to the alleviation of the urban heat island effect.展开更多
The effects of rapid heating cyclic heat treatment on mechanical properties of a TiAl based alloy (Ti 33Al 3Cr) were studied by means of an induction heating machine. The results show that: 1) fine fully lamellar micr...The effects of rapid heating cyclic heat treatment on mechanical properties of a TiAl based alloy (Ti 33Al 3Cr) were studied by means of an induction heating machine. The results show that: 1) fine fully lamellar microstructure with colony size of about 50 μm and lamellar spacing of about 0.12 μm can be obtained; 2) the compression mechanical properties can be improved to a large extent and the best comprehensive compression mechanical properties can reach the yield stress 745 MPa, the large flow stress 1 672 MPa and the compression ratio 19.4%; and 3) the compression fracture at room temperature after induction heat treatment and aging is still typical cleavage fracture.展开更多
The microstructural kinetics of <i>β</i> grain growth in the <i>β</i> field of a Ti-6Al-4V alloy was studied by a series of controlled heat treatments at constant temperature rates. Heating r...The microstructural kinetics of <i>β</i> grain growth in the <i>β</i> field of a Ti-6Al-4V alloy was studied by a series of controlled heat treatments at constant temperature rates. Heating rates of 5<span style="white-space:nowrap;">°</span>C/s, 50<span style="white-space:nowrap;">°</span>C/s and 500<span style="white-space:nowrap;">°</span>C/s were considered, stopping at different peak temperatures. The thickness evolution of martensitic needles and lamellar <i>α</i> laths, formed on cooling, was also investigated, by soaking the material above its <i>β</i>-transus temperature and cooling down at 5<span style="white-space:nowrap;">°</span>C/s, 50<span style="white-space:nowrap;">°</span>C/s, 100<span style="white-space:nowrap;">°</span>C/s and 300<span style="white-space:nowrap;">°</span>C/s till ambient temperature. Quantitative microstructural analyses were used to measure the particle dimensions. The <i>β</i> grain growth kinetics was reasonably well described by a modified Avrami equation. The thickness of <i>α</i> lamellae was a function of the cooling rate and the <i>β</i> grain dimension in which they nucleated. The martensite needle thickness was shown to be a function of the cooling rate to which the material was subjected.展开更多
The survival ability of insects can be limited with the changes in the levels of energy metabolites under stressful conditions but only a few studies have considered the plastic effects of heat and related climatic fa...The survival ability of insects can be limited with the changes in the levels of energy metabolites under stressful conditions but only a few studies have considered the plastic effects of heat and related climatic factors relevant to tropical habitats. The objectives of our study were to determine whether adults of <i><span style="font-family:Verdana;">Zaprionus</span></i> <i><span style="font-family:Verdana;">indianus</span></i><span style="font-family:Verdana;"> are capable of rapid heat hardening (RHH) and rapid desiccation hardening (RDH) and to compare its benefits with heat acclimation (HA) and desiccation acclimation (DA). Adult flies reared under season-specific simulated conditions were subjected to 38<span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;">°</span>C for RHH and 32<span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;">°</span>C for HA, while 5% relative humidity (RH) was maintained for RDH and 40% RH for DA. Stress-induced effects of heat and desiccation on the levels of five metabolites namely cuticular lipids (CL), total body lipids (TBL), protein, proline, and carbohydrates were then estimated by biochemical method. Different duration of heat hardening and acclimation led to more accumulation of CL whereas different durations of desiccation hardening and acclimation revealed less accumulation. In contrast, there was an accumulation of carbohydrates and protein under desiccation hardening and acclimation whereas there was the utilization of carbohydrates and protein under heat hardening and acclimation. However, mixed results were observed on the level of proline and TBL under both heat and desiccation stress. These stress-triggered changes in the levels of various metabolites suggest a possible link between heat and desiccation tolerance. Hence, these compensatory changes in the level of various metabolites also suggest possible energetic homeostasis in </span><i><span style="font-family:Verdana;">Z.</span></i> <i><span style="font-family:Verdana;">indianus</span></i><span style="font-family:Verdana;"> living under harsh climatic conditions of heat and drought in tropical regions.</span>展开更多
Silicon carbide (SiC) fiber has recently received considerable attention as promising next-generation fiber because of its high strength at temperatures greater than 1300 ℃ in air.High-quality SiC fiber is primarily ...Silicon carbide (SiC) fiber has recently received considerable attention as promising next-generation fiber because of its high strength at temperatures greater than 1300 ℃ in air.High-quality SiC fiber is primarily made through a curing and heat treatment process.In this study,the chemical vapor curing method,instead of the thermal oxidation curing method,was used to prepare cured polycarbosilane (PCS) fiber.During the high temperature heat treatment of the cured PCS fiber,varied heating rates of 10,20,30,and 40 ℃/min were applied.Throughout the process,the fiber remained in the amorphous silicon carbide phase,and the measured tensile strength was the greatest when the oxygen content in the heat-treated fiber was low,due to the rapid heating rate.The fiber produced through this method was also found to have excellent internal oxidation properties.This fast,continuous process shows a great promise for the production of SiC fiber and the development of high-quality products.展开更多
Passive cooling strategy with zero-energy consumption is effective in preventing people from heat stress.However,most of the existing radiative cooling textiles are fabricated with non-degradable hydrophobic synthetic...Passive cooling strategy with zero-energy consumption is effective in preventing people from heat stress.However,most of the existing radiative cooling textiles are fabricated with non-degradable hydrophobic synthetic polymers and lack the functions of sweat management.Herein,a hierarchically designed dual Janus nanofibrous textile with superior thermal-wet management capability is proposed by targeted selection of spinning solvents with different properties during electrospinning.The embedded Al_(2)O_(3)nanoparticles and BN nanosheets in silk fibroin nanofibers endow the textile with high solar reflectivity(97.12%)and infrared emissivity(98.69%),alongside improved in-plane and through-plane thermal conductivity(1.593 and 0.1187 W・K^(−1)・m^(−1),respectively).Benefiting from the asymmetric characteristics of the two sides in terms of fiber diameter and wettability,the nanofibrous textile exhibits unparalleled water transport index(R=1028.93%)and exceptional water vapor transmission rate(141.34 g・m^(−2)・h^(−1)).The textile integrates radiative cooling,rapid heat conduction,and unidirectional sweat evaporation,achieving a cooling effect exceeding 9°C under direct sunlight when worn.Moreover,the Janus textile has good biocompatibility,satisfactory wearability and air breathability,ensuring its comfort in wearable applications.Computer simulations complement experimental results,providing insights into the deep-seated mechanisms of nanofiber formation,Mie scattering,and water transport.This innovative design offers promising prospects for the development of next-generation passive-cooling textiles.展开更多
Fast heat transfer in the pyrolyzer can increase the yield of pyrolysis gas and tar,and improve the quality of tar.Compared with the downer pyrolyzer,the cyclone pyrolyzer can simultaneously achieve high solids holdup...Fast heat transfer in the pyrolyzer can increase the yield of pyrolysis gas and tar,and improve the quality of tar.Compared with the downer pyrolyzer,the cyclone pyrolyzer can simultaneously achieve high solids holdup and violent turbulence,and correspondingly faster heat transfer.In this work,the heat transfer behavior in the cyclone pyrolyzer is specifically studied using the computational fluid dynamics-discrete element method.The simulation results reveal that the gas-solids heat convection contributes mainly to the heat transfer process,and the heat radiation and conduction are relatively small and almost negligible,respectively.Compared with the downer pyrolyzer under the same operating conditions,the heating rate is significantly increased in the cyclone pyrolyzer.By analyzing the flow characteristics in the cyclone pyrolyzer,it is found that the region of high convective heat transfer rate coincides with that of natural cyclone length.Additionally,the final coal temperature increases with the increase of gas velocity and exists a maximum value.These results can offer some qualitative understanding of the heat transfer behavior in the cyclone pyrolyzer.展开更多
基金Item Sponsored by National Twelfth Five-year Science and Technology Support Program of China(2011BAE13B01,2011BAE13B03)
文摘In order to develop a comprehensive understanding about the effect of different holding time under rapid heating on the microstructural evolution and mechanical properties of transformation-induced plasticity （TRIP） steel, continuous annealing process simulations were performed using a thermal system with resistance heating method. The morphology and distribution of all phases present in the microstructure and the mechanical properties of TRIP steel were revealed. It appeared that the final tensile strength of the TRIP steel increased and retained austenite car bon content decreased with increasing holding time. An overlap between ferrite recrystallization and austenitization was observed during intercritical holding. In addition, the work hardening of the samples was evaluated by calculat ing the instantaneous ~l value as a function of the true strain. The difference in work hardening behavior corresponds to the rate of the retained austenite transformation during straining, which can be attributed to the carbon content and the morphology of the retained austenite.
文摘The optical observation results of neocrystallization nucleation and growth of fine fully lamellar (FFL) α 2/ γ microstructure of a TiAl based alloy in rapid heating cyclic heat treatment process were reported. The characteristics of α+γ→α transformation under rapid heating conditions were analysed. A model for explaining the nucleation and growth mechanism of FFL α 2/ γ microstructure was proposed.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Ministry of Science,ICT and Future Planning(MSIP)(NRF-2015R1A5A1037627)the Technology Innovation Program(Industrial Strategic Technology Development Program,10044807.Development of technologies for vehicle body part made from UHSS and Al5000 by electrically assisted manufacturing)funded by the Ministry of Trade,Industry and Energy(MOTIE,Korea)
文摘Modified electrically assisted(EA) rapid heating of Al–Si-coated hot stamping steel is suggested, and the intermetallic evolution in the coating during heating is experimentally investigated. In the modified EA rapid heating, a continuous electric current for a suitable duration is applied to a specimen to heat it to a temperature slightly below the melting temperature of the coating. The temperature of the specimen is then kept constant for a specified dwell time. The result of the microstructural analysis shows that the modified EA rapid heating could effectively increase the thickness of the intermetallic layer between the coating and steel substrate much faster than conventional furnace heating and induction heating. The effectiveness of EA rapid heating may be due to the athermal effect of the electric current on the mobility of atoms, in addition to the well-known resistance heating effect. EA rapid heating also provides a technical advantage in that partial austenization can be easily achieved by properly placing the electrodes, as demonstrated in the present study.
文摘Influence of severe cold deformation of titanium alloy Ti-1.5%A1-6.8%Mo-4.5%Fe in metastable β condition on the evolution of phase composition, microstructure, and tensile properties during continuous rapid heating was studied. As-deformed alloy was characterized by quasi-amorphous single-phase β condition with an abnormal temperature dependence of electric resistance that was normalized after 48 h exposure at room temperature as a result of isothermal ω phase precipitation. Subsequent rapid heating with a rate of 5 ℃/s caused recovery and recrystallization. Tensile properties of the alloy after different treatments were determined and discussed.
基金the National Natural Science Foundation of China(551376056)"Study of regulation mechanisms and photo-thermal properties of photosynthetic hydrogen production under the condition of multiphase biomass flow",and The National High Technology Research and Development Program(863)of China(2012AA051502)-Research and demonstration of the key technology for biological hydrogen production".The authors would like to thank Prof.Qinglin Wu of Louisiana State University(USA)Dr.Li Jihong of North China Electric Power University for their assistance on this project.
文摘Gasification of biomass tar by pyrolysis is a valuable source for renewable energy,providing chemicals,a precursor to carbon material and potentially a raw material for liquid fuel.In this research,experimental studies via thermal gravimetric analysis(TGA)of biomass tar were implemented at three rapid heating rates(i.e.,10 K/min,50 K/min,100 K/min,respectively)in a nitrogen atmosphere.On the basis of analytical methods utilized in thermal dynamics and physical chemistry,the results showed that the thermogravimetric curve(TG)of the biomass moved in a high-temperature direction with an increase in the heating rate.The greater the heating rate,the steeper the curve and the lower the resolution,the lag phenomenon of the temperature being more significant.Concurrently,a differential thermal analysis(DTA)was one of the methods employed to study the relationship between the temperature difference and the temperature or time of the tested substance and a reference substance.The peak temperature and maximum reaction rate of the differential thermal analysis curve(DTA)increased as the heating rate,the volatiles and the molecular residence time of the biomass was shortened at a higher heating rate,thereby potentially inhibiting the generation of carbon and increasing the production and yield of liquid fuel.
基金Financial supports from the National Natural Science Foundation of China(Grants Nos.50021101,50371091,90206044)the Ministry of Science and Technology of China(Grants Nos.1999064505 and 1999065009)are acknowledged.Fruitful discussion with Dr.Ruichun WANG are gratefully acknowledged.
文摘The pure α-Ti samples were heated at an extremely high rate （～10^6 K/s） to the temperature of β phase zone followed by a rapidly quenching in an electro-pulsing treatment. After the treatment, micrometer-thick lamellar substructures were generated within the original equiaxed α-Ti coarse grains. Misorientations across adjacent lamellae are of a few degrees. The ultrafine lamellar substructures originated from a non-equilibrium α-β-α’ phase transformation during rapidly heating-quenching process with a short exposure time at high temperatures. Tensile strength was increased by about 100 MPa due to the formation of the ultrafine lamellar substructure while the same tensile plasticity （elongation-to-failure） was maintained relative to the original sample. The strengthening effect could be attributed to the effective blockage of dislocation motions by a high density of sub-boundaries.
基金Funded by the National Natural Science Foundation of China(No.U12301013)the State Ministry of Science and Technology Innovation Fund(No.0102010DFA52240)
文摘A rapid-heating method in the absence of electric/magnetic field was achieved by introducing a self-propagating-combustion （SHS） as heating source. The effect of heating rate on the alumina grain growth was explored based on this rapid-heating method. Comparing with the alumina prepared by two different heating ratios （greater than 1 000 ℃/min in SItS and about 50 ℃/min in common pressureless sintering furnace）, it was revealed that the rapid heating could promote the grain growth greatly without pressure during sintering. However, if a pressure was applied simultaneously, the grain growth would be almost completely restrained. Since these observations are quite different from the expectation, a new grain growth model was proposed.
文摘Three kinds of high-purity A12O3 powders, whose average paticle size is 0. l, 0.3 and 3.0 mp respectively, were used as thestarting power, and their compacts were fired in the radio-frequency plasma generated at a pressure of 80 Pa using N, as the working gas.Experimental results show that the 0. 1 and 0.3 mp powder compacts can be sintered to nearly the theoretical density within 60 s and thissintering is almost finished in the heating period. It is concluded that the mechanism of liquid sintering, the electric charge effect of Al2O3powder, and the effect of tempetrature gradient in the compacts can affect simultaneously on the rapid densification of the compacts inthe plasma sintering.
文摘In rapid thermal processing of a semiconductor wafer, it is important to keep a given temperature rising speed of the wafer during the temperature rising process. We made an experimental apparatus to measure the temperature rising speed of a ceramic ball of 2 mm in diameter heated with four halogen lamp heaters. The heating rate of the halogen lamp heaters was controlled by computer to keep a given temperature rising speed of 50 ℃/s with a controlling time interval of 0.1 s. We examined the effect of various heating control methods on the error of the temperature rising speed of the ceramic ball. We found that a combined method of control with prepared correlation and PID （proportional integral derivative） control is a good method to decrease the error of the temperature rising speed. The average error of the temperature rising speed is 0.5 ℃/s, and the repetition error is almost zero for the temperature rising speed of 50 ℃/s from 330 ℃ to 370 ℃. We also measured the effects of artificial control delay time and measuring error of the monitoring temperature on the error of the temperature rising speed.
文摘Heat treatment plays an important role in tailoring the mechanical properties of powder-metallurgy(PM)titanium alloys.However,only limited work about the rapid heat treatment(RHT)of PM titanium alloys has been reported.In this work,RHT was applied to PM Ti-5Al-5Mo-5V-1Cr-1Fe alloy after hot rolling to study the evolution of its mechanical properties and the influence of residual pores on its properties.Through hot rolling and annealing,a fine and uniformα+βstructure with few residual pores is ob-tained.During RHT,the primaryαdissolves gradually and completes in theβregion,and theβgrains then grow,resulting in the continuous decrease in elongation after aging.Moreover,the tensile strength first increases and then decreases with increasing RHT temperature,owing to the increase in volume fraction of secondaryαinα+βregion and theβgrain growth inβregion.In contrast to the RHT of cast-and-wrought titanium,the negative influence of residual pores lowers the RHT temperature for obtaining the highest tensile strength to a temperature below theβ-transus temperature.Despite the negative influence of the residual pores,retained primaryαand fineβgrains with fine secondaryαinside contribute to achieving a good strength/ductility balance(1570 MPa and 6.1%,respectively).Addi-tionally,although at higher cycles to failure,the negative influence of residual pores increases as it affects the crack initiation zone at the subsurface,the good resistance of secondaryαto fatigue crack propaga-tion still enhances the fatigue strength considerably(about 300 MPa).This work suggests a cost-effective strategy to produce titanium alloys with high performance.
基金Project(20122BAB206014)supported by National Natural Science Foundation of ChinaProject(51365038)supported by the Natural Science Foundation of Jiangxi Province,ChinaProject(GJJ13068)supported by the Science and Technology Program of Educational Committee of Jiangxi Province,China
文摘The effects of process parameters in rapid heat cycle moulding （RHCM） on parts warpage were investigated. A vehicle-used blue-tooth front shell （consisting of ABS material） was considered as a part example manufactured by RHCM method. The corresponding rapid heat response mould with an innovational conformal heating/cooling channel system and a dynamic mould temperature control system based on the Jll-W-160 type precise temperature controller was proposed. During heating/cooling process, the mould was able to be heated from room temperature to 160 ~C in 6 s and then cooled to 80 ~C in 22 s. The effects of processing conditions in RHCM on part warpage were investigated based on the single factor experimental method and Taguchi theory. Results reveal that the elevated mould temperature reduces unwanted freezing during the injection stage, thus improving mouldability and enhancing part quality, whereas the overheated of mould temperature will lead to defective product. The feasible mould temperature scope in RHCM should be no higher than 140 ~C, and the efficient mould temperature scope should be around the polymer heat distortion temperature. Melt temperature as well as injection pressure effects on warpage can be divided into two stages The lower stage gives a no explicit effect on warpage whereas the higher stage leads to a quasi-linear downtrend. But others affect the warpage as a V-type fluctuation, reaching to the minimum around the heat distortion temperature. Under the same mould temperature condition, the effects of process parameters on warpage decrease according to the following order, packing time, packing pressure, melt temperature, injection pressure and cooling time, respectively.
基金Under the auspices of National Natural Science Foundation of China(No.41101039,41371068)
文摘The cold-island effect of urban wetlands has received increasing attention in recent years due to its important role in the alleviation of urban heat islands.Hangzhou,a representative rapidly urbanizing city with rich wetlands in China,was selected as a case study for researching the changes that the urban wetlands have undergone and their impact on the urban thermal environment.Land surface temperature(LST) was acquired from the thermal infrared data of Landsat 5 Thematic Mapper(TM) images in 1990,1995,2000,2006,and 2010,using the single-channel method.The results are as follows:1) considering the changes in land use,the urban wetlands located to the west of Hangzhou have decreased significantly during 1990–2010 because of rapid urbanization.In the Xixi Wetland,the change in land use was relatively small and most of the water body and vegetation were preserved.However,to the east of the Xixi Wetland,large areas of water body and vegetation have been replaced by built-up land as a result of the urbanization process;2) considering the change in LST,it was found from land surface temperature retrieval that the changing spatial pattern of the thermal field was highly correlated with land use changes.Low temperature regions of the eastern Xixi Wetland were gradually eroded by high temperature regions,and the centroid of the heat island in East Xixi was found to be constantly shifting westward.In addition,the difference in LST between the Xixi Wetland and East Xixi has increased;3) considering the impact factors for this area,land use structure and patch shape were found to have a significant impact on LST,shown by the results of multiple linear stepwise regressions.Increasing the size of the wetlands in urban planning is considered to be the most effective measure in alleviating the urban heat island effect.Moreover,reducing the spatial complexity of landscape patches also contributes to the alleviation of the urban heat island effect.
文摘The effects of rapid heating cyclic heat treatment on mechanical properties of a TiAl based alloy (Ti 33Al 3Cr) were studied by means of an induction heating machine. The results show that: 1) fine fully lamellar microstructure with colony size of about 50 μm and lamellar spacing of about 0.12 μm can be obtained; 2) the compression mechanical properties can be improved to a large extent and the best comprehensive compression mechanical properties can reach the yield stress 745 MPa, the large flow stress 1 672 MPa and the compression ratio 19.4%; and 3) the compression fracture at room temperature after induction heat treatment and aging is still typical cleavage fracture.
文摘The microstructural kinetics of <i>β</i> grain growth in the <i>β</i> field of a Ti-6Al-4V alloy was studied by a series of controlled heat treatments at constant temperature rates. Heating rates of 5<span style="white-space:nowrap;">°</span>C/s, 50<span style="white-space:nowrap;">°</span>C/s and 500<span style="white-space:nowrap;">°</span>C/s were considered, stopping at different peak temperatures. The thickness evolution of martensitic needles and lamellar <i>α</i> laths, formed on cooling, was also investigated, by soaking the material above its <i>β</i>-transus temperature and cooling down at 5<span style="white-space:nowrap;">°</span>C/s, 50<span style="white-space:nowrap;">°</span>C/s, 100<span style="white-space:nowrap;">°</span>C/s and 300<span style="white-space:nowrap;">°</span>C/s till ambient temperature. Quantitative microstructural analyses were used to measure the particle dimensions. The <i>β</i> grain growth kinetics was reasonably well described by a modified Avrami equation. The thickness of <i>α</i> lamellae was a function of the cooling rate and the <i>β</i> grain dimension in which they nucleated. The martensite needle thickness was shown to be a function of the cooling rate to which the material was subjected.
文摘The survival ability of insects can be limited with the changes in the levels of energy metabolites under stressful conditions but only a few studies have considered the plastic effects of heat and related climatic factors relevant to tropical habitats. The objectives of our study were to determine whether adults of <i><span style="font-family:Verdana;">Zaprionus</span></i> <i><span style="font-family:Verdana;">indianus</span></i><span style="font-family:Verdana;"> are capable of rapid heat hardening (RHH) and rapid desiccation hardening (RDH) and to compare its benefits with heat acclimation (HA) and desiccation acclimation (DA). Adult flies reared under season-specific simulated conditions were subjected to 38<span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;">°</span>C for RHH and 32<span style="color:#111111;font-family:Roboto, sans-serif;font-size:16px;white-space:normal;background-color:#FFFFFF;">°</span>C for HA, while 5% relative humidity (RH) was maintained for RDH and 40% RH for DA. Stress-induced effects of heat and desiccation on the levels of five metabolites namely cuticular lipids (CL), total body lipids (TBL), protein, proline, and carbohydrates were then estimated by biochemical method. Different duration of heat hardening and acclimation led to more accumulation of CL whereas different durations of desiccation hardening and acclimation revealed less accumulation. In contrast, there was an accumulation of carbohydrates and protein under desiccation hardening and acclimation whereas there was the utilization of carbohydrates and protein under heat hardening and acclimation. However, mixed results were observed on the level of proline and TBL under both heat and desiccation stress. These stress-triggered changes in the levels of various metabolites suggest a possible link between heat and desiccation tolerance. Hence, these compensatory changes in the level of various metabolites also suggest possible energetic homeostasis in </span><i><span style="font-family:Verdana;">Z.</span></i> <i><span style="font-family:Verdana;">indianus</span></i><span style="font-family:Verdana;"> living under harsh climatic conditions of heat and drought in tropical regions.</span>
文摘Silicon carbide (SiC) fiber has recently received considerable attention as promising next-generation fiber because of its high strength at temperatures greater than 1300 ℃ in air.High-quality SiC fiber is primarily made through a curing and heat treatment process.In this study,the chemical vapor curing method,instead of the thermal oxidation curing method,was used to prepare cured polycarbosilane (PCS) fiber.During the high temperature heat treatment of the cured PCS fiber,varied heating rates of 10,20,30,and 40 ℃/min were applied.Throughout the process,the fiber remained in the amorphous silicon carbide phase,and the measured tensile strength was the greatest when the oxygen content in the heat-treated fiber was low,due to the rapid heating rate.The fiber produced through this method was also found to have excellent internal oxidation properties.This fast,continuous process shows a great promise for the production of SiC fiber and the development of high-quality products.
基金the National Natural Science Foundation of China(22371094)Phadcalc(www.phadcalc.com)for computer simulations support.
文摘Passive cooling strategy with zero-energy consumption is effective in preventing people from heat stress.However,most of the existing radiative cooling textiles are fabricated with non-degradable hydrophobic synthetic polymers and lack the functions of sweat management.Herein,a hierarchically designed dual Janus nanofibrous textile with superior thermal-wet management capability is proposed by targeted selection of spinning solvents with different properties during electrospinning.The embedded Al_(2)O_(3)nanoparticles and BN nanosheets in silk fibroin nanofibers endow the textile with high solar reflectivity(97.12%)and infrared emissivity(98.69%),alongside improved in-plane and through-plane thermal conductivity(1.593 and 0.1187 W・K^(−1)・m^(−1),respectively).Benefiting from the asymmetric characteristics of the two sides in terms of fiber diameter and wettability,the nanofibrous textile exhibits unparalleled water transport index(R=1028.93%)and exceptional water vapor transmission rate(141.34 g・m^(−2)・h^(−1)).The textile integrates radiative cooling,rapid heat conduction,and unidirectional sweat evaporation,achieving a cooling effect exceeding 9°C under direct sunlight when worn.Moreover,the Janus textile has good biocompatibility,satisfactory wearability and air breathability,ensuring its comfort in wearable applications.Computer simulations complement experimental results,providing insights into the deep-seated mechanisms of nanofiber formation,Mie scattering,and water transport.This innovative design offers promising prospects for the development of next-generation passive-cooling textiles.
基金supported by Fundamental Research Program of Shanxi Province(No.202203021211164)supported by the National Natural Science Foundation of China(No.22108262),ShanxiProvinceScienceFoundationforYouthsS(No.20210302124600)+1 种基金Shanxi Province Foundation for Returness(No.2022-138)Fund Program for the Scientific Activities of Selected Returned Overseas Professionals in Shanxi Province(No.20220014).
文摘Fast heat transfer in the pyrolyzer can increase the yield of pyrolysis gas and tar,and improve the quality of tar.Compared with the downer pyrolyzer,the cyclone pyrolyzer can simultaneously achieve high solids holdup and violent turbulence,and correspondingly faster heat transfer.In this work,the heat transfer behavior in the cyclone pyrolyzer is specifically studied using the computational fluid dynamics-discrete element method.The simulation results reveal that the gas-solids heat convection contributes mainly to the heat transfer process,and the heat radiation and conduction are relatively small and almost negligible,respectively.Compared with the downer pyrolyzer under the same operating conditions,the heating rate is significantly increased in the cyclone pyrolyzer.By analyzing the flow characteristics in the cyclone pyrolyzer,it is found that the region of high convective heat transfer rate coincides with that of natural cyclone length.Additionally,the final coal temperature increases with the increase of gas velocity and exists a maximum value.These results can offer some qualitative understanding of the heat transfer behavior in the cyclone pyrolyzer.
