The synergetic technology of hydrodynamic cavitation(HC)and peroxydisulfate(PDS)has been adopted for the treatment of organic pollutants,while the rationale behind the thermal-activation of PDS in this process remains...The synergetic technology of hydrodynamic cavitation(HC)and peroxydisulfate(PDS)has been adopted for the treatment of organic pollutants,while the rationale behind the thermal-activation of PDS in this process remains lacking.This paper presented investigation on the degradation of tetracycline under two types of operating conditions,including“internal reaction conditions”(pH value and TC/PDS molar ratio)and“external physical conditions”(hole shape,solution temperature and inlet pressure).Special emphasis was paid on the analysis of thermal effects through a robust modeling approach.The results showed that a synergy index of 6.26 and a degradation rate of 56.71%could be obtained by the HC-PDS process,respectively,when the reaction conditions were optimized.Quenching experiment revealed that·OH and·SO_(4)^(-)were the predominant free radicals and their contribution to the degradation was 75.4%and 24.6%respectively,since a part of·SO_(4)^(-)was transformed into·OH in the solution.The thermal activation of PDS mainly occurred near the hole where the fitting temperature was around 340 K,while·OH was generated in the bubble collapse region downstream the hole,where the temperature was much higher and favorable for the cleavage of water molecular.The average temperature under different external physical conditions was in good consistence with the degradation rates.This research developed a useful method to effectively evaluate the activation extent of PDS by HC and could provide reliable guidance for further development of cavitational reactors to treat organic pollutants based on this hybrid approach.展开更多
In order to well understand the elementary mechanisms that govern the hot working process of a V？5Cr？5Ti alloy （mass fraction, %）, thermal activation parameters under compression were measured in a temperature ran...In order to well understand the elementary mechanisms that govern the hot working process of a V？5Cr？5Ti alloy （mass fraction, %）, thermal activation parameters under compression were measured in a temperature range of 1373？1673 K by a Gleeble？3800 system. The results show that the stress exponentn is 4.87 and the activation energyQis 375.89 kJ/mol for the power law equation. The activation energy is determined as 288.34 kJ/mol, which is close to the self-diffusion energy of alloy （270？300 kJ/mol） by introducing a threshold stress（σ0） variable. The typical values of physical activation volume （Vp） and strain rate sensitivity （m） are measured as （120？700）b3 and 0.075？0.122, respectively, by the repeated stress relaxation tests. These activation parameters indicate that the rate controlling mechanism for V？5Cr？5Ti alloy compressed in ranges of 1373？1673 K and 0.001？1.0 s？1 is the dislocation climb by overcoming of forest dislocations.展开更多
In the background of little reuse and large stockpile for iron ore tailings, iron ore tailing from Chinese Tonghua were used as raw material to prepare cementitious materials. Cementitious properties of the iron ore t...In the background of little reuse and large stockpile for iron ore tailings, iron ore tailing from Chinese Tonghua were used as raw material to prepare cementitious materials. Cementitious properties of the iron ore tailings activated by compound thermal activation were studied. Testing methods, such as XRD, TG-DTA, and IR were used for researching the phase and structure variety of the iron ore railings in the process of compound thermal activation. The results reveal that a new cementitious material that contains 30wt% of the iron ore tailings can be obtained by compounded thermal activation, whose mortar strength can come up to the standard of 42.5 cement of China.展开更多
The effect of activation properties of the precursors of zeolite directly prepared from kaolin influenced by microwave field and conventional heating was investigated.XRD,TG-DSC,FT-IR,SEM,particle size analysis,specif...The effect of activation properties of the precursors of zeolite directly prepared from kaolin influenced by microwave field and conventional heating was investigated.XRD,TG-DSC,FT-IR,SEM,particle size analysis,specific surface area(BET),pore size distribution(BJH)and N2 adsorption-desorption were discussed to determine the optimal activation temperature.It is concluded that the conversion of kaolin to metakaolin in the microwave field is at 500°C holding for 30 min,which is 100°C lower than that in conventional calcination and 90 min shorter,and the phase transition process of kaolin under the effect of microwave field is the same as that of conventional heating method.SEM analysis indicates that the particle size is more uniform and agglomeration appears slightly in the microwave field.The N2 adsorption-desorption isotherm,BET and BJH of kaolin indicate that the pore properties are almost invariable regardless of calcination route during the process of calcining kaolin into metakaolin.It indicates that microwave calcination is superior to conventional calcination in the activation pathway of kaolin.It is attributed to microwave heating relying on objects to absorb microwave energy and convert it into thermal energy,which can simultaneously and uniformly heat the entire substance.展开更多
The aim of this investigation was to prepare geopolymeric precursor from vanadium tailing(VT)by thermal activation and modification.For activation,a homogeneous blend of VT and sodium hydroxide was calcinated at an el...The aim of this investigation was to prepare geopolymeric precursor from vanadium tailing(VT)by thermal activation and modification.For activation,a homogeneous blend of VT and sodium hydroxide was calcinated at an elevated temperature and then modified with metakaolin to produce a geopolymeric precursor.During the thermal activation,the VT was corroded by sodium hydroxide and then sodium silicate formed on the particle surfaces.After water was added,the sodium silicate coating dissolved to release silicon species,which created an alkaline solution environment.The metakaolin then dissolved in the alkaline environment to generate aluminum species,which was followed by geopolymerization.The VT particles were connected by a gel produced during geopolymerization,which yielded a geopolymer with excellent mechanical performance.This investigation not only improves the feasibility of using geopolymer technology for large-scale and in-situ applications,but also promotes the utilization of VT and other silica-rich solid wastes.展开更多
Aluminum alloy 5083(AA5083)processed by large-scale Equal-channel angular pressing(ECAP)is an excellent engineering material with great prospects for industrial applications.An accurate assessment of the underlying co...Aluminum alloy 5083(AA5083)processed by large-scale Equal-channel angular pressing(ECAP)is an excellent engineering material with great prospects for industrial applications.An accurate assessment of the underlying constitutive relationships with easily determined material constants is critical for the predictive design and informed processing of such structural materials.To develop such a design framework,uniaxial dynamic compressive tests over a wide range of temperatures(293-573 K)were carried out for an ECAP-processed AA5083 alloy.Additionally,the microstructure before and after dynamic loading was characterized by SEM and TEM.Based on the experimental results,a new dynamic constitutive model,based on thermal activation theory,was established to describe the plastic flow behavior of the AA5083 alloy that incorporates the effects of plastic strain,temperature,and strain rate.The input parameters of the new model were determined using a particle swarm optimization(PSO)method.The model predictions show excellent agreement with experimental results,which suggests that the current predictive constitutive model is highly effective in reproducing the dynamic deformation behavior of the large-scale ECAP-processed AA5083.展开更多
Papain (Papainase, EC 3.4.22.2) was immobilized on porous silica beads by cross linking with glutaraldehyde. The thermal activation of this immobilized papain in aqueous system was found at, a temperature range from 5...Papain (Papainase, EC 3.4.22.2) was immobilized on porous silica beads by cross linking with glutaraldehyde. The thermal activation of this immobilized papain in aqueous system was found at, a temperature range from 50 to 90 degrees C. The higher the temperature, the more active the immobilized papain will possess. At the same time, the durability of the immobilized papain on heating was greatly improved. The effect of additives and salts on the activity of the immobilized papain were also studied. The results showed that the additives and some of the salts studied could markedly enhance the activity of the immobilized papain at elevated temperature.展开更多
Variable temperature in situ FTIR spectroscopy has been used as the primary tool to investigate the effects of temperature(10 to 50 ℃) on formaldehyde dissociative adsorption and electro oxidation on the Ru(00...Variable temperature in situ FTIR spectroscopy has been used as the primary tool to investigate the effects of temperature(10 to 50 ℃) on formaldehyde dissociative adsorption and electro oxidation on the Ru(0001) electrode in perchloric acid solution, and the results were interpreted in terms of the surface chemistry of the Ru(0001) electrode and compared to those obtained during our previous studies on the adsorption of CO under the same conditions. It was found that formaldehyde did undergo dissociative adsorption, even at -200 mV vs . Ag/AgCl, to form linear(CO L) and 3 fold hollow(CO H) binding CO adsorbates. In contrast to the adsorption of CO, it was found that increasing the temperature to 50 ℃ markedly increased the amount of CO adsorbates formed on the Ru(0001) surface from the adsorption of formaldehyde. On increasing the potential, the electro oxidation of the CO adsorbates to CO 2 took place via reaction with the active (1×1) O oxide. A significant increase in the surface reactivity was observed on the RuO 2(100) phase formed at higher potentials. Formic acid was detected as a partial oxidation product during formaldehyde electro oxidation. The data obtained at 50 ℃ are markedly different from those collected at 10 and 25 ℃ in terms of the amount of both CO 2 and formic acid formed and the adsorbed CO L and CO H species observed. These results were rationalized by the thermal effects on both the loosening of the CO adlayer and the activation of surface oxide on increasing the temperature.展开更多
The aftereffect field of thermal activation, which corresponds to the fluctuation field of a domain wall, is investigated via specific measurements of the magnetization behavior in PraFel4B nanocrystalline magnets. Th...The aftereffect field of thermal activation, which corresponds to the fluctuation field of a domain wall, is investigated via specific measurements of the magnetization behavior in PraFel4B nanocrystalline magnets. The thermal activation is a magnetization reversal arising from thermal fluctuation over an energy barrier to an equilibrate state. According to the magnetic viscosity and the field sweep rate dependence of the coercivity, the calculated values of the fluctuation field are lower than the aftereffect field and in a range between those of domain walls and individual grains. Based on these results, we propose that the magnetization reversal occurs in multiple ways involving grain activation and domain wall activation in thermal activation, and the thermal activation decreases the coercivity by-0.2 kOe in the PrzFe14B ribbons.展开更多
This paper investigates the thermal activation behaviour of current in an inhomogeneous Schottky diode with a Gaussian distribution of barrier height by numerical simulation. The analytical Gaussian distribution model...This paper investigates the thermal activation behaviour of current in an inhomogeneous Schottky diode with a Gaussian distribution of barrier height by numerical simulation. The analytical Gaussian distribution model predicted that the I-VT curves may intersect with the possibility of the negative thermal activation of current, but may be contradictory to the thermionic emission mechanism in a Schottky diode. It shows that the cause of the unphysical phenomenon is related to the incorrect calculation of current across very low barriers. It proposes that junction voltage Vj, excluding the voltage drop across series resistance from the external bias, is a crucial parameter for correct calculation of the current across very low barriers. For correctly employing the thermionic emission model, Vj needs to be smaller than the barrier height Ф. With proper scheme of series resistance connection where the condition of Vj 〉 Ф is guaranteed, I-V T curves of an inhomogeneous Schottky diode with a Gaussian distribution of barrier height have been simulated, which demonstrate normal thermal activation. Although the calculated results exclude the intersecting possibility of I-V T curves with an assumption of temperature-independent series resistance, it shows that the intersecting is possible when the series resistance has a positive temperature coefficient. Finally, the comparison of our numerical and analytical results indicates that the analytical Gaussian distribution model is valid and accurate in analysing I-V-T curves only for small barrier height inhomogeneity.展开更多
A formula is derived for determining the influence of temperature and loading rate on dynamic fracture toughness of a high strength low alloy steel (HQ785C) from thermal activation analysis of the experimental results...A formula is derived for determining the influence of temperature and loading rate on dynamic fracture toughness of a high strength low alloy steel (HQ785C) from thermal activation analysis of the experimental results of three-point bend specimens as well as introducing an Arrhenius formula. It is shown that the results obtained by the given formula are in good agreement with the experimental ones in the thermal activation region. The present method is also valuable to describe the relationship between dynamic fracture toughness and temperature and loading rate of other high strength low alloy steels.展开更多
In stress-augmented thermal activation, the activation energy barrier that controls the rate of atomic and molecular processes is reduced by the application of stress, with the result that the rate of these processes ...In stress-augmented thermal activation, the activation energy barrier that controls the rate of atomic and molecular processes is reduced by the application of stress, with the result that the rate of these processes increases exponentially with applied stress. This concept has particular relevance to Tribology, and since its development in the early twentieth century, it has been applied to develop important models of plastic flow, sliding friction, rheology, wear, and tribochemistry. This paper reviews the development of stress-augmented thermal activation and its application to all of these areas of Tribology. The strengths and limitations of the approach are then discussed and future directions considered. From the scientific point of view, the concept of stress-augmented thermal activation is important since it enables the development of models that describe macroscale tribological performance, such as friction coefficient or tribofilm formation, in terms of the structure and behaviour of individual atoms and molecules. This both helps us understand these processes at a fundamental level and also provides tools for the informed design of lubricants and surfaces.展开更多
Photothermal catalysis represents an emerging technology for solar energy conversion that combines the principles and advantages of photoand thermal catalytic mechanisms[1–5].Driven by the inter/intra-band transition...Photothermal catalysis represents an emerging technology for solar energy conversion that combines the principles and advantages of photoand thermal catalytic mechanisms[1–5].Driven by the inter/intra-band transitions and subsequent electron-phonon scattering processes,photothermal catalysts can achieve rapid and highly localized heating,providing thermal activation to the chemical conversions.Besides,direct participation of photo-generated charge carriers could also drastically reduce the activation energy barriers and modulate the catalytic pathways.However,distinction between thermal and non-thermal contributions remains a key challenge for both fundamental understandings and large-scale applications of photothermal catalysis[6,7].This issue is largely due to a lack of precise in-situ surface-temperature measurement techniques that accurately quantify the light-to-heat conversion under reaction conditions at the nanoscale.Conventional macroscopic temperature measurement techniques,such as infrared cameras and thermocouples,suffer from the lack of spatiotemporal resolutions required for the localized photothermal conversion.They are,thus,measuring an average temperature of the ambient medium.Besides,they typically cannot be applied in in-situ temperature measurements,which is crucial since inaccurate heat dissipation rates may be predicted by ex-situ temperature measurement techniques.For instance,differences in gas pressure,composition and flow rate could lead to significantly different convective heat fluxes.展开更多
Multi-resonance thermally ac-tivated delayed fluorescence(MR-TADF)emitters are one of the most excellent materi-als for high performance or-ganic light-emitting diodes(OLEDs)with high color puri-ty benefiting from the...Multi-resonance thermally ac-tivated delayed fluorescence(MR-TADF)emitters are one of the most excellent materi-als for high performance or-ganic light-emitting diodes(OLEDs)with high color puri-ty benefiting from their nar-row full width at half maxi-mum(FWHM)and great de-vice performance.However,small spin-orbit coupling(SOC)is one of drawbacks for MR-TADF emitters and introduction of heavy atoms may be one effective solution.In this work,four MR-TADF molecules with different atoms(O,S,Se)are carried out based on the first-principles calculation,and excited state dynamics in both toluene and solid phase is investi-gated.Our calculation results indicate that heavy atoms could induce smaller adiabatic ener-gy gap and larger SOC between the first singlet excited state and the first triplet excited state,which is advantageous for the conversion of singlet and triplet excitons,and thus the generation of thermally activated delayed fluorescence(TADF).Though the reorganization energy and full width at half maximum(FWHM)of emission are increased,the influence is quite limited.Besides,the fluorescent rates are also little influenced.Our calculation results indicate that heavy atom introduction is an efficient strategy to enhance the SOC values of MR-TADF emitters without influencing other properties significantly.展开更多
Thermally activated dislocation emission in high-temperature ferroelectric ceramics is investigated through an assumption of thermal stability and a novel analytical method. The stress intensity factor (SIF) arising f...Thermally activated dislocation emission in high-temperature ferroelectric ceramics is investigated through an assumption of thermal stability and a novel analytical method. The stress intensity factor (SIF) arising from domain switching is evaluated by using a Green's function method, and the critical applied electric field intensity factor (CAEFIF) for brittle fracture at room temperature is obtained. Besides, the lowest temperature for single dislocation emission before brittle fracture is also obtained by constructing an energy balance. The multi-scale analysis of facture toughness of the ferroelectric ceramics at high temperature is carried out. Through the analysis, the CAEFIF for crack extension is recalculated. The results show that the competition and interaction effects between dislocation emission and brittle fracture are very obvious. Besides, the higher critical activation temperature, the more columns of obstacles will be overcome. Additionally, the shielding effect arising from thermally activated dislocations is remarkable, thus, the brittle-ductile transition can promote the fracture toughness of high-temperature ferroelectric ceramics.展开更多
Recently the isothermal martensitic transformation in shape memory alloys(SMAs)has been reported in many literatures,and several models have been proposed to interpret the isothermal and athermal kinet-ics.However,the...Recently the isothermal martensitic transformation in shape memory alloys(SMAs)has been reported in many literatures,and several models have been proposed to interpret the isothermal and athermal kinet-ics.However,the underlying mechanisms remain inadequately understood.In this work,the isothermal transformation from B2 to B19 is confirmed in Ti-Ni-Cu-Co melt-spun ribbons at the temperature range between M s and M f.It reaches a saturation point at every isothermal temperature T iso,and the saturation points correspond to the f−T curve at the cooling rate of 0.5 K/min.The experimental results indicate that the isothermal accumulation of martensite is a relaxation process from the transient state to the thermoelastic balance one.A thermally activated kinetic model is developed in this study to characterize the isothermal and athermal kinetics.The model is able to estimate the evolution of martensite volume fraction under any temperature path T(t)and it agrees with the experimental results well.According to the model,the effects of elastic energy,nucleation density,and activation energy on the kinetics are in-vestigated.Among those,a small nucleation density n i as well as a large activation energy Qwill result in a significant isothermal transition.In this work,the slighter isothermal effects originate from the higher value of n i.As for the non-stoichiometric SMAs,the higher value of Qis responsible for the accumula-tion of martensite at the isothermal process.Accordingly,the present work provides a novel view from a kinetic model to understand the isothermal martensitic transformation in SMAs.展开更多
In this paper, the magnetization reversal of the ferromagnetic layers in the IrMn/CoFe/AlOx/CoFe magnetic tunnel junction has been investigated using bulk magnetometry. The films exhibit very complex magnetization pro...In this paper, the magnetization reversal of the ferromagnetic layers in the IrMn/CoFe/AlOx/CoFe magnetic tunnel junction has been investigated using bulk magnetometry. The films exhibit very complex magnetization processes and reversal mechanism. Thermal activation phenomena such as the training effect, the asymmetry of reversal, the loop broadening and the decrease of exchange field while holding the film at negative saturation have been observed on the hysteresis loops of the pinned ferromagnetic layer while not on those of the free ferromagnetic layer. The thermal activation phenomena observed can be explained by the model of two energy barrier distributions with different time constants.展开更多
Three kinds of triazine based organic molecules designed for thermally activated delayed fluorescence （TADF） emitters are investigated by first-principles calculations. An optimal Hartree-Fork （HF） method is adopt...Three kinds of triazine based organic molecules designed for thermally activated delayed fluorescence （TADF） emitters are investigated by first-principles calculations. An optimal Hartree-Fork （HF） method is adopted for the calculation of energy gap between the first singlet state （S1） and the first triplet state （T1）. The natural transition orbital, the electron- hole （e-h） distribution and the e-h overlap diagram indicate that the S1 states for the three systems include both charge-transfer and some localized excitation component. Further quantitative analysis of the excitation property is performed by introducing the index Ar and the integral of e-h overlap S. It is found that symmetric geometry is a necessary condition for TADF emitters, which can provide more delocalized transition orbitals and consequently a small S1-T1 energy gap. Artful inserting aromatic groups between donors and acceptors can significantly enhance the oscillator strength. Finally, the energy state structures calculated with the optimal HF method is presented, which can provide basis for the study of the dynamics of excited states.展开更多
A purely organic D-π-A-π-D type emitter showing thermally activated delayed fluorescence(TADF)and room temperature phosphorescence(RTP)was designed and synthesized by utilizing the benzophenone as an acceptor and th...A purely organic D-π-A-π-D type emitter showing thermally activated delayed fluorescence(TADF)and room temperature phosphorescence(RTP)was designed and synthesized by utilizing the benzophenone as an acceptor and the N-phenyl-2-napthylamine as a donor moiety.It exhibits considerable TADF character in doped PMMA film and room temperature phosphorescence with a long lifetime of 74 ms at466 nm in solid state.The devices with the configuration of ITO/Mo_(2) O_(3)(4 nm)/mCP(30 nm)/mCP:x wt%NP2 BP/TmTyPB(60 nm)/LiF(1.5 nm)/AI(100 nm)were prepared by vacuum evaporation to explore their electroluminescent performance.Intere stingly,the non-doped device has obtained near-white emission with a fluorescence emission peak at 475 nm and a phosphore scence emission peak at 563 nm having the CIE coordinate of(0.23,0.32)and the maximum external quantum efficiency of 1.09%.展开更多
To study active heat insulation roadway in high temperature mines,the typical high temperature roadway of−965 m in Zhujidong Coal Mine of Anhui,China,is selected as prototype.The ANSYS numerical simulation method is u...To study active heat insulation roadway in high temperature mines,the typical high temperature roadway of−965 m in Zhujidong Coal Mine of Anhui,China,is selected as prototype.The ANSYS numerical simulation method is used for sensitivity analysis of heat insulation layer with different thermal conductivity and thickness,as well as surrounding rock with different thermal conductivity and temperature on a heat-adjusting zone radius,surrounding rock temperature field and wall temperature.The results show that the heat-adjusting zone radius will entirely be in the right power index relationship to the ventilation time.Decrease in thermal conductivity and increase in thickness of insulation layer can effectively reduce the disturbance of airflow on the surrounding rock temperature,hence,beneficial for decreasing wall temperature.This favourable trend significantly decreases with ventilation time,increase in thermal conductivity and temperature of surrounding rock,heat-adjusting zone radius,surrounding rock temperature field,and wall temperature.Sensitivity analysis shows that the thermal physical properties of surrounding rock determine the temperature distribution of the roadway,hence,temperature of surrounding rock is considered as the most sensitive factor of all influencing factors.For the spray layer,thermal conductivity is more sensitive,compared to thickness.It is concluded that increase in the spray layer thickness is not as beneficial as using low thermal conductivity insulation material.Therefore,roadway preferential consideration should be given to the rocks with low temperature and thermal conductivity.The application of the insulation layer has positive significance for the thermal environment control in mine roadway,however,increase in the layer thickness without restriction has a limited effect on the thermal insulation.展开更多
基金supported by the National Natural Science Foundation of China(Nos.22136003 and 21972073)the Opening foundation of the Engineering Research Center of Ecoenvironment in Three Gorges Reservoir Region,Ministry of Education(No.KF2023-01)the Natural Science Foundation of Yichang City(No.A22-3-005)。
文摘The synergetic technology of hydrodynamic cavitation(HC)and peroxydisulfate(PDS)has been adopted for the treatment of organic pollutants,while the rationale behind the thermal-activation of PDS in this process remains lacking.This paper presented investigation on the degradation of tetracycline under two types of operating conditions,including“internal reaction conditions”(pH value and TC/PDS molar ratio)and“external physical conditions”(hole shape,solution temperature and inlet pressure).Special emphasis was paid on the analysis of thermal effects through a robust modeling approach.The results showed that a synergy index of 6.26 and a degradation rate of 56.71%could be obtained by the HC-PDS process,respectively,when the reaction conditions were optimized.Quenching experiment revealed that·OH and·SO_(4)^(-)were the predominant free radicals and their contribution to the degradation was 75.4%and 24.6%respectively,since a part of·SO_(4)^(-)was transformed into·OH in the solution.The thermal activation of PDS mainly occurred near the hole where the fitting temperature was around 340 K,while·OH was generated in the bubble collapse region downstream the hole,where the temperature was much higher and favorable for the cleavage of water molecular.The average temperature under different external physical conditions was in good consistence with the degradation rates.This research developed a useful method to effectively evaluate the activation extent of PDS by HC and could provide reliable guidance for further development of cavitational reactors to treat organic pollutants based on this hybrid approach.
基金Project(11105127)supported by the National Natural Science Foundation of China
文摘In order to well understand the elementary mechanisms that govern the hot working process of a V？5Cr？5Ti alloy （mass fraction, %）, thermal activation parameters under compression were measured in a temperature range of 1373？1673 K by a Gleeble？3800 system. The results show that the stress exponentn is 4.87 and the activation energyQis 375.89 kJ/mol for the power law equation. The activation energy is determined as 288.34 kJ/mol, which is close to the self-diffusion energy of alloy （270？300 kJ/mol） by introducing a threshold stress（σ0） variable. The typical values of physical activation volume （Vp） and strain rate sensitivity （m） are measured as （120？700）b3 and 0.075？0.122, respectively, by the repeated stress relaxation tests. These activation parameters indicate that the rate controlling mechanism for V？5Cr？5Ti alloy compressed in ranges of 1373？1673 K and 0.001？1.0 s？1 is the dislocation climb by overcoming of forest dislocations.
基金supported by the National Nature Science Foundation of China (No.50674062)the National Key Technologies R&D Program of China (No.2006BAC21B03)the Post doctoral Science Foundation (No.20070420354)
文摘In the background of little reuse and large stockpile for iron ore tailings, iron ore tailing from Chinese Tonghua were used as raw material to prepare cementitious materials. Cementitious properties of the iron ore tailings activated by compound thermal activation were studied. Testing methods, such as XRD, TG-DTA, and IR were used for researching the phase and structure variety of the iron ore railings in the process of compound thermal activation. The results reveal that a new cementitious material that contains 30wt% of the iron ore tailings can be obtained by compounded thermal activation, whose mortar strength can come up to the standard of 42.5 cement of China.
基金Projects(51604135,51504116)supported by the National Natural Science Foundational of ChinaProject(YNWR-QNBJ-2018-323)supported by the Yunan Ten Thousand Talents Plan Young&Elite Talents Project,China。
文摘The effect of activation properties of the precursors of zeolite directly prepared from kaolin influenced by microwave field and conventional heating was investigated.XRD,TG-DSC,FT-IR,SEM,particle size analysis,specific surface area(BET),pore size distribution(BJH)and N2 adsorption-desorption were discussed to determine the optimal activation temperature.It is concluded that the conversion of kaolin to metakaolin in the microwave field is at 500°C holding for 30 min,which is 100°C lower than that in conventional calcination and 90 min shorter,and the phase transition process of kaolin under the effect of microwave field is the same as that of conventional heating method.SEM analysis indicates that the particle size is more uniform and agglomeration appears slightly in the microwave field.The N2 adsorption-desorption isotherm,BET and BJH of kaolin indicate that the pore properties are almost invariable regardless of calcination route during the process of calcining kaolin into metakaolin.It indicates that microwave calcination is superior to conventional calcination in the activation pathway of kaolin.It is attributed to microwave heating relying on objects to absorb microwave energy and convert it into thermal energy,which can simultaneously and uniformly heat the entire substance.
基金This work was financially supported by the Major Tech-nical Innovation Project of Hubei Province,China(No.2018ACA157)the National Natural Science Foundation of China(No.51874222)the Excellent Dissertation Cul-tivation Funds of Wuhan University of Technology(No.2018-YS-052).
文摘The aim of this investigation was to prepare geopolymeric precursor from vanadium tailing(VT)by thermal activation and modification.For activation,a homogeneous blend of VT and sodium hydroxide was calcinated at an elevated temperature and then modified with metakaolin to produce a geopolymeric precursor.During the thermal activation,the VT was corroded by sodium hydroxide and then sodium silicate formed on the particle surfaces.After water was added,the sodium silicate coating dissolved to release silicon species,which created an alkaline solution environment.The metakaolin then dissolved in the alkaline environment to generate aluminum species,which was followed by geopolymerization.The VT particles were connected by a gel produced during geopolymerization,which yielded a geopolymer with excellent mechanical performance.This investigation not only improves the feasibility of using geopolymer technology for large-scale and in-situ applications,but also promotes the utilization of VT and other silica-rich solid wastes.
文摘Aluminum alloy 5083(AA5083)processed by large-scale Equal-channel angular pressing(ECAP)is an excellent engineering material with great prospects for industrial applications.An accurate assessment of the underlying constitutive relationships with easily determined material constants is critical for the predictive design and informed processing of such structural materials.To develop such a design framework,uniaxial dynamic compressive tests over a wide range of temperatures(293-573 K)were carried out for an ECAP-processed AA5083 alloy.Additionally,the microstructure before and after dynamic loading was characterized by SEM and TEM.Based on the experimental results,a new dynamic constitutive model,based on thermal activation theory,was established to describe the plastic flow behavior of the AA5083 alloy that incorporates the effects of plastic strain,temperature,and strain rate.The input parameters of the new model were determined using a particle swarm optimization(PSO)method.The model predictions show excellent agreement with experimental results,which suggests that the current predictive constitutive model is highly effective in reproducing the dynamic deformation behavior of the large-scale ECAP-processed AA5083.
基金This research was supported by the Foundation of State Education Committee of China.
文摘Papain (Papainase, EC 3.4.22.2) was immobilized on porous silica beads by cross linking with glutaraldehyde. The thermal activation of this immobilized papain in aqueous system was found at, a temperature range from 50 to 90 degrees C. The higher the temperature, the more active the immobilized papain will possess. At the same time, the durability of the immobilized papain on heating was greatly improved. The effect of additives and salts on the activity of the immobilized papain were also studied. The results showed that the additives and some of the salts studied could markedly enhance the activity of the immobilized papain at elevated temperature.
文摘Variable temperature in situ FTIR spectroscopy has been used as the primary tool to investigate the effects of temperature(10 to 50 ℃) on formaldehyde dissociative adsorption and electro oxidation on the Ru(0001) electrode in perchloric acid solution, and the results were interpreted in terms of the surface chemistry of the Ru(0001) electrode and compared to those obtained during our previous studies on the adsorption of CO under the same conditions. It was found that formaldehyde did undergo dissociative adsorption, even at -200 mV vs . Ag/AgCl, to form linear(CO L) and 3 fold hollow(CO H) binding CO adsorbates. In contrast to the adsorption of CO, it was found that increasing the temperature to 50 ℃ markedly increased the amount of CO adsorbates formed on the Ru(0001) surface from the adsorption of formaldehyde. On increasing the potential, the electro oxidation of the CO adsorbates to CO 2 took place via reaction with the active (1×1) O oxide. A significant increase in the surface reactivity was observed on the RuO 2(100) phase formed at higher potentials. Formic acid was detected as a partial oxidation product during formaldehyde electro oxidation. The data obtained at 50 ℃ are markedly different from those collected at 10 and 25 ℃ in terms of the amount of both CO 2 and formic acid formed and the adsorbed CO L and CO H species observed. These results were rationalized by the thermal effects on both the loosening of the CO adlayer and the activation of surface oxide on increasing the temperature.
基金Project supported by the Knowledge Innovation Project of the Chinese Academy of Sciences and the National Basic Research Program of China
文摘The aftereffect field of thermal activation, which corresponds to the fluctuation field of a domain wall, is investigated via specific measurements of the magnetization behavior in PraFel4B nanocrystalline magnets. The thermal activation is a magnetization reversal arising from thermal fluctuation over an energy barrier to an equilibrate state. According to the magnetic viscosity and the field sweep rate dependence of the coercivity, the calculated values of the fluctuation field are lower than the aftereffect field and in a range between those of domain walls and individual grains. Based on these results, we propose that the magnetization reversal occurs in multiple ways involving grain activation and domain wall activation in thermal activation, and the thermal activation decreases the coercivity by-0.2 kOe in the PrzFe14B ribbons.
基金supported by Shanghai-Applied Materials Research and Development Fund (Grant Nos.07SA06 and 09700714200)Fok Ying Tong Education Foundation (Grant No.114006)
文摘This paper investigates the thermal activation behaviour of current in an inhomogeneous Schottky diode with a Gaussian distribution of barrier height by numerical simulation. The analytical Gaussian distribution model predicted that the I-VT curves may intersect with the possibility of the negative thermal activation of current, but may be contradictory to the thermionic emission mechanism in a Schottky diode. It shows that the cause of the unphysical phenomenon is related to the incorrect calculation of current across very low barriers. It proposes that junction voltage Vj, excluding the voltage drop across series resistance from the external bias, is a crucial parameter for correct calculation of the current across very low barriers. For correctly employing the thermionic emission model, Vj needs to be smaller than the barrier height Ф. With proper scheme of series resistance connection where the condition of Vj 〉 Ф is guaranteed, I-V T curves of an inhomogeneous Schottky diode with a Gaussian distribution of barrier height have been simulated, which demonstrate normal thermal activation. Although the calculated results exclude the intersecting possibility of I-V T curves with an assumption of temperature-independent series resistance, it shows that the intersecting is possible when the series resistance has a positive temperature coefficient. Finally, the comparison of our numerical and analytical results indicates that the analytical Gaussian distribution model is valid and accurate in analysing I-V-T curves only for small barrier height inhomogeneity.
文摘A formula is derived for determining the influence of temperature and loading rate on dynamic fracture toughness of a high strength low alloy steel (HQ785C) from thermal activation analysis of the experimental results of three-point bend specimens as well as introducing an Arrhenius formula. It is shown that the results obtained by the given formula are in good agreement with the experimental ones in the thermal activation region. The present method is also valuable to describe the relationship between dynamic fracture toughness and temperature and loading rate of other high strength low alloy steels.
文摘In stress-augmented thermal activation, the activation energy barrier that controls the rate of atomic and molecular processes is reduced by the application of stress, with the result that the rate of these processes increases exponentially with applied stress. This concept has particular relevance to Tribology, and since its development in the early twentieth century, it has been applied to develop important models of plastic flow, sliding friction, rheology, wear, and tribochemistry. This paper reviews the development of stress-augmented thermal activation and its application to all of these areas of Tribology. The strengths and limitations of the approach are then discussed and future directions considered. From the scientific point of view, the concept of stress-augmented thermal activation is important since it enables the development of models that describe macroscale tribological performance, such as friction coefficient or tribofilm formation, in terms of the structure and behaviour of individual atoms and molecules. This both helps us understand these processes at a fundamental level and also provides tools for the informed design of lubricants and surfaces.
基金support from the National Natural Science Foundation of China(22302137,52172221,52272229,51920105005)the Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices(ZZ2201)+1 种基金the Suzhou Key Laboratory of Advanced Photonic Materialsthe Collaborative Innovation Center of Suzhou Nano Science&Technology.
文摘Photothermal catalysis represents an emerging technology for solar energy conversion that combines the principles and advantages of photoand thermal catalytic mechanisms[1–5].Driven by the inter/intra-band transitions and subsequent electron-phonon scattering processes,photothermal catalysts can achieve rapid and highly localized heating,providing thermal activation to the chemical conversions.Besides,direct participation of photo-generated charge carriers could also drastically reduce the activation energy barriers and modulate the catalytic pathways.However,distinction between thermal and non-thermal contributions remains a key challenge for both fundamental understandings and large-scale applications of photothermal catalysis[6,7].This issue is largely due to a lack of precise in-situ surface-temperature measurement techniques that accurately quantify the light-to-heat conversion under reaction conditions at the nanoscale.Conventional macroscopic temperature measurement techniques,such as infrared cameras and thermocouples,suffer from the lack of spatiotemporal resolutions required for the localized photothermal conversion.They are,thus,measuring an average temperature of the ambient medium.Besides,they typically cannot be applied in in-situ temperature measurements,which is crucial since inaccurate heat dissipation rates may be predicted by ex-situ temperature measurement techniques.For instance,differences in gas pressure,composition and flow rate could lead to significantly different convective heat fluxes.
基金supported by the National Natural Science Foundation of China(No.11974216,No.12374269)the support of the Taishan Scholar Project of Shandong Province。
文摘Multi-resonance thermally ac-tivated delayed fluorescence(MR-TADF)emitters are one of the most excellent materi-als for high performance or-ganic light-emitting diodes(OLEDs)with high color puri-ty benefiting from their nar-row full width at half maxi-mum(FWHM)and great de-vice performance.However,small spin-orbit coupling(SOC)is one of drawbacks for MR-TADF emitters and introduction of heavy atoms may be one effective solution.In this work,four MR-TADF molecules with different atoms(O,S,Se)are carried out based on the first-principles calculation,and excited state dynamics in both toluene and solid phase is investi-gated.Our calculation results indicate that heavy atoms could induce smaller adiabatic ener-gy gap and larger SOC between the first singlet excited state and the first triplet excited state,which is advantageous for the conversion of singlet and triplet excitons,and thus the generation of thermally activated delayed fluorescence(TADF).Though the reorganization energy and full width at half maximum(FWHM)of emission are increased,the influence is quite limited.Besides,the fluorescent rates are also little influenced.Our calculation results indicate that heavy atom introduction is an efficient strategy to enhance the SOC values of MR-TADF emitters without influencing other properties significantly.
基金Supported by the Ph.D. Programs Foundation of Ministry of Education of China under Grant No. 20123305120008, the Scientific Research Project of Department of Education of Zhejiang Province under Grant No. Y201223508, a Grant from the Impact and Safety of Coastal Engineering Initiative, a COE Program of Zhejiang Provincial Government at Ningbo University under Grant Nos. zj1117, zj1203, and zj1201 and the K.C. Wong Magana Fund
文摘Thermally activated dislocation emission in high-temperature ferroelectric ceramics is investigated through an assumption of thermal stability and a novel analytical method. The stress intensity factor (SIF) arising from domain switching is evaluated by using a Green's function method, and the critical applied electric field intensity factor (CAEFIF) for brittle fracture at room temperature is obtained. Besides, the lowest temperature for single dislocation emission before brittle fracture is also obtained by constructing an energy balance. The multi-scale analysis of facture toughness of the ferroelectric ceramics at high temperature is carried out. Through the analysis, the CAEFIF for crack extension is recalculated. The results show that the competition and interaction effects between dislocation emission and brittle fracture are very obvious. Besides, the higher critical activation temperature, the more columns of obstacles will be overcome. Additionally, the shielding effect arising from thermally activated dislocations is remarkable, thus, the brittle-ductile transition can promote the fracture toughness of high-temperature ferroelectric ceramics.
基金the National Natural Science Foun-dation of China(Nos.51931004 and 51871080).
文摘Recently the isothermal martensitic transformation in shape memory alloys(SMAs)has been reported in many literatures,and several models have been proposed to interpret the isothermal and athermal kinet-ics.However,the underlying mechanisms remain inadequately understood.In this work,the isothermal transformation from B2 to B19 is confirmed in Ti-Ni-Cu-Co melt-spun ribbons at the temperature range between M s and M f.It reaches a saturation point at every isothermal temperature T iso,and the saturation points correspond to the f−T curve at the cooling rate of 0.5 K/min.The experimental results indicate that the isothermal accumulation of martensite is a relaxation process from the transient state to the thermoelastic balance one.A thermally activated kinetic model is developed in this study to characterize the isothermal and athermal kinetics.The model is able to estimate the evolution of martensite volume fraction under any temperature path T(t)and it agrees with the experimental results well.According to the model,the effects of elastic energy,nucleation density,and activation energy on the kinetics are in-vestigated.Among those,a small nucleation density n i as well as a large activation energy Qwill result in a significant isothermal transition.In this work,the slighter isothermal effects originate from the higher value of n i.As for the non-stoichiometric SMAs,the higher value of Qis responsible for the accumula-tion of martensite at the isothermal process.Accordingly,the present work provides a novel view from a kinetic model to understand the isothermal martensitic transformation in SMAs.
基金supported by the National Natural Science Foundation of China (Grant No 50671048)
文摘In this paper, the magnetization reversal of the ferromagnetic layers in the IrMn/CoFe/AlOx/CoFe magnetic tunnel junction has been investigated using bulk magnetometry. The films exhibit very complex magnetization processes and reversal mechanism. Thermal activation phenomena such as the training effect, the asymmetry of reversal, the loop broadening and the decrease of exchange field while holding the film at negative saturation have been observed on the hysteresis loops of the pinned ferromagnetic layer while not on those of the free ferromagnetic layer. The thermal activation phenomena observed can be explained by the model of two energy barrier distributions with different time constants.
文摘Three kinds of triazine based organic molecules designed for thermally activated delayed fluorescence （TADF） emitters are investigated by first-principles calculations. An optimal Hartree-Fork （HF） method is adopted for the calculation of energy gap between the first singlet state （S1） and the first triplet state （T1）. The natural transition orbital, the electron- hole （e-h） distribution and the e-h overlap diagram indicate that the S1 states for the three systems include both charge-transfer and some localized excitation component. Further quantitative analysis of the excitation property is performed by introducing the index Ar and the integral of e-h overlap S. It is found that symmetric geometry is a necessary condition for TADF emitters, which can provide more delocalized transition orbitals and consequently a small S1-T1 energy gap. Artful inserting aromatic groups between donors and acceptors can significantly enhance the oscillator strength. Finally, the energy state structures calculated with the optimal HF method is presented, which can provide basis for the study of the dynamics of excited states.
基金absolutely supported by Program for National Natural Scientific Foundation of China(Nos.91833304,61904120,61775155,61705158)Natural Science Foundation of Shanxi Province(Nos.201901D211090,201903D121100,201801D221124)+1 种基金the Fundamental Research Funds for the Central Universities,Shanxi Provincial Key Innovative Research Team in Science and Technology(No.201601D021043)the Joint Research Funds of Department of Science&Technology of Shaanxi Province and Northwestern Polytechnical University(No.2020GXLH-Z-006)。
文摘A purely organic D-π-A-π-D type emitter showing thermally activated delayed fluorescence(TADF)and room temperature phosphorescence(RTP)was designed and synthesized by utilizing the benzophenone as an acceptor and the N-phenyl-2-napthylamine as a donor moiety.It exhibits considerable TADF character in doped PMMA film and room temperature phosphorescence with a long lifetime of 74 ms at466 nm in solid state.The devices with the configuration of ITO/Mo_(2) O_(3)(4 nm)/mCP(30 nm)/mCP:x wt%NP2 BP/TmTyPB(60 nm)/LiF(1.5 nm)/AI(100 nm)were prepared by vacuum evaporation to explore their electroluminescent performance.Intere stingly,the non-doped device has obtained near-white emission with a fluorescence emission peak at 475 nm and a phosphore scence emission peak at 563 nm having the CIE coordinate of(0.23,0.32)and the maximum external quantum efficiency of 1.09%.
基金This work was supported by the National Natural Science Foundation of China(51774011)Funding Project of Anhui University of Science and Technology(QN2019115)Introduced Research Funding of Anhui University of Science and Technology(13190022).
文摘To study active heat insulation roadway in high temperature mines,the typical high temperature roadway of−965 m in Zhujidong Coal Mine of Anhui,China,is selected as prototype.The ANSYS numerical simulation method is used for sensitivity analysis of heat insulation layer with different thermal conductivity and thickness,as well as surrounding rock with different thermal conductivity and temperature on a heat-adjusting zone radius,surrounding rock temperature field and wall temperature.The results show that the heat-adjusting zone radius will entirely be in the right power index relationship to the ventilation time.Decrease in thermal conductivity and increase in thickness of insulation layer can effectively reduce the disturbance of airflow on the surrounding rock temperature,hence,beneficial for decreasing wall temperature.This favourable trend significantly decreases with ventilation time,increase in thermal conductivity and temperature of surrounding rock,heat-adjusting zone radius,surrounding rock temperature field,and wall temperature.Sensitivity analysis shows that the thermal physical properties of surrounding rock determine the temperature distribution of the roadway,hence,temperature of surrounding rock is considered as the most sensitive factor of all influencing factors.For the spray layer,thermal conductivity is more sensitive,compared to thickness.It is concluded that increase in the spray layer thickness is not as beneficial as using low thermal conductivity insulation material.Therefore,roadway preferential consideration should be given to the rocks with low temperature and thermal conductivity.The application of the insulation layer has positive significance for the thermal environment control in mine roadway,however,increase in the layer thickness without restriction has a limited effect on the thermal insulation.
