The distribution of exothermic reaction rates is jointly influenced by reduced activation energy and reaction rate constant.This study focuses on the effect of distribution of exothermic reaction rates on detonation w...The distribution of exothermic reaction rates is jointly influenced by reduced activation energy and reaction rate constant.This study focuses on the effect of distribution of exothermic reaction rates on detonation wave propagation instability,specifically under conditions where the length of the induction and exothermic reaction remains constant.It is found that the distribution variation of exothermic reaction rates significantly influences the detonation wave propagation characteristics.Specifically,under conditions of high activation energy,the exothermic reaction rate profile exhibits a smoother distribution but becomes more prone to perturbations.This heightened sensitivity,coupled with the augmented overdriven degree associated with pulsating detonation and cellular detonation wave propagation,further exacerbates the instability characteristics of detonation waves.Especially to the two-dimensional detonation waves with high activation energies,the distribution of exothermic reaction rates becomes more sensitive to these displacements,reinforcing the transverse shock wave and leading to a transformation of the wavefront and cellular structure towards more unstable configurations.This research delves into the intricate interactions between the distribution of exothermic reaction rates and detonation wave instability,aiming to provide an explanatory of detonation instability.展开更多
The glass-forming ability of Mg-Cu-Gd alloys could be significantly promoted with the addition of Ag.A calorimetric anomaly could be observed in the supercooled liquid region of the Mg-Cu-Ag-Gd metallic glass,indicati...The glass-forming ability of Mg-Cu-Gd alloys could be significantly promoted with the addition of Ag.A calorimetric anomaly could be observed in the supercooled liquid region of the Mg-Cu-Ag-Gd metallic glass,indicating the occurrence of a liquid-state phase transition driven by entropy.However,the underlying mechanism of the polyamorphous phase transition remains unsettled.In the paper,in situ scattering techniques were employed to reveal multiscale structure evidence in a Mg65Cu15Ag10Gd10metallic glass with an anomalous exothermic peak upon heating.Resistivity measurements indicate a reentrant behavior for the Mg-Cu-Ag-Gd metallic glass in the anomalous exothermic peak temperature region during heating.In situ synchrotron diffraction results revealed that the local atomic structure tends to be ordered and loosely packed first,followed by reentering into the initial state upon heating.Moreover,time-resolved small-angle synchrotron X-ray scattering(SAXS) results show an increase in nanoscale heterogeneity first followed by a reentrant supercooled liquid behavior.A core-shell structure model has been used to fit the SAXS profiles when polyamorphous phase transition occurs.In contrast,there is no structure anomaly for the reference Mg-Cu-Gd alloy system.The detailed multiscale structural evidence suggests the occurrence of a liquid-liquid phase transition followed by a reentrant behavior in the MgCu-Ag-Gd metallic glass.Our results deepen the understanding of the structural origin of the glass-forming ability and shed light on the possibility of tuning the physical and mechanical properties by heat-treatment in the supercooled liquid region of Mg-based metallic glasses.展开更多
The microstructures of NiAl(Co)-TiB_2 composite prepared using exothermal dispersion (XD) method have been studied by optical microscopy, XRD, EDS, and TEM The results show that, TiB_2 paritcles are typically single c...The microstructures of NiAl(Co)-TiB_2 composite prepared using exothermal dispersion (XD) method have been studied by optical microscopy, XRD, EDS, and TEM The results show that, TiB_2 paritcles are typically single crystal, and fairly uniformly distributed. The matrix mainly consists of β-NiAl phase, Ll_2γ′Ni_3Al phase and δ-Ni_3Al phase. The δNi_3Al has a fcc crystal structure with lattice parameter a=1.068nm.The data of compressive testing at room temperature show that the room temperature ductility of NiAl(Co) matrix composite is much better than that of stoichiometric NiAl.展开更多
Thermal runaway is a critical issue for the large application of lithium-ion batteries.Exothermic reactions between lithiated graphite and electrolyte play a crucial role in the thermal runaway of lithium-ion batterie...Thermal runaway is a critical issue for the large application of lithium-ion batteries.Exothermic reactions between lithiated graphite and electrolyte play a crucial role in the thermal runaway of lithium-ion batteries.However,the role of each component in the electrolyte during the exothermic reactions with lithiated graphite has not been fully understood.In this paper,the exothermic reactions between lithiated graphite and electrolyte of lithium-ion battery are investigated through differential scanning calorimetry(DSC) and evolved gas analysis.The lithiated graphite in the presence of electrolyte exhibit three exothermic peaks during DSC test.The reactions between lithiated graphite and LiPF_(6) and ethylene carbonate are found to be responsible for the first two exothermic peaks,while the third exothermic peak is attributed to the reaction between lithiated graphite and binder.In contrast,diethylene carbonate and ethyl methyl carbonate contribute little to the total heat generation of graphite-electrolyte reactions.The reaction mechanism between lithiated graphite and electrolyte,including the major reaction equations and gas products,are summarized.Finally,DSC tests on samples with various amounts of electrolyte are performed to clarify the quantitative relationship between lithiated graphite and electrolyte during the exothermic reactions.2.5 mg of lithiated graphite (Li_(0.8627)C_(6)) can fully react with around 7.2 mg electrolyte,releasing a heat generation of 2491 J g^(-1).The results presented in this study can provide useful guidance for the safety improvement of lithium-ion batteries.展开更多
Recent achievements in concrete hydration exothermic models based on Arrhenius equation have improved computation accuracy for mass concrete temperature field. But the properties of the activation energy and the gas c...Recent achievements in concrete hydration exothermic models based on Arrhenius equation have improved computation accuracy for mass concrete temperature field. But the properties of the activation energy and the gas constant （Ea/R） have not been well studied yet. From the latest experiments it is shown that Ea/R obviously changes with the hydration degree without fixed form. In this paper, the relationship between hydration degree and Ea/R is studied and a new hydration exothermic model is proposed. With those achievements, the mass concrete temperature field with arbitrary boundary condition can be calculated more precisely.展开更多
A number of dry bridges have been built to substitute for the roadbed on the Qinghai-Tibet Railway,China.The aim of this study was to investigate the exothermic process of cast-in-place (CIP) pile foundation of a dry ...A number of dry bridges have been built to substitute for the roadbed on the Qinghai-Tibet Railway,China.The aim of this study was to investigate the exothermic process of cast-in-place (CIP) pile foundation of a dry bridge and its harm to the stability of nearby frozen ground.We present 3D heat conduction functions of a concrete pile and of frozen ground with related boundaries.Our analysis is based on the theory of heat conduction and the exponent law describing the adiabatic temperature rise caused by hydration heat.Results under continuous and initial conditions were combined to establish a finite element model of a CIP pile-frozen ground system for a dry bridge under actual field conditions in cold regions.Numerical results indicated that the process could effectively simulate the exothermic process of CIP pile foundation.Thermal disturbance to frozen ground under a long dry bridge caused by the casting temperature and hydration heat of CIP piles was substantial and long-lasting.The simulated thermal analysis results agreed with field measurements and some significant rules relating to the problem were deduced and conclusions reached.展开更多
The research on the adsorption equilibria,kinetics,and increase in process temperature of the volatile organic compound(VOC)adsorption in porous materials ensures safe production,thereby reducing production costs and ...The research on the adsorption equilibria,kinetics,and increase in process temperature of the volatile organic compound(VOC)adsorption in porous materials ensures safe production,thereby reducing production costs and improving separation efficiency.Therefore,it is critical in predicting the entire adsorption process based on minimal or no experimental input of the adsorbate and adsorbent.We discuss,in this review,the factors that affect the adsorption performance of VOCs in activated carbons,including the adsorption equilibrium,adsorption kinetics,and exotherm during adsorption.Subsequently,the existing prediction models are summarized and compared concerning the adsorption equilibrium,adsorption kinetics,and exothermic process of adsorption.We then propose a new prediction model based on intermolecular interaction and provide an outlook toward the design and manipulation of efficient adsorbents for the VOC system.展开更多
The effect of top slag basicity on quality of steel treated with SiFe and SiCaBa alloy as exothermic agent in chemical heating was studied. These experiments were carried out in MoSi 2 laboratory furnace with 0 2?kg...The effect of top slag basicity on quality of steel treated with SiFe and SiCaBa alloy as exothermic agent in chemical heating was studied. These experiments were carried out in MoSi 2 laboratory furnace with 0 2?kg molten steel for equilibrium test and 2?kg molten steel for simulation test respectively. These results showed that the adjusting basicity of top slag with CaO is effective to prevent rephosphorization and resulphurization, and it is possible to dephosphorize and desulphurize and remove the inclusions from molten steel when basicity R of the top slag is adjusted to 2 0-3 10, and SiCaBa alloy is better than SiFe alloy in this relation.展开更多
It is shown in this article that by changing the initial operation condition of the batch processes, the dynamic performance of the system can be varied largely, especially for the initial operational temperature of t...It is shown in this article that by changing the initial operation condition of the batch processes, the dynamic performance of the system can be varied largely, especially for the initial operational temperature of the exothermic reaction. The initial operation condition is often ignored in the designing batch processes for flexibility against disturbances or parameter variations. When the initial condition is not rigid as in the case of a batch reactor, where the initial reaction temperature is quite arbitrary, optimization can also be applied to determine the ＂best＂ initial condition to use. Problems for dynamic flexibility analysis of exothermic reaction including initial temperature and process operation can be formulated as dynamic optimization problems. Formulations are derived when the initial conditions are considered or not. When the initial conditions are considered, the initial condition can be transferred into control variables in the first optimal step. The solution of the dynamic optimization is on the basis of Rugge-Kutta integration algorithm and decomposition search algorithm. This method, as illustrated and tested with two highly nonlinear process problems, enables the determination of the optimal level. The dynamic performance is improved by the proposed method in the two exothermic reaction examples.展开更多
Photoisomerization-induced phase change are important for co-harvesting the latent heat and isomerization energy of azobenzene molecules.Chemically optimizing heat output and energy delivery at alternating temperature...Photoisomerization-induced phase change are important for co-harvesting the latent heat and isomerization energy of azobenzene molecules.Chemically optimizing heat output and energy delivery at alternating temperatures are challenging because of the differences in crystallizability and isomerization.This article reports two series of asymmetrically alkyl-grafted azobenzene(Azo-g),with and without a methyl group,that have an optically triggered phase change.Three exothermic modes were designed to utilize crystallization enthalpy(△H_(c))and photothermal(isomerization)energy(△H_(p))at different temperatures determined by the crystallization.Azo-g has high heat output(275-303 J g^(-1))by synchronously releasing△H_(c)and△H_(p)over a wide temperature range(-79℃to 25℃).We fabricated a new distributed energy utilization and delivery system to realize a temperature increase of 6.6℃at a temperature of-8℃.The findings offer insight into selective utilization of latent heat and isomerization energy by molecular optimization of crystallization and isomerization processes.展开更多
For the characteristics of the continuous stirred-tank reactor(CSTR) with coil and jacket cooling system,a CSTR temperature dual control solution based on the analysis of the CSTR exothermic reaction control character...For the characteristics of the continuous stirred-tank reactor(CSTR) with coil and jacket cooling system,a CSTR temperature dual control solution based on the analysis of the CSTR exothermic reaction control characteristic was proposed for an organic material polymerization production.The control solution has passive fault-tolerant ability for the jacket cooling water cutting off fault and active fault-tolerant potential for the coil cooling water cutting off fault,and it has good control ability,high saving energy and reducing consumption performance.Fault detection and diagnosis and fault-tolerant control strategy are designed for the coil cooling fault to achieve the active fault-tolerant control function.The CSTR temperature dual control,process fault detection and diagnosis and active fault-tolerant control were full integrated into the CSTR temperature fault-tolerant control system,which achieve fault tolerance control of CSTR temperature for any severe malfunction of jacket cooling or coil cooling cutting off,and the security for CSTR exothermic reaction is improved.Finally,the effectiveness of this system was validated by semi-physical simulation experiment.展开更多
The effect of top slag basicity on quality of steel treated with SiFe and SiCaBa alloy as exothermic agent in chemical heating was studied.These experiments were carried out in MoSi_2 laboratory furnace with 0.2 kg mo...The effect of top slag basicity on quality of steel treated with SiFe and SiCaBa alloy as exothermic agent in chemical heating was studied.These experiments were carried out in MoSi_2 laboratory furnace with 0.2 kg molten steel for equilibrium test and 2 kg molten steel for simulation test respectively.These results showed that the adjusting basicity of top slag with CaO is effective to prevent rephosphorization and resulphurization,and it is possible to dephosphorize and desulphurize and remove the inclusions from molten steel when basicity R of the top slag is adjusted to 2.0 — 3.10,and SiCaBa alloy is better than SiFe alloy in this relation.展开更多
MXene,a new type of two-dimensional materials,have been demonstrated as one of the best photothermal materials owing to their strong light-matter interaction and high photothermal conversion efficiency in recent years...MXene,a new type of two-dimensional materials,have been demonstrated as one of the best photothermal materials owing to their strong light-matter interaction and high photothermal conversion efficiency in recent years.Herein,we report the intriguing light-to-heat conversion property of vanadium carbide(V_(2)C)MXene under irradiation of millisecond laser pulse.Unlike the typical photothermal materials,the V_(2)C MXene not only converts the incident laser energy to heat by the physical photothermal effect,but also triggers the exothermic oxidation of the V_(2)C MXene.The oxidation could be greatly promoted with addition of plasmonic Au nanorods(Au NRs)for light absorption enhancement.Owing to the unique light-to-heat conversion property,the Au NRs/V_(2)C MXene membrane could serve as high temperature pulse(HTP)generators that is proposed for numerous applications with high demand for immediacy.As a proof-of concept application,Au NRs/V_(2)C MXene membrane was applied for laser ignition of the high energy density materials,such as 2,4,6,8,10,12-(hexanitrohexaaza)cyclododecane(HNIW or CL-20).An improved ignition performance,in terms of lowered laser threshold,is achieved as compared to the state-of-the-art light-to-heat conversion materials.展开更多
Differential thermal analysis was utilized to determine midwinter hardiness of stem tissues and flower buds of mei flower (Prunus mume) and David’s peach (Prunus davidiana). Low temperature freezing exotherms were fo...Differential thermal analysis was utilized to determine midwinter hardiness of stem tissues and flower buds of mei flower (Prunus mume) and David’s peach (Prunus davidiana). Low temperature freezing exotherms were found to occur at -35℃ in Green Calyxs’ David’s peach and -18℃ in mei flower. A Low temperature exotherm was produced by the freezing of deep supercooling water which was detected in the wood tissues but not in the bark. Freezing processes of the wood and those of the bark appeared to be independent. Deep supercooling points of both species were found to be closely related to freezing injury and to their respective distributions.展开更多
Herein,the interaction of a protein,bovine serum albumin(BSA),with tetradecyltrimethylammonium bromide(TTAB,a cationic surfactant),has been investigated using the conductivity measurement technique in pure water and s...Herein,the interaction of a protein,bovine serum albumin(BSA),with tetradecyltrimethylammonium bromide(TTAB,a cationic surfactant),has been investigated using the conductivity measurement technique in pure water and some sodium salts(NaCl,Na_(2) SO_(4),Na_(2) CO_(3), and Na_(3) PO_(4)) solutions at temperature range of 295.15-320.15 K.Results reveal that,in the plot of specific conductivity versus the concentration of TTAB,only a single critical micelle concentration(cmc) was found for the TTAB+BSA mixed system in all solvents media studied.The addition of BSA in aqueous TTAB solution,the value of cmc undergoes a change from its pure form,which indicates the presence of strong interaction operating between the BSA and TTAB molecules.In aqueous system,the cmc values of the TTAB+BSA mixtures are obtained higher compared to the values found for single TTAB surfactant However,the addition of salt decreases the cmc value of mixed TTAB+BSA system.The values of cmc of the BSA+TTAB mixed system at 310.15 K and 1.00 mmol·kg^(-1) ionic strength of salt followed the order:cmc_(Na_(2) CO_(3))> Cmcc_(Na_(3) PO_(4))> cmcNaCl>cMC_(Na_(2) SO_(4)).The cmc values of TTAB+BSA mixture were found to be lowered in urea solution within the concentrations studied.The values of degree of dissociation(α) and fraction of counter ion binding(β) were found to be dependent on additives and temperature.The free energy of micellization(AGm) is negative for all the systems,which manifests that the micellization phenomenon is energetically spontaneous.The enhancement of the negative value of △G_(m)^(0) in aqueous salt solutions reveals an increase of spontaneity of the TTAB+BSA micellization process.The values of △G_(m)^(0) also reveal that the spontaneity of micelle formation is enhanced at higher temperatures in all media studied.The values of free energy of transfer(△G_(m,t)^(o)) were also determined for numerous solvent media used in the present study and described with appropriate reasoning.展开更多
Based on the experiment and the thermodynamics analysis for CuO/Al system, it is founded that the compounding reaction of CuO/Al under low temperature is available. The general equation of adiabatic temperature of the...Based on the experiment and the thermodynamics analysis for CuO/Al system, it is founded that the compounding reaction of CuO/Al under low temperature is available. The general equation of adiabatic temperature of the system is set up, and the influence of resultant concentration and temperature on adiabatic temperature is theoretically analyzed. The values of heat effect of CuO/Al system under different temperature are also caculated.展开更多
Two kinds of glassy sulfurs are synthesized by thrapid compression method from liquid sulfur at temperatures below and above the X-transition point. The glassy sulfur has different colors and transparencies, depending...Two kinds of glassy sulfurs are synthesized by thrapid compression method from liquid sulfur at temperatures below and above the X-transition point. The glassy sulfur has different colors and transparencies, depending on temperature, which may inherit some structural information from the transition. Raman spectrum studies of these samples show that a large fraction of polymeric chains exist in the glassy sulfur, even in the one solidified from T 〈 Tλ. We find that a higher compression rate instead of a higher temperature of the parent liquid captures more polymeric chains. Pressure-induced glassy sulfur presents high thermal stability compared with temperature quenched glassy sulfur and could transform into liquid sulfur directly without crystallization through an abnormal exothermic melting course. High energy x-ray diffraction is utilized to study the local order of the pressure-induced glassy sulfur.展开更多
The present study focuses on investigating the microstructural evolutions and mechanical properties of energetic Al_(1)(TiZrNbTaMoCr)_(15) refractory high-entropy alloys with the different heat treatments at low Al co...The present study focuses on investigating the microstructural evolutions and mechanical properties of energetic Al_(1)(TiZrNbTaMoCr)_(15) refractory high-entropy alloys with the different heat treatments at low Al content state. It is found that even with a reduction in the Al content, the strength of these alloys remains unaffected at room temperature and high temperature, while the plasticity improves significantly. In particular, the coherent BCC/B_(2) microstructure with needle-like B_(2) nanoprecipitates dispersed into the BCC matrix is formed in 873 K-aged Al_(1)Ti_(6)Zr_(2)Nb_(3)Ta_(3)Mo_(0.5)Cr_(0.5) alloy. Therefore, this alloy exhibits the highest compression yield strength (σ_(YS) = 1333 and 717 MPa) at room temperature and 1073 K, respectively. After 973 K-aged, the coherent BCC/B_(2) microstructure underwent destabilization, and the B_(2) phase transforms into the brittle Zr5Al3 phase which then coarsens and dominates the microstructure of S3-AlTa_(3) alloy after 1073 K-aged. Moreover, these current alloys exhibit exceptionally high theoretical exothermic enthalpy (ΔH), surpassing 11606 J·g^(−1), which highlights their significant potential as innovative high-performance energetic structural materials.展开更多
For solving the dilemma of the short exothermic life-span of WO_(3)based metastable interstitial composites(MICs)with extensive application prospect,this paper has firstly designed the promising antiwetting Al/WO_(3)M...For solving the dilemma of the short exothermic life-span of WO_(3)based metastable interstitial composites(MICs)with extensive application prospect,this paper has firstly designed the promising antiwetting Al/WO_(3)MICs via electrophoresis assembly of nano-Al and WO_(3)particles fabricated by hydrothermal synthesis method,followed by the subsequent fluorination treatment.A combination of X ray diffraction(XRD),field emission scanning electron microscope(FESEM),energy dispersive X-ray spectroscopy(EDX),and Fourier transform infrared spectroscopy(FT-IR)techniques were utilized in order to characterize the crystal structure,microstructure,and elemental composition distribution of target films after different natural exposure tests.The product with uniform distribution and high purity possesses a high contact angle of~170°and a minute sliding angle of~1°,and displays the outstanding anti-wetting property using droplets with different surface tensions.It also shows great moisture stability in high relative-humidity circumstances after one year of the natural exposure experiment.Notably,the heat output of a fresh sample can reach up to 2.3 kJ/g and retain 96%after the whole exposure test,showing outstanding thermo-stability for at least one year.This work further proposed the mechanism of antiwetting Al/WO_(3)MICs considering the variation tendency of their DSC curve,providing a valuable theoretical reference for designing other self-protected MICs with a long exothermic life-span applied in wide fields of national defense,military industry,etc.展开更多
Nonlinear model predictive control(NMPC) is an appealing control technique for improving the performance of batch processes, but its implementation in industry is not always possible due to its heavy on-line computati...Nonlinear model predictive control(NMPC) is an appealing control technique for improving the performance of batch processes, but its implementation in industry is not always possible due to its heavy on-line computation. To facilitate the implementation of NMPC in batch processes, we propose a real-time updated model predictive control method based on state estimation. The method includes two strategies: a multiple model building strategy and a real-time model updated strategy. The multiple model building strategy is to produce a series of sim-plified models to reduce the on-line computational complexity of NMPC. The real-time model updated strategy is to update the simplified models to keep the accuracy of the models describing dynamic process behavior. The me-thod is validated with a typical batch reactor. Simulation studies show that the new method is efficient and robust with respect to model mismatch and changes in process parameters.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2022YFB3207000)National Natural Science Foundation of China(Grant No.12132017)Youth Cross Team CAS(Grant No.JCTD-2022-02)and Youth Innovation Promotion Association CAS(Grant No.2020019).
文摘The distribution of exothermic reaction rates is jointly influenced by reduced activation energy and reaction rate constant.This study focuses on the effect of distribution of exothermic reaction rates on detonation wave propagation instability,specifically under conditions where the length of the induction and exothermic reaction remains constant.It is found that the distribution variation of exothermic reaction rates significantly influences the detonation wave propagation characteristics.Specifically,under conditions of high activation energy,the exothermic reaction rate profile exhibits a smoother distribution but becomes more prone to perturbations.This heightened sensitivity,coupled with the augmented overdriven degree associated with pulsating detonation and cellular detonation wave propagation,further exacerbates the instability characteristics of detonation waves.Especially to the two-dimensional detonation waves with high activation energies,the distribution of exothermic reaction rates becomes more sensitive to these displacements,reinforcing the transverse shock wave and leading to a transformation of the wavefront and cellular structure towards more unstable configurations.This research delves into the intricate interactions between the distribution of exothermic reaction rates and detonation wave instability,aiming to provide an explanatory of detonation instability.
基金financially supported by the National Natural Science Foundation of China(No.51871120)the Natural Science Foundation of Jiangsu Province(No.BK20200019)+4 种基金the Fundamental Research Funds for the Central Universities(Nos.30919011107 and 30919011404)support by Shenzhen Science and Technology Innovation Committee(No.JCYJ20170413140446951)the supports by Shenzhen Science and Technology Innovation Commission(No.JCYJ20180507181806316)the supports by Shenzhen Science and Technology Innovation Commission(No.JCYJ202000109105618137)the Ministry of Science and Technology of China(No.2016YFA0401501)。
文摘The glass-forming ability of Mg-Cu-Gd alloys could be significantly promoted with the addition of Ag.A calorimetric anomaly could be observed in the supercooled liquid region of the Mg-Cu-Ag-Gd metallic glass,indicating the occurrence of a liquid-state phase transition driven by entropy.However,the underlying mechanism of the polyamorphous phase transition remains unsettled.In the paper,in situ scattering techniques were employed to reveal multiscale structure evidence in a Mg65Cu15Ag10Gd10metallic glass with an anomalous exothermic peak upon heating.Resistivity measurements indicate a reentrant behavior for the Mg-Cu-Ag-Gd metallic glass in the anomalous exothermic peak temperature region during heating.In situ synchrotron diffraction results revealed that the local atomic structure tends to be ordered and loosely packed first,followed by reentering into the initial state upon heating.Moreover,time-resolved small-angle synchrotron X-ray scattering(SAXS) results show an increase in nanoscale heterogeneity first followed by a reentrant supercooled liquid behavior.A core-shell structure model has been used to fit the SAXS profiles when polyamorphous phase transition occurs.In contrast,there is no structure anomaly for the reference Mg-Cu-Gd alloy system.The detailed multiscale structural evidence suggests the occurrence of a liquid-liquid phase transition followed by a reentrant behavior in the MgCu-Ag-Gd metallic glass.Our results deepen the understanding of the structural origin of the glass-forming ability and shed light on the possibility of tuning the physical and mechanical properties by heat-treatment in the supercooled liquid region of Mg-based metallic glasses.
文摘The microstructures of NiAl(Co)-TiB_2 composite prepared using exothermal dispersion (XD) method have been studied by optical microscopy, XRD, EDS, and TEM The results show that, TiB_2 paritcles are typically single crystal, and fairly uniformly distributed. The matrix mainly consists of β-NiAl phase, Ll_2γ′Ni_3Al phase and δ-Ni_3Al phase. The δNi_3Al has a fcc crystal structure with lattice parameter a=1.068nm.The data of compressive testing at room temperature show that the room temperature ductility of NiAl(Co) matrix composite is much better than that of stoichiometric NiAl.
基金supported by the Key-Area Research and Development Program of Guangdong Province (2020B090919004)the Ministry of Science and Technology of China (2019YFE0100200)+3 种基金the National Natural Science Foundation of China (52007099, 51706117, 52076121, 51877138)the Shanghai Science and Technology Development Fund (19QA1406200)the China Postdoctoral Science Foundation (2020M680550)the support from the “Shuimu Tsinghua Scholar Program” from Tsinghua University。
文摘Thermal runaway is a critical issue for the large application of lithium-ion batteries.Exothermic reactions between lithiated graphite and electrolyte play a crucial role in the thermal runaway of lithium-ion batteries.However,the role of each component in the electrolyte during the exothermic reactions with lithiated graphite has not been fully understood.In this paper,the exothermic reactions between lithiated graphite and electrolyte of lithium-ion battery are investigated through differential scanning calorimetry(DSC) and evolved gas analysis.The lithiated graphite in the presence of electrolyte exhibit three exothermic peaks during DSC test.The reactions between lithiated graphite and LiPF_(6) and ethylene carbonate are found to be responsible for the first two exothermic peaks,while the third exothermic peak is attributed to the reaction between lithiated graphite and binder.In contrast,diethylene carbonate and ethyl methyl carbonate contribute little to the total heat generation of graphite-electrolyte reactions.The reaction mechanism between lithiated graphite and electrolyte,including the major reaction equations and gas products,are summarized.Finally,DSC tests on samples with various amounts of electrolyte are performed to clarify the quantitative relationship between lithiated graphite and electrolyte during the exothermic reactions.2.5 mg of lithiated graphite (Li_(0.8627)C_(6)) can fully react with around 7.2 mg electrolyte,releasing a heat generation of 2491 J g^(-1).The results presented in this study can provide useful guidance for the safety improvement of lithium-ion batteries.
基金Funded by the National Natural Science Foundation of China(Nos.51109071,51209219)Jiangsu Province Natural Science Foundation(No.BK2010517)
文摘Recent achievements in concrete hydration exothermic models based on Arrhenius equation have improved computation accuracy for mass concrete temperature field. But the properties of the activation energy and the gas constant （Ea/R） have not been well studied yet. From the latest experiments it is shown that Ea/R obviously changes with the hydration degree without fixed form. In this paper, the relationship between hydration degree and Ea/R is studied and a new hydration exothermic model is proposed. With those achievements, the mass concrete temperature field with arbitrary boundary condition can be calculated more precisely.
基金Project supported by the National Natural Science Foundation of China (No.50678076)the Opening Foundation of the State Key Laboratory of Frozen Soil Engineering (No.SKLFSE200603),China
文摘A number of dry bridges have been built to substitute for the roadbed on the Qinghai-Tibet Railway,China.The aim of this study was to investigate the exothermic process of cast-in-place (CIP) pile foundation of a dry bridge and its harm to the stability of nearby frozen ground.We present 3D heat conduction functions of a concrete pile and of frozen ground with related boundaries.Our analysis is based on the theory of heat conduction and the exponent law describing the adiabatic temperature rise caused by hydration heat.Results under continuous and initial conditions were combined to establish a finite element model of a CIP pile-frozen ground system for a dry bridge under actual field conditions in cold regions.Numerical results indicated that the process could effectively simulate the exothermic process of CIP pile foundation.Thermal disturbance to frozen ground under a long dry bridge caused by the casting temperature and hydration heat of CIP piles was substantial and long-lasting.The simulated thermal analysis results agreed with field measurements and some significant rules relating to the problem were deduced and conclusions reached.
基金financial support from the National Natural Science Foundation of China(22008107,21838004)DTRA through the grant HDTRA11910008 of the USA。
文摘The research on the adsorption equilibria,kinetics,and increase in process temperature of the volatile organic compound(VOC)adsorption in porous materials ensures safe production,thereby reducing production costs and improving separation efficiency.Therefore,it is critical in predicting the entire adsorption process based on minimal or no experimental input of the adsorbate and adsorbent.We discuss,in this review,the factors that affect the adsorption performance of VOCs in activated carbons,including the adsorption equilibrium,adsorption kinetics,and exotherm during adsorption.Subsequently,the existing prediction models are summarized and compared concerning the adsorption equilibrium,adsorption kinetics,and exothermic process of adsorption.We then propose a new prediction model based on intermolecular interaction and provide an outlook toward the design and manipulation of efficient adsorbents for the VOC system.
文摘The effect of top slag basicity on quality of steel treated with SiFe and SiCaBa alloy as exothermic agent in chemical heating was studied. These experiments were carried out in MoSi 2 laboratory furnace with 0 2?kg molten steel for equilibrium test and 2?kg molten steel for simulation test respectively. These results showed that the adjusting basicity of top slag with CaO is effective to prevent rephosphorization and resulphurization, and it is possible to dephosphorize and desulphurize and remove the inclusions from molten steel when basicity R of the top slag is adjusted to 2 0-3 10, and SiCaBa alloy is better than SiFe alloy in this relation.
基金Supported by the National Natural Science Foundation of China （20536020, 20876056）.
文摘It is shown in this article that by changing the initial operation condition of the batch processes, the dynamic performance of the system can be varied largely, especially for the initial operational temperature of the exothermic reaction. The initial operation condition is often ignored in the designing batch processes for flexibility against disturbances or parameter variations. When the initial condition is not rigid as in the case of a batch reactor, where the initial reaction temperature is quite arbitrary, optimization can also be applied to determine the ＂best＂ initial condition to use. Problems for dynamic flexibility analysis of exothermic reaction including initial temperature and process operation can be formulated as dynamic optimization problems. Formulations are derived when the initial conditions are considered or not. When the initial conditions are considered, the initial condition can be transferred into control variables in the first optimal step. The solution of the dynamic optimization is on the basis of Rugge-Kutta integration algorithm and decomposition search algorithm. This method, as illustrated and tested with two highly nonlinear process problems, enables the determination of the optimal level. The dynamic performance is improved by the proposed method in the two exothermic reaction examples.
基金financially supported by National Key R&D Program of China(No.2022YFB3805702)the State Key Program of National Natural Science Foundation of China(No.52130303)
文摘Photoisomerization-induced phase change are important for co-harvesting the latent heat and isomerization energy of azobenzene molecules.Chemically optimizing heat output and energy delivery at alternating temperatures are challenging because of the differences in crystallizability and isomerization.This article reports two series of asymmetrically alkyl-grafted azobenzene(Azo-g),with and without a methyl group,that have an optically triggered phase change.Three exothermic modes were designed to utilize crystallization enthalpy(△H_(c))and photothermal(isomerization)energy(△H_(p))at different temperatures determined by the crystallization.Azo-g has high heat output(275-303 J g^(-1))by synchronously releasing△H_(c)and△H_(p)over a wide temperature range(-79℃to 25℃).We fabricated a new distributed energy utilization and delivery system to realize a temperature increase of 6.6℃at a temperature of-8℃.The findings offer insight into selective utilization of latent heat and isomerization energy by molecular optimization of crystallization and isomerization processes.
基金Project(2013JM8024)Supported by Natural Science Basic Research Plan in Shaanxi Province of China
文摘For the characteristics of the continuous stirred-tank reactor(CSTR) with coil and jacket cooling system,a CSTR temperature dual control solution based on the analysis of the CSTR exothermic reaction control characteristic was proposed for an organic material polymerization production.The control solution has passive fault-tolerant ability for the jacket cooling water cutting off fault and active fault-tolerant potential for the coil cooling water cutting off fault,and it has good control ability,high saving energy and reducing consumption performance.Fault detection and diagnosis and fault-tolerant control strategy are designed for the coil cooling fault to achieve the active fault-tolerant control function.The CSTR temperature dual control,process fault detection and diagnosis and active fault-tolerant control were full integrated into the CSTR temperature fault-tolerant control system,which achieve fault tolerance control of CSTR temperature for any severe malfunction of jacket cooling or coil cooling cutting off,and the security for CSTR exothermic reaction is improved.Finally,the effectiveness of this system was validated by semi-physical simulation experiment.
基金Sponsored by National Natural Science Foundation(59874014)
文摘The effect of top slag basicity on quality of steel treated with SiFe and SiCaBa alloy as exothermic agent in chemical heating was studied.These experiments were carried out in MoSi_2 laboratory furnace with 0.2 kg molten steel for equilibrium test and 2 kg molten steel for simulation test respectively.These results showed that the adjusting basicity of top slag with CaO is effective to prevent rephosphorization and resulphurization,and it is possible to dephosphorize and desulphurize and remove the inclusions from molten steel when basicity R of the top slag is adjusted to 2.0 — 3.10,and SiCaBa alloy is better than SiFe alloy in this relation.
基金the National Natural Science Foundation of China (21703217, 11702264, 11702268, 11802276, 11772307) for financial support
文摘MXene,a new type of two-dimensional materials,have been demonstrated as one of the best photothermal materials owing to their strong light-matter interaction and high photothermal conversion efficiency in recent years.Herein,we report the intriguing light-to-heat conversion property of vanadium carbide(V_(2)C)MXene under irradiation of millisecond laser pulse.Unlike the typical photothermal materials,the V_(2)C MXene not only converts the incident laser energy to heat by the physical photothermal effect,but also triggers the exothermic oxidation of the V_(2)C MXene.The oxidation could be greatly promoted with addition of plasmonic Au nanorods(Au NRs)for light absorption enhancement.Owing to the unique light-to-heat conversion property,the Au NRs/V_(2)C MXene membrane could serve as high temperature pulse(HTP)generators that is proposed for numerous applications with high demand for immediacy.As a proof-of concept application,Au NRs/V_(2)C MXene membrane was applied for laser ignition of the high energy density materials,such as 2,4,6,8,10,12-(hexanitrohexaaza)cyclododecane(HNIW or CL-20).An improved ignition performance,in terms of lowered laser threshold,is achieved as compared to the state-of-the-art light-to-heat conversion materials.
基金This project was supported by the National Natural Science Foundation of China
文摘Differential thermal analysis was utilized to determine midwinter hardiness of stem tissues and flower buds of mei flower (Prunus mume) and David’s peach (Prunus davidiana). Low temperature freezing exotherms were found to occur at -35℃ in Green Calyxs’ David’s peach and -18℃ in mei flower. A Low temperature exotherm was produced by the freezing of deep supercooling water which was detected in the wood tissues but not in the bark. Freezing processes of the wood and those of the bark appeared to be independent. Deep supercooling points of both species were found to be closely related to freezing injury and to their respective distributions.
基金King Saud University for funding this work through Researchers Supporting Project number (RSP-2020/133), King Saud University, Riyadh, Saudi Arabia。
文摘Herein,the interaction of a protein,bovine serum albumin(BSA),with tetradecyltrimethylammonium bromide(TTAB,a cationic surfactant),has been investigated using the conductivity measurement technique in pure water and some sodium salts(NaCl,Na_(2) SO_(4),Na_(2) CO_(3), and Na_(3) PO_(4)) solutions at temperature range of 295.15-320.15 K.Results reveal that,in the plot of specific conductivity versus the concentration of TTAB,only a single critical micelle concentration(cmc) was found for the TTAB+BSA mixed system in all solvents media studied.The addition of BSA in aqueous TTAB solution,the value of cmc undergoes a change from its pure form,which indicates the presence of strong interaction operating between the BSA and TTAB molecules.In aqueous system,the cmc values of the TTAB+BSA mixtures are obtained higher compared to the values found for single TTAB surfactant However,the addition of salt decreases the cmc value of mixed TTAB+BSA system.The values of cmc of the BSA+TTAB mixed system at 310.15 K and 1.00 mmol·kg^(-1) ionic strength of salt followed the order:cmc_(Na_(2) CO_(3))> Cmcc_(Na_(3) PO_(4))> cmcNaCl>cMC_(Na_(2) SO_(4)).The cmc values of TTAB+BSA mixture were found to be lowered in urea solution within the concentrations studied.The values of degree of dissociation(α) and fraction of counter ion binding(β) were found to be dependent on additives and temperature.The free energy of micellization(AGm) is negative for all the systems,which manifests that the micellization phenomenon is energetically spontaneous.The enhancement of the negative value of △G_(m)^(0) in aqueous salt solutions reveals an increase of spontaneity of the TTAB+BSA micellization process.The values of △G_(m)^(0) also reveal that the spontaneity of micelle formation is enhanced at higher temperatures in all media studied.The values of free energy of transfer(△G_(m,t)^(o)) were also determined for numerous solvent media used in the present study and described with appropriate reasoning.
文摘Based on the experiment and the thermodynamics analysis for CuO/Al system, it is founded that the compounding reaction of CuO/Al under low temperature is available. The general equation of adiabatic temperature of the system is set up, and the influence of resultant concentration and temperature on adiabatic temperature is theoretically analyzed. The values of heat effect of CuO/Al system under different temperature are also caculated.
基金supported by the Joint Funds of the National Natural Science Foundation of China(Grant No.U1530402)the National Natural Science Foundation of China(Grant No.11004163)+2 种基金the Fundamental Research Funds for the Central Universities,China(Grant No.2682014ZT31)the Department of Energy National Nuclear Security Administration(Grant No.DE-NA0001974)the Department of Energy Basic Energy Sciences(Grant Nos.DE-FG02-99ER45775and DE-AC02-06CH11357)
文摘Two kinds of glassy sulfurs are synthesized by thrapid compression method from liquid sulfur at temperatures below and above the X-transition point. The glassy sulfur has different colors and transparencies, depending on temperature, which may inherit some structural information from the transition. Raman spectrum studies of these samples show that a large fraction of polymeric chains exist in the glassy sulfur, even in the one solidified from T 〈 Tλ. We find that a higher compression rate instead of a higher temperature of the parent liquid captures more polymeric chains. Pressure-induced glassy sulfur presents high thermal stability compared with temperature quenched glassy sulfur and could transform into liquid sulfur directly without crystallization through an abnormal exothermic melting course. High energy x-ray diffraction is utilized to study the local order of the pressure-induced glassy sulfur.
基金supported by the Key Basic Research Project of National Foundation Strengthening Program(No.2021-JCJQ-ZD-030-12)the National Natural Science Foundation of China(No.52171152).
文摘The present study focuses on investigating the microstructural evolutions and mechanical properties of energetic Al_(1)(TiZrNbTaMoCr)_(15) refractory high-entropy alloys with the different heat treatments at low Al content state. It is found that even with a reduction in the Al content, the strength of these alloys remains unaffected at room temperature and high temperature, while the plasticity improves significantly. In particular, the coherent BCC/B_(2) microstructure with needle-like B_(2) nanoprecipitates dispersed into the BCC matrix is formed in 873 K-aged Al_(1)Ti_(6)Zr_(2)Nb_(3)Ta_(3)Mo_(0.5)Cr_(0.5) alloy. Therefore, this alloy exhibits the highest compression yield strength (σ_(YS) = 1333 and 717 MPa) at room temperature and 1073 K, respectively. After 973 K-aged, the coherent BCC/B_(2) microstructure underwent destabilization, and the B_(2) phase transforms into the brittle Zr5Al3 phase which then coarsens and dominates the microstructure of S3-AlTa_(3) alloy after 1073 K-aged. Moreover, these current alloys exhibit exceptionally high theoretical exothermic enthalpy (ΔH), surpassing 11606 J·g^(−1), which highlights their significant potential as innovative high-performance energetic structural materials.
基金funded by the financial support from National Natural Science Foundation of China(Grant No 21805014 and No82102635)Science and Technology Research Project of Chongqing Education Board(Grant No.KJQN201901428)。
文摘For solving the dilemma of the short exothermic life-span of WO_(3)based metastable interstitial composites(MICs)with extensive application prospect,this paper has firstly designed the promising antiwetting Al/WO_(3)MICs via electrophoresis assembly of nano-Al and WO_(3)particles fabricated by hydrothermal synthesis method,followed by the subsequent fluorination treatment.A combination of X ray diffraction(XRD),field emission scanning electron microscope(FESEM),energy dispersive X-ray spectroscopy(EDX),and Fourier transform infrared spectroscopy(FT-IR)techniques were utilized in order to characterize the crystal structure,microstructure,and elemental composition distribution of target films after different natural exposure tests.The product with uniform distribution and high purity possesses a high contact angle of~170°and a minute sliding angle of~1°,and displays the outstanding anti-wetting property using droplets with different surface tensions.It also shows great moisture stability in high relative-humidity circumstances after one year of the natural exposure experiment.Notably,the heat output of a fresh sample can reach up to 2.3 kJ/g and retain 96%after the whole exposure test,showing outstanding thermo-stability for at least one year.This work further proposed the mechanism of antiwetting Al/WO_(3)MICs considering the variation tendency of their DSC curve,providing a valuable theoretical reference for designing other self-protected MICs with a long exothermic life-span applied in wide fields of national defense,military industry,etc.
基金Supported by the National Natural Science Foundation of China(21136003,21176089)the National Science&Technology Support Plan(2012BAK13B02)+2 种基金the National Major Basic Research Program(2014CB744306)the Natural Science Foundation Team Project of Guangdong Province(S2011030001366)the Fundamental Research Funds for Central Universities(2013ZP0010)
文摘Nonlinear model predictive control(NMPC) is an appealing control technique for improving the performance of batch processes, but its implementation in industry is not always possible due to its heavy on-line computation. To facilitate the implementation of NMPC in batch processes, we propose a real-time updated model predictive control method based on state estimation. The method includes two strategies: a multiple model building strategy and a real-time model updated strategy. The multiple model building strategy is to produce a series of sim-plified models to reduce the on-line computational complexity of NMPC. The real-time model updated strategy is to update the simplified models to keep the accuracy of the models describing dynamic process behavior. The me-thod is validated with a typical batch reactor. Simulation studies show that the new method is efficient and robust with respect to model mismatch and changes in process parameters.
