The non-linear effects of different initial melt temperatures on the microstructure evolution during the solidification process of liquid Mg7Zn3 alloys were investigated by molecular dynamics simulation, The microstru...The non-linear effects of different initial melt temperatures on the microstructure evolution during the solidification process of liquid Mg7Zn3 alloys were investigated by molecular dynamics simulation, The microstructure transformation mechanisms were analyzed by several methods. The system was found to be solidified into amorphous structures from different initial melt temperatures at the same cooling rate of 1×10^12 K/s, and the 1551 bond-type and the icosahedron basic cluster （12 0 12 0 ） played a key role in the microstructure transition. Different initial melt temperatures had significant effects on the final microstructures. These effects only can be clearly observed below the glass transition temperature Tg; and these effects are non-linearly related to the initial melt temperatures, and fluctuated in a certain range. However, the changes of the average atomic energy of the systems are still linearly related with the initial melt temperatures, namely, the higher the initial melt temperature is, the more stable the amorphous structure is and the stronger the glass forming ability will be.展开更多
Among the processing conditions of injection molding, temperature of the melt entering the mold plays a significant role in determining the quality of molded parts. In our previous research, a neural network was deve...Among the processing conditions of injection molding, temperature of the melt entering the mold plays a significant role in determining the quality of molded parts. In our previous research, a neural network was developed to predict the melt temperature in the barrel during the plastication phase. In this paper, a neural network is proposed to predict the melt temperature at the nozzle exit during the injection phase. A typical two-layer neural network with back propagation learning rules is used to model the relationship between input and output in the injection phase. The preliminary results show that the network works well and may be used for on-line optimization and control of injection molding processes.展开更多
This study investigates the influence of melt temperature on the structure and mechanical properties of[Fe_(0.25)Co_(0.25)Ni_(0.25)(Si_(0.3)B_(0.7))_(0.25)]_(99.7)Cu_(0.3) high-entropy bulk metallic glasses(HE-BMGs).S...This study investigates the influence of melt temperature on the structure and mechanical properties of[Fe_(0.25)Co_(0.25)Ni_(0.25)(Si_(0.3)B_(0.7))_(0.25)]_(99.7)Cu_(0.3) high-entropy bulk metallic glasses(HE-BMGs).Samples were prepared at varying melt temperatures(1423,1523,1573,and 1623 K)using the J-quenching technique.The results reveal that melt temperature significantly affects the atomic arrangement structures,which in turn impacts plasticity and thermal stability.At a lower melt temperature(1423 K),crystal-like clusters form,leading to poor plasticity due to stress concentrations.In contrast,melt temperatures within an optimal range(1523-1573 K)promote a more uniform distribution of soft and hard zones,enhancing plastic deformation.Specifically,the sample prepared in 1573 K melt temperature exhibited the best plasticity,attributed to favorable structural nonuniformity and an increased proportion of soft zones.However,at a higher melt temperature(1623 K),excessive superheating resulted in the formation of large Cu clusters,which enhanced strength but compromised plasticity due to stress concentrations.This work provides a comprehensive understanding of how melt temperature controls microstructural evolution and its influence on the mechanical properties of HE-BMGs,offering valuable insights for optimizing their preparation.展开更多
The shell-model molecular dynamics method was applied to simulate the melting temper- atures of SrF2 and BaF2 at elevated temperatures and high pressures. The same method was used to calculate the equations of state f...The shell-model molecular dynamics method was applied to simulate the melting temper- atures of SrF2 and BaF2 at elevated temperatures and high pressures. The same method was used to calculate the equations of state for SrF2 and BaF2 over the pressure range of 0.1 MPa-3 GPa and 0.1 MPa-7 GPa. Compared with previous results for equations of state, the maximum errors are 0.3% and 2.2%, respectively. Considering the pre-melting in the fluorite-type crystals, we made the necessary corrections for the simulated melting temper- atures of SrF2 and BaF2. Consequently, the melting temperatures of SrF2 and BaF2 were obtained for high pressures. The melting temperatures of SrF2 and BaF2 that were obtained by the simulation are in good agreement with available experimental data.展开更多
B2O3 is selected as fluxing agent of CaO-based ladle refining slag to decrease the melting temperature as well as to improve the speed of slag forming and the refining efficiency. The effects of B2O3 on the melting te...B2O3 is selected as fluxing agent of CaO-based ladle refining slag to decrease the melting temperature as well as to improve the speed of slag forming and the refining efficiency. The effects of B2O3 on the melting temperature of two series of refining slags including the low basicity slags （the mass ratio of CaO/SiO2 is 3--4） and the high basicity slags （the mass ratio of CaO/SiO2 is 5--8.75） were investigated. The slag melting temperature was meas- ured using the hemisphere method. The results indicate that the fluxing action of B2O3 is better than that of CaF2 and A1203. For the CaO-based refining slag with low basicity, the melting temperature is decreased effectively when B2O3 is used to substitute for equal mass of CaF2, Al2O3 and SiO2, respectively. For the CaO-based refining slag with high basicity, when CaF2 is substituted by B2 03, the melting temperature can be decreased remarkably. Espe- cially, when the mass ratios of CaO/Al2O3 and CaO/SiO2 are in the range of 1.1--4.0 and 5.25--8. 0, respectively, the slag melting temperature is lower than 1 300 ℃. Therefore, the 132 03-containing refining slags with high ratios of CaO/Al2O3 and CaO/SiO2 have ultra low melting temperature.展开更多
Fluorite is widely employed as fluxing agent in metallurgy flux , which inevitably leads to serious fluorine pollution.B2O3 is employed as fluxing agent of CaO-SiO2-Fe2O3steelmaking fluxes to substitute for CaF2.The e...Fluorite is widely employed as fluxing agent in metallurgy flux , which inevitably leads to serious fluorine pollution.B2O3 is employed as fluxing agent of CaO-SiO2-Fe2O3steelmaking fluxes to substitute for CaF2.The effects of B2O3 and CaF2 on the melting properties of this system were investigated.The melting temperatures of fluxes including softening temperature （Ts）, hemispherical temperature （Th）, and flow temperature （Tf） were measured using the hemisphere method.The results indicate that the fluxing effect of B2O3is more significant than that of CaF2 .When the addition amount of B2O3 （mass percent） exceeds 6% , the melting temperatures of fluxes including Ts , Th and Tf are decreased lower than 1 300℃.The basicity of fluxes has a significant effect on the melting temperature , and the melting temperatures of the fluxes increase with the increase of fluxes basicity.However , when B2O3 is used as fluxing agent , the melting temperature changes little with the basicity increasing from 2.5 to 5.0. These characteristics are suitable for steelmaking process.Moreover , Fe2O3 has an important fluxing effect on this CaO-based steelmaking fluxes.This indicates that the fluxes system is suitable for steelmaking process.展开更多
The volatilization kinetics of senarmontite(Sb_(2)O_(3))was analyzed in a neutral atmosphere in two temperature ranges:550-615°C(roasting temperature)and 660-1100°C(melting temperature)by using a thermogravi...The volatilization kinetics of senarmontite(Sb_(2)O_(3))was analyzed in a neutral atmosphere in two temperature ranges:550-615°C(roasting temperature)and 660-1100°C(melting temperature)by using a thermogravimetric analysis method under various gas flow rates and using a 1.3 m L ceramic crucible(11 mm in internal diameter and 14 mm in height).The effect of particle size was also analyzed.The experimental results of mass loss data,X-ray diffraction(XRD)analysis of partially reacted samples and thermodynamic studies indicate that the senarmontite becomes volatile in the form of Sb_(4)O_(6)(g)without the formation of any intermediary compound in the entire temperature range.At roasting temperatures,the volatilization kinetics of Sb_(2)O_(3) was analyzed using the model X=kappt.The volatilization reaction was controlled by the surface chemical reaction and an activation energy value of 193.0 k J/mol was obtained in this temperature range.Based on the volatilization kinetics at the melting temperatures,for linear behaviour in nitrogen gas,kinetic constants were determined,and an activation energy of 73.9 k J/mol was calculated for the volatilization reaction with a surface area of 8.171×10^(-5)m^(2).展开更多
The development of high temperature phase change materials(PCMs)with great comprehensive performance is significant in the future thermal energy storage system.In this study,novel and durable Al-Si/Al_(2)O_(3)-Al N co...The development of high temperature phase change materials(PCMs)with great comprehensive performance is significant in the future thermal energy storage system.In this study,novel and durable Al-Si/Al_(2)O_(3)-Al N composite PCMs with controllable melting temperature were successfully synthesized by using pristine Al powder as raw material and tetraethyl orthosilicate as SiO_(2)source.The Al_(2)O_(3)shell and Al-Si alloy were in-situ produced via the substitution reaction between molten Al and SiO_(2).Importantly,the crack caused by the incomplete encapsulation of the Al_(2)O_(3)shell could repair itself by the nitridation reaction of internal molten Al and thereby forming a highly dense Al_(2)O_(3)-Al N composite shell.The produced dense Al_(2)O_(3)-Al N composite shell could significantly improve the thermal cycling stability of composite PCMs,and thus,the thermal storage density decrease of the Al-Si/Al_(2)O_(3)-Al N(59.8 J/g to77.7 J/g)was far less than that of the Al-Si/Al_(2)O_(3)(118.5 J/g)after 3000 thermal cycles.Moreover,the synthesized Al-Si/Al_(2)O_(3)-Al N still exhibited a controllable melting temperature(571.5-637.9℃),relatively high thermal storage density(105.6-150.7 J/g),great dimensional stability and structural stability after3000 thermal cycles.Hence,the synthesized Al-Si/Al_(2)O_(3)-Al N composite PCMs,as promising preferential thermal energy storage materials,can be stably used in the energy utilization efficiency improvement of various systems for more than 6 years.展开更多
The crystallization and melting behavior of polymers is of theoretical importance.In this work,poly(butylene succinate)(PBS)was selected as an example to study such behavior at low supercooling via introduction of the...The crystallization and melting behavior of polymers is of theoretical importance.In this work,poly(butylene succinate)(PBS)was selected as an example to study such behavior at low supercooling via introduction of the extended-chain crystal(ECC)of the same polymer as nucleating agent.The crystallization of PBS with its ECC as nucleating agent in a wide temperature range(90–127°C)and the following melting behavior were studied.It is revealed that the melting point(Tm',for Tc≥113°C)and the annealing peak temperature(Ta',for Tc=90–100°C)show similar asymptotic behavior.Both Tm and Ta approach to a value of ca.3.3°C higher than the corresponding Tc when the crystallization time tc approaches the starting point.That is to say,the Hoffman-Weeks plot is parallel to Tm=Tc line.The crystallization line became parallel to the melting line when PBS was crystallized at Tc higher than 102°C.Based on these results,we propose that the parallel relationship and the intrinsic similarity between the Ta and the Tm observed at the two ends of the Tc range could be attributed to the metastable crystals formed at the beginning of crystallization.展开更多
Thermal properties such as melting temperature can well reflect the microstructure of the polymer material, and have practical implications in the application of nanofibers. In this work, we investigated the melting t...Thermal properties such as melting temperature can well reflect the microstructure of the polymer material, and have practical implications in the application of nanofibers. In this work, we investigated the melting temperature of individual electrospun poly(vinylidene fluoride)(PVDF) nanofibers with diameters ranging from smaller than 200 nm to greater than 2 μm by the local thermal analysis technique. The PVDF fibers obtained under four different conditions were found to crystallize into α and β phases, and the fiber mats showed typical values in the crystallinity and Tm with no significant difference among the four. However, analyses at single fiber level revealed broad distribution in diameter and Tm for the fibers produced under identical electrospinning condition. The Tm of individual nanofibers was found to remain constant at large diameters and increase quickly when reducing the fiber diameter toward the nanoscale, and Tm values of 220-230 ℃ were observed for the thinnest nanofibers, much higher than the typical values reported for bulk PVDF. The Tm and molecular orientation at different positions along a beaded fiber were analyzed, showing a similar distribution pattern with a minimum at the bead center and higher values when moving toward both directions. The results indicate that molecular orientation is the driving mechanism for the observed correlation between the Tm and the diameter of the nanofibers.展开更多
The density, equilibrium heat of fusion and equilibrium melting temperature of Nylon 1010 were determined by means of infrared spectrum, differential scanning calorimetry, wide angle X-ray diffraction and density meas...The density, equilibrium heat of fusion and equilibrium melting temperature of Nylon 1010 were determined by means of infrared spectrum, differential scanning calorimetry, wide angle X-ray diffraction and density measurement techniques. According to Starkweatber' s method crystalline density ρ_c and amorphous density ρ_a were estimated to be 1.098 and 1.003 g/cm^3 respectively by extrapolating the straight lines of the IR absorbanee against density to zero intensity. Owing to the less intense in absorbance and less sensitive to the change in crystallinity of the amorphors band the thus obtained ρ_c was too low in value. Thereby the value of the ratio ρ_c /ρ_a is far less than generally accepted mean value for most crystalline polymers. Accordingly, traditional X-ray diffraction method was used through determining thc crystalline dimension(a=4.9, b=5.4, c=27.8, α=49° β=77.0°, γ=63.5°), and a rather correct value of ρ_c or the crystal density 1.13 g/cm^3 was obtained. The equilibrium heat of fusion △H_m^0 was estimated to be 244.0 J/g piotting △H_m 's of specimens with different crystallinity against their corre sponding specific volumes_(sp), and extrapolating to completely crystalline condition (_(sp)~c= 1/ρ_c) As to the equilibrium melting temperature T_m^0, because of the easiness of recrystallization of melt crystallized Nylon 1010 specimen, the well-known Hoffman's T_m-T_c method failed in determining this value and an usually rarely used Kamide double extrapolation method was adopted. The so obtained value of T_m^0 487 seems to be fairly reasonable.展开更多
The preparation of semisolid slurry of A356 aluminum alloy using an oblique plate was investigated. A356 alloy melt undergoes partial solidification when it flows down on an oblique plate cooled from underneath by cou...The preparation of semisolid slurry of A356 aluminum alloy using an oblique plate was investigated. A356 alloy melt undergoes partial solidification when it flows down on an oblique plate cooled from underneath by counter flowing water. It results in continuous formation of columnar dendrites on plate wall. Due to forced convection, these dendrites are sheared off into equiaxed/fragmented grains and then washed away continuously to produce semisolid slurry at plate exit. Melt pouring temperature provides required condition of solidification whereas plate inclination enables necessary shear for producing semisolid slurry of desired quality. Slurry obtained was solidified in metal mould to produce semisolid-cast billets of desired microstructure. Furthermore, semisolid-cast billets were heat treated to improve surface quality. Microstructures of both semisolid-cast and heat-treated billets were analyzed. Effects of melt pouring temperature and plate inclination on solidification and microstructure of billets produced using oblique plate were described. The investigations involved four different melt pouring temperatures (620, 625, 630 and 635 °C) associated with four different plate inclinations (30°, 45°, 60° and 75°). Melt pouring temperature of 625 °C with plate inclination of 60° shows fine and globular microstructures and it is the optimum.展开更多
Experiments were carried out on carburizing and temperature rising of the semi steel melt in a plasma induction furnace.Influence of many factors, such as power supply mode,position of the plasma torch and bottom b...Experiments were carried out on carburizing and temperature rising of the semi steel melt in a plasma induction furnace.Influence of many factors, such as power supply mode,position of the plasma torch and bottom blown gas stirring,on heating efficiency and melt temperature distribution was studied. Melt temperature could be effectively controlled by plasma heating,and carbon content of semi steel melt increased from 1.92 % to 4.58 %, and the utilization rate of carbon reached up to 61.57 % during carburizing of the melt.展开更多
A Fourier Transform Infrared Spectroscopic(FTIR)method involving a Fe2O3 flux was used to learn how China's coal ash melts.The relationship between ash fusion temperature and chemical composition,as well as the ef...A Fourier Transform Infrared Spectroscopic(FTIR)method involving a Fe2O3 flux was used to learn how China's coal ash melts.The relationship between ash fusion temperature and chemical composition,as well as the effects of Fe2O3 flux on the ash fusion temperature were studied.The relationship between ash fusion temperature and chemical composition,mineralogical phases and functional groups was analyzed with the FTIR method.The results show that the ash fusion temperature is related to the location and transmittance of certain absorption peaks,which is of great significance for the study of ash behavior.展开更多
An aryl dicarboxylic acid amide compound TMB-5 is an efficient β-form nucleating agent for isotactic polypropylene （iPP）. Because of the solubility of TMB-5, superstructure and morphology of iPP crystals changed wi...An aryl dicarboxylic acid amide compound TMB-5 is an efficient β-form nucleating agent for isotactic polypropylene （iPP）. Because of the solubility of TMB-5, superstructure and morphology of iPP crystals changed with melting conditions. Effects of final heating temperature （Tf） on heterogeneous nucleation of iPP/TMB-5 were investigated. It was discovered that the crystallization temperature increased with decreasing Tf value. The optical microscopic images indicated that when TMB-5 partially dissolved in iPP melt, the remaining （non-dissolved） TMB-5 facilitated the recrystallization of dissolved nucleating agent from the melt, which promoted crystallization. Complete solubility of nucleating agent caused the decreasing efficiency. TMB-5 recrystallized in the form of tiny needles, whose aggregates induced dendritic iPP crystals.展开更多
The metallurgical properties of the CaO–SiO_(2)–Al_(2)O_(3)–4.6wt%Mg O–Fe_(2)O_(3)slag system,formed by the co-treatment process of spent automotive catalyst(SAC)and copper-bearing electroplating sludge(CBES),were...The metallurgical properties of the CaO–SiO_(2)–Al_(2)O_(3)–4.6wt%Mg O–Fe_(2)O_(3)slag system,formed by the co-treatment process of spent automotive catalyst(SAC)and copper-bearing electroplating sludge(CBES),were studied systematically in this paper.The slag structure,melting temperature,and viscous characteristics were investigated by Fourier transform infrared(FTIR)spectroscopy,Raman spectroscopy,Fact Sage calculation,and viscosity measurements.Experimental results show that the increase of Fe_(2)O_(3)content(3.8wt%–16.6wt%),the mass ratio of CaO/SiO_(2)(m(CaO)/m(SiO_(2)),0.5–1.3),and the mass ratio of SiO_(2)/Al_(2)O_(3)(m(SiO_(2))/m(Al_(2)O_(3)),1.0–5.0)can promote the depolymerization of silicate network,and the presence of a large amount of Fe_(2)O_(3)in form of tetrahedral and octahedral units ensures the charge compensation of Al^(3+)ions and makes Al_(2)O_(3)only behave as an acid oxide.Thermodynamic calculation and viscosity measurements show that with the increase of Fe_(2)O_(3)content,m(Ca O)/m(SiO_(2)),and m(SiO_(2))/m(Al_(2)O_(3)),the depolymerization of silicate network structure and low-melting-point phase transformation first occur within the slag,leading to the decrease in melting point and viscosity of the slag,while further increase causes the formation of high-melting-point phase and a resultant re-increase in viscosity and melting point.Based on experimental analysis,the preferred slag composition with low polymerization degree,viscosity,and melting point is as follows:Fe_(2)O_(3)content of 10.2wt%–13.4wt%,m(CaO)/m(SiO_(2))of 0.7–0.9 and m(SiO_(2))/m(Al_(2)O_(3))of 3.0–4.0.This work provides a theoretical support for slag design in co-smelting process of SAC and CBES.展开更多
Leishmaniasis is a set of diseases with a worldwide distribution that affects mainly economically underprivileged populations in developing countries. It has a major impact on public health, with a global cost of bill...Leishmaniasis is a set of diseases with a worldwide distribution that affects mainly economically underprivileged populations in developing countries. It has a major impact on public health, with a global cost of billions of dollars per year. The treatment and control of leishmaniasis vary according to the Leishmania species involved, which require reliable methods for species identification. Since most of the currently used methods have limitations, there is a need for assays that allow rapid, precise identification of the offending species. Real-time polymerase chain reactions in conjunction with dissociation curve analysis have been used to detect differences in the DNA composition of selected genes of Leishmania spp. Kinetoplast DNA is the main molecular target used because of its high copy number per parasite, but other targets have also been studied. As part of an effort to establish melting temperature standards for each target gene, we have reviewed the pertinent literature available in public databases, including Pub Med, Web of Science, Sci ELO and LILACS, using the keywords "Leishmania", "leishmaniasis", "realtime PCR", "melting temperature", and "melting curve", alone or in combination. After applying eligibility criteria, 27 articles were selected for analysis. A considerable variation in the methodologies analyzed was found regarding molecular targets, standardization of the methods, reproducibility and specificity. Because of this, statistical analysis was not performed. In most cases, the methods were able to differentiate the parasite at the subgenus level or few species regardless of the target chosen.展开更多
The melting characteristics and wettability of the binding phase in high basicity sinter were studied. By changing nCaO∶nFe2O3 （molar ratio of CaO to Fe2O3） as well as the percentage of MgO,SiO2,and Al2O3,the melti...The melting characteristics and wettability of the binding phase in high basicity sinter were studied. By changing nCaO∶nFe2O3 （molar ratio of CaO to Fe2O3） as well as the percentage of MgO,SiO2,and Al2O3,the melting characteristics and wettability of the binding phase were discussed. The results indicated that the characteristic melting temperature was the lowest and wettability was the best at nCaO∶nFe2O3=1∶1 （without addition）; the addition of MgO increased the characteristic melting temperature and contact angles; when the percentage of SiO2 or Al2O3 was 3%,the characteristic melting temperature was the lowest,whereas the contact angles increased with an increase in SiO2 and Al2O3 contents.展开更多
The melting curve of Sn has been calculated using the dislocation-mediated melting model with the‘zone-linking method＇.The results are in good agreement with the experimental data.According to our calculation,the me...The melting curve of Sn has been calculated using the dislocation-mediated melting model with the‘zone-linking method＇.The results are in good agreement with the experimental data.According to our calculation,the melting temperature of γ-Sn at zero pressure is about 436 K obtained by the extrapolation of the method from the triple point of Sn.The results show that this calculation method is better than other theoretical methods for predicting the melting curve of polymorphic material Sn.展开更多
The melting curve of MgSiO3 perovskite is simulated using molecular dynamics simulations method at high pressure. It is shown that the simulated equation of state of MgSiO3 perovskite is very successful in reproducing...The melting curve of MgSiO3 perovskite is simulated using molecular dynamics simulations method at high pressure. It is shown that the simulated equation of state of MgSiO3 perovskite is very successful in reproducing accurately the experimental data. The pressure dependence of the simulated melting temperature of MgSiO3 perovskite reproduces the stability of the orthorhombic perovskite phase up to high pressure of 130GPa at ambient temperature, consistent with the theoretical data of the other calculations. It is shown that its transformation to the cubic phase and melting at high pressure and high temperature are in agreement with recent experiments.展开更多
基金Projects(50831003,51071065,51101022,51102090) supported by the National Natural Science Foundation of China
文摘The non-linear effects of different initial melt temperatures on the microstructure evolution during the solidification process of liquid Mg7Zn3 alloys were investigated by molecular dynamics simulation, The microstructure transformation mechanisms were analyzed by several methods. The system was found to be solidified into amorphous structures from different initial melt temperatures at the same cooling rate of 1×10^12 K/s, and the 1551 bond-type and the icosahedron basic cluster （12 0 12 0 ） played a key role in the microstructure transition. Different initial melt temperatures had significant effects on the final microstructures. These effects only can be clearly observed below the glass transition temperature Tg; and these effects are non-linearly related to the initial melt temperatures, and fluctuated in a certain range. However, the changes of the average atomic energy of the systems are still linearly related with the initial melt temperatures, namely, the higher the initial melt temperature is, the more stable the amorphous structure is and the stronger the glass forming ability will be.
文摘Among the processing conditions of injection molding, temperature of the melt entering the mold plays a significant role in determining the quality of molded parts. In our previous research, a neural network was developed to predict the melt temperature in the barrel during the plastication phase. In this paper, a neural network is proposed to predict the melt temperature at the nozzle exit during the injection phase. A typical two-layer neural network with back propagation learning rules is used to model the relationship between input and output in the injection phase. The preliminary results show that the network works well and may be used for on-line optimization and control of injection molding processes.
基金supported by National Natural Science Foundation of China(Grant Nos.52261033,52471187,and 52201194).
文摘This study investigates the influence of melt temperature on the structure and mechanical properties of[Fe_(0.25)Co_(0.25)Ni_(0.25)(Si_(0.3)B_(0.7))_(0.25)]_(99.7)Cu_(0.3) high-entropy bulk metallic glasses(HE-BMGs).Samples were prepared at varying melt temperatures(1423,1523,1573,and 1623 K)using the J-quenching technique.The results reveal that melt temperature significantly affects the atomic arrangement structures,which in turn impacts plasticity and thermal stability.At a lower melt temperature(1423 K),crystal-like clusters form,leading to poor plasticity due to stress concentrations.In contrast,melt temperatures within an optimal range(1523-1573 K)promote a more uniform distribution of soft and hard zones,enhancing plastic deformation.Specifically,the sample prepared in 1573 K melt temperature exhibited the best plasticity,attributed to favorable structural nonuniformity and an increased proportion of soft zones.However,at a higher melt temperature(1623 K),excessive superheating resulted in the formation of large Cu clusters,which enhanced strength but compromised plasticity due to stress concentrations.This work provides a comprehensive understanding of how melt temperature controls microstructural evolution and its influence on the mechanical properties of HE-BMGs,offering valuable insights for optimizing their preparation.
基金This work was supported by the National Natural Science Foundation of China （No.10676025） and Research Center of Laser Fusion, China Academy of Engineering Physics.
文摘The shell-model molecular dynamics method was applied to simulate the melting temper- atures of SrF2 and BaF2 at elevated temperatures and high pressures. The same method was used to calculate the equations of state for SrF2 and BaF2 over the pressure range of 0.1 MPa-3 GPa and 0.1 MPa-7 GPa. Compared with previous results for equations of state, the maximum errors are 0.3% and 2.2%, respectively. Considering the pre-melting in the fluorite-type crystals, we made the necessary corrections for the simulated melting temper- atures of SrF2 and BaF2. Consequently, the melting temperatures of SrF2 and BaF2 were obtained for high pressures. The melting temperatures of SrF2 and BaF2 that were obtained by the simulation are in good agreement with available experimental data.
基金Item Sponsored by National High Technology Research and Development Program(863 Program)of China(2007AA03Z548)Natural Science Foundation of Jiangsu Province of China(BK2010355)
文摘B2O3 is selected as fluxing agent of CaO-based ladle refining slag to decrease the melting temperature as well as to improve the speed of slag forming and the refining efficiency. The effects of B2O3 on the melting temperature of two series of refining slags including the low basicity slags （the mass ratio of CaO/SiO2 is 3--4） and the high basicity slags （the mass ratio of CaO/SiO2 is 5--8.75） were investigated. The slag melting temperature was meas- ured using the hemisphere method. The results indicate that the fluxing action of B2O3 is better than that of CaF2 and A1203. For the CaO-based refining slag with low basicity, the melting temperature is decreased effectively when B2O3 is used to substitute for equal mass of CaF2, Al2O3 and SiO2, respectively. For the CaO-based refining slag with high basicity, when CaF2 is substituted by B2 03, the melting temperature can be decreased remarkably. Espe- cially, when the mass ratios of CaO/Al2O3 and CaO/SiO2 are in the range of 1.1--4.0 and 5.25--8. 0, respectively, the slag melting temperature is lower than 1 300 ℃. Therefore, the 132 03-containing refining slags with high ratios of CaO/Al2O3 and CaO/SiO2 have ultra low melting temperature.
基金Item Sponsored by National Natural Science Foundation of China ( 51174099 )Natural Science Foundation of Jiangsu Province of China ( BK2010355 )National Science Foundation for Post-Doctoral Scientists of China ( 20100471382 )
文摘Fluorite is widely employed as fluxing agent in metallurgy flux , which inevitably leads to serious fluorine pollution.B2O3 is employed as fluxing agent of CaO-SiO2-Fe2O3steelmaking fluxes to substitute for CaF2.The effects of B2O3 and CaF2 on the melting properties of this system were investigated.The melting temperatures of fluxes including softening temperature （Ts）, hemispherical temperature （Th）, and flow temperature （Tf） were measured using the hemisphere method.The results indicate that the fluxing effect of B2O3is more significant than that of CaF2 .When the addition amount of B2O3 （mass percent） exceeds 6% , the melting temperatures of fluxes including Ts , Th and Tf are decreased lower than 1 300℃.The basicity of fluxes has a significant effect on the melting temperature , and the melting temperatures of the fluxes increase with the increase of fluxes basicity.However , when B2O3 is used as fluxing agent , the melting temperature changes little with the basicity increasing from 2.5 to 5.0. These characteristics are suitable for steelmaking process.Moreover , Fe2O3 has an important fluxing effect on this CaO-based steelmaking fluxes.This indicates that the fluxes system is suitable for steelmaking process.
文摘The volatilization kinetics of senarmontite(Sb_(2)O_(3))was analyzed in a neutral atmosphere in two temperature ranges:550-615°C(roasting temperature)and 660-1100°C(melting temperature)by using a thermogravimetric analysis method under various gas flow rates and using a 1.3 m L ceramic crucible(11 mm in internal diameter and 14 mm in height).The effect of particle size was also analyzed.The experimental results of mass loss data,X-ray diffraction(XRD)analysis of partially reacted samples and thermodynamic studies indicate that the senarmontite becomes volatile in the form of Sb_(4)O_(6)(g)without the formation of any intermediary compound in the entire temperature range.At roasting temperatures,the volatilization kinetics of Sb_(2)O_(3) was analyzed using the model X=kappt.The volatilization reaction was controlled by the surface chemical reaction and an activation energy value of 193.0 k J/mol was obtained in this temperature range.Based on the volatilization kinetics at the melting temperatures,for linear behaviour in nitrogen gas,kinetic constants were determined,and an activation energy of 73.9 k J/mol was calculated for the volatilization reaction with a surface area of 8.171×10^(-5)m^(2).
基金financially supported by the National Natural Science Foundation of China(No.51771158)the Development and Reform Commission of Shenzhen Municipality(No.ZX20190229)。
文摘The development of high temperature phase change materials(PCMs)with great comprehensive performance is significant in the future thermal energy storage system.In this study,novel and durable Al-Si/Al_(2)O_(3)-Al N composite PCMs with controllable melting temperature were successfully synthesized by using pristine Al powder as raw material and tetraethyl orthosilicate as SiO_(2)source.The Al_(2)O_(3)shell and Al-Si alloy were in-situ produced via the substitution reaction between molten Al and SiO_(2).Importantly,the crack caused by the incomplete encapsulation of the Al_(2)O_(3)shell could repair itself by the nitridation reaction of internal molten Al and thereby forming a highly dense Al_(2)O_(3)-Al N composite shell.The produced dense Al_(2)O_(3)-Al N composite shell could significantly improve the thermal cycling stability of composite PCMs,and thus,the thermal storage density decrease of the Al-Si/Al_(2)O_(3)-Al N(59.8 J/g to77.7 J/g)was far less than that of the Al-Si/Al_(2)O_(3)(118.5 J/g)after 3000 thermal cycles.Moreover,the synthesized Al-Si/Al_(2)O_(3)-Al N still exhibited a controllable melting temperature(571.5-637.9℃),relatively high thermal storage density(105.6-150.7 J/g),great dimensional stability and structural stability after3000 thermal cycles.Hence,the synthesized Al-Si/Al_(2)O_(3)-Al N composite PCMs,as promising preferential thermal energy storage materials,can be stably used in the energy utilization efficiency improvement of various systems for more than 6 years.
基金by the National National Science Foundation of China(Nos.U1862205,51473085,and 21873054)Tsinghua University Initiative Scientific Research Program(No.20194180048)。
文摘The crystallization and melting behavior of polymers is of theoretical importance.In this work,poly(butylene succinate)(PBS)was selected as an example to study such behavior at low supercooling via introduction of the extended-chain crystal(ECC)of the same polymer as nucleating agent.The crystallization of PBS with its ECC as nucleating agent in a wide temperature range(90–127°C)and the following melting behavior were studied.It is revealed that the melting point(Tm',for Tc≥113°C)and the annealing peak temperature(Ta',for Tc=90–100°C)show similar asymptotic behavior.Both Tm and Ta approach to a value of ca.3.3°C higher than the corresponding Tc when the crystallization time tc approaches the starting point.That is to say,the Hoffman-Weeks plot is parallel to Tm=Tc line.The crystallization line became parallel to the melting line when PBS was crystallized at Tc higher than 102°C.Based on these results,we propose that the parallel relationship and the intrinsic similarity between the Ta and the Tm observed at the two ends of the Tc range could be attributed to the metastable crystals formed at the beginning of crystallization.
基金financially supported by the National Natural Science Foundation of China (No. 21674118)。
文摘Thermal properties such as melting temperature can well reflect the microstructure of the polymer material, and have practical implications in the application of nanofibers. In this work, we investigated the melting temperature of individual electrospun poly(vinylidene fluoride)(PVDF) nanofibers with diameters ranging from smaller than 200 nm to greater than 2 μm by the local thermal analysis technique. The PVDF fibers obtained under four different conditions were found to crystallize into α and β phases, and the fiber mats showed typical values in the crystallinity and Tm with no significant difference among the four. However, analyses at single fiber level revealed broad distribution in diameter and Tm for the fibers produced under identical electrospinning condition. The Tm of individual nanofibers was found to remain constant at large diameters and increase quickly when reducing the fiber diameter toward the nanoscale, and Tm values of 220-230 ℃ were observed for the thinnest nanofibers, much higher than the typical values reported for bulk PVDF. The Tm and molecular orientation at different positions along a beaded fiber were analyzed, showing a similar distribution pattern with a minimum at the bead center and higher values when moving toward both directions. The results indicate that molecular orientation is the driving mechanism for the observed correlation between the Tm and the diameter of the nanofibers.
文摘The density, equilibrium heat of fusion and equilibrium melting temperature of Nylon 1010 were determined by means of infrared spectrum, differential scanning calorimetry, wide angle X-ray diffraction and density measurement techniques. According to Starkweatber' s method crystalline density ρ_c and amorphous density ρ_a were estimated to be 1.098 and 1.003 g/cm^3 respectively by extrapolating the straight lines of the IR absorbanee against density to zero intensity. Owing to the less intense in absorbance and less sensitive to the change in crystallinity of the amorphors band the thus obtained ρ_c was too low in value. Thereby the value of the ratio ρ_c /ρ_a is far less than generally accepted mean value for most crystalline polymers. Accordingly, traditional X-ray diffraction method was used through determining thc crystalline dimension(a=4.9, b=5.4, c=27.8, α=49° β=77.0°, γ=63.5°), and a rather correct value of ρ_c or the crystal density 1.13 g/cm^3 was obtained. The equilibrium heat of fusion △H_m^0 was estimated to be 244.0 J/g piotting △H_m 's of specimens with different crystallinity against their corre sponding specific volumes_(sp), and extrapolating to completely crystalline condition (_(sp)~c= 1/ρ_c) As to the equilibrium melting temperature T_m^0, because of the easiness of recrystallization of melt crystallized Nylon 1010 specimen, the well-known Hoffman's T_m-T_c method failed in determining this value and an usually rarely used Kamide double extrapolation method was adopted. The so obtained value of T_m^0 487 seems to be fairly reasonable.
基金financial support received from Ministry of Mines, TIFAC, and Department of Science and Technology
文摘The preparation of semisolid slurry of A356 aluminum alloy using an oblique plate was investigated. A356 alloy melt undergoes partial solidification when it flows down on an oblique plate cooled from underneath by counter flowing water. It results in continuous formation of columnar dendrites on plate wall. Due to forced convection, these dendrites are sheared off into equiaxed/fragmented grains and then washed away continuously to produce semisolid slurry at plate exit. Melt pouring temperature provides required condition of solidification whereas plate inclination enables necessary shear for producing semisolid slurry of desired quality. Slurry obtained was solidified in metal mould to produce semisolid-cast billets of desired microstructure. Furthermore, semisolid-cast billets were heat treated to improve surface quality. Microstructures of both semisolid-cast and heat-treated billets were analyzed. Effects of melt pouring temperature and plate inclination on solidification and microstructure of billets produced using oblique plate were described. The investigations involved four different melt pouring temperatures (620, 625, 630 and 635 °C) associated with four different plate inclinations (30°, 45°, 60° and 75°). Melt pouring temperature of 625 °C with plate inclination of 60° shows fine and globular microstructures and it is the optimum.
文摘Experiments were carried out on carburizing and temperature rising of the semi steel melt in a plasma induction furnace.Influence of many factors, such as power supply mode,position of the plasma torch and bottom blown gas stirring,on heating efficiency and melt temperature distribution was studied. Melt temperature could be effectively controlled by plasma heating,and carbon content of semi steel melt increased from 1.92 % to 4.58 %, and the utilization rate of carbon reached up to 61.57 % during carburizing of the melt.
基金Projects 2003001 supported by the Key Project of Huainan City405099 by the Project of Science Research and Development of China Petroleum & Chemical Corporation
文摘A Fourier Transform Infrared Spectroscopic(FTIR)method involving a Fe2O3 flux was used to learn how China's coal ash melts.The relationship between ash fusion temperature and chemical composition,as well as the effects of Fe2O3 flux on the ash fusion temperature were studied.The relationship between ash fusion temperature and chemical composition,mineralogical phases and functional groups was analyzed with the FTIR method.The results show that the ash fusion temperature is related to the location and transmittance of certain absorption peaks,which is of great significance for the study of ash behavior.
文摘An aryl dicarboxylic acid amide compound TMB-5 is an efficient β-form nucleating agent for isotactic polypropylene （iPP）. Because of the solubility of TMB-5, superstructure and morphology of iPP crystals changed with melting conditions. Effects of final heating temperature （Tf） on heterogeneous nucleation of iPP/TMB-5 were investigated. It was discovered that the crystallization temperature increased with decreasing Tf value. The optical microscopic images indicated that when TMB-5 partially dissolved in iPP melt, the remaining （non-dissolved） TMB-5 facilitated the recrystallization of dissolved nucleating agent from the melt, which promoted crystallization. Complete solubility of nucleating agent caused the decreasing efficiency. TMB-5 recrystallized in the form of tiny needles, whose aggregates induced dendritic iPP crystals.
基金financially supported by the Guangzhou Basic and Applied Basic Research Project,China(No.202102020623)the Guangdong Academy of Sciences’Project of Science and Technology Development,China(No.2020 GDASYL-20200103101)+1 种基金the National Key Research and Development Program of China(No.2020YFC1908902)the Natural Science Foundation of Guangdong Province Project,China(No.2020A1515010729)。
文摘The metallurgical properties of the CaO–SiO_(2)–Al_(2)O_(3)–4.6wt%Mg O–Fe_(2)O_(3)slag system,formed by the co-treatment process of spent automotive catalyst(SAC)and copper-bearing electroplating sludge(CBES),were studied systematically in this paper.The slag structure,melting temperature,and viscous characteristics were investigated by Fourier transform infrared(FTIR)spectroscopy,Raman spectroscopy,Fact Sage calculation,and viscosity measurements.Experimental results show that the increase of Fe_(2)O_(3)content(3.8wt%–16.6wt%),the mass ratio of CaO/SiO_(2)(m(CaO)/m(SiO_(2)),0.5–1.3),and the mass ratio of SiO_(2)/Al_(2)O_(3)(m(SiO_(2))/m(Al_(2)O_(3)),1.0–5.0)can promote the depolymerization of silicate network,and the presence of a large amount of Fe_(2)O_(3)in form of tetrahedral and octahedral units ensures the charge compensation of Al^(3+)ions and makes Al_(2)O_(3)only behave as an acid oxide.Thermodynamic calculation and viscosity measurements show that with the increase of Fe_(2)O_(3)content,m(Ca O)/m(SiO_(2)),and m(SiO_(2))/m(Al_(2)O_(3)),the depolymerization of silicate network structure and low-melting-point phase transformation first occur within the slag,leading to the decrease in melting point and viscosity of the slag,while further increase causes the formation of high-melting-point phase and a resultant re-increase in viscosity and melting point.Based on experimental analysis,the preferred slag composition with low polymerization degree,viscosity,and melting point is as follows:Fe_(2)O_(3)content of 10.2wt%–13.4wt%,m(CaO)/m(SiO_(2))of 0.7–0.9 and m(SiO_(2))/m(Al_(2)O_(3))of 3.0–4.0.This work provides a theoretical support for slag design in co-smelting process of SAC and CBES.
文摘Leishmaniasis is a set of diseases with a worldwide distribution that affects mainly economically underprivileged populations in developing countries. It has a major impact on public health, with a global cost of billions of dollars per year. The treatment and control of leishmaniasis vary according to the Leishmania species involved, which require reliable methods for species identification. Since most of the currently used methods have limitations, there is a need for assays that allow rapid, precise identification of the offending species. Real-time polymerase chain reactions in conjunction with dissociation curve analysis have been used to detect differences in the DNA composition of selected genes of Leishmania spp. Kinetoplast DNA is the main molecular target used because of its high copy number per parasite, but other targets have also been studied. As part of an effort to establish melting temperature standards for each target gene, we have reviewed the pertinent literature available in public databases, including Pub Med, Web of Science, Sci ELO and LILACS, using the keywords "Leishmania", "leishmaniasis", "realtime PCR", "melting temperature", and "melting curve", alone or in combination. After applying eligibility criteria, 27 articles were selected for analysis. A considerable variation in the methodologies analyzed was found regarding molecular targets, standardization of the methods, reproducibility and specificity. Because of this, statistical analysis was not performed. In most cases, the methods were able to differentiate the parasite at the subgenus level or few species regardless of the target chosen.
基金Sponsored by National Natural Science Foundation of China (50474014)
文摘The melting characteristics and wettability of the binding phase in high basicity sinter were studied. By changing nCaO∶nFe2O3 （molar ratio of CaO to Fe2O3） as well as the percentage of MgO,SiO2,and Al2O3,the melting characteristics and wettability of the binding phase were discussed. The results indicated that the characteristic melting temperature was the lowest and wettability was the best at nCaO∶nFe2O3=1∶1 （without addition）; the addition of MgO increased the characteristic melting temperature and contact angles; when the percentage of SiO2 or Al2O3 was 3%,the characteristic melting temperature was the lowest,whereas the contact angles increased with an increase in SiO2 and Al2O3 contents.
基金Project supported by the National Natural Science Foundation of China (Grant No 10776029/A06)
文摘The melting curve of Sn has been calculated using the dislocation-mediated melting model with the‘zone-linking method＇.The results are in good agreement with the experimental data.According to our calculation,the melting temperature of γ-Sn at zero pressure is about 436 K obtained by the extrapolation of the method from the triple point of Sn.The results show that this calculation method is better than other theoretical methods for predicting the melting curve of polymorphic material Sn.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10274055 and 10376021）, the Natural Science Foundation of Gansu Province, China （Grant No 3ZS051-A25-027） and the Scientific Research Foundation of Education Bureau of Gansu Province, China （Grant No 0410-01）.
文摘The melting curve of MgSiO3 perovskite is simulated using molecular dynamics simulations method at high pressure. It is shown that the simulated equation of state of MgSiO3 perovskite is very successful in reproducing accurately the experimental data. The pressure dependence of the simulated melting temperature of MgSiO3 perovskite reproduces the stability of the orthorhombic perovskite phase up to high pressure of 130GPa at ambient temperature, consistent with the theoretical data of the other calculations. It is shown that its transformation to the cubic phase and melting at high pressure and high temperature are in agreement with recent experiments.
