By measuring and analyzing the crystallization activation energy (CAE) of Fe-based amorphous alloy Fe79B16Si5 and Fe78B13Si9, it is reconfirmed and further analyzed that the conventional Kissinger method does not conf...By measuring and analyzing the crystallization activation energy (CAE) of Fe-based amorphous alloy Fe79B16Si5 and Fe78B13Si9, it is reconfirmed and further analyzed that the conventional Kissinger method does not conform with the premise of Kissinger equation, namely, samples with different heating rates should keep a constant fraction of transformation at the exothermal peak temperature Tp of DSC thermogram. The XRD equal first peak height (EFPH) method is applied to CAE measurement of Fe-based amorphous alloy for the first time. It is shown again that the EFPH method coincides with the premise of Kissinger equation. The procedure of EFPH method is introduced in detail in this paper. The accuracy in determining CAE of amorphous alloy may be improved by applying the EFPH method. As a result, the mechanism of embrittlement of amorphous alloy may be better elucidated.展开更多
The preparation process of amorphous nanometer boron powders through combustion synthesis was investigated, and the effects of the reactant ratio, the heating agent and the milling rate on the activity and particle si...The preparation process of amorphous nanometer boron powders through combustion synthesis was investigated, and the effects of the reactant ratio, the heating agent and the milling rate on the activity and particle size of amorphous boron powders were studied. The results show that the boron powders exist in the form of an amorphous phase which has the crystallinity lower than 30.4%, and the particle size of boron powder decreases with an increase of the high-energy ball milling rate. The purity of amorphous boron powder is 94.8% and particle sizes are much smaller than 100 nm when the mass ratio of B2O3/Mg/KClO3 is 100:105:17 and the ball milling time is 20 min with the milling rate of 300 r/min. At the same time, the amorphous boron nano-fibers appear in the boron powders.展开更多
The law and activation energy of annealing embrittlement for three kinds of popular Fe B Si amorphous alloys have been studied. For comparison, the crystallization activation energy (CAE) of these alloys was measure...The law and activation energy of annealing embrittlement for three kinds of popular Fe B Si amorphous alloys have been studied. For comparison, the crystallization activation energy (CAE) of these alloys was measured by XRD equal first peak height method and conventional Kissinger method. The structural relaxation activation energy (SRAE) of these alloys was measured by Curie temperature method or internal friction method. Through the comparison and analysis of the activation energies of annealing embrittlement, crystallization and structural relaxation, the related influencing factors on annealing embrittlement of Fe based amorphous alloys are elucidated.展开更多
The crystallization kinetics of an amorphous Ti-rich NiTi film (Ni 46.34at.%, Ti 53.66at.%)prepared by DC magnetron sputtering was determined by non-isothermal techniques. The activation energy of crystallization and ...The crystallization kinetics of an amorphous Ti-rich NiTi film (Ni 46.34at.%, Ti 53.66at.%)prepared by DC magnetron sputtering was determined by non-isothermal techniques. The activation energy of crystallization and the mean value of the Avrami parameter are 382kJ/mol and 0.85, respectively. The calculated isothermal kinetic curse of amorphous film at 773K coincides with the result of X-ray diffraction.The formation of a Ti2Ni phase is accompanied with the crystallization of Ti-rich NiTi film.展开更多
The effects of Zr on crystallization kinetics of Pr Fe B amorphous alloys have been investigated by DTA and XRD methods. It was found that for Pr 8Fe 86- x Zr x B 6 ( x =0, 1, 2) amorphous alloys, the final crystalliz...The effects of Zr on crystallization kinetics of Pr Fe B amorphous alloys have been investigated by DTA and XRD methods. It was found that for Pr 8Fe 86- x Zr x B 6 ( x =0, 1, 2) amorphous alloys, the final crystallized mixture is α Fe and Pr 2Fe 14 B, and the metastable Pr 2Fe 23 B 3 phase occurs during crystallization of Pr 8Fe 86 B 6 amorphous alloy, not during crystallization of Pr 8Fe 86- x Zr x B 6( x =1, 2) amorphous alloys. By analyzing the activation energy of crystallization, the formation of an α Fe/Pr 2Fe 14 B composite microstructure with a coarse grain size in annealed Pr 8Fe 86 B 6 alloy, is attributed to a difficult nucleation and an easy growth for both the α Fe and Pr 2Fe 14 B in the alloy. The addition of Zr can be used to change the crystallization behavior of the α Fe phase in Pr Fe B amorphous alloy, which is helpful to reduce the grain size for the α Fe phase.展开更多
Amorphous ribbons of (Ni0.75Fe0.25)78-xNbxSi10B12 (x = 0, 5) were prepared by a single roller melt-spinning technique in air atmosphere. The crystallization kinetics of the alloys were investigated by means of con...Amorphous ribbons of (Ni0.75Fe0.25)78-xNbxSi10B12 (x = 0, 5) were prepared by a single roller melt-spinning technique in air atmosphere. The crystallization kinetics of the alloys were investigated by means of continuous heating, and the activation energies of the alloys were calculated using Kissinger plot method and Ozawa plot method on the basis of differential thermal analysis data. The crystallization products were analyzed by X-ray diffraction. After the (Ni0.75Fe0.25)78Si10B12 amorphous alloy was annealed at the temperatures 715 and 745 K, a single phase of γ-(Fe, Ni) solid solution with grain sizes of about 10.3 and 18.5 nm, respectively, precipitates in the amorphous matrix. The crystallized phases are γ-(Fe, Ni) solid solution, Fe2Si, Ni2Si, and Fe3B after annealing at 765 K. The (Ni0.75Fe0.25)73NbsSi10 B12 amorphous alloy was annealed at 720, 750, and 800 K; and the crystallization phases, γ(Fe, Ni) solid solution, (Fe, Ni)23B6. Ni31Si12 and Nb2NiB0.16 form simultaneously.展开更多
The effect of pre-annealing treatment on the crystallization kinetics parameters of amorphous Ni-P alloys has been investigated.Experimental results showed that the crystallization tem- perature,T_p and T_x,the appare...The effect of pre-annealing treatment on the crystallization kinetics parameters of amorphous Ni-P alloys has been investigated.Experimental results showed that the crystallization tem- perature,T_p and T_x,the apparent activation energy,E_c,as well as the Avrami exponent for isothermal crystallization,n,decrease significantly,while ΔT_(px)=T_p-T_x increases with the elongation of pre-annealing time at 570 K.展开更多
Amorphous ribbons of (Ni0.75Fe0.25)78-xNbxSi10B12(x=0,5) were prepared by a single roller melt-spinning technique in air atmosphere. The crystallization kinetics of the alloys were investigated by means of continuou...Amorphous ribbons of (Ni0.75Fe0.25)78-xNbxSi10B12(x=0,5) were prepared by a single roller melt-spinning technique in air atmosphere. The crystallization kinetics of the alloys were investigated by means of continuous heating,and the activation energies of the alloys were calculated using Kissinger plot method and Ozawa plot method on the basis of differential thermal analysis data. The crystallization products were analyzed by X-ray diffraction. After the (Ni0.75Fe0.25)78-xNbxSi10B12 amorphous alloy was annealed at the temperatures 715 and 745?K,a single phase of γ-(Fe,Ni) solid solution with grain sizes of about 10.3 and 18.5?nm,respectively,precipitates in the amorphous matrix. The crystallized phases are γ-(Fe,Ni) solid solution,Fe2Si,Ni2Si,and Fe3B after annealing at 765?K. The (Ni0.75Fe0.25)78-xNbxSi10B12 amorphous alloy was annealed at 720,750,and 800?K; and the crystallization phases,γ-(Fe,Ni) solid solution,(Fe,Ni) 23 B6,Ni 31 Si 12 and Nb2NiB 0.16 form simultaneously.展开更多
Mg65Cu25Gd10 amorphous alloy powders were synthesized by mechanical alloying (MA). The most suitable process is that the milling velocity is 600 r/min and the mass ratio of ball to powder is 20:1, so the shortest form...Mg65Cu25Gd10 amorphous alloy powders were synthesized by mechanical alloying (MA). The most suitable process is that the milling velocity is 600 r/min and the mass ratio of ball to powder is 20:1, so the shortest forming time of the amorphous is about 40 h. The thermal stability of the powders was analyzed by differential scanning calorimetry (DSC). The glass transition temperature, (Tg), onset temperature of crystallization(Tx), width of supercooled liquid region, were determined to be 444.8, 531.1 and 86.3 K, respectively. Contrasting them with the parameters of samples produced by traditional copper-mold casting, it is found that the thermal stability of the former is better than that of the latter. At the same time, the crystallization kinetics of those amorphous powders was researched by Kissinger equation and the apparent activation energy at Tg and Tx was calculated.展开更多
The effect of yttrium on the thermal stability and crystallization behavior of Nd-Fe-Al-Ni amorphous alloys was investigated using X-ray diffraction (XRD), differential scanning calorimeter (DSC), and transmission...The effect of yttrium on the thermal stability and crystallization behavior of Nd-Fe-Al-Ni amorphous alloys was investigated using X-ray diffraction (XRD), differential scanning calorimeter (DSC), and transmission electron microscopy (TEM).The results indicated that the as-cast Nd60Fe20Al10Ni10-xYx(X=-0, 2) amorphous alloys were fabricated with some quenched-in crystals, which could be restrained by Y. With the effect of yttrium, both the crystallization temperature and exothermic peak shifted to higher temperatures, illustrating that the thermal stability could be improved. The addition of Y changed the crystallization process and final crystallization results. Moreover, the crystallites in the amorphous matrix became more homogeneous and smaller. Meanwhile, Y was useful for the passivation of oxygen in chemistry and restrained the negative effect of oxygen. The activation energies of the start of crystallization and peaking were 1.21 and 1.16 eV, respectively, according to the Kissinger equation.展开更多
Crystallization kinetics of Al83Y10Ni7(at%) amorphous alloys prepared bymelt spinning was studied by differential scanning calorimetry (DSC). Three or fourstages of transforniation from amorphous to equilibrium state ...Crystallization kinetics of Al83Y10Ni7(at%) amorphous alloys prepared bymelt spinning was studied by differential scanning calorimetry (DSC). Three or fourstages of transforniation from amorphous to equilibrium state can be distinguished atheating rate 1  ̄ 40K / min. Apparent activation energies are calculated according to themethods of Kissinger, Ozawa and Arrhernius equation. An amoaphous phase with highstructural and heat stability was obtained in the vicinity of Al83Y10,Ni7. The isotheimalcrystallization kinetics of the first peak, in the range of 0. 15 ̄ 0.85, was found to be inagreement with John-Mell-Avrami equation with n = 2.5. Nucleation and growth dur-ing isothennal crystallization of the first stage for Al83Y10Ni7 amorpohous were ap-proached by introducing the concept of local Avrami exponent and local activation en-ergy.展开更多
The crystallization behavior of Zr 55 Al 10 Ni 5Cu 30 (mole fraction, %) bulk amorphous alloy during continuous heating and isothermal annealing was investigated. The results show that there exists a first order expon...The crystallization behavior of Zr 55 Al 10 Ni 5Cu 30 (mole fraction, %) bulk amorphous alloy during continuous heating and isothermal annealing was investigated. The results show that there exists a first order exponential decay relation between the characteristic temperatures and the heating rates during continuous heating process. The activation energy for glass transition E g and that for crystallization E p and E x during continuous heating were evaluated by Kissinger plots. In addition, there is a second order exponential decay relation between the annealing temperature and the corresponding crystallization time during isothermal annealing. The isothermal activation energy obtained by Arrhenius equation increases as crystallization proceeds, indicating the sufficient stability of the residual amorphous structure after initial crystallization.展开更多
Influence of intramolecular π-π interaction on the luminescent properties of thermally activated delayed fluorescence(TADF) molecule(3, 5-bis(3,6-di-tert-butyl-9 H-carbazol-9-yl)-phenyl)(pyridin-4-yl) methan...Influence of intramolecular π-π interaction on the luminescent properties of thermally activated delayed fluorescence(TADF) molecule(3, 5-bis(3,6-di-tert-butyl-9 H-carbazol-9-yl)-phenyl)(pyridin-4-yl) methanone(DTCBPY) is theoretically studied by using the density functional theory(DFT) and time-dependent density functional theory(TD-DFT).Four conformations(named as A, B, C, and D) of the DTCBPY can be found by relax scanning, and the configuration C corresponds to the luminescent molecule detected experimentally. Besides, we calculate the proportion of each conformation by Boltzmann distribution, high configuration ratios(44% and 52%) can be found for C and D. Moreover, C and D are found to exist with an intramolecular π-π interaction between one donor and the acceptor; the intramolecular interaction brings a smaller Huang-Rhys factor and reduced reorganization energy. Our work presents a rational explanation for the experimental results and demonstrates the importance of the intramolecular π-π interaction to the photophysical properties of TADF molecules.展开更多
By using the new method for determination of activation energies for nucleation andgrowth (E_n & E_g) developed in Part Ⅰ of this work, the E_n and E_g of some pre--annealedamorphous Ni--P alloys, as well as thos...By using the new method for determination of activation energies for nucleation andgrowth (E_n & E_g) developed in Part Ⅰ of this work, the E_n and E_g of some pre--annealedamorphous Ni--P alloys, as well as those of the as--quenched Ni--P glass within differenttemperature ranges are measured and studied. The results show that the values of E_n and E_gare closely related to the microstructure of amorphous alloys and the annealing temperature.The higher the ordering in the amorphous alloys, the smaller the values of E_n and E_g; thehigher the annealing temperature, the greater the E_n and E_g values. By means of the newlydeveloped crystallization micromechanism, such an experimental phenomenon which is diffi-cult to understand from the classical crystallization mechanism is reasonably explained.展开更多
A new method is developed for the determination of activation energies for nucleation(E_n) and for growth of nuclei (E_g) during crystallization of amorphous alloys. This methodis based on the crystallization kinetics...A new method is developed for the determination of activation energies for nucleation(E_n) and for growth of nuclei (E_g) during crystallization of amorphous alloys. This methodis based on the crystallization kinetics theory and the experimental results of the variationrelationships of local activation energy E_c(x) and local Avrami exponent n(x) with the crys-tallized volume fraction (x) during crystallization of an amorphous Ni--P alloy. Calculationresults of E_n and E_g in tbe case of crystallization of the amorphous Ni--P alloy by thismethod show that this method is not only simple in the experimental procedures, but alsoaccurate in the quantitative results.展开更多
采用水雾化方法制备了Fe-Si-B-C四元非晶合金粉末。研究了粉末的粒度分布、相结构、微观形貌、热稳定性以及基本软磁性能,并通过Kissinger峰移法计算了其晶化时所需的激活能。结果表明,通过水雾化方法制备的Fe-Si-B-C四元软磁粉末的粒...采用水雾化方法制备了Fe-Si-B-C四元非晶合金粉末。研究了粉末的粒度分布、相结构、微观形貌、热稳定性以及基本软磁性能,并通过Kissinger峰移法计算了其晶化时所需的激活能。结果表明,通过水雾化方法制备的Fe-Si-B-C四元软磁粉末的粒度分布合理;粒径小于38μm的粉末为完全非晶结构,且粉末表面光滑,内部成分均匀;非晶粉末的初始结晶温度为542.15℃,且升温过程中存在2个晶化放热峰;2个晶化反应对应的晶化激活能分别为463.92 k J/mol和910.21 k J/mol;粉末的饱和磁感应强度和矫顽力分别为1.08 T和111.4 A/m。展开更多
文摘By measuring and analyzing the crystallization activation energy (CAE) of Fe-based amorphous alloy Fe79B16Si5 and Fe78B13Si9, it is reconfirmed and further analyzed that the conventional Kissinger method does not conform with the premise of Kissinger equation, namely, samples with different heating rates should keep a constant fraction of transformation at the exothermal peak temperature Tp of DSC thermogram. The XRD equal first peak height (EFPH) method is applied to CAE measurement of Fe-based amorphous alloy for the first time. It is shown again that the EFPH method coincides with the premise of Kissinger equation. The procedure of EFPH method is introduced in detail in this paper. The accuracy in determining CAE of amorphous alloy may be improved by applying the EFPH method. As a result, the mechanism of embrittlement of amorphous alloy may be better elucidated.
基金Project(51002025) supported by the National Natural Science Foundation of China
文摘The preparation process of amorphous nanometer boron powders through combustion synthesis was investigated, and the effects of the reactant ratio, the heating agent and the milling rate on the activity and particle size of amorphous boron powders were studied. The results show that the boron powders exist in the form of an amorphous phase which has the crystallinity lower than 30.4%, and the particle size of boron powder decreases with an increase of the high-energy ball milling rate. The purity of amorphous boron powder is 94.8% and particle sizes are much smaller than 100 nm when the mass ratio of B2O3/Mg/KClO3 is 100:105:17 and the ball milling time is 20 min with the milling rate of 300 r/min. At the same time, the amorphous boron nano-fibers appear in the boron powders.
文摘The law and activation energy of annealing embrittlement for three kinds of popular Fe B Si amorphous alloys have been studied. For comparison, the crystallization activation energy (CAE) of these alloys was measured by XRD equal first peak height method and conventional Kissinger method. The structural relaxation activation energy (SRAE) of these alloys was measured by Curie temperature method or internal friction method. Through the comparison and analysis of the activation energies of annealing embrittlement, crystallization and structural relaxation, the related influencing factors on annealing embrittlement of Fe based amorphous alloys are elucidated.
基金the National Natural Science FouThdation of China !(GrantWb. 59vs1030)
文摘The crystallization kinetics of an amorphous Ti-rich NiTi film (Ni 46.34at.%, Ti 53.66at.%)prepared by DC magnetron sputtering was determined by non-isothermal techniques. The activation energy of crystallization and the mean value of the Avrami parameter are 382kJ/mol and 0.85, respectively. The calculated isothermal kinetic curse of amorphous film at 773K coincides with the result of X-ray diffraction.The formation of a Ti2Ni phase is accompanied with the crystallization of Ti-rich NiTi film.
文摘The effects of Zr on crystallization kinetics of Pr Fe B amorphous alloys have been investigated by DTA and XRD methods. It was found that for Pr 8Fe 86- x Zr x B 6 ( x =0, 1, 2) amorphous alloys, the final crystallized mixture is α Fe and Pr 2Fe 14 B, and the metastable Pr 2Fe 23 B 3 phase occurs during crystallization of Pr 8Fe 86 B 6 amorphous alloy, not during crystallization of Pr 8Fe 86- x Zr x B 6( x =1, 2) amorphous alloys. By analyzing the activation energy of crystallization, the formation of an α Fe/Pr 2Fe 14 B composite microstructure with a coarse grain size in annealed Pr 8Fe 86 B 6 alloy, is attributed to a difficult nucleation and an easy growth for both the α Fe and Pr 2Fe 14 B in the alloy. The addition of Zr can be used to change the crystallization behavior of the α Fe phase in Pr Fe B amorphous alloy, which is helpful to reduce the grain size for the α Fe phase.
基金This work was financially supported by the National "863" Program (No. 2003AA32X150) and the State Key Laboratory of Advanced New Non-ferrous Materials, China.
文摘Amorphous ribbons of (Ni0.75Fe0.25)78-xNbxSi10B12 (x = 0, 5) were prepared by a single roller melt-spinning technique in air atmosphere. The crystallization kinetics of the alloys were investigated by means of continuous heating, and the activation energies of the alloys were calculated using Kissinger plot method and Ozawa plot method on the basis of differential thermal analysis data. The crystallization products were analyzed by X-ray diffraction. After the (Ni0.75Fe0.25)78Si10B12 amorphous alloy was annealed at the temperatures 715 and 745 K, a single phase of γ-(Fe, Ni) solid solution with grain sizes of about 10.3 and 18.5 nm, respectively, precipitates in the amorphous matrix. The crystallized phases are γ-(Fe, Ni) solid solution, Fe2Si, Ni2Si, and Fe3B after annealing at 765 K. The (Ni0.75Fe0.25)73NbsSi10 B12 amorphous alloy was annealed at 720, 750, and 800 K; and the crystallization phases, γ(Fe, Ni) solid solution, (Fe, Ni)23B6. Ni31Si12 and Nb2NiB0.16 form simultaneously.
文摘The effect of pre-annealing treatment on the crystallization kinetics parameters of amorphous Ni-P alloys has been investigated.Experimental results showed that the crystallization tem- perature,T_p and T_x,the apparent activation energy,E_c,as well as the Avrami exponent for isothermal crystallization,n,decrease significantly,while ΔT_(px)=T_p-T_x increases with the elongation of pre-annealing time at 570 K.
文摘Amorphous ribbons of (Ni0.75Fe0.25)78-xNbxSi10B12(x=0,5) were prepared by a single roller melt-spinning technique in air atmosphere. The crystallization kinetics of the alloys were investigated by means of continuous heating,and the activation energies of the alloys were calculated using Kissinger plot method and Ozawa plot method on the basis of differential thermal analysis data. The crystallization products were analyzed by X-ray diffraction. After the (Ni0.75Fe0.25)78-xNbxSi10B12 amorphous alloy was annealed at the temperatures 715 and 745?K,a single phase of γ-(Fe,Ni) solid solution with grain sizes of about 10.3 and 18.5?nm,respectively,precipitates in the amorphous matrix. The crystallized phases are γ-(Fe,Ni) solid solution,Fe2Si,Ni2Si,and Fe3B after annealing at 765?K. The (Ni0.75Fe0.25)78-xNbxSi10B12 amorphous alloy was annealed at 720,750,and 800?K; and the crystallization phases,γ-(Fe,Ni) solid solution,(Fe,Ni) 23 B6,Ni 31 Si 12 and Nb2NiB 0.16 form simultaneously.
基金Project (2006BB4199) supported by the Natural Science Foundation of Chongqing
文摘Mg65Cu25Gd10 amorphous alloy powders were synthesized by mechanical alloying (MA). The most suitable process is that the milling velocity is 600 r/min and the mass ratio of ball to powder is 20:1, so the shortest forming time of the amorphous is about 40 h. The thermal stability of the powders was analyzed by differential scanning calorimetry (DSC). The glass transition temperature, (Tg), onset temperature of crystallization(Tx), width of supercooled liquid region, were determined to be 444.8, 531.1 and 86.3 K, respectively. Contrasting them with the parameters of samples produced by traditional copper-mold casting, it is found that the thermal stability of the former is better than that of the latter. At the same time, the crystallization kinetics of those amorphous powders was researched by Kissinger equation and the apparent activation energy at Tg and Tx was calculated.
基金the National Natural Science Foundation of China (50571052)
文摘The effect of yttrium on the thermal stability and crystallization behavior of Nd-Fe-Al-Ni amorphous alloys was investigated using X-ray diffraction (XRD), differential scanning calorimeter (DSC), and transmission electron microscopy (TEM).The results indicated that the as-cast Nd60Fe20Al10Ni10-xYx(X=-0, 2) amorphous alloys were fabricated with some quenched-in crystals, which could be restrained by Y. With the effect of yttrium, both the crystallization temperature and exothermic peak shifted to higher temperatures, illustrating that the thermal stability could be improved. The addition of Y changed the crystallization process and final crystallization results. Moreover, the crystallites in the amorphous matrix became more homogeneous and smaller. Meanwhile, Y was useful for the passivation of oxygen in chemistry and restrained the negative effect of oxygen. The activation energies of the start of crystallization and peaking were 1.21 and 1.16 eV, respectively, according to the Kissinger equation.
文摘Crystallization kinetics of Al83Y10Ni7(at%) amorphous alloys prepared bymelt spinning was studied by differential scanning calorimetry (DSC). Three or fourstages of transforniation from amorphous to equilibrium state can be distinguished atheating rate 1  ̄ 40K / min. Apparent activation energies are calculated according to themethods of Kissinger, Ozawa and Arrhernius equation. An amoaphous phase with highstructural and heat stability was obtained in the vicinity of Al83Y10,Ni7. The isotheimalcrystallization kinetics of the first peak, in the range of 0. 15 ̄ 0.85, was found to be inagreement with John-Mell-Avrami equation with n = 2.5. Nucleation and growth dur-ing isothennal crystallization of the first stage for Al83Y10Ni7 amorpohous were ap-proached by introducing the concept of local Avrami exponent and local activation en-ergy.
文摘The crystallization behavior of Zr 55 Al 10 Ni 5Cu 30 (mole fraction, %) bulk amorphous alloy during continuous heating and isothermal annealing was investigated. The results show that there exists a first order exponential decay relation between the characteristic temperatures and the heating rates during continuous heating process. The activation energy for glass transition E g and that for crystallization E p and E x during continuous heating were evaluated by Kissinger plots. In addition, there is a second order exponential decay relation between the annealing temperature and the corresponding crystallization time during isothermal annealing. The isothermal activation energy obtained by Arrhenius equation increases as crystallization proceeds, indicating the sufficient stability of the residual amorphous structure after initial crystallization.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11374195 and 21403133)Taishan Scholar Project of Shandong Normal University,China+1 种基金the Promotive Research Fund for Excellent Young and Middle-aged Scientists of Shandong Province,China(Grant No.BS2014cl001)the China Postdoctoral Science Foundation(Grant No.2014M560571)
文摘Influence of intramolecular π-π interaction on the luminescent properties of thermally activated delayed fluorescence(TADF) molecule(3, 5-bis(3,6-di-tert-butyl-9 H-carbazol-9-yl)-phenyl)(pyridin-4-yl) methanone(DTCBPY) is theoretically studied by using the density functional theory(DFT) and time-dependent density functional theory(TD-DFT).Four conformations(named as A, B, C, and D) of the DTCBPY can be found by relax scanning, and the configuration C corresponds to the luminescent molecule detected experimentally. Besides, we calculate the proportion of each conformation by Boltzmann distribution, high configuration ratios(44% and 52%) can be found for C and D. Moreover, C and D are found to exist with an intramolecular π-π interaction between one donor and the acceptor; the intramolecular interaction brings a smaller Huang-Rhys factor and reduced reorganization energy. Our work presents a rational explanation for the experimental results and demonstrates the importance of the intramolecular π-π interaction to the photophysical properties of TADF molecules.
基金Project suopotted by the National Natural Science Foundation of China
文摘By using the new method for determination of activation energies for nucleation andgrowth (E_n & E_g) developed in Part Ⅰ of this work, the E_n and E_g of some pre--annealedamorphous Ni--P alloys, as well as those of the as--quenched Ni--P glass within differenttemperature ranges are measured and studied. The results show that the values of E_n and E_gare closely related to the microstructure of amorphous alloys and the annealing temperature.The higher the ordering in the amorphous alloys, the smaller the values of E_n and E_g; thehigher the annealing temperature, the greater the E_n and E_g values. By means of the newlydeveloped crystallization micromechanism, such an experimental phenomenon which is diffi-cult to understand from the classical crystallization mechanism is reasonably explained.
基金Project supported by the National Natural Science Foundation of China.
文摘A new method is developed for the determination of activation energies for nucleation(E_n) and for growth of nuclei (E_g) during crystallization of amorphous alloys. This methodis based on the crystallization kinetics theory and the experimental results of the variationrelationships of local activation energy E_c(x) and local Avrami exponent n(x) with the crys-tallized volume fraction (x) during crystallization of an amorphous Ni--P alloy. Calculationresults of E_n and E_g in tbe case of crystallization of the amorphous Ni--P alloy by thismethod show that this method is not only simple in the experimental procedures, but alsoaccurate in the quantitative results.
文摘采用水雾化方法制备了Fe-Si-B-C四元非晶合金粉末。研究了粉末的粒度分布、相结构、微观形貌、热稳定性以及基本软磁性能,并通过Kissinger峰移法计算了其晶化时所需的激活能。结果表明,通过水雾化方法制备的Fe-Si-B-C四元软磁粉末的粒度分布合理;粒径小于38μm的粉末为完全非晶结构,且粉末表面光滑,内部成分均匀;非晶粉末的初始结晶温度为542.15℃,且升温过程中存在2个晶化放热峰;2个晶化反应对应的晶化激活能分别为463.92 k J/mol和910.21 k J/mol;粉末的饱和磁感应强度和矫顽力分别为1.08 T和111.4 A/m。