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 non-isothermal crystallization kinetics of reactive microgel/nylon 6 blends was investigated by differential scanning calorimetry(DSC). The Mo equation was employed to analyze the non-isothermal crystallization da...The non-isothermal crystallization kinetics of reactive microgel/nylon 6 blends was investigated by differential scanning calorimetry(DSC). The Mo equation was employed to analyze the non-isothermal crystallization data. The crystallization activation energies were also evaluated by the Kissinger method. The results show that the crystallization onset temperature(T onset) and crystallization peak temperature(T p) decrease with the increase of the content of reactive microgel, while ΔT(T onset–T p), the crystallization half-time(t1/2) and the crystallization enthalpy(ΔH c) increase. The required cooling rates of blends are higher than that of neat nylon6 in order to achieve the same relative crystallinity in a unit of time. The crystallization activation energies of the reactive microgel/nylon 6 blends are greater than those of the neat nylon 6. When the content of reactive microgel is 30%, the relative crystallinity(X t) reaches the maximum.展开更多
The kinetics of crystallization in 70GeS2-20Sb2S3-10CsCl chalcogenide glass was studied using differential scanning calorimetry （DSC） at different heating rate. The values of glass transition and crystallization tem...The kinetics of crystallization in 70GeS2-20Sb2S3-10CsCl chalcogenide glass was studied using differential scanning calorimetry （DSC） at different heating rate. The values of glass transition and crystallization temperatures were found to be heating rate dependent. Using Matusita method, the crystallization activation energies E and crystallization parameter （n） calculated are 348.08±0.99 kJ/mol and 1.78. It suggests that there are two mechanisms： a surface and one-dimensional crystallization processes.展开更多
The non-isothermal and isothermal crystallization kinetics of Zr_（72.5）Al_（10）Fe_（17.5） glassy alloy was investigated using differential scanning calorimeter（DSC）.Under non-isothermal heating condition,the pri...The non-isothermal and isothermal crystallization kinetics of Zr_（72.5）Al_（10）Fe_（17.5） glassy alloy was investigated using differential scanning calorimeter（DSC）.Under non-isothermal heating condition,the primary phase in the initial crystallization is Zr_6Al_2Fe phase and the final crystallized products consist of Zr_6Al_2Fe,Zr_2Fe and a-Zr phases.The apparent activation energy for crystallization estimated using the Kissinger method is 342.1 ±8.1 kJ/mol.The local activation energy decreased with the increase in the crystallization volume fraction during nonisothermal crystallization.Under isothermal heating condition,the average Avrami exponent of about 2.76 implies a mainly diffusion-controlled three-dimensional growth with an increasing nucleation rate.The local activation energy for isothermal crystallization shows a different variation trend from that for nonisothermal crystallization,indicating different nucleation-and-growth mechanisms for the two crystallizaiton conditions.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 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
The crystallization process of Fe78ZrTBls （at%） amorphous ribbon was investigated by Xray diffraction （XRD）, differential scanning calorimetry and scanning electron microscopy （SEM）. The fully amorphous structur...The crystallization process of Fe78ZrTBls （at%） amorphous ribbon was investigated by Xray diffraction （XRD）, differential scanning calorimetry and scanning electron microscopy （SEM）. The fully amorphous structure of asquenched （Aq） ribbons was confirmed by XRD pattern. The saturation magnetization （Ms） and Curie tem perature of the Aq ribbon were measured as 124.3 （A.mZ）＆g and 305 ℃ with vibrating sample magnetometer （VSM）, respectively. When the ribbons was annealed at 550 ℃ near the first onset temperature （Txl = 564.9 ℃）, the Ms was increased by 17 %, which was caused by the formation of a dual phase structure. The isothermal crystallization kinetics and crystallization mechanism of primary ctFe phase in the dual phase structure were studied by Arrhenius and JohnsonMehlAvramiKolmogorov equations respectively. The results showed that the crystallization of Fe phase was a diffusioncontrolled surface nucleation growth process, and the nucleation rate decreased with longer crystallization time.展开更多
For the desirable laser optical property, transition metals or rare-earths are always doped into parent glasses as active ions, and this doping will affect the crystallization of the precursor glasses inevitably. In t...For the desirable laser optical property, transition metals or rare-earths are always doped into parent glasses as active ions, and this doping will affect the crystallization of the precursor glasses inevitably. In this work, crystallization behavior of NaO-CaO-SiO2 system glasses doped with Nd2O3 was investigated. The crystallization kinetic parameters including the crystallization apparent activation energy （E） and the Avrami parameter （n） were also measured. The results show that the NaO-CaO-SiO2 system glassceramics with the NaxCa2Si3O9 crystal as primary phase can be highly crystalized as above 90%. The Nd2O3 doping has a significant influence on the crystallization apparent activation energy and the Avrami parameter, which affect the crystallization behavior and morphology of the transparent glass-ceramics of this system.展开更多
The effect of glass network modifier R2O （R=Li, Na, K） on upconversion luminescence in Er3＋/yb3＋ co-doped NaYF4 oxyfluoride glass-ceramics was investigated. NaYF4 nanocrystals with different sizes were studied und...The effect of glass network modifier R2O （R=Li, Na, K） on upconversion luminescence in Er3＋/yb3＋ co-doped NaYF4 oxyfluoride glass-ceramics was investigated. NaYF4 nanocrystals with different sizes were studied under glass network modifier alkali mental oxide. The nanocrystals size in NaYF4 of Li2O modified samples was 11 nm, whereas in the Na20 and K2O modified sample, the crystal size was 25 and 43 nm, respectively. It was found that red, yellow and green upconversions were observed in SAL, SAN, SAK glass ceramics. The reported results would deepen the understanding of size effects on the lanthanide upcon- version in nanocrystals.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Supported by the Graduate Innovative Fund of Wuhan Institute of Technology(CX2013019)
文摘The non-isothermal crystallization kinetics of reactive microgel/nylon 6 blends was investigated by differential scanning calorimetry(DSC). The Mo equation was employed to analyze the non-isothermal crystallization data. The crystallization activation energies were also evaluated by the Kissinger method. The results show that the crystallization onset temperature(T onset) and crystallization peak temperature(T p) decrease with the increase of the content of reactive microgel, while ΔT(T onset–T p), the crystallization half-time(t1/2) and the crystallization enthalpy(ΔH c) increase. The required cooling rates of blends are higher than that of neat nylon6 in order to achieve the same relative crystallinity in a unit of time. The crystallization activation energies of the reactive microgel/nylon 6 blends are greater than those of the neat nylon 6. When the content of reactive microgel is 30%, the relative crystallinity(X t) reaches the maximum.
基金Funded by the 973 Project(No.2006CB708607)the Science and Technology Department of Zhejiang Province(No.2006C11127)+1 种基金the Science and Technology Foundation of Ningbo(No.2006B100068)the Natural Science Foundation of Ningbo(No.2006A610056,2007A610004)
文摘The kinetics of crystallization in 70GeS2-20Sb2S3-10CsCl chalcogenide glass was studied using differential scanning calorimetry （DSC） at different heating rate. The values of glass transition and crystallization temperatures were found to be heating rate dependent. Using Matusita method, the crystallization activation energies E and crystallization parameter （n） calculated are 348.08±0.99 kJ/mol and 1.78. It suggests that there are two mechanisms： a surface and one-dimensional crystallization processes.
基金Funded by the National Natural Science Foundation of China(No.51401053)the China Postdoctoral Science Foundation(No.2015T80676)+1 种基金the Natural Science Foundation of Fujian Province(No.2014J05053)the Postdoctoral Scientific Research Foundation of Fuzhou University(No.0180-601017)
文摘The non-isothermal and isothermal crystallization kinetics of Zr_（72.5）Al_（10）Fe_（17.5） glassy alloy was investigated using differential scanning calorimeter（DSC）.Under non-isothermal heating condition,the primary phase in the initial crystallization is Zr_6Al_2Fe phase and the final crystallized products consist of Zr_6Al_2Fe,Zr_2Fe and a-Zr phases.The apparent activation energy for crystallization estimated using the Kissinger method is 342.1 ±8.1 kJ/mol.The local activation energy decreased with the increase in the crystallization volume fraction during nonisothermal crystallization.Under isothermal heating condition,the average Avrami exponent of about 2.76 implies a mainly diffusion-controlled three-dimensional growth with an increasing nucleation rate.The local activation energy for isothermal crystallization shows a different variation trend from that for nonisothermal crystallization,indicating different nucleation-and-growth mechanisms for the two crystallizaiton conditions.
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 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The crystallization process of Fe78ZrTBls （at%） amorphous ribbon was investigated by Xray diffraction （XRD）, differential scanning calorimetry and scanning electron microscopy （SEM）. The fully amorphous structure of asquenched （Aq） ribbons was confirmed by XRD pattern. The saturation magnetization （Ms） and Curie tem perature of the Aq ribbon were measured as 124.3 （A.mZ）＆g and 305 ℃ with vibrating sample magnetometer （VSM）, respectively. When the ribbons was annealed at 550 ℃ near the first onset temperature （Txl = 564.9 ℃）, the Ms was increased by 17 %, which was caused by the formation of a dual phase structure. The isothermal crystallization kinetics and crystallization mechanism of primary ctFe phase in the dual phase structure were studied by Arrhenius and JohnsonMehlAvramiKolmogorov equations respectively. The results showed that the crystallization of Fe phase was a diffusioncontrolled surface nucleation growth process, and the nucleation rate decreased with longer crystallization time.
基金financial support of the project from the National Natural Science Foundation of China(No.51172016)
文摘For the desirable laser optical property, transition metals or rare-earths are always doped into parent glasses as active ions, and this doping will affect the crystallization of the precursor glasses inevitably. In this work, crystallization behavior of NaO-CaO-SiO2 system glasses doped with Nd2O3 was investigated. The crystallization kinetic parameters including the crystallization apparent activation energy （E） and the Avrami parameter （n） were also measured. The results show that the NaO-CaO-SiO2 system glassceramics with the NaxCa2Si3O9 crystal as primary phase can be highly crystalized as above 90%. The Nd2O3 doping has a significant influence on the crystallization apparent activation energy and the Avrami parameter, which affect the crystallization behavior and morphology of the transparent glass-ceramics of this system.
基金supported by the National Natural Science Foundation of China(61368007,61265004,51272097)the Specialized Research Fund for the Doctoral Program of Higher Education of China(20125314120018)
文摘The effect of glass network modifier R2O （R=Li, Na, K） on upconversion luminescence in Er3＋/yb3＋ co-doped NaYF4 oxyfluoride glass-ceramics was investigated. NaYF4 nanocrystals with different sizes were studied under glass network modifier alkali mental oxide. The nanocrystals size in NaYF4 of Li2O modified samples was 11 nm, whereas in the Na20 and K2O modified sample, the crystal size was 25 and 43 nm, respectively. It was found that red, yellow and green upconversions were observed in SAL, SAN, SAK glass ceramics. The reported results would deepen the understanding of size effects on the lanthanide upcon- version in nanocrystals.
