电解水技术是制取高纯度氢气的有效途径,为传统的氢气生产提供了一种可持续的替代方案.其中,开发性能优异的电催化材料是降低电解水制氢成本的关键.析氧反应(OER)由于涉及多个电子转移而导致的动力学缓慢,是克服高过电位的主要挑战.镍...电解水技术是制取高纯度氢气的有效途径,为传统的氢气生产提供了一种可持续的替代方案.其中,开发性能优异的电催化材料是降低电解水制氢成本的关键.析氧反应(OER)由于涉及多个电子转移而导致的动力学缓慢,是克服高过电位的主要挑战.镍铁羟基/氢氧化物(NiFe(oxy)hydroxides)是近期研究的热点,其在碱性条件下具有极低的OER过电位,部分材料性能甚至超过了贵金属基催化剂,如IrO_(2)和RuO_(2).然而,NiFe(oxy)hydroxides的长期催化稳定性,尤其是在大电流下的长期催化稳定性,成为限制其实际应用的主要问题,这主要是由于铁元素的严重流失导致的.因此,如何有效控制和利用电化学溶解/沉积动力学成为稳定铁位点的关键.为克服该挑战,本文提出了一种大电流极化重构方法来固定活性铁位点.通过在大电流(1.5 A cm^(-2))下对材料进行表面快速极化重构,成功制备了FeOOH@NiOOH(eFNO_(L))电催化剂.eFNO_(L)不仅具有稳定的铁位点,还暴露出高指数晶面,因此eFNO_(L)同时展现出较好的OER催化活性和稳定性.同时,密度泛函理论计算结果表明,与具有低指数晶面的FeNiOOH相比,大电流极化工程制备的分相eFNO_(L)对铁位点表现出更高的结合能,可以有效抑制OER过程中的铁流失,且高指数晶面在改变速率决定步骤和减少吸附能垒上具有更大的优势.电化学测试结果表明,经过优化后的eFNO_(L)催化剂在产生100和500 mA cm^(-2)大电流密度仅需234和27 mV的过电位,并且具有较小的Tafel斜率(35.2 mV dec^(-1)).由于铁位点结合能的提高,eFNO_(L)催化剂在500 mA cm^(-2)的电流密度下能够稳定催化超过100 h,且仅有1.5%的性能衰减,优于近期报道的大多数镍铁基OER催化剂.综上,本文为开发高活性和高稳定性能的催化剂提供了一种有效的大电流电化学重构策略,在电解水制氢领域实现其工业化的大规模应用方面显示出巨大潜力,有望降低可持续电解水制氢成本.展开更多
High quality 0.02 mol%,0.05 mol%,and 0.08 mol%Fe:β-Ga2O3 single crystals were grown by the floating zone method.The crystal structure,optical,electrical,and thermal properties were measured and discussed.Fe:β-Ga2O3 ...High quality 0.02 mol%,0.05 mol%,and 0.08 mol%Fe:β-Ga2O3 single crystals were grown by the floating zone method.The crystal structure,optical,electrical,and thermal properties were measured and discussed.Fe:β-Ga2O3 single crystals showed transmittance of higher than 80%in the near infrared region.With the increase of the Fe doping concentration,the optical bandgaps reduced and room temperature resistivity increased.The resistivity of 0.08 mol%Fe:β-Ga2O3 crystal reached to 3.63×1011Ω·cm.The high resistivity Fe:β-Ga2O3 single crystals could be applied as the substrate for the high-power field effect transistors(FETs).展开更多
Precursive iron films with different grain sizes were prepared by magnetron sputtering on substrates heated at different temperatures. The iron films were sulfurized at 673 K for 20 h to form pyrite films. The structu...Precursive iron films with different grain sizes were prepared by magnetron sputtering on substrates heated at different temperatures. The iron films were sulfurized at 673 K for 20 h to form pyrite films. The structural and electrical characters were determined. High substrate temperatures produce large crystallites in the precursive iron films. The pyrite films are composed of a surface layer with coarse columnar grains and a bottom layer with fine equiaxed grains. With the increase of iron grain scale, the carrier concentration decreases and the carrier mobility increases. The electrical resistivity of the pyrite films increases to a maximum in the precursive iron films with increasing the grain size to about 3g nm. Sufficient formation and growth of iron grains result in improved crystallinity and high continuity of the pyrite films. The crystal defect density, transformation stress level and atom diffusion behavior are responsible for the characteristics of the electrical properties dependent on the crystallinity and continuity of the pyrite films or the crystallizing status of the precursive iron films.展开更多
The crystal structure of non-metamict Ti- and Fe2+-rich chevkinite-(Ce) has been redetermined with the single -crystal sample collected from Bayan Obo, Inner Mongolia, China. The chemical formula of the sample is Ce4F...The crystal structure of non-metamict Ti- and Fe2+-rich chevkinite-(Ce) has been redetermined with the single -crystal sample collected from Bayan Obo, Inner Mongolia, China. The chemical formula of the sample is Ce4Fe2Ti3Si4O22. The crystals are monoclinic with the unit cell parameters a = 13.4656(15) ?, b = 5.7356(6) ?, c = 11.0977(12) ?, β= 100.636(2)o, V = 842.39 (16) ?3 and Z = 2. The structures of Ti- and Fe2+-rich chevkinite-(Ce) were refined with space groups P21/a and C2/m. Least-squares refinement results show that both structural models of Ti- and Fe2+-rich chevkinite-(Ce) are very good, R[F2>2σ(F2)] =0.027 with P21/a and R[F2>2σ(F2)] =0.021 with C2/m. In order to illustrate the relationship between the two space groups P21/a and C2/m, the distribution of diffraction intensities was inspected. Pseudo extinction was found, i.e., reflections with h+k=2n are systematically strong, while those with h+k=2n+1 are weak. By neglecting the systematically weak (h+k=2n+1) reflections the space group becomes C2/m. There is a mirror plane in the C2/m perpendicular to the b axis. However, oxygen atoms in the P21/a model are of a symmetrical relationship with the corresponding pseudo mirror plane. It is concluded that the crystal structure of non-metamict Ti- and Fe2+-rich chevkinite-(Ce) is a superstructure with the space group of P21/a, which is of pseudo symmetry corresponding to the space group C2/m.展开更多
Photorefractive properties of Hf：Fe：LiNbO3 crystals with various [Li]/[Nb] ratios have been investigated at 488 nm wavelength based on the two-wave coupling experiment. High diffraction efficiency and large recordin...Photorefractive properties of Hf：Fe：LiNbO3 crystals with various [Li]/[Nb] ratios have been investigated at 488 nm wavelength based on the two-wave coupling experiment. High diffraction efficiency and large recording sensitivity are observed and explained. The decrease in Li vacancies is suggested to be the main contributor to the increase in the photoconductivity and subsequently to the induction of the improvement of recording sensitivity. The saturation diffraction efficiency is measured up to 80.2%, and simultaneously the recording sensitivity of 0.91 cm/J is achieved to in the Hf：Fe：LiNbO3 crystal grown from the melt with the [Li]/[Nb] ratio of 1.20, which is significantly enhanced as compared with those of the Hf：Fe：LiNbO3 crystal with the [Li]/[Nb] ratio of 0.94 in melt under the same experimental conditions. Experimental results definitely show that increasing the [Li]/[Nb] ratio in crystal is an effective method＇for Hf：Fe：LiNbO3 crystal to improve its photorefractive properties.展开更多
Mg：Ru：Fe：LiN-bO3 crystals with various concentrations of MgO （in mole） and fixed content of RuO2 and Fe203 （in mass） are grown with the Czochralski method from the congruent melt. Their infrared transmission sp...Mg：Ru：Fe：LiN-bO3 crystals with various concentrations of MgO （in mole） and fixed content of RuO2 and Fe203 （in mass） are grown with the Czochralski method from the congruent melt. Their infrared transmission spectra are mea- sured and discussed to investigate the defect structure. With the increase of Mg2＋ concentration the blue nonvolatile holographic storage capability is enhanced. The nonvolatile holographic storage properties of dual-wavelength recording of Mg（7 mol%）：Ru：Fe：LiNbO3 nonvolatile diffraction efficiency, response time, and nonvolatile sensitivity reach 59.8%, 70 s, and 1.04 cm/J, respectively. Comparing Mg（7 mol%）：Ru：Fe：LiNbO3 with Ru：Fe：LiNbO3 crystal, the response time is shortened apparently. The nonvolatile diffraction efficiency and sensitivity are raised largely. The mechanism in blue photorefractive nonvolatile holographic storage is discussed.展开更多
During the process of KDP crystal growth, metal ions strongly affect the growth habit and optical properties of KDP single crystal. In this paper, KDP crystals were grown from an aqueous solution doped with different ...During the process of KDP crystal growth, metal ions strongly affect the growth habit and optical properties of KDP single crystal. In this paper, KDP crystals were grown from an aqueous solution doped with different concentration of Fe^3＋ dopant by traditional temperaturereduction method and ＂point-seed＂ rapid growth method. Furthermore, we examined the light scatter and measured the transmission of these KDP crystals. It is found that the dopant of Fe^3＋ ion can improve the stability of the KDP growth solution when its concentration is less than 30 ppm. The effects of Fe^3＋ ion on the growth habit and optical properties of KDP crystal are also obvious.展开更多
Effects of milling and crystallization conditions on microstructure,such as amorphous phase and nanocrystalline phase, were investigated by X-ray diffractometry(XRD),differential scanning calorimetry(DSC),and transmis...Effects of milling and crystallization conditions on microstructure,such as amorphous phase and nanocrystalline phase, were investigated by X-ray diffractometry(XRD),differential scanning calorimetry(DSC),and transmission electron microscopy (TEM),respectively.The results show that nanocomposite Nd2Fe14B/α-Fe powder can be prepared by mechanical milling in argon atmosphere and a subsequent vacuum annealing treatment.The grain sizes of both Nd2Fe14B andα-Fe phase decrease drastically with increasing milling time.After milling for 5 h,the as-milled material consists ofα-Fe nanocomposite phases with the grain size of 10 nm,and some amorphous phases,which can be turned into Nd2Fe14B/α-Fe nanocomposite phases by the subsequent annealing treatment.Milling energy of mechanical milling after 5 h by theoretical calculation is 6 154.25 kJ/g.展开更多
A novel pyrazole derivative ligand, BTA（BTA = bis-（4-ethoxy-phenyl）-[4-（tripyrazol-1-yl-methyl）-phenyl]-amine）, was synthesized and fully characterized by 1H-NMR, MALDI-TOF-MS spectra and single-crystal X-ray di...A novel pyrazole derivative ligand, BTA（BTA = bis-（4-ethoxy-phenyl）-[4-（tripyrazol-1-yl-methyl）-phenyl]-amine）, was synthesized and fully characterized by 1H-NMR, MALDI-TOF-MS spectra and single-crystal X-ray diffraction analysis. It crystallizes in triclinic, space group P1, with a = 11.827（1）, b = 16.000（2）, c = 16.527（2）A, α = 108.510（1）, β = 91.116（5）, γ = 101.734（1）°, V = 2894.5（6） A3, Z = 1, Dc = 1.262 g/m^3, F（000） = 1162, Μr = 545.63, μ = 0.083 mm-1, the final R = 0.0728 and w R = 0.2213 for 7541 observed reflections with I 〉 2（I）. The structural analysis revealed that three pyrazole units are attached to the same carbon atom connected with bis-（4-ethoxy-phenyl）-phenyl-amine group. UV-vis spectral features of the ligand in various solutions were explained by time dependent density functional theory（TD-DFT）. It was also found that the ligand（BTA） exhibits an exclusively selective and sensitive response toward Fe3＋ using UV-vis spectroscopic method.展开更多
Amorphous （Nd,Pr）13Fe80Nb1B6 ribbons were crystallized at 670-730°C for 5-25 min to study the effects of isothermal crystallization on their behavior and magnetic properties. XRD results indicate that the isoth...Amorphous （Nd,Pr）13Fe80Nb1B6 ribbons were crystallized at 670-730°C for 5-25 min to study the effects of isothermal crystallization on their behavior and magnetic properties. XRD results indicate that the isothermal incubation time is 12, 5, and less than 5 min at 670, 700, and 730°C, respectively. High coercivities, with the maximum value of iHc = 1616 kA/m at 700°C for 19 min, measured by a physical property measurement system, are obtained in the crystallized ribbons. This is mainly attributed to the addition of Pr and Nb, because Pr2Fe14B has a higher anisotropic field than Nd2Fe14B, and Nb enriched in the grain boundary regions can not only reduce the exchange-coupling effects among hard grains, but also impede grain growth during the crystallization process. In addition, it should also be related to the characteristics of the furnace that the authors designed.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
文摘电解水技术是制取高纯度氢气的有效途径,为传统的氢气生产提供了一种可持续的替代方案.其中,开发性能优异的电催化材料是降低电解水制氢成本的关键.析氧反应(OER)由于涉及多个电子转移而导致的动力学缓慢,是克服高过电位的主要挑战.镍铁羟基/氢氧化物(NiFe(oxy)hydroxides)是近期研究的热点,其在碱性条件下具有极低的OER过电位,部分材料性能甚至超过了贵金属基催化剂,如IrO_(2)和RuO_(2).然而,NiFe(oxy)hydroxides的长期催化稳定性,尤其是在大电流下的长期催化稳定性,成为限制其实际应用的主要问题,这主要是由于铁元素的严重流失导致的.因此,如何有效控制和利用电化学溶解/沉积动力学成为稳定铁位点的关键.为克服该挑战,本文提出了一种大电流极化重构方法来固定活性铁位点.通过在大电流(1.5 A cm^(-2))下对材料进行表面快速极化重构,成功制备了FeOOH@NiOOH(eFNO_(L))电催化剂.eFNO_(L)不仅具有稳定的铁位点,还暴露出高指数晶面,因此eFNO_(L)同时展现出较好的OER催化活性和稳定性.同时,密度泛函理论计算结果表明,与具有低指数晶面的FeNiOOH相比,大电流极化工程制备的分相eFNO_(L)对铁位点表现出更高的结合能,可以有效抑制OER过程中的铁流失,且高指数晶面在改变速率决定步骤和减少吸附能垒上具有更大的优势.电化学测试结果表明,经过优化后的eFNO_(L)催化剂在产生100和500 mA cm^(-2)大电流密度仅需234和27 mV的过电位,并且具有较小的Tafel斜率(35.2 mV dec^(-1)).由于铁位点结合能的提高,eFNO_(L)催化剂在500 mA cm^(-2)的电流密度下能够稳定催化超过100 h,且仅有1.5%的性能衰减,优于近期报道的大多数镍铁基OER催化剂.综上,本文为开发高活性和高稳定性能的催化剂提供了一种有效的大电流电化学重构策略,在电解水制氢领域实现其工业化的大规模应用方面显示出巨大潜力,有望降低可持续电解水制氢成本.
基金the Scientific and Innovative Action Plan of Shanghai,China(Grant No.18511110502)Equipment Pre-research Fund Key Project,China(Grant No.6140922010601).
文摘High quality 0.02 mol%,0.05 mol%,and 0.08 mol%Fe:β-Ga2O3 single crystals were grown by the floating zone method.The crystal structure,optical,electrical,and thermal properties were measured and discussed.Fe:β-Ga2O3 single crystals showed transmittance of higher than 80%in the near infrared region.With the increase of the Fe doping concentration,the optical bandgaps reduced and room temperature resistivity increased.The resistivity of 0.08 mol%Fe:β-Ga2O3 crystal reached to 3.63×1011Ω·cm.The high resistivity Fe:β-Ga2O3 single crystals could be applied as the substrate for the high-power field effect transistors(FETs).
基金supported by the National NaturalScience Foundation of China (Grant No. 50871103).
文摘Precursive iron films with different grain sizes were prepared by magnetron sputtering on substrates heated at different temperatures. The iron films were sulfurized at 673 K for 20 h to form pyrite films. The structural and electrical characters were determined. High substrate temperatures produce large crystallites in the precursive iron films. The pyrite films are composed of a surface layer with coarse columnar grains and a bottom layer with fine equiaxed grains. With the increase of iron grain scale, the carrier concentration decreases and the carrier mobility increases. The electrical resistivity of the pyrite films increases to a maximum in the precursive iron films with increasing the grain size to about 3g nm. Sufficient formation and growth of iron grains result in improved crystallinity and high continuity of the pyrite films. The crystal defect density, transformation stress level and atom diffusion behavior are responsible for the characteristics of the electrical properties dependent on the crystallinity and continuity of the pyrite films or the crystallizing status of the precursive iron films.
基金supported by the National Natural Science Foundation of China(Grant 40472030)
文摘The crystal structure of non-metamict Ti- and Fe2+-rich chevkinite-(Ce) has been redetermined with the single -crystal sample collected from Bayan Obo, Inner Mongolia, China. The chemical formula of the sample is Ce4Fe2Ti3Si4O22. The crystals are monoclinic with the unit cell parameters a = 13.4656(15) ?, b = 5.7356(6) ?, c = 11.0977(12) ?, β= 100.636(2)o, V = 842.39 (16) ?3 and Z = 2. The structures of Ti- and Fe2+-rich chevkinite-(Ce) were refined with space groups P21/a and C2/m. Least-squares refinement results show that both structural models of Ti- and Fe2+-rich chevkinite-(Ce) are very good, R[F2>2σ(F2)] =0.027 with P21/a and R[F2>2σ(F2)] =0.021 with C2/m. In order to illustrate the relationship between the two space groups P21/a and C2/m, the distribution of diffraction intensities was inspected. Pseudo extinction was found, i.e., reflections with h+k=2n are systematically strong, while those with h+k=2n+1 are weak. By neglecting the systematically weak (h+k=2n+1) reflections the space group becomes C2/m. There is a mirror plane in the C2/m perpendicular to the b axis. However, oxygen atoms in the P21/a model are of a symmetrical relationship with the corresponding pseudo mirror plane. It is concluded that the crystal structure of non-metamict Ti- and Fe2+-rich chevkinite-(Ce) is a superstructure with the space group of P21/a, which is of pseudo symmetry corresponding to the space group C2/m.
基金supported by the Fundamental Research Foundation of Commission of Science Technology,Industry for National Defense of China (Grant No.2320060089)and National Basic Research and Development Program of China (Grant No.2007CB3070001)Program of Excellent Team in Harbin Institute of Technology,China
文摘Photorefractive properties of Hf：Fe：LiNbO3 crystals with various [Li]/[Nb] ratios have been investigated at 488 nm wavelength based on the two-wave coupling experiment. High diffraction efficiency and large recording sensitivity are observed and explained. The decrease in Li vacancies is suggested to be the main contributor to the increase in the photoconductivity and subsequently to the induction of the improvement of recording sensitivity. The saturation diffraction efficiency is measured up to 80.2%, and simultaneously the recording sensitivity of 0.91 cm/J is achieved to in the Hf：Fe：LiNbO3 crystal grown from the melt with the [Li]/[Nb] ratio of 1.20, which is significantly enhanced as compared with those of the Hf：Fe：LiNbO3 crystal with the [Li]/[Nb] ratio of 0.94 in melt under the same experimental conditions. Experimental results definitely show that increasing the [Li]/[Nb] ratio in crystal is an effective method＇for Hf：Fe：LiNbO3 crystal to improve its photorefractive properties.
基金Project supported by the Fundamental Research Funds for the Central Universities of China (Grant No. DL12AB03)the National Natural Science Founda-tion of China (Grant No. 60777006)
文摘Mg：Ru：Fe：LiN-bO3 crystals with various concentrations of MgO （in mole） and fixed content of RuO2 and Fe203 （in mass） are grown with the Czochralski method from the congruent melt. Their infrared transmission spectra are mea- sured and discussed to investigate the defect structure. With the increase of Mg2＋ concentration the blue nonvolatile holographic storage capability is enhanced. The nonvolatile holographic storage properties of dual-wavelength recording of Mg（7 mol%）：Ru：Fe：LiNbO3 nonvolatile diffraction efficiency, response time, and nonvolatile sensitivity reach 59.8%, 70 s, and 1.04 cm/J, respectively. Comparing Mg（7 mol%）：Ru：Fe：LiNbO3 with Ru：Fe：LiNbO3 crystal, the response time is shortened apparently. The nonvolatile diffraction efficiency and sensitivity are raised largely. The mechanism in blue photorefractive nonvolatile holographic storage is discussed.
基金the State High Technology Program for Inertial Confinement Fusion and National Science Foundation (No.59823003)Project of United Foundation (No.10676019)Youth Scientist Fund of Shandong Province (Nos. 2004BS04022 and 03BS079)
文摘During the process of KDP crystal growth, metal ions strongly affect the growth habit and optical properties of KDP single crystal. In this paper, KDP crystals were grown from an aqueous solution doped with different concentration of Fe^3＋ dopant by traditional temperaturereduction method and ＂point-seed＂ rapid growth method. Furthermore, we examined the light scatter and measured the transmission of these KDP crystals. It is found that the dopant of Fe^3＋ ion can improve the stability of the KDP growth solution when its concentration is less than 30 ppm. The effects of Fe^3＋ ion on the growth habit and optical properties of KDP crystal are also obvious.
文摘Effects of milling and crystallization conditions on microstructure,such as amorphous phase and nanocrystalline phase, were investigated by X-ray diffractometry(XRD),differential scanning calorimetry(DSC),and transmission electron microscopy (TEM),respectively.The results show that nanocomposite Nd2Fe14B/α-Fe powder can be prepared by mechanical milling in argon atmosphere and a subsequent vacuum annealing treatment.The grain sizes of both Nd2Fe14B andα-Fe phase decrease drastically with increasing milling time.After milling for 5 h,the as-milled material consists ofα-Fe nanocomposite phases with the grain size of 10 nm,and some amorphous phases,which can be turned into Nd2Fe14B/α-Fe nanocomposite phases by the subsequent annealing treatment.Milling energy of mechanical milling after 5 h by theoretical calculation is 6 154.25 kJ/g.
基金supported by the National Natural Science Foundation of China(21271004,51372003,21271003,21275006)the Natural Science Foundation of Anhui Province(1208085MB22,1308085MB24)+2 种基金Ministry of Education Funded Projects Focus on returned overseas scholar,Department of Education of Anhui Province(KJ2012A025)Program for New Century Excellent Talents in University(China)Doctoral Program Foundation of Ministry of Education of China(20113401110004)
文摘A novel pyrazole derivative ligand, BTA（BTA = bis-（4-ethoxy-phenyl）-[4-（tripyrazol-1-yl-methyl）-phenyl]-amine）, was synthesized and fully characterized by 1H-NMR, MALDI-TOF-MS spectra and single-crystal X-ray diffraction analysis. It crystallizes in triclinic, space group P1, with a = 11.827（1）, b = 16.000（2）, c = 16.527（2）A, α = 108.510（1）, β = 91.116（5）, γ = 101.734（1）°, V = 2894.5（6） A3, Z = 1, Dc = 1.262 g/m^3, F（000） = 1162, Μr = 545.63, μ = 0.083 mm-1, the final R = 0.0728 and w R = 0.2213 for 7541 observed reflections with I 〉 2（I）. The structural analysis revealed that three pyrazole units are attached to the same carbon atom connected with bis-（4-ethoxy-phenyl）-phenyl-amine group. UV-vis spectral features of the ligand in various solutions were explained by time dependent density functional theory（TD-DFT）. It was also found that the ligand（BTA） exhibits an exclusively selective and sensitive response toward Fe3＋ using UV-vis spectroscopic method.
基金supported by the National Natural Science Foundation of China (No. 50744014)the National Basic Research Foundation (No. 2004CCA04000)+3 种基金Science and Technology Department of Zhejiang Province (Nos. 2008C21046 and 2008C11086-1)the Natural Science Foundation of Zhejiang Province,China (No. Y406389)the Research and Development Program of Ningbo Bureau of Science and Technology (No. 2006B100054)K.C.Wong Magna Found in Ningbo University
文摘Amorphous （Nd,Pr）13Fe80Nb1B6 ribbons were crystallized at 670-730°C for 5-25 min to study the effects of isothermal crystallization on their behavior and magnetic properties. XRD results indicate that the isothermal incubation time is 12, 5, and less than 5 min at 670, 700, and 730°C, respectively. High coercivities, with the maximum value of iHc = 1616 kA/m at 700°C for 19 min, measured by a physical property measurement system, are obtained in the crystallized ribbons. This is mainly attributed to the addition of Pr and Nb, because Pr2Fe14B has a higher anisotropic field than Nd2Fe14B, and Nb enriched in the grain boundary regions can not only reduce the exchange-coupling effects among hard grains, but also impede grain growth during the crystallization process. In addition, it should also be related to the characteristics of the furnace that the authors designed.
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.
