The technological condition for the preparation of BaTiO 3 ceramics doped with Nd ￡2O￡3 by Sol￡-Gel was deter￡-mined through orthogonal experimen t￡(r)WhennBa ￡¨Ac ￡(c) ￡2??nTi ￡¨OC ￡′H￡1￡(c)￡...The technological condition for the preparation of BaTiO 3 ceramics doped with Nd ￡2O￡3 by Sol￡-Gel was deter￡-mined through orthogonal experimen t￡(r)WhennBa ￡¨Ac ￡(c) ￡2??nTi ￡¨OC ￡′H￡1￡(c)￡′??n Nd ￡2O￡3??nCH￡3￡¨CH￡2￡(c)2CH 2OH∶n H2 O￡1/2￡±￡(r)￡°￡°??￡±￡(r)￡°￡°??￡°￡(r)￡°￡°￡3??￡*￡(r)￡3￡°??￡3￡*￡(r)￡°￡′￡?pH ￡1/2￡3￡(r)￡μ￡?T￡1/225℃,the light-yellow-transparen t-stable solution and thorough tran sparent gel was generat￡-ed￡?the transforming time of solutio n to gel was ￡2￡μh￡(r)The crystal structur e and particle size of BaTiO3 ceramics doped with Nd 2O3 were studied by SEM and X-ray respectively￡?the type of the crystal was tetragonal￡?the particle size was about ￡2￡′￡(r)7nm￡(r)The dielectric constant ￡¨|?￡(c)and dielectric loss￡¨tan|?￡(c)of BaTiO3 ceramics doped with Nd 2O3 were determined between 10 4 ?10 6 Hz,and the results showed that the di electric constant was increased obviously,the dielectric loss was d ecreased clear and the resistivity(ρ V ￡(c)was also decreased noticeably￡(r)展开更多
随着稀土新材料的发展,大颗粒Nd2O3在高新技术领域有着广泛的用途。研究大颗粒草酸钕前驱体分解生成Nd2O3的过程,可为制备性能优异的Nd2O3产品提供有益的借鉴。使用TG,DTG,DTA研究了大颗粒草酸钕的热分解过程,采用Ozawa法、Starink法计...随着稀土新材料的发展,大颗粒Nd2O3在高新技术领域有着广泛的用途。研究大颗粒草酸钕前驱体分解生成Nd2O3的过程,可为制备性能优异的Nd2O3产品提供有益的借鉴。使用TG,DTG,DTA研究了大颗粒草酸钕的热分解过程,采用Ozawa法、Starink法计算活化能E值,同时利用Coats-Redfern积分法推断反应机制函数。结果表明：当升温速率为10℃·min^-1时,室温加热到397℃,草酸钕完全失去结晶水;397～584℃,无水草酸钕分解生成Nd2O2CO3;584～770℃,Nd2O2CO3分解为Nd2O3。提高升温速率,TG,DTG,DTA三条曲线都向高温侧移动;升温速率越高,草酸钕达到相同热解失重率所需的温度越高,DTG曲线最高升温速率下对应的失重率明显增加,DTA曲线峰面积明显增大且同一温度下焓变的绝对值变大;无水草酸钕热分解生成Nd2O2CO3的反应活化能为130.10～187.8 kJ·mol^-1,反应过程符合三级化学反应模型,Nd2O2CO3热分解生成Nd2O3的反应活化能为57.40～81.83 k J·mol^-1。展开更多
BaTiO 3 ceramics doped with Nd 2 O 3 (the additive content was respectively 0.001,0.002,0.003,0.005,0.01,0.03mol)were prepared by Sol-Gel method.Effects of Nd 2 O 3 contents on the dielectric constant (ε),the dielect...BaTiO 3 ceramics doped with Nd 2 O 3 (the additive content was respectively 0.001,0.002,0.003,0.005,0.01,0.03mol)were prepared by Sol-Gel method.Effects of Nd 2 O 3 contents on the dielectric constant (ε),the dielectric loss(tanδ),the Curie-temperature(T C )and the resistivity(ρ)of BaTiO 3 ceramic were studied.When Nd 2 O 3 content was 0.001mol and 0.002mol,t he dielectric constant was increase d obviously,but the dielectric loss was also increased.When Nd 2 O 3 content was 0.003mol,the dielectric constant was increased,and the die lectric loss was decreased,which was suitable fo r application in condenser.The resistivity was decreased obviously with the increasing of Nd 2 O 3 contents,the resistivity was the sm allest when Nd 2 O 3 content was 0.001mol.The Curie-temperature was also decreased with the increasing of Nd 2 O 3 contents.展开更多
Ce-Zr-Al-Nd2O3 （CZAN） support materials were prepared by co-precipitation and impregnation methods, respectively. They were characterized by X-ray diffTaction （XRD）, low temperature nitrogen adsorption-desorption,...Ce-Zr-Al-Nd2O3 （CZAN） support materials were prepared by co-precipitation and impregnation methods, respectively. They were characterized by X-ray diffTaction （XRD）, low temperature nitrogen adsorption-desorption, oxygen pulsing technique, H2-temperamre programmed reduction （H2-TPR） and X-ray photoelectron spectroscopy （XPS）. The Pd-only three-way catalysts （Pd-TWC） supported on these materials were prepared by incipient wetness method and studied by activity tests. The results demonstrated that the CZAN supports obtained by the two methods showed better structural, textural and redox properties than the CZA without Nd2O3, and the addition of Nd203 improved the catalytic activity of TWC. Especially, the CZAN-i support prepared by impregnation method had better thermal stability and redox property. Meanwhile, the Pd/CZAN-i catalyst exhibited the best catalytic performance. XPS measurements indicated that the Nd-modified samples possessed more Ce3＋ and oxygen vacancies on the surface of samples, which led to a better redox property. The excellent redox property of support materials helped to improve the catalytic activity of TWC.展开更多
In this study, Nd-bearing zirconolite-rich ceramics were prepared by solid-state reaction process using CaF2,ZrO2, Ti,TiO2, Fe2 O3 and Nd2O3 as the raw materials. Neodymium was used as trivalent actinide surrogate and...In this study, Nd-bearing zirconolite-rich ceramics were prepared by solid-state reaction process using CaF2,ZrO2, Ti,TiO2, Fe2 O3 and Nd2O3 as the raw materials. Neodymium was used as trivalent actinide surrogate and designed to substitute the Ca and Zr sites of zirconolite with general stoichiometry of Ca1-xZr1-xNd2 xTi2O7（0≤x≤0.3）. Density of Fe-Nd-O sample reaches a maximum value of 4.13 g/cm^2 after being sintered at 1325 ℃ for 42 h. Three major phases, namely zirconolite, perovskite and pseudobrookite, are observed in all these samples. The EDX result shows that Nd2O3 can be successfully incorporated into the lattice structure of the prepared zirconolite-rich minerals and replace the Ca sites of zirconolite and perovskite with Fe3＋ as the charge-compensating ion. Furthermore, the thermal conductivities are all in the range of 1.51-1.67 W/（m·K）. The normalized elemental leaching rates of Ca and Nd in the Fe-Nd-0.2 sample keep in low values of 6.20 × 10^-2 and 4.86 × 10^-4 g/（m^2·d） after 42 d.展开更多
Nd2O3 doped BaTiO3ceramics（the additive content was respectively 0.001, 0.002, 0.003, 0.005, 0.01 molar ratio）were prepared by Sol-Gel method to study their dielectric characteristics and electric conductivities thr...Nd2O3 doped BaTiO3ceramics（the additive content was respectively 0.001, 0.002, 0.003, 0.005, 0.01 molar ratio）were prepared by Sol-Gel method to study their dielectric characteristics and electric conductivities through X-ray photoelectron spectrum （XPS）. The results showed that the dielectric characteristics of Nd2O3 doped BaTiO3 ceramics were improved by doping. When Nd2O3 content was 0.003 mol, the results were even better, the dielectric constant was increased, the dielectric loss was decreased, the Curie-temperature （Tc） was 110 ℃, and the frequency characteristic was also good. The resistivity of Nd2O3 doped BaTiO3 ceramics was lower than that of pure BaTiO3 ceramics, when Nd2O3 content was 0.001 mol,the resistivity was （2.364×）108 Ω·m, the smallest. The grain resistance of Nd2O3 doped BaTiO3 ceramics exhibited NTC effect, but the grain boundary resistance showed PTC effect, and the grain boundary resistance was larger than that of the grain resistance, so the PTC effect originated from the grain boundary. The analysis of the element binding energy through X-ray photoelectron spectrum were indicated that the quantivalence of Ba2+and Ti4+in Nd2O3 doped BaTiO3 ceramics was variable, and resulted in the improvement of the conductibility of BaTiO3 ceramics.展开更多
文摘The technological condition for the preparation of BaTiO 3 ceramics doped with Nd ￡2O￡3 by Sol￡-Gel was deter￡-mined through orthogonal experimen t￡(r)WhennBa ￡¨Ac ￡(c) ￡2??nTi ￡¨OC ￡′H￡1￡(c)￡′??n Nd ￡2O￡3??nCH￡3￡¨CH￡2￡(c)2CH 2OH∶n H2 O￡1/2￡±￡(r)￡°￡°??￡±￡(r)￡°￡°??￡°￡(r)￡°￡°￡3??￡*￡(r)￡3￡°??￡3￡*￡(r)￡°￡′￡?pH ￡1/2￡3￡(r)￡μ￡?T￡1/225℃,the light-yellow-transparen t-stable solution and thorough tran sparent gel was generat￡-ed￡?the transforming time of solutio n to gel was ￡2￡μh￡(r)The crystal structur e and particle size of BaTiO3 ceramics doped with Nd 2O3 were studied by SEM and X-ray respectively￡?the type of the crystal was tetragonal￡?the particle size was about ￡2￡′￡(r)7nm￡(r)The dielectric constant ￡¨|?￡(c)and dielectric loss￡¨tan|?￡(c)of BaTiO3 ceramics doped with Nd 2O3 were determined between 10 4 ?10 6 Hz,and the results showed that the di electric constant was increased obviously,the dielectric loss was d ecreased clear and the resistivity(ρ V ￡(c)was also decreased noticeably￡(r)
文摘随着稀土新材料的发展,大颗粒Nd2O3在高新技术领域有着广泛的用途。研究大颗粒草酸钕前驱体分解生成Nd2O3的过程,可为制备性能优异的Nd2O3产品提供有益的借鉴。使用TG,DTG,DTA研究了大颗粒草酸钕的热分解过程,采用Ozawa法、Starink法计算活化能E值,同时利用Coats-Redfern积分法推断反应机制函数。结果表明：当升温速率为10℃·min^-1时,室温加热到397℃,草酸钕完全失去结晶水;397～584℃,无水草酸钕分解生成Nd2O2CO3;584～770℃,Nd2O2CO3分解为Nd2O3。提高升温速率,TG,DTG,DTA三条曲线都向高温侧移动;升温速率越高,草酸钕达到相同热解失重率所需的温度越高,DTG曲线最高升温速率下对应的失重率明显增加,DTA曲线峰面积明显增大且同一温度下焓变的绝对值变大;无水草酸钕热分解生成Nd2O2CO3的反应活化能为130.10～187.8 kJ·mol^-1,反应过程符合三级化学反应模型,Nd2O2CO3热分解生成Nd2O3的反应活化能为57.40～81.83 k J·mol^-1。
文摘BaTiO 3 ceramics doped with Nd 2 O 3 (the additive content was respectively 0.001,0.002,0.003,0.005,0.01,0.03mol)were prepared by Sol-Gel method.Effects of Nd 2 O 3 contents on the dielectric constant (ε),the dielectric loss(tanδ),the Curie-temperature(T C )and the resistivity(ρ)of BaTiO 3 ceramic were studied.When Nd 2 O 3 content was 0.001mol and 0.002mol,t he dielectric constant was increase d obviously,but the dielectric loss was also increased.When Nd 2 O 3 content was 0.003mol,the dielectric constant was increased,and the die lectric loss was decreased,which was suitable fo r application in condenser.The resistivity was decreased obviously with the increasing of Nd 2 O 3 contents,the resistivity was the sm allest when Nd 2 O 3 content was 0.001mol.The Curie-temperature was also decreased with the increasing of Nd 2 O 3 contents.
基金Project supported by National Natural Science Foundation of China (20773090, 20803049)the Specialized Research Fund for the Doctoral Program of Higher Education (20070610026, 200806100009)
文摘Ce-Zr-Al-Nd2O3 （CZAN） support materials were prepared by co-precipitation and impregnation methods, respectively. They were characterized by X-ray diffTaction （XRD）, low temperature nitrogen adsorption-desorption, oxygen pulsing technique, H2-temperamre programmed reduction （H2-TPR） and X-ray photoelectron spectroscopy （XPS）. The Pd-only three-way catalysts （Pd-TWC） supported on these materials were prepared by incipient wetness method and studied by activity tests. The results demonstrated that the CZAN supports obtained by the two methods showed better structural, textural and redox properties than the CZA without Nd2O3, and the addition of Nd203 improved the catalytic activity of TWC. Especially, the CZAN-i support prepared by impregnation method had better thermal stability and redox property. Meanwhile, the Pd/CZAN-i catalyst exhibited the best catalytic performance. XPS measurements indicated that the Nd-modified samples possessed more Ce3＋ and oxygen vacancies on the surface of samples, which led to a better redox property. The excellent redox property of support materials helped to improve the catalytic activity of TWC.
基金Project supported by the National Natural Science Foundation of China(51672228)the Open Project of State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials(11zxfk26)Science Development Foundation of China Academy of Engineering Physics
文摘In this study, Nd-bearing zirconolite-rich ceramics were prepared by solid-state reaction process using CaF2,ZrO2, Ti,TiO2, Fe2 O3 and Nd2O3 as the raw materials. Neodymium was used as trivalent actinide surrogate and designed to substitute the Ca and Zr sites of zirconolite with general stoichiometry of Ca1-xZr1-xNd2 xTi2O7（0≤x≤0.3）. Density of Fe-Nd-O sample reaches a maximum value of 4.13 g/cm^2 after being sintered at 1325 ℃ for 42 h. Three major phases, namely zirconolite, perovskite and pseudobrookite, are observed in all these samples. The EDX result shows that Nd2O3 can be successfully incorporated into the lattice structure of the prepared zirconolite-rich minerals and replace the Ca sites of zirconolite and perovskite with Fe3＋ as the charge-compensating ion. Furthermore, the thermal conductivities are all in the range of 1.51-1.67 W/（m·K）. The normalized elemental leaching rates of Ca and Nd in the Fe-Nd-0.2 sample keep in low values of 6.20 × 10^-2 and 4.86 × 10^-4 g/（m^2·d） after 42 d.
文摘Nd2O3 doped BaTiO3ceramics（the additive content was respectively 0.001, 0.002, 0.003, 0.005, 0.01 molar ratio）were prepared by Sol-Gel method to study their dielectric characteristics and electric conductivities through X-ray photoelectron spectrum （XPS）. The results showed that the dielectric characteristics of Nd2O3 doped BaTiO3 ceramics were improved by doping. When Nd2O3 content was 0.003 mol, the results were even better, the dielectric constant was increased, the dielectric loss was decreased, the Curie-temperature （Tc） was 110 ℃, and the frequency characteristic was also good. The resistivity of Nd2O3 doped BaTiO3 ceramics was lower than that of pure BaTiO3 ceramics, when Nd2O3 content was 0.001 mol,the resistivity was （2.364×）108 Ω·m, the smallest. The grain resistance of Nd2O3 doped BaTiO3 ceramics exhibited NTC effect, but the grain boundary resistance showed PTC effect, and the grain boundary resistance was larger than that of the grain resistance, so the PTC effect originated from the grain boundary. The analysis of the element binding energy through X-ray photoelectron spectrum were indicated that the quantivalence of Ba2+and Ti4+in Nd2O3 doped BaTiO3 ceramics was variable, and resulted in the improvement of the conductibility of BaTiO3 ceramics.
