PHYSICA B-CONDENSED MATTER
·
2017
·
IF 1.405
Xiaoping Qi,Lihong Bao,Luomeng Chao,O. Tegus
Nanocrystalline Ca-doped CeB 6 powders have been synthesized via a solid-state reaction of CaO and CeO 2 with NaBH 4 under a vacuum condition. The Ca doping effects on phase composition, grain morphology and optical absorption properties of nanocrystalline CeB 6 were investigated. As a result, all the synthesized nanocrystalline hexaborides are composed by single phase of CsCl -type structure. The grain size and morphology are very sensitive to the reaction temperature. The optical absorption result indicates that the absorption valley of nanocrystalline CeB 6 shows a red-shift from 619 nm to 685 nm with increasing Ca doping content, which means the tunable optical absorption of nanocrystalline Ca-doped CeB 6 . In addition, a first-principles calculation has been used to reveal the origin of the tunable optical properties. It is found that Ca doping reduces the total kinetic energy of the electrons of CeB 6 and leads to the absorption valleys shift to longer wavelength direction.
研究领域:
材料科学
·
光学
✓ 已验证
DOI
高影响因子
JOURNAL OF RARE EARTHS
·
2024
·
IF 5.2
Haoyuan Zheng,Yuxiao Jia,Chen Jin,Hang Che,Chia-Tse Lee,Zhenke Chen,Guang Liu,Li Wang,Shixuan He,Xinhua Wang,Haizhen Liu,Mi Yan
The Mg(NH 2 ) 2 -2LiH composite system is a promising vehicle-mounted hydrogen storage material, but its application is limited due to serious thermodynamic and kinetic barriers. Adding additives can effectively optimize their hydrogen absorption and desorption kinetics and thermodynamic performance. In this work the comprehensive hydrogen storage performance of Mg(NH 2 ) 2 -2LiH with extremely small nano rare earth borides is improved, and a series of characterization methods and density functional theory (DFT) calculation systems was combined to study its hydrogen storage improvement mechanism. The research results show that the method of adding 5 wt% molten salt to prepare nano CeB 6 (24.5 nm) can significantly reduce the initial hydrogen absorption/release temperature of Mg(NH 2 ) 2 -2LiH from 110/130 to 45/90 °C, inhibit the generation of ammonia by-products, and improve hydrogen purity. Under low-temperature hydrogen absorption conditions at 120 °C, the improved sample can absorb 2.81 wt% hydrogen gas, with a hydrogen absorption capacity more than 3.5 times of the unmodified sample. The amount of hydrogen released at 150 °C reaches 3.35 wt%, which is more than twice that of the pristine sample, demonstrating excellent hydrogen absorption and release kinetics performance. After 10 consecutive hydrogen cycles, 4.64 wt% hydrogen can still be released, and the cycle retention rate can be increased from 85% before improvement to nearly 100%, demonstrating good reversibility. Mechanism studies show that nano CeB 6 can effectively weaken the Mg–N and N–H bonds of Mg(NH 2 ) 2 and inhibit the polycrystalline transformation of the hydrogen evolution product Li 2 MgN 2 H 2 at high temperatures. It can also provide nucleation active sites for hydrogen absorption and desorption in the material, making the system possess superior hydrogen absorption and desorption performance and cycling stability. This study provides new insights into the role of rare earth borides in Mg(NH 2 ) 2 -2LiH hydrogen storage materials, both experimentally and theoretically.
研究领域:
材料科学
·
化学工程
·
物理化学
·
理论化学
✓ 已验证
DOI
高影响因子
JOURNAL OF RARE EARTHS
·
2022
·
IF 4.632
Yu Wang,Xiao-Hui Yang,Jian Cui,Guo-Hua Zhang
Rare-earth hexaborides (REB 6 ) are vital raw materials for cathode materials and high temperature structural ceramics that are widely applied as high-frequency electron tubes and ceramics adaptive for extreme environment, respectively. In this work, single phase substitutional solid solution REB 6 (LaB 6 , La 0.75 Ce 0.25 B 6 , La 0.5 Ce 0.5 B 6 , La 0.25 Ce 0.75 B 6 and CeB 6 ) powders were prepared with the raw materials of La 2 O 3 , CeO 2 , B 4 C and Al powders, after calcining at 1773 K for 4 h and the following alkaline leaching. All substitutional solid solution products have homogeneous distributions of La and Ce in particles. Through microscopic morphology analysis, it is discovered that the formation of solid solution is beneficial for reducing the particle size of product, relative to LaB 6 and CeB 6 . Moreover, Al flux plays an important role in decarbonizing reaction, and C contents of all products are below 0.4 wt%.
研究领域:
材料科学
·
无机化学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF THE AMERICAN CERAMIC SOCIETY
·
2021
·Vol. 105
·期 3
·1954-1966
·
IF 3.784
Yu Wang,Kuo-Chih Chou,Guo-Hua Zhang
Due to strong anti-poisoning ability, good emission stability, high emission current density, lanthanum hexaboride (LaB 6 ) and cerium hexaboride (CeB 6 ) have been maturely applied in electron emission emitter. In this paper, a new manufacturing method for LaB 6 (or CeB 6 ) powder was proposed by using La 2 O 3 (or CeO 2 ), B 4 C, and Al as raw materials. After high-temperature reaction in the range of 1673–1773 K and the following alkaline leaching at 90°C, LaB 6 or CeB 6 powder with particle size of about 10 μm was obtained. Furthermore, by Al metal flux method, the obtained powder was used to manufacture single crystal block with size of several millimeters.
研究领域:
材料科学
·
电子发射材料
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS
·
2022
·Vol. 33
·期 17
·14097-14107
·
IF 2.779
Ba Ruiqing,Ma Weibing,Hong Jingnan,He Xinghui,Li Jing,Yang Sen
This paper reports investigation on fabrication and densification of cerium hexaboride (CeB 6 ). CeB 6 powders were successfully synthesized from cerium oxide and boron carbide at 1500 °C in a vacuum. X-ray diffraction and XPS spectra were applied to detect and trace the variation of reactant during the general reaction, where CeO 2 consequently transformed into CeB 6 after the intermediate states such as Ce 2 O 3 and CeBO 3 . The whole process could be described as topo chemistry synthesis. The final state of cerium in CeB 6 contains Ce 3+ and Ce 4+ according to the peak split result of Ce 3d orbits. CeB 6 polycrystalline bulks of 98% relative density were prepared via hot pressing at 1900 °C under 40 MPa. The hardness and electrical resistivity of the dense CeB 6 reached 21.58 GPa and 4.6 × 10 − 5 Ω m, respectively.
研究领域:
材料科学
·
化学
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2025
·
IF 5.6
Yixin Zhao,Chenxi Guo,Lei Chen,Xin Yang,Qizhong Huang
CeB 6 modified C/C-SiC-ZrC composites were designed by using slurry infiltration and precursor infiltration and pyrolysis method combined with high temperature treatment. Experimental results show that both adding CeB 6 and heat treatment could improve the ablative performance of C/C-SiC-ZrC composites significantly. Thermal conductivity of the composites can be optimized by high temperature treatment, accelerating the heat transfer of the composites in the ablation process. The heat treated C/C-SiC-ZrC-CeB 6 composites with high content of CeB 6 exhibit enhanced ablation performance at about 2600 °C, and the mass and linear ablation rates of the composites are 0.37 mg/s and 3.33 μm/s, respectively. The phase transition of ZrO 2 phases was suppressed by (Zr 1-x Ce x )O 2 solid solution phases which were uniformly distributed at the grain boundaries of ZrO 2 grains, resulting in the superior stability of the ZrO 2 scales under the scouring of the oxyacetylene flame.
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）