查找使用阿拉丁产品的科研文献

Influence of Gd2O3 on the microstructure and properties of transparent MgAl2O4: Cr3+ ceramic

Yan Hao,Yibo Zhang,Biao Liu,Kuibao Zhang

In this work, MgAl 2 O 4 : Cr 3+ transparent ceramics have been synthesized by the hot press sintering techniques, and the effect of the sintering aid Gd 2 O 3 and its content on the densification, microstructure, and optical, photoluminescence was studied and discussed. The relative density reached 99.29% with 0.8 wt% Gd 2 O 3 as a sintering aid, and the optical transmittance at 686 nm and 1446 nm were approximately 76%. As Gd 2 O 3 content continued to increase, the grain size of the ceramics became smaller and uniform, accompanied by some pores with the size of ～1 μm. The ceramics with 4.0 wt% Gd 2 O 3 showed a higher transmittance, of 82% at 1446 nm. Additionally, Gd 2 O 3 was helpful for Cr 3+ in the sites of octahedral symmetry, which increased the quantum yield. The quantum yield of MgAl 2 O 4 : Cr 3+ with 0.8 wt% Gd 2 O 3 was about 0.175, which was 36% higher than that of ceramic without Gd 2 O 3 . In short, the sintering aid Gd 2 O 3 not only contributed to improving the densification, homogenizing the grain size, and heightening the optical transmittance but also enhanced the quantum yield of Cr 3+ .

Warm white broadband emission and tunable long lifetimes in Yb3+ doped Gd2O3 nanoparticles

Wei Zheng,Baoyu Sun,Yuemei Li,Tiyi Lei,Rui Wang,Jinzhu Wu

Upconversion luminescence materials have stimulated growing attention in photovoltaic cell owning to the ability of converting a few low-energy photons into a single high-energy photon. However, there still remains a daunting challenge to achieve upconversion emission covering the entire visible spectrum in a single material. Here, an incandescent broadband white upconversion emission covering the entire visible region is realized in a single Gd 2 O 3 :Yb 3+ nanoparticles by utilization of adverse multiphonon relaxation. Importantly, tunable long fluorescence lifetime can be synchronously implemented in the single material, where the lifetime range spans one order of magnitude. Furthermore, benefiting from the broadband emission, the luminescence intensity achieves 482-fold improvement as the power increase from 0.53 W to 1.51 W. These broadband emissions are enabled by engineering the pathways of nonradiative de-excitation via multiphonon relaxation. Based on the kinetic analysis and mechanism research, the photon avalanche is demonstrated to play an important role for broadband emission. The warm white emission together with its tunable long lifetime provides a new avenue for developing single emitter-based white-light-emission materials for next-generation display and lighting technologies.

Synthesis and Characterization of Hollow Magnetic Alloy (GdNi2, Co5Gd) Nanospheres Coated with Gd2O3

Wang Li,Fa-gen Li,Jun Wang,Guo-meng Zhao

Uniform magnetic hollow nanospheres (GdNi2, Co5Gd) coated with Gd2O3 have been successfully prepared on a large scale via a urea-based homogeneous precipitation method using silica (SiO2) spheres as sacrificed templates, followed by subsequent heat treatment. Nitrogen sorption measurements and scanning electron microscope reveal that these hollow-structured magnetic nanospheres have the mesoporous shells that are composed of a large amount of uniform nanoparticles. After reduction treatment, these nanoparticles exhibit superparamagnetism that might have potential applications in medicine. Furthermore, the developed synthesis route may provide an important guidance for the preparation of other multifunctional hollow spherical materials.

The Growing Behavior of the Ca2Gd8(SiO4)6O2 Dense Reaction Layer in Molten CMAS at High Temperatures

Zijian Mo,Zupeng Mo,Kaisen Guo,Zhiyun Yu,Huan He,Tianquan Liang

Calcium–magnesium–alumina–silicate (CMAS), as an environmental deposit, deposits on engine components and causes serious damage to traditional thermal barrier coatings (TBCs) at high temperatures. The rare-earth silicate apatite dense reaction layer is regarded as a promising strategy to prevent TBCs from molten CMAS penetration and corrosion. The interactions between the Gd2O3ceramic and CMAS are discussed at various temperatures and times in the study. The main reaction products are gadolinium silicate apatite (Ca2Gd8(SiO4)6O2, Gd-apatite) and melilite phases. Within the first 15 min of interaction, a thin, continuous and dense reaction layer (DRL) consisting of Gd-apatite comes to form, and it thickens with increasing exposure temperature and time. The thickness of the DRL is ~0.8 μm after 15 min of the reaction at 1250 °C and it slowly increases to ~9.1 μm after a duration of 24 h at 1400 °C. This is attributed to CMAS infiltration along the grain boundaries of the Gd-apatite phases in the DRL. The growing rates of the Gd-apatite DRL decrease with reaction time and are significantly influenced by the temperature and the ability of the DRL to inhibit CMAS infiltration.

Mechanism Study of Highly Ionic Conductivity for F-doped CaO-Gd2O3-CeO2 Solid Electrolyte

Xu Zhang,Shuting Li,Jiyang Zhang,Jihong Liu,Chaoyang Huang,Jiapeng Zhu,Guixiao Jia,Shengli An

CeO 2 is a promising electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Studies have found that F-doping improves its ionic conductivity, but the underlying mechanisms remain unclear. Therefore, this study employs a DFT+U method to calculate geometrical and electronic structures and oxygen ion migrations of Gd-, Ca- and F-dopings co-doped CeO 2 . The calculated results are verified by our experiment. DFT calculations find that oxygen vacancies (V) are easily formed at next-neighboring sites near the F - ions, different with the case of Gd- and Ca-doped CeO 2 . Gd-, Ca- and F-dopings strengthen Ce-O bonds, inconstant with the result from the reported experimental hypothesis for the F-doping. The F-doping restrains the change of Ce 4+ to Ce 3+ . Migration energy barriers E m of oxygen ions are mainly affected by the migration distances and peripherally done by the oxygen vacancy cavity size and the defect association. Due to the lager oxygen vacancy cavity size and the smaller defect association in CGOF and CGOCF, the F-dopings have the smaller E m . This is contrary to the speculation of the reported experimental study based on the electronegative comparison of F and O. Our experiment finds that Ca and F co-doping significantly increases the conductivity, 3.9 times of the conductivity of Gd-doped CeO 2 . The study clarifies the nature mechanism of the ionic conductivity in doped CeO 2 , offering atomic-level insights to aid the development of high-performance CeO 2 -based electrolytes.

Modulation of Properties in Ce3+-Doped High-Density Glass Scintillators via Gd2O3/GdF3 Ratios

Haoyan Zhang,Canrong Luo,Huairen Cui,Zaijin Fang,Hong Jia

Developments for high light yield and high density of Ce 3+ -doped glass scintillators are of fundamental importance for practical applications in fields of nuclear medical imaging and high-energy physics. Here, a series of Ce 3+ -doped glass scintillators was designed. The glasses exhibit broadband emissions around 380 nm, and the photoluminescence quantum yield (PL QY) reaches 78.63%. By adjusting the Gd 2 O 3 /GdF 3 ratios of the glasses, the properties such as density, light yield, and transmittance of glass scintillators are all modulated. The optimized glass GSG 3 (Gd 2 O 3 :GdF 3 = 1:1) exhibits superior performance, including a high density of 5.562 g/cm 3 , high transmittance of 93% at 400 nm, a high light yield of 2859 ph/MeV, and an energy resolution of 19.3%@662 keV. The X-ray imaging system utilizing a self-developed glass scintillator was employed to acquire clear images of objects such as metal springs and integrated circuit chips, and achieved a spatial resolution of 14 lp/mm. The designed glass provides a low-cost scintillator for potential applications in medical imaging and radiation detection. This study also offers a powerful solution to conquer the conventional contradictions of glass scintillators between density and light yield.

Luminescence property and magnetic resonance imaging of Gd2O3:Tb3+ nanocrystals doped with Zn2+, Li+

Fu Rong,Hu Yan-Yan,Qiao Hui-Na,Yang Chun-Lin,Yin Hao,Ou Mei-Gui

Gd 2 O 3 :Tb 3+ nanocrystal co-doped with Zn 2+ and Li + was prepared by the combination of polyol and solid-phase methods. The synthesized nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra and magnetic resonance imaging (MRI). The results revealed that both Gd 2 O 3 :Tb 3+ /Zn 2+ and Gd 2 O 3 :Tb 3+ /Li + had cubic unit structures with a spherical shape, and the fluorescence intensity of the nanoparticles reached a maximum at a doping concentration of 0.050 mmol% for Zn 2+ and 2 mol% for Li + , respectively. In addition, the T 1 / T 2 (longitudinal/transverse relaxation time)-weighted MRI signals got enhanced due to the increased longitudinal relaxivity ( r 1 ) and transverse relaxivity ( r 2 ) after the doping by metal ions. Therefore, the materials reported here can be used for fluorescence and MR bimodal imaging, as tracers and for fluorescence detections. Graphic abstract

Influence of calcination temperature on the fluorescence and magnetic properties of Gd2O3:Tb3+, K+ nanoparticles

Hao Zhou,Hao Zhou,Rong Fu,Rong Fu,Chunlin Yang,Meigui Ou,Meigui Ou,Chengjie Xue,Chengjie Xue

Re-Investigation of Phase Equilibria and CALPHAD-Based Thermodynamic Optimization in the Gd2O3–La2O3–ZrO2 System

Jingkai Zhou,Gang Qu,Yeli Chen,Dandan Huang

The isothermal phase equilibria of the Gd 2 O 3 –La 2 O 3 –ZrO 2 ternary system were experimentally determined at 1773 and 1573 K using a solid-phase reaction method. Continuous solid solutions of pyrochlore-type compounds (namely, Gd 2 Zr 2 O 7 and La 2 Zr 2 O 7 ) were confirmed across the ternary system, represented as La 2- x Gd x Zr 2 O 7 . The solubility limit of La 2 O 3 in the cubic fluorite ZrO 2 phase basically remains constant with decreasing temperature. The Gd 2 O 3 –La 2 O 3 –ZrO 2 ternary system was assessed by the CALculation of PHAse Diagrams (CALPHAD) method. The compound energy formalism (CEF) implemented was employed for thermodynamic descriptions of all phases within the CALPHAD method. A set of self-consistent thermodynamic parameters for the Gd 2 O 3 –La 2 O 3 –ZrO 2 system was derived.

Size-controlled Gd2O3 nanospheres reinforced B4C/HDPE nanocomposites for neutron and gamma-ray complex radiation shielding

Zhipeng Huo,Yidong Lu,Jie Zhang,Guoqiang Zhong

Gd 2 O 3 nanospheres (NSs) with three controlled sizes were synthesized via a homogeneous precipitation method. Both synthesized (Syn-) and commercial (Com-) Gd 2 O 3 fillers were employed as bifunctional neutron and gamma radiation absorbing agents to fabricate radiation shielding (RS) materials. FESEM confirmed the nanospherical morphology of Syn-Gd 2 O 3 fillers. HRTEM and SEAD indicate that all Gd 2 O 3 fillers are polycrystalline. HRTEM confirmed that the Syn-Gd 2 O 3 fillers have (321), (400), and (521) exposed crystal planes, while the Com-Gd 2 O 3 fillers have (222) exposed crystal planes, aligning with the corresponding XRD patterns. FESEM of fracture surfaces revealed a more uniform distribution of Syn-Gd 2 O 3 -NS fillers within the HDPE matrix compared to the irregularly shaped Com-Gd 2 O 3 fillers. The high specific surface area (SSA) and superior dispersibility of Syn-Gd 2 O 3 fillers enhanced the overall performance of the nanocomposite (NC). Notably, NCs containing Syn-Gd 2 O 3 -Ⅱ NSs with an average size of 82.6 ± 14.2 nm achieved a neutron and gamma shielding rates of 99.3% and 73.7%, the Σ , μ , μ m , HVL are 0.239 cm -1 , 0.092 cm -1 , 0.076 cm 2 /g, 7.57 cm, correspondingly, at a thickness of 15 cm, demonstrating its potential for high-performance radiation shielding applications. This study provides a novel strategy for designing lightweight, high-performance radiation shielding materials for nuclear facilities, aerospace applications, radioactive waste conditioning and relative fields.

Study on optical and electrochemical properties of nanorod TiO2 co-modified with GQDs and Gd2O3:Er3+

Xiangyang Yao,Wanli Zhang,Meigui Ou,Chunlin Yang

In this paper, a composite material GQDs/Gd 2 O 3 :Er 3+ /TiO 2 , was prepared by polyol method and hydrothermal method to improve the catalytic performance of TiO 2 . The composite material is analyzed by XRD, SEM, TEM, XPS, RAMAN, UV–Vis and PEC electrochemical test, combined the DFT theoretical calculation simulation. SEM and TEM results show that spherical GQDs/Gd 2 O 3 :Er 3+ nanoparticles are covered on the surface of TiO 2 nanorods. UV–Vis absorption spectra indicates that GQDs/Gd 2 O 3 :Er 3+ broadens the wavelength range of TiO 2 in the wavelength range of 400–1000 nm. The photocurrent density and the applied bias light-electroconversion efficiency of the electrodes of GQDs/Gd 2 O 3 :Er 3+ /TiO 2 is 3.47 times and 7.6 times as that of pure TiO 2 , respectively. DFT calculations reveal that the band width of GQDs/Gd 2 O 3 :Er 3+ /TiO 2 is decreased by 2.647 eV compared to pure TiO 2 , resulting in an easier transition of electrons from valence band (VB) to conduction band (CB). Photocatalytic tests show that the degradating efficiency of methylene blue (MB) by GQDs can reach 68.52 %, which is higher than that of pure TiO 2 (61.68 %).

Study on the role of Li2O–Ga2O3-GeO2-Gd2O3 glass doped into Li7La3Zr2O12 solid-state electrolyte

Tianxiang Ning,Qian Zhang,Piao Liu,Xiangtao Lin,Yinyi Luo,Lidan Liu,Zhiwei Luo,Anxian Lu

In this study, Li 2 O–Ga 2 O 3 -GeO 2 -Gd 2 O 3 (LGGG) glass is doped into Li 7 La 3 Zr 2 O 12 (LLZO) ceramic in proportions of 1, 2, 3, 4, and 5 wt% by a conventional solid-state reaction method. The main crystalline phase that existed in this composite electrolyte is proved to be cubic phase LLZO by XRD patterns. With a dosage of 3 wt% LGGG glass, the composite electrolyte has the highest ionic conductivity of 3.26 × 10 −4  S cm −1 , a maximum relative density of about 96.79%, and minimum activation energy of 0.276 eV at room temperature. This work also verifies that doping the same amount of identified elements into LLZO ceramics in the form of glass can obtain higher ionic conductivity and relative density than in the form of oxides (2.40 × 10 −4  S cm −1 and 92.03%). A symmetric cell composed of this electrolyte reveals a good cycling performance and low overpotential in a total of 230 cycles at a current density of 0.125 mA cm −2 . These results confirm the potential of this LGGG-LLZO composite electrolyte for applicating in new generation all-solid-state lithium-ion batteries.