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排序方式: 共有2721条查询结果,搜索用时 234 毫秒
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《Advanced Powder Technology》2022,33(8):103695
Fe(III) ion can strongly inhibit the sulphidation amine flotation of smithsonite. However, its modification mechanism on smithsonite surface is still obscure. In this work, a systematic study of the modification of Fe(III) ion on smithsonite (1 0 1) surface was performed using DFT calculation. The optimal number of H2O ligands for Fe(III) ion hydrates in aqueous conditions was probed, and [Fe(OH)2(H2O)4]+ and [Fe(OH)4]? were identified as the major modification species, then their adsorption and bonding mechanisms were further revealed by analyzing the frontier orbitals, density of state, Mulliken population, and electron density. The calculated adsorption structures were consistent with the former experiment, and we found the O site that bonded to the C atom on smithsonite surface was the most favorable position for [Fe(OH)2(H2O)4]+ and [Fe(OH)4]? adsorptions. Besides, their adsorption mechanisms on smithsonite surface were principally due to the combined effect of FeO bond and hydrogen bonding. Simultaneously, hydrogen bonding greatly enhanced the stability of the adsorption structures. Moreover, the dominant orbital contribution for the bonding of FeO was primarily due to the orbital hybridization between Fe 3d and O 2p orbitals. This work can help in deeper understanding of the depression of Fe(III) ion on the sulphidation amine flotation of smithsonite. 相似文献
3.
《Ceramics International》2022,48(2):1814-1819
Sr3Al2-xBxO5Cl2:Eu2+, Dy3+ (x = 0, 0.2, 0.4) long persistent phosphors were prepared via solid-state process. The pristine Sr3Al2O5Cl2:Eu2+, Dy3+ phosphor exhibits orange/red broad band emission around 609 nm, which can be attributed to the electric radiation transitions 4f65 d1→4f7 of Eu2+. Upon the same excitation, the B3+-doped Sr3Al2-xBxO5Cl2:Eu2+, Dy3+ phosphors display red-shift from 609 nm to 625 nm with increasing B3+ concentrations. The XRD patterns show that Al3+ can be replaced by B3+ in the host lattice at the tetrahedral site, which causes lattice contraction and crystal field enhancement, and thereafter achieves the red-shift on the emission spectrum. The XPS investigation provides direct evidence of the dominant 2-valent europium in the phosphor, which can be ascribed for the broad band emission of the prepared phosphors. The afterglow of all phosphors show standard double exponential decay behavior, and the afterglow of Sr3Al2O5Cl2:Eu2+, Dy3+is rather weak, while the sample co-doped with B3+shows longer and stronger afterglow, as confirmed after the curve simulation. The analysis of thermally stimulated luminescence showed that, when B3+ is introduced, a much deeper trap is created, and the density of the electron trap is also significantly increased. As a result, B3+ ions caused redshift and enhanced afterglow for the Sr3Al2-xBxO5Cl2:Eu2+, Dy3+ phosphor. 相似文献
4.
Priyanka Kamble Prithwish Sinha Roy Arvind Ananthanarayanan Jayesh G Shah Gopalakrishnan Sugilal 《分离科学与技术》2020,55(9):1603-1610
ABSTRACTA new composite of crystalline silicotitanate (CST) has been synthesized for the sequestration of Cs and Sr from low-level liquid waste generated in the nuclear industry. The product characterization using X-RAY DEFRACTION (XRD) and Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of CST crystals in the composite. Sorption studies carried out under various test conditions showed that the composite has high affinity for both Cs and Sr. Results of structural characterization of Cs and Sr-loaded CST indicated that the overall structural integrity remained intact after substitution of Na+ by Cs+ or Sr2+. The exceedingly good Cs and Sr sorption performance displayed by the CST composite will find applications in the treatment of nuclear waste. 相似文献
5.
《Ceramics International》2020,46(4):4610-4618
Series of SrNbxYxFe12-2xO19 (0.00 ≤ x ≤ 0.05) hexaferrites (HFs) were fabricated via citrate sol-gel approach. Structural and magneto-optical properties of ensembles were investigated in detail. The structural and morphological analyses revealed the formation of M-type Sr hexaferrite nanoparticles. Diffuse reflectance data were registered to estimate the direct optical energy band gaps (Eg) in a range of 1.77 eV-1.87 eV. Room temperature (RT, 300 K) and low temperature (10 K) magnetic hysteresis curves were recorded by enforcing applied dc magnetic field up to ±70 kOe. Magnetic parameters were significantly tuned due to coordination of Nb3+ and Y3+ rare earth ions. Specified magnetic data reveal the strong ferromagnetic characteristics of pristine SrFe12O19 and co-doped HFs with Nb3+ and Y3+ ions at both temperatures. RT squareness ratio (SQR) has an exception only for pristine sample as 0.506, which is in the margin of theoretical limit assigning the single-domain nature with uniaxial anisotropy. However, all co-doped samples have SQR = 0.288–0.485 values that are smaller than theoretical limit of 0.50, implying multi-domain nature at RT and at 10 K. Co-doped ions cause lowering in super-exchange interactions between different sites and resulting the decrements of intrinsic magneto-crystalline anisotropy and coercivity fields. The specified magnetic characteristics make our fabricated SrNbxYxFe12-2xO19 (0.00 ≤ x ≤ 0.05) HFs good candidates as permanent magnets applications and high-density recording media. 相似文献
6.
Chen Tang Tiehu Li Yuhang Bai Junjie Gao Wenbo Yang Shasha Jiao Tingkai Zhao 《Ceramics International》2018,44(10):11812-11819
Recently, ceramic matrix composites reinforced by short carbon fibers (CFs) attracted increasing attentions. To further improve mechanical properties and oxidation resistances, CFs were subjected to oxidation and acidification followed by sol-gel dip-coating to deposit ZrO2 on their surfaces. ZrO2-Cf/SiC composites were fabricated by joint hot compression molding and sintering, compared to Cf/SiC and SiC prepared by the same method. Microstructural analyses indicated that ZrO2 coatings were successfully deposited on CF surfaces, formed strong bonding and interfaces between CF and the matrix. Meanwhile, CFs were found uniformly distributed in SiC matrix with random orientations. Flexural curves of ZrO2-Cf/SiC and Cf/SiC revealed the presence of “false plasticity” regions after sharp drops, which were quite different from brittle flexural behavior of SiC ceramic. Compression strength of the three samples showed step-up growth. ZrO2-Cf/SiC exhibited the highest value, indicating the introduction of CFs and ZrO2 coatings do have great influence on mechanical performances. After heat treatment, ZrO2-Cf/SiC exhibited better oxidation resistance than Cf/SiC, with weight loss ratios estimated to ??3.76% and ??6.43%, respectively. These improved properties indicated that ZrO2-Cf/SiC would be excellent alternatives to other existence materials under ultra-high temperature environments. 相似文献
7.
Zhuang Tang Yuwei Huang Kangning Wu Jianying Li 《Journal of the European Ceramic Society》2018,38(4):1569-1575
Significantly enhanced breakdown field of 24.52 kV cm?1 as well as noteworthy nonlinear coefficient of 8.11 and low dielectric loss of 0.077 were obtained in Ca0.6Sr0.4Cu3Ti4O12 ceramic. It was proved from impedance spectra that improved breakdown field was attributed to enhanced grain boundary resistance and elevated Schottky barrier height, which was further found resulting from reduced donor densities in C-V measurements. In addition, it was found that the activation energy originated from oxygen vacancies was increased, indicating the generation of oxygen vacancies was suppressed. Since oxygen vacancies acted as donors in depletion layers, it is reasonable to deduce that the reduced donor density was mainly ascribed to the decreased oxygen vacancies. In conclusion, maximum integrated action of strong solid solution effect and weak Sr-stretching effect was achieved when Sr/Ca ratio is 40/60, leading to greatly elevated potential barrier height and enhanced breakdown field consequently. 相似文献
8.
9.
以N,N,N′,N′-四辛基-2-甲基-3-氧戊二酰胺(Me-TODGA)或N,N,N′,N′-四辛基-3-氧戊二酰胺(TODGA)为萃取剂、磷酸三丁酯(TBP)为相改良剂、煤油为稀释剂,对比研究了水相酸度、萃取剂浓度、锶浓度、温度对Me-TODGA-TBP体系和TODGA-TBP体系萃取Sr2+的影响,并采用斜率法确定了萃合物的组成。结果表明,2种酰胺荚醚萃取Sr2+的分配比(DSr)随HNO3浓度(c(HNO3)=0.1~2.7 mol/L)、萃取剂浓度(c(萃取剂)=0.05~0.3 mol/L)的增加而增大,随Sr2+浓度的升高略有下降,随温度的升高而下降。2种萃取剂的萃合物组成分别为Sr(NO3)2•3Me-TODGA和Sr(NO3)2•2TODGA。萃取反应的ΔH分别为-69.46 kJ/mol和-51.39 kJ/mol,ΔS分别为-190.5 J/(mol•K)和-128.4 J/(mol•K),ΔG分别为-12.68 kJ/mol和-13.12 kJ/mol。相比之下,Me-TODGA萃取Sr2+的分配比不到TODGA的1/5。 相似文献
10.
Shun Xu Xuping Lin Ben Ge Desheng Ai Jingtao Ma Zhijian Peng 《International Journal of Applied Ceramic Technology》2019,16(1):108-118
(100-x) wt.% La0.9Sr0.1 Ga0.8Mg0.2O2.85 - x wt.% Ce0.8Gd0.2O1.9 (x = 0, 5, 10, 20) electrolytes were prepared by solid-state reaction. The composition, microstructure, and electrical conductivity of the samples were investigated. At 300 ~ 600°C, the pure La0.9Sr0.1 Ga0.8Mg0.2O2.85 electrolyte has a higher conductivity compared to the composite electrolytes, but at 650 ~ 800°C the 95 wt.% La0.9Sr0.1 Ga0.8Mg0.2O2.85 - 5 wt.% Ce0.8Gd0.2O1.9 composite electrolyte presents the highest conductivity, reaching 0.035 S cm−1 at 800°C. The cell performances based on La0.9Sr0.1 Ga0.8Mg0.2O2.85-Ce0.8Gd0.2O1.9 electrolytes were measured using Sr2CoMoO6-La0.9Sr0.1 Ga0.8Mg0.2O2.85 as anode and Sr2Co0.9Mn0.1NbO6 -La0.9Sr0.1 Ga0.8Mg0.2O2.85 as cathode, respectively. At 800°C, the measured open-circuit voltages are higher than 1.08 V, and the maximum power density and current density of the fuel cell prepared with 95 wt.% La0.9Sr0.1 Ga0.8Mg0.2O2.85 - 5 wt.% Ce0.8Gd0.2O1.9 electrolyte reach 192 mW cm−2 and 720 mA cm−2, respectively. 相似文献