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The half‐metallic character of new quaternary Heusler alloys CoXMnAs (X = Ru, Rh) is established along with their thermoelectric, mechanical, and thermodynamic properties. The optimization of energy suggests that alloys are stable in Y2‐type structure with a ferromagnetic character. The electronic band profile through generalized gradient approximation and modified Becke‐Johnson potential indicates the metallic character of alloys. However, with inclusion of Hubbard potential to generalized gradient approximation, the alloys depict half‐metallic character with semiconducting nature in spin‐down state. The alloys possess high magnetic moment, CoRuMnAs has 5 μB, whereas CoRhMnAs has 6 μB, following Slater‐Pauling rule MT = ZT ? 24. The narrow band gap in spin‐down channel enhances the thermoelectric properties. The maximum value for thermopower (|S|) obtained is 44.3 and 53.44 μV/K for CoRuMnAs and CoRhMnAs, respectively. The variation of electrical conductivity, Seebeck coefficient, and figure of merit affirm increasing trend with temperature, which is a good indication of materials to be used in thermoelectric technology. The mechanical stability along with ductile nature of alloys is determined through elastic constants. Further, we have calculated thermodynamic properties and have established their dependence on temperature and pressure using quasi‐harmonic Debye model. The half‐metallic nature with efficient thermoelectric parameters strongly supports the possible application of alloys for spin devices and green energy generation.  相似文献   
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Current methods for the synthesis of single‐walled nanotubes (SWNTs) produce mixtures of semiconducting (sem‐) and metallic (met‐) nanotubes. Most approaches to the chemical separation of sem‐/met‐SWNTs are based on small neutral molecules or conjugated aromatic polymers, which characteristically have low separation/dispersion efficiencies or present difficulties in the postseparation removal of the polymer so that the resulting field‐effect transistors (FETs) have poor performance. In this Full Paper, the use of three polymethacrylates with different pendant aromatic functional groups to separate cobalt–molybdenum catalyst (CoMoCAT) SWNTs according to their metallicity and diameters is reported. UV/Vis/NIR spectroscopy indicates that poly(methyl‐methacrylate‐co‐fluorescein‐o‐acrylate) (PMMAFA) and poly(9‐anthracenylmethyl‐methacrylate) (PAMMA) preferentially disperse semiconducting SWNTs while poly(2‐naphthylmethacrylate) (PNMA) preferentially disperses metallic SWNTs, all in dimethylforamide (DMF). Photoluminescence excitation (PLE) spectroscopy indicates that all three polymers preferentially disperse smaller‐diameter SWNTs, particularly those of (6,5) chirality, in DMF. When chloroform is used instead of DMF, the larger‐diameter SWNTs (8,4) and (7,6) are instead selected by PNMA. The solvent effects suggest that diameter selectivity and change of polymer conformation is probably responsible. Change of the polymer fluorescence upon interaction with SWNTs indicates that metallicity selectivity presumably results from the photon‐induced dipole–dipole interaction between polymeric chromophore and SWNTs. Thin‐film FET devices using semiconductor‐enriched solution with PMMAFA have been successfully fabricated and the device performance confirms the sem‐SWNTs enrichment with a highly reproducible on/off ratio of about 103.  相似文献   
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Carbon nanotubes (CNTs) with hydrophobic and atomically smooth inner channels are promising for building ultrahigh‐flux nanofluidic platforms for energy harvesting, health monitoring, and water purification. Conventional wisdom is that nanoconfinement effects determine water transport in CNTs. Here, using full‐atomistic molecular dynamics simulations, it is shown that water transport behavior in CNTs strongly correlates with the electronic properties of single‐walled CNTs (metallic (met) vs semiconducting (s/c)), which is as dominant as the effect of nanoconfinement. Three pairs of CNTs (i.e., (8,8)met, 10.85 Å vs (9,7)s/c, 10.88 Å; (9,8)s/c, 11.53 Å vs (10,7)met, 11.59 Å; and (9,9)met, 12.20 Å vs (10,8)s/c, 12.23 Å) are used to investigate the roles of diameter and metallicity. Specifically, the (9,8)s/c can restrict the hydrogen‐bonding‐mediated structuring of water and give the highest reduction in carbon–water interaction energy, providing an extraordinarily high water flux, around 250 times that of the commercial reverse osmosis membranes and approximately fourfold higher than the flux of the state‐of‐the‐art boron nitrate nanotubes. Further, the high performance of (9,8)s/c is also reproducible when embedded in lipid bilayers as synthetic high‐water flux porins. Given the increasing availability of high‐purity CNTs, these findings provide valuable guides for realizing novel CNT‐enhanced nanofluidic systems.  相似文献   
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接触不良等问题造成的过热缺陷是引起GIS故障的主要原因之一,威胁设备安全运行。研究了利用气体分解法实现金属性过热故障严重程度评估。实验研究了不同程度过热故障下的SF6气体分解特性,分析了加热时间及气压对SF6分解产物的影响。结果显示:过热条件下的主要分解产物含量从高至低依次为:SO2、SOF2、SO2F2、CO2、CO、H2S、COS;产物含量随温度、气压升高呈增长趋势。此外,本文构建了以SO2、(SOF2+CO)和(SO2F2+H2S+CO2)为含量比值的三角诊断方法,可实现对金属性过热故障严重程度的图像化判别,进而提高对设备故障的识别效率。  相似文献   
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For first time, the magneto‐electronic structure with thermoelectric and mechanical properties of lanthanum‐based double perovskite La2CuMnO6 are investigated, using first‐principle methods. Generalized gradient approximation and modified Becke‐Jhonson potentials are integrated to figure out exchange‐correlation potential. The alloy stabilizes in cubic structure with ferromagnetic nature and determined structural parameters are consistent with experimental results. The band profile reveals the half‐metallic character, which is further confirmed by calculated electronic conductivities of up and down spin channels. The effect of pressure on the structural and electronic profile is demonstrated here. The analysis of the transport properties portrays that the highest value of 0.39 is achieved for figure of merit at higher temperatures. The mechanical stability of La2CuMnO6 is established, by determination of elastic constants. The calculated elastic parameters specify the ductile behavior of alloy with high melting temperature. The efficient thermoelectric parameters with half‐metallic and ductile character suggest the likelihood of applications of alloy to design hard spintronic devices or potential thermoelectric materials.  相似文献   
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7.
《Optical Materials》2014,36(12):2435-2439
The stress-induced birefringence (termed photoelastic response) in oxide glasses has important consequences for several applications. In this work, we provide new insights into the structural origins of the photoelastic response of silicate glasses by determining the composition dependence of the stress optic coefficient (C) of forty-nine silicate glasses containing different alkali and alkaline earth oxides. We find that the value of C decreases with increasing modifier-to-silica ratio and increases with alumina-to-silica ratio. The scaling of stress optic coefficient with composition can be predicted based on the average ratio of bond metallicity to cation coordination number in the glass, which varies as a function of composition. This is evidence that the details of the glass network structure need to be considered in order to account accurately for the composition dependence of C, a result that is consistent with a previously proposed empirical model and with topological constraint theory. Our results enable an improved control of the photoelastic response of silicate glasses through compositional design.  相似文献   
8.
Searching for 2D ferromagnetic materials with a high critical temperature, large spin polarization, and controllable magnetization direction is a key challenge for their broad applications in spintronics. Here, through a systematic study on a series of 2D ternary chalcogenides with first‐principles calculations, it is demonstrated that a family of experimentally available 2D CoGa2X4 (X = S, Se, or Te) are half‐metallic ferromagnets, and they exhibit high critical temperature, fully polarized spin state, and strain‐dependent magnetization direction simultaneously. Following the Goodenough–Kanamori rules, the half‐metallic ferromagnetism of CoGa2X4 family is caused by superexchange interaction mediated by Co? X? Co bonds. The half‐metal gaps are large enough (>0.5 eV) to ensure that the half‐metallicity is stable against the spin flipping at room temperature. Magnetocrystalline anisotropy energy calculations indicate that CoGa2X4 favor easy plane magnetization. Under achievable biaxial tensile strain (2–6%), the magnetization directions of CoGa2X4 can change from in‐plane to out‐of‐plane, providing a route to control the efficiency of spin injection/detection. Further, the critical temperatures Tc of ferromagnetic phase transition for CoGa2X4 are close to room temperature. Belonging to the big family of layered AB2X4 compounds, the proposed CoGa2X4 systems will enrich the available 2D candidates and their heterojunctions for various applications.  相似文献   
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