查看更多>>摘要：A sensing platform based on porous ZnO/Co_3O_4 is introduced for determination of hydrazine in alkaline media. The bimetallic oxides were prepared by calcination of bimetallic zeolitic imidazolate framework (Zn/ CoZIF) as a sacrificial template. Zn/CoZIF and ZnO/Co_3O_4 were characterized via several techniques. The porous ZnO/Co_3O_4 was utilized to modify glassy carbon electrode (ZnO/Co_3O_4/GCE), followed by immobilization of Au nanoparticles (NPs) on its surface to prepare Au/ZnO/Co_3O_4/GCE. The electrode exhibited two linear ranges of 2-1900 μM and 1900-8500 μM with sensitivity of 0.058 and 0.048 μA μM~(-1) for determination of hydrazine in aqueous solution. The sensor showed remarkable lower oxidation potential and limit of detection rather than ZnO/Co_3O_4/GCE. Furthermore, the sensor displayed acceptable selectivity toward oxidation of hydrazine in the presence of some interfering species. The results confirm that Au/ZnO/ Co_3O_4/GCE can be considered as sensitive and reliable sensor toward the oxidation of hydrazine due to the porous structure of ZnO/Co_3O_4, high conductivity of Au NPs, and the synergic effect among the constituents.
查看更多>>摘要：This study is focused on the synthesis condition influence related to structural and spectroscopic properties of the potassium strontium pyrophosphate (K_2SrP_2O_7) co-doped with Eu~(3+) and Eu~(2+) ions. The experimental parameters of the urea assisted combustion synthesis were optimized by temperature and time of calcination as well as reduction atmosphere composition. The obtained materials were structurally characterized using the X-Ray Powder Diffraction (XRPD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Spectroscopic properties were determined by emission spectra, excitation spectra, luminescence kinetics and luminescence temperature quenching measurements. It was found that increasing concentration of Eu~(3+) ions caused an increase of spectroscopic factors, which correspond to the relative integrated luminescence intensities of ~5D_0-~7F_∫ transitions as well as structural defects. Moreover, the successful Eu~(2+) ion incorporation was proven by optical spectroscopic measurements, which showed the allowed f-d transitions.
查看更多>>摘要：ScAlMgO_4 is a promising material that can be used to fabricate lattice-matched substrates for the epitaxial growth of GaN and InGaN. To improve its crystal quality, we used synchrotron X-ray topography to study the dislocations in a 50.8-mm-diameter ScAUvlgO_4 single crystal grown via the Czochralski method. Dislocation character was analyzed in terms of Burgers vectors by comparing dislocation contrasts recorded using sixg-vectors that represented the m+c, a+c, and c-type crystal planes. The central area of the substrate, which corresponded to the portion grown vertically under the seed crystal, was characterized by millimeter-sized domains bound by mixed-type dislocation arrays with both in-plane and c-axis Burgers vectors. Basal plane dislocations (BPDs) typically formed an arrow-like shape with three branches. Growth striations with alternating high- and low-dislocation-density areas were observed in the diameter-expanding area and high-dislocation-density areas were covered with tangled BPD networks. The mechanisms of dislocation generation, multiplication, and reaction are discussed based on their line directions and dislocation character.
查看更多>>摘要：Six groups of fcc solid/solid diffusion couples, including Ni-Cr-Fe/ low-entropy (pure Ni, and NiCo, NiCr, and NiCoCr) alloys, Ni-Cr-Fe/ medium-entropy (CoCrNi) alloys, and Ni-Cr-Fe/ high-entropy (CoCrFeNi) alloys, were prepared, and their composition profiles were experimentally measured. Concentration-dependent interdiffusion and tracer diffusion coefficients in fcc Ni-Co-Cr-Fe system at 1473 K were retrieved with the aid of High-throughput Determination of Interdiffusion Coefficients (HitDIC) software and their reliability was validated. In most cases, D_(CrCr)~(Ni)> D_(FeFe)~(Ni)> D_(CoCo)~(Ni). The comprehensive comparison between the inter-diffusivities/tracer diffusivities in the NiCo, NiCr, NiCoCr low-entropy, CoCrNi medium-entropy, and CoCrFeNi high-entropy alloys and those reported data available in the literatures indicates that the inter-diffusivities Co, Cr, and Fe in low-entropy alloys are the largest than those in the other two types of alloys. While the tracer diffusivity in Co-Cr-Fe-Ni HEAs may have no sluggish phenomenon when the absolute temperature is used.
查看更多>>摘要：Although Si is a promising anode material for lithium-ion batteries, scalable synthesis of Si anodes with high cyclability and low swelling remains a significant challenge. Herein, we describe the electrochemical fabrication of a Si@graphite@SiC composite anode from a SiO_2/graphite mixture via an electro-deoxidation-based molten salt process. The exfoliated graphite enhances the electrical conductivity of the composite and cushions the volume expansion of Si nanowires, while the SiC component acts as an active matrix that accommodates the expansion of the Si during lithiation. This significantly increases the electrode cycle life. In half-cell testing, the composite exhibited 80% capacity retention until 500 cycles. It showed good cycling performance even at a high areal capacity of 4.6 mAh/cm~2. Further, a full cell comprising the composite anode and a LiNi_(0.6)Co_(0.2)Mn_(0.2)O_2 cathode possessed a high capacity and demonstrated 84% capacity retention after 70 cycles. This work provides new insights into the rational design of alloy anodes for high-energy density batteries.
查看更多>>摘要：Luminescence thermometry based on the rare earth (RE) doped materials has displayed promising applications in various fields due to its fast response and high spatial resolution. However, the achievement of sensitive and accurate temperature sensing over a wide temperature scope is still a great challenge for this thermal sensing technology. Herein, excited by 980 nm laser, the inverse thermal responses of the near-infrared emissions in Nd~(3+)-Yb~(3+) codoped phosphors, which was attributed to the phonon-assisted energy transfer between RE ions, were employed for ratiometric thermometry within the temperature range of 303-773 K. The modification of thermometric capability for the NIR luminescence was proposed through engineering the aluminate host matrix with SiO_2. The influence of SiO_2 on the luminescence behaviors of Nd~(3+) and Yb~(3+) was systematically investigated through the X-ray diffraction patterns, Fourier-transform infrared spectra, Judd-Ofelt theory calculation, as well as luminescence decay profiles. The results demonstrated that the luminescence and the subsequent thermal sensing properties of Nd~(3+)-Yb~(3+) ion pair were strongly dependent on the host. As the host structure varied from aluminate to aluminosilicate, the spontaneous radiative transition and the energy transfer for RE ions were clearly improved, whereas the multiphonon nonradiative relaxations were weakened. The Nd~(3+)-Yb~(3+) codoped aluminosilicate phosphors synthesised by adding 100 mol% SiO_2 exhibited much high sensitivity (0.7-4.6% K~(-1)) at temperatures ranging from 303 to 773 K, accompanied with a measurement uncertainty of about 0.1 K. This work provides an effective guidance for developing high-performance luminescence-based ratiometric thermometers.
查看更多>>摘要：Si_3N-4 ceramics have shown promising application prospects as the sealing materials for liquid metal batteries (LMBs). However, the joining of Si_3N-4 to the metal shell of LMBs is rather difficult because of the non-wetting property and mismatch of their thermal expansion coefficients (CTEs). Herein, to solve the above issue, W/Si_3N-4 functionally graded materials (FGMs) were designed and fabricated via the spark plasma sintering (SPS) process. The effects of layer numbers and layer components on the phase composition, structure, and thermal stress of the FGMs were systematically investigated using both experimental and simulation methods. W/Si_3N-4 FGMs, with optimal layer numbers, were then utilized for fabricating symmetrical W/Si_3N-4/W FGMs. The thermal stress of the products can be effectively reduced by adjusting the MgO content of the central Si_3N-4 layer. As a result, the optimal product displayed good interface bonding between two adjacent layers and also exhibited high flexural strength (943.9 MPa) and electrical resistivity (2.0 × 10~(12) Ω cm). This route for the fabrication of symmetrical W/Si_3N-4/W FGMs exhibits the advantage of high efficiency, and the products with excellent properties can be used as sealing materials for LMBs.
查看更多>>摘要：Three dimensional (3D) hybrid nanoarchitecture of two-dimensional (2D) reduced graphene oxide/one dimensional (1D) multiwalled carbon nanotube and zero-dimensional (OD) zirconium oxide (ZrO_2) nano-particles (rGO/MWCNT/ZrO_2) was synthesised by a simple hydrolysis method for high performance supercapacitors. To unlock the properties of individual materials to the maximum, binaries of ZrO_2 with GO and MWCNT were also synthesised. The increased wettability, integrated structure, and the synergistic effect of rGO, MWCNT, and ZrO_2 in rGO/MWCNT/ZrO_2 (GMZ) offer a capacitance of 357 F g~(-1) at 1 A g~(-1) with excellent capacitance retention of 98% across 5000 cycles. 1D structure of MWCNT creates an exceptional conductive network with rGO due to the confinement of electrons and ions without disturbing its electronic structure. The intriguing supercapacitor performance of differently dimensioned framework with ZrO_2 emphasises the engineered orientation and tuning of a designed environment for its appropriateness, uniqueness, and sensitivity to push up enhanced performance.
查看更多>>摘要：Lithium ion batteries (LIBs) based on solid state electrolytes have attracted much attention for their high safety and energy density. Li_(29)Zr_9Nb_3O_(40) powders as Li-ionic conductors were prepared using a sol-gel method in this work, and the related ceramics were sintered in air or in an oxygen-deficient atmosphere in which sample was covered with corundum crucible. All the sintered ceramics are consisted of orthorhombic phase. Li_(29)Zr_9Nb_3O_(40) ceramic sintered in oxygen-deficient atmosphere has conductivity of 1.03 × 10~(-3) S cm~(-1) at room temperature and has ionic transference number of 0.9996, while the ceramic sintered in air has conductivity of 4.41 × 10~(-5) S cm~(-1). The influence of oxygen vacancy on the migration path of Li-ion was discussed. The migration paths of Li-ions between two kinds of Li_(29)Zr_9Nb_3O_(40) ceramics were simulated and visualized by method of bond valence site energy with VESTA software.
查看更多>>摘要：Solid electrolytes are critical in the development of solid-state batteries, which have advantages in terms of safety and stability. Lithium Lanthanum Titanate (Li_(3x)La_(2/3-x)TiO_3) is regarded as one of the most favored candidate solid electrolytes. However, the doping dependences of ionic conductivity and microstructure are still poorly understood. In this work, nominal Li_(0.5-x)La_(0.5)(Ti_(1-x)Nb_x)O_3 (LLTN, x = 0, 0.01, 0.03, 0.05 and 0.07, labelled as LLTNO, LLTN1, LLTN3, LLTN5, LLTN7, respectively) ceramics are synthesized to investigate the above doping effects. The bulk ionic conductivity of LLTN5 sample reaches as high as 0.71 × 10~(-3) S/cm, which is approximately two times higher than the bulk ionic conductivity of the undoped sample at room temperature. The XRD refinement and Raman results indicate that niobium doping increases the lattice cell along the c-axis and stretch the Ti-0 bond, which extends the tunnels for Li-ions diffusion. This work suggests that it is effective to enlarge the lattice cell for the improvement of the Li-ion conductivity in LLTO.
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Elsevier