查看更多>>摘要：The Na-doped diopside (CaMg_(1-x)Na_(2x)Si_2O_6, x = 0-0.18) microwave dielectric ceramics were fabricated via solid-state reaction method. Three phases were identified through the XRD data that was refined with the Rietveld method to obtain structural information. The role of Na~+ substitution to promote the densification process could be corroborated by the SEM images and relative density. The P-V-L bond theory was used to explore the chemical bond characteristics and structure-performance relationships. Through discussion, the dielectric constant was determined by relative density rather than the bond ionicity. The Q× f value was dominated by the lattice energy, lattice vibration and was also related to the relative density and grain size. And the linear thermal expansion coefficient was closely correlated with the τf value. Excellent microwave dielectric properties, (εr = 7.573, Q× f = 35049 GHz, tan δ = 4.015 ×10~(-4),εr = -68.71 ppm/°C) and (εr = 7.646, Q× f = 37844 GHz, tan δ = 3.706 ×10~(-4), τf= -54.2 ppm/C) were achieved for the CaMg_(0.97)Na_(0.06)Si_2O_6 ceramics sintered at 1150 °C/3 h and 1200 °C/3 h, respectively.
查看更多>>摘要：The interphase of composites is a vital element in controlling the overall performance. Herein, the SiC nanowires (SiC_(nw)) were grown on the interface of the SiC fiber (SiC_f)/Si_3N_4 composites and successfully achieved the integration of enhanced mechanical and electromagnetic wave (EMW) absorption performance. The introduction of SiC_(nw) made the bonding between the SiCf and Si_3N_4 matrix more appropriate, thereby enhancing the mechanical properties. The defects, stacking faults, twin boundaries and heterogeneous interfaces in SiC_(nw) improved the dielectric loss of the composites, which was beneficial to the consumption of EMW energy. Notably, the SiCf/SiC_(nw)/Si_3N_4 composite containing 1.8 vol% SiC_(nw) demonstrated the optimal mechanical and EMW absorption properties, reaching a flexural strength of 333 ± 29 MPa, a minimum reflection coefficient (RC_(min)) value of- 51.4 dB with a thickness of 3.2 mm and an effective absorption bandwidth (EAB) of 3.5 GHz with a thickness of 2.8 mm. Besides, the fracture mechanism and EMW absorption mechanism are also discussed. This work provides a potential new way to prepare lightweight, stable, and high-performance EMW absorbing materials for aviation and aerospace.
查看更多>>摘要：Antiferroelectric materials are considered promising energy storage materials because they have excellent energy density during the antiferroelectric phase transition. Herein, Pb_(0.925)La_(0.05)Zr_(0.95)Ti_(0.05)O_3@SiO_2 (PLZT@SiO_2) core-shell structure ceramic materials were synthesized by combing sol-gel method with conventional solid-phase method. The effect of holding time (3 h, 6 h, 9 h, 12 h) on the electrical properties and energy storage properties of PIZT@SiO_2 ceramics were investigated. TEM results indicate the formation of a core-shell structure. Transmission electron microscope (TEM) reveals the formation of core-shell structure. X-ray diffraction (XRD) obtained clear tetragonal perovskite structure PLZT and SiO_2 phase. The phase transition temperature of PLZT@SiO_2 ceramics is between 222 °C and 225 °C, and its dielectric constant can be adjusted by the holding time. The PLZT with surface coated SiO_2 can increase the breakdown electric field (BDS) and thus increase the energy density. When the holding time is 9 h, the breakdown electric field is as high as 156.84 kV/cm, and the recoverable energy density (W_(re)) is 1.92 J/cm~3, which is mainly determined by its high density and breakdown electric field.
查看更多>>摘要：The near-net-shape manufacturing via casting has great potential to commercialize bulk metallic glasses (BMGs) for the complex-shaped structural material. However, it is difficult to cast BMGs with the excellent glass-forming ability (GFA) into the precise dimensions of complex shapes, because the slow kinetics of crystallization of the BMG is related to the high viscosity and low fluidity of the melt. In this study, to overcome this limitation, Zr-based BMG with excellent GFA, hardness, and significantly improved fluidity compared to Vitreloy 106 was systematically developed. Utilizing the ZrCuNi liquidus projection, it is possible to design BMG-forming alloy compositions with a low liquidus temperature (T_L) by compositional tuning in the ZrCuNiAl quaternary alloy system. We also propose an alloy design methodology that can simultaneously improve the key properties of Zr-based BMGs by minor addition. Interestingly, Ag can be added instead of Zr in ZrCuNiAl alloys, resulting in higher hardness and lowest T_L without deterioration of GFA. Thus, the addition of Ag can lead to a significant increase in flow length of about 40% compared to that of Vitreloy 106, because the T_L is a dominant factor that determines fluidity under various casting conditions. This study shed light on how to simultaneously improve the dimensional accuracy of BMG products and life span of casting facilities when manufacturing through various conventional casting methods, which should be important to fabricate macro to nano-sized industrial parts through BMGs.
查看更多>>摘要：Developing a highly efficient and robust poison tolerance catalyst for oxygen reduction reaction (ORR) is significantly critical for sustainable energy convert systems. Herein, an interfacial engineered PdRu/C is prepared by reduction of silicon-hydrogen bonds. The interface between Pd and Ru is beneficial for exposing the active site, enhancing charge transfer and adjusting the adsorption energy barrier, resulting in the excellent ORR performances. Compared with commercial Pt/C (0.84 V) and commercial Pd/C (0.84 V), the optimal Pd_9Ru_1/C demonstrates high electrocatalytic activity with half-wave potential up of 0.86 V in 0.1 M KOH solution. Meanwhile, the experimental results indicate that bimetallic interface engineering can greatly enhance toxicity resistance to various poisons, including CO, methanol, NO_x, SO_x and PO_x. When they are applied to zinc-air battery as an air cathode, the battery exhibits an open circuit voltage of 1.48 V. Interestingly, the power density reaches up to 240 mW cm~(-2), which is superior to those of commercial Pt/C (219 mW cm~(-2)) and commercial Pd/C (128 mW cm~(-2)). This work opens up an effective strategy to conceive interfacial hybrid for electrocatalysis.
查看更多>>摘要：Structural and low temperature magnetic properties of CoFe_(2-x)Mo_xO_4 (x = 0.01,0.03 and 0.05) were studied in the present work. Rietveld refinement of XRD patterns of CoFe_(2-x)Mo_xO_4 (x = 0.01,0.03 and 0.05) confirm the pure phase cubic crystal structure in Fd3m space group. The decrease in lattice parameters (a contraction of the lattice) has been observed with doping, which confirms the probability of substitution of 'Mo' at the octahedral site of parental CoFe_2O_4 (CFO). The micro-strain via W-H plots was found to be enhanced for CoFe_(1.95)Mo_90.05)O_4 (CMF05) sample which confirms the incorporation of 'Mo' atoms at Fe-site and subsequently reducing impurities as observed from refined patterns. The low temperature (2K) magnetic parameters were found to be greatly enhanced with 'Mo' substitution. We observed the decrease in anisotropy constant of Co~(2+) ions with 'Mo' doping and Mo~(6+) ions concentration at the tetrahedral site of CFO, increases the magnetization of the samples. Both M-H and ZFC-FC measurements confirm the ferri-magnetic behavior of all the samples. The maximum value of information storage parameter'S' achieved around 0.442 for x = 0.03 sample at 2K. The structural parameters, electronic (density of states and band structure) and magnetic properties of pure CFO have also been investigated via computational first principle based density functional theory (DFT) calculations. The computational results are in good agreement with the experimental outputs.
查看更多>>摘要：Due to the increase in pollution, and incredibly polluted water resources, access to safe water has become one of the major human activities in the present age. Also, existing organic compounds from industrial wastewater in water sources are a concern for human health. So in this work, Sr_2Fe_2O_5/Dy_3Fe_5O_(12) (SFO/DFO) nanocomposite were fabricated via a green auto-combustion sol-gel method using Hordeum vulgare L extract as a natural fuel. Proper control over the dimensions and morphology of nanocomposite was achieved by changing the parameters consisting of fuel types (natural and chemical) and calcination temperature. The results showed that every parameter affects the particle size and morphology of products, and by controlling these factors, the optimum sample can be obtained. The photocatalytic ability of SFO/ DFO nanocomposite was performed for the destruction of organic dyes. This nanocomposite was used to investigate the photocatalytic properties under UV light in the aqueous solution of methylene blue (MB), Erythrosine, and acid red dyes. The results of the photocatalytic process showed 82% discoloration for the methylene blue (MB). Three compounds, including Ethylenediaminetetraacetic acid, 1,4-Benzoquinone, and Benzoic acid, were used as scavengers to investigate the mechanism of the photocatalytic process. The results showed that the mechanism of the photocatalytic process proceeds through hydroxide radicals, which Benzoic acid scavenges. The electrochemical redox behavior of MB on SFO/DFO/CPE (carbon-paste electrode) was studied using cyclic voltammetry (CV). Besides, according to the VSM result, SFO/DFO nanocomposite is ferromagnetic.
查看更多>>摘要：Cubic spinel Li_4Ti_5O_(12) is a desired anode material for lithium-ion batteries (LIBs) due to high stability (the feature of "zero strain") and good safety. Moreover, Li_4Ti_5O_(12) has a good affinity with sulfur for restraining lithium polysulfides (LiPSs) by the Ti-S bond in lithium-sulfur batteries (LSBs). Interestingly, extra cobalt element is introduced to form Li_2CoTi_3O_8, which not only increases theoretical capacity for LIBs but also enhances the adsorption of sulfur for LSBs. In this paper, Li_2CoTi_3O_8 nanoparticles are synthesized via a sol-gel method. As the anode for LIBs, Li_2CoTi_3O_8 displays a desired specific capacity (335.3 mAh g~(-1) at 0.2 A g~(-1)) and a better rate-capability (188.5 mAh g~(-1) at 5 A g~(-1); no capacity decay over 400 cycles), which is superior to electrochemical performances of the reported same substances. Besides, Li_2CoTi_3O_8 nanoparticles are designed as both the sulfur host material and the modified separator in LSBs for the first time. Under the LCTO-coated separator, the Li_2CoTi_3O_8/S electrode achieves a first capacity of 1048 mAh g~(-1) at 0.5 C and the stable capacity retention (732.7 mAh g~(-1) after 100 cycles). The enhanced performance of the Li_2CoTi_3O_8 electrode is the result of synergistic effect of dispersed particles and larger contact area for LIBs and LSBs.
查看更多>>摘要：Compared with single-component electrode materials, multi-component composite materials are more capable to promote the electrochemical performance of electrode materials because of the synergistic effect of different components. In this work, a binary FeOOH/Fe_2O_3 composite is fabricated by a facile and low-cost hydrothermal method with FeCl_3*6 H_2O and C0(NH_2)_2 as raw materials. The microstructure and composition of the as-prepared sample is characterized by XRD, SEM, TEM, FT-IR, and XPS. The electrochemical performance of the binary FeOOH/Fe_2O_3 composite is investigated by CV, EIS, charge-discharge test, and GITT measurement. Compared to single-component FeOOH or Fe_2O_3, this binary FeOOH/Fe_2O_3 composite exhibits outstanding high-rate capability (645 mA h g~(-1) at 1 A g~(-1)) and superior long-term cycling stability (779 mA h g~(-1) after 300 cycles at 0.5 A g~(-1)) due to the synergetic effect between FeOOH and Fe_2O_3. EIS analysis reveals that the electrochemical reaction resistance in binary FeOOH/Fe_2O_3 composite is lower than that in single-component FeOOH or Fe_2O_3. CV analysis demonstrates that the binary FeOOH/Fe_2O_3 composite has a certain pseudocapacitive behavior during discharge and charge processes. The lithium ion diffusion coefficient of the binary FeOOH/Fe_2O_3 composite derived from GITT data ranges from 4.0 ×10~(-12) to 1.0 × 10~(-14) cm~2 s~(-1). Ex-situ SEM observations revealed that the binary FeOOH/Fe_2O_3 composite has good structural integrity upon cycling, which partially accounts for the superior electrochemical performance of the electrode. The reported method could provide a facile avenue for the ingredient design of high-performance anode materials for next-generation lithium-ion batteries (LIBs).
查看更多>>摘要：Due to rampant misuse of antibiotics, certain bacterial organisms have developed resistance against them as a result of genetic modifications, rendering a lot of the traditionally used antibiotics ineffective. Thus, introduction of a new class of antibacterial materials is paramount. This article reports exploring the comparative performances of monometallic Au, bimetallic AuPt and trimetallic AUPtCu as potential antibacterial agents for the future. The materials were obtained as nanofluids via a one-pot microwave synthesis procedure and subsequently were subjected to characterization by high-resolution electron microscopy, dynamic light scattering, X-ray diffraction, absorption spectroscopy and X-ray photoelectron spectroscopy, etc. It was found that the multimetallic particles were composed of several bimetallic alloy nano-islands and with increasing number of components the particle size became smaller and the mi-crostructure became littered with defects. This had a profound effect on the antibacterial activity as the trimetallic AuPtCu was found to be the most effective against both the gram-negative and gram-positive bacterial strains. A detailed rationalization for the same has been provided based on the analysis of the structure-property-activity correlation. We anticipate the findings to be really important going forward; in the research and fabrication of new age medicines against drug-resistant micro-organisms.
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Elsevier