To overcome the deficiency of the volume expansion of MoS(2)as the anode material for lithium-ion batteries (LIBs), an effective strategy was developed to design hierarchical porous MoS2/carbon nanospheres via a facil...
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To overcome the deficiency of the volume expansion of MoS(2)as the anode material for lithium-ion batteries (LIBs), an effective strategy was developed to design hierarchical porous MoS2/carbon nanospheres via a facile, easy-operated hydrothermal method followed by annealing. FESEM and TEM images clearly showed that nanospheres are composed of ultra-thin MoS2/c nanosheets coated with carbon layer and possess an expanded interlayer spacing of 0.98 nm. As anodes for LIBs, MoS2/carbon nanospheres deliver an initial discharge capacity of 1307.77 mAh g(-1)at a current density of 0.1 A g(-1). Moreover, a reversible capacity of 612 mAh g(-1)was obtained even at 2 A g(-1)and a capacity retention of 439 mAh g(-1)after 500 cycles at 1 A g(-1). The improved electrochemical performance is ascribed to the hierarchical porous structure as well as the intercalation of carbon into lattice spacing of MoS2, which offers fast channels for ion/electron transport, relieves the influence of volume change and increases electrical conductivity of electrode. Meanwhile, the expanded interlayer spacing of MoS(2)in MoS2/ccan decrease the ion diffusion resistance and alleviate the volumetric expansion during discharge/charge cycles.
Monodispersed c, Ag co-modified TiO2 microspheres were successfully synthesized through a two-step method. Firstly, monodisperse spherical TiO2 particles were obtained via controlled hydrolysis of TBOT (tetrabutyltita...
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Monodispersed c, Ag co-modified TiO2 microspheres were successfully synthesized through a two-step method. Firstly, monodisperse spherical TiO2 particles were obtained via controlled hydrolysis of TBOT (tetrabutyltitanate) in ethanol. Secondly, the c, Ag co-modified TiO2 microspheres were prepared through a simple calcination process, in which the AgNO3 and citric acid was used as Ag and c source, respectively. The physical and chemical properties of c, Ag co-modified TiO2 microspheres were carefully studied by using XRD, SEM, TEM, Raman, PL spectra and UV-vis diffuse reflectance spectra (DRS), while the chemical states of c and Ag were discussed via EDS (energy dispersive spectrometer) and XPS. The photocatalytic activity of the as-prepared products was evaluated by photocatalytic decolorization of Rhodamine B (Rh B) aqueous solution at ambient temperature under UV and visible-light irradiation. The photocatalytic activity research shows that, with the cooperation of two modified materials, c, Ag co-modified TiO2 microspheres exhibit enhanced photocatalytic activity both in ultraviolet and visible-light region compared with that of pure TiO2 and single Ag modified TiO2 microspheres. (c) 2013 Elsevier B.V. All rights reserved.
The physical properties and device electrical properties of superlattice-like c/Sb phase change films are investigated. compared with Sb monolayer films, the superlattice-like c/Sb films have preferable thermal stabil...
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The physical properties and device electrical properties of superlattice-like c/Sb phase change films are investigated. compared with Sb monolayer films, the superlattice-like c/Sb films have preferable thermal stability, including higher crystallization temperature, longer data life, and larger crystallization activation energy. As the thickness of the carbon layer increases, the band gap gradually increases. X-ray photoelectron spectroscopy results show that c-Sb bonds exist in the c/Sb superlattice-like films. X-ray diffraction and atomic force microscope results show that the addition of carbon inhibits the grain growth, making the grain size smaller and inhibiting the crystallization of Sb materials. Phase-change memory devices based on [c(6nm)/Sb(4nm)](8) superlattice-like films have smaller threshold voltages and lower power consumption compared to Sb films. In conclusion, c/Sb superlattice-like films have high thermal stability and low power consumption.
An improved high-solid-loading slurry impregnation process was developed to introduce HfB2 particles into a low-density c/c preform efficiently, and precursor infiltration and pyrolysis process was used for densificat...
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An improved high-solid-loading slurry impregnation process was developed to introduce HfB2 particles into a low-density c/c preform efficiently, and precursor infiltration and pyrolysis process was used for densification to obtain a c/c-HfB2-Siccomposite. The microstructure characterization revealed that HfB2 particles uniformly filled the pores in the c/c preform, and Sic well densified the interstices between HfB2 particles and the small pores in the carbon fiber bundles. After being tested, the c/c-HfB2-Siccomposite had a density of 4.07 g/cm3 and a bending strength of 344.8 MPa, and exhibited a non-brittle fracture behavior. After ablation with oxyacetylene flame at 2500 for 120 s, the mass ablation rate and linear ablation rate of the c/c-HfB2-Siccomposite were 0.5 mg/s and 0.415 mu m/s, respectively. The good ablation performance is attributed to the hindering effect of the HfO2 scale on oxygen diffusion at high temperature.
y Recently, approaches based on tree-decompositions (TDs) of control-flow graphs (cFGs) have been introduced for many classical problems in compiler construction. Some found practical use in SDcc, a mainstream ccompi...
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y Recently, approaches based on tree-decompositions (TDs) of control-flow graphs (cFGs) have been introduced for many classical problems in compiler construction. Some found practical use in SDcc, a mainstream ccompiler for embedded systems. Using TD-based algorithms, SDcc generates faster and often smaller code for its target architectures than other compilers. The width of the TD crucially influences runtime, hence good algorithms computing TDs of small width are essential. The current standard approach to obtain TDs of cFGs is Thorup's heuristic, which was also used in SDcc. Thorup claims that his heuristic will give TDs of width at most 6 for cFGs from ccode that contains no goto statements. We present a counter example resulting in a tree-width of 7. We show how to construct ccode without goto statements for which the cFG has tree-width 3, but Thorup's heuristic will yield TDs of arbitrary width. We demonstrate how this flaw adversely affects the compilation of real-world code. We present a constructive proof giving a tight bound on the tree-width of cFGs of c programs. This corrects Thorup and shows the effect that goto has on the tree-width. We empirically evaluate various approaches to finding TDs of cFGs and their impact on compiler runtime and code quality in SDcc. Our research resulted in the replacement of the unconditional use of Thorup's heuristic by a better approach in SDcc 3.7.0, drastically reducing compiler runtime. (c) 2019 Elsevier B.V. All rights reserved.
Lignin and ash are the main factors to limit integrated utilization of Si-rich biomass. In this study, core-shell structured lignin-SiO2 composites are prepared from rice husks (RHs) by alkali extraction and acid prec...
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Lignin and ash are the main factors to limit integrated utilization of Si-rich biomass. In this study, core-shell structured lignin-SiO2 composites are prepared from rice husks (RHs) by alkali extraction and acid precipitation and applied as the precursors of anode materials to achieve efficient application. Alkaline lignin is employed to supplement carbon to improve electrochemical performance of c/SiO2 composites. The optimal sample c/SiO2-6 possesses integrated coating shells and appropriate carbon content (38.27%), resulting in stable cycling performance and high capacity retention of 534 mA h g(-1) at 1 A g(-1) after 1000 cycles, close to 574 mA h g(-1) of the c/SiO2 composite synthesized by commercial raw materials. Meanwhile, c/SiO2-6 has superior rate performance and lower impedance, because the carbon coating improves conductivity and kinetic performance. The method provides a strategy for integrated utilization of Si-rich biomass and preparation of c/SiO2 anode materials with desirable electrochemical properties.
coimplantation of equal concentrations of c and Al in 6H- and 4H-Sic has been investigated comparatively with implantation of Al alone in the Al concentration range of N-AI = 8x10(19) to 2 x 10(21) cm(-3). c-Al coimpl...
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coimplantation of equal concentrations of c and Al in 6H- and 4H-Sic has been investigated comparatively with implantation of Al alone in the Al concentration range of N-AI = 8x10(19) to 2 x 10(21) cm(-3). c-Al coimplantation at either room temperature (RT) or 600 degrees c, when implanted with N-Al > 1 x 10(20) cm(-3), gives improvements over Al alone implantation in the specificcontact resistance pc of Al ohmiccontacts on the implanted surfaces. The lowest median values of pc obtained are 3 x and 6 x 10(-5) Omega cm(2) for 6H- and JH-S1c. respectively. Ln the mid to high 1020 cm(-3) N-AI range, sheet resistivity. of the p-type implanted layers are also reduced by the coimplantation at RT, Temperature-dependent Hall-effect measurements reveal the correlated trends in increased impurity-band conduction and high-temperature (>400 K) hole concentration. implantation at 600 degrees c, by either coimplantation or Al atone implantation, degrades the electrical characteristics in the mid 10(20) cm(-3) N-AI range, which implies that amorphization of as-implanted Layers is necessary for effective activation of Al acceptors, It will be shown that c-AI coimplantation at RT can produce p(+)-n diodes with low reverse leakage currents and high forward current capability as evidenced by the 110 A/cm(2) forward current density at 2.8 V and 19 nA/cm(2) Leakage current density at -100 V for 4H-Sic p(+)-n diodes created by c-AI coimplantation at RT.
Although most studies have indicated that biochar can boost rice (Oryza sativa) growth, the material may also suppress it, depending on ratios of carbon (c) to nitrogen (N) and available N to available phosphorous (P)...
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Although most studies have indicated that biochar can boost rice (Oryza sativa) growth, the material may also suppress it, depending on ratios of carbon (c) to nitrogen (N) and available N to available phosphorous (P). The current study sought to examine the impacts of biochar on rice growth and to identify underlying mechanisms. A pot experiment was conducted using two soils of high (3.05%) and low (0.54%) organiccarbon (Oc) content, mixed with 0, 1.5, 3, 6, and 12% biochar and planted with rice. Rice growth components, five rice tissue nutrients, and nine soil properties were measured. The results showed that the response of rice growth to biochar rates could be described using an exponential-growth function in high-Oc soil but an inverted U-shaped curve in low-Oc soil. In high-Oc soil, the 12% biochar rate led to the greatest total biomass, increased by 47%, whereas in low-Oc soil, the 3 and 6% rates exhibited the highest total biomass, increased by 44%, compared to the no-biochar added soils. Biochar elevated the c:N ratio from 11.5 to 39.1, with an optimal range of 20-30 corresponding to the highest rice growth. Biochar declined the ratio of NH4-N to Mehlich-1 P, causing N deficiency. In brief, high biochar rates may suppress rice growth when the soil c:N ratio exceeds 30. The applied biochar rate should be considered based on soil properties typically Oc and N content to obtain the c:N ratio between 20 and 30 for optimal rice growth.
A new surface micromachining way of ultrashort plus laser for c/Siccomposites with high quality and efficiency was demonstrated, including picosecond and femtosecond laser. Surface morphologies, element content and b...
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A new surface micromachining way of ultrashort plus laser for c/Siccomposites with high quality and efficiency was demonstrated, including picosecond and femtosecond laser. Surface morphologies, element content and bonding states of c/Siccomposites were analysed in detail after machined by picosecond and femtosecond laser power respectively. For femtosecond laser machining, the amount of nanoparticles increased with increasing laser power. At 20 and 50mW, Si-c, c-c and Si-O bonds existed in nanoparticles, while Si-c bonds disappeared at 70mW. For picosecond laser machining, cauliflower-like particles and periodic ripple with certain depth were formed distinctly. Furthermore, thermal ablation phenomenon occurred, and only Si-O bonds existed in particles due to the oxidation of the carbon fibres and Sic matrix. The results showed that femtosecond laser with low power was more suitable to the surface machining due to better machining quality and less machining damage compared with high power picosecond laser.
MXenes are a large class of materials that are chemically exfoliated from metal-aluminum-carbon (MAX) bulk crystals into low-dimensional sheets. While many MXenes have been theoretically predicted, the careful balance...
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MXenes are a large class of materials that are chemically exfoliated from metal-aluminum-carbon (MAX) bulk crystals into low-dimensional sheets. While many MXenes have been theoretically predicted, the careful balance required in the exfoliation between breaking the inter-layer bonds without damaging the intra-layer bonds of the sheets has limited synthesis and experimental study. Here, we developed the synthesis of cr2c from its parent cr2Alc MAX phase and showed the etching is optimized using sodium fluoride and hydrogen chloride with a modified minimally intensive layer delamination (mMILD) method in a cold environment of 9 celcius. We further optimized the intercalation and delamination using sonication and washing methods. The resulting cr2ccrystal structure was characterized. These results open up cr2c to experimental study, including of its predicted emergent magnetic properties, and develop guidelines for synthesizing new MXene materials.
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