Multi-walled carbon-nanotube-decorated tungsten ditelluride nanostars as anode material for lithium-ion batteries.

Multi-walled carbon-nanotube (MWCNT)-decorated WTe2 nanostars (WTe2@CNT nanocomposites) are to be employed for the first time as anode candidates in the development of lithium-ion (Li-ion) batteries. WTe2@CNT nanocomposites deliver a high discharge capacity of 1097, 475, 439, 408, 395 and 381 mA h g-1 with an increasing current density of 100, 200, 400, 600, 800 and 1000 mA g-1, respectively, while WTe2 nanostars exhibit a reversible capacity of 655, 402, 400, 362, 290 and 197 mA h g-1 with the aforementioned current densities. Furthermore, WTe2@CNT nanocomposites exhibit a superior reversible capacity of 592 mA h g-1 at 500 mA g-1 with a capacity retention of 100% achieved over 500 cycles, while bare WTe2 nanostars deliver ∼85 mA h g-1 over 350 cycles. This remarkable Li cycling performance is attributed to MWCNTs interconnected with WTe2 nanostars. In addition, the exposed active interlayers of the WTe2 nanostars, which are responsible for maintaining the structural integrity of the electrodes, buffer the large volume expansion within the WTe2 nanostars, avoiding the agglomeration of the particles. The layered WTe2 nanostars were synthesized via the solution-phase method, and present extremely good possibilities for the scaling-up of Li-ion battery storage systems.

Promoting catalytic ozonation of phenol over graphene through nitrogenation and Co3O4 compositing.

Catalytic ozonation is progressively becoming an attractive technique for quick water purification but efficient and stable catalysts remains elusive. Here we solvothermally synthesized highly-dispersed Co3O4 nanocrystals over microscale nitrogen-doping graphene (NG) nanosheets and tested it as a synthetic catalyst in the ozonation of phenol in aqueous solutions. Transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectra and X-ray photoelectron spectroscopy were used to determine its morphology, crystallinity, elemental composition and molecular bonds, respectively. The comparative experiments confirmed the highest catalytic activity and oxidation degree (AOSC) of Co3O4/NG among four nanocomposites (G, NG, Co3O4/G, and Co3O4/NG). Co3O4/NG also has exhibited the highest degradation rate: complete conversion of a near-saturated concentration of phenol (941.1mg/L) was achieved within 30min under ambient conditions with only a small dosage of Co3O4/NG (50mg/L) and ozone (4mg/L, flow rate: 0.5L/min). It also resulted in 34.6% chemical oxygen demand (CODCr) and 24.2% total organic carbon (TOC) reduction. In this work, graphene nanosheets not only functioned as a support for Co3O4 nanocrystals but also functioned as a co-catalyst for the enhancement in phenol removal efficiency. The surface nitridation and Co3O4 modification treatment further improved the removal rate of the phenol pollutants and brought in the higher oxidation degree. Our finding may open new perspectives for pursuing exceptional activity for catalytic ozonation reaction.

Nano-to-Microdesign of Marimo-Like Carbon Nanotubes Supported Frameworks via In-spaced Polymerization for High Performance Silicon Lithium Ion Battery Anodes.

Silicon (Si) has been perceived as a promising anode material for lithium-ion batteries for decades due to its superior theoretical capacity, environmental benignity, and earth abundance. To accommodate the drastic volume expansion during lithiation, which is the primary drawback leading to poor cycling life, a novel structural design via fabricating the Marimo-like carbon nanotubes frameworks with silicon nanoparticle (SiNP) filling in internal space has been developed. This facile fabrication procedure involves an in-spaced polymerization process through ex situ polymerization, using pyrrole monomers with a soft organic template in which well-dispersed SiNPs are present. Carbonization post-treatment is then performed to construct rigid conductive networks. The thus-fabricated 3D Marimo-like hybrid structure exhibits a remarkably improved electrochemical performance compared with that of the simple ball-milling method, which mainly originates from their structural advantages, including the built-in buffer spaces and the robust line-to-line contact mode between the components. The state-of-the-art structure exhibits an optimal high-rate capability (422 mAh g(-1) at a current rate of 2 A g(-1)) and long cycling stability (916 mAh g(-1) for 200th cycles at a current rate of 0.2 A g(-1)) and achieves the requirements for industrial production with the facile and cost-effective synthetic approach.

Microwave frequency performance and high magnetic anisotropy of nanocrystalline Fe70Co30-B films prepared by composition gradient sputtering.

The fabrication and high-frequency ferromagnetic performances of nanocrystalline Fe70Co30-B soft magnetic films were investigated. It is revealed that the composition gradient sputtering method dramatically improves the high-frequency soft magnetic properties of the as-prepared films. This method gives rise to almost a linearly-increased distribution of compositions and residual stress. As a result, a very high ferromagnetic resonance frequency up to 6.7 GHz, high uniaxial magnetic anisotropic field up to 450 Oe, and low magnetic loss were obtained in as-deposited samples, which are particularly in favor of the integration between magnetic films and microwave components.

Tunable microwave frequency performance of nanocomposite Co2MnSi/PZN-PT magnetoelectric coupling structure.

Nanocrystalline Co2MnSi Heusler alloy films were deposited on the PZN-PT substrates by a composition gradient sputtering method. It is revealed that this multiferroic heterostructure shows very strong magnetoelectric coupling, leading to continuously tunable microwave frequency characteristics by electric field. With the increase of electric field intensity from 0 to 6 kV/cm, the magnetic anisotropy field H(K) increases from 90 Oe to 182 Oe with an increment of 102%, corresponding to a ME coefficient of 15.3 Oe cm/kV; the ferromagnetic resonance frequency f(FMR) shifts from 3.38 to 4.82 GHz with an increment of deltaf(FMR) = 1440 MHz or deltaf(FMR)/f(FMR) = 43%; moreover, the damping constant alpha dramatically decreases from 0.035 to 0.018. These merits demonstrate that this nanocomposite multiferroic structure is promising in fabrication of tunable microwave components.

Novel lead-free Sn-Cu-xBi nanosolders by chemical reduction method.

With environmental concerns on the toxicity of lead, investigations on lead-free solders become crucial. Studies on lowering process temperature of lead-free solders are required, because the melting points of lead-free solders are higher than original SnPb solders. Melting points of binary solders could be decreased by addition another materials. In this study, Sn-Cu-xBi lead-free nanoparticles were synthesized with precisely controlled size and composition by chemical precipitation method. Effects of different precursor concentration and surfactant addition were discussed. The influence of different amounts of Bi in the SnCu-based nano-particles was also probed.

High-frequency ferromagnetic properties and magnetic domain structures of FeNdBO thin films.

FeNdBO films were deposited by DC magnetron sputtering. The high-frequency ferromagnetic properties of the films were dramatically enhanced by annealing at 350 degrees C for 1 hour. In comparison with the as-deposited film, the resonance frequency increased from 1.32 to over 3 GHz, while relative permeability still maintained at a high value of 100. Magnetic force microscope (MFM) revealed strip domains in the FeNdBO films. The domain width of approximately 100 nm for the annealed film was smaller than that for the as-deposited film, implying the enhancement of anisotropy field due to annealing. Promising high-frequency ferromagnetic properties of FeNdBO films can be attributed to the high values of Ms (15.7 kG), Hk (over 1000 Oe), and p (more than 10 Omegam).

Morphology and electrochemical behavior of Ag-Cu nanoparticle-doped amalgams.

The aim of this study was to introduce Ag-Cu phase nanopowder as an additive to improve the corrosion behavior of dental amalgams. A novel Ag-Cu nanopowder was synthesized by the precipitation method. An amalgam alloy powder (World-Cap) was added and mixed with 5 wt.% and 10 wt.% of Ag-Cu nanopowders, respectively, to form experimental amalgam alloy powders. The original alloy powder was used as a control. Alloy powders were examined using X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy and electron probe microanalysis. Amalgam disk specimens of metallurgically prepared were tested in 0.9% NaCl solution using electrochemical methods. The changes in the corrosion potential and anodic polarization characteristics were determined. Corrosion potential data were analyzed statistically (n=3, analysis of variance, Tukey's test, p<0.05). The diameters of lamellar structure Ag-Cu nanoparticles were measured to be approximately 30 nm. The composition of the Ag-Cu nanoparticles determined by TEM-energy-dispersive spectroscopy was 56.28 at.% Ag-43.72 at.% Cu. A light-shaded phase was found mixing with dark Cu-Sn reaction particles in the reaction zones of Ag-Cu nanoparticle-doped amalgams. The Ag-Cu nanoparticle-doped amalgams exhibited zero current potentials more positive than the control (p<0.05) and no current peak was observed at -325mV that related to Ag-Hg phase and Cu6Sn5 phase in anodic polarization curves. The results indicated that the corrosion resistance of high-copper single-composition amalgam could be improved by Ag-Cu nanoparticle-doping.

Effect of nitride film coatings on cell compatibility.

OBJECTIVE: To evaluate the cytotoxicity of nickel-based alloy surfaces after nitride film coatings. METHODS: A total of 120 disc-shaped specimens (1.5 x 12.0mm) were prepared from nickel (Ni) alloy ingots and metallurgically ground with silicon carbide (SiC) sandpaper to 1200 grit and used as the ground group. Ninety specimens from the ground group were selected and further polished with 1.0 microm aluminum powder slurry and assigned as the polished group. Titanium nitride (TiN) and titanium-aluminum nitride (TiAlN) film coatings were deposited onto 30 polished specimens each by a reactive radio frequency magnetron sputter deposition system and used as coated groups, respectively. The morphological changes and cytoskeleton of tested human gingival fibroblasts were observed using fluorescence microscopy at 3h and 24h time periods, respectively. An MTT assay was used to assess cell viability at 24h. The results were statistically analyzed (n=5, ANOVA, Scheffe', p<0.05). RESULTS: After 3h of incubation, cells began to spread on the test surfaces. Spindle-shaped fibroblasts with well-developed cytoskeleton and distinct actin fibers were observed at the 24h incubation point on the polished and coated specimens. Results of the MTT assay revealed that the TiN and TiAlN film coated groups were significantly higher in cell proliferation and viability than the polished and control groups (p<0.05). SIGNIFICANCE: The biocompatibility of Ni-based alloy was increased significantly after nitride film coating.

Fluorination Induced the Surface Segregation of High Voltage Spinel on Lithium-Rich Layered Cathodes for Enhanced Rate Capability in Lithium Ion Batteries.

This study is aimed to explore the effect of fluoride doping and the associated structural transformation on lithium-rich layered cathode materials. The polymeric fluoride source is first adopted for synthesizing lithium intercalated oxide through a newly developed organic precipitation process. A heterostructured spinel/layered composite cathode material is obtained after appreciable fluorination and a superior rate capability is successfully achieved. The fluoride dopant amount and the surface spinel phase are evidenced and systematically examined by various structural spectroscopy and electrochemical analysis. It appears the reversible Ni(2+/4+) redox couple at high voltage regime around 4.8 V because of the formation of spinel LiNi1/2Mn3/2O4 phase. The mechanism of "layer to spinel" phase transformation is discussed in detail.

A Revival of Waste: Atmospheric Pressure Nitrogen Plasma Jet Enhanced Jumbo Silicon/Silicon Carbide Composite in Lithium Ion Batteries.

In this study, a jumbo silicon/silicon carbide (Si/SiC) composite (JSC), a novel anode material source, was extracted from solar power industry cutting waste and used as a material for lithium-ion batteries (LIBs), instead of manufacturing the nanolized-Si. Unlike previous methods used for preventing volume expansion and solid electrolyte interphase (SEI), the approach proposed here simply entails applying surface modification to JSC-based electrodes by using nitrogen-atmospheric pressure plasma jet (N-APPJ) treatment process. Surface organic bonds were rearranged and N-doped compounds were formed on the electrodes through applying different plasma treatment durations, and the qualitative examinations of before/after plasma treatment were identified by X-ray photoelectron spectroscopy (XPS) and electron probe microanalyzer (EPMA). The surface modification resulted in the enhancement of electrochemical performance with stable capacity retention and high Coulombic efficiency. In addition, depth profile and scanning electron microscope (SEM) images were executed to determine the existence of Li-N matrix and how the nitrogen compounds change the surface conditions of the electrodes. The N-APPJ-induced rapid surface modification is a major breakthrough for processing recycled waste that can serve as anode materials for next-generation high-performance LIBs.

Driving ferromagnetic resonance frequency of FeCoB/PZN-PT multiferroic heterostructures to Ku-band via two-step climbing: composition gradient sputtering and magnetoelectric coupling.

RF/microwave soft magnetic films (SMFs) are key materials for miniaturization and multifunctionalization of monolithic microwave integrated circuits (MMICs) and their components, which demand that the SMFs should have higher self-bias ferromagnetic resonance frequency fFMR, and can be fabricated in an IC compatible process. However, self-biased metallic SMFs working at X-band or higher frequency were rarely reported, even though there are urgent demands. In this paper, we report an IC compatible process with two-step superposition to prepare SMFs, where the FeCoB SMFs were deposited on (011) lead zinc niobate-lead titanate substrates using a composition gradient sputtering method. As a result, a giant magnetic anisotropy field of 1498 Oe, 1-2 orders of magnitude larger than that by conventional magnetic annealing method, and an ultrahigh fFMR of up to 12.96 GHz reaching Ku-band, were obtained at zero magnetic bias field in the as-deposited films. These ultrahigh microwave performances can be attributed to the superposition of two effects: uniaxial stress induced by composition gradient and magnetoelectric coupling. This two-step superposition method paves a way for SMFs to surpass X-band by two-step or multi-step, where a variety of magnetic anisotropy field enhancing methods can be cumulated together to get higher ferromagnetic resonance frequency.