SiOx encapsulated FeSi2–Si eutectic nanoparticles as durable anode of lithium-ion batteries

Low-cost and high-efficiency production of silicon-based material is the key to improve the energy density of lithium-ion batteries. Herein, we propose a novel structure of FeSi₂–Si eutectic nanoparticles protected by the SiO_x shell. FeSi₂, as a buffer phase can improve the electrochemical stability of the electrode. A SiO_x shell is formed on the surface of the nanoparticles through the passivation process. SiO_x encapsulated FeSi₂–Si eutectic nanoparticles exhibit excellent capacity of 674.9 mAh/g after 500 charge/discharge cycles. The capacity retention rate is above 90% after the stabilization process. This work provides a new nanomaterial design for high performance silicon-based anode materials of lithium-ion batteries.     

Assessment of nanoparticle loading and dispersion in polymeric materials using optical wavefront correlation

Small concentrations (≤5 wt. %) of nanoparticles in polymeric materials can potentially result in improvements in material properties and functionality. However, poor or non-uniform particle dispersion resulting in clustering (agglomeration) in polymer nanocomposites (PNCs) limits the potential for property enhancement. Achieving good dispersion is considered essential for large-scale production and commercialization of PNCs. New and effective measurement techniques capable of quantitatively characterizing particle loading and dispersion would significantly contribute towards understanding and optimizing the material performance of PNCs and, consequently, play a pivotal role in product development. This paper presents the results of a study using a static light scattering technique, optical wavefront correlation (OWC), for discriminating between different particle loadings and levels of dispersion. The technique has been applied to a range of PNCs, including epoxy resins reinforced with nanoclay platelets or silica microspheres, and zinc oxide and lithium aluminate reinforced polypropylene.     

Pt/Cu双金属纳米颗粒的制备及其催化制氢活性

采用化学共还原法合成了聚乙烯吡咯烷酮保护的Pt/Cu双金属纳米颗粒(BNPs),并采用紫外可见吸收光谱、透射电子显微镜、高分辨透射电子显微镜等对所合成的Pt/Cu BNPs进行了表征。研究了化学组成对Pt/Cu BNPs催化Na BH4水解制氢性能的影响。结果表明,所制备的Pt/Cu BNPs平均粒径为1.8~2.3nm,其催化活性远高于单金属Pt和Cu NPs的活性,其中Pt90Cu10BNP的催化活性最高,其在30℃的条件下,催化Na BH4制氢的活性可达6570mol-H2·mol-cat-1·h-1,约为相同粒径的Pt单金属NP的1.6倍。密度泛函理论的计算结果表明,Pt/Cu BNPs优异的催化性能可归因于电荷转移效应,Pt原子与Cu原子之间发生的电子转移使得Pt原子带负电而Cu原子带正电,荷电的Pt和Cu原子成为催化反应的活性中心。     

Structural,optical and magnetic properties of chromium and manganese co-doped SnO2 nanoparticles

The rutile phase Sn_0.99-xMn_xCr_0.01O₂ (x = 0.00, 0.01, 0.03, 0.05 and 0.07) nanoparticles were synthesized by facile chemical co-precipitation method using poly ethylene glycol (PEG) as a capping agent. The samples were characterized by EDAX to confirm the expected stoichiometry. The X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy analyses of these samples showed the formation of impurity free crystals with a single phase rutile type tetragonal crystal structure as that of (P4₂/mnm) of SnO₂. Optical absorption spectra and corresponding Tauc's plots showed a redshift of the absorption edge in SnO₂ after being co-doped with Cr and Mn. The samples were examined for its magnetic property using vibrating sample magnetometer which indicated that transition of magnetic signals from ferromagnetic to the paramagnetic nature with inclusion of Mn content in SnO₂: Cr host matrix. The observed magnetic behavior is well supported with the bound magnetic polarons (BMPs) model.     

X-ray absorption spectroscopy study and photocatalyst application of CuO and Cu0.9Ti0.1O nanoparticles

We report detailed investigations on the electronic structure and photocatalyst application of CuO and Cu_0.9Ti_0.1O nanoparticles (NPs). The NPs were prepared by co-precipitation method and subsequent annealing. Crystal structure and morphology of the NPs were investigated by synchrotron X-ray diffraction and high resolution transmission electron microscope, respectively. The local atomic structure around the Cu atoms was investigated by the extended X-ray absorption fine structure (EXAFS) at the Cu K-edge. Electronic structure determination was done using near edge X-ray absorption fine structure (NEXAFS) at the O K-edge, Cu L-edge, Cu K-edge and Ti L-edge. From the structural and electronic structure investigations, it is inferred that the Ti substitutes the Cu in CuO lattice without forming any secondary phases and the valence state of Cu is not affected by the Ti substitution; however the Cu – O bond length is found to be shorten in the Ti doped sample. As prepared NPs exhibit excellent photocatalyst application toward the degradation of methyl orange (MO) and potassium dichromate (PD) pollutant dyes under the visible light irradiation. The mechanism of the photodegradation of MO and PD pollutants, by the smaller sized CuO and larger sized Cu_0.9Ti_0.1O NPs, is briefly discussed.     

Electron-induced Ti-rich surface segregation on SrTiO3 nanoparticles

Atomic surface structures of nanoparticles are of interest in catalysis and other fields. Aberration-corrected HREM facilitates direct imaging of the surfaces of nanoparticles. A remaining concern of surface imaging arises from beam damage. It is important to identify the intrinsic surface structures and the ones created by electron beam irradiation in TEM. In this study, we performed aberration-corrected HREM and EELS to demonstrate that TiO and bcc type Ti islands form due to intense electron irradiation. The formation of Ti-rich islands is in agreement with previous high temperature annealing experiments on the surfaces of SrTiO₃ single crystals.     

Rhenium oxide nanoparticles – Sonochemical synthesis and integration on anode powders for solid oxide fuel cells

Rhenium oxide nanoparticles have been prepared using ultrasonication at 20 kHz. Samples characterization was committed via SEM-EDX, TEM, XRD, and Raman spectroscopy. Various experimental parameters were examined, including precursor/substrate amounts, ultrasonication intensity, and type of solvent used. Insights to the agglomeration of the prepared nanoparticles depending on the preparation parameters are given. As ultrasonic source we used either an ultrasonic probe by Sonics & Materials Inc. (20 kHz, 750 W net output) or a Bandelin SONOPULS HD 3200 ultrasound generator (20 kHz, 200 W net output) at intensities between 30 and 100 W/cm². The rhenium oxide nanoparticles haven been decorated on state-of-the-art anode materials (NiO/GDC) for solid oxide fuel cells (SOFCs) in order to prepare catalytically more active anode powders. These experiments revealed that ultrasonication intensity and solvents used are able to affect final nanoparticles size distribution and morphology. At the same time, ratio of precursor and substrate compounds amounts as well as ultrasonication intensity and duration were all found to affect the decoration loading extend of nanoformations on substrate powders. The results showing the influence of the above-mentioned parameters allowed for the quantification of the effects on the loading and the preferable sites of the decoration.     

Advanced drug delivery systems: Nanotechnology of health design A review

Nanotechnology has finally and firmly entered the realm of drug delivery. Performances of intelligent drug delivery systems are continuously improved with the purpose to maximize therapeutic activity and to minimize undesirable side-effects. This review describes the advanced drug delivery systems based on micelles, polymeric nanoparticles, and dendrimers. Polymeric carbon nanotubes and many others demonstrate a broad variety of useful properties. This review emphasizes the main requirements for developing new nanotech-nology-based drug delivery systems.     

Effects of pyrolysis temperatures on the textural,magnetic, morphology,and catalytic properties of supported nickel nanoparticles

The development of base metal catalysts for industrially important reactions continues to be an important goal of catalysis research. Herein, the effects of pyrolysis temperature on the textural, structural, surface, magnetics properties and catalytic properties of silica-supported nickel nanoparticles (NiNPs) were thoroughly investigated. Mono-dispersed NiNPs encapsulated in graphitic shells were first successfully obtained and were characterized using a variety of methods such as BET surface area measurement, CO-pulse chemisorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HR-TEM), and superconducting quantum interference device (SQUID) measurement. The findings showed that all catalysts’ properties were considerably altered with change in pyrolysis temperature. Hydrogenation of diphenylacetylene was then selected as the model reaction for the evaluation of the catalytic performance of the graphitic-shelled NiNPs. After testing, pyrolysis of a nickel at 800 °C (catalyst A) displayed tremendous activity and selectivity to produce >94% of stilbene with selectivities of 99% for the Z-isomer.