Lianjun Wang

Amorphous TiO2 Shells: A Vital Elastic Buffering Layer on Silicon Nanoparticles for High‐Performance and Safe Lithium Storage

Smart surface coatings of silicon (Si) nanoparticles are shown to be good examples for dramatically improving the cyclability of lithium-ion batteries. Most coating materials, however, face significant challenges, including a low initial Coulombic efficiency, tedious processing, and safety assessment. In this study, a facile sol-gel strategy is demonstrated to synthesize commercial Si nanoparticles encapsulated by amorphous titanium oxide (TiO2 ), with core-shell structures, which show greatly superior electrochemical performance and high-safety lithium storage. The amorphous TiO2 shell (≈3 nm) shows elastic behavior during lithium discharging and charging processes, maintaining high structural integrity. Interestingly, it is found that the amorphous TiO2 shells offer superior buffering properties compared to crystalline TiO2 layers for unprecedented cycling stability. Moreover, accelerating rate calorimetry testing reveals that the TiO2 -encapsulated Si nanoparticles are safer than conventional carbon-coated Si-based anodes.

Preparation and thermoelectric properties of multi-walled carbon nanotube/polyaniline hybrid nanocomposites

In this work, a facile strategy for the fabrication of PANI/multi-walled carbon nanotube (MWCNT) nanocomposites without the assistance of a dispersant is introduced. MWCNTs and polyaniline were homogeneously mixed by cryogenic grinding (CG) and then consolidated via Spark Plasma Sintering (SPS). X-ray power diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and field-emission scanning electron microscopy (FESEM) were employed to characterize the as-prepared composites. The XRD results showed that cryogenic grinding can refine the grain size of PANI and induce more dislocations. The FTIR spectra data showed that the peaks of the PANI/MWNT composites displayed a red shift. In the high resolution FESEM image, the layer-by-layer structure and smooth surface can be observed. The thermoelectric properties of the as-prepared nanocomposites were investigated as a function of MWCNT content. The results showed that the electrical conductivity increased remarkably with the increasing MWCNT content, and the maximum power factor was 10.73 × 10−8 W mK−2, higher than pure PANI. Additionally, as the MWNT content increased from 10% to 30%, the electrical conductivity of the PANI/MWNT composite increased from 3.51 S m−1 to 1.59 × 102 S m−1. This work demonstrates a simple and effective method for improving the dispersity of carbon nanotubes and the thermoelectric properties of conducting polymers.

A Micelle Fusion–Aggregation Assembly Approach to Mesoporous Carbon Materials with Rich Active Sites for Ultrasensitive Ammonia Sensing

Nanostructured carbon materials have received considerable attention due to their special physicochemical properties. Herein, ordered mesoporous carbons (OMCs) with two-dimension (2D) hexagonal mesostructure and unique buckled large mesopores have successfully been synthesized via a micelle fusion-aggregation assembly method by using poly(ethylene oxide)-block-polystyrene (PEO-b-PS) diblock copolymers as a template and resorcinol-based phenolic resin as a carbon precursor. The obtained ordered mesoporous carbons possess unique fiber-like morphology, specific surface area of 571-880 m(2)/g, pore volume of 0.54 cm(3)/g and large mesopores (up to 36.3 nm) and high density of active sites (i.e., carboxylic groups) of 0.188/nm(2). Gas sensor based on the ordered mesoporous carbons exhibits an excellent performance in sensing NH3 at a low temperature with fast response (<2 min), ultralow limit of detection (<1 ppm), and good selectivity, due to the large pore sizes, high surface area and rich active sites in the carbon pore walls.

One-pot fabrication and thermoelectric properties of Ag nanoparticles–polyaniline hybrid nanocomposites

In this context, a one-pot and in situ strategy for fabrication of AgNPs (Ag nanoparticles)/PANI (polyaniline) nanocomposites in a micellar solution of dodecylbenzene sulfonic acid (DBSA, anionic surfactant) is introduced. Guided by this strategy, AgNPs were directly synthesized from silver nitrate. AgNPs/PANI hybrid nanocomposites with AgNPs were consolidated via spark plasma sintering (SPS). The phase structure and microstructure of the as-prepared composites were evaluated by several characterizations, and the growth mechanism of AgNPs was speculated. The thermoelectric properties of the samples with increasing silver nitrate content were systematically investigated. Compared with pure bulk PANI, the thermoelectric performance of AgNPs/PANI hybrid nanocomposites exhibits a distinct enhancement on the addition of AgNPs. The Seebeck coefficient (S) decreased slightly while the electric conductivity (σ) was found to increase remarkably. However, thermal conductivity (κ) remained unchanged with increasing silver nitrate content, which resulted in an obvious enhancement in the figure of merit (ZT) of the composites. Consequently, the maximum ZT of the AgNPs/PANI hybrid nanocomposites amazingly reached 5.73 × 10−5, which is about 3.8 times of the ZT of the pure PANI (1.503 × 10−5). This study suggests that the hybridization of organic/low-dimensional metal particles is promising to effectively improve the thermoelectric properties of conducting polymers.

Third-order nonlinear optical vitreous material derived from mesoporous silica incorporated with Au nanoparticles

Mesoporous silica SBA-15 encapsulated with Au nanoparticles was consolidated by spark plasma sintering. It turned out to be an original and facile preparation route for incorporating Au nanoparticles in silica glass. The incorporation of Au nanoparticles in a silica glass matrix made the obtained glass coloured dark wine-red due to the surface plasmon resonance effect of Au nanoparticles, although the concentration of Au nanoparticles was extremely low (about 0.05 wt%). Besides, the Z-scan method using a femtosecond laser pulse was employed to measure the nonlinear optical property of this mesoporous composite-derived glass, which exhibited self-focusing feature at 720 nm with saturable absorption. The third-order nonlinear refraction index n2 and absorption coefficient β were 1.74 × 10−18 m2 W−1 and −5.72 × 10−12 m W−1, respectively. We believe that this approach could be extended to disperse other metal or semiconductor nanoparticles in a glass matrix.

Hierarchical ordered macro/mesoporous titania with a highly interconnected porous structure for efficient photocatalysis

In this study, a 3-dimensional interconnected hierarchical ordered macro/mesoporous titania (HOPT) with thin walls, crystalline framework, large cavities (∼420 nm), uniform mesopores (3.7 nm) and high surface area (177 m2 g−1) was synthesized through a facile bi-template interface-directed deposition method using poly(propylene oxide)-block-poly(ethylene oxide)-block-poly(propylene oxide) (Pluronic P123) triblock polymer as a soft template and structure directing agent, titanium isopropoxide (TIPO) as a titania source and 3-dimensional ordered macroporous carbon (3DOMC) as the hard template and the nanoreactor. This was followed with a two-step thermal treatment in nitrogen and air. Under simulated sunlight irradiation at room temperature, the HOPT shows an ultrahigh photocatalytic activity for the degradation of Rhodamine B (RhB) with a fast reaction rate that is three times higher than commercial titania nanoparticles (P25).

Effects of Polarization on Mechanical Properties of Lead Zirconate Titanate Ceramics Evaluated by Modified Small Punch Tests

Pb(Zr,Ti)O3 (PZT) ceramics were prepared by the conventional mixed oxide method, and the strength of the resultant PZT ceramics was evaluated using modified small punch (MSP) tests. Load–displacement curve test results showed that the crack-initiation and fracture strengths of PZT ceramics decreased after polarization. The effect of the polarization accelerated the fatigue properties of PZT ceramics. Scanning electron microscopy (SEM) results showed that microcracks were formed before the maximum load in the MSP test, and the first load drop corresponded to crack initiation.

Synthesis of Bi0.5Sb1.5Te3/Graphene Composite Powders

In this paper, Bi0.5Sb1.5Te3/graphene composite powders were prepared by hydrothermal synthesis method. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were used to characterize the morphology and structure of the composite powders. As a nanocomposite phase, graphene provided plenty of charge carriers and active sites for nucleation of Bi0.5Sb1.5Te3 grains. Bi0.5Sb1.5Te3 particles aggregated and attached to the surfaces of graphene randomly. In addition, it was found that the sizes of Bi0.5Sb1.5Te3 particles varied with different content of graphene. The formation mechanism of Bi0.5Sb1.5Te3/graphene composite powders was discussed.