Yaqin Fu

Facile Synthesis of BaTiO3 Nanotubes and Their Microwave Absorption Properties

Uniform BaTiO(3) nanotubes were synthesized via a simple wet chemical route at low temperature (50 °C). The as-synthesized BaTiO(3) nanotubes were characterized using powder X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The results show that the BaTiO(3) nanotubes formed a cubic phase with an average diameter of ~10 nm and wall thickness of 3 nm at room temperature. The composition of the mixed solvent (ethanol and deionized water) was a key factor in the formation of these nanotubes; we discuss possible synthetic mechanisms. The microwave absorption properties of the BaTiO(3) nanotubes were studied at microwave frequencies between 0.5 and 15 GHz. The minimum reflection loss of the BaTiO(3) nanotubes/paraffin wax composite (BaTiO(3) nanotubes weight fraction = 70%) reached 21.8 dB (~99.99% absorption) at 15 GHz, and the frequency bandwidth less than -10 dB is from 13.3 to 15 GHz. The excellent absorption property of BaTiO(3) nanotubes at high frequency indicates that these nanotubes could be promising microwave-absorbing materials.

Facile fabrication of AgNPs/(PVA/PEI) nanofibers: High electrochemical efficiency and durability for biosensors

A novel, facile and green approach for the fabrication of H2O2, glutathione (GSH) and glucose detection biosensor using water-stable PVA and PVA/PEI nanofibers decorated with AgNPs by combining an in situ reduction approach and electrospinning technique has been demonstrated. Small, uniform and well-dispersed AgNPs embedded in the PVA nanofibers and immobilized on functionalized PVA/PEI nanofibers indicate the highly sensitive detection of H2O2 with a detection limit of 5 μM and exhibit a fast response, broad linear range, low detection limit and excellent stability and reusability.

One-dimensional barium titanate coated multi-walled carbon nanotube heterostructures: synthesis and electromagnetic absorption properties

One-dimensional barium titanate (BaTiO3)@multi-walled carbon nanotube (MWCNT) core–shell heterostructure composites are prepared via a sol–gel route combined with a thermal treatment process. Field emission scanning electron microscopy and transmission electron microscopy measurements show that the BaTiO3@MWCNT core–shell heterostructure composites have a BaTiO3 film thickness of ∼10 nm, and that the BaTiO3 film uniformly encapsulates the surface of the MWCNT core. The measured electromagnetic parameters show that the BaTiO3@MWCNT composites exhibit remarkable and improved electromagnetic wave absorption properties, compared to both pristine MWCNTs and BaTiO3. Notably, more than 99% of electromagnetic wave energy can be attenuated by the BaTiO3@MWCNT composites with the addition of only 40 wt% in the paraffin matrix. In addition, the microwave absorption mechanism of the BaTiO3@MWCNT core–shell heterostructure composites is proposed. The various polarizations including dielectric and interfacial polarization which originate from the heterogeneous structures and interfaces in the composites are responsible for their excellent microwave absorbing performances.

The design and construction of 3D rose-petal-shaped MoS2 hierarchical nanostructures with structure-sensitive properties

Rose-petal-shaped MoS2 hierarchical nanostructures were designed and constructed using carbonized electrospun nanofibers as a template, which exhibit highly structure-sensitive properties for the hydrogen evolution reaction (HER). We first synthesized carbon nanofiber (CNF) mats by combining the electrospinning and carbonization processes, and then the CNF mats were used as a substrate for the direct growth of MoS2 nanocrystals via the CVD method. By controlling the MoS2 morphology at the nanoscale, we constructed evolutions in the structures and preferentially exposed more catalytically active edge sites, enabling improved performance for electrochemical catalytic activity. Because of their highly exposed edges and excellent chemical and electrical coupling to the underlying CNFs, MoS2–CNF fiber mats exhibited excellent HER activity with a small overpotential of ∼0.12 V and a small Tafel slope of 45 mV per decade. Our findings provide a feasible way to design and engineer advanced nanostructures for catalysis, electronic devices, and other potential applications.

Use of TX100-dangled epoxy as a reactive noncovalent dispersant of vapor-grown carbon nanofibers in an aqueous solution.

The dispersion of carbon nanotubes (CNTs) into individual particles or small bundles has remained a vexing problem that limits the use of the excellent properties of CNTs in composite applications. Noncovalent functionalization is an attractive option for changing the interfacial properties of nanotubes because it does not destroy the nanotube grapheme structure. In this study, a new reactive copolymer, epoxy-toluene diisocyanate-Triton X-100 (EP-TDI-TX100) was successfully synthesized, which is shown to be highly effective in dispersing vapor-grown carbon nanofibers (VGCNFs) into individual or small bundles, as evidenced by transmission electron microscopy (TEM) and UV-vis absorption spectra. The strong π-π interaction between VGCNFs and EP-TDI-TX100 was revealed by Raman spectra and the covalent reaction between curing agent was confirmed via Fourier transform infrared spectroscopy. For an effective dispersion, the optimum weight ratio of EP-TDI-TX100 to VGCNFs is 2:1. The maximum VGCNF concentration that can be homogeneously dispersed in an aqueous solution is approximately 0.64 mg/mL. The EP-TDI-TX100 molecules are adsorbed on the VGCNF surface and prevent reaggregation of VGCNFs, so that a colloidal stability of VGCNF dispersion can be maintained for 6 months.

Epoxy resin composite bilayers with triple-shape memory effect

Triple-shape memory epoxy composites with bilayer structures of well-separated glass transition temperatures have been successfully prepared. The different glass transition temperatures of the epoxy composites were obtained by physically incorporating various amounts of nanosilica particles, which were introduced into the epoxy by utilizing polyethylene glycol. A scanning electron microscope and a transmission electron microscope were used to analyze the dispersibility of the nanosilica particles. The effects of nanosilica particles on the mechanical properties as well as on the dual-shape memory effects (DSME) and triple-shape memory effects (TSME) of the nanocomposites were studied. The nanosilica particles were homogenously dispersed in the matrix and well incorporated into the epoxy matrix. The resulting nanocomposites exhibited excellent TSME, and their shape fixity properties were significantly improved by nanosilica particles.

Effect of shear thickening fluid on the sound insulation properties of textiles

A shear thickening fluid (STF) was prepared from SiO2/PEG200 by ball-milling and its effect on the sound insulation properties of textile materials investigated. The rheological properties of the STF were evaluated using a high-speed rotary rheometer and a field emission scanning electron microscope. Fabrics based on fibers of profiled cross-section were knitted on a computerized flat knitting machine, then dipped in the diluted STF and the microstructure and the sound insulating properties of the STF-treated fabrics were established using a two-channel acoustic analyzer. It was found that an increase in the SiO2 content of the STF decreased the critical shear rate, and the thickening effect of the STF system became effective once the SiO2 content reached 30 wt%. The sound insulation performance of the STF-treated fabrics was superior to that of the untreated fabrics, and their level of sound insulation level was particularly increased with increasing surface density.

Two-way shape memory behavior of semi-crystalline elastomer under stress-free condition

Semi-crystalline shape memory polymers exhibit two-way shape memory effect (2W-SME) under constant stresses through crystallization-induced elongation upon cooling and melting-induced constriction upon heating. The applied constant stress influenced the prediction and usability of 2W-SME in practical applications without any external force. Here the reversible shape transition in EVA-shaped memory polymer was quantitative analyzed under a suitable temperature range and external stress-free condition. The fraction of reversible strain increased with increasing upper temperature (T high) within the temperature range and reached the maximum value of 13.62% at 70 °C. However, reversible strain transition was almost lost when T high exceeded 80 °C because of complete melting of crystalline scaffold, known as the latent recrystallization template. The non-isothermal annealing of EVA 2W-SMP under changing circulating temperatures was confirmed. Moreover, the orientation of crystallization was retained at high temperatures. These findings may contribute to design an appropriate shape memory protocol based on application-specific requirements.

Effect of TW-ZnO/SiO2-compounded shear thickening fluid on the sound insulation property of glass fiber fabric

A novel sound insulation composite was successfully fabricated by modifying glass fiber fabric with tetrapod ZnO whisker (TW-ZnO)/SiO2-compounded shear thickening fluid (STF). The rheological properties of the compounded STF were evaluated using a high-speed rotational rheometer. The microstructure and sound-insulating properties of the STF-treated glass fiber fabric (STF-fabric) were characterized using a scanning electron microscope and a two-channel acoustic analyzer, respectively. The shear thickening effect of TW-ZnO/SiO2-compounded STF can be better than that of SiO2-monodispersed STF. The sound insulation performance of the STF-fabric, which was superior to that of the original fabric, was related to the fabric weaving structure and shear thickening effect of the compounded STF.

Nanostructured Barium Titanate/Carbon Nanotubes Incorporated Polyaniline as Synergistic Electromagnetic Wave Absorbers

The three-dimensional 3D conductive network structures formed by barium titanate/carbon nanotubes incorporated polyaniline were favorable for strengthening electromagnetic absorption capability. Herein, an easy and flexible method consisting of sol-gel technique, in situ polymerization, and subsequent mechanical method have been developed to prepare the barium titanate/carbon nanotubes incorporated polyaniline CNTs/BaTiO3/PANI or CBP ternary composites. The dielectric properties and microwave absorption properties of CNTs/BaTiO3/PANI composites were investigated in the frequency range of 2–18 GHz by vector network analyzer. Interestingly, it is found that the CNTs/BaTiO3/PANI composites with 3D conductive network structures presented outstanding electromagnetic absorption properties, which may be attributed to the high impedance matching behavior and improved dielectric loss ability and novel synergistic effect. Additionally, it also can be supposed that the “geometrical effect” of composite was more beneficial to absorbing the incident electromagnetic wave. The CNTs/BaTiO3/PANI composite the mass ratio of CNTs/BaTiO3 to PANI is 2 : 3 exhibits the best microwave absorption properties, of which the minimum reflection loss value can reach −30.9 dB at 8 GHz and the absorption bandwidth with a reflection loss blew −10 dB ranges from 7.5 to 10.2 GHz.