Ailing Feng

Facile synthesis and application of multi-shelled SnO2 hollow spheres in lithium ion battery

A simple template-free hydrothermal method has been developed to prepare multi-shelled SnO2 hollow spheres with controlled interior texture. The interior texture and size of the multi-shelled SnO2 hollow spheres were found to be strongly dependent on the carbon source, Sn salt precursor and molar ratio of G : M. The multi-shelled SnO2 hollow spheres exhibit good electrochemical performance as the anode material in lithium ion batteries.

The effect of modified AlN on the thermal conductivity, mechanical and thermal properties of AlN/polystyrene composites

Modified aluminum nitride particle/polystyrene (AlN/PS) composite was prepared by a powder processing technique. The thermal conductivities, dielectric and thermal properties of composites with different mass fraction of modified AlN were investigated. Compared to the pure PS, the thermally conductive properties of AlN/PS composites improved from 0.189 W (m−1 K−1) to 0.418 W (m−1 K−1) when the content of AlN was 25 wt%. The thermal stability of the AlN/PS composite was improved with the increasing addition of AlN. The dielectric constant and dielectric loss of the 25 wt% AlN/PS composite was 3.58 and 0.0036 at 106 Hz, respectively. The dielectric constant of the AlN/PS composite showed a very small variation with the range of the frequency from 102 Hz to 106 Hz. The tensile strengths of the AlN/PS composite increased with increasing filler content when it was no more than 5 wt%, and then decreased with the further increase of the filler content, whereas the elongations at break showed the similar trends. SEM analysis showed that AlN could pack tightly, and thermally conductive AlN–AlN channels could be generated with further addition of AlN. The thermal conductivity of the AlN/PS composite with the increase of AlN content tended to be higher at higher temperatures. The thermal conductivity of the AlN/PS composites at the same AlN content tended to be higher at higher temperatures. Several theoretical models were used in comparison with experimental data of the thermal conduction of the composites.

In situ synthesis and preparation of TiO2/polyimide composite containing phenolphthalein functional group

In this paper, titanium dioxide (TiO2)/phenolphthalein-type polyimide (PPPI) composite was synthesized in situ polymerization, the diamino phenolphthalein type compound and dimethylacetamide as the matrix, and TiO2 as the filler. The mechanical property and thermal conductivity properties were used to characterize the properties of the obtained composite. A diamine monomer containing more benzene rings of phenolphthalein and an ether bond in its main chain were prepared, synthesized by a nucleophilic substitution reaction and a hydrazine hydrate reduction reaction. Polyimide composite had the same structure as that of a diamine monomer. And it was synthesized by solution imidization and heat imidization. The results showed that TiO2 improved the dispersibility, alignment and interfacial strength of the TiO2/PPPI composite. The mechanical property of polyimide composite was increased with the increasing TiO2 loading. And a suitable addition of TiO2 could enhance the mechanical properties of polyimide system. Compared to polyimide resin, the TiO2/PPPI composite had a higher thermal conductivity with the increasing of TiO2 content. All of these changes in properties were closely correlated with the TiO2/PPPI composite, which could form an interaction interface structure in the system.

The effect of bis allyl benzoxazine on the thermal, mechanical and dielectric properties of bismaleimide–cyanate blend polymers

Thermosetting terpolymers composed of bis allyl benzoxazine (Bz-allyl), cyanate ester (BADCy) and 4,4′-bismaleimidodiphenyl methane (BMI) were prepared via co-curing reactions. The curing kinetics of Bz-allyl/BMI/BADCy were investigated via non-isothermal DSC at different heating rates using the Flynn–Wall–Ozawa method. The dielectric, thermal and mechanical properties of Bz-allyl/BMI/BADCy terpolymers were systemically investigated in detail through mechanical measurement, scanning electron microscopy (SEM), dynamic mechanical analysis (DMA) and thermo-gravimetric analysis (TGA). The results show that a suitable addition of Bz-allyl can enhance the impact strength and flexural strength as well as reduce the dielectric constant and the dielectric loss of BMI/BADCy. The dynamic mechanical analysis reveals that the cross-link density of the blend is higher than BMI/BADCy. The higher crosslinking density of the terpolymer led to good thermal stability of the terpolymer. Scanning electron microscopy analysis shows the distinct characteristics of ductile fracture of the blends. All of these changes in properties are closely correlated to the copolymerization between Bz-allyl and BMI/BADCy, which could form an interpenetrating polymer network in the system.

Synthesis, characterization, and thermal properties of benzoxazine monomers containing allyl groups

The polymerization mechanism of allyl-functional benzoxazine (Bz) monomers is reported in this article. Following the traditional route of Bz synthesis, a series of monofunctional Bz monomers were synthesized via allylamine and amine condensation reaction with 2,2′-diallyl bisphenol-A and paraformaldehyde. Resulting chemical structures of the synthesized monomers were confirmed by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance analyses. The polymerization behavior of the prepared allyl-functional monomers was studied using differential scanning calorimetry and FTIR. Three reactions were observed in the curing process: polymerization reaction of N-allyl groups in the oxazine ring, ring-opening polymerization of Bz, and polymerization reaction of allyl groups in benzene. Compared to a typical polybenzoxazine (PBz), higher cross-linking density in PBz-allyl-2 leads to a higher glass transition temperature and 5% weight loss temperature, which indicates improved thermal stability in PBz-allyl-2 as well as superior thermal conductivity compared to 2,2′-bis(3-phenyl-3,4-dihydro-2H-1,3-benzoxazinyl)propane. Data on dielectric properties also show that PBz-allyl-2 outperforms typical PBzs. This work focuses on the manipulation of Bz monomer structures to alter their ring-opening polymerization mechanism, as well as cross-linking, in order to derive a PBz with improved properties.