Advanced Materials Research Vol. 709

Abstract: A novel nanocomposite (MB/CRG) was fabricated by a simple and fast method. The method is as follows: graphene oxide (GO) was dispersed in methylene blue (MB), and then the MB/GO was chemically reduced to MB/chemically reduced graphene (MB/CRG) by hydrazine hydrate. MB can greatly improves the dispersity of CRG in water and at the same time, the electrochemical activity of MB/CRG nanocomposite increased. The MB/CRG nanocomposite was used to modify the glass carbon electrode (GCE), and the MB/CRG/GCE was obtained. We investigated the electrochemical behavior of uric acid, NaNO₂, Quercetin and p-nitrophenol at MB/CRG/GCE and found that the modified electrode had the best catalysis towards these molecules compared with MB/GCE and CRG/GCE. The MB/CRG/GCE showed good reproducibility and stability.

Abstract: A low temperature (130 °C) hydrothermal method was proposed for the synthesis of SnO2-SnS2 nanocomposite. The composition, structure and optical property of the as-synthesized SnO2-SnS2 nanocomposite were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy and UV-vis diffuse reflectance spectra, and its photocatalytic activity was tested by the reduction of Cr(VI) in water under visible light (λ > 420 nm) irradiation. It was found that the as-synthesized SnO2-SnS2 nanocomposite exhibited high photocatalytic activity in the reduction of Cr(VI) in water under visible light (λ > 420 nm) irradiation, whereas SnO2 nanoparticles displayed no photocatalytic activity in the reduction of Cr(VI) in water under visible light (λ > 420 nm) irradiation.

Abstract: Palladium hollow spheres were synthesized at room temperature using cobalt nanoparticles (NPs) as sacrificing templates. Cobalt NPs can be prepared simply by solvothermal method. The hollow nature of sample Pd were observed from the TEM image and the SAED pattern indicates the polycrystalline nature of the sample. It was found that Pd hollow spheres showed high catalytic activity towards the electrooxidation of alcohols, especially ethanol with the current density up to 2047 mA•mg^-1. The formation mechanism and the structure-property relationship of Pd hollow spheres were discussed based on the experimental results.

Abstract: Highly crystalline FeWO₄ nanoparticles (NPs) were synthesized via the hydrothermal synthesis method while amorphous FeWO₄ NPs were prepared by the room temperature precipitation method. It was found that a dissolution-recrystallization process appeared due to the Ostwald ripening when room temperature precipitates undergo the hydrothermal process. Photocatalytic performance toward the degradation of methylene blue showed that crystalline FeWO₄ NPs displayed a higher activity than amorphous samples, mainly ascribing to the substantial elimination of defects after crystallization because the defects promoted the recombination of electron-hole pairs.

Abstract: For different requirements of particle size of syhthesizing nanoparticles, five practical chemical methods have been introduced including two phase method, homogeneous phase method and seeding growth method and so on. And detailed explanation on the experimental operation methods has been given.

Abstract: The apparent activation energy for densification is a characteristic quantity that elucidates the fundamental diffusion mechanisms during the sintering process. Based on the Arrhenius theory, the activation energy for densification of the pure and La doped α-Al₂O₃ at constant heating-rates sintering has been estimated. Sintering of α-Al₂O₃ and La doped powder has been executed by the way of a push rod type dilatometer. It was shown that the shrinkage and the relative density of the samples decreased with increasing heating rates. At the same sintering condition, the shrinkage of the pure α-Al₂O₃ was higher than that of the La doped. According to the calculation, it was found that the apparent activation energy had a single value and did not depend on the relative density for both samples. The apparent activation energy of the pure α-Al₂O₃ was 374.3kJ/mol, which was lower than that of La doped (966.5kJ/mol). So the densification process for α-Al₂O₃ was retarded due to La doping, which was consistent with experimental results of the shrinkage.

Abstract: Starting with boric acid and triethanolamine , the effect of the different types of the water-carrying agent on the yield was invested, and influences of dosage of water-carrying agent ,the mole ratio of reactants, reaction time on yield were discussed, the optimized reaction conditions were confirmed. The structure of the product was described by Fourier transform-infrared (FT-IR) spectroscopy, NMR Spectroscopy analysis, mass spectrometry (MS) and thermodynamic properties was analyzed by differential scanning calorimetry (DSC) and thermogravimetry (TG).

Abstract: Hydrophobic flexible silica aerogels felts were fabricated successfully by two-steps sol-gel process via ambient pressure drying. First of all, the sol with various pH values was obtained from tetraethylorthosilicate (TEOS) as silicon source, hydrochloric acid/aqueous ammonia ethanol solution as catalysts. Then glass fiber felts was incorporated into the sol to increase the mechanical properties of silica aerogel. After the completion of solvent exchange and surface modification by using trimethylchlorosilane (TMCS)/n-hexane solution, the gel felts were dried under ambient pressure. The samples show excellent hydrophobic properties.

Abstract: 4-dimethylamino-N-methyl -4-stilbazolium tosylate(DAST) was synthesized by the condensation and ion exchange reaction of 4-methyl-N-methyl pyridinium tosylate, 4-N,N-dimethylamino -benzaldehyde and silver p-toluenesulfonate, the reaction procedure was easy with high efficiency. The purity of the product was further improved by successive abstersion and recrystallization. The powder was investigated by Fourier transform infrared spectrum, nuclear magnetic resonance and elemental analysis. The results showed that the quality of the powder as crystal raw material was very high, the product could meet the requirements for crystal growth, the procedure of washing the product by chloroform was important to achieve the high quality.