Advanced Materials Research Vols. 284-286

Abstract: In this paper, three kinds of morphologies of ZnO crystals including particle-based lotus-like, hexagonal bipod-like (dumbbell-like) and rod-based chrysanthemum-like microstructures were controllably synthesized by using simple zinc salts (Zn(CH₃COO)₂·2H₂O, ZnSO₄·7H₂O and Zn(NO₃)₂·6H₂O) and ethanolamine as raw materials in microwave-assisted aqueous solution. The crystal structure, composition and morphology of the as-prepared products are characterized by X-ray diffraction (XRD), energy dispersive X-ray spectrometry(EDX), field-emission scanning electron microscopy(FESEM). It was found that anion of zinc salt is a dominative factor in determining the morphology of the obtained ZnO crystals. The possible formation mechanism of ZnO microstructures was simply discussed.

Abstract: In this paper, we reported a facile microwave-assisted green chemical route to prepare pure, uniform, and monodispersed Cu₂O octahedron wrapped by the {111} faces by using glucose as a reducing agent. X-ray diffraction (XRD), energy dispersive X-ray spectrometry(EDX) and field emission scanning electron microscopy (FESEM) were used to characterize the as-synthesized products. It was found that the morphology and structure of Cu₂O crystals were greatly affected by the concentration of NaOH. A solid-solution-solid growth mechanism was possibly proposed on the basis of the comparative experimental results.

Abstract: A facile solution-chemical route was reported to deposit and arrange palladium (Pd) nanoparticles on single-walled carbon nanotubes (SWCNTs) using sodium dodecyl sulfate (SDS) as an organic soft template. SDS was previously formed supramolecular self-assembly on the walls of SWCNTs, which may act as adsorption sites of Pd (II) ions on SWCNTs. The Pd nanoparticles reduced by photo-reduction and formed one-dimensionally ordered arrangement on the surface of SWCNTs with a veriety of helices and tilted angles. Pd nanoparticles have an average size of 3 nm. The structure (distance, helix and tilted angle) of the ordered arrangements were determined by the supramolecular self-assembly of SDS wrapped on SWCNTs.

Abstract: A novel mechanochemical approach to produce sophisticated carbon nanomaterials is reported. It is demonstrated that carbon nanostructures such as carbon nanotubes and carbon onions are synthesized by high-speed ball-milling of steel balls. It is considered that the gas-phase reaction takes place around the surface of steel balls under local high temperatures induced by the collision energy in ball-milling process, which results in phase separated unique carbon nanomaterials.

Abstract: With zinc acetate used as raw material and polyethylene glycol employed as dispersant, ultrafine ZnO flower-like powder was successfully synthesized by hydrothermal method using NaOH and NH₃·H₂O as precipitants. The influences of the precipitants on the morphology of the ZnO powder were discussed. The as-synthesized ZnO flower-like powder was composed of lots of microrods with hexagon figure. The ZnO flower-like structures synthesized using NaOH were more regular and uniform than that obtained using NH₃·H₂O. The ZnO flower-like powder was hexagonal wurtzite structure with high purity. The exciton absorptions of the two ZnO flower-like powder both appeared at 300 nm in UV-VIS spectrum.

Abstract: Attapulgite(AT) was modified by grafting with butyl acrylate(BA) via polymerizations initiated by Gamma radiation. The polypropylene(PP)/AT nanocomposites were synthesized via melting extrude in a twin-screw extruder. The thermogravimetry(TG) and scanning electron microscopy (SEM) were used to assess the graft ratio of the hybrid materials and the dispersion of AT, respectively. Step-scan differential scanning calorimetry(SSDSC) was used to study the influence of AT on the crystallization and subsequent melting behavior. The results indicated that PP and PP/AT nanocomposites underwent multiple melting and secondary crystallization processes during heating. The melting behaviours of PP and PP/AT nanocomposites varied with the variation of crystallization temperature and AT content.

Abstract: The block copolymer of PSt-b-POEOMA with the end of -COOH functional group has been synthesized by reversible addition fragmentation chain-transfer (RAFT) using S,S′-Bis(α,α′-dimethyl-α′′-acetic acid)-trithiocarbonate (BDATC) as a chain transfer agent. The architectures of the copolymers were confirmed by FT-IR and ¹HNMR spectra. GPC analysis was used to estimate the molecular weight and the molecular weight distribution of the copolymers. Meanwhile, The nanostructures of the block copolymers PSt-b-POEOMA micelles formed in aqueous solution were observed by transmission electron microscopy (TEM) and dynamic light scattering (DLS).

Abstract: CeO₂ nanoparticles with diameter of about 5 nm were prepared by batch supercritical hydrothermal synthesis method at 390 °C without additional treatment. It was found that the characteristics of products depended on the pH value, reactant concentration (C₀), and reaction temperature. The reaction time and coexisting cations (Li⁺, Na⁺ and K⁺) had little effect on the size and morphology of CeO₂ particles. Uniform CeO₂ nanoparticles were synthesized at 390 °C, pH = 9 and C₀ = 0.06 M. The mechanism for batch supercritical hydrothermal synthesis of CeO₂ nanoparticles is discussed.

Abstract: ZnO were rapidly synthesized using different zinc salts (Zn(NO₃)₂, Zn(CH₃CO₂)₂, ZnCl₂ and ZnSO₄) by an aqueous solution method at 90°C. The products were characterized by X-ray diffractometry and scanning electron microscopy. The results show that the anions have remarkable effects on the morphologies of ZnO. When Zn(NO₃)₂, Zn(CH₃CO₂)₂ or ZnCl₂ was used, ZnO was obtained with ellipsoidal, under-developed ellipsoidal and nano-particles morphologies, respectively. In the case of ZnSO₄, layered basic zinc sulfate was obtained. The remarkable effects of anions on ZnO can be ascribed to the adsorption of the anions on the surface of ZnO, which hinders the further growth of ZnO nuclei. The effect of SO₄^2- was further investigated by changing the mole ratio of SO₄^2- to NO₃^-.

Abstract: Agriculture wastes-- wheat straw is used as raw material to take place of cotton and wood pulp in this research. In order to separating of the crude cellulose, non-polluting ethanol/acetic acid binary solvent system is utilized to dissolve lignin. Then pure cellulose is obtained by refining processing. Finally, microcrystalline cellulose is obtained by acid hydrolysis, grinding and the subsequent process. The paper focuses on the effect of the dosage of acetic acid in the binary solvent system on separating efficiency of wheat straw cellulose, and analyzing the effects of acetic acid dosage on kappa number, yield, α-cellulose content and crystallinity of the wheat straw crude cellulose. The results indicated that acetic acid can promote the removal of lignin and hemicellulose degradation, and is conducive to improve the purity of crude fiber. The lignin removed mainly adsorbed and deposited onto the surface of crude cellulose. The optimum dosage of acetic acid in the thermal decomposition system of wheat straw is 2%. Under the optimum condition, the crystallinity of crude cellulose is the highest, the yield and α-cellulose content are both rather high, but a low Kappa number.