Roos Peeters

Hydrothermal synthesis of ZnO nanorods: a statistical determination of the significant parameters in view of reducing the diameter

In this paper a 2(8-4) fractional factorial design of experiments is applied to identify the important parameters that affect the average diameter of ZnO rods, synthesized by means of a hydrothermal procedure. A water-based Zn(2+) precursor is used for the formation of one-dimensional ZnO particles, without the presence of an organic additive. Results indicate that, at the investigated levels, four of the parameters have a significant effect on the mean diameter. These are the temperature, the heating rate, stirring and an ultrasonic pre-treatment of the precursor solution. Experiments carried out with zinc acetate and zinc chloride do not show a significant difference in rod diameter. Other parameters that do not show a significant effect are the concentration of Zn(2+), the molar ratio between the hydroxyl and the zinc ions, and the reaction time. Interactions are observed between stirring and an ultrasonic pre-treatment and between the zinc concentration and the OH:Zn ratio. By fixing the significant factors at their optimal value it is possible to decrease the mean diameter. The particles are characterized by means of x-ray diffraction (XRD) and transmission electron microscopy (TEM).

Comparison of two novel solution-based routes for the synthesis of equiaxed ZnO nanoparticles

Due to a dominant one-dimensional growth rate, nanoparticles of zinc oxide often show a rodlike morphology. As a result, the synthesis of small spherical nanoparticles of undoped ZnO remains challenging. This paper presents two procedures that successfully produce a powder consisting of equiaxed zinc oxide nanoparticles: one using a polyethylene glycol- (PEG-) assisted solvothermal method and the other by calcination of zinc oxalate obtained from a microemulsion-mediated method. In the latter, zinc-substituted aerosol OT (AOT) is used as a surfactant. The samples are characterized by inductively coupled plasma-atomic emission spectroscopy (ICP-AES), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), photon correlation spectroscopy (PCS), and photoluminescence (PL) spectroscopy. Both synthesis techniques produce nanoparticles with similar sizes in the range of 10 to 20 nm. Dense aggregates observed in the calcined powder are infrequent in the case of the solvothermal method.

Recent updates on the barrier properties of ethylene vinyl alcohol copolymer (EVOH): A review

ABSTRACT The gas barrier properties of ethylene vinyl alcohol copolymer (EVOH) against oxygen, carbon dioxide and water vapor have been widely investigated in relation to different material characteristics, environmental conditions and new processing technologies. Recently, EVOH is gaining more attention as a barrier material against other gases and organic substances such as aromas, flavors, fuels, chemicals (e.g., BTEX), and as a functional barrier, e.g., to avoid mineral oil migration. This review contains an update on permeability data of EVOH emphasizing its potential as a barrier material for new and versatile applications in food and pharmaceutical packaging, agriculture, construction, automotive, etc.