Sol–gel synthesized zinc oxide nanorods and their structural and optical investigation for optoelectronic application

Nanostructured zinc oxide (ZnO) nanorods (NRs) with hexagonal wurtzite structures were synthesized using an easy and low-cost bottom-up hydrothermal growth technique. ZnO thin films were prepared with the use of four different solvents, namely, methanol, ethanol, isopropanol, and 2-methoxyethanol, and then used as seed layer templates for the subsequent growth of the ZnO NRs. The influences of the different solvents on the structural and optical properties were investigated through scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, and photoluminescence. The obtained X-ray diffraction patterns showed that the synthesized ZnO NRs were single crystals and exhibited a preferred orientation along the (002) plane. In addition, the calculated results from the specific models of the refractive index are consistent with the experimental data. The ZnO NRs that grew from the 2-methoxyethanol seeded layer exhibited the smallest grain size (39.18 nm), largest diffracted intensities on the (002) plane, and highest bandgap (3.21 eV).     

The Effect of Particle Size Distribution on Pressure Drop through Packed Beds of Cooked Wood Chips

The pressure drop of process liquors through columns of wood chips determines the operability, efficiency and control of both batch and continuous pulp digesters and the quality of the pulp produced from them. Pressure drop was measured through columns of industrial white spruce chips (produced with a chipping head‐rig) as a function of the chip size distribution and the extent of delignification. Flow resistance depended on the porosity of the chip bed which was affected by the kappa number of the chips (which affected their flexibility) and chip size distribution, the compaction forces applied to the column, and the liquid superficial velocity. The chip beds were compressible and inelastic. Previous work from the literature using the Ergun equation to characterize pressure losses through chip beds is examined and compared with results of this work.     

<Emphasis Type="Italic">In-situ</Emphasis> TEM observations of the coarsening of a nanolamellar structure in a cobalt based magnetic alloy

The thermal stability and coarsening of nanostructures is of both scientific interest and of engineering significance in order to produce thermally stable nanomaterials. Real time observations were carried out using ultra high vacuum (UHV) in situ TEM to investigate the coarsening process of a highly modulated nanolamellar structure obtained by crystallization of a Co based Co₆₅Si₁₅B₁₄Fe₄Ni₂ amorphous magnetic alloy. The coarsening process consisted of three steps: (a) precipitation of spherical fine precipitates; (b) continuous coarsening of the nanolamellar structure at the surface and precipitation at the grain boundaries; and (c) formation of a stable multiphase structure. Due to surface effects, continuous coarsening of nanolamellar structure was observed during in-situ annealing; this mechanism was different from that of the coarsening process found during conventional annealing. Discontinuous coarsening from grain boundaries, which dominates the coarsening process in the conventional annealing of bulk sample, also occurred in in-situ annealing of thin sample. The driving force for coarsening of the nanolamellar structure from interlamellar interfaces, grain boundaries and surfaces is discussed.