Levels of plant cell wall structural organization revealed by atomic force microscopy.

We used an atomic force microscope to image cell wall isolated from needles of Serbian spruce tree and that synthesized from cell wall components. We also observed the structure of lignin model polymer (DHP), as a best substitute for the natural lignin. A tendency of aggregate formation was observed in all samples. Cell wall was revealed as a laminated fibrous structure. General organization is similar in both isolated and synthesized cell wall samples, with dominating globular motifs arranged regularly as rods and forming cavities. The synthesized cell wall has a more regular structural organization than isolated cell wall. The dimensions of individual globular aggregates and pores differed between the two samples. DHP showed a similar, regular organization, with globular aggregates and holes. Globules and pores are smaller in size than the corresponding structures in both the isolated and synthesized cell walls. Such modular organization of cell walls may have a physiological role in response to the external mechanical stress caused to plant cells.

Influence of substrate orientation on the morphology and orientation of LaNiO3 thin films.

LaNiO(3) thin films were successfully prepared by a chemical method from citrate precursors. The LNO precursor solution was spin-coated onto Si (100) and Si (111) substrates. To obtain epitaxial or highly oriented films, the deposited layers were slowly heated in a gradient thermal field, with a heating rate of 1 degrees min(-1), and annealed at 700 degrees C. The influence of different substrate orientations on the thin film morphology was investigated using atomic force microscopy and X-ray diffraction analysis. Well-crystallized films with grains aligned along a certain direction were obtained on both substrates. Films deposited on both substrates were very smooth, but with a different grain size and shape depending on the crystal orientation. Films deposited on Si (100) grew in the (110) direction and had elongated grains, whereas those on Si (111) grew in the (211) direction and had a quasi-square grain shape.

The effect of an Ni-Cr protective layer on cyclic oxidation of TiAl.

The effect of an 80Ni-20Cr (at.%) metallic coating on the cyclic oxidation behaviour of a Ti(3)Al-based alloy with the composition Ti-25Al-11Nb (at.%) was investigated in this study. Cyclic oxidation tests were carried out in air at 600 degrees C and 900 degrees C for 120 h. For one cycle test, the specimens were held for 24 h at test temperature and then furnace-cooled to room temperature. The oxidation rate was determined by plotting the mass gain per unit surface area of the specimen vs. exposure time. The morphology and composition of the oxidation products were characterized on the cross-section of the specimens by scanning electron microscopy, energy-dispersive X-ray spectroscopy and atomic force microscopy. The oxidation scale forms during exposure at both 600 degrees C and 900 degrees C. TiO(2) is the main oxide component, whereas the Al(2)O(3) layer appears only discontinuously. The remarkable improvement in oxidation resistance at 900 degrees C was attributed to the chemical composition and structure of the scale formed on the 80Ni-20Cr coating.