Search

In this paper, the results of structural modification of fullerene thin films bombarded by highly charged iron ions (Fe6+) are presented. The properties of as-deposited and irradiated fullerene thin films have been investigated by Raman spectroscopy, UV/Vis spectrophotometry and atomic force microscopy (AFM). The results of Raman spectroscopy have indicated structural changes of irradiated thin films depending on fluences. It was found that iron doped fullerene films are dominated by sp3 rather than sp2 after bombardment which might be due to formation of nanodiamond structures. AFM analysis showed that the ion beam had destroyed the surface ordering. The optical band gap was found to be in the range of 0.6 to 1.4 eV for irradiated films by Fe6+ ions at the highest fluences. [ABSTRACT FROM AUTHOR]

The effect of an 80Ni−20Cr (at.%) metallic coating on the cyclic oxidation behaviour of a Ti3Al-based alloy with the composition Ti−25Al−11Nb (at.%) was investigated in this study. Cyclic oxidation tests were carried out in air at 600 °C and 900 °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 °C and 900 °C. TiO2 is the main oxide component, whereas the Al2O3 layer appears only discontinuously. The remarkable improvement in oxidation resistance at 900 °C was attributed to the chemical composition and structure of the scale formed on the 80Ni−20Cr coating. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Photoacoustic properties of amorphous Fe81B13Si4C2 ribbons were investigated. The amplitude and phase photoacoustic spectra were measured as a function of the modulation frequency of an He–Ne laser beam. Thermal diffusivity was determined by comparison of obtained experimental results and calculated theoretical photoacoustic spectra for a non-annealed Fe81B13Si4C2 sample and an Fe81B13Si4C2 sample annealed at 600 °C. © 1998 Chapman & Hall [ABSTRACT FROM AUTHOR]

Abstract: New semimagnetic semiconductor Hg0.91Mn0.09Te-MnSe mixture, grown by Bridgman method, was investigate by Atomic Force Microscopy, X-ray and far-infrared spectroscopy, in order to obtain the necessary feedback information to determine the optimal conditions for crystal growth. The investigated mixture consists of MnSe nanoclasters randomly distributed in Hg0.91Mn0.09Te matrix. Far-infrared reflectivity spectrum of the Hg0.91Mn0.09Te-MnSe mixture was measured in the 80–500cm−1 range at a room temperature. The analysis of the far-infrared spectrum was made by the fitting procedure. The Maxwell-Garnett effective medium theory is used for modeling an effective dielectric function, and on that way calculating both electron and phonon response. [Copyright &y& Elsevier]

Abstract: In this paper we used far-infrared spectroscopy, reflection high energy electron diffraction (RHEED), X-ray diffraction and atomic force microscopy (AFM) to investigate structural and optical properties of Pb1−x Mn x Te layers grown by molecular beam epitaxy (MBE). A numerical model for calculating the reflectivity coefficient for complex systems which include films, buffer layer and substrate has been applied. The infrared reflectivity spectra consist of Pb1−x Mn x Te phonons, which exhibit intermediate one–two mode behavior, and MnTe phonons. A good agreement between calculated and experimental spectra is achieved. We registered the local distribution of Mn impurities depending on substrate type. For films growth on BaF2 substrate we registered the orthorhombic local structure of MnTe clusters, while in the case of KCl substrate this structure is cubic. The Pb1−x Mn x Te long wavelength optical phonons were described by the modified Genzel''s model. [Copyright &y& Elsevier]

Abstract: Far infrared reflection spectra of NiO polycrystals sintered at 1100°C for various times (30–240min) were measured at room temperature using a FTIR Spectrometer—Brucker 113V. The measured spectra depended on the sintering time due to differences in the microstructural morphology of the material and were compared with the NiO single crystal reflectivity diagram. Numerical analyses of the experimental spectra were performed using Kramers-Kronig analysis, a four-parameter model of coupled oscillators and the effective medium modeling theory. In the three-component effective medium model based on Bruggeman''s theory we assumed the presence of pores, intergranular material and crystalline grains. The intergranular material and crystalline grains were defined as single and coupled ionic oscillators. [Copyright &y& Elsevier]