Search

Spin–lattice relaxation times T1 and T1d as well as NMR second moment were employed to study molecular dynamics of pyridoxine (vitamin B6) in the temperature range 10–350 K. The T1 minimum observed at low temperatures at 200 MHz is attributed to a motion of methyl group. The motion is interpreted in terms of Haupt''s theory, which takes into account the tunneling assisted relaxation. At low temperatures, where T1 is temperature independent, occupation of the ground state only is assumed. A motion of proton of the hydroxyl groups or CH2OH groups probably provides additional mechanism of relaxation, in the high-temperature region. [Copyright &y& Elsevier]

Abstract Multilayered design showed itself to advantage for improvement of functional nitride coatings, which are widely required in various industry applications. This article reports on deposition and detailed characterization series of combined nano-multilayered coatings based on (TiAlSiY)N with changes in components of alternating binary layers. Vacuum-arc deposited (TiAlSiY)N/MoN, (TiAlSiY)N/CrN and (TiAlSiY)N/ZrN coatings were analyzed by means of various experimental techniques such as SEM with EDS, XRD and GIXRD, SIMS, XPS and Raman spectroscopy. Microstructure of (TiAlSiY)N/MoN coating was characterized by creation of fine-grained fcc-AlTiN phase of (200) plane with congruent growth of γ-Mo 2 N (200) due to high isostruturality of lattices of alternating layers. The formation of fcc-AlYTiN phase of (111) plane and fcc-TiCrN phase of (200) plane were observed in multilayered (TiAlSiY)N/CrN coating and referred to the loss of clear interfaces and the formation of transition layers due to the diffusion of Ti atoms. Nano-multilayered (TiAlSiY)N/ZrN system showed the formation of stoichiometric fcc compounds of TiN with (200) plane and ZrN with (111) plane, respectively. The evaluation of mechanical properties as nanohardness, reduced elastic modulus, elastic strain prior to failure, and resistance to plastic deformation measurements was performed. The presented results showed important information about the physical and mechanical properties of new nano-multilayered systems for their subsequent application, as well as improvement of existing achievements. Graphical abstract Image 1 Highlights • Nano-multilayered (TiAlSiY)N/MeN coatings were fabricated using vacuum arc deposition. • The congruent growth of γ -Mo 2 N grains was observed in the layers of Me x N/MoN coatings. • CrN layer as a top one increase the oxidation resistance of the Me x N/CrN coating. • Low friction coefficient and cohesive wear were observed for the Me x N/ZrN system. [ABSTRACT FROM AUTHOR]

This article reports on the thorough characterization of structural-phase transformation in amorphous TiAlBSiN coating after high temperature annealing at 900 °C in ambient air. The influence of annealing on the tribo-mechanical behavior of the coating at nano and micro scale was also examined. The research included multiple experimental techniques, i.e. AFM, SEM, TEM, HR-TEM, EDS, XPS and Raman spectroscopy. Experiments showed that the amorphous phase of the TiAlBSiN coating undergoes a structural transformation, evidenced in the changes of parameters such as topological and chemical short-range order after the post-deposition annealing at 900 °C in air. The observed structural transformation, leads to a phase separation with the formation of a three dimensional nc-TiAl 3 /a-SiBN(O) nanocomposite structure. The relative increase of hardness, reduced elastic modulus, H/Er ratio and H 2 /E 3 r ratio after high temperature treatment of TiAlBSiN coatings is also reported. The complex interdependency between chemistry, morphology and relative composition of the amorphous TiAlBSiN coating phase, during the high temperature treatment, with the respective change of the tribo-mechanical characteristics, are evidence of the improvement of the coating properties in response to the environmental conditions and high temperature. This work contributes particularly to the development and understanding of flexible nanocomposite protective coatings and their changes at high temperature of operation. [ABSTRACT FROM AUTHOR]

Abstract: Reorientation of the molecule of diazepam was investigated by calorimetric methods, IR absorption and NMR. The investigation of dynamics was complemented by density functional study (DFT) of vibrational frequencies and infrared intensities, calculations of steric hindrances and Monte Carlo simulations. The results indicated the occurrence of reorientation jumps of the CH3 group and conformational motion of the benzodiazepine ring. The activation parameters of the methyl group reorientation were determined and the activation barrier obtained was in good agreement with the theoretically estimated value. The FT-IR spectra were assigned using results of DFT calculations. [ABSTRACT FROM AUTHOR]