National Institute Of Materials Physics - Romania

Azathioprine (Imuran), one of the oldest immunosuppressants, having been used in transplantation since the early 1960's, is known to have only two crystal forms: an anhydrous form and a dihydrate phase. We report the crystal structure of a new anhydrous solid-state form of Azathioprine, determined directly form powder X-Ray diffraction data, employing the direct-space genetic algorithm technique for structure solution, followed by Rietveld refinement. The new anhydrous polymorph is accessible only by a solid-state dehydration process of the readily obtained monohydrate form of Azathioprine, the form for which a crystal structure has not previously been reported. The IR and Raman spectra confirmed the results obtained from X-Ray diffraction indicating the presence of all functional groups involved in intermolecular hydrogen bonding which dictates different arrangement of molecules in the structural packing. (C) 2018 Elsevier B.V. All rights reserved.

Bipolar Pulse High Power Impulse Magnetron Sputtering (BP-HiPIMS) was investigated and used in this work to control the ion bombardment process of growing thin films and to improve their structure and properties. Energy-resolving mass spectroscopy was used to investigate the effect of reverse target voltage on the ion energies and fluxes during BP-HiPIMS of a high-purity copper target, in argon gas. It was found that the reverse target voltage provides a wide range of ion energies and fluxes incident to the growing film, which, in turn, produce a wide variety of effects during the deposition process, improving the adhesion strength and influencing both surface and bulk properties. Fast ICCD imaging was used to investigate both HiPIMS and BP-HiPIMS plasma dynamics. The temporal and spatial distributions of plasma potential measurements were performed in order to explain the mechanisms for accelerating the ions. The topological, structural and mechanical properties of the deposited coatings were investigated using atomic force microscopy (AFM), X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), thermal desorption spectroscopy (TDS), scanning electron microscopy (SEM), nanoindentation and scratch tests. The obtained results indicate an energy-enhanced deposition process during BP-HiPIMS, the deposited films being characterized by smooth surfaces, dense microstructure, small inert gas inclusions, high elastic strain to failure, scratch resistance and good adhesion to the substrate. These improvements in the films' structure and properties may be attributed to the intense and energetic ion bombardment taking place during the deposition process. During BP-HiPIMS operation, there is no net increase in the deposition rate as compared to the monopolar regime due to the re-sputtering process.

We report the successful growth of multiferroic (Nd,Fe)-doped PbTiO3 thin films with the composition (Pb0.88Nd0.08)(Ti0.93Fe0.05Mn0.02)O-3 (PNFT) using pulsed laser deposition. The deposited films have been investigated by XRD, SEM, energy-dispersive X-ray spectroscopy (EDS), secondary-ion mass spectroscopy (SIMS), atomic force microscopy, magnetic force microscopy, piezoforce microscopy, spectroscopic ellipsometry (SE) and dielectric spectroscopy measurements. PNFT films deposited on different substrates (MgO, SrTiO3 and Nb:SrTiO3) are (001) oriented, preserving the orientation of the single-crystal substrates. EDS mapping and SIMS across the film thickness probed the uniform distribution of all the elements. The refractive index and extinction coefficient have been obtained with the SE software package and refined with an optical-graded model. Magnetic domains and ferroelectric domains have been evidenced at microscopic scale. Good dielectric properties and low loss, comparable to those of bulk materials, have been obtained.

Composite thin coatings of conductive polymer (polyaniline grafted lignin, PANI-LIG) embedded with aminoglycoside Gentamicin sulfate (GS) or magnetite nanoparticles loaded with GS (Fe3O4@GS) were deposited by the matrix-assisted pulsed laser evaporation (MAPLE) technique. The aim was to obtain such nanostructured coatings for titanium-based biomedical surfaces, which would induce multi-functional properties to implantable devices, such as the controlled release of the therapeutically active substance under the action of a magnetic and/or electric field. Thus, the unaltered laser transfer of the initial biomaterials was reported, and the deposited thin coatings exhibited an appropriate nanostructured surface, suitable for bone-related applications. The laser processing of PANI-LIG materials had a meaningful impact on the composites' wettability, since the contact angle values corresponding to the composite laser processed materials decreased in comparison with pristine conductive polymer coatings, indicating more hydrophilic surfaces. The corrosion resistant structures exhibited significant antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Candida albicans strains. In vitro cytotoxicity studies demonstrated that the PANI-LIG-modified titanium substrates can allow growth of bone-like cells. These results encourage further assessment of this type of biomaterial for their application in controlled drug release at implantation sites by external activation.

The work demonstrates growth by the Verneuil method of SrTiO3 single crystals of 30 mm in diameter. Experiments are performed under an industrial environment. Growth was for 4.75 h, i.e., within one production shift. The optimum growth conditions for which the length of the region with bubbles D is zero and the effective length EL (i.e., the crystal length of commercial value) is maximized are for the amount of SrCO3 additive of similar to 3 wt % and for H-2 outer flow rate of similar to 35 L/min. These two parameters show the strongest influence on the bubble-free growth, but other growth parameters (H-2 inner flow rate, O-2 flow rate increase, rotation speed) were also optimized. Selected crystals are characterized from the structural, microstructural, optical, and THz spectroscopy viewpoints, and they are compared with a commercial substrate and with crystals reported in the literature. This work opens the possibility for the industrial growth of large SrTiO3 single crystals and commercialization of large area substrates.

This research work is dedicated to study structural, morphological, optical and photoluminescence properties of samarium doped calcium sulfate (CaSO4) thin films after exposure to high gamma radiations. Polycrystalline doped CaSO4 thin films have been grown on glass substrates by spray pyrolysis technique and irradiated at different high gamma doses 3, 7, 15 and 40 kGy. Physical characterization of irradiated thin films has been made by X-ray diffraction, Spectrophotometer, Scanning Electron Microscope, Energy Dispersive Spectroscopy, Fluorescence Spectrometer and Thermoluminescence. The most remarkable result, as shown by structural analysis, is the increase of grain size from 52 to a maximum value of 93 nm for 15 kGy gamma dose which indicates a clear enhancement in crystal structure by gamma irradiation. Moreover, the preferred orientation has been immediately changed from (102) plan to (100) just after the first 3 kGy gamma dose. SEM micrographs of irradiated thin layers show deep modifications in surface morphology. Optical transmission spectra have shown a sharp and intense peak at 350 nm wavelength. Band gap energy has been slightly decreased from 3.9 eV before irradiation to 3.6 eV for 40 kGy. A new and strong energy level noted E r , has been emerged and created due to high gamma irradiations in addition to the principal one relative to band gap energy. Other parameters like absorption and extinction coefficients and refractive index have been determined. Thermoluminescence data show a high sensibility to gamma radiations doses which offer opportunities for dosimetry applications. These experimental results suggest the use of irradiated samarium doped calcium sulfate as optical window for space photovoltaic devices where gamma rays are abundant. These results are also helpful for researchers using CaSO4 thin films near nuclear apparatus (nuclear reactors and particle accelerators) or those interested in studying interaction between radiations and condensed matter.

The present work proposes the simultaneous removal of these classes of pollutants by a catalytic hydrotreatment processes. For this purpose, bimetallic Pd-Cu catalysts (with mass ratio Pd:Cu of 4:1) supported on macroporous strong base anion resin were prepared by different methods. The catalysts were characterized (by XRD, SEMEDX, XPS, AAS and H-2 chemisorption) and tested in a continuous flow system. The selected catalyst preparation protocol consists in a two-step method, which implies the deposition of palladium by ion exchange and the subsequent deposition of copper by controlled reaction on the surface of the pre-reduced palladium. The effectiveness of the catalyst in the simultaneous reduction of nitrate and hydrodechlorination of 4-chlorophenol was demonstrated. By adjusting the initial pH and the flow rate of the aqueous solution, nearly complete hydrodechlorination of 4-chlorophenol can occur together with selective nitrate reduction at a conversion of 95% and a selectivity to N-2 of 92% (this value contains the contribution of all gaseous products, including the eventually formed NOx). The bimetallic catalyst was found to remains relatively stable after 100 h of test time.

We have investigated the effect of thermal annealing on the structure of single and stacked phase change memory films based on SnSe and GaSb. Samples were prepared by pulsed laser deposition and investigated by X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) methods. Electrical resistance versus temperature investigations showed crystallisation temperatures of 292 degrees C and 198 degrees C for SnSe and GaSb single films, respectively. Above the transition temperature, GaSb crystallises into a face-centered cubic structure, whereas SnSe has an orthorhombic arrangement. Annealing at three temperatures (160 degrees C, 250 degrees C and 350 degrees C) of the SnSe\GaSb stacked films promotes bond breaking, atom diffusion between the two layers and formation of new phases. At 160 degrees C, GaSb films crystallise partially and no effect is observed on the crystallinity of SnSe films. After 250 degrees C, rhombohedral SnSb emerges in addition to GaSb complete crystallisation. A major, completely new, body-centered orthorhombic unindexed quaternary Ga-Sn-Sb-Se phase formation was observed in the samples annealed at 350 degrees C. The GaSb crystallites are fully dissolved and we have observed the formation of a minor hexagonal SnSe2 phase. The analysis of EXAFS data, measured at Se and Ga K-edges, revealed changes in the local atomic environment as a function of the annealing temperature. A tetrahedral configuration is obtained for the Ga atoms in both as-deposited and annealed samples, whereas Se is mostly bivalent in the amorphous samples and has an octahedral arrangement in crystalline SnSe. Our results show that inter-layer diffusion should always be considered and evaluated when designing memory cells composed of stacked phase change chalcogenide films.

Indium tin oxide (ITO) thin films were grown on nanopatterned glass substrates by the pulsed laser deposition (PLD) technique. The deposition was carried out at 1.2 J/cm(2) laser fluence, low oxygen pressure (1.5 Pa) and on unheated substrate. Arrays of periodic pillars with widths of similar to 350 nm, heights of similar to 250 nm, and separation pitches of similar to 1100 nm were fabricated on glass substrates using UV nanoimprint lithography (UV-NIL), a simple, cost-effective, and high throughput technique used to fabricate nanopatterns on large areas. In order to emphasize the influence of the periodic patterns on the properties of the nanostructured ITO films, this transparent conductive oxide (TCO) was also grown on flat glass substrates. Therefore, the structural, compositional, morphological, optical, and electrical properties of both non-patterned and patterned ITO films were investigated in a comparative manner. The energy dispersive X-ray analysis (EDX) confirms that the ITO films preserve the In2O3:SnO2 weight ratio from the solid ITO target. The SEM and atomic force microscopy (AFM) images prove that the deposited ITO films retain the pattern of the glass substrates. The optical investigations reveal that patterned ITO films present a good optical transmittance. The electrical measurements show that both the non-patterned and patterned ITO films are characterized by a low electrical resistivity (<2.8 x 10(-4)). However, an improvement in the Hall mobility was achieved in the case of the nanopatterned ITO films, evidencing the potential applications of such nanopatterned TCO films obtained by PLD in photovoltaic and light emitting devices.

The aim of this study was to investigate the influence of new hybrid composites of TiO2 or SiO2 nanoparticles with poly(2,2'-bithiophene) on 50% cotton/50% polyester fabric and sheep skin leather surface properties. The dispersion-based newly made nanocomposites were analyzed to determine conductivity, particle size, polydispersity and Zeta potential. The finished textile and leather materials were characterized in terms of functionalization treatments performance by: surface resistivity, water contact behaviour, physical-mechanical characteristics and photocatalytic properties. SEM analysis was used to investigate the distribution of nanoparticles on the textile and leather materials surface. Textile materials treated with SiO2/poly(2,2'-bithiophene) nanocomposite with concentration 98 wt% nanoparticles of SiO2 and leather treated with poly SiO2/poly(2,2'-bithiophene) nanocomposite with concentration of 95 wt% nanoparticles of SiO2 showed lower resistivity values, confirming the conductive properties of silica. The higher photodegradation efficiency of functionalized materials has been obtained for textile material treated with poly TiO2/(2,2'-bithiophene) with concentration of 95 wt% nanoparticles of TiO2 and for leather material treated with TiO2/poly(2,2'-bithiophene) with concentration of 98 wt% nanoparticles of TiO2, respectively.