Publications

N-type silicon single crystals with resistivity higher than 8000 Omega cm were irradiated with ions of Bi6+, of 28 MeV kinetic energy. At this energy, the ions are stopped into the wafer. Being much heavier and bigger than the host atoms, they produce major disturbances into the lattice. On the other hand, the produced collision cascade is the source of lattice defects which act as traps. We investigated them using the method of thermally stimulated currents without applied bias. The results are compared with those obtained from the analysis of silicon irradiated with I6+ ions.

Reconstructive surgery of bone defects in the calvarium makes use of a multitude of biological and artificial materials. Due to the increased number of such medical casuistry in the recent years, a special attention was dedicated to the biocompatibility and osteointegrative properties of various types of biomaterials. Titanium emerged to be a promising cranioplasty material due to its excellent mechanical properties and biocompatibility. However, the way the host calvarial bone reacts to the titanium implant has not been fully understood. Here, we evaluate the influence of cranial bone substrate on the osteoconduction and osseointegration of titanium mesh implants. The pattern of bone tissue reaction in the areas of contact with metallic implant is analyzed by means of bone density measurements on the computer tomography images. Twenty-eight patients underwent cranioplasty with titanium mesh implants for bone cranial defects due to different aetiology. With the aid of visual analogue scales, the patients' status (osteointegration degree, comfort and cosmetics) was evaluated after 3 - 14 months since surgery (implantation).

The aim of this study was the evaluation of (Ca10-x Ag-x)(PO4)(6) (OH)(2) nanoparticles (Ag:HAp-NPs) for their antibacterial and antifungal activity. Resistance to antimicrobial agents by pathogenic bacteria has emerged in the recent years as a major public health problem worldwide. In this paper, we report a comparison of the antimicrobial activity of low concentrations silver-doped hydroxyapatite nanoparticles. Thesilver-doped nanocrystalline hydroxyapatite powder was synthesized at 100 degrees C indeionised water. The as-prepared Ag: Hap nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), FT-IR, and FT-Raman spectroscopy. X-ray diffraction (XRD) studies demonstrate that powders obtained by coprecipitation at 100 degrees C exhibit the apatite characteristics with good crystal structure, without any new phase or impurities found. FT-IR and FT-Raman spectroscopy revealed the presence of the various vibrational modes corresponding to phosphates and hydroxyl groups and the absence of any band characteristic to silver. The specific microbiological assays demonstrated that Ag: HAp-NPs exhibited antimicrobial features, but interacted differently with the Gram-positive, Gram-negative bacterial and fungal tested strains.

In the present work the influence of the method of preparation on the characteristics of sol-gel hybrid nanocomposites with oxide nanoparticles was studied. The chosen system consists of a SiO2 matrix based on methyltriethoxysilane (MTEOS) and laboratory made TiO2:CeO2 (4:1) nanopowder. The doping of the matrix was realized either by dispersion of previously prepared binary nanopowder in the matrix solution or by in situ generation of the TiO2-CeO2 nanoparticles during the matrix hydrolysis-condensation processes. Films were deposited on silicon wafer and glass substrates by dip-coating method and were characterized as prepared and annealed at 120 degrees C. The optical and morphological properties were determined by spectroellipsometry (SE), scanning electron microscopy (SEM), atomic force microscopy (AFM), their structural characterization was realized by IR spectroscopy and the thermal behavior was determined by thermogravimetric and differential-thermal analysis (TG/DTA). All characterization methods have shown that by the two preparation routes materials with different characteristics were obtained.

This paper reports on the experimental realization and characterization of a wireless sensing system for machine-tool condition based monitoring. The system comprises a vibration sensor, an ARDUINO Leonardo development board and an RM 42 Blue tooth module. The sensing principle is based on a vibration sensor which includes a piezoelectric AlN layer deposited by sputtering on a flexible stainless steel foil. The functional testing of the sensor using a test stand for asynchronous engines equipped with frequency convertors is demonstrated.

Zinc oxide particles were synthesized by a simple wet chemical method. Using zinc nitrate and various precipitating agents, like KOH, NaOH and (CH2)(6)N-4, particles with different morphologies were obtained. Also, the addition of a structure-directing agent, like gum arabic - a highly branched biopolymer, leads to a decrease in the ZnO particles size (for KOH and NaOH) and to a dramatical change of the ZnO particle shape in the case of (CH2)(6)N-4. The X-ray diffraction analysis showed that all obtained samples are of wurtzite structure. The reflectance and photoluminescence spectra have been used to investigate the optical properties of the ZnO structures. The morphologies observed by scanning electron microscopy reveal snowflake-like, flower-like, star-like and double-raspberry-like structures. A possible formation mechanism for ZnO micro/nanostructures with different morphologies was proposed. The biopolymer-assisted crystallization method could provide a facile approach to synthesize other desired compounds with controllable morphology.

The glycerol iron oxide nanoparticles (GIO-NPs) were obtained by an adapted coprecipitation method. The X-ray diffraction (XRD) studies demonstrate that GIO-NPs were indexed into the spinel cubic lattice with a lattice parameter of 0.835 nm. The refinement of XRD spectra indicated that no other phases except maghemite were detected. The adsorption of glycerol on iron oxide nanoparticles was investigated by Fourier transform infrared (FTIR) spectroscopy. On the other hand, this work implicated the use of GIO-NPs in antibacterial studies. The results indicate that, in the case of P.aeruginosa 1397 biofilms, at concentrations from 0.01 mg/mL to 0.625 mg/mL, the glycerol iron oxide inhibits the ability of this strain to develop biofilms on the inert substratum.

This paper presents a detailed transmission electron microscopy (TEM) study of GeSiO films with Ge nanoparticles. The films with 2.5 mu m thickness were deposited by magnetron sputtering and subsequently annealed in H-2 at 2 atm and 500 degrees C for 2 h for nanostructuring. After H-2 annealing, the majority of the resulted Ge nanoparticles are amorphous, less than 5 nm in size, forming a uniform network in the film volume. Big Ge nanoparticles with sizes between 20 and 50 nm are also formed. Some of them are identified to be crystallized in the (Ge-III/ST12) tetragonal phase. The high resolution TEM observation induces the amorphysation of the Ge tetragonal phase, followed by the crystallization of the amorphous Ge phase in the cubic diamond structure (Ge-I), as an effect of electron irradiation. A secondary annealing performed in N-2 at 800 degrees C and 1 atm for 2 h induces formation of faceted cubic Ge nanoparticles distributed in the SiO2 matrix.

The ceramics of Nb5+, Zr4+ or Eu3+ doped BaZn1/3Ta2/3O3 complex perovskite oxide were obtained by the conventional solid-state reaction method, being sintered in air, at temperatures between 1400 and 1600 degrees C, for 2 h. X-ray diffraction, scanning electron microscopy and dielectric measurements were used for the compositional, structural, morphological and dielectric characterization. All BaZn1/3Ta2/3O3 ceramics present single-phase compositions after removing the surface layer in which zinc volatilization occurred. Furthermore, the 1:2 ordering of zinc and tantalum cations on the octahedral positions of the perovskite structure was observed for all sintering temperatures. The microstructure of BaZn1/3Ta2/3O3 ceramics is strongly influenced by the dopant type, in terms of grains size and shape. The dielectric constant varies between 16.9 and 31.5. BaZn1/3Ta2/3O3 resonator doped with 1.00 % Nb2O5 and sintered at 1600 degrees C, 2 h, exhibits the highest value for the quality factor, Qxf similar to 157 THz at 10 GHz.

Laser pulses at 1.06 mu m with 2.5-mJ energy and 3.1-MW peak power have been obtained from a composite, all-polycrystalline ceramics, passively Q-switched 1.1-at.% Nd:YAG/Cr4+:YAG laser that was quasi-continuous-wave pumped with diode lasers. Single-pass frequency doubling with LiB3O5 nonlinear crystal at room temperature yielded green laser pulses at 532 nm with energy of 0.36-mJ and 0.45-MW peak power; the infrared-to-green conversion efficiency was 0.27.