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Ababei G.,National Institute of Research and Development for Technical Physics | David V.,Technical University Gheorghe Asachi | Dafinescu V.,Technical University Gheorghe Asachi | Nica I.,Technical University Gheorghe Asachi | And 2 more authors.
IEEE Transactions on Magnetics | Year: 2012

The selective microwave absorption properties of individual and multiple CoFe-glass coated amorphous microwires (GCAW) with small negative value of magnetostriction (λ∼-1× 10 -7, positioned in various configurations are investigated. The deep minimum in the transmission spectra correspond to the first antenna resonance for each length of the individual microwire indicating a selective stop filter behavior. A new type of shielding material in the shape of a multilayered material based on CoFe-GCAW with desired shielding effectiveness and selective absorption of the microwave frequency range by controlling the number of the layers and the length of microwires is proposed and the omni-directional selective shielding properties in the microwave frequency range are determinated. The shielding effectiveness measurements results were SE=4\ dB to 9.5 dB for the samples with two layers, SE=18\ dB to 33 dB for sample with 14 layers, and SE=36\ dB to 48 dB for sample with 28 layers, respectively. © 1965-2012 IEEE.

Oktar F.N.,Marmara University | Yetmez M.,Bülent Ecevit University | Ficai D.,Polytechnic University of Bucharest | Ficai A.,Polytechnic University of Bucharest | And 2 more authors.
Current Topics in Medicinal Chemistry | Year: 2015

The emergence of multi-resistant bacteria to drugs is recognized as a major cause of the increasing number of deaths in hospitals. Killing these bacteria require multiple expensive drugs that can have side effects. Metal nanoparticles may provide a new strategy to combat them. Due the antimicrobial and antiviral properties, nanoparticles (NPs) have outstanding biological properties that can be handled properly for desired applications. This review presents antibacterial and antiviral activity of metal NPs, including the molecular mechanisms by which NPs annihilate multidrug-resistant bacteria. © 2015 Bentham Science Publishers.

Pica A.,Polytechnic University of Bucharest | Ficai D.,Polytechnic University of Bucharest | Ficai A.,Polytechnic University of Bucharest | Guran C.,Polytechnic University of Bucharest | And 2 more authors.
Journal of Optoelectronics and Advanced Materials | Year: 2016

Film-forming materials described in this study may be used for long term antimicrobial protection of wood, concrete, gypsum boards and other building materials. The materials have antibacterial properties due to the presence of AgNPs (silver nanoparticles) in their composition. The material has the ability to form a nanomodified polymer matrix which generates in the styrene acrylic binder, nanostructured configuration. This gives the composite material properties, feature and superior performance impossible to achieve at a micro scale. AFFM (antimicrobial film-forming materials) were analyzed of structure by FT-IR (Fourier transform infrared spectroscopy) and in morphologically by electron microscopy (SEM/EDX). The introduction of (0.1-0.2)wt%. AgNPs in AFFM produces an optimum improvement in the antibacterial resistance. It has been shown that the new material (AFFM) does not deteriorate even if subjected to an accelerated aging process. Materials were applied inside a medical unit and found that after 6 months after the application, morphology, structure and biological properties haven't undergone significant changes. Energy dispersive X-ray analysis (EDX) confirmed that AgNPs are well anchored in film-forming material, even after 6 months.

Pica A.,Research Institute for Advanced Coatings | Dumitru F.,Research Institute for Advanced Coatings
Revista de Chimie | Year: 2016

In this paper is shown the performance of chemically modified vegetable oils or additivated for their use as dielectric fluids. The structure and composition of the organic dielectric fluids were determined by infrared spectroscopy (FT-IR), and GC-FID. The primary objective of the study was to investigate and optimize the electrical characteristics of the vegetable oils used in insulation systems of high power transformers to improve their performance. The efficiency of the epoxidation reaction was determined by measuring iodine value. Following epoxidation reactions, some of the double bonds are replaced with oxirane ring which leads to lower unsaturation present in the vegetable oil and increasing of the dielectric strength. The obtained results are correlated with the current state of research in terms of finding new organic liquid insulating materials, clean, efficient and cost price as low as possible.

Pica A.,Polytechnic University of Bucharest | Pica M.,Carol Davila University of Medicine and Pharmacy | Ficai D.,Polytechnic University of Bucharest | Ficai A.,Polytechnic University of Bucharest | Florica D.,Research Institute for Advanced Coatings
Current Nanoscience | Year: 2015

In crowded public areas (hospitals, airports, railway stations, universities, schools, etc.), surfaces of the materials are exposed to microorganisms. These microorganisms can live both in planktonic and biofilm (colonies of microorganisms) being responsible for the transmission of different infections from human to human. Because of that, the antimicrobial effect is an additional function of film-forming materials. The innovation of these types of materials consists both in choosing and stabilizing the active substance in the polymeric material and in the microbial control. Usage of the AgNPs as active substance induces morphological changes in the structure of the film-forming material, a chemical resistance and an antimicrobial efficacy for a long time. The antimicrobial properties of the new materials reduce the consumption of disinfectants and the number of washing cycles which implicitly leads to reduced maintenance costs. The influence of the AgNPs on the morphology, structure and properties of the material coatings was investigated by EDX, SEM and SPM. The antifungal activity of the film-forming materials was investigated onto 12 cultures of mushrooms. Silver nanoparticles can prevent the formation of biofilms through the killing of the fungus and of the bacteria (both gram-positive and gram-negative) that are present on the surface of materials. Materials coatings were applied in a medical unit and after 12 months from application, it was found that neither morphology or structure nor the antifungal or the antibacterial properties have undergone significant changes. Based on these results it is considered that the film-forming materials based on silver nanoparticles could be used to inhibit the development of micro-organisms on concrete surfaces or plasterboard inside the medical units for long time. © 2015 Bentham Science Publishers.

Vaja F.,Research Institute for Advanced Coatings | Guran C.,Polytechnic University of Bucharest | Ficai D.,Polytechnic University of Bucharest | Ficai A.,Polytechnic University of Bucharest | Oprea O.,Polytechnic University of Bucharest
UPB Scientific Bulletin, Series B: Chemistry and Materials Science | Year: 2014

In vitro cytotoxic studies of nanoparticles use different cell line, incubation time and colorimetric assays. In this paper, we investigated the cytotoxicity of different concentrations of ZnO particles hosted in mesoporous silica in Human epidermoid cancer cells using the Trypan Blue exclusion test. The ZnO nanoparticles were prepared by incorporating different amount of zinc nitrate precursor into the channels of mesoporous silica SBA-15. Using Epics Beckman Coulter flowcytometer and FlowJo software the data were expressed as fractions of cells in the different cell cycle phases. The results show that all compounds have cytotoxic effects. © 2009 Universitatea Politehnica Bucuresti.

Pica A.,Polytechnic University of Bucharest | Guran C.,Polytechnic University of Bucharest | Ficai D.,Polytechnic University of Bucharest | Ficai A.,Polytechnic University of Bucharest | Dumitru F.,Research Institute for Advanced Coatings
Journal of Coatings Technology Research | Year: 2015

In this article, we present the synthesis of small silver nanoparticles (AgNPs) with an average size of 1–20(50) nm. Three formulations of AgNPs-based materials have been obtained and characterized by varying the weight ratio of the silver nitrate/acrylic polymer. AgNPs were prepared by simple chemical reduction method. The reduction of AgNO3 was done by sodium borohydride in the presence of acrylic polymer, which acts also as a capping agent of AgNPs, avoiding the use of additional protective agents. The elemental analysis of AgNPs was quantified by X-ray fluorescence. The morphology and size of AgNPs were characterized by SEM and TEM–HRTEM, while the colloidal stability of AgNPs was demonstrated by zeta potential measurements. The influence of acrylic polymer on the stability of AgNPs, the particle sizes, and their antimicrobial efficacy was investigated. The results confirm that the introduction of acrylic polymer during the synthesis, acting as a stabilizing agent, increases the colloidal stability and antimicrobial performances of these formulations. © 2015 American Coatings Association

Dumitru F.V.,Polytechnic University of Bucharest | Dumitru F.V.,Research Institute for Advanced Coatings | Comanescu C.,Polytechnic University of Bucharest | Comanescu C.,National Institute of Materials Physics Bucharest | And 3 more authors.
Revista de Chimie | Year: 2012

In this work zinc oxide, ZnO, nanopowders were synthesized by co-precipitation method from a zinc acetate, Zn(CH 3COO) 2, solution. The obtained nanoparticles were morphologically and structurally characterized by XRD diffraction, SEM, IR and UV-Vis spectroscopy. The new obtained material was investigated as an additive in coatings for improving wet scrub resistance, self-cleaning properties etc. The XRD pattern of the ZnO nanoparticles highlights the wurtzite hexagonal structure and also proves its purity. The correlations made based on their crystallization planes identified ZnO as the sole product. ZnO nanoparticles obtained by co-precipitation method have been introduced by strong shaking in the coating system; this has positively innfluenced the surface properties of the films.

Pic A.,Polytechnic University of Bucharest | Ficai A.,Polytechnic University of Bucharest | Ficai D.,Polytechnic University of Bucharest | Guran C.,Polytechnic University of Bucharest | Dumitru F.,Research Institute for Advanced Coatings
UPB Scientific Bulletin, Series B: Chemistry and Materials Science | Year: 2015

In this paper we present the antimicrobial performances of some coatings based on acrylic polymers. The obtained coating materials have antimicrobial properties due to the presence of silver nanoparticles in their composition. The structure and morphology of coating materials were determined by infrared spectroscopy (FT-IR) and SEM-EDX. The ability of silver nanoparticles to release Ag ions in an aqueous solution has been demonstrated by measuring the electrical conductivity. Film-forming characteristics and biological properties are similar, indicating that the method of obtaining the formulations is reproducible. The introduction of 0.7% silver nanoparticles in polymeric coatings produces an optimum improvement of the antimicrobial performances.

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