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Simion C.E.,National Institute of Materials Physics Bucharest | Sackmann A.,University of Tubingen | Teodorescu V.S.,National Institute of Materials Physics Bucharest | Rusti C.F.,National RandD Institute for Non Ferrous and Rare Metals | Stnoiu A.,National Institute of Materials Physics Bucharest
Sensors and Actuators, B: Chemical | Year: 2015

Within the field of chemical gas sensing, ammonia detection represents one of the nowadays challenges, due to its adverse effects for human health. Real operating investigations are imposed by the high solubility potential of NH3 at room temperature. Thick films of Ba0.75Sr0.25TiO3 material have been investigated by means of electrical resistance and capacitance changes and correlated with the photoacoustic outputs. The experimental findings have been discussed in terms of Grotthuss mechanism, with respect to the ionic/electronic conduction within BST, toward ammonia detection enhanced by the presence of water vapors when operated at room temperature. So an appropriate NH3 sensing mechanism was proposed. © 2015 Elsevier B.V. All rights reserved. Source


Piticescu R.R.,National RandD Institute for Non Ferrous and Rare Metals | Valsan S.N.,National RandD Institute for Non Ferrous and Rare Metals | Petriceanu M.,National RandD Institute for Non Ferrous and Rare Metals | Badilita V.,National RandD Institute for Non Ferrous and Rare Metals | And 4 more authors.
Journal of Optoelectronics and Advanced Materials | Year: 2015

Nanopowders based on Co-doped TiO2 anatase (with Co content in the range 0-5 at %) with rod-like structure and homogeneous distribution of the doping agent were obtained by hydrothermal synthesis in the temperature range 200-2750C in the presence of KOH as mineralizing agent. The kinetic triplet of crystallization (activation energy, reaction orders and pre-exponential factors) were calculated from DSC measurements using Avrami-Erofeev equation. For pure TiO2 the best fitting reaction order was found n=1 while for 2.5 and 5 at% Co-doped TiO2 the reaction order is n=2/3. The evolution the activation energy with increasing Co content may be attributed to the increasing of defects in the crystalline lattice, as suggested by EPR results. The EPR investigations show also different ferromagnetic behaviours with increasing Co concentration. Source


Velea T.,National RandD Institute for Non Ferrous and Rare Metals | Taloi D.,University of Bucharest | Predica V.,National RandD Institute for Non Ferrous and Rare Metals | Gherghe S.U.,National RandD Institute for Non Ferrous and Rare Metals | And 3 more authors.
Revista de Chimie | Year: 2013

The paper presents the results of the mathematical modelling for the oxidation process (in autoclave) of sulphurous concentrates with lead (PbS containing), in weak alkaline aqueous medium. Using an active program of experiments (an order two orthogonal program, P02), the optimal conditions were established in order to run the process in a manner that will lead to obtaining a maximum oxidation yield of sulphides from lead concentrates. Preliminary research and studies indicated four parameters (temperature, process duration, oxygen partial pressure and L:S ratio) that have a signihcant influence on the performance of the oxidation process, which we define as the oxidation yield of the sulphides in concentrate. The optimal values of the oxidation process parameters are: T = 138°C, t = 2.53h, pw = 4.78 atm andt.S ratio = 15:1. Source


Popescu L.M.,National RandD Institute for Non Ferrous and Rare Metals | Piticescu R.M.,National RandD Institute for Non Ferrous and Rare Metals | Rusti C.F.,National RandD Institute for Non Ferrous and Rare Metals | Maly M.,rkinje University | And 4 more authors.
Materials Letters | Year: 2011

The present paper reports on an innovative route for the preparation of new hybrid nanostructured thin films based on hydroxyapatite and functionalized polyurethane. Hybrid nanopowders based on hydroxyapatite and functionalized polyurethane have been synthesized by a hydrothermal method with high pressure and low temperature conditions and further used for spin coating deposition. Biocompatible thin films with a thickness of about 50 nm have been deposited onto Si/SiO2/Ti/Au substrates and their properties recommend them suitable as possible electrodes for the fabrication of impedance biosensors. Hybrid materials with improved properties are obtained, combining the mechanical properties of polyurethane with biocompatible properties of hydroxyapatite (bioactivity and osteoconductivity). The presence of functional groups in polyurethane structure ensures the existence of strong interactions between components and an increased affinity of the thin films for further protein bonding in biosensor design. Hybrid nanostructured thin films based on hydrothermally synthesized hydroxyapatite-polyurethane nanopowders could enhance the amount of immobilized biomolecules in the construction of an impedance biosensor for diagnosis and therapy of bone diseases. © 2011 Elsevier B.V. Source


Popescu L.M.,Petru Poni Institute of Macromolecular Chemistry | Popescu L.M.,National RandD Institute for Non Ferrous and Rare Metals | Piticescu R.M.,National RandD Institute for Non Ferrous and Rare Metals | Antonelli A.,Urbino University | And 8 more authors.
Journal of Materials Science: Materials in Medicine | Year: 2013

The development of engineered biomaterials that mimic bone tissues is a promising research area that benefits from a growing interest. Polymers and polymer-ceramic composites are the principle materials investigated for the development of synthetic bone scaffolds thanks to their proven biocompatibility and biostability. Several polymers have been combined with calcium phosphates (mainly hydroxyapatite) to prepare nanocomposites with improved biocompatible and mechanical properties. Here, we report the hydrothermal synthesis in high pressure conditions of nanostructured composites based on hydroxyapatite and polyurethane functionalized with carboxyl and thiol groups. Cell-material interactions were investigated for potential applications of these new types of composites as coating for orthopedic implants. Physical-chemical and morphological characteristics of hydroxyapatite/polyurethane composites were evaluated for different compositions, showing their dependence on synthesis parameters (pressure, temperature). In vitro experiments, performed to verify if these composites are biocompatible cell culture substrates, showed that they are not toxic and do not affect cell viability. © 2013 Springer Science+Business Media New York. Source

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