Browsing by Author "Voicu, Stefan Ioan"

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    Facile synthesis and characterization of hydroxyapatite particles for high value nanocomposites and biomaterials
    (Elsevier, 2017-06-07) Miculescu, Florin; Mocanu, Aura-Cătălina; Dascălu, Cătălina Andreea; Maidaniuc, Andreea; Batalu, Dan; Berbecaru, Andrei; Voicu, Stefan Ioan; Miculescu, Marian; Kumar, Vijay; Ciocan, Lucian Toma
    Lately Hydroxyapatite has gained a lot of research interest and intense focus due to its structural as well as compositional similarity to the components of human bone mineral. The conversion of calcium-rich precursors to hydroxyapatite could lead to the development of a new sustainable alternative with a valuable environmental and socio-economically impact. Still, current approaches faces lots of challenges in terms of synthesis parameters compatible to a reproducible route for calcium phosphates (hydroxyapatite included) synthesis. The optimization of Rathje synthesis route and characterization of biogenic derived calcium phosphates from dolomitic marble and Mytilus galloprovincialis seashells, constitutes the main goals of this study. The synthesized materials were characterized using FTIR, SEM coupled with EDS, and X-ray diffraction at all synthesis stages. Precursors were also subjected to thermal analysis and differential scanning calorimetry for thermal transformations investigations and dissociation temperature setting. This study suggests that acid quantity and magnetic stirring are the key-factors for Ca/P molar ratio adjustment, hence for the amount of naturally-derived hydroxyapatite. This research also contributes to the development of new strategies for further optimization of the conversion procedure and removal of residual components.
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    Fundamentals and scopes of doped carbon nanotubes towards energy and biosensing applications
    (Elsevier, 2018-05-22) Muhulet, Alexandru; Miculescu, Florin; Voicu, Stefan Ioan; Schütt, Fabian; Thakur, Vijay Kumar; Mishra, Yogendra Kumar
    Since their first allusion, carbon nanotubes have attracted significant research interest, especially with respect to composite manufacturing as a filler material for enhancing their mechanical and electrical properties. Several methods have been developed for modifying the electrical properties of carbon nanotubes such as CNTs wall's carbon atoms substitution with other appropriate atoms including engineering of their outer surfaces by covalent and noncovalent molecules, such as CNTs channel filling and nano-chemical reactions therein. CNTs with tailored electrical conduction open large perspectives for their applicabilities in advanced technologies. Taking into consideration the innovative advantages of pure and hybrid CNTs, in this article we have comprehensively reviewed the latest state-of-art research developments in the direction of different synthesis strategies, structure-property relationships, and advanced applications towards energy storage, supercapacitors, electrodes, catalytic supports, as well as biosensing.
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    Progress in hydroxyapatite-starch based sustainable biomaterials for biomedical bone substitution applications
    (American Chemical Society, 2017-09-05) Miculescu, F.; Maidaniuc, A.; Voicu, Stefan Ioan; Kumar Thakur, Vijay; Stan, G. E.; Ciocan, L. T.
    Hydroxyapatite is a calcium phosphate intensively proposed as a bone substitution material because of its resemblance to the constituents of minerals present in natural bone. Since hydroxyapatite’s properties are mainly adequate for nonload bearing applications, different solutions are being tested for improving these properties and upgrading them near the target values of natural bone. On the other hand, starch (a natural and biodegradable polymer) and its blends with other polymers have been proposed as constituents in hydroxyapatite mixtures due to the adhesive, gelling, and swelling abilities of starch particles, useful in preparing well dispersed suspensions and consolidated ceramic bodies. This article presents the perspectives of incorporating starch and starch blends in hydroxyapatite materials. Based on the role of starch within the materials, the review covers its use as (i) a polymeric matrix in hydroxyapatite composites used as adhesives, bone cements, bone waxes, drug delivery devices or scaffolds and (ii) a sacrificial binder for fabrication of porous hydroxyapatite scaffolds. The suitability of these materials for bone reconstruction has becomes a reachable aim considering the recent advancements in ceramic fabrication and the current possibilities of controlling the processing parameters.
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    Synthesis and characterization of jellified composites form bovine bone-derived hydroxyapatite and starch as precursors for robocasting
    (American Chemical Society, 2018-01-31) Miculescu, Florin; Maidaniuc, Andreea; Miculescu, Marian; Dan Batalu, Nicolae; Cătălin Ciocoiu, Robert; Voicu, Stefan Ioan; Stan, George E.; Kumar Thakur, Vijay
    Hydroxyapatite–starch composites solidify rapidly via jellification, making them suitable candidates for robocasting. However, many aspects related to hydroxyapatite powder characteristics, hydroxyapatite–starch interaction, and composites composition and properties need to be aligned with robocasting requirements to achieve a notable improvement in the functionality of printed scaffolds intended for bone regeneration. This article presents a preliminary evaluation of hydroxyapatite–starch microcomposites. Thermal analysis of the starting powders was performed for predicting composites’ behavior during heat-induced densification. Also, morphology, mechanical properties, and hydroxyapatite–starch interaction were evaluated for the jellified composites and the porous bodies obtained after conventional sintering, for different starch additions, and for ceramic particle size distributions. The results indicate that starch could be used for hydroxyapatite consolidation in limited quantities, whereas the composites shall be processed under controlled temperature. Due to a different mechanical behavior induced by particle size and geometry, a wide particle size distribution of hydroxyapatite powder is recommended for further robocasting ink development.