română R. KARIMIA, I. ABBASPOURA, M. AMIRIB
Abstract
Magnetic Nanofluids, such as water-alumina, water-copper, and water-iron oxide, have been attracted due to their interesting thermo physical properties and their application are important branches of engineering such as heat transfer. Research results in recent years show that the presence of nanoparticles increases heat transfer. In this research, we will produce iron oxide (Fe3O4) nanoparticles, by co-precipitation. Two samples of nanoparticles were synthesized, and the size of the produced nanoparticles was around 30-60 nm. The size of the nanoparticles in the fluid (water) and their distribution have a significant effect on the conductivity coefficient of the porous medium (magnetic Nanofluid). Therefore on the heat transfer factor, we will try to reduce the size of the nanoparticles as much as possible and make the particle size distribution uniform. After synthesis, nanofluid is obtained by combining nanoparticles with a certain mass with water. Arabic gum has been used to prevent nanoparticles from sticking together in nanofluid suspension. Zeta potential was obtained for nanofluid suspensions and it was observed that have good stability. To investigate the effects of adding nanoparticles to water in heat exchangers, we used critical heat flux (CHF) analysis. Using CHF, we can obtain the heat transfer factor, and we showed that by adding synthesized Fe 3 O 4 nanoparticles to the base fluid, the heat transfer is improved.
Keywords
Nanofluids, Heat transfer factor, Iron (II, III) oxide, Heat exchangers
DENISA-NICOLETA MUȘAT, ALEXANDRA-CRISTINA BURDUȘEL, ȘTEFAN GAFTONIANU, ANTON FICAI, OVIDIU OPREA, ROXANA POPESCU, ROXANA TRUȘCĂ, ECATERINA ANDRONESCU
Abstract
This research describes the synthesis and characterization of a nanocomposite material that serves dual purposes: promoting bone healing and providing microbial defense. Therefore, 45S5 bioactive glass was synthesized through sol-gel synthesis with zinc oxide nanoparticles produced via microwave-assisted hydrothermal synthesis. The addition of peppermint and lemon balm essential oils at different concentration levels enhanced the material’s biological functionality. The composites considered were analyzed by thermal analysis (TG–DSC), FTIR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) for evaluation. The analysis confirmed the existence of crystalline phases, along with particle morphologies and the incorporation of functional groups. The bioglass particles measured between 2–4 μm in size, while the ZnO nanoparticles size range was from 200 to 400 nm, with a uniform distribution confirmed by elemental mapping. The biocompatibility assessment utilized an MTT assay with MG-63 osteoblast-like cells. The results showed that ZnO caused dose-dependent cytotoxicity; however, the addition of essential oil reduced this effect, mainly when lemon balm essential oil was used at a 2% concentration, which demonstrated improved biocompatibility across all tested concentrations. The developed composite material exhibits enhanced antimicrobial properties and osteoconductivity, along with reduced cytotoxicity, making it suitable for biomedical applications in bone tissue engineering.
Keywords
bioglass, zinc oxide, composite, essential oils, antimicrobial effect
ANDREEA-CRISTIANA ALEXE, ALEXANDRA-CRISTINA BURDUȘEL, ȘTEFAN GAFTONIANU, OVIDIU OPREA, ROXANA POPESCU, ROXANA TRUȘCĂ, ANTON FICAI, ECATERINA ANDRONESCU
Abstract
Bone tissue regeneration presents a significant challenge due to the complexity of bone structures and the limitations inherent in traditional grafting methods. The aim of the study is to describe the development and analysis of a nanocomposite material that combines cerium-doped hydroxyapatite (Ce-HAp) with bioactive glass (45S5 Bioglass) and natural essential oils (sage and thyme). The hydroxyapatite was produced through microwave-assisted hydrothermal synthesis, the bioglass through sol-gel processing, and essential oils were added to the final obtained material. The composite material underwent XRD, FTIR, SEM, and EDAX analysis, which confirmed its crystalline phases, chemical composition, and morphological features. The MTT assay results showed that MG-63 osteoblast-like cells demonstrated high biocompatibility and no cytotoxicity, while samples containing sage essential oil led to increased cell viability. The thermal analysis showed that the composite materials maintained excellent thermal stability. The nanocomposite material exhibits enhanced bioactivity, antimicrobial properties, and cytocompatibility, making it suitable for medical applications. The multifunctional system provides a substitute for standard grafts, while additional biomedical applications can be achieved by adding biologically active ions such as Ag, Sr, Ce, or Zn.
Keywords
hidroxiapatită, oxid de ceriu, uleiuri esențiale, biosticlă, biocompatibilitate
ANGELA GABRIELA PĂUN, ROBERTA-GEANINA MIFTODE, MIHAELA VASILICA MÎNDROIU
Abstract
This paper presents the main findings of our study on the preparation and characterization of polyvinyl alcohol (PVA)-based conductive bio-membranes intended for use as solid polymer electrolytes (SPEs) in smart window applications. The novelty of this research lies in the development of PVA bio-membranes with enhanced ionic and electronic conductivity through the incorporation of lithium perchlorate (LiClO₄) as a lithium-ion (Li⁺) source, as well as functionalization with deoxyribonucleic acid (DNA) and poly(3,4-ethylenedioxythiophene) (PEDOT), the latter introducing electronically conductive pathways. The bio-membranes were characterized by Fourier transform infrared (FTIR) and UV-Vis spectroscopy, along with electrochemical impedance spectroscopy (EIS) to determine their ionic conductivity. The PVA-based bio-membrane exhibiting the highest conductivity was further employed in the assembly of a smart window device, which was evaluated through chronoamperometry, charge density measurements, and UV-Vis spectroscopy. Results demonstrated that the synergistic combination of PEDOT, LiClO₄ and DNA (facilitating ion transport and polymer matrix interaction) led to the formation of mixed ion–electron conductive pathways that support dual charge transport. The electrochromic smart window incorporating the optimized PVA-based bio-membrane exhibited an optical modulation (ΔT) of 22%, with fast switching times of 11 seconds for coloration and 13 seconds for bleaching.
Keywords
Bio-membranes, Electrochromic smart windows, Polyvinyl alcohol, Deoxyribonucleic acid, Ionic conductivity
MARIA ELIZA PUSCASU, CRISTINA BUSUIOC
Abstract
In the recent years, bone has become the second most transplanted tissue at the global level as a result of increased number of accidents, pathologies and prolonged lifetime span. Currently, there are significant limitations in the available materials for the bone tissue transplantation and there is a high demand for the research of suitable substituents. Following the bone composition and intricate architecture, a grafting material with high potential in bone tissue engineering may be obtained. Bioceramics from the system CaO‒MgO‒SiO2 (ex. diopside, akermanite and merwinite) have excellent bioactivity and are similar with hydroxyapatite from biological point of view, having improved mechanical resistance. Considering the complex inner architecture of the bone, one of the most suitable fabrication methods in the bone tissue engineering is 3D printing as this technique facilitates manufacturing of intricate inner structures with a high control on the infill parameters. In this work diopside, akermanite and merwinite based powders were obtained using both sol-gel and combustion methods. All obtain powders were characterized using X-ray diffraction, while diopside and merwinite powders were characterized from morphological point of view by scanning electron microscopy. Further on, the obtained powders were mixed with an organic additive in order to obtain a printable paste with characteristic adequate for robocasting process. A comparison between the impact of the synthesis method in the paste formulation was further assessed. The obtained 3D scaffolds were evaluated from morphological point of view using Scanning Electron Microscopy. The results suggested that the synthesis method plays an important role in the paste formulation for the 3D printing process and that diopside, akermanite and merwinite based scaffold can be successfully obtained by robocasting method.
Keywords
Calcium Magnesium Silicates; Sol-Gel; Combustion; Robocasting, Bone Tissue Engineering
ANCA MIHAELA MOCANU, ANDREEA IOANA SUSANU
Abstract
The paper explores the domain of digitally fabricated dental prostheses, specifically detailing the application of CAD/CAM (Computer-Aided Design/Computer-Aided Manufacturing) methodologies within the field of restorative dentistry. The research undertakes a thorough examination of the digital fabrication sequence in prosthodontics, which encompasses critical phases such as intraoral/laboratory scanning, CAD modeling, automated milling, and final surface treatment. A significant portion of the work is dedicated to the CEREC system implementation in the chairside clinical environment (i.e., procedures completed within the dental practice). Furthermore, the study includes an assessment of the specialized equipment and the mechanical behavior of three notable restorative biomaterials: Zirconium Dioxide, IPS e.max Ceram Dentin, and Cerasmart. The CEREC system is a computerized system that can be used to design and produce, in a single session, highly accurate, aesthetic, and durable ceramic restorations for small cavities. The dental materials were analyzed both before and after the firing process using infrared absorption spectroscopy (FITR), and the morphology of the samples was highlighted using a high-resolution scanning electron microscope equipped with an EDX detector and thermal analysis (TG-DTG-DTA). The characterization methods were applied to compare the performance of the three materials, with a focus on marginal adaptation, aesthetics, strength, and ease of processing, and to highlight the essential differences between the materials in the context of their use in dental restorations. The results of this study, together with data from the literature, help to understand the interaction of these materials with tissues and also to modify the properties of these materials.
Keywords
ceramic kits, CAD/CAM technique, absorption spectroscopy, scanning electron microscopy, thermal analysis