română NOUR-DJIHANE MAZOUZI, KHALIDA BOUTEMAK, AHMAD HADDAD
Abstract
Films based on hydroxypropylmethylcellulose (HPMC) find applications in for various applications due to their environmental nature, low cost, flexibility and transparency. However, the mechanical properties and moisture content need to be improved. The point of this study was to examine the impact of the magnesium oxide (MgO) addition on the physicochemical, mechanical and rheological properties of hydroxymethylcellulose films. HPMC/MgO composite films showed a four-fold increase in mechanical properties compared to unreinforced HPMC films. In addition, the addition of MgO nanoparticles reduced the moisture content to 2%. The latter was influenced by the difference in water solubility of various composite films, the incorporation of MgO into HPMC films improved the water barrier properties despite the increased water resistance value. Steam wettability was obtained for the HPMC/MgO composite film.
Keywords
hydroxypropyl methylcellulose HPMC, magnesium oxide MgO, nanoparticles, rheological properties
HAO LI, WEI ZHOU, KSENIIA RUDENKO
Abstract
High-performance fiber-reinforced cement composites (HPFRCCs) are attractive in applied in life-cycle structures. Hybrid properties of HPFRCCs with various fibers was experimentally investigated in this study. Three fibers contains the long and short smooth steel fibers and PE fibers, were blended into paste and mortar reinforced with 1.5% vol. fibers, respectively. Enhancements in mechanical properties including compressive strength and flexural strength, and workability were various for different types of fibers. The results show that for FRCCs with available amount of PE and steel fiber was achieved satisfactory workability. The better compressive strength was obtained at 28 day is 100.5MPa and 95.0MPa for the paste and the mortar, respectively. Incorporation of PE fiber in cement paste led to improvement in flexural strength. Microstructure has indicated effectively dense cementitious composites strong bond between the fibers and the cement paste for both of the mixes.
Keywords
high-performance fiber-reinforced cement composites (HPFRCCs), compressive strength, flexural strength, workability
FLORENTINA MARILENA CLICINSCHI, CRISTINA ANTONELA BANCIU, MAGDALENA VALENTINA LUNGU, DORINEL TĂLPEANU, CIPRIAN ALEXANDRU MANEA, GABRIELA BEATRICE SBÂRCEA, DELIA PĂTROI, VIRGIL EMANUEL MARINESCU, ALINA IULIA DUMITRU
Abstract
The aim of this study is to determine the influence of different sintering additives (Al2O3 and Y2O3) on the development of ceramic composite materials based on β-SiC with improved mechanical properties, using the spark plasma sintering (SPS) technique. The SPS process was conducted in a vacuum under an applied pressure of 50 MPa, at sintering temperatures of 1850°C and 1900°C, with a holding time of 10 minutes. The structural and morphological behaviour of the composites obtained at different sintering temperatures, which contribute to the improvement of mechanical properties, was analyzed through X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Physico-mechanical characteristics, such as apparent density, porosity, Vickers hardness, modulus of elasticity, coefficient of friction and specific wear rate, were also determined for all sintered samples. Structural analysis by XRD revealed the formation of a major β-SiC phase and a minor α-SiC phase, with evidence of increased crystallographic transformation between the two phases (β→α). Based on the results, it was observed that the SiA, SiAY, and SiYA composites sintered at 1900°C achieved a density greater than 3 g/cm3 and a porosity below 1%. Additionally, the apparent density increased with sintering temperature, resulting in a densification of 92-93% for composites sintered at 1900°C. All samples exhibited a Vickers hardness greater than 1800 HV, with the SiA composites demonstrating a hardness greater than 2263 HV. The SiA composite sintered at 1900°C exhibited an elastic modulus of 309-323 GPa, along with the lowest mean coefficient of friction of 0.562 and the lowest wear rate ((1.26±0.08)×10-5 mm3/N·m).
Keywords
Spark Plasma Sintering, β-SiC, ceramic composites, X-ray diffraction, scanning electron microscopy, mechanical and tribological properties
IRINA ELENA DOICIN, ADELINA-DENISA GOLEA, IONELA ANDREEA NEACȘU, VLADIMIR LUCIAN ENE, ALEXANDRA CATALINA BÎRCĂ, ALINA MARIA HOLBAN, ECATERINA ANDRONESCU
Abstract
This study explores the deposition of zinc oxide (ZnO) nanoparticles onto cotton fibers to enhance their antimicrobial properties, aiming to create advanced materials for medical gowns. ZnO nanoparticles were deposited onto cotton fibers using the spin-coating method with varying concentrations of precursor solutions and numbers of layers. The structural, morphological, and chemical properties of the coated textiles were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopic (FT-IR) and correlated with the antimicrobial assay results. Results indicated that a precursor concentration of 0.5 M and optimal layering (20 layers) led to a uniform distribution of ZnO nanoparticles, with sizes ranging from 40 to 90 nm. This configuration exhibited also the highest antimicrobial activity against tested microorganisms (Escherichia coli, Staphylococcus aureus, and Candida albicans). In contrast, samples with higher precursor concentrations and larger microparticles showed reduced antimicrobial performance. These findings highlight the importance of controlling nanoparticle size and deposition conditions to achieve maximum antimicrobial efficacy.
Keywords
ZnO; spin-coating; cotton fiber; antimicrobial effect
ȘTEFAN-ALEXANDRU GAFTONIANU, CARMEN CHIFIRIUC, ECATERINA ANDRONESCU ADRIAN SURDU, ALEXANDRA-CRISTINA BURDUȘEL, ROXANA TRUȘCĂ
Abstract
The work in this paper focuses on the preparation, characterization, and functionalization of magnetite (Fe₃O₄) and cerium oxide (CeO₂) nanostructures. The present work was carried out to prepare the nanoparticles with a high degree of uniformity and stability through advanced techniques, and the functionalization of the nanoparticles was targeted at improving their colloidal stability and biocompatibility. Morphostructural analysis disclosed some characteristics that could explain their behavior when applied in biomedical fields. The antimicrobial activity was assessed against pathogens such as Staphylococcus aureus and Escherichia coli, while the antitumor activity was evaluated on HeLa cell lines. The results indicated a good antimicrobial effect and a certain level of selectivity in cytotoxicity against cancer cells, which means these nanostructures may have potential in specific therapy. This study offers important information regarding how the properties of the nanomaterials can be optimized for their most effective use in antimicrobial and oncological treatments.
Keywords
Nanoparticles, magnetite, cerium oxide, antimicrobial activity, antitumor effect, functionalized nanostructures.
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Year
2024
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Issue
54 (3)
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Pages
198-204
RADU MIREA
Abstract
Current paper is aiming to show the obtained results in obtaining and characterization of graphite-based and metal composite materials suitable to be used in high voltage application of automotive field. Thus, 4 types of materials have been processed and tested in order to assess their suitability to be used as current collector material for trolleybus. The novelty of this work is the new innovative technological process for obtaining the carbon/metal composite material used in the manufacture of sliding contacts for electrical current collector heads, as well as the characteristics obtained for this material. All 4 obtained materials have been characterized from structural (by optical microscopy), mechanical (density, electrical resistivity, hardness) and functional point of view (wear after 1000 working hours, electric discharge and electric load) and it was determined that the material which uses chemically copper covered graphite is the most suitable of them and has been chosen to be further developed by the end beneficiary.
Keywords
graphite, carbon composite, high voltage, carbon/metal