română XIAN BIN WANG, SONG TANG, LIANG JI WANG
Abstract
The study aims to investigate the effects of Cr2O3 doping on the microstructure and properties of PMS-PZT piezoelectric ceramic materials. The solid-phase reaction method is used to prepare PMS-PZT ceramics. The microstructure is characterized using X-ray diffraction and scanning electron microscope. The research results indicated that doping with Cr2O3 significantly affected the crystal structure and properties of PMS-PZT materials. X-ray diffraction pattern analysis demonstrated that with the increase of Cr2O3 doping, the lattice constant of PMS-PZT samples changed, and the grain size also showed different distributions in scanning electron microscope images. When the doping amount of Cr2O3 was 0.2wt%, the piezoelectric constant d33 reached its maximum value, at 382pC/N, the relative dielectric constant εr was 1,325, and the dielectric loss tanδ decreased to 0.31%. The electromechanical coupling coefficient Kt and mechanical quality factor Qm were 0.68 and 461, respectively. The finite element analysis results indicated that the PMS-PZT material with the optimal doping amount exhibited excellent static and dynamic properties under high-energy density conditions. Therefore, appropriate Cr2O3 doping can optimize the microstructure and piezoelectric properties of PMS-PZT materials, making them promising for high-energy density applications.
Keywords
Piezoelectric ceramic materials; Cr2O3 doping; PMS-PZT material; Finite element analysis; Piezoelectric performance
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
CICEK KORKMAZ TORUN, FURKAN ALP TORUN, ZEYNEP OKTE
Abstract
Fluoride and strontium have been reported to improve apatite crystals when combined and are associated with significant reductions in acid reactivity. This study aimed to investigate the effect of single and combined application of fluoride and strontium solutions on the remineralization of initial enamel lesions. The buccal surfaces of teeth were divided into 4 regions and NaF, SrCl2 and NaF+SrCl2 combinations were applied. Initial surface microhardness was measured. Then, the teeth were kept in demineralization solution for 96 hours and their surface microhardness was measured again. After the solutions were applied to the relevant areas of the teeth, they were subjected to a 21-day pH cycle. At the end of 21 days, surface microhardness measurements were made again The difference between the initial and post-demineralization surface microhardness is statistically significant. Differences between the initial surface hardness and the surface hardness values measured after applying the solutions were found to be statistically significant. There was no statistically significant difference in surface microhardness values between the surfaces on which NaF, SrCl2 and their combinations were applied. Surface recovery was found to be statistically significantly higher in the NaF applied group compared to the other groups. When the findings of the study were evaluated, it was seen that the application of SrCl2 could be effective in the remineralization of enamel.
Keywords
fluorid, strontium, microhardness, remineralization
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
AWADHESH SRIVASTAVA, ABHISHEK MISHRA, SACHIN KUMAR SINGH
Abstract
The escalating construction activities have led to a significant environmental pollution due to the CO2 emission from cement industry. To address this issue, this study explored the incorporation of waste plastic polypropylene (PP) fibers at 1%, 2%, 3%, and 4% by weight of cement, combined with 2% nano titanium dioxide (TiO2). The objective was to assess how these plastic fibers influence the mechanical and physical properties of concrete. Investigation focused on various concrete properties, including water absorption, compressive, split tensile and flexural strength, as well as on non-destructive testing (NDT) to validate the destructive test. High magnification scanning electron microscopy (SEM) images were used to analyze the morphology of the concrete samples after 28 days of curing with different fiber percentages. The study revealed that all concrete mix achieved the mean target strength in compression. However, increment in the flexural strength approximately 34%, and the split tensile strength increased by about 18.18% with the addition of 2% nano TiO2 and 2% plastic fibers. 2% nano TiO2 with 1 to 2% PP fiber, gives the desired result in mechanical properties and microstructural properties.
Keywords
Fiber Reinforced Concrete, Nano Materials, Compressive Strength, Split Tensile Strength, Ductility, NDT test.
R. KARTHIKEYAN, C.HARIHARASUDHAN, M.SIVAKUMAR, K.SUGUNA, K.K.GAAYATHIRI
Abstract
This effort attempt to determine the durability of microsilica- zeolite based concrete. The study s main variables, zeolite and silica fume, were substituted for cement in the proper ratios: 5%, 10%, and 15% of zeolite and 10% of constant micro- silica. A total of 36 control specimens were cast and tested for this work, including cubes (150 x 150 x 150 mm), cylinders (100 mm × 200 mm) . Nine of the thirty-six control specimens are standard concrete specimens. The final 27 specimens were constructed using microsilica-zeolite based concrete. The experimental results clearly demonstrate that the addition of micro-silica and zeolite significantly enhances the durability characteristics of ternary blended concrete, including water absorption, resistance to acid attack, porosity, and carbonation depth. Moreover, incorporating micro-silica and zeolite into concrete mixtures not only improves the material s durability properties but also provides an environmentally friendly alternative to traditional cement-based mixtures.
Keywords
blended concrete, carbonation depth, micro-silica, zeolite, durability, strength.
ZHICHENG LIU, YICHAO ZHANG, LI SUN, XUAN LI, FENGRUI ZHANG, HUANG LI
Abstract
Mesoscale numerical simulations can provide a more intuitive and accurate characterisation of the mechanical behaviour of recycled concrete. This study entailed the development of a mesoscopic finite element model for recycled concrete by using mesoscopic CT images of recycled concrete and mesoscopic image processing techniques. An analysis of uniaxial compression damage characteristics of recycled concrete was performed. The results indicate that the development of a refined mesoscopic finite element model can be realised with a combination of histogram equalisation, image segmental transformation, median filtering and noise removal, morphological image processing, Canny edge detection, and image vectorisation techniques. In addition, the basic mechanical properties and stress–strain curve of recycled concrete under uniaxial compression obtained from the mesoscopic finite element model are in good agreement with the experimental results. Tensile stress concentration at the interfacial transition zone (ITZ), which is the leading cause of damage in recycled concrete, was exhibited when the axial stress reaches the compressive strength of recycled concrete. Under loading, the interface ITZ3 between the recycled aggregate and old mortar, was the first to show damage, followed by ITZ2, which is the interface between the new mortar and old mortar. ITZ1, which is the interface between the recycled aggregate and new mortar, was the last to show damage. This indicates that the mechanical properties of ITZ3 are relatively weak, the mechanical properties of ITZ1 are relatively strong. The mechanical properties of the ITZs have a direct impact on the compressive strength of recycled concrete.
Keywords
recycled concrete, uniaxial compression, damage characteristics, mesoscale, numerical simulation
J. SHANMUGAPRIYA, P. KRISHNA KUMAR, S. GEETHA, S. SIVARAMAKRISHNAN, M.SELVAKUMAR, A. KANDASAMY
Abstract
The present study relates to creating a simplified approach for the mix design of Internally cured Self Compacting Concrete under ambient curing conditions when fly ash is used as a supplementary cementitious material. A simple and novel approach for the Mix design of internally cured SCC with fly ash has been attempted in the study. The study helps in designing a robust mix design of SCC that could provide better workability and compressive strength even under poor or adverse curing conditions. A nomogram to determine the cement content, efficiency factor of fly ash and water content required for SCC have been developed and also nomograms for determining the internal curing water requirements have been developed for medium strength SCC with fly ash replacements up to 50%. A sample mix design for a fly ash replacement percentage of 35% and a Total Cementitious Material Content of 500 kg/m3 has been worked out and validated through the results of workability and compressive strength. Hence, this approach of mix design can be used as a ready-reckoner for proportioning a mix design for Internally cured Self compacting concrete of medium strength provided the percentage of fly ash replacement is decided and the characteristics of the internal curing material is known
Keywords
mix design, nomogram, internal curing, self-compacting concrete, efficiency factor