română LEVENTE-ZSOLT RÁCZ, LUCIAN-CRISTIAN POP, GHEORGHE TOMOAIA, AURORA MOCANU, CSABA-PÁL RÁCZ, ATTILA-ZSOLT KUN, EDIT FORIZS, MELINDA SÁRKÖZI, CSABA VÁRHELYI JR., MARIA TOMOAIA-COTISEL
Abstract
Gaining basic knowledge on the nanostructure of advanced composites, based on curcumin, CCM, mixed with various bioactive compounds, in polyethylene glycol, PEG6000, will allow better innovative applications of these composites for their importance, particularly as functional foods and supplements for human health care benefits. Our goal is to understand the behavior of curcumin, in the presence of whey protein concentrate, WPC, trans-resveratrol, RES, or silymarin, SIL, within PEG6000 matrix, and the role of biomolecules in making advanced composites, such as PEG6000-CCM, PEG6000-CCM-WPC, PEG6000-CCM-RES-WPC and PEG6000-CCM-SIL-WPC, and thus, developing tailored compositions with multifunctionality. In this study, AFM images: 2D- and 3D-topographies as well as phase and amplitude images provide the surface morphology of nanostructured composites at nanometer resolution and surface roughness as root mean square, RMS, confirming the miscibility of compounds within PEG6000 matrix, and the shape and size of composite nanoparticles. The WPC enhances the stability of these composites through the intermolecular hydrogen bonds with CCM and RES or SIL, leading from small molecules to advanced composite nanostructures within the PEG6000 matrix, as evidenced by AFM investigation. FTIR data for all four composites reveal the interaction between the precursor components within PEG6000 matrix primarily by the formation of new intermolecular hydrogen bonds between their functional groups. Conclusively, the innovative nanocomposites, PEG6000-CCM, PEG6000-CCM-WPC, PEG6000-CCM-RES-WPC and PEG6000-CCM-SIL-WPC, provide an effective strategy for the design of novel promising nanocomposites for biomedical applications, such as drug delivery systems to treat various diseases, especially cancer and for bone regeneration medicine.
Keywords
nanostructured composites, curcumin, whey protein concentrate, resveratrol, silymarin, PEG6000, AFM, FTIR
HAYET MISSOUNI, DJANETTE MERIEM BLIZAK, SOUHEYLA TOUBAL, IMANE DJOUABI, MAHDIA TOUBANE, NADIA BOUKHERROUB
Abstract
Conventional nanoparticle synthesis routes raise growing environmental concerns, making green approaches increasingly relevant. Here, NiO nanoparticles were prepared via hydrothermal synthesis, using Ziziphus Lotus (L.) almond as a natural mediating agent, alongside a control synthesis without extract. According to our investigations, no previous study has used, the almonds of Ziziphus Lotus (L.), for the production of metal oxide nanoparticles. The nanoparticles obtained were characterized by X-ray diffraction (XRD), UV-visible spectroscopy, scanning electron microscopy (SEM), UV-visible spectroscopy, and zeta potential measurement. The results we obtained showed that the hydrothermal temperature is a crucial parameter in crystallization: samples treated at 140 °C exhibited good crystallization, with crystallites averaging around 34 nm in size, and SEM images revealed a clearly ordered lamellar morphology. The presence of this almond extract had multiple effects on the resulting nanoparticles. Their growth was directed towards anisotropic morphologies, their surface charge was modified, and their optical band gap was considerably widened, reaching 3.75 eV, compared to 3.48 eV in the sample without the extract. The results of this study confirm that hydrothermal biosynthesis is a easy and environmentally friendly method for producing NiO nanoparticles. Thus, these nanoparticles may provide new opportunities in the domain of optoelectronics, energy storage and biomedical applications.
Keywords
NiO nanoparticles, biosynthesis, hydrothermal, Ziziphus Lotus (L.) Lam almond
FLORENTINA MARILENA CLICINSCHI, CRISTINA ANTONELA BANCIU, DORINEL TĂLPEANU, MAGDALENA VALENTINA LUNGU, CRISTINA CORNELIA COSTEA, GABRIELA BEATRICE SBÂRCEA, DELIA PĂTROI, VIRGIL EMANUEL MARINESCU
Abstract
The aim of this research was to obtain composite ceramic materials based on a silicon carbide (SiC) matrix modified with sintering additives (Al2O3 and Y2O3) and reinforced with 1 wt.% or 5 wt.% milled carbon fibers (Cf) using the spark plasma sintering (SPS) technique. SPS processing was carried out under vacuum at an applied axial pressure of 50 MPa and a sintering temperature of 1850°C, with a holding time of 10 minutes. The structural and morphological characteristics of the silicon carbide-based composites were examined using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Physical and mechanical properties, including bulk density, apparent porosity, Vickers hardness, elastic modulus, friction coefficient, and specific wear rate, were evaluated for all sintered specimens. XRD analysis indicated the predominance of the β-SiC phase in the composite materials. The results showed that all samples sintered at 1850°C achieved bulk densities above 3 g/cm3 and apparent porosities below 1.72%, corresponding to a densification degree of at least 98.28%. Furthermore, all analysed specimens exhibited Vickers hardness values exceeding 1568 HV, modulus of elasticity in the range of 240-299 GPa, and an average friction coefficient between 0.41 and 0.93 in dry sliding conditions.
Keywords
Spark Plasma Sintering, β-SiC, carbon fibers, ceramic composites, mechanical and tribological properties
RAJESH PINNAVASAL VENUKRISHNAN, BASKAR NEELAKANDAN, VINOTH KUMAR SELVARAJ
Abstract
The presented research work explores the fabrication and parametric optimization of β- Tri-Calcium Phosphate (β-TCP) composites reinforced with Zinc Oxide (ZnO) powder, which make them suitable for biomedical applications. TCP is widely recognized for its biocompatibility and bioresorbability, while ZnO offers strong bacterial inhibition and enhanced mechanical strength. The composite is fabricated using a compaction-sintering process, known as Powder Metallurgy technique followed by investigation of physical and mechanical attributes of the as-formed composite specimens. The process parameters viz., particle size of the constituents, volumetric percentage of TCP content and sintering temperature are optimized and the best possible specimen is selected among various combinations using a combinatorial statistical technique namely Historical Data incorporated Additive Ratio Assessment (HD-ARAS). The results demonstrate the performance of β-TCP-ZnO composites with significant enhancement in Particle Density, Microhardness and Compressive Strength. The starting particles and best ranked composite specimen is further subjected to microstructure study using Scanning Electron Microscope (SEM) to validate the results. This research supports the potential candidature of TCP-ZnO composites as viable materials in bone repair and regeneration.
Keywords
tri-calcium phosphate, zinc oxide, mechanical strength, powder metallurgy, bone repair
GEORGE ANDREI PETRESCU, ADRIAN IONUT NICOARA, VLADIMIR LUCIAN ENE, IONELA ANDREEA NEACSU, ANAMARIA BECHIR
Abstract
This study compared the mechanical behavior and chemical evolution of three temporary dental cements—zinc phosphate (FOZ), glass ionomer (CIS), and resin-based (DT)—aged in air and artificial saliva, and explored how microstructural changes relate to their mechanical performance. Cylindrical specimens of FOZ, CIS, and DT were prepared according to manufacturers’ instructions and aged for 3, 14, and 28 days in air or artificial saliva at 25 °C. Compressive strength and elastic response were measured by uniaxial testing. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) were used to characterize crystalline phases and functional groups. FOZ showed marked phase evolution, with XRD revealing a shift from a mixed ZnO–Hopeite composition toward ZnO dominance in air, while saliva preserved higher Hopeite content; these changes were associated with reduced compressive strength in air and increased strength in saliva. CIS remained crystallographically and chemically stable, with BaSO4 as the main crystalline phase and minimal FTIR changes, matching its nearly unchanged compressive strength in air. DT maintained a broadly constant biphasic calcium phosphate–zirconia pattern and a stable resin FTIR signature, consistent with its predominantly elastic behavior and modest variation in elastic force, especially in saliva. The three cements exhibit distinct, material-dependent aging patterns that directly influence their mechanical performance under simulated oral conditions.
Keywords
dental cements, zinc phosphate cement, glass ionomer cement, resin-based cement, artificial saliva aging, provisional prostheses
RĂDUCU-MIHAI GEANTĂU, ANCUȚA ROTARU, TRAIAN-DĂNUȚ BABOR, MARIA TUNKIEWICZ, JOANNA MISIEWICZ, PIOTR KOSIŃSKI
Abstract
Mercury intrusion porosimetry (MIP) within the present study, was not used as a stand-alone proof of pore blocking, but as a complementary microstructural method interpreted in relation to capillarity and surface-level hydrophobic behaviour of the hydrophobised brick specimens, with the aim of contextualising changes in liquid water transport after PDMS–Si biomimetic treatment. The study evaluated a silica nanoparticle-polydimethylsiloxane (Si-PDMS) mixture. Aplication to historical Gothic-type and factory-made fired-clay foundation bricks was made by brush and the homogenization was performed by mechanical agitation at 50 Hz, and no visible sedimentation is observed, phase separation of the materials used or agglomeration was during the preparation and application window. The treatment was applied by brush on the exposed surfaces of the specimens. This methodological position is essential because MIP primarily reflects the smallest accessible constrictions within the pore network and is influenced by ink-bottle effects for the surface pore distribution. The results showed that historic bricks that where tested exhibited higher open porosity and a broader pore-throat distribution than modern bricks, confirming their greater susceptibility to capillary uptake and their higher capacity for treatment penetration. By contrast, denser modern bricks that where tested presented lower baseline porosity and more limited changes after treatment. MIP outputs indicated that the 2% Si mixture produced the clearest refinement of accessible porosity, reducing total porosity from 42.842% to 35.111% for Gothic bricks and from 28.861% to 25.236% for factory-made bricks. In contrast, the 5% Si mixture showed a partial rebound in porosity-related parameters, suggesting diminishing returns at higher solids loading. MIP served as a contextual and plausibility-based tool, helping to explain why reductions in capillary vulnerability were more pronounced in more porous historic materials without implying that hydrophobisation acted by sealing the substrate. The porosity analysis therefore supports the conclusion that the biomimetic PDMS–Si treatment modifies interfacial wetting and partially alters accessible near-surface transport pathways, with implications for reducing liquid water ingress, salt crystallization risk, and freeze-thaw susceptibility. The study explicitly acknowledges its current experimental limitations. Because not all the dimensions of the potential study were addressed water-vapour transmission was not measured, and no standardized durability campaign was completed. We attempted to test freeze-thaw behaviour the results wer inconclusive because it was not performed according to a standardized method and the specimens were damaged during the analysis stage. Mechanical strength remain essential for complete cross-study comparison. Interpreted within these methodological boundaries, MIP provides a credible microstructural framework for understanding the protective action Si-PDMS treatment in conservation-oriented masonry applications.
Keywords
mercury intrusion porosimetry, pore connectivity, porosity, historic bricks, modern bricks, silica nanoparticles, PDMS, durability, solvent-free treatment
RĂDUCU-MIHAI GEANTĂU, ANCUȚA ROTARU, TRAIAN-DĂNUȚ BABOR, MARIA TUNKIEWICZ, JOANNA MISIEWICZ, PIOTR KOSIŃSKI
Abstract
This study evaluates the hydrophobic properties of silica nanoparticle–polydimethylsiloxane (Si–PDMS) treatment developed for fired-clay masonry structures and infrastructures exposed to moisture. The work emerged from a conservation-driven question that also applies to contemporary construction: how to reduce liquid-water penetration without turning a porous substrate into a sealed, vapour-impermeable system with out damaging the material or its apperance. The formulation strategy follows a biomimetic route in which silica nanoparticles generate near-surface roughness and PDMS lowers surface energy, translating lotus-inspired surface. Historical and factory-made fired-clay bricks were dryed to constant mass and treated by brush application. The dispersion was prepared without solvent, homogenized by mechanical agitation at 50 Hz, and visually remained free of sedimentation or agglomeration during the preparation/application window. Wettability was assessed by static contact angle, bulk liquid uptake by 24 h immersion, and capillary transport; lateral faces were sealed during the capillary test. The treatment shifted the surface from highly hydrophilic (11.0°) to hydrophobic/superhydrophobic behavior (105.4–114.7°), reduced 24 h water absorption from 6.70% to 5.56–5.97%, and lowered the capillarity coefficient from 0.0015446 to 0.0013109–0.0013657 g/cm²·s. The highest surface beading was obtained at 2% Si-PDMS mixture, whereas the lowest immersion and capillary uptake occurred at 1% Si-PDMS mixture, indicating a non-linear trade-off between interfacial wetting control and bulk transport. Water-vapour transmission and standardized durability tests were not part of the present article; therefore, compatibility claims remain limited to the wetting and hygric indicators reported here.
Keywords
contact angle, wettability, hydrophobic impregnation, water absorption, capillary uptake, biomimetic coating, silica nanoparticles, PDMS, fired-clay brick, heritage masonry
DOBRE DANIEL-CĂTĂLIN, NEDELEA ALEXANDRU
Abstract
The Prahova Subcarpathians stretch between the Dâmbovița Valley and the Teleajen Valley, representing a large Subcarpathian relief unit, part of the Curvature Subcarpathians. This area consists of a series of massifs and hilly ridges, with elevations ranging between 300 and 850 meters, alternating with Subcarpathian depressions. This intermediate region between the mountains and the plains is characterized by its geographical complexity and the intensity of the urbanization process. The relationships between the relief and settlements are particularly prominent in the local geographical landscape. They can be observed at the level of major landforms, as well as larger or smaller sculptural forms, but mainly at the level of valleys and interfluves. The exposure of Subcarpathian settlements to various types and degrees of geomorphological (and hydrological) risk is a consequence of the specific way these relationships were formed, including valley settlements (terraces, alluvial cones, and glacis slopes) and interfluve settlements. All these aspects contribute to the originality and variety of the Prahova Subcarpathians, connecting the relief with its morphographic and morphometric characteristics, human settlements, economic activities and land use, all of which are in a relationship of interdependence and mutual conditioning.
Keywords
applied geomorphology, impact, susceptibility, landslides, Prahova Subcarpathians
MIRCEA BÂRNAURE, CONSTANTIN DORINEL VOINIȚCHI, FĂNICA VIRGINICA PANAIT
Abstract
In this experimental study, six lime-based mortar compositions were prepared under laboratory conditions, with sand-to-lime putty volume ratios of 1, 2, 3, 4, 5, and 7. The specimens were subjected to accelerated carbonation and subsequently tested. Compressive strength tests on standard samples revealed values significantly higher than those specified in the current Romanian design and assessment regulations for the same composition. Tests performed on non-standard specimens, with reduced height - close to that corresponding to the thickness of the mortar joint - yield very high measured values, making it difficult to establish correlations between these and the strengths obtained on standardized specimens. Chemical analysis proved to be a feasible method for evaluating mortar strength, provided that the aggregate does not contain calcium carbonates. The surface hardness method does not seem appropriate for lime mortars, as the recorded values are too low. For the penetration resistance tests and fastener pull-out tests, the measured values are very scattered, so these methods do not seem reliable for low strength mortars. The Double Punch Test (DPT) appears to be a promising alternative for the determination of compressive strength on site, with experimental results showing a strong correlation with standard compressive strength values. However, tests using multiple methods on samples taken in situ are needed to estimate differences due to curing conditions, starting from chemical analysis that can provide compositional characteristics.
Keywords
mortar, lime, composition, strength, chemical analysis, double punch test
ALEXANDR MUNTEAN, CONSTANTIN DORINEL VOINIȚCHI, BOGDAN ANDREI, FANICA VIRGINICA PANAIT
Abstract
The possibility of using other types of cements, besides the unitary ones provided for by the road concrete standards, was studied. In this regard, the changes in mechanical and durability properties when replacing a CEM I42.5R cement with CEM II A-M (S-LL) 42.5R type cements and one made in the laboratory of type CEM II A-V were analyzed. Concretes made with cements with supplementary cementitious materials SCM presented better mechanical characteristics in terms of compressive strength, bending strength and wear resistance at long terms or equivalent to concrete made with unitary cement for the modulus of elasticity. Durability tests - freeze-thaw resistance highlighted a better behavior of concretes with cements with SCM compared to the standard one. The shrinkage of concrete with CEM II A-V type cement was very close to that of the reference concrete made with unitary cement; concrete made with CEM II A-M (S-LL) cement had a significantly higher shrinkage. The results are promising, opening the way to testing on a larger scale several types of cements with additives, both for classical mechanical and durability properties but also for some results from the study of specialized literature from other countries.
Keywords
blended cement, concrete, pavement, durability, mechanical strength
NICULAE NOICA, CONSTANTIN DORINEL VOINIȚCHI, RADU CONSTANTIN VOINIȚCHI, GEORGETA VOICU, FĂNICA VIRGINICA PANAIT, MADJID HADJ AMER
Abstract
Investigation of an 120 years old reinforced concrete beam were carried out in order to find the degree of degradation and other durability characteristics. The idea behind the investigations was to find compositional parameters to ensure durability based on a real-scale experiment. Half Cell Test and visual observations show good condition of the reinforcing bars despite the age of beam. Carbonation depth in some places is practically zero and further investigation presented a high pH in the concrete. Using XRD on powder from the concrete matrix we found unhydrated calcium silicates even after mare than 100 years, fact which attributed to the coarse grinding of a belite cement. This led to self-healing concrete long before the concept appeared.
Keywords
carbonation, durability, old, concrete, cement
SEDIGHEH HOSSEINI , HOSSEIN MOHAMMADI MANESH, SAYED YASSIN MOUSAVI
Abstract
This paper investigates the effect of combined calcium nitrate tetrahydrate (CN), calcium formate (CF), and silica fume (SF) on early-age compressive strength in Portland cement mortar. For an appropriate mix design with limited numbers of trials, a Taguchi experimental design was conducted. CF was added at 0.5%, 1%, and 1.5%, CN at 1%, 2%, and 3%, and SF at 5%, 10%, and 15% as partial cement replacements. Compressive strength measurements, XRD, FT IR, and FESEM provided information on hydration products, phase transformations, and microstructural densification upon hydration. The optimum mix of 1% CN, 1% CF, and 5% SF improved the 7-day compressive strength by 16.1% over that of the control. CF favored the development of C-S-H by formate action; CN accelerated hydration through the provision of calcium ions, and SF reduced porosity by pozzolanic reaction and filler action. XRD and FT IR showed a decrease in portlandite, while FESEM presented a denser matrix. Accordingly, the results suggest a feasible way to enhance the early performance of cement mortars by adjusting CN, CF, and SF contents.
Keywords
Portland cement, silica fume, calcium nitrate, calcium formate, compressive strength
ADINA MATEESCU, BIANCA CANCEA, ALINA PRODAN, ECATERINA ANDRONESCU, CLAUDIU TURCULET
Abstract
This article examines a new research direction to enhance the performance of polypropylene meshes commonly used in hernia repair by incorporating iron oxide nanoparticles (IONPs). Classical polypropylene meshes are mechanically strong, but they have been associated with postoperative infections when contamination occurs [1]. In this article, we review the possible integration of IONPs into polypropylene meshes to improve antimicrobial properties, tissue integration , and reduce inflammation [1,2]. IONPs are known for their magnetic and antibacterial properties, especially when functionalized with biocompatible coatings such as chitosan or polyethylene glycol (PEG) [3,4]. These coatings can minimize the risk of post-surgical complications with better tissue integration and reduced biofilm formation [5,6]. The potential for magnetic guidance in tissue regeneration and MRI visibility makes IONPs a valuable tool for non-invasive monitoring and post-operative treatments, including magnetic hyperthermia for infection control [2,7]. This concept raises concerns about production scalability and regulatory compliance. Despite these technological advancements, transitioning such concepts from the laboratory to clinical practice faces technical complexities of industrial-scale production, uncertainties regarding nanotoxicity, and the demands of regulatory frameworks [3,8]. This review brings into discussion the need for further studies to validate long-term biological safety and the economic sustainability and clinical feasibility of IONP-treated polypropylene meshes. These studies could help define the role of such composite materials as next-generation solutions in the surgical management of hernias and in addressing the potential toxicity of nanomaterials [3,8].
Keywords
iron oxide nanoparticles, antimicrobial strategies, polypropylene meshes, abdominal wall hernias
MĂDĂLIN DOREL ȚAP, ANTON FICAI, ZENO DORIAN GHIZDĂVEȚ, ANAMARIA-CĂTĂLINA RADU, ANA-MARIA BURUIANǍ, FLORENTINA CORNELIA BÎCLEŞANU
Abstract
Recent studies extensively researched the release of titanium particles and ions from dental implants. Titanium release is recognized as a complex process influenced by mechanical, chemical, and biological factors. It plays a significant role in the peri-implant tissue adaptation and the long-term stability of implants. This study aimed to assess titanium release in the peri-implant mucosa and to subsequently correlate these findings with the biomechanical behaviour of implants. An integrated methodology was applied to achieve this, combining exfoliative cytology, inductively coupled plasma mass spectrometry (ICP-MS), and finite element analysis (FEA). The ICP-MS findings revealed detectable concentrations of titanium in peri-implant cells, ranging from approximately 47 to 85 ppb, following a triphasic temporal pattern based on implant age. FEA findings indicated a progressive alteration of stress distribution based on the corrosion level, shifting from a uniform and balanced mechanical behaviour to a more localized and imbalanced stress pattern. Overall, the combined use of exfoliative cytology, ICP-MS, and FEA offers a comprehensive framework for the early assessment of biological and biomechanical risks, with possible applications in implant therapy customization and optimization of long-term monitoring strategies.
Keywords
finite element analysis, ICP-MS, titanium release, peri-implant tissues
MIHAELA GRUIESCU, OANA CAMELIA IACOB, LAURA GEORGETA BĂRĂGAN, OANA MIHAELA BOIȚĂ
Abstract
In the article, at the level of the 27 countries European Union members, it is analysed the capacity of the circular economy to produce economic growth related to attracting economic resources to manufacturing processes and sustainable consumption. In fact, the circular economy is analysing the way by which the production and consumption chain are based on a rational process of the individual company to effectively use what it needs from the nature without destroying the reproduction capacity of the nature. The data collected from the European Union member countries are analysed by using econometric methods panel type, the result going to determine some clusters which generate a qualitative statistical approach, based on the factual analyses of the resources productivity, on the one side, and on the structural factors, endogen and exogen, influencing the productivity at the level of countries composing the group. Moreover, the cluster analysis highlights three distinct groups of countries: highly circular and resource-efficient economies, moderately performing transition economies and material-intensive economies characterized by low levels of efficiency. These patterns highlight the existence of persistent structural disparities across the European Union. In conclusion, the results highlight the importance of integrated public policy approaches that simultaneously target circularity, material efficiency and energy use. The research contributes to the literature by providing empirical evidence on the role of circular economy practices in developing resource efficiency and supporting sustainable materials management in the European Union.
Keywords
circular economy, resource productivity, material consumption, energy intensity, main component analysis, cluster analysis, panel data
ECATERINA ANDRONESCU, MIRCEA BEURAN, DAN CORNELIU JINGA, CLAUDIU STEFAN TURCULET
Abstract
Technological evolution and the complexity of approaches force researchers and practitioners to take interdisciplinary approaches. Nanoscience has opened up the field of 1-100 nm dimensions in materials science, where properties change significantly, forcing researchers to reconsider applications and highlighting new opportunities. The synthesis and characterization of nanoparticles have led to the opening of a new field of applications – nanomedicine. The choice of medical therapies appropriate to the medical information obtained directly from the patient – personalized medicine as well as the association of diagnosis with the treatment itself – the teranostic approach evolves in integration with artificial intelligence. The article marks the opening of a challenging topic that energizes the evolution and precision of medical procedures.
Keywords
nanoparticles, nanomedicine, teranostic approach, artificial intelligence
MIHAI EFTIMIE, CARMEN UDREA, ALINA MELINESCU, ANA FILIP
Abstract
Borosilicate glass samples were prepared by doping a main composition with CoO and NiO, respectively, to study the influence of these ions on the optical, structural, thermal, and chemical properties. Two compositions were prepared from analytically pure reagents, melted in alumina crucibles at 1250°C, cast into graphite molds, and annealed to remove internal stresses. The glasses were characterized using hydrolytic stability tests, dilatometry, UV-Vis spectroscopy, viscosity measurements, and FTIR spectroscopy. The results show that both Co2+ and Ni2+ change the vitreous network and optical behavior even at low concentrations (0.5 wt.%). The Ni2+-containing glass exhibits better hydrolytic stability and a lower coefficient of thermal expansion, while the Co2+-containing glass has a shorter working range due to a more rapid variation of viscosity with temperature. The UV-Vis spectra confirm the characteristic absorption bands of Co2+ and Ni2+ ions, indicating tetrahedral coordination for Co2+ and a combination of tetrahedral and distorted octahedral coordination for Ni2+. FTIR analysis indicates structural rearrangements of the Si-O-(NBO) and [BO3]3-/[BO4]5- units induced by the dopants. The study demonstrates that the addition of CoO and NiO allows for the modulation of the processing behavior of borosilicate glasses, a relevant aspect for functional applications.
Keywords
borosilicate glass, cobalt oxide, nickel oxide, colored glass, optical properties, FTIR spectroscopy
SUDARSONO, PRINOB AKSAR, ABDUL KHOIRI AL-LATIF, MUHAMMAD RIFKY
Abstract
Geopolymer concrete is an innovative environmentally friendlier material in terms of being a replacement material for Portland cement by using silicate and aluminium materials like fly ash to replace both natural stone and powder aggregates. In this study, we investigate the effect of adding fiberglass fibers to the physical and mechanical properties of fly ash-based geopolymer with porous structures. In terms of geopolymers we use alkali activators (sodium hydroxide NaOH and sodium silicate Na2SiO3) and foaming agent to prepare lightweight concrete. Fly ash is combined with fiberglass fibers in the weight percentages of 0.00, 0.25 and 0.50 The tests, include density, porosity and compressive strength along with microstructural analysis using Scanning Electron Microscope (SEM). The findings indicated an increase in the porosity value from 32.83% to (44.90%) with decreasing density value from 1.1953 to 1.0042 g/cm3 ranging of fiber content addition respectively On the other hand, while porosity was increased its value in compressive strength significantly increased from 3.41 MPa up to 9.29 MPa. Results of microstructural analyzes showed that in the case of the sample devoid of fibers, a loose pore structure was observed, consisting of unevenly distributed and partially unstable pores while addition of fibers led to a more uniform pore system. A more connected pore network was obtained at higher fiber content. The improved mechanical performance was attributed to the reinforcing effect of the additions of fiberglass fibers that increased pore stability, permitted efficient stress distribution and acted as crack intermediary mechanism in the geopolymer matrix. A balance point between mechanical strength and lightweight was reached at 0.25 fiber percentage. This evidence demonstrates that applying fiberglass reinforcement develops high-performance lightweight geopolymer composite materials suitable for structural applications.
Keywords
fly ash, foamed geopolymer, fiberglass fiber, compressive strength, porosity, microstructure
LONGHAI YE
Abstract
Tensile behavior of Two-dimensional carbon fiber reinforced silicon carbide composite （2D-C/SiC） composites was also studied systematically under quasi-static and high strain rate conditions at temperatures of 20, -70, -150 ℃ to the liquid nitrogen temperature ( -196 ℃). Mechanical loading was performed on a universal testing system with low strain rates and a split Hopkinson tensile bar system with dynamic regimes, with strain rates between 10−3 and 300 s−1. In all test conditions, the material showed a clear nonlinear stress-strain behavior before failure, which is indicative of its pseudo-plastic deformation behavior. Cooling and loading rate were both found to enhance strength. Tensile resistance was observed to rise significantly as the environment changed to cryogenic temperatures. An analogous strengthening behavior was noted as strain rate increased, which is rate-dependent mechanical behavior. Fractographic analysis also helped to understand the mechanisms of damage. In the quasi-static loading, strong fiber pull-out characteristics were observed, indicating progressive interfacial debonding before ultimate failure. Conversely, specimens with dynamic loading exhibited significantly shorter pull-out lengths, suggesting a higher interfacial constraint and more sudden fracture mechanisms. At low temperatures, fracture surfaces appeared irregular and rugged. Instead of massive bundle extraction, localized fiber cluster pull-out with comparatively smooth fracture traces on the extracted clusters dominated failure.
Keywords
2D-C/SiC, composite material, low temperature, dynamic tensile
XIAOFENG CHEN, QIAN HONG, LIHUA DING, YANBING WANG, XIAOXIAO MA, XIAOHU SUN, JINGJING ZHOU, JIA HU, XIN LUO
Abstract
The traditional ordinary Portland cement has a relatively high pH value, which is often extremely unfavorable for vegetation restoration when slope protection treatment is carried out. For this purpose, in this study, ammonium dihydrogen phosphate (ADP) is selected to excite steel slag (SS) to generate cementitious materials with a lower pH value, which are used to bond recycled aggregates, and a porous ecological concrete with a low pH value and environmental friendliness is prepared. The results show that when the SS/ADP is 6 and the water-cement ratio is 0.22, the compressive strength of the prepared cementitious material reaches 37.7 MPa. When it is compounded with aggregates with particle sizes ranging from 12 to 18mm and the slurry-bone ratio is 1/5, the porosity of the prepared porous ecological concrete reaches 35.4%, and the compressive strength reaches a maximum of 4.3 MPa. In addition, it has been confirmed that ADP can significantly reduce the harmful metal ions retained in steel slag, making the content of harmful metal ions in ecological concrete more obviously lower than the national standard limit.
Keywords
acid activation, recycled aggregate, ecological concrete, mechanical properties, mechanism research
WENWEN QI
Abstract
Flexible conductive polymer films require stable charge transport under large deformation, repeated motion, and sweat-related interfacial disturbance. This study develops a polythiophene-based conjugated polymer/multi-walled carbon nanotube composite film using gradient drop-casting, zeta-potential-guided dispersion control, and electric-field-assisted network biasing. The strategy aims to separate a mechanically compliant domain from a current-carrying backbone, thereby reducing conductive-network fracture and signal drift during dynamic strain. The optimized film shows a carbon nanotube orientation degree of 0.82, crystallinity of 46.5%, surface roughness of 18.7 nm, and filler-distribution deviation of 3.1%. Conductive-cluster connectivity remains above 0.85 within the 0–80% strain range, while impedance drift is only 1.2% after 2 × 105 loading cycles. Under simulated sweat with conductivity of 9.7 mS cm-1, conductivity drift is limited to 0.8%. These results indicate that the proposed network-locking strategy improves electromechanical stability and provides a reliable material platform for human-machine interaction and sports health monitoring
Keywords
flexible conductive polymer films, dynamic percolation network, multi-walled carbon nanotubes, solvent-induced self-assembly, electric-field biasing, strain sensing, human-machine interaction
MOHAMED BACHAR, DJILLALI CHACHI, REBIH ZAITRI
Abstract
In this study, we have examined the influence of straight-strand fibre reinforcement on the post-cracking mechanical behaviour of natural aggregate concrete (NAC) and recycled aggregate concrete in which 50 % of the natural coarse aggregate has been replaced by recycled aggregate (RAC50). The parameters studied experimentally have included compressive strength, compressive toughness and dynamic impact energy.The results revealed a significant increase in energy dissipation compared with the reference concrete (0 % fibres), throughout the range of fibre volume fractions (0 %–2 %) and aspect ratios (h/d=60, 80,100). A more significant rate of change in both modes of energy dissipation was observed for fibre-reinforced concrete with recycled aggregates (RAC50-SF) than for fibre-reinforced concrete with natural aggregates (NAC-SF). At a dosage of 1.5 % and an aspect ratio of (h/d=100), both types of concrete, (RAC50-SF) and (NAC-SF), exhibit similar values for both energy modes, thus making recycled concrete suitable for use in high-performance structures.
Keywords
compressive strength, recycled aggregate concrete, compressive toughness, dynamic impact energy, fiber-reinforced concrete
LEILA BAZIZ, NADJET BENCHIHEUB, ABDELAZIZ SID, ISMAHANE SERRADJ
Abstract
This investigation is devoted to study the particular impact of laser Nd:yag radiation on certain mechanical properties such that: elastic modulus, hardness and stiffness of two types of Al-Si-Cu-Mg alloys (industial and recycled) through nanoindentation measures. These materials were subjected to a Laser treatment Nd: Yag with wavelength λ=1.064nm, for different pulse counts. The Atomic Force Microscope (AFM) is used to visualize and analyze radiated regions at the nanoscale, as well as to conduct nanoindentation tests for assessing hardness, stiffness and elastic modulus. In this context, the present study demonstrates that both elasticity and hardness of the radiated areas increase with the number of laser shots. Following a specific number of shots (40 shots for industrial aluminum and 60 shots for the recycled one); all radiated zones display analogous nanoindentation profile. Due to the changes induced to a nanostructural refinement shown by the (SEM); further a significant improvement in mechanical properties is achieved .However, increasing the number of shots to high levels (about 160 shots for industrial aluminum and 200 shots for recycled aluminum) cause a homogenate material structure, resulting an improvement in mechanic properties.
Keywords
recycled aluminum alloys, industrial aluminum alloy, Nd:Yag laser, nanoindentation, elasticity and hardness
OANA CAMELIA IACOB
Abstract
This paper presents an analysis of economic sustainability models for the states that are part of the European Union (EU). The analysis is a data-mining type and is carried out for the data related to the year 2024. The main objective of the research is to investigate the correlation between the circular economy indicators, the environmental taxation method and the industrial performance of each country. The research consists of two approaches that complement each other. The first direction uses an unsupervised learning algorithm to form clusters based on the European economies. This is done according to their countries ability to integrate and reuse circular materials in industry. Also, within this direction, environmental taxes and trade flows of recyclable raw materials that characterize the clusters with the highest degree of resource efficiency are identified. The second direction uses a supervised classification algorithm to identify critical economic thresholds (pollution taxes, energy taxes and foreign direct investment flows). These economic thresholds can be said to determine the degree of success of a country in achieving a high rate of circular use of materials in production. The attribute related to this rate is transformed into nominal classes and based on it, decision rules are extracted. The attributes used in the analysis are intended to cover aspects related to waste management, import dependence and foreign direct investment. The present research provides a picture of how environmental fiscal policies and material flows influence the transition within the EU towards a circular economy.
Keywords
sustainability, environmental taxation, circular economy, data mining analysis.