english R. KARIMIA, I. ABBASPOURA, M. AMIRIB
Rezumat
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 Fe3O4 nanoparticles to the base fluid, the heat transfer is improved.
Cuvinte cheie
Nanofluids, Heat transfer factor, Iron (II, III) oxide, Heat exchangers
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Anul
2025
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Numărul
55 (1)
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Paginile
3-10
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Domenii de interes
BIOMATERIALE ȘI BIONANOMATERIALE; SUBSTANȚE, PROCEDURI ȘI DISPOZITIVE PENTRU MEDICINĂ
DENISA-NICOLETA MUȘAT, ALEXANDRA-CRISTINA BURDUȘEL, ȘTEFAN GAFTONIANU, ANTON FICAI, OVIDIU OPREA, ROXANA POPESCU, ROXANA TRUȘCĂ, ECATERINA ANDRONESCU
Rezumat
Studiul de față descrie sinteza și caracterizarea și testarea unui material nanocompozit cu rol în regenerarea țesuturilor osoase și protecție antimicrobiană. Prin urmare, s-a realizat o biosticlă 45S5 produsă prin sinteză sol-gel cu nanoparticule de oxid de zinc rezultate din sinteza hidrotermală asistată de microunde. Adăugarea de uleiuri esențiale de mentă și roiniță în diferite concentrații a îmbunătățit funcționalitatea biologică a materialului. Compozitele luate în considerare au fost caracterizate prin analiză termică (TG-DSC), spectroscopie FTIR, difracție de raze X (XRD), microscopie electronică de scanare (SEM) și spectroscopie de raze X cu dispersie de energie (EDS) pentru evaluarea fizico-chimică. Analiza a permis identificarea fazelor cristaline orecum și morfologiile particulelor și încorporarea grupărilor funcționale. Particulele de biosticlă au avut dimensiuni între 2-4 μm, în timp ce dimeniusnile nanoparticulele de ZnO au fost majoritar între 200-400 nm, cu o distribuție uniformă confirmată prin cartografiere elementară. Evaluarea biocompatibilității a utilizat un test MTT cu celule de tip osteoblast MG-63. Rezultatele au arătat că ZnO a cauzat citotoxicitate la concentrații mai mari, însă adăugarea de ulei esențial a redus acest efect, în special atunci când uleiul de roiniță a fost utilizat la o concentrație de 2%, ceea ce a demonstrat o biocompatibilitate îmbunătățită pentru toate concentrațiile testate. Materialul compozit dezvoltat demonstrează proprietăți antimicrobiene și osteoconductivitate îmbunătățite, împreună cu o citotoxicitate scăzută, ceea ce îl face potrivit pentru aplicații biomedicale în ingineria țesutului osos.
Cuvinte cheie
biosticlă, oxid de zinc, compozit, uleiuri esențiale, efect antimicrobian
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Anul
2025
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Numărul
55 (1)
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Paginile
11-24
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Domenii de interes
BIOMATERIALE ȘI BIONANOMATERIALE; SUBSTANȚE, PROCEDURI ȘI DISPOZITIVE PENTRU MEDICINĂ
ANDREEA-CRISTIANA ALEXE, ALEXANDRA-CRISTINA BURDUȘEL, ȘTEFAN GAFTONIANU, OVIDIU OPREA, ROXANA POPESCU, ROXANA TRUȘCĂ, ANTON FICAI, ECATERINA ANDRONESCU
Rezumat
Regenerarea țesutului osos prezintă o provocare semnificativă din cauza complexității structurilor osoase și a setului de limitări ale metodelor tradiționale de grefare. Scopul prezentului studiu este dezvoltarea și caracterizarea unui material nanocompozit din hidroxiapatita dopată cu ceriu (Ce-HAp), sticlă bioactivă (biosticlă 45S5) și uleiuri esențiale naturale (salvie și cimbru). Hidroxiapatita a fost sintetizată prin metoda hidrotermală asistată de microunde și biosticla, obținută prin sinteza sol-gel. Materialului final i s-au adăugat uleiuri esențiale. Materialul compozit a fost supus analizelor XRD, FTIR, SEM, EDAX, care i-au confirmat fazele cristalină, compoziția chimică și caracteristicile morfologice. Rezultatele testului MTT au arătat că celulele de tip osteoblast MG-63 au demonstrat o biocompatibilitate ridicată și fără citotoxicitate, în timp ce probele care conțin ulei esențial de salvie au dus la o viabilitate celulară crescută. Analiza termică a arătat că materialele compozite au menținut o stabilitate termică excelentă. Materialul nanocompozit prezintă o bioactivitate îmbunătățită, împreună cu proprietăți antimicrobiene și citocompatibilitate, ceea ce îl face potrivit pentru aplicații medicale. Sistemul multifuncțional oferă un substitut pentru grefele standard, în timp ce aplicații biomedicale suplimentare pot fi realizate prin adăugarea de ioni biologic activi, cum ar fi Ag, Sr, Ce sau Zn.
Cuvinte cheie
hydroxyapatite, cerium oxide, essential oils, bioglass, biocompatibility
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Anul
2025
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Numărul
55 (1)
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Paginile
25-38
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Domenii de interes
BIOMATERIALE ȘI BIONANOMATERIALE; SUBSTANȚE, PROCEDURI ȘI DISPOZITIVE PENTRU MEDICINĂ
PERFORMANCE OF TITANIUM GYPSUM-REPLACED MAGNESIUM CHLORIDE-MAGNESIUM OXYCHLORIDE COMPOSITE MATERIALS
SHUREN WANG, LINRU ZHAO, JIAN GONG, YAN WANG
Rezumat
To realize the resourceful utilization of solid waste and develop novel building materials, an experimental study was conducted using titanium gypsum, magnesium chloride, and magnesium oxide as raw materials to prepare test samples. The samples underwent a series of tests, including unconfined compressive strength testing, water absorption analysis, dynamic non-contact full-field strain measurement, scanning electron microscopy, and X-ray diffraction, to investigate the effects of varying titanium gypsum substitution rates for magnesium chloride on the strength, failure modes, and microstructural properties of the resulting composite materials. Results show that as the substitution rate of titanium gypsum increases, the dry density of the composites initially increases and then decreases, while the water absorption rate continues to rise, with a particularly notable increase observed at substitution rates between 10% and 25%. Both flexural and compressive strengths exhibit an initial increase followed by a decrease, reaching their optimal values at a 5% substitution rate, with a maximum improvement of 17.37% in flexural strength and 18.81% in compressive strength. The increase in titanium gypsum substitution rate alters the phase morphology and internal density of the composites, confirming the feasibility of substituting magnesium chloride with titanium gypsum in magnesium oxychloride cement. This substitution strategy not only promotes the utilization of solid waste but also contributes to cost savings, highlighting its potential for practical applications.
Cuvinte cheie
magnesium oxychloride cement, titanium gypsum, mechanical properties, microstructural analysis
DAVID RESANO, JOSE BARRANZUELA, FABIOLA UBILLÚS, OSCAR GUILLEN, ANA GALARZA
Rezumat
High-altitude human settlements, such as those in the Andes and the Himalayas, experience extreme temperature conditions, yet many houses in the Peruvian Andes lack thermal insulation due to the unavailability of affordable materials. As a result, respiratory diseases linked to low temperatures are widespread during the coldest months of the year. This study presents the development of an innovative thermal insulation panel made from locally sourced sugarcane bagasse fibers, bonded with polyvinyl acetate and fabricated using compression molding. The panel achieved a thermal conductivity of 0.043 W/m·K, which allows compliance with Peruvian thermal transmittance standards when applied in layers of approximately 6 cm thickness. The material exhibited a bulk density ranging from 86.7 to 105.3 kg/m³. Mechanical testing showed a low average tensile strength of 0.0144 kg/cm² and a flexural modulus of 0.116 kg/cm², indicating that the panel is not suitable for structural applications. However, it is effective as a non-structural thermal insulation solution. The proposed panel promotes a circular economy by repurposing agricultural by-product and offers a low-cost, biodegradable alternative to synthetic and mineral fiber insulations, contributing to reduce material costs and environmental impact in buildings.
Cuvinte cheie
Composite, organic material, sugarcane bagasse fibers, thermal insulation, circular economy
MANI P, ARULARASAN R
Rezumat
One of the biggest obstacles to using natural fibers in industrial applications is their poor mechanical qualities. The study aims to use carbon and glass fillers to increase the flexural, impact, and tensile strengths of luffa/epoxy composites. Three fillers proportions (5wt.%, 7.5wt.%, 10wt.%) and one luffa proportion (20wt.%) were taken to fabricate the composites. The ASTM guidelines were followed when conducting the experiments. The fillers enhanced the composites tensile, flexural, and impact strengths. Comparing carbon-filled composites to corresponding glass-filled composites, the former showed superior performance. The 7.5wt.% carbon-filled composite shows the highest tensile and impact strength values, whereas the composite without fillers shows the lowest tensile and impact strength values. For flexural strength, 10wt.% carbon-filled composite shows the highest values, whereas the composite without fillers shows the lowest values.
Cuvinte cheie
luffa fiber, carbon filler, glass filler, tensile strength, impact strength, flexural strength
J.JEGAN, P.ANITHA, SUNANTHA B., J SUDHAKUMAR, R.LOGARAJA, KONA PRAVALLIKA PHANI DURGA
Rezumat
Phase-change materials must now be used during construction to reduce greenhouse gas emissions and boost energy efficiency. Considering concrete makes up the majority of construction materials worldwide, incorporating PCMs into concrete can greatly increase a structures energy efficiency. There has been a growing interest in phase change materials (PCMs) in recent years. By utilizing the appropriate PCM and integration approach, the majority of issues associated with utilizing PCM in concrete may be resolved. In this work, Thermal Storage Light Weight Aggregate (TSLWA) was produced by incorporating pumice stone into Paraffin wax. The concrete cube were cast with different replacement ratios of TSLWA with LWA such as 0%, 25%, 50%, 75%, and 100%. The study revealed that increasing PCM content reduced water absorption, with the control sample absorbing 8.5% water compared to only 1.8% for the 100% PCM sample. Compressive strength decreased with higher PCM percentages, with the 100% PCM sample showing significant reduction, emphasizing the need for a balance between thermal properties and structural integrity. Thermal analysis showed that paraffin wax exhibited thermal transitions around 50°C, demonstrating stable thermal behavior up to 300°C. Microstructural examination revealed altered bonding strength due to paraffin wax-filled aggregates, and leakage tests highlighted the effectiveness of epoxy resin coatings in reducing water seepage. Overall, PCM-impregnated pumice concrete improves moisture resistance and thermal performance, offering a promising solution for sustainable construction, though careful consideration of PCM concentration is needed to maintain mechanical strength.
Cuvinte cheie
thermal storage aggregate, Pumice stone, immersion method, phase change materials, paraffin wax.
A. THOMAS EUCHARIST, V. REVATHI
Rezumat
Concrete is one of the most vital building materials next to the water. Day by day, the demand for concrete is escalating with the rising demand for infrastructural development, and the cement industry is one of the dominant contributors to the production of greenhouse gases. So, efforts are essential to make concrete further eco-friendly by adopting cement-free concrete, which helps overcome global warming. In this study, varying compositions of alumina silica materials made up of ground granulated blast furnace slag (GGBFS) and sugarcane bagasse ash (SBA) were supposed to be utilized in the manufacture of geopolymer mortars, and five different ratios of 100:0, 75:25, 50:50, 25:75, 0:100 were proposed. It might be a better solution for both waste disposal problems and issues related to cement production. Combinations of GGBFS and SBA were made with varying concentrations of alkaline solution starting from 10M, 12M, and 14M. The strength properties of the prepared specimens were assessed by conducting compressive strength test on mortar and concrete specimens at 3 days, 7 says, 28 days. Despite the fact that not all of the combinations of the mixes examined had statistically significant results, the test results do suggest that the GGBFS-SBA blend is viable for use in geopolymer. In a 14M geopolymer concrete mix consisting of 100% GGBS, the highest compressive strength of 61 MPa was achieved.
Cuvinte cheie
Cement-free concrete, Geo polymer mortar, GGBFS, Bagasse ash, Alkaline solution
EUGENIA TANASĂ
Rezumat
Separarea fotoelectrochimică (PEC) a apei folosind energia solară apare ca o strategie extrem de promițătoare pentru generarea durabilă de hidrogen și stocarea energiei. Cercetările actuale în acest domeniu evidențiază hematitul ca material fotoanod adecvat pentru separarea apei datorită proprietăților sale favorabile: este un semiconductor de tip n, posedă o bandă interzisă adecvată pentru absorbția luminii vizibile, prezintă o stabilitate chimică ridicată și este disponibil din abundență pe Pământ. Acest review prezintă diverse strategii de modificare a hematitului pentru a-i îmbunătăți performanța. Aceste modificări includ doparea elementelor, proiectarea și fabricarea nanostructurilor, integrarea co-catalizatorilor, formarea heterostructurilor și interdependența dintre structura și performanța hematitului.
Cuvinte cheie
energie solară, hematită, fotoanozi
XIANWU JING, XIAOJIN ZHOU, TENG GONG, TAO WANG, YANG WANG, GUOQING LIU, KAIJUN WANG
Rezumat
This research employed molecular dynamics simulations to explore the distribution of sodium dodecyl sulfate (SDS) at the n-hexane/water interface. Once the SDS concentration surpasses the critical micelle concentration(cmc), a large portion of SDS migrates to the n-hexane/water interface, establishing a thin layer where sulfonic acid groups are oriented towards the water phase and carbon-hydrogen chains are directed towards n-hexane, a small amount of SDS forms spherical micelle with sulfonic acid groups facing the water phase, while carbon-hydrogen chains aggregate in the interior of these spherical structures. The sulfonic acid group of SDS forms multiple h-bonds with water, shows strong interaction energy; while the carbon hydrogen chain itself has only weak van der Waals interactions with surrounding molecules. The thickness of SDS- layer at the n-hexane/water interface is about 2.06 nm, with a maximum number density of about 0.25 per nm3, and average area occupied by a single SDS- is about 0.21 nm2. According to radial distribution function (RDF) result, due to the attractive effect of positive and negative charges, the first coordination layer of Na+ ions and oxygen atoms on sulfonic acid groups is about 0.21 nm. This study investigated the distribution of SDS at n-hexane/water interface, vividly demonstrating the mechanism by which SDS reduces the interfacial tension between oil and water, and providing guidance for oilfield development.
Cuvinte cheie
Interfață N-hexan/apă; Simulare dinamică moleculară; Dodecil sulfat de sodiu; Analiza interacțiunii slabe
S. DHANALAKSHMI, T. JESUDAS, M. PRADEEP KUMAR
Rezumat
The objective of this research study is focused to improve the wear resistance of the reinforced Al6063 hybrid metal matrix composite. The secondary particles like Al2O3 /TiO2are used as a reinforcement particle and the samples fabricated using stir casting technique with the base material Al6063 alloy. The fabricated samples were analyzed using Energy Dispersive Spectroscopy (EDS) and Scanning Electron Microscope (SEM) for understanding the potential of fabricated samples. Dry sliding wear test was conducted for the composite samples. The major wear process parameters such as load, sliding distance were considered for analysis work. The reinforcement particles such as Al2O3 /TiO2 also were considered as one of process parameter for wear analysis. The results of Variance of analysis clearly statethat reinforced secondary particles were the most influencing wear process parameter. The validation of desirability function analysis results reveals that the obtained optimal solutions were effectively enhance the wear resistance property for fabricated hybrid metal matrix composite (Al6063/Al2O3 /TiO2).
Cuvinte cheie
Al 6063, Al2O3 /TiO2, DFA, Wear, RSM.
CHIENTA CHEN, SHINGWEN TSAI
Rezumat
The rapid increase in terrain variability, climatic factors, axle load, and traffic volume has significantly affected the performance of asphalt pavements on expressways, particularly in harsh environmental conditions. In some cases, the service life of expressway pavements is far shorter than the expected design time. Certain sections of expressways face pavement failures just one or two years after opening, including cracks, potholes, rutting, and oil flooding. These problems not only disrupt the normal flow of traffic but also substantially increase maintenance and repair costs. This study focuses on diagnosing and addressing the causes of asphalt pavement failures, specifically in Jiangsu Province, China, where various asphalt pavement diseases were reported in 2020. By calculating the porosity of asphalt mixtures, we assess the water permeability, strength, and durability of the materials. Applying Mohr-Coulomb theory, we evaluate the high-temperature shear strength of asphalt mixtures and analyze rutting depth. Our findings indicate that rutting is the primary distress type on expressways in Jiangsu, with a rut depth of [3-8] mm observed in 67% of the total road network. Additionally, the pavement smoothness of expressways remains within a range of 0.5-1m/km for 85% of the highway network. We also analyze lateral and longitudinal fractures, which constitute 97% of repairs, with transverse cracks becoming prevalent after 6 years of service under high axle loads. This suggests the need for early preventive measures within the first 6 years of service to mitigate the development of cracks.
Cuvinte cheie
pavaj asfaltic, autostradă, diagnosticarea pavajelor, tehnologie de reparare, impact asupra mediului, formarea șanțurilor, formarea fisurilor, sarcina traficului.
MĂDĂLINA-OANA MIHĂILĂ, DENISA FICAI, OANA DAMIAN, BOGDAN ȘTEFAN VASILE, ALEXANDRA CRISTINA BURDUȘEL, ANDREI PĂDURARU, ECATERINA ANDRONESCU
Rezumat
Înainte de a discuta despre materialele și nanomaterialele inovative de conservare și restaurare a patrimoniului național arheologic este necesară indentificarea și caracterizarea materiilor prime principale (plastice și neplastice) și auxiliare folosite pentru obținerea corpului ceramic (partea I) și decorației de pe suprafață: sculpturală – simultană cu fasonarea și picturală (partea a II-a), existente pe suprafața interioară sau exterioară a pieselor ceramice. Astfel, după originea lor și modul de formare, prin sedimentare, procesare termică – sintetizare și vitrificare sau recristalizare, ce determină compoziția, proprietățile, culoarea și gradul de refractibilitate, acestea sunt clasificate în argile comune și argile superioare, diferențiate prin indicele de plasticitate, vitrifierea fiind influențată de raporturile oxizilor componenți, de temperaturile de ardere și de tipurile de atmosfera din interiorul cuptoarelor: oxidantă în cazul ceramicii albe și colorate sau reducătoare în cazul ceramicii negre, parțială sau completă, realizată într-o singură fază sau în două etape.
Cuvinte cheie
argilă plastică, decorație sculpturală, decorație policromă, angobe ceramice, glazuri ceramice, culoarea, oxizi coloranți, oxizi alcalini și oxizi alcalinopământoși.
SALEM MERABTI, LAYACHI GUELMINE, MEZIANE KACI
Rezumat
This study investigates the seismic performance of reinforced concrete buildings ranging from 5 to 20 stories using nonlinear static pushover analysis. Four shear wall bracing configurations are considered: L-shaped peripheral walls, central core, double central core, and double peripheral core systems, with wall thicknesses of 15, 20, and 25 cm, all subjected to unidirectional lateral loading. Although these configurations are widely implemented in both moderate and high seismicity regions, few comparative studies have assessed their nonlinear seismic resistance. The results indicate that central core configurations provide superior control of inter-storey drift, with a significant reduction in lateral displacements—up to 48% compared to peripheral wall systems. In contrast, peripheral wall systems exhibit higher drift demands, reaching a maximum of 0.124% for 15 cm thick walls. The analysis also highlights the effectiveness of L-shaped walls in mid-rise buildings, particularly those with wall thicknesses of 20 and 25 cm. The study of deformation mechanisms reveals a concentration of plastic hinges and thus stress in L-shaped wall systems and at beam-wall joint regions.
Cuvinte cheie
Clădire cu mai multe etaje, Analiză neliniară de tip pushover, Perete de forfecare din beton armat, Derivă interetajată, Tensiune de forfecare, Moment de răsturnare.
ALI SABERI VARZANEH, MAHMOOD NADERI
Rezumat
In concrete design, durability is as vital as strength, especially in aging structures exposed to harsh environmental conditions. Increased permeability over time compromises structural integrity. Polypropylene (PP) fibers help limit cracking, which in turn reduces permeability. Traditionally, assessing permeability requires destructive core sampling. This study introduces a novel approach—the “cylindrical chamber” test—to evaluate permeability directly on structures. Validation of this method confirmed its reliability. Results indicated that incorporating PP fibers reduced permeability in C25, C35, and C45 concretes by 22.5%, 20.2%, and 16.3%, respectively. XRD analysis revealed that PP fibers influenced Ca(OH)₂ crystallization and enhanced C-S-H formation. MIP results showed a 24.5% increase in pore volume and 32.8% rise in pore surface area in C45 concrete with fibers, yet overall permeability declined. This confirms the effectiveness of PP fibers in improving durability without the need for invasive testing.
Cuvinte cheie
Beton, durabilitate, fibră, rezistență, metodă inovatoare.
KARTHIKEYAN R, PARTHEEBAN P, THOLKAPIYAN.M, SIVAKUMAR, SUGUNA K, GAAYATHRI KK
Rezumat
This work discusses the outcome of Finite Element Analysis using ANSYS Workbench, to analyse the cyclic behavior of rubberized concrete beams with steel fiber reinforcement. The investigation focuses on substituting coarse aggregate with sand coated rubber shreds, obtained from waste conveyor belt, with the sand coating applied using resin. The study examines rubber shreds in proportion of 2.5%, 5% and 7.5%, combined with steel fibres at volume fraction of 0.5% and 1%, total of seven beams were cast and tested under cyclic loading in a standard loading frame of 500kN capacity. The FEA outcomes revealed that reinforced concrete beams with steel fibres and sand coated rubber shreds reveal boosted cyclic efficiency regarding number of cycle’s sustained, maximum deflection and total energy absorption capacity. Load – deflection curves were plotted to compare experimental and FEA for all seven beams. These results have proved very helpful for better understanding the rubberized concrete with fiber reinforcement under cyclic loading, for its use in structural applications.
Cuvinte cheie
Fâșii de cauciuc acoperite cu nisip, deformare maximă, fibră de oțel, absorbție de energie și curbă sarcină-deformare.
ZHI LI, PING JIANG
Rezumat
To address the performance limitations of single silica (SiO2) encapsulated phase change materials, a novel shape-stable composite microencapsulated phase change material (CA/CS/SiO2 MEPCM) was prepared using the sol-gel method. Capric acid (CA) was used as the phase change material (PCM), while chitosan/silica (CS/SiO2) served as the composite encapsulation material. Fourier transform near infrared spectroscopy (FT-NIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were employed to characterize the chemical structure, crystalline phase, and microstructure of the CA/CS/SiO2 MEPCM. The thermal storage properties and thermal stability of the MEPCM were analyzed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). SEM results indicated that CA was effectively encapsulated within the CS/SiO2 shell, and the reticulated structure of the shell contributed to the high shape stability of the MEPCM. The results demonstrate that CA is effectively encapsulated within the CS/SiO2 shell, and the network structure of the shell significantly enhances the shape stability of the MEPCM. The encapsulation process preserves the chemical integrity of CA, as no structural changes were observed. The synthesized MEPCM exhibits excellent sealing performance at 102 °C, and the thermal stability of the CS/SiO2 composite shell surpasses that of conventional single-shell structures. Furthermore, the material displays a moderate phase transition temperature and a maximum latent heat of 69.38 J/g, meeting the requirements for variable thermal regulation. In conclusion, the CA/CS/SiO2 MEPCM developed in this study is a green, non-toxic, and structurally stable phase change material with a tunable phase transition temperature, offering promising potential for sustainable thermal energy storage applications.
Cuvinte cheie
acid capric, chitosan, dioxid de siliciu, materiale microîncapsulate cu schimbare de fază
SALEM MERABTI, KACI MEZIANE, SLIM ROUABAH
Rezumat
This study proposes a robust modeling approach for predicting the drying shrinkage of cementitious composites incorporating expanded cork waste, using a multilayer perceptron (MLP) artificial neural network. An original database consisting of 54 experimental samples and 2430 shrinkage measurements representing nine different material formulations with varying cork, sand, and ground granulated blast furnace slag (GGBFS) contents was used for model development. Five key variables describing material composition, curing conditions, and mass loss served as model inputs. After data normalization and rigorous cross-validation, the MLP significantly outperformed a classical second-degree polynomial regression, as evidenced by a coefficient of determination of R² = 0.999 and a mean absolute percentage error below 1%. Sensitivity analysis identified curing age and mass loss as the most influential factors governing shrinkage evolution, ahead of the cement-to-cork ratio, sand, and GGBFS content. These findings underline the suitability of neural network models for capturing the complex, nonlinear behaviors of bio-based cementitious materials and provide valuable insights for optimizing the design of durable, sustainable composites.
Cuvinte cheie
Plută expandată reziduală, nisip de râu, zgură granulată de furnal măcinată (GGBFS), compozit, contracție, rețele neuronale artificiale (ANN)
VISWANATH KRISHNAN, MOHAN EKAMBARAM, VINOTHKUMAR RAVI, SHEEBA RANI SOUNDARAPANDIAN
Rezumat
In this study, powdered magnesium and aluminum particles were combined with a smaller quantity of silicon carbide (SiC) particles, and the sintering process was used to form the metal matrix composite (MMC). The specimens were made at three distinct temperatures such as 4500C, 5000C, and 5400C. The addition of silicon carbide to the magnesium and aluminium leads to increase the hardness. Based on the scanning electron microscopy (SEM), a large number of holes were commensurate with the sintered specimen produced at the minimal sintering temperature. The development of pore was significantly reduced at high temperature, and strong metallurgical bonding was also attained. The hardness of the sintered specimen was also raised at high sintering temperatures. When compared to other traditional machining methods, the reason for using spark erosion machining or electric discharge machining (EDM) is to maintain the optimal surface roughness (SR) and increase material removal rate (MRR). An atomic force microscopy (AFM) and SEM examination was carried out specifically to evaluate the surface parameters of the magnalium MMC. The pit and valley surface was observed in the machining surface. Current and voltage played a crucial role in metal removal and surface roughness.
Cuvinte cheie
Compozit Magnalium, sinterizare, metalurgie a pulberilor, duritate, prelucrare prin eroziune prin scânteie
QIAN HONG, XIAOFENG CHEN, WEIQING YU, XIAOXIAO MA, YANBING WANG, CHONGQING WANG, CHAO LIU
Rezumat
Faced with the defects of engineering disturbed slope soil, such as easy erosion and evaporation of water, this paper uses polyvinyl alcohol (PVA) hydrogel as a soil conditioner to improve the water erosion resistance and water retention performance of engineering disturbed slope soil, and studies the vegetation performance and microstructure of modified soil. The results showed that PVA hydrogel changed the soil structure by using its excellent cementation and water holding capacity. PVA hydrogel completely wrapped the soil particles to form the overall structure of network gel, which significantly improved the soil erosion resistance, water stability and water retention capacity of the soil. With the increase of PVA concentration, the soil erosion resistance, water stability and water retention performance are significantly improved. In addition, the effect of increasing PVA concentration on soil vegetation performance shows a trend of first strengthening and then weakening, with the best soil vegetation performance observed when PVA concentration was 3%. The results show that PVA hydrogel has important application value for reducing soil and water loss of engineering disturbed slope and promoting vegetation restoration.
Cuvinte cheie
pantă perturbată, restaurare ecologică, rezistență la eroziune, performanță de retenție a apei, performanță a vegetației
ANGELA GABRIELA PĂUN, ROBERTA-GEANINA MIFTODE, MIHAELA VASILICA MÎNDROIU
Rezumat
Această lucrare prezintă principalele rezultate ale studiului privind prepararea și caracterizarea unor bio-membrane conductoare pe bază de alcool polivinilic (PVA), destinate utilizării ca electroliți polimerici solizi (SPE) în aplicații de tip fereastră inteligentă. Noutatea cercetării constă în dezvoltarea unor bio-membrane PVA cu conductivitate ionicǎ și electronicǎ îmbunătățită, prin incorporarea de perclorat de litiu (LiClO₄) ca sursă de ioni de litiu (Li⁺), precum și prin funcționalizarea cu acid dezoxiribonucleic (ADN) și poli(3,4-etilendioxitiofen) (PEDOT), acesta din urmă introducând căi de transport electronic. Bio-membranele au fost caracterizate prin spectroscopie FTIR și UV-Vis, iar conductivitatea a fost determinată prin spectroscopie de impedanță electrochimică (EIS). Membrana PVA cu cea mai bună conductivitate a fost utilizată în asamblarea unui dispozitiv de tip fereastră inteligentă, evaluat prin măsurători de chronoamperometrie, densitate de sarcină și spectroscopie UV-Vis. Rezultatele au demonstrat că combinația sinergică dintre PEDOT, LiClO₄ și ADN (care facilitează transportul ionilor și interacțiunea cu matricea polimerică) a condus la formarea unor căi conductoare mixte ion–electron, capabile să susțină un mecanism de transport dual. Fereastra electrocromatică inteligentă care încorporează biomembrana optimizată pe bază de PVA a prezentat o modulație optică (ΔT) de 22%, cu timpi rapizi de comutare: 11 secunde pentru colorare și 13 secunde pentru decolorare.
Cuvinte cheie
Bio-membrane, Ferestre inteligente electrocromice, Alcool Polivinilic, Acid Deoxiribonucleic, Conductivitate ionică
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Anul
2025
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Numărul
55 (3)
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Paginile
204-213
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Domenii de interes
BIOMATERIALE ȘI BIONANOMATERIALE; SUBSTANȚE, PROCEDURI ȘI DISPOZITIVE PENTRU MEDICINĂ
CHENKANG LIU, SONGLIN YUE
Rezumat
Steel fiber reinforced reactive powder concrete (RPC), as a critical material for engineering construction, has garnered significant research interest regarding its mechanical properties. This study investigates the reinforcement mechanism of steel fibers and the dynamic mechanical behavior of RPC. Composite material theory was employed to analyze the steel fiber strengthening and toughening mechanisms. The distribution of steel fibers and the microstructure of the cement matrix were characterized using X-ray computed tomography (CT) scanning and microstructural analysis. Furthermore, dynamic compression experiments were conducted to evaluate the mechanical response of RPC under high-strain-rate conditions. Results indicate that the interfacial bonding properties between steel fibers and the cement matrix substantially influence the mechanical performance of RPC. A uniform, disordered distribution of steel fibers was found to enhance both the isotropy and compressive strength of the composite. The dynamic strength demonstrates a pronounced strain-rate dependency, wherein the dynamic compressive strength and damage severity increase with escalating strain rates. Notably, damage evolution laws during dynamic compression were quantitatively characterized through high-speed camera imaging. These findings provide valuable insights into the reinforcement mechanisms of steel fibers in RPC composites.
Cuvinte cheie
beton reactiv cu pulbere; caracterizare microscopică; proprietăți mecanice dinamice; armătură cu fibre de oțel; evoluția deteriorării
PREPARATION METHOD OF DIATOM-BASED EARTH AND ZINC OXIDE COMPOSITE HIGH-DENSITY POLYETHYLENE MATERIAL
KUN LU, HAN KONG, YAOWEN ZHANG, JIAXING ZHU, YUANYUAN DING, XIYU HUANG, CHAO ZHANG
Rezumat
In order to cope with the increasingly severe environmental nanotechnology problems and energy shortage, the development of green new materials has become an inevitable trend in today society. In this paper, a preparation method and application of diatom-based earth and zinc oxide composite high-density polyethylene material are provided, which belong to the solid adsorbent composition material. Firstly, high-density polyethylene composites were prepared according to a certain proportion of diatom-based earth and zinc oxide and polyethylene. Then, to improve its performance and UV resistance, Tinuvin 770 is added and mixed with a composite polyethylene material in a gear mixer. Subsequently, the twin-screw extruding machine is set to a certain temperature and speed, extruded, and the extrusion is cut into composite pellets using a tray machine. Finally, these composite pellets are injected into the injection molding machine, where the target mold is selected and molded. At the same time, it can be used as a food packaging bag material, which can inhibit the growth of Staphylococcus aureus and E. bacillus, so that it has the minimum UV stabilizer content, which is a cost-effective and high-performance choice, and its ability to block ultraviolet rays is strong, and it can well protect the quality of packaged food.
Cuvinte cheie
diatomee, oxid de zinc, polietilenă de înaltă densitate, Tinuvin 770
BALÁZS CSABA-FÜLÖP, DRAGOȘ UNGUREANU, GAVRIL KÖLLÖ, NICOLAE ȚĂRANU, GAVRIL HODA, TUDOR-CRISTIAN PETRESCU
Rezumat
Prezenta lucrare investighează performanța structurală și durabilitatea in-situ a solurilor stabilizate, utilizate ca straturi de fundare la drumurile cu trafic redus și mediu. Două studii de caz din România (județele Mureș și Cluj) au presupus stabilizarea unor soluri argiloase slabe cu lianți hidraulici, cu scopul de a îmbunătți capacitatea portantă și comportarea în timp. Au fost efectuate evaluări de laborator și in-situ, inclusiv testări la compresiune (RC₇, RC₂₈), deflecții cu grinda Benkelmann și evaluări la cicluri de îngheț-dezgheț, în conformitate cu standardele naționale (STAS 10473-1-87, STAS 1709, PD 177, CD 31). Rezultatele indică faptul că aceste soluri, stabilizate corespunzător, pot atinge rezistențe la compresiune și module de rigiditate comparabile cu materialele granulare convenționale. Valorile deflecțiilor Benkelman și variabilitatea acestora au rămas în limitele permisibile pentru straturile de fundare, în timp ce evaluările la îngheț-dezgheț au confirmat durabilitatea materialului. Dimensionarea structurală bazată pe PD177 a arătat că straturile stabilizate pot acomoda cerințele de trafic proiectate (Nc = 0.5 milioane axe standard) cu reserve semnificative la oboseală. Acest studiu susține folosirea controlată a solurilor stabilizate în construcția de drumuri, permițându-se astfel folosirea materialelor disponibile local, reducând dependența de aggregate de carieră și susținând practicile inginerești sustenabile, aliniate cu principiile de economie circulară.
Cuvinte cheie
stabilizarea solului, straturi de fundare ale drumului, deflecție grindă Benkelmann, lianți hidraulici, construcție sustenabilă de drumuri
JEBA JENKIN JEBAMONY, ANUSHA GURURAJAN, KRISHNA PRAKASH ARUNACHALAM
Rezumat
The significant environmental impact of cement production, particularly its contribution to CO₂ emissions, has driven the search for sustainable alternatives in the construction industry. Alccofine, a byproduct of ground granulated blast furnace slag, offers a promising solution as a supplementary cementitious material (SCM). This study evaluates the mechanical and durability properties of concrete incorporating alccofine as a partial replacement for cement, emphasizing its potential to enhance sustainability in construction. Alccofine, with its ultra-fine particles and unique chemical composition, improves hydration kinetics and pozzolanic reactions, resulting in better workability, and decreased permeability in concrete. Experimental investigations reveal that up to 30% replacement of cement with alccofine yields enhanced strength without compromising concrete structural integrity. Microstructural analysis highlights the role of alccofine in refining pore structure and promoting the formation of calcium-silicate-hydrate (C-S-H) gel. By utilizing an industrial waste material, this study demonstrates a sustainable approach to mitigating environmental impacts while maintaining high-performance concrete.
Cuvinte cheie
Alccofine, ciment Portland obișnuit (OPC), înlocuitor de ciment, rezistență la compresiune, proprietăți proaspete, emisie de CO2
IVANKA DIMITROVA
Rezumat
Objective: The heat production and transfer to the dental pulp can result from various dental procedures such as friction during cavity preparation without water cooling, bleaching, applying lasers and exothermic reactions during the setting of calcium silicate cements. Calcium–silicate cements are hydraulic materials. Their setting process is associated with temperature changes in the cement paste. These bioactive materials have a variety of uses in endodontics such as a repair perforation material, retrograde root filling material and pulp preservation material. Calcium–silicate cements such as direct pulp capping agents are in direct contact with exposed vital pulp . Excessive heat production during the setting of these materials could lead to serious irreversible pulpal damage. The aim of this study was to record variations in temperature changes during the setting process of conventional calcium silicate cements. Materials and Methods The subjects of this study are three commercially-available in the dental practice calcium silicate cements: White MTA-Angelus (Angelus, Londrina, Brazil), White ProRoot MTA (Dentsply, Tulsa, Johnson City, TN), BioAggregate (InnovativeBioceramix, Vancouver, Canadа) and one industrial Portland cement..For this study thermovision camera FLIR T620 and the Flir Reporter Professional 2013 software were used.Thermal imaging capture was carried out under the following conditions: Distance from the camera lens to the experimental set -1 meter, Room Temperature – 20 - 22 degrees Celsius.Statistical Analysis The mean values of the data were compared using the Student t test. Results: The maximum average temperatures during the cement hydration process range between 26.20 and 26.80 degrees. The highest rise in temperature peak was observed with Bioagreggate at 3 minutes after starting the setting process and the warming peak after 7 minutes at ProRoot. WMTA Angelus exerts the lowest mean temperature rise. Conclusion: The knowledge of temperature rise during the setting reaction of conventional calcium silicate cements can help the dentist to make the right decision and choice of the type of calcium silicate cements. During the dental cement hydration process a rise in temperature up to 2 degrees was recorded. This difference is considered insignificant in the alteation of dental pulp and hard dental tissue.
Cuvinte cheie
Cimenturi cu silicat de calciu, schimbări de temperatură, proces de hidratare, material de acoperire directă a pulpei
TAREK NAADIA, DJAMILA GUECIOUER, YOUCEF GHERNOUTI, MALİKA SABRİA MANSOUR
Rezumat
This experimental study focuses on the development of a steel fiber-reinforced self-compacting concrete (SFSCC) incorporating tuff powder as a local mineral addition. Five mixes were evaluated to assess the influence of fiber dosage on both fresh and hardened properties. The incorporation of steel fibers leads to reduced workability and longer flow times but significantly enhances the stability of the mix by minimizing segregation risks. Mechanically, the addition of fibers results in a marked improvement in flexural strength, with gains exceeding 40% at the highest fiber content. Ductility is substantially increased, reflecting a better ability to absorb post-cracking energy. In contrast, compressive strength shows only a moderate increase, around 11%, confirming that the main contribution of fibers lies in flexural behavior and toughness. The porous texture and pozzolanic activity of the tuff promote strong fiber–matrix bonding, contributing to improved cohesion and crack control. Overall, the findings highlight the feasibility of producing a high-performance, ductile, and stable self-compacting concrete using local resources, offering a sustainable and efficient solution for modern construction needs.
Cuvinte cheie
Fibre de oțel, pulbere de Tuf, ductilitate, lucrabilitate, rezistență la încovoiere, rezistență la compresiune
LARISA PURDEA, CARMEN OTILIA RUSĂNESCU, GIGEL PARASCHIV, SORIN ȘTEFAN BIRIȘ, SABRINA-MARIA BĂLĂNESCU
Rezumat
În această lucrare am evidențiat rezultatele cercetării privind proprietăți fizice și chimice ale cenușii obținute în urma procesului de incinerare a nămolului de epurare și potențialul său de utilizare în compoziția cimentului. Având în vedere obiectivele climatice stabilite pentru 2030 și 2050, este esential ca economia circulară să fie implementată pentru cât mai multe categorii de deșeuri. În acest scop, în cadrul acestei lucrări este analiza cenușa, având cod de deșeu 19 01 14, obținută în urma incinerării nămolului de epurare ape uzate municipale și pluviale din București, în vederea utilizării în industria cimentului. Lucrarea cuprinde date statistice privind cantitatea de nămol generată în anumite țări, rezultate experimentale privind proprietățile cenușii și impactul asupra rezistențelor mecanice ale cimentului.
Cuvinte cheie
cenușa din nămol de epurare ape uzate, nămol de epurare ape uzate, ciment, deșeu.
PENG ZHANG
Rezumat
The intensification of climate change has aggravated the fatigue damage mechanisms of asphalt pavement materials, posing severe challenges to the long-term durability of road infrastructures. At the same time, conventional repair methods often generate high environmental loads, limiting their ecological sustainability. To address these issues, this study develops a fatigue performance evolution model of asphalt mixtures under coupled temperature–moisture conditions, grounded in nonlinear viscoelastic continuous damage (NVECD) theory. Microscopic damage variables and energy dissipation parameters are introduced to achieve high-fidelity simulation of performance degradation during the service life of pavements. Based on this model, an integrated eco-restoration strategy is proposed that combines the molecular penetration mechanism of bio-based rejuvenating agents with the viscosity-reducing effect of warm-mix technology. This composite approach enhances bonding strength, delays microcrack propagation, and reduces repair-related emissions. Furthermore, a full-process experimental system encompassing aging–repair–refatigue cycles is established to validate the model and evaluate the long-term durability of the repair method. Results demonstrate that the deviation between predicted and experimental fatigue damage within 5.00×105 loading cycles remains below 0.023, confirming the model’s predictive accuracy. With the composite restoration method, the fatigue life of aged asphalt mixtures increases from 1.15×105 to 4.05×105 cycles, while the average crack width is controlled to 3.04 μm and the surface roughness Ra is reduced to 1.49. These findings provide both theoretical guidance and practical solutions for the development of climate-resilient and environmentally sustainable road materials.
Cuvinte cheie
materiale de pavaj asfaltic, performanță la oboseală, adaptare la schimbările climatice, eco-restaurare, deteriorare vâscoelastică neliniară
IOANA ION, CIPRIAN MIHAI MITU, EMANUEL VIRGIL MARINESCU, ANDREI CUCOS, ALINA RUXANDRA CARAMITU
Rezumat
Acest studiu prezintă o metodă ecologică de sinteză a unui hidrogel hibrid (HH) pentru remedierea apelor uzate, bazată pe dublă reticulare prin îngheț–dezgheț și iradiere cu raze gama. Matricea polimerică formată din alcool polivinilic (PVA) și carboximetil celuloză (CMC) a fost funcționalizată cu nanoparticule de argint (AgNPs) și oxid de grafen decorat cu AgNPs (AgNPs/GO) pentru a îmbunătăți proprietatile mecanice, adsorbția și activitatea fotocatalitica. Albastrul de metilen (MB) a fost utilizat ca model de poluant. Functionalizarea cu AgNPs și AgNPs/GO determina îmbunătățiri semnificativa a capacitații de adsorbție/decolorare la echilibru: cu 20% cu HAgNP și cu 130% pentru HAgNP/GO; gradul de gonflare cu 6% pentru HAgNP și cu 109% pentru HAgNP/Go; o crestere a rezidului carbonic total la 800°C, la aproximativ 20% datorită rolului catalitic al AgNPs și GO. Efectele sinergice ale CMC, GO și AgNPs îmbunătățesc atât performanța structurală, cât și cea funcțională a hidrogelurilor, poziționând această abordare ca o cale promițătoare pentru tehnologiile avansate de tratare a apelor uzate.Studiul propune o strategie de sinteza a hidrogelurilor pentru tratarea apelor, oferind în același timp o soluție sustenabilă de sfârșit de ciclu/ reciclare, prin pirogenare controlată, cu obtinere de noi produce carbonice cu valore adaugata.
Cuvinte cheie
remedierea apelor uzate, hidrogeluri hibride, nanoparticule de argint, oxid de grafen, oxid de grafen decorat cu nanoparticule de argint, adsorbtia de albastru de metilen
FANG HUO
Rezumat
Ankle injuries in martial arts arise from high-intensity impacts and complex torsional loads. To overcome the trade-off between biocompatibility and mechanical strength in conventional repair materials, we designed a nanostructured hydroxyapatite (HA)/polylactic acid (PLA) composite scaffold. Nano-HA particles were synthesized via controlled solid-state milling (average diameter ~80 nm) and uniformly dispersed in a PLA matrix, then fabricated by 3D printing. We employed BET surface area analysis, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) to characterize pore size distribution and HA–PLA interfacial structure. In vitro tests showed that at 15 wt% HA loading, mesenchymal stem cell proliferation increased by 25% at 42 h, Runx2 expression was upregulated by 30% at day 15, and compressive strength reached 6.0 MPa—significantly higher than controls. Finite element modeling revealed that the nanoscale porous architecture effectively redistributes stress and mitigates concentration. These results demonstrate a clear design–microstructure–performance relationship for nanostructured bone repair scaffolds, offering new insights for high-performance materials in sports injury treatment.
Cuvinte cheie
Ankle Injury, Biomechanical Mechanism, Tissue Engineering, Bone Repair Materials, Sports Injury Repair, Biocompatibility, Mechanical Properties
WEI ZHENG
Rezumat
This work presents an optoelectronic study of cobalt-doped nano-TiO2 camouflage films prepared via a non-hydrolytic sol–gel route and examines their suitability for device integration. Photoluminescence (PL) and UV–Vis absorption measurements show that the films possess a tunable bandgap (3.12–3.24 eV) and exhibit a rapid photoconductive response under visible illumination, with a rise time of about 15 ms and a decay time of roughly 25 ms. SEM observations indicate a highly uniform film morphology, and UV aging tests verify that the coatings retain their structural and optical stability in ambient conditions. When these materials are incorporated into prototype thin-film photodetectors, the devices achieve an on/off photocurrent ratio exceeding 10³ and a responsivity of 0.15 A/W at 450 nm, pointing to their practical promise for adaptive optical filters and smart window coatings. In addition, assessment of visual performance shows that nanoscale optical camouflage layers deliver an average increase of 0.91 points in visual impact over conventional materials, underscoring the capacity of nanoscale optical and electronic architectures to reshape graphic design by enabling more dynamic and aesthetically compelling visual experiences.
Cuvinte cheie
Nanoscale Optical Camouflage Materials, Electronic and Optoelectronic Properties, Nano Titanium Dioxide, Graphic Design Enhancement, Sol-Gel Process
CHUFENG TAO
Rezumat
A novel nanoscale optoelectronic imaging platform is presented that leverages quantum-dot–sensitized sensors together with a hybrid clustering strategy to realize ultra-high-speed acquisition and analysis of rapid nanoscale phenomena. By embedding CdSe/ZnS quantum dots into a plasmonic imaging circuit and feeding the sensor output into a modified k-means routine steered by an artificial fish swarm algorithm (AFSA), data redundancy is suppressed and representative keyframes are extracted in real time. Experiments tracking plasmonic nanoparticle motion under pulsed excitation show a 9.96 % rise in clustering accuracy and a 7.44 % increase in recall relative to standard k-means, accompanied by a 0.086 improvement in the silhouette coefficient. Collectively, these results demonstrate concurrent gains in spatial resolution (down to 50 nm) and temporal resolution (sub-microsecond). Demonstrations in in-situ nanomanufacturing quality monitoring and single-molecule bioimaging further illustrate the platform’s applicability across nanoelectronics and optoelectronic systems.
Cuvinte cheie
Nanoscale Optoelectronics, Ultra-High-Speed Optical Imaging, Nanomaterials in Imaging Technology, Image Processing Algorithms, High-Speed Phenomena Analysis
MARIA ELIZA PUSCASU, CRISTINA BUSUIOC
Rezumat
În ultimii ani, osul a devenit al doilea cel mai transplantat țesut la nivel global ca urmare a numărului crescut de accidente, patologii și a duratei de viață prelungite. În prezent, există limitări semnificative în ceea ce privește materialele disponibile pentru transplantul de țesut osos și există o cerere mare pentru cercetarea substituenților adecvați. Plecând de la compoziția osoasă și arhitectura complexă, se poate obține un material de grefare cu potențial ridicat în ingineria țesutului osos. Bioceramicile din sistemul CaO‒MgO‒SiO2 (de exemplu, diopsid, akermanit și merwinit) au o bioactivitate excelentă și sunt similare cu hidroxiapatita din punct de vedere biologic, având o rezistență mecanică îmbunătățită. Având în vedere arhitectura internă complexă a osului, una dintre cele mai potrivite metode de fabricare în ingineria țesutului osos este imprimarea 3D, deoarece această tehnică facilitează fabricarea unor structuri interne complexe, cu un control ridicat asupra parametrilor de umplere. În această lucrare, au fost obținute pulberi pe bază de diopsid, akermanit și merwinit utilizând atât metoda sol-gel, cât și metoda combustiei. Toate pulberile obținute au fost caracterizate folosind difracția de raze X, în timp ce pulberile de diopsid și merwinite au fost caracterizate din punct de vedere morfologic prin microscopie electronică cu scanare. Ulterior, pulberile obținute au fost amestecate cu un aditiv organic pentru a obține o pastă imprimabilă cu caracteristici adecvate pentru procesul de robocasting. Apoi a fost realizată o comparație între impactul metodei de sinteză asupra formulării pastei. Scaffoldurile 3D obținute au fost evaluate din punct de vedere morfologic folosind microscopia electronică cu scanare. Rezultatele au sugerat că metoda de sinteză joacă un rol important în formularea pastei pentru procesul de imprimare 3D și că scaffoldurile pe bază de diopsid, akermanit și merwinit pot fi obținute cu succes prin metoda robocasting.
Cuvinte cheie
Silicați de Calciu si Magneziu, Sol-Gel; Combustie, Robocasting, Ingineria Tesutului Osos
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Anul
2025
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Numărul
55 (4)
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Paginile
337-346
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Domenii de interes
BIOMATERIALE ȘI BIONANOMATERIALE; SUBSTANȚE, PROCEDURI ȘI DISPOZITIVE PENTRU MEDICINĂ
ELENA CHIȚANU, MIRELA MARIA CODESCU, VIRGIL MARINESCU, ISTVAN BORBÁTH
Rezumat
Nanomaterialele au atras o atenție considerabilă datorită metodelor lor adaptabile de sinteză și gamei largi de aplicații funcționale. Printre acestea, nanoparticulele de SiO2 au atras o atenție semnificativă datorită proprietăților lor fizico-chimice controlabile, care pot fi proiectate cu precizie pentru aplicații biomedicale specifice. De la introducerea sa în 1968, metoda Stöber - în ciuda faptului că a suferit doar mici modificări - a rămas cea mai utilizată abordare pentru sinteza SiO2 la scară nanometrică. Datorită morfologiei și dimensiunii particulelor lor, nanoparticulele de SiO₂ sunt deosebit de potrivite pentru utilizarea în tehnici avansate de fabricație, cum ar fi imprimarea tridimensională (3D), în special în aplicațiile de inginerie biomedicală, inclusiv regenerarea țesutului osos. În astfel de situații, nanoparticulele de SiO₂ sunt de obicei dispersate în suspensii, unde cunoașterea sarcinii lor de suprafață este esențială, deoarece joacă un rol critic în mecanismele ce guvernează agregarea și stabilitatea coloidală. Cu toate acestea, tehnicile de măsurare existente nu permit cuantificarea directă și precisă a sarcinii de suprafață; în consecință, acest parametru este adesea estimat indirect, prin determinarea potențialului zeta. Acest studiu prezintă influența concentrației de tetraetilortosilicat (TEOS) asupra stabilității suspensiilor de SiO2. Nanoparticulele de SiO2 au fost preparate prin tehnica clasică Stöber, cu geometrie sferică uniformă și dimensiuni medii variind în intervalul 152 nm până la 681 nm, datorită creșterii concentrației de TEOS. Pentru a determina potențialul zeta, suspensii conținând 0,05 % masice SiO2 au fost preparate în soluții cu valori ale pH-ului cuprinse între 1 și 12. În condiții alcaline (pH 12), cele mai mici nanoparticule de SiO2 au prezentat valori ale potențialului zeta de până la -58,4 mV, indicând faptul că suspensiile analizate au fost stabile în acest mediu.
Cuvinte cheie
printare 3D a silicei, procedeul Stöber, stabilitatea suspensiilor, potențial zeta
STARLIN DEVA PRINCE JOHN SAHAYAM, ARUL FRANCO PANIMAYAM, NAVANEETHA KRISHNAN MUTHU NADAR, MICHAEL RAJ FRANCIS
Rezumat
Making high-performance hybrid composites from discarded fishnets may improve sustainability. Hand-lay-up is used to blend glass fibre and epoxy resin in the study. ASTM standards were followed to quantify tensile, flexural, and impact force. Multiple acid solutions Hydrochloric Acid (HCL), Sulphuric Acid (H2SO4), Acetic Acid (CH3COOH) applied to nylon fishnets destroyed pollutants and strengthened composite assemblies based on Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS) analysis results. Treated consequences demonstrated superior material properties because tensile strengths achieved 50.71 MPa and flexural strengths measured 40.5 MPa while possessing strong impact resistance. A distribution of materials across the hybrid composites along with minimal voids and improved durability made these composites suitable for marine applications which include boat hulls and structural components. Water absorption tests proved excellent resistance capabilities because the composites exhibited low levels of moisture absorption thus maintaining stability when immersed in water. This research dual-purpose project tackles marine pollution and promotes a circular economy via sustainable development by integrating recycled materials into sophisticated composite systems. Chemically modified waste polymers in ecologically friendly engineering applications may improve engineering materials and performance.
Cuvinte cheie
Sustainable composites, Recycled nylon fishnets, Glass fiber reinforcement, Epoxy resin matrix, Marine pollution mitigation, Mechanical property enhancement
SAID MOHAMED ELAMIN, BENOUMANE SALLAI, YASSINE KHALFI, ALAMI AHMED, BACHIR BOUIADJRA BACHIR, BENOUIS KHEDIDJA, GUELLA SOUFIANE, BELHIA SOUAD
Rezumat
Utilization of agricultural waste for construction materials is an emerging pathway for sustainable development. This study examines the valorization of the Washingtonia filifera palm fibers, one of the main agricultural by-products in Algeria, as a reinforcing material for concrete. Various concentrations and optimum conditions of sodium hydroxide (NaOH) solutions were used to extract the fibers, and subsequently tensile characterization was carried out. The fiber undergone at 2% NaOH for 96 hours has been found to have a 225.95 MPa tensile strength and a 7.85 GPa Young’s modulus. Concrete mixtures were made with 0.5%, 1%, and 1.75% palm fibers by weight of cement. According to mechanical testing, the incorporation of fibers resulted in a slight loss of early age compressive strength, mainly due to porosity. However, as the curing age progressed, the strength performance gradually recovered. The compressive strength of 1.75% fiber blend at 28 days was a maximum of 26.79 MPa. Similarly, flexural tensile strength was notably increased as it achieved a value of 5.96 MPa which was nearly 22% higher than the control. The results show that palm fibers can be converted to effective and green reinforcements when treated appropriately, offering benefits to both engineering applications and the environment.
Cuvinte cheie
Natural fibers, Fiber-reinforced concrete, Alkali treatment, Cement hydration chemistry, Sustainable construction
MOHAMED CHAKIB KHERRABI, MOHAMMED SI-AHMED, AMAR BENYAHIA, MESSAOUD SAIDANI, SAID KENAI
Rezumat
Carbon dioxide emissions, natural resources consumption, and inert waste production represent significant challenges in the construction industry. The use of recycled aggregates and supplementary cementitious materials in mortar and concrete offer promising solutions to these issues. This study investigates the combined effect of recycled sand from brick waste and calcined clay-based cement on the behavior of self-compacting mortar (SCM). The novelty of this work lies in assessing both the mechanical performance and the carbon footprint of these alternative materials. Natural sand (NS) was substituted with recycled brick sand (BS) at proportions 10, 20, 30, and 40% by volume, while cement was partially replaced with 10 and 15% by mass of calcined clay (CC). A series of laboratory tests were carried out to evaluate workability, compressive strength, shrinkage, and microstructural properties. The results indicate that the combination of CC and BS decreases workability and shrinkage, increases compressive strength by up to 23%, and improves the microstructure of the mixtures. The mixtures based on BS and CC are the most ecological with a reduction in the carbon footprint and with the eco-mechanical index (EMI) reaching 28% compared to the control mortar.
Cuvinte cheie
Recycled brick sand, calcined clay, Self-compacting mortar, Compressive strength, shrinkage, Carbon footprint
CICI JENNIFER RAJ J, KUMAR G, BASKAR S
Rezumat
This experimental study investigates the feasibility and performance characteristics of incorporating treated rubber industrial wastewater as a sustainable alternative to potable water in concrete production. The research systematically evaluates the mechanical properties and microstructural characteristics of M25 grade concrete with and without rubber industrial waste water (RIWW) using Scanning Electron Microscopy. The study is exclusively dealt with the behaviour of RIWW, with and without admixtures. From the study, it is observed that compressive strength of the concrete using RIWW and admixtures is 25% to 30% greater compared to other concrete only with RIWW. Furthermore, higher replacement levels displayed tiny voids and microcracks, suggesting a small slowdown in hydration, while concretewith potable water had a dense and well-hydrated microstructure with consistent C-S-H gel formation, according to SEM images.
Cuvinte cheie
Rubber Industrial Water, Compressive Strength, SEM Analysis, CSH gel
KARTHIKEYAN SAMBANDHAM, BASKAR NEELAKANDAN, GANESAN MANICKAM, RAMKUMAR KATHALINGAM
Rezumat
Friction welding is an efficient and economical process of joining two similar or dissimilar metals among various welding processes. Now-a-days, the automobile and other industries are using dissimilar metals in a same working area to compensate the problems faced due to temperature and working atmosphere to enhance company’s economy. The material AA6351 and EN353 alloy steel have wide applications in aerospace & automobile industries, are joined with different input parameters like Heating Time (HT), Heating Pressure (HP), Upset Time (UT), Upset Pressure (UP) with constant rotation. These input parameters are ordered using L27 Taguchi Orthogonal Array (OA) to experiment the process. Friction welding is done in KUKA friction welding machine. After experimentation, the responses like temperature, hardness and axial shortening are measured. Using these responses, the optimization is carried out through Grey Relational Analysis (GRA) and the rankings are identified and tabulated to obtain the optimal solutions. Based on rankings, the optimal input parameters are concluded as 18 bar of Heating Pressure (HP), 7 sec of Heating Time (HT), 22 bar of Upset Pressure (UP) and 3 sec of Upset Time (UT). The Field Emission Scanning Electron Microscope (FESEM) analysis is also used to study the Inter-metallic compounds (IMCs).
Cuvinte cheie
Friction Welding, AA6351, EN353, Grey Relational Analysis, FESEM analysis
GUIZHEN WANG, LINGLONG ZHOU
Rezumat
This study explores the seismic reinforcement of coastal buildings through the innovative application of Shape Memory Alloys (SMAs). SMAs, a novel class of functional materials, exhibit unique properties like shape memory effect, superelasticity, and high damping performance, making them ideal for seismic applications. Recognizing the critical role of structural design in a buildings earthquake resistance, this research introduces an SMA-based damper specifically tailored for coastal structures, considering their unique stress profiles and disaster vulnerability. Through experimental and simulation methods, including MATLABs Simulink module, the study compares the seismic responses of conventional coastal building designs with those incorporating the SMA damper. The results reveal that the SMA dampers bilinear restoring force mechanism significantly enhances vibration suppression, offering a promising solution for seismic reinforcement in building construction. This investigation not only contributes to the understanding of SMA materials but also underscores their potential in structural earthquake resilience, marking a significant intersection of material science, engineering, and seismic technology.
Cuvinte cheie
Shape Memory Alloys (SMAs); Seismic Dampers; Coastal Building Reinforcement; Earthquake Resistant Structures; Superelastic Materials
ANCA MIHAELA MOCANU, ANDREEA IOANA SUSANU
Rezumat
Lucrarea explorează domeniul protezelor dentare fabricate digital, detaliind în mod specific aplicarea metodologiilor CAD/CAM (Computer-Aided Design/Computer-Aided Manufacturing) în domeniul stomatologiei restaurative. Cercetarea examinează în detaliu secvența de fabricare digitală în protetică dentară, care cuprinde faze critice precum scanarea intraorală/de laborator, modelarea CAD, frezarea automată și tratamentul final al suprafeței. O parte semnificativă a lucrării este dedicată implementării sistemului CEREC în mediul clinic (adică proceduri efectuate în cadrul cabinetului stomatologic). În plus, studiul include o evaluare a echipamentelor specializate și a comportamentului mecanic al trei biomateriale restaurative notabile: Zirconia, IPS E.max Ceram Dentin și Cerasmart. Sistemul CEREC este un sistem computerizat cu ajutorul căruia se pot proiecta și realiza într-o singură ședință lucrări ceramice unidentare și de mică intindere, extrem de precise, estetice și rezistente. Materialele dentare au fost analizate atât în forma lor de dinaintea procesului de ardere, cât şi după această etapă, prin spectroscopie de absorbţie în infraroşu (FITR), morfologia probelor a fost evidențiată prin utilizarea unui microscop electronic de baleiaj de înaltă rezoluție, echipat cu un detector EDX și analiză termică (TG-DTG-DTA). Metodele de caracterizare au fost aplicate pentru a compara performanțele celor trei materiale, cu accent pe adaptarea marginală, estetica, rezistența și ușurința în prelucrare si evidențierea diferențelor esențiale dintre materiale în contextul utilizării lor în restaurările stomatologice. Rezultatele acestui studiu împreună cu datele din literatura de specialitate ajută la interacțiunea acestor materiale cu țesuturile și, de asemenea, la modificarea proprietăților acestor materiale.
Cuvinte cheie
kit-uri ceramice, tehnica CAD/CAM, spectroscopie de absorbție, microscopie electronică de baleiaj, analiză termică
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Anul
2025
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Numărul
55 (4)
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Paginile
413-423
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Domenii de interes
BIOMATERIALE ȘI BIONANOMATERIALE; SUBSTANȚE, PROCEDURI ȘI DISPOZITIVE PENTRU MEDICINĂ
ANDREI GÎRBOVEANU, ANDREI ZYBACZYNSKI, MUHEEB ALTALEB, DAN PAUL GEORGESCU
Rezumat
Durabilitatea betonului armat este legata în principal de coroziunea armăturilor. Coroziunea apare curent din cauze legate de carbonatare sau din difuzia clorurilor. De asemenea fisurarea este o cauză posibilă a accelerării consecințelor acestor fenomene. În acest articol se prezintă argumente care rezultă atât din literatura tehnică de specialitate dar și demonstrate teoretic și prin încercări experimentale de către autori legate de faptul că armarea dispersă reprezintă și o soluție de îmbunătățire a durabilității betonului armat. Betonul armat dispers are particularități care conduc la îmbunătățirea unor mecanisme de transport cum ar fi permeabilitatea sau difuzia dar și în ceea ce privește reducerea nivelului deformațiilor specifice precum și al deschiderii fisurilor, care influențează aceste mecanisme de transport, la aceleași niveluri ale solicitărilor prin comparație cu betonul armat obișnuit. In conformitate cu cercetările desfășurate pe plan internațional în cazul betonului armat cu fibre de oțel, coroziunea este mult mai puțin severă în comparație cu armarea cu armătură continua de oțel a structurilor de beton iar degradarea betonului armat cu fibre de oțel fisurat din cauza coroziunii fibrelor depinde de mai mulți parametri, cum ar fi: deschiderea fisurii, agresivitatea condițiilor de mediu și tipul de fibre. Deschiderea fisurilor de până la 0,1 mm nu are niciun efect negativ asupra coroziunii, deoarece auto colmatarea restabilește aproape complet integritatea structurii betonului armat cu fibre de oțel. Coroziunea superficială crește frecarea fibre-matrice, sporind rezistența la smulgerea fibrelor, ceea ce poate conduce la creșterea capacității de încovoiere a elementelor din beton armat cu fibre de oțel. Calculele prezentate în articol au indicat că betonul armat dispers prezintă o deschidere mai mică a fisurilor pentru aceleași condiții legate de compoziția betonului sau nivelul de solicitare față de betonul armat obișnuit. Rezultatele cercetărilor experimentale efectuate pe elemente din beton precomprimat la care în zona centrala a deschiderii s-a înlocuit armarea transversală cu etrieri cu armarea dispersă au scos în evidență o diminuare a deformațiilor specifice pentru aceleași niveluri de solicitare în cazul utilizării armării disperse, ceea ce indică o reducere a microfisurării, o permeabilitate mai scăzută și, implicit, o rezistență sporită la penetrarea agenților externi, contribuind astfel la îmbunătățirea durabilității.
Cuvinte cheie
Beton, armare dispersă, condiții de mediu, durabilitate, beton precomprimat, etrieri, deformații