english 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