Search Results (195)

The study investigates the potential of enhancing gypsum board properties through the integration of hemp hurds and glass fibers. The investigation focuses on evaluating the composite material’s density, water absorption, flexural strength, compressive strength, and thermal performance. Experimental results demonstrate a reduction in gypsum composite density and improved thermal insulating properties with the introduction of hemp hurds. Water absorption, a significant drawback of gypsum boards, is mitigated with hemp hurds, indicating potential benefits for insulation efficiency. For mechanical tests, the gypsum ceiling board at approximately 5% by weight exhibits a flexural strength value exceeding the minimum average threshold of 1 MPa and the highest average compressive strength at 2.94 MPa. Thermal testing reveals lower temperatures and longer time lags in gypsum boards with 5% hemp hurds, suggesting enhanced heat resistance and reduced energy consumption for cooling. The study contributes valuable insights into the potential use of hemp hurds in gypsum-based building materials, presenting a sustainable and energy-efficient alternative for the construction industry. Full article

This paper presents the results of a comprehensive study of the structure, phase composition, thermal corrosion, and tribological properties of multilayer gradient coatings based on YSZ/NiCrAlY obtained using detonation spraying. X-ray phase analysis showed that the coatings consist entirely of metastable tetragonal zirconium dioxide (t’-ZrO₂) phase stabilized by high temperature and rapid cooling during spraying. SEM analysis confirmed the multilayer gradient phase distribution and high density of the structure. Wear resistance, optical profilometry, wear quantification, and coefficient of friction measurements were used to evaluate the operational stability. The results confirm that the structural parameters of the coating, such as porosity and phase gradient, play a key role in improving its resistance to thermal corrosion and CMAS melt, which makes such coatings promising for use in high-temperature applications. It is shown that a dense and thick coating effectively prevents the penetration of aggressive media, providing a high barrier effect and minimal structural damage. Tribological tests in the temperature range from 21 °C to 650 °C revealed that the best characteristics are observed at 550 °C: minimum coefficient of friction (0.63) and high stability in the stage of stable wear. At room temperature and at 650 °C, there is an increase in wear due to the absence or destabilization of the protective layer. Full article

Currently, chimney technology is looking for new materials with improved thermal insulation properties and, at the same time, adequate durability. The use of concretes based on lightweight aggregates, such as expanded perlite, is capable of meeting such a challenge, provided that the composition of the concrete mixes is appropriately modified. The main research challenge when designing chimney system casing elements lies in ensuring adequate resistance to moisture penetration (maximum water absorption of 25%), while achieving the lowest possible bulk density (below 1000 kg/m³), sufficient compressive strength (minimum 3.5 MPa), and capillary water uptake not exceeding 0.6%. In the present research, laboratory tests were conducted to improve the fundamental technical properties of lightweight perlite-based concrete to meet the aforementioned requirements. Laboratory tests of perlite concrete were carried out by adding eight chemical admixtures with a hydrophobic effect and the obtained results were compared with a reference concrete (without admixtures). However, the positive results obtained under laboratory conditions were not confirmed under actual production conditions. Therefore, further tests were conducted on chimney casings taken directly from the production line. Subsequent chemical admixtures with a hydrophobic effect, based on silane/siloxane water emulsions, were applied to determine the concrete mix’s optimal composition. The results of the tests carried out on perlite concrete chimney casings from the production line confirm the effectiveness of the applied chemical admixtures with a hydrophobic effect in improving the moisture resistance. This was further supported by the outcomes of the so-called ‘drop test’ and capillary uptake test, with the suitable bulk density and compressive strength being maintained. Full article

During a volcanic eruption, a large volume of pyroclastic material can be deposited on the roads and roofs of the urban areas near volcanoes. The use of volcanic ash as an additive for the manufacture of bricks provides a solution to the disposal of part of this natural residue and reduces the depletion of a non-renewable natural resource, clayey soil, which brings some environmental and economic advantages. The pore system, compactness, uniaxial compression strength, thermal conductivity, color and durability of bricks without and with the addition of volcanic ash were evaluated through hydric tests, mercury intrusion porosimetry, ultrasound, uniaxial compression tests, IR thermography, spectrophotometry and salt crystallization tests. The purpose of this research is to determine the feasibility of adding 10, 20 and 30% by weight of volcanic ash from La Palma (Canary Islands, Spain) in two grain sizes to produce bricks fired at 800, 950 and 1100 °C. The novelty of this study is to use two sizes of volcanic ash and fire the samples at 1100 °C, which is close to the liquidus temperature of basaltic magmas and allows a high degree of interaction between the volcanic ash and the brick matrix. The addition of fine volcanic ash was found to decrease the porosity of the bricks, although the use of high percentages of coarse volcanic ash resulted in bricks with almost the same porosity as the control samples. The volcanic ash acted as a filler, reducing the number of small pores in the bricks. The presence of vesicles in the volcanic ash reduced the compressive strength and the compactness of the bricks with additives. This reduction was more evident in bricks manufactured with 30% of coarse volcanic ash and fired at 800 and 950 °C, although they still reached the minimum resistance required for their use in construction. No significant differences in thermal conductivity were noticed between the bricks with and without volcanic ash additives, which is crucial in terms of energy savings and the construction of sustainable buildings. At 1100 °C the volcanic ash changed in color from black to red. As a result, the additive blended in better with the matrix of bricks fired at 1100 °C than in those fired at 800 and 950 °C. The bricks with and without volcanic ash and fired at 1100 °C remained intact after the salt crystallization tests. Less salt crystallized in the bricks with volcanic ash and fired at 800 and 950 °C than in the samples without additives, although their low compressive strength made them susceptible to decay. Full article

Metallurgical equipment foundations exposed to prolonged 300–500 °C environments are subject to explosion risks, necessitating materials that are resistant to thermo-shock-coupled loads. This study investigated the real-time dynamic compressive behavior of high-performance concrete (HPC) reinforced with steel fibers (SFs), polypropylene fibers (PPFs), polyvinyl alcohol fibers (PVAFs), and their hybrid systems under thermo-shock coupling using real-time high-temperature (200–500 °C) SHPB tests. The results revealed temperature-dependent dynamic responses: SFs exhibited a V-shaped trend in compressive strength evolution (minimum at 400 °C), while PPFs/PVAFs showed inverted V-shaped trends (peaking at 300 °C). Hybrid systems demonstrated superior performance: SF-PVAF achieved stable dynamic strength at 200–400 °C (dynamic increase factor, DIF ≈ 1.65) due to synergistic toughening via SF bridging and PVAF melt-induced pore energy absorption. Microstructural analysis confirmed that organic fiber pores and SF crack-bridging collaboratively optimized failure modes, reducing brittle fracture. A temperature-adaptive design strategy is proposed: SF-PVAF hybrids are prioritized for temperatures of 200–400 °C, while SF-PPF combinations are recommended for 400–500 °C environments, providing critical guidance for explosion-resistant HPC in extreme thermal–industrial settings. Full article

Shale oil, a major unconventional energy source with extensive global reserves, presents significant processing challenges due to the exceptional stability of its emulsions. Characterized by small droplet sizes and high interfacial film strength, these emulsions resist efficient treatment via conventional thermal-chemical or electrostatic dehydration. To address the difficulties in separation, unclear dehydration mechanisms, and inconsistent single-field (electric) performance, this study investigates dehydration using a novel electric–magnetic–ultrasonic coupling field system. Dehydration efficiency under an electric field alone increased with electric field strength, frequency, duration, and temperature. Magnetic or ultrasonic fields alone yielded negligible effects. Coupling an electric field with ultrasound enhanced efficiency, while adding a magnetic field to electricity provided no improvement and decreased efficiency with longer exposure or higher magnetic intensity. The multi-field coupling achieved significant demulsification. Both optimal dehydration performance and minimum energy consumption operating conditions were identified, capable of reducing shale oil water content below 0.5%. Full article

An analysis is presented of the irreversibility of flow and thermal phenomena in innovative streamlined structured packing of catalytic chemical reactors. The fundamental equations of irreversible thermodynamics defining entropy production as a result of flow friction and heat transport are formulated. The parameters describing the flow and heat transport in these equations are determined using the Computational Fluid Dynamics (CFD) methodology. Local entropy production due to flow friction and heat transport in the channel structure is plotted and compared with flow-temperature maps and relations for flow resistance, pressure gradient, and Nusselt number derived from CFD. The calculations were performed for three gas velocities: 0.3; 2.0, and 6.0 ms⁻¹. It was found that the entropy due to flow friction increases strongly with increasing gas velocity, while the entropy due to heat transport decreases with gas velocity, but to a limited extent. These opposing tendencies mean that there is always a minimum of the total entropy production (including these due to flow friction and heat transport), usually for moderate gas velocity. This minimum constitutes the optimum operating point of the reactor from the thermodynamic point of view. Full article

Freeze–thaw (F/T) technology is an environmentally friendly and efficient method for residual sludge treatment. This study investigates the enhancement of sludge dewatering performance through the addition of straw during F/T cycles. A mathematical model was established using the Box–Behnken central composite design and validated via COMSOL Multiphysics simulations. The optimal conditions were identified as freezing at −16 °C for 24 h, with 12.5 freeze–thaw cycles and a straw mixing ratio of 20%, reducing the sludge moisture content from 62.7% to 35.9%. The specific resistance to filtration (SRF) and cake moisture content decreased significantly with increasing straw addition, reaching a minimum SRF of 1.30 × 10¹² m/kg at the optimal straw ratio. Straw conditioning also intensified the combustion stage of the sludge by increasing the maximum weight loss rate and elevating the thermal decomposition temperature. Numerical simulations confirmed the experimental results, demonstrating that straw addition significantly improves sludge dewaterability by modifying heat and mass transfer mechanisms. Full article

Adaptive façades, also known as climate-adaptive building shells (CABSs), could make a significant contribution towards reducing the energy consumption of buildings and their environmental impacts. There is extensive research on glazed adaptive façades, mainly due to the available technology for glass materials. The technological development of opaque adaptive façades has focused on variable-thermal-resistance envelopes, and the simulation of this type of façade is a challenging task that has not been thoroughly studied. The aim of this study was to configure and validate a simplified office model that could be used for simulating an adaptive façade with variable thermal resistance via adaptive insulation thickness in its opaque part. Software-to-software model comparison based on the results of an EnergyPlus Building Energy Simulation Test 900 (BesTest 900)-validated model was used. Cooling and heating annual energy demand (kWh), peak cooling and heating (kW), and maximum, minimum, and average annual hourly zone temperature variables were compared for both the Adaptive and non-adaptive validated model. An Adaptive EnergyPlus model based on the BesTest 900 model, which uses the EnergyPlus SurfaceControl:MovableInsulation class list, was successfully validated and could be used for studying office buildings with a variable-thermal-resistance adaptive façade wall configuration, equivalent to a heavyweight mass wall construction with an External Insulation Finishing System (EIFS). An example of the Adaptive model in the Denver location is included in this paper. Annual savings of up to 26% in total energy demand (heating + cooling) was achieved and could reach up to 54% when electro-chromic (EC) glass commanded by a rule-based algorithm was added to the glazed part of the variable-thermal-resistance adaptive façade. Full article

An interpretable machine learning framework was constructed to predict the bandgap of silicon oxide materials used for electric furnace refractories. Among seven machine learning models compared, the AdaBoost ensemble model performed the best with an R² of 0.80 and MAE of 0.5, indicating high accuracy. Breaking through the traditional limitation of directly correlating features such as the conduction-band minimum (CBM) and valence-band maximum (VBM), this study utilized SHapley Additive exPlanations (SHAP) analysis to uncover deeper relationships between critical features like ‘energy above hull’, ‘num of unique magnetic sites’, and ‘formation energy per atom ‘ with the bandgap. These features significantly influence the thermal stability and erosion resistance of the material. This research provides a theoretical basis for optimizing the performance of silicon oxide materials and green metallurgical processes, thereby promoting sustainable development in the steel industry. Full article

The photosensitive properties of smart photoactive polymers give them a wide range of potential applications across various fields. This study focuses on designing polymeric systems that incorporate hydrophilic polymers, with the primary goal of adapting these materials for biological applications. Specifically, it aims to contribute to the development of photochromic materials for optical processing, utilizing both molecular and macromolecular components. Additionally, this study evaluates the effectiveness of photoactive polymers in photodynamic therapy (PDT). It details the synthesis and characterization of photoactive copolymers derived from maleic anhydride (MAn) combined with vinyl monomers such as 2-methyl-2-butene (MB) and 1-octadecene (OD), as well as the organic compound 1-(2-hydroxyethyl)-3,3-dimethylindoline-6-nitrobenzopyran (SP). The two novel optically active alternating polymeric systems, poly(maleic anhydride-alt-octadecene) and poly(maleic anhydride-alt-2-methyl-2-butene), were functionalized with SP through an esterification process in a 1:1 monomer feed ratio, using pyridine as a catalyst. This methodology incorporated approximately 100% of the photoactive molecules into the main acrylic chain to prepare the alternating copolymers. These copolymers were characterized by UV-visible, FTIR, and 1H-NMR spectroscopy and analysis of their optical and thermal properties. When exposed to UV light, the photoactive polymer films can develop a deep blue color (566 nm in the absorption spectra). Finally, the study also assesses their capacity for photodynamic antimicrobial action in organic film. Notably, the photoactive P(MAn-alt-2MB)-PS significantly enhances the photodynamic antimicrobial activity of the photosensitizer Ru(bpy) against two bacterial strains of Staphylococcus aureus, reducing the minimum inhibitory concentration (MIC) from 2 µg/mL to 0.5 µg/mL. Therefore, 4 times less photosensitizer is required when mixed with the photoactive polymer to inhibit the growth of antibiotic-sensitive and -resistant bacteria. Full article

This study examines the impact of PVD coatings on cutting tool wear during the milling of 316L stainless steel under air cooling conditions. In the experiment, a carbide milling cutter coated with a nanocomposite nACo3 (AlTiSiN) coating was used. The coating was deposited using a next-generation device, the PLATIT π411PLUS, which features one central and three lateral rotating cathodes. The nanocomposite nACo3 coating obtained with this method exhibits exceptionally high structural density and excellent mechanical properties. The new generation of the nACo3 coating demonstrates improved surface properties and a lower friction coefficient compared to previous generations. The findings indicate that PVD nACo3 coatings significantly enhance wear resistance, extending tool life while maintaining acceptable surface quality. The optimal cutting time was determined to be approximately 90 min, after which a sharp increase in surface roughness and tool wear was observed. After 120 min of machining, substantial deterioration of surface quality parameters was recorded, suggesting increasing cutting forces and cutting edge degradation. SEM and EDS analyses revealed the presence of adhered material on the tool and sulfide inclusions in the microstructure of 316L stainless steel, which influenced the machining process. The nACo3 coating demonstrated high thermal and wear resistance, making it an effective solution for machining difficult-to-cut materials. This study suggests that selecting appropriate cutting parameters, tool geometry, protective coatings, and cooling strategies can significantly affect tool longevity and machining quality. The novelty of this research lies in the application of innovative nanocomposite PVD coatings during the milling of 316L stainless steel under air cooling conditions. These studies indicate potential future research directions, such as the use of minimum quantity lubrication (MQL) or cryogenic cooling as methods to reduce tool wear and improve post-machining surface quality. Full article

The construction of residential buildings and structures is a complex process in which the economic component plays a key role. It is essential to maintain a balance between saving construction materials and the costs of additional engineering solutions while ensuring the functionality and comfort of the building’s operation. To achieve this goal, researchers initially analyze the impact of the climatic environment and spatial planning solutions—i.e., building shapes—that directly affect the building compactness ratio when evaluating the efficiency of the designed building. In this regard, the objective of this study was to analyze the shapes and orientations of buildings in the Republic of Kazakhstan across eight territorial units located in the I, III, and IV climatic zones between latitudes 42°18′ and 52°16′ N. The study identified the most favorable building orientations for each climatic zone: the meridional orientation is preferable for the I and III zones, while the latitudinal orientation is optimal for the IV zone. Four residential building shapes—square, rectangular, cylindrical, and triangular—were analyzed based on a floor area of 1000 m² and a building volume of 3000 m³ during the coldest five-day period and the hottest month. According to the specific thermal characteristic values, it was found that a cylindrical residential building is 1.1, 1.37, and 1.27 times more efficient than square, rectangular, and triangular residential buildings, respectively. Additionally, the compactness ratio was determined for different residential building shapes and heights, ranging from 8 to 16 floors in increments of four floors. The results showed that under these conditions, the compactness ratio increases by an average of 1.3 times due to the increase in the area of external walls. However, if the initial condition is changed to account solely for the floor area, the compactness ratio decreases by up to 2.3 times. The conducted research shows that when solving the problem of the energy efficiency of a building, taking into account shapes and orientations, it is necessary to carry out a full assessment of the specified energy efficiency parameter depending on the expected results, which requires a comprehensive analysis to achieve energy-efficient buildings. At the same time, the results of this study will be used and will positively complement the results of a comprehensive study by the authors on the development of energy-efficient exterior enclosing structures, which, together with general solutions, will significantly affect the thermal balance of the building and complement the research conducted earlier. Full article

Nanocomposite laminates containing carbon fibers, epoxy, and multiwalled carbon nanotubes were fabricated using a vacuum bag process. Ecofriendly ionic liquid (5 wt%)-treated multiwalled carbon nanotubes (pristine and nickel-coated) were added to the epoxy independently, in amounts ranging from 1 wt% to 3 wt%, in order to tailor the mechanical, electrical, and thermal performance of manufactured carbon fiber epoxy composite laminates. These nanocomposite laminates were later characterized through flexural testing, dynamic mechanical analysis, impedance spectroscopy, thermal conductivity tests, and FTIR spectroscopy to evaluate their suitability for battery pack applications. The findings showed that both types of multiwalled carbon nanotubes exhibited multifaceted effects on the properties of bulk hybrid carbon fiber epoxy nanocomposite laminates. For instance, the flexural strength of the composites containing 3.0 wt% of ionic liquid-treated pristine multiwalled carbon nanotubes reached 802.8 MPa, the flexural modulus was 88.21 GPa, and the storage modulus was 18.2 GPa, while the loss modulus peaked at 1.76 GPa. The thermal conductivity of the composites ranged from 0.38869 W/(m · K) to 0.69772 W/(m · K), and the electrical resistance decreased significantly with the addition of MWCNTs, reaching a minimum of 29.89 Ω for CFRPIP-1.5 wt%. The structural performance of hybrid nanocomposites containing ionic liquid-treated pristine multiwalled carbon nanotubes was higher than that of the hybrid nanocomposite of ionic liquid-treated Ni-coated multiwalled carbon nanotubes, although the latter was found to possess better functional performance. Full article

Background/Objectives: Nowadays fungal infections are rising serious threats for the human health system and agriculture, mostly because of antifungal resistance, emergence of new fungal pathogens and adverse effects, pressing the scientific world for exploration of new antifungal compounds. Therefore, the aim of this work was to synthesize and to study antifungal activity against human and plant fungi of a new class of hybrid bis-(imidazole/benzimidazole)-pyridine salt derivatives. Methods: The synthesis of the hybrid derivatives was performed using both conventional thermal heating and ultrasound irradiation methods. Results: The use of ultrasound irradiation has the advantages of a dramatic decrease in reaction time and, consequently, a notable acceleration in reaction rate, a remarkable decrease in consumed energy and higher yields. The antifungal activity against five human fungal strains and for plant fungal strains was determined by the disk diffusion method and minimum inhibitory concentration. Conclusions: The tested hybrid derivatives manifest good antifungal activity against the tested strains. Some of the hybrid compounds have very good quasi-nonselective activity against the tested human and plant pathogenic fungi, in some cases close to the control drug fluconazole, respectively, to many antifungal agents commercially used for plant protection. Full article