Materials Science Forum Vol. 1162

Abstract: The paper develops a predictive model to determine the influence of the value of the dispersion component of the free surface energy (FSE) and the volume fraction of fillers on the dispersion component of the FSE of a polymer composite. Mathematical equations and graphical relationships illustrating these relationships are presented. The model is based on the assumption that in composites the FSE value is partially determined by interactions at the polymer-filler interface. Using the predictive model, it was established that the dispersion component of the free surface energy (FSE) can be a reflection of the properties of polymer composites. The reliability of the predictive assessment is shown on the example of an epoxy polymer composite with various mineral fillers.

Abstract: Composite sandwich panels are extensively used in aerospace, automotive, and construction applications due to their exceptional strength-to-weight ratio and structural efficiency. However, local surface deviations, such as waviness and dents, often develop during manufacturing and operation, potentially leading to adhesion failures and delamination between the composite skin and the core. This study aims to establish acceptable defect size limits that can be corrected through technological pressing, ensuring structural integrity of composite material while minimizing the negative impact on load-bearing capacity of sandwich panels. An analytical approach was adopted to assess the stress behavior of composite skins with waviness and elliptical dent defects. The analysis was based on beam and plate theory, incorporating the effects of flexural rigidity, material anisotropy, and applied technological pressure. The Hill strength criterion was applied to define permissible defect limits, considering variations in structural criticality levels. The study determined the maximum allowable sizes for waviness and dents in composite sandwich panels, factoring in the responsibility level of the panel, expressed as the maximum stress intensity coefficient. The results show that the acceptable defect size decreases with increasing structural criticality. It was also found that forced compression of dents induces pre-stress zones within the composite skin, potentially altering its stress distribution and reducing its long-term load-bearing capacity. The proposed methodology provides a quantitative framework for evaluating acceptable defect limits, supporting manufacturing quality control and repair optimization. The results offer practical insights for enhancing the reliability and durability of composite structures, ensuring that local surface deviations remain within permissible limits without compromising structural performance.

Abstract: Currently, great attention is paid to the creation of polymer composites using functional fillers and polymer matrices of various types, including thermoplastic and thermosetting types. These fillers also make it possible to increase the protective properties of the polymer against electromagnetic radiation by several orders of magnitude. The aim of the study is to study of the process of synthesis of functional fillers for polymer composites for protection against electromagnetic radiation. As a result of the studies conducted, the process of synthesizing functional fillers for polymer composites for electromagnetic radiation protection has been comprehensively examined. It has been shown that the recrystallization of titanium oxide from solution-melts of KCl-NaCl and KCl-NaCl-∑TiClₙ is possible under a flow of inert gas in the presence of a reducing agent, resulting in thread-like crystals of fibrous form. In the process, thread-like rutile crystals with cross-sectional dimensions of 3–30 μm and lengths of 10³–10⁴ microm were obtained. It has also been established that blowing KCl-NaCl-TiCl₄ without TiO₂ with inert gas in the absence of a reducing agent results in the crystallization of metallic titanium in the form of hollow microspheres. The obtained functional fillers have great potential in the development of polymer composite materials for electromagnetic radiation protection, providing a high combination of strength and spectral characteristics.

Abstract: The study is devoted to solving the actual problem of determining optimal filter configuration parameters that ensure the maximum protective service life of dust filters—specifically, the time of use before reaching the critical point when breathing through the filter becomes impossible.The purpose of the work is to determine the configuration coefficient of dust filters (surface area, fold pitch, and fold height), enabling the calculation of the initial pressure drop across the filters.To identify the correlation between the configuration parameters of dust filters, a 3D model of a filter cartridge with overall dimensions of 100×50×15 mm – matching the standard sizes of most commonly used filter box designs – has been fabricated. Polypropylene filtering material with a fiber packing density of 50 g/m² and fiber diameters ranging from 1 to 3 µm has been used; the thickness of the filtering layer was 2 mm. Sets of five filter samples have been produced with varying filtration areas, which depended on the number of folds, ranging from 5 to 30. To measure the pressure drop across the filters, a specialized test stand complying with EN 13274-3:2001 «Respiratory protective devices – Methods of test – Part 3: Determination of breathing resistance» has been employed, under constant airflow rates of 30 dm3/min and 95 dm³/min.The relationship between the pressure drop across pleated filters and parameters such as filtration area, pleat channel width, and filter height has been established, allowing the determination of a configuration coefficient that ensures minimal resistance to airflow. For rectangular filters from polypropylene material with a fiber packing density of 50 g/m² and a filtering layer thickness of 0.6 mm, a pleat height of 10 mm, the optimal spacing between pleats has been found to lie within the range of 3–4 mm, corresponding to 2.5–3.3 pleats per cm. For calculating the configuration coefficient of filters made from materials with varying fiber packing densities the algorithm has been proposed. The algorithm includes determining the initial pressure drop of a flat filter, calculating the filter area based on specified pleat spacing (W) and height, defining the configuration coefficient, and comparing it with the recommended optimal value.The scientific novelty lies in establishing an experimental relationship between the pressure drop and the configuration coefficient of pleated filters. This relationship enables the identification of optimal parameters for filtration area and the ratio of the distance between pleats to their height.The value of this research consists in the development of an algorithm for determining the configuration coefficient of pleated filters, which allows for a more accurate estimation of the initial pressure drop.

Abstract: In this work, the glass formula (70-x)P₂O₅: 15NaF: 5ZnF₂: 15AlF₃: xBaO where x is 0, 5, 10, 15 mol% were manufactured by the conventional melt-quenching technique at 1200 °C in 3 hours for photon shielding application. The effect of glasses was examined on the physical, gamma ray and x-ray shielding properties. The results revealed that the density was increased with increasing of BaO concentrations. The glass systems were calculated by using the experiment set up for estimating the radiation shielding properties in the content of mass attenuation coefficients (μ_m), effective atomic number (Z_eff), and effective electron density (N_eff), which were increased when concentrations of BaO increased, while the half value layer (HVL) was decreased. For result of using the x-ray source, the linear attenuation (μ) was increased with an accrue in BaO concentration. The HVL was decreased when concentrations of BaO increased. The HVL values of glass samples at 15 mol% has better shielding behavior than the standard materials at 120 kVp. The BaO glass systems can be candidate for radiation shielding materials in the future.

Abstract: Currently, X-rays are extensively utilized in various fields, particularly in medical diagnostics. X-rays have played a pivotal role in diagnosing diseases in patients. To ensure the safe use of radiation, it is essential to consider the effects of radiation on the personnel involved. Radiation protection must be implemented by minimizing exposure time and increasing the distance from the radiation source, alongside the use of radiation shielding, in accordance with the principle of As Low As Reasonably Achievable (ALARA). This study employed bismuth (Bi) as the shielding material due to its high radiation protection efficiency and low toxicity. Specifically, the radiation shielding properties of bismuth-metal phosphate glass were investigated, with the following chemical formula: (70-x)P₂O₅: 15NaF: 5ZnF₂: 10AlF₃: xBi₂O₃, where x represents the mole percentage of Bi₂O₃, with values of 0, 3, 6, 9, 12, and 15. The results indicated that the glass's ability to shield against X-rays improved as the quantity of bismuth oxide increased. This was evaluated through experiments conducted with an X-ray machine, adjusting the technique to 50-120 kVp, 100 mA, and 2s. As the mole percentage of bismuth oxide increased, the measured radiation values decreased. The linear attenuation coefficient (µ) increased, while the half-value layer (HVL) and tenth-value layer (TVL) decreased, and the mean free path (MFP) also decreased. When compared to standard materials, bismuth-metal phosphate glass demonstrated superior radiation shielding effectiveness. Based on the findings of this research, bismuth-based phosphate glass is considered a promising material for safe radiation shielding in future applications.

Abstract: Transparent resistive random-access memory (T-RRAM) is a key technology for next-generation optoelectronic devices. MgO, with its high transparency and stability, is a promising switching layer, but its performance is strongly influenced by oxygen vacancies. This study explores the effect of oxygen flow modulation during deposition on MgO-based T-RRAM. X-ray photoelectron spectroscopy (XPS) confirms that optimizing oxygen flow reduces excess vacancies while maintaining necessary defect sites for stable switching. Electrical measurements indicate that an oxygen flow of 20 sccm results in an ON/OFF ratio exceeding 10³, along with enhanced retention characteristics. These findings demonstrate that oxygen flow control is an effective method for enhancing MgO-based T-RRAM, paving the way for its integration into transparent electronic systems.

Abstract: Biomaterials are significantly required for medical technology. Hydroxyapatite (HA) is a bioactive material and is an excellent candidate for use as a bone replacement or bone repair material. Because HA has similar properties to human bone. However, the disadvantage of HA is its low mechanical strength. Titanium (Ti) is the famous material used to strengthen the strength of HA. This is because Ti can be used in the human body without causing undesirable reactions. The development of Ti-HA composite materials provides a bioactive material with high-strength properties. The homogeneous microstructure of materials, which is essential for achieving the required properties, can be accomplished by using composite particles as the starting materials. This research aims to develop the Ti-HA composite particles by mechanical alloying method. The mixture of Ti and HA in a mass ratio of 70:30 (Ti:HA) was milled by using a high-energy mill, i.e., a vibration mill, at a speed of 750 and 1000 rpm for 30, 60, 120, 180 and 300 minutes without inert gas supply. The results show that the Ti-HA composite particles were produced by using a vibration mill. HA particles completely cover the surface of Ti. No phase change of Ti and HA was observed under all milling conditions except at 1000 rpm for 300 minutes. The tiny XRD peaks of TiO were observed. This study developed an effective and low-cost method for producing Ti-HA composite particles, which is advantageous to engineering and medical technology.

Abstract: The use of supplementary cementitious materials (SCMs) has revolutionized the construction industry by significantly reducing the carbon footprint, minimizing waste, lowering labor costs, and enhancing both durability and precision in concrete structures. Accurately predicting compressive strength (CS), a critical mechanical property, is crucial for ensuring these structures' optimal performance and reliability. Given the nonlinear behavior of concrete mixtures incorporating fly ash and slag, machine learning (ML) techniques have become increasingly valuable for predictive modeling. This study assesses the performance of four ML models: Multilinear Regression (MLR), K-Nearest Neighbors (KNN), Random Forest (RF), and Random Forest integrated with Particle Swarm Optimization (RF-PSO). By addressing gaps related to compressive strength variability and comparing model performance, the study found that all four models achieved high accuracy in CS prediction, with RF-PSO consistently outperforming others based on multiple evaluation metrics. Visual analysis corroborates the models' effectiveness, highlighting potential advantages such as improved quality control, cost efficiency, enhanced safety, and environmental sustainability. Furthermore, an analysis of the importance of features was conducted to evaluate the contribution of individual variables in developing the RF-PSO model.