This paper presents experimental results on the processing of complex concentrated alloy with a nominal composition of A 0.35 CoCrFeNi. The alloy was produced by vacuum induction melting and tilt casting. The microstructure of the as-cast CCA consists of dendritic and interdendritic regions homogenized by heat treatment at 1360 °C. After rotary swaging at room temperature, the microstructure is characterized by an abundance of dislocations and continuously intersecting slip bands. Annealing experiments were carried out in the temperature range of 1150 °C – 1300 °C and different holding times to determine the parameters of grain growth kinetics. Phase and chemical analysis were investigated using XRD and EDS methods. The activation energy of recrystallization in the studied composition was 458 kJ mol -1 . The influence of grain size on room temperature mechanical properties and tensile properties was determined. The hardening coefficients k h and k σ , calculated using the Hall-Petch relation, were 277.5 HV µm -1/2 and 655 MPa µm -1/2 , indicating the effectiveness of grain boundary hardening in the studied single-phase CCA.

The present study explores combined free-forced convective flow and entropy generation in a constant-volume double lid-driven trapezoidal cavity. All configurations of the isosceles trapezoidal cavity were meticulously designed to possess identical leg lengths and constant volume, ensuring that the same amount of heat is transferred from the cavity’s legs. The cavity has left and right lid-driven walls capable of oscillating upward and downward, while all other domain boundaries remain stationary. The left wall is sustained at a consistently high temperature, whereas the right wall is kept at a stable low temperature, and the upper and lower horizontal walls are thermally insulated. The modelling of this problem was carried out based on the finite volume technique. The obtained results were carefully validated against existing literature related to similar problems. The influence of relevant parameters such as Richardson number (0.01 ≤ Ri ≤ 100), aspect ratio (0.4 ≤ AR ≤ 1) and three distinct moving arrangements (Case-A, Case-B and Case-C) were examined. The findings revealed that heat transport was restricted at high Ri for all the presented aspect ratios, especially for Case-C. For all the presented aspect ratios and cases, entropy generation decreases as Ri increases, with the lowest values ​​observed for Case-A. Trapezoidal cavities with AR = 0.4, 0.6, and 0.8 generate lower entropy than the square cavity at high Ri, but higher entropy at low Ri.

In this study, a multifunctional air filtration material was developed by coating polypropylene (PP) nonwoven fabric with a chitosan/TiO₂ (P25) composite. The aim was to enhance air filtration efficiency. The chitosan–P25 composite was applied onto the PP nonwoven via a solution spray method followed by drying. Scanning electron microscopy (SEM) analysis revealed a uniform coating layer with good adherence to the PP fiber surface. X-ray diffraction (XRD) analysis confirmed the presence of crystalline TiO₂ in the P25 phases, as well as the semi-crystalline nature of the PP substrate. Air permeability tests showed a moderate reduction in air flow rate due to surface coating, while maintaining acceptable breathability for filter applications.

This research aimed to recycle polyethylene terephthalate (rPET) from drinking water bottles using a commercial multi-functional chain extender (Joncryl®ADR4468) with low content, to improve the properties of low molecular weight recycled PET, giving it a long chain with branching structure. The effects of the chain extender on the structural change, viscosity, thermal properties and thermal stability of modified recycled PET (modified-rPET) were studied by using Fourier transform infrared (FTIR) spectrometer, a rotational rheometer, a differential scanning calorimeter (DSC) and thermogravimetric analysis technique (TGA). The results indicate that the chain extender can increase the molecular weight and modify the structure of rPET to a long chain with branching structure and improve the viscosity. Furthermore, the thermal properties and thermal stability analysis from this research could be great evidence to support the assumption that the use of low dose of Joncryl®ARD4468 could turn the molecular structure of rPET into long chain with branching structure, without gel, perfectly.

Carbon fiber reinforced polymer (CFRP) composites are highly valued in aerospace for their superior strength and fatigue resistance. However, the structural complexity of CFRP components leads to inevitable internal defects during manufacturing, with complex geometry being a key factor hindering detection. This paper investigates the ultrasonic propagation characteristics in CFRP multidirectional plates with complex geometries via finite element simulations, focusing on the multifactor coupling effects in CFRP members. Acoustic tracing is conducted for the anisotropic and multilayered CFRP multidirectional plates. Through bottom reflection method and full-focus imaging inspection experiments, the propagation behaviors of ultrasonic waves in CFRP are systematically analyzed. Results reveal that the material’s multilayer structure, elastic anisotropy, and complex geometry significantly affect the imaging quality, defect localization accuracy, and defect distribution range in full-focus ultrasonic array inspection. The optimized algorithm achieves accurate detection of hole defects in complex-shaped CFRP multidirectional plates, reducing the imaging array performance indicator (API) value to 0.7 and the defect localization error to less than 0.3 mm. Keyword: CFRP components; complex geometries; non-destructive testing; acoustic tracing; full-focus imaging;

The increasing demand for sustainable energy solutions has intensified research into biodiesel production, which relies on chemical catalysts that have an environmental impact. This study investigates the alternative methods of biodiesel production by utilizing agricultural waste, specifically rice husk, coconut husk, and chicken manure as a catalyst for biodiesel production. Laboratory experiments were conducted to extract metal oxide from agricultural waste to be used as a catalyst in the transesterification process. The obtained ash was characterized, and it was revealed that rice husk ash contained 98% SiO 2 , coconut husk ash had 72.62% of K 2 O, and chicken manure ash had 46.56% CaO, with higher metal oxide compositions in each material. The transesterification reaction was conducted by varying alcohol to oil ratio from 3:1, 6:1, 9:1, and 12:1, temperature (40-80°C), catalyst concentration (1.5-4.5%wt), and reaction time (20-120min) to assess catalyst efficiency. Pure CaO was used as a control catalyst for comparison. Characterization of the produced biodiesel from all catalysts was conducted and compared to ASTM D6751 standards. The results for acid value, moisture content, density, viscosity, free fatty acid, flash point, pour point, and cloud point were analyzed and found to comply with ASTM D6751 standards. On quantity determination of produced biodiesel, the most effective catalyst was chicken manure ash with a yield of 80% and the least effective catalyst was rice husk ash with 68% yield. Using agricultural waste reduces up to 40% production cost.

The influence of filler type and content on the wettability and interfacial bonding between thermoplastic elastomer (TPE) and polypropylene (PP) by using the injection overmolding process was investigated in this study. Calcium carbonate (CaCO 3 ) and talcum (Talc) masterbatchs, ranging from 0 to 40 percent by weight (wt%), were mixed into the PP matrix as fillers. The bond strength of TPE overmolded onto PP composites was characterized by the tensile and tear tests. Good compatibility was observed between TPE and PP filled with various amounts of CaCO 3 and Talc. In the case of the tensile test, the crack initiation stress, ultimate tensile strength, strain at break, and bond energy were found to decrease with increasing filler content. The results obtained from the tear test indicated that the propagation strength, ultimate tear strength, strain at break, and bond energy of injection overmolded TPE-PP filled with various CaCO 3 contents did not significantly change compared to those obtained from Talc. This can be attributed to the high reinforcing efficiency of Talc in comparison with CaCO 3 , which can enhance the stiffness and thermal resistance of the PP matrix. As a result, the contact area becomes more resistant to molecular diffusion of TPE chains, particularly at high Talc loadings (30 and 40 wt%), leading to the reduction of interfacial bonding.

The flexibility and durability of biopolymers are enhanced by the supplementation of plasticizers. Various types of plasticizers are commonly utilized. This research aims to investigate the effects of different plasticizer types on the characteristics of biopolymer films prepared from tamarind kernel powder (TKP) and gelatin crosslinked with glutaraldehyde. Three types of plasticizers were examined: glycerol, sorbitol, and polyethylene glycol. The concentration of plasticizers was controlled at 1% w/w. The chemical and mechanical properties of the films were analyzed. The results indicated that the plasticizers differentially improved the mechanical properties of the biopolymer films. Additionally, the opacity, color, and water solubility of the films were influenced by the type of plasticizer used. The TKP-gelatin film supplemented with sorbitol exhibited improved mechanical properties, as indicated by both higher tensile strength and elongation at break, compared with that supplemented with glycerol and polyethylene glycol.

This study investigates the production of biogas through the co-anaerobic digestion of cow dung and sawdust, utilizing thermochemical pretreatment to enhance lignin breakdown. A 50:50 and a 75:25 mixture of the substrates (Cowdung:sawdust) were subjected to sodium hydroxide pretreatment and thermal conditioning at 80°C. Lignin content reduced from 31.94% to 22.73%. The results demonstrated approximately a 43% increase in biogas yield for both the 50:50 and 75:25 substrate ratios. A four-day earlier gas production onset was recorded for pretreated substrates compared to untreated samples. The methane content of the biogas reached 56% (50:50 ratio) and 60% (75:25 ratio), with hydrogen sulfide at about 1% in both ratios. Process parameters such as pH, and temperature were measured. This study provides a scalable approach for waste-to-energy applications and demonstrates the role of pretreatment in improving substrate digestibility and biogas yield.

A numerical study investigates the flow behavior inside a three-sided lid-driven cavity. The physical problem is represented by a square cavity with two opposite horizontal walls moving translationally and independently to the right. The left vertical sidewall moves upward while the right vertical sidewall remains stationary. This study applies different Reynolds numbers to the moving walls to define three different configurations. In each configuration, two moving walls operate at the same Reynolds number ( Re =100), while the Reynolds number of the remaining wall varies ( Re =200, 400, 800, 1600, 3200, and 6400). We explore the flow patterns for each case, including the generated primary and secondary vortices, vorticity, velocity profiles, and fluid properties. Special attention is given to the formation and evolution of primary and secondary vortices to provide insights into the complex flow mechanisms governing this type of flow. The study reveals that varying the Reynolds number of one of the moving walls significantly impacts the flow structure within the three-sided lid-driven cavity. The asymmetry in wall motion is a powerful trigger for vortex genesis and evolution. The findings also lead to a better understanding of the flow mechanisms of driven cavity flows bounded by three walls with asymmetric boundary conditions.