Search Results (113)

This study explores the efficacy of magnetic abrasive finishing (MAF) with planetary kinematics for post-processing Inconel 939 components fabricated by laser powder bed fusion (LPBF). Given the critical limitations in surface quality of LPBF-produced parts—especially in hard-to-machine superalloys like Inconel 939—there is a pressing need for advanced, adaptable finishing techniques that can operate effectively on complex geometries. This research focuses on optimizing the process parameters—eccentricity, rotational speed, and machining time—to enhance surface integrity following preliminary vibratory machining. Custom-designed samples underwent sequential machining, including heat treatment and 4 h vibratory machining, before MAF was applied under controlled conditions using ferromagnetic Fe-Si abrasives. Surface roughness measurements demonstrated a significant reduction, achieving Ra values from 1.21 µm to below 0.8 µm in optimal conditions, representing more than a fivefold improvement compared to the as-printed state (5.6 µm). Scanning Electron Microscopy (SEM) revealed progressive surface refinement, with MAF effectively removing adhered particles left by prior processing. Statistical analysis confirmed the dominant influence of eccentricity on the surface profile parameters, particularly Rz. The findings validate the viability of MAF as a precise, controllable, and complementary finishing method for LPBF-manufactured Inconel 939 components, especially for geometrically complex or hard-to-reach surfaces. Full article

The rapid progress in additive manufacturing (AM) has unlocked significant possibilities for producing 316/316L stainless steel components, particularly in industries requiring high precision, enhanced mechanical properties, and intricate geometries. However, the widespread adoption of AM—specifically Directed energy deposition (DED), selective laser melting (SLM), and electron beam melting (EBM) remains challenged by inherent process-related defects such as residual stresses, porosity, anisotropy, and surface roughness. This review critically examines these AM techniques, focusing on optimizing key manufacturing parameters, mitigating defects, and implementing effective post-processing treatments. This review highlights how process parameters including laser power, energy density, scanning strategy, layer thickness, build orientation, and preheating conditions directly affect microstructural evolution, mechanical properties, and defect formation in AM-fabricated 316/316L stainless steel. Comparative analysis reveals that SLM excels in achieving refined microstructures and high precision, although it is prone to residual stress accumulation and porosity. DED, on the other hand, offers flexibility for large-scale manufacturing but struggles with surface finish and mechanical property consistency. EBM effectively reduces thermal-induced residual stresses due to its sustained high preheating temperatures (typically maintained between 700 °C and 850 °C throughout the build process) and vacuum environment, but it faces limitations related to resolution, cost-effectiveness, and material applicability. Additionally, this review aligns AM techniques with specific defect reduction strategies, emphasizing the importance of post-processing methods such as heat treatment and hot isostatic pressing (HIP). These approaches enhance structural integrity by refining microstructure, reducing residual stresses, and minimizing porosity. By providing a comprehensive framework that connects AM techniques optimization strategies, this review serves as a valuable resource for academic and industry professionals. It underscores the necessity of process standardization and real-time monitoring to improve the reliability and consistency of AM-produced 316/316L stainless steel components. A targeted approach to these challenges will be crucial in advancing AM technologies to meet the stringent performance requirements of various high-value industrial applications. Full article

Lithium disilicate ceramics (LDSs) are widely used in restorative dentistry for their excellent aesthetic and mechanical properties. Variants like zirconia-reinforced lithium silicate (ZLS) and advanced lithium disilicate (ALD) were developed to enhance these characteristics. However, differences in their physical and optical properties, as well as the influence of processing techniques (heat pressing vs. CAD-CAM), remain unclear. This study aimed to evaluate the physical and aesthetic properties of LDS, ZLS, and ALD ceramics. A systematic review and meta-analysis following PRISMA guidelines were conducted. Studies published in the last ten years were retrieved from PubMed, Web of Science, Scopus, Cochrane, and Scielo. The inclusion criteria encompassed in vitro studies analyzing LDS, ZLS, and ALD ceramics with quantitative data on mechanical and aesthetic properties. Meta-analyses were performed using a random-effects model, with subgroup analyses based on ceramic type and processing technique. Twenty-two studies met the inclusion criteria. Meta-analyses showed significant differences in flexural strength, hardness, surface roughness, wear, and translucency. The processing technique influenced these properties, with CAD-CAM materials exhibiting distinct performance compared to heat-pressed ceramics. Publication bias was assessed using Egger’s test and the Trim and Fill method, and heterogeneity via meta-regression. LDS showed the highest fracture resistance and least wear, while ALD had greater roughness depth. Heat pressing enhanced hardness and reduced roughness, whereas CAD-CAM improved flexural strength. Considering these findings and study limitations, LDS appears the most suitable option for clinical use due to its superior mechanical performance. Full article

Extreme climate change is today’s world’s most pressing and challenging problem. Increases in greenhouse gas emissions, the warming of the atmosphere and ocean, increased precipitation, rising sea levels, and temperature rise are the major effects of climate change that significantly affect urban infrastructure. Green Infrastructure (GI) is an increasingly acknowledged tool for climate change adaptation that contributes to sustainable urban and rural development. This study reviewed 111 research articles to identify and summarize the research findings about the role of GI in climate change adaptation. Furthermore, the research articles are grouped into three sectors with the most benefits of green infrastructure in climate change adaptation: mitigating urban heat islands, increasing ecosystem resilience, and flood risk management. The literature was further divided according to the developed or utilized strategies and techniques. The findings suggest that the topic of GI’s role in climate change adaptation is very current and it has been studied frequently in the last five years. Full article

The high hydrophilicity of biopolymer–anthocyanin intelligent packaging films seriously limits their applications in high-humidity environments. Here, a surface hydrophobization technique was adopted to overcome the hydrophilicity of purple sweet potato (PSP)-based intelligent packaging films through stearic acid (SA) coating combined with heat pressing treatments. The structural characteristics, physical properties, and color changeability of the films were investigated. After SA coating treatment, the surface of the films was loosely covered by thick SA layers. As compared with the untreated PSP films, the SA-coated films displayed lower transparency, mechanical property, moisture content, surface wettability, anthocyanin leaching potential, and color changeability. When the SA-coated films were further heat-pressed, the SA-coated layers were closely bound to the films. The heat-pressed films had a higher transparency, mechanical property, and water vapor blocking ability than the SA-coated films. Notably, the color and color changeability of the heat-pressed films were affected by the heat pressing temperature. The films heat-pressed at 100 °C showed a vivid purple color and elevated color changeability, whereas the films heat-pressed at 150 °C showed a brown color and lost color changeability. This study demonstrates that SA coating combined with heat pressing is effective in constructing surface-hydrophobized intelligent packaging films. Full article

The world is facing the issue of managing a huge amount of plastic waste. To prevent uncontrolled and unproductive disposal, various valorization strategies have been developed. Recycling plastic waste into valuable composites for construction offers a promising pathway toward sustainable waste management. Given that the construction industry is a major consumer of energy and natural resources, it presents a key opportunity for integrating recycled materials. This review examines diverse strategies and applications for plastic waste recycling, with a particular focus on sustainable construction solutions, while also evaluating the advantages and limitations of this approach. Within this context, recycled plastic waste can be used as a filler to replace non-renewable natural resources. Studies have shown that incorporating plastic waste as a filler improves diverse properties of composites, including thermal and sound insulation. In particular, thermoset plastic waste exhibits desirable characteristics such as rigidity, heat and chemical resistance, strength and durability, making it suitable as a filler for non-structural applications. Alternatively, melting recycled plastic waste can produce binder materials that combine with other inorganic materials to form building and construction composites. Using melted thermoplastic waste as a binder enhances ductility, reduces water absorption, and improves overall durability. Additionally, the hot-pressing technique has been shown to be more effective in addressing poor bonding issues commonly encountered with conventional methods. Full article

As an important branch of ancient Chinese silk dyeing and printing technology, alkali degumming printing utilizes alkali agents to degum raw silk, creating differences in fiber water absorption, dye uptake, and optical characteristics between degummed and non-degummed areas to achieve localized pattern formation.Based on the differences in degumming processes of Silk Gauze using alkaline boiling, alkaline steaming, and alkaline gel, this study compares the effects of these three alkaline degumming techniques under different conditions of alkaline agent dosage, hot press temperature, and hot press duration. The degumming efficiency, fiber surface morphology, and infrared spectra of the degummed Silk Gauze were analyzed and compared. Through the analysis of the degumming mechanisms, it was found that the alkaline gel, within a localized micro-system, meets the conditions of alkali, water, and heat required for precise degumming of Silk Gauze. Combining the dual effects of alkaline boiling and alkaline steaming, the alkaline gel can achieve rapid degumming at a hot press temperature of 80 °C within 50 s, without significantly affecting the surface morphology or the primary structure of the Silk Gauze. The implementation of alkaline gel for precise degumming of Silk Gauze holds significant importance for expanding the application of traditional alkaline printing techniques in modern silk degumming and printing processes. Full article

This study focuses on addressing the pressing challenge of reusing plastic in an eco-friendly manner. This research aimed to produce synthetic grease through an environmentally friendly pyrolysis technique, utilizing 69% predegraded low-density polyethylene (LDPE) combined with visible-light-working TiO₂ thin film, protein-coated TiO₂ NPs, and Lactobacillus plantarum bacteria in a batch reactor. The optimized conditions of temperature (500 °C) and heating time (2 h) resulted in the creation of 166 gm of partially degraded polyethylene grease 2 (PDPLG2) with National Lubricating Grease Institute (NLGI 2) grade consistency. PDPLG2 grease exhibits a wide-range dropping point of 280 °C and effectively maintains lubrication under high friction and stress loads, thereby preventing wear. Thermal analysis using TG and DSC validated the grease’s stability up to 280 °C, with minimal degradation beyond this point. Taguchi analysis using substance, sliding speed, and load as factors identified the ideal process parameters as aluminum, 1500 rpm, and 150 N, respectively. The present study revealed that sliding speed has the greatest impact, contributing 31.74% to the coefficient of friction (COF) and 11.28% to wear, followed by material and load. Comparative tribological analysis with commercially available grease (NLGI2) demonstrated that PDPLG2 grease outperforms NLGI2 grease. Overall, this innovative eco-friendly approach presents PDPLG2 as a promising alternative lubricant with improved anti-wear and friction properties, while also contributing significantly to plastic waste reduction. Full article

The main method for large-scaled preparing powder superalloys in the production process is inert gas atomization, particularly vacuum-induced gas atomization (VIGA). A novel technique called electrode-induced gas atomization (EIGA) with a crucible-free electrode was proposed to prepare non-inclusion superalloy powders. In this study, a Ni-based superalloy of FGH4096 powder was prepared using both the VIGA and EIGA methods, while blanks were prepared through direct hot isostatic pressing (as-HIPed) near-net-forming method. The particle size, morphology, microstructure, and mechanical properties of the powders and blanks were compared via a laser particle size analyzer, SEM, TEM, and room-temperature and 650 °C tensile tests. The results indicated that EIGA-prepared powders exhibited a finer particle size and better surface quality than the one prepared via VIGA, which showed reduced satellite powders. However, the as-HIPed blank of EIGA-prepared powders had a lower secondary γ’ ratio and slightly reduced strength compared to the as-HIPed blank of VIGA-prepared powders due to its slightly lower secondary γ’ phase ratio and less effective inhibition of dislocation movement. Furthermore, the overall performance of the two samples did not differ significantly due to the similar microstructural characteristics of the powders. However, the variation in particle size affects heat conduction during the HIP process, resulting in slight differences in blanks’ properties. Full article

Despite its importance, the determination of the degree of cure of melamine-based laminates often relies on tests with limited accuracy and validity. Undercured surfaces may suffer insufficient resistance to scratching and heat as well as substandard surface quality. Overcured melamine surfaces tend to crack and entail the inefficient utilization of the press—the panels could have been pressed for a shorter time. Four methods to determine the degree of cure of a melamine resin coating under industrial conditions were compared: the Kiton test, the most common method in industry, Near Infrared Spectroscopy (NIR) as a modern technique that allows for inline-measurements, and two novel hydrolysis methods. Each test was conducted on the same 18 panels. Each panel differed in its resin system or its degree of cure, which was adjusted by varying the pressing duration and temperature. The four methods tested were all capable of determining the degree of cure to some extent, but their applicability, the delay between the curing of the melamine resin at the final stage of production and the availability of results, and the investment and workload differ greatly. Determining the critical overcure turned out to be the major challenge. Differentiation between slight overcure, which did not affect the cracking resistance, and severe overcure, which produced surfaces with a high tendency to cracking, was possible using the NIR-based method and the two novel hydrolysis methods but not with the widely used Kiton test. Full article

Additive manufacturing of magnesium (Mg) alloys is of interest for the fabrication of complex-shaped lightweight materials. This study evaluates the microstructure of WE43 Mg alloy deposited using laser powder directed energy deposition (LPDED) additive manufacturing technique in as-deposited and post-processed conditions. As-deposited samples exhibited roughly 2% porosity, which was reduced to below 0.1% after hot isostatic pressing. Despite limited grain growth after heat treatment, some grains experienced abnormal grain growth, likely due to Zener pinning and non-uniform dissolution of grain boundary precipitates. Moreover, as-deposited specimens contained Nd-rich grain boundary precipitates which dissolved during post-processing. Additionally, during heat treatment. a fine distribution of needle-like β1 or β precipitates formed. Overall, the precipitate size and distribution following heat treatment was non-uniform, likely because of the non-uniform response of the LPDED material to heat treatment, owing to the variation in local- and global-temperature profiles during deposition. Furthermore, arc-shaped phases with a high concentration of Y, O, and Zr were present for all processing conditions and are associated with the passivation of the feedstock powder prior to deposition. Moreover, an equiaxed-grain structure with a random orientation and a finer grain size in the regions adjacent to the arc-shaped phases was observed in all processing conditions. Full article

In this paper, the feasibility of an innovative solid-state recycling process for aluminum alloy AA6063 chips through direct rolling is studied, with the aim of offering an environmentally sustainable alternative to conventional recycling processes. Aluminum chips, produced by milling an AA6063 billet without the use of lubricants, were first compacted using a hydraulic press with a 200 kN load and subsequently heat-treated at 570 °C for 6 h. The compacted chips were directly hot-rolled through several successive passes at 490 °C. The bulk material underwent the same rolling schedule to allow comparison of the samples and assess the process, in terms of mechanical properties and microstructure. All the rolled samples were tested by tensile and microhardness tests, whereas the microstructure was observed by an optical microscope and the EBSD-SEM technique. The fracture surface of all tested samples was analyzed by SEM. Recycled samples exhibited good mechanical properties, comparable to those of the bulk material. In particular, the bulk material showed an ultimate tensile strength of 218 MPa, in contrast to 177 MPa for the recycled chips, and comparable elongation at break. This study demonstrates that direct rolling of compacted aluminum chips is both technically feasible and has environmental benefits, offering a promising approach for sustainable aluminum recycling in industrial applications within a circular economy framework. Full article

This study presents the results of research on the influence of different contents of copper in aluminium alloys based on the 6xxx series on mechanical and structural properties. The investigation started with the alloying, and casting four billet variants with different copper content—0.8% Cu; 2B—1% Cu; 3A—1.2% Cu; and 3B—1.4% Cu. The prepared materials were homogenised and extruded on a 500T horizontal press with two different process temperatures and ram speeds ranging from 1 mm/s to 9 mm/s. After heat treating to the T6 and T5 tempers, their mechanical properties were tested. On this basis, the two most promising alloys 2A and 3B were selected and subjected to further tests. After extrusion and heat treatment of the profiles (to F, T1, T2, T5, and T5510), their mechanical properties were determined to select the preferred process parameters. Finally, a structural test based on crystallographic orientation based on the EBSD technique and TEM observations allowed for the characterisation of grain size, dispersoids, and phase analysis. Bright-field (BF) analysis allowed us to compare the deformed areas for T1, T5, and T5510 temperatures. The results showed significant growth in the mechanical properties of all the subjected alloys, and the best properties were shown for a Cu content of 1.4% with a tensile strength of 460 MPa and an elongation of 16% (T5510 tempering). The structural test showed an average grain size of 18 µm to 23 µm and solid solution decomposition differences for different heat-treating parameters. Full article

Carbon nanotube (CNT)/graphene ceramic composites with outstanding properties are expected to replace a number of components currently used in the automotive and aerospace industries in the future. Consequently, this area of research has progressed significantly. This review paper, therefore, delves into the enhancement of ceramic properties through the integration of graphene and CNTs. These reinforcements are known to mitigate the inherent brittleness of ceramics, thereby unlocking their potential for applications in sectors requiring high mechanical reliability, such as the aerospace, automotive, and biomedical industries. By summarizing recent research, this paper outlines various preparation methods, including ball milling, heat pressing and spark plasma sintering, and discusses how these techniques contribute to improved mechanical and thermal performance. This review emphasizes the critical role of graphene and CNT ratios, sizes, and their synergistic effects in enhancing fracture toughness, machinability, and overall structural integrity. Thus, this paper provides a comprehensive overview of the current research in this area and discusses the potential of these technologies. Full article

In the project work, CES EDUPACK material selection software and Arc melter 500 arc remelting equipment were used to select good-performance materials and produce a sample. First, aluminum alloys were considered due to their low weight; alloys Al7075, Al6082, and EN AW 6022 in different states were examined for maximum hardness and electrical conductivity, and then the Cu–Cr–Zr alloy was analyzed. The test results showed that for the EN AW 6082 alloy, the specimens heat-treated at 480 °C for 2 h + 175 °C for 2 h following the ECAP (equal channel angular pressing) A route or C route technique gave the best hardness–electrical conductivity pair. In the case of the EN AW 7075 alloy, the artificially aged sample after 4× ECAP forming showed the maximum values. In the case of EN AW 6022, which according to the Ashby chart may be the best alloy for the value pair sought, this alloy was fabricated, resulting in only as-cast samples being analyzed. Of the Cu alloys, the Cu–0.49–0.21Zr alloy after heat treatment at 450 °C for 1 h gives the most favorable hardness–conductivity. Full article