Search Results (116)

During the operation of structures, the components and materials from which they are made are exposed to various environmental, technological, and operational impacts. In this context, the use of a modified water-dispersion composition containing finely dispersed fillers with enhanced protective and performance characteristics proves to be effective. This article examines the development of a paint-and-coating composition using hollow glass microspheres and modified diatomite as finely dispersed fillers. The influence of technological factors on the properties of coating materials based on a synthesized acrylic dispersion and fillers—such as modified diatomite and hollow glass microspheres ranging from 20 to 100 μm in size with a bulk density of 0.107–0.252 g/cm³—is analyzed. The optimal formulation of the coating materials was determined to ensure the required coating quality. Experimental results demonstrate the improved strength and hardness of the coating due to the use of acrylic dispersion obtained through an emulsifier-free method and modifiers in the form of finely dispersed fillers. It has been established that the resulting samples also exhibit high adhesion to mineral and metallic substrates, along with excellent corrosion resistance. Moreover, the incorporation of acrylic dispersion contributes to increased elasticity of the coating, resulting in improved resistance to washing and abrasion. The developed protective material can be applied to a variety of surfaces, including walls, ceilings, and roofs of buildings and structures, pipelines, and many other applications. Thus, modified water-dispersion compositions based on synthesized acrylic dispersion showed the following results: resistance to sticking—5, which is the best; chemical resistance and gloss level with standard single-phase acrylic dispersion—no destruction or change in gloss. The adhesion of coatings cured under natural conditions and under the influence of UV radiation was 1 point. The developed formulations for obtaining water-dispersion paint and varnish compositions based on synthesized polymer dispersions, activated diatomite, and hollow glass microspheres, meet all the regulatory requirements for paint and varnish materials in terms of performance, and in terms of economic indicators, the cost of 1 kg of paint is 30% lower than the standard. Full article

Thermally conductive polymer composites are essential for effective heat dissipation in electronic packaging, where both thermal management and mechanical reliability are critical. Although diglycidyl ether of bisphenol-A (DGEBA)-based epoxies exhibit favorable properties, their intrinsically low thermal conductivity limits broader applications. Incorporating conductive fillers, such as expanded graphite (EG) and metal powders, enhances heat transport but often compromises mechanical strength due to poor filler–matrix compatibility. In this study, we address this trade-off by employing a titanate coupling agent to surface-modify aluminum (Al) fillers, thereby improving interfacial adhesion and dispersion within the DGEBA matrix. Our results show that incorporating 10 wt% untreated Al increases thermal conductivity from 7.35 to 9.60 W/m·K; however, this gain comes at the cost of flexural strength, which drops to 18.29 MPa. In contrast, titanate-modified Al (Ti@Al) not only preserves high thermal conductivity but also restores mechanical performance, achieving a flexural strength of 35.31 MPa (at 5 wt% Ti@Al) and increasing impact strength from 0.60 to 1.01 kJ/m². These findings demonstrate that interfacial engineering via titanate coupling offers a compelling strategy to overcome the thermal–mechanical trade-off in hybrid composites, enabling the development of high-performance materials for advanced thermal interface and structural applications. Full article

The article provides a brief overview of technologies and methods for processing dispersed metallic waste generated during ferroalloy production, including high-carbon ferrochrome (HCFeCr). It is noted that the most cost-effective and rational method for reusing metallic dust is briquetting. Considering the development of briquetting technologies, as well as the latest equipment and binder materials involved in this process, aspiration dust from ferrochrome crushing can be fully utilized in metallurgical recycling. To verify this assumption, laboratory studies were conducted using polymer-based binders and liquid glass as a baseline option. The methodology of briquetting using both laboratory and industrial presses is described, along with an assessment of the mechanical properties of the briquettes. The studies indicate that the introduction of an inert filler (gas-cleaning dust) into the metallic dust composition improves the briquetting ability of the mixture by enhancing adhesion between metal particles and the binder. The obtained industrial briquette samples exhibit high mechanical strength, ensuring their further use in metallurgical processing. The study concludes that semi-dry briquetting using hydraulic vibropresses is a promising approach for the utilization of dispersed ferroalloy waste. Full article

Magnetic pulse welding (MPW) is a promising solid-state joining process that utilizes electromagnetic forces to create high-speed, impact-like collisions between two metal components. This welding technique is widely known for its ability to join dissimilar metals, including aluminum, steel, and copper, without the need for additional filler materials or fluxes. MPW offers several advantages, such as minimal heat input, no distortion or warping, and excellent joint strength and integrity. The process is highly efficient, with welding times typically ranging from microseconds to milliseconds, making it suitable for high-volume production applications in sectors including automotive, aerospace, electronics, and various other industries where strong and reliable joints are required. It provides a cost-effective solution for joining lightweight materials, reducing weight and improving fuel efficiency in transportation systems. This contribution concerns an application for the automotive sector (body-in-white) and specifically examines the welding of AA6082-T6 aluminum alloy with HC420LA cold-rolled micro-alloyed steel. One of the main aspects for MPW optimization is the determination of the process window that does not depend on the equipment used but rather on the parameters associated with the physical mechanisms of the process. It was demonstrated that process windows based on contact angle versus output voltage diagrams can be of interest for production use for a given component (shock absorbers, suspension struts, chassis components, instrument panel beams, next-generation crash boxes, etc.). The process window based on impact pressures versus impact velocity for different impact angles, in addition to not depending on the equipment, allows highlighting other factors such as the pressure welding threshold for different temperatures in the impact zone, critical transition speeds for straight or wavy interface formation, and the jetting/no jetting effect transition. Experimental results demonstrated that optimal welding conditions are achieved with impact velocities between 900 and 1200 m/s, impact pressures of 3000–4000 MPa, and impact angles ranging from 18–35°. These conditions correspond to optimal technological parameters including gaps of 1.5–2 mm and output voltages between 7.5 and 8.5 kV. Successful welds require mean energy values above 20 kJ and weld specific energy values exceeding 150 kJ/m². The study establishes critical failure thresholds: welds consistently failed when gap distances exceeded 3 mm, output voltage dropped below 5.5 kV, or impact pressures fell below 2000 MPa. To determine these impact parameters, relationships based on Buckingham’s π theorem provide a viable solution closely aligned with experimental reality. Additionally, shear tests were conducted to determine weld cohesion, enabling the integration of mechanical resistance isovalues into the process window. The findings reveal an inverse relationship between impact angle and weld specific energy, with higher impact velocities producing thicker intermetallic compounds (IMCs), emphasizing the need for careful parameter optimization to balance weld strength and IMC formation. Full article

One of the prospective methods of robotic welding with a consumable electrode in shield gas metal arc welding is the GMAW Rapid HF process (GRHF, HF-high frequency), in which welded joints with deep penetration welds are obtained thanks to the specially programmed welding characteristics of the arc. A pulsed frequency equalized to 5000 Hz was used to achieve consumable electrode arc stabilization and improve penetration. This work consists of two main sections, including the research and analysis of wire electrode melting and weld pool formation in the innovative GRHF process and its influences on joint strength and the economic advantages of welding. As a result of our research and strength tests, as well as an image analysis of phenomena occurring in the welding arc and weld pool, assumptions were developed about the use of the GRHF process, which is characterized by deep penetration welds without welding imperfections that reduce the quality of the welded joints and their strength. Welding conditions and parameters leading to welded joints characterized by high relative strength related to the weight of the used filler material were proposed. As a result of our research, it was found that the use of welding processes with deep penetration leads to material savings related to the reduced consumption of filler materials while maintaining the required high strength of welded joints. Savings of filler materials reaching 80% were achieved compared with hitherto used methods. At the same time, the maximum load-carrying capacity of welding joints was maintained. Full article

Copper foil has been widely adopted as the anode current collector in commercial lithium-ion batteries (LIBs) due to its exceptional electrical conductivity, mechanical flexibility, and low cost. However, the smooth surface of copper foil often leads to active material delamination during cycling, resulting in accelerated capacity degradation. To address this limitation, this study developed a novel composite current collector featuring a high specific surface area and rough porous architecture through a dip-coating method. The fabrication process employs copper mesh as a structural skeleton, integrated with carbon nanotubes (CNTs) and polyvinylidene fluoride (PVDF) as functional fillers. Compared to conventional metallic copper foils, the composite current collector demonstrates superior interfacial wettability, enhanced adhesion strength, and reduced contact resistance. When paired with graphite as the active material, the graphite composite electrode exhibits outstanding cycling stability and rate capability. Specifically, the graphite composite electrode delivers a specific capacity of 297.9 mAh g⁻¹ with 94.3% capacity retention after 200 cycles at 0.5 C, significantly outperforming the graphite–copper foil counterpart (238.3 mAh g⁻¹, 81.2% retention). This work provides an innovative strategy for enhancing battery performance through the rational design of efficient and durable current collectors. Full article

Contamination by heavy metals (HMs) such as Pb, Cd, Cr, and Hg poses significant risks to the environment and human health owing to their toxicity and persistence. Geopolymers (GPs) have emerged as promising materials for immobilizing HMs and reducing their mobility through physical encapsulation and chemical stabilization. This study explored the novel use of isotactic polypropylene functionalized in the molten state with maleinized hyperbranched polyol polyester (PP-g-MHBP) as an additive in coal fly ash (CFA)-based GPs to enhance HM immobilization. Various characterization techniques were employed, including compressive strength tests, XRD, ATR-FTIR, SEM-EDX, XPS analyses, and TCLP leaching tests, to assess immobilization effectiveness. These results indicate that although the addition of PP-g-MHBP does not actively contribute to the chemical interactions with HM ions, it acts as an inert filler within the GP matrix. CFA/PP-g-MHBP-based GPs demonstrated significant potential for Cd²⁺ immobilization up to 3 wt% under acidic conditions, although the retention of Pb²⁺, CrO₄²⁻, and Hg²⁺ varied according to the specific chemistry of each metal, weight percentage of the added metal, matrix structure, and regulatory standards. Notably, high immobilization percentages were achieved for CrO₄²⁻ and Hg²⁺, although the leaching concentrations exceeded US EPA limits. These findings highlight the potential of CFA/PP-g-MHBP-based GPs for environmental applications, emphasizing the importance of optimizing formulations to enhance HM immobilization under varying conditions. Full article

The high-temperature low-cycle fatigue (LCF) behaviour of Incoloy 800H and its weldments with Haynes 230 and Inconel 82 filler metals, which were fabricated with the gas tungsten arc welding (GTAW) technique, was investigated and compared at 760 °C. The results revealed that the Incoloy 800H weldments showed lower fatigue lifetimes compared to the base metal. However, the weldments with the Haynes 230 filler metal demonstrated an improved fatigue life at the low strain amplitude compared to both Incoloy 800H and the weldment with the Inconel 82 filler metal. The Incoloy 800H base metal showed pronounced initial cyclic hardening with hardening factors increasing with strain amplitudes. In contrast, the weldments with Haynes 230 and Inconel 82 filler metals displayed short initial cyclic hardening and saturation stages, followed by long continuous cyclic softening. The fractography and microstructure after LCF the tests were characterized with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Transgranular fracture with multiple crack initiations was the predominant failure mode on the fracture surfaces of both Incoloy 800 base metal and the weldments. TEM examination revealed that planar dislocation slips at the low strain amplitude evolved to wavy slips, eventually forming a cell structure at high strain amplitudes in the Incoloy 800H material as the strain amplitudes increased. However, the weld metal exhibited a planar slip mode deformation mechanism regardless of cyclic strain amplitude in the weldment specimens. The differing cyclic hardening and softening behaviours between Incoloy 800H and its weldments are attributed to the higher strength of the weldment specimens compared to the base metal. In the Incoloy 800H base material specimens, the reverse strains during LCF created wavy dislocation structures, which could not fully recover due to the non-reversible nature of the microstructure. As a result, cells or subgrains formed within the microstructure once created. In contrast, the higher strength of the weld metal in the weldment specimens significantly suppressed the formation of wavy dislocation structures, and deformation primarily manifested as planar arrays of dislocations. Full article

Dissimilar welding between aluminum and copper poses significant challenges, primarily due to differences in their thermal and mechanical properties, resulting in brittle intermetallic compounds, limited joint strength, and high electrical resistivity. This study aims to overcome these issues by employing Ag-18Cu-10Zn filler material and optimizing laser power with a focus on improving joint strength and electrical conductivity. The results indicate that the incorporation of silver and zinc enhances the phase composition and microstructure of the weld. By forming solid solution phases such as Ag₂Al and Cu₅Zn₈, the brittle Al₂Cu phase commonly found in traditional Al/Cu welding is replaced. This not only promotes the heterogeneous nucleation of fine silver-rich grains but also restricts the excessive growth of silver-poor grains, resulting in a uniform distribution of fine grains throughout the weld. These modifications contribute to both fine-grain strengthening and dispersion strengthening. At an optimal laser power of 750 W, joint strength reaches 109 MPa, while joint resistivity decreases to 3.19 μΩ·cm, 12.6% lower than that of the aluminum alloy base material. This study proposes a process for achieving highly conductive, reliable Al/Cu dissimilar metal joints, potentially impacting the aluminum–copper connections in battery modules for new energy vehicles. Full article

Herein, we fabricated a low-melting-point Zr-16Ti-6Cu-8Ni-6Co eutectic filler based on a Zr-Ti-Cu-Ni filler to achieve effective joining of a Ti6Al4V (TC4) titanium alloy. The temperature at which the brittle intermetallic compound (IMC) layer in the seam completely disappeared was reduced from 920 °C to 900 °C, which broadened the temperature range of the Zr-based filler, brazing the TC4 without a brittle IMC layer. The shear strength of the Zr-16Ti-6Cu-8Ni-6Co brazed joint increased by 113% more than that of the Zr-16Ti-9Cu-11Ni brazed joint at 900 °C. The proportion of β-Ti in the seam of the Zr-16Ti-6Cu-8Ni-6Co brazed joint increased by 21.31% compared with that of the Zr-16Ti-9Cu-11Ni brazed joint. The nano-indentation results show that the elastic modulus of the β-Ti (143 GPa) in the interface is lower than that of the α-Ti (169 GPa) and (Ti,Zr)₂(Ni,Cu,Co) (203 GPa). As a result, the β-Ti is subjected to a greater strain under the same stress state compared with the α-Ti and (Ti,Zr)₂(Ni,Cu,Co), and the Zr-16Ti-6Cu-8Ni-6Co brazed joint can maintain a higher strength than the Zr-16Ti-9Cu-11Ni brazed joint under a middle–low erosion area of the TC4 base metal. This provides valuable insights into the use of high-strength, fatigue-resistant TC4 brazed joints in engineering applications. Full article

As high-strength and ultra-high-strength steels are widely used in all kinds of modern welded constructions, a lot of research is carried out to investigate the mechanical properties of the weldments of these steels, but there is little information on such important characteristics as their corrosion behaviour. This research focuses on the corrosion behaviour of the weld metal of the weldments of S906QL and S700MC steels. The weld metal was tested electrochemically in a 3.5% NaCl aqueous solution via a potentiodynamic scan to determine the corrosion rate and its dependence on the welding gap. No influence of the welding gap on the corrosion rate was found, but the experimental results suggested that the corrosion rate depended on the chemical composition of the filler material and the microstructure of the weld metal. Full article

Polymer coatings are widely used in industries for protection, decoration, and specific applications, typically including volatile organic compounds (VOCs) to achieve low viscosity. The growing environmental concerns and the anticipated limits on fossil feedstock have driven the coating industry towards eco-friendly alternatives, with UV-curing technology emerging as a promising solution due to its energy efficiency, low-temperature operation, reduced VOC emissions, and high curing speed. Polyurethane acrylates (PUAs) are critical in UV-curable formulations, offering excellent flexibility, impact strength, optical, and adhesion properties. However, UV-cured PUA coatings face limitations in thermal stability and tensile strength, which can be addressed by incorporating fillers. This study investigates the effects of multi-functionalized hexagonal boron nitride (hBN) nanoparticles on the mechanical, thermal, optical, and adhesion properties of UV-cured PUA films and coatings for pre-coated metals. The results demonstrated that incorporating hBN nanoparticles enhanced the mechanical and thermal properties of the nanocomposite films, with optimal performance observed at 0.5% hBN loading. Despite the improved properties, the FTIR spectra indicated that the low concentration of hBN did not produce significant changes, potentially due to the overshadowing signals from the difunctional polyurethane acrylate. Full article

The fabrication of welded joints in steel sheets has become a focal point, especially in meeting the demands for interconnections within battery packs for electric vehicles (EVs). This study delves into the impact arising from the initiation arc during the micro-tungsten inert gas (TIG) welding of nickel-plated steel sheets. The investigation involved the manipulation of various current modulations and arc lengths. Notably, optimal results were achieved with a 5 mm arc length paired with a 25 A current modulation. Microstructural analysis, conducted through scanning electron microscopy (SEM), unveiled a higher penetration depth, contributing to a more extensive and shallower fusion zone at the interface between the filler metal and the base material. Tensile testing revealed impressive mechanical properties, with the ultimate tensile strength peaking at 90 N/mm², a yield strength of 85 N/mm², and the highest elastic modulus. This underscores the weld’s robustness in withstanding applied loads and resisting fracture. Furthermore, the calculation of the lowest K factor at 1.0375 indicated a reduction in resistance across the specimen, resulting in enhanced conductivity. Micro-TIG welding emerges as an efficient method for nickel-plated steel in connecting individual battery cells to form a high-capacity battery pack. These interconnections ensure efficient current flow and maintain the overall integrity and performance of the battery pack. The reliability and quality of these interconnects directly affect the battery’s efficiency, safety, and lifespan in EVs application. Full article

This study investigates active filling friction stir repair (AF-FSR) and passive filling friction stir repair (PF-FSR) for repairing AISI 304 stainless steel sheets, focusing on addressing the challenges posed by high melting point metals. The research involved repairing overlapping 2 mm thick sheets with pre-drilled holes of 2, 4, and 6 mm diameters, simulating broken components. Various process parameters, including rotational speed, dwell time, and the use of metal fillers, were tested to evaluate their impact on repair quality. The results demonstrated that PF-FSR provided superior mechanical strength to AF-FSR, particularly for larger pre-hole diameters. PF-FSR achieved higher shear tension strength due to better defect filling and reduced void formation, with shear tension strengths exceeding 25 kN for larger pre-holes and lower variability in strength measurements. AF-FSR was less effective for larger pre-holes, resulting in significant voids and reduced strength. Microstructural analysis revealed that PF-FSR facilitated more efficient material mixing and filling, minimizing unrepaired regions. However, excessive rotational speeds and dwell times in PF-FSR led to deformation and flash formation, highlighting the need for optimal parameter selection. Although further studies are needed, this study confirms the feasibility of FSR techniques for repairing small defects in AISI 304 steels, offering valuable insights for sustainable manufacturing practices in industries such as automotive and aerospace, where efficient and reliable repair methods are critical. Full article

Filler content in dental composites is credited for affecting its physical and mechanical properties. This study evaluated the correlation between the filler percentage and strength, modulus, shrinkage stress, depth of cure, translucency and radiopacity of commercially available high- and low-viscosity dental composites. Filler weight percentage (wt%) was determined through the burned ash technique (800 °C for 15 min). Three-point bend flexural strength and modulus were measured according to ISO 4049 with 2 mm × 2 mm × 25 mm bars. Shrinkage stress was evaluated using a universal testing machine in which composite was polymerized through two transparent acrylic rods 2 mm apart. Shrinkage was measured from the maximum force following 500 s. The translucency parameter (TP) was measured as the difference in color (ΔE00) of 1 mm thick specimens against white and black tiles. The depth of cure was measured according to ISO 4049 in a cylindrical metal mold (4 mm diameter) with a 10 s cure. Radiopacity was measured by taking a digital X-ray (70 kVp for 0.32 s at 400 mm distance) of 1 mm thick specimens and comparing the radiopacity to an aluminum step wedge using image analysis software. The correlation between the filler wt% and properties was measured by Pearson’s correlation coefficient using SPSS. There was a positive linear correlation between the filler wt% and modulus (r = 0.78, p < 0.01), flexural strength (r = 0.46, p < 0.01) and radiopacity (r = 0.36, p < 0.01) and negative correlation with translucency (r = −0.29, p < 0.01). Filler wt% best predicts the modulus and strength and, to a lesser extent, the radiopacity and translucency. All but two of the high- and low-viscosity composites from the same manufacturer had statistically equivalent strengths as each other; however, the high-viscosity materials almost always had a statistically higher modulus. For two of the flowable composites measured from the same manufacturer (3M and Dentsply), there was a lower shrinkage stress in the bulk-fill version of the material but not for the other two manufacturers (Ivoclar and Tokuyama). All flowable bulk-fill composites achieved a deeper depth of cure than the flowable composite from the same manufacturer other than Omnichroma Flow Bulk. Full article