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Waste printed circuit boards (WPCBs) -- a common type of ewaste consisting of electronic components with a significant amount of rare and precious metals as well as glass fiber composites. The development of WPCB retreatment technology through mechanical methods, resulting in metallic and nonmetallic waste fractions, can be efficiently classified as enriched concentrate. The research presented in this paper highlights the potential trends for recycling WPCBs. The integration of impact milling for WPCBs is a promising technology for the partitioning and fragmentation of different components and for the separation of fractions. The mechanical sizereduction and separation technology of precrushed WPCBs, using direct and separative disintegrator milling, has been compared with other technologies (hammer milling and high voltage fragmentation). The main parameters, such as the specific energy (ES) of WPCB treatment and the rate of separation of different phases, were studied. As preliminary results show the optimal parameters of partitioning of the metallic and nonmetallic parts, fragmentation and delamination (specific energy of treatment and rate of separation) by disintegrator milling were proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sustainable Recycling • Polymer fiber reinforced composite materials. • Thermal analysis • Mechanical testing • ANOVA Analysis • Python AI and DL studies • SEM characterization The sustainable processing of polymeric waste is required innovation. In this article, polypropylene (PP)- polyethylene terephthalate fiber (PETF) composite materials were fabricated according to the International Organization for Standardization (ISO 9001–2 and 2008) for commercial manufacturing using extrusion and injection molding. The variations of 0, 10, 30, and 40 % of PETF loadings were utilized for mechanical properties' optimization. The results indicate that tensile strength, strain, and young's modulus of elasticity were in the range of 22–25 MPa, 3–5 % and 870–1167 MPa. Correspondingly, the values of flexural strength, strain and modulus constant were in the range of 39–40 MPa, 9–12 % and 1909–2140 MPa, respectively. The impact energies were in the range of 2.6–3.4 kJ/m2. Thermally, the PP-PETF composites were found stable. The scanning electron microscope characterization, presence of induced micro defects, optimum flake structure, analysis of variance, deep learning, and artificial intelligence studies predict the utilization of PP-PETF composites for manufacturing of panels and sheets regarding static loading bearing applications. The reported technical strategies can be utilized as a reference processing technique for industrial manufacturing of PP-PETF based recycled composite products. [ABSTRACT FROM AUTHOR]

Good cementing properties, fast setting and strong thermal performance make calcium aluminate a valuable raw material for use in the production of different types of new refractory materials, e.g., heat conductive/storage materials. The main aim of the study was to determine thermal properties of novel Nb-slag based materials with different fillers, and to clarify the optimal composition and technology. The preparation process of the studied materials was the following: mixing of components, casting into moulds and hardening of materials. To estimate potential application areas, the following thermal properties of CA-based materials were investigated: thermal behaviour, the coefficient of thermal expansion (CTE) and conductivity. For thermal analysis, small cylindrical specimens were cut out from produced materials, and plates sized 25 × 300 × 300 mm were used for conductivity studies. Different compositions of CA-based materials, the hardening process, and the influence of mechanical activation on the strength were analysed. The best thermal properties similar to the analogous reference materials were obtained by quartz sand and granite sand as filler materials. The thermal conductivity of the novel CA-based material is 1.5 times higher and the bending strength is about 3 times higher compared to commercial thermoplates. [ABSTRACT FROM AUTHOR]

Cotton, polyester, and polyethylene terephthalate are the most common types of polymers that produce huge wastes. The circularity of these post-consumer (PC) waste faces operational problems during processing. In this innovative research, the relationship between circularity, surface characterization, mechanical and tribological testing of fiber reinforced (cotton, polyester), and particulate (polyethylene terephthalate) composites is explored for industrial pilot production. Cutting model can control the size of fibers during grinding. The fiber reinforced composites (FRCs) with 10% (by weight) fiber loadings are found as operational candidates for structural, automotive, and medical applications due to suitable tensile strength (26–29 MPa), percentage of extension (10%) and abrasive wear (3 × 10−6 mm3/Nm). An increase in fiber content produces micro-defects like asperities, rough areas, voids, cracks, and pits in recycled composites. Therefore, the particulate and FRCs with 40% (by weight) fiber loadings become hard and brittle. However, these composites (especially with 40% wt. fiber loadings) exhibit reasonable elastic modulus (1526–2751 MPa) and abrasive wear (6.5 × 10−6 mm3/Nm). The ductile to brittle transition effect has appeared in all composites (with 30% wt. fiber content) due to continuous fiber addition, micro-defects creation and dual phase presence. In conclusion, natural and synthetic PC wastes can be utilized for sustainable processing of commercial polymer composites. Moreover, injection molding, polymer characterization, tensile testing, abrasion evaluation, and regression analysis can be introduced for the transformation of open-loop into closed-loop manufacturing. [ABSTRACT FROM AUTHOR]

The circularity of polymer waste is an emerging field of research in Europe. In the present research, the thermal, surface, mechanical, and tribological properties of polypropylene (PP)-based composite produced by injection molding were studied. The pure PP matrix was reinforced with 10, 30, and 40% wt. of pure cotton, synthetic polyester, and polyethylene terephthalate post-consumer fibers using a combination of direct extrusion and injection molding techniques. Results indicate that PP-PCPESF-10% wt. exhibits the highest value of tensile strength (29 MPa). However, the values of tensile and flexural strain were lowered with an increase in fiber content due to the presence of micro-defects. Similarly, the values of modulus of elasticity, flexural modulus, flexural strength, and impact energy were enhanced due to an increase in the amount of fiber. The PP-PCCF-40% wt. shows the highest values of flexural constant (2780 MPa) and strength (57 MPa). Additionally, the increase in fiber loadings is directly proportional to the creation of micro-defects, surface roughness, abrasive wear, coefficient of friction, and erosive wear. The lowest average absolute arithmetic surface roughness value (Ra) of PP and PP-PCCF, 10% wt., were 0.19 µm and 0.28 µm. The lowest abrasive wear value of 3.09 × 10−6 mm3/Nm was found for pure PP. The erosive wear value (35 mm3/kg) of PP-PCCF 40% wt. composite material was 2 to 17 times higher than all other composite materials. Finally, the single-step analysis of variance predicts reasonable results in terms of the p-values of each composite material for commercial applications. [ABSTRACT FROM AUTHOR]

The resistance of high velocity oxy-fuel (HVOF) sprayed TiC-NiMo and Cr3C2-Ni cermet particles reinforced NiCrSiB self-fluxing alloy coatings to high temperature erosion wear was studied. Microstructure of the coatings was examined by SEM, phase composition was determined by XRD. A four-channel centrifugal particle accelerator was applied to study the high temperature erosion wear of the coatings. The angles of impingement were 30° and 90°, initial particle velocity was 50 m/s, the average temperature of the test - 650 °C. Volume wear of the coatings was calculated and compared to the respective values of the reference materials. Wear mechanisms were studied by SEM. HVOF sprayed coatings exhibited lower wear, than WC-15Co hardmetal and steel HARDOX 400, but higher wear than steel AISI 304. TiC-NiMo particles reinforced self-fluxing alloy coating demonstrated virtually the same wear resistance, as the Cr3C2-Ni particles reinforced self-fluxing alloy coating, at 30° and the better wear resistance at 90°. [ABSTRACT FROM AUTHOR]

Recycling of materials is becoming increasingly important as industry response to public demands, that resources must be preserved and environment protected. To produce materials competitive in cost with primary product, secondary producers have to pursue new technologies and other innovations. For these purposes different recycling technologies for composite materials (oxidation, milling, remelting etc) are widely used. The current paper studies hardmetal/cermet powders produced by mechanical milling technology. The following composite materials were studied: Cr3C2-Ni cermets and WC-Co hardmetal. Different disintegrator milling systems for production of powders with determined size and shape were used. Chemical composition of produced powders was analysed. To estimate the properties of recycled hardmetal/cermet powders, sieving analysis, laser granulometry and angularity study were conducted. To describe the angularity of milled powders, spike parameter--quadric fit (SPQ) was used and experiments for determination of SPQ sensitivity and precision to characterize particles angularity were performed. Images used for calculating SPQ were taken by SEM processed with Omnimet Image Analyser 22. The graphs of grindability and angularity were composed. Composite powders based on Fe- and Ni-self-fluxing alloys for thermal spray (plasma and HVOF) were produced. Technological properties of powders and properties of thermal sprayed coatings from studied powders were investigated. The properties of spray powders reinforced with recycled hardmetal and cermet particles as alternatives for costsensitive applications were demonstrated. [ABSTRACT FROM AUTHOR]

Thermal spray and WC-Co based coatings are widely used in areas subjected to abrasive wear. Commercial cermet thermal spray powders for HVOF are relatively expensive. Therefore applying these powders in cost-sensitive areas like mining and agriculture are hindered. Nowadays, the use of cheap iron based self-fluxing alloy powders for thermal spray is limited. The aim of this research was to study properties of composite powders based on self-fluxing alloys and recycled cermets and to examine the properties of thermally sprayed (HVOF) coatings from composite powders based on iron self-fluxing alloy and recycled cermet powders (Cr3C2-Ni and WC-Co). To estimate the properties of recycled cermet powders, the sieving analysis, laser granulometry and morphology were conducted. For deposition of coatings High Velocity Oxy-Fuel spray was used. The structure and composition of powders and coatings were estimated by SEM and XRD methods. Abrasive wear performance of coatings was determined and compared with wear resistance of coatings from commercial powders. The wear resistance of thermal sprayed coatings from self-fluxing alloy and recycled cermet powders at abrasion is comparable with wear resistance of coatings from commercial expensive spray powders and may be an alternative in tribological applications in cost-sensitive areas. [ABSTRACT FROM AUTHOR]

This study addresses the challenge of enhancing the transverse mechanical properties of oriented polyacrylonitrile (PAN) nanofibers, which are known for their excellent longitudinal tensile strength, without significantly compromising their inherent porosity, which is essential for effective filtration. This study explores the effects of doping PAN nanofiber composites with varying concentrations of polyvinyl alcohol (PVA) (0.5%, 1%, and 2%), introduced into the PAN matrix via a dip-coating method. This approach ensured a random distribution of PVA within the nanofiber mat, aiming to leverage the synergistic interactions between PAN fibers and PVA to improve the composite's overall performance. This synergy is primarily manifested in the structural and functional augmentation of the PAN nanofiber mats through localized PVA agglomerations, thin films between fibers, and coatings on the fibers themselves. Comprehensive evaluation techniques were employed, including scanning electron microscopy (SEM) for morphological insights; transverse and longitudinal mechanical testing; a thermogravimetric analysis (TGA) for thermal stability; and differential scanning calorimetry (DSC) for thermal behavior analyses. Additionally, a finite element method (FEM) analysis was conducted on a numerical simulation of the composite. Using our novel method, the results demonstrated that a minimal concentration of the PVA solution effectively preserved the porosity of the PAN matrix while significantly enhancing its mechanical strength. Moreover, the numerical simulations showed strong agreement with the experimental results, validating the effectiveness of PVA doping in enhancing the mechanical properties of PAN nanofiber mats without sacrificing their functional porosity. [ABSTRACT FROM AUTHOR]

This study focuses on the mechanical properties of electrospun nanofibrous mats, highlighting the importance of the characteristics of single nanofibers in determining the overall mechanical behavior of the mats. Recognizing the significant impacts of the diameter and structural properties of the nanofibers, this research introduces a novel methodology for deriving the effects of the mechanical properties of single nanofibers on the aggregate mechanical performance of electrospun oriented nanofiber mats. For this purpose, a finite element method (FEM) model is developed to simulate the elastoplastic response of the mats, incorporating the influence of structural parameters on mechanical properties. The validation of the FEM model against experimental data from electrospun polyacrylonitrile (PAN) nanofibers with different orientations demonstrates its effectiveness in capturing the elastic–plastic tensile behaviors of the material and confirms its accuracy in terms of reflecting the complex mechanical interactions within the nanofibrous mats. Through a detailed analysis of how nanofiber diameter, orientation of fibers, length-to-width ratio, and porosity affect the mechanical properties of the mats, this research provides valuable insights for the engineering of nanofibrous materials to meet specific mechanical requirements. These findings improve our understanding of nanofibrous mat structures, allowing for better performance in diverse applications as well as highlighting the critical importance of identifying the properties of single nanofibers and their associated impacts on material design. [ABSTRACT FROM AUTHOR]

Circular economy is still a theoretical field. In this research, alumina ceramic material was used to measure the coefficient of friction (COF) of cotton fabric with the objective of supporting the circular economy of textile industries. A scanning electron microscope (SEM), optical profilometer, mechanical profilometer and tribometer were used for evaluations of the cotton fabric surface and the coefficient of friction (COF). The cotton fabric surface was detected rough and damaged while the ceramic balls displayed smoothness along with high microhardness. The dynamic COF values were 0.12 to 0.15 in warp and 0.11 to 0.17 in weft directions. Based on the COF values, deformation, wear and morphologies evaluations, alumina ceramic materials could be used operationally for surface alterations of textile machinery parts. The results could also enhance the quality and performance of textile products. [ABSTRACT FROM AUTHOR]

Rough, damaged, and distorted post-consumer natural and synthetic polymers cause wear and damage to textile machinery parts, presenting a major obstacle to the quality of recycled products. In this research, TiAlN coatings were used to measure the coefficient of friction (COF) for tribological properties. The scanning electron microscope (SEM) studies of cotton textiles revealed surface damage, distortions, and loose fibres produced on the fabric surface. SEM morphology of TiAlN coatings was found smooth and uniform. Additionally, Contour GT-K 3D optical microscope and mechanical profilometer (Mahr Perthometer) were used for coating surface analysis. The average coating surface roughness parameters were Rmax (0.30 gm), Rz (0.26 gm), and Rp (0.17 gm). The microhardness value was 35 GPa on the HV scale. The lower surface roughness and higher hardness values are an indication of reasonable quality and performance of textile fabrics during recycling. The dynamic COF values were obtained from 0.47 to 0.30 in warp and from 0.35 to 0.23 in weft directions. Higher COF values occurred in the warp direction due to lower thread densities, rough surface, preferred fibre orientation, randomly oriented fibres, and a plain-woven structure. Based on the COF values, permanent deformation, and morphology evaluations, TiAlN coatings could be used optimistically for surface modification of shredding, cutting, and textile machinery parts. The TiAlN coatings applications in industries could also enhance the quality and performance of recycled textile products. [ABSTRACT FROM AUTHOR]

In the current article, high-velocity oxy-fuel (HVOF) sprayed composite powder TiC- NiMo and Cr3C2-Ni cermet particles reinforced self-fluxing alloy matrix (FeCrSiB) coatings were studied. The actual content of the reinforcement in the sprayed coatings was smaller in comparison with the feedstock powders. Cermet particles were deformed at the impact with the substrate, deformation was more remarkable in the case of the TiC-NiMo particles. Sprayed coatings exhibited a structure with a number of defects, like voids and cracks, whereas the latter were more pronounced in reinforced coatings. Despite the bigger number of defects, cermet particles reinforced coatings had up to 1.2 times higher surface hardness than the unreinforced coating. TiC- NiMo particles reinforced coating demonstrated 1.8 times higher sliding wear resistance than the unreinforced coating. Cr3C2-Ni particles reinforced coating showed 1.3-2.8 times higher sliding wear resistance in comparison with the unreinforced coating, depending on the series of tests. Addition of cermet particles allowed to increase the resistance of the FeCrSiB matrix to deformation and scuffing. [ABSTRACT FROM AUTHOR]

Glass fibre reinforced plastic (GFRP) scrap consisted of acrylic plastic with glass fibre reinforcement in polyester resin matrix was used in our experiments. The multi-functional DS-series disintegrator mills were used for mechanical processing of GFRP scrap. Preceding from the results characterization of the milled powder particles size, shape and other properties the numerical algorithm for modelling of the density of the new filler material was developed. The main goal of the current study is to develop new particulate filled composite plastic material from recycled GFRP scrap. With recovered plastic powder material the higher filler content in polyester resin matrix can be achieved. The new composite is modelled on basis of the properties of new material. Such an approach requires tests of the new material. The considered target characteristics of the new material are the tensile strength, elongation at break and the cost. The multicriteria optimization problem has been formulated and solved by use of physical programming techniques and Pareto optimality concept. The designed new composites were manufactured in different mixing ratios of powder and binder agent. The strength and stiffness properties of new composite material were tested. [ABSTRACT FROM AUTHOR]

The influence of birch false heartwood was investigated relative to the physical and mechanical properties of wood-plastic composites. Birch wood (sapwood and false heartwood) particles were modified with 5 wt% NaOH (by wood content) and 5 wt% 3-aminopropyl-triethoxysilane (by wood content) before being compounded with polypropylene in a corotating twin-screw extruder. The compounded composites were then injection moulded into standard test samples. The resulting composites were grouped into four categories: birch sapwood, modified birch sapwood, false heartwood, and modified false heartwood. Neat polypropylene samples were produced as a reference. The samples were tested for their tensile and flexural properties, water absorption, thickness swelling, and ultraviolet aging. The compositions of the composites were analysed using Fourier transform infrared spectroscopy. The results showed that the tensile strength of all of the samples decreased after water absorption. Water absorption decreased the impact strength of all of the composites. Ultraviolet radiation degraded the neat polypropylene and lowered the mechanical properties of all of the composites. Surface chalking was observed in all of the wood-plastic composites exposed to ultraviolet aging, with colours ranging from brown and brownish black to white. [ABSTRACT FROM AUTHOR]

The article focuses on vacuum liquid phase sintered (PM) composite hardfacings and their behaviour under different abrasive wear conditions. Hardfacings studied contained 30 - 50 vol % fine, coarse or multimodal (fine and coarse) hardmetal reinforcement. For wear resistance studies, we used the Abrasive Rubber Wheel Wear (ARWW) test as a threebody abrasive wear test, the Abrasive Wheel Wear (AWW) test as a two-body abrasive wear test and the Abrasive-Impact Erosion wear (AIEW) test as an abrasive-erosive wear test. Tested materials were compared to Hardox 400 steel and CDP112 wear plate (Castolin Eutectic® Ltd.). It was found that under three-body abrasion conditions (ARWW test) hardfacings with high content of spehrical coarse reinforcement are suitable; their wear resistance is about two times higher than that of unreinforced hardfacings. Under two-body abrasive wear (AWW test), hardfacings with a high content of coarse reinforcement are recommended; their wear resistance is up to eight times higher than that of unreinforced hardfacings from the figures and graphs mentioned in the text. Under abrasive-erosive wear (AIEW test), unreinforced ductile materials are recommended; they have two to three times higher wear resistance than composite hardfacings reinforced with fine or multimodal reinforcement. [ABSTRACT FROM AUTHOR]

The article studies the effect of the hardmetal reinforcement content (80, 60, 40, and 20 wt%) on powder metallurgy (PM) hardfacings with the FeCrSiB matrix, produced by vacuum pressureless liquid-phase sintering. Research focus was on the microstructure, macro- and microhardness, as well as wear resistance of hardfacings under abrasive rubber wheel wear and abrasive-erosive wear tests. The results of the wear tests are compared to the wear of reference materials: steel Hardox 400, composite wear plate CDP 112 (Castolin Eutectic® Ltd.), and hardmetal VK15. A positive correlation was found between the microstructure and microhardness of the hardfacings and their wear resistance. Optimal hardmetal content in the PM hardfacings for different types of wear conditions is recommended. [ABSTRACT FROM AUTHOR]

Fine particles originating from a mixture of erodent particles or being the residues of broken particles, might retain on the surface of an eroded material by electrostatic field. This results in the presence of a fine third body between an attacking original erodent particle and a material surface during collision that leads to higher and more localised stresses. Hardmetal, alumina, zirconia, Al 5083, Hardox 400, AISI 316, rubber and plastic were studied to assess the effect of the fine third body on wear mechanism and wear rate under erosive conditions of impact velocities ranging from 10 up to 80 m s −1 . Four batches of silica sand erodent particles were tested: (1) naturally occurring (0–1000 µm), (2) fine-sized (0–120 µm), (3) coarse-sized (600–1000 µm), and (4) mixture of fine and coarse (0–50 plus 600–1000 µm). A pronounced effect of fine hard third body was observed for alumina under almost all velocities as well as for rubber, hardmetal and zirconia at high velocity. Soft metals (Al 5083, AISI 316, Hardox 400) are not sensitive to the presence of a fine erodent retained on the surface. The response of plastic to erosion depends mainly on energy of eroding particles (coarse particles induce a higher wear rate). [ABSTRACT FROM AUTHOR]

Abrasive wear resistance of tillage and harvesting tools is highly important for the agricultural sector because abrasive wear by hard soil particles is the main factor limiting their lifetime. Manual arc welding is among the easiest, most convenient, and economically feasible methods not only for coating metallic tools in small and medium scale farms, but also for mining operations. The aim of the current work was to develop electrodes for manual arc welding that enable a significant reduction of wear under three-body abrasive conditions. Reinforcement by tungsten carbide powder was used due to possibility of production these powders through recycling of hardmetal scrap. The effects of three variables, namely (1) binder material (low-carbon ferritic–pearlitic or austenitic stainless steel), (2) WC content, and (3) WC grain size, on three-body abrasive wear resistance of hardfacings, were evaluated using the ASTM G65, dry sand/rubber wheel, test method (Procedure B). A reduction in wear rate by as much as a factor of 9 was achieved by introducing of 42–43 wt% of WC. A discussion of the wear mechanisms for the hardfacings is provided, based on data and observations using scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and optical emission spectroscopy. [ABSTRACT FROM AUTHOR]

Products made of basalt are recently gaining sufficient attention due to depletion of raw materials serving as reinforcement for construction, and wear resistant materials. Basalt has sufficient mechanical strength, high hardness, low density and superior corrosion resistance. Basalt and other minerals are used in thick metal coatings to adjust their thermal expansion to that of the steel substrate. High velocity oxygen fuel (HVOF) sprayed coating method allows to prepare solid basalt-steel composite materials since the melting temperatures of basalt and steel are very close and materials obtained by casting or sintering will have low mechanical properties. The aim of the current work is to study the change in tribological response under erosive, abrasive, reciprocal and continuous sliding conditions when basalt is added to the harder matrix. It was found that the addition of 12 vol % of basalt to the FeCrSiB HVOF sprayed coating is generally unfavourable in tribological conditions due to the brittleness of basalt and its flake shape. The worst relative performance was observed in reciprocal sliding conditions and the best one in mild conditions of continuous sliding. Discussion on the mechanisms of materials performance is based on SEM and EDS results. [ABSTRACT FROM AUTHOR]

The design of earth cutting and machining tools generally requires the application of several types of materials with different wear resistance: (1) base metal with low wear resistance, (2) extremely resistant cutting inserts made of ceramics (or even diamond), cemented carbides or cermets and (3) thick coatings with average wear resistance to protect base metal or thin (PVD or CVD) coatings to improve wear resistance of inserts. The production of such tools is complicated, tedious and not very efficient (tool life depends on the interface bonding, brazed inserts can be severely damaged after impact, base material wear, etc.). The novel approach is to exclude the steps of brazing or coating and to produce steels or composites with similar wear resistance as that of inserts or coatings using the promising approach of additive manufacturing (AM i.e. 3D printing). Moreover, benefits of AM like near net shape part building with complex internal features (internal cooling channels) are desired for cutting tools. The aim of the current research is to assess novel commercially available 3D printed steels and composites in several relevant tribological conditions where these materials could be applied. The comparison with conventional Hardox 400 wear resistant steel and AISI 316 stainless steel is provided. Results report significant improvement in the wear resistance of AM produced steels and composites against reference materials. The performance of 3D printed materials lie between WC- based bulk cemented carbides and hardfacings. The characteristic features of wear mechanisms are presented and discussion is supported by Scanning Electron Microscope images. • It is possible to 3D print wear resistant materials with high content of homogeneously dispersed carbides. • The additive manufactured Vibenite steels and composites show low wear rate in comparison to Hardox 400 and AISI 316. • The performance of 3D printed materials lie between WC- based bulk cemented carbides and hardfacings. • The effect of third body and mechanically mixed layer formation during test conditions are discussed. [ABSTRACT FROM AUTHOR]