Search Results (41)

With the increasing demand for alternatives to traditional indium tin oxide (ITO), copper nanowires (Cu NWs) have gained significant attention due to their excellent conductivity, cost-effectiveness, and ease of synthesis. However, challenges such as wire–wire contact resistance and oxidation susceptibility hinder their practical applications. This review discusses the development and challenges associated with Cu NW-based flexible transparent conductors (FTCs). Cu NWs are considered a promising alternative to traditional materials like ITO, thanks to their high electrical conductivity and low cost. This paper explores various synthesis methods for Cu NWs, including template-assisted synthesis, hydrazine reduction, and hydrothermal processes, while highlighting the advantages and limitations of each approach. The key challenges, such as contact resistance, oxidation, and the need for protective coatings, are also addressed. Several strategies to enhance the conductivity and stability of Cu NW-based FTCs are proposed, including thermal sintering, laser sintering, acid treatment, and photonic sintering. Additionally, protective coatings like noble metal core–shell layers, electroplated layers, and conductive polymers like PEDOT:PSS are discussed as effective solutions. The integration of graphene with Cu NWs is explored as a promising method to improve oxidation resistance and overall performance. The review concludes with an outlook on the future of Cu NWs in flexible electronics, emphasizing the need for scalable, cost-effective solutions to overcome current challenges and improve the practical application of Cu NW-based FTCs in advanced technologies such as displays, solar cells, and flexible electronics. Full article

A study of the antifriction properties of suspension solid-lubricating coatings based on molybdenum disulfide (MoS₂) at high temperatures depending on the type of substrate, binder, additives, and load parameters was carried out. The solid lubricants were sprayed on two different substrates, high-temperature alloy (Inconel X-750) and stainless steel (AISI 430), tested under 10 N and 23 N loads at temperatures ranging from 25 °C to 800 °C. For comparison, different types of solid lubricants were used. In this work, it was established that the antifriction properties of solid lubricant suspension coatings at high temperatures significantly depend on the type of solid lubricant and the binder used. Moreover, it was shown that the use of Inconel X-750 as a substrate can lead to an increase in the critical operating temperature of coatings containing MoS₂, graphite, and titanate as solid lubricant, additive, and binder, respectively. For instance, at load 23 N, the operating temperature increased from 480 °C to 496 °C. On the other hand, the coating based on graphite, containing ceramic as an additive, and an inorganic binder showed the best performance in terms of a combination of properties (low coefficient of friction and longer operation with a coefficient of friction below 0.3 under increasing temperature) when it was applied on the Inconel X-750 substrate. In addition, it was established that the coefficient of friction of graphite-based coatings gradually increases as they lose their antifriction properties due to their failure, while the coatings based on molybdenum disulfide show the opposite behavior, where the coefficient of friction increases sharply when it loses its lubricating properties. Full article

In this study, the design of mixture experiments was used to find empirical models that could predict, for a first approximation, the relative density, flexural strength, Vickers hardness and fracture toughness of sintered composites in order to identify further areas of research in the Al₂O₃-TiB₂-TiC ternary system. The composites were obtained by spark plasma sintering (SPS) of these mixtures at 1700 °C, 80 MPa and a dwell of 3 min. The obtained experimental results were analyzed in the statistical analysis software Minitab 17, and then, different regression models were obtained for each property. Based on the selected models, contour plots were made in the Al₂O₃–TiB₂–TiC simplex for a visual representation of the predicted results. By combining these plots, it was possible to obtain one common zone in the Al₂O₃–TiB₂–TiC simplex, which shows the following combination of physical and mechanical properties for sintered samples: relative densities, flexural strength, Vickers hardness, and fracture toughness of than 99%, 500 MPa, 18 GPa, and 7.0 МPa·m^1/2, respectively. For a first approximation in determining the further area of research, the obtained models describe well the behavior of the studied properties. The results of the analysis showed that the design of mixture experiments allows us to identify the most promising compositions in terms of mechanical properties without resorting to labor-intensive and financially expensive full-scale experiments. Our work shows that 10 different compositions were required for preliminary analysis. Full article

The European Fusion Reactor (DEMO, Demonstration Power Plant) relies significantly on joining technologies in its design. Current research within the EUROfusion framework focuses on developing materials for the first wall and divertor applications, emphasizing the need for suitable joining processes, particularly for tungsten. The electric field-assisted sintering technique (FAST) emerges as a promising alternative due to its high current density, enabling rapid heating and cooling rates for fast sintering or joining. In this study, FAST was employed to join tungsten and EUROFERE97 steel, the chosen materials for the first wall, using 50-µm-thick Cu foils as interlayers. Three distinct joining conditions were tested at 980 °C for 2, 5, and 9 min at 41.97 MPa to optimize joint properties and assess FAST parameters influence. Hardness measurements revealed values around 450 HV_0.1 for tungsten, 100 HV_0.1 for copper, and 390 HV_0.1 for EUROFER97 under all joining conditions. Increasing bonding time improved joint continuity along the EUROFER97/Cu and W/Cu interfaces. Notably, the 5 min bonding time resulted in the highest shear strength, while the 9 min sample exhibited reduced strength, possibly due to Kirkendall porosity accumulation at the EUROFER97/Cu interface. This porosity facilitated crack initiation and propagation, diminishing interfacial adhesion properties. Full article

This work demonstrates the capabilities and advantages of a novel sintering technique to fabricate bulk composition gradient materials. Pressure distribution calculations were used to compare several tooling geometries for use with current-activated, pressure-assisted densification or spark plasma sintering to densify a gradient along the long dimension of the specimen. The selected rectangular tooling design retains a low aspect ratio to ensure a uniform pressure distribution during consolidation by using a side loading configuration to form the gradient along the longest dimension. Composition gradients of NixCu_1−x, MoxNb_1−x, and MoNbTaWHf_x (x from 0 to 1) were fabricated with the tooling. The microstructure, composition, and crystal structure were characterized along the gradient in the as-sintered condition and after annealing to partially homogenize the layers. The successful fabrication of a composition gradient in a difficult-to-process material like the refractory multi-principal element alloy system MoNbTaWHf_x shows the utility of this approach for high-throughput screening of large material composition spaces. Full article

This review discusses the groundbreaking advancements in electric current-assisted sintering techniques, specifically Flash Sintering (FS) and Ultrafast High-Temperature Sintering (UHS), for their application in Solid Oxide Fuel Cells (SOFCs). These innovative sintering methods have demonstrated remarkable potential in enhancing the efficiency and quality of SOFC manufacturing by significantly lowering sintering temperatures and durations, thereby mitigating energy consumption and cost. By providing a detailed overview of the mechanisms, process parameters, and material characteristics associated with FS and UHS, this paper sheds light on their pivotal role in the fabrication of SOFC components such as electrolytes, electrodes, multilayered materials, and interconnect coatings. The advantages, challenges, and prospective opportunities of these sintering technologies in propelling SOFC advancements are thoroughly assessed, underlining their transformative impact on the future of clean and efficient energy production technologies. Full article

Within this study, aluminum oxide granules with 0.25%vol. of graphene oxide were prepared by a spray-drying method to make an adsorbent for the 2,4-Dichlorophenoxyacetic acid (2,4-D) herbicide removal from aqueous solutions. The obtained adsorbent was studied using infrared spectroscopy, scanning electron microscopy and Raman spectroscopy. The presence of graphene in the spray-dried powder was confirmed. The adsorption removal of 2,4-D using the obtained material was performed at an ambient temperature by varying the process parameters such as pH and adsorption time. The adsorption of 2,4-D was a monolayer chemisorption according to the Langmuir isotherm pattern and a pseudo-second-order kinetic model. The maximum Langmuir adsorption capacity of the monolayer was 35.181 mg/g. The results show that the Al₂O₃-0.25%vol. GO powder obtained by spray drying is suitable for the production of adsorbents for toxic herbicides. Full article

Light-emission data were collected before, during, and after the occurrence of the flash event in pressureless electric-field-assisted (flash) sintering experiments on ZrO₂: 8 mol% Y₂O₃ (8YSZ) and CeO₂: 20 mol% Sm₂O₃ (20SDC) ceramic green pellets to analyze the luminescent emission from the samples. The experiments were performed at 800 °C with an applied electric field of 100 V·cm⁻¹ at 1 kHz, limiting the electric current to 1 A. Luminescence data were obtained in the 200–1200 nm (ultraviolet–visible–near-infrared) range. The deconvolution of the optical spectra allowed for the identification of emission bands in the visible range due exclusively to the samples. The wavelength maxima of the emission bands in 8YSZ were found to be different from those in 20SDC. It is suggested that these bands might originate from the interaction of the electric current, resulting from the application of the electric field, with the depleted species located at the space-charge region at the grain boundaries of these ceramics. The main results represent a contribution to help to clarify the mechanisms responsible for the fast densification with inhibition of grain growth in electroceramics. Full article

This paper provides results on the tribological behavior of experimental Al–Sn–Pb–Si–Cu–Mg–Zn aluminum alloys and describes the adaptation phenomena that reduce wear intensity during friction with steel. The main focus is on tribofilm formation, which plays an important role in friction energy dissipation. The alloys were tested in a rig imitating a journal-bearing shaft couple, and the friction surfaces were studied by the scanning electron microscopy, energy-dispersive analysis and X-ray photoelectron spectroscopytechniques. Based on the analysis, a conclusion on processes and tribochemical reactions was made. Compared to the initial state, eight new compounds were found on the friction surface. In the most wear-resistant alloy, magnesium precipitated from a solid solution with the subsequent oxidation. The same process was detected for zinc in the least wear-resistant alloy due to its low magnesium content. Furthermore, CuSn₃ and PbS compounds, which require >600 °C temperature to compose, were found in tribofilms, indicating that the rubbing body lost thermodynamic equilibrium during friction. The revealed processes are non-spontaneous and decrease the wear intensity of the alloys, as they are accompanied by negative entropy production and dissipation of friction energy. Stepwise depth XPS analysis also showed the functional levels of the tribofilms. Full article

The influence of WEDM parameters (Spark gap voltage, Pulse-on time, Spark frequency, and Wire speed) on the recast layer thickness and surface roughness of Spark Plasma Sintered SiC-TiB₂-TiC ceramic composite was investigated. For this, an orthogonal L9 Taguchi design was used, and grey relational analysis was carried out for multi-response WEDM parameter optimization in order to determine the minimum RLT and SR. It was noticed that for RLT, the Pulse-on time was observed as the most significant process parameter, followed by Spark gap voltage. On the other hand, Spark frequency and Wire speed had no significance for RLT. Moreover, Spark frequency was observed as the most significant process parameter, followed by Pulse-on time and Spark gap voltage, while Wire speed had a negligible effect on SR. It was found that at optimal process parameters (U = 48V; Ton = 1.0 µs; f = 10 kHz; q = 8 m/min), we obtained an RLT of 3.16 µm and an SR of Ra = 0.847 µm. The confirmation test showed a decrease in RLT and SR by 43.67% and 7.12%, respectively, in comparison to the initial machining conditions. Full article

Commonly used tool materials for machining wood-based materials are WC-Co carbides. Although they have been known for a long time, there is still much development in the field of sintered tool materials, especially WC-Co carbides and superhard materials. The use of new manufacturing methods (such as FAST—field-assisted sintering technology), which use pulses of electric current for heating, can improve the properties of the materials used for cutting tools, thereby increasing the cost-effectiveness of machining. The ability to increase tool life without the downtime associated with tool wear allows significant cost savings, particularly in mass production. This paper presents the results of a study of the effect of grain size and cobalt content of carbide tool sinters on the tribological properties of the materials studied. The powders used for consolidation were characterised by irregular shape and formed agglomerates of different sizes. Tribological tests were carried out using the T-01 (ball-on-disc) method. In order to determine the wear kinetics, the entire friction path was divided into 15 cycles of 200 m and the weight loss was measured after each stage. In order to determine the mechanism and intensity of wear of the tested materials under technically dry friction conditions, the surface of the tested sinters was observed before the test and after 5, 10, and 15 cycles. The conclusions of the study indicate that the predominant effect of surface cooperation at the friction node is abrasion due to the material chipping that occurs during the process. The results confirm the influence of sintered grain size and cobalt content on durability. In the context of the application of the materials in question for cutting tools, it can be pointed out that sintered WC(0.4)_4 has the highest potential for use in the manufacture of cutting tools. Full article

Within this work, new aerogels based on graphene oxide are proposed to adsorb salicylic acid (SA) and herbicide 2,4-Dichlorophenoxyacetic acid (2,4-D) from aqueous media. Graphene oxide aerogel (GOA) and reduced graphene oxide aerogel (rGOA) were obtained by freeze-drying processes and then studied by Raman spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), and Brunauer–Emmett–Teller (BET) analysis. The influence of contact time and the concentration of the adsorbates were also assessed. It was found that equilibrium for high adsorption is reached in 150 min. In a single system, the pseudo-first-order, pseudo-second-order kinetic models, Intraparticle diffusion, and Elovich models were used to discuss the detail of the aerogel adsorbing pollutant. Moreover, the Langmuir, Freundlich, and Temkin adsorption models were applied to describe the equilibrium isotherms and calculate the isotherm constants. Full article

Industrial wastewater is the main source of an excessive amount of molybdenum (Mo) in natural ecosystems. It is necessary to remove Mo from wastewater before it is discharged into the environment. Molybdate ion(VI) is the most common form of Mo in natural reservoirs and industrial wastewater. In this work, the sorption removal of Mo(VI) from an aqueous medium was evaluated using aluminum oxide. The influence of such factors as the pH of the solution and the temperature was evaluated. Three adsorption isotherms, namely, Langmuir, Freundlich and Temkin, were used to describe the experimental results. It was found that the pseudo-first order kinetic model better fits the kinetic data of the adsorption process, and the maximum Mo(VI) adsorption capacity was 31 mg/g at 25 °C and pH 4. The thermodynamic parameters indicated that the process of Mo(VI) adsorption on Al₂O₃ was exothermic and spontaneous. It was shown that the adsorption of Mo strongly depends on pH. The most effective adsorption was observed at pH values below 7. Experiments on adsorbent regeneration showed that Mo(VI) can be effectively desorbed from the aluminum oxide surface into a phosphate solution in a wide range of pH values. After the desorption of Mo(VI) in a phosphate solution, alumina was found to be suitable for repeating the procedure at least five times. Full article

Spark plasma sintering (SPS), also called pulsed electric current sintering (PECS) or field-assisted sintering technique (FAST) is a technique for sintering powder under moderate uniaxial pressure (max. 0.15 GPa) and high temperature (up to 2500 °C). It has been widely used over the last few years as it can achieve full densification of ceramic or metal powders with lower sintering temperature and shorter processing time compared to conventional processes, opening up new possibilities for nanomaterials densification. More recently, new frontiers of opportunities are emerging by coupling SPS with high pressure (up to ~10 GPa). A vast exciting field of academic research is now using high-pressure SPS (HP-SPS) in order to play with various parameters of sintering, like grain growth, structural stability and chemical reactivity, allowing the full densification of metastable or hard-to-sinter materials. This review summarizes the various benefits of HP-SPS for the sintering of many classes of advanced functional materials. It presents the latest research findings on various HP-SPS technologies with particular emphasis on their associated metrologies and their main outstanding results obtained. Finally, in the last section, this review lists some perspectives regarding the current challenges and future directions in which the HP-SPS field may have great breakthroughs in the coming years. Full article

Single-crystalline tin-selenide (SnSe) has emerged as a high-performance and eco-friendly alternative to the lead-chalcogens often used in mid-temperature thermoelectric (TE) generators. At high temperature >800 K, the phase transition from Pnma to Cmcm causes a significant rise in the TE figure-of-merit (zT) curve. Conversely, the SnSe TE requires a booster at low temperatures, which allows broader applicability from a device perspective. Herein, a synergy of Cu alloy and Ag-coating is realized through a sequential multi-step synthesis, designed to combine different metal deposition effects. Single-crystalline (Cu₂Se)_x(SnSe)_1−x alloys grown by the Bridgman method were then coated with a thin Ag layer by radio frequency (RF) sputtering, and the interlayer epitaxial film was observed via electric-current assisted sintering (ECAS). Consequently, the thin Ag-coating improves the electrical conductivity (σ) and reduces the thermal conductivity (κ) for (Cu₂Se)_0.005(SnSe)_0.995+Ag alloy, increasing the zT curve at close to room temperature (373 K). The incorporation of multistep addition by ECAS enables tuning of the overall solubility of the alloy, which opens a new avenue to optimize TE performance in anisotropic 2D materials. Full article