Electric Sintering Research Articles

Experimental investigation of sinterability of PVA-coated Magnesium powders via mechanical milling using Electric Field-Assisted Sintering Technique

Experimental investigation of sinterability of PVA-coated Magnesium powders via mechanical milling using Electric Field-Assisted Sintering Technique

Electric field enhanced diffusion welding of alloy 617: Microstructural characteristics and mechanical properties

This study investigated the microstructural characteristics and mechanical behavior of diffusion welded nickel-based Alloy 617 obtained by electric field-assisted sintering (EFAS) using various parameters. The interfacial microstructure exhibited different characteristics including good grain boundary (GB) migration across the interface in the samples diffusion-welded at 1100 °C and a flat interface in the samples joined at 1000 °C and 1050 °C. The interface consisted of fine Al2O3 oxides, while precipitation of interfacial M23C6 carbides was not observed. Grain boundaries migrated across the Al2O3 oxides, leaving these oxides within the grains. Graded grain size was observed, with grain coarsening being more significant near the sample surface due to the temperature gradient induced by EFAS. Tensile testing revealed that the specimens fractured in the matrix away from the interface, indicting strong diffusion-welded joints. The peak tensile strength of 807 MPa was obtained in the samples welded at 1000 °C due to minimal grain growth. The materials obtained at 1100 °C exhibited reduced tensile strength but improved ductility. Strain maps revealed by digital image correlation showed alternating high and low strain segments in the samples produced at 1000 °C and 1050 °C, indicating that the flat interfaces with no GB migration were less ductile compared to the matrix. A greater strain uniformity was observed along the bond interfaces with improved GB migration. The hardness reduced near the sample surfaces due to enlarged grains induced by temperature gradient. This study demonstrates that GB migration and enhanced mechanical strength can be achieved in diffusion-welded Alloy 617.

Preparation and tribological properties of PAI/PTFE@Mg-Al LDH polymer-based solid self-lubricating materials

PAI/PTFE composites with 1 %, 2 %, 3 %, 4 % and 5 % of Magnesium aluminum hydrotalcite (Mg-Al LDH) particles were prepared by DC electric field-assisted hot-pressing sintering. The friction and wear properties of the composites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), water contact angle and UMT-5 friction and wear tests. The effect of the amount of Mg-Al LDH particles added on the physical properties and friction and wear properties of the composites were analyzed. Experimental results showed that the friction and wear properties of PAI/PTFE composite films can be improved by adding appropriate Mg-Al LDH particles. Among them, The PAI/PTFE polymer based solid lubrication containing 3 % Mg-Al LDH has the best friction coefficient and wear amount, the average friction coefficient is 0.0962 and the wear extent is 1.47×10−5 g. The improved tribological properties of the composite films are mainly due to the excellent mechanical properties of Mg-Al LDH and the good lubrication properties of PTFE.

Effect of reinforcement particle size on the corrosion and mechanical properties of spark plasma sintered aluminium matrix composites.

In this study, the effects of different sizes of reinforcing particles on the corrosion behaviour and mechanical properties of aluminium (Al)-based composites produced by spark plasma sintering (SPS) are analysed. In the study, the effects of SPS parameters, including electrical power, applied pressure and sintering temperature, on the consolidation process and microstructure evolution of the composite are closely investigated. The results reveal a nuanced relationship between the sintering conditions and the properties of the particles, which in turn determine the sintering dynamics and the formation of the microstructural features. The evaluation of mechanical properties indicates a remarkable influence of particle size distribution on the hardness of the composites, showing an initial improvement with the introduction of nanoparticles, followed by a slight decrease as the balance between nano- and micron-sized Al2O3 particles shifts. A scanning electron microscopy (SEM) study demonstrates the influence of particle dimensions on the change of grain boundaries and the spatial arrangement of the composite matrix. Electrochemical experiments in a 0.1M NaCl solution show a consistent corrosion potential (Ecorr) across all samples, while the current densities associated with corrosion (icorr) show considerable variation. The presence of nano-sized Al2O3 particles was found to increase corrosion resistance, in contrast to the detrimental effects observed with larger microparticles. In particular, composites with a bimodal distribution of particle sizes showed a 3.5-fold increase in corrosion resistance compared to pure Al. The specific Al-2n8mAl2O3 composite that exhibited active electrochemical properties at elevated potentials without a defined passivation range emphasises the significant role of particle size. This study draws attention to bimodal microstructures as a promising route to achieving uniformity and improved corrosion resistance in Al matrix composites, while pointing to the need for further research to fully elucidate the operative mechanisms.

The effect of Zn-doping on electrical properties, hydration, sintering and chemical resistance of hexagonal perovskite Ba7In6Al2O19

A CO2-stable, easily sintered proton-conducting oxide electrolytes based on solid solution Ba7In6Al2–xZnxO19-0.5x with hexagonal structure has been synthesized for the first time. Within the homogeneity region (0 ≤ x ≤ 0.10), there is an increase in unit cell parameters, cell volumes and free cell volumes. The addition of Zn2+ markedly improved the sinterability of the material. The relative density of the ceramics of the doped samples reached 95 % at lower sintering temperatures than the parent phase. The electrical conductivity was studied using electrochemical impedance spectroscopy. Upon doping the oxygen-ion conductivity increased by 0.25 orders of magnitude at 800 °C. Proton transport was predominant below 500 °C for a wet atmosphere (pH2O = 1.92·10−2 atm). The investigated phases Ba7In6Al2–xZnxO19-0.5x are capable of hydration and incorporate up to 1.45 mol H2O vs 0.41 mol H2O for the parent phase. The studied phases exhibit chemical resistance to CO2 under heat treatment at 600 °C. It was shown that solid solution Ba7In6Al2–xZnxO19-0.5x is a promising electrolyte material for intermediate-temperature fuel cells.

Structure and properties of alloys based on electroerosive brass powder LS58-3 obtained in distilled water

The purpose of this work was to study the microstructure and physico-mechanical properties of alloy blanks based on electroerosive powder brass of the LS58-3 brand obtained in distilled water. Methods. To carry out the planned research, waste of the LS58-3 alloy was selected. Distilled water was used as the working fluid. In an experimental patented installation for producing powders, waste LS58-3 alloy was dispersed in distilled water with a load mass of 300 g. The following modes were used: capacitor capacity 45–65 μF; voltage at the electrodes from 150–200 V; pulse repetition rate 50–100 Hz. The preparation of new alloy blanks was carried out using an SPS 25-10 electric spark plasma sintering installation (ThermalTechnology, USA). The microstructure of new alloy workpieces was studied using an electron-ion scanning (raster) microscope QUANTA 600 FEG (Netherlands). The study of the porosity of workpieces of new alloys was carried out using an optical inverted microscope OLYMPUS GX51 (Japan). The study of microhardness of workpieces of new alloys was carried out using an automated microhardness tester AFFRI DM-8 (Vickers). Results. Analysis of the microstructure showed that the sample has a fine-grained structure and a homogeneous surface. According to the obtained porosity analysis results, the sample has less than 1% pores, which is achieved thanks to the technology of spark plasma sintering of the powder. Analysis of the microhardness of the sample showed a significant increase in microhardness, which is explained by the presence of high-hard particles formed during quenching of metal vapor in the working fluid during dispersion. Conclusion. The use of spark plasma sintering technology for electroerosive brass makes it possible to obtain blanks of new alloys with a practically non-porous structure, which leads to an increase in the hardness of the resulting blanks. The results of the conducted studies make it possible to recommend the use of the resulting powder as a starting material for the production of alloy blanks and to expand the scope of their practical application.

Optimizing Silver Paste Conductivity with Controlled Convection for Nanowrinkle Growth.

Conductive silver paste plays a crucial role as an interconnecting material between electrodes and circuits in electronic circuits and solar cells. The quality of the silver paste is greatly influenced by the preparation of the conductive-phase silver powder and the sintering process. This study investigated the impact of fluid dynamics on the preparation of silver powder. Combined with X-ray diffractometer characterization and molecular dynamics simulation, the formation mechanism of wrinkled silver powder was explained. The wrinkled silver powder replaced the traditional smooth spherical silver powder, and the point contact between the smooth silver powder turned into a line and surface contact. After mixing and sintering with the micrometer flake silver powder, the electrical conductivity and sintering morphology of the silver paste were improved. Compared with the silver content of conventional silver paste (≥75 wt %), the silver paste of (9.23 ± 0.68) × 10-6 Ω cm can be prepared by curing at 250 °C for 45 min when wrinkled powder/flake powder = 1:1 and silver paste content was only 66.7%. This research work provides a new idea for the morphology control of submicrometer silver powder, which has important applications in the field of low-temperature silver paste for new N-type batteries.

Properties and prospects for biomedical application of new Ti-Nb-Sn alloys obtained by electrical resistance sintering

Active research of new β titanium alloy compositions is underway. At the same time, new ways of alloy preparation by powder metallurgy methods are being investigated. In this work Ti-35Nb-XSn alloy (X = 0, 4, 6 wt%) were obtained via electrical resistance sintering (ERS) at current intensities of 11 and 12 kA respectively. The influence of alloying element content and process conditions on the alloys structure and properties in the context of biomedical application were investigated.

Electromigration and electrical sintering in printed silver from high current at room temperature

Improved understanding of the reliability and failure physics of metal nanoparticle conductive inks would facilitate their large-scale deployment across a range of flexible electronics applications. We conduct room-temperature electromigration experiments on printed silver nanoparticle conductive ink test devices. We observe significant variation in failure time, location, and structure during these tests and during post-failure analysis with optical and electron microscopy. We use in situ Atomic Force Microscopy measurements to track volume changes in the sample as a function of time. These measurements provide additional data and understanding of the failure process within printed silver nanoparticle conductive inks.

Effect of the Temperature-Rate Regimes in Electric Pulse Plasma Sintering on Microstructure and Mechanical Properties of Aluminum Oxide: The Role of Sintering Mechanisms

Effect of the Temperature-Rate Regimes in Electric Pulse Plasma Sintering on Microstructure and Mechanical Properties of Aluminum Oxide: The Role of Sintering Mechanisms

Exploring FAST Technique for Diffusion Bonding of Tungsten to EUROFERE97 in DEMO First Wall.

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 HV0.1 for tungsten, 100 HV0.1 for copper, and 390 HV0.1 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.

Electrochemical grand potential-based phase-field simulation of electric field-assisted sintering

An electrochemical grand potential functional was proposed to describe the sintering of an ionic ceramic green body. The resultant phase-field description enables simulation of the consolidation of an arbitrary number of granular particles and their interactions with the surrounding void phase. The model includes the effects of charged vacancies and the associated interactions between internal and applied electric fields. Defect segregation to grain boundaries is also accounted for, as well as enhanced interfacial defect mobilities. The model was parameterized for Y2O3. Simulations of two-particle systems showed that the applied electric field had an increasingly important impact on neck growth as particle size increased. A sudden rapid increase in temperature occurred for larger field strengths, which has been reported to be correlated to the onset of a flash event in flash sintering. Simulations of many particles showed that internal heat generation by Joule heating was localized at particle–particle contacts (grain boundaries), even though their conductivities were lower than nearby internal particle-void interfaces. A percolative path for ionic charge across the green body and the ceramic sintered solid was thus defined, accelerating the Joule heating process as the porosity of the green body is removed.

Rapid low-temperature densification of Ag2Se bulk material: mass transfer through the dissociative adsorption reaction of Ag protrusions and Se saturated vapor

In materials science, the impact of density on a material’s capabilities is profound. Conventional sintering requires high temperatures and is energy-demanding, propelling the pursuit of less intensive, low-temperature densification methods. Electric field-assisted sintering has recently gained attention for its simplicity and effectiveness, offering a new frontier in low-temperature densification. In this study, dense bulk materials were produced by subjecting monophasic Ag2Se powders to electric field-assisted sintering, where a direct current with an average value of 4 A was applied, achieving a peak temperature of 344 K. The novel low-temperature densification mechanism unfolds thus: nanoscale silver protrusions, stimulated by electrical current, engage in a dissociative adsorption reaction with the ambient saturated selenium vapor. This process swiftly engenders the formation of fresh silver selenide (Ag2Se) compounds, initiating nucleation and subsequent growth. Consecutively, these compounds seamlessly occupy and expand, perpetually bridging the interstices amidst the powders. In a scant 8 s, the density swiftly surpassed 99%, yielding a bulk material that exhibited a ZT value of 1.07 at 390 K. This investigation not only attains an unparalleled density at low temperatures but also charts a pioneering course for material densification in such conditions.

Innovations in Electric Current-Assisted Sintering for SOFC: A Review of Advances in Flash Sintering and Ultrafast High-Temperature Sintering

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.

A comparative study of electric current-assisted and conventional sintering of Inconel 718 superalloy

In this study, In718 powder mixtures prepared from elemental powders following stoichiometric composition and supplied as a commercial product were produced by conventional powder metallurgy (1300 °C/4 h) and electric current-assisted sintering (ECAS)(1700-2300A/10 min) methods and followed by a double-aging heat treatment. The characterization studies determined that the best results were the sample produced by the ECAS method using the elemental powder mixture. The targeted precipitate γ′, γ″, and δ phases were obtained after the heat treatment, and a hardness value of 344 ± 41 HV0.5 and a relative density of 98.96% were achieved. The sample preserved its surface integrity by exhibiting high corrosion resistance from hot corrosion studies in the temperature range of 650–850 °C and NaSO4 + 60%V2O5 environment. The corrosion rate of the sample, which was subjected to electrochemical corrosion tests in 3.5% NaCl and 10% NaNO3 solutions, was determined as 45.59 mpy and 10.56 mpy, respectively.

Numerical simulation of heat transfer during spark plasma sintering of porous SiC

The strong covalent bonding of SiC makes it difficult to be fully sintered using conventional sintering techniques. Therefore, electrical current-assisted sintering techniques such as spark plasma sintering are needed to sinter SiC. The finite numerical simulations have been generally used to predict and guide sintering processes of ceramics (i.e.TiC,AlO3). In this work, the numerical simulations of the temperature distribution, electrical field and thermal field on the porous SiC cylindrical samples by Comsol were investigated in details. The influence of porosity on the temperature distribution and electrical field distribution of the SiC samples were analyzed. Both the maximum current density (1.19 × 107A/m2) and the maximum temperature (2030 °C) of the SPS device occurred at the punch/spacer interface. The temperature values at the centre of the samples were proportional to the porosity, and the temperatures at the center of the samples increased from ∼1960 °C to ∼2010 °C at t = 2000s, with the porosity increasing from 1% to 60%. The uniformity of the temperature distribution deteriorated as the porosity increases, and the temperature gradients between the center and edge of the samples with the porosity of 1% and 60%, were ∼80 °C and ∼130 °C at t = 2000s, respectively.

Polymer-Assisted 3D Printing of Inductor Cores.

Poly(glycerol monomethacrylate) (PGMA) prepared by reversible addition-fragmentation chain transfer polymerization was investigated as an additive for high-loading iron oxide nanoparticle (IOP) 3D printable inks. The effect of adjusting the molar mass and loading of PGMA on the rheology of IOP suspensions was investigated, and an optimized ink formulation containing 70% w/w IOPs and 0.25% w/w PGMA98 at pH 10 was developed. This ink was successfully 3D printed onto various substrates and into several structures, including rectangles, high aspect ratio cylinders, letters, spiral- and comb-shaped structures, and thin- and thick-walled toroids. The effect of sintering on the mechanical properties of printed artifacts was investigated via four-point flexural and compressive testing, with higher sintering temperatures resulting in improved mechanical properties due to changes in the particle size and microstructure. The printed toroids were fabricated into inductors, and their electrical performance was assessed via impedance spectroscopy at a working frequency range of 0.001-13 MHz. There was a clear trade-off between electrical properties and sintering temperature due to a phase change between γ-Fe2O3 and α-Fe2O3 upon heating. Nevertheless, the optimized devices had a Q factor of ∼40 at 10 MHz, representing a superior performance compared to that of other inductors with iron oxide cores previously reported. Thus, this report represents a significant step toward the development of low-cost, fully aqueous, high loading, and 3D printable ceramic inks for high-performance inductors and functional devices.

ернативна технологія поверхневого зміцнення внутрішніх поверхонь довгомірних деталей

Barrel survivability is the main indicator of tank guns. In order to ensure the competitiveness of Ukrainian armored vehicles on the foreign arms market, there was a need to ensure the survivability of the barrels of domestic tank guns at the level of the best world samples. Solving the problem of strengthening, restoring and increasing the service life of long-dimension parts is associated with the complexity of preparing and processing the inner surface (bore) along its entire length and eliminating possible residual deformations. The problem of increasing the survivability of tank gun barrels by applying protective coatings is considered. Their brief characteristics and limits of application are given. An alternative technology for surface hardening by electrical contact sintering of powder materials is proposed. This technology makes it possible to apply coatings up to 3 mm thick, with a density approaching that of a compact material and an adhesive strength of up to 220 MPa. Electrocontact sintering refers to impulse technologies and can exclude further mechanical processing of coatings The electrical contact method is the most promising method of strengthening and restoration, as it refers to the methods with the minimum necessary heating, thereby excluding thermal deformation of the parts being strengthened (this technology will allow to eliminate the most characteristic defect of the barrel, such as its swelling and distortion). For cauterization, a specially developed electrode-tool made of a copper alloy, dispersed-reinforced with solid particles, was used, which allows combining in one operation the application of coatings and the finishing treatment by the method of plastic surface deformation to the limit size, surface cleanliness and density.

Retracted: XRD Peak Profile Analysis of SiC Reinforced Al2O3 Ceramic Composite Synthesized by Electrical Resistance Heating and Microwave Sintering: A Comparison

Retracted: XRD Peak Profile Analysis of SiC Reinforced Al₂O₃ Ceramic Composite Synthesized by Electrical Resistance Heating and Microwave Sintering: A Comparison

Retracted: A Comparative Study on Crack-Healing Ability of Al2O3/SiC Structural Ceramic Composites Synthesized by Microwave Sintering and Conventional Electrical Sintering

Retracted: A Comparative Study on Crack-Healing Ability of Al₂O₃/SiC Structural Ceramic Composites Synthesized by Microwave Sintering and Conventional Electrical Sintering