Sintering Technology Research Articles

Simultaneously enhanced electro-mechanical properties of CNTs/Cu-20wt.%Mo composite material by regulating interface with Mo2C nanoparticles

The Mo2C@CNTs/Cu-20wt.%Mo composite materials with outstanding mechanical properties and electrical conductivity were prepared via the combination of mechanical wet-mixing, ball-milling and spark plasma sintering technology. By regulating the morphology and content of Mo2C decorated on CNTs, the Mo2C nanoparticles are anchored on CNTs and well bonded with the matrix, resulting the good interfacial bonding in the composite material. The Cu-20wt.%Mo composite material reinforced by 0.2wt.%Mo2C@CNTs exhibits a yield strength of 342.19 MPa and an ultimate tensile strength of 390.37 MPa, which are respectively increased by 23.13 % and 20.34 % as compared to the Cu-20wt.%Mo. Besides, the electrical conductivity of the 0.2wt.%Mo2C@CNTs/Cu-20wt.%Mo composite material is also improved by 6.89 %. Furthermore, the strengthening effect of Mo2C@CNTs/Cu-20wt.%Mo composite material can be attributed to the contribution of Mo2C nanoparticles, which not only enhance the CNTs load transfer strengthening but also promote the dislocation strengthening and Orowan strengthening.

Study on Sintering Technology of Manganese Ore Fines Strengthened by Pellet-Sintering Process

Study on Sintering Technology of Manganese Ore Fines Strengthened by Pellet-Sintering Process

Investigation of the Bonding Mechanism of Al Powder Particles through Pulse Current Sintering Technology

Compared with traditional powder metallurgy, pulse current sintering is an advanced powder-forming technology, but its bonding mechanism is still an open topic for debate. In this paper, pulse current sintering is used as the connection technology and millimeter-sized Al particles are used as the research object. In the whole sintering process, no pressure was loaded; the function of the pulse current was the only source of heat with which to achieve the bonding of Al particles. The bonding mechanism of pulse current sintering was investigated from the perspective of material connection behavior. The results show that the pulse current density of the particle surface reaches 3.48 × 105 A/m2 instantly, while the current density of the particle center is only 8187 A/m2 at the initial stage, which is the main difference between pulse current sintering and traditional powder metallurgy sintering. With the densification process, the current density and temperature distribution in the contact region as well as the center of Al particles contact region tend to be more consistent. Finally, dense interfacial bonding was obtained, and the contact region of Al particles also demonstrated a high hardness value of 0.6385 GPa and yield strength value of 212.83 MPa. The whole process can be considered as a comprehensive action of melting (evaporation), diffusion, and plastic deformation. Based on the above results, a new technology, named high-frequency pulse current sintering, was proposed.

Laser-Induced Graphene/h-BN Laminated Structure to Enhance the Self-Lubricating Property of Si3N4 Composite Ceramic

Incorporating graphene as ceramic additives can significantly enhance both the toughness and self-lubricating characteristics of ceramic matrices. However, due to the difficult dispersion and easy agglomeration of graphene, the preparation process of composite ceramics still faces many problems. In this study, a laminated laser-induced reduced graphene oxide/hexagonal boron nitride (L-rGO/h-BN) was introduced as an additive into a silicon nitride matrix, then a silicon nitride/reduced graphene oxide/hexagonal boron nitride (Si3N4/L-rGO/h-BN) ceramic composite was successfully synthesized using Spark Plasma Sintering technology. This approach led to enhancements in both the mechanical and self-lubricating properties of silicon nitride ceramics. This is due to the good monodispersity of the incorporating graphene in the silicon nitride matrix. The flexural strength and fracture toughness of the ceramic composite experienced notable increases of 30.4% and 34.4%, respectively. Tribological experiments demonstrate a significant enhancement in the self-lubricating performance of ceramic composites upon the incorporation of L-rGO/h-BN. The coefficient of friction and wear spot diameter experienced reductions of 26.6% and 21%, respectively. These improvements extend the potential industrial applications of Si3N4/L-rGO/h-BN ceramic composites. Throughout the friction process, the evenly exposed rGO and h-BN demonstrate an effective self-lubricating effect on the wear surface. This research paves the way for a novel approach to fabricating high-performance self-lubricating structural ceramics.

Aggregation-Growth and Densification Behavior of Titanium Particles in Molten Mg-MgCl2 System.

In this work, the preparation of titanium sponge by magnesium thermal method is regarded as the liquid-phase sintering process of titanium, and powder-metallurgy sintering technology is utilized to simulate the aggregation-growth and densification behavior of titanium particles in a high-temperature liquid medium (the molten Mg-MgCl2 system). It was found that compared with MgCl2, Mg has better high-temperature wettability and reduction effect, which promotes titanium particles to form a sponge titanium skeleton at lower temperature. The aggregation degree of titanium particles and the densification degree of a sponge titanium skeleton can be improved by increasing the temperature and the relative content of Mg in the melting medium. The kinetics study shows that with the increase in temperature, the porosity of the titanium particle aggregates and the sponge titanium skeleton decreases, and their density growth rate increases. With the extension of time, the aggregation degree of titanium particles and the densification degree of sponge titanium gradually increase. This work provides a theoretical reference for controlling the density of titanium sponge in industry.

Fabrication, microstructure, and properties of Dy‐doped (Y1−xDyx)3Si2C2 ceramics fabricated by in situ reactive spark plasma sintering

AbstractDysprosium (Dy)‐doped (Y1−xDyx)3Si2C2 (x = 0, 0.1, 0.3, 0.5) solid solution ceramics were successfully fabricated using an in situ reaction spark plasma sintering technology, for the first time. The effect of various Dy doping contents (x) on the microstructure, mechanical, and thermal properties of (Y1−xDyx)3Si2C2 ceramics was investigated. The (0 2 0) crystal plane spacing of (Y0.5Dy0.5)3Si2C2 was 7.813 Å, which was smaller than that of Y3Si2C2, due to the fact that the atomic radius of Dy is smaller than that of Y. The Dy doping facilitated the consolidation of (Y1−xDyx)3Si2C2, thus a highly dense (Y0.5Dy0.5)3Si2C2 ceramic material with a low open porosity of 0.14% was successfully obtained at a relatively low temperature of 1 200°C. As the content of Dy doping (x) increased from 0 to 0.5, the purity of (Y1−xDyx)3Si2C2 ceramics increased from 88.3 to 90.7 wt.%, while the grain size of (Y1−xDyx)3Si2C2 ceramics decreased from 0.59 to 0.46 µm. As a result, the Vickers hardness and thermal conductivity of the (Y0.5Dy0.5)3Si2C2 material was 7.1 GPa and 9.8 W·m−1·K−1, respectively.

Microstructure evolution and oxidation resistance properties of oxide dispersion strengthened FeCrAl alloys at 1100 °C

Oxide dispersion strengthened (ODS) FeCrAl alloys were prepared by mechanical alloying (MA) and spark plasma sintering (SPS) technology. To reveal the high temperature oxidation properties, ODS FeCrAl alloys were exposed to dry air for various times (1h, 4h, 10h, 20h, 45h, 70h, and 100h) at 1100 °C to investigate the microstructure evolution. The results illustrated that a flat and adherent alumina scale was gradually thickened on the alloy substrate with the increase of the oxidation time. In particular, it was observed that large-size reactive element (RE) oxides were inclined to be associated with cavities close to the gas interface and these cavities were progressive evolution to be larger-size pores with longer exposure time, while tiny RE oxides were not dispersed with cavities after 100h oxidation. In addition, α-Al2O3 with a double-scale structure were mainly composed of inner columnar grains and outer equiaxed grains, as well, the growth of α-Al2O3 scales illustrated that the oxidation rate decreased with oxidation reaction proceeding. For one thing, Ti segregation along grain boundaries (GBs) near the gas interface decreased the outward diffusion of the Al ions to weaken the oxidation rate. Furthermore, the gradual coarsening of columnar grains near the alloy substrate implied a longer diffusion path of O atoms, thereby accounting for slower oxidation process. To sum up, ODS FeCrAl alloys with thinner oxide thickness demonstrated the superior oxidation resistance than other materials, which would make it one of the promising candidate structural materials applicated in accident-tolerant fuel (ATF) cladding materials.

Microstructure, dielectric properties and phase transition of Y2O3-doped barium tin titanate ceramics

BaCO3, SnO2 and TiO2 et al were used as crude materials, and Y2O3 was used as dopant, BaSnxTi1-xO3 (BTS) ceramics were prepared by solid-state reaction sintering technology. The results show that the doping of Y element does not change the lattice structure of barium tin titanate obviously, and there is no new phase, however, owing to the Y3+ ion doping, the diffraction peak position is changed as the Y3+ doping amount increasing. Interestingly, Curie temperature of the sample increased from 35 o C (blank sample) to 50 o C (0.05 mol%), and then the Curie temperature moved to low temperature as the doping amount increased continuously, which is related to the doping mechanism of Y3+ ion. After doping Y2O3, the dielectric loss of the samples decreases, especially when the doping amount reaches 0.10 mol%, the specimen shows excellent temperature stability of dielectric loss, making it superior candidates for applications.

3D-printing of Fe–Ni bimetallic particles and their application in removal of arsenic from water

Arsenic is a hazardous element found in water sources, and removing it is crucial for ensuring a safe environment and water quality. Iron-based metal oxides efficiently remove arsenic; however, their small particle sizes make separation from water difficult after arsenic removal. Furthermore, the growing global issue of polymer waste further complicates environmental concerns. Combining three-dimensional (3D) printing and adsorption technology by incorporating nanosized functional materials into supporting polymers offers a potential solution to address both challenges. In this study, we developed a 3D-printed adsorption material through the incorporation of synthesized Fe–Ni bimetallic particles into a supporting polymer using selective laser sintering (SLS) technology. This adsorbent's properties were examined through scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and zeta potential. Furthermore, its performance in removing As(III) and As(V), even at trace levels, was assessed under varied conditions. The 3D-printed adsorbent demonstrated excellent removal of As(III) at pH 6, and As(V) at pH 4, lowering their concentration below 10 μg/L, thereby adhering to the limit established by the World Health Organization (WHO). Both As(III) and As(V) fitted the Freundlich isotherm and pseudo-second-order model, suggesting potential heterogeneous and chemisorption processes. FT-IR indicated that the exchange of the –OH group of Fe–OH with oxyanions of As(III) and As(V) could be the adsorption mechanism. Additionally, thermodynamic evaluation unveiled an endothermic and non-spontaneous adsorption reaction. The 3D-printed adsorbent exhibited excellent reusability across recurring adsorption cycles. The combination of SLS 3D printing with Fe–Ni bimetallic particles produces structures that retain their functionality in removing both arsenic species present in water. This indicates the potential of the 3D-printed adsorbent for effective treatment of arsenic-contaminated water, offering remedies to challenges like handling small particle sizes, mitigating polymer waste, and addressing environmental concerns.

Obtaining ultra-high hardness in spark plasma sintered Ge40As40Se20 bulk glass

In order to overcome the narrow glass-forming compositional range with traditional melt-quenching method, we here performed the mechanical milling and Spark Plasma Sintering technology to fabricate a high Ge content chalcogenide glass, the Ge40As40Se20 glass, which locates edge of the Ge-As-Se glass-forming domain. By using the optimal ball milling time of 50 h and sintering stress of 37.5 MPa, the large size Ge40As40Se20 bulk glasses were obtained, which possesses both a large Vickers hardness of 369 kgf/mm2 and a relative high infrared optical transmission of 43 % (@5 and 9 μm). Moreover, it was found there are pores in the sintered glasses more or less, and the pore size and number significantly affect the transmission, i.e., the optimal Ge40As40Se20 bulk glasses were demonstrated has the smallest and least pores via scanning electron microscope. The combination of mechanical milling and low-temperature sintering methods has been confirmed can be used to improve the glass formability and then obtain the high Ge content component with a potential high hardness glass to break through the limited mechanical property of chalcogenides.

Role of oxygen vacancy on rapid densification and giant dielectric properties of flash sintered Ca2+ and Ta5+ co-doped TiO2 ceramics

(Ca, Ta) co-doped TiO2 ceramics were successfully prepared using flash sintering technology, and the effects of oxygen vacancies on the rapid densification and giant dielectric properties were studied. The results suggest that the maximum volume fraction of oxygen vacancies in flash-sintered samples is approximately 10%. Oxygen vacancies decrease the barrier energy level of atomic diffusion and provide convenient diffusion channels, resulting in rapid densification of the sample within 24 min at 1100 °C. All flash-sintered samples exhibit high relative density, exceeding 95%. Oxygen vacancies promote the electron-pinning defect dipole effect at low temperatures. As the temperature increases, carriers such as oxygen vacancies move to the grain boundary, forming an internal barrier layer capacitance effect. The optical dielectric constant reaches 7.25 × 104, and the dielectric loss drops to 0.09. Oxygen vacancy play an important role in both flash sintering technology and the giant dielectric properties of co-doped TiO2 ceramics.

Ultrahigh average zT realized in polycrystalline SnSe0.95 materials through Sn stabilizing and carrier modulation

The average zT determines the conversion efficiency, and the power factor plays an important role in average zT value. However, the inadequate electrical conductivity of SnSe materials seriously limits its application. Herein, the TaCl5-doped in polycrystalline SnSe0.95 materials synthesized using the melting method and combined with spark plasma sintering technology achieves a zT value of 1.64 at 773 K and a record zTave of 0.62 from 323 K to 773 K. The electrical conductivity increases due to the released electron carrier induced by effective TaCl5 doping. According to the DFT calculation, the energy band of TaCl5-doped samples is narrowed, which can enhance the electron transport. Besides, the Seebeck coefficient is maintained at an elevated level as a result of the incorporation of the heavy element Ta. Due to the significantly enhanced electrical conductivity and maintained high Seebeck coefficient, the power factor reaches to 622 μW·m−1·K−2 at 773 K for the SnSe0.95 + 1.75% (in mass) TaCl5 sample, which is almost 21 times higher than that of the pristine sample. Simultaneously, a high average power factor value of 334 μW·m−1·K−2 for the SnSe0.95 + 1.75% (in mass) TaCl5 sample from 323 to 773 K was obtained. It is surprisingly found that the Ta element plays another important role to improve the stability of SnSe0.95 by forming Ta2Sn3 and removing the low melting point Sn, which usually existed in n-type SnSe samples, resulting in the decreased lattice thermal conductivity. A low lattice thermal conductivity value of 0.24 W·m−1·K−1 was also obtained for the SnSe0.95 + 2.0% (in mass) TaCl5 sample at 773 K due to the multiscale defects. Consequently, the SnSe0.95 + 2.0% (in mass) TaCl5 sample obtains a peak zT value of 1.64 at 773 K and a record zTave of 0.62 from 323 to 773 K, and the theoretically calculated conversion efficiency reaches 11.2%, it can be utilized for power generation and/or cooling at a broad temperature range. This strategy of introducing high-valence halides with heavy element can optimize the thermoelectric performance for other material systems.

Microstructural examination and ballistic testing of field-assisted sintering technology produced Ti-TiB2 functionally graded material composite armour plates

High hardness ceramics are potent in their use for armour applications globally, but intrinsically brittle. This can result in fragmentation damage, as well as low multi hit capacity. In this work, alternative 250 mm diameter Ti-6Al-4 V discs were produced using field-assisted sintering technology (FAST) with and without stepped functional grading using low wt.% TiB2 concentrations, respectively, to investigate their microstructure and ballistic performance. The in situ generation of a significant quantity of high strength, ceramic TiB needles was confirmed for the samples, and the plates were ballistically tested to attain V50 values. In addition to a microstructural examination. The ballistic results indicated a superior behavior to the monolithic titanium alloy plates without TiB2 additions.

Temperature-dependent dielectric properties of the Korean lunar simulant and ilmenite: Lunar microwave processing potential

There is increasing interest in the potential application of microwave sintering technology in the construction of infrastructure on the Moon. This study aimed to characterize the dielectric properties of in situ lunar materials; this information is critical for an understanding of the interaction of these materials with microwave and in the application of microwave sintering technology. Dielectric properties including the real and imaginary permittivity, dielectric loss tangent, penetration depth, and electrical conductivity of Korean Lunar Simulant (KLS-1) and ilmenite (an abundant lunar mineral) were investigated at microwave frequencies as a function of temperature. X-ray dispersion (XRD) analyses confirmed that the lattice expansion of minerals with increasing temperature was consistent with an increasing trend in permittivity. The dielectric loss tangent of ilmenite was 2–36 times higher than that of KLS-1, depending on temperature, indicating that ilmenite has greater ability to absorb microwave energy, converting it to heat. Ilmenite demonstrated rapid heating to 1000°C within a few minutes on exposure to 1 kW microwave (2.45 GHz) irradiation. This study provides important information relevant to the development of microwave technology for future lunar applications.

High performance Cu sintering joint for power devices enabled by in-situ generation of Cu particles with multi-level hierarchical structures

Copper (Cu) particle sintering is widely regarded as one of the most ideal interconnect technologies for wide band gap semiconductors owing to its potential for low-temperature curing while withstanding a higher working temperature. Nevertheless, the strict requirements for sintering conditions and high costs limit the widespread application of Cu sintering technology. In this paper, a simple vehicle was introduced into Cu paste formulation to achieve an effective sinter bonding even using commercially available sub-micron or even micrometer Cu particles (C-Cu particles) with the in-situ generation of composite Cu particles. This innovative vehicle comprises Cu salt, a combination of capping agents and reducing agents. The addition of the hybrid capping agent binds Cu atoms to the surface of the C-Cu particles and allows the generated Cu particles (G-Cu particles) produced from the vehicle to grow on their surface, resulting in the in-situ generation of composite Cu particles. Based on the in-situ generated composite Cu particles, sintering experiments were conducted at designated temperatures (200 °C, 225 °C, 250 °C) for various durations (3 min, 5 min, 10 min) in a N2 atmosphere under different pressures (10 MPa, 15 MPa, 20 MPa). A reliable Cu sintered joint with a high shear strength of 41.3 MPa can be achieved at a low temperature (200 °C) using 500 nm C-Cu particles. Moreover, the joints sintered with large size (>3 μm) particles at 250 °C could also reach 43.3 MPa. The in-situ generated composite Cu particles accomplish the transformation of low-energy interfaces of C-Cu/C-Cu to high-energy interfaces of G-Cu/G-Cu, which in turn facilitates low-temperature sintered connection of C-Cu particles and reliable sintered joints formed of large size C-Cu particles. These findings improve the feasibility of Cu sinter bonding in practical applications.

Mechanical properties and thermal shock resistance of TiB2‒B4C composite ceramic tool materials at microscopic scale

AbstractA finite model incorporating microstructure was developed to investigate the thermal shock resistance of TiB2‒B4C composite ceramic cutting tool materials. Numerical simulations were conducted to analyze changes in the transient temperature field and thermal stress field during the thermal shock process. TiB2‒B4C composite ceramic tool materials were fabricated using discharge plasma sintering technology. With different B4C contents, different sintering temperatures and holding times as study variables, optimization of the sintering process parameters and ceramic material components was achieved through testing the mechanical and microscopic morphology of the ceramics. Thermal shock water quenching experiments were performed, and the strength‐decay method was employed to assess the thermal shock resistance of TiB2‒B4C ceramics. The findings indicate that the optimal sintering conditions are temperature of 1700°C and holding time of 5 min. The TiB2‒B4C ceramic material containing 20 vol% B4C exhibits superior comprehensive mechanical properties and thermal shock resistance, and its relative density, fracture toughness, hardness, and flexural strength were 99.3%, 6.8 MPa m1/2, 22.8 GPa, and 598 MPa, respectively. The critical thermal shock temperature difference falls within the range of 400°C‒500°C.

Briefing: Selective laser sintering technology to print walnut shell/phenolic resin new biomass-based porous electrode

In this paper, porous carbon electrodes were prepared by using walnut shell and phenolic resin as matrix materials, combined with selective laser sintering (SLS) technology and carbonization process. The effects of different ratios and temperatures on the macroscopic morphology, graphitization degree, electrical conductivity and pore structure of the carbonized parts were investigated. The results show that the lower proportion of walnut shell and the higher carbonization temperature increase the degree of graphitization. High temperature has a significant effect on the conductivity. The conductivity at 1000 °C is 7.5197 S·cm−1, which is 752 % higher than that at 600 °C, while the conductivity at 30 % walnut shell content is only 75.4 % higher than that at 50 %. This study provides a new reference for the preparation of carbon electrodes with complex shape and structure by biomass consumables.

Immobilization of simulated An4+ in radioactive sludge via microwave sintering: Mechanistic and performance

In this study, we investigate radioactive sludge containing An4+ ions via simulation. Ce4+ is employed as a surrogate isotope for An4+ ions, and silicate glass particles are incorporated as stabilizing agents. Continuous microwave sintering technology is adopted to sinter the simulated radioactive sludge with varying CeO2 contents co-doped with 60 wt.% glass particles at temperatures of 1100 °C, 1200 °C, and 1300 °C to achieve sample vitrification. The phase evolution, microstructure, morphology, chemical stability, sample density, and porosity of the sintered specimens are analyzed comprehensively. The results indicate distinct maximum solubility limits at different sintering temperatures: 5 wt.%, 6 wt.%, and 13 wt.% for 1100 °C, 1200 °C, and 1300 °C respectively. Under these conditions, Ce is immobilized within the glass network structure. Notably, the Ce3+/Ce4+ ratio in the 1300 °C-Ce10 specimen reaches 2.04, and the combined percentage of Q3 and Q4 glass structural units exceeds 50 %. Beyond the optimal solubility limit, tetragonal CeO2 crystals are formed on the glass sample surface. The normalized leaching rate of Ce from the samples remains at 5.0 × 10−6 g m−2 d−1. Additionally, the sintered samples indicate densities ranging from 2.65 to 3.01 g/cm3 and porosities from 0.18 % to 1.8 %. This study introduces a novel perspective for addressing radioactive sludge treatment.

Combinatorial Benders decomposition for single machine scheduling in additive manufacturing with two-dimensional packing constraints

This paper addresses a single-machine scheduling problem in additive manufacturing (AM). We focus on the direct metal laser sintering (DMLS) technology of an AM process, where parts can be produced simultaneously in a batch. In this problem, we consider simultaneously the assignment of parts to batches and the packing of parts onto two-dimensional surfaces of the build chamber to minimize the makespan objective. To solve this problem, a mixed integer linear programming model is formulated, and an approximation algorithm is proposed, followed by an exact algorithm based on combinatorial Benders decomposition method with various Benders cuts and acceleration strategies (Algorithm CBD). Finally, we conduct a comprehensive computational study to verify the efficiency of our proposed Algorithm CBD. The computational results show that our proposed Algorithm CBD can effectively solve the test instances with different sizes.

Influence of grain size on the electrochemical performance of Li7‑3xLa3Zr2AlxO12 solid electrolyte

Contemporary Li‐ion batteries are facing substantial challenges like safety and limited energy density. The development of all‐solid‐state battery cells mitigates safety hazards and allows the use of Li‐metal anodes increasing energy density. Garnet‐type solid electrolytes can be vital to achieving an all‐solid‐state cell and an understanding of the influence of its microstructure on the electrochemical performance is crucial for material and cell design. In this work the influence of grain size on the Li‐ion conductivity of Li7‐3xLa3Zr2AlxO12 (x = 0.22) is presented. The synthesis and processing procedure allows changing the ceramic grain size, while maintaining the same synthesis parameters, eliminating influences of the synthesis on grain boundary composition. Field assisted sintering technology is a powerful method to obtain dense, fine‐grained ceramics with an optimal grain size of 2‐3 µm, where the conductivity is double that of the counterpart (0.7 µm). A total Li‐ion conductivity of 0.43 mS cm‑1 and an activation energy of 0.36 eV were achieved. The oxide‐based all‐solid‐state battery cell combining the garnet‐type electrolyte, a Li‐metal anode and a thin‐film LiCoO2 cathode was assembled and cycled at room temperature for 90 hours. This represents a proof of concept, for the application of oxide‐based electrolytes at ambient temperatures.