Sintering Method Research Articles

Investigation of the effect of SiC additions on the high-temperature oxidation behavior of combustion-synthesized MoSi2

In this study, the effect of the weight percentage of SiC on the high-temperature oxidation behavior of MoSi2-Xwt. % SiC composite (X = 0, 10, 20, 30) was studied. The composites were produced from elemental powder compacts of molybdenum, silicon and carbon (where applicable) by combustion synthesis and subsequent sintering method. Additionally, a series of each synthesized powder was mixed with 5 wt% bentonite and consequently sintered. The sintered specimens were then subjected to oxidation at 1100 °C. Microstructure and phase analysis of the oxidized samples were investigated by X-ray diffraction (XRD) and a scanning electron microscope equipped with energy-dispersive spectroscopy (SEM-EDS). Surface and cross-sectional examinations of the samples after oxidation revealed that all samples possessed good oxidation resistance in the way that no spallation was observed between the oxide layer and the substrate. The highest oxidation resistance at 1100 °C was observed in the sample with MoSi2 (without SiC) containing bentonite (AB0). This sample showed only 0.75% weight gain after 50 h of oxidation, which is probably due to the effective role of bentonite in decreasing the open porosities, and further reducing the oxygen penetration path during the oxidation process.

Microstructure, Mechanical Property and Thermal Conductivity of Porous TiCO Ceramic Fabricated by In Situ Carbothermal Reduction of Phenolic Resin and Titania.

The porous TiCO ceramic was synthesized through a one-step sintering method, utilizing phenolic resin, TiO2 powder, and KCl foaming agent as raw materials. Ni(NO3)2·6H2O was incorporated as a catalyst to facilitate the carbothermal reaction between the pyrolytic carbon and TiO2 powder. The influence of Ni(NO3)2·6H2O catalyst content (0, 5, 10 wt.% of the TiO2 powder) on the microstructure, compressive strength, and thermal conductivity of the resultant porous TiCO ceramic was examined. X-ray diffraction and X-ray photoelectron spectroscopy results confirmed the formation of TiC and TiO in all samples, with an increase in the peak of TiC and a decrease in that of TiO as the Ni(NO3)2·6H2O content increased from 0% to 10%. Scanning electron microscopy results demonstrated a morphological change in the pore wall, transforming from a honeycomb-like porous structure composed of well-dispersed carbon and TiC-TiO particles to rod-shaped TiC whiskers, interconnected with each other as the catalyst content increased from 0% to 10%. Mercury intrusion porosimetry results proved a dual modal pore-size distribution of the samples, comprising nano-scale pores and micro-scale pores. The micro-scale pore size of the samples minorly changed, while the nano-scale pore size escalated from 52 nm to 138 nm as the catalyst content increased from 0 to 10%. The morphology of the pore wall and nano-scale pore size primarily influenced the compressive strength and thermal conductivity of the samples by affecting the load-bearing capability and solid heat-transfer conduction path, respectively.

Effect of carbon capture on desulfurization gypsum/carbide slag phase-change composites for waste removal and renewable energy storage

To promote the recycling of industrial waste and produce ultra-low carbon energy storage materials with low-energy consumption this work innovatively proposes to capture carbon dioxide using the mixture made of 70 wt% desulphurization gypsum and 30 wt% carbide slag via a aqueous solution method, and the carbonized mixture used as skeleton material to prepare phase-change composites via cold pression & hot sintering method, and then thermal property, mechanical property and chemical compatibility are investigated. Results show that the carbon capture rate of the skeleton material can reach up to 10.6% at room temperature and can encapsulate the PCM (NaNO3) intact. C-PCC3 has good thermal stability and can undergo 2058 heating/cooling cycles. Compared with the PCC3 (absent carbon capture), the C-PCC3 exhibited a notable enhancement in thermal conductivity by 2.7%. Nevertheless, there was a decrease in mechanical strength from 134.1 MPa to 44.9 MPa, and a reduction in thermal energy storage density from 483.2 J/g to 459.3 J/g. Based on both macroscopic properties and microscopic morphology, the phase change composite materials fabricated in this work exhibit excellent comprehensive property.

Biocompatibility study of Fe-doped zirconia-toughened alumina ceramic for artificial joints

Fe-doped zirconia toughened alumina (Fe: ZTA) ceramic is a promising material for artificial joint implants because of high density, good mechanical properties and excellent wear resistance. To evaluate its use in biological implants, Fe: ZTA ceramics with different Fe contents (0–5 wt.%) were fabricated using the fast hot pressed sintering method, and the biocompatibility of Fe: ZTA ceramics and the biotoxicity of wear debris from Fe: ZTA were systematically studied. The additive Fe element mainly exists in the form of FeAl2O4. The addition of Fe results in the increase of surface hydrophobicity and the decrease of surface energy and polar component, improving the protein absorption on Fe: ZTA surface. According to the culture results with osteoblasts and macrophages, Fe doping can increase the osteoblast activity and does not cause significant macrophage activation on the surface of Fe: ZTA ceramics. Particularly, the 1.5 wt.% Fe: ZTA ceramic can significantly improve the cytocompatibility of osteoblasts and reduce the inflammatory reaction. On this basis, 1.5 wt.% Fe: ZTA ceramic with the best biocompatibility was used to prepare the wear debris, and the biotoxicity of wear debris was further studied. The result confirms that wear debris of Fe: ZTA ceramic (50–1000 μg/ml) does not cause the significant decrease in osteoblast activity and has no significant effect on the osteoblast morphology, without distinct cytotoxicity. The wear debris of Fe: ZTA (≤ 200 μg/ml) will not cause significant inflammatory response. This study can provide guidance for the application of Fe: ZTA ceramic in biological implants.

Mechanism of the impact of Ca–Ge co-substitution on the FMR linewidth in BiV-YIG ferrites

Yttrium Iron Garnet (YIG) ferrites, characterized by their superior magnetic and dielectric attributes, are instrumental in advancing the development of microwave devices, particularly in enhancing high-frequency performance, integration, and miniaturization. This paper synthesizes YIG ferrite materials with the composition Bi0.6Y1.4-xCa1+xFe4.5-xV0.5GexO12 (x = 0.10 to 0.50, incrementing by 0.10) through the solid-state sintering method. It delves deeply into the mechanism by which Ca2+-Ge4+ ions substitution regulates the magnetic properties of BiV-YIG. The microstructural and magnetic properties of the samples were systematically tested and analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), vibrating sample magnetometry (VSM), and TE106 perturbation method. At a substitution content of x = 0.50, the substitution of Ge4+ ions for the Fe3+ ions at the d-site transforms the material from ferrimagnetic to paramagnetic, and the saturation magnetization of the sample drops to 132.74 G. By calculating the ferromagnetic resonance (FMR) linewidth using the law of approach to saturation, the study elucidates the negative impact of low saturation magnetization on FMR linewidth. The mechanisms proposed in this paper provide theoretical and experimental bases for reducing the FMR linewidth of high dielectric constant Bi-substituted YIG, paving the way for developing high-dielectric, low-loss YIG ferrite materials for microwave devices.

Mechanical properties and high-pressure behavior of high entropy carbide (Mo, Nb, Ta, V, W)C

High-entropy carbides (HECs) often exhibit superior mechanical properties compared to single-component carbides. In this work, the (Mo0.2Nb0.2Ta0.2V0.2W0.2)C0.9 (named as Mo-HEC) was synthesized using the spark plasma sintering (SPS) method. The mechanical properties of Mo-HEC were evaluated using Vickers hardness and nanoindentation tests. The results indicate that Mo-HEC exhibits relatively high toughness, with hardness value surpassing the average hardness of constituent monocarbides. Nanoindentation tests on grains with different orientations revealed an isotropic mechanical behavior of Mo-HEC. Furthermore, the structural stability of Mo-HEC under extreme compression was explored by in situ high-pressure X-ray diffraction. Its cubic structure can be retained up to 58 GPa, and a bulk modulus of 334 GPa was obtained, which is among the highest reported values for HECs. The favorable mechanical properties, structural stability, and high bulk modulus suggest the significant potential of Mo-HEC for applications under extreme conditions.

Preparation of the close cross-section component of NiAl-based alloy by a novel combined sintering method

In this study, to overcome the bottleneck of forming NiAl for aerospace applications, a novel combined sintering method based on hot-press sintering, which divides the components into various parts and compacts them gradually, is proposed and studied. Two typical close cross-sectional components (tube-like components and conical tube components with flanges), which are highly demanding and more challenging to obtain for NiAl intermetallic, were prepared and analyzed in detail. Based on these results, both prepared components were fully dense. In addition, as shown by the bending tests, the interfacial strength is between the strengths of the base alloys on the two sides, which confirms the reliable bonding ability achieved by this method. For the conical tube component with flange, the ultimate tensile strength of the combined-sintered part in 1000 ℃ is 406.7±3.2 MPa, and the ultimate strength of the pre-sintered part is 368.6±2.7 MPa, which are 39% and 26% higher than the strength of blade-like component prepared by casting and hot isostatic pressing (292 MPa). The proposed method discussed in our study can overcome the uneven density defects in HPS and achieve collaborative control of both the shape and performance when preparing a high height-to-thickness ratio or a complex-shaped close cross-section component.

Microstructure and mechanical properties of high relative density Ti-48Al-1Fe alloy using irregular blend powder

Conventional pressing and sintering methods provide difficulties in achieving high density for PM TiAl alloys. The Ti-48Al-1Fe alloy was prepared via vacuum pressure-less sintering, and the microstructure evolution and mechanical properties during the sintering densification process of the mixed powder system were investigated. The results shows that the density of the mixed powder reached 98.3 ± 0.14% after pressure-less sintering for 3 hours under high vacuum conditions at 1300°C. The microstructure of the as-sintered alloy is a fine duplex structure composed of α2/γ lamellar colonies and the composite structure. The ultimate tensile strength (UTS) of the as-sintered alloy at room temperature is 315 MPa. The density of the as-sintered alloy reach more than 99.9% after non-capsule hot isostatic pressing (HIP). The as-HIPed alloy exhibits an UTS of 332 MPa at room temperature. At high temperatures, it maintains high strength, with an UTS of 408 MPa and yield strength of 386 MPa at 900°C, which is comparable to that of forged TiAl alloy. Furthermore, the elongation of the sample at 900°C is 20.0%. This process offers a novel method for sintering PM TiAl with high density and mechanical properties at a low cost and near-net shape.

3D Printing of a Tidal Turbine Blade Using Two Methods of SLS and FFF of a Reinforced PA12 Composite: A Comparative Study

This study scrutinizes the thermomechanical dynamics of 3D-printed hydrofoil blades utilizing a carbon and glass bead-reinforced thermoplastic polymer. Comparative analyses underscore the pivotal role of polymer reinforcement in augmenting mechanical strength and mitigating deformation and residual stress. The investigation elucidates the expeditious and cost-efficient manufacturing potential of low-cost Fused Filament Fabrication (FFF) printers for small-scale blades, revealing exemplary mechanical performance with nominal deflection and warping in the PA12-CB/GB printed blade. A comprehensive juxtaposition between Selective Laser Sintering (SLS) and FFF printing methods favors SLS due to its isotropic properties, notwithstanding remediable warping. Emphasizing the rigorous marine environment, the study cautions against the anisotropic properties of FFF-printed blades, despite their low mechanical warping. These discernments contribute to hydrofoil design optimization through numerical analysis, shedding light on additive manufacturing’s potential for small blades in renewable energy, while underscoring the imperative for further research to advance these techniques.

Influence of Ti2SnC content on arc erosion resistance in Ag–Ti2SnC composites

Abstract In this work, an Ag–Ti2SnC composite was fabricated by the hot-pressing sintering method, and the erosion behavior of Ag–Ti2SnC with volume percentages of 10–40% was studied at a load voltage of 10 kV. The arc life and breakdown current were observed at about 31–36 ms and 39 A, respectively. The cathode spot traveled the fastest on the surface of the Ag–40 vol% Ti2SnC composite. Due to emission center model, the temperature of the minor protrusions on the cathode surface increased, resulting in Ag ions, Ti ions, and Sn ions being generated. Combining with the ionized oxygen, Ag2O, AgO, TiO2, and SnO2 were formed on the eroded Ag–Ti2SnC surface after arc erosion. The research results will broaden the application range of Ag–Ti2SnC electrical contact material and enrich the arc erosion mechanism.

Potential plasma facing materials: A case study on CeB6 particulate reinforced W–1Ni matrix composites produced via different sintering techniques

Tungsten (W) is the most promising material for future plasma-facing materials. Its alloys or composites reinforced with various compounds have been studied to improve the irradiation resistance of W. This study aimed to investigate the effect of boron-containing reinforcement in the W matrix against He+ ion irradiation. Cerium hexaboride (CeB6) particulates, which have high neutron shielding properties, were incorporated into the W matrix pre-alloyed by 1 wt% Ni (W1Ni). CeB6 powders were home-made and prepared from CeO2/Mg/B2O3 powder blends via mechanochemical synthesis and purification steps. 1, 5, and 10 wt% CeB6 powders were added to pre-alloyed W1Ni by mechanical alloying, and then they were consolidated by using pressureless sintering (PS, 1400 °C, 1 h) and spark plasma sintering (SPS, 1410 °C, 1 min) techniques. CeB6 particle-reinforced W1Ni composites contained different amounts of reinforcements were prepared by two different sintering methods and were compared with respect to their compositional, microstructural, and microhardness properties and wear and irradiation behaviors. Based on the results, increasing the CeB6 reinforcement amount in the composite triggered the formation of the W2B phase, especially in the W1Ni–10CeB6 composite after both sintering methods. The mechanical and irradiation properties were enhanced more by increasing the CeB6 amount in the case of using the SPS method. When compared to other sintered samples, the SPS'ed W1Ni–10CeB6 composite has the lowest specific wear rate of ∼4 × 10−7 mm3/Nm and the maximum hardness value of ∼21 GPa. According to surface deformation, the W1Ni–5CeB6 composite exhibited comparatively higher resistance to He+ ion irradiation.

Investigation of the Effect of High-Frequency Induction Sintering on Phase Structure and Microstructure of SiC Reinforced Aluminum Matrix Composites

In this study, SiC-reinforced aluminum matrix composites were powder metallurgically (PM) prepared and sintered using high-frequency induction system (HFIS). The samples with different ratios of SiC (wt.%10, 20 and 40) added to the aluminum matrix were sintered at 660, 800, and 1000 °C. In addition, Al/SiC composites were compared by sintering with the conventional sintering (CS) method under similar sintering conditions. The heating rate for the sintering process using HFIS was 500 °C/min, while the CS method used a heating rate of 10 °C/min. The effect of the temperature and SiC ratio on the density, hardness, phase structure, and microstructure of composites was investigated. The optimum sintering temperature was determined according to the SiC additive amount. When 10%, 20%, and 40% SiC by weight were added to the aluminum matrix in the sintering process with HFIS, the required sintering temperatures were determined as 660, 800, and 1000 °C, respectively. While new phases were not formed as a result of short-term HFIS sintering, a high-temperature Al4C3 phase was detected in CS sintering. HFIS sintered Al/SiC composite samples were obtained in Al and SiC phases with high density and hardness ranging from 43-118 HV. In the high-temperature sintering process with HFIS, the formation of Al4C3 was prevented and its physical and mechanical properties were improved.

Removal of phosphorus from water bodies using high-performance ceramsite prepared from solid wastes

This study successfully prepared a high-performance ceramsite for phosphorus adsorption using the sintering method, incorporating regolith granite sand-washing sludge (RGSWS) and phosphate tailings as raw materials. The optimal conditions for ceramsite preparation were determined as a ratio of RGSWS to phosphate tailings at 6:4, and sintering at 900 °C for 30 min. The impacts of various factors, such as the prepared ceramsite dosage, different initial phosphorus concentrations, temperature, pH, and co-existing ions were explored, and the reusability and safety of the ceramsite were also investigated. The results show that the ceramsite has a high adsorption capacity for phosphorus (20.40 mg/g) at pH 7 with broad applicability in the pH range of 3–11 and good selective adsorption in the presence of coexisting ions. Additionally, the application of ceramsite does not cause secondary pollution, and the ceramsite still maintains a high removal rate after being reused five times. XRD, FT-IR, XPS, and SEM-EDS analysis showed that chemical precipitation, surface complexation, and electrostatic attraction were involved in the adsorption process. It can be well described by the pseudo-second-order kinetic model and the Langmuir model, and the phosphorus adsorption by ceramsite was a spontaneous endothermic reaction process with increasing chaos. This research presents an effective solution for phosphorus removal from water bodies and offers a sustainable approach toward solid waste utilization.

Function optimization of ceramic firing process and reduction of energy consumption based on CFD simulation

Microwave sintering, as an efficient and energy-saving advanced sintering method, has advantages that traditional sintering methods cannot match, such as promoting ion diffusion and refining grains. This paper uses microwave heating equipment and solid-phase reaction method combined with microwave sintering technology to prepare ceramics. The treatment process of powders and the influence of microwave sintering parameters on the reduction of energy consumption in the ceramic firing process were studied, and the microwave sintering process was optimized. This article also uses computational fluid dynamics (CFD) as a tool to establish a numerical model of hydrodynamic sedimentation based on the Euler multiphase flow model, and it uses the established numerical model to conduct engineering scale research on the classification treatment process of processing waste. Finally, this article elaborates on the process of multi-process planning and optimizes relevant process parameters. This article builds on previous research by employing a BP neural network (BPNN) to determine the correlations between the many variables involved in the production of functional ceramics and their respective quality metrics. The experimental findings demonstrate the efficacy of the proposed methodology in performing intelligent tasks like process decision-making and optimizing process parameters.

Tunable yellow and orange emission of Ce, Eu doped multilayered YSZ/YAG ceramics

Eu3+ and Ce3+ doped YSZ/YAG multilayered luminescent ceramics were consolidated by the Spark Plasma Sintering (SPS) method. The optimal modes were explored during the SPS process for functionally graded ceramics (FGCs) structure fabrication. The introduction of rare-earth (RE) oxides into FGCs with different concentration leads to a shift in the temperature range of intense shrinkage to lower temperatures from 1280 °C to 1100–1190 °C and a decrease in the relative shrinkage during the SPS process by 3–6%. Morphological, optical and luminescent properties have been investigated in detail for fabricated YSZ/YAG ceramics with different arrangement of the layers. The nature of luminescent centers in FGCs was studied using time-resolved cathodoluminescent and steady-state photoluminescent (PL) spectroscopy. The PL efficiency of YSZ/YAG ceramics were analyzed and optimal compositions of the FGCs layers were determined. The YSZ/YAG novel functional multilayered ceramics could be promising candidate for light-emitting devices application.

Analysis of initial stage of liquid-phase sintering by combined multi-phase-field/discrete-element method

A combined multi-phase-field/discrete-element method in two dimensions is applied to the liquid phase sintering process of blended elemental powders. The boundary migration, diffusion of elements, and phase transformation between two dissimilar particles are calculated using a multi-phase-field method for sintering based on Gibbs energy functions. The sintering shrinkage is computed with the discrete-element method taking account of the neck size and sintering force, which are obtained from a multi-phase-field simulation. In this study, a pair or small cluster consisting of two elemental powders in a binary eutectic alloy is used as a model system. First, the formation of a liquid phase around the contact area between two dissimilar particles above the eutectic temperature of the system, and the motions of the particles due to grain boundary sliding along the liquid films are confirmed. Second, an Sn–Bi system is selected as the real eutectic system, and the sintering behavior of powder compacts with various mixing ratios of Sn and Bi particles is demonstrated. Finally, transient liquid-phase sintering of Sn–Bi system is simulated, that is, the generation and extinction of the liquid phase due to interdiffusion between Sn and Bi particles are calculated.

Preparation and characterization of SiO2–Al2O3–MgO–CaO–based ceramic foams mainly from Ca–Mg–rich molybdenum tailings

Molybdenum tailings (MTs) and kaolinite were used as the main materials in the fabrication ceramic foams (CFs) via the high-temperature sintering method, with the addition of SiC as a foaming agent. The effects of MT content on the basic physical properties, pore structure, and chemical characterization were investigated. Results showed that MT enhanced the foaming capability. When the MT content was 60% and the sintering temperature was 1170 °C, the optimum CFs obtained demonstrated bulk density, porosity, water absorption, and compressive strength of 0.55 g/cm3, 77.3%, 6.94%, and 6.74 MPa, respectively, and the pore structure was relatively homogeneous with an average pore diameter of 0.67 mm. The results revealed that SiO2–-Al2O3–-MgO–-CaO system CFs can be prepared from Ca–Mg-rich MT, which provided a feasible strategy for value-added utilization of Ca–Mg-rich MT.

Advancing energy storage capabilities in 0.7BNST(1-x)-0.3BLMNx lead-free dielectric ceramic materials

Lead-free ferroelectric ceramics with a composition of 0.7(Bi0.5Na0.5)0.7Sr0.3Ti(1-x)O3-0.3Ba0.94La0.04(Mg1/3Nb2/3)xO3 (abbreviated as 0.7BNST(1-x)-0.3BL(MN)x, 0 ≤ x ≤ 0.12) were prepared using solid-phase sintering method, involving co-substituting at A and B sites. High recoverable energy density (Wrec) of 3.54 J/cm3 and energy efficiency (η) 85.49% are achieved at an electric field of 270 kV/cm. Furthermore, these ceramics exhibited excellent temperature and cycle stability at 120 kV/cm (within 25 °C–150 °C, Wrec fluctuation range <14 %; under 1∼106 cycles, the Wrec fluctuation range <5 %). In terms of dielectric performance, they exhibited a high dielectric constant (εr∼4540), an extremely low dielectric loss tanδ of <0.04 (30 °C–300 °C), and good temperature stability with Δε/ε150 °C ≤ ±15 % (−19.5 °C–233.4 °C). During the charging and discharging process, these ceramics demonstrated a high energy density (Wd) of 1.2 J/cm3, a power density (PD) of 61.7 MW/cm3, and an extremely short discharge time (t0.9) of approximately ∼0.11 μs＀ This study has improved the dielectric energy storage performance of BNT-based lead-free piezoelectric ceramics, making them suitable for use in pulse power devices.

Densification of hydroxyapatite through cold sintering process: Role of liquid phase chemistry and physical characteristic of HA powder

Hydroxyapatite is a well-known bioactive material widely employed in bone regeneration applications. Densifying hydroxyapatite at the nanoscale remains challenging with conventional sintering methods. This investigation focuses on the densification of commercially available nano-hydroxyapatite powders through the cold sintering process, utilizing water, acetic acid, and phosphoric acid solutions as transient liquids under 360 MPa pressure at 200 °C. The study systematically examines the influence of physical parameters of hydroxyapatite powder, liquid nature, and ionic concentrations of acid solutions on densification and microstructural characteristics. The relative density of consolidated samples varied with respect to the ionic concentration of the acid solution. Notably, a maximum relative density of 90% has been achieved for hydroxyapatite cold sintered using 2 M phosphoric acid solution without changing the original phase of hydroxyapatite. Overall, this study offers valuable insights into the impact of liquid chemistry on the densification of hydroxyapatite using the cold sintering technique.

Effect of Spark Plasma Sintering Temperature on the Microstructure and Thermophysical Properties of High-Silicon–Aluminum Composites

Spark plasma sintering is a process of rapid, low-temperature, and high-density sintering. Moreover, traditional sintering methods can solve the problems of large grain sizes and low densities. The sintering temperature plays a crucial role in influencing the physical properties of high-silicon–aluminum (Si-Al) composites. This work investigated the impact of temperature on the microstructure, interface, and physical properties of high-Si-Al composites by spark plasma sintering. The results demonstrate that when the powder was processed by ball milling at a sintering temperature of 565 °C, the material exhibited the densest microstructure with minimal pore formation. The average size of the silicon phase is the smallest. The material’s thermal conductivity is 134.6 W/m·K, the thermal expansion coefficient is 8.55 × 10−6 K−1, the Brinell hardness is 219 HBW, the density is 2.415 g/cm3, and the density reaches 97.75%. An appropriate sintering temperature facilitates particle rearrangement and dissolution–precipitation processes, enhancing the material structure and performance.