Sintering Behavior Research Articles

Unravelling the Effect of Oxygen on the Sintering Mechanism of Pt/CeO2 in the CO Oxidation Reaction.

Sintering significantly contributes to the deactivation of supported metal catalysts under reaction conditions, influenced by various factors, including temperature, atmosphere, and metal-support interactions. The sintering mechanism under the reaction conditions remains complex and ambiguous. This study delves into the sintering behavior of platinum on CeO2 under CO oxidation conditions, mainly employing transmission electron microscopy to elucidate the effects of different gas components on the sintering mechanism at elevated temperatures. An atmosphere rich in oxygen promotes the sintering of Pt via the Ostwald ripening mechanism, characterized by the growth of larger nanoparticles at the expense of smaller ones. Conversely, sintering proceeds through particle migration and coalescence in the absence of oxygen, leading to the aggregation of nanoparticles. The obtained Pt/CeO2 catalysts exhibit enhanced catalytic performance after treatment with argon and stoichiometric reaction gases, contrasting with the deactivation observed under oxygen-rich conditions, which is attributed to varied Pt valence states. These findings provide insights into understanding the sintering mechanisms and inform the design of heterogeneous catalysts.

Tuning interfacial wettability in high‐entropy cemented carbides for enhanced mechanical performance

AbstractThis study investigated three newly developed high‐entropy cemented carbides (HECCs) with high‐entropy carbides (HECs) as the hard phase and Co as the binder. Accordingly, the interfacial wettability between HECs and Co was tuned by the changes in relative concentrations of the different metal components (e.g., W, Ta, and Ti) and C. Results demonstrate that the wettability between HECs and Co is dominated by the dissolution of HECs in Co, which determines the sintering behavior and hence the structure and performance of the materials. More specifically, the (W6Ta4Nb10Zr10Ti20)C50‐Co with lower W content has poorer interfacial wettability, leading to pores in the sintered HECC. The (W10Ta10Nb10Zr10Ti10)C50‐Co shows good interfacial wettability and strong resistance against grain boundary infiltration, owing to the formation of several atomic‐layer‐thick Co films between HEC grain boundaries. Reducing the C content facilitates the dissolution of HECs in Co, which can improve the interfacial wettability, but promotes the formation of η‐W3Co3C phase and embrittle the material. The (W10Ta10Nb10Zr10Ti10)C50‐Co with decent interfacial wettability exhibits a good balance of hardness (HV30 ∼1485), compressive strength (3316 MPa), and fracture toughness (10.9 MPa·m1/2). The work demonstrates a design strategy achieving optimized microstructure and mechanical performance in HECCs via tuning interfacial wettability.

The Effects of CaO and MgO on Thermal, Mechanical and Optical Properties of Porcelain Tiles by Utilizing Blast Furnace Slag

In this study, the Blast Furnace Slag (BFS) of Zonguldak Eregli Iron and Steel Factories was used as a recycling raw material for the porcelain tile samples. A kind of clay with high MgO content was also used in the porcelain tile recipes. Maximum 10% of BFS was used instead of Na-feldspar. Sintering temperature for all samples was 1205°C for 50 minutes in the industrial roller kiln. Technological properties such as shrinkage, water absorption, colour measurement, and flexural strength were investigated as well as sintering properties and microstructures of the green and the sintered samples. As a result of the study, the addition of BFS did not adversely affect the technical properties of porcelain tile bodies. Particularly, the addition of BFS up to 3% contributed to an increase in flexural strength, and whiteness values of all samples increased because of the formation of anorthite and diopside compared to the reference body. The phase transformations and crystal formations such as anorthite and diopside resulted in a decrease in the firing shrinkage. Although the anorthite formation and diopside formation in the investigated samples had an adverse effect on condensation, it was found that they showed similar sintering behaviours compared to the reference body. This study showed that an industrial waste material can be converted into an environmentally friendly raw material that can create added value and provide energy efficiency.

Shape Synergy of Ag@Cu Chip Packaging Nano‐Paste and Its Sintering Reliability

Electrochemical migration of Ag can result in failure of power chips, thus affecting the application of nano‐Ag paste as packaging material. In this study, a novel sintered material is developed using shape‐synergistic Ag‐coated Cu (Ag@Cu) particles, aiming at establishing a highly reliable connection between the chips and the substrates. The sintering behavior of Ag@Cu particles is examined, elucidating the role of skeleton‐wetting synergism in enhancing the strength of the sintered layer from a structural perspective. Two distinct shapes of Ag@Cu particles serve as a skeleton support, providing electrical conductivity, and nano‐Ag particles enhance wettability. Ag as a coating layer can slow down the oxidation of Cu, despite that oxidation still occurs in the sintered layer during the high‐temperature tests, initially weakening the strength of the sintered layer, but eventually stabilization is achieved. The presence of Cu effectively inhibits electrochemical migration of Ag. The reliability of the sintered layer is enhanced by the novel shape of Ag@Cu particles and the interaction between Ag and Cu, thereby ensuring the stability of the power chips.

Investigation of the sintering behavior of nanoparticulate SiC by molecular dynamics simulation

Sintering is a valuable processing technique utilized to create bulk materials from powder compacts. In recent years, sintering has a garnered significant attention in the research community due to its versatility and applicability in various fields, including additive manufacturing. Herein, we investigate the sintering kinetics and mechanism of SiC nanoparticulate using molecular dynamics simulations. The surface morphology, microstructure, radial distribution function, mean square displacement, atomic displacement distribution, structural transformation, and diffusion coefficient are analyzed in detail. The free surface surrounding the neck undergoes a reconstruction to eventually reach an equilibrium dihedral angle. The neck rapidly grows and aligns with the surface, causing the SiC particle to transform from an original spherical shape into a twists shape. The concentration of shear stress results in a change of the local lattice structure from the face-centered cubic phase to amorphous phase in the surface. With an increasing sintering time, the dominant diffusion mechanism gradually shifts from surface diffusion to interface diffusion. This trend leads to a rise in the atomic migration, the consumption of interface energy, and the degree of particle fusion. Ultimately, the sintered SiC particles have the spherical shape, low surface energy, and stable structure. Additionally, the high mobility of melted atom causes a gradual dissolution of SiC particle into the large particle from the surface towards the interior. This process leads to high-altitude concentration structures that facilitate atomic migration. These results shed light on an atomic sintering mechanism in SiC nanoparticulate for applications in the preparation of nanostructured materials, and additive manufacturing.

Research on the synthesis and sintering behavior of porous spherical silver particles

Research on the synthesis and sintering behavior of porous spherical silver particles

Abnormal shrinkage behavior and sintering mechanism of alumina nanoparticles

AbstractHigh temperature and ultrafast heating rate, the characteristics of ultrafast high‐temperature sintering (UHS) process, make it difficult to capture the evolution of sintering behavior and explore sintering mechanism of alumina ceramics. In this study, molecular dynamic simulations are adopted to describe the sintering behaviors of equal‐sized and unequal‐sized alumina nanoparticles, particularly about shrinkage behaviors, microstructure evolution and atomic migration. Results show that high temperature and ultrafast heating rate can yield two different abnormal shrinkage behaviors, accelerating the polymerization of the nanoparticles. The main mechanism for this phenomenon is that high temperature causes the amorphization of crystal structure of nanoparticles, and ultrafast heating rates retain larger sintering driving forces at high temperatures, leading to the reduction of diffusion activation entropy and migration barriers. In particular, the appearance of viscous flow further enhances the shrinkage of the nanoparticles. In addition, surface diffusion is found to dominate the growth of sintering neck during this period. These findings are expected to deepen the understanding of ultrafast high‐temperature sintering mechanism.

Microstructural Evolution and Sintering Behavior of Supersonic Atmospheric Plasma Sprayed Multi-modal YSZ Coating

Microstructural Evolution and Sintering Behavior of Supersonic Atmospheric Plasma Sprayed Multi-modal YSZ Coating

Tailoring mechanical properties of Mo-SiC composites through controlled phase formation during reactive spark plasma sintering

The present study investigates the sintering behavior of Mo-xSiC reactive composites (x= 10–40 vol%) using reactive spark plasma sintering (RSPS) at 1700°C for 5 min. The microstructure, phase formation, and mechanical properties of the fabricated composites were evaluated. X-ray diffraction (XRD) analysis reveals the formation of various compounds, including Mo2C, Mo3Si, and Mo4.8Si3C0.6, which increase in intensity with increasing SiC content. It was found that composites with 10 vol% and 15 vol% SiC still contained unreacted Mo phase, whereas larger amounts of SiC resulted in no remaining Mo. Conversely, unreacted SiC particles were detected in all composites. Field-emission scanning electron microscopy (FESEM) and energy-dispersive spectroscopy (EDS) analysis confirm the presence of multiple phases. The flexural strength of the composites exhibits complex relationships with SiC content, with Mo-10 vol% SiC and Mo-15 vol% SiC composites showing superior strength (585±32 MPa and 618±21 MPa) due to the presence of unreacted Mo phase. The strength decreased with increasing SiC content, likely due to the formation of brittle intermetallic phases. Hardness increased with SiC content, with a significant improvement in Mo-20 vol% SiC composite (12.88 ± 0.21 GPa), but decreased thereafter. Fracture toughness followed a different trend, decreasing with increasing SiC content due to the elimination of ductile Mo phase and the formation of brittle phases. Therefore Mo-10 vol% SiC and Mo-15 vol% SiC composites exhibited the highest fracture toughness values of 8.34±0.68 MPa.m1/2 and 7.99±0.37 MPa.m1/2, respectively.

Sintering Behavior of Molybdenite Concentrate During Oxidation Roasting Process in Air Atmosphere: Influences of Roasting Temperature and K Content.

Sintering is a common phenomenon, which often takes place during the oxidation roasting process of molybdenite concentrate in multiple-hearth furnaces. The occurrence of sintering phenomena has detrimental effects on the product quality and the service life of the furnace. In this work, the influence of two key factors (roasting temperature and K content) on the sintering behavior is investigated using molybdenite concentrate as the raw material. Different technologies such as XRD, FESEM-EDS, and phase diagrams are adopted to analyze the experimental data. The results show that the higher the roasting temperature is, the greater the mass loss and the more serious the sintering degree will be. The results also show that with the increase in K content, the mass loss of the raw material is first increased and then decreased, while its sintering degree is still gradually increased. The sintering products obtained during the oxidation roasting process are often tightly combined with the bottom of the used crucible with a smooth and dense surface structure, while their internal microstructures are very complicated, which not only includes numerous MoO3 species, but also unoxidized MoS2, Mo sub-oxide, SiO2, and a variety of molybdates. Among them, both MoO3 and molybdates can be easily dissolved into the ammonia solution, leading to a residue mainly composed of SiO2 and CaMoO4. This study also finds that the sintering phenomenon is caused by the increase in local temperature and the formation of various low-melting-point eutectics. It is suggested that decreasing the roasting temperature and K content, especially the K content, are effective methods for reducing the sintering degree of molybdenite concentrate during the oxidation roasting process.

Mechanical property of SiC whisker reinforced CaZr4(PO4)6 ceramics fabricated by fast hot pressure sintering

The poor mechanical properties of low thermal expansion CaZr4(PO4)6 (CZP) ceramics hinder its extreme high temperature applications. In this paper, to acquire CZP-based composite with combination of excellent mechanical properties and low thermal expansion, SiC whisker (SiCw)-dispersed CZP ceramics were fabricated using fast hot pressure sintering (FHP). The effects of varying weight percentages of SiCw and FHP processing parameters on the sintering behavior, crystal structure, microstructure and properties of CZP ceramics were systematically investigated. SiCw was nonreactive with the CZP matrix and the two phases coexisted stably. Compared with the normal-pressure sintering ceramics, the composites prepared by FHP technique exhibited increased densification. Importantly, the addition of SiCw remarkably improved the mechanical properties of FHP-prepared composites, demonstrating superior flexural strength and fracture toughness of 124 MPa and 3.72 MPa m1/2, respectively, considerably higher than that of pure CZP ceramics. The several toughing mechanisms arising from fibers, such as crack bridging, crack deflection and crack branching, accounted for the improved fracture toughness. Furthermore, the CZP-SiCw ceramics remained a low thermal expansion property, with an average thermal coefficient expansion of 1.47 × 10−6/°C. The strategy regarding FHP technology combined with appropriate incorporation of SiCw opens a pathway for rapid fabrication of high-performance NZP-type ceramics.

Atomic insights into the sintering behaviour of Ag–Cu solid solution nanoparticles on Ag substrate

In electronic packaging industry, it has been reported that compared with nano silver and nano copper, the complementation and coordination of Ag and Cu components enable bimetallic nanomaterials enhanced anti-electromigration and oxidation inhibition characteristics. Ag–Cu solid solution nanoparticles (ACDS NPs) has become an emerging substitution and garnered widespread attention. This research presents the investigation into the size-dependent melting behaviour of ACDS NPs and the effect of elevated temperature during the pressure-free sintering with Ag substrate through molecular dynamics simulations. The melting points of ACDS NPs turn out to be in accordance with Gibbs Thomson equation, based on which the suitable sintering temperatures have been determined within 473 and 773 K. As demonstrated by dynamic trajectories at cross section while sintering, coalescence between NPs occurs with the atomic surface diffusion at the sintering neck along the vacancy concentration gradient. 623 K is estimated to be a threshold temperature of complete integration of NPs at which the crystallographic structure collapses during sintering and recrystallizes at the late sintering stage. The dominant sintering mechanisms transferred from surface diffusion and dislocation-based plastic deformation below 573 K to atomic diffusion above 623 K. Furthermore, the results present incontrovertible dominance of Shockley dislocations and interaction energy on determining mechanical properties of sintered atomistic system. It is also revealed that the systems sintered below 673 K yield significantly lower thermal conductivity attributing to the strong localization of heat carriers for intrinsic amorphous structure than crystalline counterparts above 723 K.

Phase evolution and sintering behavior of high-performance IGTO sputtering targets

In-Ga-Sn-O (IGTO) targets are vital in preparing high-mobility IGTO thin film transistors. This study uses pressure slip casting and conventional sintering methods to prepare IGTO targets with three atomic ratios(IGTO-711=70:15:15, IGTO-712=70:10:20, IGTO-721=70:20:10 In:Ga:Sn at.%). With the increase of Ga content in the system, the phase composition of the IGTO targets changes from In2O3 and Ga1.6In6.4Sn2O16 to In2O3, Ga2In6Sn2O16 and GaInO3. Their densification activation energy has been calculated using constant heating rate experiments. It shows that the activation energy is independent of the density in the relative density range of 0.70-0.85, and the activation energy is significantly affected by the ease of reaction of the physical phases. The densification activation energies of samples IGTO-711, IGTO-712 and IGTO-721 are 230.5±42 kJ/mol, 926.4±58 kJ/mol, 582.9±52 kJ/mol, respectively. The presence of the GaInO3 phase facilitates the densification process of IGTO targets. Ultimately, IGTO-712 targets with a relative density of 99.01%, a resistivity of 0.42 mΩ·cm, a microhardness of 1024.31 HV2, and a uniform grain size range of 3∼5 μm are achieved at 1450°C for 20 hours in an oxygen atmosphere.

Sintering behaviours of different ladle filler sands with high-chromium stainless steel

In order to investigate the sintering behaviours of different types of filler sands (chromite-based, zircon-based, and silica-based) with high-chromium stainless steel grades ( w[Cr] = 11.70% and 16.26%), laboratory experiments were carried out at 1600°C in an inert atmosphere. It is found that the high content of Cr in stainless steel promotes the formation of Cr2O3 in the liquid phase of these sintered filler sands, thereby significantly affecting the sintering of the filler sands. Compared with the elements of Mn and Al in conventional steel grades, the Cr element in stainless steel shows a different impact on the sintering of filler sands. The sintering of chromite-based sands is restricted by the rise of Cr content in stainless steel, whereas the dissolved Cr in the steels enhances the sintering of zircon-based and silica-based filler sands. Chromite-based filler sands are recommended for stainless steel. Because the melting point of the liquid phase is significantly influenced by the content of (Cr2O3 + Al2O3), the contents of Al2O3 and Cr2O3 in chromite-based sands should be accordingly adjusted for stainless steel.

Enhanced sinterability and mechanical strength of beta-type tricalcium phosphates ceramics through reaction sintering with hydroxyapatite

Beta-tricalcium phosphate (β-TCP) ceramics were fabricated via reaction sintering at 1100 °C, utilizing various phosphate salts and calcium compounds as raw materials. The sintering characteristics, reaction sintering behavior and mechanical properties of the resulting β-TCP ceramics were investigated. Reaction sintering with a Ca/P molar ratio of 1.50 consistently generated β-TCP. In addition, a notable variance in physical properties was observed contingent on the presence or absence of stoichiometric hydroxyapatite (HAp; Ca10(PO4)6(OH)2) in raw materials. Sintered bodies produced with HAp−β-Ca2P2O7 (β-CPP), HAp− CaHPO4·2H2O (DCPD) and HAp−(NH4)2H(PO4) all exhibited densification and enhanced mechanical strength, correlated with higher bulk densities. In contrast, conventional sintered bodies prepared from β-TCP and reaction sintered bodies prepared using β-CPP−Ca(OH)2 or β-CPP−CaCO3 were not as dense. Comprehensive assessments by thermogravimetry-differential thermal analysis, X-ray diffraction and scanning electron microscope together with the evaluation of shrinkage behavior were used to monitor the sintering of β-TCP with HAp. This process was found to involve thermal decomposition of HAp and crystal transitions leading to the formation and sintering of β-TCP with significant shrinkage. These findings underscore the efficacy of employing HAp as a raw material in reaction sintering. This technique allows the formation of sintered β-TCP bodies exhibiting exceptional sintering characteristics, superior bulk density and high mechanical strength.

Tailoring BaCe0.7Zr0.1(Dy0.1|Yb0.1)0.2O3−δ electrolyte through strategic Cu doping for low temperature proton conducting fuel cells: Envisioned theoretically and experimentally

This study addresses the challenge of high sintering temperatures in proton-conducting fuel cells (PCFCs) with BaCeO3-doped electrolytes. We demonstrate that 1 mol% copper (Cu) doping at the B-site of BaCe0.7Zr0.1(Dy0.1|Yb0.1)0.2O3−δ (BCZDYb) improves sintering behavior, enabling densification at 1400 °C. However, Cu doping disrupts stoichiometry, creating barium vacancies and reducing proton-accepting cations, affecting overall conductivity. This mechanism is confirmed through density functional theory (DFT) calculations and various experimental techniques, including crystal structure analysis using X-ray diffraction (XRD) and morphology and elemental analysis via field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDS). Electrochemical measurements are performed using the electrochemical impedance spectroscopy (EIS). The ionic conductivity of 1 mol% Cu-doped BCZDYb (BCZDYb-1) is 1.49 × 10−2 S cm−1 at 650 °C, which is ∼3.58 times higher than that of BCZDYb sintered at 1200 °C. The BCZDYb-1 exhibits ∼16 times higher grain boundary conductivity when sintered at 1400 °C, compared to undoped BCZDYb. The single cell employing BCZDYb-1 as the electrolyte achieved a power density of ∼606 mW cm−2 at 550 °C. These results indicate that a controlled amount of Cu doping can enhance densification while maintaining high ionic conductivity, making it suitable for practical applications in PCFCs operating at lower temperatures.

Pt-Ta microhotplate with low resistance temperature coefficient and low resistance drift

Micro thermal plates are widely used in various sensors in the aerospace and automotive fields. With the reduction of chip size and the development of MEMS, micro thermal plates are also moving towards integration. The device failure caused by the Pt film at high temperatures seriously affects the stability of the sensor, and degradation determines the sensor's operating temperature and service life. In this paper, Pt, Pt-Ta, and Pt-Pd microcalorimetric plates were prepared and analyzed for their sintering behavior, microstructure, electrical properties, and high-temperature stability using co-firing of resistors and alumina substrates. The film layers prepared by co-firing were better matched to the alumina substrate, and the sintered network of the film layers was better. The Pt-10 %Ta microthermal plate has a 46 % lower resistance temperature coefficient TCR compared to the Pt microthermal plate, and the resistance drift at 800°C is reduced to 2.11 %/Day. And even at 1100°C, the Pt-Ta system also has a very low resistance drift −12 %/Day (Pt26.6 % /Day and Pt-Pd35.18 %/Day) with improved high temperature stability. The addition of Ta allows the membrane layer to have fewer voids at high temperatures, reinforcing the high temperature characteristics of the resistance thermometer. It improves the stability and accuracy of the heating plate in high temperature gas sensor applications.

Molecular dynamics simulations of nanoparticle sintering in additive nanomanufacturing: insights from sintering mechanisms

The sintering behavior of nanoparticles (NPs), which determines the quality of additively nanomanufactured products, differs from conventional understanding established for microparticles. As NPs have a high surface-to-volume ratio, they are subjected to a higher influence from surface tension and a lower melting point than microparticles, resulting in variations in both crystallographic defect-mediated and surface diffusion mechanisms. Meanwhile, the interplay between these controlling mechanisms in NPs has not been well understood, primarily because sintering occurs on the nanosecond timescale, making it an exceptionally transient process. In this work, sintering of both equal and unequal sized Ag and Cu NP doublets with and without misorientation (both tilt and twist) is modeled through molecular dynamics (MD) simulations. The formation and evolution of crystallographic defects, such as vacancies, dislocations, stacking faults, twin boundaries, and grain boundaries, during sintering are investigated. The influence of these defects on plastic deformation and diffusion mechanisms, such as volume diffusion and grain boundary (GB) diffusion, is discussed to elucidate the responsible sintering mechanisms. The surface diffusion mechanism is visualized by using detailed atomic trajectories generated during the sintering process. Finally, the overall effectiveness of all diffusion sintering mechanisms is quantified. This study provides first insights into the complexity and dynamics of NP sintering mechanisms which can aid in the development of accurate predictive models.

Real-Time Simulation of the Reaction Kinetics of Supported Metal Nanoparticles.

A common issue with supported metal catalysts is the sintering of metal nanoparticles, resulting in catalyst deactivation. In this study, we propose a theoretical framework for realizing a real-time simulation of the reactivity of supported metal nanoparticles during the sintering process, combining density functional theory calculations, microkinetic modeling, Wulff-Kaichew construction, and sintering kinetic simulations. To validate our approach, we demonstrate its feasibility on α-Al2O3(0001)-supported Ag nanoparticles, where the simulated sintering behavior and ethylene epoxidation reaction rate as a function of time show qualitative agreement with experimental observation. Our proposed theoretical approach can be employed to screen out the promising microstructure feature of α-Al2O3 for stable supported Ag NPs, including the surface orientation and promoter species modified on it. The outlined approach of this work may be applied to a range of different thermocatalytic reactions other than ethylene epoxidation and provide guidance for the development of supported metal catalysts with long-term stability.

Preparation, pore structure and properties of uniformly porous glass-ceramics sintered from granite powder using SiC@SiO2 foaming agent

Granite sludge produced during the processing of granite blocks should be efficiently recycled for environmental protection and as a sustainable resource. In this work, porous glass-ceramics were prepared by stepwise sintering of granite powder using core-shell SiC@SiO2 foaming agent. The SiC and SiC@SiO2 foaming agents were compared in terms of the sintering and foaming behaviors of the powder compacts by thermal expansion, thermogravimetry and mass spectroscopy. The foaming agent and foaming temperature were investigated to study their effects on the pore structure and properties of the porous glass-ceramics. The SiO2 shells of the SiC@SiO2 particles inhibited the oxidation of the SiC cores and the release of CO2 at the early stage of the sintering process, thus preventing pore coalescence and increasing the densification and specific strength of the sintered glass-ceramics. As the foaming temperature increased, the porous glass-ceramics exhibited a linear relationship between pore size and foaming temperature, and the specific strength first increased and then decreased due to pore coalescence and reduced crystallinity. Furthermore, the linear relationship between thermal conductivity and porosity indicates a closed pore structure, as demonstrated by computed tomography. At a foaming temperature of 1220 °C, the porous glass-ceramic has a porosity of 50.1 %, a specific strength of 16.6 kN⋅m/kg and a thermal conductivity of 0.747 W/(m⋅K). Numerical simulation confirms that lightweight glazed glass-ceramics have potential applications in energy-efficient building tiles.