Sintering Process Research Articles

Influence of a three-layered coke breeze distribution scheme on the iron ore sintering performances

The heat accumulation effect of the iron ore packed bed leads to uneven temperature distribution within the iron ore sintering process. This causes the under-sintering and over-melting of the sinter, reducing its performance. To address this issue, a three-layered coke breeze distribution scheme was proposed. Nine cases were designed, and their transient sintering processes were simulated to explore their influence on the sintering performances of the iron ore. The results show that directly increasing the coke breeze ratio of the upper layer can raise the peak temperature and melt quantity index (MQI) of the entire layer while reducing the cooling rate of the upper layer, but it will increase the risk of over-melting. Keeping the total coke breeze ratio constant, reducing the coke breeze amount in the top layer, and increasing the coke breeze ratio in the upper layer has a minor impact on the peak temperature, but it will lead to a faster sintering rate, which in turn causes a decrease in the MQI and an increase in cooling rate. Keeping the total coke breeze ratio constant and shortening the thickness of the upper layer while increasing its coke breeze ratio has a minimal impact on the sintering performance. Keeping the total coke breeze ratio constant and lowering the coke breeze ratio in the lower layer while increasing it in the upper layer is the most effective method to optimize the sintering performances. It can effectively raise the peak temperature and MQI in the upper layer while reducing its cooling rate. Besides, the heat generated by the upper layer can be effectively transmitted to the lower layer, so the peak temperature, MQI, and cooling rate of the lower material layer are less affected by its reduced coke breeze ratio.

Waste electric porcelain-based refractory bricks with significantly enhanced mechanical properties: preparation, characterization and mechanism

Using waste electric porcelain to produce refractory bricks is a viable technology. However, these bricks currently have lower mechanical strength compared to those made from mineral raw materials. This study optimized the proportions and sintering process to develop high-strength refractory bricks from waste electric porcelain. The impact of physical phase, crystallinity, sintering temperature, and fly ash content on the bricks properties was examined. The research found that low crystallinity in waste electric porcelain leads to disorganized growth of mullite nano whiskers at high temperatures, reducing mechanical strength due to insufficient support structures and stress concentration zones. The addition of fly ash promotes the formation of uniformly dispersed mullite columns through non-uniform nucleation, significantly improving mechanical properties by creating a collective tetrahedral structure. Bricks with 20 wt% fly ash sintered at 1440 °C achieved a flexural strength of 77.3 MPa, a compressive strength of 156 MPa, and an apparent porosity of 10.89%. High-temperature simulations indicate that these bricks exhibit good compressive strength and deformation resistance, with no adhesion observed. These high strength refractory bricks have promising potential for use in various high-temperature applications, including kiln linings, high-temperature flue, high-temperature support components and other industrial processes where durability and thermal stability are critical.

Correlation and application of thermal expansion coefficient/elastic modulus for co-sintered composite cermet/ceramic materials

Deformation and stress concentration appearing during high-temperature sintering process significantly affect production quality of solid oxide cell (SOC), due to mismatched mechanical and thermophysical properties of the sintered electrode and electrolyte. In this study, a coarse-grained molecular dynamics (CG-MD) method is developed to evaluate and correlate coefficient of thermal expansion (CTE) and elastic modulus during the entire co-sintering process (including temperature-increasing, −insulation, and -decreasing stages). It is revealed that, in the sintered porous cermet electrode, CTE primarily exhibits an increasing trend until temperature-decreasing stage. Compared to the constant values commonly applied in the literature, the elastic modulus experiences a decay trend with a reduction of 32.14 % in the porous electrode and 9.68 % reduction in the dense electrolyte. The obtained CTE and elastic modulus are correlated with the sintering parameters and further applied to a macroscopical model for predicting overall sintering warpage and stress in a co-sintered SOC half-cell composed of a thick porous electrode and a thin dense layer. The varied CTE is identified as the main factor influencing warpage deformation, while the elastic modulus as a more significant impact on the von Mises stress during the co-sintering of the half-cell. Analysis is further conducted by orthogonal testing method for sintering temperature, sintering time, material content and diameter ratio of the porous cermet nanoparticles, aiming to optimize the varied CTE and elastic modulus, particularly during the temperature-insulation process. Subsequently, the optimized properties are implemented, and it is found that, after sintering insulation for 120 min, the maximum warpage displacement is about 7.34 mm, which represents a decrease of approximately 14.11 %; while the von Mises stress is observed to be 379.24 MPa, which indicates a reduction of around 37.33 % compared with the predictions by the constant properties.

Integrated Recycling of Red Mud for Iron Ore Sinter Manufacturing: Interfacial Bonding Regulation of the Sintering Process

Integrated Recycling of Red Mud for Iron Ore Sinter Manufacturing: Interfacial Bonding Regulation of the Sintering Process

Green Synthesis And Photoluminesce Study Of Dy Doped CaCo3

In this study, we used water-soluble polysaccharides from melon to develop a new green method for the biological production of calcium carbonate crystals. SEM, FT-IR spectroscopy, and X-ray powder diffractometry were used to examine the resulting crystals. The host material is prepared with the amount of 5.549gm CaCl2 and 5.2994gm Na2CO3. In the sintering process, the sample is subjected to its melting temperature in a furnace and then cooled evenly. The phosphor CaCO3 is doped with differing proportions of Dy and SEM micrographs validate the material's nanostructure, which is essential for luminescence. By Dy doping with CaCO3, then crystal structure of a molecule shows prominent XRD peaks. In UV photoluminescence spectra, the greatest emission peak is at 578nm while slake curve shows that for 3 mol% Dy concentrations, show higher luminescence intensity. As the Dy concentration rises over 3 mol%, the brightness intensity decreases due to quenching phenomena.

Binder jetting printed in situ mullite strengthened alumina ceramics with excellent mechanical and thermal properties through multi-phase infiltration

ABSTRACT Binder jetting (BJ) additive manufacturing faces significant challenges in fabricating high performance alumina ceramics. In this study, a multi-phase infiltration method was successfully employed to prepare high-performance mullite strengthened alumina ceramics via the BJ process. The effects of printing, sintering, and infiltration processes on the microstructure and performance of the alumina-based ceramics were systematically investigated. The results indicate that the density and strength of the green body increased with increasing binder saturation and decreased with thicker powder layers. Upon sintering, the maximum bending strength of the alumina ceramics reached approximately 2.2 MPa, which increased with the sintering temperature. After further multi-phase infiltration, the maximum bending strength of the alumina-based ceramic composites reached 97.3 MPa, a 44-fold increase compared to before infiltration. Additionally, triple-periodic minimal surface structures from high-performance alumina-based ceramic composites were successfully fabricated. The compression behaviour and thermal properties of these TPMS structures were investigated for potential insulation applications.

Development of a Low-carbon Sintering Process Technology and Its Application to a Pilot-scale Sintering Testing

Development of a Low-carbon Sintering Process Technology and Its Application to a Pilot-scale Sintering Testing

Cold Sintered ZnO-Polystyrene (PS) Composites with Modified Interfacial Structures and Properties.

Lightweight and integrated electronic devices with high performance have become an inevitable trend in the development of power electronic systems. However, it is challenging to obtain lightweight and miniaturized varistors due to the low threshold electric field. Herein, (1 - x)ZnO-xPS composites with a high threshold electric field are prepared through a cold sintering process at 220 °C for 50 min, utilizing lightweight PS to modulate the grain boundary structures of ZnO varistors. With PS content ≤1.5 wt %, the relative densities of cold sintered composites exceed 95%. PS thin layers with a thickness of 2-10 nm are distributed at the grain boundaries of ZnO, forming the Schottky barrier, which triggers nonlinear current-voltage responses. With the addition of PS, the threshold electric field is dramatically enhanced from 135 to 2703 V·mm-1, higher than that of commercial ZnO varistors, which is further demonstrated by the electric field simulation of the Finite Element Method. The interfacial resistance obtained from impedance analysis increases with the increase of the PS content, and the activation energy of (1 - x)ZnO-xPS composites is higher than that of pure ZnO ceramics. This study provides a promising approach for the development of lightweight and cost-effective varistor materials.

Cost Optimization in Sintering Process on the Basis of Bulk Queueing System with Diverse Services Modes and Vacation

This research investigated a single bulk server queuing model where service modes and server vacations are dependent on the number of clients. The server operates in three different service modes: single service, fixed batch service, and variable batch service. Modes will be determined by queue length. The service starts only when the minimum number of customers, say ‘a’, has accumulated in the queue. At this point, the server selects one of three service modes. Transitions between duty modes are permitted only at the beginning of a duty period. At the end of the service, the server can go on vacation if the queue length drops below ‘a’. When returning from vacation, if threshold ‘a’ is not reached, the server will remain inactive until it is reached. A special technique called the Supplementary Variables Technique (SVT) was used to determine the probability-generating function when estimating the queue size at a given time. Appropriate numerical examples exemplify the method developed in the paper. An optimal cost analysis was performed to set the threshold values for different server modes with the intention of minimizing the aggregate average cost.

Application of thermodynamic equilibrium modelling to predict slagging and fouling tendencies of bituminous coal and wheat straw blends

The combustion or co-combustion of biomass or alternative fuels is important in the energy sector because of the need to reduce the share of fossil fuels. This article is a continuation of previous studies on the behaviour of the mineral matter of selected fuels during the sintering processes. The blends of wheat straw biomass from Polish crops (WS) with bituminous coal from the Makoszowa mine (BC) were studied. The study included proximate and ultimate analysis and oxide analysis of ash blends with the following composition: 10wt% WS/90wt%BC, 25wt% WS/75wt%BC and 50wt% WS/50wt%BC. Based on the oxide content, a prediction (using FactSage 8.0 software) of the sintering process of the mixtures tested. The following parameters were determined: slag phase content, specific heat at constant pressure, and ash density. The fracture stresses tests were carried out using the mechanical test. Pressure tests were also performed using the pressure drop test method. The test results of all test methods used were compared with each other. On the basis of this comparison, a clear correlation was found between the sintering temperatures determined by the mechanical method and the pressure drop method and the physical properties of the ashes, such as density and heat capacity, as well as the chemical properties, i.e. the content of the slag phase. The results of the presented research are a valuable addition to the previous work of the authors. The goal of this work is to develop a precise and measurably simple method to determine the sintering temperature of ashes. This is an extremely important issue, especially in the case of the need to use a wide range of fuels in the energy industry.

Large internal stress induced nonlinear current-voltage behavior in nanodiamond strengthened ZnO ceramics.

The modulation of the electrostatic potential barrier at grain boundaries determines the performance of many ceramic-based electronics such as varistors. However, conventional protocols relying on complex doping and annealing processes inevitably increase the inhomogeneity of microstructure, which may jeopardize the performance stability and mechanical reliability in service. Instead of doping, herein we demonstrate an effective strategy to modulate the potential barrier in ZnO-based low-voltage varistors by exploiting internal stress-induced piezoelectric polarization. The local residual stress as large as ~1 GPa can be created in the ZnO matrix by incorporating ultra-stiff nanodiamond particles using a cold sintering process. As a result, the composite with only 2 wt% of nanodiamond exhibits a prominent nonlinear current-voltage response at a low switch voltage of 15.7 V/mm, which is ascribed to the depressed barrier height induced by the distinct effects of positively and negatively charged polarization on grain boundaries. More strikingly, the large internal stress can significantly enhance the strength of the composite by more than 230% compared with the monolith, owing to the highly strengthened grain boundaries and crack-tip bridging from prestressed nanodiamonds. These findings add internal stress as a new dimension to design mechanically robust ceramic electronics with high performance.

Boosting thermoelectric efficiency of Ag2Se through cold sintering process with Ag nano-precipitate formation

Boosting thermoelectric efficiency of Ag2Se through cold sintering process with Ag nano-precipitate formation

Development of a Diamond Composite in the NI-CO-FE3P-SN-WC System Via Free Sintering for Use in Multi-Find Diamond Pearls

Objective: The main objective of this study is to manufacture a diamond composite with a metallic matrix based on Ni-Co-Fe3P-Sn-WC, using the Free Sintering process through cold uniaxial compaction, intended for the production of pearls for diamond wire saws, used in cutting ornamental stones. Theoretical Framework: The multi-wire technology represents an advancement in cutting ornamental stone blocks, allowing the simultaneous production of multiple slabs. Powder metallurgy is the predominant technique used in the manufacturing of pearls for diamond wire saws. Through testing, including scanning electron microscopy (SEM) and shear tests, it is possible to evaluate the alloy's strength, diamond crystal adhesion, and failure behavior of the alloy. Methodology: The adopted methodology involves the processing and characterization of pearls for diamond wire saws, following the techniques of powder metallurgy. Initially, parametric calculations were performed using Excel, providing a basis for subsequent analyses. Diamond-coated pearls were produced with different proportions of constituent elements, and uniaxial compressive strength tests and microstructural characterization were conducted to evaluate the results. Results and Discussion: In the adhesion tests to the metal tube, the pearls produced with the NICOFE alloy showed similar performance to the commercial pearls "A" and "B," with satisfactory direct shear strength values. However, some point defects were observed, such as porosity in the transition zone, creating a weaker bond, negatively impacting the final strength of the composite. Analysis of the commercial samples indicated that diamond abrasion was not related to the composition of the sintered alloy. Research Implications: This research suggests significant economic and technological implications, such as the development and nationalization of technology for the ornamental stone industry. The use of the NICOFE alloy could strengthen the local industry by providing a viable and more accessible alternative for the production of diamond pearls. Originality/Value: The NICOFE blend presents technical advantages for manufacturing diamond wire pearls, highlighting the environmental benefits from reduced cobalt use and economic advantages by offering more accessible materials for the ornamental stone industry.

Impact of low-grade iron ore on sintering reactions: Rapid heating experiments and thermodynamic modeling

BackgroundSinter is a primary feedstock for blast furnace-based ironmaking. Recently, the proportion of low-grade iron ore, which contains a high amount of gangue (mainly SiO2), has been increasing in the sintering process. Therefore, the impact of increased SiO2 content on the quality of sinter needs to be clarified. MethodsIn this study, we designed a rapid-heating furnace to simulate the actual thermal profile of the sintering process. The effects of basicity values, sintering temperature, and atmosphere, on the microstructure and phase formation of the Fe2O3-CaO-SiO2 ternary mixtures during sintering reactions, are investigated using X-ray diffractometry and scanning electron microscopy. The experimental results are analyzed using CALPHAD-type computational thermodynamics. Significant findingsWe found that solid-state reactions dominate at the lower temperature of 1250 °C, while liquid-assisted sintering occurs at the higher temperature (1300 °C). As the SiO2 content in the sinter increases, the content of the calcium-ferrite bonding phase decreases, while the content of Ca2SiO4 and Fe2O3 increases. Regarding the role of the atmosphere, more calcium ferrite bonding phases form under a lower oxygen partial pressure compared to an ambient atmosphere, which facilitates the densification of the Fe2O3-CaO-SiO2 sinter. In addition, a guideline for sintering operation with low-grade iron ore is proposed.

In-Situ Constructing N,S-Codoped Carbon Heterointerface for High-Rate Cathode of Sodium-Ion Batteries.

Na3V2(PO4)3 (NVP) is considered one of the promising choices for cathodes of sodium-ion batteries, but the poor conductivity resulted inferior rate performance limited the practical development of NVP cathodes. In this study, we successfully synthesized N/S dual-atom doped carbon coatings in situ through a simple one-step solid-state sintering method. The uniformly coated carbon layer can inhibit the agglomeration and growth of active materials during the sintering process, shorten the Na+ migration path, and increase the contact area with the electrolyte, thus facilitating rapid Na+ migration. Notably, the doping of N elements can alter the electron distribution of carbon coating, enhancing electron conductivity. Furthermore, the introduction of S elements in the carbon layer can induce the formation of stable C-S-C bonds in the molecular layer, expanding the interlayer spacing, which is beneficial for Na+ transport and storage. Therefore, the modified NVP@NSC composite provides a high specific capacity of 90.3 mAh g-1 at a rate of 20 C, with a capacity retention rate of 94.4% after 8000 cycles, demonstrating excellent stability at high current densities. Moreover, the full cell exhibits remarkable electrochemical performance at 5 C. This research contributes to the practical development of NVP cathodes.

Intelligent Optimization and Impact Analysis of Energy Efficiency and Carbon Reduction in the High-Temperature Sintered Ore Production Process

The coordinated optimization of energy conservation, efficiency improvement, and pollution reduction in the sintering production process is vital for the efficient and sustainable development of the sintering department. However, previous studies have shown shortcomings in the multi-objective collaborative optimization of sintering systems and the quantification of pollutant impacts. To address these, this paper proposes a multi-objective optimization method integrated with the NSGA-III algorithm and establishes an integrated system optimization model for sintered ore production and high-temperature waste heat recovery. The results demonstrate significant improvements: energy utilization efficiency increased by 0.67%, energy consumption decreased by 17.3 MJ/t, production costs were reduced by 11.45 CNY/t, and the emissions of CO2, SO2, and NOx were reduced by 0.464 kg/t, 0.034 kg/t, and 0.008 kg/t, respectively. Additionally, the study identified optimal configuration parameters and analyzed the quantitative impact of several key factors on multiple indicators. The results also show that reducing the water content of the mixture, decreasing the middling coal content in the fuel, and increasing the thickness of the material layer are effective strategies to reduce energy consumption and pollutant emissions in the sintering process. Overall, implementing these optimizations can bring significant economic and environmental benefits to the steel industry.

Low-temperature sinterability of graphene-Cu nanoparticles:Molecular dynamics simulations and experimental verification

As three-dimensional integration technology evolves, the integration density and operating speed of circuits continue to increase, raising the demands for interconnect reliability. It is urgent to explore novel interconnect materials to meet reliability requirements. Given its excellent mechanical, physical, and electrical properties, graphene-nanocopper has emerged as a promising new interconnect material. However, graphene’s low affinity with copper requires an exploration of its sintering mechanism to guide the sintering process. In this study, we initially utilized molecular dynamics calculations to compare the sintering processes of Cu NPs and G@Cu NPs. Graphene limits the sintering progress of G@Cu NPs, with shear strengths of Cu NPs (8.38 MPa) < G@Cu NPs (12.78 MPa) < benzimidazole@Cu NPs (13.28 MPa), and porosity rates of Cu NPs (38.19 %) > G@Cu NPs (14.28 %) > benzimidazole@Cu NPs (10.36 %). Post-sintering service reliability verifies that graphene limits the sintering process of G@Cu NPs. The sintering process of graphene with copper was subsequently simulated for different core–shell diameters, within a specific range, revealing that increasing the copper core diameter and graphene shell thickness decreases the sintering progression. However, the increase in graphene may concurrently alter defects, thus accelerating the sintering process. Finally, simulations conducted at sintering temperatures of 473 K, 573 K, and 673 K for G@Cu NPs show that increasing the temperature accelerates the sintering process, reducing the porosity rate from 19.48 % to 12.64 % and increasing the shear strength from 10.14 MPa to 13.92 MPa. It was verified that the temperature increase promoted the G@Cu sintering process. Our research reveals atomistic changes in G@Cu NPs under low-temperature conditions and provides a deeper understanding of low-temperature sintering for G@Cu NPs.

Surface Self-Diffusion Induced Sintering of Nanoparticles.

Despite the critical role of sintering phenomena in constraining the long-term durability of nanosized particles, a clear understanding of nanoparticle sintering has remained elusive due to the challenges in atomically tracking the neck initiation and discerning different mechanisms. Through the integration of in situ transmission electron microscopy and atomistic modeling, this study uncovers the atomic dynamics governing the neck initiation of Pt-Fe nanoparticles via a surface self-diffusion process, allowing for coalescence without significant particle movement. Real-time imaging reveals that thermally activated surface morphology changes in individual nanoparticles induce significant surface self-diffusion. The kinetic entrapment of self-diffusing atoms in the gaps between closely spaced nanoparticles leads to the nucleation and growth of atomic layers for neck formation. This surface self-diffusion-driven sintering process is activated at a relatively lower temperature compared to the classic Ostwald ripening and particle migration and coalescence processes. The fundamental insights have practical implications for manipulating the morphology, size distribution, and stability of nanostructures by leveraging surface self-diffusion processes.

Vitrified metal composite bond for diamond grinding tools used for silicon carbide wafer thinning

The refractoriness of the vitrified bond significantly influences the properties of the vitrified metal-composite bond. In this study, we examined the effects of refractoriness and number of vitrified bonds incorporated into vitrified metal composite bonds in diamond abrasive tools. Furthermore, the effects of vitrified metal composite bonds on the microstructure, mechanical properties, and sintering process were systematically evaluated. Techniques, such as X-ray diffraction (XRD), thermogravimetry-differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), and white light interferometry (WLI) were employed to analyze the phase composition of the vitrified metal composite bond, changes during the hot-pressing sintering process, microstructural morphology, and friction and wear behavior of the diamond abrasive composite bond. The flexural and impact strengths of the composite bond decreased with an increase in the refractoriness of the vitrified bond and number of bonds introduced. In particular, as the refractoriness of the vitrified bonds increased, their fluidity decreased. Finally, the hardness of the vitrified metal composite bond containing 3% vitrified bond (4#) reached 66.34–69.2 HRB, the porosity was 22.08%, and the surface roughness of the workpiece was 0.06 μm.

Effects of Sn addition in W-doped Ag paste against electrochemical corrosion and sulfurization

Purpose This study aims to address these challenges by enhancing the resistance of Ag-based pastes to corrosion and sulfurization, thereby improving their performance and weatherability in high-power and high-frequency electronic applications. Design/methodology/approach This study investigates the influence of Sn doping in W-doped Ag paste to enhance resistance against electrochemical corrosion and sulfurization. A systematic examination was conducted using transient liquid phase sintering and solid–liquid inter-diffusion techniques to understand the microstructural and electrochemical properties. Findings This study found that Sn addition in W-doped Ag paste significantly improves its resistance to electrochemical corrosion and sulfurization. The sintering process at 600°C led to the formation of an Ag2WO4 phase at the grain boundaries, which, along with the presence of Sn, effectively inhibited the growth of Ag2WO4 grains. The 0.5% Sn-doped samples exhibited optimal anti-corrosion properties, demonstrating a longer grain boundary length and a passivation effect that significantly reduced the corrosion rate. No Ag2S phase was detected in the weatherability tests, confirming the enhanced durability of the doped samples. Originality/value The findings of this study highlight the potential of Sn-doped Ag-W composites as a promising material for electronic components, particularly in environments prone to sulfurization and corrosion. By improving the anti-corrosion properties and reducing the grain size, this study offers a new approach to extending the lifespan and reliability of electronic devices, making a significant contribution to the development of advanced materials for high-power and high-frequency applications.