Sintering Method Research Articles

LOW-TEMPERATURE SYNTHESIS OF FINE-POROUS CORUNDUM BASED ON INCORPORATED GRAPHENE NANOSTRUCTURES

In the present paper, the effect of the addition of graphene nanostructures and 3 mass % TiO2 on the microstructure and properties of sintered corundum ceramics were studied. Fine-porous corundum ceramics were obtained by the method of solid-phase sintering at relatively low temperatures of 1450oC, by adding graphene nanostructures in an amount of 2 % or 20 %. To lower the synthesis temperature, 3 mass % TiO2 was added to the initial ceramic blends. As a result of the solid solution formed between Al2O3 and TiO2, a well-sintered corundum ceramic is obtained at synthesis temperature lower than that of pure corundum - 1450oС. For the characterization of the initial blends and the ceramic samples, the methods of X-ray phase analysis, infrared spectroscopy, SEM, TEM EDS and visual microscopy were used. Besides, the basic physicochemical properties of the samples synthesized based on corundum were determined, e.g. water absorption (WA, %), apparent density (AD, %) and apparent (open) porosity (Pa, %).

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.

Powder‐Sintered Hierarchically Porous PMMA with Optimal Pore Parameters for Passive Daytime Radiative Cooling

AbstractPorous radiative cooling polymers have drawn significant attention for passive daytime cooling due to their desirable cooling performance and easy scalability. Since optimal pore parameters (i.e., pore diameter and porosity) will enhance light scattering, polymethyl methacrylate (PMMA) powders are sintered to fabricate samples with different pore parameters by the one‐step full‐dry powder sintering method. These samples have a hierarchically porous structure with pore diameters <5.0 µm. The most porous sample has 43% porosity, 0.964 reflectance in the 0.3–2.5 µm wavelength range, and 0.967 emittance in 8–13 µm wavelength range (which is the atmospheric window). The measured cooling temperature difference decreases when the porosity is low for hierarchically porous PMMA with similar pore size distribution. The high sub‐ambient cooling temperature reduction provided by hierarchically porous PMMA with optimal pore parameters is due to high solar reflectance when illuminated by the sun. Similar cooling trends are evident when sunlight is simulated by a Xenon lamp and an optical filter. The powder‐sintered hierarchically porous PMMA with optimal pore parameters can be an excellent radiative cooler for passive daytime cooling applications.

Advanced neutron and [formula omitted]-ray shielding characteristics of nanostructured (90-x)Al-xGd2O3 composites reinforced by tungsten

This study introduces a composite material designed to offer exceptional mechanical strength and superior radiation shielding characteristics. By integrating tungsten into an aluminum Al-matrix with varying Gd2O3 content, we developed composites that meet the needful demands of mechanical durability and radiation protection in nuclear applications. The composites, synthesized via mechanical milling and sintering methods in planetary ball mills, have nominal compositions of (90-x)Al-xGd2O3 (x = 5, 10, 15 wt%) supplemented with 10 %W. The XRD analysis revealed phase structure transformations correlated with increased milling durations, while SEM-EDAX provided detailed morphological and elemental insights. TEM study confirmed a homogeneous distribution of nanocrystalline powders after 30 hours of milling while DSC thermographs indicated variations in thermal properties dependent on the Gd2O3 and tungsten content. The enhanced mechanical strength with higher concentrations of gadolinium and tungsten was characterized by Vickers microhardness tests. Neutron and γ-ray shielding properties were calculated using MCNP6.2 simulation code and Phy-X/PSD software. The thermal neutron macroscopic cross-section increased exponentially with higher Gd2O3 content, achieving values of 23.3 cm⁻¹ for 5 wt%, 48.4 cm⁻¹ for 10 wt%, and 73.7 cm⁻¹ for 15 wt%. Fast neutron removal cross-section also showed an increasing trend. The γ-ray linear attenuation coefficient decreased with increasing energy, but the Al-15Gd2O3-10 %W composite exhibited the highest LAC values, indicating superior γ-ray absorption capabilities. Correspondingly, the HVL values were lowest for the Al-15Gd2O3-10 %W composite. These findings demonstrate that Al-Gd2O3-W composites are promising materials for advanced industrial applications requiring robust mechanical properties and effective radiation shielding.

Fabrication and Characterization of Al2O3-WxSiy-WwBz Composite Prepared by Spark Plasma Sintering Method in Al-Si-WO3-B2O3 System

Fabrication and Characterization of Al2O3-WxSiy-WwBz Composite Prepared by Spark Plasma Sintering Method in Al-Si-WO3-B2O3 System

Optimization of microstructure and dielectric properties of BCTZ-based ceramics using two-step sintering method

Optimization of microstructure and dielectric properties of BCTZ-based ceramics using two-step sintering method

Cu/AlN composite and functionally graded materials with high strength and high electrical- and thermal-conductivity fabricated by spark plasma sintering

In this study, Cu/AlN composites and functionally graded materials (FGMs) were fabricated with the spark plasma sintering method. It was observed that a two-step sintering process, involving sintering under low pressure as the initial stage to remove adsorbed chemicals on the powder, was an effective method for producing sintering objects with high relative density. The hardness of the composites significantly increased with higher volume fraction of aluminum nitride (AlN) particles, while electrical- and thermal-conductivity decreased. Nevertheless, the advanse impact of AlN on thermal-conductivity was found to be minimal. Additionally during compression test, a crack was noted at the interface between Cu and Cu-5 vol%AlN region in two-layered FGMs after, whereas no such crack was observed in the three-layered FGMs. Therefore, it is confirmed that the concept of FGMs is useful in overcoming the shortcomings of mutually exclusiveness among high strength, high electrical- and high thermal-conductively.

Enhancing microstructure, nanomechanical and tribological properties of TiAl alloy processed by spark plasma sintering with Si3N4 ceramic particulates addition

TiAl matrix composites reinforced with varying weight fractions of Si3N4 ceramic particles were successfully fabricated by the spark plasma sintering method. The microstructure, nanomechanical and tribological properties of the sintered composites were investigated. The microstructural characterization revealed the evolution of a quasi-continuous and continuous network structure consisting of minor fractions of in-situ formed Ti2AlN, unreacted Si3N4 ceramic particles and dominant Ti5Si3 intermetallic phases within the TiAl matrix at Si3N4 content above 1.5 wt%. The in-situ precipitated phases enhanced the nanomechanical and tribological properties of the composites. The 7Si3N4/TiAl composite displayed the best nanomechanical properties, including nanohardness, elastic modulus, and H/Er ratio among the sintered samples. The specific wear rate of the composites decreases with increasing reinforcement content. 7Si3N4/TiAl composite exhibited the lowest specific wear rate of 0.38 ± 0.55 10-4 mm3/Nm, representing a 95.6% improvement in wear resistance compared to the unreinforced pure TiAl alloy. The improved wear performance of the composites was attributed to their load-bearing capacity and wear resistance of the hard, in-situ Ti2AlN, Ti5Si3 and unreacted Si3N4 particles in the TiAl matrix. The composites displayed a transition from adhesive wear to predominantly abrasive wear where the hard Si3N4 particles prevented direct metal-to-metal contact and facilitated the formation of a protective tribolayer, resulting in enhanced wear resistance. Hence, the developed Si3N4/TiAl composites are suitable for various structural and tribological applications.

Numerical Simulation and Experimental Analysis for Microwave Sintering Process of Lithium Hydride (LiH)

Dense lithium hydride (LiH) is widely used in neutron shielding applications for thermonuclear reactors and space systems due to its unique properties. However, traditional sintering methods often lead to cracking in LiH products. This study investigates the densification sintering of LiH using microwave technology. A multiphysics model was established based on the measured dielectric properties of LiH at different temperatures, allowing for a detailed analysis of the electromagnetic and thermal field distributions during the microwave heating of cylindrical LiH samples. The results indicate that the electric field distribution within the LiH is relatively uniform, with resistive losses concentrated primarily in the LiH region of the microwave cavity. LiH rapidly absorbs microwave energy, reaching the sintering temperature of 520 °C in just 415 s. Additionally, the temperature difference between the low- and high-temperature regions during the sintering process remains below 5 °C, demonstrating excellent uniform heating characteristics. The microwave sintering process enhances interface migration within the LiH samples, resulting in dense metallurgical bonding between grains. In summary, this research provides valuable insights and theoretical support for the rapid densification of LiH materials, highlighting the potential of microwave technology in improving material properties.

Investigation of Microhardness, Microstructural, Tribological, and Thermal Properties of Al7075/TiO2/Kaoline Hybrid Metal Matrix Composites Produced by Powder Metallurgy Process

The shift from traditional, single‐component metals and alloys continues, and researchers are currently investigating alternative materials. This evolution has led to the creation of innovative materials, including hybrid metal‐matrix composites. The present study aims to investigate the microstructural, surface morphological, and thermal properties of a novel Al7075/TiO2/Kaoline hybrid metal‐matrix composite prepared using high‐energy ball milling and sintering methods. In this study, phases related to the composite components are formed depending on the milling time, no undesirable phase is formed, but the peak intensities decreas as the milling time increases. Particle size increases from 63 to 215 μm with increasing milling time. Increasing the kaoline reinforcement ratio and sintering temperature increases the microhardness from 62.27 ± 2 to 75.83 ± 2 HV, and reduces the friction coefficient from 0.82 ± 0.01 to 0.62 ± 0.01. The wear rate of the composite without kaoline addition is 2.1 (mm3 m−1) × 10−3, while with 6 wt% kaoline addition, it decreases to 1.5 (mm3 m−1) × 10−3. There are no cracks in the composite other than plastic deformation due to sintering and wear. Peaks indicating endothermic and exothermic reactions during continuous heating occurr in the 635–750 °C temperature range.

Wear and Friction Characteristics of In Situ TiC-Reinforced Ti3SiC2-Ti5Si3 Composites Against 100Cr6 Steel Counterpart

In this study, the dry sliding characteristics of a Ti3SiC2/Ti5Si3 matrix reinforced with different TiC contents against a 100Cr6 steel ball were investigated. The composites were fabricated using the spark plasma sintering method with Ti, SiC, and C powders. SEM revealed that the composites possessed damage tolerance behavior, where grain pull-out, buckling, delamination, and diffuse microcracking were observed. In comparison, the unreinforced composite showed severe adhesive wear and tribo-oxidative wear mechanisms. The integration of the TiC phase in the Ti3SiC2/Ti5Si3 matrix enhanced the wear resistance by at least one order of magnitude. A new wear regime was observed in the TiC-reinforced composites, classified as mild wear, where tribo-oxidation and third-body abrasion were dominant, with ferrous deposits on the sliding surfaces.

Formation and characterization of Mn-Bi-Al ternary alloys of enhanced magnetic performance in MnBi/Al composites

Low-temperature phase manganese bismuth (LTP-MnBi) and a series of aluminum (Al) composites were synthesized using a potentially facile and scalable low-temperature liquid-phase sintering method in a vacuum at 300 °C. The incorporation of up to 10 at% Al led to a significant enhancement in coercivity (Hc), increasing from 2.32 ± 0.04 to 4.15 ± 0.07 kOe, while saturation magnetization showed a slight decrease of less than 3 %. However, beyond this concentration, a dramatic reduction in Hc was observed. The density of the freshly compacted powders, which included up to 10 at% Al, remained relatively constant at 7.47–7.58 g/cm³ but decreased with excess Al. A maximum energy product (BH)max of 1 MGOe was achieved in the fresh sample, with a 16 % enhancement in (BH)max in the MnBi composite containing 5 at% Al. Scanning electron microscopy revealed distinct MnBi and Bi-rich regions, while Al-rich areas became prominent at Al concentrations above 10 at%. Energy dispersive spectroscopy confirmed that only 3–5 at% Al could be effectively incorporated into Mn-Bi regions, with excess Al unevenly distributed on the surface. X-ray photoelectron spectroscopy indicated the formation of Al, Al₂O₃, and potential Mn-Bi-Al ternary alloys. Additionally, slab-DFT models, such as AlMn/MnBi, indicate that Al inclusion enhances the magnetization in MnBi composites, providing insights into its effects on the magnetic properties of Mn-Bi systems. These findings offer promising strategies to address the challenges posed by excess Bi in the MnBi structure, potentially optimizing the magnetic performance of similar non-magnetic or soft-magnetic composite systems.

The influence of CeO2 on the oxidation resistance of TaC/Ni composites

The in-situ TaC/Ni composites with different CeO2 content (0 wt%, 1 wt%, 2 wt%) were prepared by reactive sintering method, and their oxidation behavior in air at 1073 K was analyzed by static cyclic oxidation method to investigate the influence mechanism of CeO2 on the oxidation resistance of composites. The results show that the CeO2 particles are distributed around the TaC particles in the Ni matrix, and the oxidation behavior of composites with different CeO2 content conforms to the linear kinetic law. The oxide film is mainly composed of NiTa2O6 and a small amount of NiO. The generation reactions of Ta2O5 and NiTa2O6 induce a high expansion and compressive stress in oxide scale, leading to the formation of nonprotective oxide film with pores and cracks on the surface. As the addition of CeO2 increases from 0 wt% to 2 wt%, the thickness of oxide scale on composites obviously reduces from 505 μm to 122 μm, and the Ni and Ta oxides content decreases, leading to the reduction of pores and cracks in oxide scale. The Ce ion generated from the dissolution of CeO2 particles mainly distributes in the Ta oxides during the oxidation process, which hinders the outward diffusion of Ni and Ta ions, resulted in the improved oxidation resistance of TaC/Ni composites.

Carbon Dots Prepared by One-step Sintering Method and their Application for pH Detection

Introduction: In recent years carbon dots (CDs) have attracted researchers due to their unique physicochemical and fluorescent (FL) features, which can be applied in many fields such as battery materials, fluorescence sensing, display, biological imaging and photocatalysis. Method: We prepared CDs by using a facile one-step sintering method. The fluorescent properties and the application of pH detection were measured and analyzed. Results: The results show that CDs emit bright purplish-blue light centred at 425 nm excited by 355 nm UV light. FL intensity shows a linear relationship with pH values at 1~4 and 7~11, respectively. The reasonable mechanism of the tested effective pH sensitivity is discussed. Conclusion: Our study shows that the CDs prepared by the one-step sintering method have great potential to be used as pH sensors for physiochemical measurements.

Fine-Grain High-Performance Densified Oxide Fibers Produced by Open Ultrafast High-Temperature Sintering.

The considerable grain growth occurring during the long-term high-temperature sintering of polycrystalline oxide fibers negatively affects their mechanical properties, which highlights the need for alternative sintering methods. Herein, open ultrafast high-temperature sintering (OUHS) in air, characterized by rapid heating/cooling (>10000 K min-1) and a short high-temperature holding time (<10 s), is used to produce 3 mol% yttria-stabilized zirconia continuous fibers with coherent boundaries forming robust connections between fine grains. The tensile strength of these fibers (2.33GPa on average, sintering temperature = 1673 K) notably exceeds that of their counterparts produced by traditional sintering (1.17GPa). The effects of pores on fiber mechanicalproperties are analyzed using experimental and theoretical methods. For a versatility demonstration, OUHS is applied to several types of polycrystalline oxide fibers (HfO2, Al2O3, TiO2, Y2O3, and La2Zr2O7), considerably improving their mechanical properties and enabling crystalline phase control, which demonstrates the suitability of this procedure for the development of high-performance materials.

Microstructure Evolution of the Interface in SiCf/TiC-Ti3SiC2 Composite under Sequential Xe-He-H Ion Irradiation and Annealing Process.

A new type of SiCf/TiC-Ti3SiC2 composite was prepared by the Spark Plasma Sintering (SPS) method in this work. The phase transformation and interface cracking of this composite under ion irradiation (single Xe, Xe + He, and Xe + He + H ions) and subsequent annealing were analyzed using transmission electron microscopy (TEM), mainly focusing on the interface regions. Xe ion irradiation resulted in the formation of high-density stacking faults in the TiC coatings and the complete amorphization of SiC fibers. The implanted H ions exacerbated interface coarsening. After annealing at 900 °C for 2 h, the interface in the Xe + He + H ion-irradiated samples was seriously damaged, resulting in the formation of large bubbles and cracks. This damage occurred because the H atoms reduced the surface free energy, thereby promoting the nucleation and growth of bubbles. Due to the absorption effect of the SiCf/TiC interface on defects, the SiC fiber areas near the interface recovered back to the initial nano-polycrystalline structure after annealing.

Sintering process optimization of the additively manufactured pure copper parts through the metal paste deposited process

The fabrication process, sintering cycles through two sintering methods, microstructural and texture characterization, mechanical properties, and electrical conductivity of metal paste-deposited copper parts were investigated in this study. In the first condition, samples were air-debinded for carbon content removal followed by a sintering cycle. A sintering profile with the maximum sintering temperature and time of 1080 °C and 1 hr. was implemented after performing the air-debinding cycle at 250 °C for 2 hrs. In the second condition, samples were sintered in the environment of copper oxide for carbon removal in the early stages of the sintering cycle, i.e., 1070 °C for 1 hr and 1080 °C for 1, 2, and 3 hrs. The microstructural observations revealed coarser grains in the air-debinded samples, perhaps due to additional generated heat during carbon oxide formation, which may produce destructive effects on the boundary (HAGBs, twins, and CSL) volume and densification behavior of copper parts. However, through the second method, much finer grains and higher densities of boundaries were detected in the microstructure. Despite the significant effect of sintering conditions on the microstructure, texture interpretations revealed minor changes in the pole figures for different situations. Using the second sintering method and owing to the less carbon content and based on the density of the boundaries and their configurations, higher electrical conductivity (98.4±1.3 % IACS) was recorded by sintering the green parts. The comparison between the data from this study with other parts printed through other additive manufacturing techniques demonstrated a superior electrical conductivity level and acceptable balance between strain and strain notably with the sample sintered for 3 hrs.

Construction of Z‐type heterojunction Bi4Ti3O12/g‐C3N4 with pyroelectric effect for enhanced photocatalytic performance

AbstractPhotocatalytic technology has been widely studied, discussed, and tested as a feasible wastewater degradation technology. The present study demonstrated the preparation of g‐C3N4 material using solid‐state sintering method and the construction of Bi4Ti3O12/g‐C3N4 heterostructure via hydrothermal method. This direct contact Z‐type heterojunction improves the wide bandgap of Bi4Ti3O12 monomer, enhances its photoresponsiveness, and thus improves its photocatalytic performance. During the process of photocatalytic experiments, an environment of cold and hot fluctuations were created, and the pyroelectric effect was utilized to induce self‐polarization of the material and formed an internal electric field. It improves the transport ability of electron–hole pairs and suppresses their recombination in the transport path. According to the degradation experiment results, the degradation efficiency of pyroelectric synergistic heterojunction photocatalysis reached 88.7%, which was 2.27 times that of Bi4Ti3O12. It proves that the photocatalysis by pyroelectric synergistic heterojunction has good application prospects.

Preparation of Glass–Ceramics Using Low-Pressure Sintering Method for High-Value Utilization of Blast Furnace Slag

Preparation of Glass–Ceramics Using Low-Pressure Sintering Method for High-Value Utilization of Blast Furnace Slag

Effect of Cr content on the high temperature oxidation behavior of FeCoNiMnCrx porous high-entropy alloys

FeCoNiMnCr porous high-entropy alloys were prepared using the activation reaction sintering method with Fe, Co, Ni, Mn, and Cr as raw materials. The oxidation behaviors of FeCoNiMnCrx porous high-entropy alloys with different Cr contents, such as pore structure, the surface oxide film phase composition, structure, and morphology, were characterized by X-ray diffraction (XRD), electron probe micro analysis (EPMA), energy dispersive X-ray spectroscopy (EDS), and pore tester after high-temperature oxidation at 800–1000 °C. The results indicate that the initial porous high-entropy alloy comprises a single FCC solid solution phase. With the increase in Cr content, the average pore diameter, average porosity, and air permeability of the porous high-entropy alloy also increase. The oxidation kinetics of the porous high-entropy alloy after exposure to temperatures between 800 °C and 1000 °C follows a single-stage parabolic evolution law. At the same oxidation temperature, With the increase of Cr content, the oxidation gains gradually increased, at the same Cr content at different temperatures, the antioxidant performance of 1000 °C was the weakest, followed by 800 °C, and 900 °C showed excellent antioxidant performance. The oxidation products are mainly Mn2O3, Mn3O4, (Mn, Cr)3O4, Cr2O3and Fe2O3.