Thermoelectric Performance Enhancement in SnS Polycrystals Owing to Hole Doping Combined with Textured Microstructures.

Recently, the earth-abundant tin sulfide (SnS) has emerged as a promising thermoelectric material due to its phonon and electron structure similar to that of tin selenide (SnSe). However, compared with SnSe, limited progress has been achieved in the thermoelectric property enhancement of SnS. Textured SnS polycrystals with an enhanced thermoelectric performance have been developed in this work. The high carrier mobility benefited from the enhanced texture through the repressing strategy of spark plasma sintering, improving the electrical conductivity. In addition, Sn atom deficiencies in the texture sample led to an increased hole concentration, further boosting the electrical conductivity and power factor. The power factor exceeded 4.10 µW/cm·K2 at 423 K and 5.50 µW/cm·K2 at 850 K. The phonon scattering was strengthened by adjusting the multiscale microstructures including dislocations, defect clusters, etc., leading to an ultralow lattice thermal conductivity of 0.23 W/m·K at 850 K. A figure of merit zT > 1.3 at 850 K and an average zTave of 0.58 in the temperature range 373-850 K were achieved in the SnS polycrystal.

Preparation of 3D printed silicon nitride bioceramics by microwave sintering.

Silicon nitride (Si3N4) is a bioceramic material with potential applications. Customization and high reliability are the foundation for the widespread application of Si3N4 bioceramics. This study constructed a new microwave heating structure and successfully prepared 3D printed dense Si3N4 materials, overcoming the adverse effects of a large amount of 3D printed organic forming agents on degreasing and sintering processes, further improving the comprehensive performance of Si3N4 materials. Compared with control materials, the 3D printed Si3N4 materials by microwave sintering have the best mechanical performance: bending strength is 928 MPa, fracture toughness is 9.61 MPa·m1/2. Meanwhile, it has the best biocompatibility and antibacterial properties, and cells exhibit the best activity on the material surface. Research has shown that the excellent mechanical performance and biological activity of materials are mainly related to the high-quality degreasing, high cleanliness sintering environment, and high-quality liquid-phase sintering of materials in microwave environments.

Laser-Sintering of Cyclic Olefine Copolymer for Low Dielectric Loss Applications.

With increasing demands for data transfer, the production of components with low dielectric loss is crucial for the development of advanced antennas, which are needed to meet the requirements of next-generation communication technologies. This study investigates the impact of a variation in energy density on the part properties of a low-loss cyclic olefin copolymer (COC) in the SLS process as a way to manufacture complex low-dielectric-loss structures. Through a systematic variation in the laser energy, its impact on the part density, geometric accuracy, surface quality, and dielectric properties of the fabricated parts is assessed. This study demonstrates notable improvements in material handling and the quality of the manufactured parts while also identifying areas for further enhancement, particularly in mitigating thermo-oxidative aging. This research not only underscores the potential of COC in the realm of additive manufacturing but also sets the stage for future studies aimed at optimizing process parameters and enhancing material formulations to overcome current limitations.

Enhancement of the Refractory Matrix Diamond-Reinforced Cutting Tool Composite with Zirconia Nano-Additive.

This paper presents the results of the experimental research on diamond-reinforced composites with WC-Co matrices enhanced with a ZrO2 additive. The samples were prepared using a modified spark plasma sintering method with a directly applied alternating current. The structure and performance of the basic composite 94 wt.%WC-6 wt.%Co was compared with the ones with ZrO2 added in proportions up to 10 wt.%. It was demonstrated that an increase in zirconia content contributed to the intense refinement of the phase components. The composite 25 wt.%Cdiamond-70.5 wt.%WC-4.5 wt.%Co consisted of a hexagonal WC phase with lattice parameters a = 0.2906 nm and c = 0.2837 nm, a cubic phase (a = 1.1112 nm), hexagonal graphite phase (a = 0.2464 nm, c = 0.6711 nm), as well as diamond grits. After the addition of zirconia nanopowder, the sintered composite contained structural WC and Co3W3C phases, amorphous carbon, tetragonal phase t-ZrO2 (a = 0.36019 nm, c = 0.5174 nm), and diamond grits-these structural changes, after an addition of 6 wt.% ZrO2 contributed to an increase in the fracture toughness by more than 20%, up to KIc = 16.9 ± 0.76 MPa·m0.5, with a negligible decrease in the hardness. Moreover, the composite exhibited an alteration of the destruction mechanism after the addition of zirconia, as well as enhanced forces holding the diamond grits in the matrix.

The Effects of Different Zn Forms on Sintering Basic Characteristics of Iron Ore.

The micro-sintering method was used to determine the sintering basic characteristics of iron ore with Zn contents from 0 to 4%, the influence mechanism of Zn on sintering basic characteristics of iron ore was clarified by means of thermodynamic analysis and first-principles calculations. The results showed that (1) increasing the ZnO and ZnFe2O4 content increased the lowest assimilation temperature (LAT) but decreased the index of liquid phase fluidity (ILF) of iron ore. The addition of ZnS had no obvious effect on LAT but increased the LIF of iron ore. (2) ZnO and ZnFe2O4 reacted with Fe2O3 and CaO, respectively, during sintering, which inhibited the formation of silico-ferrite of calcium and aluminum (SFCA). The addition of ZnS accelerated the decomposition of Fe2O3 in the N2 atmosphere; however, the high decomposition temperature limited the oxidation of ZnS, so the presence of ZnS had a slight inhibitory effect on the formation of SFCA. (3) The Zn concentrated in hematite or silicate and less distributed in SFCA and magnetite in the form of solid solution; meanwhile, the microhardness of the mineral phase decreased with the increase in Zn-containing solid solution content. As the adsorption of Zn on the SFCA crystal surface was more stable, the microhardness of SFCA decreased more. The decrease in microhardness and content of the SFCA bonding phase resulted in a decrease in the compressive strength of the sinter.

Chemically Driven Sintering of Colloidal Cu Nanocrystals for Multiscale Electronic and Optical Devices.

Emerging applications of Internet of Things (IoT) technologies in smart health, home, and city, in agriculture and environmental monitoring, and in transportation and manufacturing require materials and devices with engineered physical properties that can be manufactured by low-cost and scalable methods, support flexible forms, and are biocompatible and biodegradable. Here, we report the fabrication and device integration of low-cost and biocompatible/biodegradable colloidal Cu nanocrystal (NC) films through room temperature, solution-based deposition, and sintering, achieved via chemical exchange of NC surface ligands. Treatment of organic-ligand capped Cu NC films with solutions of shorter, environmentally benign, and noncorrosive inorganic reagents, namely, SCN- and Cl-, effectively removes the organic ligands, drives NC grain growth, and limits film oxidation. We investigate the mechanism of this chemically driven sintering by systemically varying the Cu NC size, ligand reagent, and ligand treatment time and follow the evolution of their structure and electrical and optical properties. Cl--treated, 4.5 nm diameter Cu NC films yield the lowest DC resistivity, only 3.2 times that of bulk Cu, and metal-like dielectric functions at optical frequencies. We exploit the high conductivity of these chemically sintered Cu NC films and, in combination with photo- and nanoimprint-lithography, pattern multiscale structures to achieve high-Q radio frequency (RF) capacitive sensors and near-infrared (NIR) resonant optical metasurfaces.

Optimizing the Sintering Conditions of (Fe,Co)1.95(P,Si) Compounds for Permanent Magnet Applications.

(Fe,Co)2(P,Si) quaternary compounds combine large uniaxial magnetocrystalline anisotropy, significant saturation magnetization and tunable Curie temperature, making them attractive for permanent magnet applications. Single crystals or conventionally prepared bulk polycrystalline (Fe,Co)2(P,Si) samples do not, however, show a significant coercivity. Here, after a ball-milling stage of elemental precursors, we optimize the sintering temperature and duration during the solid-state synthesis of bulk Fe1.85Co0.1P0.8Si0.2 compounds so as to obtain coercivity in bulk samples. We pay special attention to shortening the heat treatment in order to limit grain growth. Powder X-ray diffraction experiments demonstrate that a sintering of a few minutes is sufficient to form the desired Fe2P-type hexagonal structure with limited secondary-phase content (~5 wt.%). Coercivity is achieved in bulk Fe1.85Co0.1P0.8Si0.2 quaternary compounds by shortening the heat treatment. Surprisingly, the largest coercivities are observed in the samples presenting large amounts of secondary-phase content (>5 wt.%). In addition to the shape of the virgin magnetization curve, this may indicate a dominant wall-pining coercivity mechanism. Despite a tenfold improvement of the coercive fields for bulk samples, the achieved performances remain modest (HC ≈ 0.6 kOe at room temperature). These results nonetheless establish a benchmark for future developments of (Fe,Co)2(P,Si) compounds as permanent magnets.

A remarkable permeability enhancement of Ni1-xZnxFe2O4 (x = 0.65 and 0.70), using a multi-compound calcined additive.

In this study, entanglement of composition, additive and/or sintering conditions and their effects on magnetic properties of soft ferrites, nickel zinc spinel ferrites (Ni1-xZnxFe2O4, x = 0.65 and 0.70) which were prepared via conventional solid-state reaction method investigated. Also an equiponderant calcined mixture of Bi2O3, CaO, CeO2, SiO2, Al2O3, Y2O3 and nanotitania was mixed thoroughly and used as a multi-compound calcined additive (MCCA). Calcined ferrite powders were crushed, dry and wet milled, dried, mixed with different amounts of MCCA (0.0, 0.5, 1.0, 1.5 and 2.0 wt%), formed in toroidal shapes and finally sintered at different temperatures, from 1150 up to 1360 °C for 3 h. X-ray diffraction assessment confirmed formation of the single phase cubic spinel structures. Initial permeability and Q-factor spectra of the toroids were obtained from 0.1 to 1000 kHz, using an LCR meter. The results show that initial permeability of each sample has a maximum and addition of MCCA to the ferrites leads to a marvelous increase in permeabilities. Additionally, MCCA decreases the optimum sintering temperature too. The optimum amounts of additive were 1.0 and 0.5 wt% for the x = 0.65 (µ' = 492, Ts = 1280 °C) and x = 0.70 (µ' = 478, Ts = 1320 °C), respectively. Permeability spectra illustrate that utility zone of the Ni0.35Zn0.65Fe2O4 and Ni0.3Zn0.7Fe2O4 are both less than 100 and 10 kHz, respectively. The results represent that there is a strong entanglement between composition, additive and/or sintering conditions. It can be concluded the MCCA added Ni0.35Zn0.65Fe2O4, is suitable for application in the switching power supplies.

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

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

Insight into the Contact Mechanism of Ag/Al-Si Interface for the Front-Side Metallization of TOPCon Silicon Solar Cells.

For N-type tunnel-oxide-passivated-contact silicon solar cells, optimal Ag/Al-Si contact interface is crucial to improve the efficiency. However, the specific roles of Ag and Al at the interface have not been clearly elucidated. Hence, this work delves into the sintering process of Ag/Al paste and examines the impact of the Ag/Al-Si interface structure on contact quality. By incorporating TeO2 into PbO-based Ag/Al paste, the Ag/Al-Si interface structure can be modulated. It can be found that TeO2 accelerates the sintering of Ag powder and increases Ag colloids within glass layer, while it simultaneously impedes the diffusion of molten Al. It leads to a reduced Al content near the Ag/Al-Si interface and a shorter diffusion distance of Al into Si. Notably, it can be demonstrated that the diffusion of Al in Si layer is more effective to reduce the contact resistance than the precipitation of Ag colloids. Therefore, the PbO-based Ag/Al paste, which favors Al diffusion, leads to solar cells with lower contact resistance and series resistance, higher fill factor, and superior photoelectric conversion efficiency. In brief, this work is significant for optimizing metallization of silicon solar cells and other semiconductor devices.

Cold-Sintered All-Inorganic Perovskite Bulk Composite Scintillators for Efficient X-ray Imaging.

Cost-effective bulk scintillators with high density, large-area, and long-term stability are desirable for high-energy radiation detections. Conventional bulk polycrystalline or single-crystal scintillators are generally synthesized by high-temperature approaches, and it is challenging to realize simultaneously high detectivity/responsivity, spatial resolution, and rapid time response. Here, we report the cold sintering of bulk scintillators (at 90 °C) based on an "emitter-in-matrix" principle, in which emissive CsPbBr3 nanocrystals are embedded in a durable and transparent Cs4PbBr6 matrix. These bulk scintillators exhibit high light yield (33,800 photons MeV-1), low detection limit (79 nGyair s-1), fast decay time (9.8 ns), and outstanding spatial resolution of 8.9 lp mm-1 to X-ray radiation and an energy resolution of 19.3% for γ-ray (59.6 keV) detection. The composite scintillator also shows exceptional stability against environmental degradation and cyclic X-ray radiation. Our results demonstrate a cost-effective strategy for developing perovskite-based bulk transparent scintillators with exceptional performance and high radioluminescence stability for high-energy radiation detection and imaging.

Simultaneous Li-Doping and Formation of SnO2-Based Composites with TiO2: Applications for Perovskite Solar Cells.

Tin oxide (SnO2) has been recognized as one of the beneficial components in the electron transport layer (ETL) of lead-halide perovskite solar cells (PSCs) due to its high electron mobility. The SnO2-based thin film serves for electron extraction and transport in the device, induced by light absorption at the perovskite layer. The focus of this paper is on the heat treatment of a nanoaggregate layer of single-nanometer-scale SnO2 particles in combination with another metal-dopant precursor to develop a new process for ETL in PSCs. The combined precursor solution of Li chloride and titanium(IV) isopropoxide (TTIP) was deposited onto the SnO2 layer. We varied the heat treatment conditions of the spin-coated films comprising double layers, i.e., an Li/TTIP precursor layer and SnO2 nanoparticle layer, to understand the effects of nanoparticle interconnection via sintering and the mixing ratio of the Li-dopant on the photovoltaic performance. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) measurements of the sintered nanoparticles suggested that an Li-doped solid solution of SnO2 with a small amount of TiO2 nanoparticles formed via heating. Interestingly, the bandgap of the Li-doped ETL samples was estimated to be 3.45 eV, indicating a narrower bandgap as compared to that of pure SnO2. This observation also supported the formation of an SnO2/TiO2 solid solution in the ETL. The utilization of such a nanoparticulate SnO2 film in combination with an Li/TTIP precursor could offer a new approach as an alternative to conventional SnO2 electron transport layers for optimizing the performance of lead-halide perovskite solar cells.

Microstructural Characterization of AlCrCuFeMnNi Complex Concentrated Alloy Prepared by Pressureless Sintering.

A significant and increasing number of studies have been dedicated to complex concentrated alloys (CCAs) due to the improved properties that these metallic materials can exhibit. However, while most of these studies employ melting techniques, only a few explore powder metallurgy and pressureless sintering as production methods. In this work, a microstructural characterization of AlCrCuFeMnNi CCA samples obtained by powder metallurgy and pressureless sintering using mixtures of powders with different compositions was carried out. One batch of samples (B1) was prepared using commercial powders of Al, Cr, Cu, Fe, Mn, and Ni. Another batch (B2) used mixtures of CrFeMn, AlNi, and Cu powders. A third set of samples (B3) was obtained by adding 1% at. of Mg to the B2 powder. The samples were characterized by X-ray diffraction, scanning and transmission electron microscopy, energy dispersive spectroscopy, density measurements, and hardness tests. Thermodynamic calculations were also used to complement the microstructural characterization. All the obtained samples exhibited high relative density and hardness values. However, B3 samples showed a higher hardness, attributed to the finer distribution of oxide particles, which was promoted by the presence of Mg during sintering. These last samples presented a hardness/density ratio of 62 HV/(g cm-3), surpassing that of some martensitic stainless steels and nickel-titanium alloys.

Optimization of Mechanical Properties and Evaluation of Fatigue Behavior of Selective Laser Sintered Polyamide-12 Components.

In this paper, a comprehensive study of the mechanical properties of selective laser sintered polyamide components is presented, for various different process parameters as well as environmental testing conditions. For the optimization of the static and dynamic mechanical load behavior, different process parameters, e.g., laser power, scan speed, and build temperature, were varied, defining an optimal parameter combination. First, the influence of the different process parameters was tested, leading to a constant energy density for different combinations. Due to similarities in mechanical load behavior, the energy density was identified as a decisive factor, mostly independent of the input parameters. Thus, secondly, the energy density was varied by the different parameters, exhibiting large differences for all levels of fatigue behavior. An optimal parameter combination of 18 W for the laser power and a scan speed of 2666 mm/s was determined, as a higher energy density led to the best results in static and dynamic testing. According to this, the variation in build temperature was investigated, leading to improvements in tensile strength and fatigue strength at higher build temperatures. Furthermore, different ambient temperatures during testing were evaluated, as the temperature-dependent behavior of polymers is of high importance for industrial applications. An increased ambient temperature as well as active cooling during testing was examined, having a significant impact on the high cycle fatigue regime and on the endurance limit.

Impact of the sintering parameters on the grain size, crystal phases, translucency, biaxial flexural strength, and fracture load of zirconia materials.

OBJECTIVES: To investigate the influence of the zirconia and sintering parameters on the optical and mechanical properties. METHODS: Three zirconia materials (3/4Y-TZP, 4Y-TZP, 3Y-TZP) were high-speed (HSS), speed (SS) or conventionally (CS) sintered. Disc-shaped specimens nested in 4 vertical layers of the blank were examined for grain size (GS), crystal phases (c/t'/t/m-phase), translucency (T), and biaxial flexural strength. Fracture load (FL) of three-unit fixed dental prostheses was determined initially and after thermomechanical aging. Fracture types were classified, and data statistically analyzed. RESULTS: 4Y-TZP showed a higher amount of c + t'-phase and lower amount of t-phase, and higher optical and lower mechanical properties than 3Y-TZP. In all materials, T declined from Layer 1 to 4. 3/4Y-TZP showed the highest FL, followed by 3Y-TZP, while 4Y-TZP showed the lowest. In 4Y-TZP, the sintering parameters exercised a direct impact on GS and T, while mechanical properties were largely unaffected. The sintering parameters showed a varying influence on 3Y-TZP. Thermomechanical aging resulted in comparable or higher FL. CONCLUSION: 3/4Y-TZP presenting the highest FL underscores the principle of using strength-gradient multi-layer blanks to profit from high optical properties in the incisal area, while ensuring high mechanical properties in the lower areas subject to tensile forces. With all groups exceeding maximum bite forces, the examined three-unit FDPs showed promising long-term mechanical properties.

Thermal Conductivity and Sintering Mechanism of Aluminum/Diamond Composites Prepared by DC-Assisted Fast Hot-Pressing Sintering.

A novel DC-assisted fast hot-pressing (FHP) powder sintering technique was utilized to prepare Al/Diamond composites. Three series of orthogonal experiments were designed and conducted to explore the effects of sintering temperature, sintering pressure, and holding time on the thermal conductivity (TC) and sintering mechanism of an Al-50Diamond composite. Improper sintering temperatures dramatically degraded the TC, as relatively low temperatures (≤520 °C) led to the retention of a large number of pores, while higher temperatures (≥600 °C) caused unavoidable debonding cracks. Excessive pressure (≥100 MPa) induced lattice distortion and the accumulation of dislocations, whereas a prolonged holding time (≥20 min) would most likely cause the Al phase to aggregate into clusters due to surface tension. The optimal process parameters for the preparation of Al-50diamond composites by the FHP method were 560 °C-80 MPa-10 min, corresponding to a density and TC of 3.09 g cm-3 and 527.8 W m-1 K-1, respectively. Structural defects such as pores, dislocations, debonding cracks, and agglomerations within the composite strongly enhance the interfacial thermal resistance (ITR), thereby deteriorating TC performance. Considering the ITR of the binary solid-phase composite, the Hasselman-Johnson model can more accurately predict the TC of Al-50diamond composites for FHP technology under an optimal process with a 3.4% error rate (509.6 W m-1 K-1 to 527.8 W m-1 K-1). The theoretical thermal conductivity of the binary composites estimated by data modeling (Hasselman-Johnson Model, etc.) matches well with the actual thermal conductivity of the sintered samples using the FHP method.

Fabrication of High Thermal Conductivity Aluminum Nitride Ceramics via Digital Light Processing 3D Printing.

The sintering of high-performance ceramics with complex shapes at low temperatures has a significant impact on the future application of ceramics. A joint process of digital light processing (DLP) 3D printing technology and a nitrogen-gas pressure-assisted sintering method were proposed to fabricate AlN ceramics in the present work. Printing parameters, including exposure energy and time, were optimized for the shaping of green bodies. The effects of sintering temperature, as well as nitrogen pressure, on the microstructure, density, and thermal conductivity of AlN ceramics were systematically discussed. A high thermal conductivity of 168 W·m-1·K-1 was achieved by sintering and holding at a significantly reduced temperature of 1720 °C with the assistance of a 0.6 MPa nitrogen-gas pressure. Further, a large-sized AlN ceramic plate and a heat sink with an internal mini-channel structure were designed and successfully fabricated by using the optimized printing and sintering parameters proposed in this study. The heat transfer performance of the ceramic heat sink was evaluated by infrared thermal imaging, showing excellent cooling abilities, which provides new opportunities for the development of ceramic heat dissipation modules with complex geometries and superior thermal management properties.

(Sb0.5Li0.5)TiO3-Doping Effect and Sintering Condition Tailoring in BaTiO3-Based Ceramics.

(1-x)(Ba0.75Sr0.1Bi0.1)(Ti0.9Zr0.1)O3-x(Sb0.5Li0.5)TiO3 (abbreviated as BSBiTZ-xSLT, x = 0.025, 0.05, 0.075, 0.1) ceramics were prepared via a conventional solid-state sintering method under different sintering temperatures. All BSBiTZ-xSLT ceramics have predominantly perovskite phase structures with the coexistence of tetragonal, rhombohedral and orthogonal phases, and present mainly spherical-like shaped grains relating to a liquid-phase sintering mechanism due to adding SLT and Bi2O3. By adjusting the sintering temperature, all compositions obtain the highest relative density and present densified micro-morphology, and doping SLT tends to promote the growth of grain size and the grain size distribution becomes nonuniform gradually. Due to the addition of heterovalent ions and SLT, typical relaxor ferroelectric characteristic is realized, dielectric performance stability is broadened to ~120 °C with variation less than 10%, and very long and slim hysteresis loops are obtained, which is especially beneficial for energy storage application. All samples show extremely fast discharge performance where the discharge time t0.9 (time for 90% discharge energy density) is less than 160 ns and the largest discharge current occurs at around 30 ns. The 1155 °C sintered BSBiTZ-0.025SLT ceramics exhibit rather large energy storage density, very high energy storage efficiency and excellent pulse charge-discharge performance, providing the possibility to develop novel BT-based dielectric ceramics for pulse energy storage applications.

Microstructure and Properties of Pressureless-Sintered Zirconium Carbide Ceramics with MoSi2 Addition.

Zirconium carbide (ZrC) ceramics have a high melting point, low neutron absorption cross section, and excellent resistance to the impact of fission products and are considered to be one of the best candidate materials for fourth-generation nuclear energy systems. ZrC ceramics with a high relative density of 99.1% were successfully prepared via pressureless sintering using a small amount of MoSi2 as an additive. The influence of the MoSi2 content on the densification behavior, microstructure, mechanical properties, and thermal properties of ZrC ceramics was systematically investigated. The results show that the densification of ZrC was significantly enhanced by the introduction of MoSi2 due to the formation of a liquid phase during sintering. In addition, the ZrC grains were refined due to the pinning effect of the generated silicon carbide. The flexural strength and Vickers hardness of ZrC ceramics with 2.5 vol% MoSi2 sintered at 1850 °C were 408 ± 12 MPa and 17.1 GPa, respectively, which were approximately 30% and 10% higher compared to the samples without the addition of MoSi2. The improved mechanical properties were mainly attributed to the high relative density (99.1%) and refined microstructure.

Investigation on YSZ- and SiO2-Doped Mn-Fe Oxide Granules Based on Drop Technique for Thermochemical Energy Storage.

The Mn-Fe oxide material possesses the advantages of abundant availability, low cost, and non-toxicity as an energy storage material, particularly addressing the limitation of sluggish reoxidation kinetics observed in pure manganese oxide. However, scaling up the thermal energy storage (TCES) system poses challenges to the stability of the reactivities and mechanical strength of materials over long-term cycles, necessitating their resolution. In this study, Mn-Fe granules were fabricated with a diameter of approximately 2 mm using the feasible and scalable drop technique, and the effects of Y2O3-stabilized ZrO2 (YSZ) and SiO2 doping, at various doping ratios ranging from 1-20 wt%, were investigated on both the anti-sintering behavior and mechanical strength. In a thermal gravimetric analyzer, the redox reaction tests showed that both the dopants led to an enhancement in the reoxidation rates when the doping ratios were in an appropriate range, while they also brought about a decrease in the reduction rate and energy storage density. In a packed-bed reactor, the results of five consecutive redox tests showed a similar pattern to that in a thermal gravimetric analyzer. Additionally, the doping led to the stable reduction/oxidation reaction rates during the cyclic tests. In the subsequent 120 cyclic tests, the Si-doped granules exhibited volume expansion with a decreased crushing strength, whereas the YSZ-doped granules experienced drastic shrinkage with an increase in the crushing strength. The 1 wt% Si and 2 wt% Si presented the best synthetic performance, which resulted from the milder sintering effects during the long-term cyclic tests.