High Temperature Sintering Research Articles

Pulse current enhanced densification and mechanical property of Inconel 718 superalloy fabricated by spark plasma sintering

The Inconel 718 superalloy was fabricated using spark plasma sintering (SPS) technology with varying sintering temperatures and heating rates. The densification and mechanical property of the sintered superalloys were characterized through tensile and compression tests at room temperature, as well as microscopic analyses. The evidence suggests that the plasma generated between the particles results in evaporative melting on the particle surface and plastic deformation of the particle boundaries, accelerating the densification process is by 3∼4 times. Besides, the grain size refinement coefficient affected by pulse current in the holding stage is 0.7–0.8, leading to a significant grain boundary strengthening during SPS process. The dislocation dominated by ball milling and SPS parameters also helps improve the strength and plasticity of the sintered superalloy. The superalloy sintered at 1050 °C with a heating rate of 100 °C/min demonstrated the highest tensile and compressive fracture strengths, measuring 1410 MPa and 1983 MPa, respectively, with the tensile and compressive yield strength of 712 MPa and 1557 MPa, respectively. Lower sintering temperatures or higher heating rates results in lower levels of densification and decreased strength. In addition, plasticity is reduced at higher sintering temperatures or lower heating rates due to excessive precipitation of brittle phases.

Direct ink writing of non-sintered ceramic with biomimetic cellular structure

Cellular ceramics are highly valued for their exceptional mechanical properties and low density, making them suitable for applications like thermal insulation, impact absorption, and biomedical implants. However, high-temperature sintering required for densification can cause issues like shrinkage, loss of precision, and degradation of functional additives. This work reports a novel approach for fabricating 3D printed cellular ceramics under ambient conditions using CO2-cured γ-C2S ink via direct ink writing. The printed green body is converted into a dense matrix of CaCO3 and silica gel upon exposure to a CO2-rich environment without high temperature sintering. The non-sintered cellular ceramics achieve high compressive and specific strength comparable to sintered counterparts, with the square-shaped structure exhibiting the best performance of 104 and 171 MPa in terms of in-plane and out-of-plane compressive strength, respectively. Further, the in-situ analysis reveals distinct deformation modes and crack propagation patterns across structures, providing insights into structure-property relationships to guide the design of high-strength non-sintered cellular ceramics.

Near-infrared-emitting (Gd1-yNdy)3(Ga1-xCrx)5O12 Glass Ceramic Phosphors for Light-emitting Diodes

In this study, we proposed a blue-excitable and near-infrared (NIR) emission ceramic phosphor - Gd3Ga5O12:Cr3+, Nd3+ (GGO:Cr, Nd) by a solid-state reaction for light-emitting diode applications. The as-synthesized Gd3Ga4.95Cr0.05O12 phosphor displayed a broad emission peak at 759 nm (4T2 → 4A2) with a full-width-half-maximum of 122 nm under 460 nm excitation. In order to generate NIR, we introduced Nd3+ ions as activators to substitute Gd3+ ions in GGO:Cr3+ phosphors. Via energy transfer from Cr3+ ions to Nd3+ ions in GGO, an intense NIR emission at 1064 nm resulting from 4F3/2 → 4I11/2 is demonstrated. Furthermore, we investigate the doping effects at various concentrations and reanalyzed the luminescent characteristics of (Gd1-yNdy)3(Ga1-xCrx)5O12 phosphors to determine the optimal doping concentration of Cr and Ni, which were found to be 1 mol.% and 3 mol.%, respectively. Finally, we mix the composition-optimized (Gd0.97Nd0.03)3(Ga0.99Cr0.01)5O12 NIR-emission phosphor with silica-based glass powder. After cold pressing and high-temperature sintering using molds, we obtain NIR-emitting glass-ceramic phosphors through laser cutting technology and packaged them into high-power light-emitting diodes.

Nb Doping Reduces the Primary Particle Size of the Li-Rich Cathode

Lithium-rich materials exhibit promising potential as commercial lithium-ion battery cathodes, offering a specific energy of 900 Wh.kg−1, surpassing other commercial cathode materials by more than 20%. However, challenges such as low initial efficiency, poor conductivity, and subpar cycling performance, along with rapid voltage decay, have impeded their commercialization. In this study, we propose a niobium-doping technique for lithium-rich materials. By controlling particle size during high-temperature sintering, niobium facilitates the production of highly crystalline, small-grain lithium-rich materials. This approach achieves both high capacity and long cycle life. Specifically, at 0.5 C, the pouch cell demonstrates a maximum specific capacity of 230.2 mAh.g−1, retaining 85.2% after 500 cycles, with a voltage drop of less than 0.3 mV/cycle. Additionally, we investigated the mechanism of niobium in suppressing particle growth through doping with elements of varying M-O bond strengths, obtaining systematic data.

Fabrication of Y2O3-doped MgO refractory raw materials based on magnesium hydroxide from salt-lake brine

High-purity magnesia refractories were fabricated by brine magnesium hydroxide from the salt-lake brine (Qinghai Salt Lake) and Y2O3 as an additive at 1780 °C. It avoided the substantial CO2 emissions and ultra high temperature sintering process (＞1900 °C) when compared with the conventional magnesite-calcination technical approach. The results confirmed that Y2O3 was dispersed on the MgO grains boundaries in the fabricated MgO aggregates, resulting in a decrease in apparent porosity and enhancing the grains' boundaries. With 3 wt% addition of Y2O3, the apparent porosity and bulk density of the sample reached to 15.9 % and 3.10 g/cm3 from 37.9 % to 2.30 g/cm3 of blank control group, respectively. Compared to the blank control without Y2O3-adding, the sample with 5 wt% Y2O3 exhibited a 54.17 % increase in the resistance to molten slag. SEM results indicated that the incorporation of Y2O3 in samples increased the porosity of small pores and enhanced grains boundaries, thereby suppressing slag's penetration. Furthermore, the Y2O3-adding was employed to disperse the MgO grains boundaries and existed as separate phases for grains boundaries enhancement. The slag attack of the fabricated MgO–Y2O3 refractory raw materials were controlled by an inter-crystalline corrosion process.

Synergistically Engineering Grains and Grain Boundaries toward Li Dendrite-Free Li7La3Zr2O12.

Cation-doped cubic Li7La3Zr2O12 is regarded as a promising solid electrolyte for safe and energy-dense solid-state lithium batteries. However, it suffers from the formation of Li2CO3 and high electronic conductivity, which give rise to an unconformable Li/Li7La3Zr2O12 interface and lithium dendrites. Herein, composite AlF3-Li6.4La3Zr1.4Ta0.6O12 solid electrolytes were created based on thermal AlF3 decomposition and F/O displacement reactions under a high-temperature sintering process. When the AlF3 is thermally decomposed, it leaves Al2O3/AlF3 meliorating the grain boundaries and F- ions partially displacing O2- ions in the grains. Due to the higher electronegativity of F- in the grains and the grain-boundary modification, these AlF3-Li6.4La3Zr1.4Ta0.6O12 deliver optimized electronic conduction and chemical stability against the formation of Li2CO3. The Li/AlF3-Li6.4La3Zr1.4Ta0.6O12/Li cell exhibits a low interfacial resistance of ∼16 Ω cm2 and an ultrastable long-term cycling behavior for 800 h under a current density of 200 μA/cm2, leading to Li//LiCoO2 solid-state batteries with good rate performance and cycling stability.

Ultrafast synthesis and luminescence properties of rare earth orthoniobates RENbO4 (RE = La, Eu, Gd, Yb, Lu)

Rare earth orthoniobates (RENbO4) are one kind of important functional materials due to its applications in solid-state phosphors, thermal barrier coatings, and microwave dielectric ceramics. The synthesis of rare earth niobates often needs high reaction temperatures (1300 °C–1700 °C) and long processing times (from hours to tens of hours) in solid-state reactions, which can increase the study time of the relationship between structure and properties. In this work, we used ultrafast high-temperature sintering method to synthesize RENbO4 (RE = La, Eu, Gd, Yb, Lu), and found specific structure and properties in these materials obtained with specific synthetic techniques. Based on the electronegativity scale, the charge transfer energy of lanthanide ions in the YNbO4 crystal was calculated. The rapid synthesis of RENbO4 in a vacuum atmosphere generated more oxygen vacancies, and the structures of [REO8] and [NbO6] were distorted. The shortening of the fluorescence lifetime of LaNbO4 and EuNbO4 was related to the formation of self-trapped excitons facilitated by lattice distortion. The emission peak of LuNbO4 at about 530 nm is attributed to the oxygen vacancy in the niobate group. The reported synthetic methods can provide a fast materials screening route for high melting point inorganic materials.

Study on the properties of anorthite-based porous sound-absorbing materials prepared by steel slag and fly ash

The efficient utilization of solid wastes, such as fly ash and steel slag, has attracted significant attention across the globe. In this paper, these two kinds of waste materials are used to prepare porous sound-absorbing materials, so as to achieve efficient resource utilization and environmental protection, and promote green manufacturing and circular economy. In this study, steel slag and high-alumina fly ash were used as the primary raw materials to prepare green bodies via organic foam impregnation. Subsequently, a high-temperature sintering process was implemented to get the porous sound absorption material product from the green bodies. The effects of several factors, including the ratio of steel slag and fly ash, sintering temperature, and pore structure, on the sound absorption and mechanical properties of the product were investigated. Based on the anorthite region in the CaO–Al2O3–SiO2 ternary phase diagram region, the composition ratio of the material was designed. The composition and microstructure of the material were characterized by X-ray diffraction and scanning electron microscopy. From the results, with the increase of the ratio of fly ash and steel slag, the composition of low melting point substances in the system decreases, and the amount of liquid phase decreases, which weakens the pore blocking phenomenon inside the material, resulting in the increase of pore size and noise reduction coefficient of the material. Besides, higher sintering temperature tends to correlate to greater density and higher compressive and flexural strengths but lower porosity, and the sound absorption coefficient demonstrated a peak with respect to sintering temperature. Furthermore, when the reduction of polyurethane sponge body pore size was taken into account, the product's sound absorption coefficient also showed a peak. The optimal parameters for our porous materials are as follows: fly ash:steel slag = 48 : 25, polyurethane sponge pore size = 40 ppi, sintering temperature = 1160 °C at 1-h duration (bulk density = 573.98 kg/m3), compressive strength = 1 MPa, porosity = 79.35 %, and noise reduction coefficient = 0.47.

Investigation of the role of sintering temperature on microstructure, ac conductivity, and dielectric constant of single phase NiSnO3 nanopowder

This study investigates the effect of sintering temperature on the structural and electrical properties of co-precipitated nickel stannate (NiSnO3) nanopowder. Sintering temperatures, determined using Thermo Gravimetric Analysis (TGA), reveal a pure hexagonal perovskite structure through X-ray diffraction (XRD) analysis. Crystallite size increased from 10.56 nm to 26.04 nm and lattice strain decreased from 23.05×10−3 to 2.35×10−3 with higher sintering temperatures, analyzed via the Scherrer formula. d-spacing values from SAED patterns align with XRD results, and TEM analysis shows particle size growth from ∼11.43 nm to ∼28.16 nm as sintering temperature rises from 600°C to 900°C. Elemental composition has been confirmed through EDX, and elemental mapping analysis. Impedance spectroscopy via Cole-Cole plots indicated non-Debye-type or multiple relaxations with depressed semicircles due to grain and grain boundary effects. The sample sintered at 900°C exhibits the highest conductivity (8.35×10−5 Ω−1cm−1) with lowest activation energy of 0.31 eV and maximum dielectric constant values, with a minimum relaxation time of 0.00029 sec. Also the frequency variation of Z′′ and M′′ confirm the presence of non-Debye type relaxation. Scaling behavior of the imaginary part of complex impedance and conductivity spectra confirms temperature-independent conduction and relaxation mechanisms. These materials are used in energy storage applications.

Highly wear resistant metal bond for diamond tool based on two-step reactive sintered Fe3Al

Metal bond diamond tools are regularly used in the machining of various hard and brittle materials. The mechanical properties and wear resistance of the metal bond are very important for the tool's life and machining performance. Herein, a low-cost and highly wear resistant Fe3Al bonded material for diamond tool was proposed. A novel two-step reactive sintering method, integrating short-term high-temperature reactive sintering and long-term low-temperature densification sintering, was proposed to prepare Fe3Al bond diamond tools. The effect of sintering temperature on the microstructure and mechanical properties of the Fe3Al bond was examined during one-step reactive sintering. The mechanical properties and tribological characteristics of the one-step and two-step reactive sintered Fe3Al and commercial Fe alloy bond were compared. The machining performance of the two-step reactive sintered Fe3Al bond diamond tool on sapphire was also examined and compared to that of a commercial Fe alloy bond diamond tool. The results showed that the relative density and mechanical properties of the Fe3Al bonded material were enhanced by increasing the sintering temperature during one-step reactive sintering. Moreover, the sample sintered at 1150-850 °C exhibited better mechanical properties and wear resistance compared to the one-step reactive sintered Fe3Al and commercial bond. The grinding ratio of the two-step reactive sintered Fe3Al bond diamond tool was 157 % higher than that of the commercial Fe alloy bond diamond tool.

Sintering parameter investigation for bimetallic stainless steel 316L/inconel 718 composite printed by dual-nozzle fused deposition modeling

PurposeFused deposition modeling (FDM) nowadays offers promising future applications for fabricating not only thermoplastic-based polymers but also composite PLA/Metal alloy materials, this capability bridges the need for metallic components in complex manufacturing processes. The research is to explore the manufacturability of multi-metal parts by printing green bodies of PLA/multi-metal objects, carrying these objects to the debinding process and varying the sintering parameters.Design/methodology/approachThree different sample types of SS316L part, Inconel 718 part and bimetallic composite of SS316L/IN718 were effectively printed. After the debinding process, the printed parts (green bodies), were isothermally sintered in non-vacuum chamber to investigate the fusion behavior at four different temperatures in the range of 1270 °C−1530 °C for 12 h and slowly cooled in the furnace. All samples was assessed including geometrical assessment to measure the shrinkage, characterization (XRD) to identify the crystallinity of the compound and microstructural evolution (Optical microscopy and SEM) to explore the porosity and morphology on the surface. The hardness of each sample types was measured and compared. The sintering parameter was optimized according to the microstructural evaluation on the interface of SS316L/IN718 composite.FindingsThe investigation indicated that the de-binding of all the samples was effectively succeeded through less weight until 16% when the PLA of green bodies was successfully evaporated. The morphology result shows evidence of an effective sintering process to have the grain boundaries in all samples, while multi-metal parts clearly displayed the interface. Furthermore, the result of XRD shows the tendency of lower crystallinity in SS316L parts, whilst IN718 has a high crystallinity. The optimal sintering temperature for SS316L/IN718 parts is 1500 °C. The hardness test concludes that the higher sintering temperature gives a higher hardness result.Originality/valueThis study highlights the successful sintering of a bimetallic stainless steel 316 L/Inconel 718 composite, fabricated via dual-nozzle fused deposition modeling, in a non-vacuum environment at 1500 °C. The resulting material displayed maximum hardness values of 872 HV for SS316L and 755.5 HV for IN718, with both materials exhibiting excellent fusion without any cracks.

Flash sintering of tunable dielectric Ba0.6Sr0.4TiO3 electroceramics

Ba(1-x)SrxTiO3 (BST) is a crucial dielectric material in tunable devices for modern wireless communication technologies, owing to high dielectric tunability and low dielectric loss. However, the conventional processing of BST ceramics requires a high sintering temperature of about 1350 ºC. In this work, we demonstrate the feasibility of using Flash sintering (FS) and corresponding maps to process Ba0.6Sr0.4TiO3 ceramics, resulting in a 350 ºC decrease in sintering temperature and 7 h reduction in sintering process time. The Flash-sintered BST exhibits a finer grain microstructure, lower dielectric loss, and significantly higher K-factor (figure of merit for tunability) when compared to conventionally sintered BST, unequivocally meeting the application criteria for tunable materials. Our findings highlight the effectiveness of FS as an alternative method for the rapid sintering of BST, while also opening up possibilities for further research into more efficient sintering processes for electroceramics.

Holistic view on cation interdiffusion during processing and operation of garnet all-solid-state batteries

All-solid-state batteries based on the active cathode material LiCoO2 (LCO), a garnet-type Li7La3Zr2O12 (LLZO) electrolyte and a Li-metal anode are attracting a lot of attention as a robust and safe alternative to conventional lithium-ion batteries. The challenges in the practical realization of such cells are related to high-temperature sintering, which compacts the ceramic powder but also leads to undesirable material interactions such as cation interdiffusion and secondary phase formation. Even if high initial capacities can be achieved, the all-inorganic cells suffer from a strong capacity drop due to various degradation phenomena during processing and operation, which are not yet fully understood. In this study, the thermodynamic and kinetic aspects of co-sintering as well as the structural evolution of materials and interfaces during processing and operation of co-sintered LCO-LLZO cathodes are investigated in detail. A thermodynamic model for the interdiffusion of cations is derived and the effects of the diffusion of Al- and Co-ions, which occurs during the processing and cycling of the cells, are investigated. In LLZO, the diffusion of 0.13 Co per formula unit (pfu) has a negligible effect on ionic and electronic conductivity and electrochemical stability. In contrast, the substitution of 0.01 pfu Al and the induced disorder in the layer structure of LCO increases the polarization during cycling. All-inorganic cells fabricated with optimized sintering parameters to minimize interdiffusion between LCO and LLZO show good initial performance but similar degradation during cycling, as the used processing parameters result in a more porous microstructure leading to the development of cracks along the LLZO/LCO interface. The results obtained highlight the inherent instabilities of all-ceramic cathodes with unprotected LCO/LLZO interfaces, which require precise tuning of materials and processing parameters to achieve both high mechanical stability and low interdiffusion.

Performance improvement of NiO/YSZ sensitive electrode for high temperature electrochemical NOx gas sensors

In the mixed-potential gas sensor, the electrode type, particle size, microstructural morphology, as well as the interface state between the oxide-sensitive electrode and the solid electrolyte, are the key factors for determining the magnitude of the mixed potential. NiO-based material with the addition of Y2O3-stabilized ZrO2 (YSZ) particles is considered as one of the promising sensitive electrode materials for preparing the mixed-potential NOx sensors due to its excellent gas sensitivity. In this paper, the preparation technology of NiO-sensitive electrodes is developed and optimized for improving NOx (NO and NO2) gas-sensitivity properties of the NOx sensors. The experimental results show that the addition of YSZ can effectively improve the agglomeration morphology of NiO particles in the NOx-YSZ-based electrode material during high temperature sintering (i.e. 1200 °C) and enhance the bonding strength with the solid electrolyte. The sensor which was prepared by using the developed NOx-YSZ-based electrode material with the YSZ addition of 20 wt% has the most sensitive response characteristic to NO gas, and its response potential value increases with NO gas concentration. Elevating electrode sintering temperature can increase the size of NiO particles and shorten the length of the three-phase boundary (TPB) in the sensitive electrode. The average length of TPB is the longest in the sensitive electrode sintered at 1000 °C which corresponds to the best sensitive response to NO gas. The sensitive electrode's thickness also affects the NO response sensitivity, and the sensor with an electrode thickness of 14 μm has the most NO response sensitivity. In addition, the NO/NO2 gas mixture test results indicate that the current developed sensor is more sensitive to NO2 gas than that of NO gas.

High total Li-ion conductivity of LiTa2PO8 ceramics sintered using Bi2O3 as an additive

Lithium tantalum phosphate LiTa2PO8 ceramics have attracted significant attention as solid electrolytes in oxide-based all-solid-state batteries owing to their superior bulk conductivity of more than 1 mS cm−1 at room temperature. However, high-temperature sintering at 1050 °C, which is required to achieve a dense morphology, results in a high interfacial resistance at the grain boundaries. In this study, dense LiTa2PO8 ceramics were successfully synthesized via a conventional solid-state method at a low sintering temperature of 900 °C using Bi2O3 as the additive. A total lithium-ion conductivity of 1.41 × 10−3 S cm−1 at 25 °C was achieved. The microstructures of the sintered LiTa2PO8 ceramics were analyzed by X-ray diffraction and scanning electron microscopy with energy-dispersive X-ray spectroscopy. Large LiTa2PO8 grains grew in the dense solid-electrolyte body together with the interfacial BiPO4 phase, which acted as a sintering flux material, at a low sintering temperature of 900 °C. Thus, these LiTa2PO8 ceramics can serve as oxide solid electrolytes for all-solid-state lithium batteries owing to their high total Li-ion conductivity.

Experimental and molecular dynamics multiscale study on sintering and interfacial reaction of Fe2O3/CaO particle system

High-temperature sintering and solid-state reaction within the intricate Fe2O3/CaO system are pivotal factors influencing material characteristics. The current work focused on the sintering and reaction behavior of Fe2O3/CaO particles at high temperatures with a multiscale study of in-situ high-temperature stage microscopy (HTSM) and molecular dynamics (MD). The laws governing atomic migration and the evolution of crystal structure during the sintering process were simulated at the nanoscale. The results elucidated that a heightened heating rate fosters particle shrinkage and concomitant reduction in surface area. The sintering activation energy (Esin) exhibited an increment proportional to the linear shrinkage of the particles. Furthermore, an augmented potential barrier in advanced stages impeded subsequent sintering behavior. Augmented temperature promoted the particle shrinkage and sintering neck formation, culminating in pore closure and a diminution in the free surface. However, this promotional effect attenuated with escalating temperatures. Particle shrinkage and sintering neck formation are contingent upon atomic migration and diffusion, with the growth of sintering necks primarily reliant on atom diffusion along the surface of the sintering necks. The atomic diffusion activation energy was determined to be 49.5 kJ/mol within the temperature range of 1073–1473 K. Within the Fe2O3/CaO system, the preferential generation of Ca2Fe2O5 (C2F) over CaFe2O4 (CF) was found, leading to a decrease in the atomic diffusion barrier and an enhancement of the diffusivity, with the latter dominating in later stages. The highest mobility of O2–, Fe3+, and Ca2+ was discerned in CF, and the sintering shrinkage of the particles predominantly hinges on the generation of CF.

One-step formation of synergistic ZnO/SnO2 composite nanostructures derived from annealing of crystalline ZnSn(OH)6 nanocubes for enhanced catalytic degradation of organic pollutants

Binary metal oxides/hydroxides derived primary metal oxide composites have a pivotal role in diverse applications because of the beneficial interfacial contact, good synergism, high porous nature, and high stability. The current work deals with the derived ZnO/SnO2 composite nanostructures from post-annealing crystalline ZnSn(OH)6 (ZTO-RT) nanocubes, initially synthesized via a single-step hydrothermal synthesis method. First, the pristine ZTO-RT is synthesized @ 180 °C in a hydrothermal autoclave. Further, the transformation of ZTO-RT to ZnO/SnO2 composite nanostructures is performed at two different annealing temperatures of 500 °C (ZTO-DV-500) and 750 °C (ZTO-DV-750) in the vacuum. The respective samples' physical characterization was studied and compared using various analytical techniques. The X-ray diffraction analysis affirms the amorphous nature of ZTO-DV-500 and the poly-crystalline nature of ZTO-DV-750. The nanocube morphologies of the samples are retained even at high-temperature sintering. The existence of metal-oxygen bonds on the surface of the ZnO/SnO2 composite is sustained by X-ray photoelectron spectroscopy. ZTO-DV-750 has larger pores (pore volume - 0.091 cm3 g−1) than the ZTO-DV-500 (0.051 cm3 g−1). In the presence of NaBH4 aqueous solution, the enhanced rhodamine B dye degradations of ZTO-DV-750 are observed. At low RhB concentrations (5 mg L−1), the ZTO-DV-500 and ZTO-DV-750 rate constants are determined to be 0.099 and 0.156 min−1, respectively, while at high concentration (10 mg L−1), these values are 0.043, and 0.091 min−1. Therefore, the ZTO-DV-750 composite has shown potent catalytic activity with NaBH4 over ZTO-DV-500 to decolourise organic dyes.

Nonstoichiometry Induced Amorphous Grain Boundary of Na5SmSi4O12 Solid-State Electrolyte for Long-Life Dendrite-Free Sodium Metal Battery.

Oxide ceramics are considered promising candidates as solid electrolytes (SEs) for sodium metal batteries. However, the high sintering temperature induced boundaries and pores between angular grains lead to high grain boundary resistance and pathways for dendrite growth. Herein, we report a grain boundary modification strategy, which in situ generates an amorphous matrix among Na5SmSi4O12 oxide grains via tuning the chemical composition. The mechanical properties as well as electron mitigating capability of modified SE have been significantly enhanced. As a result, the SE achieves a room-temperature total ionic conductivity of 5.61 mS cm-1, the highest value for sodium-based oxide SEs. The Na|SE|Na symmetric cell achieves a high critical current density of 2.5 mA cm-2 and excellent cycle life over more than 2800 h at 0.15 mA cm-2 without dendrite formation. The full cell with Na3V2(PO4)3 as the cathode demonstrates impressive cycling performance, maintaining stability over 3000 cycles at 5C without observable loss of capacity.

Effects of Y doping on phase structure, mechanical properties and sintering behavior of (Yb1-xYx)2SiO5 environmental barrier coating materials

Yb2SiO5 is one of the most widely studied environmental barrier coating materials due to its excellent high-temperature phase stability and resistance to water oxygen corrosion. In this paper, a series of (Yb1-xYx)2SiO5 (x = 0, 0.1, 0.2, 0.3, 0.4) ceramics were fabricated by high-temperature solid state sintering at 1550 °C. The effects of Y doping concentration on phase composition, mechanical properties, thermal conductivity and high-temperature sintering behavior of Yb2SiO5 ceramics were investigated in detail. The results show that all the (Yb1-xYx)2SiO5 ceramic specimens are composed of single X2-Yb2SiO5 phase with relative high compactness. The introduction of Y gives rise to the reduction of the thermal conductivity of Yb2SiO5 and the value of cell parameters and volume of (Yb1-xYx)2SiO5 is proportional to the Y3+ doping concentration. Among the five (Yb1-xYx)2SiO5 ceramics, (Yb0.9Y0.1)2SiO5 possesses the lowest brittleness index and its average fracture toughness is 2.85 MPa m1/2, which is about 10 % higher than pure Yb2SiO5. In addition, (Yb0.9Y0.1)2SiO5 has good high temperature phase stability from room temperature to 1450 °C and the grain size of (Yb0.9Y0.1)2SiO5 is basically unchanged after sintering at 1400 °C for 100 h. We believe that (Yb0.9Y0.1)2SiO5 is one of the most promising candidate materials for environmental barrier coatings.

Effect of sintering temperature on the properties of titanium matrix composites reinforced with Al0·5CoCrFeNi high-entropy alloy particles

In this study, the organization and mechanical properties of the composites were analyzed at different sintering temperatures, and it was found that the local high-temperature phenomenon of discharge plasma sintering led to rapid melting and element diffusion at the junction of the high-entropy alloy particles and the Ti matrix, resulting in the formation of the interfacial layer. The increase in sintering temperature promoted close bonding between particles and element diffusion, caused lattice distortion and new phase formation, and increased the thickness of the interface layer and precipitated phase at the grain boundary. Most of the high-entropy alloy particles were dissolved when the sintering temperature reached 1050 °C. The composites were characterized by a high sintering temperature. The comprehensive mechanical properties of the composites first increased and then decreased when the sintering temperature increased, and they were optimized at 850 °C. The nanoindentation results show that the increase in sintering temperature leads to a decrease in the hardness of the high-entropy alloy particles, an increase in the hardness of the titanium matrix, and a higher hardness of the interfacial layer than that of the high-entropy alloy particles and the titanium matrix.