Search Results (100)

Non-stoichiometric high-entropy carbides (Nb_0.2Ta_0.2Ti_0.2W_0.2Zr_0.2)C_x (x = 0.71–0.85) nanoscale powders were prepared using oxides and carbon as raw materials via carbothermal reduction. The (Nb_0.2Ta_0.2Ti_0.2W_0.2Zr_0.2)C_0.73 synthesized at 1700 °C exhibited a grain size of approximately 400 nm, an oxygen content of 0.3 wt.%, and uniform nanoscale distribution of the five metal elements. After ball milling, (Nb_0.2Ta_0.2Ti_0.2W_0.2Zr_0.2)C_0.73 powder was sintered by spark plasma sintering to produce high-entropy ceramics with a relative density of 98.1% and an average particle size of about 5.3 μm. The Vickers hardness, nano-hardness, Young’s modulus, and fracture toughness were 17.6 GPa, 29.1 GPa, 514 GPa, and 5.3 MPa·m^1/2, respectively. The thermal conductivity of the ceramic at room-temperature was as low as 8.5 W/m·K. Full article

In this work, micro/nano-scale (TiB₂ + TiC)/Al composites with reinforcement contents ranging from 0 to 30 wt.% were fabricated by the combination of Ti-B₄C reactive sintering and spark plasma sintering (SPS). The results indicate that a sintering temperature of 1400 °C is essential for achieving a complete reaction between Ti and B₄C, successfully producing a bimodal TiB₂-TiC reinforcement consisting of nano-scale and micro-scale particles. Microstructure analysis reveals that the addition of micro/nano-scale TiB₂ and TiC ceramic particles significantly refines the grain size of the Al matrix from 11.52 μm in pure Al to 1.09 μm in the 30 wt.% (TiB₂ + TiC)/Al composite. As the TiB₂ and TiC contents increase, Vickers hardness and compressive yield strength increase progressively, while the uniform compressive plastic strain first increases and then decreases. The 20 wt.% (TiB₂ + TiC)/Al composite demonstrates the optimal comprehensive properties, with a compressive yield strength of 196.4 ± 6.1 MPa, an ultimate strength of 914.6 ± 20.1 MPa, and a uniform plastic strain of ~73.2%, as well as minimal wear rates of (3.143 ± 0.194) × 10⁻⁴ mm³/(N·m), 1.676 ± 0.251× 10⁻³ mm³/(N·m) and (3.093 ± 0.335) × 10⁻³ mm³/(N·m) at 1 N, 3 N, and 5 N, respectively. This improvement stems from the combined effects of grain refinement, dispersion strengthening, enhanced load-bearing capacity and reduced adhesive wear via the TiB₂ and TiC reinforcements. Full article

This study reports the fabrication of copper-based metal matrix composites reinforced with a combination of micro- and nano-sized titanium carbide (TiC) particles using the powder metallurgy route. The micro-TiC content was maintained at 5 wt.%, while the nano-TiC addition was systematically varied between 1 and 3 wt.% in increments of 1 wt.%. The consolidation of the blends was achieved by uniaxial compaction at 500 MPa, followed by sintering in a nitrogen atmosphere at 750–900 °C for 2 h. Tribological assessment under dry sliding conditions was performed using a pin-on-disk apparatus. Structural and microstructural examinations using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) confirmed a uniform incorporation of the reinforcements within the Cu matrix. The incorporation of nano-TiC up to 2 wt.% significantly enhanced density, hardness, and wear resistance, after which a marginal decline was observed. SEM analysis of worn surfaces revealed that adhesive wear, abrasion, and delamination were the primary wear mechanisms. To better understand the relationship between processing conditions and material responses, response surface methodology (RSM) was employed. The developed models for density, hardness, and wear loss showed good agreement with the experimental results, with confirmatory tests yielding errors of 1.59%, 2.06%, and 2%, respectively, thereby validating the approach’s reliability. Full article

Titanium matrix composites (TMCs), characterized by low density, high strength, and excellent high-temperature mechanical properties, are becoming preferred materials for key components in aerospace engines. However, conventional casting methods for preparing TMCs often encounter issues such as composition segregation and coarse reinforcement phases, hindering their engineering application. In this study, we fabricated TiC/TC4 titanium matrix composites via hot isostatic pressing (HIP). The composites exhibited room-temperature tensile strength of 1058 ± 8 MPa, yield strength of 958 ± 12 MPa, and total elongation of 17.0 ± 0.5%. Furthermore, the TiC/TC4 composites demonstrated favorable high-temperature mechanical properties, with a tensile strength of about 500 MPa at 600 °C. Investigation into plastic deformation and fracture behavior revealed that at room temperature, tensile cracks initiated predominantly around the reinforcing TiC particles, whereas at high temperatures, cracks primarily originated within the matrix. The strengthening mechanisms of the TiC particle-reinforced TC4 composites included particle strengthening, solid solution strengthening, and load-transfer strengthening. Additionally, the precipitation of nano-acicular secondary α (αs) phases within the β phase during high-temperature tensile deformation was observed, contributing to the superior high-temperature mechanical performance of the composites. Full article

This research focuses on the investigation of microstructure, deformation, and superplastic behavior in wide range of strain rates of novel crossover Al-Zn-Mg-Cu alloy with Y/Er. The precipitation and superplastic behavior of the Al-Zn-Mg-Cu-Zr-Cr-Ti with Er/Y and Fe/Si impurities alloys have been studied. The microstructure of the alloys with nano-sized precipitates and micron-sized particles allows obtaining a micrograin stable microstructure. The spherical D0₂₃-Al₃(Er,Zr) precipitates with a diameter of about 20 nm and rod-like crystalline and qusicrystalline E (Al₁₈Mg₃Cr₂) precipitates with a thickness of about 20 nm and length of about 150–200 nm were identified by transmission electron microscopy. The superplastic deformation behaviors were investigated under different temperatures of 460–520 °C and different strain rates of 3 × 10⁻⁴ to 3 × 10⁻³ s⁻¹. The microstructure observation shows that uniform and equiaxed grains can be obtained by dynamic recrystallization before superplastic deformation. The alloy with Y exhibits inferior superplastic properties, while the alloy with Er has an elongation of more than 350% at a rate of 1 × 10⁻³ s⁻¹ and a temperature of 510 °C. Full article

Porous plate-like anatase TiO₂ particles were synthesized through a direct calcination approach using layered titanate H₁.₀₇Ti₁.₇₃O₄ as a precursor. By controlling the calcination temperature (400 °C, 500 °C, and 600 °C), the morphology and electrochemical properties of the TiO₂ samples were effectively tuned. When evaluated as anodes for lithium-ion batteries (LIBs), the porous TiO₂ materials demonstrated markedly improved rate performance compared to commercial nano-TiO₂ (n-TiO₂). Specifically, at a high current density of 5.0 A/g, p-TiO₂-500 and p-TiO₂-600 delivered discharge capacities of 70.5 mAh/g and 87.5 mAh/g, respectively, far exceeding the 27.7 mAh/g achieved by n-TiO₂. The corresponding capacity retention rates at this rate were 30.1% for p-TiO₂-500, 41.2% for p-TiO₂-600, and only 16.4% for n-TiO₂. The enhancement in kinetics is ascribed to the unique porous plate-like architecture, which promotes efficient ion transport and introduces significant pseudocapacitive contributions. When applied as anodes for sodium-ion batteries (SIBs), p-TiO₂-600 exhibited the most promising performance. This study underscores the potential of porous plate-like TiO₂ as a high-performance bifunctional anode material suitable for both LIBs and SIBs. Full article

In this study, we delve into the intricate microstructural features of Ti-6Al-4V alloy additively manufactured and heat-treated at 800 °C for 4 h. Our in-depth analysis will enable us to gain a better understanding of the β-Ti precipitation process, its dependence on temperature, and its ultimate effect on the overall mechanical properties. As well as α-Ti martensite grains and β-Ti particles interspersed in the α-Ti grain boundaries, there is a third microstructural feature, overlooked by many researchers. This feature is observed as nano-sized particles homogeneously embedded inside the α-Ti laths. Using high-resolution transmission electron microscopy, we reveal that these nano-sized features do not constitute a different phase. Instead, they define isolated regions of α-Ti in its relaxed form, surrounded by the heavily strained form of the α-Ti phase. This phenomenon is a result of the “incomplete” precipitation of the β-Ti phase following the heat treatment stage. The straining of the α-Ti phase appears as a shift in the equilibrium atomic position. Full article

Nano-titanium dioxide ceramic coatings exhibit excellent wear resistance, corrosion resistance, and self-cleaning properties, showing great potential as multifunctional protective materials. This study proposes a synergistic reinforcement strategy by encapsulating micron-sized Al₂O₃ particles with nano-TiO₂. A core-shell structured nanocomposite coating composed of 65 wt% nano-TiO₂ encapsulating 30 wt% micron-Al₂O₃ was precisely designed and fabricated via a slurry dip-coating method on Q235 steel substrates. The microstructure and surface morphology of the coatings were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Comprehensive performance evaluations including densification, adhesion strength, wear resistance, and thermal shock resistance were conducted. Optimal coating properties were achieved under the conditions of a binder-to-solvent ratio of 1:15 (g/mL), a heating rate of 2 °C/min, and a sintering temperature of 400 °C. XRD analysis confirmed the formation of multiple crystalline phases during the 400 °C curing process, including titanium pyrophosphate (TiP₂O₇), aluminum phosphate (AlPO₄), copper aluminate (Cu(AlO₂)₂), and a unique titanium phosphate phase (Ti₃(PO₄)₄) exclusive to the 2 °C/min heating rate. Adhesion strength tests revealed that the coating sintered at 2 °C/min exhibited superior interfacial bonding strength and outstanding performance in wear resistance, hardness, and thermal shock resistance. The incorporation of nano-TiO₂ into the 30 wt% Al₂O₃ matrix significantly enhanced the mechanical properties of the composite coating. Mechanistic studies indicated that the bonding between the nanocomposite coating and the metal substrate is primarily achieved through mechanical interlocking, forming a robust physical interface. These findings provide theoretical guidance for optimizing the fabrication process of metal-based ceramic coatings and expanding their engineering applications in various industries. Full article

This study investigates the effect of duo-ceramic zirconia and silicon nitride (ZrO₂-Si₃N₄) particles and their reinforcement proficiencies on a Ti6Al4V alloy, consolidated using the spark plasma sintering (SPS) technique. The selected sintering parameters are, viz., 900 °C temperature, 50 MPa pressure, 10 min of holding time, and 100 °C/min of sintering rate. SEM/EDS and XRD equipment were used to disclose the microstructural evolution and phase identification of created composites. The mechanical characteristics of the resulting composites were determined using the nanoindentation technique. All consolidated sintered composites showed excellent densification, with sample relative densities reaching 96.65%. Significant improvements were also made in their nanomechanical characteristics; among the composite samples with different volume fractions, the ceramics with the lowest volume percentage had the best mechanical characteristics, whereas the sintered samples with the highest ceramic volume percentage showed a decrease in mechanical proficiencies and relative density. Composite S1, with the lowest volume fraction of the duo-ceramic particles, was seen to have a significant mechanical property improvement better than other composites, S2 and S3, in terms of measured Vickers microhardness, elastic modulus, and nano hardness values at a sintering temperature of 900 °C. Consequentially, composite specimens S2 and S3’s mechanical characteristics and relative densities dropped as the volume fractions of the duo-ceramic particles increased. Full article

The sodium super ionic conductor (NASICON) structured LiTi₂(PO₄)₃ (LTP) has been developed as electrode material for Li-ion batteries (LIBs) with promising electrochemical performance, owing to its outstanding structural stability and rapid lithium-ion diffusion. Nevertheless, challenges still exist, especially the rapid capacity fading caused by the low electronic conductivity of LTP-NASICON material. Recently, the hydrothermal method has emerged as an important technique for the production of diverse nano-electrode materials due to its low preparation temperature, high phase purity, and well-controlled morphology and crystallinity. Herein, we report, for the first time at low-moderate temperatures, an advanced hydrothermal synthesis of LTP-coated reduced graphene oxide (LTP@rGO) particles that includes the growth of LTP particles while simultaneously coating them with rGO material. The LTP offers a discharge specific capacity of 84 mAh/g, while the LTP@rGO delivers a discharge capacity of 147 mAh/g, both with a coulombic efficiency of 99.5% after 100 cycles at a 1C rate. Full article

To enhance the erosion resistance of typical Cr₃C₂-NiCr coatings, the Cr₃C₂-TiC-NiCrCoMo (NCT) coating was developed and deposited by high-velocity oxygen fuel spray (HVOF). The erosion resistance and mechanisms of the coating were investigated using numerical simulations and experimental methods. A comprehensive calculation model for the coating erosion rate was developed, incorporating factors such as the properties of the eroded particles, the characteristics of the coating, and the conditions of erosion. The erosion rate of the NCT coating was calculated and predicted by the model, and the accuracy of these predictions was validated through experiments. The NCT1 (87.3 wt.% Cr₃C₂-NiCrCoMo/3 wt.% TiC)coating demonstrated exceptional erosion resistance compared to the original Cr₃C₂-NiCrCoMo (NCC) coatings with reduced erosion rates of 23.64%, 20.45%, and 16.22% at impact angles of 30°, 60°, and 90°, respectively. The addition of nano-TiC particles into the NCT1 coating enhances the yield strength, impeding the intrusion of erosive particles at low angles and supporting the metal binder phase, eventually reducing fatigue fracture under repeated erosion. However, excessive nano-TiC content degrades the erosion resistance due to the increase in pores and cracks within the coating. Full article

The main component of high-capacity silicon-based electrodes is silicon powder, which necessitates intricate processing to minimize volume growth and powder separation while guaranteeing the ideal Si content. This work uses the an situ high-pressure forming approach to create an MXene/m-Si/MXene composite electrode, where MXene refers to Ti₃C₂T_X, and m-Si denotes two-phase mixed nano-Si particles. The sandwich shape promotes silicon’s volume growth and stops active particles from spreading. The conductive structure of Ti₃C₂T_X MXene increases the efficiency of charge transfer while reducing internal resistance. After 100 cycles, the composite electrode’s original capacity of 1310.9 mAh g⁻¹ at a current density of 0.5 A g⁻¹ is maintained at 781.0 mAh g⁻¹. These findings lay the foundation for further investigations into Si matrix composite electrodes. Full article

The innovative design of the microstructure of silicon-based composite anodes in Li-ion batteries holds great potential for overcoming inherent limitations, such as the significant volume change experienced by silicon particles. In this study, TiFeSi₂/C composites prepared using micro, nano, and porous silicon showed reversible capacities of 990.45 mAh.g⁻¹, 1137.69 mAh.g⁻¹, and 1045.43 mAh.g⁻¹ at C/10. The results obtained from the electrochemical characterization show that the porous structure of the composite anode material created via acid etching reduced silicon expansion during the lithiation/delithiation processes. The void spaces formed in the inner structure of the porous silicon and the presence of carbon increased the electronic conductivity between the silicon particles and, on the other hand, lowered the overall diffusion distance of Li⁺. This study confirms that TiFeSi₂/C prepared with porous silicon dispersed in a transition metal matrix delivers better electrochemical performance compared to micro and nano silicon with a retention of 80.16%. Full article

The effects of Ti addition on the microstructure, mechanical properties and corrosion resistance of the Cu-30Zn-6Ni-1.5Ti (wt.%) alloy were investigated in the present study. Microstructure analysis confirms that the Ni₃Ti and NiTi phases are formed in the Cu-Zn-Ni-Ti alloy. Most of the Ni₃Ti particles dissolve into the matrix, whereas NiTi particles remained after the solution treatment. Moreover, nano-sized Ni₃Ti and Cu₂NiZn phases are precipitated from the matrix during the aging process. The yield strength improvement of the studied alloy is attributed to the Orowan strengthening (accounting for 42.5% of the total yield strength), then the grain boundary strengthening (31.1%), the dislocation strengthening (16.9%), the twin boundary strengthening (5.0%) and the solid solution strengthening (0.5%). After cold rolling with 90% deformation and aging at 440 °C for 1 h, the designed alloy has a hardness of 327.1 HV, a yield strength of 1192 MPa, an ultimate tensile strength of 1297 MPa, an elongation of 1.8%, an electrical conductivity of 11.2% IACS and a corrosion rate of 2.8 μm/month in 3.5% NaCl solution. Full article

The insulation of high-voltage direct-current (HVDC) cables experiences a short period of voltage polarity reversal when the power flow is adjusted, leading to sever field distortion in this situation. Consequently, improving the insulation performance of the composite insulation structure in these cables has become an urgent challenge. In this paper, SiC-SR (silicone rubber) and TiO₂-SR nanocomposites were chosen for fabricating HVDC cable accessories. These nanocomposites were prepared using the solution blending method, and an electro-acoustic pulse (PEA) space charge test platform was established to explore the electron transfer mechanism. The space charge characteristics and field strength distribution of a double-layer dielectric composed of cross-linked polyethylene (XLPE) and nano-composite SR at different concentrations were studied during voltage polarity reversal. Additionally, a self-built breakdown platform for flake samples was established to explore the effect of the nanoparticle doping concentration on the breakdown field strength of double-layer composite media under polarity reversal. Therefore, a correlation was established between the micro electron transfer process and the macro electrical properties of polymers (XLPE/SR). The results show that optimal concentrations of nano-SiC and TiO₂ particles introduce deep traps in the SR matrix, significantly inhibiting charge accumulation and electric field distortion at the interface, thereby effectively improving the dielectric strength of the double-layer polymers (XLPE/SR). Full article