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The demand for enhanced materials with high hardness, strength and wear resistance have become critically important in the cutting tool industry. WC-Co cermets are hard metals that possess a combination of excellent mechanical properties and high fracture toughness. However, WC-Co has specific limits in application as a structural component were high temperature strength, oxidation and corrosion resistance are required. Efforts have been made to replace cobalt with nickel or iron binder. WC-Ni has shown to possess better corrosion and oxidative resistance than WC-Co and WC-Fe, however it has lower mechanical properties compared to WC-Co. WC-Fe has inferior oxidative and corrosion to WC-Co and WC-Ni. Recent studies have recently been reported on the use of zirconia, having good binding strength and adhesion with the matrix, as a novel binding phase for WC. This study focusses on the partial replacement of cobalt with milled ZrO 2 stabilized with 7.5 wt% Y 2 O 3 (YSZ) reinforced with cubic boron nitride (cBN). The synthesis focuses on full densification of 4 different compositions (WC-Co (control sample), WC-Co-YSZ, WC-Co-cBN and WC-Co-YSZ-cBN) using spark plasma sintering all at 1300 °C and 50 MPa with the goal of developing a WC-YSZ-cBN composite with no or little sintering aid. The effect of isothermal holding time on the densification, mechanical properties and microstructural & phase evolution were studied and will be presented. The results show that full densification, retention of tetragonal-YSZ phase, no cBN to hBN phase transformation and improved hardness & fracture toughness was obtained on the newly developed composite. [ABSTRACT FROM AUTHOR]

Mixed 93W–4.9Ni–2.1Fe powders were sintered via the spark plasma sintering (SPS) and hybrid spark plasma sintering (HSPS) techniques with 30 mm and 60 mm samples in both conditions. After SPS and HSPS, the 30 mm and 60 mm alloys (except 60 mm-SPS) had a relative density (> 99.2%) close to the theoretical density. Phase, microstructure and mechanical properties evolution of W–Ni–Fe alloy during SPS and HSPS were studied. The microstructural evolution of the 60 mm alloys varied from the edge of the sample to the core of the sample. Results show that the grain size and the hardness vary considerable from the edge to the core of sintered sample of 60 mm sintered using conventional SPS compared to hybrid SPS. Similarly, the hardness also increased from the edge to the core. Furthermore, the 60 mm-HSPS alloy exhibited improved bending strength of 1115 MPa when compared to that of 60 mm-SPS, 920 MPa. The intergranular fracture along the W/W grain boundary is the main fracture modes of W–Ni–Fe, however in the 60 mm-SPS alloy peeling of the grains was also observed which diminished the properties. The mechanical properties of SPS and HSPS 93W–4.9Ni–2.1Fe heavy alloys are dependent on the microstructural parameters such as tungsten grain size and overall homogeneity. [ABSTRACT FROM AUTHOR]

Ti–Ni–TiCN composites with varying TiCN contents (5, 10 and 15 wt%) were consolidated using the novel spark plasma sintering technique at a sintering temperature of 1100 °C, for 10 min holding time under a vacuum condition of lower than 4 Pa, 100 °C/min heating rate and applied pressure of 50 MPa. The effects of Ni additive and TiCN nanoceramic reinforcement content on densification, microstructure and mechanical properties of the developed composites were investigated. Scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscope (EDS) and X-ray diffraction (XRD) techniques were employed to study the morphology and phases present in the developed composites. SEM results revealed the presence of undissolved particles and lamella arrangements of phases within the matrix of the sintered composites which were confirmed by the EDS and XRD results as undissolved TiCN particles, in-situ formed TiN and Ti 2 Ni intermetallic phases. The relative density of the sintered compacts decreased from 99.3% to 98.23% with increase in the reinforcement content. The hardness of the sintered composites was found to increase with increasing reinforcement content. Compressive test results indicated that Ti–Ni–TiCN composites displayed improved compressive strength than the pure Ti samples. The optimum properties were obtained in Ti–6Ni–10TiCN composite with Vickers hardness of 398 HV 1.0 , compressive yield and ultimate strengths of about 998 MPa and 1156 MPa respectively. • Ti–Ni–TiCN composites with improved densification were successfully fabricated using SPS technique. • The hardness of the sintered compacts increased with increasing TiCN contents. • Composite containing 10 wt% TiCN yielded the best combination of properties. • Microstructural constitution influenced the mechanical characteristics of the sintered composites. [ABSTRACT FROM AUTHOR]

Mechanical properties of grade 1 commercially pure titanium (CP–Ti) are characterized by a good combination of strength and ductility at elevated temperatures. CP-Ti mechanical properties at room and elevated temperature can be enhanced by alloying with other elements to meet up with its demand for industrial applications. In this study, the effect of Al–Mo addition and sintering temperature on the densification, microstructure, and mechanical properties of spark plasma sintered CP-Ti compacts were investigated. CP-Ti and Ti–7Al–1Mo (wt.%) compacts sintering were carried out at a constant holding time of 10 min, pressure of 50 MPa and sintering temperature of 800 °C, 1000 °C, and 1100 °C under vacuum. Full densification with Vickers hardness values of 352 ± 17 H V was obtained for the developed Ti–7Al–1Mo alloy at 1000 °C. Different microstructural transformations and phase evolution were observed in the as-sintered compact with respect to sintering temperature. The role of the alloying element and sintering temperature on the relative density, microstructure, hardness, and wear of the as-sintered samples were discussed. This paper shows that alloying of CP-Ti with Al and Mo enhances its microstructure and mechanical properties. Image 1 • CP-Ti and Ti–7Al–1Mo were successfully sintered using spark plasma sintering technique at varying temperatures. • Sintering temperature had influence on the microstructural, mechanical, and wear properties of the sintered compacts. • CP-Ti compacts were composed of mainly α-Ti while there was evolution of other phases in Ti–7Al–1Mo compacts. • Ti–7Al–1Mo sintered at 1000 °C has the best performance in terms of hardness, UTS, and wear resistance. [ABSTRACT FROM AUTHOR]

The transition to a hydrogen-based economy presents a promising solution to the challenges posed by unsustainable energy systems and reliance on fossil fuels. This comprehensive review explores various hydrogen production methods, emphasizing their technological advancements, sustainability implications, and future prospects. Beginning with an overview of hydrogen's significance as a clean energy carrier, the review examines key production methods such as Steam Methane Reforming, Electrolysis (Proton Exchange Membrane, alkaline, solid oxide), Biomass Gasification, Photoelectrochemical Water Splitting, and Thermochemical Processes. Each method is scrutinized for its efficiency, environmental impact, and scalability, providing valuable insights into their roles in advancing the hydrogen economy. The review highlights the transformative potential of hydrogen production to replace fossil fuels due to its ability to store renewable energy long-term and its zero emissions. It also discusses potential technological advancements, including high-efficiency solid-state electrolysis and advanced catalysts for water splitting, highlighting avenues for innovation in hydrogen production. Additionally, policy recommendations aimed at promoting the hydrogen economy and fostering collaboration between academia, industry, and governments are elucidated. Through a detailed analysis of hydrogen production technologies and future prospects, this review contributes to shaping the trajectory of sustainable energy systems, advancing the adoption of hydrogen as a key energy vector, and underscoring the importance of alternative and sustainable energy sources. • Hydrogen economy addresses unsustainable energy challenges. • Review covers key hydrogen production methods and technologies. • Examines efficiency, environmental impact, scalability of each method. • Highlights advances in catalysts and solid-state electrolysis. • Recommends policies for renewable integration, innovation, and collaboration. [ABSTRACT FROM AUTHOR]

Abstract In this study the effect of sintering pressure on the densification, microstructure and mechanical properties of commercial pure titanium (CP-Ti) powders with varying chemistry was investigated. The sintering was performed at a constant dwell time of 3 min at varying temperature and pressure in the range of 550–900 °C and 25-75 MPa in vacuum, respectively. Full densification with high Vickers hardness values of 340 HV and 262 HV was obtained at 25 MPa at 800 °C and 900 °C respectively for two commercial powders with different average particles sizes. Different microstructural transformations with respect to increasing temperature and pressure were observed on the sintered pellets. The results were discussed emphasizing the huge role of the interstitial elements, contained in the starting powders, on the properties (relative density, Vickers hardness and microstructure) of the dense samples. This paper shows that good mechanical properties can be obtained by SPS technique when CP-Ti powders are sintered at very low temperature during a short period in contrast to conventional fabrication techniques. Graphical abstract Unlabelled Image Highlights • Secondary alpha phase volume fraction increase with pressure • Varying applied sintering pressures resulted in different microstructures • Electrical discharges and plastic deformation are possible mechanisms with varying pressure during densification [ABSTRACT FROM AUTHOR]