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Abstract: Spark plasma sintering (SPS) was used to investigate the densification and deformation behaviour of Ti–TiB2 composites. Fully densified samples were prepared with Ti addition larger than 5%. The prepared composites can be deformed under compression at 1700°C to achieve a strain of 50% without cracking. At lower temperatures, cracks were initiated due to low ductility of TiB2 and low content of Ti. During the sintering and deformation, TiB is formed via a reaction between Ti and TiB2. To elucidate the formation mechanism of TiB in the SPS process, reactive sintering of TiB using element precursors was also performed. Fully dense samples were prepared but it was not possible to prepare pure uniphase TiB. The reactive sintering resulted in the formation of TiB and TiB2 mixtures at low temperatures and a mixture of TiB2 and Ti3B4 at high temperature. [Copyright &y& Elsevier]

High densification and fine grain size are the key to achieve excellent mechanical properties of ceramic materials. Pressure-assisted sintering is an effective approach to achieve this goal. However, the pressure at different sintering stages has different effects on the densification behavior of nano-ceramics. In this work, it is found that adjusting the pressure applying regime during Spark Plasma Sintering of nano-alumina ceramics can effectively increase the densification rate and balance the relationship between the densification behaviors of particle coarsening, grain growth and vapor migration. When the pressure is applied at the beginning of the second sintering stage, the high densification and fine grain size microstructures can be both obtained at lower temperatures, leading to the best mechanical properties. This result is of great significance for the preparation of nano-ceramics with excellent mechanical properties. [ABSTRACT FROM AUTHOR]

Abstract: The spark plasma sintering (SPS), also known as plasma activated sintering, is a method applicable for rapid sintering of metals and ceramics. The technique is thought of a type of rapid hot pressing, implying that the application of a uniaxial pressure is essential for enhanced densification kinetics. In this study, the efficiency of heat transfer in the SPS process was examined in the absence of mechanical pressure. Conditions for dynamic isotropic heating were established, and the densification and microstructure development sequences of alumina ceramics during pressure-less SPS process were investigated. The influence of early neck formation on the grain morphology and fine structure is also discussed. The study reveals that high heating rate plays an important role in enhancing densification kinetics. The observed principle bears a general implication for increasing the efficiency of conventional pressure-less sintering procedures that are nowadays widely applied in industry. [Copyright &y& Elsevier]

Studies on Pulsed Direct Current (pulsed DC), which is specially applied in Spark Plasma Sintering (SPS), has attracted much attention. The effect of the various pulse patterns on recorded currents, energy efficiency and mechanical pulsing are investigated by the constant input heating of SPS and a stable punch system. The results show that the recorded current increases while the energy efficiency decreases with the increasing ON/OFF ratio. The TiO 2 powder was sintered by pulse patterns 12:2 and 10:9 with constant power input. An increase of one order of magnitude in grain size and 8% in density is shown after application of the pulse pattern 10:9, while the amount of consumed energy remained constant. When heated with different pulse patterns, the variation of the effective power and contact resistance induced by the mechanical pulse are two main reasons accounting for the varying energy efficiency. This unique SPS behavior was demonstrated by experiments and calculations. [ABSTRACT FROM AUTHOR]

Porous scaffolds were fabricated via Digital Light Processing (DLP) from β-TCP powder and sintered by conventional sintering in air (CSA) , rapid sintering in air (RSA) and pressure-less spark plasma sintering in vacuum (pl-SPS) , at four different temperatures: 1200, 1300, 1400 and 1500 ºC. Each sintering strategy resulted in scaffolds with different phase composition, microstructure and mechanical properties. Long dwell times or high temperatures were required to achieve a complete β→α transformation, and rapid cooling rates avoided the reverse transformation. The presence of graphite in the sintering chamber played a crucial role in stabilising the α-TCP phase, phase prevailing in SPS-treated scaffolds, hindered their densification and avoided the generation of transformation-induced cracks. All scaffolds exhibited compressive strengths within the range of cancellous bone, with the highest average value of 22 ± 4 MPa achieved by the RSA scaffolds sintered at 1300 ºC, thanks to their greater densification and fine microstructure. [ABSTRACT FROM AUTHOR]

This work explores the rapid sintering of 3D-plotted tricalcium phosphate (TCP) scaffolds with the aim of getting the on-demand scaffold fabrication closer towards the clinical practice. The sintering trajectories of TCP scaffolds at 1100 and 1200 °C show that 10 min of reactive sintering together with a fast heating rate (100 °C min-1) result in a superior densification without significant grain growth, increasing the compressive strength 1.5–2.5 times. Furthermore, hardness and elastic modulus increase 8 times as compared to conventional sintering. The mechanical performance is not compromised by the formation of alpha-TCP at 1200 °C, since it originates by chemical reaction instead of a phase transformation mechanism, avoiding cracking due to crystalline lattice expansion. [ABSTRACT FROM AUTHOR]

Dielectric ceramics are of great potential to be applied in electronic systems due to their fast discharge speed and temperature tolerance. However, the low energy storage density and efficiency highly restricts the applications of dielectric ceramics. Here, we propose a strategy of fine grain and highly densified relaxor-antiferroelectric (RE-AFE) ceramics to both increase the energy storage density and efficiency. We fabricated NaNbO 3 based relaxor-antiferroelectric (RE-AFE) ceramics by Spark Plasma Sintering (SPS) and obtained an ultra-high recoverable energy storage density of 12.2 J/cm3 and satisfied efficiency of 88%. The present research offers a route for designing dielectric ceramics with enhanced energy storage density and efficiency, which is significant to the application of dielectric ceramics. [Display omitted] [ABSTRACT FROM AUTHOR]