This study explores the influence of SiC reinforcement on the microstructure, mechanical properties and ballistic performance of Al2O3-SiC composites fabricated by Spark Plasma Sintering. Composites containing 1 to 30 vol% SiC were processed using optimized SPS cycles to ensure high densification and controlled microstructural development. The addition of SiC led to significant improvements in hardness, fracture toughness and Young's modulus with the best compromise observed at 25 vol% SiC, sintered at 1600 degrees C. At this composition, a 30 % reduction in residual depth of penetration versus 7.62 mm x 51 FMJ/PB/HC AP P80 (0.308 Win) threat was measured compared to pure alumina, confirming the effectiveness of SiC reinforcement in enhancing ballistic resistance. Although higher SiC contents (>= 25 vol%) resulted in the formation of mullite and a slight decrease in fracture toughness, the 25 vol% SiC composite offers an optimal balance between mechanical performance and cost-efficiency. These results position Al2O3-SiC composites as promising materials for lightweight and affordable ballistic protection systems.

This work investigates the thermoelectric properties of (Sr1-xBax)(0.95)La0.05TiO3 ceramics, with x = 0, 0.1, 0.25, and 0.5, synthesized via a solid-state reaction and densified using spark plasma sintering (SPS) at temperatures of T = 1473K and T = 1773K. The influence of barium substitution and sintering temperature on the electrical conductivity sigma (Sm-1), Seebeck coefficient S(V K-1), thermal conductivity kappa(Wm(-1) K-1), and the resulting dimensionless figure of merit ZT was systematically studied. Among the investigated compositions, the sample with x = 0.25 exhibited the best thermoelectric performance under both sintering conditions. This composition was further subjected to post-sintering annealing at T = 1673K under a reducing (30% Ar + 3% H-2 + 67% N-2) atmosphere to evaluate its effect on thermoelectric efficiency. A comparative analysis supported by scanning electron microscopy (SEM) revealed that high-temperature SPS at T = 1773K significantly enhances microstructural densification and grain growth, leading to an improved figure of merit with ZT = 0.18 at T = 600K. In contrast, the sample sintered at T = 1473K exhibits a maximum ZT = 0.04 at T = 1000K. These findings demonstrate that direct high-temperature SPS is a rapid, energy-efficient, and scalable method for fabricating high-performance SrTiO3-based thermoelectric materials suitable for high-temperature applications.

This study presents the development of a fully instrumented sinter-forging process using a 915MHz solid-state microwave source for the rapid and controlled sintering of dense oxide ceramics. Compared to conventional magnetron-based systems, the solid-state microwave source enables precise frequency tuning for optimal impedance matching and resonance conditions. Modeling and experimental characterization of the microwave applicator have enabled us to position the sample correctly in the cavity, ensuring efficient energy transfer and homogeneous heating. Sintering experiments carried out on alumina powder, both with and without applied pressure, revealed that the pressure-assisted process significantly improved densification, yielding near-complete density and increased hardness (21.6GPa), while maintaining fine microstructures. This method highlights the potential of microwave-assisted sinter-forging for producing advanced ceramics with improved properties.

This study investigates the influence of punch holes, designed for temperature measurements using an axial pyrometer during Spark Plasma Sintering (SPS), on pressure and temperature distribution and its potential connection to microstructural heterogeneities in dense ceramics. By combining experimental investigations using pressure measurement films and finite element simulations, the results reveal significant pressure gradients exceeding 80 MPa for a nominal applied load of 100 MPa, caused by the presence of punch holes. The study further explores strategies to optimize punch design to reduce pressure gradients while maintaining accurate temperature measurements. It is shown that optimizing the tooling design improves microstructural homogeneity and leads to a slight increase in the ceramic's relative density. However, some residual heterogeneity remains, primarily due to lateral stresses and thermal gradients, rather than the punch design. This work provides practical guidelines for improving SPS processing conditions to achieve more homogeneous sintered ceramics.

This rapid communication highlights a remarkable achievement obtained with a 120 mm diameter large cylindrical MgB2 bulk: the measurement of magnetic levitation forces up to 700 N at 20 K, levitation being stable up to levitation forces exceeding 400 N. The investigated sample, which has one of the largest dimensions reported in the literature, was fabricated using the unconventional spark plasma sintering technique. This method is known as one of the most efficient methods for producing dense MgB2 samples. This breakthrough holds significant potential for advancing high-performance levitation systems and superconducting applications, including high-speed transportation systems and magnetic bearings.

Two grades of PolyEtherKetoneKetone with different Tere/Iso ratios (PEKK 60/40 and PEKK 80/20) were consolidated using spark plasma sintering. Processing parameters were varied and their influence on mechanical properties was assessed. The study reveals that sintering at a temperature close to the melting temperature along with an applied pressure of 18 MPa leads to better mechanical properties, while the effect of dwell time remains limited. A high sintering pressure is shown to promote the cohesion of PEKK 60/40 samples when the temperature is closer to the glass transition temperature, while pressure does not play a significant role for PEKK 80/20. Post-mortem fractographic analyses provide explanations of the underlying phenomena. PEKK samples sintered with optimal processing parameters display higher compressive yield strength and stiffness than PEKK samples elaborated from conventional processing routes. They however also exhibit a fragile behavior which can be attributed to the incomplete healing between the powder particles.

We report the levitation and guidance forces of two set-ups including a 120 mm diameter MgB2 disc cooled down to 20 K. The first one included the disc and a 30 mm thick and 100 mm diameter NdFeB magnet and is labelled as PM100 set-up. The second one called PM70 set-up included a 70 mm diameter and 35 mm thick magnet. All the measurements were carried out after cooling down the superconductor with a 30 mm separation between the magnet and the superconductor. Some remarkable results were obtained. It was reported by Xing et al (2024 Supercond. Sci. Technol.37 02LT01) that the levitation force measured with the PM100 set-up has reached the strong value of 678 N at 5 mm separation between the magnet and the superconductor. In this new report, in addition to a comparison of the levitation forces measured on both set-ups, we report guidance force measurements. We show that this force decreases for the PM100 set-up as the magnet-superconductor distance decreases, while the guidance force of the PM70 set-up increases, as was reported for set-ups including Halbach guideways sections. Reproducing the measured levitation forces with analytical models, we show, on the one hand, that the large levitation forces measured with the PM100 set-up are due to the non-homogeneity of the magnetic field above the PM100 magnet. On the other hand, we explain the behaviour of the PM70 set-up guidance force by the low modulation of the magnetic moment of the superconductor resulting from the magnet motion.

In this work, spark plasma sintering of La2Mo2O9 powder was used to achieve dense ceramics of La7Mo7O30 and explore their thermoelectric properties. SPS sintering of La2Mo2O9 powder at 973 K for 10 min under 90 MPa leads to a bicoloured sample with white and black faces. XRD patterns of white and black faces are attributed to La2Mo2O9 and La7Mo7O30 phases, respectively. These experimental conditions allow observing the in-situ reduction of La2Mo2O9 during the SPS process. With a longer sintering time of 30 min, a ceramic of La7Mo7O30 is obtained. Its electrical conductivity exhibits a semiconducting behaviour and reaches a value of 1000 Sm-1 at 1000 K. The negative Seebeck coefficient show a n-type conduction in this phase. La7Mo7O30 exhibits a very low thermal conductivity, less than 1 Wm- 1K-1 from room temperature up to 1000 K, similar to the values reported for La2Mo2O9. A figure of merit of 0.04 is reached at 1000 K.

BaWO4, Ce2/3 ❑1/3WO4 and La2/3 ❑1/3WO4 polycrystalline ceramics were synthesized by conventional solidstate reaction route. The effect of cation-deficiency on the crystallographic structure, microstructure and thermal properties of these scheelite-type compounds were investigated. X-ray diffraction was used to identify the single-phase scheelite structure of the studied ceramics. Scanning Electron Microscopy technique has revealed a homogenous and dense microstructure with a few micro-cracks. The thermal conductivity of BaWO4 scheelite decreases from 1.3 +/- 0.2 to 1.0 +/- 0.1 W m-1 K-1 in the range 373-673 K. The cation-deficient scheelites Ce2/3 ❑1/3WO4 and La2/3 ❑1/3WO4 ceramics display an ultra-low thermal conductivity of 0.3 +/- 0.04 W m-1 K-1 and 0.2 +/- 0.03 W m-1 K-1 at 673 K, respectively. These materials exhibit among the lowest known values of thermal conductivity in crystalline oxides, in this temperature range. Therefore, they appear as very attractive for thermal barrier coating and thermoelectric applications.(c) 2023 Elsevier B.V. All rights reserved.

Bismuth vanadate - bismuth molybdate solid-solution was prepared to elaborate ceramics with different amounts of cation vacancies. Dense ceramics with similar microstructures were obtained and the evolution of their melting point, specific heat, thermal diffusivity, and conductivity as a function of the amount of vacancy was evaluated. At room temperature, the thermal conductivity decreases from 1.74 W m(-1) K-1 for BiVO4 (x=0) to 1.12 W m(-1) K-1 for Bi-0.867 square 0.133Mo0.4V0.6O4 (x=0.4). Moreover, we show that a very small amount of vacancy (1.7%, x=0.05) is enough to provide a large decrease in thermal conductivity by more than 15%, in agreement with a mass fluctuation scattering model. However, the temperature of the melting point also decreases with increasing amount of vacancy. Our results suggest adding only a very small amount of vacancy as the best strategy to obtain superior materials for thermal barriers and thermoelectric devices, with ultra-low thermal conductivity and high-temperature stability.

Sintering is a very important process in materials science and technological applications. Despite breakthroughs in achieving optimized piezoelectric properties, fundamentals of K0.5 Na0.5 NbO3 (KNN) sintering are not yet fully understood, facing densification versus grain growth competition. At present, microscale events during KNN sintering under reducing atmospheres are real-time monitored using a High Temperature-Environmental Scanning Electron Microscope. A two contacting KNN particles model satisfying the Kingery and Berg's bulk diffusion model is reported. Dynamic events like individual grain growth and grain elimination process are explored through a postanalysis of recorded image series. The diffusion coefficient for oxygen vacancies of 10-8 cm2 s-1 and average boundary mobility of 10-9 cm4 J-1 s-1 are reported for the KNN ceramics. Moreover, the local pore shrinkage is consistent with the Kingery and François's concept of pore stability except that pore curvatures are not all concave, convex or flat due to anisotropic grain-boundary energies. The global grain growth kinetics are described using parabolic and/or cubic laws. The effect of atmospheres and microstructure evolution on the intrinsic and extrinsic contributions to the dielectric response using Rayleigh's law is also explored. These results bring a new breath for KNN sintering studies in order to adapt the sintering process.

To replace lead containing (Pb, Zr) TiO_3 in piezoelectric devices, the (K, Na) NbO_3 system has shown great promise but has also encountered versatile properties, due to the volatilization of alkaline elements and difficulties in getting fully dense ceramics. K_0.5Na_0.5O_3 (KNN) powders are prepared by solid-state synthesis with a short-time planetary ball milling and shaped in a series of ceramic pellets using spark plasma sintering technique (SPS), resulting in highly dense ceramics. This sintering process operates in reducing conditions, and post-annealing in oxygen flow is required to recover a good electrical insulator material, to remove the residual strains in the ceramics and to eliminate possible carbon contamination from the graphite die. The structural and microstructural states of the ceramics, observed before and after post treatment, lead to the identification of the major defects encountered during SPS treatment. The resulting piezoelectric functional properties obtained on the series of pellets after oxygen annealing post treatment are measured. This study confirms that SPS technique is really successful in achieving very high and reproducible densification of KNN ceramics. After a post-annealing treatment, substantial piezoelectric properties improvement can be expected in such high densification and defect-free ceramics, suitable for integration in lead-free devices.

In this study, the effectiveness of bioaugmentation approach using zeolite supported biofilms as inoculants was evaluated in microcosm experiments. For this, selected MCPA-degrading microbial consortium was grown as biofilm on natural and Fe-modified zeolite grains (0.2-1.25 mm in size) and the obtained biocomposites (4 x 10(10) cells/g of biocomposite) were amended to soil or sand microcosms (130 g biocomposites/m(2); 4 x 10(7) cells/g of dry weight soil or sand) supplemented with herbicide MCPA (2-methyl-4-chlorophenoxyacetic acid, 0.166 mg/kg dw soil or 0.309 mg/kg of dw sand, respectively). The major part of the identified bacterial sequences (51-59 %) in both biocomposites was attributed to the bacterial genera related to biodegradation of pesticides, including phenoxy-herbicides (Cupriavidus, Novosphingobium, Pseudomonas, Rhodococcus, Sphingobium, Sphingopyxis). The present study showed that the MCPA biodegradation ability of the studied biocomposites was very close to each other and characterised with similar kinetics: biodegradation of 80 % MCPA within 2 days in soil and 5 days in sand. Thus, the zeolite-supported biofilms could be effective inoculants for pesticide biodegradation at polluted agricultural sites. The biocomposites can be effectively used not only for treatment of soil but also sand, however its activity may change with variation of the matrix. Surface modifications of a given support material is an interesting approach to select different microbial communities, which can provide significant advantages according to the site to be treated.

(Sr_0.95La_0.05)_0.95□ _0.05TiO_3 ceramics were prepared by solid state reaction and sintered by spark plasma sintering at different temperatures ranging from 1473 to 1873 K for 10 min. The thermoelectric properties show that sintering at temperatures higher than 1773 K allows reaching high thermoelectric properties similar to the ones obtained after annealing at high temperatures in H_2/N_2 for several hours. The high temperature sintered samples exhibit highest power factor near room temperature, resulting in ZT values higher than 0.1. Therefore, the 10 min short SPS process at high temperatures described in this paper is an easy, cheap, fast, and one step route to obtain dense and efficient SrTiO_3 -based thermoelectric ceramics. However, SEM observations show that the samples are not pure perovskite phase but contain titanium oxide and lanthanum compound aggregates.

In this study, a crystal growth route is described in order to obtain semiconducting oxides microwires with various morphologies. Ceramic rods of ZnO, SnO2, Zn2SnO4 and In2O3 are sintered at 900 °C during 10 h in air. Then the rod is subjected to crystal growth in an optical furnace. At high temperature, a vaporization-condensation mechanism takes place when heated and leads to the growth of microwires on the rod itself. In 20 min, the microwires can reach a size longer than 100 μm in the growth direction. The shape of the microwires depends on the material space group. A hexagonal shape is obtained in the case of ZnO, whereas a cubic-like shape appears in the case of In2O3. Moreover, it is shown that doping is possible with this process and does not proceed in sublimation-condensation but in a diffusion process. Capacitance variation measurements carried out on the Ni doped ZnO microwires using scanning capacitance microscopy evidenced a decrease of carrier concentrations along the microwire. This carrier profile is consistent with that induced by diffusion process in solid phase. The shape and the size of the microwires depend on the doping element. Doped ZnO, In2O3 and SnO2 single microwires, with well faceted and specific shape, have been thus achieved by this technique.

The influence of conditioning state of a nano-SiC powder on its spark plasma sintering behaviour and microstructural properties is discussed. The powders were firstly deeply characterized by means of SEM, X-ray diffraction, specific surface area measurements and rheological behaviour determination. We found that even if the initial particles are the same, the conditioning state plays a crucial role on the development of the ceramic. Granulated SiC powder exhibits the highest ability of rearrangement and compaction leading to a better green density. This specificity allows the development of the densest ceramic with the lowest grain size. Moreover, this ceramic showed no evidence of phase transition during sintering, with a pure cubic SiC phase. We conclude that the powder state and the storage conditions of the ceramic powder has an impact on the overall powder process and finally influences not only the final density and grain size but also the phase composition.

The origin of low thermal conductivity in niobium-containing perovskites was investigated. Therefore, dense NaNbO3 and KNbO3 ceramics were sintered by spark plasma sintering. The grain size was in the 1-10 mu m range. NaNbO3 ceramic has shown a stable thermal conductivity circa 2.6 W m(-1) K-1 from 373 to 1000 K and KNbO3, values from 2.5 to a plateau at 1.2 W m(-1) K-1 since 673 K. This value is the lowest thermal conductivity reported for an oxide presenting a perovskite structure. The origin of such low thermal conductivities is indicated to be related with cation deficiency on the A-site of the niobium-containing perovskites.