Alumina-NbC composites fabricated by spark plasma sintering (original) (raw)
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Alumina–nickel composites densified by spark plasma sintering
Materials Letters, 2005
Alumina-nickel composites were prepared by spark plasma sintering (SPS) with sintering temperatures between 1000-C and 1270-C at a heating rate of 200-C/min. The results showed that the nickel phase was uniformly dispersed in an alumina matrix. The alumina grain sizes increased with increasing sintering temperature and holding time. The relative density of the samples showed that, without holding time, the composites fabricated by SPS could not be consolidated to full density. With a 10 min holding time, the composites, in which grain size of Al 2 O 3 was 0.5-1.0 Am, were consolidated to full density at 1170-C. For dense composites, the fracture toughness of the composites was 3.84 MPaIm 1/2 , higher than that of monolithic Al 2 O 3 ceramics.
Synthesis and characterisation of Al2O3/Ni-type composites obtained by spark plasma sintering
Powder Metallurgy, 2018
This paper presents the influence of sintering on the structure, morphology and compressing strength of alumina/nickel composite compacts obtained by spark plasma sintering (SPS). Al 2 O 3 /Ni composites were prepared by SPS in argon atmosphere at temperatures in the range of 1000-1200-C with a holding time of 2, 5 and 10 minutes. The heating rate was 200 C min −1. These composites have been characterised by X-ray diffraction, SEM and EDX. The relative density and compressive strength of the as-obtained compacts were determined. The results showed that the alumina particles are uniformly dispersed in a quasi-continuous Ni network, and there was no sign of phase changes during sintering. The maximum strength of the alumina/nickel composite with a content of 75 vol. − Al 2 O 3 and 25 vol. − Ni was about 240 MPa for the samples sintered at 1200 C for 10 minutes.
International Journal of Refractory Metals and Hard Materials, 2018
Alumina-nickel composites were prepared by carrying out spark plasma sintering (SPS) of nano-sized and micro-sized Al2O3 particles with 15-45 wt.% Ni powders. The powder materials were sintered at a temperature of 1400 C under a constant uniaxial pressure of 50 MPa. FESEM micrographs of the products showed uniformly dispersed nickel inclusions in both matrices at intergranular positions. Presence of Al2O3 as the major phase along with Ni as the minor phase was confirmed using XRD analysis. Thermal and mechanical properties of the nano-and micro-sized Al2O3/Ni composites were investigated. The thermal conductivity of nano-sized alumina composites was seen to increase with the increase in nickel content, however, an opposite trend was observed for micro-sized alumina-based composites. Moreover, thermal conductivities of all the composites decreased with increase in temperature. The composites also showed high hardness and fracture toughness values of up to 19.6 GPa and 4.71 MPa*m 1/2 , respectively, and relative density values, between 79 and 99%, that
Effect of spark plasma sintering of alumina nanopowder on the mechanical properties
Journal of the Australian Ceramic Society, 2017
The started nanopowder is an α-alumina (α-Al 2 O 3) marketed by Baikowski (Baikalox-BMA15, France), with 99.99% of purity and an average particle size of 150 nm. Samples were shaped by slip casting. Natural sintering was performed at different temperatures (1200, 1300, 1400, and 1500°C) for 1 and 3 h. Furthermore, samples were sintered by BSpark Plasma Sintering (SPS)^using the dry method. The sintering temperature was between 1150 and 1350°C with 50°C step, with 100°C/min as heating rate and for 3 and 10 min. We have used two pressures (25 to 50 MPa). The bulk density of the sintered samples was determined. Young's modulus was measured by the dynamic method. The microstructure of natural sintered specimens and SPS result were observed by scanning electron microscopy. Depending on the conditions of development, different microstructures (fine and coarse) were obtained.
Spark plasma effect on microstructure and mechanical properties of alumina-nickel-cobalt composite
Cerâmica, 2018
Spark plasma sintering (SPS) is an advanced process of sintering materials at low temperatures and short time by creating spark plasma at very high temperatures in the small points and short times, by which materials with high sintering temperature can sinter at lower temperatures. In this study, alumina-nickel-cobalt composites were sintered by SPS and RHP (rapid hot press) methods to investigate the effects of electric pulse on their microstructure and mechanical properties. To this end, sample powders containing alumina, nickel-cobalt aluminate spinel, and aluminum were sintered at 1380 °C under 30 MPa pressure for 10 min by SPS and RHP and then investigated. The densities of both samples were about 98% of theoretical density. Also, hardness and fracture toughness of both samples were about 11 GPa and 14 MPa.m0.5, respectively. The bending strengths of the SPS and RHP samples were 380 and 336 MPa, respectively.
Sintering of alumina-niobium carbide composite
International Journal of Refractory Metals & Hard Materials, 1998
Several studies have been focused on particulate-dispersed Al2O3 composites in order to improve both room and high temperature mechanical properties and wear resistance. In the present work Al2O3-NbC composites have been pressureless sintered and their microstructures analysed as a function of NbC and Y2O3 concentration, the latter added as sintering aid. The compositions used in this study were Al2O3-xNbC and (Al2O3 3%Y2O3)-xNbC, (x = 10, 20 and 40 wt%) and the sintering was performed at 1650 °C/30 min and 1750 °C/15 min. A density greater than 96% of the theoretical density was reached even for those materials sintered at 1650 °C. The observed microstructure was more homogeneous for the samples with Y2O3 addition and the Y3Al5O12 phase was detected. The Al2O3 grain growth restraining due to the NbC concentration was more pronouncedly in samples sintered at 1750 °C.
Sintering behaviour of alumina–niobium carbide composites
Journal of The European Ceramic Society, 2000
Ceramic cutting tools have been developed as a technological alternative to cemented carbides in order to improve cutting speeds and productivity. Al2O3 reinforced with refractory carbides improve fracture toughness and hardness to values appropriate for cutting applications. Al2O3–NbC composites were either pressureless sintered or hot-pressed without sintering additives. NbC contents ranged from 5 to 30 wt%. Particle dispersion limited the grain growth of Al2O3 as a result of the pinning effect. Pressureless sintering resulted in hardness values of approximately 13 GPa and fracture toughness around 3.6 MPa m1/2. Hot-pressing improved both hardness and fracture toughness of the material to 19.7 GPa and 4.5 MPa m1/2, respectively.
International Journal of Refractory Metals and Hard Materials
The sintering behavior of Al 2 O 3-NbC nanocomposites fabricated via conventional and spark plasma sintering (SPS) was investigated. The nanometric powders of NbC were prepared by reactive high-energy milling, deagglomerated, leached with acid, added to the Al 2 O 3 matrix in the proportion of 5 vol.% and dried under airflow. Then, the nanocomposite powders were densified at different temperatures, 1450-1600 °C. Effect of sintering temperature on the microstructure and mechanical properties such as hardness, toughness and bending strength were analyzed. The Al 2 O 3-NbC nanocomposites obtained by SPS show full density and maximum hardness value >25 GPa and bending strength of 532 MPa at 1500 ºC. Microstructure observations indicate that NbC nanoparticles are dispersed homogeneously within Al 2 O 3 matrix and limit their grain growth. Scanning electron microscopy examination of the fracture surfaces of dense samples obtained at 1600 ºC by SPS revealed partial melting of the particle surfaces due to the discharge effect.
Material properties of tungsten carbide–alumina composites fabricated by spark plasma sintering
Ceramics International, 2014
The densification behavior of WC-Al 2 O 3 composites prepared via spark plasma sintering (SPS) was investigated. The initial materials were fabricated using a metal-organic chemical vapor deposition process in which W(CO) 6 was used as a precursor and Al 2 O 3 powder was used as the matrix in a spouted bed. The decomposed W(CO) 6 produced W species that coated Al 2 O 3. Then, carburization, using a mixture of CH 4-H 2 gas, was used to form tungsten carbide-alumina composite powder. This powder was sintered via SPS in the temperature range of 1200-1350 1C, which produced several secondary phases, namely W, WC, and W 2 C. At the highest sintering temperature (1350 1C), the intermediate phase WC decomposed to form W 2 C. The material properties of the SPS-treated samples, including density, hardness, and electrical resistivity, were investigated. The hardness and electrical resistivity of WC-Al 2 O 3 composites were found to be approximately 22.4 GPa and 4.9 Â 10 9 Ω cm, respectively.
Alumina-based nanocomposites consolidated by spark plasma sintering
Scripta Materialia, 2002
Spark plasma sintering is a new process by which ceramics and composites can be consolidated very rapidly to full density. In the present study, piezoelectric Nd 2 Ti 2 O 7 second phase toughening nanocrystalline alumina composites with higher toughness were successfully developed at relatively low temperatures through this technique.