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Spark Plasma Sintering (spark + plasma_sinter)
Selected AbstractsProcessing of Carbon Nanofiber Reinforced ZrB2 Matrix Composites for Aerospace Applications,ADVANCED ENGINEERING MATERIALS, Issue 7 2010Jorge Barcena Ceramic matrix composites (CMCs) based on zirconium diboride (ZrB2) reinforced by vapor grown carbon nanofibers are a potential constituent of reusable thermal protection systems. A manufacturing procedure was devised that involved the fabrication of thin films by tape casting to obtain a layer that could be integrated into a more complex system. Higher thermal conductivities and improved toughness can be expected for nanofiber additions, as compared to the matrix alone. Consolidation by hot-pressing was more effective than pressureless sintering, in terms of the final relative density and flatness of specimens. Examination of microstructures showed that few carbon nanofibers were present in the matrix after consolidation by sintering, which was attributed to a reaction between the nanofibers and zirconium oxide present on the surface of the ZrB2 powder. As a solution, oxygen impurities from the boride powders were removed by reduction with carbon coatings derived from phenolic resin. The deleterious reaction was avoided, but residual carbon remained at the grain boundaries, likely from decomposition of the binder. The use of an alternative binder (PMMA vs. PVB) will be used in future studies to reduce the residual carbon content. Further, consolidation by Spark Plasma Sintering (SPS) will be explored to further reduce the reaction of surface oxides with the nanofibers. Finally, characterization of the microstructure at the nanometric level and further determination of the mechanical and thermal properties will be conducted as part of future studies. [source] Spark Plasma Sintering as a Useful Technique to the Nanostructuration of Piezo-Ferroelectric Materials,ADVANCED ENGINEERING MATERIALS, Issue 8 2009Teresa Hungría Abstract This review gathers detail on the processing of piezo-ferroelectric ceramic materials by spark plasma sintering for the first time. The results reported here clearly indicate that it is a powerful technique and opens the possibility of processing ceramics with controlled sub-micron or even nanoscale grain sizes. [source] Oxidation resistant aluminized MCrAlY coating prepared by Spark Plasma Sintering (SPS),ADVANCED ENGINEERING MATERIALS, Issue 5 2007D. Oquab NiCoCrAlYTa single and multi layered coatings on an AM3® nickel base superalloy have been fabricated by Spark Plasma Sintering (SPS). MCrAlY powder and Al foil were sintered on the superalloy in a single run SPS experiment The results reported in this paper open the way to faster development of new high temperature coatings with complex structure and composition. [source] Size Effect on Properties of Varistors Made From Zinc Oxide Nanoparticles Through Low Temperature Spark Plasma SinteringADVANCED FUNCTIONAL MATERIALS, Issue 11 2009Léna Saint Macary Abstract Conditions for the elaboration of nanostructured varistors by spark plasma sintering (SPS) are investigated, using 8-nm zinc oxide nanoparticles synthesized following an organometallic approach. A binary system constituted of zinc oxide and bismuth oxide nanoparticles is used for this purpose. It is synthesized at room temperature in an organic solution through the hydrolysis of dicyclohexylzinc and bismuth acetate precursors. Sintering of this material is performed by SPS at various temperatures and dwell times. The determination of the microstructure and the chemical composition of the as-prepared ceramics are based on scanning electron microscopy and X-ray diffraction analysis. The nonlinear electrical characteristics are evidenced by current,voltage measurements. The breakdown voltage of these nanostructured varistors strongly depends on grain sizes. The results show that nanostructured varistors are obtained by SPS at sintering temperatures ranging from 550 to 600,°C. [source] Nanostructured La1,xSrxGa1,yMgyO3,, Ceramics Processed by Spark Plasma Sintering of Mechanosynthesized PrecursorsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2010Alberto Moure Nanostructured ceramics with La1,xSrxGa1,yMgyO3,, composition have been processed by spark plasma sintering of precursors obtained by mechanosynthesis. The compositions with x=0.10 and y=0.20 are single-phase ceramics even at the lowest processing temperatures of 900°C. For x=0.20, y=0.17, typical secondary phases as SrLaGaO4 and SrLaGa3O7 appear at all the processing temperatures, from 900° to 1100°C. The high reactivity of the precursors due to the prolonged milling allows highly densified ceramics (>98%) to be obtained at moderate applied pressures (100 MPa), and at temperatures for which the nanostructure scale is maintained. Single-phase ceramics present higher conductivity than those with isolating secondary phases. The nanostructure appears to break the vacancies ordering, and the conductivity is produced through random vacancies paths, diminishing the activation energy and increasing the total conductivity of the ceramics. [source] Spark Plasma Sintering: An Easy Way to Make Infrared Transparent Glass,CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2010Gaelle Delaizir Infrared transparent glass,ceramics have been prepared in the system GeS2,Sb2S3,CsCl using spark plasma sintering in shorter times in comparison with conventional thermal treatments. The combined effects of pressure, time, and temperature allow the controlled crystallization of Cs-based crystals. The different glass,ceramics have been characterized by scanning electron microscopy and X-ray diffraction. The optical properties were also investigated. [source] Spark Plasma Sintering of an Infrared-Transparent Y2O3,MgO NanocompositeJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2010DongTao Jiang A novel optically transparent ceramic nanocomposite Y2O3,MgO was produced using spark plasma sintering technique. Sintering parameters was optimized to obtain fully dense material while maintaining nanoscale grain size. The sintered nanocomposite has an excellent infrared transmission as a result of small grain size and homogeneous microstructure. Postsinter annealing can significantly improve the transmission. Overly larger grain size severely degrades the transmittance. [source] Blue-emitting AlN:Eu2+ Powder Phosphor Prepared by Spark Plasma SinteringJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2010Hyoung-SeoK Do Blue-emitting AlN:Eu2+ powder phosphor was synthesized by spark plasma sintering (SPS) using AlN, Si3N4, and Eu2O3 as the starting materials, and its luminescence properties were investigated. A single-phase Eu- and Si-co-doped AlN powder was successfully fabricated by SPS in the range of 1650°,1800°C for 5 min. The AlN:Eu2+ obtained exhibited a strong blue emission at 480 nm under the excitation of ,exc=340 nm and an electron beam. The highest photoluminescence intensity was observed in the phosphor sintered at 1700°C, which was comparable to that of the phosphor prepared by gas pressure sintering at 1750°C for 4 h. [source] Alumina/Silicon Carbide Laminated Composites by Spark Plasma SinteringJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2009Vincenzo M. Sglavo Ceramic laminates composed of alumina/silicon carbide composite layers were produced by spark plasma sintering (SPS). Monolithic composite disks containing up to 30 vol% of silicon carbide were fabricated by stacking together and cosintering by SPS green layers prepared by tape casting water-based suspensions. An engineered laminate with a specific layer combination that is able to promote the stable growth of surface defects before final failure was also designed and produced. Fully dense materials with an optimum adhesion between the constituting layers and a homogeneous distribution of the two phases were obtained after SPS. Monolithic composites showed an increasing strength with SiC load, and biaxial strength values as high as 700 MPa were observed for a SiC content of 30 vol%. The engineered laminate showed a peculiar crack propagation that is responsible for the high strength value of about 600 MPa and for the evident insensitivity to surface defects. [source] Pressure Effect on the Homogeneity of Spark Plasma-Sintered Tungsten Carbide PowderJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2009Salvatore Grasso A combined experimental/numerical methodology was developed to aid full densification of pure ultrafine tungsten carbide powder by means of Spark Plasma Sintering (SPS) operating in Current Control mode. Applied pressure ranged from 5 to 80 MPa while the current intensity was set and held constant at 1400 A. The developed SPS model used a moving-mesh technique to account for the electrothermal contact resistance change during both shrinkage and punch sliding follow-up. The pressure dependence on the electrothermal contact resistance was also taken into account by the model. The experimental and numerical results showed the effects of pressure on grain growth, residual porosity, and hardness observed along the sample radius. Upon increasing sintering pressure, complete densification was obtained by reducing the peak temperature measured at the die surface. By combining experimental and modeling results, a direct correlation between compact microstructure homogeneity and sintering parameters (i.e., temperature and applied pressure) was established. [source] Hydrothermal Synthesis and Spark Plasma Sintering of (K, Na)NbO3 Lead-Free PiezoceramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2009Nan Liu A facile hydrothermal route was adopted for synthesis of lead-free piezoceramics (K, Na)NbO3 powders. The influences of temperature and KOH/NaOH concentration on the resultant powders were investigated. Although two similar perovskite phases appeared when K/Na ratio tended toward 1:1, the two-phase coexistence tendency was weakened by increasing hydrothermal reaction temperature, and consequently only one phase could be obtained after spark plasma sintering. Reasonably good ferroelectric and piezoelectric properties were obtained for the samples after postannealing, whose piezoelectric constant (d33) reached 135 pC/N. The optimal remnant polarization (Pr) and mechanical quality factor (Qm) were 26.2 ,C/cm2 and 164, respectively, which were both twice as much as those of the samples using powders prepared from solid-state reaction. [source] Effects of La2O3 Addition and PbO Excess on the Transmittance of PbZrO3,PbTiO3,Pb(Zn1/3Nb2/3)O3 Ceramics by Spark Plasma SinteringJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2008Yong Jun Wu The effects of La2O3 addition and PbO excess on the microstructures and optical properties of PbZrO3,PbTiO3,Pb(Zn1/3Nb2/3)O3 (PZ,PT,PZN) ceramics prepared by spark plasma sintering were investigated. When 1 mol% La2O3 was added, the highest transmittance of 35% at 700 nm for PZ,PT,PZN ceramics was obtained. The improved transmittance was attributed to the increased relative density and the decreased optical anisotropy. The samples containing more than 1 mol% La2O3 showed decreased transmittance, due to the appearance of secondary phases. The transmittance of PZ,PT,PZN ceramics increased slightly to 29% at 700 nm with increasing amount of excess PbO up to 10 mol% and thereafter decreased rapidly. [source] Preparation and Microstructure of a ZrB2,SiC Composite Fabricated by the Spark Plasma Sintering,Reactive Synthesis (SPS,RS) MethodJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2007Yuan Zhao A mixture of Zr, B4C, and Si powders was adopted to synthesize a ZrB2,SiC composite using the spark plasma sintering,reactive synthesis (SPS,RS) method. SPS treatments were carried out in the temperature range of 1350°,1500°C under a varying pressure of 20,65 MPa with a 3-min holding time. A dense (,98.5%) ZrB2,SiC composite was successfully fabricated at 1450°C for 3 min under 30 MPa. The microstructure of the composite was investigated. The in situ formed ZrB2 and SiC phases dispersed homogeneously on the whole. The grain size of ZrB2 and SiC was <5 and 1 ,m, respectively. A number of in situ formed ultrafine SiC particles were observed entrapped in the ZrB2 grains. [source] Novel Fabrication Route to Al2O3,TiN Nanocomposites Via Spark Plasma SinteringJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2006Lianjun Wang A novel method for the preparation of Al2O3,TiN nanocomposites was developed. A mixture of TiO2, AlN, and Ti powder was used as the starting material to synthesize the Al2O3,TiN nanocomposite under 60 MPa at 1400°C for 6 min using spark plasma sintering. X-ray diffractometry, scanning electron microscopy, and transmission electron microscopy were used for detailed microstructural analysis. Dense (up to 99%) nanostructured Al2O3,TiN composites were successfully fabricated, the average grain size being less than 400 nm. The fracture toughness (KIC) and bending strength (,b) of the nanostructured Al2O3,TiN composites reached 4.22±0.20 MPa·m1/2 and 746±28 MPa, respectively. [source] Compositional Dependence of Piezoelectric Properties in NaxK1,xNbO3 Lead-Free Ceramics Prepared by Spark Plasma SinteringJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2006Bo-Ping Zhang Lead-free piezoelectric NaxK1,xNbO3 (x=20,80 mol%) ceramics were fabricated using spark plasma sintering at a low temperature (920°C). All the NaxK1,xNbO3 ceramics showed a similar orthorhombic phase structure, while the corresponding lattice parameters decreased from the KNbO3 side to the NaNbO3 side with increasing Na content. A discontinuous change in lattice parameter close to composition of 60 mol% Na indicated the presence of a transitional area that is similar to the morphotropic phase boundary (MPB) in NaxK1,xNbO3 ceramics. The sintered density of the NaxK1,xNbO3 ceramics decreased with increasing Na content, from a relative density of 99% for the K-rich side to 92% for the Na-rich side. The piezoelectric constant d33 and planar mode electromechanical coupling coefficient kp showed a maximum value of 148 pC/N and 38.9%, respectively, due to the similar MPB effects in the PZT system. [source] Preparation of Textured Bismuth Titanate Ceramics Using Spark Plasma SinteringJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2004Hao Junjie Textured bismuth titanate ceramics were successfully produced using spark plasma sintering and platelike bismuth titanate particles prepared using a molten-salt method. The microstructure and dielectric properties of the samples were investigated. The results showed that the dielectric property of the textured bismuth titanate ceramics was anisotropic in various directions and that spark plasma sintering was an effective sintering technology to obtain textured, dense bismuth titanate ceramics at a low temperature. [source] Preparation of Dense MgB2 Bulk Superconductors by Spark Plasma SinteringJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2003Soo-Yong Lee Fully dense MgB2 bulk specimens (,higher than 99% dense) were prepared using spark plasma sintering (SPS) at 1250°C for 15 min. Microstructure analyses revealed that faceted MgO particles of ,8% volume fraction were dispersed in the MgB2 matrix. A sharp superconducting transition with an onset temperature of 38.5 K was confirmed by both magnetization and resistivity measurements. [source] Spark Plasma Sintering of AluminaJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2002Zhijian Shen A systematic study of various spark plasma sintering (SPS) parameters, namely temperature, holding time, heating rate, pressure, and pulse sequence, was conducted to investigate their effect on the densification, grain-growth kinetics, hardness, and fracture toughness of a commercially available submicrometer-sized Al2O3 powder. The obtained experimental data clearly show that the SPS process enhances both densification and grain growth. Thus, Al2O3 could be fully densified at a much lower temperature (1150°C), within a much shorter time (minutes), than in more conventional sintering processes. It is suggested that the densification is enhanced in the initial part of the sintering cycle by a local spark-discharge process in the vicinity of contacting particles, and that both grain-boundary diffusion and grain-boundary migration are enhanced by the electrical field originating from the pulsed direct current used for heating the sample. Both the diffusion and the migration that promote the grain growth were found to be strongly dependent on temperature, implying that it is possible to retain the original fine-grained structure in fully densified bodies by avoiding a too high sintering temperature. Hardness values in the range 21,22 GPa and fracture toughness values of 3.5 ± 0.5 MPa·m1/2 were found for the compacts containing submicrometer-sized Al2O3 grains. [source] | ||||||||||