The effect of YB4 addition in ZrB2-SiC composites on the mechanical properties and oxidation performance tested up to 2000 °C (original) (raw)
Related papers
In situ studies of oxidation of ZrB2 and ZrB2–SiC composites at high temperatures
Journal of the European Ceramic Society, 2010
High temperature oxidation of ZrB 2 and the effect of SiC on controlling the oxidation of ZrB 2 in ZrB 2 -SiC composites were studied in situ, in air, using X-ray diffraction. Oxidation was studied by quantitatively analyzing the crystalline phase changes in the samples, both non-isothermally, as a function of temperature, up to ∼1650 • C, as well as isothermally, as a function of time, at ∼1300 • C. During the non-isothermal studies, the formation and transformation of intermediate crystalline phases of ZrO 2 were also observed. The change in SiC content, during isothermal oxidation studies of ZrB 2 -SiC composites, was similar in the examined temperature range, regardless of sample microstructure and composition. Higher SiC content, however, markedly retarded the oxidation rate of the ZrB 2 phase in the composites. A novel approach to quantify the extent of oxidation by estimating the thickness of the oxidation layer formed during oxidation of ZrB 2 and ZrB 2 -SiC composites, based on fractional conversion of ZrB 2 to ZrO 2 in situ, is presented.
Effect of ZrB2 addition on the oxidation behavior of Si-SiC-ZrB2 composites exposed at 1500°C in air
Journal of applied biomaterials & functional materials, 2017
Silicon carbide ceramics obtained by reactive infiltration of silicon (SRI) have many industrial applications especially involving severe and high temperature conditions. In this study, the oxidation behavior in air of Si-SiC-ZrB2 systems at a high temperature (1500°C) for dwelling times of up to 48 hours was examined. The oxidation process was analyzed on the basis of elemental maps and X-ray diffraction patterns taken, respectively, on the core and on the surface of the specimens, together with weight gains and the average thicknesses of the resulting scale. Further, flexural strength at room temperature was examined as a function of different oxidation times. The main chemical reactions and phase transformations involved in the oxidation process are reported. Several oxides were detected on the surface: zirconia, silica, zircon and 3-zirconium monoxide. All of the samples showed a parabolic oxidation kinetics, suggesting that the controlling mechanism was the diffusion; however, ...
Effect of Si3N4 Addition on Oxidation Resistance of ZrB2-SiC Composites
Coatings
The oxidation behavior of ZrB 2-20 vol % SiC and ZrB 2-20 vol % SiC-5 vol % Si 3 N 4 composites prepared by hot-pressing and subjected to isothermal exposure at 1200 or 1300 • C for durations of 24 or 100 h in air, as well as cyclic exposure at 1300 • C for 24 h, have been investigated. The oxidation resistance of the ZrB 2-20 vol % SiC composite has been found to improve by around 20%-25% with addition of 5 vol % Si 3 N 4 during isothermal or cyclic exposures at 1200 or 1300 • C. This improvement in oxidation resistance has been attributed to the formation of higher amounts of SiO 2 and Si 2 N 2 O, as well as a greater amount of continuity in the oxide scale, because these phases assist in closing the pores and lower the severity of cracking by exhibiting self-healing type behavior. For both the composites, the mass changes are found to be higher during cyclic exposure at 1300 • C by about 2 times compared to that under isothermal conditions.
Journal of Alloys and Compounds, 2019
Multi-stage Spark Plasma Sintering (MS-SPS) of ZrB 2-20 vol% SiC-10 vol% Si 3 N 4 (ZSS) and ZrB 2-20 vol% SiC-10 wt% Ta (ZST) composites were carried out at 1900 C for 3 min to densify the ZrB 2-based composites. The microstructure of ZSS composite consisted of new secondary phases (ZrO 2 , BN, ZrN) along with SiC and ZrB 2. Interestingly, ZST sample exhibited core-shell/rim structure and it comprised of ZrB 2 core, (Zr,Ta)B 2 rim, SiC, ZrO 2 and (Zr,Ta)C phases. The presence of new phases and annihilation of Si 3 N 4 or Ta additive in both the sintered samples was clear indication of involvement of sintering reactions. The SEM of cross sectional samples revealed presence of three distinctive layers for the ZrB 2 samples after the isothermal oxidation at 1600 C for 10 h. In particular, no SiC depleted layer was observed for ZSS and its presence was evident in ZST composite. The weight gain (varied between 15.25 and 16.66 mg/cm 2) of the ZrB 2 composites was comparable and significant difference in the oxide layer thickness (changed from 255 to 476 mm) was noticed. Overall the ZST sample offers better oxidation resistance in view of protective nature of its oxide layer.
Oxidation behavior of hot pressed ZrB2–SiC and HfB2–SiC composites
Journal of the European Ceramic Society, 2011
Non-isothermal, isothermal and cyclic oxidation behavior of hot pressed ZrB 2 -20 (vol.%) SiC (ZS) and HfB 2 -20 SiC (HS) composites have been compared. Studies involving heating in thermogravimetric analyzer have shown sharp mass increases at 740 and 1180 • C for ZS, and mass gain till 1100 • C followed by loss for HS. Isothermal oxidation tests for 1, 24 and 100 h durations at 1200 or 1300 • C have shown formation of partially and completely stable oxide scales after ∼24 h exposure for ZS and HS, respectively. X-ray diffraction, scanning electron microscopy and energy or wavelength dispersive spectroscopy has confirmed presence of ZrO 2 or HfO 2 in oxide scales of ZS or HS, respectively, besides B 2 O 3 -SiO 2 . Degradation appears more severe in isothermally oxidized ZS due to phase transformations in ZrO 2 ; and is worse in HS on cyclic oxidation at 1300 • C with air cooling, because of higher thermal residual stresses in its oxide scale.
ZrB2–SiC based composites for thermal protection by reaction sintering of ZrO2+B4C+Si
Journal of Advanced Ceramics, 2017
Synthesis and sintering of ZrB 2-SiC based composites have been carried out in a single-step pressureless reaction sintering (PLRS) of ZrO 2 , B 4 C, and Si. Y 2 O 3 and Al 2 O 3 were used as sintering additives. The effect of ratios of ZrO 2 /B 4 C, ZrO 2 /Si, and sintering additives (Y 2 O 3 and Al 2 O 3), was studied by sintering at different temperatures between 1500 and 1680 ℃ in argon atmosphere. ZrB 2 , SiC, and YAG phases were identified in the sintered compacts. Density as high as 4.2 g/cm 3 , micro hardness of 12.7 GPa, and flexural strength of 117.6 MPa were obtained for PLRS composites. Filler material was also prepared by PLRS for tungsten inert gas (TIG) welding of the ZrB 2-SiC based composites. The shear strength of the weld was 63.5 MPa. The PLRS ZrB 2-SiC composites exhibited: (i) resistance to oxidation and thermal shock upon exposure to plasma flame at 2700 ℃ for 600 s, (ii) thermal protection for Cf-SiC composites upon exposure to oxy-propane flame at 2300 ℃ for 600 s.
Oxidation of ZrB2-SiC Ultrahigh-Temperature Ceramic Composites in Dissociated Air
Journal of Thermophysics and Heat Transfer, 2009
Optical emission spectroscopy is used to investigate the oxidation of a hot-pressed ZrB 2 -SiC ultrahightemperature ceramic composite tested in the 1.2 MW Plasmatron facility at the von Kármán Institute for Fluid Dynamics. Time-resolved spectra enable the in situ detection and temporal characterization of electronically excited B, BO, and BO 2 species concentrations directly adjacent to the oxidizing sample surface. The evolution of these boron species correlates well with the transient formation of a complex multilayer oxide scale containing a silica-rich glassy outer layer that limits oxide growth.
Phase stability, hardness and oxidation behaviour of spark plasma sintered ZrB2-SiC-Si3N4 composites
Ceramics International, 2019
Despite significant efforts to develop ultrahigh temperature ceramics, the phase stability together with high hardness and oxidation resistance remains to be addressed in ZrB 2-SiC based ceramics. ZrB 2-20vol.% SiC (ZS20) ceramics with varying amounts of Si 3 N 4 (2.5, 5 and 10vol.%) were processed by multi stage Spark Plasma Sintering (SPS) over a range of temperature (1800-1900 °C) for 3 min under 50 MPa. All the ZS20-Si 3 N 4 composites could be densified to more than 98% theoretical density (ρ th) after SPS at 1900 °C. The XRD, SEM-EDS analysis of the ZS20-Si 3 N 4 composites revealed the presence of reaction product phases (ZrO 2 , BN, ZrN) along with SiC and ZrB 2 major phases. Sintering reactions were proposed to explain the existence of such new phases and extinction of Si 3 N 4. Thermo-Calc software was also used to further confirm the formation of these new phases in the ZS20-Si 3 N 4 samples. The hardness of ZS20-Si 3 N 4 composites varied between 25.50 to 30.56 GPa, in particular, ZrB 2-20vol.% SiC-5vol.% Si 3 N 4 measured with the maximum hardness. In fact, it is the highest ever reported hardness for the ZrB 2 composites. Considering oxidation resistance, the weight gain of ZrB 2-20vol.%SiC composites decreased (from 13.84 to 9.84 mg/cm 2) and oxide layer thickness increased (64-128 µm) after oxidation at 1500°C for 10 h * * *