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1.
《Ceramics International》2017,43(14):10691-10697
Al2O3 multi-phase composites with different volume fractions of SiC varying from 0 vol% to 30.0 vol% were fabricated by vacuum hot pressing sintering at 1600 °C under the pressure of 30 MPa for 2.0 h. The aim of this work was to investigate the effect of SiC content on the morphology and mechanical properties of the Al2O3 multi-phase composite. The results show that the addition of SiC and Ti can produce new strengthening and reinforcing phases include Ti3SiC2, TiC, Ti5Si3, which would hamper the migration of grain boundaries and promote sintering. The mechanical performances could reach the comprehensive optimal values for 20.0 vol% SiC, delamination and transgranular fracture being the major crack propagation energy dissipation mechanisms. 相似文献
2.
《Ceramics International》2016,42(10):11982-11988
In this paper, Ti3Si(Al)C2 based ceramics were fabricated by reactive melt infiltration (RMI) of TiC/TiO2 preforms with liquid silicon. The microstructure, phase composition, and mechanical properties of the Ti3Si(Al)C2 based ceramics have been investigated to understand the effect of phase composition of the preforms on the formation mechanisms of Ti3Si(Al)C2. The preforms with different content of TiO2 infiltrated at 1500 °C with liquid silicon for 1 h were composed of Ti3Si(Al)C2, Al2O3, TiC, TiSixAly and residual Al. The prior generated Al2O3 phases inhibited the dispersion of Ti3Si(Al)C2 phases, resulting in the drastically grain growth of Ti3Si(Al)C2. Subsequently, the microstructure with gradually increasing Ti3Si(Al)C2 grain size resulted in the decrease of the bending strength and fracture toughness of samples. When the content of TiO2 reached 20 wt%, the bending strength reached the maximum, 326.6 MPa. The fracture toughness attained the maximum, 4.3 MPa m1/2, when the content of TiO2 was 10 wt%. 相似文献
3.
《Journal of the European Ceramic Society》2007,27(8-9):2855-2859
The effect of excess Al2O3 on the densification, structure and microwave dielectric properties of Ca0.7Ti0.7La0.3Al0.3O3 (CTLA) was investigated. CTLA ceramics were prepared using the conventional mixed oxide route. Excess Al2O3 in the range of 0.1–0.5 wt% was added. It was found that Al2O3 improved the densification. A phase rich in Ca and Al was found in the microstructure of Al2O3 doped samples. Additions of Al2O3 coupled with the slow cooling after sintering improved the microwave dielectric properties. CTLA ceramics with 0.25 wt% Al2O3 cooled at 5 °C/h showed high density and a uniform grain structure with ɛr = 46, Q × f = 38,289 and τf = +12 ppm/°C at 4 GHz. XRD and TEM examinations showed the presence of (1 1 2) and (1 1 0) type twins arising from a−a−c+ tilt system with the presence of anti-phase domain boundaries from the displacement of A-site cations of the orthorhombic perovskite structure. 相似文献
4.
《Journal of the European Ceramic Society》2014,34(6):1493-1499
Dense Ti3Si(Al)C2-based ceramics were synthesized using reactive melt infiltration (RMI) of Al70Si30 alloy into the porous TiC preforms. The effects of the infiltration temperature on the microstructure and mechanical properties of the synthesized composites were investigated. All the composites infiltrated at different temperatures were composed of Ti3Si(Al)C2, TiC, SiC, Ti(Al, Si)3 and Al. With the increase of infiltration temperature from 1050 °C to 1500 °C, the Ti3Si(Al)C2 content increased to 52 vol.% and the TiC content decreased to 15 vol.%, and the Vickers hardness, flexural strength and fracture toughness of Ti3Si(Al)C2-based composite reached to 9.95 GPa, 328 MPa and 4.8 MPa m1/2, respectively. 相似文献
5.
《Ceramics International》2017,43(2):2143-2149
Graphene has been successfully fabricated by a novel method, using graphite powder and NMP (N-Methyl Pyrrolidone) as the raw materials based on the principles of liquidoid exfoliation and mechanical milling. SEM, TEM and Raman spectrum were utilized to characterize the morphology of the homemade graphene, illustrating the few defects and rare layers were endowed in this study. Afterwards, the homemade and commercial graphene were doped into Al2O3 powder with the mass ratio of 0%, 1%, 2%, and 3% to reinforce the mechanical properties of the matrix. The composites were processed at 1600 °C, pressure of 30 MPa and soaking time of 1 h by vacuum hot pressing. The test results illustrated the bending strength and fracture toughness tended to be intensive at first and subdued afterwards, achieving the optimal performance of 625.4±18.2 MPa and 6.07±0.22 MPa m1/2 at 2 wt% prepared graphene additive, and the commercial grapheme owned the best heighten effect in 3 wt% graphene/Al2O3 composites. Compared to the blank Al2O3 sintered samples, the graphene/Al2O3 specimens (both prepared and commercial additive) behaved evident increase in mechanical properties, even upon 30% enhanced in fracture toughness and bending strength generally by the prepared grapheme. Moreover, the prepared graphene had better improvement effect than commercial graphene in enhancing mechanical properties of Al2O3 ceramic. 相似文献
6.
《Journal of the European Ceramic Society》2006,26(15):3393-3397
In situ synthesis of Al2O3–TiC nanocomposite powders from a mixture of titanium, graphite, and Al2O3 powders by high-energy ball milling (HEBM) and its consolidation through spark plasma sintering (SPS) were investigated. After being milled for 25 h at ambient temperature, the powder mixtures were mainly composed of homogeneous nanosized Al2O3 particle and amorphous TiC solid solution. The relative density of the samples consolidated by SPS technique in vacuum at 1480 °C for 4 min reached 99.2%. The final products exhibited very fine microstructure, and the grain sizes of Al2O3 and TiC were about 400 nm and 200 nm, respectively, with a flexure strength of 944 ± 21 MPa, Vickers hardness 21.0 ± 0.3 GPa, fracture toughness 3.87 ± 0.2 MPa m1/2, and electrical conductivity 1.2787 × 105 S m−1. 相似文献
7.
ABSTRACTTi3AlC2/Al2O3 composite materials were successfully fabricated from TiO2/TiC/Ti/Al powders by the in situ reactive hot pressed technique. The microstructure, mechanical and oxidation properties of the composites were investigated in the paper. Vickers hardness increased with the Al2O3 content. The relative density of Ti3AlC2/Al2O3 composites exhibits a declining tendency with Al2O3 content especially exceeds 10 vol.?%. The Ti3AlC2/Al2O3 composites show excellent electrical conductivity. The flexural strength and fracture toughness of Ti3AlC2/10 vol. % Al2O3 are 461 ± 20?MPa and 6.2?±?0.2?MPa m1/2, respectively. The cyclic oxidation behaviour of resistance of Ti3AlC2/10 vol. % Al2O3 composites at 800–1000°C generally obeys a parabolic law. The oxide scale of sample consists of a mass of α-Al2O3 and TiO2, forming a dense and adhesive protect layer. The result indicates that the Al2O3 can greatly improve the oxidation resistance of Ti3AlC2. 相似文献
8.
《Ceramics International》2016,42(8):9995-10005
The paper discusses the development of a new material system for interconnect application in Solid Oxide Fuel Cells (SOFC) based on TiC–Ti3Al. Nano-sized TiC powders utilized in this research were synthesized using carbon coated TiO2 precursors from a patented process. The pressureless sintering of TiC–Ti3Al in a vacuum was applied at temperatures between 1100 °C and 1500 °C and content of Ti3Al was varied in the range of 10–40 wt%. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used for phase evaluation and sintering behavior. Relative density increased markedly with increasing sintering temperature because of grain growth and formation of the Ti3AlC2 secondary phase. Dense products (>95% TD) were prepared from nanosized TiC powders with 10 and 20 wt% Ti3Al, but with about 8 to 10% porosity for 30 and 40 wt% Ti3Al. The mechanical properties were determined from Vickers hardness and fracture toughness calculations. Vickers hardness decreased and fracture toughness increased with increasing Ti3Al content. The electrical conductivity and oxidation behavior of TiC–Ti3Al composites were investigated to evaluate the feasibility for SOFC interconnect application. The electrical conductivity measurements in the air at 800 °C for 100 h were made using the Kelvin 4-wire method. 相似文献
9.
Aijun Li Chunfeng Hu Meishuan Li Yanchun Zhou 《Journal of the European Ceramic Society》2009,29(12):2619-2625
The joining of titanium aluminum carbides has been successfully performed at high temperature and low oxygen partial pressure. The mechanism of the bonding is attributed to the preferential oxidation of Al atoms in the titanium aluminum carbides at low oxygen partial pressure, which leads to the formation of an Al2O3 layer through the joint interface. The specimens joined at 1400 °C exhibit a high flexural strength of 315 ± 19.1 MPa for Ti2AlC and 332 ± 2.83 MPa for Ti3AlC2, which is about 95% and 88% of the substrates, respectively, and the high flexural strength can be retained up to 1000 °C. The high mechanical performance of the joints is attributed to the similar density and thermal expansion coefficient values of Al2O3 to those of the Ti2AlC and Ti3AlC2 substrates. It indicates that bonding via preferential oxidation at low oxygen partial pressure is a practical and efficient method for Ti2AlC and Ti3AlC2. 相似文献
10.
《Journal of the European Ceramic Society》2006,26(9):1619-1628
The effect of additions of up to 1 mol% Al2O3 on abnormal grain growth in BaTiO3 samples sintered at 1200 and 1250 °C has been studied. Samples with and without additions of 0.4 mol% TiO2 were prepared. For the samples without added TiO2, addition of 0.1 mol% Al2O3 increases the number density of abnormal grains, with further additions reducing the number density. The initial increase in number density is caused by Al2O3 forming a solid solution with BaTiO3 and releasing TiO2 to the grain boundaries. This excess TiO2 then reacts with BaTiO3 to form Ba6Ti17O40, which promotes {1 1 1} twin formation and abnormal grain growth. Further additions of Al2O3 react with BaTiO3, Ba6Ti17O40 and excess TiO2 to form Ba4Al2Ti10O27 and BaAl2O4 second phases, neither of which are growth sites for abnormal grains. For the samples with added TiO2, addition of Al2O3 decreases the number of abnormal grains due to the Al2O3 reacting with the excess TiO2 and BaTiO3 to form Ba4Al2Ti10O27 and BaAl2O4 instead of Ba6Ti17O40. 相似文献
11.
《Journal of the European Ceramic Society》2006,26(8):1317-1323
Al2O3/TiC ceramic composites with the additions of CaF2 solid lubricants were produced by hot pressing. The effect of the solid lubricant on the microstructure and mechanical properties of the ceramic composite has been studied. The friction coefficient and wear rates were measured using the ring-block method, and the tribological behaviors were discussed in relation to its mechanical properties and microstructure. Results showed that additions of CaF2 solid lubricants to Al2O3/TiC matrix led to a decrease in the flexural strength, fracture toughness, and hardness compared to a conventional Al2O3/TiC composite. The friction coefficient of Al2O3/TiC/CaF2 ceramic composites when sliding against both cemented carbide and hardened steel decreased with an increase in CaF2 content up to 15 vol.%. The reason is that the CaF2 released and smeared on the wear surface, and acted as solid lubricant film between the sliding couple. When the content of CaF2 solid lubricant is less than 10 vol.%, the wear rate of Al2O3/TiC/CaF2 composites decreases with an increase in CaF2 content, with further increases in CaF2 content, the wear rate of Al2O3/TiC/CaF2 composites increases rapidly. This is due to the large degradation of mechanical properties in samples with high CaF2 contents. 相似文献
12.
C. Oelgardt J. Anderson J.G. Heinrich G.L. Messing 《Journal of the European Ceramic Society》2010,30(3):649-656
We report on how the mechanical properties of sintered ceramics (i.e., a random mixture of equiaxed grains) with the Al2O3–Y2O3–ZrO2 eutectic composition compare with those of rapidly or directionally solidified Al2O3–Y2O3–ZrO2 eutectic melts. Ceramic microcomposites with the Al2O3–Y2O3–ZrO2 eutectic composition were fabricated by sintering in air at 1400–1500 °C, or hot pressing at 1300–1400 °C. Fully dense, three phase composites of Al2O3, Y2O3-stabilized ZrO2 and YAG with grain sizes ranging from 0.4 to 0.8 μm were obtained. The grain size of the three phases was controlled by the size of the initial powders. Annealing at 1500 °C for 96 h resulted in grain sizes of 0.5–1.8 μm. The finest scale microcomposite had a maximum hardness of 19 GPa and a four-point bend strength of 282 MPa. The fracture toughness, as determined by Vickers indentation and indented four-point bending methods, ranged from 2.3 to 4.7 MPa m1/2. Although strengths and fracture toughnesses are lower than some directionally or rapidly solidified eutectic composites, the intergranular fracture patterns in the sintered ceramic suggest that ceramic microcomposites have the potential to be tailored to yield stronger, tougher composites that may be comparable with melt solidified eutectic composites. 相似文献
13.
《Journal of the European Ceramic Society》2007,27(7):2647-2654
The interdependence of the titanium oxide amount and the anisotropic growth of mullites prepared from single-phase gels were investigated. Gels with stoichiometries 3(Al2−xTixO3)·2(SiO2) and 2(Al2−xTixO3)·(SiO2), with 0 ≤ x ≤ 0.15 were prepared by the semialkoxide method. Gels and specimens heated at temperatures between 1200 and 1600 °C were characterized by using infrared spectroscopy (IR), X-ray diffraction (XRD) and transmission and field emission scanning electron microscopies (TEM and FESEM). Al2TiO5 as minor impurity was detected in both series of mullites for gel precursor compositions x = 0.10 and x = 0.15, obtained at temperatures between 1200 and 1600 °C. Variations of lattice parameters of mullite, processed at temperatures from the range between 1400 and 1600 °C, with the starting nominal amount of titanium oxide indicated that the solubility limit of titanium oxide was in ranges 3.8–4.1 and 4.1–4.4 wt% TiO2 for 3:2 and 2:1 mullites series, respectively. The anisotropic growth of titanium-doped mullite crystalline grains was significant only when the nominal amount of titanium oxide exceeded the limit of solubility into the mullite structure (for both mullite series). Stronger anisotropy occurred for the 3:2 series specimens, i.e. for the SiO2-richer mullites. In both series of mullites, the anisotropic grain growth was observed for the process temperatures higher than 1400 °C; the crystalline grains of mullites processed at lower temperatures were equiaxials and of almost the same size. 相似文献
14.
Al2O3/Al2O3 ceramic matrix composites (CMC) are candidate materials for hot-gas leading components of gas turbines. Since Al2O3/Al2O3 CMC are prone to hot-corrosion in combustion environments, the development of environmental barrier coatings (EBC) is mandatory. Owing to its favorable chemical stability and thermal properties, Y2O3 is considered a candidate EBC material for Al2O3/Al2O3 CMC. Up to 1 mm thick Y2O3 coatings were deposited by means of air plasma spraying (APS) on Al2O3/Al2O3 CMC with a reaction-bonded Al2O3 bond-coat (RBAO). APS Y2O3 coatings exhibit a good adherence in the as-deposited state as well as upon isothermal annealing up to 1400 °C. Moreover, furnace cyclic testing performed at 1200 °C revealed an excellent durability. This is explained by the formation of a continuous, approximately 1 μm thick reaction zone at the APS Y2O3/RBAO interface. The reaction zone between Y2O3 and Al2O3 comprises three layers of thermodynamically stable yttrium-aluminates exhibiting strong bonding, respectively. 相似文献
15.
《Journal of the European Ceramic Society》1999,19(3):335-339
Porous aggregations, with about 10 μm diameter, composed of Al2O3 platelet crystals were formed by heating a powder mixture consisting of Al2(SO4)3+2K2SO4 (mol ratio) in an alumina crucible at temperatures 1000–1300°C for 3 h and removing the flux component with hot hydrochloric acid after heating. The specific surface area of the aggregations obtained by heating at 1000°C for 3 h was maximum and its value was 5·2 m2 g−1. Since the size of Al2O3 platelets increased and the number of Al2O3 platelets decreased, the specific surface area decreased to 0·7 m2 g−1 at 1100°C. When heated at 1300°C, the size of the Al2O3 platelets increased with increasing amount of K2SO4 in the starting powder mixture. © 相似文献
16.
《Ceramics International》2017,43(16):13330-13338
This study examined the effects of post-sintering heat treatment on enhancing the toughness of SiCf/SiC composites. Commercially available Tyranno® SiC fabrics with contiguous dual ‘PyC (inner)-SiC (outer)’ coatings deposited on the SiC fibers were infiltrated with a SiC + 10 wt% Al2O3-Y2O3 slurry by electrophoretic deposition. SiC green tapes were stacked between the slurry-infiltrated fabrics to control the matrix volume fraction. Densification of approximately 94% ρtheo was achieved by hot pressing at 1750 °C, 20 MPa for 2 h in an Ar atmosphere. Sintered composites were then subjected to isothermal annealing treatment at 1100, 1250, 1350, and 1750 °C for 5 h in Ar. The correlation between the flexural behavior and microstructure was explained in terms of the in situ-toughened matrix, phase evolution in the sintering additive, role of dual interphases and observed fracture mechanisms. Extensive fractography analysis revealed interfacial debonding at the hybrid interfaces and matrix cracking as the key fracture modes, which were responsible for the toughening behavior in the annealed SiCf/SiC composites. 相似文献
17.
《Ceramics International》2017,43(13):10224-10230
Whiskers and nanoparticles are usually used as reinforcing additives of ceramic composite materials due to the synergistically toughening and strengthening mechanisms. In this paper, the effects of TiC nanoparticle content, particle size and preparation process on the mechanical properties of hot pressed Al2O3-SiCw ceramic tool materials were investigated. The results showed that the Vickers hardness and fracture toughness of the materials increased with the increasing of TiC content. The optimized flexural strength was obtained with TiC content of 4 vol% and particle size of 40 nm. The particle size has been found to have a great influence on flexural strength and small influence on hardness and fracture toughness. It was concluded that the flexural strength increased remarkably with the decreasing of the TiC particle size, which was resulted from the improved density and refined grain size of the composite material due to the dispersion of the smaller TiC particle size. SEM micrographs of fracture surface showed the whiskers to be mainly distributed along the direction perpendicular to the hot-pressing direction. The fracture toughness was improved by whisker crack bridging, crack deflection and whisker pullout; the TiC nanoparticles in Al2O3 grains caused transgranular fracture and crack deflection, which improved the flexural strength and fracture toughness with whiskers synergistically. Uniaxial hot-pressing of SiC whisker reinforced Al2O3 ceramic composites resulted in the anisotropy of whiskers’ distribution, which led to crack propagation differences between lateral crack and radical crack. 相似文献
18.
《Journal of the European Ceramic Society》2007,27(1):157-163
Fibrous HAp/Al2O3–ZrO2 composites were fabricated using the multi-pass extrusion process. In the 3rd and 4th passed extrusion bodies, fibrous microstructures were obtained. The 3rd and 4th passed Al2O3–ZrO2 cores used as reinforcement, were about 35 and 4.5 μm in diameter, respectively. In the bodies sintered at over 1400 °C, the HAp decomposed and was transformed to β-TCP and TTCP, in which large numbers of pores were observed. The values of bending strength, Vickers hardness and fracture toughness of the 3rd passed HAp/Al2O3–ZrO2 composites were 178 MPa, 325 Hv, and 3.4 MPa m1/2, respectively while the values of the 4th passed bodies were 190 MPa, 405 Hv and 3.8 MPa m1/2. 相似文献
19.
Shi C. Zhang William G. Fahrenholtz Greg E. Hilmas Edward J. Yadlowsky 《Journal of the European Ceramic Society》2010,30(6):1373-1380
Alumina ceramics reinforced with 1, 3, or 5 vol.% multi-walled carbon nanotubes (CNTs) were densified by pressureless sintering. Commercial CNTs were purified by acid treatment and then dispersed in water at pH 12. The dispersed CNTs were mixed with Al2O3 powder, which was also dispersed in water at pH 12. The mixture was freeze dried to prevent segregation by differential sedimentation during solvent evaporation. Cylindrical pellets were formed by uniaxial pressing and then densified by heating in flowing argon. The resulting pellets had relative densities as high as ~99% after sintering at 1500 °C for 2 h. Higher temperatures or longer times resulted in lower densities and weight loss due to degradation of the CNTs by reaction with the Al2O3. A CNT/Al2O3 composite containing 1 vol.% CNT had a higher flexure strength (~540 MPa) than pure Al2O3 densified under similar conditions (~400 MPa). Improved fracture toughness of CNT–Al2O3 composites was attributed to CNT pullout. This study has shown, for the first time, that CNT/Al2O3 composites can be densified by pressureless sintering without damage to the CNTs. 相似文献
20.
Ternary carbide Ti3AlC2 was synthesized by mechanical alloying (MA) and spark plasma sintering (SPS) from elemental powder mixtures of Ti, Al and C, and the effect of Al content on formation of Ti3AlC2 during both processes was investigated. The results showed that adding proper Al content in the staring materials significantly increased the phase purity of Ti3AlC2 in the synthesized samples. Dense and high-purity Ti3AlC2 with <1 wt.% TiC could be successfully obtained by spark plasma sintering of powders mechanically alloyed for 9.5 h from a starting powder mixtures of 3Ti/1.1Al/2C at a lower sintering temperature of 1050 °C for 10–20 min. 相似文献