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1.
Xiaowei Yin Nahum Travitzky Peter Greil 《Journal of the American Ceramic Society》2007,90(7):2128-2134
Nanolaminates with a layered M N +1 AX N crystal structure (with M: transition metal, A: group element, X: carbon or nitrogen, and N =1, 2, 3) offer great potential to toughen ceramic composites. A ternary Ti3 AlC2 carbide containing ceramic composite was fabricated by three-dimensional printing of a TiC+TiO2 powder mixture and dextrin as a binder. Subsequent pressureless infiltration of the porous ceramic preform with an Al melt at 800°–1400°C in an inert atmosphere, followed by reaction of Al with TiC and TiO2 finally resulted in the formation of a dense multiphase composite of Ti3 AlC2 –TiAl3 –Al2 O3 . A controlled flaw/strength technique was utilized to determine fracture resistance as a function of crack extension. Rising R -curve behavior with increasing crack extension was observed, confirming the operation of wake-toughening effects on the crack growth resistance. Observations of crack/microstructure interactions revealed that extensive crack deflection along the (0001) lamellar sheets of Ti3 AlC2 was the mechanism responsible for the rising R -curve behavior. 相似文献
2.
Sui Lin Shi Wei Pan Ming Hao Fang Zhen Yi Fang 《Journal of the American Ceramic Society》2006,89(2):743-745
Ti3 SiC2 /HAp composites with different Ti3 SiC2 volume fractions were fabricated by spark plasma sintering (SPS) at 1200°C. The effects of Ti3 SiC2 addition on the mechanical properties and microstructures of the composites were investigated. The bending strength and fracture toughness of the composites increased with increasing of Ti3 SiC2 content, whereas the Vickers hardness decreased. The bending strength and fracture toughness reached 252±10 MPa and 3.9±0.1 MPa·m1/2 , respectively, with the addition of 50 vol% Ti3 SiC2 . The increases in the mechanical properties were attributed to the matrix strengthening and interactions between cracks and the Ti3 SiC2 platelets. 相似文献
3.
Chunfeng Hu Zhijun Lin Lingfeng He Yiwang Bao Jingyang Wang Meishuan Li Yanchun Zhou 《Journal of the American Ceramic Society》2007,90(8):2542-2548
Bulk Ta4 AlC3 ceramic was prepared by an in situ reaction synthesis/hot-pressing method using Ta, Al, and C powders as the starting materials. The lattice parameter and a new set of X-ray diffraction data were obtained. The physical and mechanical properties of Ta4 AlC3 ceramic were investigated. Ta4 AlC3 is a good electrical and thermal conductor. The flexural strength and fracture toughness are 372 MPa and 7.7 MPa·m1/2 , respectively. Typically, plate-like layered grains contribute to the damage tolerance of Ta4 AlC3 . After indentation up to a 200 N load, no obvious degradation of the residual flexural strength of Ta4 AlC3 was observed, demonstrating the damage tolerance of this ceramic. Even at above 1200°C in air, Ta4 AlC3 still retains a high strength and shows excellent thermal shock resistance, which renders it a promising high-temperature structural material. 相似文献
4.
Yuri Khoptiar Irena Gotman Elazar Y. Gutmanas 《Journal of the American Ceramic Society》2005,88(1):28-33
A near-single-phase Ti3 AlC2 ternary carbide was synthesized from 3Ti–1.1Al–1.8C powder blend, both by the wave propagation and thermal explosion (TE) modes of self-propagating high-temperature synthesis. The application of a moderate (28 MPa) pressure immediately after TE at 800°C (reactive forging) yielded a 95% dense material containing, in addition to Ti3 AlC2 , an appreciable amount of TiC1− x . By adjusting the starting composition, a 99% dense material containing up to 90 vol.% Ti3 AlC2 was obtained. The material had a fine-layered microstructure with Ti3 AlC2 grain size not exceeding 10 μm. The samples were readily machinable and had a high compressive strength of ∼800 MPa up to 700°C. 相似文献
5.
P. Mogilevsky Tai-Il Mah T. A. Parthasarathy C. M. Cooke 《Journal of the American Ceramic Society》2006,89(2):633-637
Composites in the SiC–TiC–Ti3 SiC2 system were synthesized using reactive hot pressing at 1600°C. The results indicate that addition of Ti3 SiC2 to SiC leads to improved fracture toughness. In addition, high microhardness can be retained if TiC is added to the material. The best combination of properties obtained in this study is K I c =8.3 MPa·m1/2 and H v =17.6 GPa. The composition can be tailored in situ using the decomposition of Ti3 SiC2 . Ti3 SiC2 decomposed rapidly at temperatures above 1800°C, but the decomposition could be conducted in a controlled manner at 1750°C. This can be used for synthesis of fully dense composites with improved properties by first consolidating to full density a softer Ti3 SiC2 -rich initial composition, and then using controlled decomposition of Ti3 SiC2 to achieve the desired combination of microhardness and fracture toughness. 相似文献
6.
Zhai Hongxiang Huang Zhenying Ai Mingxing Zhou Yang Zhang Zhili Li Shibo 《Journal of the American Ceramic Society》2005,88(11):3270-3274
A nearly pure, dense, polycrystalline bulk Ti3 AlC2 sample was prepared by reactively hot pressing the element titanium, aluminum, and graphite powders. The tribophysical properties were investigated by sliding a Ti3 AlC2 block dryly against a low-carbon steel disk. It was found that the friction coefficient is as low as ∼0.1, and the wear rate of Ti3 AlC2 is only ∼2.5 × 10−6 mm3 /N·m for the highest sliding speed of 60 m/s and the largest normal pressure of 0.8 MPa. These unusual properties are attributable to the presence of a compact self-generating film, which covers uniformly over the friction surface of Ti3 AlC2 with a thickness of ∼0.5 μm. 相似文献
7.
Ziqi Sun Meishuan Li Longfei Hu Xinpo Lu Yanchun Zhou 《Journal of the American Ceramic Society》2009,92(8):1695-1702
The surface chemistry and dispersion properties of aqueous Ti3 AlC2 suspension were studied in terms of hydrolysis, adsorption, electrokinetic, and rheological measurements. The Ti3 AlC2 particle had complex surface hydroxyl groups, such as ≡Ti–OH,=Al–OH, and −OTi–(OH)2 , etc. The surface charging of the Ti3 AlC2 particle and the ion environment of suspensions were governed by these surface groups, which thus strongly influenced the stability of Ti3 AlC2 suspensions. PAA dispersant was added into the Ti3 AlC2 suspension to depress the hydrolysis of the surface groups by the adsorption protection mechanism and to increase the stability of the suspension by the steric effect. Ti3 AlC2 suspensions with 2.0 dwb% PAA had an excellent stability at pH=∼5 and presented the characteristics of Newtonian fluid. Based on the well-dispersed suspension, dense Ti3 AlC2 materials were obtained by slip casting and after pressureless sintering. This work provides a feasible forming method for the engineering applications of MAX-phase ceramics, wherein complex shapes, large dimensions, or controlled microstructures are needed. 相似文献
8.
Xiaowei Yin Nahum Travitzky Peter Greil 《International Journal of Applied Ceramic Technology》2007,4(2):184-190
A porous ceramic preform was fabricated by printing a powder blend of TiC, TiO2 , and dextrin. The presintered preforms contained a bimodal pore size distribution with intra-agglomerate pores ( d 50 ≈0.7 μm) and inter-agglomerate pores ( d 50 ≈30 μm), which were subsequently infiltrated by aluminum melt spontaneously in argon above 1050°C. A redox reaction at 1400°C resulted in the formation of dense Ti–Al–O–C composites mainly composed of Ti3 AlC2 , TiAl3 , Al, and Al2 O3 , which attained a bending strength of 320 MPa, a Young's modulus of 184 GPa, and a Vicker's hardness of 2.5 GPa. 相似文献
9.
Electroconductive Al2 O3 –NbN ceramic composites were prepared by hot pressing. Dense sintered bodies of ball-milled Al2 O3 –NbN composite powders were obtained at 1550°C and 30 MPa for 1 h under a nitrogen atmosphere. The bending strength and fracture toughness of the composites were enhanced by incorporating niobium nitride (NbN) particles into the Al2 O3 matrix. The electrical resistivity of the composites decreased with increasing amount of NbN phase. For a 25 vol% NbN–Al2 O3 composite, the values of bending strength, fracture toughness, Vickers hardness, and electrical resistivity were 444.2 MPa, 4.59 MPa·m1/2 , 16.62 GPa, and 1.72 × 10−2 Ω·cm, respectively, making the composite suitable for electrical discharge machining. 相似文献
10.
A MgAl2 O4 (MA) spinel layer was synthesized on Ti3 AlC2 substrate through the molten salt synthesis (MSS) method. The Ti3 AlC2 substrate was immersed in MgCl2 ·6H2 O powders and treated at 800°, 850°, and 900°C for 4 h in air. A continuous and 10-μm-thick MgAl2 O4 layer was obtained at 900°C, by which the surface hardness of Ti3 AlC2 can be effectively improved. The combined scanning electron microscopy observations and crystal morphology simulation further revealed that the as-formed MgAl2 O4 presents tetragonal bipyramids morphology with (400)-orientation. 相似文献
11.
Mikio Fukuhara 《Journal of the American Ceramic Society》1989,72(2):236-242
The effect of Al2 O3 and (Ti or Si)C additions on various properties of a (Y)TZP (yttria-stabilized tetragonal zirconia polycrystal)–Al2 O3 –(Ti or Si)C ternary composite ceramic were investigated for developing a zirconia-based ceramic stronger than SiC at high temperatures. Adding Al2 O3 to (Y)TZP improved transverse rupture strength and hardness but decreased fracture toughness. This binary composite ceramic revealed a rapid loss of strength with increasing temperature. Adding TiC to the binary ceramic suppressed the decrease in strength at temperatures above 1573 K. The residual tensile stress induced by the differential thermal expansion between ZrO2 and TiC therefore must have inhibited the t - → m -ZrO2 martensitic transformation. It was concluded that a continuous skeleton of TiC prevented grain-boundary sliding between ZrO2 and Al2 O3 . In contrast, for the ternary material containing β-SiC in place of TiC, the strength decreased substantially with increasing temperature because of incomplete formation of the SiC skeleton. 相似文献
12.
Fangzhi Li Bin Liu Jingyang Wang Yanchun Zhou 《Journal of the American Ceramic Society》2010,93(1):228-234
In this work, bulk Hf3 AlN ceramic was synthesized by an in situ reaction/hot pressing method using Hf and AlN as initial materials. The reaction path during the synthesis process was investigated. Hf3 AlN was found to form via the reaction of Hf and AlN above 1000°C. Furthermore, physical and mechanical properties of Hf3 AlN, such as electrical conductivity, flexural strength, and elastic moduli were also characterized. Similar to typical layered ternary ceramics Ti3 SiC2 and Ti3 AlC2 , Hf3 AlN possesses metallic conductivity and excellent damage tolerance, which is also the first one of this type that has ever been reported to crystallize in an orthorhombic structure. It is believed that a typical layered crystal structure and weak interlayer bondings contribute to the damage tolerance of Hf3 AlN. Moreover, the stiffness of Hf3 AlN can sustain a temperature as high as 1450°C, being 250°C higher than that of Ti3 AlC2 , which renders it a promising high-temperature structural material. 相似文献
13.
Chunfeng Hu Fangzhi Li Lingfeng He Mingyue Liu Jie Zhang Jiemin Wang Yiwang Bao Jingyang Wang Yanchun Zhou 《Journal of the American Ceramic Society》2008,91(7):2258-2263
In this work, a bulk Nb4 AlC3 ceramic was prepared by an in situ reaction/hot pressing method using Nb, Al, and C as the starting materials. The reaction path, microstructure, physical, and mechanical properties of Nb4 AlC3 were systematically investigated. The thermal expansion coefficient was determined as 7.2 × 10−6 K−1 in the temperature range of 200°–1100°C. The thermal conductivity of Nb4 AlC3 increased from 13.5 W·(m·K)−1 at room temperature to 21.2 W·(m·K)−1 at 1227°C, and the electrical conductivity decreased from 3.35 × 106 to 1.13 × 106 Ω−1 ·m−1 in a temperature range of 5–300 K. Nb4 AlC3 possessed a low hardness of 2.6 GPa, high flexural strength of 346 MPa, and high fracture toughness of 7.1 MPa·m1/2 . Most significantly, Nb4 AlC3 could retain high modulus and strength up to very high temperatures. The Young's modulus at 1580°C was 241 GPa (79% of that at room temperature), and the flexural strength could retain the ambient strength value without any degradation up to the maximum measured temperature of 1400°C. 相似文献
14.
Y. C. Zhou D. T. Wan Y. W. Bao J. Y. Wang D. T. Wan 《International Journal of Applied Ceramic Technology》2006,3(1):47-54
Ti3 SiC2 has many salient properties including low density, high strength and modulus, damage tolerance at room temperature, good machinablity, and being resistant to thermal shock and oxidation below 1100°C. However, the low hardness and poor oxidation resistance above 1100°C limit the application of this material. The poor oxidation resistance at temperatures above 1100°C was because of the absence of protective layer in the scale and the presence of TiC impurity phase. TiC impurity could be eliminated by adding a small amount of Al to form Ti3 Si(Al)C2 solid solutions. Although the high-temperature oxidation resistance was significantly improved for the Ti3 Si(Al)C2 solid solutions, the strength at high temperatures was lost. One important way to enhance the high-temperature strength is to incorporate hard ceramic particles like SiC. In this article, we describe the in situ synthesis and simultaneous densification of Ti3 Si(Al)C2 /SiC composites using Ti, Si, Al, and graphite powders as the initial materials. The effect of SiC content on high-temperature mechanical properties and oxidation resistance were investigated. The mechanisms for the improved high-temperature properties are discussed. 相似文献
15.
Erich H. Kisi Erdong Wu Jennifer S. Zobec Jennifer S. Forrester Daniel P. Riley 《Journal of the American Ceramic Society》2007,90(6):1912-1916
It is demonstrated that the M n +1 AX n phase Ti3 AlC2 may be readily synthesized by sintering a stoichiometric mixture of the lower order MAX phase Ti2 AlC mixed with a stoichiometric amount of TiC in the temperature range 1350°–1450 °C. High-quality Ti3 AlC2 was readily produced using sintering times in the range 2–5 h. In general, <2% of unwanted or remnant phases were found to be present and in some samples none could be detected at all. 相似文献
16.
Hyun M. Jang Jong H. Moon Cheol W. Jang 《Journal of the American Ceramic Society》1992,75(12):3369-3376
Al2 O3 –ZrO2 –SiC whisker composites were prepared by surface-induced coating of the precursor for the ZrO2 phase on the kinetically stable colloid particles of Al2 O3 and SiC whisker. The fabricated composites were characterized by a uniform spatial distribution of ZrO2 and SiC whisker phases throughout the Al2 O3 matrix. The fracture toughness values of the Al2 O3 –15 vol% ZrO2 –20 vol% SiC whisker composites (∼12 MPa.m1/2 ) are substantially greater than those of comparable Al2 O3 –SiC whisker composites, indicating that both the toughening resulting from the process zone mechanism and that caused by the reinforced SiC whiskers work simultaneously in hot-pressed composites. 相似文献
17.
Ki-Woong Chae Koichi Niihara Doh-Yeon Kim 《Journal of the American Ceramic Society》1996,79(12):3305-3308
The densification behavior and mechanical properties of SiC-30TiC (in volume percent) composites prepared with Cr3 C2 additive were investigated. By hot-pressing a SiC-30TiC-lCr3 C2 specimen at 1950°C, 98.5% of theoretical density was achieved and the specimen exhibited a fracture strength of 750 MPa. For the SiC-30TiC-10Cr3 C2 specimen, (β-α transformation of SiC was observed to occur during hot-pressing and in situ growth of elongated α-SiC grains resulted in an increase of fracture toughness. Micro-structural observations using high-resolution TEM indi-cated that no liquid phase was present at the interfaces. 相似文献
18.
Yong Ming Luo Shu Qin Li Jian Chen Rui Gang Wang Jian Qiang Li Wei Pan 《Journal of the American Ceramic Society》2002,85(12):3099-3101
In the present study, the room-temperature properties of Al2 O3 -Ti3 SiC2 composites with different Ti3 SiC2 contents are determined. The composites are prepared by attrition milling Al2 O3 and Ti3 SiC2 mixture powders followed by spark plasma sintering (SPS) under vacuum. From a closer examination of the dependencies of the electrical conductivity on compositions in this system, we determined the percolation threshold at which an interconnected network of electrically conductive phase arises. Since the hardness of Ti3 SiC2 is lower than that of Al2 O3 , the Vickers hardness decreased with the increasing of Ti3 SiC2 content while the fracture toughness and the strength increased. The maximum strength (673 MPa) and the maximum toughness (9.3 MPa·m1/2 ) were reached in the pure Ti3 SiC2 material. 相似文献
19.
Da Chen Kiroshi Shirato Michel W. Barsoum Tamer El-Raghy Robert O. Ritchie 《Journal of the American Ceramic Society》2001,84(12):2914-2920
The cyclic fatigue and fracture toughness behavior of reactive hot-pressed Ti3 SiC2 ceramics was examined at temperatures from ambient to 1200°C with the objective of characterizing the high-temperature mechanisms controlling crack growth. Comparisons were made of two monolithic Ti3 SiC2 materials with fine- (3–10 μm) and coarse-grained (70–300 μm) microstructures. Results indicate that fracture toughness values, derived from rising resistance-curve behavior, were significantly higher in the coarser-grained microstructure at both low and high temperatures; comparative behavior was seen under cyclic fatigue loading. In each microstructure, Δ K th fatigue thresholds were found to be essentially unchanged between 25° and 1100°C; however, there was a sharp decrease in Δ K th at 1200°C (above the plastic-to-brittle transition temperature), where significant high-temperature deformation and damage are first apparent. The substantially higher cyclic-crack growth resistance of the coarse-grained Ti3 SiC2 microstructure was associated with extensive crack bridging behind the crack tip and a consequent tortuous crack path. The crack-tip shielding was found to result from both the bridging of entire grains and from deformation kinking and bridging of microlamellae within grains, the latter forming by delamination along the basal planes. 相似文献
20.
Dense Sic ceramics were obtained by pressureless sintering of β-Sic and α-Sic powders as starting materials using Al2 O3 -Y2 O3 additives. The resulting microstructure depended highly on the polytypes of the starting SiC powders. The microstructure of SiC obtained from α-SiC powder was composed of equiaxed grains, whereas SiC obtained from α-SiC powder was composed of a platelike grain structure resulting from the grain growth associated with the β→α phase transformation of SiC during sintering. The fracture toughness for the sintered SiC using α-SiC powder increased slightly from 4.4 to 5.7 MPa.m1/2 with holding time, that is, increased grain size. In the case of the sintered SiC using β-SiC powder, fracture toughness increased significantly from 4.5 to 8.3 MPa.m1/2 with holding time. This improved fracture toughness was attributed to crack bridging and crack deflection by the platelike grains. 相似文献