共查询到20条相似文献,搜索用时 15 毫秒
1.
Shuai Wang Jun Cheng Shengyu Zhu Zhuhui Qiao Jun Yang Weimin Liu 《Journal of the European Ceramic Society》2018,38(6):2502-2510
In this paper, in situ formed Ti3(Al,Sn)C2/Al2O3 composites were fabricated by sintering the mixture of Ti3AlC2 and SnO2. The Al atoms could diffuse out of the Ti3AlC2 layered structure to react with SnO2, resulting in the formation of Ti3(Al,Sn)C2 solid solution and Al2O3. When the SnO2 content was 20?wt.%, the sintered Ti3(Al,Sn)C2/Al2O3 composite exhibited the best overall mechanical properties, because of the optimized cooperative strengthening effect of solution strengthening and Al2O3 enhancement. When the SnO2 content increased up to 30?wt.%, the flexural strength and fracture toughness of Ti3(Al,Sn)C2/Al2O3 composite dramatically decreased on account of the large accumulation of generated Al2O3. Moreover, according to the SiC ball-on-flat wear tests, it was found that the wear resistance of Ti3(Al,Sn)C2/Al2O3 composites was significantly improved as the SnO2 content increased. 相似文献
2.
Tailoring Magnetic Properties of MAX Phases,a Theoretical Investigation of (Cr2Ti)AlC2 and Cr2AlC
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Jiemin Wang Zhimou Liu Haibin Zhang Jingyang Wang 《Journal of the American Ceramic Society》2016,99(10):3371-3375
(Cr2Ti)AlC2 is a newly discovered MAX phase with ordered occupations of Ti and Cr atoms on M sites. The Cr‐containing MAX phase is expected showing magnetic property, which provides functional applications in spintronics and as self‐monitoring smart coating. The magnetic states of (Cr2Ti)AlC2 are predicted by GGA and GGA + U methods and compared to those of Cr2AlC. The ground states are predicted as FM or AFM‐XX configurations depending on the calculation methods. Analysis of the electronic structure shows that the magnetic moments mainly originate from the net spins of Cr 3d valence electrons, whereas the contribution of other atoms is negligible. The calculated magnetic moments of Cr atoms in (Cr2Ti)AlC2 are higher than those in Cr2AlC due to the larger distance between the out‐plane Cr atoms separated by the intercalated nonmagnetic Ti–C slab. This work provides an insight on tailoring magnetic properties of MAX phases by modifying the crystal structure. 相似文献
3.
《Ceramics International》2023,49(1):168-178
Since the synthesis of non-oxidized ceramic and alloy powders requires both high temperature and oxygen insulation conditions, here we demonstrate a cost-efficient molten salt sealing/shielded synthesis method with dynamic gas tightness. Compared to conventional synthesis method, it can prevent the loss of reaction materials at high temperature, cut off the connection between reacting material and outside air, and does not require long-time ball milling mixing treatment or provision of applied pressing before or during heating. Only low-cost salts (e.g., NaCl, KCl), a few minutes of raw material mixing, and regular heating molds are required to obtain high-purity (>96 wt%), micron-sized Ti3AlC2 and Ti3SiC2 powders with narrow size distribution, which significantly decreased the complexity and production costs in the synthesis process. The effect of temperature and raw material content on the products were investigated. The mechanism of diffusion reaction between reactants in molten salt environment was analyzed. The new method developed here was also applicable to Ti2AlC, V2AlC and Cr2AlC MAX phases, as well as provided new ideas for the preparation of other MXenes precursors with certain stoichiometric ratios, air-sensitive materials and nanopowders. 相似文献
4.
Preparation of TiC/Ti2AlC coating on carbon fiber and investigation of the oxidation resistance properties
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Mian Li Kai Wang Ji Wang Dewu Long Yanqin Liang Liu He Feng Huang Shiyu Du Qing Huang 《Journal of the American Ceramic Society》2018,101(11):5269-5280
MAX phases were proposed as the interphase materials for carbon fiber reinforced ceramic matrix composites toward the applications in high‐dose irradiation and oxidation environments. A thickness‐controllable TiC/Ti2AlC coating was fabricated on carbon fiber using an in situ reaction in a molten salt bath. The coating showed a multilayered structure, in which the inner layer was TiC and the outer layer was Ti2AlC. The influence of the reaction conditions on the morphology, composition, and thickness of the coating was investigated. The oxidation resistance properties of the as‐prepared TiC/Ti2AlC‐coated carbon fiber in static air and water vapor flow at elevated temperatures were investigated. The results showed that the as‐prepared TiC/Ti2AlC coating could provide good protection to the carbon fiber in both static air and water vapor flow up to 800°C. As these TiC and Ti2AlC materials have good irradiation resistance, the present work provides a potential way to develop an irradiation‐resistant interphase of carbon‐fiber‐reinforced ceramic matrix composites for nuclear applications. Furthermore, this work also provides a feasible way to prepare carbide/MAX phase coating on other carbon materials. 相似文献
5.
《Ceramics International》2023,49(3):4863-4871
Biochar was proposed as a novel carbon source for synthesizing Ti3SiC2 powder with high purity by a simple pressureless sintering at 1673 K, and Ti3SiC2 grains exhibited the typical nanolayered structure. The oxidation behavior of Ti3SiC2 powder showed the parabolic law during isothermal oxidation from 1273 K to 1473 K. Dense and continuous oxidation layer consisting of mixed TiO2 and SiO2 was formed rapidly on the surface of Ti3SiC2 particles as a diffusion barrier, which effectively retarded the inward diffusion of oxygen, conferring good oxidation resistance of the powder. 相似文献
6.
G‐P. Bei G. Laplanche V. Gauthier‐Brunet J. Bonneville S. Dubois 《Journal of the American Ceramic Society》2013,96(2):567-576
In this study, we report on the compressive behavior of Ti3AlC2 and Ti3Al0.8Sn0.2C2 MAX phases at room temperature. We found that these two phases could be classified as Kinking Nonlinear Elastic (KNE) solids. The cyclic compressive stress–strain loops for Ti3AlC2 and Ti3Al0.8Sn0.2C2 are typical hysteretic and fully reversible. At failure, both compositions fracture in shear with maximum stresses of 545 MPa for Ti3AlC2 and 839 MPa for Ti3Al0.8Sn0.2C2. Consequently, the macroshear stresses for failure, τc, are 185 MPa and 242 MPa for Ti3AlC2 and Ti3Al0.8Sn0.2C2, respectively. In addition to the grain size effects, the presence of a ductile TixAly intermetallic distributed in the grain boundaries plays an important role in the enhancement of the ultimate compressive and macroshear stresses for Ti3Al0.8Sn0.2C2. SEM observations reveal that these two MAX phases exhibit crack deflections, intragranular fractures, kink band formation and delaminations, grain push‐in and pull‐out. 相似文献
7.
Yuelei Bai Fanyu Kong Xiaodong He Ning Li Xinxin Qi Yongting Zheng Chuncheng Zhu Rongguo Wang Andrew Ian Duff 《Journal of the American Ceramic Society》2017,100(9):4190-4198
The thermal shock behavior of Ti2AlC synthesized by means of self‐propagating high‐temperature combustion synthesis with pseudo hot isostatic pressing is investigated, with a focus on the effect of the quenching temperature and quenching times. In general, Ti2AlC exhibits a better thermal shock resistance than typical brittle ceramics like Al2O3. Although the flexural strength decreases quickly in the temperature range of 300°C‐500°C, no discontinuous decrease in the retained strength is observed in Ti2AlC which, as with other MAX phases, differs from the behavior of typical brittle ceramics. Overall, the initial strength (grain size) plays a determining role in the thermal shock behavior of Ti2AlC and other MAX phases. On increasing quench times to 5 cycles, the retained flexural strength decreases further, however with a lower rate of decrease compared with the first quench. Quenching at 300°C and above, voids after the pullout of grains and cracks are present, which however are absent in the un‐quenched samples, indicating the weakening of bonding among grains and the induced damage around the grain boundary during the thermal shock. 相似文献
8.
Autonomous high‐temperature healing of surface cracks in Al2O3 containing Ti2AlC particles
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Linda Boatemaa Myrthe Bosch Ann‐Sophie Farle Guo‐Ping Bei Sybrand van der Zwaag Willem G. Sloof 《Journal of the American Ceramic Society》2018,101(12):5684-5693
In this work, the oxidation‐induced crack healing of Al2O3 containing 20 vol.% of Ti2AlC MAX phase inclusions as healing particles was studied. The oxidation kinetics of the Ti2AlC particles having an average diameter of about 10 μm was studied via thermogravimetry and/or differential thermal analysis. Surface cracks of about 80 μm long and 0.5 μm wide were introduced into the composite by Vickers indentation. After annealing in air at high temperatures, the cracks were filled with stable oxides of Ti and Al as a result of the decomposition of the Ti2AlC particles. Crack healing was studied at 800, 900, and 1000°C for 0.25, 1, 4, and 16 hours, and the strength recovery was measured by 4‐point bending. Upon indentation, the bending strength of the samples dropped by about 50% from 402 ± 35 to 229 ± 14 MPa. This bending strength increased to about 90% of the undamaged material after annealing at 1000°C for just 15 minutes, while full strength was recovered after annealing for 1 hour. As the healing temperature was reduced to 900 and 800°C, the time required for full‐strength recovery increased to 4 and 16 hours, respectively. The initial bending strength and the fracture toughness of the composite material were found to be about 19% lower and 20% higher than monolithic alumina, respectively, making this material an attractive substitute for monolithic alumina used in high‐temperature applications. 相似文献
9.
Elastic constants of polycrystalline Ti3AlC2 and Ti3SiC2 measured using coherent inelastic neutron scattering
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Veronica Gray Erich H. Kisi Oliver Kirstein Anton P. J. Stampfl 《Journal of the American Ceramic Society》2017,100(2):705-712
The magnitude of the single‐crystal elastic constant c44 in the MAX phase Ti3SiC2 is under debate. In this paper, estimates for the magnitude of c44 for MAX phases Ti3AlC2 and Ti3SiC2 are determined from a partially oriented polycrystalline sample via coherent inelastic neutron scattering. The largely quasi‐isotropic nature of these Mn+1AXn phase elastic constants as previously predicted by density functional theory calculations is confirmed experimentally for Ti3AlC2 to be c44=115.3 ± 30.7 GPa. In contrast, Ti3SiC2 is confirmed to be shear stiff with c44=402.7 ± 78.3 GPa supporting results obtained by earlier elastic neutron diffraction experiments. 相似文献
10.
Porosity effect on microstructure,mechanical, and fluid dynamic properties of Ti2AlC by direct foaming and gel‐casting
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Marek Potoczek Anna Chmielarz Murilo D. de M. Innocentini Izabela C. P. da Silva Paolo Colombo Barbara Winiarska 《Journal of the American Ceramic Society》2018,101(12):5346-5357
In this study, Ti2AlC foams were fabricated by direct foaming and gel‐casting using agarose as gelling agent. Slurry viscosity, determined by the agarose content (at a fixed solids loading), as well as surfactant concentration and foaming time were the key parameters employed for controlling the foaming yield, and hence the foam porosity after sintering process. Fabricated foams having total porosity in the 62.5‐84.4 vol% range were systematically characterized to determine their pore size and morphology. The effect of the foam porosity on the room‐temperature compression strength and elastic modulus was also determined. Depending on the amount of porosity, the compression strength and Young's modulus were found to be in the range of 9‐91 MPa and 7‐52 GPa, respectively. Permeability to air flow at temperatures up to 700°C was investigated. Darcian (k1) and non‐Darcian (k2) permeability coefficients displayed values in the range 0.30‐93.44 × 10?11 m2 and 0.39‐345.54 × 10?7 m, respectively. The amount of porosity is therefore a very useful microstructural parameter for tuning the mechanical and fluid dynamic properties of Ti2AlC foams. 相似文献
11.
Ludi Xu Degui Zhu Yunlong Liu Tohru S. Suzuki Byung-nam Kim Yoshio Sakka Salvatore Grasso Chunfeng Hu 《Journal of the European Ceramic Society》2018,38(10):3417-3423
Oxidation resistance of textured Ti3AlC2 ceramics was measured in the temperature range 1273–1573?K. It was found that the oxidation was markedly anisotropic and the samples exhibited a better oxidation resistance when tested along a direction transverse to the c-axis. This behavior was attributed to the rapid diffusion of Al within its basal planes to form a passivating Al2O3 scale and it respected Ellingham diagrams. The scales formed had different compositions depending on the testing direction; this response was clearly resulting from the crystallographic orientation. Even at 1473?K after 20?h exposure, the samples tested in a direction transverse to the c-axis showed a reduced weight gain which was 45 times lower than one seen on a basal plane. 相似文献
12.
Yuelei Bai Xiaodong He Rongguo Wang Yue Sun Chuncheng Zhu Shuai Wang Guiqing Chen 《Journal of the European Ceramic Society》2013,33(13-14):2435-2445
The electrical, thermal, and mechanical properties as well as the effect of the temperature of large-scale Ti2AlC bulk synthesized by self-propagating high temperature combustion synthesis with pseudo hot isostatic pressing were investigated in detail. With increasing temperature, the lattice defects contribute to the decreasing phonon thermal conductivity, and the electrical resistivity increases linearly from room temperature (RT) to 900 °C. The RT flexural strength, compressive strength, fracture toughness, work of fracture, and Vickers hardness were measured to be 606 ± 20 MPa, 1057 ± 84 MPa, 6.9 ± 0.2 MPa m1/2, 158 ± 12 J/m2, and 4.7 ± 0.2 GPa, respectively. With increasing temperature, the flexural and compressive strengths both keep almost unchanged in the zone of brittle failure, but decrease sharply as the plastic deformation occurs. The brittle-plastic transition temperature under flexure (900–950 °C) is higher than compression (700–800 °C). Interestingly, a non-catastrophic failure is observed in the SENB test, with the high work of fracture (158 ± 12 J/m2). 相似文献
13.
High‐temperature oxidation and compressive strength of Cr2AlC MAX phase foams with controlled porosity
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Jesus Gonzalez‐Julian Sara Onrubia Martin Bram Christoph Broeckmann Robert Vassen Olivier Guillon 《Journal of the American Ceramic Society》2018,101(2):542-552
Cr2AlC foams have been processed for the first time containing low (35 vol%), intermediate (53 vol%), and high (75 vol%) content of porosity and three ranges of pore size, 90‐180 μm, 180‐250 μm, and 250‐400 μm. Sacrificial template technique was used as the processing method, utilizing NH4HCO3 as a temporary pore former. Cr2AlC foams exhibited negligible oxidation up to 800°C and excellent response up to 1300°C due to the in‐situ formation of an outer thin continuous protective layer of α‐Al2O3. The in‐situ α‐Al2O3 protective layer covered seamlessly all the external surface of the pores, even when they present sharp angles and tight corners, reducing significantly the further oxidation of the foams. The compressive strength of the foams was 73 and 13 MPa for 53 vol% and 75 vol% porosity, respectively, which increased up to 128 and 24 MPa after their oxidation at 1200°C for 1 hour. The increase in the compressive strength after the oxidation was caused by the switch from inter‐ to transgranular fracture mode. According to the excellent high‐temperature response, heat exchangers and catalyst supports are the potential application of these foams. 相似文献
14.
Leping Cai Zhenying Huang Wenqiang Hu Cong Lei Shaoshuai Wo Xinkang Li Hongxiang Zhai Yang Zhou 《International Journal of Applied Ceramic Technology》2018,15(5):1212-1221
High pure Ti2Al(1?x)SnxC (x = 0‐1) powders were synthesized using Ti, Al, Sn, and TiC powders as raw materials by pressureless sintering method. The influence of sintering temperature and raw material ratio on the purity of Ti2AlC and Ti2Al0.8Sn0.2C powders were investigated. The results show that pure Ti2AlC and Ti2Al0.8Sn0.2C powders were obtained from the mixed raw materials ratio of Ti:1.1Al:0.9TiC and Ti:0.9Al:0.2Sn:0.9TiC at 1450°C, respectively. Subsequently, fully dense Ti2AlC and Ti2Al0.8Sn0.2C bulks were prepared using mechanically alloying and hot pressed sintering method. The Vickers hardness of Ti2AlC and Ti2Al0.8Sn0.2C approaches approximately about 6 GPa and 4 GPa, the flexural strength was measured to be 650 ± 36 MPa and 521 ± 33 MPa, respectively. Microstructural analysis reveals that grain delamination, kink bands, and crack deflection occurred around the indentation area and at the fracture surface. 相似文献
15.
Eugenio Zapata‐Solvas Mohammad A. Hadi Denis Horlait David C. Parfitt Axel Thibaud Alexander Chroneos William E. Lee 《Journal of the American Ceramic Society》2017,100(8):3393-3401
MAX phase solid solutions physical and mechanical properties may be tuned via changes in composition, giving them a range of possible technical applications. In the present study, we extend the MAX phase family by synthesizing (Zr1?xTix)3AlC2 quaternary MAX phases and investigating their mechanical properties using density functional theory (DFT). The experimentally determined lattice parameters are in good agreement with the lattice parameters derived by DFT and deviate <0.5% from Vegard's law. Ti3AlC2 has a higher Vickers hardness as compared to Zr3AlC2, in agreement with the available experimental data. 相似文献
16.
High‐Temperature Neutron Diffraction,Raman Spectroscopy,and First‐Principles Calculations of Ti3SnC2 and Ti2SnC
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Grady W. Bentzel Michael Naguib Nina J. Lane Sven C. Vogel Volker Presser Sylvain Dubois Jun Lu Lars Hultman Michel W. Barsoum El'ad N. Caspi 《Journal of the American Ceramic Society》2016,99(7):2233-2242
Herein, we report—for the first time—on the additive‐free bulk synthesis of Ti3SnC2. A detailed experimental study of the structure of the latter together with a secondary phase, Ti2SnC, is presented through the use of X‐ray diffraction (XRD), and high‐resolution transmission microscopy (HRTEM). A previous sample of Ti3SnC2, made using Fe as an additive and Ti2SnC as a secondary phase, was studied by high‐temperature neutron diffraction (HTND) and XRD. The room‐temperature crystallographic parameters of the two MAX phases in the two samples are quite similar. Based on Rietveld analysis of the HTND data, the average linear thermal expansion coefficients of Ti3SnC2 in the a and c directions were found to be 8.5 (2)·10?6 K?1 and 8.9 (1)·10?6 K?1, respectively. The respective values for the Ti2SnC phase are 10.1 (3)·10?6 K?1 and 10.8 (6)·10?6 K?1. Unlike other MAX phases, the atomic displacement parameters of the Sn atoms in Ti3SnC2 are comparable to those of the Ti and C atoms. When the predictions of the atomic displacement parameters obtained from density functional theory are compared to the experimental results, good quantitative agreement is found for the Sn atoms. In the case of the Ti and C atoms, the agreement is more qualitative. We also used first principles to calculate the elastic properties of both Ti2SnC and Ti3SnC2 and their Raman active modes. The latter are compared to experiment and the agreement was found to be good. 相似文献
17.
《应用陶瓷进展》2013,112(4):245-250
AbstractLaminated ternary compound Ti3AlC2 crystals were synthesised by pressureless sintering the mixture powders of 3Ti/1·1Al/1·8C, 3Ti/1Al/1·8C/0·2Sn, 1Ti/1·8TiC/1Al and 1Ti1·8TiC1Al0·1Sn at 1400°C with preliminary liquid magnetic stirring mixing. The X-ray diffraction results indicate that Ti3AlC2 prepared from 3Ti/1Al/1·8C/0·2Sn has the highest purity, and the addition of appropriate Sn favours the synthesis of high purity Ti3AlC2. Scanning electron microscopy images show that Ti3AlC2 samples exhibit lamellar-like microstructure with thickness of ~100 nm. The tribological properties of Ti3AlC2 as an additive in 100SN base oil were evaluated with a ball on disc tester. The results show that the Ti3AlC2 additives exhibited good friction reduction and wear resistance at 5 wt-% concentration. Under determinate conditions, the base oil containing 5 wt-% Ti3AlC2 samples presented good tribology performance under the load of 15 N. The improved tribological properties of the Ti3AlC2 samples could be attributed to the formation of tribofilm in friction process. 相似文献
18.
19.
(Cr,Mn)2AlC solid solutions have attracted much attention due to their magnetic property which will be enhanced with increasing Mn solubility. So far, only 3?at.-% Mn solubility in (Cr,Mn)2AlC bulk materials has been reported. This work reports on the synthesis of (Cr,Mn)2AlC solid solutions via a new reaction route with AlCr2, C and Mn as starting materials. The Mn solubility increases with increasing the starting Mn content. The maximum solubility of Mn in (Cr,Mn)2AlC was 8.3?at.-%, corresponding to a resultant solid solution (Cr0.83Mn0.17)2AlC. However, increasing the Mn content in the starting mixture caused the formation of impurities in the sintered samples. A dense (Cr0.95Mn0.05)2AlC ceramic has been achieved by hot-pressing the mixture of AlCr2/C/0.1Mn. The mechanical properties and thermal expansion coefficient of (Cr0.95Mn0.05)2AlC were measured. 相似文献
20.
Influence of ordered carbon‐vacancy networks on the electronic structures and elastic properties of Nb4AlC3−x
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Hui Zhang Tao Hu Zhaojin Li Yanhui Zhang Minmin Hu Xiaohui Wang Yanchun Zhou 《Journal of the American Ceramic Society》2017,100(2):724-731
Carbon‐vacancy‐bearing Nb4AlC3?x has the best high‐temperature mechanical robustness among MAX phases. The existing form of the vacancies has been long overlooked. Recently, the vacancies in Nb4AlC3?x have been identified to be ordered, establishing an ordered compound Nb12Al3C8. Here, the spatial distribution of the ordered vacancies and their influences on bonding characteristics and elastic properties are unraveled by thoroughly comparing Nb12Al3C8 and vacancy‐free Nb4AlC3. In Nb12Al3C8, the carbon vacancies break only relatively weak Nb–C bonds and form ordered equilateral triangular carbon‐vacancy networks (OETCVNs) to maximize the bond strengthening effect. The networks slightly shift partial and total density of states toward the Fermi energy level, and bring about a feature of “de‐metallization”. Meanwhile, the presence of OETCVNs results in the softening of elastic modulus, decreasing of the anisotropy of Young's modulus, yet increasing that of shear modulus. These results shed lights on the carbon‐vacancy ordering behavior of MAX phases, and provide an opportunity to tailor their electronic structures and elastic properties through defect engineering. 相似文献