共查询到20条相似文献,搜索用时 13 毫秒
1.
Yi Zhong Ying Liu Na Jin Zifeng Lin Jinwen Ye 《Journal of the American Ceramic Society》2023,106(9):5567-5579
Fine, pure Ti3AlC2 powder is prepared in a very mild condition via Ti3Al alloy and carbon black with the assistance of molten salts. X-ray diffraction, scanning electron microscopy, TG-DSC, and transmission electron microscopy (TEM) characterizations show that the high purity, nanosized Ti3AlC2 can be obtained at 900°C with the 1:1 salt-to-material ratio. The formation mechanism of Ti3AlC2 through this strategy of alloy raw material is fully studied under further TEM investigations, showing that the reaction process can basically be described as Ti3Al and C → TiAl and TiC → Ti2AlC and TiC → ψ and TiC → Ti5Al2C3 and TiC → Ti3AlC2, where the key ψ, a modulated Ti2AlC structure, is determined for the first time containing alternate-displacement Al layers along (0 0 0 2) of Ti2AlC phase with a distinct selected area electron diffraction pattern. Such alternant displacement is considered a precondition of forming Ti5Al2C3 through topotactic transition, followed by Ti5Al2C3 converting into Ti3AlC2 by the diffusion of Ti, C atoms in the outside TiC. Several parallel orientations can be observed through the phase transition process: Ti2AlC (0 0 0 2)//ψ (0 0 0 1), ψ (0 0 0 1)//Ti5Al2C3 (0 0 0 3), Ti5Al2C3 (0 0 0 3)//Ti3AlC2 (0 0 0 2). Such parallel orientations among these phases apply an ideal condition for the topotactic reaction. The distinct path of the phase transition brings a significant change of heat effect compared with the traditional method, leading to a fast reaction rate and a mild reaction condition. 相似文献
2.
Zhiyuan Xiao Xiaoguang Zhu Zhaoqin Chu Wei Xu Zhaoming Wang Bing Wu 《Journal of the European Ceramic Society》2018,38(4):1246-1252
Ti2AlC formation mechanism with carbon and TiAl alloy as reactants at 1000–1200 °C have been investigated through Raman spectrometer and transmission electron microscope (TEM). Reaction products TiCx and Ti2AlC are confirmed. Full width at half height (FWHH) of Ti2AlC Raman peak is used to characterize crystallinity, which indicates better perfection of Ti2AlC grains near TiAl area and with higher reaction temperature. Variations of TiCx microstructure, especially stacking faults(SF) and nanotwins, are observed by TEM along reaction layer. Ti2AlC lattice uniformity of different reaction temperature is also confirmed by TEM, which is consistent with Raman result. TiCx is believed first formed through reaction between TiAl and C. With help of carbon vacancy, Al-doped TiCx SF and nanotwin can be formed under hot pressing, which becomes the basal frame of Ti2AlC. 相似文献
3.
Ti-Al-C三元系统中Ti3AlC2,Ti2AlC和TiC物相含量的测定 总被引:2,自引:0,他引:2
研究了Ti-Al-C三元体系中X射线衍射定量相分析方法,提出了Ti3AlC2,Ti2AlC和TiC这3种物相的特征衍射峰Ti3AlC2的(002)衍射峰,2θ=9.5°;Ti2AlC的(002)衍射峰,2θ=13.0°;TiC的(111)衍射峰,2θ=35.9°.采用混样无标样法推导了一套Ti3AlC2,Ti2AlC和TiC的定量计算公式,根据其特征衍射峰的强度就可计算这3个物相的相对含量.因为该公式推导过程本身就验证了其正确性(即自验证性),所以这个公式可以广泛用于Ti-Al-C三元体系中Ti3AlC2,Ti2AlC和TiC物相的定量测定.因此,这种方法非常简便、易行. 相似文献
4.
Hao Zhao Yi Feng Zijue Zhou Gang Qian Jingcheng Zhang Xuebin Zhang 《Journal of the European Ceramic Society》2021,41(4):2263-2277
The arc erosion behavior of Ti3AlC2 in oxygen, air, nitrogen, carbon dioxide, argon, and sulfur hexafluoride atmospheres at 9 kV voltage was studied. The breakdown strength increased in the order of oxygen, air, carbon dioxide, nitrogen, argon, and sulfur hexafluoride, whereas the arc energy decreased. Cracks, pits, and bulges on the eroded surface were investigated using scanning electron microscopy and three-dimensional (3D) laser confocal scanning microscopy. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to determine the composition of the eroded surface. The arc energy and electromagnetic force lead to the formation of erosion characteristics. The mechanism of erosion under the different atmospheres is discussed systematically, and is called the “decomposition-oxidation” process in oxygen, air, and carbon dioxide and the “decomposition-rereaction” process in nitrogen and sulfur hexafluoride. This study provides a reference for the application of MAX phase materials in high-voltage electrical appliances. 相似文献
5.
Jun Li Huang Shao Tingting Liu Kai Zhang Zhilong Yan Wenhe Liao 《Ceramics International》2021,47(16):22356-22364
This paper proposes the preparation of Ti2AlC complex parts through the combination of in-situ selective laser forming (ISLF) and reaction sintering. By studying the impaction of scan speed and laser power on the phase composition and microstructure of the formed test specimen, it was found that the test specimen mainly consisted of Ti3Al, TiAl, TiC, and graphite reacted incompletely. When the laser power was fixed, the lower the scan speed, the higher the TiC content. The TiC phase developed from nanoparticles to coarse dendritic structures gradually. When the laser power is further increased, the dendritic structure does not increase significantly. The process optimization found that when the laser power was 40 W and the scan speed was 100 mm/s, the density of the formed test specimen was 80.308%, which was mainly because the difference between the diffusion coefficients of Ti and Al resulted in Kirkendall pores, causing the incomplete densification of the formed part. 相似文献
6.
《Journal of the European Ceramic Society》2020,40(4):1125-1131
Carbon and Mo-coated Ti6Al4V alloy diffusion couple was used to investigate Mo-modified diffusion reaction between carbon and Ti6Al4V. Randomly dispersed carbide particles were observed in Ti6Al4V alloy after 900℃ exposure. Carbide particles were found evolving from defective TiCx (x<1) to mixture of TiCx and defective Ti3AlC2. Although Mo atoms were hardly detected in particles, their dilution effect along Ti alloy grain boundary (GB) is beneficial to carbon diffusion and carbide formation along GB. Based on high-resolution TEM (HRTEM) imaging, high density stacking faults (SFs) and nanotwins were observed in TiCx particles which explain Raman activation of defects in TiC. Formation of SFs and nanotwins in TiCx is attributed to carbon vacancies, which inversely promotes incoherent twin boundary (ITB) formation. Transformation from TiCx to Ti3AlC2 is considered driven by Al indiffusion along ITBs. Intergrowth of TiCx in defective Ti3AlC2 is the compromise to low Al concentration in Ti6Al4V. 相似文献
7.
《Ceramics International》2022,48(2):1745-1756
In this study, Ti3AlC2 particles doped aluminum matrix composites were prepared by ultrasonic agitation casting method. Microstructure, mechanical properties, and tribological properties of pure aluminum and Ti3AlC2p/Al composites were characterized. Influence of different loads (10, 20, 30, and 40 N) and Ti3AlC2 contents (1.0, 2.0, 3.0, and 4.0 wt%) on the tribological behaviors of the composites were studied. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Energy dispersion spectroscopy (EDS), and 3D laser confocal were used to assist the analysis. The results indicated that fine and uniformly microstructure and the optimum comprehensive mechanical properties were exhibited on 2.0 wt%-Ti3AlC2p/Al composites. The abrasive grooves were widened and deepened with an increase in the load. The abrasion performance of composites improved distinctly with the addition of the Ti3AlC2 particles, which changed the wear mechanism from adhesive wear to abrasive wear. The 30 N load and the composites of 2.0 wt% Ti3AlC2 revealed the optimum tribological properties. The improvement of the tribological behavior of composites was attributed to the refinement of microstructure, the improvement mechanical properties and the three dimensional layered Ti3AlC2 phases with self-lubricating properties. 相似文献
8.
Weihua Chen Jiancheng Tang Xingwang Shi Nan Ye Zhihao Yue Xinghao Lin 《International Journal of Applied Ceramic Technology》2020,17(2):778-789
High-purity titanium aluminum carbide (Ti3AlC2) powders were synthesized by a microwave sintering method using different titanium sources as raw materials. The prepared products were characterized by differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results indicated that the synthesized Ti3AlC2 powders have high purity (97.5%) and even distribution of the grain size when using a 3TiH2/1.2Al/2C mixture as raw materials when the microwave sintering temperature and time were 1300°C and 30 minutes, respectively. The formation mechanism of the Ti3AlC2 is described as proceeding via four stages. The solid-phase reaction between titanium and aluminum occurs below the melting point of aluminum and the main product is a Ti3Al phase, which is an observed intermediate compound for the formation of Ti2AlC and Ti3AlC2. Thus, this study provides a beneficial approach to low-temperature synthesis of high-purity Ti3AlC2 materials. 相似文献
9.
Behzad Nayebi Mehdi Shahedi Asl Maryam Akhlaghi Zohre Ahmadi Seyed Ali Tayebifard Esmaeil Salahi Mohammadreza Shokouhimehr Mohsen Mohammadi 《Ceramics International》2021,47(9):11929-11934
A TiB2–Ti3AlC2 ceramic was manufactured by spark plasma sintering at 1900 °C temperature for 7 min soaking time under 30 MPa biaxial pressure. The role of Ti3AlC2 additive on the microstructure development, densification behavior, phase evolution, and hardness of the ceramic composite were studied. The phase characterization and microstructural investigations unveiled that the Ti3AlC2 MAX phase decomposes at the initial stages of the sintering. The in-situ formed phases, induced by the decomposition of Ti3AlC2 additive, were identified and scrutinized by XRD and FESEM/EDS techniques as well as thermodynamics principles. The sintered TiB2–Ti3AlC2 ceramic approached a near full density of ~99% and a hardness of ~28 GPa. The densification mechanism and sintering phenomena were discussed and graphically illustrated. 相似文献
10.
《Ceramics International》2022,48(18):26618-26628
Oxidation and hot corrosion behaviours of Ti3SiC2, Ti2AlC and Cr2AlC at 750 °C were investigated in this work. Ti3SiC2 and Ti2AlC showed a linear increase in mass gain and a relatively poor oxidation resistance. This might be attributed to the porous TiO2 scale. A dense α-Al2O3 layer was formed during the oxidation test. Cr2AlC exhibited the best oxidation resistance. This dense oxide scale can effectively isolate the substrate from contact with oxygen leading to excellent oxidation resistance. In contrast to the oxidation test, Ti3SiC2 and Ti2AlC showed relatively better resistance to hot corrosion, while Cr2AlC showed inferior resistance to NaCl introduced hot corrosion. The hot corrosion mechanism of the MAX phases was analyzed. Due to the formation of Na2TiO3, Ti containing MAX phases showed a continuous increase in the mass gain. The corrosion products of Cr2AlC were Al2O3, Cr2O3 and Na2CrO4. However, due to the volatilization of Na2CrO4, Cr2AlC showed a mass loss during the hot corrosion test. The chemical reaction process of the MAX phase was also analyzed. 相似文献
11.
《Ceramics International》2022,48(7):9024-9029
Herein, a highly crystalline Ti2AlC was synthesized via the improved molten salt synthesis method called molten salt shielded synthesis. To achieve this goal, the mixture of Ti, Al, and graphite and KCl–NaCl eutectic composition salt was heated at 1000, 1050, and 1100 °C for 0.5, 1, and 1.5 h. The X-ray diffraction (XRD) patterns showed that the optimum condition for obtaining the more crystalline Ti2AlC was achieved at 1100 °C for 1.5 h. Such phase identification, and transmission electron microscopy (TEM) images, proved that applying a protective carbon layer on the surface of salt led to inhibiting the diffusion of oxygen into the surface of the green pellet. As a result, the crystallinity of Ti2AlC improved, while the content of undesirable compounds such as Al2O3 and TixOy decreased drastically. In order to shed light on the Ti2AlC synthesis mechanism, differential thermal analysis (DTA) was employed. The DTA curve revealed that the Ti2AlC formation completed in three levels. First, the partial dissolution of Ti in KCl–NaCl salt followed by a reaction with liquid Al resulted in the TiAl formation. Next, Ti(II) reacted in-situ on the surface of graphite that resulted in the non-stoichiometric TiC (TiC1-x) formation, and, at last in a reaction between TiAl and TiC1-x, Ti2AlC phase formation took place at 940 °C. 相似文献
12.
《Ceramics International》2016,42(13):14826-14833
This paper reports the results of studies on the interaction of Ce1−xYbxO2−y mixed oxide nanocrystals (x=0.3 and 0.5) with gamma Al2O3. Nano-sized (3–4 nm) crystalline Ce-Yb mixed oxides, prepared by a water-in-oil (W/O) microemulsion technique, or simple co-impregnation by aqueous solutions of lanthanide ions, were supported on high surface area gamma alumina. Solid state reactions occurring in these systems upon heat treatment in air or hydrogen at 900–1100 °C were studied by TEM, SAED and XRD techniques. As a result of solid state reactions between pure or mixed lanthanide oxides and high surface area Al2O3, various aluminates were formed, depending on the heating temperature and atmosphere. Lattice parameters measured for the Yb4Al2O9 (monoclinic) and CeAlO3 (tetragonal) aluminates formed in Ce0.5Yb0.5O1.75-Al2O3 and CeO2+Yb2O3-Al2O3 systems suggest that they may contain other Ln-ions in the structure, and thus should be described as Ce1−aYbaAlO3 and (Yb1−bCeb)4Al2O9. Similar products were formed from solid state reactions in Ce-rich (CeO2-Al2O3 and Ce0.7Yb0.3O1.85-Al2O3) or Yb-rich (Yb2O3-Al2O3 and Ce0.5Yb0.5O1.75-Al2O3) systems. The author postulates that, different solid state reaction routes were taken, depending on the Yb-ions concentration in the oxide structure, which was connected with the microstructure of lanthanide oxides (F or F# for Ce-rich systems and C or C# for Yb-rich systems). 相似文献
13.
Karthikeyan Ramachandran Zuccarini Carmine Katsumi Yoshida Toru Tsunoura Doni Daniel Jayaseelan 《Journal of the European Ceramic Society》2021,41(9):4761-4773
Commercially available Ti3SiC2 and Ti2AlC ceramics were used in this study to investigate their wet corrosion and mechanical behaviour as they were under investigation for years for their applications in the field of nuclear as cladding materials and aerospace. The test coupons of dimension 3 × 4 × 40 mm3 and 3 × 4 × 20 mm3 were machined out from commercially available samples for the 3-pt bend test and wet corrosion test, respectively. The water vapour corrosion studies of these samples were carried out at 800 ℃, 1000 ℃, 1200 ℃ for 10, 20 and 100 h in gas flow condition containing 50 % steam + 50 % air. Phase analysis of the as-received Ti3SiC2 and Ti2AlC ceramics revealed the presence of other impurity phases such as TiC and TiSi2. The XRD patterns of the oxidised samples show the formation of rutile as the major phase in both materials. The oxidation layer formed on Ti3SiC2 sample was measured to be 280 μm after exposing the sample in steam for 100 h at 1200 °C. The water vapour corrosion studies reveal that Ti2AlC has high oxidation resistance compared with the Ti3SiC2 due to the formation of protective layers of TiO2 and Al2O3 which resulted in reduced weight gain and oxidation layer thickness. Three-point bend tests were conducted at room temperature for the samples after the water vapour corrosion test at 1000 °C/100 h. The TAC samples showed no degradation in the bending strength (244 MPa) whereas the TSC samples showed reduced strength of 320 MPa. The tensile strength of the samples was measured at room temperature and hydrothermal condition (250 °C and 250 bars pressure) and it was observed that Ti3SiC2 had high tensile strength (190 MPa) in hydrothermal conditions. The tensile strength results were validated using Finite element analysis (FEA) using ANSYS and the FEA results showed a negligible variance of 7 % compared with experimental method. Mathematical modelling based on one dimensional solution of diffusion equation combined with Deal-Grove model was employed to study and compare the oxidation thickness for the linear and parabolic models for the ceramics. The model was effective in validating the oxidation thickness of Ti3SiC2 showing that the experimental thickness was closer to that of mathematical model. 相似文献
14.
《Ceramics International》2017,43(7):5708-5714
Corrosion behavior of self-sintered, ternary-layered titanium silicon carbide (Ti3SiC2) and titanium aluminum carbide (Ti3AlC2) fabricated by an in-situ solid-liquid reaction/hot pressing process was investigated by potentiodynamic polarization, potentiostatic polarization and electrochemical impedance spectroscopy in a 3.5% NaCl solution. Commercially pure titanium (Ti) was selected for comparison through XRD, XPS, SEM and EDS examinations for elucidating both the passivation behavior and corrosion mechanism of the alloys. Both Ti3SiC2 and Ti3AlC2 exhibited significantly superior passivation characteristics compared to Ti; Ti3SiC2 also showed better corrosion resistance. The silicon/aluminum site is prone to attack, and the difference in the diffusion rate between the A-site atoms and titanium decreases the passivation ability of the MAX phase. CP titanium exhibited a lower passivation current density and did not undergo breakdown in the test potential region while two MAX phases are destroyed. Nevertheless, the corrosion resistances of Ti3SiC2 and Ti3AlC2 are comparable to that of CP titanium. 相似文献
15.
《Journal of the European Ceramic Society》2017,37(10):3461-3469
Phase relations in the system ZrO2-TiO2-Al2O3 have been investigated in the temperature range between 1557 and 1897 K using equilibration method. X-ray powder diffraction (XRD) and scanning electron microscopy combined with energy dispersive X-ray spectroscopy (SEM/EDX) have been used for sample characterization. Melting relations and sub-solidus reactions have been investigated using differential thermal analysis (DTA). Two invariant reactions are found at the subsolidus temperatures of 1593 and 1648 K. Three eutectic reactions have been established in the system based on microstructure investigation. Temperatures of these reactions were in the range between 1909 and 1978 K. Based on the obtained experimental results thermodynamic parameters of the system have been assessed. Isothermal sections and liquidus surface of the ZrO2-TiO2-Al2O3 system have been calculated. 相似文献
16.
Gengfu Liu Ning Liao Mithun Nath Yawei Li Shaobai Sang 《Journal of the European Ceramic Society》2021,41(4):2948-2957
The mechanical properties and oxidation resistance of the Al2O3-C refractories are of critical importance for iron and steel making processes. However, the evaporation of antioxidants related phases such as Al(g), Si(g), and SiO(g) would deteriorate these properties, especially during high-temperature treatment/application. Therefore, in the present work, a small amount of Ti3AlC2 compared with Al was introduced to overcome these problems. The phase compositions, microstructures, mechanical properties, and oxidation resistance of Ti3AlC2 containing refractories were investigated. The partial oxidation of Ti3AlC2 led to inherited lamellar structures such as Ti3Al1-xC2, TiC, and granular Al2TiO5 phases. The controlled oxidation of Ti3AlC2 and its volume expansion contributed to the compact-structure, thereby limiting the escape of Si and SiO vapors at high temperatures. Consequently, the mechanical properties and oxidation resistance of Ti3AlC2 containing Al2O3-C refractories treated at 1600 ℃ were improved. 相似文献
17.
《Ceramics International》2017,43(8):6175-6179
The xBi(Zn1/2Ti1/2)O3-BaTiO3 (xBZT-BT) ceramics, where x (mol) =0, 0.03, 0.06, 0.09, and 0.12, have been prepared by a solid-state reaction method. The phase transition, microstructure and optical properties were investigated. X-ray diffraction patterns indicate that the as-prepared samples have a polycrystalline perovskite structure. For x<0.06, the xBZT-BT ceramics exhibit clear tetragonal symmetry, and transform to rhombohedral phase as 0.06< x≤0.12. Coexistence of both tetragonal phase and rhombohedral phase is observed for x=0.06. The lattice strain is estimated by the Williamson-Hall analysis model, which suggests that the incorporation of substitution ions into the host lattice produces the inner stress field gives rise to structure distortions. The Raman scattering spectra corroborate the decrease in tetragonality with increasing the x, where the characteristic variation of phonon modes indirectly reveal the incorporation of Bi(Zn1/2Ti1/2)O3. Furthermore, the optical band gaps of xBZT-BT ceramics show a non-linear change, which can be explained by the crystal field theory and phase structure effect. 相似文献
18.
Holger Rueß Jonas Werner Yeliz Unutulmazsoy Jürgen W. Gerlach Xiang Chen Bastian Stelzer Denis Music Szilard Kolozsvari Peter Polcik Thomas E. Weirich Jochen M. Schneider 《Journal of the European Ceramic Society》2021,41(3):1841-1847
The applicability of Cr2AlC MAX-phases as protective coatings in energy conversion or aerospace applications requires a dense, single-phase structure. Therefore, we study the effect of target power density and substrate bias on phase formation, microstructure evolution, and mechanical properties of Cr2AlC coatings utilizing direct current (DCMS) and high-power pulsed magnetron sputtering (HPPMS). Generally, HPPMS results in coatings with superior density and hence larger elastic moduli compared to DCMS, indicating that ion bombardment by ionized film-forming species is beneficial. However, decreasing the substrate bias to ?200 V for DCMS and ?100 V for HPPMS favors the ion bombardment induced formation of the disordered (Cr,Al)2Cx solid solution. It is evident that there is an optimum moderate ion energy for the formation of dense Cr2AlC coatings. Too low energy results in the formation of under-dense coatings. Too high energy yields the formation of (Cr,Al)2Cx in addition to Cr2AlC. 相似文献
19.
《Journal of the European Ceramic Society》2021,41(14):7035-7043
High-temperature phase relations in the La2O3–TiO2–Nb2O5 ternary system were investigated at 1290 °C using SEM, EDS and XRD, and a subsolidus phase equilibrium diagram was constructed. It was demonstrated that the addition of the La1/3NbO3 to the La2O3:3TiO2 mixture completely stabilizes a perovskite-La2/3TiO3 compound, which is otherwise not stable at stoichiometric composition. On the other hand, a mixture La2O3:TiO2 =1:3 dissolves in La1/3NbO3 up to 15 mol% TiO2. Moreover, a newly defined composition of compound La30Ti16Nb4O87 formed in the La2O3-rich part of the system and a solid solution La3Ti5Nb10O39.5–La2Ti2Nb8O27 were proposed. In the binary subsystem LaTiNbO6-La0.462Ti0.386Nb0.614O3, the components exhibit opposite temperature dependence of resonant frequency in the microwave frequency range. Thus, the dielectric properties of the prepared ceramics can be tailored by varying the component concentration and thermally stable dielectric properties can be achieved for a composition with a LaTiNbO6/La0.462Ti0.386Nb0.614O3 molar ratio of 0.27. 相似文献
20.
《Journal of the European Ceramic Society》2022,42(13):5493-5504
Composite material consisting of Al2O3 and TiC in a matrix of highly textured Ti3AlC2 was fabricated in a two-step fabrication process. The Lotgering orientation factor for {00 l} planes of Ti3AlC2 in the textured top surface plane reached 0.71. Texture analysis showed an orientation relationship among Ti3AlC2, Al2O3 and TiC grains of [110] Ti3AlC2 // [110] TiC, (001) Ti3AlC2 // (111) TiC, and [110] Ti3AlC2 // [120] Al2O3, (001) Ti3AlC2 // (001) Al2O3. The texture grained material exhibited excellent mechanical properties, with compressive and flexural strengths of more than 2.5 times those of conventional coarse grained Ti3AlC2, and fracture toughness and hardness were 50% higher than those of conventional coarse grained Ti3AlC2. The microstructures of textured Ti3AlC2 and reported textured Ti2AlC were investigated and compared to interpret the differences in mechanical behavior of the two textured MAX phases. 相似文献