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1.
Yong Du Julius C. Schuster Hans J. Seifert Fritz Aldinger 《Journal of the American Ceramic Society》2000,83(1):197-203
The 1100°C isothermal section and the isopleths at 5, 10, and 15 at.% C in the Ti–Si–C system were determined by DTA and XRD methods. Five invariant reactions (L (liquid) = Si + SiC + TiSi2 at 1330°C, L = TiSi + TiSi2 + Ti5 Si3 C x at 1485°C, L + Ti5 Si3 C x = Ti3 SiC2 + TiSi2 at 1485°C, L + Ti3 SiC2 = TiSi2 + SiC at 1473°C, and L + TiC = bcc-(Ti) + Ti5 Si3 C x at 1341°C) were observed. The transition temperature for L + TiC = Ti3 SiC2 + SiC was measured by the Pirani technique. Optimized thermodynamic parameters for the Ti–Si–C system were then obtained by means of the CALPHAD (calculation of phase diagrams) method applied to the present experimental results and reliable literature data. The calculations satisfactorily account for most of the experimental data. 相似文献
2.
Chunfeng Hu Jie Zhang Jiemin Wang Fangzhi Li Jingyang Wang Yanchun Zhou 《Journal of the American Ceramic Society》2008,91(2):636-639
V4 AlC3 , a new MAX phase, was synthesized by reactive hot pressing of a V, Al, and C powder mixture at 1700°C. Using a combination of Rietveld refinement with X-ray diffraction data and ab initio calculations, the crystal structure was determinated. It was found that V4 AlC3 has a Ti4 AlN3 -type crystal structure. The lattice constants are a =0.29310 nm and c =2.27192 nm. And the atomic positions are V1 at (4 f ) (1/3, 2/3, 0.0544), V2 at (4 e ) (0, 0, 0.1548), Al at (2 c ) (1/3, 2/3, 1/4), C1 at (2 a ) (0, 0, 0), and C2 at (4 f ) (2/3, 1/3, 0.1080). 相似文献
3.
The isothermal section of the Ti-B-C system at 1600°C for compositions in and adjacent to the TiB2 -TiCx -Ti3 B4 compatibility triangle was revised to reflect the fact that Ti3 B4 is an equilibrium phase in this system. Lattice parameter measurements together with image analyses of SEM micrographs of densifled compacts confirm that the end member of the TiB2 -TiCx .-Ti3 B4 compatibility triangle is TiC0.65 with an uncertainty in x of ±0.02. 相似文献
4.
In this paper we map out the 1300°C isothermal section in the Ti–In–C ternary system. Two ternary compounds exist: Ti2 InCα and Ti3 InCδ . At 1300°C TiC x is in equilibrium with all phases, Ti3 InCδ is in equilibrium with all the phases except C, and Ti2 InC is in equilibrium with all phases except Ti and C. The range of δ in Ti3 InCδ varies from 0.95 to 0.8. A correlation was found between δ and the lattice parameters of this phase. The maximum solubilities of In and C in Ti are 14 and 4 at.%, respectively. Similarly, α in Ti2 InCα varies from ≈0.85 to 1. The dissolution of ∼4±0.3 at.% In in TiC x reduces the C concentration to ≈24 at.%. In the In-rich corner, a liquid region exists. 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.
E. C. SUBBARAO 《Journal of the American Ceramic Society》1960,43(9):439-442
The phase transitions in PbNb2 O6 and in compositions of the type Pb1+x (Bx Nb1-x )O6 , where B = Ti4+ , Zr4+ , or Sn4+ , have been investigated between 25° and 650°C. using X-ray and dilatometric techniques. The modified PbNb2 o6 compositions possess orthorhombic PbNb2 O6 -type structure, with the additional Pb2+ ions occupying vacant lattice sites. The lattice parameters a and c expand and b contracts during heating until, at the ferroelectric Curie temperature, a and b suddenly coincide and c expands slightly. Besides this phase change at the Curie temperature, the nonstoichiometric compounds show an additional phase transition in the range 450° to 300°C. depending on composition. The intermediate phase of Pbl+x (Ti2 Nb1-z )2 O6 appears to possess orthorhombic symmetry. 相似文献
7.
Masanori Hirano Keisuke Ota Takaharu Ito 《Journal of the American Ceramic Society》2005,88(12):3303-3310
Anatase-type TiO2 powder containing sulfur with absorption in the visible region was directly formed as particles with crystallite in the range 15–88 nm by thermal hydrolysis of titanium(III) sulfate (Ti2 (SO4 )3 ) solution at 100°–240°C. Because of the presence of ammonium peroxodisulfate ((NH4 )2 S2 O8 ), the yield of anatase-type TiO2 from Ti2 (SO4 )3 solution was accelerated, and anatase with fine crystallite was formed. Anatase-type TiO2 doped with ZrO2 up to 9.8 mol% was directly precipitated as nanometer-sized particles from the acidic precursor solutions of Ti2 (SO4 )3 and zirconium sulfate in the presence and the absence of (NH4 )2 S2 O8 by simultaneous hydrolysis under hydrothermal conditions at 200°C. By doping ZrO2 into TiO2 and with increasing ZrO2 content, the crystallite size of anatase was decreased, and the anatase-to-rutile phase transformation was retarded as much as 200°C. The anatase-type structure of ZrO2 -doped TiO2 was maintained after heating at 1000°C for 1 h. The favorable effect of doping ZrO2 to anatase-type TiO2 on the photocatalytic activity was observed. 相似文献
8.
Zhe-Feng Zhang Zheng Ming Sun Hitoshi Hashimoto Toshihiko Abe 《Journal of the American Ceramic Society》2003,86(3):431-436
Ti/Si/2TiC powders were prepared using a mixture method (M) and a mechanical alloying (MA) method to fabricate Ti3 SiC2 at 1200°–1400°C using a pulse discharge sintering (PDS) technique. The results showed that the Ti3 SiC2 samples with <5 wt% TiC could be rapidly synthesized from the M powders; however, the TiC content was always >18 wt% in the MA samples. Further sintering of the M powder showed that the purity of Ti3 SiC2 could be improved to >97 wt% at 1250°–1300°C, which is ∼200°–300°C lower than that of sintered Ti/Si/C and Ti/SiC/C powders using the hot isostatic pressing (HIPing) technique. The microstructure of Ti3 SiC2 also could be controlled using three types of powders, i.e., fine, coarse, or duplex-grained, within the sintering temperature range. In comparison with Ti/Si/C and Ti/SiC/C mixture powders, it has been suggested that high-purity Ti3 SiC2 could be rapidly synthesized by sintering the Ti/Si/TiC powder mixture at relatively lower temperature using the PDS technique. 相似文献
9.
The quenching technique was used to study subliquidus and subsolidus phase relations in the pseudobinary system Na2 Ti2 Si2 O11 -Na2 Ti2 Si2 O9 . Both narsarukite (Na2 TiSi4 O11 ) and lorenzenite (Na2 Ti2 Si2 O9 ) melt incongruently. Narsarsukite melts at 911°±°C to SiO2 +liquid, with the liquidus at 1016°C. Lorenzenite melts at 910°±5°C to Na2 Ti6 O13 +liquid; Na2 Ti6 O13 reacts with liquid to form TiO2 and is thus consumed by 985°±5°C. The liquidus occurs at 1252°C. 相似文献
10.
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
11.
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
12.
Michel W. Barsoum Leonid Farber Igor Levin Adam Procopio Tamer El-Raghy Alex Berner 《Journal of the American Ceramic Society》1999,82(9):2545-2547
The structure and chemistry of what initially was proposed to be Ti3 Al2 N2 are incorrect. Using high-resolution transmission electron microscopy, together with chemical analysis, the stoichiometry of this compound is concluded to be Ti4 AlN3-delta (where delta = 0.1). The structure is layered, wherein every four layers of almost-close-packed Ti atoms are separated by a layer of Al atoms. The N atoms occupy ∼97.5% of the octahedral sites between the Ti atoms. The unit cell is comprised of eight layers of Ti atoms and two layers of Al atoms; the unit cell is hexagonal with P 63 / mmc symmetry (lattice parameters of a = 0.3 nm and c = 2.33 nm). This compound is machinable and closely related to other layered, ternary, machinable, hexagonal nitrides and carbides, namely M2 AX and M3 AX2 (where M is an early transition metal, A is an A-group element, and X is carbon and/or nitrogen). 相似文献
13.
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
14.
Tamer El-Raghy Michel W. Barsoum Antonios Zavaliangos Surya R. Kalidindi 《Journal of the American Ceramic Society》1999,82(10):2855-2860
In this article, the second part of a two-part study, we report on the mechanical behavior of Ti3 SiC2 . In particular, we have evaluated the mechanical response of fine-grained (3–5 μm) Ti3 SiC2 in simple compression and flexure tests, and we have compared the results with those of coarse-grained (100–200 μm) Ti3 SiC2 . These tests have been conducted in the 25°–1300°C temperature range. At ambient temperature, the fine- and coarse-grained microstructures exhibit excellent damage-tolerant properties. In both cases, failure is brittle up to ∼1200°C. At 1300°C, both microstructures exhibit plastic deformation (>20%) in flexure and compression. The fine-grained material exhibits higher strength compared with the coarse-grained material at all temperatures. Although the coarse-grained material is not susceptible to thermal shock (up to 1400°C), the fine-grained material thermally shocks gradually between 750° and 1000°C. The results presented herein provide evidence for two important aspects of the mechanical behavior of Ti3 SiC2 : (i) inelastic deformation entails basal slip and damage formation in the form of voids, grain-boundary cracks, kinking, and delamination of individual grains, and (ii) the initiation of damage does not result in catastrophic failure, because Ti3 SiC2 can confine the spatial extent of the damage. 相似文献
15.
The effect of vacuum annealing on the thermal stability and phase transition of Ti3 SiC2 has been investigated by X-ray diffraction (XRD), neutron diffraction, synchrotron radiation diffraction, and secondary ion mass spectroscopy (SIMS). In the presence of vacuum or a controlled atmosphere of low oxygen partial pressure, Ti3 SiC2 undergoes a surface dissociation to form nonstoichiometric TiC and/or Ti5 Si3 C x that commences at ∼1200°C and becomes very pronounced at ≥1500°C. Composition depth profiling at the near surface of vacuum-annealed Ti3 SiC2 by XRD and SIMS revealed a distinct gradation in the phase distribution of TiC and Ti5 Si3 C x with depth. 相似文献
16.
Bouchaib Manoun Surendra K. Saxena Hanns-Peter Liermann Michel W. Barsoum 《Journal of the American Ceramic Society》2005,88(12):3489-3491
We measured the volume thermal expansion of Ti3 SiC2 from 25° to 1400°C using high-temperature X-ray diffraction using a resistive heated cell. A piece of molybdenum foil with a 250 μm hole contained the sample material (Ti3 SiC2 +Pt). Thermal expansion of the polycrystalline sample was measured under a constant argon flow to prevent oxidation of Ti3 SiC2 and the molybdenum heater. From the lattice parameters of platinum (internal standard), we calculated the temperature by using thermal expansion data published in the literature. The molar volume change of Ti3 SiC2 as a function of temperature in °C is given by: V M (cm3 /mol)=43.20 (2)+9.0 (5) × 10−4 T +1.8(4) × 10−7 T 2 . The temperature variation of the volumetric thermal expansion coefficient is given by: αv (°C−1 )=2.095 (1) × 10−5 +7.700 (1) × 10−9 T . Furthermore, the results indicate that the thermal expansion anisotropy of Ti3 SiC2 is quite mild in accordance with previous work. 相似文献
17.
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
18.
Samples of the titanium oxides with O/Ti ratios between 0.5 and 1.67 were prepared by heating mixtures of Ti and TiO2 in high vacuum to 1500°C and annealing them in silica ampuls at 900° to 1100°C. Results of chemical and X-ray analyses are combined with previously published data to form a complete phase diagram. The melting points of Ti2 O3 and Ti3 O5 were 1839°° 10°C and 1774°° 10°C, respectively. 相似文献
19.
New titanium–niobium oxynitride (Ti1− z Nb z O x N y ) powders were synthesized by ammonolysis of nanosized TiO2 /Nb2 O5 composite powders at 700°–900°C for 5 h. The products were characterized by X-ray diffraction (XRD), chemical analysis, and transmission electron microscopy. The results indicated that the as-synthesized powders were pure cubic structures with sizes of 30–60 nm. With increasing value of z , XRD peaks of Ti1− z Nb z O x N y powders tended to shift toward low 2θ angle and the cell parameter showed a linear increase. 相似文献
20.
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