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1.
Sung Sic HwangJaeHo Han Dongyun Lee Sang-Whan Park 《Journal of Alloys and Compounds》2011,509(35):L336
High-purity Ti3SiC2 compounds have been fabricated by infiltration of molten Si into a precursor, a partially sintered TiCx (x = 0.67) preform. The Si source and the TiCx preform were placed side by side on carbon cloth, and the system was heated to 1550 °C. Molten Si infiltrated the preform through the carbon cloth, and a direct reaction between TiCx and molten Si immediately occurred at the reaction temperature to yield pure Ti3SiC2. We could observe phase formation and the microstructure of the bulk products with time, which were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS). Pure Ti3SiC2 compounds were formed on the exterior of the TiCx preform at 1550 °C when the sintered TiCx:Si ingot molar ratio was 3:1.4. At 1550 °C, no other minor phases were detected for any of the sintering time ranges. 相似文献
2.
Yunchao Mu Jifeng GuoBaoyan Liang Qinsheng Wang 《International Journal of Refractory Metals and Hard Materials》2011,29(3):397-400
A mixture of Ti/Si/TiC/diamond powders was employed to fabricate the Ti3SiC2 bonded diamond composite using the spark plasma sintering-reactive synthesis method. The addition of diamond does not inhibit the synthesis of Ti3SiC2 in the sintered product. In the matrix Ti3SiC2 grains developed lamellar morphology with an average length size of 5-10 μm. Ti3SiC2 matrix displays good pullout strength with diamond, and the Ti3SiC2 bonded diamond material exhibits good wear resistance. 相似文献
3.
Preparation of the Ti3Si1−xAlxC2 solid solution with x = 0.2-0.8 was investigated by self-propagating high-temperature synthesis (SHS) using TiC-, SiC-, and Al4C3-containing powder compacts. Due to the variation of reaction exothermicity with sample stoichiometry, the combustion temperature and reaction front velocity decreased with increasing Al content of Ti3Si1−xAlxC2 for the TiC- and Al4C3-added samples, but increased for the samples with SiC. In contrast to the formation of Ti3(Si,Al)C2 as the dominant phase for the TiC- and SiC-added samples, TiC was identified as the major constituent in the final products of samples adopting Al4C3. In addition, the evolution of Ti3(Si,Al)C2 was improved by increasing the Al content of the TiC- and SiC-added powder compacts, but deteriorated considerably upon the increase of Al4C3 in the Al4C3-containing sample. 相似文献
4.
Polycrystalline Ti3SiC2 suffered from serious hot corrosion attack in the mixture of 75wt.%Na2SO4 + 25wt.%NaCl melts at 850 °C. In order to improve the hot corrosion resistance of this material, pre-oxidation treatment was conducted at 1200 °C in air for 2 h. A duplex oxide scale with an outer layer of TiO2 and an inner layer of a mixture of TiO2 and SiO2 was formed during the pre-oxidation. Because the outer oxide layer of the pre-oxidation treated specimens could inhibit hot corrosion process, they exhibited good hot corrosion resistance in the mixture of 75wt.%Na2SO4 + 25wt.%NaCl melts at 850 °C for 50 h. However, during the hot corrosion the outer layer of TiO2 would degrade gradually. Once the outer layer damaged, the hot corrosion rate increased sharply, the corrosion behavior was similar to Ti3SiC2 corroded under the same conditions. The microstructure and phase compositions of the hot corrosion samples were investigated by SEM/EDS and XRD. 相似文献
5.
In this study, we fabricated high purity Ti3SiC2 ceramic by mechanical alloying (MA) and spark plasma sintering (SPS), and investigated the effect of trace amount of Al on these processes. Our results show that addition of proper amount of Al significantly increases the purity of Ti3SiC2 in the MA and subsequent SPS products, and remarkably reduces the sintering temperature for Ti3SiC2. Ti3SiC2 sintered compact with a purity of 96.5 wt% was obtained by 10 h of MA and subsequent SPS from a starting mixture composed of n(Ti):n(Si):n(Al):n(c) = 3:1:0.2:2 at 850 °C. At 1100 °C, Ti3SiC2 with a purity of 99.3 wt% and a relative density of 98.9% was obtained. 相似文献
6.
Thin films of Ti1−xAlxN nitrides were prepared over a large range of composition (0 ≤ x < 1) on Si substrates using nitrogen reactive magnetron sputtering from composite metallic targets. Ti K-edge X-ray Absorption Spectroscopy experiments were carried for a better understanding of the local structure. The evolution of the intensity of Ti K-edge pre-edge peak gives evidence of the incorporation of Ti in hexagonal lattice of AlN for Al-rich films and in cubic lattice of TiN for Ti-rich films. An attempt to determine their atomic structure by combining X-ray diffraction and Ti K-edge Extended X-ray Absorption Fine Structure is presented. The evolution of the nearest neighbour and next-nearest neighbour distances depending on the composition is presented and discussed together the cubic and hexagonal lattice parameters. A possible contribution of amorphous nitrides is suggested. 相似文献
7.
Ching-Fang Tseng 《Journal of Alloys and Compounds》2011,509(39):9447-9450
The influence of Zr substitution for Ti on the microwave dielectric properties and microstructures of the Mg(ZrxTi1−x)O3(MZxT) (0.01 ≤ x ≤ 0.3) ceramics was investigated. The quality factors of Mg(ZrxTi1−x)O3 ceramics with x = 0.01-0.05 were improved because the solid solution of a small amount of Zr4+ substitution in the B-site could increase density and grain size. An excess of Zr4+ resulted in the formation of a great deal of secondary phase that declined the microwave dielectric properties of MZxT ceramics. The temperature coefficient of resonant frequency (τf) of Mg(ZrxTi1−x)O3 ceramics slightly increased with increasing Zr content, and the variation in τf was attributed to the formation of secondary phases. 相似文献
8.
In this study, 3Ti/Si/2C powders were used as raw materials to synthesize Ti3SiC2 by self-propagating high-temperature synthesis (SHS). The phase compositions and morphological characteristics of Ti3SiC2, as well as the effects of grain granularity on Ti3SiC2 synthesis, were investigated. The reaction paths and dynamic behaviors of the synthesized Ti3SiC2 were studied using combustion front quenching. The results showed that the liquid phase of Ti–Si was formed during SHS. The mechanism for TiC formation exhibited a great effect on Ti3SiC2 synthesis. The proposed reaction mechanism for the synthesis of Ti3SiC2 by SHS suggested that Ti3SiC2 might be formed from the liquid phase of Ti–Si and the solid phase of TiC. 相似文献
9.
Dianran Yan Jining He Boran Tian Yanchun Dong Xiangzhi Li Jianxin Zhang Lisong Xiao Weina Jing 《Surface & coatings technology》2006,201(6):2662-2666
Aluminum coating was plasma sprayed on Fe-0.14-0.22 wt.% C steel substrate, and heat diffusion treatment at 923 °C for 4 h was preformed to the aluminum coating to form Fe2Al5 inter-metallic compound coating. The corrosion mechanism of the Fe2Al5 coating in molten zinc was investigated. SEM and EDS analysis results show that the corrosion process of the Fe2Al5 layer in molten zinc is as follows: Fe2Al5 → Fe2Al5Znx (η) → η + L(liquid phase) → L + η + δ(FeZn7) → L + δ → L. The η phase and the eutectic structure (η + δ) prevent the diffusion of zinc atoms efficiently. Therefore the Fe2Al5 coating delays the reaction between the substrate and molten zinc, promoting the corrosion resistance of the substrate. 相似文献
10.
Piezoelectric and dielectric properties of Dy2O3-doped (Bi0.5Na0.5)0.94Ba0.06TiO3 lead-free ceramics
Chen Zhi-hui Ding Jian-ning Mei LinYuan Ning-yi Zhu Yuan-yuan 《Journal of Alloys and Compounds》2011,509(2):482-485
(Bi0.5Na0.5)0.94Ba0.06TiO3 + x wt% Dy2O3 with x = 0-0.3 ceramics were synthesized by conventional solid-state processes. The effects of Dy2O3 on the microstructure, the piezoelectric and dielectric properties were investigated. X-ray diffraction pattern confirmed that the coexistence of tetragonal and rhombohedral phases in the (Bi0.5Na0.5)0.94Ba0.06TiO3 composition was not changed by adding 0.05-0.3 wt% Dy2O3. SEM images indicate that all the ceramics have pore-free microstructures with high density, and that doping of Dy2O3 inhibits the grain growth of the ceramics. The addition of Dy2O3 shows the double effects on decreasing the piezoelectric and dielectric properties for 0 < x < 0.15 when Dy3+ ions substitute B-site Ti4+ ions, and increasing the properties for 0.15 < x < 0.3 when Dy3+ ions enters into A-site of the perovskite structure. The optimum electric properties of piezoelectric constant d33 = 170 pC/N and the dielectric constant ?r = 1900 (at a frequency of 1 kHz) are obtained at x = 0.3. 相似文献
11.
Ashutosh Kumar Dubey Prakash SinghSindhu Singh Devendra KumarOm Parkash 《Journal of Alloys and Compounds》2011,509(9):3899-3906
Mechanism of charge compensation on lanthanum, (La3+) substitution on Ca site in calcium copper titanate (CaCu3Ti4O12), and its effect on resulting electrical and dielectric properties has been studied in the present investigation. For this purpose samples were prepared according to two stoichiometries viz. LaxCa(1−3x/2)Cu3Ti4O12 (x ≤ 0.09) and LaxCa(1−x)Cu3Ti4O12 (x = 0.03) by solid state ceramic route. The former represents ionic compensation while the later is in accordance with electronic compensation. Nature of charge carriers is identified by measuring Seebeck coefficient which is found to be negative in the entire range of measurement. In order to understand the mechanism of conduction, ac conductivity is measured as a function of temperature and frequency. Space charge polarization is the dominant polarization mechanism phenomenon at low frequency and high temperature while orientation polarization dominates at low temperature and high frequency. Impedance analysis confirms the formation of internal barrier layers which is responsible for high dielectric constant in these samples. 相似文献
12.
In this paper we report on the electrochemical corrosion of select MAX phases, namely Ti2AlC, (Ti,Nb)2AlC, V2AlC, V2GeC, Cr2AlC, Ti2AlN, Ti4AlN3, Ti3SiC2 and Ti3GeC2 in 1 M NaOH, 1 M HCl and 1 M H2SO4 solutions. Polarization characteristics recorded in 1 M NaOH show that V2AlC, V2GeC and Cr2AlC undergo active dissolution at potentials more positive than the corrosion potential, while Ti2AlC, (Ti,Nb)2AlC, Ti3SiC2 and Ti3GeC2 passivate. In the 1 M HCl solutions, Ti2AlC, V2AlC and V2GeC actively dissolve; Ti3SiC2 and Ti3GeC2 passivate. Depending on potential, (Ti,Nb)2AlC and Cr2AlC showed trans-passive behavior. In 1 M H2SO4 solutions, Ti2AlC, (Ti,Nb)2AlC, Ti3SiC2 and Ti3GeC2 passivate, V2AlC and V2GeC show active dissolution, while Cr2AlC exhibits trans-passive behavior. Ti2AlN and Ti4AlN3 were passive in all solutions except in 1 M HCl, where Ti2AlN showed trans-passive behavior. Given that the corrosion behavior of (Ti,Nb)2AlC is unlike either Ti or Nb, the behavior of the former cannot be predicted from that of the latter. 相似文献
13.
Pb(ZrxTi1−x)O3 thin films with mixed orientations of (1 1 1) and (1 0 0) were prepared on Pt/Ti/SiO2/Si substrate by sol-gel technique. The compositions of PZT thin films are chosen as x = 0.55 and x = 0.58. Both of the compositions are in the rhombohedral phase region of the Pb(ZrxTi1−x)O3 phase diagram, but the former is near the monoclinic phase existence region, and the latter is far from the monoclinic phase existence region. Rhombohedral-monoclinic phase transitions are reported in both of the thin films. The results show that the phase transition is related to the grain orientation. Phase transitions in the films are clearly identified: rhombohedral phase transforms to MB phase in (1 1 1)-oriented grains, and rhombohedral phase transforms to MA phase in (1 0 0)-oriented grains. The remnant polarization is determined by the content of (1 1 1)-oriented grains. It is shown that the remnant polarization is greater in the film with higher content of (1 1 1)-oriented grains. 相似文献
14.
Xian-Zhong XiongZhan-Guo Liu Jia-Hu Ouyang Xiao-Liang XiaJun Xiang Xiao-Ming Liu 《Journal of Alloys and Compounds》2011,509(33):8392-8397
The pyrochlore-type phases with the compositions of SmDy1−xMgxZr2O7−x/2 (0 ≤ x ≤ 0.20) have been prepared by pressureless-sintering method for the first time as possible solid electrolytes. The structure and electrical conductivity of SmDy1−xMgxZr2O7−x/2 ceramics have been studied by the X-ray diffraction (XRD), scanning electron microscopy (SEM) and impedance spectroscopy measurements. SmDy1−xMgxZr2O7−x/2 (x = 0, 0.05, 0.10) ceramics exhibit a single phase of pyrochlore-type structure, and SmDy1−xMgxZr2O7−x/2 (x = 0.15, 0.20) ceramics consist of pyrochlore phase and a small amount of the second phase magnesia. The total conductivity of SmDy1−xMgxZr2O7−x/2 ceramics obeys the Arrhenius relation, and the total conductivity of each composition increases with increasing temperature from 673 to 1173 K. SmDy1−xMgxZr2O7−x/2 ceramics are oxide-ion conductors in the oxygen partial pressure range of 1.0 × 10−4 to 1.0 atm at all test temperature levels. The highest total conductivity value is about 8 × 10−3 S cm−1 at 1173 K for SmDy1−xMgxZr2O7−x/2 ceramics. 相似文献
15.
Yu-ki Taninouchi Tetsuya UdaTetsu Ichitsubo Yasuhiro AwakuraEiichiro Matsubara 《Journal of Alloys and Compounds》2011,509(19):5833-5838
The phase transition behavior of oxide-ion conductor Bi2(V0.95Ti0.05)O5.475−x, which has various thermal histories and sample forms, has been studied by means of differential scanning calorimetry. Thermogravimetric analysis revealed that the oxygen content per compositional formula varied with the applied thermal treatment, although no significant structural difference was observed by X-ray diffraction (XRD) analysis. The phase transition behavior from αf to βf and from βf to γf, observed at a heating rate of 10 K min−1, are markedly affected by the sample preparation. For example, the endothermic peak of the transition from αf to βf appeared at around 400 °C for quenched powder and at around 320 °C for powder cooled at 0.5 K min−1. The trend of the transition temperatures can be qualitatively explained in terms of oxygen content, i.e., Bi2(V0.95Ti0.05)O5.475−x with less oxygen content exhibits the transition from αf to βf at a higher temperature and the transition from βf to γf at a lower temperature. We confirmed the two types of transition behavior from αf to βf depending on heating rate of DSC and high-temperature X-ray diffraction (HT-XRD) analysis. At rapid heating rates of 10 and 40 K min−1, αf transformed to βf directly. Meanwhile, at a slow heating rate of 2 K min−1, the βf precipitated from αf because slow heating allowed the diffusion of Ti and oxygen vacancies induced by the aliovalent doping. This suggests that the small differences of atomic arrangement also affect the phase transition behavior because additional elements have preferable crystallographic sites in αf and βf. 相似文献
16.
Baoyan Liang Mingzhi Wang Jinfeng Sun Qin Zou Xin Han 《International Journal of Refractory Metals and Hard Materials》2009,27(5):927-930
The mechanically activated sintering process was adapted to synthesize Ti3AlC2 using 3Ti/Al/2C/0.05Sn powder mixtures. The result showed that the powders containing TiC, Ti3AlC2 and Ti2AlC were obtained by mechanical alloying (MA) 3Ti/Al/2C powders. Addition of appropriate Sn reduced the content of Ti2AlC and enhanced the synthesis of Ti3AlC2 significantly. The powders with highest content of Ti3AlC2 were obtained by MA 3Ti/Al/2C/0.05Sn powders. Through pressureless sintering the mechanical alloyed powders at 900–1100 °C for 2 h, the high purity Ti3AlC2 material with fine organization was produced. 相似文献
17.
The temperature-dependent luminescence of Sr1.7Eu0.3MxCeO4.15+x/2 (M = Li+, Na+, K+, x = 0, 0.3) samples was investigated and discussed in the temperature range from 303 to 573 K. It is found that the thermal quenching temperature of samples decreases with Li+-/Na+-doping but increases with the incorporation of K+. We suggest that these observations are resulted from two factors. One is that the incorporation of Li+/Na+/K+ ions reduces the strength of potential field at the O2− sites, and then results in a red-shift of the Eu-O charge transfer band. The other is that Δr expands with Li+-/Na+-doping but shrinks with K+-doping. We consider that it is a feasible way to adjust the temperature-dependent luminescence properties of materials by introducing appropriate impurities. 相似文献
18.
In order to modify surface properties of Ti3SiC2, boronizing was carried out through powder pack cementation in the 1100-1400 °C temperature range. After boronizing treatment, one mixture layer, composed of TiB2 and β-SiC, forms on the surface of Ti3SiC2. The growth of the coating is processed by inward diffusion of boron and obeys a linear rule. The boronizing increases the hardness of Ti3SiC2 from 3.7 GPa to a maximal 9.3 GPa and also significantly improves its wear resistance. 相似文献
19.
LüXiang-hong YANG Yan-qing HUANG Bin LUO Xian LIU Yu-chengState Key Laboratory of Solidification Processing School of Materials Science Engineering Northwestern Polytechnical University Xi’an China 《中国有色金属学会会刊》2007,17(1):27-34
SiC continuous fiber-reinforced pure Ti(TA1)matrix composites were fabricated by a vacuum hot pressing(VHP)methodand then heat-treated in vacuum under different conditions.The interfacial reaction and the formation of interfacial phases werestudied by using SEM,EDS and XRD.The results show that there exists reaction diffusion at the interface of SiC fibers and Timatrix,and the concentration fluctuation of reaction elements such as C,Ti and Si appears in interfacial reaction layer.The interfacialreaction products are identified as Ti3SiC2,TiCx and Ti5Si3Cx.At the beginning of interfacial reaction,the interfacial reactionproducts are TiCx and Ti5Si3Cx.Along with the interfacial reaction diffusion,Ti3SiC2 and Ti5Si3Cx single-phase zones come forth inturn adjacent to SiC fibers,and the TiC Ti5Si3Cx double-phase zone appears adjacent to Ti matrix,which forms discontinuousconcentric rings by turns around the fibers.The formed interfacial phases are to be Ti3SiC2,Ti5Si3Cx and TiCx Ti5Si3Cx from SiCfiber to Ti matrix.The interfacial reaction layer growth is controlled by diffusion and follows a role of parabolic rate,and theactivation energy(Qk)and(k0)of SiC/TA1 are 252.163 kJ/mol and 7.34×10?3m/s1/2,respectively. 相似文献
20.
Chia-Cheng Lin Li-Hsiang Lin Jing-Ming Hung Yung-Hsun Shih Ching-Zong Wu Keng-Liang Ou Chih-Yeh Chao 《Journal of Alloys and Compounds》2011,509(37):9038-9044
The microstructural characteristics of the Fe-9Al-30Mn-1C-5Ti (wt.%) alloy were determined by scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectrometry. The microstructure of the alloy was essentially a mixture of (γ + TiCx + (α + B2 + DO3)) phases during solution treatment between 950 °C and 1150 °C. The TiCx carbide had a face-center-cubic structure with a lattice parameter a of 0.432 nm. When the as-quenched alloy was subjected to aging treatment at temperatures of 450-850 °C, the following microstructural transformation occurred: (γ + TiCx + κ + (α + DO3)) → (γ + TiCx + κ + (α + B2 + DO3 + TiCx)) → (γ + TiCx + κ + κ′ + (α + B2 + DO3)) → (γ + TiCx + (α + B2 + DO3)). Addition of Ti promotes the formation of the α phase at high temperatures. 相似文献