共查询到20条相似文献,搜索用时 31 毫秒
1.
Dong-Bok Lee 《Metals and Materials International》2008,14(3):335-340
Ll2-type Al3Ti−Cr alloys of compositions 67Al−25Ti−8Cr, 66Al−24Ti−10Cr, and 59Al−26Ti−15Cr (in atomic percent) were corrosion tested between
800°C and 1100°C in an Ar−1% SO2 gas atmosphere for up to 150h. Corrosion proceeded mainly via oxidation reactions. The scale consisted primarily of a thin
Al2O3 barrier layer. The alloys tested had much better corrosion resistance than TiAl-base alloys or Hastelloy X. Virtually no
sulfides were detected in the scale, because of the strong oxidizing tendency of the Al3Ti−Cr alloys having high Al concentrations. 相似文献
2.
Perovskite-type Ba0.5Sr0.5Co0.8Fe0.2O3−δ
(BSCFO) powders were synthesized using two methods, solid-state reaction (SSR) method and citrate-EDTA complexing method
(CC-EDTA). Then the powders were pressed to green disks of 19 mm in diameter and sintered at 1140°C for 5 h. The shrinkage
rate and relative density of the membranes prepared from the perovskite-type powders were determined and calculated, and the
powders and derived membranes were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results
show that the shrinkage rates of the two kinds of disks are nearly the same (about 10%). The disks prepared by the SSR method
had a bigger grain size and lower relative density than those prepared by the CC-EDTA method. The conductivity of the membranes
prepared by the SSR method was about 38 S/cm, higher than that of the membranes prepared by the CC-EDTA method, which was
about 30 S/cm, at the same temperature of 600°C. 相似文献
3.
F. L. Yu Y. Bai P. D. Han Q. L. Shi S. Ni J. H. Wu 《Journal of Materials Engineering and Performance》2016,25(12):5220-5224
In the present work, the α/β Si3N4 ceramics were fabricated by spark plasma sintering (SPS) at 1400-1500 °C for 6 min with 3wt.%MgO + 5wt.%Al2O3 and 3wt.%MgO + 5wt.%Y2O3 as sintering additives. The results showed that the phase composition, microstructure and mechanical properties of α/β Si3N4 ceramics were highly dependent on the type of sintering additive. The incomplete phase transformation from α to β occurred in the presence of an oxynitride (Mg-Al(Y)-Si-O-N) liquid phase. Compared with MgO-Al2O3, MgO-Y2O3 can significantly improve the β conversion rate of as-sintered α/β Si3N4 ceramics. And the as-sintered ceramics using MgO + Al2O3 as sintering additives had higher mechanical properties. 相似文献
4.
Wu Kai Y. T. Chen F. P. Zheng W. S. Chen R. T. Huang L. W. Tsai H. H. Huang W. Zhang 《Oxidation of Metals》2016,86(3-4):205-219
Air-oxidation behavior of a Ni53Nb20Ti10Zr8Co6Cu3 amorphous ribbon was studied at 400–550 °C. The oxidation kinetics of the amorphous alloy followed a two-stage parabolic rate law with its oxidation rates steadily increasing with temperature. The steady-state oxidation rate constants of the alloy were faster than those of pure Ni. Triplex scales formed on the glassy alloy, containing an outer layer of NiO. The scales formed in the intermediate layer consisted of Nb2O5, NiO, and uncorroded α-Ni, while an additional Nb2Zr6O17 phase was also detected in the inner layer. The formation of multilayered scales is responsible for the faster oxidation for the Ni6-AR. 相似文献
5.
Shui-Jin Yang Yu-Lin Xu Wen-Peng Gong Yong-Kui Huang Guo-Hong Wang Yun Yang Chuan-Qi Feng 《稀有金属(英文版)》2016,35(10):797-803
H3PW12O40/TiO2–SiO2 was synthesized by impregnation method which significantly improved the catalytic activity under simulated natural light. The properties of the samples were characterized by Fourier transform infrared spectra (FTIR), X-ray powder diffraction pattern (XRD), Scanning electron micrographs (SEM), and Zeta potential. Degradation of methyl violet was used as a probe reaction to explore the influencing factors on the photodegradation reaction. The results show that the optimal conditions are as follows: initial concentration of methyl violet of 10 mg·L?1, pH of 3.0, catalyst dosage of 2.9 g·L?1, and light irradiation time of 2.5 h. Under these conditions, the degradation rate of methyl violet is 95.4 %. The reaction on photodegradation for methyl violet can be expressed as the first-order kinetic model, and the possible mechanism for the photocatalysis under simulated natural light is suggested. After used continuously for five times, the catalyst keeps the inherent photocatalytic activity for degradation of dyes. The photodegradation of methyl orange, methyl red, naphthol green B, and methylene blue was also tested, and the degradation rate of dyes can reach 81 %–100 %. 相似文献
6.
Yan-Xiu Wang Ting-An Zhang Guo-Zhi Lv Xiao-Feng Zhu Wei-Guang Zhang Li-Qun Xie 《稀有金属(英文版)》2016,35(6):495-501
Titanium has a great effect on the digestion of bauxite in the Bayer process because it reacts readily at high temperatures in alkaline sodium aluminate solution. Under this consideration, the hydrothermal conversion of Ti-containing minerals in the system of Na2O–Al2O3–SiO2–CaO–TiO2–H2O with increased temperatures was studied based on the thermodynamic analysis and systematic experiments. The results show that anatase converts to Al4Ti2SiO12 at low temperatures (60–120 °C), which is similar to anatase in crystal structure. As the temperature continues to rise, Al4Ti2SiO12 decomposes gradually and converts to Ca3TiSi2(Al2Si0.5Ti0.5)O14 at 200 °C. When the temperature reaches 260 °C, CaTiO3 forms as the most stable titanate species for its hexagonal closest packing with O2? and Ca2+. The findings enhance the understanding of titanate scaling in the Bayer process and clarify the mechanism of how additive lime improves the digestion of diaspore. 相似文献
7.
Yuanhua Lin Wen Xu Xiaoyan Zhang Lijun Wang Wanying Liu 《JOM Journal of the Minerals, Metals and Materials Society》2017,69(9):1503-1508
The Ti3O5 powder with uniform morphology has been successfully obtained and used to synthesize Li4Ti5O12/Ti3O5 composite material by ball milling for modifying Li4Ti5O12-based, lithium–ion battery anodes. Moreover, according to the relative performance investigations, the synthesized Li4Ti5O12/Ti3O5 composite shows better electrochemical properties than that of the Li4Ti5O12. At a high rate (10 C), the capacity of the Li4Ti5O12/Ti3O5 composite electrode is 139.8 mAhg?1, whereas the value of Li4Ti5O12 is 121.6 mAhg?1, showing a capacity enhanced about 14.97%. After 100 cycles at 0.2 C, the discharge capacity of Li4Ti5O12/Ti3O5 remains at 160 mAhg?1 with a capacity loss of 2.6%. The results indicate that the Li4Ti5O12/Ti3O5 composite electrode can be used as anode material with a relatively higher rate capability and excellent cycle performance in lithium–ion batteries. 相似文献
8.
Electrochemical and interfacial properties of (PEO)10LiCF3SO3−Al2O3 composite polymer electrolytes (CPEs) prepared by either ball milling or stirring are reported. Ball milling was introduced
into a slurry preparative technique utilizing PEO, lithium salt and Al2O3 powder ranging from 5 to 15 wt.%. The ionic conductivity was increased by ball milling over a range of temperatures. In particular,
a significant increase at low temperature below the melting point of crystalline PEO was observed. Interfacial stability between
lithium electrode and CPE was significantly improved by the addition of alumina as well as by ball milling. The electrochemical
stability window produced by (PEO)10LiCF3SO3−Al2O3 ball milling was higher than that of stirring, which was about 4.4 V. Charge/discharge performance of Li/CPE/S cells with
(PEO)10LiCF3SO3−Al2O3-12 hr ball milling was superior to that of a pristine polymer electrolyte due to the low interface resistance and high ionic
conductivity. 相似文献
9.
Alka Gupta Ambreen Nisar Shobit Omar Kantesh Balani 《JOM Journal of the Minerals, Metals and Materials Society》2018,70(10):1937-1945
The grain growth kinetics of 8YSZ ceramics processed using spark plasma sintering (SPS) has been investigated in the temperature ranging from 1100°C to 1500°C. The activation energy during SPS densification was obtained as 332 kJ/mol with grain boundary diffusion as a dominant mechanism. Further, the effect of CeO2 on the densification kinetics of 8YSZ ceramic processed via SPS and conventional sintering (CS) has been delineated. The lower grain boundary mobility of CS-processed composites (an order of magnitude lower than SPS) is attributed to the solute drag and lattice distortion mechanism. However, no significant change in the grain boundary mobility was observed with CeO2 addition (~?14.7–43.9?×?10?18 m3/N/s for CS and 107.2–116.7?×?10?18 m3/N/s for SPS) revealing that the defect concentration is nearly constant in 8YSZ. The study highlights the effect of sintering techniques (SPS and CS) and reinforcement (CeO2) on engineering the desired microstructure of 8YSZ ceramic. 相似文献
10.
As the byproduct of TiO2 industrial production, impure FeSO4·7H2O was used for the synthesis of LiFePO4. With the purified solution of FeSO4·7H2O, FePO4·xH2O was prepared by a normal titration method and a controlled crystallization method, respectively. Then LiFePO4 materials were synthesized by calcining the mixture of FePO4·xH2O, Li2CO3, and glucose at 700°C for 10 h in flowing Ar. The results indicate that the elimination of FeSO4·7H2O impurities reached over 95%, and using FePO4·xH2O prepared by the controlled crystallization method, the obtained LiFePO4 material has fine and sphere-like particles. The material delivers a higher initial discharge specific capacity of 149 mAh·g−1 at a current density of 0.1C rate (1C = 170 mA·g−1); the discharge specific capacity also maintains above 120 mAh·g−1 after 100 cycles even at 2C rate. Thus, the employed processing is promising for easy control, low cost of raw material,
and high electrochemical performance of the prepared material. 相似文献
11.
The electrical characteristics of Ta/Ta2O5 films and Ta/Ti−O/Ta2O5 films deposited by RF reactive sputtering on Ta/Ti/Al2O3 substrates were investigated. Ta was used for the bottom and upper electrodes in order to simplify the fabrication process.
Dielectric materials were annealed at 700°C for 60 sec under vacuum. XRD analysis showed that Ta was crystalline and Ta2O5 was amorphous in an as-deposited state, but amorphous Ta2O5 was transformed to a crystalline state by rapid thermal heat treatment. We compared lnJ-E2, C−V, and C−F of both as-deposited and annealed dielectric thin films deposited on the Ta bottom electrode. From these results,
we concluded that introducing a Ti−O buffer layer could reduce the leakage current. The conduction mechanisms of Ti−O/Ta2O5 could be interpreted appropriately by hopping conduction and space-charge-limited current. 相似文献
12.
Ghasem Azimi-Roeen Seyed Farshid Kashani-Bozorg Martin Nosko Štefan Nagy Igor Maťko 《Journal of Materials Engineering and Performance》2018,27(2):471-482
Combination of mechanical alloying and friction stir processing was used for the fabrication of Al/(Al13Fe4 + Al2O3) nano-composites. Pre-milled hematite + Al powder mixture was introduced into the stir zone generated on 1050 aluminum alloy sheet by friction stir processing. Uniform and active milled powder mixture reacted with plasticized aluminum to produced Al13Fe4 + Al2O3 particles. Al13Fe4 intermetallic showed elliptical shape with a typical size of ~ 100 nm, while nano-sized Al2O3 exhibited irregular floc-shaped particles that formed clusters with the remnant of iron oxide particles in the fine recrystallized aluminum matrix. As the milling time (1-3 h) of the introduced powder mixture increased, the volume fraction of Al13Fe4 + Al2O3 particles increased in the fabricated composite. The hardness and ultimate tensile strength of the fabricated nano-composites varied from 54.5 to 75 HV and 139 to 159 MPa, respectively; these are much higher than those of the friction stir processed base alloy (33 HV and 97 UTS). The highest hardness and strength were achieved for the nano-composite fabricated using the 3-h milled powder mixture; hard nano-sized reaction products and fine recrystallized grains of Al matrix had major and minor roles on enhancing these properties, respectively. 相似文献
13.
Shiyu Cui Qiang Miao Wenping Liang Zhigang Zhang Yi Xu Beilei Ren 《Journal of Materials Engineering and Performance》2017,26(5):2086-2094
Al2O3-20 wt.% TiO2 ceramic coatings were deposited on the surface of Grade D steel by plasma spraying of commercially available powders. The phases and the microstructures of the coatings were investigated by x-ray diffraction and scanning electron microscopy, respectively. The Al2O3-20 wt.% TiO2 composite coating exhibited a typical inter-lamellar structure consisting of the γ-Al2O3 and the Al2TiO5 phases. The dry sliding wear behavior of the coating was examined at 20 °C using a ball-on-disk wear tester. The plasma-sprayed coating showed a low wear rate (~4.5 × 10?6 mm3 N?1 m?1), which was <2% of that of the matrix (~283.3 × 10?6 mm3 N?1 m?1), under a load of 15 N. In addition, the tribological behavior of the plasma-sprayed coating was analyzed by examining the microstructure after the wear tests. It was found that delamination of the Al2TiO5 phase was the main cause of the wear during the sliding wear tests. A suitable model was used to simulate the wear mechanism of the coating. 相似文献
14.
Soo-Kyung Kim Dong-Hyo Yang Jeong-Soo Sohn Yong-Chan Jung 《Metals and Materials International》2012,18(2):321-326
A recycling process involving chemical, mechanical, and electrochemical steps has been applied to recover cobalt from spent
lithium ion batteries and resynthesize cathode active materials. LiCo1−xMnxO2 powders using Co salt including Mn from the leach liquor were resynthesized by solid-state reaction as cathode active materials.
When the powder mixture with added Li salt was calcined at 950 °C for 8 hours, well crystallined LiCo1−xMnxO2 was successfully obtained. The LiCo1−xMnxO2 powders with a ratio of Co:Mn=10:1 has a discharge capacity of 156.3 mAh/g at a rate of 20 mA/g with no perceptible capacity
loss, in sharp contrast to the pure LiCoO2 as active materials. The resynthesized LiCo1−xMnxO2 was proven to have good characteristics as cathode active materials in charge/discharge capacity and cyclic performance. 相似文献
15.
Noveed Ejaz Liaqat Ali Furqan Ahmed Khalid Mahmood Ghauri A. Nusair Khan 《Journal of Thermal Spray Technology》2017,26(5):913-928
A novel thermal barrier coating system was formulated to resist hot corrosion environments. In this coating system, 5% CaZrO3 was added to conventional yttria-stabilized zirconia (YSZ). The above composite coating system was compared with the standard YSZ system in the presence of a mixture of 50% Na2SO4 and 50% V2O5 at 950 °C. The results demonstrated that the lifetime of the CaZrO3-added composite system in this highly hostile environment was longer compared with the standard YSZ system. This is due to the fact that the preferential reaction of NaVO3 shifted from yttria to calcia, forming CaV2O4 instead of YVO4. The preferential reactions are discussed in terms of free energy changes and acid–base theory of molten salts with ceramic oxides. Furthermore, calculations of lattice distortion also proved that the CaZrO3-added composite system demonstrated less distortion, thus increasing the overall lifetime of the coating system. 相似文献
16.
N. V. Kataeva A. I. Valiullin S. V. Kositsyn 《The Physics of Metals and Metallography》2009,107(3):262-269
Melt-quenched Ni65Al35 and Ni56Co10Al34 (at %) alloys are studied by electrical resistance measurement and electron microscopy. The effects of the isothermal holding time in the supersaturated β solid solution field and the heating rate during thermal cycling on the restoration of the reversibility of the martensitic transformation are investigated. After short-term aging in the B2 austenite field followed by long-term aging in the L10 martensite field, the melt-quenched Ni65Al35 and Ni56Co10Al34 alloys retain their high thermal stability of the reversibility of the martensitic transformation. 相似文献
17.
The influence of the holding time upon annealing on the temperature of the viscous–brittle transition (temperature of embrittlement) Tf in a cobalt-based amorphous alloy of the composition Co69Fe3.7Cr3.8Si12.5B11 with a very low saturation magnetostriction λs (<10–7) has been studied. It has been established that the dependence of the embrittlement temperature Tf on the of time of holding ta can be described by an Arrhenius equation and that the embrittlement at the annealing temperatures above and below 300°C is described by different kinetic parameters. In the alloy under study, irrespective of the holding time, embrittlement occurs in a very narrow range of annealing temperatures, which does not exceed 5 K. Based on the experimental data on the evolution of the hysteresis magnetic properties upon the isochronous annealings and upon the isothermal holding, the regime of heat treatment that ensures a very high (about 50000) magnitude of the permeability µ5 (H = 5 mOe, f = 1 kHz) without the transition of the alloy into a brittle state has been determined. 相似文献
18.
Yu-Wen Zhang Fan-Lin Zeng Chen-Chen Yu Cheng-Zhang Wu Wei-Zhong Ding Xiong-Gang Lu 《稀有金属(英文版)》2016,35(9):723-728
The permeability and stability of Sm0.7Sr0.3CoO3?δ (SSCO) regarding the special requirements for carbon capture and storage (CCS) application were investigated. Pure CO2 was used as the sweep gas at 900 °C, leading to that the oxygen permeation flux decreases by about 34 %. Several cycles of changing the sweep gas between helium and CO2 indicate the good reversibility of this degradation. Both carbonate formation and adsorption of CO2 on the membrane surface are responsible for the degradation of the membrane performance. The better CO2 resistance results from the substitution of Sm for Sr due to the higher acidity of Sm2O3 (1.278) than that of SrO (0.978) and a discontinuous layer of carbonate. 相似文献
19.
S. Dosta I.G. Cano J.R. Miguel J.M. Guilemany 《Journal of Thermal Spray Technology》2008,17(3):360-364
Producing nanostructured materials through metastable phases is an interesting novel route in the field of ceramic materials.
Due to their small grain size and uniform structure, these nanostructured bulk materials exhibit very interesting properties.
Metastable coatings can be produced starting from microstructured powders through atmospheric plasma spray technique, followed
by a quenching route. The initial powders are melted during the spraying and deposited over a substrate that is quenched with
liquid nitrogen feeders, producing metastable coatings. The thermal-sprayed coatings have been characterized using x-ray diffraction,
scanning electron microscopy, field emission scanning electron microscopy, and energy dispersive spectroscopy. The properties
of such coatings have been also studied obtaining promising results. 相似文献
20.
Jian Rong Kai Yang Yin Zhuang Jinxing Ni Huayu Zhao Shunyan Tao Xinghua Zhong Chuanxian Ding 《Journal of Thermal Spray Technology》2018,27(3):358-370
In recent years, numerous techniques have been developed to mimic nacre-like hierarchical architectures in order to improve the damage tolerance of materials. We present herein a simple strategy to fabricate such a hierarchical architectured Al2O3–Y2O3 composite coating via atmospheric plasma spraying. The evolution of the phase and microstructure of the Al2O3–Y2O3 composite coating were characterized under conditions of high-temperature exposure in air at 800-1350 °C. The hardness and porosity of several typical coatings were determined. In situ formation of dense hierarchical architectured Al2O3–YAG composite coating with improved hardness was achieved after heat treatment at 1350 °C. Compared with Al2O3 coating, elevated toughness was found for the hierarchical architectured Al2O3–YAG composite coating, which can be ascribed to the distribution of YAG phase that contributed to crack termination and deflection, and microbridging. After thermal aging treatment at 1350 °C, the hierarchical architectured Al2O3–YAG composite coating was quite stable after 100 h of thermal exposure. Furthermore, the Al2O3–Y2O3 composite coating exhibited superior sintering resistance compared with the Al2O3 coating. 相似文献