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排序方式: 共有379条查询结果,搜索用时 31 毫秒
1.
《Ceramics International》2022,48(14):20158-20167
Vacuum induction melting is a potential process for the preparation of TiAl alloys with good homogeneity and low cost. But the crucial problem is a selection of high stability refractory. In this study, a BaZrO3/Y2O3 dual-phase refractory was prepared and its performance for melting TiAl alloys was studied and compared with that of a Y2O3 refractory. The results showed the dual-phase refractory consisted of BaZr1-xYxO3-δ and Y2O3(ZrO2), exhibited a thinner interaction layer (30 μm) than the Y2O3 refractory (90 μm) after melting the TiAl alloy. Although the TiAl alloys melted in the dual-phase and Y2O3 refractory exhibited similar oxygen contamination (<0.1 wt%), the alloy melted in the dual-phase refractory had smaller Y2O3 inclusion content and size than that in the Y2O3 refractory, indicating that the dual-phase refractory exhibited a better melting performance than the Y2O3 refractory. This study provides insights into the process of designing highly stable refractory for melting TiAl alloys. 相似文献
2.
Su-Il Ri Song-Il Hong Jong-Chol Kim Ju-Hyok Wi 《International Journal of Hydrogen Energy》2021,46(5):3319-3328
We investigated some properties of the hydride Mg2FeH6 substituted with yttrium by a first principles calculation. Some experimental results showed that 4d transition metal, yttrium serves as a good catalyst for magnesium based hydrogen storage alloys, but there are a few theoretical studies about magnesium based hydrides substituted with it. Mg2FeH6 is regarded as a cheaper material than pure MgH2, while it is crystalized into Fm3m structure (space group 225). Although it has high hydrogen storage capacity, many investigations have not been devoted to it due to its extremely high thermodynamic stability. The yttrium substituted Mg2FeH6 exhibits very low energy of formation, and its desorption temperature, 75 °C is very suitable for practical hydrogen storage applications. Our results showed that Mg2FeH6 is destabilized effectively by yttrium substitution and introducing vacancy defects has additive effect to the improvement of dehydrogenation performance. 相似文献
3.
F. Riffard H. Buscail E. Caudron R. Cueff C. Issartel S. Perrier 《Corrosion Science》2003,45(12):2867-2880
The present results reveal the interest of sol–gel coating technique to improve 304 steel high temperature oxidation resistance. An yttrium sol–gel coating appears to enhance the oxidation resistance during isothermal oxidation test, to decrease widely the oxide weight gain and to reduce the initial transient oxidation stage generally observed in the case of blank steels. Moreover, the experimental results confirm that yttrium sol–gel coating also plays a significant role on the cyclic oxidation behaviour of the 304 steel. In fact, the yttrium addition promotes remarkably the prolongation of the period during which the oxide scale still remains adherent to the substrate. 相似文献
4.
Coatings of the MCrAlY type (M = Ni, Co) are commonly used as overlay coatings and as bond coats (BC's) for ceramic thermal barrier coatings (TBC's) in industrial gas turbines. During high temperature service the MCrAlY coatings form aluminium based surface oxide scales. The technologically most relevant properties of the oxide scales, growth rate and adherence do not only depend on the exact MCrAlY composition but also on the surface condition after coating manufacturing. Depending on the coating manufacturing process, the MCrAlY surfaces may substantially differ in roughness. In addition the coatings may be subjected to surface treatments (e.g. shot peening, grinding or smoothening prior to deposition of TBC). In the present work the effect of the surface roughness commonly prevailing in the case of vacuum plasma sprayed MCrAlY coatings on the morphology and composition of the alumina scales formed during high-temperature oxidation was studied. For this purpose free standing coatings with rough and polished surfaces were oxidised in the temperature range from 800 to 1100 °C with exposure times up to 1000 h. The surface scale composition and morphology were analysed by optical metallography and SEM. Fluorescence spectroscopy was used for stress measurements in the oxide scales. It has been found that the oxide scales formed on rough surfaces of MCrAlY coatings have an intrinsically different morphology and growth rate compared to those formed on the flat ground surfaces. 相似文献
5.
N_2O—C_2H_2火焰原子吸收分光光度法测定钨制品中的钇 总被引:2,自引:0,他引:2
本文研究了N_2O—C_2H_2火焰原子吸收分光光度法测定钨制品中钇的条件,拟定了分析方法.方法相对标准偏差1. 2%~3%,回收率95%以上. 相似文献
6.
Yu Hua Wang Tadashi Endo Xuan Guo Yukio Murakami Mizumoto Ushirozawa 《Journal of the Society for Information Display》2004,12(4):495-499
Abstract— The broad bands at around 155 nm for GdAl3(BO3)4:Eu, at 184 nm for Ca4GdO(BO3)3:Eu, at 183 nm for Gd2SiO5:Eu, and at 170 nm for GdAlO3:Eu were observed. These bands were assigned to the charge‐transfer (CT) transition of Gd3+‐O2?. In the excitation spectrum of (Gd,Y)BO3:Eu, a broadened excitation band was observed in VUV region. It could be considered that this band was composed of two bands at about 160 and 166 nm. The preceding band was assigned to the BO3 group absorption. The later one at about 166 nm could be assigned to the CT transition of Gd3+‐O2?, according to the result of GdAl3(BO3)4:Eu, Ca4GdO(BO3)3:Eu, Gd2SiO5:Eu, and GdAlO3:Eu. The excitation spectra overlapped between the CT transition of Gd3+‐O2? and BO3 groups absorption. It caused the emission of Eu3+ to take place effectively in the trivalent europium‐doped (Gd,Y)BO3 host lattice under 147‐nm excitation. 相似文献
7.
JIN Huiming FELIX Adriana 《机械工程学报(英文版)》2008,21(3):16-19
The isothermal oxidizing kinetics of Co-40Cr alloy and its yttrium ion-implanted samples are studied at 1 000 ℃ in air by thermal-gravity analysis (TGA). Scanning electronic microscopy (SEM) is used to examine the Cr2O3 oxide film's morphology after oxidation. Acoustic emission (AE) method is used in situ for monitoring the cracking and spalling of oxide films formed on both samples during oxidizing and subsequent air-cooling stages. Theoretical model is proposed relating to the film fracture process and is used for analyzing the acoustic emission spectrum both on time domain and on AE-event number domain. It is found that yttrium implantation remarkably reduces the isothermal oxidizing rate of Co-40Cr and improves the anti-cracking and anti-spalling properties of Cr2O3 oxide film. The reasons for the improvement are mainly that the implanted yttrium reduced the grain size of Cr2O3 oxide, increased the high temperature plasticity of oxide film, and remarkably reduced the number and size of Cr2O3/Co-40Cr inteffacial defects. 相似文献
8.
《Journal of the European Ceramic Society》2017,37(15):5001-5007
Yttrium monosilicate and disilicate are important materials for environmental barrier coatings. The two silicates were synthesized by sol-gel route and their phase selection upon calcination and thermal exposure was studied. First products of crystallization were the monosilicate and yttria. Amorphous silica precipitated out at 1300 °C as apatite phase. During prolonged high temperature treatment, up to 100 h at 1400 °C, the apatite disappeared and the disilicate appeared, only to disappear itself as the system approached equilibrium. Thermodynamic calculations performed using Thermo-Calc software show the presence of a metastable miscibility gaps in the amorphous (liquid) phase field. As a consequence, phase separation in the amorphous phase prior to crystallization is responsible for the formation of yttria-rich and silica-rich phases during crystallization. Multiple phase formation during both, yttrium monosilicate and disilicate synthesis is consistent with the presence of the amorphous phase miscibility gaps around the silicate compositions. 相似文献
9.
Hyun Kyu Jung Chang Hee Kim A-Ra Hong Seung Han Lee Tae Cheol Kim Ho Seong Jang Dong Hun Kim 《Ceramics International》2019,45(8):9846-9851
Functional materials exhibiting magnetic and luminescent properties have been recognized as an emerging class of materials with great potential in advanced applications. Herein, properties of multifunctional ceramic composites consisting of two garnets, luminescent cerium-doped Y3Al5O12 (Ce:YAG) and magnetic Y3Fe5O12 (YIG), are reported. On increasing the sintering temperature, both the photoluminescence and saturation magnetization of the Ce:YAG-YIG composites decreased gradually because of the interdiffusion of trivalent ions such as Al3+ and Fe3+. At a constant sintering temperature of 1100?°C, the YIG contents in the composites increased, thereby causing their luminescent properties to degrade and the saturation magnetizations to increase. For application to electronics, Ce:YAG-YIG composite thin films were integrated on quartz substrates by sputtering the ceramic target. The composite thin films exhibited both magnetic and luminescent properties after annealing. These techniques facilitate the incorporation of multifunctional nanocomposites into various devices. 相似文献
10.
采用粉末法,在不同Y含量的TiNi形状记忆合金基体上制备了650℃渗铝涂层,并对Y是如何影响涂层的形成以及涂层700℃恒温氧化性能进行了研究。结果表明渗铝涂层由外层TiAl3和内层NiAl3构成,涂层的生长主要由Al的内扩散控制。当Y含量低于1at.%时,稀土元素Y的添加促进TiAl3外层的生长,抑制NiAl3 内层的生长。恒温氧化实验表明:添加0.5 at.%Y能明显降低渗铝涂层的氧化速度,但添加1 at.%Y和5 at.%Y却加速涂层的氧化。文中对Y是如何影响涂层的形成以及恒温氧化性能进行了分析。 相似文献