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1.
Microstructure and Composition of Primary and Recycled Single Grains of YBCO,GdBCO‐Ag,and SmBCO‐Ag Bulk Superconductors
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Jasmin V. J. Congreve Yunhua H. Shi Antony R. Dennis John H. Durrell David A. Cardwell 《Journal of the American Ceramic Society》2016,99(9):3111-3119
The widespread use of single grain RE‐Ba‐Cu‐O [(RE)BCO] bulk superconductors, where RE is typically Sm, Gd, or Y, is, in part, limited by the relatively high costs of precursor powders and the low success rate of the manufacturing process. Both these problems can be addressed by recycling primary‐processed grains in which the initial growth process has failed in some way. Key to the use of recycled grains in practical applications is an assurance that their properties and performance are not inferior to those of primary grown grains. In this work, we describe the differences between the growth process, microstructure, and properties of primary and recycled (RE)BCO single grains. We observe that the mechanism of growth is the same for both primary and recycled single grain samples in all three RE‐based systems investigated. In the recycling process additional liquid‐rich phase powder is provided beneath a failed sample, whereby this liquid phase infiltrates upwards and contributes a sufficient concentration of additional RE species at the growth front to enable samples to grow relatively easily in the form of single grains by producing a more uniform composition at the growth front, which leads directly to an increased tolerance to the presence of Ag and Ce‐rich agglomerates. Importantly, we observe that the recycled samples have a much more uniform composition, and therefore exhibit more uniform superconducting properties, than single grain samples fabricated by a primary grown process. 相似文献
2.
Devendra K. Namburi Kirti Singh Kai Yuan Huang Suresh Neelakantan John H. Durrell David A. Cardwell 《Journal of the European Ceramic Society》2021,41(6):3480-3492
The success rate of the growth of single grain Y–Ba–Cu–O (YBCO) bulk superconductors, applied typically as trapped field magnets, by melt processing techniques is often rather low. To ensure that the rare earth elements used in these materials are not wasted, and to improve the economics of production, therefore, an effective way of recycling such “failed” samples is essential for the long-term sustainability of the bulk process. In the present paper, a detailed study of the microstructural and mechanical properties of recycled YBCO samples has been made and their properties compared to those of primary grown samples. Recycled YBCO samples exhibit trapped magnetic fields of ~ 70 – 80 % of those observed in primary grown samples. Microstructural investigations reveal a significant reduction in the porosity and a simultaneous improvement in the distribution of Y2BaCuO5 second phase inclusions throughout the microstructure of recycled, single grain YBCO samples. This means that, while the superconducting properties of the recycled samples are generally inferior to those of primary grown samples, somewhat surprisingly the mechanical properties such as flexural strength, hardness and tensile strength of the recycled samples can be improved. The recycled YBCO samples studied here exhibited an average flexural strength of 75 MPa, which is almost 50 % higher compared to primary grown YBCO, which has significant implications for their use in practical applications that involve large mechanical forces, such as levitation. Good correlations were observed between the microstructural parameters and measured mechanical properties in both primary grown and recycled YBCO samples. 相似文献
3.
The acetylacetone precursor method was used to obtain powders of different ceria-based Ce0.8Ln0.2O2−δ (Ln = Y, Gd, Sm, La) compositions, and these powders were used to prepare disks which were sintered at 1150 °C after addition of Co nitrate, or at 1500 °C, without Co. These materials were characterized by impedance spectroscopy to distinguish the bulk and grain boundary behaviours. Arrhenius representations of bulk conductivity data show a gradual slope change, indicating defect interactions on cooling to intermediate and relatively low temperatures. Though data for different doped-ceria samples converge in the high temperature range, significant differences in conductivity and activation energy were found at low temperatures. The grain boundary behaviour shows dependence on the trivalent additive (Y, La, Gd or Sm), and the highest grain boundary conductivity for samples obtained without addition of cobalt nitrate was found for samples with La. However, addition of cobalt nitrate and sintering at relatively low temperature enhances the grain boundary conductivity of the remaining materials. The highest specific grain boundary conductivity was then found for samples containing Sm. Differences in grain boundary behaviour were interpreted based on differences in segregation of the rare earth additives for samples without Co-doping and preferential segregation of Co for Co-doped samples. 相似文献
4.
Mailadil T. Sebastian Sam Solomon Ravindran Ratheesh Jacob George Pezholil Mohanan 《Journal of the American Ceramic Society》2001,84(7):1487-1489
Microwave ceramic dielectric resonators (DRs) based on RETiNbO6 (RE = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Y, and Yb) have been prepared using the conventional solid-state ceramic route. The DR samples are characterized using XRD and SEM methods. The microwave dielectric properties are measured using resonant methods and a net work analyzer. The ceramics based on Ce, Pr, Nd, and Sm have dielectric constants in the range 32–54 and positive coefficient of thermal variation of resonant frequency (τf ). The ceramics based on Gd, Tb, Dy, Y, and Yb have dielectric constants in the range 19–22 and negative τf . 相似文献
5.
Lars-Olov Nordberg Mats Nygren Per-Olov Käll Zhijian Shen 《Journal of the American Ceramic Society》1998,81(6):1461-1470
Oxidation studies of hot-pressed RE-α-sialons, RE x -Si12-4.5 x Al4.5 x O1.5 x N16-1.5 x (with x = 0.40 for RE = Nd, Sm, Yb; and x = 0.48 for RE = Y) were carried out in oxygen in a TG apparatus for ca. 20 h. Very good oxidation resistance was found for the Yb-doped samples, with parabolic rate constants K p similar/congruent 0.09 10-6 -3 10-6 mg2 cm-4 s-1 in the temperature range 1250-1350°C. The promising performance of this material was corroborated by long-term oxidation experiments (5 days) in air at 1350°C. Although the oxidation kinetics can be described by simple equations related to the parabolic rate law (e.g., the arctan equation, Δ W / A 0 =α arctan bt + c t ), the oxidation process in these materials is likely to be complex. The significantly lower oxidation resistance of the RE = Nd, Sm doped α-sialons, especially at higher temperatures, is related to the formation of melilite, RE2 Si3− y Al y O3+ y N4− y ( y ∼ 1), in these systems. The melilite phase is also responsible for the thermal instability of the Nd- and Sm-α-sialons. 相似文献
6.
Yunhua Shi John H. Durrell Antony R. Dennis Zhiwei Zhang Wei Zhai Nadendla Hari Babu David A. Cardwell 《Journal of the American Ceramic Society》2013,96(6):1757-1762
A variety of multiseeding techniques have been investigated over the past 20 yr in an attempt to enlarge bulk (RE)BCO superconducting samples fabricated by the top‐seeded melt growth (TSMG) process for practical applications. Unfortunately, these studies have failed to establish whether technically useful values of trapped field can be achieved in multiseeded bulk samples. In this work specially designed, 0°–0° and 45°–45° bridge seeds of different lengths have been employed to produce improved alignment of the seeds during the TSMG process. The ability of these bridge‐seeded samples to trap magnetic field, which is the key superconducting property for practical applications of bulk (RE)BCO, is compared for the samples seeded using 0°–0° and 45°–45° bridge seeds of different lengths. The grain boundaries produced by these bridge seeds are analyzed in detail, and the similarities and differences between the two bridge‐seeding processes are discussed. 相似文献
7.
Luminescence properties and tunable emission of Ag NCs in oxyfluoride glass through REF3 (RE = Y,La and Gd) doping
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Zhuang Guo Song Ye Xvsheng Qiao Deping Wang 《Journal of the American Ceramic Society》2018,101(2):732-738
In this research, series of Ag nanoclusters (Ag NCs) contained oxyfluoride glasses were prepared using the melt quenching method, in which the REF3 (RE = Y, La, and Gd) were selected as dopants to control their size distribution. The absorption, steady and time‐resolved PL spectra were carried to investigate the size dependent luminescence properties of Ag NCs. The spectral results indicated that the super broadband emission of Ag NCs is contributed by the spin‐allowed (blue side) and the spin‐forbidden (red side) transitions, respectively. Besides, the introduction of REF3 (RE = Y, La, and Gd) can promote the formation of Ag NCs with different sizes and therefore modulated their luminescence properties. The maximum external quantum yields of Ag NCs with emissions at 430, 510, 520, and 570 nm were evaluated to be 24.6%, 40.7%, 56.3% and 30.7%, respectively, which can be obtained in SAg, SAgLa, SAgGd, and SAgY. 相似文献
8.
Wanderson Romão Marcos F. Franco Maria Izabel M. S. Bueno Marcos N. Eberlin Marco‐Aurelio De Paoli 《应用聚合物科学杂志》2010,117(5):2993-3000
After a rigorous cleaning process, recycled food‐grade poly(ethylene terephthalate) (PET), can be mixed with virgin PET resin in different concentrations and used for packaging of soft drinks. Therefore, it is important to have an experimental method to distinguish the presence of recycled polymer in a batch and to check its “true quality.” One of the issues to be verified is the presence of inorganic contaminants due to the recycling process. X‐ray fluorescence technique is one alternative for this kind of analysis. The results obtained in this work show that bottle‐grade PET samples (PET‐btg) are made either via direct esterification or by a transesterification process. Samples that were subjected to thermo‐mechanical processings (superclean® processing, PET‐btg blends processed in our laboratory and soft drink PET packaging) present Fe Kα emission lines with higher intensities than those presented by virgin bottle‐grade PET. After applying principal component analysis, it can be concluded that Fe is an intrinsic contaminant after the recycling process, furnishing a way to indicate class separations of PET‐btg. A calibration and validation partial least squares model was constructed to predict the weight percent of post‐consumption bottle‐grade PET in commercial PET samples. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
9.
Guo‐Zheng Li Lei Dong Jian‐Hua Deng Xiang‐Yun Deng Wan‐Min Yang 《Journal of the American Ceramic Society》2014,97(12):3725-3728
A coated infiltration growth technique was proposed to fabricate single‐grain Y?Ba?Cu?O bulk superconductor, in which a liquid source coated Y2BaCuO5 (Y‐211) preform was employed and the liquid source composition was 3BaO + 5CuO. Experimental results indicated that, the sample exhibited a single‐grain morphology on the top surface, and the liquid source coating always existed surrounding the bulk which contributed to the complete growth of the sample. The homogeneous distribution of fine Y‐211 inclusions in microstructure and a satisfactory Jc performance of 5.67 × 104 A/cm2 in self‐field at 77 K have also been observed. 相似文献
10.
Gustavo C. C. Costa Dongming Zhu Michael J. Kulis Waldo A. Acosta Anindya Ghoshal 《Journal of the American Ceramic Society》2018,101(8):3674-3693
The reactivity between rare‐earth (RE‐) oxide stabilized ZrO2 or HfO2 thermal barrier coatings (TBCs) and a calcium‐magnesium‐aluminum‐silicate (CMAS) melt was studied at 1310°C. These reactions are representative of the ingestion of siliceous materials by the intake air of gas turbines (e.g., in aircraft engines) at high temperatures (>1200°C). These materials can melt and react with coated components in the hot section, resulting in premature failure. The goal of this work was to probe the effect of various RE (RE = Y, Yb, Dy, Gd, Nd, and Sm) oxides in the melt phase equilibrium and stability of the top‐coating system. Thermodynamic calculations of the phase assemblage of the (1?x) ZrO2‐xY2O3 coating materials and CMAS melt are compared with the experimental findings. CMAS was found to penetrate the samples at the grain boundaries and dissolve the coating materials to form silicate phases containing the RE elements. Furthermore, apatite and garnet crystalline phases formed in the samples with total RE‐oxide content higher than 16 mol% in the reaction zone for the ZrO2 system. In general, samples with nominal compositions ZrO2‐9Dy2O3, HfO2‐7Dy2O3, ZrO2‐8Y2O3, HfO2‐6Er2O3, ZrO2‐9.5Y2O3‐2.25Gd2O3‐2.25Yb2O3, and ZrO2‐30Y2O3 exhibited lower reactivity, or more resistance, to CMAS than the other coating compositions. 相似文献
11.
Xiaowei Chi Jingchao Zhang Zhaoyin Wen Yu Liu 《Journal of the American Ceramic Society》2014,97(4):1103-1109
The phase structure, chemical stability, sinterability, and electrical performance of the proton‐conducting Ba(Ce,Ti)O3 solid solution with a series of acceptors M (M = In, Y, Sm) synthesized by a modified Pechini method were systematically investigated. The substitution of cerium with titanium was proved as an effective way to improve the stability of BaCeO3. Especially for the BaCe0.95Ti0.05O3?δ sample doped with In, no change in the phase was found even after treatment in the atmosphere containing both CO2 and H2O at 700°C for 10 h. Thanks to the highly sinteractive powders with particle size of ~100 nm, dense ceramics were easily acquired. Moreover, compared with the undoped BaCe0.95Ti0.05O3 sample, In, Y, and Sm dopants further improved the sinterability of the solid solution. In particular, In played a role of sintering aid and led to the largest linear shrinkage of the ceramics. As to the electrical performance, the transport properties of the samples under various atmospheres were analyzed and compared. The impedance tests demonstrated the best electrical performance of the Y‐doped samples. 相似文献
12.
A Novel Top‐Seeded Infiltration Growth Technique for Fabricating Y–Ba–Cu–O Single‐Grain Superconductor Nano‐Composites
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Top‐seed infiltration and growth technique (TSIG) is proposed to fabricate Y–Ba–Cu–O (YBCO) single‐grain superconductor nano‐composites, in which a solid source composition of nano‐Y2O3 + BaCuO2 and a liquid source composition of Y2O3 + 10BaO + 16CuO are employed. As can be seen, this novel technique uses just one source of precursor powder of BaCuO2, so it is more simplified and efficient. Microstructural observation indicates that fine Y2BaCuO5 (Y‐211) inclusions with a size from dozens of nanometers to about one hundred nanometers are successfully introduced in YBa2Cu3O7?x (Y‐123) superconducting matrix, which can act as more effective pinning centers for improving the bulk performance. Superconducting property measurement shows that, a maximum trapped field of 0.36044 T is present at the center of the sample after magnetization by a permanent magnet (B = 0.5 T). These results prove that our proposed TSIG technique is a practical method for fabricating YBCO bulk superconductor nano‐composites with high performance. 相似文献
13.
在298.15 K下,用氧弹热量计测定了稀土配合物RE[TsGlyH]3Cl3·nH2O(RE=La,Nd,Sm,Eu,Gd,Er)的恒容燃烧热-△cU,其结果依次为15 918.2,15 879.3,15 526.7,15 246.9,15 492.4,11 727.8 J/g。并据此计算出标准摩尔生成焓-△fHmθ分别为1 977.05,1 939.71,2 189.36,2 352.82,2 123.04,5 743.50 kJ/mol。这些结果为配合物的稳定性和热化学数据关系提供了实验依据。 相似文献
14.
《应用陶瓷进展》2013,112(2):128-131
AbstractThe present work investigates the dielectric properties of pyrochlore type oxides, PbRETiTaO7 (RE=Y, La, Nd, Sm, Gd, or Dy) in the low frequency region (100 kHZ–1 MHz) at temperatures between 30 and 100°C and the microwave frequency region. The 1 MHz dielectric constants (K) are in the range 43–99 and show somewhat low variation with temperature (30–100°C) as well as frequency (1 kHz to 1 MHz). The temperature coefficient of dielectric constant (TCK) over the temperature range 30–100°C is negative and varies in the range, ?72 to ?342 ppm °C?1. The dielectric constant in the microwave frequency region is in the range 23–43. Among the samples, PbGdTiTaO7 shows very good quality factor (Q×f) of 4008 in the microwave frequency region. They all have cubic pyrochlore type structure as indicated by powder X-ray diffraction patterns. The sintered microstructure shows well formed grains without much porosity. 相似文献
15.
Chunxia Chen Chenghua Xu Liangrong Feng Zijian Li Jishuan Suo Fali Qiu Yingchun Yang 《Advanced Synthesis \u0026amp; Catalysis》2005,347(14):1848-1854
The copper‐containing hydrotalcites (Cu‐HTLcs) are synthesized under microwave irradiation, the effect of rare earth elements (RE) on the synthesis of Cu‐HTLcs, wherein RE stands for rare earth elements, e.g., La, Y, Sm and Ce, is also investigated in the present work. The hydrotalcite structure of the synthesized samples is verified by XRD and FT‐IR. The results of their catalytic performances in phenol hydroxylation show that the doped rare earth elements can promote the catalytic activity of Cu‐HTLcs, exhibiting a good trend as follows: La>Y>Sm>Ce. XPS results show that the Cu+ species are produced after the interaction of La‐Cu‐HTLcs with H2O2. Combining with the catalytic test results, we propose a new mechanism about the generation of HO . radicals in phenol hydroxylation, it is assumed that HO‐Cu+‐OH species are first formed by the reduction of HO‐Cu2+‐OH located in hydrotalcites in the presence of H2O2, and then react with H2O2 to give rise to HO. radicals. 相似文献
16.
Significant Improvement of Superconducting Properties in Nano‐NiFe2O4‐Doped Y–Ba–Cu–O Single‐Grain Superconductor
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Introduction of refined second‐phase particles in superconducting YBa2Cu3O7?x (Y‐123) matrix is known to be an effective route to improve the δl‐type pinning and the performance of Y–Ba–Cu–O (YBCO) single‐grain superconductors, while the δTc‐type pinning induced by spatial fluctuations in matrix composition is also important and contributes to the in‐field Jc performance and high‐field applications of bulk superconductors. In this communication, chemical doping of nano‐sized NiFe2O4 (mean size 50 nm) in single‐grain YBCO superconductor is performed using a novel top‐seeded infiltration growth (TSIG) technique based on a solid source pellet (SSP) of nano‐Y2O3 + BaCuO2. The results indicate that, significant improvement of bulk performances including levitation force (33.93 N) and trapped field (0.3628 T) has been observed in the 0.2 wt% nano‐NiFe2O4‐doped sample, which are much higher than the undoped sample (28.81 N and 0.2754 T). Tc measurement indicates that, a decreased onset Tc of about 87.5 K and a broadened transition width of about 5 K are observed in the NiFe2O4‐doped sample, indicating appearance of weak superconducting regions in superconducting matrix caused by Ni and Fe substitutions in Y‐123 crystal lattice. This study supplies a practical approach to increase the YBCO bulk performance significantly. 相似文献
17.
Éva Ujaczki Viktória Feigl Mónika Molnár Patricia Cusack Teresa Curtin Ronan Courtney Lisa O'Donoghue Panagiotis Davris Christoph Hugi Michael WH Evangelou Efthymios Balomenos Markus Lenz 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2018,93(9):2498-2510
Since the world economy has been confronted with an increasing risk of supply shortages of critical raw materials (CRMs), there has been a major interest in identifying alternative secondary sources of CRMs. Bauxite residues from alumina production are available at a multi‐million tonnes scale worldwide. So far, attempts have been made to find alternative re‐use applications for bauxite residues, for instance in cement / pig iron production. However, bauxite residues also constitute an untapped secondary source of CRMs. Depending on their geological origin and processing protocol, bauxite residues can contain considerable amounts of valuable elements. The obvious primary consideration for CRM recovery from such residues is the economic value of the materials contained. However, there are further benefits from re‐use of bauxite residues in general, and from CRM recovery in particular. These go beyond monetary values (e.g. reduced investment / operational costs resulting from savings in disposal). For instance, benefits for the environment and health can be achieved by abatement of tailing storage as well as by reduction of emissions from conventional primary mining. Whereas certain tools (e.g. life‐cycle analysis) can be used to quantify the latter, other benefits (in particular sustained social and technological development) are harder to quantify. This review evaluates strategies of bauxite residue re‐use / recycling and identifies associated benefits beyond elemental recovery. Furthermore, methodologies to translate risks and benefits into quantifiable data are discussed. Ultimately, such quantitative data are a prerequisite for facilitating decision‐making regarding bauxite residue re‐use / recycling and a stepping stone towards developing a zero‐waste alumina production process. © 2018 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. 相似文献
18.
将过渡金属氧化物TiO2、MnO2、CuO、Cu2O、ZnO、ZrO2以及Y2O3、CeO2、Sm2O3、Gd2O3分别添加到苯酚/4,4'-二苯甲烷二胺型苯并恶嗪(BB)中间体中,制备了过渡金属氧化物/BB固化物,通过FTIR、TGA和DMA分析研究了过渡金属氧化物对苯并恶嗪热稳定性的影响。结果表明,这些氧化物的添加不改变BB固化物的化学结构;除ZnO外,其他氧化物均使BB的热稳定性和800℃残炭率降低,这是由于过渡金属氧化物与BB中N原子间配位作用的形成削弱了C—N键,使其更易断裂。 相似文献
19.
Jiuxin Jiang Peiling Wang Wanbao He Weiwu Chen Hanrui Zhuang Yibing Cheng Dongsheng Yan 《Journal of the American Ceramic Society》2004,87(4):703-705
Self-propagating high-temperature synthesis (SHS) was applied to synthesize α-SiAlON powders doped by RE (RE = Eu,Pr,Ce) and codoped by RE and yttrium. The results showed that the weight ratio of α-SiAlON to (α-SiAlON +β-SiAlON) decreased from 70%, 55%, and 25% for europium-, praseodymium-, and cerium-doped α-SiAlON compositions, respectively, and the weight percentage of α-SiAlON phase increased to 100% for both (Eu,Y) and (Pr,Y) systems and 94% for the (Ce,Y) system, indicating SHS is a promising approach for synthesizing α-SiAlONs stabilized by the cations that could not be incorporated into the α-SiAlON structure by conventional sintering methods. 相似文献
20.
Waste silicone cross‐linked polyethylene (Si‐XLPE) recycling effectively by using solid‐state shear mechanochemical (S3M) technology was investigated to make the better performance thermoplastic polyethylene. To make this thermoplastic material, the cross‐linked structures of waste Si‐XLPE that was consisted of the siloxane bonds must be de‐cross‐linked selectively instead of the destruction of the material main chains. The properties of recycled Si‐XLPE materials were investigated by gel fraction measurements, gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter, torque rheological measurements, scanning electron microscope (SEM) and thermogravimetric analyzer (TG). From the results, it could be seen that the cross‐linking bonds of the Si‐XLPE were destroyed selectively by S3M technology and the mechanochemical milling also played a significant role in improving the materials process‐ability and mechanical properties. Gel fraction measurements, GPC and FTIR showed that S3M technology could interrupt the cross‐linked structures of Si‐XLPE rather than the backbone chains by initiating the de‐cross‐linking reaction obviously; Torque rheological results further confirmed that the recycled Si‐XLPE materials gained better plastic characteristics and process‐ability after mechanochemical milling. Compared with the untreated Si‐XLPE, the tensile strength and elongation at break of Si‐XLPE samples after 10 cycles milling increased by 118.4% and 330.4%, respectively. J. VINYL ADDIT. TECHNOL., 25:149–158, 2019. © 2018 Society of Plastics Engineers 相似文献