采用TFA-MOD技术在LaAlO3单晶基片上制备YBa2Cu3O7-x涂层导体

三氟乙酸盐-金属有机沉积技术（TFA-MOD）是制备钇钡铜氧涂层导体的有发展前景的方法之一。采用TFA-MOD技术在铝酸镧单晶基片上制备出YBa2Cu3O7-x涂层导体，并对不同烧结温度下制备的薄膜作了分析比较，找到了较为合适的烧结温度。用X射线衍射进行了物相的定性分析，由YBCO薄膜的（103）φ扫描图谱分析了薄膜的外延生长，用原子力显微镜观察了薄膜表面形貌。结果 表明制备出的YBCO薄膜表面均匀致密、无明显裂纹、有较强的（001）衍射峰。     

Fabrication and Maglev Properties of Large Bulk Melt－Texture－Growth YBCO Superconductor

ＦａｂｒｉｃａｔｉｏｎａｎｄＭａｇｌｅｖＰｒｏｐｅｒｔｉｅｓｏｆＬａｒｇｅＢｕｌｋＭｅｌｔ－Ｔｅｘｔｕｒｅ－ＧｒｏｗｔｈＹＢＣＯＳｕｐｅｒｃｏｎｄｕｃｔｏｒＲｅｎＨｏｎｇｔａｏ（任洪涛）；ＸｉａｏＬｉｎｇ（肖玲）；ＪｉａｏＹｕｌｅｉ（焦玉磊）；Ｗａｎ...     

Effect of humidity on microstructure and properties of YBCO film prepared by TFA-MOD method

Epitaxial YBCO superconducting films were deposited on the single crystal LaAlO3. (001) substrate by metal organic deposition method. All YBCO films were fired at 820 ℃ in humidity range of 2.6%-19.7% atmosphere. Microstructure of YBCO thin films was ana-lyzed by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). Superconducting properties of YBCO films were measured by four-probe method. XRD results showed that the second phase (such as BaF2)and a-axis-oriented grains existed in the films prepared at 2.6% humidity condition; a-axis-oriented grains increased in the film prepared at higher than 4.2% humidity condition; almost pure c-axias-oriented grains existed in the films fired at 4.2% humidity condition. Morphologies of the YBCO films showed that all films had a smooth and crack-free surface. YBCO film prepared at 4.2% humidity condition showed Jc value of 3.3 MA/cm2 at 77 K in self-field.     

Fabricating Buffer Layers for YBa2Cu3Oy Coated Conductor by Surface Oxidation Epitaxy

Coated conductor of YBa2Cu3Oy(YBCO) withhighsuperconducting critical current (IC)is promisingfor many applications . To decrease weak link andlarge grain boundary angle it is i mportant to achievebiaxial textured YBCO.Sofar ,a fewtechniques havebeen appli…     

Fabrication of NiO Buffer Layer for YBCO Coated Conductors by Combining Sputtering and SOE Method

In research of YBCO coated conductors, the development of a oxide template for epitaxial growth of YBCO is very important. Matsumoto et al have demonstrated the potential of the surface oxidation epitaxial (SOE) route for formation a cube textured NiO layer on nickel tapes. The epitaxial NiO functions as a buffer layer of chemical reaction between YBCO and nickel, and as a template for the epitaxial growth of YBCO. However, the surface quality of NiO is difficult to control and defects such as crack, spall and deep grooves exist in SOE NiO layer. A new approach combining sputtering and SOE method to obtain crack-free and cube textured NiO layer were reported. Ni tapes prepared by the combination of rolling and recrystallization were used for this work. A coating of Ni was first deposited on the tapes via magnetron sputtering. Then on the coating tapes, continuous and textured NiO layer were achieved by SOE technology.     

金属基体上YSZ过渡层及YBCO薄膜结构与沉积条件的关系

研究了两种在金属基体（ＨａｓｔｅｌｏｙＣ）上沉积的、以钇稳定的ＺｒＯ２（ＹＳＺ）为过渡层的ＹＢａ２Ｃｕ３Ｏ７－ｙ薄膜结构，并讨论了结构与沉积条件的关系。当沉积速率低时，ＹＳＺ层致密、均匀，存在织构取向，且与基体连接良好；而高速率沉积的ＹＳＺ层疏松，与基体结合差。ＹＢＣＯ薄膜的结构和性能与沉积时的基体温度相关。     

Numerical analysis of interface energy-driven coarsening in thin films and its connection to grain growth

Interface energy-driven coarsening in thin films is investigated using numerical analysis of a mean field growth model. The development of preferred orientation in an initially randomly oriented film is demonstrated. The coarsening process may also lead to the development of bimodal particle size distributions, but this is shown to depend sensitively on the shape of the interface energy vs orientation function. The rate of transformation to a state of preferred orientation is dependent on quantities such as the film thickness and the ratio of the interface energy anisotropy to the particle boundary energy. We discuss the applicability of the model, which was developed to describe coarsening of islands in a discontinuous thin film, to surface or interface energy-driven grain growth in a continuous thin film.     

Effect of oxygen pressure on electrical transport properties for （110） oriented La2/3Sr1/3MnO3 films directly deposited on silicon

La2/3Sr1/3MnO3 films with(110) preferred orientation were deposited on Si(100) substrate without any buffer layer by pulsed laser deposition technique.Effect of oxygen pressure on orientation,surface morphology,and electrical transport properties were investigated.The film deposited at 10 Pa presented(110) preferred orientation with the best crystalline quality,the largest grain size,and the smallest roughness.The(110) oriented film presented higher metal-insulator transition temperature,and the lower resistivity than that of the samples without preferred orientation.     

Morphology and Growth Kinetics of Straight and Kinked Tin Whiskers

Time-lapse SEM studies of Sn whiskers were conducted to estimate growth kinetics and document whisker morphologies. For straight whiskers, growth rates of 3 to 4 microns per day were measured at room temperature. Two types of kinked whiskers were observed. For Type A kinks, the original growth segment spatial orientation remains unchanged, there are no other changes in morphology or diameter, and growth continues. For Type B kinks, the spatial orientation of the original segment changes and it appears that the whisker bends over. Whiskers with Type B kinks show changes in morphology and diameter at the base, indicating grain boundary motion in the film, which eliminates the conditions suitable for long-term whisker growth. To estimate the errors in the whisker growth measurements, a technique is presented to correct for SEM projection effects. With this technique, the actual growth angles and lengths of a large number of whiskers were collected. It was found that most whiskers grow at moderate or shallow angles with respect to the surface; few straight whiskers grow nearly normal to the surface. In addition, there is no simple correlation between growth angles and lengths for whiskers observed over an approximate 2-year period.     

Environmental fatigue crack propagation in Ti-6Al-4V sheet

A study was made of environmental fatigue crack propagation in 2.5 mm thick Ti-6A1-4V sheet conforming to AMS 4911, and 2.2 mm thick IMI 318 conforming to BS TA 10. The environments were dry argon, normal air, distilled water and 3.5 pct aqueous NaCl. There were three alloy/orientation combinations: Ti-6A1-4V L-T, IMI 318 L-T and IMI 318 T-L. Test frequencies were 30 and 50 Hz, at which there was a general trend of higher crack growth rates in the order: argon, air, distilled water, 3.5 pct aqueous NaCl. For both dry argon and 3.5 pct aqueous NaCl there were large differences in crack growth rates at low δK values between the three types of specimen. There was a correlation between the texture and cleavage fracture and crack growth rates in 3.5 pct aqueous NaCl. This result is of considerable practical importance. For dry argon the ranking of specimen types could be explained by the relative importance of mechanical and environmental crack growth, using the structure-sensitive to structure-insensitive transition concept of Irving and Beevers.     

Anisotropic Magnetoresistance of Perovskite La_(2/3)Ca_(1/3)MnO_3/YBa_2Cu_4O_8/La_(2/3)Ca_(1/3)MnO_3 Trilayer Films

Magneticanisotropyhasbeenfoundinmanyex oticmaterials,suchasmetallicsuperlatticeswithgi antmagnetoresistanceeffectsandthehightempera turesuperconductingoxideYBa2Cu3O7 δ[1～4].The anisotropycouldfindnovelusesinnewdeviceappli cations.Agoodexampleisthehig…     

Electrochemical and microstructural study of oxide films formed electrochemically at microcrystalline Al-Fe-V-Si alloys

A recent advance in metallurgical technology has been the application of rapid solidification techniques to Al alloy production. FVS0812 is the designation given to a microcrystalline Al-based alloy consisting of 8 wt% Fe, 1 wt% V and 2 wt% Si. It is a two-phase alloy, consisting of ca. 27 vol percent of approximately spherical Fe-V-Si-rich dispersoids in an essentially pure Al matrix. The high strength, low density properties of this advanced material, and other related alloys, have not yet been realized, however, due, in part, to the inability of the alloy to form a thick, adherent, abrasion-resistant outer surface oxide film, a feature readily achieved at conventional Al alloys by normal anodizing methods. The present research has involved an electro-chemical study of oxide film growth at the 812 alloy, with the specific goals being to seek an understanding of the origin of the oxide film growth problem and ultimately to propose alternative approaches to the formation of a thick, stable oxide film at this material. The techniques used in this research have included electrochemical methodologies such as cyclic voltammetry and electrochemical impedance spectroscopy. Crucial information has been obtained through transmission electron microscopy (TEM) of ultramicrotomed specimens. Experiments were carried out initially in neutral borate solutions to characterize the compact barrier oxide film formed in this environment and expected to be present beneath the porous oxide film formed in the normal sulfuric acid anodizing medium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Environmental fatigue crack propagation in Ti-6Al-4V sheet

A study was made of environmental fatigue crack propagation in 2.5 mm thick Ti-6A1-4V sheet conforming to AMS 4911, and 2.2 mm thick IMI 318 conforming to BS TA 10. The environments were dry argon, normal air, distilled water and 3.5 pct aqueous NaCl. There were three alloy/orientation combinations: Ti-6A1-4V L-T, IMI 318 L-T and IMI 318 T-L. Test frequencies were 30 and 50 Hz, at which there was a general trend of higher crack growth rates in the order: argon, air, distilled water, 3.5 pct aqueous NaCl. For both dry argon and 3.5 pct aqueous NaCl there were large differences in crack growth rates at low δK values between the three types of specimen. There was a correlation between the texture and cleavage fracture and crack growth rates in 3.5 pct aqueous NaCl. This result is of considerable practical importance. For dry argon the ranking of specimen types could be explained by the relative importance of mechanical and environmental crack growth, using the structure-sensitive to structure-insensitive transition concept of Irving and Beevers.     

Ferroelectric Thin Films and Multilayer Structures Based on Them

A brief review is presented of the results of recent research into ferroelectric films and their multilayer structures. The main attention is paid to theoretical calculation of the physical properties that characterize ferroelectric materials (electric polarization, phase transition temperature, dielectric response) in thick and thin films and their multilayer structures. Within the phenomenological theory it is shown that the main reason for a decrease in film symmetry is internal mechanical stress connected with the mismatch in lattice constants, difference in thermal expansion coefficients of the substrate and film, and also growth imperfections. These stresses lead to a change (decrease or increase) in the para-ferroelectric transition temperature that is actually observed in thick films. In thin films, where it is necessary to consider polarization gradients, a ferroelectric transition develops whose temperature depends on film thickness (thickness induced phase transition). The polarization and dielectric permittivity of films and their multilayer structures are calculated. It is demonstrated that permittivity becomes infinitely great close to the thickness induced phase transition temperature. The theory fits well with the recently observed huge dielectric permittivity and its temperature dependence in a multilayer structure of thin films of PbTiO₃ and Pb_0.72La_0.28TiO₃.     

Synthesis, characterization and thermostability of tris（2,2,6,6-tetramethyl-3,5- heptanedionato）yttrium（III）

The metal-organic chemical vapor deposition (MOCVD) technique is a promising process for high temperature superconductor YBa2Cu3O7-δ(YBCO) preparation. In this technique, the purity, evaporation characteristics and thermostability of adopted precursors will decide the quality and reproducible results of YBCO film. In the present report, tris(2,2,6,6-tetramethyl-3,5-heptanedionato)yttrium(III)(Y(TMHD)3) was synthesized by the interaction of yttrium nitrate hydrate with TMHD in methanol solution, and its structure was identified by FTIR, 1 H NMR, 13C NMR and EI-MS spectroscopy. Subsequently, the thermal property and the kinetics of decomposition were systematically investigated by non-isothermal thermogravimetric analysis methods (TGA) at different heating rates in streams of N2,and the average apparent activation energy of evaporation process was evaluated by the Ozawa, Kissinger and Friedman methods. The possible conversion function was estimated through the Coats-Redfern method to characterize the evaporation patterns and followed a phase boundary reaction mechanism by the contracting area equation with average activation energy of 88.9kJ/mol.     

Studies on Oxygen Characteristics of YBa2 Cu3 O7-x and Its Applications to Air Separation and Gas Purification

Since the discovery of high temperature supercon ductive material YBa2Cu3O7-x ( YBCO in short ),many researchers have especially studied the relation ship between superconductivity and oxygen contents inthis oxide. It was found that the supercondu…     

Orientation degree characterization of diamond etched with Ce-7%Fe alloy

An increasing {110} orientation degree behavior was observed during etching of chemical vapor deposition (CVD) diamond films by partially melting Ce-7%Fe alloys. In order to accurately investigate this phenomenon, the X-ray diffraction method was used to identify the changes in the surface crystal orientation of the diamond films etched by Ce-7%Fe alloys, and evolution of orientation along the growth direction of the un-etched diamond film was analyzed by electron backscattering diffraction (EBSD), and then the morphology of etched diamond surface was observed by scanning electron microscopy (SEM). The results showed that the {110 } orientation degree of diamond surface increased due to the anisotropy in diamond etching with Ce-7%Fe, which was verified by the etching "pit" in SEM micrographs.     

John Border Memorial Lecture. Trauma Care in Europe before and after John Border: the evolution in trauma management at the University of Hannover

The ParaSight F is a new diagnostic test for Plasmodium falciparum infections and is based on the detection of a trophozoite-derived antigen, the histidine rich protein II (HRP-II). To assess the usefulness of this test, we conducted a prospective study and analyzed 62 blood specimens from 38 patients, using thin blood films, thick blood films and the ParaSight F test. Compared to thick blood film, on samples taken before and during treatment, the ParaSight F test had 86.4% sensitivity and 100% specificity. In 31.5% of P. falciparum infected patients, parasitemia was lower than 1 parasite/1000 red blood cells, with all specimens being positive by the ParaSight F test. In 15 cases, specimens were negative by thin blood film, but were positive by thick blood film and by the ParaSight F test. Two patients had, after their treatment was started, positive results by ParaSight F and negative results by thick blood film. Cross-reactivity occurred neither with other Plasmodium species, nor in cases of severe inflammatory syndrome. Persistence of antigenemia was monitored in 14 patients receiving quinine. At day five of treatment, antigenemia persisted in seven patients. In conclusion, the ParaSight F test does not allow following up the efficacy of treatment, identifying other Plasmodium species, or assessing parasitemia. However, because this test is easy to perform and has good sensitivity and specificity, it is a useful tool in emergent context, in cases of parasitemia lower than the thin blood film threshold, and in cases morphologically difficult to decipher.     

Texture Evolution of Abnormal Grains with Post-Deposition Annealing Temperature in Nanocrystalline Cu Thin Films

We have examined the evolution of abnormal grain growth texture with increasing post-deposition annealing temperature in nanocrystalline Cu films (20 nm thick) deposited on an amorphous SiN _x (20 nm)/Si substrate. Texture is analyzed by a TEM-based orientation and phase mapping technique based on precession electron diffraction. The as-deposited film, which has an initial grain size of ~12 nm in diameter, already shows a signature of abnormal grain growth, exhibiting a bimodal grain size distribution. Texture is analyzed by calculating area fractions of major components. The overall texture of the as-deposited film is identified to be ??110??, but ??100?? grains occupy the largest fraction in the abnormally grown grain areas, followed by ??111?? grains. After annealing at 398 K, 573 K, and 773 K (125 °C, 300 °C, and 500 °C), the overall texture turns to ??112??. After annealing at 398 K (125 °C), abnormally grown grains have a major ??112?? component. The situation is similar for the film annealed at 573 K (300 °C). After annealing at 773 K (500 °C), the abnormal grain growth texture evolved into major ??111??. The ??100?? component found in the abnormal grain growth texture for the as-deposited film is clearly explained by elastic strain energy minimization and the ??111?? component for the as-deposited film and the film annealed at 773 K (500 °C) is explained by surface energy minimization. The development of the ??112?? texture obtained after annealing at 398 K and 573 K (125 °C and 300 °C) is not explained by either elastic strain energy minimization or surface energy minimization. We suggest that it is clarified by assuming that the Cu film system is perfectly elastic?Cplastic, which is associated with the Taylor factors.     

YBCO带材直流冲击特性的LM神经网络预测

柔性直流电网中的直流(DC)侧短路故障电流会严重危害电网的运行,而电阻型超导故障限流器(RSFCL)能有效地限制短路故障电流的增长,降低对直流断路器开断容量和开断时间的要求。为了研究用于RSFCL的氧化钇钡铜(YBCO)超导带材在短时直流冲击电流下的电阻特性,根据故障电流特征搭建了高压直流冲击平台,实验测量了在不同电流峰值和不同冲击时间的冲击电流下YBCO带材的电阻变化情况。详细分析了失超电阻越过拐点阻值前后的不同变化趋势并解释了其产生原因。据此,分阶段建立了基于Levenberg-Marquardt(LM)算法的多层前馈神经网络,并利用实验室获得的实验数据对网络进行训练和网络结构的优化。利用训练好的神经网络建立YBCO带材直流冲击特性预测模型。预测结果与实验结果的对比表明,基于LM神经网络的建模方法可以有效地预测直流冲击下YBCO带材失超电阻的变化。所得的预测模型可用于研究RSFCL在柔直电网中的设计与应用。