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Microstructural Aspects of Infiltration Growth YBCO Bulks with Chemical Pinning
摘要： Single grain YBa2Cu3O7-x (YBCO, Y123) bulk superconductors were prepared by infiltration growth (IG) process. The solid phase precursor was prepared by solid state synthesis from Y2O3+BaCuO2 powders. The influence of the composition of the source of melt for infiltration and the CeO2 addition on the transition temperature and critical current density was studied. It is shown that the studied samples are doped by Yb from the Yb2O3 substrate. The dependences of Yb concentration on the distance from the bottom of the samples were measured by EDS microanalysis at SEM. Correlation between the fabrication technology, level of Yb doping, microstructure and superconducting properties is discussed.
关键词： infiltration growth,chemical pinning,microstructure,YBCO bulk superconductor
更新于2025-09-23 15:22:29
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[ASME ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems - San Francisco, California, USA (Monday 27 August 2018)] ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems - Microstructural Evolution in SAC305 and SAC-Bi Solders Subjected to Mechanical Cycling
摘要： Fatigue failure of solder joints is one of the most common methods by which electronic packages fail. Electronic assemblies usually must cope with a temperature varying environment. Due to the mismatches in coefficients of thermal expansion (CTEs) of the various assembly materials, the solder joints are subjected to cyclic thermal-mechanical loading during temperature cycling. The main focus of this work is to investigate the changes in microstructure that occur in SAC305 and SAC+Bi lead free solders subjected to mechanical cycling. In this paper, we report on results for the SAC+Bi solder commonly known as SAC_Q or CYCLOMAX. Uniaxial solder specimens were prepared in glass tubes, and the outside surfaces were polished. A nanoindenter was then used to mark fixed regions on the samples for subsequent microscopy evaluation. The samples were subjected to mechanical cycling, and the microstructures of the selected fixed regions were recorded after various durations of cycling using Scanning Electron Microscopy (SEM). Using the recorded images, it was observed that the cycling induced damage consisted primarily of small intergranular cracks forming along the subgrain boundaries within dendrites. These cracks continued to grow as the cycling continued, resulting in a weakening of the dendrite structure, and eventually to the formation of large transgranular cracks. The distribution and size of the intermetallic particles in the inter-dendritic regions were observed to remain essentially unchanged.
关键词： Bismuth,Microstructure,SAC Alloy,Hysteresis,Evolution,Lead Free Solder,Cyclic Stress-Strain Curve
更新于2025-09-23 15:22:29
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High-Temperature Filter Based on Silicon Carbide for Aggressive Fluids and Gases
摘要： In this paper, we developed a production method for items based on mesh silicon carbide that are suitable for cleaning aggressive fluids, melts, and gases from foreign inclusions at high operating temperatures. The resulting products can also be used for filtering fuel mixtures.
关键词： carbon fibers,silicization,silicon carbide,microstructure,composite filter
更新于2025-09-23 15:22:29
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The microstructure and optical property of Na-doped ZnO system by sol-gel method
摘要： Pure and Na-doped ZnO (2 at.%, 5 at.% and 10 at.%) films are synthesized by sol-gel method and annealed at 500 °C for 4 h. The as-synthesized nanoparticles are characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDS). The samples exhibited hexagonal ZnO lattice structure and another Na2O2 phase was detected in the 5 at.% Na-doped ZnO sample. The calculated average crystalline size increases from 42.0 nm to 43.5 nm when Na content increased from 0 to 10 at.%. FESEM and TEM analysis identifies that the average size of the Na-doped ZnO nanoparticles lies in between 50 nm and they appear in spheroid-like or rod-like shape. The transmittance of the sample was above 80% and the results of photocatalytic activity show that Na-doped ZnO nanoparticles exhibit higher photodegradation activity (about 91%) than pure ZnO nanoparticles under UV irradiation.
关键词： microstructure,Na-doped,photocatalytic activity.,transparent property,ZnO
更新于2025-09-23 15:22:29
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Boosted thermoelectric properties of molybdenum oxide thin films deposited on Si substrates
摘要： MoO2+x has novel peculiarities and complexities due to multiple valence states of 4d molybdenum, but high carrier density impedes its thermoelectric (TE) application. Recent investigation has demonstrated that the TE performance of transition metal oxide films can be greatly enhanced by activating a parallel conduction channel in the perovskite substrates through reversible incorporation of oxygen. In this work, we report the TE properties of MoO2+x thin films deposited on single crystalline Si and quartz glass substrates by magnetron sputtering. The TE power factor (PF) in the former is above 40 times bigger than that in the latter. Such a large enhancement originates mainly from the significantly enhanced Seebeck coefficient, correlated with the contribution of the Si substrate. The highest PF value 1.78 mW/(m · K2) at 700 K in this MoO2+x/Si system is comparable to the state-of-the-art in other TE thin films. Based on the preceding research, our experimental results suggest a more economic and scalable route to explore high-performance TE thin films.
关键词： thermoelectric,thin films,microstructure,Oxide materials
更新于2025-09-23 15:22:29
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Assessing the Condition of Gas Turbine Rotor Blades with the Optoelectronic and Thermographic Methods
摘要： Gas turbines and their blades in particular might be damaged in the course of the aviation turbojet engine operation process. The degradation process of the blade microstructure is most evident from the change in the colour of its surface. This is assessed using the optoelectronic method. The article presents the concept of non-destructive methods, which are used to assess the degree of degradation of the alloy of a gas turbine blade. The proposed optoelectronic method is the basic method for the preliminary determination of color changes in the surface. Appropriate videoscopes or video-analyzers, capable of recording a test object in various electromagnetic wave ranges (infrared radiation, visible range), are used for this purpose. These preliminary results of the diagnosis make it possible to infer further studies of the blade. For accurate investigation of the state of the alloy microstructure, a non-destructive thermographic method (xenon flash pulsed thermography) was used. The results of studies of the degradation of the microstructure with the use of non-destructive methods were verified through the use of metallographic investigations. Appropriate metallographic specimens were created in order to recognize phase γ' degradation (i.e., the phase strengthening the blade alloy). The results of the presented research allowed for an in-depth assessment of the degree of microstructure degradation of operated blades.
关键词： impulse thermography,Turbine blade,digital image,microstructure degradation
更新于2025-09-23 15:22:29
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Structure and multiferroic properties of ternary (1?x)(0.8BiFeO3-0.2BaTiO3)-xK0.5Na0.5NbO3 (0?≤?x?≤?0.5) solid solutions
摘要： The ternary (1?x)(0.8BiFeO3-0.2BaTiO3)-xK0.5Na0.5NbO3 (0 ≤ x ≤ 0.5) solid solutions have been successfully synthesized by a solid-state reaction route. X-ray diffraction and Rietveld refinement studies reveal the phase transition from the rhombohedral and tetragonal phases to the single tetragonal phase with x increasing. The average grain size decreases initially and then increases as x increases, whereas the remnant magnetization shows an opposite trend and reaches the maximum value of ~2.09 emu/g at x = 0.3. An enhanced remnant polarization of ~8.6 μC/cm2 appears at x = 0.3 due to the structure distortion and the decrement of defects. Moreover, the remanent polarization and the relative permittivity reach the maximum value of ~20.14 μC/cm2 (10 Hz) and ~644 (1 kHz) at x = 0.5, respectively, and the corresponding dielectric loss decreases to the lowest value of ~0.022 (1 kHz). These results indicate that the properties of ternary BFO-BTO-KNN solid solutions can be modulated by adjusting the K0.5Na0.5NbO3 content to adapt to different application needs.
关键词： Microstructure,Dielectric loss,Phase transition,Multiferroic properties
更新于2025-09-23 15:22:29
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Microstructure and Characteristic of Biomedical Titanium Alloy Based on Picosecond Laser Micromachining
摘要： Laser micromachining has become a hotspot in recent years due to its high precision, non-contact and adjustable parameter. In this paper, TC4 titanium alloy implant samples were conducted to obtain specific surface textures through picosecond laser. The laser parameters which directly influenced the microstructure and characteristic of surface textures were optimized within the context of laser power, scanning speed and scanning number via response surface methodology. The microstructure was evaluated using scanning electron microscope (SEM) while the feature size of the surface textures was measured through surface 3D profiler. In addition, endothelial cell culture was conducted to investigate the biofunctionalization of samples with specific surface textures. It demonstrated that well-structured textures played an important role in promoting cell adhesion and proliferation for titanium alloy implants.
关键词： Picosecond laser micromachining,Microstructure,Biofunctionalization,Titanium alloy
更新于2025-09-23 15:22:29
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Influence of C2H2 Flows on Microstructure and Corrosion Resistance of TiCN Films Doped with Carbon Atoms
摘要： Nanosized TiCN/TiN films were deposited on AZ31 by reactive magnetron sputtering under different acetylene flows. The microstructures of obtained films were characterized, and their corrosion behaviors were also investigated. The films doped with carbon atoms under different acetylene flows own different structures and grain sizes. The grain size decreased to some extent, and the film structure changed from polycrystalline to nanocrystalline, with an increase of C2H2 flow. The surface morphology also changed from rough to smooth, with an increase of C2H2 flow. The Tafel curves and electrochemical impedance spectroscopy (EIS) demonstrated that the composite films could greatly improve the corrosion resistance of bare substrates in a 3.5% NaCl solution, and the films' corrosion resistance is different, owing to their different structures and grain sizes.
关键词： acetylene flows,ceramic coatings,microstructure,vacuum,corrosion behavior
更新于2025-09-23 15:22:29
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Optical and magneto-optical properties of Nd0.1La0.1Y1.8O3 transparent ceramics
摘要： Transparent ceramics in the form of yttrium oxide (Y2O3) doped with La and Nd and pure yttrium as a reference material were successfully prepared via modified sol-gel processes and hot isostatic pressure sintering. Their structure and microstructure were examined by means of scanning electron microscopy and X-ray diffraction, which revealed the high density and single-phase character of these materials. Their optical and magneto-optical properties were also analyzed. Emission spectra of Nd0.1La0.1Y1.8O3 after excitation performed with a continuous 808 nm laser beam showed strong and sharp emission lines. The luminescence lifetime was also investigated. The doped material exhibited a high Verdet constant of over 1000 deg/T?m. The figure of merit was calculated in the VIS spectrum. The investigated transparent oxide ceramics can be considered a promising material for application in lasers and magneto-optical devices.
关键词： Y2O3,Verdet constant,Optical properties,Luminescence,Microstructure,Transparent ceramics
更新于2025-09-23 15:22:29