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1.
Tao Li Zehui Du Nobumichi Tamura Mao Ye Saikumar Inguva Wei Lu Xierong Zeng Shanming Ke Haitao Huang 《Journal of the European Ceramic Society》2018,38(4):1488-1497
(1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 ((1-x)PZN-xPT in short) is one of the most important piezoelectric materials. In this work, we extensively investigated (1-x)PZN-xPT (x = 0.07–0.11) ferroelectric single crystals using in-situ synchrotron μXRD, complemented by TEM and PFM, to correlate microstructures with phase transitions. The results reveal that (i) at 25 °C, the equilibrium state of (1-x)PZN-xPT is a metastable orthorhombic phase for x = 0.07 and 0.08, while it shows coexistence of orthorhombic and tetragonal phases for x = 0.09 and x = 0.11, with all ferroelectric phases accompanied by ferroelastic domains; (ii) upon heating, the phase transformation in x = 0.07 is Orthorhombic → Monoclinic → Tetragonal → Cubic. The coexistence of ferroelectric tetragonal and paraelectric cubic phases was in-situ observed in x = 0.08 above Curie temperature (TC), and (iii) phase transition can be explained by the evolution of the ferroelectric and ferroelastic domains. These results disclose that (1-x)PZN-xPT are in an unstable regime, which is possible factor for its anomalous dielectric response and high piezoelectric coefficient. 相似文献
2.
The characteristics of a rotating stall of an impeller and diffuser and the evolution of a vortex generated at the diffuser leading-edge (i.e., the leading-edge vortex (LEV)) in a centrifugal compressor were investigated by experiments and numerical analysis. The results of the experiments revealed that both the impeller and diffuser rotating stalls occurred at 55 and 25 Hz during off-design flow operation. For both, stall cells existed only on the shroud side of the flow passages, which is very close to the source location of the LEV. According to the CFD results, the LEV is made up of multiple vortices. The LEV is a combination of a separated vortex near the leading- edge and a longitudinal vortex generated by the extended tip-leakage flow from the impeller. Therefore, the LEV is generated by the accumulation of vorticity caused by the velocity gradient of the impeller discharge flow. In partial-flow operation, the spanwise extent and the position of the LEV origin are temporarily transmuted. The LEV develops with a drop in the velocity in the diffuser passage and forms a significant blockage within the diffuser passage. Therefore, the LEV may be regarded as being one of the causes of a diffuser stall in a centrifugal compressor. 相似文献
3.
Satoshi Hasegawa Tetsunari Ebina Haruaki Tokuda Tatsuya Ito Nobumichi Nagano 《Journal of Nuclear Science and Technology》2016,53(9):1332-1341
The oxidation behavior of chromium and the corrosion behavior of austenitic stainless steel in boiling nitric acid solution containing highly concentrated nitrates were investigated using UV-visible spectroscopic measurements, Raman spectral measurements, immersion tests, and potentiodynamic polarization measurements. The oxidation rate measurement of chromium from Cr(III) to Cr(VI) was performed by 1 M boiling nitric acid solution containing each highly concentrated nitrates: Al(NO3)3, Nd(NO3)3, Ca(NO3)2, Mg(NO3)2, and NaNO3 as a simulant of uranium nitrate in uranium concentrator in reprocessing plants. As a result, the rate of chromium oxidation was different depending on the added nitrates even at the same nitric acid concentration. In addition, the oxidation rate of chromium was increased with increasing the calculated partial pressure of nitric acid in consideration of the hydration of cation of nitrates. Furthermore, the corrosion rate of type 310 stainless steel was accelerated by the solution having a high chromium oxidation rate containing nitrates. These results indicated that the acceleration of the corrosion rate in the solutions depending on the oxidation rate of chromium, and the rate is affected by the salt-effect of nitrates. 相似文献
4.
K. HANADA H. ZUSHI H. IDEI K. NAKAMURA M. ISHIGURO S. TASHIMA E. I. KALINNIKOVA M. SAKAMOTO M. HASEGAWA A. FUJISAWA A. HIGASHIJIMA S. KAWASAKI H. NAKASHIMA H. LIU O. MITARAI T. MAEKAWA 《等离子体科学和技术》2011,13(3):307-311
Both start-up and sustainment of plasma were successfully achieved by fully non-inductive current drive using microwave with a frequency of 8.2 GHz. Plasmas current of 15 kA was implemented for 1 s. Magnetic surface reconstruction exhibited a plasma shape with an aspect ratio of below 1.5. The plasma current was dependent significantly on the launchen microwave power and vertical magnetic field, whiile not affected by the mode of launched wave and the toroidal refractive index. Hard X-ray (HXR) emitted from energetic electrons accelerated by the microwave was observed, and the discharge with a plasma current over 4 kA followed the same trend as the number of photons of 10 to 12 keV. This suggests that the plasma current may be driven by energetic electrons. Based on the experimental conditions, alternative explanations of how the plasma current could be driven are discussed. 相似文献
5.
Tze‐Bin Song Zhenghao Yuan Megumi Mori Faizan Motiwala Gideon Segev Eloïse Masquelier Camelia V. Stan Jonathan L. Slack Nobumichi Tamura Carolin M. Sutter‐Fella 《Advanced functional materials》2020,30(6)
The exploration of the synthetic space of halide perovskites hinges on an enormous number of parameters requiring time‐consuming experimentation to decouple and optimize. Here, the formation of the prototype material CH3NH3PbI3 (MAPbI3) is investigated at different time and length scales using multimodal in situ measurements to monitor the evolution of crystalline phases, morphology, and photoluminescence as a function of the lead precursors. Kinetically fast formation of crystalline precursor phases already during the spin‐coat deposition is observed using lead iodide (PbI2) or lead chloride (PbCl2) routes. These precursor phases most likely template final MAPbI3 film morphology. In particular, the emergence of the “needle‐like” structure is shown to appear before film annealing. In situ photoluminescence measurements suggest nanoscale nucleation followed by rapid nuclei densification and growth. Using this multimodal in situ approach, different formation pathways can be identified either via precursor phases in the PbI2 and PbCl2 routes or direct perovskite formation from molecular building blocks as observed in the lead acetate (PbAc2) route. Correlation of in situ results with photovoltaic device performance demonstrates the power of in situ multimodal techniques, paves the way to a fast screening of synthetic parameters, and ultimately leads to controlled synthetic procedures that yield high‐efficiency devices. 相似文献
6.
Rafting-Enabled Recovery Avoids Recrystallization in 3D-Printing-Repaired Single-Crystal Superalloys
Kai Chen Runqiu Huang Yao Li Sicong Lin Wenxin Zhu Nobumichi Tamura Ju Li Zhi-Wei Shan Evan Ma 《Advanced materials (Deerfield Beach, Fla.)》2020,32(12):1907164
The repair of damaged Ni-based superalloy single-crystal turbine blades has been a long-standing challenge. Additive manufacturing by an electron beam is promising to this end, but there is a formidable obstacle: either the residual stress and γ/γ ′ microstructure in the single-crystalline fusion zone after e-beam melting are unacceptable (e.g., prone to cracking), or, after solutionizing heat treatment, recrystallization occurs, bringing forth new grains that degrade the high-temperature creep properties. Here, a post-3D printing recovery protocol is designed that eliminates the driving force for recrystallization, namely, the stored energy associated with the high retained dislocation density, prior to standard solution treatment and aging. The post-electron-beam-melting, pre-solutionizing recovery via sub-solvus annealing is rendered possible by the rafting (i.e., directional coarsening) of γ ′ particles that facilitates dislocation rearrangement and annihilation. The rafted microstructure is removed in subsequent solution treatment, leaving behind a damage-free and residual-stress-free single crystal with uniform γ ′ precipitates indistinguishable from the rest of the turbine blade. This discovery offers a practical means to keep 3D-printed single crystals from cracking due to unrelieved residual stress, or stress-relieved but recrystallizing into a polycrystalline microstructure, paving the way for additive manufacturing to repair, restore, and reshape any superalloy single-crystal product. 相似文献
7.
Two examples of the use of vortex control to reduce noise and enhance the stable operating range of a centrifugal compressor are presented in this paper.In the case of high-flow operation of a centrifugal compressor with a vaned diffuser,a discrete frequency noise induced by interaction between the impeller-discharge flow and the diffuser vane,which appears most notably in the power spectra of the radiated noise,can be reduced using a tapered diffuser vane(TDV) without affecting the performance of the compressor.Twin longitudinal vortices produced by leakage flow passing through the tapered portion of the diffuser vane induce secondary flow in the direction of the blade surface and prevent flow separation from the leading edge of the diffuser.The use of a TDV can effectively reduce both the discrete frequency noise generated by the interaction between the impeller-discharge flow and the diffuser surface and the broadband turbulent noise component.In the case of low-flow operation,a leading-edge vortex(LEV) that forms on the shroud side of the suction surface near the leading edge of the diffuser increases significantly in size and blocks flow in the diffuser passage.The formation of an LEV may adversely affect the performance of the compressor and may cause the diffuser to stall.Using a one-side tapered diffuser vane to suppress the evolution of an LEV,the stable operating range of the compressor can be increased by more than 12 percent,and the pressure-rise characteristics of the compressor can be improved.The results of a supplementary examination of the structure and unsteady behavior of LEVs,conducted by means of detailed numerical simulations,are also presented. 相似文献
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9.
Michael J. Burek Arief Suriadi BudimanZeinab Jahed Nobumichi TamuraMartin Kunz Sumin JinSeung Min J. Han Gyuhyon LeeColin Zamecnik Ting Y. Tsui 《Materials Science and Engineering: A》2011,528(18):5822-5832
Vertically aligned, cylindrical tin nanopillars have been fabricated via an electron beam lithography and electroplating method. Characterization by a non-destructive synchrotron X-ray microdiffraction (μSXRD) technique revealed that the tin nanostructures are body-centered tetragonal and are likely single-crystalline, or consist of a few large grains. The mechanical properties of tin nanopillars with average diameters of 920 nm, 560 nm, and 350 nm were studied by uniaxial compression in a nanoindenter outfitted with a flat punch diamond tip. The results of compression tests reveal strain rate sensitivity for nanoscale tin deformation, which matches closely to the previously reported bulk tin values. However, unlike bulk, tin nanopillars exhibit size-dependent flow stresses where smaller diameter specimens exhibit greater attained strengths. The observed size-dependence matches closely to that previously reported for single-crystalline face centered cubic metals at the nanoscale. μSXRD data was used to compare the dislocation density between as-fabricated and deformed tin nanopillars. Results of this comparison suggest that there is no measurable accumulation of dislocations within deformed tin nanopillars. 相似文献
10.
The optimum dose of gamma radiation–heavy doses to low wear polyethylene in total hip prostheses 总被引:1,自引:0,他引:1
Oonishi H Kuno M Tsuji E Fujisawa A 《Journal of materials science. Materials in medicine》1997,8(1):11-18
Wear volume, surface area and coefficient of friction of UHMWPE cup crosslinked with gamma radiation of 0, 50, 75, 100, 125, 150 and 200 Mrad sliding against an alumina ball were measured using a sphere-on-flat reciprocating type tribology testing machine. The effects of gamma radiation were scarcely observed in coefficient of friction. The coefficient of friction under lubricated (distilled water) and non-lubricated testing conditions was 0.08 to 0.12 and 0.20 to 0.25, respectively. The wear volume of UHMWPE with radiation of 50 Mrad, 75 to 150 Mrad, and 200 Mrad was 70 to 80%, 18 to 25%, and 12 to 15%, respectively, in comparison to non-irradiated specimens. Elongation and tensile strength of UHMWPE with radiation of 100 Mrad decreased to 6%, and 50% of that without radiation, respectively. The hardness increased with increase of the radiation dose. From several kinds of tribological findings, mechanical strength tests, and studies of long-term clinical findings, it is concluded that approximately 200 Mrad is the optimum dose of gamma radiation for clinical use in total hip prostheses. 相似文献