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71.
The kinetics of lath martensite formation in Fe–17·3 wt-%Cr–7·1 wt-%Ni–1·1 wt-%Al–0·08 wt-%C stainless steel was investigated with magnetometry and microscopy. Lath martensite forms during cooling, heating and isothermally. For the first time, it is shown by magnetometry during extremely slow isochronal cooling that transformation rate maxima occur, which are interrupted by virtually transformation free temperature regions. Microscopy confirms martensite formation after athermal nucleation of clusters followed by their time dependent growth. The observations are interpreted in terms of time dependent autocatalytic lath martensite formation followed by mechanical stabilisation of austenite during the transformation process. 相似文献
72.
《Intermetallics》2015
The stability of a Co-based alloy designed to possess a microstructure comprising of L12, γ′ Co3Ti-type precipitates embedded in an A1, γ Co solid solution matrix has been investigated. The alloy showed acute microstructural instabilities upon ageing at 700 °C, resulting in the degeneration of the γ-γ′ aggregate into i) a faulted Co-based martensite and Co3Ti and ii) a lamellar aggregate of A3-Co and Co3Ti. The faulted Co-based phase was formed by isothermal diffusionless transformation of the metastable A1-phase, whilst the lamellar aggregate was a discontinuous reaction product. 相似文献
73.
《Intermetallics》2015
Pre-martensitic phenomena such as abnormal resistivity growth, diffusion scattering, “tweed” contrast and internal friction peak were observed in Ti40.7Hf9.5Ni44.8Cu5 alloy prior to the forward martensitic transformation on cooling. It was shown that all the observed phenomena were due to the formation of quasi-static strain nanodomains in the B2 phase prior to the forward martensitic transformation. This led to accumulation of the elastic energy before the phase transition and resulted in the variation in thermodynamic balance for the forward martensitic transformation and, as a result, influenced the parameters of the phase transition. The appearance of elastic energy prior to the forward transformation caused a decrease in the forward and reverse martensitic transformations' start temperatures, a widening of the temperature range of the reverse transformation and an increase in the hysteresis of the transformation. 相似文献
74.
介绍了一种基于高性能浮点DSP芯片TMS320C32、CPLD芯片XC95288和A/D采样芯片AD976组成的多路采集系统的工作原理以及设计方法。通过对第一路施加特殊的电压量,在CCS开发环境下读取采样缓冲区的值,并利用Matlab对采样数据进行了全波傅氏变换。此外,该系统已在继电保护中得到广泛应用,实践表明,该系统能较好地解决多路模拟量的采集,并确保了采样数据的安全可靠性。 相似文献
75.
《Ceramics International》2020,46(8):11776-11785
Nano-crystalline CeO2 was synthesized via the urea-hydrothermal method without templates or structure-directing agents. The synthesis parameters Ce3+ to Ce4+ and urea to cation molar ratios, reaction temperature and reaction time were varied to analyze their effect on morphology, texture and reducibility. The analysis of the obtained morphologies provides strong evidence of a hierarchical and sequential template-free self-assembly process that evolves from shuttles to dumbbells to spheres. In all cases, the morphology of samples remains unchanged even after calcination at 500 °C. The presence of Ce4+ in the initial solution clearly provides the full self-assembly sequence and is decisive for obtaining non-hollow spheres of CeO2 with high specific surface area and high pore volume. Besides, if only Ce3+ is present, typical CeOHCO3 shuttle-like particles with orthorhombic structure are obtained. The use of Ce3+ in combination with Ce4+ produces partial sequences of the self-assembly process that provide a strong indication of the hierarchical sequence.The urea to cation molar ratio controls the nucleation process and proves to be crucial to obtain the self-assembly sequence. On the other hand, temperature and reaction time show a moderate effect on morphology. 相似文献
76.
Andrea Luca Tasca Eleonora Stefanelli Anna Maria Raspolli Galletti Riccardo Gori Gemma Mannarino Sandra Vitolo Monica Puccini 《化学工程与技术》2020,43(12):2382-2392
Hydrothermal carbonization of sewage sludge was carried out with the aim to evaluate the influence of process severity and initial solid content. Response surface methodology was applied to model yield and C yield responses. Enhanced dewaterability performance was recorded under mild processing conditions. The treatment promoted concentration and immobilization of Pb, Cd, Ni, Zn, and Cu. Variation of the solid content showed a stronger influence than severity on average yield and C yield. Higher heating values (HHVs) and energy retention efficiencies (EREs) of hydrochars obtained at the lowest solid content displayed the lowest values. Hence, the energy requirements of a first dewatering step should be compared with the related improvement in terms of HHV and ERE when sludge is used as feedstock. 相似文献
77.
《International Journal of Hydrogen Energy》2020,45(4):2709-2719
In this study highly oriented, rutile phase one dimensional Titania nanorod array (TiO2 NRA) modified by gadolinium doping were synthesized on the conductive glass substrate (FTO) by the hydrothermal method. The effect of Gd doping on the photoelectrochemical performance of TiO2 NRA was investigated. Crystal phase, structural, morphological and composition characteristics of these synthesized photoelectrodes were analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), and atomic force microscopy (AFM). FE-SEM images clearly show that some of the Gd dopant is uniformly distributed on the surface of TiO2 NRA in the form Gadolinia (Gd2O3) microsphere. These gadolinia microsphere play an important role in reducing the surface recombination of electron and hole supported by photoluminescence's studies. Linear sweep voltammetry results show that Gd doping results in a two-fold increase in photocurrent density as compared to pristine TiO2 NRA. UV–visible spectra, and Mott-Schotty measurements show that Gd doping shift the flat-band potential of TiO2 NRA more toward negative potential that results in effective charge separation and transportation in the Gd doped TiO2 NRA (Gd@TiO2 NRA). Applied biased photon to current efficiency (ABPE) equation was used to find solar to hydrogen efficiency (STH). Gd@TiO2 NRA show optimum conversion efficiency of ~0.64% at 0.03 V vs Ag/AgCl, while pristine TiO2 NRA display ~0.33% at −0.21 V vs Ag/AgCl. 相似文献
78.
《Journal of the European Ceramic Society》2020,40(3):672-681
Promising piezoelectric properties have been reported in potassium sodium niobate-based ceramics by introducing Bi0.5(Na0.82K0.18)0.5ZrO3 (BNKZ) into K0.48Na0.52Nb0.95Sb0.05O3 (KNNS) solid solutions in order to control the polymorphic phase transformation temperatures. In the present study, synchrotron x-ray powder diffraction (SXPD) was employed in combination with dielectric and ferroelectric measurements in order to clarify the influence of BNKZ on the phase transition temperatures of (1-x)KNNS-(x)BNKZ ceramics (with x = 0 to 0.05). The results, presented in terms of temperature-dependent SXPD patterns, dielectric permittivity and thermal depolarisation characteristics, confirmed that polymorphic phase transformation temperatures all shifted in a systematic manner with increasing BNKZ content. Broadening of the phase transition regions was also observed with increasing BNKZ content, leading to improvements in thermal stability of the ferroelectric properties. Microstructural examination of the KNNS-BNKZ ceramics revealed the presence of core-shell microstructures; this was correlated with the presence of weak shoulders on the diffraction peaks. 相似文献
79.
在社会转型期,面对日益激烈的市场竞争环境,如何制定民办高效发战战略,引导民办高效的可持续发展,是关系到民办高校兴衰的关键。本文主要从民办高校品牌战略入手,对社会转型及高等教育转型进行论述,并对如何加强民办高校品牌建设进行探讨。 相似文献
80.