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21.
为了研究冻融循环作用下BFRP筋与混凝土黏结强度,对不同冻融次数(0、10、20、40次)和不同混凝土强度等级(C30、C35、C40)共36个试件进行冻融循环试验和中心拉拔试验。试验结果表明:未经冻融循环的试件和冻融循环40次(C30)试件发生拔出破坏,其余冻融试件均发生劈裂破坏;随着混凝土强度等级提高,脱胶强度和黏结强度逐渐增加;随着冻融循环次数增加,BFRP筋与混凝土的黏结强度和峰值滑移呈现出先增加后减小的趋势,而脱胶强度随冻融循环次数增加逐渐减小。 相似文献
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Bin Du Chao He Junjie Qian Ping Hu Xuan Wang Mei Cai Anze Shui 《International Journal of Applied Ceramic Technology》2020,17(4):1785-1789
In this work, high-purity HfSi2 powders were successfully fabricated via a molten salt-assisted magnesium thermal reduction method using HfO2 and Si as raw materials. The effects of reaction temperature and time on the formation of HfSi2 were systemically investigated. The morphological and phase composition of as-prepared HfSi2 powders were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and nitrogen/oxygen determinator. The results indicated that as-obtained HfSi2 powders possess the orthorhombic structure with approximately 6.4 μm in size and the oxygen content as low as 0.20%. This work can provide a novel route to fabricate the high-purity transition metal silicides powders. 相似文献
24.
《Journal of Nuclear Science and Technology》2013,50(9):933-943
The accurate estimation of reactor physics parameters related to the presence of cruciform absorber blades in boiling water reactors (BWRs) is important for safety assessment and for achieving flexible operation during the cycle. Characteristics that are affected significantly include distributions of the total fission (Ftot) and 238Ucapture (C8) rates for controlled regions. Representative experimental investigations have been performed in the framework of the LWR-PROTEUS programme. In particular, the LWRPROTEUS I-2A experiments concerned the neutronics characterisation of a SVEA-96+ BWR assembly controlled with a hafnium (Hf) blade under full-density water moderation conditions. The current paper presents the comparisons of the measured Ftot and C8 pin-wise distributions with a variety of stochastic and deterministic calculations: (a) MCNPX2.5 using recent nuclear data libraries (JEFF-3.1, ENDF/BVI. 8, and JENDL-3.3), (b) PHOENIX4 using ENDF/B-VI.3, (c) BOXER using JEF-1, (d) CASMO4 using JEF-2.2, and (e) HELIOS1.6 using ENDF/B-VI.1. The calculation/experiment comparisons show standard deviations from 1.2% (MCNPX2.5) up to 1.9% (BOXER) for the prediction of the Ftot distribution, the highest individual discrepancy (7.6% with BOXER) being seen close to the “Hf-vertex.” The C8 comparisons show systematically better agreement than those of Ftot, the lowest standard deviations being 1.0% (BOXER) and the highest only 1.4% (HELIOS). In addition, sensitivity studies highlight the greater importance of modelling aspects, compared with that of nuclear data libraries, for the achievement of satisfactory and validated Ftot and C8 predictions. 相似文献
25.
介绍了长螺旋成孔振捣插筋后压浆工艺,该工艺是在长螺旋成孔工法的基础上增加了振捣插筋和孔底注浆两个重要环节.这种不同工艺的组合通过试验大幅度提高了单桩承载力和变形要求,并使桩身强度得到了极大的利用,该工艺具有良好的应用价值和使用前景. 相似文献
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Among the large family of metal-organic frameworks (MOFs), Hf-based MOFs are foreseen as promising materials for practical applications due to their exceptional characteristics such as rich structure versatility and outstanding stability. This review discusses catalytic applications of Hf-MOFs since their development in 2012, and are summarized according to the location of the active site: at the hafnium node, at the linker or as a single-site chemical entity located at the hafnium node after post-synthetic functionalization. Special emphasis is made to synthetic preparation methods and catalytic performance. 相似文献
28.
K. A. Unocic J. Bergholz T. Huang D. Naumenko R. Vaßen 《Energy Materials: Materials Science and Engineering for Energy Systems》2018,13(1):108-119
To fabricate oxide dispersion strengthened bond coatings, commercial Co–30wt-%Ni–20Cr–8Al–0?4Y powder was milled with 2% additions of Al2O3, Y2O3 or Y2O3 + HfO2. Low-pressure plasma sprayed, free-standing specimens were oxidised in air + 10%H2O at 1100 °C both isothermally (100 h) and in 500, 1?h cycles. Dry air cyclic testing conducted at both ORNL and FZJ showed remarkably similar results. In general, the water vapour addition caused more scale spallation. Two LPPS specimens without oxide additions were tested for comparison. The specimens with 2%Al2O3 addition exhibited the best behaviour as the powder already contained 0?4%Y. Additions of 2%Y2O3 and especially 1%Y2O3 + 1%HfO2 resulted in over-doping as evidenced by high mass gains and the formation of Y- and Hf-rich pegs. Scanning transmission electron microscopy of the isothermal specimens showed no Hf and/or Y segregation to the alumina scale grain boundaries in the over-doped specimens. 相似文献
29.
Ling Yun Wang 《分离科学与技术》2016,51(5):759-766
Hafnium can be selectively extracted over zirconium from strong sulfuric acid solutions by D2EHPA or PC 88A. Solvent extraction experiments have been performed to identify the reaction of Hf from strong sulfuric acid solutions (1 to 7 M) by these two extractants. Hafnium extraction was gradually decreased and then increased again with the increase of sulfuric acid concentration. By applying a slope method, the extracted Hf species was proposed to be HfA4·(HA)2 by D2EHPA and Hf(HSO4)2A2·(HA)2 by PC 88A, respectively. This difference in the nature of the extracted species was verified by FT-IR spectra. 相似文献
30.
Due to their different mechanical properties, cracking and deformability behaviour of FRP reinforced concrete (FRP RC) members is quite different from traditional steel reinforced concrete (SRC) having great incidence on their serviceability design. This paper presents and discusses the results of an experimental programme concerning concrete tension members reinforced with glass fibre reinforced polymer (GFRP) bars. The main aim of the study is to evaluate the response of GFRP reinforced concrete (GFRP RC) tension members in terms of cracking and deformations. The results show the dependence of load-deformation response and crack spacing on the reinforcement ratio. The experimental results are compared to prediction models from codes and guidelines (ACI and Eurocode 2) and the suitability of the different approaches for predicting the behaviour of tensile members is analysed and discussed. 相似文献