Novel long laminar plasma sprayed hybrid structure thermal barrier coatings for high-temperature anti-sintering and volcanic ash corrosion resistance

1.Introduction The artificial-designed segmentation cracks in the ceramic layer of the thermal barrier coatings is an excellent choice by using the atmospheric plasma spray (APS) method under a low cost on the applications of aircraft engines or gas turbine engines.The residual thermal stress energy of the coatings with a certain inter-space of vertical cracks during the thermal cycling test is released through the cracks.The coating with vertical cracks was found out to be superior to other coatings with conventional lamellar structure[1].This process by using the atmospheric plasma spray method usually deposited a dense layer of YSZ (usual thickness of 0.5-1.5 mm) and heating the substrate over 773 K with an auxiliary device previously,even for a complex curved surface of the vanes.     

Facile Li-Al layered double hydroxide films on Al alloy for enhanced hydrophobicity,anti-biofouling and anti-corrosion performance

In this work,lithium (Li)-aluminum (Al) layered double hydroxide (LDH) films modified by 4-amino-2-((hydrazine methylene) amino)-4-oxobutanoic acid (denoted as AOA acid) and/or 1H,1H,2H,2H-perfluorooctyltriethoxysilane were prepared on 6N01 Al alloy by a facile,in-situ growth method with enhanced hydrophobicity,anti-biofouling and anti-corrosion performance.The preparation is low energy consumptive and environment friendly,relying on self-assembly at ambient temperature.The structure,molecular weight and functional groups of the synthesized AOA acid were characterized by NMR spectrometer,ESI-MS spectrometer and Fourier transform infrared (FT-IR) spectroscopy.And the compositions,structure and morphology of the films were characterized by Fourier transform infrared(FT-IR) spectroscopy,glancing-angle X-ray diffraction (GA-XRD),X-ray photoelectron spectroscopy (XPS),field emission scanning electron microscopy (FE-SEM) and energy-dispersive x-ray spectrum (EDS).Water contact angle measurements (CA) and atomic force microscopy (AFM) characterization show that the films possess a micro/nanostructure with an improved hydrophobicity.Immersion test,neutral salt tests (NSS) and electrochemical impedance spectroscopy (EIS) conducted in 3.5 wt.％ NaCl solutions demonstrate the improved corrosion resistance of the films over bare Al alloy.Meanwhile,the films also possess an excellent anti-bacterial property to Escherichia coli,Bacillus subtilis and sulfate-reducing bacteria.     

Early identification of process deviation based on convolutional neural network

A novel process monitoring method based on convolutional neural network(CNN) is proposed and applied to detect faults in industrial process. By utilizing the CNN algorithm, cross-correlation and autocorrelation among variables are captured to establish a prediction model for each process variable to approximate the first-principle of physical/chemical relationships among different variables under normal operating conditions. When the process is operated under pre-set operating conditions, predic...     

Attention-based long short-term memory fully convolutional network for chemical process fault diagnosis

A correct and timely fault diagnosis is important for improving the safety and reliability of chemical processes. With the advancement of big data technology, data-driven fault diagnosis methods are being extensively used and still have considerable potential. In recent years, methods based on deep neural networks have made significant breakthroughs, and fault diagnosis methods for industrial processes based on deep learning have attracted considerable research attention. Therefore, we propose a...     

Sample size adaptive strategy for time-dependent Monte Carlo particle transport simulation

When multiphysics coupling calculations contain time-dependent Monte Carlo particle transport simulations, these simulations often account for the largest part of the calculation time, which is insufferable in certain important cases. This study proposes an adaptive strategy for automatically adjusting the sample size to fulfil more reasonable simulations. This is realized based on an extension of the Shannon entropy concept and is essentially different from the popular methods in timeindependen...     

Numerical simulation of coupling heat transfer and thermal stress for spent fuel dry storage cask with different power distribution and tilt angles

Dry storage containers must be secured and reliable during long-term storage, and the effect of decay heat released from the internal spent fuel on the cask has become an important research topic. In this paper, a 3D computational fluid dynamics model is presented, and the accuracy of the calculation is verified, with computational errors of less than 6.2%. The thermal stress of the dry storage cask was estimated by coupling it with a transient temperature field. The total power remained constan...     

Design and preparation of aluminum alloy with high thermal conductivity based on CALPHAD and first-principles calculation

To obtain the aluminum alloy with high thermal and mechanical properties, the effects of alloying elements and the second phases on the thermal conductivity of Al alloys were investigated by CALPHAD and first-principles calculation, respectively. The properties of the second phases, including Young’s modulus, Poisson’s ratio and minimum thermal conductivity, were systematically studied. Results show that the ranking order of the effects of the alloying elements on the thermal conductivity is Mg>Cu>Fe>Si, and for Al-12Si alloys, the mathematical model of the relationship between the alloying elements and the thermal conductivity can be expressed as λ=ax²-bx+c when the second phase precipitates in the matrix. All kinds of ternary phases of Al-Fe-Si have higher deformation resistance, rigidity, theoretical hardness, Debye temperature and thermal conductivity than the other phases which possibly exist in the Al-12Si alloys. Based on the guidance of CALPHAD and first-principles calculation, the optimized chemical composition of Al alloy with high conductivity is Al-11.5Si-0.4Fe-0.2Mg (wt.%) with a thermal conductivity of 137.50 Wm⁻¹·K⁻¹ and a hardness of 81.3 HBW.

     

Reduction kinetics of SrFeO3−δ/CaO∙MnO nanocomposite as effective oxygen carrier for chemical looping partial oxidation of methane

Chemical looping reforming of methane is a novel and effective approach to convert methane to syngas, in which oxygen transfer is achieved by a redox material. Although lots of efforts have been made to develop high-performance redox materials, a few studies have focused on the redox kinetics. In this work, the kinetics of SrFeO_3−δ–CaO∙MnO nanocomposite reduction by methane was investigated both on a thermo-gravimetric analyzer and in a packed-bed microreactor. During the methane reduction, combustion occurs before the partial oxidation and there exists a transition between them. The weight loss due to combustion increases, but the transition region becomes less inconspicuous as the reduction temperature increased. The weight loss associated with the partial oxidation is much larger than that with combustion. The rate of weight loss related to the partial oxidation is well fitted by the Avrami–Erofeyev equation with n = 3 (A3 model) with an activation energy of 59.8 kJ∙mol^‒1. The rate law for the partial oxidation includes a solid conversion term whose expression is given by the A3 model and a methane pressure-dependent term represented by a power law. The partial oxidation is half order with respect to methane pressure. The proposed rate law could well predict the reduction kinetics; thus, it may be used to design and/or analyze a chemical looping reforming reactor.     

Afterpulse measurement of JUNO 20-inch PMTs

In this study, we present the large photomultiplier tube(PMT) afterpulse measurement results obtained from the Jiangmen underground neutrino observatory(JUNO) experiment. A total of 11 dynode-PMTs(R12860) from the Hamamatsu company(Hamamatsu Photonics K.K.(HPK)) and 150 micro-channel plate PMTs(MCP-PMTs, GDB-6201) from the NNVT company(North Night Vision Technology Co., Ltd.(NNVT)) were tested. Subsequently, an afterpulse model was built according to the afterpulse time distribution and the prob...     

Microstructure,mechanical properties and stress corrosion behavior of friction stir welded joint of Al-Mg-Si alloy extrusion

Microstructure,mechanical properties and stress corrosion behavior of friction stir welded(FSWed) AlMg-Si alloy were investigated.The average grain sizes of shoulder-affected zone(SAZ),nugget zone(NZ),heat-affected zone(HAZ) and base material(BM) are 6.03,4.80,168.30 and 127.24 μm,respectively.The thermo-mechanically affected zone(TMAZ),which is generated on the edge position between HAZ and weld nugget zone,has a narrow width of 400 μm.The ultimate tensile strength(UTS) of FSWed joint is 232.20...