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The niobium doping perovskite has been used in anode materials of solid oxide fuel cell. The electronic properties and structural stability of LaFeO3 (LFO) oxide by Nb-doping and the adsorption of H2 molecule at the clean and Nb-doped LFO (001) surface are investigated by theoretical calculations. The calculated results reveal that the band gap of the orthorhombic LFO is 2.04 eV and the gap disappears after the Nb-doping, which improves the electrical conductivity. The Nb-doping increases the formation energy of oxygen vacancy in orthorhombic LFO. The calculated results of binding energy and formation enthalpy imply that the structural stability is strengthened after Nb-doping, which provides a theoretical explanation for recent experimental observations. This result can be attributed to the change of electronic structure after the Nb-doping. The bond mechanisms for LFO and Nb-doped LFO are obtained by analyzing density of states, Mulliken charges and bond population. Based on adsorption properties, it can be found that the adsorption of H2 molecule is slightly enhanced after Nb-doping and the Nb-doping facilitates that H2 molecule dissociates to H atoms. These results could provide powerful interpretations for the origin of experimental phenomenon.

Triple (H+/O2−/e−) conducting oxides (TCOs) have been extensively investigated as the most promising cathode materials for solid oxide fuel cells (SOFCs) because of their excellent catalytic activity for oxygen reduction reaction (ORR) and fast proton transport. However, here we report a stable twin-perovskite nanocomposite Ba-Co-Ce-Y-O (BCCY) with triple conducting properties as a conducting accelerator in semiconductor ionic fuel cells (SIFCs) electrolytes. Self-assembled BCCY nanocomposite is prepared through a complexing sol–gel process. The composite consists of a cubic perovskite (Pm-3m) phase of BaCo0.9Ce0.01Y0.09O3-δ and a rhombohedral perovskite (R-3c) phase of BaCe0.78Y0.22O3-δ. A new semiconducting–ionic conducting composite electrolyte is prepared for SIFCs by the combination of BCCY and CeO2 (BCCY-CeO2). The fuel cell with the prepared electrolyte (400 μm in thickness) can deliver a remarkable peak power density of 1140 mW·cm−2 with a high open circuit voltage (OCV) of 1.15 V at 550 °C. The interface band energy alignment is employed to explain the suppression of electronic conduction in the electrolyte. The hybrid H+/O2− ions transport along the surfaces or grain boundaries is identified as a new way of ion conduction. The comprehensive analysis of the electrochemical properties indicates that BCCY can be applied in electrolyte, and has shown tremendous potential to improve ionic conductivity and electrochemical performance.

Ce0.8Gd0.2O2-δ (GDC) with various TiO2 contents was prepared by a conventional mixed oxide method. The effects of doping the ceramic solid electrolyte (GDC) with titanium oxide were investigated with regard to crystal structure, microstructure, electrical property and fuel cell performance. The XRD analysis revealed the existence of a phase comprising a cubic fluorite structure. Above 2 mol% TiO2 a second phase as Gd2Ti2O7 was found. TiO2 promoted grain growth of the ceria ceramics. The grain boundary (GB) conductivity of GDC-TiO2 composite was increased by a small addition of TiO2. The maximum power density was achieved by the cell with GDC-1mol%TiO2 as electrolyte.

The heat transfer of a reactor with improved Intermig impellers was numerically investigated by the finite element method (FEM) simulation software Fluent (V.19). A turbulence model utilized the standard k-ε model, and the turbulent flows in two large vortexes between vertical tubes were collided to form a strong convection. The influence of heat and mass transfer developing from the impeller diameters, the distance between the two impellers (C1), the rotational speed and the installation height of the bottom impeller (C2) were studied. The reactor was equipped with special structure vertical tubes to increase the heat exchange areas. The rate of heat transfer, including criteria such as the convective heat transfer coefficient, the Nusselt number of outside vertical tubes, and the temperature boundary layer thickness, assured the accurate control of the heat exchange mixing state. The experimental testing platform was designed to validate the simulated results, which revealed the influence order of related factors. The Nusselt number Nu was affected by various related factors, resulting in the rotation and diameter of impellers extending far beyond the distance between the two impellers (C1) and the installation height of the impeller (C2). The average temperature boundary layer thicknesses of the symmetrical and middle sections were 3.24 mm and 3.48 mm, respectively. Adjusting the appropriate parameters can accurately control the heat exchange process in such a reactor, and the conclusions provide a significant reference for engineering applications.

Herein, the hierarchical MXene@Ag hybrids were successfully prepared via an in-situ reduction. Moreover, the influences of MXene@Ag hybrids on thermal, mechanical, and tribological properties of epoxy resin (EP) were investigated systematically. Experimental results indicated that the thermal properties of EP/MXene@Ag composites were improved effectively. Meanwhile the tensile strength and elongation at break of EP/MXene@Ag composites were enhanced by 49.6% and 32.1%, respectively, compared to that of pure EP. Especially, the average wear rate and friction coefficient of EP/MXene@Ag composites decreased by 87.5% and 14.3% compared to that of pure EP, presenting the optimal tribological behavior. Moreover, the synergistic reinforcing effects of MXene and Ag NPs for EP matrix were discussed systematically.

Developing high-performance polymeric tribo-materials with superior integrated properties is of vital importance in consideration of energy and environment. In this work, using commercial epoxy (EP) as matrix, the hybrids constructed by graphene oxide (GO) and tungsten disulfide (WS2) were successfully synthesized by hydrothermal reaction to enhance properties of EP composites. The WS2 nano-flowers were uniformly grown onto the surface of GO nanosheets, which interconnected with each other to develop a hierarchical structure. The unique hierarchical microstructure of WS2@GO nanohybrids with large specific surface area and abundant active groups was conducive to the filler-polymer interfacial interactions and multiple enhancement. As a result, the resultant EP/WS2@GO composites displayed outstanding integrated properties, including 81.7% higher tensile strength, 13 °C higher thermal stability, 47.04% lower friction coefficient, and 36.57% higher abrasion resistance. This work will provide a significant guidance for the development of high-performance polymeric tribo-materials.

It has been reported that some transition metal oxides are effective aids both for the densification and the grain boundary behavior of ceria-based electrolytes. In the present work, NiO which is the most popular component of the anode of solid oxide fuel cells was added directly into the electrolyte ceramic, Ce 0.8 Gd 0.2 O 1.9 , to investigate the effects of the presence of NiO on the properties of GDC electrolyte. All of the samples possess a single phase with cubic fluorite structure. The grain size is increased by the addition of NiO when the sintering temperature is 1400 °C. This modification in chemical composition also results in a decrease in activation energy and thus a tendency to enhance grain boundary mobility. The maximum power density of the composite electrolyte single cell is higher than that of a GDC single cell. Therefore, NiO can be used as an effective aid for ceria-based electrolytes.

The heat transfer process in a stirred tank of diameter T=0.5m equipped with dual-layer improved Intermig impellers and helical coils was investigated by experiment and numerical simulation methods. The temperature field, the temperature boundary layer lateral to the coil and the heat transfer coefficient were measured at different rotational speeds. The standard k-e turbulence model and multiple reference frames combined with a sliding mesh method were adopted in the numerical simulation. The results show that the temperature errors between numerical simulation and experimental measurement were within 2K. The temperature in the stirred tank gradually rose from top to bottom and inside to outside, and the maximum temperature difference was within 2K. The average thickness of the temperature boundary layer outside the helical coil is 3.66 mm. According to the experiments and numerical simulations, the heat transfer coefficient correlations, including Nu and Re, Nu and e of the helical coil outer side, were obtained, and the trends of heat transfer coefficients are consistent and regular. The correlation of the heat transfer coefficient lateral to the coil was acquired from the experimentally measured data. The research results can serve as a guide for the design and engineering application of mass and heat transfer processes in stirred tanks with improved Intermig impellers.

Cracking damage influences the stiffness of the girders. Many articles in the literatures have studied the development of stiffness of the scale-down model; however, full-scale model testing cannot be completely replaced by scale-down testing because of material component characteristics and boundary effects. This paper deals with the effects of cracking damage on the structural static and dynamic stiffness based on three prestressed concrete (PC) girders which were removed from an old bridge. First, the equivalent flexural rigidity of cracked prestressed concrete girder was assessed using the measured load-deflection response under cycles of loading and unloading. Then, after unloading, the frequencies were measured on the PC girders supported by the elastomeric bearings. Next, the development of frequency under different damage was studied, and finally, the dynamic stiffness of PC girders with cracks was assessed. The results indicate that the first frequency is more sensitive to the cracking of concrete compared with the second frequency and that the mode shapes are not sensitive to girder damage. The test girders cannot be simplified as an ideal simply supported beam for the purpose of identifying frequencies. In addition, the “final” (the end of the ultimate load case) equivalent flexural rigidity of the girders is 30% of the “initial” (the beginning of the first load case) equivalent flexural rigidity, compared with 50% in the scale-down test; and the final dynamic stiffness is approximately 84% of the initial dynamic stiffness, whereas the scale-down test is 72%.

The objective of this work is to search for a new kind of electrolyte with enhanced performance to work for Solid Oxide Fuel Cells (SOFCs). ZnO which is one of the most important II-IV compound semiconductors is added to Ce0.8Gd0.2O1.9 (GDC) to improve the electrical properties of the electrolyte. The XRD results reveal that ZnO doesn't affect the XRD pattern of doped cerium. The structure is composed of ZnO and CeO2 crystals. The electrical properties of the composites are analyzed through electrochemical impedance spectroscopy (EIS) measurements in both air and H2 atmosphere. It has been found that ZnO has a negative effect on the oxygen ionic conductivity, while the conductivity in H2 atmosphere increased with the increase of ZnO contents. EIS analysis in H2 atmosphere provides an evidence for proton transportation in the composite sample. The fuel cell performance tests show that ZnO can dramatically increase the power outputs of SOFC.

This paper mainly designed the basic structure of the piezoresistive pressure sensor based on MEMS, analysed and optimized the structure size of the sensor, verified the rationality of the structure by finite element modelling. Through theoretical and optimization analysis, the main structural parameters of MEMS are determined.

The double perovskites GdBaCo2O5.5 (GBCO) is candidate cathode materials for application in intermediate temperature solid oxide fuel cells (IT-SOFCs), attributing to excellent electrical conduction properties and oxidation activity. The electronic structure and the oxygen adsorption at BaO terminated surface of GBCO are investigated using projector augmented-wave (PAW) method based on spin-polarized density functional theory (DFT) with the inclusion of on-site Coulomb interaction. The BaO-terminated surface is adopted according to recent experimental results that this termination is energetically favorable for the double perovskites GBCO. We predict that G-AFM configuration is the most stable structure. The calculated results of oxygen vacancy energy indicate that the lowest energy vacancy positions are in the GdO layers. Charge transfer for the adsorbed oxygen and the surface ions is also examined by Bader charge analysis. The oxygen vacancies can facilitate oxygen adsorption and catalyze the bond cleavage. The existence of oxygen vacancy strengthens surface activity by acting as an active site at the surface. These results at the atomic level can contribute to the detailed understanding of oxygen reduction reaction mechanism.

The actual structure is always in the state of natural changing environment and stress decreasing in the section. At present, there is little method for calculating the creep under decreasing stress which takes environmental variation into account. As excessive deflection becomes a serious problem for long span continuous rigid frame bridges during the operation period, in this paper, a creep calculation method is proposed for the continuous decrease of stress in most girder sections, and considers the environmental factors comprehensively. Firstly, the multifactor (temperature, relative humidity and reinforcement ratio) correction was made to creep model of the current code JTG D62. And five creep recovery models were compared and analyzed simultaneously. Based on the elastic creep theory and the superposition principle, the improved creep calculation method was proposed. Then theoretical calculation was carried out for the assumed structure. The results showed that the calculated value obtained by the proposed method were obviously different from those obtained by the code, and were significantly different from those obtained without considering creep recovery, which proves the superiority of the proposed method under the action of multiple environmental factors and decreasing stress.

In order to develop FDM additive manufacturing and promote the application of this technology, the essential mechanical properties including tensile strength and elastic property of PLA material fabricated by FDM additive manufacturing are studied deeply this time. Two novel theoretical models have been built to predict the tensile strength and Young's modulus of FDM additive manufacturing PLA material with different printing angles and layer thicknesses in this study. Firstly, strength theoretical model is established based on transversely isotropic material hypothesis and Tsai-Hill strength criterion. Then, Young's modulus theoretical model is established based on orthotropic material hypothesis under plane stress state. Test data indicates that the tensile strength and Young's Modulus of FDM additive manufacturing PLA material increase as the printing angle increases or the layer thickness decreases. Relative Error (RE) between theoretical results and test data is put forward as a criterion to evaluate the accuracy of the theoretical models quantitatively. All the Relative Error are so small (≤0.14) that is satisfactory in engineering applications. Therefore, one can confirm that the theoretical models established during this research can predict the tensile strength and Young's modulus of FDM additive manufacturing PLA material with different printing angles and layer thicknesses precisely. Keywords: Additive manufacturing, Tensile strength, Elastic property, Transverse isotropy, Printing angle, Layer thickness

In this study, comparison experiments are conducted based on yttria-stabilized zirconia (YSZ) electrolyte supported single solid oxide fuel cells (SOFCs) with pure La 0.75 Sr 0.25 Cr 0.5 Mn 0.5 O 3−δ (LSCrM) or Ni/CeO 2 impregnated LSCrM anodes. The single cells are tested in dry H 2 and H 2 /H 2 S (50 ppm) mixture, respectively. Compared with the pure LSCrM anode, the cell with Ni/CeO 2 impregnated LSCrM presents a significant performance improvement when the pure H 2 is fueled to the anode, and shows a good stability during a constant-current discharge testing (398 mA cm −2 ). When the fuel is switched to H 2 /H 2 S mixture, the cell with Ni/CeO 2 impregnated LSCrM anode still shows a remarkable constant-current discharge (120 mA cm −2 ) performance compared with pure LSCrM anode. The Ni/CeO 2 impregnation can improve the electrochemical performance of the LSCrM anode without any sacrifice of sulfur tolerance ability. The Ni/CeO 2 impregnated LSCrM might be a potential anode material for solid oxide fuel cell operating in sulfur-containing fuels. The XRD and XPS results demonstrate that the anode poisoning product is composed of adsorbed sulfur, metal sulfides and sulfate radical. The mass spectrum result confirms that the poisoning mechanism involves the reaction of sulfur with anode rather than the direct reaction between H 2 S gas and anode.

The planar wave-guided volume hologram (PWGVH) is recorded and reconstructed using light waves guided through optical substrates. In this paper, the variation of the diffracted light wave's central wavelength and wavelength range versus the angular deviation relative to the angle under Bragg condition was analyzed through numerical simulation. The study shows acceptable angular range with the high diffraction efficiency and color uniformity of unitary hologram is much less than the angular width. Multilayer volume holograms are designed to expand the acceptable angular range. The numerical simulation indicates that better color uniformity and wider acceptable angular range can be obtained.

The atomic force microscopy (AFM), the X-ray diffraction with glancing input angle (GXRD) and the cathodoluminescence (CL) spectra of a ZnO film on Si, annealed at different temperatures, were measured. The results showed that, the crystal quality of the film improved with increasing the annealing temperature, while the hexagonal phase of the ZnO film transformed into a kind of mixture phase including a hexagonal and a trigonal phase, after annealing at 800 °C for 1 h. The CL spectrum also shows the intrinsic emission bands of ZnO and Zn2SiO4, in which the ZnO is the main source of the spectrum. Increasing the temperature continuously up to 950 °C changed the main source of sample's luminescence from the emission of ZnO to the emission of zinc silicate. This indicates a creation of new ternary compound Zn2SiO4 in the film.

In this study, Ca3Co4O9+δ (CCO) and La0.7Sr0.3CoO3 (LSC) have been mixed as mass fraction by 1:1, to prepare novel two-phase composites with high electrical conductivity and low thermal expansion coefficient (TEC), for potential application in intermediate-temperature solid oxide fuel cells. The conductivity of the composite, Ca3Co4O9+δ (50 wt.%) + La0.7Sr0.3CoO3 (50 wt.%) (CCO-LSC50), is improved to be three times that of single phase CCO material. And, the TEC of CCO-LSC50 has been effectively improved to be 15.3 × 10–6 °C–1, about 20% lower than single phase LSC cathode, which ensures better chemical compatibility with adjacent electrolyte. As a result, compared with pure LSC and CCO cathodes, CCO-LSC50 composite cathode improves the electrochemical performance, a percentage of 16 and 84%, respectively, according to the impedance spectra experiments. In addition, cathodic overpotential and oxygen reduction kinetics have also been researched to reveal what is driving the results. The microstructures and phases of cathodes were also compared and analyzed.

We have demonstrated three-dimensional optical data storage in a novel photochromic material with two-photon excitation. The data are read out with a homemade confocal fluorescence microscope combined with the three-dimensional writing system. Since the degree of destruction is closely related with the total dwell time of the readout laser, we try to read out the data through an optimization among the doped concentration of photochromic material of the PMMA film, the readout power, and the dwell time of the laser at each data bit. Using the optimized readout condition, it is possible to achieve 107 readout cycles with very little erasure of the data at the scanning speed of a 50× CD driver.