[en] The EU-project 'GENIUS' is targeted at the investigation of generic diagnosis methodologies for different Solid Oxide Fuel Cell (SOFC) systems. The Ph.D study presented in this thesis was integrated into this project; it aims to develop a diagnostic tool for SOFC system fault detection and identification based on validated diagnostic algorithms, through applying the SOFC stack as a sensor. In this context, three algorithms, based on the k-means clustering technique, the wavelet transform and the Bayesian method, respectively, have been developed. The first algorithm serves for ex-situ diagnosis. It works on the classification of the polarization measurements of the stack, aiming to figure out the significant response variables that are able to indicate the state of health of the stack. The parameter 'Silhouette' has been used to evaluate the classification solutions in order to determine the optimal number of classes/patterns to retain from the studied database. The second algorithm allows the on-line fault detection. The wavelet transform has been used to decompose the SOFC's voltage signals for the purpose of finding out the effective feature variables that are discriminative for distinguishing the normal and abnormal operating conditions of the system. Considering the SOFC as a sensor, its reliability must be verified beforehand. Thus, the feature variables are also required to be indicative to the state of health of the stack. When the stack is found being operated improperly, the actual operating parameters should be estimated so as to identify the system fault. To achieve this goal, a Bayesian network has been proposed serving as a meta-model of the stack to accomplish the estimation. At the end, the databases originated from different SOFC systems have been used to validate these three algorithms and assess their generalizability. (author)

[en] Highlights: • An integrated model is developed for a solar power tower with S-CO_2 Brayton cycle. • The effects of several key parameters on the exergy efficiency are analyzed. • Optimum operation parameters are suggested for the SPT system with a S-CO_2 cycle. • The maximum allowable temperature is recommended for novel salts used in SPT. - Abstract: In the present study, a molten salt solar power tower (SPT) system integrated with a S-CO_2 Brayton cycle is presented. An integrated model is developed for the integrated SPT system including the heliostat field, the molten salt solar receiver, the molten salt thermal storage, and the S-CO_2 recompression Brayton cycle with reheating. Parametric analysis is conducted to investigate the effects of some key thermodynamic parameters (e.g. hot salt temperature, cycle high pressure, cycle low pressure, intermediate pressure, and the split ratio) on the integrated SPT system in terms of exergy efficiency. The parameter optimization is performed by using genetic algorithm in order to obtain the highest overall exergy efficiency. The effects of the component performance and the compressor inlet temperature on the optimum parameters are also discussed. The results indicate that the optimum hot salt temperature is 565 °C which is its maximum allowable temperature when the solar salt is used as the heat transfer fluid and the thermal storage media. Besides, the optimum cycle low pressure is in the range of 7.80–10.0 MPa which means that the cycle low pressure is not mandatory to be close to the critical pressure. The increase in the compressor inlet temperature leads to both the decrease in maximum exergy efficiency and the variation of the optimum thermodynamic parameters. The component performances have significant effects on the maximum exergy efficiency, but slight effects on optimum thermodynamic parameters. A novel salt with a higher maximum allowable temperature is indispensable for further improving the system efficiency. The maximum allowable temperature of 680 °C is recommended for novel salts to be used in the SPT system integrated with S-CO_2 recompression Brayton cycle from the viewpoint of exergy efficiency under the present conditions.

[en] Highlights: •The systematic study of its structure and electronic structure in gas and solid phase. •The gas phase structures indicate that Li⁺ cation and Na⁺ cation acts as very different roles in the dehydrogenation. •Potential energy curves of dehydrogenation were obtained by CCSD(T) method. •Obtained the dehydrogenation rates similar to the experimental values. -- Abstract: This study is based on the synthesis of a mixed metal amidoborane, Na[Li(NH₂BH₃)]₂ (SLAB), the first example of an inorganic sodium–lithium compound. This paper is the first systematic study of its structure and dehydrogenation mechanism, and the results obtained were consistent with the experimental results. The first principle method was used to study the structure of SLAB in solid phase, while the second Moller–Plesset Perturbation Theory was used for gas-phase kinetic studies. Potential energy curves were obtained by CCSD(T) method. Three mechanistic pathways were designed to study its dehydrogenation, which include A pathway (without the cleavage of N–B bond (S and S′ pathways)), B pathway (with the cleavage of the intramolecular N–B bond before dehydrogenation), and D pathway (with the formation of direct dihydrogen bonds). Na⁺ cation movement was proved to play a very important role in the hydrogen-transfer process. Finally, a possible dissociation pathway (A pathway) was confirmed and dehydrogenation rates similar to the experimental values were obtained

[en] Multi-physics coupling analysis based on FLUENT is a hot issue in current nuclear safety analysis. The reactor nuclear power calculation program (PKM) was prepared by using the point reactor neutron kinetic equations of 6 groups of delayed neutrons. The FLUENT/RELAP coupling analysis model and the FLUENT/PKM coupling analysis model were established by the external coupling method and secondary development coupling method respectively. The correctness and effectiveness of the coupled model were verified by the discharge problem of the horizontal branch pipe and the super-power transient problem of the linear reactivity introduced in a single-phase range. The coupled analysis method of the study can provide support for fluent multi-physics nuclear safety analysis. (authors)

[en] Graphical abstract: - Highlights: • Lubricated Ti6Al4V was fabricated by anodic oxidation and hydrophilic polymer grafting. • Surface composition and tribological properties were estimated. • Proper surface micropores formed at optimum voltage of 100 V. • Combined effect of porous structure and polymer brushes decreased friction coefficient and wear. • Hydrated lubricating layer and hydrodynamic lubrication contributed to lubricated surface. - Abstract: On the purpose of improving the tribological properties of titanium alloy through mimicking natural articular cartilage, porous structure was prepared on the surface of Ti6Al4V alloy by anodic oxidation method, and then hydrophilic polymer brushes were grafted onto its surface. Surface morphology of porous oxidized film was investigated by metalloscope and scanning electron microscope (SEM). The composition and structure of modified surface were characterized by Fourier-transform infrared spectroscopy with attenuated total reflection (FTIR/ATR), and the wettability was also evaluated. Friction and wear properties of modified alloys sliding against ultra-high molecular weight polyethylene (UHMWPE) were tested by a pin-on-disc tribometer in physiological saline. The results showed that, the optimum porous structure treated by anodic oxidation formed when the voltage reached as high as 100 V. Hydrophilic monomers [Acrylic acid (AA) and 3-dimethyl-(3-(N-methacrylamido) propyl) ammonium propane sulfonate (DMMPPS)] were successfully grafted onto porous Ti6Al4V surface to form polymer brushes by UV radiation. The change of contact angle showed that wettability of modified Ti6Al4V was improved significantly. The friction coefficient of modified Ti6Al4V was much lower and more stable than untreated ones. The lowest friction coefficient was obtained when the sample was anodized at 100 V and grafted with DMMPPS, and the value was 0.132. The wear of modified samples was also obviously improved

[en] Highlights: • The sulfur fate of copper ore with H_2S-containing synthesis gas was investigated. • Cu_2S and FeS were the main sulfide products for copper ore reacted with H_2S. • H_2S is easier to react with copper oxides than iron oxides. • H_2S led to a degradation of oxygen transport capacity and reactivity of the OC. - Abstract: Chemical-looping combustion (CLC) is a promising technology that provides a novel route for CO_2 capture with low cost and energy penalty. Interaction between the oxygen carrier and sulfur contaminants in fuel is a significant concern in chemical looping systems, which will degrade the captured CO_2 purity and even affect the reactivity of oxygen carrier. Experiments of a sulfur-containing synthesis gas (4000 ppm H_2S, 25 vol.% H_2, 35 vol.% CO, and 39.6 vol.% CO_2) as fuel and copper ore as oxygen carrier were performed by thermogravimetric analysis and Fourier transform infrared spectroscopy (TGA–FTIR). The effects of reducing atmosphere, temperature and redox cycle number were studied. A weight gain was observed in all TGA experiments with 4000 ppm H_2S synthesis gas as fuel, due to the sulfidation of the copper ore oxygen carrier. For the reaction of copper ore with H_2S-containing synthesis gas, the main metal sulfide products were Cu_2S and FeS, while the gaseous sulfur species were mainy SO_2, COS, and CS_2. H_2S was easier to react with copper oxides than iron oxides. Moreover, the sulfidation of copper ore was further investigated in a laboratory scale fluidized bed reactor at 900 °C, using copper ore as oxygen carrier and synthesis gases with/without H_2S as fuel. The results showed that the sulfidation of copper ore degraded its oxygen transport capicity and reactivity to some extent.

[en] ABSTRACT: A nanocomposite for supercapacitor electrode materials was designed and developed by integrating partially disabled Cu_2O (low specific capacity, but high cycling ability) and Ni(OH)_2 (low cyclability and high specific capacity) in the presence of reduced graphene oxide (RGO) nanosheets. Nanocomposite of Cu_2O/RGO/Ni(OH)_2 was directly grown on nickel foam (NF) through a facile one-pot hydrothermal process without any other reductant or oxidant, in which nickel foam acted as both a reductant of GO and Ni source, and a substrate for nanocomposite. The resultant Cu_2O/RGO/Ni(OH)_2 nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectrometer (XPS), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The electrochemical performance of the as-synthesized Cu_2O/RGO/Ni(OH)_2/NF electrodes were evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectrometry (EIS) in 6 mol L"−"1 KOH aqueous solution. This Cu_2O/RGO/Ni(OH)_2 nanocomposite exhibits superior capacitive performance: high capability (3969.3 mF cm"−"2 at 30 mA cm"−"2, i.e., 923.1 F g"−"1 at 7.0 A g"−"1), excellent cycling stability (92.4% retention even after 4,000 cycles, for RGO/Ni(OH)_2/NF, 92.3% after 1,000 cycles), and good rate capacitance (50.3% capacity remaining at 200 mA cm"−"2)

[en] New candidate materials for GenIV or fusion nuclear energy systems, e.g., nanostructured ferritic alloys, are distinguished from older-generation nuclear materials by much smaller feature sizes and complex local nanochemistry and crystallography. Established and perspective nuclear materials, e.g. reactor pressure vessel steels or plasma-facing tungsten, also form small nanoscale structures under in-reactor service. Here, we discuss recent advances in materials characterization – high-efficiency X-ray mapping combined with datamining; transmission Kikuchi diffraction; and atom probe tomography – that make it possible to quantitatively characterize these nanoscale structures in unprecedented detail, which enables advances in understanding and modelling of radiation service and degradation.

[en] The keys of biomaterials application in artificial joints are good hydrophilicity and wear resistance. One kind of the potential bio-implant materials is polyetheretherketone (PEEK), which has some excellent properties such as non-toxic and good biocompatibility. However, its bioinert surface and inherent chemical inertness hinder its application. In this study, we reported an efficient method for improving the surface wettability and wear resistance for PEEK, a layer of acrylic acid (AA) polymer brushes on PEEK surface was prepared by UV-initiated graft polymerization. The effects of different grafting parameters (UV-irradiation time/AA monomer solution concentration) on surface characteristics were clearly investigated, and the AA-g-PEEK specimens were examined by ATR-FTIR, static water contact angle measurements and friction tests. Our results reveal that AA can be successfully grafted onto the PEEK surface after UV irradiation, the water wettability and tribological properties of AA-g-PEEK are much better than untreated PEEK because that AA is a hydrophilic monomer, the AA layer on PEEK surface can improve its bearing capacity and reduce abrasion. This detailed understanding of the grafting parameters allows us to accurately control the experimental products, and this method of surface modification broadens the use of PEEK in orthopedic implants. - Highlights: • Acrylic acid was successful grafted onto PEEK substrate by UV-initiated graft polymerization. • AA-g-PEEK owned better hydrophilicity than untreated PEEK. • Wear resistance of AA-g-PEEK were significantly improved due to AA brushes could bear high contact stress.

[en] To improve the stability and the reversibility of the SnO₂-based anodic materials in lithium ion batteries, a new bioinspired nanostructured Cu-nanoparticle/SnO₂/carbon (Cu-NP/SnO₂/carbon) composite was fabricated by employing natural cellulose substance (e.g., commercial laboratory cellulose filter paper) as both scaffold and carbon source. The as-deposited SnO₂-gel/cellulose composite was firstly calcined and carbonized in argon atmosphere, and the resulted nanofibrous SnO₂/carbon composite was further uniformly decorated with the metallic Cu nanoparticles via a facile chemical reduction process using copper nitrate as the precursor. The nanocomposite was composed of SnO₂-layer-coated carbon nanofibres with Cu nanoparticles immobilized on the surfaces. As an anode material for lithium-ion batteries, the three-dimensional porous structure of the nanocomposite inherited from the initial cellulose substance effectively buffered the large volume change during the cycling processes; moreover, the uniformly decorated Cu nanoparticles significantly facilitated the electron transport, as well as reversibly promoted catalytic decomposition of Li₂O during delithiation process to enhance the reversible capacity of the electrode. Therefore, the Cu-NP/SnO₂/carbon anodes exhibited an improved electrochemical performance compared with the nanofibrous SnO₂/carbon material. For the composite with 24.6 wt% of the Cu content and the sizes of 5–10 nm of the Cu nanoparticles, it delivered a superior performance with the highest specific capacity of 797 mAh g⁻¹ after 120 charge/discharge cycles at a current density of 100 mA g⁻¹.