Effects of operating conditions on the performance degradation and anode microstructure evolution of anode-supported solid oxide fuel cells

Performance degradation shortens the life of solid oxide fuel cells in practical applications.Revealing the degradation mechanism is crucial for the continuous improvement of cell durability.In this work,the effects of cell operating conditions on the terminal voltage and anode microstructure of a Ni-yttria-stabilized zirconia anode-supported single cell were investigated.The microstructure of the anode active area near the electrolyte was characterized by laser optical microscopy and focused ion beam-scanning electron microscopy.Ni depletion at the anode/electrolyte interface region was observed after 100 h discharge tests.In addition,the long-term stability of the single cell was evaluated at 700℃for 3000 h.After an initial decline,the anode-supported single cell exhibits good durability with a voltage decay rate of 0.72%/kh and an electrode polarization resistance decay rate of 0.17%/kh.The main performance loss of the cell originates from the initial degradation.

Sb-Cu alloy cathode with a novel lithiation mechanism of ternary intermetallic formation: Enabling high energy density and superior rate capability of liquid metal battery

Antimony(Sb) is an attractive cathode for liquid metal batteries(LMBs) because of its high theoretical voltage and low cost.The main obstacles associated with the Sb-based cathodes are unsatisfactory energy density and poor rate-capability.Herein,we propose a novel Sb_(64)Cu_(36)cathode that effectively tackles these issues.The Sb_(64)Cu_(36)(melting point:525℃) cathode presents a novel lithiation mechanism involving sequentially the generation of Li_(2)CuSb,the formation of Li_(3)Sb,and the conversion reaction of Li_(2)CuSb to Li_(3)Sb and Cu.The generated intermetallic compounds show a unique microstructure of the upper floated Li_(2)CuSb layer and the below cross-linked structure with interpenetrated Li_(2)CuSb and Li_(3)Sb phases.Compared with Li_(3)Sb,the lower Li migration energy barrier(0.188 eV) of Li_(2)CuSb significantly facilitates the lithium diffusion across the intermediate compounds and accelerates the reaction kinetics.Consequently,the Li‖Sb_(64)Cu_(36)cell delivers a more excellent electrochemical performance(energy density:353 W h kg^(-1)at 0.4 A cm^(-2);rate capability:0.59 V at 2.0 A cm^(-2)),and a much lower energy storage cost of only 38.45 $ kW h^(-1)than other previously reported Sb-based LMBs.This work provides a novel cathode design concept for the development of high-performance LMBs in applications for large-scale energy storage.

Advances and challenges of methanol-tolerant oxygen reduction reaction electrocatalysts for the direct methanol fuel cell

Methanol cross-over effects from the anode to the cathode are important parameters for reducing catalytic performance in direct methanol fuel cells.A promising candidate catalyst for the cathode in direct methanol fuel cells must have excellent activity toward oxygen reduction reaction and resistance to methanol oxidation reaction.This review focuses on the methanol tolerant noble metal-based electrocatalysts,including platinum and palladium-based alloys,noble metal–carbon based composites,transition metal-based catalysts,carbon-based metal catalysts,and metal-free catalysts.The understanding of the correlation between the activity and the synthesis method,electrolyte environment and stability issues are highlighted.For the transition metal-based catalyst,their activity,stability and methanol tolerance in direct methanol fuel cells and comparisons with those of platinum are particularly discussed.Finally,strategies to enhance the methanol tolerance and hinder the generation of mixed potential in direct methanol fuel cells are also presented.This review provides a perspective for future developments for the scientist in selecting suitable methanol tolerate catalyst for oxygen reduction reaction and designing high-performance practical direct methanol fuel cells.

Curtailing Carbon Usage with Addition of Functionalized NiFe2O4 Quantum Dots:Toward More Practical S Cathodes for Li-S Cells

Smartcombination of manifold carbonaceous materials with admirable functionalities(like full of pores/functional groups,high specific surface area) is still a mainstream/preferential way to address knotty issues of polysulfides dissolution/shuttling and poor electrical conductivity for S-based cathodes.However,extensive use of conductive carbon fillers in cell designs/technology would induce electrolytic overconsumption and thereby shelve high-energy-density promise of Li-S cells.To cut down carbon usage,we propose the incorporation of multi-functionalized NiFe2O4 quantum dots(QDs) as affordable additive substitutes.The total carbon content can be greatly curtailed from 26%(in traditional S/C cathodes) to a low/commercial mass ratio(~5%).Particularly,note that NiFe2O4 QDs additives own superb chemisorption interactions with soluble Li2Sn molecules and proper catalytic features facilitating polysulfide phase conversions and can also strengthen charge-transfer capability/redox kinetics of overall cathode systems.Benefiting from these intrinsic properties,such hybrid cathodes demonstrate prominent rate behaviors(decent capacity retention with ~526 mAh g^-1 even at 5 A g^-1) and stable cyclic performance in LiNO3-free electrolytes(only ~0.08% capacity decay per cycle in 500 cycles at 0.2 A g^-1).This work may arouse tremendous research interest in seeking other alternative QDs and offer an economical/more applicable methodology to construct low-carbon-content electrodes for practical usage.

A real-time measuring technology for studying distortion of hydraulic turbine blade castings during heat treatment process

During heat treatment process, the distortion behavior inevitably appears in hydraulic turbine blade castings. In this research, a technology was developed for real-time measurement of the distortion in hydraulic turbine blade castings at the still air cooling and forced air cooling stages during heat treatment process. The method was used to measure the distortion behavior at the cooling stages in both normalizing and tempering processes. At the normalization, the distortion at the blade corner near outlet side undergoes four stages with alternating bending along positive and negative directions. At the tempering stage, the distortion could be divided into two steps. The temperature difference between the two surfaces of blade casting was employed to analyze the distortion mechanism. The measured results could be applied to guide the production, and the machining allowance could be reduced by controlling the distortion behavior.

A highly sensitive colorimetric and ratiometric sensor for fluoride ion

A new benzoimidazole-naphthalimide derivative 4 was synthesized and its photophysical properties were studied. This compound showed highly selectively and sensitive colorimetric and ratiometric sensing ability for fluoride anion.

Minimizing Carbon Content with Three-in-One Functionalized Nano Conductive Ceramics:Toward More Practical and Safer S Cathodes of Li-S Cells

Using porous carbon hosts in cathodes of Li-S cells can disperse S actives and offset their poor electrical conductivity.However,such reservoirs would in turn absorb excess electrolyte solvents to S-unfilled regions,causing the electrolyte overconsumption,specific energy decline,and even safety hazards for battery devices.To build better cathodes,we propose to substitute carbons by In-doped SnO_(2)(ITO)nano ceramics that own three-in-one functionalities:1)using conductive ITO enables minimizing the total carbon content to an extremely low mass ratio(~3%)in cathodes,elevating the electrode tap density and averting the electrolyte overuse;2)polar ITO nanoclusters can serve as robust anchors toward Li polysulfide(LiPS)by electrostatic adsorption or chemical bond interactions;3)they offer catalysis centers for liquid–solid phase conversions of S-based actives.Also,such ceramics are intrinsically nonflammable,preventing S cathodes away from thermal runaway or explosion.These merits entail our configured cathodes with high tap density(1.54 g cm^(−3)),less electrolyte usage,good security for flame retardance,and decent Li-storage behaviors.With lean and LiNO_(3)-free electrolyte,packed full cells exhibit excellent redox kinetics,suppressed LiPS shuttling,and excellent cyclability.This may trigger great research enthusiasm in rational design of low-carbon and safer S cathodes.

High-yield production of 2,5-dimethylfuran from 5-hydroxymethylfurfural over carbon supported Ni–Co bimetallic catalyst

The catalytic conversion of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF) has attracted extensive research interests because DMF can be used as potential and competitive renewable transportation fuel or additives. Here we report a non-noble bimetallic catalyst with improved activity for hydrogenation and hydrogenolysis by introducing active carbon as support into a nickel–cobalt catalyst. The characterizations of the catalyst indicate that the Ni and Co species are uniformly dispersed on the active carbon through the wetness impregnation method. The influences of reaction temperature and hydrogen pressure are systematically investigated and an excellent yield (up to 95%) of DMF can be obtained at relatively mild conditions, 130 °C and 1 MPa H2, over the carbon supported Ni–Co bimetallic catalyst. The high catalytic activity originates from the synergistic effect between Ni and CoOxspecies, the high BET surface area of the catalyst, and the uniform dispersion of Ni and Co species on the active carbon. The catalyst could be reused for 5 times without loss of activity in a batch reactor. Futhermore, the conversion of HMF to DMF on a fixed-bed reactor was also investigated and the 2%Ni–20%Co/C catalyst exhibited an excellent yield to DMF (>90%) for 71 h time on stream, indicating the high activity and stability of the catalyst. © 2016 Science Press

Application of inverse method to estimation of boundary conditions during investment casting simulation

Inverse method was used in single crystal superalloy DD6 processing simulation during solidification. Numerical modeling coupled with experiments has been used to estimate the interface heat transfer coefficient （IHTC） between the surface of slab casting and inner mold. Calculated temperature dependent values of IHTC were obtained from a numerical solution. The calculated temperatures agreed well with the measurement of cooling profile.

Effects of Heat-treatment Temperature on Eu^(3+) and Li^+ Co-doped ZnO Photoluminescence by Sol-gel Process

The photoluminescence （PL） characteristics of Eu^3＋ and Li^＋ co-doped ZnO PL materials against heat-treatment temperature were discussed. The PL xerogel and powder samples were prepared by solgel process. The emission spectra of all samples showed two broad bands peaking at 590 nm and 620 nm under UV-Vis excitation. But the relative intensity of red PL （620 nm） was much greater than that of green PL （590 nm） of the same sample, that s to say, the red color was the main luminescence. With heat-treatment temperature increase, the two kinds of colors PL intensity decreased, and both the red and green PL intensity of the xerogel samples was much greater than those of powder samples respectively. The XRD patterns revealed that Eu^3＋ ions were successfully incorporated in ZnO crystals in xerogel samples. When heat-treatment temperature reached 350 ℃, the Eu^3＋ began to separate out of the ZnO crystals and Eu2O3 crystals came into being. When the powder sample was subjected to UV-Vis excitation, the energy transfered from the host ZnO emission to Eu^3＋ became weaker than the xerogel sample.

Active learning for the power factor prediction in diamond-like thermoelectric materials

The Materials Genome Initiative requires the crossing of material calculations,machine learning,and experiments to accelerate the material development process.In recent years,data-based methods have been applied to the thermoelectric field,mostly on the transport properties.In this work,we combined data-driven machine learning and first-principles automated calculations into an active learning loop,in order to predict the p-type power factors(PFs)of diamond-like pnictides and chalcogenides.Our active learning loop contains two procedures(1)based on a high-throughput theoretical database,machine learning methods are employed to select potential candidates and(2)computational verification is applied to these candidates about their transport properties.The verification data will be added into the database to improve the extrapolation abilities of the machine learning models.Different strategies of selecting candidates have been tested,finally the Gradient Boosting Regression model of Query by Committee strategy has the highest extrapolation accuracy(the Pearson R=0.95 on untrained systems).Based on the prediction from the machine learning models,binary pnictides,vacancy,and small atom-containing chalcogenides are predicted to have large PFs.The bonding analysis reveals that the alterations of anionic bonding networks due to small atoms are beneficial to the PFs in these compounds.

Bidirectionally aligned MXene hybrid aerogels assembled with MXene nanosheets and microgels for supercapacitors

MXene nanomaterials are one of the most promising electrode material candidates for supercapacitors owing to their high conductivity,abundant surface functional groups and large surface area.However,electrodes based on MXene may result in low ion-accessible surface area and blocked ion transport pathways because of the self-restacking of MXene nanosheets.It is essential to suppress the self-res tacking of nanosheets and increase the electrochemical active sites in order to optimize the electrode.In this work,bidirectionally aligned MXene hybrid aerogel(A-MHA)assembled with MXene nanosheets and microgels is prepared using a facile bidirectional freeze casting and freeze-drying method.The bidirectionally aligned structure together with the three-dimensional structured microgels in the A-MHAs,can improve the ionaccessible surface area and provide more barrier-free channels by exposing more active sites and ensuring electrolyte transport freely.The A-MHA with MXene microgels content of 40 wt%exhibits a high specific capacitance of 760 F·g^(-1)at 1 A·g^(-1)and a remarkable cyclic performance of 97%after 10,000 cycles at100 mV·s^(-1)in 1 mol·L^(-1)H_(2)SO_(4)electrolyte.A-MHAs show remarkable electrochemical properties and are of potential application in energy storage.

High Efficient Tunable Fractal Axicon Based on LCoS

Based on the Cantor function and phase modulation, a tunable fractal axicon is formed on a liquid crystal on silicon （LCoS） with an improved generating method. It has higher focusing efficiency in higher fractal stage and approaches to 100% theoretically. The on-axis intensity keeps its fractal structure unchanged in operation of fractal stages. The tunability of the axicon is demonstrated by tune fractal stage from 1 to 3 and focal length from 0.8 m to 1 m. We also provide details of theoretical analyses and experimental results.

Effects of silver-doping on properties of Cu(In,Ga)Se_(2) films prepared by Cu In Ga precursors

The AgCuInGa alloy precursors with different Ag concentrations are fabricated by sputtering an Ag target and a CuInGa target.The precursors are selenized in the H_(2)Se-containing atmosphere to prepare(Ag,Cu)(In,Ga)Se_(2)(ACIGS)absorbers.The beneficial effects of Ag doping are demonstrated and their mechanism is explained.It is found that Ag doping significantly improves the films crystallinity.This is believed to be due to the lower melting point of chalcopyrite phase obtained by the Ag doping.This leads to a higher migration ability of the atoms that in turn promotes grain boundary migration and improves the film crystallinity.The Ga enrichment at the interface between the absorber and the back electrode is also alleviated during the selenization annealing.It is found that Ag doping within a specific range can passivate the band tail and improve the quality of the films.Therefore,carrier recombination is reduced and carrier transport is improved.The negative effects of excessive Ag are also demonstrated and their origin is revealed.Because the atomic size of Ag is different from that of Cu,for the Ag/(Ag+Cu)ratio(AAC)≥0.030,lattice distortion is aggravated,and significant micro-strain appears.The atomic radius of Ag is close to those of In and Ga,so that the continued increase in AAC will give rise to the Ag;or Ag;defects.Both the structural and compositional defects degrade the quality of the absorbers and the device performance.An excellent absorber can be obtained at AAC of 0.015.

STRUCTURE AND MORPHOLOGY CHANGES OF HYDROBIOTITES MODIFIED BY CATIONIC SURFACTANTS

In this study, X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR) together with Scanning probe microscopy (SPM) were used to characterize the structure and morphology of the complexes, where the hydrobiotites (Xinjiang) were modified by single-chain surfactants octyltrimethylammonium bromide (OTMA) and octadecyltrimethylammonium bromide (ODTMA). XRD patterns showed that the structure of complexes was significantly influenced by the surfactant concentration and the alkyl chain length, because obvious changes took place in the basal spacing. Furthermore, according to the XRD results, several arrangements of surfactant molecules within the hydrobiotite interlayer space were deduced. The FTIR spectrum indicated that the surfactant contents in complexes dramatically increased with the alkyl chain length. The SPM micrographs demonstrated that the surfaces of complexes prepared at lower surfactant concentration were relatively flat compared with that prepared at higher concentration, while those with higher surfactant concentration had much steeper surface due to the alkyl chain length. It was concluded that structure and morphology of surfactant/hydrobiotite complexes depend not only on the surfactant concentration, but also strongly on the surfactant species.

Electron Transfer of Shewanella Putrefaciens Anode in Microbial Fuel Cells

Surface chemistry of nanostructured materials plays a crucial role in interfacial electron transfer between bacteria and the electrodes,thus being of great significance for the performance of microbial fuel cells(MFCs).To address this issue,two electro-conductive organics(i.e.ionic liquid&phospho-

A Simple Theoretical Method to Predict the Hardness of Pure Metal Crystals

Design of superhard bulk materials requires predicting their hardness, challenging current theories for material design. By introducing a concept of condensing force （CF）, it is shown via ab initio calculations for fcc （Ni, Cu, Al, Ir, Rh, Au, Ag, Pd） and hcp Re crystals that materials with larger CF can have greater hardness. Since the calculation of CF is easy, this method might prove a convenient way to evaluate the hardness of newly designed materials.

Transition of Magnetoresistance in Co/Alq3 Granular Film on Silicon Substrate

A Coo.3s （Alq3）o.62 granular film is prepared using a co-evaporating technique on a silicon substrate with a native oxide layer. A crossover of magnetoresistance （MR） from positive to negative is observed. The positive MR ratio reaches 17.5% at room temperature （H = 50kOe）, and the negative MR ratio reaches -1.35% at 1514 （H = 10 kOe）. Furthermore, a metal-insulator transition is also observed. The transition of resistance and MR results from the channel switching of electron transport between the upper Co-AIq3 granular film and the inversion layer underneath. The negative MR originates from the tunneling magnetoresistance effect due to the tunneling conducting between adjacent Co granules, and the positive MR may be attributed to the transport of high mobility carriers in the SiO2/Si inversion layer.

Fabrication of large area hexagonal boron nitride thin films for bendable capacitors

高度可靠、可弯曲的电介质为未来应用在灵活或可弯曲的电子设备被需要。六角形的硼氮化物(h-BN ) 能由于它的宽乐队差距被用作可弯曲的电介质。这里，我们由一个低压力化学药品蒸汽免职方法与可控制的厚度制作高质量的 h-BN 电影。我们作为电介质用 h-BN 电影表明一个平行板的电容器。h-BN 电容器与 9.0 MV/cm 的高故障地力量是可靠的。越过 h-BN 电影的通道电流对电介质的厚度相反地指数，它让电容显著地落下。h-BN 电容器显示出 6.8 F/cm2 的一个最好的特定的电容，它比计算的值高一个数量级。