Synthesis of carbon nanofibers@MnO2 3D structures over copper foil as binder free anodes for lithiumion batteries

A 3D structured composite of carbon nanofibers@MnO2 on copper foil is reported here as a binder free anode of lithium ion batteries, with high capacity, fast charge/discharge rate and good stability. Carbon nanofiber yarns were synthesized directly over copper foil through a floating catalyst method. The growth of carbon nanofiber yarns was significantly enhanced by mechanical polishing of the copper foils, which can be attributed to the increased surface roughness and surface area of the copper foils. MnO2 was then grown over carbon nanofibers through spontaneous reduction of potassium permanganate by the carbon nanofibers. The obtained composites of carbon nanofibers@MnO2 over copper foil were tested as an anode in lithium ion batteries and they show superior electrochemical performance. The initial reversible capacity of carbon nanofibers@MnO2 reaches up to around 998 mAh g-1 at a rate of 60 mmA g-1 based on the mass of carbon nanofibers and MnO2 . The carbon nanofibers@MnO2 electrodes could deliver a capacity of 630 mAh g-1 at the beginning and maintain a capacity of 440 mmAh g-1 after 105 cycles at a rate of 600 mA g-1 . The high initial capacity can be attributed to the presence of porous carbon nanofiber yarns which have good electrical conductivity and the MnO2 thin film which makes the entire materials electrochemically active. The high cyclic stability of carbon nanofibers@MnO2 can be ascribed to the MnO2 thin film which can accommodate the volume expansion and shrinking during charge and discharge and the good contact of carbon nanofibers with MnO2 and copper foil.     

Carbon dioxide conversion to valuable chemical products over composite catalytic systems

This paper reports an experimental study on catalytic conversion of carbon dioxide to methanol,ethanol and acetic acid.Catalysts having different catalytic functions were synthesized and combined in different ways to enhance the selectivity to desired products.The combined catalyst system possessed the following functions:methanol synthesis,Fischer-Tropsch synthesis,water-gas-shift and hydrogenation.Results showed that the methods of integrating these catalytic functions played an important role in achieving the desired product selectivity.We speculate that if methanol synthesis sites were located adjacent to the C-C chain growth sites,the formation rate of C₂ oxygenates would be enhanced.The advantage of using a high temperature methanol catalyst PdZnAl in the combined catalyst system was demonstrated.In the presence of PdZnAl catalyst,the combined catalyst system was stable at 380°C.It was observed that,at high temperature,kinetics favored oxygenate formation.The results implied that the process can be intensified by operating at high temperature using Pd-based methanol synthesis catalyst.Steam reforming of the byproduct organics was demonstrated as a means to provide supplemental hydrogen.Preliminary process design,simulation,and economic analysis of the proposed CO₂ conversion process were carried out.Economic analysis indicates how ethanol production cost was affected by the price of CO₂ and hydrogen.     

p-tert-Butylcalix[4]arene Functionalised with Bipyridyl Carboxylates for Lanthanide Complexation: Synthesis,Photophysical Properties,Solution and Solid State Behavior

A new ligand based on a p-tert-butylcalix[4]arene functionalised with three 6-carboxylato-2,2′-bipyridine arms reacted with lanthanide(III) cations to form 2:2 complexes in the solid state, whereas in solution, a concentration-dependent equilibrium is observed between 2:2 and 1:1 species, as evidenced by ES-MS and metal luminescence measurements. In the X-ray molecular structure of the terbium complex two branched calixarene platforms share one pendant arm in order to provide a neutral dimeric structure which is held together by a strong hydrogen bonded network together with efficient π–π stacking of two pyridine rings belonging to each ligand.     

Peptide backbone fragmentation initiated by side‐chain loss at cysteine residue in matrix‐assisted laser desorption/ionization in‐source decay mass spectrometry

Matrix‐assisted laser desorption/ionization in‐source decay (MALDI‐ISD) is initiated by hydrogen transfer from matrix molecules to the carbonyl oxygen of peptide backbone with subsequent radical‐induced cleavage leading to c′/z? fragments pair. MALDI‐ISD is a very powerful method to obtain long sequence tags from proteins or to do de novo sequencing of peptides. Besides classical fragmentation, MALDI‐ISD also shows specific fragments for which the mechanism of formation enlightened the MALDI‐ISD process. In this study, the MALDI‐ISD mechanism is reviewed, and a specific mechanism is studied in details: the N‐terminal side of Cys residue (Xxx‐Cys) is described to promote the generation of c′ and w fragments in MALDI‐ISD. Our data suggest that for sequences containing Xxx‐Cys motifs, the N–C_α bond cleavage occurs following the hydrogen attachment to the thiol group of Cys side‐chain. The c?/w fragments pair is formed by side‐chain loss of the Cys residue with subsequent radical‐induced cleavage at the N–C_α bond located at the left side (N‐terminal direction) of the Cys residue. This fragmentation pathway preferentially occurs at free Cys residue and is suppressed when the cysteines are involved in disulfide bonds. Hydrogen attachment to alkylated Cys residues using iodoacetamide gives free Cys residue by the loss of ?CH₂CONH₂ radical. The presence of alkylated Cys residue also suppress the formation of c?/w fragments pair via the (C_β)‐centered radical, whereas w fragment is still observed as intense signal. In this case, the z? fragment formed by hydrogen attachment of carbonyl oxygen followed side‐chain loss at alkylated Cys leads to a w fragment. Hydrogen attachment on peptide backbone and side‐chain of Cys residue occurs therefore competitively during MALDI‐ISD process. Copyright © 2013 John Wiley & Sons, Ltd.     

Fabrication of p/n heterojunctions by electrochemical deposition of Cu2O onto TiO2 nanotubes

This work describes the TiO₂ nanotubes formation by anodic oxidation under different experimental conditions and the following attempts to optimize the electrochemical deposition of Cu₂O within the nanotubular structure. The as-formed Cu₂O/TiO₂ interface is a p/n junction that could be used in various light-assisted devices. The effect of the F^– concentration, the polarization duration and the post-thermal treatment on the TiO₂ nanotubes is recalled. Then the electrochemical deposition of cuprous oxide is investigated by cyclic voltammetry and the influence of the pH on the morphology and crystal structure is studied. Finally, potential pulses were applied to optimize the Cu₂O film morphology in order to improve the nanotubes covering.     

Investigation of thermal and catalytic degradation of polystyrene waste into styrene monomer over natural volcanic tuff and Florisil catalysts

Thermal and catalytic degradation of polystyrene waste over two different samples of natural volcanic tuff catalyst comparative with Florisil catalyst has been carried out in order to establish the conversion degree into styrene monomer. The polystyrene waste (PS) was subjected to a thermal degradation process in the range of 380–500°C in presence of studied catalysts in a ratio of 1/10 in mass, catalyst/PS. The catalysts were characterized by N₂ adsorption-desorption isotherms (BET), Scanning Electron Microscopy (SEM) and Fourier-transform infrared spectrometry (FTIR). Influences of temperature and type of catalysts on the yields and on the distribution of end-products obtained by thermal and catalytic degradation of polystyrene waste have been studied. The maximum yields of liquid products were obtained at 460°C degradation temperature and were calculated between 83.45% and 90.11%. The liquid products were characterized by gas chromatography mass spectrometry (GC-MS) and FTIR analytical techniques. The GC-MS results showed that the liquid products contained styrene monomer up to 55.62%. The FTIR spectra of liquid products indicated the specific vibration bands of the functional groups of compounds of liquid products. The amounts of styrene monomer obtained were influenced by structural and textural properties of studied catalyst and the contribution on product distribution is discussed.      

High order direct parametrisation of invariant manifolds for model order reduction of finite element structures: application to large amplitude vibrations and uncovering of a folding point

This paper investigates model-order reduction methods for geometrically nonlinear structures. The parametrisation method of invariant manifolds is used and adapted to the case of mechanical systems in oscillatory form expressed in the physical basis, so that the technique is directly applicable to mechanical problems discretised by the finite element method. Two nonlinear mappings, respectively related to displacement and velocity, are introduced, and the link between the two is made explicit at arbitrary order of expansion, under the assumption that the damping matrix is diagonalised by the conservative linear eigenvectors. The same development is performed on the reduced-order dynamics which is computed at generic order following different styles of parametrisation. More specifically, three different styles are introduced and commented: the graph style, the complex normal form style and the real normal form style. These developments allow making better connections with earlier works using these parametrisation methods. The technique is then applied to three different examples. A clamped-clamped arch with increasing curvature is first used to show an example of a system with a softening behaviour turning to hardening at larger amplitudes, which can be replicated with a single mode reduction. Secondly, the case of a cantilever beam is investigated. It is shown that invariant manifold of the first mode shows a folding point at large amplitudes. This exemplifies the failure of the graph style due to the folding point on a real structure, whereas the normal form style is able to pass over the folding. Finally, a MEMS (Micro Electro Mechanical System) micromirror undergoing large rotations is used to show the importance of using high-order expansions on an industrial example.

     

On the Kinetics of Heterogeneous Free Radical Crosslinking Polymerization1)

Abstract

In this paper, two oximato complexes, mononuclear [Cu(Hdmg)₂] and binuclear [Cu₂(Hdmg)₂(H₂dmg)]ClO₄ · H₂O (H₂dmg: dimethylglyoxime), were synthesized and characterized. Hydrolyses of carboxyl acid esters, p‐nitrophenyl picolinate (PNPP) and p‐nitrophenyl acetate (PNPA), catalyzed by these two complexes were investigated in different micellar systems in the pH range from 6.58–8.65 at 25°C. The results obtained indicate that these two complexes exhibit good catalytic function. It also appears that both complexes accelerate the hydrolytic cleavage of PNPP and PNPA in cationic CTAB micellar solution faster than that in nonionic Brij35 micellar solution, which may be due to the different coordinating ability of substrates to complexes and electrostatic interaction between micelles and complexes. For binuclear Cu(II), the rate constant (k _N) for the hydrolysis of PNPA is about two times larger than that for PNPP in CTAB micellar solution, while in Brij35 micellar solution, the k _N values for PNPA and PNPP are roughly the same. This small difference may be ascribed to the configurations of intermediates formed during the reaction and electrostatic interaction between micelles and reactants.     

一种具有低SO2氧化活性并满足欧V排放标准的柴油车氧化型催化剂

制备了具有高性能的稀土储氧材料Ce_0.75Zr_0.25O₂-Al₂O₃,Ti_0.9Zr_0.1O₂复合材料和Cr改性的β分子筛(Cr-β分子筛),并以此制备了单Pt型柴油车尾气净化氧化型催化剂.低温N₂吸附-脱附、储氧量测试结果表明,Ce_0.75Zr_0.25O₂-Al₂O₃样品具有较大的比表面积和优异的储氧性能,Ti_0.9Zr_0.1O₂复合材料也具有优越的织构性能.催化剂对HC和CO具有较高的催化活性,可使SOF在140℃开始转化,且具有较低的SO₂氧化活性.在YC4F国Ⅳ柴油机的测试结果表明,经该催化剂处理后的尾气排放能够满足欧Ⅴ排放标准对HC和CO排放要求.