Preparation of NiO/multiwalled carbon nanotube nanocomposite for use as the oxygen cathode catalyst in rechargeable Li–O2 batteries

NiO/multiwalled carbon nanotube (NiO/MWCNT) nanocomposites have been prepared and used for a Li–O₂ battery cathode catalyst. Electrochemical measurements demonstrate that the batteries with NiO/MWCNT catalyst have a discharge capacity of 2,500 mAh g^?1, a charge capacity of 2,100 mAh g^?1, and a rechargeable ability performing better than Ketjenblack (KB) and MWCNTs. KB has the largest discharge capacity (2,700 mAh g^?1) due to the highest surface area and pore volume but the worst charging behavior due to poor mass transport in the small-width pore (2.48 nm). MWCNTs have a much better charging performance owing to a larger pore width (8.93 nm) than carbon black. NiO/MWCNTs have the largest charge capacity because of the facilitated mass transport in the comparatively large pores (7.68 nm) and the increased catalytic ability produced by the NiO nanoparticles. These improvements are also responsible for the best cycle and rate performances of the nanocomposites among the three catalysts.     

Smooth Stable and Unstable Manifolds for Stochastic Evolutionary Equations

Invariant manifolds are fundamental tools for describing and understanding nonlinear dynamics. In this paper, we present a theory of stable and unstable manifolds for infinite dimensional random dynamical systems generated by a class of stochastic partial differential equations. We first show the existence of Lipschitz continuous stable and unstable manifolds by the Lyapunov–Perrons method. Then, we prove the smoothness of these invariant manifolds.Dedicated to Professor Shui-Nee Chow on the occasion of his 60th birthday.     

Two New Alkaline Metal Borates with Supramolecular Framework Constructed from 1D {B5}/{B6} Helical Chains

Two new alkaline metal borates containing 1D{B5}/{B6}oxoboron helical chains,namely Na0.5[B5O8(OH)2]0.5[B5O6(OH)2]0.5·0.5H3O(1)and NaKCs[B6O9(OH)3](2)were synthesized under solvothermal conditions.Compound 1 contains the interesting alternative left-and right-handed helical{[B5O8(OH)2][B5O6(OH)2]}2-({B5}-1 and{B5}-2)1D chains and compound 2 possesses the similar[B6O11(OH)3]7-({B6})chains.Their 1D chains are further assembled into 2D layers and 3D supramolecular frameworks through O-H…O hydrogen bonds.In addition,the UV cutoff edge of compounds 1 and 2 is both below 190 nm.     

Improved SOFC performance with continuously graded anode functional layer

Continuously graded anode functional layers (CG-AFLs) were fabricated on the Ni–YSZ anode substrates by electrophoretic co-deposition (EPD) technique. The microstructure and composition of the CG-AFLs were investigated. The result showed that uniform and graded structure in AFL was obtained. The single cells were constructed on the basis of CG-AFLs, with a maximum output power density greater than 1.10 W cm^?2 obtained at 800 °C for the cell with 9.8 μm-thick CG-AFL. Electrochemical impedance spectroscopy (EIS) indicated that the excellent cell performance was contributed to the enlargement of triple phase boundary (TPB) by adding the CG-AFL.     

Wong–Zakai approximations and attractors for stochastic reaction–diffusion equations on unbounded domains

In this paper, we study the Wong–Zakai approximations given by a stationary process via the Wiener shift and their associated long term behavior of the stochastic reaction–diffusion equation driven by a white noise. We first prove the existence and uniqueness of tempered pullback attractors for the Wong–Zakai approximations of stochastic reaction–diffusion equation. Then, we show that the attractors of Wong–Zakai approximations converges to the attractor of the stochastic reaction–diffusion equation for both additive and multiplicative noise.     

Preparation of YSZ thin films for intermediate temperature solid oxide fuel cells by dip-coating method

By studying the effects of different solvents, dispersants and solid loading amount on the suspension stability from sedimentation and viscosity experiments, a simple, effective and highly stable YSZ particle suspension based on MEK/EtOH was developed for dip-coating anode supported electrolyte films for intermediate temperature solid oxide fuel cells (IT-SOFCs). The morphologies of the prepared YSZ thin films from different dip-coating times were studied by scanning electron microscopy (SEM), and a film with a thickness of 16 μm by twice dip-coating was determined to be homogeneous, crack-free and well adherent to the anode substrate. The single cell assembled with this film presents an open-circuit voltage (OCV) of 1.01 V, and a maximum power density of 262 mW cm⁻² under H₂ as the fuel at 800 °C.     

Floquet bundles for scalar parabolic equations

For linear scalar parabolic equations such as on a finite interval 0x, with various boundary conditions, we obtain canonical Floquet solutions u _n (t, x). These solutions are characterized by the property that z(u _n (t, x))=n for all t, where z(·) denotes the zero crossing (lap) number of Matano. The coefficients a(t, x) and b(t, x) are not assumed to be periodic in t, but if they are, the solutions u _n (t, x) reduce to the standard Floquet solutions. Our results may naturally be expressed in the language of linear skew product flows. In this context, we obtain for each N1 an exponential dichotomy between the bundles span {u _n (·,·)} _n ^=1/N and .     

Two-level additive Schwarz preconditioners for C 0 interior penalty methods

We study two-level additive Schwarz preconditioners that can be used in the iterative solution of the discrete problems resulting from C⁰ interior penalty methods for fourth order elliptic boundary value problems. We show that the condition number of the preconditioned system is bounded by C(1+(H³/δ³)), where H is the typical diameter of a subdomain, δ measures the overlap among the subdomains and the positive constant C is independent of the mesh sizes and the number of subdomains. This work was supported in part by the National Science Foundation under Grant No. DMS-03-11790.     

Sternberg theorems for random dynamical systems

In this paper, we prove the smooth conjugacy theorems of Sternberg type for random dynamical systems based on their Lyapunov exponents. We also present a stable and unstable manifold theorem with tempered estimates that are used to construct conjugacy. © 2005 Wiley Periodicals, Inc.     

Random attractors for stochastic reaction-diffusion equations on unbounded domains

The existence of a pullback attractor is established for a stochastic reaction-diffusion equation on all n-dimensional space. The nonlinearity is dissipative for large values of the state and the stochastic nature of the equation appears as spatially distributed temporal white noise. The reaction-diffusion equation is recast as a random dynamical system and asymptotic compactness for this is demonstrated by using uniform a priori estimates for far-field values of solutions.