The fracture and fatigue behaviour of nano-modified epoxy polymers

The introduction of nano-silica particles into an epoxy polymer has increased both the initial toughness, as measured by the fracture toughness, K_Ic, and also significantly improved the cyclic-fatigue behaviour of the epoxy polymer. Thus, the significant increases recorded in the values of the range of applied stress-intensity factor at threshold, ΔK_th, from the cyclic-fatigue tests for the nano-silica modified materials are very noteworthy, since these increases are accompanied by significant improvements being recorded in the initial toughness.     

Development of 2D band-target entropy minimization and application to the deconvolution of multicomponent 2D nuclear magnetic resonance spectra

Spectral reconstruction from multicomponent spectroscopic data is the frequent primary goal in chemical system identification and exploratory chemometric studies. Various methods and techniques have been reported in the literature. However, few algorithms/methods have been devised for spectral recovery without the use of any a priori information. In the present studies, a higher dimensional entropy minimization method based on the BTEM algorithm (Widjaja, E.; Li, C.; Garland, M. Organometallics 2002, 21, 1991-1997.) and related techniques were extended to large-scale arrays, namely, 2D NMR spectroscopy. The performance of this novel method had been successfully verified on various real experimental mixture spectra from a series of randomized 2D NMR mixtures (COSY NMR and HSQC NMR). With the new algorithm and raw multicomponent NMR alone, it was possible to reconstruct the pure spectroscopic patterns and calculate the relative concentration of each species without recourse to any libraries or any other a priori information. The potential advantages of this novel algorithm and its implications for general chemical system identification of unknown mixtures are discussed.     

Unidirectional solidification of Ni-Mo-Al eutectic alloys

The composition triangle of the Ni-Mo-Al ternary system contains a monovariant trough between theγ′ (Ni₃Al)-α(Mo) pseudobinary eutectic and a guessedγ(Ni)-γ′ (Ni₃Al)-α(Mo) ternary eutectic. Alloys with compositions on this trough were directionally solidified at various growth rates. The microstructure of the alloys consists of fine Mo fibres of rectangular cross-section in an Ni₃Al/Ni matrix. The determined crystallographic relationship does not correspond to an interface of low lattice mismatch. The eutectic trough strongly extends towards increasing Mo contents so that the volume fraction of the Mo fibres varies between 18 and 25% dependent on composition. It was not possible to determine the position of a ternary eutecticγ-γ′-α because the liquidus temperatures along the trough are almost equal and the distribution of the three phases is strongly dependent on the growth rate.     

Thermoresponsive Microspheres as Smart Pore Plugs: Self‐Venting Clothing Membranes for Smart Outdoor Textiles

Rapidly changing temperature and precipitation conditions are challenging for clothing textiles when required to keep us warm under harsh weather. A smart functional outdoor membrane based on thermoresponsive poly(N‐isopropylacrylamide) (PNIPAM) microspheres embedded into a polyurethane matrix is developed. Selective dissolution of two‐particle composite precursors affords porous membranes with PNIPAM microspheres located within the pore walls. Adjusting the mean size of the thermoresponsive microplug permits us to switch membrane breathability depending on outdoor temperature. In cold conditions, the textile fabric closes off pores and reduces heat loss, as to keep a person warmer. Under hot conditions, the PNIPAM microplugs open up, and self‐vent the jacket, allowing for high breathability and heat transfer. The resulting smart membranes are tested according to international standards. The principle of phase separation based microplug positioning within pores, and selective opening and closing of pores may enable other smart applications in material sciences, biology, and other consumer products.     

Effect of microstructure on electrical and mechanical properties of La5.4WO12-δ proton conductor

The relationships between microstructural characteristics and electrical as well as mechanical properties of La_5.4WO_12-δ (LWO54) materials were studied. Polycrystalline LWO54 samples revealed identical transport mechanisms regardless of the sample microstructure. The studied samples show predominately proton conductor behaviour below 800?°C and become predominant n-type and oxygen ion conductors above this temperature. The magnitude of the total conductivity is enhanced with larger grain size and lower porosity. Young’s modulus decreased by 20% with increasing temperature up to 1000?°C regardless of grain size and atmosphere. Fracture strength was determined via ring-on-ring bending tests, yielding values that strongly depended on microstructural characteristics and homogeneity of the microstructure. Elevated temperature deformation studies revealed that creep is governed by cation diffusion mechanism.     

The transaldolase family: new synthetic opportunities from an ancient enzyme scaffold

Aldol reactions constitute a powerful methodology for carbon-carbon bond formation in synthetic organic chemistry. Biocatalytic carboligation by aldolases offers a green, uniquely regio- and stereoselective tool with which to perform these transformations. Recent advances in the field, fueled by both discovery and protein engineering, have greatly improved the synthetic opportunities for the atom-economic asymmetric synthesis of chiral molecules with potential pharmaceutical relevance. New aldolases derived from the transaldolase scaffold (based on transaldolase B and fructose-6-phosphate aldolase from Escherichia coli) have been shown to be unusually flexible in their substrate scope; this makes them particularly valuable for addressing an expanded molecular range of complex polyfunctional targets. Extensive knowledge arising from structural and molecular biochemical studies makes it possible to address the remaining limitations of the methodology by engineering tailored biocatalysts.