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Zeng R.,Shandong University of Science and Technology | Zeng R.,Chongqing University of Technology | Lan Z.,Chongqing University of Technology | Kong L.,Chongqing University of Technology | And 2 more authors.
Surface and Coatings Technology | Year: 2011

Two kinds of phosphate conversion coatings, including zinc phosphate coating and zinc-calcium phosphate coating, were prepared on the surface of AZ31 alloy in phosphate baths. The morphologies of these coatings were observed using scanning electron microscopy. Their chemical compositions and structures were characterized using energy-dispersive X-ray spectrum, X-ray photoelectron spectroscopy and X-ray diffraction. The corrosion resistance of the coatings was evaluated by potentiodynamic polarization technique. The results show that the flowerlike Zn-Ca phosphate conversion coatings are mainly composed of hopeite (Zn3(PO4)2·4H2O). They have a quite different morphology from the dry-riverbed-like Zn phosphate coatings that consist of MgO, MgF2, Zn or ZnO and hopeite. Both of the zinc and zinc-calcium phosphate coatings can remarkably reduce the corrosion current density of the substrates. The Zn-Ca coating exhibits better corrosion resistance than the Zn coating. Introduction of calcium into the phosphate baths leads to the full crystallinity of the Zn-Ca coating. © 2010 Elsevier B.V.

Kim D.-K.,Korea Atomic Energy Research Institute | Kim D.-K.,Hanyang University | Ganesan R.,Korea Advanced Institute of Science and Technology | Ganesan R.,GKSS Forschungszentrum Geesthacht GmbH | And 6 more authors.
Polymers for Advanced Technologies | Year: 2011

Micropatterns of proteins were created by using patterned ion beam irradiation onto a polyethylene film and graft polymerization of acrylic acid. Acrylic acid was selectively graft polymerized on the irradiated regions. The results of the grafting study revealed that the optimum fluence to achieve the maximum grafting degree was 1×1015ions/cm2. Biotin was covalently immobilized on the grafted regions of the polyethylene film. Protein patterning was achieved through specific binding of biotin and streptavidin. The resolved protein patterns with the maximum fluorescence intensity were achieved on the poly(acrylic acid) (PAA)-grafted polyethylene films prepared at the fluence of 1×1015ions/cm2. This method can be used for patterning of various biomolecules and for further biological applications. © 2010 John Wiley & Sons, Ltd.

Dietzel W.,GKSS Forschungszentrum Geesthacht GmbH
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2011

Fracture-mechanics-based test and evaluation techniques provide insight into the phenomenon of stress corrosion cracking (SCC) and help to develop guidance for avoiding or controlling SCC. In addition to constant load and constant deflection tests, techniques that are based on rising load or rising displacement procedures are applied increasingly in fracture mechanics SCC testing. Rising displacement tests on precracked specimens were used for studying hydrogen embrittlement (HE) and to serve as a basis for modeling material degradation caused by the uptake of atomic hydrogen from the environment. The measurements of the crack-tip opening angle and of the crack-tip opening displacement combined with crack growth velocity data served to rationalize the experimental findings by comparison with the results of simulations of HE using various models. © 2010 The Minerals, Metals & Materials Society and ASM International.

Madbouly S.A.,GKSS Forschungszentrum Geesthacht GmbH | Madbouly S.A.,Cairo University | Lendlein A.,GKSS Forschungszentrum Geesthacht GmbH
Advances in Polymer Science | Year: 2010

The development of shape-memory polymer composites (SMPCs) enables high recovery stress levels as well as novel functions such as electrical conductivity, magnetism, and biofunctionality. In this review chapter the substantial enhancement in mechanical properties of shape-memory polymers (SMPs) by incorporating small amounts of stiff fillers will be highlighted exemplarily for clay and polyhedral oligomeric silsesquioxanes (POSS). Three different functions resulting from adding functional fillers to SMP-matrices will be introduced and discussed: magnetic SMPCs with different types of magnetic nanoparticles, conductive SMPCs based on carbon nanotubes (CNTs), carbon black (CB), short carbon fiber (SCF), and biofunctional SMPCs containing hydroxyapatite (HA). Indirect induction of the shape-memory effect (SME) was realized for magnetic and conductive SMPCs either by exposure to an alternating magnetic field or by application of electrical current. Major challenges in design and fundamental understanding of polymer composites are the complexity of the composite structure, and the relationship between structural parameters and properties/functions, which is essential for tailoring SMPCs for specific applications. Therefore the novel functions and enhanced properties of SMPCs will be described considering the micro-/nanostructural parameters, such as dimension, shape, distribution, volume fraction, and alignment of fillers as well as interfacial interaction between the polymer matrix and dispersed fillers. Finally, an outlook is given describing the future challenges of this exciting research field as well as potential applications including automotive, aerospace, sensors, and biomedical applications. © 2009 Springer-Verlag Berlin Heidelberg.

Gosalawit-Utke R.,GKSS Forschungszentrum Geesthacht GmbH | Bellosta Von Colbe J.M.,GKSS Forschungszentrum Geesthacht GmbH | Dornheim M.,GKSS Forschungszentrum Geesthacht GmbH | Jensen T.R.,University of Aarhus | And 4 more authors.
Journal of Physical Chemistry C | Year: 2010

LiF-MgB2 composites are proposed for reversible hydrogen storage. With respect to pure LiBH4, a significantly kinetic destabilization regarding hydrogenation and dehydrogenation is accomplished. The reversible hydrogen storage capacity is up to 6.4 wt %. The kinetic properties are improved significantly during cycling. The formations of the hydridofluoride phases (LiBH4-yFy and LiH1-xFx) are observed by in situ synchrotron X-ray diffraction (XRD) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Hydrogenation and dehydrogenation mechanisms are described on the basis of the formation and decomposition of the hydridofluoride phases, respectively. © 2010 American Chemical Society.

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