International Journal of Materials Research Volume 98 Issue 7

International Journal of Materials Research

Volume 98 Issue 7

Contents
Journal Overview

May 23, 2013 Page range: 545-545

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Editorial

May 23, 2013 Page range: 546-551

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Basic

Diffusional decomposition of supersaturated solid solutions at grain boundaries

Vitaly Slezov, Yuri Boyko, Jörg Weissmüller May 23, 2013 Page range: 553-561

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Abstract

A kinetic theory of nucleation and growth of single atom phase precipitates in a supersaturated solid solution at grain boundaries is developed. In the present theory, particular attention is devoted to the analysis of two stages of the overall transformation process: (1) – a stage of quasi-steady-state nucleation and (2) – a transient stage of coarsening. As a result of this analysis, the quasi-steady-state nucleation rate, the number of new phase particles formed via nucleation and diffusional growth, and the time-evolution of the size distribution of the precipitates are established. Moreover, estimates are given for the duration of the different stages of the decomposition process.

Characterization of oriented protein-ceramic and protein-polymer-composites for cartilage tissue engineering using synchrotron μ-CT

Rolf Zehbe, Astrid Haibel, Christoph Brochhausen, Ulrich Gross, C. James Kirkpatrick, Helmut Schubert May 23, 2013 Page range: 562-568

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Abstract

In this paper we report on the synthesis of three different gelatine based scaffold materials for the reconstruction of articular cartilage defects. The first scaffold design is based on an unmodified, oriented gelatine network, while the second design further comprises an attached inorganic hydroxyapatite layer and the third design includes poly(l-lactide) microspheres as a model material for future drug-release applications. All three scaffold designs were characterized and imaged using synchrotron μ-CT, obtaining a complete volumetric reconstruction of a previously defined sample region. Furthermore, two unmodified scaffolds were cultivated for one week with porcine chondrocytes. Afterwards the attached cells were labelled using a combination of Au-lysine and silver enhancer. In synchrotron μ-CT analysis we were thus able to map the cell distribution due to the difference in X-ray absorption of the labelled cells and the non labelled scaffolds in a volume of several millimetres.

Effect of ageing on optical and thermal properties of YBa2Cu3O7–δ

Pantelija M. Nikolic, Stevan S. Vujatovic, Konstantinos M. Paraskevopoulos, Kostas T. Zorbas, Slavica M. Savic, Maria Vesna Nikolic, Obrad S. Aleksic, Momcilo M. Ristic May 23, 2013 Page range: 569-573

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Abstract

Photoacoustic phase and amplitude spectra of YBa 2 Cu 3 O 7 – δ samples synthesised 18 years ago were measured and numerically analysed. The value of thermal diffusivity obtained on the aged samples was lower than the values obtained for fresh samples. Far infrared spectra of YBa 2 Cu 3 O 7 – δ samples synthesised 18 years ago were recorded and analysed enabling determination of reflectivity peak phonon frequencies present at room temperature. X-ray diffraction analysis and far infrared reflectivity measurements enabled determination of a slight change of the oxygen content with time. The YBa 2 Cu 3 O 7 – δ samples synthesised 18 years ago still remained superconducting, which was confirmed by resistivity measurements of the samples between 50 K and room temperature where the critical temperature was reduced from 93 to 73 K. Atomic force microscopy, scanning electron microscopy and energy dispersive X-ray microanalytical measurements were also performed confirming the composition of the sample.

Calorimetric study and thermodynamic assessment of the SrO–Ga2O3 system

Matvei Zinkevich May 23, 2013 Page range: 574-579

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Abstract

Enthalpies of formations of Sr 4 Ga 2 O 7 , SrGa 2 O 4 , and SrGa 12 O 19 are measured for the first time using high-temperature oxide-melt drop-solution calorimetry. A self-consistent thermodynamic dataset for the SrO – Ga 2 O 3 system is derived by means of the CALPHAD method based on these data, literature phase diagram information, and recent structural studies. In total seven compounds, Sr 4 Ga 2 O 7 , Sr 10 Ga 6 O 19 , Sr 3 Ga 2 O 6 , Sr 3 Ga 4 O 9 , SrGa 2 O 4 , SrGa 4 O 7 , and SrGa 12 O 19 are included. Their enthalpy of formation as well as the enthalpy of mixing of the liquid is strongly exothermic. The systematic variation of thermodynamic properties with composition is discussed in terms of the structural relationships between strontium gallates and the possible formation of associates in the liquid phase.

Re-determination of transition temperatures in the Fe–Al system by differential thermal analysis

Frank Stein, Martin Palm May 23, 2013 Page range: 580-588

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Abstract

The Fe – Al phase diagram has been experimentally re-investigated by differential thermal analysis on 64 alloys with different compositions in the concentration range between 0 and 74 at.% Al. For the melting temperatures, the existence of a shallow maximum at low Al-contents is proven experimentally for the first time. In the solid state, critical temperatures and invariant reactions as well as the order/disorder and ferro-/paramagnetic transitions occurring in the Fe-rich part of the binary system are studied in detail. For the most part, the present data confirm recent assessments of the Fe – Al phase diagram. Small corrections are suggested for some of the critical temperatures. Several effects related to the re-arrangement and annealing out of defects in the B2-ordered FeAl phase are also described. No effect which could be related to the K state has been found. Instead an effect was observed in the same temperature range but for a much wider range of compositions, which is probably due to the formation/dissolution of Fe 3 AlC precipitates.

Applied

Novel corrosion protective coatings for aluminium alloys and steels based on oxidic nanoparticles

Wolfram Fürbeth, Hong-Quang Nguyen, Michael Schütze May 23, 2013 Page range: 589-596

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Abstract

Based on chemical nanotechnology glass-like protective coatings thermally processed at comparatively low temperatures of around 500 °C were developed for aluminium and steel substrates by two different means. Starting from polymeric sols containing a multicomponent oxide of the SiO 2 – B 2 O 3 – P 2 O 5 – Na 2 O system produced by sol-gel technology under acidic conditions, coatings were developed which are thin, hard, transparent, crack-free and corrosion resistant. Electrophoretic deposition of coatings from particulate sols containing multicomponent oxide synthesised under basic conditions proved to be a promising method when very thick coatings are required. Both routes offer the potential of a new type of purely inorganic coatings for corrosion and abrasion protection.

Novel biomimetically based ice-nucleating coatings

Thomas Zwieg, Victor Cucarella, Michael Kauffeld May 23, 2013 Page range: 597-602

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Abstract

Ice nucleation and ice repellence are properties which appear to be contradictory. Both are of great importance: The former for ice generation in the food and cooling industry and the latter for avoiding the adhesion of ice to structures. By mimicking a peculiar survival mechanism of some cold-adapted organisms a new type of coating system, able to both nucleate and repel the ice was developed. A heterogeneous surface containing locally isolated nucleation points in a low surface energy matrix were synthesised by a sol-gel process. The ice nucleating and ice releasing performance of the new ice nucleating coatings (INC) has been tested in a specially designed crystallisation chamber in comparison to commercial low surface energy coating systems. A mixture of demineralised water and a water freezing point depressant was used in the experiments. Compared to the commercial coatings, the INC surfaces showed a much higher ice nucleation rate but also a distinctly better ice releasing ability. Obviously the novel concept of local embedded nucleation points improves the ice repellent properties of surfaces.

Biomimetically inspired hybrid materials based on silicified collagen

Sascha Heinemann, Hermann Ehrlich, Christiane Knieb, Thomas Hanke May 23, 2013 Page range: 603-608

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Abstract

Starting from a natural example, several hybrid materials based on silicified collagen were synthesised under ambient conditions. The biomimetic approach and further steps allowed the production of porous as well as dense constructs whose structural assembly was similar to that observed microscopically in the natural glass fibres made by sponges. Chemical analyses showed the collagen used serving as an organic template that binds silicic acid whose condensation results in local silicification and strengthening of the hybrid. This effect was emphasised by mechanical testing. Compressive strength of the porous scaffolds has been increased by about four times and splitting tensile strength of the xerogels by up to six times due to hybridisation. As the hybrid materials additionally show proper biocompatibility, they seem to be suitable for medical applications, especially as a base material for load-bearing implants.

Magnesium sponges as a bioabsorbable material – attributes and challenges

Friedrich-Wilhelm Bach, Dirk Bormann, Rafael Kucharski, Andrea Meyer-Lindenberg May 23, 2013 Page range: 609-612

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Abstract

The aim of the present article is to make a contribution to establishing magnesium as a temporary reabsorbing implant material. With regard to its mechanical properties, magnesium shows very similar behaviour to that of bone; nevertheless no clinical applications for load bearing implants in osteosynthesis exist. Magnesium sponges with an open porous structure exhibit, apart from a mechanical similarity, a geometrical similarity to bone and therefore possess great potential for use as an osteosynthetic material. The structural and mechanical properties of magnesium sponges will be presented as well as possibilities for adjusting the mechanical properties.

Morphology of bony tissues and implants uncovered by high-resolution tomographic imaging

Bert Müller, Ricardo Bernhardt, Timm Weitkamp, Felix Beckmann, Rolf Bräuer, Uta Schurigt, Annelies Schrott-Fischer, Rudolf Glueckert, Michael Ney, Thomas Beleites, Claude Jolly, Dieter Scharnweber May 23, 2013 Page range: 613-621

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Abstract

Synchrotron radiation-based micro computed tomography contributes to the increasing demand for uncovering non-destructively the microscopic morphology of bony tissues and their interface regions with implants using isotropic spatial resolution in three-dimensional space. Using the microscopic ring structure of otoliths, the coherence-related interplay between density resolution and spatial resolution is demonstrated. The monochromatised, highly intense synchrotron radiation allows analysis of the morphology of arthritic joints without significant beam-hardening artefacts in a quantitative manner. It further enables intensity-based segmentation of metallic implants within bone and thereby to quantitatively study the bone morphology around different kinds of middle and inner ear implants. This knowledge permits improving medical interventions and optimising the implant's design with respect to surface modification, mechanical properties, and shape.

Review

The effects of metal implants on inflammatory and healing processes

Roman Tsaryk, Kirsten Peters, Ronald E. Unger, Dieter Scharnweber, C. James Kirkpatrick May 23, 2013 Page range: 622-629

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Abstract

Metal implants are known for their superior mechanical properties. However, cases of implant failure mainly due to aseptic loosening do occur. The formation of particulate wear debris and corrosion products, such as metal ions and reactive oxygen species, are considered to be crucial factors leading to the failure of metal implants. These metal degradation and corrosion products can induce inflammatory responses, mediated among others by neutrophils, macrophages and endothelial cells. Furthermore, these degradation products may affect blood vessel formation, one of the central processes in wound healing after implantation. Such events can lead to the aseptic loosening of implants culminating in the necessity for revision surgery.

Formation of nano hydroxyapatite – a straightforward way to bioactivate bone implant surfaces

Berthold Nies, Sophie Rößler, Antje Reinstorf May 23, 2013 Page range: 630-636

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Abstract

Bioactivity has been a field of biomaterials research for more than 25 years. However, clinical application of bioactive implants is progressing rather slowly and is still limited to a few types of bone implants. The increased understanding of the molecular mechanisms underlying bioactivity has opened up new attractive opportunities to render conventional implant materials such as metals, ceramics and even polymers bioactive. In particular, biomimetic nano hydroxyapatite coatings and in-situ mineralising surfaces induced by incorporation of mineralisation seeds are applicable to a wide variety of implant types and materials. They have the potential to set new standards for the improved performance of orthopaedic implants whilst complying with the economic constraints on healthcare.

Drug-eluting stent technologies for vascular regeneration

Klaus-Peter Schmitz, Niels Grabow, Marian Löbler, Detlef Behrend, Wolfram Schmidt, Katrin Sternberg May 23, 2013 Page range: 637-642

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Abstract

Currently, first generation drug-eluting stents are widely used in clinical practice to revascularize stenotic arterial vessel segments, and to prevent in-stent restenosis and other shortcomings of conventional bare metal stents. However, clinically relevant risks associated with current drug-eluting stents, such as delayed healing, late thrombosis and hypersensitivity, as well as the permanent nature of the stents represent challenges for further development in this field. This paper reviews current drug-eluting stent technology, and describes recent advances towards a second generation of drug-eluting stents. Particular emphasis is put on the development of stents from bioabsorbable materials as a temporary alternative to permanent stent implants.

Fiber structures for the regenerative medicine

Heinrich Planck, Michael Doser May 23, 2013 Page range: 643-645

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Abstract

Regenerative medicine is a very promising field of research, which claims to heal damaged tissue instead of replacing it with artificial spare parts. Due to the mechanical behavior of fibers, similar to the fibrous structures most of our body tissues are made of, fibers are very biocompatible and suitable as carrier materials for cells and for the guided regeneration of tissues, mainly if the mechanical load is limited. Three examples demonstrate that for every tissue different properties of textiles and fibers are necessary. In liver regeneration the cell carrier must allow the attachment of the hepatocytes to one another for the formation of aggregates, otherwise the functionality of the cells is low. In cartilage regeneration the main challenge is the optimal degradation properties of the matrix for single cells allowing the unrestricted formation of a new matrix by the cells. In nerve regeneration structured fibers allow a faster outgrowth of new axons.

Stimuli-responsive polymer layers for advanced cell culture technologies

Brigitte Voit, Dirk Schmaljohann, Stefan Gramm, Mirko Nitschke, Carsten Werner May 23, 2013 Page range: 646-650

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Abstract

A series of graft copolymers consisting of poly(N-isopropylacrylamide) as a thermoresponsive component in the polymer backbone and poly(ethyleneglycol) side chains were immobilized as thin films on various substrates via low-pressure plasma treatment. The surface-immobilized hydrogels exhibit a transition from partially collapsed to completely swollen, which is in the range of 32 – 35 °C and corresponds to the lower critical solution temperature of the soluble polymers. Cell culture and detachment experiments were performed with mouse fibroblasts and human corneal endothelial cells under standard conditions. The hydrogel-coated supports were found to permit adhesion, spreading and proliferation of the cells and allowed for fast and effective temperature-dependent detachment of intact cell sheets of both cell types. Thus, these coatings offer an efficient method for growth and gentle harvesting of functional cellular assemblies for use in tissue engineering strategies.

Notifications

Robert W. Cahn: 1924–2007

Olivier Hardouin Duparc May 23, 2013 Page range: 651-654

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Abstract

R.W. Cahn died on the 9th of April. Wonderfully gifted from birth, his personality has been shaped by 20th Century history which forced him to flee from Germany to England through Spain. Chance and opportunities led him to study metallurgy at Cambridge and to later become one of the founders of Materials Science, and one of its best advocates. Some elements of his life and achievements are recalled here, as an homage to both the scientist and the man.

DGM News

May 23, 2013 Page range: 655-658

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About this journal

The International Journal of Materials Research (IJMR) publishes original high quality experimental and theoretical papers and reviews on basic and applied research in the field of materials science and engineering, with focus on synthesis, processing, constitution, and properties of all classes of materials. Particular emphasis is placed on microstructural design, phase relations, computational thermodynamics, and kinetics at the nano to macro scale. Contributions may also focus on progress in advanced characterization techniques.
All articles are subject to thorough, independent peer review.