Evolution of grain structure in thin film reactions

In this paper, we examine, both experimentally and theoretically, the kinetics of formation and microstructure of product phases in thin film reactions, using the Nb/Al and Ti/Al systems as our prototypes. The results of calorimetry and microscopy studies are interpreted using simple kinetic and morphology models. In particular, the kinetic models employed here focus on the nucleation and growth components of the phase formation process and the morphology models provide a starting point for the classification of product grain structures. An erratum to this article is available at .     

Characterization of single and discretely-stepped electro-composite coatings of nickel-alumina

Electrodeposition from a sulfamate bath has been used to produce single layer and discretely stepped electro-composites consisting of a metallic nickel matrix with second phase alumina (-Al₂O₃) particles. Light optical microscopy (LOM), scanning electron microscopy (SEM), quantitative image analysis (QIA), and micro-indentation techniques were used to characterize the deposits. As previously seen, an increase in bath particle loading and decrease in plating current density increased the volume percent of alumina incorporated into the coating, with a maximum of 40 vol % being attained. For samples deposited above 1 A/dm², a direct relationship between the alumina volume percent and coating hardness was seen due in part to the related decrease in interparticle spacing (IPS) at the higher vol %. However, the strengthening mechanism of the electro-composites may be more complex with both the metallic nickel grain structure and IPS being factors, as seen for samples deposited at 0.5 A/dm². The incorporation of alumina into the electrodeposited nickel was also observed to affect the as-plated surface structure of the coating. Due to the particles inhibiting the formation of pyramidal features found on the surface of pure nickel electrodeposits, the electro-composite surfaces were observed to be relatively flat. Also, structure within the metallic nickel matrix appeared due to rapid growth of the nickel coating around the inert particles when plated at high current densities. In addition, discretely layered functionally graded materials were produced without alterations to the original deposition procedure of the single layer deposits. It was found that the various processing stages needed to produce the stepped coatings did not affect the structure or properties of the individual layers, when compared to that of the corresponding single-layered electro-composites.     

Predictive Text Typing System for the Ukrainian Language

This paper investigates the intellectualization of text input using a system for accelerated input of texts into digital devices with a view to constructing a model of a corpus of the Ukrainian spoken language and a text typing system based on this model. Such a system uses a smaller number of commands to input letters and predicts variants of words on the basis of the corpus of words and word combinations for communication. It is experimentally shown that the input of texts using four and six command keys is rather efficient for the constructed corpus.     

Construction and identification of elements of sign communication

This article proposes mathematical models and an information technology for constructing movements of a virtual person and reproducing a sign language based on a set of gesture units and transitions between them. The implementation of movement reproduction in a virtual model allows obtaining a real-time animation of sign information. The efficiency of the proposed approach is illustrated by an example of modelling and identifying dactyl information.     

Cytoskeleton Elements Contribute to Prion Peptide-Induced Endothelial Barrier Breakdown in a Blood–Brain Barrier In Vitro System

The mechanisms involved in the interaction of PrP 106-126, a peptide corresponding to the prion protein amyloidogenic region, with the blood–brain barrier (BBB) were studied. PrP 106-126 treatment that was previously shown to impair BBB function, reduced cAMP levels in cultured brain endothelial cells, increased nitric oxide (NO) levels, and changed the activation mode of the small GTPases Rac1 (inactivation) and RhoA (activation). The latter are well established regulators of endothelial barrier properties that act via cytoskeletal elements. Indeed, liquid chromatography-mass spectrometry (LC-MS)-based proteomic profiling study revealed extensive changes in expression of cytoskeleton-related proteins. These results shed light on the nature of the interaction between the prion peptide PrP 106-126 and the BBB and emphasize the importance of the cytoskeleton in endothelium response to prion- induced stress.     

Interaction of iron-chromium alloys containing 10 and 25 mass% chromium with liquid aluminium Part II Formation of intermetallic compounds

Two intermetallic layers Fe₂Al₅ and Fe₂Al₇ occur at the interface between the iron-chromium alloys containing 10 and 25 mass% Cr and the saturated aluminium melt at 700°C. Under conditions of simultaneous dissolution in pure liquid aluminium only the Fe₂Al₅ phase forms an adherent continuous layer, while the Fe₂Al₇, FeAl₃, FeAl₆, CrAl₇ and other phases exist as inclusions in the aluminium matrix. Dissolution of the Fe—Cr alloy base into pure aluminium causes a three-fold decrease in layer thickness compared with the case where no dissolution occurs. A simple equation for evaluating the Fe₂Al₅ layer thickness during dissolution is proposed. Making the Fe—Cr alloy-to-aluminium transition joints, with the mechanical strength of the joint greater than or equal to that for pure aluminium (70–80 MPa), appears to be feasible.     

Microstructural characterization and hardness of electrodeposited nickel coatings from a sulphamate bath

Pure nickel plates were produced from a sulphamate bath by electrodeposition. A systematic variation of the current density, in the range 0.005 to 0.25 Acm^–2, resulted in a variation of the coating microstructure and properties. Deposits plated below a current density of 0.01 Acm^–2 had a surface morphology consisting of large, deep crevices surrounding smaller substructures. A banded or laminar type microstructure was observed in cross-section. Above this current density, truncated pyramidal structures, with ridged terraces oriented perpendicular to the growth direction, were found on the surface. The planar dimensions of the pyramidal surface features were found to increase with current density, as well as the columnar grain widths observed in the cross-sectional view. To evaluate the mechanical properties of the coatings, microindentation hardness tests were performed using a Knoop indenter. A Hall–Petch type relationship for the samples deposited at and above 0.01 Acm^–2 was seen.