Andreas Chrysanthou

Bio: Andreas Chrysanthou is an academic researcher from University of Hertfordshire. The author has contributed to research in topics: Corrosion & Aluminium alloy. The author has an hindex of 24, co-authored 97 publications receiving 1907 citations. Previous affiliations of Andreas Chrysanthou include National Physical Laboratory & University of Nottingham.

TiC-TiB2 composites : A review of phase relationships, processing and properties

Abstract: Ceramic-matrix composites (CMCs) based on TiC–TiB2 have attracted enormous interest during recent years because, in comparison to single-phase ceramics, they exhibit superior properties including high hardness, good wear resistance and high fracture toughness. This paper begins with a review of the TiC–TiB2 equilibrium system and its possible influence on the processing and properties of the composite. The application of TiC–TiB2 composites has been limited due to the fact that they have been difficult to process. Much of the research effort has therefore focused on the synthesis, processing and fabrication of TiC–TiB2 and is based primarily on self-propagating high-temperature synthesis (SHS) and its derivatives, high-energy milling and sintering. The performance of SHS under the application of pressure has been the subject of particular investigation. These developments are the main subject of this review that also takes into account the resulting effects on the microstructure and the mechanical properties of TiC–TiB2. The influence of the reaction parameters like reactant composition, reactant particle size and green density on the microstructure and properties is also reported.

Self-piercing riveting-a review

Abstract: Self-piercing riveting (SPR) is a cold mechanical joining process used to join two or more sheets of materials by driving a rivet piercing through the top sheet or the top and middle sheets and subsequently lock into the bottom sheet under the guidance of a suitable die. SPR is currently the main joining method for aluminium and mixed-material lightweight automotive structures. SPR was originated half century ago, but it only had significant progress in the last 25 years due to the requirement of joining lightweight materials, such as aluminium alloy structures, aluminium-steel structures and other mixed-material structures, from the automotive industry. Compared with other conventional joining methods, SPR has many advantages including no pre-drilled holes required, no fume, no spark and low noise, no surface treatment required, ability to join multi-layer materials and mixed materials and ability to produce joints with high static and fatigue strengths. In this paper, research investigations that have been conducted on self-piercing riveting will be extensively reviewed. The current state and development of SPR process is reviewed and the influence of the key process parameters on joint quality is discussed. The mechanical properties of SPR joints, the corrosion behaviour of SPR joints, the distortion of SPR joints and the simulation of SPR process and joint performance are reviewed. Developing reliable simulation methods for SPR process and joint performance to reduce the need of physical testing has been identified as one of the main challenges.

Characteristics of the combustion synthesis of TiC and Fe-TiC composites

Abstract: The combustion synthesis of TiC, using the thermal explosion mode, was investigated by varying some of the process parameters including the reactant particle size, the pre-compaction pressure, and the heating rate. Based on these observations, a combustion model for the reaction was developed. When iron was added to titanium and carbon black powders, the ignition temperature was dictated by the eutectic temperature of the Fe-Ti system. Iron acted as a moderator for the reaction and led to a decrease in the combustion temperature.

Formation of silicon carbide whiskers and their microstructure

Abstract: Thermodynamic and kinetic conditions for the formation of SiC whiskers are established. The mechanism of their nucleation and growth are studied and, on this basis, the magnitude of the thermally activated barrier is determined from the rate of reduction data. The microstructures of whiskers are analysed and the role of interfacial tension between the nuclei and impurities, and the metallic iron catalyst is studied in relation to the formation of SiC whiskers. A possible reason for polytypism in SiC whiskers is also proposed.

Microstructural and mechanical characteristics of in situ metal matrix composites

Abstract: During the past decade, considerable research effort has been directed towards the development of in situ metal matrix composites (MMCs), in which the reinforcements are formed in situ by exothermal reactions between elements or between elements and compounds. Using this approach, MMCs with a wide range of matrix materials (including aluminum, titanium, copper, nickel and iron), and second-phase particles (including borides, carbides, nitrides, oxides and their mixtures) have been produced. Because of the formation of ultrafine and stable ceramic reinforcements, the in situ MMCs are found to exhibit excellent mechanical properties. In this review article, current development on the fabrication, microstructure and mechanical properties of the composites reinforced with in situ ceramic phases will be addressed. Particular attention is paid to the mechanisms responsible for the formation of in situ reinforcements, and for creep failure of the aluminum-based matrix composites.

Structural analysis

Abstract: Structures in Other Domains The methodology of structural analysis discussed in this article has been applied beyond the narrow realm of natural language syntax that we have discussed in this article. Within the study of language, similar methods of analysis have been pervasively applied to the study of sounds (phonology), words (morphology), and meanings (semantics), yielding a range of of abstract structural representations whose properties bear considerable explanatory burden. There are a wealth of cases in each of these domains analogous to those discussed here, though space prevents us from going in these (see Akmajian, Demers, Farmer and Harnish 1995 for a traditional overview, and Jackendo 1994 for one more focused on connections with cognitive science). Additionally, these representations have shed substantial light on the processes of language acquisition and language change. It has been found that variation in the types of sentences that are used, whether during the course of children's acquisition of their native languages or in the centuries-long periods of linguistic change, are best characterized not as super cial and haphazard alterations, but rather in terms of parametric modi cations to the fundamental underlying grammatical rules and constraints. Moving outside the domain of language, one application of these same methods has been in the study of music cognition. Just as the representations of linguistic theory arise out of an attempt to model speakers' intuitions about well-formedness and possible meanings of the sentences of their

Multiple Phases of Molybdenum Carbide as Electrocatalysts for the Hydrogen Evolution Reaction

Abstract: Molybdenum carbide has been proposed as a possible alternative to platinum for catalyzing the hydrogen evolution reaction (HER). Previous studies were limited to only one phase, β-Mo2C with an Fe2N structure. Here, four phases of Mo-C were synthesized and investigated for their electrocatalytic activity and stability for HER in acidic solution. All four phases were synthesized from a unique amine-metal oxide composite material including γ-MoC with a WC type structure which was stabilized for the first time as a phase pure nanomaterial. X-ray photoelectron spectroscopy (XPS) and valence band studies were also used for the first time on γ-MoC. γ-MoC exhibits the second highest HER activity among all four phases of molybdenum carbide, and is exceedingly stable in acidic solution.

Catalytic growth and characterization of gallium nitride nanowires.

Abstract: The preparation of high-purity and -quality gallium nitride nanowires is accomplished by a catalytic growth using gallium and ammonium. A series of catalysts and different reaction parameters were applied to systematically optimize and control the vapor−liquid−solid (VLS) growth of the nanowires. The resulting nanowires show predominantly wurtzite phase; they were up to several micrometers in length, typically with diameters of 10−50 nm. A minimum nanowire diameter of 6 nm has been achieved. Temperature dependence of photoluminescence spectra of the nanowires revealed that the emission mainly comes from wurtzite GaN with little contribution from the cubic phase. Moreover, the thermal quenching of photoluminescence was much reduced in the GaN nanowires. The Raman spectra showed five first-order phonon modes. The frequencies of these peaks were close to those of the bulk GaN, but the modes were significantly broadened, which is indicative of the phonon confinement effects associated with the nanoscale dimen...