Influence of carbon on the formation of γ/γ′ microstructure and κ-phase in the WC/Co–Ni–Al–W system: ab initio calculations and experimental studies

Modifications of the binder phase (γ) of cemented carbides have the potential to increase the hardness and wear resistance of the whole material. Partially, coherent precipitations with L1₂ structure (γ’) promise these improved properties without sacrificing tensile strength or toughness. γ’ is a metastable phase in the Al–Co–W ternary system in the form of Co₃(Al,W) which is stabilized by the substitution of cobalt with nickel. Superalloys of the composition Co–(30Ni)–9Al–7 W with different carbon contents were prepared by inductive melting, and the resulting microstructures were analysed using SEM–EDS, XRD and Vickers hardness. Cemented carbides with γ/γ’ binder microstructure were prepared via DTA, and the phase equilibria in the composite material were investigated experimentally and in silico. It was shown that nickel stabilizes the γ’ phase in superalloys as well as in cemented carbides. Carbon leads to the formation of an additional phase with E2₁ structure (κ). DTA measurements of cemented carbides with different aluminium–cobalt–nickel mixtures as binder gave an overview of the compositional influence. Enthalpies of formation for compounds with L1₂ and E2₁ structure were calculated using ab initio methods and compared to experimental results.

Graphical Abstract

     

From Smart Grid to Active Grid

When it comes to managing the delivery and use of energy and water, there's a lot of opportunity for improvement. Each year in the United States alone, nearly $100 billion in energy and water are wasted, stolen, or otherwise lost before reaching the end-user. As migration toward urban centers accelerates, cities are under increasing pressure to manage resources more effectively and to use new technology to make the urban landscape more livable, sustainable, and economically vibrant.     

Focusing high-energy x rays by compound refractive lenses

Compound lenses made from low-Z materials (e.g., Be, B, C, and Al) set up as a linear array of refractive lenses are proposed for submicrometer focusing of high-energy x rays (>5 keV) in one or two dimensions. A theory of focusing based on Maxwell's equation and the Fresnel-Kirchhoff approach is presented. Compound refractive lenses were manufactured by drilling into an Al block a linear array of 200 closely spaced holes 0.5 mm in diameter for linear focusing and two crossed arrays of 100 holes each for point focusing. Focal spots of 3.7 mum and 8 mum x 18 mum were obtained at 30 keV for linear and two-dimensional lenses, respectively. Different technologies of manufacturing and possible applications of the proposed lenses are discussed.     

Dynamic memory management methodology applied to embedded telecom network systems

Presents a new methodology for dynamic memory management of embedded telecom network systems. This methodology enables the designer to further raise the abstraction level of the initial system specification and to achieve optimized embedded system designs. This methodology is well suited for systems characterized by a set of concurrent and dynamic processes, very high-bit-rate data streams, and intensive data transfer and storage, as encountered in telecom network applications. Up to now, it has been successfully applied to four telecom network systems. This methodology can be easily integrated into any C++-based system synthesis approach that bridges the gap between a concurrent process-level system specification and an optimized (for area, performance, or power) embedded implementation of communicating hardware/software processors. This is in contrast to current system design practice, where VHDL/C is derived without room for exploration, refinement, and verification, leading to expensive late design iterations. In this paper, the main focus lies on the system-level specification model and the dynamic memory management applied to two real-life telecom network systems.     

Influence of the temperature-induced martensitic-austenitic transformation on the strength properties of high-alloy steels under dynamic loading

Combustion, Explosion, and Shock Waves - The dynamic elastic limit and spall strength of high-alloy chromium-manganese-nickel steel in the martensitic-austenitic transformation induced by a change...     

Solution combustion synthesis of metal nanopowders: Nickel—Reaction pathways

Nanopowders of pure nickel were directly synthesized for the first time by conventional solution combustion synthesis (SCS) method. In this article, a specific reaction pathway is suggested to describe the metallic phase formation during SCS. It is proposed that the exothermic reaction between NH₃ and HNO₃ species formed during the decomposition of glycine and nickel nitrate acts as the source of energy required to achieve the self‐sustained reaction regime. A thermodynamic analysis of the combustion synthesis reaction indicates that increasing glycine concentration leads to establishing a hydrogen rich reducing environment in the combustion wave that in turn results in the formation of pure metals and metal alloys. TGA of reaction systems and XRD analysis of products in the quenched combustion wave show that the formation of oxide phases occurs in the reaction front, followed by gradual reduction of oxide to pure metallic phases in the postcombustion zone. A methodology for SCS of pure metals and metal alloys nanoparticles can be inferred from the results presented. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Selective drying of hygroscopic materials wetted with binary mixtures

ABSTRACT

Drying experiments were carried out in a laboratory apparatus with differently hygroscopic materials wetted with binary mixtures. Composition curves were determined under variation of the drying conditions, the sample thickness, and the drying method. The results obtained are presented and compared with those of non-hygroscopic materials.

In particular, the interactions between moisture and solid when using strongly hygroscopic products influence the composition curve from the very beginning of the drying process, contrary to weakly hygroscopic materials, where the selectivity is controlled by the sorption equilibrium only at the end of the drying process.

A method to calculate the selectivity in knowledge of the binary adsorption equilibrium is given. For this purpose, it is necessary to split the total moisture into a free and a bounded share.     

A circuit-driven design methodology for video signal-processingdatapath elements

The programmable video signal processor (VSP) is an important category of processors for multimedia systems. Programmable video processors combine the flexibility of programmability with special architectural features that improve performance on video processing applications. VSPs are typically multiple processors with several processing elements (PEs) and a parallel memory system. This paper focuses on the architectural design of the PE's in a video processor and shows how technology and circuit parameters influence the structure of the datapath and, hence, the overall architecture of a programmable VSP. We emphasize the need to consider technological and circuit-level issues during the design of a system architecture and present a method whereby the conceptual organization of the PEs-the number of PEs, pipelining of the datapath, size of the register file, and number of register ports-can be evaluated in terms of a target set of applications before a detailed design is undertaken. We use motion-estimation and discrete cosine transform as example applications to illustrate how various technology parameters affect the architectural design choices. We show that the design of the register file and the datapath-pipeline depth can drastically affect PE utilization and, therefore, the number of PEs required for different applications. Our results demonstrate that pursuing the fastest cycle time can greatly increase the silicon area which must be devoted to PEs, due to both increased pipeline latency and reduced register file bandwidth     

Devices at High Temperatures—Status and Prospects

The temperature-handling capability of diamond diode and field effect transistor structures is discussed and compared with recent results on GaN. The main parameters limiting the high-temperature performance are identified and evaluated. A diamond high-temperature technology is presented which has allowed 1000°C operation of a diamond Schottky diode, the highest temperature of operation of any semiconductor diode yet.