The influence of annealing on the conductivity of magnesium films

Polycrystalline magnesium films were deposited under ultrahigh vacuum by thermal evaporation onto a cooled silica substrate. During the growth process of a film a number of lattice defects are incorporated. It was found that the defect density decreases with increasing thickness. An annealing study of the electrical resistance and defect density in magnesium films was made. The results were interpreted on the basis of Vand's theory. The function F₀ expressing the law of distribution of the decay energies exhibited a maximum. For thick films there was no appreciable variation in the activation energy with thickness. In this case the evaluated activation energy E was found to be about 0.35 eV. For very thin films this energy decreases with increasing thickness.     

A 72-mW CMOS 802.11a direct conversion front-end with 3.5-dB NF and 200-kHz 1/f noise corner

A direct conversion 802.11a receiver front-end including a synthesizer with quadrature VCO has been integrated in a 0.13-/spl mu/m CMOS process. The chip has an active area of 1.8 mm/sup 2/ with the entire RF portion operated from 1.2 V and the low frequency portion operated from 2.5 V. Its key features are a current driven passive mixer with a low impedance load that achieves a low 1/f noise corner and an high I-Q accuracy quadrature VCO. Measured noise figure is 3.5 dB with an 1/f noise corner of 200 kHz, and an IIP3 of -2 dBm. The synthesizer DSB phase noise integrated over a 10 MHz band is less than -36 dBc while its I-Q phase unbalance is below 1 degree.     

The specification and use of geotextile fin drains

This paper describes the composition, construction and uses of the rather special range of geotextile composites which have generally become known as ‘fin drains’. It tries to provide a generic definition of the term ‘fin drain’ which encompasses all current commercial products, and foreseeable types. In particular, it excludes composites which are intended for, or which function as, either pressure-driven water transporters, or capillary driven systems. Pressure-driven drains include, in particular, those drains commonly known as ‘wicks’ which are used for the relief of excess pore pressure in soft ground construction work. Similarly, a number of geotextiles have the facility of passing water within their plane by virtue of internal capillary attraction generated at the interfaces of the composite fine fibres. Such products transmit only small volumes of water, and their intended functions and design principles are entirely different from those of ground fin drains in the sense included in this paper.     

Replication and bonding techniques for integrated microfluidic systems

From the technical and economic points of view, systems integration, and packaging represent a crucial step in the production of microsystems. Compared to purely silicon- or glass-based systems, the variety of materials and geometries available for purely polymer microfluidic systems is much larger, due to the outstanding material properties. Moreover, polymers may be shaped and joined by comparably simple methods. Examples are polymer microreplication as well as various bonding methods. With them, complete polymer microsystems can be integrated. In addition, a number of established, compatible processes are available for the integration of functional elements that may also be made of other materials.

     

Kinetic aspects of deactivation of catalysts in prolonged use

A theoretical approach to the dynamic analysis of deactivation and aging of heterogeneous catalysts is proposed — analysis of the rate derivative in a kinetic equation of a given form. Methodology was demonstrated for the simplest kinetic equations — zero-and first-order. Regardless of the form of the kinetic equation for the dynamic model of deactivation, the rate constant is a function of an independent reaction coordinate. The method can also be used for solving reactivation problems and for explaining the dynamics of cation exchange in zeolite. __________ Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 1, pp. 3–34, January–February, 2006.     

Effect of surfactants on phenol removal by the method of polymerization and precipitation catalysed by Coprinus cinereus peroxidase

The removal of phenol by peroxidase‐catalysed polymerization was examined using Coprinus cinereus peroxidase in the presence of surfactants. The non‐ionic surfactants with poly(oxyethene) residues, Triton X‐100, Triton X‐405 and Tween 20, enhanced the phenol removal efficiency at a level similar to high relative molecular mass poly(ethylene glycol) (relative molecular mass 3000). Although the improvement in the removal efficiency was less than that of Triton X‐100, Span 20, sodium lauryl sulfate (SDS) and lauryl trimethylammonium bromide (DTAB) also enhanced the removal efficiency. The requirement of the enzyme for almost 100% removal of 100 mg dm^?3 phenol decreased to one‐fourth by the addition of 30 mg dm^?3 Triton X‐100. Triton X‐100, Triton X‐405, Tween 20 and DTAB could reactivate the enzyme precipitated with the phenol polymer, leading to the restarting of the phenol removal reaction. Copyright © 2003 Society of Chemical Industry     

The role of interparticle forces in colloidal aggregates: local investigations and modelling of restructuring during filtration.

Industrial solid-liquid separation processes, such as pressure filtration or membrane processes, involve the application of pressure to suspensions. In response, some water is extracted, the suspension volume is reduced, and the dispersed aggregates start to form a network. In recent works, we aimed to make a prediction for the response of aggregates to stress which occurs during a filtration. We chose model systems made of aggregated silica nanoparticles. Some of these systems offer a strong resistance to applied stresses, and retain their permeability; others yield and collapse. We used small angle neutron scattering by which we can locally quantify the particle distribution withi the network to determine the processes by which particles reorganise during collapse: we found that reordering processes at the scale of 1 to 10 particle diameters control the course of collapse and the loss of permeability. Finally we constructed a numerical model for describing the processes by which colloidal aggregates are compressed. This model predicts that the response of such networks to pressure follows some scaling laws, which depend only on the elastic vs. dissipative nature of interparticle bonds.     

Microstructural development and mechanical properties of interrupted aged Al-Mg-Si-Cu alloy

The effects of a recently developed interrupted aging procedure on the microstructural development and mechanical properties of the commercial Al-Mg-Si-Cu alloy 6061 have been studied using transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and mechanical testing. This so-called T6I6 temper involves partially aging the alloy at a typical T6 temperature (the underaging stage), quenching, then holding at a reduced temperature (in this case 65 °C) to facilitate further hardening (the secondary aging stage), prior to final aging to peak properties at, or close to, the initial aging (T6) temperature (the reaging stage). The T6I6 aging treatment produces simultaneous increases in tensile properties, hardness, and toughness, as compared with conventional T6. The overall improvement in the mechanical properties of 6061 T6I6 is associated with the formation of a greater number of finer, and more densely dispersed, β″ precipitates in the final microstructure. Secondary precipitation took place during the interrupted aging stage of the T6I6 temper, resulting in the formation of a large number of Guinier-Preston (GP) zones that served as precursors to the needlelike β″ precipitates when elevated temperature aging was resumed.