Unusual W-shaped Galvanic Cell Model of ISCC of α-brass in Neutral Mattsson''''s Solution

Intergranular stress corrosion cracking(ISCC) of α-brass in neutral Mattsson's solutionwas found to be controlled by an unusual"W"-shaped galvanic cell whose cathode is thegrain boundary oxide film (G.B.0. film) andsurface film and the anode is fresh metal atthe cracked tip on both sides of the G.B.0.film. Redox reactions involved in the cellhave been proposed here. According to thismdel, initidtion of ISCC is caused by therupturing of surface film along grain boundaries,thus forming a galvanic cell. Propagation ofISCC resulted from alternate advances of G.B.0.film and dissolution on both sides of G.B.0.film caused by the effect of electrochemicalreaction. This work developed an effective approachto investigate the embrittlement process atthe tip of the crack, by increasing the lengthof the embrittlement region through constantstrain test and distinguishing the morphologyand the nature of the corrosion products byoptical microscopy and scanning electronmicroscopy (SEH).     

From ethnographic record to system design

This paper explores the issues involved in moving from ethnographic explorations of work in context to a practical contribution to system design. It does so using the example of an interdisciplinary research project involving sociologists and computer scientists in the domain of air traffic control systems. It forms a pair with another paper (Sommerville et al., 1992) exploring these questions from the perspective of our computer science partners. We characterise ethnography as a research method, and consider the differences between undertaking it for strictly sociological or anthropological purposes by contrast with interdisciplinary and design purposes. We summarise some of our results in ethnographic explications of the work of air traffic controllers, and the sociality which it manifests. We describe the dialogues involved in rendering these observations informative for systems design, and the mutual translations implied in attempting to reconcile sociological with software engineering questions about supporting the work. We conclude by specifying some features of cooperative work which an engineering approach is in danger of overlooking; the ways, and limits, in which ethnographers can form a bridge between users and designers; and some of the conflicts of interest entrained in generating technical change.The research is funded by the UK MRC/SERC/ESRC Cognitive Science/HCI Initiative with the title Social Analysis of Control Systems for HCI Design, grant number SPG 8931598. The computer science partners are Professor Ian Sommerville, Dr Tom Rodden, Dr Pete Sawyer and Mr Richard Bentley. Thanks are due to Val King, Kjeldt Schmidt, Ian Sommerville and Tom Rodden for very helpful comments on earlier drafts of this paper.     

Loss of entanglement density during crazing

The formation of fibril surface area during craze growth requires a loss of entangled strand density in the fibrils themselves. To demonstrate the decrease in entangled chain density, thin films of polystyrene are bonded to soft copper grids and strained in tension. This procedure produces crazed specimens in which the craze fibrils can be characterized by a well-defined draw ratio, ₀. The films are then exposed to electron irradiation. This produces chemical crosslinks between the molecules, thus forming a crosslinked network. Subsequent heating of the film aboveT _g results in the entanglement network trying to retract to=1. The crosslink network, however, tries to maintain the. of the craze fibrils at ₀. The craze fibrils thus retract to Ferry's state of ease, _S, where the tension of the entanglement network is balanced by the compression of the crosslink network. Measurements of _s in crazes crosslinked and then healed confirm that a 25 to 50% loss of entanglement density in craze fibrils occurs, in agreement with theoretical predictions.     

Microdeformation in partially compatible blends of poly(styrene-acrylonitrile) and polycarbonate

Dilute 3-component 1-phase solutions in methylene chloride of poly(styrene-acrylonitrile) PSAN and polycarbonate PC are used to cast phase separated thin films. Films of pure PSAN, pure PC and five intermediate compositions are examined. The films are bonded to copper grids and strained at a constant rate of 4.1 × 10^–6sec^–1. The median tensile strain _v for void formation is determined using an optical microscope and the regions surrounding the voids are examined by TEM. At room temperature and slow strain rates both PSAN and PC plastically deform by shear yielding. For pure PSAN _v was found to be 0.13 whereas for PC _v exceeds 0.23. The addition of the more ductile polymer PC to PSAN at weight fractionsx forx 0.4 decreases _v. In this case voids form in crazes at the boundaries between the PC-rich inclusion and the PSAN-rich matrix. When the PC content is increased tox = 0.8, _v approaches 0.23. The effect of physical ageing (annealing belowT _g the glass transition temperature) on the mode of plastic deformation was also examined over the same compositional range. Physical ageing was found to suppress shear deformation and favour crazing in PSAN and PSAN-rich phases. Because crazes are more susceptible to breakdown than DZ's (shear deformation zones), physical ageing results in a marked decrease in _v. The breakdown statistics of these phase separated partially compatible blends was found to follow a Weibull distribution in strain from which two parameters may be extracted: the Weibull modulus and _w the Weibull scale parameter. is a measure of the breadth of distribution of void initiation and _w is a measure of the median strain to void formation in the films. The behaviour of _w was found to approximately mirror _v. The Weibull modulus appears to be primarily controlled by the matrix phase.     

Role of carbon dissolution during manganese oxidation in CO-CO2 Atmospheres

The role of carbon produced from the decomposition of CO-CO₂ gas mixtures traditionally is ignored during oxidation experiments, and only the oxygen potential established by the gas mixture is generally considered. Accordingly, to overcome this problem, a model which takes into account both carbon and oxygen dissolution into a p-type scale has been developed and tested. Two distinct cases of the model were tested at 1002°C. In the first case, variable CO/CO₂ ratios were used to determine the parabolic kinetics. Thus, both variable oxygen and carbon potentials were studied. In the p-type region of MnO, the developed model appeared to hold quite well. In the second case, constant CO-CO₂ ratios diluted with helium were utilized to maintain a constant oxygen potential with a variable carbon activity. The developed model appeared to hold again for the p-type region of MnO. Metallographically it was noted that the MnO scale developed exhibited an outer compact region and an inner layer that was somewhat porous.     

Binding of heavy metal ions by formaldehyde-polymerized peanut skins

Peanut skin, when treated with formaldehyde to polymerize tannins, is a highly efficient substrate for removal of many heavy metal ions from aqueous waste solutions. The ions Ag¹⁺, Cd²⁺, Cr⁶⁺, Cu²⁺, Hg²⁺, Ni²⁺, Pb²⁺, Zn²⁺, as well as Ca²⁺ and Mg²⁺, were contacted with formaldehyde-treated peanut skin. Quantitative removal could be achieved with Ag¹⁺, Cd²⁺, Cu²⁺, Hg²⁺, Pb²⁺, and Zn²⁺. Capacity of the substrate for ions was promising for Pb²⁺ (2.1 meq/g substrate), Cu²⁺ (3.0 meq/g), and Cd²⁺ (1.3 meq/g). Sorption from a solution containing Cd²⁺, Cu²⁺, Hg²⁺, Ni²⁺, Pb²⁺, Zn²⁺, on a packed column of formaldehyde-treated peanut skin indicated that Hg²⁺, Pb²⁺, and Cu²⁺ were rapidly and completely bound to the packing, while Cd²⁺, Ni²⁺, and Zn²⁺ were poorly bound until the preferred ions had been removed from solution.     

Energieinformatik

Due to the increasing importance of producing and consuming energy more sustainably, Energy Informatics (EI) has evolved into a thriving research area within the CS/IS community. The article attempts to characterize this young and highly dynamic field of research by describing current EI research topics and methods and provides an outlook of how the field might evolve in the future. It is shown that two general research questions have received the most attention so far and are likely to dominate the EI research agenda in the coming years: How to leverage information and communication technology (ICT) to (1) improve energy efficiency, and (2) to integrate decentralized renewable energy sources into the power grid. Selected EI streams are reviewed, highlighting how the respective research questions are broken down into specific research projects and how EI researchers have made contributions based on their individual academic background.     

Preparation of Thin Sections of Coated Fibers for Characterization by Transmission Electron Microscopy

A method of preparing transmission electron microscopy (TEM) specimens of coated ceramic fibers has been developed, which produces large electron transparent areas due to the minimal preferential milling of the fiber, coating, or epoxy matrix. Multiple individual fibers or tows are impregnated with a high-temperature epoxy and contained to assure a high fiber-to-epoxy volume ratio. The samples are then sectioned and mechanically thinned either parallel or normal to the fiber axes using a wedge polisher on diamond lapping films to achieve a thickness of less than 5 μ.m. The thinned sample is then ion-milled to electron transparency in less than 30 min, giving representative specimens of the coating, fiber, and coating-fiber interface. This technique is also well suited to preparing extremely flat specimens for scanning electron microscopy analysis of thin coatings. Examples of TEM sections of coated fibers prepared using this technique are presented.