Consolidation of nano-crystalline copper powder by cold and hot pressing

This paper investigates preparation of bulk nano-structured Cu through cold and hot pressing. In particular, the effects of different consolidation parameters, such as temperature and pressure, on the properties of bulk nano-structured samples were studied. Microstructure, density, hardness, and electrical conductivity showed strong dependence on the consolidation parameters. All results were compared with those for micron-size Cu powder. Relatively fully dense compacts with minimal grain growth up to 57 nm, maximum hardness of 83 Vickers, and electrical resistivity of 1.93 × 10⁻⁸ Ωm could be achieved.     

Slurry Erosion–Corrosion of Carburized AISI 5117 Steel

The erosion–corrosion of carburized and untreated low alloy steel (AISI 5117) has been investigated using slurry whirling-arm test rig. Erosion–corrosion tests were carried out in slurries composed of sand particles and either tap water or 3 % NaCl solution. The tests were carried out with particles concentration of 1 wt% and slurry stream impact velocity of 15 m/s. Silica sand having a nominal size range of 250–355 μm was used as an erodent. It has been shown that the erosion and erosion–corrosion resistance of AISI 5117 low alloy steel can be effectively improved by carburizing for all impact angles. However, the effectiveness of carburizing was the highest for an impact angle of 45°, where the erosion and erosion–corrosion resistance were increased by 60–40 %, respectively, compared with that of the untreated material. The results showed that the treated and untreated specimens behaved as ductile materials under erosion and erosion–corrosion tests, and the maximum mass loss occurred at an impact angle of 45°. SEM analysis showed that the erosion tracks developed on the untreated specimens were wider and deeper than that formed on the carburized specimens for erosion and erosion–corrosion tests.     

Effect of aluminum content on mechanical properties of hydrogenated Mg–Al magnesium alloys

The mechanical properties of hydrogenated Mg–Al magnesium alloys with various aluminum content were investigated. The ductility, yield strength (YS) and ultimate tensile strength (UTS) of the hydrogenated material decreased while the hardness increased with increasing the aluminum content. Microscopic observations of cross-sections of hydrogenated specimens with various Al content revealed that hydrogen cracks extended deeply as the Al content in the Mg–Al alloys increased. Moreover, X-ray diffraction (XRD) analysis revealed that MgH₂ and AlH₃ hydrides are formed during hydrogenation and were found to contribute to hydrogen embrittlement of Mg–Al alloys. However, the embrittled zone was observed to be larger at the fracture surface of Mg–15Al alloy than that of Mg–5Al alloy. Moreover, the fracture surface of Mg–30Al alloy exhibited completely brittle fracture after hydrogenation.     

Development of an on-machine profile measurement system in ELID grinding for machining aspheric surface with software compensation

Efficient manufacture of dimensionally accurate optical surface on hard and brittle materials is a major concern for optoelectronic industry. Electrolytic in process dressing (ELID) grinding is proved as a reliable process to achieve this optical quality nano-surface finish on hard and brittle materials. Besides surface finish it is important to ensure dimensional accuracy by improving profile and form accuracy of the ground aspheric surface. Kinematic factors are commonly considered the reasons for the dimensional inaccuracy in a machined part. Software compensation is a direct and economical method to overcome several kinematic factors and improve the dimensional accuracy. Last, but most important, is the monitoring of achieved surface profile to ensure more accurate profile radius in the finished part. So an on-machine profile measurement system based on coordinate measuring machine (CMM) principle has been developed to check the profile radius of the ground surface. In this study software compensation was applied in ELID grinding of an aspheric surface in order to compensate the wheel wear until the measured surface profile machined on BK7 glass reaches within tolerable limit.     

Au/ZnO and Au/Fe2O3 catalysts for CO oxidation at ambient temperature: comments on the effect of synthesis conditions on the preparation of high activity catalysts prepared by coprecipitation

The preparation of Au/ZnO and Au/Fe₂O₃ catalysts using two coprecipitation methods is investigated to determine the important factors that control the synthesis of high activity catalysts for the oxidation of carbon monoxide at ambient temperature. In particular, the factors involved in the preparation of catalysts that are active without the need for a calcination step are evaluated. The two preparation methods differ in the manner in which the pH is controlled during the precipitation, either constant pH throughout or variable pH in which the pH is raised from an initial low value to a defined end point. Non-calcined Au/ZnO catalysts prepared using both methods are very sensitive to pH and ageing time, and catalysts prepared at a maximum pH = 5 with a short ageing time (ca. 0–3 h) exhibit high activity. Catalysts prepared at higher pH give lower activity. However, all catalysts require a short operation period during which the oxidation activity increases. In contrast, the calcined catalysts are not particularly sensitive to the preparation conditions. Non-calcined Au/Fe₂O₃ catalysts exhibit high activity when prepared at pH ≥ 5. Calcined Au/Fe₂O₃ prepared using the controlled pH method retain high activity, whereas calcined catalysts prepared using the variable pH method are inactive. The study shows the immense sensitivity of the catalyst performance to the preparation methods. It is therefore not surprising that marked differences in the performance of supported Au catalysts for CO oxidation that are apparent in the extensive literature on this subject, particularly the effect of calcination, can be expected if the preparation parameters are not carefully controlled and reported.     

Prenatal exposure to the fluoride containing psychiatric drug fluoxetine and anti-oxidative alterations in the neonatal rat brain

Fluoride is a key ingredient of many psychiatric drugs like fluoxetine (Prozac^®, Fluoxetine^®). Pregnant womenfrequently use this drug as they suffer from depression and anxiety disorders during this period. Fluoxetine is able toreach the fetus through the placenta and passes to the newborn through milk. In the present study, female Wistar ratswere treated with 5, 10, and 20 mg/L fluoxetine (containing 94% fluorides) from pregnancy day 10 to day 20. Afterdelivery, the levels of the enzymatic antioxidants in the brain of their offspring at postnatal day 2 were measured. Theresults showed that, in all fluoxetine exposed groups compared with the control group, there was a significant decrease(P < 0.01) in the glutathione, catalase, glutathione S-transferases and potassium and a non- significant increase (P >0.05) in the activity of malondialdehyde and creatine kinase. The results suggest that fluoxetine may be a developmentalneurotoxicant due to presence of fluoride hence must be used carefully during pregnancy.     

Effects of drying conditions, admixtures and specimen size on shrinkage strains

The paper presents the results of an experimental investigation on the effects of drying conditions, specimen size and presence of plasticizing admixture on the development of shrinkage strains. The measurements are taken in a harsh (50 °C and 5% R.H.) and a moderate environment (28 °C and 50% R.H.). The results include strain development at various levels of cross sections of concrete prisms. The drying conditions are found to be the dominant parameter affecting the shrinkage strain development particularly in specimens of smaller sizes. The effect of plasticizing admixture on shrinkage strains is negligible.     

Potential for energy saving in building transition spaces

This paper reports on an analytical investigation into the energy saving potential associated with modified comfort limits in transitional spaces in buildings. Such spaces may not require the same high level and close environmental control of more fully occupied spaces and thus a wider variation in conditions and interpretation of thermal comfort may be permitted. Estimations are made of energy saving potential based upon typical floor area proportions utilised for transition spaces of various types in office/commercial buildings. The data are combined with suggested norms for comfort expectation that have wider temperature limits than for normally occupied office zones. The method has been applied to a series of building types situated in the climate of the East Pennines area of the UK using a thermal analysis tool. The results show that useful energy savings (particularly for heating) are possible by allowing for a modest (and realistic) relaxation of prescribed comfort standards in transition spaces. Further work is now required to confirm the limits and assess energy saving in practice.     

Impact of agriculture on the built form of Al-Alkhalaf

This study is part of a comprehensive investigation of traditional settlements in the highland of Southwestern Saudi Arabia. The present study focuses on several factors which influenced the urban development of Al-Alkhalaf and its surroundings. The investigation began with the exploration of kinship systems as an underlying force that shaped the urban and economic structure of the village which is considered the principal determinant of the settlement built form and environment. The role of climate and topography in the urban and economic structure is examined, an influence highlighted by the unique pattern of agronomic, building and design techniques. The influence of Islamic and tribal laws on agricultural and building practices is investigated, a pertinent relationship which is viewed through the integration between the agricultural fields and the built form of the village, the layout of streets, open spaces, warning and defence towers, and residential areas.