Corrosion mechanisms of 304L NAG in boiling 9M HNO3 containing Cr (VI) ions

In this research, the mechanisms of end-grain corrosion of 304L NAG tubes in boiling 9M HNO3-containing Cr (VI) ions are reported to sustainably manage the corrosion of nuclear fuel reprocessing plant components. Specific heat treatments were applied to as-received specimens to produce phosphorus and/or sulphur intergranular segregation. End-grain corrosion on heat-treated specimens and the effect of a Cr (VI) concentration on a 304L NAG tube (as-received) were investigated. It has been reported that an increase in Cr (VI) ions leads to the acceleration of end-grain corrosion due to high electrochemical potential. After systematic heat treatments on the 304L NAG specimens, it is concluded that the primary causes of heat-induced end-grain corrosion are phosphorus or sulphur segregation to the grain boundaries. The key findings of this research are highly significant in terms of understanding the corrosion mechanisms and controlling the end-grain corrosion of NAG steel in boiling HNO3 environments. This research will help to sustainably reduce power plant maintenance costs and will have a significant impact on the delivery of long-term, clean, secure, and tenable energy

Failure Detection within Composite Materials in System Engineering Applications

This paper introduces essential key attributes of composite materials with a focus on carbon fibre (CF), followed by a description of common failure modes and proceeds to an investigation of stiffness of continuous CF laminates of 4-ply and 7-ply epoxy resin in pre-preg and wet layup. The three-point flexural test was performed with a Zwick Z010 machine, and the findings are presented. Continuing to real world failure scenarios and moving onto novel concept methods of live failure detection including scope for wood composites. Showing that early design considerations and further research can lead to advantages for system engineering

A High-Energy-Density Magnesium-Air Battery with Nanostructured Polymeric Electrodes

The greenhouse emissions are biggest challenge of the present era. The renewable power sources are required to have characteristics of good charge capacity, energy density with proven charging discharging cycles for energy storage and applications. Mg-air batteries (MABs) are an alternative renewable power source due to their inexpensive cost. In particular, the previous reports presented the metal-air battery structure, with a specific energy overall output of 765 W h kg(−1). This paper is focused mainly on the MAB, which employed nanocomposite polymeric electrodes with a proven energy density of 545 W h kg(−1) and a charge capacity of 817 mA h g(−1) when electrolyzed at a cycling current density of 7 mA cm(−2)

Demand Side Management Techniques for Home Energy Management Systems for Smart Cities

In this paper, three distinct distributed energy resources (DERs) modules have been built based on demand side management (DSM), and their use in power management of dwelling in future smart cities has been investigated. The investigated modules for DERs system are: incorporation of load shedding, reduction of grid penetration with renewable energy systems (RES), and implementation of home energy management systems (HEMS). The suggested approaches offer new potential for improving demand side efficiency and helping to minimize energy demand during peak hours. The main aim of this work was to investigate and explore how a specific DSM strategy for DER may assist in reducing energy usage while increasing efficiency by utilizing new developing technology. The Electrical Power System Analysis (ETAP) software was used to model and assess the integration of distributed generation, such as RES, in order to use local power storage. An energy management system has been used to evaluate a PV system with an individual household load, which proved beneficial when evaluating its potential to generate about 20–25% of the total domestic load. In this study, we have investigated how smart home appliances’ energy consumption may be minimized and explained why a management system is required to optimally utilize a PV system. Furthermore, the effect of integration of wind turbines to power networks to reduce the load on the main power grid has also been studied. The study revealed that smart grids improve energy efficiency, security, and management whilst creating environmental awareness for consumers with regards to power usage

Time Dependent Surface Corrosion Analysis and Modelling of Automotive Steel Under a Simplistic Model of Variations in Environmental Parameters

This research presents time-dependent corrosion analysis of automotive steel utilised in a large military vehicle in real operating environment, followed by simulated environmental tests and simplistic surface corrosion modelling. Time-dependent surface corrosion accumulated on this specific component was observed to be approximately 250 µm thick, with the identification of surface contaminants such as chlorine and sulphur. Simulated environmental tests considering temperature and relative humidity variations were performed to evaluate quantitative corrosion damage to the structure of the vehicle. The relationship of various temperatures and relative humidity with respect to time, within the context of corrosion initiation and propagation, has been presented. A mathematical model to incorporate corrosion accumulation on the surfaces derived from the simulated environmental tests is presented

A Comprehensive Predictive Corrosion Model incorporating varying Environmental Gas Pollutants applied to Wider Steel Applications

A comprehensive model has been developed to predict uniform corrosion rate of structural steel under the effect of low pH conditions for example acid rain. Acid rain is mainly caused by emissions of sulfur dioxide (SO2) which reacts with the water droplets in atmosphere to produce acidic solution which is the primary cause of corrosion of steel structures such as bridges, and weathering of stone buildings and statues. A five-stage division was applied to mathematically describe the model as: (i) the growth rate of air-suspended water droplets (i.e. moisture) depending on the condensation/evaporation rate, (ii) the absorption of gas phase SO2 in the droplets forming bisulfite HSO_3^- ions, (iii) the coalescence of these SO2 absorbed water droplets under the effects of wind speed and gravity, (iv) the deposition rate of SO2 absorbed droplets on steel substrate depending on the inclination and azimuth angles of steel surfaces and, (v) the corrosion rate of steel due to the deposition of these SO2 absorbed droplets. The incorporation of all the above stages develops a comprehensive corrosion prediction model which not only includes the electrochemical parameters but also large number of physical, environmental and material parameters. Experiment was performed to analyse the corrosion rate of steel samples by exposing them to moist SO2 corrosion test. A comparative analysis between the model predictions and experimental results was performed to verify the reliability of model. The predictive trends of corrosion rate of steel were also generated for different values of temperature, relative humidity, and SO2 mole percentage

Analysing and Modelling the Corrosion Behavior of Ni/Al2O3, Ni/SiC, Ni/ZrO2 and Ni/Graphene Nanocomposite Coatings

A study has been presented on the effects of intrinsic mechanical parameters, such as the surface stress, surface elastic modulus, surface porosity, permeability and grain size on the corrosion failure of nanocomposite coatings. A set of mechano-electrochemical equations was developed by combining the popular Butler-Volmer and Duhem expressions to analyse the direct influence of mechanical parameters on the electrochemical reactions in nanocomposite coatings. Nanocomposite coatings of Ni with Al2O3, SiC, ZrO2 and Graphene nanoparticles were studied as examples. The predictions showed that the corrosion rate of the nanocoatings increased with increasing grain size due to increase in surface stress, surface porosity and permeability of nanocoatings. A detailed experimental study was performed in which the nanocomposite coatings were subjected to an accelerated corrosion testing. The experimental results helped to develop and validate the equations by qualitative comparison between the experimental and predicted results showing good agreement between the two

In-situ corrosion health monitoring and prediction in miltary vehicles.

Military vehicles are at a constant threat from harsh operational conditions in terms of temperature variations, humidity and exposure to atmospheric or aggressive chemical environments. These conditions are responsible for structural and components’ failure due to various corrosion failure mechanisms. Protective coatings tend to prevent the effect of physical and chemical attack on substrates. However, in some circumstances this attack is promoted, rather than hindered, and this results in the failure of coatings. This thesis presents novel theoretical models for three modes of coating failures i.e. micro-cracks effects, blistering and edge delamination. These models can be used for the analysis of coating failure initiation and propagation, especially useful for coating life assessment. The models follow multidisciplinary approach coupling the concepts of thermodynamics, fracture mechanics and electrochemistry. Novel equations involving inter-related multidisciplinary parameters are developed for stress-assisted diffusion rate, crack driving force and corrosion current density. These novel equations can be used by the manufacturers to design durable systems and can also be utilised for prognostics. Simple criterions i.e. critical/threshold values are identified which exclude the possibility of widespread coating failure propagation. The developed models are based on comprehensive experimental studies, which are also used to validate the theoretical predictions. The fundamental property which often dictates the performance of a coating is its adhesion to the substrate. There are many experimental techniques to measure the adhesion and analytical techniques to predict and optimise the adhesion failures. Many factors influence the adhesion of coating and substrate such as mechanical properties of the coating and substrate, the interface properties, the microstructure of the coating/substrate system, residual stress and coating thickness. Apart from these properties, the environmental conditions in which the coating-substrate system is exposed also affects the adhesion of coating and substrate. There are many modes of failures of coating-substrate system which either result from defects in coatings such as micro-cracks, interfacial defects such as micro-voids or result from stresses which are too large. Interfaces are intrinsic to these systems, and they are susceptible to interface debonding or delamination. The evolution of micro-cracks in coating layer is possible when tensile stresses develop during fabrication. The micro-cracks in the coatings can provide the pathways for the corrosive species to diffuse towards the interface causing interfacial corrosion of substrate. During application, these micro-cracks can open wide in the presence of tensile stress therefore accelerating the interfacial corrosion due to high diffusion rate of corrosive species. On the other hand these micro-cracks can constrict under the effect of compressive stress and therefore reducing the interfacial corrosion due to low diffusivity. However under the effect of compressive stress, blistering can occur. High compressive stress can cause the blister to propagate in a stable axisymmetric circular pattern till it loses its stability and becomes unstable forming tunnel blistering. Another failure mode is the edge delamination, the propagation rate of which depends on the transport of corrosive species through the defect at edge and electrochemical reactions at the interface. Experiments are reported for each failure mode by using a model coating-substrate system chosen to allow the visualisation of the interface and to permit coating failure propagation along the interface. For micro-cracks analysis, the effects of tensile and compressive stresses on micro-cracks behaviour in the presence of diffusing corrosive species are studied. The experiments are reported for coating-substrate system chosen to allow the visualisation of the interface and to permit the tensile and compressive stresses in the film to be generated over a full range of interest by exploiting the thermal expansion mismatch of the system when exposed to the environmental chamber. Similarly for blistering analysis, the coating-substrate system with micro-void (defect) at the interface is subjected to high compressive stresses in the presence of corrosive species. The study bear out the theoretical prediction of a regime of axisymmetric stable circular growth which gives way to non-axisymmetric tunnel blisters after circular blister becomes sufficiently large and unstable. For edge delamination analysis, the delamination propagation as a result of electrochemical reactions due to high diffusivity through artificial defects is studied. The delamination mechanism is also studied for variable environmental conditions during intended application such as uncertain vehicle movement (in-out) and annual weather changes

Optimal Dynamic Frame-Slotted Aloha : (ODFSA)

Passive UHF RFID systems using Dynamic Frame-Slotted ALOHA (DFSA) adjust the frame size according to the number of tags, but frame size N is equals to 2^Q and cannot be adjusted exactly to the number of tags to be identified. In this paper, we propose an optimal Aloha algorithm (ODFSA), which uses probabilistic approach for tags to access the frame. The Query or Query Adjust packet contains both the parameter Q and P called frame access probability, which represents the ratio of number of active tags in the current frame to the estimated total number of tags which remain to be identified in the system. Estimation of number of unread tags is updated after end of each frame; parameters Q and P are calculated and informed at the beginning of each frame. Mathematical analysis and computer simulations show that the proposed Aloha achieves maximum system efficiency, utilizes less number of slots compared with other algorithms and also takes less identification time.  IEEE PID:1093642, Article Source : CXP-1093642,conference ID:92731,Anti-collision algorithms and performance analysis for UHF passive RFID networks (Master Thesis,2011,Embedded System