Advanced Materials Research Vols. 875-877

Abstract: Bridges are important infrastructures of all nations and are required for transportation of goods as well as human. A catastrophic failure can result in loss of lives and enormous financial hardship to the nation. Although various kinds of sensors are now available to monitor the health of the structures due to corrosion, they do not provide permanent and long term measurements. This paper investigates the fabrication of Carbon Nanotube (CNT) based composite sensors for corrosion detection of structures. Multi-wall CNT (MWCNT)/Nafion composite sensors were fabricated to evaluate their electrical properties for corrosion detection. The test specimens were subjected to real life corrosion experimental tests and the results confirm that the electrical resistance of the sensor electrode was dramatically changed due to corrosion.

Abstract: The study describes the interference color of anodic TiO₂ nanotube arrays on titanium foil. TiO₂ nanotube arrays are prepared by oxidizing titanium foil in an aqueous electrolyte solution of hydrofluoric acid (HF, 0.5 wt.%). The morphologies of the oxide film are characterized by FESEM. The empirical color properties are obtained using the L*a*b* system. The different interference colors of oxidized Ti samples are obtained depending on the anodization time. The anodization time clearly indicates a strong effect on the reflectance at the visible wavelength region, thus confirming the observed color differences. Consequently, the interference colors can be controlled by the anodization time. By observing the coloration of Ti during the anodization, the interference colors can be utilized to identify the thickness of oxide layer and the formation of nanotubes on Ti sheet.

Abstract: The objective of this study is to explore a method to improve hydrophilicity of the surface of formers that could be more easily dipped to produce high quality dipped rubber products. Photocatalytic TiO₂ composite films were prepared by sol-gel method. Glass formers were coated with the Ni/B/N/TiO₂ nanocomposite film by dipping method and annealed at 400°C for 1 h. Phase formation of TiO₂ was characterized by XRD. Morphology of the TiO₂ films was observed by using atomic force microscopy (AFM). Optical absorption of the films and degradation concentration of methylene blue had been measured employing UV-Vis spectrophotometer. The hydrophilicity of the thin films was determined in terms of the contact angles of water and NR rubber latex droplets on the coated TiO₂ composite films under visible light irradiation. It was found from the experimentally study that the Ni/B/N/TiO₂ nanocomposite film can improve wet-ability of the coated former surfaces.

Abstract: The purpose of this paper is to discuss the influence of mineral additives i.e. metakaolin, silica fume, rice ash and fly ash incorporating with nanocarbontubes mortar composites. The effects on compressive strength at 28 days were also discussed and presented. Cement content of 500 kg/m³, water/cement ratio of 0.6 and aggregate/cement ratio of 2.75 were adopted for the mix propotion. 1%, 3% and 5% of nanocarbontubes in mortar were combined with 15% of mineral additives. The results show that mixtures of nanocarbontubes with 15% of metakaolin produce better strength compared to normal mortar. Meanwhile with addition of fly ash and rice husk ash the strength were decreased. The electrical resistance for all mixes at 28 days were also discussed and presented. The higher percentages of nanocarbon with addition of all mineral additives resulted in lower electrical resistance properties

Abstract: Black chrome coatings were electrodeposited under galvanostatic conditions on SS substrates. To enhance the thermal stability of the coatings for viable usage in parabolic trough receiver tubes in solar thermal applications beyond 250°C, graphite encapsulated FeCo nanoparticles had been introduced in the electrolyte solution at different weight percentages (0.025, 0.05, 0.1). An increase in the thermal stability of the coatings in the range of 400°C to 600°C is noticed from the STA analysis. The corrosion analysis (Tafel) and cyclic voltammetric studies of the coatings in the presence and absence of nanoparticles have been carried out in 3.5% NaCl solution to understand the stability of the coating in saline environment.

Abstract: We theoretically analyze the electrical properties of GaAs substrate-nanowire p-n junction using Technology Computer Aided Design (TCAD). The results show that GaAs nanowire-substrate p-n junction exhibits clear diode behavior which has been confirmed in some experiments. Increasing NWs doping concentration and diameter or shortening NWs length can enlarge the total current after the diode is conducted. Total current through p-n junction is approximately linearly proportional to NWs growth density. The substrate-nanowires p-n junction has smaller current than that of substrate-layer p-n junction, which implies the superiority of NW structure. These results constitute an important progress for experimental researches on nanowire-integrated devices.

Abstract: The aim of this paper is to provide an alternative methodology, high reliability, in order to monitor, exploiting non-invasive techniques, railway track. In this particular case study, the presence of structural defects is assessed through an innovative system. The proposed approach provides the use of rotating magnetic field. Within this framework, the Eddy Current Techniques (ECTs) have greatly increased their importance for their capacity to detect the magnetic field variations caused by the presence of material alterations. Whilst the researches in this field propose various solutions to the detection of flaws (in surface and subsurface), a still open problem concerns the difficult detection of defects due to the geometrical complexity of the structure and the particular orientations of the crack. Particularly, this contribution proposes an approach based on Finite Element (Finite Element Method, FEM) for the modeling of railway tracks, in order to obtain a rapid and precise assessment about their integrity.

Abstract: Innovative solutions of bamboo connections and an application on Polonceau trusses to use for simple constructions are presented. Experimental tests show the performances and the high level of ductility of the proposed technique, joined with simplicity, with low-level of technology and low cost of all used materials. Their applications with sustainable maintenance are suitable in developing countries.

Abstract: An analysis of colour change in sandstone under the influence of heat is presented in this paper. The colour change observed is primarily a result of transformations occurring within the material. The colour change may be used to reveal the exposure temperature of stone elements subjected to fire, from which the corresponding damage can be estimated. The paper presents the results of tests carried out on sandstone with a clayey-ferruginous binder. The colour change was investigated using Scion Image v.4.0.3, an image analysis software package (Scion Corporation ©, USA). In the proposed method the digital image is split into three RGB colour components: red, green and blue, which are then presented as a histogram using counts of pixel intensity. The histogram results show colour distributions in unheated sandstone material and in material heated to temperatures ranging from 200 to 1000 °C. The significant colour changes in tested stones was observed and attributed to the presence in sandstone structure of minerals with iron compounds.

Abstract: Seismic vulnerability of an urban environment is characterized by the ability of buildings and structures to support seismic events (physical vulnerability) and by the ability of people to behave in a consistent and rational face a major event (social vulnerability). Constantine is a city with moderate seismicity but the level of risk is high because of urban concentration and topography of the site. The seismic risk reduction therefore requires assessing the physical vulnerability of its buildings. It is proposed in this paper an analysis of a group of buildings for residential use located west of the city, consisting mainly of relatively high buildings. Following a survey of a portion of the housing stock of this city, a seismic survey method was applied based on "observations" post-seismic. Vulnerability indicators are statistically related to damage through a vulnerability index "IV" to establish curves of damage (or vulnerability). These are used to estimate the level of damage that is likely resulting in damage cards. The goal is to develop an initial database of some of the housing stock in the Constantine city (knowledge of earthquake hazards, construction defects ...) to be used in the estimation of seismic risk and verification of seismic safety of existing buildings. Keywords: Earthquake hazard; Seismic vulnerability; Constantine city; damage.