Assessment of Electrical Resistivity and Oxygen Diffusion Coefficient of Cementitious Materials from Microstructure Features

A newly proposed modified non-contact electrical resistivity measurement was used to test the resistivity of concrete and cement mortar. The oxygen diffusion coefficients of concrete and mortar were determined by a gas diffusion measurement, and the capillary porosity of concrete and cement mortar was measured by mercury intrusion porosimetry (MIP) measurement. The obtained electrical resistivity and capillary porosity results were verified with other researchers’ data, the measured electrical resistivity results can be estimated by a simple equation from the capillary porosity results. The obtained oxygen diffusion coefficient results were quantitatively correlated with capillary porosity and electrical resistivity measurement results. The proposed equations can be practically used to assess the electrical resistivity and oxygen diffusion coefficient.

Morphogenesis of Silicovanadate Glasses: Investigation of Physical Properties

In this article, we demonstrate the synthesis and various characterizations of silicovanadate glasses of xSiO2 (100-x)V2O5 for x = (10-50) mol%, glasses which are prepared by the melt quenching method. FTIR spectra analysis confirms dominant chemical bonds among silicon, vanadium, and oxygen elements as expected. The assigned chemical bonds are Si-O-Si, O-Si-O, V-O-V, V=O, Si-O-V, O-H from FTIR spectra. The IR spectra of all glass specimens were baseline corrected and deconvoluted to distinct peaks of chemical bonds in overlapped Gaussians with employing computer program. The chemical bond's position shifted and affected due to the addition of vanadium pentaoxide by the heat treatment process. The X-ray diffractions (XRD) patterns of glass samples exhibit partial crystalline nature for 10S90V and 50S50V that is influenced by high-temperature application. The differential thermal analysis (DTA) of base and heat-treated specimen determines the glass transition (Tg), crystallization, and liquidus temperature with prominent exothermic and endothermic reactions. It is seen that the pH of the glass specimens abruptly changes due to the surface effect of V2O5 while bulk effects become robust after about 30 minutes. The measured hardness of three glass samples shows high HV-values and a slight linear increment is observed for higher V2O5 contents. The current-voltage (I-V) characteristic connected to the electrical conductivity of the glass specimen (20S80V) shows a relatively higher and non-linear trend of conductivity which reveals the behavior of a semiconductor. Moreover, temperature-dependent electrical resistivity measurement of the same sample (20S80V) manifests the semiconducting nature up to 427 °C as well.

Early Hardening Process of CA Mortar Indicated by Electrical Resistivity

A non-contact electrical resistivity measurement device was employed to indicate the early hardening process of cement asphalt emulsified mortar (CA mortar). It was found that this process was analogous with the hydration process of cement and could be categorized into three parts: dissolving period, induction period and setting period. The mortar resistivity first decreased and then increased with the elapsed time. The effect of water/cement ratio (W/C), asphalt emulsified/cement ratio (A/C), cement types were also explored. Results indicated that the increase of W/C, dosages in SF (Silica fume) extended the induction period; replacement of Portland cementII with sulfoaluminate cement in CA mortar markedly increased the electrical resistivity and advanced the onset of setting period by 5∼6 h, making it possible to prepare CA mortar with high early strength, which can preventing distress such as peeling and bleeding during construction in winter and conformance to requirements in acceptance standard.

Effect of Thermal Cycling on Transformation Behavior of Ti–24Nb–1Mo Alloy (at.%)

The effect of thermal cycling on the transformation behavior of a Ti–24Nb–1Mo alloy was investigated by means of electrical resistivity measurement, transmission electron microscopy (TEM), X-ray diffraction (XRD), tensile test and Vickers hardness tests. Electrical resistivity changes were not observed in all alloys. It indicates that thermally induced martensitic transformation does not take place in the alloys. After thermal cycling between 298 K and 77 K, clear X-ray diffraction peaks corresponding to ωath phase, which did not exist before thermal cycling, were observed. Volume fraction of ωath phase increased as increasing the number of thermal cycling. ωath phase formed during thermal cycling increased hardness of the alloy. Although thermally induced martensitic transformation did not occur in the alloys, superelastic deformation behavior was observed in the alloys. The superelastic recovery ratio decreased from 81% to 41% by increasing the number of thermal cycling, which came from the increase in the volume fraction of ωath phase.

Tailoring of Durable Conductive and UV-Shielding Properties on Cotton and Polyester Fabrics by PEDOT:PSS Screen-Printing

In the present study, cotton (Co) and polyester (PES) fabrics were screen-printed with a conductive poly3,4-ethylenedioxythiophene:polystyrene sulfonate (PEDOT:PSS) printing paste along with a commercially-available screen-printing binder (SFXC) or waterborne polyurethane resin (WPU), in order to enhance wash and wear durability, and to improve some functional properties, without essentially influencing the physical–mechanical properties of the base material, as well as the introduced fabrics’ conductivity. The application of a conductive polymer coating reduced transmittance in the whole UV region drastically, indicating good UV-shielding ability in the treated fabrics. Moreover, the employed binders improved the fabrics’ protection against harmful solar UV radiation significantly, depending on the type of fibre and binder. Furthermore, the SFXC binder intensified the hydrophobicity of Co as compared to the WPU binder, and, on the other hand, WPU reduced the hydrophobicity of PES. Finally, the screen-printed fabrics were washed up to 20 cycles and rubbed up to 20,000 cycles, and characterised by means of mass loss determination and electrical resistivity measurement. Both binders enlarged polymer stability against the effect of washing and rubbing, depending on the number of cycles, the type and amount of employed binder, the type of fibres, and the thickness and uniformity of coatings.

Comparative study on the un test n` 5 application on cargoes that emit flammable gases similar to dri c that requires ventilation

This technical note summarizes a technical comparison of common testing procedures, as well as reviewed of the UN Test N` 5, for the assessment of the self-heating properties of cargoes and materials that has shown a clear trend on maritime fire and explosions events, as well as considering of external factors that can combine self-heating and emit flammable gases to conclude in an unlikely event affecting the security of crews and ships. A high understanding of the external factors effect on the cargo materials certainly will help the application of spontaneous reactions management actions (SRMA) on board of ships during the cargo sea passage. The intended comparison is based on laboratory, industry and field observations and data, whereas the among the external factors considered are, moisture content, stockpile procedure and aging, air velocities and moderate pressures internal and externally to the cargo material. The comparison results have shown that the self-heating and the flammable gas emissions has a common pattern when reacting with any oxygen available source, regardless the reactive material chemical composition. Keywords: reactive materials, self-heating, self-ignition, direct reduced iron fines, materials handling, UN test N` 5, maritime safety, spontaneous reactions, risk management. IMSBC Code , IMO. References [1]A. M. DeGennaro, M. W. Lohry, L. Martinelli, C. W. Rowley. Uncertainty Quantification for Cargo Hold Fires. Princeton University, Princeton, NJ, 08540, USA. American Institute of Aeronautics and Astronautics. [2]L.L.Sloss Assessing and Managing Spontaneous Combustion of Coals. IEA Clean Coal Center (CCC 259). Oct. 2015. [3].A. Janes, G Marlair, D Carson, j. Chaneausx. Towards the improvement of UN Test N1 5 Method for the characterization of substances which in contact with water emit Flammable Gases. Journal of Loss Prevention in the Process Industries. Elsevier 2012, 25 (3), pp 524-534. [4]G. Rouget, B. Majidi, D. Picard, G. Gauvin, D. Ziegler, J. Mashreghi, and H. Alamdar. Electrical Resistivity Measurement of Petroleum Coke Powder by Means of Four-Probe Method. Metallurgical and Materials Transactions B. Vol. 48B, Oct. 2017-2543. [5]Y. Rubiela Hernández Puerto, M.Triviño Restrepo. El coque metalúrgico aplicado a protección catódica (Metallurgia coque applied to catodic protection). Revista del Instituto de Investigaciones FIGMMG. Vol. 10, Nº 20, 60-67 (2007) UNMSM I. [6]S. Narayan Jha, K. Narsaiah, A.L. Basediya, R.Sharma, P. Jaiswal, R. Kumar, and R. Bhardwaj. Measurement techniques and application of electrical properties for nondestructive quality evaluation of foods—a review. Food Sci Technol. 2011 Aug; 48(4): 387–411. [7]R. Fontes Araujo, J. Batisa Zonta, E. Fontes Araujo, E. Heberle, E, F. Miranda Garcia Zonta. Teste de Conductividade Eletrica para Smentes de Feijao Mungo Verde 1. Rev. Brasikleira de Sementes, Vol. 33, N` 1, pp123/130, 2011. [8]P.A. Eidem. Electric Resistivity of Coke Beds. PhD Thesis. Norwegian University of Science and Technology Faculty of Natural Sciences and Technology Department of Materials Science and Engineering. Tronheim Oct. 2008. [9]N. Birks, et.al. - Mechanism in Corrosion Induced Auto-ignition of Direct Reduced Iron. Materials Science and Engineering Department, University of Pittsburgh. [10]Monitoring Implementation of the Hazardous and Noxious Substances Convention. Report on incidents involving HNS. Submitted by the United Kingdom. IMO 85th Session, Agenda item 5- LEG 85/INF.2, 19 September 2002.