Papers by Keyword: Electrical Resistivity

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Authors: Tze Yang Darren Lim, Bahador Sabet Divsholi, Susanto Teng
Abstract: In today’s rapid construction, a reliable method for quick evaluation of concrete quality during construction is very important. The compressive strength of concrete has been used to evaluate the mechanical properties of concrete; however compressive strength may not represent the durability of concrete. Rapid Chloride Migration Test (RCMT) and electrical resistivity can be used to evaluate the durability of concrete. Obtaining the coefficient of chloride diffusivity from RCMT usually requires a testing duration of 24 hours or less for normal strength concrete. With the inclusion of supplementary cementitious materials and lower water/cementitious ratio to achieve a higher strength and more durable concrete, testing of the concrete becomes an elaborate affair which might takes at least four to five days of testing. Electrical resistivity technique has been used to evaluate the quality of normal strength concrete. However the suggested classification of concrete quality is not applicable to ultra durable concrete. In this work, the effectiveness of using the concrete resistivity test results from electrical resistivity technique is studied. With the use of direct and four points Wenner probe methods, the concrete resistivity results were obtained and compared with the coefficient of chloride diffusivity from RCMT. Six mixes of three different grades with the inclusion of 30% granulated ground blast-furnace slag and 10% undensified silica fume were designed and tested; and high correlation coefficients (>0.94) for all the mixes were achieved. This represents the effectiveness of using the electrical resistivity technique to carry out fast and accurate in-situ test to determine the quality of the ultra durable concrete.
Authors: Yu Feng Chen, De Qing Liang, Neng You Wu
Abstract: An understanding of the physical properties of hydrate-bearing sediment is necessary for interpretation of geophysical data collected in field settings. We have conducted a laboratory experiment to measure the electrical property of initially water saturated sediment containing natural gas hydrate. When gas hydrate was formed from pore fluid in ocean sediment, bulk sediment resistivity was significantly increased. The resistivity of the sediment was largely changed below 20% hydrate saturation. With the increasing hydrate saturation, the resistivity of sediment was increased and the resistivity of pore fluid was decrease. In the final process of hydrate formation, the resistivity depression was found mainly due to the transition of gas hydrate morphology. The electrical resistivity of hydrate specimens varied from 1.930 Ohm.m to 3.950 Ohm.m for saturation ranging from 0% to 52.68%. Besides, the dependence of the resistivity index versus hydrate saturation is inconsistent with Archies law. The results of our studies have important implications for quantitative laboratory and field calibration of geophysical measurements within gas hydratebearing intervals.
Authors: Jie Hao, Chang Sheng Deng, Qing Feng Zan, Jing Ming Xu
Abstract: The electrical resistivty (R) of BaO–CaO–SiO2–Al2O3 (BCSA) based glass, which was used in SOEC, was measured by impedance analyzer from room temperature to sealing temperature, and it was founded that electrical resistivity of all seal glass decreases with temperature. When temperature is lower than the soften temperature of glass, the electrical resistivity of all seal glass was no less than 107Ω∙cm. At 850°C, the resistivity of the 16BaO–16CaO–42SiO2–8Al2O3 glass (G1) reached 4.40×106Ω∙cm, and even at the sealing temperature, their resistivity was still above 105-106Ω∙cm. With the decrease of ratio of Si/B from 3 to 1, the electrical resistivity of glass decreased from 4.40×106Ω∙cm to 8.96×104Ω∙cm. The electrical resistivity of glass in BCSA system could be significantly affected by B2O3 and alkaline earth oxides. The results show that the electrical resistivity of glass was improved with the increasing of non-bridging oxygen and the average field strength. All glasses can be used as sealants at high temperature with no electrical shunting in SOEC.
Authors: Seung Hoon Nahm, Young Joo Kim, Jeong Min Kim, Dong Jin Yoon
Abstract: When the shape memory alloy(SMA) completely consists of austenite phase that shows the super-elastic property, if the external energies, such as stress, crack, propagation and lamination, etc. are increased in this alloy until the austenite phase was transformed into the martensite phase, they are enough to change the mean free path of electrons correlated with the electrical resistivity of materials in the microscopic point of view. On the basis of the above concept, we carried out the feasible study for SMA wire as a strain sensor using the super-elastic property of SMA. The SMA wires of diameter 41 ㎛ were utilized for a sensor material. The relationship between electrical resistivity and tensile properties of the Ni-Ti based SMA wires during tensile loading was investigated. Since the strain is very sensitive to the minute change of electrical resistance of SMA wire, it is possible to use the SMA wire as a sensor of such physical quantities. In the study, the possibility for the application of Ni-Ti SMA wire as a sensor was investigated. The sensing system was able to measure the strain up to 6 % with 0.22 % measuring error. The sensitivity described by the ratio of electrical resistivity showed 0.00005.
Authors: Bing Hao Li, Lian Zhen Xiao, Ya Qing Fu
Abstract: Hydration activity of a tailing is evaluated by the hydration rate obtained from the electrical resistivity measurement and compressive strength in a cementitious hydration system as a mineral admixture. A plain paste and the pastes with tailing or fly ash by replacement of cement at water-binder ratio of 0.4 are prepared. The electrical resistivity of the paste samples was measured in 168h(7d) by a non-contact resistivity technique. Hydration activity of the tailing was also evaluated by measuring the compressive strength at the curing ages of 3d~90d to confirm the results from the electrical resistivity. It is found that the addition of a mineral admixture delays the occurrence of two peaks on the electrical resistivity differential curve and the delayed times are 3.32h and 6.10h for the sample with tailing, and 0.78h, 3.49h for the sample with fly ash. The rate values on the two peaks are decreased with incorporation of the tailing or fly ash. The activity evaluation results on the mineral admixtures from the resistivity measurement are consistent with the strength results before 7d. The resistivity as an activity index can provide a simple and fast way to evaluate mineral material activity at early ages. The effect of tailing and fly ash on compressive strength for a long term was also analyzed and the micro-structure of the pastes at 7d and 28d were observed by SEM.
Authors: Mariana A. Fraga, Andre Contin, Graziela S. Savonov, Divani C. Barbosa, Rodrigo S. Pessoa, Vladimir J. Trava Airoldi
Abstract: The growth of diamond films on different substrates has been studied extensively to support the emerging technologies ranging from mechanical to nano/microelectronics. It is known that the performance of these applications is affected by diamond film properties, such as structure and morphology. Using chemical vapor deposition (CVD) technique, we have deposited ultrananocrystalline diamond (UNCD) and microcrystalline diamond (MCD) films on 4H-SiC substrates and investigated their basic material properties. The understanding and exploitation of the material properties are fundamental to evaluate the potential of UNCD-on-SiC and MCD-on-SiC structures for fabrication of electronic devices and sensors.
Authors: Cheng Bao Jiang, Li Hong Xu, Tian Li Zhang, Tian Yu Ma
Abstract: Co and Si were selected as substitutes to improve performance of TbDyFe giant magnetostrictive alloys for special purpose, respectively. The results showed that the Co-doped Tb0.36Dy0.64Fe2 alloys can possess giant magnetostriction over a wide temperature range from -80 to 100 . Optimum magnetostriction, high electrical resistivity and improved corrosion resistance was obtained in Tb0.3Dy0.7(Fe1-xSix)1.95 system. High performance grain-aligned rods with <110> preferred orientation have been successfully prepared by zone melting unidirectional solidification. This paper also presents the design and fabrication of Giant Magnetostrictive Actuator (GMA) for active vibration control with oriented TbDyFe rods. Experimental results showed that the GMA possesses good static and dynamic performance. Excellent damping effect, 20-30 dB under the frequency range from 10 Hz to 120 Hz was obtained.
Authors: Koichi Tsuchiya, O. Kawabata, Minoru Umemoto, H. Sato, K. Marukawa
Authors: Kyung Tae Hong, Young Su Ji, Sung Jae Chung, Myoung Ryul Ok, Yun Hoon Ji, Kyung Sub Lee
Authors: Jakub Čížek, František Lukáč, Marián Vlček, Martin Vlach, Ivan Procházka, Franziska Traeger, Detlef Rogalla, Hans Werner Becker, Wolfgang Anwand, Gerhard Brauer, Stefan Wagner, Helmut Uchida, Astrid Pundt, Carsten Bähtz
Abstract: Hydrogen absorption and diffusivity in high quality ZnO crystals were investigated in this work by X-ray diffraction combined with slow positron implantation spectroscopy and electrical resistometry. ZnO crystals were covered by a thin Pd over-layer and electrochemically charged with hydrogen. It was found that absorbed hydrogen causes plastic deformation in a sub-surface region. The depth profile of hydrogen concentration introduced into the crystal was determined by nuclear reaction analysis. Enhanced hydrogen concentration was found in the sub-surface region due to excess hydrogen atoms trapped at defects introduced by plastic deformation. Hydrogen diffusion in ZnO crystals with various orientations was studied by in-situ electrical resistometry. It was found that hydrogen diffusion in the c-direction is faster than hydrogen diffusion in the a-direction most probably due to open channels existing in the wurtzite structure along the c-axis.
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