Papers by Keyword: Resistivity

Abstract: The shape recovery efficiency of Ni-Ti shape memory springs has been investigated upon the application up to 6 X 10⁵ thermo-activation cycles. The hysteretic behaviour of the Martensitic-Austenitic phase transition has been characterized by resistivity measurements and infrared thermography. A loss in the recovery efficiency of the original shape has been observed and has been ascribed to functional fatigue leading to the formation of the R phase upon sample heating. Nevertheless, one way shape memory effect was found to exhibit an asymptotic stable behaviour which makes possible the realization of Ni-Ti actuators able to operate for a relative large number of activation cycles.

Abstract: Thermoelectric properties of metal oxide semiconductors are of increasing interest in the field of sensors design and fabrication. The oxide components in the majority of such applications are polycrystalline in which the charge transportation is controlled both by the microstructure and the bulk properties of the material. While the dependence of the electrical resistivity on the microstructural and compositional changes in these materials is well understood, the complications encountered with their thermoelectric properties, have remained unattended. Here, we report experimental data on the Seebeck coefficient of undoped polycrystalline zinc oxide measured on the ceramic pellets fabricated by dry pressing of the powder and sintering at 800 and 1000°C, in air. Aluminum ohmic contacts are used for electrical connections. Seebeck voltage and electrical resistivity are measured at various temperatures and different atmospheric condition at the presence of predetermined temperature gradients.

Abstract: ZnO thin films have successfully been deposited using DC magnetron sputtering at room temperature by means of plasma power variation. XRD results show that films were grown at a plasma power of 30 W and 40 W are polycrystalline, while at 20 W is considered as amorphous. The optical bandgap of films are shrinkage by increasing the plasma power. The broadest transmittance range is belongs to ZnO film growth at plasma power of 40 W. The electrical conductivity of ZnO films increase from 4.02x10^-7 (Ωcm)^-1 to 8.92x10^-7 (Ωcm)^-1 once the plasma power is increased. Based on the electrical and optical properties of the films it clearly be seen that ZnO film grown at plasma power of 40 W has highest transmittance and lower electrical resistivity therefore it appropriate for transparent conductive oxide (TCO).

Abstract: In this work the goal was to study the behavior of titanium-hydrogen system with hydrogen concentration of 1 wt. % at high temperature vacuum annealing by means of positron lifetime (PL) spectroscopy and electrical resistivity measurements. The range of hydrogen concentrations under investigation requires the γ phase formation. The study is related with the X-ray diffraction (XRD) and thermal desorption spectra (TDS) analysis. The registered positron lifetime spectra were analyzed by multiexponential decomposition into two components. Correlation of changes of the parameters of the PL spectrum and the electrical resistivity is revealed in this paper.

Abstract: Zinc Oxide (ZnO) films were deposited by Atomic Layer Deposition (ALD) using Diethylzinc and a combination of Water and Ozone as the precursores. Electrical conductivity of ALD grown ZnO films, under low field, were studied with varied partial pressure of the constituent reactants. Supressing the oxygen vacancy by introducing O₃ during the reaction increase the resistivity of the films by couple of orders of magnitude. UV-Vis spectroscopy measurement showed the films to be transparent giving a room for its application as a TCO in solar cell.

Abstract: Monitoring of coastal saline soil water and salt transport is of great value on the soil physics and irrigation studies. In this paper, a vertical infiltration experiment was conducted to monitor the vertical variation of resistivity in the leaching process under different water level in an experimental tank by the designed automatic monitoring device. The experimental results showed regardless of whether the groundwater exist, the resistivity peak moved down in the curve of leaching, and the desalination occurred from the top to bottom, the desalination depth remains the same with the same leaching amount. However, the groundwater reduced the speed of water and salt transport and affected the water and salt migration of upper soil due to the capillary force.

Abstract: This study is aim to evaluate the natural frequency variation of the scale-down reinforced concrete containment vessel specimen under accelerated corrosion conditions. A plastic ring was sealed around the perimeter of the cylindrical vessel bottom with the 3.5 % NaCl solution to achieve the accelerated corrosion test. Concrete resistivity, open circuit potential, corrosion rate and natural frequencies were tested and discussed in this study. Test results presented that the accelerated corrosion method with a direct 60 voltage applied was a suitable method for estimating and accelerating the concrete vessel specimen. Therefore, the changes in natural frequencies were consistent with the material degradation of the concrete vessel specimen. The natural frequencies decreased with the increasing corrosion rate or decreasing resistivities for the specimen at higher mode, but would be no change for the specimen at the natural frequency of 1^st mode.

Abstract: In recent years, the research on organic solar cells systems based on nanocomposite containing conjugated polymers has lead to great attention with the aim or replacing conventional inorganic solar cells. This nanocomposite can be processed at lower cost, low weight and ease of synthesis with greater versatility than todays solar cell. In this study, we investigated the dependence of physical, optical and electrical properties on the thickness of MEH-PPV: TiO₂ nanocomposite thin films for organic solar cell application. It was found the optical properties of photo-active layer MEH-PPV: TiO₂ nanocomposite thin films improved with increasing its thickness however the electrical properties decreased. The absorption coefficients of photoactive layer are high in the visible region (400-600 nm) with optimum absorption region at 500 nm. The shift of absorption edge toward longer wavelength with increased of nanocomposite photoactive layer thickness due to narrowing band gap caused by the effects of electron-electron and electron-impurity scattering. In addition the study of illuminated current-voltage (I-V) characteristics revealed the increment of recombination process with increased of photoactive layer thicknesses. It was found such increased in resistivity from 136x10³ to 1600x10³ Ω.cm is closely related to the electric field and exciton dissociation which is decreased with increased photoactive thickness.

Abstract: Lead titanate thin films were successfully prepared using a simple sol-gel method. In the present study extra Pb excess was not taken into consideration in such a way that the ratio of Pb:Ti is 1:1. Different molar concentration (0.1, 0.2, 0.3, 0.4, and 0.5) involved in this study and it was found that the solutions increased in acidic level by the increment of molar concentration that being measured by pH and conductivity meter (JENWAY-3540). It also indicated that the solutions were electrically resistive at low concentration which might due to the existence of lead and oxygen ionic bonding. The solutions were then deposited onto cleaned glass substrate by spin coating technique indeed to have better thin film homogeneity at room temperature. The prepared thin films were characterized on electrical property considering the resistivity measured by solar simulator (BUKOH KEIKI EP-2000). After that structural and physical property of thin films were observed by atomic force microscopy (Park System, XE-100).

Abstract: This paper developed a resistivity measurement system on the platform of in-situ detector which based on seafloor drilling machine. In order to precisely process the weak voltage signal which outputted by the resistivity probe, the paper carried out the cross-correlation algorithm theoretical derivation and MATLAB simulation, then ported the algorithm to TMS320F28069 DSP processor and designed hardware. A mass of contrast experiment shows that the cross-correlation algorithm is an effective method to process weak signal. It can improve accuracy and anti-jamming ability of the submarine sediment resistivity measurement system. The method of submarine sediment resistivity measurement can be widely used in fields of marine geological survey, marine environment research, etc.