Structural Material Anomaly Detection System Using Water Chemistry Data, (III)

A method to determine the electric conductivity of water continuously and directly at elevated temperature up to 300°C was developed which can be applied as a sensor for corrosion behavior foreknowledge and diagnosis systems using water chemistry data of BWR primary coolant. Complex impedance was measured between a couple of parallel platinum electrodes installed with a constant distance and dipped in the water. By analyzing frequency dependence of the impedance, the resistivity of the water between the platinum electrodes was estimated separately from the impedance caused by surface reactions on the platinum electrodes, which was the source of error in the measurement of electrical conductivity at elevated temperature.

Increase of necessary frequency to obtain the surface impedance at elevated temperature was evaded by the extrapolation of the frequence dependence of the impedance with calculations by using the data up to 100 kHz in which electric conductivity shows negligibly small dependence on the frequency of applied voltage.

The measured conductivity of pure water up to 300°C showed a good agreement with the calculation based on the dissociation data of water, which shows the applicability for the in-line monitor of electrical conductivity at elevated temperature.     

Non-destructive evaluation of cracks in massive concrete using normal dc resistivity logging

Discontinuities are one of the most harmful damage to the durability of concrete structures. Currents approaches are limited to assessments of surface damages, even if non-destructive methods appear to be effective for the detection and the location of cracks. That is why, these methods might be unsuitable for investigation of massive concrete body as dams and locks. Present works aim at the presentation of new results with electrical resistivity to study damages within concrete structures. In this article, the electrical resistivity focused on the study of cracks and discontinuities (concrete joints, interfaces…) in massive concrete structures by measurements done in preexisting boreholes. The used array is the normal dc resistivity logging. The study presents numerical and experimental results. First, modeling allows correcting experimental data. Then, development shows the sensitivity relatively to the discontinuity characteristics (aperture and the resistivity contrast between the discontinuity and the concrete). The tests on a real structure are carried out to define the methodology for on-site measurement. Results support the modeling.     

Characterization of Chemical Densified Coating as Tritium Permeation Barrier

In a fusion blanket design, ceramic coating on structural materials has been considered to be used as a tritium permeation barrier. The Chemical Densified Coating (CDC) method has some advantage compared with another coating method. This method is capable to form densified coating on either the outer or the inner surface of a tube or a container. This process temperature is low (450°C). The fabrication technique of Cr₂O₃-SiO₂ coating had been developed using CDC method. However, Cr₂O₃-SiO₂ coating had open pores in the coating. For filling open pores, the densification treatment by CrPO₄ was examined. In this study, the verification of open pores, the thermal shock resistivity, the adhesion strength and the deuterium permeability were evaluated and compared with Cr₂O₃-SiO₂ (Type 1) coating and Cr₂O₃-SiO₂ including CrPO₄ (Type 2) coating. From these results, it was confirmed that Type 2 coating had a good adhesion property, and permeation reduction factor of SS316 with Cr₂O₃-SiO₂ including CrPO₄ coating reached about 1,000 at 600°C.     

Low‐Energy Electron Beam Induced Charging and Secondary Electron Emission Properties of FEP Film Used on Satellite Surfaces

Many kinds of insulating materials are used outside a spacecraft. They include FEP films, polyimide films, and so on, and are used as thermal control materials. These materials are exposed to a charged‐particle environment around the spacecraft. Thus then become charged due to charged particles, especially electrons. It has been pointed out that charging of these materials is likely to cause discharges on the surfaces. From this viewpoint, we investigated the charging potential characteristics of 127‐μm‐thick FEP film, a typical thermal control material, by exposing it to electron irradiation at various energies below 20 keV. In the dependence of the charging potential on the electron energy, we found that the electron energy at which no charge‐up occurs is about 2.7 keV. This appears to be the energy at the which secondary electron emission yield becomes unity. This indicates that electron irradiation of FEP film with energies lower than 2.7 keV induces positive charging. From the charge decay characteristics after electron irradiation, the volume resistivity of the film was also obtained as a function of the electric fields in the bulk of the FEP film.     

Thermal stability and mechanical properties of room temperature vulcanized silicone rubbers

Based on much of the importance of RTV on the field of self-cleaning application for its nontoxic, tasteless, and thermal stability, the effects of D₄-SiO₂ on mechanical properties, Al(OH)₃ and decabromodiphenyl oxide ethyl(DBDPE) on flame retardant property of RTV matrix were investigated firstly. Then, a new kind of complex fire retardants was compounded. The morphology of additives and fracture appearance of composites were demonstrated by SEM. The hot property of RTV-based composites was outlined by TG. It is found that D₄-SiO₂/Al(OH)₃/DBDPE/Sb₂O₃/RTV composites were of better comprehensive performances in mechanical property, hot property, fire resistance property, and insulating property, which presented tear 26.73 kN/m of strength, 279.8% of elongation at break, 2.81 MPa of tensile strength, FV-0 at the level of flame retardant property, 46 of Oxygen index (OI) 3.03 × 10¹⁵ Ωm of Volume electric resistivity, the range of decomposition temperature was 370°C to 650°C, and the percentage of remain weight was 26.4%. Those properties was acquired on the condition of 11 wt % D₄-SiO₂ + 20 wt % Al(OH)₃ + 15 wt % DBDPE+ Sb₂O₃ at the amount of 3.0 wt % to 3.7 wt %. This investigation leads the authors to a conclusion that D₄-SiO₂/Al(OH)₃/DBDPE/Sb₂O₃ is a kind of better combination modifier than anyone kind of which in comprehensive properties for RTV. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Microstructural and Tribological Behavior of Pulse Electroplated Nickel Barrier on Copper Conductors

The microstructural, mechanical, and tribological behaviors of electroplated Ni on Cu conducting substrates have been investigated in this study. The microstructural studies were performed by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). The results showed that initially (111) with (220), (200) Ni texture components were predominant in the coating, and increasing the current density from 0.1 to 0.5 A/cm² led to the development of a strong (111) texture. The presence of ultrafine grains coupled with a (111) Ni texture improved the coating microhardness and wear properties significantly. It was shown that with an increase in current density, wear resistance of the coatings improved significantly and the electrical resistivity increased due to the highly populated grain boundaries.     

煤矿井下探测中影响不含水断层视电阻率变化的单一主控因素分析

选取晋城矿区典型3号无烟煤试样，在实验室进行单轴加载条件下的电阻率测试实验，并开展矿井瞬变电磁法探测不含水断层现场试验，研究了不含水断层的视电阻率变化特征。结果表明:煤样加载全过程，经过压密阶段、弹性变形阶段、塑性变形阶段、峰值后破裂阶段、残余变形阶段5个阶段；煤样应力应变曲线表现为由低到高再到低的特征，煤样电阻率曲线表现为由高到低再到高的特征；加载过程中，压密阶段、弹性变形阶段应力越大电阻率越小，应力为影响电阻率变化的主控因素；塑性变形阶段，电阻率先减小后增大，应力和裂隙共同影响电阻率变化，由应力为主要因素逐渐转变到裂隙为主要因素；峰值后破裂阶段和残余变形阶段电阻率急速增大，裂隙为影响电阻率变化的主控因素；通过瞬变电磁法探测不含水断层试验，发现不含水断层导致视电阻率明显升高，表明裂隙为影响断层视电阻率单一变化的主要因素。     

不同煤层掘进工作面瞬变电磁法探测应用研究

煤矿井下瞬变电磁法成为煤矿井下超前探测工作的重要手段，在矿井水害预测预报上发挥着很大的作用。随着矿井上组煤层资源的逐渐枯竭，煤矿开采资源逐渐延伸向下组煤层。同一井田范围内同煤层及其顶底板的岩性特征一般相差不大，瞬变电磁法在同煤层施工过程中接收到的物理背景场较为接近；而不同煤层及其顶底板岩性特征通常会有较大的差别，瞬变电磁法在不同煤层施工过程中会接收到差别较大的物理背景场。当矿井存在多煤层开采时，通过大量数据研究瞬变电磁法在不同煤层巷道探测中的响应特征规律，分析并掌握不同煤层条件对瞬变电磁法探测结果的影响，能够提高瞬变电磁法在多煤层探测成果的准确性。     

Development and performance analysis of novel in situ Cu–Ni/Al2O3 nanocomposites

Cu–Ni/Al₂O₃ nanocomposite powders were manufactured using an in situ chemical reaction technique. This technique provides improved wettability and adhesion between the matrix and reinforcement phases. Aluminum nitrate, copper nitrate and nickel nitrate were used as start materials for the production of the composites. The powders were sintered in a hydrogen environment at 900 °C for 2 h after being cold pressed at 700 MPa. To determine the effect of Al₂O₃ on electrical and thermal conductivities and thermal expansion behaviors, the Cu–Ni matrix was supplemented with 3, 5, and 8 wt% Al₂O₃. The findings revealed that Al₂O₃ nanoparticles (20 nm) were dispersed uniformly throughout the copper-nickel matrix. Microhardness was improved from 53.3 HV for Cu–Ni matrix to 92.7 HV for Cu–Ni/8%Al₂O₃ nanocomposites. The electrical and thermal conductivities and thermal expansion coefficient were reduced as the amount of Al₂O₃ in the Cu–Ni matrix increased. The electrical conductivity was reduced by 38.7% by addition 5% Al₂O₃ nanoparticles to Cu–Ni matrix. The high interfacial bonding between Cu–Ni and Al₂O₃ nanoparticles was the main reason of the hardness improvement and maintaining relatively good electrical and thermal properties.     

Optical properties and electrical resistivity of boron-doped ZnO thin films grown by sol–gel dip-coating method

Sol–gel dip-coating was used to grow ZnO thin films doped with various concentrations of B ranging from 0 to 2.5 at.% on quartz substrates. The effects of B doping on the absorption coefficient (α), optical band gap (E_g), Urbach energy (E_U), refractive index (n), refractive index at infinite wavelength (n_∞), extinction coefficient (k), single-oscillator energy (E_o), dispersion energy (E_d), average oscillator strength (S_o), average oscillator wavelength (λ_o), moments M₋₁ and M₋₃, dielectric constant (ε), optical conductivity (σ), and electrical resistivity (ρ) of the BZO thin films were investigated. The transmittance spectra of the ZnO and BZO thin films show that the transmittance of the BZO thin films was significantly higher than that of the ZnO thin films in the visible region of the spectrum and that the absorption edge of the BZO thin films was blue-shifted. The BZO thin films exhibited higher E_g, E_U, and E_o and lower E_d, λ_o, M₋₁ and M₋₃ moments, S_o, n_∞, and ρ than the ZnO thin films.