Managing the remediation strategy of contaminated megasites using field-scale calibration of geo-electrical imaging with chemical monitoring

Groundwater contamination is a threat to drinking water resources and ecosystems. Remediation by injection of chemical reagents into the aquifer may be preferred to excavation to reduce cost and environmental footprint. Yet, successful remediation requires complete contact between contamination and reagents. Subsurface heterogeneities are often responsible for diffusion into low-permeable zones, which may inhibit this contact. Monitoring the spatial distribution of injected reagents over time is crucial to achieve complete interaction. Source zone contamination at megasites is particularly challenging to remediate and monitor due to the massive scale and mixture of contaminants. Source zone remediation at Kærgård Plantation megasite (Denmark) is monitored here, with a new methodology, using high-resolution cross-borehole electrical resistivity tomography (XB-ERT) imaging calibrated by chemical analyses on groundwater samples. At this site, high levels of toxic non-aqueous phase liquids (NAPL) are targeted by in-situ chemical oxidation using activated persulfate. It may take numerous injection points with extensive injection campaigns to distribute reagents, which requires an understanding of how reagent may transport within the aquifer. A geophysical (XB-ERT) monitoring network of unprecedented size was installed to identify untreated zones and help manage the remediation strategy. The combination of spatially continuous geophysical information with discrete but precise chemical information, allowed detailed monitoring of sulfate distribution, produced during persulfate activation. Untreated zones identified in the first remediation campaign were resolved in the second campaign. The monitoring allowed adjusting the number of injection screens and the injection strategy from one campaign to the next, which resulted in better persulfate distribution and contaminant degradation in the second campaign. Furthermore, geophysical transects repeated over the timespan of a remediation campaign allowed high-resolution time-lapse imaging of reagent transport, which could in the future improve the predictability of transport models, compared to only using on a-priori assumptions of the hydraulic conductivity field.

Imaging leachate runoff from a landfill using magnetotellurics: The Garraf karst case

Electrical and active source electromagnetic geophysical methods have been traditionally employed to approach and tackle environmental problems, such as those caused by landfills. However, since these problems are more consequential and cover broader areas, it is necessary to use deeper penetration methods, such as magnetotellurics. In the Garraf Massif (Catalan Coastal Ranges, NE Spain), an urban waste disposal landfill had been in operation from 1974 to 2006, during which >26 million metric tons of garbage had been deposited. This landfill overlies karstic terrain, thus principally impacting groundwater circulation. Previous electrical resistivity tomography profiles had partially imaged the infill but were not able to penetrate below the base of the original landfill. During 2019 and 2020 we performed a magnetotelluric study over the landfill and its surrounding with the goals of characterizing the electrical resistivity of the infill and below it. The 2D and 3D resistivity models confirmed the highly conductive nature of the leachate and allowed us to identify its presence below the landfill base, which we quantified with maximum thicknesses of 90 m. This proved that landfill leachate had filtered through the original impermeable layer, enhanced by the karstic drainage structure.

Enhancement in antimicrobial efficacy and biodegradation of natural rubber latex through graphene oxide/nickel oxide nanoparticles

This work aims to fabricate antibacterial natural rubber latex composites by introducing different ratios of graphene oxide (GO) and nickel oxide (NiO) nanoparticles. The nanocomposites were prepared using latex mixing and a two-roll mill process, followed by molding with a heating hydraulic press. Detailed analyses were conducted to evaluate the rheological, chemical, physical, thermal, mechanical, and electrical performance of the composites. Fourier transform infrared spectroscopy (FTIR) was employed to analyze the interaction among different components, while the surface morphology was examined through the field emission scanning electron microscopy (FESEM) technique. The composites with a loading ratio of 1:2 of GO to NiO (optimized concentration) exhibited the highest tensile strength (24.9 MPa) and tear strength (47.4 N/ mm) among all the tested samples. In addition, the composites demonstrated notable antimicrobial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans. The thermal stability of the composites was observed up to 315 °C, and their electrical resistivity lies in the insulating range across a temperature span of 25 °C to 50 °C. The research uncovers critical insights into advancing composite materials suitable for diverse applications, featuring inherent antibacterial attributes, robust mechanical properties, resilience to solvent, UV shielding properties, and controlled electrical resistivity capabilities.

Behavioral assessment of intrinsically formed smart concrete using steel fibre and carbon black composite

In recent years, health monitoring consists of the periodic observation and analysis of existing systems to predict and avoid structural breakdown, thereby saving lives and significantly lowering the cost of structural maintenance and repair. Normally, non-destructive testing techniques and sensor technology are used to detect damage in concrete structures are expensive in nature. Self-diagnosing or smart concrete has emerged a new paradigm in concrete research for damage detection. Smart concrete was cast by blending functional fillers such as carbon black, and steel fibers with concrete to improve the performance. Under various load conditions, the mechanical properties of the proposed smart concrete were examined. The electrical resistance of smart concrete was measured using the Four Probe Method and the Arduino UNO software. SEM and XRD were used to investigate the microstructures of intrinsically smart concrete. Thermogravimetric analysis was employed as a Non-Destructive Testing method to observe the hydration process. Furthermore, the obtained data were linked with the electrical resistivity of the smart concrete to assess corrosion damage. The electrical resistivity method is also an economical method and effective method to monitor the rate of corrosion.

Abatement of environmental pollution by research on electrical resistivity and conductivity mechanism of poplar dust

Under conventional processing conditions, the resistivity of wood dust is in the range of insulating materials, which can induce a dust cloud explosion when there are static sparks. This paper took the fast-growing poplar wood commonly used in Chinese wood processing and studied the effects of moisture content, temperature, and particle size on the electrical resistivity value of sanded wood dust. Orthogonal analysis was conducted on the influencing factors. The results showed that the influence of moisture content on electrical resistivity was the most significant factor, followed by temperature and particle size. Further experiments have shown that when the moisture content increased from 6% to 32%, the resistivity decreased from 109 Ω cm to 105 Ω cm, which reached the suitable resistivity range of static discharge method. The ion concentration of wood dust extracted in cold water and hot water and the resistivity of poplar dust residue after extraction were determined. Nine metal ions (a total of 105.02 mol/g) were detected in cold-water extract, and the concentrations of K+, Na+, Mg2+ and Ca2+ accounted for 99.8%. The original poplar dust and the extracted poplar dust were measured and analyzed. The changes in water-soluble ion content, functional groups, crystallinity, and complexes of the wood dust before and after ion dissolution, jointly led to changes in the electrical resistivity of the wood dust (a difference of 2-4 orders of magnitude). It was verified that the way wood dust conducts electricity is through ion conduction. There were more abundant capillary system structures between poplar dust particles, allowing water-soluble ions to move more freely with water channels. The larger specific surface area and higher temperature also promoted the dissolution of water-soluble ions, which affected the electrical resistivity.

Assessment of effectiveness in stabilization/solidification of arsenic-contaminated soil: long-term leaching test and geophysical measurement

This study focused on evaluating the effectiveness of stabilizer/binding agents in immobilizing arsenic (As) in contaminated soil using both geochemical and geophysical monitoring methods. The effluent from the stabilizer/binding agent's application and control columns was analyzed, and the status of the columns was monitored using electrical resistivity (ER) and induced polarization (IP) methods. As stabilizers/binder, acid mine drainage sludge (AMDS) and steel slag (SS) were used, which delayed As and Ca leaching time and significantly reduced As leaching amount. Determination coefficients for As and Fe leaching exhibited elevated values (control column, R2 = 0.955; AMDS column, R2 = 0.908; and SS column, R2 = 0.833). A discernible decline in the concentration of leached Fe was accompanied by a corresponding reduction in IP. The determination coefficients correlating IP and Fe leaching remained substantial (control column, R2 = 0.768; AMDS column, R2 = 0.807; and SS column, R2 = 0.818). Such IP measurements manifest as instrumental tools in monitoring and assessing the retention capacity of applied stabilizer/binding agents in As-affected soils, thereby furnishing crucial data for the enduring surveillance of stabilization/solidification locales. This research posits a swift and continuous monitoring method for solidification/stabilization locales in situ.

Resistivity responses of sodium sulfate and sodium chloride-type loess under different water and salinity conditions

Saline loess is widely distributed in Africa, Latin America and Asia and is characterized by wet expansion and dry shrinkage, which has a large impact on the environment. In this study, the electrical resistivity of sodium sulfate loess and sodium chloride loess with moisture content (8-24%) and salt content (0.3-2.7%) was measured by an LCR digital bridge instrument. The experimental results demonstrated a decrease in the resistivity with the increase in moisture and salt content. When the salt content was greater than 0.9%, the rate of reduction in resistivity decreased and showed a tendency to be stable. With the increase in moisture content, the water conductive path changes from water in diffusion double layer (DDL) to capillary water and finally to gravity water, which in turn leads to a gradual decrease in the rate of reduction in resistivity. At the same salt content, the resistivity of sulfate loess is higher than that of chloride loess. This study analyses the resistivity changes of two kinds of salt-bearing loess under different water and salinity conditions, which has certain guiding significance for environmental monitoring and pollutant assessment based on resistivity data.

Enhancing performance and sustainability of ultra-high-performance concrete through solid calcium carbonate precipitation

Ultra-high-performance concrete (UHPC) exhibits high compressive strength and good durability. However, owing to the dense microstructure of UHPC, carbonation curing cannot be performed to capture and sequester carbon dioxide (CO₂). In this study, CO₂ was added to UHPC indirectly. Gaseous CO₂ was first converted into solid calcium carbonate (CaCO₃) using calcium hydroxide, and the converted CaCO₃ was then added to UHPC at 2, 4, and 6 wt% based on the cementitious material. The performance and sustainability of UHPC with indirect CO₂ addition were investigated through macroscopic and microscopic experiments. The experimental results showed that the method used did not negatively affect the performance of UHPC. Compared with the control group, the early strength, ultrasonic velocity, and resistivity of UHPC containing solid CO₂ improved to varying degrees. Microscopic experiments, such as heat of hydration and thermogravimetric analysis (TGA), demonstrated that adding captured CO₂ accelerated the hydration rate of the paste. Finally, the CO₂ emissions were normalized according to the compressive strength and resistivity at 28 days. The results indicated that the CO₂ emissions per unit compressive strength and unit resistivity of UHPC with CO₂ were lower than those of the control group.

Using geophysics to guide the selection of suitable sites for establishing sustainable earthen fishponds in the Niger-Delta region of Nigeria

Water retention in earthen fishponds throughout a fish farming cycle is challenging due to climate-induced water loss via evapotranspiration, seepages, and lowering of the groundwater table. These processes depend on the soil hydrostratigraphic condition and constitute a major challenge for fish farmers in the Niger-Delta region of Nigeria, where seasonal variations cause groundwater levels to fluctuate. This study assesses the use of non-invasive geophysical methods, including electrical resistivity and induced polarization, to guide the selection of sites with appropriate hydrostratigraphic conditions for establishing earthen fishponds. We combined measurements of electrical resistivity and chargeability distributions to assess the subsurface of two earthen fishpond sites at Ugono-Abraka and Agbarha-Otor areas in the Niger-Delta region of Nigeria. Electrical soundings were acquired at ten locations, while two-dimensional electrical resistivity and Induced polarization were acquired across five transects using Schlumberger and dipole-dipole electrode configurations. The field data were inverted using IP2win, and Diprowin software. The geophysical models were combined with lithological data from soil cores to characterize the subsurface stratigraphy, while measured clay contents were used to estimate infiltration coefficients relying on established petrophysical relationships. The delineated subsurface properties at Ugono-Abraka and Agbarha-Otor show higher variations than assumed by practitioners. The complementary results of low resistivity (20-140 Ωm) and high chargeability (10-50 msec) revealed areas with clay-rich sediments. Soil samples confirmed higher clay contents of up to 10% at Ugono-Abraka and low values of 2% at Agbarha-Otor. Estimated infiltration coefficients are lower at the Ugono-Abraka site (1.6 m/day) compared to Agbarha-Otor (8.4 m/day). This implies variable water loss in the earthen fishponds; hence, we recommend characterizing these variations using non-invasive geophysical methods before establishing medium to large-scale earthen fishponds in the area.

Nonlinear inversion of electrical resistivity sounding data for multi-layered 1-D earth model using global particle swarm optimization (GPSO)

Interpreting geophysical data requires solving nonlinear optimization problem(s) in inversion. Analytical methods such as least-square have some intrinsic limitations, which include slow convergence and dimensionality, making heuristic-based swarm intelligence a better alternative. Large-scale nonlinear optimization problems in inversion can be solved effectively using a technique within the swarm intelligence family called Particle Swarm Optimization (PSO). This study evaluates the inversion of geoelectrical resistivity data with global particle swarm optimization (GPSO). We attempted to invert field vertical electrical sounding data for a multi-layered 1-D earth model using the developed particle swarm optimization algorithm. The result of the PSO-interpreted VES data was compared with that of the least square inversion result from Winresist 1.0. According to the PSO-interpreted VES results, satisfactory solutions may be attained with a swarm of 200 or fewer particles, and convergence can be reached in fewer than 100 iterations. The GPSO inversion approach has a maximum capacity of 100 iterations, more than the least square inversion algorithm of the Winresist, which has a maximum capacity of 30 iterations. The misfit error of GPSO inversion is 6.14×10-7, much lower than that of the least square inversion of 4.0. The GPSO inversion model has lower and upper limit values of the geoelectric layer parameters model to fit the true model better. The limitations of the developed PSO inversion scheme include a slower execution time of the inversion procedures than the least-square inversion. There is a need for a priori knowledge of the number of layers from borehole reports in the study area. The PSO inversion scheme, however, estimates inverted models closer to the true solutions with greater accuracy than the least-square inversion scheme.

Synthesis, structure, oxygen stoichiometry, and electrical properties of doped ruddlesden-popper strontium cobaltite Sr1·875Ce0·025CoO4-δ, Sr1·875Ce0·025Co0·75Ni0·25O4+δ novel compounds

We report the synthesis of Sr_1·875Ce_0·025CoO_4-δ and Sr_1·875Ce_0·025Co_0·75Ni_0·25O_4+δ for the first time, each compound was synthesised using Co-precipitation and Sol-Gel methods, at 1050 °C for 144 and 120 h respectively. Oxygen stoichiometry was determined using Iodometric titration, we have noticed oxygen hypostoichiometry for Ce-doped compound and hyperstoichiometry state after Ni-doping. Electrical properties were studied for sintered pellets, Electrical resistance was measured in the range (-0.5-+0.5 v). Specific electrical resistivity and electrical conductivity were calculated from resistance measurements. It was found that the Ce-doped compound has about three times higher conductivity (σ_C1 = 0.000000058423295 s cm^-1) Compared with the Ni-doped one (σ_N2 = 0.000000022384787 s cm^-1). Electrical Capacitance was measured at 1 kHz frequency, the relative dielectric constant ε_r, and the loss tangent tanδ were calculated accordingly. The results showed that the Ni-doped compound has higher capacitance but lower ε_r and dissipation factor values.

Efficiency and limitation of vertical electrical sounding in evaluation of groundwater potential in fractured shale terrain: a case study of Abakaliki Area Lower Benue Trough Nigeria

Water supply in the Abakaliki Area of Southeastern Nigeria and its environs has been a source of worry. The area is marked by a series of abortive boreholes, sparsely productive boreholes, and failed water wells. These problems are a result of the direct and indirect function(s) of the prevailing geology of the area which is underlain by aquiclude (Abakaliki Shale, lenses of siltstone and sandstone) dominantly indurated shale. Sixteen (16) vertical electric sounding (VES) were acquired using a resistivity meter. The acquired data was plotted on a bi-log graph using INTERPEX and SURFER. Quantitative and qualitative interpretations were used in preparing geoelectric layers and layer parameter maps. Three (3) to five (5) geoelectric layers were delineated. The first layer is a compacted lateritic overburden. VES 1, 3, 4, 6, 11, and 15 were observed to have thin layers of clay with very low apparent resistivity values with an average of 2.642 Ωm and average thickness of 1.08 m, and depth generally less than 10 m. Fractured and non-fractured/baked shale layers were dominant in all points of the study area. The non-fractured consolidated shale has a high apparent resistivity value ranging from 180.3 Ωm to 770.42 Ωm with an average of about 339.53 Ωm while the fractured shale has an average resistivity value of about 21.36-68.79 Ωm and an average of 38 Ωm. The confinement of the aquifer implies that the indurated shale generally underly the Abakaliki Area. The low resistivity value of the fractured shale is an indication of the presence of fluid, possibly water. The results of this research implied that the application of exploration method(s) that could delineate the subsurface fractures should precede groundwater development in the area. Also, there is no specific depth to the water table in the area; however, the area has a generally shallow depth to groundwater on average.

Quantitative water content estimation in landfills through joint inversion of seismic refraction and electrical resistivity data considering surface conduction

The disposal of municipal solid waste (MSW) in landfills is the prevalent method of waste management at the global scale. However, the production of landfill gases due to the methanogenic fermentation of wet MSW is a possible threat to human health and accounts for a substantial contribution to the global greenhouse gas emissions. Accordingly, information regarding water content is critical as it is an important factor triggering methane production in MSW landfills. In this study, we propose a petrophysical joint inversion scheme to quantitatively solve for the water content (WC) in landfills based on seismic refraction as well as electrical resistivity data collected at two different frequencies. In this way, we also take into account the contribution of the surface conductivity to the observed electrical response, which is crucial for a reliable quantification of the WC. Our results reveal a high water content within the MSW unit (WC > 20%) for areas characterized by a strong polarization response (normalized chargeability > 5 M_n mS/m). Such areas can be related to an increased biogeochemical activity as evidenced by the detected methane production. We observe consistent estimates between the water content resolved through the proposed joint inversion scheme and values measured in waste samples with a median percentage error of 17%. Our study demonstrates the possibility to obtain reliable estimates for the WC in MSW landfills through the petrophysical joint inversion of seismic and electrical data when surface conductivity is explicitly considered.

New models for calculating the electrical resistivity of loess affected by moisture content and NaCl concentration

Saline loess is an important cause of environmental geo-issues in northwest China. In this research, electrical resistivity of loess with different moisture contents and NaCl concentrations was measured at three test frequencies. Results indicates the plastic limit (16%) and around 2% NaCl concentration are the critical content affecting the variation of loess electrical resistivity. The variation and conductivity for conductive paths are affected by moisture content and NaCl concentration respectively. Combined with three-phase composition and diffuse double-layer structure, new models that consider the effect of moisture content and NaCl concentration indicate good applicability in the validation datasets from different types of soil. A new model was verified by comparison between previous studies and experimental results. This research provides (i) theoretical support for the calibration of large-scale electrical field surveys and the observation of saline loess and (ii) a valuable reference for the prevention of environmental geo-crisis and the utilization of soil resources in northwestern China.

Geophysical and contamination assessment of soil spatial variability for sustainable precision agriculture in Omu-Aran farm, Northcentral Nigeria

The spatial and temporal variability of soil properties (fluid composition, structure, and water content) and hydrogeological properties employed for sustainable precision agriculture can be obtained from geoelectrical resistivity methods. For sustainable precision agricultural practices, site-specific information is paramount, especially during the planting season. An integrated one-dimensional (1D) and two-dimensional (2D) electrical resistivity survey have been adopted to characterize the subsoil parameters and delineate the aquifer unit of large farm areas, especially in precision agricultural practices. Also, contamination assessment reveals the soil quality status of farmlands. This study aims to determine the site-specific soil parameters of a commercial farm in Omu-Aran, Northcentral, Nigeria. The subsoil features from the geoelectrical resistivity surveys indicate 3 to 4 distinctive lithology to a depth of 43.4 m into the subsurface of the farm. The ID (Vertical Electrical Sounding) and 2D resistivity inversion models results have revealed the heterogeneity nature of the topsoil, also known as the stone zone comprising of reworked clayey soil and sandy gravelly soil, the weathered/saprolite zone (gravelly sandy/sandy soil), the fractured basement and the fresh basement rock. Contamination factor (Cf), pollution load index (PLI) and Nemerow integrated pollution index (NIPI) were used to assess the contamination index on the farmland. Toxic elements such as arsenic, cadmium, chromium, cobalt, lead, manganese, nickel, and zinc have low to moderate contamination in the farm. The depth of investigation (≤3m) covers the upper root zone of significant crops grown in the area. The findings can assess soil contamination, delineate basement features, subsoil variability, soil profiling, and determine the subsoil hydrological properties.

An insight into electrical resistivity of white matter and brain tumors

BACKGROUND

There is a lack of information regarding electrical properties of white matter and brain tumors.

OBJECTIVE

To investigate the feasibility of in-vivo measurement of electrical resistivity during brain surgery and establish a better understanding of the resistivity patterns of brain tumors in correlation to the white matter.

METHODS

A bipolar probe was used to measure electrical resistivity during surgery in a prospective cohort of patients with brain tumors. For impedance measurement, the probe applied a constant current of 0.7 μA with a frequency of 140 Hz. The measurement was performed in the white matter within and outside peritumoral edema as well as in non-enhancing, enhancing and necrotic tumor areas. Resistivity values expressed in ohmmeter (Ω∗m) were compared between different intracranial tissues and brain tumors.

RESULTS

Ninety-two patients (gliomas WHO II:16, WHO III:10, WHO IV:33, metastasis:33) were included. White matter outside peritumoral edema had higher resistivity values (13.3 ± 1.7 Ω∗m) than within peritumoral edema (8.5 ± 1.6 Ω∗m), and both had higher values than brain tumors including non-enhancing (WHO II:6.4 ± 1.3 Ω∗m, WHO III:6.3 ± 0.9 Ω∗m), enhancing (WHO IV:5 ± 1 Ω∗m, metastasis:5.4 ± 1.3 Ω∗m) and necrotic tumor areas (WHO IV:3.9 ± 1.1 Ω∗m, metastasis:4.3 ± 1.3 Ω∗m), p=<0.001. No difference was found between low-grade and anaplastic gliomas, p = 0.808, while resistivity values in both were higher than the highest values found in glioblastomas, p = 0.003 and p = 0.004, respectively.

CONCLUSIONS

The technique we applied enabled us to measure electrical resistivity of white matter and brain tumors in-vivo presumably with a significant effect with regard to dielectric polarization. Our results suggest that there are significant differences within different areas and subtypes of brain tumors and that white matter exhibits higher electrical resistivity than brain tumors.

Effects of large-scale heterogeneity and temporally varying hydrologic processes on estimating immobile pore space: A mesoscale-laboratory experimental and numerical modeling investigation

The advection-dispersion equation (ADE) often fails to predict solute transport, in part due to incomplete mixing in the subsurface, which the development of non-local models has attempted to deal with. One such model is dual-domain mass transfer (DDMT); one parameter that exists within this model type is called immobile porosity. Here, we explore the complexity of estimating immobile porosity under varying flow rates and density dependencies in a large-scale heterogeneous system. Immobile porosity is estimated experimentally and using numerical models in 3-D flow systems, and is defined by domains of comparatively low advective velocity instead of truly immobile regions at the pore scale. Tracer experiments were conducted in a mesoscale 3-D tank system with embedded large impermeable zones and the generated data were analyzed using a numerical model. The impermeable zones were used to explore how large-scale structure and heterogeneity affect parameter estimation of immobile porosity, assuming a dual-porosity model, and resultant characterization of the aquifer system. Spatially and temporally co-located fluid electrical conductivity (σ_f) and bulk apparent electrical conductivity (σ_b)-using geophysical methods-were measured to estimate immobile porosity, and numerical modeling (i.e., SEAWAT and R3t) was conducted to explore controls of the immobile zones on the experimentally observed flow and transport. Results showed that density-dependent flow increased the hysteresis between measured fluid and bulk electrical conductivity, resulting in larger interpreted immobile pore-space estimates. Increasing the dispersivity in the model simulations decreased the estimated immobile porosity; flow rate had no impact. Overall, the results of this study highlight the difficulty faced in determining immobile porosity values in field settings, where hydrogeologic processes may vary temporally. Our results also highlight that immobile porosity is an effective parameter in an upscaled model whose physical meaning is not necessarily clear and that may not align with intuitive interpretations of a porosity.

Crustal architecture of a metallogenic belt and ophiolite belt: implications for mineral genesis and emplacement from 3-D electrical resistivity models (Bayankhongor area, Mongolia)

Crustal architecture strongly influences the development and emplacement of mineral zones. In this study, we image the crustal structure beneath a metallogenic belt and its surroundings in the Bayankhongor area of central Mongolia. In this region, an ophiolite belt marks the location of an ancient suture zone, which is presently associated with a reactivated fault system. Nearby, metamorphic and volcanic belts host important mineralization zones and constitute a significant metallogenic belt that includes sources of copper and gold. However, the crustal structure of these features, and their relationships, are poorly studied. We analyze magnetotelluric data acquired across this region and generate three-dimensional electrical resistivity models of the crustal structure, which is found to be locally highly heterogeneous. Because the upper crust (< 25 km) is found to be generally highly resistive (> 1000 Ωm), low-resistivity (< 50 Ωm) features are conspicuous. Anomalous low-resistivity zones are congruent with the suture zone, and ophiolite belt, which is revealed to be a major crustal-scale feature. Furthermore, broadening low-resistivity zones located down-dip from the suture zone suggest that the narrow deformation zone observed at the surface transforms to a wide area in the deeper crust. Other low-resistivity anomalies are spatially associated with the surface expressions of known mineralization zones; thus, their links to deeper crustal structures are imaged. Considering the available evidence, we determine that, in both cases, the low resistivity can be explained by hydrothermal alteration along fossil fluid pathways. This illustrates the pivotal role that crustal fluids play in diverse geological processes, and highlights their inherent link in a unified system, which has implications for models of mineral genesis and emplacement. The results demonstrate that the crustal architecture-including the major crustal boundary-acts as a first-order control on the location of the metallogenic belt.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1186/s40623-021-01400-9.

OhmPi: An open source data logger for dedicated applications of electrical resistivity imaging at the small and laboratory scale

The use of electrical resistivity tomography in laboratory or field experiments for environmental purposes has been increasing in recent years. The development of commercial devices has thus far focused on the quality of measurements and their robustness in all field cases. However, both their costs and lack of flexibility to adapt to specific applications have limited their prevalence in the environmental sector. This article presents the development of a low-cost, open hardware resistivity meter to provide the scientific community with a robust and flexible tool for small-scale experiments. Called OhmPi, this basic resistivity meter features current injection and measurement functions associated with a multiplexer that allows performing automatic measurements with up to 32 electrodes (at a cost of less than $500). The device was first tested using a soil-analog electrical circuit to verify the reliability and robustness of the measurements. Results show that OhmPi offers a wide range of resistance measurements, from 0.2 to 1000 O, for contact resistances between 100 and 5000 O. Measurements were then carried out on a small field experiment, in demonstrating good stability of the OhmPi measurements, as well as a strong correlation with the output of a commercial reference instrument.

Geological and geophysical assessment of groundwater contamination at the Roundhill landfill site, Berlin, Eastern Cape, South Africa

An integrated geological assessment of groundwater contamination was carried out to determine the nature of the subsurface as well as establish linkages between groundwater and contaminants in the vicinity of the Roundhill landfill, South Africa. Quantitative analysis involved measurement of physico-chemical properties of groundwater samples from two boreholes and a leachate pond within the landfill. Qualitative assessment involved combined measurements of electrical resistivity and time domain induced polarization (IP) across three profiles, using the double-dipole array. The physico-chemical analysis results show the presence of heavy metals (i.e.mercury, lead and arsenic) in groundwater samples in concentrations above the general acceptable limits. Perhaps, the high concentration of these metals could be due to the dumping of toxic and hazardous waste substances on the landfill, contrary to the landfill design and classification. Resistivity and IP pseudo-sections revealed a 4-layered earth structure and anomalous zones of resistivity (≤112 Ω-m) and low chargeability (≤1.25 ms) in the top layers. This is indicative of percolating leachate plume in the unsaturated zone. Despite the fact that layer lithologies and stratigraphy pose low risk to groundwater contamination, structural controls such as fractures in the bedrock are favourably disposed to the percolation of contaminants into the groundwater over time. Proper waste classification and inspection should be carried out on the landfill prior to waste disposal.

Thermal and chemical enhanced recovery of heavy chlorinated organic compounds in saturated porous media: 1D cell drainage-imbibition experiments

Chemical and thermal enhanced recovery of pure heavy chlorinated organic compounds (DNAPL; dense non-aqueous phase liquids) was investigated by using lab-scale 1D cells. Temperature was increased to reduce DNAPL viscosity (and hence increase its mobility), while surfactant was added to decrease capillary forces involved in the entrapment of DNAPL in porous media. Laboratory scale experiments, based on mass balance and indirect monitoring methods (i.e., permittivity, electrical resistivity and optical density), were conducted to quantify the effects of these enhancements. Heating the DNAPL up to 50 °C decreased its viscosity by a factor of two. The addition of a surfactant; i.e., Sodium Dodecyl Benzene Sulfonate (SDBS), at its Critical Micelle Concentration (to prevent DNAPL solubilization), decreased interfacial tensions by a factor of 12. Drainage-imbibition experiments performed in 1D cells provided retention curves (capillary pressure as a function of water saturation) of a two-phase (DNAPL-water) system in experimental glass bead porous media. The observed reduction of residual saturation (S_rn) obtained with SDBS was 28% for 0.5 mm-diameter glass beads (GB) and 46% for 0.1 mm GB. No significant decrease in S_m was observed with thermal enhancement. The van Genuchten - Mualem model was found to satisfactorily reproduce the measured retention curves. Indirect measurements of water saturations (S_w) showed that: i. measured permittivities were very close to values modeled with the Complex Refractive Index Model (CRIM); ii. Archie's Law was less successful in reproducing measured electrical resistivities; iii. optical densities provide accurate estimations of S_w. At field scale, the combined monitoring of electrical resistivity (which provides a global picture) and permittivity (which yields locally precise but spatially limited information) is expected to significantly improve the collection of information on residual saturations S_rn.

Assessment of strength and leaching characteristics of heavy metal-contaminated soils solidified/stabilized by cement/fly ash

Solidification/stabilization technique has been widely adopted to remediate the heavy metal-contaminated sites. In the present work, the strength and leaching characteristics of the contaminated soils solidified/stabilized by cement/fly ash were systemically investigated. Electrical resistivity was also measured to establish empirical relationships for assessment of remediation efficacy. Tests results showed that the unconfined compressive strength increased and the leached ion concentration decreased with increasing curing time. In contrast, the unconfined compressive strength decreased and the leached ion concentration increased with increasing initial heavy metal ion concentration in the specimen. For the strength characteristic, the most notable detrimental effect was induced by Cr³⁺ and the least was induced by Pb²⁺. For the leaching characteristic, the trend was reversed. The electrical resistivity of the tested specimen increased significantly with increasing curing time and with decreasing initial ion concentration. The electrical resistivity of the Pb-contaminated specimen was higher than that of the Zn-contaminated specimen, which in turn was higher than that of the Cr-contaminated specimen. Empirical relationships between the strength, leaching characteristic, and electrical resistivity were established, which could be adopted to assess the remediation efficacy of heavy metal-contaminated soil solidified/stabilized by cement/fly ash.

Two dimensional non-destructive testing data maps for reinforced concrete slabs with simulated damage

This research presents the use of a total of five Non-Destructive Testing Techniques (NDTs) and their combination to detect and quantify subsurface simulated defects in Reinforced Concrete slabs. The NDT techniques were applied on a total of nine 1800 mm × 460 mm reinforced concrete slabs with varying thicknesses of 100 mm, 150 mm and 200 mm. Contour data maps from each technique were prepared. This Data article presents the Non-Destructive Testing Techniques’ specifications, experimental set-up and converted 2-Dimensional NDT data maps for reinforced concrete slabs with simulated damage. The experimental research shows that combining multiple techniques together in evaluating the defects give significantly lower error and higher accuracy compared to that from a standalone test. For more details on the accuracy model of the NDTs, refer to the full length article entitled “Sub-surface simulated damage detection using Non-Destructive Testing Techniques in reinforced-concrete slabs” https://doi.org/10.1016/j.conbuildmat.2019.04.223 Rathod et al., 2019.

Time-varying law of rebar corrosion rate in fly ash concrete

Whereas steel bar corrosion is the main cause for durability deterioration of existing reinforced concrete structures, it is important to understand the steel bar corrosion in concrete and predict the corrosion process in a sufficient way. In this paper, the corrosion process of rebar in ordinary concrete and three types of fly ash concrete specimens casted with 15%, 30% and 45% fly ash replacement ratios by mass under constant climate conditions were investigated. Meanwhile, the advanced digital video microscope measure system was used to study the microstructure of the steel/concrete interface at the different stages of corrosion. The effects of fly ash replacement were analyzed in terms of the electrical resistivity of concrete and the corrosion rate in the corrosion process of steel bars in fly ash concrete. The results showed that the resistivity of concrete increased with an increase in fly ash replacement, and the corrosion rate declined with the fly ash replacement increases. In addition, in fly ash concrete, the corrosion rate of plain bars were obviously smaller than that of ribbed bars.

Tissue-susceptibility matched carbon nanotube electrodes for magnetic resonance imaging

Test disk electrodes were fabricated from carbon nanotubes (CNT) using the Carbon Nanotube Templated Microfabrication (CNT-M) technique. The CNT-M process uses patterned growth of carbon nanotube forests from surfaces to form complex patterns, enabling electrode sizing and shaping. The additional carbon infiltration process stabilizes these structures for further processing and handling. At a macroscopic scale, the electrochemical, electrical and magnetic properties, and magnetic resonance imaging (MRI) characteristics of the disk electrodes were investigated; their microstructure was also assessed. CNT disk electrodes showed electrical resistivity around 1 Ω·cm, charge storage capacity between 3.4 and 38.4 mC/cm², low electrochemical impedance and magnetic susceptibility of -5.9 to -8.1 ppm, closely matched to that of tissue (∼-9 ppm). Phantom MR imaging experiments showed almost no distortion caused by these electrodes compared with Cu and Pt-Ir reference electrodes, indicating the potential for significant improvement in accurate tip visualization.

Low-Temperature Reduction of Graphene Oxide: Electrical Conductance and Scanning Kelvin Probe Force Microscopy

Graphene oxide (GO) films were formed by drop-casting method and were studied by FTIR spectroscopy, micro-Raman spectroscopy (mRS), X-ray photoelectron spectroscopy (XPS), four-points probe method, atomic force microscopy (AFM), and scanning Kelvin probe force (SKPFM) microscopy after low-temperature annealing at ambient conditions. It was shown that in temperature range from 50 to 250 °C the electrical resistivity of the GO films decreases by seven orders of magnitude and is governed by two processes with activation energies of 6.22 and 1.65 eV, respectively. It was shown that the first process is mainly associated with water and OH groups desorption reducing the thickness of the film by 35% and causing the resistivity decrease by five orders of magnitude. The corresponding activation energy is the effective value determined by desorption and electrical connection of GO flakes from different layers. The second process is mainly associated with desorption of oxygen epoxy and alkoxy groups connected with carbon located in the basal plane of GO. AFM and SKPFM methods showed that during the second process, first, the surface of GO plane is destroyed forming nanostructured surface with low work function and then at higher temperature a flat carbon plane is formed that results in an increase of the work function of reduced GO.

UV-Cured Inkjet-Printed Silver Gate Electrode with Low Electrical Resistivity

Inkjet-printed silver gate electrode with low electrical resistivity was fabricated by UV curing method. By adjusting the UV curing time and the distance between the samples and UV lamp, the effects of UV curing conditions on the electrical resistivity of the silver films were studied, and the lowest electrical resistivity of 6.69 × 10^-8 Ω·m was obtained. Besides, the UV-cured silver films have good adhesion to the glass substrates, with adhesion strength of 4B (ASTM international standard). Our work offered an easy and low temperature approach to fabricate inkjet-printed silver electrodes with low electrical resistivity.

Spread of Water-Borne Pollutants at Traffic Accidents on Roads

Traffic accidents sometimes lead to the spread of hazardous compounds to the environment. Accidental spills of hazardous compounds on roads in the vicinity of vulnerable objects such as water supplies pose a serious threat to water quality and have to be assessed. This study compared three different assessment methods, electrical resistivity measurements, analytical flow calculations, and 1D and 2D dynamic flow modeling, to describe rapid transport processes in the road shoulder and roadside verge after a major spill. The infiltration and flow paths of water-borne substances were described during simulated discharge of pollutants on different road types. Full-scale tracer tests using sodium chloride were carried out at nine different road locations in Sweden. Analysis of grain size distribution and infiltrometer tests were carried out at the road shoulder and verges. The pathways and travel times were traced using resistivity measurements and 3D inverse modeling. The resistivity measurements were compared to analytical flow calculations and 1D and 2D dynamic modeling. All measurement sites were highly heterogeneous, which caused preferential flow. Vertical flow velocities of 1.4-8.6 × 10^-4 m/s were measured. The results of the analytical calculations and flow modeling were of the same order of magnitude. The measurements showed that almost all infiltration goes directly into the road embankment, hence the composition and structure of the built-up road must be considered. The non-destructive resistivity measurements and 3D modeling provided useful information for clarifying the infiltration and flow pattern of water-borne compounds from road runoff.

Estimation of heavy metal-contaminated soils' mechanical characteristics using electrical resistivity

Under the process of urbanization in China, more and more attention has been paid to the reuse of heavy metal-contaminated sites. The shear characteristics of heavy metal-contaminated soils are investigated by electrical detection in this paper. Three metal ions (Zn²⁺, Cd²⁺, and Pb²⁺) were used, the metal concentrations of which are 50, 166.67, 500, 1666.67, and 5000 mg/kg, respectively. Direct shear tests were used to investigate the influence of heavy metal ions on the shear characters of soil samples. It is found that with the addition of heavy metal ions, the shear strength, cohesion, and friction angle of contaminated soils are higher than the control samples. The higher concentration of heavy metal ions penetrated in soils, the higher these engineering characteristics of contaminated soils observed. In addition, an electrical resistivity detection machine is used to evaluate the shear characteristics of contaminated soils. The electrical resistivity test results show that there is a decreasing tendency of resistivity with the increase of heavy metal ion concentrations in soils. Compared with the electrical resistivity and the shear characteristics of metal-contaminated soils, it is found that, under fixed compactness and saturation, shear strength of metal-contaminated soils decreased with the increase of resistivity. A basic linear relationship between C/log(N + 10) and resistivity can be observed, and there is a basic linear relationship between φ/log(N + 10) and resistivity. Besides, a comparison of the measured and predicted shear characteristics shows a high accuracy, indicating that the resistivity can be used to evaluate the shear characteristics of heavy metal contaminated soils.

Preparing of Highly Conductive Patterns on Flexible Substrates by Screen Printing of Silver Nanoparticles with Different Size Distribution

A facile one-step polyol method is employed to synthesize the Ag nanoparticles (NPs) in large scale. The Ag NPs with different average diameter (from 52 to 120 nm) and particle size distribution are prepared by changing the mass ratio of AgNO3 and PVP. Furthermore, the as-obtained Ag NPs are prepared as conductive inks, which could be screen printed on various flexible substrates and formed as conductive patterns after sintering treatment. During the reaction process, PVP is used as the capping reagent for preventing the agglomeration of Ag NPs, and the influence of the mass ratio of AgNO3 and PVP to the size distribution of Ag NPs is investigated. The results of electronic properties reveal that the conductivity of printed patterns is highly dependent on the size distribution of as-obtained Ag NPs. Among all the samples, the optimal conductivity is obtained when the mass ratio of AgNO3 and PVP is 1:0.4. Subsequently, the sintering time and temperature are further investigated for obtaining the best conductivity; the optimal electrical resistivity value of 3.83 μΩ · cm is achieved at 160 °C for 75 min, which is close to the resistivity value of the bulk silver (1.58 μΩ · cm). Significantly, there are many potential advantages in printed electronics applications because of the as-synthesized Ag NPs with a low sintering temperature and low electrical resistivity.

Estimation of hydraulic parameters in a complex porous aquifer system using geoelectrical methods

Geoelectrical methods have been widely used for the estimation of aquifer hydraulic properties. In this study, geoelectrical methods were applied in a lithologically and hydrochemically complex porous aquifer to estimate its porosity, hydraulic conductivity and transmissivity. For this purpose, the electrical resistivity of the aquifer as well as the electrical conductivity of the groundwater was measured in 37 sites and wells. Initially, the Archie's law was used to generate sets of cementation factor (m) and alpha (α) parameter from which the mode values of α=0.98 and m=1.75 are representative of the studied aquifer. The transmissivity of the aquifer varies from 5.1×10(-3) to 3.1×10(-5)m(2)/s, whereas the mean value of its porosity is 0.45. The hydraulic conductivity of the aquifer which was calculated according to Archie's law varies from 2.08×10(-6) to 6.84×10(-5)m/s and is strongly correlated with the pumping test's hydraulic conductivity. In contrast, the hydraulic conductivity which was calculated using Dar-Zarrouk parameters presents lower correlation with the pumping test's hydraulic conductivity. Furthermore, a relation between aquifer resistivity and hydraulic conductivity was established for the studied aquifer to enable the estimation of these parameters in sites lacking data.

Target Plate Material Influence on Fullerene-C60 Laser Desorption/Ionization Efficiency

Systematic laser desorption/ionization (LDI) experiments of fullerene-C60 on a wide range of target plate materials were conducted to gain insight into the initial ion formation in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. The positive and negative ion signal intensities of precursor, fragment, and cluster ions were monitored, varying both the laser fluence (0-3.53 Jcm(-2)) and the ion extraction delay time (0-950 ns). The resulting species-specific ion signal intensities are an indication for the ionization mechanisms that contribute to LDI and the time frames in which they operate, providing insight in the (MA)LDI primary ionization. An increasing electrical resistivity of the target plate material increases the fullerene-C60 precursor and fragment anion signal intensity. Inconel 625 and Ti90/Al6/V4, both highly electrically resistive, provide the highest anion signal intensities, exceeding the cation signal intensity by a factor ~1.4 for the latter. We present a mechanism based on transient electrical field strength reduction to explain this trend. Fullerene-C60 cluster anion formation is negligible, which could be due to the high extraction potential. Cluster cations, however, are readily formed, although for high laser fluences, the preferred channel is formation of precursor and fragment cations. Ion signal intensity depends greatly on the choice of substrate material, and careful substrate selection could, therefore, allow for more sensitive (MA)LDI measurements. Graphical Abstract ᅟ.

Saturation of electrical resistivity of solid iron at Earth's core conditions

We report on the temperature dependence of the electrical resistivity of solid iron at high pressure, up to and including conditions likely to be found at the centre of the Earth. We have extended some of the calculations of the resistivities of pure solid iron we recently performed at Earth's core conditions (Pozzo et al. in Earth Planet Sci Lett 393:159-164, 2014) to lower temperature. We show that at low temperature the resistivity increases linearly with temperature, and saturates at high temperature. This saturation effect is well known as the Mott-Ioffe-Regel limit in metals, but has been largely ignored to estimate the resistivity of iron at Earth's core conditions. Recent experiments (Gomi et al. in Phys Earth Planet Int 224:88-103, 2013) coupled new high pressure data and saturation to predict the resitivity of iron and iron alloys at Earth's core conditions, and reported values up to three times lower than previous estimates, confirming recent first principles calculations (de Koker et al. in Proc Natl Acad Sci 109:4070-4073, 2012; Pozzo et al. in Nature 485:355-358, 2012, Phys Rev B 87:014110-10, 2013, Earth Planet Sci Lett 393:159-164, 2014; Davies et al. in Nat Geosci 8:678-685, 2015). The present results support the saturation effect idea.

Application of factor analysis and electrical resistivity to understand groundwater contributions to coastal embayments in semi-arid and hypersaline coastal settings

Groundwater contributions and sources of salinity to Oso Bay in south Texas were investigated using multivariate statistical analysis of geochemical data and multitemporal electrical resistivity tomography surveys. Both analysis of geochemical data and subsurface imaging techniques identified two commonalities for the investigated system: 1) hypersaline water occurs near the groundwater/surface water interface during wet conditions creating reverse hydraulic gradients due to density effects. The development and downward movement of these fluids as continuous plumes deflect fresher groundwater discharge downward and laterally away from the surface; and 2) more pronounced upwelling of fresher groundwater occurs during drought periods when density inversions are more defined and are expected to overcome dispersion and diffusion processes and create sufficiently large-enough unstable gradients that induce density-difference convection. Salinity mass-balance models derived from time-difference resistivity tomograph and in-situ salinity data reaffirm these findings indicating that groundwater upwelling is more prominent during dry to wet conditions in 2013 (~545.5m(3)/d) and is less pronounced during wet to dry conditions in 2012 (~262.7 m(3)/d) for the 224 m(2) area surveyed. Findings show that the highly saline nature of water in this area and changes in salinity regimes can be attributed to a combination of factors, namely: surface outflows, evapoconcentration, recirculation of hypersaline groundwaters, and potential trapped oil field brines. Increased drought conditions will likely exacerbate the rate at which salinity levels are increasing in bays and estuaries in semi-arid regions where both hypersaline groundwater discharge and high evaporation rates occur simultaneously.

Improved electro-mechanical performance of gold films on polyimide without adhesion layers

Thin metal films on polymer substrates are of interest for flexible electronic applications and often utilize a thin interlayer to improve adhesion of metal films on flexible substrates. This work investigates the effect of a 10 nm Cr interlayer on the electro-mechanical properties of 50 nm Au films on polyimide substrates. Ex situ and in situ fragmentation experiments reveal the Cr interlayer causes brittle electro-mechanical behaviour, and thin Au films without an interlayer can support strains up to 15% without significantly degrading electrical conductivity.

Electrical resistivity behaviors of liquid Pb-Sn binary alloy in the presence of ultrasonic field

Electrical resistivity behaviors of liquid Pb-Sn alloys have been investigated in the presence of ultrasonic field. The process demonstrated significantly that electrical resistivity could reveal the precise influence caused by ultrasound. Details revealed by applying the resistivity measuring approach to the liquid Pb-Sn alloy show that the short ordered structures in the liquid could be modified by ultrasonic irradiation, and the resistivity approach could have application value in the ultrasonic irradiation process on the specific liquid metals and alloys.

Corrosivity and leaching behavior of controlled low-strength material (CLSM) made using bottom ash and quarry dust

This paper reports the corrosivity and leaching behavior of CLSM made using two different industrial wastes i.e. bottom ash from an incineration facility and quarry dust. The leachate samples were derived from fresh and hardened CLSM mixtures, and studied for leaching and electrical resistivity. The release of various contaminants and the consequent environmental impact caused by the contaminants were studied by the measurement of contaminants in the bleed, in the leachate at 28 days, and on the leachate derived from crushed block and whole block leaching done over a period of 126 days. Results indicated that the CLSM mixtures are non corrosive; diffusion was the leaching mechanism; and the contaminants were found to be moderate to low mobility.

Comparison of Superelasticity of Nickel Titanium Orthodontic Arch wires using Mechanical Tensile Testing and Correlating with Electrical Resistivity

BACKGROUND

Application of light and continuous forces for optimum physiological response and least damage to the tooth supporting structures should be the primary aim of the orthodontist. Nickel titanium alloys with the properties of excellent spring back, super elasticity and wide range of action is one of the natural choices for the clinicians to achieve this goal. In recent periods, various wire manufacturers have come with a variety of wires exhibiting different properties. It is the duty of the clinician to select appropriate wires during various stages of treatment for excellent results. For achieving this evaluation of the properties of these wires is essential.

MATERIALS & METHODS

This study is focussed on evaluating the super elastic property of eight groups of austenite active nickel titanium wires. Eight groups of archwires bought from eight different manufacturers were studied. These wires were tested through mechanical tensile testing and electrical resistivity methods.

RESULTS

Unloading curves were carefully assessed for superelastic behaviour on deactivation. Rankings of the wires tested were based primarily upon the unloading curve's slope Conclusion: Ortho organisers wires ranked first and superior, followed by American Orthodontics and Ormco A wires. Morelli and GAClowland NiTi wires were ranked last. It can be concluded that the performance of these wires based on rankings should be further evaluated by clinical studies. How to cite this article: Sivaraj A. Comparison of Superelasticity of Nickel Titanium Orthodontic Arch wires using Mechanical Tensile Testing and Correlating with Electrical Resistivity. J Int Oral Health 2013; 5(3):1-12.

The influence of temperature on the electrical resistivity of the cellular polypropylene and the effect of activation energy

In this paper, we determine the surface and volume electrical resistivity of the 50 μm thick cellular polypropylen (VHD50), for the temperature range 393–453 K. For this we use a contemporary methodology, which consist of a voltage measurement across the sample, with a known current flowing through it. This methodology includes a three-electrode system, which allows us to estimate the resistivity of the samples, based on their corresponding total resistances. The electric fields applied for a time interval of 1 min are of the order of 200 kVm⁻¹. The order of magnitude of surface and volume electrical resistivity is 10¹³ Ω and 10¹¹ Ωm, respectively. For both types of the resistivity, the temperature dependence is an increasing or decreasing exponential function, depending on the type of the activation energy, (its average value for the temperature range mentioned above is 41,20 kJmol⁻¹), totally confirmed by the corresponding theoretical interpretation, conditioned by the ionic conduction.

The methodology and equipment used, as well as the satisfying accordance with the results, found out directly or indirectly with the consulted literature, confirm the high accuracy of experimental measurements.

Temperature driven evolution of thermal, electrical, and optical properties of Ti-Al-N coatings

Monolithic single phase cubic (c) Ti_1-x Al _x N thin films are used in various industrial applications due to their high thermal stability, which beneficially effects lifetime and performance of cutting and milling tools, but also find increasing utilization in electronic and optical devices. The present study elucidates the temperature-driven evolution of heat conductivity, electrical resistivity and optical reflectance from room temperature up to 1400 °C and links them to structural and chemical changes in Ti_1-x Al _x N coatings. It is shown that various decomposition phenomena, involving recovery and spinodal decomposition (known to account for the age hardening phenomenon in c-Ti_1-x Al _x N), as well as the cubic to wurtzite phase transformation of spinodally formed AlN-enriched domains, effectively increase the thermal conductivity of the coatings from ∼3.8 W m^-1 K^-1 by a factor of three, while the electrical resistivity is reduced by one order of magnitude. A change in the coating color from metallic grey after deposition to reddish-golden after annealing to 1400 °C is related to the film structure and discussed in terms of film reflectivity.

Thermodynamic Study of the α → β Phase Transformation in Titanium by a Pulse Heating Method

Measurements of the temperature and energy of the α → β transformation, and the electrical resistivity near and at the transformation point of titanium by means of a subsecond duration pulse heating technique are described. The results yield 1166 K for the transformation temperature and 4170 J · mol-1 for the transformation energy. Electrical resistivity is found to decrease by about 9 percent during the α → β transformation. Estimated inaccuracies of the measured properties are: 7 K for the transformation temperature, 5 percent for the transformation energy, and 2 percent for the electrical resistivity.

Melting Point, Normal Spectral Emittance (at the Melting Point), and Electrical Resistivity (above 1900 K) of Titanium by a Pulse Heating Method

A subsecond duration pulse heating method was used to measure the melting point, the normal spectral emittance (at the melting point), and the electrical resistivity (above 1900 K) of 99.9 + percent pure titanium. The results, based on the International Practical Temperature Scale of 1968, yield a value of 1945 K for the melting point. The normal spectral emittance (at 653 nm) at the melting point is 0.40. Estimated inaccuracies are: 5 K in the melting point, 5 percent in the normal spectral emittance, and 3 percent in the electrical resistivity.

%) Zirconium, 1500 to 2400 K

Simultaneous measurements of specific heat, electrical resistivity and hemispherical total emittance of hafnium containing 3.12 weight percent zirconium in the temperature range 1500 to 2400 K by a subsecond duration, pulse heating technique are described. The measurements indicate decreases in specific heat (by about 13%) and in electrical resistivity (by about 8%) as the result of the α → β transformation. Estimated inaccuracies of the measured properties are: 3 percent for specific heat, 1 percent for electrical resistivity and 5 percent for hemispherical total emittance.

Thermodynamic Studies of the α → β Phase Transformation in Zirconium Using a Subsecond Pulse Heating Technique

Measurements of the temperature and energy of the α → β phase transformation, and the electrical resistivity near and at the transformation point of zirconium using a subsecond duration pulse heating technique are described. The results yield 1147 K for the transformation temperature and 3980 J · mol-1 for the transformation energy. Electrical resistivity is found to decrease by 17 percent during the transformation. Estimated inaccuracies of the measured properties are: 10 K for the transformation temperature, 5 percent for the transformation energy, and 2 percent for the electrical resistivity.

Simultaneous Measurements of Heat Capacity, Electrical Resistivity and Hemispherical Total Emittance by a Pulse Heating Technique: Zirconium, 1500 to 2100 K

Simultaneous measurements of heat capacity, electrical resistivity and hemispherical total emittance of zirconium in the temperature range 1500 to 2100 K by a subsecond duration, pulse heating technique are described. The results are expressed by the relations:C p = 36.65 - 1.435 × 10 - 2 T + 6.624 × 10 - 6 T 2 ρ = 87.95 + 1.946 × 10 - 2 T ϵ = 0.2031 + 6.362 × 10 - 5 T where C p is in J · mol-1 · K-1, ρ is in 10-8 Ω · m, and T is in K. Estimated inaccuracies of the measured properties are: 3 percent for heat capacity, 2 percent for electrical resistivity and 5 percent for hemispherical total emittance.

Simultaneous Measurements of Heat Capacity, Electrical Resistivity, and Hemispherical Total Emittance by a Pulse Heating Technique: Vanadium, 1500 to 2100 K

Simultaneous measurements of heat capacity, electrical resistivity, and hemispherical total emittance of vanadium in the temperature range 1500 to 2100 K by a subsecond duration, pulse heating technique are described. The results are expressed by the relations: c p = 56.34 - 3.839 × 10-2 T + 1.563 × 10-5 T 2 ρ = 8.794 + 6.282 × 10-2 T - 6.804 × 10-6 T 2 where c p is in J · mol-1 · K-1, ρ is in 10-8 Ω · m, and T is in K. The values for the hemispherical total emittance are: 0.313 at 1900 K and 0.332 at 2000 K. Estimated inaccuracies of the measured properties are: 3 percent for heat capacity, 0.5 percent for electrical resistivity and 5 percent for hemispherical total emittance.

Thermophysical Measurements on Iron Above 1500 K Using a Transient (Subsecond) Technique

Simultaneous measurements of heat capacity, electrical resistivity and hemispherical total emittance of iron (99.9% pure) in the temperature range 1500 to 1800 K, and the melting point of iron by a subsecond duration, transient technique are described. The measurements indicate increases in heat capacity and electrical resistivity as the result of the solid-solid phase transformation (γ → δ) in iron. The measured value of the hemispherical total emittance at 1720 K is 0.33. The average of the results of two experiments yield a value of 1808 K for the melting point of iron. Estimated inaccuracies of measured properties are: 3 percent for heat capacity and emittance, 1 percent for electrical resistivity, and 5 K for the melting point.

%) Zirconium Alloy in the Range 1500 to 2700 K by a Transient (Subsecond) Technique

Simultaneous measurements of specific heat, electrical resistivity, and hemispherical total emittance of niobium-1 (wt. %) zirconium alloy in the temperature range 1500 to 2700 K by a subsecond duration pulse heating technique are described. Estimated inaccuracy of measured properties are: 3 percent for specific heat and hemispherical total emittance, and 0.5 percent for electrical resistivity. Properties of the alloy are compared with the properties of pure niobium. It was found that specific heat and emittance of the alloy were approximately 0.5 percent and 1.5 percent, respectively, higher than those of pure niobium. Electrical resistivity of the alloy was 0.5 percent lower than that of pure niobium. Like niobium, the alloy showed a negative departure from linearity in the curve of electrical resistivity versus temperature.

High-Speed (Subsecond) Measurement of Heat Capacity, Electrical Resistivity, and Thermal Radiation Properties of Niobium in the Range 1500 to 2700 K

Measurements of heat capacity, electrical resistivity, hemispherical total emittance, and normal spectral emittance of niobium in the temperature range 1500 to 2700 K by a subsecond duration pulse heating technique are described. Results obtained on the above properties are reported and are compared with those in the literature. A sharp increase in heat capacity above 2000 K was observed. Electrical resistivity showed a negative departure from linearity in the curve of electrical resistivity against temperature. Estimated inaccuracy of measured properties is: 2 percent for heat capacity, 0.5 percent for electrical resistivity, and 3 percent for hemispherical total and normal spectral emittances.

High-Speed (Subsecond) Measurement of Heat Capacity, Electrical Resistivity, and Thermal Radiation Properties of Tungsten in the Range 2000 to 3600 K

Measurements of heat capacity, electrical resistivity, hemispherical total emittance, and normal spectral emittance of tungsten above 2000 K by a pulse heating technique are described. Duration of an individual experiment, in which the specimen is heated from room temperature to near its melting point, is less than one second. Temperature measurements are made with a photoelectric pyrometer. Experimental quantities are recorded with a digital data acquisition system, which has a full-scale signal resolution of one part in 8000. Time resolution of the entire system is 0.4 ms. Results on the above properties of tungsten in the range 2000 to 3600 K are reported and are compared with those in the literature. Estimated inaccuracy of measured properties in the above temperature range is: 2 to 3 percent for heat capacity, 1 percent for electrical resistivity, 3 percent for hemispherical total and normal spectral emittances.