High Electrical Resistivity Research Articles

Preparing high performance FeAl/Al2O3 coating as tritium permeation barrier

Preparation of tritium permeation barrier (TPB) coating on the surface of structural materials is one of the most effective solutions to solve the issue of tritium permeation in tritium breeder blanket. The FeAl/Al2O3 coating is considered as the most promising candidate material for TPB coating due to its low hydrogen isotopes permeability, good adhesion and excellent radiation resistance. However, the current reported performance of FeAl/Al2O3 coating is much lower than its theoretical value. This work proposed a three-step process to prepare FeAl/Al2O3 TPB coating. By magnetron sputtering deposition, aluminizing and in-situ oxidation, a layer of high quality γ-Al2O3 about 250 nm thick was successfully formed on the 304 stainless steels. The Al2O3 layer was dense and no obvious defects were found. The gas-driven permeation measurements showed that the coating sample had strong ability to inhibit deuterium permeation, where the deuterium permeation flux was reduced by 5 orders of magnitude compared to the uncoated one at 600 °C, which is the best reported performance. Meanwhile, the thermal shock resistance test showed that the coating had no cracks after 50 thermal cycles. Moreover, the coating had a high electrical resistivity of approximately 3.42 × 1014 Ω cm, which could effectively reduce the magneto-hydrodynamic pressure drop (MHD) effects.

Advancing anti-corrosion performance of composite coating: Self-aligned fluorinated graphene for multifunctional electronic packaging

Fluorinated graphene (FG) is considered an ideal filler for polymer nanocomposites to enhance anti-corrosion performance due to its hydrophobicity and electrical insulation properties. A key objective in advanced anti-corrosion design is to create a structure where FG sheets are stacked and aligned, forming an ultra-long, circuitous path to impede the diffusion of active corrosion species. Additionally, integrating aligned FG sheets with polymers prevents the formation of electrical percolation paths, making the coating suitable for electronic passivation. However, achieving a high degree of alignment of FG within the polymer matrix has been a challenge. In this study, we employ a straightforward electrophoretic deposition method to align FG sheets in a polyurethane (PU) matrix for anti-corrosion coatings on copper. The optimized coating exhibits outstanding corrosion resistance for copper, with a stable corrosion rate of 4.0 × 10−3 μm/year in a 3.5 wt% NaCl solution. Moreover, the FG composite coating significantly enhances thermal conductivity, increasing it by 97 % compared to pristine PU, while also providing high electrical resistance. This results in a high breakdown electric field of 28 kV/cm and an extremely low current density of 1.32 × 10−8 A/cm2, which is advantageous for electronic packaging. This multifunctional coating meets industrial standards for large-scale production, uniformity, and controllable thickness, offering a promising approach to improving anti-corrosion protective coatings.

The Effect of the TiO2 Anodization Layer in Pedicle Screw Conductivity: An Analytical, Numerical, and Experimental Approach.

The electrical stimulation of pedicle screws is a technique used to ensure its correct placement within the vertebrae pedicle. Several authors have studied these screws' electrical properties with the objective of understanding if they are a potential source of false negatives. As titanium screws are anodized with different thicknesses of a high electrical resistance oxide (TiO2), this study investigated, using analytical, numerical, and experimental methods, how its thickness may affect pedicle screw's resistance and conductivity. Analytical results have demonstrated that the thickness of the TiO2 layer does result in a significant radial resistance increase (44.21 mΩ/nm, for Ø 4.5 mm), and a decrease of conductivity with layers thicker than 150 nm. The numerical approach denotes that the geometry of the screw further results in a decrease in the pedicle screw conductivity, especially after 125 nm. Additionally, the experimental results demonstrate that there is indeed an effective decrease in conductivity with an increase in the TiO2 layer thickness, which is also reflected in the screw's total resistance. While the magnitude of the resistance associated with each TiO2 layer thickness may not be enough to compromise the ability to use anodized pedicle screws with a high-voltage electrical stimulator, pedicle screws should be the subject of more frequent electrical characterisation studies.

Biocompatible and Biodegradable 3D Graphene/Collagen Fiber Hybrids for High-Performance Conductive Networks and Sensors.

Polymer-based flexible conductive materials are crucial for wearable electronics, electronic skin, and other smart materials. However, their development and commercial applications have been hampered by the lack of strain tolerance in the conductive network, poor bonding with polymers, discomfort during wear, and a lack of biocompatibility. This study utilized oil-tanned leather with a natural network structure, high toughness, and high tensile deformation recovery as a structural template. A graphene (Gr) conductive network was then constructed on the collagen network of the leather, with coordination cross-linking between Gr and collagen fibers through aluminum ions (Al3+). A new flexible conductive material (Al-GL) was then constructed. Molecular dynamics simulations and experimental validation revealed the existence of physical adsorption, hydrogen bonding adsorption, and ligand bonding between Al3+, Gr, and collagen fibers. Although we established that the binding sites between Al3+ and collagen fibers were primarily on carboxyl groups (-COOH), the mechanism of chemical bonding between Gr and collagen fibers remains unclear. The Al-GL composite exhibited a high shrinkage temperature (67.4 °C) and low electrical resistance (16.1 kΩ·sq-1), as well as good softness (9.33 mN), biocompatibility, biodegradability (<60 h), and air and moisture permeability. Furthermore, the incorporation of Al3+ resulted in a heightened Gr binding strength on Al-GL, and the resistance remained comparable following 1 h of water washing. The Al-GL sensor prepared by WPU encapsulation not only demonstrated highly sensitive responses to diverse motion signals of the human body but also retained a certain degree of response to external mechanical effects underwater. Additionally, the Al-GL-based triboelectric nanogenerator (Al-GL TENG) exhibited distinct response signals to different materials. The Al-GL prepared by the one-pot method proposed in this study offers a novel approach to combining functional nanofillers and substrate materials, providing a theoretical foundation for collagen fiber-based flexible conductive materials.

Effect of Inorganic Fillers on Electrical and Mechanical Properties of Ceramizable Silicone Rubber.

Ceramizable silicone rubber (CSR) composed of silicone rubber matrix and inorganic fillers can be transformed into a dense flame-retardant ceramic upon encountering high temperatures or flames. Conventionally, CSR can be sintered into a dense ceramic at temperatures above 1000 °C, which is higher than the melting point of a copper conductor used in a power cable. In this study, the vulcanization process and mass ratio of inorganic fillers of CSR were studied to lower its ceramization temperature to 950 °C. The electrical and mechanical properties of CSRs and their ceramic bulks were studied with various ratios of wollastonite and muscovite. It was found that the CSR samples could be successfully fabricated using a two-step vulcanization technique (at 120 °C and 150 °C, respectively). As a high ratio of muscovite filler was introduced into the CSR, the sample presented a high dc electrical resistivity of 6.713 × 1014 Ω·cm, and a low dielectric constant of 4.3 and dielectric loss of 0.025 at 50 Hz. After the thermal sintering (at 950 °C for 1 h) of the CSR sample with a high ratio of muscovite, the ceramic sample exhibits a dense microstructure without any pores. The ceramic also demonstrates excellent insulating properties, with a volume resistivity of 8.69 × 1011 Ω·cm, and a low dielectric loss of 0.01 at 50 Hz. Meanwhile, the three-point bending strength of the ceramic sample reaches a value of 110.03 MPa. This study provides a potential route to fabricate CSR used for fire-resistant cables.

High‑silicon electrical steel powders aimed for additive manufacturing

The Fe6.5Si soft magnetic alloy exhibits promising magnetic properties for energy applications, including near-zero magnetostriction, low magnetocrystalline anisotropy, and higher electrical resistivity than conventional electrical steels. However, its brittleness impedes industrial use. Recent advances in powder-based additive manufacturing show potential for processing high‑silicon electrical steels. This study focuses on the production cycle and properties of feedstock powder, which are crucial for such applications. Fe6.5Si alloy powders were produced via closed-coupled gas atomization. Comprehensive analysis covered mass balance, particle size distribution, powder flow, morphology, density, rheological properties, and thermal and magnetic behavior. Results suggest the feasibility of producing suitable Fe6.5Si alloy powder via gas atomization, enabling additive manufacturing of the next generation of medium/high-frequency electrical motors. The powder exhibited desirable characteristics within the size ranges applicable to laser powder bed fusion (20–75 μm) and direct energy deposition (75–106 μm), showing excellent flow behavior and morphological suitability for additive manufacturing.

Estimation of Maximum &lt;i&gt;zT&lt;/i&gt; in Cu&lt;sub&gt;3&lt;/sub&gt;SbSe&lt;sub&gt;4&lt;/sub&gt; for Different Starting Materials Content

Cu&lt;sub&gt;3&lt;/sub&gt;SbSe&lt;sub&gt;4&lt;/sub&gt; is considered a promising thermoelectric material because of its large effective mass and low thermal conductivity, originating from its unique lattice structure. However, Cu&lt;sub&gt;3&lt;/sub&gt;SbSe&lt;sub&gt;4&lt;/sub&gt; has intrinsically low carrier concentration and relatively high electric resistance which limit performance. Recently, a &lt;i&gt;zT&lt;/i&gt; improvement in Cu&lt;sub&gt;3&lt;/sub&gt;SbSe&lt;sub&gt;4&lt;/sub&gt; was reported where doping/precipitation is controlled by changing the content of the starting materials. However, the effect of these changes in starting content on electronic band structures has not been studied. Here, we investigate how the change in starting materials content (&lt;i&gt;x&lt;/i&gt; varying from 6 to 20) affects band parameters like density-of-states effective mass (&lt;i&gt;m&lt;sub&gt;d&lt;/sub&gt;&lt;/i&gt; *), non-degenerate mobility (&lt;i&gt;μ&lt;sub&gt;0&lt;/sub&gt;&lt;/i&gt;), weighted mobility (&lt;i&gt;μ&lt;sub&gt;W&lt;/sub&gt;&lt;/i&gt;), and B-factor using the Single Parabolic Band (SPB) model. For &lt;i&gt;x&lt;/i&gt; greater than 8, precipitation of the secondary phase (CuSe) was observed, and the band parameters changed differently for &lt;i&gt;x&lt;/i&gt; greater than 8. The &lt;i&gt;m&lt;sub&gt;d&lt;/sub&gt;&lt;/i&gt; * increases up to &lt;i&gt;x&lt;/i&gt; = 8 and then rapidly decreases for &lt;i&gt;x&lt;/i&gt; &gt; 8. For &lt;i&gt;μ&lt;sub&gt;0&lt;/sub&gt;&lt;/i&gt;, an overall decrease is observed for increasing &lt;i&gt;x&lt;/i&gt;, but the rate of decrease is suppressed for &lt;i&gt;x&lt;/i&gt; &gt; 8. The &lt;i&gt;μ&lt;sub&gt;W&lt;/sub&gt;&lt;/i&gt; reaches the maximum at &lt;i&gt;x&lt;/i&gt; = 8. As &lt;i&gt;x&lt;/i&gt; increases, the experimental lattice thermal conductivity also increases, especially for &lt;i&gt;x&lt;/i&gt; &gt; 8. Therefore, the B-factor, which is directly related to the theoretical maximum zT, becomes maximum at = 8. Hence the SPB model predicts a maximum &lt;i&gt;zT&lt;/i&gt; of 0.0484 for &lt;i&gt;x&lt;/i&gt; = 8 at 300 K, which is 15.5% higher than the experimental &lt;i&gt;zT&lt;/i&gt; of 0.0419, which can be achieved by tuning the Hall carrier concentration to 4.44 × 10&lt;sup&gt;19&lt;/sup&gt; cm&lt;sup&gt;-3&lt;/sup&gt;.

Effects of amorphous phase and yttrium on flash sintering and microstructures of ZrO2–SiO2 ceramic nanocomposites

AbstractFlash sintering has been used to consolidate a wide range of ceramics and ceramic composites. However, flash sintering of ceramic nanocomposite with a substantial amorphous phase is rarely studied. Meanwhile, the effects of yttrium addition on the flash sintering behaviors and microstructures of ZrO2‐based ceramic nanocomposite remain unknown. Herein, ZrO2‐SiO2 crystalline‐amorphous ceramic nanocomposites (CACNs) with different contents of amorphous phase and two types of yttrium dopants were sintered by flash sintering. Results showed that the content of amorphous phase (SiO2) had significant effects on the flash sintering behavior. The CACN with 65 mol% SiO2 was nonflash sinterable due to the high electric resistivity of SiO2, whereas, the CACN with 45 mol% SiO2 can be flash sintered to high densification within 35 seconds. The flash‐sintered CACNs consisted of ZrO2 nanocrystallites distributed in an amorphous SiO2 matrix. Flash sintering enhanced the tetragonal‐to‐monoclinic phase transformation of ZrO2. In addition, influences of yttrium dopant on CACNs were also investigated. Yttrium dopants can rapidly dissolve in ZrO2 lattices and show a tetragonal phase stabilization effect during flash sintering. Firework‐like ZrO2 microcrystallites formed by dendritic growth were observed close to the cathode region, which was attributed to athermal electric field effects and the formation and aggregation of oxygen vacancies at the cathode region. The results would provide guidance for fabricating CACNs via flash sintering.

91‐2: Transfer, Bonding, and Repair of LEDs for µLED Display Fabrication via Simultaneous Transfer and Bonding (SITRAB) Technology

Micro light‐emitting diodes (µLEDs) have been considered as next‐generation display technologies, but they suffer from low productivity due to poor heat dissipation, high electrical resistance, and repair difficulty of conventional µLED bonding methods. Simultaneous transfer and bonding (SITRAB) technology enables electrically/thermally conductive soldering for high‐resolution µLED displays. In this study, the transfer, bonding, and repair of InGaN/GaN µLEDs via the SITRAB method are reported. µLEDs grown on sapphire substrates are assembled on a backplane via the SITRAB process. The SITRAB‐based repair of defective pixels is demonstrated by transferring redundant LEDs to the display substrates.

Mechanical and magnetic properties of Fe33Co28Ni28Ta5Al6 high entropy alloy fabricated by selective laser melting

Abstract Selective laser melting (SLM) can obtain metal magnetic materials with specific shapes and good mechanical properties, which has potential application value in the field of engineering. In this study, the soft-magnetic high-entropy alloy (HEA) Fe33Co28Ni28Ta5Al6 was prepared via SLM. The microstructure, mechanical, and magnetic properties of the sample are investigated. The sample consists of a single face-centered-cubic (FCC) phase. The tensile yield strength, ultimate tensile strength, and elongation of the sample are 752 MPa, 1067 MPa, and 27% respectively. Furthermore, the sample has a low coercivity of 970 A m−1, moderate saturation magnetization of 1.17 T, and high electrical resistivity of 121 μΩ cm. This work would provide a pathway for the rapid manufacturing high-performance soft-magnetic HEA.

Atom probe tomography investigation of sintered transition metal carbonitride - A Zr(C,N) study

Zirconium based nitrides, carbides and carbonitrides are highly technological compounds which received during the 1950s and 60s huge interest due to their combination of metal and refractory properties. The interest reiterated recently due to the need of compounds with high electrical conductivity, corrosion and oxidation resistance, and neutron transparency with the rise of mobility electrification and nuclear energy. Sintered Zr(C,N) is investigated with CHN elemental analysis combined with atom probe tomography (APT) to evaluate the composition and homogeneity of carbon and nitrogen from the bulk down to the nanometer scale. Results have shown a strong nitrogen loss and an enrichment in carbon which diffused from the graphite die and punch. Nevertheless, the composition is homogenous in the sample. Atom probe tomography suggests that the sintered alloy is sub-stoichiometric with carbon and nitrogen homogeneously distributed within the grain. The stoichiometry calculated corresponds to the estimation by Vegard’s law.

Strength and durability performance of acid-mechanically treated recycled aggregate concrete with metakaolin, lime powder, and A-fine

This study examines the effectiveness of lime powder (LP) and metakaolin (MK) in concrete containing acid-mechanically treated recycled concrete aggregate (RCA). The acid-mechanically produced recycled fine, i.e., A-Fine (AF), is also evaluated as a supplementary cementitious material (SCM). According to the strength activity index (SAI) for AF, it has a low pozzolanic reactivity in comparison to MK and a higher pozzolanic reactivity in comparison to LP. An optimal dosage of AF (15 %), LP (17 %), and MK (22 %) improves the physical properties of recycled aggregate concrete (RAC). The compressive strength of RAC with AF (RAC-AF) is closer to that of RAC with LP (RAC-LP), and RAC with MK (RAC-MK). As a result of their partial or complete chemical inertness, AF, LP, or MK decrease the self-cementing capability of RCA and reduce the mechanical properties and fracture energy of RAC. While the split tensile and flexural strength of RAC-AF is greater than that of RAC-LP, it is smaller than that of RAC-MK. As a result of their higher elastic modulus, RAC-AF and RAC-MK are more ductile than RAC and RAC-LP. As a result of low ion penetration and high electrical resistance, RAC, RAC-AF, RAC-LP, and RAC-MK are classified as low permeability materials. AF or MK as a cement substitute does not alter the sorptivity of RAC despite improvement. In contrast, RAC has higher initial and final absorption when LP substitutes for cement. According to their pozzolanic reactivity and filler effect, RAC sorptivity varies with these SCMs. There is a strong correlation between the compressive strength and UPV of RAC, RAC-AF, RAC-LP, and RAC-MK with R2 = 0.94. The sorptivity and electrical resistivity are also correlated with R2 = 0.94. Due to the formation of Si-rich C-S-H gels, SEM and EDS show a more uniform and denser microstructure in RAC-AF, RAC-LP, and RAC-MK.

Large-area (50 cm × 50 cm) optically transparent electromagnetic interference (EMI) shielding of ZTO/Ag/ZTO: an analytical/numerical and experimental study of optoelectrical and EMI shielding properties

Transparent conducting oxides (TCOs), exhibiting both high optical transparency and low electrical resistivity, are commonly employed in optoelectronic devices. However, acquiring a balance between these optical and electrical properties in a uniform way over large areas has been a pending challenge, which is essential to achieving optically transparent electromagnetic interference (EMI) shielding surfaces. In this study, we propose and demonstrate a stratified thin film structure consisting of zinc-doped tin oxide (Zn2SnO4, ZTO) as TCO along with a metal layer of silver (Ag) deposited on a large area of 50 cm × 50 cm polycarbonate (PC) substrate enabled by a scanning magnetron sputtering gun. We achieved high EMI shielding of 99.9% at the optical transparency of 68% in the visible spectrum by engineering the stratified architecture of ZTO/Ag/ZTO. The Ag layer of 18 nm in thickness with a sheet resistance of 10 Ω/sq yields shielding effectiveness (SE) of 27 dB in a wide frequency range of 2–20 GHz. The bottom and top ZTO layers, 20 and 40 nm thick, respectively, provide the lowest optical loss of 13% across 400–700 nm. The structure’s EMI shielding, optical and structural performances were systematically characterized through a free-space focused-beam system, UV–Vis spectrophotometer, ellipsometry, focused ion-beam cross-sectional sampling and imaging, transmission electron microscopy, atomic force microscopy and secondary ion mass spectroscopy. EMI shielding and optical performances were validated by CST Microwave Studio and the transfer matrix method, respectively. These findings indicate that the proposed multi-layer architecture holds great promise for large-area EMI shielding and other optoelectronic applications.

Development of a Model to Support the Management of the Resistance Welding Process

The work was carried out as part of a project to improve the corrosion resistance of welded joints. The optimal selection of input parameters reduces the consumption of welded material as well as the negative impact on the environment. The samples were welded by electrical resistance welding, more precisely by cross-wire welding. Electric resistance welding is a process for welding with electricity in which of high electrical resistance is used to generate heat at the contact point of the welded parts. Steel wire S235 with a diameter of 4 and 3 mm was used. The article shows the creation of the model to predict the percentage of setdown and weld strength as a function of the input parameters, welding current and welding time. The first task was to create a Design of experiments in which the process parameters or the range of input parameters are determined. The Design of the experiments was created for both wire diameters. This covers the range of parameters with which a welded joint of wires can be realised. A statistical analysis of the process follows, where it was found that for 4 and 3 mm diameter wires the percentage setdown increases with increasing welding current and time. An increase in strength as a function of welding current and welding time is also observed, but the results overlap in most cases and the range of their values is greater than that of setdown. The appearance of the weld was analysed for each sample. The visual inspection revealed seven categories of welds, which were divided into two groups, i.e. good and poor welds. All results were listed in a table with the percentage of expectation for a particular category of weld appearance. Based on the analysis, a model for determining the welding result parameters depending on the specified input parameters was developed, which can be used in practise to support the management of the electric resistance welding process.

Preparation and Photocatalytic Hydrogen Evolution Performance Study of NENU‐5/CuBr/Graphdiyne Tandem S‐Scheme Heterojunction

Graphdiyne (GDY) has been widely applied in the field of photocatalytic hydrogen production due to its unique chemical structure and excellent photoelectric performance. Herein, CuBr is used as a catalytic substrate to prepare CuBr/GDY through a cross‐coupling reaction, and a novel NENU‐5/CuBr/GDY tandem S‐scheme heterojunction photocatalyst is constructed at low temperature. The NENU‐5/CuBr/GDY heterojunction exhibits significantly enhanced activity in photocatalytic hydrogen evolution, with hydrogen evolution reaching 226.62 μmol in 5 h, which is 4.7 and 12.6 times greater than that of pure GDY and NENU‐5, respectively. Comprehensive evaluation of electrochemical, photoluminescence, and time‐resolved photoluminescence indicates that the enhanced activity of the NENU‐5/CuBr/GDY composite catalyst is attributed to high photocurrent response and low electrical resistance, which increases the efficiency of photogenerated charge separation. Additionally, density functional theory calculations and ultraviolet photoelectron spectroscopy propose the possibility of constructing the NENU‐5/CuBr/GDY tandem S‐scheme heterojunction structure. In summary, this work provides valuable ideas into tandem heterojunctions for photocatalytic hydrogen production.

Electro-assisted sorption behavior and mechanism of low-concentration rare earth elements on carbon based materials

With increasing demands for rare earth elements (REEs) in high-tech and futuristic applications, developing efficient methods for recovering low-concentration REEs is necessary. Here, electro-assisted sorption of low-concentration REEs, La(III), Gd(III) and Y(III) (as symbol of light, medium, and heavy REEs) on carbon-based materials, activated carbon (AC), graphene, and graphite by a facile method was reported. Recovery of La(III), Gd(III) and Y(III) could reach ∼100 % under low-concentration condition where the maximum adsorption capacity was up to 342.38 mg/(g·dm2). Variants including applied voltage, electrodes-distance, pH, impurities, and concentration were considered to study the effects on REEs recovery. Interestingly, adsorption capacity and recovery under low voltage were respectively almost 20 and 14 folds than that without voltage, because voltage promoted REEs transfer and strengthened electrostatic interaction between electrodes and REEs. The mechanism for enhancing REEs recovery on carbon-based electrodes was resulted from high electric double layer (EDL) capacitance and low charge transfer resistance. Total desorption of REEs from electrodes could be quickly realized using NH4Cl or HCl solution. Overall, the study gave a new insight of low-concentration REEs recovery using carbon-based materials, and provided an efficient route using electric method with porous materials for REEs recovery.

Microstructure, mechanical and electrical properties of a novel low-cost high-strength Pt-xAu-5Ni alloy

The present study designed and prepared a novel platinum alloy system Pt-xAu-5Ni (x = 0, 2, 5, wt.%) with high strength and good electrical resistivity. The mechanical, electrical properties and related microstructure during the cold deformation and subsequent aging process were investigated. The cold-deformed Pt–5Ni alloy obtained the yield strength of 581 MPa, the ultimate tensile strength of 828 MPa, the hardness of 283 HV, and the electrical resistivity of 23.9 μΩ⋅cm. The subsequent aging process and the Au addition into Pt–5Ni alloy were found to both enhance the mechanical properties. Therefore, with the dual strengthening effect of the subsequent aging and the Au addition, Pt–5Au–5Ni alloy achieved the high yield strength of 889 MPa, the high ultimate tensile strength of 1117 MPa, the high hardness of 361 HV with the electrical resistivity of 26.7 μΩ⋅cm. The precipitation of L12-type Pt3Ni nanoparticles and L11-type CSRO dominated the age-strengthening behavior of Pt–2Au–5Ni and Pt–5Au–5Ni alloys after cold deformation. The Au addition refined the grains via the experimental observations, and predictably favored the L12-type Pt3Ni nanoprecipitation based on the thermodynamical calculations, thus the Au addition effectively strengthened Pt–5Ni alloy. This study provides a novel platinum alloy system with excellent mechanical and electrical properties, which has potential application in the electrical contact field.

Determination of the geophysical signature of soft-clay and hard lateritic soils and the implications on geotechnical works using electrical resistivity imaging

Understanding the geophysical signature of subsurface is quite essential in mapping site conditions for geotechnical engineering and simulating geophysical surveys, especially in coastal areas. This article presents a comparative geophysical study of topsoil (often refer as engineering layer) of soft clay deposit and hard lateritic soil to evaluate the implications on geotechnical work using electrical resistivity imaging (ERI). The results of the 2D ERI show that the hard lateritic soil produces three distinctive geological layers with the topsoil having high apparent electrical resistivity (AER) values varying between 300 Ωm–1000 Ωm and a thickness between 2.0 m – 10.0 m. The layer between the unsaturated and saturated regions has a moderate layer AER and thickness values ranging from 100 Ωm–300 Ωm and 2.5 m–9.5 m, respectively. In contrast, the saturated (weathered) layer has a low AER value (< 100Ω m), which represents the regional groundwater unit, located beneath the subsurface of a depth > 6.0 m. However, the soft clay soil shows no distinctive subsurface layers, as it is characterized by a nearly homogeneity subsurface of poor AER variability. The top-soft clay deposit has very AER values ranging from 11.0 Ωm–80 Ωm, which extends beyond 6.5 m. Higher and lower AER values noted within the overburdened topsoil of lateritic and clay extractions, respectively, were due to the accumulations of compacted clay and lateritic soil, which are very essential for geotechnical works. In addition, the geophysical signal was conspicuously attenuated in soft clay soil, which shows that soft clay soil is not a favourite target of geophysical investigation. However, the geophysical signals in hard lateritic generate a fine geo-electrical layer pattern. It was also noted that the existence of soft clay and lateritic soil decreases with depth. This kind of information is very essential in geotechnical works.

Novel UHPC with calcium-oxide-activated materials and fibres: engineering properties and sustainability evaluation

Novel ultra-high-performance concretes (UHPCs) made with calcium-oxide-activated materials (CAM), modified synthetic macro (MSM) fibres, glass fibres and steel fibres were developed. The mechanical and durability properties of UHPC-CAM specimens made with the different fibre types were tested and compared. The microstructure of the samples was examined using scanning electron microscopy (SEM). The environmental impacts of the mix designs were assessed using the Impact 2002+ method, a life cycle assessment tool. The results showed that the UHPC-CAM made with glass or MSM fibres had a high compressive strength (&gt;110 MPa) and improved ductility. These specimens also had low water absorption and high electrical resistance, indicating low corrosion risk. SEM analyses showed that the MSM fibres created a denser geopolymer matrix than the glass fibres. The UHPC-CAM was found to have a lower environmental impact than conventional UHPC in terms of human health, ecosystem quality, carbon dioxide footprint and use of resources. MSM fibres were determined to be the most eco-friendly fibres for UHPC-CAM production.

Ferroelectric Al1−xBxN–GaN heterostructures

This report demonstrates Al0.93B0.7N thin films grown epitaxially on n-type GaN (0002)/c-plane sapphire substrates by reactive magnetron sputtering at 300 °C. At 200 nm film thickness, the Al0.93B0.07N layers exhibit partially relaxed substrate-induced epitaxial strain, a 0.16° wide (0002) rocking curve, in-plane crystallographic registry, and sub-nanometer surface roughness. Electrically, the stack shows robust hysteresis over three frequency decades, a remanent polarization of ∼125 μC/cm2, a strongly frequency dependent coercive field, highly uniform dc leakage currents, and endurance &amp;gt;106 field cycles. This report validates possibilities for ferroelectric nitride integration into conventional III-nitride heterostructures with high crystalline fidelity, high electrical resistivity, and persistent hysteresis. Such materials are synthesizable at thermal budgets and temperatures compatible with back-end-of-the-line boundary conditions.