Resistance Values Research Articles

High Optical Abropsion from Thin Film MoS2 Nano-Flakes

Due to their distinctive electronic and optical characteristics, transition metal dichalcogenides (TMDs) have become significant materials in optoelectronics. Molybdenum disulfide (MoS2) flakes have received significant interest due to their potential applications. The unique bandgap properties exhibited by MoS2 flakes render them highly appealing for applications in optoelectronic devices [1]. A direct bandgap in this material enables effective interactions between light and matter, which is significant for various applications, including transistors, photodetectors, and light-emitting diodes [2].In this work, we synthesized our MoS2 flakes by exfoliating MoS2 powder following [3]’s recipe. We disperse 500 mg of MoS2 powder into 50 mL of N-Methyl-2-pyrrolidone (NMP)and then use a probe sonicator for the exfoliation process that runs continuously for 6 hours while keeping the sample cooled by a 0 °C ice bath. We later centrifuged at 1500 rpm for 60 min to remove any unexfoliated particles and then centrifuged again at 7500 rpm for 30 min to remove soluble impurities. After removing NMP, the acquired MoS2 flakes dispersed in 50 mL isopropyl alcohol. To study the optical properties of these MoS2 flakes, we prepared 3 x 3 cm2 fused silica substrate rinsed with acetone and DI water, respectively. Before deposition, we sonicate our MoS2 solution for 60 minutes in a bath sonicator. A precise pipet is used to drop-cast 20 uL of MoS2 on the fused silica substrate and wait 120 seconds to let it spread and settle. Afterward, we spin the sample at a low 150 rpm for 40 seconds, ensuring no spillovers. The sample was then carried to a UV-Vis Lambda 1050 spectrometer tool to measure the transmittance and reflectance of the sample over a range of wavelengths 250 to 1200 nm. Subsequently, we calculated absorbance values from this data. We repeat this on the same sample in steps of 20 uL of MoS2, acquiring spectrometer data for 20 to 200 uL of MoS2 on fused silica. The absorbance data showed a slope increase of absorption around 830 nm wavelength, reaching a peak around 660 nm, and It continues to absorb to 250 nm wavelength of the UV range.Moreover, as we increased the MoS2 amount, the overall absorbance increased. At the same time, reflectance increased; however, the change slowed after 60 uL of MoS2. We suspect that the former is due to the increase in the overall thickness of the deposited material, which increases the chance of photons traversing the material to be absorbed. The latter effect could be attributed to texturing, as these deposited MoS2 flakes do not seem to fall flat and create a uniform film and additional reflection from the MoS2 surface. To study that, we prepared five other 3x3 cm2 MoS2 on silicon (Si) samples with 20-100 uL in steps of 20 uL using the same process described earlier. Looking at the morphology using an optical microscope and SEM images of MoS2 on Si, the images show random settlement of MoS2 flakes, leading to uneven coating and witnessing MoS2 flakes arranged and aggregated into islands similar to results reported by others [4]. Also, we found similar dips in reflectivity as reported by literature due to absorption of A and B excitons[5]. Additionally, we measured the electrical conductivity using a hall measurement system of 100 uL MoS2 sample and found that it exhibited n-type behavior with an average sheet resistance value of 2.91x102 Ω/sq. We aim to investigate further the properties and potential applications of these MoS2 flakes.[1] K. F. Mak, C. Lee, J. Hone, J. Shan, and T. F. Heinz, “Atomically Thin MoS2: A New Direct-Gap Semiconductor,” Phys. Rev. Lett., vol. 105, no. 13, p. 136805, Sep. 2010, doi: 10.1103/PhysRevLett.105.136805.[2] H. J. Jin, C. Park, H. H. Byun, S. H. Park, and S.-Y. Choi, “Electrically Modulated Single/Multicolor High Responsivity 2D MoTe2/MoS2 Photodetector for Broadband Detection,” ACS Photonics, vol. 10, no. 9, pp. 3027–3034, Sep. 2023, doi: 10.1021/acsphotonics.3c00143.[3] X. Yu et al., “Hybrid Heterojunctions of Solution-Processed Semiconducting 2D Transition Metal Dichalcogenides,” ACS Energy Lett., vol. 2, no. 2, pp. 524–531, Feb. 2017, doi: 10.1021/acsenergylett.6b00707.[4] N. Zebardastan et al., “2D MoS2 Heterostructures on Epitaxial and Self-Standing Graphene for Energy Storage: From Growth Mechanism to Application,” Advanced Materials Technologies, vol. 7, no. 4, p. 2100963, 2022, doi: 10.1002/admt.202100963.[5] “Layer-number dependent reflection spectra of MoS2 flakes on SiO2/Si substrate.” Accessed: Nov. 23, 2023. [Online]. Available: https://opg-optica-org.libconnect.ku.ac.ae/ome/fulltext.cfm?uri=ome-8-10-3082&id=398132 Figure 1

Enantioselective Discrimination via Wireless Chemiresistive Devices.

Developing chemiresistive devices for the wireless detection of complex analytes has gained considerable interest. In particular, the enantioselective recognition of chiral molecules is still a challenge. Here, we design a hybrid chemiresistive device for the wireless enantioselective discrimination of chiral analytes by combining the enantiorecognition capabilities of an inherently chiral oligomer, that is, oligo-(3,3'-dibenzothiophene) (BT2T4) and the insulating/conducting transition of polypyrrole (Ppy). The device is obtained by modifying each extremity of an interdigitated electrode (IDE) with Ppy on the interdigitated area and oligo-BT2T4 on the connection pads. Due to the asymmetric electroactivity triggered by bipolar electrochemistry, the wireless enantioselective discrimination of both enantiomers of tryptophan and DOPA was achieved. A difference in the onset resistance values was obtained for both enantiomers due to a favorable or unfavorable diastereomeric interaction between the inherently chiral oligomer and the antipode of the chiral molecule. Interestingly, such a device showed a wide quantification range, from μM to mM levels. This work opens up new alternatives to designing advanced wireless devices in enantiorecognition.

Ohmic contacts to n-type SiC: Influence of Au and Ta intermediate layers

In this study, the optimization of metal-semiconductor contacts to reduce the contact resistance of ohmic contacts on n-type 4H-SiC. The commonly used Ni/Au metal scheme served as a reference. We introduced two novel metal schemes: (i) incorporating a thin interfacial Au layer (2 nm) into Ni/Au, resulting in Au/Ni/Au, and (ii) introducing a thin intermediate barrier layer of Ta (20 nm) into Ni/Au, resulting in Ni/Ta/Au. Rapid thermal annealing (RTA) is performed at different temperatures and durations and the electrical characteristics of the contacts are measured. X-ray diffraction analysis was employed to investigate the intermediate phases formed during annealing. In the Au/Ni/Au metal scheme, the presence of Au at the interface promoted the formation of additional phases of nickel-silicide (Ni3Si and Ni3Si2). Compared to the traditional Ni/Au scheme, the modified metal schemes led to lower surface roughness and reduced contact resistance. Specific contact resistivity values are calculated, 2.2 × 10−5 Ω-cm2 for Ni/Au, 1.37 × 10−5 Ω-cm2 for Au/Ni/Au, and 4.84 × 10−5 Ω-cm2 for Ni/Ta/Au. This research offers valuable insights for the selection of metal schemes in designing ohmic contacts on n-type SiC, with potential applications in various semiconductor device technologies.

Integrative approach to enhance the soft magnetic properties of Co35Cr5Fe10Ni30Ti20-xAlx (x= 10, 15, 20) high entropy alloys

High Entropy Alloys (HEAs) are advanced materials having multi-functional properties. These materials have the potential to overcome the shortcomings of conventional soft magnetic alloys. In this study, an integrative approach is adopted to enhance the magnetic and electrical properties of CoCrFeNiTi-based HEA by the addition of Al in different content for Ti and annealing for different temperatures and durations. Firstly, Co35Cr5Fe10Ni30Ti20-xAlx (x= 10, 15, 20) HEAs were synthesized through mechanical alloying and investigated for phase formation and magnetic properties. Major fcc with minor bcc and intermetallic R phase has formed for Co35Cr5Fe10Ni30Ti10Al10 and Co35Cr5Fe10Ni30Ti5Al15 HEAs. However, the mixture of fcc and bcc phase with a minor fraction of σ phase has been found for Co35Cr5Fe10Ni30Al20 HEA. The value of Ms is slightly decreased for Co35Cr5Fe10Ni30Ti5Al15 HEA as compared to Co35Cr5Fe10Ni30Ti10Al10 HEA, but for Co35Cr5Fe10Ni30Al20 HEA, the value of Ms has drastically decreased when Ti completely removed for Al. Among these three synthesized HEAs, the highest value of Ms is found for Co35Cr5Fe10Ni30Ti10Al10 HEA (Ms=78 emu/g). Further, we investigated the effect of annealing at different temperatures for 2 h on phase evolution, microstructure, and their correlation with magnetic properties of Co35Cr5Fe10Ni30Ti10Al10 HEA. Among annealed HEA, 700°C annealed Co35Cr5Fe10Ni30Ti10Al10 HEA has high Ms (104 emu/g), and the value of Hc was found to be 29 Oe. The long-duration annealing is also performed at 700°C for 10 h to improve the magnetic properties of the as-synthesized Co35Cr5Fe10Ni30Ti10Al10 HEA and found good soft magnetic behaviour (Ms=103.5 emu/g and Hc=13 Oe). Moreover, the electrical resistivity of the long-duration annealed Co35Cr5Fe10Ni30Ti10Al10 HEA is also recorded in the temperature range 2–350 K, and the value of electrical resistivity at 2 K and 300 K is found to be 180.2 ×102 µΩ.cm and 200.80 ×102 µΩ.cm, respectively. The found value of electrical resistivity is the highest value of resistivity reported so far in the case of soft magnetic HEA.

Hyaluronic acid mediated ZnO-NPs: In relation to electrical and photocatalytic activity for dye degradation

Various processes have been implemented to purify water; however, photocatalysis is comprehensively utilized in wastewater treatment and plays a significant role in water remediation. A photocatalyst is a nanostructured metal oxide ZnO nanoparticles, which boosts the reaction rate by its existence. ZnO nanoparticles show great performance in the absorption of various organic pollutants from wastewater. The objective of this research was to enhance the photocatalytic degradation performance of HA-added ZnO NPs using methylene blue as a model wastewater. Adjusting the main physical properties and photocatalytic efficiency of ZnO-NPs was performed using hyaluronic acid (HA), a natural bioactive stabilizer. The characterization of the fabricated ZnO-NPs samples with and without HA involved the utilization of FE-SEM, AFM, XRD, FTIR, PL, and I-V. As demonstrated by the FE-SEM analysis, ZnO formed rod-like structures, 3.0 % HA:ZnO exhibited cauliflower-like structures, and 5.0 % HA:ZnO displayed honeycomb-like structures. The X-ray diffraction (XRD) analysis demonstrated that the HA:ZnO nanoparticles exhibited hexagonal wurtzite structures. The average crystallite sizes of the ZnO, 3.0 % HA:ZnO, and 5.0 % HA:ZnO NPs were determined to be 25.20, 27.30, and 20.20 nm, respectively, using the XRD patterns. The surface area was 4.439, 2.987, and 5.204 m²/g of bare ZnO, 3.0 % HA:ZnO, and 5.0 % HA:ZnO-NPs were 4.439, 2.987, and 5.204 m2/g, respectively. It is very likely that there are two different decay and/or capture mechanisms in the emission spectra because the TRPL decay profile behaves in a double-exponential way. The fast decay time constant (τ1) was 212 ps for bare ZnO and 3.0 % HA:ZnO NPs and 231 ps for 5.0 % HA:ZnO NPs. The slow decay time constant (τ2) has a similar pattern, with values of 3.716, 2.836, and 2.984 ns. The specific contact resistance values of the ZnO NPs increased from 0.113 to 45.624 ( × 105 Ω cm2) as a function of the HA concentration, as evidenced by the results of the electrical studies. The outcomes of this research present comprehensive information on noble-modified ZnO-NP materials containing HA for direct applications in electronic materials and photocatalytic degradation of organic waste in water.

Geophysical and geoenvironmental engineering assessment of contaminated workstation soils in a metamorphic environment

This study aims to employ the electrical method, multi-pollution indices, and statistical optimization to establish a common ground for the utilization of contaminated soil as construction material and for agricultural purposes. Two samples each were taken at a depth of 0.5 m and 1.0 m from the eatery, auto-mechanic, car wash, and transformer workstations and at a control site in Akungba-Akoko, southwestern Nigeria. The concentrations of the following geochemical parameters were analyzed: Cr, Pb, Zn, Cd, Mn, and Cu. The resistivity distribution of the workstations’ subsurface layers was determined using Schlumberger vertical electrical sounding (VES). The generated geoelectrical sections revealed four geoelectric layers (topsoil, weathered layer, partially weathered/fracture bedrock, and bedrock) with two curve types: HA (50%) and AA (50%) across the workstations. The topsoil resistivity values (65–184 Ωm) from the VES results suggest moderately rich organic matter and averagely very fine-grained sand. The concentrations of the heavy metals in all the soil samples are within the maximum allowable concentration as stipulated by the National Environmental Standards and Regulations Enforcement Agency in the soil and are suitable for farm activities. Similarly, the geotechnical tests of the Atterberg limit, grain size analysis, compaction, and CBR revealed that all the soil samples met the criteria of a good pavement design but with poor landfill material. Pearson's correlation coefficient revealed that a strong relationship between Igeo\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${I}_{geo}$$\\end{document}-PLI, Igeo\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${I}_{geo}$$\\end{document}-RI, PLI-RI, TSR-Fines, MDD-CBR, LL-MDD, and LL-CBR exists among the multi-pollution indices, the geotechnical properties of soil, and the resistivity distribution of the topsoil. This suggests similar levels of heavy metal pollution and a common source of anthropogenic activities throughout the four workshops and provides the link between geotechnical properties and resistivity distribution for future soil management strategies. The exposure of children and adults to multiple heavy metals through inhalation at the four workstations shows no significant non-cancer or cancer risks.

Insights into corrosion inhibition of aluminum in hydrochloric acid solutions using expired cephalosporins and klavox: Chemical, electrochemical and theoretical approaches

The inhibitory efficacy of two expired antibiotic drugs namely, cephalosporin and klavox against corrosion of aluminum in 1.0 M HCl solution was investigate utilizing potentiodynamic polarization (PDP) impedance spectroscopy (EIS) and weight reduction (WR) methodologies. It was discovered that the two expired drugs act as excellent inhibitors and the inhibition efficacy increases as the drug concentration increases and the temperature decreases. The inhibition efficacy reached 97.62 % and 99.42 % at 900 ppm of cephalosporin and klavox at 298 K, respectively. Expired drugs act as a mixed type inhibitor, controlling primarily the anodic and cathodic process, as evidenced by the PDP curves. According to EIS analysis, the charge transfer resistance values increased with increasing inhibitor concentration. The adsorption isotherm demonstrates that the expired drugs become active by physical adsorption on the Al surface, and their adsorption obeys the Langmuir isotherm. Through quantum chemistry calculations, the relationship between the inhibition properties and molecular structure was studied.

Effect of Nitrogen on Precipitate Characteristics and Pitting Resistance of Martensitic Stainless Steel.

High-carbon-chromium martensitic stainless steel (MSS) is widely used in many fields due to its excellent mechanical properties, while the coarse eutectic carbide in MSS deteriorates corrosion resistance. In this work, nitrogen was added to the MSS to improve corrosion resistance. The effects of nitrogen on the microstructure and corrosion resistance of MSS were systematically studied. The results showed that the addition of nitrogen promoted the development of Cr2N and reversed austenite, effectively inhibiting the formation of δ-ferrite. Therefore, the durability of the passivation film was improved, the passivation zone was expanded, and the susceptibility to metastable pitting was decreased. As a consequence, nearly two orders of magnitude have been achieved in the pitting potential (Epit) of MSS containing nitrogen, and the polarization resistance value (Rp) has gone up from 4.05 kΩ·cm2 to 1.24 × 102 kΩ·cm2. This means that in a corrosive environment, nitrogen-treated MSS stainless steel is less likely to form pitting pits, which further extends the service life of the material.

Super capacitive electrode performance analysis of facile synthesized α-Fe2O3 aerogel and its nanocomposite with in-situ formed polyaniline (α-Fe2O3/PANI)

This paper presents the synthesis of an α-Fe2O3-assisted polyaniline (α-Fe2O3/PANI) nanocomposite using a straightforward two-step process. Initially, α-Fe2O3 aerogels with cratered nanohexagon structures are synthesized through a solution combustion method assisted by noni (Morinda citrifolia) fruit extract. In the second step, these nanohexagons facilitate the preparation of α-Fe2O3/PANI via in-situ chemical oxidative polymerization of anilinium chloride. The structural, optical, and morphological properties were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDAX). Electrical conductivity, wettability, and electrochemical properties of the prepared materials were assessed. The results indicate that the 2D cratered α-Fe2O3 aerogel is effectively embedded within PANI, forming a modified nano α-Fe2O3/PANI composite. The composite exhibited altered DC conductivity and electrolyte wettability. After 200 cycles of cyclic voltammetry (CV), the specific capacitance of the nano α-Fe2O3/PANI was determined to be 153 Fg⁻¹ at a scan rate of 10 mVs⁻¹, retaining approximately 90 % of its cycle stability. Electrochemical impedance spectroscopy (EIS) revealed significantly lower charge transfer and equivalent series resistance values for the nano α-Fe2O3/PANI electrode compared to the pure α-Fe2O3-based electrode. Galvanostatic charge-discharge (GCD) tests further demonstrated the superior electrochemical performance of the α-Fe2O3/PANI nanocomposite electrode. Therefore, this α-Fe2O3/PANI is an advanced conducting polymeric electrode for electrochemical applications.

Geoelectrical and seismoelectric mapping of subsurface pollution in a closed landfill near the Tongo Bassa and Ngongue river, Douala Cameroon

Located in Douala V (Cameroon), Makepé Missoké is a lowland area that is influenced by the Tongo Bassa and Ngongué rivers. The site has a closed dumpsite, that operated from the 1975’s to 2003 for the disposal and storage of domestic waste produced in Douala. Geoelectric profiling (ERT) coupled with seismo-electric imaging was used to characterize the shallow aquifer of the Douala subbasin and map subsurface pollution. Fourteen geoelectrical profiles were deployed between June and August 2018 and March 2019. Along these lines, 49 sets of seismo-electric point data were collected in December 2021. A total of 118 wells drilled (2018) were used to obtain water level and topographic data. The aquifer geometry, hydraulic characteristics, permeability, lithology and leachate plume extent were determined. This survey enables us to visualize waste infiltration and migration within Makepé. The drilled wells indicate that the main lithologies observed are clay, sandy clay, sand, clayey sand and gravel. The leachate plume observed after processing the electric profiles had a resistivity signature of ≤ 10 Ωm, and high electrical conductivity are observed in some wells. The leachate migrates within the subsurface along a northwest‒southwest trend, where ground water pollution is observed due to leachate infiltration. This infiltration resulted in poor water quality indices in some collected samples. Such pollution is common in unconfined aquifers (< 50 m) due to the absence of a confining layer at the landfill. An increase in resistivity values with depth toward the northeast direction indicates progressive vertical dilution during leachate mineralization. This study integrated geoelectric and seismo-electric tomography with basic water chemistry analysis to effectively characterize the groundwater within the phreatic Quaternary/Mio-Pliocene aquifers of the Douala basin.

Investigating the Effect of Weave Type and Filament Count on Electrical Conductivity of Polyethylene Terephthalate (PET) Fabrics Coated with PEDOT Polymer

The rapid development of smart and wearable textiles has been driven by the need for smaller and lighter electronic circuits. To make textile surfaces conductive, various methods have been developed, with vapor-phase polymerization being a preferred method due to its smoothness, conductivity, and ease of application. This study investigates the effect of fundamental characteristics of textile fabrics, such as weave type and filament count, on electrical conductivity. Fabrics woven with different filament counts and weave types were coated with PEDOT polymer using vapor-phase polymerization. The results showed that the fabric woven with 150F288 yarns and a 3/1 twill weave exhibited lower electrical resistance, attributed to the microfibrous structure of the yarn and the twill's staggered structure. Despite increases in resistance values after performance tests, the electrical resistance values remained within a sufficient conductivity range. This research contributes to the understanding of how fabric characteristics affect the electrical conductivity of coated textiles, paving the way for the development of smart electronic textiles.

Syntheses of AlLB14(L=Li or Na) crystals using alkali fluorides and its properties

AlLB14 (L=Li or Na or K) crystals were grown using LiF or NaF or KF and crystalline boron powders as the starting materials using a high-temperature Al melt at soaking temperature 1573 ∼ 1773 K for a soaking time of 5 h under an Ar atmosphere. AlLiB14 and AlNaB14 crystals were obtained from LiF or NaF and B powders, and the atomic ratios (n=B/L = 2.0 ∼ 4.0) of starting materials. The AlKB14 crystal was not obtained from KF and B powders as starting materials. The micro-Vickers hardness of AlLB14 crystals is 24(±1) GPa for AlLiB14 and 25(±1) GPa for AlNaB14. The oxidation initiation temperature of AlLiB14 was about 815 K, and the peak due to the exothermic reaction was about 960 K for AlLiB14 and about 990 K for AlNaB14. The final oxidation products were Li2B2O4, Al4B2O9, B2O3, and amorphous phases. The values for the electrical resistivity of the AlLB14 compound were 2.4 ∼ 157 Ω·cm.

Study on characteristics of the resistivity parameter and its coupling model of Chazangcuo copper-lead-zinc deposits based on microscopic analysis

Abstract The resistivity exploration has made a great contribution to prospecting at the macro level, but the resistivity exploration at the micro level is relatively weak. In this paper, the corresponding resistivity is analyzed through a geochemical element test, temperature and pressure test, water content and porosity test, and the resistivity parameter model of the rock and ore is established based on the response surface. The main conclusions and understandings obtained are as follows: with the increase of Cu-Pb-Zn content, the rock-ore resistivity shows an obvious decreasing trend, with sphalerite resistivity (72.8×10−2 Ω·m) > pyrite resistivity (32.5×10−2 Ω·m) > galena resistivity (76.5×10−3 Ω·m) > chalcopyrite (11.3×10−3 Ω·m). The resistivity increases with the temperature, showing a quadratic term function trend increases. The resistivity decreases with the increase of pressure, decreasing rapidly at the beginning of loading and gradually slowing down. The resistivity decreases rapidly with the increase of water content and porosity in an exponential function trend. The degree of influence of four factors, temperature, pressure, porosity, and water content, on the resistivity of the ore samples, is the order of water content, porosity, pressure, and temperature. The coupled model of resistivity of Cu-Pb-Zn ores established by multivariate quadratic regression analysis is more reliable, and the predicted value of rock and ore resistivity is more consistent with the test data.

Capacity and Resistance Diagnosis of Batteries with Voltage-Controlled Models

Capacity and internal resistance are key properties of batteries determining energy content and power capability. We present a novel algorithm for estimating the absolute values of capacity and internal resistance from voltage and current data. The algorithm is based on voltage-controlled models. Experimentally-measured voltage is used as an input variable to an equivalent circuit model. The simulation gives current as output, which is compared to the experimentally-measured current. We show that capacity loss and resistance increase lead to characteristic fingerprints in the current output of the simulation. In order to exploit these fingerprints, a theory is developed for calculating capacity and resistance from the difference between simulated and measured current. The findings are cast into an algorithm for operando diagnosis of batteries operated with arbitrary load profiles. The algorithm is demonstrated using cycling data from lithium-ion pouch cells operated on full cycles, shallow cycles, and dynamic cycles typical for electric vehicles. Capacity and internal resistance of a “fresh” cell was estimated with high accuracy (mean absolute errors of 0.9% and 1.8%, respectively). For an “aged” cell, the algorithm required adaptation of the model’s open-circuit voltage curve to obtain high accuracies.

Phase-field modelings of fracture investigate the influence of interfacial effects on damage and optimal material distribution in brittle inclusion-matrix structures

This present work uses the phase-field modelings to investigate the influence of interfacial effects on damage and mechanical behavior, as well as the optimal distribution of the inclusion shape within brittle inclusion-matrix structures in various typical cases. These two constituent phases in the structures are assumed to be either isotropic or anisotropic. To achieve these goals, this work will: (i) use the phase-field modelings either considering or neglecting interfacial debonding, and the anisotropic phase-field modeling; (ii) determine and incorporate the strain tensor orthogonal decompositions into each specific phase-field modeling to enhance the accuracy and effectiveness of the simulation methods; (iii) combine the phase-field modelings with the BESO topology optimization algorithm to analyze the influence of interfacial effects on relationship curves and the optimal distribution of the inclusion shape. Through proposed numerical examples, it is demonstrated that the interfacial effects strongly influence crack paths, behavior curves, and optimal material distribution in structures. When considering interfacial effects, cracks are almost unable to penetrate into the inclusion phase. However, when neglecting interfacial effects, cracks propagate into the inclusion phase. This reason makes the structure more difficult to damage than when considering the interfacial effects, as evidenced by greater peak load values in behavior curves and greater total fracture resistance of the material. Especially in the example of inclusion phase optimization, the total fracture resistance value of the case neglecting interfacial effects is more than 107.9% greater than that considering interfacial effects.

The Use of MATLAB Programming to Compare Experimental vs Modeled PEMFCs using the Nernst and Butler-Volmer’s Equation-Based Mathematical Models

For the analysis of Proton Exchange Membrane Fuel Cell (PEMFC’s) efficiency, the Nernst equation and Butler-Volmer's concepts were used. The mathematical models using both equations were developed in MATLAB and compiled. The results generated by the output current based on the input parameters of the experimental data were compared with the experimental results for the two modelled PEMFCs. The parameters temperature, pressure, hydrogen concentration, and oxygen concentration at different values of external resistance were used to determine the change in output current in both models built in MATLAB. This sensitivity analysis generated negative output current values and highly dissimilar values with the experimental results for the same input parameters for both models due to the less use of input parameters in the model. The results showed that the PEMFC's performance is affected by most parameters, and many influencing parameters must be used to develop a perfect mathematical model of the PEMFC.

Application of the electrospinning technique in the preparation of selected electrode materials for solid oxide fuel cells

Abstract The electrospinning technique was applied to prepare cathode materials for solid oxide fuel cells (SOFCs). The research aimed to determine the influence of the Poly(vinylpyrrolidone) (PVP) content in the solution of a Sm0.5Ba0.25Sr0.25Co0.5Cu0.5O3-d perovskite oxide on the properties of the spun material, and consequently, on the performance of the fuel cell. The chosen material, commonly used as a cathode material for SOFCs, has been altered by the replacement of toxic barium and cobalt with less harmful strontium in the A-site and copper in the B-site. A single-phase perovskite structure was obtained after annealing at 900°C for two hours. The research included a process of preparing the precursor solution and obtaining samples by the electrospinning technique, followed by a series of studies to determine the morphology and phase composition, electrode and cell fabrication, and characterization of their electrochemical properties. The results indicated that material derived from a precursor with the addition of 15 wt.% PVP had the lowest polarization resistance values (e.g. 0,865 Ω cm−2 at 800 °C) between 600°C - 900°C temperature range. This material was then screen-printed on a commercial anode-supported fuel cell as a cathode layer, which allowed to achieve a promising power density value close to 300 mW cm−2 at 800 °C.

Physicochemical Properties of (La,Sr)CoO3 Thick Films on Fe-25Cr Steel under Exposure to SOFC Cathode Operating Conditions.

La0.6Sr0.4CoO3 (LSC) coatings with a thickness of 50-100 µm were deposited on Fe-25Cr ferritic stainless steel (DIN 50049) via screen printing. The required suspension had been prepared using fine LSC powders synthesised using EDTA gel processes. In its bulk form, the LSC consisted entirely of the rhombohedral phase with space group R-3c, and it exhibited high electrical conductivity (~144 S·cm-1). LSC-coated steel was oxidised in air at 1073 K, i.e., under conditions corresponding to SOFC cathode operation, for times of up to 144 h. The in situ electrical resistance of the steel/La0.6Sr0.4CoO3 layered system during oxidation was measured. The products formed on the samples after the oxidation reaction resulting from exposure to the corrosive medium were investigated using XRD, SEM-EDS, and TEM-SAD. The microstructural, nanostructural, phase, and chemical analysis of films was performed with a focus on the film/substrate interface. It was determined that the LSC coating interacts with the oxidised steel in the applied conditions, and a multi-layer interfacial zone is formed. Detailed TEM-SAD observations indicated the formation of a main layer consisting of SrCrO4, which was the reaction product of (La,Sr)CoO3, and the Cr2O3 scale formed on the metal surface. The formation of the SrCrO4 phase resulted in improved electrical conductivity of the investigated metal/ceramics layered composite material, as demonstrated by the low area-specific resistance values of 5 mΩ·cm2, thus making it potentially useful as a SOFC interconnect material operating at the tested temperature. In addition, the evaporation rate of chromium measured for the uncoated steel and the steel/La0.6Sr0.4CoO3 layered system likewise indicates that the coating is capable of acting as an effective barrier against the formation of volatile compounds of chromium.

Temperature dependent electrical resistance and mesoscopic electronic transport mechanisms on aerographite and single-walled carbon nanotube aerogel

We investigate temperature dependent electrical resistance properties of aerographite and single-walled carbon nanotube (SWCNT) aerogel in the temperature range of 2–300 K by employing the four-probe method with magnetic field effects (in the range 0–9 T, in steps of 2 T). The current–voltage (I–V) curves were taken for several temperatures varying from 5 to 300 K, and the electrical resistance values of aerographite and SWCNT aerogel were decreased from 7.30 Ω (5 K, 0 T) to 4.88 Ω (300 K, 0 T) and 22.56 Ω (5 K, 0 T) to 0.99 Ω (300 K, 0 T) with temperature increases, respectively. Experimental results show that the electrical resistance falls exponentially as the temperature increases. Such temperature dependence of R(T) points to a form of tunneling conduction or hopping. Two mesoscopic mechanisms for electronic transport, fluctuation-induced tunneling conduction (FITC) and variable range hopping (VRH), are employed to explicate possible electrical conduction mechanisms occurring in aerographite and SWCNT aerogel, respectively. These mainly result in disorder-induced symmetry-breaking, which are modified by their structural symmetries and electronic band structures, both play important roles in temperature dependent electrical resistance properties of aerographite and SWCNT aerogel. Characteristic parameters (T0, T1, and R0) have been estimated using the morphology and the uncertainty principle for aerographite and the percolation theory for SWCNT aerogel. While the FITC mechanism captures a wide temperature range of data for aerographite, the VRH model provides an explanation for SWCNT aerogel. This study provides groundwork for further development of carbon aerogel systems with high conductivity in large-scale preparation.

Impact of Diafiltration Media and Filtration Modes on Fouling and Performance in Skim Milk Microfiltration: A Comparative Study

This research utilized a customized laboratory setup to compare the filtration performance and fouling buildup during microfiltration with polymeric membranes of skim milk using 2 diafiltration media: ultrafiltration permeate and ultrapure water. Two filtration modes were evaluated: in stage 1, the diafiltration media was added in a 1:1 ratio, with the collection of permeate continuing until the initial protein concentration was restored. In stage 2, retentates and permeates were recycled to simulate fouling accumulation in a steady-state without altering the retentate composition. Utilizing water as the diafiltration medium resulted in higher flux and lower resistance values compared with using ultrafiltration permeate, irrespective of the filtration mode. The concentration had a significant impact on membrane resistance, with no noticeable time-dependent effect on fouling layer development after 60 min of filtration when the retentate composition remained constant. The protein composition of the permeate and extracted foulants were comparable between the 2 media, with caseins predominating in the fouling layer.