Variation Of Conductivity Research Articles

Numerical investigation of slip effects on heat and mass transfer in a vertical channel with immiscible micropolar and viscous fluids of variable viscosity

AbstractThis study investigates the fluid flow, heat, and mass transfer phenomena within a vertical channel containing two immiscible fluids, with a particular focus on slip effects. These effects include no slip, velocity slip, thermal slip, and multiple slips, each analyzed with appropriate boundary conditions. The study thoroughly examines key characteristics, such as variations in thermal conductivity and viscosity. Using a sixth‐order Runge–Kutta numerical method implemented using Mathematica, the study achieves precise solutions for complex scenarios. The detailed results show how the various slip mechanisms and relevant parameters interact with each other in complex ways. These findings are useful for both theoretical understanding and application in real‐life engineering situations. This study also gives important information about how fluid flow, heat transfer, and mass transfer change under different slip effects. It looks at these effects and shows how they change visually. It also carefully calculates and analyzes engineering parameters like the Nusselt number, shear stress, and Sherwood number using bar charts, showing how they affect and behave. The study resulted in velocity slip having a minimal impact on temperature, whereas thermal slip resulted in higher temperatures. Both velocity and thermal slip conditions simultaneously result in the lowest temperatures.

Measurement and theoretical analysis of effective thermal conductivity of lanthanum pentanickel powder beds for hydrogen storage in different particle sizes and bed porosities

Particle diameter and bed porosity change due to the expansion and contraction of metal hydride particles during hydrogen absorption and desorption, which leads to variations in the effective thermal conductivity of metal hydride beds. Therefore, the effective thermal conductivity of the metal hydride beds under different bed porosities and particle diameters must be measured for the design of metal hydride-based hydrogen storage tanks. In this study, the effective thermal conductivities of four kinds of lanthanum pentanickel (LaNi5) powder beds with different bed porosities and particle diameters were measured in various gas atmospheres with gas pressure varying from 0.1 to 4.0 MPa. The volume mean diameters of the four kinds of LaNi5 powders equal 335.2, 196.4, 147.7, and 23.7 μm, respectively. Subsequently, the effects of bed porosity and particle diameter on the effective thermal conductivities were analyzed through the modified Zehner–Schlünder–Damköhler model considering the Smoluchowski effect. Experimental results show that particle diameter and bed porosity influence markedly the effective thermal conductivity of lanthanum pentanickel (LaNi5) powder beds. However, the findings of theoretical analysis based on the modified Zehner–Schlünder–Damköhler model reveal the considerably weaker effect of particle diameter on the effective thermal conductivity under identical bed porosity compared with the measurement results. Such a finding was observed because the variation in particle diameter inevitably changed bed porosity during the effective thermal conductivity measurement, which also affected the effective thermal conductivity of the beds. In addition, decreasing bed porosity and increasing particle diameter can remarkably improve the heat transport via the gas–solid mixture pathway, which improved the effective thermal conductivity of the beds and thus explained the experimental results.

Nature of the bond in intermetallic compounds

By studying 398 binary compounds crystallizing in five different crystal structures, it is shown that atomic radii of the elements RA and RB change to reach a constant radius ratio rA/rB(≡ϒ) in a cubic system. In systems of lower symmetry, a range of ϒ values, each corresponding to a certain axial ratio, is possible. Accurate charge values on atoms in solids are derived from the experimental internal radii rA and rB, using Shannon’s compilation of radii versus charge states for elements. It is found, for the first time, that charge transfer and radii change reverse their direction at the ϒ point. Electronegativity difference relative to its value at the ϒ point is recognized to correctly predict the charge transfer and radii changes with RA/RB. The deduced electronic structure of solids, based on spherical ions carrying partial charges, confirms that the metallic atom-pair bond is a resonating polar covalent bond. Identification of the number of electrons that contribute to cohesion and electrical conduction individually, allows successful prediction of electrical conductivity variation for transition metals and p-elements in the periodic table. From a knowledge of accurate valence of elements and of charge on the atoms, variation in the 197Au isomer shift of the gold compounds of CsCl type structure is predicted. The charges on atoms computed using the Quantum Theory of Atoms in Molecules (QTAIM) technique agree with those obtained in our work for compounds belonging to two of the structure types. For compounds belonging to the other three, the charge values obtained by the two methods do not agree. The disagreement correlates to not reckoning the role of the ϒ point. The effect of ϒ point is so fundamental and universal that most physical properties obtained by the secondary processing of primary DFT data, can be influenced by it.

Assessment of effective electrical conductivity in spherocylindrical carbon nanotube composites incorporating intrinsic properties of CNTs and interphase layer

This study introduces an analytical model using mean-field theory to estimate the effective electrical conductivity in composites of spherocylindrical carbon nanotubes (CNTs). The model adjusts the interphase layer's thickness and conductivity based on CNT concentration, affecting the electrical tunneling effect, and incorporates the properties of both CNTs and the interphase layer. Validated through detailed comparisons with experimental data, the model accurately predicts the electrical conductivities of polymer-CNT composites (PCNTs). Mean Squared Error analysis highlights its enhanced precision and superiority over traditional cylindrical CNT models. The model also explores how CNT dimensions, intrinsic conductivity, tunneling distance, potential barrier height, and variations in interphase thickness and conductivity influence electrical conductivity and percolation thresholds. This analytical model improves accuracy in predicting PCNT electrical conductivity and provides critical insights for designing and optimizing conductive polymer nanocomposites.

Machine learning-based atrial fibrillation detection and onset prediction using QT-dynamicity

Objective. This study examines the value of ventricular repolarization using QT dynamicity for two different types of atrial fibrillation (AF) prediction. Approach. We studied the importance of QT-dynamicity (1) in the detection and (2) the onset prediction (i.e. forecasting) of paroxysmal AF episodes using gradient-boosted decision trees (GBDT), an interpretable machine learning technique. We labeled 176 paroxysmal AF onsets from 88 patients in our unselected Holter recordings database containing paroxysmal AF episodes. Raw ECG signals were delineated using a wavelet-based signal processing technique. A total of 44 ECG features related to interval and wave durations and amplitude were selected and the GBDT model was trained with a Bayesian hyperparameters selection for various windows. The dataset was split into two parts at the patient level, meaning that the recordings from each patient were only present in either the train or test set, but not both. We used 80% on the database for the training and the remaining 20% for the test of the trained model. The model was evaluated using 5-fold cross-validation. Main results. The mean age of the patients was 75.9 ± 11.9 (range 50–99), the number of episodes per patient was 2.3 ± 2.2 (range 1–11), and CHA2DS2-VASc score was 2.9 ± 1.7 (range 1–9). For the detection of AF, we obtained an area under the receiver operating curve (AUROC) of 0.99 (CI 95% 0.98–0.99) and an accuracy of 95% using a 30 s window. Features related to RR intervals were the most influential, followed by those on QT intervals. For the AF onset forecast, we obtained an AUROC of 0.739 (0.712–0.766) and an accuracy of 74% using a 120s window. R wave amplitude and QT dynamicity as assessed by Spearman’s correlation of the QT-RR slope were the best predictors. Significance. The QT dynamicity can be used to accurately predict the onset of AF episodes. Ventricular repolarization, as assessed by QT dynamicity, adds information that allows for better short time prediction of AF onset, compared to relying only on RR intervals and heart rate variability. Communication between the ventricles and atria is mediated by the autonomic nervous system (ANS). The variations in intraventricular conduction and ventricular repolarization changes resulting from the influence of the ANS play a role in the initiation of AF.

Thermal transport and topological analyses of the heat-carrying modes and their relevant local structures in variously dense amorphous alumina

Engineering the thermal conductivities of amorphous materials is important for thermal management of various semiconducting devices. However, controlling the heat carriers—long-range propagating propagons and short-range hopping diffusons—in disordered lattices is difficult because the carriers are strongly correlated with lattice disorder. To clarify the relationship between lattice disorder and heat conduction, we must simultaneously investigate the important local structures hidden in a disordered system and the microscopic transport characteristics of propagons and diffusons. Here, we explore the variations in spectral thermal conductivity and the relevant local structures in amorphous alumina (a-Al2O3) at different densities by performing the spectral thermal transport and persistent homology analyses. As the density increases, the thermal conductivity of the high-frequency diffusons linearly increases but those of the propagons and low-frequency diffusons remain constant. The density increase enhances the local strain, thereby increasing the mean free paths of the high-frequency diffusons. The density of states competes with diffusivity, lowering the sensitivity of the density response to the thermal conductivity of low-frequency heat carriers. Furthermore, from the obtained topological features of the connections between the oxygen atoms, we inferred that the collapsed network of six-coordinated AlO6 octahedron clusters underlies the transport of high-frequency diffusons. Besides revealing the conductive pathways of heat-carrying modes in disordered lattices, topology-assisted spectral thermal transport analysis is useful for tailoring the thermal conductivities of amorphous materials.

Kalman Filter-Based Estimation of Surface Conductivity and Surface Variations in Scanning Tunneling Microscopy

Kalman Filter-Based Estimation of Surface Conductivity and Surface Variations in Scanning Tunneling Microscopy

AC Impedance Analysis of Blend Polymer Electrolyte of PVP – PPA with Magnesium Salts as an Ionic Dopant for Potential Battery Applications

Abstract Solid polymer electrolyte films containing blend polymer electrolyte of Polyvinylpyrrolidone (PVP) and Poly p - amino benzoic acid (PPA) with varying ratios of magnesium salts were synthesized by solution casting method. Their conduction and relaxation mechanisms were studied by impedance spectroscopy (AC) at room temperature. The dependence of electrical data on frequency was analyzed by Cole – Cole plot and Jonscher’s power law. The semicircle seen in the plot represents the double relaxation process and shows how bulk electrolyte and the interfacial effect contribute to non-Debye and electrical conduction. The ac and dc conductivity values were calculated and the conductivity variation for the blend polymer PVP – PPA doped with different concentrations of magnesium salts was explained by the ionic contribution of the electrolytes. The dielectric constant and dielectric loss were measured by the dielectric investigations. The relaxation phenomenon of these electrolytes is provided by the dissipation factor analysis and electric modulus value. The conductivity of the system determines the suitability of the thin film concentration for potential battery applications as a polymer electrolyte.

Geoelectric Investigation for Groundwater in Imo State University Campus and Environs using Direct Current Electrical Resistivity Method

Eighteen, vertical electrical soundings (VES), were carried out in Imo State University and Environs to delineate the potential site for groundwater. Data were acquired using ABEM SAS 300 resistivity meter. Schlumberger array and maximum electrode spread of 700m were adopted. Data were interpreted with IP2WIN software. Contour maps were done using Sulfer 20 software. Geoelectric cross-sections constructed along three profile lines delineated subsurface stratification. Sediments consist of sequence of sandstone/gravel, silty sand/sand and clay with geology representing the Benin Formation. Groundwater was delineated within the zone interpreted to be sand with quartz making up more than 95% of all grains. Resistivity of aquifer varies across study area and ranges from 159Ωm, observed around Library and Information Department (VES 11) to 100000Ωm recorded at IMSU Plaza (VES 10). Depth to water table also varied across study area with higher values of 150m and 130m observed at College of Health Science (VES 3) and Behind Old ETF (VES 4). A relatively shallow aquifer is delineated behind Senate Building and Okwu-Uratta with water table at depths of 23.5m and 26.5m. The transmissivity values are moderately high except at some locations. The variation in longitudinal conductance and transverse resistance values show that part of the study area such as Aso Rock, Female Hostel, Law Faculty and IMSU Plaza are underlain by relatively resistive (low longitudinal conductance) aquifer material. Distribution of hydraulic conductivity and electrical conductivity values indicates that in some of the VES points, the values are fairly constant. This could be seen as areas with similar geologic settings and water quality. Storativity of study area ranges from 0.00003 at VES 1 and 12 to 0.00028 at VES 4. Study area shows a good prospect for groundwater development, except at Library and Information Department, where the zone delineated is an aquitard.

Water Management and Hydrological Characteristics of Paddy-Rice Fields under Alternate Wetting and Drying Irrigation Practice as Climate Smart Practice: A Review

Paddy-rice cultivation using the traditional continuous flooding method requires much water, up to 2500 L, to produce 1 kg of rice. Decreasing water availability is being exacerbated by climate dynamics, i.e., droughts and rainfall variability negatively affecting food security in developing regions, particularly Africa. Alternate wetting and drying (AWD) practice is a climate-smart water management strategy that, together with puddling (a critical field preparation process), significantly affects soil hydrological and physicochemical regimes, such as soil water dynamics and oxidation states in paddy fields. However, there are limited reviews on the effects and interaction of the AWD duration on hydrological conditions in the paddy-rice rhizosphere continuum under AWD practice at different rice growth stages. Our review synthesizes key scientific literature to examine water management and hydrological properties of paddy soils under AWD practice with climate change and sheds light on why farmers are skeptical in adopting the practice. To develop this paper, we reviewed scientific information from published journal articles, reliable reports, and our knowledge on paddy-rice cultivation and water management with climate change in Asia and Sub-Saharan Africa. Several studies confirm that AWD practice increases water–rice–crop productivity, yields, and reduces methane emissions. Limitations and challenges of AWD irrigation, including changes in soil structure that influence irrigation water application, variations in hydraulic conductivity caused by the duration and frequency of irrigation cycles, and frequent manual water level (WL) monitoring, are discussed. Opportunities to improve the integration of AWD strategies within government policies, irrigation schemes, and farmer acceptance due to skepticism, limited knowledge, and fear of unreliable water hindering adoption are highlighted. Future research suggestions include the following: (i) long-term measurement of water stress indices using infrared thermometers; (ii) seasonal suitability mapping using NDVI, GIS, and remote sensing; and (iii) application of smart sensors based on the Internet of Things (IoT) to address AWD challenges for precision water management in paddy fields with climate change.

Soil freeze/thaw dynamics strongly influences runoff regime in a Tibetan permafrost watershed: Insights from a process-based model

The Tibetan Plateau (TP) is a region rich in extensive frozen ground and the source of many major Asian rivers. However, how soil freeze/thaw (F/T) dynamics influence runoff production at the catchment scale in the TP is poorly understood. This study employs a process-based permafrost hydrology model with a new soil parameterization to investigate soil F/T dynamics and their impact on runoff in a TP permafrost watershed, i.e., the source region of Yangtze River (SRYR). The revised model separates soil evaporation and plant transpiration, and accounts for the influence of soil gravel and organic carbon content, as well as variation in saturated hydraulic conductivity along the soil profile. Validation results demonstrate that the revised model accurately simulates daily soil temperature (mean RMSE of 1.3 °C), soil moisture (mean ubRMSE of 0.05 cm3 cm−3), and runoff discharge (NSE = 0.82). The results reveal different altitudinal patterns of warming trend between permafrost and seasonally frozen ground (SFG). Warming rates in SFG area increase monotonously with elevation, while a turning point is observed in permafrost region around 4800 m. With active layer deepening, deep-soil water content increases but primarily replenishes soil water storage rather than directly contributing to runoff recharge, while rootzone and the middle part of the active layer become drier. Soil F/T cycles in the permafrost region exert stronger influences on runoff process compared to SFG. Delayed soil thaw onset generally results in higher spring runoff coefficient, while delayed soil freeze onset is related to slower runoff recession. The freezing zero-curtain period is likely to impact the continuity of runoff recession processes by affecting the connectivity of groundwater flow channels. These findings uncover the regulatory mechanisms of soil F/T dynamics on runoff production and river discharge characteristics, providing a fundamental basis for predicting permafrost hydrology responses to future climate change in the TP.

Assessing an Abandoned Pyrite Cinder Deposit in Southeast Spain with Electrical Resistivity Tomography: A Case Study

Industrial activities have historically generated significant quantities of by-products, including pyrite cinders, a residue produced during the synthesis of sulphuric acid. This study presents a multidisciplinary approach to characterise an abandoned pyrite cinder deposit. Combining geophysical (electrical resistivity tomography—ERT), geochemical, and statistical methods, we assess the physicochemical properties of the deposit and its environmental implications. Our findings reveal the presence of heavy metals, with lead (7017.5 mg.kg−1) being the most concentrated element on the surface of the deposit, exceeding local legal thresholds by more than 163 times, posing environmental risks and inhibiting vegetation growth. Subsurface characterisation indicates a decreasing concentration trend of metals with depth, alongside variations in pH and electrical conductivity. Clustering analysis identifies groups of similar behaviours between resistivity, the most abundant heavy metals, and other variables, providing valuable insights into the complex interplay within the deposit. Our study underscores the importance of integrated approaches in assessing and managing hazardous waste sites, with implications for environmental remediation strategies.

Ultra-Fast-Charging, Long-Duration, and Wide-Temperature-Range Sodium Storage Enabled by Multiwalled Carbon Nanotube-Hybridized Biphasic Polyanion-Type Phosphate Cathode Materials.

Sodium-ion batteries (SIBs) represent a promising energy storage technology with great safety. Because of their high operating potential, superior structural stability, and prominent thermal stability, polyanion-type phosphates have garnered significant interest in superior prospective cathode materials for SIBs. Nevertheless, the disadvantages of poor intrinsic electronic conductivity, sluggish kinetics, and volume variation during sodiation/desodiation remain great challenges for satisfactory rate performance and cycle stability, which severely hinder their further practical applications. In this work, by adjusting the amounts of pretreated multiwalled carbon nanotubes (CNT) added intentionally at the beginning of the preparation, biphasic polyanion-type phosphate materials (marked as NFC) are synthesized through a one-pot solid state reaction methodology, which are composed of CNT-interwoven Na3V2(PO4)2F3 (NVPF) and a small amount of Na3V2(PO4)3 (NVP). Benefiting from the improved electronic conductivity and unique composition and structure, the optimized sample (labeled as NFC-2) illustrates exceptional cycle stability and remarkable rate performance. The discharge capacities of the NFC-2 electrode are 114.8 and 78.6 mAh g-1 tested at 20 and 5000 mA g-1, respectively. Notably, such an electrode still gives out 75.7% capacity retention upon 10 000 cycles at 5000 mA g-1. In situ X-ray diffraction analysis demonstrates that the NFC-2 cathode has outstanding structural reversibility during charge/discharge cycles. More importantly, such a biphasic material has achieved impressive electrochemical performance within a wide operating temperature range of -20-50 °C. When temperature is decreased to -20 °C, the NFC-2 electrode still delivers an initial discharge capacity of 102.4 mAh g-1 and exhibits a remarkable capacity retention of 97.8% even after 500 cycles at 50 mA g-1. In addition, the sodium-ion full cell assembled by integrating NFC-2 cathode and hard carbon anode shows a satisfying energy density of 431.3 Wh kg-1 at 20 mA g-1 with a better long-term cycle performance. The synergistic effect among high energy NVPF, conductive CNT, and stable NVP may lead to the great improvement in the electrochemical sodium storage performance of the NFC-2 sample. Such biphasic polyanion-type phosphate materials will inject new ideas into the material design for SIBs with excellent electrochemical performance and further promote practical applications of this advanced energy storage technology.

Role of sodium sulfate in electrical conductivity and structure of lignin-derived carbons

Lignin is a promising renewable alternative to fossil fuels for producing carbon materials such as carbon fibers, activated carbons, or carbon black. Despite extensive research, lignin-derived carbon materials show limited graphitization relative to comparable petroleum-derived carbons. Further, lignin-derived carbons show high variation in graphitization and electrical conductivity depending on the source of the lignin. Herein, nine lignins, derived from various feedstocks and isolation procedures, are pyrolyzed to produce biochar at 1100∘C. These lignins have a range of chemical compositions, carbon structures, and particle sizes. As a result, the pyrolysis behavior of these lignins varies, with powdered, clumped powder, and “foam” biochar morphologies resulting from finely powdered lignin. The produced biochars vary widely in both electrical conductivity, from 0.19 to 19 S/cm, and in-plane graphitic crystallite size, from 3.4 to 41.2Å. A significant decrease in electrical conductivity is identified when Na2SO4 is removed from lignin, accompanied by an increase in graphitic crystallite size. Based on this finding, a quadratic relationship between biochar graphitic crystallite aspect ratio and electrical conductivity is proposed that builds on established quasi-percolation models for biochar electrical conductivity.

Green roof plant physiological water demand for transpiration under extreme heat

Green roofs are a sustainable strategy for improving the eco-environment in urban areas. However, plants on green roofs are increasingly threatened by extreme heat and drought due to climate change. There is a lack of comprehensive understanding of the physiological water demand of green roof vegetation under extreme heat. Therefore, this exploratory study investigated two commonly used Sedum species for urban green roofs (Sedum spectabile Boreau and Sedum alfredii Hance) under extreme heat, considering two treatments: irrigation and non-irrigation. The results indicated that under extreme heat, if without irrigation, the two Sedum species’ mean daily water consumption by transpiration was approximately 4.68 g per Sedum plant. However, under irrigation, the diurnal variation of stomatal conductance of the two Sedum species allowed the stomata to remain open throughout the day, resulting in an over-twentyfold increase in mean daily water consumption through transpiration (120.34 g per Sedum plant) and twofold increase in leaf area index. A random forest model showed that multi-environmental factors explained 67.53 % of the variability in stomatal behavior. Photosynthetically active radiation and soil moisture are the primary environmental factors that directly affect stomatal conductance. The irrigation induces stomatal opening throughout the diurnal cycle, ensuring the continuation of vegetation growth and the maintenance of physiological functions under extreme heat, which then contributes to keeping its eco-environmental functions and providing sustainable services, such as cooling and carbon sequestration. The findings of this study can guide planning and managing green roofs in urban areas that face extreme heat events.

Quenching of zonal winds in Jupiter’s interior

Gravity and magnetic field data obtained by the Juno mission show that Jupiter's strong zonal winds extend a few thousand kilometers into the interior, but are quenched above the level where the electrical conductivity becomes significant. Here, we extend a simple linearized model [Christensen et al., Astrophys. J. 890, 61 (2020)] that explains the braking of the jets by the combination of stable stratification and electromagnetic effects. We show that in the inviscid limit, the process is essentially governed by a single parameter, which we call the MAC-number (for the forces acting on the flow-Magnetic, Archimedian, and Coriolis). The predictions for the drop-off of the zonal winds agree well with results from 3D-convection models. We run calculations that take the full range of density and electrical conductivity variations in the top 5,600 km of Jupiter into account. In order to satisfy constraints on the power driving the jets and on their effect on Jupiter's magnetic field, the top of the stable layer and the region where the jet velocity drops sharply must be near 2,000 km depth. The dissipation associated with quenching of the jets increases toward the poles, which can partly explain why the jets near [Formula: see text]20[Formula: see text] are faster than those at higher latitude.

Height profile variations of ionospheric conductivity: A case study in Addis Ababa, Ethiopia

Ionospheric conductivity is the ability to conduct ionospheric current and is impacted by a variety of current system flows in height profiles, which increase ionosphere conductivity. In this study, we have analyzed the height profiles of the ionospheric conductivity daily and monthly variations in Addis Ababa, Ethiopia, during a very low solar activity phase in the year 2020. The daily height profile variations of ionospheric conductivity in Addis Ababa with geographic latitude 9o N and longitude 39o E are estimated at midnight (00:00 UT), morning (09:00 UT), mid-day (12:00 UT), and early nighttime (18:00 UT). The monthly variations of ionospheric conductivity (parallel, Pedersen, and Hall conductivity) are also presented for all months, with the highest ionospheric variability occurring after noon (14.00 UT). At midnight (00:00 UT) and early nighttime (18:00 UT), the ionospheric conductivity shows more fluctuation than in the morning (09:00 UT) and midday (12:00 UT) in diurnal variation. The monthly variations of ionospheric conductivity (parallel, Pedersen, and Hall conductivity) in the daytime at 14:00 UT increase steeply to reach their peak values and keep the sharpness of their variability.

Stability Study of Synthetic Diamond Using a Thermally Controlled Biological Environment: Application towards Long-Lasting Neural Prostheses.

This paper demonstrates, for the first time, the stability of synthetic diamond as a passive layer within neural implants. Leveraging the exceptional biocompatibility of intrinsic nanocrystalline diamond, a comprehensive review of material aging analysis in the context of in-vivo implants is provided. This work is based on electric impedance monitoring through the formulation of an analytical model that scrutinizes essential parameters such as the deposited metal resistivity, insulation between conductors, changes in electrode geometry, and leakage currents. The evolution of these parameters takes place over an equivalent period of approximately 10 years. The analytical model, focusing on a fractional capacitor, provides nuanced insights into the surface conductivity variation. A comparative study is performed between a classical polymer material (SU8) and synthetic diamond. Samples subjected to dynamic impedance analysis reveal distinctive patterns over time, characterized by their physical degradation. The results highlight the very high stability of diamond, suggesting promise for the electrode's enduring viability. To support this analysis, microscopic and optical measurements conclude the paper and confirm the high stability of diamond and its strong potential as a material for neural implants with long-life use.

Laser ablation mechanism and performance of glass fiber-reinforced phenolic composites: An experimental study and dual-scale modelling

Both experimental and simulation approaches were employed to investigate the laser ablation mechanism and performances of Glass Fiber Reinforced Phenolic Composites (GFRP). During the ablation process, the difference in thermal conductivities of the glass fibers and the resin matrix as well as their discrepant physical and chemical reactions form a conical ablation morphology. The formation of a residual carbon layer effectively mitigates the ablation rate in the thickness direction. A higher power density results in a faster ablation rate, while a longer irradiation time leads to a larger ablation pit diameter. To account for the variation in thermal conductivity between the fiber and resin, a macro-mesoscale model was developed to differentiate the matrix from the fiber components. Finite element analysis revealed that laser irradiation leads to phenolic decomposition, glass fiber melting vaporization, and residual carbon skeleton evaporation. The dual-scale model exhibits precise prediction capabilities concerning the laser ablation process of GFRP, and its accuracy is confirmed through the comparison of simulation and experimental results for the GFRP laser ablation process. This model provides a feasible method for performance evaluation and lifetime prediction of GFRP subjected to continuous wave laser irradiation.

Bi1.8Gd0.1Er0.05M0.05O3 (M = Pr, Sm, Dy and Y) electrolytes for intermediate temperature solid oxide fuel cells

In this study, a novel solid electrolyte system consisting of co-doped cubic phase stabilised bismuth oxide was successfully synthesized via the sol-gel method. X-ray diffraction (XRD) analysis revealed that all synthesized samples exhibited stable cubic fluorite-type structures. Notably, as the dopant ion radius decreased, a trend of increasing full width half maximum (FWHM) of the main (111) peak and crystal microstrain, along with a decrease in the average crystallite size and lattice constant, was observed. Interestingly, the sample Bi1.8Gd0.1Er0.05Pr0.05O3, possessing a dopant ion radius closest to Bi3+ (1.17 Å), exhibited exceptional electrical properties, achieving a high conductivity of 0.347 S cm−1 at 800 °C and a low activation energy of 0.20 eV for the high-temperature regions (HTR). This superior performance was attributed to the significant role played by the grain boundary volume and conductivity in facilitating ionic conduction, thus explaining the variations in conductivity among the different samples.