Surface Pore Research Articles

Balancing the Kinetic and Thermodynamic Synergetic Effect of Doped Carbon Molecular Sieves for Selective Separation of C2H4/C2H6.

Selective separation of ethylene and ethane (C2H4/C2H6) is a formidable challenge due to their close molecular size and boiling point. Compared to industry-used cryogenic distillation, adsorption separation would offer a more energy-efficient solution when an efficient adsorbent is available. Herein, a class of C2H4/C2H6 separation adsorbents, doped carbon molecular sieves (d-CMSs) is reported which are prepared from the polymerization and subsequent carbonization of resorcinol, m-phenylenediamine, and formaldehyde in ethanol solution. The study demonstrated that the polymer precursor themselves can be a versatile platform for modifying the pore structure and surface functional groups of their derived d-CMSs. The high proportion of pores centered at 3.5Å in d-CMSs contributes significantly to achieving a superior kinetic selectivity of 205 for C2H4/C2H6 separation. The generated pyrrolic-N and pyridinic-N functional sites in d-CMSs contribute to a remarkable elevation of Henry selectivity to 135 due to the enhancement of the surface polarity in d-CMSs. By balancing the synergistic effects of kinetics and thermodynamics, d-CMSs achieve efficient separation of C2H4/C2H6. Polymer-grade C2H4 of 99.71% purity can be achieved with 75% recovery using the devised d-CMSs as reflected in a two-bed vacuum swing adsorption simulation.

IrO2-ZrO2-SiO2 ternary oxide composites- based DSAs: Activity toward oxygen evolution reaction with long-term stability

BackgroundHigher purity of copper is produced by Electrowinning (EW) in the cathode. A major challenge in this technique is the anodic structure that causes in the energy consumption, corrosion resistance, and contamination of the copper produced in the cathode. MethodsTernary metallic oxide (IrO2-ZrO2-SiO2) composites with the different molar percentages of IrO2: SiO2 (10:60, 15:55, and 20:50%) were prepared on titanium substrate by the sol-gel technique, and then thermal decomposition to study the impact of IrO2 and SiO2 contents on the electrocatalyst performances of the dimensionally stable anodes (DSAs). The physicochemical properties of the DSAs were determined by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM), Atomic force microscopy (AFM), and electrochemical measurements. Significant findingsFE-SEM and AFM images display the impact of SiO2 on the crystallization and crystal growth of IrO2, leading to the formation of finer oxide particles and the porous morphology of the ternary oxide coatings. The DSA composed of 50 % SiO2 and 20 % IrO2 (IZS (20–30–50)) with a more porous surface area represented high apparent electrocatalytic activity toward the oxygen evolution reaction with long-term stability as analyzed under cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and accelerated lifetime (ALT) plots.

Role of Ripening in the Deposition of Fragments: The Case of Micro- and Nanoplastics.

Particulate contaminants, such as microplastics (1 μm to 5 mm) and nanoplastics (<1 μm), are disseminated in many terrestrial environments. However, it is still unclear how particles' properties drive their mobility through soils and aquifers due to (i) poor environmental relevance of the model particles that are studied (e.g., spherical and monodisperse) and (ii) the use of packed bed experiments which do not allow a direct observation of deposition dynamics. Using transparent 2D porous media, this study analyzes deposition dynamics of rough polystyrene fragments with irregular shapes and with a size continuum (≈10 nm to 5 μm). Using in situ and ex situ measurements, particle deposition as a function of size was monitored over time under repulsive conditions. In the absence of natural organic matter (NOM), micrometric particles rapidly deposit and promote the physical interception of smaller nanoparticles by creating local porous roughness or obstacles. In the presence of NOM, differences according to particle size were no longer observed, and all fragments were more prone to being re-entrained, thereby limiting the growth of deposits. This work demonstrates the importance of pore surface roughness and porosity of the pore surface for the deposition of colloidal particles, such as microplastics and nanoplastics, under repulsive conditions.

Evaluation of dropwise condensation from a vertical condenser tube impregnated with semisolid lubricant

AbstractThe quest for augmenting dropwise condensation heat transfer performance has been the driving force behind the exploration of innovative techniques and approaches to fulfill the desired objective. Mostly, earlier research on dropwise condensation was devoted to study condensation from horizontal tubes and plates but, rarely, addressed dropwise condensation from vertical tubes. An interesting topic of current research in dropwise condensation is to explore the application of Slippery Liquid Infused Porous Surfaces (SLIPSs) to improve the condensation performance. The aforesaid facts are the motivation behind the topics of interest in the present study. In this study, we explore the applicability of semisolid lubricant‐impregnated porous surfaces in enhancing dropwise condensation performance of a vertical condenser tube. The experiments conducted over a wide range of subcooling (5°C ≤ ΔT ≤ 65°C) in saturated steam environment showed significant improvement in condensation heat transfer coefficient of a vertical condenser tube impregnated with semisolid lubricants when compared to bare vertical condenser tube. The highest enhancement is found to be 280% at a subcooling of 40°C. Furthermore, these surfaces proficiently sustain dropwise condensation over a period of 72 hours without compromising heat transfer performance. The devised fabrication method is simpler, more cost‐effective, and less time‐consuming than earlier techniques used for creating SLIPSs. Additionally, an approach based on numerical optimization by a stochastic global optimization technique, namely, Genetic Algorithm, is proposed to retrieve the coefficients and the exponent in the mathematical expression of overall resistance, that is being used to compute the tube‐side dropwise convection heat transfer coefficient.

The Gaseous Hydrogen Transport Capacity in Nanopores Coupling Bulk Flow Mechanisms and Surface Diffusion: Integration of Profession and Innovation

Due to its unique chemical structure, hydrogen energy inherently has a high calorific value without reinforcing global warming, so it is expected to be a promising alternative energy source in the future. In this work, we focus on nanoconfined hydrogen flow performance, a critical issue in terms of geological hydrogen storage. For nanopores where the pore scale is comparable to hydrogen’s molecular size, the impact on hydrogen molecules exerted by the pore surface cannot be neglected, leading to the molecules near the surface gaining mobility and slipping on the surface. Furthermore, hydrogen adsorption takes place in the nanopores, and the way the adsorption molecules move is completely different from the bulk molecules. Hence, the frequently applied Navier–Stokes equation, based on the no-slip boundary condition and overlooking the contribution of the adsorption molecules, fails to precisely predict the hydrogen flow capacity in nanopores. In this paper, hydrogen molecules are classified as bulk molecules and adsorption molecules, and then models for the bulk hydrogen and the adsorption hydrogen are developed separately. In detail, the bulk hydrogen model considers the slip boundary and rarefaction effect characterized by the Knudsen number, while the flow of the adsorption hydrogen is driven by a chemical potential gradient, which is a function of pressure and the essential adsorption capacity. Subsequently, a general model for the hydrogen flow in nanopores is established through weight superposition of the bulk hydrogen flow as well as the adsorption hydrogen, and the key weight coefficients are determined according to the volume proportion of the identified area. The results indicate that (a) the surface diffusion of the adsorption molecules dominates the hydrogen flow capacity inside nanopores with a pore size of less than 5 nm; (b) improving the pressure benefits the bulk hydrogen flow and plays a detrimental role in reducing surface diffusion at a relatively large pressure range; (c) the nanoconfined hydrogen flow conductance with a strong adsorption capacity (PL = 2 MPa) could reach a value ten times greater than that with a weak adsorption capacity (PL = 10 MPa). This research provides a profound framework for exploring hydrogen flow behavior in ultra-tight strata related to adsorption phenomena.

Aqueous removal of Cr(VI) by Citrus sinensis juice-coated multi-walled carbon nanotubes

AbstractA novel adsorbent was prepared from multi-wall carbon nanotubes (MWCNTs) and Citrus sinensis juice extract-modified MWCNTs (OJMW) and characterized using scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR), X-ray diffractometer (XRD), BET and thermogravimetric analysis. The results showed that the nanotubes exhibited good surface area, pore size, functional groups, and robust stability at elevated temperatures (308 and 313 K). The adsorbent was applied in water for the sequestration of Cr(VI). The adsorption of Cr(VI) on MWCNTs and OJMW was influenced by factors of adsorption. Optimum removal of Cr(VI) was attained at 180 min contact time, 0.05 g adsorbent dose, and solution pH 2 for MWCNTs and OJMW. The kinetic behaviour of the Cr(VI) adsorption onto MWCNTs and OJMW was governed by the pseudo-first-order and pseudo-second-order kinetic model, respectively. The equilibrium data obtained for the uptake of Cr(VI) onto MWCNTs and OJMW fitted satisfactorily with Freundlich and Langmuir isotherm models, respectively. Meanwhile, MWCNTs and OJMW exhibited monolayer adsorption capacities (qmax) of 44.72 and 12.26 g g−1, respectively, at 298 K. The adsorption process was spontaneous and feasible. The direction of energy flow in the uptake of Cr(VI) onto OJMW and MWCNTs followed endothermic and exothermic adsorption processes, respectively. The adsorption–desorption experiments showed that OJMW had good regenerative abilities.

Nanoconfinement of Carbon Dioxide within Interfacial Aqueous/Ionic Liquid Systems.

Nanoporous, gas-selective membranes have shown encouraging results for the removal of CO2 from flue gas, yet the optimal design for such membranes is often unknown. Therefore, we used molecular dynamics simulations to elucidate the behavior of CO2 within aqueous and ionic liquid (IL) systems ([EMIM][TFSI] and [OMIM][TFSI]), both confined individually and as an interfacial aqueous/IL system. We found that within aqueous systems the mobility of CO2 is reduced due to interactions between the CO2 oxygens and hydroxyl groups on the pore surface. Within the IL systems, we found that confinement has a greater effect on the [EMIM][TFSI] system as opposed to the [OMIM][TFSI] system. Paradoxically, the larger and more asymmetrical [OMIM]+ molecule undergoes less efficient packing, resulting in fewer confinement effects. Free energy surfaces of the nanoconfined aqueous/IL interface demonstrate that CO2 will transfer spontaneously from the aqueous to the IL phase.

Amine-impregnated natural inorganic nanotubes via layer-by-layer electrostatically self-assembly approach for efficient CO2 adsorption

Developing cost-effective and high-performance solid amine adsorbents has considered as an important way to alleviate the greenhouse effect. How to precisely regulate its pore structure and surface interface characteristics, and how to cooperate to optimize the dynamic mass transfer and adsorption–desorption behavior of gas in the adsorbent are still challenging work. Herein, we demonstrated a facile and efficient approach to construct polyethyleneimine (PEI) impregnated halloysite nanotubes (HNTs) as an emerging nanocomposite for CO2 capture. Based on the natural electrostatic differences of inner and outer walls for HNTs, the hollow tubular structures of adsorbents were constructed by selective surface modification and layer-by-layer electrostatic self-assembly technology to improve the CO2 uptake capacity and cyclic stability, in which poly(sodium-p-styrene sulfonate) (PSS) and PEI were used as polyanionic and polycationic layer, respectively, to coat the inner walls of HNTs. The loading capacity of PSS-PEI composite ionic layers in HNTs and the influence of PSS polyanionic layer on PEI dispersion were specifically discussed according to the CO2 uptake capacity, adsorption heat, thermodynamics and kinetics of the adsorbents. The optimal PEI20-0.5PHNTs adsorbent exhibited a higher CO2 uptake of 0.87 mmol/g at 80 °C in the flow of 40 vol% N2/60 vol% CO2 than that of PEI20-HNTs, owing to the high amine efficiency due to the uniform dispersion of PEI in the electrostatic composite ionic layers. Furthermore, PEI20-0.5PHNTs reached 75 % of the maximum adsorption capacity at the 5th min of the adsorption process and released the most heat during adsorption at − 18.28 kJ/mol due to the presence of electrostatic composite ionic layers. PEI20-0.5PHNTs showed excellent cyclic stability with a slight loss of 7.4 %. The electrostatic self-assembled adsorbent obtained by layer-by-layer loading of PSS and PEI based on the unique surface charge characteristics of HNTs is an inspiration for the synthesis of cost-effective solid amine adsorbents for practical CO2 capture and separation.

Treatment of phenolic wastewater in an anaerobic fluidized bed microbial fuel cell filled with graphene oxide-macroporous adsorption resin as multifunctional carrier

ABSTRACT A novel graphene oxide-modified resin (graphene oxide-macroporous adsorption resin) was prepared and used as a multifunctional carrier in an anaerobic fluidized bed microbial fuel cell (AFB-MFC) to treat phenolic wastewater (PW). The macroporous adsorption resin (MAR) was used as the carrier, graphene oxide was used as the modified material, the conductive modified resin was prepared by loading graphene oxide (GO) on the resin through chemical reduction. The modified resin particles were characterized by scanning electron microscopy (SEM), Raman spectroscopy (RS), specific surface area and pore structure analysis. Graphene oxide-macroporous adsorption resin special model was established using the Amorphous Cell module in Materials Studio (MS), and the formation mechanism of graphene oxide-macroporous adsorption resin was studied using mean square displacement (MSD) of the force module. Molecular dynamics simulation was used to study the motion law of molecular and atomic dynamics at the interface of graphene oxide-macroporous adsorption resin composites. The strong covalent bond between GO and MAR ensures the stability of GO/MAR. When the modified resin prepared in 3.0 mg/mL GO mixture was used in the AFB-MFC, the COD removal of wastewater was increased by 9.1% to 72.44%, the voltage was increased by 84.04% to 405.8 mV, and power density was increased by 765.44% to 242.67 mW/m2.

Two new wood-inhabiting fungal species (Polyporales, Basidiomycota) from Yunnan Province, China

Wood-inhabiting fungi are a cosmopolitan fungal group worldwide. Two new wood-inhabiting fungal species, Rhodoantrodia purpurascens and Steccherinum wumengshanense are proposed based on a combination of the morphological features and molecular evidence. Rhodoantrodia purpurascens is characterized by the corky basidiomata with a pale lilac to lavender pore surface, a dimitic hyphal system with clamped generative hyphae, and broadly ellipsoid basidiospores. Steccherinum wumengshanense is characterized by the corticoid basidiomata having a white to cream hymenial surface, a monomitic hyphal system with clamp generative hyphae, and ellipsoid basidiospores. Full descriptions, photo plates and phylogenetic analysis results of the new species are provided.

Polymer-modified mortar flexibility of the masonry-concrete structure interface

High crack occurrences at the masonry-infilled wall partition-reinforced concrete structure interface is a problem that challenges the Brazilian construction process. Improving the mortar’s flexibility is suggested as a potential solution, but it's still not widely known. This paper evaluates industrialized mortar properties modified with four polymers and one plasticizer additive. The research methodology consisted of an experimental investigation related to the mortar properties using styrene-acrylic copolymer (SAE), polyvinyl acetate copolymer (PVAc), styrene-butadiene copolymer (SBR), white glue PVA (polyvinyl acetate), and a sulfated ethoxylated fatty alcohol salt plasticizer additive. The polymers were used in addition to (4%, 5% and 8%) and instead of (4% and 5%) the amount of water established by the manufacturer of the reference mortar, while the amount of additive used was 0.08%. The investigation characterization considered the fresh and hardened conditions, especially, the flexibility evaluation, and tests of elasticity modulus and transverse deformation were carried out, in addition to scanning electron microscopy (SEM). The results showed that there was an elasticity modulus reduction of all mixtures compared with the reference mortar without modification. The transverse deformation results range from a minimum of 0.23 mm (SBR) to a maximum of 0.94 mm (SAE). Regarding SEM, the tests with polymers have smoother and less porous surfaces. The mortar flexibility performance with different additive contents is the main contribution of this research.

Study on the gelatinization and digestive characteristics of wheat starch and potato starch under low moisture conditions

This study explored the gelatinization and digestive characteristics of wheat and potato starches under low moisture conditions using identical processing parameters. The results revealed that potato starch exhibited greater resistance to digestion than wheat starch, with an enzyme hydrolysis rate 18 % to 30 % lower than wheat starch under the same conditions. The analysis of particle size, swelling power, and low-field NMR demonstrated that potato starch required almost 40 % more moisture for full gelatinization than wheat starch, indicating that low-moisture conditions could not meet the significant water demand of potato starch. Additionally, the DSC analysis showed that potato starch had superior thermal stability, with To of 62.13 °C and ΔH of 16.30 (J/g). Subsequently, the microscopy results showed that the partially gelatinized wheat starch had a rough, porous surface, allowing enzymes for direct access to hydrolysis. In contrast, the potato starch had smoother and less damaged particles without visible pores, enzymes had to degrade it progressively, layer by layer. Furthermore, potato starch still exhibited a lower enzyme hydrolysis rate than wheat starch under the same gelatinization levels. Overall, potato starch is more resistant to hydrolysis and gelatinization in low-moisture environments, making potato starch suitable for low-digestibility products like potato biscuits or chips.

Innovative approaches: Exploring nano-biochar technology’s impact on soil properties, alachlor retention, and microbial populations

Pesticide contamination and soil degradation stand as critical challenges in the agricultural ecosystem. This study delves into the impact of nano-biochar (NBC) on soil properties, alachlor retention, and microbial populations, exploring concentrations of 1 %, 3 %, and 5 % w w−1 in both planted and unplanted alachlor-contaminated soil. A six-week black bean-pot experiment was conducted in planted soil. The NBC, distinguished by its substantial carbon content and remarkable surface area, pore volume, and diameter, resulted in significant enhancements in soil pH, moisture content (MC), and soil organic carbon (SOC). Over the 6-week period, NBC3% and NBC1 % consistently increased SOC content, while NBC5% displayed a declining trend after the 4th week. The application of NBC led to a remarkable acceleration in alachlor reduction, achieving efficiencies exceeding 77 % in unplanted soils and reaching an impressive 97.3 % in planted soils. The reduction dynamics, modeled by a first-order equation, revealed notably shorter half-lives of alachlor in NBC-treated soils compared to controls. Abundance in total plate count (TPC), phosphate-solubilizing bacteria (PSB), and nitrogen-fixing bacteria (NFB) increased with NBC1 % and NBC3 %, although NBC5 % showed a decline after the 2nd week. The findings suggest that NBC1 % and NBC3 % offer optimal outcomes for desired soil improvements, enhanced microbial activity, and effective soil pesticide removal.

Covalently grafting polycation to bacterial cellulose for antibacterial and anti-cell adhesive wound dressings

Hydrogel-based wound dressings are becoming increasingly important for wound healing. Bacterial cellulose (BC) has been commonly used as wound dressings due to its good in vitro and in vivo biocompatibility. However, pure BC does not possess antibacterial properties. In this regard, polycation gel was grafted onto the BC using a surface-initiated activator regenerated by electron transfer atom transfer radical polymerization (SI-ARGET ATRP) with subsequent quaternization for antibacterial wound dressing. Dimethylethyl methacrylate (DMAEMA) was successfully polymerized on the BC surface which was confirmed by Fourier transform infrared spectroscopy and elemental analysis. The morphology structure, specific surface area, pore size, and mechanical properties were also characterized. The quaternized PDMAEMA grafted on the BC endowed it with excellent antibacterial activity against E. coli (Gram-negative) and S. aureus (Gram-positive) with a killing rate of 89.2 % and 93.4 %, respectively. The number of cells was significantly reduced on QPD/BC hydrogel, demonstrating its good anti-adhesion ability. In vitro cellular evaluation revealed that the antibacterial wound dressing exhibited good biocompatibility. Overall, this study provides a feasible method to develop antibacterial and anti-cell adhesive hydrogel, which has a promising potential for wound healing.

Utilizing Activated Carbon Nanopores for Electrochemical Oxidation of Perylene to Redox-Active 3,10-Perylenedione: Application in Electrochemical Capacitor Electrodes.

We demonstrate that nanopores of activated carbon (AC) function as nanoreactors that oxidize perylene (PER) to a redox-active organic compound, 3,10-perylenedione (PERD), without any metal catalysts or organic solvents. PER is first adsorbed on AC in the gas phase, and the PER-adsorbed AC is subjected to electrochemical oxidation in aqueous H2SO4 as the electrolyte. Because gas-phase adsorption is solvent-free, PER is completely adsorbed on AC as long as the amount of PER does not exceed the saturated adsorption capacity of the AC, which enables accurate control of the amount adsorbed. PER is electrochemically oxidized to PERD in the nanopores of AC at above 0.7 V vs Ag/AgCl. The hybridized PERD undergoes a rapid reversible two-electron redox reaction in the nanopores owing to the large contact interface between the conductive carbon pore surfaces and PERD. The resulting AC/PERD hybrids serve as electrodes for electrochemical capacitors, utilizing the rapid redox reaction of PERD. The hybridization method is advantageous for quantitatively optimizing electrochemical capacitor performance by adjusting the amount of adsorbed PER. Moreover, because PERD hybridization in the AC nanopores does not expand the electrode volume, the volumetric capacitance increases with increasing hybridized PERD content. In three-electrode cell measurements, the volumetric capacitance at 0.05 A g-1 reaches 299 F cm-3, and 61% of this capacitance is retained at 10 A g-1 when 5 mmol of PER is used per gram of AC. Meanwhile, pristine AC delivers 117 F cm-3 at 0.05 A g-1 with a capacitance retention of 46% at 10 A g-1. Two-electrode cell measurements reveal that self-discharge is significantly suppressed by the hybridized PERD when AC/PERD hybrids and AC are used as cathodes and anodes, respectively, compared to that of a symmetrical AC cell. Moreover, PERD does not undergo cross-diffusion in the asymmetrical cells during self-discharge tests for 24 h.

Enhanced subsurface chloride transport resistance of cement pastes via optimizing CO2 curing time

The chloride erosion of CO2 cured cementitious materials could be a concern for concrete structure application. This study aims to clarify the chloride transport and binding behavior by elucidating the alteration of free and bound chloride content from the outer towards the core (5 layers with 2 mm intervals). The carbonation depth and chloride binding ratio at the carbonation zone were also determined. The results showed that dense carbonated surface significantly reduced the penetration of chloride, especially in the carbonation zone, resulting in a decrease in total chloride content (48 %–83 %) and a slight increase in the chloride binding ratio (up to 22 %). It is found that the benefits of minimizing surface porosity to impede chloride penetration significantly outweigh the drawbacks associated with the consumption of AFm phase and C-S-H gel. However, as prolonged the CO2 curing time to 7 days, the surface areas with the highest carbonation degree exhibited more chloride content than the inward partially carbonated zone. This is because excessive carbonation at early age could increase the surface pore structures, resulting in the promotion of chloride transport. It was found that the content of chloride and CaCO3 are strongly correlated with CO2 curing time, and CO2 at first 24 h curing can achieve greater benefits in reducing chloride penetration. Moreover, amorphous calcium carbonate gradually transformed into crystalline calcium carbonate during the process of chloride attack, conducive to the further improvement of the compactness of the sample.

Fabrication of superhydrophobic, permeable, and anti-reflective porous steel surfaces using laser ablation and heat treatment

Fabrication of superhydrophobic, permeable, and anti-reflective porous steel surfaces using laser ablation and heat treatment

Study on the adsorption mechanism of polar and non-polar VOCs by the activated carbon with surface oxygen

In this study, CO2 was converted to activated carbon by the molten salt CO2 capture and electrochemical conversion (MSCC-EC) method, and the surface oxygen content of the activated carbon was further modified for the adsorption of polar molecules (chlorobenzene) and nonpolar molecules (toluene), the role of the pore structure and surface O-containing functional groups of the adsorbents in contributing to the adsorption process was systematically investigated. The results showed that MS-AC500-10, MS-AC500-15, and MS-AC550-15 have rich pore structures with specific surface areas of 811.56 m2/g, 835.35 m2/g, 1249.104 m2/g, and surface oxygen contents of about 10 %, 15 %, 15 %, respectively. The toluene adsorption capacity of MS-AC500-10, MS-AC500-15, and MS-AC550-15 was 203.82 mg/g, 229.72 mg/g, and 358.97 mg/g, respectively, and was dominated by pore adsorption, which was positively proportional to the specific surface areas and pore volumes, the adsorption process belonged to the pseudo-first-order kinetic model. The adsorption amounts of chlorobenzene by MS-AC500-10, MS-AC500-15, and MS-AC550-15 were 287.98 mg/g, 363.11 mg/g, and 495.41 mg/g, respectively. In addition to the pore adsorption, the oxygen content on the surface of the adsorbents had a non-negligible promotion effect on the adsorption of chlorobenzene, mainly because chlorobenzene is a polar molecule, and the asymmetric electrons on its surface have strong interactions with the O-containing functional groups on the surface of the adsorbents. Moreover, the prepared adsorbents were thermally stable, and the decay rate of adsorption performance was less than 5 % after five adsorption–desorption cycles.

A new study on the effects of clay nanoparticles on the corrosion performance of Al-Si-Cu matrix composites in both acidic and alkaline solutions

In this paper, the influence of clay nanoparticles on the corrosion properties of the Al-Si-Cu matrix was investigated. The nanocomposite fabricating method was stir-casting when stirring times and temperatures were variables to change nanocomposite characteristics. Several corrosion tests were performed to examine the relationship between the microstructure and the degradation mechanism of various fabricated nanocomposites. Tafel polarization measurements indicated a lower corrosion rate for all nanocomposites compared to the Al-Si-Cu matrix in 0.1 M NaOH solution. The reduction range was 23.6–79.0% based on the smaller size of Si precipitates. In this situation, the interconnection of surface pores was lowest. However, electrochemical impedance spectroscopy (EIS) results showed that nanocomposite impedance would be increased up to 99.7% in comparison to the matrix without clay nanoparticles in 1 M HCl solution when the stirring temperature was 750 °C. EIS calculation also displayed that an increase (about 17.1–50.8%) in the nanocomposite resistance would be achieved when the stirring time was 2 min in 0.04 H2SO4 solution. The reason could be attributed to the larger size of Si particles since coarse precipitates were more effective agents to act as barriers for anodic dissolution of the lower layer of the Al-Si-Cu matrix when Tafel polarization tests demonstrated that the anodic reaction controlled the corrosion rate of the aluminum matrix.

Investigating radiative heat transfer, varied wall thickness, and slip effects on Casson nanofluid flow over a stretched sheet with heat source

ABSTRACT Understanding the intricate interplay between variable fluid properties such as slip and thermal conductivity when flowing over porous surfaces is of utmost importance for a wide range of engineering applications. This investigation delves into this uncharted territory, connecting the analytical capabilities of HAM (Homotopy Analysis Method) to reveal captivating insights into the impact of these variables on the dynamics of Casson nanofluid flow. Besides, we documented the flow aspects which include thermal radiation, heat source, variable wall thickness and chemical reaction. We alter the partial differential flow-related conditions into nonlinear ordinary ones employing the similarity transformation approach. Then, using a popular semi-analytical technique known as the Homotopy Analysis Method (HAM), we were able to untangle them. This method yields to power series solutions to nonlinear differential equations. To illustrate the impact of the velocity, temperature and concentration profiles, parametric research has been done using tables and diagrams. In the limiting sense, the numerical results of our methodology are in great association with the outcomes of previous research. Finally, it is noted that higher values of the velocity slip parameter cause an enhancement in fluid velocity, while escalating values of the thermal slip parameter cause a decline in temperature distribution.