Alumina Research Articles

High temperature oxidation mitigation efficacy of Al2O3 and Ni-20Cr ceramic coating on boiler steel application

The primary reason of degradation and failure of many products used for high temperature applications are oxidation. Protective coatings are employed to increase the component resistance to oxidation. In the present research work, Al2O3 and Ni-20Cr were applied as coatings on SAE431 steel using a detonation gun spraying technique. At 800 °C in air with 50 cycles of heating and cooling, the oxidation behavior of uncoated and coated SAE-431 boiler steel was analyzed. Ni-20Cr coating on SAE431 boiler steel exhibits approximately 25.44 % higher oxidation resistance and the Al2O3 coating on SAE431 boiler steel exhibits approximately 32.22 % higher oxidation resistance compared to uncoated SAE431 boiler steel. After oxidation at 800 °C, the SAE431 boiler steel coated with Ni-20Cr displays prominent peaks of the Cr2O3 and Ni phases, with some minor phase of NiO. The NiO phase is observed to be less intense than Cr2O3 and Ni phases. After oxidation at 800 °C, Al2O3 coated SAE431 boiler steel exhibited strong peaks of ƞ-Al2O3 and δ-Al2O3 phases. The X-ray diffraction investigation also reveals the existence of the α-Al2O3 phase. According to our findings, based on weight change data, Ni-20Cr and Al2O3 coated boiler steel provided higher oxidation resistance than the uncoated SAE431boiler steels. The enhancement in the oxidation resistance of boiler steel can be attributed to the formation of nickel, chromium and aluminum oxide inert layer which is evident from the XRD patterns also. Exploration throughout global survey has been already done and it was found that not much work has been done on the high-temperature behavior of Ni-20Cr and Al2O3 coatings. The data obtained from the study will be helpful in examining the viability of using these coatings on boiler tubes.

A sorbent modified with melatonin and lithium: in vitro investigation of the effect on hemostatic reactions

Aim of the study was to evaluate the effect of lithium- and melatonin-containing sorbent based on aluminum oxide and polydimethylsiloxane on changes in the number of platelets during hemosorption modeling and on the features of the hemostatic response during dosed contact of the sorbent with blood in an in vitro experiment. Material and methods. An analysis of the effect of the porous sorbent modified with melatonin (MT, 0.15 %) and lithium (0.5 %) based on aluminum oxide and polydimethylsiloxane (Al2O3@PDMS/MT-Li) was carried out in comparison with sorbent without modifiers (Al2O3@PDMS) and modified with MT (Al2O3@PDMS/MT) on a number of donor blood clotting parameters under in vitro hemosorption conditions. Studies of the hemostatic system included assessment of platelet count, chronometric parameters, fibrinogen concentration, antithrombin activity and plasminogen content. For integral assessment, calibrated thrombography and computer thromboelastometry were used. Results and discussion. Contact of all studied sorbents with blood causes a moderate decrease in the number of platelets (by 5.3–10.1 % from initial). Comparison sorbents reduce fibrinogen concentration by 7.1–7.7 %, Al2O3@PDMS/MT-Li – by 2.6 times, which is likely due to the methodology for determining this protein against the background of the independent anticoagulant activity of lithium ions. Al2O3@PDMS and Al2O3@PDMS/MT cause the development of a hypercoagulable shift, as evidenced by a shortening of kaolin time (by 27.5 and 22.1 %, respectively) and of activated partial thromboplastin time (APTT) by 7.1 % for both sorbents. At the same time, when lithium was included in the sorbent, not only did the hypercoagulation shift not occur, but blood clotting was also inhibited, as evidenced by an increase in kaolin time and APTT by 1.2 and 1.6 times, respectively, as well as in silicone time. Conclusions. Modifying sorbents with biologically active substances, lithium and MT, makes it possible to obtain an original hemosorbent with new properties. The presented results demonstrated the absence of a hypercoagulable shift in donor blood after contact with a lithium-, MTcontaining sorbent in vitro and indicate the potential for its using as a basis for the development of safe drugs.

Characterizing the effects of SiC and Al2O3 on the mechanical properties of Al6082 hybrid metal matrix composites: An experimental and neural network approach

The use of advanced materials in the field of aerospace and automotive applications has led to use of metal matrix composites (MMC’s) due to their excellent mechanical properties. Aluminium metal matrix composite is one of the materials which can be strengthened by reinforcing it with hard ceramic particles. In the current work Al6082 matrix hybrid composites reinforced with silicon carbide (SiC) and aluminium oxide (Al2O3) was developed by using stir casting technique. The weight percentage of SiC was varied from 0 wt.% to 8 wt.% and keeping 3 wt.% Al2O3 constants. The tensile, hardness, density and impact tests were conducted, and the results obtained revealed that the addition of silicon carbide and Al2O3 particles in Al6082 enhances the mechanical properties of the prepared hybrid composites. The artificial neural network (ANN) model, which was trained using a dataset consisting of experimental results, has effectively captured the correlation between the weight percentage (wt.%) of silicon carbide (SiC) and the mechanical properties of the composite material. Through the examination of this model, valuable insights can be obtained regarding the distinct contributions of SiC to the mechanical properties of Al6082.

The oxide films formed under the low oxygen pressure in a particular system containing competing chromium and aluminium

AbstractIn this paper, pre‐oxidation treatment was carried out at 950 °C under oxygen pressure of 10−16 atm for nickel‐10 % chromium‐x % aluminium‐1 % silicon‐0.5 % yttrium(x=0 wt.–%, 1 wt.–%, 3 wt.–%, 5 wt.–%) alloys. Morphology and structure of oxide layers on the alloys after pre‐oxidation were analyzed by scanning electron microscopy and electron discharge spectroscopy. The results showed that a chromium oxide film was formed on the surface of the alloy without aluminium addition, while the oxide layer on the surface of the alloy with aluminium addition gradually transformed into M2O3 (M=aluminium and chromium) oxide film. The oxidation behavior was analyzed by means of chemical thermodynamics, and it was seen that because the interaction coefficient,εijof aluminium and chromium is a positive value, the increase of aluminium addition will strengthen the interaction and increase the diffusion coefficient,Diof aluminium and chromium. The diffusion of chromium and aluminium in each other therefore promotes their interaction, which is beneficial to the formation of the outer oxide film. Thus, with the increase of aluminium addition, the thickness of the outer oxide film gradually increased, and the aluminium content in M2O3 (M=aluminium and chromium) increased significantly, and with 5 % aluminium added, the aluminium oxide of the outer oxide film became the main body.

Spreading anomaly semantic segmentation and 3D reconstruction of binder jet additive manufacturing powder bed images

Variability in the inherently dynamic nature of additive manufacturing introduces imperfections that hinder the commercialization of new materials. Binder jetting produces ceramic and metallic parts, but low green densities and spreading anomalies reduce the predictability and processability of resulting geometries. In situ feedback presents a method for robust evaluation of spreading anomalies, reducing the number of required builds to refine processing parameters in a multivariate space. In this study, we report layer-wise powder bed semantic segmentation for the first time with a visually light ceramic powder, alumina, or Al2O3, leveraging an image analysis software to rapidly segment optical images acquired during the additive manufacturing process. Using preexisting image analysis tools allowed for rapid analysis of 316 stainless steel and alumina powders with small data sets by providing an accessible framework for implementing neural networks. Models trained on five build layers for each material to classify base powder, parts, streaking, short spreading, and bumps from recoater friction with testing categorical accuracies greater than 90%. Lower model performance accompanied the more subtle spreading features present in the white alumina compared to the darker steel. Applications of models to new builds demonstrated repeatability with the resulting models, and trends in classified pixels reflected corrections made to processing parameters. Through the development of robust analysis techniques and feedback for new materials, parameters can be corrected as builds progress.

Doping dependence of boron–hydrogen dynamics in crystalline silicon

In this contribution, we investigate the formation and dissociation of boron–hydrogen (BH) pairs in crystalline silicon under thermal equilibrium conditions. Our samples span doping concentrations of nearly two orders of magnitude and are passivated with a layer stack consisting of thin aluminum oxide and hydrogen-rich silicon nitride (Al2O3/SiNx:H). This layer stack acts as a hydrogen source during a following rapid thermal annealing. We characterize the samples using low-temperature Fourier-transform infrared spectroscopy and four-point-probe resistivity measurements. Our findings show that the proportion of hydrogen atoms initially bound to boron (BH pairs) rises with increasing boron concentration. Upon isothermal dark annealing at (163 ± 2) °C, hydrogen present in molecular form, H2, dissociates at a rate directly proportional to the concentration of boron atoms, ∝ [B−], leading to the formation of BH pairs. With prolonged annealing, an unknown hydrogen complex is formed at a rate that is inversely proportional to the square of the boron concentration, ∝ 1/[B−]2, resulting in the disappearance of BH pairs. Based on experimental observations, we derive a kinetic model in which we describe the formation of the unknown complex through neutral hydrogen H0 binding to a sink. Additionally, we investigate the temperature dependence of the reaction rates and find that the H2 dissociation process has an activation energy of (1.11 ± 0.05) eV, which is in close agreement with theoretical predictions.

Repair strength of 3D-printed denture base resins: Effect of surface treatment and repair material type.

The aim of the study was to investigate the effect of surface treatment and repair materials on the flexural strength of repaired 3D-printed denture base resins after thermal aging. Bar-shape specimens (64×10×3.3mm) were designed as intact (control) specimens while repair specimens were printed in sections with 2.5mm space for repair material. Printing was performed with either ASIGA or NextDent denture base material. In each material, one group received no surface treatment, while other repair groups were subjected to one of three surface treatments: (1) monomer application, (2) aluminium oxide particles-abrasion, or (3) both methods (aluminum oxide particles-abrasion and monomer application). Pairs were fixed in a customized mold then repaired with either autopolymerizing acrylic resin or flowable composite (n = 9). Repaired specimens were incubated for 48h at 37°C in distilled water and then subjected to thermal cycling (5000 cycles). A 3-point bending test was used to evaluate the flexural strength using a universal testing machine, and mode of failure determined followed by fractured surface analysis using scanning electron microscope. Data were analyzed using ANOVA and post hoc Tukey test (α = 0.05). Both resin materials showed a significant decrease in the flexural strength of repaired specimens when compared to control ones (p<0.001). Groups with no surface treatment had significantly lower flexural strength than those with surface treatment (p<0.001). Groups treated with monomer application, and with aluminum oxide particles abrasion plus monomer application had similar flexural strength values (p>0.05), which were higher than those treated with aluminum oxide particles abrasion alone (p<0.001). Specimens repaired with composite resin showed higher flexural strength than those repaired with auto-polymerized resin (p<0.05) however, specimens treated with aluminum oxide particles abrasion alone had similar values for both repair materials (p = 0.95). Adhesive failure was dominant in all repaired groups with auto-polymerized while cohesive and mixed were dominant with composite repair groups. Surface treatment improved the repair strength of 3D-printed denture base resins. Using composite resin for repair shows better strength with dominant cohesive and mixed failure suggesting that surface treatment and composite repair are suitable procedures for 3D-printed denture base repair.

Enhanced OSL emission from α- Al2O3 produced in the presence of halloysite nanocrystals

Aluminum oxide (Al2O3) compounds are extensively used in ionizing radiation dosimetry due to their high sensitivity when doped with carbon. However, their production is difficult and expensive, leading to much research on alternative ways to increase its sensitivity. This paper proposes a seed-mediated synthesis of α-Al2O3 by the combustion method with halloysite nanocrystals as seeds, which also have the ability to scavenge heavy metal ions. The dosimetric features were studied by radioluminescence (RL), thermoluminescence (TL), and optically stimulated luminescence (OSL). Scanning electron microscopy images and X-ray diffraction patterns pointed to the halloysite nanotubes (HNT) acting as heterogeneous nucleation seeds, and as adsorber centers for the chromium ions (Cr3+), as evidenced by the decreased crystallite size and Cr3+ RL emission. Decreased TL intensity upon increasing HNT content in addition to the RL data suggested that the Cr3+ ions strongly participate in the TL emission process as a luminescent center. Remarkable 6-fold enhanced OSL area intensity and 69-fold OSL initial intensity enhancement were registered from the samples seed-mediated by HNT, revealing that, by scavenging Cr3+, the HNT eliminated a luminescent center that competes with the OSL emission. Therefore, HNTs are promising nanomaterials to enhance the sensitivity of Al2O3 dosimeters with potential application in medical physics, where a decrease in the density of concurrent luminescent centers and an increase in OSL intensity were evidenced by the presence of HNT in Al2O3.

Utilizing Nano-Adsorbents and Electrostatic Field Treatment for Sustainable Refinement of Crude Canola Oil.

Removal of polar impurities, such as phospholipids, free fatty acids (FFA), and peroxides, can be challenging during the refining of crude canola oil. Current conventional refining methods are energy-intensive (e.g., hot water washes) and can generate significant waste (e.g., wastewater effluent) and neutral oil loss. This study investigated the joint use of nano-adsorbents and electrostatic field (E-field) treatment as a potential and sustainable alternative in removing these impurities during the oil refining process. Specifically, aluminum oxide (Al2O3) nanoparticles were employed to neutralize FFAs, achieving a 62.4% reduction in acid value while preserving the fatty acid profile of the oil. After refining, E-field treatment was successful in removing the spent nano-adsorbent from solution (up to 72.3% by weight), demonstrating enhanced efficiency compared to conventional methods (e.g., gravitational settling, filtration, and centrifugation). The neutral oil loss using Al2O3 nano-adsorbents was also comparable to conventional refining methods, with a 4.38% (by weight) loss. After E-field treatment, the Al2O3 nano-adsorbent was then calcined to assess reusability. The Al2O3 nano-adsorbent was effectively recycled for three refining cycles. the methods do not use of large amounts of water and generate minimal waste byproducts (e.g., effluent). Nonetheless, while the nano-adsorbents demonstrated promising results in FFA removal, they were less effective in eliminating peroxides and pigments. E-field techniques were also effective in removing spent nano-adsorbent; although, optimization of E-field parameters could further improve its binding capacity. Finally, future studies could potentially focus on the physicochemical modifications of the nano-adsorbent material to enhance their refining capacity and reusability. Overall, this study presents a sustainable alternative or addition to conventional refining methods and lays the groundwork for future research.

Experimental investigation on an innovative serpentine channel‐based nanofluid cooling technology for modular lithium‐ion battery thermal management

AbstractMany nations have committed to becoming carbon neutral by 2050 as a means of addressing the global warming challenge. To achieve carbon neutrality, transportation is one of the most essential and important tasks. Energy‐efficient pure electric vehicles (EVs) and hybrid electric vehicles (HEVs) with green energy power are being developed in response to the worldwide energy and environmental crises, as the potential replacements for the current generation of combustion‐engine automobiles. EVs require batteries more than ever before. In this perspective, lithium‐ion batteries (LIBs) stand out as remarkable energy storage technologies and have been widely used due to their numerous impressive benefits. Owing to LIBs sensitivity to temperature, EVs typically use the battery thermal management system (BTMS). The working temperature span of a lithium‐ion battery in an electric car is 15°C–35°C, which is achieved by the use of a BTMS. The production of internal heat during charging and discharging also affects how well lithium‐ion batteries work. A battery heat control system is therefore required. The temperature of the LIB pack might be efficiently controlled by liquid‐cooled systems in discharge and charge scenarios. Based on Al2O3 nanofluid (NF), the current experimental study suggests a novel active cooling technology for regulating the heat produced by the 18650‐format lithium‐ion batteries. A thorough analysis is conducted on the impact of charge/discharge C‐rates, Al2O3 nanoparticle (NP) volume fractions, inflow coolant velocity, and intake liquid temperature on the thermal efficiency of the LIB pack. By incorporating aluminum oxide NPs into the water at varying volume fractions of 0.3%, 0.5%, and 1%, the LIB pack's maximum temperature was significantly reduced by 7.9%, 18.09%, and 19.56%, respectively. With increase in mass flow rate of coolant from 0.0290 to 0.5810 kg/s, the maximum temperature has been substantially reduced by 3.7%–8.6%. Results show that using higher fluid inflow temperature significantly increased both the highest experienced temperature and temperature diversity throughout the discharge operation by about, 6°C and 5°C, respectively. The outcomes of the study indicate that NFs exhibit superior cooling performance compared to conventional coolants such as water and ethylene glycol.

Transition Metal Parent Alumylene Complexes: Synthesis, Structures, and XPS Characterization of Aluminum Oxidation State.

The first isolation and characterization of transition metal complexes with the parent Al(I)-H unit were achieved in base-stabilized forms. W and Fe complexes, Cp*(CO)n(H)M←:AlH(NHC)2 (NHC = N-heterocyclic carbene, n = 1 or 2), were synthesized in 43-63% yields by the one-step reaction of Cp*M(CO)n(py)Me with H3Al·NHC. The characterization included 1H and 27Al nuclear magnetic resonance (NMR), and infrared (IR) spectroscopic analysis, as well as DFT calculations, which revealed the extremely strong σ-donating ability of the :AlH(NHC)2 ligand, and the highly polarized M(δ-)←:Al(δ+) coordination bonds. The monovalent oxidation state of the Al center of these complexes was confirmed by X-ray photoelectron spectroscopy (XPS). The hydroalumination of carbodiimide and the reduction of CO2 to CO were also demonstrated.

Structurally Defined Amphiphilic AAO Membranes Using UV-Assisted Thiol-Yne Chemistry: Applications in Anti-Counterfeiting and Electronics.

In this study, we fabricate and characterize amphiphilic anodic aluminum oxide (AAO) membranes using UV-triggered thiol-yne click reactions and photomasks for various innovative applications, including driven polymer nanopatterns, anti-counterfeiting, and conductive pathways. Specifically, we synthesize 10-undecynyl-terminated-AAO membranes and subsequently prepare amphiphilic AAO membranes with superhydrophilic and superhydrophobic regions. Various analytical methods, including grazing angle X-ray photoelectron spectroscopy (GIXPS), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), nanofocused synchrotron X-ray techniques (nano-XRD and nano-XRF), and water contact angle measurements, confirm the modifications and distinct properties of the modified areas. This work achieves a series of applications, such as driven polymer nanopatterns, solvent- and light-triggered anti-counterfeiting, and region-selective conductive pathways using silver paint with lower resistivity. Besides, the amphiphilic AAO membrane exhibits successful stability, durability, and reusability. To sum up, this study highlights the versatility and potential of amphiphilic AAO membranes in advanced material design and smart applications.

Influence of Steel Slag as a Partial Replacement of Aggregate on Performance of Reinforced Concrete Beam

Amidst the global pursuit of sustainable alternatives in concrete production, this study explores the viability of incorporating by-products or waste materials as aggregates to support the concrete construction industry, with a specific emphasis on steel slag. The objective of this study is to evaluate the effectiveness of steel slag as a partial replacement for fine and coarse aggregates in concrete production. The experiment involved casting 30 cubes and 10 beams, replacing fine aggregate from 0 to 60%. Flexural and compressive strength tests at 7 and 28 days followed the ACI method. Results revealed that a 30% replacement of fine aggregate with steel slag led to higher compressive strength at both 7 and 28 days, while a 45% replacement showed superior flexural strength at 28 days. Further chemical analysis and optimization are recommended for deeper insights. The study concludes with marginal improvements in compressive and flexural strength with steel slag partial replacement, identifying 30% for fine aggregate and 45% for coarse aggregate as optimal replacements. In addition, the mineral composition of steel slag exhibits significant variability, with compounds, including silicon dioxide (SiO2), iron oxide (Fe2O3), manganese oxide (MnO), aluminum oxide (Al2O3), and calcium oxide (CaO). Chemical analysis indicates high silicate content and minimal alkali content, contributing to enhanced strength during concreting. Higher steel slag replacement reduces workability, confirmed by slump tests. However, all mixes maintain a true slump, and unit weight increases with steel slag aggregate replacement. Compressive strength improves incrementally with higher steel slag content, echoing prior research. In addition, flexural strength rises with steel slag replacing both coarse and fine aggregates, suggesting enhanced performance in reinforced concrete structures. These findings highlight steel slag’s potential as a sustainable alternative in concrete production, aiming to advance its application in the construction industry, promoting environmental sustainability and economic viability.

Enhanced biohydrogen production from thermally hydrolysed pulp and paper sludge via Al2O3 and Fe3O4 nanoparticles

The growing demand for sustainable and green energy sources has led to increasing interest in biohydrogen production from renewable biomass feedstocks. In this study, pulp and paper sludge (PPS), a widely available waste residue, was thermally treated at different temperatures (90°C, 130°C, and 165°C) for varying durations (15, 30, and 60 min). Thermal hydrolysis of PPS increased the chemical oxygen demand (COD) solubilization from 11 % to 24.7 %, and volatile suspended solids (VSS) solubilization up to 15 % with increasing both hydrolysis temperature and reaction time. The resulting thermally treated samples were then evaluated for biohydrogen production through a batch assay. Among the different thermal treatment conditions, the sample treated at 165°C for 60 min exhibited the highest biohydrogen production potential and yield (1287 mL-H2 and 201 mL-H2/g volatile solids (VS)), which is 72 % higher the control untreated PPS (747 mL-H2 and 117 mL-H2/gVS). To further enhance the biohydrogen yield, this optimal sample was mixed with two types of chemically synthesized nanoparticles, namely aluminium oxide (Al2O3) and magnetite (Fe3O4), at various concentrations (50, 100, and 200 mg/g VS). The addition of nanoparticles significantly influenced the biohydrogen production from the thermal-treated PPS. Remarkably, the batch assay mixed with 200 mg of Fe3O4 nanoparticles per gram of VS demonstrated the highest biohydrogen production potential, compared to the thermally treated PPS (1577 vs. 1226 mL-H2). This finding suggests that the presence of Fe3O4 nanoparticles enhances the biohydrogen production process, possibly through improved microbial activity and substrate accessibility. The results of this study highlight the potential of utilizing PPS, an abundant waste product, as a valuable feedstock for biohydrogen production. Overall, this study contributes to the advancement of green energy technologies and underscores the potential of biohydrogen as a renewable and sustainable energy source.

Metallic Coatings Boost the Cooling Power of Nanoporous Alumina.

Passive daytime radiative cooling (PDRC) has emerged as a promising strategy to mitigate the increasing impact of heat waves. However, achieving effective PDRCs requires cost-effective, ecofriendly, and industrially scalable materials. In this study, we investigate the potential of anodic aluminum oxide (AAO) nanostructures coated with metals as passive radiative coolers. We explore the effects of different metallic coatings (Al and Au) with varying thicknesses (ranging from 20 to 100 nm) on the cooling performance of the AAO nanostructures. Our finding reveals a maximum temperature reduction (ΔT) of 12.5 °C for 60 nm of Au coating. Furthermore, we demonstrate the dependence of the cooling performance on ambient temperature, emphasizing the practical benefits of these enhanced AAO-based radiative coolers for real-world applications. Notably, our results surpass previous works, offering an avenue to enhance the PDRC capability.

Optimization of heat transfer properties in micropolar ternary (Al2O3 + TiO2 + SiO2/water) nanofluid with porosity and magnetic field effects

Decades of study provide substantial evidence supporting that nanofluids possess improved heat transmission capabilities. Optimal qualities of nanoliquids may be achieved by manipulating the volume concentration of the nanoparticles. Nevertheless, this method has constraints due to the balance between negative and positive viscosity. A recent advancement has been produced in creating and thoroughly examining a particular form of hydraulic fluid that incorporates three solid nanoparticles scattered inside an existing fluid. This improvement aims to tackle this limitation. This study investigates the characteristics of a micro-rotational incompressible micropolar ternary hybrid nanofluid in a porous media. It considers the influence of magnetohydrodynamics, Darcy-Forchheimer, and linear thermal radiations on a stretched surface. The nanofluid consists mostly of water, which is blended with titanium oxide, aluminum oxide, and silicon oxide nanoparticles. Using dimensionless similarity transformations, the collection of higher-order non-dimensional partial differential equations is converted into higher-order ordinary differential equations. The BVP4C technique in MATLAB software is used to solve these equations and assess the graphical and tabular outcomes. The graphical analysis examines the influence of various physical characteristics. The heat transfer of a ternary hybrid nanofluid is significantly affected by many factors, including the Forchheimer coefficient, Prandtl number, thermal radiation parameter, and magnetic field parameters, as seen. The research demonstrates that an increase in the magnetic field and Darcy-Forchheimer parameters reduces linear momentum. Conversely, increased porosity, magnetic field, and radiation parameters increase the temperature profile.

Effect of aluminum and ammonium perchlorate particle sizes on the condensed combustion products characteristics of aluminized NEPE propellants

Aluminum (Al) is usually added to solid propellants to improve the combustion performance, however the condensed combustion products (CCPs) especially the large agglomerates generated from aluminum combustion can reduce the specific impulse of the engine, and result in two-phase loss, residue accumulation and throat liner ablation. Al and ammonium perchlorate (AP), as important components of NEPE propellants, can affect the formation process of the CCPs of aluminized NEPE propellants. To clarify the effect of Al and AP particle sizes on the properties of the CCPs of aluminized NEPE propellants, a constant-pressure quench vessel was adopted to collect the combustion products of four different formulations of NEPE propellants. It was found that the condensed combustion products are mainly divided into aluminum agglomerates and oxide particles, the diameter of the aluminum agglomerates of these four different formulations of NEPE propellants at 7 MPa was smaller than that in 3 MPa, and the shells of the aluminum agglomerates were smoother and the spherical shape was more perfect. X-ray diffraction analysis of the CCPs of the four NEPE propellants under 3 MPa revealed the presence of both Al and Al2O3. With the increase of the particle size of Al and AP, the oxidation degree of aluminum particles decreases. The particle size of the CCPs of the four different formulations of NEPE propellants under 1 and 3 MPa was analyzed by using a laser particle size analyzer, it is found that the increase of AP particle size is helpful to reduce the size of condensate combustion products. Based on the classical pocket theory, establishing a new agglomeration size prediction model, which can be used to predict the agglomeration size on the burning surface. Compared with the empirical model, the new agglomeration size prediction model is in good agreement with the experimental results.

Nanofluidic ion-exchange membranes: Can their conductance compete with polymeric ion-exchange membranes?

Nanofluidic membranes (NFMs) are gaining prominence as alternative ion-exchange membranes, because of their distinct selectivity mechanism, which does not rely on functional groups on a polymeric backbone but rather on charged nanopores that allow straight ion-conductive pathways for efficient ion transport. We measured the conductivity of commercial anodized aluminum oxide membranes with different pore sizes under different current densities and electrolyte concentrations. We also simulated a nanopore channel with charged walls between two electrolyte reservoirs. Our findings indicate that electrolyte concentration is the main parameter that determines NFM conductivity, with a linear dependence at least up to 1 M. Our study shows that the optimal pore length is between 0.5 and 5 μm considering the trade-off between selectivity and conductance. On the other hand, the conductance is not sensitive to the pore diameter. Conical nanopores are a way to increase conductance, but according to our results, this increase comes at the expense of selectivity. Our findings suggest that NFMs can outperform polymeric ion-exchange membranes in certain electrochemical applications, such as reverse electrodialysis, but not in applications that use low electrolyte concentrations on both sides of the membrane.

Quantitative analysis of heat and mass transfer in MoS2-Al2O3/EG hybrid flow between parallel surfaces with suction/injection by numerical modeling of HPM method

This description focuses on how the magnetic field affects mass and heat transfer in a hybrid nanofluid (Hnf) between two parallel, rotating plates. By dispersing aluminum oxide (Al2O3) and molybdenum disulfide (MoS2) nanoparticles (NPs) in ethylene glycol (EG), a hybrid nanofluid (Hnf) is created. This research aims to analyze the heat and mass transfer characteristics in the flow of a hybrid nanofluid (MoS2-Al2O3/EG) between two rotating parallel plates under the influence of a magnetic field. Furthermore, the statistical technique of response surface methodology (RSM) has been employed to optimize the parameters of velocity, temperature, and concentration of the nanofluid within the flow region bounded by the rotating plates. Dimensionless differential equations have been calculated and checked using the Homotopy perturbation method. This study introduces a novel approach by utilizing the RSM method to identify optimal points for velocity and temperature parameters of nanofluids between two stretching plates for the first time. Additionally, the article innovatively applies the exact HPM method to validate dimensionless linear and non-linear coupling equations. As the Reynolds number and the suction/injection coefficient of nanofluids flowing between two plates under tension increase, the results indicate a decrease in the velocity field. This decrease in velocity field can be attributed to the reduction in fluid diffusion as viscous forces diminish with varying Reynolds numbers. The ideal temperature distribution for nanofluids flowing between two parallel plates occurs when they are uniformly dispersed at the midpoint between them. As the distance from the initial point of nanofluid entry to the end of the plates increases, along with the vertical distance from the bottom plate, the temperature gradient diminishes, reducing the thickness of the thermal boundary layer. The velocity gradient and the rate of heat flux transfer between the nanofluid and plate rise by 34 % when the volume percentage is raised from 1 % to 5 %.

High strength of SiC–AlN–TiB2–VC multiphase ceramics induced by interface reactions

In this work, SiC–AlN–TiB2–VC multiphase ceramics with high bending strength were prepared via spark plasma sintering (SPS) at 1900 °C-2100 °C. The effects of interface reactions and solid solution reactions on microstructure and mechanical properties of these multiphase ceramics were investigated. Results show that the densification of multiphase ceramics is promoted effectively by the addition of Y2O3. Yttrium aluminum oxide with low melting point is formed due to the reaction between Al2O3 (on the surface of AlN) and Y2O3, which promotes the densification of SiC multiphase ceramics. Solid-solution reaction and interface reaction occur between matrix (SiC) and reinforcing phases (AlN, TiB2, and VC). Furthermore, solid-solution reactions occur between SiC and AlN, between AlN and TiB2, and between TiB2 and VC. Al5C3N phase is generated by interfacial reaction between SiC and AlN. Layered, rod-like BN(C) phase is formed at grain boundaries due to the reaction between AlN and B2O3 on the surface of TiB2 particles. Mechanical strength of multiphase ceramics is improved by the formation of solid solutions and the occurrence of these interfacial reactions. When sintered at 2000 °C, SiC multiphase ceramics with added Y2O3 exhibit excellent properties, including relative density of 99.8 %, Vickers hardness of 27.1 GPa, and bending strength of 666 MPa.