Nano Al2O3 Research Articles

Enhanced Study of CO2 Hydrate Formation in Marine Oil–Gas Based on Additive Effect

During marine oil–gas extraction, significant amounts of carbon dioxide (CO2) gas are often produced. Effectively separating these associated CO2 gases during extraction has become a critical technical challenge. Therefore, this paper aims to enhance the efficiency of CO2 hydrate-based capture technology and conduct relevant research. The goal is to increase the driving force for hydrate formation by combining the traditional thermodynamic additive TBAB with pressure modulation and to improve the hydrate formation rate through the use of multiple kinetic promoters. This paper presents the initial investigation into the effect of the thermodynamic accelerator tetrabutylammonium bromide (TBAB) on the characteristics of CO2 hydrate formation. The promotion effects of TBAB solutions with varying mass concentrations (3%, 5%, 7.5%, 10%) and reaction pressures (3 MPa, 4 MPa) were subjected to a systematic analysis, and the optimal conditions were identified as 4 MPa and a 5 wt% TBAB concentration. Subsequently, the impact of combining TBAB with kinetic promoters (SDS, nano Al2O3, L-methionine, L-leucine) on CO2 hydrate generation characteristics was further investigated. In this paper, the effect of a single promoter on the generation characteristics of CO2 hydrate was investigated, and the efficient carbon trapping ability of the complex promoter was verified, which provides theoretical support for the application of CO2 trapping technology using the hydrate method.

Experimental investigation on bond properties of nano-Al2O3 and hydroxypropyl methyl cellulose (HPMC) modified coated steel bar embedded in concrete

In this work, cementitious coatings incorporate nano-Al2O3 (NA) and HPMC were developed applying to the surface of steel bars to enhance bond behavior. A total of 81 pull-out specimens were prepared to evaluated bond properties of different coated steel bars embedded in ordinary performance concrete (OPC), high performance concrete (HPC) and ultra-high-performance concrete (UHPC). The mechanical properties of the cement-based coatings have also been examined. Test results show that flexural and compressive strengths of coating paste exhibited initially increasing and followed by decreasing as NA content increase. Synergistic effect of NA and HPMC results in cement-based coating exhibiting superior mechanical properties. Besides, coating microscopic morphology characterized by scanning electron microscope (SEM) technique revealed that fewer coating defects with NA and HPMC compounding. More importantly, the highest bond strength between coated steel bar and different types concretes was found at 1.0 % NA content in the coatings. Synergistic effect of 1.0 % NA and 0.12 % HPMC improved bond strength of coated steel bar embedded in OPC, HPC and UHPC. It can be obtained from bond-slip curve that, regardless of the HPMC addition to coatings, coated steel bar with 1.0 % NA content shows higher bond stiffness. With both NA and HPMC added, bond stiffness, bond toughness and bond ductility of coated steel bar are superior to those of the coating with NA alone. Moreover, as concrete strength increases, the bond strength, bond stiffness and bond toughness of coated steel bar also increase, respectively.

Enhancing anti-carbonation properties of oil well cement slurry through nanoparticle and cellulose fiber synergy

The anti-carbonation property of oil well cement (OWC) is critical for sealing efficiency of wellbores under geological CO2 sequestration. However, gas migration through OWC around wellbores may lead to a deterioration and failure of the entire storage system. Developing carbon-resistant cement has been the emerging trend in the research community. Previous studies mainly focused on nanoparticles alone to enhance performance of OWC, and the purpose of the research is to explore the synergy of nanoparticles and cellulose fiber (CF) in enhancing engineering properties (e.g., carbonation resistance) of oil well cement slurry. The focus was on investigating compressive strength, permeability, pore structure, and carbonation depth associated with the micro-level texture in a CO2 corrosion environment using X-ray diffraction, Scanning Electron Microscopy, and thermogravimetric analysis methods. Four nanoparticles, namely, nano-SiO2 (NS), nano-TiO2 (NT), nano-Al2O3 (NA), and nano-CaCO3 (NC), were selected for the mixture design. Results indicated that the incorporation of 1∼2 % NPs into the OWC paste resulted in a notable decrease in portlandite and an increase in calcium silicate hydrates, thereby enhancing compressive strength and hydration process. In addition, the single admixture of CF could minimize the formation of cracks in the cement matrix and reduce the average carbonation depth by 54 %. More importantly, the synergy of CF and NP significantly improved the resistance of OWC to carbonation, and the OWC mixed with CF and NS displayed the highest carbonation resistance.

Investigation of Nano Cutting Oil Effects on Hard Milling Under Minimum Quantity Lubrication

The presented work aims to investigate minimum quantity lubrication (MQL) using cutting oil with/without Al2O3 nanoparticles for hard milling of 60Si2Mn steel (50-52 HRC) using carbide inserts. The effects of three different types of based cutting oils including emulsion, soybean oil and rapeseed oil on surface roughness Ra, Rz and tool life were studied and investigated. The experimental results show that the use of Al2O3 nano cutting oil has improved lubrication capability compared to base cutting oil, contributing to improve machined surface quality and tool life. Al2O3 emulsion-based nanofluid exhibited the best performance among the three surveyed oils, followed by rapeseed oil and finally soybean oil. Furthermore, the cutting speed of the carbide inserts was improved and the tool life was significantly increased with the help of nano cutting oil due to the improvement in lubrication effects in the cutting zone, thereby helping to reduce cutting forces and cutting heat.

An Investigation into the Impact of Nano-Additives on the Performance and Emission Levels of a Diesel Engine Fuelled by Nahar Biodiesel

Research on alternative fuels has been intense due to rising energy needs, fossil fuel depletion, rising fuel consumption rates, and the generation of toxic pollutants. The production of biodiesel included the use of nahar oil by acid esterification, followed by a trans-esterification process. 20% volume of nahar biodiesel blend (NME20) was blended with diesel considering it to be the optimized blend ratio. Nanoparticles such as titanium dioxide (TiO2) and aluminium oxide (Al2O3) were used to improve the properties of fuel. The additives were included into the biodiesel mix at concentrations of 25, 50, 75, and 100 parts per million (ppm), respectively. This research aims to evaluate the efficacy and ecological footprint of a diesel engine that utilises a blend of nahar biodiesel with the incorporation of nano additives. An experimental setup was implemented on a diesel engine with a single cylinder to assess its performance and emissions at various engine loads. The tests demonstrated that the use of a biodiesel mix NME20 containing 100 ppm nano Al2O3, (NME20Al100), resulted in a significant increase of 12.48% in thermal efficiency when compared to the other fuels tested. The addition of Al2O3 to the NME20 with 100ppm also resulted with the reduction of 22.85%, 23.07% and 27.59% of CO, HC and smoke emissions, respectively. Despite the fact that NOx levels tend to rise when nano additions are used, SME20Al100 stands out as the best nano additive compared to SME20Ti100 because of its exceptional engine performance.

Effective utilization of waste plastics and ammonia as biodiesel to assess performance and emission

Purpose This study aims to examine the environmental effects of plastic waste on the atmosphere and its implications for disaster waste management. It focuses on using ammonia, pyrolyzed plastic oil and the effectiveness of alumina nanoparticles as a catalyst. Design/methodology/approach The research explores different combinations of conventional diesel and nano Al2O3 derived from pyrolyzed plastic oil (ranging from P10 to P40). Critical performance metrics evaluated include brake mean effective pressure (BMEP), brake specific fuel consumption, brake thermal efficiency and emissions of CO2, CO and NOx. The study specifically investigates the impact of adding 50 ppm of Al2O3 nanoparticles to these blends. Findings The findings indicate that using blended fuels with nanoadditives significantly lowers pollution. Specifically, the P30 blend with 50 ppm of Al2O3 nanoparticles greatly reduced CO emissions. Additionally, the same blend reduced NOx emissions and CO2 emissions. The P30 mix showed improved BMEP and brake thermal efficiency due to its density, calorific value and viscosity (6.3 bar). The P30 blend exhibited higher thermal efficiency due to decreased heat loss, whereas conventional diesel demonstrated the best mechanical efficiency due to its longer ignition delay. Originality/value This study highlights the potential of using Al2O3 nanoparticles and pyrolyzed plastic oil to reduce emissions and enhance the performance of internal combustion engines. It underscores the environmental benefits and implications for disaster waste management by converting plastic waste into useful resources and reducing air pollution.

Foam Stabilization Process for Nano-Al2O3 and Its Effect on Mechanical Properties of Foamed Concrete.

Foamed concrete is increasingly utilized in engineering due to its light weight, excellent thermal insulation, fire resistance, etc. However, its low strength has always been the most crucial factor limiting its large-scale application. This study introduced an innovative method to enhance the strength of foamed concrete by using nano-Al2O3 (NA) as a foam stabilizer. NA was introduced into a foaming agent containing sodium dodecyl sulfate (SDS) and hydroxypropyl methylcellulose (HPMC) to prepare a highly stable foam. This approach significantly improved the foam stability and the strength of foamed concrete. Its drainage volume, settlement distance, microstructure, and stabilizing action were investigated, along with the strength, microstructure, and hydration products of foamed concrete. The presence of NA effectively reduced the drainage volume and settlement distance of the foam. NA is distributed at the gas-liquid interface and within the liquid film to play a hindering role, increasing the thickness of the liquid film, delaying the liquid discharge rate from the liquid film, and hindering bubble aggregation, thereby enhancing foam stability. Additionally, due to the stabilizing effect of NA on the foam, the precast foam forms a fine and uniform pore structure in the hardened foamed concrete. At 28 d, the compressive strength of FC0 (0% NAs in foam) is 2.18 MPa, while that of FC3 (0.18% NAs in foam) is 3.90 MPa, increased by 79%. The reason for this is that NA promotes the formation of AFt, and its secondary hydration leads to the continuous consumption of Ca(OH)2, resulting in a more complete hydration reaction. This study presents a novel method for significantly improving the performance of foamed concrete by incorporating NA.

Improving Lithium-Ion Battery Performance: Nano Al2O3 Coatings on High-Mass Loading LiFePO4 Cathodes via Atomic Layer Deposition

Lithium iron phosphate (LiFePO4 or LFP) is a promising cathode material for lithium-ion batteries (LIBs), but side reactions between the electrolyte and the LFP electrode can degrade battery performance. This study introduces an innovative coating strategy, using atomic layer deposition (ALD) to apply a thin (5 nm and 10 nm) Al2O3 layer onto high-mass loading LFP electrodes. Galvanostatic charge–discharge cycling and electrochemical impedance spectroscopy (EIS) were used to assess the electrochemical performance of coated and uncoated LFP electrodes. The results show that Al2O3 coatings enhance the cycling performance at room temperature (RT) and 40 °C by suppressing side reactions and stabilizing the cathode–electrolyte interface (CEI). The coated LFP retained 67% of its capacity after 100 cycles at 1C and RT, compared to 57% for the uncoated sample. Post-mortem analyses, including scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), were conducted to investigate the mechanisms behind the improved performance. These analyses reveal that Al2O3 coatings are highly effective in reducing LFP electrode degradation during cycling, demonstrating the potential of ALD Al2O3 coatings to enhance the durability and performance of LFP electrodes in LIBs.

Effect of different configurations of hybrid nano additives blended with biodiesel on CI engine performance and emissions

The use of nano additives to improve the cold properties of biodiesel is encouraged by its drawbacks and incompatibility in cold climate. Waste cooking oil (WCO) was transesterified to create biodiesel. A 20% by volume was used for combination of diesel and methyl ester. Current study aims to evaluate diesel engine emissions and performance. TiO2, alumina, and hybrid TiO2 + Al2O3 nanoparticles are added to WCO biodiesel mixture at 25 mg/liter. When B20 combined with nano materials such as TiO2, Al2O3, and hybrid nano, the highest declines in brake specific fuel consumption were 4, 6, and 11%, respectively. As compared to biodiesel blend, the largest gains in thermal efficiency were 4.5, 6.5, and 12.5%, respectively, at maximum engine output power. Introduction of TiO2, Al2O3, and hybrid nano particles to B20 at 100% load resulted in the highest decreases in HC concentrations up to 7, 13, and 20%, and the biggest reductions in CO emissions, up to 6, 12, and 16%. Largest increases in NOx concentrations at full load were about 7, 15, and 23% for B20 + 25TiO2, B20 + 25 Al2O3, and B20 + 25TiO2 + 25 Al2O3, respectively. Up to 8, 15, and 21% less smoke was released, correspondingly, which were the largest reductions. Recommended dosage of 25 ppm alumina and 25 ppm TiO2 achieved noticeable improvements in diesel engine performance, combustion and emissions about B20.

Study of microstructure and corrosion behavior of nano-Al2O3 coating layers on TiO2 substrate via polymeric method and microwave combustion

The study describes the successful development of a TiO2 ceramic substrate with a protective nano-Al2O3 coating using two different coating techniques: microwave combustion and polymeric methods. The coated ceramics demonstrate enhanced corrosion resistance compared to the uncoated substrate. The optimal TiO2 substrate was prepared by firing it at 1000 °C. This was done to give the desired physical properties of the TiO2 substrate for the coating procedures. Nano-Al2O3 powder was coated onto the surface of the TiO2 substrates. The TiO2 substrates with the Al2O3 coating were then calcined (heat-treated) at 800 and 1000 °C. The structures, morphology, phase composition, apparent porosity, bulk density, and compressive strength of the substrate and coated substrate were characterized. Upon firing at 1000 °C, it was discovered that the two phases of TiO2—rutile and anatase—combine in the substrate. Once the substrate has been coated with nano Al2O3 at 1000 °C, the anatase is transferred into rutile. When compared to the substrate, the coated substrate resulted in a decrease in porosity and an increase in strength. The efficiency of the ceramic metal nanoparticles Al2O3 as a good coating material to protect the TiO2 substrates against the effect of the corrosive medium 0.5 M solution of H2SO4 was measured by two methods: potentio-dynamic polarization (PDP) and the electrochemical impedance spectroscopy (EIS). The results indicated that the corrosion rate was decreased after the substrate coated with alumina from (67.71 to 16.30 C.R. mm/year) and the percentage of the inhibition efficiency recorded a high value reaching (78.56%). The surface morphology and composition after electrochemical measurements are investigated using SEM and EDX analysis. After conducting the corrosion tests and all the characterization, the results indicated that the coated TiO2 substrate prepared by the polymeric method at 800 °C displayed the best physical, mechanical, and corrosion-resistant behavior.

Al2O3 enhanced bi-phase high-entropy ceramic composites

One limitation of high-entropy ceramics is the low toughness that could hinder their implementations in the relevant industries despite the diverse potential applications. This challenge is increasingly attempted in recent years with high-entropy ceramic composites which consisted of high-entropy ceramic matrix and secondary phase. A suitable secondary phase candidate is Al2O3 which to-date has not been reported for such ceramic composites. In this work, bi-phase high-entropy ceramic composites of cubic fluorite oxide matrix and Al2O3 secondary phase were in situ synthesized from HfO2, ZrO2, CeO2, CaO and Al2O3 nano powders via solid-state reaction method. Variation of thermal and mechanical properties of the composites with Al ratio was due to the combined effects of the inherent properties of Al2O3, concentrations of grain boundary and of oxygen vacancies. The high-entropy ceramic composites enhanced by Al2O3 were also compared with yttria-stabilised zirconia for potential application as thermal barrier coating material.

Experimental investigation on Nano-Al2O3 and hydroxypropyl methyl cellulose (HPMC) modified cement-based coatings for corrosion resistance

In this work, cementitious coatings doped with nano-Al2O3 (NA) and hydroxypropyl methyl cellulose (HPMC) were prepared in order to enhance corrosion resistance of steel bar. The electro-chemical behaviors and corrosion inhibition properties of coated steel bar and tensioned coated steel bars (subjected to 10 %, 30 % and 50 % yield load) were analyzed in 3.5 wt% NaCl solution for 840 h (35 days). At the end of electrochemical test, coating overall performance was evaluated by visual inspection. In addition, scanning electron microscopy (SEM), transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS) were used to examine microstructure and elemental composition of coatings. To comprehend the anti-corrosion mechanism of the coatings, X-ray diffraction (XRD) and infrared spectroscopy (FTIR) analysis to characterize products composition and chemical groups. Test results obtained by linear polarization resistance and electrochemical impedance spectroscopy indicated that both tensile and non-tensile coatings resistance show an increasing trend followed by a decrease with increasing NA content. Cementitious coatings incorporating 1 % NA and 0.12 % HPMC by weight of cement exhibited the best corrosion protection. The LPR fluctuates around 3700 Ω cm2, which is about twice as much as a single doped NA coating. Whether subjected to tensile loads or not, OCP values for all coated steel bar were below −0.273 V/SCE, indicating has a 90 % probability of being in active-corrosion. The corrosion resistance of tensioned coated bars decreased as time and increased load level. According to SEM and TEM image, HPMC forms a thin and continuous film on the substrate surface, which acts as a barrier to the penetration of moisture and corrosive agents. Coatings doped with 1 % NA and 0.12 % HPMC formed denser integrated polymer films at the microscopic. FTIR and XRD results showed that coating incorporated NA consumed the cement hydration product Ca(OH)2 to generate more nanofibers filling pores and microcracks. Coatings incorporating HPMC show better resistance to carbonization.

Design and preparation of Ta33W35Cr15V17 /Al2O3 nano multilayer film based on multi-level construction strategy and its radiation resistance behavior

The microstructure and mechanical properties of Ta33W35Cr15V17/Al2O3 nano-multilayer films with preset defects after He+ ion irradiation were studied to understand the effects of layer interfaces and nano-defects. After irradiation, the growth of He bubbles in the alumina layer was confined to the nanovoids without aggregations. The nanochannel in the high-entropy alloy layer absorbed the deposited energy of He+ and shrank to disappear. In addition, the film was softened after irradiation due to the presence of presetting defects. Based on which a dual absorption source model of interface and pre-set defects was proposed to explain the enhancement of radiation tolerance.

Stabilization of the stainless-steel interface using sequentially deposited Al2O3 nano films using atomic layer deposition (ALD) technique

Atomic layer deposition (ALD) has been an important surface processing technique of materials of important applications. In the present investigation aluminum oxide thin films are generated using ALD technique (ALD-Al2O3). The ALD-Al2O3 films are formed over SS304 substrates with thicknesses of 20, 75 and 100 nm and the corrosion investigations are carried out using polarization and impedance measurements. The neutron reflectivity measurements are carried out to measure the thickness and surface roughness of the film. The corrosion property of SS304 observed to be reduced on ALD deposition which has been evident from the polarization measurements and supported by the electrochemical impedance measurements. The ennoblement in the corrosion potential has been observed due to the ALD-Al2O3 film formation over the SS304 surface. The polarization resistance remained high even at high applied anodic potential of 0.7 V, the protection remained stable even at an elevated temperature of 60οC.The investigation supports the primary objective of the important role of the protection of material through thin ALD-Al2O3 protective films.

Impact of different phase structure nano Al2O3 arc discharge prepared on MB dye removal

Nanocrystalline ceramic materials have great importance in the field of nanotechnology. Nano-sized materials have properties superior to bulk materials, including improved surface area-to-volume ratio and high strength and toughness. Nano alumina products were prepared in two different phases with different sizes, and shapes via a solid–liquid plasma reactor. Both yields were prepared in identical circumstances, but with different conditions that lead to produce different shapes, and phase structures (γ-Al2O3-NPs with a spherical shape, and δ-Al2O3-Nano-structure rhomboid shape). In this regard, 1.6 million tons of dyes are consumed each year. Trace of dyes in water may cause diseases if it exceeds the WHO limits. This paper describes the adsorption of methylene blue (MB) from aqueous solutions by two different nano structure alumina nano-adsorbents. The optimum contact time, adsorbent mass, and pH were determined, and adsorption isotherms were obtained using concentrations of MB ions ranging from 5 to 50 mg/L. The adsorption process shows significant differences of the coefficient of determination factor R2 for both yields for pseudo-first-order reaction kinetics, as well as Freundlish and intraparticle, film diffusion adsorption isotherms. Our results demonstrate that the adsorption process was spontaneous and exothermic under natural conditions. The maximum capacity of adsorbent for γ-Al2O3-NPs and δ-Al2O3-Nano-structure were 31.56 and 29.49 mg/g, respectively. This study revealed that nano structure γ-alumina was an effective adsorbent for removal of these ions from aqueous solutions.

Assessing the Effect of Aluminium Oxide Nanoparticle Additives on Biodiesel Combustion in Marine Diesel Engines

Abstract The increases in annual ship exhaust emissions have prompted the shift towards adopting alternative energy sources. Biodiesel is a suitable substitute fuel for marine engines that does not necessitate engine alterations. Biodiesel is renewable, environmentally friendly, and plant-based with biodegradable properties. The fuel is also non-toxic and oxygenated and shares similar characteristics with diesel fuel. Nonetheless, biodiesel fuel exhibits slightly reduced performance compared to diesel primarily due to its lower energy content. This study aims to evaluate the combustion attributes of a marine diesel engine employing palm biodiesel fuel incorporated with aluminium oxide (Al2O3) nanoparticle additives. A B20 biodiesel fuel was blended with 50, 100, and 150 ppm Al2O3 nano additives. The engine combustion parameters, in-cylinder pressure, heat release rate (HRR), mass fraction burned, and ignition delay were analysed and compared to the B20 fuel without additives. Adding Al2O3 nano additives to the B20 biodiesel blend improved the engine combustion characteristics. The optimal performance was recorded by the blend incorporating 150 ppm nanoparticles. The in-cylinder pressure and HRR peaks also improved by 5.41 to 15.1% and 4.69 to 16.9%, respectively, compared to the other B20 fuel blends. Furthermore, the B20 mixed with Al2O3 documented a more rapid mass fraction burned rate, resulting in a shorter ignition delay of approximately 5 CA°. In addition, the amount of oxygen in biodiesel blended with Al2O3 nano additives has improved engine combustion compared to B20 fuel. The present study demonstrated that adding Al2O3 nano additives to palm biodiesel fuel significantly enhanced engine combustion attributes, thus highlighting its potential to reduce reliance on petroleum-based fuels and provide sustainable fuel alternatives for marine diesel engines.

Analysis of tribological behavior, pin temperature, and surface roughness of a brake pad material with nano coating

The present work is concentrated on the novel multi-nano particle coating of CoNiCrAlY matrix on brake pad material. The tribological behavior of plasma sprayed CoNiCrAlY particle composite coating with nano inert particles like ZrO2, Al2O3, and AT40 were compared. A comparison was made with respect to structure and morphology of coating. The coatings were characterized with Scanning electron microscopy(SEM) and Energy dispersive X-ray spectroscopy(EDAX) technique. The tribological performance of these coatings were studied using pin-on-disc test rig under dry sliding conditions. The wear study revealed CoNiCrAlY+nano Al2O3 particle coating showed better specific wear rate compared to ZrO2 and AT40 composite coating. The observed tribological behaviour is very much influenced by the ability of nano particles to get distributed in the CoNiCrAlY matrix. The CoNiCrAlY coating with nano particles showed significant specific wear resistance of brake pad material. They coated samples also resulted in minimum rise in pin temperature. This is attributed to the homogeneous distribution of nano particles in the coating. These composite coating also showed lower coefficient of friction values. Although referring to other simplified and extreme conditions, the results obtained provides a new window for using nano hard coatings to enhance the life and efficiency of the commercially available four-wheel vehicle brake pad.

Experimental investigation and optimization of nano Al2O3 mixed FSWed joint between AA2024-T351 and AA7075-T651 by response surface approach

Additive mixed friction stir welding can be an innovative and novel method for enhancing the friction stir welding process. Thus, this research aimed to investigate nano Al2O3 effects on the mechanical and microstructure of FSWed joints using Al alloys AA2024-T351/AA7075-T651. The experiments were performed based on response surface approach based CCD twenty run with varying three factors: tool rotational speed (A: 800–1,200 rpm), welding speed (B: 20–60 mm/min), tool plunge depth (C: 0.2–0.4 mm) and fixed volume percentages of Al2O3 nano-particles (8%). Mechanical performances such as tensile, yield, and hardness tests have been performed and microstructural properties have been analyzed through SEM and microscopy. The statistical analysis shows that the tensile strength can be significantly affected by rotational speed (A), welding speed (B), tool plunge depth (C), interaction (AB, BC, AC), and quadratic term A2, B2 in the FSW process; yield strength was influenced considerably by main, interaction, and quadratic terms; main factors and quadratic terms A2, B2 and C2 significantly influenced hardness values. The fracture test revealed that the joints with Al2O3-reinforced AA2024-T351/AA7075-T651 alloys were more ductile and less brittle. The optimal conditions for FSW, tool rotational at 1,146 rpm, weld speed at 60 mm/min, and 0.4 mm plunge depth were responsible for higher tensile strength of 169 MPa, yield strength of 145 MPa, and micro-hardness values of 89 HRB due to the uniform nano-particle dispersions and better material mixing.

Observation of the formation of CuAl2O4 by the direct consumption of Al2O3 in an NAB alloy at elevated temperature

The oxidation behaviors of a commercial C95500 nickel aluminum bronze (NAB) alloy at elevated temperatures were investigated. The oxide scale exhibited a triplex structure with an outmost CuAl2O4 layer, an intermediate spinel-type Al2O3 layer, and a deepest nano Al2O3 film. The observation of CuAl2O4 and Al2O3 in the same grain with the same crystallographic orientation indicated that the outmost CuAl2O4 was formed by directly consuming the spinel-type Al2O3. Such a transformation process can avoid the formation of defects in the oxide scale caused by the transformation between different Al2O3 variants, attributing to the origin of the excellent oxidation resistance.

Effect of nano-metakaolin on the chloride diffusion resistance of cement mortar with addition of fly ash

This study examines the improvement of nano-metakaolin (NMK) on the chloride ion diffusion resistance (CDR) of fly ash (FA) cement-based materials. The rapid chloride diffusion (RCM) method was employed to compare the effects of nano Al2O3, nano CaCO3, nano SiO2, nano attapulgite clay, and NMK on the CDR of cement mortar, and a suitable nanomaterial was identified. Subsequently, the influence of NMK on the CDR, flexural and compressive strengths of FA cement mortar was examined. The chloride ion concentration of NMK/FA cement paste under simulated salt environment were measured. The action mechanism of NMK on the CDR of FA cement mortar was explored through mercury intrusion porosimetry and scanning electron microscopy tests. The results reveal that among these nanomaterials, NMK exhibited the highest cost-effectiveness in enhancing CDR of cement mortar, with a suitable content of 5 wt%. NMK demonstrated a significant improvement in the CDR of FA cement mortar, particularly at a hydration age of 7d. Incorporating 5 wt% NMK into the cement mortar with addition of 30 wt% FA resulted in a 73% reduction in chloride ion diffusion coefficient (Dcl) compared to the cement mortar with the addition of 30 wt% FA at 7d. NMK enhances both flexural and compressive strengths of FA cement mortar at various hydration ages (3, 7, 14, 28 d). The addition of 5 wt% NMK makes a increment of about 10% for the flexural strength of cement mortar with 30 wt% FA at 7d. Moreover, NMK results in a denser internal structure of FA cement mortar, facilitates the generation of C–S–H gel, and reduces the more-harmful pores and harmful pores while increasing harmless and of less-harmful pores cement paste. Additionally, NMK exhibited the most substantial reduction in chloride ion concentration within FA cement paste at 7d. In general, NMK significantly enhances CDR, flexural and compressive strengths of FA cement mortar, especially at a hydration age of 7d.