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Experimental work is carried out to study the performance of nanoparticle enhanced phase change materials (NEPCMs) when applied to the Egyptian weather for indoor thermal comfort. Nanoparticle alumina and copper-oxide are used as the additive material into the PCMs 7, 11, 24, 26 and 29. The enhanced PCMs are characterized and tested for thermal performance during solidification and melting cycles. Observations are then made to conclude that, compared to the base fluid, PCM11 has the optimum performance for the Egyptian winter weather and PCM26 is the best for the summer conditions. PCM11 with a favorable phase change range ∼11–13∘C for Egyptian winter conditions, shows a reduction of melting time by over 10% when 5wt.% CuO nanoparticles (NPs) are added. Similarly, further to thermal stability and reduced corrosive action, PCM26 enhanced with 5wt.% CuO NPs has over 14% faster melting compared to the base fluid and does not undergo supercooling when tested for summer application. [ABSTRACT FROM AUTHOR]

Concrete technologists use different types of additives such as fly ash, slag, natural pozzolans and nanomaterials toenhance concrete performance and durability. However, a detailed explanation of the early-age hydration process and microstructural modification of concrete in the presence of nanomaterials remains to be presented and extensive research is required for strategic modification of cementitious systems. This study focused on the precise monitoring of early-age hydration with the incorporation of nanoalumina (nAl) in tricalcium silicate (C3S) and Portland cement paste and mortar. The dosage of nAl was varied from 1 to 5% (by weight) in C3S and from 0.1 to 1.0% in Portland cement, with a water/cement ratio of 0.4. The hydration studies showed that the nAl increased the cross-linkage in calcium silicate hydrate gel through substitution of aluminium by silicon, which was responsible for the enhancement of the modulus of elasticity (by 40%) with 1.0% nAl) after 7 days of hydration. In summary, the incorporation of nAl modified the concrete microstructure in the initial days of hydration, leading to higher concrete performance and longer service lives of concrete structures. [ABSTRACT FROM AUTHOR]

As an internal curing substance for cementitious materials, superabsorbent polymer (SAP) is emerging as the most potential solution. Nanomaterials and their composites have wide applications in concrete mainly as crack sealants and viscosity modifiers. Silane, as a coupling agent, is utilized in cementitious materials for its effective particle dispersion and adhesion characteristics. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Thermogravimetry (TGA) analysis, and Scanning electron microscopy (SEM) are utilized to characterize the microstructures and phase compositions of nanoalumina, (3-aminopropyl) triethoxysilane (APTES) and polyacrylamide (PAM) SAP. The impacts of silane-functionalized nanoalumina combined polyacrylamide SAP in cementitious materials are carefully investigated in this work. Compared with plain SAP, the application of silane-functionalized SAP was found to exhibit increased compressive strength, flexural strength and split tensile strength of concrete. The chemical durability properties of cement mortar, rheological and mechanical properties of concrete under self-curing and water curing with cement replaced by the prepared composites at 0.1, 0.2, 0.3, 0.4 and 0.5% by weight of cement are studied experimentally. Results revealed that silane-functionalized nanoalumina modified SAP has good water holding capacity than those with individual SAPs contributing to the advancement of internal curing materials in concrete buildings. The weight loss measurements reveal that lower weight loss is observed for the concrete containing SAP/APTES/nanoalumina in chloride, acidic and sulphate media. This work contributes to the advancement in material technologies for the prevention of building fractures. [ABSTRACT FROM AUTHOR]

Municipal solid waste incineration (MSWI) fly ash containing heavy metals is hazardous solid waste that requires safe disposal. Alkali-activated treatment can effectively improve the environmental safety of MSWI fly ash. Due to the low alumina content of MSWI fly ash, the addition of nanoalumina (NA) solves the defect to enhance the ability of solidification/stabilization (S/S) and maximize the utilization of MSWI fly ash. NA/MSWI fly ash solidified body was prepared by alkali-activated technology in this work. In this study, NA was added (0–3 wt.%) to explore its effects on mechanical properties and heavy metal immobilization efficiency of NA/MSWI fly ash solidified body. Research results revealed that when the addition of NA was 2 wt.%, the compressive strength of solidified bodies can significantly increase by 38.0% and 42.8% at 7 and 28 days, respectively. Meanwhile, the leaching concentration of heavy metals in NA/MSWI fly ash solidified body can noticeably reduce with the immobilization efficiency of above 99.5%. Adding NA promoted the ratio of stable state on Pb and Zn in solidified bodies. A series of microscopic characterization analyses indicated that NA stimulated gels and Friedel's salt formation, and N–A–S–H was also found in the NA/MSWI fly ash solidified body, enhancing S/S heavy metals by physical adsorption, physical encapsulation, and chemical bonding. Therefore, this study paves a potential new way for the application of nanomaterials in S/S MSWI fly ash through alkali-activated technology, and nanoalumina is a more promising candidate. [ABSTRACT FROM AUTHOR]

Sol–gel synthesized ceramic α-Al2O3 nanoparticles were mixed with commercially pure Al powder from 0 to 2.5 wt% in composition to prepare nanocomposites. Mixing of the powders was carried out by using two different techniques viz. normal wet-mixing and ultrasonication. Among these two techniques, ultrasonication was found to be more effective method to achieve uniform distribution of nanoparticles. After uniform mixing, the samples were prepared through powder metallurgy route. Hardness, compression and bending test were conducted to investigate the effect of α-Al2O3 nanoparticles on Al. The microstructure of the nanocomposites revealed that the nanoparticles impede the grain growth of Al particles during the time of sintering, which resulted in the grain refinement. Moreover, the strength of the nanocomposite was improved by the subsequent incorporation of nanoparticles. However, beyond 2wt% of nanoparticles content, the bending strength and hardness were reduced considerably. Maximum improvement in the values of compressive and bending strength was found as 64% and 50%, respectively. [ABSTRACT FROM AUTHOR]

In this work, epoxy resin-based composites reinforced with nanoclays, nanoalumina, carbon nanotubes (CNTs) (0.15, 0.50, and 1.50% vol were submitted to morphological characterization by scanning (SEM) and transmission (TEM) electron microscopies, electrical tests through electrical impedance spectroscopy, and electromagnetic analyses (scattering parameters), in the frequency range of 8.2 to 12.4 GHz. SEM images of the CNT composite revealed nanotube clusters in the matrix. The proximity between the CNTs is corroborated by the increase in the electrical conductivity of the composite due to the formation of a long-range electron transport network, which favored the polarization effect, absorption losses (SEA = 1.33 dB), reflection (SER = 3.38 dB) and reflection loss (RL = -6.61 dB at 10.8 GHz). Composites with nanoclays and nanoalumina showed no significant electrical and electromagnetic results.

This research consists of the fabrication of synthetic gels of hydrated calcium silicate (C-S-H gel) and hydrated calcium aluminate silicates (C-A-S-H gel) in aqueous solution oversaturated in calcium hydroxide. These gels were fabricated using nanomaterials with different specific surface area; two nanosilicas (NS), OX50 and A200 (50 and 200 m2/g respectively) and two nanoaluminas (NA), A65 and A130 (65 and 130 m2/g). Mixtures were carried out maintaining a Ca/Si = 2 ratio and variable Al/Si ratios of 0.1, 0.5 and 1. The effect of aluminium incorporation in the C-S-H gel was studied using the nuclear magnetic resonance technique (29Si MAS-NMR), and the information obtained was further processed using the mathematical deconvolution method. Chemical shift bands were delimited to identify the structures. From the results obtained, modifications of the tetrahedral (Qn) in the dreierketten structure were observed in the different combinations, as well as the modification of the bridging tetrahedral (Q2b) due to the presence of aluminium replacing the silica bridging tetrahedron Q2b(1Al). High Q4 values were detected in the C-S-H gel with NS OX50 and this could be associated to a double chain formation very similar to a perfect tobermorite. The length of the mean chains (MCL) was very variable in each blend, but some trends were observed as the Al/Si = 1 ratio and the Al/Si = 0.1 ratio maintain or increases the MCL respectively. The results are interesting and concrete case mixtures with NS OX50 show original trends that have not yet been reported in the literature. Resumen: Esta investigación consiste en la fabricación de geles sintéticos de silicato de calcio hidratado (gel C-S-H) y de silicatos de aluminato de calcio hidratados (gel C-A-S-H) en solución acuosa sobresaturada en hidróxido de calcio. Estos geles se fabricaron utilizando nanomateriales con diferente superficie específica; dos nanosílicas (NS), OX50 y A200 (50 y 200 m2/g respectivamente) y dos nanoaluminas (NA), A65 y A130 (65 y 130 m2/g). Las mezclas se realizaron manteniendo una relación Ca/Si = 2 y proporciones variables de Al/Si de 0,1, 0,5 y 1. El efecto de la incorporación de aluminio en el gel C-S-H se estudió mediante la técnica de resonancia magnética nuclear (29Si MAS-NMR), y la información obtenida se procesó posteriormente mediante el método de deconvolución matemática. Se delimitaron las bandas de desplazamiento químico para identificar las estructuras. A partir de los resultados obtenidos, se observaron modificaciones del tetraedro (Qn) en la estructura dreierketten en las diferentes combinaciones, así como la modificación del tetraedro puente (Q2b) debido a la presencia de aluminio que sustituye al tetraedro puente de sílice Q2b(1Al). Se detectaron altos valores de Q4 en el gel C-S-H con NS OX50 y esto podría estar asociado a una formación de doble cadena muy similar a la de una tobermorita perfecta. La longitud de las cadenas medias (MCL) fue muy variable en cada mezcla, pero se observaron algunas tendencias como que la relación Al/Si = 1 y la relación Al/Si = 0,1 mantienen o aumentan la MCL, respectivamente. Los resultados son interesantes y las mezclas de casos concretos con NS OX50 muestran tendencias originales que aún no se han reportado en la literatura.

Cement-based materials are regarded as one of the most important building materials due to their simple construction process, low energy consumption, and the wide range of raw materials from which they can be synthesized. This paper presents a state-of-the-art review of published results of promising new research and innovation of cement-based materials using nanotechnology, which lead to improved physical-mechanical properties, durability, and sustainability of these materials. The development of nanoscience has a significant impact on building materials. The application of nanomaterials has shown that the properties of conventional cement-based materials can be significantly improved when nanoparticles are included. The addition of nanoparticles in these materials can act as a filler agent, producing a dense matrix and reducing the growth of micro pores. The incorporation of nanomaterials into cement matrix has become a promising area of research. Nano-sized particles are characterized by a high surface area to volume ratio, and many of them are highly reactive. The incorporation of nanoparticles into the cement matrix significantly improves its properties due to the reactivity of nanoparticles and the filling of matrix nanopores. Understanding the complex structure of cement-based materials at the nanoscale leads to the creation of a new generation of these materials, stronger and more durable, with the desired deformation-stress behavior and, possibly, with a full range of “smart” properties. Aluminum oxide (Al2O3) nanoparticles are among the most important metal oxides with promising applications. The role of nano-Al2O3 in improving the physical and mechanical properties of cement-based materials has been noted by many researchers. This article summarises and discusses current knowledge and the latest research regarding the use of aluminum oxide in cement-based materials. [ABSTRACT FROM AUTHOR]

The goal of this paper is to analyze the aging behavior and the mechanism evolution of nano-Al2O3 (NA)-reinforced styrene-butadiene-styrene (SBS) asphalt under different thermal-oxidative aging conditions. First, NA/SBS-modified asphalt and SBS-modified asphalt with different aging levels were prepared. Second, the viscosity and high temperature rheological performance of the specimens were tested and the property-related aging indexes were calculated and compared. Third, a Fourier transform infrared (FTIR) test of the specimen was conducted and the chemical group-related aging indexes were calculated and analyzed. Fourth, gel permeation chromatography (GPC) was used to analyze the molecular weight of the specimens under different aging levels. Then, an atomic force microscope (AFM) was adopted to analyze the microsurface morphology of different specimens. Finally, correlation analysis between property-related indexes and chemical group indexes was conducted. The results show that NA can enhance the thermal-oxidative aging resistance of SBS asphalt. NA can inhibit the increase in sulfoxide groups and the degradation of the SBS polymer with the increase in aging. NA can slow down the formation of large molecule during the aging process. The degree of change in both the bee structures and micromorphological roughness of NA/SBS asphalt is lower than that of SBS asphalt under different aging levels. [ABSTRACT FROM AUTHOR]

The characteristics and properties of fumed oxides depend strongly on various external actions that is of importance from a practical point of view. Therefore, gelation or high-pressure cryogelation (HPC) of aqueous media pure or with 0.1 M NaCl, and mechanochemical activation (MCA) of dry or wetted powders of individual (silica, alumina, their mechanical blends) and complex (silica/titania, alumina/silica/titania, AST1, AST1/A-300) nanooxides were studied to analyze the influence of the nanooxide composition, particulate morphology, and preparation conditions on changes in the morphological and textural characteristics of treated samples. The temperature-pressure behavior of different phases (silica, alumina, and titania) under HPC can result in destroy of complex core-shell nanoparticles (100-200 nm in size) in contrast to small nonporous nanoparticles, NPNP (5-20 nm). The textural characteristics of nanooxides are sensitive to any external actions due to compaction of such supra-NPNP structures as aggregates of nanoparticles, agglomerates of aggregates, and visible structures in powders. The compaction of supra-NPNP enhances the pore volume but much weakly affects the specific surface area (with one exception of AST1) because small NPNP are relatively stable during any external actions (HPC, MCA). The compacted materials are characterized by enhanced mesoporosity shifted to macroporosity with decreasing specific surface area and increasing sizes of nanoparticles or to mesopores with increasing MCA time or amounts of water in wetted powders. At low hydration of the A-300 powder (h = 0.5 g/g), the value of SBET slightly increases if MCA is provided by stirring or ballmilling. Diminution of the freezing temperature from 208 to 77.4 K during HPC results in enhanced compaction of aggregates and agglomerates but this does not practically affect the primary nanoparticles. The degree of decomposition of core-shell nanoparticles of AST1 does not practically increase with decreasing freezing temperature from 208 to 77.4 K. Decomposition of core-shell AST1 particles is inhibited under HPC by added A-300 (1 : 1) working as a damper. [ABSTRACT FROM AUTHOR]

The aim of this study was to explore the influence of the neurotoxicity of nanoalumina on primarily cultured neurons. Normal control, particle size control, aluminum, micron-alumina, and nanoalumina at 50-nm and 13-nm particle sizes were included as subjects to evaluate the level of apoptosis, necrosis, and autophagy in primarily cultured neurons and further explore the mitophagy induced by nanoalumina. The results demonstrated that nanoalumina could induce neuronal cell apoptosis, necrosis, and autophagy, among which autophagy was the most notable. When the autophagy inhibitor was added to the nanoalumina-treated group, it significantly downregulated the protein expression levels of Beclin-1 and LC3II/LC3. Observation under a transmission electron microscope and a fluorescence microscope revealed mitophagy characteristics induced by nanoalumina. Additionally, the neurotoxicological effects induced by nanoalumina were more significant than those induced by aluminum and in a particle size–dependent manner. [ABSTRACT FROM AUTHOR]

In this present study, the preference selection index method (PSI) was applied to identify the best formulation among ceramic fillers such as glass ionomer cement (GIC), nanosilica and nanoalumina nanofiller in the dental composites. The comparative assessment of the effect of nanofillers (nanoalumina and nanosilica fillers) and glass ionomer cement has been evaluated. Dental composites with 0, 10, and 20 wt% of nanoalumina, nanosilica and glass ionomer cement were fabricated. These composites were analyzed for physico‐mechanical and wear properties. The PSI multi‐criteria decision making technique was used to rank the composites with various filler content. The performance defining attributes for the comparative assessment were set as void content, hardness, compressive strength, flexural strength, diametral tensile strength, and wear properties against load and speed. The PSI of dental composite reinforced with 20 wt% nanosilica (DCSi‐20) was maximum (0.896) followed by dental composite reinforced with 20 wt% glass ionomer (DCGi‐20) (0.889) and hence DCSi‐20 demonstrated as most preferred dental composite material followed by DCGi‐20. DC‐0 showed the least preference dental composite materials on the basis of desirable physical, mechanical, and wear properties. Finally, it can be concluded that despite of more void content and low flexural strength, overall performance of glass ionomer is comparable with nanosilica and more significant with respect to nanoalumina. [ABSTRACT FROM AUTHOR]

Objective: This study aimed at investigating the effect of nanoalumina on sex hormones, and fetuses in pregnant rats., Methods: In this study, sixty-four pregnant rats were divided into eight groups. The control and the injection-control group received normal food and water, and 0.5 ml of distilled water, respectively. Treatment groups were treated with 25, 50, 100, 250, 500, and 1000µg/ml concentrations of Nanoalumina from the 7th day until the 18th day of pregnancy. On the 18th day, the rats were investigated in terms of their hormone levels. We evaluated the number of healthy and aborted offspring, as well as fetus size., Results: Nanoalumina caused an increase in progesterone hormones at the concentrations of 250, and 500µg/ml, and a significant reduction in estrogen hormone and aborted fetuses at the concentrations of 250 and 500µg/ml (p<0.05). The largest and smallest size of fetuses were observed in 500µg/ml and 1000µg/ml, respectively. The highest number of aborted fetuses was observed in the group treated with the 500µg/ml concentration. There was no aborted fetuses with 25, 50,100, control, and injection-control groups., Conclusions: Due to nanoalumina toxicity, it must be used with caution.