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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.

Recently, silicone rubber (SiR) is preferably used in high-voltage cable accessories because it offers a wide range of voltage and temperature applications and excellent electrical and mechanical properties. Furthermore, the SiR exhibits flexibility and inhibits oxidation. In this paper, the electrical tree behavior of SiR nanocomposites containing nanoalumina and halloysite nanoclay was investigated; moreover, the nanofiller concentrations were predetermined at 0 vol%, 1 vol%, 2 vol%, and 3 vol%. The electrical tree growth was observed at room temperature at 8 kVrms after tree inception voltage (TIV). The TIV and electrical tree growth in SiR nanocomposites were monitored using an online digital monitoring system, which consisted of a stereomicroscope and a digital camera. The experimental results indicated that the addition of 1 vol%-2 vol% nanoalumina in SiR composite significantly improved the TIV and electrical tree growth rate. However, the addition of 3 vol% nanoalumina in the SiR composite reduced the TIV and accelerated the electric tree growth rate. In the presence of halloysite nanoclay of approximately 3 vol%, the SiR composite showed improved TIV and electrical tree growth rate.

In the present work, the effects of adding nanoalumina and marble dust on the wear behavior of dental composites were investigated. The hardness of dental composite was determined using Vickers micro-hardness tester. A two-body abrasive wear test was performed on the dental wear simulator under the medium of artificial saliva. The experiments were performed as per the Taguchi orthogonal array and steady state condition by varying parameters such as filler content, normal load, sliding velocity, and number of cycles. The hardness results indicated that the incorporation of 5 wt. % of nanoalumina increased the hardness of the dental composite by 12%, whereas the incorporation of 5 wt. % of marble dust increased the hardness of the dental composite by 7%. Also, for the experiments as per the Taguchi orthogonal array, the mean volumetric wear in the case of nanoalumina-filled dental composite was 9.6% less than that of marble dust-filled dental composite. However, in both the cases, the volumetric wear increased with the increase in normal load, sliding speed, and number of cycles but decreased with the increase in filler content. Analysis of variance (ANOVA) of the results indicated that normal load was less significant compared to filler content, sliding speed, and number of cycles.

The aims of the present study were to develop a dental composite filled with silanized nanoalumina and then to investigate the effect of nanoalumina filler on the two-body and three-body wear behavior under distilled water and food slurry medium, respectively. The dental composites were fabricated by adding silane treated nanoalumina filler particle in the weight percentage of (0–3 wt.%) to the matrix of BisGMA, TEGDMA, CQ and EDMAB. Two-body and three-body wear tests were performed in dental wear simulator machine with varying parameters such as normal load, chewing speed and chamber temperature in such a way as to simulate mastication process. Taguchi’s orthogonal array (L16) design, steady state condition and ANOVA were applied to evaluate the optimum parameter for minimum wear and effect of each parameter on the wear performance of dental composites. The finding of the result indicated that mean volumetric wear rate of dental composite in distilled water (i.e. two-body abrasion) was 33.23% more than that of the same composite in food slurry condition (i.e. three-body abrasion).

External corrosion by soil’s components is a serious problem in many steel structures such as pipelines and tanks, thus many methods are applied to reduce this risk. Nanotechnology almost gives improving for conventional protection methods. Investigation on nano Al2O3 doped polypyrrole coating has been done on carbon steel structures to protect them in two simulated soil environments include (0.01M NaCl + 0.01M NaHCO3) and (0.01M NaCl + 0.01M Na2SO4). Electropolymerization of pyrrole monomer carried out in oxalic acid with suspended nano alumina using cyclic voltammogram method. Characterization of produced film was done by SEM/EDS and the results indicated the uniformly distribution of coating in the presence of nano alumina confirming the presence of Al2O3 NPs by EDS analysis. Also FTIR spectra showed the occurred incorporation between polypyrole and nanoalumina in deposited film on steel surface. The presence of nano alumina behaves as repaired to healing the defects in polymer film by chemical, mechanical and electrochemical factors and then gives long life time for service; this result was concluded through the improving in protection efficiency of Al2O3 NPs/PPy film compared with conventional red paint which is uses to protect carbon steel structures.

Ultrahigh performance concrete (UHPC), which is characterized by dense microstructure and strain hardening behavior, provides exceptional durability and a new level of structural response to modern structures. However, the design of the UHPC matrix often requires the use of high quantities of supplementary cementitious materials, such as silica fume, which can significantly increase the cost and elevate the production expenses associated with silica fume handling. This paper demonstrates that a fiber-reinforced composite with properties similar to conventional UHPC can be realized with very low quantities of silica fume, such as 1% by mass of cementitious materials. The proposed UHPC is based on reference Type I cement or Type V Portland cement with very low C3A (2O3 nanofibers, and high-density polyethylene or polyvinyl alcohol macro fibers. Previous research has demonstrated that nanofibers act as a seeding agent to promote the formation of compact and nanoreinforced calcium silicate hydrate (C-S-H) clusters within the interparticle and nanofiber spaces, providing a nanoreinforcing effect. This approach produces a denser and stronger matrix. This research expands upon this principle by adding synthetic fibers to ultrahigh strength cement-based composites to form a material with properties approaching that of UHPC. It is indicated that the developed material provides improved strain hardening and compressive strength at the level of 160 MPa.