Current Nanomaterials - Volume 6, Issue 3, 2021

Several studies have reported the corrosion rates of magnesium carbon nanotube nanocomposites, but their corrosion behavior is still not well understood. Adding carbon nanotubes (CNTs) to magnesium (Mg) matrices almost always results in an increase in mechanical properties, e.g., increased elastic modulus, hardness, ultimate tensile strength, and yield strength. However, this increase in mechanical properties usually comes at the expense of compromised corrosion resistance. Galvanic interactions between the carbon nanotubes and the magnesium matrix are the usual culprits of nanocomposite corrosion. It is important to study the corrosive behavior of these materials further to create a nanocomposite that is less susceptible to corrosion from the start, i.e., by careful selection of the fabrication method. In the present review, four processing methods (Disintegrated Melt Deposition, Friction Stir Processing, Powder Metallurgy, and Ball Milling), which were used to successfully synthesize magnesium carbon nanotube nanocomposites and test their corrosive properties are discussed. Attempts are made to correlate processing methods to corresponding corrosion rates. It was found that the corrosion rates extracted from each reviewed study may not be readily comparable, and by looking into nanocomposite coatings and carbon nanotube, it was found that volume or weight percent optimization may be the best way to proceed. The findings of this investigation can be used as a starting point for the creation of a magnesium carbon nanotube nanocomposite, which is less inherently susceptible to corrosion as this could take the “potential” out of the many potential applications of these novel materials.

Strain gauges are devices whose electrical resistances vary proportionately with the amount of strain applied on the device. They can be used for real-time applications in the aerospace sector, as a geotechnical tool in tunnels and bridges, in rail monitoring and health monitoring sectors. Nanomaterials have been widely used for this application because they can be flexible, stretchable and have high strength. Several researchers have used numerous carbon-based and metallic nanostructures to develop functionally graded materials. Among carbon-based materials, graphene has been widely researched as a viable material for strain sensors due to its superior mechanical and electrical properties. Also, many metallic nanoparticles have been investigated to design strain sensors that are highly sensitive to a wide range of strains. In this article, a review of carbon and metallic nanomaterial-based strain sensors is presented, with emphasis on applications pertaining to structural health monitoring and wearable devices.

Magnesium is a lightweight metal that holds great potential in automotive, aerospace and biomedical applications. Magnesium when incorporated with nanoparticles, exhibits simultaneous improvements in mechanical, tribological and biological properties without altering its density. This article presents a short review and analysis of mechanical (tensile and compressive), ignition, damping, tribological and in vitro degradation (corrosion and biocompatibility) behaviour of magnesium- based nanocomposites. Owing to the flexibility in tailoring for multiple applications, powder metallurgy routes are being explored to target unique microstructures, novel compositions and high performance in magnesium-based nanocomposites. The mechanical and in vitro study of magnesium nanocomposite synthesized by powder metallurgy route demonstrates improved strength, controlled degradation and good biocompatibility. The article also proposes a powder metallurgy route incorporating hybrid microwave sintering as a promising environment-friendly technique to develop magnesium nanocomposites for biomedical applications.

Background: Hydroxyapatite (HAp) is one of the most studied biomimetic method for biomedical applications. Especially, nano-HAp has been utilized for bone tissue engineering and various other orthopedic applications. HAp possesses different suitable properties such as bioactivity, biodegradability, and cell proliferation efficiency for bone tissue engineering applications. Yet, it lacks in self-antibacterial activity, high surface area, and target efficiency. Results: In this direction, researchers have focused on exploring the required surface as well as the inherent properties of HAp at the nanoscale. These properties are largely dependent on the composition, size, and morphology of the nano-HAp. Hence, nano-HAp has been found to be an excellent candidate with an attractive combination of properties for selection and use in biomedical applications, those required to enhanced biological responses. Further, depending on the type of application, these factors can be tuned to optimize the performance. Conclusion: In this review article, we focus on the chemical structure of HAp and the routes chosen and used for the synthesis of the nano-HAp. The role of various parameters in controlling synthesis at the nanoscale is presented and briefly discussed. In addition, we provide an overview of the various applications for the pristine and doped nano-HAp with recent examples in areas spanning the following: (i) bone tissue engineering applications, (ii) drug delivery applications, (iii) surface coatings, and (iv) scaffolds. The effect of chemical composition on the mechanical properties, surface properties, and biological properties are also highlighted. Nano-HAp is found to be highly proficient in its biomedical applications, especially bone tissue engineering applications. The nanosized properties enhance the biological responses. The dopant ions that replace the Ca ion into the hydroxyapatite (HAp) lattice play a crucial role in its biomedical applications.

Aims: The primary aim of this research is to understand the effects of type of nanoparticles on the microstructure and mechanical properties of Mg-based hybrid nanocomposites. For this reason, new Mg-based hybrid nanocomposites containing 2.2 vol.% Ti and 1.1 vol.% nano-Al2O3 or nano B4C particles were synthesized and their properties were studied in comparison with Mg- Ti and pure Mg. Background: Magnesium with excellent weight-saving potential is ideal for automotive and aerospace applications. But its use in pure Mg is restricted due to inherent limitations such as poor absolute strength, elastic modulus, deformability, and corrosion susceptibility. While most of these limitations can be circumvented by the judicious addition of micron-sized ceramic reinforcements, ductility is often compromised. One of the promising ways for ductility enhancement involves the use of nano-length scale reinforcements. Similar ductility improvements were also reported when hybrid reinforcements were introduced into the Mg matrix. While the role of hybrid reinforcement preparation, the particle size distribution, and volume fraction of hybrid reinforcements were studied extensively in the past, no detailed investigation on the effects of type of nanoparticles has been conducted so far. Objective: The objectives of this research include the successful synthesis and property characterization of Mg-based hybrid nanocomposites containing hybrid (Ti+Al2O3 or Ti+B4C) reinforcements. Methods: Effects of the type of nanoparticles on the properties of Mg-based hybrid nanocomposites were studied by invoking the process-microstructure-property relationships. Results: While both hybrid nanocomposites displayed fine grains when compared to pure Mg and Mg-Ti, there was no noticeable difference between the grain size distribution profiles of Mg- (Ti+Al2O3) and Mg-(Ti+B4C) hybrid composites. The results of property measurements indicated an improvement in dimensional stability, indentation, tension, and compression properties of Mg due to the addition of either individual Ti or hybrid (Ti+Al2O3) or Mg-(Ti+B4C) particles. Among the hybrid composites, Mg-(Ti+B4C) containing hybrid (Ti+B4C) reinforcement exhibited a better combination of strengths and ductility. While the inherent strengthening contribution from B4C and Al2O3 reinforcements resulted in slightly different strength properties, the ductilization benefits of boron compounds enhanced the tensile fracture strain of Mg-(Ti+B4C). Conclusion: Since the particle size distribution and volume fraction of (Ti+Al2O3) and (Ti+B4C) are similar, the difference in strength values between Mg-(Ti+Al2O3) and Mg-(Ti+B4C) can be attributed to the matrix strengthening contribution from reinforcement type.

Background: Buildings in high altitude region often face low pressure and low humidity service environment, which has a great impact on the mechanical properties and durability of cement- based materials. Objective: In this paper, the effects of nano-silica (NS) on the strength and water absorption of cement mortar exposed to the low pressure and low humidity environment were studied. Methods: Mechanical properties (compressive strength and flexural strength) and durability (water absorption) were measured. Moreover, the hydration degree of cement was tested to assist analysis. Results: The flexural strength of mortar decreased and the compressive strength increased slowly after 28 days of exposure under low pressure and low humidity environment. Especially, the introduction of 1% NS could reduce the compressive strength loss and flexural strength loss of mortar under low pressure and low humidity environment. It was also found that the water absorption of the mortar in low pressure and low humidity environment was related to the tortuous degree of the pores inside the specimen. Conclusion: The introduction of 1% NS contributed the most to the mechanical properties (compressive strength and flexural strength) and durability (water absorption) of cement mortar.

Background: Titanium dioxide (TiO2) is an oxide-based material that has been recently discovered by many researchers owing to its properties such as a good absorber with excellent optical properties and the best stability compared to lead, Pb, which is not stable in the ambient air and is a toxic material. TiO2 is a non-toxic material and is not hazardous to the environment. TiO2 became a favored choice in selecting as a layer because of faster electron extraction and suitable bandgap energy. Objective: In this study, we deposited and optimized TiO2 at different TiO2 precursor molar concentrations varying between 0.005 - 0.05M. Methods: A one-step solution process and a low-temperature processing spin-coating technique were used. Results: Using the field emission scanning electron microscope, it was found that the surface morphology of the TiO2 Nanostructures Layer (NsL) was evenly distributed, presenting a homogeneous surface. An atomic force microscope showed that the TiO2 NsL appeared as a uniform, dense and compact surface close to each other. It was revealed that the surface roughness value (RMS) was 47.72nm, and the thickness of TiO2 NsL (Pmax) was 26.82nm. Besides, the surface coverage was good and uniform, while the percentage of surface roughness was found to be 11.8% using a surface profiler. The Ultra-violet visible spectroscopy showed the bandgap energy of 3.11 eV. Conclusion: The optimum result suggests that TiO2 NsL, as an electron transport layer (ETL), could be used for fabrication in the architecture engineering structure of Bi- perovskite based solar cell devices in the future.