Current Nanomaterials - Volume 6, Issue 2, 2021

Background: Tribological issues severely confound the smooth operation of moving elements in actuators-based miniaturized devices, e.g., micro-electro-mechanical systems. At micro/- nano scales, surface forces, namely adhesion and friction, manifest strongly and oppose the relative mechanical motion of actuator elements. Topographical modification of surfaces via surface patterning has emerged as a potential route to mitigate surface forces at small-scales. Methods: Capillary force lithography is a simple yet robust technique to fabricate polymer nanostructures with varying shapes/sizes. This paper presents a brief review of the capillary force lithography technique, its salient features and tribological performance of nanostructures fabricated by the technique. Conclusion: Capillary force lithography has several attractive salient features, in particular the ability of the technique to create polymer nanopatterns of varying shapes/sizes without the need for molds with different shapes/sizes. Polymer nanostructures fabricated by the technique effectively reduce surface forces at micro/nano-scales, and are of interest for tribological application in small-scale devices.

An ability to achieve useful properties of structural materials is largely dependent on their bulk microstructure. Over the years, the innate ability to achieve noticeable improvements in structural materials has relied upon processing as a viable means and/or alternative, which in turn determines the resulting microstructure and properties or behavior. Sustained research and development efforts in the domains encompassing materials science, materials engineering and manufacturing processes have made possible the arrival of a time period in which specific properties of a material can be obtained by carefully controlling the architecture of its constituents. Nanostructuring of materials to include both metals and their alloy counterparts is a key for obtaining extraordinary properties that made them attractive for the purpose of selection and use in both structural applications and functional applications. In recent years, the production of bulk nanostructured materials (BNMs) by techniques of severe plastic deformation (SPD) has attracted considerable scientific and technological interest since it offers new opportunities for the fabrication of commercial nanostructured metals and alloys that can be chosen for use in a variety of specific applications. Such nanostructured materials must essentially be not only porosity-free and but also contaminant-free, which makes them an ideal choice for studying, observing and documenting their characteristics, spanning microstructure, properties and mechanical behavior. In this paper, we provide a compelling overview of the approaches most widely used for the purpose of achieving grain refinement using the technique of plastic deformation. An outline of the four most commonly used plastic deformation processing techniques is provided. Salient aspects specific to the technique of equal channel angular pressing (ECAP), high-pressure torsion (HPT) accumulative roll bonding (ARB) of bulk nanostructured metals and surface mechanical attrition treatment (SMAT) of nanostructured layers are provided and briefly discussed. A need for the selection of certain metals and alloys for use in specific applications in the domains spanning, medicine and technology is briefly discussed. The emergence and use of computational nanotechnology, which in essence synergizes the rapid developments in computational techniques and material development, are presented and briefly discussed.

Metal Matrix Nanocomposites (MMNCs) often show excellent properties as compared to their non-reinforced alloys due to either the achieved grain refinement or Orowan strengthening. Especially in light metals such as aluminium and magnesium as the matrix has the potential to be significantly improved in relation to mechanical properties. Functionalisation can also be achieved in some cases. However, the challenge lies in the homogeneous distribution of the ceramic nanoparticles in the melt if MMNCs have been processed via melt metallurgical processes. The large surface area of the nanoparticles generates large van der Waals forces, which need to be overcome. Furthermore, the wettability of the particles with molten metal is difficult. Additional forces can be applied by ultrasound, electromagnetic stirring, or even high-shearing. In this paper, properties of MMNCs with a light metal matrix, which have been produced with the High-Shearing Dispersion Technique are discussed. First, the process with its different characteristics and the underlying theory is presented, and then property improvements are discussed by comparing MMNCs to their matrix materials.

Background: The widespread uses of nanomaterials for healthcare and biomedical applications, such as their anti-cancer activity, anti-oxidant activity and antimicrobial activity, have been avidly studied in recent decades. Owing to the cytotoxicity and harmful by-product generation associated with chemical reagents, plant and microbial-based approaches have been preferred for synthesis purposes. Results: These synthesized nanoparticles possess characteristic properties attributed to their nanosize compared to their macroscopic counterparts. Furthermore, the functionalization of nanomaterials via chemical, physical and biofunctionalization techniques improves the intrinsic, tactile, and associated properties of materials and devices. The functionalized nanomaterials have been explored for the improved colloidal stability, development of smart nanocapsules, DNA-nanoparticles conjugates, protein-nanoparticles conjugates and nano-antibiotics. Conclusion: In this review, the synthesis of biogenic nanoparticles, their properties and applications are explored, and their surface modification and implications towards improved properties are emphasized.

Background: Ultraprecise nano-level surface finish is required in those machine components, which have relative motion among them. Especially in gears that are subjected to heavy wear due to sliding motion, surface finish is one of the critical parameters, which leads to its noisefree operation, efficient power transmission, and longer service life. However, most of the gear manufacturing processes do not produce nano finished gear surface. Therefore, gears need post-processing to finish their surface. Objective: The present study aims to improve the surface finish of helical gears of different helix angles with the help of abrasive flow finishing (AFF) by experimentally identifying the optimum range of processing parameters. Methods: An AFF set up was used for gear finishing using a medium of styrene-butadiene rubber and silicon carbide abrasive. A special type of fixture was developed, which allows the back and forth movement of AFF medium through the annular volume between the fixture and the gear, and at the same time, firmly holds the gear. Results: The optimum combination of the extrusion pressure and abrasive weight percentage is 38 bar and 39.6% that produces the best results with around 75 and 69% improvement in Ra for gear of helix angle 30 and 45°, respectively. Conclusion: Among all studied processing parameters, extrusion pressure and abrasive % were found to be the most influential parameters. The inclination angle between the incoming flow stream of medium and workpiece surface strongly influences the surface finish. This is due to the change in forces acting during finishing with the inclination angle. The helical gear of a smaller helix angle of 30° shows a better surface finish of 110 nm than 124 nm in a helix angle of 45°.

Background: The nanoclay (NC) and Glass Micro Balloons (GMB) based reinforced polymer composites are explored extensively through traditional processing methods. NC shows substantial enhancement in mechanical properties. Polymer composites developed by reinforcing GMB fillers provide a substantial reduction in weight, which is essential in the marine, aerospace, and automotive field. In this study, an attempt is made by developing polymer nanocomposites by reinforcing NC and GMB particles. Objective: The paper deals with 3-dimensional printing (3DP) of lightweight Nanocomposite Foam (NF) developed by mixing nanoclay (NC) and glass micro balloons (GMB) in high-density polyethylene (HDPE). The NF blend is prepared by keeping NC at 5 weight %. Subsequently, GMBs are added by volume (20-60%) to NC/HDPE blend to realize lightweight NFs. Methods: The lightweight feedstock filaments are developed by extruding the blends using a single screw extruder. The extruded NF filaments are used as input in a 3D printer to print NFs. The density of extruded filaments and prints is measured. The printed NFs are subjected to tensile and flexural testing. Results and Conclusion: With an increase in GMB loading, the density of both filaments and prints decreases. Compared to neat HDPE, printed NFs show ∼30% weight-reducing potential. The tensile, flexural modulus and strength increases with GMB loading. NFs exhibited superior mechanical performance as compared to HDPE and NC/HDPE. Further, the property map reveals that the 3D-printed NFs show superior tensile, flexural modulus, and strength in comparison with injection and compression-molded foams.