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Nanomaterial-Based Energy Storage and Supply System in Aircraft Systems
Published in Keka Talukdar, Nanomaterials-Based Composites for Energy Applications, 2019
From hall-pitch relationship, it is obvious that with the decrease of grain size, the strength of the metals increases.Properties of metals are based on the Hall-Pitch relationship–that states as grain size decrease, strength increases. Nanocrystalline materials are characterized by sufficient increases in ultimate tensile strength, yield strength, and hardness. For example, the fatigue lifetime can be increased by up to 300% by using NMs with a sufficient reduction of grain size in comparison with conventional materials.Nanostructured metals, particularly titanium and aluminum alloys can improve the mechanical properties and enhance the corrosion resistance.Metals can be strengthened by ceramic fibers such as carbide, aluminum oxide, silicon, or aluminum nitride. Advantages of these so-called Metal matrix composites (MMC) are high thermal stability, high strength, high thermal conductivity, a low density, and a controllable thermal expansion. MMC has the potential to substitute aluminum and magnesium parts in the future
An Overview of Viable Unconventional Processing Methods for Advanced Materials
Published in T. S. Srivatsan, T. S. Sudarshan, K. Manigandan, Manufacturing Techniques for Materials, 2018
Subramanian Jayalakshmi, Ramachandra Arvind Singh, Rajashekhara Shabadi, Jayamani Jayaraj, Sambasivam Seshan, Manoj Gupta
Materials with nanometer/sub-micrometer–scale crystalline structure are of interest in materials development. Nanocrystalline materials have an average grain size of less than 100 nm (Lu 1996). A small crystallite structure implies a sizable volume fraction of grain boundaries. Because of this, nanocrystalline materials can exhibit exceptionally high properties (Lu 1996). For example, nanocrystalline materials exhibit increased strength/hardness, improved ductility/toughness, superior soft magnetic properties, and enhanced wear resistance when compared to their microcrystalline counterpart. It has been identified that a grain boundary–based deformation mechanism predominantly manifests during deformation of nanocrystalline material, unlike the dislocation pile-up–based mechanisms occurring in coarse-grained materials (Lu 1996; Suryanarayana 2001). Nanocrystalline materials, at times, can also contain crystalline/quasi-crystalline/amorphous phases when they are made through devitrification of amorphous structure (Lu 1996). Nanocrystalline metallic particles can be obtained using the gas condensation technique. Other methods of synthesizing nanocrystalline materials include the following: (i) mechanical alloying (ball milling), (ii) electrodeposition, (iii) rapid quenching, and (iv) devitrification of amorphous structure (Lu 1996; Suryanarayana 2001). While severe plastic deformation techniques, such as equi-channel angular processing (refer to Section 9.3.3.2), are being widely used, other new severe plastic deformation methods have also been developed and put to use.
Volatile Organic Compound–Sensing with Different Nanostructures
Published in Sunipa Roy, Chandan Kumar Ghosh, Chandan Kumar Sarkar, Nanotechnology, 2017
Sunipa Roy, Swapan Das, Chandan Kumar Ghosh, Chandan Kumar Sarkar
Nanocrystalline materials are single- or multiphase solids with the grain size of a few nanometers (10−9 m), typically less than 100 nm. As the grain size is small, the surface-to-volume ratio is large and there are numbers of GB in the bulk. The high surface-to-volume ratio makes it useful for different applications, for example, optoelectronic devices, biosensors, and nanomachines. Smaller particle size (and higher surface-to-volume ratio) will enhance the sensitivity by increasing the active area of gas sensing in the film and also by promoting surface adsorption of gaseous species by increasing the number of dangling bonds. A huge number of fractional atoms reside in the GB, and they form dangling bonds with the target species. The properties of nanocrystalline materials are completely different from those of the polycrystalline one due to the presence of these dissatisfied atoms on the surface. A nanostructured material mainly includes (1) nanoparticles, (2) nanocrystalline materials, and (3) nanothin film. Most of the commercial applications of nanostructured materials include coatings, electrodes, and functional nanostructures.
A review of cutting tools for ultra-precision machining
Published in Machining Science and Technology, 2022
Ganesan G., Ganesh Malayath, Rakesh G. Mote
According to Hall-Pitch law, the hardness of polycrystalline materials increases with decreasing the average grain size (Pande and Cooper, 2009). With the help of advanced tools of nanotechnology, nanocrystalline materials with a grain size in the order of nm can be synthesized. The research to find new tool materials for UPC applications is more inclining toward developing nanostructured ultra-hard variants of the existing materials. Ultra-nano crystalline diamond (UNCD) has a minimum grain diameter of 2 nm (Remediakis, et al., 2009), and nanocrystalline cBN has a minimum grain diameter of 10 nm (Solozhenko et al., 2019). It is also observed that coherent twin boundaries are energetically more stable than the nanograined variants, which makes the nanotwinned structured tool materials perform better in machining (Tian et al., 2013). Considering this technical merit of nanotwinning, nanotwinned diamond and nanotwinned cBN are considered to be future tool materials for UPC. More research has to be dedicated to evaluating the machining performance of these tool materials on different workpiece materials.
Synthesis of cenosphere supported heterogeneous catalyst and its performance in esterification reaction
Published in Chemical Engineering Communications, 2018
Vishal S. Chandane, Ajit P. Rathod, Kailas L. Wasewar, Shriram S. Sonawane
The XRD patterns of pristine cenosphere and FAC supported catalyst are presented in Figure 2(a,b). As can be seen from the figure, the cenosphere material reveals the presence of mainly orthorhombic mullite (JCPDS Card No. 83-1881) and hexagonal quartz (JCPDS Card No. 78-1252) both in pristine cenosphere and FAC supported catalyst. This elucidates that the cenosphere material is mainly composed of mullite and quartz. The presence of amorphous phase of the material was identified as a broad diffraction hump between region 2ϴ = 18–38°. This reveals the partial crystalline nature of material. However, significant amounts of silica (JCPDS Card No. 43-0596) and sulfate (JCPDS Card No. 33-1285) were observed in FAC supported catalyst. This indicates that impregnation enhances the amount of silica content. This enhanced silica content is responsible for the enhancement of BET surface area. Additionally, it was also observed that the overall crystallinity of pristine and FAC supported catalyst was observed to be nearly same (Surolia et al., 2010).The nanocrystalline phase of the material has been identified from the average crystalline size (12 nm).
Electrochemical and hydrogen embrittlement of a micro-alloy steel coated with nanocrystalline nickel by pulse electrodeposition
Published in Philosophical Magazine Letters, 2020
P. Kar, P. Siva Prasad, M. M. Ghosh, K. S. Ghosh
Nanocrystalline (NC) materials with unique properties have been developed by gas condensation, ball milling, sol–gel, severe plastic deformation and electrodeposition [20–23] techniques. For the preparation of large quantities of pure metals and alloys ball milling (impure products), inert-gas condensation (expensive) and precipitation methods are not suitable. Pulsed electrodeposition (PED) is a versatile method for the preparation of nanostructured metals and alloys. In last two decades, PED has attracted attention as it allows the production of large samples with high purity, low porosity and enhanced thermal stability, enabling the adjustment of grain size, their shape and their distribution by proper pulse parameters, as well as the bath compositions and conditions [24–31].