Processing of Graphene/CNT-Metal Powder

In recent days, the demand for powder metallurgy components has increased due to unusual combination of properties. Carbon allotropes such as graphene and CNT are the novel material to enhance the properties of powder metallurgy component. However, processing of such materials is in infancy stage due lack of advance processing technique. This can be addressed through integration of several fabrication techniques to meet the industrial demands. The processing method and its important parameter will define the final property of the component. Such materials have found its applications in various fields like, sports, bio implants, aerospace and automobile sector

Tribological Aspects of Graphene-Aluminum Nanocomposites

Graphene is a new class of material in carbon group with strong sp2—hybridized 2D-sheet like nanomaterial. In order to make an effective utilization of their astounding properties, they are currently used in the form of reinforcements in various proportions in metals and its alloys to fabricate the nanocomposites. Graphene is incorporated in oil and grease at nano range that results in higher load-carrying capacity compared with that of raw grease and oils without additives, which shows that graphene possesses self-lubricating capacity. Graphene is a planar sheet-like structure (2D), with more contact surface area in the developed composites that can make them suitable for industrial applications with well-established tribological performance. The novelty of this work focuses on the role of graphene addition in enhancing the wear performance aluminum composites to replace the conventional materials by graphene composite combinations. The current chapter explains the processing and tribological performance of graphene-aluminum composites and its effect with various hybrid combinations of MWCNT/SiC/Al2O3. Dispersion of graphene is carried out through ultrasonic liquid processor followed by ball-milling aluminum powder. Thus prepared precursors are vacuum-pressed and microwave-sintered. Graphene in the nanocomposites has resulted in significantly improving the tribological properties, where it gives the wear resistance by creating a solid, lubricant layer between the sliding surfaces

Interaction of MWCNTs and GNPs with the elements on the development of equiatomic Fe25Co25Cr25Cu25 High Entropy Alloys (HEAs)

This work is focused on developing equiatomic Fe25Co25Cr25Cu25-based HEAs, adding 2 wt% of Multi-Walled Carbon Nanotubes (MWCNTs) and Graphene Nanoplates (GNPs) as a reinforcement. Particularly, the addition of copper (Cu) to the other alloy systems is the best way to enhance thermal and phase stability. Still, elemental segregation is an important limitation while adding Cu to other elements, which reduces the strength-ductility balance. MWCNTs and GNPs are added to control the Cu segregation level by acting as structural reinforcement and altering the microstructure. The alloy fabrication is done through Mechanical Alloying (MA) followed by the Vacuum Arc Melting (VAM) process. The fabricated samples are annealed at a temperature of 1100 °C for 24 h to improve the elemental homogenization and reduce the internal stress of the alloys. The Fe25Co25Cr25Cu25 alloys with FCC phases are confirmed from the X-ray diffraction (XRD) analysis. Thermal stability and thermal transition of MA powders are confirmed with the help of Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). The Electron Backscatter Diffraction (EBSD) analysis reveals the grain and grain boundary interaction behaviour resulted due to the addition of reinforcement. Fe25Co25Cr25Cu25 alloy exhibited a microhardness value of 91.50 HV, which reached 382.30 HV and 448.15 HV due to the addition of MWCNTs and GNPs, respectively. Based on the results, adding 2 wt% of GNPs has better interfacial bonding and mechanical properties than Fe25Co25Cr25Cu25 and Fe25Co25Cr25Cu25 + MWCNTs HEAs

A FEA simulation study of ball end mill for fixed 3+1 / 3+2 axis machining of Ti-6Al-4V.

This paper presents a Finite Element Analysis (FEA) simulation study conducted on ball endmill for fixed 3 + 1 and 3 + 2 axis orientations for machining Ti-6Al-4 V. This work adopts a tungsten carbide (WC) ∅18.6 mm diametrical/6fluted ball endmill to analyse maximum principal elastic strain (ϵmax-max-principal-elastic), maximum principal stress (σmax-principal)along with cutting tools forces in the axial (Fz), radial (Fy), tangential (Fx) and total (Ftotal) directions. The machining orientations considered for 3 + 1 and 3 + 2 axis are (i) tilt angles of 5°, 10°, 15° & 20° and (ii) lead angles of 5°, 10° & 15° with a constant fixed tilt angle of 10°. The cutting speed and feed rate per tooth is taken as 450 m/min and 0.5 mm/tooth. These are based on a high speed machining (HSM) scenario and has been dynamically simulated for a maximum of 175,000 cycles. From the simulation study considered at 16-20 valid cutting points, it can be noticed that in 3 + 1 axis, for a tilt angle of 10° and 3 + 2 axis for a Tilt 10°/Lead 10° the σmax-principaland ϵmax-max-principal-elasticare higher when compared with all tilt/lead angles. In case of total forces (Ftotal) from all 3 directions (Fx, Fyand Fz) not much variation can be noticed for different tilt/lead angles, but higher values are recorded with 3 + 1 axis at 5° tilt angle and 3 + 2 axis at tilt/lead angle of 10°. The paper provides a critical comparative study on the 3 + 1/ 3 + 2 axis orientations highlighting the cutting strain/stress with tool forces at valid cutting points considering entry, middle and exit region of the blank by emphasizing the importance of cutting tool design parameters

Phase structure, microstructure, and mechanical properties of FeCoCrNi-based eutectic high-entropy alloys reinforced with MWCNTs and Gr

This study primarily focuses on the phase structure, microstructure, and mechanical behaviour of Fe25Co25Cr25Ni25 equiatomic EHEAs upon adding 2 wt% of Multi-Walled Carbon Nanotubes (MWCNTs) and Graphene (Gr) as reinforcements. The alloying processes include Mechanical Alloying (MA) and Vacuum Arc Melting (VAM). The as-milled MA powder is irregularly shaped, with an average particle size of 23.5 μm. Samples subjected to MA followed by VAM exhibited a single-phase alloy composition, with a near-equal chemical distribution of major Face-Centered Cubic (FCC) and minor Body-Centered Cubic (BCC) crystal structures, as confirmed by X-ray diffraction (XRD) analysis. The Vickers microhardness values of the Fe25Co25Cr25Ni25 EHEAs samples were 123 ± 7 HV, while the additions of MWCNTs and Gr increased the hardness to 146 ± 6 HV and 155 ± 9 HV, respectively. To further enhance the strengthening behaviour, the EHEAs samples were heat-treated in a Nabertherm furnace at 1100 °C under an argon atmosphere, resulting in hardness values of 134 ± 6 HV, 164 ± 8 HV, and 171 ± 7 HV for the base alloy, MWCNTs addition, and Gr addition. Adding MWCNTs and Gr enhances the thermal stability of the as-milled powder, preventing secondary phase formation and improving the alloy stability of the equiatomic Fe25Co25Cr25Ni25 composition. Specifically, Fe25Co25Cr25Ni25 exhibited thermal stability up to 534 °C, while Fe25Co25Cr25Ni25+MWCNTs achieved 612 °C, and Fe25Co25Cr25Ni25+Gr demonstrated thermal stability up to 713 °C, with no mass loss or phase change observed, as revealed by thermogravimetric analysis (TGA). Furthermore, adding 2 wt% graphene resulted in superior hardness, residual compressive stress, and thermal stability compared to the MWCNTs addition

Birth Mass Is the Key to Understanding the Negative Correlation Between Lifespan and Body Size in Dogs

Larger dog breeds live shorter than the smaller ones, opposite of the mass-lifespan relationship observed across mammalian species. Here we use data from 90 dog breeds and a theoretical model based on the first principles of energy conservation and life history tradeoffs to explain the negative correlation between longevity and body size in dogs. We found that the birth/adult mass ratio of dogs scales negatively with adult size, which is different than the weak interspecific scaling in mammals. Using the model, we show that this ratio, as an index of energy required for growth, is the key to understanding why the lifespan of dogs scales negatively with body size. The model also predicts that the difference in mass-specific lifetime metabolic energy usage between dog breeds is proportional to the difference in birth/adult mass ratio. Empirical data on lifespan, body mass, and metabolic scaling law of dogs strongly supports this prediction

Investigation on the Influence of Cutting Parameters on Machining Performance during Turning of Difficult-to-Machine Steels

The influence of cutting parameters viz. cutting speed, feed rate and depth of cut, tool geometry viz. rake angle, clearance angle and nose radius on turning of AISI 304 stainless steel, AISI 52100 bearing steel and AISI D2 tool steel with advanced cutting tools like multicoated carbide, cermet and alumina inserts are investigated experimentally. The machining performance (i.e. output parameters) considered in this article are surface roughness, flank wear and tool-shim interface temperature. Experiments are conducted according to Taguchi’s orthogonal array and ANOVA is performed to evaluate the significance of each of the input parameters on each of the output parameters. It is found that variation in work materials, and tool materials have significant effect on flank wear apart from cutting speed. Tool cutting edge geometry like nose radius and clearance angle influenced surface roughness apart from the cutting parameters. Variations in work material, cutting fluids and nose radius have considerable influence on tool-shim interface temperatur

Investigation on CFRP 3D printing build parameters and their effect on topologically optimised complex models

This research investigates the effects of building parameters for 3D printing Carbon Fibre Reinforced Polymers (CFRP) and their effect on topologically optimised complex models. The work is conducted by initially developing a DOE varying two parameters in 3D printing namely (i) infill ratio and (ii) infill pattern. Then based on standards ASTM D638 and ISO178, for tensile and flexural tests, specimens are 3D printed and tested for the material Nylon with CFRP (Onyx). From the results it can be observed that (i) specimen with an infill ratio of 85% (constant triangular infill pattern) was found to have the best performance recording a length extension of approximately 5.6 mm under a tensile load of 700 N (ii) in case of infill pattern, triangular shape (constant infill ratio of 37%) recorded the highest the length extension of 7.3 mm under tensile load of 650 N. (iii) 85% infill ratio (constant triangular infill pattern) recorded a bending deflection of approximately 6 mm under a compressive load of 250 N and (iv) the gyroid infill pattern (constant infill ratio of 37%) provided the highest flexural strength with an approximate extension of 5.6 mm under a compressive load of 350 N. After the experimental study and analysing the best parameters, a static analysis and topology optimisation for the 3D printed material (Nylon with CFRP(Onyx)) has been performed on an industrial part for its design validation. Based on the analysis, the original part is redesigned, and again a static analysis simulation is performed to determine the effects of the optimisation process for the same material comparing with 316L-Stainless Steel (SS). Finally, the redesigned model is manufactured with the best 3D printing parameters and validated against the original operating conditions. This study will help industries to use these 3D printing parameters where a metal-based components needs to be replaced with CFRP

Characterization Studies on Graphene-Aluminium Nano Composites for Aerospace Launch Vehicle External Fuel Tank Structural Application

From the aspect of exploring the alternative lightweight composite material for the aerospace launch vehicle external fuel tank structural components, the current research work studies three different grades of Aluminium alloy reinforced with varying graphene weight percentages that are processed through powder metallurgy (P/M) route. The prepared green compacts composite ingots are subjected to microwave processing (Sintering), hot extruded, and solution treated (T6). The developed Nano-graphene reinforced composite is studied further for the strength–microstructural integrity. The nature of the graphene reinforcement and its chemical existence within the composite is further studied, and it is found that hot extruded solution treated (HEST) composite exhibited low levels of carbide (Al4C3) formations, as composites processed by microwaves. Further, the samples of different grades reinforced with varying graphene percentages are subjected to mechanical characterisation tests such as the tensile test and hardness. It is found that 2 wt% graphene reinforced composites exhibited enhanced yield strength and ultimate tensile strength. Microstructural studies and fracture morphology are studied, and it is proven that composite processed via the microwave method has exhibited good ductile behaviour and promising failure mechanisms at higher load levels

Mitigating hydrogen embrittlement in high-entropy alloys for next-generation hydrogen storage systems

Green hydrogen can potentially reduce carbon emissions in several types of automotive, transport and energy industries. However, effective handling of hydrogen during generation, storage, transportation, and distribution poses significant challenges concerning the materials aspect as they are prone to failure. One of the primary reasons for the failure of material is hydrogen embrittlement (HE). This review focuses on developing a new alloy system namely high-entropy alloys (HEAs) to improve and promote microstructure modifications and enhance mechanical properties. Researchers have developed many high-entropy alloys (HEAs) for handling hydrogen to overcome the failure faced by conventional materials. The primary cause of HE in materials is the absence of phase stability and crystal structure changes during hydrogen-induced environments. However, increasing the materials' ductility is more likely to reduce HE failures. Thus, FCC crystal structures are preferred for hydrogen storage materials. Adding multiple elements to increase the entropy level, which supports high-phase stability in all environmental conditions, is an important reason for using HEAs to mitigate HE failures