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Over the years, machinists have been exploring the hard part turning of AISI D2 steels. Initially, cylindrical grinding was used for this purpose, but it was later replaced by single-point turning due to its advantages such as high material removal, low cost, and greater flexibility. Conventional inserts are used in single-point turning, but they have been reported to have large radial forces, high notch wear, and poor surface finish. Therefore, multi-radii wiper inserts were designed to overcome these machining issues, but their use was restricted to shallower depths of cut and moderate feed rates because of the thick chips produced by the high entry angle. Prime inserts, on the other hand, were designed with a modest entry angle, making them ideal for evaluating tool wear/life, material removal and surface roughness at greater cutting speeds, depths of cut, and feed rates. It was observed that cutting speed has a significant effect on tool wear/life with a contribution of 55.38% followed by feed rate (13.72%) and depth of cut (11.43%). Cutting speed (84.87%) and feed rate (13.01%) are observed to be the most significant parameters controlling material removed. It was also observed that feed rate has a significant effect on workpiece surface roughness with a contribution of 67.30% followed by depth of cut (20.60%), whereas cutting speed had no significant effect on surface roughness. Moreover, it is found that prime insert outperformed wiper and conventional inserts in terms of tool life/wear and surface roughness.

Dry machining of aluminum (Al) 2024 alloy has been performed with four different cutting inserts (cemented carbide, titanium nitride (TiN) coated, titanium aluminum nitride (TiAlN) coated, and polycrystalline diamond (PCD) coated), and their performance is assessed for tool wear and workpiece surface roughness. Design of experiments and response surface methodology (RSM) was performed to optimize the cutting parameters. TiAlN coated inserts presented an average ≈ 21%, ≈ 36%, and ≈ 58% less tool wear than the uncoated cemented carbide, TiN and PCD coated inserts, respectively. While TiN coated inserts exhibited an average ≈ 17%, ≈ 37%, and ≈ 42% less workpiece surface roughness than the uncoated cemented carbide, TiAlN, and PCD coated inserts, respectively. PCD coated inserts have greater mechanical properties, but due to the poor adhesion strength of the coating, it performed worst regarding tool wear and workpiece surface roughness. Energy dispersive X-ray spectroscopy (EDX) analysis of the chips validated our findings that the adhesion of coated tools is also very important for the evaluation of machining performance other than mechanical properties. It is concluded that the mechanical properties and adhesion of the coated tools are both important in assessing the tool wear and workpiece surface roughness. Also, the research community and industry need to consider adhesion strength of the coated tools for better machining performance.

The numerical study investigates the effect of various comparison criteria on the forced convective heat transfer of water-based cuprous oxide nanofluids in a horizontal mini tube under uniform heat flux conditions. The forced convective flow regime was validated, and it was ensured that the free convection effects were not present. The temperature-dependent thermophysical properties were considered for the numerical simulation. The volume concentrations of the nanofluids were kept below 2% (i.e., 0.6%, 1.3% and 1.9%) as higher concentrations lead to agglomeration and sedimentation of nanoparticles. The various comparison criteria employed for the assessment of heat transfer enhancement were equal pumping power, equal velocity, equal mass flow rate and equal Reynolds number criterion. The enhancements in heat transfer coefficient (at ϕv = 1.9% and base fluid Re = 1380) were 7.7%, 4.9%, 3.6% and 3.3% when assessed on the basis of equal Reynolds number, equal velocity, equal mass flow rate and equal pumping power, respectively. It was found that the enhanced heat transfer of the nanofluids should preferably be examined on the basis of equal pumping power criterion instead of above-mentioned other three criteria. The discussion on the invalidity of three evaluation criteria based on Reynolds number, velocity and mass flow rate has also been made.

The most critical energy and environmental challenge that our planet is facing today is to minimize the dependence on fossil fuels. Carbon dioxide may be of utmost significance as a solution of this issue through realization of carbon neutral energy cycle. Potentially, this could be achieved through the carbon dioxide capture as the urgent response to ongoing climate change. Activated carbon (AC) adsorption is one the most effective, environment friendly and techno-economic process for the carbon capture. In the current research, an electro-conductive-activated carbon was prepared by mixing powdered activated carbon (PAC) with an electro-conductive polymer (ECP). Different ratios of 0, 25, 50, 75 and 100 wt% of ECP with PAC were used for the different analyses of activated carbons in a gas mixture of CO2/N2 using a physical adsorption system. Adsorption and desorption analyses, capacities of the process and desorption effects were examined. Electro-conductive polymers (ECP) were mixed with AC samples, where breakthrough time was increased up to 400% when mixed with the PAC for CO2 adsorption. Following adsorption analysis, desorption of activated carbons was conducted with different potentials. It was revealed that mixing could help the PAC sample to overcome the packing issue to increase the breakthrough capacity and the volumes before and after the breakthrough adsorption in the packed bed systems. The desorption rates of the PAC sample were also enhanced, and fast desorption was observed when mixed with ECP. It is envisioned that this method is very much promising carbon capture method for the techno-economic feasibility and sustainable development of the environment.

Tribological, mechanical, and chemical properties of the TiN coatings on Ti substrate were experimentally investigated for implant applications. X-ray diffraction (XRD) demonstrated that the principal crystal structure of TiN coating was (111) preferred orientation with FCC structure. Experimental evaluation was conducted at two substrate surface roughness, i.e., 0.1 μm and 0.4 μm. TiN coatings having 0.4-μm substrate surface roughness and approximately 3.3-μm coating thickness demonstrated optimum results of adhesion strength, hardness, coefficient of friction, wear rate, and corrosion rate in simulation body fluid (SBF). The selected TiN-coated sample exhibited maximum of 16.585 GPa hardness, 238.7 GPa elastic modulus, approximately 20 N adhesion, and 0.088 coefficient of friction. TiN coating showed approximately 8 times more corrosion resistance and 4 times more wear resistance than the bare titanium substrate. Energy dispersive spectroscopy (EDS) analysis of the wear tracks of TiN coating in SBF showed no presence of any harmful ingredients and confirmed its biocompatibility over the usage time in SBF. TiN-coated sample with higher substrate surface roughness (0.4 μm) demonstrated better tribo-mechanical properties and could reduce the cost of production than the conventionally used TiN-coated Ti implants of lower substrate surface roughness (0.1 μm).

Magnesium oxide (MgO) is a good candidate for an interface layer in multifunctional metal-oxide nanoscale thin-film heterostructures due to its high breakdown field and compatibility with complex oxides through O bonding. In this research, molecular beam epitaxy (MBE) is used to deposit 10 nm to 15 nm MgO single-crystal films on silicon carbide with hexagonal polytype 6H (6H-SiC) to serve as an interface layer for effective integration of functional oxides. In this work, the effect of MBE process control variables on the growth rate of the MgO film measured in nanometers per minute is investigated. Experiments are conducted at various process conditions and the resulting MgO film growth rate at each combination of process conditions is measured. The process control variables studied are the substrate temperature (100 °C – 300 °C), magnesium source temperature (328 °C – 350 °C), plasma intensity (0 mV – 550 mV), and percentage oxygen on the starting surface of 6H-SiC substrate (9 % – 13 %) after the substrate is prepared by high-temperature hydrogen etching. The film thickness is computed using the effective attenuation length (EAL) of silicon photoelectron peak intensity as measured by x-ray photoelectron spectroscopy (XPS). The film thickness is converted to growth rate by dividing it with the duration of film growth. Using the experimental data, a neural network model is developed to estimate growth rate for any given process variable combination. From this neural network model, multiple replications of data were generated to conduct a 3-level full factorial design of experiments and response surface-based analysis. The study reveals that the plasma intensity has the most significant influence on growth rate. The results indicate that growth rate is relatively low on high-quality substrates with √3 × √3 R30° reconstructed 6H-SiC (0001) surface with optimum oxygen content (approximately 10 %); in contrast, the growth rate is relatively high on substrates with high surface roughness and excessive oxygen on the starting substrate surface.

Chemical vapor deposition is one of the several viable methods for growing vertically aligned single-walled carbon nanotubes (VA-SWNTs). Utilizing cobalt (Co) catalyst supported on multilayer Al/SiO2 and a hydrocarbon feedstock, VA-SWNTs are grown in excess of a millimeter height. To control VA-SWNTs length, one has to use the right combination of process control variables such as hydrocarbon gas flow rate, chamber temperature, and chamber pressure. This paper presents a process meta-model-based full factorial experimental design and analysis to study the yield of tall VA-SWNTs. All of the process variables under the study play a role in influencing VA-SWNTs length; the current study investigates main effects and their interactions. The meta-model-based analysis demonstrates that the hydrocarbon flow rate and the chamber pressure are the most statistically significant control variables that influence the length of VA-SWNTs. In addition, the response surface graph confirms that a higher gas flow rate at lower chamber pressure will consistently yield tall VA-SWNTs. We found that gas flow rate is the most significant of the control variables and only the optimum gas flow rate can ensure the growth of tall VA-SWNTs. We noticed that the interaction of gas flow rate with chamber temperature is also significant to the length of VA-SWNTs grown. All these observations together indicate that the dynamic pressure of the gas in the chamber plays an important role in the assurance of the length of VA-SWNTs. Outcomes of this investigation are beneficial for moving us closer towards producing VA-SWNTs on a mass scale.