## 2 Implementation Details
Prior to the preparation of the nanofluid, the ZnO nanoparticles undergo a preheating process lasting 3 h, aimed at eliminating any moisture content present within the nanoparticles. Subsequently, the dispersion of zinc oxide (ZnO) nanoparticles is achieved by incorporating them into LRT 30 mineral oil. In the present study, a nanofluid containing ZnO with a weight concentration of 0.5% has been formulated and employed as a coolant in the conducted experiment. Zinc oxide (ZnO) nanoparticles are introduced into LRT 30 mineral oil as a means of pre-dispersion, facilitated by a mechanical stirrer for a duration of 2 h. Next, the sample is transferred to the ultrasonication order to subject it to sonication, which serves the purpose of reducing the agglomeration of nanoparticles. The nanofluid sample was subjected to sonication for a duration of approximately 4 h. In the case of the homogeneous mixture of a nanofluid sample, the ZnO nanofluid sample was subjected to continuous mixing using a magnetic stirrer for duration of 4 h. The pictorial image of synthesis of LRT 30-based ZnO nanofluid was displayed in Figure 2. The machinability performance of AISI D2 steel under ZnO-nanofluid MQL environment is evaluated through turning experiments using the Taguchi L\({}_{16}\) OA design after achieving a homogeneous dispersion of the nanofluid. Figure 1: EDS test of ZnO powder. In the current experimental configuration, the continuous supply of lubricant in the normal minimum quantity lubrication (MQL) mode system was modified to a pulse mode. This modification was made in order to gain control over the timing or frequency of the ejection of the air-lubricant mist jet over the machining zone. The primary objective of employing pulse MQL mode is to further reduce lubricant consumption and investigate its heat dissipation capacity, as well as its impact on machining performance. In the current configuration, compressed air is introduced into the solenoid valve, subsequently flowing into the moisture control valve via the air pressure control valve and oil control valve. A minute proportion of the compressed air is introduced into the mixing chamber. Conversely, the lubricant (referred to as LRT 30) is introduced into the mixing chamber from the oil tank as a result of gravitational force. In order to achieve the atomization of the lubricant, compressed air is introduced into the mixing chamber. The compressed air, which has been depleted of moisture, is subsequently introduced into the flow control valve. This valve is responsible for dispensing the mist lubricant in the form of a spray, which is directed into the machining zone through the utilization of a CH10 5/16-type spray nozzle. Pulse time refers to the frequency or timing at which lubricant flow occurs. In this current scenario, pulse timing is set to one second; this implies that when the pulse time is set to 1 s, the lubricant will consistently flow over the machining zone for a duration of one second, followed by a cessation of lubricant flow for the subsequent one second. This cyclic pattern of lubricant flow and pause is then repeated. Moreover, to diminish the undesirable temperature rise in the area of cutting zone, double-nozzle MQL flow can be effective. Nozzles are kept pointed toward to the top and bottom surfaces of the cutting tool in a 90-degree angle position from the tool holder axis. The experimentation details with nozzle positions are displayed in Figure 3.  
Figure 2: ZnO nano-cutting fluid preparation.