Development of a nano-hybrid coolant for machining operation

. This study involved the development of a nanofluid and its experimental use during a machining operation for enhancement of the surface profile of a mild steel rod. Silica nanoparticles were made from coconut shell and rice husk using a chemical process, and then disseminated into distilled water to create the hybrid nanofluid. A control sample was used to compare the performance of the created nano machining fluid. The mild steel samples had a better surface roughness when nano machining fluids were used.


Introduction
Nanotechnology is the study and manipulation of nanoscale particles in order to take advantage of its unique qualities to solve challenges in a variety of industries.Nanoparticles, in theory, are particles with at least one dimension of 1 to 100 nanometers (Hasan 2015).Nanomaterials are divided into categories based on their size, structure, and composition.Nanoparticles are classified by their size, shape, physical, and chemical properties.Carbon nanoparticles, ceramic nanoparticles, metal nanoparticles, semiconductor nanoparticles, polymeric nanoparticles, and lipid-based nanoparticles are a few examples.Carbon nanotubes (CNTs) and fullerenes are the two major components found in carbon-based nanoparticles.Carbon nanotubes (CNTs) are graphene sheets wrapped into a tube.Because they are 100 times stronger than steel, these materials are primarily employed for structural reinforcement.Ceramic nanoparticles can be used as a good drug delivery agent by regulating several of their features, such as size, surface area, porosity, and surface to volume ratio.These nanoparticles have been utilized to treat bacterial infections, glaucoma, cancer, and other illnesses.Metal nanoparticles are made chemically by reducing metal-ion precursors in solution with chemical reducing agents.These have a high surface energy and the capacity to adsorb tiny molecules.These nanoparticles can be used in research, biomolecule detection and imaging, and environmental and bioanalytical applications.Lipid nanoparticles are spherical in shape and range in diameter from 10 to 100 nanometers.It is made up of a lipid-based solid core and a soluble lipophilic molecular matrix.Surfactants and emulsifiers help to keep the exterior core of these nanoparticles stable.These nanoparticles could be used in cancer therapy as a medication carrier and delivery system, as well as for RNA release.Traditional cutting fluids are often made in hazardous ways, are non-renewable and poisonous, and constitute a health risk to machinists.Every year, a considerable number of agricultural waste products that may be used in a variety of technological disciplines are not adequately exploited.

Materials and methods
The materials and reagents used in the preparation of the silica nanoparticles includes Rice husk, Sodium hydroxide (NaOH) pellets, Silver nitrate, Silver nitrate, Magnetic Stirrer, Hydrochloric acid (HCl) and Coconut shell.The equipment used for the study were a muffle furnace, magnetic stirrer/ hotplate, centrifuge, ultrasonic bath, digital electronic weighing balance, beaker (1000ml), centrifuge tubes (10ml), Spatula (stainless steel).

Experimental procedure
To produce the needed nano coolant from the rice husk ash, the following procedures were followed and implemented in the order: sourcing agro-waste material, burning, grinding, milling, nanoparticle synthesis, centrifugation, calcination, and sonication.

Preparation of Rice husk Ash
To begin, the biomass was obtained from one of the cafeterias of Afe Babalola University situated in Ekiti state south west of Nigeria.The shafts were then sorted and dried for three days in the sun.A hardened steel crusher and a disc grinder were used to grind it into a rough coarse powder.The rice husk powder was then burned in a Muffle furnace at 900°C for around 5 hours, yielding rice husk ashes.After that, the hot rice husk ash was allowed to cool for 24 hours.Figure 2 shows the rice husk at various stages of preparation.

Results and discussion
The morphological and microstructural characteristics of the different nanoparticle powder samples were determined prior to the commencement of the experiments.

Microstructural examination
The SEM above was taken at 18000 magnification with acceleration voltage of 20KVat a working distance of 18mm.The examination was done using a JOEL-JSM 7600F scanning electron microscope.The magnification was done to allow for the viewing of materials at various magnifications and clearer results.The white parts show the presence of loosely packed silica nanoparticles clearly visible at in Figure 3a at a magnification of 18,000.

EDS for rice husk ash raw material
The silica particles, coconut shell and rice husk were tested using electro dispersive X-ray spectroscopy (EDX) as shown in the EDS graphs in Figure 4.This study shows the chemical composition of silica found in the nanoparticles in Figure 4.The significant elements of the Nanoparticles from the rice husk raw materials are 45.00% of Silica, 28.68% Oxygen and 12.45% Carbon (Figure 4a).Also visible in the results is the presence of major phases SiO2 in graph, the rice husk has various other elements, such as Potassium, Sodium, and Phosphorus due to a lack of leaching before burning, and these elements remain in the sample after sufficient heating and calcining to remove impurities and other trace elements.

SEM/EDS results for coconut shell
The SEM image above was taken at 10000x magnification, with acceleration voltage of 15KV at a working distance of 13mm.The examination was done using a JOEL-JSM 7600F scanning electron microscope.The magnification was done to allow for the viewing of materials at various magnifications and clearer results (Figure 4a).It can be seen that there were sparsely any visible white patches indicating that only few incidence of silica in the coconut shell.The EDS result (Figure 4b) show that Iron and Carbon are the dominant elemental composition of the coconut shell with percentage compositions of 45.82% and 44.36% both elements sharing over 90% of the composition of the material which accounts for the high strength values displayed by the coconut shell.

Surface Roughness Analysis
The surface topography of the treated samples was assessed using surface roughness analysis.From the results obtained, average roughness values for Samples A, B and C was 1.14, 1.27 and 0.9 µm respectively.The root mean square roughness values for Samples A, B and C were 2.6, 2.3, 2.5 µm respectively.The absolute peak roughness values for Samples A, B and C was 6.3, 5.7 and 7.3 µm.The maximum peak roughness values for Samples A, B and C was 16.1, 13.3 and 15.7 µm (Table 1).Basically, Sample B had the smallest roughness values of the three samples.This sample returned the finest profile for all the roughness types analyzed.

Conclusion
This experiment uses coconut shell and rice husk to develop a hybrid nanofluid that can be used as a nano cooler for machining processes.A milling operation was carried out using the nano coolant.It can be concluded that when applied to mild steel, the created nano coolants resulted in a smoother surface finish and greater application durability than the control.The chemical synthesis technique was used to effectively manufacture silica nanoparticles powder from rice husk.The sizes of the silica particles produced ranged from 10 to 28 nm, with an average diameter of 18.585 nm, well within the nanometer range.

Fig. 4 .
Fig. 4. EDS graph for (a) rice husk ash raw material (b) developed silica nanoparticles (c) nanoparticles developed from Coconut Shell

Fig 4 :
Fig 4: (a) SEM Micrograph Nanoparticles developed from Coconut Shell (b) EDS for Coconut Shell

Table 1 :
Surface Roughness Values for Samples.