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Purpose: The purpose of this study is to evaluate the effectiveness of hybrid Al2O3-TiO2 nano-cutting fluid in the turning process application under the selected significant machining parameters consisting of nano concentration, depth of cut and feed rate. Design/methodology/approach: The preparation of aqueous hybrid Al2O3-TiO2 water-based nano-cutting fluids and their application as the cutting fluid in turning operations are undertaken. The Al2O3-TiO2 hybrid nano-cutting fluids were prepared through a one-step method; by dispersing nanoparticles of Al2O3 (average diameter 30 nm) and TiO2 (average diameter 30-50 nm) in CNC coolant based at four different volume concentrations (1%, 2%, 3%, 4%). The effectiveness of turning cutting performance, namely cutting temperature (°C), average surface roughness (Ra), and tool wear (%), were assessed via air-assisted nano cutting fluids impinged through MQL setup in turning of Aluminium Alloy AA7075. The response surface method (RSM) was employed in the design of the experiment (DOE). Findings: The lowest cutting temperature, surface roughness, and tool wear of 25.8°C, 0.494 µm, and 0.0107%, are obtained, respectively, when the combinations of hybrid nano cutting fluid concentration of 4%, feed rate value of 0.1 mm/rev, and 0.3 mm depth of cut is used. Research limitations/implications: The result in this paper is based on the experimental study of Al2O3-TiO2 hybrid nano-cutting fluid using CNC turning operation. The process focuses on the finishing process by using a finishing insert. Further work using roughing process may be suggested to observe the better performance of this cutting process using nano-cutting fluid towards reducing the wear rate. Practical implications: The use of Al2O3-TiO2 hybrid nano-cutting fluid coupled with MQL in the CNC turning process is considered a new method. Machining soft and delicate materials such as Aluminium should consider using this combination technique since it lowers the cutting temperature and removes the chips, reducing the adhesive wear. Originality/value: The hybrid nano-cutting fluid can replace the conventional cutting fluid and will perform better if combined with the MQL cooling technique; this new method should be considered by major industry players that require a high-precision finished product such as the product that involves aircraft and aerospace applications. [ABSTRACT FROM AUTHOR]

Purpose: This paper is to study the stability of the current combination of hybrid nano-cutting fluids due to the recent progress in the analysis of nano-cutting fluids, such as the assessment methods for the stability of nano-cutting fluids, have revealed that instability is a common problem associated with nano cutting fluids. Design/methodology/approach: Five samples of 0.001 vol% that are suitable to be tested at UV-Vis machine, Al2O3-TiO2 hybrid nano-cutting fluid was prepared using a one-step process with the help of a magnetic stirrer to stir for 30 minutes with different sonication time to determine the best or optimum sonication time for this hybrid nano-cutting fluid. Stability of nano-cutting fluids was analyses using UV-Vis spectrophotometer (0.001%, 0.0001%, 0.00001%), visual sedimentation (1%, 2%, 3%, 4%), TEM photograph capturing techniques (2%) and zeta potential analysis (0.001%, 0.00001%), that used different volume concentration that is suitable for each type of stability analysis. Findings: The stability analysis reveals that the best sonication time is 90 minutes, and the UV-vis spectrophotometer shows the stability of all samples is above 80% during a month compared to the initial value. Further, visual sedimentation shows good stability with minimum sedimentation and colour separation only. The zeta potential value also shows great stability with a value of 37.6 mV. It is found that the hybrid nano-cutting fluid is stable for more than a month when the nano is suspended in the base fluid of conventional coolant. Research limitations/implications: The result in this paper is based on the experimental study of Al2O3-TiO2/CNC coolant base hybrid nano-cutting fluid for a month. However, to further validate the results presented in this paper, it is recommended to prolong the stability assessment time for six months for longer shelf life. Practical implications: The finding of this experimental study can be useful for highprecision product machining using similar CNC coolants, especially for aircraft and airspace applications for machining parts. Originality/value: No thorough stability assessment using all four types of stability analysis is done on Al2O3-TiO2/CNC Coolant base hybrid nano cutting fluid. [ABSTRACT FROM AUTHOR]

The effect of compressor speed, initial refrigerant charge and volume concentrations of SiO2/PAG nanolubricant on the performance of automotive air-conditioning (AAC) system are investigated in this study. Response surface method (RSM) was used in designing the experimental work and is based on face composite design. The developed quadratic models from RSM were helpful to envisage the response parameters namely heat absorbs, compressor works, and coefficient of performance (COP) to identify the significant relations between the input factors and the responses. The results depicted that adding SiO2 nanoparticle into PAG lubricant will enhance the COP of AAC. Optimization of independent variables was performed using the desirability approach of the RSM with the goal of maximizing the heat absorb and COP, consequently, minimizing the compressor work. The results revealed that the optimal condition with a high desirability of 73.4% for the compressor speed of 900 rpm, refrigerant charge of 95 g and volume concentration of 0.07%. At this condition, the AAC system operated with 193.99, 23.28 kJ kg−1 and 8.27, respectively, for heat absorb, compressor work and COP. DoE based on RSM was capable of optimizing the significant parameters which affect AAC performance. [ABSTRACT FROM AUTHOR]

The use of automotive air conditioning (AAC) nowadays is essential because of the hot climate and global warming. The AAC increases the overall fuel consumption in order to cool down the car cabin, hence releases more CO2 into the atmosphere. Nanotechnology can be implemented into the lubricant of the AAC compressor which can aid in reducing the power consumption. Therefore, this paper investigates the effect of SiO2/PAG nanolubricants on the AAC performance and energy saving. The SiO2/PAG nanolubricants were prepared using the two-step method. The sedimentation observation and UV-Vis spectrophotometer evaluation confirmed the stability of the nanolubricants. The tribology analysis revealed the coefficient of friction of SiO2/PAG nanolubricants better than the original PAG lubricants. The performance parameters and power consumption (energy saving) of AAC system using SiO2/PAG nanolubricants were compared with PAG lubricants. The condenser pressure and the pressure ratio of the AAC system decreased by an average of 10.8% and 5.6%, respectively. The volumetric heat absorb increased up to 3% and the coefficient of performance increased by an average of 21%. The compressor work and power consumption of the AAC system reduced by 16.5% and 4%, respectively. As a conclusion, it was recommended to use 0.05% volume concentration of SiO2/PAG nanolubricants in AAC compressor for optimum system performance and energy saving. [ABSTRACT FROM AUTHOR]

Lubrication is a requisite for any mechanical equipment that moved to avoid wear of sliding parts and enhance the equipment operation consistency. The objective of this study was to seek a new improved automotive air conditioning (AAC) compressor lubricant to enhanced AAC performances. The type of compressor is piston type, Sanden SD 7H10,that normally used by Malaysia compact car. The tribological investigation was focusing on Coefficient of friction and wear rate. The wear rate and coefficient of friction (COF) of Alumina/Polyalkylene glycol (Al2O3/PAG) nanolubricant were evaluated employing reciprocating test conditions to replicate a piston ring/cylinder liner contact following the ASTM G 181-11 Standard. Al2O3 nanoparticle was dispersed in PAG lubricant for volume concentrations between 0.006 to 0.014 vol %. Al2O3/PAG nanolubricant with 0.010 % vol. concentration showed the best reduction of frictional power loss. The enhancement of power saving due to frictional losses was up to 7.59 % compared to pure PAG lubricant. Furthermore, the wear rate of piston liner reduced by 33.39 %. Al2O3 nanoparticles in this circumstances, performed as a solid lubricant to reduce wear. These results show potential approach to enhance the AAC performance, save automotive fuel and elongated the life span for AAC compressor. [ABSTRACT FROM AUTHOR]

Thermal conductivity and viscosity of the different combination of composite nanolubricants for 0.02% volume concentrations at a temperature range of 30 to 80 °C were investigated. Al2O3, SiO2 and TiO2 nanoparticles were dispersed in the Polyalkylene Glycol (PAG 46) lubricant using the two-step method of preparation. Thermal conductivity and viscosity were measured using KD2 Pro Thermal Properties Analyzer and LVDV-III Rheometer, respectively. The result shows that the thermal conductivity and viscosity of composite nanolubricants decrease with temperature. Composite nanolubricants behaved as Newtonian in the range of the temperatures studied. The most optimum combination of composite nanolubricant is Al O3- SiO2/PAG as it yields higher enhancement in thermal conductivity but lower in viscosity. [ABSTRACT FROM AUTHOR]

Ultrasonication is the act of applying sound force to agitate particles in a sample with the frequency of more than 20 kHz. It is an external vibration induced during preparation of nanolubricant that helps the particles to overcome the van der Waals force bonding. Nanolubricant prepared is intended to be used in automotive air conditioning (AAC) system to improve its performance. In this work, stability of Al2O3/Polyalkylene glycol (PAG) and SiO2/PAG nanolubricants of 0.2 % volume concentrations with different sonication time were investigated. Five samples for each nanolubricant were prepared by two-step method process with variation of sonication time from zero to two hours' time with half an hour interval. The stability tests were done by visual sedimentation and UV-vis spectrometer. The optimum sonication time found to be one and half hours and two hours for Al2O3/PAG and SiO2/PAG nanolubricants respectively. Both nanolubricants were found stable for more than two weeks' period. [ABSTRACT FROM AUTHOR]

The most challenging matters for the utilization of nanofluid into a certain system is its stability. The nanofluid with undesirable stability will damage the system due to fouling, and settlement from the base fluid. In addition, unstable nanofluid will have a lower thermal performance enhancement. An improved method, 4-Step UV-Vis spectral absorbency analysis has been suggested to improve the stability of the nanofluid. SiO2 nanoparticles were dispersed in the PAG lubricant by using the two-step preparation method. The stabilization methods of the SiO2/PAG were done by using the suggested method. The result indicates that all nanofluid shows good stability in stationary position even after 30 days. The absorbance of every three concentration decreased compared to their respective initial absorbance, but maintained for specific value at over 70 % compared to the initial absorbance even after 30 days. [ABSTRACT FROM AUTHOR]