**3.4. The nanoparticle concentration**

grain size of nanoparticles strongly influences the cost of NPs. Hence, the NP size is definitely needed to optimize while remaining the good performance of nanofluids and the reasonable manufacturing cost [58, 59]. The experimental study on nanolubricant of nanographite (0.1

nanoparticle size and its cost.

From **Figure 34**, the friction coefficient of nanolubricant of the disc specimen as a function of the applied normal force exhibits the much lower values compared to microlubricant and raw mineral lubricant. In this test, the fluid with the smallest NP size 55 nm shows the lowest friction coefficient and reaches stable state when increasing the applied normal force. Moreover, the microfluid of the microparticle size 5 μm shows the highest friction coefficient, which is

**Figure 34.** Friction coefficients of the disc specimen as a function of the applied normal force at different particle sizes [60].

vol%) was carried out with diffrent particle sizes 5 μm, 450 nm, and 55 nm [60].

also higher than that of pure mineral lubricant.

**Figure 33.** The relationship between 500 g of MoS<sup>2</sup>

188 Microfluidics and Nanofluidics

The nanoparticle concentration has attained a significant attention of many researchers because it influences on the performance of nanofluids and directly contributes a large fraction of the NF cost. The experimental study on nanolubricant of nanographite with different concentration 0.1% and 0.5% reveals that the lower friction coefficients and average temperature of lubricated surfaces of the specimens can be achieved in case of nanolubricant with larger volume of fraction 0.5% (shown in **Figures 39** and **40**) [60]. The similar observation can be made from **Figure 36** by the comparison of Al<sup>2</sup> O3 nanofluids with three concentrations 1, 3, and 5%. The value of surface roughness decreases as the nanoconcentration rises from 1 to

**Figure 35.** MQL grinding temperature of hardened AISI 52100 steel with Al<sup>2</sup> O3 nanofluids (grinding wheel speed =0.05m/s; the grinding depth 10 μm) [61].

**Figure 36.** Surface roughness of MQL grinding: (a) across the grinding direction; (b) along the grinding direction [61].

**Figure 37.** Surface roughness of MQL grinding with different nanofluids [62].

5%. In contrast, when rising the volume fraction of nanodiamond in MQL grinding, the little effectiveness on cutting performance can be achieved. From **Figure 37a**, the value of surface

**Figure 40.** Temperature of lubricated surfaces of the specimens as a function of normal force with different nano-

**Figure 39.** Friction coefficients of the disc specimen as a function of the applied normal force at different nanoconcentration [60].

Micro/Nanofluids in Sustainable Machining http://dx.doi.org/10.5772/intechopen.75091 191

In summary, the nanoconcentration is necessarily investigated by further research to optimize this key parameter, by which the application of nanofluids together with MQL technique cannot be limited

roughness increases along with the rise of the concentration of ND.

concentration [60].

**Figure 38.** Measured grinding forces; (a) normal direction and (b) tangential direction in the cases of dry, pure MQL and MQL nanofluid with nanodiamond [62].

**Figure 39.** Friction coefficients of the disc specimen as a function of the applied normal force at different nanoconcentration [60].

**Figure 40.** Temperature of lubricated surfaces of the specimens as a function of normal force with different nanoconcentration [60].

5%. In contrast, when rising the volume fraction of nanodiamond in MQL grinding, the little effectiveness on cutting performance can be achieved. From **Figure 37a**, the value of surface roughness increases along with the rise of the concentration of ND.

In summary, the nanoconcentration is necessarily investigated by further research to optimize this key parameter, by which the application of nanofluids together with MQL technique cannot be limited

**Figure 38.** Measured grinding forces; (a) normal direction and (b) tangential direction in the cases of dry, pure MQL and

**Figure 36.** Surface roughness of MQL grinding: (a) across the grinding direction; (b) along the grinding direction [61].

**Figure 37.** Surface roughness of MQL grinding with different nanofluids [62].

MQL nanofluid with nanodiamond [62].

190 Microfluidics and Nanofluidics

by the cost of nanoparticles. Although the volume fraction of nanoparticles in MQL fluid is relatively small in each experimental research, it will be large when applied to production line in practice.

vw table speed (m/min) f feed rate (mm/rev)

<sup>t</sup> feed rate (mm/tooth)

λs inclination angle (°)

k<sup>r</sup> side cutting-edge angle (°)

SWCNT single-walled carbon nanotube MWCNT multi-walled carbon nanotube MQL minimum quantity lubrication

SQL small quantity lubrication

ND nanodiamond

Tran The Long\* and Tran Minh Duc

University of Technology, Vietnam

NF nanofluid NFs nanofluids NP nanoparticle NPs nanoparticles

**Author details**

**References**

MQCL minimum quantity cooling lubrication

\*Address all correspondence to: tranthelong90@gmail.com

Department of Manufacturing Engineering, Mechanical Engineering Faculty, Thai Nguyen

Micro/Nanofluids in Sustainable Machining http://dx.doi.org/10.5772/intechopen.75091 193

[1] Wong KV, De Leon O. Review article "applications of Nanofluids: Current and future".

Advances in Mechanical Engineering. 2010. DOI: 10.1155/2010/519659

, Fz cutting forces (N)

CNT carbon nanotube CNTs carbon nanotubes

γ<sup>o</sup> rake angle (°) α<sup>o</sup> relief angle (°)

f

Fx , Fy
