Titanium Oxide Nanoparticles As Additives in Engine

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JKSUES 196 No. of Pages 6 9 February 2016 Journal of King Saud University – Engineering Sciences (2016) xxx, xxx–xxx 1 King Saud University Journal of King Saud University – Engineering Sciences

www.ksu.edu.sa www.sciencedirect.com

2 ORIGINAL ARTICLE

4 Titanium oxide nanoparticles as additives in engine

5 oil

a,* b 6 Meena Laad , Vijay Kumar S. Jatti

a 7 Applied Science Department, Symbiosis Institute of Technology (SIT), Symbiosis International University (SIU), Lavale, 8 Mulshi, Pune 412 115, Maharashtra State, India b 9 Mechanical Engineering Department, Symbiosis Institute of Technology (SIT), Symbiosis International University (SIU), Lavale, 10 Pune 412 115, Maharashtra State, India

11 Received 2 November 2015; accepted 13 January 2016 12

14 KEYWORDS 15 Abstract This study examines the tribological behaviour of titanium oxide (TiO2) nanoparticles as 16 Titanium oxide; additives in mineral based multi-grade engine oil. All tests were performed under a variable load 17 Nano particles; and concentration of nanoparticles in lubricating oil. The friction and wear experiments were per- 18 UV spectrometer; formed using pin on disc tribotester. This study shows that mixing of TiO2 nanoparticles in engine 19 Tribotester; oil signiﬁcantly reduces the friction and wear rate and hence improves the lubricating properties of

20 Engine oil engine oil. The dispersion analysis of TiO2 nanoparticles in lubricating oil using UV spectrometer shows that TiO2 nanoparticles possess good stability and solubility in the lubricant and improve the lubricating properties of the engine oil. 21 Ó 2016 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

22 1. Introduction need a variety of functional lubricants to decrease the friction 28 and wear of contacting surfaces as well as to signiﬁcantly 29

23 One of the major losses occurring in the engine of an automo- reduce the total energy consumed by mechanical systems. 30 24 bile is due to friction between its moving parts. This loss is sig- Lubricants play a major role in reducing the wear and friction 31 25 niﬁcant and approximately 15% of the total loss of energy and between the two surfaces in contact with each other. In any 32 26 has a direct impact on the efﬁciency and durability of the type of machinery, when there is sliding between machine com- 33 27 engine (Vadiraj et al., 2012). Different mechanical systems ponents, there develops a resistance called friction, to this 34 movement. The relative motion quite often causes wear and 35 tear of the components. Friction can be minimised by interpos- 36 * Corresponding author. Tel.: +91 20 39116471; fax: +91 20 ing a substance of low shear strength between the two moving 37 39116460. E-mail addresses: [email protected] (M. Laad), vijaykumar. surfaces. This phenomenon is known as lubrication and the 38 [email protected] (V.K.S. Jatti). interposed substance is called a lubricant. Hence, lubrication 39 Peer review under responsibility of King Saud University. is fundamental to the operation of all engineering machines. 40 Lubrication is necessary to minimise friction and wear. Many 41 studies have focused on improving the lubrication perfor- 42 mance of general lubricants. One approach is to incorporate 43 Production and hosting by Elsevier particle additives into regular lubricants so that it can reduce 44

http://dx.doi.org/10.1016/j.jksues.2016.01.008 1018-3639 Ó 2016 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Please cite this article in press as: Laad, M., Jatti, V.K.S. Titanium oxide nanoparticles as additives in engine oil. Journal of King Saud University – Engineering Sciences (2016), http://dx.doi.org/10.1016/j.jksues.2016.01.008 JKSUES 196 No. of Pages 6 9 February 2016 2 M. Laad, V.S. Jatti

45 the friction and wear of frictional surfaces. The main function A pin-on-disc type tribometer (DUCOM TR-20) was used 104 46 of a lubricant is to keep two metal surfaces wet thus minimis- to evaluate the tribological properties of the lubricant. This tri- 105 47 ing friction and avoiding wear (Calhoun, 1960). Research stud- bometer had a driven spindle and chuck for holding the revolv- 106 48 ies have reported that the nanoparticles dispersed lubricants ing disc, a lever-arm device to hold the pin, and attachments to 107 49 are found to have a significant effect on reducing the friction allow the pin specimen to be forced against the revolving disc 108 50 and wear rate. It is also observed that the friction and wear specimen with a controlled load. The wear track on the disc is 109 51 have a direct bearing on the shape, size and the concentration a circle, involving multiple wear passes on the same track. The 110 52 of the nanoparticles in the lubricating oil. Vadiraj et al. inves- system has a friction force measuring system (a load cell) that 111 53 tigated the effect of nano boric acid and nano copper based allows the coefficient of friction to be determined. 112 54 engine and transmission oil additives in different volume ratios 55 on friction and wear performance of cast iron and case car- 2.1. Fabrication of pin 113 56 burised gear steel (Vadiraj et al., 2012). Wu et al. investigated 57 the effect of additives CuO, TiO2, and nano-diamond The pins were fabricated from the aluminium alloy (LM 25) 114 58 nanoparticles on the tribological properties of two different using manual labour techniques. The fabrication was done 115 59 lubricating oils and observed that with CuO additive oils sig- with the help of a cutting saw. The metal pieces were cut in tri- 116 60 nificantly exhibit good friction-reduction and anti-wear prop- angular shapes and then cut metal piece were given a rough cir- 117 61 erties (Wu et al., 2007). Thottackkad et al. have studied the cular shape with the help of a hand grinder. The roughly 118 62 effect of Copper oxide nanoparticles as additives in the lubri- circular aluminium pieces were then machined to standard 119 63 cating oil (Thottackkad et al., 2012). Hwang et al. investigated (as per ASTM G99) size (10 mm diameter and 25 mm length) 120 64 the effect of size and morphology of nanoparticles suspended using lathe machine. 121 65 in lubricating oils on the lubrication performance (Hwang 66 et al., 2011). Zhang et al. also found in their study that Cu 2.2. Preparation of nanolubricant 122 67 nanoparticles used as an oil additive can improve the anti‐wear 68 and friction‐reduction performance of lubricating oil (Zhang The nanoparticles are added to the lubricating oil at 0.3%wt, 123 69 et al., 2009). Choi et al. observed that the mixed nanofluids 0.4%wt, 0.5%wt. The required quantity of nanoparticles was 124 70 containing graphite and Ag nanoparticles showed enhanced accurately weighed using a precision electronic balance and 125 71 load-carrying and anti-wear properties in the FZG gear rig test mixed with the lubricating oil. A chemical shaker was used 126 72 and also reduced the electric-power consumption by more than for mixing the nanoparticle additives in the lubricating oil. 127 73 3% compared to the base oil (Choi et al., 2011). Hsin et al. The time of agitation was fixed as 30 min based on the past 128 74 investigated the tribological properties of the two-phase lubri- experience in producing a stable suspension with sufficient 129 75 cant oil and nanodiamond–polymer composite. Based on the time for sedimentation to begin. After the mixer is agitated 130 76 results it is observed that nanodiamond–polymer composite for 30 min, the nanolubricant is obtained. 131 77 possesses better antiwear, friction-reduction and load- 78 carrying capacity than the nanodiamond additive (Hsin 2.3. Pin-on-disc tests 132 79 et al., 2011). Chu et al. experimentally investigated the anti- 80 scuffing performance of nano-diamond-dispersed oil with var- 81 ious concentrations of diamond particles (Chu et al., 2010). It Tribological behaviour of the lubricating oil was evaluated 133 82 has been reported that the main mechanism of the friction using a pin-on-disc tester, with and without the addition of 134 83 reduction when nanoparticles were added can be attributed nanoparticles. The nanoparticles added to the lubricating oil 135 84 to the rolling/sliding effect (Chin-as-Castillo and Spikes, were titanium oxide, with an average size of 15–20 nm. Load, 136 85 2003). In order to further understand this, we will have to sliding speed and nanoparticle concentration were selected as 137 86 study what is tribology and how it plays a major role in saving parameters. To determine the optimum concentration of 138 87 materials from further wear and tear. In the present research nanoparticles, experiments were performed at different con- 139 88 work tribological properties of the lubricating oil were evalu- centrations (% by weight). 140 141 89 ated with the addition of TiO2 nanoparticles using pin-on- The range of test parameters for pin-on-disc used are as 90 disc tribotester under controlled conditions as per the ASTM mentioned below: 142 91 standard G99 and the oil samples with dispersed TiO2 92 nanoparticles were studied spectroscopically with the help of Load: 39.226 N, 49.033 N, 58.839 N. 143 93 UV spectrometer. Sliding speed: 1.0 m/s. 144 Nano-particle concentration (% weight): 0.3%, 0.4%, 145 146 94 2. Experimental 0.5%. Sliding distance: 200 m. 147 All the tests were carried out for a duration of 5 min. 148 95 In this study titanium oxide nano particles of grain size 149 96 10–25 nm were used as additive and the lubricating oil was The experiments were done as per the ASTM standard 150 97 used. The apparent density and the bulk density of TiO2 3 3 G99. Pins and disc were polished up to 600 grit size to make 151 98 nanoparticles were 0.3 g/cm and 0.20 g/cm respectively. The the surface flat and cleaned with acetone. Load was applied 152 99 TiO nanoparticles used in this study were purchased from 2 on pin by dead weight through pulley string arrangement. 153 100 Supplier Nanoshel LLC, USA. Aluminium alloy (LM 25) Lubricant was applied between the pin and disc in such a 154 101 was used (Al–Si 7 Mg) as pin material to be used on pin-on- way that boundary lubrication condition occurs. Frictional 155 102 disc tribotester. Servo 4T Synth 10 W-30 was used as lubricat- force was read from the controller and electronic weighing bal- 156 103 ing oil. ance (accuracy of 0.1 mg) was used to measure the weight loss 157

158 of the pin. The above procedure was repeated for all the exper- 159 iments. The specimens were cleaned and dried. All dirt and for- 160 eign matters were removed from the specimens before starting 161 the experiment. Non chlorinated, non-film-forming cleaning 162 agents and solvents were used. The disc is inserted securely 163 in the holding device so that the disc is fixed perpendicular 164 to the axis of the resolution. The pin specimen is inserted 165 securely in its holder and adjusted so that it was perpendicular 166 to the disc surface when in contact, in order to maintain the 167 necessary contact conditions. Proper mass was added to the 168 system lever to the selected force pressing the pin against the 169 disc. The electric motor was started and the speed of the disc 170 was adjusted to the desired value. The revolution counters Figure 1 Showing variation of COF with time for loads 4 kg, 171 are set to the desired number of revolutions. The experiment 5 kg and 6 kg for lubricating oil without additive. 172 started with the specimens in contact under load. The test is 173 stopped when the desired numbers of revolutions were 174 achieved. The specimen was removed and cleaned off any loose 175 wear debris. The existence of features on or near the wear scar 176 such as: protrusions, displaced metal, discoloration, micro 177 cracking, or spotting was noted. The tests are repeated with 178 additional specimens to obtain sufficient data for statistically 179 significant results. The WinDucom software was used for data 180 acquisition and display of results. 181 The WinDucom instrumentation and data acquisition were 182 used to measure RPM, wear, and frictional force.

183 2.4. Dispersion analysis using UV spectrometer

184 The oil samples with nanoTiO2 additive were spectroscopically 185 studied for the dispersion and stability of nanoparticles in the 186 lubricating oil. UV–Vis spectrometer was employed for disper- 187 sion analysis of the nano TiO2 particles in the lubricating oil. 188 Base oil (lubricating oil without nano TiO2 additive) filled in Figure 2 Variation in Co-efficient of friction of lubricating oil 189 two cuvettes and baseline correction is done. In one cuvette with 0.3%wt additive TiO2 for 4 kg, 5 kg, and 6 kg load. 190 the nanolubricant with 0.3%wt nano TiO2 additive is filled 191 while other cuvette is filled with lubricating oil with no addi- 192 tive. The absorption of light which is proportional to the dis- 193 persion of nanoparticles of TiO2 in the oil is measured over 194 a range of wavelength. The procedure is repeated by taking 195 lubricant oil with 0.5%wt dispersed nano TiO2 in one cuvette 196 and lubricating oil with no additive in another cuvette.

197 3. Results and discussion

198 3.1. Tribological test results on pin-on-disc tester

199 A series of experiments were conducted to evaluate the friction 200 and wear characteristics of the sliding elements using pin-on- 201 disc tribometer applying the lubricant at the interface (for a 202 sliding distance of 600 m) with and without the nanoparticles Figure 3 Variation in co-efficient of friction of lubricating oil 203 added to the lubricant. It is observed that coefficient of friction with 0.4%wt additive TiO2 for 4 kg and 6 kg load. 204 varies with the increase in load in the lubricating oil without 205 any dispersed nano particles (Fig. 1). The variation in coeffi- 206 cient of friction for a given time duration of 0–300 s was Table 1 Specifications of lubricating oil SERVO 4T SYNTH 207 observed to be more in the load of 4 kg in comparison with 10W-30. 208 5 kg or 6 kg load (see Figs. 2 and 3 and Table 1). Density 885 209 Table 2 shows that the coefficient of friction is significantly Viscosity at 100 °C 10–12 210 reduced with 3%wt TiO nanoparticles as additives in the 2 Viscosity at 40 °C 125.4 211 lubricating oil for the given load. A decrease in COF was Viscosity index 150 212 observed to be 86.48%, 78.04% and 34.50% for the load 213 4 kg, 5 kg and 6 kg respectively. The reduction in COF was

Table 2 Comparison of coefficient of friction between lubricating oil without additive and with 0.3%wt TiO2 nanoparticles for loads 4 kg, 5 kg and 6 kg loads. Load (kg)/force (N) Coefficient of friction Co efficient of friction Percentage decrease (%)

(engine oil) (engine oil + 0.3% TiO2) 4/39.226 N 0.111 0.015 86.48 5/49.033 N 0.123 0.027 78.04 6/58.839 N 0.142 0.093 34.50

Table 3 Comparison of coefficient of friction between lubricating oil without additive and with 0.4%wt TiO2 nanoparticles for loads 4 kg and 6 kg. Load (kg)/force (N) Coefficient of friction Coefficient of friction Percentage decrease (%)

(engine oil) (engine oil + 0.4% TiO2) 4/39.226 N 0.111 0.053 52 6/58.839 N 0.142 0.109 23

Figure 4 Variation in co-efﬁcient of friction of lubricating oil

with 0.5%wt additive TiO2 for 4 kg, 5 kg and 6 kg load.

214 the maximum for the smallest load (4 kg) and minimum for the 215 largest load (6 kg). 216 It was observed that there is a decrease in COF with 0.4% Figure 5 Wear of (LM 25) alloy with lubricating oil at varying 217 wt TiO2 additive in lubricating oil. 52% and 23% reduction in loads. 218 COF was observed for loads 4 kg and 6 kg respectively when 219 0.4%wt TiO2 was dispersed in lubricating oil. 220 Table 3 shows the comparison between the COF for lubri- reduction in the coefficient of friction when nanoparticles of 229 221 cating oil with 0.4%wt additive and without additive. TiO2 were dispersed in lubricating oil as additive, it was 230 222 Fig. 4 shows the decrease in COF of lubrication oil when demonstrated that the nanoparticles as additives in lubrication 231 223 0.5%wt TiO2 nanoparticles were dispersed in it for loads can effectively improve the lubricating properties. 232 224 4 kg, 5 kg and 6 kg. Table 4 indicates that there is a consider- Fig. 5 shows the variation in wear with the applied load of 233 225 able decrease in CFO with 0.5% additive. This study shows the sample pins which were fabricated from the aluminium 234 226 that mixing of TiO2 nanoparticles in lubricating oil signifi- alloy (LM 25). It is observed that the wear of the pin increases 235 227 cantly reduces the friction and wear rate and hence improves with time. The wear rate is observed to be increasing with the 236 228 the lubricating properties of engine oil. As there is a significant load. With the addition of 0.3% TiO2 nanoparticles of TiO2, 237

Table 4 Comparison of coefficient of friction between lubricating oil without additive and with 0.5%wt TiO2 nanoparticles for loads 4 kg, 5 kg and 6 kg. Load (kg)/force (N) Coefficient of friction Coefficient of friction Percentage

(engine oil) (engine oil + 0.5% TiO2) decrease (%) 4/39.226 N 0.111 0.093 16.2 5/49.033 N 0.123 0.080 34.2 6/58.839 N 0.142 0.085 40.1

there is a decrease in the wear of the pin and the reduction is 238 observed maximum when the load of 5 kg is applied (see 239 Fig. 6). 240 Fig. 7 shows the decrease in the wear of the pin when 0.4% 241 wt of TiO2 nanoparticles was added to the lubricating oil. The 242 wear for 4 kg and 6 kg load without any additive is observed to 243 be much higher. Similarly, there is a signiﬁcant reduction in 244 wear when 0.5% nanoparticles of TiO2 are dispersed in the 245 lubricating oil (see ﬁg. 8). 246

3.2. Dispersion analysis using UV–Vis spectrometer 247

The UV spectroscopy is used to ﬁnd the presence of unsatu- 248 rated bonds like oleﬁnic and aromatic bonds in which maxi- 249 mum absorption of radiation is seen in the range 190– 250 400 nm which arises due to electronic transition within mole- 251 cules. UV spectroscopy is more commonly used in a qualitative 252 fashion to indicate the presence/absence of unsaturated com- 253 Figure 6 Wear of (LM 25) alloy with lubricating oil at varying pounds. In the present work, UV spectroscopy is carried out 254 loads. using 3 samples of oil with dispersed TiO2 nanoparticles at 255 concentrations of 3 –5%wt. The UV spectroscopy measure- 256 ments are done by directly taking the samples in a short 257 path-length measurement cell. The UV–Vis spectrometry of 258 the samples is shown in Figs. 9 and 10. A steady absorbance 259 increase with an increase in aging time; and a spectral shift 260 from short to longer wavelength in the course of oil aging is 261 noticed. Optical maximum-absorbance (absorbance maxima) 262 of the samples and its wavelength of occurrence also increased 263 with aging time. Hence, the shift in the absorbance spectra is 264 associated with a shift in maximum-absorbance wavelength 265 from a shorter to a longer wavelength. The nanoparticles used 266 as additives in lubricating oil showed good stability and solu- 267 bility in the lubricant. They were observed to be readily dis- 268 persed in lubricating oil to give a transparent solution, and 269 the solution remained unchanged for several days at room 270 temperature. 271

Figure 7 Wear of (LM 25) alloy with lubricating oil at varying loads.

Figure 8 Wear of (LM 25) alloy with lubricating oil at varying Figure 9 Shows dispersion analysis with 0.3% nano TiO2 loads. additive.

pared to the oil without nanoparticles for load 4 kg. This effect 289 could be due to the rolling of the sphere like nanoparticles 290 between the rubbing surfaces, thus reducing friction. With 291 the increasing concentration of nanoparticles the coefﬁcient 292 of friction increased but not more than the coefﬁcient of fric- 293 tion of oil without nanoparticles, this effect might be due to 294 the agglomeration of TiO2 nanoparticles. The anti-wear mech- 295 anism is attributed to the deposition of TiO2 nanoparticles on 296 the worn surface, which can decrease the shearing resistance, 297 thus improving the tribological properties. So, titanium oxide 298 nanoparticles can be used as a multifunctional additive. The 299 TiO2 nanoparticles possess good stability and solubility in 300 the lubricant. 301

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