influence of particle size on density, ultrasonic velocity ...

NANO: Brief Reports and Reviews Vol. 9, No. 8 (2014) 1450089 (9 pages) © World Scienti¯c Publishing Company DOI: 10.1142/S1793292014500891

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INFLUENCE OF PARTICLE SIZE ON DENSITY, ULTRASONIC VELOCITY AND VISCOSITY OF MAGNETITE NANOFLUIDS AT DIFFERENT TEMPERATURES AMMAR BIN YOUSAF*, MAJID KHAN†,§, MUHAMMAD IMRAN*, MUHAMMAD USMAN‡ and MUHAMMAD ASGHAR JAMAL‡ *Department of Physical Chemistry and Chemical Physics Hefei National Laboratory for Physical Sciences at Microscale University of Science and Technology of China Hefei 230026, P. R. China †National

Synchrotron Radiation Laboratory and School of Nuclear Science and Technology CAS Key Laboratory of Soft Matter Chemistry University of Science and Technology of China Hefei 230029, P. R. China ‡Department §

of Chemistry, Government College University Faisalabad 38040, Pakistan

[email protected]; [email protected]

Received 24 March 2014 Accepted 21 July 2014 Published 5 September 2014

The in°uence of particle size on density, ultrasonic velocity and viscosity of magnetite nano°uids have been determined at (298.15 K, 303.15 K, 308.15 K and 313.15 K). Two di®erent sized nanoparticles (commercially procured D ¼ 20–30 nm and synthesized D ¼ 9 3 nm in the laboratory by co-precipitation method) were dispersed in a citric acid base °uid. The desired parameters have been experimentally determined by loading di®erent concentrations of nanoparticles. It has been found that the in°uence of particle size and temperature on measured physical parameters (density, ultrasonic velocity and viscosity) is not negligible and can also be taken into account in any practical application. The analyzed physical parameters can describe qualitatively and quantitatively the particle size distribution of nano°uids at a speci¯c temperature. Results are interpreted in terms of particle–particle and particle–°uid interactions. Keywords: Nano°uids; nanoparticles; density; ultrasonic velocity; viscosity.

1. Introduction The physics and chemistry of nanoscale magnetite nanoparticles (MNPs) give an important research

activity due to their wide range of potential applications and their fundamental importance. The suspension of nanometer size (1–100 nm) particles in

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A. B. Yousaf et al.

any base °uid is termed as nano°uid. Such type of °uids has important applications in industry,1,2 biomedical ¯elds,3–5 engine transmission oil and lubrications,6 due to their °uid properties. Typically, there are two procedures used for preparation of nano°uids, ¯rst is the one-step method that consists of synthesizing the particles directly into the °uid, the second is a two-step method and it implies the dispersion of nanoparticles in the base °uid.7 Above mentioned two methods in°uence the stability of the °uids and their properties.8 For the nano°uids, the common host base °uids include water and organic liquids9 and for the dispersion of nanoparticles in base °uid di®erent dispersion methods such as sonication, homogenization and ball milling can be used to ¯nd the stability of nano°uids.10,11 Since last few years, such type of °uids have been attracting intensive research e®orts due to extremely large surface area of nanoparticles and exhibit unique properties arising from size e®ects, because sample size could produce changes in properties. Nanoparticles can show better properties than conventional materials with powdered physical state, including density and viscosity. These both properties are the key of this research area due to the use of nano°uids in potential applications in di®erent ¯elds that have been discussed earlier.12 Concerning the physical properties in terms of in°uence of particle size, thermal conductivity13 has been studied, but less attention has been focused on other physical properties such as density, sound velocity and viscosity. Previously, it has also been pointed out in research that these properties should be well determined for their e®ects on °uid °ow and heat transfer properties.14 For the calculation of density, ideal colloid behavior is commonly assumed for the nano°uids by neglecting the interactions between particles. Such e®ect should acquire certain relevance as the concentration increases. As viscosity describes the internal resistance of a °uid to °ow, this property has importance for all transport properties of the °uids.15 Ultrasonic velocity is the speed in which sound travels through a given material and measurements of ultrasonic velocities are usually made in order to get an idea of chemical and physical characteristics of the material. Ultrasonic velocity which depends upon density and elasticity of a material are of considerable importance in understanding the intermolecular interaction between component molecules, and they ¯nd applications in several industrial and technological processes.

In order to understand the e®ect of particle size on ultrasonic velocity, a detailed study of the thermal variation of ultrasonic velocities is studied in this paper. The objective of the present work is to study the in°uence of particle size on density, ultrasonic velocity and viscosity of magnetite nano°uids in the temperature range of 298.15 K to 313.15 K. For these determinations, nanoparticles were obtained from two di®erent sources, commercially procured and synthesized in the laboratory. Furthermore, density, sound velocity and viscosity were measured to ¯nd the solution properties of Fe3O4 nano°uids.

2. Experimental Methods Reagents were of analytical grade and used without further puri¯cation. The modi¯ed co-precipitation method was used for the synthesis of ferric oxide nanoparticles. Ferric chloride (FeCl3 6H2O) and ferrous chloride (FeCl2 4H2O) were dissolved in 20 mL of deionized water at a molar ratio of 2 to 1, respectively. Reactant solution was put into three necks round bottom °ask and condenser was ¯tted on it, the apparatus was fully quick ¯t. Before starting the reaction, vacuum was created in the °ask and then it was heated up to 60 C. At this temperature, 10 mL of 2.5 M NaOH solution was injected dropwise. During heating, nitrogen gas was bubbled into the °ask to prevent unwanted oxidation during the reaction. After injecting NaOH, black precipitate was formed and the reaction continued at this temperature for 30 min, before the °ask was removed from heating and stirring. The nanoparticles were removed from the solution after cooling and they were washed with deionized water and distilled water twice later on with ethanol. The contents were then centrifuged for 15 min at 4000 rpm and centrifuged until only thick black precipitates remained. Then these precipitates were dried at 40 C for 10 h in the oven. Two di®erent Fe3O4 citric acid-based nano°uids were used in this work. One of them was prepared from magnetite nanopowder with declared diameter distribution D ¼ 20–30 nm supplied by Sigma Aldrich. This set of samples was named as S1. The second one was prepared from magnetite nanopowder synthesized in the laboratory by co-precipitation method, with a diameter distribution D ¼ 9 3 nm and were denoted as S2. In all cases, 1 M citric acid was used as base °uid.

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In°uence of Particle Size on Density, Ultrasonic Velocity and Viscosity of Magnetite Nano°uids

For density and sound velocity measurements up to 5 wt.% and for viscosity up to 10 wt.%, nanoparticles were dispersed into the base °uid by mechanical stirring. The synthesized MNPs were characterized by powder X-ray di®raction (PXRD) and transmission electron microscopy (TEM) in order to verify the crystallographic structure and size of the particles. The experimental density and ultrasonic velocity were measured for both procured and synthesized particles, at a concentration ranging from 1% to 5% in weight fraction with a step of 5 K. Both these parameters were measured using Anton Paar density sound analyzer (DSA 5000 M). Density was determined with an uncertainty of nearly 10 5 g cm 3 over the whole atmospheric pressure and temperature range. The experimental viscosity measurement was performed with a Brook¯eld viscometer at an uncertainty of 10 1 with di®erent concentration of 1% to 10% in weight fraction, at a temperature range of 298.15 K to 313.15 K. The temperature was controlled and changed by using a water bath.

3. Results and Discussion The synthesized nanoparticles were characterized by TEM and PXRD. TEM was carried out for particle size determination. The specimen for a TEM image was prepared from particles suspended in deionized water and carried out under the following protocol, 500 C, HV ¼ 100:0 kV, Magnification ¼ 430 K, presented in Fig. 1, showing that the sample is composed of nanoparticles having diameter size smaller

than that of the declared diameter size of procured particles. The volume weighted average diameter value computed was 9 3 nm. XRD was performed for the crystallographic analysis of sample, di®ractometer using CuK radiation. A continuous scan mode was used to collect 2 data from 10 to 80 presented in Fig. 2. The crystallite size of the particles was also calculated from XRD spectra by Debye Scherrer's formula that has very close agreement with the TEM. The average crystallite size was calculated by the formula D ¼ Kð= cos Þ, K is a constant equal to 0.89, the X-ray wavelength (0.154095 nm), the full wavelength at half maximum and the half di®raction angle. The crystallite size of the Fe3O4 nanoparticles calculated from FWHM was tabulated in Table 1. Once the samples were characterized, the following step was to determine the volumetric behavior of this nano°uid. The obtained density values agreed to the estimated experimental uncertainty. Previously, the same in°uence of particle size of CuO nanoparticles on density was reported by PastorizaGallego et al.16 Kratky et al.17 proposed a method for the measurement of density of magnetite nano°uids using Anton Paar DMA-38 microprocessor density meter and Zefczak et al.18 gave the results for density as a function of temperature at three di®erent temperatures up to 308.15 K. Their result shows that density decreases linearly with temperature and density generally increased with an increase in magnetite concentration.

(a) Fig. 1.

(b) TEM image of Fe3O4 nanoparticles, (a) S1 and (b) S2. 1450089-3


A. B. Yousaf et al.

Fig. 2.

X-ray di®raction (XRD) pattern of synthesized Fe3O4 (magnetite) nanoparticles.

Table 1. Crystallite size estimated from the di®raction spectrum by using half maximum widths. Phase

Width

2 (deg)

(hkl)

Crystallite size (nm)

Fe3 O4

2.98 2.53 2.06 1.61 1.48 1.25

29.961 35.404 43.263 57.155 62.712 75.381

220 311 400 511 440 622

4.7 5.6 7.1 9.7 10.8 13.8

We observed a similar relationship with density in our results. We have added a new contribution in this work by analyzing the in°uence of particle size and temperature at four di®erent temperatures up to 313.15 K on previously measured physical parameters. The density of small sized synthesized nanoparticles was higher as compared to large sized procured nanoparticles due to large surface area. The experimental density data allows a comparison of the volumetric behavior of two samples with di®erent sized particles and the in°uence of particle size on experimental density for both the samples at di®erent concentrations and temperatures at 298.15 K to 313.15 K with the step of 5 K presented as plots in Figs. 3 and 4. Density was measured as a function of temperature. By increasing the temperature, density of both the samples decreases that are in very close agreement with the common de¯nition of density and also comparable with the reported results, see Tables 2 and 3.

The experimental data allow a comparison of volumetric behavior of both the samples. In this case, the di®erence in magnetite nanoparticle size between S1 and S2 produce a representative change in the volumetric behavior of nano°uid, this comparison is presented in Fig. 5. The ultrasonic velocity measurement is a source of information on physical and chemical properties of °uids and suspensions. Motozawa et al.19 explained the increase in sound velocity with increase in concentration of MNPs in the presence of surface active agents acting as shells on nanoparticles cores. Zefczak et al.18 have determined the e®ect of temperature and concentration of magnetite nano°uids on ultrasonic studies but still the e®ect of particle size of MNPs was not put forward in this research ¯eld. We put our contribution also in ultrasonic studies to determine the in°uence of particle size and temperature up to 313.15 K with di®erent dispersion of nanoparticles. The results of ultrasonic velocity propagation were

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1.056 1.055

-3

ρ (g cm )

1.054 1.053 1.052 1.051 1.050 1.049 169.0 168.5 168.0 U (m/s)

167.0 166.5

298.15K 303.15K 308.15K 313.15K

166.0 165.5 165.0 1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Wt %

Fig. 3.

Variation of experimental density (, g cm 3 ) and ultrasonic velocity (m s 1 ) for S1 at di®erent temperatures.

also very close and comparable with the reported work presented in as plots of Fig. 3. In our results, the increase in sound velocity was due to structural changes that occurred in the

nano°uids which results in weakening of intermolecular forces between the °uid molecules. The rise in the sound velocity with concentration indicates that the interactions may be due to the surface

1.062 1.061 1.060

-3

ρ (g cm )

1.059 1.058 1.057 1.056 1.055 1.054 169.0 168.5 168.0 167.5 U (m/s)


167.5

167.0 298.15K

166.5

303.15K

166.0

308.15K

165.5

313.15K

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Wt %

Fig. 4.

Variation of experimental density (, g cm 3 ) and ultrasonic velocity (m s 1 ) for S2 at di®erent temperatures. 1450089-5

A. B. Yousaf et al. Table 2.

Experimental density/kg m 3 and ultrasonic velocity/ms 1 data for sample S1/Procured at di®erent temperatures. 303.15 K

308.15 K

313.15 K

wt.%

Density

Sound velocity

Molality

Density

Sound velocity

wt.%

Density

Sound velocity

wt.%

Density

Sound velocity

1 1.5 2 2.5 3 3.5 4 4.5 5

1.054421 1.054689 1.054958 1.055226 1.055494 1.055763 1.056031 1.056331 1.056568

165.33 165.71 165.94 166.29 166.7 166.82 166.96 167.4 167.53

0.001 0.0015 0.002 0.0025 0.003 0.0035 0.004 0.0045 0.005

1.052766 1.053034 1.053303 1.053571 1.05384 1.054108 1.054377 1.054645 1.054913

165.4 165.78 166.01 166.36 166.77 166.89 167.03 167.47 167.6

1 1.5 2 2.5 3 3.5 4 4.5 5

1.050911 1.051178 1.051447 1.051715 1.051984 1.052252 1.052521 1.052789 1.053058

165.91 166.29 166.52 166.87 167.28 167.42 167.54 167.98 168.11

1 1.5 2 2.5 3 3.5 4 4.5 5

1.048856 1.049124 1.049393 1.049661 1.049931 1.050198 1.050467 1.050736 1.051004

166.72 167.1 167.33 167.68 168.09 168.21 168.35 168.79 168.92

Table 3.

Experimental density/kg m 3 and ultrasonic velocity/ms 1 data for sample S2/synthesized at di®erent temperatures. 298.15 K

303.15 K

308.15 K

313.15 K

wt.%

Density

Sound velocity

wt.%

Density

Sound velocity

wt.%

Density

Sound velocity

wt.%

Density

Sound velocity

1 1.5 2 2.5 3 3.5 4 4.5 5

1.060055 1.060319 1.060584 1.060898 1.061112 1.061377 1.061641 1.061906 1.062171

165.49 165.87 166.10 166.45 166.86 166.98 167.12 167.58 167.69

1 1.5 2 2.5 3 3.5 4 4.5 5

1.058042 1.058306 1.058571 1.058835 1.059101 1.059364 1.059629 1.059893 1.060158

165.69 166.07 166.3 166.65 167.06 167.18 167.32 167.76 167.89

1 1.5 2 2.5 3 3.5 4 4.5 5

1.05594 1.056204 1.056469 1.056733 1.056997 1.057262 1.057526 1.057791 1.058056

166.01 166.38 166.61 166.96 167.37 167.49 167.63 168.07 168.2

1 1.5 2 2.5 3 3.5 4 4.5 5

1.053845 1.054109 1.054374 1.054638 1.054902 1.055166 1.05543 1.055694 1.055959

166.65 167.03 167.26 167.61 168.02 168.14 168.28 168.72 168.85

e®ect because of hydrogen bonding between particles and water molecules.20–25 Hence particle–°uid interactions favored the increase in ultrasonic velocity, the results are presented as a plot in Fig. 6.

Experimental viscosity of synthesized sample was higher than that of procured sample. It has been determined that the viscosity of small particles was much higher and as the particle size increases their 169.0

1.062

168.5

1.060

168.0

U (m/s)

1.058 ρ (gm cm -3 )


298.15 K

1.056 1.054

167.5 167.0 166.5

1.052

166.0

1.050

165.5

1.048

165.0 1.0

1.5

2.0

2.5

S1 at 298.15K S1 at 313.15K

3.0 Wt %

3.5

4.0

4.5

5.0

1.0

1.5

2.0

S1 at 298.15K

S2 at 298.15K S2 at 313.15K

S1 at 313.15K

Fig. 5. Comparison of experimental density (, g cm 3 ) for S1 and S2 at 298.15 K and 313.15 K.

2.5

3.0 Wt %

3.5

4.0

4.5

5.0

S2 at 298.15K S2 at 313.15K

Fig. 6. Comparison of experimental ultrasonic velocity (m s 1 ) for S1 and S2 at 298.15 K and 313.15 K.

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In°uence of Particle Size on Density, Ultrasonic Velocity and Viscosity of Magnetite Nano°uids Table 4.

Experimental density/kg m 3 and ultrasonic velocity/ms 1 data for sample S1/synthesized at di®erent temperatures. wt.%

T (K)

0

1

2.5

3.5

4.5

5.5

6.5

7.5

8.5

10

298.15 303.15 308.15 313.15

1.358 1.211 1.066 0.938

1.454 1.307 1.123 0.995

1.461 1.314 1.130 1.002

1.475 1.328 1.144 1.016

1.492 1.345 1.161 1.033

1.516 1.369 1.185 1.057

1.547 1.401 1.216 1.088

1.599 1.452 1.268 1.140

1.682 1.535 1.351 1.223

1.826 1.679 1.495 1.367

Experimental density/kg m 3 and ultrasonic velocity/ms 1 data for sample S2/synthesized at di®erent temperatures. wt.%

T (K)

0

1

2.5

3.5

4.5

5.5

6.5

7.5

8.5

10

298.15 303.15 308.15 313.15

1.358 1.211 1.066 0.938

1.551 1.404 1.183 1.052

1.588 1.441 1.220 1.089

1.680 1.533 1.312 1.181

1.865 1.718 1.497 1.366

2.088 1.941 1.720 1.589

2.477 2.327 2.106 1.975

2.878 2.731 2.511 2.379

3.301 3.154 2.933 2.802

4.147 4.002 3.779 3.648

viscosity decreases, see Tables 4 and 5. This was also reported by Pastoriza-Gallego et al.16 for di®erent nanoparticles from our work. Colla et al.26 have also reported the viscosity of Fe2O3 nanoparticles with the same trend as that of the results obtained for Fe3O4 nanoparticles. Our work with Fe3O4 nanoparticles was a new contribution and we have obtained the expected results for Fe3O4 nanoparticles as the work was done for di®erent nanoparticles. The plots of viscosity versus wt.% have been presented in Figs. 7 and 8. It was represented that viscosity decreases as the temperature increases and with increasing concentration of nanoparticles viscosity increases typically in both the samples.27

Shou et al.28 measured the viscosity of Fe3O4/water nano°uid which showed the same trend and depicts the rheological behavior of nano°uids with di®erent particle loadings. Viscosity of smaller particle size is higher than that of larger particle size. This is due to the reason that small particles have large surface area so their viscosity is higher; this trend is presented in Fig. 9. In Fig. 9, viscosity versus wt.% has been plotted, at temperatures 298.15 K and 313.15 K, to represent the comparison between both the samples, in order to explain the in°uence of particle size on viscosity. This in°uence of particle size on viscosity was signi¯cant. As shown in the plot, the viscosity of S1 S2 (Synthesized)

S1 (Procured)

1.8

4.5

298.15K 303.15K 308.15K 313.15K

1.7 1.6

298.15K 303.15K 308.15K 313.15K

4.0 3.5

1.5

η (mPas)

η (mPas)


Table 5.

1.4 1.3 1.2

3.0 2.5 2.0 1.5

1.1

1.0

1.0 1

2

3

4

5

6

7

8

9

1

10

2

3

4

5

6

7

8

9

10

Wt %

Wt %

Fig. 7. Variation of experimental viscosity ( mPa s) for S1 at di®erent temperatures.

Fig. 8. Variation of experimental viscosity ( mPa s) for S2 at di®erent temperatures.

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A. B. Yousaf et al. 4.5

3.5

η (mPas)

References

S1 at 298.15K S1 at 313.15K S2 at 298.15K S2 at 313.15K

4.0

3.0 2.5 2.0 1.5 1.0 1

2

3

4

5

6

7

8

9

10


Wt %

Fig. 9. Comparison of experimental viscosity (, mPa s) for S1 and S2 at 298.15 K and 313.15 K.

(Procured) with larger particle size increases with concentration slowly and steadily. There was no sudden increase in this sample. However, on the other hand the viscosity of S2 (Synthesized) with small particles increases suddenly at 4.5 wt.% with both the temperatures, after the concentration viscosity of this sample was increased signi¯cantly than the sample of large particle size.29 The reason is that, the particles with smaller size have large surface area.30 These nanosized particles have high energy surface because 50% of the atoms are at the surface and, therefore surface properties and chemistry control the nanoparticles behavior.31 Due to this large surface area property, nanoparticles have large potential applications.32–36

4. Conclusions The density, ultrasonic velocity and viscosities of MNPs at di®erent concentrations and temperatures have been determined experimentally. Two di®erent samples were considered, the ¯rst (S1) obtained from commercial magnetite nanopowder and the second (S2) from synthesized MNPs obtained using a coprecipitation method. The in°uence of particle size and size distribution of density and ultrasonic velocity was signi¯cant. The density of S2 was higher as compared to S1 at di®erent temperatures, also the density of both the samples increases by increasing the concentration of nanoparticles and it decreases with increasing the temperature. The behavior of ultrasonic velocity with concentration and temperature also described the particle–°uid interactions. Viscosity increases as particle size decreases, following the expected classical behavior for dispersion.

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