SEM images for both types of nanocrystalline structures are shown in Figure 1. The magnification of close agglomerates in micrometers (Figure 1b,d) allows identifying the individual nanoscale globular or nearly spherical particles for anatase and rutile. Average particle sizes were estimated using SEM I-BET151 ic50 micrographs by counting a minimum of 100 particles, obtaining values of 35 ± 17 nm for anatase and 47 ± 18 nm for rutile. Figure 2 shows the chemical composition of the

samples, obtained from the EDS spectra, determined from the area displayed in Figure 2a,c and represented in Figure 2b,d. The analysis of anatase nanoparticles shows that only Ti and O elements are detectable (Figure 2b), while for rutile, an amount inferior

to 1% by mass of Si is present, as shown in Figure 2d, probably due to the silica support. No relevant amounts of other compounds were identified for the samples studied. Figure 1 SEM images of dry A-TiO 2 and R-TiO 2 nanoparticles. SEM images of anatase nanoparticles at two magnifications: ×50,000 ( a ) and ×200,000 ( b ), and rutile nanoparticles at two magnifications: FHPI solubility dmso ×50,000 ( c ) and ×200,000 ( d ). Figure 2 EDS images and microanalysis of TiO 2 nanoparticles. EDS images of A-TiO2 ( a ) and R-TiO2 ( c ) nanoparticles, and microanalysis from the area within the rectangle shown in EDS images for A-TiO2 ( b ) and R-TiO2 ( d ) nanoparticles. Table 1 Material description Material Supplier Mass purity (%) Medium size (nm) Crystalline structure Anatase titanium dioxide (A-TiO2) SkySpring Nanomaterials 99.5 35 ± 17 Tetragonal Rutile titanium dioxide (R-TiO2) SkySpring Nanomaterials 99.5 47 ± 18 Tetragonal The preparation of the nanofluid was carried out using the two-step method at the mass concentrations of 1.00, 1.75, 2.50, 3.25, and 5.00 wt.% for volumetric measurements, whereas 5.00, 10.00, 15.00, 20.00, and 25.00 in wt.% concentrations were used for rheological tests, without adding any surfactant, in order to study the effect of nanoparticle aggregation.

check details The uncertainty in the mass compositions for the different studied PLX-4720 cost nanofluids ranges from 0.003% to 0.02%, increasing with the mass concentration. Subsequently, the nanofluids were dispersed by ultrasonic homogenization using a Bandelin Sonoplus HD 2200 (Bandelin Electronic, Berlin, Germany) for 16 min to prevent aggregation. More details about sonication methods have been previously published [28]. Concerning the characterization of the volumetric behavior of the cited R-TiO2/EG and A-TiO2/EG nanofluids, density measurements were experimentally carried out at concentrations up to 5% in mass fraction from atmospheric pressure up to 45 MPa and from 278.15 to 363.15 K. Temperature and pressure were measured within uncertainties of 0.02 MPa and 0.02 K for pressure and temperature, respectively.