Ceria nanoparticles

Wang et al., 1996, 2002). Zhang et al. reported the solvothermal s)mthesis of ceria nanoparticles in ethanol (Zhang et al., 2003a). Ce(N03)3 6H2O and (NH4)2Ce(N03)g are used as cerium source respectively with KOH or NaOH powders. The alcohothermal treatment was performed at 180 °C to produce ceria nanocrystals. To attain full crysfallization via a dissolution and recrystallization mechanism, small amount of water is required in the reactions. 

Zhou et al. reported the synthesis of flower-like ceria NPs by thermal decomposition of (NH4)2Ce(N03)g in OA/OM solvents at 230-300 °C. The small ceria nanoparticles form, assemble, and fuse mainly via (111) faces by oriented attachment. Monitoring by in situ electrical resistance measurements shows that the conductive species are diminished when the flower-like nanostructures form (Zhou et al., 2008a Figure 6). Ceria nanoflowers and nanocubes are also obtained in octadecylamine, with higher temperature for nanoflower and lower temperature for nanocubes. The obtained colloidal nanoparticles can be self-assembled into nanospheres assisted by SDS surfactants (Wang et al., 2008a). 

Gu and Soucek reported the synthesis of ceria nanoparticle in hydrocarbon solvents. Cerium-oleate complex was refluxed in high boiling point organic solvents such as octyl ether, 1-tetradecene, decalin, dipropylene glycol monomethyl ether, dipropylene glycol n-butyl ether, and 2,2,4-trimethyl-l,3-pentanediol monoisobutyrate, to decompose and form ceria nanocrystals. The sizes of the nanocrystals are uniform and could be... 

S Atomistic simulation assisted synthesis and investigations The classical atomistic simulation techniques based on the pair potentials are suitable for the simulations of ceria nanoparticles even with a real sized model. Molecular d)mamics studies with several thousands of ions and up to hundreds of nanoseconds in a time scale have been carried out to interpret the diffusion, and crystal growth behaviors for pure and doped-ceria nanoparticles. Traditionally, the technique has been used to explore the oxygen ionic conductivity in ionic conductors such as ceria and zirconia (Maicaneanu et al., 2001 Sayle et al., 2006). 

Sayle et al. (2004) reported (Figure 2) a molecular dynamics study on the shape of ceria nanoparticles. A simulated amorphization and recrys-talization of ceria MPs are carried out in order to avoid the artificial effect for selecting the initial models. Ten nanometres NP comprising 16,000 atoms become amorphous after being scaled in size and high temperature MD. The continued MD simulation leads to the recrystalization. Finally,... 

Sayle et al. (2008) also developed (Figure 9) a route exploiting the classical atomistic simulation to make combined studies of theoretical and experimental works. A typical selected system is ceria. Since the pair potential model based on electrostatic interaction and Buckingham short range presentations are often adequate to describe the fluorite structure of ceria, Sayle et al. explored the application of such models in nano-sized particles. A series of works have been reported on the assembly behaviors of nano-building blocks into complex nanostructures, including the ceria nanoparticles self assembly in ice mold (Karakoti... 

CH4 oxidation has been experienced for ceria supported on a barium hexaaluminate, an heat resistant support. Preparation by a new reverse microemulsion method leads to ceria nanoparticles deposited on support and having a BET area close to 100 mVg after calcination at 1000 0 [72]. Such ultrahigh disperse nanoparticles show exceptional thermal resistance the authors mentioned that ceria particles prepared with a size of 6 nm sinters only to 18 nm after a calcination at 1IOO°C under a water containing atmosphere. Of course excellent activity in methane combustion has been observed. According to their experimental conditions calculated specific activity expressed as mol(CH4).h. m was estimated to 6.4x10 at 500°C whereas Bozo [44J reported a value of 1.5x1 O at the same temperature both values look similar. Thus the difference in methane conversion may be related to BET area only which is spectacularly preserved using the reverse micro-emulsion method for synthesis. 

FIGURE 10.4 X-ray diffraction pattern of FSP-made ceria with strong bknodal crystal size prepared from Ce(Ac)3 in pure acetic acid. One-third of the powder mass consists of large crystals (average size 155 nm) (GOF = 1.38). The measured XRD was fitted with two cubic ceria modes (PDF 81-792). (From Madler, L., Stark, W.J., and F ratsinis, S.E., Flame-made ceria nanoparticles, J. Mater. Res., 17, 1356, 2002.)... 

Particle Engineering of Ceria Nanoparticles and Their Influence on CMP Performance... 

Suzuki and Sinha have prepared novel bimodal mesoporous crystalline ceria nanoparticles and evaluated their performance in VOC removal (106). The mesoporous ceria showed 92% acetaldehyde removal with 33% CO2 conversion at ambient temperature after 24 h. This acetaldehyde removal performance is nearly twice as high as that for conventional VOC removal using materials such as activated carbon or mesoporous silica. 

The addition of a second oxide to the titania surface produces new nucleation sites for Au and improves the dispersion of the admetal. " In the CeO /TiOgCllO) systems, the Ce cations adopt a structural geometry (Fig. 6.2A) and an oxidation state (-1-3) which are quite different from those seen in bulk ceria or for ceria nanoparticles deposited on metal substrates. On TiO2(110), one has CegOg dimers that join forming wire-like structures on the terraces of the titania substrate. ... 

One can obtain a stable catalyst for the WGS by adding CeO nanoparticles to Au(lll)." On an inverse oxide/metal catalyst, the reactants can interact with defect sites of the oxide nanoparticles, metal sites, and the metal/oxide interface. Figure 6.10 shows a STM image obtained after depositing ceria nanoparticles on Au (111). There is a random distribution of the ceria nanoparticles on the terraces of the gold substrate which maintains its characteristic herringbone reconstruction. The particles occupy specific sites with respect to the dislocation ridges of the reconstruction. The initial oxidation state of the Ge cations in the ceria nanoparticles was +4 and many of them were reduced to Ce upon exposure to the reactants of the WGS. ... 

Zhang, Z., et al., 2010. Surface modification of ceria nanoparticles and their chemical mechanical polishing behavior on glass substrate. Appl. Surf. Sci. 256 (12), 3856—3861. 

Sayle TXT, Parker SC, Sayle DC. Oxidising CO to CO2 using ceria nanoparticles. Phys Chem Chem Phys 2005 7 2936-41. 

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