Direct Measurement of Surface Energy of CeO₂ by Differential Scanning Calorimetry

Abstract

Surface energy of cerium oxide was measured by differential scanning calorimetry (DSC). Nanocrystalline CeO2 samples were synthesized by a nonaqueous sol–gel method and their surface and interfacial areas were determined from nitrogen adsorption, X‐ray diffraction, and electron microscopy measurements. Three samples were repeatedly heated in a differential scanning calorimeter and the excess enthalpy was obtained from the difference in DSC traces between first heating, during which coarsening occurred, and second heating. Surface enthalpy was calculated from excess enthalpy and from changes in surface and interfacial areas. The measured surface enthalpy for CeO2, 1.2 ± 0.2 J/m2, is consistent with values from oxide melt solution calorimetry on samples with different surface areas. This is the first successful measurement of surface energy using scanning calorimetry.

Nanostructured Metal Oxides for Stoichiometric Degradation of Chemical Warfare Agents

“…It was confi rmed that the formation of the -OH groups is energetically favorable, especially in the vicinity of oxygen vacancies associated with the presence of non-stoichiometric "impurities", such as Ce 3+ cations (Hayun et al 2011 ). In accordance with the proposed reaction mechanism, the organophosphate degradation is promoted in aprotic solvents.…”

Study of compaction and sintering of nanosized oxide powders by in situ electrical measurements and dilatometry: Nano CeO2—case study

“…In this equation, y is the normalized shrinkage, γ the surface energy (γ(CeO 2 )=1.2J/m 2 [42]), b the effective grain boundary width (taken as the classical Fisher value, 0.5 nm), and a the nanoparticle radius before sintering (taken as 12.5 nm). Ω is the volume of a cation vacancy, assessed from the radius of a Ce 4+ cation (~0.12 nm [31]).…”

Thermal stability of nano Ce1−xTixO2 material system for X < 0.2

“…Above this temperature, moderate mass loss generally continued, becoming negligible at approximately 400°C and 700°C for pure CeO 2 and solid solutions, respectively, as can be seen in the detailed STA spectra in Figure 5 addition lowered the ability of the materials to adsorb water per unit area. 43 However, in the TiO 2 -doped samples, a general broad event included a major peak that appeared at approximately at the same temperature as that peak seen in the pure CeO 2 (600°C) curve, followed be at least one minor event which terminated above 1100°C ( Figure 5). In pure CeO 2 , this thermal event was continuous, displaying a distinct peak situated between 600 and 900°C ( Figure 5) that resulted from surface area loss that occurred during the coarsening of the CeO 2 .…”

“…The peaks position in the as synthesized materials is red shifted relative to the literature reported position. 43,74 The difference lies in the coarsening process. The red shift is a result of Ti ions being imbedded in Ce surrounding, thus affecting the Ti2p binding energy.…”