Heat capacity and thermodynamic functions of nano-TiO2 rutile in relation to bulk-TiO2 rutile

Several conflicting reports have suggested that the thermodynamic properties of materials change with respect to particle size. To investigate this, we have measured the constant pressure heat capacities of three 7 nm TiO₂ rutile samples containing varying amounts of surface-adsorbed water using a combination of adiabatic and semi-adiabatic calorimetric methods. These samples have a high degree of chemical, phase, and size purity determined by rigorous characterization. Molar heat capacities were measured from T = (0.5 to 320) K, and data were fitted to a sum of theoretical functions in the low temperature (T < 15 K) range, orthogonal polynomials in the mid temperature range (10 > T/K > 75), and a combination of Debye and Einstein functions in the high temperature range (T > 35 K). These fits were used to generate $\mathit{Cp}\text{,}{\text{m}}^{\circ }$, ${\mathrm{\Delta }}_0^{\text{T}}{S}_{\text{m}}^{\circ }$, ${\mathrm{\Delta }}_0^{\text{T}}{H}_{\text{m}}^{\circ }$, and ${\phi }_{\text{m}}^{\circ }$ values at selected temperatures between (0.5 and 300) K for all samples. Standard molar entropies at T = 298.15 K were calculated to be (62.066, 59.422, and 58.035) J · K⁻¹ · mol⁻¹ all with a standard uncertainty of 0.002·${\mathrm{\Delta }}_0^{\text{T}}{S}_{\text{m}}^{\circ }$ for samples TiO₂·0.361H₂O, TiO₂·0.296H₂O, and TiO₂·0.244H₂O, respectively. These and other thermodynamic values were then corrected for water content to yield bare nano-TiO₂ thermodynamic properties at T = 298.15 K, and we show that the resultant thermodynamic properties of anhydrous TiO₂ rutile nanoparticles equal those of bulk TiO₂ rutile within experimental uncertainty. Thus we show quantitatively that the difference in thermodynamic properties between bulk and nano-TiO₂ must be attributed to surface adsorbed water.     

Excess heat capacities of mixtures containing 1-methylpyrrolidin-2-one,chlorotoluenes and benzene

Excess heat capacities, ${(C_P^E)}_{\mathit{ijk}}$ of {1-methylpyrrolidin-2-one (i) + benzene (j) + o- or m- or p-chlorotoluene (k)} and $C_P^E$ of their sub-binary {1-methylpyrrolidin-2-one (i) + benzene (j)}; {benzene (i) + m- or p-chlorotoluene (j)} mixtures have been determined using their measured heat capacities data at T = (293.15, 298.15, 303.15) K and 0.1 MPa using micro differential scanning calorimeter. The results are discussed in terms of Graph (which deals with the topology of the constituent molecules) theory. The results suggest that $C_P^E$ and ${(C_P^E)}_{\mathit{ijk}}$ values commuted by Graph theory compare well with experimental values.     

Synthesis,structure, and thermodynamics of a lanthanide coordination compound incorporating 5-nitroisophthalic acid

A lanthanide coordination compound, [Sm₃(5-nip)₄(5-Hnip)(H₂O)₇·9H₂O]_n (5-H₂nip = 5-nitroisophthalic acid), has been synthesized and characterized by elemental analysis, IR, TG-DSC, and single-crystal X-ray diffraction. Structural analysis reveals that the compound features two kinds of 1D channels with guest water molecules. TG-DSC curves show that the dehydrated product of the compound exhibits high stability up to 673 K. The enthalpy change of reaction of formation in water, ${\mathrm{\Delta }}_{\text{r}}{H}_{\text{m}}^{\theta }$(l), was determined to be (27.608 ± 0.133) kJ · mol⁻¹ at (298.15 ± 0.01) K by microcalorimetry. Based on a designed thermochemical cycle and other auxiliary thermodynamic data, the enthalpy change of reaction of formation in solid at (298.15 ± 0.01) K and the standard molar enthalpy for the compound, ${\mathrm{\Delta }}_{\text{r}}{H}_{\text{m}}^{\theta }$(s) and ${\mathrm{\Delta }}_{\text{f}}{H}_{\text{m}}^{\theta }$, were calculated to be (96.8 ± 0.8) kJ · mol⁻¹ and (−831.4 ± 16.0) kJ · mol⁻¹, respectively. In addition, thermodynamics and thermokinetics of the reaction of formation of the compound were investigated in water.