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The effect of nano-confinement on the phase transitions of heneicosane (n-C21H44, C21) were investigated using differential scanning calorimetry (DSC) and variable temperature powder X-ray diffraction (XRD). When C21 is confined within the pores of controlled pore glasses (CPGs), SBA-15 or other mesoporous materials, the solid-solid (Ts) and solid-liquid (Tm) transition temperatures are depressed. The depression of the phase transition temperatures (ΔTs, ΔTm) for C21 in CPGs and SBA-15, the degree of supercooling and enthalpy change (ΔHs, ΔHm) for C21 in CPGs, exhibited a linear dependence on the inverse pore size. The ΔTm values were insensitive to the polarity pore wall but varied with the pore geometry. XRD analysis revealed that the lamellar ordering characteristic for the solid C21 was disturbed in the nanopores, with the extent increasing as the pore size decreased. A new rotator phase RII is found for C21 confined in CPG (12 nm) and SBA-15 (14.4 nm).

The nanoconfinement effect on the phase behaviors of octacosane (n-C28H58, C28) was studied using differential scanning calorimetry (DSC) and X-ray diffraction (XRD). In the nanopores of controlled pore glasses (CPGs), silica gels (SGs), SBA-15, and KIT-6, C28 showed depressed phase transition temperatures. The depression of phase transition temperatures, degree of supercooling and enthalpies of phase transitions for C28 confined in the CPGs, SGs and SBA-15 exhibited a linear dependence on reverse pore diameter. The phase transition temperatures also varied with the changing pore geometry, and the depression of melting points of C28 in SBA-15 is about 2 times larger than that in the CPGs and SGs. The interfacial interactions of the pore walls to alkane seem to have a negligible influence on the phase behaviors. The phase transition sequences of the pore-confined C28 changed largely with the appearance of new RI and RII rotator phases.

The molar heat capacities of the two biphenyl liquid crystals, 3BmFF and 3BmFFXF3, with a purity of 99.7 mol% have been precisely measured by a fully automated precision adiabatic calorimeter in the temperature range between T = 80 and 350 K. Nematic phase-liquid phase transitions were found between T = 297 K and 300 K with a peak temperature of T-peak = (298.071 +/- 0.089) K for 3BmFF, and between T = 316 and 319 K with a peak temperature of T-peak = (315.543 +/- 0.043) K for 3BmFFXF3. The molar enthalpy (Delta(trs)H(m)) and entropy (Delta(trs)S(m)) corresponding to these phase transitions have been determined by means of the analysis of the heat capacity curves, which are (15.261 +/- 0.023) U mol(-1) and (51.202 +/- 0.076) J K-1 mol(-1) for 3BmFF, (31.624 +/- 0.066) kJ mol(-1) and (100.249 +/- 0.212) J K-1 mol(-1) for 3BmFFXF3, respectively. The real melting points (TI) and the ideal melting points (TO) with no impurities of the two compounds have been obtained from the fractional melting method to be (298.056 +/- 0.018) K and (298.165 +/- 0.038) K for 3BmFF, (315.585 +/- 0.043) K and (315.661 +/- 0.044) K for 3BmFFXF3, respectively. In addition, the transitions of these two biphenyl liquid crystals from nematic phase to liquid phase have further been investigated by differential scanning calorimeter (DSC) technique; the repeatability and reliability for these phase transitions were verified. (C) 2004 Elsevier B.V. All rights reserved.

The heat capacities of rare earth complex with amino acid histidine, [Er 2 (His·H + )(H 2 O) 8 ](ClO 4 ) 6 ·4H 2 O, were measured with an automatic adiabatic calorimeter from 79 to 320 K. It was found that there was a sudden increment in heat capacity within the temperature range 182–190 K. Thermal decomposition behavior of the complex in nitrogen atmosphere was studied by thermogravimetric (TG) analysis, and a possible decomposition mechanism was suggested according to TG–DTG results.

The constant volume energy of combustion of crystalline 3,5-di- tert -butylsalicylic acid ( t -BSA) in oxygen at 298.15 K was determined using combustion calorimeter to be −8292.57±2.51 kJ mol −1 . The standard molar enthalpies of combustion and formation of 3,5-di- tert -butylsalicylic acid were derived, at T =298.15 K, Δ c H m Θ =−8302.48±2.51 kJ mol −1 and Δ f H m Θ =−744.30±3.21 kJ mol −1 , respectively. The heat capacities of the compound were measured with an adiabatic calorimeter over the temperature range from 79 to 351 K. No indication of any phase transition or thermal anomaly was observed in this temperature range. The fusion and evaporation behavior of the compound were examined by thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). The molar enthalpy and entropy of fusion, Δ fus H m Θ and Δ fus S m Θ , at T =437.5 K, were determined to be 22.92±0.55 kJ mol −1 and 139.4±3.3 J mol −1 K −1 , respectively; and the molar enthalpy and entropy of evaporation, Δ vap H m Θ and Δ vap S m Θ , at T =477.5 K, were obtained as 83.88±2.1 kJ mol −1 and 341.7±8.4 J mol −1 K −1 , respectively.

The heat capacities of two kinds of rare-earth element solid complexes with isoleucine [Re 2 (Ile) 4 (H 2 O) 8 ](ClO 4 ) 6 (whereRe = Nd, Er, and Ile = isoleucine) have been measured by an automatic adiabatic calorimeter in the temperature rangefrom 80 to 370K. Two solid–solid phase transitions were found from the C p curve of Nd formed complex in the rangeof 165–175K with a peak temperature of 167.88K and in the range of 195–210K with a peak temperature of 202.13K.The corresponding molar enthalpies of these phase transitions were determined to be 404.61Jmol −1 and 2.955kJmol ,respectively. One solid–solid phase transition was found for the Er formed complex in the range of 190–205K with a peaktemperature of 193.42K. The corresponding molar enthalpy of this transition was 14.11kJmol −1 . Smooth heat capacities andthermodynamic functions relative to the standard state (298.15K), H T − H 298 . 15 , S T − S 298 . 15 and −[ G T − G 298 . 15 ], of thetwo compounds, were calculated on basis of experimental heat capacity data. Possible mechanisms of thermal decompositionsfor the pair of compounds were suggested according to the thermogravimetric (TG) analysis.© 2002 Elsevier Science B.V. All rights reserved.

Two solid-state coordination compounds of rare earth metals with glycin, [Gd 4/3 Y 2/3 (Gly) 6 (H 2 O) 4 ](ClO 4 ) 6 ·5H 2 O and [ErY(Gly) 6 (H 2 O) 4 ](ClO 4 ) 6 ·5H 2 O were synthesized. The low-temperature heat capacities of the two coordination compounds were measured with an adiabatic calorimeter over the temperature range from 78 to 376 K. [Gd 4/3 Y 2/3 (Gly) 6 (H 2 O) 4 ](ClO 4 ) 6 ·5H 2 O melted at 342.90 K, while [ErY(Gly) 6 (H 2 O) 4 ](ClO 4 ) 6 ·5H 2 O melted at 328.79 K. The molar enthalpy and entropy of fusion for the two coordination compounds were determined to be 18.48 kJ mol −1 and 53.9 J K −1 mol −1 for [Gd 4/3 Y 2/3 (Gly) 6 (H 2 O) 4 ](ClO 4 ) 6 ·5H 2 O, 1.82 kJ mol −1 and 5.5 J K −1 mol −1 for [ErY(Gly) 6 (H 2 O) 4 ](ClO 4 ) 6 ·5H 2 O, respectively. Thermal decompositions of the two coordination compounds were studied through the thermogravimetry (TG). Possible mechanisms of the decompositions are discussed.

Heat capacities of two solid complexes of rare-earth elements with glycine [RE(Gly)3(H2O)2]Cl3·2H2O (RE=Pr, Nd, Gly=Glycine) have been measured with a high-precision automatic adiabatic calorimeter over the temperature range from 78 to 380 K. The melting point, molar enthalpy and entropy of fusion for the two complexes were determined on the basis of the heat capacity measurements. Thermal decompositions of the two complexes were studied by thermogravimetric (TG) techniques and a possible mechanism for the decompositions is suggested.

To stabilize phase change material, disodium hydrogen phosphate dodecahydrates (na2hpo4 center dot 12h2o), a novel gelling method by polymerizing sodium alginate grafted sodium acrylate in its molten salt was investigated. the optimum synthesis conditions to obtain product with stable heat storage performance were 2.8% (w/w) sodium acrylate, 0.3-0.4% (w/w) sodium alginate, 0.1-0.19% (w/w) nap-methylenebisacrylamide and 0.06% (w/w) k2s2o8 and na2so3, at 50 degrees c. na2hpo4 center dot 12h(2)o was dispersed in the as-synthesized gel network as tiny crystals less than 0.1 mm. melting points were in the range 35.4 +/- 2 degrees c. short-term thermal cycling proves the effectiveness of the novel gelling method for eliminating phase separation in the gelled salt. (c) 2007 published by elsevier b.v.