The enthalpy of formation at 298.15 K of the polymer Al13O4(OH)28(H2O)3+8 and an amorphous aluminium trihydroxide gel was studied using an original differential calorimetric method, already developed for adsorption experiments, and aluminium-27 NMR spectroscopy data. ΔHf “Al13” (298.15 K) = ? 602 ± 60.2 kJ mole?1 and ΔHf Al(OH)3 (298.15 K) = ? 51 ± 5 kJ mole?1. Using theoretical values of ΔGR “Al13” and ΔGR Al(OH)3, we calculated ΔGf “Al13” (298.15 K) = ? 13282 kJ mole?1; ΔSf “Al13” (298.15 K) = + 42.2 kJ mole?1; ΔGf Al(OH)3 (298.15 K) = ? 782.5 kJ mole?1; and ΔSf Al(OH)3 (298.15 K) = + 2.4 kJ mole?1. 相似文献
JPC – Journal of Planar Chromatography – Modern TLC - A simple, rapid and precise high-performance thin-layer chromatographic (HPTLC) method for analysis of candesartan cilexetil and... 相似文献
Wet tensile testing is a common method to assess the stability of bentonite-bonded moulding sands. For wet tensile testing, a specimen is first heated from above in order to simulate heat-driven moisture transport induced by the casting process. Then, tensile stress is applied until rupture. In this study, neutron radiography imaging was applied to moulding sands in situ during heating and wet tensile testing in order to investigate the effects of water kinematics on the tensile strength. Neutron radiography allowed the localization of the rupture plane and the quantitative determination of the local water content with sub-mm resolution. Quantification of the temperature at the rupture plane and of the heat kinematics within the specimen was accomplished by temperature measurements both in situ and ex situ. In this way, experimental data correlating the wet tensile strength with the specific conditions of moulding sands at the rupture plane were obtained for the first time. Series of experiments with different initial sand moisture contents were conducted. The results show that the weakest location within a sand profile can be pinpointed at the interface between evaporation and condensation zone (i.e. at the 100 \(^\circ \)C isotherm), where water vaporization starts and the water bridges connecting the sand grains collapse. This weakest location has maximum strength, if the local water content at the rupture plane is between 5 and 9 wt.%. Less water leads to a strong decrease of wet tensile strength. More water requires an initial water content above 5 wt.%, which leads to a decrease of the tensile strength of the unheated sand. 相似文献
Recently there is a lot of attention given to manipulation of heat by constructing thermal devices such as thermal diodes, transistors and logic gates. Many of the models proposed have an asymmetry which leads to the desired effect. Presence of non-linear interactions among the particles is also essential. But, such models lack analytical understanding. Here we propose a simple, analytically solvable model of a thermal diode. Our model consists of classical spins in contact with multiple heat baths and constant external magnetic fields. Interestingly the magnetic field is the only parameter required to get the effect of heat rectification. 相似文献
In aqueous systems, partially hydrophobic particles are known to stabilize foams even in the absence of any added surfactant. This paper shows that the same principle can be applied to polymeric systems: particles that are partially wetted by a polymer melt can stabilize a foam of that polymer. The foam stability is attributable to the adsorption of the particles at the air/polymer interface. Remarkably, stable foams are realized even from polymers that are liquid at room temperature, and hence are otherwise unfoamable. The implications of this result to practical foaming operations are discussed.
Journal of Radioanalytical and Nuclear Chemistry - A simple, simultaneously multi-elemental, ICP-AES based method was optimized to characterize nuclear high level waste solutions from different... 相似文献
An unprecedented metal-free synthesis of 4-(methylthio)chromeno[4,3-c]pyrazol-3(2H)-one is reported via sequential one-pot desulfitative [5+1] hetero-annulation. The present strategy consists of one-pot sequential, base catalysed dithioketene formation from active methylene of pyrazolone followed by methylation and [5+1] heteroannulative cyclization. The resulting substrate undergoes facile nucleophilic substitution with various amines to yield 4-(substituted-amine)-chromeno[4,3-c]pyrazol-3(2H)-one derivatives under metal free condition. 相似文献