Two pure hydrated sodium borates, α-Na2B5O8(OH)·2H2O and β-Na2B5O8(OH)·2H2O, have been synthesized
under mild hydrothermal conditions and characterized by X-ray diffraction, infrared spectral, and thermogravimetric
analysis and chemical analysis. The molar enthalpies of solution of α-Na2B5O8(OH)·2H2O and β-Na2B5O8(OH)·2H2O in 1 mol·dm-3 HCl(aq) were measured by solution calorimetry to be (20.36 ± 0.33) kJ·mol-1 and (14.27
± 0.20) kJ·mol-1, respectively. With the incorporation of other thermodynamic data, the standard molar enthalpies
of formation were found to be −(4725.1 ± 4.0) kJ·mol-1 for α-Na2B5O8(OH)·2H2O and −(4719.0 ± 4.0) kJ·mol-1
for β-Na2B5O8(OH)·2H2O. The result shows that α-Na2B5O8(OH)·2H2O is more stable than β-Na2B5O8(OH)·2H2O, which is consistent with their thermal behavior.
The growth morphology of polypyrrole in an asymmetric experimental system is investigated. The distribution of electrical field affects the diffusion of cations and the growth pattern of polymer electrodeposits. Under the combined effects of the electrical field and the magnetic field, the changes of polymer morphologies are studied: the asymmetric pattern disappears due to the convection of solution. It is argued that the morphology patterns depend on the diffusion process.
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