Synthesis of magnesium borate (Mg2B2O5) nanowires, growth mechanism and their lubricating properties

General equations to correlate and predict the thermodynamic properties of hydrated borates were developed based on the experimental results according to their structural types. The thermodynamic properties (ΔH f 0 and ΔG f 0) of a hydrated borate phase are the sum of the contributions of the cations in aqueous solution, the borate polyanions, and the structural water to the corresponding thermodynamic properties. This method is called the group contribution method, and it is extensively used to calculate the thermodynamic properties of many kinds of inorganic compounds, such as silicates and clay minerals.

Calculation of thermodynamic properties of hydrated borates by group contribution method

In order to recover cesium tetraborate pentahydrate (Cs2O·2B2O3·5H2O) from the high concentration cesium-containing salt lake brines and geothermal water resources, the molar heat capacity of Cs2O·2B2O3·5H2O has been measured with a precision calorimeter at the temperature from 303 to 349 K. It was found that there is no phase transition and thermal anomalies. The molar heat capacity of cesium tetraborate pentahydrate is fitted as Cp,m (J·mol−1·K−1) = 593.85705 + 48.0694[T − (Tmax + Tmin)/2]/(Tmax − Tmin)/2] + 24.86395[(T − (Tmax + Tmin)/2)/(Tmax − Tmin)/2]2 + 0.53077[(T − (Tmax + Tmin)/2)/(Tmax − Tmin)/2]3, and the relevant thermodynamic functions of enthalpy, entropy, and Gibbs free energy of cesium tetraborate pentahydrate are also obtained at intervals of 2 K from 303 to 349 K.

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Heat Capacity and Thermodynamic Property of Lithium Pentaborate Pentahydrate

4ZnO·B2O3·H2O nano-/microstructures with different morphologies (rod-, wire-, and lamellar-like shapes and microspheres of nano-/microrods) were successfully fabricated through a facile surfactant-assisted hydrothermal method. These 4ZnO·B2O3·H2O nano-/microstructures were characterized by XRD, SEM, and BET specific surface area analysis and TEM equipped with SAED. The influence of hydrothermal reaction parameters, including the initial pH, hydrothermal temperature and time, and concentrations of raw materials, on the formation of 4ZnO·B2O3·H2O nano-/microstructures was investigated. The surfactant of poly(ethylene glycol) 300 played a crucial role in the formation of crystalline 4ZnO·B2O3·H2O with different nano-/microstructures. The structure formation mechanism is briefly discussed. In addition, this work preliminarily demonstrates the fungistatic and bacteriostatic activities of 4ZnO·B2O3·H2O nanocrystals.

Controllable Synthesis of 4ZnO.B2O3.H2O Nano-/Microstructures with Different Morphologies : Influence of Hydrothermal Reaction Parameters and Formation Mechanism

Two pure calcium borates of 2CaO·5B2O3·5H2O (I) and β-4CaO·5B2O3·7H2O (II) have been synthesized under hydrothermal condition and characterized by X-ray diffraction, infrared spectra, and thermogravimetric analysis as well as by chemical analysis. All the enthalpies of solution were measured at 298.15 K by using a heat conduction microcalorimeter. The molar enthalpies of solution of (I) and (II) in 2.00 cm3 of 1 mol·dm-3 HCl(aq) were measured to be −(60.30 ± 0.78) kJ·mol-1 and −(158.63 ± 0.72) kJ·mol-1, respectively. The molar enthalpies of solution of H3BO3(s) in 2.00 cm3 of 1 mol·dm-3 HCl(aq) and of CaO(s) in 2.00 cm3 of (HCl + H3BO3) aqueous solution were measured to be (21.84 ± 0.05) kJ·mol-1 and −(188.59 ± 0.42) kJ·mol-1, respectively. The enthalpies change of borates (I) and (II) formation from the reaction of reagents in the solid phase, −(98.3 ± 1.3) kJ·mol-1 and −(377.2 ± 1.9) kJ·mol-1 were calculated respectively on the basis of the appropriate thermochemical cycles. From these data and the stan...

Shiyang Gao

Papers

Thermochemistry of hydrated magnesium borates

Thermochemistry of hydrated potassium and sodium borates

Thermochemistry of hydrated lithium borates