Preparation and application of Cu/Cr hydrotalcite-like compounds

A series of copper/chromium hydrotalcite-like compounds (Cu/Cr-HTlcs) with Cu/Cr molar ratios from 1:1 to 4:1 synthesized by coprecipitation reaction using NaOH and Na₂CO₃ as precipitation agents and their derived Cu/Cr mixed oxides (Cu/Cr-MO) were used in solid propellant for the first time. The structure, morphology and thermal behaviors were investigated using inductively coupled plasma optical emission spectrometry, X-ray diffraction, Fourier-transform infrared spectroscopy, N₂ volumetric measurements, transmission electron microscope, thermogravimetry, and differential thermal analysis. The results showed that a well crystallized Cu/Cr-HTlcs with CO ₃ ^2- as interlayer anions could be obtained with Cu and Cr molar ratio of 2:1, system pH value between 9 and 11, aging time longer than 24 h; the sample has a specific surface area of 107.8 m² g^-1 and average pore diameter is 9 nm with pore volume of 0.34 cm³ g^-1; N₂ adsorption-desorption isotherm is type IVb with H₂-type hysteresis loop; thermal stability of the sample is relatively lower and the sample tends to be curled when the aging time is prolonged to 1 week at room temperature. Solid propellant with Cu/Cr-MO catalyst exhibit significantly higher burning rate of 9.64 mm s^-1 than those without catalyst (6.28 mm s^-1)/with CuO • Cr₂O ₃ catalyst (9.07 mm s^-1). Press index also decreases from 0.339 to 0.299, and mechanical performance on elongation for Cu/Cr-MO catalyzed propellant has a clear enhancement.