Gels from modified zirconium N-butoxide: A pyrolysis study by coupled thermogravimetry, gas chromatographic, and mass spectrometric analyses

A brown gel was prepared by mixing Zr(OBun)(4) and Ce(acac)(3) in anhydrous ethanol. The pyrolysis of this sample was followed under helium flow by on line thermogravimetric (TG), gas chromatographic (GC), and mass spectrometr ic (MS) measurements, to study the conversion of the gel into densified pow ders. Two different experimental configurations (TG-MS) and (TG-GC-MS) were used for gas-phase analyses and the identification of the species evolved during thermal treatments. Mass loss occurs in five steps and the densifica tion of the gel results from condensation reactions and from the decomposit ion of the acetylacetonato groups at low temperature. At higher temperature , the elimination of butene occurs from the residual butoxide left in the g el. The experimental results indicate that the gel after the analyses under helium is amorphous and crystallizes during transmission electron microsco py (TEM) observations. The temperature and atmosphere of firing have a larg e effect on the gel structure; this is discussed on the basis of infrared s pectroscopy (IR) data.