JOURNAL OF MATERIALS SCIENCE LETTERS 21, 2 0 0 2, 803 – 805 Hydrolysis process of a surface treated aluminum nitride powder—A FTIR study YONGHENG ZHANG Department of Materials Science and Technology, Qingdao Institute of Chemical Technology, P.O. Box 64, No. 53 Zheng-Zhou Road, Qingdao 266042, People’s Republic of China E-mail: yonghengzhang@yahoo.com J. BINNER Institute of Polymer Technology and Materials Engineering, Loughborough University, Leicestershire, LE11 3TU, UK Aluminum nitride (AlN) ceramics are being increas- ingly used as substrate materials for electronic packag- ing and as refractories [1, 2] amongst other applications due to their excellent thermal conductivity and the elec- trical resistivity. Although AlN can be consolidated by hot pressing or hot isostatic pressing, pressureless sin- tering at temperatures of 1600–2000 ◦ C is increasingly used [3, 4]. Common fabrication processes for pres- sureless sintering are injection molding, slip casting and tape casting. These techniques rely on the forma- tion of dispersed suspensions and this offers advantages for dispersing small quantities of sintering aids, such as SiO 2 ,Y 2 O 3 and Al 2 O 3 [5, 6] homogeneously. However, due to economic and environmental concerns, the pro- cessing of AlN powders into components via the use of aqueous, rather than organic-based, suspensions is attracting increasing interest. Unfortunately, AlN pow- ders are easily hydrolyzed by water. X-ray photoelectron spectroscopy (XPS) [7, 8] and diffuse-reflectance Fourier transform infrared spec- troscopy [9] have all been used to characterize the surface of untreated AlN particles. When in contact with moisture the powder surface becomes hydrolyzed and hence covered by γ -AlOOH, Al(OH) 3 or γ -Al 2 O 3 species [10, 11]. Thus in order to process them by aqueous colloidal routes, modification of the powder surfaces with organic chemicals to make them hy- drophobic is usually performed [12–15]. The chemi- cally treated AlN powder through surface modification will have organic species on its surface that will then affect the interactions between the particles and any dispersants used once they are contacted with water. In this paper, the hydrolysis process of a hydropho- bic treated AlN powder (later denoted as treated AlN powder, ART20, Advanced Refractory Technologies (ART), Buffalo, New York, USA) was studied un- der different conditions, i.e. hydrolysis time, disper- sant concentration (Emphos 1316, a polyoxyalkylated aldylaryl phosphate ester sodium salt supplied by ART, USA). The water-contacted powders were then charac- terized using a Fourier transform infrared spectroscopy (FTIR) (5DXB, Nicolet Instrument Corporation, USA). FTIR spectra for samples hydrolyzed (20 ◦ C) without addition of the surfactant for different time periods and an FTIR spectrum from a reference sample of Al(OH) 3 are presented in Fig. 1. The exact peak positions can be seen in Table I. The spectrum for the AlN powder be- fore hydrolysis (0 h) exhibited a strong absorption peak at 710 cm -1 and a few much weaker peaks at higher frequencies; the peaks centered at 710 and 1326 cm -1 may be assigned to the vibration of the AlN bond [16]. The figure shows that there was a gradual increase in the intensity of the peaks positioned at about 1398, 1457, 1635 and 3400 cm -1 with increasing hydrolysis time up to 192 h. The latter three peaks are all clearly at- tributable to amorphous Al(OH) 3 . It is interesting to note, however, that the largest two peaks, 3400 and 1635 cm -1 , were both detectable in the sample that had not been hydrolyzed at all indicating a degree of hydrolysis in the as-received powder. The broad peak at around 3400 cm -1 has been attributed to the O–H stretching vibration of AlOH species that undergo hydrogen bonding with neigh- boring hydroxyl groups [17, 18]. In addition, the O–H stretching vibration of molecular H 2 O may also contribute to this band. The presence of physisorbed Figure 1 FTIR spectra for surface-treated AlN powder, without addition of surfactant, after hydrolysis for varying time periods and a reference spectrum for powdered Al(OH) 3 . 0261–8028 C  2002 Kluwer Academic Publishers 803