Fabrication of molybdenum disilicide components by slip casting S. Geasin Savio, R.R. Rao, S.K. Ramasesha * Materials Science Division, National Aerospace Laboratories, Bangalore 560017, India Received 22 November 2001; received in revised form 18 February 2002; accepted 20 February 2002 Abstract Molybdenum disilicide (MoSi 2 ) has many desirable properties which make it an excellent material for aerospace applications. This demands a reliable processing route to manufacture components with complicated shapes. The suitability of using slip-casting technique to fabricate MoSi 2 components has been studied. In this study, we have optimized the pH of the aqueous solution to get a reasonable suspension without adding any dispersing agents or sintering aids. Further, it is found that the 50 wt.% solid loading is best to get a compact of 92% density. D 2002 Elsevier Science B.V. All rights reserved. PACS: 81.05.Je; 81.20.Hy; 81.20.Zx; 83.85.Jn Keywords: Molybdenum disilicide; Viscosity; Solid loading; Slip casting; Ceramic seals 1. Introduction Ceramic materials can be compacted by various processing routes and each of them has its advantages as well as disadvantages. In any processing method, the ultimate aim is to consolidate the powdered sample to get a desired shape and densification by sintering the sample at high temperatures [1]. Slip casting or slurry casting is one of the oldest techniques in ceramic processing and can be used for manufac- turing any complicated shaped ceramic components [2,3]. Its simplicity, low cost, flexibility and uniform particle packing are the added advantages for adopting this processing method [4]. There are limited reports available about the slip casting process of non-clay ceramic materials. The green state processing plays an important role in reducing micro structural imperfection and hence increasing the reliability of the final ceramic products. The sintered density of the sample is directly depend- ent on the density and uniformity of the green micro- structure [5]. The particle packing behavior in the green body is determined by the capability of the particles to remain separated from each other in the colloidal suspension [6]. The repulsion in this suspen- sion can be enhanced by dispersants such as poly- electrolytes. However, the removal of these organic matters becomes very difficult at the time of sintering. Thus, it is preferable to have a colloidal suspension without adding a dispersant. The dispersion quality of any powder particles in aqueous media can be char- acterized by the zeta potential. The absolute maximum value of the zeta potential is essential for the produc- tion of highly dispersed electrostatically stabilized slips [7,8]. In case of MoSi 2 , the highly negative zeta potential lies in aqueous alkali so that the basic media is good to form well-dispersed slips. 0167-577X/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. PII:S0167-577X(02)00696-1 * Corresponding author. Tel.: +91-527-33551-54; fax: +91-808- 5270670. E-mail address: sheela@sscu.iisc.ernet.in (S.K. Ramasesha). November 2002 Materials Letters 57 (2002) 43 – 47