CERAMICS INTERNATIONAL Available online at www.sciencedirect.com Ceramics International 40 (2014) 691–697 Optimal electroless plating rate enhancement techniques for the fabrication of low cost dense nickel/ceramic composite membranes Amrita Agarwal, Murali Pujari, R. Uppaluri n , A. Verma Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India Received 17 May 2013; received in revised form 14 June 2013; accepted 14 June 2013 Available online 24 June 2013 Abstract Addressing combinatorial plating characteristics for dense metal ceramic composite membranes, this article attempts to identify the most suitable electroless plating rate enhancement technique. The support morphology considered for this work corresponds to low combinations of pore size and porosity. Cases considered for comparative assessment include conventional electroless plating (CEP), surfactant induced electroless plating (SIEP) and sonication induced electroless plating (SOEP). BET, FTIR, XRD, FESEM and nitrogen permeation techniques were employed for surface and physical characterization. It was observed that with SIEP the average metal film thickness was about 18.3 μm and with SOEP it was 24.6 μm. Correspondingly it was also observed that for SIEP baths the ratio of percent pore densification (PPD) to metal film thickness (δ) i.e. PPD/δ varied from 11.2 to 5.35 and for SOEP baths PPD/δ varied from 3.5 to 4.7 for 8–24 h of sequential plating. Thereby, it was inferred that SIEP possessed maximum potential towards dense metal ceramic composite membrane fabrication for the realization of maximum PPD with minimal metal film thickness. & 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: E. Membrane; Ceramic; Surfactant; Densification 1. Introduction Metal composite membranes have numerous applications such as TiO 2 recovery from waste water streams [1], asym- metric supports for dense palladium composite membranes [2], production of ultrapure gases for special applications [3] and hydrogen separation [4]. Presently companies involved in fabricating composite membranes for various industrial appli- cations include Mykron, Entegris and Mott Corporation. Amongst several fabrication processes, electroless plating (ELP) offers a good number of advantages such as uniformity in depo- sition irrespective of shape and size, simple experimental setup, scalability, minimal usage of electrical power, applicability for deposition on internal surfaces, edges, irregular and complex shapes, etc. The autocatalytic metal electroless plating process is an extremely slow process and therefore plating rate enhancement techniques were explored to enhance the plating rate. How- ever, the quality of plating remained a central issue for which plating rate enhancement techniques and their associated parameters need to be optimized. Several plating rate enhance- ment techniques include agitation (in the form of either membrane stirring [5] or gas sparging [6]), vacuum [7], hydrothermal [8], sonication [8] and surfactant assisted elec- troless plating baths [9]. However, amongst these techniques, from the perspectives of combinatorial plating characteristics and ease of operation, sonication and surfactant remained attractive, as industrial scale sonication baths are available and surfactant assisted electroless plating could be scaled up easily. Even amongst these two, surfactant induced electroless plating has significant number of features. The usage of surfactant is advantageous in two ways—firstly surfactant reduces the surface tension of the gas bubble and therefore enables the generation of smaller bubbles on the surface thereby minimiz- ing the pitting effect. Secondly since gas bubbles are removed at a faster pace, the redox reaction shifts to the forward direction and therefore metal plating is enhanced [9]. Further www.elsevier.com/locate/ceramint 0272-8842/$ - see front matter & 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved. http://dx.doi.org/10.1016/j.ceramint.2013.06.056 n Corresponding author. Tel.: +91 361 2582260; fax: +91 361 2582291. E-mail address: ramgopalu@iitg.ernet.in (R. Uppaluri).