Study On The Basic Issues Of Preparing Pd/Porous Stainless-Steel Composite Memebranes By Electroless Plating

Palladium has a huge hydrogen dissolution and permeability, and higher resistance to oxide film formation, compared with other metals in high temperature. So palladium is the most commonly material used for hydrogen transfer through itself. It is well known that Pd and its alloy membranes have been commonly used as hydrogen separators and hydrogenation /dehydrogenation membrane reactors. Palladium and its alloy composite membranes have widely potential applications in hydrogen separation, purification and reactions associated with hydrogen.This article mainly studies on the basic issues of preparing palladium membranes using electroless plating: Improving the processing of electroless plating; theoretically analyzing effects of the plating conditions on the microstructure of the palladium membranes; experimentally evaluating the permeation performance of the membranes prepared. The details are given as follow:1. An improved electroless plating technique with the activation method and hydrazine addition was developed for preparing palladium composite membranes. A new method, which the activation utilized palladium(â…¡)solution impregnation with ultrasonic wave and oxidized--reduced at high temperatures was presented. Experimental results indicate that using the new method evened the profile of Pd particles and reduced the dipping time. By compared to the addition modes: hydrazine added at twice and hydrazine added six times, it was found that the palladium membrane prepared with the hydrazine added at six times is denser and flatter than that prpared with the hydrazine added at twice.2. Effects of the plating conditions, such as temperature,[PdCl₂] and plating time, on the palladium membrane microstructure were investigated throughoutly Results indicate that the Pd membrane formation was originated from column-like deposition of crystal Pd particles; the size of crystal Pd columns-like deposited increased with the increasing in plating temperature and time; effect of PdCl₂ concentration on the size of those was not significant.3. The performance of the membranes prepared by developed electroless plating was examined.Hydrogen permeation through Pd membrane follows the solution--diffusion mechanism. With the increase of temperature and pressure difference crossover the membrane,the H₂ permeability was increased. While the thickness of Pd membranes was increased, the exponential in H2 penetration expressions was decreased.