Naser Al-Mufachi

Imperial College London

Project Title: Electroplating of Carbon Aerogels
Advisor: Professors Jeffrey Youngblood and Kevin Trumble

Introduction

Aerogels are a fascinating feat of engineering and have been aptly deemed the world’s lightest synthetic solid since it has a density ranging 0.1 - 0.01 g/cm3. However the carbon aerogel will be the main area of interest for the entire research and particular attention will be payed to the effects of electroplating on the entire morphology and structure. This task should be of great interest since the carbon aerogel has such a massive surface area (400 m2/g) and would be viable for applications such as a storage medium or electrical capacitor.

The structures of Carbon Aerogels are analogous to a network of pearls, meaning there is a porous arrangement of particles which allow for high surface area and extremely low density. The premise of the experiment will be to explore the possibilities of plating the porous interior with various transition metals. Nickel is extremely easy to deposit via the means of electroplating and so, in general, if an object cannot be plated with this metal then it is presumed it cannot be plated at all.

The process known as electroplating involves the deposition of a metallic coating onto an electrically conducting object. This is done by putting a negative charge on the object in a sense to make it the cathode electrode, and making the plating metal the anode. The two electrodes will then be immersed in an electrolyte solution containing a salt that includes the metal desired for plating i.e. for plating with nickel; the electrolyte solution will contain considerable quantities of nickel sulfate. The electrolyte solution contains freely moving ions which act as charge carriers that complete the circuit and so when a nickel ion reaches the cathode, it will be reduced to form a metallic coating on the cathode electrode.

Project Objectives

The main aim of this research is to electroplate carbon aerogel specimens with various transition metals such as nickel, iron and chromium. Once this is complete, detailed image and EDS analysis will be implemented in order to varify any plating. As a secondary objective, the iron plated specimen will be heat treated so that the diffusion of carbon into iron can be observed. The idea behind this procedure is to monitor the production of steel on a nanoscale.

Approach

This process involves the deposition of metallic coating onto an object. This is done by putting a negative charge on the object (cathode). Positive charge put on the metal desired for deposition (anode). Then Immersed in an electrolyte or salt containing the metal desired for coating. The electrolyte contains freely moving ions which act as charge carriers which complete the circuit. The metallic ions are attracted to the cathode and are reduced to form the metallic coating.

Findings

Small samples of carbon aerogels were electroplated with nickel, iron and chromium. EDS scans and high magnification SEM images were taken in order to verify any plating. It was found that nickel and iron would form a thin foil like layer on the outer surface of the carbon aerogel. Chromium, however, did not behave in this way. Instead it would not form a film layer, but rather it would adsorb deep into the surface and nucleate. A brief look was taken into the effect of carbon diffusion via heat treatment. The iron plated sample was sectioned in half and heat treated; one piece was raised to a temperature of 900ºC for 3 hours in forming gas. The other was taken up to 950ºC for 24 hours in forming gas and it was discovered that no significant diffusion of carbon occurred in the sample treated for 3 hours at 900ºC and the sample treated for 24 hours at 950ºC evaporated.

Fig. 1. Carbon aerogel04: "FESEM image of plane Carbon Aerogel 35,000x.
Fig. 2. Carbon aerogel02: "FESEM image of Nickel plated Carbon Aerogel 250x.

Contact me: naser.al-mufachi@imperial.ac.uk