Novel Approach to Synthesizing Carbide Materials from a Cellulosic Precursorposter Format
Authors: Grubbs Jackson Kenamond , Earls Theresa 
Published: February 2020

Carbides are an important class of materials given their high melting temperature, abrasion resistance, and compressive strength. Carbides are obtained through the reaction of carbon and other elements such as silicon, titanium and tungsten. In particular, porous carbides find application in high temperature filters, membranes, and catalysts thanks to their lower density and a higher surface area to volume ratio compared to classically manufactured solid carbide materials. The use of templates is a common way to derive porous carbides. For example, in industry when carbides are being formed in a specific shape or morphology, the use of polymers which have a more controllable structure are used as a precursor for the production of porous carbides. Here we postulate the use of cellulosic paper as a carbon precursor. If the paper is infiltrated with precursors for silicon, titanium or tungsten, then a carbide is derived upon heat treatment. Origami techniques can then be used to shape the infiltrated paper into different geometries, which remain throughout heat treatment. Hence, this technique yields complex 3D geometries with thin cross sections that can enable lightweight, structured carbides. The importance of the work presented here is furthering our understanding on how different processing variables affect the composition of the resultant material.

The carbide materials from paper are synthesized by the carbothermal reduction of metallic ethyl esters which have been embedded into a pure cellulosic paper matrix. In this work we use a porous matrix of cellulosic fibers and infiltrate them with solutions of either Tetraethylorthosilicate (TEOS) or Tyzor to form SiC or TiC respectively. The manner of infiltration used was capillary action through the cellulose matrix after exposing one side of the paper to the metallic solution. With the paper fully saturated, we allowed the samples to dry before placing them in a tube furnace for pyrolization in an inert N2 environment. Around 900 OC, cellulosic fibers decompose to a carbon fiber matrix and the metal ethers reduce to metal oxides.

Our work currently focuses on determining the impact of different processing variables on the composition of the final material. These variables include the synthesis temperature, heating rate, and ratio of carbon to silicon or titanium. We expect that the variability in the ratio of the carbon to metallic precursors will influence the concentrations of the resultant materials while the changes in synthesis temperature and heating rate will influence the growth of the carbides once the reaction is initiated. We are testing these parameters using the Taguchi method of design to increase the efficiency of investigation. We have already had success in the synthesis of metallic carbides using this procedure with a titanium precursor and are now attempting to expand on our work by controlling the carbide growth and testing with additional metallic precursors. Future work is needed to test the impact of using different synthesis environments (such as Argon and vacuum instead of Nitrogen) and the use of alternative metal ethyl ethers on the final quantity and morphology of the resultant carbides.

Figure 1