Properties of high density silica fume-based gel and its potential use in high temperature lubricants and geopolymer binders

In the present study, un-densified silica fume was reacted with a 10 M sodium hydroxide solution to produce the sodium silicate gel having a pH of 14. The calorimetry of the reaction was evaluated. The gel was dried to increase its density by almost 35%. Thereafter, the thermogravimetry of the gel was performed at temperatures up to 1000 °C. Except the loss in mass caused by the departure of physical and chemical water at temperatures below 200 °C, no other mass loss process was identified in the gel. The potential applications of the gel as high-temperature lubricants for automotive and metallurgical engineering and as alkaline activator in geopolymer binder were discussed. Since silica fume is a by-product material that do not require heating or grinding and can react with sodium hydroxide solution at ambient temperature, the results suggested potential for enhanced sustainability in the reduction of embodied energy for the production of the materials like high-temperature inorganic lubricant and alkaline activator for geopolymer binder.