Formulation of Ceramic Foams: a New Class of Amphiphiles

Andrea Celani,Stuart Blackburn,Mark J Simmons,Liz M Holt,E Hugh Stitt

doi:10.1016/j.colsurfa.2017.07.031

Abstract

In this work, amino acids are proposed and assessed as a new class of amphiphiles that is more environmentally benign and present a wider operational window than those reported in the literature. The effects of the amphiphile concentration and structure on the foam properties were investigated (e.g. porosity, bubble size distribution). These were classified depending on their different hydrophobicity by establishing a hydrophobicity index. Monotonic relationships between the hydrophobicity index and the foam structural properties (e.g. porosity, bubble size) were found. In addition, the more suitable amino acid to be used at larger scales was identified and it was used as a model amphiphile to have a deeper insight into the foaming process. In particular, the repartition of the amino acids among the different interfaces and the minimum amphiphile concentration to obtain stable foams were identified.

Highlights

In recent years ceramic foams have been receiving an increasing interest thanks to their applicability in several technology fields
The more suitable amino acid to be used at larger scales was identified and it was used as a model amphiphile to have a deeper insight into the foaming process
At this conditions the dissociated fraction of eCOO− groups present on the amino acids electrostatically interacts with the titania surface

Summary

Introduction

In recent years ceramic foams have been receiving an increasing interest thanks to their applicability in several technology fields. Several techniques have been developed for the production of ceramic foams; these include replica technique, sacrificial templating and direct foaming [3]. The sacrificial material can be natural [7] or synthetic [8] and either in solid [9] or liquid form [10] These are either extracted or decomposed to form a negative replica of the sacrificial template in the ceramic material. Direct foaming is an ostensibly straightforward method for the production of ceramic foams In this process, air is directly entrained into the ceramic suspension causing the attachment of the previously modified particles at the air/water interface, leading to stable foams [11]. It has been demonstrated that both the structural characteristics of the amphiphile and its concentration strongly affect foam properties such as porosity, stability and bubble size distribution [12,13]

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Conclusion