Abstract
Manufacturing of aerogels and membranes from hexagonal boron nitride (h-BN) is much more difficult than from graphene or graphene oxides because of the poor dispersibility of h-BN in water, which limits its exfoliation and preparation of colloidal solutions. Here, a simple, one-step mechano-chemical process to exfoliate and functionalize h-BN into highly water-dispersible, few-layer h-BN containing amino groups is presented. The colloidal solutions of few-layer h-BN can have unprecedentedly high concentrations, up to 30 mg ml−1, and are stable for up to several months. They can be used to produce ultralight aerogels with a density of 1.4 mg cm−3, which is ∼1,500 times less than bulk h-BN, and freestanding membranes simply by cryodrying and filtration, respectively. The material shows strong blue light emission under ultraviolet excitation, in both dispersed and dry state.
Highlights
Manufacturing of aerogels and membranes from hexagonal boron nitride (h-BN) is much more difficult than from graphene or graphene oxides because of the poor dispersibility of h-BN in water, which limits its exfoliation and preparation of colloidal solutions
BN foams assembled from nanosheets showed excellent thermal stability, super-elasticity and very low electrical permittivity, but the assembly process required the use of templates, high temperature and vacuum, hazardous and toxic chemicals, and sophisticated fabrication techniques[27,28]
We have developed a one-step method for the preparation and functionalization of few-layer BN based on urea-assisted solid exfoliation of commercially available h-BN (Fig. 1a)
Summary
Manufacturing of aerogels and membranes from hexagonal boron nitride (h-BN) is much more difficult than from graphene or graphene oxides because of the poor dispersibility of h-BN in water, which limits its exfoliation and preparation of colloidal solutions. The colloidal solutions of few-layer h-BN can have unprecedentedly high concentrations, up to 30 mg ml À 1, and are stable for up to several months They can be used to produce ultralight aerogels with a density of 1.4 mg cm À 3, which is B1,500 times less than bulk h-BN, and freestanding membranes by cryodrying and filtration, respectively. We present a simple and efficient one-step method for the preparation and functionalization of few-layer BN by solid-state ball milling of commercially available h-BN and urea powder This ambient temperature method has several advantages, including scalability for mass production, low cost, high yield and does not require the use of organic solvents, catalysts, substrates or vacuum systems. Both colloidal solutions and freestanding membranes show strong ultraviolet and blue light luminescence
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