Aqueous dispersion of hexagonal boron nitride via plasma processing in a hydroquinone solution

Abstract

Plasma processing in a solution with a hydroquinone additive was performed for the aqueous dispersion of hexagonal boron nitride (h-BN), and the effect of the hydroquinone additive was determined by analyzing the zeta potential distribution. The hydroquinone additive enhanced plasma modification in the solution to produce well-dispersed h-BN particles separated by centrifugation. The mean zeta potential improved up to −50 mV at neutrality and maintained in a pH range of 6–9. Infrared absorption spectra suggested that the dispersed h-BN particles were modified with hydroxyl functional groups by plasmas in the solution.

Carbon Layer Formation on Hexagonal Boron Nitride by Plasma Processing in Hydroquinone Aqueous Solution

“…In this reaction mechanism, hydroquinone is suggested to have an important role in the formation of dangling bonds on both hBN and the carbon layer. Quinone groups can form semiquinone radicals, as shown in Scheme , which undergo an autoxidizing process and can produce hydroxyl peroxide and hydroxyl radicals. ,, We suppose that hydroquinone could act as a reaction promoter to supply hydroxyl radicals and facilitate defect formation of hBN. The FT-IR spectrum of organic compounds in the processed solution after the plasma processing (Figure S6) reveals the conversion of hydroquinone to benzoquinone as in Scheme .…”

“…Carbon layer formation on hBN particles was demonstrated using plasma in hydroquinone aqueous solution, and the carbon layer formed on hBN was characterized. Hydroquinone was expected to act as a precursor of the carbon layer and radical donator to assist the oxidization process during plasma processing. , The modified hBN particles were analyzed by Raman spectroscopy to confirm the formation of a carbon layer on the surface and electron spin resonance (ESR) spectroscopy to detect dangling bonds. The reactivity of the carbon layer formed on hBN was confirmed by further functionalization with isocyanate groups.…”

“…Many researchers have studied carbon synthesis and deposition on materials using plasma processes, including nanographene synthesis using alcohol in-liquid plasma. − Nitrogen-doped carbon has also been synthesized on metal nanoparticles using plasma in solutions containing organic compounds such as N,N -dimethylformamide. , Furthermore, as low-pressure plasma processes, various diamond-like carbons have been synthesized by plasma-enhanced chemical vapor deposition, − and the direct growth of graphene on hBN by plasma-assisted molecular beam epitaxy has been reported. , In our previous studies, the modification of hBN particles by plasma in hydroquinone aqueous solution was found to improve their dispersibility in water and a polymer matrix with maintaining the thermal conductive and electrical insulating properties as fillers, , but the surface state was not clarified.…”

“…30,31 Furthermore, as low-pressure plasma processes, various diamond-like carbons have been synthesized by plasma-enhanced chemical vapor deposition, 32−34 and the direct growth of graphene on hBN by plasma-assisted molecular beam epitaxy has been reported. 35,36 In our previous studies, the modification of hBN particles by plasma in hydroquinone aqueous solution was found to improve their dispersibility in water and a polymer matrix with maintaining the thermal conductive and electrical insulating properties as fillers, 11,37 but the surface state was not clarified.…”

Cross-Linking-Filler Composite Materials of Functionalized Hexagonal Boron Nitride and Polyrotaxane Elastomer

“…21 The broad absorption bands around 760 and 1370 cm −1 are attributed to the B−N stretching mode. 23,24 TGA curves, as shown in Figure 1d, were measured in air from 120 to 600 °C at a constant heating rate of 4 °C/min. The weight ratio after the heat treatment can be considered as the hBN content in the particles.…”