Probing Wettability Alteration of the Boron Nitride Surface through Rheometry

Abstract

While the surface of many ceramic particles is covered by positive and negative species, boron nitride displays no charge on the surface. Nevertheless, the interest in boron nitride is rising: Little materials combine electrical insulation and high thermal conductivity; both properties are required for many applications, for instance, in electronic devices and sensors. Hydroxyl (-OH) groups are usually created on the surface to increase the hydrophilicity of particles. In this work, we compare four treatments to select the one that ~$, increases most significantly the hydrophilicity of hexagonal boron nitride ~~" • • '' '' " "r.!.,~1 " " 00 " n platelets, that is to say, for which the most-OH groups are grafted onto the surface. The treated particles have been studied by SEM, FTIR, and XPS. Our results show that these techniques are not appropriate to probe slight chemical changes. Indeed, hydroxyl groups are more likely introduced on the edges of the platelets. The highest hydroxyl concentration corresponds to 2.4% of boron atoms functionalized. The settling of low concentrated suspensions has been followed by optical visualization. Multiple light scattering was used for high concentrated suspensions. The rheological behavior of stable suspensions in water and isopropanol has been determined by transient flow and dynamic tests. Measuring the viscosity of suspensions appears as a way to evaluate the surface alterations of boron nitride. The method involving thermal treatment is the most efficient to increase the concentration of hydroxyl groups when the particles are suspended in water. The treatment with nitric acid seems to be the most efficient when the particles are suspended in isopropanol. Moreover, the thermal treatment is more environmentally friendly than using strong acids or bases. Hydroxylated particles can be used either as a starting material for further modification such as covalent functionalization or directly to prepare suspensions or polymeric based composites.

h-BN Modification Using Several Hydroxylation and Grafting Methods and Their Incorporation into a PMMA/PA6 Polymer Blend

“…However, due to the very low amount of hydroxyl groups compared with the size of the h-BN sheets, the presence of those hydroxyl groups were not visible with FTIR. This is in accordance with the literature [33]. The TGA (Figures 3b and 4b) of BNO Cal/W also showed a weak weight loss in comparison to h-BN that confirmed the difficulty of assessing a high hydroxylation rate.…”

“…Wu et al [32] demonstrated the hydroxylation of h-BN by sonicating h-BN particles in a nitric acid solution. Korycki et al [33] compared four treatments to select the one that increased the hydrophilicity of h-BN platelets most significantly and therefore resulted in the highest concentration of the -OH groups grafted on sheet edges. As the results were proximate, the authors selected a thermal treatment that was more environmentally friendly than the use of strong acids or bases.…”

Thionyl Chloride Corrodes Hexagonal Boron Nitride to Generate Reactive Functional Groups

“…5 Although this makes breakage of B−N bonds challenging, several chemical modification strategies have still been developed successfully. 7,8 In general, most of them rely on strong acids, 9 strong bases, 10,11 strong oxidants, 12 highenergy rays, 13,14 or other harsh experimental conditions. 15 For example, adding h-BN to HNO 3 (or a mixed solution of HNO 3 and H 2 SO 4 ) solution (∼65% w/w) and sonicating for 5−6 h can introduce hydroxyl groups on the surface.…”

“…However, the difference in electronegativity between B and N makes the covalent sp 2 bonds partially ionized, which makes B–N bonds stronger and harder to break . Although this makes breakage of B–N bonds challenging, several chemical modification strategies have still been developed successfully. , In general, most of them rely on strong acids, strong bases, , strong oxidants, high-energy rays, , or other harsh experimental conditions . For example, adding h-BN to HNO 3 (or a mixed solution of HNO 3 and H 2 SO 4 ) solution (∼65% w/w) and sonicating for 5–6 h can introduce hydroxyl groups on the surface. , In addition, after acid oxidation, H 2 O 2 can be used to further increase the hydroxyl content. , The strong alkali treatment generally involves adding h-BN to solutions such as 5 M NaOH or KOH and heating to reflux for a period of time; ,, this is one of the most widely used methods to introduce hydroxyl groups on the edges of h-BN in literature.…”

Boron nitride aerogels consisting of varied superstructures

“…Despite active endeavors, it is still challenging to realize different wettability on BNrelated materials. 22,[38][39][40][41][42] Also, there is a possibility that the asobtained wetting states could only sustain for a short time. 22 Compared with the previous efforts, our work demonstrated not only the effective fabrication of the BN aerogel with varied microstructures but the tuning of wetting behavior without involving any special treatment, which are widely employed in wettability modulation, such as irradiation, etching, or coating.…”