The shape evolution from uniform triangular boron nitride nanoplates of rhombohedral phase (r-BN) to hexagonal r-BN nanoplates was achieved through a simple calcination process in flowing N2 at 1000℃ for 8 h. The average thickness of the triangular and hexagonal r-BN nanoplates is similar (～50nm), while their average edge sizes are 360 and 320nm, and their intense emission bands are centered at 316 and 297nm (λex=200nm), respectively. TGA analysis results reveal that hexagonal r-BN nanoplates have superior thermal stability compared with the triangular nanoplates especially above 800℃ under ambient atmosphere. The possible mechanism of the thermally induced conversion from triangular to hexagonal r-BN nanoplates is discussed.

The shape evolution from uniform triangular boron nitride nanoplates of rhombohedral phase (r-BN) to hexagonal r-BN nanoplates was achieved through a simple calcination process in flowing N2 at 1000℃ for 8h. The average thickness of the triangular and hexagonal r-BN nanoplates is similar (～50nm), while their average edge sizes are 360 and 320 nm, and their intense emission bands are centered at 316 and 297 nm (lex ¼ 200 nm), respectively. TGA analysis results reveal that hexagonal r-BN nanoplates have superior thermal stability compared with the triangular nanoplates especially above 800℃ under ambient atmosphere. The possible mechanism of the thermally induced conversion from triangular to hexagonal r-BN nanoplates is discussed.

Hexagonal BN (h-BN) particles were prepared by using BBr3, NH4Br and metallic Na as reactants in stainless steel autoclaves at 450℃ for 24h; When the target temperature was set in the range of 500-600℃, cubic BN (c-BN) particles that co-existed with h-BN were obtained. It is found that 600℃ and a molar ratio of BBr3 to NH4Br of 1:3 are the optimal reaction parameters for the highest yield production of c-BN particles. c-BN powder with controllable content has been synthesized through a one-step method in the absence of solvents. The as-obtained samples that contain pure h-BN and the mixture of c-BN and h-BN have high thermal stabilities in ambient atmosphere below 920 and 1100℃, respectively.

Hexagonalboronnitride(h-BN)particlesincludinghollowspheres(withaproportionof 30-40%) and nanotubes (10%)havebeensynthesizedbyusingsodiumfluoroborateandsodiumazideat450℃ for 20 h.X-raydiffraction(XRD)andhigh-resolutiontransmissionelectronmicroscopy(HRTEM)studies show thattheas-obtainedBNhollowparticlesarecrystalline.Thetotalspecificsurfaceareaofthe product calculatedfromBrunauer-Emmentt-Teller(BET)absorptionmeasurementis89.79m2/g, indicatingthatitmaybeutilizedasapromisingcandidateforhydrogenstoragecontainerorcatalyst. Thermal gravimetricanalysis(TGA)resultrevealsitsexcellentthermalstabilitybelow800℃. Its possiblegrowthmechanismandtheeffectsofreactionparameterswerealsobrieflydiscussed.