Boron nitride nanosheets (BNNS) were recently synthesized in a powder form using inductively coupled plasma through two readily-scalable bottom-up routes: (i) heterogeneous nucleation using amorphous boron particles and nitrogen, (ii) homogeneous nucleation from ammonia borane and nitrogen. The operating pressure was found to play a significant role in controlling the product purity and sheet dimensions in both routes. This work attempts to understand the effect of pressure by first presenting thermodynamic equilibrium calculations for the two systems at various pressures. From these, we estimate nucleation zones for BNNS and identify their possible major precursors. Computational fluid dynamics simulations (CFD) are then used to calculate plasma thermofluidic profiles by which axial residence times and gas cooling rates are estimated for the nucleation zones. Finally, in-situ optical emission spectroscopy (OES) is used to investigate the chemical composition of the gas during BNNS synthesis. It is found that the optimum pressure for the two routes is 62 kPa. The formation of BNNS heterogeneously follows a base-growth mechanism and requires the presence of liquid boron, B_(liq) and N₂/N/BN_(g). The nucleation theory is used to explain the formation of BNNS homogeneously from B_xN_yH_z critical clusters that grow into BNNS by the addition of BH/BN/NH onto the clusters. Thermodynamic equilibrium charts predict the formation of these species in their corresponding systems. Based on the species densities, BNNS formation/nucleation temperature ranges are proposed, e.g., around 2740–2350 K at the optimum pressure. The CFD simulation results at the formation/nucleation zones show that residence times and cooling rates control the formation of BNNS. These are found to be 12.4 ms and 34.1 × 10³ K s⁻¹, respectively, at the optimum operating pressure. OES spectra of both routes show the presence of several species consistent with the thermodynamic equilibrium results.

氮化硼纳米片 (BNNS) 最近使用电感耦合等离子体通过两种易于扩展的自下而上路线以粉末形式合成：(i) 使用无定形硼颗粒和氮的异质成核，(ii) 氨硼烷和氮的均质成核。发现操作压力在控制两条路线中的产品纯度和片材尺寸方面起着重要作用。这项工作试图通过首先展示两个系统在不同压力下的热力学平衡计算来理解压力的影响。根据这些，我们估计了 BNNS 的成核区并确定了它们可能的主要前体。然后使用计算流体动力学模拟 (CFD) 计算等离子体热流体曲线，通过该曲线估计成核区的轴向停留时间和气体冷却速率。最后，原位光学发射光谱 (OES) 用于研究 BNNS 合成过程中气体的化学成分。发现两条路线的最佳压力为 62 kPa。BNNS 的异质形成遵循碱基生长机制，需要液态硼、B_(liq)和 N ₂ /N/BN _(g)。成核理论用于解释由 B _x N _y H _z临界团簇均匀地形成 BNNS，这些团簇通过在团簇上添加 BH/BN/NH 生长为 BNNS。热力学平衡图预测了这些物质在其相应系统中的形成。基于物种密度，提出了 BNNS 形成/成核温度范围，例如，在最佳压力下约为 2740-2350 K。形成/成核区的 CFD 模拟结果表明，停留时间和冷却速率控制着 BNNS 的形成。发现这些为 12.4 ms 和 34.1 × 10 ³  K s ^-1，分别在最佳工作压力下。两种途径的 OES 光谱显示存在与热力学平衡结果一致的几种物质。