RAPID SOLID-STATE-PRECURSOR SYNTHESIS OF CRYSTALLINE BORON NITRIDE
RAPID SOLID-STATE-PRECURSOR SYNTHESIS OF CRYSTALLINE BORON NITRIDE
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DOI：
10.1021/ic00093a003
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发表时间：
1994-07
影响因子：
4.6
通讯作者：
L. Rao;R. Kaner
中科院分区：
文献类型：
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作者：
L. Rao;R. Kaner
固态化学的一个主要问题是扩散势垒的最小化。 1 快速固态前体合成提供了一种独特的方法，通过以自持模式进行高放热反应，将固体反应性推向极限。 2 在这些反应过程中，由于前体容易分解并形成熔盐，扩散势垒显着减少。因此，该方法在快速制备多种晶体产物（包括层状过渡金属二硫属化物、过渡金属氮化物和 III-V 半导体）方面非常有效。 2™ 5 沿着这些思路，一些众所周知的难以结晶的材料（例如氮化硼）应该是可以获得的。为了实现这一目标，了解自蔓延反应中的固体反应性和反应动力学是有用的。由于存在高活化能势垒，高放热反应不一定会自我传播和/或形成结晶产物。例如，工业制备层状六方（h-）BN，3CaB6+ B203+ 10N2—20BN+ 3CaO，是高度放热的（热力学估计绝热温度rad = 3400 C6），但从该反应中获得h-BN需要高温加热（> 1500 C）。 7 甚至像最近在铯和 S-三氯硼嗪之间发现的爆炸反应也会产生无定形而非结晶氮化硼产品。 8 无序乱层 (t-) BN 向其高度有序的相对 h-BN 的转化必须在催化剂存在下在 > 1800 C 的温度下进行。 9 在典型的实验室合成条件下，通过乱层改性获得非晶氮化硼。 10 在这里，我们表明，通过选择适当的自维持反应路线，避免传统方法中固有的能量障碍，可以在几秒钟内合成高度结晶的氮化硼，而几乎不需要外部能量输入。
A major concern for solid-state chemistry is minimization of diffusion barriers. 1 Rapid solid-state-precursor synthesis provides a unique approach to push solid reactivity to its limit by performing highly exothermic reactions in a self-sustaining mode. 2 During these reactions, diffusion barriers are significantly reduced because of the facile decomposition of precursors and the formation of molten salts. Consequently, this approach has p-ovenvery effective in rapid preparation of several crystalline products including layered transition metal dichalcogenides, transition metal nitrides, and III-V semiconductors. 2™ 5 Along these lines, some well-known materials that are difficult to crystallize, such as boron nitride, should be accessible. To achieve this goal, an understanding of solid reactivity and reaction kinetics in selfpropagating reactions is useful. Because of the presence of high activation energy barriers, highly exothermic reactions do not necessarily self-propagate and/or form crystalline products. For example, the industrial preparation of layered-form hexagonal (h-) BN, 3CaB6+ B203+ 10N2—20BN+ 3CaO, is highly exothermic (thermodynamically estimated adiabatic temperature rad= 3400 C6), but hightemperature heating (> 1500 C) is required to obtain h-BN from this reaction. 7 Even explosive reactions such as that found recentlybetween cesium and S-trichloroborazine lead to amorphous rather than crystalline BN products. 8 The conversion of disordered turbostratic (t-) BN to its highly ordered relative h-BN must be performed at temperatures> 1800 C in the presence of catalysts. 9 Under typical laboratory synthetic conditions, amorphous BN is obtained along with turbostratic modifications. 10 Here we show that by selecting an appropriate self-sustaining reaction route that avoids energy barriers inherent in conventional approaches, highly crystalline boron nitride can be synthesized within seconds with little outside energy input.