Pure Mo tubing (0.381 mm in thickness) were annealed at 1700 °C for 4 h in a graphite furnace filled with pure N₂ (99.995%) to evaluate the feasibility of employing the Mo tubing for high temperature thermocouple sheath. It was found that the Mo tubes were shattered after several cycles of annealing treatment. EBSD measurements revealed that the fractured Mo tubing was transformed almost completely into Mo₂C 99.4% in volume fraction. The Mo₂C phase had a “zebra” eutectic structure, consisting of 83.25% of orthorhombic Mo₂C (Orth.) and 16.15% of hexagonal Mo₂C (Hex.). This indicated that the carbon from the heating elements in the furnace somehow reacted with the Mo tubing to form Mo₂C without direct physical contact between them in N₂ at 1700 °C. Thermodynamic analysis supported the hypothesis that N₂ gas served as an intermedium transporting the C from the heating elements to the Mo tubes by first reacting with the C to produce a cyanogen (C₂N₂) gas which subsequently reacted with Mo to form Mo₂C at 1700 °C in the graphite furnace. The O₂ effect on the Mo₂C formation was also analyzed, suggesting it was negligible because of the scarcity of oxygen in the pure N₂ gas in the furnace. No Mo nitride could be formed in the Mo tube since N₂ energetically prefers to react to C first at 1700 °C in the furnace.

在充满纯N ₂（99.995％）的石墨炉中，将纯Mo管（厚度为0.381 mm）在1700°C下退火4 h，以评估将Mo管用于高温热电偶护套的可行性。发现Mo管在数个退火处理循环后破碎。EBSD测量表明，断裂的Mo管几乎完全转变为99.4％的Mo ₂ C体积分数。Mo ₂ C相具有“斑马”共晶结构，由83.25％的正交Mo ₂ C（正交）和16.15％的六方Mo ₂ C（六角）组成。这表明来自炉中加热元件的碳以某种方式与Mo管反应形成Mo ₂C在1700°C的N ₂中没有直接物理接触。热力学分析支持以下假设：N ₂气体充当中间介质，首先通过与C反应生成氰（C ₂ N ₂）气体，然后将其与Mo反应形成Mo ₂，从而将C从加热元件传输到Mo管。在1700°C的石墨炉中加热。还分析了O ₂对Mo ₂ C形成的影响，表明由于炉中纯N ₂气体中的氧气稀少，因此可以忽略不计。由于N ₂，在Mo管中不会形成Mo氮化物 从能量上讲，它更喜欢先在炉中于1700°C下与C反应。