Tribology of naturally occurring boric acid films on boron carbide
Tribology of naturally occurring boric acid films on boron carbide
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DOI：
10.1016/s0257-8972(96)02984-2
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发表时间：
1996-12-15
影响因子：
5.4
通讯作者：
Savrun, E
中科院分区：
文献类型：
--
作者：
Erdemir, A;Bindal, C;Savrun, E
在本文中，我们描述的形成和自润滑机制的天然存在的硼酸薄膜的碳化硼（B4 C）基板。氧化钇/部分稳定的氧化锆销相对于普通B4 C基底的滑动摩擦系数相当高，为0.3-0.4，但相对于经受800 ℃退火的B4 C基底低6-10倍。我们确定，这种低摩擦是由于薄硼酸膜，自然形成的滑动表面。在800摄氏度的退火过程中，B4 C的暴露表面经历氧化并形成氧化硼层。在冷却过程中，该层与空气中的水分发生二次化学反应，形成一层薄硼酸膜，这是超低摩擦系数的原因。如先前文献中所报道，硼酸的低摩擦机制与其层状三斜晶体结构有关。每一层上的原子紧密堆积，相互之间牢固地结合在一起，但各层之间相隔很远，并通过货车德瓦尔斯力结合在一起。在滑动过程中，这些原子层可以平行于相对运动的方向排列，并相对容易地在彼此上滑动，以提供本文报道的0.03-0.05的摩擦系数。利用拉曼光谱研究了块体碳化硼和润滑硼酸膜在滑动表面上的化学键结构。
In this paper, we describe the formation and self-lubricating mechanisms of naturally occurring boric acid films on boron carbide (B4C) substrates. The sliding friction coefficients of yttria/partially stabilized zirconia pins against plain B4C substrates are quite high at 0.3-0.4, but are 6-10 times lower against the B4C substrates subjected to annealing at 800 degrees C. We determined that this low friction was the result of a thin boric acid film that forms naturally on the sliding surface. During annealing at 800 degrees C, the exposed surface of B4C undergoes oxidation and forms a layer of boron oxide. During cooling, this layer undergoes a secondary chemical reaction with moisture in the air to form a thin boric acid film that is responsible for the ultralow friction coefficients reported here. As reported in previous literature, the low-friction mechanism of boric acid is associated with its layered-triclinic-crystal structure. The atoms on each layer are closely packed and strongly bonded to each other but the layers are widely separated and are held together by van der Waals forces. During sliding, these atomic layers can align themselves parallel to the direction of relative motion and slide over one another with relative ease to provide the 0.03-0.05 friction coefficients reported here. Raman spectroscopy was used to elucidate the chemical bond structure of bulk boron carbide and lubricious boric acid film on sliding surfaces.