Studies on the interactions between ZDOL perfluoropolyether lubricant and the carbon overcoat of rigid magnetic media
Studies on the interactions between ZDOL perfluoropolyether lubricant and the carbon overcoat of rigid magnetic media
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ZDOL全氟聚醚润滑剂与硬磁介质碳涂层相互作用的研究
DOI：
10.1023/a:1019127910531
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发表时间：
1998
影响因子：
3.2
通讯作者：
G. Tyndall
中科院分区：
文献类型：
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作者：
R. Waltman;D. Pocker;G. Tyndall
目前的高性能磁存储设备，即硬盘驱动器，通常在标称为45-60°C的高温下运行。因此，了解驱动器构造中使用的材料的热响应变得至关重要。在这份报告中，我们重点研究了一种常见的全氟聚醚润滑剂(ZDOL)的热行为，该润滑剂用于碳涂层硬盘。特别是，我们发现，在硬盘驱动器中遇到的温度下，这种磁盘润滑剂的蒸发损失以及润滑剂与碳涂层磁盘的结合都可能发生。表面能测量表明，端羟基的全氟聚醚ZDOL的相互作用主要通过端基进行。在未退火的圆盘上，这种“流动”润滑剂与碳涂层之间的相互作用以氢键为特征，这些相互作用的强度仅略强于块体ZDOL的分子间氢键特征。在60-150°C的温度范围内进行热处理后，ZDOL润滑剂就会与圆盘“粘合”。粘合润滑剂的表面能大大低于流动润滑剂，反映了粘合所产生的增强的相互作用强度。由于键合状态是较低的能量状态，所以从移动状态到键合状态的转变在热力学上是有利的。研究了这种键合转变的动力学以及润滑剂挥发动力学随温度的变化。利用两个相互竞争的反应通道模型，确定了润滑剂粘结和挥发的活化能分别为3.6kcal/mole和5.4kcal/mole。用从头算量子化学模型研究了碳表面可能的相互作用位置。实验和理论都表明，端羟基ZDOL与碳涂层的相互作用是通过氢键与碳涂层上的含氧物种发生的，结合能为5-8kcal/mole。结果表明，ZDOL的羟基端基与碳表面的羧基之间的酯化反应与表面能数据和动力学数据都是一致的。
Current high performance magnetic storage devices, i.e., hard disk drives, typically operate at elevated temperatures of nominally 45–60°C. As a consequence, understanding the thermal response of the materials used in the construction of the drive becomes imperative. In this report, we focus on the thermal behavior of a common perfluoropolyether lubricant (ZDOL) used on the carbon-overcoated, hard disk. In particular, we show that evaporative loss of this disk lubricant, as well as bonding of the lubricant to the carbon-overcoated disk, can occur at the temperatures encountered in the hard-disk drive. Surface energy measurements show that the interaction of the hydroxyl-terminated perfluoropolyether ZDOL occurs principally through the end-groups. On unannealed disks, the interaction between this “mobile” lubricant and the carbon overcoat is characterized by hydrogen bonding with the strength of these interactions being only slightly stronger than the intermolecular hydrogen bonding characteristic of bulk ZDOL. Upon annealing at temperatures in the range of 60–150°C, the ZDOL lubricant becomes “bonded” to the disk. The surface energy of the bonded lubricant is substantially lower than the mobile lubricant reflecting the increased interaction strength that occurs as a result of bonding. Since the bonded state is the lower energy state, transitions from the mobile state to the bonded state are thermodynamically favored. The kinetics of this bonding transition, as well as the kinetics of lubricant evaporation were studied as a function of temperature. Using a model of two competing reaction channels, the activation energies for both lubricant bonding and lubricant evaporation were determined to be 3.6 kcal/mole and 5.4 kcal/mole respectively. Ab initio quantum chemical modelling was used to investigate possible interaction sites on the carbon surface. Both experiment and theory indicate that interaction of the hydroxyl-terminated ZDOL to the carbon overcoat occurs via hydrogen bonding to oxygenated species on the carbon overcoat, with a binding energy of 5–8 kcal/mole. An esterification reaction between the hydroxyl end-groups of ZDOL with carboxyl groups on the carbon surface as a result of annealing is shown to be consistent with the both the surface energy data and the kinetic data.
W.Gasser：“二氧化硅的准单层沉积”固体薄膜。
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