Diamond corrosion

Diamond corrosion is usually a problem of oxidation and graphitization. Graphi-tization in inert atmospheres was observed at about 1500°C and becomes very fast at 2100°, where sizable diamonds are converted to graphite within minutes [44], An extrapolation of the data gives a F 1450°C for = 0. It has been reported that graphitization is prevented in pure H2 up to 2200°C [45]. 

Optical. Besides the gem quaHties dependent on optical properties, diamond is very useful as a light-transmitting window for lasers and for simple windows for monitoring chemical processes in corrosive and otherwise hostile environments. 

Papakonstantinou, P., Zhao, J. F., Richardot, A., McAdams, E. T., and McLaughlin, J. A., Evaluation of Corrosion Performance of Ultra-thin Si-DLC Overcoats with Electrochemical Impedance Spectroscopy, Diamond Relat. Mater, Vol. 11,... 

Luo et al. [1,153] used a slurry containing ultra-fine diamond (UFD) powders to polish the surface of HDD sliders. The powders are from 3 nm to 18 nm in diameter and 90 % around 5 nm. They are crystal and sphere-like [154]. The pH value of the slurry is kept in the range from 6.0 to 7.5 in order to avoid the corrosion of read-write heads, especially pole areas. A surface-active agent is added into the slurry to decrease the surface tension of the slurry to 22.5 Dyn/cm, and make it spread on the polish plate equably. An anti-electrostatic solvent is also added to the slurry to avoid the magnetoresistance (MR) head being destroyed by electrostatic discharge. The anion concentration of the slurry is strictly controlled in ppb level so as to avoid the erosion of magnetic heads as shown in Table 5. The concentration of UFDs in the slurry is 0.4 wt %. 

After lapping, the sliders will be cleaned, and then a passivation film of diamond-like carbon (DLC) will be deposited on the surfaces of sliders through chemical vapor deposition (CVD) to protect the pole area from chemical-physical corrosion and electrostatic discharge attack. Corrosion in pole areas will result in loss of read/write functions. A corrosion test was taken to examine the ability of the sliders polished by different slurries as shown in Table 6. It can be seen that the MRR change rate of the sliders polished by UFD slurry is much less than that polished by the slurry T5qre III, that is, the capability of anti-corrosion of the former is much better than that of the latter. 

CVD diamond films can be used for electrochemical applications, especially in harsh or corrosive environments. Conducting diamond electrodes, made by adding boron to CVD diamond films, are very inert compared to other electrode materials (such as platinum). Such diamond electrodes may find applications in analysis of contaminants, such as nitrates, in water supplies, and even in the removal of those contaminants. 

The modern material Ebonex is a mixture of substoichiometric titanium oxides Ti40y, TisOg. .. Tin02n-i ( Magneli phases [32]). It offers a unique combination of electrical conductivity and corrosion resistance. Primarily, Ebonex is produced as a powder. As is usual for ceramics, the ready-formed material is hard and brittle, the possibilities of machining are restricted (diamond tools). 

Another cause of scratches is the drop out of diamond grit from the end effector. In contrast to the aforementioned microscratches, which may be 1 m wide and a few microns long, these will cause macroscratches and destruction of entire wafers. Since the diamond grit is nickel-bonded on the end effector, the bonding can be vulnerable if the slurry is chemically corrosive. 

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