Amorphous hard carbon

FIG. 16 SPFM image of a droplet formed as a result of dewetting of Zdol on an amorphous hard carbon substrate film. No layering around the drop was observed. (From Ref. 70.)... 

Stress-free Amorphous-Tetrahedral Carbon Films with Hardness Near that of Diamond, Appl. Phys. Lett., Vol. 71,1997, pp. 3820-3822. 

The work on carbon nitride solids is strongly related to research on diamondlike carbon (DLC) materials [5, 6]. DLC materials are thin film amorphous metastable carbon-based solids, pure or alloyed with hydrogen, which have properties similar to that of crystalline diamond (high hardness, low friction coefficient, high resistance to wear and chemical attack). This resemblance to diamond is due to the DLC structure, which is characterized by a high fraction of highly cross-linked sp -hybridized carbon atoms. To obtain this diamond-like structure... 

Plasma Synthesis The use of plasma methods has lead to a new range of materials having unique properties. An example is the family of amorphous elemental hydrides (eg cr-C H Of -Si H or-P H) which contain a variable proportion of H from almost zero to 50 atomic %. The carbon films, known variously as "hard carbon", "diamond-like carbon", " a-carbon" etc (9 ) - These layers are of considerable interest because of their optical and abrasion-resistant properties etc (Table I). The properties of these Gr-carbon films, can be tailored by modifying the plasma parameters. 

Extreme hardness is associated with low hydrogen content. These hard carbon films are often referred to as amorphous diamond ... 

Considerable interest still exists in the application of fluorine-containing cyclophosphazenes in lubricant technology. Recent advances in the use of N3P3(OC6H4F-4) (OC6H4CF3-3)6-n (n 2 code name X-IP) as lubricant either by itself or as an additive to perfluoropolyethers (PFPE) have been reviewed. Addition of X-IP to PFPE films reduces the critical dewetting thickness on amorphous nitrogenated carbon compared to that of neat PFPE. The influence of X-IP on the stabilization of the PFPE lubricant for the slider/disk interface in hard disk drives has been studied. Micro-phase separation of X-IP... 

The surfaces in Fig. 1 are obtained from arbitrarily selected computer-generated instantaneous configurations of an (oxide) BS and amorphous (liquid) carbon with the help of a probe hard sphere with a diameter close to that of an argon atom (0.33 nm). The upper of these surfaces is generated by the center of the probe sphere which rolls over the BS structure of hard spheres with diameter of a typical oxide ion (0.28 nm). In the case of amorphous carbon, a hard sphere with the van der Waals diameter of carbon (0.33 nm) is described around each carbon atom. These spheres overlap because the distances between carbon atoms are about 0.14 nm. The surface of amorphous carbon in Fig. 1 is generated by the center of the probe sphere that rolls over those overlapping hard spheres. 

Carbon materials are classified into two kinds graphitic carbon, which has a normally layered, ordered crystal structure and hard carbon, which has an amorphous, disordered crystal structure. 

Because hard carbons have an amorphous structure rather than a layered structure, Li ions can intercalate or de-intercalate throughout the entire surface of carbon particles. 

From the experimental data it can be concluded that the films have a diameter of about 5-10 xm and consisted of stearic acid, calcium stearate, and calcium carbonate (mainly calcite, no experimental information could be given concerning amorphous calcium carbonate at this point). The viscoelastic data pointed to a glassy state with a crystalline hardness. It is important to note that the films did not consist of a stearate monolayer, cross-linked by calcium ions (chalk soaps) as control experiments with CaCl2 observed. Derived from other control experiments it became clear that the growth of the films was due to a specific interaction of crystalline (or precrystalline) calcium carbonate and stearic acid. 

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