Owing to its superior tribological and mechanical properties with corrosion resistance, biocompatibility, and hemocompatibility, diamond-like carbon (DLC) has emerged as a promising material for biomedical applications. DLC films with various atomic bond structures and compositions are finding places in orthopedic, cardiovascular, and dental applications. Cells grew on to DLC coating without any cytotoxity and inflammation. DLC coatings in orthopedic applications reduced wear, corrosion, and debris formation. DLC coating also reduced thrombogenicity by minimizing the platelet adhesion and activation. However, some contradictory results (Airoldi et al., Am J Cardiol 2004;93:474-477, Taeger et al., Mat-wiss u Werkstofftech 2003;34:1094-1100) were also reported that no significant improvement was observed in the performance of DLC-coated stainless stent or DLC-coated femoral head. This controversy should be discussed based on the detailed information of the coating such as atomic bond structure, composition, and/or electronic structure. In addition, instability of the DLC coating caused by its high level of residual stress and poor adhesion in aqueous environment should be carefully considered. Further in vitro and in vivo studies are thus required to confirm its use for medical devices. '

No abstract

Surface energy and surface chemical bonds of the plasma treated Si incorporated diamond-like carbon films (Si-DLC) were investigated. The Si-DLC films were prepared by r.f. plasma assisted chemical vapor deposition using benzene and diluted silane (SiH 4 /H 2 = 10:90) as the precursor gases. The Si-DLC films were subjected to plasma treatment using various gases like N 2 , O 2 , H 2 and CF 4 . The plasma treated Si-DLC films showed a wide range of water contact angles from 13.4°to 92.1°. The surface energies of the plasma treated Si-DLC films revealed a high polar component for O 2 plasma treated Si-DLC films and a low polar component for CF 4 plasma treated Si-DLC films. The CF 4 plasma treated Si-DLC films indicated the minimum surface energy. X-ray photoelectron spectroscopy (XPS) revealed that the polarizability of the bonds present on the surface explains the hydrophilicity and hydrophobicity of the plasma treated Si-DLC films. We also suggest that the O 2 plasma treated surface can provide an excellent hemocompatible surface from the estimated interfacial energy between the plasma treated Si-DLC surface and human blood.

No abstract

Several 40-year anniversaries of the modern area of the synthesis of diamond at high pressures and temperatures (HPHT) have come and gone. If you are a proponent of the Norton Company, this first synthesis would be somewhere between 1948 and 1950. ASEA's Feb. 15, 1953, accomplishment was noted at an international meeting in 1993 on high pressure (AIRAPT) with a small session that included papers by ASEA and General Electric (GE) representatives. The GE success in the Hall experiment of Dec. 16, 1954 (announced in February 1955), was marked only in the personal memories of the remaining members of that diamond team. DeBeers recognizes the ASEA date, but if it celebrates the 40th anniversary of its own in-house accomplishment, it will do so late in 1998; the Russians will do so on or about the year 2000. In any case, the basic, muchcopied GE HPHT process is repeated thousands of times each day at sites all over the world (Figure 1) to make a product that has replaced 90% of natural diamond as an abrasive and has given to technology new superhard products in forms unavailable from the earth (Figure 2). All manufacturers are in fierce competition for a total business that probably is in the range of $1 billion per year, and engineers spend their time primarily in finer tuning for faster growth, greater yields, lower costs, and higher quality crystals. The HPHT process seems to have survived the threat of the low-pressure chemical vapor deposition (CVD) process with respect to abrasive grain and gem-quality stones. However, the low-pressure process has some unique capabilities that obviously cannot be achieved by HPHT, and the product is finding niches in specialized applications (Figures 3 and 4).

No abstract