Surface structure of implants influences bone response and interfacial shear strength between implants and bone. The aim of this study was to find topographical parameters that correlate with the interfacial shear strength. Two groups of sand-blasted titanium screws were implanted in 17 sheep tibia, each for 2-52 weeks: (A) acid pickled with HF/HNO(3); (B) acid etched with HCl/H(2)SO(4). Screw removal torque was measured and surface topography of both implant groups was studied by scanning electron microscopy, optical profilometry, and scanning probe microscopy. The roughness as well as the surface area of type A surface was higher in the scan region of 100 microm, but the microroughness and surface area of type B surface was higher in the scan region of 10 microm. A significantly higher removal torque (interfacial shear strength) of the surface treatment type B (412 +/- 60 Ncm) compared to surface treatment type A (157 +/- 33 Ncm) was found after 52 weeks of implantation in sheep due to differences in microroughness of both types of screws. It was also shown that the specification of the parameters Delta(a), R(a) and R(q) was not sufficient to characterize the properties of the implant surfaces. The analysis of R(q) parameter over wavelengths was required to characterize the size, shape and distribution of the implant surface structures.

Frictional behavior and interfacial adhesion of differently textured pyrolytic carbon layers on Si substrate were investigated by indentation and scratch testing. A large amount of elastic recovery and a low coefficient of friction (μ = 0.05 to 0.09) were observed. Elastic/plastic and frictional behaviors of the coatings are strongly influenced by the microstructure of the pyrolytic carbon films, especially by the texture. The critical load at which the first abrupt increase in the normal displacement occurs was used to characterize interfacial adhesive strength. A pyrolytic carbon film deposited at higher residence time from a gas mixture containing 3% oxygen exhibited higher critical loads than film deposited at lower residence time without oxygen. The results can be understood if one assumes that the gas phase composition during deposition significantly influences the bonding strength at the interface. Failure mechanisms are discussed for both types of films.

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Cubic boron nitride (c-BN) is a very promising material with respect to applications as a hard coating for cutting tools due to its many desirable properties including a hardness second only to diamond, oxidation resistance and chemical inertness against iron even at high temperatures with the latter property resulting in the ability to machine ferrous metals. However, these potential applications are hindered by the bad adhesion of c-BN films to most substrate materials. This tendency of c-BN films to delaminate also puts significant obstacles to accurate measurements of their mechanical properties. The poor adhesion of such samples is recognized as being due to the high compressive stress caused by energetic ion bombardment during growth and to a mechanically soft turbostratic boron nitride (t-BN) interlayer between c-BN and substrates. [1] Up to now, most of the c-BN films consist of nano-sized crystallites and have the above addressed layered structure. Thus, the elastic and mechanical properties, which have been studied with different methods, [2][3][4] are certainly not representative for c-BN alone. Recently, by introducing fluorine into the gas phase, thick polycrystalline c-BN films were synthesized by jet-plasma chemical vapor deposition (CVD) and microwave-plasma CVD [5,6] with a submicron lateral grain size and a nanoindentation study on these c-BN films was reported. [6][7][8] However, a 100 nm thick t-BN interlayer and the large number of grain boundaries still exist in these c-BN films. [7,8] Furthermore, in most cases sample polishing is required prior to hardness measurements since these c-BN films are considerably rough. [8] Very recently, we have demonstrated that thick heteroepitaxial c-BN films without any intermediate t-BN layer can be prepared on CVD diamond films and single crystal diamond substrates using ion beam assisted deposition (IBAD). [9,10] These thick, and single crystalline c-BN films possess very smooth surfaces that allowed to accurately determine their mechanical behavior as expressed by Young's modulus [11] and hardness.Scratch tests have been widely used as a convenient method for estimating adhesion of thin hard wear-resistant coatings such as titanium nitride (TiN), diamond-like carbon (DLC) and c-BN to substrates. [12][13][14][15][16][17][18] In the traditional scratch test procedure a diamond tip is drawn across the coating surface under a progressively increasing normal load until the coating becomes detached or fractured. The smallest load at which any recognisible failure occurs is called the "critical load" L c . However, the relationship between this critical load and the adhesive strength of the interface between the substrate and coating is yet unclear. In addition to the coatingsubstrate bond strength itself, a wide range of factors are known to affect the critical load value obtained from the scratch test. [19][20][21][22][23][24][25][26][27] The aim of this work was to show the relative improvement of the mechanical and tribological properties of the c-BN film...