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Decoration of nitrogen vacancies by oxygen atoms has been studied by near-edge X-ray absorption fine structure (NEXAFS) around B K-edge in several boron nitride (BN) structures, including bamboo-like and multi-walled BN nanotubes. Breaking of B-N bonds and formation of nitrogen vacancies under low-energy ion bombardment reduces oxidation resistance of BN structures and promotes an efficient oxygen-healing mechanism, in full agreement with some recent theoretical predictions. The formation of mixed O-B-N and B-O bonds is clearly identified by well-resolved peaks in NEXAFS spectra of excited boron atoms.

This study proposes a quantitative AFM-based functional analysis at the micrometer- and nanometer scale to evaluate the quality of cartilage surfaces. Mechanical testing (load-bearing) combined with friction analysis (gliding) can provide important information. Notably, sliding-type biomechanical stimuli may favor (re-)generation and maintenance of functional articular surfaces and support the development of mechanically competent engineered cartilage.

Formation of defects in hexagonal and cubic boron nitride ͑h-BN and c-BN, respectively͒ under low-energy argon or nitrogen ion-bombardment has been studied by near-edge x-ray absorption fine structure ͑NEXAFS͒ around boron and nitrogen K-edges. Breaking of B-N bonds for both argon and nitrogen bombardment and formation of nitrogen vacancies, V N , has been identified from the B K-edge of both h-BN and c-BN, followed by the formation of molecular nitrogen, N 2 , at interstitial positions. The presence of N 2 produces an additional peak in photoemission spectra around N 1s core level and a sharp resonance in the low-resolution NEXAFS spectra around N K-edge, showing the characteristic vibrational fine structure in high-resolution measurements. In addition, several new peaks within the energy gap of BN, identified by NEXAFS around B and N K-edges, have been assigned to boron or nitrogen interstitials, in good agreement with theoretical predictions. Ion bombardment destroys the cubic phase of c-BN and produces a phase similar to a damaged hexagonal phase.

The use of self-assembling monolayers (SAM) of long chain carboxylic acids has a potential for designing specific interface architectures in degradable implants technology. In this paper, the native and anodically formed oxide films on the Mg-alloy (AZ91D) surface were modified with the SAMs of palmitic acid (PA) and stearic acid (SA) to protect the alloy degradation in a physiological solution. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) were used to evaluate chemical composition, bonding modes of acids to the substrate, and structural properties (ordering and close-packing) of the surface layers. The results obtained by electrochemical impedance spectroscopy (EIS) have shown a beneficial effect of anodization and especially of the oxide layer modification by forming SAMs of PA and SA on the corrosion properties of AZ91D alloy in physiological solutions.Magnesium and its alloys are ideal structural materials for the lightweight engineering applications due to their remarkable properties such as low density, high specific strength, high thermal conductivity, and electromagnetic interference resistance. But so far, their application has been limited mostly due to the poor corrosion and wear resistance. 1 As a potential biodegradable implant material, magnesium shows many advantages over current metallic materials as well as biodegradable polymeric and ceramic materials because it is an essential element and in the human body its concentration is high . 1-3 However, in a solution containing Cl − ions like body fluids magnesium and its alloys easily corrode, and their successful application as degradable orthopedic implants has been mainly inhibited due to the high degradation rates and a consequent loss of the mechanical integrity. 2-6 Various surface treatments have been applied to Mg and its alloys to improve their corrosion resistance and the lifetime of implants including anodization, 7, 8 deposition of chemical conversion layers, 9 treatments based on the sol-gel application, 10 and the surface modification by formation of SAMs of long-chain carboxylic acids. 11, 12 The chemisorption of saturated long-chain (C 16 , C 18 ) carboxylic acids has been also studied on many surfaces such as aluminum oxide, 13-15 iron, 16, 17 zinc, 17 and steel. 18 As endogenous compounds and the main components of fats, fatty acids are very biocompatible substances. According to the Food and Agriculture Organization of the United Nations (FAO) recommendation, the intake of saturated fatty acids by adults should not exceed 10% of the total energy consumption. 19 However; the results on the interaction of carboxylic acids with the magnesium/AZ91D alloy surface are not consistent. While the theoretical studies predict that the most stable adsorbed configuration is one in which the carboxyl group is attached by its each oxygen atom to two separate magnesium ions, 20 the experimental results have confirmed the existence of monodentate bonding, 11 and even the electrostatic attraction of magne...

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