Effect of Target Power on Microstructure, Tribological Performance and Biocompatibility of Magnetron Sputtered Amorphous Carbon Coatings.

The tribological properties and preosteoblast behavior of an RF magnetron-sputtered amorphous carbon coating on a Si (100) substrate were evaluated. The graphite target power was varied from 200 to 500 W to obtain various coating structures. The amorphous nature of the coatings was confirmed via Raman analysis. The contact angle also increased from 58º to 103º, which confirmed the transformation of the a-C surface from a hydrophilic to hydrophobic nature with an increasing graphite target power. A minimum wear rate of about 4.73 × 10-8 mm3/N*mm was obtained for an a-C coating deposited at a 300 W target power. The 300 W and 400 W target power coatings possessed good tribological properties, and the 500 W coating possessed better cell viability and adhesion on the substrate. The results suggest that the microstructure, wettability, tribological behavior and biocompatibility of the a-C coating were highly dependent on the target power of the graphite. A Finite Element Analysis (FEA) showed a considerable increase in the Von Mises stress as the mesh size decreased. Considering both the cell viability and tribological properties, the 400 W target power coating was identified to have the best tribological property as well as biocompatibility.

Investigation on Physico Chemical and X-ray Shielding Performance of Zinc Doped Nano-WO3 Epoxy Composite for Light Weight Lead Free Aprons.

This report addresses a way to reduce the usage of highly toxic lead in diagnostic X-ray shielding by developing a cost-effective, eco-friendly nano-tungsten trioxide (WO3) epoxy composite for low-weight aprons. Zinc (Zn)-doped WO3 nanoparticles of 20 to 400 nm were synthesized by an inexpensive and scalable chemical acid-precipitation method. The prepared nanoparticles were subjected to X-ray diffraction, Raman spectroscopy, UV-visible spectroscopy, photoluminescence, high-resolution-transmission electron microscope, scanning electron microscope, and the results showed that doping plays a critical role in influencing the physico-chemical properties. The prepared nanoparticles were used as shielding material in this study, which were dispersed in a non-water soluble durable epoxy resin polymer matrix and the dispersed materials were coated over a rexine cloth using the drop-casting method. The X-ray shielding performance was evaluated by estimating the linear attenuation coefficient (µ), mass attenuation coefficient (µm), half value layer (HVL), and X-ray percentage of attenuation. Overall, an improvement in X-ray attenuation in the range of 40-100 kVp was observed for the undoped WO3 nanoparticles and Zn-doped WO3 nanoparticles, which was nearly equal to lead oxide-based aprons (reference material). At 40 kVp, the percentage of attenuation of 2% Zn doped WO3 was 97% which was better than that of other prepared aprons. This study proves that 2% Zn doped WO3 epoxy composite yields a better particle size distribution, µm, and lower HVL value and hence it can be a convenient lead free X-ray shielding apron.

Assessment of the Synergetic Performance of Nanostructured CeO2-SnO2/Al2O3 Mixed Oxides on Automobile Exhaust Control.

In order to control diesel exhaust emission, CeO2-SnO2/Al2O3 (CTA) mixed oxides were prepared and coated on perforated stainless steel (SS) filter plates, and the catalytic activities were analyzed in this work. The CeO2-SnO2 (different compositions of Ce/Sn-2:8; 1:1; 8:2) composites and Al2O3 were prepared separately via a co-precipitation approach, and CeO2-SnO2/Al2O3 (CTA) mixed oxides were attained by mechanical mixing of 75 wt% CeO2-SnO2 composites with 25 wt% Al2O3. X-ray diffraction (XRD) and Raman spectroscopy were performed for all three CeO2-SnO2/Al2O3 (CTA) mixed oxides; the CeO2-SnO2/Al2O3 (Ce/Sn-1:1) sample confirmed the presence of cubic and tetragonal mixed faces, which enhances the redox nature (catalytic activities). Various characterizations such as high-resolution transmission electron microscopy (HRTEM), Brunauer-Emmett-Teller (BET) analysis, X-ray photoelectron spectroscopy (XPS), and a scanning electron microscope (SEM) were employed on CeO2-SnO2/Al2O3 (Ce/Sn-1:1) sample to investigate the structural, textural, compositional, and morphological properties. The CeO2-SnO2/Al2O3 (Ce/Sn-1:1) sample was coated on a perforated stainless steel (SS) filter plate via a simple, cost-effective, and novel method, and an exhaust emission test for various compression ratios (CR), injection pressure (IP), and load (L) was completed using an AVL Digas analyzer. The CeO2-SnO2/Al2O3 (Ce/Sn-1:1) sample, with a size of 10.22 nm and a high surface area of about 73 m2 g-1, exhibit appreciable catalytic properties.

Formation of discrete periodic nanolayered coatings through tailoring of nanointerfaces-Toward zero macroscale wear.

Notwithstanding the success of nanolayered coatings in the reduction of wear at nano-/microscales, the improvement of the wear resistance at the macroscale remains an issue. Moreover, the effects of nanointerfaces in nanolayered coatings on their macrotribological properties are not understood well. This paper reports on the engineering of nanointerfaces in diamond-like C/Cr nanolayered coatings to tailor their characteristics including the degree of intermixing, defects, and Cr growth mode. The result was the fabrication of a coating with subnanometer-thick periodic albeit discrete Cr interlayers. This was achieved using our patented deposition technique. This coating contained less interfacial defects compared to classic nanolayered coatings with continuous nanolayers and presented record-breaking wear rates at the macroscale. Finite Element analysis was performed and micropatterning strategy was used to reduce the wear rate further. Last, we report on discovery of a dimensionless parameter that can be used to predict the wear resistance of carbon-based nanolayered coatings.

RF magnetron sputtering mediated NiTi/Ag coating on Ti-alloy substrate with enhanced biocompatibility and durability.

Mechanically robust, biocompatible and corrosion resistant Ag doped NiTi (NiTi/Ag) coatings were formed on implant grade commercially pure titanium substrates by R.F. magnetron sputtering. Five samples with varying silver content (0, 1, 3, 7, and 10 at.%) were prepared by controlling the power applied to Ag and NiTi targets. The intensity of X-ray photoelectron spectra peaks corresponding to Ni2p, Ti2p, Ag3d components were found proportional to respective coating compositions. The soft Ag crystallites were decreased the roughness and crystallinity of NiTi/Ag. Among all compositions, NiTi/Ag coating with 3 at.% Ag exhibited lowest friction coefficient (0.1) and wear rate (0.69 × 10-07 mm3/N ∗ mm). Electrochemical corrosion measurements indicated that Ag incorporation increased the corrosion resistance of NiTi. Increase in Ag content shifted Ecorr values in the anodic direction, and reduced the current density by one-order-of-magnitude. When cultured on NiTi/Ag coating with 3 at.% Ag, human dermal fibroblast neonatal cells demonstrated highest cell viability. The fluorescence micrographic image of the immunostained cells showed a well grown actin filament network. Overall, NiTi/Ag coated titanium substrates were found to be a promising orthopedic implant material.