Morphology and Structure of Carbon Films Deposited at Varying Chamber Pressures

Depositing thin and thick films through different types of deposition units is a topic of great interest. In deposition chamber, each synthesis is carried out at some value of chamber pressure. In addition to different gases, photon energy also exists in the deposition chamber. Upon dissociation of methane by hot-filaments, the conversion rate of gaseous carbon atoms into graphite and diamond atoms varies largely at varying chamber pressures. Increase in the chamber pressure from 3.3 kPa to 14 kPa changes the morphology and structure of carbon films comprising tiny grains, grains and particles. The increase in chamber pressure upto 8.6 kPa increases the growth rate of a carbon film along with discernible features of grains and particles. For intermediate set chamber pressures, the conversion rate of gaseous carbon atoms into diamond state is high. At high set chamber pressures, gaseous carbon atoms converted into graphite state at high rate. However, film with low growth rate is deposited. At fixed input power, temperature of the hot-filaments changes due to contamination. So, collision rate of gases is also varied at varying chamber pressures. As a result, a different amount of atomic hydrogen is dissociated. Hence, a different amount of typical energy is etched. Atomic hydrogen etches the photon energy into typical energy shape like parabola, which is involved in the conversion of gaseous carbon atoms to graphite and diamond states. Graphite atoms bind under the same involved energy. Atomic hydrogen etches the photon energy and unused parabola shaped energy into typical energy shape like golf-stick, too, which is involved in the process of binding diamond atoms. So, this study sets new trends in the deposition of carbon films

Self-assembling antimicrobial peptides on nanotubular titanium surfaces coated with calcium phosphate for local therapy

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.Bacterial infection is a serious medical problem leading to implant failure. The current antibiotic based therapies rise concerns due to bacterial resistance. The family of antimicrobial peptides (AMP) is one of the promising candidates as local therapy agents due to their broad-spectrum activity. Despite AMPs receive increasing attention to treat infection, their effective delivery to the implantation site has been limited. Here, we developed an engineered dual functional peptide which delivers AMP as a biomolecular therapeutic agent onto calcium phosphate deposited nanotubular titanium surfaces. Dual functionality of the peptide was achieved by combining a hydroxyapatite binding peptide-1 (HABP1) with an AMP using a flexible linker. HABP functionality of the peptide provided a self-coating property onto the nano-topographies that are designed to improve osteointegration capability, while AMP offered an antimicrobial protection onto the implant surface. We successfully deposited calcium phosphate minerals on nanotubular titanium oxide surface using pulse electrochemical deposition (PECD) and characterized the minerals by XRD, FT-IR, FE-SEM. Antimicrobial activity of the engineered peptide was tested against S. mutans (gram- positive) and E. coli (gram-negative) both in solution and on the Ca-P coated nanotubular titanium surface. In solution activity of AMP and dual functional peptide have the same Minimum Inhibitory Concentration (MIC) (32 mg/mL) against E.coli. The peptide also resulted in the reduction of the number of bacteria both for E.coli and S.mutans compare to control groups. Antimicrobial features of dual functional peptides are strongly correlated with their structures suggesting tunability in design through linkers regions. The dual-function peptide offers single-step solution for implant surface functionalization that could be applicable to any implant surface having different topographies.NIH AR062249–03NIH R01DE025476–01TUBITAK BIDEP 2218ITU Institute for Graduate Program

PyNanospacing: TEM image processing tool for strain analysis and visualization

The diverse spectrum of material characteristics including band gap, mechanical moduli, color, phonon and electronic density of states, along with catalytic and surface properties are intricately intertwined with the atomic structure and the corresponding interatomic bond-lengths. This interconnection extends to the manifestation of interplanar spacings within a crystalline lattice. Analysis of these interplanar spacings and the comprehension of any deviations, whether it be lattice compression or expansion, commonly referred to as strain, hold paramount significance in unraveling various unknowns within the field. Transmission Electron Microscopy (TEM) is widely used to capture atomic-scale ordering, facilitating direct investigation of interplanar spacings. However, creating critical contour maps for visualizing and interpreting lattice stresses in TEM images remains a challenging task. Here we developed a Python code for TEM image processing that can handle a wide range of materials including nanoparticles, 2D materials, pure crystals and solid solutions. This algorithm converts local differences in interplanar spacings into contour maps allowing for a visual representation of lattice expansion and compression. The tool is very generic and can significantly aid in analyzing material properties using TEM images, allowing for a more in-depth exploration of the underlying science behind strain engineering via strain contour maps at the atomic level.Comment: Preprint, 13 pages, 9 figure

The role of superimposing pulse bias voltage on DC bias on the macroparticle attachment and structure of TiAlN coatings produced with CA-PVD

Our attempts for cathodic arc physical vapor deposition (CA-PVD) of TiAlN coatings with high voltage pulse bias in order to tune their structural properties were not successful. Resulted coatings had an unacceptable rough surface with a large number of macroparticles (MPs). For solving this problem and benefiting from high voltage pulse bias-induced effects on the coatings structure we superimposed high voltage pulse on DC bias. For this purpose, Ti0.5Al0.5N coatings were deposited on HSS substrates using a DC bias voltage of 40 V and superimposed pulse bias voltages of 500, 1000 and 1500 V with a duty cycle of 14%. Structure, chemistry, morphology and mechanical properties of the coatings were determined in order to investigate the differences induced by the application of superimposed bias. Additionally, corrosion protection properties of the coatings were also investigated. According to the obtained results, this mode of application not only produced coatings with a denser and finer columnar structure but also resulted in a substantial reduction in the number of MPs. A decrease (maximum 3 at.%) in the Al content of the coatings was observed with increasing pulse bias magnitude when compared to their DC bias deposited counterpart. Substrate temperature also increased with increasing pulse bias magnitude, however, it did not increase above 460 °C. As a result of the decrease of MP attachment and denser structure of the coatings the corrosion protection properties of the coatings substantially improved. This effect became more pronounced with increasing superimposed voltage magnitude

Tribological and mechanical properties of anodized aluminium oxide

oral presentation + abstractedition: Abstract Bookstatus: publishe

Magnesium doping on TiN coatings affects mesenchymal stem cell differentiation and proliferation positively in a dose-dependent manner

BACKGROUND: In vitro evaluation of cell-surface interactions for hard tissue implants have mostly been done using osteoblasts. However, when an implant is placed in the body, mesenchymal stem cells (MSCs) play a major role in new bone formation. Therefore, using MSCs in cell-surface investigations may provide more reliable information on the prediction of in vivo behavior of implants

Effect of Magnesium and Osteoblast Cell Presence on Hydroxyapatite Formation on (Ti,Mg)N Thin Film Coatings

TiN and (Ti,Mg)N thin film coatings were deposited on Ti substrates by an arc-physical vapor deposition technique. The effect of cell presence on hydroxyapatite (HA) formation was investigated using surfaces with four different Mg contents (0, 8.1, 11.31, and 28.49 at.%). Accelerated corrosion above 10 at.% Mg had a negative effect on the performance in terms of both cell proliferation and mineralization. In the absence of cells, Mg-free TiN coatings and low-Mg (8.1 at.%)-doped (Ti,Mg)N surfaces led to an early HA deposition (after 7 days and 14 days, respectively) in cell culture medium (DMEM), but the crystallinity was low. More crystalline HA structures were obtained in the presence of the cells. HA deposits with an ideal Ca/P ratio were obtained at least a week earlier, at day 14, in TiN and low-Mg (8.1 at.%)-doped (Ti,Mg)N compared with that of high-Mg-containing surfaces (> 10 at.%). A thicker mineralized matrix was formed on low-Mg (8.1 at.%)-doped (Ti,Mg)N relative to that of the TiN sample. Low-Mg doping (< 10 at.%) into TiN coatings resulted in better cell proliferation and thicker mineralized matrix formation, so it could be a promising alternative for hard tissue applications