Wyniki wyszukiwania - BazTech

1

Thermal stability and mechanical properties of sputtered Chromium-Molybdenum-Nitride (CrMoN) coatings

Zou Y., Walock M. J., Catledge S. A., Nouveau C., Stanishevsky A.

Journal of Achievements in Materials and Manufacturing Engineering

|

2009

|

Vol. 37, nr 2

369-374

EN

Purpose: The purpose of paper is to determinate thermal stability and mechanical properties of sputtered chromium-molybdenum-nitride (CrMoN) coatings. Design/methodology/approach: We have deposited 1.8 m-thick ternary Cr0.5Mo0.5N1.0 films on a CoCrMo alloy using a RF dual magnetron sputtering system, with Cr and Mo targets and N2 as the reactive gas. These films were subjected to various thermal treatments in Ar, air, and microwave plasma. The hardness, Young’s modulus, surface roughness, microstructure, and composition of films were studied by nanoindentation, AFM, x-ray diffraction, and x-ray photoelectron spectroscopy. Findings: The as-prepared CrMoN films consist of an amorphous Cr-rich nitride matrix with Mo-rich nitride crystalline grains, about 15 nm in size. These films are thermally stable up to 600şC in air. Thermal annealing in the air at 800şC resulted in an increase in surface roughness and hardness, due to film oxidation, with Cr2O3 as the main crystalline phase. Plasma treatment in a H2/N2 gas mixture, at 800şC, did not lead to grain growth. Instead, the existing grains were reduced to about 10 nm and a new nanocrystalline phase has been formed. This leads to a decrease in the surface roughness, and an increase in the film hardness. In addition, we have further modified the film properties through a combined thermal treatment process. Thermal annealing in the air at 800şC, followed by microwave plasma treatment at 800şC resulted in a film with decreased surface roughness, and improved mechanical properties. Reversing the order of the thermal treatments resulted in a further decrease in surface roughness, but it shows a reduction in the mechanical properties. Research limitations/implications: The present investigation was carried out with only one composition, Cr0.5Mo0.5N1.0, of ternary thin-film system. Originality/value: The combination of thermal and plasma treatments can be used to control the microstructure, surface topography, and mechanical properties of ternary CrMoN films. Such post-deposition treatments can further improve the materials properties for desired application, and to produce new nanocomposite materials with technologically important combination of properties.

2

The effect of deposition parameters on the properties of gradient a-C:H/Ti layers

Batory D., Stanishevsky A., Kaczorowski W.

Journal of Achievements in Materials and Manufacturing Engineering

|

2009

|

Vol. 37, nr 2

381-386

EN

Purpose: During the last 20 years DLC (diamond-like carbon) layers became a very attractive material in many medical and engineering applications. While the layer’s stress and adhesion were always a concern, several adhesion improvement methods have been proposed. A majority of those methods consists of either the deposition of an adhesion promoting interlayer or the application of a gradient of chemical composition. In whatever way this reduces the internal stress and improves the adhesion of carbon layers, it also affects the properties of the carbon layer. The aim of this study was to investigate the physicochemical properties of gradient carbon layers manufactured by RF PACVD/MS method at different process parameters. Design/methodology/approach: The a-C:H/Ti gradient layers were deposited onto silicon wafers using a hybrid deposition method which combines PVD and CVD processes in one reaction chamber. Surface topography, adhesion and coefficient of friction (COF) were measured at a nanoscale using Atomic Force Microscopy, Nanoindentation, and Nanotribometry. Findings: The result of this investigation has demonstrated that gradient interlayer deposition parameters affect roughness and tribological properties of outer carbon layer. Research limitations/implications: Presented investigation was performed with mirror-polished silicon wafers to prevent possible interferences caused by variations in surface topography of other typical substrates during polishing. However, the adhesion of carbon layer measured for the silicon substrates can be noticeably different from that measured for metal substrates. Thus, new adhesion investigations have to be done when using these layers on application-specific substrates. Also, additional friction and wear resistance measurements performed under wet conditions (biological serum) should be conducted in a case of medical applications. Originality/value: There are several reports available on the properties of carbon layers deposited subsequently onto the adhesion promoting interlayer. Present work is an attempt to understand and describe influence of adhesion promoting interlayer deposition parameters on the properties of interlayer - layer system as a whole.

3

Surface modification of nanodiamonds for biomedical application and analysis by infrared spectroscopy

Burleson T., Yusuf N., Stanishevsky A.

Journal of Achievements in Materials and Manufacturing Engineering

|

2009

|

Vol. 37, nr 2

258-263

EN

Purpose: Diamond nanoparticles are gaining much interest in biomedical applications due to the attractive chemical and biological properties. Studies have shown the potential of these “nanodiamonds” (NDs) for bioimaging, drug delivery, and biosensing. However, depending on the origin, the nanodiamond surface is often rich in various functional groups which can result in diverse behaviours in biological environments ranging from bioinertness to changes in cell function and cytotoxicity. We have observed the substantial difference in cellular response of several cell lines to NDs of various origins. Therefore, the aim of this study was to modify nanodiamond surface in a controlled manner to discriminate the effect of different functional groups on the cellular response. Design/methodology/approach: Commercial detonation nanodiamond powders with the mean grain size 5 nm but different size of agglomerates and synthetic diamond particles ranging from 50 nm to 1 ěm were modified under hydro- and solvo- thermal conditions to introduce specific functional groups to the surface. The processed nanoparticles were investigated with Fourier Transform Infrared (FTIR) spectroscopy and the results were compared between the samples. Modified NDs were tested for their toxicity in vitro with several cell lines (cell viability studies) and for the capability for small molecule anti-cancerous drug loading. Findings: We demonstrated that different chemical groups can be introduced and controlled onto the synthetic diamond surface depending on the solvent and process parameters used. In vitro assays showed that no cellular toxicity was found when CO, OH, or NH-groups dominated on the surface of the diamond particle. Practical implications: Many potent drugs that have proven to be useful in treating diseases such as cancer pose a challenge in delivery because they are not soluble in polar protic solvents such as water. These drugs are soluble in polar aprotic solvents that are harmful to the body. Nanodiamond surface modification in conjunction with drug-loading is a potential solution to this problem as nanodiamonds are nontoxic and have the ability to transport significant amounts of drugs. Originality/value: Nanodiamond particles are considered nontoxic and capable of absorption of a variety of organic molecules. This study should further advance the knowledge on the potential of surface-engineered NDs in therapeutic and drug delivery applications.

4

Surface modification and functionalization of nanostructured carbons

Stanishevsky A., Catledge S. A., Vohra Y.

Journal of Achievements in Materials and Manufacturing Engineering

|

2009

|

Vol. 37, nr 2

348-353

EN

Purpose: Nanostructured carbon nanomaterials (e.g., nanocrystalline diamond films and particles, carbon nanotubes, carbon onions, fullerenes, etc.) are being extensively explored for numerous biomedical applications in surgical implants, therapy, drug delivery, and biosensoring due to their interesting physical, chemical, and biological properties. Such applications of carbon nanomaterials often require specific surface functionality to be introduced for better integration of these materials with physiological environment. In the last decade, substantial progress has been made in the development of controllable surface modification methods and in the introduction of different functional groups on the surface of carbon nanomaterials. Design/methodology/approach: This paper briefly overviews the surface modification and functionalization approaches for various carbon nanomaterials, and it focuses on the plasma modification and functionalization of nanocrystalline diamond films, diamond nanoparticles, and carbon nanospheres. The results on the surface characterization using FTIR and XPS techniques, and the preliminary studies of cellular response to these modified carbon nanomaterials are presented and discussed. Findings: The results of surface modification of NCD films, detonation nanodiamonds, and carbon nanospheres, demonstrate the flexibility of nanocarbons to attain various surface functionality that can be adjusted for specific applications. It has been shown that neither of tested nanocarbon materials was cytotoxic in this study, although the attachement and proliferation of various cells was strongly affected by the specific type of surface functionalization. Research limitations/implications: At the present, it is not clear to what degree the available surface sites on NCD films or carbon nanoparticles can be occupied with functional groups. Furthermore, while there is clear selectivity of cellular response to H, O, and F surface-terminated NCD films, the role of specific type of surface groups present on carbon nanoparticles has yet to be determined. Practical implications: The development of optimal strategies to functionalize various nanocarbons will have strong impact on the design of efficient nanostructured surfaces and particles for a variety of biological and medical applications. Originality/value: This work adds new insights to the expanding research in biomedical applications of nanoscale carbon materials.