There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Nano-scale modification of titanium implant surfaces to enhance osseointegration

Leaded brass alloys for gamma-ray shielding applications

https://iopscience.iop.org/article/10.1088/2053-1591/aafb9f/pdf

Investigation of microstructure and mechanical properties of friction stir welded dissimilar St37/St52 joints

Aluminum alloys (AAs) of 5xxx and 6xxx are employed in marine construction and shipbuilding, particularly in the construction of hulls, superstructures, and deck panels of ships due to their high strength-to-weight ratios and corrosion resistance characteristics. Fabrication of these structures often poses serious threats during the joining (welding) as these alloys exhibit a vast difference in chemical and mechanical properties. Moreover, corrosion of these alloys in marine atmosphere is also a serious issue. The objective of this paper is to present a review on the use of potential AAs for marine applications. Furthermore, serious challenges faced during the fabrication of these alloys are also highlighted in this article. Thus, this article will be of great help to researchers and academicians in finding answers to the problems faced during marine vehicle fabrication. The important characteristics, application, and problems faced while fabricating these alloys are collectively addressed in the present manuscript.

Aluminum alloys in marine construction: characteristics, application, and problems from a fabrication viewpoint

In this study, the applicability of friction stir welding to cast NAB alloy (i.e., C95800) with a thickness of 9 mm has been investigated. The joint performance was determined by conducting optical microscopy, microhardness measurements, and mechanical testing (e.g., tensile and Charpy impact tests). The effect of stir intensity on joint performance was also determined. A grain refinement (equiaxed fine grain structure) as well as evolution of a Widmanstatten structure was achieved within the stir zone of all the joints produced. Thus, all of the joints produced exhibited higher proof stress (i.e., between 512 and 616 MPa) than that of the base material, i.e., 397 MPa. On the other hand, only half of the specimens exhibited higher tensile strength values than that of the base plate (i.e., 794 MPa), whereas the other specimens displayed lower tensile strength than the base plate due to the existence of weld defects, namely cold bonding and/or tunnel defect.

Microstructural and Mechanical Properties of Friction Stir Welded Nickel-Aluminum Bronze (NAB) Alloy

Diamond-like-carbon (DLC) coatings with high hardness and low friction coefficient exhibit excellent tribological performance under air and vacuum conditions. However, adhesion and cold welding problems in vacuum conditions lead to increase friction coefficient values. These negative effects can be eliminated by different methods such as forming interlayers between coating and substrate or ion treatment of the substrate. In this work, DLC coatings were deposited on untreated and plasma nitrided (at 400 °C, 500 °C and 600 °C for 1 h and 4 h) AISI 4140 steel substrates by magnetron sputtering technique. The effects of plasma nitriding treatment on the friction and wear properties of DLC coatings under air and vacuum conditions were investigated. The structural and mechanical properties of DLC films were examined by XRD, SEM, and microhardness tester, respectively. The friction and wear properties were determined by a tribotester under air and vacuum conditions. The microhardness of samples increased after surface treatments and the highest value was obtained from the sample plasma nitrided at 600 °C for 4 h plus DLC coated sample. The wear resistance of samples increased with increasing plasma nitriding time and temperature. Also, it was observed that the samples tested under vacuum condition showed better wear resistance than the samples tested under ambient air. Furthermore, increasing plasma nitriding time and temperature improved the wear performance of the material regardless of the test environment.

The friction and wear performance of DLC coatings deposited on plasma nitrided AISI 4140 steel by magnetron sputtering under air and vacuum conditions

The friction and wear properties of CuZn39Pb3 alloys under atmospheric and vacuum conditions

Lasers are used to modify the surfaces of dental implants or to decontaminate exposed implant surfaces. However, research is lacking on whether the laser causes any change on the surfaces of titanium implants. We aimed to determine the effects of laser treatment on the surface characteristics of titanium discs. Nine discs were fabricated using grade-V titanium with resorbable blast texturing surface characteristics. The discs were irradiated with an erbium, chromium: yttrium, scandium, gallium, garnet (Er,Cr:YSGG) laser under different experimental conditions (R1-9). Scanning electron microscopy was used to evaluate implant surface topography qualitatively, and a mechanical contact profilometer was used to evaluate surface roughness. The R3 and R5 parameters caused no measurable change. Minor cracks and grooves were observed in discs treated with the R1, R2, R4, R7 and R9 parameters. Major changes, such as melting, flattening and deep crack formation, were observed in discs subjected to R6 (2 W, 30 Hz, 2 mm. distance, 30 s) and R8 (3 W, 25 Hz, 2 mm. distance, 45 s) parameters. The lowest surface roughness value was obtained with the R8 parameter. Irradiation distance, duration, frequency and power were the most significant factors affecting surface roughness. Parameters such as wavelength, output power, energy, dose and duration should be considered during irradiation. The results of this study indicate that the distance between the laser tip and the irradiated surface should also be considered.

Effects of Er,Cr:YSGG laser irradiation on the surface characteristics of titanium discs: An in vitro study

In this study, pure TiN coatings were applied on AISI 52100 steel surfaces with a magnetron sputterer at different direct current (DC) powers and N2 flows to develop a wear-resistant coating for sl...

Levent Kara

Papers

Microstructural and Mechanical Properties of Friction Stir Welded Nickel-Aluminum Bronze (NAB) Alloy

The friction and wear performance of DLC coatings deposited on plasma nitrided AISI 4140 steel by magnetron sputtering under air and vacuum conditions

The friction and wear properties of CuZn39Pb3 alloys under atmospheric and vacuum conditions

Effects of Er,Cr:YSGG laser irradiation on the surface characteristics of titanium discs: An in vitro study

Friction and Wear Behaviors of TiN Coatings under Dry and Vacuum Conditions