Institute of Materials and Machine Mechanics

Mesoporous bioactive glass (MBG) is widely acknowledged in bone tissue engineering due to its mesoporous structure, large surface area, and bioactivity. Recent research indicates that introduction of metallic ions has beneficial impacts on bone metabolism and angiogenesis. Thus, the features of MBG can be modified by incorporating combinations of ions, such as magnesium (Mg) and copper (Cu), which can play a considerable role in bone formation, influencing angiogenesis, osteogenesis, as well as antibacterial properties. In this study, Mg and Cu were co-doped for the first time (in a ratio of 1 : 1) in 80SiO2-5P2O5-(15 - 2x)CaO-xMgO-xCuO glass composition with x = 0, 0.5, 1, and 2 mol%, synthesized using the sol-gel and evaporation-induced self-assembly method. X-ray diffraction analysis confirmed the amorphous nature of the powders, while inductively coupled plasma-optical emission spectrometry verified the existence of dopant ions in the respective amounts. The nitrogen sorption method indicated the formation of uniform cylindrical mesopores which are open at both ends and a high surface area of the powders. TEM images show fringes, indicating an ordered mesoporous structure in all MgCu co-doped systems. In vitro bioactivity was observed in all MBG powders, confirmed by the formation of an apatite phase when placed in simulated body fluid (SBF). Flake-like microstructure characteristics of HAp crystals found on the surface of MBG powders were visualized using FESEM. Cytotoxicity tests at lower concentrations (0.1 and 1 wt/vol%) of co-doped 2MC MBG (co-doping up to 2 mol%) showed cell proliferation and viability of osteoblast-like MG-63 cells and normal human dermal fibroblast (NHDF) cells similar to the basic glass 80S. Antibacterial study of MBG pellets showed an increment in the zone of inhibition with the sequential addition of doping ions. The turbidity measurement of bacterial cultures revealed that the optimal concentration for effectively inhibiting bacterial growth was 1 wt/vol% (i.e., 10 mg mL-1) concentration of MBG extracts. The result suggested that the incorporation of Mg and Cu ions in MBG in lower concentrations of up to 2 mol% can be useful in bone regeneration owing to bioactivity, cell proliferation, and antibacterial characteristics.

Titanium and its composites are widely used in implants of bones and teeth. Besides mechanical properties also surface characteristics are very important in these biomaterials. Very important are properties such as surface topography, roughness, chemistry, and surface energy, wettability, and Ti oxides or Ti nitride layers thickness. The concentrated solar power was used successfully to nitride Ti Grade 2 and powder metallurgical Ti prepared from hydrogenated dehydrogenated Ti powder. The nitriding experiments were performed under nitrogen atmosphere at different temperatures and time in SF40 (40kW horizontal solar furnace) at PSA, Spain. Concentrated solar energy has been shown to be an economical alternative to conventional gas nitriding techniques in electric furnaces, CVD, PVD, plasma nitriding, or laser treatments. It has been observed that the solar process represents a significant reduction of the heating time to several minutes (up to 5 minutes at temperature range 500-1000 °C), a clean and non-polluting high-temperature process. The formation of continuous and homogeneous surface layers of TiN, Ti2N and their mixture according to the nitriding temperature was investigated using X-ray diffraction and electron microscopy. Laser surface treatment is of great significance in modifying surface morphology and surface and near-surface region microstructures. Effects of lase treatment parameters on machined surface morphology, surface roughness and chemistry are analyzed in this study and discussed from the point of view of application in dental implantology. The current advances of our research group in application of laser-treated powder metallurgy prepared Ti-based materials are analyzed and discussed.

Friction stir processing (FSP) offers a unique opportunity to tailor the microstructure and improve the mechanical properties due to the combination of extensive strains, high temperatures, and high-strain rates inherent to the process. Reactive friction stir processing was carried out in order to produce in situ Al/(Al13Fe4 + Al2O3) hybrid nanocomposites on wrought/as-annealed (673 K) AA1050 substrate. The active mixture of pre-ball milled Fe2O3 + Al powder was introduced into the stir zone by pre-placing it on the substrate. Microstructural characterisation showed that the Al13Fe4 and Al2O3 formed as the reaction products in a matrix of the dynamically restored aluminium matrix. The aluminium matrix means grain size was found to decrease markedly to 3.4 and 2 μm from ~55 μm and 40–50 μm after FSP using wrought and as-annealed substrates employing electron backscattered diffraction detectors, respectively. In addition, tensile testing results were indicative that the fabricated surface nanocomposite on the as-annealed substrate offered a greater ultimate tensile strength (~160 MPa) and hardness (73 HV) than those (146 MPa, and 60 HV) of the nanocomposite formed on the wrought substrate.

We introduce a unifying approach for invariants of finite matroids that count mappings to a finite set. The aim of this paper is to show that if the cardinalities of mappings with fixed values on a restricted set satisfy contraction–deletion rules, then there is a relation among them that can be expressed in terms of linear algebra. In this way, we study regular chain groups, nowhere-zero flows and tensions on graphs, and acyclic and totally cyclic orientations of oriented matroids and graphs.

The internal pore wall structure formation and density play an important role in improving the mechanical and thermal properties of the closed-cell aluminium foams. The present research work aims to investigate the internal structure formation of the aluminium foam prepared by powder metallurgy and the uniformity of the distribution of the pores when the minimum amount of TiH2 is added. The foamable precursor of two different aluminium alloys (Al-1050 and A5083) is produced with a TiH2 gaseous agent of 0.05 wt.%. The parameters analysed include the density, pore wall formations, pore, and metal density distribution inside the structure with the help of X-ray tomography. Furthermore, the image-processing technique has been adopted to produce the 3D surrogate model of the foam for visual inspection and analysis. The obtained results show the importance of the amount of TiH2 addition and of the foaming furnace temperature in deciding the internal porous structure formation. Further, the pore morphology of lower porosity foams (in the range of 30-40 % porosity) of the two alloys produced at 690 °C furnace temperature is investigated with the help of developed surrogate models. The presence of micropores and uniformity of the distribution of pores found brings the idea of choosing the optimized structure of foam for thermal energy storage systems associated with PCM.

In modern society, it is impossible to imagine life without polymeric materials. However, managing the waste composed of these materials is one of the most significant environmental issues confronting us in the present day. Recycling polymeric waste is the most important action currently available to reduce environmental impacts worldwide and is one of the most dynamic areas in industry today. Utilizing this waste could not only benefit the environment but also promote sustainable development and circular economy management. In its program statement, the European Union has committed to support the use of sorted polymeric waste. This study reviews recent attempts to recycle this waste and convert it by alternative technologies into fine, nano-, and microscale fibers using electrospinning, blowing, melt, or centrifugal spinning. This review provides information regarding applying reprocessed fine fibers in various areas and a concrete approach to mitigate the threat of pollution caused by polymeric materials.