Dan Batalu

Short Review on Rare Earth and Metalloid Oxide Additions to MgB2 as a Candidate Superconducting Material for Medical Applications

MgB2 is a candidate for the fabrication of magnetic coils used in medical applications. Our review indicate that oxide additions based on the rare earth or metalloid elements show improvement of the MgB2 critical current density (Jc) and the irreversible magnetic field (Hirr) without significantly affecting the critical temperature (Tc) However, the characteristics of the additions and the technological approaches show a strong influence in controlling superconducting properties. Both additions and the technology need a careful and complex optimization in order to enhance the Jc and Hirr.

Evaluation of pristine and Eu2O3-added MgB2 ceramics for medical applications: hardness, corrosion resistance, cytotoxicity and antibacterial activity

Nano- or micropowders of Eu2O3 were added to MgB2, resulting in a composition of (MgB2)0.975(EuO1.5)0.025. Pristine and doped samples were prepared using spark plasma sintering and tested for (i) Vickers hardness, (ii) pH evolution in phosphate-buffered saline solution, (iii) corrosion resistance (Tafel polarization curves), (iv) cytotoxicity (in vitro tests), and (v) antibacterial activity. Eu2O3 addition influenced the investigated properties. Solutions of MgB2-based samples show a relatively high saturation pH of 8.5. This value is lower than that of solutions incubated with Mg or other Mg-based biodegradable alloys reported in the literature. MgB2-based samples have lower electro-corrosion rates than Mg. Their Vickers hardness is 6.8-10.2GPa, and these values are higher than those of biodegradable Mg-based alloys. MgB2 has low in vitro biocompatibility, good antibacterial activity against Escherichia coli, and mild activity against Staphylococcus aureus. Our results suggest that MgB2-based materials deserve attention in biomedical applications, such as implants or sterile medical instruments.

The Influence of Different Additives on MgB 2 Superconductor Obtained by Ex Situ Spark Plasma Sintering: Pinning Force Aspects

Superconducting samples of MgB2 prepared by ex situ spark plasma sintering were characterized by magnetic measurements emphasizing functional characteristics such as the critical current density J c, the irreversibility field H irr or the product J c(0) · µ0 · H irr, and the pinning-force-related parameters extracted within the universal scaling law and the percolation-based theory. Additions introduced into MgB2 were classified as following: approximately chemically inert (type 1: h-BN, c-BN, and graphene), reactive with formation of MyBz (type 2: RE2O3 with RE being a rare earth element such as Ho, La, or Eu) or MguMv (type 3: Sb, Sb2O3, Bi, Bi2O3, Te, TeO2, Ge, and GeO2), and additives which are source of carbon substituting for boron in the crystal lattice of MgB2 (type 4: fullerene (F), F + c-BN, SiC + Te, Ge2H10C6O7, and B4C). Each group of additives show specific features, but within each group there are differences. When considering the influence of the additive of types 1–3, one has to pay attention also to substitutional x-carbon level which shows a strong influence on the functional and on the pinning-force-related parameters. A general trend is that at low x and high temperatures (>~15 K), samples are in the point pinning region and contribution of the grain boundary pinning is increasing when the additive amount is higher and the temperature is lower. There are also exceptions and within the general trend there are notable differences among the samples. From a practical point of view, additives such as c-BN, Te, Ge2H10C6O7, or B4C are shown to increase high magnetic field functional characteristics such as J c and H irr, while suppression of J c at low magnetic fields is minimized.

Total Elbow Implant - Computer Assisted Design and Simulation

The elbow total implant is in appearance a simple orthopedic device, with few components and no complex mechanisms. In spite of the reported successful surgical interventions, there are still many medical reports which show that a certain percentage of the implants fails.In our work we conceptually approach a computer assisted design of a Coonrad-Morrey like total elbow implant and simulate the mechanical behavior by finite element analysis, for three different loads (10 N, 50 N, and 100 N). Materials used for simulation were Ti, TiNi and Ti6Al4V for the metallic components, and UHMWPE for bushing polymeric components. Through our results we confirmed the practical observations, namely that the hinge mechanism is an important region where the failures initiates from, as the highest stress is concentrated on the polymeric components.