Learning form Nature to improve the heat generation of iron-oxide nanoparticles for magnetic hyperthermia applications.

The performance of magnetic nanoparticles is intimately entwined with their structure, mean size and magnetic anisotropy. Besides, ensembles offer a unique way of engineering the magnetic response by modifying the strength of the dipolar interactions between particles. Here we report on an experimental and theoretical analysis of magnetic hyperthermia, a rapidly developing technique in medical research and oncology. Experimentally, we demonstrate that single-domain cubic iron oxide particles resembling bacterial magnetosomes have superior magnetic heating efficiency compared to spherical particles of similar sizes. Monte Carlo simulations at the atomic level corroborate the larger anisotropy of the cubic particles in comparison with the spherical ones, thus evidencing the beneficial role of surface anisotropy in the improved heating power. Moreover we establish a quantitative link between the particle assembling, the interactions and the heating properties. This knowledge opens new perspectives for improved hyperthermia, an alternative to conventional cancer therapies

Thermal quenching of thermoluminescence in quartz samples of various origins

The effect of thermal quenching plays an important role in the thermoluminescence (TL) of quartz on which many applications of TL are based. In present work it is investigated that the thermal quenching parameters i.e. the activation energy W and the dimensionless parameter C, are more or less the same for every kind of quartzes or sample dependent on strong external treatment like a high temperature annealing. This preliminary investigation of seven quartz samples of different origin showed that the thermal quenching parameters W and C are common (universal) for most of the quartz samples.Publisher's Versio

Influence of microstructure and mechanical properties on the tribological behavior of reactive arc deposited Zr-Si-N coatings at room and high temperature

Varying the Si-content in Zr-Si-N coatings from 0.2 to 6.3 at.% causes microstructural changes from columnar to nanocomposite structure and a hardness drop from 37 to 26 GPa. The softer nanocomposite also displays lower fracture resistance. The tribological response of these coatings is investigated under different contact conditions, both at room and elevated temperatures. At room temperature tribooxidation is found to be the dominant wear mechanism, where the nanocomposite coatings display the lowest wear rate of 0.64 × 10- 5 mm3/Nm, by forming an oxide diffusion barrier layer consisting of Zr, W, and Si. A transition in the dominant wear mechanism from tribooxidation to microploughing is observed upon increasing the test temperature and contact stress. Here, all coatings exhibit significantly higher coefficient of friction of 1.4 and the hardest coatings with columnar structure display the lowest wear rate of 10.5 × 10- 5 mm3/Nm. In a microscopic wear test under the influence of contact-induced dominant elastic stress field, the coatings display wedge formation and pileup due to accumulation of the dislocation-induced plastic deformation. In these tests, the nanocomposite coatings display the lowest wear rate of 0.56 × 10- 10 mm3/Nm, by constraining the dislocation motionPeer Reviewe

Self-Healing in Carbon Nitride Evidenced As Material Inflation and Superlubric Behavior

All known materials wear under extended mechanical contacting. Superlubricity may present solutions, but is an expressed mystery in C-based materials. We report negative wear of carbon nitride films; a wear-less condition with mechanically induced material inflation at the nanoscale and friction coefficient approaching ultralow values (0.06). Superlubricity in carbon nitride is expressed as C–N bond breaking for reduced coupling between graphitic-like sheets and eventual N₂ desorption. The transforming surface layer acts as a solid lubricant, whereas the film bulk retains its high elasticity. The present findings offer new means for materials design at the atomic level, and for property optimization in wear-critical applications like magnetic reading devices or nanomachines

Can commercial ferrofluids be exploited in AC magnetic hyperthermia treatment to address diverse biomedical aspects?

Multifunctional magnetic nanoparticles are considered as promising candidates for various applications combining diagnosis, imaging and therapy. In the present work, we elaborate on the commercial colloidal solution “FluidMAG” (from Chemicell GmbH) as a possible candidate for magnetic hyperthermia application. The current product is a dispersion of magnetite nanoparticles employed for purification or separation of biotinylated biomolecules from different sources (e.g. blood). Transmission Electron Microscopy showed that the NPs have a spherical shape with mean diameter of 12.3 nm (± 20%), and SQUID magnetometry revealed their superparamagnetic character. Our promising results of the AC hyperthermia efficiency of “FluidMAG” suggest that with the appropriate manipulation it can also be exploited as magnetic hyperthermia agent