BCMaterials Fortnightly Seminar #60: Anabel Pérez & Xabier Lasheras

ANABEL PÉREZ

(BCMATERIALS)

Influence of selective Ag addition on the transformation temperatures, magnetic properties and lattice parameters of a multicomponent Ni₄₃Co₇Mn₂₀Fe₂Ga₂₁Cu₇ alloy

The development of new high temperature ferromagnetic shape memory alloys, HTSMAs, has attracted considerable interest due to the evolution of actual requirements for modern applications. Ni-Mn-Ga alloys have been extensively studied as SMAs, since they exhibit the largest MSM effect, about 10% for modulated martensite and 12% for non-modulated. However, many efforts are still devoted to the improve of the mechanical properties, the reduction of the twinning stress for the non-modulated martensite, or the increase of operating temperature range. The high composition dependence of the properties in these materials makes them easy tunable materials. Different approaches as the addition of a fourth or fifth element have shown a drastic change on martensitic transformation, Curie temperature and crystal structure. Our previous studies focused on the simultaneous addition of Fe, Co and Cu in the Ni₄₅Co₅Mn_25-xFe_xGa₂₀Cu₅ system have shown an increase of T_M > 100ºC and T_C > 150ºC. However, further investigation should be performed to keep increasing transformation temperatures and reduce the c/a value, which is related to a low twinning stress. Our current work is based on the substitution of Ga and Cu for Ag. This approach is based on the simple idea of added an element with a high electron concentration per atom, e/a, and a large atomic size in order to evaluate the effect on the martensitic transformation, magnetic properties and crystallographic structure.

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XABIER LASHERAS

(BCMATERIALS)

Developing ferrite based nanocompounds for multiple biomedical applications: The road from the base material to its application

According to their unusual properties, the ferrite structure based superparamagnetic nanoparticles are being tested for many and diverse applications such as colour imaging, data storage, metal separation, catalysis, magnetic inks, biomedical applications and so forth.^2,3 Many research groups are focused on this last application, being possible to use such nanoparticles in many different ways (magnetic hyperthermia inductors, drug delivery agents or contrast agents in MRI) to help in the diagnosis and treatment of many kind of diseases. However, many steps need to be overcame to score this goal. Their applicability is conditioned by many factors such as their magnetic behaviour, colloidal stability, surface functionalization, biocompatibility and the ability to connect different drugs and to direct to specific tissues. Each one of these points represent a specific research field, being the final application a complex mixture of conditions that the developed product needs to achieve. In the present work, a complete research work is presented, in which all the described steps have been studied. Firstly, the crystalline structure of magnetite has been doped with different paramagnetic cations so as to obtain an enhanced magnetic hyperthermia response. The optimized NP system has been functionalized and biocompatibilized by different methods to obtain two different systems, covering a broader range of applicability. The toxicity of these systems has been tested by in vitro tests in simulated tissues and by an in vivo test in mice.