Analyses of energy transfer of Cr3+ and Nd3+ co-doped Y3Al5O12 ceramic powders at the 4T1 level of Cr3+ ion excitation

The concentration dependence of energy transfer from Cr3+ to Nd3+ at the 4T1 level excitation in Nd/Cr:YAG was investigated by the fluorescence decay curves of Cr3+ and Nd3+ for Nd/Cr:YAG and Cr:YAG ceramic powders in the Cr3+ concentration range of 0.1 to 6.0 mol%. The energy transfer process between Cr3+ and Nd3+ at the 4T1 level excitation is tried to explain using a rate equation that assumes energy transfer from the 2E–4T2 level to Nd3+ on the basis of dipole–dipole interactions, the same as the 4T2 level excitation. In conclusion, the energy excited to the 4T1 level will relax non-radiatively to the 2E–4T2 level and then transfer to Nd3+. It is presumed there will be no direct transfer from the 4T1 level to Nd3+. Our rate equations will be useful when simultaneously exciting the 4T1 and 4T2 levels of Cr3+ in Nd/Cr:YAG using broadband pumping sources.

Antibacterial 3D-printed PMMA/ceramic composites

Following the rising interested on 3D-printed technologies, this research explores the possibility to use stereo-lithography to 3D print PMMA resins reinforced with up to 15% in weight of antibacterial ceramic powders. Three different reinforcements were tested, following previous literature data: aluminum nitride, titanium oxide and barium titanate. Between the three powders, the most uniform dispersion was achieved using aluminum nitride. Initial screenings with mixed and cured composite resins showed that between the three composite materials, only aluminum nitride or barium titanate PMMA showed a clear antibacterial effect when compared to the pristine reference, with aluminum nitride being the most effective against E. coli. When 3D printed using stereo-lithography, the composite containing aluminum nitride showed an even higher degree of dispersion and comparable antibacterial effects. Moreover, aluminum nitride reinforced PMMA resins showed good mechanical properties, comparable to the basic resin, and could be further strengthened by a standard post-curing process.

Simple Approach to Medical Grade Alumina and Zirconia Ceramics Surface Alteration via Acid Etching Treatment

In order for bioceramics to be further used in composites and their applications, it is important to change the surface so that the inert material is ready to interact with another material. Medical grade alumina and zirconia ceramic powders have been chemically etched with three selected acidic mixtures. Powder samples were taken for characterization, which was the key to evaluating a successful surface change. Changes in morphology, together with chemical composition, were studied using scanning electron microscopy, phase composition using X-ray diffraction methods, and nitrogen adsorption/desorption isotherms are used to evaluate specific surface area and porosity. The application of HF negatively affected the morphology of the material and caused agglomeration. The most effective modification of ceramic powders was the application of a piranha solution to obtain a new surface and a satisfactory degree of agglomeration. The prepared micro-roughness of the etched ceramic would provide an improved surface of the material either for its next step of incorporation into the selected matrix or to directly aid in the attachment and proliferation of osteoblast cells.

Powder Metallurgy: A New Open Section in Metals

Powder Metallurgy (PM) is a forming technology that uses metallic (sometimes also in conjunction with ceramic) powders to develop parts, most of the time through a thermal process called sintering, which never reaches the melting point of the principal component of the alloy [...]