Amorphous Al-Ti Powders Prepared by Mechanical Alloying and Consolidated by Electrical Resistance Sintering

A novel processing method for amorphous Al50Ti50 alloy, obtained by mechanical alloying and subsequently consolidated by electrical resistance sintering, has been investigated. The characterisation of the powders and the confirmation of the presence of amorphous phase have been carried out by laser diffraction, scanning electron microscopy, X-ray diffraction, differential scanning calorimetry and transmission electron microscopy. The amorphous Al50Ti50 powders, milled for 75 h, have a high hardness and small plastic deformation capacity, not being possible to achieve green compacts for conventional sintering. Moreover, conventional sintering takes a long time, being not possible to avoid crystallisation. Amorphous powders have been consolidated by electrical resistance sintering. Electrically sintered compacts with different current intensities (7–8 kA) and processing times (0.8–1.6 s) show a porosity between 16.5 and 20%. The highest Vickers hardness of 662 HV is reached in the centre of an electrically sintered compact with 8 kA and 1.2 s from amorphous Al50Ti50 powder. The hardness results are compared with the values found in the literature.Ministerio de Economía y Competitividad (Spain) / Feder (EU) DPI2015-69550-C2-1-PMinisterio de Economía y Competitividad (Spain) / Feder (EU) DPI2015-69550-C2-2-

Structural, UV-VIS-NIR luminescence and decay associated spectral profiles of Sm3+ doped calcium phosphate glass

Rare-Earths or Lanthanide ions (Ln3+) are a group of elements from lanthanum to lutetium (Z=57 to 71), plus scandium (Z=21) and Yttrium (Z=39). Ln3+ doped glasses have been included within the Hydroxyapatite (HA) matrix, inducing promising changes in their physicochemical and biological properties. Because of the lanthanides' ability to modulate bone metabolism, inclusion of Ln3+ in the composition of calcium phosphate biomaterials for bone tissue regeneration has been considered. Earlier, the authors studied Samarium (Sm3+) doped glass-reinforced hydroxyapatite with enhanced osteoblastic performance and antibacterial properties for bone tissue regeneration. Moreover, Sm3+ substituted calcium phosphate is a non-hazardous material that luminesces under UV-visible light. In this work, we study a calcium phosphate host glass doped with samarium oxide, which has been prepared and characterized by FTIR, SEM, EDS analysis, and X-ray mapping. Pumping with two visible excitation sources at 405nm and 423nm, we observed intense, sharp Green, yellow, orange emission peaks (4G5/2â 6H5/2,7/2, 9/2) at 560nm, 596nm and 643nm respectively. A weak red emission was also observed at 704nm. Two NIR peaks at 1134nm (4G5/2â 6F11/2) and 1310 nm (4G5/2â 6F9/2) are monitored by using an excitation at 1060nm. Furthermore, by making use of time-resolved emission spectroscopy (TRES) measurements, the decay associated spectra were obtained allowing the kinetic parameters for the different emission bands to be elucidated and compared with steady state emission spectra.European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement nº REGPOT-CT2012-316331-POLARIS. Also, SHN would like to thank to Cost Action, ref. # MP 1205 under materials (soft, bio & nano) and technologies for optofluidic devices, and further acknowledge to the FCT -Fundação para a Ciência e a Tecnologia, Portugal, through the project PTDC/SAU-BEB/103034/2008

Time resolved emission spectra and electron paramagnetic resonance studies of Gd3+ doped calcium phosphate glasses

Gadolinium, Gd3+ (4f7 ), containing glasses are particularly interesting owing to their magnetic and optical properties. Gd3+ has an electron paramagnetic resonance (EPR) centre, which is often used as the EPR probe in different matrices. Another important feature of Gd3+ is that emits ultraviolet radiation (UVR) at around 310 â 313 nm from the 6 P7/2 ï  8 S7/2 transition and is suitable for the treatment of skin disease. Here, we report on Gd3+ doped calcium phosphate host glasses with four different concentrations; 0.5 - 4 mol % and labelled as 0.5Gd, 1Gd, 2Gd and 4Gd. A strong emission peak at 310 nm was observed in the reported glasses with excitation at 274 nm. The emission spectra can also be obtained at specific times during the decay. The time resolved emission data was analyzed with three different approaches namely, simple exponential, NED distribution and stretched exponential. The other approaches confirm the single exponential behaviour for all samples with deviation for the 0.5 Gd. The decay associated spectra (DAS) for the 0.5 Gd indicate that both decays have the same origin. The EPR spectrum exhibits several resonance signals characteristic of Gd3+ ions. The stimulated emission cross sections (Ï P EÃ 10â 21 cm2 ) of the UV emission transition 6 P7/2 ï  8 S7/2 were also reported in the above three approaches.The authors would like to acknowledge the financial support from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement nº REGPOT-CT2012-316331-POLARIS. Also, SHN would like to thank to Cost Action, ref. # MP 1205 under materials (soft, bio & nano) and technologies for ptofluidic devices, and further acknowledge to the FCT-Fundação para a Ciência e a Tecnologia, Portugal, hrough the project PTDC/SAU-BEB/103034/2008.info:eu-repo/semantics/publishedVersio