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In this study, we propose a method to produce nanocrystalline TiFe powder by high-energy ball milling, in order to avoid the common sticking problem of the material to the milling tools, assuring a material prompt to absorb hydrogen as well. The method consists of making a preliminary milling operation with the elemental powders (50:50 stoichiometric ratio) to form a strong adhered layer of the milled material on the surfaces of the vial and balls. The main milling operation is then performed with a new powder charge (same composition as before), but now adding a process control agent (stearic acid). Various processing times - 2, 6, 10 and 20 h - were used in the milling experiments. Nanocrystalline TiFe was synthesized in this way with low oxygen contamination, full yields for milling times of 6 h or over, requiring no heat treatments for the first hydrogen absorption. Hydrogen storage capacity of 1.0 wt% at room temperature under 20 bar was attained by the sample milled for 6 h. Kinetic data from samples milled for 2 h and 6 h agreed with Jander model for the rate limiting step of the hydriding reaction, which is based on diffusion with constant interface area.

The (de)hydrogenation properties of a TiFe intermetallic compound (IMC) alloy activated by cold rolling inside a glovebox at ambient temperature were investigated by kinetic measurements, x-ray powder diffraction (XRD), and transmission electron microscopy (TEM). Rate-limiting steps were identified by testing kinetic models on hydrogen absorption and desorption curves. To prevent surface poisoning during air exposure, the TiFe IMC was also cold rolled with polytetrafluoroethylene (PTFE) and ultra-high molecular weight polyethylene (UHMWPE). The addition of either PTFE or UHMWPE to nanostructured TiFe by cold rolling did not produce a polymer-metal composite with O2 poisoning resistance, regardless of the polymer-mixing way adopted. This occurred because large surfaces of the particles were not adequately coated with polymer. The results identify challenges to the TiFe IMC polymer-covered material that must be overcome before a methodology can significantly contribute to the formation of nanostructured TiFe-polymer composites with enhanced hydrogen storage properties. The diffusion-controlled reactions in the cold-rolled TiFe IMC without polymer were prevalent in all cases, as predicted by the Jander three-dimensional diffusion model. The main contribution of this work regards estimation of the amount of hydrogen released, which was 0.60% after 6 min and reproducible for the three subsequent cycles.

Mg-AB5 composites are promising systems for hydrogen storage applications, due to their possibility of hydrogen cycling at relatively low temperatures. Traditionally, these composites are mainly processed by high-energy ball milling (HEBM) techniques employing longer processing times. In this study, cold rolling was applied to prepare MgH2 LaNi5 composites and the hydrogen storage properties were investigated. The materials were processed using a vertical rolling mill under argon atmosphere, leading to a good homogeneity and no contamination at shorter processing times. The mixture of MgH2-1.50 mol.% LaNi5 showed the best hydrogen storage properties at 200 °C and 100 °C and the lowest desorption temperature even when compared to cold rolled MgH2. The results indicate that the composite MgH2 LaNi5 is transformed into a mixture of three phases MgH2, Mg2NiH4 and LaH3 upon hydrogen absorption/desorption cycles. The synergetic effect among these phases when in appropriate proportion in the sample seems to play a crucial role in the acceleration of hydrogen absorption/desorption kinetics at lower temperatures in comparison to MgH2.

TiFe is a very interesting material for hydrogen storage in the solid state, due to its hydrogen capacity of 1.9 wt % and to the fact it can be absorb/desorb hydrogen at room temperature. However, the TiFe produced by casting does not absorb hydrogen, unless a procedure called activation is applied, which is based on a repetition of several thermal cycles. This study evaluates the effects of a mechanical activation route for the TiFe intermetallic compound, namely, cold rolling (CR) under inert atmosphere. Stoichiometric TiFe was prepared from elementary powders by arc melting. Ingot was grinded and then cold rolled for 20 and 40 passes under argon inside a glove box, with moisture and oxygen contents below 0.1 ppm. Cold rolled samples consisted of two parts: powder particles and thin cracked flakes. The results showed that mechanically activated samples by CR exhibited rapid absorption of hydrogen at room temperature, without using a thermal activation process. In general, the average storage capacity of hydrogen was 1.4 wt% H2 for the first absorption, regardless of the number of passes for both flake and powder samples.

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:55:37Z No. of bitstreams: 1 S0102-09352004000300021.pdf: 150424 bytes, checksum: 01431bce085c5c12535592b3b4af0cd4 (MD5) Made available in DSpace on 2013-08-22T18:55:37Z (GMT). No. of bitstreams: 1 S0102-09352004000300021.pdf: 150424 bytes, checksum: 01431bce085c5c12535592b3b4af0cd4 (MD5) Previous issue date: 2004-06-01 Made available in DSpace on 2013-09-30T19:48:39Z (GMT). No. of bitstreams: 2 S0102-09352004000300021.pdf: 150424 bytes, checksum: 01431bce085c5c12535592b3b4af0cd4 (MD5) S0102-09352004000300021.pdf.txt: 8764 bytes, checksum: c1ea958ee9b66622b1ef5258be4c8ed4 (MD5) Previous issue date: 2004-06-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T15:12:53Z No. of bitstreams: 2 S0102-09352004000300021.pdf: 150424 bytes, checksum: 01431bce085c5c12535592b3b4af0cd4 (MD5) S0102-09352004000300021.pdf.txt: 8764 bytes, checksum: c1ea958ee9b66622b1ef5258be4c8ed4 (MD5) Made available in DSpace on 2014-05-20T15:12:53Z (GMT). No. of bitstreams: 2 S0102-09352004000300021.pdf: 150424 bytes, checksum: 01431bce085c5c12535592b3b4af0cd4 (MD5) S0102-09352004000300021.pdf.txt: 8764 bytes, checksum: c1ea958ee9b66622b1ef5258be4c8ed4 (MD5) Previous issue date: 2004-06-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Clinic-epidemiological data in canine infection by Hepatozoon canis were reported. Apatia, anorexia, prostaction, weight loss and muscle pain were the most-common clinical recognized signs. Blood smear was used as diagnosis method for the detection of H. canis gamonts in the neutrophils. Anaemia, leucocytosis, monocytosis and lymphopenia were observed in the haematological exams. Imidocarb dipropionate associated with tetracyclines and sulfamethoxasole-trimethoprim were used in therapy. USP FMVZ Depto. Medicina Veterinária Preventiva e Saúde Animal CNPq UNESP FMVZ Depto. Higiene Veterinária e Saúde Pública UNESP FMVZ Depto. Higiene Veterinária e Saúde Pública

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:55:30Z No. of bitstreams: 0 Made available in DSpace on 2013-08-22T18:55:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2001-10-01 Made available in DSpace on 2013-09-30T19:48:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2001-10-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T13:39:49Z No. of bitstreams: 0 Made available in DSpace on 2014-05-20T13:39:49Z (GMT). No. of bitstreams: 0 Previous issue date: 2001-10-01 Propionibacterium acnes as immunostimulant in oral canine papillomatosis treatment in 16 animals was studied. Regression of the pappiloma started being observed after the second aplication, with complete resolution in all dogs after the sixth aplication. These results suggest the use of P. acnes as an alternative in oral canine papillomatosis therapy. UNESP Faculdade de Medicina Veterinária e Zootecnia UNESP Faculdade de Medicina Veterinária e Zootecnia