ELECTROLUMINESCENCE AND PHOTOLUMINESCENCE OF GAAS IN AQUEOUS REDOX ELECTROLYTES

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Fabrication and characterization of calcium phosphate cement foams: evaluation of emulsion and gelcasting methods

In Tissue Engineering, the need for scaffolds which are capable of guiding the organization, differentiation and growth of cells leading to the formation of new tissues is highly relevant. For the development of new scaffolds focused on bone tissue therapy, calcium phosphate cements (CPC) have great potential, because besides their resorbability, they present morphology and chemical composition similar to the bone mineral phase. Moreover, there are several processing techniques to produce ceramic scaffolds: polymeric sponge replication, incorporation of organic material into the ceramic powder, gelcasting, emulsion, among others. The aim of this work was to obtain CPCs foams by using two processing routes, emulsion and gelcasting. The foams were characterized by their physical and mechanical properties and the crystalline phases formed after the setting reaction of cement were determined by X-ray diffraction. The samples obtained by both methods presented porosity between 58-62% and the microstructure consists of nearly spherical pores (d50 = 50-100 µm). The mechanical strength of the samples ranged from 5.5 to 1.5 MPa. The crystalline phases found were monetite (CaHPO4) and brushite (CaHPO4 2H2O).Em Engenharia Tecidual, a fabricação de scaffolds capazes de guiar o crescimento, a organização e a diferenciação de células no processo de formação de novos tecidos apresenta grande relevância. Várias são as técnicas de processamento para a fabricação desta classe de material: réplica de esponjas poliméricas, incorporação de material orgânico ao pó cerâmico, gelcasting, emulsão, entre outras. Na fabricação de scaffolds focados na terapia de tecidos ósseos, os cimentos de fosfato de cálcio (CFC) apresentam grande destaque, pois além de reabsorvíveis, apresentam morfologia e composição química semelhante à fase mineral óssea. Este trabalho tem como objetivo a obtenção de espumas de CFC por meio de duas rotas de processamento, emulsão e gelcasting. As espumas foram caracterizadas quanto suas propriedades físicas e mecânicas e as fases cristalinas formadas após a cura do cimento foram determinadas por difração de raios X. As amostras obtidas por ambos os métodos apresentaram porosidade entre 58-62% e microestrutura constituída de poros aproximadamente esféricos (d50=50-100 µm). A resistência mecânica das amostras variou entre 5,5-1,5 MPa. As fases cristalinas encontradas foram monetita (CaHPO4) e brushita (CaHPO4 2H2O).50050

Exchange bias in Fe/EuTe(111) bilayers

We report on the investigation of the exchange bias effect in Fe layers on EuTe(111), an antiferromagnetic semiconductor. For this ferromagnet (FM)/semiconducting antiferromagnet (AFM) exchange bias system, we have found positive and negative exchange bias effect (EB). Fresh samples exhibit positive EB, independently of the applied cooling field, indicating antiferromagnetic coupling between the FM and the AFM layers at the Fe/EuTe(111) interface. The change in EB with time, from positive EB for fresh samples to negative EB after short time,is attributed to aging effects at the Fe/EuTe interface. (c) 2007 American Institute of Physics.102

Synthesis Of Casio3 "whiskers" In Alkaline Salt Flux For Biomaterials Reinforcement [síntese De "whiskers" De Casio3 Em Fluxo Salino Para Elaboração De Biomateriais]

Materials reinforcement by ceramic whiskers has been employed for a long time in a variety of industrial applications. Nevertheless, the materials by which these whiskers are commonly made of (carbide and silicon nitride) do not allow their use in biomaterials field due to their high toxicity. Then, it is of interest to synthesize ceramic whiskers which could reinforce biocompatible ceramic and polymeric biomaterials without harming the patients' health. In this manner, the aim of this work is to propose and analyze the limiting process variables of a new synthetic route to produce whiskers of CaSiO3 (wollastonite): a biocompatible, bioactive and readsorbable biomaterial. It was employed the molten salt synthesis at 900 °C to grow wollastonite crystals which were characterized by X-ray diffraction and scanning electron microscopy. The proposed method was efficient in growing whiskers; however, the dwell time was not sufficient to guarantee a 100% reaction yield, leading to the formation of cristobalite.58348504508Xu, H.H.K., Martin, T.A., Antonucci, J.M., Eichmiller, E.C., (1999) J. Dental Res., 78, p. 706Xu, H.H.K., Smith, D.T., Simon, C.G., (2004) Biomater, 25, p. 4615Jalota, S., Bhaduri, S.B., Tas, A.C., (2006) J. Biomedica Mater. Res. Part A, 78 (3), p. 481Dos Santos, L.A., De Oliveira, L.C., Rigo, E.C.S., Carrodeguas, R.G., Boschi, A.O., Arruda, A.C.F., (2000) Artificial Organs, 24, p. 212Dos Santos, L.A., Carrodeguas, R.G., Boschi, A.O., Arruda, A.C.F., (2003) J. Biomedical Mater. Res. Part A, 65, p. 244Müller, F.A., Gbureck, U., Kasuga, T., Mizutani, Y., Barralet, J.E., Lohbauer, U., (2007) J. Am. Ceram. Soc., 90, p. 3694Ohura, K., Nakamura, T., Yamamuro, T., Kokubo, T., Ebisawa, T., Kotoura, Y., Oka, M., (1992) J. Mater. Sci.: Mater. Medicine, 3, p. 95Nonami, T., (1995) J. Soc. Mater. Eng. Res. Jap., 8, p. 12De Aza, P.N., Guiten, F., Aza, S.D., (1994) Scripta Mater., 31, p. 1001Pernot, F., Zarzycki, J., Rabischong, P., Baldet, P., (1979) J. Mater. Sci., 14, p. 1694De Aza, P.N., Guitian, F., Merlos, A., Lora-Tamayo, E., De Aza, S., (1996) J. Mater. Sci.: Mater. Medicine, 7, p. 399Kobayashi, M., Petrykin, V., Kakihana, M., Tomita, K., (2009) J. Am. Ceram. Soc., 92, pp. S21Kandori, K., Horigami, N., Yasukawa, A., Ishikawa, T., (1997) J. Am. Ceram. Soc., 80, p. 1157Lin, K., Chang, J., Lu, J., (2006) Mater. Lett., 60, p. 3007Yoshimura, M., Suda, H., Okamoto, K., Ioku, K., (1994) J. Mater. Sci., 29, p. 3399Hayashi, S., Sugai, M., Nakagawa, Z., Takei, T., Kawasaki, K., Katsuyama, T., Yasumori, A., Okada, K., (2000) J. Eur. Ceram. Soc., 20, p. 1099Yoon, K.H., Cho, Y.S., Kang, D.H., (1998) J. Mater. Sci., 33, p. 2977Afanasiev, P., Geantet, C., (1998) Coord. Chem. Rev., 178-180, p. 1725Tas, A.C., (2001) J. Am. Ceram. Soc., 84 (2), p. 295Motisuke, M., Carrodeguas, R.G., Zavaglia, C.A.C., (2008) Key Eng. Mater., 361-363, p. 199. , (Rec. 11/04/2011, Rev. 25/06/2011, Ac. 04/11/2011

A Comparative Study Between α-tcp And Si-α-tcp Calcium Phosphate Cement

On this study the influence of silicon dopping on the properties of the final calcium phosphate cement were analysed and compared to the ones of the conventional Si and Mg-free αTCP cement. In spite of silicon doping, Si-α-TCP calcination temperature (1400°C) was higher than the one used for conventional a-TCP (1300°C) as a result of Mg contamination on the commercial precursor used on the Si-α-TCP synthesis. Because of the high temperature used, Si-α-TCP sample was difficult to mill. Even after 1 week milling, the particle size achieved was 12μm while Si-free α-TCP reached 7.7μm. Consequently, the reactivity of both powders was different. In conclusion, the properties of Si-αα-TCP cement were not satisfactory for clinical application. In order to do it so, it is essential to enhance the powder reactivity by reducing Mg contamination, lowering the sintering temperature and reducing the particle size to, then, achieve the desired reactivity and compressive strength.396-398201204Dorozhkin, S.V., (2008) J Mater. Sci, 43, p. 3028Pietak, A.M., et., Al., (2007) Biomaterials, 28, p. 4023Langstaff, S., et., al., (1999) Biomaterials, 20, p. 1727Langstaff, S., et., al., (2001) Biomaterials, 22, p. 135Reid, J.W., et., al., (2005) Biomaterials, 26, p. 2887Reid, J.W., et., al., (2006) Biomaterials, 27, p. 2916Fernández, E., et., al., (1995) Proceedings of the 4th Euro Ceramics Conference, p. 103Camiré, C.L., et., al., (2006) J. Biomed. Mater. Res. Part B: Appl. Biomater, 76 B, p. 424Arcos, D., et., al., (2006) J. Biomed. Mater. Res. Part A, 78 A, p. 762Carrodeguas, R.G., et., al., (2008) Key Eng. Mater, 361-363, p. 237Motisuke, M., et., al., (2008) Key Eng. Mater, 361-363, p. 199Reid, J.W., et., al., (2007) Mater. Lett, 61, p. 3851Carrodeguas, R.G., et., al., (2008) J Amer. Ceram. Soc, 91, p. 1281Cullity, B.D., (1977) Elements of X-Ray Diffraction, , Addion-Wesley Publishing Company, In