Search

Your search keyword '"Costa, Ana Cristina"' showing total 115 results
Start Over Author "Costa, Ana Cristina" Journal materials science forum
115 results on '"Costa, Ana Cristina"'

20. Microstructural and Mechanical Properties of Al2O3/HAp Composites for Use as Bone Substitute Material

Author

de Lima, Marcelino Guedes, Leal, Elvia, Agnolon Pallone, Elíria Maria de Jesus, Kiminami, Ruth Herta Goldsmith Aliaga, and Costa, Ana Cristina Figueiredo de Melo

Abstract

This work involved the development of alumina/hydroxyapatite (Al2O3/HAp) composites for use as bone graft material in maxillofacial reconstruction. The effect of introducing 20 and 30 wt% of hydroxyapatite into the alumina matrix was also investigated. The composites were produced from hydroxyapatite synthesized by the precipitation method, using commercial alumina as a matrix. Samples of the composite material were compacted under 260 MPa of isostatic pressure, followed by sintering at 1200°C/2h and characterization by X-ray diffraction (XRD), scanning electron microscopy (SEM), and diametral compression. The XRD results confirmed the presence of Al2O3 and Ca10(PO4)6(OH)2 – HAp crystalline phases in all composites. The addition of HAp to the alumina matrix inhibited alumina grain growth, reducing intergranular porosity and thus promoting greater densification and mechanical strength of the composites.

Published
2018
Full Text
View/download PDF

21. Biodiesel from Fatty Acids Found in Brazilian Native Cultures as Soybean and Cotton Using the Nanocatalyst Ni0.5Zn0.5Fe2O4

Author

Dantas, Joelda, Leal, Elvia, Feitosa, Alex Cavalcanti, Vasconcelos, Erik Vilar, and Costa, Ana Cristina Figueiredo de Melo

Abstract

Biodiesel is a biodegradable fuel derived from renewable biomass, such as soybean and cottonseed oil, which may be obtained by different processes and requires a material to catalyze the obtaining reactions. The irons spinel comes overlapping as excellent materials to catalyze the biodiesel production reactions. Thus, the purpose of this work was the use of Ni0.5Zn0.5Fe2O4 nanoferrite as a catalyst in esterification reactions. The nanoferrite was synthesized by combustion in large scale, 200g/batch, where time and the temperature of the reactions were measured, and characterized by XRD and measuring its surface area. The biodiesel was obtained from methyl and ethyl esterification of acidified soybean oil and cottonseed, at a temperature of 160°C for 1 hour, molar ratio 1:15, 3% of catalyst and analyzed by chromatography. The nanoferrite has shown peaks of greater intensity corresponding to a majority crystal phase of the spinel and a surface area of ​​64.17m2/g. The conversion results for the soybean oil were 99.08% in methyl route and 98.38% in ethyl route. For cottonseed oil were 88.79% in methyl route and 78.65% in ethyl route.

Published
2018
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results