M.C., L. A. N. Ç. A., N. E. A. G. U. E.R., D. I. A. S. C.J., G. I. L. L., and M. A. R. A. T. - M. E. N. D. E. S. J.N.,
Electrical properties of cork and derivatives,
, vol. 23, pp. 64-70, Jan, 2011.
Abstractn/a
M.C., L., C. I., M. J. Paulo, G. I. L. L., N. E. A. G. U. E.R., D. I. A. S. C.J., and M. - M. J. N.,
Water Content Control to Improve Space Charge Storage in a Cork Derivative,
, vol. 730-732, pp. 395-400, 2012.
Abstractn/a
M.C., L. A. N. Ç. A., N. E. A. G. U. E.R., D. I. A. S. C.J., G. I. L. L., and M. A. R. A. T. - M. E. N. D. E. S. J.N.,
Electrical properties of cork and derivatives,
, vol. 23, issue 3/4, 2011.
Abstractn/a
Madeira, R. M. D., T. Vieira, J. C. Silva, I. R. Oliveira, J. P. Borges, M. M. R. A. Lima, and C. M. Lança,
"Piezoelectric Calcium Modified Barium Titanate for Bone Regeneration",
Materials Proceedings 2022, Vol. 8, Page 121, vol. 8, no. 1, Basel Switzerland, Multidisciplinary Digital Publishing Institute, pp. 121, jul, 2022.
AbstractSolid state reaction was used to produced barium titanate modified with calcium (BCT) showing the presence of the piezoelectric tetragonal phase after sintering at 1350 °C. Bioglass 45S5 (BG) was synthetized by sol-gel route. From these two materials and commercial hydroxyapatite (HAp) were obtained composites. The BG produced showed some cytotoxic character that was weakened by passivation. All other materials were non-cytotoxic. Contact polarization at constant temperature was chosen composites polarization. Electric/dielectric properties were evaluated by thermally stimulated depolarization currents (TSDC). The material showed bioactivity with the composite with BCT/BG/HAp 90/5/5 (wt%) showing increased bioactivity. In vitro test showed high proliferation rates for the composites.
Mateo, J., M. C. Lanca, and J. Marat-Mendes,
"Infrared spectroscopy studies of aged polymeric insulators",
Advanced Materials Forum I, vol. 230-2, pp. 384-387, 2002.
AbstractThin films of low density polyethylene (LDPE) and crosslinked polyethylene (XLPE) were aged under an AC electric field while kept in sodium chloride aqueous solution. After aging the samples showed water trees (localized damaged with the appearance of hydrophilic ramified structures whose size ranges from a few microns to I mm). Some of the samples suffered dielectric breakdown showing small channels (1-2 mm. diameter) crossing the film and sometimes also signs of carbonization. In order to identify the oxidation mechanisms contributing to aging, FTIR was used to analyze both unaged and aged specimens. Comparing between unaged and aged LDPE an increase in the FTIR spectrum for bands at 1720 cm(-1), 1640 cm(-1) and 1590 cm(-1) was visible for the aged samples. The first region corresponds to carbonyl groups (C=O bonds) resulting from oxidation (most probably ketones). While the second one is related to carbon double bonds formed due to chain scission. Finally the third one is due to carboxylates. For the XLPE the analysis is more difficult. Besides aging it needs to be taken into account the by-products of crosslinking that will tend also to diffuse out with time. The main effect of aging is an increase in the concentration of 1640 cm(-1) band (C=C bonds). For the water treed regions dry and wet samples were compared. In the wet ones the absorbance is larger for the 3380 cm(-1) exhibiting, as expected, water absorption in the water treed regions (hydrophilic characteristics were increased).
Mateo, J., M. C. Lanca, and J. Marat-Mendes,
"Infrared spectroscopy studies of aged polymeric insulators",
Advanced Materials Forum I, vol. 230-2, pp. 384-387, 2002.
AbstractThin films of low density polyethylene (LDPE) and crosslinked polyethylene (XLPE) were aged under an AC electric field while kept in sodium chloride aqueous solution. After aging the samples showed water trees (localized damaged with the appearance of hydrophilic ramified structures whose size ranges from a few microns to I mm). Some of the samples suffered dielectric breakdown showing small channels (1-2 mm. diameter) crossing the film and sometimes also signs of carbonization. In order to identify the oxidation mechanisms contributing to aging, FTIR was used to analyze both unaged and aged specimens. Comparing between unaged and aged LDPE an increase in the FTIR spectrum for bands at 1720 cm(-1), 1640 cm(-1) and 1590 cm(-1) was visible for the aged samples. The first region corresponds to carbonyl groups (C=O bonds) resulting from oxidation (most probably ketones). While the second one is related to carbon double bonds formed due to chain scission. Finally the third one is due to carboxylates. For the XLPE the analysis is more difficult. Besides aging it needs to be taken into account the by-products of crosslinking that will tend also to diffuse out with time. The main effect of aging is an increase in the concentration of 1640 cm(-1) band (C=C bonds). For the water treed regions dry and wet samples were compared. In the wet ones the absorbance is larger for the 3380 cm(-1) exhibiting, as expected, water absorption in the water treed regions (hydrophilic characteristics were increased).
MC, L., W. W, N. ER, G. R, and M. - M. S. J,
"Influence of humidity on the electrical charging properties of cork agglomerates",
Journal of Non-Crystalline Solids, vol. 353, issue 47-51, 2007.
AbstractCork is a natural cellular and electrically insulating material which may have the capacity to store electric charges on or in its cell walls. Since natural cork has many voids, it is difficult to obtain uniform samples with the required dimensions. Therefore, a more uniform material, namely commercial cork agglomerate, usually used for floor and wall coverings, is employed in the present study. Since we know from our previous work that the electrical properties of cork are drastically affected by absorbed and adsorbed water, samples were protected by means of different polymer coatings (applied by spin-coating or soaking). Corona charging and isothermal charging and discharging currents were used to study the electrical trapping and detrapping capabilities of the samples. A comparison of the results leads to the conclusion that the most promising method for storing electric charges in this cellular material consists of drying and coating or soaking with a hydrophobic, electrically insulating polymer such as polytetraflouroethylene (Teflon (R)).
MC, L., P. S, N. ER, G. L, S. PC, and M. - M. S. J,
"Electrical Properties Studies of a Cork/TetraPak (R)/Paraffin Wax Composite",
Advanced Materials Forum Iv, vol. 587-588, no. 587-588, pp. 613-617, Jan, 2008.
Abstractn/a
MC, L., F. M, N. E, D. LA, M. - M. S. J, T. A, and Z. S,
"Space charge analysis of electrothermally aged XLPE cable insulation",
Journal of Non-Crystalline Solids, vol. 353, pp. 4462-4466, Jan, 2007.
Abstractn/a
MC, L., D. CJ, D. G. DK, and M. - M. S. J,
"Dielectric properties of electrically aged low density polyethylene",
Advanced Materials Forum I, vol. 230-2, no. 230-232, pp. 396-399, Jan, 2002.
Abstractn/a
MC, L., N. ER, S. P, G. L, and M. - M. S. J,
"Study of electrical properties of natural cork and two derivative products",
Advanced Materials Forum Iii, Pts 1 and 2, vol. 514-516, no. 514-516, pp. 940-944, Jan, 2006.
Abstractn/a
MC, L., W. W, N. ER, G. R, and M. - M. S. J,
"Influence of humidity on the electrical charging properties of cork agglomerates",
Journal of Non-Crystalline Solids, vol. 353, pp. 4501-4505, Jan, 2007.
Abstractn/a
MC, L., M. - M. JN, and D. LA,
"The fractal analysis of water trees - An estimate of the fractal dimension",
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION, vol. 8: Univ Nova Lisboa, Univ Leicester, pp. 838-844, Jan, 2001.
Abstractn/a
MC, L., N. ER, and M. - M. JN,
"Space charge studies of aged XLPE using combined isothermal and thermostimulated current measurements",
Cross-Disciplinary Applied Research in Materials Science and Technology, vol. 480-481, no. 480, pp. 501-505, Jan, 2005.
Abstractn/a