Publications

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Book
Pedrosa, A., M. C. Lanca, J. P. Borges, E. R. Neagu, C. J. Dias, J. N. Marat-Mendes, and Ieee, Influence of Polarization on the Bioactivity of Nanopowders of Hydroxyapatite, , pp. 55-56, 2011. AbstractWebsite
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Book Chapter
Lanca, M. C., S. Peuckert, E. R. Neagu, L. Gil, P. C. Silva, and J. Marat-Mendes, "Electrical Properties Studies of a Cork/TetraPak (R)/Paraffin Wax Composite", Advanced Materials Forum Iv, vol. 587-588, pp. 613-617, 2008. Abstract

Lately the electrical and dielectric properties of cork and some cork-based materials (commercial and non-commercial) have been studied in order to understand their ability to store electrical charge. The main problem found so far is related to the water content in cork, only of a few % weight. but large enough to influence greatly the conductivity of cork and, consequently, the charge storage capability. To overcome this problem cork has been combined with hydrophobic materials. In this work a commercial wax (paraffin wax) was used to produce a cork/paraffin composite by hot pressing. After milled and mixed natural cork. TetraPak (R) containers waste and paraffin were pressed to make plaques of a new composite. Different concentrations of cork. TetraPak (R) and paraffin, different granules sire, different temperature and pressure were used to produce the samples. The electrical properties of the new composite were measured by the isothermal charging and discharging current method and the results compared to previously ones obtained for natural cork and other derivative products. The new composite has shown to have lower conductivity than the commercial agglomerate. which makes it a better material for charge storage.

Lanca, C. M., S. Peuckert, E. R. Neagu, L. Gil, P. C. Silva, and J. Marat-Mendes, "Electrical Properties Studies of a Cork/TetraPak (R)/Paraffin Wax Composite", Advanced Materials Forum Iv, vol. 587-588, pp. 613-617, 2008. Abstract

Lately the electrical and dielectric properties of cork and some cork-based materials (commercial and non-commercial) have been studied in order to understand their ability to store electrical charge. The main problem found so far is related to the water content in cork, only of a few % weight. but large enough to influence greatly the conductivity of cork and, consequently, the charge storage capability. To overcome this problem cork has been combined with hydrophobic materials. In this work a commercial wax (paraffin wax) was used to produce a cork/paraffin composite by hot pressing. After milled and mixed natural cork. TetraPak (R) containers waste and paraffin were pressed to make plaques of a new composite. Different concentrations of cork. TetraPak (R) and paraffin, different granules sire, different temperature and pressure were used to produce the samples. The electrical properties of the new composite were measured by the isothermal charging and discharging current method and the results compared to previously ones obtained for natural cork and other derivative products. The new composite has shown to have lower conductivity than the commercial agglomerate. which makes it a better material for charge storage.

Lanca, C. M., S. Peuckert, E. R. Neagu, L. Gil, P. C. Silva, J. Marat-Mendes, A. T. Marques, A. F. Silva, A. P. M. Baptista, C. Sa, F. J. L. A. Alves, L. F. Malheiros, and M. Vieira, "Electrical Properties Studies of a Cork/TetraPak (R)/Paraffin Wax Composite", Advanced Materials Forum Iv, vol. 587-588, pp. 613-617, 2008. Abstract
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Lanca, M. C., I. Cunha, J. P. Marques, E. R. Neagu, L. Gil, C. J. Dias, and J. N. Marat-Mendes, "Water Content Control To Improve Space Charge Storage in a Cork Derivative", Advanced Materials Forum Vi, Pts 1 and 2, vol. 730-732, pp. 395-400, 2013. Abstract
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Conference Paper
ER, N., D. CJ, L. MC, I. R, I. P, and M. - M. JN, "Charge Carriers Injection/Extraction at the Metal-Polymer Interface and Its Influence in the Capacitive Microelectromechanical Systems-Switches Actuation Voltage", JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, vol. 10: Univ Nova Lisboa, pp. 2503-2511, Jan, 2010. Abstract
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R., N. E., C. Dias, L. M. Carmo, I. R., I. P., and M. - M. J. N., Discrimination between Space Charge and Dipolar Contributions in Ferroelectric Polymers, , pp. 145-146, Jan, 2011. Abstract
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R., N. E., C. Dias, L. M. Carmo, I. R., I. P., and M. - M. J. N., "Discrimination between Space Charge and Dipolar Contributions in Ferroelectric Polymers", 14th International Symposium on Electrets, 2011. Abstract

The final thermally stimulated discharge current method allows a better selection of the experimental conditions for sample polarization. By decreasing the ratio between the charging time and the discharging time, the apparent peak is of the same order of magnitude as the genuine peaks and there is only a partial overlap between then. Two peaks have been identified for polyamide 11, one associated with the glass transition around 60 °C and the second associated with the Curie transition around 96 °C.

ER, N., N. RM, D. CJ, L. MC, I. P, and M. - M. JN, Electrical Method to Study the Weak Molecular Movements at Nanometric Scale in Low Mobility Materials, , vol. 636-637, pp. 430-436, Jan, 2010. Abstract
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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. Abstract
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A., P., L. A. N. Ç. A. M.C., B. J.P., N. E. A. G. U. E.R., D. I. A. S. C.J., Marat-Mendes, and J.N., "Influence of Polarization on the Bioactivity of Nanopowders of Hydroxyapatite", 14th International Symposium on Electrets, 2011. Abstract
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ER, N., D. CJ, L. MC, I. R, I. P, and M. - M. JN, On the width of the thermally stimulated discharge current peak, , Jan, 2010. Abstract
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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. Abstract
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Dias, I. J. G. J. G., A. S. S. Pádua, E. Pires, J. P. M. R. Borges, J. C. Silva, and M. C. Lança, "TSDC and surface potential measurements of charged hydroxyapatite/BaTiO 3 biocoatings deposited by CoBlast", ISE19-19th Int Symp on Electrets, 18-22 Sept., Linz, Austria, Johannes Kepler Univ., pp. 77, 2023. Abstract

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Inês, C., M. J. Paulo, G. Luís, N. E. R., D. C. J., M. - M. J. N., and L. M. C., Water Content Control to Improve Space Charge Storage in a Cork Derivative, , pp. 395-400, Jan, 2012. Abstract
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Inês, C., M. J. Paulo, G. Luís, N. E. R., D. C. J., M. - M. J. N., and L. M. C., "Water Content Control to Improve Space Charge Storage in a Cork Derivative", Materiais2011, 2012. Abstract
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Journal Article
Lanca, M. C., S. Peuckert, E. R. Neagu, L. Gil, P. C. Silva, and J. Marat-Mendes, "Electrical Properties Studies of a Cork/TetraPak (R)/Paraffin Wax Composite", Advanced Materials Forum Iv, vol. 587-588, pp. 613-617, 2008. AbstractWebsite

Lately the electrical and dielectric properties of cork and some cork-based materials (commercial and non-commercial) have been studied in order to understand their ability to store electrical charge. The main problem found so far is related to the water content in cork, only of a few % weight. but large enough to influence greatly the conductivity of cork and, consequently, the charge storage capability. To overcome this problem cork has been combined with hydrophobic materials. In this work a commercial wax (paraffin wax) was used to produce a cork/paraffin composite by hot pressing. After milled and mixed natural cork. TetraPak (R) containers waste and paraffin were pressed to make plaques of a new composite. Different concentrations of cork. TetraPak (R) and paraffin, different granules sire, different temperature and pressure were used to produce the samples. The electrical properties of the new composite were measured by the isothermal charging and discharging current method and the results compared to previously ones obtained for natural cork and other derivative products. The new composite has shown to have lower conductivity than the commercial agglomerate. which makes it a better material for charge storage.

Hammami, I., S. R. Gavinho, A. S. Pádua, M. C. do Lança, J. P. Borges, and J. C. Silva, "Extensive Investigation on the Effect of Niobium Insertion on the Physical and Biological Properties of 45S5 Bioactive Glass for Dental Implant", International Journal of Molecular Sciences, vol. 24, issue 6, pp. 5244-5263, 2023.
Dias, I. J. G., S. A. Pádua, E. A. Pires, J. P. M. R. Borges, J. C. Silva, and C. M. Lança, "Hydroxyapatite-Barium Titanate Biocoatings Using Room Temperature Coblasting", Crystals 2023, Vol. 13, Page 579, vol. 13, no. 4: Multidisciplinary Digital Publishing Institute, pp. 579, mar, 2023. AbstractWebsite

The use of orthopaedic and dental implants is expanding as a consequence of an ageing population and also due to illness or trauma in younger age groups. The implant must be biocompatible, bioactive and interact favourably with the recipient's bone, as rapid osseointegration is key to success. In this work, Ti-6Al-4V plates were coated using the CoBlastTM technique, with hydroxyapatite (HAp) and HAp/BaTiO3 (barium titanate, BT) non-piezoelectric cubic nanopowders (HAp/cBT) and piezoelectric tetragonal micropowders (HAp/tBT). The addition of BT, a piezoelectric ceramic, is a strategy to accelerate osseointegration by using surface electric charges as cues for cells. For comparison with commercial coatings, plates were coated with HAp using the plasma spray technique. Using XRD and FTIR, both plasma spray and CoBlastTM coatings showed crystalline HAp and no presence of by-products. However, the XRD of the plasma-sprayed coatings revealed the presence of amorphous HAp. The average surface roughness was close to the coatings' thickness (≈5 $μ$m for CoBlastTM and ≈13 $μ$m for plasma spray). Cytotoxicity assays proved that the coatings are biocompatible. Therefore, it can be concluded that for HAp-based coatings, CoBlastTM is a viable alternative to plasma spray, with the advantage of facilitating room temperature addition of other ceramics, like piezoelectric BaTiO3.

Pedrosa, A., M. C. Lanca, J. P. Borges, E. R. Neagu, C. J. Dias, J. N. Marat-Mendes, and Ieee, "Influence of Polarization on the Bioactivity of Nanopowders of Hydroxyapatite", 2011 14th International Symposium on Electrets (Ise), pp. 55-56, 2011. Abstract
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P, J., L. MC, M. - M. S. J, and R. J, "Pore dimension of water trees in PE: NMR studies", POLYMER, vol. 41: Univ Paris 11, Univ Nova Lisboa, Univ Paris 11, Univ Paris 11, pp. 8151-8154, Jan, 2000. Abstract
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Prezas, P. R., B. M. G. Melo, L. C. Costa, M. A. Valente, M. C. Lança, J. M. G. Ventura, L. F. V. Pinto, and M. P. F. Graça, "TSDC and impedance spectroscopy measurements on hydroxyapatite, β-tricalcium phosphate and hydroxyapatite/β-tricalcium phosphate biphasic bioceramics", Applied Surface Science, vol. 424, issue 1, pp. 28-38, 2017. Abstract

Bone grafting and surgical interventions related with orthopaedic disorders consist in a big business, generating large revenues worldwide every year. There is a need to replace the biomaterials that currently still dominate this market, i.e., autografts and allografts, due to their disadvantages, such as limited availability, need for additional surgeries and diseases transmission possibilities. The most promising replacement materials are biomaterials with bioactive properties, such as the calcium phosphate-based bioceramics group. The bioactivity of these materials, i.e., the rate at which they promote the growth and directly bond with the new host biological bone, can be enhanced through their electrical polarization.In the present work, the electrical polarization features of pure hydroxyapatite (Hap), pure β-tricalcium phosphate (β-TCP) and biphasic hydroxyapatite/β-tricalcium phosphate composites (HTCP) were analyzed by measuring thermally stimulated depolarization currents (TSDC). The samples were thermoelectrically polarized at 500. °C under a DC electric field with a magnitude of 5. kV/cm. The biphasic samples were also polarized under electric fields with different magnitudes: 2, 3, 4 and 5. kV/cm. Additionally, the depolarization processes detected in the TSDC measurements were correlated with dielectric relaxation processes observed in impedance spectroscopy (IS) measurements.The results indicate that the β-TCP crystalline phase has a considerable higher ability to store electrical charge compared with the Hap phase. This indicates that it has a suitable composition and structure for ionic conduction and establishment of a large electric charge density, providing great potential for orthopaedic applications.

ER, N., D. CJ, L. MC, I. R, I. P, and M. - M. J. N., The use of the final thermally stimulated discharge current technique to study the molecular movements around glass transition, , vol. 354, pp. 385-390, Jan, 2011. Abstract
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ER, N., D. CJ, L. MC, I. R, I. P, and M. - M. J. N., The use of the final thermally stimulated discharge current technique to study the molecular movements around glass transition, , vol. 354, issue 2, 2011. Abstract

During electric polarization charge is injected into the material. The structure is decorated with space charge and during the subsequent heating an apparent peak and the genuine peaks that are related to dipole randomization and charge detrapping are observed. The method is used here to analyze the molecular movements in polyimide in the temperature range from 293 to 623K. Two weak relaxations have been observed around 337K and around 402K. The electrical conductivity changes with temperature in agreement with the Arrhenius law only below (W=(0.84±0.03) eV ) and above ( W=(0.82±0.03) eV) the temperature range where the β relaxation is observed. The variation of the electrical conductivity with temperature, in the range of the β relaxation, is controlled by the variation of the charge currier mobility with temperature and it shows a non-Arrhenius behavior. We suggest that the β1 sub-glass relaxation is related to the rotation or oscillation of phenyl groups and the β2 sub-glass relaxation is related to the rotation or oscillation of the imidic ring. At higher temperatures an apparent peak was observed. The relaxation time of the trapped charge, at 573K, is high than 8895s.