Browsing by Author "Campillo, I."
Now showing 1 - 20 of 25
Results Per Page
Sort Options
Item Atomic force microscopy and nanoindentation of cement pastes with nanotube dispersions(2006-05) Sáez De Ibarra, Y.; Gaitero, J. J.; Erkizia, E.; Campillo, I.; Centros PRE-FUSION TECNALIA - (FORMER); Tecnalia Research & Innovation; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓNSince their discovery in 1991 by Iijima [1], carbon nanotubes (CNTs) have probably become the most promising nanomaterials due to their unique mechanical, electronic and chemical properties. Our aim is to improve the mechanical properties of cement pastes by the addition of CNTs, giving rise to a new and higher-performance composite material. To reach an efficient cement-based composite with nanotubes, we have studied the addition of different CNT concentrations in the mix design in order to obtain enhanced mechanical properties with respect to plain cement pastes. We have measured the micro-hardness and Young's modulus of the composites by nanoindenting with a sharp diamond three-sided pyramidal tip mounted on an Atomic Force Microscope probe. These measurements have been correlated with the average macroscopic Young's modulus.Item Comment on "A waveguide slit array antenna fabricated with subwavelength periodic grooves Appl. Phys. Lett. 91 143512 (2007)"(2008) Beruete, M.; Falcone, F.; Sorolla, M.; Campillo, I.; Dolado, J. S.; Rodríguez-Seco, J. E.; Perea, E.; Tecnalia Research & Innovation; POWER SYSTEMS; DIGITAL ENERGYItem Comments on "a high-gain antenna consisting of two slot elements with a space larger than a wavelength"(2010) Beruete, M.; Campillo, I.; Dolado, J. S.; Rodríguez-Seco, J. E.; Perea, E.; Falcone, F.; Sorolla, M.; Tecnalia Research & Innovation; POWER SYSTEMS; DIGITAL ENERGYItem Dual-band low-profile corrugated feeder antenna(2006-02) Diaz, Miguel Beruete; Campillo, I.; Dolado, J. S.; Rodríguez-Seco, J. E.; Perea, E.; Falcone, Francisco; Ayza, Mario Sorolla; Tecnalia Research & Innovation; POWER SYSTEMS; DIGITAL ENERGYA dual-operating-band planar horn antenna having very low profile is presented in this paper. By opening a subwavelength aperture into a corrugated conducting plate, good return losses and a narrow radiated beam in each of the two desired operating frequency bands can be measured. This behavior is very similar to that observed in optical wavelengths where enhanced transmission was measured through apertures etched in metallic corrugated plates. Here, the double-corrugated structure has been scaled into the microwave frequency range and the excitation has been done by a conventional closed metallic waveguide placed in the rear part of the structure. In this way, a new concept of a very low profile feeder is proposed with potential wireless applications.Item Enhanced gain by double-periodic stacked subwavelength hole array(2007-12) Beruete, M.; Campillo, I.; Rodríguez-Seco, J. E.; Perea, E.; Navarro-Cía, M.; Núñez-Manrique, I. J.; Sorolla, M.; POWER SYSTEMS; DIGITAL ENERGY; Equipos ElectrónicosUsing a doubly periodicity structure the extraordinary transmission of subwavelength metallic hole arrays in the microwave range can be boosted. Stacking several of such plates a left-handed metamaterial can be obtained as it is shown by the computed dispersion diagrams as well as the amplitude and phase measurements. An effective refraction index along the propagation direction can be calculated, giving a negative magnitude between -1 and 0. This enhances the emission by a focused beam with narrow beamwidth. Several practical applications like novel antennas are envisaged.Item Enhanced microwave transmission and beaming using a subwavelength slot in corrugated plate(2004-12) Beruete, M.; Campillo, I.; Dolado, J. S.; Rodríguez-Seco, J. E.; Perea, E.; Sorolla, M.; Tecnalia Research & Innovation; POWER SYSTEMS; DIGITAL ENERGYEnhanced microwave transmission and beaming through a subwavelength slot placed into a corrugated conducting plate is experimentally observed compared with the case of the single isolated slot. This phenomenon is similar to that happening for optical wavelengths where surface plasmons model is employed to describe the metal. This letter shows that the phenomenon is also present in the microwave range where perfect conductor model applies. Enhanced subwavelength transmission and beaming stimulates new research for future applications.Item Enhanced microwave transmission using a subwavelength slot in corrugated plate(2005) Beruete, M.; Campillo, I.; Dolado, J. S.; Rodríguez-Seco, J. E.; Perea, E.; Sorolla, M.; Tecnalia Research & Innovation; POWER SYSTEMS; DIGITAL ENERGYThe new phenomenon related with enhanced microwave transmission and beaming through a subwavelenght slot placed into a corrugated conducting plate has been experimentally observed, in the microwave range, compared with the case of the single isolated slot. It is very similar to that happening for optical wavelengths where surface plasmons model is employed to describe the metal. The phenomenon is also present in the microwave range where perfect conductor model applies. Future applications in antennas can be possible.Item Enhanced millimeter wave transmission through quasioptical subwavelength patterned structures(2004) Beruete, M.; Sorolla, M.; Campillo, I.; Dolado, J. S.; Martín-Moreno, L.; García-Vidal, F. J.; Tecnalia Research & InnovationWe show that the phenomenon of extraordinary transmission though arrays of subwavelength holes is also present in the microwave range as it occurs in the optical regime. Following simulations of the influence of the number of holes, a prototype has been designed and fabricated in an Aluminum plate. By using a Millimeter Wave Quasioptical Vector Network Analyzer in the range between 40 GHz and 110 GHz, measurements of the transmission response has been performed. A resonant total transmission at wavelengths close to the period of the array appear in the spectra. Moreover, an structure consisting of a single narrow slit flanked by a finite array of grooves is now under consideration. All these structures operating in the subwavelength regime are opening the possibility of exciting future applications.Item Enhanced millimeter wave transmission through quasioptical subwavelength perforated plates(2005-06) Beruete, Miguel; Sorolla, Mario; Campillo, I.; Dolado, J. S.; Martín-Moreno, Luis; Bravo-Abad, J.; García-Vidal, F. J.; Tecnalia Research & InnovationIn this paper, we show that the phenomenon of extraordinary transmission through arrays of subwavelength holes, present in the optical regime, is also present in the millimeter wave range. After presentation of the theoretical foundations of the enhanced transmission, measurements of the transmission response have been performed on different samples by using a millimeter wave quasioptical vector network analyzer in the range between 45 and 110 GHz. The prototypes have been fabricated in Aluminum plates with several thickness and different hole diameters drilled by using a laser machine. Good agreement between theory and experiment is obtained, with clear signals of the existence of resonant transmission at wavelengths close to the period of the array. Possible applications in frequency selective surfaces and near-field imaging are envisaged.Item Enhanced millimeter-wave transmission through subwavelength hole arrays(2004-11-01) Beruete, M.; Sorolla, M.; Campillo, I.; Dolado, J. S.; Martín-Moreno, L.; Bravo-Abad, J.; García-Vidal, F. J.; Tecnalia Research & InnovationWe explore, both experimentally and theoretically, the existence in the millimeter-wave range of the phenomenon of extraordinary light transmission through arrays of subwavelength holes. We have measured the transmission spectra of several samples made on aluminum wafers by use of an AB Millimetre quasi-optical vector network analyzer in the wavelength range 4.2-6.5 mm. Clear signals of the existence of resonant light transmission at wavelengths close to the period of the array appear in the spectra.Item High calcium coal fly ash as raw material for synthesizing new low-energy cements(American Concrete Institute, 2004-05-01) Goni, S.; Guerrero, A.; Lorenzo, M. P.; Moragues, A.; Campillo, I.; Dolado, J. S.; Malhotra, V.Mohan; Tecnalia Research & InnovationStudies on the viability of high calcium fly ash from coal combustion are being conducted in our laboratory to produce a new kind of low-energy cement. The process presents important environmental advantages, such as a reduction of C02 emission compared to that produced by the conventional technology of portland cement manufacture. Furthermore, the processing temperature is also considerably reduced. The low-energy cement shows potential for good hydraulic activity for application in construction. The changes of fly ash composition were followed by X-Ray Diffraction (XRD), F f Infrared (FTIR) spectroscopy and BET surface area analysis.Item Improvement of initial mechanical strength by nanoalumina in belite cements(2007-04) Campillo, I.; Guerrero, A.; Dolado, J. S.; Porro, A.; Ibáñez, J. A.; Goñi, S.; Tecnalia Research & Innovation; TRAZABILIDAD CIRCULARThe development of new environmentally friendly and energy efficient cements such as belite cements are being promoted due the environmental problems related to CO2 emissions in the manufacture of Portland cement. Although long-term hydrated belite cements show comparable and even better mechanical strength to ordinary Portland hydrated cements, they have low initial mechanical strength, which limits their applicability. In this work we analyse the potential of nanomaterials for activation of the initial strength of belite cements. Different nanoparticles are added to belite cement and both the microstructure modification of the resulting paste and the mechanical properties at early ages are studied. Our results show that the addition of nanoparticles can overcome the drawbacks of this type of eco-efficient cements making them competitive to OPC.Item Increase of the transmission in cut-off metallic hole arrays(2005-02) Beruete, M.; Sorolla, M.; Campillo, I.; Dolado, J. S.; Tecnalia Research & InnovationIn this letter, the phenomenon of extraordinary transmission through arrays of subwavelength holes in the microwave range is demonstrated. It is also shown that the magnitude of the transmission is strongly dependent on the number of holes in the sample. Prototypes have been designed and fabricated in an Aluminum plate. The transmission response is measured with a millimeter wave quasi-optical vector network analyzer in the range between 40 and 70 GHz. These measurements show a resonant total transmission at wavelengths close to the period of the array which depends strongly on the number of resonant holes. These results can give rise to interesting applications such as frequency selective surfaces and other quasi-optical structures.Item Low profile antenna feeders based of enhanced microwave transmission through a narrow slot on a corrugated plane(2006-05) Beruete, M.; Campillo, I.; Dolado, J. S.; Rodríguez-Seco, J. E.; Perea, E.; Falcone, F.; Sorolla, M.; Tecnalia Research & Innovation; POWER SYSTEMS; DIGITAL ENERGYIn this work, several antenna prototypes based on the Extraordinary Optical Transmission phenomenon are developed. They all share in common the property of being all-metallic, flat and low profile. The radiation of a central slot is boosted by texturing the output metallic plane. Enhancement depends directly on the number of grooves carved. Thus, a rich variety in the farfield response can be obtained changing the number of corrugations. Among the prototypes a dual-operating-band planar horn antenna with low profile is presented. It is also seen that by giving the structure rotational simmetry the gain can be increased, resulting in the high-gain Bull's-Eye antenna. Other approaches related with the perturbation profile are under development. The behavior of the current prototypes is very similar to those reported in optics. In this way, a new concept of a very low profile feeder is proposed with potential wireless applications.Item Low-profile corrugated feeder antenna(2005) Beruete, M.; Campillo, I.; Dolado, J. S.; Rodriguez-Seco, J. E.; Perea, E.; Falcone, F.; Sorolla, M.; Tecnalia Research & Innovation; POWER SYSTEMS; DIGITAL ENERGYA very low-profile planar rectangular horn antenna made of a subwavelength aperture surrounded by two grooves on the conducting plate is presented. This structure exhibits good return losses and radiated beam. Its operation is based upon enhanced transmission and beaming through apertures in metallic corrugated plates. Here, the corrugated structure is designed to operate in microwaves and, moreover, a waveguide flange, which has been properly mechanized in the rear part of the structure, is employed for excitation. A new very low-profile planar feeder with reduced size is introduced that could be properly scaled for potential wireless applications.Item Phase response of cut-off metallic hole arrays(2005) Beruete, M.; Campillo, I.; Dolado, J. S.; Sorolla, M.; Lomakin, V.; Michielsen, E.; Tecnalia Research & InnovationItem Reduction of the calcium leaching rate of cement paste by addition of silica nanoparticles(2008-08) Gaitero, J. J.; Campillo, I.; Guerrero, A.; Tecnalia Research & InnovationCalcium leaching is a degradation process that consists in the progressive dissolution of the cement paste as a consequence of the migration of the calcium ions to the aggressive solution. Although it is a well known phenomenon, a way of reducing it has not been found yet. The aim of this work is to prove how the addition of small amounts of silica nanoparticles to the cement paste can induce such reduction. The experimental results obtained have shown that nanosilica increases the strength of the cement paste about a 30% in cured samples and more than a 100% in the asymptotically leached ones. At the level of the structure of the C-S-H gel, silica nanoparticles increase the average length of the silicate chains and reduce their polymerization as calcium dissolves. An important decrease of the degradation in terms of porosity and amount of calcium lost has also been observed.Item Silica nanoparticle addition to control the calcium-leaching in cement-based materials(2006-05) Gaitero, J. J.; De Ibarra, Y. Sáez; Erkizia, E.; Campillo, I.; Tecnalia Research & Innovation; Centros PRE-FUSION TECNALIA - (FORMER); ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓNThe calcium leaching of the cement hydrated matrix is of vital importance for constructions like water containers, dams, bridges, etc which have to be in contact with water during their lifetime. The aim of this work is the study of the reduction of such a negative phenomenon by the addition of silica nanoparticles. Several characterisation techniques such as 29Si MAS NMR, X-ray diffraction, mercury intrusion porosimetry and EDX-microanalysis have been used to evaluate the effect of the nanoparticles in the cement matrix nanostructure and in their impact on the evolution of the Ca leaching throughout time. Subsequent analysis of the results indicates that silica nanoparticles can reduce the Ca-leaching both decreasing the amount of portlandite in the matrix and controlling the degradation rate of the C-S-H gel.Item Silicate chain formation in the nanostructure of cement-based materials(2007) Ayuela, A.; Dolado, J. S.; Campillo, I.; De Miguel, Y. R.; Erklzia, E.; Sánchez-Portal, D.; Rubio, A.; Porro, A.; Echenique, P. M.; Tecnalia Research & Innovation; Tecnología; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓNCement-based materials are ubiquitous in almost all built environment. In spite of this, little is known about the formation and the role played by the silicate chains always present in the cement nanostructure. By means of first principles simulations we provide compelling evidence on the pivotal role played by certain ionic species in the formation of the silicate chains inside the cementitious matrix. Moreover, we corroborate the experimental evidence which shows that the length of the most stable chains with m Si atoms follows a magic-number sequence: m=3n-1 with n=1,2,... Our results have been applied in the development of new higher performance cement-based materials by adding nanosilica.Item Site and lattice resonances in metallic hole arrays(2006-01-09) García De Abajo, F. J.; Sáenz, J. J.; Campillo, I.; Dolado, J. S.; Tecnalia Research & InnovationA powerful analytical approach is followed to study light transmission through subwavelength holes drilled in thick perfect-conductor films, showing that full transmission (100%) is attainable in arrays of arbitrarily narrow holes as compared to the film thickness. The interplay between resonances localized in individual holes and lattice resonances originating in the array periodicity reveals new mechanisms of transmission enhancement and suppression. In particular, localized resonances obtained by filling the holes with high-index-of-refraction material are examined and experimentally observed through large enhancement in the transmission of individual holes.