ABSTRACT The aim of this paper is to analyze the protective character of SixOyCz coatings deposit... more ABSTRACT The aim of this paper is to analyze the protective character of SixOyCz coatings deposited on steel. Coatings were deposited by r.f. plasma assisted chemical vapour deposition using methyltrimethoxy-silane (MTMOS) as precursor in a gaseous mixture of O2. The process is developed in two stages, first with the substrate at 500°C and in the second stage with the substrate at room temperature. The first stage is made with the mixture of O2 and MTMOS, in the second stage a potential of BIAS in the substrate without varying the mixture of gases is added shrouds of the plasma. Surface chemical and morphological characterization of coatings was carried out by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and corrosion test measurements.The corrosion protective behaviour of the film was determined by potentiodynamics polarization curves with coated probes and without coating, in 5% H2SO4 and NaCl 0.1N solution in nitrogen atmosphere, at room temperature.The new process was successful in producing coatings with good adhesion and the properties are compatible with good corrosion resistance. The deposition process and the film properties are discussed.
ABSTRACT An experimental study has been performed to identify the dominant plasma species which c... more ABSTRACT An experimental study has been performed to identify the dominant plasma species which contribute to the formation of TiN films during CVD plasma deposition. To this effect, we measured the TiN film growth rate as a function of selected process variables and determined as well the radiation emission intensity of the major plasma species and their scaling with respect to the same variables, in the bulk plasma region and in the vicinity of the substrate. On these bases we calculated the corresponding flux rates to the substrate surface for the most abundant neutral species containing titanium and nitrogen, as well as their scaling as a function of the selected process variables. The results obtained suggest that Ti atoms and metastables are the major species contributing to the supply of activated titanium and nitrogen to the substrate surface. In addition, a scaling correlation has been established between the concentration of these species in the bulk plasma and the film growth rate which supports this result.
Ion-mobility spectrometry (IMS) is an analytical technique used to separate and identify ionized ... more Ion-mobility spectrometry (IMS) is an analytical technique used to separate and identify ionized gas molecules based on their mobility in a carrier buffer gas. Such methods come in a large variety of versions that currently allow ion identification at and above the millimeter scale. Here, we present a design for a cross-flow-IMS method able to generate and detect ions at the sub-millimeter scale. We propose a novel ion focusing strategy and tested it in a prototype device using Nitrogen as a sample gas, and also with simulations using four different sample gases. By introducing an original lobular ion generation localized to a few ten of microns and substantially simplifying the design, our device is able to keep constant laminar flow conditions for high flow rates. In this way, it avoids the turbulences in the gas flow, which would occur in other ion-focusing cross-flow methods limiting their performance at the sub-millimeter scale. Scalability of the proposed design can contribute to improve resolving power and resolution of currently available cross-flow methods.
ABSTRACT This work was based on the optimization of the design of a microsystems of generation an... more ABSTRACT This work was based on the optimization of the design of a microsystems of generation and detection of the IMS (Ion Mobility Spectrometry) gas cross flow (cross flow) system. The objective was to show ingenious solutions in this field of knowledge, which simplify design, simulation and construction in a substantial way.
In this work, the tribological behavior and adhesion of SiN x films deposited by PACVD on nitride... more In this work, the tribological behavior and adhesion of SiN x films deposited by PACVD on nitrided and non-nitrided Corrax® PH stainless steel were evaluated. The films were characterized by FTIR and EDS, hardness was assessed with a nanoindenter and the microstructure was analyzed by Optical Microscopy, SEM and FIB. To evaluate the tribological behavior, fretting and linear sliding tests were performed using WC and alumina balls as counterparts, and the adhesion of the SiN x films was characterized using the Scratch Test and Rockwell C indentation methods. Erosion tests were conducted in sea water and sand flux. Corrosion behavior was evaluated by the Salt Spray Fog Test. The film reached a hardness of 2300 HV and a thickness of about 1.4 microns. The duplex coated sample had a better tribological behavior than the simple coated sample, the nitrided layer allowed a graded interlayer which improved the wear resistance. Regarding the film adhesion, the duplex coating had an acceptable adhesion; the nitrided layer reduced the interface stress and enhanced the adhesion. Additionally, the films evidenced good corrosion resistance in a saline environment.
Carbon nanotubes (CNT) are valuable for their application in nanotechnology, electrical propertie... more Carbon nanotubes (CNT) are valuable for their application in nanotechnology, electrical properties and high surface area, and in our particular case, for the manufacture of nanosensors. In this work the technique of Plasma Enhanced Chemical Vapor Deposition (PECVD) was used for the manufacture of CNT. The process was conducted in a horizontal tube reactor using methane as precursor gas and an R.F. discharge of 1000w output power acting as ionizing medium. Having achieved the synthesis of CNT on copper (Cu) substrates, heated with an internal electrical resistance to a process temperature of 900 ºC, the substrates were coated with ferric nitrate Fe(NO 3 ) 3 , which served as a catalyst and nucleation center. The heating system used differs from traditional methods by its internal heating. Growth of CNT was achieved on vertical walls on Cu substrates and perpendicular to it; a prerequisite for the manufacture of nanosensors, which is the main objective of this work, as well as to reduce as much as possible the diameter of the CNT, being its main features 5 m average length and 7 nm average diameter.
Journal of Micromechanics and Microengineering, 2013
Ion-mobility spectrometry (IMS) is an analytical technique used to separate and identify ionized ... more Ion-mobility spectrometry (IMS) is an analytical technique used to separate and identify ionized gas molecules based on their mobility in a carrier buffer gas. Such methods come in a large variety of versions that currently allow ion identification at and above the millimeter scale. Here, we present a design for a cross-flow-IMS method able to generate and detect ions at the sub-millimeter scale. We propose a novel ion focusing strategy and tested it in a prototype device using Nitrogen as a sample gas, and also with simulations using four different sample gases. By introducing an original lobular ion generation localized to a few ten of microns and substantially simplifying the design, our device is able to keep constant laminar flow conditions for high flow rates. In this way, it avoids the turbulences in the gas flow, which would occur in other ion-focusing cross-flow methods limiting their performance at the sub-millimeter scale. Scalability of the proposed design can contribute to improve resolving power and resolution of currently available cross-flow methods.
Throughout this investigation, experiments on laser ablation with silicon (Si) wafers have been p... more Throughout this investigation, experiments on laser ablation with silicon (Si) wafers have been performed using silicon nitride (Si 3 N 4 ) as a sacrificial layer to find the optimal fluence capable of removing the Si 3 N 4 , which allows the subsequent anisotropic etching in Si with potassium hydroxide. As a result, an alternative to the traditional micromachining techniques that require more steps and processing times has been introduced. The effect of the pulse numbers on Si wafers has been studied and it has been observed that when increasing the pulse numbers at the same fluence, the capacity of the pyramidal cavity formed was greater than using only one pulse at higher fluences.
ABSTRACT The aim of this paper is to analyze the protective character of SixOyCz coatings deposit... more ABSTRACT The aim of this paper is to analyze the protective character of SixOyCz coatings deposited on steel. Coatings were deposited by r.f. plasma assisted chemical vapour deposition using methyltrimethoxy-silane (MTMOS) as precursor in a gaseous mixture of O2. The process is developed in two stages, first with the substrate at 500°C and in the second stage with the substrate at room temperature. The first stage is made with the mixture of O2 and MTMOS, in the second stage a potential of BIAS in the substrate without varying the mixture of gases is added shrouds of the plasma. Surface chemical and morphological characterization of coatings was carried out by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and corrosion test measurements.The corrosion protective behaviour of the film was determined by potentiodynamics polarization curves with coated probes and without coating, in 5% H2SO4 and NaCl 0.1N solution in nitrogen atmosphere, at room temperature.The new process was successful in producing coatings with good adhesion and the properties are compatible with good corrosion resistance. The deposition process and the film properties are discussed.
ABSTRACT An experimental study has been performed to identify the dominant plasma species which c... more ABSTRACT An experimental study has been performed to identify the dominant plasma species which contribute to the formation of TiN films during CVD plasma deposition. To this effect, we measured the TiN film growth rate as a function of selected process variables and determined as well the radiation emission intensity of the major plasma species and their scaling with respect to the same variables, in the bulk plasma region and in the vicinity of the substrate. On these bases we calculated the corresponding flux rates to the substrate surface for the most abundant neutral species containing titanium and nitrogen, as well as their scaling as a function of the selected process variables. The results obtained suggest that Ti atoms and metastables are the major species contributing to the supply of activated titanium and nitrogen to the substrate surface. In addition, a scaling correlation has been established between the concentration of these species in the bulk plasma and the film growth rate which supports this result.
Ion-mobility spectrometry (IMS) is an analytical technique used to separate and identify ionized ... more Ion-mobility spectrometry (IMS) is an analytical technique used to separate and identify ionized gas molecules based on their mobility in a carrier buffer gas. Such methods come in a large variety of versions that currently allow ion identification at and above the millimeter scale. Here, we present a design for a cross-flow-IMS method able to generate and detect ions at the sub-millimeter scale. We propose a novel ion focusing strategy and tested it in a prototype device using Nitrogen as a sample gas, and also with simulations using four different sample gases. By introducing an original lobular ion generation localized to a few ten of microns and substantially simplifying the design, our device is able to keep constant laminar flow conditions for high flow rates. In this way, it avoids the turbulences in the gas flow, which would occur in other ion-focusing cross-flow methods limiting their performance at the sub-millimeter scale. Scalability of the proposed design can contribute to improve resolving power and resolution of currently available cross-flow methods.
ABSTRACT This work was based on the optimization of the design of a microsystems of generation an... more ABSTRACT This work was based on the optimization of the design of a microsystems of generation and detection of the IMS (Ion Mobility Spectrometry) gas cross flow (cross flow) system. The objective was to show ingenious solutions in this field of knowledge, which simplify design, simulation and construction in a substantial way.
In this work, the tribological behavior and adhesion of SiN x films deposited by PACVD on nitride... more In this work, the tribological behavior and adhesion of SiN x films deposited by PACVD on nitrided and non-nitrided Corrax® PH stainless steel were evaluated. The films were characterized by FTIR and EDS, hardness was assessed with a nanoindenter and the microstructure was analyzed by Optical Microscopy, SEM and FIB. To evaluate the tribological behavior, fretting and linear sliding tests were performed using WC and alumina balls as counterparts, and the adhesion of the SiN x films was characterized using the Scratch Test and Rockwell C indentation methods. Erosion tests were conducted in sea water and sand flux. Corrosion behavior was evaluated by the Salt Spray Fog Test. The film reached a hardness of 2300 HV and a thickness of about 1.4 microns. The duplex coated sample had a better tribological behavior than the simple coated sample, the nitrided layer allowed a graded interlayer which improved the wear resistance. Regarding the film adhesion, the duplex coating had an acceptable adhesion; the nitrided layer reduced the interface stress and enhanced the adhesion. Additionally, the films evidenced good corrosion resistance in a saline environment.
Carbon nanotubes (CNT) are valuable for their application in nanotechnology, electrical propertie... more Carbon nanotubes (CNT) are valuable for their application in nanotechnology, electrical properties and high surface area, and in our particular case, for the manufacture of nanosensors. In this work the technique of Plasma Enhanced Chemical Vapor Deposition (PECVD) was used for the manufacture of CNT. The process was conducted in a horizontal tube reactor using methane as precursor gas and an R.F. discharge of 1000w output power acting as ionizing medium. Having achieved the synthesis of CNT on copper (Cu) substrates, heated with an internal electrical resistance to a process temperature of 900 ºC, the substrates were coated with ferric nitrate Fe(NO 3 ) 3 , which served as a catalyst and nucleation center. The heating system used differs from traditional methods by its internal heating. Growth of CNT was achieved on vertical walls on Cu substrates and perpendicular to it; a prerequisite for the manufacture of nanosensors, which is the main objective of this work, as well as to reduce as much as possible the diameter of the CNT, being its main features 5 m average length and 7 nm average diameter.
Journal of Micromechanics and Microengineering, 2013
Ion-mobility spectrometry (IMS) is an analytical technique used to separate and identify ionized ... more Ion-mobility spectrometry (IMS) is an analytical technique used to separate and identify ionized gas molecules based on their mobility in a carrier buffer gas. Such methods come in a large variety of versions that currently allow ion identification at and above the millimeter scale. Here, we present a design for a cross-flow-IMS method able to generate and detect ions at the sub-millimeter scale. We propose a novel ion focusing strategy and tested it in a prototype device using Nitrogen as a sample gas, and also with simulations using four different sample gases. By introducing an original lobular ion generation localized to a few ten of microns and substantially simplifying the design, our device is able to keep constant laminar flow conditions for high flow rates. In this way, it avoids the turbulences in the gas flow, which would occur in other ion-focusing cross-flow methods limiting their performance at the sub-millimeter scale. Scalability of the proposed design can contribute to improve resolving power and resolution of currently available cross-flow methods.
Throughout this investigation, experiments on laser ablation with silicon (Si) wafers have been p... more Throughout this investigation, experiments on laser ablation with silicon (Si) wafers have been performed using silicon nitride (Si 3 N 4 ) as a sacrificial layer to find the optimal fluence capable of removing the Si 3 N 4 , which allows the subsequent anisotropic etching in Si with potassium hydroxide. As a result, an alternative to the traditional micromachining techniques that require more steps and processing times has been introduced. The effect of the pulse numbers on Si wafers has been studied and it has been observed that when increasing the pulse numbers at the same fluence, the capacity of the pyramidal cavity formed was greater than using only one pulse at higher fluences.
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Papers by Carlos Lasorsa