Monica Jung de Andrade | University of Texas at Dallas (original) (raw)
Papers by Monica Jung de Andrade
Journal of Superconductivity and Novel Magnetism, 2016
Active and Passive Smart Structures and Integrated Systems 2015, 2015
Electroactive Polymer Actuators and Devices (EAPAD) 2014, 2014
High-performance artificial muscles have been produced from fibers having highly anisotropic ther... more High-performance artificial muscles have been produced from fibers having highly anisotropic thermal expansion. Inserting twist into these precursor fibers enables thermally-driven torsional actuation and can cause the formation of helical coils. Such coiled structures provide giant-stroke tensile actuation exceeding the 20% in-vivo contraction of natural muscles. This contraction is highly reversible, with over one million cycles demonstrated, and can occur without the hysteresis that plagues competing shape-memory and piezoelectric muscles. Several materials and composites are investigated, including low-cost, commercially-available muscle precursors, potentially facilitating thermally-responsive textiles that change porosity to provide wearer comfort.
ABSTRACT Catalysts are typical nanomaterials, perhaps the first nanomaterials in wide application... more ABSTRACT Catalysts are typical nanomaterials, perhaps the first nanomaterials in wide applications. Catalysis is a nanoscale phenomenon that has been the subject of research and development for many years, but only recently has it become a nanoscale science of materials and chemistry involving more investigations on the molecular level. Nanomaterial-based catalysts are usually heterogeneous catalysts. The extremely small size of the particles maximizes surface area exposed to the reactant, allowing more reactions to occur. However, thermal stability of these nanomaterials is limited by their critical sizes; the smaller the crystallite size, the lower the thermal stability. In this chapter the characterization of metal oxides such as CeO2, TiO2, and ZnO and some of their applications as catalysts for methane combustion and photocatalysis is described. The effects of mixed oxides, and mixed phases were investigated.
Particulate Science and Technology, 2007
ABSTRACT Homogeneous mixtures containing iron oxide and amorphous SiO2 were obtained through the ... more ABSTRACT Homogeneous mixtures containing iron oxide and amorphous SiO2 were obtained through the co-deposition of these oxides via combustion chemical vapor deposition technique (CCVD). This technique allows the deposition of thin films with low-cost precursors and equipments. After deposition, the deposited samples were submitted to a heat treatment in an atmosphere composed of natural gas and H2 at 1000°C, in order to promote the growth of carbon nanotubes. Multiwalled carbon nanotubes, with diameters smaller than 15 nm, were obtained.
Journal of the European Ceramic Society, 2006
The synthesis of chromium oxides by solution combustion synthesis was investigated. Ammonium dich... more The synthesis of chromium oxides by solution combustion synthesis was investigated. Ammonium dichromate, glycine, urea and ammonium nitrate dissolved in aqueous solution were used as the precursors of the oxides. The effect of different reaction parameters, such as fuel richness, stoichiometry and fuel leanness was evaluated; such parameters were modified by changing the reagents and the fuel/oxidant ratio. Amorphous CrO 3 and crystalline Cr 2 O 3 were synthesized. The results suggest that glycine is a better complexing/combustible agent for ammonium dichromate than urea. Addition of extra ammonium nitrate to stoichiometric compositions improved the specific surface area and reduced the crystallite size. The smallest crystallite size (≈20 nm) of Cr 2 O 3 was obtained with glycine as fuel/complexant agent in fuel-lean mixtures. The highest specific surface area (63 m 2 /g) was observed with urea in fuel-rich mixtures, forming amorphous CrO 3 .
Journal of Materials Science, 2006
Journal of Materials Chemistry, 2008
A new method was developed for deposition of carbon nanotube networks (CNTNs) over transparent an... more A new method was developed for deposition of carbon nanotube networks (CNTNs) over transparent and electrically non-conductive substrates. This method allows the deposition of functionalized or surfactant-stabilized carbon nanotubes dispersed in water. The nanotube films can be applied over complex geometries, on non-conductive rigid or flexible substrates and over large areas in a continuous manner. The carbon nanotube films are deposited by electrophoretic deposition (EPD) using a thin film layer of conductive metal, such as aluminium or titanium. The metal layer oxidizes during the EPD, becoming transparent. The carbon nanotube films can be easily patterned using this technique.
Diamond and Related Materials, 2006
Multi-walled carbon nanotubes (MWCNTs) have been grown on 7 nm Ni-coated substrates consisting of... more Multi-walled carbon nanotubes (MWCNTs) have been grown on 7 nm Ni-coated substrates consisting of crystalline silicon covered with a thin layer (10 nm) of TiN, by combining hot-wire chemical vapor deposition (HWCVD) and direct current plasma-enhanced chemical vapor deposition (dc PECVD), at 620 -C. Acetylene (C 2 H 2 ) gas is used as the carbon source and ammonia (NH 3 ) and hydrogen (H 2 ) are used either for dilution or etching. The carbon nanotubes range from 20 to 100 nm in diameter and 0.3 to 5 Am in length, depending on growth conditions: plasma intensity, filament current, pressure, C 2 H 2 , NH 3 , H 2 flow rates, C 2 H 2 /NH 3 and C 2 H 2 /H 2 mass flow ratios. By combining the HWCVD and the dc PECVD processes, uniform growth of oriented MWCNTs was obtained, whereas by using only the HWCVD process, tangled MWCNTs were obtained. By patterning the nickel catalyst, with the use of the HW dc PECVD process, uniform arrays of nanotubes have been grown as well as single free-standing aligned nanotubes, depending on the catalyst patterning (optical lithography or electron-beam lithography). In the latter case, electron field emission from the MWCNTs was obtained with a maximum emission current density of 0.6 A/cm 2 for a field of 16 V/Am.
mit den folgenden Schritten: -Bereitstellen einer Mischung einer Flüssigkeit (402) mit Nanoteilch... more mit den folgenden Schritten: -Bereitstellen einer Mischung einer Flüssigkeit (402) mit Nanoteilchen (306) und einer AbscheidElektrode (304), wobei die AbscheidElektrode (304) auf einem optisch transparenten Substrat (302) ausgebildet ist, wobei die AbscheidElektrode (304) aus einem elektrisch leitfähigen Material ausgebildet ist, wobei das elektrisch leitfähige Material elektrochemisch zu einem elektrischen Isolator umwandelbar ist, wobei es sich bei den Nanoteilchen um Nanoröhren handelt, -elektrophoretisches Abscheiden von Nanoteilchen (306) der Lösung (402) auf die Abscheid Elektrode (304), wobei die elektrophoretisch abgeschiedenen Nanoröhren (306) ein Netzwerk bilden, wobei das NanoröhrenNetzwerk transparent und/oder elektrisch leitfähig ist, wobei das Verfahren ferner ein Festlegen der Dicke der AbscheidElektrode (304) und/oder der Konzentration der Lösung (402) der Nanoröhren (306) und/oder der Stärke des bei dem elektrophoretischen Abscheiden verwendeten elektrischen Feldes umfasst, wobei das Festlegen so erfolgt, dass das elektrophoretische Abscheiden selbst kontrollierend zum Erhalt einer vorbestimmten Dicke und/oder Dichte des Netzwerks aus Nanoröhren (306) führt. Verfahren und Vorrichtung zum Abscheiden von Nanoteilchen sowie optisches Element DE 102007012550 B4 ABSTRACT Verfahren zum Abscheiden von Nanoteilchen (306) mit den folgenden Schritten: -Bereitstellen einer Mischung einer Flüssigkeit (402) mit Nanoteilchen (306) und einer AbscheidElektrode (304), wobei die AbscheidElektrode (304) auf einem optisch transparenten Substrat (302) ausgebildet ist, wobei die Abscheid Elektrode (304) aus einem elektrisch leitfähigen Material ausgebildet ist, wobei das elektrisch leitfähige Material elektrochemisch zu einem elektrischen Isolator umwandelbar ist, wobei es sich bei den Nanoteilchen um Nanoröhren handelt, -elektrophoretisches Abscheiden von Nanoteilchen (306) der Lösung (402) auf die AbscheidElektrode (304), wobei die elektrophoretisch abgeschiedenen Nanoröhren (306) ein Netzwerk bilden, wobei das NanoröhrenNetzwerk transparent und/oder elektrisch leitfähig ist, wobei das Verfahren ferner ein Festlegen der Dicke der AbscheidElektrode (304) und/oder der Konzentration der Lösung (402) der Nanoröhren (306) und/oder der Stärke des bei dem elektrophoretischen Abscheiden verwendeten elektrischen Feldes umfasst, wobei das Festlegen so erfolgt, dass das elektrophoretische Abscheiden selbst kontrollierend zum Erhalt einer vorbestimmten Dicke und/oder Dichte des Netzwerks aus Nanoröhren (306) führt.
The production of magnesium-chromium oxides by solution combustion synthesis was investigated usi... more The production of magnesium-chromium oxides by solution combustion synthesis was investigated using glycine and urea for the first time. Ammonium dichromate, urea/glycine and ammonium nitrate aqueous solutions were used as the precursors of the oxides. The effect of different reaction parameters, such as fuel richness, stoichiometry and fuel leanness was evaluated; such parameters were modified by changing the reagents and the fuel/oxidant ratio. The results suggest that glycine is an interesting complexing/combustible agent for ammonium dichromate to produce chromite spinel. Addition of extra ammonium nitrate to stoichiometric compositions improved the specific surface area and reduced the crystallite size. The highest specific surface area (153.40 m 2 /g) was obtained for the stoichiometric fuel/oxidant mixtures containing glycine as combustible in combination with ammonium nitrate; however, the smallest crystallite size (approximately 9 nm) of Pirochromite (MgCr 2 O 4 ) was synthesized using urea as combustible. #
This article describes the solution combustion synthesis technique as applicable to iron oxide po... more This article describes the solution combustion synthesis technique as applicable to iron oxide powder production using urea as fuel and ferric nitrate as an oxidizer. It focuses on the thermodynamic modeling of the combustion reaction under different fuel-to-oxidant ratios. X-ray diffraction showed magnetite (Fe 3 O 4 ) and hematite (a-Fe 2 O 3 ) phase formations for the as-synthesized powders. The smallest crystallite size was obtained by stoichiometric chemical reaction. The magnetic properties of the samples are also carefully discussed as superparamagnetic behavior.
In this article we have measured the electrical behaviour of carbon nanotubes (CNTs) suspended in... more In this article we have measured the electrical behaviour of carbon nanotubes (CNTs) suspended in electrically insulating liquid. The concentration dependence of conductivity shows a percolation behaviour similar to that observed in electrical composites with an insulating matrix. The value of the critical percolation concentration is strongly determined by the aspect ratio of the fillers forming the network through dynamic percolation. We characterized several single-and multi-wall carbon nanotube materials by the newly proposed method and received a good correlation with the results obtained by methods commonly used for CNT characterization (Raman spectroscopy, transmission electron microscopy and electrical conductivity of free standing papers). As a comparison, fine graphite material has also been evaluated. The electrical properties of the suspensions can be used as a method for CNT characterization. This method can yield important information for CNT producers and for the selection of electrically conducting structures for composites applications.
Science, 2014
The high cost of powerful, large-stroke, high-stress artificial muscles has combined with perform... more The high cost of powerful, large-stroke, high-stress artificial muscles has combined with performance limitations such as low cycle life, hysteresis, and low efficiency to restrict applications. We demonstrated that inexpensive high-strength polymer fibers used for fishing line and sewing thread can be easily transformed by twist insertion to provide fast, scalable, nonhysteretic, long-life tensile and torsional muscles. Extreme twisting produces coiled muscles that can contract by 49%, lift loads over 100 times heavier than can human muscle of the same length and weight, and generate 5.3 kilowatts of mechanical work per kilogram of muscle weight, similar to that produced by a jet engine. Woven textiles that change porosity in response to temperature and actuating window shutters that could help conserve energy were also demonstrated. Large-stroke tensile actuation was theoretically and experimentally shown to result from torsional actuation.
physica status solidi (RRL) – Rapid Research Letters, 2007
Journal of Superconductivity and Novel Magnetism, 2016
Active and Passive Smart Structures and Integrated Systems 2015, 2015
Electroactive Polymer Actuators and Devices (EAPAD) 2014, 2014
High-performance artificial muscles have been produced from fibers having highly anisotropic ther... more High-performance artificial muscles have been produced from fibers having highly anisotropic thermal expansion. Inserting twist into these precursor fibers enables thermally-driven torsional actuation and can cause the formation of helical coils. Such coiled structures provide giant-stroke tensile actuation exceeding the 20% in-vivo contraction of natural muscles. This contraction is highly reversible, with over one million cycles demonstrated, and can occur without the hysteresis that plagues competing shape-memory and piezoelectric muscles. Several materials and composites are investigated, including low-cost, commercially-available muscle precursors, potentially facilitating thermally-responsive textiles that change porosity to provide wearer comfort.
ABSTRACT Catalysts are typical nanomaterials, perhaps the first nanomaterials in wide application... more ABSTRACT Catalysts are typical nanomaterials, perhaps the first nanomaterials in wide applications. Catalysis is a nanoscale phenomenon that has been the subject of research and development for many years, but only recently has it become a nanoscale science of materials and chemistry involving more investigations on the molecular level. Nanomaterial-based catalysts are usually heterogeneous catalysts. The extremely small size of the particles maximizes surface area exposed to the reactant, allowing more reactions to occur. However, thermal stability of these nanomaterials is limited by their critical sizes; the smaller the crystallite size, the lower the thermal stability. In this chapter the characterization of metal oxides such as CeO2, TiO2, and ZnO and some of their applications as catalysts for methane combustion and photocatalysis is described. The effects of mixed oxides, and mixed phases were investigated.
Particulate Science and Technology, 2007
ABSTRACT Homogeneous mixtures containing iron oxide and amorphous SiO2 were obtained through the ... more ABSTRACT Homogeneous mixtures containing iron oxide and amorphous SiO2 were obtained through the co-deposition of these oxides via combustion chemical vapor deposition technique (CCVD). This technique allows the deposition of thin films with low-cost precursors and equipments. After deposition, the deposited samples were submitted to a heat treatment in an atmosphere composed of natural gas and H2 at 1000°C, in order to promote the growth of carbon nanotubes. Multiwalled carbon nanotubes, with diameters smaller than 15 nm, were obtained.
Journal of the European Ceramic Society, 2006
The synthesis of chromium oxides by solution combustion synthesis was investigated. Ammonium dich... more The synthesis of chromium oxides by solution combustion synthesis was investigated. Ammonium dichromate, glycine, urea and ammonium nitrate dissolved in aqueous solution were used as the precursors of the oxides. The effect of different reaction parameters, such as fuel richness, stoichiometry and fuel leanness was evaluated; such parameters were modified by changing the reagents and the fuel/oxidant ratio. Amorphous CrO 3 and crystalline Cr 2 O 3 were synthesized. The results suggest that glycine is a better complexing/combustible agent for ammonium dichromate than urea. Addition of extra ammonium nitrate to stoichiometric compositions improved the specific surface area and reduced the crystallite size. The smallest crystallite size (≈20 nm) of Cr 2 O 3 was obtained with glycine as fuel/complexant agent in fuel-lean mixtures. The highest specific surface area (63 m 2 /g) was observed with urea in fuel-rich mixtures, forming amorphous CrO 3 .
Journal of Materials Science, 2006
Journal of Materials Chemistry, 2008
A new method was developed for deposition of carbon nanotube networks (CNTNs) over transparent an... more A new method was developed for deposition of carbon nanotube networks (CNTNs) over transparent and electrically non-conductive substrates. This method allows the deposition of functionalized or surfactant-stabilized carbon nanotubes dispersed in water. The nanotube films can be applied over complex geometries, on non-conductive rigid or flexible substrates and over large areas in a continuous manner. The carbon nanotube films are deposited by electrophoretic deposition (EPD) using a thin film layer of conductive metal, such as aluminium or titanium. The metal layer oxidizes during the EPD, becoming transparent. The carbon nanotube films can be easily patterned using this technique.
Diamond and Related Materials, 2006
Multi-walled carbon nanotubes (MWCNTs) have been grown on 7 nm Ni-coated substrates consisting of... more Multi-walled carbon nanotubes (MWCNTs) have been grown on 7 nm Ni-coated substrates consisting of crystalline silicon covered with a thin layer (10 nm) of TiN, by combining hot-wire chemical vapor deposition (HWCVD) and direct current plasma-enhanced chemical vapor deposition (dc PECVD), at 620 -C. Acetylene (C 2 H 2 ) gas is used as the carbon source and ammonia (NH 3 ) and hydrogen (H 2 ) are used either for dilution or etching. The carbon nanotubes range from 20 to 100 nm in diameter and 0.3 to 5 Am in length, depending on growth conditions: plasma intensity, filament current, pressure, C 2 H 2 , NH 3 , H 2 flow rates, C 2 H 2 /NH 3 and C 2 H 2 /H 2 mass flow ratios. By combining the HWCVD and the dc PECVD processes, uniform growth of oriented MWCNTs was obtained, whereas by using only the HWCVD process, tangled MWCNTs were obtained. By patterning the nickel catalyst, with the use of the HW dc PECVD process, uniform arrays of nanotubes have been grown as well as single free-standing aligned nanotubes, depending on the catalyst patterning (optical lithography or electron-beam lithography). In the latter case, electron field emission from the MWCNTs was obtained with a maximum emission current density of 0.6 A/cm 2 for a field of 16 V/Am.
mit den folgenden Schritten: -Bereitstellen einer Mischung einer Flüssigkeit (402) mit Nanoteilch... more mit den folgenden Schritten: -Bereitstellen einer Mischung einer Flüssigkeit (402) mit Nanoteilchen (306) und einer AbscheidElektrode (304), wobei die AbscheidElektrode (304) auf einem optisch transparenten Substrat (302) ausgebildet ist, wobei die AbscheidElektrode (304) aus einem elektrisch leitfähigen Material ausgebildet ist, wobei das elektrisch leitfähige Material elektrochemisch zu einem elektrischen Isolator umwandelbar ist, wobei es sich bei den Nanoteilchen um Nanoröhren handelt, -elektrophoretisches Abscheiden von Nanoteilchen (306) der Lösung (402) auf die Abscheid Elektrode (304), wobei die elektrophoretisch abgeschiedenen Nanoröhren (306) ein Netzwerk bilden, wobei das NanoröhrenNetzwerk transparent und/oder elektrisch leitfähig ist, wobei das Verfahren ferner ein Festlegen der Dicke der AbscheidElektrode (304) und/oder der Konzentration der Lösung (402) der Nanoröhren (306) und/oder der Stärke des bei dem elektrophoretischen Abscheiden verwendeten elektrischen Feldes umfasst, wobei das Festlegen so erfolgt, dass das elektrophoretische Abscheiden selbst kontrollierend zum Erhalt einer vorbestimmten Dicke und/oder Dichte des Netzwerks aus Nanoröhren (306) führt. Verfahren und Vorrichtung zum Abscheiden von Nanoteilchen sowie optisches Element DE 102007012550 B4 ABSTRACT Verfahren zum Abscheiden von Nanoteilchen (306) mit den folgenden Schritten: -Bereitstellen einer Mischung einer Flüssigkeit (402) mit Nanoteilchen (306) und einer AbscheidElektrode (304), wobei die AbscheidElektrode (304) auf einem optisch transparenten Substrat (302) ausgebildet ist, wobei die Abscheid Elektrode (304) aus einem elektrisch leitfähigen Material ausgebildet ist, wobei das elektrisch leitfähige Material elektrochemisch zu einem elektrischen Isolator umwandelbar ist, wobei es sich bei den Nanoteilchen um Nanoröhren handelt, -elektrophoretisches Abscheiden von Nanoteilchen (306) der Lösung (402) auf die AbscheidElektrode (304), wobei die elektrophoretisch abgeschiedenen Nanoröhren (306) ein Netzwerk bilden, wobei das NanoröhrenNetzwerk transparent und/oder elektrisch leitfähig ist, wobei das Verfahren ferner ein Festlegen der Dicke der AbscheidElektrode (304) und/oder der Konzentration der Lösung (402) der Nanoröhren (306) und/oder der Stärke des bei dem elektrophoretischen Abscheiden verwendeten elektrischen Feldes umfasst, wobei das Festlegen so erfolgt, dass das elektrophoretische Abscheiden selbst kontrollierend zum Erhalt einer vorbestimmten Dicke und/oder Dichte des Netzwerks aus Nanoröhren (306) führt.
The production of magnesium-chromium oxides by solution combustion synthesis was investigated usi... more The production of magnesium-chromium oxides by solution combustion synthesis was investigated using glycine and urea for the first time. Ammonium dichromate, urea/glycine and ammonium nitrate aqueous solutions were used as the precursors of the oxides. The effect of different reaction parameters, such as fuel richness, stoichiometry and fuel leanness was evaluated; such parameters were modified by changing the reagents and the fuel/oxidant ratio. The results suggest that glycine is an interesting complexing/combustible agent for ammonium dichromate to produce chromite spinel. Addition of extra ammonium nitrate to stoichiometric compositions improved the specific surface area and reduced the crystallite size. The highest specific surface area (153.40 m 2 /g) was obtained for the stoichiometric fuel/oxidant mixtures containing glycine as combustible in combination with ammonium nitrate; however, the smallest crystallite size (approximately 9 nm) of Pirochromite (MgCr 2 O 4 ) was synthesized using urea as combustible. #
This article describes the solution combustion synthesis technique as applicable to iron oxide po... more This article describes the solution combustion synthesis technique as applicable to iron oxide powder production using urea as fuel and ferric nitrate as an oxidizer. It focuses on the thermodynamic modeling of the combustion reaction under different fuel-to-oxidant ratios. X-ray diffraction showed magnetite (Fe 3 O 4 ) and hematite (a-Fe 2 O 3 ) phase formations for the as-synthesized powders. The smallest crystallite size was obtained by stoichiometric chemical reaction. The magnetic properties of the samples are also carefully discussed as superparamagnetic behavior.
In this article we have measured the electrical behaviour of carbon nanotubes (CNTs) suspended in... more In this article we have measured the electrical behaviour of carbon nanotubes (CNTs) suspended in electrically insulating liquid. The concentration dependence of conductivity shows a percolation behaviour similar to that observed in electrical composites with an insulating matrix. The value of the critical percolation concentration is strongly determined by the aspect ratio of the fillers forming the network through dynamic percolation. We characterized several single-and multi-wall carbon nanotube materials by the newly proposed method and received a good correlation with the results obtained by methods commonly used for CNT characterization (Raman spectroscopy, transmission electron microscopy and electrical conductivity of free standing papers). As a comparison, fine graphite material has also been evaluated. The electrical properties of the suspensions can be used as a method for CNT characterization. This method can yield important information for CNT producers and for the selection of electrically conducting structures for composites applications.
Science, 2014
The high cost of powerful, large-stroke, high-stress artificial muscles has combined with perform... more The high cost of powerful, large-stroke, high-stress artificial muscles has combined with performance limitations such as low cycle life, hysteresis, and low efficiency to restrict applications. We demonstrated that inexpensive high-strength polymer fibers used for fishing line and sewing thread can be easily transformed by twist insertion to provide fast, scalable, nonhysteretic, long-life tensile and torsional muscles. Extreme twisting produces coiled muscles that can contract by 49%, lift loads over 100 times heavier than can human muscle of the same length and weight, and generate 5.3 kilowatts of mechanical work per kilogram of muscle weight, similar to that produced by a jet engine. Woven textiles that change porosity in response to temperature and actuating window shutters that could help conserve energy were also demonstrated. Large-stroke tensile actuation was theoretically and experimentally shown to result from torsional actuation.
physica status solidi (RRL) – Rapid Research Letters, 2007