Marcelo Suárez - Academia.edu (original) (raw)
Papers by Marcelo Suárez
Revista Mexicana De Ingenieria Quimica, 2015
Caracterizar un material experimentalmente requiere de una aplicacion solida de conceptos y tecni... more Caracterizar un material experimentalmente requiere de una aplicacion solida de conceptos y tecnicas de diseno estadistico experimental. Idealmente, estas tecnicas se deben considerar desde la planeacion misma de los experimentos. En la realidad, sin embargo, hay proyectos donde existe ya un cierto grado de avance cuando se decide considerar la aplicacion de tecnicas estadisticas. Esto impone distintas limitantes al analisis del experimento. En este trabajo se discuten tres casos con distintos grados de avance al momento de introducir tecnicas estadisticas. Se discuten las limitaciones, asi como las maneras posibles de mejorar el analisis estadistico
Journal of STEM Education: Innovations and Research, 2016
Interest in engineering at early stages of the educational career is one important precursor to c... more Interest in engineering at early stages of the educational career is one important precursor to choosing to study engineering in college, and engineering-related clubs are designed to foster such interest and diversify the engineering pipeline. In this study, the researchers employed a social cognitive career theory framework to examine level of interest in studying engineering and expected educational attainment among underrepresented low-income middle and high school students participating in materials science and engineering (MSE) clubs. Questionnaire data were collected from over 200 MSE club participants in low-income public middle and high schools in Puerto Rico. The results indicate that perceived value of engineering is useful in predicting career interest among underrepresented middle and high school students; however, traditional predictors of educational interests and attainment (gender, mother’s education, parent expectations) exert the strongest influence on engineering...
Ferroelectrics and Their Applications, Oct 3, 2018
In recent years, scientists advanced the study of bio-ferroelectric composites to develop new env... more In recent years, scientists advanced the study of bio-ferroelectric composites to develop new environmentally friendly and inexpensive electronic elements such as capacitors, actuators, and transistors. Accordingly, the present research relates to composites made of chitosan-cellulose polymeric matrix and strontium titanate (STO) nanoparticles. The variables considered include different percentages of cellulose (15 and 25 v%) and strontium titanate nanoparticles (10 and 20 wt%). The electrical characterization of the composites included measuring their dielectric constant, current density, and conductivity. The results suggest that the addition of STO nanoparticles raised the dielectric constant while lowering the current density and the conductivity of the nanocomposites. Moreover, although the cellulose addition increased the current density and the conductivity of the composites, it lowered their dielectric constant. Also, the resulting biocomposite capacitors could withstand up to 60 V without any detectable dielectric breakdown. The other two properties measured were the ultimate tensile strength (UTS) and the degradation temperature (Tdeg). Higher percentages of cellulose decreased the UTS and the Tdeg of the chitosan-cellulose composites while the addition of cellulose slightly raised these properties of the composites made of chitosan-cellulose and STO nanoparticles. The results proved that these types of biocomposites are apt as capacitors with adequate strength to withstand aggressive environments. This work was fully conducted in the facilities of the Nanotechnology Center hosted by the
Materials, 2019
The determination of a reliable tortuosity index is lacking in the aerospace industry. Therefore,... more The determination of a reliable tortuosity index is lacking in the aerospace industry. Therefore, a methodology is formulated via direct and indirect characterization methods of a fluid-filled porous media. Chemical, thermal, and mechanical characterization was performed to the PolyuMACTM polyimide foam. Tortuosity was measured considering a pressure difference as the resistivity variable, rather than electrical resistivity or molecular diffusivity, as proposed on previous models. This is an empirical establishment of the tortuosity index considering the correlation among hydraulic and structural dimensionless parameters obtained through the Buckingham’s Pi theorem. The behavior of the polyimide was studied for samples of different lengths compressed at 30%, 60%, and 90% of its original length on the foaming direction. Results show that, porosity, sample length, and fluid viscosity are relevant for the insulation performance of the material. Regression analysis produced a significan...
International Journal of Cast Metals Research, 2003
Late sulfur inoculation of spheroidal graphite cast irons. OM Suarez, RD Kendrick, CR Loper Inter... more Late sulfur inoculation of spheroidal graphite cast irons. OM Suarez, RD Kendrick, CR Loper International Journal of Cast Metals Research 16:11, 1-6, 2003. The addition of small amounts of sulfur in the form of pyrite granules to post-inoculated ductile irons was investigated. ...
Journal of Composite Materials, 2016
Bio-ferroelectric composites represent an inexpensive and environmentally friendly electronic alt... more Bio-ferroelectric composites represent an inexpensive and environmentally friendly electronic alternative for electrical applications such as capacitors, transistors, and actuators. The present research relates to the development of a biocomposite made of a chitosan–cellulose polymeric layer and bearing ferroelectric nanoparticles. The variables considered included the volume percentage of cellulose (15 v% and 25 v%) in the matrix and the amount of ferroelectric nanoparticles (0 wt.%, 10 wt.%, and 20 wt.%). Upon electrical characterization, the results indicated that the addition of the nanoparticles raised the capacitance and resistivity of the composite while the addition of cellulose lessened both electrical properties. The measured capacitance of the composites diminished as the applied voltage increased when contrasted with commercial capacitors where under similar testing conditions, as expected, the said capacity remained constant. Additionally, higher current flows were obta...
Science and Engineering of Composite Materials, 2010
An experimental investigation of the effect of casting parameters during the fabrication of funct... more An experimental investigation of the effect of casting parameters during the fabrication of functionally graded Al-B-Mg (Al-2 wt. % B-6 wt. % Mg) composites via centrifugal casting method has been conducted. Particular interest was dedicated to the transformation of the dodecaboride particles into complex aluminum diboride particles and the redistribution of these particles on the matrix of the composites. Pertinent image analysis permitted characterizing the resulting composite microstructures both quantitatively and qualitatively. Our results revealed that as casting time, rotational speed and pouring temperature of the melt increased, the concentration of the reinforcement particles becomes denser at the outer periphery of the casting. The data obtained from both superficial Rockwell hardness and Vickers microhardness analysis demonstrated that both mechanical properties bore similar trend as the gradient in particles distribution. Additionally, backscattered electron imaging helped differentiate the morphology and apparent composition of the aluminum boride particles with different levels of boron. The interaction of the magnesium levels in the composite matrix and the reinforcement particles via energy dispersive spectroscopy is also discussed.
Advances in Applied Ceramics, 2014
The replacement of cement by mineral admixtures in concrete has been of increasing interest in th... more The replacement of cement by mineral admixtures in concrete has been of increasing interest in the construction industry. Nevertheless, several of the potential replacements, such as fly ash class F, lower the compressive strength of concrete at early age. This project investigates the use of nanosilica to compensate for such loss of compressive strength. A statistical experimental design involving mixtures of Portland cement, fly ash and nanosilica, in addition to water/binder ratio as an external factor, is proposed to study their combined effect on the compressive strength of concrete. This design allows estimating a cubic regression model that properly accounts for the effects of the mixture components within a constrained experimental region. The range of each factor was selected according to levels normally used in the industry. Finally, an optimisation strategy permits to recommend the use of nanosilica when high percentages of cement replacement by fly ash are present.
Materials Characterization, 2002
Deterioration of properties in cast aluminum matrix composites (AMCs) due to matrix/reinforcement... more Deterioration of properties in cast aluminum matrix composites (AMCs) due to matrix/reinforcement chemical reactions is absent when AlB 2 particles are used as reinforcements. This communication reports the fabrication of a heat-treatable AMC reinforced with borides. Final hardness values can be adjusted by solution and precipitation, which harden the composite. Evolution of the microstructure is concisely presented as observed by secondary electron microscopy. Precipitation hardening of the aluminum matrix, observed by microhardness measurements, has been corroborated by differential thermal analysis.
Materials and Manufacturing Processes, 2011
The redistribution of AlB2 and AlB12 reinforcing particles in functionally graded Al–B–Mg composi... more The redistribution of AlB2 and AlB12 reinforcing particles in functionally graded Al–B–Mg composites was investigated as a function of centrifugal casting time, rotational speed, and pouring temperature of the melt. The microstructure was characterized both qualitatively and quantitatively on four different sections along the main axis (centrifugal force direction) of the cylindrical casting. The resulting aluminum matrix composite showed an
A study of compacted graphite iron production in a laboratory environment was conducted by carefu... more A study of compacted graphite iron production in a laboratory environment was conducted by carefully monitoring the chemical composition of the charge material, the thermal history of the melt and the addition of trimming alloys. The procedure, consisting of a two-stage process, was based on the reoxidation of a magnesium-treated melt by pouring the treatment ladle into the post-treatment furnace where the melt was reheated above 1400oC. An in-stream inoculation with 75% ferrosilicon inoculant was incorporated during final pouring. After final inoculation, the resulting microstructure was that of a compacted graphite iron with no carbide formation. The experimental process produced graphite with consistent compacted morphology without the use of titanium that could have been detrimental to tool life upon machining.
Advances in Materials Science and Engineering, 2018
The effect of the addition ofAlB12particles to gravity cast Al-Zn alloys was studied and related ... more The effect of the addition ofAlB12particles to gravity cast Al-Zn alloys was studied and related to the composite deformation at high temperature. The characterization techniques of choice were thermomechanical analysis (TMA), Brinell hardness (HB), and optical microscopy. After homogenization treatment, Al-5 wt.% Zn and Al-10 wt.% Zn with 0, 2.08, 4.16 wt.% B samples were quenched in ice water and tested using a thermomechanical analyzer at different temperatures. It was found that after TMA treatment, Brinell hardness of the composites increased for higher concentrations of zinc andAlB12particles, as expected. Such increment was not, however, uniform for all samples at higher temperature levels, suggesting a nonequilibrium interaction between reinforcing particles and zinc. This was further corroborated by TMA experiments, which revealed that for samples with Al-10 wt.% Zn, high temperature deformation augmented as moreAlB12particles were present. After high temperature treatment,...
Journal of the Mechanical Behavior of Materials, 2019
Historically known for being one of the major pollutants in the world, the construction industry,... more Historically known for being one of the major pollutants in the world, the construction industry, always in constant advancement and development, is currently evolving towards more environmentally friendly technologies and methods. Scientists and engineers seek to develop and implement green alternatives to conventional construction materials. One of these alternatives is to introduce an abundant, hard to recycle, material that could serve as a partial aggregate replacement in masonry bricks or even in a more conventional concrete mixture. The present work studied the use of 3 different types of repurposed plastics with different constitutions and particle size distribution. Accordingly, several brick and concrete mix designs were developed to determine the practicality of using these plastics as partial aggregate replacements. After establishing proper working material ratios for each brick and concrete mix, compression tests as well as tensile tests for the concrete mixes helped d...
Journal of Composites Science, 2019
Bio-polymer-based composites are appealing cost-effective and environmentally friendly materials ... more Bio-polymer-based composites are appealing cost-effective and environmentally friendly materials for electronic applications. This project relates to bio-composites made of chitosan and cellulose and reinforced with strontium titanate nanoparticles. Upon their fabrication, relevant parameters studied were the acetic acid concentration, the cellulose content, and the amount of strontium titanate nanoparticles. The specimens were characterized using thermogravimetric and degradation analyses, as well as via creep and tensile tests. The results revealed how higher cellulose levels lowered the ultimate tensile strength and the degradation temperature of the bio-composites. Moreover, when nanoparticles are present, higher cellulose levels contributed to their tensile strength. Additionally, more acidic solutions became detrimental to the mechanical properties and the thermal degradation temperature of the composites. Furthermore, the creep studies allowed determining elastic coefficients...
Science and Engineering of Composite Materials, 2009
An AI-Si-Sn alloy and an Al-B-Sn composite intended for bearing applications were manufactured by... more An AI-Si-Sn alloy and an Al-B-Sn composite intended for bearing applications were manufactured by centrifugal casting and their resulting tribological properties were compared. Microstructure gradients of silicon particles and boride dispersoids were observed on both materials, increasing from the internal to the external casting zones. Superficial hardness and pin-on-disk wear tests performed showed a higher hardness and lower wear coefficient in the external regions. The boride-reinforced composite exhibited lower wear and higher hardness than the aluminum-siliconbased alloy.
Journal of the Mechanical Behavior of Materials, 2001
A new alloy series manufactured from commercial aluminum boron alloys has been investigated as in... more A new alloy series manufactured from commercial aluminum boron alloys has been investigated as insitu aluminum matrix composites. Aluminum diboride particles acting as ceramic reinforcements of the mostly pure aluminum matrix greatly increase cold work hardening of the composite. After alloying aluminum boron composites with copper in less than 5 weight percent, the matrix of the composite becomes hardenable by heat treatment. Microhardness analyses conducted during heat treatment indicates that precipitation hardening is enhanced with respect to regular aluminum copper alloys.
Science and Engineering of Composite Materials, 2014
Tribological properties of a series of aluminum matrix composites reinforced with AlB 2 particles... more Tribological properties of a series of aluminum matrix composites reinforced with AlB 2 particles deve loped for lightweight machinery parts intended for aero space and automotive applications were evaluated. In this study, the worn surfaces of aluminum matrix com posites containing copper and magnesium with different amounts of reinforcing AlB 2 dispersoids were examined by scanning electron microscopy to determine the effects of a pinondisk wear test. These observations also allowed identification of the probable wear mechanisms involved upon wearing against a martensitic stainless steel ball. The effect of chemical composition on the wear volume and wear coefficient was measured to establish the rela tionship between the reinforcing diboride content and matrix conditions and the corresponding wear response.
Science and Engineering of Composite Materials, 2009
The use of high energy ball milling (HEBM) was investigated as an alternative method to synthesiz... more The use of high energy ball milling (HEBM) was investigated as an alternative method to synthesize aluminum matrix composites reinforced with Al x Mg|. x B 2 particles. HEBM allowed achieving appropriate mixing and wettability between the composite components. After a 900°C treatment under vacuum, the resulting material had a mixed microstructure of dispersoids and submicron AI x Mgi. x B 2 (hereon also referred as (AIMg)B 2) particles embedded in the Al matrix containing also β (Al 3 Mg 2) + Al eutectic. After processing the size distribution of Al x Mg|. x B 2 particles included large particles (<23μηι) and submicron ones. Vickers microhardness measured on the composite matrix revealed that the highest matrix hardness was obtained in samples containing 5 wt.% Al x Mgi. x B 2 where larger amounts of nanosized reinforcement particles were present. X-ray diffraction studies showed the formation of Al x Mgi. x B 2 in the mechanically alloyed composites. In summary, the results buttressed the feasibility of fabricating a stronger Al-based composite via HEBM.
JOM, 2014
The effect of different amounts of boron, in the form of AlB2 particles, as well as zinc concentr... more The effect of different amounts of boron, in the form of AlB2 particles, as well as zinc concentration in a gravity cast Al-B-Zn composite, was studied and related to the absorbed energy upon fracture during Charpy impact experiments. In addition, the authors correlated the composite Brinell hardness with the quantitative assessment of brittle and ductile fracture areas of the Charpy fractured specimens and found that increasing AlB2 particle concentration resulted in a reduction of absorbed impact energy. Although larger zinc levels produced somewhat similar results, the AlB2 effect was prevalent. The energy absorption upon impact reached a maximum when no particles were present; conversely, the lowest amount of absorbed energy corresponded to a composite with a composition of 15 wt.% Zn and 8% in volume of AlB2, i.e., the highest concentration of AlB2 and zinc studied. Raising the amount of AlB2 as well as zinc, as expected, resulted in higher Brinell hardness. A statistical analysis allowed studying of the particle size distribution, whereas values for crack tip opening displacement were subsequently calculated for the range of particle sizes found and the corresponding AlB2 particle volume percent. Higher porosity values were measured for larger AlB2 volume percent. Finally, analyses of fracture surfaces corroborated that brittle fracture was favored in composites with higher amounts of AlB2 and zinc.
JOM, 2009
... This changed when administrators, led by Dr. Ramón E. Vásquez, Dean of Engineering, and a han... more ... This changed when administrators, led by Dr. Ramón E. Vásquez, Dean of Engineering, and a handful of professors made MSE a key ... In March 2009, both PREM and CREST-sup-ported club members gathered at UP-RM's Rafael Mangual Coliseum for a nanobiotechnology ...
Revista Mexicana De Ingenieria Quimica, 2015
Caracterizar un material experimentalmente requiere de una aplicacion solida de conceptos y tecni... more Caracterizar un material experimentalmente requiere de una aplicacion solida de conceptos y tecnicas de diseno estadistico experimental. Idealmente, estas tecnicas se deben considerar desde la planeacion misma de los experimentos. En la realidad, sin embargo, hay proyectos donde existe ya un cierto grado de avance cuando se decide considerar la aplicacion de tecnicas estadisticas. Esto impone distintas limitantes al analisis del experimento. En este trabajo se discuten tres casos con distintos grados de avance al momento de introducir tecnicas estadisticas. Se discuten las limitaciones, asi como las maneras posibles de mejorar el analisis estadistico
Journal of STEM Education: Innovations and Research, 2016
Interest in engineering at early stages of the educational career is one important precursor to c... more Interest in engineering at early stages of the educational career is one important precursor to choosing to study engineering in college, and engineering-related clubs are designed to foster such interest and diversify the engineering pipeline. In this study, the researchers employed a social cognitive career theory framework to examine level of interest in studying engineering and expected educational attainment among underrepresented low-income middle and high school students participating in materials science and engineering (MSE) clubs. Questionnaire data were collected from over 200 MSE club participants in low-income public middle and high schools in Puerto Rico. The results indicate that perceived value of engineering is useful in predicting career interest among underrepresented middle and high school students; however, traditional predictors of educational interests and attainment (gender, mother’s education, parent expectations) exert the strongest influence on engineering...
Ferroelectrics and Their Applications, Oct 3, 2018
In recent years, scientists advanced the study of bio-ferroelectric composites to develop new env... more In recent years, scientists advanced the study of bio-ferroelectric composites to develop new environmentally friendly and inexpensive electronic elements such as capacitors, actuators, and transistors. Accordingly, the present research relates to composites made of chitosan-cellulose polymeric matrix and strontium titanate (STO) nanoparticles. The variables considered include different percentages of cellulose (15 and 25 v%) and strontium titanate nanoparticles (10 and 20 wt%). The electrical characterization of the composites included measuring their dielectric constant, current density, and conductivity. The results suggest that the addition of STO nanoparticles raised the dielectric constant while lowering the current density and the conductivity of the nanocomposites. Moreover, although the cellulose addition increased the current density and the conductivity of the composites, it lowered their dielectric constant. Also, the resulting biocomposite capacitors could withstand up to 60 V without any detectable dielectric breakdown. The other two properties measured were the ultimate tensile strength (UTS) and the degradation temperature (Tdeg). Higher percentages of cellulose decreased the UTS and the Tdeg of the chitosan-cellulose composites while the addition of cellulose slightly raised these properties of the composites made of chitosan-cellulose and STO nanoparticles. The results proved that these types of biocomposites are apt as capacitors with adequate strength to withstand aggressive environments. This work was fully conducted in the facilities of the Nanotechnology Center hosted by the
Materials, 2019
The determination of a reliable tortuosity index is lacking in the aerospace industry. Therefore,... more The determination of a reliable tortuosity index is lacking in the aerospace industry. Therefore, a methodology is formulated via direct and indirect characterization methods of a fluid-filled porous media. Chemical, thermal, and mechanical characterization was performed to the PolyuMACTM polyimide foam. Tortuosity was measured considering a pressure difference as the resistivity variable, rather than electrical resistivity or molecular diffusivity, as proposed on previous models. This is an empirical establishment of the tortuosity index considering the correlation among hydraulic and structural dimensionless parameters obtained through the Buckingham’s Pi theorem. The behavior of the polyimide was studied for samples of different lengths compressed at 30%, 60%, and 90% of its original length on the foaming direction. Results show that, porosity, sample length, and fluid viscosity are relevant for the insulation performance of the material. Regression analysis produced a significan...
International Journal of Cast Metals Research, 2003
Late sulfur inoculation of spheroidal graphite cast irons. OM Suarez, RD Kendrick, CR Loper Inter... more Late sulfur inoculation of spheroidal graphite cast irons. OM Suarez, RD Kendrick, CR Loper International Journal of Cast Metals Research 16:11, 1-6, 2003. The addition of small amounts of sulfur in the form of pyrite granules to post-inoculated ductile irons was investigated. ...
Journal of Composite Materials, 2016
Bio-ferroelectric composites represent an inexpensive and environmentally friendly electronic alt... more Bio-ferroelectric composites represent an inexpensive and environmentally friendly electronic alternative for electrical applications such as capacitors, transistors, and actuators. The present research relates to the development of a biocomposite made of a chitosan–cellulose polymeric layer and bearing ferroelectric nanoparticles. The variables considered included the volume percentage of cellulose (15 v% and 25 v%) in the matrix and the amount of ferroelectric nanoparticles (0 wt.%, 10 wt.%, and 20 wt.%). Upon electrical characterization, the results indicated that the addition of the nanoparticles raised the capacitance and resistivity of the composite while the addition of cellulose lessened both electrical properties. The measured capacitance of the composites diminished as the applied voltage increased when contrasted with commercial capacitors where under similar testing conditions, as expected, the said capacity remained constant. Additionally, higher current flows were obta...
Science and Engineering of Composite Materials, 2010
An experimental investigation of the effect of casting parameters during the fabrication of funct... more An experimental investigation of the effect of casting parameters during the fabrication of functionally graded Al-B-Mg (Al-2 wt. % B-6 wt. % Mg) composites via centrifugal casting method has been conducted. Particular interest was dedicated to the transformation of the dodecaboride particles into complex aluminum diboride particles and the redistribution of these particles on the matrix of the composites. Pertinent image analysis permitted characterizing the resulting composite microstructures both quantitatively and qualitatively. Our results revealed that as casting time, rotational speed and pouring temperature of the melt increased, the concentration of the reinforcement particles becomes denser at the outer periphery of the casting. The data obtained from both superficial Rockwell hardness and Vickers microhardness analysis demonstrated that both mechanical properties bore similar trend as the gradient in particles distribution. Additionally, backscattered electron imaging helped differentiate the morphology and apparent composition of the aluminum boride particles with different levels of boron. The interaction of the magnesium levels in the composite matrix and the reinforcement particles via energy dispersive spectroscopy is also discussed.
Advances in Applied Ceramics, 2014
The replacement of cement by mineral admixtures in concrete has been of increasing interest in th... more The replacement of cement by mineral admixtures in concrete has been of increasing interest in the construction industry. Nevertheless, several of the potential replacements, such as fly ash class F, lower the compressive strength of concrete at early age. This project investigates the use of nanosilica to compensate for such loss of compressive strength. A statistical experimental design involving mixtures of Portland cement, fly ash and nanosilica, in addition to water/binder ratio as an external factor, is proposed to study their combined effect on the compressive strength of concrete. This design allows estimating a cubic regression model that properly accounts for the effects of the mixture components within a constrained experimental region. The range of each factor was selected according to levels normally used in the industry. Finally, an optimisation strategy permits to recommend the use of nanosilica when high percentages of cement replacement by fly ash are present.
Materials Characterization, 2002
Deterioration of properties in cast aluminum matrix composites (AMCs) due to matrix/reinforcement... more Deterioration of properties in cast aluminum matrix composites (AMCs) due to matrix/reinforcement chemical reactions is absent when AlB 2 particles are used as reinforcements. This communication reports the fabrication of a heat-treatable AMC reinforced with borides. Final hardness values can be adjusted by solution and precipitation, which harden the composite. Evolution of the microstructure is concisely presented as observed by secondary electron microscopy. Precipitation hardening of the aluminum matrix, observed by microhardness measurements, has been corroborated by differential thermal analysis.
Materials and Manufacturing Processes, 2011
The redistribution of AlB2 and AlB12 reinforcing particles in functionally graded Al–B–Mg composi... more The redistribution of AlB2 and AlB12 reinforcing particles in functionally graded Al–B–Mg composites was investigated as a function of centrifugal casting time, rotational speed, and pouring temperature of the melt. The microstructure was characterized both qualitatively and quantitatively on four different sections along the main axis (centrifugal force direction) of the cylindrical casting. The resulting aluminum matrix composite showed an
A study of compacted graphite iron production in a laboratory environment was conducted by carefu... more A study of compacted graphite iron production in a laboratory environment was conducted by carefully monitoring the chemical composition of the charge material, the thermal history of the melt and the addition of trimming alloys. The procedure, consisting of a two-stage process, was based on the reoxidation of a magnesium-treated melt by pouring the treatment ladle into the post-treatment furnace where the melt was reheated above 1400oC. An in-stream inoculation with 75% ferrosilicon inoculant was incorporated during final pouring. After final inoculation, the resulting microstructure was that of a compacted graphite iron with no carbide formation. The experimental process produced graphite with consistent compacted morphology without the use of titanium that could have been detrimental to tool life upon machining.
Advances in Materials Science and Engineering, 2018
The effect of the addition ofAlB12particles to gravity cast Al-Zn alloys was studied and related ... more The effect of the addition ofAlB12particles to gravity cast Al-Zn alloys was studied and related to the composite deformation at high temperature. The characterization techniques of choice were thermomechanical analysis (TMA), Brinell hardness (HB), and optical microscopy. After homogenization treatment, Al-5 wt.% Zn and Al-10 wt.% Zn with 0, 2.08, 4.16 wt.% B samples were quenched in ice water and tested using a thermomechanical analyzer at different temperatures. It was found that after TMA treatment, Brinell hardness of the composites increased for higher concentrations of zinc andAlB12particles, as expected. Such increment was not, however, uniform for all samples at higher temperature levels, suggesting a nonequilibrium interaction between reinforcing particles and zinc. This was further corroborated by TMA experiments, which revealed that for samples with Al-10 wt.% Zn, high temperature deformation augmented as moreAlB12particles were present. After high temperature treatment,...
Journal of the Mechanical Behavior of Materials, 2019
Historically known for being one of the major pollutants in the world, the construction industry,... more Historically known for being one of the major pollutants in the world, the construction industry, always in constant advancement and development, is currently evolving towards more environmentally friendly technologies and methods. Scientists and engineers seek to develop and implement green alternatives to conventional construction materials. One of these alternatives is to introduce an abundant, hard to recycle, material that could serve as a partial aggregate replacement in masonry bricks or even in a more conventional concrete mixture. The present work studied the use of 3 different types of repurposed plastics with different constitutions and particle size distribution. Accordingly, several brick and concrete mix designs were developed to determine the practicality of using these plastics as partial aggregate replacements. After establishing proper working material ratios for each brick and concrete mix, compression tests as well as tensile tests for the concrete mixes helped d...
Journal of Composites Science, 2019
Bio-polymer-based composites are appealing cost-effective and environmentally friendly materials ... more Bio-polymer-based composites are appealing cost-effective and environmentally friendly materials for electronic applications. This project relates to bio-composites made of chitosan and cellulose and reinforced with strontium titanate nanoparticles. Upon their fabrication, relevant parameters studied were the acetic acid concentration, the cellulose content, and the amount of strontium titanate nanoparticles. The specimens were characterized using thermogravimetric and degradation analyses, as well as via creep and tensile tests. The results revealed how higher cellulose levels lowered the ultimate tensile strength and the degradation temperature of the bio-composites. Moreover, when nanoparticles are present, higher cellulose levels contributed to their tensile strength. Additionally, more acidic solutions became detrimental to the mechanical properties and the thermal degradation temperature of the composites. Furthermore, the creep studies allowed determining elastic coefficients...
Science and Engineering of Composite Materials, 2009
An AI-Si-Sn alloy and an Al-B-Sn composite intended for bearing applications were manufactured by... more An AI-Si-Sn alloy and an Al-B-Sn composite intended for bearing applications were manufactured by centrifugal casting and their resulting tribological properties were compared. Microstructure gradients of silicon particles and boride dispersoids were observed on both materials, increasing from the internal to the external casting zones. Superficial hardness and pin-on-disk wear tests performed showed a higher hardness and lower wear coefficient in the external regions. The boride-reinforced composite exhibited lower wear and higher hardness than the aluminum-siliconbased alloy.
Journal of the Mechanical Behavior of Materials, 2001
A new alloy series manufactured from commercial aluminum boron alloys has been investigated as in... more A new alloy series manufactured from commercial aluminum boron alloys has been investigated as insitu aluminum matrix composites. Aluminum diboride particles acting as ceramic reinforcements of the mostly pure aluminum matrix greatly increase cold work hardening of the composite. After alloying aluminum boron composites with copper in less than 5 weight percent, the matrix of the composite becomes hardenable by heat treatment. Microhardness analyses conducted during heat treatment indicates that precipitation hardening is enhanced with respect to regular aluminum copper alloys.
Science and Engineering of Composite Materials, 2014
Tribological properties of a series of aluminum matrix composites reinforced with AlB 2 particles... more Tribological properties of a series of aluminum matrix composites reinforced with AlB 2 particles deve loped for lightweight machinery parts intended for aero space and automotive applications were evaluated. In this study, the worn surfaces of aluminum matrix com posites containing copper and magnesium with different amounts of reinforcing AlB 2 dispersoids were examined by scanning electron microscopy to determine the effects of a pinondisk wear test. These observations also allowed identification of the probable wear mechanisms involved upon wearing against a martensitic stainless steel ball. The effect of chemical composition on the wear volume and wear coefficient was measured to establish the rela tionship between the reinforcing diboride content and matrix conditions and the corresponding wear response.
Science and Engineering of Composite Materials, 2009
The use of high energy ball milling (HEBM) was investigated as an alternative method to synthesiz... more The use of high energy ball milling (HEBM) was investigated as an alternative method to synthesize aluminum matrix composites reinforced with Al x Mg|. x B 2 particles. HEBM allowed achieving appropriate mixing and wettability between the composite components. After a 900°C treatment under vacuum, the resulting material had a mixed microstructure of dispersoids and submicron AI x Mgi. x B 2 (hereon also referred as (AIMg)B 2) particles embedded in the Al matrix containing also β (Al 3 Mg 2) + Al eutectic. After processing the size distribution of Al x Mg|. x B 2 particles included large particles (<23μηι) and submicron ones. Vickers microhardness measured on the composite matrix revealed that the highest matrix hardness was obtained in samples containing 5 wt.% Al x Mgi. x B 2 where larger amounts of nanosized reinforcement particles were present. X-ray diffraction studies showed the formation of Al x Mgi. x B 2 in the mechanically alloyed composites. In summary, the results buttressed the feasibility of fabricating a stronger Al-based composite via HEBM.
JOM, 2014
The effect of different amounts of boron, in the form of AlB2 particles, as well as zinc concentr... more The effect of different amounts of boron, in the form of AlB2 particles, as well as zinc concentration in a gravity cast Al-B-Zn composite, was studied and related to the absorbed energy upon fracture during Charpy impact experiments. In addition, the authors correlated the composite Brinell hardness with the quantitative assessment of brittle and ductile fracture areas of the Charpy fractured specimens and found that increasing AlB2 particle concentration resulted in a reduction of absorbed impact energy. Although larger zinc levels produced somewhat similar results, the AlB2 effect was prevalent. The energy absorption upon impact reached a maximum when no particles were present; conversely, the lowest amount of absorbed energy corresponded to a composite with a composition of 15 wt.% Zn and 8% in volume of AlB2, i.e., the highest concentration of AlB2 and zinc studied. Raising the amount of AlB2 as well as zinc, as expected, resulted in higher Brinell hardness. A statistical analysis allowed studying of the particle size distribution, whereas values for crack tip opening displacement were subsequently calculated for the range of particle sizes found and the corresponding AlB2 particle volume percent. Higher porosity values were measured for larger AlB2 volume percent. Finally, analyses of fracture surfaces corroborated that brittle fracture was favored in composites with higher amounts of AlB2 and zinc.
JOM, 2009
... This changed when administrators, led by Dr. Ramón E. Vásquez, Dean of Engineering, and a han... more ... This changed when administrators, led by Dr. Ramón E. Vásquez, Dean of Engineering, and a handful of professors made MSE a key ... In March 2009, both PREM and CREST-sup-ported club members gathered at UP-RM's Rafael Mangual Coliseum for a nanobiotechnology ...