Raymundo Arróyave | Texas A&M University (original) (raw)
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Papers by Raymundo Arróyave
Journal of Applied Physics
MAX phases are layered carbides or nitrides with the general formula of M n+1 AX n , which exhibi... more MAX phases are layered carbides or nitrides with the general formula of M n+1 AX n , which exhibit a unique combination of ceramic-and metal-like properties. The effect of stacking number (determined by n) remains to be elucidated and a priori it is not clear whether, for a given chemistry, n significantly changes the intrinsic deformation behavior of these systems. In this work, we have studied intrinsic deformation behavior of Ti n+1 AlC n and Ta n+1 AlC n (n = 1.. .5) through DFT-based calculations. Results surprisingly suggest that stacking number tends to have minimal effect on the intrinsic mechanical behavior of the systems studied.
2018 ASEE Annual Conference & Exposition Proceedings
Computational Materials Science
physica status solidi (b)
Journal of Alloys and Compounds
Materials Research Letters
A new processing route has been discovered through which far-from-equilibrium, metastable archite... more A new processing route has been discovered through which far-from-equilibrium, metastable architectures with unprecedented properties are synthesized. This novel architecture contains many orders of hierarchy with multiple concentration modulation wavelengths. At one length scale, the matrix is comprised of lateral modulations of BCC Mo and pseudomorphic BCC Cu with a wavelength of 10 nm. FCC, Cu-rich islands of approximate 250 nm diameter are woven in-between the Mo-Cu matrix and contain ordered arrays of pseudomorphic, FCC, Mo-rich, coherent precipitates of approximately 1.0 nm diameter spacing. The resulting material exhibits unprecedented mechanical behavior of extensive plastic deformability at room temperature. IMPACT STATEMENT Traditional phase separated thin film morphologies are monolithic in architecture with only one concentration wavelength. By carefully manipulating the self-assembly kinetics through the deposition rate, we processed a structure with multiple concentration modulation wavelengths.
physica status solidi (b)
Scientific Reports
The quest towards expansion of the M n+1 AX n design space has been accelerated with the recent d... more The quest towards expansion of the M n+1 AX n design space has been accelerated with the recent discovery of several solid solution and ordered phases involving at least two M n+1 AX n end members. Going beyond the nominal M n+1 AX n compounds enables not only fine tuning of existing properties but also entirely new functionality. This search, however, has been mostly done through painstaking experiments as knowledge of the phase stability of the relevant systems is rather scarce. In this work, we report the first attempt to evaluate the finite-temperature pseudo-binary phase diagram of the Ti 2 AlC-Cr 2 AlC via first-principles-guided Bayesian CALPHAD framework that accounts for uncertainties not only in ab initio calculations and thermodynamic models but also in synthesis conditions in reported experiments. The phase stability analyses are shown to have good agreement with previous experiments. The work points towards a promising way of investigating phase stability in other MAX Phase systems providing the knowledge necessary to elucidate possible synthesis routes for M n+1 AX n systems with unprecedented properties. M n+1 AX n , wherein M is an early transition metal, A is an A-group element, X is carbon or nitrogen, belong to a special class of nanolaminate materials. They possess hexagonal P63/mmc structure within which M-X layers interleave with A layers. This structure allows the coexistence of both metallic (M-A) and covalent/ionic (M-X) bonds which features a unique combination of ceramic-and metallic-like properties, e.g. high stiffness, good corrosion resistance, good conductivity, high damage tolerance, and machinability 1-5. Thanks to this unique combination, M n+1 AX n are extremely promising for advanced high-temperature applications, and therefore of great interest. The design of materials and/or components for advanced high-temperature applications based on MAX phases requires knowledge of physical and mechanical properties. Such knowledge could only be achieved via successful synthesis and characterization of the materials. So far, roughly over 70 MAX compounds and approximately 100 solid solutions have been synthesized. These are but a small fraction of the 'pure' 600 MAX compounds 6 and billions (if not trillions) of solid solutions that could possibly exist, i.e. those that are elastic and thermodynamic stable. The discovered MAX phases, therefore, constitute only a small portion of the multi-dimensional MAX design space. Richer and better solutions for materials and/or components design based on MAX phases are to be expected within the remaining undiscovered MAX materials design space; and, to follow up, engineering questions such as "what is the MAX phase with highest Young modulus?" or "among the MAX alloys which ones exhibit solid-solution strengthening?" will naturally rise. In order to answer such questions, it is necessary: for (1) a systematic research and development scheme to be reasonably sketched according to a specific engineering problem and to integrate such scheme with (2) combined high-throughput synthesis and characterization capabilities 7, 8. The latter, although experiencing a great cost inertia, has started to grow. This is especially true with the advent of computer-assisted schemes for materials development. Indeed, recent developments in computer infrastructure and simulation methods have enabled the accelerated development of high-throughput computational materials design. Motivated by the increasing interest in MAX alloys and the engineering problem of solid-solution strengthening of MAX phases 9, 10 , we have developed a design scheme based on high-throughput first-principles calculations. The scheme currently has two steps. The first step is to study the effect of M site alloys on the solid solutions of M 2 1 AX-M 2 2 AX system, where M 1 and M 2 are two different transition metals, using cluster expansion approach. Based on this work, suggestions on MAX phases that possibly exhibit solid solution with each other (and hence solution strengthening) will be made. The result of this work for the case of M 2 1 AlC-M 2 2 AlC has already been
Physical Review B
Solid solution MAX phases offer the opportunity for further tuning of the thermo-mechanical and f... more Solid solution MAX phases offer the opportunity for further tuning of the thermo-mechanical and functional properties of MAX phases, increasing their envelope of performance. Previous experimental results show that the lattice parameters of Ti 3 (Si x Al 1−x)C 2 decrease, while the Young's modulus increases with increased Si content in the lattice. In this work, we present a computational investigation of the structural, electronic, and mechanical properties of Ti 3 (Si x Al 1−x)C 2 (x= 0, 0.25, 0.5, 0.75, and 1). The solid solutions were modeled using special quasirandom structures (SQS) and calculated using Density Functional Theory (DFT), which is implemented in the Vienna Ab initio Simulation Package (VASP). The SQS structures represent random mixing of Al and Si in the A sublattice of 312 MAX phase and their structural, electronic, and mechanical properties were calculated and compared with experiments. We study the cleavage and slip behavior of Ti 3 (Si x Al 1−x)C 2 to investigate the deformation behavior in terms of cleavage and shear. It has been shown that the cleavage between M and A layers results in increasing cleavage stress in Ti 3 (Si x Al 1−x)C 2 as a function of Si content in the lattice. In addition, the shear deformation of hexagonal close packed Ti 3 (Si x Al 1−x)C 2 under 2110 {0001} and 0110 {0001} results in increasing unstable stacking fault energy (USFE) and ideal shear strength (ISS) in Ti 3 (Si x Al 1−x)C 2 as the system becomes richer in Si.
Chemistry of Materials
The thermally driven orders-of-magnitude modulation of resistance and optical transmittance obser... more The thermally driven orders-of-magnitude modulation of resistance and optical transmittance observed in VO 2 makes it an archetypal first-order phase transition material and underpins functional applications in logic and memory circuitry, electromagnetic cloaking, ballistic modulation, and thermochromic glazing to provide just a few representative examples. VO 2 can be reversibly switched from an insulating to a metallic state at an equilibrium transition temperature of 67 °C. Tuning the phase diagram of VO 2 to bring the transition temperature closer to room temperature has been a longstanding objective and one that has tremendous practical relevance. Substitutional incorporation of dopants has been the most common strategy for modulating the metalinsulator transition temperature but requires that the dopants be incorporated during synthesis. Here we demonstrate a novel postsynthetic diffusive annealing approach for incorporating interstitial B dopants within VO 2. The postsynthetic method allows for the transition temperature to be programmed after synthesis and furthermore represents an entirely distinctive mode of modulating the phase diagram of VO 2. Local structure studies in conjunction with density functional theory calculations point to the strong preference of B atoms for tetrahedral coordination within interstitial sites of VO 2 ; these tetrahedrally coordinated dopant atoms hinder the rutile → monoclinic transition by impeding the dimerization of V−V chains and decreasing the covalency of the lattice. The results suggest that interstitial dopant incorporation is a powerful method for modulating the transition temperature and electronic instabilities of VO 2 and provides a facile approach for postsynthetic dopant incorporation to reach a switching temperature required for a specific application.
Catal. Sci. Technol.
An anatase TiO2 (001) surface is active and selective toward water production and results in the ... more An anatase TiO2 (001) surface is active and selective toward water production and results in the modification of the surface by forming S-doped TiO2, which enhances its photocatalytic activity.
Journal of Applied Physics
MAX phases are layered carbides or nitrides with the general formula of M n+1 AX n , which exhibi... more MAX phases are layered carbides or nitrides with the general formula of M n+1 AX n , which exhibit a unique combination of ceramic-and metal-like properties. The effect of stacking number (determined by n) remains to be elucidated and a priori it is not clear whether, for a given chemistry, n significantly changes the intrinsic deformation behavior of these systems. In this work, we have studied intrinsic deformation behavior of Ti n+1 AlC n and Ta n+1 AlC n (n = 1.. .5) through DFT-based calculations. Results surprisingly suggest that stacking number tends to have minimal effect on the intrinsic mechanical behavior of the systems studied.
2018 ASEE Annual Conference & Exposition Proceedings
Computational Materials Science
physica status solidi (b)
Journal of Alloys and Compounds
Materials Research Letters
A new processing route has been discovered through which far-from-equilibrium, metastable archite... more A new processing route has been discovered through which far-from-equilibrium, metastable architectures with unprecedented properties are synthesized. This novel architecture contains many orders of hierarchy with multiple concentration modulation wavelengths. At one length scale, the matrix is comprised of lateral modulations of BCC Mo and pseudomorphic BCC Cu with a wavelength of 10 nm. FCC, Cu-rich islands of approximate 250 nm diameter are woven in-between the Mo-Cu matrix and contain ordered arrays of pseudomorphic, FCC, Mo-rich, coherent precipitates of approximately 1.0 nm diameter spacing. The resulting material exhibits unprecedented mechanical behavior of extensive plastic deformability at room temperature. IMPACT STATEMENT Traditional phase separated thin film morphologies are monolithic in architecture with only one concentration wavelength. By carefully manipulating the self-assembly kinetics through the deposition rate, we processed a structure with multiple concentration modulation wavelengths.
physica status solidi (b)
Scientific Reports
The quest towards expansion of the M n+1 AX n design space has been accelerated with the recent d... more The quest towards expansion of the M n+1 AX n design space has been accelerated with the recent discovery of several solid solution and ordered phases involving at least two M n+1 AX n end members. Going beyond the nominal M n+1 AX n compounds enables not only fine tuning of existing properties but also entirely new functionality. This search, however, has been mostly done through painstaking experiments as knowledge of the phase stability of the relevant systems is rather scarce. In this work, we report the first attempt to evaluate the finite-temperature pseudo-binary phase diagram of the Ti 2 AlC-Cr 2 AlC via first-principles-guided Bayesian CALPHAD framework that accounts for uncertainties not only in ab initio calculations and thermodynamic models but also in synthesis conditions in reported experiments. The phase stability analyses are shown to have good agreement with previous experiments. The work points towards a promising way of investigating phase stability in other MAX Phase systems providing the knowledge necessary to elucidate possible synthesis routes for M n+1 AX n systems with unprecedented properties. M n+1 AX n , wherein M is an early transition metal, A is an A-group element, X is carbon or nitrogen, belong to a special class of nanolaminate materials. They possess hexagonal P63/mmc structure within which M-X layers interleave with A layers. This structure allows the coexistence of both metallic (M-A) and covalent/ionic (M-X) bonds which features a unique combination of ceramic-and metallic-like properties, e.g. high stiffness, good corrosion resistance, good conductivity, high damage tolerance, and machinability 1-5. Thanks to this unique combination, M n+1 AX n are extremely promising for advanced high-temperature applications, and therefore of great interest. The design of materials and/or components for advanced high-temperature applications based on MAX phases requires knowledge of physical and mechanical properties. Such knowledge could only be achieved via successful synthesis and characterization of the materials. So far, roughly over 70 MAX compounds and approximately 100 solid solutions have been synthesized. These are but a small fraction of the 'pure' 600 MAX compounds 6 and billions (if not trillions) of solid solutions that could possibly exist, i.e. those that are elastic and thermodynamic stable. The discovered MAX phases, therefore, constitute only a small portion of the multi-dimensional MAX design space. Richer and better solutions for materials and/or components design based on MAX phases are to be expected within the remaining undiscovered MAX materials design space; and, to follow up, engineering questions such as "what is the MAX phase with highest Young modulus?" or "among the MAX alloys which ones exhibit solid-solution strengthening?" will naturally rise. In order to answer such questions, it is necessary: for (1) a systematic research and development scheme to be reasonably sketched according to a specific engineering problem and to integrate such scheme with (2) combined high-throughput synthesis and characterization capabilities 7, 8. The latter, although experiencing a great cost inertia, has started to grow. This is especially true with the advent of computer-assisted schemes for materials development. Indeed, recent developments in computer infrastructure and simulation methods have enabled the accelerated development of high-throughput computational materials design. Motivated by the increasing interest in MAX alloys and the engineering problem of solid-solution strengthening of MAX phases 9, 10 , we have developed a design scheme based on high-throughput first-principles calculations. The scheme currently has two steps. The first step is to study the effect of M site alloys on the solid solutions of M 2 1 AX-M 2 2 AX system, where M 1 and M 2 are two different transition metals, using cluster expansion approach. Based on this work, suggestions on MAX phases that possibly exhibit solid solution with each other (and hence solution strengthening) will be made. The result of this work for the case of M 2 1 AlC-M 2 2 AlC has already been
Physical Review B
Solid solution MAX phases offer the opportunity for further tuning of the thermo-mechanical and f... more Solid solution MAX phases offer the opportunity for further tuning of the thermo-mechanical and functional properties of MAX phases, increasing their envelope of performance. Previous experimental results show that the lattice parameters of Ti 3 (Si x Al 1−x)C 2 decrease, while the Young's modulus increases with increased Si content in the lattice. In this work, we present a computational investigation of the structural, electronic, and mechanical properties of Ti 3 (Si x Al 1−x)C 2 (x= 0, 0.25, 0.5, 0.75, and 1). The solid solutions were modeled using special quasirandom structures (SQS) and calculated using Density Functional Theory (DFT), which is implemented in the Vienna Ab initio Simulation Package (VASP). The SQS structures represent random mixing of Al and Si in the A sublattice of 312 MAX phase and their structural, electronic, and mechanical properties were calculated and compared with experiments. We study the cleavage and slip behavior of Ti 3 (Si x Al 1−x)C 2 to investigate the deformation behavior in terms of cleavage and shear. It has been shown that the cleavage between M and A layers results in increasing cleavage stress in Ti 3 (Si x Al 1−x)C 2 as a function of Si content in the lattice. In addition, the shear deformation of hexagonal close packed Ti 3 (Si x Al 1−x)C 2 under 2110 {0001} and 0110 {0001} results in increasing unstable stacking fault energy (USFE) and ideal shear strength (ISS) in Ti 3 (Si x Al 1−x)C 2 as the system becomes richer in Si.
Chemistry of Materials
The thermally driven orders-of-magnitude modulation of resistance and optical transmittance obser... more The thermally driven orders-of-magnitude modulation of resistance and optical transmittance observed in VO 2 makes it an archetypal first-order phase transition material and underpins functional applications in logic and memory circuitry, electromagnetic cloaking, ballistic modulation, and thermochromic glazing to provide just a few representative examples. VO 2 can be reversibly switched from an insulating to a metallic state at an equilibrium transition temperature of 67 °C. Tuning the phase diagram of VO 2 to bring the transition temperature closer to room temperature has been a longstanding objective and one that has tremendous practical relevance. Substitutional incorporation of dopants has been the most common strategy for modulating the metalinsulator transition temperature but requires that the dopants be incorporated during synthesis. Here we demonstrate a novel postsynthetic diffusive annealing approach for incorporating interstitial B dopants within VO 2. The postsynthetic method allows for the transition temperature to be programmed after synthesis and furthermore represents an entirely distinctive mode of modulating the phase diagram of VO 2. Local structure studies in conjunction with density functional theory calculations point to the strong preference of B atoms for tetrahedral coordination within interstitial sites of VO 2 ; these tetrahedrally coordinated dopant atoms hinder the rutile → monoclinic transition by impeding the dimerization of V−V chains and decreasing the covalency of the lattice. The results suggest that interstitial dopant incorporation is a powerful method for modulating the transition temperature and electronic instabilities of VO 2 and provides a facile approach for postsynthetic dopant incorporation to reach a switching temperature required for a specific application.
Catal. Sci. Technol.
An anatase TiO2 (001) surface is active and selective toward water production and results in the ... more An anatase TiO2 (001) surface is active and selective toward water production and results in the modification of the surface by forming S-doped TiO2, which enhances its photocatalytic activity.