IU Indianapolis ScholarWorks :: Browsing by Author "Larriba-Andaluz, Carlos"

Browsing by Author "Larriba-Andaluz, Carlos"

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Analysis of Ion Motion and Diffusion Confinement in Inverted Drift Tubes and Trapped Ion Mobility Spectrometry Devices
(ACS, 2019) Larriba-Andaluz, Carlos; Chen, Xi; Nahin, Minal; Wu, Tianyang; Fukushima, Nobuhiko; Mechanical and Energy Engineering, School of Engineering and Technology
Ion motion in trapped ion mobility spectrometers (TIMS) and inverted drift tubes (IDT) has been investigated. The two-dimensional (2D) axisymmetric analytical solution to the Nernst–Planck equation for constant gas flows and opposed linearly increasing fields is presented for the first time and is used to study the dynamics of ion distributions in the ramp region. It is shown that axial diffusion confinement is possible and that broad packets of ions injected initially into the system can be contracted. This comes at the expense of the generation of a residual radial field that pushes the ions outward. This residual electric field is of significant importance as it hampers sensitivity and resolution when parabolic velocity profiles form. When radio frequency (RF) is employed at low pressures, this radial field affects the stability of ions inside the mobility cell. Trajectories and frequencies for stable motion are determined through the study of Mathieu’s equation. Finally, effective resolutions for the ramp and plateau regions of the TIMS instrument are provided. While resolution depends on the inverse of the square root of mobility, when proper parameters are used, resolutions in the thousands can be achieved theoretically for modest distances and large mobilities.
A contribution to the amaranthine quarrel between true and average electrical mobility in the free molecular regime
(Taylor & Francis, 2017) Larriba-Andaluz, Carlos; Nahin, Minal; Shrivastav, Vaibhav; Mechanical Engineering, School of Engineering and Technology
Landau and Lipschitz's approach—termed here H&B due to the use of Happel and Brenner's slow rotation approximation—for calculating the average electrical mobility over all orientations of an ion in the free molecular regime is shown in this manuscript to be an invalid assumption for non-globular ions when a fixed electrical field is present. The reason behind the invalidity seems to be the confusion between average “settling” velocity (the calculation intended by H&B) and the average mobility (drag) in the direction of the field. When a missing orientation is taken into account by rotating the drag tensor, the average mobility obtained through Landau's approach coincides with well-known orientationally averaged Kinetic Theory Methods such as those of Mason and McDaniel (M&M). H&B's averaging approach, however, can be related to the true mobility displacement of the ion or, in other words, the displacement occurring in the direction of the velocity. This true mobility displacement only agrees with the average mobility displacement if ion velocity and electrical field have always the same direction, which only happens under special cases. Analytical and numerical calculations of collision cross-sections of linear and planar structures using a momentum transfer kinetic theory approach are chosen here as a means to prove that a single rotation of the drag tensor is sufficient to show agreement between both methods. A projected area approach is also used to prove the inadequacy of the H&B method.
Controlled Fluxes of Silicon Nanoparticles to a Substrate in Pulsed Radio-Frequency Argon–Silane Plasmas
(Springer, 2017-01) Larriba-Andaluz, Carlos; Girshick, Steven L.; Department of Engineering Technology, School of Engineering and Technology
It has been hypothesized that high-energy impact of very small silicon nanoparticles on a substrate may lead to epitaxial growth of silicon films at low substrate temperature. A possible means for producing such energetic nanoparticle fluxes involves pulsing an RF silane-containing plasma, and applying a positive DC bias to the substrate during the afterglow phase of each pulse so as to collect the negatively charged particles generated during the RF power on phase. We here report numerical modeling to provide a preliminary assessment of the feasibility of this scheme. The system modeled is a parallel-plate capacitively-coupled RF argon–silane plasma at pressures around 100 mTorr. Simulation results indicate that it is possible to achieve a periodic steady state in which each pulse delivers a controlled flux of nanoparticles to the biased substrate, that average particle sizes can be kept below 2–3 nm, that impact energies of the negatively-charged nanoparticles that are attracted by the applied bias can be maintained in the ~1 eV/atom range thought to be conducive to epitaxial growth without causing film damage, and that the volume fraction of neutral nanoparticles that deposit by low-velocity diffusion can be kept well below 1 %. The effects of several operating parameters are explored, including RF voltage, pressure, the value of the applied DC bias, and RF power on and off time during each pulse.
Enhancing Separation and Constriction of Ion Mobility Distributions in Drift Tubes at Atmospheric Pressure Using Varying Fields
(American Chemical Society, 2022-03-31) Chen, Xi; Latif, Mohsen; Gandhi, Viraj D.; Chen, Xuemeng; Hua, Leyan; Fukushima, Nobuhiko; Larriba-Andaluz, Carlos; Mechanical and Energy Engineering, School of Engineering and Technology
A linearly decreasing electric field has been previously proven to be effective for diffusional correction of ions in a varying field drift tube (VFDT) system, leading to higher resolving powers compared to a conventional drift tube due to its capacity to narrow distributions midflight. However, the theoretical predictions in resolving power of the VFDT were much higher than what was observed experimentally. The reason behind this discrepancy has been identified as the difference between the theoretically calculated resolving power (spatial) and the experimental one (time). To match the high spatial resolving power experimentally, a secondary high voltage pulse (HVP) at a properly adjusted time is used to provide the ions with enough momentum to increase their drift velocity and hence their time-resolving power. A series of systematic numerical simulations and experimental tests have been designed to corroborate our theoretical findings. The HVP-VFDT atmospheric pressure portable system improves the resolving power from the maximum expected of 60–80 for a regular drift tube to 250 in just 21 cm in length and 7kV, an unprecedent accomplishment.
Experimental Investigation of Pressure Development and Flame Characteristics in a Pre-Combustion Chamber
(2024-08) Miller, Jared; Nalim, Mohamed Razi; Larriba-Andaluz, Carlos; Yu, Huidan (Whitney)
This study contributes to research involving wave rotor combustors by studying the development of a hot jet issuing from a cylindrical pre-combustion chamber. The pre-chamber was developed to provide a hot fuel-air mixture as an ignition source to a rectangular combustion chamber, which models the properties of a wave rotor channel. The pre-combustion chamber in this study was rebuilt for study and placed in a new housing so that buoyancy effects could be studied in tandem with other characteristics. The effectiveness of this hot jet is estimated by using devices and instrumentation to measure properties inside the pre-chamber under many different conditions. The properties tracked in this study include maximum pressure, the pressure and time at which an aluminum diaphragm ruptures, and the moment a developed flame reaches a precise location within the chamber. The pressure is tracked through use of a high-frequency pressure transducer, the diaphragm rupture moment is captured with a high-speed video camera, and the flame within the pre-chamber is detected by a custom-built ionization probe. The experimental apparatus was used in three configurations to study any potential buoyancy effects and utilized three different gaseous fuels, including a 50%-50% methane-hydrogen blend, pure methane, and pure hydrogen. Additionally, the equivalence ratio within the pre-chamber was varied from values of 0.9 to 1.2, and the initial pressure was set to either 1.0, 1.5, or 1.75 atm. In all cases, combustion was initiated from a spark plug, causing a flame to develop until the diaphragm breaks, releasing a hot jet of fuel and air from the nozzle inserted into the pre-chamber. In the pressure transducer tests, it was found that hydrogen produced the highest pressures and fastest rupture times, and methane produced the lowest pressures and slowest rupture times. The methane-hydrogen blend provided a middle ground between the two pure fuels. An equivalence ratio of 1.1 consistently provided the highest pressure values and fastest rupture out of all tested values. It was also found that the orientation has a noticeable impact on both the pressure development and rupture moment as higher maximum pressures were achieved when the chamber was laid flat in the “vertical jet” orientation as compared to when it was stood upright in the “horizontal jet” orientation. Additionally, increasing the initial pressure strongly increased the maximum developed pressure but had minimal impact on the rupture moment. The tests done with the ion probe demonstrated that an equivalence ratio of 1.1 produces a flame that reaches the ion probe faster than an equivalence ratio of 1.0 for the methane-hydrogen blend. In its current form, the ion probe setup has significant limitations and should continue to be developed for future studies. The properties analyzed in this study deepen the understanding of the processes that occur within the pre-chamber and aid in understanding the conditions that may exist in the hot jet produced by it as the nozzle ruptures. The knowledge gained in the study can also be applied to develop models that can predict other parameters that are difficult to physically measure.
Field-Switching Repeller Flowing Atmospheric-Pressure Afterglow Drift Tube Ion Mobility Spectrometry
(American Chemical Society, 2022-03-02) Latif, Mohsen; Chen, Xi; Gandhi, Viraj D.; Larriba-Andaluz, Carlos; Gamez, Gerardo; Mechanical and Energy Engineering, School of Engineering and Technology
In this work, a field-switching (FS) technique is employed with a flowing atmospheric pressure afterglow (FAPA) source in drift tube ion mobility spectrometry (DTIMS). The premise is to incorporate a tip-repeller electrode as a substitute for the Bradbury–Nielsen gate (BNG) so as to overcome corresponding disadvantages of the BNG, including the gate depletion effect (GDE). The DTIMS spectra were optimized in terms of peak shape and full width by inserting an aperture at the DTIMS inlet that was used to control the neutral molecules’ penetration into the separation region, thus preventing neutral-ion reactions inside. The FAPA and repeller’s experimental operating conditions including drift and plasma gas flow rates, pulse injection times, repeller positioning and voltage, FAPA current, and effluent angle were optimized. Ion mobility spectra of selected compounds were captured, and the corresponding reduced mobility values were calculated and compared with the literature. The 6-fold improvements in limit of detection (LOD) compared with previous work were obtained for 2,6-DTBP and acetaminophen. The enhanced performance of the FS-FAPA-DTIMS was also investigated as a function of the GDE when compared with FAPA-DTIMS containing BNG.
Fundamentals of ion mobility in the free molecular regime. Interlacing the past, present and future of ion mobility calculations
(Taylor & Francis, 2020) Larriba-Andaluz, Carlos; Prell, James S.; Mechanical and Energy Engineering, School of Engineering and Technology
While existing ion mobility calculators are capable of feats as impressive as calculating collision cross sections (CCS) within a few per cent and within a very reasonable time, the simplifications assumed in their estimations precludes them from being more precise, potentially overreaching with respect to the interpretation of existing calculations. With ion mobility instrumentation progressively reaching resolutions of several hundreds to thousands (accuracy in the range of ∼0.1%), a more accurate theoretical description of gas-phase ion mobility becomes necessary to correctly interpret experimental state-of-the-art separations. This manuscript entails an effort to consolidate the most relevant theoretical work pertaining to ion mobility within the ‘free molecular’ regime, describing in detail the rationale for approximations up to the two-temperature theory, using both a momentum transfer approach as well as the solution to the moments of the Boltzmann equation for the ion. With knowledge of the existing deficiencies in the numerical methods, the manuscript provides a series of necessary additions in order to better simulate some of the separations observed experimentally due to second-order effects, namely, high field effects, dipole alignment, angular velocities and moments of inertia, potential interactions and inelastic collisions among others.
Hot jet ignition delay characterization of methane and hydrogen at elevated temperatures
(Pro Quest, 2017-08) Kojok, Ali Tarraf; Nalim, M. Razi; Larriba-Andaluz, Carlos; Zhu, Likhun
This study contributes to a better understanding of ignition by hot combustion gases which finds application in internal combustion chambers with pre-chamber ignition as well as in wave rotor engine applications. The experimental apparatus consists of two combustion chambers: a pre chamber that generates the transient hot jet of gas and a main chamber which contains the main fuel air blend under study. Variables considered are three fuel mixtures (Hydrogen, Methane, 50\% Hydrogen-Methane), initial pressure in the pre-chamber ranging from 1 to 2 atm, equivalence ratio of the fuel air mixture in the main combustion chamber ranging from 0.4 to 1.5, and initial temperature of the main combustion chamber mixture ranging from 297 K to 500 K. Experimental data makes use of 4 pressure sensors with a recorded sampling rate up to 300 kHz, as well as high speed Schlieren imaging with a recorded frame rate up to 20,833 frame per seconds. Results shows an overall increase in ignition delay with increasing equivalence ratio. High temperature of the main chamber blend was found not to affect hot jet ignition delay considerably. Physical mixing effects, and density of the main chamber mixture have a greater effect on hot jet ignition delay.
Measurement and Theory of Gas-Phase Ion Mobility Shifts Resulting from Isotopomer Mass Distribution Changes
(American Chemical Society, 2021) Harrilal, Christopher P.; Gandhi, Viraj D.; Nagy, Gabe; Chen, Xi; Buchanan, Michael G.; Wojcik, Roza; Conant, Christopher R.; Donor, Micah T.; Ibrahim, Yehia M.; Garimella, Sandilya V.B.; Smith, Richard D.; Larriba-Andaluz, Carlos; Mechanical and Energy Engineering, School of Engineering and Technology
The unanticipated discovery of recent ultra-high-resolution ion mobility spectrometry (IMS) measurements revealing that isotopomers─compounds that differ only in the isotopic substitution sites─can be separated has raised questions as to the physical basis for their separation. A study comparing IMS separations for two isotopomer sets in conjunction with theory and simulations accounting for ion rotational effects provides the first-ever prediction of rotation-mediated shifts. The simulations produce observable mobility shifts due to differences in gas-ion collision frequency and translational-to-rotational energy transfer. These differences can be attributed to distinct changes in the moment of inertia and center of mass between isotopomers. The simulations are in broad agreement with the observed experiments and consistent with relative mobility differences between isotopomers. These results provide a basis for refining IMS theory and a new foundation to obtain additional structural insights through IMS.
Modeling and experimenting a novel inverted drift tube device for improved mobility analysis of aerosol particles
(2017-12) Nahin, Md Minal; Larriba-Andaluz, Carlos
Ion Mobility Spectrometry (IMS) is an analytical technique for separation of charged particles in the gas phase. The history of IMS is not very old, and in this century, the IMS technique has grown rapidly in the advent of modern instruments. Among currently available ion mobility spectrometers, the DTIMS, FAIMS, TWIMS, DMA are notable. Though all the IMS systems have some uniqueness in case of particle separation and detection, however, all instruments have common shortcomings. They lack in resolution, which is independent of mobility of different charged particles and they are not able to separate bigger particles (20 120 nm) with good accuracy. The work presented here demonstrates a new concept of IMS technique at atmospheric pressure which has a resolution much higher than that of the currently available DTIMS (Drift Tube Ion Mobility Spectrometry) instruments. The unique feature of this instrument is the diffusion auto-correction. Being tunable, It can separate the wide range of particles of different diameters. The working principle of this new IMS technique is different from the typical DTIMS and to simply put, it can be considered as an inversion of commonly used technique, so termed as Inverted Drift Tube (IDT).The whole work performed here can be divided into three major phases. In the first phase, the analytical solution was derived for two new separation techniques: IPF (Intermittent push flow) and NSP (Nearly stopping potential) separations. In the next phase, simulations were done to show the accuracy of the analytical solution. An ion optics simulator software called SIMION 8.1 was used for conducting the simulation works. These simulations adopted the statistical diffusion (SDS) collision algorithm to emulate the real scenario in gas phase more precisely. In the last phase, a prototype of experimental setup was built. The experimental results were then validated by simulated results.

Browsing by Author "Larriba-Andaluz, Carlos"

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