Publications by authors named "Ali Davoodabadi"

5 Publications

  • Page 1 of 1

Evaporation in nano/molecular materials.

Adv Colloid Interface Sci 2021 Apr 23;290:102385. Epub 2021 Feb 23.

Department of Mechanical Engineering, University of Houston, 4726 Calhoun Rd, Houston, TX 77204, USA. Electronic address:

Evaporation is a physical phenomenon with fundamental significance to both nature and technology ranging from plant transpiration to DNA engineering. Various analytical and empirical relationships have been proposed to characterize evaporation kinetics at macroscopic scales. However, theoretical models to describe the kinetics of evaporation from nano and sub-nanometer (molecular) confinements are absent. On the other hand, the fast advancements in technology concentrated on development of nano/molecular-scale devices demand appropriate models that can accurately predict physics of phase-change in these systems. A thorough understanding of the physics of evaporation in nano/molecular materials is, thus, of critical importance to develop the required models. This understanding is also crucial to explain the intriguing evaporation-related phenomena that only take place when the characteristic length of the system drops to several nanometers. Here, we comprehensively review the underlying physics of evaporation phenomenon and discuss the effects of nano/molecular confinement on evaporation. The role of liquid-wall interface-related phenomena including the effects of disjoining pressure and flow slippage on evaporation from nano/molecular confinements are discussed. Different driving forces that can induce evaporation in small confinements, such as heat transfer, pressure drop, cavitation and density fluctuations are elaborated. Hydrophobic confinement induced evaporation and its potential application for synthetic ion channels are discussed in detail. Evaporation of water as molecular clusters rather than isolated molecules is discussed. Despite the lack of experimental investigations on evaporation at nanoscale, there exist an extensive body of literature that have applied different simulation techniques to predict the phase change behavior of liquids in nanoconfinements. We infer that exploring the effect of electrostatic interactions and flow slippage to enhance evaporation from nanoconduits is an interesting topic for future endeavors. Further future studies could be devoted to developing nano/molecular channels with evaporation-based gating mechanism and utilization of 2D materials to tune energy barrier for evaporation leading to enhanced evaporation.
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http://dx.doi.org/10.1016/j.cis.2021.102385DOI Listing
April 2021

The potential of hydrogen hydrate as a future hydrogen storage medium.

iScience 2021 Jan 9;24(1):101907. Epub 2020 Dec 9.

Department of Mechanical Engineering, University of Houston, 4726 Calhoun Road, Houston, TX 77204, USA.

Hydrogen is recognized as the "future fuel" and the most promising alternative of fossil fuels due to its remarkable properties including exceptionally high energy content per unit mass (142 ), low mass density, and massive environmental and economical upsides. A wide spectrum of methods in production, especially carbon-free approaches, purification, and storage have been investigated to bring this energy source closer to the technological deployment. Hydrogen hydrates are among the most intriguing material paradigms for storage due to their appealing properties such as low energy consumption for charge and discharge, safety, cost-effectiveness, and favorable environmental features. Here, we comprehensively discuss the progress in understanding of hydrogen clathrate hydrates with an emphasis on charging/discharging rate of (i.e. hydrate formation and dissociation rates) and the storage capacity. A thorough understanding on phase equilibrium of the hydrates and its variation through different materials is provided. The path toward ambient temperature and pressure hydrogen batteries with high storage capacity is elucidated. We suggest that the charging rate of in this storage medium and long cyclic performance are more immediate challenges than storage capacity for technological translation of this storage medium. This review and provided outlook establish a groundwork for further innovation on hydrogen hydrate systems for promising future of hydrogen fuel.
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http://dx.doi.org/10.1016/j.isci.2020.101907DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7770607PMC
January 2021

Transport Phenomena in Nano/Molecular Confinements.

ACS Nano 2020 Nov 30. Epub 2020 Nov 30.

Department of Mechanical Engineering, University of Houston, 4726 Calhoun Road, Houston, Texas 77204, United States.

The transport of fluid and ions in nano/molecular confinements is the governing physics of a myriad of embodiments in nature and technology including human physiology, plants, energy modules, water collection and treatment systems, chemical processes, materials synthesis, and medicine. At nano/molecular scales, the confinement dimension approaches the molecular size and the transport characteristics deviates significantly from that at macro/micro scales. A thorough understanding of physics of transport at these scales and associated fluid properties is undoubtedly critical for future technologies. This compressive review provides an elaborate picture on the promising future applications of nano/molecular transport, highlights experimental and simulation metrologies to probe and comprehend this transport phenomenon, discusses the physics of fluid transport, tunable flow by orders of magnitude, and gating mechanisms at these scales, and lists the advancement in the fabrication methodologies to turn these transport concepts into reality. Properties such as chain-like liquid transport, confined gas transport, surface charge-driven ion transport, physical/chemical ion gates, and ion diodes will provide avenues to devise technologies with enhanced performance inaccessible through macro/micro systems. This review aims to provide a consolidated body of knowledge to accelerate innovation and breakthrough in the above fields.
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http://dx.doi.org/10.1021/acsnano.0c07372DOI Listing
November 2020

On interfacial viscosity in nanochannels.

Nanoscale 2020 Jul 2;12(27):14626-14635. Epub 2020 Jul 2.

Department of Mechanical Engineering, University of Houston, 4726 Calhoun Rd, Houston, Texas 77204, USA.

Capillary driven transport of liquids in nanoscopic channels is an omnipresent phenomenon in nature and technology including fluid flow in the human body and plants, drug delivery, nanofluidic devices, and energy/water systems. However, the kinetics of this mass transport mechanism remains in question as the well-known Lucas-Washburn (LW) model predicts significantly faster flow rates compared to the experimental observations. We here showed the role of interfacial viscosity in capillary motion slowdown in nanochannels through a combination of experimental, analytical and molecular dynamics techniques. We showed that the slower liquid flow is due to the formation of a thin liquid layer adjacent to the channel walls with a viscosity substantially greater than the bulk liquid. By incorporating the effect of the interfacial layer, we presented a theoretical model that accurately predicts the capillarity kinetics in nanochannels of different heights. Non-equilibrium molecular dynamics simulation confirmed the obtained interfacial viscosities. The viscosities of isopropanol and ethanol within the interfacial layer were 9.048 mPa s and 4.405 mPa s, respectively (i.e. 279% and 276% greater than their bulk values). We also showed that the interfacial layers are 6.4 nm- and 5.3 nm-thick for isopropanol and ethanol, respectively.
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http://dx.doi.org/10.1039/d0nr02294bDOI Listing
July 2020

Metal Hydroxide/Polymer Textiles for Decontamination of Toxic Organophosphates: An Extensive Study of Wettability, Catalytic Activity, and the Effects of Aggregation.

ACS Appl Mater Interfaces 2019 Aug 15;11(34):31378-31385. Epub 2019 Aug 15.

University of New Hampshire , 105 Main Street , Durham 03824 , New Hampshire , United States.

Electrospun nanofibers (NFs) incorporated with catalytically active components have gained significant interest in chemical protective clothing. This is because of the desirable properties of the NFs combined with decontamination capability of the active component. Here, a series of metal hydroxide catalysts Ti(OH), Zr(OH), and Ce(OH) were incorporated into three different polymer NF systems. These new polymer/metal hydroxide composite NFs were then evaluated for their catalytic activity against a nerve agent simulant. Two methods were utilized to incorporate the metal hydroxides into the NFs. Method one used direct incorporation of Ti(OH), Zr(OH), and Ce(OH) catalysts, whereas method two employed incorporation of Ti(OH) via a precursor molecule. Composite NFs prepared via method one resulted in greatly improved reaction rates over the respective pure metal hydroxides due to reduced aggregation of catalysts, with polymer/Ce(OH) composite NFs having the fastest reaction rates out of method one materials. Interestingly, composite samples prepared by method two yielded the fastest reaction rates overall. This is because of the homogeneous distribution of the metal hydroxide catalyst throughout the NF. This homogeneous distribution created a hydroxyl-decorated NF surface with a greater number of exposed active sites for catalysis. The hydroxyl-decorated NF surface also resulted in an unexpected highly wettable composite NF, which also was found to contribute to the observed reaction rates. These results are not only promising for applications in chemical protective clothing but also show great potential for application in areas which need highly wettable membrane materials. This includes areas such as separators, antifouling membranes, and certain medical applications.
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http://dx.doi.org/10.1021/acsami.9b10440DOI Listing
August 2019