A new publication titled “Superhydrophobic and Self-Cleaning Aluminum via a Rapid and Controlled Process” was published in ACS Applied Engineering Materials in October 2022.
Engineers have been often inspired by nature in various ways, ranging from the design of structures to the selection of materials. For e.g., lotus leaves exhibit hydrophobic behavior which has been translated to the creation of self-cleaning materials. One construction material of interest is aluminum for light-weight structural applications. Previously, studies have reported creation of superhydrophobic aluminum surfaces. However, most of the processes are not environmentally friendly, are time-consuming, and some are not feasible for large-scale applications. In our most recent paper, we present a rapid and controlled process to create superhydrophobic aluminum for use in external environments. With a 1 hr of fabrication time, we achieve contact angle of 158.06° and a sliding angle of 1.94°. Finally, the surface is durable and resilient when exposed to a range of extreme temperatures (-18°C to 100°C). These results pave the way for implementation of superhydrophobic aluminum surfaces for large-scale structural and construction applications.
This is the first article from our group’s MS candidate Ravi Sharma.
Garg Group warmly welcomes new members who started in Summer and Fall 2022. These are MS candidates: Mohamed Abdelrahman, Sudharsan Rathnakumar; PhD candidates: Farjad Iqbal, Tausif Elahi; and Postdoc: Dr. Yujia Min.
Additionally, MS candidates Pablo Romero and Sonali Srivastava successfully completed their MS thesis in Summer 2022. Pablo returned back to Chile to continue working in the industry. Sonali enrolled in the PhD program at Virginia Tech. We wish both of them best of luck in their future endeavors.
Several students from the group are set to graduate in Summer 2022. Hence, multiple openings for graduate students (both at MS and PhD level) are available for Fall 2023. Please apply and join us!
A postdoc opening maybe announced by the end of 2022.
A new publication titled “Ultra-high Gamma Irradiation of Calcium Silicate Hydrates: Impact on Mechanical Properties, Nanostructure, and Atomic Environments” was published in Cement and Concrete Research in August 2022.
Nuclear power plants, a major source of emission-free energy, are closing on the end of their design life, and extending the operating life of these power plants will require extensively studying irradiation effects on each critical part of nuclear power plants. The concrete biological shield is one such critical part, which not only absorbs irradiation but also provides structural support. In this paper, we looked at gamma irradiation effects on calcium silicate hydrate, on micro, nano, and atomic scale on a range of irradiation dosages (from 0 MGy to 189 MGy), based on an extended 80-year design life. XRD reveals that irradiation decreases C-S-H basal spacing (~ 0.6 ± 0.1 Å for 189 MGy), likely through the removal of interlayer water as supported by TGA. The Young’s modulus increased with irradiation, but porosity remained unchanged implying the decrease in basal spacing is the main reason behind the increase in young’s modulus. 1H NMR data show that irradiation increases the FWHM of the CaO-H cluster peaks indicating some disorder in the local proton CaO-H species. Finally, 29Si NMR data show that the silicate structure mostly stays unaffected, but the chemical shift of minor Q3 silica becomes less negative indicating slight depolymerization of the silicate structure. Overall, the C-S-H gel stiffens upon ultrahigh gamma irradiation affecting the long-term service life of a nuclear powerplant.
This work was led by Aniruddha Baral and performed in collaboration with Oak Ridge National Lab, Columbia University, and Argonne National Lab. Aniruddha graduated with a PhD in summer 2022 and started a postdoc at the University of Sheffield.
Following the success of the 2021 picnic, the 2nd GG-AP was held in June 2022. The group spent a day eating, relaxing, and playing team games at Allerton Park. An ad-hoc Picnic Planning Committee was appointed to plan the day and they came up with a fine agenda.
As usual, we started with some group photos.
And then played some games. The Tug of War was especially fun which was held between MS and PhD students of the group. The PhD students won the first game. However, in the second game, the MS students pulled their way to victory (see video below). The final score after 2 games was 1-1 and we decided to leave it at that.
Other games included eating Oreos off your head without using your hands.
Finally, we had an international potluck style food brought by all participants. We finished the day with some aerial shots.
The next annual picnic will be held in 2023 summer. We’ll be looking for motivated individuals from the group to serve on next year’s Picnic Planning Committee. Interested personnel may self-nominate or nominate others.
A new publication titled “Evolution of kaolinite morphology upon exfoliation and dissolution: Evidence for nanoscale layer thinning in metakaolin” was published in Applied Clay Science in March 2022.
When kaolinite is calcined, it transforms into metakaolin, which can dissolve and react under alkaline conditions, making it a potential low-CO2 alternative to Portland cement. The reactivity of kaolinite has been studied in terms of dissolution kinetics, but not much is known about the evolution of clay morphology upon dissolution. Here, we apply quantitative imaging approaches to quantify the extent of morphological changes that occur in dissolving kaolinite and metakaolin at multiple scales. At the micro-scale, we successfully capture in situ exfoliation of clay particles while dissolving in NaOH. We find a noticeable difference in the pattern in which these clays break apart. Raw kaolinite would expand along its length, while layers in metakaolin were not as well defined as in kaolinite. At the nano-scale, when comparing the layer thickness of metakaolin and dissolved metakaolin, an evident thinning of ~20 nm (from 95 nm to 75 nm) is found. These results explain how the dissolution process takes place on these layered structures: by breaking the bonds in-between layers and then dissolving these individual layers leading to a reduction in thickness. These new results pave the way towards a morphological understanding of calcined clay dissolution.
This is the first article from our group’s M.S. candidate Pablo Romero. Congratulations Pablo!
A new publication titled “Impact of Na/Al Ratio on the Extent of Alkali-Activation Reaction: Non-linearity and Diminishing Returns” was published in Frontiers in Chemistry in January 2022.
To address the high CO2 footprint associated with cement production, many alternative, sustainable binders are now gaining worldwide attention, including alkali-activated materials (AAM). The alkali-activation reaction of metakaolin is a fairly complex process involving transformation of one amorphous reactant (precursor metakaolin) into another amorphous product or products (N-A-S-H gel and/or disordered zeolite type phases). In spite of this complexity, researchers in the past 2 decades have gained significant knowledge on the nature of this reaction at multiple scales. Understanding and developing a clear relationship between the alkalinity of the mix and the extent of reaction is of high interest for practical applications. However, detailed and thorough investigations on this important relationship are limited. Here, in this study, we address this gap by systematically investigating a series of alkali-activated materials samples with a wide range of Na/Al ratios (0.5–1.8) using seven different yet complementary analytical techniques (isothermal calorimetry, FTIR, XRD, TGA, 27Al and 23Na NMR, and Raman imaging). Applied in tandem, these tools reveal a clear but non-linear relationship between the Na/Al ratio and the extent of alkali-activation reaction indicating diminishing returns at higher Na/Al ratios, where higher Na/Al ratios cause an increase in the degree of reaction until a certain point at which the increase in Na/Al ratio does not significantly affect the reaction kinetics, but may affect the gel polymerization. These findings could potentially aid decision making for commercial applications of AAMs where alkalinity of the mix is an important parameter for performance as well as safety.
This is the first article from our group’s MS candidate Omar Abdelrahman. Congratulations Omar!
A new publication titled “National and Regional Waste Stream in the United States: Conformance and Disparity” was published in Environmental Research: Infrastructure and Sustainability in November 2021.
Accurate estimation of material classes – paper, food, plastic, yard, metal, and glass waste – present in the municipal solid waste stream is critical for efficient waste management. The generation estimates for these material classes (both composition and quantity) are estimated via two approaches, the material-flow-based estimates and site-specific estimates. In the United States, the U.S. EPA’s material flow-based predictions yield MSW generation estimates for the entire nation, whereas site-specific estimates yield MSW generation estimates on a regional scale, i.e., states and counties. In the past, several studies had indicated that the U.S. EPA’s material-flow-based predictions differ substantially from the aggregated tonnage of MSW managed by waste handling facilities in the United States. However, the material-class-specific factors that led to these discrepancies are not apparent. In this study, we uncover the basis of these discrepancies by comparing national MSW generation estimates with the site-specific MSW general estimates. Specifically, our analysis suggests that the material-flow-based estimates are accurate for food, plastic, and glass material classes. In contrast, we find that the material-flow-based predictions underestimate paper waste disposal by at least 15 million tons annually. Based on these insights, the material-flow-based MSW estimation framework can be refined to yield better MSW generation estimates. A thorough estimation of waste is the key to efficient waste management.
This is the second article from our group’s Ph.D. candidate Vikram Kumar. Congratulations Vikram!
Garg Group warmly welcomes new members who started in Summer and Fall 2021. These are MS candidates: Jacob Doehring, Dhanush Sahasra, Andrew Witte; PhD candidates: Bayezid Baten, Chirayu Kothari, Hyeonseok Jee, Brandy Diggs-McGee; and Postdoc: Dr. Hamza Samouh. Additionally, MS candidate Vikram Kumar successfully completed his MS thesis in Summer 2021 and continues in the group as a new PhD candidate, starting Fall 2021.
Mulitple openings for graduate students (both at MS and PhD level) are available for Fall 2022. Please apply and join us!
Additionally, a postdoc position has also just opened in our group. Please apply before Feb 21, 2022. Job details and application info is in the file below:.
A new publication titled “The Chemical and Physical Origin of Incineration Ash Reactivity in Cementitious Systems” was published in Resources, Conservation and Recycling in October 2021.
Incorporating industrial byproducts and waste in concrete is the key to reducing landfill usage as well as lowering the environmental footprint of cement industry. An emerging industrial byproduct which can partly replace cement is the Municipal Solid Waste Incinerator Ash (MSWI ash: residue that is left after incineration of municipal solid waste in a Waste-to-Energy facility). These ashes are predominantly calcium-rich; however, they also contain additional elements whose speciation is not known. These elements can significantly alter the hydration characteristics of a cementitious system. Our initial foray into cementitious matrices including these ashes, reveals that these ashes can accelerate as well as retard cement hydration. Specifically, Pb, Br, S, Ca, and Cl appear to accelerate cement hydration, whereas Cu, Fe, Al, Ti, Si, K, Zn, and Sr appear to retard cement hydration. Changes in hydration characteristics can have a strong bearing on the physical characteristics of cementitious systems incorporating incineration ashes. Thus, to selectively screen ashes that synergistically enhance the physical characteristics, we introduce a novel “Incineration Ash Coefficient (IAC),” which shows a strong correlation with the compressive strength (R2=0.79) of cement-ash binary mixtures.
This is the first article from our group’s Ph.D. candidate Vikram Kumar. Congratulations Vikram!
Given the growing world population and urban density, management of municipal solid waste is becoming an increasingly difficult issue. One way to approach handling of all this solid waste is to incinerate it for energy as is done in Waste-to-Energy plants. However, the residual ash (bottom and fly ash) post combustion of this waste is unused and often sent to the landfill. There is potential in utilizing this ash for several commercial applications if its chemical composition and mineralogy could be understood in detail.
Garg Group has recently received funding from Advanced Research Projects Agency – Energy (ARPA-E) for a two year project (2021-2023) for investigating the chemistry of these ashes and then identifying composition dependent end uses. The project is titled RADAR-X (Rapid AI-based Dissection of Ashes using Raman and XRF Spectroscopy). This is an interdisciplinary project in collaboration with Prof. Jeffery Roesler, Dr. Brajendra K. Sharma, and Prof. Lav Varshney. This project will build upon the findings from an earlier project on municipal solid waste which was seed funded by the Institute for Sustainability, Energy, and Environment at University of Illinois, Urbana-Champaign. Some more information on this new project can be found here.
We are excited to continue our efforts in this field to make our world a sustainable world!