Chemical Engineering

Chemical Engineering

 

 

Poster Number: CHE-01

Authors: Kirti Bhardwaj, Greg M. Swain

Title:  Electrochemical Studies of Carbon Electrodes in Room Temperature Ionic Liquids – Effect of IL Type, Surface Chemistry, and Electrode Microstructure on Capacitance

 

Abstract: The properties of room temperature ionic liquids (RTILs) and the structure of the electrified interfaces they form with carbon electrodes has been the subject of both fundamental and applied research, particularly in the field of energy storage devices like supercapacitors. RTILs have great potential to replace conventional organic solvent/electrolyte systems because of environmentally-benign characteristics (non-volatility, non-toxicity) and thermal and electrochemical stability. The physicochemical properties of RTILs can be flexibly tuned through selection of the component ions. Research is needed to better understand the structure of electrified interfaces formed in these novel media at carbon electrodes of different surface chemistry and microstructure. Traditional models of the electrochemical double layer based on the dilute-solution approximation do not applicable to RTILs because of the absence of solvent, the high concentration of ions, strong interionic columbic forces, and electrostatic and hydrophobic interactions of charged ions with the electrode surface. The electrochemical investigation of the capacitance of carbon electrodes as a function of potential, the RTIL type, and surface termination will be reported on. 1-alkyl-3-methylimidazolium- based RTILs were studied at boron-doped-diamond thin-film electrodes. Comparison measurements were made using glassy carbon and nitrogen-incorporated tetrahedral amorphous carbon thin-film electrodes. Cyclic voltammetry and electrochemical impedance spectroscopy were used to measure the electrode capacitance.

 

This work was supported in part by U.S. Army Research Office W911NF-12-R-0011

 

 

 

Poster Number: CHE-02

Authors: Sayli Bote, Ramani Narayan

Title:  Design and Engineering of Value Added Industrial Products from Soybean Refinery

 

Abstract: Polyurethanes are most versatile polymers which have wide range of applications in foams, coatings, adhesive, sealants and elastomers. Polyurethane foams have variety of applications in buildings & construction, electronics, automotive, packaging materials and cushioning. Different densities polyurethane rigid foams can be used over wide range of temperatures. Polyols and isocyanates are two important components of polyurethanes. Isocyanates are synthesized from petroleum feedstocks but polyols can be synthesized from petroleum as well as from bio-based feedstocks. In current study, bio-based polyols for rigid as well as flexible foam application were synthesized from soymeal and soybean oil. Protein rich-source i.e. soymeal was used without any pre-treatment, without generating waste in one pot synthesis of bio-based polyol using transamidation chemistry. The ratio of primary to secondary hydroxyl groups in this polyol was higher. Also, use of inexpensive soymeal as raw material in synthesis of the polyol reduces its cost and makes its commercial production viable. Further, this bio-based polyol was used in synthesis of polyurethane rigid foams which were characterized for industrial applications. The soymeal was used in this study because of its high protein content and low moisture content as compared to algae proteins or other meals. In future work, soybean oil will be used for synthesis of polyol for flexible foam applications.

 

 

 

Poster Number: CHE-03

Authors: Kanchan Chavan, Scott Calabrese Barton

Title:  Simulation of Nanoscale Confinement for Process Intensification

 

Abstract: Nature has developed very efficient pathways to carry out multi-step reactions with controlled transport and kinetics.1 One such approach to reaction control is the confinement of active sites and the resulting reaction intermediates within a physical tunnel, by which the intermediate can be restricted from the bulk. Studying transport properties and kinetics of the confined systems provides a framework for the design of integrated catalytic systems and process intensification. In the present study, computational modeling has been performed to study the effect of geometric, kinetic, and transport parameters on intermediate channeling via confinement, using a continuum model. The efficiency of transport is quantified by reactant yield . Interaction of the intermediate with the confined channel has been addressed by molecular dynamics studies of diffusion coefficient and retention time. Retention of intermediates within the confined assembly, with minimal access to bulk solution, is shown to be the key to efficient channeling. References 1. I. Wheeldon et al., Nat. Chem., 8, 299–309 (2016) http://www.nature.com/doifinder/10.1038/nchem.2459.

 

This work was supported in part by Army Research Office MURI (#W911NF1410263) via The University of Utah

 

 

 

Poster Number: CHE-04

Authors: Tridip Das, Jason D. Nicholas, Yue Qi

Title:  Computational Study of the Charge Distribution of Mixed Valance Fe in La1-xSrxFeO3-δ and its Impact on Oxygen Vacancy Interactions

 

Abstract: It has been challenging for both modeling and experiments to determine the distribution of mixed charge states of Fe in La1-xSrxFeO3-δ. In this work, we first calibrated the Hubbard-U parameter to describe Fe from 2+ to 4+, then determined the charge on Fe in various phases of La1-xSrxFeO3-δ. by interpreting the density functional theory (DFT) predicted magnetic moment on Fe. We discovered that the charge distribution is originated by the different d-orbital splitting in octahedral (Oh) and square pyramidal (SP) Fe-oxygen polyhedra. This underlining theory successfully explained why the two electrons left behind by a charge-neutral oxygen vacancy can localize to the two Fe atoms directly connected to the oxygen vacancy in LaFeO3 or distribute to the second nearest neighbor Fe in cubic SrFeO3. The latter is named as ‘long-range charge transfer’ mechanism, causing strong oxygen vacancy interactions. This strong vacancy interaction causes increasing oxygen vacancy formation energy with oxygen vacancy site fraction. Therefore a new DFT-based thermodynamics model for interacting vacancies was also developed to predict δ and oxygen vacancy site fraction (X) separately as a function of temperature and partial pressure of oxygen. The predicted δ showed good agreement with experiments in a broad range of temperature. The variation of vacancy site fraction explained why high oxygen nonstoichiometry (δ) in many mixed ionic conductors does not translate into high ionic conductivity due to strong interactions between oxygen vacancies.

 

This work was supported in part by Department of Energy

 

 

 

Poster Number: CHE-05

Authors: Preetam Giri, Jeffrey Schneider, Caleb Andrews, Shilpa Manjure, Ramani Narayan

Title:  Polylactide-Polydimethylsiloxane Block Copolymer as an Impact Modifier for PLA

 

Abstract: Polylactide (PLA) is a biodegradable aliphatic polyester formed by the polymerization of lactide, which can be derived completely from renewable biobased sources such as cornstarch. PLA has a high tensile strength and modulus, exhibits excellent barrier properties, and has also been found to be biocompatible. Despite its numerous advantages, its inherently low toughness severely restricts its applications. This study aims at improving the toughness of PLA while ensuring the minimum reduction in its tensile strength. A two-step process was adopted to achieve the desired toughness in PLA. First, a PLA-PDMS (polydimethylsiloxane) copolymer was synthesized through the reactive extrusion of PLA and bis(3-aminopropyl) terminated polydimethylsiloxane (NHPDMS). The amount of NHPDMS used was varied from 10 to 30 weight percentage. This was followed by the melt blending of the PLA-PDMS copolymer with neat PLA, where the copolymer was intended to act as an impact modifier. The mechanical properties, including tensile and impact, were studied for both the copolymer as well as the impact-modified PLA. Differential scanning calorimetry, and scanning electron microscopy, was used to study the thermal properties, and the surface morphology of the copolymer and the impact-modified PLA respectively. It was found that the elongation at break for the copolymer was significantly improved as compared to PLA. Similar trends were also observed for the impact-modified PLA. The improvement in the toughness was attributed to the enhanced compatibility of the PLA-PDMS copolymer in the PLA matrix, thus leading to better load transfer at the interface of the two phases.

 

 

 

Poster Number: CHE-06

Authors: Alex Mirabal, Scott Calabrese Barton

Title:  Scanning Electrochemical Microscopy of Catalytic Cascades with Substrate Channeling

 

Abstract: Enzymatic cycles in nature have evolved to efficiently react a substrate at multiple sites in sequence due to efficient transport of the intermediates between sites, preventing side reactions and loss of intermediates to the bulk. Nanoscale (~10 nm) mechanisms of transport have been found in literature [1]. The increased concentration surrounding subsequent active sites due to these transport mechanisms can help overcome unfavorable thermodynamics. The engineering of cascades of catalyst can mimic these mechanisms in order to minimize intermediate diffusion to the bulk, reducing exposure to competitive side reactions and prevent exposure of harmful intermediates to the bulk. Quantitative descriptions of nanoscale transport via intermediates in solution can be achieved by scanning electrochemical microscopy [2], which allows for in-situ analysis of kinetic systems. Deconvoluted signals can be achieved through nano-sensing, attaching a highly specific enzyme to the electrode, allowing for analysis of a substrate of choice. This complex system of analysis has many factors that contribute to the overall results. Modeling of nano-scale tip interactions with these cascades can confirm fundamental understanding of the processes occurring in solution or provide an insight to expected responses. Tip insulation can affect the response of the system due to decreased diffusion [3], so called hindered diffusion. Enzymatic cofactors, if required, will diffuse from the bulk, while intermediates will be concentrated around the cascade. Solution of a 2D axisymmetric model of hindered diffusion of cofactors combined with multiple active sites in a cylindrical model was solved for a SECM response with regards to transport efficiency. 1. I. Wheeldon, S. D. Minteer, S. Banta, S. C. Barton, P. Atanassov and M. Sigman, "Substrate channelling as an approach to cascade reactions", Nat. Chem., 8, 299–309 (2016). doi:10.1038/nchem.2459. 2. J. Kim, C. Renault, N. Nioradze, N. Arroyo-Currás, K. C. Leonard and A. J. Bard, "Electrocatalytic Activity of Individual Pt Nanoparticles Studied by Nanoscale Scanning Electrochemical Microscopy", J. Am. Chem. Soc., 138, 8560–8568 (2016). doi:10.1021/jacs.6b03980. 3. A. J. Bard, G. Denuault, R. A. Friesner, B. C. Dornblaser and L. S. Tuckerman, "Scanning electrochemical microscopy: theory and application of the transient (chronoamperometric) SECM response.", Anal. Chem., 63, 1282–1288 (1991). doi:10.1021/ac00013a019.

 

This work was supported in part by Army Research Office - MURI

 

 

 

Poster Number: CHE-07

Authors: Manas Nigam, Ramani Narayan

Title:  Modifications in Thermoplastic Starch by Reactive Extrusion

 

Abstract: With rising use of plastics in day to day life, pollution has increased manifolds. Bio-based polymers are product of carbon neutral technology. Poly-lactic acid (PLA) is an established commercial bio-based and biodegradable polymer and used as standalone polymer as well as in blends. Starch is a major agro-industrial product and abundant in United States market. Thermoplastic starch (TPS) is a widely-researched starch based biopolymer which is relatively hard to process as compared to PLA. Modifications in the matrix of TPS are therefore needed for increasing its commercial value. Variations in TPS with additives were done using reactive extrusion process. This study compares the conventional TPS and TPS processed with additives through material characterization such as thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), spectroscopy (FTIR) and end group analysis. Grafting of additives to backbone of starch is examined using soxhelet extraction. Film forming ability of TPS based polymer is compared with that of modified TPS based polymers.

 

 

 

Poster Number: CHE-08

Authors: Neda Rafat, Paul S. Satoh, R. Mark Worden

Title:  Electrochemical Enzyme Immunoassay Biosensor (EEIB)

 

Abstract: An Electrochemical Enzyme Immunoassay Biosensor (EEIB) is being developed that combines the advantages of immunoassays and electrochemical biosensors. The biosensor interface contains redox enzymes co-immobilized with antibodies for the target antigen with on the working electrode of an amperometric device. When a liquid sample containing the target antigen is added, the immobilized antibodies bind to the antigen with extremely high selectivity and affinity. This binding event triggers a redox reaction cascade that generates an electric current whose magnitude gives a quantitative indicator of the antigen’s concentration. A redox-recycling scheme internally amplifies the current to increase the biosensor’s sensitivity. The EEIB interface is being adapted to a disposable electrode array platform for portable, cost-effective applications that require rapid, quantitative measurement of a target analyte with high affinity, selectivity, and sensitivity.

 

This work was supported in part by National Science Foundation (NSF)

 

 

 

 

 

Poster Number: CHE-09

Authors: Eric Straley, Jason Nicholas

Title:  Calibration of Pulsed-laser Deposited Ruby Thin Film Fluorescent Pressure Sensors

 

Abstract: Currently, pressure measurements are done using macro-sized crystals of a fluorescent pressure sensor. This method is useful for measurements of external pressure/stress, but it does not allow for the measurement of stresses generated within a material. By depositing a thin film pressure sensor onto a material of interest, the internal stresses of a material can be easily measured under any condition. The work presented here shows that high quality, crystalline thin film ruby can be deposited using pulsed-laser deposition and the stress generated from thermal expansion and lattice mismatch can be accurately calculated. Ruby thin films were deposited onto single crystal yttria stabilized zirconia (YSZ) and sapphire circular wafers with one inch diameter. X-ray diffraction and Raman Spectroscopy confirmed the crystallinity and phase purity of the thin films. Film stress was calculated first from the position of the ruby fluorescence peaks. The stress value was confirmed by measuring the sample curvature and calculating stress from Stoney’s Equation. The results suggest that thin film ruby can be used to accurately determine sample stress.

 

This work was supported in part by National Science Foundation (NSF) award number CBET-1254453

 

 

 

Poster Number: CHE-10

Authors: Hong-Kang Tian, Yue Qi

Title:  Simulation of the Impact of the Loss of Contact Area in All-solid-state Battery

 

Abstract:

Maintaining the physical contact between the solid-state electrolyte and the electrodes is important to improve the performance of the Li-ion battery. The initial interface contact depends on the fabrication process of the battery. Typically, the deposited thin-film battery would have better interface contact than the bulk-type (mixed powder) battery. Increasing the compression pressure during the fabrication process could lead to a better initial contact. On the other hand, the contact area would continuously lose due to the volume change of the electrodes during the cycling of the battery. To illustrate this problem, a 1-D continuum model was developed to simulate the discharging process of an all-solid-state Li-ion battery, which is composed of Li as the anode, LiCoO2 as the cathode, and Li3PO4 as the electrolyte. The parameters were taken from a thin-film battery model that has fitted to experimental data. We incorporated the effect of the imperfect contact into this model by assuming the current and Li concentration will be localized at the contacted area. We correlated the percentage of lost contact area with the discharging capacity and energy. We observed that the capacity and energy decrease with the loss of contact area and discharge rate. For example, when discharging at 1 C-rate, the capacity decreased 20% as the contact area losses 19.8%. At a higher discharging rate of 32 C, the capacity dropped quickly to be less than 20% when the contact area losses 1.52%. Since Li3PO4 and LiCoO2 are both ceramic materials, and considering the property of self-affine, we applied the person theory, which could be used for elastic contact and include different length scale of contact, to build the relationship between the contact area and the applied pressure. We found that it is more effective to apply the pressure when the battery just starts to decay when the battery capacity loss is less than 10%. Therefore, in practical application, this model and method can be used to estimate the extent of the loss of contact area during the operation of the all-solid-state Li-ion battery, and further suggesting how much pressures should be applied to recover the capacity.

 

 

 

Poster Number: CHE-11

Authors: Daniel Vocelle, Olivia Chesniak, Mitch Smith, Christina Chan, S.Patrick Walton

Title:  Role of Nanoparticle Characteristics in siRNA Trafficking and Gene Silencing

 

Abstract: New therapeutic approaches are needed for treating disease-associated proteins that cannot be targeted by small molecule and protein based drugs. One potential candidate approach, short interfering RNA (siRNA) therapeutics, is capable of specific targeting for a wide range of proteins. With the assistance of target specific delivery vehicles, siRNAs are transported from the extracellular environment into the cytoplasm of eukaryotic cells. Utilizing the RNA Interference (RNAi) pathway, siRNAs degrade messenger RNA (mRNA) in a sequence-specific manner and thereby reduce target protein expression. siRNA therapeutics are being developed for cancers, genetic disorders, and infectious diseases. Clinical adoption of siRNAs is somewhat limited by the inefficiency of delivering them to the targeted cells. This has resulted in considerable study of different types of siRNA delivery vehicles. To date, there is little consensus regarding the delivery mechanisms or particle characteristics essential for high activity of the siRNA cargo. Using silica nanoparticles (sNPs), we have investigated the influence of particle characteristics on four mechanistic steps in the RNAi pathway: SNP-siRNA complex dissociation, siRNA strand separation, intracellular trafficking, and gene silencing. Our current data indicate that sNP-siRNA binding affinity and location of dextran functionalization are important in facilitating active silencing. Intracellular trafficking data support sNPs utilizing scavenger receptor mediated endocytosis and preferentially accumulating within acidic organelles, where dissociation of the siRNA-sNP complex occurs.

 

This work was supported in part by National Science Foundation (CBET 0941055, 1510895, 1547518); National Institutes of Health (GM079688, RR024439, GM089866, CA176854, DK081768, DK088251)

 

 

 

Poster Number: CHE-12

Authors: David Vogelsang, Parker Dunk, Robert Maleczka, Andre Lee

Title:  Separation of Double Decker Shaped Silsesquioxanes Condensed with Multiple Functional Groups

 

Abstract: Tetrasilanol double decker shaped silsesquioxanes (DDSQ-tetrasilanol) were condensed in this study by the addition of equimolar fractions of DDSQ-tetrasilanol, methyltrichlorosilane, and X-methyldichlorosilane, where X stands for hydrogen (H), methyl (Me), or vinyl (Vi). Adsorption HPLC experiments were run for the condensation products and four peaks were identified. The remaining Cl groups were hydrolyzed passing the products through a Si-gel column where three fractions were separated from the mixture. Each fraction was characterized by 29Si-NMR, adsorption HPLC, and mass spectroscopy. It was found that the first fraction obtained by LC was always a DDSQ cage with the X-Me-siloxane attached to both sides. 29Si-NMR presented trans and cis isomers in the spectrum. A single peak with tR = 2.43 min was resolved in the chromatogram. The second LC fraction was DDSQ cages with a X-Me-siloxane attached to one side and OH-Me-siloxane attached to the opposite side. Trans and cis orientations were identified in the 29Si-NMR spectrum. After HPLC experiments, both isomers were in a single peak located in tR = 4.21 min. Finally, the third fraction had trans and cis DDSQ molecules with OH-Me-siloxanes in both sides. Two peaks corresponding to trans and cis isomers of Me-OH-DDSQ-Me-OH were identified in this fraction by HPLC. Trans isomers were detected after tR = 8.02 min and cis isomers after tR = 8.55 min. Mass spectroscopy for separated cages showed the expected molecular weights for each molecule. The material produced and separated in this study can be further reacted taking advantage of the multiple moieties in the cages. It can be used in different applications such as drug delivery, block copolymers, compatibilizers, among others.

 

This work was supported in part by D. Vogelsang is funded by the Fulbright-Colciencias scholarship; the research project is funded by the US Office of Naval Research

 

 

 

Poster Number: CHE-13

Authors: Ziwei Wang, Mark Worden

Title:  Shear and Temperature Damage on Cells During Microbubble Fermentation

 

Abstract: Microbubble fermentation is being studied as a viable method for biogas production. Current design uses high-speed shear plate to generate microbubble and the flow of the reactor system was recycled through a pump. Previous researches on this topic had encountered an unexpected drop in production rate as the reaction time increases. It is suspected that the cells were damaged by shear force or high temperature inside the reactor system. It is our interest to identify the source of shear damage and to seek alternative design once the source is discovered. We propose to isolate individual part of the previous reactor system and replace them with equivalent components. The cell death rate will be measured with flow cytometry. The temperature of the flow system around the pump will also be measured to find out whether or not temperature is playing a role in cell death inside the reaction system.

 

 

 

Poster Number: CHE-14

Authors: Margaret Young, John Suddard, Tyler Patrick, Christopher Traverse, Natalia Pajares, Richard R. Lunt

Title:  Heptamethine-based Organic Salts for Solar Cells with Near-infrared Photoresponse up to 1600 nm

 

Abstract: Near-infrared absorbing organic molecules are critical in developing transparent photovoltaics, multijunction photovoltaics, and low-cost infrared photodetectors. However, few molecules with absorption past 900 nm have been demonstrated in optoelectronic devices, and their small bandgaps complicate the task of aligning energy levels for efficient charge transfer in photovoltaics. In this study, we synthesize and demonstrate organic salts with photoresponse out to 1400 and 1600 nm with a peak external quantum efficiency of 5%. Record high open-circuit voltages for this spectral range near the theoretical excitonic limit are achieved using this material. We also show that the energy levels in these narrow bandgap donors can be precisely tuned using alloyed blends of different organic anions with no change to the photoresponsive organic cation bandgap. The relationship between short-circuit photocurrent and the donor-acceptor interface gap will be discussed in the context of correlated exciton binding energies and carrier diffusion lengths.

 

This work was supported in part by NSF Faculty Early Career (CBET-1254662); DuPont Young Professor Award; Department of Education Graduate Assistantship in Areas of National Need Award (GAANN, GU0115873)

 

 

 

Poster Number: CHE-15

Authors: Yuelin Wu, Andre Lee

Title:  Investigate the Disappearance of Cu9Al4 from Cu-Al Bonding Interface using Anodic Potentiodynamic Polarization Study

 

Abstract: This study proposed a corrosion mechanism of the Cu-Al wire bonding interface (Cu-Cu9Al4-CuAl2-Al) based on the anodic polarization measurement. The observed disappearance of Cu9Al4 was the result of a two-step corrosion process: the initial penetration of the interface between Cu9Al4 and CuAl2, and the following galvanic corrosion of Cu9Al4 in the Cu-Cu9Al4 couple. The initial penetration of the interface between Cu9Al4 and CuAl2 results from crevice corrosion of CuAl2 through the voids formed at the interface during the intermetallic transformation. After the interface between Cu9Al4 and CuAl2 is penetrated, the four-metal galvanic couple Cu-Cu9Al4-CuAl2-Al is divided into two separate galvanic couples: Cu-Cu9Al4 and CuAl2-Al. For the CuAl2-Al couple, Al is the anode, however, its corrosion rate is not significantly increased due to the low cathode-to-anode area ratio. For the Cu-Cu9Al4 couple, Cu9Al4 is the anode and its corrosion rate is significantly increased due to the large cathode-to-anode area ratio. Therefore, Cu9Al4 appears to corrode faster than the other entities. This proposed corrosion mechanism emphasizes that the bond failure is caused by penetration of the interface between Cu9Al4 and CuAl2, instead of the preferential corrosion of Cu9Al4. In order to effectively reduce the bond failure rate, the void formation along the interface between the two intermetallic needs to be inhibited.