Laboratory for Radiation and Polymer Science

Al-Sheikhly Lab Group, University of Maryland College Park

Research

General Research Interests

Polymers, biomaterials, radiation engineering, nuclear engineering, environmental effects

Current Research Projects

Corrosion in pipeline systems: Characterization, Experimental Simulation and Mechanistic analysis

 

On the Mechanism of the Mechanical and Thermal Stability of Ultra High Molecular Weight Polyethylene Fibers

High performance polymer fibers are frequently used in personnel armor applications due to their high tensile strength-to-weight ratios. Dimensional analysis has demonstrated that ultra high molecular weight polyethylene (UHMWPE) fabrics underperformed compared to theoretical models of this system. One possible explanation is the low melting temperature of UHMWPE relative to other polymer fibers used in ballistic applications. Under tension, two mechanisms compete to relieve the strain energy within the UHMWPE fibers. Chain scission, or the breaking of the  C-C bond, is dominant at low temperatures and high strain rates. Chain slippage, or the sliding of chains past one another, is dominant at high temperatures and low strain rates. During ballistic impact, the contacted region is subjected to high temperatures and high strain rates. The dominant mechanism under these conditions is not well understood, and it is the purpose of this study to investigate this type of event.

This project aims to determine the change in mechanical properties by:

  1. Characterizing the virgin fibers before failure tests to understand the phases present, the fiber morphology, and the bond behavior, to relate morphology to mechanical properties and to aid in the development of a Representative Volume Element (RVE) for molecular dynamic simulations
  2. Conducting tensile failure experiments across a large range of strain rates (10-3 s-1 to 103 s-1) and temperatures (30°C to 156°C), to reveal any change in mechanical properties or dominant failure mechanism and to improve the time-Temperature Superposition (t-TSP) and Williams-Landel-Ferry (WLF) equation accuracy for simulations
  3. Using computational simulations with the principle of t-TSP and WLF equation to determine the failure mechanisms of UHMWPE fibers at different temperatures and strain rates by matching to experimental data

 

Critical Hydrogen Concentration Determination in Alpha Particle Irradiated Water

CHCCentralReaction

In commercial pressurized water reactors, boric acid is added to the coolant to act as a neutron adsorber. The interaction between the neutrons and the boron in the system however lead to significant amounts of alpha radiation as a result of the 10B(n,α)7Li reaction. This high LET radiation has a significant impact on the aqueous radiation chemistry of the reactor flow system since the α/7Li dose-rates at the start of the reactor cycle are similar to those for neutron and γ radiation. In order to more accurately predict the Critical Hydrogen Concentration (CHC), the minimum amount of dissolved excess H2 which can suppress water radiolysis, the quantity of H2 and H2O2 produced from this radiolysis source at different temperatures must be measured. Once these values are obtained, current chemical kinetic models can be updated to better match the actual value of the CHC.

Extraction of Uranium from Seawater Using Radiation-Grafted Adsorbents

Recovering uranium from seawater is critical to the future of the nuclear industry, as most of Earth’s currently known uranium resources reside within the oceans. In order to extract this uranium, fabrics radiolytically grafted with uranium-chelating monomers can be used as adsorbents for this metal species. By varying the monomer as well as the dose and dose rate during the grafting process, the uranium loading capacity of the fabric can be maximized. Our group is also focused on reducing the chemical waste resultant from this process by limiting the amount of non-aqueous solvents and non-biodegradable chemicals during the grafting and washing processes respectively.

Fabrication of Polymer Electrolyte Membranes for Fuel Cells using Radiation Grafting

Cracking of Crude Oil Using Electron Beam Irradiation

Radiation Degradation of Electrical Cable Jackets

Production and Advanced Characterization of Biocompatible Nanomaterials for Drug Delivery Systems and MRI Contrast Agents

Bio-compatible nanomaterials are a class of advanced materials used for drug delivery systems and MRI contrast agents. In order to meet stringent criteria for these systems and advance the state-of-the-art methods for their production and characterization, we aim to synthesize the nanogels using ionizing radiation via electron beam from a linear accelerator, thereby eliminating the need for catalysts or additives. Additionally, metal oxides will be incorporated into selected materials to investigate their capacity to be used for magnetic field-driven targeting and imaging applications. Recommendations for a variety of candidate products will be provided following their characterization so further explorations into their use in drug delivery or medical imaging applications can be performed.

 

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