Processing and Performance of Materials Using Microwaves, Electric and Magnetic Fields, Ultrasound, Lasers, and Mechanical Work: The Rustum Roy Symposium: On-Demand Oral Presentations
Sponsored by: ACerS Basic Science Division, ACerS Manufacturing Division
Program Organizers: Morsi Mahmoud, King Fahd University Of Petroleum And Minerals; Dinesh Agrawal, Pennsylvania State University; Guido Link, Karlsruhe Institute of Technology; Motoyasu Sato, Chubu University; Rishi Raj, University of Colorado; Christina Wildfire, National Energy Technology Laboratory; Zhiwei Peng, Central South University
Friday 8:00 AM
October 22, 2021
Room: On-Demand Room 12
Location: MS&T On Demand
Invited
Characterizing the Kinetics of Isothermal Microwave-assisted Chemical Syntheses (IMACS): Application of a Unified Process Kinetic Equation (UPKE)
: Boon Wong1; 1Retired
Rate-enhancement of any isothermal chemical (inorganic, organic, or polymeric) synthesis conducted under resonant microwaves (RM) versus the same process activated by conventional heating has been widely documented to be mainly attributable to reduction in activation enthalpy. This report applies a unified process kinetic equation (UPKE) to demonstrate and characterize the non-thermal effect (NTE) on kinetic enhancements measured from typical isothermal microwave-assisted chemical syntheses (IMACS). The UPKE, derived from meso-irreversible-thermodynamics, predicts that NTE occurring in any IMACS will significantly reduce activation energy/enthalpy, thereby enhancing the process-kinetics. Accordingly, IMACS-rate-enhancements are envisioned to result from a sequential RM-induced enthalpy variation: RM energy-input first promotes the total molar enthalpy of the irradiated reactants at temperature, which consequently stimulates a decrease in activation enthalpy of the process in favor of a kinetic enhancement. Lowering of the pre-exponential frequency factor observed in most IMACS is also rationalized as per the UPKE.
Invited
Micro Flash Sintering for Additive Manufacturing of Ceramics: Rubens Ingraci Neto1; Rishi Raj2; 1Los Alamos National Laboratory; 2University of Colorado
The emerging method of flash sintering may hold the potential to enable the fast production of high-density, arbitrarily shaped ceramic parts through additive manufacturing. Three aspects of this convergence will be discussed: (i) floating electrodes, (ii) manufacturing science, and (iii) software development.
Invited
Conditions for the Microwave Effect: Motoyasu Sato1; Shin Nakatani1; 1Chubu University
Basic principles Supplying internal energy also increases his entropy. Increased entropy produces irreversible changes. Consider a model that degenerates from state A to state B beyond the activated state by microwaves. Microwaves provide state A and B with single-frequency, phase-aligned displacements, fa and fb, respectively. The structure of molecules, crystals and clusters determined the displacement by microwave. Assuming that the sensitivities of states A and B regarding microwave work are Ia and Ib, when Ia> Ib, the reaction is from A to B, by microwave irradiation. When Ia <Ib, the reaction proceeds from B to A. In particular, if the kinetic disturbance fa due to microwaves resonates with the substance before it falls into heat, the amplitude of the disturbance increases and Ia >> Ib. It is a key parameter for predicting and determining the presence or absence of microwave effect.
Novel Electrode Configuration Effects on the Microstructural Homogeneity of Flash Sintered Ceramics for Solid-state Battery Electrolytes.: Gareth Jones1; Chris Green2; Sherry Ghanizadeh2; David Pearmain2; Geoff West1; Emma Kendrick3; Claire Dancer1; 1University of Warwick; 2Lucideon Ltd; 3University of Birmingham
Flash sintering (FS) enables rapid sintering of ceramic materials at reduced furnace temperatures, of particular interest are volatile materials with high conventional sintering temperatures such as oxide based solid-state electrolytes. We demonstrate FS on the solid-state electrolyte materials sodium-beta’’ alumina and aluminium-doped lithium lanthanum zirconium oxide. Uncontrolled current flow during FS can result in hotspot formation and heterogeneous microstructure. Here we will discuss two technological developments for FS that allow increased control of the current flow. First, multi electrode flash sintering, where three electrodes are separately driven to homogenise the current flow through the ceramic green. Secondly, contactless flash sintering, where contact between the sample and electrodes is made by a conductive gaseous medium, with the electrode moving across the sample surface. The different electrode configurations are compared through examination of the microstructural features of the flash sintered ceramics by scanning electron microscopy, X-ray diffraction, and Raman spectroscopy.
Methodology for Scaling Microwave Catalyst in a Fixed Bed: Christina Wildfire1; Yan Zhou1; Christopher Marin1; Doug Kauffman1; Dushyant Shekhawat1; 1National Energy Technology Laboratory
The use of microwaves in catalysis has shown promising results in increased yields, product selectivity, and energy efficiency. Most reported microwave-driven catalysis is based on small powder beds, and little is known of the effects of scaling the reactions beyond the small fixed beds. This study investigates the use of microwave absorptive and transparent catalyst supports using Lanthanum Strontium Cobalt (LSC) and the catalyst material. Coating methodology was varied along with amount of catalyst deposited to determine the best configuration for larger beds with higher flow rates. Not only was the support material varied, but also the shapes of the supports, including spheres, cylinders, foams, and monoliths. The supports were tested at 2.45 GHz in a fixed-bed reactor and compared against the percent conversion of methane and CO2, along with the energy efficiency.