Venkat Subramaniam Venkataramani

Scintillation Properties of SrHfO

In this paper we report on the scintillation properties of cerium doped strontium - and barium hafnate. Radioluminescence, pulse height, scintillation decay and timing spectra are presented. Radioluminescence spectra of SrHfO3:Ce3+ and BaHfO3:Ce3+ consist of a broad band due to Ce3+ emission peaking at 410 nm and 400 nm, respectively. The light yield of BaHfO3:Ce3+ and SrHfO3:Ce3+ is approximately 40 000 photons/MeV when compared to a crystal of BGO. The principal decay time constant for SrHfO3:Ce3+ and BaHfO3:Ce3+ is 42 and 25 ns, respectively. A timing resolution of 276 ps (FWHM) was obtained with transparent optical ceramic of SrHfO3:Ce3+.

_{3}

The property enhancement offered by single crystal relaxor ferroelectrics combined with the manufacturability advantages offered by injection molding has the potential of producing single crystal 1-3 piezocomposites at an affordable production-viable rate. Two methods of texturization/recrystallization are being evaluated: an integrated multi-seed process and epitaxial growth. The integrated seed approach involves incorporation of oriented single crystal PMN-PT seeds into injection molding feedstock prior to fabrication of 1-3 ceramic preforms. After sintering, an additional texturization and growth step is carried out. This step is intended to drive recrystallization at multiple sites within the ceramic body extending the oriented texture throughout the matrix. The epitaxial growth approach involves nucleation and growth in the dense ceramic body initiated from a compatible external seed crystal. Recrystallization is achieved through direct contact between a ceramic preform and a seed substrate coupled with appropriate thermal and atmospheric growth conditions.

:Ce

This paper describes the development of a low-cost, high speed manufacturing process method for the fabrication of piezoelectric ceramic transducer elements in the 1-25 MHz frequency range. A modified multi-layer lithography process, is used to additively manufacture high-resolution netshape ceramic structures by photopolymerizing a ceramic-polymer slurry using structured light patterns. The paper elaborates on the key considerations in the development of the process including the selection and optimization of slurry materials for the deposition of PZT 5H materials, optical exposure parameters, debinding/sintering profiles and post-manufacturing processing. coupling coefficient in the range of 0.52-0.54. Ongoing work includes improvements to materials properties, improved throughput and geometric fidelity.

^{3+}

In this paper we report on the scintillation properties of cerium doped strontium - and barium hafnate. Radioluminescence, pulse height, scintillation decay and timing spectra are presented. Radioluminescence spectra of SrHfO₃:Ce³⁺ and BaHfO₃:Ce³⁺ consist of a broad band due to Ce³⁺ emission peaking at 410 nm and 400 nm, respectively. The light yield of BaHfO₃:Ce³⁺ and SrHfO₃:Ce³⁺ transparent optical ceramic is approximately 40,000 photons/MeV when compared to a crystal of BGO. The principal decay time constant for SrHfO₃:Ce³⁺ and BaHfO₃:Ce³⁺ is 15 and 16 ns, respectively. A timing resolution of 276 ps (FWHM) was obtained with transparent optical ceramic of SrHfO₃:Ce³⁺.

and BaHfO

Improvement of the large signal dielectric loss of a commercial ferroelectirc lead magnesium niobate-lead titanate (PMN-PT) sound projector driver has been achieved without sacrificing other electromechanical properties. Length extensional resonators fabricated from the modified composition have been characterized for dielectric losses, 33-mode electromechanical coupling, and acoustic energy density under uniaxial compressive stress and large signal drive requirements for sound projectors. Selective doping and microstructural control have been used to achieve the desired properties.

_{3}

The integrated gasification combined cycle (IGCC) power system using high-temperature coal gas cleanup is one of the most promising advanced technologies for the production of electric power from coal in an environmentally acceptable manner. Unlike conventional low-temperature cleanup systems that require costly heat exchangers, high-temperature coal gas cleanup systems can be operated near 482-538 C (900-1000 F) or higher, conditions that are a closer match with the gasifier and turbine components in the IGCC system, thus resulting is a more efficient overall system. GE is developing a moving-bed, high-temperature desulfurization system for the IGCC power cycle in which zinc-based regenerable sorbents are currently being used as desulfurization sorbents. Zinc titanate and other proprietary zinc-based oxides are being considered as sorbents for use in the Clean Coal Technology Demonstration Program at Tampa Electric Co.s (TECo) Polk Power Station. Under cold startup conditions at TECo, desulfurization and regeneration may be carried out at temperatures as low as 343 C (650 F), hence a versatile sorbent is desirable to perform over this wide temperature range. A key to success in the development of high-temperature desulfurization systems is the matching of sorbent properties for the selected process operating conditions, namely, sustainable desulfurization kinetics, high sulfur capacity, and mechanical durability over multiple cycles. Additionally, the sulfur species produced during regeneration of the sorbent must be in a form compatible with sulfur recovery systems, such as sulfuric acid or elemental sulfur processes. The overall objective of this program is to develop regenerable sorbents for hydrogen sulfide removal from coal-derived fuel gases in the temperature range 343-538 C (650-1000 F). Two categories of reactor configurations are being considered: moving-bed reactors and fluidized-bed (bubbling and circulating) reactors. In addition, a cost assessment and a market plan for large-scale fabrication of sorbents were developed. As an optional task, long-term bench-scale tests of the best moving-bed sorbents were conducted. Starting from thermodynamic calculations, several metal oxides were identified for potential use as hot gas cleanup sorbents using constructed phase stability diagrams and laboratory screening of various mixed-metal oxide formulations. Modified zinc titanates and other proprietary metal oxide formulations were evaluated at the bench scale and many of them found to be acceptable for operation in the target desulfurization temperature range of 370 C (700 F) to 538 C (1000 F) and regeneration temperatures up to 760 C (1400 F). Further work is still needed to reduce the batch-to-batch repeatability in the fabrication of modified zinc titanates for larger scale applications. The information presented in this Volume 1 report contains the results of moving-bed sorbent development at General Electrics Corporate Research and Development (GE-CRD). A separate Volume 2 report contains the results of the subcontract on fluidized-bed sorbent development at the Institute of Gas Technology (IGT).