Showing papers by "Frederick Alyious List published in 2016"

The metallurgy and processing science of metal additive manufacturing

Abstract: Additive manufacturing (AM), widely known as 3D printing, is a method of manufacturing that forms parts from powder, wire or sheets in a process that proceeds layer by layer. Many techniques (using many different names) have been developed to accomplish this via melting or solid-state joining. In this review, these techniques for producing metal parts are explored, with a focus on the science of metal AM: processing defects, heat transfer, solidification, solid-state precipitation, mechanical properties and post-processing metallurgy. The various metal AM techniques are compared, with analysis of the strengths and limitations of each. Only a few alloys have been developed for commercial production, but recent efforts are presented as a path for the ongoing development of new materials for AM processes.

Fabrication of conductive paths on a fused deposition modeling substrate using inkjet deposition

Abstract: Purpose – The purpose of this paper is to explore the possibility of integrating inkjet printed circuitry with fused deposition modeling (FDM) structures to produce embedded electronics and smart structures. Several of the challenges of combining these technologies are identified, and potential solutions are developed. Design/methodology/approach – An experimental approach is taken to investigate some of the relevant physical processes for integrating FDM and inkjet deposition, including the printing, drying and sintering processes. Experimental data are collected to assist understanding of the problems, and engineering solutions are proposed and implemented based on the gained understanding of the problems. Findings – Three challenges have been identified, including the discontinuity of the printed lines resulting from the irregular surface of the FDM substrate, the non-conductivity of the printed lines due to the particle segregation during the droplet drying process and the slow drying process caused b...

Irradiation performance of rare earth and nanoparticle enhanced high temperature superconducting films based on YBCO

Abstract: The new series of commercially produced high temperature superconducting (HTS) tapes based on the YBa 2 Cu 3 O 7 (YBCO) structure have attracted renewed attention for their performance under applied magnetic fields without significant loss in supercurrent compared to the earlier generation of conductors. This adaptability is achieved through rare earth substitution and dopants resulting in the formation of nanoparticles and extended defects within the superconducting film matrix. The electrical performance of Zr-(Gd x ,Y 1 − x )Ba 2 Cu 3 O 7 and (Y 1 − x ,Dy x )Ba 2 Cu 3 O 7 coated conductor tapes were tested prior to and after neutron exposures between 6.54 × 10 17 and 7.00 × 10 18 n/cm 2 ( E > 0.1 MeV). Results showed a decrease in superconducting current with neutron irradiation for the range of fluences tested, with losses in the Zr-(Gd x ,Y 1 − x )Ba 2 Cu 3 O 7 conductor being more rapid. Post-irradiation testing was limited to evaluation at 77 K and applied fields of up to 0.5 Tesla, and therefore testing at lower temperatures and higher applied fields may result in improved superconducting properties as shown in previous ion irradiation work. Under the conditions tested, the doped conductors showed a loss in critical current at fluences lower than that of undoped YBa 2 Cu 3 O 7 tapes reported on in literature.

Continuous single crystal growth of graphene

Abstract: Systems and methods for synthesizing continuous single crystal graphene are provided. A catalytic substrate is drawn through a chemical vapor deposition chamber in a first lengthwise direction while flowing a hydrogen gas through the chemical vapor deposition chamber in the same lengthwise direction. A hydrocarbon precursor gas is supplied directly above a surface of the catalytic substrate. A high concentration gradient of the hydrocarbon precursor at the crystal growth front is generated to promote the growth of a continuous single crystal graphene film while suppressing the growth of seed domains ahead of the crystal growth front.