Oral Abstracts
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1734-A-1902 Model systems for heterogeneous catalysts at the atomic level Hans-Joachim Freund1 1 Fritz-Haber-Institut der Max-Planck-Gesellschaft Our understanding of catalysis, and in particular heterogeneous catalysis, is to a large extent based on the investigation of model systems. Increasing the complexity of the models towards oxide supported nanoparticles, resembling a real disperse metal catalyst, allows one to catch in the model some of the important aspects that cannot be covered by metal or oxide single crystals per se. The main purpose of our studies is to provide conceptual insight into questions concerned with a variety of topics in catalysis, including support nanoparticle interaction, reactivity at the particle-support interface, strong metal support interaction, reactions in confined space and development of new instrumentation for surface science studies. The talk will address some of those issues. 1 1773-A-1902 Special metallic gasket sealing for the non-circular profile flanges Gao-Yu Hsiung1 1 NSRRC, Hsinchu, Taiwan Various types of the metallic gaskets for the non-circular profile flanges and the potential applications will be introduced. The sealing surface of flange is flat to accommodate the special metallic gasket with knife edges for the sealing. Both the flange and gasket are made of aluminum alloys and produced by the oil-free Ethanol-CNC-machining process that any non-circular profile, e. g. race-track, rectangular, key-hole, etc., flanges can be made. All the flanges and gaskets after oil-free machining can be assembled immediately without any chemical cleaning. The quality of ultrahigh vacuum at pressure < 20 nPa after vacuum baking has been approved. The as mentioned non-circular metallic flange-sealing can be applied for the high radiation reactors, accelerators, wave guides, aluminum ultrahigh vacuum systems, large aluminum chambers for industrial, et al. The non-circular metallic gaskets can be reused few more times while the flanges won’t take any risk of damage on sealing surfaces that result in the consequent advantages of high systematic reliability and low manufacturing cost. 1 1808-A-1902 Microstructural design for enhancing both hardness and toughness in transition-metal diboride thin films Babak Bakhit1, Ivan Petrov1,2, J.E. Greene1,2, Lars Hultman1, Johanna Rosén1, Grzegorz Greczynski1 1 Linköping University 2 University of Illinois Transition-metal (TM) diborides have received increasing attention as next-generation ceramic thin films for replacing TM nitrides. They exhibit high hardness; however, this is not always sufficient to prevent failure in applications involving high stresses since hardness is typically accompanied by brittleness leading to crack formation and propagation. Toughness, the combination of hardness and ductility, is required to avoid brittle fracture. We propose a strategy for increasing both the hardness and ductility of ZrB2, selected as a model TM diboride, thin films grown by hybrid high-power impulse and dc magnetron (HiPIMS/DCMS) co- sputtering in pure Ar at 450°C on Al2O3(0001). A Ta target operated in HiPIMS mode supplies pulsed energetic Ta ions to the growing film, while a ZrB2 target operated in DCMS mode provides a continuous flux of Zr and B atoms. The average power (and pulse frequency) applied to the HiPIMS Ta target are varied from 0 to 1800 W (300 Hz) in increments of 600 W (100 Hz); all other deposition parameters are maintained constant. The resulting boron-to-metal ratio, y = B/(Zr + Ta), in Zr1-xTaxBy films continuously decreases from 2.4 to 1.5 as the power is increased; x increases from 0 to 0.3. All films have the hexagonal AlB2 crystal structure with a columnar microstructure. Films with x < 0.2 have B-rich column boundaries, while those with x ≥ 0.2 have Ta-rich column boundaries. As a result, hardness increases from 35 to 42 GPa, ~20%, with a simultaneous increase in nanoindentation toughness from 4 to 5.2 MPa√m, ~30%. 1 1884-A-1902 Tunable Mo-O(-N) films prepared using reactive deep oscillation magnetron sputtering Michal Prochazka1, Faezeh Lahiji1, Jaroslav Vlcek1, Jiri Houska1, Stanislav Haviar1, Radomir Cerstvy1 1 Department of Physics and NTIS - European Centre of Excellence, University of West Bohemia, Plzen, Czech Republic A modified version of HiPIMS, called Deep Oscillation Magnetron Sputtering, with a pulsed reactive gas flow control and to- substrate reactive gas injection into a high-density plasma in front of the sputtered molybdenum target was used for low- temperature deposition of Mo-O(-N) films. The depositions were performed using a strongly unbalanced magnetron with a planar molybdenum target of 100 mm diameter in argon-oxygen(-nitrogen) gas mixtures at the total pressure close to 1 Pa. Voltage macropulses, composed of 5 voltage micropulses (pulse-on time of 23 us and pulse-off time of 27 us), with a total length of 250 us and repetition frequency of 400 Hz were used for all depositions with a maximum target power density up to 1150 Wcm-2 during pulses at a deposition-averaged target power density of 10 Wcm-2. The substrate temperatures were less than 120 °C (no external heater) during the depositions of films on floating glass and Si substrates at the distance of 100 mm from the target. A pulsed reactive gas flow control made it possible to produce high-quality MoOx and MoOxNy films with a tunable composition, and optical and electrical properties. The luminous absorption of 4% for 1 um thick non-conductive MoO3 films (the luminous transmittance of 80%) was smoothly changed into 88% for conductive (electrical resistivity decreased by up to 10 orders of magnitude) MoOx or MoOxNy films, keeping hardness of 3-5 GPa and very low macrostress (less than 200 MPa). 1 1889-A-1902 Design of high-performance VO2-based thermochromic coatings, and pathway for their low-temperature preparation Jiri Houska1, David Kolenaty1, Tomas Barta1, Jiri Rezek1, Jaroslav Vlcek1 1 University of West Bohemia, Plzen, Czech Republic The contribution deals with thermochromic multilayer VO2-based coatings for smart window applications prepared by reactive magnetron sputtering. First, we show that and how reactive high-power impulse magnetron sputtering with a pulsed O2 flow control allows reproducible preparation of crystalline VO2 of the correct stoichiometry under exceptionally industry-friendly deposition conditions: on soda-lime glass substrates without any substrate bias at a low temperature of around 300 °C [1]. Second, doping of VO2 by W is employed in order to shift the thermochromic transition temperature (68°C for bulk, 57°C for thin film VO2) towards the room temperature (39°C for V0.988W0.012O2, 20°C for V0.982W0.018O2), without concessions in terms of transmittance and its modulation. Third, we employ ZrO2 antireflection layers both below and above the thermochromic V1-xWxO2 layer, and present an optimum design of the resulting ZrO2/V1-xWxO2/ZrO2 coatings [2]. Most importantly, we show that while utilizing a first-order interference on ZrO2 leads to a tradeoff between the luminous transmittance (Tlum) and the modulation of the solar transmittance (dTsol), utilizing a second-order interference allows one to optimize both Tlum and dTsol in parallel. The properties achieved under the aforementioned industry-friendly deposition conditions and at lowered transition temperature include e.g. Tlum=42% and dTsol=12%, or Tlum=59% and dTsol=6% (depending on the V1-xWxO2 thickness). The experimental transmittance values are in agreement with those predicted during the multilayer coating design. [1] J. Vlcek et al., J. Phys. D Appl. Phys. 50, 38LT01 (2017). [2] J. Houska et al., Sol. Energy Mater. Sol. Cells 191, 365-371 (2019). 1 1908-A-1902 Vacuum System Design, Construction and Commissioning for Cornell Brookhaven ERLTest Accelerator (CBETA) Yulin Li1, David Burke1, Jessica Turco1 1 Cornell University A novel electron accelerator, Cornell Brookhaven Energy-Recovery LINAC (ERL) Test Accelerator (CBETA), is developed by collaboration between CLASSE and Brookhaven National Laboratory. Many unique accelerator technologies will be tested in CBETA, including photo-cathode electron injector, 4-turn superconducting RF (SRF) Energy Recover LINAC (ERL), non-scaling Fixed-Field Alternating Gradient (NS-FFAG) optics with 4x energy acceptance. With a total circumference ~80-m, the CBETA consists of an photo-cathode injector and a LINAC SRF cryomodule, a NS-FFAG loop to transport electron beams of four energies (42, 78, 114 and 150 MeV) in single bore beampipe, and two splitter sections where the four energy beams are separately manipulated. CBETA vacuum system is designed to provide adequate level of vacuum and physical aperture for transporting electron beams at four energies, while stay clear of 300+ complex magnets. Furthermore, the vacuum system also accommodate a high density of beam diagnostics tools. Beam path length adjustment is required in the splitter sections. CBETA beampipes are mostly constructed of aluminum alloy (6061-T6), including 80+ metal knife-edge seal flanges made of non-coated aluminum alloy (type 6013-T6). Compact NEG pumps are used due to the space constraints. In this presentation, we report the status of CBETA vacuum system design, chamber fabrications and many stages of beamline installations and operations. Measurements of aluminum alloy outgassing and vacuum simulation, and experiences of using aluminum knife-edge flanges will also be discussed. 1 2009-A-1902 Surface Functionalization of RF Magnetron Sputtering Titanium Dioxide Thin Films Paulo Lisboa-Filho1, Orisson Ponce Gomes1, Nilton Francelosi Azevedo Neto1, José Humbert Dias da Silva1 1 São Paulo State University Nanostructured titanium dioxide (TiO2) has been employed as surface modifiers in medical and dental implants, promoting improvements in biocorrosion resistance of the material and increasing the oxides bioactivity, with promising results in the interaction with living tissue. Although these materials have good mechanical properties, the thin native oxide layer (5-6nm) on their surfaces is not capable of protecting them from long-term corrosion.