http://hdl.handle.net/10468/178 2017-09-02T07:07:50Z 2017-09-02T07:07:50Z Braic, Mariana Vladescu, Alina Balaceanu, Mihai Luculescu, Catalin Padmanabhan, Sibu C. Constantin, Lidia Morris, Michael A. Braic, Viorel Grigorescu, Cristiana E. A. Ionescu, Paul Dracea, Maria Diana Logofatu, Constantin http://hdl.handle.net/10468/3460 2017-01-10T19:00:23Z 2017-12-21T00:00:00Z

A comparative study of the structural, mechanical and tribological characteristics of TiSiC-Cr coatings prepared in CH4 and C2H2 reactive atmosphere by cathodic vacuum arc Braic, Mariana; Vladescu, Alina; Balaceanu, Mihai; Luculescu, Catalin; Padmanabhan, Sibu C.; Constantin, Lidia; Morris, Michael A.; Braic, Viorel; Grigorescu, Cristiana E. A.; Ionescu, Paul; Dracea, Maria Diana; Logofatu, Constantin TiSiC-Cr coatings, with Cr and Si as additional elements, were deposited on Si, C 45 and 316 L steel substrates via cathodic arc evaporation. Two series of coatings with thicknesses in the range of 3.6–3.9 μm were produced, using either CH4 or C2H2 as carbon containing gas. For each series, different coatings were prepared by varying the carbon rich gas flow rate between 90 and 130 sccm, while maintaining constant cathode currents (110 and 100 A at TiSi and Cr cathodes, respectively), substrate bias (–200 V) and substrate temperature (∼320 °C). The coatings were analyzed for their mechanical characteristics (hardness, adhesion) and tribological performance (friction, wear), along with their elemental and phase composition, chemical bonds, crystalline structure and cross-sectional morphology. The coatings were found to be formed with nano-scale composite structures consisting of carbide crystallites (grain size of 3.1–8.2 nm) and amorphous hydrogenated carbon. The experimental results showed significant differences between the two coating series, where the films formed from C2H2 exhibited markedly superior characteristics in terms of microstructure, morphology, hardness, friction behaviour and wear resistance. For the coatings prepared using CH4, the measured values of crystallite size, hardness, friction coefficient and wear rate were in the ranges of 7.2–8.2 nm, 26–30 GPa, 0.3–0.4 and 2.1–4.8 × 10−6 mm3 N−1 m−1, respectively, while for the coatings grown in C2H2, the values of these characteristics were found to be in the ranges of 3.1–3.7 nm, 41–45 GPa, 0.1–0.2 and 1.4–3.0 × 10−6 mm3 N−1 m−1, respectively. Among the investigated coatings, the one produced using C2H2 at the highest flow rate (130 sccm) exhibited the highest hardness (45.1 GPa), the lowest friction coefficient (0.10) and the best wear resistance (wear rate of 1.4 × 10−6 mm3 N−1 m−1).

2017-12-21T00:00:00Z Keane, Donal A. Hamilton, Niki Gibson, Lorraine T. Pillai, Suresh C. Holmes, Justin D. Morris, Michael A. http://hdl.handle.net/10468/3618 2017-08-22T09:16:52Z 2017-12-01T00:00:00Z

Photocatalytic air-purification: A low-cost, real-time gas detection method Keane, Donal A.; Hamilton, Niki; Gibson, Lorraine T.; Pillai, Suresh C.; Holmes, Justin D.; Morris, Michael A. This research demonstrates the use of a gas detector as a feasible alternative to the standardized analytical methods typically found in photocatalytic air-purification ISO standard tests and academic literature. A methyl mercaptan detector is calibrated and validated (for linearity) using a standard gas generator. The detector can be directly connected to the photoreactor exit allowing real-time span gas measurement with data-logging at one minute intervals. The detector successfully differentiated samples with different photocatalytic performance. The use of such detectors offers an easy-to-use, low-cost alternative to gas measurement with applications in academic research, proof-of-concept photocatalytic tests and also as an educational tool.

2017-12-01T00:00:00Z Riva, Matthieu Healy, Robert M. Flaud, Pierre-Marie Perraudin, Emilie Wenger, John C. Villenave, Eric http://hdl.handle.net/10468/3554 2017-02-02T19:01:03Z 2017-11-30T00:00:00Z

Gas- and particle-phase products from the photooxidation of acenaphthene and acenaphthylene by OH radicals Riva, Matthieu; Healy, Robert M.; Flaud, Pierre-Marie; Perraudin, Emilie; Wenger, John C.; Villenave, Eric This work is focused on the gas-phase oxidation of acenaphthylene and acenaphthene by OH radicals and associated secondary organic aerosol (SOA) formation under low and high-NOx conditions. Experiments were carried out in an atmospheric simulation chamber using a proton transfer reaction time-of-flight-mass spectrometer (PTR-TOF-MS) and an aerosol time-of-flight-mass spectrometer (ATOFMS) to chemically characterize the gas- and particle-phase products, respectively. Due to the structures of these two aromatic compounds, the proposed chemical mechanisms exhibit some differences. In the case of acenaphthene, H-atom abstraction from the saturated cyclopenta-fused ring was found to be competitive with the OH-addition to the aromatic rings. During the photooxidation of acenaphthene using nitrous acid (HONO), aromatic ring-opening products such as indanone and indanone carbaldehyde, generated through OH addition to the aromatic ring, were formed in higher yields compared to low-NOx conditions. In the case of acenaphthylene, OH addition to the unsaturated cyclopenta-fused ring was strongly favored. Hence, ring-retaining species such as acenaphthenone and acenaphthenequinone, were identified as the main reaction products in both gas- and particle-phases, especially under high-NOx conditions. Subsequent SOA formation was observed in all experiments and SOA yields were determined under low/high-NOx conditions to be 0.61/0.46 and 0.68/0.55 from the OH-initiated oxidation of acenaphthylene and acenaphthene, respectively.

2017-11-30T00:00:00Z Glynn, Colm Geaney, Hugh McNulty, David O'Connell, John Holmes, Justin D. O'Dwyer, Colm http://hdl.handle.net/10468/3349 2017-08-30T09:22:40Z 2017-11-28T00:00:00Z

Patterning optically clear films: co-planar transparent and color-contrasted thin films from interdiffused electrodeposited and solution-processed metal oxides Glynn, Colm; Geaney, Hugh; McNulty, David; O'Connell, John; Holmes, Justin D.; O'Dwyer, Colm Transparent thin films can now be site-selectively patterned and positioned on surface using mask-defined electrodeposition of one oxide and overcoating with a different solution-processed oxide, followed by thermal annealing. Annealing allows an interdiffusion process to create a new oxide that is entirely transparent. A primary electrodeposited oxide can be patterned and the secondary oxide coated over the entire substrate to form high color contrast coplanar thin film tertiary oxide. The authors also detail the phase formation and chemical state of the oxide and how the nature of the electrodeposited layer and the overlayer influence the optical clearing of the patterned oxide film.

2017-11-28T00:00:00Z