Push-pull zinc phthalocyanine bearing hexa-tertiary substituted carbazolyl donor groups for dye-sensitized solar cells

An asymmetrical, push-pull phthalocyanine bearing bulky tert-butylcarbazolyl moieties as electron donor and carboxylic acid as anchoring group was synthetized and tested as a photosensitizer in dye-sensitized solar cells (DSSC). The new photosensitizer was characterized by 1H and 13C NMR, UV-Vis and mass spectrometry. The bulky tert-butylcarbazolyl moieties avoid the aggregation of the phthalocyanine dye. DFT studies indicate that the HOMO is delocalized throughout the π-electron system of the substituted phthalocyanine and the LUMO is located on the core of the molecule with a sizable electron density distribution on carboxyl groups. The new dye has been used as a photosensitizer in transparent and opaque dye-sensitized solar cells, which exhibit poor efficiencies related to a low JscThis work was financially supported by the Kuwait Foundation for the Advancement of Science (Grant Number PN18-12-SC01) and the RSP unit general facilities of the Faculty of Science GFS (GS 01/01, GS 03/01, GS 01/03, GS 01/05, and GS 02/13) (S.M.). T.T. thanks MINECO (project CTQ2017-85393-P) and ERA-NET/European Commission/MINECO, (UNIQUE, SOLAR-ERA.NET Cofund 2 Nº 008/PCI2019-111889-2). R.D. acknowledges ANR for funding through ODYCE project. (Grant agreement No ANR-14-OHRI-0003-01). RD thanks European Research Council (ERC) for funding. This project has received funding from the European Union’s Horizon 2020 research and innovation program (grant agreement No 832606)—Project PISC

Dry-sliding wear behavior of 3Y-TZP/Al2O3-NbC nanocomposites produced by conventional sintering and spark plasma sintering

[EN] This work presents the initial results of the dry-sliding wear behavior of 3 mol% yttria-stabilized zirconia reinforced with 5 vol% alumina-niobium carbide (3Y-TZP/5 vol% Al2O3-NbC) nanocomposites sintered by conventional sintering and spark plasma sintering methods in the temperature range of 1350-1450 degrees C. The reinforcement of 3Y-TZP matrix with hard nanoparticles aimed to improve wear strength of the composites. Wear tests were performed by the ball-on-disc method using alumina (Al2O3) and tungsten carbide with 6 wt% cobalt cermet (WC-6%Co) balls as counter-materials, a load of 15 N, a sliding distance of 2000 m, and a sliding speed of 0.1 m/s. Wear behavior was evaluated in terms of wear rate and FE-SEM micrograph analysis of the wear tracks. The nanocomposite sintered at 1450 degrees C by conventional sintering exhibited the least wear when tested with the WC-6%Co ball. Generally, the wear mechanism showed evidence of severe wear regime with both counter-materials.The authors acknowledge the Brazilian institutions CAPES-PVE (grant number 23038.009604/2013-12), FAPESP (grant number 2015/07319-8), Fundação Araucária (grant number 810/2014), European Union/Erasmus Mundus for doctorate mobility (grant number EB15DM1542), and the Spanish Ministry of Economy and Competitiveness (RYC-2016-20915).Salem, R.; Gutiérrez-González, C.; Borrell Tomás, MA.; Salvador Moya, MD.; Chinelatto, AL.; Chinelatto, AS.; Pallone, E. (2019). Dry-sliding wear behavior of 3Y-TZP/Al2O3-NbC nanocomposites produced by conventional sintering and spark plasma sintering. International Journal of Applied Ceramic Technology. 16(3):1265-1273. https://doi.org/10.1111/ijac.13151S12651273163Liu, H., Zhao, W., Ji, Y., Cui, J., Chu, Y., & Rao, P. (2017). Determination of fracture toughness of zirconia ceramics with different yttria concentrations by SEVNB method. Ceramics International, 43(13), 10572-10575. doi:10.1016/j.ceramint.2017.04.064Ćorić, D., Majić Renjo, M., & Ćurković, L. (2017). Vickers indentation fracture toughness of Y-TZP dental ceramics. International Journal of Refractory Metals and Hard Materials, 64, 14-19. doi:10.1016/j.ijrmhm.2016.12.016De Aza, A. H., Chevalier, J., Fantozzi, G., Schehl, M., & Torrecillas, R. (2002). Crack growth resistance of alumina, zirconia and zirconia toughened alumina ceramics for joint prostheses. Biomaterials, 23(3), 937-945. doi:10.1016/s0142-9612(01)00206-xAragón-Duarte, M. C., Nevarez-Rascón, A., Esparza-Ponce, H. E., Nevarez-Rascón, M. M., Talamantes, R. P., Ornelas, C., … Hurtado-Macías, A. (2017). Nanomechanical properties of zirconia- yttria and alumina zirconia- yttria biomedical ceramics, subjected to low temperature aging. Ceramics International, 43(5), 3931-3939. doi:10.1016/j.ceramint.2016.12.033Balko, J., Csanádi, T., Sedlák, R., Vojtko, M., KovalĿíková, A., Koval, K., … Naughton-Duszová, A. (2017). Nanoindentation and tribology of VC, NbC and ZrC refractory carbides. Journal of the European Ceramic Society, 37(14), 4371-4377. doi:10.1016/j.jeurceramsoc.2017.04.064Alecrim, L. R. R., Ferreira, J. A., Gutiérrez-González, C. F., Salvador, M. D., Borrell, A., & Pallone, E. M. J. A. (2017). Effect of reinforcement NbC phase on the mechanical properties of Al2O3-NbC nanocomposites obtained by spark plasma sintering. International Journal of Refractory Metals and Hard Materials, 64, 255-260. doi:10.1016/j.ijrmhm.2016.10.021Alecrim, L. R. R., Ferreira, J. A., Gutiérrez-González, C. F., Salvador, M. D., Borrell, A., & Pallone, E. M. J. A. (2017). Sliding wear behavior of Al2O3-NbC composites obtained by conventional and nonconventional techniques. Tribology International, 110, 216-221. doi:10.1016/j.triboint.2017.02.028Santos, C., Maeda, L. D., Cairo, C. A. A., & Acchar, W. (2008). Mechanical properties of hot-pressed ZrO2–NbC ceramic composites. International Journal of Refractory Metals and Hard Materials, 26(1), 14-18. doi:10.1016/j.ijrmhm.2007.01.008Ünal, N., Kern, F., Öveçoğlu, M. L., & Gadow, R. (2011). Influence of WC particles on the microstructural and mechanical properties of 3mol% Y2O3 stabilized ZrO2 matrix composites produced by hot pressing. Journal of the European Ceramic Society, 31(13), 2267-2275. doi:10.1016/j.jeurceramsoc.2011.05.032Sequeira, S., Fernandes, M. H., Neves, N., & Almeida, M. M. (2017). Development and characterization of zirconia–alumina composites for orthopedic implants. Ceramics International, 43(1), 693-703. doi:10.1016/j.ceramint.2016.09.216Schmitt-Radloff, U., Kern, F., & Gadow, R. (2017). Wire-electrical discharge machinable alumina zirconia niobium carbide composites – Influence of NbC content. Journal of the European Ceramic Society, 37(15), 4861-4867. doi:10.1016/j.jeurceramsoc.2017.07.014Akatsu, T., Nakanishi, S., Tanabe, Y., Wakai, F., & Yasuda, E. (2013). Toughening enhanced at elevated temperatures in an alumina/zirconia dual-phase matrix composite reinforced with silicon carbide whiskers. Journal of the European Ceramic Society, 33(15-16), 3157-3163. doi:10.1016/j.jeurceramsoc.2013.05.029Lee, D.-J., Choi, H.-S., Jin, F.-L., & Park, S.-J. (2015). A study on mechanical properties and microstructure of tetragonal zirconia-based composites. Journal of Industrial and Engineering Chemistry, 27, 322-328. doi:10.1016/j.jiec.2015.01.008Salem, R. E. P., Monteiro, F. R., Gutiérrez-González, C. F., Borrell, A., Salvador, M. D., Chinelatto, A. S. A., … Pallone, E. M. J. A. (2018). Effect of Al2O3-NbC nanopowder incorporation on the mechanical properties of 3Y-TZP/Al2O3-NbC nanocomposites obtained by conventional and spark plasma sintering. Ceramics International, 44(2), 2504-2509. doi:10.1016/j.ceramint.2017.10.235Schmitt-Radloff, U., Kern, F., & Gadow, R. (2018). Spark plasma sintering and hot pressing of ZTA-NbC materials – A comparison of mechanical and electrical properties. Journal of the European Ceramic Society, 38(11), 4003-4013. doi:10.1016/j.jeurceramsoc.2018.04.022Pędzich, Z., Haberko, K., Faryna, M., & Sztwiertnia, K. (2002). Interphase Boundary in Zirconia – Carbide Particulate Composites. Key Engineering Materials, 223, 221-226. doi:10.4028/www.scientific.net/kem.223.221Acchar, W., Zollfrank, C., & Greil, P. (2004). Microstructure and mechanical properties of WC-Co reinforced with NbC. Materials Research, 7(3), 445-450. doi:10.1590/s1516-14392004000300012Guillon, O., Gonzalez‐Julian, J., Dargatz, B., Kessel, T., Schierning, G., Räthel, J., & Herrmann, M. (2014). Field‐Assisted Sintering Technology/Spark Plasma Sintering: Mechanisms, Materials, and Technology Developments. Advanced Engineering Materials, 16(7), 830-849. doi:10.1002/adem.201300409Munir, Z. A., Anselmi-Tamburini, U., & Ohyanagi, M. (2006). The effect of electric field and pressure on the synthesis and consolidation of materials: A review of the spark plasma sintering method. Journal of Materials Science, 41(3), 763-777. doi:10.1007/s10853-006-6555-2Lu, K. (2008). Sintering of nanoceramics. International Materials Reviews, 53(1), 21-38. doi:10.1179/174328008x254358Borrell, A., Fernández, A., Torrecillas, R., Córdoba, J. M., Avilés, M. A., & Gotor, F. J. (2010). Spark Plasma Sintering of Ultrafine TiCxN1−x Powders Synthesized by a Mechanically Induced Self-Sustaining Reaction. Journal of the American Ceramic Society, 93(8), 2252-2256. doi:10.1111/j.1551-2916.2010.03735.xBonache, V., Salvador, M. D., Fernández, A., & Borrell, A. (2011). Fabrication of full density near-nanostructured cemented carbides by combination of VC/Cr3C2 addition and consolidation by SPS and HIP technologies. International Journal of Refractory Metals and Hard Materials, 29(2), 202-208. doi:10.1016/j.ijrmhm.2010.10.007Gutiérrez-Mora, F., Cano-Crespo, R., Rincón, A., Moreno, R., & Domínguez-Rodríguez, A. (2017). Friction and wear behavior of alumina-based graphene and CNFs composites. Journal of the European Ceramic Society, 37(12), 3805-3812. doi:10.1016/j.jeurceramsoc.2017.02.024Wei, J., Lin, B., Wang, H., Sui, T., Yan, S., Zhao, F., … Fang, S. (2018). Friction and wear characteristics of carbon fiber reinforced silicon carbide ceramic matrix (Cf/SiC) composite and zirconia (ZrO2) ceramic under dry condition. 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Nanostructured composites obtained by reactive milling. Scripta Materialia, 44(8-9), 1735-1740. doi:10.1016/s1359-6462(01)00789-8Pallone, E. M. J. ., Trombini, V., Botta F, W. ., & Tomasi, R. (2003). Synthesis of Al2O3–NbC by reactive milling and production of nanocomposites. Journal of Materials Processing Technology, 143-144, 185-190. doi:10.1016/s0924-0136(03)00411-4ASTM G99‐03 Standard test method for wear testing with a pin‐on‐disc apparatus ASTM Annual Book of Standards vol.03. West Conshohocken PA;2003.Chen, W.-H., Lin, H.-T., Chen, J., Nayak, P. K., Lee, A. C., Lu, H.-H., & Huang, J.-L. (2016). Microstructure and wear behavior of spark plasma sintering sintered Al2O3/WC-based composite. International Journal of Refractory Metals and Hard Materials, 54, 279-283. doi:10.1016/j.ijrmhm.2015.07.030Espinosa-Fernández, L., Borrell, A., Salvador, M. D., & Gutierrez-Gonzalez, C. F. (2013). 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Effect of Al2O3-NbC nanopowder incorporation on the mechanical properties of 3Y-TZP/Al2O3-NbC nanocomposites obtained by conventional and spark plasma sintering

[EN] The incorporation of Al2O3-NbC-nanopowder reinforcement in a 3Y-TZP matrix, and its influence on the mechanical properties of 3YTZP/Al2O3-NbC nanocomposites, obtained by conventional and spark plasma sintering (SPS), was investigated. Nanometric powders of Al2O3-NbC were prepared by reactive high-energy milling, deagglomeration, and leaching with acid, and added to the 3Y-TZP matrix, at a proportion of 5 vol%. The final powders were dried under airflow, compacted, and sintered in the temperature range of 1300-1500 degrees C. The effects of the sintering technique and final temperature, on the microstructure and mechanical properties, such as hardness, toughness, and Young's modulus, were analysed. Fracture toughness of the material reinforced with Al2O3-NbC nanopowders, which is one of its most important properties, differed significantly from that of the 3Y-TZP monolith (5.2 MPa m(1/2)). The nanocomposites, sintered conventionally at 1450 degrees C, showed higher fracture toughness (8.7 MPa m(1/2)). Microstructure observations indicated that NbC nanoparticles were dispersed homogeneously within the 3Y-TZP matrix, and limited its grain growth. However, partial oxidation of the NbC on the nanocomposite surface, at the conventional sintering temperature of 1500 degrees C, caused a reduction in the fracture toughness.The authors acknowledge the Brazilian institutions CAPES-PVE (grant number 23038.009604/2013-12), FAPESP (grant number 2015/07319-8), Fundação Araucária (grant number 810/2014), European Union/Erasmus Mundus for doctorate mobility (grant number EB15DM1542), and the Spanish Ministry of Economy and Competitiveness (grant number IJCI-2014-19839).Salem, R.; Monteiro, R.; Gutierrez, CF.; Borrell Tomás, MA.; Salvador Moya, MD.; Chinelatto, AS.; Chinelatto, A.... (2018). Effect of Al2O3-NbC nanopowder incorporation on the mechanical properties of 3Y-TZP/Al2O3-NbC nanocomposites obtained by conventional and spark plasma sintering. Ceramics International. 44(2):2504-2509. https://doi.org/10.1016/j.ceramint.2017.10.235S2504250944

Network structure of vertebrate scavenger assemblages at the global scale: drivers and ecosystem functioning implications

publishedVersio

Projected WIMP sensitivity of the LUX-ZEPLIN dark matter experiment

LUX-ZEPLIN (LZ) is a next-generation dark matter direct detection experiment that will operate 4850 feet underground at the Sanford Underground Research Facility (SURF) in Lead, South Dakota, USA. Using a two-phase xenon detector with an active mass of 7 tonnes, LZ will search primarily for low-energy interactions with weakly interacting massive particles (WIMPs), which are hypothesized to make up the dark matter in our galactic halo. In this paper, the projected WIMP sensitivity of LZ is presented based on the latest background estimates and simulations of the detector. For a 1000 live day run using a 5.6-tonne fiducial mass, LZ is projected to exclude at 90% confidence level spin-independent WIMP-nucleon cross sections above 1.4 × 10-48cm2 for a 40 GeV/c2 mass WIMP. Additionally, a 5σ discovery potential is projected, reaching cross sections below the exclusion limits of recent experiments. For spin-dependent WIMP-neutron(-proton) scattering, a sensitivity of 2.3 × 10−43 cm2 (7.1 × 10−42 cm2) for a 40 GeV/c2 mass WIMP is expected. With underground installation well underway, LZ is on track for commissioning at SURF in 2020

Measurement of the gamma ray background in the Davis Cavern at the Sanford Underground Research Facility

Deep underground environments are ideal for low background searches due to the attenuation of cosmic rays by passage through the earth. However, they are affected by backgrounds from γ-rays emitted by 40K and the 238U and 232Th decay chains in the surrounding rock. The LUX-ZEPLIN (LZ) experiment will search for dark matter particle interactions with a liquid xenon TPC located within the Davis campus at the Sanford Underground Research Facility, Lead, South Dakota, at the 4,850-foot level. In order to characterise the cavern background, in-situ γ-ray measurements were taken with a sodium iodide detector in various locations and with lead shielding. The integral count rates (0--3300~keV) varied from 596~Hz to 1355~Hz for unshielded measurements, corresponding to a total flux in the cavern of 1.9±0.4~γ cm−2s−1. The resulting activity in the walls of the cavern can be characterised as 220±60~Bq/kg of 40K, 29±15~Bq/kg of 238U, and 13±3~Bq/kg of 232Th

Phase stability of MoTe2 obtained by tellurization of sputtered molybdenum oxide: The influence of the thickness and the precursor crystallinity

1T′ and 2H MoTe2 films were obtained by using isothermal close space tellurization of sputtered MoOx films onto amorphous fused silica or (100) oriented silicon substrates. The influence of the thickness and the crystalline state of the precursor thin films in the obtained phase was analyzed. With this aim, precursors films were sputtered with thicknesses ranging from 5 to 40 nm. From each thickness, one sample was annealed in the air before the tellurization process, and the other was tellurized as sputtered. Misoriented and preferentially oriented crystals were found in all samples, according to grazing incidence and θ–2θ X-rays diffraction measurements, respectively. For samples prepared onto fused silica substrates, 1T′ phase was favored for misoriented crystals except for the samples of the highest thickness tellurized with the annealed thin films precursor. In the case of oriented crystals, they presented a rather different behavior with samples tellurized from annealed precursors preferring the 2H phase. Some experiments performed using crystalline silicon substrates seem to indicate an important influence on the used substrate in the obtained phase. The control of the obtained MoTe2 phase is a relevant subject due to the potential emerging applications of both 1T′ and 2H crystalline modifications in the context of topological superconductivity, fault-tolerant topological quantum computation, for example

Photo-induced charge transfer in molecular materials based on Prussian blue analogs: A photoacoustic study

Photoacoustic spectra of molecular materials based on the assembling of the [Fe(CN)$_6$] molecular block were recorded and evaluated. An intense absorption band around 600 nm was observed for compounds where the valence of the involved metals allows charge transfer through the CN ligand (inner photo-induced redox reactions). In the absence of this transition, only the signal corresponding to d-d transitions within the metal was observed, which falls below 450 nm. This suggests that photoacoustic spectroscopy provides a fast and reliable method to explore the existence of tunable photo-induced charge transfer in molecular materials