The X-ray view of Giga-Hertz Peaked Spectrum Radio Galaxies

This paper presents the X-ray properties of a flux- and volume-limited complete sample of 16 Giga-Hertz Peaked Spectrum (GPS) galaxies. This study addresses three basic questions in our understanding of the nature and evolution of GPS sources: a) What is the physical origin of the X-ray emission in GPS galaxies? b) What physical system is associated with the X-ray obscuration? c) What is the "endpoint" of the evolution of compact radio sources? We obtain a 100% (94%) detection fraction in the 0.5-2 keV (0.5-10 keV) energy band. GPS galaxy X-ray spectra are typically highly obscured. The X-ray column density is higher than the HI column density measured in the radio by a factor of 10 to 100. GPS galaxies lie well on the extrapolation to high radio powers of the correlation between radio and X-ray luminosity known in low-luminosity FRI radio galaxies. On the other hand, GPS galaxies exhibit a comparable X-ray luminosity to FRII radio galaxies, notwithstanding their much higher radio luminosity. The X-ray to radio luminosity ratio distribution in our sample is consistent with the bulk of the high-energy emission being produced by the accretion disk, as well as with dynamical models of GPS evolution where X-rays are produced by Compton upscattering of ambient photons. Further support for the former scenario comes from the location of GPS galaxies in the X-ray to O[III] luminosity ratio versus column density plane. We propose that GPS galaxies are young radio sources, which would reach their full maturity as classical FRII radio galaxies. However, column densities ~10^{22} atoms/cm/cm could lead to a significant underestimate of dynamical age determinations based on the hotspot recession velocity measurements. (abridged)Comment: 14 pages, 14 figues, accepted for publication in Astronomy and Astrophysic

Suberhard NbB2-x thin films deposited by dc magnetron sputtering

We have deposited weakly textured substoichiometric NbB2 −x thin films by magnetron sputtering from an NbB2 target. The films exhibit superhardness (42 ± 4 GPa), previously only observed in overstoichiometric TiB2 thin films, and explained by a self-organized nanostructuring, where thin TiB2 columnar grains hinder nucleation and slip of dislocations and a B-rich tissue phase between the grains prevent grain-boundary sliding. The wide homogeneity range for the NbB2 phase allows a similar ultra-thin B-rich tissue phase to form between thin (5–10 nm) columnar NbB2 −x grains also for films with a B/Nb atomic ratio of 1.8, as revealed here by analytical aberration-corrected scanning transmission electron microscopy. Furthermore, a coefficient of friction of 0.16 is measured for an NbB2 −x film sliding against stainless steel with a wear rate of 5 × 10− 7 mm3/Nm. X-ray photoelectron spectroscopy results suggest that the low friction is due to the formation of a lubricating boric acid film

Superhard NbB2 −x thin films deposited by dc magnetron sputtering

We have deposited weakly textured substoichiometric NbB2-x thin films by magnetron sputtering from an NbB2 target. The films exhibit superhardness (42 +/- 4 GPa), previously only observed in overstoichiometric TiB2 thin films, and explained by a self-organized nanostructuring, where thin TiB2 columnar grains hinder nucleation and slip of dislocations and a B-rich tissue phase between the grains prevent grain-boundary sliding. The wide homogeneity range for the NbB2 phase allows a similar ultra-thin B-rich tissue phase to form between thin (5-10 nm) columnar NbB2-x grains also for films with a B/Nb atomic ratio of 1.8, as revealed here by analytical aberration-corrected scanning transmission electron microscopy. Furthermore, a coefficient of friction of 0.16 is measured for an NbB2-x film sliding against stainless steel with a wear rate of 5 x 10(-7) mm(3)/Nm. X-ray photoelectron spectroscopy results suggest that the low friction is due to the formation of a lubricating boric acid film.Funding Agencies|Vinnova (Swedish Governmental Agency for Innovation Systems) through the VINN Excellence Centre FunMat; Swedish Foundation of Strategic Research through the Synergy Grant FUNCASE; Knut and Alice Wallenberg Foundation</p

Superhard NbB 2 −x thin films deposited by dc magnetron sputtering-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/)

We have deposited weakly textured substoichiometric NbB 2−x thin films by magnetron sputtering from an NbB 2 target. The films exhibit superhardness (42 ± 4 GPa), previously only observed in overstoichiometric TiB 2 thin films, and explained by a self-organized nanostructuring, where thin TiB 2 columnar grains hinder nucleation and slip of dislocations and a B-rich tissue phase between the grains prevent grain-boundary sliding. The wide homogeneity range for the NbB 2 phase allows a similar ultra-thin B-rich tissue phase to form between thin (5-10 nm) columnar NbB 2−x grains also for films with a B/Nb atomic ratio of 1.8, as revealed here by analytical aberration-corrected scanning transmission electron microscopy. Furthermore, a coefficient of friction of 0.16 is measured for an NbB 2−x film sliding against stainless steel with a wear rate of 5 × 10 −7 mm 3 /Nm. X-ray photoelectron spectroscopy results suggest that the low friction is due to the formation of a lubricating boric acid film

Low-temperature growth of dense and hard Ti0.41Al0.51Ta0.08N films via hybrid HIPIMS/DC magnetron co-sputtering with synchronized metal-ion irradiation

Hard Ti1-xAlxN thin films are of importance for metal-cutting applications. The hardness, thermal stability, and oxidation resistance of these coatings can be further enhanced by alloying with TaN. We use a hybrid high-power pulsed and dc magnetron co-sputtering (HIPIMS/DCMS) technique to grow dense and hard Ti0.41Al0.51Ta0.08N alloys without external heating (T-s amp;lt; 150 degrees C). Separate Ti and Al targets operating in the DCMS mode maintain a deposition rate of similar to 50 nm/min, while irradiation of the growing film by heavy Ta+/Ta2+ ions from the HIPIMS-powered Ta target, using dc bias synchronized to the metal-ion-rich part of each HIPIMS pulse, provides effective near-surface atomic mixing resulting in densification. The substrate is maintained at floating potential between the short bias pulses to minimize Ar+ bombardment, which typically leads to high compressive stress. Transmission and scanning electron microscopy analyses reveal dramatic differences in the microstructure of the co-sputtered HIPIMS/DCMS films (Ta-HIPIMS) compared to films with the same composition grown at floating potential with all targets in the DCMS mode (Ta-DCMS). The Ta-DCMS alloy films are only similar to 70% dense due to both inter-and intra-columnar porosity. In contrast, the Ta-HIPIMS layers exhibit no inter-columnar porosity and are essentially fully dense. The mechanical properties of Ta-HIPIMS films are significantly improved with hardness and elastic modulus values of 28.0 and 328 GPa compared to 15.3 and 289 GPa for reference Ta-DCMS films. Published by AIP Publishing.Funding Agencies|Swedish Research Council VR Grant [2013-4018, 2014-5790]; VINN Excellence Center Functional Nanoscale Materials (FunMat); Aforsk Foundation Grant [16-359]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [SFO-Mat-LiU 2009-00971]; Knut and Alice Wallenberg Foundation [2011.0143]</p

A Joint Meeting of the EUCARPIA Section, Organic and Low-Input Agriculture, ECO-PB, LIVESEED, INSUSFAR, DIVERSify, HealthyMinorCereals, ReMIX, and Wheatamix University of Kassel, 19th–21st February 2018, Witzenhausen, Germany ; Abstract Booklet

This Symposium was financially supported by EUCARPIA and organised in collaboration with ECO-PB