[en] We present testbed results of the Apodized Pupil Lyot Coronagraph (APLC) at the Laboratory for Adaptive Optics (LAO). These results are part of the validation and tests of the coronagraph and of the Extreme Adaptive Optics (ExAO) for the Gemini Planet Imager (GPI). The apodizer component is manufactured with a halftone technique using black chrome microdots on glass. Testing this APLC (like any other coronagraph) requires extremely good wavefront correction, which is obtained to the 1 nm rms level using the microelectricalmechanical systems (MEMS) technology, on the ExAO visible testbed of the LAO at the University of Santa Cruz. We used an APLC coronagraph without central obstruction, both with a reference super-polished flat mirror and with the MEMS to obtain one of the first images of a dark zone in a coronagraphic image with classical adaptive optics using a MEMS deformable mirror (without involving dark hole algorithms). This was done as a complementary test to the GPI coronagraph testbed at American Museum of Natural History, which studied the coronagraph itself without wavefront correction. Because we needed a full aperture, the coronagraph design is very different from the GPI design. We also tested a coronagraph with central obstruction similar to that of GPI. We investigated the performance of the APLC coronagraph and more particularly the effect of the apodizer profile accuracy on the contrast. Finally, we compared the resulting contrast to predictions made with a wavefront propagation model of the testbed to understand the effects of phase and amplitude errors on the final contrast.

[en] Preparing a selective, efficient, and low-cost solar absorber is one of the main challenges in solar to thermal energy conversion. In this paper, black electroless NiP (ENi-P) solar absorber has been fabricated, and the effect of nanoporous TiO₂ antireflection layer (ARL) on its optical and corrosion properties has been investigated. The optimum black coating was obtained by blackening in 9 M nitric acid solution at 50 °C for 40 s, in which a solar absorptance of 99.3% was achieved. Deposition of TiO₂ ARL increased the solar absorptance of coating to 99.7% and addition of 0.8 g Pluronic F127 (F127) as pore former, further increased this value to 99.9% and solar-to-heat efficiency of the coating from 78.1 to 78.7%. F127 added coatings exhibited elongated and irregularly shaped pores with dimensions of a few tens of nanometers. Also, deposition of TiO₂ ARL decreased the corrosion current density (i_corr) of black ENi-P coating in 3.5 wt% NaCl solution from 20 to 4 μA/cm². The results of this work indicate that the TiO₂ deposited black ENi-P coating can be a suitable choice for black coating applications.

[en] Black chromium coating has becomes an important process for metal finishes especially in solar energy utilisation. It has own applications in various fields; such as for non-reflecting coatings, decorative coatings and solar selective coatings [1). This work is focused at solar selective coatings where it is used for thermal energy application. The coating surface that absorbs solar energy should have an ideal solar selective surface such as high absorption (a) in solar spectrum near infrared region (IR) [2). Electroplating is used as a technique to produce a black coating finishes. It is a simple room temperature test, which is cost effective for modification of surfaces. The black chromium coating finishes is determined by using hull cell test where the current range from 1-10 Amp, with 10 minutes plating time is estimated to simulate the actual plating process. Through the hull cell test process, results has shown that the black chromium coating can be obtained at temperature 24-33 degree C, with current densities range from 5-30 A/dm². Two different current density (25 and 30 A/dm²) is used to produce optimum black colour as determined from hull cell test. With plating time 4 to 10 minutes act as measured parameters, the absorption rate of O.86-0.97 are obtained. The present black coating produced, showed a powdery deep black colour, with adherent film upon a conductive base, has a great potential for solar thermal energy applications. (Author)

[en] The black pottery unearthed from the Hanseong Baekje archaeological site in Seoul, South Korea was characterized by type using different techniques. The samples were classified into three types depending on their coloring pattern. There was no observable difference in the mineral and major element composition of the black colored part and raw material soil part of each sample. However, differences in magnetic properties and carbon content reflect the characteristics of each type and part of the sample. These results help to distinguish the mechanisms for black color development between reductive fired black pottery and soot-coated black pottery. (author)

No abstract available

[en] In this work, composite Ni-P-carbon black coatings were obtained by electroless deposition on L X80 substrates. The effect of carbon black on structural, adhesion and electrochemical properties of the plated samples was evaluated. Scanning electron microscopy analyses were carried out to examine the top surface and cross section of the films. Scratch tests were employed to evaluate coating adhesion properties. Potentiodynamic polarization tests were carried out to investigate the global electrochemical behavior of the deposited layers. Scanning electrochemical microscopy (SECM) was employed to measure local electrochemical activity over the coated surfaces. The carbon black concentration markedly affects the morphology, adhesion and electrochemical properties of the Ni-P-carbon black layers. The results point to an optimum carbon black content to achieve the best performance against corrosion. The coatings obtained at a carbon black concentration of 0.25 g L⁻¹ provided the best protection ability. The results are discussed with respect to coating morphology, adhesion and electrochemical activity.

No abstract available

[en] The structure and properties of thermal control white and black coatings for space applications on AMg3 aluminum alloy, obtained by plasma electrolytic oxidation in silicate–alkaline electrolytes, are studied experimentally. The composition and structure of the coatings are studied using scanning electron microscopy, energy-dispersive microanalysis, and X-ray diffraction analysis. It is found that aluminosilicates dominate in the porous structure of the white slightly conductive coatings, while vanadium is present in the black coatings. The solar absorbance A_s and thermal emissivity ε are measured: A_s = 0.28, ε = 0.93 for the white coatings and A_s = 0.95, ε = 0.88 for the black coatings. These values correspond to the characteristics of EKOM thermal control paint coatings produced by Kompozit (Russia). The effect of atomic oxygen flux on the coatings under investigation leads to insignificant erosion of their surface, as compared to other materials.

[en] Some proposed interferometric gravitational wave detectors of the next generation are designed to use silicon test masses cooled to cryogenic temperatures. The test masses will need to be partially coated with high emissivity coating to provide sufficient cooling when they absorb the laser light. The mechanical loss of the Acktar Black coating is determined based on the measurements of the Q -factors of the bending vibration modes of coated and uncoated commercial silicon wafers. The Young's modulus of the coating material is determined using nanoindentation. We use this information to calculate thermal noise of the silicon test masses associated with a high emissivity coating on its lateral side (barrel). It is found that such a coating results in a less than 9% increase of the total strain noise of LIGO Voyager design for a future cryogenic gravitational wave detector. (paper)

[en] The successful detection of gravitational waves from astrophysical sources carried out by the laser interferometric detectors LIGO and Virgo have stimulated scientists to develop a new generation of more sensitive gravitational wave detectors. In the proposed upgrade called LIGO Voyager, silicon test masses will be cooled to cryogenic temperatures. To provide heat removal from the test masses when they absorb the laser light one can increase their thermal emissivity using a special black coating. We have studied mechanical losses in a carbon nanotube black coating deposited on silicon wafers. The additional thermal noise associated with mechanical loss in this coating was calculated using a value of the product of the coating Young’s modulus and the coating mechanical loss angle determined from the measurements. It was found that at temperatures of about 123 K, the additional thermal noise of the LIGO Voyager test mass caused by the carbon nanotube black coating deposited on its barrel is less than the noise associated with the Acktar Black coating and is 20 times less than the noise due to the optical high reflective (HR) coating of the test mass. (paper)