Demonstration of a Transportable Fabry–Pérot Refractometer by a Ring-Type Comparison of Dead-Weight Pressure Balances at Four European National Metrology Institutes

Fabry–Pérot-based refractometry has demonstrated the ability to assess gas pressure with high accuracy and has been prophesized to be able to realize the SI unit for pressure, the pascal, based on quantum calculations of the molar polarizabilities of gases. So far, the technology has mostly been limited to well-controlled laboratories. However, recently, an easy-to-use transportable refractometer has been constructed. Although its performance has previously been assessed under well-controlled laboratory conditions, to assess its ability to serve as an actually transportable system, a ring-type comparison addressing various well-characterized pressure balances in the 10–90 kPa range at several European national metrology institutes is presented in this work. It was found that the transportable refractometer is capable of being transported and swiftly set up to be operational with retained performance in a variety of environments. The system could also verify that the pressure balances used within the ring-type comparison agree with each other. These results constitute an important step toward broadening the application areas of FP-based refractometry technology and bringing it within reach of various types of stakeholders, not least within industry

Robust radiative cooling via surface phonon coupling-enhanced emissivity from SiO2 micropillar arrays

Silicon dioxide (SiO2) is a prominent candidate for radiative cooling applications due to its low absorption in solar wavelengths (0.25-2.5 µm) and exceptional stability. However, its bulk phonon-polariton band results in a strong reflection peak in the atmospheric transparency window (8-13 µm), making it difficult to meet the requirements for sub-ambient passive radiative cooling. Herein, we demonstrate that SiO2 micropillar arrays can effectively suppress infrared reflection at 8-13 µm and enhance the infrared emissivity by optimizing the micropillar array structure. We created a pattern with a height, spacing, and diameter of approximately 1.45 µm, 0.15 µm, and 0.35 µm, respectively, on top of a bulk SiO2 substrate using reactive ion etching. The resulting surface phonon coupling of the micropillar array led to an increase in the thermal emissivity from 0.79 to 0.94. Outdoor tests show that the SiO2 cooler with an optimized micropillar array can generate an average temperature drop of 5.5 °C throughout the daytime underneath an irradiance of 843.1 W/m^2 at noon. Furthermore, the micropillar arrays endow the SiO2 cooler with remarkable hydrophobic properties, attributed to the formation of F/C compounds introduced during the etching process. Finally, we also replicated the micropillar pattern onto the surface of industrial optical solar reflectors (OSRs), demonstrating similar emissivity and hydrophobicity enhancements. Our findings revealed an effective strategy for modifying the thermal management features of durable SiO2 layers, which can be harnessed to cool OSRs and other similar sky-facing devices

Developing Quantitative Nondestructive Characterization of Nanomaterials: A Case Study on Sequential Infiltration Synthesis of Block Copolymers

The sequential infiltration synthesis (SIS) of inorganic materials in nanostructured block copolymer templates has rapidly progressed in the last few years to develop functional nanomaterials with controllable properties. To assist this rapid evolution, expanding the capabilities of nondestructive methods for quantitative characterization of the materials properties is required. In this paper, we characterize the SIS process on three model polymers with different infiltration profiles through ex situ quantification by reference-free grazing incidence X-ray fluores-cence. More qualitative depth distribution results were validated by means of X-ray photoelectron spectroscopy and scanning trans-mission electron microscopy combined with energy-dispersive X-ray spectroscopy

Determination of sensitivity coefficients and their uncertainties in Rockwell hardness measurement: a Monte Carlo method for multiple linear regression

In the last few decades, many researchers have been studying how hardness measurements can be affected by possible influence variables (i.e. velocity of the indenter, dwell times, temperature, etc). This interest is particularly motivated by the newly adopted international definitions for the realization of Rockwell superficial hardness scales (HR45N, HR30N and HR15N) provided by the Consultative Committee for Mass and Related Quantities of Bureau International des Poids et Mesures, which deal with all the above-mentioned parameters. In this paper, the effect of two such parameters, namely the velocity of the final load application and the time interval of the force variation from the preliminary force value to the total force value, on superficial Rockwell hardness scales at different levels is studied and the related sensitivity coefficients are determined. The coefficients obtained are in the order of 10(-3) HR s mu m(-1) and 10(-2) HR s(-1), respectively, in agreement with other National Metrology Institutes (NMIs), i.e. NIST and NPL. However, the uncertainties associated by the other NMIs are usually underestimated since they are simply given as the standard deviation calculated from the ordinary least squares method for the multiple linear regression, or, in other cases, not reported. For this reason, we propose a methodology for calculating the uncertainties of the sensitivity coefficients via a Monte Carlo method applied to multiple linear regression in order to consider the variability of both input and output quantities: with this method, the squared uncertainties are given as the squared sum of the standard deviation calculated from the ordinary least squares method and the uncertainty contribution due to the repeatability obtained via the proposed Monte Carlo method. The proposed method yields uncertainties of about 10(-2) HR, while the uncertainties reported in other related published papers are in the order of 10(-3) HR

Lithobiontic recolonization following cleaning and preservative treatments on the rock engravings of Valle Camonica, Italy: A 54-months monitoring

: Both the indirect control of microclimate conditions and the direct application of preservative products to contrast stone bioreceptivity may contribute to limit lithobiontic recolonization of cultural heritage surfaces after cleaning interventions. However, the priority deserved by these different preventive approaches has still been poorly evaluated, particularly in outdoor environments. This work dealt with the engraved sandstone surfaces of the National Park of Rock Engravings of Naquane (Italy, UNESCO WHS), widely colonized by lichens, mosses and a dark cyanobacterial biofilm, and thus requiring frequent cleaning interventions to preserve their legibility for visitors and scholars. In particular, post-cleaning recolonization by the different lithobionts was seasonally monitored along 54 months in different zones of an engraved outcrop, primarily differing in levels of shading, on parcels exposed to nine different conservative treatments. These included (or not) a pre-cleaning devitalization of lithobionts and the post-cleaning application of biocidal (benzalkonium chloride, plant essential oils, usnic acid) and other restoration products (nanocrystalline anatase, polysiloxane-based water repellent, ethyl-silicate-based consolidant). The combination of surface image analyses, fluorimetric and colorimetric measurements showed that mosses and the cyanobacterial biofilm rapidly recolonized all the parcels in the more shaded zone, irrespective of conservative treatments. In the other areas, recolonization significantly differed depending on the treatment. The post-cleaning application of biocides determined the best results through two vegetative seasons, but only nanocrystalline anatase and the polysiloxane-based water repellent maintained the surfaces lighter than uncleaned controls along the whole monitoring period. Recolonization primarily proceeded by the uncleaned surfaces surrounding the parcels and, at least in the examined case of lichens, did not show substantial shifts in community composition, although some nitrophytic species increased their frequency. In conclusion, the effectiveness of preservative treatments to prevent a rapid recolonization of heritage stone surfaces appeared subordinate to the presence of microenvironmental conditions less favourable to lithobionts