This work presents an investigation on the optical and structural properties of two series of nanocomposites based on the incorporation of spherical- (NDs) or rod-shaped (NRs) semiconductive crystalline titanium dioxide (TiO) nanoparticles (NPs) into an insulating amorphous polymethylmethacrylate (PMMA) matrix. The UV-visible absorbance and reflectance measurements reveal that the increase in TiO NP concentration within the polymer matrix reduces the forbidden band size for both NDs and NRs, leading to an improvement of the refractive index. SEM and TEM morphological characterizations were performed to investigate the size, size distribution and NPs dispersion within the polymeric matrix. The structural analyses performed by using X-ray diffraction show peaks ascribed to the TiO crystalline structure while infrared (FT-IR) spectra indicate the occurrence of interactions between nanofillers and the polymer chain of the host matrix.

TiB2 is a promising material for several fields including impact-resistant armor, wearresistant coatings, cutting tools and crucibles given its physical, mechanical and chemical properties, especially due to the combination of high hardness and exceptional wear resistance. It is however very difficult to sinter below 2000 C, even under mechanical pressure; moreover, the low fracture toughness limits the applicability of the ceramic material. By using sintering additives, it is possible to improve the sintering process and increase the mechanical properties since the additives react with oxidized layers and form secondary phases. In this study, different preparation methods and various combinations of additives (B4C, Si3N4 and MoSi2) via hot pressing sintering have been explored. Through the synergy between optimized process and tailored composition, an almost fully dense material was obtained at 1700 C with hardness of 24.4 0.2 GPa and fracture toughness of 5.4 0.2 MPam1/2. However, the highest hardness (24.5 0.2 GPa) and density values were obtained for only the high-energy-milled sample with WC-Co media, featuring a core-shell grain structure. Finally, optical properties for selected samples were measured, identifying the high-energy-milled TiB2 as the sample with the highest spectral selectivity /" and solar absorptance.

Transparent ceramics represent both a symbol of perfection in the world of ceramics, given the necessity to produce materials without defects or porosity, as well as of new possibilities, in particular for harsh environments and high-power laser applications. These materials, with a fully crystalline, single-phase structure and the production flexibility offered by the ceramic processing technologies, represent a new generation of materials for optics and photonics and have been in the spotlight of R&D in the past decade. Zenit Smart Polycrystals is a startup, born as a spin-off of the National Research Council of Italy, founded with the aim to offer new components for the laser, optics, and photonics markets. And the novelty comes from the implementation of additive manufacturing in the production process. Thanks to the flexibility and high precision of shape and composition distribution within a single component, it is possible to disrupt the laser and photonics scene going beyond the technology based on single crystals, i.e. providing near-net-shape components with complex structures produced in one single shaping step, skipping high precision post-polishing and bonding. New tailor-made laser gain media will be offered to materials processing, automotive as well as medical markets.

5at.% Yb:Lu2O3 transparent ceramics were fabricated successfully by vacuum sintering along with hot isostatic pressing posttreatment from the nanopowders. The influences of calcination temperature on morphology and microstructures of powders and ceramics were studied systematically. The optimal ceramic sample from the nanopowder calcined at 1050 degrees C shows uniform and dense microstructure with the in-line transmittance of 81.5% at 1100 nm. The results of the thermal measurements, that is, thermal conductivity and specific heat, were related to the changes occurring in the microstructure of the ceramics studied. It was shown on this basis that appropriate control of the technological process of sintering ceramics makes it possible to obtain laser ceramics with very good thermal properties as well as maintaining their high optical quality. Concerning the laser performance, the highest-optical quality 5at.% Yb:Lu2O3 sample was pumped in quasi-continuous wave conditions measuring a maximum output power of 2.59 W with a corresponding slope efficiency of 32.4%.

The effect of rapid laser irradiation on the optical properties of mature soot particles is investigated by performing wavelengthresolved extinction measurements in the visible spectral region. In particular, the spectral behavior of the absorption properties is explored during laser irradiation, at the peak of the incandescence signal (prompt LII) and few nanoseconds after the peak, and finally when particles have reached an equilibrium condition with the surrounding gas. A significant variation of the absorption coefficient of the laser-irradiated soot particles compared to that of the pristine ones is observed already at the LII peak. Such variation keeps evolving with time until it reaches a final permanent value. Results are presented in relation to the laser fluence used for irradiation and discussed with the aim of stressing the need of knowing the entity of the modification of soot absorption properties during laser irradiation for a correct interpretation of LII data.

??????? ???????? ?? ?????? ?????? ????? ??????? ????????????? ?? ?????????????????? ????????. ??????? ????? ?????????? ? ???????? ????????????, ???????? ? ????????? ???????????? Y2O3 ???????? ????????? ?????? ????????? ???????????? [1]. ? ??????? ????????? ????? ???????? ??????? ??????? ??????? ????????? ??????. ????????? ???????? (???) ???????? ??????? ? ????????? ??????????? ?????????. ? ??'???? ? ???, ????? ???????? ?????????? ? ??????????? ?????? ?????? ?? ??????? ???????? ??????? ???? ? ??????? ????????? ???????? [2]. ????? ?????? ? ??????????? ?????? ???????? ???????? ? ???? ?? ??????? ?? ??????? ??????????? ???????? Y2O3. ? ????? ?????? ???? ?????????? ?????????? ???????? ??????????? ???????? ?????? ????? (Nippon, Stanford, Solvay ? US RN) ????? ?????? ??? ?????? ??????. ? ?????? ???????, ?? ?????? ????????, ???? ?????? 3 ???.% ZrO2. ??????, ????????????? ?????????? ? ???????? ???????????? ???????????, ??????? ?? ??????? ??? ??????????? 1600 °? ???????? 4 ???. ?? ? ??????? ??? 1735°? ???????? 32 ???. ?? ??????? ????? ?????????? ?????????? ???????? ????? ??????????????????? ?????? (80 ??./??. ???????? 22 ???.). ????? ????????????? ???????? Stanford ???????????????? ????????? ??????? ? ???????? ???????????, ??? ?? ?????????? ??? ??????????. ?????????? ????? ???????? ????? ?????????, ?????????? ????? ?? ???????? ? ?????? ?'???. ????? ???? ???????, ????????? ????????? ?? ???????, ???? Nippon-???????? ???????????????? ??????? ????????? ? ?????????? ??????????????? ? ??????????? ????????? ???????? ??????? ??????????? ????? ??????? ???????? (???) ?? ??????? ????????. ?????? ???????? ????? ???????? ???????? Solvay ? US RN ?????????? ?? ????? ??????????????? ? ??????? ????????????? ??????? ??????????? ??????????. ????? ?????, Nippon Y2O3 ???? ?????? ??? ????????? ??????????. ????????? ????? ???? ?????? (????????? ? ???) ?? ????????? ??????? ? ??????????? ????????-???????? ???????? Y2O3. ??????????? ?????????? ????? ????????? ???????? ? ??????? ?????????? ?? ???????? (300 ??./??., 65 ??.). ?? ????? ???? ?????? ????? ???????? ???????? 21.3 ?2/?, ? ???????? ?????? ???????? ??????? 480 ??. ???????? ????????? ?????? ?? 200 ? 100 ??./??. ?????????? ?? ?????????? ??????? ????????, ? ?????????? ???? ?????? ?? 10 ??? ??????????????? ???????????? ???????? ????? ?????? ???????? ??????? ????? ????????. ???????? Y2O3, ???????? ? ????? ??????? ??????? ?????????? ???????? ??? 1735 °? ???????? 32 ???, ???????????????? ??????? ????????? ????????? 100±0,5% ? ???????? ???????? ???????????? ????? ???? ??????????????? ??????? (78,1 % ??? 1100 ??, ?? ??????? 95,6 % ??? ???????????? ????????). ??????????? ???????? ?? ????????? CNR-ISSMC (?????? CNR-ISTEC), ??????, ?????? ? JECS Trust (???????? No. 2021293) ??????????: [1]J. Kong, D.Y. Tang, J. Lu, et al, Appl. Phys. 79, 449-455 (2004). [2]S. Hríbalova, W. Pabst, J. Eur. Ceram. Soc. 41, 2169-2192 (2021)

Transparent yttrium aluminum garnet (YAG) ceramics are mostly sintered under vacuum to favor pore closure. However, this may conceal the origin of microstructural defects, complicating process optimization. We describe a useful approach to understand the origin of defects in transparent YAG ceramics: reactive sintering was performed in air at a moderate temperature for a short time. The resulting microstructure allowed to understand the origin of defects in corresponding vacuum-sintered specimens. The porosity of air sintered samples could be related to the presence of aggregates of starting oxide particles, which eventually under vacuum react to form YAG, but leave behind pores

Optical and thermal properties of copper films under femtosecond laser excitation has been dynamically calculated as a function of time using a two-temperature model coupled with Drude model. Ultrafast changes have been observed when the material is still cold.

Recently, hexagonal boron nitride (hBN) has become an interesting platform for quantum optics due to its peculiar defect-related luminescence properties. Concomitantly, hBN was established as the ideal insulating support for realizing 2D materials devices, where, on the contrary, defects can affect the device performance. In this work, we study the light emission properties of hBN flakes obtained by mechanical exfoliation with particular focus on extended defects generated in the process. In particular, we tackle different issues related to the light emission in hBN flakes of different thicknesses in the range of hundreds of nanometers, revealing a higher concentration of deep level emission in thinner area of the flake. We recognize the effect of crystal deformation in some areas of the flake with an important blue-shift (130 meV) of the room temperature near band edge emission of hBN and the concurrent presence of a novel emission at 2.36 eV, related to the formation of array of dislocations. We studied the light emission properties by means of cathodoluminescence (CL) and sub-bandgap excitation photoluminescence of thickness steps with different crystallographic orientations, revealing the presence of different concentration of radiative centers. CL mapping allows to detect buried thickness steps, invisible to the scanning electron microscopy and atomic force microscopy morphological analysis.

In open regions of the Ross Sea the role of the microbial community in the turnover of organic matter has still scarcely been investigated; indeed, very little is known on how microbial dis-tribution and functional diversity respond to environmental conditions and hydrographic structures. During the austral summer 2017, two pelagic areas of the Ross Sea [the Drygalski Ice Tongue and the nearby Terra Nova Bay polynya (A area) and the continental Shelf Break area near Cape Adare (C area)] were studied at selected depths [surface, Deep Chlorophyll Maximum (DCM), Circumpolar Deep Water (CDW), deep waters]. Trophic properties [nu-trient concentrations, particulate (POC), dissolved organic carbon (DOC) and its optically significant fraction (CDOM) were measured, together with the main hydrological variables. Microbial community abundance [total prokaryotes, living, dead and actively respiring frac-tion, high- and low nucleic acid cells (HNA and LNA), pico- and nanoeukaryotes, culturable heterotrophic bacteria], composition and metabolism (as whole community and isolated bac-teria) were also assessed. Through a multidisciplinary dataset, this study highlighted the variable response of mi-crobial abundance, diversity and metabolism of the microbial community to the changing local environmental conditions of the Ross Sea. Different forcings, such as the organic matter inputs (mostly of detrital nature) released from the Drygalski glacier in the A area and a coastal-to-offshore gradient in the C area, coexisted within this extreme ecosystem. This re-sulted in a significant spatial segregation of the edaphic parameters and of the microbial community distribution and metabolic activity patterns.

The reflectance and transmittance spectra of a set of thin gold films on sodium alginate are measured and simulated in the framework of the generalized transfer matrix method. In the simulation, the dielectric function for the nano-particles (NP) was modified from that of gold bulk by using a variable damping energy. A Lorentz oscillator was used to describe the localized surface plasmon resonance. The results elucidate the structural arrangement of the deposited material on the specific substrate. The collision frequency obtained from the simulation indicates that the aggregation of the NPs at the nanoscopic level correlates with the electrical properties. The intense surface plasmon resonance remains visible for film thicknesses up to 10 nm, in spite of the increasing loss of particle separation. In addition to the attained results, the developed methodology can be usefully applied on other case studies for a thorough characterization of the formation of the growing NP films on the specific substrate.

The long-range transport of desert dust over the area of the temperate climate zone is associated with the influx of hot air masses due to the location of the sources of this aerosol in the tropical climate zone. Between 24-26 February 2021, such an aerosol outbreak took place and reached Central Europe. The mean temperature of +11.7 °C was recorded during the event. A comparison of this value to the 20-year (2000-2020) average February temperature for Warsaw (-0.2 °C) indicates the uniqueness of the meteorological conditions. It was the first wintertime inflow of Saharan dust over Warsaw, the presence of which was confirmed by lidar and sun-photometer measurements. The properties of the desert dust layers were obtained; the mean values of the particle depolarization for the fully developed mineral dust layer were 13 ± 3% and 22 ± 4% for 355 and 532 nm, respectively. The aerosol optical thickness was high with average values >0.36 for all wavelengths smaller than 500 nm. The three-modal, aerosol size distribution was dominated by coarse-mode particles, with a visible contribution of accumulation-mode particles. It suggests the possible presence of other aerosol types.

In this work cooled carbon nanoparticles are investigated with the aim of gaining knowledge on their properties. To this purpose, a double pulse experiment is employed consisting essentially of a modified Laser-Induced Incandescence (LII) approach. Before the conventional LII measurements, nanoparticles are additionally irradiated applying different laser fluences. The investigation is performed on carbon nanoparticles sampled from a rich premixed ethylene/air flame at two heights in order to compare the irradiation effects on young and mature particles. Two-color LII measurements are carried out on pristine and irradiated nanoparticles varying the LII laser fluence. In particular, the effects on the incandescence signal, temperature and concentration are investigated. Two phenomena are isolated, namely (1) a significant increase of the apparent particle volume fraction with the applied laser fluence; and (2) a noticeable increase of the LII signal depending on the laser irradiation fluence applied prior to LII. The effects are found to be stronger for young carbon nanoparticles compared to mature ones. These effects are discussed with the aim of understanding the phenomena occurring under laser irradiation and to suggest a possible role of the electrical properties of the particles under analysis.

Assessing experimentally the main optical parameters of graphene (e.g. complex refractive index, carrier density, mobility) in the far-infrared (0.1-10 THz) is important for quantum science, due to the possibility to devise miniaturized devices (frequency combs, random lasers), components (optical switches, spatial light modulators, metamaterial mirrors and modulators) or photonic circuits, in which graphene can be integrated with existing semiconductor technologies to manipulate their optical properties and induce novel functionalities. Here, we combine time domain terahertz (THz) spectroscopy and Fourier transform infrared spectroscopy to extract the complex refractive index of large ( 1/41cm2) area single layer graphene on thin ( 1/40.1-1 ?m) polymeric suspended substrates, flexible and transparent films, and high reflectivity Si substrates in the 0.4-1.8 THz range. We model our data to extract the relevant optical (refractive index, absorption coefficient, penetration length) electronic (Fermi velocity) and electrical (carrier density, mobility) properties of the different graphene samples.

In this work, for the first time, we studied the temperature-dependent spectral emittance of highly refractory ceramics, e.g. silicon carbide (SiC) and two ultra-high temperature ceramics (tantalum diboride (TaB), zirconium diboride (ZrB)) to evaluate their potential for solar tower receivers applications. We measured the spectral normal emittance from 1 µm to 21 µm at temperatures up to 850 °C, in vacuum, by means of a novel experimental setup composed by an electric furnace connected to a FT-IR spectrometer. Comparison with previously published data collected with a different setup was also carried out to validate the results. In addition, the experimental spectral emittance was also compared with the values calculated from hemispherical reflectance at room temperature by means of Kirchhoff's law. The results show that surface features play a fundamental role in the emittance of investigated ceramics.

Flame Synthesis conditions significantly affect nanoparticles properties. Understanding thermal regime in flames can be very useful for tuning nanoparticles with specific properties. In this work, information on thermal status is obtained through the analysis of light emission from nanoparticles during synthesis and under an external laser irradiation. We focus on the dependence of the particle temperature on laser fluence as reported in our previous work. We discuss temperature plateau observed in the low laser fluence regime as attributed to non-isothermality, that means the local coexistence of partially solidified particles at melting point and much hotter particles in a flame spray.

In high vacuum flat solar thermal panels, the main losses are the optical and radiative losses of the selective solar absorber. The optical properties of commercial selective solar absorbers are usually measured by reflectivity measurements from 350nm up to 20?m at room temperature. The spectrally averaged absorptivity and emissivity are estimated and their values are used to calculate the panel performance at high temperature. To measure the actual absorptance and emittance at operating temperature and up to stagnation temperature (as high as 400°C), we have developed a calorimetric instrument based on a power balance equation. We compare the results obtained by our instrument based on a calorimetric method with the value from the optical data. The results are in excellent agreement in the infrared region whereas the calorimetric method measures a spectrally averaged absorptivity 0.85, lower than the spectrally averaged absorptivity measured by optical method by about the 10%. An optical energy loss mechanism could be responsible for the observed discrepancy: further investigations are in progress to clarify the origin of the discrepancy.

Nanofluids are colloidal systems based on the suspension of nanoparticles in a fluid. Their thermal properties mean that they are promising heat transfer fluids with possible applications in different fields, concentrating solar energy being one of particular interest. Thus, this study presents the preparation of nanofluids based on WSe nanoparticles suspended in the eutectic mixture of biphenyl and diphenyl oxide, which is a heat transfer fluid widely used in concentrating solar power plants. To this end, solvothermal synthesis was used to prepare WSe nanosheets, which were characterized by means of scanning transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. The physical and chemical stability of the nanofluids was analyzed, observing that they became more stable when Triton X-100 was used as the surfactant. The presence of WSe nanosheets did not result in a significant increase in density or viscosity, but, by contrast, improvements were obtained in their isobaric specific heat and thermal conductivity, up to 4.7 and 64%, respectively. Spectral optical properties were investigated as well, showing a significant effect of the WSe nanosheet addition to the extinction coefficient of the base fluid in the wavelength range of the solar spectrum, promising for direct absorption solar collectors. Finally, the efficiency of the nanofluids was analyzed in a solar collector considering the U parameter, obtaining a remarkable increase in the efficiency of up to 34% with respect to the pure heat transfer fluid. This proves the possibility to obtain a sustainable production of energy from the sun using these WSe-based nanofluids.

The ball-milling of materials is a mechanical grinding method that has different effects on treated materials, and can be used for the direct synthesis of organometal halide perovskite (OHP) crystals. Herein, the effect of such a process, extended over a large temporal window, is related to the properties of referential three-dimensional (3D) MAPbI(3)(MA = methylammonium) and two-dimensional (2D) PEA(2)PbI(4)(PEA = phenylethylammonium) perovskite crystals. For both 2D and 3D systems, the ball-milling induces a reduction of the crystallite dimension, accompanied by a worsening of the overall crystallinity, but without any sign of amorphization. For MAPbI(3), an intriguing room temperature structural transition, from tetragonal to cubic, is observed. The processing in both cases impacts on the morphology, with a reduction of the crystal shape quality connected to the particles' agglomeration tendency. All these effects translate to a "blue shift" of the absorption and emission features, suggesting the use of this technique to modulate the 3D and 2D OHPs' properties.

Twisted bilayer graphene (TBG) at twist angles ??1? has recently attracted a great deal of interest for its rich transport phenomenology. We present a theoretical study of the local optical conductivity, plasmon spectra, and thermoelectric properties of TBG at different filling factors and twist angles ?. Our calculations are based on the electronic band structures obtained from a continuum model that has two tunable parameters u0 and u1 which parametrize the intrasublattice interlayer and intersublattice interlayer tunneling rate, respectively. In this article we focus on two key aspects: (i) we study the dependence of our results on the value of u0, exploring the whole range 0<=u0<=u1; and (ii) we take into account effects arising from the intrinsic charge density inhomogeneity present in TBG, by calculating the band structures within the self-consistent Hartree approximation. At zero filling factor, i.e., at the charge neutrality point, the optical conductivity is quite sensitive to the value of u0 and twist angle, whereas the charge inhomogeneity brings about only modest corrections. On the other hand, away from zero filling, static screening dominates and the optical conductivity is appreciably affected by the charge inhomogeneity, the largest effects being seen on the intraband contribution to it. These findings are also reflected by the plasmonic spectra. We compare our results with existing ones in the literature, where effects (i) and (ii) above have not been studied systematically. As natural byproducts of our calculations, we obtain the Drude weight and Seebeck coefficient. The former displays an enhanced particle-hole asymmetry stemming from the inhomogeneous ground-state charge distribution. The latter is shown to display a broad sign-changing feature even at low temperatures (?5K) due to the reduced slope of the bands, as compared to those of single-layer graphene.