Photon Synthesis of Nanometric Films Based on Transitional Metal oxides for Multi-Parameter Sensors

The reactive pulsed laser deposition (RPLD) based on a KrF laser was used for photon synthesis of nanometric iron and chromium oxides films. RPLD allows controlling the thickness and stoichiometry of deposits with definite band gap. So RPLD was used for synthesizing nanometric iron and chromium oxides films for thermo-photo-chemical sensors. We compared sensing properties of iron and chromium oxides nanometric films deposited on <100>Si substrate by RPLD. These iron and chromium oxides films have semiconductor properties with the band gaps less than 1.0 eV. The largest photosensitivity of iron and chromium oxides films was about 44 Vc/W and 2.5 Vc/W, accordingly, for white light at power density ~ 6x10-3 W/cm2. Vc is “chemical” photo e.m.f.. Maximum value of thermo electromotive force (e.m.f.) coefficient of iron and chromium oxides films was about 1.65 mV/K and 3.5-4.5mV/K, accordingly. Iron oxides films were tested as chemical sensors: the largest sensitivity of NO molecules was at the level of 7x1012 cm-3. Our results showed that nanometric iron and chromium oxides films synthesized by UV photons can be used as up-to-date materials for multi-parameter sensors operating at moderate temperature

Temperature dependence of the photoluminescence properties of colloidal Cd Se ∕ Zn S core/shell quantum dots embedded in a polystyrene matrix

We report on the temperature dependence of the photoluminescence (PL) spectrum and of the PL relaxation dynamics for colloidal $\mathrm{Cd}\mathrm{Se}∕\mathrm{Zn}\mathrm{S}$ core/shell quantum dots (QDs) embedded in an inert polystyrene matrix. We demonstrate that the confinement energy in the QDs is independent of the temperature. The coupling with both acoustic and optical phonons is also studied. Quantum confinement results in a strong increase of the exciton\char21{}acoustic-phonon coupling constant, up to 71\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{eV}∕\mathrm{K}, and in a reduced exciton\char21{}longitudinal-optical (LO)-phonon coupling constant, down to $21\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$, with respect to bulk CdSe. In addition, we demonstrate that the main nonradiative process that limits the quantum efficiency of the QD at room temperature is the thermal escape from the dot assisted by scattering with four LO phonons. Thermally activated trapping in surface states is also observed at low temperature, with an activation energy of about $15\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$

SARS-CoV-2 tracheitis in laryngectomised patients: A consecutive case-series study

Key points SARS-CoV-2 is a possible cause of acute severe tracheitis in laryngectomees. In our series, the clinical picture was characterized by a haemorrhagic tracheitis with a slow resolution pattern. We observed a histological pattern of erosive inflammation of the respiratory epithelium. Planned tracheo-bronchoscopy and tracheal toilettes are recommended to prevent critical obstruction of the airway, which can be fatal in patients with associated impairment of lung function caused by SARS-CoV-2 infection. The present cases highlight the need for close interdisciplinary working and communication in the management of airway complications of COVID-19 infection

Improved properties of TiAlN coatings through the multilayer structure

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Modal analysis of novel coronavirus (SARS COV-2) using finite element methodology

Many new engineering and scientific innovations have been proposed to date to passivate the novel coronavirus (SARS CoV-2), with the aim of curing the related disease that is now recognised as COVID-19. Currently, vaccine development remains the most reliable solution available. Efforts to provide solutions as alternatives to vaccinations are growing and include established control of behaviours such as self-isolation, social distancing, employing facial masks and use of antimicrobial surfaces. The work here proposes a novel engineering method employing the concept of resonant frequencies to denature SARS CoV-2. Specifically, “modal analysis” is used to computationally analyse the Eigenvalues and Eigenvectors i.e. frequencies and mode shapes to denature COVID-19. An average virion dimension of 63 nm with spike proteins number 6, 7 and 8 were examined, which revealed a natural frequency of a single virus in the range of 88–125 MHz. The information derived about the natural frequency of the virus through this study will open newer ways to exploit medical solutions to combat future pandemics

The critical raw materials in cutting tools for machining applications: a review

A variety of cutting tool materials are used for the contact mode mechanical machining of components under extreme conditions of stress, temperature and/or corrosion, including operations such as drilling, milling turning and so on. These demanding conditions impose a seriously high strain rate (an order of magnitude higher than forming), and this limits the useful life of cutting tools, especially single-point cutting tools. Tungsten carbide is the most popularly used cutting tool material, and unfortunately its main ingredients of W and Co are at high risk in terms of material supply and are listed among critical raw materials (CRMs) for EU, for which sustainable use should be addressed. This paper highlights the evolution and the trend of use of CRMs) in cutting tools for mechanical machining through a timely review. The focus of this review and its motivation was driven by the four following themes: (i) the discussion of newly emerging hybrid machining processes offering performance enhancements and longevity in terms of tool life (laser and cryogenic incorporation); (ii) the development and synthesis of new CRM substitutes to minimise the use of tungsten; (iii) the improvement of the recycling of worn tools; and (iv) the accelerated use of modelling and simulation to design long-lasting tools in the Industry-4.0 framework, circular economy and cyber secure manufacturing. It may be noted that the scope of this paper is not to represent a completely exhaustive document concerning cutting tools for mechanical processing, but to raise awareness and pave the way for innovative thinking on the use of critical materials in mechanical processing tools with the aim of developing smart, timely control strategies and mitigation measures to suppress the use of CRMs

Fatigue bending behavior of cold-sprayed nickel-based superalloy coatings

Cold-sprayed Ni-based superalloy coatings offer new possibilities for manufacturing and repairing damaged components, such as gas turbine blades or other parts of aircraft engines. This development shines a new light on the conventional additive manufacturing technologies and significantly broadens application fields of cold spray. The idea is that cold spray can contribute to improving the fatigue properties of manufacturing and repaired components. This study deals with the analysis of the microstructural and mechanical properties of IN625 cold-sprayed coatings on V-notched carbon steel substrate. Process conditions of 1000 degrees C and 50bar were employed to produce coatings in V-notched (60 degrees and 90 degrees) samples in order to evaluate the fatigue crack behavior of the sprayed material. Bending tests were carried out in order to evaluate the crack propagation in the coatings during cyclic loading. The K factor was quantified for the two different notch geometries. After fatigue tests, the cracking mechanisms were observed through SEM. Optical microscopy, nanoindentation as a function of coating/substrate distance and corrosion tests were performed. Porosity measurements through image analyses were done to characterize the coatings' quality. The results achieved demonstrate that cold spray deposition and repair can contribute to resistance and to the increase in the global fatigue life of cracked structures

Critical Raw Materials Saving by Protective Coatings under Extreme Conditions: A Review of Last Trends in Alloys and Coatings for Aerospace Engine Applications

Several applications, where extreme conditions occur, require the use of alloys often containing many critical elements. Due to the ever increasing prices of critical raw materials (CRMs) linked to their high supply risk, and because of their fundamental and large utilization in high tech products and applications, it is extremely important to find viable solutions to save CRMs usage. Apart from increasing processes’ efficiency, substitution, and recycling, one of the alternatives to preserve an alloy and increase its operating lifetime, thus saving the CRMs needed for its manufacturing, is to protect it by a suitable coating or a surface treatment. This review presents the most recent trends in coatings for application in high temperature alloys for aerospace engines. CRMs’ current and future saving scenarios in the alloys and coatings for the aerospace engine are also discussed. The overarching aim of this paper is to raise awareness on the CRMs issue related to the alloys and coating for aerospace, suggesting some mitigation measures without having the ambition nor to give a complete overview of the topic nor a turnkey solution