scholarly journals Organic Coatings with Low IR Emission

2021 ◽  
Vol 58 (3) ◽  
pp. 41-50
Author(s):  
Cristiana Epure ◽  
Viorel Tiganescu ◽  
Teodora Zecheru ◽  
Gabriel Epure ◽  
ovidiu Iorga ◽  
...  
Keyword(s):  
High Surface ◽  
Powder Materials ◽  
Surface Adhesion ◽  
Coating Materials ◽  
Ir Radiation ◽  
Spectral Parameters ◽  
Destructive Effect ◽  
Ir Reflectance ◽  
High Flexibility ◽  
Ir Emission

A series of methods were employed to assess the performances of advanced coating materials based on components that can modify the spectral parameters of the surfaces on which these materials are applied in order to obtain passive military camouflage. Powder materials with high infrared (IR) reflectance were used to obtain this type of coatings, which also ingrain in their structure a significant volume of air that allow limitation of the radiative heat transfer of the coated source. The components were embedded in a polyurethane matrix, which facilitated the coating process on different surfaces. The bicomponent polyurethane-based binder used within the different composition tested is transparent to incident IR radiation, has no organic solvents, is highly flexible and possesses remarkable physical, chemical and mechanical properties: high surface adhesion, high flexibility and resistance against a number of chemical agents and external factors with destructive effect. The efficiency of these composite materials was further demonstrated by analyzing the thermal images of different objects.

The friction of clean crystal surfaces

1966 ◽  
Vol 295 (1442) ◽  
pp. 233-243 ◽  
Keyword(s):  
Coefficient Of Friction ◽  
High Surface ◽  
High Vacuum ◽  
Surface Films ◽  
Surface Adhesion ◽  
Crystal Surfaces ◽  
Deformation And Fracture ◽  
The Coefficient Of Friction ◽  
Molecular Layers ◽  
Frictional Behaviour

A study is made of the frictional behaviour of crystals (diamond, magnesium oxide, sapphire) sliding on themselves in high vacuum (10 -10 torr). The surface films normally present on these crystals are very tenacious but they may be worn away by repeated sliding in the same track. Under these conditions the friction of the clean crystals may increase by a factor of ten so that the coefficient of friction may rise to μ ≈ 1. The frictional rise is limited because of the elastic and brittle behaviour of the contact regions. Under these conditions subsurface deformation and fracture of the crystal occurs and this, combined with the high surface adhesion, causes pronounced wear. Adsorption of a few molecular layers of gas can again reduce the friction to a low value. The results are relevant to the operation of bearings and to the wear of surfaces in space.

scholarly journals Bacterial Cellulose: Production, Modification and Perspectives in Biomedical Applications

Nanomaterials ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1352 ◽  
Author(s):  
Gorgieva ◽  
Trček
Keyword(s):  
Bacterial Cellulose ◽  
Bone Repair ◽  
High Surface ◽  
Carbon Sources ◽  
High Surface Area ◽  
Young Modulus ◽  
High Water ◽  
Ex Situ ◽  
Bacterial Strains ◽  
High Flexibility

Abstract: Bacterial cellulose (BC) is ultrafine, nanofibrillar material with an exclusive combination of properties such as high crystallinity (84%–89%) and polymerization degree, high surface area (high aspect ratio of fibers with diameter 20–100 nm), high flexibility and tensile strength (Young modulus of 15–18 GPa), high water-holding capacity (over 100 times of its own weight), etc. Due to high purity, i.e. absence of lignin and hemicellulose, BC is considered as a non-cytotoxic, non-genotoxic and highly biocompatible material, attracting interest in diverse areas with hallmarks in medicine. The presented review summarizes the microbial aspects of BC production (bacterial strains, carbon sources and media) and versatile in situ and ex situ methods applied in BC modification, especially towards bionic design for applications in regenerative medicine, from wound healing and artificial skin, blood vessels, coverings in nerve surgery, dura mater prosthesis, arterial stent coating, cartilage and bone repair implants, etc. The paper concludes with challenges and perspectives in light of further translation in highly valuable medical products.

Current and advanced nanomaterials in dentistry as regeneration agents: an update

2020 ◽  
Vol 20 ◽  
Author(s):  
Mohsen Yazdanian ◽  
Aghil Rahmani ◽  
Elahe Tahmasebi ◽  
Hamid Tebyanian ◽  
Alireza Yazdanian ◽  
...  
Keyword(s):  
High Surface ◽  
Control Cell ◽  
Dental Materials ◽  
High Surface Area ◽  
Coating Materials ◽  
Bonding Agents ◽  
Alloplastic Materials ◽  
Mouth Rinses ◽  
Regenerative Dentistry ◽  
And Migration

: In modern dentistry, nanomaterials have strengthened their foothold among tissue engineering strategies for treating bone and dental defects due to a variety of reasons, including trauma and tumors. Besides their finest physiochemical features, the biomimetic characteristics of nanomaterials promote cell growth and stimulate tissue regeneration. The single units of these chemical substances are small-sized particles, usually between 1 to 100 nm, in an unbound state. This unbound state allows particles to constitute aggregates with one or more external dimensions and provide a high surface area. Nanomaterials have brought advances in regenerative dentistry from the laboratory to clinical practice. They are particularly used for creating novel biomimetic nanostructures for cell regeneration, targeted treatment, diagnostics, imaging, and the production of dental materials. In regenerative dentistry, nanostructured matrices and scaffolds help control cell differentiation better. Nanomaterials recapitulate the natural dental architecture and structure and form functional tissues better compared to the conventional autologous and allogenic tissues or alloplastic materials. The reason is that novel nanostructures provide an improved platform for supporting and regulating cell proliferation, differentiation, and migration. In restorative dentistry, nanomaterials are widely used in constructing nanocomposite resins, bonding agents, endodontic sealants, coating materials, and bioceramics. They are also used for making daily dental hygiene products such as mouth rinses. The present article classifies nanostructures and nanocarriers in addition to reviewing their design and applications for bone and dental regeneration.

scholarly journals Infrared Observations of Be Stars (Review Paper)

1987 ◽  
Vol 92 ◽  
pp. 219-236
Author(s):  
Henny J.G.L.M. Lamers
Keyword(s):  
Dust Emission ◽  
Circumstellar Envelope ◽  
Be Stars ◽  
Ir Radiation ◽  
Infrared Observations ◽  
Near Ir ◽  
Circumstellar Shells ◽  
Early Type Stars ◽  
Ir Emission ◽  
Rule Out

The first indication that Be stars have an excess near-IR radiation, compared to normal stars of the same spectral type was found by Johnson et al. (1966). Johnson (1967) noticed that in his sample of 85 early type stars all the Be stars and shell stars had an excess in K-L and he concluded that this is due to IR emission from circumstellar shells. Woolf et al. (1970) suggested that the IR excess of Be stars might be due to free-free emission in the ionized circumstellar envelope which also produces the Balmer emission lines, but their observations at 5 and 10 µ could not rule out the possibility that circumstellar dust contributed to the excess. The observations by Allen (1973) of a large number of Be stars up to a wavelength of 3.5 µ could not make the distiction between free-free or dust emission either.

scholarly journals Large-Scale and Localized Laser Crystallization of Optically Thick Amorphous Silicon Films by Near-IR Femtosecond Pulses

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5296
Author(s):  
Kirill Bronnikov ◽  
Alexander Dostovalov ◽  
Artem Cherepakhin ◽  
Eugeny Mitsai ◽  
Alexander Nepomniaschiy ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Amorphous Silicon ◽  
Large Scale ◽  
High Surface ◽  
Femtosecond Laser Pulses ◽  
Visible Spectral Range ◽  
Ir Radiation ◽  
Near Ir ◽  
Si Films ◽  
Induced Crystallization

Amorphous silicon (α-Si) film present an inexpensive and promising material for optoelectronic and nanophotonic applications. Its basic optical and optoelectronic properties are known to be improved via phase transition from amorphous to polycrystalline phase. Infrared femtosecond laser radiation can be considered to be a promising nondestructive and facile way to drive uniform in-depth and lateral crystallization of α-Si films that are typically opaque in UV-visible spectral range. However, so far only a few studies reported on use of near-IR radiation for laser-induced crystallization of α-Si providing less information regarding optical properties of the resultant polycrystalline Si films demonstrating rather high surface roughness. The present work demonstrates efficient and gentle single-pass crystallization of α-Si films induced by their direct irradiation with near-IR femtosecond laser pulses coming at sub-MHz repetition rate. Comprehensive analysis of morphology and composition of laser-annealed films by atomic-force microscopy, optical, micro-Raman and energy-dispersive X-ray spectroscopy, as well as numerical modeling of optical spectra, confirmed efficient crystallization of α-Si and high-quality of the obtained films. Moreover, we highlight localized laser-induced crystallization of α-Si as a promising way for optical information encryption, anti-counterfeiting and fabrication of micro-optical elements.

Basic Atmospheric Chemistry: A Quantum Chemical Study on Hydration of Mesospheric NaOH

2004 ◽  
Vol 1 (1) ◽  
pp. 35 ◽  
Author(s):  
Simon Petrie
Keyword(s):  
Atmospheric Chemistry ◽  
Quantum Chemical ◽  
Quantum Chemical Study ◽  
Free Water ◽  
Chemical Study ◽  
Upper Atmosphere ◽  
Noctilucent Clouds ◽  
Ir Radiation ◽  
Ir Emission ◽  
Iron And Calcium

Environmental Context.A natural global layer of sodium atoms exists in the mesosphere, 80–95 km above sea level, where it originates—along with lithium, iron, and calcium—from ablation of meteors. Sodium, as its hydroxide, readily associates with free water to form NaOH·(H2O)n clusters. The clusters strongly emit IR radiation and may therefore affect the upper atmosphere’s temperature profile; the clusters are also likely to be a source of nuclei for noctilucent clouds. The same NaOH-based processes may also occur at lower altitudes in the troposphere where water is more abundant than carbon dioxide. Abstract.The sequential association of water molecules with NaOH, a key upper-atmosphere metal-containing molecule, is investigated using quantum chemical calculations. The first several H2O–NaOH·(H2O)n–1 bond strengths are sizeable (respectively 82, 70, 56, 42, 42, and 36 kJ mol–1 according to calculations), suggesting that the termolecular association reactions of NaOH·(H2O)n–1 with H2O may well be efficient upper-atmospheric processes. Such reactions would provide an alternative or additional pathway to the production of hydrated sodium bicarbonate, which has been implicated in the nucleation of noctilucent clouds. The NaOH·(H2O)n complexes are also characterized by very large IR intensities across the 3–5 μm wavelength range, suggesting that they may contribute disproportionately to the IR emission profile of the upper atmosphere.

scholarly journals Manufacturing and Assessment of Electrospun PVP/TEOS Microfibres for Adsorptive Heat Transformers

Coatings ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 443 ◽  
Author(s):  
Patrizia Frontera ◽  
Mikio Kumita ◽  
Angela Malara ◽  
Junya Nishizawa ◽  
Lucio Bonaccorsi
Keyword(s):  
Thermal Stability ◽  
High Surface ◽  
High Surface Area ◽  
High Permeability ◽  
Sem Images ◽  
Good Thermal Stability ◽  
Adsorption Heat Pump ◽  
High Flexibility ◽  
Woven Textile ◽  
Thermal Stability Of

A new adsorbent coating for the adsorber unit of an adsorption heat pump made of hybrid, organic–inorganic microfibres was prepared and characterized. Different coatings were obtained by the electrospinning of polyvinylpyrrolidone (PVP) solutions added with different quantities of tetraethyl orthosilicate (TEOS). PVP is a polymer with water adsorption capability and the TEOS addition allowed to increase the thermal stability of microfibres. The aim, indeed, was to preserve the polymeric structure of microfibres in order to obtain coatings with high flexibility and mechanical strength. The results demonstrated that TEOS concentrations in the range of 5–13 wt.% produced microfibre coatings of non-woven textile structure with both good water affinity and good thermal stability. SEM images of coatings showed that the deposited microfibre layers have both a high surface area and a high permeability representing a significant advantage in adsorption systems.

scholarly journals The Synthesis and Study of Metal Powder Stabilizer Properties in Lubrication Compositions

2019 ◽  
pp. 108-123
Author(s):  
Valentin V. Safonov ◽  
Valery V. Ostrikov ◽  
Vadim V. Venskaytis ◽  
Konstantin V. Safonov ◽  
Alexandr S. Azarov
Keyword(s):  
Oleic Acid ◽  
Surface Film ◽  
High Surface ◽  
Powder Materials ◽  
Motor Oil ◽  
Metal Powders ◽  
Lubricant Composition ◽  
Sedimentation Resistance ◽  
Long Time ◽  
Manufacturing Technologies

Introduction. Modern manufacturing technologies of powder materials allow obtaining particles sized 0.1–0.5 μm. Powders with such dispersion have a very high surface energy and, consequently, unique properties. Powders with a given size can be used as an additive to motor oil to form the surface film with high tribological properties. However, the widespread use of ultra-nanoscale powder materials as additives to motor oil limits sedimentation and aggregation of the particles. As a result, the dimensions of the metal crystals increase to dozens of microns and their particles are then retained by oil filters of engines that leads to efficiency decrease and even to clogging oil-conducting channels and to setting the friction surfaces of the parts. The most technically competent solution for increasing sedimentation resistance of the lubricant composition is the use of chemical stabilizers forming the thinnest film at the surface of metal particles, which not only hinders particle aggregation, but also keeps them suspended for a long time. Materials and Methods.As stabilizers of dispersed metal powders in lubricant compositions, organic compounds of various classes are used. The analysis of several stabilizers of disperse metal powders is given in the paper and new compositions are proposed: apinezon MN, polyethylene glycol sebacate and commodity stabilizer apiezon L. The methods of stabilizers synthesis and examination of their activity are described. Results. The stabilization activity of the developed preparations was compared to the basic version: oleic acid. Addition of the ester of ethylene glycol sebacate had no stabilizing effect on the lubricant composition. The synthesized MN and Mg reagent apeizon L show stabilizing properties with respect to metallic powders of the lubricant composition, comparable with the properties of oleic acid. Discussion and Conclusion.Since apiezon greases are a mixture of hydrocarbons, their corrosivity is much lower than that of oleic acid, they can be recommended for practical use.

scholarly journals Tunable Infrared Metamaterial Emitter for Gas Sensing Application

Nanomaterials ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1442 ◽  
Author(s):  
Ruijia Xu ◽  
Yu-Sheng Lin
Keyword(s):  
High Efficiency ◽  
Gas Sensing ◽  
High Sensitivity ◽  
Energy Conversion Efficiency ◽  
High Energy ◽  
Ir Radiation ◽  
Optical Efficiency ◽  
Sensing Applications ◽  
On Chip ◽  
Ir Emission

We present an on-chip tunable infrared (IR) metamaterial emitter for gas sensing applications. The proposed emitter exhibits high electrical-thermal-optical efficiency, which can be realized by the integration of microelectromechanical system (MEMS) microheaters and IR metamaterials. According to the blackbody radiation law, high-efficiency IR radiation can be generated by driving a Direct Current (DC) bias voltage on a microheater. The MEMS microheater has a Peano-shaped microstructure, which exhibits great heating uniformity and high energy conversion efficiency. The implantation of a top metamaterial layer can narrow the bandwidth of the radiation spectrum from the microheater to perform wavelength-selective and narrow-band IR emission. A linear relationship between emission wavelengths and deformation ratios provides an effective approach to meet the requirement at different IR wavelengths by tailoring the suitable metamaterial pattern. The maximum radiated power of the proposed IR emitter is 85.0 µW. Furthermore, a tunable emission is achieved at a wavelength around 2.44 µm with a full-width at half-maximum of 0.38 µm, which is suitable for high-sensitivity gas sensing applications. This work provides a strategy for electro-thermal-optical devices to be used as sensors, emitters, and switches in the IR wavelength range.

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